阅读说明：本技术 一种用于负极片的水溶性聚合物、制备方法和负极片 (Water-soluble polymer for negative plate, preparation method and negative plate ) 是由 彭冲 李俊义 于 2020-11-20 设计创作，主要内容包括：本发明提供一种用于负极片的水溶性聚合物、制备方法和负极片,所述聚合物为苯丙共聚物-b-PEO-b-苯丙共聚物嵌段共聚物的交联物,所述聚合物中具有网络结构,且所述聚合物中具有亲水基团。该水溶性聚合物是将苯丙共聚物-b-PEO-b-苯丙共聚物共聚物先与交联剂进行交联得到多孔聚合物,再水解得到水溶性多孔聚合物。本发明中的水溶性聚合物与电解液的亲和性好,可吸收电解液,吸收电解液后适度溶胀而不溶解；同时所述水溶性聚合物具有足够多的孔,增大与电解液接触面积,能够有效储存电解液,提升保液量。将水溶性聚合物作为一种添加剂加入负极浆料中从而引入到负极片中,可有效提升保液量,提升高能量密度电芯的性能。(The invention provides a water-soluble polymer for a negative plate, a preparation method and the negative plate, wherein the polymer is a cross-linked product of a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer, the polymer has a network structure, and the polymer has a hydrophilic group. The water-soluble polymer is prepared by crosslinking a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer with a crosslinking agent to obtain a porous polymer, and hydrolyzing the porous polymer. The water-soluble polymer has good affinity with the electrolyte, can absorb the electrolyte, and can swell moderately without dissolving after absorbing the electrolyte; meanwhile, the water-soluble polymer has enough holes, so that the contact area between the water-soluble polymer and the electrolyte is increased, the electrolyte can be effectively stored, and the liquid retention capacity is improved. The water-soluble polymer is added into the negative pole slurry as an additive to be introduced into the negative pole piece, so that the liquid retention capacity can be effectively improved, and the performance of the high-energy density battery cell is improved.)

1. The water-soluble polymer for the negative electrode plate is characterized in that the polymer is a cross-linked product of a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer, the polymer has a network structure, and the polymer has hydrophilic groups.

2. The water-soluble polymer according to claim 1, wherein the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer is a triblock copolymer in which the styrene-acrylic copolymer block is bonded to both ends of the PEO block and the hydrophilic group is bonded to the styrene-acrylic copolymer block.

3. The water-soluble polymer according to claim 1, wherein the hydrophilic group in the polymer comprises one or more of a carboxyl group, an amino group and a hydroxyl group.

4. The water-soluble polymer according to claim 1, wherein the polymer has a carboxyl group, and the content of the carboxyl group is 0.1% to 1.5%.

5. The water-soluble polymer according to claim 1, further comprising a benzene ring, a chloromethyl group, and an amide group, wherein the content of the benzene ring is 3% to 10%, the content of the chloromethyl group is 0.5% to 1%, and the content of the amide group is 0.2% to 0.8%.

6. The water-soluble polymer according to claim 1, wherein the molecular weight of the polymer is 10KDa to 100 KDa.

7. A negative electrode sheet, characterized in that the water-soluble polymer according to claim 1 is contained in the negative electrode sheet.

8. A negative electrode sheet according to claim 7, comprising a negative current collector and a negative active layer coated on at least one side surface of the negative current collector, wherein the negative active layer contains the water-soluble polymer according to claim 1.

9. The negative electrode sheet according to claim 7, wherein the water-soluble polymer accounts for 0.1-0.5% of the mass fraction of the negative active layer.

10. A lithium ion battery, characterized in that the lithium ion battery comprises the negative electrode sheet of any one of claims 7 to 9.

Technical Field

The invention relates to the technical field of batteries, in particular to a water-soluble polymer for a negative plate, a preparation method and the negative plate.

Background

With the development of 5G technology and new energy automobiles, no matter 3C consumer lithium ion batteries or vehicle power lithium ion batteries, higher requirements are provided for the energy density of the lithium ion batteries, in order to meet high energy density, starting from a battery design end, the thickness of a pole piece needs to be increased, and the compaction density of the pole piece is improved.

Disclosure of Invention

In view of the above, the invention provides a water-soluble polymer for a negative plate, a preparation method and the negative plate, which are used for solving the problems of abnormal increase of internal resistance of a battery and early cycle water-jumping failure caused by uneven and insufficient electrolyte infiltration and small electrolyte residue in a high-compaction-density thick-plate battery.

In order to solve the technical problems, the invention adopts the following technical scheme:

in a first aspect, the invention provides a water-soluble polymer for a negative electrode plate, wherein the polymer is a cross-linked product of a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer, the polymer has a network structure, and the polymer has a hydrophilic group.

Further, the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer is a triblock copolymer, wherein the two ends of the PEO block are connected with the styrene-acrylic copolymer block, and the hydrophilic group is connected on the styrene-acrylic copolymer block.

