WO2024066211A1 - Bab型嵌段共聚物、制备方法、粘结剂、正极极片、二次电池及用电装置 - Google Patents

Bab型嵌段共聚物、制备方法、粘结剂、正极极片、二次电池及用电装置 Download PDF

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WO2024066211A1
WO2024066211A1 PCT/CN2023/080637 CN2023080637W WO2024066211A1 WO 2024066211 A1 WO2024066211 A1 WO 2024066211A1 CN 2023080637 W CN2023080637 W CN 2023080637W WO 2024066211 A1 WO2024066211 A1 WO 2024066211A1
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Prior art keywords
block
positive electrode
block copolymer
formula
type block
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PCT/CN2023/080637
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English (en)
French (fr)
Inventor
曾子鹏
孙成栋
李�诚
刘会会
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宁德时代新能源科技股份有限公司
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Priority claimed from CN202211205567.3A external-priority patent/CN115286802B/zh
Priority claimed from PCT/CN2022/128035 external-priority patent/WO2024087112A1/zh
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
Publication of WO2024066211A1 publication Critical patent/WO2024066211A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
    • C08G81/02—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers at least one of the polymers being obtained by reactions involving only carbon-to-carbon unsaturated bonds
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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

Definitions

  • the present application relates to the technical field of secondary batteries, and in particular to a BAB-type block copolymer, a preparation method, a binder, a positive electrode sheet, a secondary battery and an electrical device.
  • secondary ion batteries have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • Binders are commonly used materials in secondary ion batteries and are widely used in battery pole pieces, separators, packaging, etc.
  • traditional binders have high production costs, insufficient production capacity, and great environmental hazards.
  • gelation is easy to occur during the preparation process, resulting in poor slurry stability and high processing costs.
  • the pole pieces prepared with them have poor conductivity, high resistance, low yield, and unstable battery performance, which makes it difficult to meet the market's requirements for battery cost and performance. Therefore, existing binders still need to be improved.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a BAB
  • the block copolymer can be used as a binder to effectively slow down the gelation of the slurry, improve the stability of the slurry, and at the same time improve the bonding force and flexibility of the electrode.
  • the first aspect of the present application provides a BAB type block copolymer, comprising an A-block and a B-block, wherein the A-block contains a structural unit derived from a monomer represented by formula I, and the B-block contains a structural unit derived from a monomer represented by formula II.
  • the A-block contains structural units derived from the monomers of formula II
  • the B-block contains structural units derived from the monomers of formula I
  • R 1 , R 2 , and R 3 are each independently selected from one or more of hydrogen, fluorine, and C 1-3 alkyl containing at least one fluorine atom; and R 4 , R 5 , R 6 , R 7 , and R 8 are each independently selected from hydrogen, and substituted or unsubstituted C 1-3 alkyl.
  • the BAB type block copolymer can maximize the weight average molecular weight of the fluorine-containing block and the non-fluorine block, give full play to the advantages of the fluorine-containing binder and the non-fluorine binder, and achieve complementary advantages.
  • Using it as a binder can significantly slow down the gelation of the slurry, improve the stability of the slurry, the flexibility and adhesion of the pole piece, and at the same time improve the wettability of the pole piece in the electrolyte by increasing the liquid absorption rate of the pole piece, and the pole piece has a low membrane resistance.
  • the molar content of the structural unit derived from the monomer represented by formula I is 40% to 60%
  • the molar content of the structural unit derived from the monomer represented by formula II is 40% to 60%, based on the total molar number of all structural units in the block copolymer.
  • the molar content of the structural unit derived from the monomer represented by Formula I is controlled within a suitable range, so that the electrode has excellent bonding force, good electrode liquid absorption rate and low membrane resistance.
  • the weight average molecular weight of the block copolymer is 400,000 to 2,000,000, and can be 1,200,000 to 2,000,000.
  • the block copolymer with a weight average molecular weight in a suitable range makes the electrode have good adhesion. Strengthening strength and flexibility, improving the performance of the electrode.
  • the weight average molecular weight of the A-block in the block copolymer is 200,000 to 1.1 million, and can be 400,000 to 1.1 million.
  • the block copolymer with the weight average molecular weight of the A-block within a suitable range enables the pole piece to have good adhesion and flexibility, thereby improving the performance of the pole piece.
  • the weight average molecular weight of each B-block in the block copolymer is 100,000 to 500,000, and can be 200,000 to 500,000.
  • the block copolymer in which the weight average molecular weight of each B-block is within a suitable range enables the pole piece to have good adhesion and flexibility, thereby improving the performance of the pole piece.
  • the monomer represented by formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene.
  • the monomer represented by formula II is selected from one or more of acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-tert-butylacrylamide, N-tert-butyl(methyl)acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, and N,N-diethylmethacrylamide.
  • the BAB type block copolymer is one or more of a polyacrylamide-polyvinylidene fluoride-polyacrylamide triblock copolymer, a polymethacrylamide-polytetrafluoroethylene-polymethacrylamide triblock copolymer, a poly-N-methylmethacrylamide-poly(vinylidene fluoride-hexafluoropropylene)-poly-N-methylmethacrylamide triblock copolymer, a poly-N-isopropylacrylamide-poly(vinylidene fluoride-tetrafluoroethylene)-poly-N-isopropylacrylamide triblock copolymer, a polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride triblock copolymer, a polytetrafluoroethylene-polymethacrylamide-polytetrafluoroethylene triblock copolymer, a poly(
  • the second aspect of the present application also provides a method for preparing a BAB type block copolymer, comprising the following steps:
  • Preparation of A-block polymerizing at least one monomer represented by formula I or at least one monomer represented by formula II to prepare A-block,
  • R 1 , R 2 , and R 3 are each independently selected from one or more of hydrogen, fluorine, and C 1-3 alkyl containing at least one fluorine atom; and R 4 , R 5 , R 6 , R 7 , and R 8 are each independently selected from hydrogen, and substituted or unsubstituted C 1-3 alkyl;
  • B-block polymerizing at least one monomer represented by formula II or at least one monomer represented by formula I to prepare B-block,
  • Preparation of a BAB type block copolymer The A-block and the B-block are joined to prepare a BAB type block copolymer, wherein the A-block and the B-block contain different structural units.
  • this preparation method can maximize the weight average molecular weight of the fluorine-containing block and the non-fluorine block, give full play to the respective advantages of the fluorine-containing binder and the non-fluorine binder, and achieve the role of complementary advantages.
  • the binder prepared by this method can slow down the gelation phenomenon of the slurry, improve the stability of the slurry, improve the adhesion and flexibility of the pole piece, and at the same time improve the wettability of the pole piece in the electrolyte by increasing the liquid absorption rate of the pole piece, so that the pole piece has excellent membrane resistance.
  • the method of preparing the A-block comprises:
  • At least one monomer represented by formula I or at least one monomer represented by formula II and a first initiator are polymerized at a reaction temperature of 80 to 95° C. for 2.5 to 5 hours, and the product is subjected to a substitution reaction to prepare an A-block having an azide group or an alkynyl group at both ends.
  • the method of preparing the B-block comprises:
  • At least one monomer represented by formula II or at least one monomer represented by formula I, a chain transfer agent and a second initiator are polymerized by reversible addition-fragmentation chain transfer at a reaction temperature of 60 to 75° C., The reaction is carried out for 4.5 to 6 hours to obtain a B-block having an alkynyl or azide group at the terminal.
  • controllable polymerization can be achieved, and the molecular weight distribution of the product is relatively narrow.
  • the method for preparing a BAB type block copolymer comprises:
  • the A-block having an azide group or an alkynyl group at both ends is mixed with the B-block having an alkynyl group or an azide group at the end, and a click reaction is performed to prepare a BAB type block copolymer, wherein the end groups of the A-block and the B-block are different.
  • the above preparation method has the advantages of high efficiency, stability and high specificity, and can improve the yield rate of the product.
  • the chain transfer agent is a RAFT chain transfer agent containing a terminal alkynyl or azide group.
  • the first initiator is a symmetrical bifunctional initiator.
  • the second initiator is an azo initiator.
  • a BAB type block copolymer is provided for use in a secondary battery.
  • the fourth aspect of the present application provides a positive electrode plate, including a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, a conductive agent and a binder, and the binder is a BAB type block copolymer in any embodiment or a BAB type block copolymer prepared by the preparation method in any embodiment.
  • the positive electrode sheet has excellent flexibility, adhesion and low film resistance.
  • the mass fraction of the binder is 0.1% to 3%, optionally 1% to 3%, based on the total mass of the positive electrode active material.
  • the slurry has better stability.
  • the bonding force per unit length between the positive electrode film layer and the positive electrode current collector is not less than 11 N/m, and can be 11-22 N/m.
  • the positive electrode film layer of the pole piece has high bonding strength with the positive electrode current collector. During use, the positive electrode film layer is not easy to fall off from the positive electrode current collector, which helps to improve the cycle performance and safety of the battery.
  • the positive electrode plate after the positive electrode plate has been subjected to no less than three bending tests, the positive electrode plate becomes light-transmissive.
  • the electrode has excellent flexibility and is not prone to cracking during the production process, which helps to improve the yield rate.
  • the electrolyte absorption rate of the positive electrode plate is greater than 0.30 ⁇ g/s, and may be 0.35-0.6 ⁇ g/s, and the electrolyte has a density of 1.1-1.2 g/cm 3 .
  • the electrode has a high liquid absorption rate, which can improve the electrolyte infiltration efficiency of the electrode, improve the ion transmission path, reduce the interface resistance, and improve the battery performance.
  • a secondary battery comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises a separator, a negative electrode plate and the positive electrode plate of the fourth aspect of the present application.
  • an electrical device comprising the secondary battery of the fifth aspect of the present application.
  • FIG1 is a schematic diagram of the preparation of a BAB type block copolymer according to an embodiment of the present application.
  • FIG2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG3 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG2 ;
  • FIG4 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG5 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG6 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG5 ;
  • FIG. 7 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • 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.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • composition may include or contain other components not listed, or may include or contain only the listed components.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: 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).
  • PVDF polyvinylidene fluoride
  • the strong polar groups on PVDF will activate the residual hydroxyl groups on the positive electrode active materials, and then react with the metal elements (such as nickel elements) in the positive electrode active materials to form chemical crosslinks, which eventually lead to slurry gelation, affecting the normal preparation of the slurry and subsequent pole piece processing.
  • PVDF is easy to crystallize, which is not conducive to the transmission of electrons in the pole piece, which in turn leads to high resistance of the pole piece and poor electron transmission performance, which is not conducive to the performance of high-capacity positive electrode active materials.
  • the present application proposes a BAB type block copolymer, wherein the A-block contains a structural unit derived from a monomer shown in formula I, and the B-block contains a structural unit derived from a monomer shown in formula II.
  • the A-block contains structural units derived from the monomers of formula II
  • the B-block contains structural units derived from the monomers of formula I
  • R 1 , R 2 , and R 3 are each independently selected from one or more of hydrogen, fluorine, and C 1-3 alkyl containing at least one fluorine atom; and R 4 , R 5 , R 6 , R 7 , and R 8 are each independently selected from hydrogen, and substituted or unsubstituted C 1-3 alkyl.
  • block copolymer refers to a special type of polymer made by linking two or more polymer segments with different properties. Block polymers with specific structures will exhibit different properties from simple linear polymers, many random copolymers, and even mixtures of homopolymers. Common types include AB and BAB types, in which A and B are both long chain segments; there are also (AB)n type multi-segment copolymers, in which A and B segments are relatively short.
  • BAB type block copolymer refers to a triblock copolymer with an A-block in the middle and B-blocks on both sides.
  • A-block and B-block are polymer segments with a predetermined weight average molecular weight formed by polymerization of different monomers.
  • A-block is a long sequence segment formed by polymerization of fluorine-containing monomers
  • B-block is a long sequence segment formed by polymerization of one or more fluorine-free monomers.
  • A-block and B-block are covalently bonded in an orderly manner to form a BAB type block copolymer.
  • B-block polyacrylamide formed by polymerization of acrylamide monomer, has a weight average molecular weight of 400,000;
  • A-block is polyvinylidene fluoride, formed by polymerization of vinylidene fluoride monomer, with a weight average molecular weight of 450,000;
  • the end groups on both sides of B-block and A-block are bonded to obtain polyacrylamide-polyvinylidene fluoride-polyacrylamide block copolymer (BAB type block copolymer), and the weight average molecular weight of the block copolymer is 1.2 million.
  • the A-block of the BAB-type block copolymer contains structural units derived from the monomer of Formula I, and the B-block contains structural units derived from the monomer of Formula II.
  • the A-block of the BAB type block copolymer contains structural units derived from the monomers shown in formula II, and the B-block contains structural units derived from the monomers shown in formula I.
  • the A-block is a long sequence segment formed by the polymerization of one or more fluorine-free monomers
  • the B-block is a long sequence segment formed by the polymerization of one or more fluorine-containing monomers.
  • the A-block and the B-block are covalently bonded in an orderly manner to form a BAB type block copolymer.
  • the A-block is polyacrylamide, which is formed by the polymerization of acrylamide monomers, and the weight average molecular weight is 660,000;
  • the B-block is polyvinylidene fluoride, which is formed by the polymerization of vinylidene fluoride monomers, and the weight average molecular weight is 270,000;
  • the end groups on both sides of the B-block and the A-block are bonded to obtain polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride block copolymer (BAB type block copolymer), and the weight average molecular weight of the block copolymer is 1.2 million.
  • polymer includes, on the one hand, a collection of macromolecules that are chemically uniform but differ in degree of polymerization, molar mass and chain length, prepared by polymerization.
  • the term also includes, on the other hand, derivatives of such a collection of macromolecules formed by polymerization, i.e. compounds that can be obtained by reaction, for example addition or substitution, of functional groups in the above-mentioned macromolecules and can be chemically uniform or chemically heterogeneous.
  • C 1-3 alkyl refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, with no unsaturation in the radical, having from one to three carbon atoms, and attached to the remainder of the molecule by a single bond.
  • Examples of C 1-3 alkyl include, but are not limited to: methyl, ethyl, n-propyl, 1-methylethyl (isopropyl).
  • substituted means that at least one hydrogen atom of the compound or chemical moiety is replaced by another chemical moiety with a substituent, wherein the substituent is independently selected from: hydroxyl, thiol, amino, cyano, nitro, aldehyde, halogen atom, alkenyl, alkynyl, aryl, heteroaryl, C 1-6 alkyl, C 1-6 alkoxy.
  • R 1 in Formula I is fluorine
  • R 2 and R 3 are each independently selected from hydrogen, fluorine, chlorine or trifluoromethyl.
  • trifluoromethyl refers to a -CF3 group.
  • the monomer represented by formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene.
  • the monomer represented by formula I is selected from one or more of vinylidene fluoride, chlorotrifluoroethylene, vinyl fluoride, tetrafluoroethylene, and hexafluoropropylene.
  • the monomer represented by formula II is selected from one or more of acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-tert-butylacrylamide, N-tert-butyl(methyl)acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, and N,N-diethylmethacrylamide.
  • the BAB type block copolymer can be selected from polyacrylamide-polyvinylidene fluoride-polyacrylamide triblock copolymer, polymethacrylamide-polytetrafluoroethylene-polymethacrylamide triblock copolymer, poly-N-methylmethacrylamide-poly(vinylidene fluoride-hexafluoropropylene)-poly-N-methylmethacrylamide triblock copolymer, poly-N-isopropyl One or more of acrylamide-poly(vinylidene fluoride-tetrafluoroethylene)-polyN-isopropylacrylamide triblock copolymers.
  • the BAB type block copolymer can be selected from one or more of polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride triblock copolymer, polytetrafluoroethylene-polymethacrylamide-polytetrafluoroethylene triblock copolymer, poly(vinylidene fluoride-hexafluoropropylene)-poly N-methylmethacrylamide-poly(vinylidene fluoride-hexafluoropropylene) triblock copolymer, and poly(vinylidene fluoride-tetrafluoroethylene)-poly N-isopropylacrylamide-poly(vinylidene fluoride-tetrafluoroethylene) triblock copolymer.
  • the BAB type block copolymer serves as an electrode binder.
  • binder refers to a chemical compound, polymer or 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, that is, the binder is dissolved in the aqueous solvent.
  • the dispersion medium of the binder is an oily solvent, examples of which include but are not limited to dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, dimethyl carbonate, ethyl cellulose, and polycarbonate. That is, the binder is dissolved in the oily solvent.
  • a binder is used to hold the electrode material and/or the conductive agent in place and adhere them to the conductive metal part to form an electrode.
  • the binder is used as a positive electrode binder to bind the positive electrode active material and/or the conductive agent to form an electrode.
  • the binder is used as a negative electrode binder to bind the negative electrode active material and/or the conductive agent to form an electrode.
  • the fluorine element contained in the A-block forms hydrogen bonds with the hydroxyl and/or carboxyl groups on the surface of the active material and the current collector, so that the pole piece has excellent adhesion.
  • the amide group contained in the B-block forms hydrogen bonds with the hydroxyl groups on the surface of the positive electrode active material and the conductive agent particles. On the one hand, it helps to improve the adhesion of the pole piece, and on the other hand, it changes the surface state of the positive electrode active material and the conductive agent particles and reduces the solid-liquid interface energy.
  • the molecular chain of the B-block can provide steric hindrance, effectively hindering the agglomeration of the positive electrode active material and the conductive agent.
  • the molecular chain of the B-block is adsorbed on the surface of the positive electrode active material and the conductive agent.
  • the defects and dangling bonds weaken the interconnection between particles, achieving a certain repulsion effect, so that the molecular chain of the B-block plays a certain dispersing role, slowing down the gelation of the slurry and improving the stability of the slurry.
  • the amide bond in the B-block can improve the liquid absorption capacity of the electrode, improve the wettability of the electrode in the electrolyte, and help form a conductive network on the electrode to reduce the membrane resistance.
  • BAB type block copolymers can reduce the crystallinity of polymers, increase the mobility of chain segments, and improve the flexibility of pole pieces.
  • the structural units derived from the monomers shown in formula II can weaken the intermolecular forces between the structural units derived from the monomers shown in formula I, improve the flexibility of pole pieces, reduce the risk of brittle fracture of high-load high-voltage dense pole pieces, and improve the safety performance of batteries.
  • BAB type block copolymer can maximize the weight average molecular weight of fluorinated block and non-fluorinated block, give full play to the advantages of fluorinated binder and non-fluorinated binder, and achieve complementary advantages. Moreover, compared with the simple blending of fluorinated polymer and non-fluorinated polymer, BAB type block copolymer can effectively inhibit the stratification of polymer in the slurry preparation process through the interaction between blocks.
  • BAB-type block copolymers as binders can significantly slow down the gelation phenomenon of the slurry, improve the slurry stability, the flexibility and adhesion of the electrode, and at the same time improve the wettability of the electrode in the electrolyte by increasing the electrode absorption rate, thereby reducing the membrane resistance.
  • the fluorine element contained in the B-block forms hydrogen bonds with the hydroxyl and/or carboxyl groups on the surface of the active material and the current collector, so that the pole piece has excellent adhesion.
  • the amide group contained in the A-block forms hydrogen bonds with the hydroxyl groups on the surface of the positive electrode active material and the conductive agent particles, which on the one hand helps to improve the adhesion of the pole piece, and on the other hand will change the surface state of the positive electrode active material and the conductive agent particles, reducing the solid-liquid interface energy.
