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CN-119050279-B - Preparation method of low-temperature curing polyimide binder for lithium ion battery, binder prepared by method and electrode plate prepared by method

CN119050279BCN 119050279 BCN119050279 BCN 119050279BCN-119050279-B

Abstract

The invention relates to a preparation method of a low-temperature curing polyimide binder for a lithium ion battery, and the binder and an electrode plate prepared by the same. The preparation method comprises the steps of carrying out condensation polymerization on dianhydride, diamine monomer and monomer containing special functional groups in a solvent to obtain copolymerized polyamic acid, adding a blocking agent and fully and uniformly stirring to obtain blocked polyamic acid, and adding a catalyst and fully and uniformly stirring to obtain a precursor solution of polyimide. The lithium ion battery pole piece is prepared by uniformly mixing the lithium ion battery pole piece, active substances and a conductive agent to prepare slurry, coating the slurry on the surface of a current collector, and then carrying out heat treatment at 100-150 ℃ to prepare the lithium ion battery pole piece with the low-temperature cured polyimide as an adhesive. The method can greatly reduce the process use temperature of the polyimide binder, save energy and reduce cost, and simultaneously avoid the influence of the high-temperature treatment of the traditional thermal imidization on the performance of the electrode material. The lithium ion battery assembled by the electrode pole piece prepared by the invention has higher specific capacity, excellent capacity retention rate and other excellent electrical performance and safety performance.

Inventors

  • QI SHENGLI
  • WANG CHANGQI
  • LIN DAOLEI
  • TIAN GUOFENG
  • WU DEZHEN

Assignees

  • 北京化工大学常州先进材料研究院

Dates

Publication Date
20260508
Application Date
20240821

Claims (6)

  1. 1. The preparation method of the low-temperature curing polyimide binder for the lithium ion battery is characterized by comprising the following steps of: (1) Under the conditions of nitrogen atmosphere and ice water bath, carrying out condensation polymerization reaction on excessive dianhydride monomer, diamine monomer and third monomer containing special functional groups in a reaction solvent to obtain copolymerized polyamic acid solution, wherein the molecular weight of polyimide can be adjusted by the relative addition amount of the dianhydride monomer; (2) Adding a blocking agent into the polyamic acid solution obtained by copolymerization, and fully and uniformly stirring to obtain a blocked polyamic acid solution; (3) Adding a catalyst into the blocked polyamic acid solution obtained in the step (2) and fully and uniformly stirring to obtain a precursor solution of low-temperature cured polyimide; (4) Uniformly mixing an active substance, a conductive agent and the precursor solution obtained in the step (3) to obtain slurry, coating the slurry on the surface of a current collector, and performing thermal imidization treatment to obtain the electrode slice with the polyimide cured at low temperature as an adhesive.
  2. 2. The method according to claim 1, wherein the solid content of the polyamic acid solution in the step (1) is 0.5 to 40% by weight; the molar ratio of the dianhydride monomer to the diamine monomer is 1.01:1-1.3:1, the molar ratio of the dianhydride monomer to the diamine monomer is 9-25:1, the reaction time is 0.5-12h, the dianhydride monomer in the step (1) is one or more of pyromellitic dianhydride (PMDA), 4, 4 '-diphenyl ether dianhydride (ODPA), biphenyl dianhydride (BPDA), 3',4, 4 '-diphenyl sulfone tetracarboxylic dianhydride (DSDA), hexafluorodianhydride (6 FDA), 3',4, 4 '-Benzophenone Tetracarboxylic Dianhydride (BTDA), 4, 4' - (4, 4 '-isopropylidene diphenoxy) diphthalic anhydride (BPADA), p-phenylene-diphenyl trimellitate dianhydride (TAHQ), the diamine monomer in the step (1) is one or more of p-phenylene diamine, m-phenylene diamine (m-PDA), 4, 4' -diaminodiphenyl ether (ODA), 3,4 '-diaminodiphenyl ether (3' -diaminodiphenyl ether), 3,4 '-diaminodiphenyl ether (3, 4' -diaminosulfone), 4 '-diaminodiphenyl ether (3, 4' -diaminosulfone), 4 '-diaminomethane (2, 4' -diaminosulfone) Mixing one or more of 1, 3-bis (4' -aminophenoxy) benzene (TPE) in any proportion; the third monomer containing special functional groups in the step (1) is one or more of 2, 3-diaminopyridine, 2, 4-diaminopyridine, 2, 5-diaminopyridine, 3, 4-diaminopyridine, 5, 6-diaminobenzimidazolone, 2, 4-diamino-6- [ 2-methyl- (-imidazolyl) ethyl ] -1,3, 5-quinoline and 5-amino-2- (4-aminophenyl) benzimidazole, and the solvent in the step (1) is one or more of N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), N-Dimethylacetamide (DMAC), N-ethylpyrrolidone (NEP), dimethyl sulfoxide (DMSO) and Hexamethylphosphoramide (HMPA).
  3. 3. The preparation method according to claim 1, wherein the molar ratio of the end-capping agent to the dianhydride monomer in the step (2) is 0.01:1-5:1, the reaction time is 0.5-12h, and the end-capping agent in the step (2) is any ratio of one or more of 5-Aminobenzimidazole (ABZ), 2-aminoimidazole, 2-aminopyridine and aminopyrazine.
  4. 4. The preparation method according to claim 1, wherein the molar ratio of the catalyst to dianhydride monomer in the step (3) is 0.01:1-5:1, the reaction time is 0.5-12h, and the catalyst in the step (3) is any ratio of one or more of N-N' -Carbonyldiimidazole (CDI), 6-Aminoquinoline (AQL), benzotriazol (BTA) and 1, 8-diazabicyclo [5.4.0] undec-7-ene (DBU).
  5. 5. The preparation method according to claim 1, wherein the solid content of the electrode slurry in the step (4) is 20-90wt%, the non-solvent part of the electrode slurry contains 80-99wt% of active substances, 0.5-10wt% of conductive agents and 0.5-10wt% of precursor solutions, the positive electrode active substances in the step (4) are any proportion of one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate, the negative electrode active substances in the step (4) are any proportion of one or more of carbon materials, silicon and oxides thereof, tin and oxides thereof, silicon-carbon composite, silicon-oxygen-carbon composite and tin-carbon composite, the conductive agents in the step (4) are any proportion of one or more of conductive carbon black, conductive graphite, graphene and carbon nanotubes, the current collector in the step (4) is carbon-containing aluminum foil or carbon-containing copper foil, the thickness of the electrode slurry in the step (4) is 75-200 μm, and the thermal imidization time is 0-150 ℃ and the thermal imidization time is 0.5-150 ℃.
  6. 6. A low temperature cured polyimide binder for lithium ion batteries prepared according to any one of claims 1 to 5 and electrode sheets prepared therefrom.

