A binder with multi-stage crosslinking structure and its preparation method and application

Abstract

The application provides a binder with a multi-section cross-linking structure and a preparation method thereof. The binder comprises a polymer, deionized water and a polyamine; the polymer is composed of three sections of monomers and has the advantages of three types of binders, i.e., polyacrylic acid, polyamide and polyacrylate, and is particularly suitable for use as a lithium battery binder. The binder has the advantages of good bonding performance, high tensile strength, good flexibility, good chemical stability, good electrochemical stability and excellent processing performance, and when the binder is used as a lithium battery binder, the battery cycle life of the lithium battery is improved, the electrode capacity is improved, the platform voltage is improved, and the demand of high-end lithium battery manufacturing can be met.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to an adhesive with a multi-segment cross-linked structure, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are rechargeable batteries that primarily function by the movement of lithium ions between the positive and negative electrodes. During charging and discharging, Li... + Intercalation and deintercalation back and forth between the two electrodes: During charging, Li + Lithium-ion batteries deintercalate from the positive electrode, pass through the electrolyte, and intercalate into the negative electrode, which is then in a lithium-rich state; the process reverses during discharge. Since their commercialization, lithium-ion batteries have been widely used in smartphones, tablets, Bluetooth headsets, electric bicycles, and electric vehicles due to their high capacity, high cycle life, lack of memory effect, high energy density, long cycle life, environmental friendliness, wide operating temperature range, high rate capability, and safety. Lithium-ion battery binders comprise 5-8 wt% of the active material in the electrode, playing a crucial role in stabilizing the electrode structure. They bind and retain the active material, enhancing the contact between the active material and the conductive agent. As a significant component of the electrode, they significantly influence the battery's cycle stability and rate performance. High-performance lithium-ion battery binders not only need excellent adhesion to resist volume changes and maintain a good electronic conductivity network in the electrode, but also should minimize the diffusion of soluble sulfides into the electrolyte during charging.

[0003] Currently, the binders used in lithium-ion battery electrode materials on the market mainly include oil-soluble binders represented by fluoropolymers (PVDF) and water-soluble binders such as styrene-butadiene emulsions and polyacrylates. Fluoropolymer oil-based binders require the addition of solvents to dissolve them before being formulated into a slurry. During the electrode fabrication process, the evaporation of the solvent pollutes the environment and harms the health of workers. Furthermore, their adhesion and flexibility are poor, and their effect on inhibiting electrode expansion is very limited, making it difficult to improve battery capacity and rate performance. In addition, fluoropolymers are expensive, increasing the cost of lithium-ion batteries. Therefore, in recent years, the development of water-based lithium-ion battery binders has become a trend in the battery industry.

[0004] Patent CN 104448158 A describes a method for preparing a water-based adhesive for lithium batteries. This method involves adding water-soluble acrylic monomers, oil-soluble acrylic monomers, and an initiator dropwise into a styrene-butadiene-styrene block copolymer (SBS) emulsion, and then reacting the mixture with stirring and heating to obtain the water-based adhesive for lithium batteries. Essentially, this is an acrylate-grafted styrene-butadiene emulsion. This type of modified styrene-butadiene rubber emulsion adhesive has highly hydrophobic groups, making it difficult to disperse effectively in an aqueous medium. Without a suitable dispersant, electrode coating is impossible, the tensile strength of the electrode sheet is low, and low-temperature discharge performance needs improvement.

[0005] Polyacrylate-based aqueous lithium battery electrode binders, represented by patents CN1209433C and CN1195036C, provide a soap-free copolymer aqueous solution dispersion latex that can be used as a lithium battery electrode powder material and an adhesive for coating separators. However, their main chain structure, consisting of highly polar polyacrylic acid and acrylonitrile, has a high glass transition temperature. When used to prepare electrode sheets, the electrode sheets become brittle during the drying process as moisture evaporates, making them prone to curling, cracking, and breakage. Furthermore, their poor mechanical properties, poor processability, and water-induced swelling limit their widespread application. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an adhesive with a multi-segment cross-linked structure that combines the advantages of three types of adhesives: polyacrylic acid, polyamide, and polyacrylate.

[0007] Another object of the present invention is to provide a method for preparing the adhesive having a multi-segment cross-linked structure.