  • the molecular chain of the A-block can provide steric hindrance, effectively hindering the agglomeration of the positive electrode active material and the conductive agent.
  • the A-block molecular chain is adsorbed on the defects and dangling bonds on the surface of the positive electrode active material and the conductive agent, weakening the mutual connection between the particles and achieving a certain repulsion effect, so that the molecular chain of the A-block plays a certain dispersing role, slowing down the gelation phenomenon of the slurry and improving the stability of the slurry.
  • the amide bond in the A-block can improve the liquid absorption energy of the pole piece. force, improves the wetting ability of the electrode in the electrolyte, helps to form a conductive network on the electrode, makes the electrode have a low membrane resistance, and reduces the DC impedance growth rate of the battery.
  • using BAB-type block copolymers as binders can significantly slow down the gelation phenomenon of the slurry, improve the slurry stability, the flexibility and adhesion of the electrode, and at the same time improve the wetting ability of the electrode in the electrolyte by increasing the electrode absorption rate.
  • the electrode has a low membrane resistance and reduces the DC impedance growth rate of the battery.
  • the molar content of the structural unit derived from the monomer represented by formula I in the A-block is 10% to 90%
  • the molar content of the structural unit derived from the monomer represented by formula II in the B-block is 10% to 90%, based on the total molar number of all structural units in the block copolymer.
  • the molar content of the structural units derived from the monomer represented by Formula I in the A-block can be selected as one of 10% to 90%, 20% to 80%, 30% to 70%, 40% to 60%, based on the total molar number of all structural units in the block copolymer.
  • the molar content of the structural unit derived from the monomer represented by Formula II in the B-block can be selected as one of 10% to 90%, 20% to 80%, 30% to 70%, and 40% to 60%, based on the total molar number of all structural units in the block copolymer.
  • the molar content of the structural unit derived from the monomer represented by formula I in the A-block is 40% to 60%
  • the molar content of the structural unit derived from the monomer represented by formula II in the B-block is 40% to 60%, based on the total molar number of all structural units in the block copolymer.
  • the molar content of the structural units derived from the monomer represented by Formula I in the A-block can be selected as any one of 40% to 45%, 45% to 50%, 50% to 55%, 55% to 60%, 40% to 50%, 50% to 60%, 45% to 55%, and 45% to 60%, based on the total moles of all structural units in the block copolymer.
  • the molar content of the structural units derived from the monomer represented by Formula II in the B-block can be selected as any one of 40% to 45%, 45% to 50%, 50% to 55%, 55% to 60%, 40% to 50%, 50% to 60%, 45% to 55%, and 45% to 60%, based on the total moles of all structural units in the block copolymer.
  • the pole piece The bonding force decreases; if the molar content of the structural unit derived from the monomer represented by formula I in the A-block is too high, and the molar content of the structural unit derived from the monomer represented by formula II in the B-block is too low, the liquid absorption capacity of the electrode decreases and the membrane resistance increases.
  • the electrode By controlling the molar content of the structural unit derived from the monomer represented by Formula I in the A-block within a suitable range, not only the stability of the slurry is improved, but also the electrode can have excellent adhesion, good electrode liquid absorption rate and low membrane resistance.
  • the molar content of the structural unit derived from the monomer represented by formula I in the B-block is 10% to 90%
  • the molar content of the structural unit derived from the monomer represented by formula II in the A-block is 10% to 90%, based on the total molar number of all structural units in the block copolymer.
  • the molar content of the structural units derived from the monomer represented by Formula I in the B-block can be selected as one of 10% to 90%, 20% to 80%, 30% to 70%, and 40% to 60%, based on the total moles of all structural units in the block copolymer.
  • the molar content of the structural units derived from the monomer represented by Formula II in the A-block can be selected as one of 10% to 90%, 20% to 80%, 30% to 70%, and 40% to 60%, based on the total molar number of all structural units in the block copolymer.
  • the molar content of the structural unit derived from the monomer represented by formula I in the B-block is 40% to 60%
  • the molar content of the structural unit derived from the monomer represented by formula II in the A-block is 40% to 60%, based on the total molar number of all structural units in the block copolymer.
  • the molar content of the structural units derived from the monomer represented by Formula I in the B-block can be selected as any one of 40% to 45%, 45% to 50%, 50% to 55%, 55% to 60%, 40% to 50%, 50% to 60%, 45% to 55%, and 45% to 60%, based on the total moles of all structural units in the block copolymer.
  • the molar content of the structural units derived from the monomer represented by Formula II in the A-block can be selected as any one of 40% to 45%, 45% to 50%, 50% to 55%, 55% to 60%, 40% to 50%, 50% to 60%, 45% to 55%, and 45% to 60%, based on the total moles of all structural units in the block copolymer.
  • the pole piece The bonding force decreases; if the molar content of the structural unit derived from the monomer represented by formula I in the B block is too high, and the molar content of the structural unit derived from the monomer represented by formula II in the A block is too low, the liquid absorption capacity of the electrode decreases, the internal resistance growth rate of the battery increases, and the cycle capacity retention rate of the battery decreases.
  • the molar content of the structural unit derived from the monomer represented by Formula I in the B-block is controlled within a suitable range, so that the pole piece has excellent bonding force, good pole piece liquid absorption rate and low membrane resistance, thereby improving the cycle performance of the battery.
  • the A-block contains structural units derived from the monomers of Formula I
  • the B-block contains structural units derived from the monomers of Formula II
  • the weight average molecular weight of the block copolymer is 400,000 to 2,000,000.
  • the A-block contains structural units derived from the monomers shown in formula I
  • the B-block contains structural units derived from the monomers shown in formula II.
  • the weight-average molecular weight of the block copolymer can be selected as any one of 400,000 to 600,000, 600,000 to 800,000, 800,000 to 1,000,000, 1,000,000 to 1,200,000, 1,200,000 to 1,400,000, 1,400,000 to 1,600,000, 1,600,000 to 1,800,000, 1,800,000 to 2,000,000, 600,000 to 900,000, 900,000 to 1,200,000, 1,200,000 to 1,500,000, 1,500,000 to 1,800,000, 1,800,000 to 2,000,000.
  • weight average molecular weight refers to the sum of the products of the weight fractions of molecules with different molecular weights in a polymer and their corresponding molecular weights.
  • the binder will be difficult to dissolve and will easily agglomerate with the conductive agent, increasing the internal resistance of the diaphragm.
  • the viscosity of the slurry will increase, reducing the dispersibility of the substances in the slurry and affecting the flexibility of the electrode.
  • the weight-average molecular weight of the block copolymer is too small, it will be difficult to form a three-dimensional network bonding structure and will not be able to play an effective bonding role.
  • the electrode's liquid absorption capacity and wettability in the electrolyte will decrease, resulting in an increase in the internal resistance of the electrode diaphragm.
  • the binder can slow down the gelation of the slurry and improve the stability of the slurry.
  • the A-block contains structural units derived from the monomers of Formula I
  • the B-block contains structural units derived from the monomers of Formula II
  • the weight average molecular weight of the block copolymer is 1.2 million to 2 million.
  • the A-block contains structural units derived from monomers of formula I
  • the B-block contains structural units derived from the monomer represented by formula II
  • the weight average molecular weight of the block copolymer can be selected as any one of 1.2 million to 1.4 million, 1.4 million to 1.6 million, 1.6 million to 1.8 million, 1.8 million to 2 million, 600,000 to 900,000, 900,000 to 1.2 million, 1.2 million to 1.5 million, 1.5 million to 1.8 million, 1.8 million to 2 million, and 1.2 million to 2 million.
  • the weight average molecular weight of the block copolymer has a suitable weight average molecular weight.
  • the binder of the block copolymer can improve the adhesion and flexibility of the electrode. At the same time, by increasing the liquid absorption rate of the electrode, the electrode's wettability to the electrolyte is improved, the membrane resistance is reduced, and the internal resistance growth rate of the battery is reduced and the cycle capacity retention rate of the battery is improved.
  • the B-block contains structural units derived from the monomers of Formula I
  • the A-block contains structural units derived from the monomers of Formula II
  • the weight average molecular weight of the block copolymer is 400,000 to 2,000,000.
  • the B-block contains structural units derived from the monomers shown in formula I
  • the A-block contains structural units derived from the monomers shown in formula II
  • the weight average molecular weight of the block copolymer is 400,000 to 600,000, 600,000 to 800,000, 800,000 to 1,000,000, 1,000,000 to 1,200,000, 1,200,000 to 1,400,000, 1,400,000 to 1,600,000, 1,600,000 to 1,800,000, 1,800,000 to 2,000,000, 600,000 to 900,000, 900,000 to 1,200,000, 1,200,000 to 1,500,000, 1,500,000 to 1,800,000, 1,800,000 to 2,000,000, and 1,200,000 to 2,000,000.
  • the binder will be difficult to dissolve and will easily agglomerate with the conductive agent, increasing the internal resistance of the membrane. In addition, it will increase the viscosity of the slurry, reduce the dispersibility of the substances in the slurry, and affect the flexibility of the electrode. If the weight-average molecular weight of the block copolymer is too small, it will be difficult to form a three-dimensional network bonding structure, and it will not be able to play an effective bonding role, affecting the bonding performance of the electrode.
  • the binder can make the electrode have good adhesion and flexibility, thereby improving the performance of the electrode.
  • the B-block contains structural units derived from the monomers of Formula I
  • the A-block contains structural units derived from the monomers of Formula II
  • the weight average molecular weight of the block copolymer is 1.2 million to 2 million.
  • the B-block contains a structural unit derived from a monomer of formula I
  • the A-block contains a structural unit derived from a monomer of formula II
  • the weight average molecular weight of the block copolymer can be selected from 1.2 million to 1.4 million, 1.4 million to 1.6 million, 1.6 million to 1.8 million, 1.8 million to 1.5 million. Any one of: 1.2 million to 2 million, 600,000 to 900,000, 900,000 to 1.2 million, 1.2 million to 1.5 million, 1.5 million to 1.8 million, 1.8 million to 2 million, and 1.2 million to 2 million.
  • the binder can improve the bonding force of the pole piece and improve the cycle performance of the battery.
  • the A-block contains a structural unit derived from a monomer represented by Formula I, and the weight average molecular weight of the A-block in the block copolymer is 200,000 to 1.1 million.
  • the A-block contains structural units derived from the monomers shown in Formula I, and the weight average molecular weight of the A-block can be selected from any one of 200,000 to 300,000, 300,000 to 400,000, 400,000 to 500,000, 500,000 to 600,000, 600,000 to 700,000, 700,000 to 800,000, 800,000 to 900,000, 900,000 to 1,050,000, 400,000 to 600,000, 400,000 to 800,000, and 400,000 to 1,050,000.
  • the structural unit derived from the monomer represented by Formula I contains too many fluorine-containing groups, which affects the stability of the slurry; if the weight average molecular weight of the A-block in the block copolymer is too small, the bonding force of the pole piece decreases.
  • the block copolymer with the weight average molecular weight of the A-block within a suitable range can slow down the gelation of the slurry and improve the stability of the slurry.
  • the A-block contains structural units derived from the monomers represented by Formula I, and the weight average molecular weight of the A-block in the block copolymer is 400,000 to 1.1 million.
  • the A-block contains structural units derived from the monomer represented by Formula I, and the weight average molecular weight of the A-block can be selected from any one of 400,000 to 500,000, 500,000 to 600,000, 600,000 to 700,000, 700,000 to 800,000, 800,000 to 900,000, 900,000 to 1,050,000, 400,000 to 600,000, 400,000 to 800,000, and 400,000 to 1,050,000.
  • the block copolymer has a weight average molecular weight of the A-block within a suitable range.
  • the binder can improve the bonding force and flexibility of the pole piece, so that the pole piece has a lower membrane resistance, reduces the internal resistance growth rate of the battery, and improves the cycle capacity retention rate of the battery.
  • the A-block contains a structural unit derived from a monomer represented by Formula II, and the weight average molecular weight of the A-block in the block copolymer is 200,000 to 1.1 million.
  • the A-block contains a structural unit derived from a monomer represented by Formula II, and the weight average molecular weight of the A-block can be selected from any one of 200,000 to 300,000, 300,000 to 400,000, 400,000 to 500,000, 500,000 to 600,000, 600,000 to 700,000, 700,000 to 800,000, 800,000 to 900,000, 900,000 to 1,050,000, 400,000 to 600,000, 400,000 to 800,000, and 400,000 to 1,050,000.
  • the structural unit derived from the monomer represented by Formula II has too many strong polar groups, which affects the dispersibility of the slurry and the flexibility of the electrode; if the weight average molecular weight of the A-block in the block copolymer is too small, the bonding force of the electrode decreases.
  • the block copolymer with the weight average molecular weight of the A-block within a suitable range can take into account both the flexibility and adhesion of the pole piece, thereby improving the performance of the pole piece.
  • the A-block contains a structural unit derived from a monomer represented by Formula II, and the weight average molecular weight of the A-block in the block copolymer is 400,000 to 1.1 million.
  • the A-block contains a structural unit derived from a monomer represented by Formula II, and the weight average molecular weight of the A-block can be selected from any one of 400,000 to 500,000, 500,000 to 600,000, 600,000 to 700,000, 700,000 to 800,000, 800,000 to 900,000, 900,000 to 1,050,000, 400,000 to 600,000, 400,000 to 800,000, and 400,000 to 1,050,000.
  • the block copolymer has an A-block weight average molecular weight within a suitable range.
  • the binder can improve the bonding force of the pole piece and improve the cycle performance of the battery.
  • the B-block contains a structural unit of a monomer represented by Formula II, and the weight average molecular weight of each B-block is 100,000 to 500,000.
  • the B-block contains a structural unit of a monomer represented by formula II, and the weight average molecular weight of each B-block can be selected from any one of 100,000 to 200,000, 200,000 to 300,000, 300,000 to 400,000, 400,000 to 500,000, 200,000 to 400,000, and 200,000 to 500,000.
  • the block copolymers with a weight average molecular weight of each B-block within a suitable range can slow down the gelation of the slurry and improve the slurry stability.
  • the B-block contains a structural unit of a monomer represented by Formula II, and the weight average molecular weight of each B-block is 200,000 to 500,000.
  • the B-block contains a structural unit of a monomer represented by Formula II, and the weight average molecular weight of each B-block can be selected from any one of 200,000 to 300,000, 300,000 to 400,000, 400,000 to 500,000, 200,000 to 400,000, and 200,000 to 500,000.
  • the block copolymer with a weight average molecular weight of each B-block within a suitable range can improve the adhesion and flexibility of the electrode, and at the same time improve the wettability of the electrode by the electrolyte by increasing the liquid absorption rate of the electrode, thereby reducing the membrane resistance of the electrode.
  • the B-block contains structural units of monomers represented by Formula I, each The weight average molecular weight of the B-block is 100,000 to 500,000.
  • the B-block contains structural units of the monomers represented by Formula I, and the weight average molecular weight of each B-block is 100,000-200,000, 200,000-300,000, 300,000-400,000, 400,000-500,000, 200,000-400,000, or 200,000-500,000.
  • the block copolymer in which the weight average molecular weight of each B-block is within a suitable range can take into account both the adhesion and flexibility of the pole piece, thereby improving the performance of the pole piece.
  • the B-block contains a structural unit of a monomer represented by Formula I, and the weight average molecular weight of each B-block is 200,000 to 500,000.
  • the B-block contains a structural unit of a monomer represented by Formula I, and the weight average molecular weight of each B-block can be selected from any one of 200,000 to 300,000, 300,000 to 400,000, 400,000 to 500,000, 200,000 to 400,000, and 200,000 to 500,000.
  • the block copolymers with a weight average molecular weight of each B-block within a suitable range can improve the bonding force of the pole piece and improve the cycle performance of the battery.
  • a method for preparing a BAB type block copolymer comprising the following steps:
  • Preparation of A-block polymerizing at least one monomer represented by formula I or at least one monomer represented by formula II to prepare A-block,
  • R 1 , R 2 , and R 3 are each independently selected from one or more of hydrogen, fluorine, and C 1-3 alkyl containing at least one fluorine atom; and R 4 , R 5 , R 6 , R 7 , and R 8 are each independently selected from hydrogen, and substituted or unsubstituted C 1-3 alkyl;
  • B-block polymerizing at least one monomer represented by formula II or at least one monomer represented by formula I to prepare B-block,
  • BAB-type block copolymers A-blocks and B-blocks are joined to prepare BAB-type block copolymers, wherein the A-blocks and the B-blocks contain different structural units.
  • a method for preparing a BAB type block copolymer is provided. The following steps are involved:
  • Preparation of A-block polymerizing at least one monomer represented by formula I to prepare A-block,
  • B-block polymerizing at least one monomer represented by formula II to prepare B-block,
  • BAB-type block copolymers A-blocks and B-blocks are joined to prepare BAB-type block copolymers, wherein the A-blocks and the B-blocks contain different structural units.
  • a method for preparing a BAB type block copolymer comprising the following steps:
  • Preparation of A-block polymerizing at least one monomer represented by formula II to prepare A-block,
  • B-block polymerizing at least one monomer represented by formula II to prepare B-block,
  • BAB-type block copolymers A-blocks and B-blocks are joined to prepare BAB-type block copolymers, wherein the A-blocks and the B-blocks contain different structural units.
  • FIG1 a schematic diagram of a method for preparing a BAB type block copolymer is shown in FIG1 , wherein the end groups 611 of an A-block 61 comprising a structural unit derived from a monomer represented by Formula I are active groups, and the terminal groups 621 of a B-block 62 comprising a structural unit derived from a monomer represented by Formula II are active groups, and the end groups 611 of the A-block react with the terminal groups 621 of the B-block to achieve bonding of polymer segments, thereby preparing a BAB type block copolymer 6.
  • the preparation method has cheap raw materials, can reduce costs, reduce environmental pollution, and is conducive to the increase of adhesive production.
  • the adhesive prepared by this method can slow down the gelation phenomenon of the slurry, improve the stability of the slurry, and improve the adhesion, flexibility and conductivity of the pole piece.
  • FIG1 a schematic diagram of a method for preparing a BAB-type block copolymer is shown in FIG1 , wherein the end groups 611 of an A-block 61 comprising a structural unit derived from a monomer represented by Formula II are active groups, and the terminal groups 621 of a B-block 62 comprising a structural unit derived from a monomer represented by Formula I are active groups, and the end groups 611 of the A-block react with the terminal groups 621 of the B-block to achieve bonding of polymer segments, thereby preparing a BAB-type block copolymer 6.
  • the method of preparing the A-block comprises:
  • At least one monomer represented by Formula I or at least one monomer represented by Formula II and a first initiator are polymerized at a reaction temperature of 80 to 95° C. for 2.5 to 5 hours, and the end groups of the products are substituted. Accordingly, an A-block having an azide group or an alkyne group at both ends is prepared.
  • azide group refers to a -N3 group.
  • alkynyl refers to a -C ⁇ CH group.
  • the method of preparing the A-block comprises:
  • At least one monomer represented by formula I and a first initiator are polymerized at a reaction temperature of 80 to 95° C. for 2.5 to 5 hours, and the end groups of the products are substituted to prepare an A-block having an azide group or an alkynyl group at both ends.
  • azide group refers to a -N3 group.
  • alkynyl refers to a -C ⁇ CH group.
  • the synthesis route of the A-block is as follows: under the action of the first initiator, the monomer shown in Formula I undergoes a polymerization reaction to generate the A-block. Since the terminal groups on both sides of the first initiator are halogen-substituted alkyl or trimethylsilyl acetylene groups, the halogen or trimethylsilyl groups on both sides of the A-block are easily substituted, so that both ends of the A-block have an azide group or an alkynyl group.
