WO2022121334A1 - 负极材料及其制备方法、锂离子电池 - Google Patents

负极材料及其制备方法、锂离子电池 Download PDF

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WO2022121334A1
WO2022121334A1 PCT/CN2021/109137 CN2021109137W WO2022121334A1 WO 2022121334 A1 WO2022121334 A1 WO 2022121334A1 CN 2021109137 W CN2021109137 W CN 2021109137W WO 2022121334 A1 WO2022121334 A1 WO 2022121334A1
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Prior art keywords
negative electrode
electrode material
layer
silicon
alloy
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PCT/CN2021/109137
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English (en)
French (fr)
Inventor
何鹏
安威力
任建国
贺雪琴
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BTR New Material Group Co Ltd
Dingyuan New Energy Technology Co Ltd
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BTR New Material Group Co Ltd
Dingyuan New Energy Technology Co Ltd
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Priority claimed from CN202011459903.8A external-priority patent/CN114628661A/zh
Priority claimed from CN202110013364.3A external-priority patent/CN114725327B/zh
Priority claimed from CN202110363721.9A external-priority patent/CN115172746A/zh
Priority claimed from CN202110468548.9A external-priority patent/CN115347151B/zh
Application filed by BTR New Material Group Co Ltd, Dingyuan New Energy Technology Co Ltd filed Critical BTR New Material Group Co Ltd
Priority to KR1020227013073A priority Critical patent/KR102873162B1/ko
Priority to EP21895928.6A priority patent/EP4053944A4/en
Priority to US17/781,920 priority patent/US20230261177A1/en
Priority to JP2022523360A priority patent/JP7477119B2/ja
Publication of WO2022121334A1 publication Critical patent/WO2022121334A1/zh
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/387—Tin or alloys based on tin
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of negative electrode materials, in particular, to negative electrode materials and preparation methods thereof, and lithium ion batteries.
  • Lithium-ion batteries are widely used in electric vehicles and consumer electronic products due to their advantages of high energy density, high output power, long cycle life and low environmental pollution.
  • silicon anode materials In order to improve the energy density of batteries, the research and development of silicon anode materials is becoming more and more mature.
  • the volume expansion of the silicon anode material is relatively large (>300%) during the lithium deintercalation process, and the silicon anode material will be pulverized and dropped from the current collector during the charging and discharging process, causing the active material and the current collector to lose electrical contact, resulting in The electrochemical performance deteriorates, the capacity decays, and the cycle stability decreases, making it difficult to obtain commercial applications.
  • the present application provides a composite negative electrode material, a preparation method thereof, and a lithium ion battery, which can reduce the expansion rate of the negative electrode material and improve the charge-discharge cycle performance of the negative electrode material, and the preparation method can reduce the production cost.
  • the present application provides a negative electrode material, the negative electrode material includes primary particles, the primary particles include a skeleton, and the skeleton includes a main skeleton located inside the primary particle and extending from the main skeleton to the multiple branches on the surface of the primary particle.
  • the negative electrode material is a primary particle, the main skeleton inside the primary particle and the multiple branches extending from the main skeleton to the surface of the primary particle are integrated as a whole, and the entire skeleton structure enhances the electron conduction and ion diffusion of the material, which can Effectively release the stress after lithiation, and avoid stress concentration at the grain boundary leading to material cracking and pulverization.
  • the negative electrode material has the advantages of a more stable integrated structure, and can have both a smaller specific surface area and a higher porosity.
  • the present application is a complete particle, the entire skeleton is connected, and the electron transfer and ion diffusion of the reinforcing material can effectively release the stress after lithiation, and avoid the material pulverization caused by stress concentration.
  • a negative electrode material in a second aspect, includes primary particles, the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles.
  • a third aspect provides a negative electrode material, the negative electrode material includes primary particles, through holes are formed inside the primary particles, and the porosity of the primary particles is not less than 30%.
  • the negative electrode material further includes a coating layer on the surface of the primary particles.
  • the coating layer on the surface of the primary particles can further improve the structural stability and cycle stability of the negative electrode material, and further alleviate the volume expansion of the negative electrode material.
  • the negative electrode material further includes a protective layer, and the protective layer is located on the surface of the framework.
  • the protective layer formed on the surface of the skeleton of the negative electrode material can further improve the conductivity and cycle stability of the negative electrode material, and at the same time further alleviate the volume expansion of the negative electrode material, thereby further improving the conductivity and rate performance of the negative electrode material.
  • the negative electrode material further includes a nanoparticle layer on the surface of the primary particles and a coating layer coated on the nanoparticle layer, and the nanoparticle layer is formed with micropores and/or mesopores.
  • the nanoparticle layer can effectively avoid material pulverization, can alleviate the volume expansion of the material, and ensure the structural stability of the primary particles inside the negative electrode material.
  • it After being coated with a coating layer, it has better electrical conductivity and stability, which can effectively avoid the internal pores of the carbon filling material, improve the first effect of the material, and enable the composite negative electrode material to exhibit high capacity, long cycle life, high rate performance and Features such as low expansion.
  • the present application provides a method for preparing a negative electrode material, the method comprising the following steps:
  • M in the N-M material includes at least one of Mg, Al, Li and Ca;
  • N in the N-M material includes at least one of Si, Ge, Sn, B and Sb.
  • the present application obtains a porous N negative electrode material by reacting the N-M material with a transition metal halide at a high temperature, and then removing the metal M component of the N-M material. Due to the metal halide generated by the reaction, taking silicon-magnesium alloy or silicon-aluminum alloy as an example, the generated metal halide is a metal halide of magnesium or aluminum in a molten state at the reaction temperature, and the molten halide has a continuous It also provides a connected liquid template for the formation of the connected nano-N material. After removing the metal halide, a porous N negative electrode material is obtained. On the structure, the nano-units grow along the connected liquid template to form a connected skeleton structure. After removing the template, the formation of The primary particles have a macroporous structure, and pores are formed inside the primary particles, and the pores extend to the surface of the primary particles.
  • the present application provides a method for preparing a negative electrode material, comprising the following steps:
  • the mixture containing the N-M alloy and the halogen-containing six-membered ring organic compound is placed in a protective atmosphere to carry out a displacement reaction to obtain a reaction product comprising an oxide of M, a halide of M;
  • N in the N-M alloy includes at least one of silicon, germanium, antimony, tin, and boron
  • M in the N-M alloy includes at least one of magnesium, aluminum, calcium, and zinc.
  • the anode material is prepared by a one-step composite method, and the N-M alloy reacts directly with the six-membered ring organic matter at high temperature to remove the metal M component in the N-M alloy, and at the same time deposit a carbon layer on the surface of the N material in situ.
  • the overall reaction is mild and has no by-products, the N material has a complete and stable structure, and the carbon layer is uniformly deposited.
  • the raw materials involved in the reaction are commonly used alloys, organics and metal salts, which can reduce costs.
  • the present application provides a method for preparing a negative electrode material, the method comprising the following steps:
  • the mixture containing the N-M alloy and the carbon-containing ammonium salt is placed in a protective atmosphere to carry out a displacement reaction to obtain a reaction product, the reaction product comprising an oxide of M, a nitride of M;
  • N in the N-M alloy includes at least one of silicon, germanium, antimony, tin, and boron
  • M in the N-M alloy includes at least one of magnesium, aluminum, calcium, and zinc.
  • the present application uses a carbon-containing ammonium salt as a carbon source and an N-M alloy to prepare a composite negative electrode material by a one-step composite method under high temperature conditions. Compared with the two-step composite method, the preparation efficiency can be effectively improved, and the process is simple.
  • the present application provides a method for preparing a negative electrode material, comprising the following steps:
  • a cladding layer is formed on the surface of the N-M alloy to obtain an N-M alloy containing the cladding layer;
  • the N-M alloy containing the coating layer is added to the ammonium salt solution to carry out redox reaction to obtain an intermediate;
  • the intermediate is subjected to dealloying heat treatment in a protective atmosphere, and the reaction product is acid washed to obtain a composite negative electrode material, wherein the N in the N-M alloy includes silicon, germanium, antimony, tin, and boron. At least one, M in the N-M alloy includes at least one of magnesium, aluminum, calcium and zinc.
  • the present application can prepare a composite negative electrode material with two pore structures in one step through a simple in-situ reaction.
  • the composite negative electrode can be obtained by reacting the coated N-M alloy with the ammonium salt solution and heating in a protective atmosphere. Materials, the morphology and pore structure of the composite anode material are easy to control, the alloy composition can be controlled to change the size and porosity of the pores, and the depth of the pores can be controlled by the reaction time and reaction temperature.
  • the pores in the prepared negative electrode material can provide space for internal expansion during the process of lithium deintercalation of the negative electrode material, and can be used as a channel for the electrolyte to flow, which can improve the lithium storage performance and reduce the expansion of the lithium battery, which is conducive to the lithiation of the negative electrode material. It expands inward and reduces the thickness of the entire electrode film, which greatly improves the safety of lithium-ion batteries.
  • the nanoparticle layer of the outer layer can effectively avoid material pulverization, can alleviate the volume expansion of the material, and ensure the structural stability of the primary particles inside the negative electrode material.
  • the coating material After being coated with the coating material, it has better conductivity and stability, which can effectively avoid carbon filling the three-dimensional pores of the primary particles, improve the first effect of the material, and enable the composite negative electrode material to exhibit high capacity, long cycle life, and high rate. properties and low expansion.
  • the present application provides a lithium ion battery, the lithium ion battery comprising the above-mentioned composite negative electrode material or the composite negative electrode material prepared according to the above-mentioned preparation method.
  • FIG. 1 is a schematic structural diagram of a negative electrode material according to an embodiment
  • 2a is a schematic structural diagram of a negative electrode material according to an embodiment
  • 2b is a schematic diagram of a graphene layer structure of a negative electrode material according to an embodiment
  • 3a is a schematic structural diagram of a negative electrode material according to an embodiment
  • 3b is a schematic structural diagram of a negative electrode material according to another embodiment
  • FIG. 4a is a schematic structural diagram of a negative electrode material according to an embodiment
  • 4b is a schematic structural diagram of a nanoparticle layer in a negative electrode material according to an embodiment
  • FIG. 5 is a flow chart of a method for preparing a silicon negative electrode material according to an embodiment
  • FIG. 6 is a schematic flowchart of a method for preparing a silicon negative electrode material according to an embodiment
  • Fig. 7a is the electron microscope picture of silicon negative electrode material in embodiment 1;
  • Example 7b is the XRD pattern of the silicon negative electrode material in Example 1;
  • Fig. 7e is the scanning electron microscope picture of the silicon negative electrode material in Comparative Example 1;
  • FIG. 8 is a schematic flowchart of a method for preparing a negative electrode material according to an embodiment
  • FIG. 9 is a schematic diagram of a synthesis process of a silicon-carbon composite negative electrode material provided in an embodiment
  • FIG. 10 is a schematic diagram of a synthesis process of a silicon/metal oxide and silicon/metal nitride composite negative electrode material according to an embodiment
  • Example 11a is a scanning electron microscope picture of the silicon-carbon composite negative electrode material provided in Example 1;
  • 11b is another scanning electron microscope picture of the silicon-carbon composite negative electrode material provided in Example 1;
  • Example 12a is an XRD pattern of the silicon-carbon composite negative electrode material provided in Example 1;
  • Example 12b is a Raman diagram of the silicon-carbon composite negative electrode material provided in Example 1;
  • Example 12c is a cycle performance curve diagram of the silicon-carbon composite negative electrode material provided in Example 1;
  • FIG. 13 is a schematic diagram of a synthesis process of a composite negative electrode material provided by an embodiment
  • Example 14a is a scanning electron microscope picture of the silicon-carbon composite negative electrode material provided in Example 15;
  • Example 14b is another scanning electron microscope picture of the silicon-carbon composite negative electrode material provided in Example 15;
  • Example 15a is a Raman diagram of the silicon-carbon composite negative electrode material provided in Example 15;
  • Example 15b is an XRD pattern of the silicon-carbon composite negative electrode material provided in Example 15;
  • Figure 15c is a graph of the cycle performance of the silicon-carbon composite negative electrode material provided in this embodiment.
  • 16 is a flowchart of a method for preparing a negative electrode material provided by an embodiment
  • 17a is a scanning electron microscope picture of the silicon-carbon composite negative electrode material provided in Example 25;
  • 17b is an XRD pattern of the silicon-carbon composite negative electrode material provided in Example 25;
  • FIG. 17c is a cycle performance curve diagram of the silicon-carbon composite negative electrode material provided in Example 25.
  • FIG. 17c is a cycle performance curve diagram of the silicon-carbon composite negative electrode material provided in Example 25.
  • Dealloying refers to a method of selectively removing one or more constituents of an alloy through a chemical or electrochemical corrosion process.
  • the removal of old lattice sites and the formation of new lattice sites are involved in the dealloying process, as well as the nucleation and growth of new crystals, where the formation of nanoporous structures during dealloying is related to the atomic level at the alloy/solution interface.
  • the reorganization process is closely related to the surface diffusion of undissolved metal atoms and vacancies, and the speed of surface diffusion has an important impact on the size of the ligaments/channels in the final formed nanoporous metal.
  • the negative electrode material includes primary particles, the primary particles include a skeleton, and the skeleton includes a main skeleton 11 located inside the primary particles and a plurality of branches 12 extending from the main skeleton 11 to the surface of the primary particles .
  • the primary particles in this embodiment have a macroporous structure, and the primary particles are formed with channels 13 extending to the surface of the primary particles.
  • the pore size larger than 50nm is called macropore.
  • the negative electrode material of this embodiment includes primary particles.
  • the main skeleton inside the primary particle and the multiple branches extending from the primary skeleton to the surface of the primary particle form a whole.
  • the electron transfer and ion diffusion of the entire skeleton structure enhances the material, which can be effectively released. Stress after lithiation to avoid stress concentration at the grain boundaries leading to material cracking and powdering.
  • the pore structure in which the pores of the negative electrode material extend to the surface of the primary particles has the following advantages: 1. It can reduce the expansion of the lithium battery while improving the lithium storage performance. It can not only alleviate the volume expansion during the lithium intercalation process, but also help to provide an internal expansion space for lithiation, so that the electrode material expands inward after lithiation to reduce the thickness of the entire electrode film, which greatly improves the safety of lithium ion batteries. Second, it provides a channel for the electrolyte to flow, which is beneficial to the contact of the electrolyte. The pore structure can also bring about a higher tap density, which can increase the volumetric energy density of the battery.
  • the porous negative electrode material prepared in this embodiment has the advantages of a more stable integrated structure, and can have both a smaller specific surface area and a higher porosity.
  • the present application is a complete particle, the entire skeleton is connected, and the electron transfer and ion diffusion of the reinforcing material can effectively release the stress after lithiation, and avoid the material pulverization caused by stress concentration. There are obvious grain boundaries, which lead to the concentration of lithiation stress, the fragmentation of the particles, the destruction of the whole structure, and finally the deterioration of the electrochemical performance.
  • the negative electrode material is primary particles
  • the main backbone is a three-dimensional network structure
  • a single branch is a single grain; there is no obvious grain boundary between the branch and the main skeleton, and the surface of the primary particle is dispersed; the branch on the porous silicon secondary particle in the prior art solution It is mainly composed of multiple small grains with many grain boundaries.
  • the branch on the primary grain in this embodiment is a single large grain, and there are not too many grain boundaries, and the stress after lithiation is Better dispersion can be obtained to avoid material damage caused by stress concentration; at the same time, the crystal plane curve of a single grain is the same, which is more conducive to reducing the relative volume expansion of the material in a certain direction, while the structural volume composed of multiple small grains The expansion is relatively large, and the structural stability is relatively poor, resulting in poor cycle stability.
  • the size of the crystal grain is 30 nm-100 nm; for example, the size of the crystal grain may be 30 nm, 45 nm, 50 nm, 60 nm, 75 nm, 100 nm.
  • the maximum width of the cross section of the branch is 20nm-350nm, and the maximum length of the cross section of the branch is 50nm-2500nm; preferably, the maximum width 12W of the cross section of the branch 12 is 20nm-250nm, the branch
  • the maximum length 12L of the cross section is 100nm-1500nm; for example, the maximum width 12W of the cross section of the branch 12 can be 20nm, 40nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm or 250nm, and the branch 12
  • the maximum length 12L of the cross-section can be specifically 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 800 nm, 1000 nm, 1200 nm or 1500 nm, which is not limited herein.
  • the branches are selected from at least one of rod-shaped nanoparticles, nanoplatelets, nanowires, and nanotubes.
  • the diameter of the channel 13 is 10nm-150nm as measured by the mercury intrusion test method; the depth of the channel is 50nm-1500nm.
  • the pore diameter may be 10 nm, 50 nm, 60 nm, 80 nm, 100 nm or 150 nm, which is not limited herein.
  • the depth of the channel 13 can be specifically 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 800 nm or 1000 nm, which is not limited herein.
  • the depth of the hole can be changed by controlling the reaction time and temperature (generally, the longer the reaction time and the higher the reaction temperature, the deeper the hole will be.)
  • the negative electrode material of this embodiment includes primary particles, through holes are formed inside the primary particles, and the porosity of the primary particles is not less than 30%.
  • the primary particles of the present application have high porosity, which can effectively alleviate the volume expansion of the silicon negative electrode by more than 300%. Combined with the advantages of the macroporous through-structure structure, the pore structure after lithiation can also be kept intact.
  • the porosity of the prior art is relatively high. Low and there are many micropores and mesopores, which cannot meet the huge volume expansion of silicon. After the pores are filled after lithiation, the pores are eventually filled due to electrochemical sintering, and the porous structure cannot be maintained.
  • the negative electrode material of the above-mentioned embodiment can be silicon negative electrode material, germanium negative electrode material, tin negative electrode material, boron negative electrode material, antimony negative electrode material and other negative electrode materials; a typical example is silicon negative electrode material.
  • the primary particles are selected from silicon negative electrode materials.
  • germanium, tin, boron and antimony at least one of germanium, tin, boron and antimony; its skeleton can be silicon skeleton, germanium skeleton, tin skeleton, boron skeleton, antimony skeleton, etc.; if the negative electrode material selects silicon negative electrode material, its silicon negative electrode material is primary particle,
  • the primary particle includes a silicon skeleton, including a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the framework structures of germanium, boron, tin and antimony are similar to those of the silicon framework described above.
  • the median particle size of the primary particles is 0.2 ⁇ m to 15 ⁇ m, such as 0.2 ⁇ m, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m or 15 ⁇ m, and the like. It is preferably 0.5 ⁇ m to 10 ⁇ m, and more preferably 1 ⁇ m to 5 ⁇ m.
  • the specific surface area of the primary particles is 5 m 2 /g to 100 m 2 /g, such as 5 m 2 /g, 10 m 2 /g, 20 m 2 /g, 30 m 2 /g, 40 m 2 /g, 50 m 2 /g, 60m 2 /g, 80m 2 /g or 100m 2 /g, etc. It is preferably 10 m 2 /g to 50 m 2 /g.
  • the porosity of the primary particles is 30%-70%, such as 30%, 35%, 40%, 50%, 55%, 60% or 70%, etc., preferably 40%-60%.
  • the powder tap density of the primary particles is 0.2g/cm 3 to 0.8g/cm 3 , such as 0.2g/cm 3 , 0.3g/cm 3 , 0.5g/cm 3 , 0.6g/cm 3 . 3 , 0.7g/cm 3 or 0.8g/cm 3 , etc. It is preferably 0.4 g/cm 3 to 0.7 g/cm 3 .
  • the powder compaction density of the primary particles is 1.2 g/cm 3 to 1.8 g/cm 3 , such as 1.2 g/cm 3 , 1.3 g/cm 3 , 1.4 g/cm 3 , 1.5 g/cm 3 . 3 , 1.6 g/cm 3 or 1.8 g/cm 3 , etc., preferably 1.4 g/cm 3 to 1.7 g/cm 3 .
  • the negative electrode material includes primary particles 10 and a coating layer 20 on the surface of the primary particles 10 .
  • the negative electrode material includes an inner core 10 and a coating layer 20 formed on the surface of the inner core, wherein the inner core 10 is a primary particle.
  • the primary particle includes a skeleton, and the skeleton includes a main skeleton 11 located inside the primary particle and a plurality of branches 12 extending from the main skeleton 11 to the surface of the primary particle; the primary particle has a macroporous structure, and the primary particle is formed with extending To the channel 13 on the surface of the primary particle; it can be understood that through holes are formed inside the primary particle, and the porosity of the primary particle is not less than 30%.
  • the structural stability and cycle stability of the negative electrode material can be further improved, and the volume expansion of the negative electrode material can be further alleviated.
  • the specific structure skeleton structure, pore structure
  • performance parameters porosity, median particle size, specific surface area, powder tap density, powder compaction density, etc.
  • the median particle size of the negative electrode material is 0.1 ⁇ m to 15 ⁇ m, optionally, the median particle size of the negative electrode material may be 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m. , 7 ⁇ m, 8 ⁇ m, 9 ⁇ m or 10 ⁇ m, etc., which are not limited here.
  • the median particle diameter of the composite negative electrode material is preferably 0.5 ⁇ m to 10 ⁇ m, and more preferably 1 ⁇ m to 8 ⁇ m.
  • the specific surface area of the negative electrode material is 1 m 2 /g to 150 m 2 /g.
  • the specific surface area ratio of the negative electrode material may be 1 m 2 /g, 5 m 2 /g, 10 m 2 /g, 20 m 2 /g, 30 m 2 /g, 40 m 2 /g, 50 m 2 /g, 60 m 2 /g g, 70 m 2 /g, 100 m 2 /g, 120 m 2 /g or 150 m 2 /g, etc., which are not limited here; the specific surface area ratio of the negative electrode material is preferably 1 m 2 /g to 50 m 2 /g.
  • the specific surface area is controlled at 10m 2 /g ⁇ 50m 2 /g.
  • the negative electrode material has a porosity of 30% to 70%.
  • the coating layer includes at least one of a carbon layer, a metal oxide layer and a metal nitride layer; the above types of coating layers can further improve the conductivity, structural stability and cycle stability of the negative electrode material , while further relieving the volume expansion of the negative electrode material;
  • the coating layer includes a carbon layer, and further, the carbon layer includes at least one of a graphene layer and an amorphous carbon layer;
  • the graphene layer has a wrinkled structure, and the wrinkled morphology of the graphene layer can provide more active sites, thereby further improving the conductivity and rate performance of the negative electrode material;
  • the wrinkled structure includes protrusions (peaks) 201 and depressions (valleys) 202, between two adjacent protrusions 201 is a depression 202, and between two adjacent depressions 202 is a protrusion 201; wherein,
  • the surface roughness Rz (maximum peak-valley height) of the wrinkled structure is greater than 10 nm and less than 1 ⁇ m, further, Rz may be greater than 50 nm and less than 500 nm, and further, Rz may be greater than 100 nm and less than 350 nm.
  • the distance H between the highest points of two adjacent protrusions or the lowest points of two depressions is greater than 10 nm and less than 1 ⁇ m; further, H is greater than 50 nm and less than 800 ⁇ m, and further, H is greater than 100 nm and less than 500 nm.
  • the folded structure is classified according to the curved shape of the fold surface, and the folded structure can be selected from at least one of arc folds, sharp-edged folds and fan-shaped folds; Fan pleats.
  • the fold structure is classified according to the occurrence of the axial plane and the occurrence of the two wings, and the fold structure can be selected from at least one of upright folds, oblique folds, inverted folds and lying folds; Crooked pleats, inverted pleats and horizontal pleats.
  • the graphene layer has the above-mentioned wrinkled structure, which can provide more active sites, thereby further improving the conductivity and rate performance of the negative electrode material.
  • the carbon layer includes an amorphous carbon layer, and the thickness of the amorphous carbon layer is 5 nm ⁇ 150 nm;
  • the mass percentage content of carbon is 2% to 50%;
  • the cladding layer includes a metal oxide layer, and the metal in the metal oxide layer includes at least one of Ti, V, Nb, Ta, W, and Zr;
  • the molar ratio of metal element and oxygen element in the metal oxide layer is 1:(0.1-3); the thickness of the metal oxide layer is 1nm-200nm;
  • the mass percentage content of the composite negative electrode material is 2% to 60%;
  • the cladding layer includes a metal nitride layer
  • the metal element in the metal nitride layer includes at least one of Ti, V, Nb, Ta, W and Zr. Further, the thickness of the metal nitride layer is 1nm ⁇ 250nm.
  • the mass percentage content of the composite negative electrode material is 2% to 70%.
  • the metal oxide layer and its nitride layer act as a rigid protective shell, preventing the volume expansion of the primary particles from breaking through the entire material, ensuring excellent structural stability and long cycle life.
  • the negative electrode material further includes a protective layer 30, and the protective layer 30 is located on the surface of the framework. That is, the negative electrode material includes a primary particle protective layer.
  • the protective layer on the surface of the skeleton can improve the conductivity and stability, facilitate the entry and exit of lithium ions, and improve the rate performance of the negative electrode material.
  • the primary particle includes a skeleton, and the skeleton includes a main skeleton 11 located inside the primary particle and a plurality of branches 12 extending from the main skeleton 11 to the surface of the primary particle; the primary particle has a macroporous structure, and the primary particle is formed with extending To the channel 13 on the surface of the primary particle; it can be understood that through holes are formed inside the primary particle, and the porosity of the primary particle is not less than 30%.
  • the specific structure skeleton structure, pore structure
  • performance parameters porosity, median particle size, specific surface area, powder tap density, powder compaction density
  • the protective layer includes at least one of a carbon layer, a metal oxide layer, and a metal nitride layer;
  • the carbon layer is an amorphous carbon layer and/or a graphitic carbon layer
  • the carbon layer is only located on the surface of the framework, and based on the mass percentage of the composite negative electrode material being 100%, the carbon mass percentage is 5% to 25%; specifically, it may be 5%, 8%, 10% %, 12%, 15%, 18%, 20% or 25%, which are not limited here.
  • the thickness of the carbon layer is 1 nm to 300 nm.
  • the protective layer when the content of the protective layer is relatively high, the protective layer also fills the pores, which can further enhance the electrical conductivity and structural stability.
  • the carbon layer is also filled in the channel; the carbon filled in the channel structure can provide more ion and electron transport paths, has good carbon conductivity, is conducive to the entry and exit of lithium ions, improves the rate performance of the material, and can Further improve stability.
  • the mass percentage of carbon when the carbon layer is located on the surface of the framework and fills the pores, is 25% to 75% and excluding 25% based on the mass percentage of the composite negative electrode material of 100%; It is 25%, 28%, 30%, 35%, 40%, 45%, 50% or 75%, which is not limited here.
  • the protective layer includes a metal oxide layer
  • the metal element of the metal oxide layer includes at least one of Si, Sn, Ge, Li, V, Al, Fe, and Zn; the metal oxide layer has good rigidity , excellent compactness and other advantages, can effectively inhibit the entire structure damage caused by the volume expansion of N, reduce the volume expansion of the material and avoid the contact between the electrolyte and the N material, reduce side reactions, and improve the first effect of the entire composite material.
  • the mass percentage content of the composite negative electrode material is 5% to 25%.
  • the mass percentage of the metal oxide is 25% to 75% and 25% is not included based on the mass percentage of the composite negative electrode material as 100%.
  • the protective layer includes a metal nitride layer, and the metal elements in the metal nitride layer include at least one of Ti, V, Nb, Ta, W and Zr; the metal nitride layer not only has good rigidity, but also has excellent conductivity, which can effectively alleviate the
  • the volume expansion of silicon also increases the conductivity of the material, improves the rate capability of the material, reduces the irreversible capacity loss of the material, and brings high capacity.
  • the mass percentage of the composite negative electrode material is 5% to 25%.
  • the mass percentage of the metal nitride is 25% to 75%, excluding 25%, based on the mass percentage of the composite negative electrode material being 100%.
  • the carbon layer is also filled in the through holes of the primary particles; the carbon filled in the through holes can provide more ion and electron transport paths, and has good carbon conductivity. It is conducive to the in and out of lithium ions, improves the rate performance of the material, and can further improve the stability.
  • the mass percentage of carbon is 25% to 75%, excluding 25%, based on 100% of the composite negative electrode material mass; specifically It can be 25%, 28%, 30%, 35%, 40%, 45%, 50% or 75%, which is not limited here.
  • the protective layer is a metal oxide layer
  • the metal element of the metal oxide layer includes at least one of oxides of Si, Sn, Ge, Li, V, Al, Fe, and Zn.
  • the mass percentage of the composite negative electrode material is 25% to 75% and 25% is not included.
  • the protective layer is a metal nitride layer
  • the metal element in the metal nitride layer includes at least one of Ti, V, Nb, Ta, W, and Zr.
  • the mass percentage of the metal nitride is 25% to 75% and 25% is not included.
  • the median particle size of the negative electrode material is 0.1 ⁇ m to 15 ⁇ m, optionally, the median particle size of the negative electrode material may be 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m. , 7 ⁇ m, 8 ⁇ m, 9 ⁇ m or 10 ⁇ m, etc., which are not limited here.
  • the median particle diameter of the composite negative electrode material is preferably 0.5 ⁇ m to 10 ⁇ m, and more preferably 1 ⁇ m to 8 ⁇ m.
  • the specific surface area ratio of the negative electrode material is 1 m 2 /g to 150 m 2 /g.
  • the specific surface area ratio of the negative electrode material may be 1 m 2 /g, 5 m 2 /g, 10 m 2 /g, 20 m 2 /g, 30 m 2 /g, 40 m 2 /g, 50 m 2 /g, 60 m 2 /g g, 70m 2 /g, 100m 2 /g, 120m 2 /g or 150m 2 /g, etc., which are not limited here; the specific surface area ratio of the composite negative electrode material is preferably 1m 2 /g ⁇ 50m 2 /g. Understandably, the smaller the specific surface area, the better.
  • the specific surface area is controlled at 10m 2 /g ⁇ 50m 2 /g.
  • the porosity of the negative electrode material is 10% to 70%, specifically 10%, 30%, 35%, 40%, 50%, 55%, 60% or 70%, etc., preferably 40% ⁇ 60%.
  • the negative electrode material further includes a nanoparticle layer 40 located on the surface of the primary particle 10 and a coating layer 50 coated on the surface of the nanoparticle layer, and the nanoparticle layer 40 is formed with micropores and/or or mesoporous.
  • the negative electrode material of this embodiment includes an inner core and a coating layer 50 located on the surface of the inner core; wherein, the inner core includes primary particles 10 and a nanoparticle layer 40 located on the surface of the primary particle 10; the nanoparticle layer 40 is formed with microparticles. Pores and/or Mesopores.
  • the primary particle 10 includes a skeleton, and the skeleton includes a main skeleton 11 located inside the primary particle and a plurality of branches 12 extending from the main skeleton 11 to the surface of the primary particle 10 ; the primary particle 10 has a macroporous structure, and the primary particle is formed to extend to the primary Pores 13 on the particle surface.
  • the nanoparticle layer is composed of nanoparticles, which can effectively avoid material pulverization; the nanoparticle layer is formed with micropores and/or mesopores, which can effectively alleviate the volume expansion of the material, and at the same time promote the infiltration of electrolyte and the contact surface, and accelerate the lithium ion transmission, improve the rate performance of the entire material, and at the same time ensure the structural stability of the primary particles inside the negative electrode material.
  • After being coated with a coating layer it has better conductivity and stability, which can effectively avoid the internal pores of the carbon filling material, improve the first effect of the material, and enable the negative electrode material to exhibit high capacity, long cycle life, high rate performance and low expansion, etc.
  • the specific structure skeleton structure, pore structure
  • performance parameters median particle size, specific surface area, powder tap density, powder compaction density, etc.
  • the nanoparticle layer 40 includes a plurality of nanoparticles 41, and the plurality of nanoparticles 41 are stacked on each other.
  • the shape of the nanoparticles 41 may be spherical, quasi-spherical, flat or any other shape, which is not limited herein.
  • the nanoparticles 41 are formed with micropores 42 and/or mesopores 43.
  • the pore diameter of the micropores is less than 2 nm, and the pore diameter of the mesopores is greater than 2 nm and less than 50 nm. It is understood that the pore diameters of the micropores and the mesopores are smaller than the pore diameter of the primary particle channels. .
  • the nanoparticles are selected from at least one of nano silicon particles, nano germanium particles, nano antimony particles, nano tin particles, and nano boron particles.
  • the porosity of the negative electrode material is 30% to 70%, specifically 30%, 40%, 50%, 60% or 70%, which is not limited here, and the porosity of the composite negative electrode material is preferably 40% to 60%.
  • the porosity of the primary particles 10 is 15% to 75%, specifically, 15%, 20%, 35%, 40%, 50%, 60% or 75%, which is not limited herein.
  • the porosity of the nanoparticle layer is 5% to 35%, specifically 5%, 10%, 15%, 20%, 25%, 30% or 35%;
  • the ratio of the total porosity of the mesopores in the particle layer to the total porosity of the micropores is (2-10):1.
  • the number of mesopores in the nanoparticle layer is greater than the number of micropores.
  • the number of mesopores is more than the number of micropores, which is beneficial to the circulation of the electrolyte.
  • the nanoparticles 41 are formed on the surface of the primary particles 10 and are closely combined with the primary particles 10 to form the nanoparticle layer 40. There is an obvious grain boundary between the nanoparticle layer 40 and the primary particles 10, which is not a van der Waals force combination. The binding force is higher, the connection between the primary particle 10 and the nanoparticle layer 40 is more stable, and the overall structure is also more stable.
  • the volume ratio of pores in all pore structures is 35% to 90%
  • the volume ratio of mesopores in all pore structures is 5% to 45%
  • the volume ratio of micropores in all pore structures is 5% to 20%.
  • the volume of open pores in all the above pore structures accounts for 60% to 95%, and the volume of closed pores accounts for 5% to 40%.
  • the open pores can be divided into cross-linked pores, through pores and blind pores according to the type of pore structure.
  • the cross-linked pores account for 79% to 95% of the volume of all the openings
  • the through holes account for 4% to 20% of the volume of all the openings
  • the blind holes account for all the openings.
  • the volume ratio of pores is 1% to 10%.
  • the blind hole is a conductive hole that connects the surface layer and the inner layer of the primary particle without penetrating the primary particle, and the cross-linked hole is formed by intersecting a plurality of channels.
  • the larger proportion of cross-linked pores can provide a channel for the electrolyte, and the electrolyte can circulate in the primary particles along the cross-linked pores, which can improve the lithium storage performance of silicon and reduce the expansion of lithium batteries. It can provide a fluid flow channel for the electrolyte, but it will reduce the flow rate of the electrolyte, so the volume ratio of the through-holes should be less than that of the cross-linked pores.
  • the blind holes are not conducive to the circulation of the electrolyte, and the electrolyte flowing into the blind holes can only flow out through the original path. During the preparation process, the generation of blind holes should be minimized.
  • the median diameter of the nanoparticles 41 is 20 nm to 200 nm; the median diameter of the nanoparticles 41 may specifically be 20 nm, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, 150 nm or 200 nm, of course, the nanoparticles 41
  • the median particle size can also be set according to the actual situation, which is not limited here.
  • the small-sized nanoparticles 41 are wrapped on the surface of the primary particles, which can prevent the carbon layer from filling and blocking the pores, and increase the flow channel of the electrolyte, thereby improving the lithium storage performance of silicon and reducing the expansion of the lithium battery.
  • the thickness of the nanoparticle layer 40 is 20 nm to 2000 nm, specifically 20 nm, 50 nm, 100 nm, 200 nm, 300 nm, 500 nm, 800 nm, 1000 nm or 2000 nm, etc.
  • the thickness of the nanoparticle layer 40 can also be based on actual Set according to the situation, which is not limited here.
  • the nanoparticle layer 40 with an appropriate thickness can effectively avoid material pulverization, can alleviate the volume expansion of the material, and ensure the structural stability of the primary particles inside the material.
  • the median particle size of the negative electrode material is 0.1 ⁇ m ⁇ 15 ⁇ m, optionally, it can be 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m or 15 ⁇ m, etc., are not limited here.
  • the median particle diameter of the composite negative electrode material is preferably 0.5 ⁇ m to 10 ⁇ m, and more preferably 1 ⁇ m to 8 ⁇ m.
  • the specific surface area ratio of the negative electrode material is 1 m 2 /g to 100 m 2 /g.
  • the specific surface area of the composite negative electrode material may be 1 m 2 /g, 5 m 2 /g, 10 m 2 /g, 15 m 2 /g, 20 m 2 /g, 25 m 2 /g, 30 m 2 /g, 35 m 2 /g g, 40m 2 /g, 45m 2 /g, 50m 2 /g, 60m 2 /g, 80m 2 /g or 100m 2 /g, etc., which are not limited here; the specific surface area of the composite negative electrode material is preferably 10m 2 /g g ⁇ 50m 2 /g.