[0008] Another object of the present invention is to provide the application of the adhesive having a multi-segment crosslinked structure.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] An adhesive with a multi-segment crosslinked structure includes a polymer, deionized water, and a polyamine; the polymer includes acrylic unit segments, acrylamide unit segments, and acrylate unit segments; wherein the acrylic unit segments are polymerized from acrylic monomers and butenedioic acid monoalkyl ester monomers; the acrylamide unit segments are polymerized from acrylamide monomers and hydroxyalkyl acrylamide monomers; and the acrylate unit segments are polymerized from hydrophilic acrylate monomers and multifunctional crosslinked acrylate monomers.

[0011] The acrylic unit monomer accounts for 20-35% of the weight of the polymer;

[0012] The acrylamide unit monomer accounts for 25-40% of the weight of the polymer;

[0013] The acrylate unit monomer accounts for 35-55% of the weight of the polymer.

[0014] The inventors discovered that acrylic unit segments polymerized from acrylic monomers and butadiene monoalkyl ester monomers can enhance adhesive strength and improve its flexibility and dispersibility. Acrylamide unit segments polymerized from acrylamide monomers and hydroxyalkyl acrylamide monomers can improve the adhesive's bonding force and crosslinking strength. Furthermore, when used in lithium-ion battery bonding, they can improve the battery's cycle performance. The hydrophilic acrylate monomers and multifunctional crosslinked acrylates in the acrylate unit segments can lower the glass transition temperature of the entire adhesive film, maintaining electrolyte resistance while improving its flexibility, making it easier to process and disperse, thus better meeting the performance requirements of lithium-ion battery electrodes for adhesives.

[0015] In this invention, the synthesis of each unit segment is carried out under anaerobic conditions. To achieve anaerobic conditions, the conventional operation is to introduce an inert gas into the system, with nitrogen being the most commonly used inert gas.

[0016] Preferably, in the acrylic unit segment, the acrylic monomer is one or more of acrylic acid, methacrylic acid, sodium acrylate, lithium acrylate, sodium methacrylate, or lithium methacrylate.

[0017] Preferably, in the acrylic unit segment, the butenedioic acid monoalkyl ester monomer is one or more of monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, or monobutyl fumarate.

[0018] Preferably, in the acrylamide unit segment, the acrylamide monomer is one or more of methacrylamide, dimethacrylamide, diethylacrylamide, isopropylacrylamide, dimethylaminoacrylamide, or diacetoneacrylamide.

[0019] Preferably, in the acrylamide unit segment, the hydroxyalkyl acrylamide monomer is one or more of N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, N-hydroxymethylacrylamide, or N-hydroxyethylacrylamide.

[0020] Preferably, in the acrylate unit segment, the hydrophilic acrylate monomer is one or more of hydroxyethyl acrylate, hydroxyethyl acrylate, methoxyethyl acrylate, or methoxy polyethylene glycol (meth)acrylate.

[0021] The methoxy polyethylene glycol (meth)acrylate may be one or more of methoxy polyethylene glycol (350) (meth)acrylate, methoxy polyethylene glycol (500) (meth)acrylate, methoxy polyethylene glycol (600) (meth)acrylate, or methoxy polyethylene glycol (1000) (meth)acrylate.

[0022] The multifunctional crosslinked acrylate monomer may be one or more of polyethylene glycol (200) di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate, or polyethylene glycol (600) di(meth)acrylate.

[0023] Preferably, the acrylate unit segment further contains an oleophilic acrylate monomer.

[0024] More preferably, the lipophilic acrylate monomer is one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, or isooctyl acrylate.

[0025] The method for preparing the adhesive with a multi-segment cross-linked structure includes the following steps:

[0026] S1. Preparation of acrylic unit segments:

[0027] Acrylic monomers and butenedioic acid monoalkyl ester monomers are mixed, and an initiator and deionized water are added. The mixture is reacted at 50-85°C for 2-5 hours to obtain acrylic unit segments.

[0028] S2. Preparation of Acrylamide Unit Segments:

[0029] In the system after the S1 reaction, deionized water was added and the pH of the system was adjusted to 6.5-7. Acrylamide monomers, hydroxyalkyl acrylamide monomers, and initiators were added. The system temperature was adjusted to 60-75℃ and the reaction was carried out for 1-4 hours to obtain acrylic unit segments with acrylamide unit segments on the surface.

[0030] S3. Preparation of acrylate unit segments:

[0031] In the system after S2 reaction, deionized water, hydrophilic acrylate monomers, multifunctional crosslinked acrylate monomers, and initiators are added. The system temperature is adjusted to 55~65℃ and the reaction is carried out for 2~4 hours.