Further, the hydrophilic group in the polymer includes one or more of a carboxyl group, an amino group, and a hydroxyl group.

Furthermore, the polymer has carboxyl, and the content of the carboxyl is 0.1-1.5%.

Further, the polymerization also comprises a benzene ring, chloromethyl and acylamino, wherein the content of the benzene ring is 3-10%, the content of the chloromethyl is 0.5-1%, and the content of the acylamino is 0.2-0.8%.

Further, the molecular weight of the polymer is 10 KDa-100 KDa.

In a second aspect, the present invention provides a process for the preparation of a water-soluble polymer comprising:

adding 5-15 parts of styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer and 0.1-5 parts of cross-linking agent into a first solvent in parts by mole, mixing, and reacting at 80-120 ℃ for 10-20h to obtain a cross-linked substance;

5-15 parts of the cross-linked material, 100 parts of dichloromethane and 150 parts of trifluoroacetic acid are mixed and reacted for 6-10h at room temperature to obtain the water-soluble polymer.

Wherein the cross-linking agent comprises one or more of hydroxyethyl acrylate, divinyl benzene, allylamine, and 1, 4-p-chloromethyl styrene;

the first solvent comprises one or more of toluene, xylene, tetrahydrofuran, chloroform and dimethyl sulfoxide.

Preferably, the water-soluble polymer is further reacted with water and sodium hydroxide to obtain the final product.

The preparation method of the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer comprises the following steps:

adding 3-10 parts of bromine-terminated PEO, 1-4 parts of ligand, 1-3 parts of catalyst and 1-10 parts of monomer into a first solvent in parts by mole, mixing, and reacting at 70-90 ℃ for 8-24h to obtain a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer;

the ligand comprises one or more of 2,2 '-bipyridine, N, N, N' -pentamethyl diethylenetriamine, terpyridine and N, N, N, N-tetramethyl ethylenediamine; the catalyst comprises one or more of cuprous bromide, cuprous chloride, cuprous acetate, ferrous chloride, ferric chloride, cupric bromide and cupric chloride;

the monomer comprises at least one of styrene and p-chloromethyl styrene, and at least one of tert-propyl acrylate, methacrylic acid, methyl methacrylate, n-butyl acrylate, acrylonitrile and acrylamide.

Wherein the preparation method of the bromine-terminated PEO comprises the following steps:

adding 3-15 parts of PEO into a reactor according to molar parts, dissolving in a second solvent to obtain a first mixture, adding 0.5-2 parts of triethylamine and 0.5-2 parts of 2-bromoisobutyryl bromide into the first mixture, reacting at room temperature for 6-48h to obtain a second mixture, filtering and drying to obtain bromine-terminated PEO;

the second solvent comprises one or more of toluene, xylene, tetrahydrofuran, chloroform and dimethyl sulfoxide.

Preferably, the PEO has a molecular weight of 500Da to 4500 Da.

In a third aspect, the invention provides a negative electrode sheet, which contains the above-mentioned water-soluble polymer.

Preferably, the negative plate comprises a negative current collector and a negative active layer, the negative active layer is coated on at least one side surface of the negative current collector, and the negative active layer contains the water-soluble polymer.

Preferably, the water-soluble polymer in the negative plate accounts for 0.1-0.5% of the mass fraction of the negative active layer.

In a fourth aspect, the invention provides a lithium ion battery, and the lithium ion battery comprises the above negative electrode sheet.

The technical scheme of the invention has the following beneficial effects:

the invention provides a water-soluble polymer for a negative electrode plate, which is provided with pores and hydrophilic groups. The water-soluble polymer has good affinity with the electrolyte, can absorb the electrolyte, and can swell moderately without dissolving after absorbing the electrolyte; meanwhile, the water-soluble polymer has enough holes, so that the contact area between the water-soluble polymer and the electrolyte is increased, the electrolyte can be effectively stored, and the liquid retention capacity is improved.

According to the invention, the water-soluble polymer is used as an additive, and is added into the negative electrode slurry in the batching process so as to be introduced into the negative electrode plate, so that the electrolyte wettability of the high-compaction thick electrode plate and the high-energy-density battery cell can be effectively improved, the liquid retention capacity is improved, and the performance of the high-energy-density battery cell is improved.

Drawings

FIG. 1 is a schematic view of the structure of a water-soluble polymer before and after contact with an electrolyte.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention in conjunction with the following examples, but it will be understood that the description is intended to illustrate the features and advantages of the invention further, and not to limit the invention.

In a first aspect, the invention provides a water-soluble polymer for a negative electrode plate, wherein the polymer is a cross-linked product of a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer, the polymer has a network structure, and the polymer has a hydrophilic group. The styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer is a triblock copolymer, wherein the two ends of the PEO block are connected with the styrene-acrylic copolymer block, and the hydrophilic group is connected on the styrene-acrylic copolymer block. That is, the styrene-acrylic copolymer-B-PEO-B-styrene-acrylic copolymer block copolymer is a triblock copolymer, and it can be understood as a BAB structure in which a is a PEO block, B is a styrene-acrylic copolymer block, and a block are linked by a covalent bond.

