CN114573812B

CN114573812B - Adhesive for lithium ion battery and preparation method thereof

Info

Publication number: CN114573812B
Application number: CN202011587447.5A
Authority: CN
Inventors: 路广明; 钱超; 周竹欣; 王路海; 张倡; 刘博�; 岳敏; 张艺
Original assignee: Shenzhen Yanyi New Materials Co Ltd
Current assignee: Shenzhen Yanyi New Materials Co Ltd
Priority date: 2020-12-29
Filing date: 2020-12-29
Publication date: 2023-06-09
Anticipated expiration: 2040-12-29
Also published as: CN114573812A

Abstract

The invention relates to a binder for a lithium ion battery, which is characterized by comprising a polyamide imide compound, wherein the polyamide imide compound has a structure shown as a general formula I, and R is as follows ¹ And R is ² Respectively an alkylene or divalent aryl group; n is an integer of 20-100, preferably 39-82; ar and Ar' are each a 4-valent aromatic group; ar and Ar' may be the same or different. The invention also relates to a preparation method of the binder for the lithium ion battery, and the binder for the lithium ion battery is prepared by the preparation method. In addition, the invention relates to the application of the binder for the lithium ion battery or the binder for the lithium ion battery prepared by the preparation method as the binder for the positive electrode plate of the lithium ion battery and the binder for the edge coating of the positive electrode plate.

Description

Adhesive for lithium ion battery and preparation method thereof

Technical Field

The invention belongs to the field of lithium ion batteries, and particularly relates to a binder for a lithium ion battery and a preparation method thereof.

Background

With the acceleration of the application of lithium ion batteries in power, particularly the strong popularization of power batteries for automobiles, the country has continuously come out of a series of policies to encourage scientific research institutions and enterprises to strive to promote the rapid development of clean energy. Among many clean energy sources, lithium ion batteries are widely used due to the characteristics of high energy density, high working voltage, high safety coefficient, light weight, no pollution and the like, and particularly, the application in the automobile industry is steadily advancing.

The lithium ion battery inevitably has defects such as strip-splitting burrs and the like in the pole piece cutting process, and the burrs are easy to pierce through a diaphragm to cause short circuit of the anode and the cathode, so that potential safety hazards are generated, and the safety performance of the battery is often improved by coating an insulating layer on the edge of the pole piece when the power lithium battery is prepared.

With the continuous acceleration of the application of lithium ion batteries, the following safety performance of the lithium ion batteries is attracting attention. In order to improve the safety performance of the battery and prevent the negative electrode from contacting with the positive electrode, a layer of high-insulation material is added to the foil at the edge of the pole piece at present, so that the positive electrode aluminum foil is ensured not to contact with a negative electrode material area, or the negative electrode foil and the material area are ensured not to contact with the positive electrode foil. The most common practice is to size a proportion of binder with an electroless filler such as boehmite or aluminum oxide followed by coating, where peel strength after soaking such edge coating layer in electrolyte is of particular concern.

The types of binders for lithium batteries are numerous. Currently, the binder used for coating the positive electrode edge of a lithium ion battery is generally a high molecular compound, and the binder commonly used is mainly polyvinylidene fluoride (PVDF). However, researchers have shown that as the time of use increases, the immersion time of the pole piece in the electrolyte increases, and the insulating coating made of PVDF gradually drops off, thus failing to achieve long-lasting safety barrier properties. In addition, since PVDF has a large crystallinity, a difference in shrinkage ratio between the PVDF binder and the current collector is relatively large, and thus stress in the electrode increases as PVDF crystallinity increases. In the use process, the internal stress of the electrode leads the insulating layer to be partially or completely stripped from the current collector along with the time, so that short circuit is easy to be caused, and safety accidents are caused.

The PVDF is used as a binder for lithium ion batteries, and the moisture content needs to be strictly controlled in the slurry mixing process, because free amine exists in an N-methylpyrrolidone (NMP) solvent used in the slurry mixing process, the pH value of a system is increased after the NMP solvent absorbs water, and then alkaline groups attack adjacent C-F, C-H bonds in PVDF molecular chains, so that elimination reaction occurs, partial double bonds are generated in the PVDF molecular chains, the viscosity of a slurry system is increased, gel state is generated when the viscosity of the slurry system is severe, and coating difficulty is caused.

Therefore, there is an urgent need to develop a new binder for lithium ion batteries, which has excellent slurry stability, allows no gel state to appear when placed for a long time, and can greatly improve the peel strength of the edge insulating layer of the pole piece of the lithium ion battery, thereby improving the electrolyte resistance of the insulating layer and further improving the cycle performance such as the capacity retention rate of the battery.

Disclosure of Invention

The invention aims to overcome the defects and the shortcomings of the prior art and provide an adhesive for a lithium ion battery.

Specifically, the invention provides the following technical scheme.

A binder for a lithium ion battery, comprising a polyamideimide compound having a structure represented by general formula I:

Wherein,,

R ¹ and R is ² Respectively an alkylene or divalent aryl group;

n is an integer of 20-100, preferably 39-82;

ar and Ar' are each a 4-valent aromatic group, for example, one of the following structural formulas:

wherein R is ³ O, S is carbonyl, sulfonyl, sulfinyl, alkylene, alkyleneoxy alkylene, alkylenethio alkylene, alkylenecarbonyl, alkylenecarbonylalkylene, alkylenesulfonyl alkylene, alkylenesulfinyl or alkylenesulfinyl alkylene, preferably O or carbonyl;

ar and Ar' may be the same or different.

The preparation method of the binder for the lithium ion battery comprises the following steps:

in the first step, a dianhydride and a compound containing an amino group and a carboxyl group are dissolved in an organic solvent to obtain a reaction mixture, the reaction mixture is subjected to dehydration condensation to prepare an imide diacid monomer,

a second step of dissolving dianhydride and diamine in an organic solvent to obtain a reaction mixture, dehydrating-condensing the reaction mixture to prepare an imide diamine monomer,

thirdly, dissolving an imide diacid monomer, an imide diamine monomer and a catalyst in an organic solvent to obtain a reaction mixture, and carrying out dehydration polycondensation reaction on the reaction mixture to obtain the polyamide imide.

The beneficial effects obtained by the invention are as follows:

the invention provides a polyamide imide binder (abbreviated as PI binder) for a high molecular weight lithium ion battery, which improves the phenomena that the traditional PVDF binder is subjected to HF removal in water environment and is easy to cause gelation, reduces the consumption of the binder, improves the specific discharge capacity, specific charge capacity, first coulombic efficiency (abbreviated as first effect) and cycle performance of the battery, and greatly improves the peeling strength of an insulating layer at the edge of a pole piece of the lithium ion battery, thereby improving the electrolyte resistance of the insulating layer.

