Battery diaphragm and preparation method thereof

Abstract

The present invention discloses a battery diaphragm and a preparation method thereof. The battery diaphragm of the present invention comprises a micro-nano laminated polyolefin microporous membrane; the micro-nano laminated polyolefin microporous membrane is composed of an upper surface layer, a middle layer and a lower surface layer; and the middle layer is of a multilayer structure formed by polypropylene layers and polyethylene layers through a micro-nano lamination technique. According to the battery diaphragm, the middle layer of the multilayer structure formed by the polypropylene layersand the polyethylene layers through the micro-nano lamination technique is adopted, and therefore, on the one hand, the multi-layer structure has better safety, and on the other hand, the micro-nanolamination technique can assist in improving the tensile strength, puncture strength and other mechanical properties of the battery diaphragm, and can make the battery diaphragm thinner when forming the middle layer, thereby satisfying the requirements of the thin and high-safety lithium battery diaphragm for mechanical properties and safety; and distances from the polyethylene layers in the middle layer to the surface of the battery diaphragm can be adjusted, so that fast breaking functions of different effects can be realized, and therefore, the use requirements of the different breaking functions can be satisfied.

Description

technical field [0001] The present application relates to the field of lithium-ion battery separators, in particular to a battery separator and a preparation method thereof. Background technique [0002] With the development of electric vehicles and energy storage industries, the requirements for lithium batteries are getting higher and higher, requiring lithium batteries to be safer and have higher energy density. The lithium battery separator is one of the most critical materials in the lithium battery, which directly affects the safety and energy density of the lithium battery. Therefore, the preparation of a safe, environmentally friendly, thin, and low-cost microporous membrane is a difficulty in the development of the lithium battery separator. At present, there are two methods of manufacturing lithium battery separators: wet method and dry method. Among them, the wet process needs to use a large amount of organic diluent, the equipment is complicated, the cost is hig...

AI Technical Summary

Problems solved by technology

The existing wet-process diaphragm is usually made of ultra-high molecular weight polyethylene, the melt flow rate is slow, the thermal shrinkage is large during the heating process, and the pores cannot be closed in time

The closed cell temperature of the dry-process polypropylene separator is relatively high, and the heat shrinks greatly during the heating process, so it cannot respond quickly and protect the safety of the battery

In the dry-process polypropylene / polyethylene / polypropylene three-layer separator, although the polyethylene layer is designed as a protection, the polyethylene layer is in the middle, and it takes a certain amount of heat transfer and time to function as a circuit breaker.

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