[0032] S4. After the reaction in S3, deionized water and initiator are added, the temperature is raised to 80~90℃, and the reaction is carried out for 2~5 hours to obtain the polymer;

[0033] S5. Cool the system after the reaction in S4 to below 40°C, add deionized water and polyamine, and disperse to obtain the binder with the multi-segment cross-linked structure.

[0034] In this invention, the preparation method adopts solution polymerization. Therefore, the amount of deionized water added in each step can refer to the prior art. More preferably, the amount of deionized water added in each step is 5 to 8 times the mass of the monomer.

[0035] In this invention, the initiator is a commonly used initiator in the art. More preferably, the initiator is selected from one or more of azo compounds, organic peroxides, or inorganic persulfates. More specifically, the azo compound may be selected from 2,2-azobisisobutyronitrile, 2,2-azobis-2-methylbutyronitrile, 2,2-azobis-2,4-dimethylpentanitrile, 2,2-azobis-4-methoxy-2,4-dimethylpentanitrile, 2,2-azobis(2-methylpropionate), 2,2-azobis(2-methylpropionamide)•2 hydrochloride, etc. The organic peroxides are selected from cumene hydroperoxide (CHP), di-tert-butyl peroxide, dicumyl peroxide, benzoyl peroxide (BPO), lauroyl peroxide (LPO), dimethyl bis(tert-butyl peroxide)hexane, dimethyl bis(tert-butyl peroxide)-3-hexyne, bis(tert-butyl peroxide isopropyl)benzene, bis(tert-butyl peroxide)trimethylcyclohexane, butyl-bis(tert-butyl peroxide)valerate, tert-butyl peroxy-2-ethylhexanoate, benzoyl peroxide, terpene hydroperoxide, and tert-butyl peroxide, etc. The inorganic persulfates are selected from ammonium persulfate, methyl persulfate, and sodium persulfate, etc.

[0036] Preferably, the amount of the initiator is 0.1-0.5% of the monomer weight. When an organic peroxide is used as the initiator, it can also be used in combination with a reducing agent to form a redox system. The reducing agent can be ferrous sulfate, cuprous naphthenate, or sodium formaldehyde sulfoxylate.

[0037] The application of the binder with a multi-segment cross-linked structure in the preparation of lithium battery adhesives.

[0038] Compared with the prior art, the present invention has the following beneficial technical effects:

[0039] This invention provides an adhesive with a multi-segment cross-linked structure. The polymer contained in this adhesive is composed of specific acrylic unit segments, acrylamide unit segments, and acrylate unit segments, combining the advantages of polyacrylic acid, polyamide, and polyacrylate adhesives. It is particularly suitable for use as a lithium battery adhesive. The adhesive exhibits advantages such as good adhesion, high tensile strength, good flexibility, good chemical stability, good electrochemical stability, and excellent processability. When used as a lithium battery adhesive, it can improve the cycle life of lithium batteries, increase electrode capacity, and improve plateau voltage, meeting the requirements of high-end lithium battery manufacturing. Detailed Implementation

[0040] Unless otherwise specified, all raw materials, reagents, and solvents used in this invention are commercially purchased and unprocessed. The invention is further described in detail below with reference to embodiments; however, the implementation of this invention is not limited to the following embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this invention should be considered equivalent substitutions and are included within the scope of protection of this invention. Furthermore, regarding the terms "parts" and "%" in this specification, unless otherwise specified, they respectively represent "parts by mass" and "% by mass".

[0041] The various performance tests in this invention are conducted using the following methods.

[0042] Simulated electrode preparation

[0043] The binder, conductive carbon black, and graphite were mixed at a mass ratio of 5:10:85, and a certain amount of deionized water was added. The mixture was dispersed in a pulper for 20 minutes to prepare a negative electrode material with a solid content of 45 wt%. The dispersed negative electrode material was coated onto copper foil, and a 300 µm film was prepared using a coating machine to ensure uniform adhesion of the negative electrode material to the copper foil. The copper foil coated with the negative electrode material was placed in a vacuum drying oven and dried at 80 °C for 10 hours.

[0044] 1. Electrolyte resistance test

[0045] The electrode was immersed in the electrolyte at 60℃ for 240 h. Then, the surface moisture was absorbed and the film swelling was measured; the solubility was measured after drying. The electrolyte composition was ethylene carbonate: methyl ethyl carbonate: diethyl carbonate in a mass ratio of 3:5:2.

