WO2024108574A1 - 碳材料及其制备方法、以及含有其的二次电池和用电装置 - Google Patents

碳材料及其制备方法、以及含有其的二次电池和用电装置 Download PDF

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WO2024108574A1
WO2024108574A1 PCT/CN2022/134444 CN2022134444W WO2024108574A1 WO 2024108574 A1 WO2024108574 A1 WO 2024108574A1 CN 2022134444 W CN2022134444 W CN 2022134444W WO 2024108574 A1 WO2024108574 A1 WO 2024108574A1
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Prior art keywords
carbon material
optionally
temperature
secondary battery
carbon
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English (en)
French (fr)
Inventor
李连川
李远源
沈睿
何立兵
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to JP2024571314A priority Critical patent/JP7846257B2/ja
Priority to CN202280095102.9A priority patent/CN119054110B/zh
Priority to KR1020247040229A priority patent/KR20250004368A/ko
Priority to PCT/CN2022/134444 priority patent/WO2024108574A1/zh
Priority to EP22966262.2A priority patent/EP4513596A4/en
Publication of WO2024108574A1 publication Critical patent/WO2024108574A1/zh
Priority to US18/974,782 priority patent/US20250100889A1/en
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/205—Preparation
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/11—Powder tap density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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 belongs to the field of battery technology, and specifically relates to a carbon material and a preparation method thereof, as well as a secondary battery and an electrical device containing the same.
  • secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • the negative electrode active material is an important component of the secondary battery, which affects the performance of the secondary battery.
  • the negative electrode active material mainly includes graphite.
  • the problem faced in the prior art is that it is difficult for high-capacity graphite to take into account high first coulomb efficiency, and it is also difficult for secondary batteries to take into account good cycle performance and storage performance.
  • the purpose of the present application is to provide a carbon material and a preparation method thereof, as well as a secondary battery and an electrical device containing the same, which can enable the secondary battery to have high first coulombic efficiency, high energy density, and good cycle performance and storage performance.
  • the carbon material provided in the present application can effectively reduce the irreversible capacity loss of the secondary battery, improve the capacity utilization characteristics of the secondary battery, and enable the secondary battery to have high initial coulombic efficiency, high energy density, and good cycle performance and storage performance.
  • 38 ⁇ A ⁇ B ⁇ 65, and optionally, 39 ⁇ A ⁇ B ⁇ 55 is beneficial for the secondary battery to better balance high initial coulombic efficiency, high energy density, and good cycle performance and storage performance.
  • the specific surface area B of the carbon material is 0.5m2/ g- 2.1m2 /g, and can be optionally 0.7m2 / g- 1.8m2 /g.
  • the carbon material can have a lower surface side reaction activity, thereby reducing the consumption of active ions in SEI film formation and improving the first coulombic efficiency of the carbon material; on the other hand, it can also have a higher active ion transport performance.
  • the carbon material includes one or more pore structures with a pore area greater than or equal to 0.1 ⁇ m 2 , and optionally includes one or more pore structures with a pore area of 0.12 ⁇ m 2 -2.5 ⁇ m 2.
  • the pore structure can reserve the required expansion space for the volume change of the carbon material particles, thereby further reducing the risk of carbon material particles breaking and generating new interfaces, thereby reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and further improving the cycle performance and storage performance of the secondary battery.
  • the carbon material includes an external region and an internal region located inside the external region
  • the external region refers to a region extending from the surface of the carbon material particle to the inside of the particle by a distance of 0.25L
  • L refers to the minor axis length of the carbon material particle
  • the total pore area of the external region is recorded as S 1
  • the total pore area of the internal region is recorded as S 2
  • S 2 > S 1 the irreversible capacity loss of the secondary battery can be effectively reduced, the capacity performance characteristics of the secondary battery can be improved, and the secondary battery can better balance high initial coulomb efficiency, high energy density, and good cycle performance and storage performance.
  • S 2 /S 1 also satisfies the above range, the secondary battery can better balance high first coulombic efficiency, high energy density, and good cycle performance and storage performance.
  • the carbon material particles can have fewer surface defects and a more stable structure, and the electrolyte can be prevented from penetrating into the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions and reducing the consumption of active ions by SEI film formation inside the carbon material particles.
  • the transmission performance of active ions and electrons will not be affected.
  • 2.5 ⁇ m 2 ⁇ S 2 ⁇ 25.0 ⁇ m 2 optionally, 3.0 ⁇ m 2 ⁇ S 2 ⁇ 20.5 ⁇ m 2 .
  • sufficient and stable expansion space can be reserved for the volume change of the carbon material particles, reducing the risk of carbon material particles breaking to generate new interfaces, reducing the occurrence of side reactions on the new interface surface, and reducing the consumption of active ions by SEI film formation on the new interface surface.
  • the capacity and first coulombic efficiency of the carbon material can also be improved.
  • L ⁇ 4 ⁇ m optionally, 6 ⁇ m ⁇ L ⁇ 18 ⁇ m.
  • the area of the pore structure in the outer region of the carbon material is less than or equal to 0.2 ⁇ m 2 , and can be less than or equal to 0.15 ⁇ m 2 .
  • the outer region of the carbon material can have a denser structure, thereby effectively reducing the surface defects of the carbon material, improving the structural stability of the carbon material, and avoiding the electrolyte from penetrating into the pore structure inside the carbon material particles as much as possible, thereby further improving the cycle performance and storage performance of the secondary battery.
  • the internal region of the carbon material includes one or more pore structures with an area greater than or equal to 0.15 ⁇ m 2 , and optionally includes one or more pore structures with an area of 0.18 ⁇ m 2 -2.5 ⁇ m 2.
  • the interlayer spacing of the outer region of the carbon material is denoted as d 1
  • the interlayer spacing of the inner region of the carbon material is denoted as d 2
  • the carbon material satisfies d 1 ⁇ d 2 , and optionally, d 1 > d 2 .
  • the interlayer spacing of the outer region of the carbon material is larger, which is more conducive to the rapid embedding and extraction of active ions, thereby further improving the kinetic performance of the secondary battery
  • the interlayer spacing of the inner region of the carbon material is smaller, which is conducive to improving the gram capacity and compaction density of the carbon material, thereby further improving the energy density of the secondary battery.
  • d1 is 0.33565 nm-0.33610 nm.
  • d2 is 0.33557nm-0.33585nm.
  • the graphitization degree of the carbon material is 94%-98%, and can be 95%-97%.
  • the graphitization degree of the carbon material is within the above range, it is beneficial to improve the energy density of the secondary battery, and also to improve the cycle performance, storage performance and/or rate performance of the secondary battery.
  • La(110) of the carbon material is 100nm-150nm, and can be optionally 110nm-130nm.
  • Lc(002) of the carbon material is 20nm-45nm, and can be optionally 28nm-40nm.
  • the carbon material is beneficial to having higher crystallinity and/or degree of graphitization, which is beneficial to improving the gram capacity of the carbon material, and is also beneficial to improving the active ion and electron transport properties of the negative electrode film layer, thereby helping to improve the cycle performance, storage performance and/or rate performance of the secondary battery.
  • the volume distribution particle size Dv50 of the carbon material is 8.0 ⁇ m-24.0 ⁇ m, and can be optionally 9.5 ⁇ m-22.5 ⁇ m.
  • the volume distribution particle size Dv10 of the carbon material is 5.0 ⁇ m-15.0 ⁇ m, and can be optionally 6.0 ⁇ m-14.0 ⁇ m.
  • the volume distribution particle size Dv90 of the carbon material is 16.0 ⁇ m-35.0 ⁇ m, and can be optionally 17.0 ⁇ m-34.0 ⁇ m.
  • volume distribution particle size Dv10, Dv50 and/or Dv90 of the carbon material is within the above range, it is beneficial to improve the transport performance of active ions and electrons, and is also beneficial to form a reasonable pore structure between the particles of the negative electrode film layer, thereby further improving the cycle performance and/or rate performance of the secondary battery.
  • the (Dv90-Dv10)/Dv50 of the carbon material is 0.55-1.55, and can be optionally 0.8-1.4.
  • the (Dv90-Dv10)/Dv50 of the carbon material is within the above range, its particle stacking performance is good, which is conducive to improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery; in addition, it is also conducive to forming a reasonable pore structure between the particles of the negative electrode film layer.
  • the tap density of the carbon material is 0.80 g/cm 3 -1.32 g/cm 3 , and can be 0.82 g/cm 3 -1.28 g/cm 3 .
  • the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery; it is also beneficial to form a reasonable pore structure between particles of the negative electrode film layer, improve the transmission performance of active ions and electrons, and improve the cycle performance and storage performance of the secondary battery.
  • the gram capacity of the carbon material is 355 mAh/g-371 mAh/g, and can be 360 mAh/g-370 mAh/g.
  • the energy density of the secondary battery can be improved.
  • the morphology of the carbon material includes one or more of block, spherical and quasi-spherical.
  • the second aspect of the present application provides a method for preparing a carbon material, comprising the following steps: step 1, providing a raw material having a plurality of pore structures; step 2, uniformly mixing the raw material and a filling material in a predetermined ratio, and then keeping the mixture at a first temperature T 1 for a first time t 1 to obtain an intermediate; step 3, keeping the obtained intermediate at a second temperature T 2 for a second time t 2 to obtain a carbon material, wherein the carbon material comprises a pore structure, the amount of linseed oil adsorbed by 100g of the carbon material is denoted as A, and the specific surface area of the carbon material is denoted as B, and the carbon material satisfies: 36 ⁇ A ⁇ B ⁇ 75, the unit of the amount of linseed oil adsorbed by 100g of the carbon material is ml, and the unit of the specific surface area B of the carbon material is m 2 /g.
  • the raw material includes natural graphite.
  • the natural graphite includes one or more of flake graphite, natural spherical graphite and microcrystalline graphite.
  • the volume distribution particle size Dv50 of the raw material is 8.5 ⁇ m-24.0 ⁇ m, and can be optionally 10.5 ⁇ m-22.5 ⁇ m.
  • the ash content in the raw material is ⁇ 1 wt%.
  • the softening point temperature of the filler material is 110° C.-175° C., and can be optionally 120° C.-170° C.
  • the carbon material it is beneficial for the carbon material to have a suitable adsorption amount A of linseed oil and/or a suitable specific surface area B, to make A ⁇ B of the carbon material within a suitable range, and to adjust the pore size and/or pore number in the outer region and the inner region of the carbon material within a suitable range, and to adjust S 2 /S 1 within a suitable range.
  • the coking value of the filler material is 26%-50%, and can be optionally 33%-45%.
  • the carbon material it is beneficial for the carbon material to have a suitable adsorption amount A of linseed oil and/or a suitable specific surface area B, to make A ⁇ B of the carbon material within a suitable range, and to adjust the pore size and/or pore number in the outer region and the inner region of the carbon material within a suitable range, and to adjust S2 / S1 within a suitable range.
  • the volume distribution particle size Dv50 of the filler material is less than or equal to 6 ⁇ m, and can be 1 ⁇ m-5 ⁇ m, which is conducive to filling the filler material into the pore structure of the raw material after being heated and melted, and is also conducive to improving the dispersion uniformity of the filler material and the raw material.
  • the content of quinoline insoluble matter in the filling material is ⁇ 1 wt %, and can be optionally ⁇ 0.8 wt %.
  • the filling material includes one or more of coal tar and petroleum asphalt.
  • the mass ratio of the filler material to the raw material is (10-32):100, and can be (10-25):100.
  • This is conducive to the carbon material having a suitable adsorption amount A for linseed oil and/or a suitable specific surface area B, and is conducive to making A ⁇ B of the carbon material within a suitable range, and is also conducive to adjusting the pore size and/or pore number in the outer region and the inner region of the carbon material within a suitable range, and adjusting S2 / S1 within a suitable range.
  • the heating process of uniformly mixing the raw material and the filling material in a predetermined ratio and then heating the mixture to the first temperature T1 is a staged heating process, which may optionally include a first heating process, a second heating process and a third heating process.
  • the first temperature rising process is to raise the temperature to 200° C.-250° C. and keep the temperature at this temperature for 0.5 h-2 h.
  • the second temperature rising process is to raise the temperature to 450° C.-550° C. and keep the temperature at this temperature for 0.5 h-2 h.
  • the third temperature increasing process is to increase the temperature to the first temperature T 1 and keep the temperature at the first time t 1 .
  • the temperature is increased to the first temperature T 1 at a rate of 1° C./min-10° C./min, optionally 1.5° C./min-8° C./min.
  • the first temperature T1 is 700°C-1100°C, and can be optionally 750°C-1100°C.
  • the first time t1 is 0.5h-5h, and can be optionally 0.5h-3h.
  • the heating rate, the first temperature, the first time, the heating process, etc. within the above ranges, it is beneficial to prepare the desired carbon material, for example, it is beneficial for the carbon material to have a suitable adsorption amount A for linseed oil and/or a suitable specific surface area B, it is beneficial to make the A ⁇ B of the carbon material within a suitable range, and it is also beneficial to adjust the pore size and/or the number of pores in the outer region and the inner region of the carbon material within a suitable range, and adjust S2 / S1 within a suitable range.
  • the second temperature T2 is 1920°C-2520°C, and can be optionally 2050°C-2400°C.
  • the second time t2 is 1h-6h, and can be optionally 2h-5h.
  • the carbon material By adjusting one or more of the second temperature and the second time within the above-mentioned range, it is beneficial to reduce the content of disordered carbon in the carbon material, and it is also beneficial for the carbon material to have a suitable adsorption amount A for linseed oil and/or a suitable specific surface area B, and it is also beneficial to make the A ⁇ B of the carbon material within a suitable range.
  • a third aspect of the present application provides a secondary battery, which includes a negative electrode plate, wherein the negative electrode plate includes the carbon material of the first aspect of the present application or the carbon material prepared by the method of the second aspect of the present application.
  • a fourth aspect of the present application provides an electrical device, which includes the secondary battery of the third aspect of the present application.
  • the electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of a cross-sectional image of a particle of the carbon material of the present application.
  • FIG. 2 is a schematic diagram of an embodiment of a secondary battery of the present application.
  • FIG. 3 is an exploded schematic diagram of an embodiment of a secondary battery of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of a battery module of the present application.
  • FIG. 5 is a schematic diagram of an embodiment of a battery pack of the present application.
  • FIG. 6 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 5 .
  • FIG. 7 is a schematic diagram of an embodiment of an electric device including the secondary battery of the present application as a power source.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • the values of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in this application.
  • active ions refers to ions that can be intercalated and extracted back and forth between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.
  • graphite can be divided into artificial graphite and natural graphite.
  • Artificial graphite generally needs to go through a high-temperature graphitization process when it is prepared. This process is energy-intensive and costly, which results in a high cost for artificial graphite.
  • Natural graphite comes from nature, so it has the advantage of relatively low cost. In addition, natural graphite also has the advantage of high capacity.
  • Natural graphite mainly includes flake graphite, natural spherical graphite and microcrystalline graphite. Unlike artificial graphite, natural graphite has a lot of pores and defects inside and outside the particles. During the first charging process of the secondary battery, the electrolyte produces more side reactions with the pores on the surface and inside the particles, which leads to high first irreversible capacity loss of the secondary battery, low first coulomb efficiency, and poor cycle performance and storage performance. In particular, flake graphite and natural spherical graphite have high crystallinity and high graphitization degree, and the microstructure is mostly layered.
  • the particle surface coating treatment mainly involves mixing natural graphite with a coating agent (such as asphalt, polymer compounds, etc.) and then heat treating it to coat a layer of carbon on the surface of the natural graphite particles to slightly repair the defects on the particle surface.
  • a coating agent such as asphalt, polymer compounds, etc.
  • the inventors of this application found during the research process that the surface-coated amorphous carbon layer will cause the gram capacity and/or compaction density of natural graphite to decrease, affecting the energy density of the secondary battery; at the same time, the surface defects of the particles are still relatively large after the surface-coated amorphous carbon layer; in addition, the surface-coated amorphous carbon layer cannot effectively prevent the electrolyte from penetrating into the pore structure inside the particles, resulting in limited improvement in the first coulombic efficiency, cycle performance and/or storage performance of the secondary battery.
  • the internal filling treatment of particles mainly involves mixing natural graphite with fillers (such as asphalt, polymer compounds, etc.), and filling the fillers into the internal pores of the particles by means of preset pressure, vacuuming and heating, so as to obtain natural graphite without pores inside the particles.
  • fillers such as asphalt, polymer compounds, etc.
  • the inventors of the present application found in the research process that a large amount of carbon filled inside the particles, especially soft carbon, will lead to a decrease in the gram capacity of natural graphite, affecting the energy density of the secondary battery; at the same time, since the pores inside the natural graphite particles are all filled with carbon, the volume change of natural graphite during the process of active ion escape and embedding is large, and the particles are more easily broken, which leads to repeated destruction and reconstruction of the SEI film on the surface of the particles, further increasing the irreversible consumption of active ions, increasing the irreversible capacity loss of the secondary battery, and shortening the service life of the secondary battery.
  • the prior art will continue to coat a layer of amorphous carbon layer on the surface of the natural graphite without pores inside the above-mentioned particles, which will lead to a further decrease in the gram capacity and/or compacted density of natural graphite, and at this time, there are still many defects on the surface of the particles, which cannot effectively improve the service life of the secondary battery.
  • the inventors of this application have proposed a new type of carbon material after extensive research, which has both high gram capacity and high first coulombic efficiency, and can also enable secondary batteries to have high first coulombic efficiency, high energy density, and good cycle performance and storage performance.
  • a first aspect of the embodiments of the present application provides a carbon material.
  • the carbon material includes a pore structure.
  • the amount of linseed oil adsorbed by 100g of the carbon material is recorded as A, and the specific surface area of the carbon material is recorded as B. Then the carbon material satisfies: 36 ⁇ A ⁇ B ⁇ 75, the unit of the amount of linseed oil adsorbed by 100g of the carbon material is ml, and the unit of the specific surface area B of the carbon material is m2 /g.
