WO2024031327A1 - 负极极片及二次电池 - Google Patents

负极极片及二次电池 Download PDF

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Publication number
WO2024031327A1
WO2024031327A1 PCT/CN2022/111134 CN2022111134W WO2024031327A1 WO 2024031327 A1 WO2024031327 A1 WO 2024031327A1 CN 2022111134 W CN2022111134 W CN 2022111134W WO 2024031327 A1 WO2024031327 A1 WO 2024031327A1
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WO
WIPO (PCT)
Prior art keywords
negative electrode
electrode sheet
cross
polyether
preparing
Prior art date
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PCT/CN2022/111134
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English (en)
French (fr)
Inventor
王兴辉
刘会会
张文梦
陈淑华
Original Assignee
宁德时代新能源科技股份有限公司
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Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to PCT/CN2022/111134 priority Critical patent/WO2024031327A1/zh
Priority to EP22950447.7A priority patent/EP4358193A1/en
Publication of WO2024031327A1 publication Critical patent/WO2024031327A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • 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

Definitions

  • the present application relates to a negative electrode plate.
  • the present application also relates to a secondary battery including the negative electrode plate.
  • lithium-ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, and electric vehicles. , military equipment, aerospace and other fields. Due to the great development of secondary ion batteries, higher requirements have been placed on their capacity and cycle performance.
  • Improving the binder in the negative electrode sheet is one way to improve the performance of secondary batteries.
  • the existing binders still have the problem that the negative electrode diaphragm is relatively brittle, which is not conducive to the processing of the electrode piece and the cycle performance of the secondary battery. Therefore, the binder used for the negative electrode plate still needs to be improved.
  • This application was made in view of the above problems, and its purpose is to provide a negative electrode sheet, the negative electrode film of the negative electrode sheet includes a cross-linked polymer as a binder, the cross-linked polymer can strengthen and Maintaining the binding of active materials and improving the adhesion between substances in the diaphragm improves the capacity and cycle performance of the secondary battery.
  • a first aspect of the present application provides a negative electrode sheet, which includes a current collector and a negative electrode diaphragm.
  • the negative electrode diaphragm includes a negative electrode active material and the following group point:
  • Optional other components which are optionally selected from one of methacrylic acid, acrylate, hydroxyethyl acrylate, vinyl acetate, and dimethyldiallylammonium chloride or more;
  • Polyhydric alcohol which can be selected from one or more of polyvinyl alcohol, ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, and 1,4-butanediol.
  • the negative electrode membrane includes the above-mentioned cross-linked polymer as a binder.
  • the cross-linked polymer is obtained by an esterification cross-linking reaction between a copolymer of acrylonitrile and acrylic acid and a polyol cross-linking agent. It is now believed that the cross-linked polymer has a three-dimensional network structure, which can not only have strong binding force but also have strong binding force on the active material. Therefore, it can play a very good bonding role and be useful in the battery cycle process. It has a certain improvement effect on the problems such as the rebound of the negative electrode piece caused by the problem.
  • the adhesive described in this application has excellent bonding ability and adhesive force retention. It is good, can better cover the negative active material, and has high adhesion, so it can reduce the rebound of the negative electrode during the cycle and improve the cycle performance of the battery.
  • SBR styrene-butadiene rubber
  • the negative electrode sheet according to claim 1 characterized in that the mass content of the polyol ranges from 0.1 to 30%, optionally from 1 to 15%, based on components (A) and The total mass of (B).
  • the content of the polyol cross-linking agent is too low, the number of ester groups formed by the esterification reaction between the hydroxyl groups in the cross-linking agent and the carboxyl groups in acrylic acid is too low, and the cross-linking rate of the acrylonitrile-acrylic acid copolymer binder is also low. will be too low, so it may not be able to form a three-dimensional network structure, thereby failing to achieve the effect of suppressing the rebound of the pole piece.
  • An appropriate amount of polyol cross-linking agent can ensure that the acrylonitrile-acrylic acid copolymer and the cross-linking agent form a suitable three-dimensional network structure, which can constrain the expansion of the active material and the rebound of the pole piece, while allowing the pole piece to retain sufficient flexibility. Avoid problems such as pole piece defilming during battery cycling.
  • component (A) has a weight average molecular weight in the range of 300,000-1.2 million.
  • the weight average molecular weight of component (A) is less than 300,000, the final cross-linked polymer has low bonding force and is prone to problems such as defilming; when the weight average molecular weight of component (A) is higher than 120.
  • the viscosity of the glue and slurry may increase during the preparation process of the negative electrode slurry, which is not conducive to the preparation of the negative electrode slurry and the coating of the negative electrode sheets.
  • the negative electrode membrane further includes polyether, and the polyether can be selected from one of polyethylene oxide, polytetrahydrofuran diol, polyethylene glycol, polypropylene glycol, and polyoxypropylene triol, or Various.
  • the weight average molecular weight of the polyether ranges from 100 to 500,000, and the PDI ranges from 2 to 5.
  • the binder described in this application is a water-based binder. Compared with SBR, due to the strong intermolecular and intramolecular hydrogen bonding, the glass transition temperature Tg is higher (for example, 120°C) and the brittleness is relatively high. , problems such as coating cracking or cold pressing edge explosion are prone to occur during processing. Based on this, this application introduces polyether additives with a wide molecular weight distribution.
  • the polyether additives refer to polyether polyols with a molecular weight of 100 to 500,000, optionally including polyoxyethylene, polytetrahydrofuran glycol, polyethylene One or more of glycol, polypropylene glycol, and polyoxypropylene triol.
  • Polyether can be compatible with relatively polar groups, thereby destroying the hydrogen bonds and van der Waals forces between the molecules of acrylonitrile acrylic acid copolymer, increasing the distance between molecules, and thus chemically modifying and toughening the binder. , increasing the flexibility of the pole piece.
  • the mass ratio of the polyether to the cross-linked polymer is in the range of 0.015-0.6, optionally in the range of 0.02-0.5.
  • the ratio When the ratio is lower than 0.015, the content of the polyether additive is too low, and the compatibility rate with the strong polar groups in the binder (cross-linked polymer) is low, which can only destroy the polar polarity between the molecules of the acrylonitrile-acrylic acid copolymer. A small amount of hydrogen bonds cannot achieve sufficient softening effect.
