WO2022057668A1 - 一种负极片及制备方法、电池 - Google Patents

一种负极片及制备方法、电池 Download PDF

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WO2022057668A1
WO2022057668A1 PCT/CN2021/116767 CN2021116767W WO2022057668A1 WO 2022057668 A1 WO2022057668 A1 WO 2022057668A1 CN 2021116767 W CN2021116767 W CN 2021116767W WO 2022057668 A1 WO2022057668 A1 WO 2022057668A1
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active
active material
ratio
active layer
graphite
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PCT/CN2021/116767
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English (en)
French (fr)
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贺伟
彭冲
陈博
李俊义
徐延铭
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珠海冠宇电池股份有限公司
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Priority to EP21868493.4A priority Critical patent/EP4131475A1/en
Publication of WO2022057668A1 publication Critical patent/WO2022057668A1/zh
Priority to US17/979,299 priority patent/US20230066253A1/en

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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
    • H01M4/13—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
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—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
    • 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
    • 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 application belongs to the technical field of batteries, and in particular relates to a negative electrode sheet and a preparation method thereof, and a battery.
  • Lithium batteries are widely used in consumer electronic products such as mobile phones and notebooks, as well as in electric vehicles, power tools and other products.
  • the performance of the negative electrode sheet has an important impact on the performance of the battery. Due to the problems of short cycle life, cycle expansion and low capacity of the negative electrode material, the volume energy density of the battery is not high, and the cycle life is short, which is difficult to meet. need.
  • the present application provides a negative electrode sheet, a preparation method, and a battery to solve the problems of short cycle life and low capacity of negative electrode materials, resulting in low volume energy density and short cycle life of the battery.
  • the negative electrode sheet according to the embodiment of the present application includes:
  • a first active layer is provided on at least one surface of the current collector, a second active layer is provided on the surface of the first active layer away from the current collector, and the first active layer is connected to the second active layer.
  • the active layers are different.
  • the first active layer includes a first active material, the first active material includes a first graphite, the second active layer includes a second active material, and the second active material includes a second active material. graphite;
  • the ratio of the capacity per unit mass of the first active material to the specific surface area of the first active material is the first capacity ratio, and the capacity per unit mass of the second active material to the specific surface area of the second active material
  • the ratio is a second capacity ratio, and the ratio of the second capacity ratio to the first capacity ratio is greater than 1.
  • the ratio of the second capacity ratio to the first capacity ratio is 1.05-1.5.
  • the first active material further includes a first silicon material; and/or,
  • the second active material also includes a second silicon material.
  • the specific surface area of the first graphite is 1.0m 2 /g-1.8m 2 /g
  • the specific surface area of the second graphite is 1.0m 2 /g-1.8m 2 /g.
  • the gram capacity of the first graphite and the second graphite is the same, and the specific surface area of the first graphite and the second graphite is different; and/or,
  • the first active material further includes a first silicon material
  • the second active material further includes a second silicon material
  • the first silicon material and the second silicon material have the same gram capacity, the first silicon material Different from the specific surface area of the second silicon material.
  • the first active material further includes a first silicon material
  • the second active material further includes a second silicon material
  • the mass ratio of the first silicon material to the first active material is 5%-40%
  • the mass ratio of the second silicon material to the second active material is 5%-40%.
  • the first active material further includes a first silicon material
  • the second active material further includes a second silicon material
  • the specific surface area of the first silicon material is 1.1m 2 /g-4.0m 2 /g
  • the specific surface area of the second silicon material is 1.1 m 2 /g-4.0 m 2 /g.
  • the first active layer includes a first conductive agent
  • the second active layer includes a second conductive agent
  • the first active layer includes a first adhesive
  • the second active layer includes a second adhesive.
  • the method for preparing a negative electrode sheet according to an embodiment of the present application includes:
  • the first active layer is different from the second active layer.
  • the first active layer includes a first active material, the first active material includes a first graphite, and the second active layer includes a first active layer.
  • Two active materials the second active material includes second graphite; the ratio of the capacity per unit mass of the first active material to the specific surface area of the first active material is the first capacity ratio, and the second active material
  • the ratio of the capacity per unit mass to the specific surface area of the second active material is a second capacity ratio, and the ratio of the second capacity ratio to the first capacity ratio is greater than 1.
  • a battery according to an embodiment of the present application includes the negative electrode sheet described in the above embodiments.
  • a first active layer is provided on at least one surface of the current collector, a second active layer is provided on a surface of the first active layer away from the current collector, and the first active layer is The active layer is different from the second active layer, the first active layer includes a first active material, the first active material includes a first graphite, the second active layer includes a second active material, the The second active material includes second graphite; the ratio of the capacity per unit mass of the first active material to the specific surface area of the first active material is the first capacity ratio, and the capacity per unit mass of the second active material is the same as the The ratio of the specific surface area of the second active material is a second volume ratio, and the ratio of the second volume ratio to the first volume ratio is greater than 1.
  • the negative electrode sheet of the present application different composite active layers are coated on the current collector, a first active layer is provided on the surface of at least one side of the current collector, and the side away from the current collector is on the first active layer A second active layer is arranged on the surface, so that the ratio of the second capacity ratio of the second active material to the first capacity ratio of the first active material is greater than 1, so as to improve the cycle life of the negative electrode material, reduce the expansion rate, and increase the capacity of the negative electrode sheet. Improve the volume energy density of the battery, prolong the cycle life, and meet the high energy demand.
  • FIG. 1 is a schematic structural diagram of a negative electrode sheet according to an embodiment of the application.
  • FIG. 2 is another schematic structural diagram of a negative electrode sheet according to an embodiment of the present application.
  • the negative electrode sheet according to the embodiment of the present application will be specifically described below.
  • the negative electrode sheet of the embodiment of the present application includes a current collector 10 , at least one surface of the current collector 10 is provided with a first active layer 11 , and the side of the first active layer 11 is far from the current collector 10 .
  • a second active layer 12 is provided on the surface.
  • the first active layer 11 is different from the second active layer 12.
  • the first active layer 11 includes a first active material, the first active material includes first graphite, and the second active layer 12 includes The second active material, the second active material includes second graphite; the ratio of the capacity per unit mass of the first active material to the specific surface area of the first active material is the first capacity ratio, and the capacity per unit mass of the second active material is the same as the second active material.