The water-soluble polymer has good affinity with electrolyte, can absorb the electrolyte, and can swell moderately without dissolving after absorbing the electrolyte; meanwhile, the water-soluble polymer has enough holes, so that the contact area between the water-soluble polymer and the electrolyte is increased, the electrolyte can be effectively stored, and the liquid retention capacity is improved. Fig. 1 is a schematic structural diagram of a water-soluble polymer before and after contacting with an electrolyte, and it can be seen from fig. 1 that the water-soluble polymer of the present invention sufficiently absorbs the electrolyte after contacting with the electrolyte to cause moderate swelling.

According to some embodiments of the invention, the polymer has carboxyl groups in an amount of 0.1% to 1.5%.

Further, the polymerization also comprises a benzene ring, chloromethyl and acylamino, wherein the content of the benzene ring is 3-10%, the content of the chloromethyl is 0.5-1%, and the content of the acylamino is 0.2-0.8%.

Further, the molecular weight of the polymer is 10 KDa-100 KDa.

Further, the polymer is a network structure.

In a second aspect, embodiments of the present disclosure disclose a method for preparing the water-soluble polymer, comprising:

adding 5-15 parts of styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer and 0.1-5 parts of cross-linking agent into a first solvent in parts by mole, mixing, and reacting at 80-120 ℃ for 10-20h to obtain a cross-linked substance;

5-15 parts of the cross-linked material, 100 parts of dichloromethane and 150 parts of trifluoroacetic acid are mixed and reacted for 6-10h at room temperature to obtain the water-soluble polymer.

Wherein the cross-linking agent comprises one or more of hydroxyethyl acrylate, divinyl benzene, allylamine, and 1, 4-p-chloromethyl styrene; the first solvent comprises one or more of toluene, xylene, tetrahydrofuran, chloroform and dimethyl sulfoxide. In the reaction, the cross-linking agent can cross-link long molecular chains in the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer, so that a porous molecular structure is obtained. Changing the amount of the crosslinking agent added will result in a crosslinked product with different crosslinking degrees, but too high or too low a crosslinking degree will affect the properties of the finally prepared water-soluble polymer, and thus the amount of the crosslinking agent added needs to be kept within a proper range. It is well known to those skilled in the art that the negative electrode slurry for preparing the negative electrode of the battery is an aqueous solvent, and therefore, in order to apply the cross-linked product to the negative electrode of the battery, the cross-linked product needs to have hydrophilic characteristics, so that in the preparation process, methylene chloride and trifluoroacetic acid are added to play a role in hydrolyzing the cross-linked product, and a large number of hydrophilic carboxyl groups appear in the molecular structure through hydrolysis reaction, so that a soluble and porous polymer is obtained.

Preferably, the water-soluble polymer is further reacted with water and sodium hydroxide to obtain the final product. Wherein the adding amount of water is 200-500 parts by mole, the adding amount of sodium hydroxide is 2-5 parts by mole, and the mixture is stirred for 8-14 hours at 60 ℃ to obtain a clear and transparent aqueous solution, namely the final product.

In an embodiment of the present invention, the method for preparing the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer comprises:

adding 3-10 parts of bromine-terminated PEO, 1-4 parts of ligand, 1-3 parts of catalyst and 1-10 parts of monomer into a first solvent in parts by mole, mixing, and reacting at 70-90 ℃ for 8-24h to obtain a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer;

the ligand comprises one or more of 2,2 '-bipyridine, N, N, N' -pentamethyl diethylenetriamine, terpyridine and N, N, N, N-tetramethyl ethylenediamine; the catalyst comprises one or more of cuprous bromide, cuprous chloride, cuprous acetate, ferrous chloride, ferric chloride, cupric bromide and cupric chloride;

the monomer comprises at least one of styrene and p-chloromethyl styrene, and at least one of tert-propyl acrylate, methacrylic acid, methyl methacrylate, n-butyl acrylate, acrylonitrile and acrylamide.

Preferably, 3-10 parts of bromine-terminated PEO, 1-4 parts of ligand, 1-3 parts of catalyst and 1-10 parts of monomer are added into a first solvent and mixed, oxygen and water are removed through freeze-thaw cycle, nitrogen is introduced to react for 8-24h at 70-90 ℃, after the reaction is finished, the obtained product is dissolved in a benign solvent, then the benign solvent passes through an aluminum oxide column, and then vacuum drying is carried out, so that the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer is obtained. Wherein, the benign solvent can be one or more of tetrahydrofuran, toluene, xylene and dimethylformamide.