  • the inventors of the present application have found in the research process that when the carbon material satisfies 36 ⁇ A ⁇ B ⁇ 75, the secondary battery can have high initial coulombic efficiency, high energy density, and good cycle performance and storage performance. Possible reasons include the following.
  • the surface of the carbon material particles is relatively dense at this time, so that the carbon material particles have a stable structure and can avoid the electrolyte from penetrating into the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions and reducing the consumption of active ions by SEI film formation inside the particles, thereby improving the first coulombic efficiency of the carbon material and further improving the cycle performance and storage performance of the secondary battery.
  • the carbon material particles can also enable the negative electrode film layer to form a reasonable pore structure, thereby improving the wettability of the negative electrode plate to the electrolyte.
  • the carbon material provided in the present application can effectively reduce the irreversible capacity loss of the secondary battery, improve the capacity utilization characteristics of the secondary battery, and enable the secondary battery to have high first coulombic efficiency, high energy density, and good cycle performance and storage performance.
  • the amount of linseed oil adsorbed by the carbon material may be small and/or the specific surface area of the carbon material may be small.
  • the surface structure of the carbon material is highly densified, which may cause a large volume change of the carbon material particles during the process of active ion extraction and embedding. At this time, the particles are more easily broken, which in turn causes the SEI film on the surface of the particles to be easily repeatedly destroyed and rebuilt, which in turn increases the irreversible consumption of active ions, increases the irreversible capacity loss of the secondary battery, and shortens the service life of the secondary battery.
  • the specific surface area of the carbon material is small, it may be unfavorable for the transmission of active ions, thereby affecting the capacity, cycle performance and/or rate performance of the secondary battery.
  • the amount of linseed oil adsorbed by the carbon material may be large and/or the specific surface area of the carbon material may be large.
  • the amount of linseed oil adsorbed by the carbon material is large, the surface defects and/or pore structures of the carbon material particles are large, which leads to more side reactions of the electrolyte, and the SEI film formation consumes more active ions, thereby reducing the first coulomb efficiency of the secondary battery; at the same time, as the number of charge and discharge times of the secondary battery increases, the thickness of the SEI film on the surface of the carbon material particles continues to increase, which also affects the cycle performance and/or rate performance of the secondary battery.
  • the adsorption amount A of 100g of the carbon material on linseed oil is 30ml-50mL, and can be optionally 35ml-47mL.
  • the surface side reaction activity of the carbon material particles is low, thereby reducing the consumption of active ions by SEI film formation, while also preventing the particle surface from being too dense and affecting the active ion transmission; in addition, it is also beneficial to form a reasonable pore structure between the particles of the negative electrode film layer, and improve the wettability of the negative electrode plate to the electrolyte.
  • the secondary battery can better balance high initial coulomb efficiency, high energy density, and good cycle performance and storage performance.
  • the specific surface area B of the carbon material is 0.5m 2 /g-2.1m 2 /g, and can be 0.7m 2 /g-1.8m 2 /g, 0.9m 2 /g-1.8m 2 /g, 1.0m 2 /g-1.8m 2 /g, 1.0m 2 /g-1.7m 2 / g, 1.0m 2 /g-1.6m 2 /g.
  • the specific surface area of the carbon material is within the above range, on the one hand, the carbon material can have a lower surface side reaction activity, thereby reducing the consumption of active ions by SEI film formation and improving the first coulomb efficiency of the carbon material; on the other hand, it can also have a higher active ion transport performance.
  • the secondary battery can better balance high first coulomb efficiency, high energy density, good cycle performance and storage performance.
  • the secondary battery can also have good rate performance.
  • the specific surface area of carbon materials is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be tested by nitrogen adsorption specific surface area analysis test method according to GB/T 19587-2017 and calculated by BET (Brunauer Emmett Teller) method.
  • the test instrument can be the Tri-Star 3020 specific surface area pore size analysis tester from Micromeritics, USA.
  • the adsorption amount A of 100g carbon material on linseed oil can be tested as follows: refer to GB/T 3780.2-2017, weigh a certain mass (e.g. 20g) of the dried test sample, place the weighed sample in the mixing chamber of the oil absorption meter, the temperature of the mixing chamber is 23°C, and the lid is closed; align the oil delivery pipe of the constant-speed burette with the top of the hole of the mixing chamber cover; start the oil absorption meter, the instrument starts to run and linseed oil is added dropwise. As the oil absorption of the sample increases, the mixed material changes from a free-flowing state to a semi-plastic agglomerate.
  • a certain mass e.g. 20g
  • the carbon material includes one or more pore structures with a pore area greater than or equal to 0.1 ⁇ m 2 , and optionally includes one or more pore structures with a pore area of 0.12 ⁇ m 2 to 2.5 ⁇ m 2.
  • the pore structure can reserve the required expansion space for the volume change of the carbon material particles, thereby further reducing the risk of carbon material particles breaking and generating new interfaces, thereby reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and further improving the cycle performance and storage performance of the secondary battery.
  • the carbon material includes an external region and an internal region located inside the external region
  • the external region refers to a region extending from the particle surface of the carbon material to the interior of the particle by a distance of 0.25L
  • L refers to the minor axis length of the carbon material particle
  • the total pore area of the external region is denoted as S 1
  • the total pore area of the internal region is denoted as S 2
  • the total pore area S1 of the outer region and the total pore area S2 of the inner region of the first carbon-based material can be obtained by testing the cross-sectional image of the first carbon-based material.
  • the cross-sectional image of the first carbon-based material includes a cross-sectional image passing through the center of the first carbon-based material particle.
  • “Particle center” refers to a range within a radius of 0.1 ⁇ m extending from the geometric center of the particle to the particle surface.
  • the minor axis length of a particle refers to the minimum value when a line connecting two points on the particle surface passes through the geometric center of the particle.
  • Fig. 1 is a schematic diagram of a cross-sectional image of a particle of the carbon material 100 of the present application, and the cross-sectional image passes through the particle center of the carbon material 100.
  • L represents the minor axis length of the particle of the carbon material 100
  • the area extending from the particle surface of the carbon material 100 to the inside of the particle by a distance of 0.25L is the outer area 101
  • the area inside the outer area 101 is the inner area 102.
  • a cross-section polisher (e.g., IB-09010 CP argon ion cross-section polisher produced by JEOL of Japan) can be used to prepare the cross-section of the first carbon-based material; then, referring to JY/T010-1996, a scanning electron microscope (e.g., Sigma 300 scanning electron microscope produced by ZEISS of Germany) is used to scan the cross-section of the first carbon-based material; finally, the total pore area S1 of the outer region and the total pore area S2 of the inner region of the first carbon-based material are calculated by image processing software (e.g., AVIZO).
  • image processing software e.g., AVIZO
  • the carbon material particles may have the following characteristics: the number of pores in the inner region is large and/or the pore size is large, while the number of pores in the outer region is small and/or the pore size is small.
  • the number of pores in the inner region of the carbon material is large and/or the pore size is large, so that the pore structure can reserve the required expansion space for the volume change of the carbon material particles, thereby reducing the risk of carbon material particles breaking and generating new interfaces, thereby reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and improving the cycle performance and storage performance of the secondary battery;
  • the number of pores in the outer region of the carbon material is small and/or the pore size is small, thereby making the carbon material particles have fewer surface defects and a more stable structure, and can avoid the electrolyte from penetrating into the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions, reducing the consumption of active ions by the SEI film formation inside the particles, thereby improving the first coulomb efficiency of the carbon material, and further improving the cycle performance and storage performance of the secondary battery.
  • the carbon material particles further satisfy S 2 >S 1 , the irreversible capacity loss of the secondary battery can be effectively reduced, the capacity utilization characteristics of the secondary battery can be improved, and the secondary battery can better balance high first coulombic efficiency, high energy density, and good cycle performance and storage performance.
  • 0.01 ⁇ m 2 ⁇ S 1 ⁇ 12.0 ⁇ m 2 optionally, 0.02 ⁇ m 2 ⁇ S 1 ⁇ 10.0 ⁇ m 2 , 0.02 ⁇ m 2 ⁇ S 1 ⁇ 8.0 ⁇ m 2 , 0.02 ⁇ m 2 ⁇ S 1 ⁇ 7.0 ⁇ m 2 , 0.1 ⁇ m 2 ⁇ S 1 ⁇ 10.0 ⁇ m 2 , 0.1 ⁇ m 2 ⁇ S 1 ⁇ 7.0 ⁇ m 2 .
  • the carbon material particles can have fewer surface defects and a more stable structure, and the electrolyte can be prevented from penetrating into the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions and reducing the consumption of active ions by SEI film formation inside the carbon material particles.
  • the transport performance of active ions and electrons will not be affected.
  • 2.5 ⁇ m 2 ⁇ S 2 ⁇ 25.0 ⁇ m 2 optionally, 3.0 ⁇ m 2 ⁇ S 2 ⁇ 22.5 ⁇ m 2 , 3.0 ⁇ m 2 ⁇ S 2 ⁇ 20.5 ⁇ m 2 , 4.0 ⁇ m 2 ⁇ S 2 ⁇ 17.5 ⁇ m 2 .
  • the total pore area of the inner region of the carbon material is within the above range, on the one hand, sufficient and stable expansion space can be reserved for the volume change of the carbon material particles, the risk of carbon material particles breaking to generate new interfaces can be reduced, the occurrence of side reactions on the new interface surface can be reduced, and the consumption of active ions by SEI film formation on the new interface surface can be reduced; on the other hand, the capacity and first coulombic efficiency of the carbon material can be improved.
  • L ⁇ 4 ⁇ m optionally, 4 ⁇ m ⁇ L ⁇ 20 ⁇ m, 6 ⁇ m ⁇ L ⁇ 18 ⁇ m, 8 ⁇ m ⁇ L ⁇ 18 ⁇ m, 8 ⁇ m ⁇ L ⁇ 16 ⁇ m.
  • the area of the pore structure in the outer region of the carbon material is less than or equal to 0.2 ⁇ m 2 , and can be less than or equal to 0.15 ⁇ m 2.
  • the inventors have also found in further research that by controlling the area size of the pore structure in the outer region of the carbon material within the above range, the outer region of the carbon material can have a denser structure, thereby effectively reducing the surface defects of the carbon material, improving the structural stability of the carbon material, and avoiding the electrolyte from penetrating into the pore structure inside the carbon material particles as much as possible, thereby further improving the cycle performance and storage performance of the secondary battery.
  • the present application is not intended to limit the area of all pore structures in the outer region of the carbon material to be less than or equal to 0.2 ⁇ m 2.
  • the area of the pore structure can be controlled to be less than or equal to 0.2 ⁇ m 2, and can be less than or equal to 0.15 ⁇ m 2 , which can be controlled to be more than 95%, and can be more than 99%.
  • the internal region of the carbon material includes one or more pore structures with an area greater than or equal to 0.15 ⁇ m 2 , and optionally includes one or more pore structures with an area of 0.18 ⁇ m 2 -2.5 ⁇ m 2.
  • the inventors have also found in further research that by making the internal region of the carbon material include pore structures of the above size, on the one hand, sufficient and stable expansion space can be reserved for the volume change of the carbon material particles, reducing the risk of carbon material particle breakage, and on the other hand, the compaction density of the carbon material can be increased.
  • the interlayer spacing in the outer region of the carbon material is larger, which is more conducive to the rapid embedding and extraction of active ions, thereby further improving the kinetic performance of the secondary battery; the interlayer spacing in the inner region of the carbon material is smaller, which is conducive to improving the gram capacity and compaction density of the carbon material, thereby further improving the energy density of the secondary battery.
  • d1 is 0.33565 nm - 0.33610 nm.
  • d2 is 0.33557 nm - 0.33585 nm.
  • the interlayer spacing of different regions of the carbon material particles can be tested using instruments and methods known in the art.
  • a high-resolution transmission electron microscope HRTEM
  • the testing instrument can be a Spectra S/TEM scanning transmission electron microscope from Thermo Fisher Scientific.
  • La(110) of the carbon material is 100nm-150nm, and can be optionally 110nm-130nm.
  • the carbon material is beneficial to having higher crystallinity and/or degree of graphitization, which is beneficial to improving the gram capacity of the carbon material, and is also beneficial to improving the active ion and electron transport properties of the negative electrode film layer, thereby helping to improve the cycle performance, storage performance and/or rate performance of the secondary battery.
  • La(110) represents the crystallite size along the a-axis in the (110) crystal plane of the carbon material
  • Lc(002) represents the crystallite size along the c-axis in the (002) crystal plane of the carbon material, which can be tested using instruments and methods known in the art.
  • an X-ray diffractometer (such as Bruker D8 Discover) can be used for testing, and the test can refer to JIS K 0131-1996 and JB/T 4220-2011 to obtain the peak intensity and half-maximum full width (FWHM) of the diffraction peak corresponding to the (110) crystal plane of the carbon material, and the peak intensity and half-maximum full width (FWHM) of the diffraction peak corresponding to the (002) crystal plane, and then calculate according to the Scherrer formula.
  • FWHM peak intensity and half-maximum full width
  • the graphitization degree of the carbon material is 94%-98%, optionally 95%-97%.
  • the graphitization degree of the carbon material is within the above range, it is beneficial to improve the energy density of the secondary battery, and also to improve the cycle performance, storage performance and/or rate performance of the secondary battery.
  • the graphitization degree of carbon materials is a well-known meaning in the art and can be tested using instruments and methods known in the art.
  • an X-ray diffractometer such as Bruker D8 Discover
  • d 002 is the average interlayer spacing of the (002) crystal plane in the crystal structure of the carbon material expressed in nanometers (nm).
  • the morphology of the carbon material includes one or more of block, spherical and quasi-spherical shapes, which is helpful to improve the compaction density of the negative electrode sheet, thereby improving the energy density of the secondary battery.
  • the carbon material includes primary particles, and optionally, the amount of the primary particles in the carbon material is ⁇ 50%, for example, it can be 55%-95%, 60%-100%, 65%-90%, 65%-80%, 70%-100%, 75%-90%, 80%-100%, 90%-100%, or 95%-100%.
  • the carbon material contains an appropriate proportion of primary particles, which can make it have higher structural stability and reduce the occurrence of side reactions; in addition, it can also improve the compaction density of the negative electrode sheet, thereby improving the energy density of the secondary battery.
  • the carbon materials may all be primary particles, that is, the number of the primary particles in the carbon materials accounts for 100%.
  • Primary particles refer to non-agglomerated particles.
  • Secondary particles refer to agglomerated particles formed by the aggregation of two or more primary particles.
  • Primary particles and secondary particles can be distinguished by using a scanning electron microscope (SEM) image.
  • the number ratio of primary particles in the carbon material can be tested according to the following method: randomly select a test sample in the negative electrode film layer, randomly select multiple test areas in the test sample, use a scanning electron microscope to obtain images of the multiple test areas, and count the ratio of the number of carbon material particles with primary particle morphology in each image to the total number of carbon material particles. The average value of multiple statistical results is the number ratio of primary particles in the carbon material.
  • the volume distribution particle size Dv50 of the carbon material is 8.0 ⁇ m-24.0 ⁇ m, and optionally 9.5 ⁇ m-22.5 ⁇ m.
  • the volume distribution particle size Dv10 of the carbon material is 5.0 ⁇ m-15.0 ⁇ m, and optionally 6.0 ⁇ m-14.0 ⁇ m.
  • the volume distribution particle size Dv90 of the carbon material is 16.0 ⁇ m-35.0 ⁇ m, and optionally 17.0 ⁇ m-34.0 ⁇ m.
  • volume distribution particle size Dv10, Dv50 and/or Dv90 of the carbon material is within the above range, it is beneficial to improve the transport performance of active ions and electrons, and is also beneficial to form a reasonable pore structure between the particles of the negative electrode film layer, thereby further improving the cycle performance and/or rate performance of the secondary battery.
  • the (Dv90-Dv10)/Dv50 of the carbon material is 0.55-1.55, and can be optionally 0.8-1.4.
  • the (Dv90-Dv10)/Dv50 of the carbon material is within the above range, its particle stacking performance is good, which is conducive to improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery; in addition, it is also conducive to forming a reasonable pore structure between the particles of the negative electrode film layer.
  • the volume distribution particle sizes Dv10, Dv50, and Dv90 of carbon materials are well-known in the art, and respectively represent the particle sizes corresponding to the cumulative volume distribution percentages of the materials reaching 10%, 50%, and 90%, and can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer with reference to the particle size distribution laser diffraction method of GB/T 19077-2016.
  • the test instrument can be a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK.
  • the tap density of the carbon material is 0.80 g/cm 3 -1.32 g/cm 3 , and can be 0.82 g/cm 3 -1.28 g/cm 3 .
  • the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery; it is also beneficial to form a reasonable pore structure between particles of the negative electrode film layer, improving the transmission performance of active ions and electrons, and improving the cycle performance and storage performance of the secondary battery.
  • the tap density of carbon materials is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester with reference to GB/T 5162-2006.
  • the test instrument can be Dandong Better BT-301.
  • the gram capacity of the carbon material is 355 mAh/g-371 mAh/g, and can be 360 mAh/g-370 mAh/g.
  • the energy density of the secondary battery can be improved.
  • the gram capacity of carbon materials is a well-known meaning in the art and can be tested by methods known in the art.
  • An exemplary test method is as follows: a carbon material sample is fully stirred and mixed with a binder styrene-butadiene rubber (SBR), a thickener sodium carboxymethyl cellulose (CMC), and a conductive agent carbon black in a mass ratio of 96.2:1.8:1.2:0.8 in an appropriate amount of solvent deionized water to form a uniform negative electrode slurry; the negative electrode slurry is evenly coated on the surface of the negative electrode current collector copper foil, and dried in an oven for use; ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then LiPF 6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol/L; then a metal lithium sheet is used as a counter electrode and a
  • the button cell prepared above was first discharged at a constant current of 0.15 mA to 0.005 V, left to stand for 5 min, and then discharged at a constant current of 10 ⁇ A to 0.005 V, and the first cycle discharge capacity of the button cell was recorded; then, the button cell was charged at a constant current of 0.3 mA to 2.0 V, and the charging capacity of the button cell was recorded.
