WO2025036070A1 - 一种负极活性材料、二次电池和电子设备 - Google Patents

一种负极活性材料、二次电池和电子设备 Download PDF

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WO2025036070A1
WO2025036070A1 PCT/CN2024/105936 CN2024105936W WO2025036070A1 WO 2025036070 A1 WO2025036070 A1 WO 2025036070A1 CN 2024105936 W CN2024105936 W CN 2024105936W WO 2025036070 A1 WO2025036070 A1 WO 2025036070A1
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negative electrode
active material
electrode active
present application
secondary battery
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French (fr)
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李达禄
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—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
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemical technology, and in particular to a negative electrode active material, a secondary battery and an electronic device.
  • energy storage As a supporting industry and key driver of energy structure adjustment, the energy storage industry has broad application prospects in different fields such as traditional power generation, transmission and distribution, power demand side, auxiliary services, and new energy.
  • energy storage mainly relies on secondary batteries, such as lithium-ion batteries, which are widely used in industrial production and people's daily life because of their outstanding advantages such as high energy density, low self-discharge rate, long cycle life, and stable discharge performance.
  • the negative electrode active material in the negative electrode plate of a lithium-ion battery is one of the key factors affecting the performance of the lithium-ion battery.
  • the cycle performance of traditional artificial graphite as a negative electrode active material needs to be improved.
  • natural graphite which is low-cost and has huge reserves, has problems of cycle expansion and low cycle capacity retention rate, which also affects the cycle performance of lithium-ion batteries.
  • the purpose of this application is to provide a negative electrode active material, a secondary battery and an electronic device to improve the cycle performance, expansion performance and rate performance of the secondary battery.
  • the specific technical solution is as follows:
  • the obtained negative electrode active material has a suitable particle size distribution and a narrow particle size distribution, which can reduce the tortuosity of the diffusion of active ions in the pole piece, and at the same time, the isotropic performance of the negative electrode active material is strong. Applying the above negative electrode active material to the negative pole piece of a secondary battery can improve the cycle performance, expansion performance, and rate performance of the secondary battery.
  • the negative electrode active material not only has a narrow particle size distribution and strong isotropic performance, but also can take into account the diffusion path of active ions and the deformation of the negative electrode sheet during the charge and discharge process of the secondary battery, further improving the cycle performance and expansion performance of the secondary battery.
  • the negative electrode active material satisfies at least one of the following conditions: (1) Dn10 is 2 ⁇ m to 4 ⁇ m; (2) Dv90 is 14 ⁇ m to 30 ⁇ m; (3) Dv50 is 8 ⁇ m to 15 ⁇ m; (4) 2 ⁇ I ⁇ 4.
  • the negative electrode active material satisfies at least one of the above conditions (1) to (4), and its application to the negative electrode sheet of a secondary battery can improve the cycle performance, expansion performance and rate performance of the secondary battery.
  • the sphericity C and D/C+1 of the negative electrode active material are within the above ranges, the negative electrode active material has a suitable sphericity and particle size distribution, and the particle size distribution is narrow, the sphericity and particle size match each other, which can further improve the cycle performance and expansion performance of the secondary battery, and the secondary battery has a higher energy density and good rate performance.
  • the negative electrode active material satisfies at least one of the following conditions: (a) the tap density TD of the negative electrode active material is 0.8 g/cm 3 to 1.2 g/cm 3 ; (b) the graphitization degree G of the negative electrode active material is 90% to 96%; (c) the gram capacity W of the negative electrode active material is 344 mAh/g to 358 mAh/g.
  • the negative electrode active material satisfies at least one of the above conditions (a) to (c), and its application to the negative electrode sheet of the secondary battery can improve the cycle performance, expansion performance and rate performance of the secondary battery.
  • the peak intensity ratio of the d peak to the g peak Id/Ig is 0.1 to 0.3.
  • the value of Id/Ig of the negative electrode active material is within the above range, the negative electrode active material has a suitable defect degree and particle size distribution and a narrow particle size distribution, which can further improve the cycle performance and expansion performance of the secondary battery, and has good rate performance.
  • graphite includes natural graphite and artificial graphite. Natural graphite can provide high gram capacity and better kinetics, and artificial graphite can provide good cycle performance. When the two types of graphite are used, the cycle performance and rate performance of the secondary battery can be further improved.
  • the second aspect of the present application provides a secondary battery, which includes a positive electrode plate, a negative electrode plate and an electrolyte, the negative electrode plate includes a negative electrode collector and a negative electrode material layer arranged on at least one surface of the negative electrode collector, and the negative electrode material layer includes the negative electrode active material in any of the above embodiments.
  • the negative electrode sheet satisfies at least one of the following conditions: (i) the porosity of the negative electrode sheet is 25% to 40%; (ii) the OI value of the negative electrode sheet is 8 to 15.
  • the negative electrode sheet satisfies at least one of the above conditions (i) or (ii), and is applied to a secondary battery, which is beneficial to improving the cycle performance and expansion performance of the secondary battery.
  • a third aspect of the present application provides an electronic device, which includes the secondary battery in any one of the above embodiments.
  • the negative electrode active material provided by the present application can improve the cycle performance of the secondary battery.
  • FIG1 is an electron microscope photograph of the negative electrode active material in Example 1-1;
  • FIG2 is an X-ray diffraction pattern of the negative electrode active material in Examples 1-3;
  • FIG3 is an X-ray diffraction pattern of the negative electrode sheet in Example 1-3;
  • FIG4 is a graph showing the change in cycle capacity retention rate of the lithium ion batteries in Example 1-1 and Comparative Example 1-1;
  • FIG5 is a graph showing the thickness expansion rate variation of the lithium ion batteries in Example 1-1 and Comparative Example 1-1;
  • FIG. 6 is a Raman spectrum of the negative electrode active material in Example 1-3.
  • the present application is explained by taking a lithium-ion battery as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium-ion battery.
  • the value of D can be 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, or a range consisting of any two of the values therein.
  • the Dn10 of the negative electrode active material is 1 ⁇ m to 5 ⁇ m; in some embodiments of the present application, the Dn10 of the negative electrode active material is 2 ⁇ m to 4 ⁇ m.
  • the Dn10 of the negative electrode active material can be 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, or a range consisting of any two of the values therein.
  • the peak intensity ratio of the characteristic peak C004 and the characteristic peak C110 is 1; the negative electrode active material satisfies: 2 ⁇ I/D ⁇ 4.
  • 2.4 ⁇ I/D ⁇ 3.5 the value of I/D can be 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, or a range consisting of any two of the values.
  • the D value is too small, for example, less than 0.8, it means that the particle size distribution range of the negative electrode active material is too narrow, and the fine powder content is significantly reduced, which will make the conduction of electrons between particles worse, affect the conductive network, and thus affect the cycle performance and rate performance of the secondary battery;
  • the D value is too large, for example, greater than 1.5, it means that the particle size distribution range of the negative electrode active material is relatively wide, which will make the diffusion path of active ions such as lithium ions in the negative electrode sheet containing the above negative electrode active material longer, and the diffusion impedance of active ions increases, affecting the cycle performance and rate performance of the secondary battery.
  • I/D within the above range indicates that the particle size distribution of the negative electrode active material is moderate, which can reduce the tortuosity of the diffusion of active ions in the sheet, and the isotropic performance of the negative electrode active material is relatively strong, which is conducive to improving the cycle performance and expansion performance of the secondary battery.
  • the obtained negative electrode active material has a suitable particle size distribution and a narrow particle size distribution, which can reduce the tortuosity of the diffusion of active ions in the pole piece.
  • the isotropic performance of the negative electrode active material is strong. Applying the above negative electrode active material to the negative electrode pole piece of the secondary battery can improve the cycle performance, expansion performance and rate performance of the secondary battery.
  • active ions refer to active ions that participate in the charge and discharge electrochemical reaction during the charge and discharge process of the secondary battery, which can be lithium ions or sodium ions.
  • the negative electrode active material not only has a narrow particle size distribution and strong isotropic performance, but also can take into account the diffusion path of active ions and the deformation of the negative electrode sheet during the charge and discharge process of the secondary battery, further improving the cycle performance and expansion performance of the secondary battery.
  • the Dv90 of the negative electrode active material is 14 ⁇ m to 30 ⁇ m.
  • the Dv90 of the negative electrode active material can be 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, 21 ⁇ m, 22 ⁇ m, 23 ⁇ m, 24 ⁇ m, 25 ⁇ m, 26 ⁇ m, 27 ⁇ m, 28 ⁇ m, 29 ⁇ m, 30 ⁇ m or a range consisting of any two of the values.
  • the Dv90 of the negative electrode active material is within the above-mentioned range, indicating that the negative electrode active material has a suitable particle size and particle size distribution and a narrow particle size distribution, which can reduce the tortuosity of the diffusion of active ions in the pole piece, and at the same time, the isotropic performance of the negative electrode active material is strong. Applying the above-mentioned negative electrode active material to the negative electrode pole piece of the secondary battery can improve the cycle performance, expansion performance and rate performance of the secondary battery.
  • the Dv50 of the negative electrode active material is 8 ⁇ m to 15 ⁇ m.
  • the Dv50 of the negative electrode active material can be 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, or a range consisting of any two of these values.
  • the negative electrode active material meets the above ranges of D, Dn10, and I/D
  • the negative electrode The Dv50 of the active material is within the above range, which indicates that the negative electrode active material has a suitable particle size and particle size distribution and a narrow particle size distribution, which can reduce the tortuosity of the diffusion of active ions in the electrode sheet.
  • the isotropic properties of the negative electrode active material are strong. Applying the above negative electrode active material to the negative electrode sheet of a secondary battery can improve the cycle performance, expansion performance and rate performance of the secondary battery.
  • the value of C can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range consisting of any two values therein;
  • the value of D/C+1 can be 1.8, 2, 2.2, 2.5, 2.7, 3, 3.3, 3.5, 3.8, 4, or a range consisting of any two values therein.
  • the negative electrode active material has a suitable sphericity, which is beneficial to the diffusion of active ions, as well as the embedding and extraction of active ions, and can further improve the cycle performance of the secondary battery; moreover, the negative electrode active material particles can be closely stacked, and the negative electrode sheet has a high compaction density, which is conducive to obtaining a secondary battery with a higher energy density.
  • the negative electrode active material meets the above ranges of D, Dn10, and I/D, the sphericity C and D/C+1 of the negative electrode active material are within the above range, the negative electrode active material has a suitable sphericity and particle size distribution, and the particle size distribution is narrow, and the sphericity and particle size match each other, which can further improve the cycle performance and expansion performance of the secondary battery, and at the same time, the secondary battery has a high energy density and good rate performance.