In an embodiment of the invention, a method of making the bromine-capped PEO comprises:

adding 3-15 parts of PEO into a reactor according to molar parts, dissolving in a second solvent to obtain a first mixture, adding 0.5-2 parts of triethylamine and 0.5-2 parts of 2-bromoisobutyryl bromide into the first mixture, reacting at room temperature for 6-48h to obtain a second mixture, filtering and drying to obtain bromine-terminated PEO;

the second solvent comprises one or more of toluene, xylene, tetrahydrofuran, chloroform and dimethyl sulfoxide.

Preferably, the PEO has a molecular weight of 500Da to 4500Da, for example, the PEO may have a molecular weight of one or more of 500Da, 1000Da, 1500Da, 2000Da, 2500Da, and 4500 Da.

Preferably, during the preparation of the bromine-terminated PEO, the reaction is carried out at room temperature for 6-48h, triethylamine hydrobromide is filtered out after the reaction is finished, then the product is precipitated in a poor solvent, filtered and dried in vacuum, and the molecular chain bromine-terminated PEO is obtained. Wherein the poor solvent can be one or more of methanol, ethanol, propanol, benzyl alcohol and ethylene glycol.

The following are given formulas 1 to 4 for understanding the preparation and reaction of the water-soluble polymer in the present invention.

Wherein R1 can be one or more of phenyl, p-chlorophenyl and tert-butyl; r2 can be one or more of methoxyl, amido and tert-butyl; r3 is carboxy.

In a third aspect, the invention provides a negative electrode sheet, which contains the above-mentioned water-soluble polymer. The cathode plate with the water-soluble polymer can effectively improve the electrolyte wettability of a high-compaction thick pole piece and a high-energy-density battery cell, improve the liquid retention capacity and improve the performance of the high-energy-density battery cell.

Preferably, the negative plate comprises a negative current collector and a negative active layer, the negative active layer is coated on at least one side surface of the negative current collector, and the negative active layer contains the water-soluble polymer.

Preferably, the water-soluble polymer in the negative plate accounts for 0.1-0.5% of the mass fraction of the negative active layer.

In a fourth aspect, the invention provides a lithium ion battery, and the lithium ion battery comprises the above negative electrode sheet. According to the invention, the water-soluble polymer is used as an additive, and is added into the negative electrode slurry in the batching process so as to be introduced into the negative electrode plate, so that the electrolyte wettability of the high-compaction thick electrode plate and the high-energy-density battery cell can be effectively improved, the liquid retention capacity is improved, and the performance of the high-energy-density battery cell is improved. Meanwhile, when the water-soluble polymer exists in the negative plate, the water-soluble polymer has good electrochemical stability and does not react with electrolyte.

The invention is further illustrated by the following specific examples.

Example 1

(1) Adding 3 parts of PEO and 100ml of toluene in a reactor by mole parts, removing water in the PEO by azeotropic distillation, cooling the solution to 0 ℃, adding 2 parts of triethylamine and 2 parts of 2-bromoisobutyryl bromide into the reactor, reacting at room temperature for 24 hours, filtering to remove triethylamine hydrobromide after the reaction is finished, precipitating the product in poor solvent methanol, filtering, and drying in vacuum to obtain PEO with molecular chain bromine end capping;

(2) adding 3 parts of bromine-terminated PEO, 1 part of ligand 2,2' -bipyridine, 1 part of cuprous bromide serving as a catalyst, 1 part of styrene serving as a monomer and 1 part of tert-propyl acrylate serving as a monomer into a reactor, adding toluene serving as a solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting for 12 hours at 70 ℃, dissolving the obtained product in tetrahydrofuran serving as a benign solvent after the reaction is finished, passing through an aluminum oxide column, and then performing vacuum drying to obtain a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer;

(3) adding 5 parts of the segmented copolymer obtained in the step (2) and 0.1 part of cross-linking agent allylamine into a reactor in parts by mole, dissolving the segmented copolymer and the cross-linking agent allylamine into a solvent toluene, raising the temperature to 80 ℃, reacting for 20 hours under stirring, and evaporating the solvent after the reaction is finished to obtain a cross-linked porous polymer;

(4) adding 5 parts of the porous polymer obtained in the step (3), 100 parts of dichloromethane and 2 parts of trifluoroacetic acid into a reactor in parts by mole, reacting at room temperature for 10 hours, and evaporating the solvent after the reaction is finished to obtain the water-soluble porous polymer;

(5) and (3) adding the block copolymer obtained in the step (4) into a reactor, adding 200 parts of water, adding 2 parts of sodium hydroxide, and stirring at 60 ℃ for 10 hours to obtain a clear and transparent aqueous solution, so as to obtain the required functional porous block copolymer aqueous solution.