  • the ratio of the charging capacity of the button cell to the mass of the carbon material sample is the gram capacity of the carbon material.
  • a second aspect of the embodiments of the present application provides a method for preparing a carbon material, which can prepare the carbon material of the first aspect of the embodiments of the present application.
  • the preparation method of the carbon material comprises the following steps: step 1, providing a raw material having a plurality of pore structures; step 2, uniformly mixing the raw material and a filling material in a predetermined ratio, and then keeping the mixture at a first temperature T 1 for a first time t 1 to obtain an intermediate; step 3, keeping the obtained intermediate at a second temperature T 2 for a second time t 2 to obtain a carbon material, wherein the carbon material comprises a pore structure, the amount of linseed oil adsorbed by 100g of the carbon material is recorded as A, and the specific surface area of the carbon material is recorded as B, then the carbon material satisfies: 36 ⁇ A ⁇ B ⁇ 75, the unit of the amount of linseed oil adsorbed by 100g of the carbon material is ml, and the unit of the specific surface area B of the carbon material is m 2 /g.
  • the raw material for preparing the carbon material includes natural graphite.
  • the natural graphite includes one or more of flake graphite, natural spherical graphite and microcrystalline graphite, and may optionally include natural spherical graphite.
  • Natural spherical graphite refers to natural graphite with a spherical or quasi-spherical shape, and not all natural graphite particles are controlled to be ideal spheres.
  • natural spherical graphite with a desired particle size and morphology can be obtained by pre-treating flake graphite, and optionally, the pre-treatment includes crushing, classification, spheroidization, purification and other processes.
  • the morphology of the raw material includes one or more of spherical and quasi-spherical.
  • the volume distribution particle size Dv50 of the raw material is 8.5 ⁇ m-24.0 ⁇ m, and can be optionally 10.5 ⁇ m-22.5 ⁇ m.
  • the agglomeration of the raw material in the subsequent preparation process can be reduced, thereby reducing the problems of increased surface defects of carbon material particles and increased surface side reaction sites due to the need to add a depolymerization step.
  • the ash content in the raw material is ⁇ 1 wt%.
  • the softening point temperature of the filling material is 110° C.-175° C.
  • the softening point temperature of the filling material can be 110° C., 115° C., 120° C., 125° C., 130° C., 135° C., 140° C., 145° C., 150° C., 155° C., 160° C., 165° C., 170° C., 175° C. or any range thereof.
  • the softening point temperature of the filling material is 120° C.-170° C.
  • the filling material when the softening point temperature of the filling material is too high, the filling material is not easy to flow and fill into the pore structure of the raw material, thereby failing to effectively reduce the surface and internal defects of the obtained carbon material particles, and failing to effectively prevent the electrolyte from penetrating into the pore structure inside the obtained carbon material particles, and at this time, the adsorption amount A of the carbon material for linseed oil and/or the specific surface area B of the carbon material are likely to be large, and the A ⁇ B of the carbon material is likely to be large, thereby affecting the initial coulomb efficiency, cycle performance and storage performance of the secondary battery; when the softening point temperature of the filling material is too low, the filling material contains more small molecules, which are easily volatilized by heat, so Therefore, although the filling material can easily flow and fill into the pore structure of the raw material, the small molecules in the filling material volatilize during heat treatment at high temperature, resulting in the actual residual carbon being unable
  • the carbon material particles have more surface defects, the adsorption amount A of linseed oil by the carbon material and/or the specific surface area B of the carbon material are likely to be larger, and the A ⁇ B of the carbon material is likely to be larger, which in turn cannot reduce the consumption of active ions by SEI film formation and reduce the irreversible capacity loss of the secondary battery, and will also affect the cycle performance and storage performance of the secondary battery.
  • the coking value of the filler material is 26%-50%, and can be 33%-45%.
  • the coking value of the filling material is well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured with reference to GB/T 8727-2008.
  • the filler material has a softening point temperature of 120° C.-170° C. and a coking value of 33%-45%.
  • the volume distribution particle size Dv50 of the filler material is less than or equal to 6 ⁇ m, and can be 1 ⁇ m-6 ⁇ m, 1 ⁇ m-5 ⁇ m, 2 ⁇ m-5 ⁇ m, or 3 ⁇ m-5 ⁇ m. This is beneficial for the filler material to be melted by heat and filled into the pore structure of the raw material, and is also beneficial for improving the dispersion uniformity of the filler material and the raw material.
  • the content of quinoline insolubles in the filling material is ⁇ 1wt%, and can be ⁇ 0.8wt%.
  • the content of quinoline insolubles is high, it will affect the atomic arrangement of the actual residual carbon in the filling area, affect the powder compaction density of the carbon material and the energy density of the secondary battery.
  • the filler material includes one or more of coal tar and petroleum tar.
  • the mass ratio of the filler material to the raw material is (10-32):100, and can be (10-25):100, (11-22):100, (11-20):100.
  • This is beneficial for the carbon material to have a suitable adsorption amount A for linseed oil and/or a suitable specific surface area B, and is beneficial for making the A ⁇ B of the carbon material within a suitable range. It is also beneficial for adjusting the pore size and/or the number of pores in the outer region and the inner region of the carbon material within a suitable range, and adjusting S2 / S1 within a suitable range.
  • the following situations can be avoided: when the mass ratio of the filler material to the raw material is too small, the filler material is not easy to flow and fill into the pore structure of the raw material, thereby failing to effectively reduce the internal defects of the obtained carbon material particles, failing to effectively prevent the electrolyte from penetrating into the pore structure inside the obtained carbon material particles, and at this time, the adsorption amount A of the carbon material for linseed oil and/or the specific surface area B of the carbon material are likely to be large, and the A ⁇ B of the carbon material is likely to be large, thereby affecting the first coulombic efficiency, cycle performance and storage performance of the secondary battery; when the mass ratio of the filler material to the raw material is too large, it is easy to cause the internal pore structure of the raw material to be completely is filled, at this time, the adsorption amount A of linseed oil by the carbon material and/or the specific surface area B of the carbon material are likely to be smaller, and the A ⁇ B of the carbon material is
  • the carbon material is advantageously provided with a suitable adsorption amount A for linseed oil and/or a suitable specific surface area B, and is advantageously provided with A ⁇ B of the carbon material within a suitable range. It is also advantageously provided with the pore size and/or the number of pores in the outer region and the inner region of the carbon material within a suitable range, and with S2 / S1 within a suitable range. In addition, after the filling material is heated and melted, the viscosity is not high, and good fluidity is maintained.
  • the heating process of mixing the raw material and the filling material in a predetermined ratio and then heating the temperature to the first temperature T1 is a staged heating process, which may optionally include a first heating process, a second heating process and a third heating process.
  • the first temperature increasing process is to increase the temperature to 200° C.-250° C. and keep the temperature at this temperature for 0.5 h-2 h.
  • the filling material when the insulation time is too short, the filling material is not easy to flow and fill into the pore structure of the raw material, but may be carbonized on the surface of the particles, thereby failing to effectively reduce the internal defects of the obtained carbon material particles, failing to effectively prevent the electrolyte from penetrating into the pore structure inside the obtained carbon material particles, at this time, the adsorption amount A of linseed oil by the carbon material and/or the specific surface area B of the carbon material are still easy to be large, and the A ⁇ B of the carbon material is easy to be large, thereby affecting the initial coulomb efficiency, cycle performance and storage performance of the secondary battery; when the insulation time is too long, the filling material is easy to flow and fill into all the pore structures of the raw material, the adsorption amount A of linseed oil by the carbon material and/or the specific surface area B of the carbon material are still easy to be small, and the A ⁇ B of the carbon material is easy to be small, thereby causing
  • the second temperature increasing process is to increase the temperature to 450° C.-550° C. and keep the temperature at this temperature for 0.5 h-2 h.
  • the third temperature increasing process is to increase the temperature to the first temperature T 1 and keep the temperature at the first time t 1 .
  • the temperature is first raised to 200°C-250°C. Since the heating temperature is higher than the softening point temperature of the filling material, the filling material is melted and softened by the heat. The temperature is kept for 0.5h-2h so that it can flow and fill into the pore structure of the raw material. Then the temperature is raised to 450°C-550°C. At this time, the melted and softened filling material undergoes a carbonization reaction, gradually forms a semi-coke state, and becomes a viscous liquid or solid, thereby preventing the filling material from entering all the pore structures of the raw material. Finally, the temperature is raised to the first temperature T1 .
  • the filling material undergoes a carbonization reaction, thereby enabling the pore structure occupied by the filling material to be effectively filled, reducing surface defects, and thus facilitating the carbon material to have a suitable adsorption amount A for linseed oil and/or a suitable specific surface area B, facilitating the A ⁇ B of the carbon material to be within a suitable range, and facilitating the adjustment of the pore size and/or pore number in the outer region and the inner region of the carbon material to be within a suitable range, and adjusting S2 / S1 to be within a suitable range.
  • the temperature is raised to the first temperature T 1 at a rate of 1° C./min-10° C./min.
  • the heating rate may be 1.5° C./min, 2° C./min, 3° C./min, 4° C./min, 5° C./min, 6° C./min, 7° C./min, 8° C./min, 9° C./min, 10° C./min or any range thereof.
  • the heating rate is 1.5° C./min-8° C./min.
  • the heating rate of the first heating process may be 1° C./min-10° C./min, and may be optionally 1.5° C./min-8° C./min.
  • the filling material when the heating rate is too high, the filling material may be carbonized on the surface of the raw material particles, resulting in the filling material not being easy to flow and fill into the pore structure of the raw material, thereby failing to effectively reduce the internal defects of the obtained carbon material particles, and failing to effectively prevent the electrolyte from penetrating into the pore structure inside the obtained carbon material particles, thereby affecting the first coulomb efficiency, cycle performance and storage performance of the secondary battery; when the heating rate is too low, the filling material is easy to flow and fill into all the pore structures of the raw material, thereby resulting in a large volume change of the carbon material during the process of active ion extraction and embedding, and the particles are more easily broken, thereby increasing the consumption of active ions by SEI film formation, increasing the irreversible capacity loss of the secondary battery, and also affecting the cycle performance, storage performance and rate performance of the secondary battery.
  • the heating rate of the second heating process may be 1° C./min-10° C./min, and may be optionally 1.5° C./min-8° C./min.
  • the heating rate of the third heating process may be 1° C./min-10° C./min, and may be optionally 1.5° C./min-8° C./min.
  • the first temperature T1 is 700°C-1100°C.
  • the first temperature T1 can be 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C or any range thereof.
  • the first temperature T1 is 750°C-1100°C.
  • the filling material may not be completely converted into carbon material, and will continue to decompose into small molecular substances during the subsequent heat treatment, thereby causing the actual residual carbon in the filling area to have more pore structures, failing to effectively reduce the internal defects of the obtained carbon material particles, and failing to effectively prevent the electrolyte from penetrating into the pore structure inside the obtained carbon material particles, and at the same time, it also makes the obtained carbon material surface defects more, the carbon material adsorption amount A of linseed oil and/or the specific surface area B of the carbon material are easy to be large, and the carbon material A ⁇ B is easy to be large, thereby affecting the first coulomb efficiency, cycle performance and storage performance of the secondary battery; when the first temperature is too high, the energy consumption and cost in the preparation process of the carbon material increase.
  • the first time t1 is 0.5h-5h.
  • the first time t1 can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or any range thereof.
  • the first time t1 is 0.5h-3h.
  • the filling material may not be completely converted into carbon material, and will continue to decompose into small molecules during the subsequent heat treatment, thereby causing the actual residual carbon in the filling area to have more pore structures, failing to effectively reduce the internal defects of the obtained carbon material particles, and failing to effectively prevent the electrolyte from penetrating into the pore structure inside the obtained carbon material particles.
  • the carbon material adsorption amount A of linseed oil and/or the specific surface area B of the carbon material are easy to be large, and the A ⁇ B of the carbon material is easy to be large, thereby affecting the first coulomb efficiency, cycle performance and storage performance of the secondary battery; when the first time is too long, it is easy to increase the energy consumption and cost in the preparation process of the carbon material.
  • the heat treatment may be performed in a medium frequency furnace, a roller kiln, a rotary kiln, or a pusher kiln.
  • the heat treatment atmosphere may be a protective gas atmosphere, which may include one or more of nitrogen, argon, and helium.
  • step 2 by adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc. within the above range, it is beneficial to prepare the desired carbon material, for example, it is beneficial for the carbon material to have a suitable adsorption amount A for linseed oil and/or a suitable specific surface area B, it is beneficial to make the A ⁇ B of the carbon material within a suitable range, and it is also beneficial to adjust the pore size and/or the number of pores in the outer region and the inner region of the carbon material within a suitable range, and adjust S2 / S1 within a suitable range.
  • the second temperature T2 is 1920°C-2520°C, for example, the second temperature can be 1950°C, 2000°C, 2050°C, 2100°C, 2150°C, 2200°C, 2250°C, 2300°C, 2350°C, 2400°C, 2450°C, 2500°C or any range thereof.
  • the second temperature T2 is 2050°C-2400°C.
  • the second temperature when the second temperature is too low, the surface defects of the obtained carbon material particles are relatively large, and the adsorption amount A of linseed oil of the carbon material and/or the specific surface area B of the carbon material are also likely to be large, and the A ⁇ B of the carbon material is also likely to be large, thereby affecting the initial coulomb efficiency, cycle performance and storage performance of the secondary battery; when the second temperature is too high, the content of disordered carbon in the obtained carbon material is too small, and the crystallinity and graphitization degree of the carbon material are both very high, which is not conducive to the rapid release and embedding of active ions, and the volume change of the carbon material during the charge and discharge process is also large, thereby increasing the risk of carbon material particle breakage, thereby affecting the cycle performance and/or kinetic performance of the secondary battery; in addition, when the second temperature is too high, the energy consumption and cost in the preparation process of the carbon material will also increase.
  • the second time t2 is 1 hour to 6 hours.
  • the second time t1 can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours or any range thereof.
  • the second time t2 is 2 hours to 6 hours.
  • the second time when the second time is too short, the surface defects of the obtained carbon material particles are relatively large, and the adsorption amount A of linseed oil of the carbon material and/or the specific surface area B of the carbon material are still easy to be large, and the A ⁇ B of the carbon material is also easy to be large, thereby affecting the initial coulomb efficiency, cycle performance and storage performance of the secondary battery; when the second time is too long, the content of disordered carbon in the obtained carbon material is too small, and the crystallinity and graphitization degree of the carbon material are both very high, which is not conducive to the rapid release and embedding of active ions, and the volume change of the carbon material during the charge and discharge process is still large, thereby increasing the risk of carbon material particle breakage, thereby affecting the cycle performance and/or kinetic performance of the secondary battery; in addition, when the second time is too long, the energy consumption and cost in the preparation process of the carbon material will also increase.
  • the heat treatment may be performed in a medium frequency furnace, a box-type graphitization furnace, an Acheson graphitization furnace, a continuous graphitization furnace, or an inner string graphitization furnace.
  • the medium frequency furnace and the continuous graphitization heat treatment atmosphere may be a protective gas atmosphere.
  • the protective gas may include one or more of nitrogen, argon, and helium.
  • the carbon material By adjusting one or more of the second temperature and the second time within the above-mentioned range, it is beneficial to reduce the content of disordered carbon in the carbon material, and it is also beneficial for the carbon material to have a suitable adsorption amount A for linseed oil and/or a suitable specific surface area B, and it is also beneficial to make the A ⁇ B of the carbon material within a suitable range.
  • the preparation method of the carbon material of the present application is simple in process and highly safe, does not require a preset pressure or vacuum treatment, and does not require an additional depolymerization process during the heat treatment process.
  • the carbon material prepared in the present application has a small volume expansion, high structural stability, and few surface defects, and can have both a high gram capacity and a high first coulombic efficiency, and can also enable the secondary battery to have a high first coulombic efficiency, a high energy density, and good cycle performance and storage performance.
  • the preparation method of the present application has low cost, high practicability and is suitable for large-scale production.
  • a third aspect of the embodiments of the present application provides a secondary battery.
  • the secondary battery can be a lithium-ion battery, etc.
  • a secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte, etc.
  • active ions are embedded and removed back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.
  • the present application has no particular restrictions on the type of the electrolyte, which can be selected according to actual needs.
  • the electrolyte can be selected from at least one of a solid electrolyte and a liquid electrolyte (ie, an electrolyte).
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes may also include a separator, which is arranged between the positive electrode plate and the negative electrode plate to play an isolation role.
  • the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode film layer comprises the carbon material of the first aspect of the embodiment of the present application or the carbon material prepared by the method described in the second aspect of the embodiment of the present application, thereby enabling the secondary battery to have high first coulombic efficiency, high energy density, and good cycle performance and storage performance.
  • the negative electrode film layer may further include other negative electrode active materials in addition to the above-mentioned carbon materials.
  • the other negative electrode active materials include but are not limited to one or more of conventional natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material.
  • the tin-based material may include one or more of elemental tin, tin oxide and tin alloy material.
  • the negative electrode film layer may further include a negative electrode conductive agent.
  • a negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode film layer may further include a negative electrode binder.
  • the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include other additives.
  • the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • a metal foil a copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them uniformly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode plate described in the present application also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode collector and the negative electrode film layer and disposed on the surface of the negative electrode collector; in some embodiments, the negative electrode plate described in the present application also includes a protective layer covering the surface of the negative electrode film layer.
  • the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the positive electrode film layer generally comprises a positive electrode active material, an optional binder and an optional conductive agent.
  • the positive electrode film layer is generally formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the positive electrode slurry is generally formed by dispersing the positive electrode active material, the optional conductive agent, the optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the binder for the positive electrode film layer may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • tetrafluoroethylene-hexafluoropropylene copolymer tetraflu
  • the conductive agent for the positive electrode film layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode active material may be a positive electrode active material for a secondary battery known in the art.
  • the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds.
  • the lithium transition metal oxide may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.
  • lithium-containing phosphate may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.
