WO2024077933A1 - 硬碳材料及其制备方法、电化学装置及电子装置 - Google Patents

硬碳材料及其制备方法、电化学装置及电子装置 Download PDF

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WO2024077933A1
WO2024077933A1 PCT/CN2023/091366 CN2023091366W WO2024077933A1 WO 2024077933 A1 WO2024077933 A1 WO 2024077933A1 CN 2023091366 W CN2023091366 W CN 2023091366W WO 2024077933 A1 WO2024077933 A1 WO 2024077933A1
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hard carbon
carbon material
recorded
capacity
negative electrode
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French (fr)
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易政
谭福金
郑子桂
谢远森
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to EP23876144.9A priority Critical patent/EP4601042A4/en
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Publication of WO2024077933A1 publication Critical patent/WO2024077933A1/zh
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G9/00—Compounds of zinc
    • C01G9/006—Compounds containing zinc, with or without oxygen or hydrogen, and containing two or more other elements
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    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M10/00—Secondary cells; Manufacture thereof
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    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
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    • 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
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
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    • 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
    • H—ELECTRICITY
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    • 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
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    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/82—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by IR- or Raman-data
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    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
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    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2006/40—Electric properties
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of energy storage technology, and more specifically, to hard carbon materials and preparation methods thereof, electrochemical devices and electronic devices.
  • Electrochemical devices have the characteristics of high energy density, high operating voltage, and light weight, so they are widely used in electronic products such as mobile phones, laptops, and cameras. While improving the electrochemical performance of electrochemical devices, their safety performance cannot be ignored. With the improvement of the performance requirements of electronic products, the performance requirements of electrochemical devices are also gradually increasing.
  • the migration of active ions between the positive electrode active material and the negative electrode active material in an electrochemical device is the core process of charging and discharging. Therefore, the negative electrode active material has a significant impact on the performance of the electrochemical device, such as the energy density.
  • the reversible capacity and low platform capacity of existing negative electrode active materials are relatively low, which makes the energy density of the electrochemical device low when the negative electrode active material is used in the electrochemical device.
  • the present application provides a hard carbon material and a preparation method thereof, an electrochemical device and an electronic device.
  • the hard carbon material has a high reversible capacity and a low plateau capacity.
  • the performance of the electrical device can be significantly improved.
  • the present application proposes a hard carbon material, comprising a porous skeleton, a first element and a zinc element, wherein the first element comprises one or more of nitrogen, sulfur, boron, phosphorus and selenium; the content of the first element relative to the total mass of the hard carbon material is denoted as A 1 wt%; the content of the zinc element relative to the total mass of the hard carbon material is denoted as A 2 wt%, wherein the hard carbon material satisfies: 1.5 ⁇ A 1 /A 2 ⁇ 5.
  • the first element includes nitrogen, and 2 ⁇ A 1 /A 2 ⁇ 4.5.
  • the first element includes nitrogen, and a content of the first element based on the total mass of the hard carbon material is denoted as W 1 wt %, 2 ⁇ W 1 ⁇ 5.
  • the first element includes one or more of sulfur, boron, phosphorus, and selenium, and 2 ⁇ A 1 /A 2 ⁇ 4.
  • the first element includes one or more of sulfur, boron, phosphorus and selenium.
  • the content of the first element based on the total mass of the hard carbon material is denoted as W 2 wt %, 2.5 ⁇ W 2 ⁇ 9.
  • the content of zinc element relative to the total mass of the hard carbon material is denoted as A 2 wt %, and 0.6 ⁇ A 2 ⁇ 1.2.
  • the hard carbon material uses lithium metal as the counter electrode.
  • the charge and discharge curves obtained by testing in the range of 0 to 2.5 V vs Li + /Li the gram capacity from 0 (vs Li + /Li) to 0.15 V (vs Li + /Li) is recorded as C 11 mAh/g; the gram capacity from 0.15 V (vs Li + /Li) to 0.8 V (vs Li + /Li) is recorded as C 12 mAh/g, and the hard carbon material satisfies: 1.6 ⁇ C 11 /C 12 ⁇ 2.1.
  • the hard carbon material uses sodium metal as the counter electrode, and in the charge and discharge curves obtained by testing in the range of 0 to 2.5 V vs Na + /Na, the gram capacity from 0 (vs Na + /Na) to 0.15 V (vs Na + /Na) is recorded as C 21 mAh/g; the gram capacity from 0.15 V (vs Na + /Na) to 1.00 V (vs Na + /Na) is recorded as C 22 mAh/g, and the hard carbon material satisfies: 3.55 ⁇ C 21 /C 22 ⁇ 3.95.
  • the 2-fold scattering angle of the diffraction peak is less than 24°.
  • the Raman spectrum of the hard carbon material within the scanning range of 200um*500um there is a characteristic peak D in the range of 1320cm -1 to 1370cm -1 , and a characteristic peak G in the range of 1570cm -1 to 1620cm -1 , the peak intensity of the characteristic peak D is ID , the peak intensity of the characteristic peak G is IG , and 0.5 ⁇ ID / IG ⁇ 1.5 .
  • the hard carbon material further satisfies the following conditions (1) and/or (2):
  • the volume distribution particle size Dv50 ⁇ m of the hard carbon material satisfies: 3 ⁇ Dv50 ⁇ 15;
  • the hard carbon material further includes a carbon layer coated outside the porous framework.
  • the present application proposes a method for preparing a hard carbon material, the method comprising: uniformly mixing a carbon-containing precursor material, a porogen containing a zinc element, and a first material containing a first element into a mixed system; heat treating the mixed system to carbonize the precursor material, during the carbonization process the porogen volatilizes and etches the precursor material to form a porous skeleton, on which the first element and zinc elements are arranged, wherein the first element comprises one or more of nitrogen, sulfur, boron, phosphorus and selenium; the content of the first element relative to the total mass of the hard carbon material is denoted as A1wt %; the content of the zinc element relative to the total mass of the hard carbon material is denoted as A2wt %, wherein the hard carbon material satisfies: 1.5 ⁇ A1 / A2 ⁇ 5 .
  • the heat treatment includes a first heat treatment and a second heat treatment, and a temperature of the first heat treatment is lower than a temperature of the second heat treatment.
  • a carbon layer is coated on the porous framework.
  • the present application proposes an electrochemical device, comprising a negative electrode plate, wherein the negative electrode plate comprises a hard carbon material as described in any embodiment of the first aspect of the present application or a hard carbon material prepared by the method described in any embodiment of the second aspect of the present application.
  • the present application proposes an electronic device, comprising the electrochemical device as described in the third aspect of the present application.
  • the first element when 1.5 ⁇ A 1 /A 2 ⁇ 5 is satisfied, the first element can be evenly distributed in the porous skeleton. Due to the combination of the first element and the zinc element, the zinc element can be evenly distributed in the porous skeleton, so that the porous skeleton has a sufficient pore structure and the pore distribution is more uniform, which is beneficial to improving the reversible capacity and low platform capacity of the hard carbon material; thereby, the hard carbon material can significantly improve the energy density of the electrochemical device when applied to the electrochemical device.
  • FIG. 1 is a charge and discharge curve diagram of the lithium ion battery of Examples 1-5 of the present application.
  • a list of items connected by the terms “one or more of,” “one or more of,” “one or more of,” or other similar terms may mean any combination of the listed items.
  • the phrase “at least one of A and B” means only A; only B; or A and B.
  • the phrase “at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may include a single element or multiple elements.
  • Item B may include a single element or multiple elements.
  • Item C may include a single element or multiple elements.
  • the electrochemical device includes a positive electrode sheet, a negative electrode sheet and a separator; the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes graphite, hard carbon, etc.
  • the theoretical capacity of graphite is 372mAh/g. In recent years, it has almost been developed to the upper limit of the theoretical capacity of graphite, and there is little room for further improvement.
  • Hard carbon materials have been widely studied due to their advantages such as small volume expansion, strong rapid charge and discharge capabilities, and high gram capacity. The inventors found that the reversible capacity and low low platform capacity of hard carbon materials are low, which leads to the fact that hard carbon materials limit the energy density of electrochemical devices.
  • the inventors from the perspective of improving the hard carbon material, make pores in the hard carbon material so that the hard carbon material has a porous structure, thereby increasing the reversible capacity and low platform capacity of the hard carbon material.
  • the solution of this application is further described.
  • the present application proposes a hard carbon material, which includes a porous skeleton, a first element and a zinc element, wherein the first element includes one or more of nitrogen, sulfur, boron, phosphorus and selenium, the content of the first element relative to the total mass of the hard carbon material is recorded as A1wt %, and the content of the zinc element relative to the total mass of the hard carbon material is recorded as A2wt %, and the hard carbon material satisfies: 1.5 ⁇ A1 / A2 ⁇ 5 .
  • the hard carbon material of the present application satisfies the above relationship, its reversible capacity is relatively high and its low platform capacity is relatively high. When applied to an electrochemical device, it can improve the energy density and other properties of the electrochemical device.
  • the microstructure of hard carbon materials has short-range ordered micro-regions formed by disordered stacking of curved graphite-like sheets, and also has defects such as microporous structure.
  • active ions such as lithium ions and sodium ions will migrate from the positive electrode active material to the negative electrode active material such as hard carbon material and embed into the hard carbon material.
  • the low voltage platform area (0 to 0.15V vs Li+/Li) in the charge and discharge curve of hard carbon materials for storing active ions represents the capacity provided by lithium ions or sodium ions filling the hard carbon pores
  • the high voltage oblique area (0.15V to 0.8V) represents the intercalation of lithium ions into the hard carbon microcrystal layers, or the adsorption of sodium ions into the hard carbon microcrystals.
  • the relatively low voltage region in the charge-discharge curve is generally considered to be more conducive to contributing to energy density, so improving the capacity in the low voltage platform region can significantly improve the energy density of the electrochemical device.
  • the hard carbon material can be obtained by hydrothermal or chemical process treatment of a precursor material, wherein the precursor material includes one or more of a resin-based precursor, an asphalt-based precursor, and a biomass-based precursor; illustratively, the resin-based precursor includes one or more of phenolic resin, epoxy resin, and polyfurfuryl alcohol; the asphalt-based precursor includes one or more of coal tar pitch, petroleum asphalt, and natural asphalt; the biomass-based precursor includes one or more of cellulose, lignin, starch, chitosan, sucrose, and glucose. Relatively low molecular weight precursors have more defects than hard carbon formed by high molecular weight precursors, and can provide more active sites for active ions, thereby increasing the capacity of the hard carbon material.
  • the precursor material of the present application may be a biomass-based precursor.
  • the porous skeleton contains zinc element, which is mainly distributed in the porous skeleton and can also be distributed on the surface of the porous skeleton.
  • a porogen containing zinc element is selected, such as one or more of zinc gluconate, zinc citrate, zinc sulfate, zinc nitrate, etc.
  • the above-mentioned porogen can volatilize during the carbonization process of the precursor material, thereby etching the structure of the precursor material to form pores, so that the hard carbon material formed after carbonization has a porous skeleton.
  • the formation of the porous skeleton increases the pore volume and the embedding sites of active ions, thereby significantly improving the reversible capacity of the hard carbon material, especially improving the capacity of the low platform segment.
  • the porous skeleton contains a first element, which is mainly distributed in the porous skeleton and can also be distributed on the surface of the porous skeleton.
  • a first material containing the first element is selected.
  • the corresponding first material may include melamine, urea, dicyandiamide, etc.
  • the corresponding first material may include sulfur powder.
  • the corresponding first material may include boric acid.
  • the corresponding first material may include ammonium dihydrogen phosphate.
  • the corresponding first material may include diphenyl selenium.
  • the precursor material and the substance containing the first element are mixed, and the first element can be more evenly distributed in the precursor material, and the first element can provide a binding site for the zinc element, which is conducive to the uniform distribution of the zinc element, so that the porogen can form pores evenly, the pore structure in the hard carbon material is more evenly distributed, and the pores are more fully utilized, which can improve the first coulomb efficiency of the electrochemical device.
  • the first element has good lithium-affinity wettability, which is beneficial for the embedding of lithium ions into the porous skeleton, so that the capacity of the low platform voltage is further significantly improved.
  • the above analysis is a separate analysis of the porous skeleton, the first element and the zinc element of the hard carbon material, the three are an organic whole and are interrelated, and together affect the final performance of the hard carbon material.
  • the hard carbon material of the present application satisfies 1.5 ⁇ A 1 /A 2 ⁇ 5
  • the first element can be evenly distributed in the porous skeleton.
  • the zinc element can be evenly distributed in the porous skeleton, so that the porous skeleton has a sufficient pore structure, and the pore distribution is more uniform, which is beneficial to improve the reversible capacity and low platform capacity of the hard carbon material; thereby, the hard carbon material can significantly improve the energy density of the electrochemical device when applied to the electrochemical device.
  • a 1 /A 2 can be 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5, or a range consisting of any two of the above values.