Example 2

(1) Adding 3 parts of PEO and 100ml of toluene in a reactor by mole parts, removing water in the PEO by azeotropic distillation, cooling the solution to 0 ℃, adding 0.5 part of triethylamine and 0.5 part of 2-bromoisobutyryl bromide into the reactor, reacting at room temperature for 24 hours, filtering to remove triethylamine hydrobromide after the reaction is finished, precipitating the product in poor solvent methanol, filtering, and drying in vacuum to obtain PEO with molecular chain bromine blocked;

(2) adding 3 parts of bromine-terminated PEO, 4 parts of ligand 2,2' -bipyridine, 1 part of cuprous bromide as a catalyst, 5 parts of styrene as a monomer and 5 parts of tert-propyl acrylate as a monomer into a reactor, adding toluene as a solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting at 90 ℃ for 12 hours, dissolving the obtained product in tetrahydrofuran as a benign solvent after the reaction is finished, passing through an aluminum oxide column, and then performing vacuum drying to obtain the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer;

(3) adding 5 parts of the segmented copolymer obtained in the step (2) and 5 parts of cross-linking agent allylamine into a reactor in parts by mole, dissolving the segmented copolymer and the cross-linking agent allylamine into a solvent toluene, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent after the reaction is finished to obtain a cross-linked porous polymer;

(4) adding 5 parts of the porous polymer obtained in the step (3), 150 parts of dichloromethane and 15 parts of trifluoroacetic acid into a reactor in parts by mole, reacting at room temperature for 6 hours, and evaporating the solvent after the reaction is finished to obtain the water-soluble porous polymer;

(5) and (3) adding the block copolymer obtained in the step (4) into a reactor, adding 500 parts of water, adding 5 parts of sodium hydroxide, and stirring at 60 ℃ for 10 hours to obtain a clear and transparent aqueous solution, so as to obtain the required functional porous block copolymer aqueous solution.

Example 3

(1) Adding 10 parts of PEO and 200ml of toluene in a reactor by mole parts, removing water in the PEO by azeotropic distillation, cooling the solution to 0 ℃, adding 1 part of triethylamine and 1 part of 2-bromoisobutyryl bromide into the reactor, reacting at room temperature for 24 hours, filtering to remove triethylamine hydrobromide after the reaction is finished, precipitating the product in a poor solvent ethylene glycol, filtering, and drying in vacuum to obtain PEO with molecular chain bromine end capping;

(2) adding 3 parts of bromine-terminated PEO, 3 parts of ligand 2,2' -bipyridine, 1 part of cuprous bromide as a catalyst, 3 parts of styrene as a monomer and 3 parts of tert-propyl acrylate as a monomer into a reactor, adding toluene as a solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting at 90 ℃ for 12 hours, dissolving the obtained product in tetrahydrofuran as a benign solvent after the reaction is finished, passing through an aluminum oxide column, and then performing vacuum drying to obtain the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer;

(3) adding 5 parts of the segmented copolymer obtained in the step (2) and 1 part of cross-linking agent allylamine into a reactor in parts by mole, dissolving the segmented copolymer and the cross-linking agent allylamine into a solvent toluene, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent after the reaction is finished to obtain a cross-linked porous polymer;

(4) adding 5 parts of the porous polymer obtained in the step (3), 100 parts of dichloromethane and 5 parts of trifluoroacetic acid into a reactor in parts by mole, reacting at room temperature for 8 hours, and evaporating the solvent after the reaction is finished to obtain the water-soluble porous polymer;

(5) and (3) adding the block copolymer obtained in the step (4) into a reactor, adding 500 parts of water, adding 5 parts of sodium hydroxide, and stirring at 60 ℃ for 10 hours to obtain a clear and transparent aqueous solution, so as to obtain the required functional porous block copolymer aqueous solution.

Example 4

(1) Adding 15 parts of PEO and 200ml of toluene in a reactor by mole parts, removing water in the PEO by azeotropic distillation, cooling the solution to 0 ℃, adding 0.5 part of triethylamine and 0.5 part of 2-bromoisobutyryl bromide into the reactor, reacting at room temperature for 24 hours, filtering to remove triethylamine hydrobromide after the reaction is finished, precipitating the product in a poor solvent ethylene glycol, filtering, and drying in vacuum to obtain PEO with the molecular chain blocked by bromine;

(2) adding 10 parts of bromine-terminated PEO, 1 part of ligand 2,2' -bipyridine, 1 part of cuprous bromide serving as a catalyst, 1 part of styrene serving as a monomer and 1 part of tert-propyl acrylate serving as a monomer into a reactor, adding toluene serving as a solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting for 12 hours at 90 ℃, dissolving the obtained product in tetrahydrofuran serving as a benign solvent after the reaction is finished, passing through an aluminum oxide column, and then performing vacuum drying to obtain a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer;

(3) adding 5 parts of the segmented copolymer obtained in the step (2) and 1 part of cross-linking agent allylamine into a reactor in parts by mole, dissolving the segmented copolymer and the cross-linking agent allylamine into a solvent toluene, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent after the reaction is finished to obtain a cross-linked porous polymer;

(4) adding 5 parts of the porous polymer obtained in the step (3), 100 parts of dichloromethane and 5 parts of trifluoroacetic acid into a reactor in parts by mole, reacting at room temperature for 8 hours, and evaporating the solvent after the reaction is finished to obtain the water-soluble porous polymer;

(5) and (3) adding the block copolymer obtained in the step (4) into a reactor, adding 500 parts of water, adding 5 parts of sodium hydroxide, and stirring at 60 ℃ for 10 hours to obtain a clear and transparent aqueous solution, so as to obtain the required functional porous block copolymer aqueous solution.

