WO2024087112A1 - Bab型嵌段共聚物、制备方法、正极极片、二次电池、电池模块、电池包及用电装置 - Google Patents

Bab型嵌段共聚物、制备方法、正极极片、二次电池、电池模块、电池包及用电装置 Download PDF

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WO2024087112A1
WO2024087112A1 PCT/CN2022/128035 CN2022128035W WO2024087112A1 WO 2024087112 A1 WO2024087112 A1 WO 2024087112A1 CN 2022128035 W CN2022128035 W CN 2022128035W WO 2024087112 A1 WO2024087112 A1 WO 2024087112A1
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block
battery
block copolymer
positive electrode
formula
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PCT/CN2022/128035
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English (en)
French (fr)
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曾子鹏
李�诚
刘会会
王景明
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/128035 priority Critical patent/WO2024087112A1/zh
Priority to PCT/CN2023/080637 priority patent/WO2024066211A1/zh
Priority to PCT/CN2023/080636 priority patent/WO2024066210A1/zh
Priority to PCT/CN2023/094007 priority patent/WO2024066382A1/zh
Priority to PCT/CN2023/101439 priority patent/WO2024066507A1/zh
Publication of WO2024087112A1 publication Critical patent/WO2024087112A1/zh

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  • the present application relates to the technical field of secondary batteries, and in particular to a BAB-type block copolymer, a preparation method, a positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. With the popularization of secondary battery applications, higher requirements have been put forward for their energy density and cycle performance.
  • 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 type block copolymer, which can effectively improve the bonding force of the electrode sheet by using the block copolymer as a binder, reduce the DC impedance growth rate and metal deposition amount of the battery, so that the electrode sheet has both low membrane resistance and excellent flexibility, and the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • a BAB type block copolymer wherein the B-block contains a structural unit represented by formula I, and the A-block contains a structural unit represented by formula II, a structural unit represented by formula III or one or more thereof,
  • R1 , R2 , and R3 are each independently selected from one or more of hydrogen, fluorine, and C1-3 alkyl containing at least one fluorine atom;
  • R4 , R5 , and R6 are each independently selected from hydrogen, substituted or unsubstituted C1-5 alkyl;
  • R7 is selected from carboxyl, ester, hydroxyl, amide, cyano, and substituted or unsubstituted aromatic.
  • the binder prepared with BAB type block copolymer can effectively reduce the orderly arrangement of fluorinated block polymers because the non-fluorinated block polymer is located in the middle of the fluorinated block polymer.
  • the introduction of functional groups in the non-fluorinated polymer can improve the bonding performance of BAB type block copolymers, giving full play to the respective advantages of fluorinated binders and non-fluorinated binders to achieve complementary advantages.
  • this binder can effectively improve the bonding force of the pole piece, reduce the DC impedance growth rate and metal deposition of the battery, and ensure that the pole piece has both low membrane resistance and excellent flexibility, and the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • the A-block contains a structural unit represented by formula II in which R 7 is an amide group.
  • the A-block contains a structural unit represented by formula II in which R 7 is an amide group, which is beneficial for improving the bonding strength and flexibility of the electrode piece, reducing the film resistance of the electrode piece, and significantly reducing the dissolution of transition metals in the positive electrode.
  • the A-block contains a structural unit represented by formula II in which R 7 is a cyano group and a structural unit represented by formula II in which R 7 is an ester group.
  • the A-block contains both the structural unit of formula II in which R 7 is a cyano group and the structural unit of formula II in which R 7 is an ester group, which is beneficial to improving the adhesion and flexibility of the electrode, reducing the membrane resistance of the electrode, reducing the DC impedance growth rate and metal deposition amount of the battery, and at the same time ensuring that the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • the A-block contains a structural unit of formula II in which R 7 is a cyano group, a structural unit of formula II in which R 7 is an ester group, and a structural unit of formula II in which R 7 is a substituted or unsubstituted aromatic group.
  • the A-block contains a structural unit of formula II in which R7 is a cyano group, a structural unit of formula II in which R7 is an ester group, and a structural unit of formula II in which R7 is a substituted or unsubstituted aromatic group, which is beneficial to further improve the adhesion and flexibility of the electrode, as well as the cycle capacity retention rate and 45°C capacity retention rate of the battery.
  • the A-block contains a structural unit of formula II in which R 7 is a cyano group, a structural unit of formula II in which R 7 is an amide group, and a structural unit of formula II in which R 7 is an ester group.
  • the A-block contains a structural unit of formula II in which R7 is a cyano group, a structural unit of formula II in which R7 is an amide group, and a structural unit of formula II in which R7 is an ester group. This can significantly reduce the metal deposition amount of the battery while ensuring that the electrode has low membrane resistance, excellent adhesion and flexibility.
  • the mass content of the A-block is 40% to 60%, based on the total mass of all structural units in the block copolymer.
  • the binder can effectively improve the bonding force and flexibility of the pole piece, reduce the diaphragm resistance of the pole piece, improve the cycle capacity retention rate and 45°C capacity retention rate of the battery, and reduce the DC impedance growth rate and metal deposition amount of the battery.
  • the block copolymer has a weight average molecular weight of 400,000 to 2,000,000.
  • the binder can improve the adhesion of the electrode, reduce the DC impedance growth rate and metal deposition amount of the battery, and at the same time ensure that the electrode has both low membrane resistance and excellent flexibility, and the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • the weight average molecular weight of the A-block is 200,000 to 1.1 million.
  • the binder can improve the adhesion of the pole piece, reduce the DC impedance growth rate and metal deposition amount of the battery, and at the same time ensure that the pole piece has both low membrane resistance and excellent flexibility, and the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • the weight average molecular weight of each of the B-blocks is 100,000 to 500,000.
  • the binder can improve the adhesion of the pole piece, reduce the DC impedance growth rate and metal deposition amount of the battery, and at the same time ensure that the pole piece has both low membrane resistance and excellent flexibility, and the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • the structural unit represented by formula I is derived from the group consisting of vinylidene fluoride, tetrafluoroethylene, vinyl fluoride, hexafluoropropylene and combinations thereof.
  • the structural unit represented by formula II is derived from acrylonitrile, crotononitrile, styrene, vinyl alcohol, acrylamide, ethyl acrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid, ethyl acrylic acid, 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, N,N-diethylmethacrylamide, acrylic acid, vinylbenzoic acid, propylene acetate, acrylic acid esters and combinations thereof.
  • the above raw materials are simple and easy to obtain, and can significantly reduce production costs compared to traditional adhesives.
  • the second aspect of the present application also provides a method for preparing a BAB type block copolymer, comprising the following steps:
  • B-block polymerizing at least one monomer represented by formula V to prepare B-block,
  • R ⁇ 1 , R ⁇ 2 , and R ⁇ 3 are each independently selected from one or more of hydrogen, fluorine, and a C 1-3 alkyl group containing at least one fluorine atom;
  • Preparation of A-block polymerizing at least one monomer represented by formula VI to prepare A-block, or ring-opening polymerizing a monomer represented by formula VII to prepare A-block,
  • R ⁇ 4 , R ⁇ 5 , and R ⁇ 6 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl, and R ⁇ 7 is selected from one of carboxyl, ester, hydroxyl, amide, cyano, and substituted or unsubstituted aromatic groups;
  • BAB type block copolymer The B-block and the A-block are joined to prepare a BAB type block copolymer.
  • 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 of the BAB-type triblock copolymer prepared by this method can effectively improve the bonding force of the pole piece, reduce the DC impedance growth rate and metal deposition amount of the battery, and ensure that the pole piece has both low membrane resistance and excellent flexibility, and the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • the method for preparing the B-block comprises:
  • At least one monomer represented by formula V, a chain transfer agent and a first initiator are subjected to reversible addition-fragmentation chain transfer polymerization at a reaction temperature of 60 to 75° C. for 4 to 6 hours to obtain a B-block having an azide group or an alkynyl group at the end.
  • controllable polymerization can be achieved, and the molecular weight distribution of the product is relatively narrow.
  • the method for preparing the A-block comprises:
  • the monomer represented by formula VI and the second initiator are polymerized at a reaction temperature of 80 to 95° C. for 2.5 to 5 hours to obtain the A-block having alkynyl groups or azide groups at both ends.
  • the method for preparing the A-block comprises:
  • the monomer represented by formula VII, an ionic initiator and water are polymerized at a reaction temperature of 60° C. to 80° C. for 6 to 8 hours to obtain a product having hydroxyl groups at both ends;
  • the hydroxyl group of the product is functionalized to obtain the A-block having alkynyl or azide groups at both ends.
  • the preparation of the 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 terminal 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 improves the yield rate of the product.
  • the chain transfer agent is a RAFT chain transfer agent containing a terminal alkynyl group or an azide group.
  • the second initiator is a symmetrical bifunctional initiator.
  • the first initiator is selected from one or both of azobisisobutyronitrile and azobisisoheptanenitrile.
  • the third aspect of the present application provides a use of a BAB type block copolymer in any embodiment 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 low film resistance, excellent adhesion and good flexibility. At the same time, the battery has low metal deposition, excellent cycle performance and high-temperature storage performance.
  • 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.
  • the positive electrode film layer of the pole piece has a 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 3 bending tests, the positive electrode plate has a light-transmitting phenomenon.
  • the fact that the plate can be subjected to no less than 3 bending tests indicates that the plate has good flexibility and is not prone to plate cracking during production or brittle fracture during use, which helps to improve the yield rate of the battery and improve the safety performance of the battery.
  • the film resistance of the positive electrode plate is less than or equal to 1.0 ⁇ .
  • the lower film resistance of the plate indicates that the material in the positive electrode film layer is evenly dispersed, and the positive electrode film layer has good electron transmission efficiency, which is beneficial to the performance of the battery.
  • 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 provided in the fourth aspect of the present application.
  • a battery module comprising the secondary battery of the fifth aspect of the present application.
  • a battery pack comprising the battery module of the sixth aspect of the present application.
  • an electrical device comprising at least one of the secondary battery of the fifth aspect, the battery module of the sixth aspect, or the battery pack of the seventh aspect.
  • 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 the 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), indicating 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), indicating that step (c) may be added to the method in any order, for example, 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.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • 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 B-block contains the structural unit shown in formula I, and the A-block contains one or more of the structural units shown in formula II and the structural units shown in formula III.
  • R1 , R2 , and R3 are each independently selected from one or more of hydrogen, fluorine, and C1-3 alkyl containing at least one fluorine atom;
  • R4 , R5 , and R6 are each independently selected from hydrogen, substituted or unsubstituted C1-5 alkyl;
  • R7 is selected from carboxyl, ester, hydroxyl, amide, cyano, and substituted or unsubstituted aromatic.
  • 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.
  • the term "BAB type block copolymer” refers to a triblock copolymer with an A-block in the middle and B-blocks on both sides.
  • the A-block and the B-block are polymer segments with a predetermined weight average molecular weight formed by polymerization of different monomers.