  • the present application can adjust the wettability of the hard carbon material to active ions such as lithium ions by regulating the addition amount of the first element.
  • the addition amount of the first element increases, the better the wettability to lithium ions, the more conducive it is for lithium ions to embed into the porous skeleton, which is beneficial to improving the low platform voltage capacity; and the number of binding sites provided for the zinc element can also be adjusted.
  • the present application regulates the addition amount of the first element to meet one or more of the following conditions, which can further improve the reversible capacity, low platform capacity and structural stability of the hard carbon material.
  • the first element includes nitrogen, and 2 ⁇ A 1 /A 2 ⁇ 4.5.
  • the first element includes nitrogen
  • the content of the first element relative to the total mass of the hard carbon material is recorded as W 1 wt%, 2 ⁇ W 1 ⁇ 5.
  • the content of the first element W 1 wt% can be 2wt%, 3wt%, 4wt% or 5wt%, or a range consisting of any two of the above values.
  • the content of nitrogen can be tested using equipment and methods known in the art, for example, an elemental analyzer can be used for analysis and testing.
  • the sample is placed in an elemental analyzer, and the sample is completely burned into elemental substances by heating, and then the moisture in the sample is removed by a condenser, and the unnecessary compounds and oxygen are eliminated by a reduction reaction tube, and the nitrogen oxides are converted into nitrogen, and the moisture in the sample is continued to be removed, and the nitrogen content is detected.
  • the first element includes one or more of sulfur, boron, phosphorus, and selenium, and 2 ⁇ A 1 /A 2 ⁇ 4.
  • the first element includes one or more of sulfur, boron, phosphorus and selenium
  • the content of the first element relative to the total mass of the hard carbon material is recorded as W 2 wt%, 2.5 ⁇ W 2 ⁇ 9.
  • the content of the first element W 2 wt% can be 2.5wt%, 3wt%, 4wt% or 5wt%, or a range consisting of any two of the above values.
  • the content of sulfur, boron, phosphorus and selenium can be tested using equipment and methods known in the art, for example, an element analyzer can be used for analysis and testing.
  • the elements such as sulfur, boron, phosphorus and selenium are quantitatively obtained by X-ray photoelectron spectroscopy XPS.
  • the present application can adjust the pore structure of the porous skeleton of the hard carbon material by regulating the addition amount of zinc element. Too little zinc element may result in fewer pores in the porous skeleton, and the pore volume of the hard carbon material will not change significantly, which is not conducive to improving the low-voltage platform capacity. With the increase of the addition amount of zinc element, the pores in the porous skeleton increase, and the low-voltage platform capacity is significantly improved. However, too much zinc element may lead to an excessive number of pores formed, resulting in poor stability of the porous skeleton structure. Therefore, regulating the addition amount of zinc element to meet the following conditions can further improve the reversible capacity, low platform capacity and structural stability of the hard carbon material.
  • the content of zinc element relative to the total mass of the hard carbon material is recorded as A 2 wt%, 0.6 ⁇ A 2 ⁇ 1.2.
  • the content of zinc element A 2 wt% can be 0.6wt%, 0.7wt%, 0.9wt%, 1.0wt% or 1.2wt%, or a range consisting of any two of the above values.
  • the content of zinc element can be tested using equipment and methods known in the art, for example, it can be analyzed and tested using an inductively coupled plasma emission spectrometer.
  • a plasma excitation light source can be used to evaporate and vaporize the sample, dissociate or decompose it into an atomic state, and the atoms may be further ionized into an ionic state, and the atoms and ions are excited to emit light in the light source.
  • the light emitted by the light source is decomposed into a spectrum arranged by wavelength using an inductively coupled plasma emission spectrometer.
  • the spectrum is detected using a photoelectric device, and the sample is qualitatively analyzed according to the measured spectral wavelength, and quantitatively analyzed according to the intensity of the emitted light.
  • the hard carbon material further includes hydrogen and carbon.
  • the content of hydrogen relative to the total mass of the hard carbon material is denoted as W 4 wt %, and the content of carbon relative to the total mass of the hard carbon material is denoted as W 5 wt %.
  • the hard carbon material satisfies: 0.02 ⁇ W 4 /W 5 ⁇ 0.20.
  • the hard carbon materials of the present application are not only suitable for lithium-ion batteries, but also for sodium-ion batteries.
  • Lithium-ion batteries have the advantages of high volume and mass energy density, environmental friendliness, high operating voltage, small size, light weight, and long cycle life.
  • the hard carbon materials of the present application when applied to lithium-ion batteries, can improve the energy density and other properties of lithium-ion batteries. Compared with lithium, sodium has a higher standard electrode potential, resulting in a lower energy density of sodium-ion batteries than lithium-ion batteries, and the large ionic radius makes it difficult for sodium ions to undergo embedding and extraction reactions.
  • the hard carbon materials of the present application are also suitable for sodium-ion batteries, which is beneficial for sodium-ion batteries to be embedded in hard carbon materials, and can improve Improve the energy density and other performance of sodium ion batteries.
  • the inventors have found that when the hard carbon material further satisfies one or more of the following conditions, the reversible capacity and low plateau voltage capacity of the hard carbon material can be further improved.
  • the hard carbon material uses lithium metal as a counter electrode, and in the charge-discharge curves obtained by testing in the range of 0 to 2.5 V vs Li + /Li, the gram capacity from 0 (vs Li + /Li) to 0.15 V (vs Li + /Li) is recorded as C 11 mAh/g; the gram capacity from 0.15 V (vs Li + /Li) to 0.8 V (vs Li + /Li) is recorded as C 12 mAh/g, and the hard carbon material satisfies: 1.6 ⁇ C 11 /C 12 ⁇ 2.1. Optionally, 250 ⁇ C 11 ⁇ 350.
  • the hard carbon material is used as the negative electrode, and the lithium metal (lithium sheet with a diameter of 18 mm and a thickness of 0.6 mm) is used as the counter electrode.
  • the hard carbon electrode, the isolation membrane and the lithium sheet are assembled and stacked in sequence, and an electrolyte (1 mol/L lithium salt LiPF 6 ) is added.
  • the positive and negative electrodes are packaged in a button-type stainless steel shell to obtain a button-type battery. The charge and discharge curves of the button-type battery are tested, and the gram capacity distribution during the de-lithiation process is obtained.
  • the hard carbon material of the embodiment of the present application can further significantly improve the capacity of the hard carbon material on a low voltage platform under the condition that the above-mentioned gram-capacity relationship is satisfied.
  • the hard carbon material uses sodium metal as the counter electrode, and in the charge and discharge curves obtained by testing in the range of 0 to 2.5V vs Na + /Na, the gram capacity from 0 (vs Na + /Na to 0.15V (vs Na + /Na) is recorded as C 21 mAh/g; the gram capacity from 0.15V (vs Na + /Na) to 1.00V (vs Na + /Na) is recorded as C 22 mAh/g, and the hard carbon material satisfies: 3.55 ⁇ C 21 /C 22 ⁇ 3.95.
  • 300 ⁇ C 21 ⁇ 340 the hard carbon material satisfies: 3.55 ⁇ C 21 /C 22 ⁇ 3.95.
  • the hard carbon material is used as the negative electrode, and the sodium metal (sodium sheet with a diameter of 18 mm and a thickness of 0.6 mm) is used as the counter electrode.
  • the hard carbon electrode, the isolation membrane and the sodium sheet are assembled and stacked in sequence, and an electrolyte (1 mol/L sodium salt NaPF 6 ) is added.
  • the positive and negative electrodes are placed in a button-type stainless steel shell and sealed to obtain a button-type battery. The charge and discharge curves of the button-type battery are tested, and the gram capacity distribution during the sodium removal process is obtained.
  • the hard carbon material of the embodiment of the present application can further significantly improve the capacity of the hard carbon material on a low voltage platform under the condition that the above-mentioned gram-capacity relationship is satisfied.
  • a diffraction peak exists at a 2-fold scattering angle in the range of 15° to 30°, and the 2-fold scattering angle of the diffraction peak is less than 24°.
  • the interplanar spacing of the hard carbon material is large, which is conducive to the interlayer transmission of active ions such as lithium ions and sodium ions in the hard carbon material.
  • the Raman spectrum of the hard carbon material within the scanning range of 200um*500um there is a characteristic peak D in the range of 1320cm -1 to 1370cm -1 , and a characteristic peak G in the range of 1570cm -1 to 1620cm -1 , the peak intensity of the characteristic peak D is ID , the peak intensity of the characteristic peak G is IG , and 0.5 ⁇ ID / IG ⁇ 1.5 .
  • the volume distribution particle size Dv50 ⁇ m of the hard carbon material satisfies: 3 ⁇ Dv50 ⁇ 15.
  • the physical definition of Dv50 the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%; it can be tested by methods known in the art. For example, it can be measured with reference to the standard GB/T 19077.1-2016 using a laser particle size analyzer (such as Malvern Master Size 3000).
  • the volume distribution particle size Dv99 ⁇ m of the hard carbon material satisfies: 10 ⁇ Dv99 ⁇ 45.
  • the physical definition of Dv99 the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 99%; it can be tested by methods known in the art. For example, it can be measured with reference to the standard GB/T 19077.1-2016 using a laser particle size analyzer (such as Malvern Master Size 3000).
  • the diffusion distance of active ions in the hard carbon material is relatively short, which is conducive to the full utilization of the gram capacity of the hard carbon material; and the particle specific surface area of the hard carbon material is relatively small, and the kinetic performance is Relatively good, which is beneficial to improving the first-cycle Coulomb efficiency of hard carbon materials.
  • the hard carbon material further includes a carbon layer coated outside the porous framework.
  • the porous skeleton may form an open structure on its surface.
  • the open structure can provide more active sites for storing active ions and improve the capacity of the hard carbon material on the low voltage platform.
  • too many open structures will lead to a relatively large specific surface area of the hard carbon material, and excessive formation of the solid electrolyte interface (SEI) film will deteriorate the first-cycle coulomb efficiency.
  • SEI solid electrolyte interface
  • the present application provides a carbon layer outside the porous skeleton, which can improve the first-cycle coulomb efficiency of the hard carbon material while taking into account the higher capacity of the low voltage platform.
  • the second aspect of the present application also provides a method for preparing a hard carbon material.
  • the method comprises:
  • Step S100 uniformly mixing a carbon-containing precursor material, a zinc-containing porogen, and a first material containing a first element into a mixed system;
  • Step S200 heat-treating the mixed system to carbonize the precursor material, wherein the porogen volatilizes and etches the precursor material to form a porous skeleton, wherein the first element and the zinc element are disposed on the porous skeleton.
  • the first element includes one or more of nitrogen, sulfur, boron, phosphorus and selenium;
  • the content of the first element relative to the total mass of the hard carbon material is recorded as A 1 wt %;
  • the content of the zinc element relative to the total mass of the hard carbon material is recorded as A 2 wt%
  • the hard carbon material satisfies: 1.5 ⁇ A 1 /A 2 ⁇ 5.
  • the types of the precursor material, porogen and first material of the present application are as described above and will not be repeated here.
  • the present application facilitates porogenesis of the precursor material during the carbonization process by mixing the three types of substances.
  • the mixing method may be ball milling or the like.
  • the heat treatment in step S200 may include a first heat treatment and a second heat treatment, and the temperature of the first heat treatment is lower than the temperature of the second heat treatment.
  • the first heat treatment can be used as a pre-carbonization process, for example, calcining the mixed system at a temperature ranging from 400°C to 700°C, which is conducive to fixing the zinc element in the porogen on the precursor material, and on the basis of the uniform distribution of the first element on the precursor material, the zinc element can be evenly distributed on the precursor material.
  • the mixed system can be crushed and graded so that the particle size is more in line with production requirements.
  • the second heat treatment can be used as a carbonization process, for example, calcining the mixed system in the range of 900° C. to 1300° C. to carbonize the precursor material into a porous skeleton.
  • the second heat treatment process can be performed after crushing and grading, which is conducive to obtaining a hard carbon material with a particle size that meets production requirements.
  • the method further comprises step S300, coating the porous skeleton with a carbon layer.
  • the carbon source may be coated on the porous skeleton to form a carbon layer by vapor deposition (e.g., chemical vapor deposition CVD), liquid sol-gel method, asphalt coating, etc.
  • vapor deposition e.g., chemical vapor deposition CVD
  • liquid sol-gel method e.g., asphalt coating
  • asphalt coating e.g., asphalt coating, etc.
  • the specific process parameters may be the existing parameters in the art, which will not be described in detail here.
  • the third aspect of the present application also provides an electrochemical device, which includes a negative electrode plate.
  • the negative electrode active material of the negative electrode plate may include the hard carbon material of any embodiment of the first aspect of the present application or the hard carbon material prepared by the method described in any embodiment of the second aspect of the present application.
  • the voltage drop K value per unit time of the electrochemical device satisfies: 0.01mV/h ⁇ K ⁇ 2mV/h.
  • the K value is an indicator of the self-discharge rate of the electrochemical device.