  • the A-block with azidation or alkyne at both ends prepared by the preparation method facilitates the A-block to be connected with the B-block in an efficient and mild manner to generate a BAB-type block copolymer.
  • the method of preparing the A-block comprises:
  • At least one monomer represented by formula II and a first initiator are polymerized at a reaction temperature of 80 to 95° C. for 2.5 to 5 hours, and the end groups of the products are substituted to prepare an A-block having an azide group or an alkynyl group at both ends.
  • azide group refers to a -N3 group.
  • alkynyl refers to a -C ⁇ CH group.
  • the synthesis route of the A-block is as follows: under the action of the first initiator, the monomer shown in formula II undergoes a polymerization reaction to generate the A-block. Since the terminal groups on both sides of the first initiator are halogen-substituted alkyl or trimethylsilyl acetylene groups, the halogen or trimethylsilyl groups on both sides of the A-block are easily substituted, so that both ends of the A-block have an azide group or an alkynyl group.
  • the method of preparing the B-block comprises:
  • At least one monomer represented by formula II or at least one monomer represented by formula I, a chain transfer agent and a second initiator are polymerized by reversible addition-fragmentation chain transfer at a reaction temperature of 60 to 75° C. for 4.5 to 6 hours to obtain a B-block having an alkynyl or azide group at the end.
  • RAFT polymerization is a type of reversibly deactivated free radical polymerization, also known as a "living"/controlled free radical polymerization method.
  • the main principle of RAFT polymerization is to add a RAFT agent as a chain transfer agent to the free radical polymerization, and protect the easily terminated free radicals through chain transfer, so that most of the free radicals in the polymerization reaction are converted into dormant free radicals.
  • dormant segments and active segments exist at the same time and are constantly and rapidly switched with each other through dynamic reversible reactions, resulting in only a few polymer chains existing in the form of active chains and growing at any one time, which ultimately makes the growth probability of each polymer segment roughly equal, thus showing the characteristics of living polymerization.
  • the method of preparing the B-block comprises:
  • At least one monomer of formula II, a chain transfer agent and a second initiator are heated to 60 to 75°C.
  • the B-block having an alkynyl or azide group at the end is obtained by reversible addition-fragmentation chain transfer polymerization at a reaction temperature of 4.5 to 6 hours.
  • the synthesis route of the B-block is shown in the figure below, wherein the chain transfer agent is trithiocarbonate, Z' is an active group having an alkynyl or azide group at the end, and R is an alkyl group.
  • the B-block having an alkynyl or azide group at the end is prepared by the following reaction.
  • the reversible addition-fragmentation chain transfer polymerization can achieve controllable polymerization, and the molecular weight distribution of the product is narrow.
  • the B-block only has an alkynyl or azide group at the end, which is convenient for directing and bonding with the A-block in an efficient and mild manner to generate a BAB-type block copolymer.
  • the method of preparing the B-block comprises:
  • At least one monomer of formula I, a chain transfer agent and a second initiator are polymerized by reversible addition-fragmentation chain transfer at a reaction temperature of 60 to 75° C. for 4.5 to 6 hours to obtain a B-block having an alkynyl or azide group at the end.
  • the synthesis route of the B-block is shown in the figure below, wherein the chain transfer agent is trithiocarbonate, Z' is an active group having an alkynyl or azide group at the end, and R is an alkyl group.
  • the B-block having an alkynyl or azide group at the end is prepared by the following reaction.
  • the method of preparing a BAB-type block copolymer comprises:
  • the A-block having an azide group or an alkynyl group at both ends is mixed with the B-block having an alkynyl group or an azide group at the end, and a click reaction is performed to prepare a BAB type block copolymer, wherein The A-block and the B-block have different terminal groups.
  • click reaction refers to a cycloaddition reaction between an alkynyl group and an azide group, so that the A-block is connected to the B-block.
  • the click reaction is carried out in the presence of a Cu(I) catalyst at room temperature and pressure.
  • the terminal group of the A-block is an azide group and the terminal group of the B-block is an alkynyl group.
  • the terminal group of the A-block is an alkynyl group and the terminal group of the B-block is an azide group.
  • the above preparation method has the advantages of high yield, harmless by-products, simple and mild reaction conditions, and readily available reaction raw materials. It can achieve controlled polymerization of block polymers, which is beneficial to improving the yield rate of products.
  • the chain transfer agent is a RAFT chain transfer agent containing a terminal alkynyl or azide group. In some embodiments, the chain transfer agent is a trithiocarbonate containing a terminal alkynyl or azide group. In some embodiments, the structural formula of the chain transfer agent is selected from the following formula,
  • the RAFT chain transfer agent containing a terminal alkynyl or azide group allows the terminal of the B-block to carry an alkynyl or azide group during the synthesis of the B-block, providing a basis for the click reaction between the B-block and the A-block, avoiding complex post-processing steps, and improving the reaction efficiency.
  • the first initiator is a symmetrical bifunctional initiator.
  • the first initiator is 4-(chloromethyl)benzoyl peroxide.
  • the symmetrical bifunctional initiator allows both sides of the A-block to carry the same active functional groups symmetrically, which helps to achieve simultaneous azidation or alkyneation of the terminal groups on both sides of the A-block.
  • the second initiator is an azo initiator.
  • the azo initiator is selected from one or more of azobisisobutyronitrile and azobisisoheptanenitrile.
  • Azo initiator is a commonly used free radical polymerization initiator, which is easy to decompose to form free radicals, and is convenient for initiating free radical polymerization.
  • the BAB type block copolymer may be used in a secondary battery.
  • the secondary battery includes at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.
  • the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, a conductive agent and a binder, and the binder is a BAB type block copolymer in some embodiments or a BAB type block copolymer prepared by the preparation method in some embodiments.
  • the positive electrode sheet has excellent flexibility and adhesion, as well as low membrane resistance.
  • the mass fraction of the binder is 0.1% to 3%, based on the total mass of the positive electrode active material. In some embodiments, the mass fraction of the binder can be selected from any one of 0.1% to 0.2%, 0.2% to 1%, 0.2% to 1.03%, 1% to 3%, and 1.03% to 3%.
  • the binder content When the binder content is too low, the binder cannot exert sufficient bonding effect. On the one hand, the binder cannot fully disperse the conductive agent and active material, resulting in an increase in the membrane resistance of the electrode; on the contrary, when the binder content is too high, the viscosity of the slurry is too high, resulting in a too thick binder coating layer on the surface of the positive electrode active material, which affects the transmission of electrons and ions during the battery cycle and increases the internal resistance of the membrane.
  • the electrode By controlling the mass fraction of the binder within a reasonable range, the electrode has both excellent bonding strength and diaphragm resistance.
  • the mass fraction of the binder is 1% to 3%, based on the total mass of the positive electrode active material. In some embodiments, the mass fraction of the binder can be selected from any one of 1% to 1.03%, 1% to 2%, 2% to 3%, 1% to 3%, and 1.03% to 3%.
  • the mass fraction of the binder is controlled within a reasonable range.
  • the binder can improve the bonding force and flexibility of the electrode, and at the same time improve the electrode's resistance to the electrolyte by increasing the electrode's liquid absorption rate.
  • the wettability of the liquid can be improved, thereby reducing the membrane resistance and improving the cycle performance of the battery.
  • the bonding force per unit length between the positive electrode film layer and the positive electrode current collector is not less than 11 N/m, and can be 11-22 N/m. In some embodiments, the bonding force per unit length between the positive electrode film layer and the positive electrode current collector can be any one of 11 N/m, 11.5 N/m, 12.5 N/m, 13 N/m, 13.5 N/m, 14 N/m, 14.5 N/m, 15 N/m, 15.5 N/m, 16 N/m, 16.5 N/m, 17 N/m, 17.5 N/m, 18 N/m, 18.5 N/m, 19 N/m, 19.5 N/m, 20 N/m, 20.5 N/m, 21 N/m, 21.5 N/m, and 22 N/m.
  • the bonding force per unit length between the positive electrode film layer and the positive electrode current collector can be tested by any means known in the art, such as testing with reference to GB-T2790-1995 national standard "Adhesive 180° Peel Strength Test Method".
  • the positive electrode sheet is cut into a test sample of 20* 100mm2 size for standby use; the electrode sheet is bonded to one side of the positive electrode film layer with double-sided tape, and compacted with a roller to make the double-sided tape and the electrode sheet completely fit; the other side of the double-sided tape is attached to the stainless steel surface, and one end of the sample is bent in the opposite direction with a bending angle of 180°; the high-speed rail tensile machine is used for testing, one end of the stainless steel is fixed to the lower fixture of the tensile machine, the bent end of the sample is fixed to the upper fixture, the angle of the sample is adjusted to ensure that the upper and lower ends are in a vertical position, and then the sample is stretched at a speed of 50mm/min until the
  • the force when the force is balanced divided by the width of the electrode attached to the double-sided tape (the width direction of the electrode is perpendicular to the peeling direction) is taken as the bonding force of the electrode per unit length.
  • the width of the electrode is 20 mm.
  • the positive electrode film layer of the pole piece has high bonding strength with the positive electrode current collector. During use, the positive electrode film layer is not easy to fall off from the positive electrode current collector, which helps to improve the cycle performance and safety of the battery.
  • the positive electrode sheet has a light transmission phenomenon after being subjected to at least 2 bending tests. In some embodiments, the positive electrode sheet has a light transmission phenomenon after being subjected to at least 2, 2.3, 2.7, 3.3, 3.5, 3.7 or 4 bending tests.
  • the positive electrode sheet after the positive electrode sheet has been subjected to at least 3 bending tests, the positive electrode sheet has a light transmission phenomenon. In some embodiments, after the positive electrode sheet has been subjected to at least 3.3, 3.5, 3.7 or 4 bending tests, the positive electrode sheet has a light transmission phenomenon.
  • the bending test also known as the flexibility test, can be used to test the flexibility of the electrode.
  • the test can be performed by any means known in the art.
  • the cold-pressed positive electrode is cut into a test sample of 20 *100mm2; after folding it in the forward direction, it is flattened with a 2kg roller, and unfolded to check whether the gap is transparent. If it is not transparent, it is folded in the reverse direction, flattened with a 2kg roller, and checked again against the light. This is repeated until the gap is transparent, and the number of folds is recorded; at least three samples are tested, and the average value is taken as the test result of the bending test.
  • the electrode can undergo no less than 3 bending tests, indicating that the electrode has good flexibility and is not prone to cracking during the production process or brittle breakage during use, which helps to improve the yield rate of the battery and improve the safety performance of the battery.
  • the electrolyte absorption rate of the positive electrode plate is greater than 0.30 ⁇ g/s, and may be 0.35-0.6 ⁇ g/s, and the density of the electrolyte is 1.1-1.2 g/cm 3 .
  • the electrolyte absorption rate of the positive electrode plate is 0.36 ⁇ g/s, 0.37 ⁇ g/s, 0.38 ⁇ g/s, 0.39 ⁇ g/s, 0.40 ⁇ g/s, 0.41 ⁇ g/s, 0.42 ⁇ g/s, 0.43 ⁇ g/s, 0.44 ⁇ g/s, 0.45 ⁇ g/s, 0.46 ⁇ g/s, 0.47 ⁇ g/s, 0.484 ⁇ g/s, 0.49 ⁇ g/s, 0.50 ⁇ g/s or 0.6 ⁇ g/s, and the density of the electrolyte is 1.1-1.2 g/cm 3 .
  • the liquid absorption rate of the electrode can reflect the ability of the electrode to wet in the electrolyte.
  • the electrolyte can be prepared by dissolving lithium hexafluorophosphate in a mixed solvent of ethylene carbonate and ethyl methyl carbonate, the mass content of the lithium hexafluorophosphate solution is 12.5%, and the volume ratio of ethylene carbonate to ethyl methyl carbonate in the solution is 3:7.
  • the electrode has a high liquid absorption rate, which can improve the electrolyte infiltration efficiency of the electrode, improve the ion transmission path, reduce the interface resistance, and improve the battery performance.
  • the positive electrode current collector has two surfaces opposite to each other in its 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 may be used.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material for a battery known in the art.
  • the positive electrode 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 for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to , lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide (such as LiNiO2 ), lithium manganese oxide (such as LiMnO2 , LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333 ), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ) , LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211 ) , LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622 ), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode film layer may also optionally include a conductive agent.
  • the conductive agent may include superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, etc. At least one of graphene, carbon nanofibers and graphene.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet 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, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its 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 metal foil copper foil may 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 substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may adopt the negative electrode active material for the battery known in the art.
  • the negative electrode 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, etc.
  • 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 negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate At least one of poly(methacrylic acid) (SA), poly(methacrylic acid) (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • SA poly(methacrylic acid)
  • PMAA poly(methacrylic acid)
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • a conductive agent which 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 may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may also optionally include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of Additives that improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • 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 membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the 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 package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG2 is a secondary battery 5 of a square structure as an example.
  • the secondary battery may also be a sodium ion battery, a magnesium ion battery, or a potassium ion battery.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in 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 make adjustments according to specific actual needs. choose.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG4 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. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG5 and FIG6 are battery packs 1 as an example.
  • 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 body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • an electric device comprising at least one of a secondary battery of any embodiment, a battery module of any embodiment, or a battery pack of any embodiment.
  • the power-consuming device includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the power-consuming device, or as an energy storage unit for the power-consuming device.
  • the power-consuming device may include a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, Ships, satellites, energy storage systems, etc., but not limited to these.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • FIG7 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.
  • B-block Preparation of B-block: Acrylamide monomer, RAFT chain transfer agent (CTA-alkyne) and azobisisobutyronitrile in a molar ratio of 700:1:0.1 were added to 500 ml of tetrahydrofuran solution. The mixture was subjected to at least three freeze-pump-thaw cycles and placed in an oil bath preheated to 70°C. After 6 h of reaction, the reaction was terminated by cooling in liquid nitrogen and the solution was precipitated in excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting polymer was dried under vacuum at room temperature for 10 hours to remove all traces of residual solvent to obtain an alkynyl-terminated polyacrylamide with a weight average molecular weight of 400,000.
  • CTA-alkyne RAFT chain transfer agent
  • azobisisobutyronitrile in a molar ratio of 700:1:0.1
  • A-block 1% of the monomer mass of 4-(chloromethyl)benzoyl peroxide was dissolved in 300 mL of anhydrous acetonitrile, and the solution was then introduced into a high-pressure reactor and purged with N2 for 30 minutes. Subsequently, 4 g of vinylidene fluoride monomer was transferred to the reactor at room temperature. The temperature inside the reactor was raised to 90°C, and the reaction mixture was stirred at 500 rpm for another 3 h. The reactor was cooled to room temperature with water and decompressed to remove unreacted monomers. Vacuum removal The solvent was removed and the solid was washed with chloroform several times to remove the initiator residues.
  • the polymer was vacuum dried at 45°C to obtain a white product.
  • 3mmol of chlorine-terminated polyvinylidene fluoride and 60mmol of NaN 3 were dissolved in 600mL of N,N-dimethylformamide (DMF) and stirred at 60°C for 10 hours.
  • the polymer solution was concentrated and precipitated three times in a mixed solvent (methanol to water volume ratio of 1:1).
  • the light yellow polymer was then vacuum dried at 45°C to obtain an azide-terminated PVDF with a weight average molecular weight of 450,000, i.e., the A-block polymer.
  • BAB-type block copolymers Azide-terminated polyvinylidene fluoride, alkyne-terminated polyacrylamide and CuBr were added to a dry Schlenk tube in a molar ratio of 1:2.5:4. After a degassing procedure (three repeated cycles of evacuation and backfilling with N2) , 4 mL of anhydrous N,N-dimethylformamide (DMF) was added, followed by 0.14 mmol of N,N,N',N,'N"-pentamethyldiethylenetriamine (PMDETA). The reaction was stirred at 60°C for 3 days and terminated by exposure to air. The reaction mixture was filtered through a neutral alumina column to remove the copper catalyst.
  • DMF N,N-dimethylformamide
  • PMDETA N,N,N',N,'N"-pentamethyldiethylenetriamine
  • the solution was concentrated under reduced pressure and precipitated in a 20-fold excess of a mixed solvent (methanol to water volume ratio of 1:1) to fully dissolve the polyacrylamide blocks that did not participate in the reaction.
  • a mixed solvent methanol to water volume ratio of 1:1
  • the product was collected by filtration and dried under vacuum at room temperature for 10 hours to obtain a polyacrylamide-polyvinylidene fluoride-polyacrylamide triblock copolymer with a weight average molecular weight of 1.2 million.
  • LiNi 0.8 Co 0.1 Mn 0.1 O 2 lithium nickel cobalt manganese (NCM) material, conductive agent carbon black, binder of Example 1, and N-methylpyrrolidone (NMP) were stirred and mixed in a weight ratio of 96.9:2.1:1:21 to obtain a positive electrode slurry with a solid content of 73%.
  • the positive electrode slurry was then evenly coated on the positive electrode collector, and then dried, cold pressed, and cut to obtain a positive electrode sheet.
  • the active material artificial graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR), and the thickener sodium hydroxymethyl cellulose (CMC) are dissolved in the solvent deionized water in a weight ratio of 96.2:0.8:0.8:1.2, and the negative electrode slurry is prepared after being evenly mixed; the negative electrode slurry is evenly coated on the negative electrode collector copper foil once or multiple times, and the negative electrode sheet is obtained after drying, cold pressing, and slitting.
  • Polypropylene film is used as the isolation film.
  • the positive electrode sheet, the separator, and the negative electrode sheet of Example 1 are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare cell, and the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum shell, and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain the lithium ion battery product of Example 1.
  • the preparation method of the batteries of Examples 2 to 7 is similar to that of the battery of Example 1, but the weight average molecular weight of the A-block and the B-block is adjusted by adjusting the polymerization monomer amount, reaction temperature and reaction time of the A-block and the B-block respectively, and the weight average molecular weight of the polyacrylamide-polyvinylidene fluoride-polyacrylamide triblock copolymer is ensured to be 1.2 million.
  • the specific adjustment parameters are shown in Table 1.
  • the preparation methods of the batteries of Examples 2 to 7 are similar to those of the battery of Example 1, but the weight average molecular weights of the A-block and the B-block are adjusted by adjusting the polymerization monomer amounts, reaction temperature and reaction time of the A-block and the B-block, respectively, and then the weight average molecular weight of the polyacrylamide-polyvinylidene fluoride-polyacrylamide triblock copolymer is adjusted.
  • the specific adjustment parameters are shown in Table 1.
  • the preparation method of the battery of Example 16 is similar to that of the battery of Example 4, but the B-block is replaced by a poly (N-isopropylacrylamide) block.
  • the specific parameters are shown in Table 1.
  • the preparation method is as follows:
  • N-isopropylacrylamide monomer, RAFT chain transfer agent (CTA-alkyne) and azobisisobutyronitrile in a molar ratio of 700:1:0.1 were added to 500 ml of tetrahydrofuran solution.
  • the mixture was subjected to at least three freeze-pump-thaw cycles and placed in an oil bath preheated to 70°C. After 6 h of reaction, the reaction was terminated by cooling in liquid nitrogen and the solution was precipitated in a large excess of methanol.
  • the polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting polymer was dried under vacuum at room temperature for 10 hours to remove all traces of residual solvent.
  • the preparation method of the battery of Example 17 is similar to that of the battery of Example 1, but the A-block is replaced by a poly(vinylidene fluoride-hexafluoropropylene) block.
