WO2023230786A1 - 粘结剂、制备方法、二次电池、电池模块、电池包及用电装置 - Google Patents

粘结剂、制备方法、二次电池、电池模块、电池包及用电装置 Download PDF

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WO2023230786A1
WO2023230786A1 PCT/CN2022/096059 CN2022096059W WO2023230786A1 WO 2023230786 A1 WO2023230786 A1 WO 2023230786A1 CN 2022096059 W CN2022096059 W CN 2022096059W WO 2023230786 A1 WO2023230786 A1 WO 2023230786A1
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group
battery
monomer
polymer
preparation
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PCT/CN2022/096059
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English (en)
French (fr)
Inventor
陈煜�
艾少华
张玉玺
曾琦
周鑫
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宁德时代新能源科技股份有限公司
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Priority to KR1020237036984A priority Critical patent/KR20230168182A/ko
Priority to PCT/CN2022/096059 priority patent/WO2023230786A1/zh
Priority to EP22938758.4A priority patent/EP4318679A4/en
Priority to CN202280041647.1A priority patent/CN117480638A/zh
Priority to JP2023565900A priority patent/JP2024526517A/ja
Publication of WO2023230786A1 publication Critical patent/WO2023230786A1/zh
Priority to US18/426,374 priority patent/US20240194879A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/02—Ethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C08F220/12—Esters of monohydric alcohols or phenols
    • C08F220/14—Methyl esters, e.g. methyl (meth)acrylate
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/12—Hydrolysis
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/42—Introducing metal atoms or metal-containing groups
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium batteries, and in particular to a binder, a preparation method, a secondary battery, a battery module, a battery pack and an electrical device.
  • lithium-ion batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. With the popularization of lithium-ion battery applications, higher requirements have been placed on its cycle performance and service life.
  • Binders are commonly used materials in lithium-ion batteries and are in great demand for battery pole pieces, separators, packaging, etc.
  • the existing adhesives have poor adhesion, causing the performance of the battery to drop significantly during use, thereby affecting the service life of the battery. Therefore, existing adhesives still need to be improved.
  • This application was made in view of the above problems, and its purpose is to provide a binder and an electrode containing the binder to reduce swelling of the binder in the electrolyte, thereby improving battery performance.
  • the first aspect of this application provides a binder.
  • the binder is a polymer containing structural units as shown in Formula I and Formula II,
  • R 1 , R 2 , R 3 , R 5 , R 6 and R 7 are each independently selected from hydrogen or a C 1-3 alkyl group substituted or unsubstituted by a substituent, and R 4 is selected from hydrogen, cyano group, Aldehyde group or ester group, M is selected from H, Li, Na, K or NH 4 .
  • -COOM groups that is, carboxylic acid or carboxylate groups
  • this application can improve the polarity of the polymer, reduce the absorption of solvents by the binder in the electrolyte, and thereby reduce the resistance of the electrode.
  • the swelling rate reduces the DC resistance of the battery and improves the power performance and cycle performance of the battery.
  • carboxylic acid or carboxylate groups have higher chemical stability and oxidation stability in the electrolyte.
  • metal cations such as Li + and Na + generated after ionization of carboxylates present in the polymer can increase the content of dissociated ions in the battery electrolyte, promote the transmission of charge carriers, and improve the dynamic performance of the battery.
  • the molar content of the structural units represented by Formula II is 0.1% to 60%, or 10% to 40%, based on the total moles of all structural units in the polymer.
  • the polymer includes a first structural unit shown in formula I in which R 4 is an aldehyde group or an ester group and a second structural unit shown in formula I in which R 4 is hydrogen or cyano group, wherein the first structure
  • the unit is not the same as the second structural unit.
  • the combination of the first structural unit and the second structural unit enables the polymer to have a certain strength, flexibility, and adhesive properties, and the binder absorbs less electrolyte, making the electrode highly resistant to swelling.
  • the molar content of the second structural unit is 20% to 90%, optionally 50% to 80%, based on the total moles of all structural units in the polymer. Controlling the proportion of the second structural unit in the polymer can improve the adhesion of the polymer while reducing the absorption of the electrolyte by the polymer.
  • the second aspect of this application provides a method for preparing an adhesive.
  • the preparation method includes:
  • Preparing the intermediate polymer polymerizing the monomer represented by Formula III to form an intermediate polymer, which contains at least a cyano group, an aldehyde group or an ester group,
  • R 1 , R 2 , and R 3 are each independently selected from hydrogen, substituted or unsubstituted C 1-3 alkyl, and R 4 is selected from hydrogen, cyano group, aldehyde group, or ester group;
  • Modification reaction a modification reaction occurs between the intermediate polymer and an aqueous solution of an alkaline substance, so that at least part of the cyano group, aldehyde group or ester group in the intermediate polymer is converted into COOM, M is selected from H, Li, Na, K or NH 4 .
  • the method has simple preparation process, abundant raw materials and low cost.
  • the ester electrolyte absorbs the electrolyte and simultaneously improves the chemical stability and oxidative stability of the binder.
  • metal cations such as Li + and Na + generated after ionization of carboxylates present in the polymer can increase the content of dissociated ions in the battery electrolyte, promote the transmission of charge carriers, and improve the dynamic performance of the battery.
  • the monomer in the step of preparing the intermediate polymer, is selected from the first monomer represented by formula III in which R 4 is a cyano group, an aldehyde group or an ester group, and a hydrogen or cyano group in which R 4 is
  • the second monomer represented by formula III has a different structure from the first monomer.
  • the first monomer is selected from one or more of acrolein, acrylonitrile, methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, and methyl methacrylate.
  • the second monomer is selected from one or more of ethylene, propylene, butene, and acrylonitrile.
  • the molar ratio of the second monomer to the first monomer is 2:8-9:1, optionally 3:7-8:2, further optionally 5:5-8:2. Adjusting the ratio of the second monomer to the first monomer within a suitable range can take into account the liquid absorbency, flexibility and processability of the adhesive.
  • the weight average molecular weight of the intermediate polymer is 5 ⁇ 10 4 to 1.5 ⁇ 10 6 , optionally 1.5 ⁇ 10 5 to 8 ⁇ 10 5 . Controlling the weight average molecular weight of the intermediate polymer can adjust the processing performance of the intermediate polymer. If the molecular weight is too low, it will be brittle and the adhesive force will be insufficient; if the molecular weight is too high, it will be easy to gel and the modified product will be easy to agglomerate. , difficult to extract.
  • the alkaline substance is selected from one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia water.
  • the above-mentioned materials are simple, easy to obtain, low in cost and conducive to popularization and application.
  • the molar ratio of the total amount of cyano group, aldehyde group, and ester functional group in the first monomer to the basic substance is 1:0.1 ⁇ 1:2, or 1:0.5 ⁇ 1:1.5. Regulating the molar ratio of the total amount of cyano, aldehyde, and ester functional groups in the first monomer to the alkaline substance within an appropriate range can control the degree of hydrolysis of the functional groups, ensuring that the intermediate polymer absorbs less electrolyte and is resistant to oily solvents. It has high solubility and takes into account the usability and processing performance of the pole piece.
  • the reaction temperature of the modification reaction is 35°C to 120°C, optionally 60 to 90°C. Regulating the reaction temperature within an appropriate range can control the degree of hydrolysis of the functional groups, ensuring that the intermediate polymer has less absorption of the electrolyte and high solubility in oily solvents, while taking into account the usability and processing performance of the pole piece.
  • the reaction time of the modification reaction is 1 to 24 hours, optionally 4 to 10 hours. Adjusting the reaction time within an appropriate range can control the degree of hydrolysis of the functional groups, ensuring that the intermediate polymer has less absorption of the electrolyte and high solubility in oily solvents, while taking into account the usability and processing performance of the pole piece.
  • the method further includes: after the modification reaction is completed, adding an acidic solution to the reaction product to adjust the pH value of the reaction system to 6-8. Adjusting the pH value of the reaction system to weakly acidic or neutral can prevent the binder from causing the slurry to gel during the preparation of the electrode slurry, and can improve the stability of the slurry.
  • the third aspect of this application provides a secondary battery, including an electrode assembly and an electrolyte.
  • the electrode assembly includes a positive electrode piece, a separator, and a negative electrode piece.
  • the positive electrode piece includes a positive active material and the first or second aspect of this application. of adhesive.
  • the positive electrode sheet has a low swelling rate in the electrolyte, which can reduce the internal resistance of the battery and improve the power performance and cycle performance of the battery.
  • a fourth aspect of the present application provides a battery module, including the secondary battery of the third aspect of the present application.
  • the battery has reduced internal resistance and improved power performance and cycle performance.
  • a fifth aspect of the present application provides a battery pack, including the battery module of the fourth aspect of the present application.
  • a sixth aspect of this application provides an electrical device, including at least one of the secondary battery of the third aspect of this application, the battery module of the fourth aspect of this application, and the battery pack of the fifth aspect of this application.
  • the battery module of the fourth aspect and the battery pack of the fifth aspect of the present application include the secondary battery of the third aspect, and therefore have the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • 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 2-5.
  • 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
  • a 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) can be added to the method in any order.
  • the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and 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).
  • the binder is a polymer containing structural units as shown in formula I and formula II.