The PI binder for the lithium ion battery does not contain fluorine elements, does not generate elimination reaction in an NMP system, does not generate gel state after being placed for a long time, and has excellent slurry stability.

The PI binder for the lithium ion battery is in a solution state, does not need to be dissolved when in use, and improves the production efficiency.

The PI binder for lithium ion batteries of the present invention has excellent thermal stability with a decomposition temperature >400 ℃, as shown in fig. 3. The PI binder for lithium ion batteries of the present invention has stable electrochemical performance in a voltage range of 0 to 5V, as shown in fig. 4 and 5.

The PI binder can be used for lithium ion batteries, and can be used as a positive pole piece binder of the lithium ion batteries and a binder for coating edges of the positive pole piece.

Drawings

Fig. 1 shows the stability curves of the PI binder of example 1 and the edge coating slurry (solids content 35%) prepared from the binder and boehmite (model BG 613), with the time of rest (h) on the abscissa and the rotational viscosity (cP) on the ordinate.

Fig. 2 shows the change in peel strength of the edge coating layer on the aluminum foil in example 1, with the abscissa being the spline number and the ordinate being the peel strength (N/m).

Fig. 3 shows a thermogravimetric profile of the PI binder of example 1, with temperature (c) on the abscissa and mass% on the ordinate.

FIG. 4 shows the current-potential curve (CV curve) of the PI adhesive of example 1 in the low voltage range (0V-2.5V), with the ordinate being the current (A/cm ² ) The abscissa is the potential (V).

FIG. 5 shows the current-potential curve (CV curve) of the PI adhesive of example 1 in the working voltage range (2.5V-4.9V), with the ordinate being the current (A/cm ² ) The abscissa is the potential (V).

Fig. 6 shows the stability curves of the PI binder of example 2 and the edge coating slurry (solid content 35%) prepared from the binder and boehmite (model BG 613), with the time of rest (h) on the abscissa and the rotational viscosity (cP) on the ordinate.

Fig. 7 shows the change in peel strength of the edge coating layer on the aluminum foil in example 2, with spline numbers on the abscissa and peel strength (N/m) on the ordinate.

Fig. 8 shows the stability curves of the PI binder of example 3 and the edge coating slurry (solid content 35%) prepared from the binder and boehmite (model BG 613), with the time of rest (h) on the abscissa and the rotational viscosity (cP) on the ordinate.

Fig. 9 shows the change in peel strength of the edge coating layer on the aluminum foil in example 3, with the abscissa being the spline number and the ordinate being the peel strength (N/m).

Fig. 10 shows the stability curves of PVDF900 binder cement and its edge coating slurry (35% solids) of comparative example 1, with the rest time (h) on the abscissa and the rotational viscosity (cP) on the ordinate.

Fig. 11 shows the change in peel strength of the edge coating layer on the aluminum foil in comparative example 1, with spline numbers on the abscissa and peel strength (N/m) on the ordinate.

Detailed Description

As described above, the present invention provides a binder for lithium ion batteries, comprising a polyamideimide compound having a structure represented by general formula I:

wherein,,

R ¹ and R is ² Respectively an alkylene or divalent aryl group;

n is an integer of 20-100, preferably 39-82;

ar and Ar' may be the same or different.

In a preferred embodiment of the invention, the alkylene group has 1 to 15 carbon atoms, preferably 2 to 10 carbon atoms; for example, one or a combination of two or more of methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene.

In a preferred embodiment of the invention, the divalent aryl radical has 6 to 18 carbon atoms, preferably 6 to 12 carbon atoms; it is, for example, phenylene, biphenylene or phenylene ether, a radical.

In a preferred embodiment of the present invention, the attachment position of the 4-valent aromatic group is not particularly limited, and is preferably para, for example, 1, 2 and 4, 5 or Ph-R of the benzene ring ³ -the 3, 4 or 4, 5 positions of the two benzene rings in Ph.

In a preferred embodiment of the invention, the rotational viscosity of the binder for lithium ion batteries is 1500-20000cP, preferably 1800-20000cP.

In a preferred embodiment of the present invention, the weight average molecular weight of the binder for lithium ion batteries is not particularly limited, and is preferably 20,000 to 120,000, preferably 40,000 to 100,000, more preferably 42,000 to 96,000.

The invention also provides a preparation method of the binder for the lithium ion battery, which comprises the following steps:

In a preferred embodiment of the invention, the dianhydride in the first step and the dianhydride in the second step may be the same or different, preferably the same.

In a preferred embodiment of the invention, in the first step, the dianhydride is

Preferably 1,2,4, 5-benzene tetracarboxylic dianhydride, 3', 4' -diphenyl ether tetracarboxylic dianhydride, 3', 4' -benzophenone tetracarboxylic dianhydride, 3',4,4' -diphenylmethane tetracarboxylic dianhydride or 3,3', 4' -diphenyl sulfone tetracarboxylic dianhydride. />

In a preferred embodiment of the invention, in the second step, the dianhydride is

Preferably 1,2,4, 5-benzene tetracarboxylic dianhydride, 3', 4' -diphenyl ether tetracarboxylic dianhydride, 3', 4' -benzophenone tetracarboxylic dianhydride, 3',4,4' -diphenylmethane tetracarboxylic dianhydride or 3,3', 4' -diphenyl sulfone tetracarboxylic dianhydride.

In a preferred embodiment of the invention, in the first step, the compound containing amino and carboxyl groups is HOOC-R ² -NH ₂ Wherein the compound is preferably one or more than two of aminoundecanoic acid, aminodecanoic acid, aminononanoic acid, aminooctanoic acid, aminoheptanoic acid, aminocaproic acid, aminovaleric acid, aminobutyric acid, aminopropionic acid, aminobenzoic acid or aminodiphenic acid;

In a preferred embodiment of the invention, in the second step, the diamineIs H ₂ N-R ¹ -NH ₂ Wherein the diamine is preferably one or more than two of decanediamine, nonanediamine, octanediamine, heptanediamine, hexanediamine, pentanediamine, butanediamine, propanediamine, ethylenediamine, p-phenylenediamine, m-phenylenediamine, biphenyldiamine or diaminodiphenyl ether.

In a preferred embodiment of the invention, in the second step, the diamine is H ₂ N-R ¹ -NH ₂ Wherein the diamine is preferably one or more of 1, 10-decanediamine, 1, 9-nonanediamine, 1, 8-octanediamine, 1, 7-heptanediamine, 1, 6-hexanediamine, 1, 5-pentanediamine, 1, 4-butanediamine, 1, 3-propanediamine, ethylenediamine, p-phenylenediamine, m-phenylenediamine, 4 '-biphenyldiamine, or 4,4' -diaminodiphenyl ether.

