WO2023143035A1 - 负极粘结剂及其制备方法、负极片和电池 - Google Patents

负极粘结剂及其制备方法、负极片和电池 Download PDF

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WO2023143035A1
WO2023143035A1 PCT/CN2023/071487 CN2023071487W WO2023143035A1 WO 2023143035 A1 WO2023143035 A1 WO 2023143035A1 CN 2023071487 W CN2023071487 W CN 2023071487W WO 2023143035 A1 WO2023143035 A1 WO 2023143035A1
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negative electrode
binder
monomer
type
substituted
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PCT/CN2023/071487
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English (en)
French (fr)
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那睿琦
黄振军
马强
洪响
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华为技术有限公司
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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 embodiment of the present application relates to the field of battery technology, in particular to a negative electrode binder, a preparation method thereof, a negative electrode sheet and a battery.
  • lithium-ion batteries have received widespread attention in new energy vehicles, energy storage and other fields, so the demand for improving the energy density of lithium-ion batteries is also increasing.
  • Carbon-based materials such as graphite currently used in lithium-ion battery anodes have reached their theoretical capacity and are difficult to increase. Therefore, the development of active materials such as alloys and metal oxides with higher theoretical capacity is considered to be the next generation of lithium-ion batteries.
  • the development trend of ion battery negative electrode Among them, silicon materials have attracted extensive attention of researchers because of their high theoretical specific capacity, low lithium extraction/intercalation potential, and abundant reserves.
  • the embodiment of the present application provides a negative electrode binder, which can better adapt to the preparation of silicon-based negative electrode sheets, has a good bonding effect, and can solve the problem of volume expansion of silicon-based negative electrode materials to a certain extent. The problem of battery performance deterioration is coming.
  • the first aspect of the embodiment of the present application provides a negative electrode binder
  • the negative electrode binder includes an aqueous solution of a first binder
  • the first binder is a first-type monomer, a second-type A copolymer of a monomer and a third type of monomer
  • the first type of monomer includes one or more of acrylic monomers and acrylate monomers
  • the second type of monomer includes acrylonitrile or propylene
  • the third type of monomers include vinylpyrrolidone.
  • the first binder is a modified polyacrylic acid (PAA) multi-polymer, which is formed by the copolymerization of the above three types of monomers.
  • PAA polyacrylic acid
  • the first binder can better cover silicon-based materials and reduce SEI
  • the repeated regeneration of the membrane and the occurrence of side reactions can also have a strong bonding effect on silicon-based materials.
  • the first binder also has a thickening effect, promotes the uniform dispersion of active materials, and prevents sedimentation. It can be better applied to Preparation of negative electrode sheets containing silicon-based materials.
  • the three types of monomer designs of the first binder of the present application have different effects respectively.
  • the effects of the first type of monomers include: the first type of monomers have better adhesion and coating effects on silicon-based materials, and the carboxyl groups can be lithiated
  • the first type of monomers have better adhesion and coating effects on silicon-based materials
  • the carboxyl groups can be lithiated
  • hydrophilic carboxyl groups and hydrophobic ester groups that is, the regulation of the amount of acrylic monomers and acrylic ester monomers
  • the effects of the second type of monomers include: the second type of monomers have better wettability with the electrolyte, and have better electrochemical stability.
  • the effects of the third type of monomer include: the third type of monomer is the main component of solid glue, and has the characteristics of hydrophilicity and thickening, and can play the role of CMC (sodium carboxymethylcellulose).
  • the negative electrode binder provided in the examples of the present application can be used in the preparation of silicon-based negative electrodes for lithium-ion batteries.
  • a silicon-based negative electrode refers to a negative electrode comprising a silicon-based active material.
  • the general structural formula of the first type of monomer is Wherein, R 1 is a hydrogen atom or a methyl group, and R 2 is a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group.
  • R 1 is a hydrogen atom or a methyl group
  • R 2 is a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group.
  • the R 2 is a hydrogen atom, a substituted or unsubstituted alkyl group with 1-8 carbon atoms, or a substituted or unsubstituted cycloalkyl group with 3-8 carbon atoms.
  • R 2 selects a substituted or non-substituted alkyl group, a substituted or non-substituted cycloalkyl group with a small number of carbon atoms to make the first type of monomer easy to obtain.
  • R 3 is a hydrogen atom or a methyl group
  • R 7 is a substituted or unsubstituted alkylene group.
  • the acrylonitrile monomers, acrylamide monomers, and glycidyl ether monomers with the above structure are not only easy to obtain monomer materials, but also can better control the wettability of the binder and electrolyte, and improve the stability of the battery system. electrochemical stability.
  • the R 5 and R 6 are respectively selected from a hydrogen atom, a substituted or unsubstituted alkyl group with 1-8 carbon atoms, or a substituted or unsubstituted cycloalkyl group with 3-8 carbon atoms ;
  • the R 7 is a substituted or unsubstituted alkylene group with 1-8 carbon atoms. Monomers with lower carbon numbers are more readily available.
  • the R 7 is methylene (-CH 2 -) or benzylene (-C 6 H 4 -CH 2 -).
  • R 3 is a hydrogen atom, R 7 is a methylene group, and the glycidyl ether monomer is allyl glycidyl ether.
  • R 3 is a hydrogen atom, R 7 is a benzyl group, and the glycidyl ether monomer is 4-vinylbenzyl glycidyl ether.
  • the mass proportion of the structural units derived from the first type of monomer is greater than or equal to 40%. That is, the mass ratio of the amount of the first type of monomer to the total amount of the first binder monomer is greater than or equal to 40%. Controlling the mass proportion of the structural units derived from the first type of monomer in the first binder to 40% or more can better ensure the coating and bonding effect of the first binder on the silicon-based material.
  • the structural units derived from the first type of monomer account for 40%-80% by mass. Controlling the structural units derived from the first type of monomer in the first binder to the above-mentioned mass ratio can better ensure the coating and bonding effect of the first binder on the silicon-based material, and ensure that the first adhesive The binder is less brittle.
  • the mass proportion of the structural units derived from the second type of monomer may be 10%-40%. Controlling the structural units derived from the second type of monomer in the first binder to the above-mentioned mass ratio can better ensure the affinity effect between the first binder and the electrolyte, and better reduce the first binding agent. The swelling performance of the agent, thereby improving the mechanical properties of the first binder itself.
  • the mass proportion of the structural units derived from the third type of monomer may be 10%-40%. Controlling the structural units derived from the third type of monomer in the first binder to the above mass ratio can better improve the thickening effect of the first binder and improve the adhesion of the first binder to the current collector Effect; at the same time, it can effectively control the poor wetting effect of pyrrolidone and electrolyte, which leads to the increase of electrode interface resistance and the decrease of cell rate performance.
  • R 1 and R 3 are respectively selected from a hydrogen atom or a methyl group
  • R 2 is a hydrogen atom, a lithium atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group
  • R 5 and R 6 are respectively selected from hydrogen atoms, substituted or unsubstituted alkyl groups, or substituted or unsubstituted cycloalkyl groups
  • R 7 is substituted or unsubstituted alkylene groups
  • the weight average molecular weight of the first binder is 500,000-1,000,000. Appropriate molecular weight control can make the first binder itself have higher mechanical properties.
  • the negative electrode binder further includes an aqueous emulsion of a second binder.
  • aqueous emulsion of the second binder and the aqueous solution of the first binder are prepared into the negative electrode slurry, they can be stored and stored independently, and the two are not mixed.
  • the second binder can make up for the shortcomings of the first binder, so that the negative electrode binder can obtain better comprehensive performance under the synergistic effect of the two types of binders, thereby effectively improving the active material and electrical conductivity.
  • the problem of contact and adhesion between the agent and the current collector makes the silicon-based negative electrode sheet bonded into a firm whole, and at the same time, the rate performance, expansion inhibition, and cycle performance of the active material are fully exerted.
  • the second binder can also improve the toughness of the negative electrode sheet.
  • the second binder includes one or more of styrene-butadiene rubber, modified styrene-butadiene rubber, styrene-acrylic rubber and vinyl acetate-ethylene copolymer. These types of second binders can better cooperate with the first binder to improve the stability of the negative electrode sheet.
  • the mass of the first binder accounts for greater than or equal to 20% of the total mass of the first binder and the second binder.
  • the content of the first binder is controlled to be above a certain proportion, so that the performance advantages of the first binder can be better utilized, and the comprehensive performance of the negative electrode sheet can be improved.
  • the mass of the first binder accounts for 20%-70% of the total mass of the first binder and the second binder. Further controlling the content of the first binder in the negative electrode binder within a certain percentage range can make better use of the performance advantages of the first binder and the second binder and improve the overall performance of the negative electrode sheet.
  • the modified styrene-butadiene rubber is a copolymer of styrene, butadiene and the first type of monomer.
  • R 1 is a hydrogen atom or a methyl group
  • R 2 is a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group
  • the modified styrene-butadiene rubber having the structure shown in formula (2) can better cooperate with the first binder of the present application, and the two cooperate with each other to improve the comprehensive performance of the negative electrode binder, thereby improving the performance of the negative electrode sheet.
  • the weight average molecular weight of the modified styrene-butadiene rubber is 100,000-400,000. Controlling the modified styrene-butadiene rubber in a suitable molecular weight range is conducive to maintaining the viscosity and other properties of the negative electrode binder system at a more suitable level.
  • the second aspect of the embodiment of the present application provides a method for preparing a negative electrode binder, including:
  • the first type of monomer, the second type of monomer and the third type of monomer are added to water, and a copolymerization reaction occurs under the action of an initiator to obtain an aqueous solution of the first binder;
  • the first binder is the first A copolymer of a type monomer, a second type monomer, and a third type monomer, the first type monomer includes one or more of acrylic monomers and acrylic ester monomers, and the second type monomer
  • the monomers include one or more of acrylonitrile monomers, acrylamide monomers and glycidyl ether monomers, and the third type of monomers includes vinylpyrrolidone.
  • the above-mentioned copolymerization reaction is carried out under a protective atmosphere, and the protective atmosphere is an inert gas atmosphere, such as nitrogen, helium and the like.
  • the temperature of the above-mentioned copolymerization reaction may be 60°C-90°C.
  • Mechanical stirring can be carried out during the copolymerization reaction, and the time of the copolymerization reaction can be 9-12 hours.
  • the preparation method of the embodiment of the present application has a simple process, the copolymerization reaction can be completed at a relatively low temperature, and it is easy to realize the large-scale production and preparation of the first binder.
  • the preparation method further includes providing an aqueous emulsion of a second binder, and the second binder includes styrene-butadiene rubber, modified styrene-butadiene rubber, styrene-propylene rubber, and vinyl acetate-ethylene copolymer. one or more of .
  • the aqueous emulsion of the second binder and the aqueous solution of the first binder are prepared into the negative electrode slurry, they can be stored and stored independently, and the two are not mixed.
  • the first binder system and the second binder system are stored independently, which is more conducive to adjusting the dosage ratio of the two according to actual needs, more flexible use, and more conducive to maintaining the stability of each binder system.
  • the mass of the first binder accounts for greater than or equal to 20% of the total mass of the first binder and the second binder.
  • the content of the first binder is controlled to be above a certain proportion, so that the performance advantages of the first binder can be better utilized, and the comprehensive performance of the negative electrode sheet can be improved.
  • the third aspect of the embodiment of the present application provides a negative electrode slurry
  • the negative electrode slurry includes the negative electrode binder described in the first aspect of the embodiment of the present application.
  • the negative electrode binder in the negative electrode slurry has the above-mentioned technical effect, which will not be repeated here.
  • the fourth aspect of the embodiment of the present application provides a negative electrode sheet, the negative electrode sheet includes a current collector and a negative electrode active layer arranged on the current collector, and the negative electrode active layer adopts the negative electrode described in the first aspect of the embodiment of the present application binder.
  • the negative electrode binder in the negative electrode active layer has the above-mentioned technical effects, which will not be repeated here.
  • the negative electrode active layer using the above negative electrode binder has been fully dried during the preparation process, so the solvent water in the negative electrode binder has been removed, so the negative electrode active layer includes the negative electrode binder.
  • the solute of the negative electrode binder, in the negative electrode active layer the mass proportion of the solute of the negative electrode binder is 1%-12%.
  • the solute of the negative electrode binder refers to the first binder and the second binder. In some embodiments, the solute of the negative electrode binder includes the first binder; in some embodiments, the solute of the negative electrode binder includes the first binder and the second binder.
  • the negative electrode active layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material. Silicon-based materials have high capacity, which can increase the capacity of the negative electrode sheet.
  • the negative electrode active layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material and a carbon-based material.
  • the negative electrode active layer contains both silicon-based materials and carbon-based materials, which can combine the advantages of both, so that the negative electrode sheet can obtain better comprehensive performance.
  • the mass proportion of the silicon-based material is 0.5%-20%. Controlling the silicon-based material to a certain mass ratio is conducive to improving the structural stability of the negative electrode sheet.
  • the mass proportion of the carbon-based material is 80%-95%. Controlling the carbon-based material to a certain mass ratio is conducive to improving the structural stability of the negative electrode sheet.
  • the fifth aspect of the embodiment of the present application also provides a battery, including a positive electrode, a negative electrode, a separator and an electrolyte disposed between the positive electrode and the negative electrode, and the negative electrode includes the negative electrode described in the fourth aspect of the embodiment of the present application
  • the sheet or the negative electrode includes the negative electrode binder described in the first aspect of the embodiment of the present application.
  • the battery in the embodiment of the present application may be, for example, a lithium ion battery, a sodium ion battery, or the like. Because the battery of the embodiment of the present application uses the above-mentioned negative electrode binder, the cycle stability of the battery can be improved, and the service life of the battery can be improved.
  • An embodiment of the present application further provides an electronic device, and the electronic device includes the battery described in the fifth aspect of the embodiment of the present application.
  • the electronic equipment using the above-mentioned battery in the embodiment of the present application is more stable and can improve product competitiveness.
  • An embodiment of the present application further provides an energy storage system, which is characterized in that the energy storage system includes the battery described in the fifth aspect of the embodiment of the present application.
  • the energy storage system using the above-mentioned battery in the embodiment of the present application is more stable and can improve product competitiveness.
  • FIG. 1 is a schematic structural diagram of a lithium-ion battery 100 provided in an embodiment of the present application
  • FIG. 2 is a schematic structural view of the negative electrode sheet 200 provided in the embodiment of the present application.
  • FIG. 3 is a schematic structural diagram of an electronic device 300 provided by an embodiment of the present application.
  • Fig. 4 is a schematic structural diagram of an energy storage system 400 provided by an embodiment of the present application.
  • FIG. 5 is a diagram of the cycle performance of lithium-ion batteries prepared in Examples 1-2 and Comparative Examples 1-3 of the present application.
  • FIG. 1 is a schematic structural diagram of a lithium-ion battery 100 provided in an embodiment of the present application.
  • Lithium-ion battery 100 is a commonly used rechargeable battery, mainly composed of positive electrode 101, negative electrode 102, electrolyte 103, diaphragm 104 and corresponding circuits. Among them, the lithium-ion battery 100 realizes the storage and release of energy through the deintercalation of lithium ions (Li + ) between the positive and negative electrodes.
  • the electrolyte 103 is the carrier for the transmission of lithium ions between the positive and negative electrodes.
  • the insulating separator 104 ensures the migration of lithium ions (Li + ) while separating the positive and negative electrodes to prevent short circuit.
  • the positive and negative active materials are the main part of the lithium-ion battery to perform the energy storage function, which determines the energy density, cycle performance and safety performance of the battery. After determining the positive electrode active material system, the capacity of the negative electrode active material is crucial to the improvement of the energy density of the entire battery.
  • the current commercial graphite anode material actually uses a gram capacity of 360mAh/g, which is close to its theoretical value (372mAh/g), and it is difficult to further increase the energy density of lithium-ion batteries. Therefore, there is a need to develop anode active materials with higher theoretical capacities.