  • R 1 , R 2 , R 3 , R 5 , R 6 and R 7 are each independently selected from hydrogen or a C 1-3 alkyl group substituted or unsubstituted by a substituent, and R 4 is selected from hydrogen, cyano group, Aldehyde group or ester group, M is selected from H, Li, Na, K or NH 4 .
  • binder refers to a chemical compound, polymer, mixture that forms a colloidal solution or colloidal dispersion in a dispersion medium.
  • the dispersion medium of the binder is an aqueous solvent, such as water.
  • the dispersion medium of the adhesive is an oily solvent.
  • the oily solvent include but are not limited to dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, dicarbonate Methyl ester, ethyl cellulose, polycarbonate.
  • adhesives are used to hold electrode materials and/or conductive agents in place and adhere them to conductive metal components to form electrodes.
  • the binder serves as a positive electrode binder and is used to bind the positive electrode active material and/or conductive agent to form an electrode.
  • the binder serves as a negative electrode binder and is used to bind the negative electrode active material and/or conductive agent to form an electrode.
  • polymer includes on the one hand an assembly of chemically homogeneous macromolecules prepared by polymerization reactions (copolymerization, homopolymerization), but differing in degree of polymerization, molar mass and chain length.
  • the term on the other hand also includes derivatives of aggregates of macromolecules formed by polymerization reactions which are obtainable by reaction, for example addition or substitution, of functional groups in said macromolecules and which may be chemically homogeneous or chemically non-uniform compounds.
  • C 1-3 alkyl refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, with no unsaturation present in the radical, having from one to three carbon atoms, and Attached to the rest of the molecule by a single bond.
  • C 1-5 alkyl should be interpreted accordingly. Examples of C 1-3 alkyl groups include, but are not limited to: methyl, ethyl, n-propyl, 1-methylethyl (isopropyl).
  • cyano refers to the -CN group.
  • aldehyde group refers to the -CHO group.
  • ester group refers to a group with the general formula -COOR 9 structural unit, R 9 is selected from a C 1-5 alkyl group substituted or unsubstituted by a substituent, examples of ester groups include but are not limited to : Methyl ester, ethyl ester, propyl ester, butyl ester, amyl ester, isooctyl ester, etc.
  • substituted means substituted by a substituent, each of which is independently selected from: hydroxyl, mercapto, amino, cyano, nitro, aldehyde, halogen atom, C 1-6 alkyl, C 1-6 alkoxy.
  • swelling is a phenomenon in which a polymer absorbs solvent, causing the volume of itself and the electrode in which it is located to expand.
  • a -COOM group that is, a carboxylic acid or carboxylate group
  • this application can improve the polarity of the polymer, reduce the absorption of solvent by the binder in the electrolyte, and thereby reduce the swelling rate of the electrode. Reduce the DC resistance of the battery and improve the power performance and cycle performance of the battery.
  • carboxylic acid or carboxylate groups have higher chemical stability and oxidation stability in the electrolyte.
  • metal cations such as Li + and Na + generated after ionization of carboxylates present in the polymer can increase the content of dissociated ions in the battery electrolyte, promote the transmission of charge carriers, and improve the dynamic performance of the battery.
  • the molar content of the structural units represented by Formula II is 0.1% to 60%, or 10% to 40%, based on the total moles of all structural units in the polymer. In some embodiments, the molar content of the structural unit represented by Formula II is 1% to 60%, or 2% to 60%, or 5% to 60%, or 8% to 60%, or 10 % ⁇ 60%, or 0.1% ⁇ 70%, or 0.1% ⁇ 60%, or 0.1% ⁇ 50%, or 2% ⁇ 40%, or 2% ⁇ 30%, or 5% ⁇ 50%, or 5% to 40%, or 5% to 30%, or 5% to 20%, or 10% to 40%, or 10% to 30%, based on all structural units in the polymer of total moles.
  • the proportion of structural units represented by Formula II is too high, the polymer will be too polar and difficult to dissolve in an oily solvent to form an electrode, especially to form a positive electrode. If the proportion of the structural unit represented by Formula II is too low, the polymer will easily absorb the electrolyte, and the battery cycle performance and power performance will decrease.
  • the solubility of the binder in the oily solvent and the absorption rate of the electrolyte can be taken into consideration, thereby reducing the DC resistance of the battery and improving the power performance and cycle performance of the battery.
  • the polymer includes a first structural unit shown in formula I in which R 4 is an aldehyde group or an ester group and a second structural unit shown in formula I in which R 4 is a hydrogen or cyano group, wherein the first structure The unit is not the same as the second structural unit.
  • the polymer includes a first structural unit in which R 4 is an aldehyde group or an ester group and a second structural unit in which R 4 is hydrogen.
  • the second structural unit in which R 4 is hydrogen or cyano provides a hard segment for the polymer, which enables the polymer to have a certain degree of crystallinity, provides mechanical strength to the binder, and reduces the binder's absorption of the electrolyte.
  • Combining the first structural unit containing an ester group or an aldehyde group can provide soft segments for the polymer, making the polymer flexible. Therefore, the combination of the first structural unit and the second structural unit makes the polymer have a certain strength, flexibility, and adhesive properties, and the binder absorbs less electrolyte, making the electrode highly resistant to swelling. .
  • the molar content of the second structural unit is from 20% to 90%, or from 50% to 80%, based on the total moles of all structural units in the polymer. In some embodiments, the molar content of the second structural unit is 20% to 85%, or 20% to 80%, or 30% to 90%, or 30% to 85%, or 30% to 80%. %, or 40% to 90%, or 40% to 85%, or 40% to 80%, or 45% to 90%, or 45% to 85%, or 45% to 80%, Either 55% to 80%, or 60% to 80%, based on the total moles of all structural units in the polymer.
  • the proportion of the second structural unit in the polymer is too high, the rigidity of the polymer increases and the cohesiveness decreases, making it difficult to function as a binder. If the proportion of the first structural unit in the polymer is too high, the polymer's absorption of the electrolyte increases. , the swelling resistance of the electrode, the power performance and cycle performance of the battery decrease. Controlling the proportion of the second structural unit in the polymer can improve the adhesion of the polymer and simultaneously reduce the absorption of the electrolyte by the polymer.
  • the weight average molecular weight of the polymer ranges from 5 ⁇ 10 4 to 1.5 ⁇ 10 6 , or from 1.5 ⁇ 10 5 to 8 ⁇ 10 5 . In some embodiments, the weight average molecular weight of the polymer is 2 ⁇ 10 5 to 8 ⁇ 10 5 , or 2 ⁇ 10 5 to 7 ⁇ 10 5 , or 3 ⁇ 10 5 to 7 ⁇ 10 5 , or 2 ⁇ 10 5 ⁇ 6 ⁇ 10 5 .
  • weight average molecular weight refers to the statistical average molecular weight averaged over molecular weights of different molecular weights in a polymer.
  • Controlling the weight average molecular weight of the polymer can ensure the viscosity of the polymer and the reasonable matching of chain segments with different molecular weights, improve electrode kinetic conditions, and thereby improve battery performance.
  • a method for preparing an adhesive which method includes:
  • Preparing the intermediate polymer polymerizing the monomer represented by Formula III to form an intermediate polymer, which contains at least a cyano group, an aldehyde group or an ester group,
  • R 1 , R 2 , and R 3 are each independently selected from hydrogen, substituted or unsubstituted C 1-3 alkyl, and R 4 is selected from hydrogen, cyano group, aldehyde group, or ester group;
  • Modification reaction a modification reaction occurs between the intermediate polymer and an aqueous solution of an alkaline substance, so that at least part of the cyano group, aldehyde group or ester group in the intermediate polymer is converted into COOM, M is selected from H, Li, Na, K or NH 4 .
  • the modification reaction will not have a significant impact on the weight average molecular weight of the intermediate polymer.
  • the difference between the weight average molecular weight of the binder and the weight average molecular weight of the corresponding intermediate polymer does not exceed 1,000.
  • the intermediate polymer is obtained by homopolymerizing one monomer. In some embodiments, the intermediate polymer is obtained by copolymerizing two or more monomers. In some embodiments, the intermediate polymer is selected from the group consisting of ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-amyl acrylate copolymer, ethylene-isoacrylate copolymer.
  • octyl copolymer ethylene-acrylonitrile copolymer, ethylene-acrolein copolymer, acrylonitrile-methyl acrylate copolymer, acrylonitrile-isooctyl acrylate copolymer, and acrylonitrile-acrolein copolymer. kind.
  • the cyano group, aldehyde group or ester group on the intermediate polymer is converted into a sodium carboxylate group under the action of NaOH in the modification reaction. In some embodiments, the cyano group, aldehyde group or ester group on the intermediate polymer is converted into a potassium carboxylate group under the action of KOH in the modification reaction. In some embodiments, the cyano group, aldehyde group or ester group on the intermediate polymer is converted into an ammonium carboxylate group under the action of ammonia water in the modification reaction. In some embodiments, after the modification reaction, an acidic solution is added to the reaction system to adjust the pH value to acidic, so that the -COOM group on the intermediate polymer is converted into a carboxylic acid group.
  • the monomer in the step of preparing the intermediate polymer, is selected from the first monomer shown in Formula III in which R 4 is a cyano group, an aldehyde group or an ester group, and the first monomer in which R 4 is a hydrogen or cyano group.
  • the second monomer represented by formula III has a different structure from the first monomer.
  • the method has simple preparation process, abundant raw materials and low cost.