  • the B-block is a long sequence segment formed by polymerization of fluorinated monomers
  • the A-block is a long sequence segment formed by polymerization of one or more fluorinated 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 poly(acrylonitrile-butyl methacrylate-styrene) is formed by polymerization of acrylonitrile monomer, butyl methacrylate monomer and styrene monomer, and has a weight average molecular weight of 480,000;
  • the B-block is polyvinylidene fluoride, formed by polymerization of vinylidene fluoride monomer, and has a weight average molecular weight of 400,000;
  • the end groups on both sides of the B-block and the A-block are bonded to obtain polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-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, mass content 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 of functional groups in the above macromolecules, such as addition or substitution, 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).
  • C 1-5 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 five carbon atoms, and attached to the remainder of the molecule by a single bond.
  • Examples of C 1-5 alkyl include, but are not limited to: methyl, ethyl, n-propyl, 1-methylethyl (isopropyl), n-butyl, n-pentyl.
  • carboxyl refers to a -COOH group.
  • ester group refers to a -COOR 10 group, wherein R 10 is selected from a substituted or unsubstituted C 1-5 alkyl group.
  • hydroxyl refers to an -OH group.
  • amido refers to a -CO-NR 8 R 9 group, wherein R 8 and R 9 are each independently selected from a substituted or unsubstituted C 1-5 alkyl group.
  • cyano refers to a -CN group.
  • 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.
  • 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 B-block forms hydrogen bonds with the hydroxyl or/and carboxyl groups on the surface of the active material and the current collector, so that the pole piece has excellent bonding force.
  • the amide group, carboxyl group, ester group, hydroxyl group or cyano group contained in the A-block can form hydrogen bonds with the hydroxyl groups on the surface of the positive electrode active material and the conductive agent particles on the one hand to improve the bonding force of the pole piece, and on the other hand can effectively combine with the transition metal in the positive electrode active material, inhibit the dissolution of the transition metal during use, and improve the cycle performance.
  • the insertion of the A-block between the B-blocks can reduce the large-area orderly arrangement of the fluorine-containing chain segments, reduce the crystallinity, and play a role in softening.
  • the binder prepared with the BAB type block copolymer can effectively reduce the orderly arrangement of the fluorine-containing block polymer because the non-fluorine-containing block polymer is located in the middle of the fluorine-containing block polymer.
  • the introduction of functional groups in the non-fluorine-containing polymer can improve the bonding performance of the BAB type block copolymer, give full play to the respective advantages of the fluorine-containing binder and the non-fluorine-containing binder, and achieve the role of complementary advantages.
  • BAB-type block copolymers can effectively inhibit the delamination of polymers during the slurry preparation process through the interaction between blocks.
  • BAB-type block copolymers as binders can improve the bonding strength of the pole pieces, reduce the DC impedance growth rate and transition metal dissolution of the battery, while ensuring that the pole pieces have both low membrane resistance and excellent flexibility, and that the battery has high cycle capacity retention and 45°C capacity retention.
  • the bonding force is mainly used to characterize the bonding strength between the film layer prepared by the positive electrode slurry and the current collector in the positive electrode sheet, which can be tested by any known method.
  • the diaphragm resistance is mainly used to characterize the resistance of the positive electrode sheet, which can reflect the electronic conductivity of the positive electrode sheet and can be tested by any known method.
  • flexibility is mainly used to characterize the bending resistance of the positive electrode sheet, which can reflect the ductility of the positive electrode sheet and can be tested by any known method.
  • the DC impedance growth rate is mainly used to characterize the impedance performance of the battery, which can reflect the increase rate of the impedance of the battery during the cycle process, and can be tested by any known method.
  • the cycle performance is mainly used to characterize the cycle performance of the battery, which can reflect the cycle performance of the battery and can be tested by any known method.
  • high temperature storage performance is mainly used to characterize the high temperature performance of the battery, which can reflect the high temperature stability of the battery, and can be tested by any known method.
  • the A-block contains a structural unit of formula II in which R 7 is an amide group.
  • R 7 in formula II is a structural unit of formula IV
  • R 8 and R 9 are each independently selected from hydrogen, and substituted or unsubstituted C 1-5 alkyl.
  • the amide groups contained in the A-block can easily form hydrogen bonds with the hydroxyl groups of the positive electrode active material and the current collector, which can improve the adhesion of the electrode.
  • the amide groups contained in the A-block can improve the wettability of the electrode in the electrolyte, help to quickly form ion transmission channels on the electrode, help to reduce the membrane resistance of the electrode, and improve the cycle performance of the battery.
  • the A-block contains a structural unit represented by formula II in which R 7 is an amide group, which is beneficial for improving the bonding strength and flexibility of the electrode piece, reducing the film resistance of the electrode piece, and significantly reducing the dissolution of transition metals in the positive electrode.
  • the A-block contains a structural unit of formula II in which R 7 is a cyano group and a structural unit of formula II in which R 7 is an ester group.
  • the A-block contains a strong polar group cyano, which can form strong hydrogen bonds and dipole-dipole effects with the hydroxyl groups on the surface of the positive electrode active material, that is, it can play a role in stabilizing and dispersing in the slurry, which helps to further improve the bonding force of the pole piece and promote the dispersion of the positive electrode active material, and reduce the membrane resistance of the pole piece.
  • the strong polar group cyano can enhance the stability of the molecular structure, increase the glass transition temperature of the block copolymer, improve the rigidity and thermal stability of the block copolymer, help improve the oxidation stability of the pole piece, and improve the cycle and rate performance of the battery.
  • the cyano group makes the A-block have a certain coating property for the positive electrode active material.
  • the cyano group in the A-block can complex with the transition metal ions on the surface of the positive electrode active material, hinder the dissolution of the transition metal ions, and then reduce the deposition of the transition metal ions on the negative electrode surface;
  • the ester group contained in the A-block helps to weaken the excessively strong dipole moment between the cyano groups, reduce the pole piece brittleness problem caused by the obstruction of the free movement of the binder chain segment due to the excessively strong force between the heavy cyano groups in the A-block, and improve the safety performance of the battery.
  • the ester group has a good affinity with the electrolyte, which helps to enhance the contact between the electrolyte and the positive electrode active material, thereby improving the ionic conductivity and reducing the membrane resistance of the electrode.
  • the A-block contains both the structural unit of formula II in which R 7 is a cyano group and the structural unit of formula II in which R 7 is an ester group, which is beneficial to improving the adhesion and flexibility of the electrode, reducing the membrane resistance of the electrode, reducing the DC impedance growth rate and metal deposition amount of the battery, and at the same time ensuring that the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • the A-block contains a structural unit of formula II in which R 7 is a cyano group, a structural unit of formula II in which R 7 is an ester group, and a structural unit of formula II in which R 7 is a substituted or unsubstituted aromatic group.
  • the aromatic groups contained in the A-block help to improve the mechanical strength of the electrode to cope with the volume change of the positive electrode active material during the charge and discharge process, so that the electrode maintains structural integrity during the charge and discharge process and improves the cycle performance of the battery.
  • the A-block contains the structural unit of formula II in which R 7 is a cyano group, the structural unit of formula II in which R 7 is an ester group, and the structural unit of formula II in which R 7 is a substituted or unsubstituted aromatic group, which is also beneficial to further improve the adhesion and flexibility of the pole piece.
  • the A-block contains a structural unit of formula II in which R 7 is a cyano group, a structural unit of formula II in which R 7 is an amide group, and a structural unit of formula II in which R 7 is an ester group.
  • the A-block contains the structural unit of formula II in which R7 is a cyano group, the structural unit of formula II in which R7 is an amide group, and the structural unit of formula II in which R7 is an ester group. While ensuring that the electrode has low film resistance, excellent adhesion and flexibility, the metal deposition amount of the battery is greatly reduced, so that the battery has low DC impedance growth rate, high cycle capacity retention rate and 45°C capacity retention rate.
  • R7 in Formula II can be selected from one or more of carboxyl and hydroxyl groups.
  • the structural unit represented by Formula II is derived from the group consisting of acrylonitrile, crotononitrile, styrene, vinyl alcohol, acrylamide, ethyl acrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid, ethyl acrylic acid, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-tert-butylacrylamide, N-tert-butyl(meth)acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, acrylic acid, vinylbenzoic acid, propylene acetate, acrylic acid esters, and combinations thereof.
  • the structural unit represented by Formula I is derived from the group consisting of vinylidene fluoride, tetrafluoroethylene, vinyl fluoride, hexafluoropropylene and combinations thereof.
  • the BAB block copolymer is one of polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride block copolymer, polyvinylidene fluoride-polyacrylamide-polyvinylidene fluoride block copolymer, polyvinylidene fluoride-poly(acrylic acid-acrylamide-ethyl methacrylate-polyvinylidene fluoride block copolymer, polyvinylidene fluoride-poly(acrylonitrile-acrylamide-acrylate)-polyvinylidene fluoride block copolymer, polyvinylidene fluoride-polystyrene-polyvinylidene fluoride block copolymer, polyvinylidene fluoride-polyethylene oxide-polyvinylidene fluoride block copolymer, polyvinylidene fluor
  • the mass content of A-block is 40% to 60%, based on the total mass of block copolymer. In some embodiments, the mass content of A-block can be 40%, 42%, 44%, 45%, 46%, 48%, 50%, 42%, 54%, 54%, 55%, 56%, 58%, 60%, based on the total mass of block copolymer.
  • the BAB-type block copolymer with the mass content of the A-block within an appropriate range can improve the adhesion and flexibility of the electrode, reduce the membrane resistance of the electrode, improve the cycle capacity retention rate and 45°C capacity retention rate of the battery, and reduce the DC impedance growth rate and metal deposition amount of the battery.
  • the weight average molecular weight of the block copolymer is 400,000 to 2,000,000. In some embodiments, the weight average molecular weight of the block copolymer can be 400,000, 420,000, 450,000, 480,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, 800,000, 850,000, 900,000, 950,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000, 1,500,000, 1,600,000, 1,700,000, 1,800,000, 1,900,000, 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 weight average molecular weight of the polymer can be tested by methods known in the art, such as gel chromatography, such as using a Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141).
  • gel chromatography such as using a Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141).
  • a polystyrene solution sample with a mass fraction of 3.0% is used as a reference, and a matching chromatographic column is selected (oily: Styragel HT5DMF7.8 ⁇ 300mm+Styragel HT4).
  • a 3.0% fluorine-containing polymer solution is prepared with purified N-methylpyrrolidone (NMP) solvent, and the prepared solution is allowed to stand for one day for use.
  • NMP N-methylpyrrolidone
  • tetrahydrofuran is first drawn with a syringe, rinsed, and repeated several times. Then draw 5 ml of the experimental solution, remove the air in the syringe, and wipe the needle tip dry. Finally, slowly inject the sample solution into the injection port. After the indication is stable, obtain the data and read the weight average molecular weight.
  • 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 will not be able to play an effective bonding role.
  • BAB block copolymers with a weight average molecular weight within a suitable range can improve the adhesion of the pole piece, reduce the DC impedance growth rate and metal deposition amount of the battery, while ensuring that the pole piece has both low membrane resistance and excellent flexibility, and that the battery has both high cycle capacity retention and 45°C capacity retention.
