Diaphragm, preparation method thereof and secondary battery

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a diaphragm and a preparation method thereof and a secondary battery, and the preparation method of the diaphragm comprises the following steps: S1, mixing and dispersing a ceramic material, a dispersing agent, a wetting agent, a part of active diluting monomer and a cross-linking agent to obtain ceramic slurry; s2, mixing and dissolving an initiator and the residual active diluted monomer to obtain a mixed solution; s3, mixing the ceramic slurry with the mixed solution to obtain composite slurry; and S4, coating at least one surface of a base membrane with the composite slurry to obtain the diaphragm. The composite slurry contains the initiator, the active diluent monomer and the ceramic material, the active diluent monomer can be cured and crosslinked with the ceramic material to form a heat-resistant skeleton, the formed cured material cannot swell with an electrolyte, and the swelling problem of a polyacrylate binder used by a traditional diaphragm is solved.

Description

technical field [0001] The invention belongs to the technical field of secondary batteries, and in particular relates to a diaphragm, a preparation method thereof and a secondary battery. Background technique [0002] Polyolefin separators are currently the most widely used lithium battery separators. However, the existing polyolefin separators on the market have problems with electrophilic electrolyte performance, insufficient heat resistance, and adhesion. In order to improve the electrolyte wettability and heat resistance of the polyolefin separator, the current main solution is to coat the ceramic composite polyacrylate and PVDF binder on one or both sides of the polyolefin separator. This coating is Currently the most widely used solution to solve the wettability and heat resistance of the diaphragm electrolyte, in order to solve the problem of battery hardness, by coating PMMA and PVDF particles on the surface of the ceramic coating and the surface of the base film to ...

AI Technical Summary

Problems solved by technology

Among them, the polyacrylate binder has problems such as low glass transition temperature and poor water resistance, which limit the improvement of the heat resistance of the diaphragm and the improvement of production efficiency; in the polyacrylate system described in the patent number: CN 106953050 Adding an initiator to improve the heat resistance of the separator, but the system is still polyacrylate with low heat resistance and high electrolyte swelling, its effect is limited and many additives are not conducive to production operations

However, the unfavorable factors of PVDF, such as high raw material prices, difficult NMP treatment, and large electrostatic force of the diaphragm, have increased the cost of production and environmental treatment, and at the same time, the large electrostatic force affects the yield rate of subsequent processes.

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