  • the ester electrolyte absorbs the electrolyte and simultaneously improves the chemical stability and oxidative stability of the binder.
  • metal cations such as Li + and Na + generated after ionization of carboxylates present in the polymer can increase the content of dissociated ions in the battery electrolyte, promote the transmission of charge carriers, and improve the dynamic performance of the battery.
  • the first monomer is selected from one or more of acrolein, acrylonitrile, methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, and methyl methacrylate.
  • acrolein acrylonitrile
  • methyl acrylate ethyl acrylate
  • butyl acrylate isooctyl acrylate
  • methyl methacrylate methyl methacrylate.
  • the second monomer is selected from one or more of ethylene, propylene, butene, and acrylonitrile.
  • the above-mentioned materials are simple and easy to obtain, low in cost, and are conducive to popularization and application.
  • the molar ratio of the second monomer to the first monomer is 2:8-9:1, optionally 3:7-8:2, further optionally 5:5-8:2.
  • the binder will have poor flexibility, causing the pole piece to be too brittle and difficult to process; if the proportion of the first monomer is too high, the binder will be too polar and difficult to dissolve in organic solvents. . Adjusting the ratio of the second monomer to the first monomer within a suitable range can take into account the liquid absorbency, flexibility and processability of the adhesive.
  • the weight average molecular weight of the intermediate polymer ranges from 5 ⁇ 10 4 to 1.5 ⁇ 10 6 , or from 1.5 ⁇ 10 5 to 8 ⁇ 10 5 . In some embodiments, the weight average molecular weight of the intermediate polymer is 2 ⁇ 10 5 to 8 ⁇ 10 5 , or 2 ⁇ 10 5 to 7 ⁇ 10 5 , or 3 ⁇ 10 5 to 7 ⁇ 10 5 , or 2 ⁇ 10 5 ⁇ 6 ⁇ 10 5 .
  • Controlling the weight average molecular weight of the intermediate polymer can adjust the processing performance of the intermediate polymer. If the molecular weight is too low, it will be brittle and the adhesive force will be insufficient; if the molecular weight is too high, it will be easy to gel and the modified product will be easy to agglomerate. , difficult to extract.
  • the alkaline substance is selected from one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia water. In some embodiments, the alkaline substance is an organic base. The above-mentioned materials are simple and easy to obtain, low in cost, and are conducive to popularization and application.
  • the molar ratio of the total amount of cyano group, aldehyde group, and ester functional group in the first monomer to the basic substance is 1:0.1-1:2, or 1:0.5-1:1.5. In some embodiments, the molar ratio of the total amount of cyano group, aldehyde group, and ester functional group to the basic substance in the first monomer is 1:0.5-1:2. Regulating the molar ratio of the total amount of cyano, aldehyde, and ester functional groups in the first monomer to the alkaline substance within an appropriate range can control the degree of hydrolysis of the functional groups, ensuring that the intermediate polymer absorbs less electrolyte and is resistant to oily solvents. It has high solubility and takes into account the usability and processing performance of the pole piece.
  • the reaction temperature of the modification reaction is 35°C to 120°C, optionally 60 to 90°C.
  • the upper or lower limit of the reaction temperature at which the intermediate polymer reacts with the aqueous solution of the alkaline substance is selected from the group consisting of 35°C, 45°C, 55°C, 60°C, 70°C, 80°C, 90°C, 100°C °C, 120°C. Regulating the reaction temperature within an appropriate range can control the degree of hydrolysis of the functional groups, ensuring that the intermediate polymer has less absorption of the electrolyte and high solubility in oily solvents, while taking into account the usability and processing performance of the pole piece.
  • the reaction time of the modification reaction is 1 to 24 hours, optionally 4 to 10 hours.
  • the reaction time for the intermediate polymer and the aqueous solution of the alkaline substance to react is 1 h, 4 h, 8 h, 10 h, 12 h, 18 h, or 24 h. Adjusting the reaction time within an appropriate range can control the degree of hydrolysis of the functional groups, ensuring that the intermediate polymer has less absorption of the electrolyte and high solubility in oily solvents, while taking into account the usability and processing performance of the pole piece.
  • the method further includes: after the modification reaction is completed, adding an acidic solution to the reaction product to adjust the pH value of the reaction system to 6-8.
  • the acidic solution is one or more of hydrochloric acid solution, sulfuric acid solution, oxalic acid solution, and acetic acid solution.
  • the mass fraction of the acidic solution is 5 to 20% by weight.
  • Adjusting the pH value of the binder to weakly acidic or neutral can prevent the binder from causing the slurry to gel during the preparation of the electrode slurry, and can improve the stability of the slurry.
  • an electrode including an electrode active material and a binder of any embodiment or a binder prepared according to the preparation method of any embodiment.
  • the electrode has a low swelling rate in the electrolyte, which can reduce the internal resistance of the battery and improve the power performance and cycle performance of the battery.
  • the electrode active material is a cathode active material
  • the cathode active material includes a lithium-containing transition metal oxide
  • the electrode pole piece includes a current collector and an electrode diaphragm coated on the surface of the current collector.
  • the electrode diaphragm includes an electrode active material and a binder of any embodiment or a preparation method according to any embodiment. Prepared adhesive.
  • the mass percentage of the adhesive of any embodiment or the adhesive prepared according to the preparation method of any embodiment in the film is 1% to 8%, or 1% to 4%. %, or 2% to 4%.
  • a battery including the electrode in any embodiment.
  • the battery has reduced internal resistance and improved power performance and cycle performance.
  • 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 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 includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • 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 binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • 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
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • This application has no specific restrictions on the type of electrolyte and can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely 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.
  • FIG. 1 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3.
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4.
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • an electrical device including the battery in any embodiment.
  • the electrical device includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 6 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • the binder is prepared as follows:
  • Preparation of intermediate polymer Add 100g methyl acrylate (first monomer), 300mL deionized water, 2g emulsifier alkylphenol polyoxyethylene ether OP-10 and 3g ammonium persulfate as initiator in a high-pressure reactor. After stirring and mixing, raise the temperature to 90°C, introduce 8.2g of ethylene (second monomer), control the pressure and react at 10MPa for 6 hours.
  • ethylene-methyl acrylate (second monomer-first monomer) polymer which is an intermediate polymer, in which the molar ratio of ethylene to methyl acrylate in the ethylene-methyl acrylate copolymer is 8 :2.
  • Modification reaction Add 100g of ethylene-methyl acrylate polymer powder and 300mL of deionized water into the reaction kettle, stir for 30 minutes and mix evenly. Then 12.1g LiOH was dissolved in 50mL deionized water to prepare an alkaline solution and added to the reaction kettle. Then, the temperature of the reaction kettle was raised to 90°C for 4 hours. After the reaction was completed, the temperature of the reaction kettle returned to room temperature, a 5% acetic acid solution was prepared, and added dropwise to the reaction kettle to adjust the pH value of the product to neutral, and then the product was dried. , that is, a binder is obtained, and the modification reaction converts the ester functional group derived from the first monomer methyl acrylate on the intermediate polymer into a -COOLi group.
  • the binder prepared in Example 1, the lithium iron phosphate cathode active material, the conductive agent carbon black, and N-methylpyrrolidone (NMP) were stirred and mixed evenly in a weight ratio of 1.28:62.2:0.52:36 to obtain a cathode slurry. material; then, the positive electrode slurry is evenly coated on the positive electrode current collector, and then dried, cold pressed, and cut to obtain the positive electrode piece.
  • NMP N-methylpyrrolidone
  • Ionized water mix evenly to prepare negative electrode slurry; apply the negative electrode slurry one or more times evenly on the negative electrode current collector copper foil, dry, cold press, and cut to obtain negative electrode pieces.
  • the positive electrode sheet, isolation film and negative electrode sheet prepared in Example 1 are stacked in order so that the isolation film is between the positive and negative electrode sheets to play an isolation role. Then, the bare battery core is obtained by winding and welding to the bare battery core. The tabs are removed, and the bare battery core is put into an aluminum case, baked at 80°C to remove water, and then electrolyte is injected and sealed to obtain an uncharged battery. The uncharged battery then undergoes processes such as standing, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product of Example 1.
  • the batteries of Examples 2 to 28 and the batteries of Comparative Examples 1 to 10 are similar to the battery preparation methods of Example 1, but the raw materials and reaction conditions for binder preparation are adjusted. The different parameters are detailed in Table 1.
  • Example 2 the monomers used to prepare the intermediate polymer are ethylene and acrylonitrile, and the modification reaction causes the cyano group derived from the first monomer acrylonitrile on the intermediate polymer to be converted into a -COOLi group.
  • Example 3 the monomers used to prepare the intermediate polymer are ethylene and acrolein, and the modification reaction converts the aldehyde group derived from the first monomer acrolein on the intermediate polymer into a -COOLi group.
  • Example 4 the monomers used to prepare the intermediate polymer are acrylonitrile and methyl acrylate, and the modification reaction causes the ester group derived from the first monomer methyl acrylate on the intermediate polymer to be converted into a -COOLi group.
  • Example 5 the monomers used to prepare the intermediate polymer are acrylonitrile and acrolein, and the modification reaction converts the aldehyde group derived from the first monomer acrylic aldehyde on the intermediate polymer into a -COOLi group.