In a preferred embodiment of the invention, in the first step the molar ratio of the dianhydride to the amino-and carboxyl-containing compound is from 1:2 to 1:2.2, preferably 1:2.1.

In a preferred embodiment of the invention, in the first step the solids content of the reaction mixture is from 30% to 60%, preferably from 30% to 45%.

In a preferred embodiment of the present invention, in the first step, the organic solvent is a mixed solvent of glacial acetic acid and pyridine.

In a preferred embodiment of the present invention, in the first step, the solid content of the reaction mixture is adjusted by using a mixed solvent of glacial acetic acid and pyridine, and the weight ratio of pyridine in the mixed solvent is not particularly limited as long as the mixed solvent can adjust the solid content of the reaction mixture to 30% to 60%. Preferably, the weight proportion of pyridine in the mixed solvent is 8-15%.

In a preferred embodiment of the present invention, in the first step, the reaction temperature of the dehydration condensation reaction is 100 to 130℃and preferably 120 ℃.

In a preferred embodiment of the invention, in the first step, the reaction time is from 4 to 16 hours, preferably from 6 to 10 hours.

In a preferred embodiment of the invention, in the second step, the diamine is an aliphatic diamine or an aromatic diamine.

In a preferred embodiment of the invention, in the second step, the molar ratio of the dianhydride to the aliphatic diamine or the aromatic diamine is from 1:2 to 1:2.2, preferably 1:2.1.

In a preferred embodiment of the invention, in the second step the solid content of the reaction mixture is 30% to 60%, preferably 30% to 45%.

In a preferred embodiment of the present invention, in the second step, the organic solvent is a mixed solvent of glacial acetic acid and pyridine.

In a preferred embodiment of the present invention, in the second step, the solid content of the reaction mixture is adjusted by using a mixed solvent of glacial acetic acid and pyridine, and the weight ratio of pyridine in the mixed solvent is not particularly limited as long as the mixed solvent can adjust the solid content of the reaction mixture to 30% to 60%. Preferably, the weight proportion of pyridine in the mixed solvent is 8-15%.

In a preferred embodiment of the present invention, in the second step, the reaction temperature of the dehydration condensation reaction is 100 to 130℃and preferably 120 ℃.

In a preferred embodiment of the invention, in the second step, the reaction time is from 4 to 16 hours, preferably from 6 to 10 hours.

In a preferred embodiment of the invention, in the third step, the molar ratio of the imide diacid monomer to the imide diamine monomer is from 1:1 to 1:1.1, preferably 1:1.02;

in a preferred embodiment of the present invention, in the third step, the catalyst is a mixture of pyridine and triphenyl phosphite, wherein the mass ratio of pyridine to triphenyl phosphite is not particularly limited, and preferably the mass ratio is 0.7:1 to 1:1.

In a preferred embodiment of the present invention, in the third step, there is no particular limitation in the mass ratio of the catalyst to the imide diacid monomer, and preferably, the mass ratio is 0.5:1 to 1:1.

In a preferred embodiment of the invention, in the third step the solid content of the reaction mixture is between 10% and 30%, preferably between 15% and 26%.

In a preferred embodiment of the invention, in the third step, the organic solvent is preferably N-methylpyrrolidone.

In a preferred embodiment of the invention, in the third step, the reaction temperature of the dehydration polycondensation reaction is 40 to 150℃and preferably 50 to 130 ℃.

In a preferred embodiment of the invention, in the third step the reaction time is from 8 to 20 hours, preferably from 10 to 15 hours.

In a preferred embodiment of the present invention, in the third step, the synthesis reaction can be promoted by a gradient temperature increase to increase the reaction yield, and the specific temperature and time of each gradient are not particularly limited as long as they can function as intended.

In a preferred embodiment of the present invention, in the third step, the reaction conditions of the dehydration polycondensation reaction include:

reacting for 1 hour at 50-80 ℃, heating to 110-130 ℃ at a heating rate of 10 ℃/h, and continuing reacting for 3-7 hours at 110-130 ℃.

In a preferred embodiment of the invention, a post-treatment step is further included after the third step, the post-treatment step comprising spin-steaming under reduced pressure at 100-130 ℃ to obtain the binder for lithium ion batteries.

In a preferred embodiment of the present invention, after the reduced pressure rotary evaporation after the third step, the binder for lithium ion batteries is diluted with N-methylpyrrolidone, thereby obtaining a binder dope for lithium ion batteries having a solid content of 5% to 15%, preferably 10%.

In addition, the invention also provides a binder for the lithium ion battery, which is prepared by the preparation method.

In addition, the invention also provides application of the binder for the lithium ion battery or the binder for the lithium ion battery prepared by the preparation method as a positive electrode plate binder for the lithium ion battery and a binder for coating the edges of the positive electrode plate.

In order to make the contents of the present invention more easily understood, the technical scheme of the present invention will be further described with reference to the specific embodiments, but the present invention is not limited thereto.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the technical scope of the present invention is not limited to these examples. Unless otherwise specified, all percentages, parts and ratios used in the present invention are based on mass.

The manufacturers of the raw materials and instruments used in the examples, and the instruments and analysis methods used for the analysis of the products are described below. The embodiments of the present invention are not to be construed as specific techniques or conditions, according to techniques or conditions described in the literature in this field or according to the product specifications. The apparatus or raw materials used are not specific to the manufacturer, and are conventional products which can be obtained commercially, and the reagents used are not specific to the manufacturer or concentration, and are all analytically pure-grade reagents which can be obtained conventionally, so long as the intended effect can be achieved, and are not particularly limited.

Raw materials and instruments used in the examples:

boehmite, model BG613, purchased from Anhui yi shitong materials science and technology Co., ltd;

diphenyl ether dianhydride, purchased from ala Ding Shiji mesh;

triphenyl phosphite, purchased from an ala Ding Shiji mesh;

nickel cobalt aluminum active substances are purchased from Shenzhen Bei Terui new energy science and technology Co;

a film coater, purchased from Jiangsu Rabo science instruments Co., ltd;

a tensile testing machine purchased from Dongguan general test equipment Co., ltd;

new Williams cell testing cabinets are available from Shenzhen New Wils electronics Inc.

Examples

Example 1

< preparation of adhesive glue solution for lithium ion Battery >

The first step:

0.21mol (42.5 g) of 11-aminoundecanoic Acid (AU) and 0.1mol (31.0 g) of 3,3', 4' -diphenylether tetracarboxylic dianhydride (ODPA) were dissolved in 171.5g of a mixed solvent of glacial acetic acid (purity: 99.5%) and pyridine, wherein pyridine accounted for 10% of the mixed solvent, to obtain a reaction mixture having a solid content of 30%. After refluxing the reaction mixture at 120 ℃ for 8 hours, it was cooled to room temperature. After the product precipitated by standing, it was filtered and the filter cake was washed to neutrality with deionized water. Then, the mixture was dried under vacuum at 90℃for 3 hours to obtain 61.8g (0.091 mol) of an imide diacid monomer (DIDA monomer) in a yield of 91.0%.

