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WO2025035587A1 - Negative electrode sheet and manufacturing method therefor, and lithium-ion battery - Google Patents

Negative electrode sheet and manufacturing method therefor, and lithium-ion battery Download PDF

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Publication number
WO2025035587A1
WO2025035587A1 PCT/CN2023/127290 CN2023127290W WO2025035587A1 WO 2025035587 A1 WO2025035587 A1 WO 2025035587A1 CN 2023127290 W CN2023127290 W CN 2023127290W WO 2025035587 A1 WO2025035587 A1 WO 2025035587A1
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WIPO (PCT)
Prior art keywords
active material
material layer
electrode sheet
silicon
negative electrode
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PCT/CN2023/127290
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French (fr)
Chinese (zh)
Inventor
彭成龙
朱伯礼
高云雷
袁学强
于子龙
项海标
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Zhejiang Liwinon Energy Technology Co Ltd
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Zhejiang Liwinon Energy Technology Co Ltd
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Publication of WO2025035587A1 publication Critical patent/WO2025035587A1/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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—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
    • 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
    • H01M2004/026—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 invention belongs to the technical field of lithium ion batteries, and in particular relates to a negative electrode sheet and a preparation method thereof, and a lithium ion battery.
  • Another direction is to solve the volume expansion problem of silicon-based electrodes by optimizing the battery cell production process.
  • Selecting silicon-based materials with excellent performance and combining them with optimized battery cell production processes can better solve the adverse effects of electrode structure destruction caused by silicon volume expansion, which leads to a decrease in battery cell performance.
  • placing graphite in the first layer plays a role in fast charging
  • placing silicon particles in the second layer plays a role in improving energy density
  • these methods cannot solve the problem of increased battery cell thickness caused by the volume expansion of silicon.
  • there are currently technologies designed for graphite orientation which accelerate the ion transfer rate and thus improve the charging capacity by designing vertically oriented graphite.
  • the purpose of the present invention is: in order to reduce the risk of demolding and increase the energy density of the battery cell, the present invention designs a double-layer coating process, the first active material layer serves as the bottom layer, including silicon-based granular material, the second active material layer serves as the surface layer, including vertically oriented graphite, and the gaps between the vertical graphite on the surface layer provide expansion buffer space for the expansion of the silicon particles in the bottom layer.
  • a negative electrode sheet comprises a current collector, a first active material layer coated on at least one surface of the current collector and a second active material layer coated on the surface of the first active material layer, wherein the first active material layer comprises a silicon-based material and the second active material layer comprises vertically oriented graphite.
  • the viscosity ⁇ 1 of the first active material layer and the viscosity ⁇ 2 of the second active material layer satisfy the relationship: 0.5 ⁇ 1/ ⁇ 2 ⁇ 2.5.
  • the viscosity ⁇ 1 of the first active material layer is 3000-7000 mPa ⁇ s; and the viscosity ⁇ 2 of the second active material layer is 3000-5000 mPa ⁇ s.
  • the mass ratio of the silicon-based material to the vertically oriented graphite is (2-6):(4-8); and the silicon content in the silicon-based material is 2-15%.
  • the current collector includes at least one of copper foil, carbon paper and nickel foil; and the thickness of the current collector is 3 ⁇ m to 20 ⁇ m.
  • the silicon-based material includes at least one of silicon particles, silicon nanowires, and silicon-carbon skeleton composite materials; more preferably, silicon particles.
  • the vertically oriented graphite includes at least one of magnetic graphite and ordinary graphite magnetized by a magnetic fluid; wherein the magnetic fluid includes at least one of ferrosoferric oxide, ferrous oxide and ferric oxide.
  • the present invention also provides a method for preparing the above-mentioned negative electrode sheet, comprising the following steps:
  • the first active material layer slurry and the second active material layer slurry are coated on the current collector and dried to obtain a negative electrode sheet.
  • the mass ratio of the silicon-based material, the binder, the thickener and the conductive agent is (92-97%): (2.0-3.5%): (0.1-0.5%): (0.05-0.2%).
  • the mass ratio of the magnetic graphite, the binder and the thickener is (95% to 98%): (0.6 to 1.5%): (1.0 to 1.5%).
  • the binder includes at least one of PPA and SBR; the thickener includes at least one of CMC, PAA, PAN and polyacrylate; the conductive agent includes at least one of carbon nanotubes and graphene; the solvent is an aqueous solvent or an oil solvent, and the oil solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide and dimethyl sulfoxide.
  • the drying wind box is provided with a magnetic field emission device for converting part or all of the magnetic graphite material in the second active material layer slurry into vertically oriented graphite and vertically distributing it on the current collector.
  • the drying temperature is 60°C to 80°C.
  • the present invention also provides a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator spaced between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet mentioned above.
  • the present invention has at least the following beneficial effects:
  • the present invention designs a double-layer coating process.
  • the first active material layer serves as the bottom layer and includes a silicon-based granular material.
  • the second active material layer serves as the surface layer and includes vertically oriented graphite. The gaps between the vertical graphite on the surface layer provide an expansion buffer space for the expansion of the silicon particles in the bottom layer.
  • the double-layer coating structure and magnetic field deflection process of the negative electrode sheet of the present invention increase the energy density of the battery and avoid the risk of demolding of the vertically oriented graphite on the surface.
  • the vertically oriented graphite layer on the surface accelerates the transmission speed of lithium ions, adapts to the large volume change during charging and discharging, shortens the transmission path of electrons in the vertical direction, improves the electrode conductivity and the electron collection efficiency of the battery, and the electrolyte and the electrode are fully in contact, increasing the active sites and providing a certain buffer space for the expansion of the bottom silicon-based material. It is beneficial to reduce the expansion rate of the battery cell, while also ensuring the structural stability, which is beneficial to improving the cycle performance and charging capacity of the battery cell.
  • FIG1 is a schematic diagram of the structure of a negative electrode sheet in one embodiment of the present invention.
  • the present invention provides a negative electrode sheet, including a current collector, a first active material layer coated on at least one surface of the current collector, and a second active material layer coated on the surface of the first active material layer, the first active material layer includes a silicon-based material, and the second active material layer includes vertically oriented graphite.
  • the viscosity ⁇ 1 of the first active material layer and the viscosity ⁇ 2 of the second active material layer satisfy the relationship: 0.5 ⁇ 1/ ⁇ 2 ⁇ 2.5; ⁇ 1/ ⁇ 2 can specifically be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5; when the viscosity ⁇ 1 of the first active material layer and the viscosity ⁇ 2 of the second active material layer are controlled within the above range, the adhesion between the first active material layer and the second active material layer can be ensured to be better, so that the electrode is not prone to stratification, and the battery can form a complete path for electrons and ions, thereby solving the problem of battery performance deterioration due to electrode stratification, affecting the capacity retention rate of the battery during cycling.
  • the viscosity ⁇ 1 of the first active material layer is 3000-7000 mPa ⁇ s, specifically 3000 mPa ⁇ s, 3500 mPa ⁇ s, 4000 mPa ⁇ s, 4500 mPa ⁇ s, 5000 mPa ⁇ s, 5500 mPa ⁇ s, 6000 mPa ⁇ s, 6500 mPa ⁇ s, 7000 mPa ⁇ s; when the viscosity ⁇ 1 of the first active material layer is controlled within the above range, a uniform and fixed coating can be formed to ensure that the battery has good electrochemical properties; if the viscosity is too small, it will lead to excessive fluidity and fail to form a uniform and fixed coating. If the viscosity is too high, the slurry will lack fluidity and will easily become uneven, affecting the electrochemical performance of the battery cell.
  • the viscosity ⁇ 2 of the second active material layer is 3000-5000mPa ⁇ s, specifically 3000mPa ⁇ s, 3200mPa ⁇ s, 3500mPa ⁇ s, 3800mPa ⁇ s, 4000mPa ⁇ s, 4200mPa ⁇ s, 4500mPa ⁇ s, 4800mPa ⁇ s, 5000mPa ⁇ s; when the viscosity ⁇ 2 of the second active material layer is controlled within the above range, it can be well bonded with the first active material layer, so that the two coatings are not prone to stratification, so that the battery can form a complete path for electrons and ions, thereby solving the problem of battery performance deterioration due to electrode stratification, affecting the capacity retention rate of the battery during cycling.