  • Example 6 the alkaline substance is sodium hydroxide, and the modification reaction causes the ester functional group derived from the first monomer methyl acrylate on the intermediate polymer to be converted into a -COONa group.
  • the alkaline substance is ammonia water
  • the modification reaction converts the ester functional group derived from the first monomer methyl acrylate on the intermediate polymer into a -COONH4 group.
  • Example 8 the basic substance is potassium hydroxide, and the modification reaction causes the ester functional group derived from the first monomer methyl acrylate on the intermediate polymer to be converted into a -COOK group.
  • Example 9 after the modification reaction is completed during the preparation of the binder, 5% acetic acid solution is added dropwise, the pH value of the product in the reaction kettle is adjusted to 2-3, stirring is continued for 2 hours, and then the product is dried and then used. Wash with deionized water three times, dry, and the modification reaction converts the ester functional group derived from the first monomer methyl acrylate into a -COOH group on the intermediate polymer.
  • Example 10 the input molar ratio of ethylene and methyl acrylate is 6:4.
  • Example 11 the input molar ratio of ethylene and methyl acrylate is 5:5.
  • Example 12 the input molar ratio of ethylene and methyl acrylate is 4:6.
  • Example 13 the molar ratio of ethylene and methyl acrylate was 3:7.
  • Example 14 the molar ratio of ethylene and methyl acrylate was 2:8.
  • Example 15 the molar ratio of ethylene and methyl acrylate was 9:1.
  • Example 16 the molar ratio of methyl acrylate to lithium hydroxide is 1:0.5.
  • Example 17 The molar ratio of methyl acrylate to lithium hydroxide in Example 17 is 1:1.5.
  • Example 18 the molar ratio of methyl acrylate to lithium hydroxide is 1:2.
  • the molar ratio of methyl acrylate to lithium hydroxide in Example 19 is 1:0.1.
  • the reaction temperature of the modification reaction in Example 20 is 35°C.
  • the reaction temperature of the modification reaction in Example 21 is 60°C.
  • the reaction temperature of the modification reaction in Example 22 is 75°C.
  • the reaction temperature of the modification reaction in Example 23 is 120°C.
  • the reaction temperature of the modification reaction in Example 24 is 60°C, and the reaction time is 0.2h.
  • the reaction temperature of the modification reaction in Example 25 is 60°C, and the reaction time is 1 hour.
  • the reaction temperature of the modification reaction in Example 26 is 60°C, and the reaction time is 8 hours.
  • the reaction temperature of the modification reaction in Example 27 is 60°C, and the reaction time is 10 h.
  • the reaction temperature of the modification reaction in Example 28 is 60°C, and the reaction time is 24h.
  • Comparative Examples 1-5 directly used the intermediate polymer prepared in Examples 1-5 as the binder, and the intermediate polymer was modified without adding alkaline substances;
  • Comparative Examples 6-11 directly used the intermediate polymer prepared in Examples 10-15 as the binder, and the intermediate polymer was converted without adding alkaline substances. The specific parameters are shown in Table 1.
  • pole pieces and batteries obtained in the above-mentioned Examples 1 to 28 and Comparative Examples 1 to 11 were subjected to performance tests.
  • the test methods are as follows:
  • the binder obtained in Example 1 was dried in a vacuum oven at 80°C for 12 hours, 0.1 g was dissolved in 20 mL of N-methylpyrrolidone, filtered using a filter membrane with a pore size of 10 ⁇ m, and 5 mL was used to test the weight average molecular weight with a gel permeation chromatograph. , the detector used is differential refraction detection method, and the standard material is polystyrene.
  • M in formula II is a metal element, that is, Li, Na, K
  • inductively coupled plasma emission spectrometry ICP
  • the digestion solvent is concentrated nitric acid.
  • the molar content N II (%) of the structural unit of formula II can be calculated by the following formula:
  • M is the molecular weight of the total binder structural unit
  • M M is the molecular weight of the M element.
  • the binder needs to be subjected to ion replacement treatment first to replace M with Na.
  • the specific scheme is as follows: Pour 10g of binder powder into 200mL of 5wt% sodium chloride aqueous solution. , stir for 1 hour at 40°C for ion replacement, and then filter. The resulting powder is washed three times in deionization to remove sodium ions adsorbed on the surface. The product is then dried and sent to ICP for testing the mass percentage of sodium element W Na (%) .
  • the molar content N II (%) of the structural unit of formula II can be calculated by the following formula:
  • M is the molecular weight of the total binder structural unit.
  • the molar content of the second structural unit the input amount of the second monomer/(the input amount of the second monomer + the input amount of the first monomer)
  • the test process for the swelling rate of the electrode piece is as follows: After cold pressing, the positive electrode piece prepared in the Example or Comparative Example is cut into an area of 5*5cm, weighed and recorded as m 0 , and the corresponding battery in the Example or Comparative Example is placed at 60 After 7 days of storage at °C, cut out 5*5cm from the positive electrode piece, quickly wipe the residual electrolyte on the surface and weigh it, record it as m 1.
  • the swelling rate of the electrode piece can be calculated by the following formula:
  • Pole piece swelling rate (%) (m 1 -m 0 )/m 0 ⁇ 100%
  • the battery DC impedance test process is as follows: at 25°C, charge the battery prepared in the Example or Comparative Example with a constant current of 1/3C to 4.3V, then charge with a constant voltage of 4.3V until the current is 0.05C, and then leave it aside for 5 minutes. , record the voltage V 1 . Then discharge at 1/3C for 30 seconds and record the voltage V 2 , then (V 2 -V 1 )/1/3C, and obtain the internal resistance DCR of the battery after the first cycle.
  • the battery capacity retention rate data corresponding to the examples or comparative examples in Table 2 is the data measured after 100 cycles under the above test conditions, that is, the value of P100.
  • the testing procedures of other examples and comparative examples are the same as above.
  • a binder which is a polymer containing structural units as shown in Formula I and Formula II,
  • R 1 , R 2 , R 3 , R 5 , R 6 and R 7 are each independently selected from hydrogen, R 4 is selected from hydrogen, cyano group, aldehyde group or ester group, M is selected from H, Li, Na, K or NH 4 .
  • R 4 is selected from hydrogen, cyano group, aldehyde group or ester group
  • M is selected from H, Li, Na, K or NH 4 .
  • the molar content of the structural unit represented by Formula II is 0.1% to 60%, based on the total number of moles of all structural units in the polymer. Compared with Comparative Examples 1 to 11, the swelling rate of the pole pieces is reduced, the internal resistance of the battery is reduced, and the capacity retention rate is increased. In Examples 1 to 28, when the molar content of the structural unit represented by Formula II is 10% to 40%, the internal resistance of the battery decreases more significantly, and the cycle capacity retention rate is higher.
  • the polymer includes a first structural unit represented by Formula I in which R 4 is a cyano group, an aldehyde group or an ester group, and a second structural unit represented by the Formula I in which R 4 is hydrogen or a cyano group,
  • the first structural unit and the second structural unit are different.
  • the swelling rate of the pole pieces is reduced, the internal resistance of the battery is reduced, and the cycle capacity retention rate is increased.
  • the molar content of the second structural unit is 20% to 90%, based on the total number of moles of all structural units in the polymer. Compared with Comparative Examples 1 to 11, the swelling rate of the pole pieces is reduced, the internal resistance of the battery is reduced, and the cycle capacity retention rate is increased. In Example 15, when the proportion of structural units derived from ethylene monomer in the polymer is 90%, although the swelling rate of the electrode piece is lower, the adhesion of the electrode piece is poor and the cycle stability of the battery becomes worse. Therefore, the cycle capacity retention rate of the battery decreases. When the molar content of the second structural unit is 50% to 80%, based on the total number of moles of all structural units in the polymer, the battery has lower resistance and a higher cycle capacity retention rate.