  • silicon-based materials have attracted extensive attention of researchers due to their high theoretical specific capacity, low lithium extraction/intercalation potential, and abundant reserves.
  • the negative electrode binder provided in the embodiment of the present application includes an aqueous solution of the first binder, the first binder is a copolymer of the first type monomer, the second type monomer and the third type monomer, and the first type monomer
  • the body includes at least one of acrylic monomers and acrylate monomers, the second type of monomers includes at least one of acrylonitrile monomers, acrylamide monomers and glycidyl ether monomers, and the third type of monomers Monomers include vinylpyrrolidone.
  • the first binder is a modified polyacrylic acid (PAA) multi-polymer, which is formed by the copolymerization of the above three types of monomers.
  • PAA polyacrylic acid
  • the first binder can better cover silicon-based materials and reduce SEI
  • the repeated regeneration of the membrane and the occurrence of side reactions can also have a strong bonding effect on silicon-based materials.
  • the first binder also has a thickening effect, promotes the uniform dispersion of active materials, and prevents sedimentation. It can be better applied to Preparation of negative electrode sheets containing silicon-based materials.
  • the three types of monomer designs of the first binder of the present application have different effects respectively.
  • the effects of the first type of monomers include: the first type of monomers have better adhesion and coating effects on silicon-based materials, and the carboxyl groups can be lithiated
  • the first type of monomers have better adhesion and coating effects on silicon-based materials
  • the carboxyl groups can be lithiated
  • hydrophilic carboxyl groups and hydrophobic ester groups that is, the regulation of the amount of acrylic monomers and acrylic ester monomers
  • the effects of the second type of monomers include: the second type of monomers have better wettability with the electrolyte, and have better electrochemical stability.
  • the effects of the third type of monomer include: the third type of monomer is the main component of solid glue, and has the characteristics of hydrophilicity and thickening, and can play the role of CMC (sodium carboxymethylcellulose).
  • the negative electrode binder provided in the examples of the present application can be used in the preparation of silicon-based negative electrodes for lithium-ion batteries.
  • a silicon-based negative electrode refers to a negative electrode comprising a silicon-based active material.
  • the general structural formula of the first type of monomer is the general formula (A): Wherein, R 1 is a hydrogen atom or a methyl group, and R 2 is a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group.
  • R 1 is a hydrogen atom or a methyl group
  • R 2 is a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group.
  • the general formula (A) represents an acrylic monomer.
  • the general formula (1) represents an acrylic acid monomer; when R 1 is a methyl group, the general formula (A) represents a methacrylic acid monomer.
  • R 1 is a hydrogen atom or a methyl group
  • R 2 is a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group
  • the general formula (A) represents an acrylate monomer.
  • R 2 may be a substituted or unsubstituted alkyl group with 1-8 carbon atoms, or a substituted or unsubstituted cycloalkyl group with 3-8 carbon atoms.
  • R 2 selects a substituted or non-substituted alkyl group, a substituted or non-substituted cycloalkyl group with a small number of carbon atoms to make the first type of monomer easy to obtain.
  • R 2 can be a substituted or unsubstituted alkyl group with 1, 2, 3, 4, 5, 6, 7 or 8 carbon atoms; R 2 can be 3, 4, 5, 6, A substituted or unsubstituted cycloalkyl group of 7 or 8.
  • the acrylate monomer can be, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, ethyl methacrylate, propyl methacrylate, methyl acrylate, One or more of butyl acrylate, pentyl methacrylate, and hexyl methacrylate.
  • the first type of monomer includes at least one of acrylic monomers and acrylate monomers.
  • the first type of monomer only includes acrylic monomers, and there can be one type of acrylic monomer, or multiple types; for example, the first type of monomer only includes acrylic acid or methacrylic acid, or Includes both acrylic and methacrylic.
  • the first type of monomer only includes acrylate monomers, and the acrylate monomer can be one or more; for example, the first type of monomer only includes methyl acrylate or methacrylic acid ethyl ester, or both methyl acrylate or ethyl methacrylate.
  • the first type of monomer includes acrylic monomers and acrylic ester monomers, and the acrylic monomers can be one type or multiple types; the acrylic monomers can be one type, or It can be multiple; for example, the first type of monomer includes both methacrylic acid and ethyl methacrylate.
  • the amounts of the two types of monomers can be adjusted as required.
  • the content of hydrophilic carboxyl groups and hydrophobic ester groups in the first binder can be adjusted, so as to better realize the affinity and hydrophobicity of different surfaces.
  • the bonding of silicon-based materials with water performance is better suitable for the preparation of different silicon-based negative electrodes.
  • the acrylonitrile monomers, acrylamide monomers, and glycidyl ether monomers with the above structure are not only easy to obtain monomer materials, but also can better control the wettability of the binder and electrolyte, and improve the stability of the battery system. electrochemical stability.
  • the general formula (B) represents an acrylonitrile monomer.
  • the general formula (B) represents an acrylonitrile monomer; when R 3 is a methyl group, the general formula (B) represents a methacrylonitrile monomer.
  • R 3 is a hydrogen atom or a methyl group
  • the general formula (B) represents an acrylamide monomer.
  • R 5 and R 6 may both be hydrogen atoms, that is, the general formula (B) represents a non-substituted acrylamide monomer, that is, acrylamide.
  • the general formula (B) represents an acrylamide monomer
  • R3 is a methyl group
  • the general formula (B) represents a methacrylamide monomer.
  • one of R 5 and R 6 may be a hydrogen atom, and the other may be a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group; both may be substituted or unsubstituted An alkyl group, or a substituted or unsubstituted cycloalkyl group, that is, the general formula (B) represents an N-substituted acrylamide monomer.
  • R 5 can be a substituted or unsubstituted alkyl group with 1-8 carbon atoms, or a substituted or unsubstituted cycloalkyl group with 3-8 carbon atoms; specifically, R 5 can be a carbon atom A substituted or unsubstituted alkyl group whose number is 1, 2, 3, 4, 5, 6 , 7 or 8; R may be a substituted or unsubstituted ring with 3, 4, 5, 6, 7 or 8 carbon atoms alkyl.
  • R 6 may be a substituted or unsubstituted alkyl group with 3-8 carbon atoms, or a substituted or unsubstituted cycloalkyl group with 3-8 carbon atoms.
  • R 6 may be a substituted or unsubstituted alkyl group with 1, 2, 3, 4, 5, 6, 7 or 8 carbon atoms; R 6 may be 3, 4, 5, 6, A substituted or unsubstituted cycloalkyl group of 7 or 8.
  • the acrylamide monomer can be, for example, one of N-methacrylamide, N,N-dimethylacrylamide, N-hydroxyethylacrylamide, and N-methylolacrylamide one or more species.
  • R 7 is a substituted or unsubstituted alkylene group.
  • R 7 may be a substituted or unsubstituted alkylene group with 1-8 carbon atoms.
  • R7 may be a substituted or unsubstituted alkylene group having 1, 2, 3, 4, 5, 6, 7 or 8 carbon atoms.
  • R 7 is methylene (-CH 2 -) or benzylene (-C 6 H 4 -CH 2 -).
  • R 3 is a hydrogen atom
  • R 7 is a methylene group
  • the glycidyl ether monomer is allyl glycidyl ether.
  • R 3 is a hydrogen atom
  • R 7 is a benzyl group
  • the glycidyl ether monomer is 4-vinylbenzyl glycidyl ether.
  • the glycidyl ether monomer may include one or more of allyl glycidyl ether and 4-vinylbenzyl glycidyl ether.
  • the second type of monomer includes at least one of acrylonitrile monomer, acrylamide monomer and glycidyl ether monomer.
  • the second type of monomer only includes acrylonitrile monomers, and the acrylonitrile monomers can be one or more; for example, the second type of monomers only includes acrylonitrile or methacrylonitrile, Or both acrylonitrile and methacrylonitrile.
  • the second type of monomer only includes acrylamide monomer, and the acrylamide type monomer can be one or more; for example, the second type of monomer only includes acrylamide or N-hydroxyethyl hydroxyacrylamide, or both acrylamide or N-hydroxyethylacrylamide.
  • the second type of monomers includes acrylonitrile monomers and acrylamide monomers, and the acrylonitrile monomers can be one or more; the acrylamide monomers can be one , can also be multiple; for example, the second type of monomer includes both acrylonitrile and acrylamide.
  • the second type of monomer includes only glycidyl ether type monomers.
  • the second type of monomer includes acrylonitrile type monomer and glycidyl ether type monomer. In some embodiments, the second type of monomer includes acrylamide type monomer and glycidyl ether type monomer. In some embodiments, the second type of monomer includes acrylonitrile-based monomers, acrylamide-based monomers, and glycidyl ether-based monomers.
  • the second type of monomer in the present application has strong polarity, which can increase the wettability of the electrolyte to the active material and reduce the problem of excessive resistance caused by ion migration.
  • the three types of monomers of the first binder can play different roles respectively.
  • the types and dosages of the three types of monomers can be regulated for different silicon-based negative electrodes to achieve better performance. performance.
  • the first binder is a copolymer of the first type monomer, the second type monomer, and the third type monomer.
  • the first binder includes The structural monomers, the structural units derived from the second type of monomers and the structural units derived from the third type of monomers.
  • the mass proportion of structural units derived from the first type of monomer may be greater than or equal to 40%. That is, the mass ratio of the amount of the first type of monomer to the total amount of the first binder monomer is greater than or equal to 40%.
  • the structural units derived from the first type of monomer account for 40%-80% by mass.
  • the mass proportion of structural units derived from the first type of monomer can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80% etc.
  • Controlling the structural units derived from the first type of monomer in the first binder to the above-mentioned mass ratio can better ensure the coating and bonding effect of the first binder on the silicon-based material, and ensure that the first adhesive The binder is less brittle.
  • the mass proportion of the structural units derived from the second type of monomer may be 10%-40%. That is, the amount of the second type of monomer accounts for 10%-40% by mass of the total amount of the first binder monomer. In some embodiments of the present application, in the molecular structure of the first binder, the mass proportion of structural units derived from the second type of monomer is 15%-25%. Specifically, in the molecular structure of the first binder, the mass proportion of structural units derived from the first type of monomer may be 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc. .
  • Controlling the structural units derived from the second type of monomer in the first binder to the above-mentioned mass ratio can better ensure the affinity effect between the first binder and the electrolyte, and better reduce the first binding agent.
  • the mass proportion of the structural units derived from the third type of monomer may be 10%-40%. That is, the amount of the third type of monomer accounts for 10%-40% by mass of the total amount of monomers used in the first binder. In some embodiments of the present application, in the molecular structure of the first binder, the structural units derived from the third type of monomer account for 20%-30% by mass. Specifically, in the molecular structure of the first binder, the mass proportion of structural units derived from the third type of monomer can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc. .
  • Controlling the structural units derived from the third type of monomer in the first binder to the above mass ratio can better improve the thickening effect of the first binder and improve the adhesion of the first binder to the current collector Effect; at the same time, it can effectively control the poor wetting effect of pyrrolidone and electrolyte, which leads to the increase of electrode interface resistance and the decrease of cell rate performance.
  • the general structural formula of the first binder may be as shown in formula (1):
  • R 1 and R 3 are independently a hydrogen atom or a methyl group
  • R 2 is a hydrogen atom, a lithium atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group
  • R 5 and R 6 are independently a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group
  • R 7 is a substituted or unsubstituted alkylene group
  • the structural units corresponding to R 1 and R 2 are derived from the first type of monomer, and the structural units corresponding to R 3 and R 4 are derived from the second type of monomer.
  • R 2 is a lithium atom
  • the first binder can be obtained by lithiation after the copolymerization of three types of monomers, and the lithiation can be realized by lithium carbonate or lithium hydroxide.
  • the weight average molecular weight of the first binder is 500,000-1,000,000. Appropriate molecular weight control can make the first binder itself have higher mechanical properties. In some embodiments, the weight average molecular weight of the first binder may be, for example, 500,000, 600,000, 700,000, 800,000, 900,000, 1 million, etc.
  • the negative electrode binder includes the aqueous solution of the above-mentioned first binder, and the solid content of the aqueous solution of the first binder is 1%-10%. Specifically, the solid content of the aqueous solution of the first binder is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. In some embodiments, the solid content of the aqueous solution of the first binder is 3%-8%. Appropriate solid content control can enable the negative electrode binder to obtain a suitable viscosity, which is conducive to the dispersion of the negative electrode material in the solution, and at the same time greatly alleviates the possible settlement problem of the slurry during storage.
  • the negative electrode binder also includes an aqueous emulsion of the second binder, that is, in this embodiment, the negative electrode binder is composed of an aqueous solution of the first binder and an aqueous emulsion of the second binder.
  • a combined binder of two binders can be used in combination when preparing the negative electrode sheet. Before the aqueous emulsion of the second binder and the aqueous solution of the first binder are prepared into the negative electrode slurry, they are stored and stored independently, and the two are not mixed.
  • the second binder may be one or more of styrene-butadiene rubber, modified styrene-butadiene rubber, styrene-acrylic rubber, and vinyl acetate-ethylene copolymer.
  • the second binder can form a combined binder system with the first binder, and the second binder can make up for the deficiencies of the first binder, so that the negative electrode binder can be used in two types of binders.
  • the second binder can also improve the toughness of the negative electrode sheet.
  • the mass of the first binder accounts for greater than or equal to 20% of the total mass of the first binder and the second binder.
  • the content of the first binder is controlled to be above a certain proportion, so that the performance advantages of the first binder can be better utilized, and the comprehensive performance of the negative electrode sheet can be improved.
  • the mass of the first binder accounts for 20% of the total mass of the first binder and the second binder -70%.
  • the proportion of the mass of the first binder relative to the total mass of the first binder and the second binder can be 20%, 25%, 30%, 35%, 40% , 45%, 50%, 55%, 60%, 65%, 70%.
  • the quality of the first binder and the quality of the second binder both refer to the quality of the simple solute in the aqueous emulsion of the first binder and the second binder, excluding other solvents such as solvents. components.
  • the negative electrode binder includes the above-mentioned aqueous emulsion of the second binder, and the solid content of the aqueous emulsion of the second binder may be 20%-60%. Appropriate solid content control is beneficial to obtain better mixing and dispersing effect and bonding effect.
  • the second binder includes modified styrene-butadiene rubber
  • the modified styrene-butadiene rubber can be styrene, butadiene and the aforementioned first type of monomer (ie, acrylic acid and/or acrylates) monomer) copolymers.
  • the structure of styrene-butadiene rubber in the modified styrene-butadiene rubber of this application can ensure more effective adhesion to carbon-based materials such as graphite, while the polyacrylic acid derived from the first type of monomer introduced in the molecular structure of the modified styrene-butadiene rubber And/or polyacrylate segment, can increase its compatibility with the first binder, so that the composite system has more excellent mechanical properties; it can also reduce the swelling of styrene-butadiene rubber in the electrolyte, improve the mechanical strength, It can better inhibit the falling off of the active material caused by the volume expansion of silicon particles; it can also change the glass transition temperature Tg of the modified styrene-butadiene rubber polymer, so that the binder does not undergo glass transition within the applicable range of the battery, and improves the low-temperature performance of the battery .
  • R 1 is a hydrogen atom or a methyl group
  • R 2 is a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group
  • the structural units corresponding to R 1 and R 2 are derived from the first type of monomer.
  • the introduction of an appropriate amount of segments derived from the first type of monomer can simultaneously obtain the dual advantages of styrene-butadiene rubber and modified segments.
  • the value of b may be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.5 and so on. The larger the value of b, the greater the mass proportion of structural units derived from the first type of monomer in the molecular structure of the modified styrene-butadiene rubber.
  • the value of a may be 0.2, 0.25, 0.3, 0.35, 0.4, etc.
  • the larger the value of a the larger the mass proportion of structural units derived from butadiene in the molecular structure of the modified styrene-butadiene rubber.