  • the specific parameters are shown in Table 2.
  • the preparation method is as follows:
  • the polymer was vacuum dried at 45°C to obtain a white product.
  • 3 mmol of chlorine-terminated poly(vinylidene fluoride-hexafluoropropylene) and 60 mmol of NaN 3 were dissolved in 600 mL of N,N-dimethylformamide (DMF) and stirred at 60°C for 10 hours.
  • the polymer solution was concentrated and precipitated three times in a mixed solvent (methanol to water volume ratio of 1:1).
  • the light yellow polymer was then dried in vacuo at 45° C. to obtain an azide-terminated poly(vinylidene fluoride-hexafluoropropylene) having a weight average molecular weight of 450,000, ie, the A-block polymer.
  • the preparation method of the battery of Example 18 is similar to that of the battery of Example 1, but the A-block is replaced with a poly(vinylidene fluoride-tetrafluoroethylene) block.
  • the specific parameters are shown in Table 2.
  • the preparation method is as follows:
  • the light yellow polymer was then vacuum dried at 45°C to obtain azide-terminated poly(vinylidene fluoride-tetrafluoropropylene) with a weight average molecular weight of 450,000, i.e., A-block polymer.
  • RAFT chain transfer agent CTA-alkyne
  • polymerization reaction is used to prepare alkynyl-terminated polyvinylidene fluoride; wherein the structural formula of RAFT chain transfer agent is as follows
  • Polyacrylamide with azide groups at both ends, polyvinylidene fluoride with alkynyl groups at the ends, and cuprous bromide were added to a dry Schlenk tube in a molar ratio of 1:2.5:4. After degassing, 4 ml of anhydrous N,N-dimethylformamide (DMF) and 0.14 mmol N,N,N',N,'N"-pentamethyldiethylenetriamine (PMDETA) were added. The reaction was stirred at 60°C for 3 days and terminated by exposure to air.
  • DMF N,N-dimethylformamide
  • PMDETA 0.14 mmol N,N,N',N,'N"-pentamethyldiethylenetriamine
  • the reaction mixture was filtered through a neutral alumina column to remove the copper catalyst, the solution was concentrated under reduced pressure and precipitated in a 20-fold excess of a mixed solvent (the volume ratio of methanol to water was 1:1), the product was collected by filtration, and vacuum dried to obtain a polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride block copolymer with a weight average molecular weight of 1.2 million, which was used as a battery binder.
  • Embodiments 20 to 25 are identical to Embodiments 20 to 25.
  • the preparation method of the batteries of Examples 20 to 25 is similar to that of the battery of Example 19, but the polymerization reaction temperature and reaction temperature of the A-block and the B-block are adjusted respectively, the polymerization degree of the A-block and the B-block is adjusted, the weight average molecular weight of the A-block and the B-block is adjusted, and the weight average molecular weight of the polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride triblock copolymer is ensured to be 1.2 million.
  • the specific adjustment parameters are shown in Table 2.
  • the preparation method of the battery of Examples 26 to 29 is similar to that of the battery of Example 19, but the polymerization reaction temperature and reaction temperature of the A-block and the B-block are adjusted respectively, the polymerization degree of the A-block and the B-block is adjusted, and the weight average molecular weight of the A-block and the B-block is adjusted, thereby adjusting the polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride triblock copolymer.
  • the specific adjustment parameters are shown in Table 2.
  • the preparation methods of the batteries of Examples 30 to 33 are similar to those of the batteries of Example 19, but the mass fraction of the binder is adjusted.
  • the specific parameters are shown in Table 2 based on the mass of the positive electrode active material.
  • the preparation method of the battery of Example 34 is similar to that of the battery of Example 19, but the A-block is replaced by a poly (N-isopropylacrylamide) block.
  • the specific parameters are shown in Table 2.
  • the preparation method is as follows:
  • the preparation method of the battery of Example 35 is similar to that of the battery of Example 19, but the B-block is replaced with a poly(vinylidene fluoride-hexafluoropropylene) block.
  • the specific parameters are shown in Table 2.
  • the preparation method is as follows:
  • the preparation method of the battery of Example 36 is similar to that of the battery of Example 19, but the B-block is replaced with a poly(vinylidene fluoride-tetrafluoroethylene) block.
  • the specific parameters are shown in Table 2.
  • the preparation method is as follows:
  • the product is vacuum dried overnight at room temperature to remove all traces of residual solvent to obtain a poly (vinylidene fluoride-tetrafluoroethylene) with an alkynyl group at the end, i.e., a B-block polymer.
  • the preparation method of the battery of Comparative Example 1 is similar to that of the battery of Example 1, but the binder is polyvinylidene fluoride with a weight average molecular weight of 1.2 million, which is 5130 purchased from Solvay Group.
  • the preparation method of the battery of Comparative Example 2 is similar to that of the battery of Example 1, but the binder is polyacrylamide with a weight average molecular weight of 1.2 million, purchased from France's Essen Company AN934SHUC/PWG.
  • the preparation method of the battery of Comparative Example 3 is similar to that of the battery of Example 1, but the binder is a blend of polyvinylidene fluoride and polyacrylamide, and the preparation method is as follows:
  • Blending The polyacrylamide in Comparative Example 2 and the polyvinylidene fluoride in Comparative Example 1 are blended in a molar ratio of 6:4 to obtain a polyvinylidene fluoride and polyacrylamide blend adhesive.
  • a Waters 2695 Isocratic Hour PLC gel chromatograph (differential refractive index detector 2141) was used.
  • a polystyrene solution sample with a mass fraction of 3.0% was used as a reference, and a matching chromatographic column was selected (oily: Styragel Hour T5DMF7.8*300mm+Styragel Hour T4).
  • a 3.0% polymer gel solution was prepared with purified N-methylpyrrolidone (NMP) solvent, and the prepared solution was allowed to stand for one day for use.
  • NMP N-methylpyrrolidone
  • tetrahydrofuran was first drawn with a syringe, rinsed, and repeated several times. Then 5 ml of the experimental solution was drawn, the air in the syringe was expelled, and the needle tip was wiped dry. Finally, the sample solution was slowly injected into the injection port. Data was obtained after the indication stabilized.
  • test After re-stirring the slurry for 30 minutes, take a certain amount of slurry and pour it into the sample bottle of the stability instrument. After putting it into the sample bottle, close the test tower cover, open the test tower cover, and a scanning curve will begin to appear on the test interface, and the sample stability test will begin. The test will be completed after more than 48 hours of continuous testing.
  • the force at force balance divided by the width of the electrode piece bonded to the double-sided tape (the width direction of the electrode piece is perpendicular to the peeling direction) is taken as the bonding force of the electrode piece per unit length.
  • the width of the electrode piece bonded to the double-sided tape is 20mm.
  • the cold-pressed positive electrode sheet is cut into test specimens of 20 *100mm2 size; after folding it in the forward direction, it is flattened with a 2kg roller, and unfolded to check whether there is light transmittance through the gap. If there is no light transmittance, fold it in the reverse direction, flatten it with a 2kg roller, and check again against the light. Repeat this process until light transmittance appears in the gap, and record the number of folding times; repeat the test three times, and take the average value as the reference data for the flexibility of the electrode sheet.
  • the 500 point values of P1, P2...P500 are used as the vertical coordinates, and the corresponding number of cycles is used as the horizontal coordinates to obtain a curve graph of the battery capacity retention rate and the number of cycles.
  • the battery capacity retention rate data corresponding to the embodiments or comparative examples in Table 1 are obtained under the above test conditions.
  • the data measured after 500 cycles under the condition is the value of P500.
  • the test process of the comparative example and other embodiments is the same as above.
  • the battery DC impedance test process is as follows: at 25°C, charge the battery at a constant current of 1/3C to 4.3V, then charge at a constant voltage of 4.3V to a current of 0.05C, leave it for 5 minutes, and record the voltage V1. Then discharge it at 1/3C for 30s, record the voltage V2, and then (V2-V1)/(1/3C) is the internal resistance DCR1 of the battery after the first cycle.
  • Example 1 (DCRn-DCR1)/DCR1*100%, and the test process of the comparative example and other embodiments is the same as above.
  • the data in Table 1 are measured after 100 cycles under the above test conditions.
  • the preparation parameters and performance tests of the block copolymer are shown in Table 1.
  • the performance tests of the slurry and the battery are shown in Table 2.
  • the binder in Examples 1 to 36 is a BAB type block copolymer, comprising an A-block and a B-block, wherein the B-block in Examples 1 to 18 contains a structural unit derived from acrylamide or N-isopropylacrylamide, and the A-block contains a structural unit derived from vinylidene fluoride or vinylidene fluoride-hexafluoropropylene or vinylidene fluoride-tetrafluoroethylene; the B-block in Examples 19 to 36 contains a structural unit derived from vinylidene fluoride or vinylidene fluoride-hexafluoropropylene or vinylidene fluoride-tetrafluoroethylene, and the A-block contains a structural unit derived from acrylamide or N-isopropylacrylamide.
  • the B-block contains a structural unit derived from acrylamide or N-isopropylacrylamide
  • the A-block contains at least a structural unit derived from vinylidene fluoride.
  • the BAB type block copolymer can significantly slow down the gelation of the slurry, improve the stability of the slurry, improve the flexibility of the pole piece, and improve the adhesion of the pole piece.