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Abstract

本申请提供了一种粘结剂、制备方法、二次电池、电池模块、电池包及用电装置。该粘结剂为含有如式(I)、式(II)所示的结构单元的聚合物，其中，R 1、R 2、R 3、R 5、R 6、R 7各自独立地选自氢或被取代基取代或未取代的C 1-3烷基，R 4选自氢、氰基、醛基或酯基，M选自H、Li、Na、K或NH 4。本申请的粘结剂具有优良的抗溶胀性能，对应的二次电池的循环性能和功率性能显著提高。

Description

粘结剂、制备方法、二次电池、电池模块、电池包及用电装置 技术领域
本申请涉及锂电池技术领域，尤其涉及一种粘结剂、制备方法、二次电池、电池模块、电池包及用电装置。
背景技术
近年来，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。随着锂离子电池应用的普及，对其循环性能、使用寿命等也提出了更高的要求。
粘结剂是锂离子电池中的常用材料，在电池的极片、隔离膜、封装处等均有很大需求。但是现有的粘结剂粘结性差，导致电池在使用过程中性能大幅度下降，进而影响电池的使用寿命。因此，现有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，提供一种粘结剂及包含该粘结剂的电极，以降低粘结剂在电解液中的溶胀，从而提高电池性能。
本申请的第一方面提供了一种粘结剂，粘结剂为含有如式I、式II所示的结构单元的聚合物，
Figure PCTCN2022096059-appb-000001
其中，R 1、R 2、R 3、R 5、R 6、R 7各自独立地选自氢或被取代基取代或未取代的C 1-3烷基，R 4选自氢、氰基、醛基或酯基，M选自H、Li、Na、K或NH 4。
由此，本申请通过在聚合物中包括-COOM基团，即羧酸或羧酸盐基团，能够提高聚合物极性，减少粘结剂在电解液中对溶剂的吸收，进而降低电极的溶胀率，减小电池的直流电阻，提高电池的功率性能和循环性能。同时，羧酸或羧酸盐基团在电解液中具有较高的化学稳定性和氧化稳定性。另外，聚合物中存在的羧酸盐电离后生成的Li +、Na +等金属阳离子可增加电池电解液中的解离离子含量，促进电荷载体的传输，提升电池的动力学性能。
在任意实施方式中，式II所示的结构单元的摩尔含量为0.1％～60％，或为10％～40％，基于聚合物中所有结构单元的总摩尔数计。通过控制式II所示的结构单元的比例能够兼顾粘结剂在油性溶剂中的溶解性和对电解液的吸收率，进而降低电池的直流电阻，提高电池的功率性能和循环性能。
在任意实施方式中，聚合物包含R 4为醛基或酯基的式I所示的第一结构单元和R 4为氢或氰基的式I所示的第二结构单元，其中第一结构单元与第二结构单元不相同。第一结构单元和第二结构单元的搭配使得聚合物既具有一定的强度，又兼具柔韧性、粘结性，而且粘结剂对电解液的吸收少，使得电极抗溶胀性强。
在任意实施方式中，第二结构单元的摩尔含量为20％～90％，可选为50％～80％，基于聚合物中所有结构单元的总摩尔数计。控制第二结构单元在聚合物中的比例可以提高聚合物的粘结性，同时减少聚合物对电解液的吸收。
本申请的第二方面提供了一种粘结剂的制备方法，制备方法包括：
制备中间体聚合物：将式III所示的单体进行聚合形成中间体聚合物，中间体聚合物至少含有氰基、醛基或酯基，
Figure PCTCN2022096059-appb-000002
在式III中，R 1、R 2、R 3各自独立地选自氢、取代或未取代的C 1- 3烷基，R 4选自氢、氰基、醛基或酯基；
改性反应：使中间体聚合物与碱性物质的水溶液发生改性反应，使得中间体聚合物中的至少部分氰基、醛基或酯基转化为COOM，M选自H、Li、Na、K或NH 4。
该方法制备过程简单，原材料丰富，成本低。通过氰基、醛基和酯基在碱性条件下发生水解反应，部分或全部转化为羧酸或羧酸盐基团，提高聚合物的极性，降低粘结剂在电解液、尤其是聚酯类电解液中对电解液的吸收，同时提高粘结剂的化学稳定性和氧化稳定性。另外，聚合物中存在的羧酸盐电离后生成的Li +、Na +等金属阳离子可增加电池电解液中的解离离子含量，促进电荷载体的传输，提升电池的动力学性能。
在任意实施方式中，在制备中间体聚合物的步骤中，单体选自R 4为氰基、醛基或酯基的式III所示的第一单体和R 4为氢或氰基的式III所示的第二单体，第二单体与第一单体结构不同。
在任意实施方式中，第一单体选自丙烯醛、丙烯腈、丙烯酸甲酯、丙烯酸乙酯、丙烯酸丁酯、丙烯酸异辛酯、甲基丙烯酸甲酯中的一种或多种。
在任意实施方式中，第二单体选自乙烯、丙烯、丁烯、丙烯腈中的一种或多种。
在任意实施方式中，第二单体与第一单体的摩尔比为2∶8～9∶1，可选为3∶7～8∶2，进一步可选为5∶5～8∶2。调控第二单体与第一单体的比例在合适范围可以兼顾粘结剂的吸液性、柔性和可加工性。
在任意实施方式中，中间体聚合物的重均分子量为5×10 4～1.5×10 6，可选为1.5×10 5～8×10 5。控制中间体聚合物的重均分子量可以调节中间体聚合物的加工性能，分子量过低，则脆性大，粘结力不足；分子量过高，则容易凝胶，且改性后的产物容易结块，不易提取。
在任意实施方式中，碱性物质选自氢氧化锂、氢氧化钠、氢氧化钾、氨水中的一种或多种。上述材料简单易得、成本低、利于推广应用。
在任意实施方式中，第一单体中的氰基、醛基、酯基官能团总量 与碱性物质的摩尔比为1∶0.1～1∶2，或为1∶0.5～1∶1.5。调控第一单体中的氰基、醛基、酯基官能团总量与碱性物质的摩尔比在合适范围可以控制官能团的水解程度，保证中间体聚合物对电解液的吸收少以及在油性溶剂中的溶解性高，同时兼顾极片的使用性能和加工性能。
在任意实施方式中，改性反应的反应温度为35℃～120℃，可选为60～90℃。调控反应温度在合适范围可以控制官能团的水解程度，保证中间体聚合物对电解液的吸收少以及在油性溶剂中的溶解性高，同时兼顾极片的使用性能和加工性能。
在任意实施方式中，改性反应的反应时间为1～24h，可选为4～10h。调控反应时间在合适范围可以控制官能团的水解程度，保证中间体聚合物对电解液的吸收少以及在油性溶剂中的溶解性高，同时兼顾极片的使用性能和加工性能。
在任意实施方式中，该方法还包括：改性反应结束后，向反应产物中加入酸性溶液将反应体系的pH值调至6～8。调节反应体系的pH值至弱酸性或中性可以防止粘结剂在制备电极浆料过程中导致浆料出现凝胶，能够提高浆料稳定性。
本申请的第三方面提供一种二次电池，包括电极组件和电解液，电极组件包括正极极片、隔离膜、负极极片，正极极片包括正极活性物质和本申请第一或第二方面的粘结剂。该正极极片在电解液中溶胀率低，能够降低电池内阻、提高电池的功率性能和循环性能。
本申请的第四方面提供一种电池模块，包括本申请第三方面的二次电池。该电池具有降低的内阻和提高的功率性能以及循环性能。
本申请的第五方面提供一种电池包，包括本申请第四方面的电池模块。
本申请第六方面提供一种用电装置，包括本申请第三方面的二次电池、本申请第四方面的电池模块、本申请第五方面的电池包中的至少一种。
本申请第四方面的电池模块、第五方面的电池包因包括与第三方面的二次电池，故具有与二次电池相同的优势。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的粘结剂、制备方法、电极、电池及用电装置的实施方式。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，附图及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2-5。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，方法包括步骤(a)和(b)，表示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，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，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，“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)。
随着PVDF原料成本的增加，一些具有优良柔性的非氟含酯类粘结剂被应用于极片制造过程，但是这类含酯类粘结剂由于其自身吸收电解液而显著加剧极片在电解液中的溶胀程度，进而导致电池的循环性能和功率性能显著降低。基于上述技术问题，本申请开发出一种使极片具有优良抗溶胀性能的粘结剂，显著提高电池的功率性能和循环性能。
[粘结剂]
基于此，本申请提出了一种粘结剂，粘结剂为含有如式I、式II 所示的结构单元的聚合物，
Figure PCTCN2022096059-appb-000003
其中，R 1、R 2、R 3、R 5、R 6、R 7各自独立地选自氢或被取代基取代或未取代的C 1-3烷基，R 4选自氢、氰基、醛基或酯基，M选自H、Li、Na、K或NH 4。
在本文中，术语“粘结剂”是指在分散介质中形成胶体溶液或胶体分散液的化学化合物、聚合物、混合物。
在一些实施方式中，粘结剂的分散介质是水性溶剂，如水。在一些实施方式中，粘接剂的分散介质是油性溶剂，油性溶剂的示例包括但不限于二甲基乙酰胺、N，N-二甲基甲酰胺、N-甲基吡咯烷酮、丙酮、碳酸二甲酯、乙基纤维素、聚碳酸酯。
在一些实施方式中，粘结剂用于将电极材料及/或导电剂固定在合适位置并将它们粘附在导电金属部件以形成电极。