  • the weight average molecular weight of the A-block in the block copolymer is 200,000 to 1.1 million. In some embodiments, the weight average molecular weight of the A-block in the block copolymer can be 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, 800,000, 850,000, 900,000, 950,000, 1,050,000, 1,100,000.
  • the structural unit of the monomer represented by Formula II or Formula III has too many strong polar 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.
  • BAB block copolymers with a weight average molecular weight of the A-block within a suitable range can improve the adhesion of the pole piece, reduce the DC impedance growth rate and metal deposition amount of the battery, while ensuring that the pole piece has both low membrane resistance and excellent flexibility, and the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • the weight average molecular weight of each B-block in the block copolymer is 100,000 to 500,000. In some embodiments, the weight average molecular weight of each B-block in the block copolymer can be selected as 100,000, 120,000, 150,000, 170,000, 200,000, 220,000, 250,000, 280,000, 300,000, 320,000, 350,000, 370,000, 400,000, 430,000, 450,000, 470,000, 500,000.
  • BAB block copolymers with a weight average molecular weight of each B-block within a suitable range can improve the adhesion of the pole piece, reduce the DC impedance growth rate and metal deposition amount of the battery, while ensuring that the pole piece has both low membrane resistance and excellent flexibility, and the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • a method for preparing a BAB type block copolymer comprising the following steps:
  • B-block polymerizing at least one monomer represented by formula V to prepare B-block,
  • R ⁇ 1 , R ⁇ 2 , and R ⁇ 3 are each independently selected from one or more of hydrogen, fluorine, and a C 1-3 alkyl group containing at least one fluorine atom;
  • Preparation of A-block polymerizing at least one monomer represented by formula VI to prepare A-block, or ring-opening polymerizing a monomer represented by formula VII to prepare A-block,
  • R ⁇ 4 , R ⁇ 5 , and R ⁇ 6 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl, and R ⁇ 7 is selected from one of carboxyl, ester, hydroxyl, amide, cyano, and substituted or unsubstituted aromatic groups;
  • B-block and A-block are joined to prepare BAB type block copolymer.
  • the preparation method uses cheap raw materials, can reduce costs, reduce environmental pollution, and is conducive to the increase of binder production.
  • the binder prepared by this method can effectively improve the bonding force of the pole piece, reduce the DC impedance growth rate and metal deposition of the battery, and ensure that the pole piece has both low film resistance and excellent flexibility, and the battery has both high cycle capacity retention rate and 45°C capacity retention rate.
  • the method of preparing the B-block comprises:
  • At least one monomer represented by formula V, a chain transfer agent and a first initiator are subjected to reversible addition-fragmentation chain transfer polymerization at a reaction temperature of 60 to 75° C. for 4 to 6 hours to obtain a B-block having an azide group or an alkynyl group at the end.
  • azide group refers to a -N3 group.
  • alkynyl refers to a -C ⁇ CH group.
  • 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 to 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, and finally making the growth probability of each polymer segment roughly equal, thus showing the characteristics of living polymerization.
  • the schematic diagram of 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 containing 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 A-block comprises:
  • the monomer represented by formula VI and the second initiator are polymerized at a reaction temperature of 80 to 95° C. for 2.5 to 5 hours to obtain an A-block having alkynyl groups or azide groups at both ends.
  • 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 ( B1 in the figure is a halogen-substituted alkyl or trimethylsilyl acetylene group, and B2 is 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 form a BAB type block copolymer.
  • the method of preparing the A-block comprises:
  • the monomer represented by formula VII, an ionic initiator and water are polymerized at a reaction temperature of 60° C. to 80° C. for 6 to 8 hours to obtain a product having hydroxyl groups at both ends;
  • the hydroxyl groups of the product are functionalized to obtain an A-block having alkynyl or azide groups at both ends.
  • 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 ( B1 in the figure is a halogen-substituted alkyl or trimethylsilyl acetylene group, and B2 is 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.
  • 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.
  • 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 second initiator is a symmetrical bifunctional initiator.
  • the second initiator is 4-(chloromethyl)benzoyl peroxide.
  • the symmetrical bifunctional initiator allows the A-block to have the same active functional groups symmetrically on both sides, which helps to achieve the simultaneous azidation or alkyne of the terminal groups on both sides of the A-block.
  • the first initiator is selected from one or both 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 can 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.
  • a 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, wherein the positive electrode film layer includes a positive electrode active material, a conductive agent and a binder, wherein the binder is a BAB type block copolymer in some embodiments or a BAB type block copolymer prepared by a preparation method in some embodiments.
  • the positive electrode sheet has excellent flexibility and adhesion, as well as low membrane resistance.
  • 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. In some embodiments, the bonding force per unit length between the positive electrode film layer and the positive electrode current collector may be 11 N/m, 11.5 N/m, 12 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.
  • 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 20mm ⁇ 100mm 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 plate after the positive electrode plate has been subjected to at least 3 bending tests, the positive electrode plate has a light transmission phenomenon. In some embodiments, after the positive electrode plate has been subjected to at least 3.3, 3.5, 3.7 or 4 bending tests, the positive electrode plate has a light transmission phenomenon.
  • the flexibility test of the positive electrode plate can be tested by a well-known method; as an example, the cold-pressed positive electrode plate is cut into a test sample of 20 ⁇ 100mm 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 plate.
  • the positive electrode plate can undergo no less than 3 bending tests, indicating that the plate has good flexibility and is not prone to cracking during the production process or brittle breakage during use, which helps to improve the battery yield and improve the battery safety performance.
  • the sheet resistance of the positive electrode sheet is less than or equal to 1.0 ⁇ .
  • the film resistance refers to the resistance of the positive film layer of the electrode sheet, and can be tested by any means known in the art. As an example, a resistance meter can be used for testing.
  • the diaphragm resistance can be tested by a known method. As an example, cut small discs with a diameter of 3 mm at the left, middle and right of the electrode. Turn on the indicator light of the Yuanneng Technology electrode resistance meter, place the probe in the appropriate position of the diaphragm resistance meter, click the "start" button, and wait for the reading to stabilize before reading. Each small disc is tested at two positions, and the average of the six measurements is finally calculated, which is the diaphragm resistance of the electrode.
  • the electrode sheet has a low membrane resistance, which means that the material in the positive electrode film layer is evenly dispersed and the positive electrode film layer has good electron transmission efficiency, which is beneficial to 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.
  • aluminum foil may be used as the metal foil.
  • 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 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 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 further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared 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.
  • a metal foil a 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 at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • 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 further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can 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 film 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 select according to specific actual needs.
  • 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 electrical 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 electrical device, or as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • a secondary battery, a battery module or a battery pack can 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.
  • RAFT chain transfer agent CTA-alkyne
  • polymerization reaction is used to prepare acetylene-terminated polyvinylidene fluoride; wherein the structural formula of RAFT chain transfer agent is as follows
  • the reaction process for preparing the B-block polymer is as follows:
  • A-block using azide as an initiator, preparing azide-terminated poly(acrylonitrile-butyl methacrylate-styrene) by polymerization reaction;
  • Poly(acrylonitrile-butyl methacrylate-styrene) having azide groups at both ends, polyvinylidene fluoride having an alkynyl group at the end, 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-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride block copolymer with a weight average molecular weight of 1.2 million, which was used as a battery binder.
  • NCM Lithium nickel cobalt manganese
  • conductive agent carbon black Lithium nickel cobalt manganese (NCM) material
  • binder prepared in Example 1 Lithium nickel cobalt manganese (NMP) material
  • NMP N-methylpyrrolidone
  • 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 mixed evenly to prepare a negative electrode slurry; 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 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, 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 methods of the batteries of Examples 2 to 5 are similar to those of Example 1, but only the weight average molecular weight and mass content of the A-block and the B-block are adjusted respectively to maintain the weight average molecular weight of the polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride block copolymer at 1.2 million.
  • the specific parameters are shown in Table 1.
  • the preparation method of the batteries of Examples 6 to 9 is similar to that of the battery of Example 1, but the weight average molecular weight of the polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride block copolymer is adjusted by adjusting the weight average molecular weight and mass content of the A-block and the B-block respectively.
  • the specific parameters are shown in Table 1.
  • the preparation method of the battery of Example 10 is similar to that of the battery of Example 1, but the A-block is replaced by polyacrylamide having azide groups at both ends.
  • the specific parameters are shown in Table 1, and the preparation method is as follows:
  • the preparation method of the battery of Example 11 is similar to that of the battery of Example 1, but the A-block is replaced with poly(acrylic acid-acrylamide-ethyl methacrylate) having azide groups at both ends.
  • the specific parameters are shown in Table 1, and the preparation method is as follows:
  • the preparation method of the battery of Example 12 is similar to that of the battery of Example 1, but the A-block is replaced with poly(acrylonitrile-acrylamide-acrylate) having azide groups at both ends.
  • the specific parameters are shown in Table 1, and the preparation method is as follows:
  • the preparation method of the battery of Example 13 is similar to that of the battery of Example 1, but the A-block is replaced with polystyrene having azide groups at both ends.
  • the specific parameters are shown in Table 1, and the preparation method is as follows:
  • the polymer was vacuum dried at 45°C to obtain a white product.
  • 3 mmol of chlorine-terminated polystyrene and 60 mmol of sodium azide (NaN 3 ) were dissolved in 600 ml of N,N-dimethylformamide (DMF) and stirred at 60°C overnight.
  • the polymer solution was concentrated and precipitated three times in a mixed solvent (the volume ratio of methanol to water was 1:1).
  • the pale yellow product was then vacuum dried at 45°C to obtain polystyrene containing azides at both ends, i.e., A-block polymer.
  • the preparation method of the battery of Example 14 is similar to that of the battery of Example 1, but the A-block is replaced with polyethylene oxide having azide groups at both ends.
  • the specific parameters are shown in Table 1, and the preparation method is as follows:
  • Ethylene oxide monomer, water and potassium hydroxide (KOH) in a molar ratio of 1:0.1:0.02 are added to a high-pressure stirred autoclave, and a large amount of nitrogen is introduced to remove air, and then the pressure is increased to 0.3MPa, and the stirring speed is gradually increased to 1000 rpm, and the temperature is raised to 80°C.
  • KOH potassium hydroxide
  • the preparation method of the battery of Example 15 is similar to that of the battery of Example 1, but the A-block is replaced with polyvinyl alcohol.
  • the specific parameters are shown in Table 1.
  • the preparation method is as follows:
  • the polymer was vacuum dried at 45°C to obtain a white product; the chlorine-terminated polyvinyl acetate obtained by the above reaction was dissolved in a mixed solvent (the volume ratio of methanol to water was 79.5:0.5), wherein the mass fraction of polyvinyl acetate was 20%, and a sodium hydroxide solution with a mass fraction of 1.5% was added at 30°C for alcoholysis for 2 hours, and the mixture was fully washed and filtered to obtain chlorine-terminated polyvinyl alcohol; 3mmol of chlorine-terminated polyvinyl alcohol and 60mmol of sodium azide (NaN3) were dissolved in 600ml of N,N-dimethylformamide (DMF) and stirred at 60°C overnight.