  • the electrode's wettability to the electrolyte is improved, thereby reducing the membrane resistance.
  • the B-block contains structural units derived from vinylidene fluoride, and the A-block contains at least structural units derived from acrylamide or N-isopropylacrylamide.
  • the BAB-type block copolymer can significantly slow down the gelation phenomenon of the slurry, improve the slurry stability, and improve the adhesion and flexibility of the electrode.
  • the electrode's ability to infiltrate the electrolyte is improved, so that the electrode has a low membrane resistance and reduces the DC impedance growth rate of the current.
  • Example 1 From the comparison between Example 1 and Comparative Example 3, it can be seen that the polyacrylamide-polyvinylidene fluoride-polyacrylamide triblock copolymer can slow down the gelation phenomenon of the slurry, improve the slurry stability, improve the flexibility of the electrode, and improve the bonding strength. At the same time, by increasing the electrode liquid absorption rate, the electrode's ability to infiltrate the electrolyte is improved, thereby reducing the membrane resistance, reducing the internal resistance growth rate of the battery and improving the battery's cycle capacity retention rate.
  • Example 23 From the comparison between Example 23 and Comparative Example 3, it can be seen that the polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride triblock copolymer can slow down the gelation phenomenon of the slurry, improve the slurry stability, improve the flexibility of the electrode, and improve the adhesion of the electrode. At the same time, by increasing the liquid absorption rate of the electrode, the electrode's ability to infiltrate the electrolyte is improved, so that the electrode has a low membrane resistance, and reduces the internal resistance growth rate of the battery and improves the battery's cycle capacity retention rate.
  • the molar content of the structural unit derived from the vinylidene fluoride monomer in the polymer is 40% to 60%, based on the total molar number of all structural units in the block copolymer, so that the electrode has excellent adhesion, good electrode liquid absorption rate and low membrane resistance.
  • a comparison of Examples 19 to 23 and Examples 24 to 25 shows that the molar content of the structural unit derived from the vinylidene fluoride monomer in the polymer is 40% to 60%, based on the total molar number of all structural units in the block copolymer, so that the electrode has excellent adhesion, good electrode liquid absorption rate and low membrane resistance, thereby improving the cycle performance of the battery.
  • the weight average molecular weight of the polyacrylamide-polyvinylidene fluoride-polyacrylamide triblock copolymer is 1.2 million to 2 million.
  • the binder can improve the adhesion and flexibility of the electrode, and at the same time improve the wettability of the electrode to the electrolyte by increasing the liquid absorption rate of the electrode, thereby reducing the membrane resistance, reducing the internal resistance growth rate of the battery and improving the cycle capacity retention rate of the battery.
  • Example 4 By comparing Examples 10 to 11 with Examples 8 to 9, it can be seen that when the weight average molecular weight of the polyvinylidene fluoride block in the polyacrylamide-polyvinylidene fluoride-polyacrylamide block copolymer is 400,000 to 1.1 million, the binder can improve the adhesion and flexibility of the electrode, so that the electrode has a lower diaphragm resistance, reduce the internal resistance growth rate of the battery, and improve the cycle capacity retention rate of the battery.
  • the weight average molecular weight of the polyacrylamide in the polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride triblock copolymer is 400,000 to 1.1 million, and the binder can improve the bonding force of the pole piece and improve the cycle performance of the battery.
  • the mass fraction of the binder of the polyacrylamide-polyvinylidene fluoride-polyacrylamide block copolymer is 0.1% to 3%, and the slurry has good stability based on the mass of the positive electrode active material. From the comparison of Examples 1, 14 to 15 with Examples 12 to 13, it can be seen that the mass fraction of the binder is 1% to 3%, and the binder can improve the bonding force and flexibility of the pole piece by increasing the liquid absorption rate of the pole piece, thereby improving the wettability of the pole piece to the electrolyte, thereby reducing the membrane resistance and improving the cycle performance of the battery.
  • the mass fraction of the binder of the polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride triblock copolymer is 0.1% to 3%, and the slurry has good stability based on the mass of the positive electrode active material.
  • the mass fraction of the binder is 1% to 3%, and the binder can improve the bonding force and flexibility of the pole piece by increasing the liquid absorption rate of the pole piece, improving the wettability of the pole piece to the electrolyte, reducing the membrane resistance, reducing the internal resistance growth rate of the battery, and improving the cycle performance of the battery.

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Abstract

本申请提供了一种BAB型嵌段共聚物、制备方法、粘结剂、正极极片、二次电池及用电装置。A-嵌段含有衍生自式I所示单体的结构单元，B-嵌段含有衍生自式II所示单体的结构单元，或者A-嵌段含有衍生自式II所示单体的结构单元，B-嵌段含有衍生自式I所示单体的结构单元，其中R1、R2、R3各自独立地选自氢、氟、三氟甲基中的一种或多种，R4、R5、R6、R7、R8各自独立地选自氢、取代或未取代的C1-3烷基。

Description

BAB型嵌段共聚物、制备方法、粘结剂、正极极片、二次电池及用电装置
交叉引用
本申请引用于2022年9月30日递交的名称为“BAB型嵌段共聚物、制备方法、粘结剂、正极极片、二次电池及用电装置”的第202211205567.3号中国专利申请以及于2022年10月27日递交的名称为“BAB型嵌段共聚物、制备方法、正极极片、二次电池、电池模板、电池包及用电装置”的第PCT/CN2022/128035号专利申请，其通过引用被全部并入本申请。
技术领域
本申请涉及二次电池技术领域，尤其涉及一种BAB型嵌段共聚物、制备方法、粘结剂、正极极片、二次电池和用电装置。
背景技术
近年来，二次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。
粘结剂是二次离子电池中的常用材料，广泛应用于电池极片、隔离膜、封装处等。但是传统的粘结剂生产成本高、产能不足，对环境危害大，且在制备过程中容易出现凝胶，导致浆料稳定性差、加工成本高，以其制备的极片导电性差、电阻高、良品率低，电池性能不稳定，难以满足市场对于电池成本和性能的要求。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BAB 型嵌段共聚物，以该嵌段共聚物作为粘结剂能够有效减缓浆料的凝胶现象，提高浆料的稳定性，同时提高极片的粘结力和柔韧性。
本申请的第一方面提供一种BAB型嵌段共聚物，包含A-嵌段和B-嵌段，A-嵌段含有衍生自式I所示单体的结构单元，B-嵌段含有衍生自式II所示单体的结构单元，
或者A-嵌段含有衍生自式II所示单体的结构单元，B-嵌段含有衍生自式I所示单体的结构单元，
其中，R1、R2、R3各自独立地选自氢、氟、至少含有一个氟原子的C1-3烷基中的一种或多种，R4、R5、R6、R7、R8各自独立地选自氢、取代或未取代的C1-3烷基。
该BAB型嵌段共聚物可以将含氟嵌段和非氟嵌段的重均分子量最大化，充分发挥含氟粘结剂和非氟粘结剂各自的优势，实现优势互补的作用。以其作为粘结剂能够显著减缓浆料的凝胶现象，提高浆料稳定性、极片的柔韧性和粘结力，同时通过提高极片吸液速率，能够改善极片在电解液中的浸润能力，极片具有低的膜片电阻。
在任意实施方式中，衍生自式I所示单体的结构单元的摩尔含量为40％～60％，衍生自式II所示单体的结构单元的摩尔含量为40％～60％，基于嵌段共聚物中所有结构单元的总摩尔数计。
控制衍生自式I所示单体的结构单元的摩尔含量在合适范围内，使得极片兼具优异的粘结力、良好的极片吸液速率以及较低的膜片电阻。
在任意实施方式中，嵌段共聚物的重均分子量为40万～200万，可选为120万～200万。
重均分子量在合适范围内的嵌段共聚物使得极片具有良好的粘 结力和柔韧性，改善极片的使用性能。
在任意实施方式中，嵌段共聚物中A-嵌段的重均分子量为20万～110万，可选为40万～110万。
A-嵌段的重均分子量在合适范围内的嵌段共聚物使得极片具有良好的粘结力和柔韧性，改善极片的使用性能。
在任意实施方式中，嵌段共聚物中每个B-嵌段的重均分子量为10万～50万，可选为20万～50万。
每个B-嵌段的重均分子量在合适范围内的嵌段共聚物使得极片具有良好的粘结力和柔韧性，改善极片的使用性能。
在任意实施方式中，式I所示单体选自偏氟乙烯、四氟乙烯、六氟丙烯中的一种或多种。
在任意实施方式中，式II所示单体选自丙烯酰胺、甲基丙烯酰胺、N-甲基丙烯酰胺、N-甲基甲基丙烯酰胺、N-异丙基丙烯酰胺、N-异丙基甲基丙烯酰胺、N-叔丁基丙烯酰胺、N-叔丁基(甲基)丙烯酰胺、N,N-二甲基丙烯酰胺、N,N-二甲基甲基丙烯酰胺、N,N-二乙基丙烯酰胺、N,N-二乙基甲基丙烯酰胺的一种或多种。
上述原材料简单易得，相比于现有技术中的粘结剂能够大幅度降低生产成本，提高产量。
任意实施方式中，BAB型嵌段共聚物为聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺三嵌段共聚物、聚甲基丙烯酰胺-聚四氟乙烯-聚甲基丙烯酰胺三嵌段共聚物、聚N-甲基甲基丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)-聚N-甲基甲基丙烯酰胺三嵌段共聚物、聚N-异丙基丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)-聚N-异丙基丙烯酰胺三嵌段共聚物、聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物、聚四氟乙烯-聚甲基丙烯酰胺-聚四氟乙烯三嵌段共聚物、聚(偏二氟乙烯-六氟丙烯)-聚N-甲基甲基丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)三嵌段共聚物、聚(偏二氟乙烯-四氟乙烯)-聚N-异丙基丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)三嵌段共聚物中的一种或多种。
本申请的第二方面还提供一种BAB型嵌段共聚物的制备方法，包括以下步骤：
制备A-嵌段：将至少一种式I所示单体或至少一种式II所示单体聚合制备A-嵌段，
其中，R1、R2、R3各自独立地选自氢、氟、至少含有一个氟原子的C1-3烷基中的一种或多种，R4、R5、R6、R7、R8各自独立地选自氢、取代或未取代的C1-3烷基；
制备B-嵌段：将至少一种式II所示单体或至少一种式I所示单体聚合制备B-嵌段，
制备BAB型嵌段共聚物：将所述A-嵌段和所述B-嵌段接合制备BAB型嵌段共聚物，其中所述A-嵌段和所述B-嵌段含有不同的结构单元。
该制备方法相对于现有技术中常用的共聚方法可以将含氟嵌段和非氟嵌段的重均分子量最大化，充分发挥含氟粘结剂和非氟粘结剂各自的优势，实现优势互补的作用。该方法制备的粘结剂能够减缓浆料的凝胶现象，提高浆料的稳定性，提高极片的粘结力和柔韧性，同时通过提高极片吸液速率，改善极片在电解液中的浸润能力，极片具有优异的膜片电阻。
在任意实施方式中，制备A-嵌段的方法包括：
将至少一种式I所示单体或至少一种式II所示单体、第一引发剂在80～95℃的反应温度下聚合反应2.5～5h，对产物进行取代反应，制备两端均具有叠氮基团或炔基的A-嵌段。
采用该制备方法，成功制备出末端叠氮化或炔基化的A-嵌段。
在任意实施方式中，制备B-嵌段的方法包括：
将至少一种式II所示单体或至少一种式I所示单体、链转移剂和第二引发剂在60～75℃的反应温度下通过可逆加成-裂解链转移聚合， 反应4.5～6h，得到末端具有炔基或叠氮基团的B-嵌段。
采用该制备方法，可实现可控聚合，且产物分子量分布较窄。
在任意实施方式中，制备BAB型嵌段共聚物的方法包括：
将两端均具有叠氮基团或炔基的A-嵌段与末端具有炔基或叠氮基团的B-嵌段混合，进行点击反应，制备BAB型嵌段共聚物，其中，所述A-嵌段和所述B-嵌段的端基不同。
上述制备方法，具有高效稳定、高特异性的优点，能够提高产品的良品率。
在任意实施方式中，链转移剂为含末端炔基或叠氮基团的RAFT链转移剂。
在任意实施方式中，第一引发剂对称型双官能度引发剂。
在任意实施方式中，第二引发剂为偶氮引发剂。
在本申请的第三方面，提供一种BAB型嵌段共聚物在二次电池中的应用。
本申请的第四方面提供一种正极极片，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，所述正极膜层包括正极活性材料、导电剂和粘结剂，所述粘结剂为任意实施方式中的BAB型嵌段共聚物或任意实施方式中的制备方法制备的BAB型嵌段共聚物。
该正极极片具有优异的柔韧性、粘结力和较低的膜片电阻。
在任意实施方式中，粘结剂的质量分数为0.1％～3％，可选为1％～3％，基于正极活性材料的总质量计。
控制粘结剂的质量分数在合理范围内，浆料具有较好的稳定性。
在任意实施方式中，所述正极膜层与所述正极集流体间单位长度的粘结力不小于11N/m，可选为11-22N/m。
该极片的正极膜层与正极集流体之间具有高的粘结强度，在使用过程中，正极膜层不容易从正极集流体上脱落，有助于提高电池的循环性能和安全性。
在任意实施方式中，所述正极极片在经过不少于3次的弯折测试后，所述正极极片出现透光现象。
该极片具有优异的柔韧性，不易在生产过程中出现极片崩裂的现象，有助于提高良品率。
在任意实施方式中，所述正极极片对电解液的吸液速率大于0.30μg/s，可选为0.35-0.6μg/s，所述电解液的密度为1.1-1.2g/cm3。
该极片具有较高的吸液速率，能够提高电解液对极片的浸润效率，改善离子传输路径，降低界面电阻，提高电池性能。
在本申请的第五方面，提供一种二次电池，包括电极组件和电解液，所述电极组件包括隔离膜、负极极片和本申请第四方面的正极极片。
在本申请的第六方面，提供一种用电装置，包括本申请第五方面的二次电池。
附图说明
图1是本申请一实施方式的BAB型嵌段共聚物的制备示意图；
图2是本申请一实施方式的二次电池的示意图；
图3是图2所示的本申请一实施方式的二次电池的分解图；
图4是本申请一实施方式的电池模块的示意图；
图5是本申请一实施方式的电池包的示意图；
图6是图5所示的本申请一实施方式的电池包的分解图；
图7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盖板；6BAB型嵌段共聚物；61A-嵌段；611A-嵌段的两端基团；62B-嵌段，621B-嵌段的末端基团。
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正极活性材料及其制造方法、正极极片、二次电池、电池模块、电池包和电学装置的实施方式。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，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)。
现有技术中常以聚偏二氟乙烯(PVDF)作为极片粘结剂，然而PVDF在使用过程中存在诸多问题，如生产过程中对水含量较为敏感；在电池回收过程中，会产生大量HF污染环境，受环保政策的限制无法大规模回收利用；在与高容量的正极活性材料(如高镍三元材料)混合制备正极浆料的过程中，PVDF上的强极性基团会活化正极活性材料上残留的羟基，进而与正极活性材料中的金属元素(如镍元素)发生键合反应，形成化学交联，最终导致浆料凝胶，影响浆料的正常制备以及后续的极片加工。另外PVDF容易结晶，不利于电子在极片中的传输，进而导致极片的电阻高、电子传输性能差，不利于高容量的正极活性材料性能的发挥。
[BAB型嵌段共聚物]
基于此，本申请提出了一种BAB型嵌段共聚物，A-嵌段含有衍生自式I所示单体的结构单元，B-嵌段含有衍生自式II所示单体的结构单元，
或者A-嵌段含有衍生自式II所示单体的结构单元，B-嵌段含有衍生自式I所示单体的结构单元，
其中，R1、R2、R3各自独立地选自氢、氟、至少含有一个氟原子的C1-3烷基中的一种或多种，R4、R5、R6、R7、R8各自独立地选自氢、取代或未取代的C1-3烷基。
在本文中，术语“嵌段共聚物”是将两种或两种以上性质不同的聚合物链段连在一起制备而成的一种特殊聚合物。具有特定结构的嵌段聚合物会表现出与简单线形聚合物，以及许多无规共聚物甚至均聚物的混合物不同的性质。常见的有AB型和BAB型，其中A、B都是长链段；也有(AB)n型多段共聚物，其中A、B链段相对较短。