Example 5

(1) Adding 10 parts of PEO and 200ml of toluene in a reactor by mole parts, removing water in the PEO by azeotropic distillation, cooling the solution to 0 ℃, adding 1 part of triethylamine and 1 part of 2-bromoisobutyryl bromide into the reactor, reacting at room temperature for 24 hours, filtering to remove triethylamine hydrobromide after the reaction is finished, precipitating the product in a poor solvent ethylene glycol, filtering, and drying in vacuum to obtain PEO with molecular chain bromine end capping;

(2) adding 3 parts of bromine-terminated PEO, 3 parts of ligand diethylenetriamine, 1 part of catalyst ferric chloride, 3 parts of monomer p-chloromethyl styrene and 3 parts of monomer methacrylic acid into a reactor in terms of molar parts, adding a solvent toluene, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting for 12 hours at 90 ℃, dissolving the obtained product in a benign solvent tetrahydrofuran after the reaction is finished, then passing through an aluminum oxide column, and then carrying out vacuum drying to obtain the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer;

(3) adding 5 parts of the block copolymer obtained in the step (2) and 1 part of cross-linking agent hydroxyethyl acrylate into a reactor in parts by mole, dissolving the mixture in tetrahydrofuran solvent, raising the temperature to 120 ℃, reacting the mixture for 10 hours under stirring, and evaporating the solvent after the reaction is finished to obtain a cross-linked porous polymer;

(4) adding 5 parts of the porous polymer obtained in the step (3), 100 parts of dichloromethane and 5 parts of trifluoroacetic acid into a reactor in parts by mole, reacting at room temperature for 8 hours, and evaporating the solvent after the reaction is finished to obtain the water-soluble porous polymer;

(5) and (3) adding the block copolymer obtained in the step (4) into a reactor, adding 500 parts of water, adding 5 parts of sodium hydroxide, and stirring at 60 ℃ for 10 hours to obtain a clear and transparent aqueous solution, so as to obtain the required functional porous block copolymer aqueous solution.

Example 6

(1) Adding 10 parts of PEO and 200ml of toluene in a reactor by mole parts, removing water in the PEO by azeotropic distillation, cooling the solution to 0 ℃, adding 1 part of triethylamine and 1 part of 2-bromoisobutyryl bromide into the reactor, reacting at room temperature for 24 hours, filtering to remove triethylamine hydrobromide after the reaction is finished, precipitating the product in poor solvent propanol, filtering, and drying in vacuum to obtain PEO with molecular chain bromine end capping;

(2) adding 3 parts of bromine-terminated PEO, 3 parts of ligand N, N, N, N-tetramethylethylenediamine, 1 part of copper bromide catalyst, 3 parts of monomer p-chloromethyl styrene and 3 parts of monomer methacrylic acid into a reactor, adding toluene solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting for 12 hours at 90 ℃, dissolving the obtained product in tetrahydrofuran which is a benign solvent after the reaction is finished, passing through an aluminum oxide column, and then carrying out vacuum drying to obtain the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer;

(3) adding 5 parts of the block copolymer obtained in the step (2) and 1 part of cross-linking agent hydroxyethyl acrylate into a reactor in parts by mole, dissolving the mixture in a solvent dimethyl sulfoxide, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent after the reaction is finished to obtain a cross-linked porous polymer;

(4) adding 5 parts of the porous polymer obtained in the step (3), 100 parts of dichloromethane and 5 parts of trifluoroacetic acid into a reactor in parts by mole, reacting at room temperature for 8 hours, and evaporating the solvent after the reaction is finished to obtain the water-soluble porous polymer;

(5) and (3) adding the block copolymer obtained in the step (4) into a reactor, adding 500 parts of water, adding 5 parts of sodium hydroxide, and stirring at 60 ℃ for 10 hours to obtain a clear and transparent aqueous solution, so as to obtain the required functional porous block copolymer aqueous solution.