  • adjusting the value of a can effectively control the glass transition temperature Tg of the modified styrene-butadiene rubber.
  • the above value range can adjust the glass transition temperature Tg of the B-type binder to not lower than 30°C.
  • c in formula (2), 0.3 ⁇ c ⁇ 0.5.
  • the value of c may be 0.3, 0.35, 0.4, 0.45, 0.5 and so on.
  • the weight average molecular weight of the modified styrene-butadiene rubber is 100,000-400,000.
  • the weight average molecular weight of the modified styrene-butadiene rubber may be 100,000, 200,000, 300,000 or 400,000.
  • the second binder is uniformly dispersed in water to form an aqueous emulsion of the second binder.
  • the modified styrene-butadiene rubber in the water emulsion has an emulsion particle structure, which can increase the bonding area (point-like bonding) between the modified styrene-butadiene rubber and the negative electrode active material, and strengthen the negative electrode active material (such as carbon-based materials such as graphite) The bonding strength between them can reduce the resistance of lithium ion transmission, increase the elasticity of the pole piece, and improve the processing characteristics.
  • the particle diameter of the modified styrene-butadiene rubber polymer particles may be 50nm-500nm, and in some embodiments, the particle diameter may be 100nm-300nm.
  • the negative electrode binder is a combined binder including the first binder and modified styrene-butadiene rubber, and each component in the combined binder performs its duties in the silicon-based negative electrode. It can improve silicon-based materials and graphite and other carbon-based materials respectively.
  • the two types of polymers have a synergistic effect.
  • the first binder is a chain polymer
  • the modified styrene-butadiene rubber is a granular polymer.
  • the chain polymer and The granular polymer can form bridging points, build a three-dimensional network structure, effectively improve the mechanical properties of the composite system, and ultimately improve the comprehensive performance of the silicon-based negative electrode.
  • the combined binder composed of the first binder and the second binder in the embodiment of the present application can achieve a good bonding effect for each component in the negative electrode sheet at a relatively lower total binder usage. , so as to ensure the expansion inhibition effect on silicon-based materials, ensure the cycle performance of the negative electrode sheet, and at the same time ensure the rate performance of the negative electrode material.
  • the embodiment of the present application also provides a method for preparing a negative electrode binder, including:
  • the first binder is the first type monomer
  • the copolymer of the monomer and the second type of monomer and the third type of monomer includes one or more of acrylic monomers and acrylate monomers
  • the second type of monomers includes acrylonitrile
  • the third type of monomers includes vinylpyrrolidone.
  • the above-mentioned copolymerization reaction is carried out under a protective atmosphere, and the protective atmosphere is an inert gas atmosphere, such as nitrogen, helium and the like.
  • the temperature of the above-mentioned copolymerization reaction may be 60°C-90°C, for example, it may be 60°C, 70°C, 80°C, or 90°C.
  • Mechanical stirring can be carried out during the copolymerization reaction, and the time of the copolymerization reaction can be 9-12 hours.
  • the first type of monomer, the second type of monomer and the third type of monomer are added to the mixed solution obtained by adding water, the mass of water and the total mass of the monomers can be determined according to the final aqueous solution of the first binder Adjust the solids content as needed.
  • the initiator may be various initiators capable of initiating the copolymerization of the above-mentioned monomers, including but not limited to ammonium persulfate.
  • the aqueous solution of the first binder can be prepared in the following manner: under an inert gas atmosphere, add the first mass part of water into the reaction vessel, and the total mass part is the second mass part of the second mass part.
  • the first type of monomer, the second type of monomer and the third type of monomer and then stir until a uniform mixed solution is formed; then add 0.05-0.5 parts by mass of initiator, and raise the temperature to 70°C-90°C, under mechanical stirring React for 9-12 hours; after the reaction, cool down to room temperature to obtain a transparent and uniform first binder aqueous solution.
  • the part values of the first part by mass and the second part by mass can be adjusted according to the solid content requirement, the first part by mass can be, for example, 950 parts, and the second part by mass can be, for example, 50 parts.
  • the parts by mass of each monomer are added according to the pre-designed monomer dosage.
  • the preparation method further includes providing an aqueous emulsion of a second binder, and the second binder can be selected from various available negative electrode binders according to needs, so as to make up for the deficiency of the first binder,
  • the second binder may include, but is not limited to, one or more of the second binder including styrene-butadiene rubber, modified styrene-butadiene rubber, styrene-acrylic rubber, and vinyl acetate-ethylene copolymer.
  • the solute mass in the aqueous solution of the first binder and the solute in the aqueous emulsion of the second binder quality to match.
  • the mass of solute in the aqueous solution of the first binder is the mass of the first binder
  • the mass of solute in the aqueous emulsion of the second binder is the mass of the second binder.
  • the mass ratio of the first binder relative to the total mass of the first binder and the second binder may be greater than or equal to 20%.
  • the modified styrene-butadiene rubber is a copolymer of styrene, butadiene and the first type of monomer (ie, acrylic acid and/or acrylic acid ester monomer).
  • the aqueous emulsion of the second binder is the aqueous emulsion of modified styrene-butadiene rubber.
  • the aqueous emulsion of modified styrene-butadiene rubber can be prepared in the following manner: under an inert gas atmosphere, the total mass parts are the third mass parts butadiene monomer, styrene monomer, the first Add the quasi-monomer into the fourth mass part of water, stir until the mixture is uniform, then add 0.1 to 5.0 mass parts of emulsifier, stir at room temperature, add 0.05-0.5 mass part of oxidant, 0.01-0.1 mass part of reducing The agent is fully mixed, and the temperature is lowered to 5°C-8°C for emulsion polymerization.
  • the pressure of emulsion polymerization can be 0.1-0.3MPa, and the time of emulsion polymerization can be 7-12h. Then, after adding 0.1-0.45 parts by mass of a terminator, the polymerization is terminated to obtain an aqueous emulsion of modified styrene-butadiene rubber.
  • Emulsifiers, oxidants, reducing agents, and terminators can be mature industrial additives used in the industrial production of styrene-butadiene rubber.
  • the emulsifier can be a cationic emulsifier, an anionic emulsifier, a nonionic emulsifier such as fatty acid soap or disproportionated abietic acid soap.
  • the oxidizing agent can be an organic peroxide, such as cumene hydroperoxide and the like.
  • the reducing agent can be ferrous salt series, such as ferrous sulfate.
  • the terminator may be sodium dimethyldithiocarbamate or the like.
  • the part values of the third part by mass and the fourth part by mass can be adjusted according to the requirement of solid content, the third part by mass can be, for example, 50 parts, and the fourth part by mass can be, for example, 70 parts.
  • the parts by mass of each monomer are added according to the pre-designed monomer dosage.
  • the embodiment of the present application also provides a negative electrode slurry, the negative electrode slurry includes the above-mentioned negative electrode binder in the embodiment of the present application.
  • the negative electrode slurry also includes negative electrode active materials and conductive agents.
  • the negative electrode slurry can be prepared in the following manner: add the negative electrode active material to the aqueous solution of the first binder, stir, then add the conductive agent, continue stirring, and then add the second binder. water emulsion to obtain a uniformly dispersed negative electrode slurry.
  • the embodiment of the present application also provides a negative electrode sheet 200.
  • the negative electrode sheet 200 includes a current collector 201 and a negative electrode active layer 202 disposed on the current collector 201.
  • the negative electrode active layer 202 adopts the negative electrode adhesive provided above in the embodiment of the present application. Binder or the negative electrode slurry provided above.
  • the negative electrode active layer 202 using the above-mentioned negative electrode binder is fully dried in the negative electrode sheet preparation process, so the solvent water in the negative electrode binder has been removed, so the negative electrode active layer 202 includes the negative electrode binder.
  • the solute of the agent in the negative electrode active layer 202, the solute of the negative electrode binder accounts for 1%-12% by mass.
  • the solute of the negative electrode binder refers to the first binder and the second binder.
  • the solute of the negative electrode binder includes the first binder; in some embodiments, the solute of the negative electrode binder includes the first binder and the second binder.
  • the mass proportion of the solute in the negative electrode binder can be, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. , 11%, 12%. In some embodiments, the mass proportion of the solute in the negative electrode binder may be 1%-7%.
  • the negative electrode active layer further includes a negative electrode active material
  • the negative electrode active material includes a silicon-based material or includes a silicon-based material and a carbon-based material.
  • the negative electrode active material may also include carbon-based materials.
  • the silicon-based material can be a variety of silicon-containing materials that contain silicon and can be used as negative electrode active materials, including but not limited to micro-silicon, nano-silicon, silicon-carbon composites, silicon alloys, silicon oxide compounds SiO One or more of x (0 ⁇ x ⁇ 2).
  • the silicon-based material can be either crystalline silicon or amorphous silicon.
  • the silicon-carbon composite can be a composite of silicon and carbon in various structural forms, such as a silicon material doped with carbon on the surface, a silicon material coated with carbon on the surface (such as graphene-wrapped amorphous silicon particles), and the like.
  • the silicon oxide compound may be a silicon oxide compound whose surface has not been modified by doping or coating, or a silicon oxide compound whose surface has been modified by doping or coating.
  • the carbon-based material may include graphite, and the graphite may be selected from one or more of natural graphite, artificial graphite, and surface-modified natural graphite.
  • the negative electrode active material includes a mixture of silicon-based materials and graphite.
  • the mass proportion of the silicon-based material in the negative electrode active layer, may be 0.5%-20%. Specifically, in the negative electrode active layer, the mass proportion of the silicon-based material may be 0.5%, 1%, 5%, 10%, 15%, or 20%.
  • the mass proportion of the carbon-based material in the negative electrode active layer, may be 80%-95%. Specifically, in the negative electrode active layer, the mass proportion of the carbon-based material may be 80%, 85%, 90%, or 95%.
  • the negative electrode active layer further includes a conductive agent, and the mass proportion of the conductive agent in the negative electrode active layer may be 0.5%-6%. Specifically, in the negative electrode active layer, the mass proportion of the conductive agent may be 0.5%, 1%, 3%, 4%, 5%, or 6%.
  • the conductive agent may be, for example but not limited to, one or more of conductive graphite, carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene.
  • the negative electrode sheet in the embodiment of the present application can be prepared by mixing the above-mentioned negative electrode binder, negative electrode active material, and conductive agent to form a slurry, and then coating the slurry on the current collector, drying, and rolling.
  • the embodiment of the present application also provides a lithium ion battery 100, including a positive electrode 101, a negative electrode 102, a separator 104 and an electrolyte 103 arranged between the positive electrode 101 and the negative electrode 102, and the negative electrode 102 includes the negative electrode sheet 200 provided above in the embodiment of the present application .
  • the positive electrode 101 includes a current collector and a positive electrode active layer disposed on the current collector, and the positive electrode active layer includes a positive electrode active material, a conductive agent and a positive electrode binder.
  • the positive electrode active material can be a variety of lithium-containing compounds that can intercalate/extract lithium ions, such as lithium-containing layered metal oxides, lithium-containing spinel structure metal oxides, lithium metal phosphate, lithium metal fluorine One or more of sulfuric acid salts and lithium metal vanadates.
  • the lithium-containing layered metal oxide can be one or more of lithium cobalt oxide (LiCoO 2 ), nickel-cobalt-manganese ternary material (NCM), nickel-cobalt-aluminum ternary material (NCA); lithium-containing
  • the metal oxide with spinel structure can be lithium manganate (LiMn 2 O 4 ), etc.
  • the lithium metal phosphate can be lithium iron phosphate (LiFePO 4 ), etc.
  • the lithium metal fluorinated sulfate can be lithium cobalt sulfate (LiCoFSO 4 ), etc.
  • the lithium metal vanadate may be lithium nickel vanadate (LiNiVO 4 ) and the like.
  • the conductive agent in the positive electrode active layer can be one or more of conductive graphite, carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene.
  • the mass proportion of the conductive agent may be 1%-8%. In some embodiments, the mass proportion of the conductive agent may be 2%-5%.
  • the binder in the positive active layer may be polyvinylidene fluoride or the like.
  • the embodiment of the present application further provides an electronic device 300 , and the electronic device 300 includes the battery 100 provided above in the embodiment of the present application.
  • the electronic device 300 may include various consumer electronic products, such as mobile phones, tablet computers, mobile power supplies, laptops, notebook computers and other wearable or mobile electronic devices, televisions, DVD players, video recorders, camcorders, Radios, tape recorders, stereos, record players, CD players, home office equipment, home electronic health care equipment, and electronic products such as automobiles and energy storage equipment.
  • the electronic device 300 includes a casing 301 , electronic components (not shown in the figure) accommodated in the casing 301 and a battery 100 , and the battery 100 provides power for the electronic device 300 .
  • the embodiment of the present application also provides an energy storage system 400
  • the energy storage system 400 includes a battery pack 401 and a battery management system 402 electrically connected to the battery pack 401
  • the battery pack 401 includes the battery provided above in the embodiment of the present application 100.
  • the negative electrode binder in this embodiment is composed of an aqueous solution of the first binder and an aqueous emulsion of modified styrene-butadiene rubber, and the mass ratio of the first binder to the modified styrene-butadiene rubber is 30%:70%.
  • Preparation of the aqueous solution of the first binder under the protection of nitrogen, methacrylic acid, amyl methacrylate, acrylonitrile, and vinylpyrrolidone are added to water according to the mass percentage of 30%: 20%: 20%: 30% , the solid content of the control system is 6.5wt%.
  • Stir at room temperature for 30 minutes until the reactants form a uniform solution add the initiator ammonium persulfate and continue stirring for 1 hour, raise the temperature to 80°C and stir for 9-10 hours until the polymer reaction is complete, and obtain a transparent and uniform first binder aqueous solution.
  • the solid content of the aqueous solution of the first binder is about 6.5wt%, the viscosity is about 5500cP, and the pH is 6.5-7.
  • Preparation of water emulsion of modified styrene-butadiene rubber under the protection of nitrogen, add butadiene, styrene, and methacrylic acid to water according to the mass percentage of 35%: 45%: 20%, stir until the mixture is uniform, and then add emulsification After stirring evenly at room temperature, add an oxidizing agent and a reducing agent to mix thoroughly, and cool down to 5°C-8°C to carry out emulsion polymerization. After 7-12 hours of emulsion polymerization, add a terminator to terminate the polymerization to obtain modified styrene-butadiene rubber. water emulsion.
  • the solid content of the water emulsion of the modified styrene-butadiene rubber is 40wt%
  • the particle diameter of the modified styrene-butadiene rubber emulsion is 50nm-120nm
  • the viscosity is 120cP.
  • the negative electrode binder in this embodiment is composed of an aqueous solution of the first binder and an aqueous emulsion of modified styrene-butadiene rubber, and the mass ratio of the first binder to the modified styrene-butadiene rubber is 30%:70%.
  • Preparation of the aqueous solution of the first binder under the protection of nitrogen, acrylic acid, methyl acrylate, acrylamide, and vinylpyrrolidone were added to water according to the mass percentage of 30%: 25%: 20%: 25%, and the solidity of the system was controlled. The content is 6.5 wt%.
  • Stir at room temperature for 30 minutes until the reactants form a uniform solution add the initiator ammonium persulfate and continue stirring for 1 hour, raise the temperature to 80°C and stir for 9-10 hours until the polymer reaction is complete, and obtain a transparent and uniform first binder aqueous solution.
  • the solid content of the aqueous solution of the first binder is about 6.5wt%, the viscosity is about 5000cP, and the pH is 6.5-7.
  • the negative electrode binder in this embodiment is composed of an aqueous solution of the first binder and an aqueous emulsion of modified styrene-butadiene rubber, and the mass percentages of the first binder and the modified styrene-butadiene rubber are 30% and 70% respectively.
  • Preparation of the aqueous solution of the first binder under the protection of nitrogen, methacrylic acid, amyl methacrylate, acrylamide, and vinylpyrrolidone were added to water according to the mass percentage of 30%: 20%: 20%: 30%,
  • the solid content of the control system is 6.5wt%.
