WO2025001355A1 - 负极片及电池 - Google Patents

负极片及电池 Download PDF

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Publication number
WO2025001355A1
WO2025001355A1 PCT/CN2024/083505 CN2024083505W WO2025001355A1 WO 2025001355 A1 WO2025001355 A1 WO 2025001355A1 CN 2024083505 W CN2024083505 W CN 2024083505W WO 2025001355 A1 WO2025001355 A1 WO 2025001355A1
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Prior art keywords
carbon
silicon
negative electrode
electrode sheet
group
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PCT/CN2024/083505
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English (en)
French (fr)
Inventor
范洪生
郭盼龙
汪辉
刘春洋
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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Publication of WO2025001355A1 publication Critical patent/WO2025001355A1/zh
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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 relates to the field of electrochemical device energy storage, and in particular to a negative electrode sheet and a battery.
  • silicon-doped negative electrodes have the advantage of high energy density and are gradually being widely used.
  • silicon-doped negative electrodes have defects such as large thickness expansion rate and fast capacity decay, which need to be solved urgently.
  • the present invention provides a negative electrode sheet and a battery, which at least solve the problems of large expansion rate and fast capacity decay of silicon-doped negative electrode in the prior art.
  • a negative electrode sheet comprising a current collector and an active material layer arranged on the surface of the current collector, wherein the active material layer comprises a silicon-carbon material and a first binder, wherein the first binder comprises a first group and a second group, wherein the first group comprises a carboxyl group, and the second group comprises a cyano group and/or an amide group.
  • the silicon-carbon material includes porous carbon and silicon material present in the pores of the porous carbon.
  • the mass ratio of the porous carbon to the silicon material is 7:3 to 3:7; and/or the average pore diameter of the porous carbon is less than or equal to 20 nm.
  • the particle size Dv50 of the silicon-carbon material is 5 ⁇ m to 15 ⁇ m; and/or the specific surface area of the silicon-carbon material is less than or equal to 15 m 2 /g.
  • the mass percentage of the silicon-carbon material is 3% to 20%, and/or the surface density of the negative electrode active material layer is 5 mg/cm 2 to 8 mg/cm 2 .
  • the carboxyl group includes a carboxylic acid group and/or a carboxylate group, and the carboxylate group includes one or more of -COOLi, -COONa, -COOK, and -COONH 4 ; and/or, in the first binder, the molar number of the first group is M 1 , and the molar number of the second group is The number of moles is M 2 , 0.4 ⁇ M 1 /(M 1 +M 2 ) ⁇ 0.95.
  • the weight average molecular weight of the first binder is 3,000 to 2,000,000.
  • the mass percentage of the first binder is 1% to 10%.
  • the active material layer also includes a carbon-based material, wherein the carbon-based material includes one or more of artificial graphite, natural graphite, mesophase carbon microbeads, soft carbon, hard carbon, carbon black, acetylene black, carbon fiber, single-walled carbon tube, and multi-walled carbon tube; and/or, in the active material layer, the mass percentage of the carbon-based material is 60% to 96%.
  • the carbon-based material includes one or more of artificial graphite, natural graphite, mesophase carbon microbeads, soft carbon, hard carbon, carbon black, acetylene black, carbon fiber, single-walled carbon tube, and multi-walled carbon tube; and/or, in the active material layer, the mass percentage of the carbon-based material is 60% to 96%.
  • Another aspect of the present invention provides a battery, comprising the negative electrode sheet mentioned above.
  • the active material layer includes a silicon-carbon material having a higher capacity, and at the same time, a first binder containing a first group and a second group is introduced, which has a strong bonding effect with the silicon-carbon material and can inhibit the silicon-carbon material from generating voids through an expansion-contraction process during the battery cycle, thereby reducing the expansion rate of the negative electrode sheet, and further reducing the expansion rate of the battery, and at the same time can reduce the battery capacity decay rate.
  • FIG1 is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present invention.
  • FIG2 is a pore size distribution curve of the porous carbon in Example 1;
  • FIG3 is a SEM image of the silicon-carbon material in Example 1;
  • FIG. 4 is a cross-sectional EDS line scan of the silicon-carbon material in Example 1.
  • negative electrode silicon-doped batteries generally have problems such as large expansion rate and poor capacity retention rate, which need to be solved urgently.
  • the electrode sheet is an important component of the battery.
  • the negative electrode sheet with silicon-based materials as the active material has a relatively high capacity, but it is more prone to excessive expansion (during the battery cycle, the silicon-based material particles have a large expansion rate, and their expansion and contraction process produces excessive voids), resulting in severe expansion of the silicon-doped negative electrode (mainly expansion in the thickness direction), affecting the battery's cyclability performance.
  • the reversible lithium storage capacity of graphite is 372mAh/g
  • the reversible lithium storage capacity of silicon at room temperature is about 3600mAh/g
  • the use of silicon materials can significantly improve the energy density of lithium-ion batteries.
  • the volume expansion rate of silicon when fully embedded with lithium is usually more than 300%, which makes the active material layer using silicon materials as active materials fluffy, the conductive contact between active material particles deteriorates, the difficulty of lithium extraction from the material increases, and the precipitation of metallic lithium easily occurs, resulting in rapid attenuation of battery capacity and a sharp increase in thickness expansion rate.
  • an embodiment of the present invention provides a negative electrode sheet, as shown in Figure 1, the negative electrode sheet includes a current collector 2 and an active material layer 1 arranged on the surface of the current collector 2, the active material layer 1 includes a silicon-carbon material 11 and a first binder, the first binder includes a first group and a second group, the first group includes a carboxyl group, and the second group includes a cyano group and/or an amide group.
  • the silicon-carbon material as an active material has a higher capacity.
  • a first binder comprising a first group and a second group is introduced, which has a strong bonding effect with the silicon-carbon material and can inhibit the silicon-carbon material from generating excessive voids when the lithium is inserted and expanded, thereby effectively inhibiting the expansion of the negative electrode sheet, reducing the expansion rate of the negative electrode sheet, and then reducing the expansion rate of the battery.
  • it can reduce the battery capacity decay rate and improve the battery cycle performance. Studies have shown that the capacity retention rate of the battery after 200 cycles (or 200 times) is more than 95.5%, and the thickness expansion rate is less than 6%.
  • the capacity retention rate after 400 cycles is more than 91.5%, and the thickness expansion rate is not higher than 8.1%.
  • the capacity retention rate after 600 cycles is more than 87.5%, and the thickness expansion rate is less than 10%.
  • the capacity retention rate after 800 cycles is more than 81%, and the thickness expansion rate is not higher than 11.1%, showing high energy density and high capacity retention rate.
  • the silicon-carbon material 11 is in a granular form, and its macroscopic appearance is powder, and serves as the negative electrode active material of the active material layer 1 .
  • the silicon-carbon material 11 may specifically include a carbon material and a silicon material composited with the carbon material, wherein the carbon material may specifically be porous carbon having a porous structure, that is, it has pores.
  • the silicon material exists in the pores of the porous carbon, that is, the silicon material fills the pores of the porous carbon, and specifically can fill the pores of the porous carbon (that is, all the pores of the porous carbon are basically filled with the silicon material), which can prevent the electrolyte from penetrating into the pores of the porous carbon and reduce the occurrence of side reactions.
  • the pores of the porous carbon may include mesopores and/or micropores.
  • the average pore size of the porous carbon may be less than or equal to 20 nm, specifically 0.5 nm to 20 nm, such as 0.5 nm, 1 nm, 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm or a range consisting of any two of them.
  • the pore size of the porous carbon is too large (greater than 20 nm), the size of the silicon material is large, which will affect the structural stability of the silicon-carbon material 11 to a certain extent.
  • controlling the pore size of the porous carbon to be less than or equal to 20 nm can further improve the structural stability of the silicon-carbon material 11 and avoid the occurrence of side reactions and expansion.
  • the pore size of the porous carbon is less than or equal to 20 nm, which can have a good bonding effect with the first binder and effectively alleviate the expansion of silicon.
  • the embodiment of the present invention can measure the average pore size of the porous carbon in the silicon-carbon material 11 by conventional methods in the art.
  • the silicon-carbon material can be immersed in an alkaline aqueous solution (such as a sodium hydroxide solution) with a pH of 9-12 to react until no bubbles are generated to remove the silicon therein; then drying is performed to obtain a porous carbon sample; and then the specific surface area and total pore volume of the porous carbon sample are measured by a nitrogen adsorption method, and the average pore size of the porous carbon is calculated based on the measured specific surface area and total pore volume of the porous carbon sample.
  • an alkaline aqueous solution such as a sodium hydroxide solution
  • porous carbon has a large specific surface area, usually greater than 100 m 2 /g.
  • the specific surface area of the formed silicon-carbon material 11 is usually significantly reduced relative to the specific surface area of porous carbon.
  • the specific surface area of the silicon-carbon material 11 is less than or equal to 15m 2 /g, specifically 1m 2 /g to 15m 2 /g, for example, 1m 2 /g, 2m 2 /g, 3m 2 /g, 4m 2 / g , 5m 2 /g, 6m 2 /g, 7m 2 /g, 8m 2 /g, 9m 2 /g, 10m 2 /g, 11m 2 /g, 12m 2 /g, 13m 2 /g, 14m 2 /g, 15m 2 /g or a range consisting of any two of them.