  • the tap density TD of the negative electrode active material is 0.8 g/cm 3 to 1.2 g/cm 3.
  • the tap density TD of the negative electrode active material can be 0.8 g/cm 3 , 0.9 g/cm 3 , 0.95 g/cm 3 , 1 g/cm 3 , 1.05 g/cm 3 , 1.1 g/cm 3 , 1.15 g/cm 3 , 1.2 g/cm 3 , or a range consisting of any two of the values.
  • the tap density of the negative electrode active material is within the above range, less dispersant is required during the slurrying process, the prepared slurry is more stable, less prone to sedimentation, and the particles in the negative electrode sheet can be in close contact, thereby improving the electronic conductivity and active ion diffusion rate, and improving the cycle performance of the secondary battery.
  • the negative electrode active material satisfies the above-mentioned ranges of D, Dn10, and I/D
  • the TD of the negative electrode active material is within the above-mentioned range
  • the negative electrode active material has a suitable tap density and particle size distribution and the particle size distribution is narrow, which can improve the cycle performance, expansion performance, and rate performance of the secondary battery, while improving the processing performance of the secondary battery.
  • the graphitization degree G of the negative electrode active material is 90% to 96%.
  • the graphitization degree G of the negative electrode active material can be 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96% or a range consisting of any two of the values.
  • the graphitization degree G is within the above range, indicating that the graphitization degree of the negative electrode active material is low, which is beneficial to improving the cycle performance and expansion performance of the secondary battery.
  • the degree of graphitization of the negative electrode active material is within the above-mentioned range, the negative electrode active material has a suitable degree of graphitization and particle size distribution, and the particle size distribution is narrow, which can further improve the cycle performance and expansion performance of the secondary battery, and at the same time has good rate performance.
  • the gram capacity W of the negative electrode active material is 344mAh/g to 358mAh/g.
  • the gram capacity W of the negative electrode active material can be 344mAh/g, 345mAh/g, 346mAh/g, 347mAh/g, 348mAh/g, 349mAh/g, 350mAh/g, 351mAh/g, 352mAh/g, 353mAh/g, 354mAh/g, 355mAh/g, 356mAh/g, 357mAh/g, 358mAh/g or a range composed of any two values.
  • the gram capacity W of the negative electrode active material is within the above range, indicating that it has a higher gram capacity.
  • the negative electrode active material meets the above-mentioned D, Dn10, I/D range, the negative electrode active material has a higher gram capacity, suitable and particle size distribution and a narrow particle size distribution, which can improve the cycle performance and expansion performance of the secondary battery, and has good rate performance and a higher energy density.
  • the peak intensity ratio of the d peak and the g peak Id/Ig is 0.1 to 0.3.
  • the value of Id/Ig can be 0.1, 0.12, 0.14, 0.15, 0.16, 0.18, 0.2, 0.22, 0.24, 0.25, 0.26, 0.28, 0.3 or a range consisting of any two of the values.
  • the value of Id/Ig is within the above range, indicating that the surface of the negative electrode active material has a suitable degree of defect, which is beneficial to improve the cycle performance and expansion performance.
  • the negative electrode active material meets the above ranges of D, Dn10, and I/D, its Id/Ig value is within the above range, has a suitable degree of defect and particle size distribution, and has a narrow particle size distribution, which can further improve the cycle performance and expansion performance of the secondary battery, and has good rate performance.
  • At least one of the characteristics I, Dv90, sphericity C, tap density TD, degree of graphitization G, gram capacity W, and Id/Ig of the above-mentioned negative electrode active materials can be combined with the characteristics "D, Dn10, I/D", and the embodiments covered by the above combinations are all within the protection scope of the present application.
  • graphite includes natural graphite and artificial graphite.
  • Natural graphite refers to graphite made of flakes produced from natural ores. The origin, properties, and types of natural graphite used in the embodiments of the present application are not particularly limited.
  • Artificial graphite refers to graphite that is prepared by artificial methods and is close to complete graphite crystals. Artificial graphite can be obtained by graphitization, coating carbonization processes, and other processes of precursor raw material coke such as petroleum coke, coal coke, asphalt coke, etc.
  • the two types of graphite can be distinguished by observing the cross-sectional morphology of the negative electrode sheet along the thickness direction or observing the negative electrode active material powder by scanning electron microscopy.
  • Graphite particles with irregular shapes and flat shapes are artificial graphite particles, and graphite particles with rounded surfaces and higher sphericity are natural graphite particles.
  • the types of precursors, graphitization methods, carbonization methods, and other processes of artificial graphite used in the embodiments of the present application are not particularly limited.
  • the preparation method of the negative electrode active material may include but is not limited to the following preparation steps:
  • S1 Provide natural graphite raw materials with a particle size of 6 ⁇ m to 23 ⁇ m and a purity of more than 95%;
  • the present application has no particular restrictions on the raw coke in S2, as long as the purpose of the present application can be achieved.
  • the raw coke may include but is not limited to at least one of petroleum coke, asphalt coke, and coal coke.
  • the high coking value asphalt in S3 refers to asphalt with a coking value of 30% to 80%.
  • the present application has no particular restrictions on the classification and shaping in S7, and the screening and demagnetization in S8, which are conventional steps known in the art.
  • the Dn10, Dv50, and Dv90 of the negative electrode active material can be regulated by regulating the parameters of grading, shaping, and sieving, thereby regulating the value of D.
  • the sphericity C and tap density of the negative electrode active material can also be regulated by regulating the parameters of grading, shaping, and sieving.
  • the value of I can be regulated by regulating the mass proportion of the binder in the mixed raw material. For example, the smaller the mass proportion of the binder in the mixed raw material, the greater the value of I; the greater the mass proportion of the binder in the mixed raw material, the smaller the value of I.
  • the degree of graphitization G can be regulated by regulating the temperature and time of the low-temperature graphitization treatment.
  • the gram capacity W can be regulated by regulating the proportion of natural graphite and artificial graphite precursors in this application.
  • the value of Id/Ig can be controlled by regulating the temperature of the low-temperature graphitization treatment or the mass proportion of the binder in the mixed raw materials.
  • the lower the temperature of the low-temperature graphitization treatment or the higher the mass proportion of the binder in the mixed raw materials the greater the value of Id/Ig; the higher the temperature of the low-temperature graphitization treatment or the lower the mass proportion of the binder in the mixed raw materials, the smaller the value of Id/Ig.
  • the second aspect of the present application provides a secondary battery, which includes a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the negative electrode sheet
  • the electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode material layer includes the negative electrode active material in any of the above embodiments.
  • the secondary battery of the present application has good cycle performance, expansion performance and rate performance.
  • the above-mentioned "negative electrode material layer disposed on at least one surface of the negative electrode current collector” means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface” here can be the entire area of the surface of the negative electrode current collector, or it can be a partial area of the surface of the negative electrode current collector. This application is not particularly limited, as long as the purpose of this application can be achieved.
  • the porosity of the negative electrode sheet is 25% to 40%.
  • the porosity of the negative electrode sheet can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or a range consisting of any two of these values. This indicates that the negative electrode sheet has a higher porosity, which is beneficial to the transmission and diffusion of active ions, thereby improving the cycle performance, expansion performance, and rate performance of the secondary battery.
  • the OI value of the negative electrode plate is 8 to 15.
  • the OI value of the negative electrode plate can be 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two of these values.
  • the negative electrode plate with an OI value within the above range has good ion diffusion performance. Applying it to a secondary battery is beneficial to improving the cycle performance and expansion performance of the secondary battery.
  • the negative electrode active material may also include other negative electrode active materials known in the prior art.
  • other negative electrode active materials may include but are not limited to at least one of mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon materials, silicon-oxygen materials, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO 2 , lithiated TiO 2 -Li 4 Ti 5 O 12 with spinel structure, or Li-Al alloys.
  • the present application does not limit the content of other negative electrode active materials, as long as the purpose of the present application can be achieved.
  • the negative electrode current collector may include copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or a polymer substrate covered with a conductive metal, etc.
  • the conductive metal includes but is not limited to copper, nickel or titanium
  • the material of the polymer substrate includes but is not limited to at least one of polyethylene, polypropylene, ethylene propylene copolymer, polyethylene terephthalate, polyethylene naphthalate or poly(p-phenylene terephthalamide).
  • the thickness of the negative electrode current collector and the negative electrode material layer there is no particular restriction on the thickness of the negative electrode current collector and the negative electrode material layer, as long as the purpose of the present application can be achieved.
  • the thickness of the negative electrode current collector is 4 ⁇ m to 12 ⁇ m
  • the thickness of the single-sided negative electrode material layer is 50 ⁇ m to 200 ⁇ m.
  • the negative electrode material layer in the present application may also include at least one of a conductive agent, a binder or a thickener.
  • a conductive agent may include but is not limited to at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, Ketjen black, graphene, metal materials or conductive polymers.
  • the above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
  • the above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and/or nano-carbon fibers.
  • the above-mentioned metal materials may include but are not limited to metal powders and/or metal fibers, and specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver.
  • the above-mentioned conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole.
  • the binder may include but is not limited to at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber or polyvinylidene fluoride.
  • the thickener may include but is not limited to at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.
  • the present application has no particular restriction on the mass ratio of the negative electrode active material, the conductive agent, the binder, and the thickener in the negative electrode material layer. Those skilled in the art can select the ratio according to actual needs as long as the purpose of the present application can be achieved.
  • the negative electrode plate may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer.
  • the composition of the conductive layer is not particularly limited, and it can be a conductive layer commonly used in the art.
  • the conductive layer includes a conductive agent and a binder.
  • the present application has no particular restrictions on the conductive agent and the binder in the conductive layer, for example, it can be at least one of the above conductive agent and the above binder.
  • the positive electrode plate includes a positive electrode collector and a positive electrode material layer arranged on at least one surface of the positive electrode collector.
  • the above-mentioned "positive electrode material layer arranged on at least one surface of the positive electrode collector” means that the positive electrode material layer can be arranged on one surface of the positive electrode collector along the thickness direction of itself, or it can be arranged on two surfaces of the positive electrode collector along the thickness direction of itself.
  • the "surface” here can be the entire area of the surface of the positive electrode collector, or it can be a partial area of the surface of the positive electrode collector.
  • the present application has no special restrictions, as long as the purpose of the present application can be achieved.