  • the positive electrode active material for the lithium ion battery may include one or more of a lithium transition metal oxide and a modified compound thereof of the general formula Li a Ni b Co c M d O e A f . 0.8 ⁇ a ⁇ 1.2, 0.5 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1, 1 ⁇ e ⁇ 2, 0 ⁇ f ⁇ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A is selected from one or more of N, F, S and Cl.
  • a positive electrode active material for a lithium ion battery may include one or more of LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O 2 , LiFePO 4 , and LiMnPO 4 .
  • the modified compound of each positive electrode active material mentioned above may be a compound obtained by doping and/or surface coating the positive electrode active material.
  • the electrolyte is an electrolyte solution
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the type of the electrolyte salt is not particularly limited and can be selected according to actual needs.
  • the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium perchlorate
  • the solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sul
  • the electrolyte may further include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high temperature performance of the secondary battery, and additives that improve the low temperature power performance of the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different.
  • the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging can also be a soft package, such as a bag-type soft package.
  • the material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).
  • FIG2 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be adjusted according to demand.
  • the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a secondary battery.
  • the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying, and the secondary battery is obtained through vacuum packaging, standing, forming, shaping and other processes.
  • the secondary batteries according to the present application can be assembled into a battery module.
  • the battery module can contain multiple secondary batteries, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG4 is a schematic diagram of an exemplary battery module 4.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.
  • the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.
  • FIG5 and FIG6 are schematic diagrams of a battery pack 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, wherein the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 may be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack of the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.
  • the electrical device may select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • Fig. 7 is a schematic diagram of an electric device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the electric device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • Step 1 Mechanically crush, classify, spheroidize and purify 100 mesh flake graphite to obtain natural spherical graphite with a volume distribution particle size Dv50 of 17 ⁇ m and an ash content of 0.01%.
  • Step 2 The obtained natural spherical graphite and petroleum asphalt (softening point temperature of 120 ° C, volume distribution particle size Dv50 of 4.3 ⁇ m, coking value of 33%) are mixed in a VC mixer at a mass ratio of 100:15 for 30 minutes, and then the mixed material is placed in a roller kiln, heated to 230 ° C at a rate of 5 ° C / min and kept warm for 1 hour (first heating process), then heated to 500 ° C at a rate of 5 ° C / min and kept warm for 1 hour (second heating process), and then heated to 1100 ° C at a rate of 5 ° C / min and kept warm for 1 hour (third heating process), and then cooled to room temperature to obtain an intermediate.
  • Step 3 Place the obtained intermediate in an Acheson graphitization furnace, heat it to 2300°C and keep it warm for 2 hours. After the graphitization is completed, demagnetize and sieve to obtain the carbon material.
  • the carbon material prepared above is fully stirred and mixed with the binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC), and the conductive agent carbon black in a mass ratio of 96.2:1.8:1.2:0.8 in an appropriate amount of solvent deionized water to form a uniform negative electrode slurry; the negative electrode slurry is evenly coated on the surface of the negative electrode current collector copper foil, and dried in an oven for use.
  • SBR binder styrene-butadiene rubber
  • CMC thickener sodium carboxymethyl cellulose
  • conductive agent carbon black in a mass ratio of 96.2:1.8:1.2:0.8 in an appropriate amount of solvent deionized water
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then LiPF 6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol/L.
  • a metal lithium sheet is used as a counter electrode and a polyethylene (PE) film is used as an isolation membrane to assemble a CR2430 button battery in an argon-protected glove box.
  • PE polyethylene
  • the carbon material prepared above, the conductive agent carbon black (Super P), the binder styrene-butadiene rubber, and the thickener sodium carboxymethyl cellulose were fully stirred and mixed in an appropriate amount of solvent deionized water at a weight ratio of 96:1:1:2 to form a negative electrode slurry.
  • the negative electrode slurry was coated on both surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet was obtained.
  • LiFePO 4 , conductive carbon black and polyvinylidene fluoride were mixed in a weight ratio of 96:2.5:1.5, and an appropriate amount of solvent NMP was added and stirred evenly to obtain a positive electrode slurry.
  • the positive electrode slurry was coated on both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.
  • a polypropylene film with a thickness of 12 ⁇ m is used as an isolation membrane, and is placed in order with the positive electrode sheet and the negative electrode sheet prepared above, so that the isolation membrane is located between the positive electrode sheet and the negative electrode sheet to play an isolation role, and then the electrode assembly is obtained by winding; the electrode assembly is placed in an outer package, and after drying, the same electrolyte as the button battery prepared above is injected, and after vacuum packaging, standing, formation, capacity and other processes, a secondary battery is obtained.
  • the 100-mesh flake graphite is mechanically crushed, classified, spheroidized, and purified to obtain natural spherical graphite with a volume distribution particle size Dv50 of 17 ⁇ m and an ash content of 0.01%.
  • the obtained natural spherical graphite is then used as a carbon material to prepare half cells and full cells.
  • the 100 mesh flake graphite is mechanically crushed, classified, spheroidized and purified to obtain natural spherical graphite with a volume distribution particle size Dv50 of 17 ⁇ m and an ash content of 0.01%.
  • the obtained natural spherical graphite and petroleum asphalt (softening point temperature of 120°C, volume distribution particle size Dv50 of 4.3 ⁇ m, coking value of 33%) were mixed in a VC mixer at a mass ratio of 100:15 for 30 minutes, and then the mixed material was graphitized at 3200°C for 10 hours and then cooled to room temperature to obtain a carbon material.
  • the 100 mesh flake graphite is mechanically crushed, classified, spheroidized and purified to obtain natural spherical graphite with a volume distribution particle size Dv50 of 17 ⁇ m and an ash content of 0.01%.
  • the obtained natural spherical graphite and petroleum asphalt (softening point temperature of 120°C, volume distribution particle size Dv50 of 4.3 ⁇ m, coking value of 33%) were mixed in a VC mixer at a mass ratio of 100:15 for 30 minutes, and the mixed materials were carbonized at 1300°C for 2 hours. After completion, they were cooled to room temperature to obtain carbon materials.
  • the 100 mesh flake graphite is mechanically crushed, classified, spheroidized and purified to obtain natural spherical graphite with a volume distribution particle size Dv50 of 17 ⁇ m and an ash content of 0.01%.
  • the preparation method of the half-cell and the full-cell is similar to that of Example 1, except that the preparation process parameters of the carbon material are adjusted, as shown in Table 1 for details.
  • GB/T 3780.2-2017 weigh 20g of the dried test sample and place the weighed sample in the mixing chamber of the oil absorption meter at a temperature of 23°C and cover the lid; align the oil delivery pipe of the constant-speed burette with the top of the hole in the mixing chamber cover; start the oil absorption meter, the instrument starts to run and drip linseed oil.
  • the oil absorption of the sample increases, the mixed material changes from a free-flowing state to a semi-plastic agglomerate, and the viscosity of the mixture continues to increase. The viscosity is transmitted to the torque sensor system of the oil absorption meter.
  • the nitrogen adsorption specific surface area analysis test method is used for testing, and the specific surface area B of the carbon material is calculated by the BET (Brunauer Emmett Teller) method.
  • the test instrument can be the Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.
  • an X-ray diffractometer is used for testing to obtain the peak intensity and full width at half maximum (FWHM) of the diffraction peak corresponding to the (110) crystal plane of the carbon material, and the peak intensity and full width at half maximum (FWHM) of the diffraction peak corresponding to the (002) crystal plane, and then the La(110) and Lc(002) of the carbon material are calculated according to the Scherrer formula.
  • La(110) represents the crystallite size along the a-axis in the (110) crystal plane of the carbon material
  • Lc(002) represents the crystallite size along the c-axis in the (002) crystal plane of the carbon material.
  • the testing instrument can be a Bruker D8 Discover X-ray diffractometer.
  • test instrument can be IB-09010 CP type argon ion cross section polisher of JEOL Company of Japan.
  • the cross section of the carbon material is scanned using a scanning electron microscope.
  • the test may refer to JY/T010-1996.
  • the test instrument may be a Sigma 300 scanning electron microscope from the German ZEISS company.
  • the area extending from the surface of the carbon material particle to the inside of the particle by a distance of 0.25L is recorded as the outer area, and the area inside the outer area is recorded as the inner area, and L represents the minor axis length of the carbon material particle.
  • the total pore area S1 of the outer area of the carbon material particle and the total pore area S2 of the inner area are calculated using image processing software.
  • the image processing software can be AVIZO.
  • the button cell prepared above was first discharged at a constant current of 0.15 mA to 0.005 V, left to stand for 5 min, and then discharged at a constant current of 10 ⁇ A to 0.005 V, and the first cycle discharge capacity of the button cell was recorded; then, the button cell was charged at a constant current of 0.3 mA to 2.0 V, and the first cycle charge capacity of the button cell was recorded.
  • the first coulomb efficiency of carbon material (%) the first cycle charge capacity of the button cell/the first cycle discharge capacity of the button cell ⁇ 100%.
  • the secondary battery prepared above is charged at a constant current of 1C to the upper cut-off voltage (corresponding to 100% SOC), and then charged at a constant voltage to a current of 0.05C. After standing for 5 minutes, the secondary battery is discharged at a constant current of 1C to the lower cut-off voltage (corresponding to 0% SOC), and the discharge capacity at this time is recorded, which is the discharge capacity of the first cycle.
  • the secondary battery is subjected to a cyclic charge and discharge test according to the above method, and the discharge capacity after each cycle is recorded.
  • the capacity retention rate (%) of the secondary battery after 2000 cycles at 25°C discharge capacity after 2000 cycles/discharge capacity of the first cycle ⁇ 100%.
  • the secondary battery prepared above was charged at a constant current of 1C to an upper cutoff voltage (corresponding to 100% SOC), and then charged at a constant voltage to a current of 0.05C. After standing for 5 minutes, the secondary battery was discharged at a constant current of 1C to a lower cutoff voltage (corresponding to 0% SOC), and the discharge capacity at this time was recorded, which was the discharge capacity before storage.
  • the prepared secondary battery was charged at a constant current of 1C to an upper cutoff voltage (corresponding to 100% SOC), and then charged at a constant voltage to a current of 0.05C.
  • the secondary battery was then stored in a 60°C constant temperature box until the discharge capacity of the secondary battery after storage decayed to 90% of the discharge capacity before storage, the test was stopped, and the storage days of the secondary battery were recorded.
  • volume distribution particle size, tap density and other parameters of the carbon materials prepared in Examples 1-23 are all within the ranges described in the specification of this application.
  • the carbon materials prepared in Comparative Examples 1-4 do not satisfy 36 ⁇ A ⁇ B ⁇ 75, and cannot enable the battery to have high initial coulombic efficiency, high energy density, and good cycle performance and storage performance.
  • Comparative Example 1 uses untreated natural spherical graphite as the carbon material, which has a large number of pores inside. Combined with the test results in Table 2, it can be seen that the gram capacity, first coulomb efficiency, cycle performance and storage performance of the battery prepared therefrom are all poor, and when the number of cycles of the battery has not reached 2000, the discharge capacity has decayed to 80% of the discharge capacity of the first cycle.
  • the carbon material prepared in Comparative Examples 2-3 forms a carbon layer coating on the surface of natural spherical graphite, but the carbon layer only exists on the surface of natural spherical graphite and fails to achieve a filling effect. Moreover, the carbon layer cannot effectively prevent the electrolyte from penetrating into the pore structure inside the particles, which leads to limited improvement in the battery's first coulombic efficiency, cycle performance and storage performance.
  • the filling material is filled into all the pore structures inside the natural spherical graphite particles by isostatic pressing, which will cause the volume of the carbon material particles to change greatly during the extraction and embedding of active ions.
  • the particles are more easily broken, which leads to limited improvement in the cycle performance and storage performance of the battery; in addition, there is a large amount of soft carbon inside and/or on the surface of the carbon material particles, which will increase the side reactions on the particle surface, further affecting the cycle performance and storage performance of the battery.
  • the preparation process is complicated and not suitable for large-scale production.
  • the carbon material particles further satisfy S 2 >S 1 , optionally satisfy 1.3 ⁇ S 2 /S 1 ⁇ 450, and more optionally satisfy 1.8 ⁇ S 2 /S 1 ⁇ 400, the comprehensive performance of the battery is further improved.
  • the carbon material particles further have the following characteristics: the number of pores in the internal region is large and/or the pore size is large, while the number of pores in the external region is small and/or the pore size is small.
  • the pore structure in the internal region of the carbon material can reserve the required expansion space for the volume change of the carbon material particles, thereby reducing the risk of the carbon material particles breaking and generating new interfaces, thereby reducing the occurrence of side reactions and reducing the irreversible capacity loss of the secondary battery; the number of pores in the external region of the carbon material is small and/or the pore size is small, thereby making the carbon material particles have a more stable structure and avoiding the electrolyte from penetrating into the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions and reducing the consumption of active ions by the SEI film formation inside the particles. Therefore, the carbon material that further meets the above structural characteristics can further improve the comprehensive performance of the battery.