[0046] 2. Adhesive electrode peel strength test

[0047] The peel strength test of the adhesive was performed using a universal testing machine. A 100mm long and 25mm wide aluminum sheet was cleaned with alcohol. The adhesive to be tested was then applied to two aluminum sheets (coating area 75mm × 25mm). After 10 minutes, a second layer was applied. The two aluminum sheets were then bonded and pressed together, and placed in an oven at 40℃ for 2 hours. The aluminum sheets were then removed and fixed on the universal testing machine. A 180° peel was performed at a speed of 20mm / min, and the peel strength was calculated based on the stress during the peeling process and the coating area.

[0048] 5. Brittleness temperature test

[0049] The brittleness temperature (Tb) is tested according to GB / T 1682-1994 (single specimen method).

[0050] 6. Charge / discharge and electrical cycle performance tests

[0051] Take 2 parts of the binder from the example or comparative example and 98 parts of modified graphite and conductive agent, stir them thoroughly to form a slurry, filter it, and then coat it evenly on a clean copper foil. Dry and compact the slurry to obtain a negative electrode sheet.

[0052] Five parts of positive electrode binder (PTFE polytetrafluoroethylene) and 95 parts of LiCoO2 and conductive agent are thoroughly mixed into a slurry. After filtration, the slurry is evenly coated onto a clean aluminum foil, dried, and compacted to obtain a positive electrode sheet.

[0053] Cut the electrode sheets, vacuum dry them at 100℃ for 24 hours, assemble them with a battery separator to form a battery cell, inject electrolyte, seal the cell, and conduct performance tests such as charge / discharge and cycle life.

[0054] Example 1

[0055] S1. Preparation of acrylic unit segments:

[0056] Mix 19 parts acrylic acid and 1 part monomethyl maleate, add 0.01 parts 2,2-azobis(2-methylpropanediamine)•2 hydrochloride and 400 parts deionized water, and react at 50°C for 5 hours with nitrogen purging to obtain acrylic acid unit segments;

[0057] S2. Preparation of Acrylamide Unit Segments:

[0058] In the system after the S1 reaction, 100 parts of deionized water and 7 parts of lithium hydroxide were added to adjust the pH of the system to 6.5-7. 39 parts of acrylamide, 1 part of N-hydroxymethylacrylamide, and 0.01 parts of 2,2-azobis(2-methylpropanediamine)•2 hydrochloride were added. The system temperature was adjusted to 65℃ and the reaction was carried out for 2 hours to obtain acrylic acid unit segments coated with acrylamide unit segments.

[0059] S3. Preparation of acrylate unit segments:

[0060] In the system after the S2 reaction, add 100 parts of deionized water, 5.5 parts of hydroxyethyl acrylate, 34 parts of methoxy polyethylene glycol (1000) acrylate, 0.5 parts of polyethylene glycol (200) di(meth) acrylate, and 0.02 parts of 2,2-azobis(2-methylpropanediamine)•2 hydrochloride. Adjust the system temperature to 65°C and react for 2 hours.

[0061] S4. After the reaction in S3, add 0.01 parts of 2,2-azobis(2-methylpropanedin)•2 hydrochloride, heat to 80°C, and react for 2 hours to obtain the polymer;

[0062] S5. Cool the system after reaction S4 to 40°C, add 50 parts of deionized water and 0.001 parts of ethylenediamine, and disperse to obtain the binder with the multi-segment cross-linked structure.

[0063] Example 2

[0064] S1. Preparation of acrylic unit segments:

[0065] Mix 34 parts acrylic acid and 1 part monoethyl maleate, add 0.01 parts ammonium persulfate and 450 parts deionized water, and react at 65°C for 3 hours with nitrogen purging to obtain acrylic acid unit segments.

[0066] S2. Preparation of Acrylamide Unit Segments:

[0067] In the system after the S1 reaction, 100 parts of deionized water and 8 parts of lithium hydroxide were added to adjust the pH of the system to 6.5-7. 24 parts of acrylamide, 1 part of N-hydroxyethylacrylamide and 0.01 parts of ammonium persulfate were added, the system temperature was adjusted to 75℃, and the reaction was carried out for 1 hour to obtain acrylic unit segments with acrylamide unit segments on the surface.