  • the positive electrode current collector may include a metal foil or a composite current collector, etc.
  • the metal foil may be an aluminum foil.
  • the composite current collector may include a polymer material base layer and a metal material layer located on at least one surface of the polymer material base layer.
  • the material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver or silver alloy.
  • the polymer material base layer may include at least one of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene or polyethylene.
  • the positive electrode material layer of the present application contains positive electrode active material.
  • the positive electrode active material includes lithium cobalt oxide, lithium nickel cobalt manganese oxide (N 0.95 C 0.05 M 0.05 , NCM811, NCM622, NCM523, NCM111), at least one of lithium nickel manganese aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel lithium manganese oxide, spinel lithium nickel manganese oxide or lithium titanate.
  • lithium cobalt oxide lithium nickel cobalt manganese oxide (N 0.95 C 0.05 M 0.05 , NCM811, NCM622, NCM523, NCM111), at least one of lithium nickel manganese aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate,
  • the present application has no particular restrictions on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of the present application can be achieved.
  • the thickness of the positive electrode current collector is 5 ⁇ m to 20 ⁇ m.
  • the thickness of the single-sided positive electrode material layer is 50 ⁇ m to 300 ⁇ m.
  • the positive electrode material layer of the present application may also include the above-mentioned binder and the above-mentioned conductive agent.
  • the present application has no particular restrictions on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved.
  • the electrolyte includes a lithium salt and an organic solvent.
  • the lithium salt may include, but is not limited to, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ), lithium trifluoromethanesulfonyl imide (LiTFSI), lithium bis(fluorosulfonyl) imide (LiFSI), lithium bis(oxalate borate) (LiBOB) or lithium difluorooxalate borate (LiDFOB).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiPO 2 F 2 lithium difluorophosphate
  • LiTFSI lithium trifluoromethanesulfonyl imide
  • LiFSI lithium bis(fluorosulfonyl) imide
  • LiBOB lithium bis(oxalate borate)
  • the present application has no particular restrictions on the above-mentioned organic solvent, as long as the purpose of the present application can be achieved, for example, it may include, but is not limited to, at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents.
  • the above-mentioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds or cyclic carbonate compounds.
  • the above-mentioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate or methyl ethyl carbonate.
  • the above-mentioned cyclic carbonate compound may include but is not limited to at least one of ethylene carbonate, propylene carbonate, butylene carbonate or vinyl ethylene carbonate.
  • the above-mentioned carboxylate compound may include but is not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decalactone, valerolactone or caprolactone.
  • the above-mentioned ether compound may include but is not limited to at least one of ethylene glycol dimethyl ether, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran.
  • the above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate.
  • the electrolyte may also include additives, and the additives may include but are not limited to at least one of fluoroethylene carbonate, 1,3-propane sultone or adiponitrile.
  • the secondary battery of the present application may also include a diaphragm to separate the positive electrode plate and the negative electrode plate, prevent the internal short circuit of the secondary battery, allow the electrolyte ions to pass freely, and do not affect the electrochemical charge and discharge process.
  • the present application has no special restrictions on the diaphragm, as long as it can achieve the purpose of the present application.
  • the material of the diaphragm can include but is not limited to polyethylene, At least one of polyolefin membranes mainly composed of polypropylene and polytetrafluoroethylene, polyester membranes (such as polyethylene terephthalate (PET) membranes), cellulose membranes, polyimide membranes, polyamide membranes, spandex or aramid membranes, etc.
  • the types of the membranes may include, but are not limited to, at least one of woven membranes, nonwoven membranes (nonwoven fabrics), microporous membranes, composite membranes, rolled membranes or spun membranes, etc.
  • the membrane of the present application may have a porous structure, and the porous layer is arranged on at least one surface of the membrane, and the porous layer includes inorganic particles and a binder, and the inorganic particles may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate.
  • the binder may include at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinyl pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the present application does not particularly limit the size of the pore size of the porous structure, as long as the purpose of the present application can be achieved, for example, the size of the pore size can be 0.01 ⁇ m to 1 ⁇ m.
  • the thickness of the diaphragm is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness can be 3 ⁇ m to 30 ⁇ m.
  • the secondary battery of the present application also includes a packaging bag for containing a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, as well as other components known in the art in the secondary battery, and the present application does not limit the above-mentioned other components.
  • the present application does not specifically limit the packaging bag, and it can be a packaging bag known in the art, as long as it can achieve the purpose of the present application.
  • an aluminum-plastic film packaging bag can be used.
  • the secondary battery of the present application is not particularly limited, and may include any device that undergoes an electrochemical reaction.
  • the secondary battery may include, but is not limited to: a lithium ion battery or a sodium ion battery.
  • the preparation process of the secondary battery of the present application is well known to those skilled in the art, and the present application has no special restrictions.
  • it may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly of a winding structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly of a stacked structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery.
  • overcurrent protection elements, guide plates, etc. may also be placed in the packaging bag as needed to prevent the pressure inside the secondary battery from rising and overcharging and discharging.
  • the third aspect of the present application provides an electronic device, which includes a secondary battery in any of the above embodiments.
  • the electronic device of the present application is not particularly limited, and it can be used for any electronic device known in the prior art.
  • the electronic device can include but is 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, Video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the lithium-ion battery was discharged at a constant current of 1C until the voltage reached 3.0V, then disassembled, the negative electrode sheet was taken out, and it was soaked in dimethyl carbonate (DMC) for 20 minutes, and then rinsed with DMC and acetone in turn. After that, the negative electrode sheet was placed in an oven and baked at 80°C for 12 hours to obtain the treated negative electrode sheet sample.
  • DMC dimethyl carbonate
  • the negative electrode sheet samples in the following porosity test were sampled using the above method.
  • the negative electrode material layer on the negative electrode sheet was scraped off with a scraper, and the powder of the scraped negative electrode material layer was heat treated at 400°C for 4 hours in a tube furnace under argon protection to remove the binder adhering to the surface of the negative electrode active material to obtain a powder sample of the negative electrode active material.
  • the negative electrode active material samples in the following particle size test, sphericity test, X-ray diffraction (XRD) test, tap density, Raman test and scanning electron microscope test were all sampled using the above method.
  • the powder particle size test method refers to GB/T 19077-2016.
  • the specific process is to weigh 1g of the sample and mix it with 20mL of deionized water and a trace amount of dispersant. After placing it in an ultrasonic device for 5 minutes, the solution is poured into the sampling system Hydro 2000SM for testing.
  • the test equipment used is the Mastersizer 3000 produced by Malvern.
  • the particle size measurement is completed by measuring the intensity of the scattered light.
  • the data is then used to analyze and calculate the powder particle size distribution that forms the scattering spectrum.
  • the refractive index of the particles used in the test is 1.8.
  • Dn10 represents the particle size that reaches 10% of the number accumulation from the small particle size in the particle size distribution based on the number.
  • Dv50 represents the particle size that reaches 50% of the volume accumulation from the small particle size in the particle size distribution based on the volume.
  • Dv90 indicates the particle size at which 90% of the volume is accumulated, measured from the smallest particle size in the volume-based particle size distribution.
  • the particle shape image analysis device was used to continuously focus and shoot the particles of the dynamically flowing sample to obtain 50 particle images.
  • the negative electrode piece is scanned to obtain an XRD spectrum, and the peak values of the (004) crystal plane diffraction peak and the (110) crystal plane diffraction peak are obtained by analysis.
  • the ratio of the peak values of the (004) crystal plane diffraction peak and the (110) crystal plane diffraction peak is calculated to obtain the OI value of the negative electrode piece.
  • An X-ray diffractometer (Bruker D8ADVANCE) was used, Cu K ⁇ radiation, voltage 40KV, current 40mA, test angle 52° to 58°, and each step time 0.3s.
  • a silicon standard containing a carbon-silicon standard ratio of C:Si 5:1 (mass ratio) was used as a reference sample for scanning test, and the XRD spectrum of the negative electrode active material powder was processed to obtain the crystal plane spacing d 002 of the (002) peak position of the negative electrode active material, and the graphitization degree G of the negative electrode active material was calculated to be (3.44-d 002 )/(3.44-3.354) ⁇ 100%.
  • the national standard GB/T 5162-2006 "Determination of the tap density of metal powders" test method was adopted.
  • the GeoPyc1365 equipment from McMerritt was used to weigh 50 ⁇ 0.2g of powder sample and test its tap density at a vibration frequency of 250 times/mim.
  • the Raman spectrum of the negative electrode active material is tested by a laser microscopic confocal Raman spectrometer (the instrument model is HR Evolution, the manufacturer is HORIBA, France).
  • the laser wavelength of the Raman spectrometer can be in the range of 532nm to 633nm.
  • the peak that appears between 1300cm -1 and 1400cm -1 is recorded as the d peak, and the peak that appears between 1500cm -1 and 1600cm -1 is recorded as the g peak.
  • La Spec software is used for data processing to obtain the peak intensities of the d peak and g peak of the particles, which are recorded as Id and Ig respectively.
  • the intensity ratio of Id / Ig at each point is counted, and then the average value of 100 points is calculated as the final intensity ratio of Id / Ig .
  • the JSM-6360LV scanning electron microscope and its supporting X-ray energy spectrometer from JEOL were used to analyze the morphology and structure of the negative electrode active material samples, observe the morphological characteristics of the samples and take scanning electron microscope photos.
  • the negative electrode sheet was prepared into a disc with a diameter of 10 cm, and 30 samples were tested for each embodiment or comparative example, and the volume of each sample was about 0.35 cm 3 .
  • the porosity of the negative electrode material layer was tested using an AccuPycII1340 true density meter, and the test gas was helium.
  • the lithium-ion battery is charged to 3.6V at 0.2C constant current, then charged to 0.05C at 3.6V constant voltage, left to stand for 5 minutes, and then discharged to 2.5V at 0.2C rate to obtain 0.2C discharge capacity. Then, it is charged to 3.6V at 0.2C rate constant current, charged to 0.05C at 3.6V constant voltage, left to stand for 30 minutes, and then discharged to 2.5V at 3C rate to obtain 3C discharge capacity.
  • the 3C/0.2C rate performance of the lithium-ion battery 3C discharge capacity/0.2C discharge capacity ⁇ 100%.
  • the lithium-ion battery was placed in a constant temperature box at 25°C ⁇ 1°C for 30 minutes.