  • the mass ratio of silicon-based material to vertically oriented graphite is (2-6):(4-8), specifically 2:8, 3:7, 4:6, 5:5, 6:4.
  • the mass ratio of silicon-based material to vertically oriented graphite is controlled within the above range, while ensuring that the battery has a high energy density, the underlying silicon-based material can be protected by the vertically oriented graphite, thereby effectively suppressing the volume expansion caused by the silicon-based material. If the content of silicon-based material is too much, the volume expansion of the battery will increase seriously, thereby deteriorating the battery and affecting the performance of the battery. If the content of silicon-based material is too little, the battery cannot be guaranteed to have a high energy density.
  • the silicon content in the silicon-based material is 2-15%, specifically 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%; when the silicon content in the silicon-based material is controlled within the above range, the second active material layer can effectively control the volume expansion of the silicon-based material, thereby ensuring that the battery has a higher energy density while also having better performance.
  • the current collector includes at least one of copper foil, carbon paper, and nickel foil; the thickness of the current collector is 3 ⁇ m to 20 ⁇ m, specifically 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, and 20 ⁇ m.
  • the silicon-based material includes at least one of silicon particles, silicon nanowires, and silicon-carbon skeleton composite materials; preferably silicon particles.
  • the vertically oriented graphite includes at least one of magnetic graphite and ordinary graphite magnetized by a magnetic fluid; wherein the magnetic fluid includes at least one of ferrosoferric oxide, ferrous oxide and ferric oxide.
  • the present invention further provides a method for preparing the above-mentioned negative electrode sheet, comprising the following steps:
  • the first active material layer slurry and the second active material layer slurry are coated on the current collector and dried to obtain a negative electrode sheet.
  • the present invention designs a double-layer coating process, in which the bottom coating is a silicon-based granular material slurry layer, and the surface coating is a vertically oriented graphite slurry layer.
  • the gaps between the vertical graphites on the surface provide expansion buffer space for the expansion of the bottom silicon particles.
  • the bottom silicon-based material layer increases the energy density of the battery and avoids the risk of demolding of the vertically oriented graphite on the surface, while the vertically oriented graphite layer on the surface accelerates the lithium ion transmission speed, adapts to the large volume change during charging and discharging, shortens the electron transmission path in the vertical direction, improves the electrode conductivity and the electron collection efficiency of the battery, the electrolyte and the electrode are in full contact, the active sites are increased, and a certain buffer space is provided for the expansion of the bottom silicon-based material, which is beneficial to reducing the expansion rate of the battery cell, while also ensuring the structural stability, which is beneficial to improving the cycle performance and charging capacity of the battery cell.
  • the mass ratio of silicon-based material, binder, thickener and conductive agent is (92-97%): (2.0-3.5%): (0.1-0.5%): (0.05-0.2%); preferably 96.9%: 2.7%: 0.3%: 0.1%;
  • the mass ratio of magnetic graphite, binder and thickener is (95% to 98%): (0.6 to 1.5%): (1.0 to 1.5%); preferably 97.7%: 1.3%: 1.0%.
  • the binder includes at least one of PPA and SBR; the thickener includes at least one of CMC, PAA, PAN and polyacrylate; the conductive agent includes at least one of carbon nanotubes and graphene; the solvent is an aqueous solvent or an oil solvent, and the oil solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide and dimethyl sulfoxide.
  • a magnetic field emission device is provided in the bellows during drying to convert part or all of the magnetic graphite material in the second active material layer slurry into vertically oriented graphite and distribute it vertically on the current collector.
  • the drying temperature is 60°C-80°C, specifically 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C.
  • the present invention further provides a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet mentioned above.
  • the positive electrode active material in the positive electrode sheet may include but is not limited to at least one of LiCoO2 , LiNiO2 , LiMnO2 , LiMn2O4 , LiMnPO4 , LiFePO4 , LiNi1 / 3Co1 / 3Mn1 / 3O2, LiNi0.5Co0.2Mn0.3O2 , LiNi0.6Co0.2Mn0.2O2 , LiNi0.8Co0.1Mn0.1O2 , LiNi0.6Co0.1Mn0.3O2 , and LiNi0.85Co0.15Al0.05O2 .
  • the separator may be at least one of, but not limited to, polyethylene, polypropylene, polyvinylidene fluoride, and multilayer composite films thereof;
  • the electrolyte includes an electrolyte salt and an organic solvent, wherein the specific types and compositions of the electrolyte salt and the organic solvent are not subject to specific restrictions, and include positive electrode film-forming additives, negative electrode film-forming additives, and cycle-improving and low-temperature additives, etc.;
  • This embodiment provides a negative electrode sheet, including a current collector 1, and a A first active material layer and a second active material layer coated on the surface of the first active material layer, the first active material layer includes a silicon-based material 2 , and the second active material layer includes vertically oriented graphite 3 .
  • This embodiment also provides a method for preparing the above-mentioned negative electrode sheet, comprising the following steps:
  • (1) Configuration of the first active material layer slurry: silicon-based active material: carbon nanotube: PPA: SBR: CMC 96.9%: 0.1: 2.4: 0.3: 0.3 is mixed evenly, deionized water is added, and stirred evenly to obtain the first active material layer slurry, i.e., the bottom coating slurry; wherein the doping amount of silicon in the silicon-based active material is 3%; and the viscosity ⁇ 1 of the slurry is 3000 mPa ⁇ s;
  • step (3) the mass ratio of the first active material layer slurry to the second active material layer slurry is 3:7; the rest is the same as embodiment 1 and will not be repeated here.
  • step (3) the mass ratio of the first active material layer slurry to the second active material layer slurry is 4:6; the rest is the same as embodiment 1 and will not be repeated here.
  • step (3) the mass ratio of the first active material layer slurry to the second active material layer slurry is 5:5; the rest is the same as embodiment 1 and will not be repeated here.
  • step (3) the mass ratio of the first active material layer slurry to the second active material layer slurry is 6:4; the rest is the same as embodiment 1 and will not be repeated here.
  • step (1) the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 1 and will not be repeated here.
  • step (1) the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 2 and will not be repeated here.
  • step (1) the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 3 and will not be repeated here.
  • step (1) the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 4 and will not be repeated here.
  • step (1) the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 5 and will not be repeated here.
  • step (3) the mass ratio of the first active material layer slurry to the second active material layer slurry is 7:3; the rest is the same as Example 1 and will not be repeated here.
  • step (3) the mass ratio of the first active material layer slurry to the second active material layer slurry is 1:9; the rest is the same as Example 1 and will not be repeated here.
  • the negative electrode sheets and positive electrode sheets prepared in Examples 1-10 and Comparative Examples 1-4 are processed into finished batteries through post-processing such as rolling, slitting, tab welding, winding, packaging, baking, liquid injection, formation, and degassing.
  • the reason is that when the viscosity ⁇ 1 of the first active material layer slurry and the viscosity ⁇ 2 of the second active material layer slurry differ too much, the first active material layer and the second active material layer cannot be well bonded, so that the two coatings are prone to stratification, so that the battery cannot form a complete path for electrons and ions, resulting in the deterioration of the performance of the electrode stratification battery, affecting the capacity retention rate of the battery during cycling; further, when the viscosity ⁇ 1 of the first active material layer slurry is too large or too small, the fluidity of the first active material layer slurry will be too small or too large to form a uniform and fixed coating, thereby affecting the performance of the battery.
  • the bottom silicon-based material layer increases the energy density of the battery and avoids the risk of demolding of the surface vertically oriented graphite, while the surface vertically oriented graphite layer accelerates the lithium ion transmission speed, adapts to the large volume changes during charging and discharging, shortens the electron transmission path in the vertical direction, improves the electrode conductivity and the electron collection efficiency of the battery, and the electrolyte and the electrode are fully in contact, which increases the active sites and provides a certain buffer space for the expansion of the bottom silicon-based material, which is beneficial to reducing the expansion rate of the battery cell. At the same time, it also ensures the structural stability, which is beneficial to improving the cycle performance and charging capacity of the battery cell.