Example 7

(1) Adding 10 parts of PEO and 200ml of toluene in a reactor by mole parts, removing water in the PEO by azeotropic distillation, cooling the solution to 0 ℃, adding 1 part of triethylamine and 1 part of 2-bromoisobutyryl bromide into the reactor, reacting at room temperature for 24 hours, filtering to remove triethylamine hydrobromide after the reaction is finished, precipitating the product in poor solvent propanol, filtering, and drying in vacuum to obtain PEO with molecular chain bromine end capping;

(2) adding 3 parts of bromine-terminated PEO, 3 parts of ligand N, N, N, N-tetramethylethylenediamine, 1 part of cuprous chloride catalyst, 3 parts of monomer p-chloromethyl styrene and 3 parts of monomer acrylamide into a reactor, adding toluene solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting for 12 hours at 90 ℃, dissolving the obtained product in dimethyl sulfoxide (benign solvent) after the reaction is finished, passing through an aluminum oxide column, and then carrying out vacuum drying to obtain the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer;

(3) adding 5 parts of the segmented copolymer obtained in the step (2) and 1 part of cross-linking agent hydroxyethyl acrylate into a reactor in parts by mole, dissolving the mixture in chloroform solvent, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent after the reaction is finished to obtain a cross-linked porous polymer;

(4) adding 5 parts of the porous polymer obtained in the step (3), 100 parts of dichloromethane and 5 parts of trifluoroacetic acid into a reactor in parts by mole, reacting at room temperature for 8 hours, and evaporating the solvent after the reaction is finished to obtain the water-soluble porous polymer;

(5) and (3) adding the block copolymer obtained in the step (4) into a reactor, adding 500 parts of water, adding 5 parts of sodium hydroxide, and stirring at 60 ℃ for 10 hours to obtain a clear and transparent aqueous solution, so as to obtain the required functional porous block copolymer aqueous solution.

Example 8

(1) Adding 10 parts of PEO and 200ml of toluene in a reactor by mole parts, removing water in the PEO by azeotropic distillation, cooling the solution to 0 ℃, adding 1 part of triethylamine and 1 part of 2-bromoisobutyryl bromide into the reactor, reacting at room temperature for 24 hours, filtering to remove triethylamine hydrobromide after the reaction is finished, precipitating the product in poor solvent propanol, filtering, and drying in vacuum to obtain PEO with molecular chain bromine end capping;

(2) adding 3 parts of bromine-terminated PEO, 3 parts of ligand N, N, N' -pentamethyldiethylenetriamine, 1 part of cuprous acetate catalyst, 3 parts of monomer styrene and 3 parts of monomer N-butyl acrylate into a reactor, adding toluene solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting for 12 hours at 90 ℃, dissolving the obtained product in dimethyl sulfoxide (benign solvent) after the reaction is finished, passing through an aluminum oxide column, and then carrying out vacuum drying to obtain the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer;

(3) adding 5 parts of the segmented copolymer obtained in the step (2) and 1 part of divinyl benzene serving as a crosslinking agent into a reactor in parts by mole, dissolving the segmented copolymer and the divinyl benzene serving as the crosslinking agent into chloroform serving as a solvent, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent after the reaction is finished to obtain a crosslinked porous polymer;

(4) adding 5 parts of the porous polymer obtained in the step (3), 100 parts of dichloromethane and 5 parts of trifluoroacetic acid into a reactor in parts by mole, reacting at room temperature for 8 hours, and evaporating the solvent after the reaction is finished to obtain the water-soluble porous polymer;

(5) and (3) adding the block copolymer obtained in the step (4) into a reactor, adding 500 parts of water, adding 5 parts of sodium hydroxide, and stirring at 60 ℃ for 10 hours to obtain a clear and transparent aqueous solution, so as to obtain the required functional porous block copolymer aqueous solution.

Performance testing

Structural characterization: the functional porous block copolymer aqueous solution prepared in examples 1 to 8 was characterized by nuclear magnetic hydrogen spectroscopy, and both the benzene ring and the chloromethyl group had corresponding nuclear magnetic hydrogen spectroscopy characteristic peaks.

The content of each group in the functional porous block copolymer prepared in the embodiments 1 to 8 is quantitatively characterized by infrared spectroscopy, wherein the content of the carboxyl group of the key group is 0.1 to 1.5 percent, the content of the benzene ring is 3 to 10 percent, the content of the chloromethyl group is 0.5 to 1 percent, and the content of the amido group is 0.2 to 0.8 percent.

And (3) testing the absorption of the electrolyte of the negative plate:

preparing 1-8 of negative electrode slurry: mixing the negative active material graphite, the SBR binder, the thickener sodium carboxymethyl cellulose and the conductive carbon black, respectively adding the water-soluble polymers prepared in the embodiments 1-8, and stirring at a high speed to obtain a mixture containing the negative active material, wherein the mixture is uniformly dispersed. In the mixture, the solid component contained 94.9 wt% of graphite, 1.5 wt% of sodium carboxymethylcellulose, 1.5 wt% of conductive carbon black, 2 wt% of a binder, and 0.1 wt% of a water-soluble polymer. Deionized water is used as a solvent to prepare cathode active substance slurry, and the solid content of the slurry is 50 wt%.