  • the ratio is higher than 0.6, the content of polyether additives is too high, which will reduce the modulus of the acrylonitrile-acrylic acid copolymer binder. Therefore, during the battery cycle, the binder may change with the active material. The expansion leads to fatigue failure, which accelerates the capacity fading of the battery.
  • component (A) the mass fraction of component (a) acrylonitrile is 20-60%, the mass fraction of component (b) acrylic acid is 30-70%, and the mass fraction of component (c) The proportion is 0-10%, based on the total mass of components (a), (b) and (c).
  • acrylonitrile plays a major role in the bonding force.
  • the acrylonitrile content is less than 20%, the bonding force of the negative electrode sheet is insufficient.
  • the content is higher than 60%, due to the polarity of acrylonitrile, Larger, resulting in poor fluidity of the glue formed during the processing of the negative electrode piece, and the viscosity of the negative electrode slurry is too large, which is not conducive to the coating of the negative electrode piece; acrylic acid plays a role in cross-linking and improving lithium ion transmission, and the content is lower than When the content is 30%, there are few cross-linking sites and the cross-linking effect is insufficient.
  • the content is higher than 70%, the adhesive force of the negative electrode sheet decreases.
  • the mass content of the polyether in the negative electrode sheet ranges from 0.05 to 1%, optionally from 0.08 to 0.5%, based on the total mass of the negative electrode membrane.
  • An appropriate amount of polyether additives can ensure appropriate compatibility with the strong polar groups in the binder, achieve a certain softening effect, and ensure that there is no coating cracking or cold-pressed edge detachment during the processing of the negative electrode piece. carbon issues and enable the acrylonitrile-acrylic acid copolymer binder to maintain sufficient modulus to ensure superior cycling performance over the life of the battery.
  • the mass content of the cross-linked polymer ranges from 0.5 to 3%, optionally from 0.8 to 2.3%, based on the total mass of the negative electrode membrane.
  • the amount of the cross-linked polymer is within the above range, it can better reduce the rebound of the negative electrode sheet during the cycle, thereby better improving the cycle performance of the battery.
  • a second aspect of the application provides a secondary battery, which includes the negative electrode plate described in the first aspect of the application.
  • a third aspect of the application provides a method of preparing a secondary battery, the secondary battery including the negative electrode plate described in the first aspect of the application, the method comprising:
  • the method also includes the steps of preparing or preparing the positive electrode sheet, preparing or preparing the electrolyte, and preparing or preparing the isolation film,
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-6.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • this application provides a negative electrode sheet.
  • the negative electrode film sheet includes a cross-linked polymer as a binder.
  • the cross-linked polymer has a three-dimensional network structure, so it has strong binding to the active material and can Improve the capacity and cycle performance of secondary batteries.
  • this application also provides a polyether additive added to the negative electrode membrane, which can further improve the brittleness of the negative electrode membrane added with the cross-linked polymer.
  • a first aspect of the present application provides a negative electrode sheet, which includes a current collector and a negative electrode diaphragm, where the negative electrode diaphragm includes a negative electrode active material and the following components:
  • Optional other components which are optionally selected from one of methacrylic acid, acrylate, hydroxyethyl acrylate, vinyl acetate, and dimethyldiallylammonium chloride or more;
  • Polyhydric alcohol which can be selected from one or more of polyvinyl alcohol, ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, and 1,4-butanediol.
  • the negative electrode sheet diaphragm includes the above-mentioned cross-linked polymer as a binder.
  • the cross-linked polymer is obtained by an esterification cross-linking reaction between a copolymer of acrylonitrile and acrylic acid and a polyol cross-linking agent. It is now believed that the cross-linked polymer has a three-dimensional network structure, which not only has strong adhesion but also has strong binding to the active material. Therefore, it can play a very good bonding role and is responsible for the generation of chemical components during the battery cycle. It has a certain effect in reducing problems such as negative electrode plate rebound.
  • the adhesive described in this application also has the following advantages:
  • the cross-linked polymer binder has strong polar groups nitrile group (dielectric constant of nitrile group (-CN) is 6.5), carboxyl group, etc. in the main chain, which can make the bonding
  • the molecular chains of the binder and the groups on the surface of the pole piece current collector form hydrogen bonds, complexes, etc. to ensure that the active material is firmly attached to the current collector. Therefore, the binder of the present application has excellent bonding performance. It can ensure that the negative electrode plate will not have problems such as peeling off or powder loss during processing and recycling;
  • the acrylonitrile-acrylic acid copolymer i.e., the copolymer in component (A)
  • Better coating of the material inhibits the expansion and rebound of the negative electrode during the battery cycle through the dual functions of bonding and coating, thereby effectively mitigating the structure caused by expansion that may occur during the charging and discharging process of the active material.
  • the negative electrode sheet including the binder described in this application has low rebound during the battery cycle, so it can also be used
  • the limited battery space accommodates more active materials, thereby increasing the energy density of the battery.
  • component (A) is also called the matrix component of the adhesive described in this application, and component (B) is called the cross-linking component of the adhesive described in this application.
  • the negative electrode membrane is described herein as including component (A) and component (B), in some cases, a cross-linked polymer formed by cross-linking polymerization of components (A) and (B) It is also existence. Therefore, in some optional embodiments, the negative electrode membrane further includes a cross-linked polymer formed by cross-linking polymerization of components (A) and (B).
  • the cross-linked polymer has a three-dimensional network structure as a binder. When the binder is added, it can better bond or bind the negative active material, thereby reducing the expansion of the negative electrode sheet during cycles and improving the cycle performance of the battery.
  • the negative electrode sheet according to claim 1 characterized in that the mass content of the polyhydric alcohol ranges from 0.1 to 30%, optionally from 1 to 15%, based on component (A) and The total mass of (B).
  • the content of the polyol cross-linking agent is too low, the number of ester groups formed by the esterification reaction between the hydroxyl groups in the cross-linking agent and the carboxyl groups in acrylic acid is too low, and the cross-linking rate of the acrylonitrile-acrylic acid copolymer will also be too low. , so it may not be possible to form a three-dimensional network structure, thereby failing to achieve the effect of suppressing the rebound of the pole piece.