In the first step, the solid content of the reaction mixture may be adjusted to 30 to 60% by using a mixed solvent of glacial acetic acid and pyridine, and the ratio of pyridine in the mixed solvent may be 8 to 15% so long as the intended effect is achieved, and the method is not particularly limited.

And a second step of:

0.21mol (24.4 g) of hexamethylenediamine and 0.1mol (31.0 g) of 3,3', 4' -diphenylether tetracarboxylic dianhydride (ODPA) were dissolved in 129.3g of a mixed solvent of glacial acetic acid (purity: 99.5%) and pyridine, the pyridine constituting 10% of the mixed solvent, to obtain a reaction mixture having a solid content of 30%. After refluxing the reaction mixture at 120 ℃ for 8 hours, it was cooled to room temperature. After the product precipitated by standing, it was filtered and the filter cake was washed to neutrality with deionized water. Then, the mixture was dried under vacuum at 90℃for 3 hours to obtain 46.6g (0.092 mol) of an imide diamine monomer (DINA monomer) in a yield of 92.0%.

In the second step, the solid content of the reaction mixture may be adjusted to 30 to 60% by using a mixed solvent of glacial acetic acid and pyridine, and the ratio of pyridine in the mixed solvent may be 8 to 15% so long as the intended effect is achieved, and the method is not particularly limited.

And a third step of:

into a 100ml three-necked flask, 0.01mol (6.788 g) of the imide diacid monomer (DIDA monomer) obtained in the first step and 0.0102mol (5.167 g) of the imide diamine monomer (DINA monomer) obtained in the second step were charged. Subsequently, 30g of NMP solvent having a purity of 98% was added, and a mixture of 2.5g of pyridine and 2.5g of triphenyl phosphite as a catalyst, the mass ratio of the catalyst (5.0 g) to the imide diacid monomer being 0.74:1, wherein the mass ratio of pyridine to triphenyl phosphite is 1:1, a reaction mixture having a solids content of 25.5% is obtained. The reaction mixture is reacted for 1 hour at 50 ℃, then gradually heated to 130 ℃ at a heating rate of 10 ℃ per hour, then reacted for 5 hours at 130 ℃, the total reaction time is 14 hours, and after the temperature is reduced to 100 ℃, the reaction mixture is decompressed and distilled for 2 hours at minus 0.1MPa to remove pyridine, so that the PI binder for the lithium ion battery is obtained. The binder was then diluted with NMP to a solids content of 10% to give a uniform stable PI binder gum for a brown lithium ion battery, which was used directly without further treatment. The weight average molecular weight was 96,000 as measured by gel permeation chromatography (Gel Permeation Chromatography, GPC).

The molecular structural formula of the reaction product is shown as follows:

wherein Ar is a tetravalent diphenyl ether, and n is about 82 on average, calculated from the weight average molecular weight recited above.

In the third step, the solid content of the reaction mixture may be adjusted to 10% to 30%, preferably 15% to 26%, by using an NMP solvent. After the polymerization, a small amount of solvent is lost during the spin-steaming under reduced pressure, resulting in an increase in the solid content, and the final step is to dilute with NMP to adjust the solid content of the binder dope to 5% -15%, preferably 10%. The mass ratio of the catalyst to the imide diacid monomer is set to be 0.5:1-1:1, the catalyst is a mixture of pyridine and triphenyl phosphite, and the mass ratio of the pyridine to the triphenyl phosphite is set to be 0.7:1-1:1, so long as the expected effect can be achieved, and the catalyst is not particularly limited. The synthesis reaction can be promoted and the reaction yield can be improved by gradient heating, and the specific temperature and time of each gradient are not particularly limited as long as the gradient can play an expected role. The PI binder for lithium ion batteries has a weight average molecular weight of 20,000 to 120,000, and is not particularly limited as long as it can perform its intended function, but is preferably 40,000 to 100,000, more preferably 42,000 to 96,000.

The adhesive cement solution for lithium ion batteries having a solid content of 10% prepared in example 1 was subjected to measurement of a rotational viscosity of 3200cP at 25℃using a rotational viscometer.

< preparation of edge coating slurry and edge coating layer >

70 parts of boehmite (model BG 613) was dispersed in a portion of N-methylpyrrolidone, followed by addition of 30 parts of the PI binder dope (solid content 10%) prepared in example 1, and addition of another portion of N-methylpyrrolidone, to obtain an edge coating slurry having a solid content of 35%.

The slurry was applied to an aluminum foil using a doctor blade having a height clearance of 200 μm using a film coater, and after the completion of the application, the film was dried in an oven at 105℃for 1 hour to obtain an edge coating layer having a dry film thickness of about 30. Mu.m.

The PI binder dope prepared in example 1 and the above edge coating paste having a solid content of 35% were monitored for changes in rotational viscosity by a rotational viscometer, and the results are shown in fig. 1. The peel strength of the edge coating layer on the aluminum foil of 8 sets of parallel specimens was measured using a tensile tester, and the results are shown in fig. 2.

< preparation of button cell >

Preparing a positive electrode of a lithium ion battery: 1.2g of the PI binder gum (solid content: 10%) prepared in example 1, 0.12g of conductive carbon black (SP) and 9.76g of Nickel Cobalt Aluminum (NCA) active material (the mass ratio of PI binder gum to SP to NCA is 1.2:1.2:97.6 by dry weight) were added to a closed vessel, then 9.92g of NMP solvent was added, and the mixture was stirred at a high speed of 2000rpm/min for 10 minutes to uniformly mix the slurry, and the solid content of the obtained slurry was 47.6%, which was macroscopically judged as a glossy state.

The solid content of the slurry is preferably adjusted to 40% to 70% by using an NMP solvent.

And uniformly coating the obtained slurry on a common aluminum foil, and putting the coated aluminum foil into a blast oven at 100 ℃ for drying for 2 hours to obtain the dried positive electrode plate.

The obtained positive electrode plate is pressed according to the compaction density of 3.2g/mm ³ Cold pressing, cutting the compacted pole piece into a round pole piece with the diameter of 8mm, baking for 2 hours in vacuum, and taking out to prepare the button cell according to the following method.