  • the ratio of the specific surface areas of the two active materials is a second volume ratio, and the ratio of the second volume ratio to the first volume ratio is greater than 1.
  • the negative electrode sheet of the embodiment of the present application includes a current collector 10, wherein the current collector 10 may be copper foil, the thickness of the current collector 10 may be 8 ⁇ m, and one side or both sides of the current collector 10 is provided with a first
  • the active layer 11 is provided with a second active layer 12 on the surface of the first active layer 11 on the side away from the current collector 10 .
  • the first active layer 11 is different from the second active layer 12 , and the first active layer 11 includes a first active material.
  • the first active material includes a first graphite
  • the second active layer 12 includes a second active material
  • the second active material includes a second graphite
  • the first graphite and the second graphite can be the same or different, such as the first graphite and the second graphite
  • the particle size or specific surface area of the graphite is different, the gram capacity of the first graphite and the second graphite can be both 355mAh/g, the specific surface area of the first graphite can be 1.75m 2 /g, and the specific surface area of the second graphite can be 1.36m 2 /g;
  • the coating areal densities of the first active layer 11 and the second active layer 12 can be the same or different, and the ratio of the coating areal densities of the second active layer 12 to the first active layer 11
  • the ratio of the capacity per unit mass of the material to the specific surface area of the first active material is taken as the first capacity ratio
  • the negative electrode sheet of the present application different active layers are coated on the current collector, the first active layer 11 is provided on at least one surface of the current collector 10, and the surface of the first active layer 11 on the side away from the current collector 10 is provided
  • the second active layer 12 is provided, and the ratio of the second capacity ratio of the second active material to the first capacity ratio of the first active material is greater than 1, which can improve the cycle life of the negative electrode material, reduce the expansion rate, and increase the capacity of the negative electrode sheet. , improve the volume energy density of the battery, prolong the cycle life, and meet the high energy demand.
  • the ratio of the second capacity ratio to the first capacity ratio may be 1.05-1.5, which effectively improves the cycle life of the negative electrode material, increases the capacity of the negative electrode sheet, and is beneficial to improve the volumetric energy density of the battery and prolong the cycle life.
  • the first active material may comprise a first silicon material
  • the second active material includes a second silicon material.
  • the first silicon material and the second silicon material may be the same or different, and the first silicon material and the second silicon material may be silicon-based materials, respectively.
  • the first silicon material and the second silicon material may include SiO, SiC, and SiN, respectively. at least one of them.
  • the mass ratio of the first silicon material in the first active material may be 5%-20%, and the mass ratio of the second silicon material in the second active material may be 5%-20%, which can be selected according to needs.
  • Including graphite and silicon materials in the active layer can not only prevent the problems of short cycle life and large cycle expansion of silicon-based anode materials, but also effectively improve the cycle performance and energy density of silicon-doped anode materials, which is beneficial to improve the battery performance. capacity and prolong battery cycle life.
  • the first graphite is different from the second graphite, for example, the specific surface area of the first graphite is 1.0m 2 /g-1.8m 2 /g, and the specific surface area of the second graphite is 1.0m 2 /g-1.8m 2 /g.
  • the first graphite and the second graphite have the same gram capacity, and the first graphite and the second graphite have different specific surface areas; and/or, the first active material includes a first silicon material, and the second active material includes a second silicon The gram capacity of the first silicon material and the second silicon material are the same, and the specific surface area of the first silicon material and the second silicon material are different.
  • the gram capacity of the first graphite and the second graphite is the same, the gram capacity of the first graphite and the second graphite can both be 355mAh/g, and the specific surface area of the first graphite and the second graphite is different, the specific surface area of the first graphite It may be 1.4 m 2 /g, and the specific surface area of the second graphite may be 1.2 m 2 /g.
  • the first active material includes a first silicon material
  • the second active material includes a second silicon material
  • the first silicon material is different from the second silicon material
  • the first silicon material may be SiO
  • the second silicon material may be is SiN.
  • the gram capacity of the first silicon material and the second silicon material can be the same, and the specific surface area of the first silicon material and the second silicon material can be different, for example, the gram capacity of the first silicon material and the second silicon material can both be 1360mAh/g
  • the specific surface area of the first silicon material can be 1.80m 2 /g
  • the specific surface area of the second silicon material can be 2.01m 2 /g, which is beneficial to prevent cyclic expansion and effectively improve the energy density.
  • the first active material further includes a first silicon material
  • the second active material further includes a second silicon material
  • the mass ratio of the first silicon material to the first active material is 5%-40%, for example, the first The mass ratio of the silicon material to the first active material is 5%-20%
  • the mass ratio of the second silicon material to the second active material is 5%-40%.
  • the mass ratio of the second silicon material to the second active material is 5%-20%, which can be selected according to actual needs.
  • the first active material further includes a first silicon material
  • the second active material further includes a second silicon material
  • the specific surface area of the first silicon material is 1.1 m 2 /g-4.0 m 2 /g
  • the specific surface area of the dissilicon material is 1.1m 2 /g-4.0m 2 /g, which can be selected according to actual needs.
  • the coating areal densities of the first active layer 11 and the second active layer 12 may be the same, the mass fraction of the first silicon material in the first active layer 11 is X1%, and the mass fraction of the first silicon material in the second active layer 12 is X1%.
  • the mass fraction of the second silicon material is X2%, the specific surface area of the first silicon material is b1, the specific surface area of the second silicon material is b2, the gram capacity of the first silicon material is d1, and the gram capacity of the second silicon material is d2;
  • the specific surface area of the first graphite in the first active layer 11 is a1, the specific surface area of the second graphite in the second active layer 12 is a2, the gram capacity of the first graphite is c1, and the gram capacity of the second graphite is c2;
  • the capacity per unit mass of the active layer 11 is c1*(1-X1%)+d1X1%mAh/g, and the capacity per unit mass of the second active layer 12 is c2*(1-X2%)+d2X2%mAh/g;
  • the ratio of the capacity per unit mass of the first active layer 11 to the specific surface area of the first active layer 11 is taken as the first capacity ratio Y1, and the ratio of the capacity per unit mass of the second active layer
  • the first active layer 11 includes a first conductive agent
  • the second active layer 12 includes a second conductive agent
  • the first active layer 11 includes a first adhesive
  • the second active layer 12 includes a first adhesive
  • a second adhesive is included.