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Abstract

本申请提供一种碳材料及其制备方法、以及含有其的二次电池和用电装置，所述碳材料包括孔结构，100g所述碳材料对亚麻仁油的吸附量记为A，所述碳材料的比表面积记为B，则所述碳材料满足：36≤A×B≤75，100g所述碳材料对亚麻仁油的吸附量A的单位为ml，所述碳材料的比表面积B的单位为m 2/g。本申请提供的碳材料能使二次电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。

Description

碳材料及其制备方法、以及含有其的二次电池和用电装置 技术领域
本申请属于电池技术领域，具体涉及一种碳材料及其制备方法、以及含有其的二次电池和用电装置。
背景技术
近年来，二次电池被广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着二次电池应用范围越来越广泛，人们对二次电池的性能提出了严峻挑战，例如要求二次电池兼顾高能量密度以及长使用寿命等各种性能。负极活性材料是二次电池的重要组成部分，其影响了二次电池的性能。目前，负极活性材料主要包括石墨，然而，现有技术中面临的问题是：高容量的石墨难以兼顾高首次库伦效率，同时也难以使二次电池兼顾良好的循环性能和存储性能。
发明内容
本申请的目的在于提供一种碳材料及其制备方法、以及含有其的二次电池和用电装置，其能使二次电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
本申请第一方面提供一种碳材料，所述碳材料包括孔结构，100g所述碳材料对亚麻仁油的吸附量记为A，所述碳材料的比表面积记为B，则所述碳材料满足：36≤A×B≤75，100g所述碳材料对亚麻仁油的吸附量A的单位为ml，所述碳材料的比表面积B的单位为m 2/g。
本申请提供的碳材料可以有效降低二次电池的不可逆容量损失、改善二次电池的容量发挥特性，并使二次电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
在本申请的任意实施方式中，38≤A×B≤65，可选地，39≤A×B≤55。此时有利于二次电池更好地兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
在本申请的任意实施方式中，100g所述碳材料对亚麻仁油的吸附量A为30ml-50mL，可选为35ml-47mL。当碳材料对亚麻仁油的吸附量在上述范围内时，碳材料颗粒的表面副反应活性较低，由此可以减少SEI膜成膜对活性离子的消耗，同时还能避免颗粒表面过于致密而影响活性离子传输；此外，还有利于负极膜层的颗粒之间形成合理的孔道结构，提高负极极片对电解液的浸润性。
在本申请的任意实施方式中，所述碳材料的比表面积B为0.5m 2/g-2.1m 2/g，可选为0.7m 2/g-1.8m 2/g。当碳材料的比表面积在上述范围内时，一方面碳材料可具有较低的表面副反应活性，由此能够减少SEI膜成膜对活性离子的消耗，提升碳材料的首次库伦效率； 另一方面还能具有较高的活性离子传输性能。
在本申请的任意实施方式中，所述碳材料包括一个以上孔面积大于等于0.1μm 2的孔结构，可选地包括一个以上孔面积为0.12μm 2-2.5μm 2的孔结构。当碳材料进一步包括具有上述孔面积的孔结构时，所述孔结构可以为碳材料颗粒体积变化预留所需的膨胀空间，由此能够进一步降低碳材料颗粒破碎产生新界面的风险，进而能够减少副反应的发生，降低二次电池的不可逆容量损失，并进一步改善二次电池的循环性能和存储性能。
在本申请的任意实施方式中，所述碳材料包括外部区域以及位于所述外部区域内侧的内部区域，所述外部区域是指从所述碳材料的颗粒表面向颗粒内部延伸0.25L的距离所构成的区域，L是指所述碳材料颗粒的短轴长度，所述外部区域的总孔面积记为S 1，所述内部区域的总孔面积记为S 2，并且S 2>S 1。当碳材料颗粒进一步满足S 2>S 1时，可以有效降低二次电池的不可逆容量损失、改善二次电池的容量发挥特性，并使二次电池更好地兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
在本申请的任意实施方式中，1.3≤S 2/S 1≤450，可选地，1.8≤S 2/S 1≤400。当S 2/S 1还满足在上述范围内时，能够使二次电池更好地兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
在本申请的任意实施方式中，0.01μm 2≤S 1≤12.0μm 2，可选地，0.02μm 2≤S 1≤7.0μm 2。当碳材料的外部区域的总孔面积在上述范围内时，一方面可以使碳材料颗粒具有更少的表面缺陷和更稳定的结构，尽可能避免电解液渗入到碳材料颗粒内部的孔结构中，从而减少副反应的发生，降低碳材料颗粒内部SEI膜成膜对活性离子的消耗，另一方面还不会影响活性离子和电子的传输性能。
在本申请的任意实施方式中，2.5μm 2≤S 2≤25.0μm 2，可选地，3.0μm 2≤S 2≤20.5μm 2。当碳材料的内部区域的总孔面积在上述范围内时，一方面可以为碳材料颗粒体积变化预留足够且稳定的膨胀空间，降低碳材料颗粒破碎产生新界面的风险，减少新界面表面副反应的发生，减少新界面表面SEI膜成膜对活性离子的消耗，另一方面还可以提高碳材料的容量和首次库伦效率。
在本申请的任意实施方式中，L≥4μm，可选地，6μm≤L≤18μm。
在本申请的任意实施方式中，所述碳材料的外部区域中的所述孔结构的面积为小于等于0.2μm 2，可选为小于等于0.15μm 2。通过控制碳材料的外部区域中的所述孔结构的面积大小在上述范围内，可以使碳材料的外部区域具有较密实结构，由此能够有效降低碳材料的表面缺陷、提升碳材料的结构稳定性，尽可能避免电解液渗入到碳材料颗粒内部的孔结构中，进而能进一步提升二次电池的循环性能和存储性能。
在本申请的任意实施方式中，所述碳材料的内部区域中包括一个以上面积大于等于0.15μm 2的孔结构，可选地包括一个以上面积为0.18μm 2-2.5μm 2的孔结构。通过使碳材料的内部区域包括上述大小的孔结构，一方面可以为碳材料颗粒体积变化预留足够且稳定的膨胀空间，降低碳材料颗粒破碎风险，另一方面还可以提高碳材料的压实密度。
在本申请的任意实施方式中，所述碳材料的外部区域的层间距记为d 1，所述碳材料的内部区域的层间距记为d 2，所述碳材料满足d 1≥d 2，可选地，d 1>d 2。碳材料的外部区域的层间距较大，更有利于活性离子的快速嵌入和脱出，由此能够进一步提升二次电池的动力学性能；碳材料的内部区域的层间距较小，有利于提升碳材料的克容量和压实密 度，从而能够进一步提升二次电池的能量密度。
在本申请的任意实施方式中，d 1为0.33565nm-0.33610nm。
在本申请的任意实施方式中，d 2为0.33557nm-0.33585nm。
在本申请的任意实施方式中，所述碳材料的石墨化度为94％-98％，可选为95％-97％。当碳材料的石墨化度在上述范围内时，有利于提升二次电池的能量密度，还有利于提升二次电池的循环性能、存储性能和/或倍率性能。
在本申请的任意实施方式中，所述碳材料的La(110)为100nm-150nm，可选为110nm-130nm。
在本申请的任意实施方式中，所述碳材料的Lc(002)为20nm-45nm，可选为28nm-40nm。
当碳材料的La(110)和/或Lc(002)在合适的范围内时，有利于碳材料具有较高的结晶性和/或石墨化度，有利于提升碳材料的克容量，还有利于提升负极膜层的活性离子和电子传输性能，进而有利于提升二次电池的循环性能、存储性能和/或倍率性能。
在本申请的任意实施方式中，所述碳材料的体积分布粒径Dv50为8.0μm-24.0μm，可选为9.5μm-22.5μm。
在本申请的任意实施方式中，所述碳材料的体积分布粒径Dv10为5.0μm-15.0μm，可选为6.0μm-14.0μm。
在本申请的任意实施方式中，所述碳材料的体积分布粒径Dv90为16.0μm-35.0μm，可选为17.0μm-34.0μm。
碳材料的体积分布粒径Dv10、Dv50和/或Dv90在上述范围内时，有利于提升活性离子和电子的传输性能，还有利于负极膜层的颗粒之间形成合理的孔道结构，从而能够进一步提升二次电池的循环性能和/或倍率性能。
在本申请的任意实施方式中，所述碳材料的(Dv90-Dv10)/Dv50为0.55-1.55，可选为0.8-1.4。碳材料的(Dv90-Dv10)/Dv50在上述范围内时，其颗粒堆积性能较好，有利于提升负极膜层的压实密度，从而能够进一步提升二次电池的能量密度；另外，还有利于负极膜层的颗粒之间形成合理的孔道结构。
在本申请的任意实施方式中，所述碳材料的振实密度为0.80g/cm 3-1.32g/cm 3，可选为0.82g/cm 3-1.28g/cm 3。碳材料的振实密度在上述范围内时，可以提升负极极片的压实密度，进而提高二次电池的能量密度；还有利于负极膜层的颗粒之间形成合理的孔道结构，提升活性离子和电子的传输性能，提升二次电池的循环性能和存储性能。
在本申请的任意实施方式中，所述碳材料的克容量为355mAh/g-371mAh/g，可选为360mAh/g-370mAh/g。碳材料的克容量在上述范围内时，可以提升二次电池的能量密度。
在本申请的任意实施方式中，所述碳材料的形貌包括块状、球状和类球状中的一种或多种。
本申请第二方面提供一种碳材料的制备方法，包括如下步骤：步骤1，提供具有多个孔结构的原料；步骤2，将所述原料与填充材料按照预定比例混合均匀，之后在第一温度T 1下保温第一时间t 1，得到中间体；步骤3，将所获得的中间体在第二温度T 2下保温第二时间t 2，得到碳材料，其中，所述碳材料包括孔结构，100g所述碳材料对亚麻仁油的吸附量记为A，所述碳材料的比表面积记为B，则所述碳材料满足：36≤A×B≤75，100g所述 碳材料对亚麻仁油的吸附量A的单位为ml，所述碳材料的比表面积B的单位为m 2/g。
在本申请的任意实施方式中，所述原料包括天然石墨，可选地，所述天然石墨包括鳞片石墨、天然球形石墨和微晶石墨中的一种或多种。
在本申请的任意实施方式中，所述原料的体积分布粒径Dv50为8.5μm-24.0μm，可选为10.5μm-22.5μm。
在本申请的任意实施方式中，所述原料中的灰分含量为≤1wt％。原料中的灰分含量较低时，有利于碳材料具有较低的表面缺陷。
在本申请的任意实施方式中，所述填充材料的软化点温度为110℃-175℃，可选为120℃-170℃。填充材料的软化点温度在上述范围内时，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。
在本申请的任意实施方式中，所述填充材料的结焦值为26％-50％，可选为33％-45％。填充材料的结焦值在上述范围内时，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。
在本申请的任意实施方式中，所述填充材料的体积分布粒径Dv50为小于等于6μm，可选为1μm-5μm。由此有利于填充材料受热熔融后填充进入原料的孔结构中，还有利于提高填充材料与原料的分散均匀性。
在本申请的任意实施方式中，所述填充材料中的喹啉不溶物的含量为≤1wt％，可选为≤0.8wt％。
在本申请的任意实施方式中，所述填充材料包括煤沥青和石油沥青中的一种或多种。
在本申请的任意实施方式中，所述填充材料与所述原料的质量比为(10-32):100，可选为(10-25):100。由此有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。
在本申请的任意实施方式中，将所述原料与所述填充材料按照预定比例混合均匀后升温至第一温度T 1的升温工艺为分阶段升温工艺，可选地包括第一升温工艺、第二升温工艺和第三升温工艺。
在本申请的任意实施方式中，所述第一升温工艺为升温至200℃-250℃并在该温度下保温0.5h-2h。
在本申请的任意实施方式中，所述第二升温工艺为升温至450℃-550℃并在该温度下保温0.5h-2h。
在本申请的任意实施方式中，所述第三升温工艺为升温至所述第一温度T 1并在该温度下保温第一时间t 1。
在本申请的任意实施方式中，以1℃/min-10℃/min，可选为1.5℃/min-8℃/min的速率升温至所述第一温度T 1。
在本申请的任意实施方式中，所述第一温度T 1为700℃-1100℃，可选为750℃-1100℃。
在本申请的任意实施方式中，所述第一时间t 1为0.5h-5h，可选为0.5h-3h。
通过调节升温速率、第一温度、第一时间、升温工艺等中的一者或者多者在上述范围内，有利于制备获得所需的碳材料，例如有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。
在本申请的任意实施方式中，所述第二温度T 2为1920℃-2520℃，可选为2050℃-2400℃。
在本申请的任意实施方式中，所述第二时间t 2为1h-6h，可选为2h-5h。
通过调节第二温度、第二时间中的一者或者多者在上述范围内，有利于降低碳材料中无序碳的含量，还有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，并有利于使碳材料的A×B在合适的范围内。
本申请第三方面提供一种二次电池，其包括负极极片，所述负极极片包括本申请第一方面的碳材料或通过本申请第二方面的方法制备得到的碳材料。
本申请第四方面提供一种用电装置，其包括本申请第三方面的二次电池。
本申请的用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍。显而易见地，下面所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的碳材料的颗粒的一截面图像的示意图。
图2是本申请的二次电池的一实施方式的示意图。
图3是本申请的二次电池的一实施方式的分解示意图。
图4是本申请的电池模块的一实施方式的示意图。
图5是本申请的电池包的一实施方式的示意图。
图6是图5所示的电池包的实施方式的分解示意图。
图7是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
在附图中，附图未必按照实际的比例绘制。附图标记说明如下：1电池包，2上箱体，3下箱体，4电池模块，5二次电池，51壳体，52电极组件，53盖板，100碳材料，101外部区域，102内部区域。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的碳材料及其制备方法、以及含 有其的二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案，并且这样的技术方案应被认为包含在本申请的公开内容中。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案，并且这样的技术方案应被认为包含在本申请的公开内容中。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
如果没有特别的说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。
如果没有特别的说明，本申请中提到的各参数的数值可以用本领域常用的各种测试方法进行测定，例如，可以按照本申请给出的测试方法进行测定。
如果没有特别的说明，在本申请中，术语“活性离子”是指能在二次电池正极和负极之间往返嵌入和脱出的离子，包括但不限于锂离子。
在本申请中，术语“多个”、“多种”是指两个或两种以上。
依据制备工艺或来源不同，石墨可以分为人造石墨和天然石墨。人造石墨制备时一般需要经过高温石墨化处理过程，该过程能耗高、成本高，由此导致人造石墨的成本较高。天然石墨来源于自然界，因此具有成本相对低廉的优势。此外，天然石墨还具有容量高的优势。
天然石墨主要包括鳞片石墨、天然球形石墨和微晶石墨，通常与人造石墨不同，天然石墨的颗粒内部和外部具有非常多的孔隙和缺陷。二次电池首次充电过程中，电解液与颗粒表面、颗粒内部的孔产生较多副反应，由此导致二次电池的首次不可逆容量损失高、首次库伦效率低且循环性能和存储性能差。特别地，鳞片石墨和天然球形石墨具有高结晶度和高石墨化度，且微观结构多为层状结构，这种结构导致了天然石墨在活性离子脱出和嵌入过程中产生的体积变化较大，由此容易导致石墨层状结构破碎和颗粒破碎。颗粒破碎后，暴露出的新鲜表面会与电解液继续反应，从而进一步增加了二次电池的不可逆容量损失。
目前，主要通过颗粒表面包覆处理和/或颗粒内部填充处理来改善天然石墨的性能。
颗粒表面包覆处理主要是将天然石墨与包覆剂(例如沥青、高分子化合物等)混合均匀后进行热处理以在天然石墨颗粒表面包覆一层碳层，轻微修复颗粒表面的缺陷。但是，本申请的发明人在研究过程中发现，表面包覆的无定形碳层会导致天然石墨的克容量和/或压实密度降低，影响二次电池的能量密度；同时，表面包覆的无定形碳层后颗粒表面缺陷依旧较多；此外，表面包覆的无定形碳层也并不能有效阻止电解液渗入到颗粒内部的孔结构中，由此导致对二次电池首次库伦效率、循环性能和/或存储性能的改善作用有限。
颗粒内部填充处理主要是将天然石墨与填充剂(例如沥青、高分子化合物等)混合，通过预设压力、抽真空和升温等方式将填充剂填充至颗粒内部孔隙中，以得到颗粒内部没有孔隙的天然石墨。但是，本申请的发明人在研究过程中发现，颗粒内部大量填充的碳，特别是软碳，会导致天然石墨的克容量降低，影响二次电池的能量密度；同时由于天然石墨颗粒内部的孔隙全部被碳填充，由此还导致天然石墨在活性离子脱出和嵌入过程中产生的体积变化较大，颗粒更易破碎，进而导致颗粒表面的SEI膜反复破坏与重建，进一步增加了活性离子的不可逆消耗，增加了二次电池的不可逆容量损失，缩短了二次电池的使用寿命。现有技术还会在上述颗粒内部没有孔隙的天然石墨表面继续包覆一层无定形碳层，其会导致天然石墨的克容量和/或压实密度进一步降低，并且此时颗粒表面缺陷依旧较多，由此也不能有效改善二次电池的使用寿命。
因此，通过上述颗粒表面包覆处理和/或颗粒内部填充处理改性天然石墨后，虽然可以在一定程度上降低二次电池的不可逆容量损失，提升二次电池的首次库伦效率，但是，其对二次电池首次库伦效率的改善作用有限，并且还会损失二次电池的能量密度，此外，二次电池长期循环和存储过程中的容量发挥特性依旧较差。
鉴于此，本申请的发明人经过大量研究，提出了一种新型的碳材料，其兼具较高的克容量和较高的首次库伦效率，并且还能使二次电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
碳材料
本申请实施方式的第一方面提供一种碳材料。
所述碳材料包括孔结构，100g所述碳材料对亚麻仁油的吸附量记为A，所述碳材料的比表面积记为B，则所述碳材料满足：36≤A×B≤75，100g所述碳材料对亚麻仁油的吸附量A的单位为ml，所述碳材料的比表面积B的单位为m 2/g。
本申请的发明人在研究过程中发现，当碳材料满足36≤A×B≤75时，能使二次电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。可能的原因包括如下几点。
第一，此时碳材料颗粒表面较致密，由此可以使碳材料颗粒具有稳定的结构，并尽可能避免电解液渗入到碳材料颗粒内部的孔结构中，从而能够减少副反应的发生，降低颗粒内部SEI膜成膜对活性离子的消耗，进而能够提升碳材料的首次库伦效率，并进一步改善二次电池的循环性能和存储性能。
第二，此时碳材料颗粒表面的缺陷较少，由此颗粒对油性物质的吸附能力较弱，从而有利于减少电池副反应。
第三，此时碳材料颗粒还能使负极膜层形成合理的孔道结构，提高负极极片对电解液的浸润性。
因此，本申请提供的碳材料可以有效降低二次电池的不可逆容量损失、改善二次电池的容量发挥特性，并使二次电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
当A×B小于36时，碳材料对亚麻仁油的吸附量可能较小和/或碳材料的比表面积可能较小。碳材料对亚麻仁油的吸附量较小时，碳材料表面结构致密化度较高，由此可能使得活性离子脱出和嵌入过程中碳材料颗粒的体积变化较大，此时颗粒更易破碎，进而导致颗粒表面的SEI膜容易反复破坏与重建，反而增加了活性离子的不可逆消耗，增加了二次电池的不可逆容量损失，同时缩短了二次电池的使用寿命。碳材料的比表面积较小时，可能不利于活性离子的传输，由此会影响二次电池的容量发挥、循环性能和/或倍率性能。
当A×B大于75时，碳材料对亚麻仁油的吸附量可能较大和/或碳材料的比表面积可能较大。碳材料对亚麻仁油的吸附量较大时，碳材料颗粒表面缺陷和/或孔结构较多，由此导致电解液副反应较多，SEI膜成膜对活性离子的消耗较多，由此会降低二次电池的首次库伦效率；同时，随着二次电池充放电次数增加，碳材料颗粒表面SEI膜厚度不断增加，由此还会影响二次电池的循环性能和/或倍率性能。碳材料的比表面积较大时，碳材料颗粒表面副反应活性较高，SEI膜成膜对活性离子的消耗较多，由此会降低二次电池的首次库伦效率，影响二次电池的存储性能。
