A double-sided heat-resistant ceramic coating composite diaphragm

Abstract

A double-sided heat-resistant ceramic coating composite diaphragm adopts the design concept of complementary performance, adopts ultra-high PE microporous diaphragm as the base film, and coats ceramic coating materials on both sides to form a composite diaphragm material structure. The high PE base film has the following advantages: appropriate pore size suitable for coating processing, with an average pore size between 80-200 nanometers; the base film has excellent mechanical properties; the PE material has a thermal shutdown capability of 140 ° C; double-sided heat-resistant ceramic coating The composite separator comprehensively utilizes the above-mentioned advantages of the ultra-high PE base film and the unique advantages of stress symmetry, low thermal shrinkage rate, and high-voltage oxidation resistance of the double-sided ceramic coating structure, which can meet the application requirements of power batteries and other applications.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion battery diaphragms, in particular to the field of power battery composite diaphragms. Background technique [0002] Lithium-ion battery separators belong to the "functional membrane materials" clearly proposed in the "12th Five-Year Plan for New Material Industry" of the Ministry of Industry and Information Technology of China. As "new materials" and "new energy vehicles" in my country's seven strategic emerging industries Covering the core functional materials that need to be the first to break through, the 239th item in the "Key Product Catalog of the New Material Industry" issued by the Ministry of Industry and Information Technology in 2012 clearly listed "temperature-resistant power battery separators" that need to be developed; my country's "New Energy Vehicle Industry Twelve The five-year plan aims to achieve an annual production and sales of more than 500,000 electric vehicles by 2015, a...

AI Technical Summary

Problems solved by technology

[0004] (1) Due to the memory effect of polymer materials after thermal stretching, there is a disadvantage of large thermal shrinkage at high temperatures of 105-130°C;

[0005] (2), poor liquid absorption;

[0006] (3) Oxidation at a high voltage above 4.35V will easily lead to a decrease in the mechanical strength of the diaphragm

[0007] Chinese invention patent application 200510086061.5 reports the technical scheme of forming a porous coating on the surface of a polyolefin microporous diaphragm with a melting point above 180°C of high temperature resistant polyamide, polyamideimide, polyimide, etc.; Chinese invention patent application 200480034190.3 proposes The technical scheme of coating the surface of polyolefin microporous diaphragm with fluororesin that can be gelled to form a coating; some domestic manufacturers try to prepare porous polyimide diaphragm by electrospinning process, which has low production efficiency and does not have low temperature shutdown. breaking capacity, the formed high temperature resistant porous material has low mechanical strength, and it is difficult to prepare a high-strength porous diaphragm with a thickness of 6-12 microns to meet the needs of the composite process

[0008] Germany's Degussa company has prepared PET non-woven fabric composite inorganic coating lithium-ion battery separator "Separion", which has both the flexibility of organic matter and the thermal stability of inorganic ceramics, and can withstand high temperatures up to 200 °C; the fourth with PE as the base film Compared with the coating composite separator, PET non-woven fabric has the following disadvantages as the base film: the thermal shutdown temperature is too high, the pore size is large, the mechanical strength of the material is low, the battery is easy to short circuit, self-discharge, etc.

[0016] The single-sided ceramic composite diaphragm can improve the heat shrinkage performance of the PE base film from 105°C of the PE base film to 120-130°C, and the single-sided ceramic structure can inhibit the heat shrinkage of the PE base film at a higher temperature of 130-210°C Insufficient, the thermal shrinkage performance of the composite diaphragm at a high temperature of 130-210°C still needs to be improved

[0017] The second disadvantage of the existing single-sided ceramic coating composite diaphragm is: due to the asymmetrical stress, the single-sided coating diaphragm is a typical "layered composite material". If the residual stress in it cannot be effectively controlled, it is easy to split after cutting Process problems such as composite diaphragm curling appear, which affect the safety of the battery

[0019] (1) The non-woven fabric is not strengthened by thermal stretching, and the longitudinal tensile strength is lower than 50MPa. The product has quality defects such as fluctuations in porosity and thickness after stretching under the presence of tension such as winding during lithium battery production and application;

[0020] (2) The use of monomer thermal crosslinking and the use of peroxides BPO, AIBN, etc. are prone to monomer or initiator residues, which are prone to side reactions and gas production in battery applications.

[0021] (3), the pore size of non-woven fabrics is on the order of 5 microns or more, the thermal shutdown temperature is high, and the safety is unreliable