Polymer material, binder composition and preparation method thereof, binder, electrode slurry, pole piece and battery

Abstract

The invention discloses a polymer material, a binder composition and a preparation method thereof, a binder, electrode slurry, a pole piece and a battery. The polymer material comprises an inner core and a shell covering the inner core, the inner core comprises a polymer A1; the polymer A1 contains repetitive units b1 and c; the shell comprises a polymer B1, and the polymer B1 contains repetitive units a, b1, c and d; the mass ratio of the repeating unit a to the repeating unit d is (20-50): (50-80), and the mass ratio of the repeating unit b1 to the repeating unit c is (40-80): (20-60). A pole piece prepared from the polymer material and binder composition has excellent tensile strength, elastic modulus and peel strength, and a battery prepared from the pole piece is long in cycle life; meanwhile, when the polymer material and the binder composition are applied to the battery, the cold pressing rebound inhibition effect is excellent.

Description

Technical Field

[0001] The present invention relates to a polymer material, a binder composition, a preparation method thereof, a binder, an electrode paste, a pole piece and a battery. Background Art

[0002] Styrene-butadiene rubber (SBR) emulsion binder, as one of the auxiliary materials of lithium-ion batteries, although used in very small amounts, is an indispensable component. Existing research shows that SBR containing carboxyl groups is an important anode binder, and in some processes, SBR and polyacrylic acid (PAA) are also used in a blended manner. However, during use, the SBR or PAA emulsion containing carboxyl groups degrades, resulting in a decrease in the binding effect and mechanical properties of the anode binder, thereby causing a decline in the performance of the battery.

[0003] The swelling of the battery mainly comes from the anode. In actual production, in order to improve the energy density of the battery cell, the energy density is usually increased by increasing the coating thickness of the pole piece or the cold pressing compaction density. However, this is likely to cause problems such as cracking of the anode pole piece, low peel strength and large rebound, seriously reducing the use efficiency; secondly, current technology more pursues the fast charging ability of the battery, but fast charging is also likely to bring about pole piece rebound.

[0004] Therefore, there is an urgent need for a binder with better binding effect, mechanical properties and cold pressing rebound suppression effect to be applied to the anode. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defect that the binders in the prior art cannot have both good binding effect and mechanical properties, and provides a polymer material, a binder composition, a preparation method thereof, a binder, an electrode paste, a pole piece and a battery. The pole piece prepared from the polymer material and the binder composition of the present invention has excellent tensile strength, elastic modulus and peel strength, and the battery prepared from the pole piece has a long cycle life; at the same time, the polymer material and the binder composition of the present invention have excellent cold pressing rebound suppression effect when applied to the battery.

[0006] The present invention adopts the following technical solutions to solve the above technical problems.

[0007] The present invention provides a polymer material, which comprises a core and a shell covering the core;

[0008] Wherein, the core comprises a polymer A1; the polymer A1 contains a repeating unit b1 and a repeating unit c;

[0009] Wherein, the shell comprises a polymer B1; the polymer B1 contains a repeating unit a, a repeating unit b1, a repeating unit c and a repeating unit d;

[0010] The mass ratio of the repeating unit a to the repeating unit d is (20 - 50):(50 - 80), and the mass ratio of the repeating unit b1 to the repeating unit c is (40 - 80):(20 - 60);

[0011] The structure of the repeating unit a is as shown in Formula I:

[0012]

[0013] I

[0014] In each repeating unit a, R1 - R4 are each independently hydrogen or an alkyl group having 1 - 4 carbon atoms;

[0015] The structure of the repeating unit b1 is as shown in Formula II1:

[0016]

[0017] II1

[0018] In each repeating unit b1, R5 - R8 are each independently hydrogen or an alkyl group having 1 - 4 carbon atoms;

[0019] The structure of the repeating unit c is as shown in Formula III:

[0020]

[0021] III

[0022] In each repeating unit c, R9 - R 15 are each independently hydrogen or an alkyl group having 1 - 4 carbon atoms;

[0023] The structure of the repeating unit d is as shown in Formula IV:

[0024]

[0025] IV

[0026] In each repeating unit d, R 16 and R 17 are each independently hydrogen or an alkyl group having 1 - 4 carbon atoms;

[0027] In the present invention, the mass ratio of the repeating unit a to the repeating unit d is (25 - 40):(60 - 75), such as 28.57:71.43 or 33.33:66.67.

[0028] In the present invention, the mass ratio of the repeating unit b1 to the repeating unit c is (40 - 70):(30 - 60), such as 50:50, 55:45, 40:60 or 70:30.

[0029] In the present invention, based on the total weight parts of the repeating units a, b1, c, and d being 100 parts, the repeating unit a can be 2 - 8 parts, preferably 3 - 6 parts, such as 5 parts.

[0030] In the present invention, based on the total weight parts of the repeating units a, b1, c, and d being 100 parts, the repeating unit b1 can be 20 - 80 parts, preferably 30 - 60 parts, such as 34, 46.75, 51.15, or 59.5 parts.

[0031] In the present invention, based on the total weight parts of the repeating units a, b1, c, and d being 100 parts, the repeating unit c can be 20 - 55 parts, preferably 25 - 53 parts, such as 25.5, 38.25, 41.85, or 51 parts.

[0032] In the present invention, based on the total weight parts of the repeating units a, b1, c, and d being 100 parts, the repeating unit d can be 3 - 10 parts, preferably 5 - 12 parts, such as 10 parts.

[0033] In the present invention, the weight parts ratio of the repeating unit b1 in the core to the repeating unit b1 in the shell can be 1:(1 - 2), such as 1:1.5.

[0034] In the present invention, the repeating unit b1 in the core can be 12 - 25 parts, preferably 13 - 24 parts, such as 13.6, 18.7, 20.46, or 23.8 parts.

[0035] In the present invention, the repeating unit b1 in the shell can be 15 - 35 parts, preferably 17 - 36 parts, such as 20.4, 28.05, 30.69, or 35.7 parts.

[0036] In the present invention, the weight parts ratio of the repeating unit c in the core to the repeating unit c in the shell can be 1:(1 - 2), such as 1:1.5.

[0037] In the present invention, the repeating unit c in the core can be 8 - 22 parts, preferably 10 - 21 parts, such as 10.2, 15.3, 16.74, or 20.4 parts.

[0038] In the present invention, the repeating unit c in the shell can be 12 - 33 parts, preferably 15 - 32 parts, such as 15.3, 22.95, 25.11, or 30.6 parts.

[0039] In the present invention, the C1 - C4 alkyl group is, for example, methyl, ethyl, propyl, or isopropyl.

[0040] In the present invention, the number-average molecular weight of the polymer material may be 20,000 - 200,000, preferably 30,000 - 50,000, such as 34580, 45242, 42053 or 39045.

[0041] In the present invention, the glass transition temperature of the polymer material may be -50 to 20 °C, preferably -20 to 15 °C, more preferably -18 to 12 °C, such as -8 °C or -4 °C.

[0042] In the present invention, the crosslinking density of the polymer material may be more than 90%, such as 95%, 96%, 98% or 99%. The crosslinking density represents the number of crosslinking points in a unit volume of the polymer material. The crosslinking points are the connection points formed by the chemical bonding between rubber molecular chains, and these crosslinking points connect the originally independent polymer molecular chains into a three-dimensional network structure.