  • An appropriate amount of polyol cross-linking agent can ensure that the acrylonitrile-acrylic acid copolymer and cross-linking agent form a suitable three-dimensional network structure, which has the effect of restraining the expansion of the active material and the rebound of the pole piece, while allowing the pole piece to retain sufficient flexibility to avoid Problems such as pole piece defilming occur during battery cycling.
  • component (A) has a weight average molecular weight in the range of 300,000-1.2 million.
  • the weight average molecular weight of component (A) may be 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, 800,000, 850,000 , 900,000, 950,000, 1 million, 1.05 million, 1.1 million, 1.15 million, 1.2 million, or a value within any range between the above values. More optionally, the weight average molecular weight of component (A) is in the range of 600,000 to 1,000,000.
  • the final cross-linked polymer has low bonding force and is prone to problems such as defilming; when the weight average molecular weight of component (A) is higher than 120
  • the viscosity of the glue and slurry may increase during the preparation process of the negative electrode slurry, which is not conducive to the preparation of the negative electrode slurry and the coating of the negative electrode sheets.
  • the negative electrode membrane further includes polyether, and the polyether can be selected from one of polyoxyethylene, polytetrahydrofuran diol, polyethylene glycol, polypropylene glycol, and polyoxypropylene triol, or Various.
  • the polyether has a weight average molecular weight ranging from 100 to 500,000, and a PDI ranging from 2 to 5.
  • the weight average molecular weight of the polyether ranges from 100 to 200,000.
  • the binder described in this application is a water-based binder. Compared with SBR, due to the strong intermolecular and intramolecular hydrogen bonding, the glass transition temperature Tg is higher (for example, 120°C) and the brittleness is biased. Large, problems such as coating cracking or cold-pressed edge explosion may easily occur during processing. Based on this, this application introduces polyether additives with a wider molecular weight distribution (larger dispersion index PDI).
  • the polyether additives refer to polyether polyols with a molecular weight of 100 to 500,000, optionally including polyethylene oxide. , one or more of polytetrahydrofuran glycol, polyethylene glycol, polypropylene glycol, and polyoxypropylene triol.
  • Polyether can be compatible with highly polar groups, thereby destroying the hydrogen bonds and van der Waals forces between the molecules of the acrylonitrile acrylic acid copolymer, increasing the distance between the molecules, and thus chemically modifying and toughening the binder. , increasing the flexibility of the pole piece.
  • the mass ratio of the polyether to the cross-linked polymer is in the range of 0.015-0.6, optionally in the range of 0.02-0.5. More optionally, the mass ratio of the polyether to the cross-linked polymer is in the range of 0.02-0.35.
  • the ratio When the ratio is lower than 0.015, the content of the polyether additive is too low, and the compatibility rate with the strong polar groups in the binder (cross-linked polymer) is low, which can only destroy the polar polarity between the molecules of the acrylonitrile-acrylic acid copolymer. A small amount of hydrogen bonds cannot achieve sufficient softening effect.
  • the ratio is higher than 0.6, the content of polyether additives is too high, which will reduce the modulus of the acrylonitrile-acrylic acid copolymer binder. Therefore, during the battery cycle, the binder may change with the active material. The expansion leads to fatigue failure, which accelerates the capacity fading of the battery and reduces the battery capacity retention rate.
  • the mass fraction of component (a) acrylonitrile is 20-60%
  • the mass fraction of component (b) acrylic acid is 30-70%
  • the mass fraction of component (c) The mass fraction is 0-10%, based on the total mass of components (a), (b) and (c).
  • acrylonitrile plays a major role in the bonding force.
  • the acrylonitrile content is less than 20%, the bonding force of the negative electrode sheet is insufficient.
  • the content is higher than 60%, due to the polarity of acrylonitrile, Larger, resulting in poor fluidity of the glue formed during the processing of the negative electrode piece, and the viscosity of the negative electrode slurry is too large, which is not conducive to the coating of the negative electrode piece; acrylic acid plays a role in cross-linking and improving lithium ion transmission, and the content is lower than When the content is 30%, there are few cross-linking sites and the cross-linking effect is insufficient.
  • the content is higher than 70%, the bonding force of the negative electrode sheet decreases.
  • the mass content of the polyether in the negative electrode sheet ranges from 0.05 to 1%, optionally from 0.08 to 0.5%, based on the total mass of the negative electrode membrane.
  • An appropriate amount of polyether additives can ensure appropriate compatibility with the strong polar groups in the binder, achieve a certain softening effect, and ensure that there is no coating cracking or cold-pressed edge detachment during the processing of the negative electrode piece. carbon issues and enable the acrylonitrile-acrylic acid copolymer binder to maintain sufficient modulus to ensure superior cycling performance over the life of the battery.
  • the mass content of the cross-linked polymer ranges from 0.5 to 3%, optionally from 0.8 to 2.3%, based on the total mass of the negative electrode membrane.
  • the amount of the cross-linked polymer is within the above range, it can better reduce the rebound of the negative electrode sheet during the cycle, thereby better improving the cycle performance of the battery.
  • a second aspect of the application provides a secondary battery, which includes the negative electrode plate described in the first aspect of the application.
  • a third aspect of the application provides a method for preparing the secondary battery described in the second aspect of the application.
  • the secondary battery includes the negative electrode sheet described in the first aspect of the application.
  • the method includes:
  • the method also includes the steps of preparing or preparing the positive electrode sheet, preparing or preparing the electrolyte, and preparing or preparing the isolation film,
  • At least part of the cross-linking of the cross-linked polymer of the present application is completed during the assembly process of the secondary battery, that is, after assembling the negative electrode sheet, the positive electrode sheet, the electrolyte, and the separator, The at least part of the cross-linking is completed after heating under vacuum at high temperature for a period of time.
  • cross-linking components (A) and (B) in the battery assembly step, cross-linking of components (A) and (B) may also occur during the battery preparation process. various stages, therefore, the present application is not limited to the above description.
  • this application only describes the conditions of vacuum heating to cross-link components (A) and (B), other methods in the prior art are used to cross-link components (A) and (B). ) cross-linking is also within the scope of this application.
  • the secondary battery, battery module, battery pack and power device of the present application will be described below.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composites of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon.
  • At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet is the negative electrode sheet described in the first aspect of the present application, which includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a negative electrode active material and the cross-linked polymer.