在一些实施例中，38≤A×B≤65，可选地，38≤A×B≤60，39≤A×B≤55，39≤A×B≤52，39≤A×B≤50。发明人在进一步研究中发现，此时有利于二次电池更好地兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
在一些实施例中，100g所述碳材料对亚麻仁油的吸附量A为30ml-50mL，可选为35ml-47mL。当碳材料对亚麻仁油的吸附量在上述范围内时，碳材料颗粒的表面副反应活性较低，由此可以减少SEI膜成膜对活性离子的消耗，同时还能避免颗粒表面过于致密而影响活性离子传输；此外，还有利于负极膜层的颗粒之间形成合理的孔道结构，提高负极极片对电解液的浸润性。由此，能够使二次电池更好地兼顾高首次库伦效率、高能量 密度以及良好的循环性能和存储性能。
在一些实施例中，所述碳材料的比表面积B为0.5m 2/g-2.1m 2/g，可选为0.7m 2/g-1.8m 2/g，0.9m 2/g-1.8m 2/g，1.0m 2/g-1.8m 2/g，1.0m 2/g-1.7m 2/g，1.0m 2/g-1.6m 2/g。当碳材料的比表面积在上述范围内时，一方面碳材料可具有较低的表面副反应活性，由此能够减少SEI膜成膜对活性离子的消耗，提升碳材料的首次库伦效率；另一方面还能具有较高的活性离子传输性能。由此，能够使二次电池更好地兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能，此外，还能够使二次电池具有良好的倍率性能。
碳材料的比表面积为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19587-2017，采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出。测试仪器可以采用美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪。
100g碳材料对亚麻仁油的吸附量A可以按照如下方法测试：参考GB/T 3780.2-2017，称取一定质量(例如20g)干燥后的测试样品，将称好的样品置于吸油计的混合室中，混合室温度为23℃，盖好盖子；将恒速滴定管输油管口对准混合室盖孔口上方；启动吸油计，仪器开始运转并滴加亚麻仁油，随着样品吸油量的增加，混合物料从自由流动状态变成一种半塑性的团聚物，且混合物的黏度不断增加，该黏度被传送到吸油计的扭矩传感器系统，当滴加的油使半塑性的团聚物达到预设扭矩水平时，吸油计和恒速滴定管自动关闭；读取拟合曲线的最大扭距70％对应的数值，使用公式A＝(V/m)×100，计算得到100g碳材料对亚麻仁油的吸附量A，V表示最大扭矩70％处对应样品消耗的亚麻仁油的体积，单位为ml；m为加入的样品的质量，单位为g。
在一些实施例中，所述碳材料包括一个以上孔面积大于等于0.1μm 2的孔结构，可选地包括一个以上孔面积为0.12μm 2-2.5μm 2的孔结构。当碳材料进一步包括具有上述孔面积的孔结构时，所述孔结构可以为碳材料颗粒体积变化预留所需的膨胀空间，由此能够进一步降低碳材料颗粒破碎产生新界面的风险，进而能够减少副反应的发生，降低二次电池的不可逆容量损失，并进一步改善二次电池的循环性能和存储性能。
在一些实施例中，所述碳材料包括外部区域以及位于所述外部区域内侧的内部区域，所述外部区域是指从所述碳材料的颗粒表面向颗粒内部延伸0.25L的距离所构成的区域，L是指所述碳材料颗粒的短轴长度，所述外部区域的总孔面积记为S 1，所述内部区域的总孔面积记为S 2，并且S 2>S 1。
在本申请中，第一碳基材料的外部区域的总孔面积S 1和内部区域的总孔面积S 2，可以通过第一碳基材料的截面图像进行测试得到。
在本申请中，第一碳基材料的截面图像包括经过第一碳基材料颗粒中心的截面图像。“颗粒中心”是指从颗粒的几何中心向颗粒表面延伸0.1μm的半径内的范围。
在本申请中，颗粒的短轴长度是指颗粒表面两点连线经过颗粒几何中心时的最小值。
图1是本申请的碳材料100的颗粒的一截面图像的示意图，且该截面图像经过碳材料100的颗粒中心。如图1所示，L表示碳材料100的颗粒的短轴长度，从碳材料100的颗粒表面向颗粒内部延伸0.25L的距离所构成的区域即为外部区域101，外部区域101内侧的区域即为内部区域102。
可以采用截面抛光仪(例如日本JEOL公司的IB-09010 CP型氩离子截面抛光仪)制 备第一碳基材料的截面；然后参考JY/T010-1996，使用扫描电子显微镜(例如德国ZEISS公司的Sigma 300型扫描电子显微镜)扫描第一碳基材料的截面；最后通过图像处理软件(例如AVIZO)计算第一碳基材料的外部区域的总孔面积S 1和内部区域的总孔面积S 2。
当碳材料还满足S 2>S 1时，碳材料颗粒可具有如下特征：内部区域的孔数量多和/或孔尺寸大，而外部区域的孔数量少和/或孔尺寸小。碳材料内部区域的孔数量多和/或孔尺寸大，由此该孔结构可为碳材料颗粒体积变化预留所需的膨胀空间，由此能够降低碳材料颗粒破碎产生新界面的风险，进而减少副反应的发生，降低二次电池的不可逆容量损失，并改善二次电池的循环性能和存储性能；碳材料外部区域的孔数量少和/或孔尺寸小，由此可以使碳材料颗粒具有较少的表面缺陷和更稳定的结构，并可以尽可能避免电解液渗入到碳材料颗粒内部的孔结构中，从而能够减少副反应的发生，降低颗粒内部SEI膜成膜对活性离子的消耗，进而能够提升碳材料的首次库伦效率，并进一步改善二次电池的循环性能和存储性能。因此，当碳材料颗粒进一步满足S 2>S 1时，可以有效降低二次电池的不可逆容量损失、改善二次电池的容量发挥特性，并使二次电池更好地兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
在一些实施例中，1.3≤S 2/S 1≤450，1.8≤S 2/S 1≤400，2.0≤S 2/S 1≤300，2.5≤S 2/S 1≤200，3.0≤S 2/S 1≤150。发明人在进一步研究中发现，当S 2/S 1还满足在上述范围内时，能够使二次电池更好地兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
在一些实施例中，0.01μm 2≤S 1≤12.0μm 2，可选地，0.02μm 2≤S 1≤10.0μm 2，0.02μm 2≤S 1≤8.0μm 2，0.02μm 2≤S 1≤7.0μm 2，0.1μm 2≤S 1≤10.0μm 2，0.1μm 2≤S 1≤7.0μm 2。当碳材料的外部区域的总孔面积在上述范围内时，一方面可以使碳材料颗粒具有更少的表面缺陷和更稳定的结构，尽可能避免电解液渗入到碳材料颗粒内部的孔结构中，从而减少副反应的发生，降低碳材料颗粒内部SEI膜成膜对活性离子的消耗，另一方面还不会影响活性离子和电子的传输性能。
在一些实施例中，2.5μm 2≤S 2≤25.0μm 2，可选地，3.0μm 2≤S 2≤22.5μm 2，3.0μm 2≤S 2≤20.5μm 2，4.0μm 2≤S 2≤17.5μm 2。当碳材料的内部区域的总孔面积在上述范围内时，一方面可以为碳材料颗粒体积变化预留足够且稳定的膨胀空间，降低碳材料颗粒破碎产生新界面的风险，减少新界面表面副反应的发生，减少新界面表面SEI膜成膜对活性离子的消耗，另一方面还可以提高碳材料的容量和首次库伦效率。
在一些实施例中，L≥4μm，可选地，4μm≤L≤20μm，6μm≤L≤18μm，8μm≤L≤18μm，8μm≤L≤16μm。
在一些实施例中，所述碳材料的外部区域中的所述孔结构的面积为小于等于0.2μm 2，可选为小于等于0.15μm 2。发明人在进一步研究中还发现，通过控制碳材料的外部区域中的所述孔结构的面积大小在上述范围内，可以使碳材料的外部区域具有较密实结构，由此能够有效降低碳材料的表面缺陷、提升碳材料的结构稳定性，尽可能避免电解液渗入到碳材料颗粒内部的孔结构中，进而能进一步提升二次电池的循环性能和存储性能。当然，本申请并不意欲限制碳材料的外部区域中的所有孔结构的面积均小于等于0.2μm 2，例如，可控制95％以上，可选为99％以上的孔结构的面积小于等于0.2μm 2，可选为小于等于0.15μm 2。
在一些实施例中，所述碳材料的内部区域中包括一个以上面积大于等于0.15μm 2的孔结构，可选地包括一个以上面积为0.18μm 2-2.5μm 2的孔结构。发明人在进一步研究中还发现，通过使碳材料的内部区域包括上述大小的孔结构，一方面可以为碳材料颗粒体积变化预留足够且稳定的膨胀空间，降低碳材料颗粒破碎风险，另一方面还可以提高碳材料的压实密度。
在一些实施例中，所述碳材料的外部区域的层间距记为d 1，所述碳材料的内部区域的层间距记为d 2，所述碳材料满足d 1≥d 2，可选地，d 1>d 2。
碳材料的外部区域的层间距较大，更有利于活性离子的快速嵌入和脱出，由此能够进一步提升二次电池的动力学性能；碳材料的内部区域的层间距较小，有利于提升碳材料的克容量和压实密度，从而能够进一步提升二次电池的能量密度。
在一些实施例中，d 1为0.33565nm-0.33610nm。
在一些实施例中，d 2为0.33557nm-0.33585nm。
碳材料颗粒不同区域的层间距可以用本领域已知的仪器及方法进行测试。例如可以采用高分辨透射电镜(High Resolution Transmission Electron Microscope，HRTEM)进行测试。测试仪器可以采用赛默飞世尔公司的Spectra S/TEM扫描透射电子显微镜。
在一些实施例中，所述碳材料的La(110)为100nm-150nm，可选为110nm-130nm。
在一些实施例中，所述碳材料的Lc(002)为20nm-45nm，可选为28nm-40nm。
当碳材料的La(110)和/或Lc(002)在合适的范围内时，有利于碳材料具有较高的结晶性和/或石墨化度，有利于提升碳材料的克容量，还有利于提升负极膜层的活性离子和电子传输性能，进而有利于提升二次电池的循环性能、存储性能和/或倍率性能。
La(110)表示碳材料的(110)晶面中沿a轴的微晶尺寸，Lc(002)可表示碳材料的(002)晶面中沿c轴的微晶尺寸，可以用本领域已知的仪器及方法进行测试。例如可以使用X射线衍射仪(如Bruker D8 Discover)进行测试，测试可参考JIS K 0131-1996、JB/T 4220-2011，得到碳材料的(110)晶面对应的衍射峰的峰强和半峰全宽(FWHM)、(002)晶面对应的衍射峰的峰强和半峰全宽(FWHM)，然后根据谢乐公式计算得到。
在一些实施例中，所述碳材料的石墨化度为94％-98％，可选为95％-97％。当碳材料的石墨化度在上述范围内时，有利于提升二次电池的能量密度，还有利于提升二次电池的循环性能、存储性能和/或倍率性能。
碳材料的石墨化度为本领域公知的含义，可以用本领域已知的仪器及方法进行测试。例如可以使用X射线衍射仪(如Bruker D8 Discover)进行测试，测试可参考JIS K 0131-1996、JB/T 4220-2011，得到碳材料晶体结构中(002)晶面的平均层间距d 002，然后根据公式g＝(0.344-d 002)/(0.344-0.3354)×100％计算得出石墨化度。在上述公式中，d 002是以纳米(nm)表示的碳材料晶体结构中(002)晶面的平均层间距。
在一些实施例中，所述碳材料的形貌包括块状、球状和类球状中的一种或多种。由此有利于提升负极极片的压实密度，进而提高二次电池的能量密度。
在一些实施例中，所述碳材料包括一次颗粒，可选地，所述碳材料中的所述一次颗粒的数量占比为≥50％，例如，可以为55％-95％，60％-100％，65％-90％，65％-80％，70％-100％，75％-90％，80％-100％，90％-100％，或95％-100％。碳材料包含适当比例的一次颗粒，能使其具有较高的结构稳定性，还能减少副反应的发生；另外，还可以提升 负极极片的压实密度，从而提高二次电池的能量密度。
在一些实施例中，所述碳材料可均为一次颗粒，即所述碳材料中的所述一次颗粒的数量占比为100％。
一次颗粒和二次颗粒均为本领域公知的含义。一次颗粒是指非团聚态的颗粒。二次颗粒是指由两个或两个以上一次颗粒聚集而成的团聚态的颗粒。一次颗粒和二次颗粒可以通过使用扫描电子显微镜(SEM)图进行区分。
在本申请中，碳材料中的一次颗粒的数量占比可以按照如下方法进行测试：在负极膜层中任取一个测试样品，在该测试样品中任取多个测试区域，采用扫描电子显微镜获取多个测试区域的图像，统计各个图像中一次颗粒形貌的碳材料颗粒的个数占碳材料颗粒总个数的比例，多个统计结果的平均值即为碳材料中的一次颗粒的数量占比。
在一些实施例中，所述碳材料的体积分布粒径Dv50为8.0μm-24.0μm，可选为9.5μm-22.5μm。
在一些实施例中，所述碳材料的体积分布粒径Dv10为5.0μm-15.0μm，可选为6.0μm-14.0μm。
在一些实施例中，所述碳材料的体积分布粒径Dv90为16.0μm-35.0μm，可选为17.0μm-34.0μm。
碳材料的体积分布粒径Dv10、Dv50和/或Dv90在上述范围内时，有利于提升活性离子和电子的传输性能，还有利于负极膜层的颗粒之间形成合理的孔道结构，从而能够进一步提升二次电池的循环性能和/或倍率性能。
在一些实施例中，所述碳材料的(Dv90-Dv10)/Dv50为0.55-1.55，可选为0.8-1.4。碳材料的(Dv90-Dv10)/Dv50在上述范围内时，其颗粒堆积性能较好，有利于提升负极膜层的压实密度，从而能够进一步提升二次电池的能量密度；另外，还有利于负极膜层的颗粒之间形成合理的孔道结构。
碳材料的体积分布粒径Dv10、Dv50、Dv90为本领域公知的含义，其分别表示材料累计体积分布百分数达到10％、50％、90％时所对应的粒径，可以用本领域已知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定。测试仪器可以为英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
在一些实施例中，所述碳材料的振实密度为0.80g/cm 3-1.32g/cm 3，可选为0.82g/cm 3-1.28g/cm 3。碳材料的振实密度在上述范围内时，可以提升负极极片的压实密度，进而提高二次电池的能量密度；还有利于负极膜层的颗粒之间形成合理的孔道结构，提升活性离子和电子的传输性能，提升二次电池的循环性能和存储性能。
碳材料的振实密度为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可参照GB/T 5162-2006，使用粉体振实密度测试仪进行测定。测试仪器可以采用丹东百特BT-301。
在一些实施例中，所述碳材料的克容量为355mAh/g-371mAh/g，可选为360mAh/g-370mAh/g。碳材料的克容量在上述范围内时，可以提升二次电池的能量密度。
碳材料的克容量为本领域公知的含义，可以采用本领域已知的方法测试。示例性测试方法如下：将碳材料样品与粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠 (CMC)、导电剂炭黑按照质量比96.2:1.8:1.2:0.8在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，于烘箱中干燥后备用；将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照体积比1:1:1进行混合得到有机溶剂，然后将LiPF 6溶解于上述有机溶剂中，配制成浓度为1mol/L的电解液；之后以金属锂片为对电极，聚乙烯(PE)薄膜作为隔离膜，在氩气保护的手套箱组装成CR2430型扣式电池。在25℃下，首先以0.15mA的电流将上述制备的扣式电池恒流放电至0.005V，静置5min，再以10μA恒流放电至0.005V，记录扣式电池的首圈放电容量；之后以0.3mA的电流恒流充电至2.0V，记录扣式电池的充电容量。扣式电池的充电容量与碳材料样品质量的比值即为碳材料的克容量。
制备方法
本申请实施方式的第二方面提供一种碳材料的制备方法，其能制备本申请实施方式第一方面的碳材料。
所述碳材料的制备方法包括如下步骤：步骤1，提供具有多个孔结构的原料；步骤2，将所述原料与填充材料按照预定比例混合均匀，之后在第一温度T 1下保温第一时间t 1，得到中间体；步骤3，将所获得的中间体在第二温度T 2下保温第二时间t 2，得到碳材料，其中，所述碳材料包括孔结构，100g所述碳材料对亚麻仁油的吸附量记为A，所述碳材料的比表面积记为B，则所述碳材料满足：36≤A×B≤75，100g所述碳材料对亚麻仁油的吸附量A的单位为ml，所述碳材料的比表面积B的单位为m 2/g。
在一些实施例中，用于制备所述碳材料的所述原料包括天然石墨。可选地，所述天然石墨包括鳞片石墨、天然球形石墨和微晶石墨中的一种或多种，可选为包括天然球形石墨。
“天然球形石墨”是指具有球状或类球状的天然石墨，并且并非将所有的天然石墨颗粒都控制为理想的球。在一些实施例中，可以通过对鳞片石墨进行预处理以获得所需的颗粒尺寸和形貌的天然球形石墨，可选地，所述预处理包括破碎、分级、球化、纯化等工序。
在一些实施例中，所述原料的形貌包括球状和类球状中的一种或多种。
在一些实施例中，所述原料的体积分布粒径Dv50为8.5μm-24.0μm，可选为10.5μm-22.5μm。
通过调节原料的颗粒尺寸在上述范围内，能够减少原料在后续制备过程中团聚，由此能够减少由于需要增加解聚工序而导致碳材料颗粒表面缺陷增加、表面副反应位点增多等问题。
在一些实施例中，所述原料中的灰分含量为≤1wt％。原料中的灰分含量较低时，有利于碳材料具有较低的表面缺陷。
在一些实施例中，所述填充材料的软化点温度为110℃-175℃。例如，填充材料的软化点温度可以为110℃，115℃，120℃，125℃，130℃，135℃，140℃，145℃，150℃，155℃，160℃，165℃，170℃，175℃或以上任何数值组成的范围。可选地，所述填充材料的软化点温度为120℃-170℃。
发明人在研究过程中发现，填充材料的软化点温度在上述范围内时，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合 适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。并且还能避免以下情况：当填充材料的软化点温度过高时，填充材料不易流动填充到原料的孔结构中，由此不能有效减少所获得的碳材料颗粒表面和内部缺陷，也不能有效阻止电解液渗入到所获得的碳材料颗粒内部的孔结构中，并且此时碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B容易较大，碳材料的A×B容易较大，进而影响了二次电池的首次库伦效率、循环性能和存储性能；当填充材料的软化点温度过低时，填充材料中含有较多的小分子物质，这些小分子物质受热易挥发，因此，尽管填充材料容易流动填充进入原料的孔结构中，但是在高温下热处理时，填充材料中的小分子物质挥发，由此导致实际残留碳不能有效填充原料的孔结构，未能实现有效填充效果，或者导致填充区域实际残留碳具有较多的孔结构，此时碳材料颗粒的表面缺陷较多，碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B容易较大，碳材料的A×B容易较大，进而不能降低SEI膜成膜对活性离子的消耗和降低二次电池的不可逆容量损失，同时还会影响二次电池的循环性能和存储性能。
在一些实施例中，所述填充材料的结焦值为26％-50％，可选为33％-45％。发明人在研究过程中发现，填充材料的结焦值在上述范围内时，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。
填充材料的结焦值为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可以参照GB/T 8727-2008进行测定。
在一些实施例中，所述填充材料的软化点温度为120℃-170℃且结焦值为33％-45％。
在一些实施例中，所述填充材料的体积分布粒径Dv50为小于等于6μm，可选为1μm-6μm，1μm-5μm，2μm-5μm，3μm-5μm。由此有利于填充材料受热熔融后填充进入原料的孔结构中，还有利于提高填充材料与原料的分散均匀性。
在一些实施例中，所述填充材料中的喹啉不溶物的含量为≤1wt％，可选为≤0.8wt％。喹啉不溶物含量较多时，会影响填充区域实际残留碳的原子排布，影响碳材料的粉体压实密度和二次电池的能量密度。
在一些实施例中，所述填充材料包括煤沥青和石油沥青中的一种或多种。