  • the specific surface area is controlled within 10m 2 /g ⁇ 50m 2 /g .
  • the coating layer in the negative electrode material of this embodiment is a carbon layer, and the thickness of the carbon layer is 5 nm to 100 nm, specifically 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, or 100 nm, etc. Thick, lithium ion transmission efficiency is reduced, which is not conducive to high-rate charge and discharge of the material, reducing the overall performance of the negative electrode material, and the carbon layer is too thin, which is not conducive to increasing the conductivity of the negative electrode material and has a weak inhibitory performance on the volume expansion of the material, resulting in long cycles. Performance price difference.
  • the mass percentage content of carbon in the negative electrode material is 5% to 50%, specifically 5%, 8%, 10%, 15%, 20%, 25%, 30%, 40% or 50%. %, which is not limited here.
  • the mass percentage content of carbon is 10% to 30%.
  • the negative electrode material includes primary particles, the primary particles include a framework, and the framework includes a main framework 10 located inside the primary particles and a plurality of branches 11 extending from the main framework 10 to the surface of the primary particles
  • the primary particles are of macroporous structure, and the primary particles are formed with pore channels 13 extending to the surface of the primary particles; through holes are formed inside the primary particles, and the porosity of the primary particles is not less than 30%.
  • the preparation method of the negative electrode material includes the following steps S11 to S14:
  • a method for preparing a negative electrode material includes steps S11-S14.
  • the N-M material includes at least one of N-M alloys and N-M intermetallic compounds; wherein, N in the N-M material includes at least one of Si, Ge, Sn, B, and Sb; M in the N-M material At least one of Mg, Al, Li and Ca is included.
  • the N-M material may be Si-Mg alloy, Si-Al alloy, Ge-Mg alloy, Ge-Al alloy, or the like.
  • the N-M powder is mixed with the M powder and heated in a protective atmosphere to obtain the N-M material.
  • silicon powder and magnesium powder are mixed, and a heating reaction is performed in a protective atmosphere to obtain a Si-Mg alloy.
  • the D50 of the N powder is 0.2 ⁇ m to 15 ⁇ m, such as 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 6 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 13 ⁇ m or 15 ⁇ m, etc.
  • the molar ratio of the N powder to the M powder is 1:(1.5-2.5), such as 1:1.5, 1:1.8, 1:2.0, 1:2.1, 1:2.3 or 1:2.5, etc. .
  • the N powder has a solid structure, and the N powder includes at least one of particles, spheres, flakes, fibers and squares.
  • the heating rate of the heating reaction in the steps of the preparation method of the N-M material is 1°C/min ⁇ 10°C/min, such as 1°C/min, 3°C/min, 4°C/min, 5°C/min, 6°C/min, 8°C/min or 10°C/min, etc.
  • the heating reaction in the steps of the preparation method of the N-M material is to keep the temperature at 400°C ⁇ 900°C for 2h ⁇ 8h, for example, at a temperature of 400°C, 500°C, 600°C, 700°C, 800°C or 850°C, etc.; time For example 2h, 4h, 5h, 6h, 7h or 8h etc.
  • the resulting N-M material is pulverized to a D50 of 0.2 ⁇ m to 15 ⁇ m after the reaction, such as 0.2 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3.5 ⁇ m, 5 ⁇ m, 7 ⁇ m, 10 ⁇ m, 12 ⁇ m or 15 ⁇ m, etc.
  • the equipment used for pulverization includes any one of a planetary ball mill, a sand mill, or a jet mill.
  • N-M materials can also be prepared by other preparation methods, such as high-energy ball milling, vacuum smelting, and hot pressing sintering.
  • step S11 can be omitted.
  • the N-M material has a D50 of 0.1 ⁇ m to 15 ⁇ m, eg, 0.1 ⁇ m, 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, or 15 ⁇ m, and the like.
  • N-M materials can obtain framework units of different shapes, including at least one of rod-shaped nanoparticles, nanosheets, nanowires and nanotubes.
  • different types of silicon alloys can obtain skeleton units of different shapes, including at least one of rod-shaped silicon nanoparticles, silicon nanosheets, silicon nanowires and silicon nanotubes.
  • the molar ratio of N-M material to transition metal halide is 1:(0.2-2), eg, 1:0.2, 1:0.5, 1:1, 1:1.2, 1:1.5, or 1:2, etc. .
  • the step of mixing the N-M material with the transition metal halide further adds at least one of an alkali metal halide and an alkaline earth metal halide.
  • the molar ratio of at least one of alkali metal halide and alkaline earth metal halide to transition metal halide is 1:(0.2-1.5).
  • Alkali metal halide and/or alkaline earth metal halide act as molten salt medium at high temperature. On the one hand, it can absorb the heat released during the reaction to maintain the stability of the structure, and on the other hand, it can increase the solubility of transition metal halide in it and promote the full reaction. proceed to improve yield and purity.
  • the reasons for the formation of the negative electrode material structure in the embodiments of the present application are explained as follows: 1. If a high melting point transition metal chloride (the melting point is greater than the melting point of the reaction product M z B x ) is selected to participate in the dealloying process, the reactant M z B x (for example, MgCl 2 , MgF 2 or MgBr 2 ) are all in the molten state, which provides a connected liquid template for the formation of the connected nano-framework and ensures the continuity of the pores of the porous anode material; if an alkali metal halide (AB x ) or alkaline earth is added Metal halide (ZBy) can further reduce the reaction temperature, so that the melting point of the mixture of MzBx and ABx is lower than the melting point of MzBx itself, so that MzBx can also be used as a liquid template at a temperature below the melting point.
  • AB x alkali metal halide
  • a transition metal chloride with a melting point lower than the melting point of the reaction product MzBx is selected as the reactant, in order to avoid the volatilization of such transition metal chloride (such as ZnCl 2 or SnCl 2 ) at high temperature, an alkali metal halide (AB x ) or alkaline earth metal halide (ZB y ) to prevent the volatilization of these transition metal chlorides and promote the reaction to proceed fully; at the same time, the melting point of the reaction product M z B x can be lowered, the reaction temperature can be lowered, and the M z B x can be guaranteed to be in a molten state , providing continuous liquid formwork.
  • AB x alkali metal halide
  • ZB y alkaline earth metal halide
  • step S12 can be omitted.
  • reaction product which includes a halide of M and a transition metal.
  • the heating rate of the heating reaction ranges from 1°C/min to 20°C/min, such as 1°C/min, 3°C/min, 5°C/min, 8°C/min, 10°C/min, 12°C /min, 14°C/min, 16°C/min, 18°C/min or 20°C/min, etc.
  • the heating reaction is maintained at 200°C ⁇ 950°C for 2h ⁇ 18h, and the temperature is such as 200°C, 235°C, 260°C, 300°C, 400°C, 450°C, 500°C, 600°C, 700°C, 800°C °C or 900°C, etc.
  • the gas in the protective atmosphere includes at least one of nitrogen, helium, neon, argon, krypton, and xenon.
  • the method for removing M halides and transition metals in the reaction product is to treat the reaction product in an acid solution and/or a transition metal halide solution.
  • the treated product can still be recycled and reused.
  • the acid in the acid solution includes at least one of hydrochloric acid, nitric acid, and sulfuric acid.
  • the concentration of the acid solution is 1 mol/L to 5 mol/L
  • the treatment time in the acid solution is 1 h to 10 h.
  • the concentration of the acid solution is for example 1mol/L, 2mol/L, 2.5mol/L, 3mol/L, 4mol/L or 5mol/L, etc.
  • the treatment time is for example 1h, 3h, 5h, 6h, 8h, 9h or 10h, etc.
  • the concentration of the transition metal halide solution is 0.5 mol/L ⁇ 5 mol/L
  • the treatment time in the transition metal halide solution is 1 h ⁇ 12 h.
  • the concentration of metal halide solution such as 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, 2.5mol/L, 3.5mol/L, 4mol/L or 5mol/L, etc.; treatment time such as 1h, 3h , 5h, 6h, 8h, 9h, 10h or 11h, etc.
  • the method for preparing the negative electrode material utilizes the N-M material to react with a transition metal halide at a high temperature, and then removes M in the N-M material to obtain a porous N negative electrode material. Due to the metal halide generated by the reaction, taking silicon-magnesium alloy or silicon-aluminum alloy as an example, the generated metal halide is a metal halide of magnesium or aluminum in a molten state at the reaction temperature, and the molten halide has a continuous It also provides a connected liquid template for the formation of connected nano-silicon. After removing the metal halide, porous silicon is obtained.
  • silicon nano-units grow along the connected liquid template to form a connected silicon skeleton.
  • the skeleton has a continuous through-hole structure in the three-dimensional direction.
  • the present application is a primary complete particle, the entire skeleton is connected, and the electron transfer and ion diffusion of the reinforcing material can effectively release the stress after lithiation, and avoid the material pulverization caused by stress concentration.
  • the prior art is generally secondary particles, that is, primary nano The particles are assembled or stacked into a porous silicon with secondary large particles, such as pomegranate-shaped silicon anode, raspberry-shaped and watermelon-shaped silicon anode. Due to the obvious grain boundaries between these primary particles, the stress is concentrated after lithiation, and the structure instability, which eventually leads to deterioration of electrochemical performance.
  • the preparation method of the negative electrode material provided in the embodiment of the present application has the outstanding advantages of simplicity, safety, and environmental protection, and can be produced on a large scale.
  • N-M materials such as silicon alloys
  • transition metal halides react with transition metal halides at high temperature and remove the metal components in the silicon alloys
  • a large amount of porous silicon can be obtained with high yields.
  • the method has wide source of raw materials, low cost, and by-products can be recycled and reused.
  • the porous silicon negative electrode material can be prepared by using cheap commercial silicon as the raw material, and the obtained N negative electrode material (Ge, B, Sn and Sb) has a porous structure and The morphology and pore structure are easy to control. Since the reaction is in a liquid environment, the sufficient progress of the reaction is ensured, and the yield and product purity are greatly improved.
  • the morphology of the product can be controlled to realize the regulation of performance.
  • the alloy composition can be controlled to change the pore size and porosity (generally, the higher the silicon content in a silicon alloy, the smaller the pore size); the reaction time and reaction temperature can be controlled to change the pore depth (generally, the longer the reaction time, the smaller the reaction temperature).
  • the maximum reaction temperature should not exceed 950 ° C.
  • the generated silicon and transition metals may react to form silicides, such as copper silicide or nickel silicide, which will deteriorate the performance of the product).
  • the preparation method of silicon anode material includes the following steps: 1) preparing Si-M alloy; 2) combining Si-M alloy with transition metal halide Mixing to obtain a mixture, wherein M in the Si-M alloy includes at least one of Mg, Al, Li and Ca; 3) placing the mixture in a protective atmosphere to perform a replacement reaction to obtain a reaction product, The reaction product includes M halide, silicon and transition metal; 4) removing the M halide and transition metal to obtain a silicon negative electrode material.
  • the preparation method of the Ge, B, Sn and Sb negative electrode materials is also similar to the above-mentioned preparation method of the porous silicon negative electrode material.
  • a lithium-ion battery in yet another embodiment, includes the silicon negative electrode material according to the first aspect.
  • the lithium-ion battery has the advantages of high capacity, long cycle life, and low expansion.
  • the silicon-magnesium alloy is ball-milled to obtain 1 ⁇ m silicon-magnesium alloy powder, and then 1 mol of silicon-magnesium alloy powder is mixed with 1 mol of stannous chloride (SnCl 2 ) and 1 mol of sodium chloride (NaCl) is mixed uniformly; Put it in an argon atmosphere and heat it to 750°C at a heating rate of 3°C/min, then keep it for 8h to fully react to obtain the reaction product; after mechanically stirring the reaction product in a 1mol/L hydrochloric acid solution for 2h, suction filtration, washing, After drying, a porous silicon negative electrode material with a median particle size of 1 ⁇ m was obtained.
  • stannous chloride SnCl 2
  • NaCl sodium chloride
  • FIG. 7a is an electron microscope picture of the porous silicon negative electrode material in this embodiment
  • FIG. 7b is an XRD pattern of the porous silicon negative electrode material in this embodiment.
  • the prepared silicon anode material is a primary particle
  • the primary particle includes a silicon skeleton
  • the silicon skeleton includes a main skeleton located inside the primary particle and extending from the main skeleton to the primary skeleton.
  • the primary particle has a macroporous structure
  • a channel is formed inside the primary particle, and the channel extends to the surface of the primary particle.
  • the silicon-magnesium alloy is ball-milled to obtain 0.5 ⁇ m silicon-magnesium alloy powder, and then 1 mol of the alloy powder is mixed with 1 mol of copper chloride (CuCl 2 ) uniformly; the obtained mixture is placed in an argon atmosphere at a temperature of 3°C/min
  • the reaction product was heated to 800°C and kept for 6 hours to fully react to obtain the reaction product; the reaction product was placed in 1 L of 2 mol/L ferric chloride solution for mechanical stirring for 3 hours, filtered, washed and dried to obtain the median particle size It is a 0.5 ⁇ m porous silicon anode material.
  • the silicon-magnesium alloy is ball-milled to obtain 1 ⁇ m silicon-magnesium alloy powder, and then 1 mol of the alloy powder is uniformly mixed with 1 mol of stannous chloride (SnCl 2 ) and 1 mol of lithium chloride (LiCl); the obtained mixture is put into argon gas
  • the reaction product was heated to 400°C at a heating rate of 3°C/min in the atmosphere and then kept for 8h to fully react to obtain the reaction product; the reaction product was placed in 2L of 1mol/L hydrochloric acid solution for mechanical stirring for 3h, suction filtration, washing, After drying, a porous silicon negative electrode material with a median particle size of 1.2 ⁇ m was obtained.
  • the 1.5 ⁇ m silicon powder and aluminum powder were evenly mixed in a molar ratio of 1:2 and then placed in an atmosphere furnace. Under the protection of argon inert gas, the temperature was heated to 650 °C at a heating rate of 10 °C/min, and then kept for 6 hours to make it fully The reaction obtains silicon-aluminum alloy.
  • a 1 ⁇ m silicon aluminum alloy powder is obtained, and then 1 mol of the alloy powder is mixed with 1 mol of stannous bromide (SnBr 2 ) uniformly; the obtained mixture is placed in an argon atmosphere at a temperature of 5°C/min
  • the reaction product was heated to 650 °C for 6 h and then fully reacted to obtain a reaction product; the reaction product was placed in 1 L of 1 mol/L hydrochloric acid solution for mechanical stirring for 5 h, filtered, washed, and dried to obtain a porous silicon anode material.
  • the 2.5 ⁇ m silicon powder and magnesium powder were mixed evenly in a molar ratio of 1:2 and then placed in an atmosphere furnace. Under the protection of argon inert gas, the temperature was heated to 650 °C at a heating rate of 10 °C/min, and then kept for 6 hours to make it fully The reaction obtains a silicon-magnesium alloy.
  • the silicon-magnesium alloy is ball-milled to obtain 1 ⁇ m silicon-magnesium alloy powder, and then 1 mol of the alloy powder is mixed with 1 mol of stannous bromide (SnBr2) and 1 mol of potassium bromide (KBr); the obtained mixture is placed in an argon atmosphere
  • the reaction product was heated to 450°C at a heating rate of 5°C/min and kept for 6 hours to fully react to obtain the reaction product; the reaction product was placed in 1 L of 1 mol/L hydrochloric acid solution for mechanical stirring for 4 hours, then filtered, washed and dried. Then the porous silicon negative electrode material is obtained.
  • a 2- ⁇ m silicon-aluminum alloy powder is obtained, and then 1 mol of the alloy powder is uniformly mixed with 0.8 mol of zinc chloride (ZnCl 2 ); the obtained mixture is placed in an argon atmosphere at a temperature of 5°C/min
  • the reaction product was heated to 600°C and kept for 6 hours to fully react to obtain the reaction product; the reaction product was placed in 1 L of 1 mol/L hydrochloric acid solution for mechanical stirring for 2 hours, and filtered, washed and dried to obtain a median particle size of 2 ⁇ m. silicon anode material.
  • the germanium-magnesium alloy is ball-milled to obtain 1 ⁇ m germanium-magnesium alloy powder, and then 1 mol of germanium-magnesium alloy powder is uniformly mixed with 1 mol of stannous chloride and 1 mol of sodium chloride; the obtained mixture is put into an argon atmosphere to The heating rate of 3°C/min was heated to 750°C and then kept for 8h to fully react to obtain the reaction product; the reaction product was mechanically stirred in a 1mol/L hydrochloric acid solution for 2h, filtered, washed and dried to obtain the median particle size It is a 1 ⁇ m porous germanium negative electrode material.
  • the boron-magnesium alloy is ball-milled to obtain 1 ⁇ m boron-magnesium alloy powder, and then 1 mol of boron-magnesium alloy powder is mixed with 1 mol of zinc chloride and 1 mol of potassium chloride uniformly; the obtained mixture is put into an argon atmosphere for 3
  • the heating rate of °C/min was heated to 750 °C and then kept for 8 hours to fully react to obtain the reaction product; after mechanical stirring of the reaction product in a 1 mol/L hydrochloric acid solution for 2 hours, suction filtration, washing and drying were performed to obtain a median particle size of 1 ⁇ m porous boron anode material.
  • tin-magnesium alloy After the tin-magnesium alloy is ball-milled, a 1- ⁇ m tin-magnesium alloy powder is obtained, and then 1 mol of the tin-magnesium alloy powder is uniformly mixed with 1 mol of zinc chloride and 1 mol of potassium chloride; the obtained mixture is placed in an argon atmosphere for 3 The heating rate of °C/min was heated to 750 °C and then kept for 8 hours to fully react to obtain the reaction product; the reaction product was mechanically stirred in a 1 mol/L hydrochloric acid solution for 2 hours, filtered, washed and dried to obtain a median particle size of 1 ⁇ m porous tin anode material.
  • the 1 ⁇ m tellurium powder and magnesium powder were mixed evenly in a molar ratio of 1:1, and then placed in an atmosphere furnace. Under the protection of argon inert gas, they were heated to 600 °C at a heating rate of 3 °C/min, and then kept for 6 hours to make them fully react. A tellurium magnesium alloy is obtained.
  • the tellurium-magnesium alloy powder of 1 ⁇ m is obtained by ball-milling the tellurium-magnesium alloy, and then 1 mol of the tellurium-magnesium alloy powder is uniformly mixed with 1 mol of copper chloride and 1 mol of sodium chloride; the obtained mixture is put into an argon atmosphere with 3 The heating rate of °C/min was heated to 750 °C and then kept for 8 hours to fully react to obtain the reaction product; after mechanical stirring of the reaction product in a 1 mol/L hydrochloric acid solution for 2 hours, suction filtration, washing and drying were performed to obtain a median particle size of 1 ⁇ m porous tellurium anode material.
  • This comparative example is Example 1 of patent CN 105399100 A.
  • the SEM image of the prepared nanoporous silicon is shown in Figure 7e, and the porous silicon structure cannot be obtained.
  • the tap density was tested with the Canta AutoTap tap density meter.
  • the specific surface area of the material was tested by Tristar3000 automatic specific surface area and porosity analyzer from Mack Instruments.
  • Porosity The porosity was tested by the automatic mercury porosimeter AutoPore IV9510 of American Mack Instruments.
  • Performance test for the first week of deduction The first week of deduction was performed on the Blue Power CT2001A battery test system, and the charge and discharge current was 0.05C.
  • Cyclic test is performed on the battery test system of Blue Power CT2001A, the current is 0.2C, and the cycle is 150 circles.
  • Figure 7c is the first charge-discharge curve of the porous silicon anode material in this embodiment, the charge-discharge current is 0.05C, and a half-cell test is used;
  • Figure 7d is the cycle performance curve of the porous silicon anode material in this embodiment, and the charge-discharge current is 0.2C . It can be seen in Fig. 7c and Fig. 7d that the materials have high initial charge-discharge efficiency and excellent cycling performance.
  • Example 7-Example 9 the molar ratio of reactants, reaction temperature and time were adjusted, and porous silicon could still be obtained, but the performance was somewhat lower than that of Example 1.
  • Example 7 According to the test data in Tables 1 to 2, by comparing Example 7 with Example 1, the molar ratio of silicon powder to magnesium powder is increased, the porosity is more, the tap density is decreased, the first effect is decreased, and the energy density is decreased.
  • Example 8 is compared with Example 1, the temperature is too low, the reaction is insufficient, the structure is uneven, the internal and external pore structures are inconsistent, the structure is unstable, and the cycle performance is reduced.
  • Example 9 Comparing Example 9 with Example 1, the temperature is too high, the grain size becomes larger, the silicon skeleton becomes thicker, easy to pulverize, the first effect is reduced, and the cycle performance is reduced.
  • Example 1 By comparing Example 1 with Comparative Example 1, the specific surface area of porous silicon obtained in Example 1 is smaller than that of Comparative Example 1.
  • Comparative Example 1 zinc chloride is used, and the reaction temperature is 300° C.
  • the magnesium chloride produced at this temperature is Solid particles are solid templates, resulting in the final porous silicon being piled up by nano-silicon particles, which eventually leads to a larger specific surface area and a lower first effect; while in Example 1, the reaction temperature is 750 °C, and the generated magnesium chloride is a continuous liquid state. , are connected liquid templates, resulting in porous silicon being a skeleton structure, which greatly reduces the specific surface area of the material and improves the first effect.
  • Examples 11-14 porous germanium, porous boron, porous tin and porous tellurium with skeleton structure were prepared by a method similar to that in Example 1, respectively, by changing the raw materials.
  • the negative electrode material according to the first aspect includes primary particles and a coating layer.
  • the preparation method of the negative electrode material includes the following steps S21 to S24:
  • N in the N-M alloy includes at least one of Si, Ge, Sn, B, and Sb; and M in the N-M alloy includes at least one of Mg, Al, Zn, and Ca.
  • the N-M alloy may be Si-Mg alloy, Si-Al alloy, Ge-Mg alloy, Ge-Al alloy, and the like. Different types of alloys can obtain branches of different shapes, including at least one of rod-shaped nanoparticles, nanosheets, nanowires, and nanotubes.
  • the preparation method of N-M alloy is to mix N powder and active metal M, and then heat and react under protective gas to prepare N-M alloy.
  • the powder particle size of the N powder is 0.1 ⁇ m to 15 ⁇ m, specifically 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m or 15 ⁇ m, etc., which are not limited here.
  • the powder particle size of the active metal M is 0.1 ⁇ m to 80 ⁇ m, specifically 0.1 ⁇ m, 5 ⁇ m, 10 ⁇ m, 20 ⁇ m, 40 ⁇ m, 50 ⁇ m or 80 ⁇ m, etc., which are not limited here.
  • the molar ratio of N powder to active metal M is 1:(1-3), specifically 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, which is not limited here.
  • the temperature of the heating reaction ranges from 400°C to 900°C, specifically, 400°C, 500°C, 600°C, 700°C, 800°C or 900°C.
  • the holding time of the heating reaction is 2h to 8h, specifically, it may be 2h, 4h, 6h or 8h, which is not limited here.
  • the heating rate of the heating reaction is 1°C/min ⁇ 10°C/min, specifically, it can be 1°C/min, 3°C/min, 5°C/min, 8°C/min or 10°C/min, which is not limited here .
  • the N-M alloy can also be prepared by other preparation methods, specifically: high-energy ball milling, vacuum smelting, and hot pressing sintering. It can be understood that the N-M alloy can be obtained commercially, and in this case, step S21 can be omitted.
  • the mass percent content of N in the N-M alloy is 15% to 60%, optionally, the mass percent content of N may be 15%, 20%, 30%, 40%, 50% or 60% , which is not limited here.
  • the N-M alloy may be at least one of a silicon-magnesium alloy, a silicon-aluminum alloy, a silicon-calcium alloy, and a silicon-zinc alloy. It can be understood that the size and porosity of the pores of the N material can be changed by controlling the composition of the N-M alloy. Generally, the higher the N content in the N-M alloy, the smaller the pore size. The heating reaction time and reaction temperature can be controlled to change the depth of the hole. Generally, the longer the reaction time and the higher the reaction temperature, the deeper the hole is.
  • the method further includes:
  • the prepared N-M alloy is pulverized to adjust the particle size of the N-M alloy powder to 0.1 ⁇ m to 15 ⁇ m, which can be 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 5 ⁇ m, 10 ⁇ m or 15 ⁇ m, which is not limited here. .
  • the equipment for pulverization includes at least one of a planetary ball mill, a sand mill and an airflow pulverizer. It can be understood that the smaller the particle size of the N-M alloy, the larger the specific surface area, and the more sufficient the reaction can be during the dealloying heat treatment.
  • the N-M alloy can also be prepared by other preparation methods, specifically: high-energy ball milling, vacuum smelting, and hot pressing sintering. It can be understood that the N-M alloy can be obtained commercially, and in this case, step S21 can be omitted.
  • the mass percent content of N in the N-M alloy is 15% to 60%, optionally, the mass percent content of N may be 15%, 20%, 30%, 40%, 50% or 60% , which is not limited here.
  • the N-M alloy may be at least one of a silicon-magnesium alloy, a silicon-aluminum alloy, a silicon-calcium alloy, and a silicon-zinc alloy. It can be understood that the size and porosity of the pores of the N material can be changed by controlling the composition of the N-M alloy. Generally, the higher the N content in the N-M alloy, the smaller the pore size. The heating reaction time and reaction temperature can be controlled to change the depth of the hole. Generally, the longer the reaction time and the higher the reaction temperature, the deeper the hole is.
  • the molar ratio of the N-M alloy and the halogen-containing six-membered ring organic compound is 1:(0.2-6), which may be 1:0.2, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5 or 1:6, which is not limited here.
  • the halogen-containing six-membered ring organic compound includes at least one of halogenated cyclohexane and its derivatives, halogenated benzene, halogenated benzoic acid and halogenated aniline.
  • the halogen includes at least one of fluorine, chlorine and bromine.
  • Halogenated cyclohexane is a six-membered cyclic hydrocarbon, and its structural stability is worse than that of halogenated benzene, and the hydrocarbon chain is prone to breakage at high temperature.
  • the halogenated cyclohexane can be chlorocyclohexane, hexachlorocyclohexane, hexabromocyclohexane, and trichlorocyclohexane.
  • the halogenated benzene can be tribromobenzene, hexachlorobenzene, hexabromobenzene and the like.
  • the halogenated benzoic acid may be chlorobenzoic acid, bromobenzoic acid, 2-bromobenzoic acid, 4-bromobenzoic acid, 3-chlorobenzoic acid and the like.
  • the halogenated aniline can be p-chloroaniline, 4-bromoaniline, 2-chloroaniline and the like.
  • step S23 When the halogen-containing six-membered ring organic compound adopts halogenated cyclohexane, before performing step S23, the method further includes step S221:
  • a cleavage inhibitor is added to the mixture, wherein the cleavage inhibitor includes an amide compound and a cyanate.
  • the amide compound includes at least one of carbonamide, formamide, acetamide, dimethylformamide and lactam; the cyanate includes at least one of potassium cyanate, sodium cyanate and ammonium cyanate. kind.
  • the molar ratio of the N-M alloy to the amide compound is 1:(0.1-10), specifically, it can be 1:0.1, 1:0.5, 1:1, 1:5 or 1:10, etc., This is not limited.
  • the molar ratio of N-M alloy to cyanate is 1:(0.1-10), specifically, it may be 1:0.1, 1:0.5, 1:1, 1:5 or 1:10, etc., which is not limited here.
  • the temperature of the displacement reaction is 200°C to 1000°C, specifically 200°C, 300°C, 400°C, 600°C, 800°C or 950°C.
  • the holding time is 1h to 24h, specifically, 1h, 3h, 6h, 9h, 12h, 15h, 18h or 24h, which is not limited here.
  • the generated carbon layer when the temperature is 200-750°C, the generated carbon layer is an amorphous carbon layer; when the temperature is higher than 750°C, the generated carbon layer is wrinkled graphene.
  • the heating rate of the displacement reaction is 1°C/min to 20°C/min, specifically, 1°C/min, 5°C/min, 10°C/min, 15°C/min or 20°C/min. Thereby effectively improving the reaction efficiency.
  • the substitution reaction is carried out under a protective atmosphere
  • the gas of the protective atmosphere includes at least one of nitrogen, helium, neon, argon and hernia.
  • the flow of protective gas can be controlled at 1L/min-10L/min.
  • reaction product includes the halide of M, the oxide of M, carbon and N, therefore, it is necessary to remove the metal oxide and halide in the reaction product.
  • the removal method includes acid washing, and the reaction product is acid washed to remove metal oxides and halides in the reaction product.
  • the acid solution used for pickling includes at least one of hydrochloric acid, nitric acid and sulfuric acid.
  • the mass concentration of the acid solution ranges from 1 mol/L to 5 mol/L, and may specifically be 1 mol/L, 2 mol/L, 3 mol/L, 4 mol/L or 5 mol/L.
  • the mass concentration of the acid solution can also be adjusted according to actual needs, which is not limited here.
  • the duration of the pickling is 1h to 10h, specifically 1h, 3h, 5h, 7h or 10h.
  • the acid-washed product can still be recovered and recycled.
  • the anode material is prepared by a one-step composite method, and the N-M alloy reacts directly with the six-membered ring organic matter at high temperature to remove the metal M component in the N-M alloy, and at the same time deposit a carbon layer on the surface of the N material in situ.
  • the overall reaction is mild without by-products, the N material has a complete and stable structure, and the carbon layer is uniformly deposited.
  • the raw materials involved in the reaction are commonly used alloys, organics and metal salts, which can reduce costs.
  • the graphene layer and the amorphous carbon layer are formed by in-situ growth.
  • a composite negative electrode material was prepared by one-step dealloying with a six-membered ring organic compound containing halogen as the carbon source and N-M alloy. This method utilizes the metal vapor generated in the N-M alloy at high temperature, which has a strong reducibility and can interact with the six-membered ring organic compound. After the reaction, the metal M component in the N-M alloy is removed, and the six-membered ring itself grows in-situ and self-assembles in an orderly manner to form a wrinkled graphene layer or an amorphous carbon layer.
  • the composite negative electrode material is prepared by a one-step composite method, which can effectively improve the preparation efficiency, the preparation method is simple and feasible, green and environmentally friendly, the preparation process is highly controllable, the cost is low, and it can be mass-produced.
  • the prepared composite negative electrode material has the advantages of high capacity, high charge-discharge cycle stability, low expansion rate, etc., and can be widely used in lithium batteries.
  • the one-step composite method refers to the simultaneous preparation of the silicon material and the carbon coating, and the preparation efficiency is higher than that of the two-step composite method.
  • the composite negative electrode material prepared by the method of this embodiment includes an inner core 10 and a coating layer 20 formed on the surface of the inner core 10, and the coating layer 20 is a carbon coating layer.
  • the inner core 10 is a primary particle, the primary particle includes a skeleton, and the skeleton includes a main skeleton 11 located inside the primary particle and a plurality of branches 12 extending from the main skeleton 11 to the surface of the primary particle.
  • the inner core 10 of this embodiment is a primary particle, the primary particle has a macroporous structure, and the primary particle is formed with a channel 13 extending to the surface of the primary particle.
  • Through holes are formed inside the primary particles, and the porosity of the primary particles is not less than 30%.
  • FIG. 5 is a schematic diagram of a synthesis process of a silicon-carbon composite negative electrode material.
  • the method for preparing a negative electrode material includes the following steps S21' to S24':
  • the N1-M1 material is at least one of an intermetallic compound and an alloy.
  • N1 in the N1-M1 material includes at least one of silicon, germanium, antimony, tin, and boron; and M1 in the N1-M1 material includes at least one of magnesium, aluminum, calcium, and zinc.
  • the preparation method of the N1-M1 alloy is the same as that of step S11; it will not be described in detail here;
  • the metal element of the metal oxide layer includes at least one of Ti, V, Nb, Ta, W, and Zr.
  • the molar ratio of metal element to oxygen element in the metal oxide layer is 1:(0.1-3).
  • the thickness of the metal oxide layer is 1 nm-200 nm.
  • the molar ratio of the N1-M1 material and the metal oxide of the metal oxide layer is 1:(0.01-5), specifically, 1:0.02, 1:0.05, 1:1, 1:2 , 1:3, 1:4 or 1:5, which are not limited here.
  • the method for forming the metal oxide layer on the surface of the N1-M1 material adopts a conventional method in the art, such as a hydrothermal method, a sol-gel method, a precipitation method, a chemical vapor deposition method, a magnetron sputtering or a solid-phase reaction. Law.
  • the reaction product includes oxides of M1, N1, and metal oxides.
  • the degree of vacuum in the vacuum environment is less than 1000 Pa.
  • the temperature of the displacement reaction is 500°C to 1100°C, specifically, 500°C, 600°C, 700°C, 800°C, 900°C or 1200°C.
  • the incubation time for the displacement reaction is 1 h to 48 h, and specifically may be 1 h, 24 h, 36 h or 48 h, which is not limited herein.
  • the heating rate of the reduction reaction is 1°C/min ⁇ 20°C/min, specifically, it can be 1°C/min, 3°C/min, 5°C/min, 8°C/min or 20°C/min, which is not limited here .
  • the method for removing oxides of M1 includes acid washing.
  • the acid solution used for pickling includes at least one of hydrochloric acid, nitric acid and sulfuric acid.
  • the mass concentration of the acid solution ranges from 1 mol/L to 5 mol/L, and may specifically be 1 mol/L, 2 mol/L, 3 mol/L, 4 mol/L or 5 mol/L.
  • the mass concentration of the acid solution can also be adjusted according to actual needs, which is not limited here.
  • the duration of the pickling is 1h to 10h, specifically 1h, 3h, 5h, 7h or 10h.
  • the acid-washed product can still be recovered and recycled.
  • a metal oxide layer is coated on the surface of the N1-M1 material, and the N1-M1 material and part of the metal oxide layer undergo a replacement reaction at high temperature to remove the M1 component in the N1-M1 material, and at the same time, the N1-M1 material is in the N1 material.
  • An incompletely reacted metal oxide layer is formed on the surface, and the composite negative electrode material can be obtained after pickling.
  • the metal oxide layer has the advantages of good rigidity and excellent compactness.
  • the current price and flexibility of the carbon layer material can effectively suppress the entire structure damage caused by the volume expansion of N1, reduce the volume expansion of the material and avoid the electrolyte and the electrolyte.
  • the silicon negative electrode is in contact to reduce side reactions and improve the first effect of the entire composite material.
  • the composite negative electrode material prepared by the preparation method of the negative electrode material provided in the embodiment of the present application can effectively improve the stability of the charge-discharge cycle of the lithium battery, and has many advantages such as high capacity, long cycle life, high first efficiency and low expansion.
  • the composite negative electrode material prepared by the method of this embodiment includes an inner core 10 and a cladding layer 20 formed on the surface of the inner core 10, and the cladding layer 20 is a metal oxide layer.
  • the method for preparing a negative electrode material includes the following steps S21"-S24":
  • steps S21'' and S22'' are the same as the above-mentioned steps S21' and S22', and will not be described repeatedly here.
  • reaction products include oxides of M1, N1, and metal oxides.
  • the heat treatment temperature in the protective atmosphere is 500-800°C
  • the holding time is 1h-24h
  • the reaction heating rate of the heat treatment is 1-20°C/min.
  • the protective atmosphere includes at least one of helium, neon, argon, krypton, and xenon.
  • the treatment temperature is 400-950° C.
  • the holding time is 2 h to 24 h
  • the nitriding atmosphere is at least one of an ammonia gas atmosphere and a plasma nitrogen atmosphere.
  • step S24 ′ The method for removing the oxide of M1 is the same as step S24 ′, and the description is not repeated here.
  • the composite negative electrode material prepared by the method of this embodiment includes an inner core 10 and a cladding layer 20 formed on the surface of the inner core 10; the cladding layer 20 is a metal nitride layer.
  • the N1-M1 material after coating the surface of the N1-M1 material with a metal oxide layer, heat treatment in a protective atmosphere, on the one hand, ensures that the N1-M1 material and part of the metal oxide layer undergo a replacement reaction, and removes the N1-M1 material.
  • the metal M1 composition on the other hand, to ensure that the oxide is transformed from amorphous to crystalline at high temperature and normal pressure.
  • the metal oxide layer on the surface of the inner core is nitrided into metal nitride, followed by pickling to obtain a composite negative electrode material.
  • the metal nitride layer not only has good rigidity, but also has excellent electrical conductivity, which can effectively alleviate the volume expansion of silicon while increasing the electrical conductivity of the material, improve the rate capability of the material, reduce the irreversible capacity loss of the material, and bring high capacity.
  • FIG. 9 is a schematic diagram of the synthesis process of silicon/metal oxide and silicon/metal nitride composite negative electrode materials.
  • the composite negative electrode material prepared by the preparation method of the negative electrode material provided in the embodiment of the present application can effectively improve the stability of the charge-discharge cycle of the lithium battery, and has multiple advantages such as high capacity, long cycle life, good rate performance and low expansion.
