阅读说明：本技术 一种用于正极片的脂溶性聚合物、制备方法和正极片 (Fat-soluble polymer for positive plate, preparation method and positive 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正极片的脂溶性聚合物、制备方法和正极片,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,所述聚合物具有网络结构,且所述聚合物中具有亲油基团。该脂溶性聚合物是将苯丙共聚物-b-PEO-b-苯丙共聚物三嵌段共聚物与交联剂进行交联得到的。本发明中的脂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；同时所述脂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。通过将脂溶性聚合物作为添加剂引入到正极片中,可有效改善高压实厚极片、高能量密度电芯的电解液浸润性,提升保液量,提升高能量密度电芯的性能。(The invention provides a fat-soluble polymer for a positive plate, a preparation method and the positive 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 lipophilic groups. The liposoluble polymer is obtained by crosslinking a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer triblock copolymer with a crosslinking agent. The fat-soluble polymer has good affinity with the electrolyte, can absorb the electrolyte, and can swell moderately without dissolving after absorbing the electrolyte; meanwhile, the fat-soluble polymer has enough pores, so that the contact area between the polymer and the electrolyte is increased, the electrolyte can be effectively stored, and the liquid retention capacity is improved. The electrolyte wettability of the high-compaction thick pole piece and the high-energy-density battery cell can be effectively improved by introducing the fat-soluble polymer into the positive pole piece as an additive, so that the liquid retention capacity is improved, and the performance of the high-energy-density battery cell is improved.)

1. The fat-soluble polymer for the positive electrode sheet 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 lipophilic groups are arranged in the polymer.

2. The fat-soluble polymer as claimed in 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 attached to both ends of the PEO block and the lipophilic group is attached to the styrene-acrylic copolymer block.

3. The liposoluble polymer according to claim 1, wherein the lipophilic groups of the polymer comprise one or more of benzene ring, chloromethyl, methoxy, nitrile group.

4. The fat-soluble polymer according to claim 1, wherein the polymer comprises benzene rings, chloromethyl groups and nitrile groups, the content of the benzene rings is 2% -10%, the content of the chloromethyl groups is 0.3% -1.8%, and the content of the nitrile groups is 0.1% -0.5%.

5. The liposoluble polymer according to claim 1, characterized in that the molecular weight of the polymer is between 10 and 100 kDa.

6. The fat-soluble polymer according to claim 1, wherein the polymer is a cross-linked product obtained by reacting a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer with a cross-linking agent, wherein the cross-linking agent comprises one or more of hydroxyethyl acrylate, divinyl benzene, allylamine, and 1, 4-p-chloromethyl styrene.

7. A positive electrode sheet characterized by containing the fat-soluble polymer according to claim 1.

8. The positive electrode sheet according to claim 7, comprising a positive current collector and a positive active layer coated on at least one surface of the positive current collector, wherein the positive active layer contains the liposoluble polymer according to claim 1.

9. The positive electrode sheet according to claim 7, wherein the liposoluble polymer accounts for 0.1 to 0.5% of the mass fraction of the positive active layer.

10. A lithium ion battery comprising the positive electrode sheet according to any one of claims 7 to 9.

Technical Field

The invention relates to the technical field of batteries, in particular to a fat-soluble polymer for a positive plate, a preparation method and the positive 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 liposoluble polymer for a positive plate, a preparation method and the positive 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 liposoluble polymer for a positive electrode sheet, 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 lipophilic groups.

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 lipophilic group is connected on the styrene-acrylic copolymer block.

Further, the lipophilic group in the polymer comprises one or more of benzene ring, chloromethyl, methoxyl and nitrile group.

Further, the polymer comprises a benzene ring, chloromethyl and nitrile group, wherein the content of the benzene ring is 2-10%, the content of the chloromethyl is 0.3-1.8%, and the content of the nitrile group is 0.1-0.5%.

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

Further, the polymer is a cross-linked product obtained by reacting a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer with a cross-linking agent, wherein the cross-linking agent comprises one or more of hydroxyethyl acrylate, divinyl benzene, allylamine and 1, 4-p-chloromethyl styrene.

In a second aspect, the present invention provides a preparation method of the liposoluble polymer for the positive electrode sheet, including:

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 the liposoluble polymer;

or adding 5-15 parts of styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer into a first solvent in parts by mole, stirring for 5-10 hours to obtain a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer solution, adding the solution into the positive electrode slurry, adding 0.1-5 parts of a cross-linking agent, and coating and baking to obtain the liposoluble 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.

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 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 present invention provides a positive electrode sheet containing the above-described liposoluble polymer.