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Manufacturing & Machinery (AREA)
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  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

Disclosed in the present invention are a negative electrode sheet and a manufacturing method therefor, and a lithium-ion battery. The negative electrode sheet comprises a current collector, a first active material layer applied to coat at least one surface of the current collector, and a second active material layer applied to coat the surface of the first active material layer. The first active material layer comprises a silicon-based material, and the second active material layer comprises vertically oriented graphite. According to the present invention, the first active material layer increases the energy density of a battery and avoids the demolding risk of the second active material layer; a second active material accelerates lithium ion transport, thereby adapting to a large volume change in a charging and discharging process, shortening the transport path of electrons in the vertical direction, and improving the electrical conductivity of an electrode and the electron collection efficiency of the battery; and an electrolyte is in full contact with the electrode, thereby increasing active sites, providing a certain buffer space for the expansion of the silicon-based material in the first active material layer, reducing the expansion rate of a battery cell, ensuring the structural stability, and improving the cycle performance and charging capability of the battery cell.

Description

一种负极片及其制备方法和锂离子电池Negative electrode sheet and preparation method thereof and lithium ion battery 技术领域Technical Field

本发明属于锂离子电池技术领域，具体涉及一种负极片及其制备方法和锂离子电池。The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a negative electrode sheet and a preparation method thereof, and a lithium ion battery.

背景技术Background Art

随着市场对电池的能量密度要求越来越高，单纯的石墨负极的理论容量仅有372mAh g-1，已经不能满足市场需求。开发具有高比容量的负极材料是一种有效的策略，其中硅材料由于具有高的理论容量4200mAh g-1，成为当前研究热点。然而，硅材料存在较大的体积膨胀(400％)导致硅颗粒破裂、电极膨胀、SEI破坏、较低的库伦效率和快速的容量衰减问题，给商业化应用带来严峻的挑战。As the market demands higher and higher energy density for batteries, the theoretical capacity of pure graphite anode is only 372mAh g -1 , which can no longer meet the market demand. Developing anode materials with high specific capacity is an effective strategy, among which silicon materials have become a current research hotspot due to their high theoretical capacity of 4200mAh g -1 . However, silicon materials have large volume expansion (400%), which leads to silicon particle rupture, electrode expansion, SEI destruction, low coulombic efficiency and rapid capacity decay, bringing severe challenges to commercial applications.

因此，除了对硅材料进行改性复合，如包覆、纳米化、与其他材料复合等优化策略外，另外一种方向就是通过优化电芯生产工艺来解决硅基电极的体积膨胀问题。选择性能优异的硅基材料，再配合优化的电芯生产工艺可以较好的解决硅体积膨胀带来的电极结构破坏而导致电芯性能下降的不利影响。Therefore, in addition to optimizing strategies such as modifying and compounding silicon materials, such as coating, nano-crystallization, and compounding with other materials, another direction is to solve the volume expansion problem of silicon-based electrodes by optimizing the battery cell production process. Selecting silicon-based materials with excellent performance and combining them with optimized battery cell production processes can better solve the adverse effects of electrode structure destruction caused by silicon volume expansion, which leads to a decrease in battery cell performance.

在现有技术中，将石墨放置第一层起到快充作用，将硅颗粒放在第二层起到提升能量密度的作用；以及有将硅基颗粒、与石墨颗粒尺寸进行设计，来抑制电芯体积膨胀。然而，这些方法并不能很好解决硅的体积膨胀带来电芯厚度增加的问题。此外，当前也有技术针对石墨取向进行设计，通过设计了垂直取向石墨，来加速离子传输速率，从而提高充电能力。但单层垂直取向石墨与集流体涂布后容易发生脱模问题，故有人通过在底层涂覆常规石墨，上层涂覆垂直取向石墨来增加降低脱模风险，但这种方式没有进一步增加电芯能量密度。 In the prior art, placing graphite in the first layer plays a role in fast charging, and placing silicon particles in the second layer plays a role in improving energy density; and there are designs for silicon-based particles and graphite particle sizes to suppress the volume expansion of the battery cell. However, these methods cannot solve the problem of increased battery cell thickness caused by the volume expansion of silicon. In addition, there are currently technologies designed for graphite orientation, which accelerate the ion transfer rate and thus improve the charging capacity by designing vertically oriented graphite. However, single-layer vertically oriented graphite is prone to demolding problems after coating with the current collector, so some people increase the risk of demolding by coating conventional graphite on the bottom layer and vertically oriented graphite on the upper layer, but this method does not further increase the energy density of the battery cell.

发明内容Summary of the invention

本发明的目的在于：本发明为了降低脱模风险和增加电芯能量密度，设计了双层涂布工艺，第一活性物质层作为底层，包括硅基颗粒材料，第二活性物质层作为表层，包括垂直取向石墨，表层的垂直石墨之间的间隙为底层硅颗粒膨胀提供了膨胀缓冲空间。The purpose of the present invention is: in order to reduce the risk of demolding and increase the energy density of the battery cell, the present invention designs a double-layer coating process, the first active material layer serves as the bottom layer, including silicon-based granular material, the second active material layer serves as the surface layer, including vertically oriented graphite, and the gaps between the vertical graphite on the surface layer provide expansion buffer space for the expansion of the silicon particles in the bottom layer.

为了实现上述目的，本发明采用以下技术方案：In order to achieve the above object, the present invention adopts the following technical solutions:

一种负极片，包括集流体、涂覆在集流体至少一表面上的第一活性物质层和涂覆在所述第一活性物质层表面的第二活性物质层，所述第一活性物质层包括硅基材料，所述第二活性物质层包括垂直取向石墨。A negative electrode sheet comprises a current collector, a first active material layer coated on at least one surface of the current collector and a second active material layer coated on the surface of the first active material layer, wherein the first active material layer comprises a silicon-based material and the second active material layer comprises vertically oriented graphite.

优选的，所述第一活性物质层的粘度η1和所述第二活性物质层的粘度η2满足关系式：0.5≤η1/η2≤2.5。Preferably, the viscosity η1 of the first active material layer and the viscosity η2 of the second active material layer satisfy the relationship: 0.5≤η1/η2≤2.5.

优选的，所述第一活性物质层的粘度η1为3000～7000mPa·s；所述第二活性物质层的粘度η2为3000～5000mPa·s。Preferably, the viscosity η1 of the first active material layer is 3000-7000 mPa·s; and the viscosity η2 of the second active material layer is 3000-5000 mPa·s.

优选的，所述硅基材料与所述垂直取向石墨的质量比为(2～6):(4～8)；所述硅基材料中硅的含量为2～15％。Preferably, the mass ratio of the silicon-based material to the vertically oriented graphite is (2-6):(4-8); and the silicon content in the silicon-based material is 2-15%.

优选的，所述集流体包括铜箔、碳纸、镍箔中的至少一种；所述集流体的厚度为3μm～20μm。Preferably, the current collector includes at least one of copper foil, carbon paper and nickel foil; and the thickness of the current collector is 3 μm to 20 μm.

优选的，所述硅基材料包括硅颗粒、硅纳米线、硅碳骨架复合材料中的至少一种；更优选为硅颗粒。Preferably, the silicon-based material includes at least one of silicon particles, silicon nanowires, and silicon-carbon skeleton composite materials; more preferably, silicon particles.

优选的，所述垂直取向石墨包括磁性石墨、经磁流体磁化的普通石墨中的至少一种；其中，磁流体包括四氧化三铁、氧化亚铁和氧化铁中的至少一种。Preferably, the vertically oriented graphite includes at least one of magnetic graphite and ordinary graphite magnetized by a magnetic fluid; wherein the magnetic fluid includes at least one of ferrosoferric oxide, ferrous oxide and ferric oxide.