在一些实施方式中，粘结剂作为正极粘结剂，用于粘结正极活性材料及/或导电剂以形成电极。
在一些实施方式中，粘结剂作为负极粘结剂，用于粘结负极活性材料及/或导电剂以形成电极。
在本文中，术语“聚合物”一方面包括通过聚合反应(共聚、均聚)制备的化学上均一的、但在聚合度、摩尔质量和链长方面不同的大分子的集合体。该术语另一方面也包括由聚合反应形成的这样的大分子集合体的衍生物，即可以通过上述大分子中的官能团的反应，例如加成或取代获得的并且可以是化学上均一的或化学上不均一的化合物。
在本文中，术语“C 1-3烷基”是指仅由碳和氢原子组成的直链或支链烃链基团，基团中不存在不饱和，具有从一至三个碳原子，并且通过单键附接到分子的其余部分。术语“C 1-5烷基”应相应解释。C 1-3烷基的示例包括但不限于：甲基、乙基、正丙基、1-甲基乙基(异丙基)。
在本文中，术语“氰基”指的是-CN基团。
在本文中，术语“醛基”指的是-CHO基团。
在本文中，术语“酯基”是指通式为-COOR 9结构单元的基团，R 9选自被取代基取代或未取代的C 1-5烷基，酯基的示例包括但不限于：甲酯、乙酯、丙酯、丁酯、戊酯、异辛酯等。
在本文中，术语“取代”是指被取代基取代，其中的取代基各自独立地选自：羟基、巯基、氨基、氰基、硝基、醛基、卤素原子、C 1-6烷基、C 1-6烷氧基。
在本文中，术语“溶胀”是高分子聚合物吸收溶剂，使得自身及其所在的电极体积发生膨胀的现象。
本申请通过在聚合物中包括-COOM基团，即羧酸或羧酸盐基团，能够提高聚合物极性，减少粘结剂在电解液中对溶剂的吸收，进而降低电极的溶胀率，减小电池的直流电阻，提高电池的功率性能和循环性能。同时，羧酸或羧酸盐基团在电解液中具有较高的化学稳定性和氧化稳定性。另外，聚合物中存在的羧酸盐电离后生成的Li +、Na +等金属阳离子可增加电池电解液中的解离离子含量，促进电荷载体的传输，提升电池的动力学性能。
在一些实施方式中，式II所示的结构单元的摩尔含量为0.1％～60％，或为10％～40％，基于聚合物中所有结构单元的总摩尔数计。在一些实施方式中，式II所示的结构单元的摩尔含量为1％～60％，或为2％～60％，或为5％～60％，或为8％～60％，或为10％～60％，或为0.1％～70％，或为0.1％～60％，或为0.1％～50％，或为2％～40％，或为2％～30％，或为5％～50％，或为5％～40％，或为5％～30％，或为5％～20％，或为10％～40％，或为10％～30％，基于聚合物中所有结构单元的总摩尔数计。
若式II所示的结构单元的比例过高，聚合物极性过大，难以溶解在油性溶剂中成型电极，尤其是成型为正极电极。若式II所示的结构单元的比例过低，聚合物易吸收电解液，电池循环性能和功率性能下降。通过控制式II所示的结构单元的比例能够兼顾粘结剂在油性溶剂中的溶解性和对电解液的吸收率，进而降低电池的直流电阻，提高电池的功率性能和循环性能。
在一些实施方式中，聚合物包含R 4为醛基或酯基的式I所示的第一结构单元和R 4为氢或氰基的式I所示的第二结构单元，其中第一结构单元与第二结构单元不相同。
在一些实施方式中，聚合物包含R 4为醛基或酯基的第一结构单元和R 4为氢的第二结构单元。
R 4为氢或氰基的第二结构单元为聚合物提供硬链段，能够使得聚合物具有一定的结晶性，为粘结剂提供力学强度，同时降低粘结剂对电解液的吸收，同时配合含有酯基或醛基的第一结构单元，可以为聚合物提供软链段，使聚合物兼具柔韧性。由此，第一结构单元和第二结构单元的搭配使得聚合物既具有一定的强度，又兼具柔韧性、粘结性，而且粘结剂对电解液的吸收少，使得电极抗溶胀性强。
在一些实施方式中，第二结构单元的摩尔含量为20％～90％，或为50％～80％，基于聚合物中所有结构单元的总摩尔数计。在一些实施方式中，第二结构单元的摩尔含量为20％～85％，或为20％～80％，或为30％～90％，或为30％～85％，或为30％～80％，或为40％～90％，或为40％～85％，或为40％～80％，或为45％～90％，或为45％～85％，或为45％～80％，或为55％～80％，或为60％～80％，基于聚合物中所有结构单元的总摩尔数计。
第二结构单元在聚合物中比例过高，聚合物刚性增加、粘结性下降，难以发挥粘结剂的作用，第一结构单元在聚合物中比例过高，聚合物对电解液的吸收增加，电极的抗溶胀性、电池的功率性能和循环性能下降。控制第二结构单元在聚合物中的比例可以提高聚合物的粘结性，同时降低聚合物对电解液的吸收。
在一些实施方式中，聚合物的重均分子量为5×10 4～1.5×10 6，或为1.5×10 5～8×10 5。在一些实施方式中，聚合物的重均分子量为2×10 5～8×10 5，或2×10 5～7×10 5，或3×10 5～7×10 5，或2×10 5～6×10 5。
在本文中，术语“重均分子量”是指聚合物中用不同分子量的分子重量平均的统计平均分子量。
控制聚合物的重均分子量可以保证聚合物的粘性，以及具有不同分子量的链段的合理搭配，提高电极动力学条件，进而提高电池性能。
本申请的一个实施方式中，提供一种粘结剂的制备方法，该方法包括：
制备中间体聚合物：将式III所示的单体进行聚合形成中间体聚合物，中间体聚合物至少含有氰基、醛基或酯基，
Figure PCTCN2022096059-appb-000004
在式III中，R 1、R 2、R 3各自独立地选自氢、取代或未取代的C 1- 3烷基，R 4选自氢、氰基、醛基或酯基；
改性反应：使中间体聚合物与碱性物质的水溶液发生改性反应，使得中间体聚合物中的至少部分氰基、醛基或酯基转化为COOM，M选自H、Li、Na、K或NH 4。
可以理解，改性反应不会对中间体聚合物的重均分子量产生显著影响，本申请中粘结剂的重均分子量与其对应的中间体聚合物的重均分子量的差值不超过1000。
在一些实施方式中，中间体聚合物为一种单体均聚获得的。在一些实施方式中，中间体聚合物为两种或更多种单体共聚获得的。在一些实施方式中，中间体聚合物选自乙烯-丙烯酸甲酯共聚物、乙烯-甲基丙烯酸甲酯共聚物、乙烯-丙烯酸乙酯共聚物、乙烯-丙烯酸戊酯共聚物、乙烯-丙烯酸异辛酯共聚物、乙烯-丙烯腈共聚物、乙烯-丙烯醛共聚物、丙烯腈-丙烯酸甲酯共聚物、丙烯腈-丙烯酸异辛酯共聚物、丙烯腈-丙烯醛共聚物的一种或多种。
在一些实施方式中，中间体聚合物上的氰基、醛基或酯基在改性反应中NaOH的作用下转化为羧酸钠基团。在一些实施方式中，中间体聚合物上的氰基、醛基或酯基在改性反应中KOH的作用下转化为羧酸钾基团。在一些实施方式中，中间体聚合物上的氰基、醛基或酯基在改性反应中氨水的作用下转化为羧酸铵基团。在一些实施方式中，在改性反应后向反应体系中加入酸性溶液，调节pH值为酸性，使得中间体聚合物上的-COOM基团转化为羧酸基团。
在一些实施方式中，在制备中间体聚合物的步骤中，单体选自R 4 为氰基、醛基或酯基的式III所示的第一单体和R 4为氢或氰基的式III所示的第二单体，第二单体与第一单体结构不同。
该方法制备过程简单，原材料丰富，成本低。通过氰基、醛基和酯基在碱性条件下发生水解反应，部分或全部转化为羧酸或羧酸盐基团，提高聚合物的极性，降低粘结剂在电解液、尤其是聚酯类电解液中对电解液的吸收，同时提高粘结剂的化学稳定性和氧化稳定性。另外，聚合物中存在的羧酸盐电离后生成的Li +、Na +等金属阳离子可增加电池电解液中的解离离子含量，促进电荷载体的传输，提升电池的动力学性能。
在一些实施方式中，第一单体选自丙烯醛、丙烯腈、丙烯酸甲酯、丙烯酸乙酯、丙烯酸丁酯、丙烯酸异辛酯、甲基丙烯酸甲酯中的一种或多种。上述材料简单易得、成本低，利于推广应用。
在一些实施方式中，第二单体选自乙烯、丙烯、丁烯、丙烯腈中的一种或多种。上述材料简单易得、成本低，利于推广应用。
在一些实施方式中，第二单体与第一单体的摩尔比为2∶8～9∶1，可选为3∶7～8∶2，进一步可选为5∶5～8∶2。
若第二单体比例过高，则粘结剂柔性差，导致极片脆性过高，难以加工；若第一单体比例过高，则粘结剂极性过高，难以溶解在有机溶剂中。调控第二单体与第一单体的比例在合适范围可以兼顾粘结剂的吸液性、柔性和可加工性。
在一些实施方式中，中间体聚合物的重均分子量为5×10 4～1.5×10 6，或为1.5×10 5～8×10 5。在一些实施方式中，中间体聚合物的重均分子量为2×10 5～8×10 5，或2×10 5～7×10 5，或3×10 5～7×10 5，或2×10 5～6×10 5。
控制中间体聚合物的重均分子量可以调节中间体聚合物的加工性能，分子量过低，则脆性大，粘结力不足；分子量过高，则容易凝胶，且改性后的产物容易结块，不易提取。
在一些实施方式中，碱性物质选自氢氧化锂、氢氧化钠、氢氧化钾、氨水中的一种或多种。在一些实施方式中，碱性物质为有机碱。上述材料简单易得、成本低，利于推广应用。
在一些实施方式中，第一单体中的氰基、醛基、酯基官能团总量与碱性物质的摩尔比为1∶0.1～1∶2，或为1∶0.5～1∶1.5。在一些实施方式中，第一单体中的氰基、醛基、酯基官能团总量与碱性物质的摩尔比为1∶0.5～1∶2。调控第一单体中的氰基、醛基、酯基官能团总量与碱性物质的摩尔比在合适范围可以控制官能团的水解程度，保证中间体聚合物对电解液的吸收少以及在油性溶剂中的溶解性高，同时兼顾极片的使用性能和加工性能。
在一些实施方式中，改性反应的反应温度为35℃～120℃，可选为60～90℃。在一些实施方式中，中间体聚合物与碱性物质的水溶液混合发生反应的反应温度的上限或下限选自35℃、45℃、55℃、60℃、70℃、80℃、90℃、100℃、120℃。调控反应温度在合适范围可以控制官能团的水解程度，保证中间体聚合物对电解液的吸收少以及在油性溶剂中的溶解性高，同时兼顾极片的使用性能和加工性能。