  • the electrochemical device The self-discharge performance is excellent.
  • the negative electrode plate is a negative electrode plate that can be used in an electrochemical device as known in the art.
  • the negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer.
  • the negative electrode active material layer is disposed on the surface of the negative electrode current collector.
  • the negative electrode active material layer comprises a negative electrode active material.
  • the negative electrode active material may include the hard carbon material of any embodiment of the first aspect of the present application or the hard carbon material prepared by the method described in any embodiment of the second aspect of the present application.
  • the structure of the negative electrode sheet is a structure of a negative electrode sheet that is well known in the art and can be used in an electrochemical device.
  • the negative electrode current collector is a metal, such as but not limited to copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.
  • the negative electrode active material may also additionally be various conventionally known substances that can be used as negative electrode active materials for electrochemical devices and can reversibly embed and de-embed active ions, or conventionally known substances that can reversibly dope and de-dope active ions, which are known in the art.
  • the negative electrode active material comprises at least one of lithium metal, lithium metal alloy, carbon material, material capable of being doped/dedoped with lithium, or transition metal oxide.
  • the carbon material may be selected from various carbon materials known in the art that can be used as carbon-based negative electrode active materials for electrochemical devices.
  • the carbon material comprises at least one of crystalline carbon and amorphous carbon.
  • the crystalline carbon is natural graphite or artificial graphite.
  • the shape of the crystalline carbon is amorphous, plate-shaped, flake-shaped, spherical or fibrous.
  • the crystalline carbon is low-crystalline carbon or high-crystalline carbon.
  • low-crystalline carbon comprises at least one of soft carbon and hard carbon.
  • high-crystalline carbon comprises at least one of natural graphite, crystalline graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase carbon microbeads, mesophase pitch, and high-temperature calcined carbon.
  • the high temperature calcined carbon is petroleum or coke derived from coal tar pitch.
  • amorphous carbon comprises at least one of soft carbon, hard carbon, mesophase pitch carbonization product, and fired coke.
  • the negative electrode active material comprises a transition metal oxide.
  • the transition metal oxide comprises at least one of vanadium oxide and lithium vanadium oxide.
  • the negative electrode active material comprises at least one of Si, SiOx (0 ⁇ x ⁇ 2), Si/C composite, Si-Q alloy, Sn, SnOz, Sn-C composite, and Sn-R alloy, wherein Q is selected from at least one of alkali metals, alkaline earth metals, elements from Groups 13 to 16, transition elements, and rare earth elements, and Q is not Si, and R is selected from at least one of alkali metals, alkaline earth metals, elements from Groups 13 to 16, transition elements, and rare earth elements, and R is not Sn.
  • Q and R include at least one of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, and Po.
  • the negative electrode active material layer further comprises a negative electrode binder and a negative electrode conductive agent.
  • the negative electrode binder comprises at least one of difluoroethylene-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin, and nylon.
  • PVDF-co-HFP difluoroethylene-hexafluoropropylene copolymer
  • PVDF-co-HFP difluoroethylene-
  • the negative electrode conductive agent is used to provide conductivity to the electrode, which may include any conductive material as long as it does not cause chemical changes.
  • the negative electrode conductive agent comprises any one of a carbon-based material, a metal-based material, a conductive polymer, or a mixture thereof.
  • the carbon-based material comprises at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber.
  • the metal-based material comprises at least one of metal powders or metal fibers of copper, nickel, aluminum, silver, etc.
  • the conductive polymer comprises a polyphenylene derivative.
  • the method for preparing the negative electrode sheet is a method for preparing the negative electrode that can be used for an electrochemical device that is well known in the art.
  • a solvent is usually added, and the negative electrode active material is added with a binder and a conductive material and a thickener as needed, and then dissolved or dispersed in the solvent to form a negative electrode slurry.
  • the solvent evaporates and is removed during the drying process.
  • the solvent is a solvent that can be used as a negative electrode active material layer that is well known in the art, and the solvent is, for example, but not limited to, water.
  • the thickener is a thickener that can be used as a negative electrode active material layer that is well known in the art, and the thickener is, for example, but not limited to, sodium carboxymethyl cellulose.
  • the present application has no particular limitation on the mixing ratio of the negative electrode active material, the binder, and the thickener in the negative electrode active material layer, and the mixing ratio can be controlled according to the desired performance of the electrochemical device.
  • the electrochemical device of the embodiment of the present application may also include a positive electrode sheet.
  • the positive electrode sheet is a positive electrode sheet that can be used in an electrochemical device and is well known in the art.
  • the positive electrode sheet includes a positive current collector and a positive active material layer.
  • the positive active material layer is disposed on the surface of the positive current collector.
  • the positive active material layer includes a positive active material.
  • the structure of the positive electrode sheet is a structure of a positive electrode sheet that is well known in the art and can be used in an electrochemical device.
  • the positive electrode current collector is a metal, such as but not limited to aluminum foil.
  • the positive electrode active material can be selected from various conventionally known materials that can be used as positive electrode active materials for electrochemical devices and can reversibly embed and de-embed active ions.
  • the positive electrode active material usually contains lithium ions; for sodium-ion batteries, the positive electrode active material usually contains sodium ions. The following is an example of lithium ions.
  • the positive electrode active material includes a composite oxide of lithium and at least one selected from cobalt, manganese, and nickel.
  • the positive electrode active material layer further comprises a positive electrode binder and a positive electrode conductor.
  • the positive electrode binder is used to improve the bonding performance between the positive electrode active material particles and between the positive electrode active material particles and the current collector.
  • the positive electrode binder includes polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin, and nylon.
  • the positive electrode conductor is used to provide conductivity for the electrode, which may include any conductive material as long as it does not cause chemical changes.
  • the positive electrode conductor is at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, metal fiber, and polyphenylene derivatives.
  • the metal in the metal powder and metal fiber includes at least one of copper, nickel, aluminum, and silver.
  • the method for preparing the positive electrode sheet is a method for preparing the positive electrode sheet that is well known in the art and can be used for an electrochemical device.
  • a solvent is usually added, and the positive electrode active material is added with a binder and a conductive material and a thickener as needed, and then dissolved or dispersed in the solvent to form a positive electrode slurry.
  • the solvent evaporates and is removed during the drying process.
  • the solvent is a solvent that is well known in the art and can be used as a positive electrode active material layer, and the solvent is, for example, but not limited to, N-methylpyrrolidone (NMP).
  • the separator is a separator known in the art that can be used in electrochemical devices, such as but not limited to a polyolefin microporous membrane.
  • the separator comprises at least one of polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-methyl methacrylate copolymer.
  • the isolation film is a single-layer isolation film or a multi-layer isolation film.
  • the isolation film is coated with a coating.
  • the coating comprises at least one of an organic coating and an inorganic coating, wherein the organic coating is selected from at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, acrylic acid-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, and sodium carboxymethyl cellulose, and the inorganic coating is selected from at least one of SiO 2 , Al 2 O 3 , CaO, TiO 2 , ZnO 2 , MgO, ZrO 2 , and SnO 2 .
  • the present application has no particular limitation on the shape and thickness of the isolation membrane.
  • the method for preparing the isolation membrane is a method for preparing an isolation membrane that can be used in an electrochemical device and is well known in the art.
  • the electrochemical device of the embodiment of the present application may also include an electrolyte.
  • the electrolyte of the present application contains an electrolyte salt.
  • the electrolyte salt is an electrolyte salt suitable for electrochemical devices that is well known in the art.
  • a suitable electrolyte salt can be selected.
  • lithium-ion batteries lithium salts are usually used as electrolyte salts.
  • sodium-ion batteries sodium salts are usually used as electrolyte salts. The following is an explanation using lithium-ion batteries as an example.
  • the lithium salt includes or is selected from at least one of an organic lithium salt and an inorganic lithium salt.
  • the lithium salt includes or is selected from at least one of lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroantimonate (LiSbF 6 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium perfluorobutylsulfonate (LiC 4 F 9 SO 3 ), lithium perchlorate (LiClO 4 ), lithium aluminate (LiAlO 2 ), lithium tetrachloroaluminate (LiAlCl 4 ), lithium bis(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ), wherein x and y are natural numbers), lithium chloride (LiCl) or lithium fluoride (LiF).
  • the mass percentage of the lithium salt in the electrolyte of the present application is 10 wt % to 15 wt %, for example, 10%, 11%, 12%, 13%
  • the electrolyte of the present application may also contain a non-aqueous organic solvent.
  • the non-aqueous organic solvent includes at least one of carbonate, carboxylate, ether compound, sulfone compound or other aprotic solvent.
  • the mass percentage of the non-aqueous organic solvent is 21% to 90%, for example, 21%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or any range therebetween.
  • the carbonate solvent comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, and bis(2,2,2-trifluoroethyl) carbonate.
  • the carboxylate solvent comprises methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, At least one of gamma-butyrolactone, valerolactone and butyrolactone.
  • the ether compound solvent comprises at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, bis(2,2,2-trifluoroethyl) ether, 1,3-dioxane, and 1,4-dioxane.
  • the sulfone compound comprises at least one of ethyl vinyl sulfone, methyl isopropyl sulfone, isopropyl sec-butyl sulfone, and sulfolane.
  • the non-aqueous organic solvent in the electrolyte may be a single non-aqueous organic solvent or a mixture of multiple non-aqueous organic solvents.
  • the mixing ratio can be controlled according to the desired performance of the electrochemical device.
  • the electrolyte of the present application may also contain functional additives, such as film-forming additives and positive electrode film-forming additives.
  • the film-forming additives may form an interface film on the surface of the negative electrode sheet and/or the positive electrode sheet, thereby protecting the negative electrode sheet and/or the positive electrode sheet.
  • the film-forming additive may be a polynitrile additive, a sulfonate additive, and the like.
  • the present application also provides an electronic device.
  • the electronic device of the present application is any electronic device, such as but not limited to a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.
  • Air vehicles include air vehicles within the atmosphere and air vehicles
  • the electronic device comprises the electrochemical device described above in the present application.
  • the hard carbon prepared above, styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) were fully stirred and mixed in an appropriate amount of deionized water at a weight ratio of 97:2:1 to form a uniform negative electrode slurry, wherein the solid content of the negative electrode slurry was The amount is 40wt%.
  • the slurry is coated on the negative electrode current collector (copper foil), dried at 85°C, and then cold pressed, cut and slit, and dried at 120°C under vacuum for 12 hours to obtain a negative electrode sheet.
  • Lithium cobalt oxide (LiCoO 2 ) is used as a positive electrode active material of a lithium ion battery.
  • the positive electrode active material LiCoO 2
  • the conductive agent Super P and the binder polyvinylidene fluoride (PVDF) were fully stirred and mixed in a proper amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 97:1.4:1.6 to form a uniform positive electrode slurry, wherein the solid content of the positive electrode slurry was 72wt%.
  • NMP N-methylpyrrolidone
  • the slurry was coated on the positive electrode current collector aluminum foil, dried at 85°C, and then cold pressed, cut and slit, and dried at 85°C under vacuum conditions for 4 hours to obtain a positive electrode sheet.
  • a 9 ⁇ m thick polyethylene (PE) porous polymer film coated with Al 2 O 3 was used as the isolation membrane.
  • Preparation of full battery stack the positive electrode sheet, separator and negative electrode sheet in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, then wind and weld the ear, place it in the outer packaging foil aluminum-plastic film, inject electrolyte, and go through vacuum packaging, standing, formation, shaping, capacity testing and other processes to obtain a soft-pack full battery.
  • Example 1-2 uses a method similar to Example 1-1 to prepare hard carbon. The difference from Example 1-1 is that Example 1-2 adjusts the weight parts of raw materials to: 268 parts by weight of zinc gluconate, 133 parts by weight of glucose and 10 parts by weight of melamine.
  • Example 1-3 uses a method similar to Example 1-1 to prepare hard carbon. The difference from Example 1-1 is that Example 1-3 adjusts the weight parts of raw materials to: 532 parts by weight of zinc gluconate, 67 parts by weight of glucose and 10 parts by weight of melamine.
  • Example 1-4 uses a method similar to Example 1-1 to prepare hard carbon. The difference from Example 1-1 is that Example 1-4 adjusts the weight parts of raw materials to: 400 parts by weight of zinc gluconate, 100 parts by weight of glucose and 5 parts by weight of melamine.
  • Example 1-5 uses a method similar to Example 1-1 to prepare hard carbon. The difference from Example 1-1 is that Example 1-5 adjusts the weight parts of raw materials to: 400 parts by weight of zinc gluconate, 100 parts by weight of glucose and 15 parts by weight of melamine.
  • Example 1-6 uses a method similar to Example 1-1 to prepare hard carbon. The difference from Example 1-1 is that Example 1-6 adjusts the weight parts of the raw materials to: 400 parts by weight of zinc gluconate, 100 parts by weight of glucose and 20 parts by weight of melamine.
  • Example 1-7 uses a method similar to that of Example 1-5 to prepare hard carbon. The difference from Example 1-5 is that Example 1-7 changes the raw material melamine to urea.
