Preparation method and application of long-durability polyolefin-coated diaphragm

Abstract

The invention provides a preparation method and application of a long-durability polyolefin-coated diaphragm. According to the invention, a layer of crosslinked polyethylene and ceramic mixture coats on one side or two sides of a base diaphragm, and the crosslinked polyethylene is prepared by irradiation crosslinking or siloxane crosslinking. The crosslinked polyethylene coating the surface of the base diaphragm can greatly improve the electrolyte-resistant size stability of the diaphragm, decrease the moisture content of the diaphragm, reduce the risk that the diaphragm is stabbed under pressurization, and enhance the quality and electrochemical stability of the coated diaphragm, so the long-durability battery diaphragm has better electrolyte aging resistance and is more beneficial for improving the high-temperature cycle performance, the high-temperature storage performance and the like of the lithium ion battery.

Description

technical field [0001] The invention belongs to the field of lithium-ion batteries, and in particular relates to a preparation method and application of a long-durable coated polyolefin diaphragm for a high-energy-density lithium-ion battery diaphragm. Background technique [0002] The development of power batteries determines the future of new energy vehicles, and the improvement of the energy density of power batteries largely determines the development of power batteries. Due to the consideration of cruising range, the new energy automobile industry has more and more urgent requirements for high energy density batteries to enter the stage of practical application. As power batteries have higher and higher requirements for long battery life and high energy density, the requirements for safety performance are also getting higher and higher. As one of the four main materials of the battery, the battery separator needs to have a certain pore size (about 100nm) and porosity (...

AI Technical Summary

Problems solved by technology

However, the main problems are: (1) The ceramic coating is mainly composed of inorganic particles, such as alumina ceramics and boehmite ceramics, which will cause a large mass of the coated diaphragm per unit area (area density), which is not conducive to reducing the battery life. quality; (2) The ceramic coating layer is relatively easy to absorb moisture, which will cause the ceramic moisture content to be relatively high. Large, and the ceramic diaphragm needs to be sealed and washed into other dry substances during transportation, and the packaging cost is high; (3) The coating used for ceramic diaphragm coating is inorganic particles, and its hardness is relatively high. When pressure is applied, the inorganic coating may damage the base membrane, resulting in an increase in the air permeability of the separator, which is not conducive to the penetration of lithium ions; (4) when the ceramic separator is in the electrolyte environment for a long time, as the ceramic binder swells in the electrolyte , the peeling strength of the ceramic layer will continue to decrease, and some ceramics may fall off, which is not conducive to the long-term service life of the coated diaphragm

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