  • the negative electrode film layer includes the polyether.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • binders may also be included, for example, selected from the group consisting of styrene-butadiene rubber (SBR), polyethylene Acrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS) at least one of them.
  • SBR styrene-butadiene rubber
  • PAA polyethylene Acrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application there is no specific restriction on the type of electrolyte in this application, and it can be selected according to needs.
  • the electrolyte may be liquid, gel, semi-solid or fully solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte solution includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally further includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape.
  • Step 1 Prepare a mixture of acrylonitrile-acrylic acid copolymer and polyol
  • Step 2 Prepare the negative electrode piece
  • CMC carboxymethylcellulose
  • Step 3 Prepare the positive electrode plate
  • NCM nickel-cobalt-manganese
  • conductive agent carbon black
  • binder polyvinylidene fluoride PVDF
  • NMP N-methylpyrrolidone
  • Example 2-17 and Comparative Example 1-2 are identical to Example 2-17 and Comparative Example 1-2:
  • Example 2-17 and Comparative Example 1-2 are the same as those of Example 1. See Table 1 for differences.
  • Examples 18-24 are the same as those of Example 4, except that different polyether additives and different amounts are added in the preparation of the negative electrode piece in step 2 (see Table 2 for details).
  • Example 1 use a micrometer to measure the thickness of the negative electrode piece 0 hours after cold pressing, and record it as d0.
  • the full charge rebound rate test process of the negative electrode plate after cycling for 500cls is as follows: at 25°C, charge the battery corresponding to Example 1 with a constant current of 1/3C to 4.3V, and then charge with a constant voltage of 4.3V until the current is 0.05C , leave it for 5 minutes, and then discharge it to 2.8V at 1/3C. Repeat the above steps for the same battery, cycle 500 times. Charge the cycled battery to 4.3V at a constant current of 1/3C, then charge at a constant voltage of 4.3V to a current of 0.05C, and disassemble the fully charged battery.
  • the testing procedures of the comparative examples and other examples are the same as above.

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

Abstract

本申请提供一种负极极片，其包括集流体和负极膜片，所述负极膜片包括负极活性材料以及由丙烯腈和丙烯酸组分形成的共聚物和多元醇。可选地，所述负极膜片还包括聚醚。本申请的交联聚合物和聚醚可以降低循环过程中负极极片的反弹率，进而提高电池的容量保持率。

Description

负极极片及二次电池 技术领域
本申请涉及一种负极极片。此外，本申请还涉及包含所述负极极片的二次电池。
背景技术
近年来，随着二次离子电池的应用范围越来越广泛，锂离子电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次离子电池取得了极大的发展，因此对其容量和循环性能提出了更高的要求。