  • Example 1-8 uses a method similar to that of Example 1-5 to prepare hard carbon. The difference from Example 1-5 is that Example 1-8 changes the raw material glucose to sucrose.
  • Comparative Example 1-1 uses a method similar to that of Example 1-1 to prepare hard carbon. The difference from Example 1-1 is that the raw material in Comparative Example 1-1 is adjusted to 100 parts by weight of glucose, and zinc gluconate and melamine are not added.
  • Comparative Example 1-2 uses a method similar to that of Example 1-1 to prepare hard carbon. The difference from Example 1-1 is that the raw materials in Comparative Example 1-2 are adjusted to 400 parts by weight of zinc gluconate and 100 parts by weight of glucose, and melamine is not added.
  • Comparative Example 1-3 uses a method similar to that of Example 1-1 to prepare hard carbon. The difference from Example 1-1 is that the raw materials in Comparative Example 1-3 are adjusted to 10 parts by weight of melamine and 100 parts by weight of glucose, and zinc gluconate is not added.
  • Example 2-1 uses a method similar to that of Example 1-5 to prepare hard carbon. The difference from Example 1-5 is that Example 2-1 changes the raw material melamine to diphenylselenide.
  • Example 2-2 uses a method similar to that of Example 1-5 to prepare hard carbon. The difference from Example 1-5 is that Example 2-2 changes the raw material melamine to sulfur powder.
  • Example 2-3 uses a method similar to that of Example 1-5 to prepare hard carbon. The difference from Example 1-5 is that Example 2-3 changes the raw material melamine to diammonium phosphate.
  • Example 2-4 uses a method similar to that of Example 1-5 to prepare hard carbon. The difference from Example 1-5 is that Example 2-4 changes the raw material melamine to boric acid.
  • Example 3-1 uses a method similar to that of Example 1-5 to prepare hard carbon. The difference from Example 1-5 is that in Example 3-1, the particle size Dv99 is controlled at 70 ⁇ m during crushing and classification.
  • Example 3-2 uses a method similar to that of Example 1-5 to prepare hard carbon. The difference from Example 1-5 is that in Example 3-2, the particle size Dv99 is controlled at 21 ⁇ m during crushing and classification.
  • Example 4-1 uses a method similar to that of Example 1-1 to prepare hard carbon. The difference from Example 1-1 is that Example 4-1 adjusts the secondary calcination temperature to 1400°C.
  • the hard carbon prepared above, styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) were fully stirred and mixed in an appropriate amount of deionized water at a weight ratio of 97:2:1 to form a uniform negative electrode slurry, wherein the solid content of the negative electrode slurry was 40wt%.
  • the slurry was coated on the negative electrode collector (aluminum foil), dried at 85°C, and then cold pressed, cut and slit, and dried under vacuum conditions at 120°C for 12 hours to obtain a negative electrode sheet.
  • Copper-nickel-iron-manganese oxide (NaCu 1/9 Ni 2/9 Fe 1/3 Mn 1/3 O 2 ) is used as a positive electrode active material of a sodium ion battery.
  • the positive electrode active material NaCu 1/9 Ni 2/9 Fe 1/3 Mn 1/3 O 2
  • the conductive agent Super P and the binder polyvinylidene fluoride (PVDF) were fully stirred and mixed in a proper amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 97:1.4:1.6 to form a uniform positive electrode slurry, wherein the solid content of the positive electrode slurry was 72wt%.
  • NMP N-methylpyrrolidone
  • the slurry was coated on the positive electrode current collector aluminum foil, dried at 85°C, and then cold pressed, cut and slit, and dried under vacuum conditions at 85°C for 4 hours to obtain a positive electrode sheet.
  • PE polyethylene
  • Preparation of full battery stack the positive electrode sheet, separator and negative electrode sheet in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, then wind and weld the ear, place it in the outer packaging foil aluminum-plastic film, inject electrolyte, and go through vacuum packaging, standing, formation, shaping, capacity testing and other processes to obtain a soft-pack full battery.
  • Example 4-2 uses a method similar to Example 4-1 to prepare a sodium ion full battery. The difference from Example 4-1 is that Example 4-2 uses a method similar to Example 1-5 to prepare hard carbon, and Example 4-2 adjusts the secondary calcination temperature to 1400°C.
  • Example 4-3 uses a method similar to Example 4-1 to prepare a sodium ion full battery. The difference from Example 4-1 is that Example 4-3 uses a method similar to Example 1-6 to prepare hard carbon, and Example 4-3 adjusts the secondary calcination temperature to 1400°C.
  • Example 4-4 uses a method similar to Example 4-1 to prepare a sodium ion full battery. The difference from Example 4-1 is that Example 4-4 uses a method similar to Example 1-7 to prepare hard carbon, and Example 4-4 adjusts the secondary calcination temperature to 1400°C.
  • Comparative Example 4-1 uses a method similar to Example 4-1 to prepare a sodium ion full battery. The difference from Example 4-1 is that Comparative Example 4-1 uses a method similar to Comparative Example 1-1 to prepare hard carbon, and Comparative Example 4-1 adjusts the secondary calcination temperature to 1400°C.
  • buttons use metallic lithium or metallic sodium as the counter electrode. Lithium/sodium sheets with a diameter of 18 mm and a thickness of 0.6 mm are assembled and stacked together with an isolation membrane and a hard carbon electrode in sequence, and an electrolyte is added. The positive and negative electrodes are placed in button-shaped stainless steel shells and sealed to obtain button cells.
  • the assembled button cell was left to stand for 5 hours before the charge and discharge test.
  • the test process was to discharge at a current density of 0.1mA/cm2 to 0V, and then discharge at a constant voltage of 0V until the current dropped to 12uA/cm2; the discharge (lithium insertion/sodium insertion) process was completed; after standing for 5 minutes, the charge (lithium removal/sodium removal) test was performed.
  • the test process was as follows: at a current density of 0.1mA/cm2 The current density is constant and the charge is up to 2V.
  • the first coulombic efficiency first charge capacity/first discharge capacity*100%
  • the lithium-ion battery or sodium-ion battery is charged at a constant current of 0.2C to a voltage of 4.48V or 3.95V, and then charged at a constant voltage; discharged at a constant current of 0.2C to a voltage of 2V, which is recorded as one cycle, and the discharge capacity and discharge energy of the first cycle are recorded; the discharge energy is divided by the discharge capacity to obtain the average discharge voltage; and the length, width and height of the battery at 50% SOC are tested to obtain the volume of the battery; therefore:
  • Energy density ED discharge capacity ⁇ average discharge voltage/cell volume.
  • the electrode piece containing hard carbon material is cut into a cross section by ion polishing, and then the cross section is placed on the test bench of Raman spectroscopy and tested after focusing.
  • a range of 200um*500um is selected, and more than 200 points are tested at equal intervals within the range, and the test range of each point is between 1000cm -1 and 2000cm -1 ; the peak appearing between 1320cm -1 and 1370cm -1 is recorded as the D peak, and the peak appearing between 1570cm -1 and 1620cm -1 is recorded as the G peak, and the intensity ratio of ID / IG of each point is counted, and then the average value of multiple points is calculated as the final ID / IG intensity ratio.
  • the hard carbon material is subjected to a powder XRD test, and the test scanning range is 2 times the scattering angle of 10 degrees to 60 degrees.
  • the obtained scanning curve is sorted, and the peak (half-peak width greater than 3 degrees) appearing in the 2 times scattering angle range of 15° to 30° is recorded as Peak A, and the 2 times scattering angle of the peak value of Peak A is obtained.
  • the Zn element was tested by inductively coupled plasma emission spectrometry; the N/S/H/C and other elements were tested by elemental analyzer, and the atmosphere content was tested after the hard carbon material was fully burned in oxygen to obtain the element ratio and content; the P/B/Se and other elements were quantitatively obtained by XPS.
  • This application uses a Malvern particle size tester to measure the particle size of hard carbon particles: disperse the hard carbon particle material in a dispersant (ethanol), ultrasonicate for 30 minutes, add the sample into the Malvern particle size tester, and start testing.
  • the particle size that reaches 50% of the volume accumulation from the small particle size side is the Dv50 of the hard carbon particles, that is, the average particle size; at the same time, in the volume-based particle size distribution of the hard carbon particles, the particle size that reaches 99% of the volume accumulation from the small particle size side is the Dv99 of the hard carbon particles.
  • Comparative Example 1-3 adds heteroatom N element.
  • the N element can increase the defect concentration of the sample, thereby improving the capacity of the oblique segment from 0.15V to 0.8V; at the same time, the N element can also increase the lithium-affinity wettability of the sample, thereby improving the capacity of the low-voltage platform segment.
  • FIG1 is a schematic diagram of the charge and discharge curve of the lithium ion battery of Example 1-5) added zinc and heteroatom N elements, zinc element is conducive to the capacity improvement of the low voltage platform segment, nitrogen element is conducive to the capacity improvement of the oblique line segment 0.15V to 0.8V; at the same time, N element can also increase the lithium affinity wettability of the sample, so that the capacity of the low voltage platform segment is further significantly improved; the capacity of the low voltage platform stage of hard carbon is higher, the total capacity and the first cycle coulomb efficiency are increased, so that its energy density ED is greatly improved compared with comparative examples 1 and 2.
  • button cells their high voltage platform makes their voltage output low in the full battery, which reduces their energy density; therefore, improving the gram capacity of the low platform 0V to 0.15V segment of the button cell is the key to improving the energy density ED.
  • Examples 1-5, 3-1 and 3-2 also illustrate that the particle size has a slight effect on the sample.
  • the diffusion distance is longer, which is not conducive to the full utilization of the gram capacity.
  • the particles are smaller, the BET specific surface area is larger and the first coulomb efficiency is lower, so the particle size should be controlled within an appropriate range.