[0043] In the present invention, the core preferably further comprises a polymer A2 containing branches.

[0044] Among them, preferably, in the polymer A2 containing branches, the main chain contains repeating units b2 and c; the repeating unit b2 contains a branch E, and the branch E contains repeating unit b1 and / or repeating unit c.

[0045] In the present invention, the shell preferably further comprises a polymer B2 containing branches.

[0046] Among them, preferably, in the polymer B2 containing branches, the main chain of the shell contains repeating units a, b2, c and d; the repeating unit b2 contains a branch E, and the branch E contains one or more of repeating units a, b1, c and d;

[0047] The structure of the repeating unit b2 is as shown in formula II2:

[0048] II2.

[0049] In certain specific embodiments of the present invention, the polymer material comprises a core and a shell coating the core; the core comprises a polymer A1, and the polymer A1 contains repeating units b1 and c; by mass, the repeating unit b1 is 12 - 25 parts, and the repeating unit c is 8 - 22 parts; the shell comprises a polymer B1, and the polymer B1 contains repeating units a, b1, c and d, by mass, the repeating unit a is 2 - 8 parts, the repeating unit b1 is 15 - 35 parts, the repeating unit c is 12 - 33 parts, and the repeating unit d is 3 - 10 parts.

[0050] Among them, in a specific embodiment of the present invention, the polymer material includes a core and a shell coating the core; the core includes polymer A1, and the polymer A1 contains repeating unit b1 and repeating unit c; by mass parts, the repeating unit b1 is 18.7 parts, and the repeating unit c is 15.3 parts; the shell includes polymer B1, and the polymer B1 contains repeating unit a, repeating unit b1, repeating unit c, and repeating unit d. By mass parts, the repeating unit a is 5 parts, the repeating unit b1 is 28.05 parts, the repeating unit c is 22.95 parts, and the repeating unit d is 10 parts.

[0051] Among them, in a specific embodiment of the present invention, the polymer material includes a core and a shell coating the core; the core includes polymer A1, and the polymer A1 contains repeating unit b1 and repeating unit c; by mass parts, the repeating unit b1 is 13.6 parts, and the repeating unit c is 20.4 parts; the shell includes polymer B1, and the polymer B1 contains repeating unit a, repeating unit b1, repeating unit c, and repeating unit d. By mass parts, the repeating unit a is 5 parts, the repeating unit b1 is 20.4 parts, the repeating unit c is 30.6 parts, and the repeating unit d is 10 parts.

[0052] Among them, in a specific embodiment of the present invention, the polymer material includes a core and a shell coating the core; the core includes polymer A1, and the polymer A1 contains repeating unit b1 and repeating unit c; by mass parts, the repeating unit b1 is 23.8 parts, and the repeating unit c is 10.2 parts; the shell includes polymer B1, and the polymer B1 contains repeating unit a, repeating unit b1, repeating unit c, and repeating unit d. By mass parts, the repeating unit a is 5 parts, the repeating unit b1 is 35.7 parts, the repeating unit c is 15.3 parts, and the repeating unit d is 10 parts.

[0053] Among them, in a specific embodiment of the present invention, the polymer material includes a core and a shell coating the core; the core includes polymer A1, and the polymer A1 contains repeating unit b1 and repeating unit c; by mass parts, the repeating unit b1 is 20.46 parts, and the repeating unit c is 16.74 parts; the shell includes polymer B1, and the polymer B1 contains repeating unit a, repeating unit b1, repeating unit c, and repeating unit d. By mass parts, the repeating unit a is 2 parts, the repeating unit b1 is 30.69 parts, the repeating unit c is 25.11 parts, and the repeating unit d is 5 parts.

[0054] The present invention also provides a binder composition, which includes a solvent and the polymer material as described above.

[0055] In the present invention, the viscosity of the binder composition can be 10-100 mPa·S, preferably 30-80 mPa·S, more preferably 32-77 mPa·S, such as 40 or 53 mPa·S.

[0056] In the present invention, the pH of the binder composition can be 7-9, preferably 7.5-8.1, such as 7.6 or 7.8.

[0057] In the present invention, the solid content of the binder composition can be 45%-55%, preferably 50%-51%, such as 50.2%, 50.5% or 50.8%. Herein, the meaning of the solid content is the mass percentage of the total mass of the solids in the binder composition accounting for the total mass of the binder composition.

[0058] In the present invention, the solvent is, for example, water.

[0059] In the present invention, the binder composition is preferably an emulsion. Among them, the average particle size of the droplets in the emulsion can be 80-200 nm, preferably 100-150 nm, more preferably 110-145 nm, such as 118, 125 or 142 nm.

[0060] The present invention provides a method for preparing a binder composition, which includes the following steps:

[0061] S1. Under a protective atmosphere, in the presence of an emulsifier, a chain transfer agent and an initiator, perform a first free radical polymerization reaction of a first premix in a solvent to obtain a first reaction product; the first premix includes monomer B and monomer C;

[0062] S2. Perform a second free radical polymerization reaction on a second premix and the first reaction product to obtain the composition; the second premix includes monomer B, monomer C, monomer A and monomer D; adjust the pH of monomer D to 7-9 by ammonia water;

[0063] The mass ratio of monomer A to monomer D is (20-50):(50-80), and the mass ratio of monomer B to monomer C is (40-80):(20-60);

[0064] The structural formula of monomer A is as shown in formula I’:

[0065]

[0066] I’

[0067] The structural formula of monomer B is as shown in formula II’:

[0068]

[0069] II’

[0070] The structural formula of the monomer C is as shown in Formula III’;

[0071]

[0072] III’

[0073] The structural formula of the monomer D is as shown in Formula Ⅳ’;

[0074]

[0075] Ⅳ’

[0076] wherein, R1-R 17 are as defined above.

[0077] In the present invention, the mass ratio of the monomer A to the monomer D is preferably (25-40):(60-75), such as 28.57:71.43 or 33.33:66.67.

[0078] In the present invention, the mass ratio of the monomer B to the monomer C is preferably (40-70):(30-60), such as 50:50, 55:45, 40:60 or 70:30.

[0079] In the present invention, based on the total weight parts of the monomers A, B, C and D being 100 parts, the monomer A can be 2-8 parts, preferably 3-6 parts, such as 5 parts.

[0080] In the present invention, based on the total weight parts of the monomers A, B, C and D being 100 parts, the monomer B can be 20-80 parts, preferably 30-60 parts, such as 34, 46.75, 51.15 or 59.5 parts.

[0081] In the present invention, based on the total weight parts of the monomers A, B, C and D being 100 parts, the monomer C can be 20-55 parts, preferably 25-53 parts, such as 25.5, 38.25, 41.85 or 51 parts.

[0082] In the present invention, based on the total weight parts of the monomers A, B, C and D being 100 parts, the monomer D can be 3-10 parts, preferably 5-12 parts, such as 10 parts.

[0083] In the present invention, the weight parts ratio of the monomer B in the first premix to the monomer B in the second premix can be 1:(1-2), such as 1:1.5.