  • a mixed solvent the volume ratio of methanol to water was 79.5:0.5
  • a sodium hydroxide solution with a mass fraction of 1.5% was added at 30°C for alcoholysis for 2 hours, and the mixture was fully washed and filtered to obtain chlorine-terminated poly
  • the polymer solution was concentrated and precipitated three times in a mixed solvent (the volume ratio of methanol to water was 1:1).
  • the light yellow product was then vacuum dried at 45°C to obtain polyvinyl alcohol containing azides at both ends, i.e., A-block polymer.
  • the preparation method of the battery of Example 16 is similar to that of the battery of Example 1, but the A-block is replaced with poly(acrylonitrile-acrylic acetate). The specific parameters are shown in Table 1.
  • 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(acrylonitrile-propylene acetate) and 60 mmol of sodium azide (NaN 3 ) were dissolved in 600 ml of N,N-dimethylformamide (DMF) and stirred at 60°C overnight.
  • the polymer solution was concentrated and precipitated three times in a mixed solvent (methanol to water volume ratio of 1:1).
  • the pale yellow product was then dried in vacuo at 45° C. to obtain poly(acrylonitrile-acrylic acetate) containing azides at both ends, ie, the A-block polymer.
  • the preparation method of the battery of Example 17 is similar to that of the battery of Example 1, but the B-block is replaced by a polyvinyl fluoride block.
  • the specific parameters are shown in Table 1.
  • the preparation method is as follows:
  • the preparation method of the battery of Example 18 is similar to that of the battery of Example 1, but the B-block is replaced by a polytetrafluoroethylene block.
  • the specific parameters are shown in Table 1.
  • the preparation method is as follows:
  • 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 purchased from Solvay Group with a brand number of 5130. The specific parameters are shown in Table 1.
  • the preparation method of the battery of Comparative Example 2 is similar to that of the battery of Comparative Example 1, but the binder is poly(acrylonitrile-butyl methacrylate-styrene), and the preparation method of poly(acrylonitrile-butyl methacrylate-styrene) is as follows:
  • the preparation method of the battery of Comparative Example 3 is similar to that of the battery of Comparative Example 1, but the binder is a blend of polyvinylidene fluoride and poly(acrylonitrile-butyl methacrylate-styrene), the specific parameters are shown in Table 1, and the preparation method is as follows:
  • Blending The poly(acrylonitrile-butyl methacrylate-styrene) 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 polyvinyl alcohol blend adhesive.
  • the preparation method of the battery of Comparative Example 4 is similar to that of the battery of Comparative Example 3, but the binder is a blend of polyvinylidene fluoride and polyacrylamide.
  • the specific parameters are shown in Table 1.
  • the preparation method of the battery of Comparative Example 5 is similar to that of the battery of Comparative Example 3, but the binder is a blend of polyvinylidene fluoride and poly(acrylic acid-acrylamide-ethyl methacrylate), and the specific parameters are shown in Table 1.
  • the preparation method of the battery of Comparative Example 6 is similar to that of the battery of Comparative Example 3, but the binder is a blend of polyvinylidene fluoride and polyvinyl alcohol.
  • the specific parameters are shown in Table 1.
  • 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.
  • the positive electrode sheet was cut into a test sample of 20mm ⁇ 100mm size for standby use; the sheet was 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 sheet completely fit; the other side of the double-sided tape was pasted to the stainless steel surface, and one end of the sample was bent in the opposite direction with a bending angle of 180°; the high-speed rail tensile machine was used for testing, one end of the stainless steel was fixed to the lower fixture of the tensile machine, and the bent end of the sample was fixed to the upper fixture, and the angle of the sample was adjusted to ensure that the upper and lower ends were in a vertical position, and then the sample was stretched at a speed of 50mm/min until the current collector was completely peeled off from the positive electrode film, and the displacement and force during the process were recorded.
  • the force at the time of force balance divided by the width of the sheet bonded with the double-sided tape (the width direction of the sheet is perpendicular to the peeling direction) is taken as the bonding force of the sheet per unit length.
  • the width of the sheet is 20mm.
  • the cold-pressed positive electrode sheet is cut into test specimens of 20 ⁇ 100mm 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 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.
  • the battery internal resistance increase ratio of Example 1 in Table 2 (DCRn-DCR1)/DCR1*100%, and the test process of the comparative example and other embodiments is the same as above.
  • the data in Table 2 are measured after 100 cycles under the above test conditions.
  • the battery capacity retention rate data corresponding to the embodiment or comparative example in Table 2 is the data measured after 500 cycles under the above test conditions, that is, the value of P500.
  • the test process of the comparative example and other embodiments is the same as above.
  • the prepared lithium-ion battery was charged and discharged for the first time with a current of 0.5C (i.e., the current value that completely discharges the theoretical capacity within 2 hours).
  • the charging was constant current and constant voltage charging, the termination voltage was 4.2V, the cut-off current was 0.05C, and the discharge termination voltage was 2.8V.
  • the battery was left for 24 hours and charged to 4.2V with a constant current and constant voltage of 0.5C.
  • the fully charged battery was discharged with a current of 1C, and the discharge termination voltage was 2.8V.
  • the battery cell was disassembled, the negative electrode plate was taken out, and the deposition amount of metal Co and Mn was tested by inductively coupled plasma (ICP) method.
  • ICP inductively coupled plasma
  • Lithium ion secondary battery storage capacity retention rate (%) CAP 2 /CAP 1 ⁇ 100%.
  • the batteries of the embodiments and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in Tables 1 and 2 below.
  • the binder in Examples 1 to 18 is a BAB type block copolymer, comprising an A-block and a B-block, wherein the B-block contains at least one structural unit derived from vinylidene fluoride, vinyl fluoride or tetrafluoroethylene, and the A-block contains at least one structural unit derived from acrylonitrile, butyl methacrylate, styrene, acrylamide, acrylic acid, ethyl methacrylate, acrylate, ethylene oxide, vinyl alcohol, and propylene acetate.
  • the binder in Examples 1 to 18 is a BAB type block copolymer, comprising an A-block and a B-block, wherein the B-block contains a fluorinated polymer and the A-block contains a non-fluorinated polymer.
  • the binder in Comparative Examples 3 to 6 is a blend of a fluorinated polymer and a non-fluorinated polymer.
  • the binder in Examples 10 to 12 is a BAB type block copolymer, comprising an A-block and a B-block, wherein the B-block contains a structural unit derived from vinylidene fluoride, and the A-block contains at least a structural unit derived from acrylamide.
  • the above-mentioned BAB type block copolymer can effectively improve the bonding force and flexibility of the pole piece, reduce the membrane resistance of the pole piece, improve the cycle capacity retention rate and 45°C capacity retention rate of the battery, and reduce the DC impedance growth rate and metal deposition amount of the battery.
  • the binder in Examples 1 to 5, 12, and 16 is a BAB type block copolymer, comprising an A-block and a B-block, wherein the B-block contains a structural unit derived from vinylidene fluoride, and the A-block contains at least a structural unit derived from acrylonitrile, and a structural unit derived from butyl methacrylate, acrylate, or propylene acetate.
  • the binder of Example 4 is a BAB type block copolymer, comprising an A-block and a B-block, wherein the B-block contains a structural unit derived from vinylidene fluoride, and the A-block contains a structural unit derived from acrylonitrile, a structural unit derived from butyl methacrylate, and a structural unit derived from styrene.
  • Example 4 From the comparison between Example 4 and Examples 10 to 16, it can be seen that the polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride BAB type block copolymer as a binder can further significantly improve the bonding force and flexibility of the pole piece, and at the same time, the cycle capacity retention rate and 45°C capacity retention rate of the battery are also further improved.
  • the binder of Example 12 is a BAB type block copolymer, comprising an A-block and a B-block, wherein the B-block comprises a structural unit derived from vinylidene fluoride, and the A-block comprises a structural unit derived from acrylonitrile, a structural unit derived from acrylamide, and a structural unit derived from acrylate. From the comparison between Example 12 and Examples 4, 10 to 11, and 13 to 16, it can be seen that the polyvinylidene fluoride-poly(acrylonitrile-acrylamide-acrylate)-polyvinylidene fluoride block copolymer BAB type block copolymer as a binder can significantly reduce the amount of metal deposition in the battery.
  • the BAB type block copolymer with a mass content of 40% to 60% of the A-block as a binder can improve the bonding force and flexibility of the pole piece, reduce the membrane resistance of the pole piece, improve the cycle capacity retention rate of the battery, and reduce the DC impedance growth rate and metal deposition of the battery.
  • the BAB type block copolymer with a mass content of 40% to 60% of the A-block as a binder can improve the bonding force and flexibility of the pole piece, reduce the DC impedance growth rate of the battery, and ensure that the pole piece has both low membrane resistance and the battery has both low metal deposition, high cycle capacity retention rate and 45°C capacity retention rate.
  • the BAB-type block copolymer with a weight average molecular weight of 400,000 to 2 million as a binder can improve the bonding force of the pole piece, reduce the DC impedance growth rate of the battery, and ensure that the pole piece has both low diaphragm resistance and excellent flexibility, and the battery has both low metal deposition and high cycle capacity retention rate.
  • the BAB-type block copolymer with a weight average molecular weight of 400,000 to 2 million as a binder can improve the bonding force and flexibility of the pole piece, reduce the DC impedance growth rate of the battery, and ensure that the pole piece has low diaphragm resistance, and the battery has both low metal deposition, high cycle capacity retention rate and 45°C capacity retention rate.
  • the BAB-type block copolymer with a weight average molecular weight of the fluorinated block A-block of 200,000 to 1.1 million and a weight average molecular weight of the B-block of 100,000 to 500,000 as a binder can improve the adhesion and flexibility of the electrode, reduce the diaphragm resistance of the electrode, improve the battery's cycle capacity retention rate and 45°C capacity retention rate, and reduce the battery's DC impedance growth rate and metal deposition amount.
  • the BAB-type block copolymer with a weight average molecular weight of the fluorinated block A-block of 200,000 to 1.1 million and a weight average molecular weight of the B-block of 100,000 to 500,000 as a binder can improve the adhesion and flexibility of the pole piece, reduce the DC impedance growth rate of the battery, and at the same time ensure that the pole piece has low membrane resistance and the battery has low metal deposition, high cycle capacity retention rate and 45°C capacity retention rate.