Preferably, the positive active layer comprises a positive current collector and a positive active layer, wherein the positive active layer is coated on at least one side surface of the positive current collector, and the positive active layer contains the liposoluble polymer.

Preferably, the liposoluble polymer in the positive electrode sheet accounts for 0.1-0.5% of the mass fraction of the positive active layer.

In a fourth aspect, the invention provides a lithium ion battery, which includes the above positive plate.

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

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

According to the invention, the fat-soluble polymer is introduced into the positive plate as an additive, so that the electrolyte wettability of the high-compaction thick 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 showing the state of a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer in a solvent and after crosslinking.

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.

The embodiment of the invention discloses a fat-soluble polymer for a positive plate, wherein the polymer is a cross-linked product of a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer, has a network structure, and has lipophilic groups. 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 lipophilic group is connected on the styrene-acrylic copolymer block. The fat-soluble polymer has good affinity with the electrolyte, can absorb the electrolyte, and can swell moderately without dissolving after absorbing the electrolyte; meanwhile, the fat-soluble polymer has enough pores, so that the contact area between the polymer and the electrolyte is increased, the electrolyte can be effectively stored, and the liquid retention capacity is improved.

Further, the lipophilic group in the polymer comprises one or more of benzene ring, chloromethyl, methoxyl and nitrile group.

Furthermore, the polymer comprises benzene ring, chloromethyl and nitrile group, wherein the content of the benzene ring is 2-10%, the content of the chloromethyl is 0.3-1.8%, and the content of the nitrile group is 0.1-0.5%.

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

Further, the polymer is a cross-linked product obtained by reacting a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer with a cross-linking agent, wherein the cross-linking agent comprises one or more of hydroxyethyl acrylate, divinyl benzene, allylamine and 1, 4-p-chloromethyl styrene.

The embodiment of the invention discloses a preparation method of a fat-soluble polymer for a positive plate, which comprises the following steps:

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 the liposoluble polymer;

or adding 5-15 parts of styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer into a first solvent in parts by mole, stirring for 5-10 hours to obtain a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer solution, adding the solution into the positive electrode slurry, adding 0.1-5 parts of a cross-linking agent, and coating and baking to obtain the liposoluble 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.

The first method is to directly mix the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer and a cross-linking agent in a solvent, heat up for cross-linking reaction to obtain a fat-soluble polymer, and then add the fat-soluble polymer obtained by the reaction as an additive into the positive electrode slurry to obtain the positive electrode sheet with the fat-soluble polymer in the positive active layer. And secondly, dissolving the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer in a solvent, adding the solution into positive electrode slurry, adding a cross-linking agent into the positive electrode slurry, coating the positive electrode slurry, and baking to obtain the positive electrode sheet with the positive active layer containing the liposoluble polymer. 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 addition amount of the cross-linking agent can obtain cross-linked products with different cross-linking degrees, but too high or too low cross-linking degree can affect the properties of the finally prepared fat-soluble polymer, so the addition amount of the cross-linking agent needs to be kept in a proper range. FIG. 1 shows a schematic view of the state of a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer block copolymer in a solvent and after crosslinking.

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 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.

Formulas 1 to 3 are given below for understanding the preparation and reaction of the fat-soluble polymerization in the present invention.

Wherein, R1 can be one of phenyl and p-chlorophenyl, and R2 can be one or more of methoxyl, amide and nitrile.

In a third aspect, the present invention provides a positive electrode sheet containing the above-described liposoluble polymer. The positive plate with the liposoluble 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 positive electrode sheet comprises a positive current collector and a positive active layer, the positive active layer is coated on at least one side surface of the positive current collector, and the positive active layer contains the liposoluble polymer.

Preferably, the liposoluble polymer in the positive electrode sheet accounts for 0.1-0.5% of the mass fraction of the positive active layer.

In a fourth aspect, the invention provides a lithium ion battery, which includes the above positive plate. According to the invention, the fat-soluble polymer is introduced into the positive plate as an additive, so that the electrolyte wettability of the high-compaction thick 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 fat-soluble polymer exists in the positive plate, the fat-soluble polymer has good electrochemical stability and does not generate chemical reaction 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 catalyst, 1 part of styrene monomer and 1 part of methacrylic acid monomer into a reactor in terms of molar parts, adding toluene solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting for 12 hours at 70 ℃, dissolving the obtained product in tetrahydrofuran which is 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 block copolymer obtained in the step (2) into a reactor according to the molar parts, adding a solvent toluene, stirring for 5 hours, and fully dissolving to obtain a styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer solution;

(4) preparing a positive plate: and (3) mixing a positive electrode active substance lithium cobaltate, a PVDF (polyvinylidene fluoride) binder and conductive carbon black serving as a conductive agent, and adding the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer solution prepared in the step (3) and allyl amine serving as a crosslinking agent into the mixture. And stirring at high speed to obtain a mixture containing the positive active material. In the mixture, the solid component contained 96 wt% of lithium cobaltate, 1.5 wt% of PVDF, 2 wt% of conductive carbon black, and 0.5 wt% of a block copolymer. The addition amount of the block copolymer is 5 parts by mole, and the addition amount of the cross-linking agent allylamine is 0.1 part by mole. The solids content in the slurry was 75 wt%.