[0084] In the present invention, the monomer B in the first premix can be 12-25 parts, preferably 13-24 parts, such as 13.6, 18.7, 20.46 or 23.8 parts.

[0085] In the present invention, the monomer B in the second premix may be 15 - 35 parts, preferably 17 - 36 parts, such as 20.4, 28.05, 30.69 or 35.7 parts.

[0086] In the present invention, the weight ratio of monomer C in the first premix to monomer C in the second premix may be 1:(1 - 2), such as 1:1.5.

[0087] In the present invention, the monomer C in the first premix may be 8 - 22 parts, preferably 10 - 21 parts, such as 10.2, 15.3, 16.74 or 20.4 parts.

[0088] In the present invention, the monomer C in the second premix may be 12 - 33 parts, preferably 15 - 32 parts, such as 15.3, 22.95, 25.11 or 30.6 parts.

[0089] In the present invention, the monomer A represented by formula I' is an addition - polymerizable oxazoline and its derivatives, which can rapidly react with carboxyl groups above 80 °C to form a three - dimensional network structure.

[0090] In the present invention, the monomer A is preferably one or more of 2 - vinyl - 2 - oxazoline, 2 - vinyl - 4 - methyl - 2 - oxazoline, 2 - vinyl - 5 - methyl - 2 - oxazoline, 2 - isopropenyl - 2 - oxazoline, 2 - isopropenyl - 4 - methyl - 2 - oxazoline and 2 - isopropenyl - 5 - ethyl - 2 - oxazoline, such as 2 - isopropenyl - 2 - oxazoline.

[0091] In the present invention, the monomer B represented by formula II' is a di - addition - polymerizable olefinic substance and its derivatives. After polymerization, there are rotatable double bonds in the molecular chain, which can provide toughness for the molecular chain.

[0092] In the present invention, the monomer B is preferably one or more of conjugated dienes, linear non - conjugated dienes and cyclic dienes, such as conjugated dienes.

[0093] Among them, the conjugated diene is preferably one or more of butadiene, isoprene and hexadiene, such as 1,3 - butadiene.

[0094] Among them, the linear non - conjugated diene is preferably 1,4 - pentadiene and / or 1,5 - hexadiene.

[0095] Among them, the cyclic diene is preferably one or more of cyclopentadiene, cyclohexadiene and cycloheptadiene.

[0096] In the present invention, the monomer C represented by formula III' has a rigid structure, which can provide good thermal stability. The glass transition temperature of the polymer can be adjusted by adjusting the amount of monomer C.

[0097] In the present invention, the monomer C is preferably one or more of styrene, isopropenylbenzene, allylbenzene, p-methylstyrene, o-methylstyrene, and m-methylstyrene, such as styrene.

[0098] In the present invention, the carboxyl group in the monomer D as shown in Formula IV' can provide good adhesiveness and crosslinking functional groups.

[0099] In the present invention, the monomer D is preferably a monocarboxylic acid containing an unsaturated group, preferably including one or more of acrylic acid, methacrylic acid, and itaconic acid, such as methacrylic acid.

[0100] In the present invention, the solvent can be a conventional solvent in the art, such as water.

[0101] In the present invention, the emulsifier can include an anionic surfactant and / or a nonionic surfactant. The nonionic surfactant can be polyethylene glycol alkyl ester, polyethylene glycol alkyl phenyl ether, or polyethylene glycol alkyl ether. The anionic surfactant can be sulfate ester salt of higher alcohol, alkyl benzene sulfonate, alkyl diphenyl ether disulfonate, aliphatic sulfonate, aliphatic carboxylate, dehydroabietate, formalin condensate of naphthalene sulfonic acid, or sulfate ester salt of the nonionic surfactant, such as sodium dodecyl sulfate.

[0102] In the present invention, based on 100 parts by weight of the solvent, the weight part of the emulsifier is 1 - 5 parts, such as 3 parts.

[0103] In the present invention, the chain transfer agent can include alkyl mercaptan, xanthate compound, phenolic compound, allyl compound, halogenated hydrocarbon compound, vinyl ether, triphenylethane, pentaphenylethane, acrolein, methacrolein, mercaptoacetic acid, mercaptosuccinic acid, terpinolene, or α-methylstyrene dimer. The alkyl mercaptan can be n-hexyl mercaptan, n-octyl mercaptan, tert-octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, or n-octadecyl mercaptan, such as n-dodecyl mercaptan. The xanthate compound can be dimethylxanthogen disulfide or diisopropylxanthogen disulfide. The phenolic compound can be 2,6-di-tert-butyl-4-methylphenol or styrenol. The allyl compound can be allyl alcohol. The halogenated hydrocarbon compound can be dichloromethane, dibromomethane, or tetrabromomethane. The vinyl ether can be α-benzyloxy styrene, α-benzyloxy acrylonitrile, or α-benzyloxy acrylamide.

[0104] In the present invention, based on 100 parts by weight of the solvent, the weight part of the chain transfer agent is 0.1 - 2 parts, such as 1 part.

[0105] In the present invention, the initiator may include a water-soluble polymerization initiator and / or an oil-soluble polymerization initiator. The water-soluble polymerization initiator may be a persulfate, such as lithium persulfate, potassium persulfate, sodium persulfate or ammonium persulfate, for example ammonium persulfate. The oil-soluble polymerization initiator may be a peroxide organic compound or an azo compound. The peroxide organic compound is, for example, cumene hydroperoxide, benzoyl peroxide, tert-butyl hydroperoxide, acetyl peroxide or diisopropylbenzene hydroperoxide. The azo compound is, for example, one or more of 2,2'-azobisisobutyronitrile, 2,2'-azobis-(2,4-dimethylvaleronitrile), azobiscyanovaleric acid and 2,2' azobis-(2-amidinopropane)·2 hydrochloride.

[0106] In the present invention, based on 100 parts by weight of the solvent, the weight parts of the initiator may be 0.4 - 5 parts, for example 0.5 part.

[0107] In the present invention, the temperature of the first free radical polymerization reaction may be 50 - 90 °C, for example 70 or 80 °C.

[0108] In the present invention, the time of the first free radical polymerization reaction may be 1 - 3 h, for example 2 h.

[0109] In the present invention, preferably, the second premix is added to the first reactant by dropwise addition; more preferably, the mixture of monomer B, monomer C and monomer A is first added to the first reactant by the first dropwise addition method, and then monomer D is added to the first reactant by the second dropwise addition method. The rate of the first dropwise addition may be 20 - 30 parts / h, for example 28 parts / h. The rate of the second dropwise addition may be 3 - 8 parts / h, for example 5 parts / h.

[0110] In the present invention, the temperature of the second free radical polymerization reaction may be less than 80 °C, preferably 50 - 80 °C, for example 70 or 80 °C.

[0111] In the present invention, the time of the second free radical polymerization reaction may be 3 - 9 h, for example 6 h.

[0112] In the present invention, after the second free radical polymerization reaction, preferably, a cooling step is further carried out. The end point of the cooling may be room temperature, generally 20 - 30 °C.

[0113] In the present invention, the first free radical polymerization reaction and the second free radical polymerization reaction are preferably free radical emulsion polymerization.