在一些实施方式中，改性反应的反应时间为1～24h，可选为4～10h。在一些实施方式中，中间体聚合物与碱性物质的水溶液混合发生反应的反应时间为1h、4h、8h、10h、12h、18h、24h。调控反应时间在合适范围可以控制官能团的水解程度，保证中间体聚合物对电解液的吸收少以及在油性溶剂中的溶解性高，同时兼顾极片的使用性能和加工性能。
在一些实施方式中，该方法还包括：改性反应结束后，向反应产物中加入酸性溶液将反应体系的pH值调至6～8。在一些实施方式中，酸性溶液为盐酸溶液，硫酸溶液，草酸溶液、醋酸溶液中的一种或多种。在一些实施方式中，酸性溶液的质量分数为5～20重量％。
调节粘结剂的pH值至弱酸性或中性可以防止粘结剂在制备电极浆料过程中导致浆料出现凝胶，能够提高浆料稳定性。
本申请的一个实施方式中，提供一种电极，包括电极活性物质和任一实施方式的粘结剂或根据任一实施方式的制备方法制备的粘结剂。该电极在电解液中溶胀率低，能够降低电池内阻、提高电池的功率性能和循环性能。
在一些实施方式中，电极活性物质为正极活性材料，正极活性材 料包括含锂的过渡金属氧化物。
在一些实施方式中，电极极片包括集流体及涂布在集流体表面的电极膜片，电极膜片中包括电极活性物质和任一实施方式的粘结剂或根据任一实施方式的制备方法制备的粘结剂。
在一些实施方式中，任一实施方式的粘结剂或根据任一实施方式的制备方法制备的粘结剂在膜片中的质量百分含量为1％～8％，或为1％～4％，或为2％～4％。
本申请的一个实施方式中，提供一种电池，包括任一实施方式中的电极。该电池具有降低的内阻和提高的功率性能以及循环性能。
另外，以下适当参照附图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。
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粘结剂。所述粘结剂可选自丁苯橡胶(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。
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。
[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。
[二次电池]
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。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
[电池模块]
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
[电池包]
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池 箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
[用电装置]
本申请的一个实施方式中，提供一种用电装置，包括任一实施方式中的电池。
所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
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。
实施例1
1)粘结剂的制备
粘结剂的制备方法如下：
制备中间体聚合物：在高压反应釜中加入100g丙烯酸甲酯(第 一单体)，300mL去离子水，2g乳化剂烷基酚聚氧乙烯醚OP-10以及3g过硫酸铵作为引发剂，待搅拌混匀后，将温度升至90℃，通入8.2g乙烯(第二单体)，控制压力在10MPa下反应6h，反应结束后，将反应乳液置于0℃下10h析出固体，随后抽滤，烘干得到乙烯-丙烯酸甲酯(第二单体-第一单体)聚合物，即中间体聚合物，其中乙烯-丙烯酸甲酯共聚物中乙烯与丙烯酸甲酯的摩尔比为8∶2。
改性反应：取100g乙烯-丙烯酸甲酯聚合物粉末与300mL去离子水加入反应釜中，搅拌30min混合均匀。随后将12.1g LiOH溶于50mL去离子水中配制成碱性溶液，加入反应釜中。接着，反应釜温度升至90℃反应4h，反应结束后，待反应釜温度回复至室温，配置5％乙酸溶液，逐滴加入反应釜中将产物pH值调节至中性，随后将产物烘干，即得到粘结剂，改性反应使得中间体聚合物上衍生自第一单体丙烯酸甲酯中的酯基官能团转化为-COOLi基团。
2)正极极片的制备
将实施例1中制备的粘结剂和磷酸铁锂正极活性材料、导电剂碳黑、N-甲基吡咯烷酮(NMP)按重量比为：1.28∶62.2∶0.52∶36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。
3)负极极片的制备
将活性物质人造石墨、导电剂碳黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照重量比为96.2∶0.8∶0.8∶1.2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。
4)隔离膜
以聚丙烯膜作为隔离膜。
5)电解液的制备
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，将LiPF6锂盐溶解于有机溶剂中配置成12.5％溶液，得到电解液。
6)电池的制备
将实施例1制备的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕得到裸电芯，给裸电芯焊接极耳，并将裸电芯装入铝壳中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得实施例1的锂离子电池产品。
实施例2～28的电池和对比例1～10的电池与实施例1的电池制备方法相似，但是调整了粘结剂制备的原料和反应条件，不同的参数详见表1。
具体地：
实施例2中制备中间体聚合物的单体为乙烯、丙烯腈，改性反应使得中间体聚合物上衍生自第一单体丙烯腈中的氰基转化为-COOLi基团。
实施例3中制备中间体聚合物的单体为乙烯、丙烯醛，改性反应使得中间体聚合物上衍生自第一单体丙烯醛中的醛基转化为-COOLi基团。
实施例4中制备中间体聚合物的单体为丙烯腈、丙烯酸甲酯，改性反应使得中间体聚合物上衍生自第一单体丙烯酸甲酯中的酯基转化为-COOLi基团。
实施例5中制备中间体聚合物的单体为丙烯腈、丙烯醛，改性反应使得中间体聚合物上衍生自第一单体丙烯酸醛中的醛基转化为-COOLi基团。
实施例2-5中其他参数与实施例1保持一致。
实施例6中碱性物质为氢氧化钠，改性反应使得中间体聚合物上衍生自第一单体丙烯酸甲酯中的酯基官能团转化为-COONa基团。
实施例7中碱性物质为氨水，改性反应使得中间体聚合物上衍生自第一单体丙烯酸甲酯中的酯基官能团转化为-COONH4基团。
实施例6-7中其他参数与实施例1保持一致。
实施例8中碱性物质为氢氧化钾，改性反应使得中间体聚合物上 衍生自第一单体丙烯酸甲酯中的酯基官能团转化为-COOK基团。
实施例9中在粘结剂制备过程中改性反应结束后，逐滴加入5％乙酸溶液，将反应釜中产物pH值调节至2～3，继续搅拌2h，随后将产物烘干，再用去离子水清洗3遍，烘干，改性反应使得中间体聚合物上衍生自第一单体丙烯酸甲酯中的酯基官能团转化为-COOH基团。
实施例10中乙烯、丙烯酸甲酯的投入摩尔比例为6∶4。
实施例11中乙烯、丙烯酸甲酯的投入摩尔比例为5∶5。
实施例12中乙烯、丙烯酸甲酯的投入摩尔比例为4∶6。
实施例13中乙烯、丙烯酸甲酯的投入摩尔比例为3∶7。
实施例14中乙烯、丙烯酸甲酯的投入摩尔比例为2∶8。
实施例15中乙烯、丙烯酸甲酯的投入摩尔比例为9∶1。
实施例10-15中其他参数与实施例1保持一致。
实施例16中丙烯酸甲酯与氢氧化锂的摩尔比为1∶0.5。
实施例17中丙烯酸甲酯与氢氧化锂的摩尔比为1∶1.5。
实施例18中丙烯酸甲酯与氢氧化锂的摩尔比为1∶2。
实施例19中丙烯酸甲酯与氢氧化锂的摩尔比为1∶0.1。
实施例16-19中其他参数与实施例1保持一致。
实施例20中改性反应的反应温度为35℃，
实施例21中改性反应的反应温度为60℃，
实施例22中改性反应的反应温度为75℃，
实施例23中改性反应的反应温度为120℃，
实施例16-23中其他参数与实施例1保持一致。
实施例24中改性反应的反应温度为60℃，反应时间为0.2h，
实施例25中改性反应的反应温度为60℃，反应时间为1h，
实施例26中改性反应的反应温度为60℃，反应时间为8h，
实施例27中改性反应的反应温度为60℃，反应时间为10h，
实施例28中改性反应的反应温度为60℃，反应时间为24h，
实施例24-28中其他参数与实施例1保持一致。
对比例1-5分别直接以实施例1-5中制备的中间体聚合物作为粘结剂，中间体聚合物不加碱性物质进行改性反应；
对比例6-11分别直接以实施例10-15中制备的中间体聚合物作为粘结剂，中间体聚合物不加碱性物质进行转化，具体参数如表1所示。
上述实施例1～28、对比例1～11的粘结剂的相关参数如下述表1所示。
另外，将上述实施例1～28和对比例1～11中得到的极片和电池进行性能测试，测试方法如下：
1、重均分子量测试方法
将实施例1所得粘结剂于真空烘箱80℃真空干燥12h，取0.1g溶解于20mL N-甲基吡咯烷酮中，使用孔径10μm滤膜过滤，取其中5mL通过凝胶渗透色谱仪测试重均分子量，所用检测器为差示折光检测法，标准物质为聚苯乙烯。
2、式II所示的结构单元摩尔含量N II(％)的测试