Abstract

本申请提供了一种BAB型嵌段共聚物、制备方法、正极极片、二次电池、电池模块、电池包和及用电装置。该BAB型嵌段共聚物包括B-嵌段和A-嵌段，B-嵌段含有式I所示的结构单元，A-嵌段含有式II所示的结构单元、式Ⅲ所示的结构单元中的一种或多种，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各自独立地选自氢、取代或未取代的C1-5烷基，R7选自羧基、酯基、羟基、酰胺基、氰基、取代或未取代的芳香基。

Description

BAB型嵌段共聚物、制备方法、正极极片、二次电池、电池模块、电池包及用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种BAB型嵌段共聚物、制备方法、正极极片、二次电池、电池模块、电池包和及用电装置。
背景技术
近年来，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着二次电池应用的普及，对其能量密度、循环性能等也提出了更高的要求。
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提高极片的粘结力，降低电池的直流阻抗增长率和金属沉积量，使得极片兼具低膜片电阻和优异的柔韧性、电池兼具高循环容量保持率和45℃容量保持率。
本申请的第一方面，提供了一种BAB型嵌段共聚物，所述B-嵌段含有式I所示的结构单元，所述A-嵌段含有式II所示的结构单元、 式Ⅲ所示的结构单元中的一种或多种，
Figure PCTCN2022128035-appb-000001
Figure PCTCN2022128035-appb-000002
-CH 2-CH 2-O-式III
其中R 1、R 2、R 3各自独立地选自氢、氟、至少含有一个氟原子的C 1- 3烷基中的一种或多种，R 4、R 5、R 6各自独立地选自氢、取代或未取代的C 1-5烷基，R 7选自羧基、酯基、羟基、酰胺基、氰基、取代或未取代的芳香基。
以BAB型嵌段共聚物制备的粘结剂，由于非氟嵌段聚合物位于含氟嵌段聚合物中间，可以有效的减少含氟嵌段聚合物的有序排列，同时，非含氟聚合物中官能团的引入可提高BAB型嵌段共聚物的粘结性能，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。相比于传统的PVDF粘结剂，该粘结剂能够有效提高极片的粘结力，降低电池的直流阻抗增长率和金属沉积量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
在任意实施方式中，所述A-嵌段含有R 7为酰胺基的式II所示的结构单元。
A-嵌段含有R 7为酰胺基的式II所示的结构单元，有利于在提高极片的粘结力和柔韧性，降低极片的膜片电阻的同时，显著减少过渡金属在正极的溶出。
在任意实施方式中，所述A-嵌段含有R 7为氰基的式II所示的结构单元和R 7为酯基的式II所示的结构单元。
A-嵌段中同时含有R 7为氰基的式II所示的结构单元和R 7为酯基的式II所示的结构单元，有利于提高极片的粘结力和柔韧性，降低 极片的膜片电阻，降低电池的直流阻抗增长率和金属沉积量，同时保证电池兼具高循环容量保持率和45℃容量保持率。
在任意实施方式中，所述A-嵌段含有R 7为氰基的式II所示的结构单元、R 7为酯基的式II所示的结构单元和R 7为取代或未取代的芳香基的式II所示的结构单元。
申请人意外的发现，A-嵌段中同时含有R 7为氰基的式II所示的结构单元、R 7为酯基的式II所示的结构单元和R 7为取代或未取代的芳香基的式II所示的结构单元，有利于进一步提高极片的粘结力和柔韧性、以及电池的循环容量保持率和和45℃容量保持率。
在任意实施方式中，所述A-嵌段含有R 7为氰基的式II所示的结构单元、R 7为酰胺基的式II所示的结构单元和R 7为酯基的式II所示的结构单元。
A-嵌段中同时含有R 7为氰基的式II所示的结构单元、R 7为酰胺基的式II所示的结构单元和R 7为酯基的式II所示的结构单元，能够在保证极片兼具低膜片电阻、优异的粘结力和柔韧性的同时，大幅度降低电池的金属沉积量。
在任意实施方式中，所述A-嵌段的质量含量为40％～60％，基于所述嵌段共聚物中所有结构单元的总质量计。
控制BAB型嵌段共聚物中所述式I所示的结构单元的质量含量在合适范围内，粘结剂能够有效提高极片的粘结力和柔韧性，降低极片的膜片电阻，提升电池的循环容量保持率和45℃容量保持率，降低电池的直流阻抗增长率和金属沉积量。
在任意实施方式中，所述嵌段共聚物的重均分子量为40万～200万。
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，降低电池的直流阻抗增长率和金属沉积量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
在任意实施方式中，所述嵌段共聚物中，所述A-嵌段的重均分子量为20万～110万。
控制嵌段共聚物中A-嵌段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，降低电池的直流阻抗增长率和金属沉积量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
在任意实施方式中，所述嵌段共聚物中，每个所述B-嵌段的重均分子量为10万～50万。
控制嵌段共聚物中每个B-嵌段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，降低电池的直流阻抗增长率和金属沉积量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
在任意实施方式中，所述式I所示的结构单元衍生自偏二氟乙烯、四氟乙烯、氟乙烯、六氟丙烯及其组合构成的群组。
在任意实施方式中，所述式II所示的结构单元衍生自丙烯腈、丁烯腈、苯乙烯、乙烯醇、丙烯酰胺、丙烯酸乙酯、甲基丙烯酸乙酯、甲基丙烯酸丁酯、甲基丙烯酸、乙基丙烯酸、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、丙烯酸、乙烯基苯甲酸、丙烯乙酸酯、丙烯酸酯及其组合构成的群组。
上述原材料简单易得，相比于传统粘结剂能够大幅度降低生产成本。
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B-嵌段：将至少一种式V所示的单体聚合制备B-嵌段，
Figure PCTCN2022128035-appb-000003
其中Rˊ 1、Rˊ 2、Rˊ 3各自独立地选自氢、氟、至少含有一个氟原子的C 1-3烷基中的一种或多种；
制备A-嵌段：将至少一种式VI所示的单体聚合制备A-嵌段，或者将式VII所示的单体开环聚合制备A-嵌段，
Figure PCTCN2022128035-appb-000004
其中，Rˊ 4、Rˊ 5、Rˊ 6各自独立地选自氢、取代或未取代的C 1-5烷基，Rˊ 7选自羧基、酯基、羟基、酰胺基、氰基、取代或未取代的芳香基中的一种；
制备BAB型嵌段共聚物：将所述B-嵌段和所述A-嵌段接合制备BAB型嵌段共聚物。
该制备方法相对于传统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BAB型三嵌段共聚物的粘结剂能够有效提高极片的粘结力，降低电池的直流阻抗增长率和金属沉积量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
在任意实施方式中，所述制备B-嵌段的方法包括：
将至少一种式V所示单体、链转移剂和第一引发剂在60～75℃的反应温度下通过可逆加成-裂解链转移聚合，反应4～6小时得到末端具有叠氮基团或炔基的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，所述制备A-嵌段的方法包括：
将式VI所示的单体和第二引发剂在80～95℃的反应温度下聚合反应2.5～5小时，得到两端均具有炔基或叠氮基团的所述A-嵌段。
采用该制备方法，成功制备出两端均具有叠氮化或末端炔基化的A-嵌段。
在任意实施方式中，所述制备A-嵌段的方法包括：
将式VII所示的单体、离子引发剂和水在60℃-80℃的反应温度下聚合反应6-8小时，得到两端均具有羟基的产物；
对产物的羟基进行官能化反应，得到两端均具有炔基或叠氮基团的所述A-嵌段。
采用该制备方法，成功制备出两端均具有叠氮化或末端炔基化的A-嵌段。
在任意实施方式中，所述制备BAB型嵌段共聚物包括：
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。
上述制备方法，具有高效稳定，高特异性的优点，提高产品的良品率。
在任意实施方式中，所述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，所述第二引发剂为对称型双官能度引发剂。
在任意实施方式中，所述第一引发剂选自偶氮二异丁腈，偶氮二异庚腈的一种或两种。
本申请的第三方面，提供一种任意实施方式中的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。
该正极极片具有低膜片电阻、优异的粘结力和良好的柔韧性，同时电池具有低金属沉积量、优异的循环性能和高温存储性能。
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。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。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。
在任意实施方式中，所述正极极片的膜片电阻小于等于1.0Ω。该极片具有较低的膜片电阻，说明正极膜层中的材料分散均匀，正极膜层具有良好的电子传输效率，有利于电池性能的发挥。
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提供的正极极片。
在本申请的第六方面，提供一种电池模块，包括本申请第五方面的二次电池。
在本申请的第七方面，提供一种电池包，包括本申请第六方面的电池模块。
在本申请的第八方面，提供一种用电装置，包括本申请第五方面的二次电池、第六方面的电池模块或第七方面的电池包中的至少一种。
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。
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。
[粘结剂]
基于此，本申请提出了一种BAB型嵌段共聚物，B-嵌段含有式I所示的结构单元，A-嵌段含有式II所示的结构单元、式Ⅲ所示的结构单元中的一种或多种，
Figure PCTCN2022128035-appb-000005
-CH 2-CH 2-O-式III
其中R 1、R 2、R 3各自独立地选自氢、氟、至少含有一个氟原子的C 1- 3烷基中的一种或多种，R 4、R 5、R 6各自独立地选自氢、取代或未取代的C 1-5烷基，R 7选自羧基、酯基、羟基、酰胺基、氰基、取代或未取代的芳香基。
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，B-嵌段是由含氟单体聚合形成的长序列链段，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。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A-嵌段聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)，由丙烯腈单体、甲基丙烯酸丁酯单体和苯乙烯单体聚合形成，重均分子量为48万；B-嵌段为聚偏二氟乙烯，由偏氟乙烯单体聚合形成，重均分子量为40万；B-嵌段和A-嵌段两侧的端基键合得到聚偏二氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-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、质量含量和链长方面不同的大分子的集合体。该术语另一方面也包括由聚合反应形成的这样的大分子集合体的衍生物，即可以通过上述大分子中的官能团的反应，例如加成或取代获得的并且可以是化学上均一的或化学上不均一的化合物。
在本文中，术语“C 1-3烷基”是指仅由碳和氢原子组成的直链或支链烃链基团，基团中不存在不饱和，具有从一至三个碳原子，并且通过单键附接到分子的其余部分。C 1-3烷基的示例包括但不限于：甲基、乙基、正丙基、1-甲基乙基(异丙基)。
在本文中，术语“C 1-5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，具有从一至五个碳原子，并且通过单键附接到分子的其余部分。C 1-5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)、正丁基、正戊基。
在本文中，术语“羧基”是指-COOH基团。
在本文中，术语“酯基”是指-COOR 10基团，其中R 10选自取代或不取代的C 1-5烷基。
在本文中，术语“羟基”是指-OH基团。
在本文中，术语“酰胺基”是指-CO-NR 8R 9基团，其中R 8、R 9各自独立地选自取代或不取代的C 1-5烷基。
在本文中，术语“氰基”是指-CN基团。
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、C 1-6烷基、C 1-6烷氧基。
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。
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、羧基基团、酯基基团、羟基基团或氰基基团一方面可以与正极活性材料和导电剂颗粒表面的羟基形成氢键以提高极片的粘结力，另一方面可以与正极活性材料中的过渡金属产生有效结合，抑制过渡金属在使用过程中的溶出，提高循环性能。同时A-嵌段在B-嵌段间的插入可以减少含氟链段大面积的有序排列，降低结晶度，起到增柔的作用。以BAB型嵌段共聚物制备的粘结剂，由于非含氟嵌段聚合物位于含氟嵌段聚合物中间，可以有效的减少含氟嵌段聚合物的有序排列，同时，非含氟聚合物中官能团的引入可提高BAB型嵌段共聚物的粘结性能，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能够提高极片的粘结力，降低电池的直流阻抗增长率和过渡金属的溶出量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池具有高循环容量保持率和45℃容量保持率。
在本文中，粘结力主要用于表征正极极片中正极浆料制备的膜层与集流体之间的粘结强度，其可以通过任意公知方法进行测试。
在本文中，膜片电阻主要用于表征正极极片的电阻，能够反映正极极片的电子导电性能，其可以通过任意公知方法进行测试。
