CN-121663113-B - High-flexibility heat-resistant composite battery diaphragm and preparation method and application thereof

CN121663113BCN 121663113 BCN121663113 BCN 121663113BCN-121663113-B

Abstract

The invention discloses a high-flexibility heat-resistant composite battery diaphragm, and a preparation method and application thereof, and belongs to the technical field of diaphragms. The preparation method comprises the steps of preparing high-temperature-resistant coating raw materials and flexible coating raw materials into high-temperature-resistant coating materials and flexible coating materials respectively, coating the high-temperature-resistant coating materials and the flexible coating materials on the surface of a porous polymer base film in sequence, and drying to obtain the high-flexibility heat-resistant composite battery diaphragm. According to the invention, through preparing the flexible particles with the self-repairing function, the high-flexibility heat-resistant composite battery diaphragm which is easy to obtain raw materials and feasible in industrialization is provided, the synergic promotion of flexibility, self-repairing and heat resistance is realized, the expansion of the anode and the cathode is effectively buffered, the puncture of lithium dendrites is resisted, the thermal runaway risk is reduced, and the safety and the cycling stability of the battery are remarkably improved.

Inventors

CHEN BAOHUI
GUO XIAOHAN
LI BO
LIU JINGJU
WANG JIANGFENG
LIU JIARUI
XIE LINJIN
WEI HANXIN
XIANG ZIQIAN
Gong Xuanlin

Assignees

湖南防灾科技有限公司
国网湖南省电力有限公司防灾减灾中心
湖南省湘电试研技术有限公司

Dates

Publication Date: 20260505
Application Date: 20260205

Claims (10)

1. The high-flexibility heat-resistant composite battery diaphragm is characterized by comprising a porous polymer base film, a flexible coating and a high-temperature-resistant coating; The preparation raw materials of the flexible coating comprise flexible particles, wherein the flexible particles are hydroxyl-terminated polybutadiene and carboxyl-terminated nitrile rubber.
2. The highly flexible heat resistant composite battery separator of claim 1 wherein the porous polymer-based film is polyethylene, polypropylene, polyamide, polyimide or polyaramid; And/or the thickness of the porous polymer base film is 2-20 microns; And/or the porosity of the porous polymer base film is 30% -80%; And/or the air permeability of the porous polymer base film is 100-150 sec/100ml.
3. The high-flexibility heat-resistant composite battery diaphragm according to claim 2, wherein the flexible coating comprises, by mass, 5% -40% of flexible particles, 3% -10% of auxiliary agents and the balance of water; and/or, the high-temperature resistant coating comprises, by mass, 1% -20% of high-temperature resistant fibers, 5% -20% of inorganic fillers, 3% -10% of auxiliary agents and the balance of water.
4. The high-flexibility heat-resistant composite battery separator according to claim 3, wherein the mass ratio of the hydroxyl-terminated polybutadiene to the carboxyl-terminated nitrile rubber is 1-5:1; and/or the hydroxyl value of the hydroxyl-terminated polybutadiene is 0.5 mmol/g-0.7 mmol/g; and/or the hydroxyl-terminated polybutadiene has a number average molecular weight of 3000-4600; and/or, at 40 ℃, the viscosity of the hydroxyl-terminated polybutadiene is less than or equal to 8.5 Pa.s; and/or the carboxyl content of the carboxyl-terminated nitrile rubber is 0.5 mmol/g-0.65 mmol/g; And/or the number average molecular weight of the carboxyl-terminated nitrile rubber is 2000-3500; And/or, at 40 ℃, the viscosity of the carboxyl-terminated nitrile rubber is 7 Pa.s-50 Pa.s; and/or the acrylonitrile content of the carboxyl-terminated nitrile rubber is 8% -20%; And/or the high temperature resistant fiber is an alumina nanofiber, a silicon carbide nanofiber, a boron nitride nanofiber, a silicon oxide nanofiber, a chitin/chitosan nanofiber, a cellulose fiber or an aramid fiber; and/or the average particle size of the high temperature resistant fiber is 10 nm-80 nm; And/or the inorganic filler is at least one of alumina, silica, molecular sieve, hydrotalcite, diatomite, montmorillonite, titanium oxide and magnesium oxide; And/or the particle size of the inorganic filler is 20 nm-100 nm.
5. The high-flexibility heat-resistant composite battery separator according to claim 4, wherein the auxiliary agent is a wetting agent, a binder, a thickener and a dispersant; And/or the wetting agent is at least one of polyacrylate, polyether modified silane surfactant and fatty alcohol polyether wetting agent; And/or the binder is polyvinylidene fluoride, polyvinyl alcohol, polyvinyl butyral, poly (vinylidene fluoride) Hexafluoropropylene), sodium alginate, lithium alginate, polymethacrylic acid, acrylic acid, carboxymethyl chitosan, polyethylene oxide and styrene butadiene rubber; and/or the thickener is at least one of sodium cellulose, lithium cellulose and polyvinyl amide; and/or the dispersing agent is one of lithium polyacrylate, sodium polyacrylate and ammonium polyacrylate.
6. The high-flexibility heat-resistant composite battery diaphragm according to claim 5, wherein the flexible coating comprises, in mass percent, 5% -40% of flexible particles, 1% -4% of binder, 1% -4% of thickener, 0.05% -1% of dispersant, 0.05% -1% of wetting agent and the balance of water; The high-temperature-resistant coating comprises, by mass, 1% -20% of high-temperature-resistant fibers, 5% -20% of inorganic fillers, 1% -4% of binders, 1% -4% of thickeners, 0.05% -1% of dispersing agents, 0.05% -1% of wetting agents and the balance of water.
7. The highly flexible heat resistant composite battery separator of claim 1 wherein the flexible coating and the high temperature resistant coating are on the same side or different sides of the porous polymer-based membrane; and/or when the flexible coating and the high temperature resistant coating are positioned on the same side of the porous polymer base film, the high temperature resistant coating and the flexible coating are sequentially arranged; and/or the thickness of the flexible coating is 0.2-4 microns; and/or the thickness of the high temperature resistant coating is 0.2-4 microns.
8. The high flexibility heat resistant composite battery separator of claim 1, wherein at least one of the following conditions a-d is satisfied: a. the air permeability of the high-flexibility heat-resistant composite battery diaphragm is more than or equal to 140s/100mL; the longitudinal heat shrinkage rate of the high-flexibility heat-resistant composite battery diaphragm is less than or equal to 3.0 percent at 180 ℃; The transverse heat shrinkage rate of the high-flexibility heat-resistant composite battery diaphragm is less than or equal to 0.6 percent at 180 ℃; d. the puncture strength of the high-flexibility heat-resistant composite battery diaphragm is more than or equal to 600gf.
9. A method for preparing the high-flexibility heat-resistant composite battery separator according to any one of claims 1 to 8, comprising the steps of: preparing a high-temperature-resistant coating and a flexible coating from a preparation raw material of the high-temperature-resistant coating and a preparation raw material of the flexible coating respectively; And respectively coating the high-temperature resistant coating and the flexible coating on the surface of the porous polymer base film, and drying to obtain the high-flexibility heat-resistant composite battery diaphragm.
10. The use of the high-flexibility heat-resistant composite battery separator according to any one of claims 1 to 8 or the high-flexibility heat-resistant composite battery separator manufactured by the manufacturing method according to claim 9 in a secondary battery.