  • the first conductive agent and the second conductive agent may respectively comprise at least one of conductive carbon black, carbon nanotubes, carbon black, and carbon fibers
  • the particle size of the first conductive agent and the second conductive agent may be 0.01-50 ⁇ m, The type and particle size of the conductive agent can be reasonably selected according to actual needs.
  • the first adhesive and the second adhesive may respectively include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethyleneimine (PEI), polyaniline (PAN), polyacrylic acid (PAA), One or more of high molecular polymers such as sodium alginate, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), phenolic resin or epoxy resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PEI polyethyleneimine
  • PAN polyaniline
  • PAA polyacrylic acid
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • epoxy resin epoxy resin
  • the embodiment of the present application provides a preparation method of a negative electrode sheet, and the preparation method of the negative electrode sheet includes:
  • a second active layer 12 is formed on the side surface of the first active layer 11 away from the current collector 10 to obtain a negative electrode sheet;
  • the first active layer 11 is different from the second active layer 12.
  • the first active layer 11 includes a first active material, the first active material includes a first graphite, the second active layer 12 includes a second active material, and the second active layer 12 includes a second active material.
  • the active material includes second graphite; the ratio of the capacity per unit mass of the first active material to the specific surface area of the first active material is the first capacity ratio, and the ratio of the capacity per unit mass of the second active material to the specific surface area of the second active material.
  • the ratio is a second capacity ratio, and the ratio of the second capacity ratio to the first capacity ratio is greater than 1.
  • the ratio of the second capacity ratio of the second active material to the first capacity ratio of the first active material is greater than 1, which can improve the cycle life of the negative electrode material, reduce the expansion rate, increase the capacity of the negative electrode sheet, and improve the The volumetric energy density of the battery to meet high energy needs.
  • the ratio of the second capacity ratio to the first capacity ratio is 1.05-1.5.
  • the first active material comprises a first silicon material
  • the second active material includes a second silicon material.
  • the first graphite is different from the second graphite, the specific surface area of the first graphite is 1.0 m 2 /g-1.8 m 2 /g, and the specific surface area of the second graphite is 1.0 m 2 /g-1.8 m 2 /g.
  • the gram capacities of the first graphite and the second graphite are the same, and the specific surface areas of the first graphite and the second graphite are different; and/or,
  • the first active material further includes a first silicon material
  • the second active material further includes a second silicon material
  • the first silicon material and the second silicon material have the same gram capacity
  • the first silicon material and the second silicon material have different specific surface areas.
  • the first active material includes a first silicon material
  • the second active material includes a second silicon material
  • the first silicon material is different from the second silicon material.
  • the gram capacity of the first silicon material and the second silicon material are the same, and the specific surface areas of the first silicon material and the second silicon material are different.
  • the first active material further includes a first silicon material
  • the second active material further includes a second silicon material
  • the mass ratio of the first silicon material to the first active material is 5%-40%
  • the second silicon material The mass ratio of the second active material is 5%-40%.
  • the first active material further includes a first silicon material
  • the second active material further includes a second silicon material, the specific surface area of the first silicon material is 1.1m 2 /g-4.0m 2 /g, and the specific surface area of the second silicon material is 1.1m 2 /g-4.0m 2 /g.
  • the first active layer 11 includes a first conductive agent, and the second active layer 12 includes a second conductive agent; and/or, the first active layer 11 includes a first adhesive, and the first active layer 11 includes a first adhesive.
  • the second active layer 12 includes a second adhesive.
  • the embodiments of the present application provide a battery, which may be a lithium-ion battery, and the battery includes the negative electrode sheet described in the above embodiments.
  • the battery with the negative electrode sheet in the above embodiment has a long cycle life and a high volume energy density, which can meet the high energy demand.
  • the positive active material lithium cobalt oxide (LiCoO 2 ), the conductive agent carbon black, the binder polyvinylidene fluoride (PVDF) and the solvent N-methylpyrrolidone (NMP) are uniformly mixed in a weight ratio of 96:2.5:1.5:80 , to obtain the positive electrode slurry to be coated;
  • the positive electrode slurry was uniformly coated on an aluminum foil current collector with a thickness of 13 ⁇ m, and a positive electrode sheet to be rolled was obtained after coating and drying treatment.
  • the first graphite of the negative electrode active material the first silicon material, the conductive agent, the binder carboxymethyl cellulose (CMC), the styrene-butadiene rubber (SBR) and the deionized water according to a certain mass ratio
  • the first graphite is added to the mixer for mixing and stirring according to the steps, wherein the first graphite accounts for 90% of the total mass of the first graphite and the first silicon material, and the first silicon material accounts for 10% of the total mass of the graphite and the first silicon material.
  • Coated first slurry the first graphite of the negative electrode active material, the first silicon material, the conductive agent, the binder carboxymethyl cellulose (CMC), the styrene-butadiene rubber (SBR) and the deionized water according to a certain mass ratio
  • the gram capacity of the first graphite is 355mAh/g
  • the specific surface area of the first graphite is 1.4m 2 /g
  • the first silicon material is SiO
  • the gram capacity of the first silicon material is 1360mAh/g
  • the first silicon material has a gram capacity of 1360mAh/g.
  • the specific surface area is 1.95m 2 /g;
  • the second graphite of the negative electrode active material the second silicon material, the conductive agent, the binder carboxymethyl cellulose (CMC), the styrene-butadiene rubber (SBR) and the deionized water according to a certain mass ratio
  • the second graphite accounts for 90% of the total mass of the second graphite and the second silicon material
  • the second silicon material accounts for 10% of the total mass of the second graphite and the second silicon material, and the dispersion is uniform.