本发明还提供一种上述的负极片的制备方法，包括以下步骤：The present invention also provides a method for preparing the above-mentioned negative electrode sheet, comprising the following steps:

(1)将硅基材料、粘结剂、增稠剂、导电剂进行混合，加入溶剂，搅拌均匀，即得到第一活性物质层浆料；(1) mixing a silicon-based material, a binder, a thickener, and a conductive agent, adding a solvent, and stirring uniformly to obtain a first active material layer slurry;

(2)将磁性石墨、粘结剂、增稠剂进行混合，加入溶剂，搅拌均匀，即得到第二活性物质层浆料； (2) mixing magnetic graphite, a binder, and a thickener, adding a solvent, and stirring evenly to obtain a second active material layer slurry;

(3)将第一活性物质层浆料和第二活性物质层浆料在集流体上进行涂布，烘干，即得到负极片。(3) The first active material layer slurry and the second active material layer slurry are coated on the current collector and dried to obtain a negative electrode sheet.

优选的，所述硅基材料、粘结剂、增稠剂、导电剂的质量比为(92-97％):(2.0～3.5％):(0.1～0.5％):(0.05～0.2％)。Preferably, the mass ratio of the silicon-based material, the binder, the thickener and the conductive agent is (92-97%): (2.0-3.5%): (0.1-0.5%): (0.05-0.2%).

优选的，所述磁性石墨、粘结剂、增稠剂的质量比为(95％～98％):(0.6～1.5％):(1.0～1.5％)。Preferably, the mass ratio of the magnetic graphite, the binder and the thickener is (95% to 98%): (0.6 to 1.5%): (1.0 to 1.5%).

优选的，所述粘结剂包括PPA、SBR中的至少一种；所述增稠剂包括CMC、PAA、PAN和聚丙烯酸酯中的至少一种；所述导电剂包括碳纳米管、石墨烯中的至少一种；所述溶剂为水系溶剂或油系溶剂，所述油系溶剂包括N-甲基吡咯烷酮、N,N-二甲基甲酰胺、二甲基亚砜中的至少一种。Preferably, the binder includes at least one of PPA and SBR; the thickener includes at least one of CMC, PAA, PAN and polyacrylate; the conductive agent includes at least one of carbon nanotubes and graphene; the solvent is an aqueous solvent or an oil solvent, and the oil solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide and dimethyl sulfoxide.

优选的，步骤(3)中，所述烘干的风箱中设置有磁场发射装置，用于使第二活性物质层浆料中的磁性石墨材料部分或全部变成垂直取向石墨并垂直分布于集流体。Preferably, in step (3), the drying wind box is provided with a magnetic field emission device for converting part or all of the magnetic graphite material in the second active material layer slurry into vertically oriented graphite and vertically distributing it on the current collector.

优选的，步骤(3)中，所述烘干的温度为60℃～80℃。Preferably, in step (3), the drying temperature is 60°C to 80°C.

本发明还提供一种锂离子电池，包括正极片、负极片、电解液以及间隔于所述正极片与所述负极片之间的隔膜，所述负极片为上述的负极片。The present invention also provides a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator spaced between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet mentioned above.

与现有技术相比，本发明至少具有以下有益效果：Compared with the prior art, the present invention has at least the following beneficial effects:

(1)本发明为了降低脱模风险和增加电芯能量密度，设计了双层涂布工艺，第一活性物质层作为底层，包括硅基颗粒材料，第二活性物质层作为表层，包括垂直取向石墨，表层的垂直石墨之间的间隙为底层硅颗粒膨胀提供了膨胀缓冲空间。(1) In order to reduce the risk of demolding and increase the energy density of the battery cell, the present invention designs a double-layer coating process. The first active material layer serves as the bottom layer and includes a silicon-based granular material. The second active material layer serves as the surface layer and includes vertically oriented graphite. The gaps between the vertical graphite on the surface layer provide an expansion buffer space for the expansion of the silicon particles in the bottom layer.

(2)本发明负极片的双层涂布结构和磁场偏转工艺，底层硅基材料层增大了电池的能量密度和避免了表层垂直取向石墨脱模风险，而表层垂直取向石墨层加快了锂离子传输速度，适应充放电过程中较大的体积变化，缩短了电子在垂直方向的传输路径，提升了电极电导率和电池的电子收集效率，电解液与电极之间充分接触，增加了活性位点，为底层硅基材料膨胀提供了一定的缓冲空 间，有利于降低电芯膨胀率，同时也保证了结构稳定性，有利于提升电芯的循环性能和充电能力。(2) The double-layer coating structure and magnetic field deflection process of the negative electrode sheet of the present invention increase the energy density of the battery and avoid the risk of demolding of the vertically oriented graphite on the surface. The vertically oriented graphite layer on the surface accelerates the transmission speed of lithium ions, adapts to the large volume change during charging and discharging, shortens the transmission path of electrons in the vertical direction, improves the electrode conductivity and the electron collection efficiency of the battery, and the electrolyte and the electrode are fully in contact, increasing the active sites and providing a certain buffer space for the expansion of the bottom silicon-based material. It is beneficial to reduce the expansion rate of the battery cell, while also ensuring the structural stability, which is beneficial to improving the cycle performance and charging capacity of the battery cell.

附图说明BRIEF DESCRIPTION OF THE DRAWINGS

图1为本发明一实施例中负极片的结构示意图；FIG1 is a schematic diagram of the structure of a negative electrode sheet in one embodiment of the present invention;

其中，1-集流体，2-硅基材料，3-垂直取向石墨。Among them, 1-current collector, 2-silicon-based material, 3-vertically oriented graphite.

具体实施方式DETAILED DESCRIPTION

为使本发明的技术方案和优点更加清楚，下面将结合具体实施例，对本发明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发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。In order to make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

在根据本发明的第一方面，本发明提供一种负极片，包括集流体、涂覆在集流体至少一表面上的第一活性物质层和涂覆在第一活性物质层表面的第二活性物质层，第一活性物质层包括硅基材料，第二活性物质层包括垂直取向石墨。According to the first aspect of the present invention, the present invention provides a negative electrode sheet, including a current collector, a first active material layer coated on at least one surface of the current collector, and a second active material layer coated on the surface of the first active material layer, the first active material layer includes a silicon-based material, and the second active material layer includes vertically oriented graphite.

在根据本发明的一实施例中，第一活性物质层的粘度η1和第二活性物质层的粘度η2满足关系式：0.5≤η1/η2≤2.5；η1/η2具体可以是0.5、0.6、0.7、0.8、0.9、1.0、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9、2.0、2.1、2.2、2.3、2.4、2.5；将第一活性物质层的粘度η1与第二活性物质层的粘度η2控制在上述范围内时，能保证第一活性物质层与第二活性物质层的粘结性更好，使得极片不容易出现分层，使得电池能形成电子离子完整通路，解决了因极片分层而导致电池性能恶化，影响电池在循环时的容量保持率的问题。In one embodiment according to the present invention, the viscosity η1 of the first active material layer and the viscosity η2 of the second active material layer satisfy the relationship: 0.5≤η1/η2≤2.5; η1/η2 can specifically be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5; when the viscosity η1 of the first active material layer and the viscosity η2 of the second active material layer are controlled within the above range, the adhesion between the first active material layer and the second active material layer can be ensured to be better, so that the electrode is not prone to stratification, and the battery can form a complete path for electrons and ions, thereby solving the problem of battery performance deterioration due to electrode stratification, affecting the capacity retention rate of the battery during cycling.