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Abstract

本申请涉及一种硬碳材料及其制备方法、电化学装置及电子装置，所述硬碳材料包括多孔骨架以及第一元素和锌元素，第一元素包括氮元素、硫元素、硼元素、磷元素和硒元素中的一种或多种；第一元素相对于硬碳材料总质量的含量记为A1％；锌元素相对于硬碳材料总质量的含量记为A2％，其中，硬碳材料满足：1.5≤A1/A2≤5。本申请的硬碳材料在应用于电化学装置时能够显著改善电化学装置的能量密度。

Description

硬碳材料及其制备方法、电化学装置及电子装置
相关申请的交叉引用
本申请要求享有于2022年10月12日提交的名称为“硬碳材料及其制备方法、电化学装置及电子装置”的中国专利申请202211248809.7的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及储能技术领域，更具体地，涉及硬碳材料及其制备方法、电化学装置及电子装置。
背景技术
电化学装置具有能量密度高、工作电压高、重量轻等特性，故广泛应用于手机、笔记本电脑、相机等电子产品。在提升电化学装置的电化学性能的同时，其安全性能也不容忽视。随着对电子产品性能要求的提高，对电化学装置的性能要求也逐步提升。
研究发现，电化学装置内活性离子在正极活性物质和负极活性物质之间迁移是充放电的核心过程，由此负极活性物质对电化学装置的性能例如能量密度具有显著影响，而现有的负极活性物质的可逆容量和低平台容量相对较低，使得负极活性物质在应用于电化学装置时，电化学装置的能量密度较低。
发明内容
本申请提供一种硬碳材料及其制备方法、电化学装置及电子装置，所述硬碳材料具有较高的可逆容量和低平台容量，在将硬碳材料应用于电化学装置时，可以显著改善电学装置的性能。
第一方面，本申请提出了一种硬碳材料，所述硬碳材料包括多孔骨架以及第一元素和锌元素，第一元素包括氮元素、硫元素、硼元素、磷元素和硒元素中的一种或多种；第一元素相对于硬碳材料总质量的含量记为A1wt％；锌元素相对于硬碳材料总质量的含量记为A2wt％，其中，硬碳材料满足：1.5≤A1/A2≤5。
在一些实施例中，第一元素包括氮元素，2≤A1/A2≤4.5。
在一些实施例中，第一元素包括氮元素，第一元素基于硬碳材料总质量的含量记为W1wt％，2≤W1≤5。
在一些实施例中，第一元素包括硫元素、硼元素、磷元素和硒元素中的一种或多种，2≤A1/A2≤4。
在一些实施例中，第一元素包括硫元素、硼元素、磷元素和硒元素中的一种或多种，第一元素基于硬碳材料总质量的含量记为W2wt％，2.5≤W2≤9。
在一些实施例中，锌元素相对于硬碳材料总质量的含量记为A2wt％，0.6≤A2≤1.2。
在一些实施例中，硬碳材料以锂金属为对电极，在0至2.5V vs Li+/Li范围内测试得到的充放电曲线中，0(vs Li+/Li)至0.15V(vs Li+/Li)的克容量记为C11mAh/g；0.15V(vs Li+/Li)至0.8V(vs Li+/Li)的克容量记为C12mAh/g，硬碳材料满足：1.6≤C11/C12≤2.1。
在一些实施例中，250≤C11≤350。
在一些实施例中，硬碳材料以钠金属为对电极，在0至2.5V vs Na+/Na范围内测试得到的充放电曲线中，0(vs Na+/Na)至0.15V(vs Na+/Na)的克容量记为C21mAh/g；0.15V(vs Na+/Na)至1.00V(vs Na+/Na)的克容量记为C22mAh/g，硬碳材料满足：3.55≤C21/C22≤3.95。
在一些实施例中，300≤C21≤340。
在一些实施例中，硬碳材料的X射线衍射图谱中，在2倍散射角位于15°至30°范围内存在衍射峰，衍射峰的2倍散射角<24°。
在一些实施例中，硬碳材料在200um*500um扫面范围内的拉曼谱图中，在1320cm-1至1370cm-1范围内存在特征峰D，在1570cm-1至1620cm-1范围内存在特征峰G，特征峰D的峰强为ID，特征峰G的峰强为IG，0.5＜ID/IG≤1.5。
在一些实施例中，硬碳材料还满足以下条件(1)和/或条件(2)：
(1)硬碳材料的体积分布粒径Dv50μm满足：3≤Dv50≤15；
(2)硬碳材料的体积分布粒径Dv99μm满足：10≤Dv99≤45。
在一些实施例中，硬碳材料还包括包覆于多孔骨架外的碳层。
第二方面，本申请提出了一种制备硬碳材料的方法，所述方法包括：将含碳的前驱体材料、含锌元素的致孔剂和含第一元素的第一材料均匀混合为混合体系；热处理混合体系，以使前驱体材料碳化，在碳化过程中致孔剂挥发并刻蚀前驱体材料形成多孔骨架，多孔骨架上设置有第一元素和锌元素，其中，第一元素包括氮元素、硫元素、硼元素、磷元素和硒元素中的一种或多种；第一元素相对于硬碳材料总质量的含量记为A1wt％；锌元素相对于硬碳材料总质量的含量记为A2wt％，其中，硬碳材料满足：1.5≤A1/A2≤5。
在一些实施例中，热处理包括第一热处理和第二热处理，第一热处理的温度小于第二热处理的温度。
在一些实施例中，在多孔骨架外包覆碳层。
第三方面，本申请提出了一种电化学装置，所述电化学装置包括负极极片，所述负极极片包括如本申请第一方面任一实施方式所述的硬碳材料或如本申请第二方面任一实施方式所述的方法制备得到的硬碳材料。
第四方面，本申请提出了一种电子装置，包括如本申请第三方面所述的电化学装置。
根据本申请实施例的硬碳材料，其满足1.5≤A1/A2≤5时，第一元素能够均匀分布于多孔骨架中，由于第一元素和锌元素的结合作用，使得锌元素能够均匀分布于多孔骨架中，从而使得多孔骨架中具有充足的孔道结构，且孔道分布更为均匀，有利于改善硬碳材料的可逆容量和低平台容量；从而使得硬碳材料在应用于电化学装置时能够显著改善电化学装置的能量密度。
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例，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是本申请的实施例1-5锂离子电池的充放电曲线图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。在本申请说明书全文中，将相同或相似的组件以及具有相同或相似的功能的组件通过类似附图标记来表示。在此所描述的有关附图的实施例为说明性质的、图解性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
在具体实施方式及权利要求书中，由术语“中的一者或多者”、“中的一个或多个”、“中的一种或多种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
电化学装置包括正极极片、负极极片和隔离膜；负极极片包括负极活性物质，负极活性物质包括石墨、硬碳等，石墨的理论容量为372mAh/g，近年来几乎已开发到石墨的理论容量上限，继续提升的空间较小。由于硬碳材料具有体积膨胀小、快速充放电能力强以及克容量高等优势，得到了广泛研究。发明人研究发现，硬碳材料的可逆容量较低、低平台容量较低，导致硬碳材料限制了电化学装置的能量密度。
鉴于此，发明人从改善硬碳材料的角度出发，对硬碳材料进行造孔，使得硬碳材料为多孔结构，从而增加硬碳材料的可逆容量和低平台容量。接下来对本申请的方案进行进一步说明。
硬碳材料
本申请第一方面提出了一种硬碳材料，所述硬碳材料包括多孔骨架以及第一元素和锌元素，第一元素包括氮元素、硫元素、硼元素、磷元素和硒元素中的一种或多种，第一元素相对于硬碳材料总质量的含量记为A1wt％，锌元素相对于硬碳材料总质量的含量记为A2wt％，硬碳材料满足：1.5≤A1/A2≤5。虽然机理尚不明确，但是本申请的硬碳材料在满足上述关系时，其可逆容量相对较高，低平台容量相对较高，在应用于电化学装置时，可以改善电化学装置的能量密度等性能。
发明人推测，本申请的作用机理如下：
硬碳材料的微观结构具有由弯曲的类石墨片无序堆叠形成短程有序的微区，同时还具有微孔结构等缺陷。在充电过程中，活性离子例如锂离子、钠离子等会由正极活性物质向负极活性物质例如硬碳材料中迁移并嵌入硬碳材料中。硬碳材料储存活性离子的充放电曲线中低电压平台区域(0至0.15V vs Li+/Li)表示锂离子或钠离子填入硬碳孔隙中所提供的容量，高电压斜线区域(0.15V至0.8V)表示锂离子插层至硬碳微晶层间，或钠离子吸附于 硬碳微晶端面所提供的容量。充放电曲线中电压相对较低的区域通常认为更有利于贡献能量密度，故改善低电压平台区域的容量，可以显著改善电化学装置的能量密度。
可选地，硬碳材料可以经前驱体材料水热或化学过程处理得到，前驱体材料包括树脂基前驱体、沥青基前驱体和生物质基前驱体中的一种或多种；示例性地，树脂基前驱体包括酚醛树脂、环氧树脂、聚糠醇中的一种或多种；沥青基前驱体包括煤焦油沥青、石油沥青、天然沥青中的一种或多种；生物质基前驱体包括纤维素、木质素、淀粉、壳聚糖、蔗糖、葡萄糖中的一种或多种。相对较低的分子量前驱体相较于高分子量前驱体所形成的硬碳，具有更多的缺陷，能够为活性离子提供更多的活性位点，提升硬碳材料的容量。本申请前驱体材料可选为生物质基前驱体。
多孔骨架中具有锌元素，锌元素主要分布于多孔骨架内，也可以分布于多孔骨架的表面，在制备硬碳材料的过程中，选取包含锌元素的致孔剂，例如葡萄糖酸锌、柠檬酸锌、硫酸锌、硝酸锌等中的一种或多种。上述致孔剂在前驱体材料碳化过程中能够挥发，由此刻蚀前驱体材料的结构以形成孔道，使得碳化后所形成的硬碳材料具有多孔骨架。多孔骨架的形成使得孔容积增加，活性离子的嵌入位点增加，从而能够显著提升硬碳材料的可逆容量，尤其提升低平台段的容量。
多孔骨架中具有第一元素，第一元素主要分布于多孔骨架内，也可以分布于多孔骨架的表面，在制备硬碳材料的过程中，选取包含第一元素的第一材料，例如第一元素包括氮元素时，对应的第一材料可以包括三聚氰胺、尿素、双氰胺等。又例如第一元素包括硫元素时，对应的第一材料可以包括硫粉。又例如，第一元素包括硼元素时，对应的第一材料可以包括硼酸。又例如，第一元素包括磷元素时，对应的第一材料可以包括磷酸二氢铵。又例如，第一元素包括硒元素时，对应的第一材料可以包括二苯基硒。前驱体材料和包含第一元素的物质混合，第一元素能够较为均匀地分布于前驱体材料中，且第一元素能够为锌元素提供结合位点，有利于锌元素的均匀分布，使得致孔剂能够均匀造孔，硬碳材料中的孔道结构分布更为均匀，孔的利用更为充分，能够改善电化学装置的首次库仑效率。并且第一元素具有较好的亲锂浸润性，有利于锂离子嵌入多孔骨架中，使得低平台电压的容量得到进一步显著提升。
虽然上述分析是对硬碳材料的多孔骨架、第一元素和锌元素的单独分析，但是由于三者是一个有机整体，三者之间具有相互关联关系，共同影响硬碳材料的最终性能。本申请的硬碳材料满足1.5≤A1/A2≤5时，第一元素能够均匀分布于多孔骨架中，由于第一元素和锌元素的结合作用，使得锌元素能够均匀分布于多孔骨架中，从而使得多孔骨架中具有充足的孔道结构，且孔道分布更为均匀，有利于改善硬碳材料的可逆容量和低平台容量；从而使得硬碳材料在应用于电化学装置时能够显著改善电化学装置的能量密度。示例性地，A1/A2可以为1.5、2、2.5、3、3.5、4、4.5或5，或是上述任意两个数值组成的范围。
本申请通过对第一元素的添加量进行调控，可以调节硬碳材料对活性离子例如锂离子的浸润性能，随着第一元素的添加量的提高，对锂离子的浸润性能越好，越有利于锂离子嵌入多孔骨架中，对提升低平台电压容量有利；并且还可以调节为锌元素提供的结合位点的数量，随着第一元素的添加量的提高，为锌元素提供的结合位点越多，有利于锌元素的更均匀化分布，从而能够更均匀造孔。本申请调控第一元素的添加量满足以下条件中的一个或多个，能够进一步改善硬碳材料的可逆容量和低平台容量以及结构稳定性。
在一些实施例中，第一元素包括氮元素，2≤A1/A2≤4.5。
在一些实施例中，第一元素包括氮元素，第一元素相对于硬碳材料总质量的含量记为W1wt％，2≤W1≤5。示例性地，第一元素的含量W1wt％可以为2wt％、3wt％、4wt％或5wt％，或者是上述任意两个数值组成的范围。氮元素的含量可以采用本领域公知的设备和方法进行测试，例如可以采用元素分析仪分析测试，具体地，将试样置于元素分析仪中，经加热将试样完全燃烧为元素物质，然后利用冷凝器去除试样中的水分，并利用还原反应管消除不需要的化合物和氧气，将氮氧化合物转化为氮气，继续去除试样中的水分，检测氮气含量。
在一些实施例中，第一元素包括硫元素、硼元素、磷元素和硒元素中的一种或多种，2≤A1/A2≤4。