  • a preparation method of silicon carbon anode material comprising the following steps:
  • the obtained silicon-carbon composite negative electrode material has a median particle size of about 1 ⁇ m, a specific surface area of 53 m 2 /g, a porosity of 48%, and a mass percentage of carbon content of 12%.
  • FIG. 10a and 10b are scanning electron microscope pictures of the silicon-carbon composite negative electrode material
  • FIG. 11a is a Raman diagram of the silicon-carbon composite negative electrode material provided in this embodiment
  • FIG. 11b is an XRD pattern of the silicon-carbon composite negative electrode material provided by this embodiment.
  • the inner core is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles.
  • the cladding layer is 2nm wrinkled graphene.
  • the average diameter of the channels is about 100 nm, and the depth of the channels is about 700 nm.
  • a preparation method of silicon carbon anode material comprising the following steps:
  • the median particle size of the silicon-carbon composite negative electrode material is about 0.6 ⁇ m, the specific surface area is 79 m 2 /g, the porosity is 56%, and the mass percentage of carbon is 20%.
  • the silicon-carbon composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle
  • the primary particle includes a silicon skeleton
  • the skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles.
  • the coating layer is a 10nm amorphous carbon layer, the average diameter of the channels is about 130nm, and the depth of the channels is about 800nm.
  • a preparation method of silicon carbon anode material comprising the following steps:
  • the obtained silicon-carbon composite negative electrode material has a median particle size of about 10 ⁇ m, a specific surface area of 43 m 2 /g, a porosity of 61%, and a mass percentage of carbon content of 15%.
  • the silicon-carbon composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle
  • the primary particle includes a silicon skeleton
  • the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particles have a macroporous structure
  • the primary particles have a macroporous structure
  • the primary particles are formed with channels extending to the surface of the primary particles.
  • the coating layer is a 5nm wrinkled graphene layer, the average diameter of the three-dimensional channel is about 110nm, and the pore depth of the three-dimensional channel is about 670nm.
  • a preparation method of silicon carbon anode material comprising the following steps:
  • the obtained silicon-carbon composite negative electrode material has a median particle size of about 1 ⁇ m, a specific surface area of 38 m 2 /g, a porosity of 47%, and a mass percentage of carbon content of 5%.
  • the silicon-carbon composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particle has a macroporous structure, and the primary particle is formed with a channel extending to the surface of the primary particle; the coating layer is a 4nm wrinkled graphene layer; the average diameter of the channel is about 65nm, and the depth of the three-dimensional channel is about 680nm.
  • a preparation method of silicon carbon anode material comprising the following steps:
  • the obtained silicon-carbon composite negative electrode material has a median particle size of about 0.5 ⁇ m, a specific surface area of 80 m 2 /g, a porosity of 53%, and a mass percentage of carbon content of 22%.
  • the silicon-carbon composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particle has a macroporous structure, and the primary particle is formed with a channel extending to the surface of the primary particle; the coating layer is a 6nm wrinkled graphene layer.
  • the average diameter of the channels is about 130 nm, and the depth of the channels is about 940 nm.
  • a preparation method of germanium carbon negative electrode material comprising the following steps:
  • the obtained germanium-carbon composite negative electrode material has a median particle size of about 0.6 ⁇ m, a specific surface area of 75 m 2 /g, a porosity of 63%, and a mass percentage of carbon content of 18%.
  • the germanium-carbon composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle, the primary particle includes a germanium skeleton, and the germanium skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles; the coating layer is a 12 nm amorphous carbon layer.
  • the average pore diameter of the three-dimensional channel is about 120 nm, and the pore depth of the three-dimensional channel is about 35 nm.
  • a preparation method of silicon carbon anode material comprising the following steps:
  • the obtained silicon-carbon composite negative electrode material has a median particle size of about 0.5 ⁇ m, a specific surface area of 64 m 2 /g, a porosity of 53%, and a mass percentage of carbon content of 19%.
  • the silicon-carbon composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particle has a macroporous structure, and the primary particle is formed with a channel extending to the surface of the primary particle; the coating layer is a 3.2nm wrinkled graphene layer, the average diameter of the channel is about 110nm, and the depth of the channel is about 780nm.
  • a preparation method of a silicon negative electrode material comprising the following steps:
  • reaction kettle (4) Put the above-mentioned composite into a sealed stainless steel reaction kettle, evacuate to 100pa, then heat the reaction kettle to 750°C at a heating rate of 3°C/min in an argon atmosphere, and keep the temperature for 8h to fully react to obtain reaction product;
  • reaction product was placed in 4 L of 1 mol/L hydrochloric acid solution and subjected to mechanical stirring for pickling for 3 hours, suction filtration, washing and drying to obtain a porous silicon/titanium oxide composite negative electrode material.
  • the median particle size of the obtained composite negative electrode material is about 0.6 ⁇ m, the specific surface area is 44 m 2 /g, the porosity is 43%, and the mass percentage content of titanium oxide is 12%.
  • the composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles; the coating layer is a titanium oxide layer.
  • the average diameter of the channels is about 20 nm, and the depth of the channels is about 150 nm.
  • a preparation method of a silicon negative electrode material comprising the following steps:
  • the obtained composite negative electrode material has a median particle size of about 0.7 ⁇ m, a specific surface area of 40 m 2 /g, a porosity of 48%, and a mass percentage content of titanium nitride of 32%.
  • the composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles; the coating layer is a titanium nitride layer.
  • the average diameter of the channels is about 50 nm, and the depth of the channels is about 400 nm.
  • a preparation method of a silicon negative electrode material comprising the following steps:
  • the vanadium pentoxide-coated silicon-magnesium alloy is prepared by a sol-gel process. First, 500 ml of an alcohol solution of vanadium triisopropoxide with a concentration of 0.15M/L is prepared, and 30 ml of acetylacetone is added to obtain a mixed solution; 0.5 mol of silicon-magnesium alloy powder was added to the above mixed solution, stirred for 36 hours, and dispersed uniformly to obtain a sol.
  • the median particle size of the obtained composite negative electrode material is about 0.6 ⁇ m, the specific surface area is 51 m 2 /g, the porosity is 40%, and the mass percentage content of titanium nitride is 25%.
  • the composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles; the coating layer is a 60 nm vanadium nitride layer. The average diameter of the channels is about 125 nm, and the depth of the channels is about 350 nm.
  • a preparation method of a negative electrode material comprising the following steps:
  • reaction kettle (4) Put the above-mentioned composite into a sealed stainless steel reaction kettle, evacuate to 100pa, then heat the reaction kettle to 750°C at a heating rate of 3°C/min in an argon atmosphere, and keep the temperature for 8h to fully react to obtain reaction product;
  • the median particle size of the obtained composite negative electrode material is about 0.55 ⁇ m, the specific surface area is 41 m 2 /g, the porosity is 45%, and the mass percentage content of titanium oxide is 13%.
  • the composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle, the primary particle includes a germanium skeleton, and the germanium skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles; the coating layer is a titanium oxide layer.
  • the average diameter of the channels is about 600 nm, and the depth of the channels is about 180 nm.
  • a preparation method of a negative electrode material comprising the following steps:
  • the vanadium pentoxide-wrapped germanium-magnesium alloy was prepared by a sol-gel process. First, 500 ml of an alcohol solution of vanadium triisopropoxide with a concentration of 0.1 M/L was prepared, and 30 ml of acetylacetone was added to obtain a mixed solution; 0.5 mol of germanium-magnesium alloy powder was added to the above mixed solution, stirred for 36 hours, and dispersed uniformly to obtain a sol.
  • the median particle size of the obtained composite negative electrode material is about 1.2 ⁇ m, the specific surface area is 52 m 2 /g, the porosity is 43%, and the mass percentage content of titanium nitride is 24%.
  • the composite negative electrode material includes an inner core and a coating layer formed on the surface of the inner core; wherein,
  • the inner core is a primary particle, the primary particle includes a germanium skeleton, and the germanium skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles; the coating layer is a 50 nm vanadium nitride layer.
  • the average diameter of the channels is about 150 nm, and the depth of the channels is about 900 nm.
  • a preparation method of a negative electrode material comprising the following steps:
  • the obtained silicon-carbon composite negative electrode material has a median particle size of about 0.6 ⁇ m, a specific surface area of 79 m 2 /g, a porosity of 56%, a mass percentage of carbon content of 20%, and an average diameter of the pores of about 130 nm.
  • the depth is about 800nm.
  • the obtained silicon-carbon composite anode material has a median particle size of about 1 ⁇ m, a specific surface area of 77 m 2 /g, a porosity of 56%, a mass percentage of carbon content of 19%, and a median particle size of primary particles of about 0.5 ⁇ m , the average pore diameter of the three-dimensional channel is about 100 nm, the pore depth of the three-dimensional channel is about 730 nm, and the graphene layer cannot be formed, and the thickness of the carbon layer is 25 nm.
  • the silicon-carbon composite negative electrode material SiO/C is used, and the median particle size of the silicon-carbon composite negative electrode material is 1.5 ⁇ m.
  • the negative electrode material is prepared with sodium carboxymethyl cellulose, styrene-butadiene rubber, conductive graphite (KS-6) and carbon black (SP) in a ratio of 92:2:2:2:2, respectively, and uniformly coated with copper foil.
  • the negative pole pieces are made by drying on the top and assembled into a button battery in an argon atmosphere glove box. ester and dimethyl carbonate), and the counter electrode used is a metal lithium sheet.
  • the first coulomb efficiency test was carried out on the above 15 sets of batteries on the Blue Power CT2001A battery test system, and the charge and discharge current was 0.05C, and the first coulomb efficiency was measured.
  • the above 15 sets of batteries were tested on the Blue Power CT2001A battery test system for 100 cycles, and the charge and discharge current was 0.2C. After 100 cycles, the battery capacity and the capacity retention rate after the cycle were calculated.
  • the composite negative electrode material of the present application has the advantages of low expansion and good cycle stability.
  • Example 27 the main difference between Example 27 and Example 26 is that the mixing ratio of silicon-magnesium alloy and hexachlorobenzene is relatively low, resulting in a significant decrease in the thickness of the graphene layer on the surface of the silicon material, which is not conducive to increasing the negative electrode material.
  • the electrical conductivity of the material is weak and the volume expansion inhibition performance of the material is weak, resulting in poor long-term cycle performance.
  • Example 28 The main difference between Example 28 and Example 15 is that, without adding cracking inhibitors (carbonamide, potassium cyanate and sodium cyanate), chlorocyclohexane is decomposed in large quantities during the reaction process, and it is difficult to deposit graphite on the surface of the silicon material.
  • the olefin layer leads to a decrease in the battery's specific charge-discharge capacity, first Coulomb efficiency, and capacity retention rate after the cycle.
  • Comparative Example 3 is a carbon-coated porous silicon negative electrode material. The capacity and capacity retention rate of the battery made of this material decreased after 100 cycles at 0.2C, and the electrode film expansion rate of Comparative Example 3 was also higher than that of the embodiment. 15.
  • the preparation method of the silicon carbon negative electrode material provided by the present application is simple and easy to operate, the preparation process is safe and efficient; the manufacturing cost is effectively reduced, and it is suitable for quantitative production; Good charge-discharge cycle performance.
  • the negative electrode material according to the first aspect includes primary particles and a protective layer, and the protective layer is a carbon layer.
  • the preparation method of the negative electrode material includes the following steps S31 to S34:
  • the obtained composite negative electrode material includes primary particles and a carbon layer; wherein the primary particles include a skeleton, and the skeleton includes a main skeleton located inside the primary particles and a plurality of branches extending from the main skeleton to the surface of the primary particles; the carbon layer is located on the surface of the skeleton.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles.
  • the negative electrode material is prepared by a one-step composite method.
  • the N-M alloy reacts directly with the carbon-containing ammonium salt at high temperature to remove the metal component in the N-M alloy, and at the same time, a carbon layer is formed on the surface of the N material by in-situ deposition, and the composite is obtained after pickling.
  • Negative electrode material the overall reaction is mild and no by-products, the N material structure is complete and stable, and the carbon layer is uniformly deposited.
  • the raw materials involved in the reaction are commonly used alloys, ammonium salts and commonly used inorganic compounds, which can reduce costs.
  • Step S31 preparing N-M alloy
  • N in the N-M alloy includes at least one of Si, Ge, Sn, B, and Sb; and M in the N-M alloy includes at least one of Mg, Al, Zn, and Ca.
  • Step S31 is substantially the same as step S21 and will not be described in detail here.
  • the N-M alloy can also be prepared by other preparation methods, specifically: high-energy ball milling, vacuum smelting, and hot pressing sintering. It can be understood that the N-M alloy can be obtained commercially, and in this case, step S31 can be omitted.
  • the mass percent content of N in the N-M alloy is 15%-60%, optionally, the mass percent content of N may be 15%, 20%, 30%, 40%, 50% or 60%, which is not limited here.
  • the size and porosity of the three-dimensional pores of the N material can be changed by controlling the composition of the N-M alloy. Generally, the higher the N content in the N-M alloy, the smaller the pore size.
  • the heating reaction time and reaction temperature can be controlled to change the depth of the hole. Generally, the longer the reaction time and the higher the reaction temperature, the deeper the hole is.
  • carbon-containing ammonium salt refers to a salt containing carbon and ammonium ions.
  • the molar ratio of the N-M alloy mixed with the carbon-containing ammonium salt is 1:(0.1-10), specifically 1:0.1, 1:0.5, 1:1, 1:2, 1:4, 1 :5, 1:7 or 1:10, which is not limited here.
  • the carbon-containing ammonium salt includes at least one of ammonium carbonate, ammonium bicarbonate and ammonium carbamate; ammonium carbonate, ammonium bicarbonate and ammonium carbamate are thermally unstable and easily decomposed into ammonia and carbon dioxide.
  • an ammonium salt inhibitor is also added to inhibit the pyrolysis of the ammonium salt.
  • the molar ratio of the N-M alloy and the ammonium salt decomposition inhibitor is 1:(0.2-10), specifically, 1:0.2, 1:0.5, 1:1, 1:2, 1:4 , 1:5, 1:7 or 1:10, which are not limited here.
  • the ammonium salt decomposition inhibitor includes carbonate and/or bicarbonate.
  • the chemical formula of carbonate is MyCO 3
  • the chemical formula of bicarbonate is M(HCO 3 ) y
  • M includes at least one of Na, K, Li, Mg, Ca, Zn, and Ba
  • y 1 or 2.
  • bicarbonate is unstable at high temperature, and is easily decomposed into carbonate, carbon dioxide and water.
  • the decomposed carbon dioxide gas, inorganic salt and water are not harmful to the environment, absorb part of the reaction energy, and inhibit the ammonium salt under high temperature. A decomposition reaction occurs.
  • a molten salt medium in order to improve the reaction sufficiency, is also added, optionally, the molten salt medium includes at least one of ammonium halide salt and halide salt.
  • the molar ratio of the NM alloy and the ammonium halide salt is 1:(0.1-10), specifically 1:0.1, 1:0.5, 1:1, 1:2, 1:4, 1:5, 1:7 or 1:10, which is not limited here.
  • the chemical formula of the ammonium halide salt is NH 4 Y, wherein Y includes at least one of Cl, Br, F and I.
  • the ammonium salt decomposition inhibitor can be used to inhibit the decomposition of the ammonium salt and keep it in a high temperature liquid state, which is beneficial to the ammonium salt from the outside to the inside. It slowly reacts with the alloy to achieve the purpose of dealloying, and at the same time, it gradually flows into the pore structure of the N material, and acts as a liquid template for the connected skeleton, which facilitates the gradual and uniform deposition of carbon in the pore structure of the silicon material, and enhances the conductivity of the entire composite structure.
  • molten salt medium ammonium halide
  • molten salt can increase the solubility of ammonium salt in it, promote the reaction to proceed fully, ensure the high temperature liquid environment and the uniformity of the reaction temperature when the alloy powder reacts with the ammonium salt, and avoid excessive local temperature leading to porous Structural disruption to improve yield and purity.
  • the corresponding ammonium halide as the molten salt medium, it can further ensure the high temperature liquid environment and the uniformity of the reaction temperature when the alloy powder reacts with the ammonium salt, and avoid the damage of the porous structure caused by the high local temperature.
  • the obtained negative electrode material Excellent stability, uniform carbon composite structure, and excellent electrochemical performance.
  • the molar ratio of N-M alloy to halide is 1:(0.1-10), specifically 1:0.1, 1:0.5, 1:1, 1:2, 1:4, 1:5, 1:7 or 1:10, which is not limited here.
  • reaction product which includes M nitride and M oxide.
  • This reaction may be referred to as a dealloying reaction.
  • the reaction product of the replacement reaction includes M nitride, M oxide, carbon and N element.
  • the NM alloy is a silicon-magnesium alloy
  • the ammonium salt is ammonium carbonate
  • the chemical reaction formula of dealloying is: 5Mg 2 Si+2(NH 4 ) 2 CO 3 ⁇ 5Si+2C+4MgO+2Mg 3 N 2 + 2H 2 O + 6H 2 , after the reaction occurs, the metal oxide (MgO) and nitride (Mg 3 N 2 ) in the reaction product are removed to obtain a composite negative electrode material.
  • the ammonium salt is selected to participate in the dealloying process, and the ammonium salt is in a molten state during the reaction process, which provides a connected liquid template for the formation of the connected N skeleton and ensures the continuity of the pore structure of the N skeleton;
  • the carbon source, the carbon layer formed after the reaction is also continuously filled in the pore structure to form a three-dimensional conductive carbon network structure. Due to the mild reaction at high temperature, the carbon-oxygen bond in the ammonium salt can be reorganized in an orderly manner after being broken to form a carbon layer, which improves the electrical conductivity, which is also more conducive to the entry and exit of lithium ions, and improves the rate capability of the material.
  • the dealloying heat treatment is performed under vacuum conditions, and the vacuum degree is 1Pa ⁇ 20KPa. It is understandable that in the embodiments of the present application, the alloying heat treatment is carried out in a high temperature vacuum environment, the reaction rate is increased, and the reaction is safer.
  • the temperature of the dealloying heat treatment is 200°C to 950°C, specifically 200°C, 300°C, 400°C, 600°C, 800°C or 950°C.
  • the holding time of the dealloying heat treatment is 1h to 24h, specifically, it may be 1h, 3h, 6h, 9h, 12h, 15h, 18h or 24h, which is not limited here.
  • the heating rate of the dealloying heat treatment ranges from 1°C/min to 20°C/min, and specifically may be 1°C/min, 5°C/min, 10°C/min, 15°C/min or 20°C/min. Thereby effectively improving the reaction efficiency.
  • the dealloying heat treatment is carried out under the protection of protective gas, and the protective gas includes at least one of nitrogen, helium, neon, argon and hernia.
  • the flow rate of the protective gas can be controlled from 1L/min to 10L/min to improve the safety of the reaction.
  • the removal method includes acid washing, and the reaction product is acid washed to remove M oxides and nitrides in the reaction product.
  • the mass concentration of the acid solution ranges from 1 mol/L to 5 mol/L, and may specifically be 1 mol/L, 2 mol/L, 3 mol/L, 4 mol/L or 5 mol/L.
  • the mass concentration of the acid solution can also be adjusted according to actual needs, which is not limited here.
  • the duration of the pickling is 1h to 10h, specifically 1h, 3h, 5h, 7h or 10h.
  • the acid-washed product can still be recovered and recycled.
  • the preparation method of the negative electrode material includes the following steps S31' to S35':
  • N material is a primary particle, the primary particle includes a skeleton, and the skeleton includes a main skeleton located inside the primary particle and a main skeleton from the primary particle. a plurality of branches extending from the backbone to the surface of the primary particle;
  • the obtained negative electrode material includes primary particles and a metal oxide layer; wherein, the primary particles include a framework, and the framework includes a main framework located inside the primary particles and a plurality of branches extending from the main framework to the surface of the primary particles; the metal oxide Layers are on the surface of the skeleton.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles.
  • through holes are formed inside the primary particles, and the porosity of the primary particles is not less than 30%.
  • N in the N-M alloy includes at least one of Si, Ge, Sn, B, and Sb; and M in the N-M alloy includes at least one of Mg, Al, Zn, and Ca.
  • the N-M alloy may be Si-Mg alloy, Si-Al alloy, Ge-Mg alloy, Ge-Al alloy, or the like. Different types of alloys can obtain branches of different shapes, including at least one of rod-shaped nanoparticles, nanosheets, nanowires, and nanotubes.
  • the preparation method of the N-M alloy is the same as that of step S31; it will not be described in detail here.
  • the molar ratio of N-M alloy to transition metal halide is 1:(0.1-2).
  • step S32' can be omitted.
  • the temperature of the displacement reaction is 500°C-1100°C, which may be 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C or 1100°C.
  • the reaction time is 1h to 48h, such as 1h, 5h, 10h, 15h, 20h, 25h, 30h, 35h or 45h and the like.
  • the gas of the protective atmosphere includes at least one of helium, neon, argon, krypton and xenon.
  • N material is a primary particle
  • the primary particle includes a skeleton
  • the skeleton includes a main skeleton located inside the primary particle and a main skeleton extending to the surface of the primary particle multiple branches.
  • the removal method is the same as step S34, and will not be described in detail here.
  • the method of forming the metal oxide layer includes at least one of a hydrothermal method, a sol-gel method, a precipitation method, a chemical vapor deposition method, a magnetron sputtering, and a solid state reaction method.
  • the metal element in the metal oxide layer includes at least one of Si, Sn, Ge, Li, V, Al, Fe, and Zn.
  • the preparation method of the negative electrode material includes the following steps S31"-S36":
  • the N material is a primary particle, the primary particle includes a skeleton, and the skeleton includes a main skeleton located inside the primary particle and a main skeleton extending to the surface of the primary particle.
  • the obtained negative electrode material includes primary particles and a metal nitride layer; wherein, the primary particles include a framework, and the framework includes a main framework located inside the primary particles and a plurality of branches extending from the main framework to the surface of the primary particles; the metal nitride layer is located in the framework. surface.
  • the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles.
  • through holes are formed inside the primary particles, and the porosity of the primary particles is not less than 30%.
  • steps S31"-S35 are the same as steps S31'-S35', and will not be described in detail here.
  • the heat treatment temperature is 500°C-800°C
  • the holding time is 1 h to 24 h.
  • the protective atmosphere includes at least one of helium, neon, argon, krypton, and xenon.
  • the nitriding treatment is maintained at 400°C-950°C for 2 h to 24 h.
  • the atmosphere of the nitriding treatment adopts at least one of ammonia gas atmosphere and nitrogen gas atmosphere.
  • the tap density of the prepared silicon composite negative electrode material is 0.73g/cm 3
  • the powder compaction density is 1.2g/cm 3
  • the porosity is 50%
  • the specific surface area is 18m 2 /g
  • the carbon content is 12 %.
  • Figures 14a-14b are SEM pictures of the silicon-carbon composite negative electrode material in this embodiment;
  • Figure 15a is a Raman diagram of the silicon-carbon composite negative electrode material in this embodiment;
  • Figure 15b is a XRD of the silicon-carbon composite negative electrode material in this embodiment
  • Figure 15c shows the cycle performance curve of the silicon-carbon composite negative electrode material in this example, and the charge-discharge current is 0.5C.
  • the prepared silicon material is a primary particle
  • the primary particle includes a silicon skeleton
  • the silicon skeleton includes a main skeleton located inside the primary particle and the main skeleton extends to the surface of the primary particle
  • the primary particles have a macroporous structure
  • the primary particles are formed with channels extending to the surface of the primary particles
  • the surface of the silicon skeleton is wrapped with a graphitic carbon layer
  • the thickness of the carbon layer is 25nm
  • the branches of the skeleton are rod-shaped nano-silicon
  • the average diameter of the channel is about 80nm
  • the depth of the channel is about 250nm.
  • the lithium-ion battery prepared from the silicon-carbon composite anode material has high and excellent cycle performance, and still has a capacity of 897mAh/g after 1200 cycles at 0.5C high current. Therefore, the silicon-carbon composite negative electrode material prepared according to the method provided in the present application at least has the advantage of high charge-discharge cycle stability.
  • the tap density of the prepared silicon composite anode material is 0.77g/cm 3
  • the powder compaction density is 1.26g/cm 3
  • the porosity is 52%
  • the specific surface area is 25m 2 /g
  • the carbon content is 15 %.
  • the silicon carbon composite material includes a silicon material and a carbon layer, the silicon material is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle;
  • the branches are rod-shaped nano-silicon particles;
  • the primary particles have a macroporous structure, the primary particles are formed with channels extending to the surface of the primary particles, and the carbon layer wrapped on the surface of the silicon skeleton is amorphous carbon, the thickness of the carbon layer is 15nm, and the average diameter of the channels is about is 80 nm, and the depth of the channel is about 300 nm.
  • the tap density of the prepared silicon composite negative electrode material is 0.45g/cm 3
  • the powder compaction density is 1.09g/cm 3
  • the porosity is 65%
  • the specific surface area is 53m 2 /g
  • the carbon content is 38 %.
  • the silicon-carbon composite material includes a silicon material and a carbon layer, the silicon material is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of skeletons extending from the main skeleton to the surface of the primary particle.
  • the branches are nano-silicon chips
  • the primary particles have a macroporous structure, the primary particles are formed with pores extending to the surface of the primary particles, and the carbon layer wrapped on the surface of the silicon skeleton is an amorphous carbon layer, and the thickness of the carbon layer is 25 nm; and the pores
  • the channels are filled with carbon material; the average diameter of the channels is about 50 nm, and the depth of the channels is about 500 nm.
  • the tap density of the prepared silicon composite anode material is 0.58g/cm 3
  • the powder compaction density is 1.12g/cm 3
  • the porosity is 32%
  • the specific surface area is 60m 2 /g
  • the carbon content is 40 %.
  • the silicon carbon composite material includes a silicon material and a carbon layer, the silicon material is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a main skeleton extending from the main skeleton to the surface of the primary particle.
  • Multiple branches; the branches are rod-shaped nano-silicon particles; the primary particles have a macroporous structure, the primary particles are formed with channels extending to the surface of the primary particles, and the carbon layer wrapped on the surface of the silicon skeleton is a graphitic carbon layer, and the thickness of the carbon layer is 50nm and
  • the channels are filled with carbon material; the average diameter of the channels is about 150 nm, and the depth of the channels is about 1000 nm.
  • the tap density of the prepared silicon composite anode material is 0.8g/cm 3
  • the powder compaction density is 1.38g/cm 3
  • the porosity is 30%
  • the specific surface area is 10m 2 /g
  • the carbon content is 5 %.
  • the silicon carbon composite material includes a silicon material and a carbon layer, the silicon material is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle;
  • the primary particle has a macroporous structure, and the primary particle is formed with a channel extending to the surface of the primary particle, and the carbon layer wrapped on the surface of the silicon skeleton is graphitic carbon, and the thickness of the carbon layer is 5nm; the average diameter of the channel is about 20nm, and the depth of the channel is about 60nm.
  • a preparation method of germanium carbon negative electrode material comprising the following steps:
  • the obtained germanium-carbon composite negative electrode material has a median particle size of about 0.6 ⁇ m, a tap density of 0.78 g/cm 3 , a compacted density of 1.1 g/cm 3 , a specific surface area of 16 m 2 /g, and a porosity of 24%.
  • the mass percentage content of carbon is 75%.
  • the germanium-carbon composite material includes a germanium material and a carbon layer, the germanium material is a primary particle, the primary particle includes a germanium skeleton, and the germanium skeleton includes a main skeleton located inside the primary particle and a main skeleton extending from the main skeleton to the surface of the primary particle.
  • Multiple branches; the branches are rod-shaped nanoparticles; the primary particles have a macroporous structure, the primary particles are formed with channels extending to the surface of the primary particles, and the surface of the germanium skeleton is wrapped with a carbon layer with a thickness of 80 nm; the average diameter of the pores is about 100 nm , the depth of the channel is about 800 nm.
  • a preparation method of germanium carbon negative electrode material comprising the following steps:
  • the obtained germanium-carbon composite negative electrode material has a median particle size of about 0.6 ⁇ m, a tap density of 0.88 g/cm 3 , a compacted density of 1.3 g/cm 3 , a specific surface area of 11 m 2 /g, and a porosity of 44%.
  • the mass percentage content of carbon is 25%.
  • the germanium-carbon composite material includes a germanium material and a carbon layer, the germanium material is a primary particle, the primary particle includes a germanium skeleton, and the germanium skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle; branches; Rod-shaped nanoparticles; the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles, and the surface of the germanium skeleton is wrapped with a carbon layer with a thickness of 50nm; the average diameter of the channels is about 60nm, and the depth of the channels is about 1500nm .
  • a preparation method of a silicon negative electrode material comprising the following steps:
  • the median particle size of the obtained composite negative electrode material is about 0.6 ⁇ m, the specific surface area is 44 m 2 /g, the porosity is 43%, and the mass percentage content of titanium oxide is 12%.
  • the composite material includes a silicon material and a titanium oxide layer, the silicon material is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and multiple skeletons extending from the main skeleton to the surface of the primary particle.
  • the branches are rod-shaped nanoparticles; the primary particles have a macroporous structure, and the primary particles are formed with channels extending to the surface of the primary particles, and the surface of the silicon skeleton is wrapped with a titanium oxide layer; the average diameter of the channels is about 100nm, and the depth of the channels about 700nm.
  • a preparation method of a silicon negative electrode material comprising the following steps:
  • the obtained composite negative electrode material has a median particle size of about 0.7 ⁇ m, a specific surface area of 40 m 2 /g, a porosity of 48%, and a mass percentage content of titanium nitride of 32%.
  • the composite material includes a silicon material and a titanium nitride layer, the silicon material is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle; branches; It is a nanowire; the primary particle has a macroporous structure, the primary particle is formed with a channel extending to the surface of the primary particle, and the surface of the silicon skeleton is wrapped with a titanium nitride layer; the average diameter of the channel is about 58nm, and the depth of the channel is about 1000nm.
  • a preparation method of a silicon negative electrode material comprising the following steps:
  • the median particle size of the obtained composite negative electrode material is about 0.6 ⁇ m, the specific surface area is 51 m 2 /g, the porosity is 40%, and the mass percentage content of vanadium nitride is 25%.
  • the composite material includes a silicon material and a vanadium nitride layer, the silicon material is a primary particle, the primary particle includes a silicon skeleton, and the silicon skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle; branches; It is a rod-shaped nanoparticle; the primary particle has a macroporous structure, and the primary particle is formed with a channel extending to the surface of the primary particle, and the surface of the silicon skeleton is wrapped with a vanadium nitride layer; the average diameter of the channel is about 100nm, and the depth of the channel is about 900nm.
  • the silicon-carbon composite negative electrode material SiO/C is used, and the median particle size of the silicon-carbon composite negative electrode material is 1.5 ⁇ m.
  • the negative electrode materials prepared in Examples 29-37 and Comparative Examples 4-6, the same positive electrode material and current collector were used to make lithium ion batteries, and battery performance tests were carried out.
  • the test items included discharge specific capacity, first coulomb efficiency, and 0.5C cycle 1200
  • the capacity after lap, and the capacity retention rate after 1200 laps at 0.5C, the sample numbers are S29 ⁇ S37 and R4 ⁇ R6, and the performance parameters of the samples are described in Table 5:
  • the composite negative electrode materials provided in Examples 29, 30, 33, and 34 have a three-dimensional pore structure, and the carbon layer is coated on the skeleton surface of the negative electrode material.
  • the composite negative electrode materials provided in Examples 31 and 32 have Three-dimensional channel structure, the carbon layer is coated on the skeleton surface of the negative electrode material and filled into the three-dimensional channel structure, which has good structural stability. As a channel for the electrolyte to flow, it can improve the lithium storage performance of silicon while reducing the expansion of the lithium battery and improve the capacity retention rate of the battery.
  • Comparative Example 4 the molten salt medium was not added during the preparation process, and the local temperature of the high-temperature liquid environment when the alloy powder reacted with the ammonium salt was too high, resulting in the destruction of part of the three-dimensional pore structure and the deterioration of the charge-discharge cycle stability of the battery. Comparative Example 5 In the preparation process, no ammonium salt decomposition inhibitor was added. During the reaction process, the ammonium salt was decomposed into ammonia and carbon dioxide. When the carbon content decreases, the electrical conductivity of the negative electrode material becomes poor, and the volume expansion inhibition performance is weak, resulting in a price difference in long-cycle performance.
  • the battery made of the silicon-carbon composite negative electrode material prepared in the present application has good charge-discharge cycle stability, high capacity and high cycle life.
  • the preparation method of the porous silicon carbon anode material provided by the present application is simple and easy to operate, the preparation process is safe and efficient; the manufacturing cost is effectively reduced, and it is suitable for quantitative production; the obtained product is used as a battery pole piece, and has Better charge-discharge cycle performance.
  • the negative electrode material according to the first aspect includes primary particles, a nanoparticle layer on the surface of the primary particles, and a coating layer coated on the nanoparticle layer.
  • the embodiment of the present application provides a method for preparing a negative electrode material, as shown in FIG. 16 . , including the following steps S41-S44:
  • N in the N-M alloy includes silicon, germanium, antimony, tin, boron
  • M in the N-M alloy includes at least one of magnesium, aluminum, calcium and zinc.
  • a composite anode material with two pore structures can be prepared in one step through a simple in-situ reaction.
  • the carbon-coated N-M alloy is reacted with a cheap and common ammonium salt solution to obtain an intermediate, and then in a protective atmosphere High-temperature dealloying treatment.
  • the active metals in the N-M alloy are reacted to form a nanoparticle layer on the surface of the N-M alloy, and finally a composite negative electrode material is obtained.
  • the obtained negative electrode material has pores, mesopores and Micropores, and the morphology and pore structure are easy to control, the alloy composition can be controlled to change the size and porosity of the pores, and the depth of the pores can be controlled by the reaction time and reaction temperature.
  • the primary particles obtained by dealloying the inner layer of N-M alloy have continuous through-hole channels.
  • the continuous channels can provide internal expansion pore size for the lithiation process, and can also provide a circulation channel for the electrolyte.
  • the generated nanoparticle layer is formed with mesopores and micropores, which can not only avoid material pulverization, but also relieve the volume expansion of the material and ensure the structural stability of the negative electrode material.
  • Using carbon-coated N-M alloy as the raw material can avoid the blocking of the pore structure by carbon coating in the later stage, and improve the first efficiency of the battery.
  • the composite negative electrode material obtained by the method comprises an inner core and a coating layer on the surface of the inner core; wherein,
  • the inner core includes a primary particle and a nanoparticle layer located on the surface of the primary particle; the primary particle includes a skeleton, and the skeleton includes a main skeleton located inside the primary particle and a plurality of branches extending from the main skeleton to the surface of the primary particle; the nanoparticle layer is formed with micropores and/or mesoporous.
  • N in the N-M alloy includes at least one of Si, Ge, Sn, B, and Sb; and M in the N-M alloy includes at least one of Mg, Al, Zn, and Ca.
  • the N-M alloy may be Si-Mg alloy, Si-Al alloy, Ge-Mg alloy, Ge-Al alloy, or the like. Different types of alloys can obtain branches of different shapes, including at least one of rod-shaped nanoparticles, nanosheets, nanowires, and nanotubes.
  • step S41 is substantially the same as step S21 and will not be described in detail here.
  • the mass percent content of N in the N-M alloy is 15% to 60%, optionally, the mass percent content of N may be 15%, 20%, 30%, 40%, 50% or 60% , which is not limited here.
  • the N-M alloy may specifically be at least one of a silicon-magnesium alloy, a silicon-aluminum alloy, a silicon-calcium alloy, and a silicon-zinc alloy. It can be understood that the size and porosity of the pores of the N material can be changed by controlling the composition of the N-M alloy. Generally, the higher the N content in the N-M alloy, the smaller the pore size. The heating reaction time and reaction temperature can be controlled to change the depth of the hole. Generally, the longer the reaction time and the higher the reaction temperature, the deeper the hole is.
  • N-M alloys can also be prepared by other preparation methods, specifically: high-energy ball milling, vacuum smelting, and hot pressing sintering.
  • step S41 can be omitted.
  • Step S42 forming a cladding layer on the surface of the N-M alloy to obtain an N-M alloy containing the cladding layer;
  • a carbon layer is formed by vapor deposition on the surface of the N-M alloy using a carbon source gas under a protective gas, and the carbon source gas used includes at least one of methane, acetylene, acetone and alcohol.
  • a carbon layer may also be formed on the surface of the N-M alloy by means of liquid phase coating and solid phase coating.
  • the solid phase carbon source includes at least one of calcium carbonate, lithium carbonate, iron carbonate, zinc carbonate and magnesium carbonate.
  • the protective gas used in the vapor deposition process includes at least one of helium, neon, argon, krypton and xenon.