  • the cycle process was as follows: charging to 3.6V at 0.5C constant current, then charging to 0.02C at 3.6V constant voltage, and then standing for 15 minutes. Then, it was discharged to 2.5V at 0.5C rate and stood for 30 minutes. This was a charge and discharge cycle process.
  • the thickness H0 and the first cycle discharge capacity C0 of the lithium-ion battery were recorded . After that, the above cycle process was followed for 3000 cycles, and a small rate capacity recovery was performed at the 100th, 200th, 300th, 400th, 500th, every 200 cycles from 501st to 1500th, and every 500 cycles from 1501st to 3000th.
  • the small rate capacity recovery charge and discharge process is as follows: the lithium ion battery was placed in a constant temperature box at 25°C ⁇ 1°C for 30 minutes, and the cycle process was as follows: charging to 3.6V at a constant current of 0.2C, then charging to 0.02C at a constant voltage of 3.6V, and then standing for 15 minutes, and then discharging to 2.5V at a rate of 0.2C, and standing for 30 minutes.
  • the thickness H1 and the cycle discharge capacity C1 of the lithium ion battery at the 3000th cycle were recorded.
  • Thickness expansion ratio after 3000 cycles (H 1 -H 0 )/H 0 ⁇ 100%.
  • the Dn10, Dv50, Dv90, I, sphericity C and tap density TD of the negative electrode active material are shown in Table 1.
  • the negative electrode active material, binder styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) prepared above are mixed in a mass ratio of 97.4:1.5:1.5, and then deionized water is added as a solvent and stirred evenly to prepare a negative electrode slurry with a solid content of 50wt%.
  • the negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6 ⁇ m, and dried at 85°C for 4 hours to obtain a negative electrode sheet with a single-sided coating of a negative electrode material layer with a coating thickness of 80 ⁇ m.
  • the positive electrode active material lithium iron phosphate, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96.3:2.2:1.5, N-methylpyrrolidone (NMP) is added as a solvent and stirred evenly to prepare a positive electrode slurry with a solid content of 75wt%.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 13 ⁇ m, and dried at 85°C to obtain a positive electrode sheet with a single-sided positive electrode material coating and a positive electrode material layer thickness of 130 ⁇ m. Repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. After cold pressing, cutting, and slitting, a positive electrode sheet with a specification of 74mm ⁇ 867mm is obtained.
  • the mass percentage of the lithium salt was 12.5%
  • the mass percentage of the fluoroethylene carbonate was 2%
  • the mass percentage of the 1,3-propane sultone was 2%
  • the balance was the basic solvent.
  • a polyethylene film with a thickness of 7 ⁇ m (provided by Celgard) was used as a separator.
  • the positive electrode sheet, separator and negative electrode sheet prepared above are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then wound to obtain an electrode assembly. After welding the pole ear, the electrode assembly is placed in the aluminum-plastic film.
  • the packaging bag was placed in a vacuum oven at 80°C for 12 hours to remove moisture, and the prepared electrolyte was injected.
  • the lithium-ion battery was obtained through vacuum packaging, standing, formation (temperature 45°C, 0.1C constant current charging, end time 1800s, and then 0.5C constant current charging to 3.6V), degassing, and trimming.
  • Example 1-1 Except for adjusting the parameters according to Table 1, the rest is the same as Example 1-1.
  • Example 1-3 Except for adjusting the parameters according to Table 2, the rest is the same as Example 1-3.
  • Example 1-1 Except for adjusting the parameters according to Table 1, the rest is the same as Example 1-1.
  • Example 1-1 Except that the natural graphite in Example 1-1 is directly used as the negative electrode active material to prepare the negative electrode plate, the rest is the same as Example 1-1.
  • Example 1-1 to Example 1-18 Dn10, Dv50, Dv90, C, and TD of the negative electrode active material are interrelated and influence each other, which in turn affect the value of D, the value of I, the value of I/D, and the value of D/C+1, and the values of the above characteristics are all within the scope of the present application.
  • the porosity and OI value of the obtained negative electrode sheet are also within the scope of the present application.
  • the lithium-ion batteries have a higher cycle capacity retention rate and a lower cycle thickness expansion rate, which means that the lithium-ion batteries have good cycle performance and expansion performance.
  • FIG1 it is an electron microscope photo of the negative electrode active material in Example 1-1. It can be seen from the electron microscope photo that the particle size of the negative electrode active material is relatively uniform, which is conducive to improving the diffusion of lithium ions and electronic conductivity, thereby improving the cycle performance and rate performance of the lithium ion battery.