  • Stir at room temperature for 30 minutes until the reactants form a uniform solution add the initiator ammonium persulfate and continue stirring for 1 hour, raise the temperature to 80°C and stir for 9-10 hours until the polymer reaction is complete, and obtain a transparent and uniform first binder aqueous solution.
  • the solid content of the aqueous solution of the first binder is about 6.5wt%, the viscosity is about 5500cP, and the pH is 6.5-7.
  • Preparation of water emulsion of modified styrene-butadiene rubber under nitrogen protection, add butadiene, styrene, and acrylic acid to water according to the mass percentage of 35%: 45%: 20%, stir until uniformly mixed, and then add emulsifier, After stirring evenly at room temperature, add an oxidizing agent and a reducing agent to mix thoroughly, and cool down to 5°C-8°C for emulsion polymerization. After 7-12 hours of emulsion polymerization, add a terminator to terminate the polymerization, and obtain an aqueous emulsion of modified styrene-butadiene rubber. .
  • the solid content of the water emulsion of the modified styrene-butadiene rubber is 40wt%
  • the particle diameter of the modified styrene-butadiene rubber emulsion is 50nm-120nm
  • the viscosity is 120cP.
  • the negative electrode binder in this embodiment is composed of an aqueous solution of the first binder and an aqueous emulsion of modified styrene-butadiene rubber, and the mass percentages of the first binder and the modified styrene-butadiene rubber are 30% and 70% respectively.
  • Preparation of the aqueous solution of the first binder under the protection of nitrogen, acrylic acid, methyl acrylate, acrylamide, and vinylpyrrolidone were added to water according to the mass percentage of 35%: 30%: 15%: 20%, and the solidity of the system was controlled. The content is 5.5 wt%.
  • Stir at room temperature for 30 minutes until the reactants form a uniform solution add the initiator ammonium persulfate and continue stirring for 1 hour, raise the temperature to 80°C and stir for 9-10 hours until the polymer reaction is complete, and obtain a transparent and uniform first binder aqueous solution.
  • the aqueous solution of the first binder has a solid content of about 5.5 wt%, a viscosity of about 5000 cP, and a pH of 6.5-7.
  • the negative electrode binder in this embodiment is composed of an aqueous solution of the first binder and an aqueous emulsion of modified styrene-butadiene rubber, and the mass percentages of the first binder and the modified styrene-butadiene rubber are 30% and 70% respectively.
  • Preparation of the aqueous solution of the first binder under the protection of nitrogen, acrylic acid, methyl acrylate, allyl glycidyl ether, and vinyl pyrrolidone were added to water according to the mass percentage of 30%: 20%: 20%: 30%, The solid content of the control system was 6.0 wt%.
  • Stir at room temperature for 30 minutes until the reactants form a uniform solution add the initiator ammonium persulfate and continue stirring for 1 hour, raise the temperature to 80°C and stir for 9-10 hours until the polymer reaction is complete, and obtain a transparent and uniform first binder aqueous solution.
  • the aqueous solution of the first binder has a solid content of about 6.0 wt%, a viscosity of about 5000 cP, and a pH of 6.5-7.
  • Example 1 The difference between the negative electrode binder in this example and Example 1 is only that the mass percentages of the first binder and the modified styrene-butadiene rubber are 40% and 60%, respectively.
  • Example 1 The difference between the negative electrode binder in this example and Example 1 is only that the mass percentages of the first binder and the modified styrene-butadiene rubber are 50% and 50% respectively.
  • the negative electrode binder in this example is composed of the aqueous solution of the first binder prepared in Example 1 and the styrene-butadiene rubber emulsion, and the mass percentages of the first binder and the styrene-butadiene rubber are 30% and 70% respectively.
  • the styrene-butadiene rubber emulsion is unmodified styrene-butadiene rubber.
  • the negative electrode binder in this example is composed of the aqueous solution of the first binder prepared in Example 1 mixed with the styrene-acrylic rubber emulsion, and the mass percentages of the first binder and the styrene-acrylic rubber are 30% and 70% respectively.
  • the negative electrode binder of Comparative Example 1 is composed of commercially available CMC solution and the modified styrene-butadiene rubber aqueous emulsion of Example 1, and the solute mass percentages of CMC and modified styrene-butadiene rubber are 30% and 70% respectively.
  • the negative electrode binder of Comparative Example 2 is composed of a commercially available CMC solution and a commercially available modified PAA binder, and the solute mass percentages of CMC and modified PAA are 30% and 70% respectively.
  • the negative electrode binder of Comparative Example 3 is composed of commercially available CMC solution and commercially available styrene-butadiene rubber emulsion, and the solute mass percentages of CMC and styrene-butadiene rubber are 30% and 70% respectively.
  • the negative electrode binders of Examples 1-9 and Comparative Examples 1-3 were respectively used to prepare silicon-based negative electrode sheets.
  • the only difference in the preparation and composition of the silicon-based negative electrode sheets of each example and comparative example lies in the difference in the negative electrode binder.
  • the mass ratio of artificial graphite: silicon oxide coated with carbon on the surface: conductive carbon black: carbon nanotube: negative electrode binder is 89wt%: 5wt%: 2wt%: 0.4wt%: 3.6wt%.
  • the preparation process of the negative electrode sheet can be: after stirring and mixing the artificial graphite and the silicon oxide active material coated with carbon on the surface, add the aqueous solution of the first binder prepared in Example 1, and continue to stir , then add conductive carbon black and carbon nanotube slurry, continue to stir, add the aqueous emulsion of modified styrene-butadiene rubber prepared in Example 1, to obtain a uniformly dispersed negative electrode slurry, after defoaming and sieving, the negative electrode slurry Sequentially coated on both sides of the copper foil, dried and rolled to obtain a silicon-based negative electrode sheet, the surface capacity of the electrode sheet is about 3mAh/cm 2 , and the compacted density is about 1.6g/cm 3 .
  • the present application has carried out following performance test to the negative electrode sheet and lithium ion battery prepared by embodiment 1-9 and comparative example 1-3:
  • peeling force test of the negative electrode sheet cut the negative electrode sheet into a strip-shaped test sample of 2cm ⁇ 10cm, bond the electrode sheet to the side to be tested with 3M double-sided tape, and compact it with a pressure roller to make it consistent with the The pole pieces are completely attached; then paste the other side of the double-sided adhesive on the surface of the stainless steel plate, bend one end of the sample in the opposite direction, and the bending angle is 180 degrees, and use a universal material testing machine to clamp the sample and the stainless steel plate respectively for stretching.
  • the force value required for stretching is recorded in real time, and the average value of all forces is the peeling force of the negative electrode sheet.