  • the volume ratio of the carbon source gas to the protective gas is 1:(0.1-100), specifically 1:0.1, 1:10, 1:20, 1:40, 1:60, 1:80 or 1:100.
  • the carbon source gas feeding time is 5min to 60min, specifically 5min, 15min, 25min, 35min, 45min or 60min. Of course, it can also be set according to the actual situation, which is not limited here.
  • the flow rate of the carbon source gas is 0.1L/min ⁇ 2L/min, specifically 0.1L/min, 0.5L/min, 0.8L/min, 0.8L/min, 1.5L/min or 2L/min, of course Set according to the actual situation, which is not limited here.
  • the temperature of vapor deposition is 400°C to 950°C, specifically 400°C, 500°C, 600°C, 700°C, 800°C, 900°C or 950°C, of course, it can also be set according to the actual situation, which is not limited here. .
  • the heating rate is 1°C/min to 20°C/min, specifically 1°C/min, 5°C/min, 10°C/min, 15°C/min or 20°C/min, thereby effectively improving the reaction efficiency.
  • the molar mass ratio of the solid phase carbon source to the N-M alloy is 2:(1-10), specifically 2:1, 2:3, 2:5, 2:7, 2: 8, 2:9 or 2:10, of course, can also be set according to the actual situation, which is not limited here.
  • the reaction temperature between solid carbon source and N-M alloy is 500°C ⁇ 1000°C, specifically 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C. Of course, it can also be set according to the actual situation. Do limit.
  • the thickness of the carbon layer formed on the surface of the N-M alloy is 5 nm to 100 nm, specifically 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm or 100 nm, etc.
  • the deposition thickness of the carbon layer can be Controlled by deposition time.
  • the median particle size of the carbon-coated N-M alloy is 0.1 ⁇ m to 15 ⁇ m, specifically 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m or 15 ⁇ m, etc. Not limited.
  • step S43 the N-M alloy containing the coating layer is added to the ammonium salt solution to carry out a redox reaction to obtain an intermediate.
  • the ammonium salt includes at least one of ammonium fluoride, ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium carbonate, ammonium perchlorate, ammonium sulfate and ammonium sulfide.
  • the mass concentration of the ammonium salt solution is 0.1mol/L ⁇ 5mol/L, specifically 0.1mol/L, 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, 2.5mol/L, 3mol/L , 4mol/L or 5mol/L, of course, it can also be set according to the actual situation.
  • the molar ratio of the N-M alloy containing the cladding layer to the ammonium salt is 1: (0.1-2), specifically 1:0.1, 1:0.5, 1:0.8, 1:1, 1:1.5 or 1:1: 2 and so on.
  • the redox reaction time of N-M alloy and ammonium salt solution is 0.5h ⁇ 12h, specifically 0.5h, 1h, 2h, 3h, 6h, 9h, 10h or 12h, and the temperature of redox reaction is 20°C ⁇ 80°C, specifically It can be 20°C, 40°C, 50°C, 60°C, 70°C or 80°C.
  • the N-M alloy is a Si-M alloy
  • the carbon-coated Si-M alloy is immersed in an ammonium salt solution, and a layer of silicic acid is formed on the surface of the Si-M alloy after the Si-M alloy reacts with the ammonium salt solution.
  • the silicon-magnesium alloy can be placed in an ammonium chloride solution, and silicic acid, magnesium chloride, ammonia and hydrogen are generated on the surface of the silicon-magnesium alloy.
  • silicic acid is in the form of colloidal particles, precipitates or gels It adheres to the surface of the silicon-magnesium alloy, and after further drying treatment, the silicon-magnesium alloy surface is attached with silicic acid nano-colloid particles.
  • step S44 the intermediate body is subjected to dealloying heat treatment in a protective atmosphere, and the reaction product is subjected to post-treatment to obtain a negative electrode material.
  • the active metal vapor evaporated from the Si-M alloy reacts with silicic acid, so that the silicic acid is reduced in situ at high temperature.
  • Nano-silicon particles, nano-silicon particles are stacked to form a nano-particle layer, so that the nano-particle layer has micropores and/or mesopores, that is, silicic acid nano-colloids react with active metal vapor to form oxides, and the nano-particle layer can be formed after the oxide is removed Microporous or mesoporous. Its reaction chemical formula is as follows:
  • the temperature of the de-alloying heat treatment is 200°C to 950°C, specifically 200°C, 300°C, 400°C, 600°C, 800°C or 950°C, and the holding time is 2h to 18h, specifically 2h , 3h, 6h, 9h, 12h, 15h or 18h, which are not limited here.
  • the heating rate of the dealloying heat treatment is 1°C/min ⁇ 20°C/min, specifically 1°C/min, 5°C/min, 10°C/min, 15°C/min or 20°C/min, so as to effectively improve the reaction efficiency.
  • the dealloying heat treatment is carried out under the protection of an inert gas
  • the inert gas includes at least one of helium, neon, argon, krypton and hernia.
  • the flow of inert gas can be controlled at 1L/min-10L/min.
  • the acid washing is to use an acid solution to wash the reaction product, thereby removing metal oxides in the reaction product.
  • the acid solution used for the acid washing includes at least one of hydrochloric acid, nitric acid and sulfuric acid. A sort of.
  • the mass concentration of the acid solution is 1 mol/L to 5 mol/L, specifically 1 mol/L, 2 mol/L, 3 mol/L, 4 mol/L or 5 mol/L.
  • the mass concentration of the acid solution can also be adjusted according to actual needs, which is not limited here.
  • the duration of pickling is 1h to 10h, specifically 1h, 3h, 5h, 7h or 10h.
  • the acid-washed product can still be recovered and recycled.
  • a layer of silicic acid is formed on the surface of the Si-M alloy after the reaction between the Si-M alloy and the ammonium salt solution.
  • the metal vapor of the active metal in the Si-M alloy Reacting with silicic acid, the silicic acid is reduced in situ at high temperature to nano-silicon particles, which form a nano-particle layer with micropores and/or mesopores.
  • the final prepared negative electrode material has a pore structure with various pore sizes, and the pore size of the surface layer of the silicon material is smaller than that of the inner layer, thereby relieving the volume expansion of silicon, effectively inhibiting material pulverization, and enhancing structural stability.
  • the prepared composite anode material can also effectively improve the stability of lithium battery charge-discharge cycles, and has multiple advantages such as high capacity, long cycle life, high rate performance, and low expansion.
  • a preparation method of a negative electrode material comprising the following steps:
  • the median particle size of the obtained composite negative electrode material is 1.2 ⁇ m, the mass percentage of carbon is 15%, the specific surface area is 45 m 2 /g, and the thickness of the carbon layer is 50 nm.
  • the porosity of the obtained composite negative electrode material is 55%, the porosity of the primary particles is 40%, the porosity of the nanoparticle layer is 25%, and the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is 4:1, the volume of open pores in all pore structures is about 80%, and the volume of closed pores is about 20%; the maximum width of the cross-section of the branches is about 40 nm, and the thickness of the nanoparticle layer is 100 nm.
  • Figure 17a is a scanning electron microscope picture of the composite negative electrode material
  • Figure 17b is an XRD pattern of the composite negative electrode material provided in this embodiment
  • Figure 17c is a cycle performance curve of the porous silicon negative electrode material in this embodiment, and the charge-discharge current is 0.5C.
  • the scanning electron microscope picture in Fig. 17a the prepared porous silicon has an obvious porous structure, and the surface of the porous silicon is wrapped with a carbon layer.
  • the XRD pattern of Fig. 17b that the triplet peaks at 28.4°, 47.3° and 56.1° correspond to the triplet peaks of silicon (JCPDS No. 27-1402), and there is basically no impurity phase.
  • the composite negative electrode material is obtained after suction filtration, washing and drying.
  • the obtained composite negative electrode material has a median particle size of 1.8 ⁇ m, a mass percentage of carbon of 16%, a specific surface area of 55 m 2 /g, and a carbon layer thickness of 53 nm.
  • the porosity of the obtained composite negative electrode material is 55%, the porosity of the primary particles is 35%, the porosity of the nanoparticle layer is 23%, and the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is 5:1, the volume of open pores in all pore structures is about 83%, and the volume of closed pores is about 17%; the maximum width of the cross-section of the branches is about 35 nm, and the thickness of the nanoparticle layer is 150 nm.
  • the composite negative electrode material is obtained after suction filtration, washing and drying.
  • the obtained composite negative electrode material has a median particle size of 3.5 ⁇ m, a mass percentage of carbon of 15%, a specific surface area of 40 m 2 /g, and a carbon layer thickness of 80 nm.
  • the porosity of the obtained composite anode material is 45%, the porosity of the primary particles is 36%, the porosity of the nanoparticle layer is 27%, and the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is 5:1, the volume of open pores in all pore structures is about 83%, and the volume of closed pores is about 17%; the maximum width of the cross-section of the branches is about 50 nm, and the thickness of the nanoparticle layer is 50 nm.
  • the composite negative electrode material is obtained after suction filtration, washing and drying.
  • the obtained composite negative electrode material has a median particle size of 1.5 ⁇ m, a mass percentage of carbon of 18%, a specific surface area of 90 m 2 /g, and a carbon layer thickness of 50 nm.
  • the porosity of the obtained composite negative electrode material is 45%, the porosity of the primary particles is 30%, the porosity of the nanoparticle layer is 15%, and the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores It is 8:1, the volume of open pores in all pore structures is about 81%, and the volume of closed pores is about 19%; the maximum width of the cross-section of the branches is about 30 nm, and the thickness of the nanoparticle layer is 500 nm.
  • the composite negative electrode material is obtained after suction filtration, washing and drying.
  • the median particle size of the obtained composite negative electrode material is 1.2 ⁇ m, the mass percentage of carbon is 20%, the specific surface area is 50 m 2 /g, and the thickness of the carbon layer is 100 nm.
  • the porosity of the obtained composite negative electrode material is 55%, the porosity of the primary particles is 40%, the porosity of the nanoparticle layer is 25%, and the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is 4:1, the volume of open pores in all pore structures is about 80%, and the volume of closed pores is about 20%; the maximum width of the cross-section of the branches is about 40 nm, and the thickness of the nanoparticle layer is 100 nm.
  • the composite negative electrode material is obtained after suction filtration, washing and drying.
  • the obtained composite negative electrode material has a median particle size of 1.6 ⁇ m, a mass percentage of carbon of 20%, a specific surface area of 30 m 2 /g, and a carbon layer thickness of 50 nm.
  • the porosity of the obtained composite anode material is 55%, the porosity of the primary particles is 40%, the porosity of the nanoparticle layer is 32%, and the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores It is 4:1, the volume of open pores in all pore structures is about 80%, and the volume of closed pores is about 20%; the maximum width of the cross-section of the branches is about 40 nm, and the thickness of the nanoparticle layer is 100 nm.
  • the composite negative electrode material is obtained after suction filtration, washing and drying.
  • the median particle size of the obtained composite negative electrode material is 1.3 ⁇ m, the mass percentage of carbon is 20%, the specific surface area is 30 m 2 /g, and the thickness of the carbon layer is 50 nm.
  • the porosity of the obtained composite anode material is 50%, the porosity of the primary particles is 65%, the porosity of the nanoparticle layer is 22%, and the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is 4:1, the volume of open pores in all pore structures is about 80%, and the volume of closed pores is about 20%; the maximum width of the cross-section of the branches is about 60 nm, and the thickness of the nanoparticle layer is 70 nm.
  • germanium powder with a particle size of 1 ⁇ m and the magnesium powder with a molar ratio of 1:2 are evenly mixed and placed in an atmosphere furnace, heated to 650 °C at a heating rate of 3 °C/min under the protection of argon inert gas, and then kept warm 8h, make it fully react to obtain germanium-magnesium alloy; ball-mill the germanium-magnesium alloy to obtain 1 ⁇ m germanium-magnesium alloy powder;
  • the composite negative electrode material is obtained after suction filtration, washing and drying.
  • the median particle size of the obtained composite negative electrode material was 1.3 ⁇ m, the mass percentage of carbon was 21%, the specific surface area was 31 m 2 /g, and the thickness of the carbon layer was 40 nm.
  • the porosity of the obtained composite anode material is 52%, the porosity of the primary particles is 64%, the porosity of the nanoparticle layer is 23%, and the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is 4:1, the volume of open pores in all pore structures is about 81%, and the volume of closed pores is about 19%; the maximum width of the cross-section of the branches is about 62 nm, and the thickness of the nanoparticle layer is 73 nm.
  • the obtained composite negative electrode material has a median particle size of 1.4 ⁇ m, a mass percentage of carbon content of 20%, a specific surface area of 15 m 2 /g, and a carbon layer thickness of 50 nm.
  • the porosity of the obtained composite anode material is 70%, the volume of open pores in all pore structures is about 70%, and the volume of closed pores is about 30%; the maximum diameter of the nano-silicon skeleton unit is about 65 nm.
  • the composite negative electrode material is obtained after suction filtration, washing and drying.
  • the median particle size of the obtained composite negative electrode material is 1.8 ⁇ m, the mass percentage of carbon is 25%, the specific surface area is 45 m 2 /g, and the thickness of the carbon layer is 50 nm.
  • the porosity of the obtained composite negative electrode material is 55%, the porosity of the primary particles is 40%, the porosity of the nanoparticle layer is 7%, and the ratio of the total porosity of the mesopores in the nanoparticle layer to the total porosity of the micropores is 1.8:1, the volume of open pores in all pore structures is about 58%, and the volume of closed pores is about 42%; the maximum width of the cross-section of the branches is about 40 nm, and the thickness of the nanoparticle layer is 200 nm.
  • the composite negative electrode material Si/C is used, the median particle size of the composite negative electrode material is 1.5 ⁇ m, the inner core of the composite material is a porous silicon structure stacked with nano-silicon particles, and the outer shell is wrapped by a carbon layer; the mass percentage of carbon is 22%. , the specific surface area is 38m 2 /g, the thickness of the carbon layer is 50nm, and the porosity of the composite negative electrode material is 67%.
  • the selected test instrument was: OXFORD EDS (X-max-20mm2), the acceleration voltage was 10KV to adjust the focal length, and the observation magnification was from 50K for high magnification observation, and 500 for low magnification. To 2000, the particle agglomeration was mainly observed.
  • the cores of 20 anode materials were randomly selected by SEM, and the diameter and length of the skeleton and the size of the branches were tested.
  • the sample is heated and burned at high temperature in a high-frequency furnace under oxygen-rich conditions to oxidize carbon and sulfur into carbon dioxide and sulfur dioxide. .
  • This signal is sampled by the computer, converted into a value proportional to the concentration of carbon dioxide and sulfur dioxide after linear correction, and then the value of the whole analysis process is accumulated. After the analysis, the accumulated value is divided by the weight value in the computer, and then multiplied by Correction factor, subtracting the blank, you can get the percentage of carbon in the sample.
  • the samples were tested using a high-frequency infrared carbon-sulfur analyzer (Shanghai Dekai HCS-140).
  • the adsorption amount of the sample monolayer is calculated based on the Brownnauer-Etter-Taylor adsorption theory and its formula (BET formula), and then calculate The specific surface area of a solid.
  • the cross-section polisher uses an ion source to ionize an inert gas to generate inert ions. After acceleration and focusing, the high-speed inert ions knock out atoms or molecules on the surface of the sample to achieve ion polishing. After being cut by CP, the sample was placed on the SEM special sample stage for SEM test. The instrument model is IB-09010CP, the ion accelerating voltage is 2-6kV, and the gas used is argon. After the silicon carbon negative electrode material is cut through the cross-section test, the thickness of the nanoparticle layer and the thickness of the carbon layer in the cross-section can be tested.
  • the sample numbers are S39-S46 and R7-R9; 6)
  • the slurry with carbon black (SP) according to the ratio of 92:2:2:2:2, evenly coat it and dry it on the copper foil to make a negative pole piece, and assemble it into a button battery in an argon atmosphere glove box
  • the separator used is a polypropylene microporous membrane
  • the electrolyte used is 1 mol/L lithium hexafluorophosphate (the solvent is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate)
  • the used counter electrode is a metal lithium sheet.
  • the above-mentioned 11 sets of batteries were tested on the Blue Power CT2001A battery test system.
  • the ratio of the electricity discharged in 1 hour to the battery capacity was the discharge specific capacity.
  • the first coulomb efficiency test was carried out on the above 11 sets of batteries on the Blue Power CT2001A battery test system, and the charge and discharge current was 0.05C, and the first coulomb efficiency was measured.
  • the above 11 sets of batteries were tested on the Blue Power CT2001A battery test system for 100 cycles, and the charge and discharge current was 0.2C. After 100 cycles, the battery capacity and the capacity retention rate after the cycle were calculated.
  • Example 39 has high and excellent cycle performance, and has a capacity of 997mAh/g after 1000 cycles of cycling at a high current of 0.5C.
  • the main difference between Example 42 and Example 39 is that the concentration of ammonium chloride is higher and the soaking time is longer, so that more silicic acid particles are generated on the surface of the carbon-coated silicon-magnesium alloy, so that the final The thickness of the nano-silicon particle layer of the product is larger, the mesopores and micro-pores of the nano-silicon particle layer are reduced, and the electrolyte is not easy to flow into the primary particles in the inner layer, so that the expansion rate of the pole piece increases during the charging and discharging process of the battery. Stability deteriorates.