在根据本发明的一实施例中，第一活性物质层的粘度η1为3000～7000mPa·s，具体可以是3000mPa·s、3500mPa·s、4000mPa·s、4500mPa·s、5000mPa·s、5500mPa·s、6000mPa·s、6500mPa·s、7000mPa·s；将第一活性物质层的粘度η1控制在上述范围内时能够形成均一固定的涂层，保证电池具有良好的电化学性能；若是粘度过小会导致流动性太大而不能形成均一固定涂 层；若是粘度太大则缺少流动性，也容易使得浆料不均一，影响电芯的电化学性能。In one embodiment of the present invention, the viscosity η1 of the first active material layer is 3000-7000 mPa·s, specifically 3000 mPa·s, 3500 mPa·s, 4000 mPa·s, 4500 mPa·s, 5000 mPa·s, 5500 mPa·s, 6000 mPa·s, 6500 mPa·s, 7000 mPa·s; when the viscosity η1 of the first active material layer is controlled within the above range, a uniform and fixed coating can be formed to ensure that the battery has good electrochemical properties; if the viscosity is too small, it will lead to excessive fluidity and fail to form a uniform and fixed coating. If the viscosity is too high, the slurry will lack fluidity and will easily become uneven, affecting the electrochemical performance of the battery cell.

在根据本发明的一实施例中，第二活性物质层的粘度η2为3000～5000mPa·s，具体可以是3000mPa·s、3200mPa·s、3500mPa·s、3800mPa·s、4000mPa·s、4200mPa·s、4500mPa·s、4800mPa·s、5000mPa·s；将第二活性物质层的粘度η2控制在上述范围内时，能与第一活性物质层较好的粘合，使得两个涂层不易出现分层，使得电池能形成电子离子完整通路，解决了因极片分层而导致电池性能恶化，影响电池在循环时的容量保持率的问题。In one embodiment of the present invention, the viscosity η2 of the second active material layer is 3000-5000mPa·s, specifically 3000mPa·s, 3200mPa·s, 3500mPa·s, 3800mPa·s, 4000mPa·s, 4200mPa·s, 4500mPa·s, 4800mPa·s, 5000mPa·s; when the viscosity η2 of the second active material layer is controlled within the above range, it can be well bonded with the first active material layer, so that the two coatings are not prone to stratification, so that the battery can form a complete path for electrons and ions, thereby solving the problem of battery performance deterioration due to electrode stratification, affecting the capacity retention rate of the battery during cycling.

在根据本发明的一实施例中，硅基材料与垂直取向石墨的质量比为(2～6):(4～8)，具体可以是2:8、3:7、4:6、5:5、6:4，将硅基材料与垂直取向石墨的质量比控制在上述范围内时，能在保证电池具有较高能量密度的同时，还能通过垂直取向石墨保护底层硅基材料，有效抑制因硅基材料而产生的体积膨胀；若是硅基材料的含量过多，会导致电池的体积膨胀严重增加，进而恶化电池，影响电池的性能；若是硅基材料的含量过少，则不能保证电池具有较高的能量密度。In one embodiment of the present invention, the mass ratio of silicon-based material to vertically oriented graphite is (2-6):(4-8), specifically 2:8, 3:7, 4:6, 5:5, 6:4. When the mass ratio of silicon-based material to vertically oriented graphite is controlled within the above range, while ensuring that the battery has a high energy density, the underlying silicon-based material can be protected by the vertically oriented graphite, thereby effectively suppressing the volume expansion caused by the silicon-based material. If the content of silicon-based material is too much, the volume expansion of the battery will increase seriously, thereby deteriorating the battery and affecting the performance of the battery. If the content of silicon-based material is too little, the battery cannot be guaranteed to have a high energy density.

在根据本发明的一实施例中，硅基材料中硅的含量为2～15％，具体可以是2％、3％、4％、5％、6％、7％、8％、9％、10％、11％、12％、13％、14％、15％；将硅基材料中硅的含量控制在上述范围内时，第二活性物质层能有效的一直硅基材料产生的体积膨胀，进而保证电池在具有较高的能量密度的同时也具有较好的性能。In one embodiment of the present invention, the silicon content in the silicon-based material is 2-15%, specifically 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%; when the silicon content in the silicon-based material is controlled within the above range, the second active material layer can effectively control the volume expansion of the silicon-based material, thereby ensuring that the battery has a higher energy density while also having better performance.

在根据本发明的一实施例中，集流体包括铜箔、碳纸、镍箔中的至少一种；集流体的厚度为3μm～20μm，具体可以是3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm、20μm。In one embodiment of the present invention, the current collector includes at least one of copper foil, carbon paper, and nickel foil; the thickness of the current collector is 3μm to 20μm, specifically 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, and 20μm.

在根据本发明的一实施例中，硅基材料包括硅颗粒、硅纳米线、硅碳骨架复合材料中的至少一种；优选为硅颗粒。 In one embodiment of the present invention, the silicon-based material includes at least one of silicon particles, silicon nanowires, and silicon-carbon skeleton composite materials; preferably silicon particles.

在根据本发明的一实施例中，垂直取向石墨包括磁性石墨、经磁流体磁化的普通石墨中的至少一种；其中，磁流体包括四氧化三铁、氧化亚铁和氧化铁中的至少一种。In one embodiment of the present invention, the vertically oriented graphite includes at least one of magnetic graphite and ordinary graphite magnetized by a magnetic fluid; wherein the magnetic fluid includes at least one of ferrosoferric oxide, ferrous oxide and ferric oxide.

在根据本发明的第二方面，本发明还提供一种上述的负极片的制备方法，包括以下步骤：According to a second aspect of the present invention, the present invention further provides a method for preparing the above-mentioned negative electrode sheet, comprising the following steps:

(1)将硅基材料、粘结剂、增稠剂、导电剂进行混合，加入溶剂，搅拌均匀，即得到第一活性物质层浆料；(1) mixing a silicon-based material, a binder, a thickener, and a conductive agent, adding a solvent, and stirring uniformly to obtain a first active material layer slurry;

(2)将磁性石墨、粘结剂、增稠剂进行混合，加入溶剂，搅拌均匀，即得到第二活性物质层浆料；(2) mixing magnetic graphite, a binder, and a thickener, adding a solvent, and stirring evenly to obtain a second active material layer slurry;

(3)将第一活性物质层浆料和第二活性物质层浆料在集流体上进行涂布，烘干，即得到负极片。(3) The first active material layer slurry and the second active material layer slurry are coated on the current collector and dried to obtain a negative electrode sheet.

本发明为了降低脱模风险和增加电芯能量密度，设计了双层涂布工艺，底层涂层为硅基颗粒材料浆料层，表层涂层为垂直取向石墨浆料层，表层的垂直石墨之间的间隙为底层硅颗粒膨胀提供了膨胀缓冲空间。In order to reduce the risk of demolding and increase the energy density of the battery core, the present invention designs a double-layer coating process, in which the bottom coating is a silicon-based granular material slurry layer, and the surface coating is a vertically oriented graphite slurry layer. The gaps between the vertical graphites on the surface provide expansion buffer space for the expansion of the bottom silicon particles.

本发明负极片的双层涂布结构和磁场偏转工艺，底层硅基材料层增大了电池的能量密度和避免了表层垂直取向石墨脱模风险，而表层垂直取向石墨层加快了锂离子传输速度，适应充放电过程中较大的体积变化，缩短了电子在垂直方向的传输路径，提升了电极电导率和电池的电子收集效率，电解液与电极之间充分接触，增加了活性位点，为底层硅基材料膨胀提供了一定的缓冲空间，有利于降低电芯膨胀率，同时也保证了结构稳定性，有利于提升电芯的循环性能和充电能力。The double-layer coating structure and magnetic field deflection process of the negative electrode sheet of the present invention, the bottom silicon-based material layer increases the energy density of the battery and avoids the risk of demolding of the vertically oriented graphite on the surface, while the vertically oriented graphite layer on the surface accelerates the lithium ion transmission speed, adapts to the large volume change during charging and discharging, shortens the electron transmission path in the vertical direction, improves the electrode conductivity and the electron collection efficiency of the battery, the electrolyte and the electrode are in full contact, the active sites are increased, and a certain buffer space is provided for the expansion of the bottom silicon-based material, which is beneficial to reducing the expansion rate of the battery cell, while also ensuring the structural stability, which is beneficial to improving the cycle performance and charging capacity of the battery cell.