  • Negative sheet film resistance test cut the negative electrode sheet into a strip-shaped test sample of 2cm ⁇ 10cm, after measuring the thickness, put it in the test box of the film resistance meter, input the parameters, and obtain the film resistance value of the electrode sheet, namely Get the membrane conductivity.
  • Negative plate expansion rate test charge and discharge the soft-packed lithium-ion battery according to the test requirements (half-charged state, full-charged state, 3C charge rate for 20 laps, then fully-charged state, 1.5C charge rate for charge-discharge fully charged state after 100 cycles, and fully charged state after 200 cycles of 1.5C stage charge), disassemble the battery cell in the glove box, take out the negative electrode piece, clean the surface of the electrode piece with dimethyl carbonate (DMC) solvent and dry it, Use a spiral micrometer to measure the thickness of different regions of the pole piece, take the average value, and divide the difference between the average value and the initial thickness of the pole piece by the initial thickness of the pole piece (excluding the thickness of the current collector), which is the expansion of the pole piece Rate.
  • DMC dimethyl carbonate
  • Cycle retention rate test The lithium-ion pouch battery prepared in the example was cycled for 100 cycles at a charge-discharge rate of 0.5C/0.7C, and the capacity retention rate relative to the capacity of the first cycle was tested.
  • Example 1 24.5 7.39 1.62
  • Example 2 23.8 7.41 1.62
  • Example 3 25.3 7.36 1.62
  • Example 4 24.9 7.42 1.61
  • Example 5 25.2 7.40 1.61
  • Example 6 21.5 7.56 1.62
  • Example 8 23.0 7.32 1.61
  • Example 9 23.5 7.25 1.62 Comparative example 1 14.2 7.63 1.62 Comparative example 2 16.3 7.15 1.62 Comparative example 3 18.5 7.22 1.61
  • Table 2 shows the test results of the thickness expansion rate of the negative electrode sheets corresponding to different negative electrode binders under different charge and discharge operations in Examples 1-9 and Comparative Examples 1-3:
  • the second binder of embodiment 1-5 has adopted the aqueous emulsion of modified styrene-butadiene rubber, has better bonding effect relative to embodiment 8 and embodiment 9, and this is because the water of modified styrene-butadiene rubber
  • the emulsion particle structure in the emulsion increases the bonding area (point bonding) between the binder and the active material, which can effectively enhance the bonding strength between the graphite; and the modified styrene-butadiene rubber has the
  • the similar molecular structure can produce synergy to form a similar network structure, improve the mechanical properties of the composite system, and further enhance the overall bonding effect of the pole piece.
  • CMC and the modified styrene-butadiene rubber Styrene-butadiene rubber does not have a good compatibility effect, and at the same time, the coating effect of CMC on silicon-based materials is not as good as that of the first binder in this application, so it cannot suppress the volume change caused by silicon in the process of lithium deintercalation and the excessive growth of SEI .
  • FIG. 5 is a graph showing the cycle performance results of the batteries of Example 1 and Example 2, and Comparative Example 1, Comparative Example 2, and Comparative Example 3.
  • the full battery using the negative electrode binder of the present application has better cycle performance, which is mainly because the combined binder of the present application can have a relatively good effect on graphite, silicon-based materials, etc. Strong bonding effect; at the same time, it can reduce side reactions, effectively resist the stress caused by the large volume expansion of silicon materials in the process of lithium intercalation, and maintain the integrity of the silicon-based negative electrode sheet structure, thereby improving battery cycle performance.

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Abstract

本申请实施例提供一种负极粘结剂，该负极粘结剂包括第一粘结剂的水溶液，第一粘结剂为第一类单体、第二类单体和第三类单体的共聚物，第一类单体包括丙烯酸类单体和丙烯酸酯类单体中的至少一种，第二类单体包括丙烯腈类单体、丙烯酰胺类单体和缩水甘油醚类单体中的至少一种，第三类单体包括乙烯基吡咯烷酮。该负极粘结剂能够较好地适配硅基负极片的制备，粘接效果好，能一定程度解决硅基材料体积膨胀带来的电池性能恶化问题。本申请实施例还提供了该负极粘结剂的制备方法，以及包含该负极粘结剂的负极片和电池。

Description

负极粘结剂及其制备方法、负极片和电池
本申请要求于2022年1月26日提交中国专利局、申请号为202210091771.0、申请名称为“负极粘结剂及其制备方法、负极片和电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请实施例涉及电池技术领域，特别是涉及一种负极粘结剂及其制备方法、负极片和电池。
背景技术
近年来，锂离子电池在新能源汽车、储能等领域受到广泛关注，因此对提高锂离子电池能量密度的需求也不断增大。现阶段使用的石墨等碳基材料用于锂离子电池负极已经发挥至其理论容量，难以再有提高，因此，开发具有更高理论容量的合金、金属氧化物等活性材料被认为是下一代锂离子电池负极的发展趋势。其中，硅材料因其较高的理论比容量、低的脱/嵌锂电位以及丰富的储量等优点引起了研究人员的广泛关注。研究人员通过向石墨中加入硅等高容量的活性材料来提高负极的克容量，但添加高容量的硅基活性材料时，会造成如下后果：(1)脱嵌锂时硅体积变化较大，膨胀应力导致硅基材料结构粉碎，从而破坏电极活性物质与集流体之间的导电连接，造成极片劣化；(2)Si体积变化导致其表面固态电解质界面层(Solid electrolyte interphase，SEI)不断破裂，暴露的新鲜Si表面持续与电解液接触，生成新的SEI，持续消耗电解液并使Si表面副反应层逐渐加厚；(3)Si类材料较低的首次库伦效率会消耗较多的来自正极的活性锂，降低电池的容量及能量密度；这些原因造成电芯容量衰减过快，同时使电芯厚度膨胀严重，严重阻碍了其产业化应用。因此，寻找一种针对硅材料膨胀所带来的电池性能恶化等问题的解决方案是非常紧迫的。其中，设计一种能够适配硅基负极的负极粘结剂是一种有效解决方案。
发明内容
鉴于此，本申请实施例提供一种负极粘结剂，该负极粘结剂能够较好地适配硅基负极片的制备，粘接效果好，能一定程度解决硅基负极材料的体积膨胀带来的电池性能恶化问题。
具体地，本申请实施例第一方面提供一种负极粘结剂，所述负极粘结剂包括第一粘结剂的水溶液，所述第一粘结剂为第一类单体、第二类单体和第三类单体的共聚物，所述第一类单体包括丙烯酸类单体和丙烯酸酯类单体中的一种或多种，所述第二类单体包括丙烯腈或丙烯酰胺类单体和缩水甘油醚类单体中的一种或多种，所述第三类单体包括乙烯基吡咯烷酮。
本申请中，第一粘结剂为改性聚丙烯酸(PAA)多元共聚物，由上述三类单体共聚而成，第一粘结剂能够对硅基材料实现较好的包覆，减少SEI膜的重复再生和副反应的发生，也能够对硅基材料具有强粘接作用，同时第一粘结剂还具有增稠效果、促进活性材料的均匀分散，防止沉降，能够较好地适用于含硅基材料的负极片的制备。具体地，本申请第一粘结剂的三类单体设计，分别起到不同效果。其中，第一类单体(即丙烯酸类单体、丙烯酸酯类单体)的效果包括：第一类单体对硅基材料具有较好的粘接及包覆效果，且羧基可通过锂化处理， 提高离子迁移速率；另外通过亲水羧基与疏水酯基的调控(即丙烯酸类单体和丙烯酸酯类单体的用量调控)可实现对不同表面亲疏水性能的硅基材料的粘接。第二类单体(即丙烯腈类单体、丙烯酰胺类单体、缩水甘油醚类单体)的效果包括：第二类单体与电解液具有较好的浸润性，且具有较好的电化学稳定性。第三类单体(即乙烯基吡咯烷酮单体)的效果包括：第三类单体是固体胶主要成分，同时具有亲水与增稠作用等特点，可起到CMC(羧甲基纤维素钠)效果，提高硅基材料与负极中其他碳基活性材料的分散稳定性，同时对金属、玻璃、塑料等表面具有优异的粘结效果，从而可提高负极材料在集流体表面的粘接。本申请实施例提供的负极粘结剂可以用于锂离子电池硅基负极的制备。硅基负极是指包含硅基活性材料的负极。
本申请实施方式中，所述第一类单体的结构通式为
Figure PCTCN2023071487-appb-000001
其中，R 1为氢原子或甲基，R 2为氢原子、取代或非取代烷基、或取代或非取代环烷基。具有上述结构的丙烯酸类单体和丙烯酸酯类单体的结构简单易得，且有利于使第一粘结剂获得较好粘接效果。
本申请实施方式中，所述R 2为氢原子、碳原子数为1-8的取代或非取代烷基、或碳原子数为3-8的取代或非取代环烷基。R 2选择具有较少碳原子数的取代或非取代烷基、取代或非取代环烷基能够使第一类单体易于获得。
本申请实施方式中，所述第二类单体的结构通式为
Figure PCTCN2023071487-appb-000002
其中，R 3为氢原子或甲基，R 4为-CN、-C(＝O)-N(R 5R 6)或
Figure PCTCN2023071487-appb-000003
R 5、R 6分别选自氢原子、取代或非取代烷基、或取代或非取代环烷基，R 7为取代或非取代亚烷基。具有上述结构的丙烯腈类单体、丙烯酰胺类单体、缩水甘油醚类单体，不仅单体材料易得，且能够更好的控制粘结剂与电解液的浸润性，提高电池体系的电化学稳定性。
本申请实施方式中，所述R 5、R 6分别选自氢原子、碳原子数为1-8的取代或非取代烷基、或碳原子数为3-8的取代或非取代环烷基；所述R 7为碳原子数1-8的取代或非取代亚烷基。较少碳数的单体更易于获得。
本申请一些实施方式中，所述R 7为亚甲基(-CH 2-)或亚苯甲基(-C 6H 4-CH 2-)。R 3为氢原子、R 7为亚甲基，则缩水甘油醚类单体为烯丙基缩水甘油醚。R 3为氢原子、R 7为亚苯甲基，则缩水甘油醚类单体为4-乙烯基苄基缩水甘油醚。
本申请实施方式中，所述第一粘结剂的分子结构中，衍生自所述第一类单体的结构单元的质量占比大于或等于40％。即第一类单体的用量占第一粘结剂单体总用量的质量占比大于或等于40％。将第一粘结剂中衍生自第一类单体的结构单元的质量占比控制在40％及以上，可以更好地保证第一粘结剂对硅基材料的包覆及粘接效果。
本申请实施方式中，所述第一粘结剂的分子结构中，衍生自所述第一类单体的结构单元的质量占比为40％-80％。将第一粘结剂中衍生自第一类单体的结构单元控制在上述质量占比可以更好地保证第一粘结剂对硅基材料的包覆及粘接效果，以及保证第一粘结剂具有更低脆 性。
本申请实施方式中，第一粘结剂的分子结构中，衍生自第二类单体的结构单元的质量占比可以是10％-40％。将第一粘结剂中衍生自第二类单体的结构单元控制在上述质量占比可以更好地保证第一粘结剂与电解液的亲和效果，以及更好地降低第一粘结剂的溶胀性能，从而提高第一粘结剂本身的力学性能。
本申请实施方式中，第一粘结剂的分子结构中，衍生自第三类单体的结构单元的质量占比可以是10％-40％。将第一粘结剂中衍生自第三类单体的结构单元控制在上述质量占比可以更好地提高第一粘结剂的增稠效果，提高第一粘结剂对集流体的粘接效果；同时可以有效控制吡咯烷酮与电解液的浸润效果不佳，导致极片界面电阻增加，电芯倍率性能下降的问题。
本申请实施方式中，所述第一粘结剂的结构通式如式(1)所示：
Figure PCTCN2023071487-appb-000004
式(1)中，R 1、R 3分别选自氢原子或甲基，R 2为氢原子、锂原子、取代或非取代烷基、或取代或非取代环烷基，R 4为-CN、-C(＝O)-N(R 5R 6)或
Figure PCTCN2023071487-appb-000005
R 5、R 6分别选自氢原子、取代或非取代烷基、或取代或非取代环烷基，R 7为取代或非取代亚烷基；x、y、z为结构单元的质量占比，x＞0，y＞0，z＞0，x+y+z＝1。
本申请实施方式中，所述第一粘结剂的重均分子量为50-100万。适合的分子量控制可以使第一粘结剂本身具有更高的力学性能。