  • FIG2 is an XRD spectrum of the negative electrode active material in Example 1-3. It can be seen from the figure that the peak area corresponding to the characteristic peak C004 at 54.56° is 3021.82, the peak area corresponding to the characteristic peak C110 at 77.41° is 712.44, and the peak area ratio I of the characteristic peak C004 and the characteristic peak C110 is 4.2.
  • FIG3 is an XRD spectrum of the negative electrode sheet in Example 1-3. It can be seen from the figure that the peak area corresponding to the (004) crystal plane diffraction peak at 54.65° is 2665.10, and the peak area corresponding to the (110) crystal plane diffraction peak at 77.49° is 222.09, so the OI value of the negative electrode sheet is 12.
  • FIG4 and FIG5 are graphs of the cycle retention rate and thickness expansion rate of the lithium ion batteries in Example 1-1 and Comparative Example 1-1 as a function of the number of cycles. It can be seen from the figure that the cycle capacity retention rate of Example 1-1 is always higher than that of Comparative Example 1-1, and the thickness expansion rate is always lower than that of Comparative Example 1-1.
  • the porosity and OI value of the obtained negative electrode sheet are also within the scope of the present application, and the lithium-ion batteries have a higher cycle capacity retention rate and a lower cycle thickness expansion rate, which means that when the degree of graphitization G, gram capacity W and Id/Ig of the negative electrode active material are within the scope of the present application, the lithium-ion batteries have better cycle performance and expansion performance.
  • FIG6 is a Raman spectrum of the negative electrode active material in Example 1-3, the peak intensity corresponding to the d peak is 89.52, the peak intensity corresponding to the g peak is 710.92, and the Id/Ig of the negative electrode active material is 0.13.

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Abstract

一种负极活性材料、二次电池和电子设备，负极活性材料包括石墨，负极活性材料的Dn10、Dv50、Dv90满足：D＝(Dv90-Dn10)/Dv50，0.8≤D≤1.5；负极活性材料的Dn10为1μm至5μm；负极活性材料的X射线衍射图谱中，特征峰C004和特征峰C110的峰强比值为I；负极活性材料满足：2≤I/D≤4。采用该负极活性材料能够改善二次电池的循环性能。

Description

一种负极活性材料、二次电池和电子设备
本申请要求于2023年8月11日提交中国专利局、申请号为202311017464.9发明名称为“一种负极活性材料、负极极片、二次电池和电子设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电化学技术领域，特别是涉及一种负极活性材料、二次电池和电子设备。
背景技术
储能产业作为能源结构调整的支撑产业和关键推手，在传统发电、输配电、电力需求侧、辅助服务、新能源等不同领域有着广阔的应用前景。目前的储能主要依赖二次电池，如锂离子电池，因其具有能量密度高、自放电率低、循环寿命长、放电性能稳定等突出优势，目前也被广泛应用于工业生产和人们日常生活中。
锂离子电池负极极片中的负极活性材料是影响锂离子电池性能的关键因素之一，传统的人造石墨作为负极活性材料，其循环性能也有待提高；现阶段成本低廉且储量巨大的天然石墨存在循环膨大以及循环容量保持率低的问题，也影响锂离子电池的循环性能。
发明内容
本申请的目的在于提供一种负极活性材料、二次电池和电子设备，以提高二次电池的循环性能、膨胀性能和倍率性能。具体技术方案如下：
本申请的第一方面提供了一种负极活性材料，其包括石墨，负极活性材料的Dn10、Dv50、Dv90满足：D＝(Dv90-Dn10)/Dv50，0.8≤D≤1.5；负极活性材料的Dn10为1μm至5μm；负极活性材料的X射线衍射图谱中，特征峰C004和特征峰C110的峰强比值为I；负极活性材料满足：2≤I/D≤4。通过调控D的值、Dn10和I/D的值在上述范围内，得到的负极活性材料具有合适的粒度分布且粒度分布较窄，能够降低活性离子在极片中扩散的迂曲度，同时负极活性材料的各项同性性能较强，将上述负极活性材料应用于二次电池的负极极片能够改善二次电池的循环性能、膨胀性能和倍率性能。
在本申请的一些实施方案中，2≤I≤6。说明负极活性材料不仅粒度分布较窄、各项同性性能较强，在二次电池充放电过程中能够兼顾活性离子的扩散路径和负极极片的形变，进一步改善二次电池的循环性能和膨胀性能。
在本申请的一些实施方案中，负极活性材料满足以下条件中的至少一者：(1)Dn10为2μm至4μm；(2)Dv90为14μm至30μm；(3)Dv50为8μm至15μm；(4)2≤I≤4。 负极活性材料满足以上条件(1)至(4)中的至少一者，将其应用于二次电池的负极极片能够改善二次电池的循环性能、膨胀性能和倍率性能。
在本申请的一些实施方案中，负极活性材料的球形度C＝4πA/P2，0.5≤C≤1，A为负极活性材料颗粒的正投影的面积，P为负极活性材料颗粒的正投影的周长；负极活性材料满足：1.8≤D/C+1≤4。负极活性材料的球形度C和D/C+1在上述范围内，负极活性材料具有合适的球形度和粒度分布且粒度分布较窄，球形度与粒度之间相互匹配，能够进一步改善二次电池的循环性能和膨胀性能，同时二次电池具有较高的能量密度和良好的倍率性能。
在本申请的一些实施方案中，负极活性材料满足以下条件中的至少一者：(a)负极活性材料的振实密度TD为0.8g/cm3至1.2g/cm3；(b)负极活性材料的石墨化度G为90％至96％；(c)负极活性材料的克容量W为344mAh/g至358mAh/g。负极活性材料满足以上条件(a)至(c)中的至少一者，将其应用于二次电池的负极极片能够改善二次电池的循环性能、膨胀性能和倍率性能。
在本申请的一些实施方案中，0.8≤D≤1.3。
在本申请的一些实施方案中，2.4≤I/D≤3.5。
在本申请的一些实施方案中，负极活性材料的拉曼光谱图中，d峰和g峰的峰强比值Id/Ig为0.1至0.3。负极活性材料的Id/Ig的值在上述范围内，负极活性材料具有合适的缺陷度和粒度分布且粒度分布较窄，能够进一步改善二次电池的循环性能和膨胀性能，同时具有良好的倍率性能。
在本申请的一些实施方案中，石墨包括天然石墨和人造石墨。天然石墨能够提供高的克容量和较优的动力学，人造石墨可提供良好的循环性能，使用两种石墨时，能够进一步改善二次电池的循环性能和倍率性能。
本申请的第二方面提供了一种二次电池，其包括正极极片、负极极片和电解液，负极极片包括负极集流体和设置在负极集流体至少一个表面上的负极材料层，负极材料层包括上述任一实施方案中的负极活性材料。
在本申请的一些实施方案中，负极极片满足以下条件中的至少一者：(ⅰ)负极极片的孔隙率为25％至40％；(ⅱ)负极极片的OI值为8至15。负极极片满足以上条件(ⅰ)或(ⅱ)中的至少一者，将其应用于二次电池，有利于改善二次电池循环性能和膨胀性能。
本申请的第三方面提供了一种电子设备，其包括上述任一实施方案中的二次电池。
本申请的有益效果：
本申请提供了一种负极活性材料，其包括石墨，负极活性材料的Dn10、Dv50、Dv90满足：D＝(Dv90-Dn10)/Dv50，0.8≤D≤1.5；负极活性材料的Dn10为1μm至5μm；负极活性材料的X射线衍射图谱中，特征峰C004和特征峰C110的峰强比值为I；负极活性材料满足：2≤I/D≤4。采用本申请提供的负极活性材料，能够改善二次电池的循环性能。
当然，实施本申请的任一产品或方法并不一定需要同时达到以上所述的所有优点。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中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，还可以根据这些附图获得其他的实施例。
图1为实施例1-1中的负极活性材料的电镜照片；
图2为实施例1-3中的负极活性材料的X射线衍射图谱；
图3为实施例1-3中的负极极片的X射线衍射图谱；
图4为实施例1-1和对比例1-1中的锂离子电池的循环容量保持率变化图；
图5为实施例1-1和对比例1-1中的锂离子电池的厚度膨胀率变化图；
图6为实施例1-3中的负极活性材料的拉曼图谱。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。本领域技术人员基于本申请所获得的所有其他实施例，都属于本申请保护的范围。
需要说明的是，本申请的具体实施方式中，以锂离子电池作为二次电池的例子来解释本申请，但是本申请的二次电池并不仅限于锂离子电池。
本申请的第一方面提供了一种负极活性材料，其包括石墨，负极活性材料的Dn10、Dv50、Dv90满足：D＝(Dv90-Dn10)/Dv50，0.8≤D≤1.5。在本申请的一些实施方案中，0.8≤D≤1.3。例如，D的值可以为0.8、0.9、1、1.1、1.2、1.3、1.4、1.5或为其中任意两个数值组成的范围。负极活性材料的Dn10为1μm至5μm；在本申请的一些实施方案中，负极活性材料的Dn10为2μm至4μm。例如，负极活性材料的Dn10可以为1μm、1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm或为其中任意两个数值组成的范围。负极活性材料的X射线衍射图谱中，特征峰C004和特征峰C110的峰强比值为I；负极活性材料满足： 2≤I/D≤4。在本申请的一些实施方案中，2.4≤I/D≤3.5。例如，I/D的值可以为2.4、2.5、2.6、2.7、2.8、2.9、3、3.1、3.2、3.3、3.4、3.5或为其中任意两个数值组成的范围。