在本文中，术语“BAB型嵌段共聚物”是指中间为A-嵌段，两侧为B-嵌段的三嵌段共聚物。其中，A-嵌段和B-嵌段分别是由不同的单体聚合形成的具有预定重均分子量的聚合物链段。在一些实施方式中，A-嵌段是由含氟单体聚合形成的长序列链段，B-嵌段是由一种或多种不含氟单体聚合形成的长序列链段。A-嵌段和B-嵌段以有序的方式经共价键结合形成BAB型嵌段共聚物。以实施例1中制备的BAB型嵌段聚合物为例，其中B-嵌段聚丙烯酰胺，由丙烯酰胺单体聚合形成，重均分子量为40万；A-嵌段为聚偏二氟乙烯，由偏二氟乙烯单体聚合形成，重均分子量为45万；B-嵌段和A-嵌段的两侧的端基键合得到聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺嵌段共聚物(BAB型嵌段共聚物)，该嵌段共聚物的重均分子量为120万。
在一些实施方式中，BAB型嵌段共聚物中A-嵌段含有衍生自式I所示单体的结构单元，B-嵌段含有衍生自式II所示单体的结构单元。
在一些实施方式中，BAB型嵌段共聚物中A-嵌段含有衍生自式II所示单体的结构单元，B-嵌段含有衍生自式I所示单体的结构单元，
在一些实施方式中，A-嵌段是由一种或多种不含氟单体聚合形成的长序列链段，B-嵌段是由一种或多种含氟单体聚合形成的长序列链段。A-嵌段和B-嵌段以有序的方式经共价键结合形成BAB型嵌段共聚物。以实施例19中制备的BAB型嵌段聚合物为例，其中A-嵌段为聚丙烯酰胺，由丙烯酰胺单体聚合形成，重均分子量为66万；B-嵌段为聚偏二氟乙烯，由偏二氟乙烯单体聚合形成，重均分子量为27万；B-嵌段和A-嵌段的两侧的端基键合得到聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯嵌段共聚物(BAB型嵌段共聚物)，该嵌段共聚物的重均分子量为120万。
在本文中，术语“聚合物”一方面包括通过聚合反应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“C1-3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。C1-3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“取代的”是指该化合物或化学部分的至少一个氢原子被另一种化学部分被取代基取代，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、烯基、炔基、芳基、杂芳基、C1-6烷基、C1-6烷氧基。
在一些实施方式中，式I中的R1为氟，R2、R3各自独立地选自氢、氟、氯或三氟甲基。
在本文中，术语“三氟甲基”是指-CF3基团。
在一些实施方式中，式I所示单体选自偏氟乙烯、四氟乙烯、六氟丙烯中的一种或多种。
在一些实施方式中，式I所示单体选自偏氟乙烯、三氟氯乙烯、氟乙烯、四氟乙烯、六氟丙烯中的一种或多种。
在一些实施方式中，式II所示单体选自丙烯酰胺、甲基丙烯酰胺、N-甲基丙烯酰胺、N-甲基甲基丙烯酰胺、N-异丙基丙烯酰胺、N-异丙基甲基丙烯酰胺、N-叔丁基丙烯酰胺、N-叔丁基(甲基)丙烯酰胺、N,N-二甲基丙烯酰胺、N,N-二甲基甲基丙烯酰胺、N,N-二乙基丙烯酰胺、N,N-二乙基甲基丙烯酰胺中的一种或多种。
在一些实施方式中，BAB型嵌段共聚物可选为聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺三嵌段共聚物、聚甲基丙烯酰胺-聚四氟乙烯-聚甲基丙烯酰胺三嵌段共聚物、聚N-甲基甲基丙烯酰胺-聚(偏氟乙烯-六氟丙烯)-聚N-甲基甲基丙烯酰胺三嵌段共聚物、聚N-异丙基 丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)-聚N-异丙基丙烯酰胺三嵌段共聚物中的一种或多种。
在一些实施方式中，BAB型嵌段共聚物可选为聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物、聚四氟乙烯-聚甲基丙烯酰胺-聚四氟乙烯三嵌段共聚物、聚(偏二氟乙烯-六氟丙烯)-聚N-甲基甲基丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)三嵌段共聚物、聚(偏二氟乙烯-四氟乙烯)-聚N-异丙基丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)三嵌段共聚物中的一种或多种。
在一些实施方式中，BAB型嵌段共聚物作为电极粘结剂。
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、聚合物或混合物。
在一些实施方式中，粘结剂的分散介质是水性溶剂，如水。即粘结剂溶解于水性溶剂中。
在一些实施方式中，粘结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。即，粘结剂溶解于油性溶剂中。
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。
在一些实施方式中，依靠A-嵌段含有的氟元素与活性材料表面及集流体表面的羟基或/和羧基形成氢键作用，使得极片具有优异的粘结力。依靠B-嵌段含有的酰胺基团与正极活性材料和导电剂颗粒表面的羟基形成氢键，一方面有助于提高极片的粘结力，另一方面会改变正极活性材料和导电剂颗粒的表面状态，降低固液界面能。同时B-嵌段的分子链可以提供空间位阻，有效阻碍正极活性材料和导电剂的团聚。B-嵌段分子链吸附于正极活性材料和导电剂表面的 缺陷及悬空键上，弱化了颗粒间的相互连接，达到一定的排斥效果，从而B-嵌段的分子链起到了一定的分散作用，减缓浆料的凝胶现象，提高浆料稳定性。而且B-嵌段中的酰胺键，能够提高极片的吸液能力，改善极片在电解液中的浸润能力，有助于极片上导电网络的形成以降低膜片电阻。
BAB型嵌段共聚物能够降低聚合物的结晶度，增加链段的可移动性，提高极片的柔韧性。同时衍生自式II所示单体的结构单元可削弱衍生自式I所示单体的结构单元之间的分子间作用力，提高极片的柔韧性，降低高负载高压密极片的脆断风险，提高电池的安全性能。
BAB型嵌段共聚物相比于现有技术中的含氟单体与非氟单体的共聚物可以将含氟嵌段和非氟嵌段的重均分子量最大化，充分发挥含氟粘结剂和非氟粘结剂各自的优势，实现优势互补的作用。且BAB型嵌段共聚物相比于含氟聚合物与非氟聚合物的简单共混，可以通过嵌段间的相互作用有效抑制聚合物在浆料制备过程中出现的分层现象。
综上所述，以BAB型嵌段共聚物作为粘结剂可以显著减缓浆料的凝胶现象，提高浆料稳定性、极片的柔韧性和粘结力，同时通过提高极片吸液速率可以改善极片在电解液中的浸润能力，进而降低膜片电阻。
在一些实施方式中，B-嵌段中含有的氟元素与活性材料表面及集流体表面的羟基或/和羧基形成氢键作用，使得极片具有优异的粘结力。A-嵌段中含有的酰胺基团与正极活性材料和导电剂颗粒表面的羟基形成氢键，一方面有助于提高极片的粘结力，另一方面会改变正极活性材料和导电剂颗粒的表面状态，降低固液界面能。同时A-嵌段的分子链可以提供空间位阻，有效阻碍正极活性材料和导电剂的团聚。A-嵌段分子链吸附于正极活性材料和导电剂表面的缺陷及悬空键上，弱化了颗粒间的相互连接，达到一定的排斥效果，从而A-嵌段的分子链起到了一定的分散作用，减缓浆料的凝胶现象，提高浆料稳定性。而且A-嵌段中的酰胺键，能够提高极片的吸液能 力，改善极片在电解液中的浸润能力，有助于极片上导电网络的形成，使得极片具有低的膜片电阻，降低电池的直流阻抗增长率。
综上所述，以BAB型嵌段共聚物作为粘结剂可以显著减缓浆料的凝胶现象，提高浆料稳定性、极片的柔韧性和粘结力，同时通过提高极片吸液速率可以改善极片在电解液中的浸润能力，极片具有低的膜片电阻，降低电池的直流阻抗增长率。
在一些实施方式中，A-嵌段中衍生自式I所示单体的结构单元的摩尔含量为10％～90％，B-嵌段中衍生自式II所示单体的结构单元的摩尔含量为10％～90％，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，A-嵌段中衍生自式I所示单体的结构单元的摩尔含量可选为10％～90％、20％～80％、30％～70％、40％～60％中的一种，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，B-嵌段中衍生自式II所示单体的结构单元的摩尔含量可选为10％～90％、20％～80％、30％～70％、40％～60％中的一种，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，A-嵌段中衍生自式I所示单体的结构单元的摩尔含量为40％～60％，B-嵌段中衍生自式II所示单体的结构单元的摩尔含量为40％～60％，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，A-嵌段中衍生自式I所示单体的结构单元的摩尔含量可选为40％～45％、45％～50％、50％～55％、55％～60％、40％～50％、50％～60％、45％～55％、45％～60％中的任意一种，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，B-嵌段中衍生自式II所示单体的结构单元的摩尔含量可选为40％～45％、45％～50％、50％～55％、55％～60％、40％～50％、50％～60％、45％～55％、45％～60％中的任意一种，基于嵌段共聚物中所有结构单元的总摩尔数计。
若A-嵌段中衍生自式I所示单体的结构单元的摩尔含量过低，B-嵌段中衍生自式II所示单体的结构单元的摩尔含量过高，极片的 粘结力下降；若A-嵌段中衍生自式I所示单体的结构单元的摩尔含量过高，B-嵌段中衍生自式II所示单体的结构单元的摩尔含量过低，极片吸液能力下降，膜片电阻变大。
控制A-嵌段中衍生自式I所示单体的结构单元的摩尔含量在合适范围内，不但浆料的稳定性得到了改善，而且能够使得极片兼具优异的粘结力、良好的极片吸液速率和较低的膜片电阻。
在一些实施方式中，B-嵌段中衍生自式I所示单体的结构单元的摩尔含量为10％～90％，A-嵌段中衍生自式II所示单体的结构单元的摩尔含量为10％～90％，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，B-嵌段中衍生自式I所示单体的结构单元的摩尔含量可选为10％～90％、20％～80％、30％～70％、40％～60％中的一种，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，A-嵌段中衍生自式II所示单体的结构单元的摩尔含量可选为10％～90％、20％～80％、30％～70％、40％～60％中的一种，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，B-嵌段中衍生自式I所示单体的结构单元的摩尔含量为40％～60％，A-嵌段中衍生自式II所示单体的结构单元的摩尔含量为40％～60％，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，B-嵌段中衍生自式I所示单体的结构单元的摩尔含量可选为40％～45％、45％～50％、50％～55％、55％～60％、40％～50％、50％～60％、45％～55％、45％～60％中的任意一种，基于嵌段共聚物中所有结构单元的总摩尔数计。
在一些实施方式中，A-嵌段中衍生自式II所示单体的结构单元的摩尔含量可选为40％～45％、45％～50％、50％～55％、55％～60％、40％～50％、50％～60％、45％～55％、45％～60％中的任意一种，基于嵌段共聚物中所有结构单元的总摩尔数计。
若B-嵌段中衍生自式I所示单体的结构单元的摩尔含量过低，A-嵌段中衍生自式II所示单体的结构单元的摩尔含量过高，极片的 粘结力下降；若B嵌段中衍生自式I所示单体的结构单元的摩尔含量过高，A-嵌段中衍生自式II所示单体的结构单元的摩尔含量过低，极片吸液能力下降，电池的内阻增长率增大，电池的循环容量保持率下降。
控制B-嵌段中衍生自式I所示单体的结构单元的摩尔含量在合适范围内，使得极片兼具优异的粘结力、良好的极片吸液速率以及较低的膜片电阻，提高电池的循环性能。
在一些实施方式中，A-嵌段含有衍生自式I所示单体的结构单元，B-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物的重均分子量为40万～200万。
在一些实施方式中，A-嵌段含有衍生自式I所示单体的结构单元，B-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物的重均分子量可选为40万～60万、60万～80万、80万～100万、100万～120万、120万～140万、140万～160万、160万～180万、180万～200万、60万～90万、90万～120万、120万～150万、150万～180万、180万～200万、120万～200万中的任意一种。
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所占的重量分数与其对应的分子量乘积的总和。
若嵌段共聚物的重均分子量过大，粘结剂溶解困难，易与导电剂团聚，膜片内阻增大，另外会增大浆料的粘度，降低浆料中物质的分散性，影响极片的柔韧性；若嵌段共聚物的重均分子量过小，难以形成三维网状粘结结构，无法起到有效的粘结作用，另外极片的吸液能力和在电解液中的浸润性会下降，导致极片的膜片内阻变大。
控制嵌段共聚物的重均分子量在合适范围内，粘结剂可以减缓浆料的凝胶现象，提高浆料稳定性。
在一些实施方式中，A-嵌段含有衍生自式I所示单体的结构单元，B-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物的重均分子量为120万～200万。
在一些实施方式中，A-嵌段含有衍生自式I所示单体的结构单元， B-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物的重均分子量可选为120万～140万、140万～160万、160万～180万、180万～200万、60万～90万、90万～120万、120万～150万、150万～180万、180万～200万、120万～200万中的任意一种。
嵌段共聚物的重均分子量具有合适的重均分子量，嵌段共聚物的粘结剂可以提高极片的粘结力和柔性，同时通过提高极片的吸液速率，改善极片对电解液的浸润能力，降低膜片电阻，并且降低电池的内阻增长率和提高电池的循环容量保持率。
在一些实施方式中，B-嵌段含有衍生自式I所示单体的结构单元，A-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物的重均分子量为40万～200万。
在一些实施方式中，B-嵌段含有衍生自式I所示单体的结构单元，A-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物的重均分子量为40万～60万、60万～80万、80万～100万、100万～120万、120万～140万、140万～160万、160万～180万、180万～200万、60万～90万、90万～120万、120万～150万、150万～180万、180万～200万、120万～200万。
若嵌段共聚物的重均分子量过大，粘结剂溶解困难，易与导电剂团聚，膜片内阻增大，另外会增大浆料的粘度，降低浆料中物质的分散性，影响极片的柔韧性；若嵌段共聚物的重均分子量过小，难以形成三维网状粘结结构，无法起到有效的粘结作用，影响极片的粘结性能。
控制嵌段共聚物的重均分子量在合适范围内，粘结剂可以使得极片具有良好的粘结力和柔韧性，提高极片的使用性能。
在一些实施方式中，B-嵌段含有衍生自式I所示单体的结构单元，A-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物的重均分子量为120万～200万。
在一些实施方式中，B-嵌段含有衍生自式I所示单体的结构单元，A-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物的重均分子量可选为120万～140万、140万～160万、160万～180万、180万 ～200万、60万～90万、90万～120万、120万～150万、150万～180万、180万～200万、120万～200万中的任意一种。
控制嵌段共聚物的重均分子量在合适范围内，粘结剂可以提高极片的粘结力，提高电池的循环性能。
在一些实施方式中，A-嵌段含有衍生自式I所示单体的结构单元，嵌段共聚物中A-嵌段的重均分子量为20万～110万。
在一些实施方式中，A-嵌段含有衍生自式I所示单体的结构单元，A-嵌段的重均分子量可选为20万～30万、30万～40万、40万～50万、50万～60万、60万～70万、70万～80万、80万～90万、90万～105万、40万～60万、40万～80万、40万～105万中的任意一种。
若嵌段共聚物中A-嵌段的重均分子量过大，衍生自式I所示单体的结构单元的含氟基团过多，影响浆料的稳定性；若嵌段共聚物中A-嵌段的重均分子量过小，极片的粘结力下降。
A-嵌段的重均分子量在合适范围内的嵌段共聚物可以减缓浆料的凝胶现象，提高浆料的稳定性。
在一些实施方式中，A-嵌段含有衍生自式I所示单体的结构单元，嵌段共聚物中A-嵌段的重均分子量为40万～110万。
在一些实施方式中，A-嵌段含有衍生自式I所示单体的结构单元，A-嵌段的重均分子量可选为40万～50万、50万～60万、60万～70万、70万～80万、80万～90万、90万～105万、40万～60万、40万～80万、40万～105万中的任意一种。
A-嵌段的重均分子量在合适范围内的嵌段共聚物，该粘结剂能够提高极片的粘结力和柔性，使得极片具有较低的膜片电阻，降低的电池的内阻增长率，提高电池的循环容量保持率。
在一些实施方式中，A-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物中A-嵌段的重均分子量为20万～110万。
在一些实施方式中，A-嵌段含有衍生自式II所示单体的结构单元，A-嵌段的重均分子量可选为20万～30万、30万～40万、40万～50万、50万～60万、60万～70万、70万～80万、80万～90万、90万～105万、40万～60万、40万～80万、40万～105万中的任意一种。
若嵌段共聚物中A-嵌段的重均分子量过大，衍生自式II所示单体的结构单元强极性基团过多，影响浆料的分散性，影响极片的柔韧性；若嵌段共聚物中A-嵌段的重均分子量过小，极片的粘结力下降。
A-嵌段的重均分子量在合适范围内的嵌段共聚物可以兼顾极片的柔韧性和粘结性，改善极片的使用性能。
在一些实施方式中，A-嵌段含有衍生自式II所示单体的结构单元，嵌段共聚物中A-嵌段的重均分子量为40万～110万。
在一些实施方式中，A-嵌段含有衍生自式II所示单体的结构单元，A-嵌段的重均分子量可选为40万～50万、50万～60万、60万～70万、70万～80万、80万～90万、90万～105万、40万～60万、40万～80万、40万～105万中的任意一种。
A-嵌段的重均分子量在合适范围内的嵌段共聚物，该粘结剂可以提高极片的粘结力，提高电池的循环性能。
在一些实施方式中，B-嵌段含有式II所示单体的结构单元，每个B-嵌段的重均分子量为10万～50万。
在一些实施方式中，B-嵌段含有式II所示单体的结构单元，每个B-嵌段的重均分子量可选为10万～20万、20万～30万、30万～40万、40万～50万、20万～40万、20万～50万中的任意一种。
每个B-嵌段的重均分子量在合适范围内的嵌段共聚物可以减缓浆料的凝胶现象，提高浆料稳定性。
在一些实施方式中，B-嵌段含有式II所示单体的结构单元，每个B-嵌段的重均分子量为20万～50万。
在一些实施方式中，B-嵌段含有式II所示单体的结构单元，每个B-嵌段的重均分子量可选为20万～30万、30万～40万、40万～50万、20万～40万、20万～50万中的任意一种。
每个B-嵌段的重均分子量在合适范围内的嵌段共聚物可以提高极片的粘结力和柔性，同时通过提高极片的吸液速率改善电解液对极片的浸润能力，进而降低极片的膜片电阻。
在一些实施方式中，B-嵌段含有式I所示单体的结构单元，每个 B-嵌段的重均分子量为10万～50万。
在一些实施方式中，B-嵌段含有式I所示单体的结构单元，每个B-嵌段的重均分子量为10万～20万、20万～30万、30万～40万、40万～50万、20万～40万、20万～50万。
每个B-嵌段的重均分子量在合适范围内的嵌段共聚物可以兼顾极片的粘结力和柔韧性，改善极片的使用性能。
在一些实施方式中，B-嵌段含有式I所示单体的结构单元，每个B-嵌段的重均分子量为20万～50万。
在一些实施方式中，B-嵌段含有式I所示单体的结构单元，每个B-嵌段的重均分子量可选为20万～30万、30万～40万、40万～50万、20万～40万、20万～50万中的任意一种。
每个B-嵌段的重均分子量在合适范围内的嵌段共聚物可以提高极片的粘结力，提高电池的循环性能。
本申请的一个实施方式中，提供一种BAB型嵌段共聚物的制备方法，包括以下步骤：
制备A-嵌段：将至少一种式I所示单体或至少一种式II所示单体聚合制备A-嵌段，
其中，R1、R2、R3各自独立地选自氢、氟、至少含有一个氟原子的C1-3烷基中的一种或多种，R4、R5、R6、R7、R8各自独立地选自氢、取代或未取代的C1-3烷基；
制备B-嵌段：将至少一种式II所示单体或至少一种式I所示单体聚合制备B-嵌段，
制备BAB型嵌段共聚物：将A-嵌段和B-嵌段接合制备BAB型嵌段共聚物，其中A-嵌段和B-嵌段含有不同的结构单元。
在一些实施方式中，提供一种BAB型嵌段共聚物的制备方法， 包括以下步骤：
制备A-嵌段：将至少一种式I所示单体聚合制备A-嵌段，
制备B-嵌段：将至少一种式II所示单体聚合制备B-嵌段，
制备BAB型嵌段共聚物：将A-嵌段和B-嵌段接合制备BAB型嵌段共聚物，其中A-嵌段和B-嵌段含有不同的结构单元。
在一些实施方式中，提供一种BAB型嵌段共聚物的制备方法，包括以下步骤：
制备A-嵌段：将至少一种式II所示单体聚合制备A-嵌段，
制备B-嵌段：将至少一种式II所示单体聚合制备B-嵌段，
制备BAB型嵌段共聚物：将A-嵌段和B-嵌段接合制备BAB型嵌段共聚物，其中A-嵌段和B-嵌段含有不同的结构单元。
在一些实施方式中，BAB型嵌段共聚物的制备方法示意图如图1所示，其中，包含衍生自式I所示单体的结构单元的A-嵌段61的两端基团611为活性基团，包含衍生自式II所示单体的结构单元的B-嵌段62的末端基团621为活性基团，A-嵌段的两端基团611与B-嵌段的末端基团621反应实现聚合物链段的接合，从而制备BAB型嵌段共聚物6。
该制备方法原料便宜，可以降低成本，减少对环境的污染，有利于粘结剂产量的提升。同时该方法制备的粘结剂能够减缓浆料的凝胶现象，提高浆料的稳定性，提高极片的粘结力、柔韧性和导电性。
在一些实施方式中，BAB型嵌段共聚物的制备方法示意图如图1所示，其中，包含衍生自式II所示单体的结构单元的A-嵌段61的两端基团611为活性基团，包含衍生自式I所示单体的结构单元的B-嵌段62的末端基团621为活性基团，A-嵌段的两端基团611与B-嵌段的末端基团621反应实现聚合物链段的接合，从而制备BAB型嵌段共聚物6。
在一些实施方式中，制备A-嵌段的方法包括：
将至少一种式I所示单体或至少一种式II所示单体、第一引发剂在80～95℃的反应温度下聚合反应2.5～5h，对产物的端基进行取代反 应，制备两端均具有叠氮基团或炔基的A-嵌段。
在本文中，术语“叠氮基团”是指-N3基团。
在本文中，术语“炔基”是指-C≡CH基团。
在一些实施方式中，制备A-嵌段的方法包括：
将至少一种式I所示单体、第一引发剂在80～95℃的反应温度下聚合反应2.5～5h，对产物的端基进行取代反应，制备两端均具有叠氮基团或炔基的A-嵌段。
在本文中，术语“叠氮基团”是指-N3基团。
在本文中，术语“炔基”是指-C≡CH基团。
在一些实施方式中，A-嵌段的合成路线如下所示，在第一引发剂的作用下，式I所示单体发生聚合反应，生成A-嵌段。由于第一引发剂两侧的端基为卤素取代的烷基或三甲基硅基乙炔基团，A-嵌段两侧的卤素或三甲基硅基容易被取代，使得A-嵌段两端均具有叠氮基团或炔基。
采用该制备方法制备出的两侧末端叠氮化或炔基化的A-嵌段，便于A-嵌段以高效温和的方式与B-嵌段发生嵌段间的连接，生成BAB型嵌段共聚物。