[0114] In certain specific embodiments of the present invention, R1 - R of the monomer A, the monomer B, the monomer C and the monomer D 16 is selected from hydrogen, R 17Selected from methyl; based on 100 parts by total weight of monomers A, B, C and D, monomer A is 2 - 8 parts, monomer B is 20 - 80 parts, monomer C is 20 - 55 parts, and monomer D is 3 - 10 parts; wherein, in the first premix, monomer B is 12 - 25 parts and monomer C is 8 - 22 parts; in the second premix, monomer B is 15 - 35 parts and monomer C is 12 - 33 parts.

[0115] Wherein, in a specific embodiment of the present invention, based on 100 parts by total weight of monomers A, B, C and D, monomer A is 5 parts, monomer B is 46.75 parts, monomer C is 38.25 parts, and monomer D is 10 parts; wherein, in the first premix, monomer B is 18.7 parts and monomer C is 15.3 parts; in the second premix, monomer B is 28.05 parts and monomer C is 22.95 parts.

[0116] Wherein, in a specific embodiment of the present invention, based on 100 parts by total weight of monomers A, B, C and D, monomer A is 5 parts, monomer B is 34 parts, monomer C is 51 parts, and monomer D is 10 parts; wherein, in the first premix, monomer B is 13.6 parts and monomer C is 20.4 parts; in the second premix, monomer B is 20.4 parts and monomer C is 30.6 parts.

[0117] Wherein, in a specific embodiment of the present invention, based on 100 parts by total weight of monomers A, B, C and D, monomer A is 5 parts, monomer B is 59.5 parts, monomer C is 25.5 parts, and monomer D is 10 parts; wherein, in the first premix, monomer B is 23.8 parts and monomer C is 10.2 parts; in the second premix, monomer B is 35.7 parts and monomer C is 15.3 parts.

[0118] Wherein, in a specific embodiment of the present invention, based on 100 parts by total weight of monomers A, B, C and D, monomer A is 2 parts, monomer B is 51.15 parts, monomer C is 41.85 parts, and monomer D is 5 parts; wherein, in the first premix, monomer B is 20.46 parts and monomer C is 16.74 parts; in the second premix, monomer B is 30.69 parts and monomer C is 25.11 parts.

[0119] In the present invention, by placing the carboxyl - containing monomer (monomer D) in the shell structure, the reaction activity of the carboxyl group can be further enhanced, thereby improving the cross - linking density and bonding performance of the polymer. When this polymer is applied to the negative electrode material of a lithium - ion battery to prepare a lithium - ion battery, the volume change caused by the negative electrode material during the cycling process can be slowed down, thereby improving the cycling performance of the battery.

[0120] The present invention also provides a binder composition, which is prepared by using the preparation method of the binder composition as described above.

[0121] In the present invention, the viscosity of the binder composition may be 10 - 100 mPa·S, preferably 30 - 80 mPa·S, more preferably 32 - 77 mPa·S, such as 40 or 53 mPa·S.

[0122] In the present invention, the pH of the binder composition may be 7 - 9, preferably 7.5 - 8.1, such as 7.6 or 7.8.

[0123] In the present invention, the solid content of the binder composition may be 45% - 55%, preferably 50% - 51%, such as 50.2%, 50.5% or 50.8%. Wherein, the meaning of the solid content is the mass percentage of the total mass of the solids in the binder composition accounting for the total mass of the binder composition.

[0124] In the present invention, the solvent is, for example, water.

[0125] In the present invention, the binder composition is preferably an emulsion. Wherein, the average particle size of the droplets in the emulsion may be 80 - 200 nm, preferably 100 - 150 nm, more preferably 110 - 145 nm, such as 118, 125 or 142 nm.

[0126] The present invention also provides a preparation method of a polymer material, which comprises the following step: removing the solvent from the binder composition as described above to obtain the polymer material.

[0127] In the present invention, the method for removing the solvent is preferably heating and evaporation.

[0128] The present invention also provides a binder, which comprises the polymer material as described above, or the binder composition as described above.

[0129] In the present invention, the binder preferably further comprises a matrix binder. The matrix binder refers to a binder commonly used in the field of battery electrode sheets.

[0130] Wherein, the matrix binder may be SBR. In the present invention, SBR means an ethylene copolymer containing structural units derived from ethylenically unsaturated carboxylic acid monomers and structural units derived from monomers capable of copolymerizing with the ethylenically unsaturated carboxylic acid monomers.

[0131] Wherein, the matrix binder may be PAA (polyacrylic acid) and / or CMC (sodium carboxymethyl cellulose).

[0132] The present invention also provides an electrode paste, which comprises an electrode active material, a solvent and the binder as described above.

[0133] The present invention also provides a pole piece, which is prepared by using the above electrode paste.

[0134] The present invention also provides a battery, which includes the above pole piece.

[0135] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0136] The reagents and raw materials used in the present invention are all commercially available.

[0137] The positive and progressive effects of the present invention are as follows:

[0138] (1) The present invention provides a polymer material with a core-shell structure. By specially designing the content relationship between repeating units a and d, and repeating units b and c, when the polymer material is used as an electrode binder, its binding performance can be improved, and at the same time, the mechanical properties and corrosion resistance of the obtained pole piece can be improved. It can slow down the volume change caused by the negative electrode material during the cycling process, further alleviate the problem of battery performance decay, and thus improve the battery performance and cycle life. At the same time, the polymer material of the present invention also has an excellent effect of suppressing cold pressing rebound when applied to a battery.

[0139] (2) The preparation method of the polymer material provided by the present invention is to first polymerize a part of monomers B and C, and then polymerize the remaining monomer B, the remaining monomer C, monomer A and monomer D. If monomers A, B, C and D are polymerized simultaneously, the viscosity of the obtained polymer material is relatively high, the molecular weight is too large; the crosslinking density of the obtained pole piece is relatively low, the mechanical properties are poor, and the binding performance is poor. Specific Embodiments

[0140] The present invention will be further illustrated below by way of examples, but the present invention is not limited to the scope of the described examples. The experimental methods without specific conditions in the following examples are carried out according to conventional methods and conditions, or selected according to the product instructions.

[0141] In the following examples and comparative examples, monomer A is 2-isopropenyl-2-oxazoline, industrial grade, purchased from Shanghai Merck Chemical Technology Co., Ltd., and its structural formula is , where R1-R4 are H; monomer B is 1,3-butadiene, industrial grade, purchased from Chengdu Taiyu Industrial Gas Co., Ltd., and its structural formula is , where R5-R8 are H; monomer C is styrene, industrial grade, purchased from Jiangsu Runfeng Synthetic Technology Co., Ltd., and its structural formula is , where R9-R 15 are H; monomer D is methacrylic acid, industrial grade, purchased from Jinan Century Tongda Chemical Co., Ltd., and its structural formula is , where R 16It is H, R 17 It is -CH3.

[0142] Example 1

[0143] S1: (1) Exclude air by passing nitrogen. After the reaction kettle 1 is evacuated, add 100 parts of deionized water, 3 parts of emulsifier: sodium dodecyl sulfate, 1 part of chain transfer agent: dodecyl mercaptan, and 0.5 part of initiator: ammonium persulfate, and stir and mix evenly.