  • Comparative Example 8 and Example 43 The main difference between Comparative Example 8 and Example 43 is that the concentration of ammonium chloride is higher, the soaking temperature is higher, and the time is longer, so that more silicic acid particles are generated on the surface of the carbon-coated silicon-magnesium alloy, so that the nano-silicon of the final product is produced.
  • the thickness of the particle layer is larger, the mesopores and micropores of the nano-silicon particle layer are reduced, and the electrolyte is not easy to flow into the primary particles in the inner layer, so that the expansion rate of the pole piece increases and the cycle stability deteriorates during the charging and discharging process of the battery. .
  • Comparative Example 9 is a carbon-coated porous silicon negative electrode material.
  • the capacity and capacity retention rate of the battery made of this material decreased after 100 cycles at 0.2C, and the electrode film expansion rate of Comparative Example 9 was also higher than that of the embodiment. 39.
  • the nanoparticle layer on the surface of the primary particles of the negative electrode material of the present application has excellent mesopores and micropores, which can effectively avoid material pulverization, and form a rigid silicon-lithium alloy layer after lithiation, which further inhibits
  • the volume expansion of the primary particles ensures the structural stability of the porous silicon.
  • silicon intercalation expands and fills the mesoporous pores, which can further avoid side reactions caused by the contact between the electrolyte solvent molecules and the primary particles, resulting in more SEI and lower first effect.
  • the pore structure on the primary particles is different from the mesopores and micropores of the nanoparticle layer in structure, which can further relieve the stress caused by the volume expansion of porous silicon, reduce the expansion of the electrode film, and improve the safety; excellent structural stability, resulting in long cycle life.
  • the carbon layer wraps the silicon material, it has better electrical conductivity and stability.
  • the sequence of coating carbon first and then reacting to prepare pores can effectively avoid carbon filling or closing the pore structure, reduce the first effect of the material, and even cause side reactions. Therefore, the composite anode material is beneficial to meet the requirements of long cycle life, high capacity and low expansion of the battery, and can be widely used in the field of lithium-ion battery anode materials.
  • the preparation method of the negative electrode material provided by the present application is simple and easy to operate, and the preparation process is safe and efficient; the manufacturing cost is effectively reduced, and it is suitable for quantitative production; the prepared product is used as a battery pole piece and has better charge and discharge performance cycle performance.
  • the embodiments of the present application also provide a lithium-ion battery negative pole piece and a lithium ion battery, which are prepared by using the composite negative electrode material provided in the above-mentioned embodiment of the present application or the preparation method of the negative-electrode material provided by the above-mentioned embodiment of the present application. negative electrode material.
  • the present application illustrates the detailed process equipment and process flow of the present application through the above-mentioned embodiments, but the present application is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that the present application must rely on the above-mentioned detailed process equipment and process flow. Process flow can be implemented. Those skilled in the art should understand that any improvement to the application, the equivalent replacement of each raw material of the product of the application, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the application.

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Abstract

本申请涉及一种负极材料、其制备方法及锂离子电池，负极材料为一次颗粒，一次颗粒包括骨架，所述骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝；一次颗粒为大孔结构，一次颗粒的内部形成有孔道，所述孔道延伸至一次颗粒的表面。相较于纳米颗粒堆积而成的二次多孔结构，本申请负极材料具有结构更加稳定、体积膨胀低的优点，并可以兼具更小的比表面积和更高的孔隙率。

Description

负极材料及其制备方法、锂离子电池
本申请要求于2020年12月11日提交中国专利局，申请号为202011459903.8、申请名称为“一种锂离子电池硅负极材料及其制备方法”的中国专利、2021年01月06日提交中国专利局，申请号为202110013364.3、申请名称为“复合负极材料及其制备方法、锂离子电池”的中国专利、于2021年04月28日提交中国专利局，申请号为202110468548.9、申请名称为“复合负极材料及其制备方法、锂离子二次电池”的中国专利以及于2021年04月02日提交中国专利局，申请号为202110363721.9、申请名称为“复合负极材料及其制备方法、锂离子电池”的中国专利申请的优先权，上述四件中国专利的全部内容通过引用结合在本申请中。
技术领域
本申请涉及负极材料技术领域，具体地讲，涉及负极材料及其制备方法、锂离子电池。
背景技术
锂离子电池由于具备能量密度大、输出功率高、循环寿命长和环境污染小等优点而被广泛应用于电动汽车以及消费类电子产品中。为了提高电池能量密度，硅负极材料的研究和开发日趋成熟。但是硅负极材料脱嵌锂过程中体积膨胀较大(>300％)，硅负极材料在充放电过程中会粉化从集流体上掉落，使得活性物质与集流体之间失掉电触摸，导致电化学性能变差，容量衰减、循环稳定性下降，难以得到商业应用。
基于此，亟需开发一种膨胀率低、循环稳定性高的负极材料及其制备方法。
申请内容
鉴于此，本申请提供复合负极材料及其制备方法、锂离子电池，能够降低负极材料的膨胀率，提高负极材料的充放电循环性能，该制备方法可降低制备成本。
为达此目的，本申请采用以下技术方案：
第一方面，本申请提供一种负极材料，所述负极材料包括一次颗粒，所述一次颗粒包括骨架，所述骨架包括位于所述一次颗粒的内部的主骨架及自所述主骨架延伸至所述一次颗粒表面的多个分枝。
在上述方案中，负极材料为一次颗粒，一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝为一个整体，整个骨架结构增强材料的电子传导和离子扩散，可以有效释放锂化后的应力，避免应力在晶界处集中导致材料破裂和粉化。该负极材料具有一体化结构更加稳定的优点，并可以兼具更小的比表面积和更高的孔隙率。本申请是一次完整颗粒，整个骨架相连，增强材料的电子传到和离子扩散，可以有效释放锂化后的应力，避免应力集中导致材料粉化，二次颗粒组装的多孔材料，由于颗粒之间存在明显的晶界，导致锂化应力集中，颗粒破碎，整个结构破坏，最终导致电化学性能恶化。
第二方面，一种负极材料，所述负极材料包括一次颗粒，所述一次颗粒为大孔结构，所述一次颗粒形成有延伸至所述一次颗粒表面的孔道。
第三方面，一种负极材料，所述负极材料包括一次颗粒，所述一次颗粒内部形成有通孔，所述一次颗粒的孔隙率不低于30％。
一实施方式中，负极材料还包括位于所述一次颗粒表面的包覆层。
此外，在一次颗粒表面的包覆层能够进一步提高负极材料的结构稳定性和循环稳定性，同时进一步缓解负极材料的体积膨胀。
一实施方式中，负极材料还包括保护层，所述保护层位于所述骨架表面。
形成在负极材料骨架表面的保护层，能够进一步提高负极材料的导电性和循环稳定性，同时进一步缓解负极材料的体积膨胀，从而进一步提升负极材料的导电性、倍率性能。
一实施方式中，负极材料还包括位于一次颗粒表面的纳米颗粒层及包覆于所述纳米颗粒层的包覆层，所述纳米颗粒层形成有微孔和/或介孔。
在上述方案中，纳米颗粒层可以有效避免材料粉化，可以缓解材料的体积膨胀，保证负极材料内部的一次颗粒的结构稳定性。采用包覆层包覆后，具有更好的导电性和稳定性，可以有效避免碳填充材料内部孔隙，提高材料首效，使得复合负极材料能够表现出高容量、长循环寿命、高倍率性能以及低膨胀等特性。
第四方面，本申请提供一种负极材料的制备方法，所述方法包括以下步骤：
将含有N-M材料与过渡金属卤化物的混合物置于保护性气氛中进行置换反应，得到反应产物，所述反应产物包括M的卤化物和过渡金属；及
去除所述M的卤化物和过渡金属，得到负极材料；
其中，所述N-M材料中的M包括Mg、Al、Li和Ca中的至少一种；
所述N-M材料中的N包括Si、Ge、Sn、B及Sb中的至少一种。
在上述方案中，本申请通过N-M材料在高温下与过渡金属卤化物发生反应，之后去除N-M材料的金属M成分得到多孔N负极材料。由于反应生成的金属的卤化物，以采用硅镁合金或硅铝合金作为原料举例，生成的金属卤化物为镁或铝的金属卤化物在反应温度下为熔融态，熔融态的卤化物具有连续性，且为相连纳米N材料的形成提供了相连的液态模板，除去金属卤化物后得多孔N负极材料，结构上纳米单元沿着相连的液态模板生长形成相连骨架结构，除去模板后，使形成的一次颗粒为大孔结构，所述一次颗粒的内部形成有孔道，所述孔道延伸至所述一次颗粒的表面。
第五方面，本申请提供一种负极材料的制备方法，包括以下步骤：
将含有N-M合金和含卤素的六元环有机物的混合物置于保护性气氛中进行置换反应，得到反应产物，所述反应产物包括M的氧化物、M的卤化物；及
去除所述M的氧化物及M的卤化物，得到复合负极材料；
其中，所述N-M合金中的N包括硅、锗、锑、锡、硼中的至少一种，所述N-M合金中的M包括镁、铝、钙和锌中的至少一种。
在上述方案中，通过一步复合法制备负极材料，高温下N-M合金与六元环有机物直接反应，去除N-M合金中的金属M成分，同时在N材料表面原位沉积碳层。整体反应温和且没有副产物，N材料结构完整、稳定，碳层沉积均匀，参与反应的原 材料都是常用的合金、有机物以及金属盐，能够降低成本。
第六方面，本申请提供一种负极材料的制备方法，所述方法包括以下步骤：
将含有N-M合金和含碳铵盐的混合物置于保护性气氛中进行置换反应，得到反应产物，所述反应产物包括M的氧化物、M的氮化物；及
去除所述M的氧化物及M的氮化物，得到复合负极材料；
其中，所述N-M合金中的N包括硅、锗、锑、锡、硼中的至少一种，所述N-M合金中的M包括镁、铝、钙和锌中的至少一种。
在上述方案中，本申请以含碳铵盐为碳源和N-M合金在高温条件下采用一步复合法制备复合负极材料，相比于两步复合法，能够有效提高制备效率，工艺简单。
第七方面，本申请提供一种负极材料的制备方法，包括以下步骤：
在N-M合金表面形成包覆层，得到含有包覆层的N-M合金；
将含有包覆层的N-M合金加入铵盐溶液中进行氧化还原反应，得到中间体；
将所述中间体在保护性气氛下进行去合金化热处理，并对反应产物进行酸洗，得到复合负极材料，其中，所述N-M合金中的N包括硅、锗、锑、锡、硼中的至少一种，所述N-M合金中的M包括镁、铝、钙和锌中的至少一种。
在上述方案中，本申请通过简单的原位反应且可以一步制备两种孔结构的复合负极材料，将包覆后的N-M合金与的铵盐溶液反应后在保护气氛中加热便可以得到复合负极材料，复合负极材料的形貌和孔结构易调控，可以控制合金成分来改变孔的大小以及孔隙率，孔的深度可以由反应时间与反应温度来控制。制得负极材料中的孔能够在负极材料脱嵌锂过程中提供内膨胀的空间，并可以作为电解液流动的通道，在提高储锂性能的同时降低锂电池的膨胀，有利于负极材料锂化后向内膨胀进而降低整个电极膜的厚度，大大提高锂离子电池的安全性。外层的纳米颗粒层可以有效避免材料粉化，可以缓解材料的体积膨胀，保证负极材料内部的一次颗粒的结构稳定性。采用包覆材料包覆后，具有更好的导电性和稳定性，可以有效避免碳填充一次颗粒的三维孔道，提高材料首效，使得复合负极材料能够表现出高容量、长循环寿命、高倍率性能以及低膨胀等特性。
第八方面，本申请提供一种锂离子电池，所述锂离子电池包含上述的复合负极材料或根据上述的制备方法制得的复合负极材料。
附图说明
图1为一实施方式的负极材料的结构示意图；
图2a为一实施方式的负极材料的结构示意图；
图2b为一实施方式的负极材料的石墨烯层结构示意图；
图3a为一实施方式的负极材料的结构示意图；
图3b为另一实施方式的负极材料的结构示意图；
图4a为一实施方式的负极材料的结构示意图；
图4b为一实施方式的负极材料中的纳米颗粒层的结构示意图；
图5为一实施方式的硅负极材料的制备方法流程图；
图6为一实施方式的硅负极材料的制备方法流程示意图；
图7a为实施例1中硅负极材料的电镜图片；
图7b为实施例1中硅负极材料的XRD图；
图7c为实施例1中硅负极材料的首次充放电曲线；
图7d为实施例1的硅负极材料循环性能曲线；
图7e为对比例1中硅负极材料的扫描电镜图片；
图8为一实施例提供的负极材料的制备方法的流程示意图；
图9为一实施例提供的硅碳复合负极材料的合成流程示意图；
图10为一实施例提供的硅/金属氧化物及硅/金属氮化物复合负极材料的合成流程示意图；
图11a为实施例1提供的硅碳复合负极材料的扫描电镜图片；
图11b为实施例1提供的硅碳复合负极材料的另一扫描电镜图片；
图12a为实施例1提供的硅碳复合负极材料的XRD图；
图12b为实施例1提供的硅碳复合负极材料的拉曼图；
图12c为实施例1提供的硅碳复合负极材料的循环性能曲线图；
图13为一实施例提供的复合负极材料的合成流程示意图；
图14a为实施例15提供的硅碳复合负极材料的扫描电镜图片；
图14b为实施例15提供的硅碳复合负极材料的另一扫描电镜图片；
图15a为实施例15提供的硅碳复合负极材料的拉曼图；
图15b为实施例15提供的硅碳复合负极材料的XRD图；
图15c本实施例提供的硅碳复合负极材料的循环性能曲线图；
图16为一实施例提供的负极材料的制备方法的流程图；
图17a为实施例25提供的硅碳复合负极材料的扫描电镜图片；
图17b为实施例25提供的硅碳复合负极材料的XRD图；
图17c为实施例25提供的硅碳复合负极材料的循环性能曲线图。
具体实施方式
为更好地说明本申请，便于理解本申请的技术方案，下面对本申请进一步详细说明。但下述的实施例仅仅是本申请的简易例子，并不代表或限制本申请的权利保护范围，本申请保护范围以权利要求书为准。
以下为本申请典型但非限制性实施例：
本文中“去合金化”是指通过化学或是电化学腐蚀过程将合金中的一种或多种组元有选择性的去除的一种方法。去合金化过程中涉及旧晶格位的去除和新晶格位的形成，也涉及新晶体的形核和生长，其中，去合金化过程中纳米多孔结构的形成与合金/溶液界面上原子层次的重组密切相关，而重组过程是通过未溶解的金属原子和空位的表面扩散完成的，而且表面扩散的快慢对最终形成的纳米多孔金属中韧带/通道的尺寸有重要影响。
第一方面
一实施方式的负极材料，如图1所示，负极材料包括一次颗粒，一次颗粒包括骨 架，骨架包括位于一次颗粒的内部的主骨架11及自主骨架11延伸至一次颗粒表面的多个分枝12。
请进一步参阅图1，该实施方式的一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道13。其中，根据国际纯粹与应用化学协会(IUPAC)的定义，孔径大于50nm的称为大孔。
本实施方式的负极材料包括一次颗粒，一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝为一个整体，整个骨架结构增强材料的电子传到和离子扩散，可以有效释放锂化后的应力，避免应力在晶界处集中导致材料破裂和粉化。
该负极材料的孔道延伸至一次颗粒的表面的孔道结构具有如下优点：一、在提高储锂性能的同时能降低了锂电池的膨胀。不仅可以缓解嵌锂过程中的体积膨胀，还有利于为锂化提供内膨胀的空间，使电极材料锂化后向内膨胀而降低整个电极膜的厚度，大大提高了锂离子电池的安全性。二、提供了电解液流动的通道，有利于电解液的接触。孔道结构还可以带来更高的振实密度，能够增加电池的体积能量密度。
相较于纳米颗粒堆积而成的二次多孔结构，本实施方式所制备的多孔负极材料具有一体化结构更加稳定的优点，并可以兼具更小的比表面积和更高的孔隙率。本申请是一次完整颗粒，整个骨架相连，增强材料的电子传到和离子扩散，可以有效释放锂化后的应力，避免应力集中导致材料粉化，二次颗粒组装的多孔材料，由于颗粒之间存在明显的晶界，导致锂化应力集中，颗粒破碎，整个结构破坏，最终导致电化学性能恶化。
在一些实施方式中，负极材料为一次颗粒；
在一些实施方式中，主骨架为三维网状结构；
在一些实施方式中，单个分枝为单独的晶粒；分枝与主骨架之间没有明显的晶界，一次颗粒的表面分散晶粒；现有技术方案中多孔硅二次颗粒上的分枝主要由多个小晶粒组成，晶界较多，相较于这种结构，本实施方式中一次颗粒上的分枝为单独一个大晶粒，没有过多的晶界存在，锂化后应力可以得到较好的分散，避免应力集中导致材料的破坏；同时单独一个晶粒的晶面曲线相同，更有利于减小材料某一方向的相对体积膨胀，而多个小晶粒组成的结构体积膨胀相对较大，同时结构稳定性也相对较差，导致循环稳定性较差。
具体地，晶粒的尺寸为30nm-100nm；示例性地，晶粒的尺寸可以是30nm、45nm、50nm、60nm、75nm、100nm。
在一些实施方式中，分枝的横截面最大宽度为20nm-350nm，分枝的横截面最大长度为50nm-2500nm；优选地，分枝12的横截面最大宽度12W为20nm-250nm，分枝的横截面最大长度12L为100nm-1500nm；示例性地，分枝12的横截面的最大宽度12W具体可以是可以是20nm、40nm、80nm、100nm、120nm、150nm、180nm、200nm或250nm，分枝12的横截面的最大长度12L具体可以是可以是100nm、200nm、300nm、400nm、500nm、800nm、1000nm、1200nm或1500nm，在此不做限定。
在一些实施方式中，分枝选自棒状纳米颗粒、纳米片、纳米线及纳米管中的至少一种。
在一些实施方式中，通过压汞测试方法测得孔道13的直径为10nm-150nm；孔 道的深度为50nm-1500nm。示例性地，孔道直径具体可以为10nm、50nm、60nm、80nm、100nm或150nm，在此不做限定。孔道13深度具体可以是50nm、100nm、200nm、300nm、400nm、500nm、800nm或1000nm，在此不做限定。可以控制反应时间与反应温度来改变孔的深度(一般反应时间越长、反应温度越高，孔的深度越深。)
本实施方式的负极材料包括一次颗粒，一次颗粒内部形成有通孔，一次颗粒的孔隙率不低于30％。本申请的一次颗粒具有较高的孔隙率，可以有效缓解硅负极300％以上的体积膨胀，结合大孔贯通结构结构优势，锂化后的孔结构也可以保持完好，现有技术的孔隙率较低以及存在较多的微孔和介孔，无法满足硅的巨大体积膨胀，锂化后孔洞被填充后，由于电化学烧结最终导致孔洞被填堵，无法继续保持多孔结构。
上述实施方式的负极材料可以为硅负极材料，锗负极材料、锡负极材料、硼负极材料、锑负极材料等负极材料；比较典型的例子如硅负极材料在一些实施方式中，一次颗粒选自硅、锗、锡、硼及锑中的至少一种；其骨架可以为硅骨架、锗骨架、锡骨架、硼骨架、锑骨架等；如负极材料选用硅负极材料，其硅负极材料为一次颗粒，一次颗粒包括硅骨架，包括位于所述一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。锗、硼、锡及锑的骨架结构与上述硅骨架结构相似。
在一些实施方式中，一次颗粒的中值粒径为0.2μm～15μm，例如0.2μm、1μm、3μm、5μm、8μm、10μm、12μm或15μm等。优选为0.5μm～10μm，进一步优选为1μm～5μm。
在一些实施方式中，一次颗粒的比表面积为5m 2/g～100m 2/g，例如5m 2/g、10m 2/g、20m 2/g、30m 2/g、40m 2/g、50m 2/g、60m 2/g、80m 2/g或100m 2/g等。优选为10m 2/g～50m 2/g。
在一些实施方式中，一次颗粒的孔隙率为30％～70％，例如30％、35％、40％、50％、55％、60％或70％等，优选为40％～60％。
在一些实施方式中，一次颗粒的粉体振实密度为0.2g/cm 3～0.8g/cm 3，例如0.2g/cm 3、0.3g/cm 3、0.5g/cm 3、0.6g/cm 3、0.7g/cm 3或0.8g/cm 3等。优选为0.4g/cm 3～0.7g/cm 3。
在一些实施方式中，一次颗粒的粉体压实密度为1.2g/cm 3～1.8g/cm 3，例如1.2g/cm 3、1.3g/cm 3、1.4g/cm 3、1.5g/cm 3、1.6g/cm 3或1.8g/cm 3等，优选为1.4g/cm 3～1.7g/cm 3。
在一些实施方式中，如图2a所示，负极材料包括一次颗粒10及位于一次颗粒10表面的包覆层20。
可以理解地，负极材料包括内核10及形成于内核表面的包覆层20，其中，内核10为一次颗粒。
可以理解地，该一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架11及自主骨架11延伸至一次颗粒表面的多个分枝12；该一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道13；可以理解地，该一次颗粒内部形成有通孔，一次颗粒的孔隙率不低于30％。
通过在一次颗粒(内核)表面形成包覆层，能够进一步提高负极材料的结构稳定性和循环稳定性，同时进一步缓解负极材料的体积膨胀。
在本实施例中，一次颗粒的具体结构(骨架结构、孔结构)以及性能参数(孔隙率、中值粒径、比表面积、粉体振实密度、粉体压实密度等参数)如前面实施方式所述，在此不再重复阐述。
在一些实施方式中，负极材料的中值粒径为0.1μm～15μm，可选地，负极材料的中值粒径具体可以是0.1μm、0.5μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm或10μm等，在此不做限定。复合负极材料的中值粒径优选为0.5μm～10μm，更优选为1μm～8μm。
在一些实施方式中，负极材料的比表面积为1m 2/g～150m 2/g。可选地，负极材料的比表面积比可以是1m 2/g、5m 2/g、10m 2/g、20m 2/g、30m 2/g、40m 2/g、50m 2/g、60m 2/g、70m 2/g、100m 2/g、120m 2/g或150m 2/g等，在此不做限定；负极材料的比表面积比优选为1m 2/g～50m 2/g。可以理解地，比表面积越小越好，过大的比表面积容易导致SEI膜形成，消耗不可逆锂盐过多，降低电池的首次效率低，综合考虑制备工艺的成本，将比表面积控制在10m 2/g～50m 2/g。
在一些实施方式中，该负极材料的孔隙率为30％～70％。
在一些实施方式中，包覆层包括碳层、金属氧化物层及金属氮化物层中的至少一种；上述种类的包覆层能够进一步提高负极材料的导电性、结构稳定性和循环稳定性，同时进一步缓解负极材料的体积膨胀；
其中，包覆层包括碳层，进一步地，碳层包括石墨烯层及非晶碳层中的至少一种；
更进一步地，石墨烯层具有褶皱结构，石墨烯层的褶皱形貌能够提供更多的活性位点，从而进一步提升负极材料的导电性、倍率性能；
如图2b所示，褶皱结构包括凸起(峰)201和凹陷(谷)202，相邻两个凸起201之间为凹陷202，相邻两个凹陷202之间为凸起201；其中，该褶皱结构的表面粗糙度Rz(最大峰-谷高度)大于10nm且小于1μm，进一步地，Rz可大于50nm且小于500nm，更进一步地，Rz可大于100nm且小于350nm。相近两凸起最高点或两凹陷最低点之间的距离H大于10nm且小于1μm；进一步地，H大于50nm且小于800μm，更进一步地，H大于100nm且小于500nm。
具体地，褶皱结构根据褶皱面弯曲形态分类，褶皱结构可选自圆弧褶皱、尖棱褶皱及扇状褶皱中的至少一种；更进一步地，褶皱结构可同时具有圆弧褶皱、尖棱褶皱及扇状褶皱。
褶皱结构根据轴面产状和两翼产状分类，褶皱结构可选自直立褶皱、斜歪褶皱、倒转褶皱及平卧褶皱中的至少一种；更进一步地，褶皱结构可同时具有直立褶皱、斜歪褶皱、倒转褶皱和平卧褶皱。
石墨烯层具有上述形态的褶皱结构，能够提供更多的活性位点，从而进一步提升负极材料的导电性、倍率性能。
在一些实施方式中，碳层包括非晶碳层，非晶碳层的厚度为5nm～150nm；
在一些实施方式中，以复合负极材料质量百分含量为100％计，碳的质量百分比含量为2％～50％；
在一些实施方式中，包覆层包括金属氧化物层，金属氧化物层中的金属包括Ti、 V、Nb、Ta、W和Zr中的至少一种；
其中，金属氧化物层中的金属元素与氧元素的摩尔比为1：(0.1-3)；金属氧化物层的厚度为1nm-200nm；
以复合负极材料质量百分含量为100％计，金属氧化物的质量百分比含量为2％～60％；
在一些实施方式中，包覆层包括金属氮化物层，金属氮化物层中的金属元素包括Ti、V、Nb、Ta、W和Zr中的至少一种，进一步地，金属氮化物层厚度为1nm～250nm。
以复合负极材料质量百分含量为100％计，金属氮化物的质量百分比含量为2％～70％。
金属氧化物层及其氮化物层充当刚性保护壳，避免一次颗粒的体积膨胀撑破整个材料，保证优异的结构稳定性和长的循环寿命。
在一些实施方式中，如图3a所示，该负极材料还包括保护层30，保护层30位于骨架表面。即该负极材料包括一次颗粒保护层。
位于骨架表面的保护层，能够提高导电性和稳定性，有利于锂离子进出，提高负极材料的倍率性能。
可以理解地，该一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架11及自主骨架11延伸至一次颗粒表面的多个分枝12；该一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道13；可以理解地，该一次颗粒内部形成有通孔，一次颗粒的孔隙率不低于30％。
在本实施例中，一次颗粒的具体结构(骨架结构、孔结构)以及性能参数(孔隙率、中值粒径、比表面积、粉体振实密度、粉体压实密度、)如前面实施方式所述，在此不再重复阐述。
在一些实施方式中，保护层包括碳层、金属氧化物层、金属氮化物层中的至少一种；
在一些实施方式中，碳层为无定形碳层及/或石墨碳层；
在一些实施方式中，碳层仅位于骨架表面，以所述复合负极材料质量百分含量为100％计，碳质量百分含量为5％～25％；具体可以是5％、8％、10％、12％、15％、18％、20％或25％，在此不做限定。
在一些实施方式中，碳层的厚度为1nm～300nm。
在一些实施方式中，参阅图3b，当保护层含量较高时，保护层还填充孔道内，可进一步加强导电性和结构稳定性。
具体地，碳层还填充于孔道内；填充在孔道结构内的碳可以提供更多的离子和电子传输路径，具有好的碳导电性，有利于锂离子进出，提高材料的倍率性能，且可进一步提高稳定性。
在一些实施方式中，当碳层位于骨架表面并填充孔道内时，以复合负极材料质量百分含量为100％计，碳质量百分含量为25％～75％且不包括25％；具体可以是25％、28％、30％、35％、40％、45％、50％或75％，在此不做限定。
在一些实施方式中，保护层包括金属氧化物层，金属氧化物层的金属元素包括Si、Sn、Ge、Li、V、Al、Fe和Zn中的至少一种；金属氧化物层具有刚性好，致密 性优等优点，可以有效抑制N的体积膨胀而导致的整个结构破坏，减少材料的体积膨胀同时避免电解液与N材料接触，减少副反应，提高整个复合材料的首效。
以复合负极材料质量百分含量为100％计，当金属氧化物层仅位于所述骨架表面时，金属氧化物质量百分含量为5％～25％。
当金属氧化物层位于所述骨架表面并填充孔道内时，以复合负极材料质量百分含量为100％计，金属氧化物质量百分含量为25％～75％且不包括25％。
保护层包括金属氮化物层，金属氮化物层中的金属元素包括Ti、V、Nb、Ta、W和Zr中的至少一种；金属氮化物层不仅刚性好，而且导电性优异，可以有效缓解硅的体积膨胀同时增加材料的导电性，提高材料的倍率性，减少材料不可逆容量损失，带来高的容量。
以复合负极材料质量百分含量为100％计，当金属氮化物层仅位于骨架表面，金属氮化物质量百分含量为5％～25％。
当金属氮化物位于骨架表面并填充孔道内，以复合负极材料质量百分含量为100％计，金属氮化物质量百分含量为25％～75％且不包括25％。
如图3b所示，在一些实施方式中，碳层还填充于一次颗粒的通孔内；填充在通孔内的碳可以提供更多的离子和电子传输路径，具有好的碳导电性，有利于锂离子进出，提高材料的倍率性能，且可进一步提高稳定性。
在一些实施方式中，当碳层位于骨架表面并填充通孔内时，以复合负极材料质量百分含量为100％计，碳质量百分含量为25％～75％且不包括25％；具体可以是25％、28％、30％、35％、40％、45％、50％或75％，在此不做限定。
在一些实施方式中，保护层为金属氧化物层，金属氧化物层的金属元素包括Si、Sn、Ge、Li、V、Al、Fe和Zn的氧化物中的至少一种。
以复合负极材料质量百分含量为100％计，当氧化物层位于骨架表面并填充所述通孔内时,金属氧化物质量百分含量为25％～75％且不包括25％。
在一些实施方式中，保护层为金属氮化物层，金属氮化物层中的金属元素包括Ti、V、Nb、Ta、W和Zr中的至少一种。
在一些实施方式中，当金属氮化物层位于骨架表面并填充所述通孔内时，金属氮化物质量百分含量为25％～75％且不包括25％。
在一些实施方式中，负极材料的中值粒径为0.1μm～15μm，可选地，负极材料的中值粒径具体可以是0.1μm、0.5μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm或10μm等，在此不做限定。复合负极材料的中值粒径优选为0.5μm～10μm，更优选为1μm～8μm。
在一些实施方式中，负极材料的比表面积比为1m 2/g～150m 2/g。可选地，负极材料的比表面积比可以是1m 2/g、5m 2/g、10m 2/g、20m 2/g、30m 2/g、40m 2/g、50m 2/g、60m 2/g、70m 2/g、100m 2/g、120m 2/g或150m 2/g等，在此不做限定；复合负极材料的比表面积比优选为1m 2/g～50m 2/g。可以理解地，比表面积越小越好，过大的比表面积容易导致SEI膜形成，消耗不可逆锂盐过多，降低电池的首次效率低，综合考虑制备工艺的成本，将比表面积控制在10m 2/g～50m 2/g。
在一些实施方式中，负极材料的孔隙率为10％～70％，具体可以是10％、30％、 35％、40％、50％、55％、60％或70％等，优选为40％～60％。
在一些实施方式中，如图4a所示，负极材料还包括位于一次颗粒10表面的纳米颗粒层40及包覆于纳米颗粒层表面的包覆层50，纳米颗粒层40形成有微孔和/或介孔。
可以理解地，该实施方式的负极材料包括内核及位于所述内核表面的包覆层50；其中，内核包括一次颗粒10及位于一次颗粒10表面的纳米颗粒层40；纳米颗粒层40形成有微孔和/或介孔。
该一次颗粒10包括骨架，骨架包括位于一次颗粒的内部的主骨架11及自主骨架11延伸至一次颗粒10表面的多个分枝12；一次颗粒10为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道13。
纳米颗粒层由纳米颗粒组成，纳米颗粒可以有效避免材料粉化；纳米颗粒层形成有微孔和/或介孔，可以有效缓解材料的体积膨胀，同时促进电解液浸润和接触面，加快锂离子传输，提升整个材料的倍率性能，同时保证负极材料内部的一次颗粒的结构稳定性。采用包覆层包覆后，具有更好的导电性和稳定性，可以有效避免碳填充材料内部孔隙，提高材料首效，使得负极材料能够表现出高容量、长循环寿命、高倍率性能以及低膨胀等特性。
在本实施例中，一次颗粒的具体结构(骨架结构、孔结构)以及性能参数(中值粒径、比表面积、粉体振实密度、粉体压实密度等参数)如第一方面所述，在此不再重复阐述。
如图4b所示，纳米颗粒层40包括多个纳米颗粒41，多个纳米颗粒41相互堆叠。纳米颗粒41的形状可以是球形、类球形、扁平状或其他任意形状，在此不做限定。纳米颗粒41之前形成有微孔42和/或介孔43，微孔的孔径小于2nm，介孔的孔径大于2nm且小于50nm，可以理解地，微孔与介孔的孔径小于一次颗粒孔道的孔径。
在一些实施方式中，纳米颗粒选自纳米硅颗粒、纳米锗颗粒、纳米锑颗粒、纳米锡颗粒、纳米硼颗粒中的至少一种。
在一些实施方式中，负极材料的孔隙率为30％～70％，具体可以是30％、40％、50％、60％或70％，在此不做限定，复合负极材料的孔隙率优选为40％～60％。
在一些实施方式中，一次颗粒10的孔隙率为15％～75％，具体可以是15％、20％、35％、40％、50％、60％或75％，在此不做限定。
在一些实施方式中，纳米颗粒层的孔隙率为5％～35％，具体可以是5％、10％、15％、20％、25％、30％或35％；在本实施例中，纳米颗粒层的介孔的总孔隙率与微孔的总孔隙率比值为(2～10)：1。可以理解地，纳米颗粒层中的介孔数量多于微孔数量。介孔数量多于微孔数量，有利于电解液的流通。
可以理解地，纳米颗粒41形成于一次颗粒10表面，并且与一次颗粒10紧密结合，形成纳米颗粒层40，纳米颗粒层40与一次颗粒10之间有明显的晶界，并不是范德华力结合，其结合力更高，一次颗粒10与纳米颗粒层40连接更稳定，整体结构也更稳定。
更具体地，孔道在所有孔结构中的体积占比为35％～90％，介孔在所有孔结构中 的体积占比为5％～45％，微孔在所有孔结构中的体积占比为5％～20％。
上述所有孔结构中的开孔体积占比为60％～95％，闭孔体积占比为5％～40％，其中，开孔按孔结构类型可以分为交联孔、通孔及盲孔，在所有孔结构的开孔中，交联孔占所有开孔的体积占比为79％～95％，通孔占所有开孔的体积占比为4％～20％，盲孔占所有开孔的体积占比为1％～10％。
需要说明的是，盲孔是连接一次颗粒表层和内层而不贯通一次颗粒的导通孔，交联孔由多个孔道交叉形成。可以理解地，占比较多的交联孔可以给电解液提供流通的通道，电解液可以沿交联孔在一次颗粒中流通，在提高硅储锂性能的同时降低锂电池的膨胀，通孔也可以给电解液提供流体的流道，但是会降低电解液流通速率，所以通孔的体积占比应少于交联孔的体积占比。进一步地，盲孔不利于电解液流通，流入盲孔内的电解液只能原路径流出，在制备过程中，应尽量降低盲孔的生成。
在一些实施方式中，纳米颗粒41的中值粒径为20nm～200nm；纳米颗粒41的中值粒径具体可以是20nm、40nm、50nm、60nm、80nm、100nm、150nm或200nm，当然纳米颗粒41的中值粒径也可以根据实际情况进行设置，在此不做限定。小粒径的纳米颗粒41包裹在一次颗粒的表面，可以避免碳层填充、堵塞孔道，增加电解液流动的通道，从而提高硅储锂性能的同时降低锂电池的膨胀。
在一些实施方式中，纳米颗粒层40的厚度为20nm～2000nm，具体可以是20nm、50nm、100nm、200nm、300nm、500nm、800nm、1000nm或2000nm等，当然纳米颗粒层40的厚度也可以根据实际情况进行设置，在此不做限定。
可以理解地，适宜厚度的纳米颗粒层40可以有效避免材料粉化，可以缓解材料的体积膨胀，保证材料内部的一次颗粒的结构稳定性。
在一些实施方式中，负极材料的中值粒径为0.1μm～15μm，可选地，具体可以是0.1μm、0.5μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm或15μm等，在此不做限定。复合负极材料的中值粒径优选为0.5μm～10μm，更优选为1μm～8μm。
在一些实施方式中，负极材料的比表面积比为1m 2/g～100m 2/g。可选地，复合负极材料的比表面积可以是1m 2/g、5m 2/g、10m 2/g、15m 2/g、20m 2/g、25m 2/g、30m 2/g、35m 2/g、40m 2/g、45m 2/g、50m 2/g、60m 2/g、80m 2/g或100m 2/g等，在此不做限定；复合负极材料的比表面积优选为10m 2/g～50m 2/g。可以理解地，过大的比表面积容易导致SEI膜形成，消耗不可逆锂盐过多，降低电池的首次效率低，综合考虑制备工艺的成本，将比表面积控制在10m 2/g～50m 2/g。
该实施方式的负极材料中的包覆层为碳层，碳层厚度为5nm～100nm，具体可以是5nm、10nm、20nm、30nm、40nm、50nm、60nm、70nm、80nm或100nm等，碳层过厚，锂离子传输效率降低，不利于材料大倍率充放电，降低负极材料的综合性能，碳层过薄，不利于增加负极材料的导电性且对材料的体积膨胀抑制性能较弱，导致长循环性能价差。
在一些实施方式中，负极材料中的碳的质量百分比含量为5％～50％，具体可以是5％、8％、10％、15％、20％、25％、30％、40％或50％，在此不做限定。可选地，碳的质量百分比含量为10％～30％。
第二方面
如第一方面所述的负极材料，该负极材料包括一次颗粒，一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架10及自主骨架10延伸至所述一次颗粒表面的多个分枝11；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道13；一次颗粒内部形成有通孔，一次颗粒的孔隙率不低于30％。
该负极材料的制备方法，如图5所示，方法包括以下步骤S11～S14：
在一实施方式提供负极材料的制备方法，方法包括步骤S11-S14。
S11、制备N-M材料。
在一些实施方式中，N-M材料包括N-M合金及N-M金属间化合物中的至少一种；其中，N-M材料中的N包括Si、Ge、Sn、B及Sb中的至少一种；N-M材料中的M包括Mg、Al、Li和Ca中的至少一种。具体的示例中，N-M材料可以为Si-Mg合金、Si-Al合金、Ge-Mg合金、Ge-Al合金等。
在一些实施方式中，将N粉与M粉混合，在保护性气氛进行加热反应，得到N-M材料。如具体的示例中，将硅粉与镁粉混合，在保护性气氛下进行加热反应，得到Si-Mg合金。
在一些实施方式中，N粉的D50为0.2μm～15μm，例如0.2μm、0.5μm、1μm、3μm、5μm、6μm、8μm、10μm、12μm、13μm或15μm等。
在一些实施方式中，所述N粉与M粉的摩尔比为1:(1.5～2.5)，例如1:1.5、1:1.8、1:2.0、1:2.1、1:2.3或1:2.5等。
进一步地，N粉为实心结构，N粉包括颗粒、球状、片状、纤维状及方块状中的至少一种。
在一些实施方式中，所述N-M材料的制备方法步骤中的所述加热反应的升温速率为1℃/min～10℃/min，例如1℃/min、3℃/min、4℃/min、5℃/min、6℃/min、8℃/min或10℃/min等。
在一些实施方式中，N-M材料的制备方法步骤中的加热反应为在400℃～900℃保温2h～8h，温度例如400℃、500℃、600℃、700℃、800℃或850℃等；时间例如2h、4h、5h、6h、7h或8h等。
在一些实施方式中，反应之后将得到的N-M材料粉碎至D50为0.2μm～15μm，例如0.2μm、1μm、2μm、3.5μm、5μm、7μm、10μm、12μm或15μm等。
在一些实施方式中，粉碎采用的设备包括行星式球磨机、砂磨机或气流粉碎机中的任意一种。
当然，N-M材料还可以通过其他制备方法制备，例如：高能球磨、真空冶炼以及热压烧结等。
可以理解，N-M材料可以通过市售获得，此时步骤S11可以省略。
S12、将N-M材料与过渡金属卤化物混合，得到混合物。