  • the specific surface area of the silicon-carbon material 11 may be measured by conventional methods in the art such as nitrogen adsorption method.
  • the silicon material in the silicon-carbon material 11 is filled in the pores of the porous carbon, and the particle size of the silicon-carbon material 11 is substantially consistent with the particle size of the porous carbon.
  • the particle size Dv50 of the silicon-carbon material 11 may be 5 ⁇ m to 15 ⁇ m, for example, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 15 ⁇ m or a range consisting of any two of them.
  • Dv50 is the median particle size of the silicon-carbon material 11 based on the volume density distribution, which indicates that in the volume-based particle size distribution, the silicon-carbon material particles start from the small particle size side and reach a particle size of 50% of the volume accumulation.
  • the particle size of the silicon-carbon material 11 is too small (Dv50 ⁇ 5 ⁇ m), the surface side reaction of the silicon-carbon material 11 is large, and if the particle size of the silicon-carbon material 11 is too large (Dv50>15 ⁇ m), the volume expansion of the silicon-carbon material 11 is too large. Therefore, controlling the particle size Dv50 of the silicon-carbon material 11 to 5 ⁇ m to 15 ⁇ m can further improve the performance of the negative electrode sheet and reduce its expansion rate.
  • the mass ratio of the carbon material (porous carbon) to the silicon material can be 7:3 to 3:7, for example, 7:3, 6:4, 5:5, 4:6, 3:7 or a range consisting of any two of them.
  • the mass ratio of the carbon material to the silicon material in the silicon-carbon material 11 is too large (greater than 7:3), the first coulomb efficiency of the silicon-carbon material 11 is low, and if the mass ratio of the carbon material to the silicon material is too small (less than 3:7), the silicon content in the silicon-carbon material 11 is too high, affecting the structural stability of the silicon-carbon material 11. Therefore, controlling the mass ratio of the carbon material to the silicon material to be 7:3 to 3:7 can further take into account the improvement of its first coulomb efficiency and structural stability and other properties, so as to facilitate the function of the silicon-carbon material 11 as an electrode active material.
  • the silicon-carbon material 11 can be prepared by chemical vapor deposition.
  • the preparation process of the silicon-carbon material 11 can include: placing a porous carbon material in a vapor deposition furnace, introducing a mixed gas of an inert gas and silane therein, and then heating it to 400°C to 600°C for reaction, and the reaction time is 4h to 20h.
  • silane is cracked to form a silicon element that is deposited in the pores filled in the porous carbon material to form the silicon-carbon material 11.
  • the porous carbon material used can be purchased commercially or homemade, such as porous carbon purchased from Aladdin;
  • the volume ratio of the inert gas to silane in the mixed gas can be (10-1):1, and the inert gas includes, for example, argon;
  • the silane used can include one or more of monosilane, disilane, and trichlorosilane.
  • the current collector 2 has two opposite surfaces (i.e., the front and back surfaces), one of which may have the active material layer 1, or both surfaces may have the active material layer 1, which may be arranged as required during implementation.
  • the mass percentage of the silicon-carbon material 11 can be 3% to 20% (that is, the mass of the silicon-carbon material 11 in the active material layer 1 accounts for 3% to 20% of the total mass of the active material layer 1), for example, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20% or any two thereof.
  • the content of the silicon-carbon material 11 is too low (less than 3%), it will affect the capacity of the negative electrode sheet to a certain extent, and if the content of the silicon-carbon material 11 is too high (greater than 50%), It will also increase the expansion rate of the negative electrode sheet to a certain extent. Therefore, controlling the content of the silicon-carbon material 11 to 3% to 20% can make the active material layer 1 have a higher gram capacity, thereby increasing the capacity of the negative electrode sheet while reducing the expansion rate of the negative electrode sheet.
  • the introduction of the first binder into the active material layer 1 can improve the bonding between the components in the negative electrode active material layer 1, as well as the bonding between the negative electrode active material layer 1 and the current collector.
  • the first binder has a strong bonding effect with the above-mentioned silicon-carbon material 11, which can inhibit the silicon-carbon material 11 from generating excessive voids when expanding due to lithium insertion, thereby reducing the expansion rate of the negative electrode sheet and the battery.
  • the carboxyl group in the first binder may include a carboxylic acid group (—COOH) and/or a carboxylate group.
  • the carboxylate group for example, includes one or more of —COOLi, —COONa, —COOK, and —COONH 4 .
  • the second group in the first binder includes a cyano group (—CN) and/or an amide group, and the amide group is, for example, —CONH 2 .
  • the first binder can be polymerized from a monomer containing a first group and a monomer containing a second group.
  • the monomer containing the first group and the monomer containing the second group respectively contain unsaturated bonds, specifically double bonds, so that polymerization reaction can occur through the unsaturated bonds to generate the first binder containing the first group and the second group.
  • M is a metal ion, for example, M is Li (the first group is -COOLi), Na (the first group is -COONa), K (the first group is -COOK) or NH 4 (the first group is -COONH 4 ), etc.
  • the molar number of the first group is M 1
  • the molar number of the second group is M 2
  • 0.05 ⁇ M 2 /(M 1 +M 2 ) ⁇ 0.6 the binding effect of the first binder on the silicon-carbon material 11 and other components in the active material layer 1 can be improved, and the preparation of the negative electrode sheet is facilitated.
  • M 1 /(M 1 +M 2 ) may be 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or a range consisting of any two thereof.
  • the negative electrode sheet can be prepared by a conventional coating method in the present invention, that is, the first binder, the silicon-carbon material 11 and other materials used to form the active material layer 1 are placed in a first solvent to form a slurry, and then the slurry is coated on the current collector 2, and then dried, rolled, and cut (i.e., sheared).
  • the negative electrode sheet is made by processes such as forming a negative electrode sheet into a preset shape.
  • controlling 0.4 ⁇ M 1 /(M 1 +M 2 ) ⁇ 0.95 can reduce the above problems, and can make the slurry stable and easy to process, thereby facilitating the preparation of the negative electrode sheet and improving the preparation yield and performance of the negative electrode sheet.
  • the amounts of the monomer containing the first group and the monomer containing the second group used in preparing the first binder can be adjusted to control the contents of the first group and the second group in the formed first binder, thereby obtaining the first binder meeting the preset M1 /( M1 + M2 ) value.
  • the weight average molecular weight of the first adhesive can be 3000-2000000 (i.e. 3000-2 million), for example, 3000, 5000, 8000, 10,000, 50,000, 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1 million, 1.2 million, 1.5 million, 1.8 million, 2 million.
  • the first adhesive has good dispersibility and adhesion (when the weight average molecular weight of the first adhesive is less than 3000, the cohesion between the molecules is weak and the adhesion effect is poor; when the weight average molecular weight of the first adhesive is greater than 2 million, the molecules are severely entangled and the dispersion effect is poor).
  • the mass percentage of the first binder is 1% to 10% (i.e., the mass of the first binder accounts for 1% to 10% of the total mass of the active material layer 1), for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two of them.
  • the mass percentage of the first binder can take into account both the binding force between the material particles in the active material layer 1 and the conductivity of the negative electrode sheet.
  • the active material layer 1 may also include carbon-based materials, which may specifically include one or more of artificial graphite, natural graphite, mesophase carbon microbeads, soft carbon, hard carbon, carbon black, acetylene black, carbon fiber, single-walled carbon tubes, and multi-walled carbon tubes.
  • carbon-based materials may specifically include one or more of artificial graphite, natural graphite, mesophase carbon microbeads, soft carbon, hard carbon, carbon black, acetylene black, carbon fiber, single-walled carbon tubes, and multi-walled carbon tubes.
  • the carbon-based material may include a first carbon-based material and/or a second carbon-based material
  • the first carbon-based material includes one or more of graphite (artificial graphite and/or natural graphite), mesophase carbon microspheres, soft carbon, and hard carbon, which may be used with silicon-carbon materials as active substances, that is, the active substance layer may also include other active substances (that is, the first carbon-based material) in addition to silicon-carbon materials
  • the second carbon substrate includes one or more of carbon black, acetylene black, carbon fiber, single-walled carbon tube, and multi-walled carbon tube, which is mainly used as a conductive agent for the active material layer.
  • the second carbon-based material can specifically include zero-dimensional carbon-based materials (such as the above-mentioned carbon black and/or acetylene black, etc.) and/or one-dimensional carbon-based materials (such as the above-mentioned carbon fiber and/or single-walled carbon tube, etc.).
  • the gram capacity of the above-mentioned graphite in the range of 0.005 to 0.7V can generally be 345 to 355 mAh/g, and the first coulomb efficiency can be 91% to 95%.
  • the mass percentage of the first carbon-based material in the active material layer 1 (the ratio of the mass of the first carbon-based material to the mass of the active material layer 1) can be greater than the mass percentage of the silicon-carbon material 11 (the ratio of the mass of the silicon-carbon material 11 to the mass of the active material layer 1), that is, the mass ratio of the first carbon-based material in the active material layer 1 to the silicon-carbon material 11 is greater than 1, and specifically can be (3 to 32):1, for example 3:1, 5:1, 8:1, 10:1, 12:1, 15:1, 18:1, 20:1, 22:1, 25:1, 28:1, 30:1, 32:1 or a range consisting of any two of them.
