Lithium battery diaphragm and preparation method thereof

Abstract

The invention discloses a lithium battery diaphragm and a preparation method thereof. The lithium battery diaphragm consists of a base membrane and a functional coating positioned on the surface of the base membrane, wherein the thickness of the functional coating is 2-4 microns, and the functional coating is formed by curing diaphragm slurry; the diaphragm slurry comprises the following components in parts by weight: 100 parts of deionized water, 0.5-1.5 parts of a dispersing agent, 10-15 parts of a flocculating agent, 1-5 parts of a binder, 0.5-1.0 part of a wetting agent and 15-45 parts of ceramic powder; the flocculating agent is high molecular weight polyoxyethylene; and the wetting agent is selected from any one of an anionic surfactant or a nonionic surfactant. The preparation method comprises the following steps of: (1) preheating the base membrane; (2) coating the diaphragm slurry on the surface of the base membrane; and (3) drying the diaphragm slurry to form a functional coating, thereby acquiring the lithium battery diaphragm. The lithium battery diaphragm disclosed by the invention is high in safety and good in ionic conductivity; and the lithium battery diaphragm disclosed by the invention improves the adhesive property and the thermal stability. The invention further provides the preparation method of the lithium battery diaphragm, and the preparation process is high in efficiency and low in energy consumption.

Description

Technical field [0001] The present invention relates to the field of lithium ion battery diaphragm, and more particularly to a lithium battery diaphragm and a preparation method thereof. Background technique [0002] The lithium-ion battery serves as the latest generation of green high-energy rechargeable batteries, which have better secondary cycle performance and high energy density, so in convenient electronic products, electric toys, electric vehicles, large power power and energy storage. Got rapid development. The lithium battery isolation membrane is one of the four major main materials of the lithium ion battery. The performance and function of the separator in the lithium battery is to separate the positive and negative electrodes of the battery and make lithium ions. Free shuttle between the positive and negative two poles. At present, the lithium battery diaphragm substrate in the industry is mainly polyethylene or polypropylene. Due to the chemical characteristics of ...

AI Technical Summary

Problems solved by technology

At present, the lithium battery separator base material in the industry is mainly polyethylene or polypropylene. Due to the chemical characteristics of the material itself, the polyethylene or polypropylene separator has poor thermal stability; at the same time, there is no bonding between the separator and the battery pole piece. During the long-term charge and discharge process, the performance of the battery will be seriously affected due to the expansion and contraction of the pole piece

In this case, the industry usually coats a layer of polyvinylidene fluoride on the surface of the substrate to improve the adhesion between the diaphragm and the pole piece. Layer ceramic coating to solve the safety problem of the diaphragm

Although the ceramic coating has high safety, it has poor conductivity and no adhesive ability. If it is directly used in the lithium battery separator, it will cause the ion conductivity of polyvinylidene fluoride to be small, which will hinder lithium ion conductivity in the coating. The conduction of ions reduces the ion conduction rate of the coated separator, which leads to the increase of the internal resistance of the existing lithium battery and the decrease of the related electrical properties of the battery.