在根据本发明的一实施例中，硅基材料、粘结剂、增稠剂、导电剂的质量比为(92-97％):(2.0～3.5％):(0.1～0.5％):(0.05～0.2％)；优选为96.9％:2.7％:0.3％：0.1％；In one embodiment of the present invention, the mass ratio of silicon-based material, binder, thickener and conductive agent is (92-97%): (2.0-3.5%): (0.1-0.5%): (0.05-0.2%); preferably 96.9%: 2.7%: 0.3%: 0.1%;

在根据本发明的一实施例中，磁性石墨、粘结剂、增稠剂的质量比为(95％～98％):(0.6～1.5％):(1.0～1.5％)；优选为97.7％:1.3％:1.0％。 In one embodiment of the present invention, the mass ratio of magnetic graphite, binder and thickener is (95% to 98%): (0.6 to 1.5%): (1.0 to 1.5%); preferably 97.7%: 1.3%: 1.0%.

在根据本发明的一实施例中，粘结剂包括PPA、SBR中的至少一种；增稠剂包括CMC、PAA、PAN和聚丙烯酸酯中的至少一种；导电剂包括碳纳米管、石墨烯中的至少一种；溶剂为水系溶剂或油系溶剂，油系溶剂包括N-甲基吡咯烷酮、N,N-二甲基甲酰胺、二甲基亚砜中的至少一种。In one embodiment of the present invention, the binder includes at least one of PPA and SBR; the thickener includes at least one of CMC, PAA, PAN and polyacrylate; the conductive agent includes at least one of carbon nanotubes and graphene; the solvent is an aqueous solvent or an oil solvent, and the oil solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide and dimethyl sulfoxide.

在根据本发明的一实施例中，步骤(3)中，烘干时风箱中设置有磁场发射装置，用于使第二活性物质层浆料中的磁性石墨材料部分或全部变成垂直取向石墨并垂直分布于集流体。In one embodiment of the present invention, in step (3), a magnetic field emission device is provided in the bellows during drying to convert part or all of the magnetic graphite material in the second active material layer slurry into vertically oriented graphite and distribute it vertically on the current collector.

在根据本发明的一实施例中，步骤(3)中，烘干的温度为60℃～80℃，具体可以是60℃、61℃、62℃、63℃、64℃、65℃、66℃、67℃、68℃、69℃、70℃、71℃、72℃、73℃、74℃、75℃、76℃、77℃、78℃、79℃、80℃。In one embodiment of the present invention, in step (3), the drying temperature is 60°C-80°C, specifically 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C.

在根据本发明的第三方面，本发明还提供一种锂离子电池，包括正极片、负极片、电解液以及间隔于所述正极片与所述负极片之间的隔膜，所述负极片为上述的负极片。According to the third aspect of the present invention, the present invention further provides a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet mentioned above.

所述正极片中的正极活性物质可以是包括但不限于LiCoO2、LiNiO2、LiMnO2、LiMn2O4、LiMnPO4、LiFePO4、LiNi1/3Co1/3Mn1/3O2、LiNi0.5Co0.2Mn0.3O2、LiNi0.6Co0.2Mn0.2O2、LiNi0.8Co0.1Mn0.1O2、LiNi0.6Co0.1Mn0.3O2、LiNi0.85Co0.15Al0.05O2中的至少一种。The positive electrode active material in the positive electrode sheet may include but is not limited to at least one of LiCoO2 , LiNiO2 , LiMnO2 , LiMn2O4 , LiMnPO4 , LiFePO4 , LiNi1 / 3Co1 / 3Mn1 / 3O2, LiNi0.5Co0.2Mn0.3O2 , LiNi0.6Co0.2Mn0.2O2 , LiNi0.8Co0.1Mn0.1O2 , LiNi0.6Co0.1Mn0.3O2 , and LiNi0.85Co0.15Al0.05O2 .

所述隔膜可以是包括但不限于聚乙烯、聚丙烯、聚偏氟乙烯以及它们的多层复合膜中的至少一种；The separator may be at least one of, but not limited to, polyethylene, polypropylene, polyvinylidene fluoride, and multilayer composite films thereof;

所述电解液包括电解质盐和有机溶剂，其中，电解质盐和有机溶剂的具体种类及组成均不受到具体的限制，包含正极成膜添加剂，负极成膜添加剂以及改善循环和低温添加剂等；The electrolyte includes an electrolyte salt and an organic solvent, wherein the specific types and compositions of the electrolyte salt and the organic solvent are not subject to specific restrictions, and include positive electrode film-forming additives, negative electrode film-forming additives, and cycle-improving and low-temperature additives, etc.;

下面通过具体实施方式对本发明作进一步详细的描述，但本发明的实施方式并不限于此。The present invention is further described in detail below through specific implementation modes, but the implementation modes of the present invention are not limited thereto.

实施例1Example 1

本实施例提供一种负极片，包括集流体1、涂覆在集流体1至少一表面上的 第一活性物质层和涂覆在第一活性物质层表面的第二活性物质层，第一活性物质层包括硅基材料2，第二活性物质层包括垂直取向石墨3。This embodiment provides a negative electrode sheet, including a current collector 1, and a A first active material layer and a second active material layer coated on the surface of the first active material layer, the first active material layer includes a silicon-based material 2 , and the second active material layer includes vertically oriented graphite 3 .

本实施例还提供一种上述负极片的制备方法，包括以下步骤：This embodiment also provides a method for preparing the above-mentioned negative electrode sheet, comprising the following steps:

(1)第一活性物质层浆料的配置：按照硅基活性物质：碳纳米管：PPA：SBR：CMC＝96.9％：0.1：2.4：0.3：0.3混合均匀，加入去离子水，搅拌均匀后，得到第一活性物质层浆料，即底层涂层浆料；其中，硅基活性物质中硅的掺杂量为3％；浆料的粘度η1为3000mPa·s；(1) Configuration of the first active material layer slurry: silicon-based active material: carbon nanotube: PPA: SBR: CMC = 96.9%: 0.1: 2.4: 0.3: 0.3 is mixed evenly, deionized water is added, and stirred evenly to obtain the first active material layer slurry, i.e., the bottom coating slurry; wherein the doping amount of silicon in the silicon-based active material is 3%; and the viscosity η1 of the slurry is 3000 mPa·s;

(2)第二活性物质层浆料的配置：按照石墨活性物质：CMC：SBR＝97.7％：1.3％：1.0％混合均匀，加入去离子水，搅拌均匀后，得到第二活性物质层浆料，即表层涂层浆料；其中，浆料的粘度η2为3000mPa·s；(2) Configuration of the second active material layer slurry: mixing graphite active material: CMC: SBR = 97.7%: 1.3%: 1.0% evenly, adding deionized water, stirring evenly, to obtain the second active material layer slurry, i.e., the surface coating slurry; wherein the viscosity η2 of the slurry is 3000 mPa·s;

(3)浆料涂布：将第一活性物质层浆料与第二活性物质层浆料按照质量比为2:8在厚度为5μm的铜箔上进行涂布，在烘箱中以60℃烘干，即得到负极片；其中，烘箱中配有磁场反射装置，在烘干过程中表层磁性石墨装置通过磁场作用，成为垂直取向石墨并垂直分布于铜箔。(3) Slurry coating: The first active material layer slurry and the second active material layer slurry are coated on a copper foil with a thickness of 5 μm in a mass ratio of 2:8, and dried in an oven at 60°C to obtain a negative electrode sheet; wherein, the oven is equipped with a magnetic field reflection device. During the drying process, the surface magnetic graphite device is acted upon by the magnetic field to become vertically oriented graphite and vertically distributed on the copper foil.

实施例2Example 2

本实施例与实施例1的不同之处在于，步骤(3)中，第一活性物质层浆料与第二活性物质层浆料的质量比为3:7；其余同实施例1相同，此处不再赘述。The difference between this embodiment and embodiment 1 is that in step (3), the mass ratio of the first active material layer slurry to the second active material layer slurry is 3:7; the rest is the same as embodiment 1 and will not be repeated here.