  • the mass percentage of the carbon-based material in the active material layer 1, can be 60% to 96% (that is, the mass of the carbon-based material accounts for 70% to 96% of the total mass of the active material layer 1), for example, 60%, 62%, 65%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 93%, 96% or a range composed of any two of them, which is beneficial to further cooperate with the silicon-carbon material 11 and other components in the active material layer 1 to improve the conductivity, stability and other properties of the electrode.
  • the mass percentage of the first carbon-based material can be 60% to 96%, for example, 60%, 62%, 65%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 93%, 96% or a range consisting of any two of them
  • the mass percentage of the second carbon-based material can be 0 to 10%, for example, 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two of them.
  • the surface density of the active material layer 1 may be 5 mg/ cm2 to 8 mg/ cm2 , for example, 5 mg/ cm2 , 5.5 mg/ cm2 , 6 mg/ cm2 , 6.5 mg/ cm2 , 7 mg/ cm2 , 7.5 mg/ cm2 , 8 mg/ cm2 or any two thereof, but is not limited thereto.
  • the thickness of the active material layer 1 can be 15 ⁇ m to 60 ⁇ m, for example, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, 55 ⁇ m, 60 ⁇ m or any two thereof. Relatively speaking, if the thickness of the active material layer 1 is too small (less than 15 ⁇ m), the capacity of the negative electrode sheet is low, and it is easy to have undesirable phenomena such as coating scraping and deformation of the collector during rolling during the preparation of the negative electrode sheet.
  • the thickness of the material layer 1 is 15 ⁇ m to 60 ⁇ m, which can further improve the performance of the negative electrode sheet and the battery.
  • the thickness of the active material layer 1 is greater than the maximum size of the material particles such as the silicon-carbon material 11 therein (i.e., the maximum particle size, which can specifically be the Dv99 of the material particles in the active material layer 1, where Dv99 represents the particle size from the small particle size side to 99% of the volume accumulation in the volume-based particle size distribution), so as to facilitate the coating process during the preparation of the negative electrode sheet, avoid scraping during the coating process, and avoid excessive pressure on the current collector 2 during rolling, as well as the resulting compression deformation of the current collector 2.
  • the maximum particle size which can specifically be the Dv99 of the material particles in the active material layer 1, where Dv99 represents the particle size from the small particle size side to 99% of the volume accumulation in the volume-based particle size distribution
  • the above-mentioned current collector (negative electrode current collector) 2 may include copper foil, which may include pure copper foil formed only by copper metal or copper foil containing a first doping element, the first doping element may include carbon element and/or a first metal element, and the first metal element may include one or more of nickel, tin, zinc, lead, silver, chromium, tungsten, iron, and cobalt.
  • the current collector 2 may further include a first coating present on the surface of the copper foil.
  • the first coating may be a first coating layer provided on the surface of the copper foil.
  • the first coating may include one or more of amorphous carbon, silver, and gold.
  • the thickness of the current collector 2 may be in the range of 3 ⁇ m to 15 ⁇ m, for example, 3 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m or any two thereof.
  • the negative electrode sheet of the embodiment of the present invention can be prepared by conventional methods in the field such as coating method.
  • silicon-carbon material 11, binder, carbon-based material and first solvent (such as water) are mixed to form slurry; the slurry is coated on the surface of the current collector 2, sliced after drying, and then rolled, slid, and made into a negative electrode sheet through processes such as sheet making.
  • the preparation process of the negative electrode sheet may include: mixing the silicon-carbon material and at least part of the carbon-based material, then adding the first solvent and the first binder thereto, stirring evenly, and if there is any remaining carbon-based material, then adding the remaining carbon-based material, stirring evenly to obtain a slurry, and then applying the slurry to the surface of the current collector 2, drying and slicing, and then undergoing rolling, slitting, sheet making and other processes to obtain a negative electrode sheet.
  • the carbon-based materials used include graphite, zero-dimensional carbon-based materials (such as carbon black, etc.), and one-dimensional carbon-based materials (such as single-walled carbon tubes, etc.).
  • the preparation process of the negative electrode sheet may include mixing the silicon-carbon material, graphite and the zero-dimensional carbon-based material, and then adding the first solvent and the first binder thereto, stirring evenly, and then adding the one-dimensional carbon-based material, stirring evenly, to obtain a slurry; then applying the slurry to the surface of the current collector 2, drying and slicing, and then rolling, slitting, and making sheets to obtain a negative electrode sheet. Get the negative electrode.
  • the battery provided by the embodiment of the present invention includes the above-mentioned negative electrode sheet, and its advantages over the prior art are the same as those of the above-mentioned negative electrode sheet, which will not be described in detail.
  • the battery may include a lithium-ion battery.
  • the above-mentioned battery also includes a positive electrode sheet, a diaphragm, an electrolyte and a shell.
  • the diaphragm is located between the positive electrode sheet and the negative electrode sheet to separate/isolate the positive electrode sheet and the negative electrode sheet to avoid short circuit caused by contact between the positive electrode sheet and the negative electrode sheet.
  • the positive electrode sheet, the diaphragm and the negative electrode sheet form a battery cell, which can be formed into a stacked battery cell by stacking the sheets or formed into a wound battery cell by winding.
  • the shell is surrounded by a cavity, the battery cell is located in the cavity, and the electrolyte exists in the cavity.
  • the battery of the embodiment of the present invention can be manufactured by conventional methods in the art, for example, after welding the positive electrode tab on the positive electrode sheet and welding the negative electrode tab on the negative electrode sheet, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence, and then wound to form a wound battery cell; the battery cell is placed in a cavity surrounded by a shell and dried, and then an electrolyte is injected therein, and then the battery is manufactured through processes such as packaging, formation, secondary sealing, and sorting.
  • the shell can include one or more of aluminum-plastic film, aluminum shell, and steel shell, but is not limited thereto.
  • the negative electrode tab may include a nickel tab
  • the positive electrode tab may include an aluminum tab
  • the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer arranged on the surface of the positive electrode collector, and the positive electrode active material layer includes a positive electrode active material, a conductive agent and a second binder.
  • the mass percentage of the positive electrode active material can be 90% to 99%
  • the mass percentage of the conductive agent can be 0.5% to 5%
  • the mass percentage of the second binder can be 0.5% to 5%.
  • the positive electrode active material may include a lithium-containing active material, for example, one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, lithium iron silicate, lithium cobalt oxide, nickel-cobalt-manganese ternary material, nickel-manganese binary material, cobalt-manganese binary material, nickel-cobalt binary material, lithium manganese oxide, lithium nickel oxide and lithium-rich manganese-based material.
  • a lithium-containing active material for example, one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, lithium iron silicate, lithium cobalt oxide, nickel-cobalt-manganese ternary material, nickel-manganese binary material, cobalt-manganese binary material, nickel-cobalt binary material, lithium manganese oxide, lithium nickel oxide and lithium-rich manganese-based material.
  • the conductive agent may be a conventional conductive material in the art, for example, one or more of conductive carbon black, acetylene black, carbon nanotubes, conductive graphite, and graphene.
  • the second binder can be a conventional bonding material in the art, for example, one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose (CMC-Na), polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.
  • PVDF polyvinylidene fluoride
  • SBR styrene-butadiene rubber
  • copolymer of vinylidene fluoride and hexafluoropropylene polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose (CMC-Na), polyvinylpyrrolidon
  • the positive electrode current collector has two opposite surfaces (ie, front and back surfaces), one of which may have a positive electrode active material layer, or both of which may have a positive electrode active material layer.
  • the positive electrode current collector may include aluminum foil, which may include pure aluminum foil formed only of aluminum metal or doped aluminum foil containing a second doping element, the second doping element may include silicon element and/or a second metal element, and the second metal element may include, for example, one or more of copper, magnesium, zinc, manganese, nickel, iron, titanium, chromium, and lithium.
  • the positive electrode current collector may further include a second coating present on the surface of the aluminum foil.
  • the second coating may be a second coating layer provided on the surface of the aluminum foil.
  • the second coating may include one or more of amorphous carbon, silver, and gold.
  • the positive electrode sheet of the embodiment of the present invention can be prepared by conventional methods in the field such as coating method.
  • the positive electrode active material, binder, conductive agent and second solvent such as N-methylpyrrolidone (NMP)
  • NMP N-methylpyrrolidone
  • the diaphragm includes a polymer film, which can be a single-layer film formed by one or more polymers, or a composite film formed by stacking at least two sides of films.
  • the polymer film can specifically include polyethylene and/or polypropylene, etc.
  • the above-mentioned diaphragm is, for example, a polyethylene film formed by polyethylene, etc.
  • the diaphragm may further include a third coating disposed on the surface of the polymer film.
  • the third coating may include a polymer and/or a ceramic material, for example, one or more of polyvinylidene fluoride, alumina, and boehmite.
  • the electrolyte includes a third solvent and a lithium salt
  • the third solvent includes an organic solvent, specifically an ester solvent, for example, one or more of ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC);
  • the lithium salt may include one or more of LiPF 6 , LiBF 4 , LiSbF 6 , LiClO 4 , LiCF 3 SO 3 , LiAlO 4 , LiAlCl 4 , Li(CF 3 SO 2 ) 2 N, LiBOB and LiDFOB.