对负极极片中的粘结剂进行改进是提高二次电池性能的一种方式。然而现有的粘结剂仍存在负极膜片的脆性较大的问题，不利于极片加工，也不利于二次电池的循环性能。因此，用于负极极片的粘结剂仍有待改进。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种负极极片，该负极极片的负极膜片中包括一种交联聚合物作为粘结剂，该交联聚合物能够增强并保持对活性材料的束缚并且提高膜片中各物质之间的粘结力，进而提高了二次电池的容量和循环性能。
为了实现上述目的，本申请的第一方面提供了一种本申请的第一方面提供了一种负极极片，其包括集流体和负极膜片，所述负极膜片包括负极活性材料以及以下组分：
(A)由以下组分形成的共聚物：
(a)丙烯腈；
(b)含有3-6个碳原子且含有至少一个双键的羧酸，可选为丙烯酸；
(c)任选地其他组分，所述其他组分可选地选自甲基丙烯酸、丙烯酸酯、丙烯酸羟乙酯、醋酸乙烯酯、二甲基二烯丙基氯化铵中的一种或多种；
(B)多元醇，其可选为聚乙烯醇、乙二醇、丙二醇、丙三醇、三羟甲基丙烷、季戊四醇、1,4-丁二醇中的一种或多种。
根据本申请，负极膜片包括上述交联聚合物作为粘结剂，该交联聚合物为丙烯腈和丙烯酸的共聚物与多元醇类交联剂发生酯化交联反应得到。现认为，该交联聚合物具有三维网络结构，能够在具有较强的粘结力的同时对活性材料也具有较强的束缚，因此能够起到非常好的粘结作用并且对于在电池循环过程中产生的负极极片反弹等问题有一定的改善作用。
此外，与本领域中常规使用的丁苯橡胶(SBR)或未交联的线性粘结剂等其他粘结剂相比，本申请所述的粘结剂粘结能力优异、粘结力保持性好、能够对负极活性材料更好地包覆、粘结力高，因而能够降低负极极片在循环过程中的反弹并且提高电池的循环性能。
在任意实施方式中，根据权利要求1所述的负极极片，其特征在于，所述多元醇的质量含量范围为0.1-30％，可选为1-15％，基于组分(A)和(B)的总质量计。
当多元醇交联剂的含量过低时，交联剂中的羟基与丙烯酸中的羧基发生酯化反应所形成的酯基数量过低，丙烯腈-丙烯酸共聚物粘结剂的交联率也会过低，因此可能无法形成具有三维网状结构，从而达不到抑制极片反弹的效果。相反，多元醇交联剂的含量过高时，丙烯腈-丙烯酸共聚物粘结剂的交联率过高，羧基数量减少，不仅导致粘结力降低，而且可能导致交联后的粘结剂脆性及模量过大，柔性变差，因而在电池循环过程中，随着活性材料的膨胀和收缩，容易出现极片脱膜等问题。
合适量的多元醇交联剂能够确保丙烯腈-丙烯酸共聚物与交联剂形成合适的三维网络结构，起到束缚活性材料膨胀和极片反弹的效果，同时能够使极片保留足够的柔性，避免电池循环过程中出现极片脱膜等问题。
在任意实施方式中，组分(A)的重均分子量在30万-120万范围内。当组分(A)的重均分子量低于30万时，最终形成的交联聚合物的粘结力偏低，易出现脱膜等问题；当组分(A)的重均分子量高于120万时，在负极浆料的制备过程中可能导致胶液及浆料粘度变大，不利于负极浆料制备及负极极片的涂布。
在任意实施方式中，所述负极膜片还包括聚醚，所述聚醚可选为聚氧化乙烯、聚四氢呋喃二醇、聚乙二醇、聚丙二醇、聚氧化丙烯三醇中的一种或多种。
在任意实施方式中，所述聚醚的重均分子量范围为100～500000，PDI范围为2-5。
本申请所述粘结剂为水性粘结剂，与SBR相比，由于存在较强的分子间、分子内氢键作用，因此玻璃化转变温度Tg较高(例如120℃)，且脆性偏大，在加工过程中易出现涂布开裂或冷压爆边等问题。基于此，本申请引入了分子量分布较宽的聚醚类添加剂，所述聚醚类添加剂指分子量为100～500000的聚醚多元醇，可选地包括聚氧化乙烯、聚四氢呋喃二醇、聚乙二醇、聚丙二醇、聚氧化丙烯三醇中的一种或多种。聚醚能与极性较高的基团配伍，从而破坏丙烯腈丙烯酸共聚物分子间的氢键和范德华作用力，加大分子间距离，进而对粘结剂起到化学改性增韧的效果，增加了极片的柔性。
在任意实施方式中，所述聚醚与所述交联聚合物的质量之比在0.015-0.6范围内、可选在0.02-0.5范围内。
当比例低于0.015时，聚醚类添加剂的含量过低，与粘结剂(交联聚合物)中强极性基团的配伍率低，只能破坏丙烯腈-丙烯酸共聚物分子间的极少量氢键，达不到足够的增柔效果。当比例高于0.6时，聚醚类添加剂的含量过高，会降低丙烯腈-丙烯酸共聚物粘结剂的模 量，因而，在电池循环过程中，所述粘结剂可能会随着活性材料的膨胀而疲劳失效，加快了电池的容量衰减。
在任意实施方式中，组分(A)中，组分(a)丙烯腈的质量分数为20-60％，组分(b)丙烯酸的质量分数为30-70％，组分(c)质量占比为0-10％，基于组分(a)、(b)、(c)的总质量计。
作为粘结剂的交联聚合物中，丙烯腈对粘结力起主要作用，丙烯腈含量低于20％时，负极极片粘结力不足，含量高于60％时，因丙烯腈极性较大，导致负极极片加工过程中形成的胶液流动性变差，负极浆料粘度过大，不利于负极极片涂布；丙烯酸起到交联、改善锂离子传输的作用，含量低于30％时，交联位点少，交联效果不足，含量高于70％时，负极极片粘结力下降。
在任意实施方式中，负极极片中的聚醚的质量含量范围为0.05-1％，可选为0.08-0.5％，基于负极膜片的总质量计。
合适量的聚醚类添加剂能够确保与粘结剂中强极性基团的合适的配伍率，起到一定的增柔效果，确保负极极片的加工过程中无涂布开裂及冷压边缘脱碳问题，并使丙烯腈-丙烯酸共聚物粘结剂保持足够的模量，以确保电池生命周期中优越的循环性能。
在任意实施方式中，所述交联聚合物的质量含量范围为0.5-3％，可选为0.8-2.3％，基于负极膜片的总质量计。
所述交联聚合物的量在上述范围内，能够更好地降低负极极片在循环过程中的反弹，进而更好地提高电池的循环性能。
本申请的第二方面提供了一种二次电池，其包括本申请第一方面所述的负极极片。
本申请的第三方面提供一种制备二次电池的方法，所述二次电池包括本申请第一方面所述的负极极片，所述方法包括：
(1)将组分(A)与(B)混合，得到交联混合物；
(2)制备负极极片，将负极活性物质、任选地导电剂、任选地增稠剂以及(1)中得到的所述交联混合物混合均匀制成负极浆料，涂覆于负极集流体上，经过烘干、冷压、分切得到负极极片；
所述方法还包括制备或准备正极极片、制备或准备电解液、制备或准备隔离膜的步骤，
将上述步骤中得到的负极极片、正极极片、电解液、隔离膜组装，在100-130℃下真空加热5-15h以便完成负极膜片中组分(A)与(B)的至少一部分的交联。
具体实施方式
以下，详细说明具体公开了本申请的粘结剂体系、负极极片及二次电池的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-6。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