  • the second slurry to be coated is obtained, the gram capacity of the second graphite is 355mAh/g, the specific surface area of the second graphite is 1.2m 2 /g, the second silicon material is SiO, and the gram capacity of the second silicon material is 1360mAh /g, the specific surface area of the second silicon material is 1.95m 2 /g;
  • Coating with a double-layer coating machine uniformly coating the first slurry on the copper foil current collector with a thickness of 8 ⁇ m to form a first slurry layer, and coating the second slurry on the second slurry layer at the same time,
  • the coating surface densities of the first slurry layer and the second slurry layer are the same, and the negative electrode sheet to be rolled is obtained after the drying treatment is completed.
  • the finished battery After baking the above-mentioned coated positive electrode sheet and negative electrode sheet, the finished battery is prepared through the steps of rolling and slitting, filming, winding, packaging and baking, liquid injection, and chemical formation.
  • Example 6-8 and Comparative Examples 2-3 The production of the negative electrode sheets in Examples 6-8 and Comparative Examples 2-3 is the same as that in Example 1, except that the mass fraction of the silicon material is different.
  • Table 2 is as follows, according to the gram capacity and the given specific surface area value of the graphite and silicon materials in Example 1.
  • the negative electrode active material graphite 1 and the first graphite in Example 1 are the same material, the silicon material 1 and the first silicon material in Example 1 are the same material; the negative electrode active material graphite 2 is the same as the example
  • the second graphite in 1 is the same kind of material, and the silicon material 2 and the second silicon material in Example 1 are the same kind of material;
  • Preparation of negative electrode slurry Add negative electrode active material graphite 1, silicon material 1, conductive carbon black, binder carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR) and deionized water according to a certain mass ratio according to the steps. Mixing and stirring in a mixer to disperse uniformly, wherein, graphite 1 accounts for 90% of the total mass of graphite 1 and silicon material 1, silicon material 1 accounts for 10% of the total mass of graphite 1 and silicon material 1, and the silicon material is SiO. negative electrode slurry;
  • the negative electrode slurry is uniformly coated on the copper foil current collector with a thickness of 8 ⁇ m, and the negative electrode sheet to be rolled is obtained after the coating is dried and processed.
  • Preparation of negative electrode slurry Add negative electrode active material graphite 1, silicon material 2, conductive carbon black, binder carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR) and deionized water according to a certain mass ratio according to the steps. Mixing and stirring in the mixer to disperse evenly, wherein, graphite 1 accounts for 90% of the total mass of graphite 1 and silicon material 2, and silicon material 2 accounts for 10% of the total mass of graphite 1 and silicon material 1, so as to obtain the negative electrode slurry to be coated;
