Battery composite diaphragm, lithium ion battery and preparation method

Abstract

The invention provides a battery composite separator, a lithium ion battery and a preparation method. The preparation of the battery composite separator includes: mixing nano-inorganic powder and a diluent to obtain a mixed liquid; mixing polyolefin powder and the mixed liquid and performing Mixing and plasticizing to form a homogeneous melt; cooling the homogeneous melt to form a cast film, stretching the cast film; removing the diluent, and performing shaping and winding treatment to obtain the battery composite Diaphragm. In the present invention, nano-scale inorganic powder is added to the polyolefin separator through an in-situ blending method. The nano-inorganic powder has high thermal stability and can reduce the thermal shrinkage of the lithium battery separator after being heated; the nano-inorganic powder has a large specific The surface area and polar functional groups on the surface can improve the lyophilicity between the polyolefin separator and the electrolyte; the nano-inorganic powder plays a heterogeneous nucleation role in the system and can increase the crystallization of polyolefin during the polyolefin molding process. degree and improve the mechanical strength of the diaphragm.

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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