[0068] S3. Preparation of acrylate unit segments:

[0069] In the system after the S2 reaction, add 150 parts of deionized water, 4.5 parts of hydroxyethyl acrylate, 35 parts of methoxy polyethylene glycol (600) acrylate, 0.5 parts of polyethylene glycol (400) di(meth) acrylate, and 0.02 parts of ammonium persulfate. Adjust the system temperature to 65°C and react for 3 hours.

[0070] S4. After the reaction in S3, add 0.01 parts of ammonium persulfate, heat to 90°C, and react for 2 hours to obtain the polymer;

[0071] S5. Cool the system after reaction S4 to 40°C, add 50 parts of deionized water and 0.001 parts of hexamethylenediamine, and disperse to obtain the binder with multi-segment cross-linked structure.

[0072] Example 3

[0073] S1. Preparation of acrylic unit segments:

[0074] Mix 19 parts methacrylic acid and 1 part monomethyl maleate, add 0.01 parts tert-butyl hydroperoxide, 0.001 parts ferrous sulfite and 350 parts deionized water, and react at 50°C for 2 hours with nitrogen purging to obtain acrylic acid unit segments.

[0075] S2. Preparation of Acrylamide Unit Segments:

[0076] In the system after the S1 reaction, 150 parts of deionized water and 6 parts of lithium hydroxide were added; the pH of the system was adjusted to 6.5-7, and 24 parts of dimethylacrylamide, 1 part of N-hydroxymethylacrylamide, 0.01 parts of tert-butyl hydroperoxide and 0.001 parts of ferrous sulfite were added. The system temperature was adjusted to 60℃ and the reaction was carried out for 2 hours to obtain acrylic acid unit segments coated with acrylamide unit segments.

[0077] S3. Preparation of acrylate unit segments:

[0078] In the system after the S2 reaction, add 200 parts of deionized water, 2.5 parts of hydroxypropyl acrylate, 52 parts of methoxy polyethylene glycol (1000) acrylate, 0.5 parts of polyethylene glycol (200) di(meth) acrylate, 0.02 parts of tert-butyl hydroperoxide, and 0.001 parts of ferrous sulfite. Adjust the system temperature to 55°C and react for 2 hours.

[0079] S4. After the reaction in S3, add 0.01 parts of tert-butyl hydroperoxide and 0.001 parts of ferrous sulfite, heat to 80°C, and react for 3 hours to obtain the polymer;

[0080] S5. Cool the system after the reaction in S4 to 40°C, add 50 parts of deionized water and 0.001 parts of hexamethylene diaminocarbamate, and disperse to obtain the binder with the multi-segment cross-linked structure.

[0081] Example 4

[0082] S1. Preparation of acrylic unit segments:

[0083] 29 parts of acrylic acid and 1 part of monoethyl maleate were mixed, and 0.01 parts of 2,2-azobis(2-methylpropanediamine)•2 hydrochloride and 500 parts of deionized water were added. The mixture was then reacted at 70°C for 3 hours under nitrogen purging to obtain acrylic acid unit segments.

[0084] S2. Preparation of Acrylamide Unit Segments:

[0085] In the system after the S1 reaction, 100 parts of deionized water and 10 parts of lithium hydroxide were added to adjust the pH of the system to 6.5-7. 34 parts of acrylamide, 1 part of N-hydroxyethylacrylamide, and 0.01 parts of 2,2-azobis(2-methylpropanediamine)•2 hydrochloride were added. The system temperature was adjusted to 75℃ and the reaction was carried out for 4 hours to obtain acrylic unit segments coated with acrylamide unit segments.

[0086] S3. Preparation of acrylate unit segments:

[0087] In the system after the S2 reaction, add 100 parts of deionized water, 10 parts of hydroxyethyl acrylate, 23 parts of methoxy polyethylene glycol (1000) acrylate, 0.5 parts of polyethylene glycol (200) di(meth) acrylate, 1 part of ethyl acrylate, and 0.02 parts of 2,2-azobis(2-methylpropanediamine)•2 hydrochloride. Adjust the system temperature to 65°C and react for 2 hours.

[0088] S4. After the reaction in S3, add 0.01 parts of 2,2-azobis(2-methylpropanedin)•2 hydrochloride, heat to 80°C, and react for 2 hours to obtain the polymer;

[0089] S5. Cool the system after reaction S4 to 40°C, add 50 parts of deionized water and 0.001 parts of ethylenediamine, and disperse to obtain the binder with the multi-segment cross-linked structure.