The button cell assembly was performed in a glove box. According to the method, an electrolyte solution is dripped on a negative electrode cover-foam nickel-lithium sheet-isolating film (3 drops of the electrolyte solution are dripped on the isolating film after the isolating film is placed, wherein the electrolyte solution is composed of Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) (EC: EMC: DEC volume ratio=1:1:1) and LiPF ₆ (concentration 1.0M) composition) -positive electrode sheet-spacer-spring-positive electrode cap. Wherein the separator was a ceramic coated separator film (available from Shanghai Enjetsche New Material technologies Co., ltd.) having a thickness of 12. Mu.m. The assembled button cell was placed in the mold cavity of a hydraulic sealer (available from Shenzhen Kogyo Co., ltd.) and locked, and the handle was shaken to apply a pressure of > 500kg/cm ² And then unlocking, and taking out the button cell with the sealed mouth.

The cold-pressed positive electrode sheet was subjected to a coating peel strength test using a tensile tester, and the results are shown in table 2.

Detecting the charge-discharge cycle characteristics of the battery by using a new-Wei battery test cabinet: charging and discharging are carried out in a voltage interval of 2.3V-4.3V at a charging and discharging rate of 0.1C, specifically, charging is carried out to 4.3V at a constant current of 0.1C, then charging is carried out to a cut-off current of 0.02C at a constant voltage of 4.3V, the charging and discharging are carried out for 5min, discharging is carried out to 2.3V at 0.1C, the charging and discharging capacity after the first circulation is recorded after the 5 min. And thirdly, charging to 4.3V at a constant current of 0.1C, charging to 0.02C at a constant voltage of 4.3V, standing for 5min, discharging to 2.3V at 0.1C, standing for 5min, cycling according to the rest, recording the charge and discharge capacity after 100 th cycle after 100 times of charge/discharge cycles, and determining the discharge specific capacity, the charge specific capacity, the initial effect and the capacity retention rate after 100 times of cycles of the battery.

The capacity retention rate of the battery after 100 cycles was calculated using the following formula:

capacity retention after 100 cycles (%) =discharge capacity after 100 th cycle/discharge capacity after first cycle

The results are shown in Table 2.

Example 2

< preparation of adhesive glue solution for lithium ion Battery >

The first step:

0.2mol (40.5 g) of 11-aminoundecanoic Acid (AU) and 0.1mol (31.0 g) of 3,3', 4' -diphenylether tetracarboxylic dianhydride (ODPA) were dissolved in 87.4g of a mixed solvent of glacial acetic acid (purity: 99.5%) and pyridine, wherein pyridine represented 8% of the mixed solvent, to obtain a reaction mixture having a solid content of 45%. After refluxing the reaction mixture at 120 ℃ for 8 hours, it was cooled to room temperature. After the product precipitated by standing, it was filtered and the filter cake was washed to neutrality with deionized water. Then, the mixture was dried under vacuum at 90℃for 3 hours to obtain 61.3g (0.0903 mol) of an imide diacid monomer (DIDA monomer) in a yield of 90.3%.

And a second step of:

0.2mol (14.82 g) of propylenediamine and 0.1mol (31.0 g) of 3,3', 4' -diphenylether tetracarboxylic dianhydride (ODPA) were dissolved in 56.0g of a mixed solvent of glacial acetic acid (purity: 99.5%) and pyridine, wherein pyridine accounted for 8% of the mixed solvent, to obtain a reaction mixture having a solid content of 45%. After refluxing the reaction mixture at 120 ℃ for 8 hours, it was cooled to room temperature. After the product precipitated by standing, it was filtered and the filter cake was washed to neutrality with deionized water. Then, the resultant was dried under vacuum at 90℃for 3 hours to obtain 38.23g (0.0905 mol) of an imide diamine monomer (DINA monomer) in a yield of 90.5%.

And a third step of:

into a 100ml three-necked flask, 0.01mol (6.788 g) of the imide diacid monomer (DIDA monomer) obtained in the first step and 0.01mol (4.22 g) of the imide diamine monomer (DINA monomer) obtained in the second step were charged. 95.68g of NMP solvent (i.e., N-methylpyrrolidone) having a purity of 98% was then added, and a mixture of 1.40g of pyridine and 1.99g of triphenyl phosphite was further added as a catalyst, the mass ratio of the catalyst (3.39 g) to the imide diacid monomer being 0.5:1, wherein the mass ratio of pyridine to triphenyl phosphite was 0.7:1, to give a reaction mixture having a solid content of 10%. The reaction mixture is reacted for 1 hour at 80 ℃, then gradually heated to 130 ℃ at a heating rate of 10 ℃ per hour, then reacted for 5 hours at 130 ℃, the total reaction time is 11 hours, and after the temperature is reduced to 100 ℃, the reaction mixture is decompressed and distilled for 2 hours at minus 0.1MPa to remove pyridine, so that the PI binder for the lithium ion battery is obtained. The binder was then diluted with NMP to a solids content of 10% to give a uniform stable PI binder gum for a brown lithium ion battery, which was used directly without further treatment. The weight average molecular weight was measured to be 42,000 by gel permeation chromatography.

The molecular structural formula of the reaction product is shown as follows:

wherein Ar is a tetravalent diphenyl ether and n is on average about 39.

The adhesive cement solution for lithium ion batteries having a solid content of 10% prepared in example 2 was measured to have a rotational viscosity of 2800cP at 25 ℃ using a rotational viscometer.

< preparation of edge coating slurry and edge coating layer >

The preparation was performed as in example 1 to prepare an edge coating paste and an edge coating layer, except that the PI binder dope prepared in example 2 was used.

The PI binder dope prepared in example 2 and the change in rotational viscosity of the edge coating paste were monitored by a rotational viscometer, and the results are shown in fig. 6. The peel strength of the edge coating layer on the aluminum foil of 8 sets of parallel specimens was measured using a tensile tester, and the results are shown in fig. 7.

< preparation of button cell >

The procedure for preparation of a button cell was followed as in example 1, except that the PI binder gum prepared from example 2 was used.

The cold-pressed positive electrode sheet was subjected to a coating peel strength test in the same manner as in example 1, and the results are shown in table 2.

The charge-discharge cycle characteristics of the battery were measured in the same manner as in example 1, and the specific discharge capacity, specific charge capacity, initial efficiency and capacity retention after 100 cycles of the battery were measured, and the results are shown in table 2.

Example 3

< preparation of adhesive glue solution for lithium ion Battery >

The first step:

0.22mol (19.6 g) of 3-aminopropionic acid and 0.1mol (31.0 g) of 3,3', 4' -diphenylether tetracarboxylic dianhydride (ODPA) were dissolved in 33.7g of a mixed solvent of glacial acetic acid (purity: 99.5%) and pyridine, wherein pyridine accounted for 15% of the mixed solvent, to obtain a reaction mixture having a solid content of 60%. After refluxing the reaction mixture at 120 ℃ for 8 hours, it was cooled to room temperature. After the product precipitated by standing, it was filtered and the filter cake was washed to neutrality with deionized water. Subsequently, the mixture was dried under vacuum at 90℃for 3 hours to obtain 41.21g (0.0911 mol) of an imide diacid monomer (DIDA monomer) in a yield of 91.1%.