在本文中，柔韧性主要用于表征正极极片的抗弯折能力，能够反映正极极片的延展性能，其可以通过任意公知方法进行测试。
在本文中，直流阻抗增长率主要用于表征电池的阻抗性能，能够反映电池在循环过程中阻抗的增加率，其可以通过任意公知方法进行测试。
在本文中，循环性能主要用于表征电池的循环使用性能，能够反映电池的循环性能，其可以通过任意公知方法进行测试。
在本文中，高温存储性能主要用于表征电池的高温使用性能，能够反映电池的高温稳定性，其可以通过任意公知方法进行测试。
在一些实施方式中，A-嵌段含有R 7为酰胺基的式II所示的结构单元。在一些实施方式中，式II中的R 7为式IV所示
Figure PCTCN2022128035-appb-000006
其中，R 8、R 9各自独立地选自氢、取代或未取代的C 1-5烷基。
A-嵌段含有的酰胺基与正极活性材料和集流体的羟基易于形成氢键，能够提高极片的粘结力。另外A-嵌段含有的酰胺基团，能够改善极片在电解液中的浸润能力，有助于极片上离子传输通道的快速形成，有助于降低极片的膜片电阻，提高电池的循环性能。
A-嵌段含有R 7为酰胺基的式II所示的结构单元，有利于在提高极片的粘结力和柔韧性，降低极片的膜片电阻的同时，显著减少过渡金属在正极的溶出。
在一些实施方式中，A-嵌段含有R 7为氰基的式II所示的结构单元和R 7为酯基的式II所示的结构单元。
A-嵌段中包含强极性基团氰基，可以与正极活性材料表面上的羟基形成作用力强的氢键和偶极-偶极作用，即能够在浆料中起到维稳、分散的作用，有助于进一步提高极片的粘结力以及促进正极活 性物质的分散，降低极片的膜片电阻。而且强极性基团氰基可以增强分子结构的稳定性，提高嵌段共聚物的玻璃化转变温度，改善嵌段共聚物的刚性和热稳定性，有助于提高极片的氧化稳定性，能够提升电池的循环和倍率性能。另外氰基使得A-嵌段对正极活性材料具有一定的包覆性，A-嵌段中的氰基基团能够与正极活性材料表面的过渡金属离子络合，阻碍过渡金属离子的溶出，进而减少过渡金属离子在负极表面的沉积；A-嵌段含有的酯基有助于削弱氰基之间过强的偶极矩，减少由于A-嵌段重氰基之间作用力过强导致的粘结剂链段自由运动受阻而引发的极片脆性问题，提高电池的安全性能。另外酯基与电解液具有良好的亲和力，有助于增强电解液和正极活性材料之间的接触，从而提高离子导电性，降低极片的膜片电阻。
A-嵌段中同时含有R 7为氰基的式II所示的结构单元和R 7为酯基的式II所示的结构单元，有利于提高极片的粘结力和柔韧性，降低极片的膜片电阻，降低电池的直流阻抗增长率和金属沉积量，同时保证电池兼具高循环容量保持率和45℃容量保持率。
在一些实施方式中，A-嵌段含有R 7为氰基的式II所示的结构单元、R 7为酯基的式II所示的结构单元和R 7为取代或未取代的芳香基的式II所示的结构单元。
A-嵌段含有的芳香基有助于提高极片的机械强度，以应对充放电过程中正极活性材料的体积变化，使电极在充放电过程中保持结构完整性，提高电池的循环性能。
A-嵌段中同时含有R 7为氰基的式II所示的结构单元、R 7为酯基的式II所示的结构单元和R 7为取代或未取代的芳香基的式II所示的结构单元，还有利于进一步提高极片的粘结力和柔韧性。
在一些实施方式中，A-嵌段含有R 7为氰基的式II所示的结构单元、R 7为酰胺基的式II所示的结构单元和R 7为酯基的式II所示的结构单元。
A-嵌段中同时含有R 7为氰基的式II所示的结构单元、R 7为酰胺基的式II所示的结构单元和R 7为酯基的式II所示的结构单元，能够在保证极片兼具低膜片电阻、优异的粘结力和柔韧性的同时，大幅 度降低电池的金属沉积量，使得电池兼具低直流阻抗增长率、高循环容量保持率和45℃容量保持率。
在一些实施方式中，式II中的R 7可选为羧基、羟基中的一种或多种。
在一些实施方式中，式II所示的结构单元衍生自丙烯腈、丁烯腈、苯乙烯、乙烯醇、丙烯酰胺、丙烯酸乙酯、甲基丙烯酸乙酯、甲基丙烯酸丁酯、甲基丙烯酸、乙基丙烯酸、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、丙烯酸、乙烯基苯甲酸、丙烯乙酸酯、丙烯酸酯及其组合构成的群组。
在一些实施方式中，式I所示的结构单元衍生自偏二氟乙烯、四氟乙烯、氟乙烯、六氟丙烯及其组合构成的群组。
在一些实施方式中，BAB嵌段共聚物为聚偏二氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚(丙烯酸-丙烯酰胺-甲基丙烯酸乙酯-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚(丙烯腈-丙烯酰胺-丙烯酸酯)-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚苯乙烯-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚环氧乙烷-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚乙烯醇-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚(丙烯腈-丙烯乙酸酯)-聚偏二氟乙烯嵌段共聚物、聚氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚氟乙烯嵌段共聚物和聚四氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚四氟乙烯嵌段共聚物中的一种。
在一些实施方式中，A-嵌段的质量含量为40％～60％，基于嵌段共聚物的总质量计。在一些实施方式中，A-嵌段的质量含量可选为40％、42％、44％、45％、46％、48％、50％、42％、54％、54％、55％、56％、58％、60％，基于嵌段共聚物的总质量计。
A-嵌段的质量含量在合适范围内的BAB型嵌段共聚物能够提高 极片的粘结力和柔韧性，降低极片的膜片电阻，提升电池的循环容量保持率和45℃容量保持率，降低电池的直流阻抗增长率和金属沉积量。
在一些实施方式中，嵌段共聚物的重均分子量为40万～200万。在一些实施方式中，嵌段共聚物的重均分子量可选为40万、42万、45万、48万、50万、55万、60万、65万、70万、75万、80万、85万、90万、95万、100万、110万、120万、130万、140万、150万、160万、170万、180万、190万、200万。
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。
在本申请中，聚合物的重均分子量的测试可以选用本领域已知的方法进行测试，例如采用凝胶色谱法进行测试，如采用Waters 2695 Isocratic HPLC型凝胶色谱仪(示差折光检测器2141)。以质量分数为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 HT5DMF7.8×300mm+Styragel HT4)。用纯化后的N-甲基吡咯烷酮(NMP)溶剂配置3.0％的含氟聚合物溶液，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，读取重均分子量。
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。
重均分子量在合适范围内的BAB嵌段共聚物可以提高极片的粘结力，降低电池的直流阻抗增长率和金属沉积量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
在一些实施方式中，嵌段共聚物中A-嵌段的重均分子量为20万～110万。在一些实施方式中，嵌段共聚物中A-嵌段的重均分子量可 选为20万、25万、30万、35万、40万、45万、50万、55万、60万、65万、70万、75万、80万、85万、90万、95万、100万、105万、110万。
若嵌段共聚物中A-嵌段的重均分子量过大，式II或式III所示单体的结构单元强极性基团过多，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BAB嵌段共聚物可以提高极片的粘结力，降低电池的直流阻抗增长率和金属沉积量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
在一些实施方式中，嵌段共聚物中每个B-嵌段的重均分子量为10万～50万。在一些实施方式中，嵌段共聚物中每个B-嵌段的重均分子量可选为10万、12万、15万、17万、20万、22万、25万、28万、30万、32万、35万、37万、40万、43万、45万、47万、50万。
每个B-嵌段的重均分子量在合适范围内的BAB嵌段共聚物可以提高极片的粘结力，降低电池的直流阻抗增长率和金属沉积量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
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B-嵌段：将至少一种式V所示的单体聚合制备B-嵌段，
Figure PCTCN2022128035-appb-000007
其中Rˊ 1、Rˊ 2、Rˊ 3各自独立地选自氢、氟、至少含有一个氟原子的C 1-3烷基中的一种或多种；
制备A-嵌段：将至少一种式VI所示的单体聚合制备A-嵌段，或者将式VII所示的单体开环聚合制备A-嵌段，
Figure PCTCN2022128035-appb-000008
其中，Rˊ 4、Rˊ 5、Rˊ 6各自独立地选自氢、取代或未取代的C 1-5烷基，Rˊ 7选自羧基、酯基、羟基、酰胺基、氰基、取代或未取代的芳香基中的一种；
制备BAB型嵌段共聚物：将B-嵌段和A-嵌段接合制备BAB型嵌段共聚物。
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有效提高极片的粘结力，降低电池的直流阻抗增长率和金属沉积量，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
在一些实施方式中，制备B-嵌段的方法包括：
将至少一种式V所示单体、链转移剂和第一引发剂在60～75℃的反应温度下通过可逆加成-裂解链转移聚合，反应4～6小时得到末端具有叠氮基团或炔基的B-嵌段。
在本文中，术语“叠氮基团”是指-N 3基团。
在本文中，术语“炔基”是指-C≡CH基团。
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，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。
Figure PCTCN2022128035-appb-000009
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A-嵌段的方法包括：
将式VI所示的单体和第二引发剂在80～95℃的反应温度下聚合反应2.5～5小时，得到两端均具有炔基或叠氮基团的A-嵌段。
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(图中B 1为卤素取代的烷基或三甲基硅基乙炔基团，B 2为叠氮基团或炔基)。
Figure PCTCN2022128035-appb-000010
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：
将式VII所示的单体、离子引发剂和水在60℃～80℃的反应温度下聚合反应6～8小时，得到两端均具有羟基的产物；
对产物的羟基进行官能化反应，得到两端均具有炔基或叠氮基团的A-嵌段。
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(图中B 1为卤素取代的烷基或三甲基硅基乙炔基团，B 2为叠氮基团或炔基)。
Figure PCTCN2022128035-appb-000011
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BAB型嵌段共聚物包括：
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，
Figure PCTCN2022128035-appb-000012
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，第二引发剂为对称型双官能度引发剂。在一些实施方式中，第二引发剂为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，第一引发剂选自偶氮二异丁腈，偶氮二异庚腈的一种或两种。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，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，正极膜层与正极集流体间单位长度的粘结力不小于11N/m。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可选为11N/m、11.5N/m、12N/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。
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20mm×100mm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。
正极极片的柔性测试可采用公知的方法进行测试；作为示例，将冷压后的正极极片裁剪为20×100mm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。
正极极片能经过不少于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，正极极片的膜片电阻小于等于1.0Ω。
膜片电阻是指极片正极膜层的电阻，可以采用本领域公知的任意手段进行测试。作为示例，可以采用电阻仪进行测试。
膜片电阻可采用公知的方法进行测试，作为示例，分别在极片的左、中、右处裁剪直径3mm的小圆片。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。
该极片具有较低的膜片电阻，说明正极膜层中的材料分散均匀，正极膜层具有良好的电子传输效率，有利于电池性能的发挥。