Preparing 9-16 parts of negative electrode slurry: mixing the negative active material graphite, the SBR binder, the thickener sodium carboxymethyl cellulose and the conductive carbon black, respectively adding the water-soluble polymers prepared in the embodiments 1-8, and stirring at a high speed to obtain a mixture containing the negative active material, wherein the mixture is uniformly dispersed. In the mixture, the solid component contained 94.5 wt% of graphite, 1.5 wt% of sodium carboxymethylcellulose, 1.5 wt% of conductive carbon black, 2 wt% of a binder, and 0.5 wt% of a water-soluble polymer. Deionized water is used as a solvent to prepare cathode active substance slurry, and the solid content of the slurry is 50 wt%.

Preparing negative electrode slurry 17: mixing the negative active material graphite, SBR binder, thickener carboxymethylcellulose sodium and conductive carbon black as a conductive agent, and stirring at a high speed to obtain a mixture containing the negative active material. In the mixture, the solid component contained 95 wt% of graphite, 1.5 wt% of sodium carboxymethyl cellulose, 1.5 wt% of conductive carbon black, and 2 wt% of a binder. Deionized water is used as a solvent to prepare cathode active substance slurry, and the solid content of the slurry is 50 wt%.

And uniformly coating the negative electrode slurry 1-17 on two surfaces of a negative electrode current collector copper foil, drying, and compacting by a roller press to obtain the negative electrode sheet 1-17 with active substances coated on two surfaces, wherein the thickness of the coating on the two surfaces is 130 micrometers.

And (3) liquid absorption amount test: preparing the prepared negative plate into a circular plate with the diameter of 2cm by using a puncher, weighing and recording as m₀Then placing the wafer in electrolyte for 6h, taking out the pole piece, and using the electrodeAbsorbing electrolyte on the surface of the pole piece by dust paper, weighing and recording as m₁The liquid absorption amount is expressed by the liquid absorption rate,% of liquid absorption is (m)₁-m₀)/m₀。

And (3) testing the absorption time of the electrolyte: and (3) dripping 200 mu L of electrolyte on the surface of the pole piece by using a liquid-transferring gun, and simultaneously timing by using a stopwatch to record the time when the electrolyte liquid drop is completely absorbed by the pole piece.

The test results are shown in table 1.

TABLE 1

Compared with the negative plate 17 without the water-soluble polymer, the liquid absorption rate and the liquid absorption time of the negative plates 1-16 with the water-soluble polymer are better than those of the negative plate 17, which shows that the water-soluble polymer can improve the wettability of the electrolyte on the negative plate and can improve the liquid retention capacity of the battery; the liquid absorption amount and the liquid absorption time of the negative plates 9-16 are superior to those of the negative plates 1-8 because the amount of the water-soluble polymer in the negative plates 9-16 is higher than that of the negative plates 1-8; the liquid absorption amount and the liquid absorption time of the negative electrode sheets 1-4 are superior to those of the negative electrode sheets 5-8 due to the structural difference of the water-soluble polymer.

And (3) testing the battery performance:

(1) battery preparation method

Preparing anode slurry: mixing the positive active material lithium cobaltate, the PVDF binder and the conductive carbon black as the conductive agent, and stirring at a high speed to obtain a mixture containing the positive active material, wherein the mixture is uniformly dispersed. In the mixture, the solid component contained 97.5 wt% of lithium cobaltate, 1.5 wt% of PVDF, and 1 wt% of conductive carbon black. The solids content in the slurry was 75 wt%.

And uniformly coating the positive electrode slurry on two surfaces of an aluminum foil of a positive electrode current collector, drying, and compacting by a roller press to obtain the positive electrode plate with active substances coated on two surfaces, wherein the thickness of the coating on the two surfaces is 100 mu m.

The positive plate is matched with the negative plates 1-4, 9-12 and 17, a PE diaphragm with the diameter of 9 mu m is selected, and a series of soft package full cells are obtained by winding, wherein the voltage range is 4.45V-2.8V, and the capacity is 4000 mAh.

(2) Battery performance testing

And (3) testing the cycle performance: 1. standing at 25 +/-2 ℃ for 10 min;

2. 0.2C to 2.8V; standing for 10 min;

3. filling 1C to 4.2V, filling 0.7C and stopping 0.05C;

4. standing at 25 +/-2 ℃ for 10 min;

5. 0.5C to 2.8V; standing for 10 min;

6. charging 1C to 4.2V, charging 0.7C, stopping charging 0.05C, standing for 10 min;

and circulating for 5-6 steps until the capacity retention rate is 80% cut off.

The test results are shown in table 2.

TABLE 2

Negative plate	Capacity retention ratio/%)
		Negative plate 1	85.7％
Negative plate 2	84.8％
		Negative plate 3	86.1％
Negative plate 4	85.5％
		Negative plate 9	82.3％
Negative electrode sheet 10	81.4％
		Negative plate 11	82.4％
Negative electrode sheet 12	81.2％
		Negative electrode sheet 17	78.5％

Note: the capacity retention rate was after 500 weeks of cycling.

As can be seen from the data in table 2, the negative electrode tabs 1 to 4, 9 to 12 are superior to the negative electrode tab 17 in capacity retention rate.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships are changed accordingly.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.