[0090] Example 5

[0091] S1. Preparation of acrylic unit segments:

[0092] Mix 28 parts acrylic acid and 2 parts monomethyl maleate, add 0.02 parts ammonium persulfate and 400 parts deionized water, and react at 70°C for 3 hours with nitrogen purging to obtain acrylic acid unit segments;

[0093] S2. Preparation of Acrylamide Unit Segments:

[0094] In the system after the S1 reaction, 200 parts of deionized water and 10 parts of sodium carbonate were added to adjust the pH of the system to 6.5-7. 38 parts of acrylamide, 2 parts of N-hydroxyethylacrylamide and 0.02 parts of ammonium persulfate were added, the system temperature was adjusted to 75℃, and the reaction was carried out for 4 hours to obtain acrylic unit segments with acrylamide unit segments on the surface.

[0095] S3. Preparation of acrylate unit segments:

[0096] In the system after the S2 reaction, add 100 parts of deionized water, 2 parts of hydroxyethyl acrylate, 26 parts of methoxy polyethylene glycol (1000) acrylate, 1 part of polyethylene glycol (400) di(meth) acrylate, 1 part of butyl acrylate, and 0.02 parts of ammonium persulfate. Adjust the system temperature to 65°C and react for 2 hours.

[0097] S4. After the reaction in S3, add 0.02 parts of ammonium persulfate, heat to 90°C, and react for 2 hours to obtain the polymer;

[0098] S5. Cool the system after reaction S4 to 40°C, add 50 parts of deionized water and 0.001 parts of ethylenediamine, and disperse to obtain the binder with the multi-segment cross-linked structure.

[0099] Example 6

[0100] S1. Preparation of acrylic unit segments:

[0101] Mix 23 parts acrylic acid and 2 parts monoethyl maleate, add 0.02 parts ammonium persulfate and 400 parts deionized water, and react at 85°C for 3 hours with nitrogen purging to obtain acrylic acid unit segments;

[0102] S2. Preparation of Acrylamide Unit Segments:

[0103] In the system after the S1 reaction, 150 parts of deionized water and 6 parts of lithium hydroxide were added to adjust the pH of the system to 6.5-7. 28 parts of dimethylacrylamide, 2 parts of N-hydroxymethylacrylamide and 0.02 parts of ammonium persulfate were added, the system temperature was adjusted to 75℃, and the reaction was carried out for 2 hours to obtain acrylic unit segments with acrylamide unit segments on the surface.

[0104] S3. Preparation of acrylate unit segments:

[0105] In the system after the S2 reaction, add 150 parts of deionized water, 4 parts of hydroxypropyl acrylate, 1 part of methoxyethyl acrylate, 38 parts of methoxy polyethylene glycol (200) acrylate, 1 part of polyethylene glycol (200) di(meth)acrylate, 1 part of butyl acrylate, and 0.02 parts of ammonium persulfate. Adjust the system temperature to 65°C and react for 2 hours.

[0106] S4. After the reaction in S3, add 0.02 parts of ammonium persulfate, heat to 90°C, and react for 2 hours to obtain the polymer;

[0107] S5. Cool the system after reaction S4 to 40°C, add 50 parts of deionized water and 0.001 parts of hexamethylenediamine, and disperse to obtain the binder with multi-segment cross-linked structure.

[0108] Example 7

[0109] S1. Preparation of acrylic unit segments:

[0110] 19 parts acrylic acid and 1 part monoethyl maleate were mixed, and 0.01 parts tert-butyl hydrogen peroxide, 0.001 parts ferrous sulfite and 350 parts deionized water were added. The mixture was then heated to 60°C with nitrogen and reacted for 3 hours to obtain acrylic acid unit segments.

[0111] S2. Preparation of Acrylamide Unit Segments:

[0112] In the system after the S1 reaction, 150 parts of deionized water and 6 parts of lithium hydroxide were added to adjust the pH of the system to 6.5-7. 27 parts of dimethylacrylamide, 3 parts of N-hydroxymethylacrylamide, 0.01 parts of tert-butyl hydroperoxide and 0.001 parts of ferrous sulfite were added. The system temperature was adjusted to 75℃ and the reaction was carried out for 3 hours to obtain acrylic acid unit segments coated with acrylamide unit segments.