本申请一些实施方式中，所述负极粘结剂还包括第二粘结剂的水乳液。第二粘结剂的水乳液和第一粘结剂的水溶液在制备成负极浆料之前可以是独立储存、存放，两者不混合。第二粘结剂可以弥补第一粘结剂的不足之处，从而能够使负极粘结剂在两类粘结剂的协同作用下，获得更好的综合性能，从而可以有效改善活性材料与导电剂、集流体的接触与粘接问题，使硅基负极片粘接成为一个牢固的整体，同时使活性材料的倍率性能、膨胀抑制、循环性能得到充分发挥。第二粘结剂还可以改善负极片的韧性。
本申请实施方式中，所述第二粘结剂包括丁苯橡胶、改性丁苯橡胶、苯丙橡胶和醋酸乙烯-乙烯共聚物中的一种或多种。这几类第二粘结剂可以较好地与第一粘结剂配合提高负极片的稳定性。
本申请实施方式中，所述第一粘结剂的质量相对所述第一粘结剂和所述第二粘结剂的总质量的占比大于或等于20％。将负极粘结剂中，第一粘结剂的含量控制在一定占比以上，可以更好地利用第一粘结剂的性能优势，提高负极片的综合性能。
本申请实施方式中，所述第一粘结剂的质量相对所述第一粘结剂和所述第二粘结剂的总质量的占比为20％-70％。进一步将负极粘结剂中，第一粘结剂的含量控制在一定占比范围，可以更好地利用第一粘结剂和第二粘结剂的性能优势，提高负极片的综合性能。
本申请实施方式中，所述改性丁苯橡胶为苯乙烯、丁二烯与所述第一类单体的共聚物。
本申请实施方式中，所述改性丁苯橡胶的结构通式如式(2)所示：
Figure PCTCN2023071487-appb-000006
式(2)中，R 1为氢原子或甲基，R 2为氢原子、取代或非取代烷基、或取代或非取代环烷基，a、b、c为结构单元的质量占比，a＞0，b＞0，c＞0，a+b+c＝1。具有式(2)所示结构的改性丁苯橡胶能够更好地与本申请第一粘结剂进行配合，两者相互协同提高负极粘结剂的综合性能，进而提高负极片的性能。
本申请实施方式中，所述改性丁苯橡胶的重均分子量为10-40万。控制改性丁苯橡胶在适合分子量范围有利于保持负极粘结剂体系的粘度等性能在更适合的水平。
本申请实施例第二方面提供一种负极粘结剂的制备方法，包括：
将第一类单体、第二类单体和第三类单体加入水中，在引发剂的作用下发生共聚反应，得到第一粘结剂的水溶液；所述第一粘结剂为第一类单体与第二类单体、第三类单体的共聚物，所述第一类单体包括丙烯酸类单体和丙烯酸酯类单体中的一种或多种，所述第二类单体包括丙烯腈类单体、丙烯酰胺类单体和缩水甘油醚类单体中的一种或多种，所述第三类单体包括乙烯基吡咯烷酮。
本申请实施方式中，上述共聚反应在保护气氛下进行，保护气氛为惰性气体气氛，例如可以是氮气、氦气等。本申请实施方式中，上述共聚反应的温度可以是60℃-90℃。共聚反应过程中可进行机械搅拌，共聚反应的时间可以是9-12小时。本申请实施例制备方法工艺简单，共聚反应可以在较低的温度下完成，易实现第一粘结剂的规模化生产制备。
本申请一些实施方式中，制备方法还包括提供第二粘结剂的水乳液，所述第二粘结剂包括丁苯橡胶、改性丁苯橡胶、苯丙橡胶和醋酸乙烯-乙烯共聚物中的一种或多种。第二粘结剂的水乳液和第一粘结剂的水溶液在制备成负极浆料之前可以是独立储存、存放，两者不混合。第一粘结剂体系和第二粘结剂体系独立储存，更有利于根据实际需求调整两者的用量配比，使用更灵活，同时也更有利于维持各粘结剂的体系稳定性。
本申请实施方式中，所述第一粘结剂的质量相对所述第一粘结剂和所述第二粘结剂的总质量的占比大于或等于20％。将负极粘结剂中，第一粘结剂的含量控制在一定占比以上，可以更好地利用第一粘结剂的性能优势，提高负极片的综合性能。
本申请实施例第三方面提供一种负极浆料，所述负极浆料包括本申请实施例第一方面所述的负极粘结剂。该负极浆料中的负极粘结剂具有如前文所述的技术效果，此处不再赘述。
本申请实施例第四方面提供一种负极片，所述负极片包括集流体和设置在所述集流体上的负极活性层，所述负极活性层采用本申请实施例第一方面所述的负极粘结剂。该负极活性层中的负极粘结剂具有如前文所述的技术效果，此处不再赘述。
本申请实施方式中，采用上述负极粘结剂的负极活性层，由于在制备过程经过充分干燥，因此负极粘结剂中的溶剂水已经被除去，因此所述负极活性层包括所述负极粘结剂的溶质，所述负极活性层中，所述负极粘结剂的溶质的质量占比为1％-12％。负极粘结剂的溶质即指第一粘结剂、第二粘结剂。一些实施例中，负极粘结剂的溶质包括第一粘结剂；一些实施例中，负极粘结剂的溶质包括第一粘结剂和第二粘结剂。
本申请一些实施方式中，所述负极活性层包括负极活性材料，所述负极活性材料包括硅基材料。硅基材料具有高容量，可以提高负极片容量。
本申请一些实施方式中，所述负极活性层包括负极活性材料，所述负极活性材料包括硅基材料和碳基材料。负极活性层同时包含硅基材料和碳基材料，可以兼具两者的优势，使负极片获得更好的综合性能。
本申请实施方式中，所述负极活性层中，所述硅基材料的质量占比为0.5％-20％。将硅基材料控制在一定的质量占比，有利于提高负极片的结构稳定性。
本申请实施方式中，所述负极活性层中，所述碳基材料的质量占比为80％-95％。将碳基材料控制在一定的质量占比，有利于提高负极片的结构稳定性。
本申请实施例第五方面还提供一种电池，包括正极、负极和设置在所述正极与所述负极之间的隔膜和电解液，所述负极包括本申请实施例第四方面所述的负极片或所述负极包括本申请实施例第一方面所述的负极粘结剂。本申请实施例电池例如可以是锂离子电池、钠离子电池等。本申请实施例电池由于采用上述负极粘结剂，能够提高电池的循环稳定性，提升电池寿命。
本申请实施例还提供一种电子设备，所述电子设备包括本申请实施例第五方面所述的电池。采用本申请实施例上述电池的电子设备更稳定，能够提升产品竞争力。
本申请实施例还提供一种储能系统，其特性在于，所述储能系统包括本申请实施例第五方面所述的电池。采用本申请实施例上述电池的储能系统更稳定，能够提升产品竞争力。
附图说明
图1为本申请实施例提供的锂离子电池100的结构示意图；
图2为本申请实施例提供的负极片200的结构示意图；
图3本申请实施例提供的电子设备300的结构示意图；
图4本申请实施例提供的储能系统400的结构示意图；
图5为本申请实施例1-2和对比例1-3制备的锂离子电池的循环性能图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例进行说明。
参见图1，图1是本申请实施例提供的锂离子电池100的结构示意图。锂离子电池100是一种常用的充电电池，主要由正极101、负极102、电解液103、隔膜104以及相应的回路组成。其中，锂离子电池100通过锂离子(Li +)在正负极间的脱嵌来实现能量的存储和释放，电解液103是锂离子在正负极之间传输的载体，离子导通但电子绝缘的隔膜104保证锂离子(Li +)迁移的同时将正负极隔开防止短路。正负极活性材料是锂离子电池发挥储能功用的主体部分，决定了电池的能量密度、循环性能及安全性能。在确定了正极活性材料体系后，负极活性材料的容量对于整个电芯的能量密度的提升显得至关重要。然而，目前商用石墨负极材料实际使用克容量360mAh/g，已接近其理论值(372mAh/g)，难以对锂离子电池的能量密度进一步提高。因此，需要开发具有更高理论容量的负极活性材料。其中，硅基材料因其较高的理论比容量、低的脱/嵌锂电位以及储量丰富等优点引起了研究人员的广泛关注。研究人员通过向石墨中加入硅等高容量的活性材料来提高负极的克容量，但添加高容量的硅活性材料时，会造成如下后果：(1)脱嵌锂时硅体积变化较大，膨胀应力导致硅基材料结构粉碎，从而破坏电极活性物质与集流体之间的导电连接，造成极片劣化；(2)硅体积变化导致其表面固态电解质界面层(SEI)不断破裂，暴露的新鲜硅表面持续与电解液接触，生成新的SEI，持续消耗电解液并使硅表面副反应层逐渐加厚；(3)硅类材料较低的首次库伦效率会消耗较 多的来自正极的活性锂，降低电池的容量；这些原因造成电芯容量衰减过快，同时使电芯厚度膨胀增加，严重阻碍了其产业化应用。针对硅材料膨胀所带来的电池性能恶化等问题，本申请提供一种适配硅基负极的负极粘结剂，本申请锂离子电池100的负极102采用该负极粘结剂。
本申请实施例提供的负极粘结剂包括第一粘结剂的水溶液，第一粘结剂为第一类单体、第二类单体和第三类单体的共聚物，第一类单体包括丙烯酸类单体和丙烯酸酯类单体中的至少一种，第二类单体包括丙烯腈类单体、丙烯酰胺类单体和缩水甘油醚类单体中的至少一种，第三类单体包括乙烯基吡咯烷酮。
本申请中，第一粘结剂为改性聚丙烯酸(PAA)多元共聚物，由上述三类单体共聚而成，第一粘结剂能够对硅基材料实现较好的包覆，减少SEI膜的重复再生和副反应的发生，也能够对硅基材料具有强粘接作用，同时第一粘结剂还具有增稠效果、促进活性材料的均匀分散，防止沉降，能够较好地适用于含硅基材料的负极片的制备。具体地，本申请第一粘结剂的三类单体设计，分别起到不同效果。其中，第一类单体(即丙烯酸类单体、丙烯酸酯类单体)的效果包括：第一类单体对硅基材料具有较好的粘接及包覆效果，且羧基可通过锂化处理，提高离子迁移速率；另外通过亲水羧基与疏水酯基的调控(即丙烯酸类单体和丙烯酸酯类单体的用量调控)可实现对不同表面亲疏水性能的硅基材料的粘接。第二类单体(即丙烯腈类单体、丙烯酰胺类单体、缩水甘油醚类单体)的效果包括：第二类单体与电解液具有较好的浸润性，且具有较好的电化学稳定性。第三类单体(即乙烯基吡咯烷酮单体)的效果包括：第三类单体是固体胶主要成分，同时具有亲水与增稠作用等特点，可起到CMC(羧甲基纤维素钠)效果，提高硅基材料与负极中其他碳基活性材料的分散稳定性，同时对金属、玻璃、塑料等表面具有优异的粘结效果，从而可提高负极材料在集流体表面的粘接。本申请实施例提供的负极粘结剂可以用于锂离子电池硅基负极的制备。硅基负极是指包含硅基活性材料的负极。
本申请实施方式中，第一类单体的结构通式为通式(A)：
Figure PCTCN2023071487-appb-000007
其中，R 1为氢原子或甲基，R 2为氢原子、取代或非取代烷基、或取代或非取代环烷基。具有上述结构的丙烯酸类单体和丙烯酸酯类单体的结构简单易得，且有利于使第一粘结剂获得较好粘接效果。
当R 1为氢原子或甲基，R 2为氢原子时，通式(A)表示丙烯酸类单体。其中，当R 1为氢原子时，通式(1)表示丙烯酸单体；当R 1为甲基时，通式(A)表示甲基丙烯酸单体。
当R 1为氢原子或甲基，R 2为取代或非取代烷基、或取代或非取代环烷基时，通式(A)表示丙烯酸酯类单体。本申请实施方式中，R 2可以是碳原子数为1-8的取代或非取代烷基、或碳原子数为3-8的取代或非取代环烷基。R 2选择具有较少碳原子数的取代或非取代烷基、取代或非取代环烷基能够使第一类单体易于获得。具体地，R 2可以是碳原子数为1、2、3、4、5、6、7或8的取代或非取代烷基；R 2可以是碳原子数为3、4、5、6、7或8的取代或非取代环烷基。一些实施例中，丙烯酸酯类单体例如可以是丙烯酸甲酯、丙烯酸乙酯、丙烯酸丙酯、丙烯酸丁酯、丙烯酸戊酯、丙烯酸己酯、甲基丙烯酸乙酯、甲基丙烯酸丙酯、甲基丙烯酸丁酯、甲基丙烯酸戊酯、甲基丙烯酸己酯中的一种或多种。
本申请实施方式中，第一类单体包括丙烯酸类单体和丙烯酸酯类单体中的至少一种。具 体地，一些实施例中，第一类单体仅包括丙烯酸类单体，丙烯酸类单体可以是一种，也可以是多种；例如第一类单体仅包括丙烯酸或甲基丙烯酸，或者同时包括丙烯酸和甲基丙烯酸。另一些实施例中，第一类单体仅包括丙烯酸酯类单体，丙烯酸酯类单体可以是一种，也可以是多种；例如第一类单体仅包括丙烯酸甲酯或甲基丙烯酸乙酯，或者同时包括丙烯酸甲酯或甲基丙烯酸乙酯。另一些实施例中，第一类单体同时包括丙烯酸类单体和丙烯酸酯类单体，丙烯酸类单体可以是一种，也可以是多种；丙烯酸酯类单体可以是一种，也可以是多种；例如第一类单体同时包括甲基丙烯酸和甲基丙烯酸乙酯。第一类单体同时包括丙烯酸类单体和丙烯酸酯类单体两类单体时，可以根据需要调整两类单体的用量。本申请实施例中，通过调控丙烯酸类单体和丙烯酸酯类单体的用量，可以对第一粘结剂中亲水羧基与疏水酯基的含量进行调控，从而更好地实现对不同表面亲疏水性能的硅基材料的粘接，更好地适用不同硅基负极的制备。
本申请实施方式中，第二类单体的结构通式为通式(B)：
Figure PCTCN2023071487-appb-000008
其中，R 3为氢原子或甲基，R 4为-CN、-C(＝O)-N(R 5R 6)或
Figure PCTCN2023071487-appb-000009
R 5、R 6独立地为氢原子、取代或非取代烷基、或取代或非取代环烷基，R 7为取代或非取代亚烷基。具有上述结构的丙烯腈类单体、丙烯酰胺类单体、缩水甘油醚类单体，不仅单体材料易得，且能够更好的控制粘结剂与电解液的浸润性，提高电池体系的电化学稳定性。
当R 3为氢原子或甲基，R 4为-CN时，通式(B)表示丙烯腈类单体。其中，当R 3为氢原子时，通式(B)表示丙烯腈单体；当R 3为甲基时，通式(B)表示甲基丙烯腈单体。
当R 3为氢原子或甲基，R 4为-C(＝O)-N(R 5R 6)时，通式(B)表示丙烯酰胺类单体。
本申请一些实施方式中，R 5、R 6可以是都为氢原子，即通式(B)表示非取代丙烯酰胺单体，即丙烯酰胺，当R 3为氢原子时，通式(B)表示丙烯酰胺单体，当R 3为甲基时，通式(B)表示甲基丙烯酰胺单体。
本申请另一些实施方式中，R 5、R 6也可以是其中一个为氢原子，另一个为取代或非取代烷基、或取代或非取代环烷基；还可以是均为取代或非取代烷基、或取代或非取代环烷基，即通式(B)表示N-取代丙烯酰胺单体。一些实施例中，R 5可以是碳原子数为1-8的取代或非取代烷基、或碳原子数为3-8的取代或非取代环烷基；具体地，R 5可以是碳原子数为1、2、3、4、5、6、7或8的取代或非取代烷基；R 5可以是碳原子数为3、4、5、6、7或8的取代或非取代环烷基。一些实施例中，R 6可以是碳原子数为3-8的取代或非取代烷基、或碳原子数为3-8的取代或非取代环烷基。具体地，R 6可以是碳原子数为1、2、3、4、5、6、7或8的取代或非取代烷基；R 6可以是碳原子数为3、4、5、6、7或8的取代或非取代环烷基。本申请一些实施例中，丙烯酰胺类单体例如可以是N-甲基丙烯酰胺、N，N-二甲基丙烯酰胺、N-羟乙基丙烯酰胺、N-羟甲基丙烯酰胺中的一种或多种。
当R 3为氢原子或甲基，R 4为
Figure PCTCN2023071487-appb-000010
时，通式(B)表示缩水甘油醚类单体。R 7为取代或非取代亚烷基。一些实施例中，R 7可以是碳原子数为1-8的取代或非取代亚烷基。具体地，R 7可以是碳原子数为1、2、3、4、5、6、7或8的取代或非取代亚烷基。本申请一 些实施方式中，R 7为亚甲基(-CH 2-)或亚苯甲基(-C 6H 4-CH 2-)。其中，R 3为氢原子、R 7为亚甲基，则缩水甘油醚类单体为烯丙基缩水甘油醚。R 3为氢原子、R 7为亚苯甲基，则缩水甘油醚类单体为4-乙烯基苄基缩水甘油醚。本申请实施方式中，缩水甘油醚类单体可以是包括烯丙基缩水甘油醚、4-乙烯基苄基缩水甘油醚中的一种或多种。
本申请实施方式中，第二类单体包括丙烯腈类单体、丙烯酰胺类单体和缩水甘油醚类单体中的至少一种。一些实施例中，第二类单体仅包括丙烯腈类单体，丙烯腈类单体可以是一种，也可以是多种；例如第二类单体仅包括丙烯腈或甲基丙烯腈，或者同时包括丙烯腈和甲基丙烯腈。另一些实施例中，第二类单体仅包括丙烯酰胺类单体，丙烯酰胺类单体可以是一种，也可以是多种；例如第二类单体仅包括丙烯酰胺或N-羟乙基丙烯酰胺，或者同时包括丙烯酰胺或N-羟乙基丙烯酰胺。另一些实施例中，第二类单体同时包括丙烯腈类单体和丙烯酰胺类单体，丙烯腈类单体可以是一种，也可以是多种；丙烯酰胺类单体可以是一种，也可以是多种；例如第二类单体同时包括丙烯腈和丙烯酰胺。一些实施例中，第二类单体仅包括缩水甘油醚类单体。一些实施例中，第二类单体包括丙烯腈类单体和缩水甘油醚类单体。一些实施例中，第二类单体包括丙烯酰胺类单体和缩水甘油醚类单体。一些实施例中，第二类单体包括丙烯腈类单体、丙烯酰胺类单体和缩水甘油醚类单体。本申请第二类单体具有较强极性，可以增加电解液对活性材料的浸润性，减少因离子迁移导致的阻力过大的问题。
本申请实施方式中，第一粘结剂的三类单体可以分别起到不同作用，实际应用时，可以针对不同硅基负极，通过对三类单体种类与用量进行调控，以达到更优性能。
本申请中，第一粘结剂为第一类单体与第二类单体、第三类单体的共聚物，在第一粘结剂的分子结构中，包括衍生自第一类单体的结构单体、衍生自第二类单体的结构单元和衍生自第三类单体的结构单元。
本申请实施方式中，第一粘结剂的分子结构中，衍生自第一类单体的结构单元的质量占比可以是大于或等于40％。即第一类单体的用量占第一粘结剂单体总用量的质量占比大于或等于40％。本申请一些实施方式中，第一粘结剂的分子结构中，衍生自第一类单体的结构单元的质量占比为40％-80％。具体地，第一粘结剂的分子结构中，衍生自第一类单体的结构单元的质量占比可以是40％、45％、50％、55％、60％、65％、70％、80％等。将第一粘结剂中衍生自第一类单体的结构单元控制在上述质量占比可以更好地保证第一粘结剂对硅基材料的包覆及粘接效果，以及保证第一粘结剂具有更低脆性。
本申请实施方式中，第一粘结剂的分子结构中，衍生自第二类单体的结构单元的质量占比可以是10％-40％。即第二类单体的用量占第一粘结剂单体总用量的质量占比为10％-40％。本申请一些实施方式中，第一粘结剂的分子结构中，衍生自第二类单体的结构单元的质量占比为15％-25％。具体地，第一粘结剂的分子结构中，衍生自第一类单体的结构单元的质量占比可以是10％、15％、20％、25％、30％、35％、40％等。将第一粘结剂中衍生自第二类单体的结构单元控制在上述质量占比可以更好地保证第一粘结剂与电解液的亲和效果，以及更好地降低第一粘结剂的溶胀性能，从而提高第一粘结剂本身的力学性能。