在一些实施方式中，N-M材料的D50为0.1μm～15μm，例如0.1μm、0.2μm、0.5μm、1μm、3μm、5μm、8μm、10μm、12μm或15μm等。
不同种类的N-M材料可得到不同形状的骨架单元，包括棒状纳米颗粒、纳米片、 纳米线及纳米管中的至少一种。如不同种类的硅合金可得到不同形状的骨架单元，包括棒状硅纳米颗粒、硅纳米片、硅纳米线及硅纳米管中的至少一种。
在一些实施方式中，过渡金属卤化物的化学式为ABx，其中，x＝2或3，A包括Sn、Cu、Fe、Zn、Co及Ni中的至少一种，B包括Cl、F及Br中的至少一种。
在一些实施方式中，N-M材料与过渡金属卤化物的摩尔比为1:(0.2-2)，例如1:0.2、1:0.5、1:1、1:1.2、1:1.5或1:2等。
在其中一些实施方式中，将N-M材料与过渡金属卤化物混合步骤还加入碱金属卤化物和碱土金属卤化物中的至少一种。
在一些实施方式中，碱金属卤化物和/或碱土金属卤化物的化学式为ZBy，其中，y＝1或2，Z包括Li、Na、K、Mg及Ca中的至少一种，B包括Cl、F及Br中的至少一种。
在一些实施方式中，碱金属卤化物和碱土金属卤化物中的至少一种与过渡金属卤化物的摩尔比为1:(0.2-1.5)。
碱金属卤化物和/或碱土金属卤化物高温下充当熔盐介质，一方面可以吸收反应时放出的热量，保持结构的稳定性，另一方面增加过渡金属卤化物在其中的溶解度，促进反应充分进行，提高产率和纯度。
对于本申请实施例负极材料结构形成的原因做如下说明：一、如果选择高熔点过渡金属氯化物(熔点大于反应产物M zB x熔点)参与去合金过程中，反应物M zB x(例如MgCl 2、MgF 2或MgBr 2)都处于熔融态，为相连纳米骨架的形成提供了相连的液态模板，保证了多孔负极材料孔道的连续性；如果再加入碱金属卤化物(AB x)或碱土金属卤化物(ZBy)，可以进一步降低反应温度，使得M zB x和AB x混合物熔点低于MzBx本身熔点，达到MzBx在低于熔点温度下也可以作为液态模板的目的。二、当选择熔点低于反应产物MzBx熔点的过渡金属氯化物作为反应物时，为避免此类过渡金属氯化物(例如ZnCl 2或SnCl 2)在高温下挥发，选择加入碱金属卤化物(AB x)或碱土金属卤化物(ZB y)来防止这些过渡金属氯化物挥发，促使反应充分进行；同时可以降低反应产物M zB x的熔点，降低反应温度，并保证M zB x处于熔融状态，提供连续液态模板。
可以理解，该混合物可以通过市售获得，此时步骤S12可以省略。
S13、将混合物置于保护性气氛中进行置换反应，得到反应产物，反应产物包括M的卤化物和过渡金属。
在一些实施方式中，加热反应的升温速率为1℃/min～20℃/min，例如1℃/min、3℃/min、5℃/min、8℃/min、10℃/min、12℃/min、14℃/min、16℃/min、18℃/min或20℃/min等。
在一些实施方式中，加热反应为在200℃～950℃保温2h～18h，温度例如200℃、235℃、260℃、300℃、400℃、450℃、500℃、600℃、700℃、800℃或900℃等。
在一些实施方式中，保护性气氛中的气体包括氮气、氦气、氖气、氩气、氪气及氙气中的至少一种。
S14、去除M的卤化物和过渡金属，得到负极材料。
在一些实施方式中，去除反应产物中的M的卤化物以及过渡金属的方法为：将 反应产物在酸溶液和/或过渡金属卤化物溶液中处理。处理后的产物仍可以回收循环使用。
在一些实施方式中，酸溶液中的酸包括盐酸、硝酸及硫酸中的至少一种。
在一些实施方式中，酸溶液的浓度为1mol/L～5mol/L，在酸溶液中处理的时间为1h～10h。酸溶液的浓度例如1mol/L、2mol/L、2.5mol/L、3mol/L、4mol/L或5mol/L等；处理时间例如1h、3h、5h、6h、8h、9h或10h等。
在一些实施方式中，过渡金属卤化物溶液的浓度为0.5mol/L～5mol/L，在所述过渡金属卤化物溶液中处理的时间为1h～12h。金属卤化物溶液的浓度例如0.5mol/L、1mol/L、1.5mol/L、2mol/L、2.5mol/L、3.5mol/L、4mol/L或5mol/L等；处理时间例如1h、3h、5h、6h、8h、9h、10h或11h等。
本申请实施例提供的负极材料制备方法利用N-M材料在高温下与过渡金属卤化物发生反应，之后去除N-M材料中的M得到多孔N负极材料。由于反应生成的金属的卤化物，以采用硅镁合金或硅铝合金作为原料举例，生成的金属卤化物为镁或铝的金属卤化物在反应温度下为熔融态，熔融态的卤化物具有连续性，且为相连纳米硅的形成提供了相连的液态模板，除去金属卤化物后得多孔硅，结构上硅纳米单元沿着相连的液态模板生长形成相连硅骨架，除去模板后，使形成的硅骨架在三维方向上具有连续贯通的孔道结构。本申请是一次完整颗粒，整个骨架相连，增强材料的电子传到和离子扩散，可以有效释放锂化后的应力，避免应力集中导致材料粉化，现有技术普遍为二次颗粒，即一次纳米颗粒组装或者堆垛成一个二次大颗粒的多孔硅，如石榴状硅负极，树莓状以及西瓜状硅负极，由于这些一次颗粒之间存在明显的晶界，导致锂化后应力集中，结构不稳，最终导致电化学性能恶化。
本申请实施例提供的负极材料的制备方法，具有简单易行、安全且绿色环保的突出优点，可大规模生产。只需N-M材料(如硅合金)在高温下与过渡金属卤化物发生反应后去除硅合金中的金属成分便可以得到大量的多孔硅，产率高，以过渡金属卤化物的化学式为ABx(x＝2或3，所述A包括Sn、Cu、Fe、Zn、Co及Ni中的至少一种，所述B包括Cl、F及Br中的至少一种)，硅合金的化学式为MzSi(Z＝1～3，M包括Mg和Al)为例，发生的反应方程式为ABx+MzSi＝Si+A+MzBx。
此外，该方法原料来源广、成本低，副产物可回收重复使用，可采用廉价的商业硅作为原料制备多孔硅负极材料，得到的N负极材料(Ge、B、Sn及Sb)为多孔结构且形貌和孔结构易调控。由于该反应处于液态环境中，保证了反应的充分进行，大大提高产率和产品纯度。
通过对整体工艺流程、以及各个反应步骤的参数条件(如反应物的种类及配比、反应温度及时间等)进行改进，可控制产物的形貌进而实现对性能的调控。例如，可以控制合金成分来改变孔的大小以及孔隙率(一般硅合金中硅含量越高，孔径越小)；可以控制反应时间与反应温度来改变孔的深度(一般反应时间越长、反应温度越高，孔的深度越深，当然，反应温度最高不能超过950℃，如因为反应温度过高可能导致生成的硅和过渡金属反应形成硅化物，如硅化铜或硅化镍，劣化产物性能)。
在具体的示例中，如图6所示，以硅负极材料为例，硅负极材料的制备方法，包括以下步骤：1)制备Si-M合金；2)将Si-M合金与过渡金属卤化物混合，得到 混合物，其中，所述Si-M合金中的M包括Mg、Al、Li和Ca中的至少一种；3)将所述混合物置于保护性气氛中进行置换反应，得到反应产物，所述反应产物包括M的卤化物、硅和过渡金属；4)将所述M的卤化物和过渡金属去除，得到硅负极材料。
其中，Ge、B、Sn及Sb负极材料制备方法也与上述多孔硅负极材料制备方法相似。
又一实施方式中的一种锂离子电池，所述锂离子电池包含如第一方面所述的硅负极材料。该锂离子电池具有高容量、长循环寿命以及低膨胀的优点。
实施例1
将1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金。将硅镁合金球磨后得到1μm的硅镁合金粉末，然后将1mol的硅镁合金粉末与1mol的氯化亚锡(SnCl 2)混合均匀和1mol的氯化钠(NaCl)混合均匀；将所得混合物放入氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应得到反应产物；将反应产物在1mol/L的盐酸溶液机械搅拌处理2h后，抽滤、洗涤、干燥后得到中值粒径为1μm的多孔硅负极材料。
图7a为本实施例中多孔硅负极材料的电镜图片；图7b为本实施例中多孔硅负极材料的XRD图。
从图7a中可以看出，制得的硅负极材料为一次颗粒，所述一次颗粒包括硅骨架，硅骨架包括位于所述一次颗粒的内部的主骨架及自所述主骨架延伸至所述一次颗粒表面的多个分枝，一次颗粒为大孔结构，一次颗粒的内部形成有孔道，孔道延伸至所述一次颗粒的表面。从图7b中酸洗后样品XRD衍射图谱可知，在28.4°、47.3°和56.1°的三强峰与硅(JCPDS No.27-1402)的三强峰相对应，并基本无杂相。
实施例2
将1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到650℃后保温3h，使其充分反应得到硅镁合金。将硅镁合金球磨后得到0.5μm的硅镁合金粉末，然后将1mol的合金粉末与1mol的氯化铜(CuCl 2)混合均匀；将所得混合物放入氩气气氛中以3℃/min的升温速率加热到800℃后保温6h使其充分反应得到反应产物；将反应产物放入在1L的2mol/L氯化铁溶液中机械搅拌处理3h后，抽滤、洗涤、干燥后得到中值粒径为0.5μm的多孔硅负极材料。
实施例3
将1.5μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金。将硅镁合金球磨后得到1μm的硅镁合金粉末，然后将1mol的合金粉末与1mol的氯化亚锡(SnCl 2)和1mol的氯化锂(LiCl)混合均匀；将所得混合物放入氩气气氛中以3℃/min的升温速率加热到400℃后保温8h使其充分反应得到反应产物；将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌处理3h后，抽滤、洗涤、干燥后得到中值粒径为1.2μm的多孔硅负极材料。
实施例4
将1.5μm的硅粉与铝粉按摩尔比为1:1.5混合均匀后放入气氛炉，在氩气惰性气体保护下以10℃/min的升温速率加热到650℃后保温6h，使其充分反应得到硅铝合金。将硅铝合金球磨后得到2μm的硅铝合金粉末，然后将1mol的合金粉末与0.8mol的氯化亚锡(SnCl 2)混合均匀；将所得混合物放入氩气气氛中以5℃/min的升温速率加热到600℃后保温6h使其充分反应得到反应产物；将反应产物放入在1L的1mol/L盐酸溶液中机械搅拌处理2h后，抽滤、洗涤、干燥后得到中值粒径为2μm的多孔硅负极材料。
实施例5
将1.5μm的硅粉与铝粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以10℃/min的升温速率加热到650℃后保温6h，使其充分反应得到硅铝合金。将硅铝合金球磨后得到1μm的硅铝合金粉末，然后将1mol的合金粉末与1mol的溴化亚锡(SnBr 2)混合均匀；将所得混合物放入氩气气氛中以5℃/min的升温速率加热到650℃后保温6h使其充分反应得到反应产物；将反应产物放入在1L的1mol/L盐酸溶液中机械搅拌处理5h后，抽滤、洗涤、干燥后得到多孔硅负极材料。
实施例6
将2.5μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以10℃/min的升温速率加热到650℃后保温6h，使其充分反应得到硅镁合金。将硅镁合金球磨后得到1μm的硅镁合金粉末，然后将1mol的合金粉末与1mol的溴化亚锡(SnBr2)和1mol的溴化钾(KBr)混合均匀；将所得混合物放入氩气气氛中以5℃/min的升温速率加热到450℃后保温6h使其充分反应得到反应产物；将反应产物放入在1L的1mol/L盐酸溶液中机械搅拌处理4h后，抽滤、洗涤、干燥后得到多孔硅负极材料。
实施例7
除了将硅粉与镁粉按摩尔比调整为1:5外，其他方法和条件与实施例1相同。
实施例8
除了调整硅镁合金与氯化亚锡反应时的温度为300℃外，其他方法和条件与实施例1相同。
实施例9
除了调整硅镁合金与氯化亚锡反应时的温度为850℃外，其他方法和条件与实施例1相同。
实施例10
将1.5μm的硅粉与铝粉按摩尔比为1:1.5混合均匀后放入气氛炉，在氩气惰性气体保护下以10℃/min的升温速率加热到650℃后保温6h，使其充分反应得到硅铝合金。将硅铝合金球磨后得到2μm的硅铝合金粉末，然后将1mol的合金粉末与0.8mol的氯化锌(ZnCl 2)混合均匀；将所得混合物放入氩气气氛中以5℃/min的升温速率加热到600℃后保温6h使其充分反应得到反应产物；将反应产物放入在1L的1mol/L盐酸溶液中机械搅拌处理2h后，抽滤、洗涤、干燥后得到中值粒径为2μm的硅负极材料。
实施例11
将1μm的锗粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的升温速率加热到650℃后保温6h，使其充分反应得到锗镁合金。将锗镁合金球磨后得到1μm的锗镁合金粉末，然后将1mol的锗镁合金粉末与1mol的氯化亚锡混合均匀和1mol的氯化钠混合均匀；将所得混合物放入氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应得到反应产物；将反应产物在1mol/L的盐酸溶液机械搅拌处理2h后，抽滤、洗涤、干燥后得到中值粒径为1μm的多孔锗负极材料。
实施例12
将1μm的硼粉与镁粉按摩尔比为2:1混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硼镁合金。将硼镁合金球磨后得到1μm的硼镁合金粉末，然后将1mol的硼镁合金粉末与1mol的氯化锌混合均匀和1mol的氯化钾混合均匀；将所得混合物放入氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应得到反应产物；将反应产物在1mol/L的盐酸溶液机械搅拌处理2h后，抽滤、洗涤、干燥后得到中值粒径为1μm的多孔硼负极材料。
实施例13
将1μm的锡粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的升温速率加热到650℃后保温6h，使其充分反应得到锡镁合金。将锡镁合金球磨后得到1μm的锡镁合金粉末，然后将1mol的锡镁合金粉末与1mol的氯化锌混合均匀和1mol的氯化钾混合均匀；将所得混合物放入氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应得到反应产物；将反应产物在1mol/L的盐酸溶液机械搅拌处理2h后，抽滤、洗涤、干燥后得到中值粒径为1μm的多孔锡负极材料。
实施例14
将1μm的碲粉与镁粉按摩尔比为1:1混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的升温速率加热到600℃后保温6h，使其充分反应得到碲镁合金。将碲镁合金球磨后得到1μm的碲镁合金粉末，然后将1mol的碲镁合金粉末与1mol的氯化铜混合均匀和1mol的氯化钠混合均匀；将所得混合物放入氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应得到反应产物；将反应产物在1mol/L的盐酸溶液机械搅拌处理2h后，抽滤、洗涤、干燥后得到中值粒径为1μm的多孔碲负极材料。
对比例1
本对比例为专利CN 105399100 A的实施例1，制备得到的纳米多孔硅的扫描电镜图如图7e，得不到多孔硅结构。
对比例2
除了不加入氯化亚锡外，其他方法和条件与实施例1相同。
性能测试：
采用以下方法对各实施例1～14(记为S1～S14)和对比例1～2(记为R1～R2)的负极材料进行测试：
振实密度采用康塔AutoTap振实密度仪测试。
采用美国麦克仪器公司的Tristar3000全自动比表面积和孔隙度分析仪测试材料的比表面积。
孔隙率：采用美国麦克仪器全自动压汞仪AutoPoreⅣ9510进行孔隙率测试粉体压实密度：采用国产粉末压实密度测定仪FT-100F，按照标准：GBT 24533-2009进行测试。
扣电首周性能测试：扣电首周测试在蓝电CT2001A电池测试系统上进行，充放电电流为0.05C。
循环测试：在蓝电CT2001A电池测试系统上对扣电进行循环测试，电流为0.2C，循环150圈。
测试结果如表1和表2所示：
表1
Figure PCTCN2021109137-appb-000001
表2
Figure PCTCN2021109137-appb-000002
Figure PCTCN2021109137-appb-000003
表中“-”表示无。
图7c为本实施例中多孔硅负极材料的首次充放电曲线，充放电电流为0.05C，采用半电池测试；图7d为本实施例的多孔硅负极材料循环性能曲线，充放电电流为0.2C。图7c和图7d中可以看出材料具有较高的首次充放电效率并且具有优异的循环性能。实施例7-实施例9调变了反应物摩尔比，反应温度和时间，依然可以得到多孔硅，但是性能相对于实施例1有一定的下降。
根据表1至表2的测试数据可知，通过实施例7与实施例1对比，硅粉与镁粉的摩尔比增大，孔隙率更多，振实密度降低，首效降低，能量密度降低。
实施例8与实施例1对比，温度过低，反应不充分，结构不均匀，内外孔结构不一致，结构不稳定，循环性能降低。
实施例9与实施例1对比，温度过高，晶粒尺寸变大，硅骨架变粗，易粉化，首效降低，循环性能降低。
通过实施例1与对比例1对比，实施例1中得到的多孔硅比表面积相对对比例1的较小，对比例1中采用氯化锌，反应温度为300℃，该温度下产生的氯化镁为固态颗粒状，是固态模板，导致最终的多孔硅是由纳米硅颗粒堆积而成，最终导致比表面积较大，首效降低；而实施例1反应温度为750℃，生成的氯化镁为连续液态状，是相连的液态模板，导致多孔硅是骨架结构，大大降低材料的比表面积，提高首效。
通过实施例1与对比例2对比，不加入氯化亚锡无法制备出多孔硅。
实施例11-14通过与实施例1相似方法，改变原料分别制备出具有骨架结构的多孔锗、多孔硼、多孔锡以及多孔碲。
第三方面
如第一方面所述的负极材料，包括一次颗粒和包覆层，包覆层为碳层时，该负极材料的制备方法，如图8所示，包括以下步骤S21～S24：
S21、制备N-M合金；
在一些实施方式中，N-M合金中的N包括Si、Ge、Sn、B及Sb中的至少一种；N-M合金中的M包括Mg、Al、Zn和Ca中的至少一种。具体的示例中，N-M合金 可以为Si-Mg合金、Si-Al合金、Ge-Mg合金、Ge-Al合金等。不同种类的合金可得到不同形状的分枝，包括棒状纳米颗粒、纳米片、纳米线及纳米管中的至少一种。
在一些实施方式中，N-M合金制备方法为将N粉和活泼金属M混合后在保护性气体下加热反应，制得N-M合金。
其中，所述N粉的粉末粒径为0.1μm～15μm，具体可以是0.1μm、0.5μm、1μm、3μm、5μm、8μm、10μm或15μm等，在此不做限定。
活泼金属M的粉末粒径为0.1μm～80μm，具体可以是0.1μm、5μm、10μm、20μm、40μm、50μm或80μm等，在此不做限定。
N粉与活泼金属M的摩尔比为1：(1～3)，具体可以是1:1、1:1.5、1:2、1:2.5或1:3，在此不作限定。
加热反应的温度为400℃～900℃，具体可以是可以是400℃、500℃、600℃、700℃、800℃或900℃。
加热反应的保温时间为2h～8h，具体可以是可以是2h、4h、6h或8h，在此不做限定。
加热反应的升温速率为1℃/min～10℃/min，具体可以是可以是1℃/min、3℃/min、5℃/min、8℃/min或10℃/min，在此不作限定。
在本申请中，通过控制硅粉粒径、活泼金属粒径、反应温度、反应时间等参数，有利于N-M合金的生成，提高N-M合金的金属元素的掺杂均匀性。
当然，N-M合金还可以通过其他制备方法制备，具体可以是：高能球磨、真空冶炼以及热压烧结等。可以理解，N-M合金可以通过市售获得，此时步骤S21可以省略。
在一些实施例中，N-M合金中的N的质量百分比含量为15％～60％，可选地，N的质量百分比含量可以是15％、20％、30％、40％、50％或60％，在此不做限定。在具体实施例中，N-M合金具体可以是可以是硅镁合金、硅铝合金、硅钙合金、硅锌合金中的至少一种。可以理解地，可以通过控制N-M合金的成分来改变N材料的孔道的孔的大小以及孔隙率，一般N-M合金中N含量越高，孔径越小。可以控制加热反应时间与反应温度来改变孔的深度，一般反应时间越长、反应温度越高，孔的深度越深。
在具体实施例中，所述方法还包括：
将制得的N-M合金进行粉碎处理，调整N-M合金粉末的粒径尺寸至0.1μm～15μm，具体可以是可以是0.1μm、0.5μm、1μm、2μm、5μm、10μm或15μm，在此不做限定。
具体地，粉碎处理的设备包括行星式球磨机、砂磨机及气流粉粹机中的至少一种。可以理解地，N-M合金粒径越小，其比表面积更大，去合金化热处理时能够反应能够更充分。
当然，N-M合金还可以通过其他制备方法制备，具体可以是：高能球磨、真空冶炼以及热压烧结等。可以理解，N-M合金可以通过市售获得，此时步骤S21可以省略。
在一些实施例中，N-M合金中的N的质量百分比含量为15％～60％，可选地，N 的质量百分比含量可以是15％、20％、30％、40％、50％或60％，在此不做限定。在具体实施例中，N-M合金具体可以是可以是硅镁合金、硅铝合金、硅钙合金、硅锌合金中的至少一种。可以理解地，可以通过控制N-M合金的成分来改变N材料的孔道的孔的大小以及孔隙率，一般N-M合金中N含量越高，孔径越小。可以控制加热反应时间与反应温度来改变孔的深度，一般反应时间越长、反应温度越高，孔的深度越深。
S22、将N-M合金和含卤素的六元环有机物进行混合，得到混合物。
具体地，N-M合金和含卤素的六元环有机物的摩尔比为1:(0.2-6)，具体可以是可以是1:0.2、1:0.5、1:1、1:2、1:3、1:4、1:5或1:6，在此不做限定。
具体地，含卤素的六元环有机物包括卤代环己烷及其衍生物、卤代苯、卤代苯甲酸和卤代苯胺中的至少一种。所述卤素包括氟、氯和溴中的至少一种。
卤代环己烷为六元环状烃，其结构稳定性相较于卤代苯更差，在高温下容易发生烃链断裂。卤代环己烷具体可以是可以是氯代环己烷、六氯环己烷、六溴环己烷、三氯环己烷。卤代苯具体可以是可以是三溴苯、六氯苯、六溴苯等等。卤代苯甲酸具体可以是可以是氯苯甲酸、溴苯甲酸、2-溴苯甲酸、4-溴苯甲酸、3-氯苯甲酸等等。卤代苯胺具体可以是可以是对氯苯胺、4-溴苯胺、2-氯苯胺等等。
当含卤素的六元环有机物采用卤代环己烷时，进行步骤S23之前，所述方法还包括步骤S221：
往混合物中加入裂解抑制剂，其中，所述裂解抑制剂包括酰胺类化合物和氰酸盐。所述酰胺类化合物包括碳酰胺、甲酰胺、乙酰胺、二甲基甲酰胺及内酰胺中的至少一种；所述氰酸盐包括氰酸钾、氰酸钠及氰酸铵中的至少一种。
需要说明的是，碳酰胺加热至(150℃～160℃)就会分解脱氨成为异氰酸。氰酸钾在高温(700℃～900℃)且隔绝空气时能够分解为氰氨化钾与二氧化碳，同样地，氰酸钠在550℃左右分解为氰氨化钠与二氧化碳。可以理解地，分解出来的二氧化碳气体、无机盐对环境没有危害，裂解抑制剂在高温且隔绝空气时能够发生分解反应，吸收部分反应能量，从而抑制卤代环己烷或其衍生物发生自身裂解。
在具体实施例中，N-M合金与酰胺类化合物的摩尔比为1:(0.1-10)，具体可以是可以是1:0.1、1:0.5、1:1、1:5或1:10等，在此不做限定。N-M合金与氰酸盐的摩尔比为1:(0.1-10)，具体可以是可以是1:0.1、1:0.5、1:1、1:5或1:10等，在此不做限定。
S23、将混合物在保护性气氛下进行置换反应，得到反应产物，反应产物包括M的氧化物、M的卤化物；
在具体实施例中，为了混合物充分反应，置换反应的温度为200℃～1000℃，具体可以是可以是200℃、300℃、400℃、600℃、800℃或950℃。
保温时间1h～24h，具体可以是可以是1h、3h、6h、9h、12h、15h、18h或24h，在此不做限定。
其中，当温度为200～750℃时，生成的碳层为非晶碳层；当大于750℃时，生成的碳层为褶皱石墨烯。
置换反应的加热速率为1℃/min～20℃/min，具体可以是可以是1℃/min、5℃/min、 10℃/min、15℃/min或20℃/min。从而有效提高反应效率。
可以理解地，在上述适宜的热处理的温度、时间、升温速率范围内，有助于提高去合金效率，有助于硅合金在去合金过程中形成骨架结构。
为了提高反应的安全性，在保护性气氛条件下进行置换反应，所述保护性气氛的气体包括氮气、氦气、氖气、氩气和疝气中的至少一种。保护性气体的流量可以控制在1L/min-10L/min。
S24、去除M的氧化物、M的卤化物，得到复合负极材料。
需要说明的是，反应产物包括M的卤化物、M的氧化物、碳及N，因此，需要去除反应产物中的金属氧化物及卤化物。
去除方法包括酸洗，将反应产物进行酸洗，可以去除反应产物中的金属氧化物及卤化物。
可选地，酸洗采用的酸溶液包括盐酸、硝酸及硫酸中的至少一种。
酸溶液的质量浓度为1mol/L～5mol/L，具体可以是可以是1mol/L、2mol/L、3mol/L、4mol/L或5mol/L。当然也可以根据实际需求调制酸溶液的质量浓度，在此不做限定。
酸洗的时长为1h～10h，具体可以是可以是1h、3h、5h、7h或10h。在本实施例中，酸洗的产物仍可以回收循环使用。
在本方案中，通过一步复合法制备负极材料，高温下N-M合金与六元环有机物直接反应，去除N-M合金中的金属M成分，同时在N材料表面原位沉积碳层。整体反应温和且没有副产物，N材料结构完整、稳定，碳层沉积均匀。参与反应的原材料都是常用的合金、有机物以及金属盐，能够降低成本。
在本方案中，石墨烯层和非晶碳层是原位生长形成的。以含有卤素的六元环有机物为碳源和N-M合金在一步去合金制备出复合负极材料，该方法利用N-M合金中在高温下产生的金属蒸气具有较强的还原性，与六元环有机物发生反应后去除N-M合金中的金属M成分，自身六元环原位生长且有序自组装形成褶皱石墨烯层或者非晶碳层，酸洗后得到褶皱石墨烯或者非晶碳层包裹N材料，采用一步复合法制备得到复合负极材料，能够有效提高制备效率，制备方法简单易行，绿色环保，制备过程可控程度高，成本低且可以大规模生产。制备得到复合负极材料具有容量高、充放电循环稳定性高、膨胀率低等优点，能够广泛应用于锂电池中。需要说明的是，一步复合法是指硅材料制备与碳包覆同时进行，其制备效率高于两步复合法。
该实施方式的方法制备得到的复合负极材料包括内核10及形成于内核10表面的包覆层20，包覆层20为碳包覆层。其中，
内核10为一次颗粒，一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架11及自主骨架11延伸至一次颗粒表面的多个分枝12。
该实施方式的内核10为一次颗粒，一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道13。
该一次颗粒内部形成有通孔，一次颗粒的孔隙率不低于30％。
示例性地，图5为硅碳复合负极材料的合成流程示意图。
当包覆层为金属氧化物层时，一实施方式的负极材料的制备方法，包括以下步骤S21′～S24′：
S21′、制备N1-M1材料；
在一些实施方式中，N1-M1材料为金属间化合物及合金中的至少一种。
其中，N1-M1材料中的N1包括硅、锗、锑、锡、硼中的至少一种；N1-M1材料中的M1包括镁、铝、钙和锌中的至少一种。
具体地，N1-M1合金的制备方法同步骤S11；在此不做详细描述；
S22′、在N1-M1材料表面形成金属氧化物层，得到复合物；
在具体实施例中，金属氧化物层的金属元素包括Ti、V、Nb、Ta、W和Zr中的至少一种。金属氧化物层中金属元素与氧元素的摩尔比为1：(0.1-3)。
在一些实施方式中，金属氧化物层的厚度为1nm-200nm。
具体地，所述N1-M1材料和金属氧化物层的金属氧化物的摩尔比为1:(0.01-5)，具体可以是可以是1:0.02、1:0.05、1:1、1:2、1:3、1:4或1:5，在此不做限定。
具体地，在N1-M1材料表面形成金属氧化物层方法采用本领域常规的方法，如可为水热法，溶胶凝胶法、沉淀法、化学气相沉积法、磁控溅射或固相反应法。
S23′、将复合物至于真空环境下进行置换反应，得到反应产物。
具体地，反应产物包括M1的氧化物、N1、金属氧化物。
在一些实施方式中，真空环境下的真空度小于1000Pa。
置换反应的温度为500℃～1100℃，具体可以是可以500℃、600℃、700℃、800℃、900℃或1200℃。
置换反应的保温时间为1h～48h，具体可以是可以是1h、24h、36h或48h，在此不做限定。
还原反应的升温速率为1℃/min～20℃/min，具体可以是可以是1℃/min、3℃/min、5℃/min、8℃/min或20℃/min，在此不作限定。
S24′、去除所述M1的氧化物，得到复合负极材料。
具体地，去除M1的氧化物的方法包括酸洗。
进一步地，酸洗采用的酸溶液包括盐酸、硝酸及硫酸中的至少一种。
酸溶液的质量浓度为1mol/L～5mol/L，具体可以是可以是1mol/L、2mol/L、3mol/L、4mol/L或5mol/L。当然也可以根据实际需求调制酸溶液的质量浓度，在此不做限定。
酸洗的时长为1h～10h，具体可以是可以是1h、3h、5h、7h或10h。在本实施例中，酸洗的产物仍可以回收循环使用。
在本实施方式中，通过在N1-M1材料表面包覆一层金属氧化层，高温下N1-M1材料与部分金属氧化层发生置换反应，去除N1-M1材料中的M1成分，同时在N1材料表面生成未完全反应的金属氧化层，酸洗后便可得到复合负极材料。在本方案中，金属氧化物层具有刚性好，致密性优等优点，现价与柔性的碳层材料，可以有效抑制N1的体积膨胀而导致的整个结构破坏，减少材料的体积膨胀同时避免电解液与硅负极接触，减少副反应，提高整个复合材料的首效。
本申请实施例提供的负极材料的制备方法制备得到复合负极材料能够有效提高锂电池充放电循环的稳定性，具有高容量、长循环寿命、首效高以及低膨胀等多个优点。
该实施方式的方法制备得到的复合负极材料包括内核10及形成于内核10表面 的包覆层20，包覆层20为金属氧化层。
当包覆层为金属氮化物层时，一实施方式的负极材料的制备方法，包括以下步骤S21″～S24″：
S21″、制备N1-M1材料；
S22″、在N1-M1材料表面形成金属氧化物层，得到复合物；
其中步骤S21″与S22″如同上述步骤S21′与S22′，在此不做重复描述。
S23″、将复合物在保护气氛下进行热处理后再进行氮化处理，得到反应产物；
其中，反应产物包括M1的氧化物、N1、金属氧化物。
其中，保护气氛中热处理温度为500-800℃，保温时间1h～24h，热处理的反应加热速率为1～20℃/min。
保护性气氛包括氦气、氖气、氩气、氪气及氙气中的至少一种。
具体地，氮化处理中，处理温度为400-950℃，保温时间为2h～24h；氮化气氛为氨气气氛、等离子氮气气氛中的至少一种。
S24″、去除M1的氧化物，得到复合负极材料；
去除M1的氧化物的方法如同步骤S24′在此不做重复描述。
该实施方式的方法制备得到的复合负极材料包括内核10及形成于内核10表面的包覆层20；包覆层20为金属氮化层。
在本实施方式中，通过在N1-M1材料表面包覆一层金属氧化层后，在保护气氛下热处理，一方面保证N1-M1材料与部分金属氧化层发生置换反应，去除N1-M1材料中的金属M1成分；另一方面，保证氧化物在高温常压下由非晶转化为晶体。进一步通过氮化处理使得在内核表面的金属氧化层被氮化为金属氮化物，紧接着酸洗后便可得到复合负极材料。在本方案中，金属氮化物层不仅刚性好，而且导电性优异，可以有效缓解硅的体积膨胀同时增加材料的导电性，提高材料的倍率性，减少材料不可逆容量损失，带来高的容量。
示例性地，图9为硅/金属氧化物及硅/金属氮化物复合负极材料的合成流程示意图。
本申请实施例提供的负极材料的制备方法制备得到复合负极材料能够有效提高锂电池充放电循环的稳定性，具有高容量、长循环寿命、倍率性能好以及低膨胀等多个优点。
下面分多个实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。在不变主权利的范围内，可以适当的进行变更实施。
实施例15
一种硅碳负极材料的制备方法，包括以下步骤：
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末。
(2)将1mol的硅镁合金粉末与1mol的六氯环己烷混合均匀，再加入碳酰胺、氰酸钾和氰酸钠各1mol，得到混合物。
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，抽真空到10pa，然后将 反应釜在氩气气氛中以3℃/min的加热速率加热到780℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到硅碳复合负极材料。
所得的硅碳复合负极材料的中值粒径约为1μm，比表面积为53m 2/g，孔隙率为48％，碳的质量百分比含量为12％。
图10a、图10b为硅碳复合负极材料的扫描电镜图片，图11a为本实施例提供的硅碳复合负极材料的拉曼图；图11b为本实施例提供的硅碳复合负极材料的XRD图，从图10a、图10b中的扫描电镜图片可以看出，所得产物的硅碳复合负极材料包括内核及形成于所述内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道。
包覆层为2nm褶皱石墨烯。孔道的平均直径约为100nm，孔道的深度约为700nm。
图11a的拉曼图谱进一步证明在2680cm -1附近存在一个2D峰，这是石墨的特征峰，进一步说明原位生成的碳为类石墨碳，具有更好的导电性和稳定性。从图11b的XRD图谱中可以看出在28.4°、47.3°和56.1°的三强峰与硅(JCPDS No.27-1402)的三强峰相对应，基本无杂相。图11c为复合负极材料制成的电池的循环性能曲线图，可见该复合负极材料具有优异的循环性能。
实施例16
一种硅碳负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到650℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末与1mol的六氯苯混合均匀，得到混合物。
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，抽真空到100pa，然后将反应釜在氩气气氛中以3℃/min的升温速率加热到650℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到多孔硅复合负极材料。
硅碳复合负极材料的中值粒径约为0.6μm，比表面积为79m 2/g，孔隙率为56％，碳的质量百分比含量为20％。
硅碳复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括硅骨架，骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道。
包覆层为10nm非晶碳层，孔道的平均直径约为130nm，孔道的深度约为800nm。
实施例17
一种硅碳负极材料的制备方法，包括以下步骤：
(1)将12μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到10μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末与1mol的六氯苯混合均匀，得到混合物。
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，抽真空到100pa，然后将反应釜在氩气气氛中以3℃/min的升温速率加热到800℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到多孔硅复合负极材料。
所得的硅碳复合负极材料的中值粒径约为10μm，比表面积为43m 2/g，孔隙率为61％，碳的质量百分比含量为15％。
硅碳复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒为大孔结构，一次颗粒形成有延伸至所述一次颗粒表面的孔道。
包覆层为5nm褶皱石墨烯层，三维孔道的平均直径约为110nm，三维孔道的孔深度约为670nm。
实施例18
一种硅碳负极材料的制备方法，包括以下步骤：
(1)将1μm的硅粉与镁粉按摩尔比为1:1.2混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末与0.5mol的六氯苯混合均匀，得到混合物；
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，抽真空到10pa，然后将反应釜在氩气气氛中以3℃/min的升温速率加热到800℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到复合负极材料。
所得的硅碳复合负极材料的中值粒径约为1μm，比表面积为38m 2/g，孔隙率为47％，碳的质量百分比含量为5％。
硅碳复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道；包覆层为4nm褶皱石墨烯层；孔道的平均直径约为65nm，三维孔道的深度约为680nm。
实施例19
一种硅碳负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到800℃后保温6h，使其充分反应得到 硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末与4mol的六氯苯混合均匀，得到混合物。
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，抽真空到100pa，然后将反应釜在氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到复合负极材料。
所得的硅碳复合负极材料的中值粒径约为0.5μm，比表面积为80m 2/g，孔隙率为53％，碳的质量百分比含量为22％。
硅碳复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至所述一次颗粒表面的孔道；包覆层为6nm褶皱石墨烯层。孔道的平均直径约为130nm，孔道的深度约为940nm。
实施例20
一种锗碳负极材料的制备方法，包括以下步骤：
(1)将1.5μm的锗粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到480℃后保温6h，使其充分反应得到锗镁合金；将锗镁合金球磨后得到0.5μm的锗镁合金粉末；
(2)将1mol的锗镁合金粉末与3mol的六氯苯混合均匀，得到混合物。
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，抽真空到100pa，然后将反应釜在氩气气氛中以3℃/min的升温速率加热到600℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到复合负极材料。
所得的锗碳复合负极材料的中值粒径约为0.6μm，比表面积为75m 2/g，孔隙率为63％，碳的质量百分比含量为18％。
锗碳复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括锗骨架，锗骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道；包覆层为12nm非晶碳层。三维孔道的平均孔直径约为120nm，三维孔道的孔深度约为35nm。
实施例21
一种硅碳负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末、2.6mol的氯代环己烷及0.5mol的碳酰胺混合均匀，得到混合物；
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，抽真空到100pa，然后将反应釜在氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到多孔硅复合负极材料。
所得的硅碳复合负极材料的中值粒径约为0.5μm，比表面积为64m 2/g，孔隙率为53％，碳的质量百分比含量为19％。
硅碳复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道；包覆层为3.2nm褶皱石墨烯层，孔道的平均直径约为110nm，孔道的深度约为780nm。
实施例22
一种硅负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末、0.7g纤维素溶于500ml无水乙醇中分散均匀后得到混合溶液；
(3)将3g钛酸四丁酯合逐滴加入到上述混合溶液中，加热至80℃后快速搅拌3小时后进行抽滤，在60℃条件下真空干燥24小时后得到氧化钛前驱体包裹硅镁合金复合物；
(4)将上述复合物放入密封不锈钢反应釜中，抽真空到100pa，然后将反应釜在氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在4L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到多孔硅/氧化钛复合负极材料。
所得的复合负极材料的中值粒径约为0.6μm，比表面积为44m 2/g，孔隙率为43％，氧化钛的质量百分比含量为12％。
复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道；包覆层为氧化钛层。孔道的平均直径约为20nm，孔道的深度约为150nm。
实施例23
一种硅负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末、0.7g纤维素溶于500ml无水乙醇中分散均匀后得到混合溶液；
(3)将4g钛酸四丁酯合逐滴加入到上述混合溶液中，加热至80℃后快速搅拌3小时后进行抽滤，在60℃条件下真空干燥24小时后得到氧化钛前驱体包裹硅镁合金复合物；
(4)将上述复合物放入管式气氛炉中，在氩气气氛中以3℃/min的升温速率加热到650℃后保温5h使其充分反应，接着将氩气换成氨气后将温度升到800℃后保温8h后，得到反应产物；
(4)将反应产物放入在4L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到多孔硅/氮化钛复合负极材料。
所得的复合负极材料的中值粒径约为0.7μm，比表面积为40m 2/g，孔隙率为48％，氮化钛的质量百分比含量为32％。
复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道；包覆层为氮化钛层。孔道的平均直径约为50nm，孔道的深度约为400nm。
实施例24
一种硅负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)通过溶胶-凝胶过程制备五氧化二钒包裹硅镁合金，首先配置0.15M/L浓度的三异丙氧基氧化钒的酒精溶液500ml，加入30ml的乙酰丙酮，得到混合溶液；将0.5mol的硅镁合金粉末加入上述混合溶液中搅拌36小时后分散均匀后得到溶胶。
(3)溶胶进行抽滤，在60℃条件下真空干燥24小时后得到五氧化二钒前驱体包裹硅镁合金复合物；
(4)将上述复合物放入管式气氛炉中，在氩气气氛中以3℃/min的升温速率加热到600℃后保温3h使其充分反应，接着将氩气换成氨气后将温度升到750℃后保温8h后，得到反应产物；
(5)将反应产物放入在4L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到多孔硅/氮化钒复合负极材料。
所得的复合负极材料的中值粒径约为0.6μm，比表面积为51m 2/g，孔隙率为40％，氮化钛的质量百分比含量为25％。
复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道；包覆层为60nm氮化钒层。孔道的平均直径约为125nm，孔道的深度约为350nm。
实施例25
一种负极材料的制备方法，包括以下步骤：
(1)将1.5μm的锗粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到锗镁合金；将锗镁合金球磨后得到0.5μm的锗镁合金粉末；
(2)将1mol的锗镁合金粉末、0.7g纤维素溶于500ml无水乙醇中分散均匀后得到混合溶液；
(3)将3g钛酸四丁酯合逐滴加入到上述混合溶液中，加热至80℃后快速搅拌3小时后进行抽滤，在60℃条件下真空干燥24小时后得到氧化钛前驱体包裹锗镁合金复合物；
(4)将上述复合物放入密封不锈钢反应釜中，抽真空到100pa，然后将反应釜在氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在4L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到多孔锗/氧化钛复合负极材料。
所得的复合负极材料的中值粒径约为0.55μm，比表面积为41m 2/g，孔隙率为45％，氧化钛的质量百分比含量为13％。
复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括锗骨架，锗骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道；包覆层为氧化钛层。孔道的平均直径约为600nm，孔道的深度约为180nm。
实施例26
一种负极材料的制备方法，包括以下步骤：
(1)将1.5μm的锗粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到锗镁合金；将锗镁合金球磨后得到1.0μm的锗镁合金粉末；