[0113] S3. Preparation of acrylate unit segments:

[0114] In the system after the S2 reaction, add 200 parts of deionized water, 4 parts of hydroxyethyl acrylate, 1 part of methoxyethyl acrylate, 33 parts of methoxy polyethylene glycol (1000) acrylate, 2 parts of polyethylene glycol (400) di(meth) acrylate, 0.02 parts of tert-butyl hydroperoxide, and 0.001 parts of ferrous sulfite. Adjust the system temperature to 65°C and react for 2 hours.

[0115] S4. After the reaction in S3, add 0.02 parts of tert-butyl hydroperoxide and 0.001 parts of ferrous sulfite, heat to 85°C, and react for 2 hours to obtain the polymer;

[0116] S5. Cool the system after the reaction in S4 to 40°C, add 50 parts of deionized water and 0.001 parts of hexamethylene diaminocarbamate, and disperse to obtain the binder with the multi-segment cross-linked structure.

[0117] Example 8

[0118] S1. Preparation of acrylic unit segments:

[0119] Mix 30 parts acrylic acid, 4 parts methacrylic acid, and 1 part monomethyl maleate, add 0.03 parts ammonium persulfate and 500 parts deionized water, and react at 70°C for 3 hours with nitrogen purging to obtain acrylic acid unit segments.

[0120] S2. Preparation of Acrylamide Unit Segments:

[0121] In the system after the S1 reaction, 150 parts of deionized water and 6 parts of lithium hydroxide were added to adjust the pH of the system to 6.5-7. 22 parts of acrylamide, 3 parts of N-hydroxyethylacrylamide and 0.03 parts of ammonium persulfate were added, the system temperature was adjusted to 75℃, and the reaction was carried out for 2 hours to obtain acrylic unit segments with acrylamide unit segments on the surface.

[0122] S3. Preparation of acrylate unit segments:

[0123] In the system after the S2 reaction, add 100 parts of deionized water, 4 parts of hydroxyethyl acrylate, 40 parts of methoxy polyethylene glycol (350) acrylate, 1 part of polyethylene glycol (200) di(meth) acrylate, and 0.02 parts of ammonium persulfate. Adjust the system temperature to 65°C and react for 3 hours.

[0124] S4. After the reaction in S3, add 0.02 parts of ammonium persulfate, heat to 85°C, and react for 2 hours to obtain the polymer;

[0125] S5. Cool the system after reaction S4 to 40°C, add 50 parts of deionized water and 0.001 parts of ethylenediamine, and disperse to obtain the binder with the multi-segment cross-linked structure.

[0126] Example 9

[0127] S1. Preparation of acrylic unit segments:

[0128] Mix 20 parts acrylic acid and 2.5 parts monomethyl maleate, add 0.01 parts ammonium persulfate and 500 parts deionized water, and react at 65°C for 3 hours with nitrogen purging to obtain acrylic acid unit segments;

[0129] S2. Preparation of Acrylamide Unit Segments:

[0130] In the system after the S1 reaction, 150 parts of deionized water and 10 parts of lithium hydroxide were added to adjust the pH of the system to 6.5-7. 28 parts of acrylamide, 2.5 parts of N-hydroxymethylacrylamide and 0.01 parts of ammonium persulfate were added, the system temperature was adjusted to 75℃, and the reaction was carried out for 4 hours to obtain acrylic unit segments with acrylamide unit segments on the surface.

[0131] S3. Preparation of acrylate unit segments:

[0132] In the system after the S2 reaction, add 100 parts of deionized water, 6 parts of hydroxyethyl acrylate, 40 parts of methoxy polyethylene glycol (1000) acrylate, 1 part of polyethylene glycol (400) di(meth) acrylate, 1 part of ethyl acrylate, and 0.02 parts of ammonium persulfate. Adjust the system temperature to 65°C and react for 3 hours.

[0133] S4. After the reaction in S3, add 0.02 parts of ammonium persulfate, heat to 85°C, and react for 2 hours to obtain the polymer;

[0134] S5. Cool the system after the reaction in S4 to 40°C, add 0.001 parts of ethylenediamine, and disperse to obtain the binder with the multi-segment cross-linked structure.

[0135] Test Implementation Comparison Results

[0136] Comparative Example 1 uses a commercially available styrene-butadiene emulsion as the negative electrode binder for lithium batteries, and Comparative Example 2 uses a commercially available PAA lithium battery aqueous binder as the negative electrode binder.

[0137] The test results of the examples and comparative examples are shown in Tables 1 and 2.

[0138] Table 1

[0139]

[0140] As can be seen from Table 1, the adhesives prepared in the various embodiments of the present invention have better adhesion, flexibility and solvent resistance than the comparative examples.