  • CMC carboxymethyl cellulose
  • SBR styrene butadiene rubber
  • the negative electrode slurry is uniformly coated on the copper foil current collector with a thickness of 8 ⁇ m, and the negative electrode sheet to be rolled is obtained after the coating is dried and processed;
  • the negative electrode active material graphite 2 silicon material 1, conductive carbon black, binder carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR) and deionized water are added in a mixer according to a certain mass ratio according to the steps, mixed and stirred, and dispersed. uniform, wherein the graphite 2 accounts for 90% of the total mass of the graphite 2 and the silicon material 1, and the silicon material 1 accounts for 10% of the total mass of the graphite 2 and the silicon material 1, to obtain the negative electrode slurry to be coated;
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the negative electrode slurry is uniformly coated on the copper foil current collector with a thickness of 8 ⁇ m, and the negative electrode sheet to be rolled is obtained after the coating is dried and processed;
  • a charge-discharge cycle test of 0.7C/0.5C was performed on the prepared battery at 25°C;
  • a charge-discharge cycle test of 0.7C/0.5C was performed on the prepared battery at 45°C;
  • Example 1 83.2% 82.5%
  • Example 2 84.9% 84.8%
  • Example 3 84.1% 82.9%
  • Example 4 84.3% 83.7%
  • Example 5 82.6% 81.9%
  • Example 6 83.0% 82.2%
  • Example 7 84.7% 84.2%
  • Example 8 84.5% 83.9% Comparative Example 1 77.3% 78.4% Comparative Example 2 79.1% 79.9% Comparative Example 3 77.1% 78.2% Comparative Example 4 77.9% 78.5% Comparative Example 5 76.6% 76.2% Comparative Example 6 78.3% 78.8%

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Abstract

本申请提供一种负极片及制备方法、电池，负极片包括：集流体；集流体的至少一侧表面设有第一活性层，第一活性层上远离集流体的一侧表面设有第二活性层，第一活性层与第二活性层不同，第一活性层中包括第一活性材料，第一活性材料包括第一石墨，第二活性层中包括第二活性材料，第二活性材料包括第二石墨；第一活性材料的单位质量的容量与第一活性材料的比表面积之比为第一容量比，第二活性材料的单位质量的容量与第二活性材料的比表面积之比为第二容量比，第二容量比与第一容量比的比值大于1。在本申请的负极片中，在集流体上涂覆不同的活性层，提高负极材料的循环寿命，降低膨胀率，提高容量，提高电池的体积能量密度，延长循环寿命。

Description

一种负极片及制备方法、电池
本申请要求于2020年09月21日提交中国专利局、申请号为202010995090.8、申请名称为“一种负极片及制备方法、电池”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
本申请属于电池技术领域，具体涉及一种负极片及制备方法、电池。
背景技术
锂电池被广泛应用于手机、笔记本等消费类电子产品，以及电动汽车、电动工具等系类产品中。锂电池在使用过程中，负极片的性能对电池性能具有重要影响，由于负极材料存在循环寿命短，循环膨胀，容量不高的问题，导致电池的体积能量密度不高，循环寿命短，难以满足需要。
发明内容
有鉴于此，本申请提供一种负极片及制备方法、电池，用以解决负极材料存在循环寿命短，容量不高，导致电池的体积能量密度不高，循环寿命短的问题。
为解决上述技术问题，本申请采用以下技术方案：
第一方面，根据本申请实施例的负极片，包括：
集流体；
所述集流体的至少一侧表面设有第一活性层，所述第一活性层上远离所述集流体的一侧表面设有第二活性层，所述第一活性层与所述第二活性层不同，所述第一活性层中包括第一活性材料，所述第一活性材料包括第一石墨，所述第二活性层中包括第二活性材料，所述第二活性材料包括第二石墨；
所述第一活性材料的单位质量的容量与所述第一活性材料的比表面积之比为第一容量比，所述第二活性材料的单位质量的容量与所述第二活性材料的比表面积之比为第二容量比，所述第二容量比与所述第一容量比的比值大于1。
其中，所述第二容量比与所述第一容量比的比值为1.05-1.5。
其中，所述第一活性材料还包括第一硅材料；和/或，
所述第二活性材料还包括第二硅材料。
其中，所述第一石墨的比表面积为1.0m 2/g-1.8m 2/g，所述第二石墨的比表面积为1.0m 2/g-1.8m 2/g。
其中，所述第一石墨与所述第二石墨的克容量相同，所述第一石墨与所述第二石墨的比表面积不同；和/或，
所述第一活性材料还包括第一硅材料，所述第二活性材料还包括第二硅材料，所述第一硅材料与所述第二硅材料的克容量相同，所述第一硅材料与所述第二硅材料的比表面积不同。