本申请实施方式中，第一粘结剂的分子结构中，衍生自第三类单体的结构单元的质量占比可以是10％-40％。即第三类单体的用量占第一粘结剂单体总用量的质量占比为10％-40％。本申请一些实施方式中，第一粘结剂的分子结构中，衍生自第三类单体的结构单元的质量占比为20％-30％。具体地，第一粘结剂的分子结构中，衍生自第三类单体的结构单元的质量占比可以是10％、15％、20％、25％、30％、35％、40％等。将第一粘结剂中衍生自第三类单体 的结构单元控制在上述质量占比可以更好地提高第一粘结剂的增稠效果，提高第一粘结剂对集流体的粘接效果；同时可以有效控制吡咯烷酮与电解液的浸润效果不佳，导致极片界面电阻增加，电芯倍率性能下降的问题。
本申请一些实施方式中，第一粘结剂的结构通式可以是如式(1)所示：
Figure PCTCN2023071487-appb-000011
式(1)中，R 1、R 3独立地为氢原子或甲基，R 2为氢原子、锂原子、取代或非取代烷基、或取代或非取代环烷基，R 4为-CN、-C(＝O)-N(R 5R 6)或
Figure PCTCN2023071487-appb-000012
R 5、R 6独立地为氢原子、取代或非取代烷基、或取代或非取代环烷基，R 7为取代或非取代亚烷基；x、y、z为结构单元的质量占比，x＞0，y＞0，z＞0，x+y+z＝1。其中，R 1、R 2对应的结构单元衍生自第一类单体，R 3、R 4对应的结构单元衍生自第二类单体。其中，当R 2为锂原子时，第一粘结剂可以是通过三类单体共聚后经锂化得到，锂化可以采用碳酸锂或氢氧化锂等实现。
本申请一些实施方式中，式(1)中，y≥0.4。一些实施例中，0.4≤y≤0.8。具体地，y的取值可以是0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.8等。本申请一些实施方式中，0.1≤z≤0.4。一些实施例中，0.15≤z≤0.25。具体地，z的取值可以是0.1、0.15、0.2、0.25、0.3、0.35、0.4等。本申请一些实施方式中，0.1≤x≤0.4。一些实施例中，0.2≤x≤0.3。具体地，x的取值可以是0.1、0.15、0.2、0.25、0.3、0.35、0.4等。
本申请实施方式中，第一粘结剂的重均分子量为50-100万。适合的分子量控制可以使第一粘结剂本身具有更高的力学性能。一些实施例中，第一粘结剂的重均分子量例如可以是50万、60万、70万、80万、90万、100万等。
本申请实施方式中，负极粘结剂中包含上述第一粘结剂的水溶液，第一粘结剂的水溶液的固含量为1％-10％。具体地，第一粘结剂的水溶液的固含量为1％、2％、3％、4％、5％、6％、7％、8％、9％、10％。一些实施例中，第一粘结剂的水溶液的固含量为3％-8％。适合固含量的控制可以使负极粘结剂获得适合粘稠度，有利于负极材料在溶液中的分散，同时极大缓解了浆料在储存过程中可能出现的沉降问题。
本申请一些实施方式中，负极粘结剂还包括第二粘结剂的水乳液，即该实施方式中负极粘结剂为包括第一粘结剂的水溶液和第二粘结剂的水乳液两种粘结剂的组合型粘结剂，在负极片制备时可将两种粘结剂进行组合使用。第二粘结剂的水乳液和第一粘结剂的水溶液在制备成负极浆料之前是独立储存、存放，两者不混合。本申请实施方式中，第二粘结剂可以是包括丁苯橡胶、改性丁苯橡胶、苯丙橡胶、醋酸乙烯-乙烯共聚物中的一种或多种。第二粘结剂可以与第一粘结剂构成组合型粘结剂体系，第二粘结剂可以弥补第一粘结剂的不足之处，从而能够使负极粘结剂在两类粘结剂的协同作用下，获得更好的综合性能，从而可以有效改善活性材料与导电剂、集流体的接触与粘接问题，使硅基负极片粘接成为一个牢固的整体，同时使活性材料的倍率性能、膨胀抑制、循环性能得到充分发挥。第二粘结剂还可以改善负 极片的韧性。
本申请一些实施方式中，负极粘结剂中，第一粘结剂的质量相对第一粘结剂和第二粘结剂的总质量的占比大于或等于20％。将负极粘结剂中，第一粘结剂的含量控制在一定占比以上，可以更好地利用第一粘结剂的性能优势，提高负极片的综合性能。本申请一些实施方式中，负极粘结剂中，即复合体系负极粘结剂中，第一粘结剂的质量相对第一粘结剂和第二粘结剂的总质量的占比为20％-70％。具体地，负极粘结剂中，第一粘结剂的质量相对第一粘结剂和第二粘结剂的总质量的占比可以是20％、25％、30％、35％、40％、45％、50％、55％、60％、65％、70％。需要说明的是，第一粘结剂的质量和第二粘结剂的质量都是指的第一粘结剂水溶液和第二粘结剂的水乳液中单纯溶质的质量，不包括溶剂等其它组分。
本申请实施方式中，负极粘结剂中包含上述第二粘结剂的水乳液，第二粘结剂的水乳液的固含量可以是20％-60％。适合的固含量控制有利于获得更好的混合分散效果及粘接效果。
本申请一些实施方式中，第二粘结剂包括改性丁苯橡胶，改性丁苯橡胶可以是为苯乙烯、丁二烯与前述的第一类单体(即丙烯酸和/或丙烯酸酯类单体)的共聚物。本申请改性丁苯橡胶中丁苯橡胶的结构可以保证对石墨等碳基材料的更有效粘接，而在改性丁苯橡胶在分子结构中引入的衍生自第一类单体的聚丙烯酸和/或聚丙烯酸酯链段，可以增加其与第一粘结剂的相容性，使复合体系具有更优异的力学性能；还可以降低丁苯橡胶在电解液中的溶胀，提高力学强度，更好地抑制硅颗粒体积膨胀导致的活性物质脱落；还可以改变改性丁苯橡胶聚合物的玻璃化转变温度Tg，使粘结剂在电池适用范围内不发生玻璃化转变，改善电池低温性能。
本申请一些实施方式中，改性丁苯橡胶的结构通式如式(2)所示：
Figure PCTCN2023071487-appb-000013
式(2)中，R 1为氢原子或甲基，R 2为氢原子、取代或非取代烷基、或取代或非取代环烷基，a、b、c为结构单元的质量占比，a＞0，b＞0，c＞0，a+b+c＝1。其中，R 1、R 2对应的结构单元衍生自第一类单体。
本申请一些实施方式中，式(2)中，0.1≤b≤0.5。一些实施例中，0.15≤b≤0.4。适合量衍生自第一类单体的链段的引入可以同时获得丁苯橡胶和改性链段的双重优势。具体地，b的取值可以是0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.5等。b的取值越大，表明改性丁苯橡胶分子结构中衍生自第一类单体的结构单元的质量占比更大。
本申请一些实施方式中，式(2)中，0.2≤a≤0.4。具体地，a的取值可以是0.2、0.25、0.3、0.35、0.4等。a的取值越大，表明改性丁苯橡胶分子结构中衍生自丁二烯的结构单元的质量占比更大。其中，调节a的取值大小可以有效调控改性丁苯橡胶的玻璃化转变温度Tg。上述取值范围可以将B类粘结剂的玻璃化转变温度Tg调节在不低于30℃。
本申请一些实施方式中，式(2)中，0.3≤c≤0.5。具体地，c的取值可以是0.3、0.35、0.4、0.45、0.5等。c的取值越大，表明改性丁苯橡胶分子结构中衍生自苯乙烯的结构单元的质量占比更大。
本申请实施方式中，改性丁苯橡胶的重均分子量为10-40万。具体例如可以是改性丁苯橡胶的重均分子量为10万、20万、30万或40万。
本申请实施方式中，第二粘结剂均匀分散在水中形成第二粘结剂的水乳液。水乳液中的 改性丁苯橡胶为乳液粒子结构，该结构可以增加改性丁苯橡胶与负极活性材料间粘接面积(点状粘接)，增强负极活性材料(如石墨等碳基材料)间的粘接强度，减少锂离子传输阻力，增加极片弹性，提高加工特性。本申请中，改性丁苯橡胶聚合物粒子的粒径可以是50nm-500nm，一些实施例中，粒径可以是100nm-300nm。
本申请一些实施方式中，负极粘结剂为包括第一粘结剂和改性丁苯橡胶的组合型粘结剂，组合型粘结剂中各组分在硅基负极中各司其职，可分别对硅基材料及石墨等碳基材料产生改善效果，两类聚合物发生协同作用，第一粘结剂为链状聚合物，改性丁苯橡胶为粒状聚合物，链状聚合物与粒状聚合物可形成桥连点，构筑三维网络结构，有效提高复合体系的力学性能，最终改善硅基负极的综合性能。
本申请实施例由第一粘结剂和第二粘结剂构成的组合型粘结剂，可以在相对更低的总粘结剂使用量下，使负极片中各组分获得良好粘接效果，从而保证对硅基材料的膨胀抑制作用，保证负极片循环性能，同时保证负极材料的倍率性能。
本申请实施例还提供一种负极粘结剂的制备方法，包括：
将第一类单体、第二类单体和第三类单体加入水中，在引发剂的作用下发生共聚反应，得到第一粘结剂的水溶液；第一粘结剂为第一类单体与第二类单体、第三类单体的共聚物，第一类单体包括丙烯酸类单体和丙烯酸酯类单体中的一种或多种，第二类单体包括丙烯腈类单体、丙烯酰胺类单体和缩水甘油醚类单体中的一种或多种，第三类单体包括乙烯基吡咯烷酮。
本申请实施方式中，上述共聚反应在保护气氛下进行，保护气氛为惰性气体气氛，例如可以是氮气、氦气等。本申请实施方式中，上述共聚反应的温度可以是60℃-90℃，具体例如可以是60℃、70℃、80℃、90℃。共聚反应过程中可进行机械搅拌，共聚反应的时间可以是9-12小时。本申请实施方式中，第一类单体、第二类单体和第三类单体加入水得到的混合溶液中，水的质量与单体总质量可以根据最终第一粘结剂的水溶液所需要的固含量进行调整。本申请中，引发剂可以是能够引发上述单体发生共聚的各种引发剂，包括但不限于过硫酸铵。
本申请一具体实施方式中，第一粘结剂的水溶液可以是通过下述方式制备：惰性气体氛围下，在反应容器中加入第一质量份的水，总质量份为第二质量份的第一类单体、第二类单体和第三类单体，然后搅拌直至形成均一混合溶液；随后加入0.05-0.5质量份引发剂，并将温度升高至70℃-90℃，机械搅拌下反应9-12小时；反应结束后，降至室温，制得透明均一的第一粘结剂的水溶液。第一质量份和第二质量份的份数值可以根据固含量需求调整，第一质量份例如可以是950份，第二质量份例如可以是50份。各单体的质量份根据预设计的单体用量加入。
本申请一些实施方式中，制备方法还包括提供第二粘结剂的水乳液，第二粘结剂可以是根据需要选择各种可用的负极粘结剂，以弥补第一粘结剂的不足，第二粘结剂可以但不限于包括第二粘结剂包括丁苯橡胶、改性丁苯橡胶、苯丙橡胶和醋酸乙烯-乙烯共聚物中的一种或多种。第二粘结剂的水乳液和第一粘结剂的水溶液在制备成负极浆料之前可以是独立储存、存放，两者不混合。第二粘结剂与第一粘结剂在制备成负极浆料时，两者为物理共混，两者不发生化学反应。
本申请实施方式中，第一粘结剂的水溶液与第二粘结剂的水乳液组合使用时，以第一粘结剂的水溶液中的溶质质量与第二粘结剂的水乳液中的溶质质量进行配合。第一粘结剂的水溶液中的溶质质量即为第一粘结剂的质量，第二粘结剂的水乳液中的溶质质量即为第二粘结剂的质量。第一粘结剂的质量相对第一粘结剂和第二粘结剂的总质量的占比可以是大于或等 于20％。
本申请一些实施方式中，改性丁苯橡胶为苯乙烯、丁二烯与第一类单体(即丙烯酸和/或丙烯酸酯类单体)的共聚物。该实施方式中，第二粘结剂的水乳液即为改性丁苯橡胶的水乳液。本申请实施方式中，改性丁苯橡胶的水乳液可以是通过下述方式制备：惰性气体氛围下，将总质量份为第三质量份的丁二烯单体、苯乙烯单体、第一类单体加入到第四质量份的水中，搅拌至混合均匀，然后加入0.1～5.0质量份乳化剂，在室温下搅拌均匀后，加入0.05-0.5质量份的氧化剂、0.01-0.1质量份的还原剂充分混合，并降温至5℃-8℃，进行乳液聚合。其中乳液聚合的压力可以是0.1-0.3MPa，乳液聚合的时间可以是7-12h。随后加入0.1-0.45质量份终止剂后，使聚合终止，得到改性丁苯橡胶的水乳液。乳化剂、氧化剂、还原剂、终止剂可以是丁苯橡胶产业化生产中使用的成熟的工业助剂。乳化剂可以是阳离子型乳化剂、阴离子型乳化剂、非离子型乳化剂，如脂肪酸皂或歧化松香酸皂。氧化剂可以是有机过氧化物，如异丙苯过氧化氢等。还原剂可以是亚铁盐系，如硫酸亚铁等。终止剂可以是二甲基二硫代氨基甲酸钠等。第三质量份和第四质量份的份数值可以根据固含量需求调整，第三质量份例如可以是50份，第四质量份例如可以是70份。各单体的质量份根据预设计的单体用量加入。
本申请实施例还提供一种负极浆料，负极浆料包括本申请实施例上述的负极粘结剂。负极浆料还包括负极活性材料、导电剂。
本申请一些实施方式中，负极浆料可以是采用如下方式制备：将负极活性材料加入到第一粘结剂的水溶液中，搅拌，随后加入导电剂，继续搅拌，再加入第二粘结剂的水乳液，得到均匀分散的负极浆料。
参见图2，本申请实施例还提供一种负极片200，负极片200包括集流体201和设置在集流体201上的负极活性层202，负极活性层202采用本申请实施例上述提供的负极粘结剂或上述提供的负极浆料。
本申请实施方式中，采用上述负极粘结剂的负极活性层202，由于在负极片制备过程经过充分干燥，因此负极粘结剂中的溶剂水已经被除去，因此负极活性层202包括负极粘结剂的溶质。本申请一些实施例中，负极活性层202中，负极粘结剂的溶质的质量占比为1％-12％。负极粘结剂的溶质即指第一粘结剂、第二粘结剂。一些实施例中，负极粘结剂的溶质包括第一粘结剂；一些实施例中，负极粘结剂的溶质包括第一粘结剂和第二粘结剂。本申请一些实施方式中，负极粘结剂的溶质的质量占比具体例如可以是1％、2％、3％、4％、5％、6％、7％、8％、9％、10％、11％、12％。一些实施例中，负极粘结剂的溶质的质量占比可以是1％-7％。
本申请实施方式中，负极活性层还包括负极活性材料，负极活性材料包括硅基材料或者包括硅基材料和碳基材料。一些实施例中，负极活性材料也可以是包括碳基材料。本申请实施方式中，硅基材料可以是各种包含硅元素的可作为负极活性材料的含硅材料，包括但不限于是微米硅、纳米硅、硅碳复合物、硅合金、硅氧化合物SiO x(0<x≤2)中的一种或多种。硅基材料可以是晶体硅，也可以是非晶硅。硅碳复合物可以是各种结构形式的硅与碳的复合体，例如为表面碳掺杂的硅材料、表面碳包覆的硅材料(如石墨烯包裹非晶硅颗粒)等。硅氧化合物可以是表面未进行掺杂或包覆等改性的硅氧化合物，也可以是表面经掺杂或包覆等改性的硅氧化合物。本申请实施方式中，碳基材料可以是包括石墨，石墨可选自天然石墨、人造石墨、表面改性的天然石墨中的一种或多种。
本申请一些实施例中，负极活性材料包括硅基材料与石墨的混合物。本申请一些实施方式中，负极活性层中，硅基材料的质量占比可以是0.5％-20％。具体地，负极活性层中，硅基材料的质量占比可以是0.5％、1％、5％、10％、15％、20％。本申请一些实施方式中，负极活 性层中，碳基材料的质量占比可以是80％-95％。具体地，负极活性层中，碳基材料的质量占比可以是80％、85％、90％、95％。
本申请实施方式中，负极活性层中还包括导电剂，负极活性层中，导电剂的质量占比可以是0.5％-6％。具体地，负极活性层中，导电剂的质量占比可以是0.5％、1％、3％、4％、5％、6％。导电剂例如可以是但不限于导电石墨、炭黑、乙炔黑、科琴黑、碳纳米管、石墨烯中的一种或多种。
本申请实施例负极片可以是将上述负极粘结剂与负极活性材料、导电剂混合制备成浆料，再将浆料涂布在集流体上经烘干、辊压制成。
本申请实施例还提供一种锂离子电池100，包括正极101、负极102和设置在正极101与负极102之间的隔膜104和电解液103，负极102包括本申请实施例上述提供的负极片200。
本申请中，正极101包括集流体和设置在集流体上的正极活性层，正极活性层包括正极活性材料、导电剂和正极粘结剂。正极活性材料可以是各种具备可嵌入/脱出锂离子的含锂化合物，例如可以是含锂的层状金属氧化物、含锂的尖晶石结构金属氧化物、锂金属磷酸盐、锂金属氟化硫酸盐和锂金属钒酸盐中的一种或几种。其中，含锂的层状金属氧化物可以是钴酸锂(LiCoO 2)、镍钴锰三元材料(NCM)、镍钴铝三元材料(NCA)中的一种或多种；含锂的尖晶石结构金属氧化物可以是锰酸锂(LiMn 2O 4)等；锂金属磷酸盐可以是磷酸铁锂(LiFePO 4)等；锂金属氟化硫酸盐可以是氟化硫酸钴锂(LiCoFSO 4)等；锂金属钒酸盐可以是钒酸镍锂(LiNiVO 4)等。正极活性层中的导电剂可以是导电石墨、炭黑、乙炔黑、科琴黑、碳纳米管、石墨烯中的一种或多种。正极活性层中，导电剂的质量占比可以是1％-8％。一些实施例中，导电剂的质量占比可以是2％-5％。正极活性层中的粘结剂可以是聚偏氟乙烯等。
参见图3，本申请实施例还提供一种电子设备300，电子设备300包括本申请实施例上述提供的电池100。电子设备300可以是包括各种消费类电子产品，如手机、平板电脑、移动电源、便携机、笔记本电脑以及其它可穿戴或可移动的电子设备、电视机、影碟机、录像机、摄录机、收音机、收录机、组合音响、电唱机、激光唱机、家庭办公设备、家用电子保健设备，还可以是汽车、储能设备等电子产品。一些实施例中，电子设备300包括壳体301和容纳于壳体301内的电子元器件(图中未示出)和电池100，电池100为电子设备300供电。
参见图4，本申请实施例还提供一种储能系统400，储能系统400包括电池组401和与电池组401电连接的电池管理系统402，电池组401包括本申请实施例上述提供的电池100。
下面分多个实施例对本申请实施例进行进一步的说明。
实施例1
本实施例的负极粘结剂由第一粘结剂的水溶液与改性丁苯橡胶的水乳液组成，第一粘结剂与改性丁苯橡胶的质量比为30％：70％。
第一粘结剂的水溶液的制备：在氮气保护下，将甲基丙烯酸、甲基丙烯酸戊酯、丙烯腈、和乙烯基吡咯烷酮按质量百分比30％：20％：20％：30％加入到水中，控制体系的固含量为6.5wt％。室温搅拌30min至反应物形成均一溶液后，加入引发剂过硫酸铵继续搅拌1h，升温至80℃搅拌9-10h至聚合物反应完全，制得透明均一的第一粘结剂的水溶液。第一粘结剂的水溶液的固含量约为6.5wt％，粘度约为5500cP，pH为6.5-7。