[0144] (2) The first premix includes 18.7 parts of monomer B and 15.3 parts of monomer C.

[0145] (3) Add the first premix to the reaction kettle 1, and carry out the first free radical polymerization reaction at a constant temperature of 70 °C for 2 h to obtain the first reactant.

[0146] S2: (1) Preparation of the second premix: Add the remaining 28.05 parts of monomer B, 22.95 parts of monomer C, and 5 parts of monomer A to another dropping kettle. After stirring and mixing evenly, add them dropwise to the reaction kettle 1 at a constant speed (the dropping speed is 28 parts / h) (for about 2 h); at the same time, add 10 parts of monomer D to the dropping kettle 2, add 5 parts of ammonia water to adjust the pH to 7-9, stir and mix evenly, and then add them dropwise to the reaction kettle 1 at a constant speed (the dropping speed is 5 parts / h) (for about 2 h).

[0147] (2) After the second premix is added dropwise, raise the temperature to 80 °C to carry out the second free radical polymerization reaction, and keep the temperature constant for 6 h.

[0148] (3) After the reaction is completed, cool to room temperature and filter to obtain the binder composition.

[0149] The preparation methods of Examples 2-4 and Comparative Examples 1-6 are the same as those of Example 1, and the weight parts of monomers A, B, C, and D are shown in Table 1 below.

[0150] Comparative Example 5

[0151] The difference from Example 1 is only that ammonia water is not added to adjust the pH in step S2. Specifically:

[0152] S2: (1) Preparation of the second premix: Add the remaining 28.05 parts of monomer B, 22.95 parts of monomer C, and 5 parts of monomer A to another dropping kettle. After stirring and mixing evenly, add them dropwise to the reaction kettle 1 at a constant speed (the dropping speed is 28 parts / h) (for about 2 h); at the same time, add 10 parts of monomer D to the dropping kettle 2, do not add ammonia water to adjust the pH (pH is 2), and add them dropwise to the reaction kettle 1 at a constant speed (for about 2 h).

[0153] Table 1

[0154]

[0155] The binder compositions of Examples 1-4 are heated and evaporated to obtain polymer materials. The polymer materials of Examples 1-4 include a core and a shell coating the core;

[0156] Among them, the core includes polymer A1, and polymer A1 contains repeating unit b1 and repeating unit c;

[0157] The shell includes polymer B1, and polymer B1 contains repeating unit a, repeating unit b1, repeating unit c and repeating unit d;

[0158] The structure of the repeating unit a is shown in Formula I:

[0159]

[0160] I

[0161] The structure of the repeating unit b1 is shown in Formula II1:

[0162]

[0163] II1

[0164] The structure of the repeating unit c is shown in Formula III:

[0165]

[0166] III

[0167] The structure of the repeating unit d is shown in Formula IV:

[0168]

[0169] IV

[0170] Among them, R1-R 16 is selected from hydrogen, and R 17 is selected from -CH3.

[0171] Among them, by mass parts, the specific contents of the repeating unit a, the repeating unit b1, the repeating unit c and the repeating unit d are listed in Table 2 below:

[0172] Table 2

[0173]

[0174] Example 5

[0175] Example 5 provides an adhesive which is composed of the adhesive composition prepared in Example 1, PAA (polyacrylic acid) and CMC (sodium carboxymethyl cellulose). Among them, the mass ratio of the adhesive composition, PAA and CMC is 3:1:1. Among them, PAA is purchased from Huitian New Materials, with the model number 1205; CMC is purchased from Changshu Weiyi Technology Co., Ltd., with the model number BH90-II. The manufacturers and model numbers of PAA and CMC used in the following Examples 6-8 are the same as those in this example.

[0176] Its preparation method is: mix the adhesive composition prepared in Example 1, PAA and CMC.

[0177] Example 6

[0178] Example 6 provides an adhesive which is composed of the adhesive composition prepared in Example 2, PAA (polyacrylic acid) and CMC (sodium carboxymethyl cellulose). Among them, the mass ratio of the adhesive composition, PAA and CMC is 3:1:1.

[0179] Its preparation method is: mix the adhesive composition prepared in Example 2, PAA and CMC.

[0180] Example 7

[0181] Example 7 provides an adhesive which is composed of the adhesive composition prepared in Example 3, PAA (polyacrylic acid) and CMC (sodium carboxymethyl cellulose). Among them, the mass ratio of the adhesive composition, PAA and CMC is 3:1:1.

[0182] Its preparation method is: mix the adhesive composition prepared in Example 3, PAA and CMC.

[0183] Example 8

[0184] Example 8 provides an adhesive which is composed of the adhesive composition prepared in Example 4, PAA (polyacrylic acid) and CMC (sodium carboxymethyl cellulose). Among them, the mass ratio of the adhesive composition, PAA and CMC is 3:1:1.

[0185] Its preparation method is: mix the adhesive composition prepared in Example 4, PAA and CMC.

[0186] Effect Example 1

[0187] (1) Solids content test:

[0188] The binder compositions obtained in the above Examples 1-4 and Comparative Examples 1-6 were tested for solid content. The test method was as follows: Take a clean weighing dish (weight denoted as m0), then take 5 g of the composition obtained in the above Examples 1-4 or Comparative Examples 1-6, denoted as m1, and place it in an oven at 100 °C for 4 h. After taking it out and weighing the dried weight, denoted as m2. The calculation method of the solid content is as follows: Solid content = (m2 - m0) / m1 × 100%.

[0189] (2) Viscosity test

[0190] The binder compositions obtained in the above Examples 1-4 and Comparative Examples 1-6 were tested for viscosity. The test method was as follows: A rotational viscometer (SNB-1, Shanghai Precision Instrument and Meter Co., Ltd.) was used for testing with reference to GB / T 2794-2013.

[0191] (3) pH measurement

[0192] The binder compositions obtained in the above Examples 1-4 and Comparative Examples 1-6 were tested for pH. The test method was as follows: A Mettler Toledo SevenExcellence S400-Micro pH meter was used for testing with reference to GB / T 9724-2007.

[0193] (4) Average particle size test

[0194] The binder compositions obtained in the above Examples 1-4 and Comparative Examples 1-6 were tested for average particle size. The test method was as follows: A particle size (Bettersize3000Plus) tester was used. First, add the sample solution to be tested into the sample cell of the tester. Stop adding the sample when the displayed test sample strength is in the range of 5-20. Click the automatic test to start the test. After the test is completed, read the test result, which is the average particle size of the sample. The meaning of this average particle size is the average particle size of the droplets in the composition emulsion.

[0195] (5) Glass transition temperature test

[0196] The polymer materials obtained in the above Examples 1-4 and Comparative Examples 1-6 were tested for glass transition temperature using a Mettler Toledo differential scanning calorimeter DSC 5+ with reference to GB / T 2794-2013. The test method was as follows: Under a nitrogen atmosphere, set the heating rate to 10 °C / min, heat the temperature from 30 °C to 200 °C, then cool from 200 °C to 30 °C, and finally heat from 30 °C to 200 °C to obtain the DSC curve of the polymer material. The glass transition temperature of the polymer material can be obtained by analyzing the curve.