And a second step of:

0.22mol (38.35 g) of decamethylene diamine and 0.1mol (31.0 g) of 3,3', 4' -diphenylether tetracarboxylic dianhydride (ODPA) were dissolved in 46.25g of a mixed solvent of glacial acetic acid (purity: 99.5%) and pyridine, wherein pyridine accounted for 15% of the mixed solvent, to obtain a reaction mixture having a solid content of 60%. After refluxing the reaction mixture at 100 ℃ for 8 hours, it was cooled to room temperature. After the product precipitated by standing, it was filtered and the filter cake was washed to neutrality with deionized water. Subsequently, the mixture was dried under vacuum at 90℃for 3 hours to obtain 56.43g (0.0906 mol) of an imide diamine monomer (DINA) in a yield of 90.6%.

And a third step of:

into a 100ml three-necked flask, 0.01mol (4.524 g) of the DIDA monomer obtained in the first step and 0.011mol (6.85 g) of the DINA monomer obtained in the second step were charged. 22.02g of NMP solvent having a purity of 98% was then added, followed by a mixture of 2.08g of pyridine and 2.44g of triphenyl phosphite as a catalyst, the mass ratio of the catalyst (4.52 g) to the imide diacid monomer being 1:1, wherein the mass ratio of pyridine to triphenyl phosphite was 0.85:1, to give a reaction mixture having a solid content of 30%. The reaction mixture is reacted for 1 hour at 80 ℃, then gradually heated to 130 ℃ at a heating rate of 10 ℃ per hour, then reacted for 5 hours at 130 ℃, the total reaction time is 11 hours, and after the temperature is reduced to 100 ℃, the reaction mixture is decompressed and distilled for 2 hours at minus 0.1MPa to remove pyridine, so that the PI binder for the lithium ion battery is obtained. The binder was then diluted with NMP to a solids content of 10% to give a uniform stable PI binder gum for a brown lithium ion battery, which was used directly without further treatment. The weight average molecular weight was 86,000 as measured by gel permeation chromatography.

The molecular structural formula of the reaction product is shown as follows:

wherein Ar is a tetravalent diphenyl ether and n is on average about 79.

The adhesive cement solution for lithium ion batteries having a solid content of 10% prepared in example 3 was measured to have a rotational viscosity of 1800cP at 25 ℃ using a rotational viscometer.

< preparation of edge coating slurry and edge coating layer >

The preparation was performed as in example 1 to prepare an edge coating paste and an edge coating layer, except that the PI binder dope prepared in example 3 was used.

The PI binder dope prepared in example 3 and the change in rotational viscosity of the edge coating paste were monitored by a rotational viscometer, and the results are shown in fig. 8. The peel strength of the edge coating layer on the aluminum foil of 8 sets of parallel specimens was measured using a tensile tester, and the results are shown in fig. 9.

< preparation of button cell >

The procedure for preparation of a button cell was followed as in example 1, except that the PI binder gum prepared from example 3 was used.

Examples 4 to 9

Examples 4-9 were conducted as described in example 1, except that the main variables such as composition, molar ratio, solids content, etc., were varied, as shown in Table 1, and the results were shown in Table 2.

It should be noted that the present disclosure does not show the related drawings because the PI binder glue solutions of examples 4 to 9 and the variation of the rotational viscosity of the edge coating paste prepared from the glue solutions and the peel strength of the edge coating layer on the aluminum foil are similar to those of fig. 1 and 2.

Comparative example 1

< preparation of PVDF900 adhesive glue solution >

PVDF900 binder cement with a solids content of 10% was prepared from binder PVDF900 (from Achroma) and solvent NMP.

< preparation of edge coating slurry and edge coating layer >

The preparation was performed as in example 1, except that PVDF900 binder dope having a solid content of 10% of comparative example 1 was used.

The change in rotational viscosity of the PVDF900 binder dope prepared in comparative example 1 and the above edge coating paste was monitored using a rotational viscometer, and the result is shown in fig. 10. The peel strength of the edge coating layer on the aluminum foil of 8 sets of parallel specimens was measured using a tensile tester, and the results are shown in fig. 11.

< preparation of button cell >

The preparation was carried out as in example 1, except that a PVDF900 binder dope (1.2 g) having a solids content of 10% of comparative example 1 was used.

TABLE 1

In table 1, "compound containing amino group and carboxyl group" is simply referred to as "amino acid".

TABLE 2

As is apparent from table 2, the first efficiencies of the button cells of examples 1 to 9 were higher than those of the button cell of comparative example 1, and the charge-discharge specific capacities of examples 1 to 9 at the first cycle and the capacity retention after 100 cycles were also significantly better than those of comparative example 1. In addition, the peel strength of the coating layer of the positive electrode sheet in each of examples 1 to 9 was significantly better than that of comparative example 1.

As shown in fig. 1, the PI binder dope having a solid content of 10% of example 1 and the edge coating paste made of the dope were both high in rotational viscosity, and the rotational viscosity change was small after 3 days at room temperature, and no gel state occurred, indicating good stability of the dope and the slurry.

Figures 2 and 7 show data for 8 sets of parallel samples of edge coating layers of examples 1 and 2, respectively, each having a peel strength of 380N/m or more, wherein the peel strength of the bars after 7 days of electrolyte soaking is slightly higher, probably because during electrolyte soaking, the electrolyte solvent small molecules play a role of intermolecular plasticization with time extension, PI segments are more prone to hydrogen bonding with aluminum foil, thereby increasing the density of hydrogen bonding, causing an increase in peel strength.

As shown in fig. 9, data of 8 sets of parallel samples of the edge coating layer made of the edge coating paste of example 3 were tested, and the peel strength of the edge coating layer was 150N/m or more, wherein the peel strength of the bars 1-1, 1-2, 1-5, 1-6, 1-7 and 1-8 after immersing the electrolyte for 7 days was slightly lower, which may be because, during the electrolyte immersing process, the electrolyte solvent small molecules play a plasticizing role on the one hand, the adhesive segment activation energy was lowered, and the formation of hydrogen bonds with aluminum foil was more prone, and on the other hand, the small molecule plasticization also easily breaks the intermolecular hydrogen bonds due to the steric hindrance effect, and in summary, the electrolyte solvent small molecules increase the activity of the adhesive molecule segments on the one hand, and the steric hindrance effect of the small molecules also affects the formation of hydrogen bonds. In example 3, the proportion of soft segments in the repeating units was decreased as compared with examples 1 and 2, and the segment activation energy was increased as compared with examples 1 and 2, and the flexibility of the segment was deteriorated, so that the peel strength was decreased after immersing the electrolyte under the combined action.