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，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，锂金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，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，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，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。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。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。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，电解质采用电解液。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，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。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能够盖设于开口，以封闭容纳腔。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。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。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：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
Figure PCTCN2022128035-appb-000013
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75℃。反应6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B-嵌段聚合物的反应过程如下所示：
Figure PCTCN2022128035-appb-000014
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(丙烯腈-甲基丙烯酸丁酯-苯乙烯)；
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N 2吹扫30分钟。随后在室 温下，以8:1:1的摩尔比分别称取丙烯腈单体、甲基丙烯酸丁酯单体以及苯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(丙烯腈-甲基丙烯酸丁酯-苯乙烯)和60mmol叠氮化钠(NaN 3)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(丙烯腈-甲基丙烯酸丁酯-苯乙烯)，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(丙烯腈-甲基丙烯酸丁酯-苯乙烯)、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(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚偏二氟乙烯嵌段共聚物，其作为电池粘结剂使用。
2)正极极片的制备
将锂镍钴锰(NCM)材料、导电剂碳黑、实施例1制备的粘结剂、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(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，加入12.5％LiPF 6锂盐溶解于有机溶剂中，搅拌均匀，得到实施例1的电解液。
6)电池的制备
将正极极片、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2～5
实施例2～5的电池与实施例1的电池制备方法相似，但是仅分别调整A-嵌段以及B-嵌段的重均分子量以及其质量含量，维持聚偏二氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚偏二氟乙烯嵌段共聚物的重均分子量为120万，具体参数如表1所示。
实施例6～9
实施例6～9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-嵌段的重均分子量以及其质量含量，从而调整聚偏二氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚偏二氟乙烯嵌段共聚物的重均分子量，具体参数如表1所示。
实施例10
实施例10的电池与实施例1的电池制备方法相似，但是将A-嵌 段替换成两端均具有叠氮基的聚丙烯酰胺，具体参数如表1所示，制备方法如下所示：
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N 2吹扫30分钟。随后在室温下，称取一定摩尔量的称取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(NaN 3)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。
实施例11
实施例11的电池与实施例1的电池制备方法相似，但是将A-嵌段替换成两端均具有叠氮基的聚(丙烯酸-丙烯酰胺-甲基丙烯酸乙酯)，具体参数如表1所示，制备方法如下所示：
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N 2吹扫30分钟。随后在室温下，以8:1:1的摩尔比分别称取丙烯酸单体、丙烯酰胺单体以及甲基丙烯酸乙酯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(丙烯酸-丙烯酰胺-甲基丙烯酸乙酯)和60mmol叠氮化钠(NaN 3)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(丙烯酸-丙 烯酰胺-甲基丙烯酸乙酯)，即A-嵌段聚合物。
实施例12
实施例12的电池与实施例1的电池制备方法相似，但是将A-嵌段替换成两端均具有叠氮基的聚(丙烯腈-丙烯酰胺-丙烯酸酯)，具体参数如表1所示，制备方法如下所示：
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N 2吹扫30分钟。随后在室温下，以8:1:1的摩尔比分别称取丙烯腈单体、丙烯酰胺单体以及丙烯酸酯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(丙烯腈-丙烯酰胺-丙烯酸酯)和60mmol叠氮化钠(NaN 3)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(丙烯腈-丙烯酰胺-丙烯酸酯)，即A-嵌段聚合物。
实施例13
实施例13的电池与实施例1的电池制备方法相似，但是将A-嵌段替换成两端均具有叠氮基的聚苯乙烯，具体参数如表1所示，制备方法如下所示：
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N 2吹扫30分钟。随后在室温下，称取一定摩尔量的苯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氯封端的聚苯乙烯和60mmol叠氮化钠(NaN 3)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苯乙烯，即A-嵌段聚合物。
实施例14
实施例14的电池与实施例1的电池制备方法相似，但是将A-嵌段替换成两端均具有叠氮基的聚环氧乙烷，具体参数如表1所示，制备方法如下所示：
以摩尔比为1:0.1:0.02的环氧乙烷单体、水和氢氧化钾(KOH)，加入高压搅拌釜，通入大量氮气除尽空气后，加压至0.3MPa，并逐渐加大搅拌速度，至1000转/分钟，升温至80℃。反应6小时后，釜内压力下降，短暂加压除去多余单体，提纯后得到聚环氧乙烷；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氮气(N 2)吹扫30分钟。随后在室温下将上述聚环氧乙烷转移到反应器中。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氯封端的聚环氧乙烷和60mmol叠氮化钠(NaN 3)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环氧乙烷，即A-嵌段聚合物。
实施例15
实施例15的电池与实施例1的电池制备方法相似，但是将A-嵌段替换成聚乙烯醇，具体参数如表1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N 2吹扫30分钟。随后在室温下，称取一定摩尔量的乙酸乙烯酯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；再将上述反应获得的氯封端的聚乙酸乙烯酯溶于混合溶剂(甲醇与水的体积比为79.5:0.5)中，其中聚乙酸乙烯酯的质量分数为20％，在30℃温度下，加入质量分数为1.5％的氢氧化钠溶液醇解2小时，充分洗涤过滤，得到氯封端的聚乙烯醇；将3mmol氯封端的聚乙烯醇和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乙烯醇，即A-嵌段聚合物。
实施例16
实施例16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(丙烯腈-丙烯乙酸酯)，具体参数如表1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N 2吹扫30分钟。随后在室温下，以8:1的摩尔比分别称取丙烯腈单体和丙烯乙酸酯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(丙烯腈-丙烯乙酸酯)和60mmol叠氮化钠(NaN 3)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(丙烯腈-丙烯乙酸酯)，即A-嵌段聚合物。
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B-嵌段替换成聚氟乙烯嵌段，具体参数如表1所示，制备方法如下：
称取4g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75℃。反应6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氟乙烯，即B-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B-嵌段替换成聚四氟乙烯嵌段，具体参数如表1所示，制备方法如下：
称取4g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75℃。反应6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，购买于索尔维集团，牌号为5130，具体参数如表1所示。
对比例2
对比例2的电池与对比例1的电池制备方法相似，但是粘结剂为聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)，聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)的制备方法如下：
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N 2吹扫30分钟。随后在室温下，以8:1:1的摩尔比分别称取丙烯腈单体、甲基丙烯酸丁酯单体以及苯乙烯单体加入到300ml无水乙腈中，将反应器内部的温度提高到55℃，并将反应混合物以500rpm的速度再搅拌12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，即聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)。
对比例3
对比例3的电池与对比例1的电池制备方法相似，但是粘结剂为聚偏二氟乙烯与聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)的共混物，具体参数如表1所示，制备方法如下：
共混：将对比例2中聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)与对比例1中的聚偏二氟乙烯按照摩尔比例6:4进行共混，得到聚偏二氟乙烯与聚乙烯醇共混物粘结剂。
对比例4
对比例4的电池与对比例3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，具体参数如表1所示。
对比例5
对比例5的电池与对比例3的电池制备方法相似，但是粘结剂为聚偏二氟乙烯与聚(丙烯酸-丙烯酰胺-甲基丙烯酸乙酯)的共混物，具体参数如表1所示。
对比例6
对比例6的电池与对比例3的电池制备方法相似，但是粘结剂为聚偏二氟乙烯与聚乙烯醇的共混物，具体参数如表1所示。
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、极片性能测试
1)膜片电阻测试
分别在极片的左、中、右处裁剪直径3mm的小圆片。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20mm×100mm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，本测试中极片的宽度为20mm。
3)柔性测试
将冷压后的正极极片裁剪为20×100mm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。
3、电池性能测试
1)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2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2中的数据是在上述测试条件下循环100次之后测得的数据。
2)电池循环容量保持率测试
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……500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2中实施例或对比例对应的电池容量保持率数据是在上述测试条件下循环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。
3)金属沉积量测试
常温下，所制作锂离子电池以0.5C(即2小时内完全放掉理论容量的电流值)的电流进行第一次充电和放电，充电为恒流恒压充电，终止电压为4.2V，截至电流为0.05C，放电终止电压为2.8V，然后电池搁置24小时后以0.5C恒流恒压充电至4.2V，然后用1C的电流对满充电池进行放电，放电终止电压均为2.8V，电芯进行拆解，取出负极极片，采用电感耦合等离子体(ICP)法测试金属Co、Mn的沉积量。
4)45℃容量保持率测试