在一些实施例中，第一元素包括硫元素、硼元素、磷元素和硒元素中的一种或多种，第一元素相对于硬碳材料总质量的含量记为W2wt％，2.5≤W2≤9。示例性地，第一元素的含量W2wt％可以为2.5wt％、3wt％、4wt％或5wt％，或者是上述任意两个数值组成的范围。硫元素、硼元素、磷元素和硒元素的含量可以采用本领域公知的设备和方法进行测试，例如可以采用元素分析仪分析测试，具体地，硫元素、硼元素、磷元素和硒元素等元素通过X射线光电子能谱XPS定量获得。
本申请通过对锌元素的添加量进行调控，可以调节硬碳材料的多孔骨架的孔结构，过少的锌元素可能使得多孔骨架中的孔道较少，硬碳材料的孔容积改变不明显，不利于提升低电压平台容量，随着锌元素的添加量的提高，多孔骨架中的孔道增多，低电压平台容量得到显著提升，但是过多的锌元素可能导致所形成的孔道数量过多，使得多孔骨架结构稳定性较差，故，调控锌元素的添加量满足以下条件，能够进一步改善硬碳材料的可逆容量和低平台容量以及结构稳定性。
在一些实施例中，锌元素相对于硬碳材料总质量的含量记为A2wt％，0.6≤A2≤1.2。示例性地，锌元素的含量A2wt％可以为0.6wt％、0.7wt％、0.9wt％、1.0wt％或1.2wt％，或者是上述任意两个数值组成的范围。锌元素的含量可以采用本领域公知的设备和方法进行测试，例如可以采用电感耦合等离子体发射光谱仪分析测试。具体地，可以利用等离子体激发光源使试样蒸发汽化，离解或分解为原子状态，原子可能进一步电离成离子状态，原子及离子在光源中激发发光。利用电感耦合等离子体发射光谱仪将光源发射的光分解为按波长排列的光谱。利用光电器件检测光谱，按测定得到的光谱波长对试样进行定性分析，按发射光强度进行定量分析。
在一些实施例中，硬碳材料还包括氢元素和碳元素，氢元素相对于硬碳材料总质量的含量记为W4wt％，碳元素相对于硬碳材料总质量的含量记为W5wt％，硬碳材料满足：0.02≤W4/W5≤0.20。
发明人经过对硬碳材料进行深入研究，本申请的硬碳材料不仅适用于锂离子电池，还适用于钠离子电池。锂离子电池具有体积和质量能量密度大、环境友好、工作电压高、体积小、重量轻、循环寿命长等优点，本申请的硬碳材料在应用于锂离子电池时，可以改善锂离子电池的能量密度等性能。相较于锂，钠具有更高的标准电极电势，导致钠离子电池的能量密度低于锂离子电池，而大的离子半径使得钠离子很难发生嵌入和脱出反应。而本申请的硬碳材料也同样适用于钠离子电池，有利于钠离子电池嵌入硬碳材料中，并能够改 善钠离子电池的能量密度等性能。
发明人发现当硬碳材料还满足以下条件中的一个或多个时，能够进一步改善硬碳材料的可逆容量和低平台电压容量。
在一些实施例中，硬碳材料以锂金属为对电极，在0至2.5V vs Li+/Li范围内测试得到的充放电曲线中，0(vs Li+/Li)至0.15V(vs Li+/Li)的克容量记为C11mAh/g；0.15V(vs Li+/Li)至0.8V(vs Li+/Li)的克容量记为C12mAh/g，硬碳材料满足：1.6≤C11/C12≤2.1。可选地，250≤C11≤350。
硬碳材料作为负极，锂金属(直径18mm厚度0.6mm的锂片)作为对电极，将硬碳电极、隔离膜和锂片按顺序组装叠在一起，并加入电解液(1mol/L锂盐LiPF6)，装入正负极扣式不锈钢壳中封装，获得扣式电池。测试该扣式电池的充放电曲线，由此得到脱锂过程中克容量分布。
本申请实施例的硬碳材料在满足上述克容量关系的条件下，能够进一步显著提升硬碳材料在低电压平台的容量。
在一些实施例中，硬碳材料以钠金属为对电极，在0至2.5V vs Na+/Na范围内测试得到的充放电曲线中，0(vs Na+/Na至0.15V(vs Na+/Na)的克容量记为C21mAh/g；0.15V(vs Na+/Na)至1.00V(vs Na+/Na)的克容量记为C22mAh/g，硬碳材料满足：3.55≤C21/C22≤3.95。可选地，300≤C21≤340。
硬碳材料作为负极，钠金属(直径18mm厚度0.6mm的钠片)作为对电极，将硬碳电极、隔离膜和钠片按顺序组装叠在一起，并加入电解液(1mol/L钠盐NaPF6)，装入正负极扣式不锈钢壳中封装，获得扣式电池。测试该扣式电池的充放电曲线，由此得到脱钠过程中克容量分布。
本申请实施例的硬碳材料在满足上述克容量关系的条件下，能够进一步显著提升硬碳材料在低电压平台的容量。
在一些实施例中，硬碳材料的X射线衍射(X-Ray Diffraction，XRD)图谱中，在2倍散射角位于15°至30°范围内存在衍射峰，衍射峰的2倍散射角<24°。硬碳材料的面间距较大，有利于活性离子例如锂离子、钠离子等在硬碳材料的层间传输。
在一些实施例中，硬碳材料在200um*500um扫面范围内的拉曼谱图中，在1320cm-1至1370cm-1范围内存在特征峰D，在1570cm-1至1620cm-1范围内存在特征峰G，特征峰D的峰强为ID，特征峰G的峰强为IG，0.5＜ID/IG≤1.5。
在一些实施例中，硬碳材料的体积分布粒径Dv50μm满足：3≤Dv50≤15。Dv50的物理定义：材料累计体积分布百分数达到50％时所对应的粒径；可以采用本领域已知的方法测试。例如可以参照标准GB/T 19077.1-2016，使用激光粒度分析仪(如Malvern Master Size 3000)测定。
在一些实施例中，硬碳材料的体积分布粒径Dv99μm满足：10≤Dv99≤45。Dv99的物理定义：材料累计体积分布百分数达到99％时所对应的粒径；可以采用本领域已知的方法测试。例如可以参照标准GB/T 19077.1-2016，使用激光粒度分析仪(如Malvern Master Size 3000)测定。
本申请的硬碳材料的粒径满足上述范围时，活性离子在硬碳材料中扩散距离相对较短，有利于硬碳材料克容量的充分发挥；且硬碳材料的颗粒比表面积相对较较小，动力学性能 相对较好，有利于提高硬碳材料的首圈库伦效率。
在一些实施例中，硬碳材料还包括包覆于多孔骨架外的碳层。
多孔骨架由于致孔剂的刻蚀，可能会在其表面形成开孔结构，开孔结构可以提供更多储存活性离子的活性位点，提高硬碳材料在低电压平台的容量。但是开孔结构过多，会导致硬碳材料的比表面相对较大，过多的形成固体电解质界面(Solid Electrolyte Interface，SEI)膜恶化首圈库伦效率。本申请在多孔骨架外设置碳层，可以使得硬碳材料在兼顾低电压平台较高容量的同时，改善首圈库伦效率。
制备硬碳材料的方法
本申请第二方面还提供了一种制备硬碳材料的方法。
所述方法包括：
步骤S100，将含碳的前驱体材料、含锌元素的致孔剂和含第一元素的第一材料均匀混合为混合体系；
步骤S200，热处理所述混合体系，以使所述前驱体材料碳化，在碳化过程中所述致孔剂挥发并刻蚀所述前驱体材料形成多孔骨架，所述多孔骨架上设置有第一元素和锌元素，
其中，所述第一元素包括氮元素、硫元素、硼元素、磷元素和硒元素中的一种或多种；
所述第一元素相对于所述硬碳材料总质量的含量记为A1wt％；
所述锌元素相对于所述硬碳材料总质量的含量记为A2wt％，
其中，所述硬碳材料满足：1.5≤A1/A2≤5。
本申请的前驱体材料、致孔剂和第一材料的种类如前文所述，在此不再赘述。本申请通过将三类物质进行混合，有利于在碳化过程中对前驱体材料进行致孔。混合的手段可以采用球磨混合等。
在一些实施例中，步骤S200中的热处理可以包括第一热处理和第二热处理，第一热处理的温度小于第二热处理的温度。
第一热处理可以作为预碳化过程，例如在400℃至700℃范围内煅烧混合体系，该步骤有利于将致孔剂中的锌元素固定于前驱体材料上，并且在第一元素均匀分布于前驱体材料的基础上，能够使得锌元素均匀分布于前驱体材料上。可选地，在第一热处理后可以将混合体系进行破碎分级，使得粒径更符合生产要求。
第二热处理可以作为碳化过程，例如在900℃至1300℃范围内煅烧混合体系，使得前驱体材料碳化为多孔骨架。尤其是可以在破碎分级之后进行第二热处理过程，有利于获得粒径符合生产要求的硬碳材料。
在一些实施例中，所述方法还包括步骤S300，在多孔骨架外包覆碳层。可以采用气相沉积法(例如化学气相沉积法CVD)、液相溶胶凝胶法、沥青包覆等方法将碳源包覆于多孔骨架外形成碳层，具体的工艺参数可以采用本领域现有的参数，在此不再赘述。
电化学装置
本申请第三方面还提供了一种电化学装置，所述电化学装置包括负极极片，负极极片的负极活性物质可以包括本申请第一方面任一实施方式的硬碳材料或本申请第二方面任一实施方式所述的方法制备得到的硬碳材料。
在一些实施例中，所述电化学装置的单位时间内的电压降K值满足：0.01mV/h≤K≤2mV/h。K值是衡量电化学装置自放电率的指标，K值在上述范围时，电化学装置 的自放电性能较为优异。
[负极极片]
负极极片是本领域技术公知的可被用于电化学装置的负极极片。在一些实施例中，负极极片包含负极集流体以及负极活性物质层。负极活性物质层设置于负极集流体的表面上。负极活性物质层包含负极活性物质。负极活性物质可以包括本申请第一方面任一实施方式的硬碳材料或本申请第二方面任一实施方式所述的方法制备得到的硬碳材料。
在一些实施例中，负极极片的结构为本领域技术公知的可被用于电化学装置的负极极片的结构。
在一些实施例中，负极集流体为金属，例如但不限于铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、包覆有导电金属的聚合物基板或它们的组合。
负极活性物质除了可以采用本申请第一方面任一实施方式的硬碳材料或本申请第二方面任一实施方式所述的方法制备得到的硬碳材料，还可额外选用本领域技术公知的各种可被用作电化学装置的负极活性物质的能够可逆地嵌入、脱嵌活性离子的传统公知的物质或能够可逆地掺杂、脱掺杂活性离子的传统公知的物质。
在一些实施例中，负极活性物质包含锂金属、锂金属合金、碳材料、能够掺杂/脱掺杂锂的材料或过渡金属氧化物中的至少一种。在一些实施例中，碳材料可选用本领域技术公知的各种可被用作电化学装置的碳基负极活性物质的碳材料。在一些实施例中，碳材料包含结晶碳、非晶碳中的至少一种。在一些实施例中，结晶碳为天然石墨或人造石墨。在一些实施例中，结晶碳的形状为无定形、板形、小片形、球形或纤维形。在一些实施例中，结晶碳为低结晶碳或高结晶碳。在一些实施例中，低结晶碳包含软碳、硬碳中的至少一种。在一些实施例中，高结晶碳包含天然石墨、结晶石墨、热解碳、中间相沥青基碳纤维、中间相碳微珠、中间相沥青、高温锻烧炭中的至少一种。
在一些实施例中，高温锻烧炭为石油或衍生自煤焦油沥青的焦炭。在一些实施例中，非晶碳包含软碳、硬碳、中间相沥青碳化产物、烧制焦炭中的至少一种。在一些实施例中，负极活性物质包含过渡金属氧化物。在一些实施例中，过渡金属氧化物包含氧化钒、氧化锂钒中的至少一种。在一些实施例中，负极活性物质包含Si、SiOx(0<x<2)、Si/C复合物、Si-Q合金、Sn、SnOz、Sn-C复合物、Sn-R合金中的至少一种，其中，Q选自碱金属、碱土金属、第13族至第16族元素、过渡元素、稀土元素中的至少一种且Q不为Si，R选自碱金属、碱土金属、第13族至第16族元素、过渡元素、稀土元素中的至少一种且R不为Sn。在一些实施例中，Q和R包含Mg、Ca、Sr、Ba、Ra、Sc、Y、Ti、Zr、Hf、Rf、V、Nb、Ta、Db、Cr、Mo、W、Sg、Tc、Re、Bh、Fe、Pb、Ru、Os、Hs、Rh、Ir、Pd、Pt、Cu、Ag、Au、Zn、Cd、B、Al、Ga、Sn、In、Tl、Ge、P、As、Sb、Bi、S、Se、Te、Po中的至少一种。
在一些实施例中，负极活性物质层还包含负极粘结剂和负极导电剂。在一些实施例中，负极粘结剂包含二氟乙烯一六氟丙烯共聚物(PVDF-co-HFP)，聚偏二氟乙烯、聚丙烯睛、聚甲基丙烯酸甲醋、聚乙烯醇、羧甲基纤维素、羟丙基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙中的至少一种。在一些实施例中，负极导电剂用于为电极提供导电性，其可以包括任何导电的材料，只要它不引起化学变化 即可。在一些实施例中，负极导电剂包含碳基材料、金属基材料、导电聚合物中的任意一种或它们的混合物。在一些实施例中，碳基材料包含天然石墨、人造石墨、炭黑、乙炔黑、科琴黑、碳纤维中的至少一种。在一些实施例中，金属基材料包含铜、镍、铝、银等的金属粉或金属纤维中的至少一种。在一些实施例中，导电聚合物包含聚亚苯基衍生物。
在一些实施例中，负极极片的制备方法是本领域技术公知的可被用于电化学装置的负极的制备方法。在一些实施例中，在负极浆料的制备中，通常加入溶剂，负极活性物质加入粘合剂并根据需要加入导电材料和增稠剂后溶解或分散于溶剂中制成负极浆料。溶剂在干燥过程中挥发去除。溶剂是本领域公知的可被用作负极活性物质层的溶剂，溶剂例如但不限于水。增稠剂是本领域公知的可被用作负极活性物质层的增稠剂，增稠剂例如但不限于羧甲基纤维素钠。
本申请对于负极活性物质层中的负极活性物质、粘合剂、增稠剂的混合比例没有特别的限制，可以根据期望的电化学装置性能控制其混合比例。
[正极极片]