在一些实施例中，所述填充材料与所述原料的质量比为(10-32):100，可选为(10-25):100，(11-22):100，(11-20):100。由此有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。并且还能避免以下情况：填充材料与原料的质量比过小时，填充材料不易流动填充到原料的孔结构中，由此不能有效减少所获得的碳材料颗粒内部缺陷，不能有效阻止电解液渗入到所获得的碳材料颗粒内部的孔结构中，并且此时碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B容易较大，碳材料的A×B容易较大，进而影响了二次电池的首次库伦效率、循环性能和存储性能；填充材料与原料的质量比过大时，容易导致原料内部孔结构完全被填充，此时碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B容易较小，碳材料的A×B容易较小，由此所获得的碳材料在活性离子脱出和嵌入过程中产生的 体积变化较大，从而颗粒更易破碎，进而SEI膜成膜对活性离子的消耗增加，二次电池的不可逆容量损失增加；此外，填充材料与原料的质量比过大时，大量填充材料还会残留在颗粒表面，此时颗粒更易团聚，不仅增加了解聚工序，还会降低所获得的碳材料的克容量和压实密度。
通过调节填充材料的种类、软化点、结焦值、添加量等中的一个或多个参数在上述范围内，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内；此外，填充材料受热熔融后，黏度不高，保持良好的流动性，同时不易粘接原料颗粒，能够减少原料颗粒在后续制备过程中团聚，由此能够减少由于需要增加解聚工序而导致所获得的碳材料颗粒表面缺陷增加、表面副反应位点增多等问题。
在一些实施例中，在步骤2中，将所述原料与所述填充材料按照预定比例混合均匀后升温至第一温度T 1的升温工艺为分阶段升温工艺，可选地包括第一升温工艺、第二升温工艺和第三升温工艺。
在一些实施例中，所述第一升温工艺为升温至200℃-250℃并在该温度下保温0.5h-2h。
发明人在研究过程中发现，第一升温工艺的保温时间在上述范围内时，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。并且还能避免以下情况：保温时间过短时，填充材料不易流动填充到原料的孔结构中，而是可能在颗粒表面碳化，由此不能有效减少所获得的碳材料颗粒内部缺陷，不能有效阻止电解液渗入到所获得的碳材料颗粒内部的孔结构中，此时碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B还容易较大，碳材料的A×B容易较大，进而影响了二次电池的首次库伦效率、循环性能和存储性能；保温时间过长时，填充材料容易流动填充进入原料的全部孔结构中，碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B还容易较小，碳材料的A×B容易较小，由此导致碳材料在活性离子脱出和嵌入过程中产生的体积变化较大，颗粒更易破碎，从而会增加SEI膜成膜对活性离子的消耗，增加二次电池的不可逆容量损失，同时还会影响二次电池的循环性能、存储性能和倍率性能。
在一些实施例中，所述第二升温工艺为升温至450℃-550℃并在该温度下保温0.5h-2h。
在一些实施例中，所述第三升温工艺为升温至所述第一温度T 1并在该温度下保温第一时间t 1。
在分阶段升温过程中，首先升温至200℃-250℃，由于加热温度高于填充材料的软化点温度，因此，此时填充材料受热熔融软化，保温0.5h-2h可以使其流动填充至原料的孔结构中；之后升温至450℃-550℃，此时熔融软化的填充材料发生碳化反应，逐渐形成半焦状态，变为粘稠液体或者固体，由此避免填充材料进入原料的全部孔结构中；最后升温至第一温度T 1，此时填充材料发生碳化反应，由此能够使得填充材料占据的孔结构被有效填充，减少表面缺陷，进而有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合 适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。
在一些实施例中，在步骤2中，以1℃/min-10℃/min的速率升温至所述第一温度T 1。例如升温速率可以为1.5℃/min，2℃/min，3℃/min，4℃/min，5℃/min，6℃/min，7℃/min，8℃/min，9℃/min，10℃/min或以上任何数值组成的范围。可选地，升温速率为1.5℃/min-8℃/min。
在一些实施例中，所述第一升温工艺的升温速率可为1℃/min-10℃/min，可选为1.5℃/min-8℃/min。
发明人在研究过程中发现，第一升温工艺的升温速率在上述范围内时，有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。并且还能避免以下情况：升温速率过大时，填充材料可能在原料颗粒表面发生碳化，导致填充材料不易流动填充到原料的孔结构中，由此不能有效减少所获得的碳材料颗粒内部缺陷，不能有效阻止电解液渗入到所获得的碳材料颗粒内部的孔结构中，进而影响了二次电池的首次库伦效率、循环性能和存储性能；升温速率过小时，填充材料容易流动填充进入原料的全部孔结构中，由此导致碳材料在活性离子脱出和嵌入过程中产生的体积变化较大，颗粒更易破碎，从而会增加SEI膜成膜对活性离子的消耗，增加二次电池的不可逆容量损失，同时还会影响二次电池的循环性能、存储性能和倍率性能。
在一些实施例中，所述第二升温工艺的升温速率可为1℃/min-10℃/min，可选为1.5℃/min-8℃/min。
在一些实施例中，所述第三升温工艺的升温速率可为1℃/min-10℃/min，可选为1.5℃/min-8℃/min。
在一些实施例中，在步骤2中，所述第一温度T 1为700℃-1100℃。例如第一温度T 1可以为750℃，800℃，850℃，900℃，950℃，1000℃，1050℃，1100℃或以上任何数值组成的范围。可选地，所述第一温度T 1为750℃-1100℃。
发明人在研究过程中发现，第一温度在上述范围内时，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。并且还能避免以下情况：第一温度过低时，填充材料可能未完全转化为碳材料，后续热处理时将继续分解为小分子物质，由此导致填充区域实际残留碳具有较多的孔结构，未能起到有效减少所获得的碳材料颗粒内部缺陷的作用，也不能有效阻止电解液渗入到所获得的碳材料颗粒内部的孔结构中，同时还使得所获得的碳材料表面缺陷较多，碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B容易较大，碳材料的A×B容易较大，进而影响了二次电池的首次库伦效率、循环性能和存储性能；第一温度过高时，碳材料制备过程中的能耗和成本增加。
在一些实施例中，所述第一时间t 1为0.5h-5h。例如第一时间t 1可以为1h，1.5h，2h，2.5h，3h，3.5h，4h，4.5h，5h或以上任何数值组成的范围。可选地，所述第一时间t 1为0.5h-3h。
发明人在研究过程中发现，第一时间在上述范围内时，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内， 还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。并且还能避免以下情况：第一时间过短时，填充材料可能未完全转化为碳材料，后续热处理时将继续分解为小分子物质，由此导致填充区域实际残留碳具有较多的孔结构，未能起到有效减少所获得的碳材料颗粒内部缺陷的作用，也不能有效阻止电解液渗入到所获得的碳材料颗粒内部的孔结构中，同时还使得所获得的碳材料表面缺陷较多，碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B容易较大，碳材料的A×B容易较大，进而影响了二次电池的首次库伦效率、循环性能和存储性能；第一时间过长时，容易碳材料制备过程中的能耗和成本增加。
在一些实施例中，在步骤2中，热处理可在中频炉、辊道窑、回转窑或推板窑进行。
在一些实施例中，在步骤2中，热处理气氛可为保护气体气氛。所述保护气体可包括氮气、氩气、氦气中的一种或多种。
在步骤2中，通过调节升温速率、第一温度、第一时间、升温工艺等中的一者或者多者在上述范围内，有利于制备获得所需的碳材料，例如有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于调节碳材料的外部区域和内部区域中的孔尺寸和/或孔数量在合适的范围内，调节S 2/S 1在合适范围内。
在一些实施例中，所述第二温度T 2为1920℃-2520℃，例如第二温度可以为1950℃，2000℃，2050℃，2100℃，2150℃，2200℃，2250℃，2300℃，2350℃，2400℃，2450℃，2500℃或以上任何数值组成的范围。可选地，所述第二温度T 2为2050℃-2400℃。
发明人在研究过程中发现，第二温度在上述范围内时，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于碳材料具有低表面缺陷、高克容量和/或高压实密度。并且还能避免以下情况：当第二温度过低时，所获得的碳材料颗粒表面缺陷较多，此时碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B还容易较大，碳材料的A×B也容易较大，进而影响了二次电池的首次库伦效率、循环性能和存储性能；当第二温度过高时，所获得的碳材料中无序碳的含量过少，碳材料的结晶度和石墨化度均很高，此时并不利于活性离子的快速脱出和嵌入，同时充放电过程中碳材料的体积变化还较大，由此还增加了碳材料颗粒破碎的风险，因此影响了二次电池的循环性能和/或动力学性能；此外，当第二温度过高时，碳材料制备过程中的能耗和成本还会增加。
在一些实施例中，所述第二时间t 2为1h-6h。例如第二时间t 1可以为2h，2.5h，3h，3.5h，4h，4.5h，5h，5.5h，6h或以上任何数值组成的范围。可选地，所述第二时间t 2为2h-6h。
发明人在研究过程中发现，第二时间在上述范围内时，有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，有利于使碳材料的A×B在合适的范围内，还有利于碳材料具有低表面缺陷、高克容量和/或高压实密度。并且还能避免以下情况：第二时间过短时，所获得的碳材料颗粒表面缺陷较多，此时碳材料对亚麻仁油的吸附量A和/或碳材料的比表面积B还容易较大，碳材料的A×B也容易较大，进而影响了二次电池的首次库伦效率、循环性能和存储性能；第二时间过长时，所获得的碳材料中无序碳的 含量过少，碳材料的结晶度和石墨化度均很高，此时并不利于活性离子的快速脱出和嵌入，同时充放电过程中碳材料的体积变化还较大，由此还增加了碳材料颗粒破碎的风险，因此影响了二次电池的循环性能和/或动力学性能；此外，当第二时间过长时，碳材料制备过程中的能耗和成本还会增加。
在一些实施例中，在步骤3中，所述热处理可在中频炉、箱式石墨化炉、艾奇逊石墨化炉、连续式石墨化炉或内串石墨化炉中进行。
在一些实施例中，在步骤3中，中频炉、连续石墨化热处理气氛可为保护气体气氛。所述保护气体可包括氮气、氩气、氦气中的一种或多种。
通过调节第二温度、第二时间中的一者或者多者在上述范围内，有利于降低碳材料中无序碳的含量，还有利于碳材料具有合适的对亚麻仁油的吸附量A和/或合适的比表面积B，并有利于使碳材料的A×B在合适的范围内。
本申请的碳材料的制备方法工艺简单，安全性高，不需要进行预设压力或者抽真空处理，并且在热处理过程中可以不需要额外增加解聚工序。本申请制备的碳材料的体积膨胀小、结构稳定性高且表面缺陷少，进而可以兼具较高的克容量和较高的首次库伦效率，并且还能使二次电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
本申请的制备方法成本低廉，具有较高的实用性，适于进行规模化生产。
二次电池
本申请实施方式第三方面提供一种二次电池。
本申请对二次电池种类没有特别的限制，例如，二次电池可以为锂离子电池等。通常情况下，二次电池包括正极极片、负极极片以及电解质等。在二次电池充放电过程中，活性离子在所述正极极片和所述负极极片之间往返嵌入和脱出，所述电解质在所述正极极片和所述负极极片之间起到传导活性离子的作用。本申请对所述电解质的种类没有特别的限制，可根据实际需求进行选择。例如，所述电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还可以包括隔离膜，所述隔离膜设置在所述正极极片和所述负极极片之间，起到隔离的作用。
[负极极片]
在一些实施例中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上的负极膜层。例如，所述负极集流体具有在自身厚度方向相对的两个表面，所述负极膜层设置在所述负极集流体的两个相对表面中的任意一者或两者上。
在一些实施例中，所述负极膜层包括本申请实施方式第一方面的碳材料或通过本申请实施方式第二方面所述的方法制备得到的碳材料。由此能使二次电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
在一些实施例中，所述负极膜层还可以进一步包括除了上述碳材料以外的其他负极活性材料。在一些实施例中，所述其他负极活性材料包括但不限于常规天然石墨、人造石墨、软碳、硬碳、硅基材料、锡基材料和钛酸锂中的一种或多种。所述硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物和硅合金材料中的一种或多种。所述锡基材料可包括单质锡、锡氧化物和锡合金材料中的一种或多种。
在一些实施例中，所述负极膜层还可选地包括负极导电剂。本申请对所述负极导电剂的种类没有特别的限制，作为示例，所述负极导电剂可包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种。
在一些实施例中，所述负极膜层还可选地包括负极粘结剂。本申请对所述负极粘结剂的种类没有特别的限制，作为示例，所述负极粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的一种或多种。
在一些实施例中，所述负极膜层还可选地包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC)、PTC热敏电阻材料等。
在一些实施例中，所述负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铜、铜合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种。作为示例，所述高分子材料基层可包括聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)和聚乙烯(PE)中的一种或多种。
所述负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。所述负极浆料通常是将负极活性材料、可选的导电剂、可选的粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
所述负极极片并不排除除了所述负极膜层之外的其他附加功能层。例如，在一些实施例中，本申请所述的负极极片还包括夹在所述负极集流体和所述负极膜层之间、设置在所述负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)；在一些实施例中，本申请所述的负极极片还包括覆盖在所述负极膜层表面的保护层。
[正极极片]
在一些实施例中，所述正极极片包括正极集流体以及设置在所述正极集流体至少一个表面的正极膜层。例如，所述正极集流体具有在自身厚度方向相对的两个表面，所述正极膜层设置于所述正极集流体的两个相对表面中的任意一者或两者上。
所述正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铝、铝合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种。作为示例，所述高分子材料基层可包括聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)和聚乙烯(PE)中的一种或多种。
所述正极膜层通常包含正极活性材料、可选的粘结剂和可选的导电剂。所述正极膜层通常是将正极浆料涂布在所述正极集流体上，经干燥、冷压而成的。所述正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。作为示例，用于正极膜层的粘结剂可包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯- 四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物和含氟丙烯酸酯树脂中的一种或多种。作为示例，用于正极膜层的导电剂包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种。
所述正极活性材料可采用本领域公知的用于二次电池的正极活性材料。
当本申请的二次电池为锂离子电池时，所述正极活性材料所述正极活性材料可包括但不限于含锂过渡金属氧化物、含锂磷酸盐及其各自的改性化合物中的一种或多种。所述锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其各自的改性化合物中的一种或多种。所述含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或多种。
在一些实施例中，为了进一步提高二次电池的能量密度，用于锂离子电池的正极活性材料可以包括通式为Li aNi bCo cM dO eA f的锂过渡金属氧化物及其改性化合物中的一种或多种。0.8≤a≤1.2，0.5≤b<1，0<c<1，0<d<1，1≤e≤2，0≤f≤1，M选自Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti和B中的一种或多种，A选自N、F、S和Cl中的一种或多种。
在一些实施例中，作为示例，用于锂离子电池的正极活性材料可包括LiCoO 2、LiNiO 2、LiMnO 2、LiMn 2O 4、LiNi 1/3Co 1/3Mn 1/3O 2(NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、LiNi 0.85Co 0.15Al 0.05O 2、LiFePO 4和LiMnPO 4中的一种或多种。
在本申请中，上述各正极活性材料的改性化合物可以是对所述正极活性材料进行掺杂改性和/或表面包覆改性。
[电解质]
在一些实施例中，所述电解质采用电解液，所述电解液包括电解质盐和溶剂。
所述电解质盐的种类不受具体的限制，可根据实际需求进行选择。
当本申请的二次电池为锂离子电池时，作为示例，所述电解质盐可包括六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)和四氟草酸磷酸锂(LiTFOP)中的一种或多种。
所述溶剂的种类不受具体的限制，可根据实际需求进行选择。在一些实施例中，作为示例，所述溶剂可包括碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸乙烯酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)和二乙砜(ESE)中的一种或多种。
在一些实施例中，所述电解液还可选地包括添加剂。例如，所述添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善二次电池某些性能的添加剂，例如改善二次电池过充性能的添加剂、改善二次电池高温性能的添加剂、改善二次电池低温功率性能的添加剂等。
[隔离膜]
本申请对所述隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施例中，所述隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯和聚偏二氟乙烯中的一种或多种。所述隔离膜可以是单层薄膜，也可以是多层复合薄膜。所述隔离膜为多层复合薄膜时，各层的材料相同或不同。
在一些实施例中，所述正极极片、所述隔离膜和所述负极极片可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施例中，所述二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施例中，外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。外包装也可以是软包，例如袋式软包。所述软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)和聚丁二酸丁二醇酯(PBS)中的一种或多种。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图2是作为一个示例的方形结构的二次电池5。