[0197] (6) Number average molecular weight test

[0198] The polymer materials obtained in the above Examples 1-4 and Comparative Examples 1-6 were tested for number-average molecular weight. The testing method was as follows: Using a gel permeation chromatograph HLC-8420GPC (Tosoh (Shanghai) Biotech Co., Ltd.), the test was carried out with reference to GB / T 2794-2013. The specific chromatographic conditions were as follows: The polymer materials obtained in the above Examples 1-4 and Comparative Examples 1-6 were dissolved in a uniform solution (concentration 10 mg / mL) in the solvent THF (tetrahydrofuran); mobile phase: 0.1 M aqueous sodium nitrate solution; standard: polyethylene glycol PEG; flow rate: 1 mL / min; column temperature: 40 °C.

[0199] (7)Testing of crosslinking density

[0200] The polymer materials obtained in the above Examples 1-4 and Comparative Examples 1-6 were tested for crosslinking density. The testing method was as follows: Weigh 5 g of the prepared binder composition in a weighing pan and denote it as m1. Place it in an oven at 100 °C for 4 h for drying treatment. Take it out and cut it into small granular shapes with a cutter. Take 1 g of the dried small granular sample and place it in a stainless steel filter mesh. Then place the stainless steel filter mesh containing the sample to be tested in xylene solution and soak it for 12 h. Take out the filter mesh and dry it at 120 °C for 2 h to remove the residual solvent. Weigh the dried small granular sample and denote it as m2. The crosslinking density was calculated as follows: Crosslinking density = m2 / m1 × 100%.

[0201] (8)Corrosion resistance testing

[0202] The polymer materials obtained in the above Examples 1-4 and Comparative Examples 1-6 were tested for corrosion resistance. The testing method was as follows: Weigh 10 g of the prepared binder composition in a weighing pan. Place it in an oven at 100 °C for 4 h for drying treatment. Take it out and cut it into strips with a length × width of 2 × 5 mm with a cutter. Place the cut strips in toluene solvent and soak for 30 days. Check the surface state of the sample after soaking. The evaluation grades are as follows:

[0203] √: There are no cracks, bubbles, corners missing or swelling phenomena on the surface of the sample.

[0204] ×: There are cracks, bubbles, corners missing or swelling phenomena on the surface of the sample.

[0205] The above test results are shown in Table 3.

[0206] Table 3

[0207]

[0208] As can be seen from Table 4, the average particle size of the binder compositions obtained in Examples 1-4 is relatively small, below 150 nm. The crosslinking density of the polymer materials obtained in Examples 1-4 is relatively high.

[0209] Effect Example 2

[0210] (1)Test of Elastic Modulus and Elongation at Break

[0211] Mix CMC and the binder compositions obtained in the above Examples 1-4 and Comparative Examples 1-6 evenly according to the mass ratio = 1:4, dry them into films at 50°C, and use CMT4000 (Shenzhen Sansi Testing Instruments Co., Ltd.) to test the elastic modulus and elongation at break with reference to the test method for the tensile properties of plastics in GB / T 1040.1-2018.

[0212] Dry the binders of Examples 5-8 into films at 50°C, cut the specimens into 20*100mm, and use CMT4000 (Shenzhen Sansi Testing Instruments Co., Ltd.) to test the elastic modulus and elongation at break with reference to the test method for the tensile properties of plastics in GB / T 1040.1-2018.

[0213] (2)Test of Cycling Performance

[0214] Mix graphite, conductive agent (SP), CMC and the binder compositions obtained in the above Examples 1-4 and Comparative Examples 1-6 evenly according to the mass ratio = 96:0.8:1.4:1.8, or mix graphite, conductive agent (SP), CMC and the binders obtained in the above Examples 5-8 evenly according to the mass ratio = 96:0.8:1.4:1.8; add deionized water to prepare a slurry with a solid content of 40%, evenly coat the slurry on a copper foil with a thickness of 10μm, dry it at 80°C for 1h, set the roll gap of rolling to 0.03mm, and roll once to obtain a negative electrode sheet with a single-sided areal density of 130g / m 2 , and a single-sided compaction density of 1.0g / cc. Assemble the negative electrode sheet, positive electrode sheet (lithium iron phosphate single-sided electrode sheet (01008501), Shenzhen Kejing), electrolyte (TCD-LFPX, Tianci Materials) and separator (XX-9C, Xingyuan Materials) into a lithium-ion battery and test the lithium-ion battery. The lithium-ion battery is subjected to constant current charge and discharge cycling at different current densities in the voltage range of 4.6-3.0V. The first 10 cycles are charged at 0.1C / discharged at 0.1C, the 11-30th cycles are charged at 0.5C / discharged at 0.5C, and the 31-100th cycles are charged at 1C / discharged at 1C. Record the capacity retention rate after 100 cycles.

[0215] (3)Test of Peel Strength

[0216] The negative electrode sheets were prepared from the above Examples 1-8 and Comparative Examples 1-6 according to the method in (2) above. The prepared negative electrode sheets were cut into strips of 100×20 mm for standby. 3M VHB double-sided tape of the same size was pasted on the rectangular stainless steel plate (cleaned with alcohol before pasting), and rolled back and forth three times with a 2 Kg standard roller to make the tape fit tightly with the steel plate. Then, the electrode sheet (active material side) was precisely attached to the other side of the tape, and rolled back and forth three times with a 2 Kg standard roller. The sample was placed in a micro-controlled electronic universal testing machine (Model: CMT4204, Manufacturer: MTS Industrial Systems (China) Co., Ltd.). One end of the steel plate was placed in the fixture under the machine, and the steel plate was vertically clamped to the ground. It was gently torn from the bottom to the middle position of the electrode sheet, bent 180° to be clamped by the fixture above the machine, the position of the upper fixture was adjusted by controlling the machine, the testing software was opened, the testing conditions were set (tensile rate 20 mm / min, the horizontal and vertical coordinates respectively showed the displacement distance and force), all the initial parameters were reset to zero, and the test was started. The measured peeling force was the peeling strength.

[0217] (4)Cold Press Rebound Test

[0218] ① Graphite, conductive agent (SP), the binder obtained from the above Examples 5-8, and the binder composition obtained from Comparative Examples 1-6 were mixed evenly according to the mass ratio = 96:0.8:3.2, and deionized water was added to prepare an electrode slurry with a solid content of 40%. The slurry was evenly coated on the surface of a 10-μm-thick copper foil and dried at 80°C for 1 h to prepare a dried negative electrode sheet.

[0219] ② The above dried negative electrode sheet was pre-cold pressed at a pressure of 25 MPa and a cold pressing speed of 3 m / min; then, through a second cold pressing process, it was secondarily cold pressed at a pressure of 55 MPa and a cold pressing speed of 6 m / min to obtain a negative electrode sheet with a target thickness of 145 μm.

[0220] ③ The above negative electrode sheet was cut into 30*150 mm splines and stored at room temperature. The thickness of the electrode sheet was recorded at 12 h, 24 h, and one week after cold pressing. The calculation method of the cold press rebound rate was as follows:

[0221] Cold press rebound rate = (h 放置一定时间极片厚度 -h 初始冷压极片厚度 ) / h 初始冷压极片厚度 *100%.