本申请实施例的电化学装置还可以包括正极极片。正极极片是本领域技术公知的可被用于电化学装置的正极极片。在一些实施例中，正极极片包含正极集流体以及正极活性物质层。正极活性物质层设置于正极集流体的表面上。正极活性物质层包含正极活性物质。
在一些实施例中，正极极片的结构为本领域技术公知的可被用于电化学装置的正极极片的结构。
在一些实施例中，正极集流体为金属，金属例如但不限于铝箔。
正极活性物质可选用本领域技术公知的各种可被用作电化学装置的正极活性物质的能够可逆地嵌入、脱嵌活性离子的传统公知的物质。对于锂离子电池，正极活性物质中通常包含锂离子；对于钠离子电池，正极活性物质中通常包含钠离子。接下来以锂离子为例进行说明。
在一些实施例中，正极活性物质包含锂以及从钴、锰和镍中选择的至少一种的复合氧化物。具体地讲，可以使用下面的化合物：使用LiCoO2、LiNiO2、LiMnO2、LiMn2O4、Li(NiaCobMnc)O2(0<a<1，0<b<1，0<c<1，a+b+c＝1)、LiMn2O4LiNi1-yCoyO2、LiCol-yMnyO2、LiNil-yMnyO2(0<y<1)、Li(NiaMnbCoc)04(0<a<2，0<b<2，0<c<2，a+b+c＝2)、LiMn2-zNizO4、LiMn2-zCozO4(0<z<2)、Li(NiaCobAlc)O2(0<a<1，0<b<1，0<c<1，a+b+c＝1)、LiCoPO4和LiFePO4中的至少一种或两种以上的混合物。在一些实施例中，正极活性物质还包含硫化物、硒化物和卤化物中的至少一种。
在一些实施例中，正极活性物质层还包含正极粘结剂和正极导电剂。正极粘结剂用于改善正极活性物质颗粒彼此间以及正极活性物质颗粒与集流体的粘结性能。在一些实施例中，正极粘结剂包括聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙中的至少一种。正极导电剂用于为电极提供导电性，其可以包括任何导电的材料，只要它不引起化学变化即可。在一些实施例中，正极导电剂天然石墨、人造石墨、炭黑、乙炔黑、科琴黑、碳纤维、金属粉、金属纤维、聚亚苯基衍生物中的至少一种。在一些实施例中，金属粉、金属纤维中的金属包括铜、镍、铝、银中的至少一种。
在一些实施例中，正极极片的制备方法是本领域技术公知的可被用于电化学装置的正极极片的制备方法。在一些实施例中，在正极浆料的制备中，通常加入溶剂，正极活性物质加入粘结剂并根据需要加入导电材料和增稠剂后溶解或分散于溶剂中制成正极浆料。溶剂在干燥过程中挥发去除。溶剂是本领域公知的可被用作正极活性物质层的溶剂，溶剂例如但不限于N-甲基吡咯烷酮(NMP)。
[隔离膜]
隔离膜是本领域技术公知的可被用于电化学装置的隔离膜，例如但不限于聚烯烃类微多孔膜。在一些实施例中，隔离膜包含聚乙烯(PE)、乙烯丙烯共聚物、聚丙烯(PP)、乙烯-丁烯共聚物、乙烯-己烯共聚、乙烯-甲基丙烯酸甲酯共聚物中的至少一种。
在一些实施例中，隔离膜为单层隔离膜或多层隔离膜。
在一些实施例中，隔离膜上涂覆有涂层。在一些实施例中，涂层包含有机涂层和无机涂层中的至少一种，其中，有机涂层选自聚偏氟乙烯、偏氟乙烯-六氟丙烯共聚物、聚丙烯腈、聚酰亚胺、丙烯腈-丁二烯共聚物、丙烯腈-苯乙烯-丁二烯共聚物、聚甲基丙烯酸甲酯、聚丙烯酸甲酯、聚丙烯酸乙酯、丙烯酸-苯乙烯共聚物、聚二甲基硅氧烷、聚丙烯酸钠、羧甲基纤维素钠中的至少一种，无机涂层选自SiO2、Al2O3、CaO、TiO2、ZnO2、MgO、ZrO2、SnO2中至少一种。
本申请对隔离膜的形态和厚度没有特别的限制。隔离膜的制备方法是本领域技术公知的可被用于电化学装置的隔离膜的制备方法。
[电解液]
本申请实施例的电化学装置还可以包括电解液。本申请的电解液中含有电解质盐。电解质盐是本领域技术公知的适用于电化学装置的电解质盐。针对不同的电化学装置，可以选用合适的电解质盐。例如对于锂离子电池，电解质盐通常使用锂盐。又例如对于钠离子电池，电解质盐通常使用钠盐。接下来以锂离子电池为例进行说明。
在一些实施例中，锂盐包括或选自有机锂盐和无机锂盐中的至少一种。
在一些实施例中，锂盐包括或选自六氟磷酸锂(LiPF6)、六氟锑酸锂(LiSbF6)、六氟砷酸锂(LiAsF6)、全氟丁基磺酸锂(LiC4F9SO3)、高氯酸锂(LiClO4)、铝酸锂(LiAlO2)、四氯铝酸锂(LiAlCl4)、双氟磺酰亚胺锂(LiN(CxF2x+1SO2)(CyF2y+1SO2)，其中x和y是自然数)、氯化锂(LiCl)或氟化锂(LiF)中的至少一种。在一些实施例中，本申请的电解液中的锂盐的质量百分含量为10wt％至15wt％，例如可以为10％、11％、12％、13％、14％、15％或为其间的任意范围。
本申请的电解液中还可以含有非水有机溶剂，在一些实施例中，非水有机溶剂包含碳酸酯、羧酸酯、醚化合物、砜化合物或其他非质子溶剂中至少一种。在一些实施例中，非水有机溶剂的质量百分含量为21％至90％，例如可以为21％、30％、40％、50％、60％、70％、80％、90％或为其间的任意范围。
在一些实施例中，碳酸酯溶剂包含碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸二丙酯、碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、二(2,2,2-三氟乙基)碳酸酯中的至少一种。
在一些实施例中，羧酸酯溶剂包含乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸正丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸丁酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、丁酸丁酯、 γ-丁内酯、戊内酯、丁内酯中至少一种。
在一些实施例中，醚化合物溶剂包含乙二醇二甲醚、二乙二醇二甲醚、四乙二醇二甲醚、二丁醚、四氢呋喃、2-甲基四氢呋喃、双(2,2,2-三氟乙基)醚、1,3-二氧六环、1,4-二氧六环中至少一种。
在一些实施例中，砜化合物包含乙基乙烯基砜、甲基异丙基砜、异丙基仲丁基砜、环丁砜中至少一种。
电解液中非水有机溶剂，可以使用单非水有机溶剂，也可以使用多种非水有机溶剂混合，当使用混合溶剂时，可以根据期望的电化学装置性能进行控制混合比。
本申请的电解液中还可以含有功能性添加剂，例如成膜添加剂、正极成膜添加剂。成膜添加剂可以在负极极片和/或正极极片的表面形成界面膜，从而防护负极极片和/或正极极片。在一些实施例中，成膜添加剂可以为多腈类添加剂、磺酸酯类添加剂等。
基于同一发明构思，本申请还提供了一种电子装置。
本申请的电子装置是任何电子装置，例如但不限于笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池、锂离子电容器。注意的是，本申请的电化学装置除了适用于上述例举的电子装置外，还适用于储能电站、海运运载工具、空运运载工具。空运运载装置包含在大气层内的空运运载装置和大气层外的空运运载装置。
在一些实施例中，电子装置包含本申请前述的电化学装置。
下面以锂离子电池为例并且结合对比例及实施例对本申请的技术方案作进一步的说明，但并不局限于此。本领域的技术人员将理解，本申请中描述的制备方法仅是示范实施例，凡是对本申请技术方案进行修改或者同替换，而不脱离本申请技术方案的范围，均应涵盖在本申请的保护范围中。
在下述实施例、对比例中，所使用到的试剂、材料以及仪器如没有特殊的说明，均可商购获得或合成获得。
实施例至对比例
实施例1-1锂离子电池的制备
实施例1-1
1、硬碳材料的制备
将400重量份葡萄糖酸锌、100重量份葡萄糖和10重量份三聚氰胺采用机械球磨法充分混合后，转入箱式炉中在氮气保护下在400℃下煅烧2h，降温，破碎分级使Dv99控制在45um；然后，将分级后的粉末转入氮气气氛保护炉中二次煅烧，煅烧温度为1200℃，煅烧时间为2h；然后，将炉温降温至900摄氏度，通入甲烷气体，进行CVD沉积1h后，断开甲烷气体，冷却至室温获得最终产物硬碳。
2、负极极片的制备
将上述制备得到的硬碳、与丁苯橡胶(SBR)和羧甲基纤维素钠(CMC)按照重量比97:2:1在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料，其中负极浆料的固含 量为40wt％。将此浆料涂覆于负极集流体(铜箔)上，在85℃下烘干，然后经过冷压、裁片、分切后，在120℃的真空条件下干燥12小时，得到负极极片。
3、正极极片的制备
使用钴酸锂(LiCoO2)作为锂离子电池的正极活性物质。
将正极活性物质(LiCoO2)、导电剂Super P和粘结剂聚偏二氟乙烯(PVDF)按重量比97:1.4:1.6在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料，其中正极浆料的固含量为72wt％。将此浆料涂覆于正极集流体铝箔上，在85℃下烘干，然后经过冷压、裁片、分切后，在85℃的真空条件下干燥4小时，得到正极极片。
4、电解液的制备
在干燥的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)按照质量比为EC:DEC＝50:50进行混合，接着加入2％(体积比)的碳酸亚乙烯酯，溶解并充分搅拌后加入锂盐LiPF6或钠盐NaPF6，混合均匀后获得电解液，其中LiPF6或NaPF6的浓度为1mol/L。
5、隔离膜的制备
以表面涂有Al2O3的9μm厚的聚乙烯(PE)多孔聚合物薄膜作为隔离膜。
6、锂离子全电池/钠离子全电池的制备
全电池制备：将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片之间起到隔离的作用，然后卷绕、焊接极耳后、置于外包装箔铝塑膜中，注入电解液，经过真空封装、静置、化成、整形、容量测试等工序，获得软包全电池。
实施例1-2
实施例1-2采用与实施例1-1相似的方法制备硬碳，与实施例1-1不同的是，实施例1-2调整了原料重量份数为：268重量份葡萄糖酸锌、133重量份葡萄糖和10重量份三聚氰胺。
实施例1-3
实施例1-3采用与实施例1-1相似的方法制备硬碳，与实施例1-1不同的是，实施例1-3调整了原料重量份数为：532重量份葡萄糖酸锌、67重量份葡萄糖和10重量份三聚氰胺。
实施例1-4
实施例1-4采用与实施例1-1相似的方法制备硬碳，与实施例1-1不同的是，实施例1-4调整了原料重量份数为：400重量份葡萄糖酸锌、100重量份葡萄糖和5重量份三聚氰胺。
实施例1-5
实施例1-5采用与实施例1-1相似的方法制备硬碳，与实施例1-1不同的是，实施例1-5调整了原料重量份数为：400重量份葡萄糖酸锌、100重量份葡萄糖和15重量份三聚氰胺。
实施例1-6
实施例1-6采用与实施例1-1相似的方法制备硬碳，与实施例1-1不同的是，实施例1-6调整了原料重量份数为：400重量份葡萄糖酸锌、100重量份葡萄糖和20重量份三聚氰胺。
实施例1-7
实施例1-7采用与实施例1-5相似的方法制备硬碳，与实施例1-5不同的是，实施例1-7调整了原料三聚氰胺为尿素。
实施例1-8
实施例1-8采用与实施例1-5相似的方法制备硬碳，与实施例1-5不同的是，实施例1-8调整了原料葡萄糖为蔗糖。
对比例1-1锂离子电池的制备
对比例1-1采用与实施例1-1相似的方法制备硬碳，与实施例1-1不同的是，对比例1-1调整了原料为100重量份葡萄糖，不添加葡萄糖酸锌和三聚氰胺。
对比例1-2锂离子电池的制备
对比例1-2采用与实施例1-1相似的方法制备硬碳，与实施例1-1不同的是，对比例1-2调整了原料为400重量份葡萄糖酸锌和100重量份葡萄糖，不添加三聚氰胺。
对比例1-3锂离子电池的制备
对比例1-3采用与实施例1-1相似的方法制备硬碳，与实施例1-1不同的是，对比例1-3调整了原料为10重量份三聚氰胺和100重量份葡萄糖，不添加葡萄糖酸锌。
实施例2锂离子电池的制备
实施例2-1
实施例2-1采用与实施例1-5相似的方法制备硬碳，与实施例1-5不同的是，实施例2-1调整了原料三聚氰胺为二苯基硒。
实施例2-2
实施例2-2采用与实施例1-5相似的方法制备硬碳，与实施例1-5不同的是，实施例2-2调整了原料三聚氰胺为硫粉。
实施例2-3
实施例2-3采用与实施例1-5相似的方法制备硬碳，与实施例1-5不同的是，实施例2-3调整了原料三聚氰胺为磷酸二氢铵。
实施例2-4
实施例2-4采用与实施例1-5相似的方法制备硬碳，与实施例1-5不同的是，实施例2-4调整了原料三聚氰胺改为硼酸。
实施例3-1
实施例3-1采用与实施例1-5相似的方法制备硬碳，与实施例1-5不同的是，实施例3-1在破碎分级时将颗粒尺寸Dv99控制在70μm。