  • the porous carbon was purchased from a commercial source and had a Dv50 of 7 ⁇ m and a specific surface area of 1289 m 2 /g.
  • the pore size was analyzed using a pore analyzer TriStar from Micromeritics Instrument Corp. based on a nitrogen adsorption method. II
  • the pore size distribution curve of the porous carbon measured is shown in Figure 2. From the pore size distribution curve, it can be seen that the porous carbon contains abundant micropores and mesopores, and the volume contained in the pores increases as the pore size decreases.
  • the average pore size calculated by the BJH model is 2.4nm.
  • Preparation of silicon-carbon material 500 g of the above-mentioned porous carbon was placed in a vapor deposition furnace, and a mixed gas of argon and silane with a volume ratio of 8:2 was introduced. Then the temperature was raised to 500°C to crack the silane into silicon and deposit it to fill the porous carbon. The reaction time was 10 hours to obtain the silicon-carbon material.
  • the SEM image of the silicon-carbon material measured using a scanning electron microscope (SEM) is shown in Figure 3. It can be seen that the silicon in the silicon-carbon material is filled in the pores of the porous carbon, so that the pores of the porous carbon in the silicon-carbon material are basically filled with silicon, and the pores of the porous carbon in the silicon-carbon material are basically not observed in the SEM image of the silicon-carbon material.
  • the silicon-carbon material particles were cut by argon ion milling to obtain a particle cross-section.
  • SEM image of the cross-section measured by SEM and the EDS line scan curve measured by X-ray energy dispersive spectrometer (EDS) are shown in Figure 4. From the EDS line scan curve, it can be seen that the C and Si elements in the silicon-carbon material particles are evenly distributed, because Si is filled in the pores of the porous carbon.
  • the weight average molecular weight of the first binder is 500,000.
  • the copper foil with the negative electrode coating was then transferred to a 100°C vacuum oven for drying for 10 hours, and after natural cooling, rolled at a compaction density of 1.65 g/ cm3.
  • the negative electrode coatings on both sides of the copper foil formed negative electrode active material layers, which were then cut to obtain negative electrode sheets.
  • the compaction density of the negative electrode active material layer reached a stable value of about 1.57 g/ cm3 after about 48 hours.
  • the thickness of the layer is about 40 ⁇ m, and the surface density of the negative electrode active material layer is about 6.487 mg/cm 2 (basically the same as the surface density of the above-mentioned negative electrode coating (6.5 mg/cm 2 ), and the surface density of the negative electrode active material layer formed after rolling is usually reduced by about 0.2% relative to the negative electrode coating before rolling).
  • Lithium cobalt oxide, polyvinylidene fluoride, and carbon black are mixed in a mass ratio of 96:2:2, N-methylpyrrolidone is added thereto, and the mixture is stirred under the action of a vacuum stirrer until a uniform positive electrode slurry is formed;
  • the positive electrode slurry was evenly coated on the front and back surfaces of an aluminum foil with a thickness of 10 ⁇ m, and dried to form a positive electrode coating with a surface density of 17 mg/ cm2 ;
  • the aluminum foil with the positive electrode coating was placed in a vacuum oven at 120°C and dried for 8 hours, and then rolled at a compaction density of 4.1 g/ cm3 .
  • the positive electrode coating on both surfaces of the aluminum foil formed a positive electrode active material layer, which was then cut to obtain a positive electrode sheet.
  • An aluminum tab is welded on the positive electrode sheet, and a nickel tab is welded on the negative electrode sheet; then the positive electrode sheet, a polyethylene separator with a thickness of 8 ⁇ m, and the negative electrode sheet are stacked in sequence and wound to form a wound battery cell; the wound battery cell is placed in a cavity surrounded by an aluminum-plastic film and dried, and an electrolyte is injected into the battery cell. After packaging, formation, secondary sealing, sorting and other processes, a lithium-ion battery cell is obtained.
  • Example 1 Referring to the process of Example 1, the silicon-carbon material, the first binder, the negative electrode sheet, the positive electrode sheet and the lithium-ion battery of Examples 2 to 17 were prepared. The differences between Examples 2 to 17 and Example 1 are shown in Table 1. Except for the differences shown in Table 1, the other conditions are the same.
  • Example 1 Referring to the preparation method of the negative electrode sheet in Example 1 (using silicon-carbon material as the negative electrode active material, eliminating the addition of graphite, and the other conditions are the same as those in Example 1), a negative electrode sheet is prepared;
  • the negative electrode sheet is used as the working electrode and the lithium metal sheet is used as the counter electrode to assemble into a button cell;
  • the discharge current was 50 mA/g (i.e., the ratio of current to the mass of the silicon-carbon material was 50 mA: 1 g) to 0.005 V to obtain the discharge capacity, which was then allowed to stand for 10 min and then The material was charged to 0.7 V at a current of 50 mA/g to obtain a charge capacity, which was taken as the gram capacity of the silicon-carbon material.
  • the ratio of the charge capacity divided by the discharge capacity was taken as the first coulombic efficiency.
  • the gram capacity of the artificial graphite used in the negative electrode sheet of each embodiment was 352 mAh/g in the range of 0.005-0.7V, and the first coulombic efficiency was 93.9%.
  • the other conditions are the same as those of the embodiment 1.
  • the other conditions are the same as those of example 1.
  • Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that 1.9 parts of sodium carboxymethyl cellulose and 2.1 parts of styrene-butadiene rubber are used as binders to replace 4 parts of the first binder in Example 1, and the other conditions are the same as those in Example 1.
  • the surface density of the negative electrode coating is adjusted to the above value, so that the positive electrode working state of these embodiments and comparative examples can be similar.
  • the cycle performance of the lithium-ion battery of each embodiment and comparative example is tested through the following process:
  • the lithium-ion batteries of Examples 1 to 17 have the advantages of high energy density (greater than 730Wh/L), high capacity retention rate (the capacity retention rate after 800 cycles is higher than 79%), and low thickness expansion rate (the thickness expansion rate after 800 cycles is not higher than 13.1%).
  • the lithium-ion batteries of Examples 1 to 17 achieve higher capacity retention and lower thickness expansion while improving energy density.
  • the lithium-ion batteries of Examples 1 to 17 have higher capacity retention rates and lower thickness expansion rates while improving energy density.
  • Example 1 and Examples 4 to 7 that, relative to Example 6 and Example 7, the molar number M1 of the first group and the molar number M2 of the second group in the first binder used in Example 1, Example 4 and Example 5 satisfy 0.4 ⁇ M1 /( M1 + M2 ) ⁇ 0.95, and have better capacity retention and lower thickness expansion rate.
  • Example 1 and Examples 11 to 14 that, relative to Example 14, the average pore size of the porous carbon in Example 1 and Examples 11 to 13 is no greater than 20 nm, and their batteries have a higher capacity retention rate and a lower thickness expansion rate.
  • Example 15 compared with Example 17.
  • the specific surface areas of the silicon-carbon materials in Example 1, Example 15 and Example 16 are all no greater than 15 m 2 /g, and the batteries thereof have a higher capacity retention rate and a lower thickness expansion rate.