在一些实施例中，如图3所示，外包装可包括壳体51和盖板53。壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或几个，可根据需求来调节。
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
在本申请的一些实施例中，根据本申请的二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图4是作为一个示例的电池模块4的示意图。如图4所示，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图5和图6是作为一个示例的电池包1的示意图。如图5和图6所示，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3， 上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
用电装置
本申请还提供一种用电装置，所述用电装置包括本申请的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以但不限于是移动设备(例如手机、平板电脑、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图7是作为一个示例的用电装置的示意图。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
(1)碳材料的制备
步骤1：将100目鳞片石墨进行机械粉碎、分级、球化、纯化处理，获得天然球形石墨，其体积分布粒径Dv50为17μm，灰分含量为0.01％。
步骤2：将所获得的天然球形石墨与石油沥青(软化点温度为120℃、体积分布粒径Dv50为4.3μm、结焦值为33％)按照质量比100:15在VC混合机中混合30min，之后将混合后的物料置于辊道窑中，以5℃/min的速率升温至230℃并保温1h(第一升温工艺)，之后以5℃/min的速率升温至500℃并保温1h(第二升温工艺)，再以5℃/min的速率升温至1100℃并保温1h(第三升温工艺)，结束后冷却至室温，得到中间体。
步骤3：将所获得的中间体置于艾奇逊石墨化炉中，升温至2300℃并保温2h，结束后除磁、筛分得到碳材料。
(2)扣式电池(半电池)的制备
将上述制备的碳材料与粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)、导电剂炭黑按照质量比96.2:1.8:1.2:0.8在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，于烘箱中干燥后备用。将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照体积比1:1:1进行混合得到有机溶剂，然后将LiPF 6溶解于上述有机溶剂中，配制成浓度为1mol/L的电解液。之后以金属锂片为对电极，聚乙烯(PE)薄膜作为隔离膜，在氩气保 护的手套箱组装成CR2430型扣式电池。
(3)二次电池(全电池)的制备
将上述制备的碳材料、导电剂炭黑(Super P)、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠按照重量比96:1:1:2在适量的溶剂去离子水中充分搅拌混合，形成负极浆料。将负极浆料涂布在负极集流体铜箔的两个表面上，经干燥、冷压后，获得负极极片。
将LiFePO 4与导电炭黑、聚偏氟乙烯按照重量比96:2.5:1.5混合，加入适量溶剂NMP，搅拌均匀，获得正极浆料。将正极浆料涂布在正极集流体铝箔的两个表面上，经干燥、冷压后，获得正极极片。
采用厚度为12μm的聚丙烯薄膜作为隔离膜，与上述制备的正极极片和负极极片按顺序放好，使隔离膜处于正极极片和负极极片中间起到隔离作用，之后卷绕得到电极组件；将电极组件置于外包装中，干燥后注入与上述制备扣式电池相同的电解液，经过真空封装、静置、化成、容量等工序，得到二次电池。
对比例1
半电池和全电池的制备方法与实施例1类似，不同之处在于碳材料的制备工艺。
将100目鳞片石墨进行机械粉碎、分级、球化、纯化处理，获得天然球形石墨，其体积分布粒径Dv50为17μm，灰分含量为0.01％，之后以所获的天然球形石墨作为碳材料制备半电池和全电池。
对比例2
半电池和全电池的制备方法与实施例1类似，不同之处在于碳材料的制备工艺。
将100目鳞片石墨进行机械粉碎、分级、球化、纯化处理，获得天然球形石墨，其体积分布粒径Dv50为17μm，灰分含量为0.01％。
将所获得的天然球形石墨与石油沥青(软化点温度为120℃、体积分布粒径Dv50为4.3μm、结焦值为33％)按照质量比100:15在VC混合机中混合30min，之后将混合后的物料在3200℃下石墨化处理10h，结束后冷却至室温，得到碳材料。
对比例3
半电池和全电池的制备方法与实施例1类似，不同之处在于碳材料的制备工艺。
将100目鳞片石墨进行机械粉碎、分级、球化、纯化处理，获得天然球形石墨，其体积分布粒径Dv50为17μm，灰分含量为0.01％。
将所获得的天然球形石墨与石油沥青(软化点温度为120℃、体积分布粒径Dv50为4.3μm、结焦值为33％)按照质量比100:15在VC混合机中混合30min，之后将混合后的物料在1300℃下碳化处理2h，结束后冷却至室温，得到碳材料。
对比例4
半电池和全电池的制备方法与实施例1类似，不同之处在于碳材料的制备工艺。
将100目鳞片石墨进行机械粉碎、分级、球化、纯化处理，获得天然球形石墨，其体积分布粒径Dv50为17μm，灰分含量为0.01％。
将沥青添加到洗油中，高速搅拌使沥青充分溶解，得到沥青溶液。将100g天然石球形墨放入反应釜，抽真空60min，当反应釜真空度达到0.07MPa，打开沥青溶液抽吸阀门，将沥青溶液全部吸入反应釜，进液完毕后关闭抽吸阀门，停止抽真空，同时对混合液高速搅拌40min后，加压(12MPa)浸渍完毕后，减压使反应釜内外压力相同后，通入 氮气加热到230℃除去洗油。当反应釜内的洗油全部排出后，在压力为1.5MPa的条件下，按照升温速率为5℃/min将反应釜加热到410℃进行热聚合反应10h后，冷却到室温出料。将获得的物料等静压(10MPa)下保压30min后，进行石墨化高温(2800℃)处理4h，冷却到室温，然后粉碎。将粉碎后的物料与沥青按照100:5混合均匀，在氮气保护下，1000℃下碳化处理5h，冷却到室温得到内部没有孔隙的碳材料。
实施例2-23
半电池和全电池的制备方法与实施例1类似，不同之处在于调整了碳材料的制备工艺参数，具体详见表1。
性能测试
(1)碳材料对亚麻仁油的吸附量测试
参考GB/T 3780.2-2017，称取20g干燥后的测试样品，将称好的样品置于吸油计的混合室中，混合室温度为23℃，盖好盖子；将恒速滴定管输油管口对准混合室盖孔口上方；启动吸油计，仪器开始运转并滴加亚麻仁油，随着样品吸油量的增加，混合物料从自由流动状态变成一种半塑性的团聚物，且混合物的黏度不断增加，该黏度被传送到吸油计的扭矩传感器系统，当滴加的油使半塑性的团聚物达到预设扭矩水平时，吸油计和恒速滴定管自动关闭；读取拟合曲线的最大扭距70％对应的数值，使用公式A＝(V/m)×100，计算得到100g碳材料对亚麻仁油的吸附量A，V表示最大扭矩70％处对应样品消耗的亚麻仁油的体积，单位为ml；m为加入的样品的质量，单位为g。
(2)碳材料的比表面积测试
参照GB/T 19587-2017，采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出碳材料的比表面积B。测试仪器可以采用美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪。
(3)碳材料的X射线衍射分析测试
参考JIS K 0131-1996、JB/T 4220-2011，使用X射线衍射仪进行测试，得到碳材料的(110)晶面对应的衍射峰的峰强和半峰全宽(FWHM)、(002)晶面对应的衍射峰的峰强和半峰全宽(FWHM)，然后根据谢乐公式计算得到碳材料的La(110)和Lc(002)。La(110)表示碳材料的(110)晶面中沿a轴的微晶尺寸，Lc(002)可表示碳材料的(002)晶面中沿c轴的微晶尺寸。测试仪器可以为Bruker D8 Discover X射线衍射仪。
(4)碳材料的外部区域和内部区域中的总孔面积测试
将制样用粘结剂与碳材料粉末混合均匀后涂到铜箔上，60℃烘干30min备用；将样品剪成6mm×6mm大小粘贴在CP型氩离子截面抛光仪的样品台上；使用等离子束对样品进行切割，获得碳材料的截面，且碳材料颗粒的截面经过碳材料颗粒中心。测试仪器可以为日本JEOL公司的IB-09010 CP型氩离子截面抛光仪。
使用扫描电子显微镜对碳材料的截面进行扫描。测试可参考JY/T010-1996。测试仪器可以为德国ZEISS公司的Sigma 300型扫描电子显微镜。
从碳材料的颗粒表面向颗粒内部延伸0.25L的距离所构成的区域记为外部区域，外部区域内侧的区域记为内部区域，L表示碳材料的颗粒的短轴长度。使用图像处理软件计算碳材料颗粒的外部区域的总孔面积S 1以及内部区域的总孔面积S 2。图像处理软件可以为AVIZO。
(5)碳材料的首次库伦效率测试
在25℃下，首先以0.15mA的电流将上述制备的扣式电池恒流放电至0.005V，静置5min，再以10μA恒流放电至0.005V，记录扣式电池的首圈放电容量；之后以0.3mA的电流恒流充电至2.0V，记录扣式电池的首圈充电容量。碳材料的首次库伦效率(％)＝扣式电池的首圈充电容量/扣式电池的首圈放电容量×100％。
(6)二次电池的循环性能测试
在25℃下，将上述制备的二次电池以1C恒流充电至上限截止电压(对应100％SOC)，然后恒压充电至电流为0.05C，静置5min之后，将二次电池以1C恒流放电至下限截止电压(对应0％SOC)，记录此时的放电容量，即为第1圈放电容量。将二次电池按照上述方法进行循环充放电测试，记录每圈循环后的放电容量。二次电池25℃循环2000圈容量保持率(％)＝2000圈循环后的放电容量/第1圈放电容量×100％。
(7)二次电池的存储性能测试
在25℃下，将上述制备的二次电池以1C恒流充电至上限截止电压(对应100％SOC)，然后恒压充电至电流为0.05C，静置5min之后，将二次电池以1C恒流放电至下限截止电压(对应0％SOC)，记录此时的放电容量，即为存储前放电容量。
在25℃下，将上述制备的二次电池以1C恒流充电至上限截止电压(对应100％SOC)，然后恒压充电至电流为0.05C。之后将二次电池置于60℃恒温箱中存储，直至二次电池存储后的放电容量衰减为存储前放电容量的90％，停止测试，记录二次电池的存储天数。
实施例1-23制备的碳材料的体积分布粒径、振实密度等参数均在本申请说明书记载的范围内。
综合表2测试结果可知，当碳材料满足36≤A×B≤75，能使电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。此外，当碳材料进一步满足38≤A×B≤65，可选地满足39≤A×B≤55时，电池的综合性能得到进一步改善。
对比例1-4制备的碳材料均不满足36≤A×B≤75，并且也均不能使电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储性能。
对比例1以未处理的天然球形石墨作为碳材料，其内部具有较多的孔隙，结合表2测试结果可知，由此制备的电池的克容量、首次库伦效率、循环性能和存储性能均较差，且电池的循环圈数尚未达到2000圈时，放电容量已衰减为第1圈放电容量的80％。
对比例2-3制备的碳材料为在天然球形石墨表面形成碳层包覆层，但是该碳层仅存在于天然球形石墨表面，未能实现填充效果，且碳层并不能有效阻止电解液渗入到颗粒内部的孔结构中，进而导致对电池首次库伦效率、循环性能和存储性能的改善作用有限。
对比例4制备碳材料时，通过等静压方式将填充材料填充至天然球形石墨颗粒内部的全部孔结构中，由此会使得活性离子脱出和嵌入过程中碳材料颗粒的体积变化较大，此时颗粒更易破碎，进而导致对电池的循环性能和存储性能的改善作用有限；此外，碳材料颗粒内部和/或表面存在大量软碳，其会增加颗粒表面副反应，进一步影响电池的循环性能和存储性能。同时，该制备工艺复杂，不适合进行规模化生产。
综合表2的测试结果还可知，当碳材料颗粒进一步满足S 2>S 1，可选地满足1.3≤S 2/S 1≤450，更可选地满足1.8≤S 2/S 1≤400时，电池的综合性能得到进一步改善。此时，碳材 料颗粒进一步具有如下特征：内部区域的孔数量多和/或孔尺寸大，而外部区域的孔数量少和/或孔尺寸小。碳材料内部区域的孔结构可为碳材料颗粒体积变化预留所需的膨胀空间，由此能够降低碳材料颗粒破碎产生新界面的风险，进而减少副反应的发生，降低二次电池的不可逆容量损失；碳材料外部区域的孔数量少和/或孔尺寸小，由此可以使碳材料颗粒具有更稳定的结构，并尽可能避免电解液渗入到碳材料颗粒内部的孔结构中，从而能够减少副反应的发生，降低颗粒内部SEI膜成膜对活性离子的消耗。由此，进一步满足上述结构特征的碳材料能进一步提升电池的综合性能。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。
Figure PCTCN2022134444-appb-000001
Figure PCTCN2022134444-appb-000002

Claims (24)

  1. 一种碳材料，其中，所述碳材料包括孔结构，100g所述碳材料对亚麻仁油的吸附量记为A，所述碳材料的比表面积记为B，则所述碳材料满足：36≤A×B≤75，100g所述碳材料对亚麻仁油的吸附量A的单位为ml，所述碳材料的比表面积B的单位为m 2/g。
  2. 根据权利要求1所述的碳材料，其中，38≤A×B≤65，可选地，39≤A×B≤55。
  3. 根据权利要求1或2所述的碳材料，其中，
    100g所述碳材料对亚麻仁油的吸附量A为30ml-50mL，可选为35ml-47mL；和/或，
    所述碳材料的比表面积B为0.5m 2/g-2.1m 2/g，可选为0.7m 2/g-1.8m 2/g。
  4. 根据权利要求1-3任一项所述的碳材料，其中，所述碳材料包括一个以上孔面积大于等于0.1μm 2的孔结构，可选地包括一个以上孔面积为0.12μm 2-2.5μm 2的孔结构。
  5. 根据权利要求1-4任一项所述的碳材料，其中，所述碳材料包括外部区域以及位于所述外部区域内侧的内部区域，所述外部区域是指从所述碳材料的颗粒表面向颗粒内部延伸0.25L的距离所构成的区域，L是指所述碳材料颗粒的短轴长度，所述外部区域的总孔面积记为S 1，所述内部区域的总孔面积记为S 2，并且S 2>S 1。
  6. 根据权利要求5所述的碳材料，其中，1.3≤S 2/S 1≤450，可选地，1.8≤S 2/S 1≤400。
  7. 根据权利要求5或6所述的碳材料，其中，
    0.01μm 2≤S 1≤12.0μm 2，可选地，0.02μm 2≤S 1≤7.0μm 2；和/或，
    2.5μm 2≤S 2≤25.0μm 2，可选地，3.0μm 2≤S 2≤20.5μm 2；和/或，
    L≥4μm，可选地，6μm≤L≤18μm。
  8. 根据权利要求5-7任一项所述的碳材料，其中，
    所述碳材料的外部区域中的所述孔结构的面积为小于等于0.2μm 2，可选为小于等于0.15μm 2；和/或，
    所述碳材料的内部区域中包括一个以上面积大于等于0.15μm 2的孔结构，可选地包括一个以上面积为0.18μm 2-2.5μm 2的孔结构。
  9. 根据权利要求5-8任一项所述的碳材料，其中，所述碳材料的外部区域的层间距记为d 1，所述碳材料的内部区域的层间距记为d 2，所述碳材料满足d 1≥d 2；
    可选地，d 1>d 2。
  10. 根据权利要求9所述的碳材料，其中，
    d 1为0.33565nm-0.33610nm；和/或，
    d 2为0.33557nm-0.33585nm。
  11. 根据权利要求1-10任一项所述的碳材料，其中，
    所述碳材料的石墨化度为94％-98％，可选为95％-97％；和/或，
    所述碳材料的La(110)为100nm-150nm，可选为110nm-130nm；和/或，
    所述碳材料的Lc(002)为20nm-45nm，可选为28nm-40nm。
  12. 根据权利要求1-11任一项所述的碳材料，其中，所述碳材料满足如下中的至少一者：
    (1)所述碳材料的体积分布粒径Dv50为8.0μm-24.0μm，可选为9.5μm-22.5μm；
    (2)所述碳材料的体积分布粒径Dv10为5.0μm-15.0μm，可选为6.0μm-14.0μm；
    (3)所述碳材料的体积分布粒径Dv90为16.0μm-35.0μm，可选为17.0μm-34.0μm；
    (4)所述碳材料的(Dv90-Dv10)/Dv50为0.55-1.55，可选为0.8-1.4；
    (5)所述碳材料的振实密度为0.80g/cm 3-1.32g/cm 3，可选为0.82g/cm 3-1.28g/cm 3；
    (6)所述碳材料的克容量为355mAh/g-371mAh/g，可选为360mAh/g-370mAh/g；
    (7)所述碳材料的形貌包括块状、球状和类球状中的一种或多种。
  13. 一种碳材料的制备方法，包括如下步骤：步骤1，提供具有多个孔结构的原料；步骤2，将所述原料与填充材料按照预定比例混合均匀，之后在第一温度T 1下保温第一时间t 1，得到中间体；步骤3，将所获得的中间体在第二温度T 2下保温第二时间t 2，得到碳材料，其中，所述碳材料包括孔结构，100g所述碳材料对亚麻仁油的吸附量记为A，所述碳材料的比表面积记为B，则所述碳材料满足：36≤A×B≤75，100g所述碳材料对亚麻仁油的吸附量A的单位为ml，所述碳材料的比表面积B的单位为m 2/g。
  14. 根据权利要求13所述的方法，其中，所述原料满足如下中的至少一者：
    (1)所述原料包括天然石墨，可选地，所述天然石墨包括鳞片石墨、天然球形石墨和微晶石墨中的一种或多种；
    (2)所述原料的体积分布粒径Dv50为8.5μm-24.0μm，可选为10.5μm-22.5μm；
    (3)所述原料中的灰分含量为≤1wt％。
  15. 根据权利要求13或14所述的方法，其中，所述填充材料满足如下中的至少一者：
    (1)所述填充材料的软化点温度为110℃-175℃，可选为120℃-170℃；
    (2)所述填充材料的结焦值为26％-50％，可选为33％-45％；
    (3)所述填充材料的体积分布粒径Dv50为小于等于6μm，可选为1μm-5μm；
    (4)所述填充材料中的喹啉不溶物的含量为≤1wt％，可选为≤0.8wt％。
  16. 根据权利要求15所述的方法，其中，所述填充材料包括煤沥青和石油沥青中的一种或多种。
  17. 根据权利要求13-16任一项所述的方法，其中，所述填充材料与所述原料的质量比为(10-32):100，可选为(10-25):100。
  18. 根据权利要求13-17任一项所述的方法，其中，将所述原料与所述填充材料按照预定比例混合均匀后升温至第一温度T 1的升温工艺为分阶段升温工艺，可选地包括第一升温工艺、第二升温工艺和第三升温工艺。
  19. 根据权利要求18所述的方法，其中，
    所述第一升温工艺为升温至200℃-250℃并在该温度下保温0.5h-2h；和/或，
    所述第二升温工艺为升温至450℃-550℃并在该温度下保温0.5h-2h；和/或，
    所述第三升温工艺为升温至所述第一温度T 1并在该温度下保温第一时间t 1。
  20. 根据权利要求13-19任一项所述的方法，其中，以1℃/min-10℃/min，可选为1.5℃/min-8℃/min的速率升温至所述第一温度T 1。
  21. 根据权利要求13-20任一项所述的方法，其中，
    所述第一温度T 1为700℃-1100℃，可选为750℃-1100℃；和/或，
    所述第一时间t 1为0.5h-5h，可选为0.5h-3h。
  22. 根据权利要求13-21任一项所述的方法，其中，
    所述第二温度T 2为1920℃-2520℃，可选为2050℃-2400℃；和/或，
    所述第二时间t 2为1h-6h，可选为2h-5h。
  23. 一种二次电池，包括负极极片，所述负极极片包括权利要求1-12任一项所述的碳材料或通过权利要求13-22任一项所述的方法制备得到的碳材料。
  24. 一种用电装置，包括权利要求23所述的二次电池。
PCT/CN2022/134444 2022-11-25 2022-11-25 碳材料及其制备方法、以及含有其的二次电池和用电装置 Ceased WO2024108574A1 (zh)

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