目前，在锂离子电池循环过程中，随着在负极中发生的脱嵌锂反应以及电解液的溶胀，普通负极粘结剂难以维持对负极活性材料的束缚，导致负极极片反弹较大，进而电池膨胀力较大，由此劣化了二次电池的电性能及循环性能。针对上述问题，本申请提供了一种负极极片，其负极膜片中包括作为粘结剂的交联聚合物，该交联聚合物具有三维网络结构，因此对活性材料的束缚较强，能够改善二次电池的容量和循环性能。另外，本申请还提供了一种在负极膜片中添加的聚醚添加剂，其能够进一步地改善添加了所述交联聚合物的负极膜片的脆性。
因此，本申请的第一方面提供了一种负极极片，其包括集流体和负极膜片，所述负极膜片包括负极活性材料以及以下组分：
(A)由以下组分形成的共聚物：
(a)丙烯腈；
(b)含有3-6个碳原子且含有至少一个双键的羧酸，可选为丙烯酸；
(c)任选地其他组分，所述其他组分可选地选自甲基丙烯酸、丙烯酸酯、丙烯酸羟乙酯、醋酸乙烯酯、二甲基二烯丙基氯化铵中的一种或多种；
(B)多元醇，其可选为聚乙烯醇、乙二醇、丙二醇、丙三醇、三羟甲基丙烷、季戊四醇、1,4-丁二醇中的一种或多种。
根据本申请，负极极片膜片包括上述交联聚合物作为粘结剂，该交联聚合物为丙烯腈和丙烯酸的共聚物与多元醇类交联剂发生酯化交联反应得到。现认为，该交联聚合物具有三维网络结构，在具有较强的粘结力的同时对活性材料也具有较强的束缚，因此能够起到非常好粘结作用并且对于在电池循环过程中产生的负极极片反弹等问题有一定的降低作用。
此外，与本领域中常规使用的丁苯橡胶(SBR)或未交联的线性粘结剂等其他粘结剂相比，本申请所述的粘结剂还具有以下优势：
(1)优异的粘结能力：所述交联聚合物粘结剂主链中具有强极性基团腈基(腈基(-CN)的介电常数为6.5)、羧基等，可使粘结剂分子链与极片集流体表面的基团之间形成氢键、络合等作用，以确保活性材料牢固附着在集流体上，因此，本申请的粘结剂具有优异的粘结性能，能够确保负极极片在加工及循环过程中均不会出现脱膜或掉粉等问题；
(2)保持的极片的粘结力：本申请所述粘结剂在电解液中的溶胀率较低，有利于在电池循环过程中保持极片的粘结力并进而保证电池的容量和循环性能；
(3)包覆效果：丙烯腈-丙烯酸共聚物(即组分(A)中的共聚物)与多元醇类交联剂发生酯化交联反应，形成的三维网状结构能够实现对负极活性材料更好的包覆，通过粘结和包覆的双重作用来抑制负极极片在电池循环过程中的膨胀和反弹，从而有效缓解活性材料在 充放电过程中可能会产生的因膨胀造成的结构坍塌，降低循环过程中的锂离子消耗，提高锂电池的循环容量保持率；此外，本申请所述的包括所述粘结剂的负极极片在电池循环过程中反弹较低，因此还可以使有限的电池空间容纳更多的活性材料，从而提高电池的能量密度。
本申请中，组分(A)也称为本申请所述粘结剂的基体组分，组分(B)称为本申请所述粘结剂的交联组分。
应理解，虽然本文中描述负极膜片包括组分(A)和组分(B)，然而，在一些情况下，由组分(A)和(B)通过交联聚合形成的交联聚合物也是存在。因此，在一些可选实施方式中，所述负极膜片还包括由组分(A)和(B)通过交联聚合形成的交联聚合物，该交联聚合物具有三维网络结构，作为粘结剂添加时，能够更好地粘结或束缚负极活性材料，从而降低负极极片在循环中的膨胀并且提高电池的循环性能。
在一些实施方式中，根据权利要求1所述的负极极片，其特征在于，所述元醇的质量含量范围为0.1-30％，可选为1-15％，基于组分(A)和(B)的总质量计。
当多元醇交联剂的含量过低时，交联剂中的羟基与丙烯酸中的羧基发生酯化反应所形成的酯基数量过低，丙烯腈-丙烯酸共聚物的交联率也会过低，因此可能无法形成三维网状结构，从而达不到抑制极片反弹的效果。相反，多元醇交联剂的含量过高时，丙烯腈-丙烯酸共聚物粘结剂的交联率过高，羧基数量减少，不仅导致粘结力降低，而且可能导致交联后的粘结剂脆性及模量过大，柔性变差，因而在电池循环过程中，随着活性材料的膨胀和收缩，容易出现极片脱膜等问题。
合适量的多元醇交联剂能够确保丙烯腈-丙烯酸共聚物与交联剂形成合适的三维网络结构，起到束缚活性材料膨胀和极片反弹的效果，同时使极片保留足够的柔性，避免电池循环过程中出现极片脱膜等问题。
在一些实施方式中，组分(A)的重均分子量在30万-120万范围内。可选地，组分(A)的重均分子量可为30万、35万、40万、45万、50万、55万、60万、65万、70万、75万、80万、85万、90万、95万、100万、105万、110万、115万、120万，也可以是上述各数值之间的任意范围内的值。更可选地，组分(A)的重均分子量在60万-100万范围内。当组分(A)的重均分子量低于30万时，最终形成的交联聚合物的粘结力偏低，易出现脱膜等问题；当组分(A)的重均分子量高于120万时，在负极浆料的制备过程中可能导致胶液及浆料粘度变大，不利于负极浆料制备及负极极片的涂布。
在一些实施方式中，所述负极膜片还包括聚醚，所述聚醚可选为聚氧化乙烯、聚四氢呋喃二醇、聚乙二醇、聚丙二醇、聚氧化丙烯三醇中的一种或多种。
在一些实施方式中，所述聚醚的重均分子量范围为100～500000，PDI范围为2-5。可选地，所述聚醚的重均分子量范围为100～200000。
本申请所述粘结剂为水性粘结剂，与SBR相比，由于存在较强的分子间、分子内氢键作用，因此玻璃化转变温度T g较高(例如120℃)，且脆性偏大，在加工过程中可能易出现涂布开裂或冷压爆边等问题。基于此，本申请引入了分子量分布较宽的(分散性指数PDI较大)聚醚类添加剂，所述聚醚类添加剂指分子量为100～500000的聚醚多元醇，可选地包括聚氧化乙烯、聚四氢呋喃二醇、聚乙二醇、聚丙二醇、聚氧化丙烯三醇中的一种或多种。聚醚能与极性较高的基团配伍，从而破坏丙烯腈丙烯酸共聚物分子间的氢键和范德华作用力，加大分子间距离，进而对粘结剂起到化学改性增韧的效果，增加了极片的柔性。
在一些实施方式中，所述聚醚与所述交联聚合物的质量之比在0.015-0.6范围内、可选在0.02-0.5范围内。更可选地，所述聚醚与所述交联聚合物的质量之比在0.02-0.35范围内。
当比例低于0.015时，聚醚类添加剂的含量过低，与粘结剂(交联聚合物)中强极性基团的配伍率低，只能破坏丙烯腈-丙烯酸共聚 物分子间的极少量氢键，达不到足够的增柔效果。当比例高于0.6时，聚醚类添加剂的含量过高，会降低丙烯腈-丙烯酸共聚物粘结剂的模量，因而，在电池循环过程中，所述粘结剂可能会随着活性材料的膨胀而疲劳失效，加快了电池的容量衰减，导致电池容量保持率降低。