其中，所述第一活性材料还包括第一硅材料，所述第二活性材料还包括第二硅材料，所述第一硅材料占所述第一活性材料的质量比为5％-40％，所述第二硅材料占所述第二活性材料的质量比为5％-40％。
其中，所述第一活性材料还包括第一硅材料，所述第二活性材料还包括第二硅材料，所述第一硅材料的比表面积为1.1m 2/g-4.0m 2/g，所述第二硅材料的比表面积为1.1m 2/g-4.0m 2/g。
其中，所述第一活性层中包括第一导电剂，所述第二活性层中包括第二导电剂；和/或，
所述第一活性层中包括第一粘接剂，所述第二活性层中包括第二粘接剂。第二方面，根据本申请实施例的负极片的制备方法，包括：
提供集流体；
在所述集流体的至少一侧表面形成第一活性层；
在所述第一活性层上远离所述集流体的一侧表面形成第二活性层；
其中，所述第一活性层与所述第二活性层不同，所述第一活性层中包括第一活性材料，所述第一活性材料包括第一石墨，所述第二活性层中包括第二活性材料，所述第二活性材料包括第二石墨；所述第一活性材料的单位质量的容量与所述第一活性材料的比表面积之比为第一容量比，所述第二活性材料的单位质量的容量与所述第二活性材料的比表面积之比为第二容量比，所述第二容量比与所述第一容量比的比值大于1。
第三方面，根据本申请实施例的电池，包括如上述实施例中所述的负极 片。
本申请的上述技术方案的有益效果如下：
根据本申请实施例的负极片，集流体的至少一侧表面设有第一活性层，所述第一活性层上远离所述集流体的一侧表面设有第二活性层，所述第一活性层与所述第二活性层不同，所述第一活性层中包括第一活性材料，所述第一活性材料包括第一石墨，所述第二活性层中包括第二活性材料，所述第二活性材料包括第二石墨；所述第一活性材料的单位质量的容量与所述第一活性材料的比表面积之比为第一容量比，所述第二活性材料的单位质量的容量与所述第二活性材料的比表面积之比为第二容量比，所述第二容量比与所述第一容量比的比值大于1。在本申请的负极片中，在集流体上涂覆不同的复合活性层，集流体的至少一侧表面设有第一活性层，在所述第一活性层上远离所述集流体的一侧表面设有第二活性层，让第二活性材料的第二容量比与第一活性材料的第一容量比的比值大于1，提高负极材料的循环寿命，降低膨胀率，提高负极片的容量，提高电池的体积能量密度，延长循环寿命，满足高能量需要。
附图说明
图1为本申请实施例的负极片的一个结构示意图；
图2为本申请实施例的负极片的另一个结构示意图。
附图标记
集流体10；第一活性层11；第二活性层12。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例的附图，对本申请实施例的技术方案进行清楚、完整地描述。显然，所描述的实施例是本申请的一部分实施例，而不是全部的实施例。基于所描述的本申请的实施例，本领域普通技术人员所获得的所有其他实施例，都属于本申请保护的范围。
下面具体描述根据本申请实施例的负极片。
如图1和图2所示，本申请实施例的负极片包括集流体10，集流体10的 至少一侧表面设有第一活性层11，第一活性层11上远离集流体10的一侧表面设有第二活性层12，第一活性层11与第二活性层12不同，第一活性层11中包括第一活性材料，第一活性材料包括第一石墨，第二活性层12中包括第二活性材料，第二活性材料包括第二石墨；第一活性材料的单位质量的容量与第一活性材料的比表面积之比为第一容量比，第二活性材料的单位质量的容量与第二活性材料的比表面积之比为第二容量比，所述第二容量比与所述第一容量比的比值大于1。
也就是说，本申请实施例的负极片包括集流体10，其中，集流体10可以为铜箔，集流体10的厚度可以为8μm，在集流体10的一侧或两侧表面设有第一活性层11，第一活性层11上远离集流体10的一侧表面设有第二活性层12，第一活性层11与第二活性层12不同，第一活性层11中包括第一活性材料，第一活性材料包括第一石墨，第二活性层12中包括第二活性材料，第二活性材料包括第二石墨，第一石墨和第二石墨可以相同或不同，比如第一石墨和第二石墨的粒径或比表面积不同，第一石墨和第二石墨的克容量可以均为355mAh/g，第一石墨的比表面积可以为1.75m 2/g，第二石墨的比表面积可以为1.36m 2/g；第一活性层11与第二活性层12的涂覆面密度可以相同或不同，第二活性层12与第一活性层11的涂覆面密度之比可以为0.25-4，第一活性材料的单位质量的容量与第一活性材料的比表面积之比作为第一容量比，第二活性材料的单位质量的容量与第二活性材料的比表面积之比作为第二容量比，第二容量比与第一容量比的比值可以大于1。在本申请的负极片中，在集流体上涂覆不同的活性层，集流体10的至少一侧表面设有第一活性层11，在第一活性层11上远离集流体10的一侧表面设有第二活性层12，让第二活性材料的第二容量比与第一活性材料的第一容量比的比值大于1，可以提高负极材料的循环寿命，降低膨胀率，提高负极片的容量，提高电池的体积能量密度，延长循环寿命，满足高能量需要。
在一些实施例中，第二容量比与第一容量比的比值可以为1.05-1.5，有效提高负极材料的循环寿命，提高负极片的容量，有利于提高电池的体积能量密度，延长循环寿命。
在本申请的实施例中，第一活性材料可以包括第一硅材料；和/或，
第二活性材料包括第二硅材料。其中，第一硅材料和第二硅材料可以相 同或不同，第一硅材料和第二硅材料可以分别为硅基材料，比如第一硅材料和第二硅材料可以分别包括SiO、SiC和SiN中的至少一种。第一活性材料中第一硅材料的质量占比可以为5％-20％，第二活性材料中第二硅材料的质量占比可以为5％-20％，具体可以根据需要选择。在活性层中分别包括石墨和硅材料，既能够防止硅基负极材料存在循环寿命短，循环膨胀大的问题，又可以有效提升掺硅负极材料的循环性能，提高能量密度，有利于提高电池的容量，延长电池循环寿命。
可选地，第一石墨与第二石墨不同，比如，第一石墨的比表面积为1.0m 2/g-1.8m 2/g，第二石墨的比表面积为1.0m 2/g-1.8m 2/g。
可选地，第一石墨与第二石墨的克容量相同，第一石墨与第二石墨的比表面积不同；和/或，第一活性材料包括第一硅材料，第二活性材料包括第二硅材料，第一硅材料与第二硅材料的克容量相同，第一硅材料与第二硅材料的比表面积不同。比如，第一石墨与第二石墨的克容量相同，第一石墨和第二石墨的克容量可以均为355mAh/g，且第一石墨与第二石墨的比表面积不同，第一石墨的比表面积可以为1.4m 2/g，第二石墨的比表面积可以为1.2m 2/g。
可选地，第一活性材料包括第一硅材料，第二活性材料包括第二硅材料，第一硅材料与第二硅材料不同，比如，第一硅材料可以为SiO，第二硅材料可以为SiN。第一硅材料与第二硅材料的克容量可以相同，第一硅材料与第二硅材料的比表面积可以不同，比如，第一硅材料和第二硅材料的克容量可以均为1360mAh/g，第一硅材料的比表面积可以为1.80m 2/g，第二硅材料的比表面积可以为2.01m 2/g，有利于防止循环膨胀，有效提升能量密度。
在一些实施例中，第一活性材料还包括第一硅材料，第二活性材料还包括第二硅材料，第一硅材料占第一活性材料的质量比为5％-40％，比如第一硅材料占第一活性材料的质量比为5％-20％，第二硅材料占第二活性材料的质量比为5％-40％，比如第二硅材料占第二活性材料的质量比为5％-20％，具体可以根据实际需要选择。