And (3) 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 containing the fat-soluble polymer, wherein the thickness of the coating on the two surfaces is 100 mu m, and the positive electrode plate is counted as a positive electrode plate 1.

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 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 catalyst, 1 part of styrene monomer and 1 part of methacrylic acid monomer into a reactor in terms of molar parts, adding toluene solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting for 12 hours at 70 ℃, dissolving the obtained product in tetrahydrofuran which is 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), 0.1 part of cross-linking agent allylamine and a solvent methylbenzene into a reactor in parts by mole, uniformly mixing, raising the temperature to 80 ℃, reacting for 20 hours under stirring, and evaporating the solvent after the reaction is finished to obtain the liposoluble polymer.

Example 3

(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 catalyst, 5 parts of styrene monomer and 5 parts of methacrylic acid monomer into a reactor, adding toluene solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting at 90 ℃ for 12 hours, dissolving the obtained product in tetrahydrofuran which is 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) and (3) adding 5 parts of the block copolymer obtained in the step (2), 5 parts of cross-linking agent allylamine and solvent methylbenzene into a reactor in parts by mole, uniformly mixing, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent to dryness after the reaction is finished to obtain the liposoluble polymer.

Example 4

(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 catalyst, 3 parts of styrene monomer and 3 parts of methacrylic acid monomer into a reactor, adding toluene solvent, removing oxygen and water by freeze-thaw cycle, introducing nitrogen, reacting at 90 ℃ for 12 hours, dissolving the obtained product in tetrahydrofuran which is 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) and (3) adding 5 parts of the block copolymer obtained in the step (2), 1 part of cross-linking agent allylamine and a solvent methylbenzene into a reactor in parts by mole, uniformly mixing, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent to dryness after the reaction is finished to obtain the liposoluble polymer.

Example 5

(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 methanol, filtering, and drying in vacuum to obtain PEO with the molecular chain bromine blocked;

(2) adding 10 parts of bromine-terminated PEO, 1 part of ligand 2,2' -bipyridine, 1 part of cuprous bromide catalyst, 1 part of styrene monomer and 1 part of methacrylic acid monomer into a reactor in terms of molar parts, 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 performing vacuum drying to obtain the styrene-acrylic copolymer-b-PEO-b-styrene-acrylic copolymer type block copolymer;

(3) and (3) adding 5 parts of the block copolymer obtained in the step (2), 1 part of cross-linking agent allylamine and a solvent methylbenzene into a reactor in parts by mole, uniformly mixing, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent to dryness after the reaction is finished to obtain the liposoluble polymer.

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 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 methyl methacrylate into a reactor in 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) and (3) adding 5 parts of the block copolymer obtained in the step (2), 1 part of cross-linking agent hydroxyethyl acrylate and a solvent methylbenzene into a reactor in parts by mole, uniformly mixing, raising the temperature to 120 ℃, reacting for 10 hours under stirring, finishing the reaction, and evaporating the solvent to dryness to obtain the liposoluble polymer.

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 copper bromide catalyst, 3 parts of monomer p-chloromethyl 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 a benign solvent tetrahydrofuran 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) and (3) adding 5 parts of the block copolymer obtained in the step (2), 1 part of cross-linking agent hydroxyethyl acrylate and a solvent methylbenzene into a reactor in parts by mole, uniformly mixing, raising the temperature to 120 ℃, reacting for 10 hours under stirring, finishing the reaction, and evaporating the solvent to dryness to obtain the liposoluble polymer.

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, 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) and (3) adding 5 parts of the block copolymer obtained in the step (2), 1 part of cross-linking agent hydroxyethyl acrylate and a solvent methylbenzene into a reactor in parts by mole, uniformly mixing, raising the temperature to 120 ℃, reacting for 10 hours under stirring, finishing the reaction, and evaporating the solvent to dryness to obtain the liposoluble polymer.