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Abstract

一种负极片及电池，负极片包括集流体（2）和设于集流体（2）表面的活性物质层（1），活性物质层（1）包括硅碳材料（11）和第一粘结剂，第一粘结剂含有第一基团和第二基团，第一基团包括羧基基团，第二基团包括氰基和/或酰胺基。

Description

负极片及电池 技术领域
本发明涉及电化学装置储能领域，具体涉及一种负极片及电池。
背景技术
目前，与纯石墨负极相比，掺硅负极具有能量密度高的优势，逐渐受到广泛应用。然而，相关技术中，掺硅负极存在着厚度膨胀率大、容量衰减快等缺陷，亟待解决。
发明内容
本发明提供一种负极片及电池，以至少解决现有技术存在的掺硅负极膨胀率大、容量衰减快等问题。
本发明的一方面，提供一种负极片，包括集流体和设于所述集流体表面的活性物质层，所述活性物质层包括硅碳材料和第一粘结剂，所述第一粘结剂包含第一基团和第二基团，所述第一基团包括羧基基团，所述第二基团包括氰基和/或酰胺基。
根据本发明的一实施方式，所述硅碳材料包括多孔碳、以及存在于所述多孔碳的孔隙中的硅材料。
根据本发明的一实施方式，所述多孔碳与所述硅材料的质量比为7:3～3:7；和/或，所述多孔碳的平均孔径小于或等于20nm。
根据本发明的一实施方式，所述硅碳材料的粒径Dv50为5μm～15μm；和/或，所述硅碳材料的比表面积小于或等于15m2/g。
根据本发明的一实施方式，所述活性物质层中，所述硅碳材料的质量百分含量为3％～20％，和/或，所述负极活性物质层的面密度为5mg/cm2～8mg/cm2。
根据本发明的一实施方式，所述羧基基团包括羧酸基团和/或羧酸盐基团，所述羧酸盐基团包括-COOLi、-COONa、-COOK、-COONH4中的一种或多种；和/或，所述第一粘结剂中，所述第一基团的摩尔数为M1，所述第二基团的 摩尔数为M2，0.4≤M1/(M1+M2)≤0.95。
根据本发明的一实施方式，所述第一粘结剂的重均分子量为3000～2000000。
根据本发明的一实施方式，所述活性物质层中，所述第一粘结剂的质量百分含量为1％～10％。
根据本发明的一实施方式，所述活性物质层还包括碳基材料，其中，所述碳基材料包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、碳黑、乙炔黑、碳纤维、单壁碳管、多壁碳管中的一种或多种；和/或，所述活性物质层中，所述碳基材料的质量百分含量为60％～96％。
本发明的另一方面，提供一种电池，包括上述负极片。
本发明中，活性物质层中包括硅碳材料，具有更高的容量，同时引入含有第一基团和第二基团的第一粘结剂，其与硅碳材料粘结作用强，可抑制硅碳材料在电池循环过程中通过膨胀-收缩过程产生空隙，从而减少负极片的膨胀率，进而降低电池的膨胀率，同时能够降低电池容量衰减速率。
附图说明
图1为本发明一实施例的负极片的结构示意图；
图2为实施例1中的多孔碳的孔径分布曲线图；
图3为实施例1中的硅碳材料的SEM图；
图4为实施例1中的硅碳材料的截面EDS线扫图。
附图标记说明：1：活性物质层；2：集流体；11：硅碳材料。
具体实施方式
为使本领域技术人员更好地理解本发明的方案，下面对本发明作进一步地详细说明。以下所列举具体实施方式只是对本发明的原理和特征进行描述，所举实例仅用于解释本发明，并非限定本发明的范围。基于本发明实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施方式，都属于本发明保护的范围。
在本发明的描述中，“第一”、“第二”、“第三”等术语仅用于描述目的，例如区分各部件，以更清楚说明/解释技术方案，而不能理解为指示或 暗示所指示的技术特征的数量或具有实质性意义的顺序等含义。
目前，负极掺硅电池普遍存在着膨胀率大、容量保持率差等问题，亟待解决。
电极片是电池的重要组成部分，以硅类材料为活性物质的负极片具有相对较高的容量，但其更易发生过度膨胀(在电池循环过程中，硅类材料颗粒膨胀率大，其膨胀收缩过程产生过量空隙)，导致掺硅负极膨胀(主要是厚度方向的膨胀)严重，影响电池的循环性性能。
举例来说，石墨的可逆储存锂容量为372mAh/g，而常温下硅的可逆储锂容量约为3600mAh/g，因此采用硅类材料可以显著提高锂离子电池的能量密度。然而，硅在满嵌锂时的体积膨胀率通常超过300％，这使采用硅类材料作为活性物质的活性物质层变得蓬松，活性物质颗粒间的导电接触性变差，材料脱嵌锂难度增大，容易发生金属锂的析出，从而导致电池容量快速衰减、厚度膨胀率急剧增大等问题。
鉴于上述问题，本发明实施例提供一种负极片，如图1所示，该负极片包括集流体2和设于集流体2表面的活性物质层1，活性物质层1包括硅碳材料11和第一粘结剂，第一粘结剂包含第一基团和第二基团，第一基团包括羧基基团，第二基团包括氰基和/或酰胺基。
这样，硅碳材料作为活性物质，其具有更高的容量，同时引入包含第一基团和第二基团的第一粘结剂，其与硅碳材料粘结作用强，可抑制硅碳材料在嵌锂膨胀时产生过量的空隙，从而有效抑制负极片的膨胀，降低负极片的膨胀率，进而降低电池的膨胀率，同时能够降低电池容量衰减速率，提高电池的循环性能，研究显示，电池循环200圈(或称200次)后的容量保持率达95.5％以上、厚度膨胀率低于6％，循环400圈后的容量保持率达91.5％以上、厚度膨胀率不高于8.1％，循环600圈后的容量保持率达87.5％以上、厚度膨胀率低于10％，循环800圈后的容量保持率达81％以上、厚度膨胀率不高于11.1％，表现出高能量密度和高容量保持率。
一般情况下，上述硅碳材料11为颗粒状，其宏观表象为粉末，作为活性物质层1的负极活性物质。
在一些实施例中，硅碳材料11具体可以包括碳材料、以及与碳材料复合的硅材料，其中，碳材料具体可以为具有多孔结构的多孔碳，即其具有孔隙， 硅材料存在于多孔碳的孔隙中，即硅材料填充在多孔碳的孔隙中，具体可以填满多孔碳的孔隙(即多孔碳的所有孔隙基本均被硅材料填满)，可以避免电解液透入多孔碳的孔隙中，减少副反应的发生。
具体地，上述多孔碳的孔隙可以包括介孔和/或微孔。在一些实施例中，多孔碳的平均孔径可以小于或等于20nm，具体可以为0.5nm～20nm，例如0.5nm、1nm、3nm、5nm、8nm、10nm、12nm、15nm、18nm、20nm或其中的任意两者组成的范围。根据发明人的研究，若多孔碳的孔隙的孔径过大(大于20nm)，硅材料的尺寸较大，会在一定程度上影响硅碳材料11的结构稳定性，因此，控制多孔碳的孔径小于或等于20nm，能够进一步提高硅碳材料11的结构稳定性，避免副反应的发生和膨胀等现象。同时，多孔碳的孔径小于或等于20nm，可以与第一粘结剂具有较好的结合作用，有效缓解硅的膨胀。
本发明实施例可通过本领域常规方法测得硅碳材料11中的多孔碳的平均孔径，例如，可以将硅碳材料浸泡在pH为9-12的碱性水溶液(如氢氧化钠溶液)中进行反应，直至没有气泡产生，以除去其中的硅；然后进行干燥，得到多孔碳样品；再采用氮气吸附法测得多孔碳样品的比表面积和总孔体积，根据所测得的多孔碳样品的比表面积和总孔体积计算得到多孔碳的平均孔径。
一般情况下，多孔碳具有较大的比表面积，通常可大于100m2/g，而当硅材料填充于其孔隙中后，所形成的硅碳材料11的比表面积相对于多孔碳的比表面积通常会显著下降。
研究显示，当硅碳材料11的比表面积过大(大于15m2/g)时，硅碳材料11表面副反应量较大，因此，一般优选硅碳材料11的比表面积小于或等于15m2/g，具体可以为1m2/g～15m2/g，例如1m2/g、2m2/g、3m2/g、4m2/g、5m2/g、6m2/g、7m2/g、8m2/g、9m2/g、10m2/g、11m2/g、12m2/g、13m2/g、14m2/g、15m2/g或其中的任意两者组成的范围。
具体实施时，可采用氮气吸附法等本领域常规方法测得硅碳材料11的比表面积。
此外，硅碳材料11中的硅材料填充于多孔碳的孔隙中，硅碳材料11的粒径与多孔碳的粒径基本一致。
在一些实施例中，硅碳材料11的粒径Dv50可以为5μm～15μm，例如5μm、 6μm、7μm、8μm、9μm、10μm、11μm、12μm、15μm或其中的任意两者组成的范围。Dv50为硅碳材料11基于体积密度分布的中值粒径，其表示在体积基准的粒度分布中，硅碳材料颗粒从小粒径侧起、达到体积累积50％的粒径。相对而言，若硅碳材料11的粒径过小(Dv50＜5μm)，则硅碳材料11的表面副反应较大，而若硅碳材料11的粒径过大(Dv50＞15μm)，硅碳材料11体积膨胀过大，因此，控制硅碳材料11的粒径Dv50为5μm～15μm，能够进一步提高负极片的性能，并降低其膨胀率。