Description

Preparation method of low-temperature curing polyimide binder for lithium ion battery, binder prepared by method and electrode plate prepared by method Technical Field The invention relates to the technical field of electrode materials, in particular to a preparation method of a low-temperature curing polyimide binder for a lithium ion battery, and the binder and an electrode plate prepared by the same. Background Lithium ion batteries have been developed as one of the most potential new generation of energy sources nowadays due to their high specific energy, low self-discharge, no memory effect, and environmental protection. However, as the energy density and capacity thereof are continuously increased, the problem of battery safety is increasingly raised. The binder is an important component of the lithium ion battery electrode, and the function of the binder is not negligible although the mass of the binder in the electrode material is relatively low. The binder is not only responsible for tightly combining the active material, the conductive agent and the current collector, but also plays a key role in the performance and stability of the electrode. Specifically, the binder can inhibit volume expansion of the electrode during charge and discharge, and effectively reduce side reactions between the active material and the electrolyte, thereby improving cycle life and safety of the battery. At present, although the conventional adhesive has lower cost, the conventional adhesive has poor stability under high-temperature environment. During long-term use of lithium ion batteries, an increase in the internal temperature of the battery may cause thermal degradation of the binder, which not only affects the mechanical integrity of the battery, but may also cause serious safety hazards. In addition, the adhesive property of the existing adhesive can be weakened after multiple charge and discharge cycles, so that the interface connection between the active material and the current collector is invalid, and the volume expansion of the electrode cannot be effectively restrained. These problems ultimately lead to reduced cycle life of lithium ion batteries, and increased capacity fade, limiting their use in high performance applications. Therefore, aiming at the defects of the existing adhesive in heat resistance and adhesive performance, the development of a novel adhesive material with higher thermal stability and stronger adhesive force has become a key research direction for improving the performance of the lithium ion battery. This not only helps to improve the safety and cycle life of the battery, but also supports the application of lithium ion batteries under more severe operating conditions. Polyimide (PI) monomer has various types and strong designability of molecular structure, and is used as an adhesive, has the characteristics of high and low temperature resistance, high adhesive strength, chemical stability, self-extinguishing flame retardant property and the like, and is considered as the first choice of the lithium ion battery adhesive. The excellent heat resistance can keep the structural stability of the electrode material under high temperature and high pressure, and the capacity of the electrode under high-pressure circulation is improved. The polyimide adhesive is not easy to oxidize or reduce due to good chemical stability, does not have side reaction with other materials, and ensures the electrochemical stability of the electrode. In addition, the polyimide molecular structure enables the polyimide to have higher tensile strength and elastic recovery capability, can effectively adapt to the contraction and expansion of the electrode, and ensures the structural integrity and stability of the electrode in the circulation process. However, the imidization process of polyimide generally requires a high temperature treatment of 300 ℃ or more, which is disadvantageous in reducing power consumption, and may also affect the performance of the electrode material itself. Therefore, a low temperature curing technology is urgently needed to reduce the imidization temperature of polyimide, so that the polyimide has more industrial application potential. Disclosure of Invention The invention aims to solve the problems that the traditional adhesive has poor safety performance in a lithium ion battery with high specific capacity, and the traditional polyimide adhesive has high imidization temperature, so that the energy consumption is high, the cost is high, and the industrial application is not facilitated. The preparation method can greatly reduce the thermal imidization temperature of the later polyimide adhesive and reduce the energy consumption by specially designing the molecular structure of polyimide and under the synergistic effect of the later polyimide adhesive and a catalyst, and has more excellent electrical property than the traditional adhesive. In order to achieve the above purpose, the invent