在一些实施方式中，组分(A)中，组分(a)丙烯腈的质量分数为20-60％，组分(b)丙烯酸的质量分数为30-70％，组分(c)的质量分数为0-10％，基于组分(a)、(b)、(c)的总质量计。
作为粘结剂的交联聚合物中，丙烯腈对粘结力起主要作用，丙烯腈含量低于20％时，负极极片粘结力不足，含量高于60％时，因丙烯腈极性较大，导致负极极片加工过程中形成的胶液流动性变差，负极浆料粘度过大，不利于负极极片涂布；丙烯酸起到交联、改善锂离子传输的作用，含量低于30％时，交联位点少，交联效果不足，含量高于70％时，负极极片粘结力下降。
在一些实施方式中，负极极片中的聚醚的质量含量范围为0.05-1％，可选为0.08-0.5％，基于负极膜片的总质量计。
合适量的聚醚类添加剂能够确保与粘结剂中强极性基团的合适的配伍率，起到一定的增柔效果，确保负极极片的加工过程中无涂布开裂及冷压边缘脱碳问题，并使丙烯腈-丙烯酸共聚物粘结剂保持足够的模量，以确保电池生命周期中优越的循环性能。
在一些实施方式中，所述交联聚合物的质量含量范围为0.5-3％，可选为0.8-2.3％，基于负极膜片的总质量计。
所述交联聚合物的量在上述范围内，能够更好地降低负极极片在循环过程中的反弹，进而更好地提高电池的循环性能。
本申请的第二方面提供一种二次电池，其包括本申请第一方面所述的负极极片。
本申请的第三方面提供一种制备本申请第二方面所述二次电池的方法，所述二次电池包括本申请第一方面所述的负极极片，所述方法包括：
(1)将组分(A)与(B)混合，得到交联混合物；
(2)制备负极极片，将负极活性物质、任选地导电剂、任选地增稠剂以及(1)中得到的所述交联混合物混合均匀制成负极浆料，涂覆于负极集流体上，经过烘干、冷压、分切得到负极极片；
所述方法还包括制备或准备正极极片、制备或准备电解液、制备或准备隔离膜的步骤，
将上述步骤中得到的负极极片、正极极片、电解液、隔离膜组装，在100-130℃下真空加热5-15h以便完成负极膜片中组分(A)与(B)的至少一部分的交联。
在可选的实施方式中，本申请的交联聚合物至少一部分的交联在二次电池的组装过程中完成，即，在将负极极片、正极极片、电解液、隔离膜组装后，在高温下真空下加热一段时间后完成所述至少一部分交联。
应理解，虽然本申请仅限定了在电池组装步骤中使组分(A)与(B)交联，然而，组分(A)与(B)的交联也可能发生在电池制备过程中的各个阶段，因此，本申请不限于上述描述。另外，还应理解的是，虽然本申请仅描述了真空加热的条件使组分(A)与(B)交联，然而，采用现有技术中的其他方式使组分(A)与(B)交联也在本申请构思范围内。
下面对本申请的二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏 氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片为本申请第一方面所述的负极极片，其包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料和所述交联聚合物。可选地，所述负极膜层包括所述聚醚。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅 氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
应理解，在本申请所述的负极极片中，除本申请所述的交联聚合物粘结剂外，可能还包括其他粘结剂，例如，包括选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。本申请不意在限制负极极片中使用的粘结剂仅为所述交联聚合物。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的、半固态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
I.包含本申请所述粘结剂的负极极片及二次电池的制备
实施例1：
步骤1：制备丙烯腈-丙烯酸共聚物和多元醇的混合物
称取31.8g丙烯腈、32.8g丙烯酸单体加入装有回流冷凝器及搅拌器的三口烧瓶中，加入500ml去离子水，最后加入过硫酸铵引发剂和N,N-二甲基双丙烯酰胺，引发剂用量为单体总质量的0.05％，N,N-二甲基双丙烯酰胺用量为单体总质量的0.015％。搅拌一定时间，控制搅拌转速500rpm，在80℃恒温反应3h，反应完毕得到丙烯腈丙烯酸共聚物。加去离子水将产物稀释至固含量5wt％，使用氢氧化锂进行中和，调节pH为7.0-8.5，得到透明的水性分散液。重均分子量80万，采用GPC凝胶色谱法测定。
将上述丙烯腈-丙烯酸共聚物的水性分散液与交联组分聚乙烯醇混合，使丙烯腈-丙烯酸三元共聚物与聚乙烯醇的重量比为99.9：0.1，以500rpm的转速机械搅拌40min，得到丙烯腈-丙烯酸共聚物与聚乙烯醇的混合物，其为交联聚合物的原料，经后面步骤中的交联反应而形成交联聚合物。
步骤2：制备负极极片
将活性物质人造石墨、导电剂碳黑、步骤1中得到的交联聚合物、增稠剂羟甲基纤维素钠(CMC)按照重量比为96.9：0.4：1.8：0.9溶于溶剂去离子水中，混合均匀后制备成负极浆料；将负极浆料一次或多次均匀涂覆在负极集流体铜箔上，经过烘干、冷压、分切得到负极极片。
步骤3：制备正极极片
将镍钴锰(NCM)三元材料、导电剂碳黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为93：4：3与N-甲基吡咯烷酮(NMP)搅拌混合均匀，得到正极浆料；之后将正极浆料均匀涂覆于正极集流体上，之后经过烘干、冷压、分切，得到正极极片。
步骤4：制备电解液
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，加入12.5％LiPF6锂盐溶解于有机溶剂中，搅拌均匀，得到实施例1的电解液。
步骤5：隔离膜
以聚丙烯膜作为隔离膜。
步骤6：制备二次电池
将正极极片、隔离膜、负极极片卷绕后，进行热压整形，装入铝壳中，110℃下真空加热10h完成负极膜片中交联组分和基体组分的交联并去除极片中的水分，注入电解液，焊接密封，化成容量后得到二次电池。
实施例2-17和对比例1-2：
实施例2-17和对比例1-2与实施例1操作相同，不同之处参见表1。
实施例18-24与实施例4操作相同，不同之处在于步骤2中负极极片的制备中添加了不同的聚醚类添加剂及不同添加量(详见表2)。
II.性能测试
1.翘起高度