此外，硅碳材料11中，碳材料(多孔碳)与硅材料的质量比可以为7:3～3:7，例如7:3、6:4、5:5、4:6、3:7或其中的任意两者组成的范围。相对而言，若硅碳材料11中的碳材料与硅材料的质量比过大(大于7:3)，硅碳材料11的首次库伦效率较低，若碳材料与硅材料的质量比过小(小于3:7)，硅碳材料11中的硅含量过高，影响硅碳材料11的结构稳定性，因此，控制碳材料与硅材料的质量比为7:3～3:7，能够进一步兼顾提高其首次库伦效率和结构稳定性等性能，便于硅碳材料11作为电极活性材料的功能发挥。
上述硅碳材料11可以通过化学气相沉积法制得，在一些具体实施例中，上述硅碳材料11的制备过程可以包括：将多孔碳材料放置在气相沉积炉中，向其中通入惰性气体和硅烷的混合气体，随后升温至400℃～600℃进行反应，反应时间为4h～20h，在反应过程中，硅烷裂解形成硅单质沉积于填充于多孔碳材料的孔隙内，形成硅碳材料11。其中，所用多孔碳材料可以商购或自制，例如购自阿拉丁的多孔碳；混合气体中的惰性气体与硅烷的体积比可以为(10～1)：1，惰性气体例如包括氩气；所用硅烷可以包括甲硅烷、乙硅烷、三氯硅烷中的一种或多种。
此外，集流体2具有相对的两个表面(即正反两个表面)，可以是其中的一个表面具有活性物质层1，或者两个表面均具有活性物质层1，具体实施时，可以根据需要设置。
在一些实施例中，上述活性物质层1中，硅碳材料11的质量百分含量可以为3％～20％(即活性物质层1中的硅碳材料11的质量占活性物质层1的总质量的3％～20％)，例如3％、5％、8％、10％、12％、15％、18％、20％或其中的任意两者组成的范围。相对而言，若硅碳材料11的含量过低(小于3％)，会在一定程度上影响负极片的容量，而若硅碳材料11的含量过高(大于50％)， 也会在一定程度上使负极片的膨胀率较大，因此，控制硅碳材料11的含量为3％～20％，能够使活性物质层1具有较高的克容量，从而提高负极片的容量，同时兼顾降低负极片的膨胀率。
活性物质层1中引入第一粘结剂，可以提高负极活性物质层1中各成分之间的粘结性、以及负极活性物质层1与集流体的粘结性，该第一粘结剂与上述硅碳材料11具有较强的粘结作用，可抑制硅碳材料11在嵌锂膨胀时产生过量的空隙，从而减少负极片和电池的膨胀率。
具体地，第一粘结剂中的羧基基团可以包括羧酸基团(-COOH)和/或羧酸盐基团，羧酸盐基团例如包括-COOLi、-COONa、-COOK、-COONH4中的一种或多种。
此外，第一粘结剂中的第二基团包括氰基(-CN)和/或酰胺基，该酰胺基例如为-CONH2。
具体地，上述第一粘结剂可以由含有第一基团的单体与含有第二基团的单体聚合而成，含有第一基团的单体、含有第二基团的单体中分别含有不饱和键，具体可以为双键，由此可以通过不饱和键发生聚合反应，生成含有第一基团和第二基团的第一粘结剂。
示例性地，含有第一基团的单体包括CH2＝CHCOOH(第一基团为-COOH)和/或CH2＝CHCOOM，M为金属离子，例如M为Li(第一基团为-COOLi)、Na(第一基团为-COONa)、K(第一基团为-COOK)或NH4(第一基团为-COONH4)等，含有第二基团的单体包括CH2＝CHCN(第二基团为-CN)和/或CH2＝CHCONH2(第二基团为CONH2)。
在一些实施例中，上述第一粘结剂中，第一基团的摩尔数为M1，第二基团的摩尔数为M2，0.4≤M1/(M1+M2)≤0.95，相应地，0.05≤M2/(M1+M2)≤0.6，这样，可以提高第一粘结剂对活性物质层1中的硅碳材料11等成分的粘结作用，同时便于负极片的制备。
示例性地，M1/(M1+M2)可以为0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95或其中的任意两者组成的范围。
具体来说，本发明实施例可以通过本领域常规涂覆法制备负极片，即将第一粘结剂、硅碳材料11等用于形成活性物质层1的材料置于第一溶剂中，制成浆料，再将该浆料涂覆于集流体2上，再经烘干、辊压、分切(即剪切 成预设形状的负极片)等过程制成负极片。研究显示，在负极片的制备过程中，当M1/(M1+M2)＜0.4时，涂敷于集流体的浆料不易烘干，会增加副反应的发生，而当M1/(M1+M2)＞0.95时，第一粘结剂对硅碳材料11的粘接作用较弱，且涂敷于集流体2的浆料烘干后形成的活性物质层1硬度较大(即偏硬)，在后续的分切等过程中容易产生掉粉(涂层粉末掉落)等现象。因此，控制0.4≤M1/(M1+M2)≤0.95，可减少上述问题，并可以使浆料稳定，易于加工，从而便于负极片的制备，提高负极片的制备良率和性能。
具体实施时，可以调节制备第一粘结剂时所用的含有第一基团的单体与含有第二基团的单体的用量，以控制所形成的第一粘结剂中第一基团和第二基团的含量，从而获得符合预设M1/(M1+M2)值的第一粘结剂。
此外，第一粘结剂的重均分子量可以为3000～2000000(即3000～200万)，例如3000、5000、8000、1万、5万、10万、20万、30万、40万、50万、60万、70万、80万、90万、100万、120万、150万、180万、200万，这样，第一粘结剂兼顾良好的分散性和粘结性(当第一粘结剂的重均分子量小于3000时，分子之间的内聚力较弱，粘结效果较差；当第一粘结剂的重均分子量大于200万时，分子之间缠绕严重，分散效果较差)。
在一些实施例中，活性物质层1中，第一粘结剂的质量百分含量为1％～10％(即第一粘结剂的质量占活性物质层1的总质量的1％～10％)，例如1％、2％、3％、4％、5％、6％、7％、8％、9％、10％或其中的任意两者组成的范围。相对而言，若第一粘结剂的含量过小(小于1％)，则活性物质层1中的材料颗粒之间的束缚力过弱，而若第一粘结剂的含量过大(大于10％)，则负极片的导电性较差，因此，控制第一粘结剂的质量百分含量为1％～10％，可以兼顾活性物质层1中的材料颗粒之间的粘结力和负极片的导电性。
此外，活性物质层1还可以包括碳基材料，碳基材料具体可以包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、碳黑、乙炔黑、碳纤维、单壁碳管、多壁碳管中的一种或多种。
在一些具体实施例中，碳基材料可以包括第一碳基材料和/或第二碳基材料，第一碳基材料包括石墨(人造石墨和/或天然石墨)、中间相碳微球、软碳、硬碳中的一种或几种，其可与硅碳材料作为活性物质，即活性物质层还可以包括除硅碳材料之外的其他活性物质(即第一碳基材料)，第二碳基材 料包括炭黑、乙炔黑、碳纤维、单壁碳管、多壁碳管中的一种或几种，其主要作为活性物质层的导电剂，第二碳基材料具体可以包括零维碳基材料(如上述炭黑和/或乙炔黑等)和/或一维碳基材料(如上述碳纤维和/或单壁碳管等)。其中上述石墨在0.005～0.7V区间的克容量一般可以为345～355mAh/g，首次库伦效率可以为91％～95％。
一般情况下，活性物质层1中的第一碳基材料的质量百分含量(第一碳基材料的质量与活性物质层1的质量之比)可以大于硅碳材料11的质量百分含量(硅碳材料11的质量与活性物质层1的质量之比)，即活性物质层1中的第一碳基材料与硅碳材料11的质量之比大于1，具体可以为(3～32)：1，例如3:1、5:1、8:1、10:1、12:1、15:1、18:1、20:1、22:1、25:1、28:1、30:1、32:1或其中的任意两者组成的范围。
在一些实施例中，1活性物质层1中，碳基材料的质量百分含量可以为60％～96％(即碳基材料的质量占活性物质层1的总质量的70％～96％)，例如60％、62％、65％、70％、72％、75％、78％、80％、82％、85％、88％、90％、93％、96％或其中的任意两者组成的范围，利于进一步与活性物质层1中的硅碳材料11等成分配合，提高极片的导电性和稳定性等性能。
其中，活性物质层1中，第一碳基材料的质量百分含量可以为60％～96％，例如60％、62％、65％、70％、72％、75％、78％、80％、82％、85％、88％、90％、93％、96％或其中的任意两者组成的范围，第二碳基材料的质量百分含量可以为0～10％，例如0、1％、2％、3％、4％、5％、6％、7％、8％、9％、10％或其中的任意两者组成的范围。
此外，上述活性物质层1的面密度可以为5mg/cm2～8mg/cm2，例如5mg/cm2、5.5mg/cm2、6mg/cm2、6.5mg/cm2、7mg/cm2、7.5mg/cm2、8mg/cm2或其中的任意两者组成的范围，但不局限于此。
在一些实施例中，活性物质层1的厚度可以为15μm～60μm，例如15μm、20μm、25μm、30μm、35μm、40μm、45μm、50μm、55μm、60μm或其中的任意两者组成的范围。相对而言，若活性物质层1的厚度过小(小于15μm)，则负极片的容量较低，同时在负极片制备过程中容易出现涂布刮料、以及辊压时集流体变形等不良现象，而若活性物质层1的厚度过大(大于60μm)，则电池充放电时极化现象较重，脱嵌锂的不均匀性较大，因此，控制活性物 质层1的厚度为15μm～60μm能够进一步提高负极片和电池的性能。