发明人发现，上述D值和Dn10可以表征负极活性材料的粒度分布，当D值过小时，例如小于0.8，说明负极活性材料的粒度分布范围过窄，细粉含量明显减小，会使电子在颗粒间的传导变差，影响导电网络，从而影响二次电池的循环性能和倍率性能；当D值过大时，例如大于1.5，说明负极活性材料的粒度分布范围较宽，会使得活性如锂离子在包含上述负极活性材料的负极极片中扩散的路径较长，活性离子的扩散阻抗增大，影响二次电池的循环性能和倍率性能。I/D在上述范围内说明负极活性材料粒度分布适中，能够降低活性离子在极片中扩散的迂曲度，而且负极活性材料的各项同性性能较强，有利于改善二次电池的循环性能和膨胀性能。通过调控D的值、Dn10和I/D的值在上述范围内，得到的负极活性材料具有合适的粒度分布且粒度分布较窄，能够降低活性离子在极片中扩散的迂曲度，同时负极活性材料的各项同性性能较强，将上述负极活性材料应用于二次电池的负极极片能够改善二次电池的循环性能、膨胀性能和倍率性能。在本申请中，活性离子是指在二次电池充放电过程中参与充放电电化学反应的活性离子，具体可以为锂离子或钠离子等。
在本申请的一些实施方案中，2≤I≤6。在本申请的一些实施方案中，2≤I≤4。例如，I的值可以为2、2.5、3、3.5、4、4.5、5、5.5、6或为其中任意两个数值组成的范围。说明负极活性材料不仅粒度分布较窄、各项同性性能较强，在二次电池充放电过程中能够兼顾活性离子的扩散路径和负极极片的形变，进一步改善二次电池的循环性能和膨胀性能。
在本申请的一些实施方案中，负极活性材料的Dv90为14μm至30μm。例如，负极活性材料的Dv90可以为14μm、15μm、16μm、17μm、18μm、19μm、20μm、21μm、22μm、23μm、24μm、25μm、26μm、27μm、28μm、29μm、30μm或为其中任意两个数值组成的范围。负极活性材料满足上述D、Dn10、I/D的范围的前提下，负极活性材料的Dv90在上述范围内，说明负极活性材料具有合适的粒径和粒度分布且粒度分布较窄，能够降低活性离子在极片中扩散的迂曲度，同时负极活性材料的各项同性性能较强，将上述负极活性材料应用于二次电池的负极极片能够改善二次电池的循环性能、膨胀性能和倍率性能。
在本申请的一些实施方案中，负极活性材料的Dv50为8μm至15μm。例如，负极活性材料的Dv50可以为8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm或为其中任意两个数值组成的范围。负极活性材料满足上述D、Dn10、I/D的范围的前提下，负极 活性材料的Dv50在上述范围内，说明负极活性材料具有合适的粒径和粒度分布且粒度分布较窄，能够降低活性离子在极片中扩散的迂曲度，同时负极活性材料的各项同性性能较强，将上述负极活性材料应用于二次电池的负极极片能够改善二次电池的循环性能、膨胀性能和倍率性能。
在本申请的一些实施方案中，负极活性材料的球形度C＝4πA/P2，0.5≤C≤1，A为负极活性材料颗粒的正投影的面积，P为负极活性材料颗粒的正投影的周长；负极活性材料满足：1.8≤D/C+1≤4。例如，C的值可以为0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1或为其中任意两个数值组成的范围；D/C+1的值可以为1.8、2、2.2、2.5、2.7、3、3.3、3.5、3.8、4或为其中任意两个数值组成的范围。当负极活性材料的球形度C的值在上述范围内，说明负极活性材料具有合适的球形度，既利于活性离子的扩散，也有利于活性离子的嵌入和脱出，能够进一步改善二次电池的循环性能；而且，负极活性材料颗粒之间能够紧密堆积，负极极片具有较高的压实密度，从而有利于得到能量密度较高的二次电池。从而，负极活性材料满足上述D、Dn10、I/D的范围的前提下，负极活性材料的球形度C和D/C+1在上述范围内，负极活性材料具有合适的球形度和粒度分布且粒度分布较窄，球形度与粒度之间相互匹配，能够进一步改善二次电池的循环性能和膨胀性能，同时二次电池具有较高的能量密度和良好的倍率性能。
在本申请的一些实施方案中，负极活性材料的振实密度TD为0.8g/cm3至1.2g/cm3。例如，负极活性材料的振实密度为TD可以为0.8g/cm3、0.9g/cm3、0.95g/cm3、1g/cm3、1.05g/cm3、1.1g/cm3、1.15g/cm3、1.2g/cm3或为其中任意两个数值组成的范围。负极活性材料的振实密度在上述范围内，在制浆的过程中需要的分散剂较少，制成的浆料也更稳定，不容易出现沉降，在负极极片中颗粒之间能紧密接触，改善电子导电率和活性离子扩散速率，改善二次电池的循环性能性能。从而，负极活性材料满足上述D、Dn10、I/D的范围的前提下，负极活性材料的TD在上述范围内，负极活性材料具有合适的振实密度和粒度分布且粒度分布较窄，能够改善二次电池的循环性能、膨胀性能和倍率性能，同时改善二次电池加工性能。
在本申请的一些实施方案中，负极活性材料的石墨化度G为90％至96％。例如，负极活性材料的石墨化度G可以为90％、90.5％、91％、91.5％、92％、92.5％、93％、93.5％、94％、94.5％、95％、95.5％、96％或为其中任意两个数值组成的范围。石墨化度G在上述范围内，说明负极活性材料的石墨化度较低，有利于改善二次电池的循环性能和膨胀性能。 从而，负极活性材料满足上述D、Dn10、I/D的范围的前提下，负极活性材料的石墨化度在上述范围内，负极活性材料具有合适的石墨化度和粒度分布且粒度分布较窄，能够进一步改善二次电池的循环性能和膨胀性能，同时具有良好的倍率性能。
在本申请的一些实施方案中，负极活性材料的克容量W为344mAh/g至358mAh/g。例如，负极活性材料的克容量W可以为344mAh/g、345mAh/g、346mAh/g、347mAh/g、348mAh/g、349mAh/g、350mAh/g、351mAh/g、352mAh/g、353mAh/g、354mAh/g、355mAh/g、356mAh/g、357mAh/g、358mAh/g或为其中任意两个数值组成的范围。负极活性材料的克容量W在上述范围内，说明具有较高的克容量。从而，负极活性材料满足上述D、Dn10、I/D的范围的前提下，负极活性材料具有较高的克容量、合适和粒度分布且粒度分布较窄，能够改善二次电池的循环性能和膨胀性能，同时具有良好的倍率性能和较高的能量密度。
在本申请的一些实施方案中，负极活性材料的拉曼光谱图中，d峰和g峰的峰强比值Id/Ig为0.1至0.3。例如，Id/Ig的值可以为0.1、0.12、0.14、0.15、0.16、0.18、0.2、0.22、0.24、0.25、0.26、0.28、0.3或为其中任意两个数值组成的范围。Id/Ig的值在上述范围内，说明负极活性材料表面具有合适的缺陷度，有利于改善循环性能和膨胀性能。从而，负极活性材料满足上述D、Dn10、I/D的范围的前提下，其Id/Ig的值在上述范围内，具有合适的缺陷度和粒度分布且粒度分布较窄，能够进一步改善二次电池的循环性能和膨胀性能，同时具有良好的倍率性能。
在本申请中，上述负极活性材料的特征I、Dv90、球形度C、振实密度为TD、石墨化度G、克容量W、Id/Ig中的至少一者均可以与特征“D、Dn10、I/D”进行组合，上述组合涵盖的实施方式均在本申请的保护范围内。
在本申请的一些实施方案中，石墨包括天然石墨和人造石墨。天然石墨是指由天然矿石产出的鳞片制成的石墨，作为本申请实施方式使用的天然石墨的产地、性状、种类没有特别限定。人造石墨是指通过人工方法制备而近似石墨完整晶体的石墨，人造石墨可以通过前驱体原料焦如石油焦、煤焦、沥青焦等经由石墨化、包覆碳化工序等处理来获得。在本申请的一些实施方案中，可通过扫描电镜观察负极极片沿厚度方向的截面形貌或观察负极活性材料粉末分辨两种石墨，具有无规则形状且呈扁平状的石墨颗粒为人造石墨颗粒，表面圆润且球形度更高的石墨颗粒为天然石墨颗粒。作为本申请实施方式使用的人造石墨的前驱体种类、石墨化方式、碳化方式等工艺没有特别限定。
本申请对负极活性材料的制备方法没有特别限制，只要能实现本申请的目的即可。例 如，负极活性材料的制备方法可以包括但不限于以下制备步骤：
S1：提供粒度6μm至23μm、纯度为95％以上的天然石墨生球原料；
S2：提供粒度为8μm至15um的原料焦作为人造石墨前驱体组分；
S3：提供高结焦值沥青作为粘接剂；
S4：将天然石墨组分、人造石墨前驱体组分和粘接剂按照质量比为(10至90):(10至90):(2至10)混合得到混合原料，投入反应釜中；
S5：将反应釜在温度T1为300℃至800℃温度下进行热处理，热处理时间t1为2h至8h，粘接剂熔融，使天然石墨和人造石墨前驱体组分粘接在一起，并冷却至室温得到样品；
S6：将样品装入坩埚进行低温石墨化处理得到处理样品，低温石墨化处理的温度T2为1800℃至2600℃、时间t2为36h至48h；
S7：将处理样品进行分级和整形，得到所需的粒度分布和球形度；
S8：然后过筛、除磁得到负极活性材料。
本申请对上述S2中的原料焦的没有特别限制，只要能实现本申请的目的即可，例如，原料焦可以包括但不限于石油焦、沥青焦、煤焦中的至少一种。S3中高结焦值沥青是指结焦值为30％至80％的沥青。本申请对S7中的分级和整形、S8中的过筛和除磁没有特别限制，其为本领域已知的常规步骤。
通常情况下，可以通过调控分级、整形和过筛的参数来调控负极活性材料的Dn10、Dv50、Dv90，进而调控D的值。也可以通过调控分级、整形和过筛的参数来调控负极活性材料的球形度C、振实密度。可以通过调控混合原料中粘接剂的质量占比来调控I的值，例如，混合原料中粘接剂的质量占比越小，I的值增大；混合原料中粘接剂的质量占比越大，I的值减小。可以通过调控低温石墨化处理的温度和时间来调控石墨化度G，例如，低温石墨化处理的温度越高、时间越长，石墨化度G增大；低温石墨化处理的温度越低、时间越短，石墨化度G减小。可以通过调控本申请中天然石墨和人造石墨前驱体的占比来调控克容量W，例如，本申请中的人造石墨前驱体的占比越低，克容量W增大；本申请中的人造石墨前驱体的占比越高，克容量W减小。可以通过调控低温石墨化处理的温度或者混合原料中粘接剂的质量占比来调控Id/Ig的值，例如，低温石墨化处理的温度越低或者混合原料中粘接剂的质量占比越高，Id/Ig的值增大；低温石墨化处理的温度越高或者混合原料中粘接剂的质量占比越低，Id/Ig的值减小。
本申请的第二方面提供了一种二次电池，其包括正极极片、负极极片和电解液，负极 极片包括负极集流体和设置在负极集流体至少一个表面上的负极材料层，负极材料层包括上述任一实施方案中的负极活性材料。本申请的二次电池具有良好的循环性能、膨胀性能和倍率性能。
上述“设置在负极集流体至少一个表面上的负极材料层”是指，负极材料层可以设置于负极集流体沿自身厚度方向上的一个表面上，也可以设置于负极集流体沿自身厚度方向上的两个表面上。需要说明，这里的“表面”可以是负极集流体表面的全部区域，也可以是负极集流体表面的部分区域，本申请没有特别限制，只要能实现本申请目的即可。
在本申请的一些实施方案中，负极极片的孔隙率为25％至40％。例如，负极极片的孔隙率可以为25％、26％、27％、28％、29％、30％、31％、32％、33％、34％、35％、36％、37％、38％、39％、40％或为其中任意两个数值组成的范围。说明负极极片的具有较高的孔隙率，有利于活性离子的传输和扩散，进而改善二次电池的循环性能、膨胀性能和倍率性能。
在本申请的一些实施方案中，负极极片的OI值为8至15。例如，负极极片的OI值可以为8、9、10、11、12、13、14、15或为其中任意两个数值组成的范围。OI值在上述范围内的负极极片，具有良好的离子扩散性能。将其应用于二次电池，有利于改善二次电池循环性能和膨胀性能。
在本申请中，负极活性材料还可以包括现有技术中已知的其它负极活性材料，示例性地，其它负极活性材料可以包括但不限于中间相微碳球、硬碳、软碳、硅、硅碳材料、硅氧材料、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO2、尖晶石结构的锂化TiO2-Li4Ti5O12或Li-Al合金中的至少一种。本申请对其它负极活性材料的含量不做限定，只要能实现本申请的目的即可。