在一些实施方式中，制备A-嵌段的方法包括：
将至少一种式II所示单体、第一引发剂在80～95℃的反应温度下聚合反应2.5～5h，对产物的端基进行取代反应，制备两端均具有叠氮基团或炔基的A-嵌段。
在本文中，术语“叠氮基团”是指-N3基团。
在本文中，术语“炔基”是指-C≡CH基团。
在一些实施方式中，A-嵌段的合成路线如下所示，在第一引发剂的作用下，式II所示单体发生聚合反应，生成A-嵌段。由于第一引发剂两侧的端基为卤素取代的烷基或三甲基硅基乙炔基团，A-嵌段两侧的卤素或三甲基硅基容易被取代，使得A-嵌段两端均具有叠氮基团或炔基。
在一些实施方式中，制备B-嵌段的方法包括：
将至少一种式II所示单体或至少一种式I所示单体、链转移剂和第二引发剂在60～75℃的反应温度下通过可逆加成-裂解链转移聚合，反应4.5～6h得到末端具有炔基或叠氮基团的B-嵌段。
在本文中，术语“可逆加成-裂解链转移聚合”(RAFT聚合)是一种可逆失活自由基聚合，也被称为“活性”/可控自由基聚合方法。RAFT聚合的主要原理是通过在自由基聚合中加入作为链转移试剂的RAFT试剂，将易终止的自由基通过链转移的方式保护起来使得聚合反应中大多数自由基转变为休眠种自由基，在反应过程中休眠链段与活性链段同时存在并通过动态可逆的反应不断进行快速的相互切换，从而导致在任一时刻只有少数的聚合物链以活性链形式存在并进行增长最终使得每条聚合物链段的增长几率大致相等进而表现出活性聚合的特征。
在一些实施方式中，制备B-嵌段的方法包括：
将至少一种式II所示单体、链转移剂和第二引发剂在60～75℃ 的反应温度下通过可逆加成-裂解链转移聚合，反应4.5～6h得到末端具有炔基或叠氮基团的B-嵌段。
在一些实施方式中，B-嵌段的合成路线示意图如下图所示，其中，链转移剂为三硫代碳酸酯，Z’为末端含有炔基或叠氮基团的活性基团，R为烷基。通过下述反应，制备了末端具有炔基或叠氮基团的B-嵌段。
采用可逆加成-裂解链转移聚合，可实现可控聚合，且产物分子量分布较窄。而且通过上述反应，B-嵌段只在末端具有炔基或叠氮基团，方便以高效温和的方式定向地与A-嵌段发生接合，生成BAB型嵌段共聚物。
在一些实施方式中，制备B-嵌段的方法包括：
将至少一种式I所示单体、链转移剂和第二引发剂在60～75℃的反应温度下通过可逆加成-裂解链转移聚合，反应4.5～6h得到末端具有炔基或叠氮基团的B-嵌段。
在一些实施方式中，B-嵌段的合成路线示意图如下图所示，其中，链转移剂为三硫代碳酸酯，Z’为末端含有炔基或叠氮基团的活性基团，R为烷基。通过下述反应，制备了末端具有炔基或叠氮基团的B-嵌段。
在一些实施方式中，制备BAB型嵌段共聚物的方法包括：
将两端均具有叠氮基团或炔基的A-嵌段与末端具有炔基或叠氮基团的B-嵌段混合，进行点击反应，制备BAB型嵌段共聚物，其中 A-嵌段和B-嵌段的端基不同。
在本文中，术语“点击反应”是指炔基与叠氮基发生环加成反应，使得A-嵌段与B-嵌段相连的反应。在一些实施方式中，点击反应在Cu(I)催化剂的存在下，常温常压下进行。
在一些实施方式中，A-嵌段的端基为叠氮基团，B-嵌段的端基为炔基。
在一些实施方式中，A-嵌段的端基为炔基，B-嵌段的端基为叠氮基团。
上述制备方法，具有产率高、副产物无害、反应条件简单温和、反应原料易得的优点，能够实现嵌段聚合物的可控聚合，有利于提高产品的良品率。
在一些实施方式中，链转移剂为含末端炔基或叠氮基团的RAFT链转移剂。在一些实施方式中，链转移剂为含末端炔基或叠氮基团的三硫代碳酸酯。在一些实施方式中，链转移剂的结构式选自下式，
含末端炔基或叠氮基团的RAFT链转移剂在B-嵌段合成的同时使得B-嵌段的末端带有炔基或叠氮基团，为B-嵌段与A-嵌段发生点击反应提供了基础，避免了复杂的后处理步骤，能够提高反应效率。
在一些实施方式中，第一引发剂为对称型双官能度引发剂。在一些实施方式中，第一引发剂为4-(氯甲基)过氧化苯甲酰。对称型双官能度引发剂使得A-嵌段两侧能够对称地带有相同的活性官能团，有助于A-嵌段两侧端基叠氮化或炔化的同时实现。
在一些实施方式中，第二引发剂为偶氮引发剂。在一些实施方式中，偶氮引发剂选自偶氮二异丁腈，偶氮二异庚腈中的一种或多种。偶氮引发剂是一种常用的自由基聚合引发剂，易于分解形成自由基，便于引发自由基聚合。
在一些实施方式中，BAB型嵌段共聚物可以应用在二次电池中，可选地，所述二次电池包括锂离子电池、钠离子电池、镁离子电池、钾离子电池中的至少一种。
[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，正极膜层包括正极活性材料、导电剂和粘结剂，该粘结剂为一些实施方式中的BAB型嵌段共聚物或一些实施方式中的制备方法制备的BAB型嵌段共聚物。
该正极极片具有优异的柔韧性和粘结力，同时具有较低的膜片电阻。
在一些实施方式中，粘结剂的质量分数为0.1％～3％，基于正极活性材料的总质量计。在一些实施方式中，粘结剂的质量分数可选为0.1％～0.2％、0.2％～1％、0.2％～1.03％、1％～3％、1.03％～3％中的任意一种。
当粘结剂含量过低时，粘结剂无法发挥足够的粘结效果。一方面粘结剂无法充分分散导电剂和活性物质，导致极片的膜片电阻升高；相反，粘结剂含量过高时，浆料的粘度过大，导致包覆于正极活性材料表面的粘结剂包覆层过厚，在电池循环过程中影响电子和离子的传输，膜片内阻增大。
控制粘结剂的质量分数在合理范围内，极片兼具优异的粘结力和膜片电阻。
在一些实施方式中，粘结剂的质量分数为1％～3％，基于正极活性材料的总质量计。在一些实施方式中，粘结剂的质量分数可选为1％～1.03％、1％～2％、2％～3％、1％～3％、1.03％～3％中的任意一种。
控制粘结剂的质量分数在合理范围内，该粘结剂能够提高极片的粘结力和柔性，同时通过提高极片的吸液速率，改善极片对电解 液的浸润能力，进而降低膜片电阻，提高电池的循环性能。
在一些实施方式中，正极膜层与正极集流体间单位长度的粘结力不小于11N/m，可选为11-22N/m。在一些实施方式中，所述正极膜层与所述正极集流体间单位长度的粘结力可选为11N/m、11.5N/m、12.5N/m、13N/m、13.5N/m、14N/m、14.5N/m、15N/m、15.5N/m、16N/m、16.5N/m、17N/m、17.5N/m、18N/m、18.5N/m、19N/m、19.5N/m、20N/m、20.5N/m、21N/m、21.5N/m、22N/m中的任意一种。
正极膜层与正极集流体间单位长度的粘结力可以采用本领域公知的任意手段进行测试，如参照GB-T2790-1995国标《胶粘剂180°剥离强度实验方法》进行测试。作为示例，将正极极片裁剪为20*100mm2尺寸的测试试样，备用；极片用双面胶粘接正极膜层一面，并用压辊压实，使双面胶与极片完全贴合；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，直到正极集流体全部从正极膜片剥离，记录过程中的位移和作用力。以受力平衡时的力除以与双面胶贴合的极片的宽度(极片的宽度方向垂直于剥离方向)作为单位长度的极片的粘结力，本测试中极片的宽度为20mm。
该极片的正极膜层与正极集流体之间具有高的粘结强度，在使用过程中，正极膜层不容易从正极集流体上脱落，有助于提高电池的循环性能和安全性。
在一些实施方式中，正极极片在经过不少于2次的弯折测试后，正极极片出现透光现象。在一些实施方式中，正极极片在经过不少于2、2.3、2.7、3.3、3.5、3.7或4次的弯折测试后，正极极片出现透光现象。
在一些实施方式中，正极极片在经过不少于3次的弯折测试后，正极极片出现透光现象。在一些实施方式中，正极极片在经过不少于3.3、3.5、3.7或4次的弯折测试后，正极极片出现透光现象。
弯折测试，也称为柔韧性测试，可以用于测试极片的柔韧性，该测试可以采用本领域公知的任意手段进行。作为示例，将冷压后的正极极片裁剪为20*100mm2尺寸的测试试样；将其正向对折后，用2kg压辊压平，并展开对着光检查缝隙是否出现透光，如未出现透光，则反向对折，用2kg压辊压平，并对着光再次检查，如此反复直至，缝隙出现透光现象，记录对折次数；取至少三个式样进行测试，并取平均值，作为弯折测试的测试结果。
极片能经过不少于3次的弯折测试，表明极片具有良好的柔韧性，不易在生产过程中出现极片崩裂、使用过程中出现极片脆断的现象，有助于提高电池的良品率，提高电池的安全性能。
在一些实施方式中，正极极片对电解液的吸液速率大于0.30μg/s，可选为0.35-0.6μg/s，电解液的密度为1.1-1.2g/cm3。
在一些实施方式中，正极极片对电解液的吸液速率为0.36μg/s、0.37μg/s、0.38μg/s、0.39μg/s、0.40μg/s、0.41μg/s、0.42μg/s、0.43μg/s、0.44μg/s、0.45μg/s、0.46μg/s、0.47μg/s、0.484μg/s、0.49μg/s、0.50μg/s或0.6μg/s，电解液的密度为1.1-1.2g/cm3。
极片的吸液速率可以反应极片在电解液中润湿的能力。该测试可以采用本领域公知的任意手段进行。作为示例，将冷压后的正极极片裁剪为5*5cm2尺寸的测试样品；首先，将样品在80℃下干燥4h，测试极片厚度后，固定在样品台上，然后挑选d＝200μm的毛细管，用5000目砂纸打磨端面至平整，利用显微镜观察毛细管与极片间状态；用毛细管吸取电解液，控制电解液高度h＝3mm，下降毛细管与极片接触，同时用秒表计时，当液面下降完毕后，停止计时，读取吸液时间t，记录数据；利用公式计算极片的平均吸液速率v，v＝π×(d/2)2×h×ρ/t。本测试中，选用的电解液的密度ρ为1.1-1.2g/cm3。作为示例，电解液可以通过六氟磷酸锂溶解于碳酸乙烯酯和碳酸甲乙酯的混合溶剂中配置，六氟磷酸锂溶液的质量含量为12.5％，溶液中碳酸乙烯酯和碳酸甲乙酯的体积比为3:7。
该极片具有较高的吸液速率，能够提高电解液对极片的浸润效率，改善离子传输路径，降低界面电阻，提高电池性能。
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LiCoO2)、锂镍氧化物(如LiNiO2)、锂锰氧化物(如LiMnO2、LiMn2O4)、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LiNi1/3Co1/3Mn1/3O2(也可以简称为NCM333)、LiNi0.5Co0.2Mn0.3O2(也可以简称为NCM523)、LiNi0.5Co0.25Mn0.25O2(也可以简称为NCM211)、LiNi0.6Co0.2Mn0.2O2(也可以简称为NCM622)、LiNi0.8Co0.1Mn0.1O2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi0.85Co0.15Al0.05O2)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LiFePO4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO4)、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。
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。
[二次电池]
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2是作为一个示例的方形结构的二次电池5。所述二次电池也可以为钠离子电池、镁离子电池、钾离子电池。
在一些实施方式中，参照图3，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4是作为一个示例的电池模块4。参照图4，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5和图6是作为一个示例的电池包1。参照图5和图6，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，包括任意实施方式的二次电池、任意实施方式的电池模块或任意实施方式的电池包中的至少一种。
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7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。
一、制备方法
实施例1
1)粘结剂的制备
制备B-嵌段：将摩尔比为700:1:0.1的丙烯酰胺单体、RAFT链转移剂(CTA-炔烃)和偶氮二异丁腈添加500ml的四氢呋喃溶液中。将混合物进行至少三个冷冻-泵-解冻循环并置于预热至70℃的油浴中。反应6h后，通过在液氮中冷却终止反应，溶液在过量的甲醇中沉淀。通过过滤收集聚合物，并用甲醇从氯仿中再沉淀两次。将所得聚合物在室温下真空干燥10小时以除去所有痕量的残留溶剂，得到重均分子量为40万的炔基封端的聚丙烯酰胺。
制备A-嵌段：将单体质量1％的4-(氯甲基)过氧化苯甲酰溶解在300mL无水乙腈中，然后将溶液引入高压反应器中并用N2吹扫30分钟。随后在室温下将4g的偏氟乙烯单体转移到反应器中。将反应器内部的温度提高到90℃，并将反应混合物以500rpm的速度再搅拌3h。将反应器用水冷却至室温并减压以除去未反应的单体。真空除 去溶剂，所得固体用氯仿洗涤多次以除去引发剂残留物。最后将聚合物在45℃真空干燥，得到白色产物。将3mmol氯封端的聚偏氟乙烯和60mmol NaN3溶解在600mL N,N-二甲基甲酰胺(DMF)中并在60℃下搅拌10小时。将聚合物溶液浓缩并在混合溶剂(甲醇与水的体积比为1:1)中沉淀三次。随后在45℃下真空干燥淡黄色聚合物，得到重均分子量为45万的叠氮化物封端的PVDF，即A-嵌段聚合物。
制备BAB型嵌段共聚物：将叠氮化物封端的聚偏二氟乙烯、炔基封端的聚丙烯酰胺和CuBr按照摩尔比1:2.5:4，添加到干燥的Schlenk管中。执行脱气程序(抽空和用N2回填的三个重复循环后，加入4mL无水N,N-二甲基甲酰胺(DMF)，然后加入0.14mmol N,N,N',N,'N”-五甲基二亚乙基三胺(PMDETA)。反应在60℃下搅拌3天，通过暴露于空气中终止反应。将反应混合物通过中性氧化铝柱过滤以除去铜催化剂。将溶液减压浓缩并在20倍过量的混合溶剂(甲醇与水的体积比为1:1)中进行沉淀，使得未参与反应的聚丙烯酰胺嵌段物充分溶解。过滤后，通过过滤收集产物并在室温下真空干燥10小时得到重均分子量为120万的聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺三嵌段共聚物。
2)正极极片的制备
将LiNi0.8Co0.1Mn0.1O2锂镍钴锰(NCM)材料、导电剂碳黑、实施例1粘结剂、N-甲基吡咯烷酮(NMP)按重量比为96.9:2.1:1:21搅拌混合均匀，得到正极浆料，浆料的固含量为73％；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)、增稠剂羟甲基纤维素钠(CMC)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(H2O<0.1ppm，O2<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LiPF6锂盐溶解于有机溶剂中，LiPF6在溶液中的质量含量为12.5％，搅拌均匀，得到实施例1的电解液。
6)电池的制备
将实施例1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2～7
实施例2～7的电池与实施例1的电池制备方法相似，但是通过分别调整A-嵌段以及B-嵌段的聚合单体量、反应温度和反应时间，调整A-嵌段以及B-嵌段的重均分子量，并且保证聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺三嵌段共聚物的重均分子量为120万，具体调整参数如表1所示。
实施例8～11
实施例2～7的电池与实施例1的电池制备方法相似，但是通过分别调整A-嵌段以及B-嵌段的聚合单体量、反应温度和反应时间，调整A-嵌段以及B-嵌段的重均分子量，进而调整聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺三嵌段共聚物的重均分子量，具体调整参数如表1所示。
实施例12～15
实施例12～15的电池与实施例1的电池制备方法相似，但是调整了粘结剂的质量分数，具体参数如表2所示。
实施例16
实施例16的电池与实施例4的电池制备方法相似，但是将B-嵌段替换成聚N-异丙基丙烯酰胺嵌段，具体参数如表1所示，制备方法如下：
将摩尔比为700:1:0.1的N-异丙基丙烯酰胺单体、RAFT链转移剂(CTA-炔烃)和偶氮二异丁腈添加到500ml的四氢呋喃溶液中。将混合物进行至少三个冷冻-泵-解冻循环并置于预热至70℃的油浴中。反应6h后，通过在液氮中冷却终止反应，溶液在大量过量的甲醇中沉淀。通过过滤收集聚合物并用甲醇从氯仿中再沉淀两次。将所得聚合物在室温下真空干燥10小时以除去所有痕量的残留溶剂。
实施例17
实施例17的电池与实施例1的电池制备方法相似，但是将A-嵌段替换成聚(偏二氟乙烯-六氟丙烯)嵌段，具体参数如表2所示，制备方法如下：
将单体质量1％的4-(氯甲基)过氧化苯甲酰溶解在300mL无水乙腈中，然后将溶液引入高压反应器中并用N2吹扫30分钟。随后在室温下将15g的偏二氟乙烯单体和5g的六氟丙烯转移到反应器中。将反应器内部的温度提高到90℃，并将反应混合物以500rpm的速度再搅拌3h。将反应器用水冷却至室温并减压以除去未反应的单体。真空除去溶剂，所得固体用氯仿洗涤多次以除去引发剂残留物。最后将聚合物在45℃真空干燥，得到白色产物。将3mmol氯封端的聚(偏氟乙烯-六氟丙烯)和60mmol NaN3溶解在600mL N,N-二甲基甲酰胺(DMF)中并在60℃下搅拌10小时。将聚合物溶液浓缩并在混合溶剂(甲醇与水的体积比为1:1)中沉淀三次。随后在45℃下真空干燥淡黄色聚合物，得到重均分子量为45万的叠氮化物封端的聚(偏二氟乙烯-六氟丙烯)，即A-嵌段聚合物。
实施例18
实施例18的电池与实施例1的电池制备方法相似，但是将A-嵌段替换成聚(偏二氟乙烯-四氟乙烯)嵌段，具体参数如表2所示，制备方法如下：
将单体质量1％的4-(氯甲基)过氧化苯甲酰溶解在300mL无水乙 腈中，然后将溶液引入高压反应器中并用N2吹扫30分钟。随后在室温下将15g的偏二氟乙烯单体和5g的四氟乙烯转移到反应器中。将反应器内部的温度提高到90℃，并将反应混合物以500rpm的速度再搅拌3h。将反应器用水冷却至室温并减压以除去未反应的单体。真空除去溶剂，所得固体用氯仿洗涤多次以除去引发剂残留物。最后将聚合物在45℃真空干燥，得到白色产物。将3mmol氯封端的聚(偏氟乙烯-六氟丙烯)和60mmol NaN3溶解在600mL N,N-二甲基甲酰胺(DMF)中并在60℃下搅拌10小时。将聚合物溶液浓缩并在混合溶剂(甲醇与水的体积比为1:1)中沉淀三次。随后在45℃下真空干燥淡黄色聚合物，得到重均分子量为45万的叠氮化物封端的聚(偏二氟乙烯-四氟丙烯)，即A-嵌段聚合物。
实施例19
制备B-嵌段：利用RAFT链转移剂(CTA-炔烃)作为链转移剂，聚合反应制备炔基封端的聚偏二氟乙烯；其中RAFT链转移剂的结构式如下所示
称取4g偏二氟乙烯，量取500ml四氢呋喃，加入四口烧瓶，通入大量氮气，并逐渐加大搅拌速度，至1200rpm，加入单体质量1％的RAFT链转移剂(CTA-炔烃)和单体质量0.1％的偶氮二异丁腈，升温至70℃。反应5小时后，通过在液氮中冷却终止反应，溶液在大量过量的甲醇中沉淀。通过过滤收集聚合物并用甲醇从氯仿中再沉淀两次。将所得产物在室温下真空干燥过夜以除去所有痕量的残留溶剂，得到末端具有炔基的聚偏二氟乙烯，即B-嵌段聚合物。
制备A-嵌段：利用叠氮化物作为引发剂，聚合反应制备叠氮化物封端的聚丙烯酰胺；
将单体质量1％的4-(氯甲基)过氧化苯甲酰溶解在300ml无水乙腈中，然后将溶液引入高压反应器中并用N2吹扫30分钟。随后在室 温下，称取一定摩尔量的丙烯酰胺单体转移到反应器中。将反应器内部的温度提高到90℃，并将反应混合物以500rpm的速度再搅拌3小时。将反应器用水冷却至室温并减压以除去未反应的单体。真空除去溶剂，所得固体用氯仿洗涤多次以除去引发剂残留物。最后将聚合物在45℃真空干燥，得到白色产物。将3mmol氯封端的聚丙烯酰胺和60mmol叠氮化钠(NaN3)溶解在600ml的N,N-二甲基甲酰胺(DMF)中并在60℃下搅拌过夜。将聚合物溶液浓缩并在混合溶剂(甲醇与水的体积比为1:1)中沉淀三次。随后在45℃下真空干燥淡黄色产物，得到两端均包含叠氮化物的聚丙烯酰胺，即A-嵌段聚合物。
制备BAB型嵌段共聚物：
将两端均具有叠氮基团的聚丙烯酰胺、末端具有炔基的聚偏二氟乙烯和溴化亚铜按照摩尔比1:2.5:4，添加到干燥的Schlenk管中，脱气处理后加入4ml无水N,N-二甲基甲酰胺(DMF)和0.14mmolN,N,N',N,'N”-五甲基二亚乙基三胺(PMDETA)。在60℃下搅拌反应3天，通过暴露于空气中终止反应。反应混合物通过中性氧化铝柱过滤除去铜催化剂，将溶液减压浓缩并在20倍过量的混合溶剂(甲醇与水的体积比为1:1)中进行沉淀，过滤收集产物，真空干燥得到重均分子量为120万的聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯嵌段共聚物，其作为电池粘结剂使用。
实施例20～25
实施例20～25的电池与实施例19的电池制备方法相似，但是通过分别调整A-嵌段以及B-嵌段的聚合反应温度和反应温度，调整A-嵌段以及B-嵌段的聚合度，调整A-嵌段以及B-嵌段的重均分子量，并且保证聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物的重均分子量为120万，具体调整参数如表2所示。
实施例26～29的电池与实施例19的电池制备方法相似，但是通过分别调整A-嵌段以及B-嵌段的聚合反应温度和反应温度，调整A-嵌段以及B-嵌段的聚合度，调整A-嵌段以及B-嵌段的重均分子量，进而调整了聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物 的重均分子量，具体调整参数如表2所示。
实施例30～33
实施例30～33的电池与实施例19的电池制备方法相似，但是调整了粘结剂的质量分数，基于正极活性物质的质量计，具体参数如表2所示。
实施例34
实施例34的电池与实施例19的电池制备方法相似，但是将A-嵌段替换成聚N-异丙基丙烯酰胺嵌段，具体参数如表2所示，制备方法如下：
将单体质量1％的4-(氯甲基)过氧化苯甲酰溶解在300ml无水乙腈中，然后将溶液引入高压反应器中并用N2吹扫30分钟。随后在室温下，称取一定摩尔量的N-异丙基丙烯酰胺单体转移到反应器中。将反应器内部的温度提高到90℃，并将反应混合物以500rpm的速度再搅拌3小时。将反应器用水冷却至室温并减压以除去未反应的单体。真空除去溶剂，所得固体用氯仿洗涤多次以除去引发剂残留物。最后将聚合物在45℃真空干燥，得到白色产物。将3mmol氯封端的聚N-异丙基丙烯酰和60mmol叠氮化钠(NaN3)溶解在600ml的N,N-二甲基甲酰胺(DMF)中并在60℃下搅拌过夜。将聚合物溶液浓缩并在混合溶剂(甲醇与水的体积比为1:1)中沉淀三次。随后在45℃下真空干燥淡黄色产物，得到两端均包含叠氮化物的聚N-异丙基丙烯酰，即A-嵌段聚合物。
实施例35
实施例35的电池与实施例19的电池制备方法相似，但是将B-嵌段替换成聚(偏二氟乙烯-六氟丙烯)嵌段，具体参数如表2所示，制备方法如下：
称取15g偏二氟乙烯和5g的六氟丙烯，量取500ml四氢呋喃，加入四口烧瓶，通入大量氮气，并逐渐加大搅拌速度，至1200rpm，加入单体质量1％的RAFT链转移剂(CTA-炔烃)和单体质量0.1％的偶氮二异丁腈，升温至70℃。反应5小时后，通过在液氮中冷却终止反应，溶液在大量过量的甲醇中沉淀。通过过滤收集聚合物并 用甲醇从氯仿中再沉淀两次。将所得产物在室温下真空干燥过夜以除去所有痕量的残留溶剂，得到末端具有炔基的聚(偏二氟乙烯-六氟丙烯)，即B-嵌段聚合物。
实施例36
实施例36的电池与实施例19的电池制备方法相似，但是将B-嵌段替换成聚(偏二氟乙烯-四氟乙烯)嵌段，具体参数如表2所示，制备方法如下：
