Battery composite separator, lithium ion battery and preparation method thereof

Abstract

The invention provides a battery composite separator, a lithium ion battery and a preparation method thereof. The preparation of the battery composite separator comprises the following steps: mixing nano inorganic powder and diluent to obtain a mixed solution; Mixing the polyolefin powder with the mixed liquid and performing mixing plasticization to form a homogeneous melt; The homogeneous melt iscooled to form a cast sheet film, and the cast sheet film is stretched; The diluent is removed and the shaped winding process is carried out to obtain a battery composite separator. As that nanometerinorganic power is added into the polyolefin separator through an in-situ blended method, the nanometer inorganic powder has high thermal stability and can reduce the thermal shrinkage of the lithiumbattery separator after being heat; Nano-inorganic powders have large specific surface area and polar functional groups on the surface, which can improve the hydrophilicity between polyolefin membrane and electrolyte. Nano-inorganic powders play a heterogeneous nucleation role in the system, which can increase the crystallinity of polyolefin and improve the mechanical strength of diaphragm in theprocess of polyolefin molding.

Description

technical field [0001] The invention belongs to the preparation of battery diaphragms, in particular to a battery composite diaphragm, a lithium ion battery and a preparation method. Background technique [0002] Lithium-ion batteries are composed of four key materials: positive electrode material, negative electrode material, electrolyte, and separator. Among them, the role of the separator is to isolate the positive and negative electrode materials and prevent the internal short circuit of the battery; the separator must have a porous structure and be able to retain a large amount of energy. The electrolyte ensures the rapid conduction of lithium ions inside the separator. [0003] At present, the diaphragm materials used commercially are mainly made of polyethylene and polypropylene, and the processing and forming methods include wet forming and dry forming. However, the single-component polyolefin separator material has the following defects in battery applications: pol...

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Problems solved by technology

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a battery composite diaphragm, which is used to solve the problems of poor temperature resistance and poor lyophilicity of the polyolefin diaphragm in the prior art.

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