本申请对负极集流体没有特别限制，只要能够实现本申请目的即可。例如，负极集流体可以包含铜箔、铝箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或覆有导电金属的聚合物基底等。其中，导电金属包括但不限于铜、镍或钛，聚合物基底的材料包括但不限于聚乙烯、聚丙烯、乙烯丙烯共聚物、聚对苯二甲酸乙二醇酯、聚对萘二甲酸乙二醇酯或聚对苯二甲酰对苯二胺中的至少一种。在本申请中，对负极集流体和负极材料层的厚度没有特别限制，只要能够实现本申请目的即可。例如，负极集流体的厚度为4μm至12μm，单面负极材料层的厚度为50μm至200μm。
本申请中的负极材料层还可以包括导电剂、粘结剂或增稠剂中的至少一种。本申请对 导电剂和粘结剂的种类没有特别限制，只要能够实现本申请目的即可。例如，导电剂可以包括但不限于导电炭黑(Super P)、碳纳米管(CNTs)、碳纤维、科琴黑、石墨烯、金属材料或导电聚合物中的至少一种。上述碳纳米管可以包括但不限于单壁碳纳米管和/或多壁碳纳米管。上述碳纤维可以包括但不限于气相生长碳纤维(VGCF)和/或纳米碳纤维。上述金属材料可以包括但不限于金属粉和/或金属纤维，具体地，金属可以包括但不限于铜、镍、铝或银中的至少一种。上述导电聚合物可以包括但不限于聚亚苯基衍生物、聚苯胺、聚噻吩、聚乙炔或聚吡咯中的至少一种。例如，粘结剂可以包括但不限于聚丙烯酸、聚丙烯酸钠、聚丙烯酸钾、聚丙烯酸锂、聚酰亚胺、聚乙烯醇、羧甲基纤维素、聚酰亚胺、聚酰胺酰亚胺、丁苯橡胶或聚偏二氟乙烯中的至少一种。增稠剂可以包括但不限于羧甲基纤维素钠或羧甲基纤维素锂中的至少一种。本申请对负极材料层中负极活性材料、导电剂、粘结剂、增稠剂的质量比没有特别限制，本领域技术人员可以根据实际需要选择，只要能够实现本申请目的即可。
任选地，负极极片还可以包含导电层，导电层位于负极集流体和负极材料层之间。导电层的组成没有特别限制，可以是本领域常用的导电层。导电层包括导电剂和粘结剂。本申请对导电层中的导电剂和粘结剂没有特别限制，例如，可以是上述导电剂和上述粘结剂中的至少一种。
本申请对正极极片没有特别限制，只要能够实现本申请目的即可。例如，正极极片包含正极集流体和设置在正极集流体至少一个表面上的正极材料层。上述“设置在正极集流体至少一个表面上的正极材料层”是指，正极材料层可以设置于正极集流体沿自身厚度方向上的一个表面上，也可以设置于正极集流体沿自身厚度方向上的两个表面上。需要说明，这里的“表面”可以是正极集流体表面的全部区域，也可以是正极集流体表面的部分区域，本申请没有特别限制，只要能实现本申请目的即可。
本申请对正极集流体没有特别限制，只要能够实现本申请目的即可。例如，正极集流体可以包含金属箔片或复合集流体等。例如金属箔片可以为铝箔。复合集流体可包括高分子材料基层以及位于高分子材料基层至少一个表面上的金属材料层。金属材料层的材料可以包括铝、铝合金、镍、镍合金、钛、钛合金、银或银合金中的至少一种。高分子材料基层可以包括聚丙烯、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚苯乙烯或聚乙烯中的至少一种。本申请的正极材料层包含正极活性材料。本申请对正极活性材料的种类没有特别限制，只要能够实现本申请目的即可。例如正极活性材料包括钴酸锂、镍钴锰酸锂 (N0.95C0.05M0.05、NCM811、NCM622、NCM523、NCM111)、镍锰铝酸锂、磷酸铁锂、磷酸钒锂、磷酸钴锂、磷酸锰锂、磷酸锰铁锂、硅酸铁锂、硅酸钒锂、硅酸钴锂、硅酸锰锂、尖晶石型锰酸锂、尖晶石型镍锰酸锂或钛酸锂中的至少一种。
本申请对正极集流体和正极材料层的厚度没有特别限制，只要能够实现本申请目的即可。例如，正极集流体的厚度为5μm至20μm。单面正极材料层的厚度为50μm至300μm。本申请的正极材料层还可以包含上述粘结剂和上述导电剂。本申请对正极材料层中正极活性材料、导电剂、粘结剂的质量比没有特别限制，本领域技术人员可以根据实际需要选择，只要能够实现本申请目的即可。
本申请中，电解液包括锂盐和有机溶剂。锂盐可以包括但不限于六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、二氟磷酸锂(LiPO2F2)、双三氟甲烷磺酰亚胺锂(LiTFSI)、双(氟磺酰)亚胺锂(LiFSI)、双草酸硼酸锂(LiBOB)或二氟草酸硼酸锂(LiDFOB)中的至少一种。本申请对锂盐在电解液中的浓度没有特别限制，只要能实现本申请的目的即可。本申请对上述有机溶剂没有特别限制，只要能实现本申请的目的即可，例如可以包括但不限于碳酸酯化合物、羧酸酯化合物、醚化合物或其它有机溶剂中的至少一种。上述碳酸酯化合物可以包括但不限于链状碳酸酯化合物或环状碳酸酯化合物中的至少一种。上述链状碳酸酯化合物可以包括但不限于碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯或碳酸甲乙酯中的至少一种。上述环状碳酸酯化合物可以包括但不限于碳酸乙烯酯、碳酸丙烯酯、碳酸亚丁酯或碳酸乙烯亚乙酯中的至少一种。上述羧酸酯化合物可以包括但不限于甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯或己内酯中的至少一种。上述醚化合物可以包括但不限于乙二醇二甲醚、二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、1-乙氧基-1-甲氧基乙烷、2-甲基四氢呋喃或四氢呋喃中的至少一种。上述其它有机溶剂可以包括但不限于二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯或磷酸三辛酯中的至少一种。电解液还可以包括添加剂，添加剂可以包括但不限于氟代碳酸乙烯酯、1,3-丙烷磺内酯或己二腈等中的至少一种。
本申请的二次电池还可以包括隔膜，用以分隔正极极片和负极极片，防止二次电池内部短路，允许电解质离子自由通过，且不影响电化学充放电过程的进行。本申请对隔膜没有特别限制，只要能够实现本申请目的即可，例如隔膜的材料可以包括但不限于聚乙烯、 聚丙烯、聚四氟乙烯为主的聚烯烃类隔膜、聚酯膜(例如聚对苯二甲酸二乙酯(PET)膜)、纤维素膜、聚酰亚胺膜、聚酰胺膜、氨纶或芳纶膜等中的至少一种。隔膜的类型可以包括但不限于织造膜、非织造膜(无纺布)、微孔膜、复合膜、碾压膜或纺丝膜等中的至少一种。本申请的隔膜可以具有多孔结构，多孔层设置在隔膜的至少一个表面上，多孔层包括无机颗粒和粘结剂，无机颗粒可以包括氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。粘结剂可以包括聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素纳、聚乙烯吡咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。本申请对多孔结构的孔径的尺寸没有特别限制，只要能实现本申请的目的即可，例如，孔径的尺寸可以为0.01μm至1μm。在本申请中，隔膜的厚度没有特别限制，只要能实现本申请的目的即可，例如厚度可以为3μm至30μm。
本申请的二次电池还包括包装袋，用于容纳正极极片、隔膜、负极极片和电解液，以及二次电池中本领域已知的其它部件，本申请对上述其它部件不做限定。本申请对包装袋没有特别限制，可以为本领域公知的包装袋，只要能够实现本申请目的即可。例如，可采用铝塑膜包装袋。
本申请的二次电池没有特别限制，其可以包括发生电化学反应的任何装置。在本申请的一种实施方案中，二次电池可以包括但不限于：锂离子电池或钠离子电池。
本申请的二次电池的制备过程为本领域技术人员所熟知的，本申请没有特别的限制，例如，可以包括但不限于以下步骤：将正极极片、隔膜和负极极片按顺序堆叠，并根据需要将其卷绕、折叠等操作得到卷绕结构的电极组件，将电极组件放入包装袋内，将电解液注入包装袋并封口，得到二次电池；或者，将正极极片、隔膜和负极极片按顺序堆叠，然后用胶带将整个叠片结构的四个角固定好得到叠片结构的电极组件，将电极组件置入包装袋内，将电解液注入包装袋并封口，得到二次电池。此外，也可以根据需要将防过电流元件、导板等置于包装袋中，从而防止二次电池内部的压力上升、过充放电。
本申请的第三方面提供了一种电子设备，其包括上述任一实施方案中的二次电池。本申请的电子设备没有特别限定，其可以是用于现有技术中已知的任何电子设备。在一些实施例中，电子设备可以包括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、家庭用大型蓄电池和锂离子电容器等。
实施例
以下，举出锂离子电池作为实施例及对比例来对本申请的实施方式进行更具体地说明。各种的试验及评价按照下述的方法进行。另外，只要无特别说明，“份”、“％”为质量基准。
测试方法和设备：
负极极片和负极活性材料取样方法：
将锂离子电池以1C恒流放电至电压为3.0V后拆解，取出负极极片，用碳酸二甲酯(DMC)浸泡20分钟后，再依次用DMC、丙酮各淋洗一遍。之后将负极极片置于烘箱内，80℃烘烤12小时，获得处理后的负极极片样品。以下孔隙率测试中的负极极片样品采用上述方法取样。
用刮刀刮下负极极片上的负极材料层，并将刮下的负极材料层的粉末在氩气保护条件下，于管式炉中在400℃下热处理4小时，以除去负极活性材料表面黏附的粘结剂，获得负极活性材料的粉末样品。以下粒度测试、球形度测试、X-射线衍射(XRD)测试、振实密度、拉曼测试测试以及扫描电镜测试中的负极活性材料样品均采用上述方法取样。
粉末粒度测试：
粉末粒度测试方法参照GB/T 19077-2016。具体流程为称量样品1g与20mL去离子水和微量分散剂混合均匀，置于超声设备中超声5min后将溶液倒入进样系统Hydro 2000SM中进行测试，所用测试设备为马尔文公司生产的Mastersizer 3000。测试过程中当激光束穿过分散的颗粒样品时，通过测量散射光的强度来完成粒度测量。然后数据用于分析计算形成该散射光谱图的粉末粒度分布。测试所用颗粒折射率为1.8，一个样品测试三次，颗粒粒度Dn10、Dv50和Dv90最终取三次测试的平均值作为最终结果。Dn10表示颗粒在数量基准的粒度分布中，从小粒径测起，达到数量累积10％的粒径。Dv50表示颗粒在体积基准的粒度分布中，从小粒径测起，达到体积累积50％的粒径。Dv90表示颗粒在体积基准的粒度分布中，从小粒径测起，达到体积累积90％的粒径。
球形度测试：
采用粒子形状画像解析装置，对动态流动的样品的粒子进行持续聚焦拍摄，得到50张粒子图片。通过图像处理软件得到图片中每个粒子的平面投影面积A，以及投影周长P，然后通过计算得到球形度C＝4πA/P2，取所有粒子球形度的平均值作为最终结果。
XRD测试：
根据国际标准JJS K 0131-1996《X射线衍射分析法通则》，采用X-射线衍射仪(仪器型号为Bruker D8 ADVANCE)，Cu Kα射线，电压40KV、电流40mA，测试角度为20°至80°，每步长时间为0.3s。对负极活性材料粉末进行扫描，得到XRD谱图，分析得到(004)晶面衍射峰峰值和(110)晶面衍射峰峰值，计算(004)晶面衍射峰峰值和(110)晶面衍射峰峰值的比值得到负极活性材料的粉末特征峰C004和特征峰C110的峰强比值I。
对负极极片进行扫描，得到XRD谱图，分析得到(004)晶面衍射峰峰值和(110)晶面衍射峰峰值，计算(004)晶面衍射峰峰值和(110)晶面衍射峰峰值的比值得到负极极片的OI值。
采用X-射线衍射仪(仪器型号为Bruker D8ADVANCE)，Cu Kα射线，电压40KV、电流40mA，测试角度为52°至58°，每步长时间为0.3s。对含有碳硅标比值为C:Si＝5:1(质量比)的硅标作为参比样品进行扫描测试，对负极活性材料粉末的XRD图谱进行处理，得到负极活性材料的(002)峰位置的晶面间距d002，通过计算得到负极活性材料的石墨化度G＝(3.44-d002)/(3.44-3.354)×100％。
振实密度测试：
采用国家标准GB/T 5162-2006《金属粉末振实密度的测定》测试方法，使用麦克默瑞提克GeoPyc1365设备仪器，称取粉末样品50±0.2g，振动频率为250次/mim，测试其振实密度。
拉曼测试：