称取15g偏二氟乙烯和5g的四氟乙烯，量取500ml四氢呋喃，加入四口烧瓶，通入大量氮气，并逐渐加大搅拌速度，至1200rpm，加入单体质量1％的RAFT链转移剂(CTA-炔烃)和单体质量0.1％的偶氮二异丁腈，升温至70℃。反应5小时后，通过在液氮中冷却终止反应，溶液在大量过量的甲醇中沉淀。通过过滤收集聚合物并用甲醇从氯仿中再沉淀两次。将所得产物在室温下真空干燥过夜以除去所有痕量的残留溶剂，得到末端具有炔基的聚(偏二氟乙烯-四氟乙烯)，即B-嵌段聚合物。
对比例1
对比例1的电池与实施例1的电池制备方法相似，但是粘结剂为聚偏二氟乙烯，重均分子量为120万，购买自索尔维集团的5130。
对比例2
对比例2的电池与实施例1的电池制备方法相似，但是粘结剂为聚丙烯酰胺，重均分子量为120万，购买自法国爱森公司AN934SHUC/PWG。
对比例3
对比例3的电池与实施例1的电池制备方法相似，但是粘结剂为聚偏二氟乙烯与聚丙烯酰胺的共混物，制备方法如下：
共混：将对比例2中的聚丙烯酰胺与对比例1中聚偏二氟乙烯共混按照摩尔比例6:4进行共混，得到聚偏二氟乙烯与聚丙烯酰胺共混物粘结剂。
二、性能测试
1、聚合物性质测试
1)重均分子量测试方法
采用Waters2695Isocratic小时PLC型凝胶色谱仪(示差折光检测器2141)。质量分数为3.0％的聚苯乙烯溶液试样做参比，选择匹配的色谱柱(油性：Styragel小时T5DMF7.8*300mm+Styragel小时T4)。用纯化后的N-甲基吡咯烷酮(NMP)溶剂配置3.0％的聚合物胶液，配置好的溶液静置一天，备用。测试时，先用注射器吸取四氢呋喃，进行冲洗，重复几次。然后吸取5ml实验溶液，排除注射器中的空气，将针尖擦干。最后将试样溶液缓缓注入进样口。待示数稳定后获取数据。
2、浆料性能测试
1)浆料粘度测试
浆料出货后，取500ml浆料放置在烧杯中，利用旋转粘度计，选取转子，转速设置为12rpm，转动时间设置为5min，数值稳定后，读取并记录粘度数值。
2)浆料稳定性测试
将浆料复搅30min后，取一定量的浆料倒入稳定性仪的样品瓶，放入样品瓶后，关闭测试塔盖，打开测试塔盖，测试界面开始出现扫描曲线，开始测试样品稳定性，持续测试48h以上完成测试。
3、极片性能测试
1)膜片电阻测试
将极片左、中、右处裁剪3*3mm小圆片。打开元能科技极片电阻仪指示灯，将置于膜片电阻仪“探头”合适位置，点击“开始”按钮，待示数稳定，读取即可。每个小圆片测试两个位置，最后计算六次测量的平均值，即为该极片的膜片电阻。
2)粘结力测试
将正极极片裁剪为20*100mm2尺寸的测试试样，备用；极片用双面胶粘接正极膜层一面，并用压辊压实，使双面胶与极片完全贴合；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，直到集流体全部从正极膜片剥离，记录过程中的位移和作用力。以受力平衡时的力除以与双面胶贴合的极片的宽度(极片的宽度方向垂直于剥离方向)作为单位长度的极片的粘结力，本测试中与双面胶贴合的极片的宽度为20mm。
3)柔性测试(弯曲测试)
将冷压后的正极极片裁剪为20*100mm2尺寸的测试试样；将其正向对折后，用2kg压辊压平，并展开对着光检查缝隙是否出现透光，如未出现透光，则反向对折，用2kg压辊压平，并对着光再次检查，如此反复直至，缝隙出现透光现象，记录对折次数；重复三次测试，并取平均值，作为极片柔性的参考数据。
4)极片吸液速率测试
将冷压后的正极极片裁剪为5*5cm2尺寸的测试样品；首先，将样品在80℃下干燥4h，测试极片厚度后，固定在样品台上，然后挑选d＝200μm的毛细管，用5000目砂纸打磨端面至平整，利用显微镜观察毛细管与极片间状态；用毛细管吸取电解液，控制电解液高度h＝3mm，下降毛细管与极片接触，同时用秒表计时，当液面下降完毕后，停止计时，读取吸液时间t，记录数据；利用公式计算极片的平均吸液速率v，v＝π×(d/2)2×h×ρ/t。电解液密度为1.194g/cm3。
4、电池性能测试
1)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……P500这500个点值为纵坐标，以对应的循环次数为横坐标，得到电池容量保持率与循环次数的曲线图。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500次循环对应n＝500。表1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500次之后测得的数据，即P500的值。对比例以及其他实施例的测试过程同上。
2)电池直流阻抗测试
电池直流阻抗测试过程如下：在25℃下，将电池，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V1。然后再以1/3C放电30s，记录电压V2，则(V2-V1)/(1/3C)，得到第一次循环后电池的内阻DCR1。对上述同一个电池重复以上步骤，并同时记录循环第n次后电池的内阻DCRn(n＝1、2、3……100)，将上述DCR1、DCR2、DCR3……DCR100这100个点值为纵坐标，以对应的循环次数为横坐标，得到电池放电DCR与循环次数的曲线图。
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1中实施例1的电池内阻增大比率＝(DCRn-DCR1)/DCR1*100％，对比例以及其他实施例的测试过程同上。表1中的数据是在上述测试条件下循环100次之后测得的数据。
嵌段共聚物的制备参数和性能测试如表1所示。浆料和电池的性能测试如表2所示。
表1嵌段共聚物的制备参数和性能测试



表2实施例和对比例的浆料和电池性能测试



三、各实施例、对比例测试结果分析
根据上述结果可知，实施例1～36中的粘结剂为BAB型嵌段共聚物，包含A-嵌段和B-嵌段，其中实施例1～18中的B-嵌段含有衍生自丙烯酰胺或N-异丙基丙烯酰胺的结构单元，A-嵌段含有衍生自偏氟乙烯或偏氟乙烯-六氟丙烯或偏氟乙烯-四氟乙烯的结构单元；实施例19～36中的B-嵌段含有衍生自偏氟乙烯或偏氟乙烯-六氟丙烯或偏氟乙烯-四氟乙烯的结构单元，A-嵌段含有衍生自丙烯酰胺或N-异丙基丙烯酰胺的结构单元。
从实施例1～7、实施例16和对比例1的对比可见，B-嵌段含有衍生自丙烯酰胺或N-异丙基丙烯酰胺的结构单元，A-嵌段至少包含衍生自偏二氟乙烯的结构单元，该BAB型嵌段共聚物可以显著减缓浆料的凝胶现象，提高浆料稳定性、提高极片的柔性，提高极片的粘 结力，同时通过提高极片吸液速率，改善极片对电解液的浸润能力，进而降低膜片电阻。
从实施例19～25、实施例34和对比例1的对比可见，B-嵌段含有衍生自偏二氟乙烯的结构单元，A-嵌段至少包含衍生自丙烯酰胺或N-异丙基丙烯酰胺的结构单元，该BAB型嵌段共聚物可以显著减缓浆料的凝胶现象，提高浆料稳定性，提高极片的粘结力和柔韧性，同时通过提高极片吸液速率，改善极片对电解液的浸润能力，使得极片具有低的膜片电阻，降低电流的直流阻抗增长率。
从实施例1～7、实施例17～18、实施例19～25、实施例35～36和对比例2的对比可见，聚合物中包含衍生自偏氟乙烯或偏氟乙烯-六氟丙烯或偏氟乙烯-四氟乙烯的结构单元可以提高极片的粘结力。
从实施例1和对比例3的对比可见，聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺三嵌段共聚物可以减缓浆料的凝胶现象，提高浆料稳定性、提高极片的柔性、提高粘结力，同时通过提高极片吸液速率，改善极片对电解液的浸润能力，进而降低膜片电阻，并且降低电池的内阻增长率和提高电池的循环容量保持率。
实施例23与对比例3的对比可见，聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物可以减缓浆料的凝胶现象，提高浆料稳定性、提高极片的柔性，提高极片的粘结力，同时通过提高极片吸液速率，改善极片对电解液的浸润能力，使得极片具有低的膜片电阻，并且降低电池的内阻增长率和提高电池的循环容量保持率。
从实施例1～5和实施例6～7的对比可见，聚合物中衍生自偏二氟乙烯单体的结构单元的摩尔含量为40％～60％，基于嵌段共聚物中所有结构单元的总摩尔数计，使得极片兼具优异的粘结力、良好的极片吸液速率以及较低的膜片电阻。
实施例19～23和实施例24～25的对比可见，聚合物中衍生自偏二氟乙烯单体的结构单元的摩尔含量为40％～60％，基于嵌段共聚物中所有结构单元的总摩尔数计，使得极片兼具优异的粘结力、良好的极片吸液速率以及较低的膜片电阻，提高电池的循环性能。
从实施例1～11、16～18可见，聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺三嵌段共聚物、聚N-异丙基丙烯酰胺-聚偏二氟乙烯-聚N-异丙基丙烯酰胺三嵌段共聚物、聚丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)-聚丙烯酰胺三嵌段共聚物或聚丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)-聚丙烯酰胺三嵌段共聚物的重均分子量为40万～200万时，该粘结剂可以减缓浆料的凝胶现象，提高浆料稳定性，并且极片具有良好的粘结力和柔韧性，提高极片的使用性能。从实施例4、10～11与实施例8～9对比可见，聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺三嵌段共聚物的重均分子量为120万～200万，该粘结剂可以提高极片的粘结力和柔性，同时通过提高极片的吸液速率，改善极片对电解液的浸润能力，进而降低膜片电阻，并且降低电池的内阻增长率和提高电池的循环容量保持率。
从实施例19～29、34～36可见，聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物、聚偏二氟乙烯-聚N-异丙基丙烯酰胺-聚偏二氟乙烯三嵌段共聚物、聚(偏二氟乙烯-六氟丙烯)-聚丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)三嵌段共聚物或聚(偏二氟乙烯-四氟乙烯)-聚丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)三嵌段共聚物的重均分子量为40万～200万时，该粘结剂可以使得极片具有良好的粘结力和柔韧性，提高极片的使用性能。从实施例19、28～29与实施例26～27对比可见，聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物的重均分子量为120万～200万，该粘结剂可以提高极片的粘结力，提高电池的循环性能。
从实施例1～11、16～18可见，聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺嵌段共聚物或聚N-异丙基丙烯酰胺-聚偏二氟乙烯-聚N-异丙基丙烯酰胺三嵌段共聚物中聚偏二氟乙烯嵌段、聚丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)-聚丙烯酰胺三嵌段共聚物中的聚(偏二氟乙烯-六氟丙烯)、聚丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)-聚丙烯酰胺三嵌段共聚物中的聚(偏二氟乙烯-四氟乙烯)的重均分子量为20万～110万时，该粘结剂可以减缓浆料的凝胶现象，提高浆料稳定性，并且极片具有良好的粘结力和柔韧性，提高极片的使用性能。从实施例4、 10～11与实施例8～9对比可见，聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺嵌段共聚物中聚偏二氟乙烯嵌段的重均分子量为40万～110万时，该粘结剂能够提高极片的粘结力和柔性，使得极片具有较低的膜片电阻，降低的电池的内阻增长率，提高电池的循环容量保持率。
从实施例19～29、34～36可见，聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物、聚(偏二氟乙烯-六氟丙烯)-聚丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)三嵌段共聚物或聚(偏二氟乙烯-四氟乙烯)-聚丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)三嵌段共聚物中的聚丙烯酰胺嵌段、聚偏二氟乙烯-聚N-异丙基丙烯酰胺-聚偏二氟乙烯三嵌段共聚物中的聚N-异丙基丙烯酰胺的重均分子量为20万-110万，该粘结剂可以使得极片具有良好的粘结力和柔韧性，提高极片的使用性能。从实施例19、28～29与实施例26～27对比可见，聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物中的聚丙烯酰胺的重均分子量为40万～110万，该粘结剂可以提高极片的粘结力，提高电池的循环性能。
从实施例1～11、16～18可见，聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺嵌段共聚物、聚丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)-聚丙烯酰胺三嵌段共聚物或聚丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)-聚丙烯酰胺三嵌段共聚物中聚丙烯酰胺嵌段、聚N-异丙基丙烯酰胺-聚偏二氟乙烯-聚N-异丙基丙烯酰胺三嵌段共聚物中的聚N-异丙基丙烯酰胺的重均分子量为10万～50万时，该粘结剂可以减缓浆料的凝胶现象，提高浆料稳定性，并且极片具有良好的粘结力和柔韧性，提高极片的使用性能。从实施例4、10～11与实施例8～9对比可见，聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺嵌段共聚物中聚丙烯酰胺嵌段的重均分子量为20万～50万时，该粘结剂可以提高极片的粘结力和柔性，同时通过提高极片的吸液速率改善电解液对极片的浸润能力，进而降低极片的膜片电阻。
从实施例19～29、34～36可见，聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物或聚偏二氟乙烯-聚N-异丙基丙烯酰胺-聚偏二氟乙烯三嵌段共聚物中的聚偏二氟乙烯嵌段、聚(偏二氟乙烯-六 氟丙烯)-聚丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)三嵌段共聚物中的聚(偏二氟乙烯-六氟丙烯)、聚(偏二氟乙烯-四氟乙烯)-聚丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)三嵌段共聚物中的聚(偏二氟乙烯-四氟乙烯)的重均分子量为10万-50万时，该粘结剂可以使得极片具有良好的粘结力和柔韧性，提高极片的使用性能。从实施例19、28～29与实施例26～27对比可见，聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物中聚偏二氟乙烯嵌段的重均分子量为20万-50万时，该粘结剂可以提高极片的粘结力，提高电池的循环性能。
从实施例1、实施例12～15可见，聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺嵌段共聚物的粘结剂的质量分数为0.1％～3％，基于正极活性材料的质量计时，浆料具有较好的稳定性。从实施例1、14～15与实施例12～13对比可见，粘结剂的质量分数为1％～3％，基于正极活性材料的质量计时，该粘结剂能够提高极片的粘结力和柔性，同时通过提高极片的吸液速率，改善极片对电解液的浸润能力，进而降低膜片电阻，提高电池的循环性能。
从实施例19、实施例30～33可见，聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物的粘结剂的质量分数为0.1％～3％，基于正极活性材料的质量计时，浆料具有较好的稳定性。从实施例19、32～33与实施例30～31对比可见，粘结剂的质量分数为1％～3％，基于正极活性材料的质量计时，该粘结剂能够提高极片的粘结力和柔性，同时通过提高极片的吸液速率，改善极片对电解液的浸润能力，降低膜片电阻，降低电池的内阻增长率，提高电池的循环性能。
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 (30)

  1. 一种BAB型嵌段共聚物，其特征在于，包含A-嵌段和B-嵌段，
    所述A-嵌段含有衍生自式I所示单体的结构单元，所述B-嵌段含有衍生自式II所示单体的结构单元；
    或者所述A-嵌段含有衍生自式II所示单体的结构单元，所述B-嵌段含有衍生自式I所示单体的结构单元，
    其中，R1、R2、R3各自独立地选自氢、氟、至少含有一个氟原子的C1-3烷基中的一种或多种，R4、R5、R6、R7、R8各自独立地选自氢、取代或未取代的C1-3烷基。
  2. 根据权利要求1所述的BAB型嵌段共聚物，其特征在于，所述衍生自式I所示单体的结构单元的摩尔含量为40％～60％，所述衍生自式II所示单体的结构单元的摩尔含量为40％～60％，基于所述BAB型嵌段共聚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BAB型嵌段共聚物，其特征在于，所述BAB型嵌段共聚物的重均分子量为40万～200万。
  4. 根据权利要求1至3中任一项所述的BAB型嵌段共聚物，其特征在于，所述BAB型嵌段共聚物的重均分子量为120万～200万。
  5. 根据权利要求1至4中任一项所述的BAB型嵌段共聚物，其特征在于，所述BAB型嵌段共聚物中，所述A-嵌段的重均分子量为20万～110万。
  6. 根据权利要求1至5中任一项所述的BAB型嵌段共聚物，其特征在于，所述BAB型嵌段共聚物中，所述A-嵌段的重均分子量为40万～110万。
  7. 根据权利要求1至6中任一项所述的BAB型嵌段共聚物，其特征在于，所述BAB型嵌段共聚物中，每个B-嵌段的重均分子量为10万～50万。
  8. 根据权利要求1至7中任一项所述的BAB型嵌段共聚物，其特征在于，所述BAB型嵌段共聚物中，每个B-嵌段的重均分子量为20万～50万。
  9. 根据权利要求1至8中任一项所述的BAB型嵌段共聚物，其特征在于，所述式I所示单体选自偏氟乙烯、四氟乙烯、六氟丙烯中的一种或多种。
  10. 根据权利要求1至9中任一项所述的BAB型嵌段共聚物，其特征在于，所述式II所示单体选自丙烯酰胺、甲基丙烯酰胺、N-甲基丙烯酰胺、N-甲基甲基丙烯酰胺、N-异丙基丙烯酰胺、N-异丙基甲基丙烯酰胺、N-叔丁基丙烯酰胺、N-叔丁基(甲基)丙烯酰胺、N,N-二甲基丙烯酰胺、N,N-二甲基甲基丙烯酰胺、N,N-二乙基丙烯酰胺、N,N-二乙基甲基丙烯酰胺中的一种或多种。
  11. 根据权利要求1至10中任一项所述的BAB型嵌段共聚物，其特征在于，所述BAB型嵌段共聚物为聚丙烯酰胺-聚偏二氟乙烯-聚丙烯酰胺三嵌段共聚物、聚甲基丙烯酰胺-聚四氟乙烯-聚甲基丙烯酰胺三嵌段共聚物、聚N-甲基甲基丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)-聚N-甲基甲基丙烯酰胺三嵌段共聚物、聚N-异丙基丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)-聚N-异丙基丙烯酰胺三嵌段共聚 物、聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯三嵌段共聚物、聚四氟乙烯-聚甲基丙烯酰胺-聚四氟乙烯三嵌段共聚物、聚(偏二氟乙烯-六氟丙烯)-聚N-甲基甲基丙烯酰胺-聚(偏二氟乙烯-六氟丙烯)三嵌段共聚物、聚(偏二氟乙烯-四氟乙烯)-聚N-异丙基丙烯酰胺-聚(偏二氟乙烯-四氟乙烯)三嵌段共聚物中的一种或多种。
  12. 一种BAB型嵌段共聚物的制备方法，其特征在于，包括以下步骤：
    制备A-嵌段：将至少一种式I所示单体或至少一种式II所示单体聚合制备A-嵌段，
    其中，R1、R2、R3各自独立地选自氢、氟、至少含有一个氟原子的C1-3烷基中的一种或多种，R4、R5、R6、R7、R8各自独立地选自氢、取代或未取代的C1-3烷基；
    制备B-嵌段：将至少一种式II所示单体或至少一种式I所示单体聚合制备B-嵌段，
    制备BAB型嵌段共聚物：将所述A-嵌段和所述B-嵌段接合制备BAB型嵌段共聚物，其中所述A-嵌段和所述B-嵌段含有不同的结构单元。
  13. 根据权利要求12所述的制备方法，其特征在于，所述制备A-嵌段的方法包括：
    将至少一种式I所示单体或至少一种式II所示单体、第一引发剂在80～95℃的反应温度下聚合反应2.5～5h，对产物的端基进行取代反应，制备两端均具有叠氮基团或炔基的A-嵌段。
  14. 根据权利要求12或13所述的制备方法，其特征在于，所述 制备B-嵌段的方法包括：
    将至少一种式II所示单体或至少一种式I所示单体、链转移剂和第二引发剂在60～75℃的反应温度下通过可逆加成-裂解链转移聚合，反应4.5～6h得到末端具有炔基或叠氮基团的B-嵌段。
  15. 根据权利要求12至14中任一项所述的制备方法，其特征在于，所述制备BAB型嵌段共聚物的方法包括：
    将两端均具有叠氮基团或炔基的所述A-嵌段与末端具有炔基或叠氮基团的所述B-嵌段混合，进行点击反应，制备BAB型嵌段共聚物，其中，所述A-嵌段和所述B-嵌段的端基不同。
  16. 根据权利要求14或15所述的制备方法，其特征在于，所述链转移剂为含末端炔基或叠氮基团的RAFT链转移剂。
  17. 根据权利要求13至16中任一项所述的制备方法，其特征在于，所述第一引发剂为对称型双官能度引发剂。
  18. 根据权利要求14至17中任一项所述的制备方法，其特征在于，所述第二引发剂为偶氮引发剂。
  19. 权利要求1至11中任一项所述的BAB型嵌段共聚物在二次电池中的应用。
  20. 根据权利要求19所述的BAB型嵌段共聚物在二次电池中的应用，其特征在于，所述二次电池包括锂离子电池、钠离子电池、镁离子电池、钾离子电池中的至少一种。
  21. 一种正极极片，其特征在于，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，所述正极膜层包括正极活性材料、导电剂和粘结剂，所述粘结剂为权利要求1至11中任一项所 述的BAB型嵌段共聚物或权利要求12至18中任一项所述的制备方法制备的BAB型嵌段共聚物。
  22. 根据权利要求21所述的正极极片，其特征在于，所述粘结剂的质量分数为0.1％～3％，基于所述正极活性材料的总质量计。
  23. 根据权利要求21或22所述的正极极片，其特征在于，所述粘结剂的质量分数为1％～3％，基于所述正极活性材料的总质量计。
  24. 根据权利要求21至23中任一项所述的正极极片，其特征在于，所述正极膜层与所述正极集流体间单位长度的粘结力不小于11N/m。
  25. 根据权利要求21至24中任一项所述的正极极片，其特征在于，所述正极膜层与所述正极集流体间单位长度的粘结力为11-22N/m。
  26. 根据权利要求21至25中任一项所述的正极极片，其特征在于，所述正极极片在经过不少于3次的弯折测试后，所述正极极片出现透光现象。
  27. 根据权利要求21至26中任一项所述的正极极片，其特征在于，所述正极极片对电解液的吸液速率大于0.30μg/s，所述电解液的密度为1.1-1.2g/cm3。
  28. 根据权利要求21至27中任一项所述的正极极片，其特征在于，所述正极极片对电解液的吸液速率为0.35-0.6μg/s，所述电解液的密度为1.1-1.2g/cm3。
  29. 一种二次电池，其特征在于，包括电极组件和电解液，所 述电极组件包括隔离膜、负极极片和权利要求21至28中任一项所述的正极极片。
  30. 一种用电装置，其特征在于，包括权利要求29所述的二次电池。
PCT/CN2023/080637 2022-09-30 2023-03-09 Bab型嵌段共聚物、制备方法、粘结剂、正极极片、二次电池及用电装置 WO2024066211A1 (zh)

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