The thermal characteristics of the PI binder gum solution with a solid content of 10% of example 1 were analyzed by a thermogravimetric analyzer (shimadzu corporation), and as shown in fig. 3, the decomposition temperature of the PI binder was more than 400 ℃, which is far enough to meet the normal use requirements of lithium batteries.

Fig. 4 and 5 show electrochemical reactions of PI binder gum solution with a solid content of 10% in example 1 in a low voltage range (0V-2.5V) and an operating voltage range (2.5V-4.9V), respectively, and show that PI binder can exist stably in the above ranges, almost no oxidation-reduction reaction is generated, and the use condition of binder for lithium battery is satisfied.

As shown in fig. 10, the rotational viscosity of the PVDF900 binder dope having a solid content of 10% of comparative example 1 and the edge coating paste prepared therefrom was increased with the lapse of the standing time, and the rotational viscosity was not measured after the standing for 24 hours, which indicates that both the dope and the paste were gelled, thereby indicating that the stability of the dope and the paste was poor,

fig. 11 shows data of 8 sets of parallel samples of the edge coating layer of comparative example 1, each having a peel strength of 37N/m or less.

In a word, the PI binder of the invention contains abundant carbonyl groups, so that intermolecular hydrogen bonds can be formed, the hydrogen bonds and hydroxyl groups on the current collector and the active material form strong interaction, the binding force between the film active material and the current collector is greatly improved, the stability of the positive electrode plate is improved, the falling-off condition of the active material along with the volume change of the electrode plate in the charging and discharging process is lightened, and the cycle capacity retention rate of the battery is improved.

The above description is not intended to limit the invention in any way, but is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims

1. A binder for a lithium ion battery, comprising a polyamideimide compound having a structure represented by general formula I:

general formula I

Wherein,,

R ¹ and R is ² Respectively alkylene;

n is an integer of 20-100;

ar and Ar' are respectively 4-valent aromatic groups, and are one of the following structural formulas:

or->

Wherein R is ³ Is O, S, carbonyl, sulfonyl, sulfinyl, alkylene, alkyleneoxy alkylene, alkylenethio alkylene, alkyleneAlkylcarbonyl, alkylcarbonylalkylene, alkylsulfonyl, alkylsulfonylalkylene, alkylsulfinyl or alkylsulfinylalkylene;

ar and Ar' may be the same or different.

2. The binder for lithium ion batteries according to claim 1, wherein n is an integer of 39.ltoreq.n.ltoreq.82.

3. The binder for a lithium ion battery according to claim 1, wherein the alkylene group has 1 to 15 carbon atoms.

4. A binder for a lithium ion battery according to claim 3 wherein the alkylene group has 2 to 10 carbon atoms.

5. The binder for lithium ion batteries according to claim 3, wherein the alkylene group is one or a combination of two or more of methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene.

6. The binder for lithium ion battery according to claim 1, wherein the connection positions of the 4-valent aromatic groups are 1, 2 and 4, 5 or Ph-R positions of the benzene ring ³ -the 3, 4 or 4, 5 positions of the two benzene rings in Ph.

7. The binder for lithium ion battery according to claim 3, wherein the connection positions of the 4-valent aromatic groups are 1, 2 and 4, 5 or Ph-R positions of the benzene ring ³ -the 3, 4 or 4, 5 positions of the two benzene rings in Ph.

8. The binder for lithium ion batteries according to claim 1, characterized in that it has a rotational viscosity of 1500-20000 cP.

9. The binder for lithium ion batteries according to claim 8, wherein the rotational viscosity thereof is 1800-20000 cP.

10. The binder for lithium ion batteries according to claim 1, wherein the weight average molecular weight of the binder is 20,000-120,000.

11. The binder for lithium ion batteries according to claim 10, wherein the weight average molecular weight of the binder is 40,000-100,000.

12. The binder for lithium ion batteries according to claim 11, wherein the weight average molecular weight of the binder is 42,000-96,000.

13. The method for producing a binder for lithium ion batteries according to any one of claims 1 to 12, characterized by comprising the steps of:

a second step of dissolving dianhydride and diamine in an organic solvent to obtain a reaction mixture, dehydrating and condensing the reaction mixture to prepare an imide diamine monomer, wherein the diamine is aliphatic diamine,

14. The process according to claim 13, wherein in the first step, the dianhydride is 1,2,4, 5-benzene tetracarboxylic dianhydride, 3', 4' -diphenyl ether tetracarboxylic dianhydride, 3',4,4' -diphenyl methane tetracarboxylic dianhydride, 3', 4' -diphenyl methane tetracarboxylic dianhydride or 3,3', 4' -diphenyl sulfone tetracarboxylic dianhydride.

15. The process according to claim 13, wherein in the second step, the dianhydride is 1,2,4, 5-benzene tetracarboxylic dianhydride, 3', 4' -diphenyl ether tetracarboxylic dianhydride, 3',4,4' -diphenyl methane tetracarboxylic dianhydride, 3', 4' -diphenyl methane tetracarboxylic dianhydride or 3,3', 4' -diphenyl sulfone tetracarboxylic dianhydride.

16. The method according to claim 13, wherein in the first step, the compound containing an amino group and a carboxyl group is one or a combination of two or more of aminoundecanoic acid, aminodecanoic acid, aminononanoic acid, aminooctanoic acid, aminoheptanoic acid, aminocaproic acid, aminopentanoic acid, aminobutyric acid, and aminopropionic acid.

17. The method according to claim 14, wherein in the second step, the diamine is one or a combination of two or more of decamethylene diamine, nonanediamine, octamethylene diamine, heptanediamine, hexamethylenediamine, pentalene diamine, butanediamine, propanediamine, and ethylenediamine.

18. The method according to claim 15, wherein in the second step, the diamine is one or a combination of two or more of 1, 10-decamethylene diamine, 1, 9-nonanediamine, 1, 8-octamethylene diamine, 1, 7-heptanediamine, 1, 6-hexanediamine, 1, 5-pentanediamine, 1, 4-butanediamine, 1, 3-propanediamine, and ethylenediamine.

19. The method according to claim 13, wherein in the first step, the molar ratio of the dianhydride to the compound containing an amino group and a carboxyl group is 1:2 to 1:2.2.

20. The method according to claim 14, wherein in the first step, the molar ratio of the dianhydride to the compound containing an amino group and a carboxyl group is 1:2 to 1:2.2.

21. The method according to claim 16, wherein in the first step, the molar ratio of the dianhydride to the compound containing an amino group and a carboxyl group is 1:2 to 1:2.2.

22. The method according to claim 19, wherein in the first step, the molar ratio of the dianhydride to the compound containing an amino group and a carboxyl group is 1:2.1.