Description

High-flexibility heat-resistant composite battery diaphragm and preparation method and application thereof Technical Field The invention belongs to the technical field of diaphragms, and particularly relates to a high-flexibility heat-resistant composite battery diaphragm, and a preparation method and application thereof. Background The current commercial battery diaphragm mainly comprises a polyolefin-based film, and has the advantages of low cost, good air permeability and the like, but has two main defects of poor heat resistance, easy thermal shrinkage when the battery is locally overheated (such as more than 120 ℃), short circuit and even thermal runaway caused by direct contact of positive and negative electrodes, insufficient flexibility, continuous mechanical stress on the diaphragm caused by volume expansion of the positive and negative electrodes in the process of charging and discharging the battery, diaphragm cracking or coating falling off, and dendrite penetration risk. At present, in order to improve heat resistance, the heat stability of the diaphragm can be improved by coating a ceramic coating or a high-temperature-resistant polymer in the industry, but the ceramic coating has high brittleness and is easy to fall off, and the flexibility and the air permeability of the diaphragm can be reduced. In order to improve the flexibility, the shock resistance of the diaphragm can be improved by adopting flexible materials such as styrene-butadiene rubber, polyurethane and the like for coating, but the materials have poor electrolyte swelling resistance, are easy to generate structural failure after long-term use, lack self-repairing capability and cannot cope with micro damage caused by lithium dendrites, and adopt a double-layer structure of a flexible layer and a heat-resistant layer, but the existing flexible materials have poor compatibility with the heat-resistant materials, weak interface binding force and no synergistic action mechanism, and are difficult to simultaneously meet multiple requirements such as high flexibility, high heat resistance, electrolyte resistance and the like. Disclosure of Invention The invention aims to overcome the technical problems, and therefore provides a high-flexibility heat-resistant composite battery diaphragm, and a preparation method and application thereof. According to the invention, through preparing the flexible particles with the self-repairing function, the high-flexibility heat-resistant composite battery diaphragm which is easy to obtain raw materials and feasible in industrialization is provided, the synergic promotion of flexibility, self-repairing and heat resistance is realized, the expansion of the anode and the cathode is effectively buffered, the puncture of lithium dendrites is resisted, the thermal runaway risk is reduced, and the safety and the cycling stability of the battery are remarkably improved. The invention solves the technical problems through the following technical proposal. The invention discloses a high-flexibility heat-resistant composite battery diaphragm which is characterized by comprising a porous polymer base film, a flexible coating and a high-temperature-resistant coating; The preparation raw materials of the flexible coating comprise flexible particles, wherein the flexible particles are hydroxyl-terminated polybutadiene and carboxyl-terminated nitrile rubber. The flexible particles in the invention are selected essentially by utilizing the dynamic hydrogen bonding action of hydroxyl and carboxyl to form a self-repairing mechanism, so that the flexibility of the diaphragm is improved. According to some embodiments of the invention, the porous polymer-based film is Polyethylene (PE), polypropylene (PP), polyamide (PA), polyimide (PI) or polyaramid (AR); According to some embodiments of the invention, the porous polymer-based film has a thickness of 2 micrometers to 20 micrometers. According to some embodiments of the invention, the porous polymer-based film has a porosity of 30% -80%. According to some embodiments of the invention, the porous polymer-based film has an air permeability of 100sec/100mL to 150sec/100mL. According to some embodiments of the invention, the flexible coating comprises, by mass, 5% -40% of flexible particles, 3% -10% of an auxiliary agent and the balance of water; According to some embodiments of the invention, the high temperature resistant coating comprises, by mass, 1% -20% of high temperature resistant fibers, 5% -20% of inorganic fillers, 3% -10% of auxiliary agents and the balance of water. The high-temperature resistant fiber forms a supporting framework, and the filler fills the gaps of the framework, so that the air permeability of the coating is ensured, and the heat resistance is improved. According to some embodiments of the present invention, the mass ratio of the hydroxyl-terminated polybutadiene to the carboxyl-terminated nitrile rubber is 1-5:1, preferably 1-3:1. According to