Example 9

(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) and (3) adding 5 parts of the block copolymer obtained in the step (2), 1 part of divinyl benzene serving as a crosslinking agent and methylbenzene serving as a solvent into a reactor in parts by mole, uniformly mixing, raising the temperature to 120 ℃, reacting for 10 hours under stirring, and evaporating the solvent after the reaction is finished to obtain the liposoluble polymer.

Example 10

Preparing a positive plate 2-9: mixing the positive active material lithium cobaltate, the PVDF binder and the conductive carbon black as the conductive agent, respectively adding the liposoluble polymers prepared in the embodiments 2-9, and stirring at high speed to obtain a mixture containing the positive active material. In the mixture, the solid component contained 96 wt% of lithium cobaltate, 1.5 wt% of PVDF, 2 wt% of conductive carbon black, and 0.5 wt% of a fat-soluble polymer. The solids content in the slurry was 75 wt%.

And (3) 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 containing the fat-soluble polymer, wherein the thickness of the coating on the two surfaces is 100 mu m, and the positive electrode plate is 2-9.

Example 11

Preparing a positive plate 10-17: mixing the positive active material lithium cobaltate, the PVDF binder and the conductive carbon black as the conductive agent, respectively adding the liposoluble polymers prepared in the embodiments 2-9, and stirring at high speed to obtain a mixture containing the positive active material. In the mixture, the solid component contained 96.4 wt% of lithium cobaltate, 1.5 wt% of PVDF, 2 wt% of conductive carbon black, and 0.1 wt% of a fat-soluble polymer. 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 containing the fat-soluble polymer, wherein the thickness of the coating on the two surfaces is 100 mu m, and the positive electrode plate is counted as 10-17.

Comparative example 1

Preparing a positive plate 18: 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 96.5 wt% of lithium cobaltate, 1.5 wt% of PVDF, and 2 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 a positive electrode plate, wherein the thickness of the coating on the two surfaces is 100 mu m, and the positive electrode plate is counted as 18.

Performance testing

Structural characterization: the functional porous block copolymer aqueous solution prepared in examples 1 to 9 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 infrared spectrum is utilized to quantitatively characterize the content of each group in the functional porous block copolymer prepared in the embodiment 1-9, wherein the content of a key group, namely a benzene ring is 2-10%, the content of chloromethyl is 0.3-1.8%, and the content of nitrile group is 0.1-0.5%.

Electrolyte absorption test of the positive plate:

and (3) liquid absorption amount test: preparing the prepared positive plate 1-18 into a wafer with the diameter of 2cm by using a puncher, weighing, and recording as m₀Then subjecting the wafer to electrolysisTaking out the pole piece after 6h in the solution, absorbing the electrolyte on the surface of the pole piece by using dust-free 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 positive plate 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.

TABLE 1

As can be seen from table 1, compared with the positive plate 18 without adding the liposoluble polymer, the positive plate 1-17 with the liposoluble polymer added has a liquid absorption rate and a liquid absorption time superior to those of the positive plate 18, which indicates that the liposoluble polymer can improve the wettability of the electrolyte to the positive plate and the liquid retention capacity of the battery; the liquid absorption amount and the liquid absorption time of the positive plate 1 and the positive plate 2 are equivalent, which shows that the two preparation methods can achieve the same effect; the liquid absorption amount and the liquid absorption time of the positive plate 2-9 are superior to those of the positive plate 10-17, because the amount of the fat-soluble polymer in the positive plate 2-9 is higher than that of the positive plate 10-7; the liquid absorption amount and the liquid absorption time of the positive electrode sheets 2-5 are superior to those of the positive electrode sheets 6-9, which are caused by the structural difference of the liposoluble polymers.

And (3) testing the battery performance:

(1) battery preparation method

Preparing anode slurry: 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 on two surfaces of a copper foil of a negative electrode current collector, drying, and compacting by a roller press to obtain the negative electrode plate with the active material coated on two surfaces, wherein the thickness of the coating on the two surfaces is 130 mu m.

The negative plate is matched with the positive plate by 1-5, 10-13 and 18, 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

Positive plate	Capacity retention ratio/%)
		Positive plate 1	86.7％
Positive plate 2	87.6％
		Positive plate 3	88.1％
Positive plate 4	85.4％
		Positive plate 5	81.8％
Positive electrode plate 10	82.1％
		Positive plate 11	81.4％
Positive electrode plate 12	83.2％
		Positive plate 13	84.1％
Positive plate 18	75.1％

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

As can be seen from the data in Table 2, the positive electrode sheets 1 to 5 and 10 to 13 are superior to the positive electrode sheet 18 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.