通过激光显微共聚焦拉曼光谱仪(仪器型号为HR Evolution，厂商法国HORIBA)测试负极活性材料的拉曼光谱，拉曼光谱仪的激光波长可处于532nm至633nm的范围内。取负极活性材料的粉末进行测试，测试时扫描100μm×100μm范围，扫描该面积内的颗粒，等间距地测试出100个点，每个点的测试范围均在0.02cm-1至0.05cm-1之间。记在1300cm-1至1400cm-1之间出现的峰为d峰，在1500cm-1至1600cm-1之间出现的峰为g峰。采用La Spec软件进行数据处理得到颗粒的d峰和g峰的峰强，分别记为Id和Ig，统计每个点的Id/Ig的强度比，然后计算出100个点的平均值作为最终的Id/Ig的强度比。
扫描电镜(SEM)测试：
采用JEOL公司的JSM-6360LV型扫描电镜及其配套的X射线能谱仪，对负极活性材料样品形貌结构进行分析，观察样品的形貌特征并拍摄扫描电镜照片。
极片孔隙率测试：
将负极极片制备成直径10cm的圆片，每个实施例或对比例测试30个样品，每个样品体积为约0.35cm3。根据国家标准GB/T24586-2009《铁矿石表观密度、真密度和孔隙率的测定》、采用AccuPycⅡ1340真密度仪测试负极材料层的孔隙率，测试气体为氦气。
倍率性能测试：
在25℃温度下，将锂离子电池以0.2C电流恒流充电至3.6V，再以3.6V恒压充电至0.05C，静置5分钟，然后以0.2C倍率放电至2.5V，得到0.2C放电容量。然后再以0.2C的倍率电流恒流充电至3.6V，以3.6V的恒压充电至0.05C，静置30分钟，然后以3C倍率放电至2.5V，得到3C放电容量。则锂离子电池的3C/0.2C倍率性能＝3C放电容量/0.2C放电容量×100％。
循环性能测试：
将锂离子电池在25℃±1℃的恒温箱中静置30分钟，循环过程为：以0.5C电流恒流充电至3.6V，再以3.6V恒压充电至0.02C，静置15分钟，然后以0.5C倍率放电至2.5V，静置30分钟，此为一次充放电循环过程，记录锂离子电池的厚度H0和首次循环放电容量C0，之后，按照上述循环过程循环3000圈，在第100圈、200圈、300圈、400圈、500圈、第501至1500圈每200圈以及第1501至3000圈每500圈进行一次小倍率容量恢复，小倍率容量恢复充放电过程如下：将锂离子电池在25℃±1℃的恒温箱中静置30分钟，循环过程为：以0.2C电流恒流充电至3.6V，再以3.6V恒压充电至0.02C，静置15分钟，然后以0.2C倍率放电至2.5V，静置30分钟。记录第3000圈锂离子电池的厚度H1和循环放电容量C1。
3000圈循环容量保持率＝C1/C0×100％。
3000圈循环厚度膨胀率＝(H1-H0)/H0×100％。
实施例1-1
<负极活性材料的制备>
将天然石墨(粒径为8μm、纯度为99.5％)、人造石墨前驱体组分石油焦(粒度为10μm)、粘接剂沥青(结焦值为70％)按照质量比x:y:z＝48:48:4混合均匀，然后投入反应釜中。以 4℃/min的升温速率升温至T1＝500℃进行热处理，热处理时间t1＝4h。将热处理后的样品装入坩埚中，然后氩气气氛下进行低温石墨化处理，低温石墨化处理的温度T2＝2200℃、时间t2＝24h。然后冷却至室温，分级、整形、过筛、通过电除磁机除磁得到负极活性材料。
负极活性材料的Dn10、Dv50、Dv90、I、球形度C、振实密度TD如表1所示。
<负极极片的制备>
将上述制得的负极活性材料、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照质量比为97.4:1.5:1.5进行混合，然后加入去离子水作为溶剂并搅拌均匀，调配成固含量为50wt％的负极浆料。将负极浆料均匀涂覆于厚度为6μm的负极集流体铜箔的一个表面上，在85℃下烘干处理4小时，得到涂层厚度为80μm的单面涂覆负极材料层的负极极片。在铜箔的另一个表面上重复上述步骤，得到双面涂覆负极材料层的负极极片。经过冷压(冷压压力为15T)、裁片、分切后，得到负极极片，规格为76.6mm×875mm。
<正极极片的制备>
将正极活性材料磷酸铁锂、导电剂乙炔黑、粘结剂聚偏氟乙烯(PVDF)按照质量比96.3:2.2:1.5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂并搅拌均匀，调配成固含量为75wt％的正极浆料。将正极浆料均匀涂覆在厚度为13μm的正极集流体铝箔的一个表面上，85℃条件下烘干，得到正极材料层厚度为130μm的单面涂布正极材料的正极极片。在铝箔的另一个表面上重复上述步骤，得到双面涂覆正极材料层的正极极片。经过冷压、裁片、分切后，得到正极极片，规格为74mm×867mm。
<电解液的制备>
在干燥氩气气氛手套箱中，将基础溶剂碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照质量比为EC:PC:EMC:DEC＝1:3:3:3进行混合，然后加入氟代碳酸乙烯酯和1,3-丙烷磺内酯，溶解并搅拌均匀后加入锂盐LiPF6，混合均匀后获得电解液。基于电解液的质量，锂盐的质量百分含量为12.5％，氟代碳酸乙烯酯的质量百分含量为2％，1,3-丙烷磺内酯的质量百分含量为2％，余量为基础溶剂。
<隔膜>
采用厚度为7μm的聚乙烯薄膜(Celgard公司提供)作为隔膜。
<锂离子电池的制备>
将上述制备的正极极片、隔膜、负极极片按顺序依次叠好，使隔膜处于正极极片和负极极片中间起到隔离的作用，然后卷绕得到电极组件。焊接极耳后将电极组件装入铝塑膜 包装袋中，放置在80℃真空烘箱中干燥12小时脱去水分，注入上述配好的电解液，经过真空封装、静置、化成(温度45℃、0.1C恒流充电，截至时间1800s，再以0.5C恒流充电至3.6V)、脱气、切边等工序得到锂离子电池。
实施例1-2至实施例1-18
除了按照表1调整参数以外，其余与实施例1-1相同。
实施例2-1至实施例2-6
除了按照表2调整参数以外，其余与实施例1-3相同。
对比例1-1至对比例1-4
除了按照表1调整参数以外，其余与实施例1-1相同。
对比例1-5
除了将实施例1-1中的天然石墨直接作为负极活性材料制备负极极片以外，其余与实施例1-1相同。
各实施例和各对比例的相关参数及性能测试如表1至表2所示。
表1

从实施例1-1至实施例1-18、对比例1-1至1-5可以看出，当负极活性材料的D值、I/D的值均在本申请的范围内，得到的锂离子电池具有更高的循环容量保持率和更低的厚度膨胀率，说明本申请的锂离子电池具有更好的循环性能和膨胀性能。
从实施例1-1至实施例1-18可以出，负极活性材料的Dn10、Dv50、Dv90、C、TD之间相互关联和影响，进而影响D的值、I的值、I/D的值、D/C+1的值，且以上特征的值均在本申请的范围内，得到的负极极片的孔隙率和OI值也在本申请的范围内，锂离子电池均具有较高的循环容量保持率和较低的循环厚度膨胀率，从而说明锂离子电池均具有良好的循环性能和膨胀性能。
具体地，如图1所示，其为实施例1-1中的负极活性材料的电镜照片，从电镜照片中可以看出，负极活性材料颗粒大小较为均一，有利于提高锂离子的扩散和电子导电率，从而改善锂离子电池的循环性能和倍率性能。图2为实施例1-3中的负极活性材料的XRD图谱，从图中可以看出，位于54.56°的特征峰C004对应的峰面积为3021.82，位于77.41°的特征峰C110对应的峰面积为712.44，特征峰C004和特征峰C110的峰面积比值I为4.2。图3为实施例1-3中的负极极片的XRD图谱，从图中可以看出，位于54.65°的(004)晶面衍射峰对应的峰面积为2665.10，位于77.49°的(110)晶面衍射峰对应的峰面积为222.09，则负极极片的OI值为12。图4和图5为实施例1-1和对比例1-1中的锂离子电池的循环保持率图和厚度膨胀率随循环圈数变化的图，从图中可以看出，实施例1-1的循环容量保持率一直高于对比例1-1，且厚度膨胀率一直低于对比例1-1。
表2

从实施例1-3、实施例2-1至实施例2-6可以看出，负极活性材料的石墨化度G、克容量W和Id/Ig的值随制备参数的变化而变化，且负极活性材料的石墨化度G、克容量W和Id/Ig之间相关关联和影响，当以上特征的值均在本申请的范围内，得到的负极极片的孔隙率和OI值也在本申请的范围内，锂离子电池均具有更高的循环容量保持率和更低的循环厚度膨胀率，从而说明当负极活性材料的石墨化度G、克容量W和Id/Ig在本申请的范围内，锂离子电池均具有更好的循环性能和膨胀性能。
具体地，图6为实施例1-3中的负极活性材料的拉曼图谱，d峰对应的峰强为89.52，g峰对应的峰强为710.92，则负极活性材料的Id/Ig为0.13。
需要说明的是，在本文中，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法、物品或者设备不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法、物品或者设备所固有的要素。
本说明书中的各个实施例均采用相关的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其他实施例的不同之处。

Claims (11)

  1. 一种负极活性材料，其包括石墨，所述负极活性材料的Dn10、Dv50、Dv90满足：D＝(Dv90-Dn10)/Dv50，0.8≤D≤1.5；
    所述负极活性材料的Dn10为1μm至5μm；
    所述负极活性材料的X射线衍射图谱中，特征峰C004和特征峰C110的峰强比值为I；
    所述负极活性材料满足：2≤I/D≤4。
  2. 根据权利要求1所述的负极活性材料，其中，2≤I≤6。
  3. 根据权利要求1或2所述的负极活性材料，其中，所述负极活性材料满足以下条件中的至少一者：
    (1)Dn10为2μm至4μm；
    (2)Dv90为14μm至30μm；
    (3)Dv50为8μm至15μm；
    (4)2≤I≤4；
    (5)所述石墨包括天然石墨和人造石墨。
  4. 根据权利要求1至3中任一项所述的负极活性材料，其中，所述负极活性材料的球形度C＝4πA/P2，0.5≤C≤1，A为所述负极活性材料颗粒的正投影的面积，P为所述负极活性材料颗粒的正投影的周长；
    所述负极活性材料满足：1.8≤D/C+1≤4。
  5. 根据权利要求1至4中任一项所述的负极活性材料，其中，所述负极活性材料满足以下条件中的至少一者：
    (a)所述负极活性材料的振实密度TD为0.8g/cm3至1.2g/cm3；
    (b)所述负极活性材料的石墨化度G为90％至96％；
    (c)所述负极活性材料的克容量W为344mAh/g至358mAh/g。
  6. 根据权利要求1至5中任一项所述的负极活性材料，其中，0.8≤D≤1.3。
  7. 根据权利要求1至6中任一项所述的负极活性材料，其中，2.4≤I/D≤3.5。
  8. 根据权利要求1至7中任一项所述的负极活性材料，其中，所述负极活性材料的拉曼光谱图中，d峰和g峰的峰强比值Id/Ig为0.1至0.3。
  9. 一种二次电池，包括正极极片、负极极片和电解液，所述负极极片包括负极集流体和设置在所述负极集流体至少一个表面上的负极材料层，所述负极材料层包括权利要求1 至8中任一项所述的负极活性材料。
  10. 根据权利要求9所述的二次电池，其中，所述负极极片满足以下条件中的至少一者：
    (ⅰ)所述负极极片的孔隙率为25％至40％；
    (ⅱ)所述负极极片的OI值为8至15。
  11. 一种电子设备，其包括权利要求9或10所述的二次电池。
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CN113437250A (zh) * 2021-06-21 2021-09-24 宁德新能源科技有限公司 电化学装置和电子装置
CN114975996A (zh) * 2021-06-21 2022-08-30 宁德新能源科技有限公司 负极活性材料、二次电池和电子装置
CN115939493A (zh) * 2022-12-29 2023-04-07 东莞新能源科技有限公司 二次电池和电子装置
CN117059800A (zh) * 2023-08-11 2023-11-14 宁德新能源科技有限公司 一种负极活性材料、负极极片、二次电池和电子设备

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