[0141] Table 2. Charge / discharge and cycle life performance test results

[0142]

[0143] As can be seen from Table 2, the lithium batteries prepared with the binders in the various embodiments of the present invention have advantages such as long battery cycle life and high plateau voltage, which meet the needs of high-end lithium battery manufacturing.

Claims

1. An adhesive having a multi-segment cross-linked structure, characterized in that, The product comprises polymers, deionized water, and polyamines; the polymers include acrylic acid unit segments, acrylamide unit segments, and acrylate unit segments; wherein the acrylic acid unit segments are polymerized from acrylic acid monomers and butenedioic acid monoalkyl ester monomers; the acrylamide unit segments are polymerized from acrylamide monomers and hydroxyalkyl acrylamide monomers; and the acrylate unit segments are polymerized from hydrophilic acrylate monomers and multifunctional crosslinked acrylate monomers. The acrylic unit monomer accounts for 20-35% of the weight of the polymer; The acrylamide unit monomer accounts for 25-40% of the weight of the polymer; The acrylate unit monomer accounts for 35-55% of the weight of the polymer; The multifunctional crosslinked acrylate monomer is one or more of polyethylene glycol (200) di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate or polyethylene glycol (600) di(meth)acrylate; The adhesive with the multi-segment cross-linked structure is prepared by the following steps: S1. Preparation of acrylic unit segments: Acrylic monomers and butenedioic acid monoalkyl ester monomers are mixed, and an initiator and deionized water are added. The mixture is reacted at 50-85°C for 2-5 hours to obtain acrylic unit segments. S2. Preparation of Acrylamide Unit Segments: In the system after the S1 reaction, deionized water was added and the pH of the system was adjusted to 6.5-7. Acrylamide monomers, hydroxyalkyl acrylamide monomers, and initiators were added. The system temperature was adjusted to 60-75℃ and the reaction was carried out for 1-4 hours to obtain acrylic unit segments with acrylamide unit segments on the surface. S3. Preparation of acrylate unit segments: In the system after S2 reaction, deionized water, hydrophilic acrylate monomers, multifunctional crosslinked acrylate monomers, and initiators are added. The system temperature is adjusted to 55~65℃ and the reaction is carried out for 2~4 hours. S4. After the reaction in S3, deionized water and initiator are added, the temperature is raised to 80~90℃, and the reaction is carried out for 2~5 hours to obtain the polymer; S5. Cool the system after the reaction in S4 to below 40°C, add deionized water and polyamine, and disperse to obtain the binder with the multi-segment cross-linked structure.

2. The adhesive with a multi-segment cross-linked structure according to claim 1, characterized in that, In the acrylic unit segment, the acrylic monomer is one or more of acrylic acid, methacrylic acid, sodium acrylate, lithium acrylate, sodium methacrylate, or lithium methacrylate.

3. The adhesive with a multi-segment cross-linked structure according to claim 1, characterized in that, In the acrylic acid unit segment, the butenedioic acid monoalkyl ester monomer is one or more of monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, or monobutyl fumarate.

4. The adhesive with a multi-segment crosslinked structure according to claim 1, characterized in that, In the acrylamide unit segment, the acrylamide monomer is one or more of methacrylamide, dimethacrylamide, diethylacrylamide, isopropylacrylamide, dimethylaminoacrylamide, or diacetoneacrylamide.

5. The adhesive with a multi-segment crosslinked structure according to claim 1, characterized in that, In the acrylamide unit segment, the hydroxyalkyl acrylamide monomer is one or more of N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, N-hydroxymethylacrylamide, or N-hydroxyethylacrylamide.

6. The adhesive with a multi-segment cross-linked structure according to claim 1, characterized in that, In the acrylate unit segment, the hydrophilic acrylate monomer is one or more of hydroxyethyl acrylate, hydroxyethyl acrylate, methoxyethyl acrylate, or methoxy polyethylene glycol (meth)acrylate.

7. The adhesive with a multi-segment cross-linked structure according to claim 1, characterized in that, The acrylate unit segment also contains lipophilic acrylate monomers.

8. The adhesive having a multi-segment crosslinked structure according to claim 7, characterized in that, The lipophilic acrylate monomer is one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, or isooctyl acrylate.

9. The use of the binder having a multi-segment cross-linked structure according to any one of claims 1 to 8 in the preparation of lithium battery adhesives.

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