一般情况下，活性物质层1的厚度大于其中的硅碳材料11等材料颗粒的最大尺寸(即最大粒径，该最大粒径具体可以是活性物质层1中的材料颗粒的Dv99，Dv99表示在体积基准的粒度分布中，颗粒从小粒径侧起、达到体积累积99％的粒径)，以便于负极片制备过程中的涂覆过程，避免涂布过程中出现刮料现象，并避免辊压时对集流体2造成过大压力、以及由此导致的集流体2受压变形等现象。
上述集流体(负极集流体)2可以包括铜箔，其可以包括仅由铜金属形成的纯铜箔或含有第一掺杂元素的铜箔，第一掺杂元素可以包括碳元素和/或第一金属元素，第一金属元素例如包括镍、锡、锌、铅、银、铬、钨、铁、钴中的一种或几种。
此外，集流体2还可以包括存在于铜箔表面的第一涂覆物，该第一涂覆物具体可以为设于铜箔表面的第一涂层，第一涂覆物可以包括无定形碳、银、金中的一种或几种。
此外，集流体2的厚度可以为3μm～15μm，例如3μm、5μm、8μm、10μm、12μm、15μm或其中的任意两者组成的范围。
本发明实施例的负极片可通过涂覆法等本领域常规方法制得，例如，将硅碳材料11、粘结剂、碳基材料和第一溶剂(如水)混合，制成浆料；将该浆料涂覆于集流体2表面，烘干后切片，然后经过辊压、分切、制片等工序，制得负极片。
在一些实施例中，负极片的制备过程可以包括：将硅碳材料和至少部分碳基材料混合，然后再向其中加入第一溶剂和第一粘结剂，搅拌均匀后，若还有剩余部分的碳基材料，则再加入剩余部分的碳基材料，搅拌均匀后，得到浆料，再将浆料涂敷于集流体2表面，烘干后切片，然后经过辊压、分切、制片等工序，制得负极片。
例如，在一些具体实施例中，所用碳基材料包括石墨、零维碳基材料(如炭黑等)、一维碳基材料(如单壁碳管等)，负极片的制备过程可以包括将硅碳材料、石墨和零维碳基材料混合，然后向其中加入第一溶剂和第一粘结剂，搅拌均匀后，再加入一维碳基材料，搅拌均匀后，得到浆料；再将浆料涂敷于集流体2表面，烘干后切片，然后经过辊压、分切、制片等工序，制 得负极片。
本发明实施例提供的电池包括上述负极片，其相对于现有技术所具有的优势与上述负极片相同，不再赘述。
具体地，上述电池可以包括锂离子电池。
具体地，上述电池还包括正极片、以及隔膜、电解液和壳体，隔膜位于正极片和负极片之间，以间隔/隔离正极片和负极片，避免正极片和负极片接触发生短路，正极片、隔膜、负极片形成电芯，具体可以通过叠片形成叠片式电芯或经卷绕后形成卷绕式电芯，壳体围设成腔体，电芯位于腔体内，电解液存在于腔体内。
本发明实施例的电池可通过本领域常规方法制得，例如，在正极片上焊接正极极耳、在负极片上焊接负极极耳后，将正极片、隔膜、负极片按顺序依次叠放后，通过卷绕形成卷绕式电芯；将电芯置于由壳体围设成的腔体中并干燥，然后向其中注入电解液，再经过封装、化成、二封、分选等工序，制得电池。其中，壳体可以包括铝塑膜、铝壳、钢壳中的一种或几种，但不局限于此。
具体地，负极极耳可以包括镍极耳，正极极耳可以包括铝极耳。
其中，正极片包括正极集流体和设于正极集流体表面的正极活性物质层，正极活性物质层包括正极活性物质、导电剂和第二粘结剂，其中，正极活性物质的质量百分含量可以为90％～99％，导电剂的质量百分含量可以为0.5％～5％，第二粘结剂的质量百分含量可以为0.5％～5％。
正极活性物质可以包括含锂活性材料，例如包括磷酸铁锂、磷酸锰锂、磷酸钒锂、硅酸铁锂、钴酸锂、镍钴锰三元材料、镍锰二元材料、钴锰二元材料、镍钴二元材料、锰酸锂、镍酸锂和富锂锰基材料中的一种或几种。
导电剂可以是本领域常规导电材料，例如包括导电炭黑、乙炔黑、碳纳米管、导电石墨、石墨烯中的一种或几种。
第二粘结剂可以是本领域常规粘结材料，例如包括聚偏氟乙烯(PVDF)、丁苯橡胶(SBR)、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素钠(CMC-Na)、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯、聚六氟丙烯中的一种或几种。
正极集流体具有相对的两个表面(即正反两个表面)，可以是其中的一个表面具有正极活性物质层，或者两个表面均具有正极活性物质层。
正极集流体可以包括铝箔，其可以包括仅由铝金属形成的纯铝箔或含有第二掺杂元素的掺杂型铝箔，第二掺杂元素可以包括硅元素和/或第二金属元素，第二金属元素例如包括铜、镁、锌、锰、镍、铁、钛、铬、锂中的一种或几种。
此外，正极集流体还可以包括存在于铝箔表面的第二涂覆物，该第二涂覆物具体可以为设于铝箔表面的第二涂层，第二涂覆物可以包括无定形碳、银、金中的一种或几种。
本发明实施例的正极片可通过涂覆法等本领域常规方法制得，例如，将正极活性物质、粘结剂、导电剂和第二溶剂(如N-甲基吡咯烷酮(NMP)等)混合，制成正极浆料；将该正极浆料涂覆于集流体表面，烘干后切片，然后经过辊压、分切、制片等工序，制得正极片。
隔膜包括聚合物膜，该聚合物膜可以是由一种或多种聚合物形成的单层膜、或者由至少两侧膜层叠设置而成的复合膜，该聚合物膜具体可以包括聚乙烯和/或聚丙烯等，示例性地，上述隔膜例如是由聚乙烯形成的聚乙烯膜等。
此外，隔膜还可以包括设于聚合物膜表面的第三涂层，第三涂层可以包括聚合物和/或陶瓷材料，例如包括聚偏氟乙烯、氧化铝、勃姆石中的一种或几种。
电解液包括第三溶剂和锂盐，第三溶剂包括有机溶剂，具体可以包括酯类溶剂，例如包括碳酸亚乙酯(EC)、碳酸丙烯酯(PC)、丙酸丙酯(PP)、碳酸二乙酯(DEC)、氟代碳酸乙烯酯(FEC)、1,3丙磺酸内脂(PS)、碳酸二甲酯(DMC)和碳酸甲乙酯(EMC)中的一种或几种；锂盐可以包括LiPF6、LiBF4、LiSbF6、LiClO4、LiCF3SO3、LiAlO4、LiAlCl4、Li(CF3SO2)2N、LiBOB和LiDFOB中的一种或几种。
下面通过具体实施例和对比例对本发明作进一步的说明。
实施例1
1、硅碳材料的制备
多孔碳由商业途径购得，其Dv50为7μm，比表面积为1289m2/g，基于氮气吸附方法，使用Micromeritics Instrument Corp.的孔隙分析仪TriStar  II测得多孔碳的孔径分布曲线见图2，从孔径分布曲线上可以看到，所述多孔碳含有丰富的微孔和介孔，且孔隙所包含的体积随着孔径的减小而增加，由BJH模型计算的平均孔径为2.4nm。
硅碳材料的制备：将500g上述多孔碳放置在气相沉积炉中，通入体积比为8：2的氩气和硅烷的混合气体，随后温度升高至500℃，使硅烷裂解为硅并沉积填充于多孔碳，反应时长10h，即得到硅碳材料。
使用扫描电子显微镜(SEM)测得的硅碳材料的SEM图见图3，可以看到，硅碳材料中的硅填充于多孔碳的孔隙中，使得硅碳材料中的多孔碳的孔隙基本被硅填满，在硅碳材料的SEM图中已基本观测不到其中的多孔碳的孔隙。
此外，采用氩离子研磨的方法将硅碳材料颗粒切开，得到颗粒截面，使用SEM测得的该截面的SEM图和使用X射线能谱仪(EDS)测得的EDS线扫曲线见图4，从EDS线扫曲线可以看到，硅碳材料颗粒中的C和Si元素分布均匀，这是因为Si填充在多孔碳的孔隙之中。
此外，测得多孔碳和硅的质量比为4.4:5.6；硅碳材料的粒径Dv50＝7μm，硅碳材料的比表面积为5.2m2/g。
2、第一粘结剂
第一粘结剂由CH2＝CHCOOH和CH2＝CHCN聚合而成，该第一粘结剂中，-COOH的摩尔数M1、-CN的摩尔数为M2满足M1/(M1+M2)＝0.8、M2/(M1+M2)＝0.2；该第一粘结剂的重均分子量为50万。
3、负极片的制备
按重量份计，将85.86份人造石墨、9.54份上述硅碳材料和0.5份的碳黑充分混合，然后向其中加入去离子水和4份上述第一粘结剂，搅拌均匀，再加入0.1份单壁碳管，搅拌均匀后得到负极浆料；将负极浆料均匀涂覆在厚度为8μm的纯铜箔的正反两个表面，烘干，形成面密度为6.5mg/cm2的负极涂层；
然后再将形成有上述负极涂层的铜箔转移至100℃真空烘箱中干燥10h，自然冷却后以1.65g/cm3的压实密度进行辊压，铜箔正反两个表面的负极涂层形成负极活性物质层，然后分切，得到负极片，其中的负极活性物质层的压实密度在约48h后达到稳定值，约为1.57g/cm3，负极活性物质 层的厚度约为40μm左右，负极活性物质层的面密度约为6.487mg/cm2(与上述负极涂层的面密度(6.5mg/cm2)基本相同，通常辊压后形成的负极活性物质层相对于辊压前的负极涂层的面密度降低约0.2％)。
4、正极片的制备
将钴酸锂、聚偏氟乙烯、碳黑按照质量比96:2:2混合，向其中加入N-甲基吡咯烷酮，在真空搅拌机作用下搅拌，直至混合成均匀的正极浆料；
将正极浆料均匀涂覆于厚度为10μm的铝箔的正反两个表面，烘干，形成面密度为17mg/cm2的正极涂层；
将形成有上述正极涂层的铝箔转入120℃的真空烘箱中干燥8h，以4.1g/cm3的压实密度进行辊压，铝箔正反两个表面的正极涂层形成正极活性物质层，然后分切，得到正极片。
5、锂离子电池的制备