实施例3Example 3

本实施例与实施例1的不同之处在于，步骤(3)中，第一活性物质层浆料与第二活性物质层浆料的质量比为4:6；其余同实施例1相同，此处不再赘述。The difference between this embodiment and embodiment 1 is that in step (3), the mass ratio of the first active material layer slurry to the second active material layer slurry is 4:6; the rest is the same as embodiment 1 and will not be repeated here.

实施例4Example 4

本实施例与实施例1的不同之处在于，步骤(3)中，第一活性物质层浆料与第二活性物质层浆料的质量比为5:5；其余同实施例1相同，此处不再赘述。The difference between this embodiment and embodiment 1 is that in step (3), the mass ratio of the first active material layer slurry to the second active material layer slurry is 5:5; the rest is the same as embodiment 1 and will not be repeated here.

实施例5Example 5

本实施例与实施例1的不同之处在于，步骤(3)中，第一活性物质层浆料与第二活性物质层浆料的质量比为6:4；其余同实施例1相同，此处不再赘述。 The difference between this embodiment and embodiment 1 is that in step (3), the mass ratio of the first active material layer slurry to the second active material layer slurry is 6:4; the rest is the same as embodiment 1 and will not be repeated here.

实施例6Example 6

本实施例与实施例1的不同之处在于，步骤(1)中，硅基活性物质中硅的掺杂量为5％；其余同实施例1相同，此处不再赘述。The difference between this embodiment and embodiment 1 is that in step (1), the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 1 and will not be repeated here.

实施例7Example 7

本实施例与实施例2的不同之处在于，步骤(1)中，硅基活性物质中硅的掺杂量为5％；其余同实施例2相同，此处不再赘述。The difference between this embodiment and embodiment 2 is that in step (1), the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 2 and will not be repeated here.

实施例8Example 8

本实施例与实施例3的不同之处在于，步骤(1)中，硅基活性物质中硅的掺杂量为5％；其余同实施例3相同，此处不再赘述。The difference between this embodiment and embodiment 3 is that in step (1), the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 3 and will not be repeated here.

实施例9Example 9

本实施例与实施例4的不同之处在于，步骤(1)中，硅基活性物质中硅的掺杂量为5％；其余同实施例4相同，此处不再赘述。The difference between this embodiment and embodiment 4 is that in step (1), the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 4 and will not be repeated here.

实施例10Example 10

本实施例与实施例5的不同之处在于，步骤(1)中，硅基活性物质中硅的掺杂量为5％；其余同实施例5相同，此处不再赘述。The difference between this embodiment and embodiment 5 is that in step (1), the doping amount of silicon in the silicon-based active material is 5%; the rest is the same as embodiment 5 and will not be repeated here.

对比例1Comparative Example 1

本对比例与实施例1的不同之处在于，步骤(3)中，第一活性物质层浆料与第二活性物质层浆料的质量比为7:3；其余同实施例1相同，此处不再赘述。The difference between this comparative example and Example 1 is that in step (3), the mass ratio of the first active material layer slurry to the second active material layer slurry is 7:3; the rest is the same as Example 1 and will not be repeated here.

对比例2Comparative Example 2

本对比例与实施例1的不同之处在于，步骤(3)中，第一活性物质层浆料与第二活性物质层浆料的质量比为1:9；其余同实施例1相同，此处不再赘述。The difference between this comparative example and Example 1 is that in step (3), the mass ratio of the first active material layer slurry to the second active material layer slurry is 1:9; the rest is the same as Example 1 and will not be repeated here.

对比例3Comparative Example 3

本对比例与实施例1的不同之处在于，第一活性物质层浆料的粘度η1为2450mPa·s；第二活性物质层浆料的粘度η2为5000mPa·s，即η1/η2＝0.49；其余同实施例1相同，此处不再赘述。The difference between this comparative example and Example 1 is that the viscosity η1 of the first active material layer slurry is 2450 mPa·s; the viscosity η2 of the second active material layer slurry is 5000 mPa·s, that is, η1/η2=0.49; the rest is the same as Example 1 and will not be repeated here.

对比例4 Comparative Example 4

本对比例与实施例1的不同之处在于，第一活性物质层浆料的粘度η1为7600mPa·s，即η1/η2＝2.53；其余同实施例1相同，此处不再赘述。The difference between this comparative example and Example 1 is that the viscosity η1 of the first active material layer slurry is 7600 mPa·s, that is, η1/η2=2.53; the rest is the same as Example 1 and will not be repeated here.

将实施例1-10与对比例1-4中制得的负极片与正极片经过辊压、分条、极耳焊接、卷绕、封装、烘烤、注液、化成、除气等后工序制作成电池成品。The negative electrode sheets and positive electrode sheets prepared in Examples 1-10 and Comparative Examples 1-4 are processed into finished batteries through post-processing such as rolling, slitting, tab welding, winding, packaging, baking, liquid injection, formation, and degassing.

将制得的电池进行性能测试，测试结果如表1所示：The prepared battery was subjected to performance tests, and the test results are shown in Table 1:

表1
Table 1

从表1的测试结果可知，本发明通过底层硅基材料涂层克服了垂直取向石墨涂层容易脱模的问题。从实施例1-5的测试结果对比可知，底层硅基涂层越多容量保持率就越低，电芯体积膨胀就越高；再从实施例1-5与对比例1-2的测试结果对比可知，当底层硅基材料涂层与垂直取向石墨涂层的质量比不在(2-6)：(4-8)范围内时，对比例1中的电池容量保持率低于80％，膨胀率大于10％， 其原因是因为当硅含量过多时，会导致电池的体积膨胀严重增加，进而恶化电池，影响电池的性能；而对比例2中的虽然电池容量保持率能达到80％，膨胀也相对较小，但是硅含量涂层中硅基材料的含量过少，则不能保证电池具有较高的能量密度。From the test results in Table 1, it can be seen that the present invention overcomes the problem of easy demolding of the vertically oriented graphite coating by using the underlying silicon-based material coating. From the comparison of the test results of Examples 1-5, it can be seen that the more the underlying silicon-based coating, the lower the capacity retention rate and the higher the volume expansion of the battery cell; from the comparison of the test results of Examples 1-5 and Comparative Examples 1-2, it can be seen that when the mass ratio of the underlying silicon-based material coating to the vertically oriented graphite coating is not within the range of (2-6): (4-8), the battery capacity retention rate in Comparative Example 1 is less than 80%, the expansion rate is greater than 10%, The reason is that when the silicon content is too high, the volume expansion of the battery will increase seriously, thereby deteriorating the battery and affecting the battery performance; while in Comparative Example 2, although the battery capacity retention rate can reach 80% and the expansion is relatively small, the content of silicon-based material in the silicon content coating is too low, and the battery cannot be guaranteed to have a high energy density.

从实施例1-5分别与对应的实施例6-10的测试结果可以看出，电芯底层硅基涂层的掺硅量越高，电芯的容量保持率越低，电芯体积膨胀就越大；从实施例1与对比例3-4的测试结果可以看出，当第一活性物质层浆料的粘度η1与第二活性物质层浆料的粘度η2不满足关系式0.5≤η1/η2≤2.5时，在进行循环后电池的容量保持率低于80％，其原因是当第一活性物质层浆料的粘度η1与第二活性物质层浆料的粘度η2相差过大时，第一活性物质层与第二活性物质层不能较好的粘合，使得两个涂层易出现分层，使得电池不能形成电子离子完整通路，导致极片分层电池性能恶化，影响电池在循环时的容量保持率；进一步的，当第一活性物质层浆料的粘度η1过大过小时，会使得第一活性物质层浆料的流动性太小或太大而不能形成均一固定涂层，进而影响电池的性能。It can be seen from the test results of Examples 1-5 and the corresponding Examples 6-10 that the higher the silicon doping amount of the silicon-based coating at the bottom of the battery cell, the lower the capacity retention rate of the battery cell, and the greater the volume expansion of the battery cell; it can be seen from the test results of Example 1 and Comparative Examples 3-4 that when the viscosity η1 of the first active material layer slurry and the viscosity η2 of the second active material layer slurry do not satisfy the relationship 0.5≤η1/η2≤2.5, the capacity retention rate of the battery after cycling is lower than 80%. The reason is that when the viscosity η1 of the first active material layer slurry and the viscosity η2 of the second active material layer slurry differ too much, the first active material layer and the second active material layer cannot be well bonded, so that the two coatings are prone to stratification, so that the battery cannot form a complete path for electrons and ions, resulting in the deterioration of the performance of the electrode stratification battery, affecting the capacity retention rate of the battery during cycling; further, when the viscosity η1 of the first active material layer slurry is too large or too small, the fluidity of the first active material layer slurry will be too small or too large to form a uniform and fixed coating, thereby affecting the performance of the battery.