实施例3-2
实施例3-2采用与实施例1-5相似的方法制备硬碳，与实施例1-5不同的是，实施例3-2在破碎分级时将颗粒尺寸Dv99控制在21μm。
实施例4钠离子电池的制备
1、硬碳材料的制备
实施例4-1采用与实施例1-1相似的方法制备硬碳，与实施例1-1不同的是，实施例4-1调整了二次煅烧温度为1400℃。
2、负极极片的制备
将上述制备得到的硬碳、与丁苯橡胶(SBR)和羧甲基纤维素钠(CMC)按照重量比97:2:1在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料，其中负极浆料的固含量为40wt％。将此浆料涂覆于负极集流体(铝箔)上，在85℃下烘干，然后经过冷压、裁片、分切后，在120℃的真空条件下干燥12小时，得到负极极片。
3、正极极片的制备
使用铜镍铁锰氧化物(NaCu1/9Ni2/9Fe1/3Mn1/3O2)作为钠离子电池的正极活性物质。
将正极活性物质(NaCu1/9Ni2/9Fe1/3Mn1/3O2)、导电剂Super P和粘结剂聚偏二氟乙烯(PVDF)按重量比97:1.4:1.6在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料，其中正极浆料的固含量为72wt％。将此浆料涂覆于正极集流体铝箔上，在85℃下烘干，然后经过冷压、裁片、分切后，在85℃的真空条件下干燥4小时，得到正极极片。
4、电解液的制备
在干燥的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)按照质量比为EC:DEC＝50:50进行混合，接着加入2％(体积比)的氟代碳酸乙烯酯，溶解并充分搅拌后加入钠盐NaPF6，混合均匀后获得电解液，其中NaPF6的浓度为1mol/L。
5、隔离膜的制备
以表面涂有Al2O3的9μm厚的聚乙烯(PE)多孔聚合物薄膜作为隔离膜，孔隙率为35％。
6、钠离子全电池的制备
全电池制备：将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片之间起到隔离的作用，然后卷绕、焊接极耳后、置于外包装箔铝塑膜中，注入电解液，经过真空封装、静置、化成、整形、容量测试等工序，获得软包全电池。
实施例4-2
实施例4-2采用与实施例4-1相似的方法制备钠离子全电池，与实施例4-1不同的是，实施例4-2采用与实施例1-5相似的方法制备硬碳，且实施例4-2调整了二次煅烧温度为1400℃。
实施例4-3
实施例4-3采用与实施例4-1相似的方法制备钠离子全电池，与实施例4-1不同的是，实施例4-3采用与实施例1-6相似的方法制备硬碳，且实施例4-3调整了二次煅烧温度为1400℃。
实施例4-4
实施例4-4采用与实施例4-1相似的方法制备钠离子全电池，与实施例4-1不同的是，实施例4-4采用与实施例1-7相似的方法制备硬碳，且实施例4-4调整了二次煅烧温度为1400℃。
对比例4-1
对比例4-1采用与实施例4-1相似的方法制备钠离子全电池，与实施例4-1不同的是，对比例4-1采用与对比例1-1相似的方法制备硬碳，且对比例4-1调整了二次煅烧温度为1400℃。
测试部分：
1、扣式电池充放电曲线测试方法：
扣式电池制备：扣式电池以金属锂或金属钠为对电极，将直径18mm厚度0.6mm的锂/钠片与隔离膜及硬碳电极按顺序组装叠在一起，并加入电解液，装入正负极扣式不锈钢壳中封装，获得扣式电池。
在25℃的环境中，将组装后的扣式电池静置5h后进行充放电测试，测试流程为，以0.1mA/cm2的电流密度恒流放电至0V，然后以0V恒压放电至电流降至12uA/cm2；放电(嵌锂/钠)过程结束；搁置5min后转入充电(脱锂/钠)测试，测试流程为：以0.1mA/cm2的 电流密度恒流充电至2V。
分别记录首次放电和首次充电的克容量，首次库伦效率＝首次充电容量/首次放电容量*100％；
分别记录充放电过程的克容量和电压，统计脱锂/钠过程各电压区间内的克容量分布。例如在首次脱锂曲线中，分别记录0至0.15V及0.15V至0.8V的容量；在首次脱钠曲线中，分别记录0至0.15V及0.15V至1V的容量；
2、能量密度ED的测试方法
在25℃的环境中，将锂离子电池或钠离子电池以0.2C恒流充电至电压4.48V或3.95V，然后恒压充电；以0.2C恒流放电至电压2V，此记为一个循环，并记录首次循环的放电容量，和放电能量；放电能量除以放电容量可得到平均放电电压；并测试电池在50％SOC下的长宽高，获得电池的体积；因此：
能量密度ED＝放电容量×平均放电电压/电芯体积。
3.Raman拉曼测试
将包含硬碳材料的极片用离子抛光的方法切出截面，然后将截面置于拉曼光谱的测试台上，聚焦后测试。测试时选择200um*500um的范围，在该范围内等间距地测试出200个点以上，每个点的测试范围均在1000cm-1至2000cm-1之间；记在1320cm-1至1370cm-1之间出现的峰为D峰，在1570cm-1至1620cm-1之间出现的峰为G峰，统计每个点的ID/IG的强度比，然后计算出多个点的平均值作为最终的ID/IG的强度比。
4.XRD测试
将硬碳材料进行粉末XRD测试，测试扫描范围为2倍散射角10degree至60degree。对获得的扫描曲线进行整理，记2倍散射角位于15°至30°范围内出现的峰(半峰宽大于3degree)为峰A，获取峰A峰值的2倍散射角。
5.元素分析
Zn元素以电感耦合等离子体发射光谱仪消解测试；N/S/H/C等元素以元素分析仪测试，将硬碳材料在氧气中充分燃烧后测试气氛含量，获得元素比例及含量；P/B/Se等元素通过XPS定量获得。
6.Dv50、Dv99测试
本申请使用马尔文粒度测试仪对硬碳颗粒粒径进行测量：将硬碳颗粒材料分散在分散剂(乙醇)中，超声30分钟后，将样品加入到马尔文粒度测试仪内，开始测试。所述硬碳颗粒在体积基准的粒度分布中，从小粒径侧起、达到体积累积50％的粒径即为所述硬碳颗粒的Dv50，即平均粒径；同时所述硬碳颗粒在体积基准的粒度分布中，从小粒径侧起、达到体积累积99％的粒径即为所述硬碳颗粒的Dv99。
测试结果
测试结果如表1至表4所示：
表1
从表1可以看出，相比于对比例1-1，对比例1-2加入锌盐后，样品的可逆容量得到快速增加，而容量增加主要增加在0V至0.15V段，说明锌盐的加入有益于低电压平台段的容量提升，这归因于孔容积的增加提升了低电压平台段的容量；
相比于对比例1-1，对比例1-3加入了杂原子N元素，N元素可增加样品的缺陷浓度，因此提升了斜线段0.15V至0.8V的容量；同时，N元素还可增加样品的亲锂润湿性，使得低电压平台段的容量得到提升。
相比于对比例，实施例1-1至实施例1-8(如图1所示，图1是实施例1-5的锂离子电池的充放电曲线示意图)加入了锌元素和杂原子N元素，锌元素有利于低电压平台段的容量提升，氮元素有利于提升斜线段0.15V至0.8V的容量；同时，N元素还可增加样品的亲锂润湿性，使得低电压平台段的容量进一步显著提升；硬碳的低电压平台阶段容量更高，总容量及首圈库伦效率增加，使得其能量密度ED相比对比例1和2大幅提升。而对于扣式电池而言，其电压平台高，使得其在全电池中电压输出低，拉低了其能量密度；因此，提升扣式电池中低平台0V至0.15V段的克容量是提升能量密度ED的关键所在。
表2
从表2可以看出，实施例2-1至实施例2-4将N元素替换为其他无机杂原子，仍然可增加样品的亲锂润湿性，使得低平台段的容量进一步显著提升。
表3
从表3可以看出，实施例1-5、实施例3-1和实施例3-2制备的硬碳材料的XRD衍射图谱中，002峰2倍衍射峰在21°左右，说明硬碳材料的面间距较大，利于锂离子在层间传输。
实施例1-5、实施例3-1和实施例3-2还说明了，颗粒尺寸对样品具有轻微影响，颗粒较大时扩散距离较长，不利于克容量的充分发挥，颗粒较小时比表面积BET较大，首次库伦效率较低，所以应将颗粒尺寸控制在合适范围之内。
表4
从表4可以看出，在钠离子电池中，相比于对比例4-1,加入锌盐及杂原子N可有效提升样品的低平台区0至0.15V容量，使得0至0.15V容量/0.15V至1V容量数值增加，有利于降低负极极片的平均电位，增加全电池的平均输出电位，从而提升能量密度。另外，由于0至0.15V容量显著增加，使得总可逆容量显著增加，也将提升能量密度。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (13)

  1. 一种硬碳材料，包括多孔骨架以及第一元素和锌元素，所述第一元素包括氮元素、硫元素、硼元素、磷元素和硒元素中的一种或多种；
    所述第一元素相对于所述硬碳材料总质量的含量记为A1wt％；
    所述锌元素相对于所述硬碳材料总质量的含量记为A2wt％，
    其中，所述硬碳材料满足：1.5≤A1/A2≤5。
  2. 根据权利要求1所述的硬碳材料，其中，所述第一元素包括氮元素，2≤A1/A2≤4.5；和/或
    所述第一元素包括氮元素，所述氮元素基于所述硬碳材料总质量的含量记为W1wt％，2≤W1≤5。
  3. 根据权利要求1或2所述的硬碳材料，其中，所述第一元素包括硫元素、硼元素、磷元素和硒元素中的一种或多种，2≤A1/A2≤4；和/或
    所述第一元素包括硫元素、硼元素、磷元素和硒元素中的一种或多种，所述第一元素基于所述硬碳材料总质量的含量记为W2wt％，2.5≤W2≤9。
  4. 根据权利要求1至3中任一项所述的硬碳材料，其中，所述锌元素相对于所述硬碳材料总质量的含量记为A2wt％，0.6≤A2≤1.2。
  5. 根据权利要求1至4中任一项所述的硬碳材料，其中，所述硬碳材料以锂金属为对电极，在0至2.5V vs Li+/Li范围内测试得到的充放电曲线中，
    0(vs Li+/Li)至0.15V(vs Li+/Li)的克容量记为C11mAh/g；
    0.15V(vs Li+/Li)至0.8V(vs Li+/Li)的克容量记为C12mAh/g，
    所述硬碳材料满足：1.6≤C11/C12≤2.1；
    可选地，250≤C11≤350。
  6. 根据权利要求1至5中任一项所述的硬碳材料，其中，所述硬碳材料以钠金属为对电极，在0至2.5V vs Na+/Na范围内测试得到的充放电曲线中，
    0(vs Na+/Na)至0.15V(vs Na+/Na)的克容量记为C21mAh/g；
    0.15V(vs Na+/Na)至1.00V(vs Na+/Na)的克容量记为C22mAh/g，
    所述硬碳材料满足：3.55≤C21/C22≤3.95；
    可选地，300≤C21≤340。
  7. 根据权利要求1至6中任一项所述的硬碳材料，其中，
    所述硬碳材料的X射线衍射图谱中，在2倍散射角位于15°至30°范围内存在衍射峰，所述衍射峰的2倍散射角<24°；和/或
    所述硬碳材料在200um*500um扫面范围内的拉曼谱图中，在1320cm-1至1370cm-1范围内存在特征峰D，在1570cm-1至1620cm-1范围内存在特征峰G，所述特征峰D的峰强为ID，所述特征峰G的峰强为IG，0.5＜ID/IG≤1.5。
  8. 根据权利要求1至7中任一项所述的硬碳材料，其中，所述硬碳材料还满足以下条件(1)和/或条件(2)：
    (1)所述硬碳材料的体积分布粒径Dv50μm满足：3≤Dv50≤15；
    (2)所述硬碳材料的体积分布粒径Dv99μm满足：10≤Dv99≤45。
  9. 根据权利要求1至8中任一项所述的硬碳材料，其中，所述硬碳材料还包括包覆于所述多孔骨架外的碳层。
  10. 一种制备硬碳材料的方法，包括：
    将含碳的前驱体材料、含锌元素的致孔剂和含第一元素的第一材料均匀混合为混合体系；
    热处理所述混合体系，以使所述前驱体材料碳化，在碳化过程中所述致孔剂挥发并刻蚀所述前驱体材料形成多孔骨架，
    其中，所述第一元素包括氮元素、硫元素、硼元素、磷元素和硒元素中的一种或多种；
    所述第一元素相对于所述硬碳材料总质量的含量记为A1wt％；
    所述锌元素相对于所述硬碳材料总质量的含量记为A2wt％，
    其中，所述硬碳材料满足：1.5≤A1/A2≤5。
  11. 根据权利要求10所述的方法，其中，
    所述热处理包括第一热处理和第二热处理，所述第一热处理的温度小于所述第二热处理的温度，和/或
    在所述多孔骨架外包覆碳层。
  12. 一种电化学装置，包括负极极片，所述负极极片包括如权利要求1至9中任一项所述的硬碳材料或如权利要求10至11中任一项所述的方法制备得到的硬碳材料。
  13. 一种电子装置，包括如权利要求12所述的电化学装置。
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