在另一些实施例中，第一活性材料还包括第一硅材料，第二活性材料还包括第二硅材料，第一硅材料的比表面积为1.1m 2/g-4.0m 2/g，第二硅材料的比表面积为1.1m 2/g-4.0m 2/g，具体可以根据实际需要选择。
在本申请的实施例中，第一活性层11与第二活性层12的涂覆面密度可 以相同，第一活性层11中第一硅材料的质量分数为X1％，第二活性层12中第二硅材料的质量分数为X2％，第一硅材料的比表面积为b1，第二硅材料的比表面积为b2，第一硅材料的克容量为d1，第二硅材料的克容量为d2；第一活性层11中第一石墨的比表面积为a1，第二活性层12中第二石墨的比表面积为a2，第一石墨的克容量为c1，第二石墨的克容量为c2；第一活性层11的单位质量的容量为c1*(1-X1％)+d1X1％mAh/g，第二活性层12的单位质量的容量为c2*(1-X2％)+d2X2％mAh/g；第一活性层11的单位质量的容量与第一活性层11的比表面积之比作为第一容量比Y1，第二活性层12的单位质量的容量与第二活性层12的比表面积之比作为第二容量比Y2，Y1＝[c1*(1-X1％)+d1X1％]/[a1*(1-X1％)+b1X1％]，Y2＝[c2*(1-X2％)+d2X2％]/[a2*(1-X2％)+b2X2％]，Y2/Y1大于1，Y2/Y1优选为1.05-1.5。
具体地，第一活性层11中包括第一导电剂，第二活性层12中包括第二导电剂；和/或，第一活性层11中包括第一粘接剂，第二活性层12中包括第二粘接剂。其中，第一导电剂和第二导电剂可以分别包括导电炭黑、碳纳米管、炭黑、碳纤维中的至少一种，第一导电剂和第二导电剂的粒径可以为0.01-50μm，导电剂的种类以及粒径具体可以根据实际需要合理选择。第一粘接剂和第二粘接剂可以分别包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯亚胺(PEI)、聚苯胺(PAN)、聚丙烯酸(PAA)、海藻酸钠、丁苯橡胶(SBR)、羧甲基纤维素钠(CMC)、酚醛树脂或环氧树脂等高分子聚合物中的一种或多种。
本申请实施例提供一种负极片的制备方法，负极片的制备方法包括：
提供集流体10；
在集流体10的至少一侧表面形成第一活性层11；
在第一活性层11上远离集流体10的一侧表面形成第二活性层12，得到负极片；
其中，第一活性层11与第二活性层12不同，第一活性层11中包括第一活性材料，第一活性材料包括第一石墨，第二活性层12中包括第二活性材料，第二活性材料包括第二石墨；第一活性材料的单位质量的容量与第一活性材料的比表面积之比为第一容量比，第二活性材料的单位质量的容量与第二活性材料的比表面积之比为第二容量比，所述第二容量比与所述第一容量比的 比值大于1。在本申请的负极片中，在集流体上涂覆不同的活性层，集流体10的至少一侧表面形成第一活性层11，在第一活性层11上远离集流体10的一侧表面形成第二活性层12，让第二活性材料的第二容量比与第一活性材料的第一容量比的比值大于1，可以提高负极材料的循环寿命，降低膨胀率，提高负极片的容量，提高电池的体积能量密度，满足高能量需要。
在一些实施例中，所述第二容量比与所述第一容量比的比值为1.05-1.5。
在另一些实施例中，第一活性材料包括第一硅材料；和/或
第二活性材料包括第二硅材料。
具体地，第一石墨与第二石墨不同，第一石墨的比表面积为1.0m 2/g-1.8m 2/g，第二石墨的比表面积为1.0m 2/g-1.8m 2/g。
其中，第一石墨与第二石墨的克容量相同，第一石墨与第二石墨的比表面积不同；和/或，
第一活性材料还包括第一硅材料，第二活性材料还包括第二硅材料，第一硅材料与第二硅材料的克容量相同，第一硅材料与第二硅材料的比表面积不同。
可选地，第一活性材料包括第一硅材料，第二活性材料包括第二硅材料，第一硅材料与第二硅材料不同。比如，第一硅材料与第二硅材料的克容量相同，第一硅材料与第二硅材料的比表面积不同。
可选地，第一活性材料还包括第一硅材料，第二活性材料还包括第二硅材料，第一硅材料占第一活性材料的质量比为5％-40％，第二硅材料占第二活性材料的质量比为5％-40％。第一活性材料还包括第一硅材料，第二活性材料还包括第二硅材料，第一硅材料的比表面积为1.1m 2/g-4.0m 2/g，第二硅材料的比表面积为1.1m 2/g-4.0m 2/g。
在本申请的实施例中，第一活性层11中包括第一导电剂，第二活性层12中包括第二导电剂；和/或，第一活性层11中包括第一粘接剂，第二活性层12中包括第二粘接剂。
本申请实施例提供一种电池，电池可以为锂离子电池，电池包括上述实施例中所述的负极片。具有上述实施例中负极片的电池，循环寿命长，电池的体积能量密度高，可以满足高能量需要。
下面通过一些具体的实施例对本申请做进一步说明。
实施例1
正极片的制备：
将正极活性物质钴酸锂(LiCoO 2)、导电剂炭黑、粘结剂聚偏二氟乙烯(PVDF)和溶剂N-甲基吡咯烷酮(NMP)按照重量比96：2.5：1.5：80均匀混合，得到待涂覆的正极浆料；
正极浆料均匀涂覆在厚度为13μm的铝箔集流体上，涂覆完成烘干处理后得到待辊压的正极片。
负极片的制备：
第一浆料的制备：将负极活性物质第一石墨、第一硅材料、导电剂、粘结剂羧甲基纤维素(CMC)、丁苯橡胶(SBR)和去离子水按照一定质量比，按照步骤加入搅拌机内混合搅拌，其中，第一石墨占第一石墨和第一硅材料总质量的90％，第一硅材料占石墨和第一硅材料总质量的10％，分散均匀，得到待涂覆的第一浆料。其中，第一石墨的克容量为355mAh/g，第一石墨的比表面积为1.4m 2/g，第一硅材料为SiO，第一硅材料的克容量为1360mAh/g，第一硅材料的比表面积分别为1.95m 2/g；
第二浆料的制备：将负极活性物质第二石墨、第二硅材料、导电剂、粘结剂羧甲基纤维素(CMC)、丁苯橡胶(SBR)和去离子水按照一定质量比，按照步骤加入搅拌机内混合搅拌，其中，第二石墨占第二石墨和第二硅材料总质量的90％，第二硅材料占第二石墨和第二硅材料总质量的10％，分散均匀，得到待涂覆的第二浆料，第二石墨的克容量为355mAh/g，第二石墨的比表面积为1.2m 2/g，第二硅材料为SiO，第二硅材料的克容量为1360mAh/g，第二硅材料的比表面积分别为1.95m 2/g；
用双层涂布机涂覆，将第一浆料均匀涂覆在厚度为8μm的铜箔集流体上形成第一浆料层，将第二浆料同时涂覆在第二浆料层上，第一浆料层和第二浆料层的涂覆面密度一致，涂覆完成烘干处理后得到待辊压的负极片。
成品电池的制作：取上述已经涂覆好的正极片和负极片烘烤之后通过辊压分切、制片、卷绕、封装烘烤、注液、化成等步骤制备得到成品电池。
实施例2-5和对比例1
实施例2-5和对比例1中正极片的制作和成品电池的制作与实施例1相 同。
实施例2-5和对比例1中负极片的制作和实施例1相同，不同之处在于：活性层中石墨与硅材料的比表面积，具体如下表1。
表1实施例1-5和对比例1中的石墨与硅材料的比表面积
Figure PCTCN2021116767-appb-000001
实施例6-8和对比例2-3
实施例6-8和对比例2-3中正极片的制作和成品电池的制作与实施例1相同。
实施例6-8和对比例2-3中负极片的制作和实施例1相同，不同之处在于：硅材料的质量分数不一样。具体如下表2，按照实施例1中石墨和硅材料的克容量以及给定的比表面积值。
表2实施例6-7以及对比例2-3的硅材料含量
Figure PCTCN2021116767-appb-000002