取各实施例和对比例中的负极浆料，用刮刀将负极浆料均匀涂布在铜箔上，涂布厚度250μm，将已涂布的带有负极浆料的铜箔裁切成10×10cm的小片，放置于140℃加热台上烘烤30min，用刻度尺测量已烘干极片的四角翘起高度，计算平均值即为极片的翘起高度。
2.粘结力
本申请实施例和对比例的负极极片粘结力采用如下测试方法得到的：
取步骤2中制备的极片裁剪为20×100mm尺寸的测试试样，备用；用双面胶粘结极片需要测试的那一面，并用压辊压实，使之与极片完全贴合；试样的双面胶的另外一面粘贴于不锈钢表面，将试样一端反向弯曲，弯曲角度为180°。采用高铁拉力机测试，将不锈钢一端固定于拉力机下方夹具，试样弯曲末端固定于上方夹具，调整试样角度，保证上下端位于垂直位置，然后以50mm/min的速度拉伸试样，直到试样全部从基板剥离，记录过程中的位移和作用力，一般认为受力平衡时的力为极片的粘结力，单位为N/m。
3.内聚力
本申请实施例和对比例的负极极片内聚力采用如下测试方法得到的：
将步骤2中制备的极片裁剪为20×100mm尺寸的测试试样，备用；用低粘性透明胶纸粘结极片需要测试的那一面，并用压辊压实，使之与极片完全贴合；试样的透明胶纸的另外一面粘贴于不锈钢表面，将试样一端反向弯曲，弯曲角度为180°；采用高铁拉力机测试，将不锈钢一端固定于拉力机下方夹具，试样弯曲末端固定于上方夹具，调整试样角度，保证上下端位于垂直位置，然后以50mm/min的速度拉伸试样，直到膜片表层活性物质颗粒剥离，记录过程中的位移和作用力，一般认为受力平衡时的力为极片的内聚力，单位为N/m。
4.负极极片循环500cls后满充反弹率测试
以实施例1为例，用万分尺测量负极极片冷压后0h的极片厚度，记为d0。负极极片循环500cls后满充反弹率测试过程如下：在25℃下，将实施例1对应的电池，以1/3C恒流充电至4.3V，再以4.3V恒定电压充电至电流为0.05C，搁置5min，再以1/3C放电至2.8V。对上述同一个电池重复以上步骤，循环500次。将循环后的电池，以1/3C恒流充电至4.3V，再以4.3V恒定电压充电至电流为0.05C，拆解满充后的电池。用万分尺测试拆解后的负极极片厚度，记为d1， 则负极极片循环500cls后满充反弹率＝(d1-d0)/d0×100％。对比例以及其他实施例的测试过程同上。
5.电池容量保持率测试
以实施例1为例，电池容量保持率测试过程如下：在25℃下，将实施例1对应的电池，以1/3C恒流充电至4.3V，再以4.3V恒定电压充电至电流为0.05C，搁置5min，再以1/3C放电至2.8V，所得容量记为初始容量C 0。对上述同一个电池重复以上步骤，并同时记录循环第500次后电池的放电容量C 500，则500次循环后电池容量保持率P 500＝C 500/C 0×100％。对比例以及其他实施例的测试过程同上。
各实施例和对比例的测试结果参见下表1。
Figure PCTCN2022111134-appb-000001
Figure PCTCN2022111134-appb-000002
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (11)

  1. 一种负极极片，其包括集流体和负极膜片，所述负极膜片包括负极活性材料以及以下组分：
    (A)由以下组分形成的共聚物：
    (a)丙烯腈；
    (b)含有3-6个碳原子且含有至少一个双键的羧酸，可选为丙烯酸；
    (c)任选地其他组分，所述其他组分可选地选自甲基丙烯酸、丙烯酸酯、丙烯酸羟乙酯、醋酸乙烯酯、二甲基二烯丙基氯化铵中的一种或多种；
    (B)多元醇，其可选为聚乙烯醇、乙二醇、丙二醇、丙三醇、三羟甲基丙烷、季戊四醇、1,4-丁二醇中的一种或多种。
  2. 根据权利要求1所述的负极极片，其特征在于，所述多元醇的质量含量范围为0.1-30％，可选为1-15％，基于组分(A)和(B)的总质量计。
  3. 根据权利要求1或2所述的负极极片，其特征在于，组分(A)的重均分子量在30万-120万范围内。
  4. 根据权利要求1-3中任一项所述的负极极片，其特征在于，所述负极膜片还包括聚醚，所述聚醚可选为聚氧化乙烯、聚四氢呋喃二醇、聚乙二醇、聚丙二醇、聚氧化丙烯三醇、硬脂酸聚氧乙烯醚、十二烷基醇聚氧乙烯醚中的一种或多种。
  5. 根据权利要求4所述的负极极片，其特征在于，所述聚醚的重均分子量范围为100～500000，PDI范围为2-5。
  6. 根据权利要求4或5所述的负极极片，其特征在于，所述聚醚与所述交联聚合物的质量之比在0.015-0.6范围内、可选在0.02-0.5范围内。
  7. 根据权利要求1-6中任一项所述的负极极片，其特征在于，组分(A)中，组分(a)丙烯腈的质量分数为20-60％，组分(b)丙烯酸的质量分数为30-70％，组分(c)的质量分数为0-10％，基于组分(a)、(b)、(c)的总质量计。
  8. 根据权利要求4-7中任一项所述的负极极片，其特征在于，所述聚醚的质量含量范围为0.05-1％，可选为0.08-0.5％，基于负极膜片的总质量计。
  9. 根据权利要求1-8中任一项所述的负极极片，其特征在于，所述交联聚合物的质量含量范围为0.5-3％，可选为0.8-2.3％，基于负极膜片的总质量计。
  10. 一种二次电池，其包括权利要求1-9中任一项所述的负极极片。
  11. 一种制备二次电池的方法，所述二次电池包括权利要求1-9中任一项所述的负极极片，所述方法包括：
    (1)将组分(A)与(B)混合，得到交联混合物；
    (2)制备负极极片，将负极活性物质、任选地导电剂、任选地增稠剂以及(1)中得到的所述交联混合物混合均匀制成负极浆料，涂覆于负极集流体上，经过烘干、冷压、分切得到负极极片；
    所述方法还包括制备或准备正极极片、制备或准备电解液、制备或准备隔离膜的步骤，
    将上述步骤中得到的负极极片、正极极片、电解液、隔离膜组装，在100-130℃下真空加热5-15h以便完成负极膜片中组分(A)与(B)的至少一部分的交联。
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CN113258068A (zh) * 2021-04-28 2021-08-13 东莞市创明电池技术有限公司 一种锂离子电池硅负极用粘结剂及负极浆料及其制备方法
CN114122323A (zh) * 2021-11-30 2022-03-01 珠海冠宇电池股份有限公司 一种负极片、电池及制备方法

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