(2)通过溶胶-凝胶过程制备五氧化二钒包裹锗镁合金，首先配置0.1M/L浓度的三异丙氧基氧化钒的酒精溶液500ml，加入30ml的乙酰丙酮，得到混合溶液；将0.5mol的锗镁合金粉末加入上述混合溶液中搅拌36小时后分散均匀后得到溶胶。
(3)溶胶进行抽滤，在60℃条件下真空干燥24小时后得到五氧化二钒前驱体包裹锗镁合金复合物；
(4)将上述复合物放入管式气氛炉中，在氩气气氛中以3℃/min的升温速率加热到600℃后保温3h使其充分反应，接着将氩气换成氨气后将温度升到750℃后保温8h后，得到反应产物；
(5)将反应产物放入在4L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到多孔锗/氮化钒复合负极材料。
所得的复合负极材料的中值粒径约为1.2μm，比表面积为52m 2/g，孔隙率为43％，氮化钛的质量百分比含量为24％。
复合负极材料包括内核及形成于内核表面的包覆层；其中，
内核为一次颗粒，一次颗粒包括锗骨架，锗骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至所述一次颗粒表面的多个分枝。一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道；包覆层为50nm氮化钒层。孔道的平均直径约为150nm，孔道的深度约为900nm。
实施例27
一种负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到650℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末与0.1mol的六氯苯混合均匀，得到混合物。
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，抽真空到100pa，然后将反应釜在氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到多孔硅复合负极材料。
所得的硅碳复合负极材料的中值粒径约为0.6μm，比表面积为79m 2/g，孔隙率为56％，碳的质量百分比含量为20％，孔道的平均直径约为130nm，孔道的深度约为800nm。
实施例28
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末。
(2)将1mol的硅镁合金粉末与2.6mol的六氯环己烷混合均匀，得到混合物。
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，抽真空到10pa，然后将反应釜在氩气气氛中以3℃/min的加热速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到硅碳复合负极材料。
所得的硅碳复合负极材料的中值粒径约为1μm，比表面积为77m 2/g，孔隙率为56％，碳的质量百分比含量为19％，一次粒子的中值粒径约为0.5μm，三维孔道的平均孔直径约为100nm，三维孔道的孔深度约为730nm，不能形成石墨烯层，碳层厚度25nm。
对比例3
采用硅碳复合负极材料SiO/C，硅碳复合负极材料的中值粒径为1.5μm，复合材料中内核为纳米硅粒子堆积的多孔硅结构，外壳为碳层包裹；其中，碳的质量百分比含量为22％，比表面积为38m 2/g，碳层厚度为50nm，硅碳复合负极材料的孔隙率为67％。即为SiOx/C负极材料，其中x＝1.0。
综上所述，实施例15～28与对比例3制得的负极材料，样本编号对应为S15～S28 及R3；负极材料的性能参数如表3所述：
表3
Figure PCTCN2021109137-appb-000004
性能测试：
将负极材料分别与羧甲基纤维素钠、丁苯橡胶以及导电石墨(KS-6)和碳黑(SP)按照比例92:2:2:2:2配置浆料，均匀涂覆与铜箔上烘干制成负极极片，在氩气气氛手套箱中组装成扣式电池，所用隔膜为聚丙烯微孔膜，所用电解液为1mol/L的六氟磷酸锂(溶剂为碳酸乙烯酯、碳酸甲乙酯和碳酸二甲酯的混合液)，所用对电极为金属锂片。
对上述15组电池在蓝电CT2001A电池测试系统上进行放电比容量测试，1小时放电的电量与电池容量的比为放电比容量。
对上述15组电池在蓝电CT2001A电池测试系统上进行首次库伦效率测试，充放电电流为0.05C，测得首次库伦效率。
对上述15组电池在蓝电CT2001A电池测试系统上进行循环100周测试，充放电电流为0.2C，循环100圈后测试计算圈后电池容量及圈后容量保持率。
其中，0.2C循环100圈后容量保持率＝第100圈循环放电容量/第一周放电容量*100％，结果如表4所示。
表4各电池的参数性能比对表
Figure PCTCN2021109137-appb-000005
Figure PCTCN2021109137-appb-000006
本申请的复合负极材料具有低膨胀、循环稳定佳优点。
由上表3～4可知，实施例27与实施例26的主要区别在于，硅镁合金与六氯苯的混合比例较低，导致硅材料表面的石墨烯层厚度大幅下降，不利于增加负极材料的导电性且对材料的体积膨胀抑制性能较弱，导致长循环性能差。
实施例28与实施例15的主要区别在于，没有加入裂解抑制剂(碳酰胺、氰酸钾和氰酸钠)，氯代环己烷在反应过程中大量分解，难以在硅材料表面沉积形成石墨烯层，导致电池的充放电比容量、首次库伦效率、圈后容量保持率等各项性能有所下降。对比例3是碳包覆的多孔硅负极材料，该材质制成的电池的0.2C循环100圈后容量及容量保持率均有所下降，并且对比例3的电极膜膨胀率也高于实施例15。
综上所述，本申请提供的硅碳负极材料的制备方法，简单易操作，制备过程安全、高效；制造成本有效降低，适于量化生产；制得的产物用作电池极片使用，具有较好的充放电循环性能。
第四方面
如第一方面所述的负极材料，包括一次颗粒和保护层，保护层为碳层，该负极材料的制备方法，如图13所示，括以下步骤S31～S34：
S31、制备N-M合金；
S32、将N-M合金和含碳铵盐混合，得到混合物；
S33、将混合物在保护性气氛下进行置换反应，得到反应产物，反应产物包括M的氮化物、M的氧化物；
S34、去除M的氧化物、M的氮化物，得到复合负极材料。
得到的复合负极材料包括一次颗粒及碳层；其中，一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；碳层位于骨架表面。
该一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道。
且该一次颗粒内部形成有通孔，一次颗粒的孔隙率不低于30％。
在本方案中，通过一步复合法制备负极材料，高温下N-M合金与含碳铵盐直接反应，去除N-M合金中的金属成分，同时在N材料表面原位沉积生成碳层，酸洗后得到复合负极材料，整体反应温和且没有副产物，N材料结构完整、稳定，碳层沉积均匀。参与反应的原材料都是常用的合金、铵盐以及常用的无机化合物，能够降低成本。
以下为负极材料的制备方法具体的描述。
步骤S31、制备N-M合金；
在一些实施方式中，N-M合金中的N包括Si、Ge、Sn、B及Sb中的至少一种；N-M合金中的M包括Mg、Al、Zn和Ca中的至少一种。
步骤S31与步骤S21大致相同，在此不做详细描述。
当然，N-M合金还可以通过其他制备方法制备，具体可以是：高能球磨、真空冶炼以及热压烧结等。可以理解，N-M合金可以通过市售获得，此时步骤S31可以省略。
在一些实施例中，所述N-M合金中的N的质量百分比含量为15％～60％，可选地，N的质量百分比含量可以是15％、20％、30％、40％、50％或60％，在此不做限定。可以理解地，可以通过控制N-M合金的成分来改变N材料的三维孔道的孔的大小以及孔隙率，一般N-M合金中N含量越高，孔径越小。可以控制加热反应时间与反应温度来改变孔的深度，一般反应时间越长、反应温度越高，孔的深度越深。
S32、将N-M合金和含碳铵盐混合，得到混合物；
需要说明的是，含碳铵盐指含有碳与铵根离子的盐。
在一些实施方式中，N-M合金与含碳铵盐混合的摩尔比为1:(0.1-10)，具体可以是1:0.1、1:0.5、1:1、1:2、1:4、1:5、1:7或1:10，在此不做限定。
具体地，含碳铵盐包括碳酸铵、碳酸氢铵及氨基甲酸铵中的至少一种；碳酸铵、碳酸氢铵及氨基甲酸铵对热不稳定，容易分解成为氨和二氧化碳，因此在反应过程中，混合物中还加入铵盐抑制剂，以抑制铵盐高温分解。
在一些实施方式中，N-M合金和铵盐分解抑制剂的摩尔比为1:(0.2-10)，具体可以是可以是1:0.2、1:0.5、1:1、1:2、1:4、1:5、1:7或1:10，在此不做限定。
在一些实施方式中，铵盐分解抑制剂包括碳酸盐和/或碳酸氢盐。
其中，碳酸盐的化学式为M yCO 3，碳酸氢盐的化学式为M(HCO 3) y，M包括Na、K、Li、Mg、Ca、Zn、及Ba中的至少一种，y＝1或2。
可以理解地，碳酸氢盐在高温下不稳定，容易分解成为碳酸盐、二氧化碳和水，分解出来的二氧化碳气体、无机盐、水对环境没有危害，吸收部分反应能量，抑制铵盐在高温下发生分解反应。
在一些实施方式中，为了提高反应充分度，还加入熔盐介质，可选地，熔盐介质 包括卤化铵盐、卤化盐中的至少一种。
所述N-M合金和卤化铵盐的摩尔比为1:(0.1-10)，具体可以是1:0.1、1:0.5、1:1、1:2、1:4、1:5、1:7或1:10，在此不做限定。所述卤化铵盐的化学式为NH 4Y，其中，Y包括Cl、Br、F和I中的至少一种。
在反应中加入铵盐分解抑制剂和适量的熔盐介质(卤化铵盐)，一方面可以通过铵盐分解抑制剂来抑制铵盐的分解，使其保持高温液态，有利于铵盐由外向里慢慢与合金反应达到去合金化的目的同时，逐渐流入N材料的孔道结构之中，作为相连骨架的液态模板，便于碳逐渐在硅材料的孔道结构中均匀沉积，加强整个复合结构的导电性和结构稳定性；另一方面熔盐可增加铵盐在其中的溶解度，促进反应充分进行，保证合金粉末与铵盐反应时的高温液态环境以及反应温度的均匀性，避免局部温度过高导致多孔结构破坏，提高产率和纯度。
加入对应的卤化铵物作为熔盐介质后，可进一步保证合金粉末与铵盐反应时的高温液态环境以及反应温度的均匀性，避免局部温度过高导致多孔结构破坏，所制得的负极材料，稳定性优异，碳复合结构均匀，表现优异的电化学性能。
同样地，N-M合金与卤化物的摩尔比为1：(0.1-10)，具体可以是1:0.1、1:0.5、1:1、1:2、1:4、1:5、1:7或1:10，在此不做限定。其中，卤化物化学式为MYa，其中a＝1，M包括Na、K、Li、Mg、Ca、Zn及Ba中的至少一种，Y包括Cl、Br、F和I中的至少一种。
S33、将混合物在保护性气氛下进行置换反应，得到反应产物，反应产物包括M的氮化物、M的氧化物。
该反应可以称为去合金化反应。
其中，置换反应的反应产物包括M的氮化物、M的氧化物、碳及N单质。示例性地，N-M合金为硅镁合金，铵盐为碳酸铵，去合金化的化学反应式为：5Mg 2Si+2(NH 4) 2CO 3→5Si+2C+4MgO+2Mg 3N 2+2H 2O+6H 2，发生反应后去除反应产物中的金属氧化物(MgO)及氮化物(Mg 3N 2)，即可得到复合负极材料。
可以理解地，选择铵盐参与去合金过程中，反应过程中铵盐处于熔融态，为相连N骨架的形成提供了相连的液态模板，保证了N骨架的孔道结构的连续性；此外铵盐作为碳源，反应后形成的碳层也是连续的填充在孔道结构中，形成三维的导电碳网络结构。由于高温下反应较为温和，铵盐中的碳氧键打断后可进行有序重组，形成碳层，提高导电性，也更有利于锂离子进出，提高材料的倍率性。
在具体实施例中，去合金化热处理在真空条件下进行，真空度为1Pa～20KPa。可以理解地，本申请实施例在高温真空环境下去合金化热处理，提高反应速率，反应更安全。
为了混合物充分反应，去合金化热处理的温度为200℃～950℃，具体可以是可以是200℃、300℃、400℃、600℃、800℃或950℃。
去合金化热处理的保温时间1h～24h，具体可以是可以是1h、3h、6h、9h、12h、15h、18h或24h，在此不做限定。
去合金化热处理的加热速率为1℃/min～20℃/min，具体可以是可以是1℃/min、5℃/min、10℃/min、15℃/min或20℃/min。从而有效提高反应效率。
可以理解地，在上述适宜的热处理的温度、时间、升温速率范围内，有助于提高去合金效率，有助于N-M合金在去合金过程中形成N骨架结构。为了提高反应的安全性，在保护性气体的保护下进行去合金化热处理，所述保护性气体包括氮气、氦气、氖气、氩气、疝气中的至少一种。保护性气体的流量可以控制1L/min～10L/min，以提高反应的安全性。
S34、去除M的氧化物、M的氮化物，得到复合负极材料。
在一些实施方式中，去除方法包括酸洗，将反应产物进行酸洗，可以去除反应产物中的M的氧化物及氮化物。
酸溶液的质量浓度为1mol/L～5mol/L，具体可以是可以是1mol/L、2mol/L、3mol/L、4mol/L或5mol/L。当然也可以根据实际需求调制酸溶液的质量浓度，在此不做限定。
酸洗的时长为1h～10h，具体可以是可以是1h、3h、5h、7h或10h。在本实施例中，酸洗的产物仍可以回收循环使用。
当保护层为金属氧化物层时，负极材料的制备方法包括以下步骤S31′～S35′：
S31′、制备N-M合金；
S32′、将N-M合金与过渡金属卤化物混合，得到混合物；
S33′、将混合物置于保护性气氛中进行置换反应，得到反应产物，反应产物包括M的卤化物和过渡金属；
S34′、去除所述反应产物中的M的卤化物和过渡金属，得到N材料；N材料为一次颗粒，一次颗粒包括骨架，骨架包括位于所述一次颗粒的内部的主骨架及自所述主骨架延伸至所述一次颗粒表面的多个分枝；
S35′、在所述N材料的骨架表面形成金属氧化物层，得到复合负极材料。
得到的负极材料包括一次颗粒及金属氧化物层；其中，一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架及自所述主骨架延伸至一次颗粒表面的多个分枝；金属氧化物层位于骨架表面。
可以理解，该一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道。
也可以理解，该一次颗粒内部形成有通孔，一次颗粒的孔隙率不低于30％。
以下为负极材料的制备方法的具体描述。
S31′、制备N-M合金；
在一些实施方式中，N-M合金中的N包括Si、Ge、Sn、B及Sb中的至少一种；N-M合金中的M包括Mg、Al、Zn和Ca中的至少一种。具体的示例中，N-M合金可以为Si-Mg合金、Si-Al合金、Ge-Mg合金、Ge-Al合金等。不同种类的合金可得到不同形状的分枝，包括棒状纳米颗粒、纳米片、纳米线及纳米管中的至少一种。
具体地，N-M合金的制备方法同步骤S31；在此不做详细描述。
S32′、将N-M合金与过渡金属卤化物混合，得到混合物；
在一些实施方式中，过渡金属卤化物的化学式为ABx，其中，x＝2或3，所述A包括Sn、Cu、Fe、Zn、Co、Mn、Cr及Ni中的至少一种，所述B包括Cl、F及Br中的至少一种。
其中，N-M合金与过渡金属卤化物的摩尔比为1:(0.1-2)。
可以理解，该混合物可以通过市售获得，此时步骤S32′可以省略。
S33′、将混合物置于保护性气氛中进行置换反应，得到反应产物，反应产物包括M的卤化物和过渡金属；
在一些实施方式中，置换反应的温度为500℃-1100℃，可以是500℃、600℃、700℃、800℃、900℃、1000℃或1100℃。
反应时间为1h～48h，如可以为1h、5h、10h、15h、20h、25h、30h、35h或45h等。
保护性气氛的气体包括氦气、氖气、氩气、氪气及氙气中的至少一种。
S34′、去除反应产物中的M的卤化物和过渡金属，得到N材料；N材料为一次颗粒，一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝。
去除方法同步骤S34，在此不做详细描述。
S35′、在N材料的骨架结构表面形成金属氧化物层，得到复合负极材料。
在一些实施方式中，形成金属氧化物层的方法包括水热法，溶胶凝胶法、沉淀法、化学气相沉积法、磁控溅射及固相反应法中的至少一种。
金属氧化物层中的金属元素包括Si、Sn、Ge、Li、V、Al、Fe和Zn的中的至少一种。
当保护层为金属氮化物层时，负极材料的制备方法包括以下步骤S31″～S36″：
S31″、制备N-M合金；
S32″、将N-M合金与过渡金属卤化物混合，得到混合物；
S33″、将混合物置于保护性气氛中进行置换反应，得到反应产物，反应产物包括M的卤化物和过渡金属；
S34″、去除反应产物中的M的卤化物和过渡金属，得到N材料，N材料为一次颗粒，一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；
S35″、在N材料的表面形成金属氧化物层，得到复合物；
S36″、将复合物在保护气氛下进行热处理后再进行氮化处理，得到负极材料。
得到的负极材料包括一次颗粒及金属氮化物层；其中，一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；金属氮化物层位于骨架表面。
可以理解，该一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道。
也可以理解，该一次颗粒内部形成有通孔，一次颗粒的孔隙率不低于30％。
其中，步骤S31″～S35″与步骤S31′～S35′相同，在此不做详细描述。
在一些实施方式中，热处理温度为500℃-800℃，保温时间1h～24h。
在一些实施方式中，保护性气氛包括氦气、氖气、氩气、氪气及氙气中的至少一种。
在一些实施方式中，氮化处理在400℃-950℃下保温2h～24h。
所述氮化处理的气氛采用氨气气氛、氮气气氛中的至少一种。
下面分多个实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。在不变主权利的范围内，可以适当的进行变更实施。
实施例29
本实施例的硅碳负极材料的制备方法，包括以下步骤：
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入真空炉，抽真空到10Pa，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末、1mol的碳酸铵、1mol的碳酸钠和1mol的氯化铵混合均匀后，再加入1.5mol氯化钠，得到混合物；
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，将反应釜在氩气气氛中以3℃/min的加热速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到硅碳复合负极材料。
经测试，制备的硅复合负极材料的振实密度为0.73g/cm 3，粉体压实密度为1.2g/cm 3，孔隙率为50％，比表面积为18m 2/g，碳含量为12％。
图14a～14b为本实施例中硅碳复合负极材料的扫描电镜图片；图15a为本实施例中硅碳复合负极材料的拉曼图；图15b为本实施例中硅碳复合负极材料的XRD图谱；图15c本实施例中硅碳复合负极材料的循环性能曲线，充放电电流为0.5C。
如图14a～14b中的扫描电镜图片可以看出，制得的硅材料为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于所述一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且硅骨架表面包裹一层石墨碳层，碳层厚度为25nm，骨架的分枝为棒状纳米硅，孔道的平均直径约为80nm，孔道的深度约为250nm。
图15a的拉曼图谱进一步证明在2680cm -1附近存在一个2D峰，这是石墨的特征峰，进一步说明原位生成的碳为类石墨碳，具有更好的导电性和稳定性。从图15b的XRD图谱中可以看出在28.4°、47.3°和56.1°的三强峰与硅(JCPDS No.27-1402)的三强峰相对应，基本无杂相。
图15c中可以看出由硅碳复合负极材料制备的锂离子电池具有较高具有优异的循环性能，在0.5C大电流下循环1200周还有897mAh/g的容量。因此，根据本申请提供的方法制备得到的硅碳复合负极材料至少具有充放电循环稳定性高的优点。
实施例30
本实施例的硅碳负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与锌粉按摩尔比为1:2.2混合均匀后放入真空炉，抽真空到10Pa，在氩气惰性气体保护下以5℃/min的升温速率加热到650℃后保温3h，使其充分反应得到硅锌合金，反应过程真空度始终保持不变；将硅锌合金球磨后得到1μm的硅锌合金粉末；
(2)将1mol的硅锌合金粉末与3mol的氨基甲酸铵、1mol的碳酸钾和1.5mol的氯化铵混合均匀后，再加入1.5mol氯化钠，得到混合物；
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，将反应釜在氩气气氛 中以3℃/min的升温速率加热到800℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到硅复合负极材料。
经过测试，制备的硅复合负极材料的振实密度为0.77g/cm 3，粉体压实密度为1.26g/cm 3，孔隙率为52％，比表面积为25m 2/g，碳含量为15％。
硅碳复合材料包括硅材料及碳层，硅材料为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于所述一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；分枝为棒状纳米硅颗粒；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且硅骨架表面包裹碳层为无定形碳，碳层厚度为15nm，孔道的平均直径约为80nm，孔道的深度约为300nm。
实施例31
本实施例的硅碳负极材料的制备方法，包括以下步骤：
(1)将2μm的硅粉与镁粉按摩尔比为1:2.8混合均匀后放入真空炉，抽真空到10Pa，在氩气惰性气体保护下以5℃/min的升温速率加热到620℃后保温4h，使其充分反应得到硅镁合金，反应过程真空度始终保持不变；将硅镁合金球磨后得到2μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末与5mol的氨基甲酸铵、2mol的碳酸氢铵和2.5mol的溴化铵混合均匀后，再加入1.5mol氯化钾，得到混合物；
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，将反应釜在氩气气氛中以3℃/min的升温速率加热到820℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在3L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到硅复合负极材料。
经过测试，制备的硅复合负极材料的振实密度为0.45g/cm 3，粉体压实密度为1.09g/cm 3，孔隙率为65％，比表面积为53m 2/g，碳含量为38％。
硅碳复合材料包括硅材料及碳层，硅材料为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于所述一次颗粒的内部的主骨架及自所述主骨架延伸至一次颗粒表面的多个分枝；分枝为纳米硅片；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且硅骨架表面包裹碳层为无定形碳层，碳层厚度为25nm；且孔道内填充有碳材料；孔道的平均直径约为50nm，孔道的深度约为500nm。
实施例32
本实施例的硅碳负极材料的制备方法，包括以下步骤：
(1)将3μm的硅粉与铝粉按摩尔比为1:3混合均匀后放入真空炉，抽真空到10Pa，在氩气惰性气体保护下以5℃/min的升温速率加热到660℃后保温3h，使其充分反应得到硅铝合金，反应过程真空度始终保持不变；将硅铝合金球磨后得到3μm的硅铝合金粉末；
(2)将1mol的硅铝合金粉末与4.5mol的氨基甲酸铵、1.8mol的碳酸铵和2.2mol的溴化铵混合均匀后，再加入1.5mol氯化钠，得到混合物；
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，将反应釜在氩气气氛中以2℃/min的升温速率加热到810℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在4L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到硅复合负极材料。
经过测试，制备的硅复合负极材料的振实密度为0.58g/cm 3，粉体压实密度为1.12g/cm 3，孔隙率为32％，比表面积为60m 2/g，碳含量为40％。
硅碳复合材料包括硅材料及碳层，硅材料为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于所述一次颗粒的内部的主骨架及自所述主骨架延伸至所述一次颗粒表面的多个分枝；分枝为棒状纳米硅颗粒；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且硅骨架表面包裹碳层为石墨碳层，碳层厚度为50nm且孔道内填充有碳材料；孔道的平均直径约为150nm，孔道的深度约为1000nm。
实施例33
(1)将2μm的硅粉与镁粉按摩尔比为1:1.8混合均匀后放入真空炉，抽真空到10Pa，在氩气惰性气体保护下以5℃/min的升温速率加热到650℃后保温3h，使其充分反应得到硅镁合金，反应过程真空度始终保持不变；将硅镁合金球磨后得到3μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末与1.5mol的氨基甲酸铵、0.8mol的碳酸铵和1.2mol的溴化铵混合均匀后，再加入0.5mol氯化钠，得到混合物；
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，将反应釜在氩气气氛中以4℃/min的升温速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到硅复合负极材料。
经过测试，制备的硅复合负极材料的振实密度为0.8g/cm 3，粉体压实密度为1.38g/cm 3，孔隙率为30％，比表面积为10m 2/g，碳含量为5％。
硅碳复合材料包括硅材料及碳层，硅材料为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于所述一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且硅骨架表面包裹的碳层为石墨碳，碳层厚度为5nm；孔道的平均直径约为20nm，孔道的深度约为60nm。
实施例34
一种锗碳负极材料的制备方法，包括以下步骤：
(1)将1.5μm的锗粉与铝粉按摩尔比为1:3混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到480℃后保温6h，使其充分反应得到锗铝合金；将锗铝合金球磨后得到0.5μm的锗铝合金粉末；
(2)将1mol的锗铝合金粉末与2.5mol的氨基甲酸铵、1.8mol的碳酸铵和2.2mol的溴化铵混合均匀后，再加入1.5mol氯化钠，得到混合物；
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，将反应釜在氩气气氛中以4℃/min的升温速率加热到780℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到锗碳复合负极材料。
所得的锗碳复合负极材料的中值粒径约为0.6μm，振实密度为0.78g/cm 3，压实 密度1.1g/cm 3，比表面积为16m 2/g，孔隙率为24％，碳的质量百分比含量为75％。
锗碳复合材料包括锗材料及碳层，锗材料为一次颗粒，一次颗粒包括锗骨架，锗骨架包括位于所述一次颗粒的内部的主骨架及自所述主骨架延伸至所述一次颗粒表面的多个分枝；分枝为棒状纳米颗粒；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且锗骨架表面包裹厚度为80nm的碳层；孔道的平均直径约为100nm，孔道的深度约为800nm。
实施例35
一种锗碳负极材料的制备方法，包括以下步骤：
(1)将1.5μm的锗粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到480℃后保温6h，使其充分反应得到锗镁合金；将锗镁合金球磨后得到0.5μm的锗镁合金粉末；
(2)将1mol的锗镁合金粉末与1.5mol的氨基甲酸铵、0.8mol的碳酸铵和1.2mol的溴化铵混合均匀后，再加入0.5mol氯化钠，得到混合物；
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，将反应釜在氩气气氛中以4℃/min的升温速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到锗碳复合负极材料。
所得的锗碳复合负极材料的中值粒径约为0.6μm，振实密度为0.88g/cm 3，压实密度1.3g/cm 3，比表面积为11m 2/g，孔隙率为44％，碳的质量百分比含量为25％。
锗碳复合材料包括锗材料及碳层，锗材料为一次颗粒，一次颗粒包括锗骨架，锗骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；分枝为棒状纳米颗粒；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且锗骨架表面包裹厚度为50nm的碳层；孔道的平均直径约为60nm，孔道的深度约为1500nm。
实施例36
一种硅负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末、1mol的氯化铜混合均匀和1mol的氯化钠混合均匀，得到混合物；
(3)将所得混合物放入氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应得到反应产物；将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到骨架结构的硅负极材料；
(4)将1mol上述硅负极材料、0.7g纤维素溶于500ml无水乙醇中分散均匀后得到混合溶液；
(5)将3g钛酸四丁酯合逐滴加入到上述混合溶液中，加热至80℃后快速搅拌3小时后进行抽滤，在60℃条件下真空干燥24小时后得到氧化钛前驱体包裹硅镁合金复合物；
(6)将上述复合物在氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应，得到硅/氧化钛复合负极材料。
所得的复合负极材料的中值粒径约为0.6μm，比表面积为44m 2/g，孔隙率为43％，氧化钛的质量百分比含量为12％。
复合材料包括硅材料及氧化钛层，硅材料为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于所述一次颗粒的内部的主骨架及自所述主骨架延伸至所述一次颗粒表面的多个分枝；分枝为棒状纳米颗粒；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且硅骨架表面包裹氧化钛层；孔道的平均直径约为100nm，孔道的深度约为700nm。
实施例37
一种硅负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末、1mol的氯化铜(CuCl 2)混合均匀和1mol的氯化钠(NaCl)混合均匀，得到混合物；
(3)将所得混合物放入氩气气氛中以3℃/min的升温速率加热到750℃后保温8h使其充分反应得到反应产物；将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到骨架结构的硅负极材料；
(4)将1mol上述硅负极材料、0.7g纤维素溶于500ml无水乙醇中分散均匀后得到混合溶液；
(5)将3g钛酸四丁酯合逐滴加入到上述混合溶液中，加热至80℃后快速搅拌3小时后进行抽滤，在60℃条件下真空干燥24小时后得到氧化钛前驱体包裹硅镁合金复合物；
(6)将上述复合物放入管式气氛炉中，在氩气气氛中以3℃/min的升温速率加热到650℃后保温5h使其充分反应，接着将氩气换成氨气后将温度升到800℃后保温8h后，得到硅/氮化钛复合负极材料；
所得的复合负极材料的中值粒径约为0.7μm，比表面积为40m 2/g，孔隙率为48％，氮化钛的质量百分比含量为32％。
复合材料包括硅材料及氮化钛层，硅材料为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；分枝为纳米线；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且硅骨架表面包裹氮化钛层；孔道的平均直径约为58nm，孔道的深度约为1000nm。
实施例38
一种硅负极材料的制备方法，包括以下步骤：
(1)将1.5μm的硅粉与镁粉按摩尔比为1:2.5混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到0.5μm的硅镁合金粉末；
(2)将1mol的硅镁合金粉末、1mol的氯化铜(CuCl 2)混合均匀和1mol的氯 化钠(NaCl)混合均匀，得到混合物；
(3)将所得混合物放入氩气气氛中以3℃/min的升温速率加热到700℃后保温6h使其充分反应得到反应产物；将反应产物放入在2L的1mol/L盐酸溶液中机械搅拌酸洗处理3h后，抽滤、洗涤、干燥后得到骨架结构的硅负极材料；
(4)通过溶胶-凝胶过程制备五氧化二钒包裹硅负极材料，首先配置0.15M/L浓度的三异丙氧基氧化钒的酒精溶液500ml，加入30ml的乙酰丙酮，得到混合溶液；将0.5mol的硅负极材料粉末加入上述混合溶液中搅拌36小时后分散均匀后得到溶胶。
(5)溶胶进行抽滤，在60℃条件下真空干燥24小时后得到五氧化二钒前驱体包裹硅负极材料复合物；
(6)将上述复合物放入管式气氛炉中，在氩气气氛中以3℃/min的升温速率加热到600℃后保温3h使其充分反应，接着将氩气换成氨气后将温度升到750℃后保温8h后，得到硅/氮化钒复合负极材料。
所得的复合负极材料的中值粒径约为0.6μm，比表面积为51m 2/g，孔隙率为40％，氮化钒的质量百分比含量为25％。
复合材料包括硅材料及氮化钒层，硅材料为一次颗粒，一次颗粒包括硅骨架，硅骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；分枝为棒状纳米颗粒；一次颗粒为大孔结构，一次颗粒形成有延伸至一次颗粒表面的孔道，且硅骨架表面包裹氮化钒层；孔道的平均直径约为100nm，孔道的深度约为900nm。
对比例4
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入真空炉，抽真空到10Pa，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末。
(2)将1mol的硅镁合金粉末与1mol的碳酸铵、1mol的碳酸钠和1mol的氯化铵混合均匀后，得到混合物。
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，将反应釜在氩气气氛中以3℃/min的加热速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到硅碳复合负极材料。
对比例5
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入真空炉，抽真空到10Pa，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末。
(2)将1mol的硅镁合金粉末与1mol的碳酸铵和1mol的氯化铵混合均匀后，再加入1.5mol氯化钠，得到混合物。
(3)将所得混合物混合均匀后放入密封不锈钢反应釜中，将反应釜在氩气气氛中以3℃/min的加热速率加热到750℃后保温8h使其充分反应，得到反应产物；
(4)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、 干燥后得到硅碳复合负极材料。
对比例6
采用硅碳复合负极材料SiO/C，硅碳复合负极材料的中值粒径为1.5μm，复合材料中内核为纳米硅粒子堆积的多孔硅结构，外壳为碳层包裹；其中，碳的质量百分比含量为22％，比表面积为38m 2/g，硅碳复合负极材料的孔隙率为67％。即为SiOx/C负极材料，其中x＝1.0。
性能测试：
将实施例29～37与对比例4～6制得的负极材料与同一正极材料、集流体制成锂离子电池，进行电池性能测试，测试项目包括放电比容量、首次库伦效率、0.5C循环1200圈后容量、0.5C循环1200圈后容量保持率，样本编号为S29～S37及R4～R6，样本的性能参数如表5所述：
表5.性能比对结果表
Figure PCTCN2021109137-appb-000007
综合上述实施例和对比例可知，实施例29、30、33、34提供的复合负极材料具有三维孔道结构，碳层包覆在负极材料的骨架表面，实施例31和32提供的复合负极材料具有三维孔道结构，碳层包覆在负极材料的骨架表面并填充至三维孔道结构内，具有良好的结构稳定性，贯通的孔道结构能够在负极材料脱嵌锂过程中提供内膨胀的空间，并可以作为电解液流动的通道，在提高硅储锂性能的同时降低锂电池的膨胀，提高电池的容量保持率。
对比例4在制备过程中没有加入熔盐介质，合金粉末与铵盐反应时的高温液态环境局部温度过高，导致部分三维孔道结构破坏，电池的充放电循环稳定性变差。对比例5在制备过程中没有加入铵盐分解抑制剂，铵盐在反应过程中，分解成为氨和二氧化碳，难以在硅材料的表面或三维孔道内均匀沉积形成碳层，使得最终的负极材料的碳含量降低，负极材料的导电性能变差，体积膨胀抑制性能较弱，导致长循环性能价差。
根据上述实施例及试验结果可知，本申请制备得到硅碳复合负极材料制成的电池，具有较好的充放电循环稳定性，容量高，循环寿命高。综上所述，本申请提供的多孔硅碳负极材料的制备方法，简单易操作，制备过程安全、高效；制造成本有效降低，适于量化生产；制得的产物用作电池极片使用，具有较好的充放电循环性能。
第五方面
如第一方面所述的负极材料，包括一次颗粒和位于一次颗粒表面的纳米颗粒层以及包覆于纳米颗粒层的包覆层，本申请实施例提供负极材料的制备方法，如图16所示，包括以下步骤S41～S44：
S41、制备N-M合金；
S42、在N-M合金表面形成包覆层，得到含有包覆层的N-M合金；
S43、将含有包覆层的N-M合金加入铵盐溶液中进行氧化还原反应，得到中间体；
S44、将所述中间体在保护性气氛下进行去合金化热处理，并对反应产物进行酸洗，得到复合负极材料，其中，所述N-M合金中的N包括硅、锗、锑、锡、硼中的至少一种，所述N-M合金中的M包括镁、铝、钙和锌中的至少一种。
在本方案中，通过简单的原位反应且可以一步制备两种孔结构的复合负极材料，将碳包覆后的N-M合金与廉价常见的铵盐溶液反应后得到中间体，然后在保护气氛中高温去合金化处理，去合金化处理过程中，N-M合金中的活泼金属被反应，从而在N-M合金的表面形成纳米颗粒层，最终得到复合负极材料，得到的负极材料同时具有孔道、介孔和微孔，且形貌和孔结构易调控，可以控制合金成分来改变孔的大小以及孔隙率，孔的深度可以由反应时间与反应温度来控制。
由内层N-M合金去合金化得到的一次颗粒具有连续贯通的孔道，连续的孔道可以为锂化过程提供内膨胀的孔径，还可以为电解液提供流通的通道，在提高负极材料储锂性能的同时降低锂电池的膨胀。生成的纳米颗粒层形成有介孔和微孔，既可以避免材料粉化，又可以缓解材料的体积膨胀，保证负极材料结构稳定性。采用碳包覆的N-M合金作为原料，能够避免后期碳包覆堵死孔道结构，提高电池首效。
该方法得到复合负极材料包括内核及位于所述内核表面的包覆层；其中，
内核包括一次颗粒及位于一次颗粒表面的纳米颗粒层；一次颗粒包括骨架，骨架包括位于一次颗粒的内部的主骨架及自主骨架延伸至一次颗粒表面的多个分枝；纳米颗粒层形成有微孔和/或介孔。
以下详细解释本制备方法：
S41，制备N-M合金；
在一些实施方式中，N-M合金中的N包括Si、Ge、Sn、B及Sb中的至少一种；N-M合金中的M包括Mg、Al、Zn和Ca中的至少一种。具体的示例中，N-M合金可以为Si-Mg合金、Si-Al合金、Ge-Mg合金、Ge-Al合金等。不同种类的合金可得到不同形状的分枝，包括棒状纳米颗粒、纳米片、纳米线及纳米管中的至少一种。
S41与步骤S21大致相同，在此不做详细描述。
在一些实施方式中，N-M合金中的N的质量百分比含量为15％～60％，可选地，N的质量百分比含量可以是15％、20％、30％、40％、50％或60％，在此不做限定。在具体实施例中，N-M合金具体可以是硅镁合金、硅铝合金、硅钙合金、硅锌合金中的至少一种。可以理解地，可以通过控制N-M合金的成分来改变N材料的孔道的孔的大小以及孔隙率，一般N-M合金中N含量越高，孔径越小。可以控制加热反应时间与反应温度来改变孔的深度，一般反应时间越长、反应温度越高，孔的深度越深。
当然，N-M合金还可以通过其他制备方法制备，具体：高能球磨、真空冶炼以及热压烧结等。
可以理解，N-M合金可以通过市售获得，此时步骤S41可以省略。
步骤S42，在N-M合金表面形成包覆层，得到含有包覆层的N-M合金；
在本实施例中，在保护气体下采用碳源气体在N-M合金表面气相沉积形成一层碳层，采用的碳源气体包括甲烷、乙炔、丙酮和酒精中的至少一种。在其他实施方式中，还可以采用液相包覆和固相包覆等方式在N-M合金表面形成碳层。其中固相碳源包括碳酸钙、碳酸锂、碳酸铁、碳酸锌和碳酸镁中的至少一种。
当采用气相沉积的方式时，气相沉积过程中采用的保护气体包括氦气、氖气、氩气、氪气及氙气中的至少一种。
碳源气体与保护气体的体积比为1：(0.1～100)，具体可以是1:0.1、1:10、1:20、1:40、1:60、1:80或1:100。
碳源气体通入时间为5min～60min，具体可以是5min、15min、25min、35min、45min或60min，当然也可以根据实际情况进行设定，在此不做限定。
碳源气体的流速为0.1L/min～2L/min，具体可以是0.1L/min、0.5L/min、0.8L/min、0.8L/min、1.5L/min或2L/min，当然也可以根据实际情况进行设定，在此不做限定。
气相沉积的温度为400℃～950℃，具体可以是400℃、500℃、600℃、700℃、800℃、900℃或950℃，当然也可以根据实际情况进行设定，在此不做限定。
升温速率为1℃/min～20℃/min，具体可以是1℃/min、5℃/min、10℃/min、15℃/min或20℃/min，从而有效提高反应效率。
需要说明的是，在上述适宜的碳源通入时间或流速、气相沉积温度和升温速率范围内，有助于提高碳层能够均匀地沉积在N-M合金的表面。
当采用固相包覆的方式时，固相碳源与N-M合金摩尔质量比为2：(1-10)，具体可以是2：1、2：3、2：5、2：7、2：8、2：9或2：10，当然也可以根据实际情况进行设定，在此不做限定。
固相碳源与N-M合金反应温度为500℃～1000℃，具体可以是500℃、600℃、700℃、800℃、900℃或1000℃，当然也可以根据实际情况进行设定，在此不做限定。
在本实施例中，N-M合金表面形成的碳层的厚度为5nm～100nm，具体可以是5nm、10nm、20nm、30nm、40nm、50nm、60nm、70nm、80nm或100nm等，碳层的沉积厚度可以根据沉积时间来控制。
碳包覆N-M合金的中值粒径为0.1μm～15μm，具体可以是0.1μm、0.5μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm或15μm等，在此不做限定。
步骤S43，将含有包覆层的N-M合金加入铵盐溶液中进行氧化还原反应，得到中间体。
在本实施例中，铵盐包括氟化铵、氯化铵、溴化铵、碘化铵、硝酸铵、碳酸铵、高氯酸铵、硫酸铵和硫化铵中的至少一种。铵盐溶液的质量浓度为0.1mol/L～5mol/L，具体可以是0.1mol/L、0.5mol/L、1mol/L、1.5mol/L、2mol/L、2.5mol/L、3mol/L、4mol/L或5mol/L，当然也可以根据实际情况进行设定。
可选地，含有包覆层的N-M合金与铵盐的摩尔比为1：(0.1～2)具体可以是1:0.1、1:0.5、1:0.8、1:1、1:1.5或1:2等。
N-M合金与铵盐溶液的氧化还原反应时间为0.5h～12h，具体可以是0.5h、1h、2h、3h、6h、9h、10h或12h，氧化还原反应的温度为20℃～80℃，具体可以是20℃、40℃、50℃、60℃、70℃或80℃。
举例说明，当N-M合金为Si-M合金时，将碳包覆Si-M合金浸泡在铵盐溶液中，Si-M合金与铵盐溶液反应后在Si-M合金表面形成一层硅酸，其反应化学式如下式所示：
MSi+NH 4Y+H 2O→H 2SiO 3+MY+NH 3+H 2
