Composite expansion film, preparation method and application thereof

Abstract

The invention provides a composite expansion film, a preparation method and application thereof. The composite expansion film comprises a base layer, a first bonding layer, a temperature-resistant layer and a second bonding layer which are sequentially arranged, wherein the material of the base layer comprises polystyrene, and the material of the temperature-resistant layer is a material of which the thermal expansion coefficient is not greater than 6*10<-6> / K; according to the composite expansion film, the material with a relatively good expansion effect is used as the base layer, and the material with a relatively small thermal expansion coefficient is used as the temperature-resistant layer, so that the composite expansion film has a very good temperature-resistant effect while having excellent expansion performance; the width of the composite expansion film is not changed when the composite expansion film is baked at a high temperature of 90DEG C, so that the problem of exposure of a metal current collector caused by shrinkage of the width of the film is avoided, and the use risk is reduced.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a composite expansion film and a preparation method and application thereof. Background technique [0002] Cylindrical steel shell lithium-ion batteries are often assembled in various devices and equipment, and there will be frequent and repeated vibrations and shakes when the end user operates the equipment; since the lithium battery is loaded with active materials, it has a certain weight, and through The metal conductive drain is welded and connected to the shell to conduct electricity. Therefore, during use, as the number of vibrations increases, the metal drain will break and the battery will fail, which will cause a great safety hazard. [0003] In order to solve the above problems, a series of organic material base films are usually pasted on the surface of the roll core. After the organic base film is soaked in the electrolyte containing organic ...

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Problems solved by technology

[0004] The expansion films obtained in the above-mentioned patents all have good expansion effects, which can reduce the risk of metal drainage fluid breakage, but these base films with good expansion effects will shrink and deform after being baked at 45-60°C; therefore, When they are applied to lithium-ion batteries, when the core with the expansion film is baked at a high temperature of 80-90°C, the film width of the expansion film will become smaller due to shrinkage, resulting in the outflow of the electrolyte in the core of the lithium-ion battery. Cause the problem of unqualified products, and even have potential safety hazards

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