以1C恒流充电至4.2V，再以4.2V恒定电压充电至电流为0.05C， 搁置10min，然后以1C的恒定电流放电至截止电压2.8V，记录存储前容量CAP 1；以1C的恒定电流充电至截止4.2V，再以以4.2V恒定电压充电至电流为0.05C，将锂离子电池在45℃的烘箱中放置120天后，取出进行1C恒流放电至2.8V，记录存储后容量CAP 2，依照如下公式计算锂离子二次电池存储容量保持率：
锂离子二次电池存储容量保持率(％)＝CAP 2/CAP 1×100％。
三、各实施例、对比例测试结果分析
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表1和表2。
表1实施例和对比例制备参数与重均分子量测试结果
Figure PCTCN2022128035-appb-000015
Figure PCTCN2022128035-appb-000016
表2实施例和对比例的性能测试结果
Figure PCTCN2022128035-appb-000017
Figure PCTCN2022128035-appb-000018
根据上述结果可知，实施例1～18中的粘结剂为BAB型嵌段共聚物，包含A-嵌段和B-嵌段，B-嵌段含有至少一种衍生自偏二氟乙烯、氟乙烯或四氟乙烯的结构单元，A-嵌段含有至少一种衍生自丙烯腈、甲基丙烯酸丁酯、苯乙烯、丙烯酰胺、丙烯酸、甲基丙烯酸乙酯、丙烯酸酯、环氧乙烷、乙烯醇、丙烯乙酸酯的结构单元。从实施例1～18和对比例1的对比可见，相比于纯偏二氟乙烯聚合物作为粘结剂，聚偏二氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚丙烯酰胺-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚(丙烯酸-丙烯酰胺-甲基丙烯酸乙酯-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚(丙烯腈-丙烯酰胺-丙烯酸酯)-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚苯乙烯-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚环氧乙烷-聚偏二氟乙烯嵌 段共聚物、聚偏二氟乙烯-聚乙烯醇-聚偏二氟乙烯嵌段共聚物、聚偏二氟乙烯-聚(丙烯腈-丙烯乙酸酯)-聚偏二氟乙烯嵌段共聚物、聚氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚氟乙烯嵌段共聚物和聚四氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚四氟乙烯BAB型嵌段共聚物作为粘结剂能够有效提高极片的粘结力，降低电池的直流阻抗增长率和金属沉积量，使得极片兼具低膜片电阻和优异的柔韧性、以及电池兼具高循环容量保持率和45℃容量保持率。
实施例1～18中的粘结剂为BAB型嵌段共聚物，包含A-嵌段和B-嵌段，B-嵌段含有含氟聚合物，A-嵌段包含非含氟聚合物，对比例3～6的粘结剂为含氟聚合物和非含氟聚合物的共混物，从实施例1～18和对比例3～6的对比可见，相比于以含氟聚合物和非含氟聚合物的共混物作为粘结剂，上述BAB型嵌段共聚物能有效提高极片的粘结性和柔韧性，降低电池的直流阻抗增长率和金属沉积量，同时保证极片的低膜片电阻、以及电池兼具高循环容量保持率和45℃容量保持率。
实施例10～12中的粘结剂为BAB型嵌段共聚物，包含A-嵌段和B-嵌段，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的结构单元。从实施例10～12和对比例1的对比可见，相比于纯聚偏二氟乙烯聚合物作为粘结剂，上述BAB型嵌段共聚物能够有效提高极片的粘结力和柔韧性，降低极片的膜片电阻，提升电池的循环容量保持率和45℃容量保持率，降低电池的直流阻抗增长率和金属沉积量。
实施例1～5、12、16中的粘结剂为BAB型嵌段共聚物，包含A-嵌段和B-嵌段，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腈的结构单元、以及衍生自甲基丙烯酸丁酯、丙烯酸酯或丙烯乙酸酯的结构单元。从实施例1～5、12、16和对比例1的对比可见，相比于纯聚偏二氟乙烯聚合物作为粘结剂，上述BAB型嵌段共聚物作为粘结剂可以有效提高极片的粘结力和柔韧性，降低极片的膜片电阻，降低电池的直流阻抗增长率和金属沉积量，同时保证电池兼具高循环容量保持率和45℃容量保持率。
实施例4的粘结剂为BAB型嵌段共聚物，包含A-嵌段和B-嵌段，B-嵌段含有衍生自偏二氟乙烯的结构单元，A-嵌段包含衍生自丙烯腈的结构单元、衍生自甲基丙烯酸丁酯的结构单元和衍生自苯乙烯的结构单元。从实施例4和实施例10～16的对比可见，聚偏二氟乙烯-聚(丙烯腈-甲基丙烯酸丁酯-苯乙烯)-聚偏二氟乙烯BAB型嵌段共聚物作为粘结剂可以进一步大幅提高极片的粘结力和柔韧性，同时使得电池的循环容量保持率和45℃容量保持率也得到进一步提升。
实施例12的粘结剂为BAB型嵌段共聚物，包含A-嵌段和B-嵌段，B-嵌段含有衍生自偏二氟乙烯的结构单元，A-嵌段包含衍生自丙烯腈的结构单元、衍生自丙烯酰胺的结构单元和衍生自丙烯酸酯的结构单元。从实施例12和实施例4、10～11、13～16的对比可见，聚偏二氟乙烯-聚(丙烯腈-丙烯酰胺-丙烯酸酯)-聚偏二氟乙烯嵌段共聚物BAB型嵌段共聚物作为粘结剂可以大幅降低电池的金属沉积量。
从实施例1～5和对比例1的对比可见，相比于纯聚偏二氟乙烯聚合物作为粘结剂，A-嵌段的质量含量为40％～60％的BAB型嵌段共聚物作为粘结剂能够提高极片的粘结力和柔韧性，降低极片的膜片电阻，提升电池的循环容量保持率，降低电池的直流阻抗增长率和金属沉积量。从实施例1～5和对比例3的对比可见，相比于含氟聚合物和非含氟聚合物的共混物作为粘结剂，A-嵌段的质量含量为40％～60％的BAB型嵌段共聚物作为粘结剂能够提高极片的粘结力和柔韧性，降低电池的直流阻抗增长率，同时保证极片兼具低膜片电阻、以及电池兼具低金属沉积量、高循环容量保持率和45℃容量保持率。
从实施例1、6～9和对比例1的对比可见，相比于传统PVDF粘结剂，重均分子量为40万～200万的BAB型嵌段共聚物作为粘结剂能够提高极片的粘结力，降低电池的直流阻抗增长率，同时保证极片兼具低膜片电阻和优异的柔韧性、以及电池兼具低金属沉积量和高循环容量保持率。从实施例1、6～9和对比例3的对比可见，相比 于含氟聚合物和非含氟聚合物的共混物作为粘结剂，重均分子量为40万～200万的BAB型嵌段共聚物作为粘结剂能够提高极片的粘结力和柔韧性，降低电池的直流阻抗增长率，同时保证极片具有低膜片电阻、以及电池兼具低金属沉积量、高循环容量保持率和45℃容量保持率。
从实施例1～5和对比例1的对比可见，相比于纯聚偏二氟乙烯聚合物作为粘结剂，含氟嵌段A-嵌段的重均分子量为20万～110万、B-嵌段的重均分子量为10万～50万的BAB型嵌段共聚物作为粘结剂能够提高极片的粘结力和柔韧性，降低极片的膜片电阻，提升电池的循环容量保持率和45℃容量保持率，降低电池的直流阻抗增长率和金属沉积量。
从实施例1～5和对比例3的对比可见，相比于含氟聚合物和非含氟聚合物的共混物作为粘结剂，含氟嵌段A-嵌段的重均分子量为20万～110万、B-嵌段的重均分子量为10万～50万的BAB型嵌段共聚物，作为粘结剂能够提高极片的粘结力和柔韧性，降低电池的直流阻抗增长率，同时保证极片兼具低膜片电阻、以及电池兼具低金属沉积量、高循环容量保持率和45℃容量保持率。
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 (29)

  1. 一种BAB型嵌段共聚物，其特征在于，所述B-嵌段含有式I所示的结构单元，所述A-嵌段含有式II所示的结构单元、式Ⅲ所示的结构单元中的一种或多种，
    Figure PCTCN2022128035-appb-100001
    其中R 1、R 2、R 3各自独立地选自氢、氟、至少含有一个氟原子的C 1- 3烷基中的一种或多种，R 4、R 5、R 6各自独立地选自氢、取代或未取代的C 1-5烷基，R 7选自羧基、酯基、羟基、酰胺基、氰基、取代或未取代的芳香基。
  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A-嵌段含有R 7为酰胺基的式II所示的结构单元。
  3. 根据权利要求1所述的BAB型嵌段共聚物，其特征在于，所述A-嵌段含有R 7为氰基的式II所示的结构单元和R 7为酯基的式II所示的结构单元。
  4. 根据权利要求1所述的BAB型嵌段共聚物，其特征在于，所述A-嵌段含有R 7为氰基的式II所示的结构单元、R 7为酯基的式II所示的结构单元和R 7为取代或未取代的芳香基的式II所示的结构单元。
  5. 根据权利要求1所述的BAB型嵌段共聚物，其特征在于，所述A-嵌段含有R 7为氰基的式II所示的结构单元、R 7为酰胺基的式II所示的结构单元和R 7为酯基的式II所示的结构单元。
  6. 根据权利要求1所述的BAB型嵌段共聚物，其特征在于，所述A-嵌段的质量含量为40％～60％，基于所述嵌段共聚物的总质量计。
  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，所述嵌段共聚物的重均分子量为40万～200万。
  8. 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，所述嵌段共聚物中，所述A-嵌段的重均分子量为20万～110万。
  9. 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，所述嵌段共聚物中，每个所述B-嵌段的重均分子量为10万～50万。
  10. 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，所述式I所示的结构单元衍生自偏二氟乙烯、四氟乙烯、氟乙烯、六氟丙烯及其组合构成的群组。
  11. 根据权利要求1所述的BAB型嵌段共聚物，其特征在于，所述式II所示的结构单元衍生自丙烯腈、丁烯腈、苯乙烯、乙烯醇、丙烯酰胺、丙烯酸乙酯、甲基丙烯酸乙酯、甲基丙烯酸丁酯、甲基丙烯酸、乙基丙烯酸、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、丙烯酸、乙烯基苯甲酸、丙烯乙酸酯、丙烯酸酯及其组合构成的群组。
  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B-嵌段：将至少一种式V所示的单体聚合制备B-嵌段，
    Figure PCTCN2022128035-appb-100002
    其中Rˊ 1、Rˊ 2、Rˊ 3各自独立地选自氢、氟、至少含有一个氟原子的C 1-3烷基中的一种或多种；
    制备A-嵌段：将至少一种式VI所示的单体聚合制备A-嵌段，或者将式VII所示的单体开环聚合制备A-嵌段，
    Figure PCTCN2022128035-appb-100003
    其中，Rˊ 4、Rˊ 5、Rˊ 6各自独立地选自氢、取代或未取代的C 1-5烷基，Rˊ 7选自羧基、酯基、羟基、酰胺基、氰基、取代或未取代的芳香基中的一种；
    制备BAB型嵌段共聚物：将所述B-嵌段和所述A-嵌段接合制备BAB型嵌段共聚物。
  13. 根据权利要求12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V所示单体、链转移剂和第一引发剂在60～75℃的反应温度下通过可逆加成-裂解链转移聚合，反应4～6小时得到末 端具有叠氮基团或炔基的B-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A-嵌段的方法包括：
    将至少一种式VI所示的单体和第二引发剂在80～95℃的反应温度下聚合反应2.5～5小时，得到两端均具有炔基或叠氮基团的所述A-嵌段。
  15. 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A-嵌段的方法包括：
    将式VII所示的单体、离子引发剂和水在60℃～80℃的反应温度下聚合反应6～8小时，得到两端均具有羟基的产物；
    对产物的羟基进行官能化反应，得到两端均具有炔基或叠氮基团的所述A-嵌段。
  16. 根据权利要求12至15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。
  17. 根据权利要求12或13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。
  18. 根据权利要求12或13所述的制备方法，其特征在于，所述第二引发剂为对称型双官能度引发剂。
  19. 根据权利要求12或13所述的制备方法，其特征在于，所述第一引发剂选自偶氮二异丁腈，偶氮二异庚腈的一种或两种。
  20. 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。
  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19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。
  23. 根据权利要求21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。
  24. 根据权利要求21所述的正极极片，其特征在于，所述正极极片的膜片电阻小于等于1.0Ω。
  25. 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24中任一项所述的正极极片。
  26. 根据权利要求25所述的二次电池，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。
  27. 一种电池模块，其特征在于，包括权利要求25或26所述的二次电池。
  28. 一种电池包，其特征在于，包括权利要求25或26所述的二 次电池和权利要求27所述的电池模块。
  29. 一种用电装置，其特征在于，包括选自权利要求25或26所述的二次电池、权利要求27所述的电池模块或权利要求28所述的电池包中的至少一种。
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US20150057419A1 (en) * 2013-08-23 2015-02-26 University Of Connecticut Free radical and controlled radical polymerization processes using azide radical initiators
CN105449273A (zh) * 2014-09-19 2016-03-30 三星电子株式会社 电解质、制备该电解质的方法和含该电解质的锂二次电池
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