综上，本发明负极片的双层涂布结构和磁场偏转工艺，底层硅基材料层增大了电池的能量密度和避免了表层垂直取向石墨脱模风险，而表层垂直取向石墨层加快了锂离子传输速度，适应充放电过程中较大的体积变化，缩短了电子在垂直方向的传输路径，提升了电极电导率和电池的电子收集效率，电解液与电极之间充分接触，增加了活性位点，为底层硅基材料膨胀提供了一定的缓冲空间，有利于降低电芯膨胀率，同时也保证了结构稳定性，有利于提升电芯的循环性能和充电能力。In summary, the double-layer coating structure and magnetic field deflection process of the negative electrode sheet of the present invention, the bottom silicon-based material layer increases the energy density of the battery and avoids the risk of demolding of the surface vertically oriented graphite, while the surface vertically oriented graphite layer accelerates the lithium ion transmission speed, adapts to the large volume changes during charging and discharging, shortens the electron transmission path in the vertical direction, improves the electrode conductivity and the electron collection efficiency of the battery, and the electrolyte and the electrode are fully in contact, which increases the active sites and provides a certain buffer space for the expansion of the bottom silicon-based material, which is beneficial to reducing the expansion rate of the battery cell. At the same time, it also ensures the structural stability, which is beneficial to improving the cycle performance and charging capacity of the battery cell.

根据上述说明书的揭示和教导，本发明所属领域的技术人员还能够对上述实施方式进行变更和修改。因此，本发明并不局限于上述的具体实施方式，凡是本领域技术人员在本发明的基础上所作出的任何显而易见的改进、替换或变型均属于本发明的保护范围。此外，尽管本说明书中使用了一些特定的 术语，但这些术语只是为了方便说明，并不对本发明构成任何限制。 According to the disclosure and teaching of the above description, those skilled in the art can also change and modify the above implementation. Therefore, the present invention is not limited to the above specific implementation. Any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific However, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (10)

一种负极片，其特征在于，包括集流体、涂覆在集流体至少一表面上的第一活性物质层和涂覆在所述第一活性物质层表面的第二活性物质层，所述第一活性物质层包括硅基材料，所述第二活性物质层包括垂直取向石墨。A negative electrode sheet, characterized in that it includes a current collector, a first active material layer coated on at least one surface of the current collector, and a second active material layer coated on the surface of the first active material layer, wherein the first active material layer includes a silicon-based material and the second active material layer includes vertically oriented graphite. 根据权利要求1中所述的负极片，其特征在于，所述第一活性物质层的粘度η1和所述第二活性物质层的粘度η2满足关系式：0.5≤η1/η2≤2.5。The negative electrode sheet according to claim 1, characterized in that the viscosity η1 of the first active material layer and the viscosity η2 of the second active material layer satisfy the relationship: 0.5≤η1 / η2≤2.5 . 根据权利要求1或2中所述的负极片，其特征在于，所述第一活性物质层的粘度η1为3000～7000mPa·s；所述第二活性物质层的粘度η2为3000～5000mPa·s。The negative electrode sheet according to claim 1 or 2 is characterized in that the viscosity η1 of the first active material layer is 3000 to 7000 mPa·s; and the viscosity η2 of the second active material layer is 3000 to 5000 mPa·s. 根据权利要求1中所述的负极片，其特征在于，所述硅基材料与所述垂直取向石墨的质量比为(2～6):(4～8)；所述硅基材料中硅的含量为2～15％。The negative electrode sheet according to claim 1 is characterized in that the mass ratio of the silicon-based material to the vertically oriented graphite is (2-6):(4-8); and the silicon content in the silicon-based material is 2-15%. 根据权利要求1中所述的负极片，其特征在于，所述集流体包括铜箔、碳纸、镍箔中的至少一种；The negative electrode sheet according to claim 1, characterized in that the current collector comprises at least one of copper foil, carbon paper, and nickel foil; 所述硅基材料包括硅颗粒、硅纳米线、硅碳骨架复合材料中的至少一种；The silicon-based material includes at least one of silicon particles, silicon nanowires, and silicon-carbon skeleton composite materials; 所述垂直取向石墨包括磁性石墨、经磁流体磁化的普通石墨中的至少一种；其中，磁流体包括四氧化三铁、氧化亚铁和氧化铁中的至少一种。The vertically oriented graphite includes at least one of magnetic graphite and ordinary graphite magnetized by magnetic fluid; wherein the magnetic fluid includes at least one of ferroferric oxide, ferrous oxide and ferric oxide. 一种根据权利要求1-5任一项中所述的负极片的制备方法，其特征在于，包括以下步骤：A method for preparing a negative electrode sheet according to any one of claims 1 to 5, characterized in that it comprises the following steps: (1)将硅基材料、粘结剂、增稠剂、导电剂进行混合，加入溶剂，搅拌均匀，即得到第一活性物质层浆料；(1) mixing a silicon-based material, a binder, a thickener, and a conductive agent, adding a solvent, and stirring uniformly to obtain a first active material layer slurry; (2)将磁性石墨、粘结剂、增稠剂进行混合，加入溶剂，搅拌均匀，即得到第二活性物质层浆料；(2) mixing magnetic graphite, a binder, and a thickener, adding a solvent, and stirring evenly to obtain a second active material layer slurry; (3)将第一活性物质层浆料和第二活性物质层浆料在集流体上进行涂布，烘干，即得到负极片。(3) The first active material layer slurry and the second active material layer slurry are coated on the current collector and dried to obtain a negative electrode sheet. 根据权利要求6中所述的负极片的制备方法，其特征在于，所述硅基材料、粘结剂、增稠剂、导电剂的质量比为(92-97％):(2.0～3.5％):(0.1～0.5％): (0.05～0.2％)；所述磁性石墨、粘结剂、增稠剂的质量比为(95％～98％):(0.6～1.5％):(1.0～1.5％)。The method for preparing a negative electrode sheet according to claim 6 is characterized in that the mass ratio of the silicon-based material, the binder, the thickener, and the conductive agent is (92-97%): (2.0-3.5%): (0.1-0.5%): (0.05～0.2%); the mass ratio of the magnetic graphite, binder and thickener is (95%～98%):(0.6～1.5%):(1.0～1.5%). 根据权利要求6中所述的负极片的制备方法，其特征在于，步骤(3)中，所述烘干的风箱中设置有磁场发射装置，用于使第二活性物质层浆料中的磁性石墨材料部分或全部变成垂直取向石墨并垂直分布于集流体。The method for preparing a negative electrode sheet according to claim 6 is characterized in that, in step (3), a magnetic field transmitting device is provided in the drying bellows to convert part or all of the magnetic graphite material in the second active material layer slurry into vertically oriented graphite and distribute it vertically on the current collector. 根据权利要求6中所述的负极片的制备方法，其特征在于，步骤(3)中，所述烘干的温度为60℃～80℃。The method for preparing a negative electrode sheet according to claim 6, characterized in that in step (3), the drying temperature is 60°C to 80°C. 一种锂离子电池，包括正极片、负极片、电解液以及间隔于所述正极片与所述负极片之间的隔膜，其特征在于，所述负极片为权利要求1-5任一项中所述的负极片。 A lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet described in any one of claims 1 to 5.
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