具体可以是将硅镁合金置于氯化铵溶液中，硅镁合金的表面生成硅酸、氯化镁、氨气和氢气，需要说明的是，硅酸以胶态粒子、沉淀物或凝胶的形式粘附在硅镁合金的表面，经过进一步地干燥处理使得硅镁合金表面附着硅酸纳米胶粒。
步骤S44，将中间体在保护性气氛下进行去合金化热处理，并对反应产物进行后处理，得到负极材料。
可以理解地，举例说明，当N-M合金为Si-M合金时,在去合金化处理过程中，Si-M合金中蒸发出来的活泼金属蒸汽与硅酸反应，使得硅酸在高温下原位还原纳米硅粒子，纳米硅颗粒堆叠形成纳米颗粒层，使得纳米颗粒层具有微孔和/或介孔，即硅酸纳米胶粒与活泼金属蒸气反应形成氧化物，去除氧化物后纳米颗粒层可以形成微孔或介孔。其反应化学式如下式所示：
M+H 2SiO 3→Si+MO+H 2O，
为了让混合物充分反应，去合金化热处理的温度为200℃～950℃，具体可以是200℃、300℃、400℃、600℃、800℃或950℃，保温时间2h～18h，具体可以是2h、3h、6h、9h、12h、15h或18h，在此不做限定。
去合金化热处理的升温速率为1℃/min～20℃/min，具体可以是1℃/min、5℃/min、10℃/min、15℃/min或20℃/min，从而有效提高反应效率。
为了提高反应的安全性，在惰性气体的保护下进行去合金化热处理，惰性气体包括氦气、氖气、氩气、氪气及疝气中的至少一种。惰性气体的流量可以控制在1L/min-10L/min。
可以理解地，在上述适宜的热处理的温度、时间、升温速率范围内，有助于提高去合金效率，有助于Si-M合金在去合金过程中形成骨架结构，有助于在Si-M合金表面形成纳米颗粒层。
在具体实施例中，酸洗即采用酸溶液洗涤反应产物，从而去除反应产物中的金属氧化物，在一种可行的实施方式中，酸洗采用的酸溶液包括盐酸、硝酸及硫酸中的至少一种。
酸溶液的质量浓度为1mol/L～5mol/L，具体可以是1mol/L、2mol/L、3mol/L、4mol/L或5mol/L。当然也可以根据实际需求调制酸溶液的质量浓度，在此不做限定。
酸洗的时长为1h～10h，具体可以是1h、3h、5h、7h或10h。在本实施例中，酸洗的产物仍可以回收循环使用。
可以理解地，在上述适宜的酸溶液的浓度、酸洗时间范围内，有助于提高酸洗效率，减少负极材料中的杂质。
在本实施方式中，利用Si-M合金与铵盐溶液反应后在Si-M合金表面形成一层硅酸层，在高温去合金化处理过程中，Si-M合金中的活泼金属的金属蒸汽与硅酸反应，使得硅酸在高温下原位还原成纳米硅颗粒，该纳米硅颗粒形成具有微孔和/或介孔的纳米颗粒层。使得最终制备的负极材料，具有多种孔径的孔结构，并且硅材料表层的孔径小于内层的孔径，从而缓解硅的体积膨胀，有效抑制材料粉化，增强结构稳定性。制备得到的复合负极材料还能够有效提高锂电池充放电循环的稳定性，具有高容量、长循环寿命、高倍率性能以及低膨胀等多个优点。
下面分多个实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。在不变主权利的范围内，可以适当的进行变更实施。
实施例39
一种负极材料的制备方法，包括以下步骤：
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末；
(2)将硅镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到500℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温30min后关闭乙炔气体，冷却得到碳包覆硅镁合金粉末；
(3)取1mol的碳包覆硅镁合金粉末加入1L的氯化铵溶液中，氯化铵溶液的浓度为1mol/L，在60℃的水浴条件下反应1h，过滤、干燥后得到的中间体；
(4)将中间体放入氩气气氛中以3℃/min的升温速率加热到700℃后保温8h，使其充分反应得到反应产物；
(5)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、 干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为1.2μm，碳的质量百分比含量为15％，比表面积为45m 2/g，碳层厚度为50nm。所得的复合负极材料的孔隙率为55％，一次颗粒的孔隙率为40％，纳米颗粒层的孔隙率为25％，纳米颗粒层中的介孔的总孔隙率与微孔的总孔隙率比值为4:1，所有孔结构中的开孔体积占比约为80％，闭孔体积占比约为20％；分枝的横截面最大宽度约为40nm，纳米颗粒层的厚度为100nm。
图17a为复合负极材料的扫描电镜图片，图17b为本实施例提供的复合负极材料的XRD图；图17c为本实施例中多孔硅负极材料的循环性能曲线，充放电电流为0.5C。从图17a中的扫描电镜图片可以看出，制得的多孔硅具有明显多孔结构，多孔硅表面包裹一层碳层。从图17b的XRD图谱中可以看出在28.4°、47.3°和56.1°的三强峰与硅(JCPDS No.27-1402)的三强峰相对应，基本无杂相。
实施例40
(1)将2μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的升温速率加热到650℃后保温5h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1.5μm的硅镁合金粉末；
(2)将硅镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到600℃后，通入0.5L/mind的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温30min后关闭乙炔气体，冷却得到碳包覆硅镁合金粉末。
(3)取1mol的碳包覆硅镁合金粉末加入1L的氯化铵溶液中，氯化铵溶液的浓度为1mol/L，在60℃的水浴条件下反应2h，过滤、干燥后得到的中间体；
(4)将中间体放入氩气气氛中以1℃/min的升温速率加热到650℃后保温6h，使其充分反应得到反应产物；
(5)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为1.8μm，碳的质量百分比含量为16％，比表面积为55m 2/g，碳层厚度为53nm。所得的复合负极材料的孔隙率为55％，一次颗粒的孔隙率为35％，纳米颗粒层的孔隙率为23％，纳米颗粒层中的介孔的总孔隙率与微孔的总孔隙率比值为5:1，所有孔结构中的开孔体积占比约为83％，闭孔体积占比约为17％；分枝的横截面最大宽度约为35nm，纳米颗粒层的厚度为150nm。
实施例41
(1)将2μm的硅粉与铝粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以5℃/min的升温速率加热到650℃后保温5h，使其充分反应得到硅铝合金；将硅镁合金球磨后得到3μm的硅镁合金粉末；
(2)将硅镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到600℃后，通入0.5L/mind的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温30min后关闭乙炔气体，冷却得到碳包覆硅镁合金粉末；
(3)取1mol的碳包覆硅镁合金粉末加入1L的氯化铵溶液中，氯化铵溶液的浓度为0.5mol/L，在60℃的水浴条件下反应1h，过滤、干燥后得到的中间体；
(4)将中间体放入氩气气氛中以3℃/min的升温速率加热到650℃后保温6h， 使其充分反应得到反应产物；
(5)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为3.5μm，碳的质量百分比含量为15％，比表面积为40m 2/g，碳层厚度为80nm。所得的复合负极材料的孔隙率为45％，一次颗粒的孔隙率为36％，纳米颗粒层的孔隙率为27％，纳米颗粒层中的介孔的总孔隙率与微孔的总孔隙率比值为5:1，所有孔结构中的开孔体积占比约为83％，闭孔体积占比约为17％；分枝的横截面最大宽度约为50nm，纳米颗粒层的厚度为50nm。
实施例42
(1)将2μm的硅粉与铝粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的升温速率加热到650℃后保温5h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅铝合金粉末；
(2)将硅镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到650℃后，通入0.5L/mind的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温30min后关闭乙炔气体，冷却得到碳包覆硅镁合金粉末；
(3)取1mol的碳包覆硅镁合金粉末加入1L的氯化铵溶液中，氯化铵溶液的浓度为5mol/L，在60℃的水浴条件下反应2h，过滤、干燥后得到的中间体；
(4)将中间体放入氩气气氛中以3℃/min的升温速率加热到650℃后保温6h，使其充分反应得到反应产物；
(5)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为1.5μm，碳的质量百分比含量为18％，比表面积为90m 2/g，碳层厚度为50nm。所得的复合负极材料的孔隙率为45％，一次颗粒的孔隙率为30％，纳米颗粒层的孔隙率为15％，纳米颗粒层中的介孔的总孔隙率与微孔的总孔隙率比值为8:1，所有孔结构中的开孔体积占比约为81％，闭孔体积占比约为19％；分枝的横截面最大宽度约为30nm，纳米颗粒层的厚度为500nm。
实施例43
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末；
(2)将硅镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到500℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温60min后关闭乙炔气体，冷却得到碳包覆硅镁合金粉末；
(3)取1mol的碳包覆硅镁合金粉末加入1L的氯化铵溶液中，氯化铵溶液的浓度为1mol/L，在60℃的水浴条件下反应1h，过滤、干燥后得到的中间体；
(4)将中间体放入氩气气氛中以3℃/min的升温速率加热到700℃后保温8h，使其充分反应得到反应产物；
(5)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为1.2μm，碳的质量百分比含量为20％，比表面积为50m 2/g，碳层厚度为100nm。所得的复合负极材料的孔隙率为55％，一次颗粒的孔隙率为40％，纳米颗粒层的孔隙率为25％，纳米颗粒层中的介孔的总孔隙率与微孔的总孔隙率比值为4:1，所有孔结构中的开孔体积占比约为80％，闭孔体积占比约为20％；分枝的横截面最大宽度约为40nm，纳米颗粒层的厚度为100nm。
实施例44
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末；
(2)将硅镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到500℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温30min后关闭乙炔气体，冷却得到碳包覆硅镁合金粉末；
(3)取1mol的碳包覆硅镁合金粉末加入1L的氯化铵溶液中，氯化铵溶液的浓度为1mol/L，在90℃的水浴条件下反应12h，过滤、干燥后得到的中间体；
(4)将中间体放入氩气气氛中以3℃/min的升温速率加热到800℃后保温8h，使其充分反应得到反应产物；
(5)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为1.6μm，碳的质量百分比含量为20％，比表面积为30m 2/g，碳层厚度为50nm。所得的复合负极材料的孔隙率为55％，一次颗粒的孔隙率为40％，纳米颗粒层的孔隙率为32％，纳米颗粒层中的介孔的总孔隙率与微孔的总孔隙率比值为4:1，所有孔结构中的开孔体积占比约为80％，闭孔体积占比约为20％；分枝的横截面最大宽度约为40nm，纳米颗粒层的厚度为100nm。
实施例45
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末；
(2)将硅镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到500℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温30min后关闭乙炔气体，冷却得到碳包覆硅镁合金粉末；
(3)取1mol的碳包覆硅镁合金粉末加入1L的氯化铵溶液中，氯化铵溶液的浓度为1mol/L，在60℃的水浴条件下反应1h，过滤、干燥后得到的中间体；
(4)将中间体放入氩气气氛中以3℃/min的升温速率加热到1000℃后保温8h，使其充分反应得到反应产物；
(5)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为1.3μm，碳的质量百分比含量为20％，比表面积为30m 2/g，碳层厚度为50nm。所得的复合负极材料的孔隙率为50％，一次颗粒的孔隙率为65％，纳米颗粒层的孔隙率为22％，纳米颗粒层中的介孔的总 孔隙率与微孔的总孔隙率比值为4:1，所有孔结构中的开孔体积占比约为80％，闭孔体积占比约为20％；分枝的横截面最大宽度约为60nm，纳米颗粒层的厚度为70nm。
实施例46
(1)将粒径为1μm的锗粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的加热速率加热到650℃后保温8h，使其充分反应得到锗镁合金；将锗镁合金球磨后得到1μm的锗镁合金粉末；
(2)将锗镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到500℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温30min后关闭乙炔气体，冷却得到碳包覆锗镁合金粉末；
(3)取1mol的碳包覆锗镁合金粉末加入1L的氯化铵溶液中，氯化铵溶液的浓度为1mol/L，在60℃的水浴条件下反应2h，过滤、干燥后得到的中间体；
(4)将中间体放入氩气气氛中以3℃/min的升温速率加热到1000℃后保温8h，使其充分反应得到反应产物；
(5)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为1.3μm，碳的质量百分比含量为21％，比表面积为31m 2/g，碳层厚度为40nm。所得的复合负极材料的孔隙率为52％，一次颗粒的孔隙率为64％，纳米颗粒层的孔隙率为23％，纳米颗粒层中的介孔的总孔隙率与微孔的总孔隙率比值为4:1，所有孔结构中的开孔体积占比约为81％，闭孔体积占比约为19％；分枝的横截面最大宽度约为62nm，纳米颗粒层的厚度为73nm。
对比例7
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末；
(2)将硅镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到500℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温30min后关闭乙炔气体，冷却得到碳包覆硅镁合金粉末；
(3)将碳包覆硅镁合金粉末放入氩气气氛中以3℃/min的升温速率加热到700℃后保温8h，使其充分反应得到反应产物；
(4)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为1.4μm，碳的质量百分比含量为20％，比表面积为15m 2/g，碳层厚度为50nm。所得的复合负极材料的孔隙率为70％，所有孔结构中的开孔体积占比约为70％，闭孔体积占比约为30％；纳米硅骨架单元的骨架最大直径约为65nm。
对比例8
(1)将粒径为1μm的硅粉与镁粉按摩尔比为1:2混合均匀后放入气氛炉，在氩气惰性气体保护下以3℃/min的加热速率加热到600℃后保温6h，使其充分反应得到硅镁合金；将硅镁合金球磨后得到1μm的硅镁合金粉末；
(2)将硅镁合金粉末放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到500℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温30min后关闭乙炔气体，冷却得到碳包覆硅镁合金粉末；
(3)取1mol的碳包覆硅镁合金粉末加入1L的氯化铵溶液中，氯化铵溶液的浓度为10mol/L，在100℃的水浴条件下反应12h，过滤、干燥后得到的中间体；
(4)将中间体放入氩气气氛中以3℃/min的升温速率加热到700℃后保温8h，使其充分反应得到反应产物；
(5)将反应产物在1mol/L的盐酸溶液机械搅拌酸洗处理2h后，抽滤、洗涤、干燥后得到复合负极材料。
经过测试，所得的复合负极材料的中值粒径为1.8μm，碳的质量百分比含量为25％，比表面积为45m 2/g，碳层厚度为50nm。所得的复合负极材料的孔隙率为55％，一次颗粒的孔隙率为40％，纳米颗粒层的孔隙率为7％，纳米颗粒层中的介孔的总孔隙率与微孔的总孔隙率比值为1.8:1，所有孔结构中的开孔体积占比约为58％，闭孔体积占比约为42％；分枝的横截面最大宽度约为40nm，纳米颗粒层的厚度为200nm。
对比例9
采用复合负极材料Si/C，复合负极材料的中值粒径为1.5μm，复合材料中内核为纳米硅粒子堆积的多孔硅结构，外壳为碳层包裹；其中，碳的质量百分比含量为22％，比表面积为38m 2/g，碳层厚度为50nm，复合负极材料的孔隙率为67％。
性能测试：
(1)复合负极材料粉末颗粒微观形貌观察：
利用扫面电镜进行粉末微观形貌观察表征材料表面情况，所选测试仪器为：OXFORD EDS(X-max-20mm2),加速电压为10KV调整焦距，观测倍数从50K进行高倍观察，低倍下500至2000主要观察颗粒团聚情况。
(2)粒径测试：
50ml洁净烧杯中加入约0.02g粉末样品，加入约2 0ml去离子水，再滴加几滴1％的表面活性剂，使粉末完全分散于水中，120W超声清洗机中超声5min，利用MasterSizer 2000测试粒径分布。
(3)骨架的直径测试方法：
采用SEM随机挑选20颗负极材料的内核，测试骨架的直径和长度以及分枝的尺寸。
(4)负极材料中碳含量的测试方法:
样品在富氧条件下由高频炉高温加热燃烧使碳、硫氧化成二氧化碳、二氧化硫，该气体经处理后进入相应的吸收池，对相应的红外辐射进行吸收再由探测器转化成对应的信号。此信号由计算机采样，经线性校正后转换成与二氧化碳、二氧化硫浓度成正比的数值，然后把整个分析过程的取值累加，分析结束后，此累加值在计算机中除以重量值，再乘以校正系数，扣除空白，即可获得样品中碳百分含量。利用高频红外碳硫分析仪(上海徳凯HCS-140)进行样品测试。
(5)负极材料比表面积的测试方法:
在恒温低温下，测定不同相对压力时的气体在固体表面的吸附量后，基于布朗诺尔-埃特-泰勒吸附理论及其公式(BET公式)求得试样单分子层吸附量，从而计算出固体的比表面积。
(6)孔隙率测试：
采用气体置换法测试所述负极材料和负极极片的孔隙率。计算方法：样品孔体积占总面积的百分比，P＝(V-V0)/V*100％，V0：真体积，V：表观体积。
(7)负极材料的横断面测试：
截面抛光仪采用离子源将惰性气体电离产生惰性离子，经过加速、聚焦后，高速惰性离子将样品表面的原子或分子撞击出去，实现离子抛光。经CP切割后，将样品放到SEM专用样品台上，进行SEM测试。仪器型号IB-09010CP，离子加速电压2-6kV，使用气体为氩气。通过横断面测试将所述硅碳负极材料切割后，可测试截面纳米颗粒层的厚度、碳层厚度。
利用实施例39～46与对比例7～9制得的负极材料，样本编号为S39～S46及R7～R9；将负极材料分别与羧甲基纤维素钠、丁苯橡胶以及导电石墨(KS-6)和碳黑(SP)按照比例92:2:2:2:2配置浆料，均匀涂覆与铜箔上烘干制成负极极片，在氩气气氛手套箱中组装成扣式电池，所用隔膜为聚丙烯微孔膜，所用电解液为1mol/L的六氟磷酸锂(溶剂为碳酸乙烯酯、碳酸甲乙酯和碳酸二甲酯的混合液)，所用对电极为金属锂片。
对上述11组电池在蓝电CT2001A电池测试系统上进行放电比容量测试，1小时放电的电量与电池容量的比为放电比容量。
对上述11组电池在蓝电CT2001A电池测试系统上进行首次库伦效率测试，充放电电流为0.05C，测得首次库伦效率。
对上述11组电池在蓝电CT2001A电池测试系统上进行循环100周测试，充放电电流为0.2C，循环100圈后测试计算圈后电池容量及圈后容量保持率。
其中，0.2C循环100圈后容量保持率＝第100圈循环放电容量/首周放电容量*100％，结果如表6所示。
表6.各负极材料的参数性能比对表
Figure PCTCN2021109137-appb-000008
Figure PCTCN2021109137-appb-000009
表7.各电池的参数性能比对表
Figure PCTCN2021109137-appb-000010
图17c中可以看出实施例39的材料具有较高具有优异的循环性能，在0.5C大电流下循环1000周还有997mAh/g的容量。由上表6及7可知，实施例42与实施例39的主要区别在氯化铵浓度更高，浸泡时长更久，使得碳包覆硅镁合金表面生成的硅酸粒子更多，从而使得最终产物的纳米硅颗粒层厚度更大，纳米硅颗粒层的介孔及微孔减少，电解液不容易流入内层的一次颗粒中，从而使得电池在充放电过程中，极片膨胀率提高，循环稳定性变差。
对比例7的负极材料在制备过程中相比于实施例39，没有进行氯化铵溶液浸泡处理，硅镁合金表面不会生成硅酸粒子，进而使得最终产物仅包括碳层和一次颗粒， 碳层的碳颗粒容易堵塞一次颗粒的孔道结构，从而使得电池在充放电过程中，极片膨胀率提高，循环稳定性变差。
对比例8与实施例43的主要区别在氯化铵浓度更高，浸泡温度更高，时长更久，使得碳包覆硅镁合金表面生成的硅酸粒子更多，从而使得最终产物的纳米硅颗粒层厚度更大，纳米硅颗粒层的介孔及微孔减少，电解液不容易流入内层的一次颗粒中，从而使得电池在充放电过程中，极片膨胀率提高，循环稳定性变差。
对比例9是碳包覆的多孔硅负极材料，该材质制成的电池的0.2C循环100圈后容量及容量保持率均有所下降，并且对比例9的电极膜膨胀率也高于实施例39。
根据上述实施例及对比例可见，本申请负极材料的一次颗粒表面的纳米颗粒层具有优异的介孔和微孔，既可以有效避免材料粉化，锂化后形成刚性硅锂合金层，进一步抑制一次颗粒的体积膨胀，保证多孔硅的结构稳定性。在锂化过程中，硅嵌锂膨胀填充介孔孔隙，也可进一步避免电解液溶剂分子与一次颗粒接触形成副反应，生成更多SEI，较低首效。并且，一次颗粒上的孔道结构与纳米颗粒层的介孔、微孔在结构上不同，可以进一步缓解多孔硅体积膨胀产生的应力，降低电极膜膨胀，提高安全性；避免材料结构破坏，保证材料的结构稳定性，带来长循环寿命。碳层包裹硅材料后，具有更好的导电性和稳定性，采用先包覆碳，后反应制备多孔的顺序，可以有效避免碳填充或封闭孔结构，降低材料首效，甚至引发副反应。因此复合负极材料有利于满足电池的长循环寿命、高容量和低膨胀的要求，可广泛应用于锂离子电池负极材料领域。
综上，本申请提供的负极材料的制备方法，简单易操作，制备过程安全、高效；制造成本有效降低，适于量化生产；制得的产物用作电池极片使用，具有较好的充放电循环性能。
第六方面
本申请实施例还提供了一种锂离子电池负极极片和一种锂离子电池，采用本申请上述实施例提供的复合负极材料或采用本申请上述实施例提供的负极材料的制备方法制得的负极材料。
申请人声明，本申请通过上述实施例来说明本申请的详细工艺设备和工艺流程，但本申请并不局限于上述详细工艺设备和工艺流程，即不意味着本申请必须依赖上述详细工艺设备和工艺流程才能实施。所属技术领域的技术人员应该明了，对本申请的任何改进，对本申请产品各原料的等效替换及辅助成分的添加、具体方式的选择等，均落在本申请的保护范围和公开范围之内。

Claims (26)

  1. 一种负极材料，其特征在于，所述负极材料包括一次颗粒，所述一次颗粒包括骨架，所述骨架包括位于所述一次颗粒的内部的主骨架及自所述主骨架延伸至所述一次颗粒表面的多个分枝。
  2. 根据权利要求1所述的负极材料，其特征在于，包括如下特征(1)～(5)中的至少一个：
    (1)所述主骨架为三维网状结构；
    (2)单个所述分枝为单独的晶粒；
    (3)所述晶粒的尺寸为30nm～100nm；
    (4)所述分枝的横截面最大宽度为20nm～350nm，所述分枝的横截面最大长度为50nm～2500nm；
    (5)所述分枝选自棒状纳米颗粒、纳米片、纳米线及纳米管中的至少一种。
  3. 一种负极材料，所述负极材料包括一次颗粒，所述一次颗粒为大孔结构，所述一次颗粒形成有延伸至所述一次颗粒表面的孔道。
  4. 根据权利要求3所述的负极材料，其特征在于，所述孔道的直径为10nm～150nm；所述孔道的深度为50nm～1500nm。
  5. 一种负极材料，其特征在于，所述负极材料包括一次颗粒，所述一次颗粒内部形成有通孔，所述一次颗粒的孔隙率不低于30％。
  6. 根据权利要求1～5任一项所述的负极材料，其特征在于，所述负极材料还包括位于所述一次颗粒表面的包覆层。
  7. 根据权利要求6所述的负极材料，其特征在于，包括如下特征(1)～(15)中的至少一个：
    (1)所述包覆层包括碳层、金属氧化物层及金属氮化物层中的至少一种；
    (2)所述包覆层包括碳层，以所述复合负极材料质量百分含量为100％计，碳的质量百分比含量为2％～50％；
    (3)所述包覆层包括金属氧化物层，以所述复合负极材料质量百分含量为100％计，金属氧化物的质量百分比含量为2％～60％；
    (4)所述包覆层包括金属氮化物层，以所述复合负极材料质量百分含量为100％计，金属氮化物的质量百分比含量为2％～70％；
    (5)所述碳层包括石墨烯层及非晶碳层中的至少一种；
    (6)所述碳层包括石墨烯层，所述石墨烯层具有褶皱结构；
    (7)所述碳层包括石墨烯层，所述石墨烯层具有褶皱结构，所述褶皱结构的粗糙度最大峰-谷高度差大于10nm且小于1μm，所述褶皱结构的相邻两波峰或相邻两波谷之间的距离大于10nm且小于1μm；
    (8)所述碳层包括石墨烯层，所述石墨烯层具有褶皱结构，根据所述褶皱结构的褶皱面弯曲形态分类，所述褶皱结构选自圆弧褶皱、尖棱褶皱及扇状褶皱中的至少一种；
    (9)所述碳层包括石墨烯层，所述石墨烯层具有褶皱结构，根据所述褶皱结构的轴面产状和两翼产状分类，所述褶皱结构选自直立褶皱、斜歪褶皱、倒转褶皱及平 卧褶皱中的至少一种；
    (10)所述碳层包括非晶碳层，所述非晶碳层的厚度为5nm～150nm；
    (11)所述包覆层包括金属氧化物层，所述金属氧化物层中的金属元素包括Ti、V、Nb、Ta、W和Zr中的至少一种；
    (12)所述金属氧化物层中的金属元素与氧元素的摩尔比为1：(0.1-3)；
    (13)所述金属氧化物层的厚度为1nm-200nm；
    (14)所述包覆层包括金属氮化物层，所述金属氮化物层中的金属元素包括Ti、V、Nb、Ta、W和Zr中的至少一种；
    (15)所述金属氮化物层的厚度为1nm～250nm。
  8. 根据权利要求1～5任一项所述的负极材料，其特征在于，所述负极材料还包括保护层，所述保护层位于所述骨架表面。
  9. 根据权利要求8所述的负极材料，其特征在于，包括如下特征(1)～(6)中的至少一个：
    (1)所述保护层还填充于所述孔道内或所述通孔内；
    (2)所述保护层包括碳层、金属氧化物层及金属氮化物层中的至少一种；
    (3)所述保护层包括碳层，所述碳层为无定形碳层及/或石墨碳层，以所述复合负极材料质量百分含量为100％计，当所述碳层仅位于所述骨架表面时，碳质量百分含量为5％～25％；当所述碳层位于所述骨架表面并填充所述孔道内或所述通孔内时，以所述复合负极材料质量百分含量为100％计，碳质量百分含量为25％～75％且不包括25％；
    (4)所述保护层包括金属氧化物层，所述金属氧化物层的金属元素包括Si、Sn、Ge、Li、V、Al、Fe和Zn中的至少一种，以所述复合负极材料质量百分含量为100％计，当所述金属氧化物层仅位于所述骨架表面时，金属氧化物质量百分含量为5％～25％；当所述金属氧化物层位于所述骨架表面并填充所述孔道内或所述通孔内时，以所述复合负极材料质量百分含量为100％计，金属氧化物质量百分含量为25％～75％且不包括25％；
    (5)所述保护层包括金属氮化物层，所述金属氮化物层中的金属元素包括Ti、V、Nb、Ta、W和Zr中的至少一种，以所述复合负极材料质量百分含量为100％计，当所述金属氮化物层仅位于所述骨架表面，金属氮化物质量百分含量为5％～25％；当所述金属氮化物位于所述骨架表面并填充所述孔道内或通孔内时，以所述复合负极材料质量百分含量为100％计，金属氮化物质量百分含量为25％～75％且不包括25％；
    (6)位于所述骨架表面的保护层的厚度为1nm～300nm。
  10. 根据权利要求1～5任一项所述的负极材料，其特征在于，所述负极材料还包括位于所述一次颗粒表面的纳米颗粒层以及包覆于所述纳米颗粒层表面的包覆层，所述纳米颗粒层形成有微孔和/或介孔。
  11. 根据权利要求10所述的负极材料，其特征在于，包括如下特征(1)～(6)中的至少一个：
    (1)所述孔道在所有孔结构中的体积占比为35％～90％，所述介孔在所有孔结构中的体积占比为5％～45％，所述微孔在所有孔结构中的体积占比为5％～20％；
    (2)所述一次颗粒的孔隙率为15％～75％，所述纳米颗粒层的孔隙率5％～35％；
    (3)所述纳米颗粒层中的介孔的总孔隙率与微孔的总孔隙率比值为(2～10)：1；
    (4)所述复合负极材料的所有孔结构中的开孔体积占比为60％～95％，闭孔体积占比为5％～40％；
    (5)在所有孔结构的开孔中，交联孔占所有开孔的体积占比为79％～95％，通孔占所有开孔的体积占比为4％～20％，盲孔占所有开孔的体积占比为1％～10％；
    (6)所述纳米颗粒层包括多个堆叠的纳米颗粒；
    (7)所述纳米颗粒选自纳米硅颗粒、纳米锗颗粒、纳米锑颗粒、纳米锡颗粒、纳米硼颗粒中的至少一种；
    (8)所述纳米颗粒层包括多个纳米颗粒，所述纳米颗粒的中值粒径为20nm～200nm；
    (9)所述纳米颗粒层的厚度为20nm～2000nm；
    (10)所述包覆层包括碳层；
    (11)所述包覆层包括碳层，所述碳层的厚度为5nm～100nm；
    (12)所述复合负极材料中的碳的质量百分比含量为5％～50％。
  12. 根据权利要求1～11任一项所述的负极材料，其特征在于，包括如下特征(1)～(9)中的至少一个：
    (1)所述一次颗粒选自硅、锗、锑、锡、硼中的至少一种；
    (2)所述一次颗粒的中值粒径为0.2μm～15μm；
    (3)所述一次颗粒的比表面积为5m 2/g～100m 2/g；
    (4)所述一次颗粒的孔隙率为30％～70％；
    (5)所述一次颗粒的粉体振实密度为0.2g/cm 3～0.8g/cm 3；
    (6)所述一次颗粒的粉体压实密度为1.2g/cm 3～1.8g/cm 3；
    (7)所述复合负极材料的中值粒径为0.1μm～15μm；
    (8)所述复合负极材料的比表面积为1m 2/g～150m 2/g；
    (9)所述复合负极材料的孔隙率为10％～70％。
  13. 一种负极材料的制备方法，其特征在于，所述方法包括以下步骤：
    将含有N-M材料与过渡金属卤化物的混合物置于保护性气氛中进行置换反应，得到反应产物，所述反应产物包括M的卤化物和过渡金属；及
    去除所述反应产物中的M的卤化物和过渡金属，得到负极材料；
    其中，所述N-M材料中的M包括Mg、Al、Li和Ca中的至少一种，所述N-M材料中的N包括Si、Ge、Sn、B及Sb中的至少一种。
  14. 根据权利要求13所述的负极材料，其特征在于，包括如下特征(1)～(21)中的至少一个：
    (1)所述N-M材料为金属间化合物及合金中的至少一种；
    (2)所述N-M材料的D50为0.1μm～15μm；
    (3)所述过渡金属卤化物的化学式为ABx，其中，x＝2或3，A包括Sn、Cu、Fe、Zn、Co、Mn、Cr及Ni中的至少一种，B包括Cl、F及Br中的至少一种；
    (4)所述N-M材料与过渡金属卤化物的摩尔比为1:(0.2～2)；
    (5)所述置换反应的升温速率为1℃/min～20℃/min；
    (6)所述置换反应为在200℃～950℃保温2h～18h；
    (7)所述保护性气氛中的气体包括氮气、氦气、氖气、氩气、氪气及氙气中的至少一种；
    (8)所述去除反应产物中的M的卤化物以及过渡金属的方法为：将所述反应产物在酸溶液和/或过渡金属卤化物溶液中处理；
    (9)所述酸溶液中的酸包括盐酸、硝酸及硫酸中的至少一种；
    (10)所述酸溶液的浓度为1mol/L～5mol/L，在酸溶液中处理的时间为1h～10h；
    (11)所述过渡金属卤化物溶液的浓度为0.5mol/L～5mol/L，在所述过渡金属卤化物溶液中处理的时间为1h～12h；
    (12)所述N-M材料的制备方法为将M粉与N粉混合，在保护性气氛下进行加热反应，得到N-M合金或N-M金属间化合物；
    (13)所述N粉为实心结构，所述N粉包括颗粒、球状、片状、纤维状及方块状中的至少一种；
    (14)所述N粉的D50为0.1μm～15μm；
    (15)所述N粉与M粉的摩尔比为1:(1.5～2.5)；
    (16)所述N-M材料的制备方法步骤中的所述加热反应为在400℃～900℃保温2h～8h；
    (17)所述N-M材料的制备方法步骤中的所述加热反应的升温速率为1℃/min～10℃/min；
    (18)所述反应之后将得到的N-M材料粉碎至D50为0.1μm～15μm；
    (19)所述混合物中还加入碱金属卤化物和/或碱土金属卤化物；
    (20)所述碱金属卤化物和碱土金属卤化物的化学式为ZBy，其中，y为1或2，Z包括Li、Na、K、Mg及Ca中的至少一种，B包括Cl、F及Br中的至少一种；
    (21)所述碱金属卤化物和碱土金属卤化物中的至少一种与过渡金属卤化物的摩尔比为(0.2～1.5):1。
  15. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    将含有N-M合金和含卤素的六元环有机物的混合物置于保护性气氛中进行置换反应，得到反应产物，所述反应产物包括M的氧化物、M的卤化物；及
    去除所述M的氧化物及M的卤化物，得到负极材料；
    其中，所述N-M合金中的N包括硅、锗、锑、锡、硼中的至少一种，所述N-M合金中的M包括镁、铝、钙和锌中的至少一种。
  16. 根据权利要求15所述的负极材料的制备方法，其特征在于，所述制备方法包括如下特征(1)～(6)中的至少一种：
    (1)所述N-M合金和所述含卤素的六元环有机物的摩尔比为1:(0.2～6)；
    (2)所述含卤素的六元环有机物包括卤代环己烷及其衍生物、卤代苯、卤代苯甲酸及卤代苯胺中的至少一种，且所述卤素包括氟、氯及溴中的至少一种；
    (3)当所述含卤素的六元环有机物使用卤代环己烷时，所述混合物还包括裂解抑制剂，其中，所述裂解抑制剂包括酰胺类化合物和氰酸盐；及/或
    所述N-M合金与所述酰胺类化合物的摩尔比为1:(0.1-10)；所述N-M合金与所述氰酸盐的摩尔比为1:(0.1-10)；及/或
    所述酰胺类化合物包括碳酰胺、甲酰胺、乙酰胺、二甲基甲酰胺及内酰胺中的至少一种；及/或
    所述氰酸盐包括氰酸钾、氰酸钠及氰酸铵中的至少一种；
    (4)所述置换反应的反应温度为200℃～1000℃，反应时间为1h～24h；
    (5)所述保护性气氛的气体包括氦气、氖气、氩气、氪气及氙气中的至少一种；
    (6)所述去除所述M的氧化物及M的卤化物的方法包括酸洗，所述酸洗采用的酸溶液的质量浓度为1mol/L～5mol/L。
  17. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    将复合物在真空环境下进行置换反应，得到反应产物，所述反应产物包括M1的氧化物，所述复合物包括表面形成有金属氧化物层的N1-M1材料；及
    去除所述M1的氧化物，得到负极材料；
    其中，所述N1-M1材料中的N1包括硅、锗、锑、锡及硼中的至少一种，所述N1-M1材料中的M1包括镁、铝、钙及锌中的至少一种。
  18. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    将复合物在保护气氛下进行热处理后再进行氮化处理，得到反应产物，所述反应产物包括M1的氧化物，所述复合物包括表面形成有金属氧化物层的N1-M1材料；及
    去除所述M1的氧化物，得到负极材料；
    其中，所述N1-M1材料中的N1包括硅、锗、锑、锡及硼中的至少一种；所述N1-M1材料中的M1包括镁、铝、钙及锌中的至少一种。
  19. 根据权利要求17或18所述的制备方法，其特征在于，所述制备方法包括如下特征(1)～(8)中的至少一种：
    (1)所述N1-M1材料为金属间化合物及合金中的至少一种；
    (2)所述表面形成有金属氧化物层的N1-M1材料的方法包括水热法，溶胶凝胶法、沉淀法、化学气相沉积法、磁控溅射及固相反应法中的至少一种；
    (3)所述金属氧化物层中的金属元素包括Ti、V、Nb、Ta、W和Zr中的至少一种；
    (4)所述真空环境下的真空度小于1000Pa；
    (5)所述置换反应的温度为500℃-1100℃，保温时间1h～48h；
    (6)所述热处理温度为500℃-800℃，保温时间1h～24h；及/或，所述保护性气氛包括氦气、氖气、氩气、氪气及氙气中的至少一种；
    (7)所述氮化处理在400℃-950℃下保温2h～24h；及/或，所述氮化处理的气氛采用氨气气氛、氮气气氛中的至少一种；
    (8)所述去除所述M的氧化物的方法为酸洗。
  20. 一种负极材料的制备方法，其特征在于，所述方法包括以下步骤：
    将含有N-M合金和含碳铵盐的混合物置于保护性气氛中进行置换反应，得到反应产物，所述反应产物包括M的氧化物、M的氮化物；及
    去除所述M的氧化物及M的氮化物，得到负极材料；
    其中，所述N-M合金中的N包括硅、锗、锑、锡、硼中的至少一种，所述N-M合金中的M包括镁、铝、钙和锌中的至少一种。
  21. 根据权利要求20所述的负极材料的制备方法，其特征在于，所述方法包括如下特征(1)～(9)中的至少一种：
    (1)所述N-M合金的粒径为0.2μm～15μm；
    (2)所述N-M合金和所述含碳铵盐混合的摩尔比为1:(0.1-10)；
    (3)所述含碳铵盐包括碳酸铵、碳酸氢铵及氨基甲酸铵中的至少一种；
    (4)所述混合物还包括含碳铵盐分解抑制剂；
    (5)所述混合物还包括含碳铵盐分解抑制剂，所述N-M合金与所述含碳铵盐分解抑制剂的摩尔比为1:(0.2-10)，所述铵盐分解抑制剂包括碳酸盐和/或碳酸氢盐；
    (6)所述混合物还包括熔盐介质；
    (7)所述N-M合金和所述熔盐介质的摩尔比为1:(0.1-10)；
    (8)所述熔盐介质包括卤化铵盐、卤化盐中的至少一种；
    (9)所述卤化铵盐的化学式为NH4Y，其中，Y包括Cl、Br、F和I中的至少一种；
    (10)所述置换反应的反应温度为200℃～950℃，保温时间1h～24h；
    (11)所述置换反应的反应加热速率为1℃/min～20℃/min；
    (12)所述保护性气氛的气体包括氦气、氖气、氩气、氪气及氙气中的至少一种；
    (13)去除所述M的氧化物及M的氮化物的方法包括酸洗；
    (14)去除所述M的氧化物及M的氮化物的方法包括酸洗，所述酸洗采用的酸溶液包括盐酸、硝酸及硫酸中的至少一种；
    (15)去除所述M的氧化物及M的氮化物的方法包括酸洗，所述酸洗采用的酸溶液的质量浓度为1mol/L～5mol/L；
    (16)所述去除所述M的氧化物及M的氮化物的方法包括酸洗，所述酸洗的时间为1h～10h。
  22. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    将含有N-M合金与过渡金属卤化物的混合物置于保护性气氛中进行置换反应，得到反应产物，所述反应产物包括M的卤化物和过渡金属；及
    去除所述反应产物中的M的卤化物和过渡金属，得到N材料，所述N材料为一次颗粒，一次颗粒包括骨架，所述骨架包括位于所述一次颗粒的内部的主骨架及自所述主骨架延伸至所述一次颗粒表面的多个分枝；及
    在所述N材料的骨架表面形成金属氧化物层，得到复合物，所述复合物包括N材料以及位于所述骨架表面的金属氧化层；
    其中，所述N-M合金中的N包括硅、锗、锑、锡及硼中的至少一种，所述N-M合金中的M包括镁、铝、钙及锌中的至少一种。
  23. 根据权利要求22所述的负极材料的制备方法，其特征在于，包括如下特征(1)～(9)中的至少一个：
    (1)所述负极材料的制备方法还包括将所述复合物在保护气氛下进行热处理后 再进行氮化处理，得到负极材料，所述负极材料包括N材料以及位于所述骨架表面的金属氮化层；
    (2)所述过渡金属卤化物的化学式为ABx，其中，x＝2或3，所述A包括Sn、Cu、Fe、Zn、Co、Mn、Cr及Ni中的至少一种，所述B包括Cl、F及Br中的至少一种；
    (3)形成所述金属氧化物层的方法包括水热法、溶胶凝胶法、沉淀法、化学气相沉积法、磁控溅射及固相反应法中的至少一种；
    (4)所述金属氧化物层中的金属元素包括Si、Sn、Ge、Li、V、Al、Fe和Zn的中的至少一种；
    (5)所述置换反应的温度为500℃-1100℃，保温时间1h～48h；
    (6)所述热处理温度为500℃-800℃，保温时间1h～24h；及/或，所述保护性气氛包括氦气、氖气、氩气、氪气及氙气中的至少一种；
    (7)所述去除所述过渡金属和M的卤化物的方法为酸洗；
    (8)所述氮化处理在400℃-950℃下保温2h～24h；
    (9)所述氮化处理的气氛采用氨气气氛、氮气气氛中的至少一种。
  24. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    在N-M合金表面形成包覆层，得到含有包覆层的N-M合金；
    将含有包覆层的N-M合金加入铵盐溶液中进行氧化还原反应，得到中间体；
    将所述中间体在保护性气氛下进行去合金化热处理，并对反应产物进行酸洗，得到负极材料，其中，所述N-M合金中的N包括硅、锗、锑、锡、硼中的至少一种，所述N-M合金中的M包括镁、铝、钙和锌中的至少一种。
  25. 根据权利要求24所述的制备方法，其特征在于，所述制备方法包括如下特征(1)～(15)中的至少一种：
    (1)所述包覆层的形成方法包括：在N-M合金表面采用碳源进行包覆形成碳层；
    (2)所述包覆层的形成方法包括：在N-M合金表面采用碳源进行包覆形成碳层；所述碳源包括气相碳源和固相碳源中的至少一种，所述气相碳源包括甲烷、乙炔、丙酮和酒精中的至少一种；所述固相碳源包括碳酸钙、碳酸锂、碳酸铁、碳酸锌和碳酸镁中的至少一种；
    (3)所述N-M合金表面形成的包覆层的厚度为5nm～100nm；
    (4)所述N-M合金的中值粒径为0.1μm～15μm；
    (5)所述含有包覆层的N-M合金的中值粒径为0.1μm～15μm；
    (6)所述铵盐包括氟化铵、氯化铵、溴化铵、碘化铵、硝酸铵、碳酸铵、高氯酸铵、硫酸铵和硫化铵中的至少一种；
    (7)所述铵盐溶液的质量浓度为0.1mol/L～5mol/L；
    (8)所述含有包覆层的N-M合金与所述铵盐的摩尔比为1：(0.1～2)；
    (9)所述含有包覆层的N-M合金与所述铵盐溶液的氧化还原反应时间为0.5h～12h，温度为20℃～80℃；
    (10)所述去合金化热处理的温度为200℃～950℃，所述去合金化热处理的保温 时间2h～18h；
    (11)所述去合金化热处理的升温速率为1℃/min～20℃/min；
    (12)所述保护性气氛的气体包括氦气、氖气、氩气、氪气及氙气中的至少一种；
    (13)所述酸洗采用的酸溶液包括盐酸、硝酸及硫酸中的至少一种；
    (14)所述酸溶液的质量浓度为1mol/L～5mol/L；
    (15)所述酸洗的时间为1h～10h。
  26. 一种锂离子电池，其特征在于，包括如权利要求1～12任一项所述的复合负极材料或根据权利要求13～25任一项所述负极材料的制备方法制备的负极材料。
PCT/CN2021/109137 2020-12-11 2021-07-29 负极材料及其制备方法、锂离子电池 Ceased WO2022121334A1 (zh)

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