在惰性气氛(氮气)下，将EC、PC、PP、LiPF6、FEC、PS按照质量比13:13:50:15:5:4混合，搅拌均匀，得到电解液；
在正极片上焊接铝极耳，在负极片上焊接镍极耳；然后将正极片、厚度为8μm的聚乙烯隔膜、负极片依次叠放后，卷绕形成卷绕式电芯；将卷绕式电芯置于由铝塑膜围设成的腔体中并干燥，将电解液注入电芯中，经过封装、化成、二封、分选等工序，制得锂离子电池电池。
实施例2～实施例17
参照实施例1的过程，制得实施例2～实施例17的硅碳材料、第一粘结剂、负极片、正极片和锂离子电池，实施例2～实施例17与实施例1的区别见表1，除表1示出的区别外，其余条件相同。
此外，分别采用实施例1～实施例17的硅碳材料，通过如下过程测得各实施例的硅碳材料在0.005-0.7V区间的克容量和首次库伦效率，结果见表1：
参照实施例1中负极片的制备方法(以硅碳材料作为负极活性材料，取消添加石墨，其余条件与实施例1相同)，制得负极片；
以上述负极片为工作电极，以锂金属片为对电极，组装成扣式电池中；
基于硅碳材料的重量，以50mA/g(即电流与硅碳材料的质量之比为50mA：1g)的电流放电至0.005V，得到放电容量，静置10min，然后以 50mA/g的电流充电至0.7V，得到充电容量，以所述充电容量为硅碳材料的克容量，以充电容量除以放电容量所得到的比值为首次库伦效率。
此外，参照上述硅碳材料的克容量和首次库伦效率的测试过程，测得各实施例负极片中所用的人造石墨在0.005-0.7V区间的克容量为352mAh/g，首次库伦效率为93.9％。
表1
对比例1
该对比例1与实施例1的区别在于，以硅氧碳材料代替硅碳材料，该硅氧碳材料由预锂化的氧化亚硅、以及包覆于预锂化的氧化亚硅表面的无定型碳组成，无定型碳的质量为硅氧碳材料总质量的2.1％，该硅氧碳材料的粒径Dv50＝7μm，比表面积为4.1m2/g，在0.005-0.7V区间的克容量为1240mAh/g，首次库伦效率为76.1％；该对比例2的负极片制备过程中，负极涂层的面密度为7.15mg/cm2。其余条件与实施例1相同。
对比例2
该对比例2与实施例1的区别在于，以硅氧碳材料代替硅碳材料，该硅氧碳材料由预锂化的氧化亚硅、以及包覆于预锂化的氧化亚硅表面的无定型碳组成，无定型碳的质量为硅氧碳材料总质量的44％，该硅氧碳材料的粒径Dv50＝7μm，比表面积为4.1m2/g，在0.005-0.7V区间的克容量为730mAh/g，首次库伦效率为64.8％；该对比例3的负极片制备过程中，负极涂层的面密度为7.95mg/cm2。其余条件与实施例1相同。
对比例3
该对比例3与实施例1的区别在于，采用1.9份羧甲基纤维素钠和2.1份丁苯橡胶作为粘结剂，替代实施例1中的4份第一粘结剂，其余条件与实施例1相同。
上述各实施例和对比例中，调控其负极涂层的面密度为上述值，可以使这些实施例和对比例的正极工作状态相近。使用蓝电(LAND)测试系统，在45℃的测试温度下，通过如下过程测试各实施例和对比例的锂离子电池的循环性能：
以1.5C恒流充电至4.48V，恒压充电到0.05C，静置10分钟，以0.7C放电至3.0V，以此放电容量为初始容量，以此放电能量为初始能量(实施例1～实施例7的测试结果见表2，实施例8～实施例17的测试结果与实施例1类似，不再赘述)；
以1.5C恒流充电至3.82V，恒压充电到0.025C，静置10分钟，测试电池的厚度，以此厚度为初始厚度，以初始厚度和电池的长度及宽度的乘积为电池的初始体积，以初始能量除以初始体积为电池的能量密度(实施例1～实施例7的初始厚度和能量密度测试结果见表2，实施例8～实施例17的初始厚度和能量密度测试结果与实施例1类似，不再赘述)；
以0.7C放电至3.0V，静置10分钟，以1.5C恒流充电至4.48V，恒压充电到0.05C，静置10分钟，以该步骤进行循环充放电测试；以每一次放电容量除以初始容量的比值为容量保持率，循环800次；每隔200次循环，测试满电态电池厚度，以此厚度除以初始厚度的比值为厚度膨胀率(实施例1～实施例17的厚度膨胀率测试结果见表3)。
表2
表3
可以看到，实施例1～实施例17的锂离子电池兼具能量密度高(大于730Wh/L)、容量保持率高(循环800次后的容量保持率高于79％)、厚度膨胀率低(循环800次后的厚度膨胀率不高于13.1％)等优点。
此外，相对于对比例1和对比例2(采用包括预锂化的氧化亚硅和包覆在预锂化的氧化亚硅表面的无定型碳的硅氧材料作为负极活性物质)，实施例1～实施例17的锂离子电池在提升能量密度的同时，还达到更高的容量保持率和更低的厚度膨胀率。
此外，相对于对比例3(采用羧甲基纤维素钠和丁苯橡胶作为粘结剂)，实施例1～实施例17的锂离子电池在提升能量密度的同时，还具有更高的容量保持率和更低的厚度膨胀率。
此外，从实施例1和实施例4～实施例7可以看到，相对于实施例6和实施例7，实施例1、实施例4和实施例5中所用的第一粘结剂中第一基团的摩尔数M1和第二基团的摩尔数M2满足0.4≤M1/(M1+M2)≤0.95，具有更好的容量保持率和更低的厚度膨胀率。
此外，从实施例1和实施例11～实施例14可以看到，相对于实施例14，实施例1和实施例11～实施例13中的多孔碳的平均孔径均不大于20nm，其电池具有更高的容量保持率和更低的厚度膨胀率。
此外，从实施例1和实施例15～实施例17可以看到，相对于实施例 17，实施例1、实施例15和实施例16中的硅碳材料的比表面积均不大于15m2/g，其电池具有更高的容量保持率和更低的厚度膨胀率。
最后应说明的是：以上各实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述各实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的范围。

Claims (10)

  1. 一种负极片，其特征在于，包括集流体和设于所述集流体表面的活性物质层，所述活性物质层包括硅碳材料和第一粘结剂，所述第一粘结剂包含第一基团和第二基团，所述第一基团包括羧基基团，所述第二基团包括氰基和/或酰胺基。
  2. 根据权利要求1所述的负极片，其特征在于，所述硅碳材料包括多孔碳、以及存在于所述多孔碳的孔隙中的硅材料。
  3. 根据权利要求2所述的负极片，其特征在于，
    所述多孔碳与所述硅材料的质量比为7:3～3:7；
    和/或，所述多孔碳的平均孔径小于或等于20nm。
  4. 根据权利要求1-3任一项所述的负极片，其特征在于，
    所述硅碳材料的粒径Dv50为5μm～15μm；
    和/或，所述硅碳材料的比表面积小于或等于15m2/g。
  5. 根据权利要求1-3任一项所述的负极片，其特征在于，
    所述活性物质层中，所述硅碳材料的质量百分含量为3％～20％；
    和/或，所述活性物质层的面密度为5mg/cm2～8mg/cm2。
  6. 根据权利要求1所述的负极片，其特征在于，
    所述羧基基团包括羧酸基团和/或羧酸盐基团，所述羧酸盐基团包括-COOLi、-COONa、-COOK、-COONH4中的一种或多种；
    和/或，所述第一粘结剂中，所述第一基团的摩尔数为M1，所述第二基团的摩尔数为M2，0.4≤M1/(M1+M2)≤0.95。
  7. 根据权利要求1或6所述的负极片，其特征在于，所述第一粘结剂的重均分子量为3000～2000000。
  8. 根据权利要求1-6任一项所述的负极片，其特征在于，所述活性物质层中，所述第一粘结剂的质量百分含量为1％～10％。
  9. 根据权利要求1所述的负极片，其特征在于，所述活性物质层还包括碳基材料，其中，
    所述碳基材料包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、碳黑、乙炔黑、碳纤维、单壁碳管、多壁碳管中的一种或多种；
    和/或，所述活性物质层中，所述碳基材料的质量百分含量为60％～96％。
  10. 一种电池，其特征在于，包括权利要求1-9任一项所述的负极片。
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CN111725509A (zh) * 2020-06-24 2020-09-29 名添科技（深圳）有限公司 一种负极材料、负极浆料、负极片及锂离子电池
CN113555551A (zh) * 2021-06-02 2021-10-26 浙江中科玖源新材料有限公司 一种硅碳负极用粘接剂及锂离子电池用电极材料
CN115064697A (zh) * 2022-07-14 2022-09-16 中国科学院山西煤炭化学研究所 一种改性聚丙烯腈的应用、粘结剂、负极片及锂离子电池
CN116565140A (zh) * 2023-06-26 2023-08-08 珠海冠宇电池股份有限公司 负极片及电池

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