Figure PCTCN2021116767-appb-000003
对比例4
负极片的制作：负极活性物质石墨1与实施例1中的第一石墨为同种材料，硅材料1与实施例1中的第一硅材料为同种材料；负极活性物质石墨2与实施例1中的第二石墨为同种材料，硅材料2与实施例1中的第二硅材料为同种材料；
负极浆料的制备：将负极活性物质石墨1、硅材料1、导电炭黑、粘结剂羧甲基纤维素(CMC)、丁苯橡胶(SBR)和去离子水按照一定质量比按照步骤加入搅拌机内混合搅拌，分散均匀，其中，石墨1占石墨1和硅材料1总质量的90％，硅材料1占石墨1和硅材料1总质量的10％，硅材料为SiO，得到待涂覆的负极浆料；
将负极浆料均匀涂覆在厚度为8μm的铜箔集流体上，涂覆完成烘干处理后得到待辊压的负极片。
正极片的制作和成品电池的制作与实施例1相同。
对比例5
负极片的制作：
负极浆料的制备：将负极活性物质石墨1、硅材料2、导电炭黑、粘结剂羧甲基纤维素(CMC)、丁苯橡胶(SBR)和去离子水按照一定质量比按照步骤加入搅拌机内混合搅拌，分散均匀，其中，石墨1占石墨1和硅材料2总质量的90％，硅材料2占石墨1和硅材料1总质量的10％，得到待涂覆的负极浆料；
将负极浆料均匀涂覆在厚度为8μm的铜箔集流体上，涂覆完成烘干处理后得到待辊压的负极片；
正极片的制作和成品电池的制作与实施例1相同。
对比例6
负极浆料的制备：
将负极活性物质石墨2、硅材料1、导电炭黑、粘结剂羧甲基纤维素(CMC)、丁苯橡胶(SBR)和去离子水按照一定质量比按照步骤加入搅拌机内混合搅拌，分散均匀，其中，石墨2占石墨2和硅材料1总质量的90％，硅材料1占石墨2和硅材料1总质量的10％，得到待涂覆的负极浆料；
将负极浆料均匀涂覆在厚度为8μm的铜箔集流体上，涂覆完成烘干处理后得到待辊压的负极片；
正极片的制作和成品电池的制作与实施例1相同。
对比例4-6中的活性层中的石墨与硅材料如下表3。
表3对比例4-6中的活性层中的石墨与硅材料
Figure PCTCN2021116767-appb-000004
对实施例1-8和对比例1-6中的电池进行性能测试
(1)25度循环测试
对所制电池在25℃条件下进行0.7C/0.5C的充放循环测试；
(2)45度循环测试
对所制电池在45℃条件下进行0.7C/0.5C的充放循环测试；
实施例1-8和对比例1-6中的电池测试结果如表4所示。
表4实施例1-8和对比例1-6的循环测试结果
名称 25℃循环500T容量保持率 45℃循环500T容量保持率
实施例1 83.2％ 82.5％
实施例2 84.9％ 84.8％
实施例3 84.1％ 82.9％
实施例4 84.3％ 83.7％
实施例5 82.6％ 81.9％
实施例6 83.0％ 82.2％
实施例7 84.7％ 84.2％
实施例8 84.5％ 83.9％
对比例1 77.3％ 78.4％
对比例2 79.1％ 79.9％
对比例3 77.1％ 78.2％
对比例4 77.9％ 78.5％
对比例5 76.6％ 76.2％
对比例6 78.3％ 78.8％
从上述表4可知，25℃和45℃循环500圈后，相比于对比例1-6中电池的容量保持率，实施例1-8中的容量保持率较高，循环性能较好。
除非另作定义，本申请中使用的技术术语或者科学术语应当为本申请所属领域内具有一般技能的人士所理解的通常意义。本申请中使用的“第一”、“第二”以及类似的词语并不表示任何顺序、数量或者重要性，而只是用来区分不同的组成部分。“连接”或者“相连”等类似的词语并非限定于物理的或者机械的连接，而是可以包括电性的连接，不管是直接的还是间接的。 “上”、“下”、“左”、“右”等仅用于表示相对位置关系，当被描述对象的绝对位置改变后，则该相对位置关系也相应地改变。
以上所述是本申请的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请所述原理的前提下，还可以作出若干改进和润饰，这些改进和润饰也应视为本申请的保护范围。

Claims (11)

  1. 一种负极片，其中，包括：
    集流体；
    所述集流体的至少一侧表面设有第一活性层，所述第一活性层上远离所述集流体的一侧表面设有第二活性层，所述第一活性层与所述第二活性层不同，所述第一活性层中包括第一活性材料，所述第一活性材料包括第一石墨，所述第二活性层中包括第二活性材料，所述第二活性材料包括第二石墨；
    所述第一活性材料的单位质量的容量与所述第一活性材料的比表面积之比为第一容量比，所述第二活性材料的单位质量的容量与所述第二活性材料的比表面积之比为第二容量比，所述第二容量比与所述第一容量比的比值大于1。
  2. 根据权利要求1所述的负极片，其中，所述第二容量比与所述第一容量比的比值为1.05-1.5。
  3. 根据权利要求1或2所述的负极片，其中，所述第一活性材料还包括第一硅材料；和/或，
    所述第二活性材料还包括第二硅材料。
  4. 根据权利要求1-3任一项所述的负极片，其中，所述第一石墨的比表面积为1.0m 2/g-1.8m 2/g，所述第二石墨的比表面积为1.0m 2/g-1.8m 2/g。
  5. 根据权利要求1-4任一项所述的负极片，其中，所述第一石墨与所述第二石墨的克容量相同，所述第一石墨与所述第二石墨的比表面积不同；和/或，
    所述第一活性材料还包括第一硅材料，所述第二活性材料还包括第二硅材料，所述第一硅材料与所述第二硅材料的克容量相同，所述第一硅材料与所述第二硅材料的比表面积不同。
  6. 根据权利要求1-5任一项所述的负极片，其中，所述第一活性材料还包括第一硅材料，所述第二活性材料还包括第二硅材料，所述第一硅材料占所述第一活性材料的质量比为5％-40％，所述第二硅材料占所述第二活性材料的质量比为5％-40％。
  7. 根据权利要求6所述的负极片，其中，所述第一硅材料占所述第一活性材料的质量比为5％-20％，所述第二硅材料占所述第二活性材料的质量比为 5％-20％。
  8. 根据权利要求1-7任一项所述的负极片，其中，所述第一活性材料还包括第一硅材料，所述第二活性材料还包括第二硅材料，所述第一硅材料的比表面积为1.1m 2/g-4.0m 2/g，所述第二硅材料的比表面积为1.1m 2/g-4.0m 2/g。
  9. 根据权利要求1-8任一项所述的负极片，其中，所述第一活性层中包括第一导电剂，所述第二活性层中包括第二导电剂；和/或，
    所述第一活性层中包括第一粘接剂，所述第二活性层中包括第二粘接剂。
  10. 一种负极片的制备方法，其中，包括：
    提供集流体；
    在所述集流体的至少一侧表面形成第一活性层；
    在所述第一活性层上远离所述集流体的一侧表面形成第二活性层；
    其中，所述第一活性层与所述第二活性层不同，所述第一活性层中包括第一活性材料，所述第一活性材料包括第一石墨，所述第二活性层中包括第二活性材料，所述第二活性材料包括第二石墨；所述第一活性材料的单位质量的容量与所述第一活性材料的比表面积之比为第一容量比，所述第二活性材料的单位质量的容量与所述第二活性材料的比表面积之比为第二容量比，所述第二容量比与所述第一容量比的比值大于1。
  11. 一种电池，其中，包括如权利要求1-9中任一项所述的负极片。
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