23. The process according to claim 13, wherein in the first step the solid content of the reaction mixture is 30% to 60%.

24. The process according to claim 23, wherein in the first step the solid content of the reaction mixture is 30% -45%.

25. The preparation method according to claim 13, wherein in the first step, the organic solvent is a mixed solvent of glacial acetic acid and pyridine, and the weight ratio of pyridine in the mixed solvent is 8% -15%.

26. The preparation method according to claim 13, wherein in the first step, the reaction temperature of the dehydration condensation reaction is 100 to 130 ℃.

27. The process according to claim 26, wherein in the first step, the reaction temperature of the dehydration condensation reaction is 120 ℃.

28. The method according to claim 13, wherein in the first step, the reaction time of the dehydration condensation reaction is 4 to 16 hours.

29. The process according to claim 26, wherein in the first step, the reaction time of the dehydration condensation reaction is 4 to 16 hours.

30. The process according to claim 28, wherein in the first step, the reaction time of the dehydration condensation reaction is 6 to 10 hours.

31. The method according to claim 13, wherein in the second step, the molar ratio of the dianhydride to the aliphatic diamine is 1:2 to 1:2.2.

32. The method according to claim 15, wherein in the second step, the molar ratio of the dianhydride to the aliphatic diamine is 1:2 to 1:2.2.

33. The method according to claim 17, wherein in the second step, the molar ratio of the dianhydride to the aliphatic diamine is 1:2 to 1:2.2.

34. The process according to claim 31, wherein in the second step the molar ratio of dianhydride to aliphatic diamine is 1:2.1.

35. The process according to claim 13, wherein in the second step the solid content of the reaction mixture is between 30% and 60%.

36. The process of claim 35, wherein in the second step the solid content of the reaction mixture is 30% -45%.

37. The preparation method according to claim 13, wherein in the second step, the organic solvent is a mixed solvent of glacial acetic acid and pyridine, and the weight ratio of pyridine in the mixed solvent is 8% -15%.

38. The preparation method according to claim 13, wherein in the second step, the reaction temperature of the dehydration condensation reaction is 100 to 130 ℃.

39. The process according to claim 38, wherein in the second step, the reaction temperature of the dehydration condensation reaction is 120 ℃.

40. The method according to claim 13, wherein in the second step, the reaction time of the dehydration condensation reaction is 4 to 16 hours.

41. The process according to claim 38, wherein in the second step, the reaction time of the dehydration condensation reaction is 4 to 16 hours.

42. The process according to claim 40, wherein in the second step, the dehydration condensation reaction is carried out for a reaction time of 6 to 10 hours.

43. The method of claim 13, wherein in the third step, the molar ratio of the imide diacid monomer to the imide diamine monomer is from 1:1 to 1:1.1.

44. The method of claim 19, wherein in the third step, the molar ratio of the imide diacid monomer to the imide diamine monomer is from 1:1 to 1:1.1.

45. The method of claim 31, wherein in the third step, the molar ratio of the imide diacid monomer to the imide diamine monomer is from 1:1 to 1:1.1.

46. The process of claim 43 wherein in the third step the molar ratio of imide diacid monomer to imide diamine monomer is 1:1.02.

47. The preparation method according to claim 13, wherein in the third step, the catalyst is a mixture of pyridine and triphenyl phosphite, and the mass ratio of pyridine to triphenyl phosphite is 0.7:1-1:1.

48. The method according to claim 19, wherein in the third step, the catalyst is a mixture of pyridine and triphenyl phosphite, and the mass ratio of pyridine to triphenyl phosphite is 0.7:1 to 1:1.

49. The process according to claim 31, wherein in the third step, the catalyst is a mixture of pyridine and triphenyl phosphite, and the mass ratio of pyridine to triphenyl phosphite is 0.7:1 to 1:1.

50. The process according to claim 43, wherein in the third step, the catalyst is a mixture of pyridine and triphenyl phosphite, and the mass ratio of pyridine to triphenyl phosphite is 0.7:1 to 1:1.

51. The production method according to claim 13, wherein in the third step, the mass ratio of the catalyst to the imide diacid monomer is 0.5:1 to 1:1.

52. The production method according to claim 19, wherein in the third step, the mass ratio of the catalyst to the imide diacid monomer is 0.5:1 to 1:1.

53. The method according to claim 31, wherein in the third step, the mass ratio of the catalyst to the imide diacid monomer is 0.5:1 to 1:1.

54. The process of claim 43, wherein in the third step, the mass ratio of the catalyst to the imide diacid monomer is 0.5:1 to 1:1.

55. The process of claim 47, wherein in the third step, the mass ratio of the catalyst to the imide diacid monomer is 0.5:1 to 1:1.

56. The process according to claim 13, wherein in the third step the solid content of the reaction mixture is between 10% and 30%.

57. The process of claim 56, wherein in the third step the solid content of the reaction mixture is 15% to 26%.

58. The process according to claim 13, wherein in the third step, the organic solvent is N-methylpyrrolidone.

59. The process according to claim 13, wherein in the third step, the reaction temperature of the dehydration polycondensation reaction is 40 to 150 ℃.

60. The process of claim 59, wherein in the third step, the reaction temperature of the dehydrating polycondensation is 50 to 130 ℃.

61. The process according to claim 13, wherein in the third step, the reaction time of the dehydration polycondensation reaction is 8 to 20 hours.

62. The process of claim 59, wherein in the third step, the reaction time for the dehydration polycondensation is 8 to 20 hours.

63. The process according to claim 61, wherein in the third step, the reaction time of the dehydrating polycondensation is 10 to 15 hours.

64. The process of any one of claims 43 to 63 wherein in the third step, the reaction conditions for the dehydrating polycondensation reaction comprise:

65. The method according to any one of claims 13 to 18, further comprising a post-treatment step after the third step, wherein the post-treatment step comprises spin-steaming under reduced pressure at 100 to 130 ℃ to obtain a binder for lithium ion batteries.

66. The process according to claim 65, wherein the binder for lithium ion batteries is diluted with N-methylpyrrolidone after the spin-drying under reduced pressure to obtain a binder dope for lithium ion batteries having a solid content of 5% to 15%.

67. The method according to claim 65, wherein the binder for lithium ion batteries is diluted with N-methylpyrrolidone after the spin-drying under reduced pressure to obtain a binder dope for lithium ion batteries having a solid content of 10%.

68. A binder for a lithium ion battery, prepared by the preparation method of any one of claims 13-67.

69. Use of the binder for a lithium ion battery according to any one of claims 1 to 12 or the binder for a lithium ion battery prepared by the preparation method according to any one of claims 13 to 67 as a positive electrode tab binder and a positive electrode tab edge coating binder for a lithium ion battery.