式II中M为金属元素，即Li，Na，K的情况下，采用电感耦合等离子体发射光谱法(ICP)测试粘结剂中金属元素M的质量百分数W M(％)，消解方法为平板法，消解溶剂为浓硝酸。测试前将粘结剂样品粉末在去离子中清洗3遍除去吸附于表面的游离金属离子，随后将产物烘干送测。
式II的结构单元摩尔含量N II(％)可通过以下公式计算得到：
N II(％)＝W M*M 总/M M
式中M 总粘结剂结构单元的分子量，M M为M元素的分子量。
式II中M为H或NH 4的情况下，需先对粘结剂进行离子置换处理将M置换为Na，具体方案如下：将10g粘结剂粉末倒入200mL的5wt％氯化钠水溶液中，40℃下搅拌1h进行离子置换，随后过滤，所得粉末在去离子中清洗3遍除去吸附于表面的钠离子，随后将产物烘干，送测ICP测试钠元素的质量百分数W Na(％)。
式II的结构单元摩尔含量N II(％)可通过以下公式计算得到：
N II(％)＝W Na*M 总/23
式中M 总粘结剂结构单元分子量。
3、第二结构单元的摩尔含量
第二结构单元的摩尔含量＝第二单体投入量/(第二单体投入量+第一单体投入量)
4、极片溶胀率测试
极片溶胀率测试过程如下：实施例或对比例中制备的正极极片冷压后裁取5*5cm面积，称重记录为m 0，同时将实施例或对比例中对应的电池置于60℃下存储7天后，从正极极片中裁取5*5cm，快速擦拭其表面残留电解液后称重，记录为m 1，极片溶胀率可通过以下公式计算得到：
极片溶胀率(％)＝(m 1-m 0)/m 0×100％
5、电池直流阻抗测试
电池直流阻抗测试过程如下：在25℃下，将实施例或对比例中制备的电池，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后，记录电压V 1。然后再以1/3C放电30s，记录电压V 2，则(V 2-V 1)/1/3C，得到第一次循环后电池的内阻DCR。
6、电池容量保持率测试
电池容量保持率测试过程如下：在25℃下，将制备的电池，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C0。对上述同一个电池重复以上步骤，并同时记录循环第n次后电池的放电容量Cn，则每次循环后电池容量保持率Pn＝Cn/C0*100％，以P1、P2......P100这100个点值为纵坐标，以对应的循环次数为横坐标。该测试过程中，第一次循环对应n＝1、第二次循环对应n＝2、......第100次循环对应n＝100。表2中实施例或对比例对应的电池容量保持率数据是在上述测试条件下循环100次之后测得的数据，即P100的值。其他实施例以及对比例的测试过程同上。
上述实施例1～28和对比例1～11中得到的极片和电池的性能测试结果如表1所示。
Figure PCTCN2022096059-appb-000005
Figure PCTCN2022096059-appb-000006
Figure PCTCN2022096059-appb-000007
Figure PCTCN2022096059-appb-000008
Figure PCTCN2022096059-appb-000009
Figure PCTCN2022096059-appb-000010
实施例1～28中，提供了一种粘结剂，该粘结剂为含有如式I、式II所示的结构单元的聚合物，
Figure PCTCN2022096059-appb-000011
其中，R 1、R 2、R 3、R 5、R 6、R 7各自独立地选自氢，R 4选自氢、氰基、醛基或酯基，M选自H、Li、Na、K或NH 4。相比于对比例1～11，其极片溶胀率均有所降低，电池内阻下降，循环容量保持率增高。
实施例1～28中，式II所示的结构单元的摩尔含量为0.1％～60％，基于聚合物中所有结构单元的总摩尔数计。相比于对比例1～11，其极片溶胀率均有所降低，电池内阻下降，容量保持率增高。实施例1～28中，式II所示的结构单元的摩尔含量为10％～40％时，电池内阻下降更为明显，循环容量保持率更高。
实施例1～28中，聚合物包含R 4为氰基、醛基或酯基的式I所示的第一结构单元和R 4为氢或氰基的式I所示的第二结构单元，其中第一结构单元与第二结构单元不相同。相比于对比例1～11，其极片溶胀率均有所降低，电池内阻下降，循环容量保持率增高。
实施例1～28中，第二结构单元的摩尔含量为20％～90％，基于聚合物中所有结构单元的总摩尔数计。相比于对比例1～11，其极片溶胀率均有所降低，电池内阻下降，循环容量保持率增高。实施例15中，当聚合物中衍生自乙烯单体的结构单元的比例为90％时，虽然极片的溶胀率更低，但是极片粘结性不佳，电池的循环稳定性变差，因此，电池的循环容量保持率降低。当第二结构单元的摩尔含量为50％～80％时，基于聚合物中所有结构单元的总摩尔数计，电池的电阻更低，循环容量保持率更高。
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 (19)

  1. 一种粘结剂，其特征在于，所述粘结剂为含有如式I、式II所示的结构单元的聚合物，
    Figure PCTCN2022096059-appb-100001
    其中，R 1、R 2、R 3、R 5、R 6、R 7各自独立地选自氢或取代或未取代的C 1-3烷基，R 4选自氢、氰基、醛基或酯基，M选自H、Li、Na、K或NH 4。
  2. 根据权利要求1所述的粘结剂，其特征在于，所述式II所示的结构单元的摩尔含量为0.1％～60％，可选为10％～40％，基于所述聚合物中所有结构单元的总摩尔数计。
  3. 根据权利要求1或2所述的粘结剂，其特征在于，所述聚合物包含R 4为醛基或酯基的式I所示的第一结构单元和R 4为氢或氰基的式I所示的第二结构单元，其中所述第一结构单元与所述第二结构单元不相同。
  4. 根据权利要求3所述的粘结剂，其特征在于，所述第二结构单元的摩尔含量为20％～90％，可选为50％～80％，基于所述聚合物中所有结构单元的总摩尔数计。
  5. 一种粘结剂的制备方法，其特征在于，所述制备方法包括：
    制备中间体聚合物：将式III所示的单体进行聚合形成中间体聚合物，所述中间体聚合物至少含有氰基、醛基或酯基，
    Figure PCTCN2022096059-appb-100002
    在所述式III中，R 1、R 2、R 3各自独立地选自氢、取代或未取代的C 1-3烷基，R 4选自氢、氰基、醛基或酯基；
    改性反应：使所述中间体聚合物与碱性物质的水溶液发生改性反应，使得所述中间体聚合物中的至少部分氰基、醛基或酯基转化为COOM，M选自H、Li、Na、K或NH 4。
  6. 根据权利要求5所述的粘结剂的制备方法，其特征在于，
    在所述制备中间体聚合物的步骤中，所述单体选自R 4为醛基或酯基的式III所示的第一单体和R 4为氢或氰基的式III所示的第二单体，所述第二单体与所述第一单体结构不同。
  7. 根据权利要求6所述的粘结剂的制备方法，其特征在于，
    所述第二单体与所述第一单体的摩尔比为2∶8～9∶1，可选为3∶7～8∶2，进一步可选为5∶5～8∶2。
  8. 根据权利要求6至7中任一项所述的粘结剂的制备方法，其特征在于，
    所述第一单体选自丙烯醛、丙烯腈、丙烯酸甲酯、丙烯酸乙酯、丙烯酸丁酯、丙烯酸异辛酯、甲基丙烯酸甲酯中的一种或多种。
  9. 根据权利要求6至8中任一项所述的粘结剂的制备方法，其特征在于，
    所述第二单体选自乙烯、丙烯、丁烯、丙烯腈中的一种或多种。
  10. 根据权利要求5至9中所述的粘结剂的制备方法，其特征在于，
    所述中间体聚合物的重均分子量为5×10 4～1.5×10 6，可选为 1.5×10 5～8×10 5。
  11. 根据权利要求5至10中任一项所述的粘结剂的制备方法，其特征在于：
    所述碱性物质选自氢氧化锂、氢氧化钠、氢氧化钾、氨水中的一种或多种。
  12. 根据权利要求6至11中任一项所述的粘结剂的制备方法，其特征在于：
    所述第一单体中的氰基、醛基、酯基官能团总量与所述碱性物质的摩尔比为1∶0.1～1∶2，或为1∶0.5～1∶1.5。
  13. 根据权利要求5至12中的任一项所述的粘结剂的制备方法，其特征在于：
    所述改性反应的反应温度为35℃～120℃，可选为60～90℃。
  14. 根据权利要求5至13中任一项所述的粘结剂的制备方法，其特征在于：
    所述改性反应的反应时间为1～24h，可选为4～10h。
  15. 根据权利要求5至14中任一项所述的粘结剂的制备方法，其特征在于，还包括：
    所述改性反应结束后，向反应产物中加入酸性溶液将反应体系的pH值调至6～8。
  16. 一种二次电池，其特征在于，包括电极组件和电解液，所述电极组件包括正极极片、隔离膜、负极极片，所述正极极片包括正极活性物质和权利要求1～4中任一项所述的粘结剂或权利要求5～15中任一项所述的制备方法制备的粘结剂。
  17. 一种电池模块，其特征在于，包括权利要求16所述的二次电池。
  18. 一种电池包，其特征在于，包括权利要求17所述的电池模块。
  19. 一种用电装置，其特征在于，包括选自权利要求16所述的二次电池、权利要求17所述的电池模块或权利要求18所述的电池包中的至少一种。
PCT/CN2022/096059 2022-05-30 2022-05-30 粘结剂、制备方法、二次电池、电池模块、电池包及用电装置 WO2023230786A1 (zh)

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