[0222] The above test results are shown in Tables 4 and 5.

[0223] Table 4

[0224]

[0225] Table 5

[0226]

[0227] As can be seen from Table 4-5 above, the electrode slurries prepared from the binder compositions prepared in Examples 1-4 have relatively excellent elastic modulus and elongation at break after drying and film formation. The negative electrode sheets prepared from the binder compositions prepared in Examples 1-4 have better peel strength. In some preferred embodiments, after the binder compositions prepared in Examples 1-4 are compounded with other binders (PAA and CMC) to form a binder and form a film, they can have more excellent elastic modulus under the condition that the elongation at break and peel strength are comparable to those of other examples.

[0228] Compared with Comparative Examples 1 and 6, the batteries prepared from the binder compositions prepared in Examples 1 and 2 have better cycling performance.

[0229] Examples 1-4 have a lower cold pressing rebound rate compared to Comparative Examples 1-6, indicating that Examples 1-4 have excellent effects in suppressing cold pressing rebound.

Claims

1. A polymer material, characterized in that, It includes a core and a shell covering the core; Wherein, the core includes polymer A1; the polymer A1 contains repeating unit b1 and repeating unit c; The shell includes polymer B1, and the polymer B1 contains repeating unit a, repeating unit b1, repeating unit c and repeating unit d; The mass ratio of the repeating unit a to the repeating unit d is (20 - 50):(50 - 80), and the mass ratio of the repeating unit b1 to the repeating unit c is (40 - 80):(20 - 60); Wherein, the structure of the repeating unit a is shown in Formula I: I In each repeating unit a, R1 - R4 are each independently hydrogen or an alkyl group with 1 - 4 carbon atoms; The structure of the repeating unit b1 is shown in Formula II1: II1 In each repeating unit b1, R5 - R8 are each independently hydrogen or an alkyl group with 1 - 4 carbon atoms; The structure of the repeating unit c is shown in Formula III: III In each repeating unit c, R9-R 15 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms; The structure of the repeating unit d is shown in Formula IV: Ⅳ In each repeating unit d, R 16 and R 17 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms.

2. The polymeric material according to claim 1, wherein The polymer material satisfies one or more of the following conditions: (1) The mass ratio of the repeating unit a to the repeating unit d is (25 - 40):(60 - 75), such as 28.57:71.43 or 33.33:66.67; (2) The mass ratio of the repeating unit b1 to the repeating unit c is (40 - 70):(30 - 60), such as 50:50, 55:45, 40:60 or 70:30; (3) Based on the total weight of 100 parts of the repeating units a, b1, c and d, the repeating unit a is 2 - 8 parts, preferably 3 - 6 parts, such as 5 parts; (4) Based on the total weight of 100 parts of the repeating units a, b1, c and d, the repeating unit b1 is 20 - 80 parts, preferably 30 - 60 parts, such as 34, 46.75, 51.15 or 59.5 parts; (5) Based on the total weight of 100 parts of the repeating units a, b1, c and d, the repeating unit c is 20 - 55 parts, preferably 25 - 53 parts, such as 25.5, 38.25, 41.85 or 51 parts; (6) Based on the total weight of 100 parts of the repeating units a, b1, c and d, the repeating unit d is 3 - 10 parts, preferably 5 - 12 parts, such as 10 parts; (7) The weight ratio of the repeating unit b1 in the core to the repeating unit b1 in the shell is 1:(1 - 2), such as 1:1.5; (8) The repeating unit b1 in the core is 12 - 25 parts, preferably 13 - 24 parts, such as 13.6, 18.7, 20.46 or 23.8 parts; (9) The repeating unit b1 in the shell is 15 - 35 parts, preferably 17 - 36 parts, such as 20.4, 28.05, 30.69 or 35.7 parts; (10) The weight ratio of the repeating unit c in the core to the repeating unit c in the shell is 1:(1 - 2), such as 1:1.5; (11) The repeating unit c in the core is 8 - 22 parts, preferably 10 - 21 parts, such as 10.2, 15.3, 16.74 or 20.4 parts; In the casing, the repeating unit c is 12-33 parts, preferably 15-32 parts, such as 15.3, 22.95, 25.11 or 30.6 parts; (13) The C1-C4 alkyl group is methyl, ethyl, propyl or isopropyl; (14) The number average molecular weight of the polymer material is 20,000-200,000, preferably 30,000-50,000, such as 34580, 45242, 42053 or 39045; (15) The glass transition temperature of the polymer material is -50 to 20 °C, preferably -20 to 15 °C, preferably -18 to 12 °C, such as -8 °C or -4 °C; (16) The crosslinking density of the polymer material is more than 90%, such as 95%, 96%, 98% or 99%; (17) The core further includes a polymer A2 containing branches; Among them, preferably, in the polymer A2 containing branches, the main chain contains repeating unit b2 and repeating unit c; the repeating unit b2 contains branch E, and the branch E contains repeating unit b1 and / or repeating unit c; (18) The casing further includes a polymer B2 containing branches; Among them, preferably, in the polymer B2 containing branches, the main chain of the casing contains repeating unit a, repeating unit b2, repeating unit c and repeating unit d; the repeating unit b2 contains branch E, and the branch E contains one or more of repeating unit a, repeating unit b1, repeating unit c and repeating unit d; The structure of the repeating unit b2 is shown in formula II2: II2。 3. A binder composition, characterized in that, It includes a solvent and the polymer material according to any one of claims 1 or 2; The viscosity of the binder composition is preferably 10-100 mPa·S, more preferably 30-80 mPa·S, preferably 32-77 mPa·S, such as 40 or 53 mPa·S; The pH of the binder composition is preferably 7-9, more preferably 7.5-8.1, such as 7.6 or 7.8; The solid content of the binder composition is preferably 45%-55%, more preferably 50%-51%, such as 50.2%, 50.5% or 50.8%; The solvent is preferably water; The binder composition is preferably an emulsion; among them, the average particle size of the droplets in the emulsion is preferably 80-200 nm, more preferably 100-150 nm, further preferably 110-145 nm, such as 118, 125 or 142 nm.

4. A method for preparing an adhesive composition, characterized in that, It includes the following steps: S1. Under a protective atmosphere, in the presence of an emulsifier, a chain transfer agent and an initiator, carry out a first radical polymerization reaction on a first premix in a solvent to obtain a first reaction product; the first premix includes monomer B and monomer C; S2. Carry out a second radical polymerization reaction on a second premix and the first reaction product to obtain the binder composition; the second premix includes monomer B, monomer C, monomer A and monomer D; Adjust the pH of the monomer D to 7-9 with ammonia water; The mass ratio of the monomer A to the monomer D is (20 - 50):(50 - 80), and the mass ratio of the monomer B to the monomer C is (40 - 80):(20 - 60); The structural formula of the monomer A is as shown in Formula I': I’； The structural formula of the monomer B is as shown in Formula II': II’; The structural formula of the monomer C is as shown in Formula III'; III’; The structural formula of the monomer D is as shown in Formula IV'; Ⅳ’； wherein, R1-R 17 are as defined above.