改性丁苯橡胶的水乳液的制备：在氮气保护下，将丁二烯、苯乙烯、甲基丙烯酸按质量百分比35％：45％：20％加入到水中，搅拌至混合均匀，然后加入乳化剂，在室温下搅拌均 匀后，加入氧化剂、还原剂充分混合，并降温至5℃-8℃，进行乳液聚合，乳液聚合7-12h后加入终止剂使聚合终止，得到改性丁苯橡胶的水乳液。改性丁苯橡胶的水乳液的固含量为40wt％，改性丁苯橡胶乳液粒子直径为50nm-120nm，粘度为120cP。
实施例2
本实施例的负极粘结剂由第一粘结剂的水溶液与改性丁苯橡胶的水乳液组成，第一粘结剂与改性丁苯橡胶的质量比为30％：70％。
第一粘结剂的水溶液的制备：在氮气保护下，将丙烯酸、丙烯酸甲酯、丙烯酰胺、乙烯基吡咯烷酮按质量百分比30％：25％：20％：25％加入到水中，控制体系的固含量为6.5wt％。室温搅拌30min至反应物形成均一溶液后，加入引发剂过硫酸铵继续搅拌1h，升温至80℃搅拌9-10h至聚合物反应完全，制得透明均一的第一粘结剂的水溶液。第一粘结剂的水溶液的固含量约为6.5wt％，粘度约为5000cP，pH为6.5-7。
改性丁苯橡胶的水乳液的制备：同实施例1。
实施例3
本实施例的负极粘结剂由第一粘结剂的水溶液与改性丁苯橡胶的水乳液组成，第一粘结剂与改性丁苯橡胶的质量百分比分别为30％和70％。
第一粘结剂的水溶液的制备：在氮气保护下，将甲基丙烯酸、甲基丙烯酸戊酯、丙烯酰胺、乙烯基吡咯烷酮按质量百分比30％：20％：20％：30％加入到水中，控制体系的固含量为6.5wt％。室温搅拌30min至反应物形成均一溶液后，加入引发剂过硫酸铵继续搅拌1h，升温至80℃搅拌9-10h至聚合物反应完全，制得透明均一的第一粘结剂的水溶液。第一粘结剂的水溶液的固含量约为6.5wt％，粘度约为5500cP，pH为6.5-7。
改性丁苯橡胶的水乳液的制备：在氮气保护下，将丁二烯、苯乙烯、丙烯酸按质量百分比35％：45％：20％加入到水中，搅拌至混合均匀，然后加入乳化剂，在室温下搅拌均匀后，加入氧化剂、还原剂充分混合，并降温至5℃-8℃，进行乳液聚合，乳液聚合7-12h后加入终止剂使聚合终止，得到改性丁苯橡胶的水乳液。改性丁苯橡胶的水乳液的固含量为40wt％，改性丁苯橡胶乳液粒子直径为50nm-120nm，粘度为120cP。
实施例4
本实施例的负极粘结剂由第一粘结剂的水溶液与改性丁苯橡胶的水乳液组成，第一粘结剂与改性丁苯橡胶的质量百分比分别为30％和70％。
第一粘结剂的水溶液的制备：在氮气保护下，将丙烯酸、丙烯酸甲酯、丙烯酰胺、乙烯基吡咯烷酮按质量百分比35％：30％：15％：20％加入到水中，控制体系的固含量为5.5wt％。室温搅拌30min至反应物形成均一溶液后，加入引发剂过硫酸铵继续搅拌1h，升温至80℃搅拌9-10h至聚合物反应完全，制得透明均一的第一粘结剂的水溶液。第一粘结剂的水溶液的固含量约为5.5wt％，粘度约为5000cP，pH为6.5-7。
改性丁苯橡胶的水乳液的制备：同实施例1。
实施例5
本实施例的负极粘结剂由第一粘结剂的水溶液与改性丁苯橡胶的水乳液组成，第一粘结剂与改性丁苯橡胶的质量百分比分别为30％和70％。
第一粘结剂的水溶液的制备：在氮气保护下，将丙烯酸、丙烯酸甲酯、烯丙基缩水甘油醚、乙烯基吡咯烷酮按质量百分比30％：20％：20％：30％加入到水中，控制体系的固含量为6.0wt％。室温搅拌30min至反应物形成均一溶液后，加入引发剂过硫酸铵继续搅拌1h，升温至80℃搅拌9-10h至聚合物反应完全，制得透明均一的第一粘结剂的水溶液。第一粘结剂的水溶液的固含量约为6.0wt％，粘度约为5000cP，pH为6.5-7。
改性丁苯橡胶的水乳液的制备：同实施例1。
实施例6
本实施例负极粘结剂与实施例1的区别仅在于：第一粘结剂与改性丁苯橡胶的质量百分比分别为40％和60％。
实施例7
本实施例负极粘结剂与实施例1的区别仅在于：第一粘结剂与改性丁苯橡胶的质量百分比分别为50％和50％。
实施例8
本实施例负极粘结剂由实施例1制备的第一粘结剂的水溶液与丁苯橡胶乳液混合组成，第一粘结剂与丁苯橡胶的质质量百分比分别为30％和70％。丁苯橡胶乳液为未改性的丁苯橡胶。
实施例9
本实施例负极粘结剂由实施例1制备的第一粘结剂的水溶液与苯丙橡胶乳液混合组成，第一粘结剂与苯丙橡胶的质量百分比分别为30％和70％。
对比例1
对比例1的负极粘结剂是由市售CMC溶液与实施例1的改性丁苯橡胶水乳液复配组成，CMC与改性丁苯橡胶的溶质质量百分比分别为30％和70％。
对比例2
对比例2的负极粘结剂是由市售CMC溶液与市售改性PAA粘结剂复配组成，CMC与改性PAA的溶质质量百分比分别为30％和70％。
对比例3
对比例3的负极粘结剂是由市售CMC溶液与市售丁苯橡胶乳液复配组成，CMC与丁苯橡胶的溶质质量百分比分别为30％和70％。
负极片制备：
分别采用实施例1-9和对比例1-3的负极粘结剂制备硅基负极片，各实施例与对比例硅基负极片的制备和组成区别仅在于负极粘结剂不同。其中，人造石墨：表面包覆碳的硅氧化物：导电炭黑：碳纳米管：负极粘结剂的质量比为89wt％：5wt％：2wt％：0.4wt％：3.6wt％。
以实施例1为例，负极片的制备过程可以是：将人造石墨与表面碳包覆的硅氧化物活性 材料搅拌混合均匀后，加入实施例1制备的第一粘结剂的水溶液，继续搅拌，随后加入导电炭黑与碳纳米管浆料，继续搅拌，加入实施例1制备的改性丁苯橡胶的水乳液，得到均匀分散的负极浆料，脱泡过筛后，将该负极浆料依次涂布在铜箔的两面，烘干辊压后得到硅基负极片，极片面容量约为3mAh/cm 2，压实密度约为1.6g/cm 3。
锂离子电池的制备：
分别将实施例1-9和对比例1-3制备的硅基负极片模切后与容量匹配的钴酸锂正极片(LiCoO 2：导电炭黑：PVDF粘结剂＝95wt％：2wt％：3wt％；负极容量与正极容量的比值为1:1)进行叠片，制作软包锂离子电池(容量550mAh)。同时将硅基负极片与隔膜、锂金属片组装成纽扣式半电池。
本申请对实施例1-9与对比例1-3制备的负极片和锂离子电池进行了如下性能测试：
(1)负极片剥离力测试：将负极片裁切成2cm×10cm的长条状测试试样，将极片用3M双面胶粘接需要测试的一面，并用压辊压实，使之与极片完全贴合；然后将双面胶的另一面粘贴于不锈钢板表面，将试样一端反向弯曲，弯曲角度180度，用万能材料实验机分别夹住试样与不锈钢板进行拉伸，实时记录拉伸时所需的力值，所有力的平均值即为负极片的剥离力。
(2)负极片膜电阻测试：将负极片裁切成2cm×10cm的长条状测试试样，测试厚度后，置于膜电阻仪测试箱内，输入参数，得到极片膜电阻值，即得到膜电导率。
(3)负极片膨胀率测试：将软包锂离子电池按照测试要求进行充放电(半电态、满电态、3C充电倍率进行充放20圈后满电态、1.5C充电倍率进行充放100圈后满电态、1.5C阶充200圈后满电态)，在手套箱中拆解电芯，取出负极片，用碳酸二甲酯(DMC)溶剂清洗极片表面并烘干后，用螺旋测微仪测量极片的不同区域的厚度，取平均值，此平均值与极片初始厚度的差值再除以极片初始厚度(除去集流体厚度)，即为该极片的膨胀率。
(4)首次库伦效率测试：将扣式半电池用蓝电测试仪CT2001A测试得到半电池首次充、放电容量，计算首次库伦效率(首次库伦效率＝充电容量/放电容量×100％)。
(5)循环保持率测试：将实施例制备的锂离子软包电池在0.5C/0.7C的充放电速率下循环100圈，测试相对第一圈容量的容量保持率。
实施例1-9与对比例1-3中不同负极粘结剂对应负极片的剥离力、膜电导率及孔隙率测试结果见表1：
表1不同负极粘结剂对应负极片的剥离力、膜电导率及孔隙率测试结果
项目 剥离力N/m 电导率S/cm 压实密度g/cm 3
实施例1 24.5 7.39 1.62
实施例2 23.8 7.41 1.62
实施例3 25.3 7.36 1.62
实施例4 24.9 7.42 1.61
实施例5 25.2 7.40 1.61
实施例6 21.5 7.56 1.62
实施例8 23.0 7.32 1.61
实施例9 23.5 7.25 1.62
对比例1 14.2 7.63 1.62
对比例2 16.3 7.15 1.62
对比例3 18.5 7.22 1.61
实施例1-9与对比例1-3中不同负极粘结剂对应负极片在不同充放电操作下的厚度膨胀率测试结果见表2：
表2不同负极粘结剂对应负极片的膨胀测试结果
Figure PCTCN2023071487-appb-000014
实施例1-9与对比例1-3中不同负极粘结剂对应负极片制备的全电池的循环性能测试结果见表3：
表3采用不同负极粘结剂对应负极片制备的全电池的循环性能测试结果
Figure PCTCN2023071487-appb-000015
从表1的测试结果可以获知，实施例1-9使用本申请的负极粘结剂的负极片，相比对比例1-3的负极片，在保证相似的极片电阻与压实密度的条件下，具有更加优异的极片剥离力，由此说明本申请的负极粘结剂对粉末材料(石墨、硅基材料、导电剂等)以及集流体具有更好的粘接效果。这是由于，本申请第一粘结剂对硅具有较好的包覆以及强粘接作用，可以提升包含硅基材料的极片的粘接效果，减少SEI膜的重复再生，减少副反应的发生；而第二粘 结剂的加入可以更好地增强石墨的粘接，减少锂离子传输阻力，也能增加极片的弹性。其中，实施例1-5的第二粘结剂采用了改性丁苯橡胶的水乳液，相对实施例8和实施例9具有更好的粘接效果，这是由于改性丁苯橡胶的水乳液中的乳液粒子结构增加了粘结剂与活性材料间的粘接面积(点状粘接)，可有效增强石墨间的粘接强度；而且，改性丁苯橡胶与第一粘结剂具有相近的分子结构，可以发生协同作用，形成类似网络结构，提高复合体系的力学性能，进一步使极片整体的粘接效果增强。
从表2测试结果可以获知，实施例1-9使用本申请的负极粘结剂的负极片，厚度膨胀明显小于对比例1-3的粘结剂体系对应的负极片。其中，对比例1将常规CMC粘结剂与本申请实施例1中的改性丁苯橡胶复配用于负极片，并未产生较好的极片体积膨胀抑制效果，原因是CMC与改性丁苯橡胶没有较好的相容效果，同时CMC对硅基材料的包覆效果不如本申请第一粘结剂，因此无法抑制硅在脱嵌锂过程中导致的体积变化以及SEI过度生长的问题。
另外，图5为实施例1和实施例2，以及对比例1、对比例2和对比例3的电池的循环性能结果图。从表3和图5可得知，使用本申请的负极粘结剂的全电池具有更好的循环性能，这主要是因为本申请的组合型粘结剂可以对石墨、硅基材料等具有较强粘接作用；同时可以减少副反应，并有效抵抗硅材料在脱嵌锂过程中较大的体积膨胀产生的应力，保持硅基负极片结构的完整性，从而改善电池循环性能。

Claims (30)

  1. 一种负极粘结剂，其特征在于，所述负极粘结剂包括第一粘结剂的水溶液，所述第一粘结剂为第一类单体、第二类单体和第三类单体的共聚物，所述第一类单体包括丙烯酸类单体和丙烯酸酯类单体中的一种或多种，所述第二类单体包括丙烯腈类单体、丙烯酰胺类单体和缩水甘油醚类单体中的一种或多种，所述第三类单体包括乙烯基吡咯烷酮。
  2. 如权利要求1所述的负极粘结剂，其特征在于，所述第一类单体的结构通式为
    Figure PCTCN2023071487-appb-100001
    其中，R 1为氢原子或甲基，R 2为氢原子、取代或非取代烷基、或取代或非取代环烷基。
  3. 如权利要求2所述的负极粘结剂，其特征在于，所述R 2为氢原子、碳原子数为1-8的取代或非取代烷基、或碳原子数为3-8的取代或非取代环烷基。
  4. 如权利要求1-3任一项所述的负极粘结剂，其特征在于，所述第二类单体的结构通式为
    Figure PCTCN2023071487-appb-100002
    其中，R 3为氢原子或甲基，R 4为-CN、-C(＝O)-N(R 5R 6)或
    Figure PCTCN2023071487-appb-100003
    R 5、R 6分别选自氢原子、取代或非取代烷基、或取代或非取代环烷基，R 7为取代或非取代亚烷基。
  5. 如权利要求4所述的负极粘结剂，其特征在于，所述R 5、R 6分别选自氢原子、碳原子数为1-8的取代或非取代烷基、或碳原子数为3-8的取代或非取代环烷基；所述R 7为碳原子数1-8的取代或非取代亚烷基。
  6. 如权利要求4所述的负极粘结剂，其特征在于，所述R 7为亚甲基-CH 2-、或亚苯甲基-C 6H 4-CH 2-。
  7. 如权利要求1-6任一项所述的负极粘结剂，其特征在于，所述第一粘结剂的分子结构中，衍生自所述第一类单体的结构单元的质量占比大于或等于40％。
  8. 如权利要求7所述的负极粘结剂，其特征在于，所述第一粘结剂的分子结构中，衍生自所述第一类单体的结构单元的质量占比为40％-80％。
  9. 如权利要求1-8任一项所述的负极粘结剂，其特征在于，所述第一粘结剂的结构通式如式(1)所示：
    Figure PCTCN2023071487-appb-100004
    式(1)中，R 1、R 3分别选自氢原子或甲基，R 2为氢原子、锂原子、取代或非取代烷基、或取代或非取代环烷基，R 4为-CN、-C(＝O)-N(R 5R 6)或
    Figure PCTCN2023071487-appb-100005
    R 5、R 6分别选自氢原 子、取代或非取代烷基、或取代或非取代环烷基，R 7为取代或非取代亚烷基；x、y、z为结构单元的质量占比，x＞0，y＞0，z＞0，x+y+z＝1。
  10. 如权利要求1-9任一项所述的负极粘结剂，其特征在于，所述第一粘结剂的重均分子量为50万-100万。
  11. 如权利要求1-10任一项所述的负极粘结剂，其特征在于，所述负极粘结剂还包括第二粘结剂的水乳液。
  12. 如权利要求11所述的负极粘结剂，其特征在于，所述第二粘结剂包括丁苯橡胶、改性丁苯橡胶、苯丙橡胶和醋酸乙烯-乙烯共聚物中的一种或多种。
  13. 如权利要求11或12所述的负极粘结剂，其特征在于，所述第一粘结剂的质量相对所述第一粘结剂和所述第二粘结剂的总质量的占比大于或等于20％。
  14. 如权利要求13所述的负极粘结剂，其特征在于，所述第一粘结剂的质量相对所述第一粘结剂和所述第二粘结剂的总质量的占比为20％-70％。
  15. 如权利要求12所述的负极粘结剂，其特征在于，所述改性丁苯橡胶为苯乙烯、丁二烯与所述第一类单体的共聚物。
  16. 如权利要求15所述的负极粘结剂，其特征在于，所述改性丁苯橡胶的结构通式如式(2)所示：
    Figure PCTCN2023071487-appb-100006
    式(2)中，R 1为氢原子或甲基，R 2为氢原子、取代或非取代烷基、或取代或非取代环烷基，a、b、c为结构单元的质量占比，a＞0，b＞0，c＞0，a+b+c＝1。
  17. 如权利要求16所述的负极粘结剂，其特征在于，所述改性丁苯橡胶的重均分子量为10万-40万。
  18. 一种负极粘结剂的制备方法，其特征在于，包括：
    将第一类单体、第二类单体和第三类单体加入水中，在引发剂的作用下发生共聚反应，得到第一粘结剂的水溶液；所述第一粘结剂为第一类单体与第二类单体、第三类单体的共聚物，所述第一类单体包括丙烯酸类单体和丙烯酸酯类单体中的一种或多种，所述第二类单体包括丙烯腈类单体、丙烯酰胺类单体和缩水甘油醚类单体中的一种或多种，所述第三类单体包括乙烯基吡咯烷酮。
  19. 如权利要求18所述的制备方法，其特征在于，还包括提供第二粘结剂的水乳液，所述第二粘结剂包括丁苯橡胶、改性丁苯橡胶、苯丙橡胶和醋酸乙烯-乙烯共聚物中的一种或多种。
  20. 如权利要求19所述的制备方法，其特征在于，所述第一粘结剂的质量相对所述第一粘结剂和所述第二粘结剂的总质量的占比大于或等于20％。
  21. 一种负极浆料，其特征在于，所述负极浆料包括权利要求1-17任一项所述的负极粘结剂。
  22. 一种负极片，其特征在于，所述负极片包括集流体和设置在所述集流体上的负极活性层，所述负极活性层采用权利要求1-17任一项所述的负极粘结剂或采用权利要求21所述的 负极浆料。
  23. 如权利要求22所述的负极片，其特征在于，所述负极活性层包括所述负极粘结剂的溶质，所述负极活性层中，所述负极粘结剂的溶质的质量占比为1％-12％。
  24. 如权利要求22或23所述的负极片，其特征在于，所述负极活性层包括负极活性材料，所述负极活性材料包括硅基材料。
  25. 如权利要求22或23所述的负极片，其特征在于，所述负极活性层包括负极活性材料，所述负极活性材料包括硅基材料和碳基材料。
  26. 如权利要求24或25所述的负极片，其特征在于，所述负极活性层中，所述硅基材料的质量占比为0.5％-20％。
  27. 如权利要求25或26所述的负极片，其特征在于，所述负极活性层中，所述碳基材料的质量占比为80％-95％。
  28. 一种电池，其特征在于，包括正极、负极和设置在所述正极与所述负极之间的隔膜和电解液，所述负极包括权利要求22-27任一项所述的负极片或所述负极包括权利要求1-17任一项所述的负极粘结剂。
  29. 一种电子设备，其特征在于，所述电子设备包括权利要求28所述的电池。
  30. 一种储能系统，其特性在于，所述储能系统包括权利要求28所述的电池。
PCT/CN2023/071487 2022-01-26 2023-01-10 负极粘结剂及其制备方法、负极片和电池 WO2023143035A1 (zh)

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