Battery diaphragm and preparation method and application thereof

Abstract

The invention relates to a battery diaphragm and a preparation method and an application thereof. The diaphragm consists of a lithium ion battery diaphragm base material and an inorganic coating layer; the base material consists of a supporting layer and a compact layer; the compact layer is coated with the inorganic coating layer; the diaphragm has excellent high-temperature resistance, has certain strength after treatment at a temperature of 300 DEG C for 1h, and has the thermal shrinkage rate of less than or equal to 2%; the rigid structure stability and isolation performance of the diaphragm coating layer at a high temperature are ensured; the base material has a uniform and compact dual-layer structure, so that pin holes and a filler particle falling-off phenomena in a subsequent coating process can be controlled effectively, and requirements of the lithium ion battery diaphragm on the aspects of thermal resistance, porosity and strength can be satisfied; and therefore, the battery diaphragm is excellent in the comprehensive performance.

Description

technical field [0001] The invention relates to the technical field of batteries, in particular to a battery diaphragm and its preparation method and application. Background technique [0002] Separator is a key technical material to prevent battery short circuit, which will greatly accelerate the decomposition and heat generation of battery materials. Therefore, improving the thermal stability and fusing temperature of separator is very important for battery safety. [0003] Compared with the traditional polyolefin diaphragm, the ceramic coated diaphragm has a greater improvement in heat resistance and stability. There are two main types according to the substrate used. One is based on traditional polyolefin and coated with ceramic particles. A type of diaphragm has entered the market in batches; the other is a polymer non-woven fabric as a substrate, which is coated to form a ceramic diaphragm. Polyolefin stretched film (such as polyethylene (PE) or polypropylene (PP) fil...

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Problems solved by technology

The temperature resistance of the diaphragm reaches 200°C. Although the filler particles can improve the pinholes to a certain extent and obtain a good average pore size, due to the composition of the substrate in this patent, it is inevitable that there will be large pores in the diaphragm, and the filler particles will fall off easily. Test, the separator is treated at 300°C for 1 hour, the substrate melts, and the strength of the separator is completely lost

The patent application of South China University of Technology (publication number CN104157812A) proposes to use a multi-layer inclined wire former to prepare a three-layer lithium-ion battery separator with an inorganic coating, but the dense layer of the separator uses some synthetic fibers, and the thermal stability of the separator It can only make the heat shrinkage rate less than 1.0% at 110°C, which cannot meet the requirements for high-temperature resistant lithium-ion battery separators; the support layer of the separator is completely made of synthetic fibers, and the synthetic fibers are relatively poor in lyophilicity, which is easy to introduce air bubbles, and the separator has large pores.

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