5. The method for preparing the binder composition according to claim 4, wherein, The preparation method of the binder composition satisfies one or more of the following conditions: (1) The mass ratio of the monomer A to the monomer D is (25 - 40):(60 - 75), such as 28.57:71.43 or 33.33:66.67; (2) The mass ratio of the monomer B to the monomer C is (40 - 70):(30 - 60), such as 50:50, 55:45, 40:60 or 70:30; (3) Based on the total weight of 100 parts of the monomers A, B, C and D, the monomer A is 2 - 8 parts, preferably 3 - 6 parts, such as 5 parts; (4) Based on the total weight of 100 parts of the monomers A, B, C and D, the monomer B is 20 - 80 parts, preferably 30 - 60 parts, such as 34, 46.75, 51.15 or 59.5 parts; (5) Based on the total weight of 100 parts of the monomers A, B, C and D, the monomer C is 20 - 55 parts, preferably 25 - 53 parts, such as 25.5, 38.25, 41.85 or 51 parts; (6) Based on the total weight of 100 parts of the monomers A, B, C and D, the monomer D is 3 - 10 parts, preferably 5 - 12 parts, such as 10 parts; (7) The weight ratio of the monomer B in the first premix to the monomer B in the second premix is 1:(1 - 2), such as 1:1.5; (8) The monomer B in the first premix is 12 - 25 parts, preferably 13 - 24 parts, such as 13.6, 18.7, 20.46 or 23.8 parts; (9) The monomer B in the second premix is 15 - 35 parts, preferably 17 - 36 parts, such as 20.4, 28.05, 30.69 or 35.7 parts; (10) The weight ratio of the monomer C in the first premix to the monomer C in the second premix is 1:(1 - 2), such as 1:1.5; (11) The monomer C in the first premix is 8 - 22 parts, preferably 10 - 21 parts, such as 10.2, 15.3, 16.74 or 20.4 parts; (12) The monomer C in the second premix is 12 - 33 parts, preferably 15 - 32 parts, such as 15.3, 22.95, 25.11 or 30.6 parts; (13) The monomer A is one or more of 2 - vinyl - 2 - oxazoline, 2 - vinyl - 4 - methyl - 2 - oxazoline, 2 - vinyl - 5 - methyl - 2 - oxazoline, 2 - isopropenyl - 2 - oxazoline, 2 - isopropenyl - 4 - methyl - 2 - oxazoline and 2 - isopropenyl - 5 - ethyl - 2 - oxazoline, such as 2 - isopropenyl - 2 - oxazoline; (14)Monomer B is one or more of conjugated dienes, linear non-conjugated dienes and cyclic dienes, such as conjugated dienes; Among them, the conjugated diene is preferably one or more of butadiene, isoprene and hexadiene, such as 1,3-butadiene; Among them, the linear non-conjugated diene is preferably 1,4-pentadiene and / or 1,5-hexadiene; Among them, the cyclic diene is preferably one or more of cyclopentadiene, cyclohexadiene and cycloheptadiene; (15)Monomer C is one or more of styrene, isopropenylbenzene, allylbenzene, p-methylstyrene, o-methylstyrene and m-methylstyrene, such as styrene; (16)Monomer D is a monocarboxylic acid containing an unsaturated group, preferably including one or more of acrylic acid, methacrylic acid and itaconic acid, such as methacrylic acid; (17)The solvent is water; (18)The emulsifier includes an anionic surfactant and / or a non-ionic surfactant; Among them, the non-ionic surfactant is preferably polyethylene glycol alkyl ester, polyethylene glycol alkyl phenyl ether or polyethylene glycol alkyl ether; Among them, the anionic surfactant is preferably sulfate ester salt of higher alcohol, alkylbenzene sulfonate, alkyl diphenyl ether disulfonate, aliphatic sulfonate, aliphatic carboxylate, dehydroabietate, formalin condensate of naphthalene sulfonic acid or sulfate ester salt of the non-ionic surfactant, such as sodium dodecyl sulfate; Among them, based on 100 parts by weight of the solvent, the weight part of the emulsifier is preferably 1-5 parts, such as 3 parts; (19)The chain transfer agent includes alkyl mercaptan, xanthate compound, phenolic compound, allyl compound, halogenated hydrocarbon compound, vinyl ether, triphenylethane, pentaphenylethane, acrolein, methacrolein, mercaptoacetic acid, mercaptosuccinic acid, terpinolene or α-methylstyrene dimer, such as alkyl mercaptan; Among them, the alkyl mercaptan is preferably n-hexyl mercaptan, n-octyl mercaptan, tert-octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan or n-octadecyl mercaptan, such as n-dodecyl mercaptan; Among them, the xanthate compound is preferably dimethyl xanthogen disulfide or diisopropyl xanthogen disulfide; Among them, the phenolic compound is preferably 2,6-di-tert-butyl-4-methylphenol or styrenol; Among them, the allyl compound is preferably allyl alcohol; Among them, the halogenated hydrocarbon compound is preferably dichloromethane, dibromomethane or tetrabromomethane; Among them, the vinyl ether is preferably α-benzyloxy styrene, α-benzyloxy acrylonitrile or α-benzyloxy acrylamide; Among them, based on 100 parts by weight of the solvent, the weight part of the chain transfer agent is preferably 0.1-2 parts, such as 1 part; (20)The initiator includes a water-soluble polymerization initiator and / or an oil-soluble polymerization initiator; Among them, the water-soluble polymerization initiator is preferably persulfate, more preferably lithium persulfate, potassium persulfate, sodium persulfate or ammonium persulfate, such as ammonium persulfate; Among them, the oil-soluble polymerization initiator is preferably a peroxide organic compound or an azo compound; the peroxide organic compound is, for example, cumene hydroperoxide, benzoyl peroxide, tert-butyl hydroperoxide, acetyl peroxide or diisopropylbenzene hydroperoxide; the azo compound is, for example, one or more of 2,2'-azobisisobutyronitrile, 2,2'-azobis-(2,4-dimethylvaleronitrile), azodicyanovaleric acid and 2,2' azobis-(2-amidinopropane)·2 hydrochloride; Among them, based on 100 parts by weight of the solvent, the weight part of the initiator is preferably 0.4-5 parts, for example 0.5 part; (21) The temperature of the first free radical polymerization reaction is 50-90 °C, for example 70 or 80 °C; (22) The time of the first free radical polymerization reaction is 1-3 h, for example 2 h; (23) The temperature of the second free radical polymerization reaction is less than 80 °C, preferably 50-80 °C, for example 70 or 80 °C; (24) The time of the second free radical polymerization reaction is 3-9 h, for example 6 h.

6. A binder composition, characterized in that, It is prepared by using the preparation method of the binder composition as described in claim 4 or 5.

7. A method for preparing a polymer material, characterized in that, It includes the following steps: removing the solvent from the binder composition as described in claim 6 to obtain it.

8. An adhesive, characterized in that, It includes the polymer material as described in claim 1 or 2, or the binder composition as described in claim 3 or 6.

9. An electrode paste, characterized in that, It includes an electrode active material, a solvent and the binder as described in claim 8.

10. A pole piece, characterized in that, It is prepared by using the electrode paste as described in claim 9.

11. A battery, characterized in that, It includes the electrode sheet as described in claim 10.

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