Polyethylene microporous diaphragm and preparation method thereof

Abstract

The invention discloses a polyethylene microporous diaphragm. The microporous membrane comprises a polyethylene matrix microporous membrane and a modified reinforced coating compounded on one side ortwo sides of the polyethylene matrix microporous membrane, the thickness of the polyethylene matrix microporous membrane is 4-30 microns, the porosity is 30%-65%, the aperture is 0.5-3 microns, and the thickness of the single-layer modified reinforced coating is 2-5 microns; in modified reinforced coating, due to the addition of the nano inorganic micro-powder, the polyethylene matrix microporousmembrane can be enhanced, so that the thermal shrinkage performance of the polyethylene matrix microporous membrane is reduced, meanwhile, the graphene material uniformly coated on the surface of thenano inorganic micro-powder can enable lithium ions to be rapidly propagated in the nano inorganic micro-powder, so that the charge-discharge performance of the lithium ion battery can be effectivelyimproved, the influence of a coating on lithium ion transmission is reduced, a cross-linked product of sodium alginate has good water retention and water absorption capacity, and the performance of the lithium ion battery diaphragm is improved.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a polyethylene microporous diaphragm and a preparation method thereof Background technique [0002] Due to its high energy density and environment-friendly characteristics, lithium-ion batteries are currently the most important type of secondary battery on the market. The structure of lithium-ion batteries includes positive and negative electrodes and a diaphragm, in which the diaphragm is used to separate the positive and negative electrodes and ensure electrolysis. The ions in the liquid can penetrate it, which is one of the structures that determine the performance of lithium-ion batteries. It has a great impact on the capacity, cycle performance and internal resistance of lithium-ion batteries. Therefore, how to improve the quality of lithium-ion battery diaphragm structure is An important research direction to improve the quality of lithium-ion batt...

AI Technical Summary

Problems solved by technology

[0003] In the prior art, the diaphragm structure of lithium-ion batteries is mainly processed and prepared from polyolefin materials. The raw material cost of polyolefin diaphragms is low and the processing is convenient, so it is widely used. However, polyethylene materials are prone to Heat shrinkage reduces the isolation effect of the diaphragm and leads to the risk of short circuit. This property also greatly reduces the scope of use of polyolefin diaphragms. In addition, the poor hydrophilicity of polyolefin materials will reduce the liquid absorption of the diaphragm. Liquid retention capacity and poor wettability will also reduce the cycle capacity of lithium-ion batteries. In order to solve the above problems, polyolefin materials are modified to improve the liquid absorption and retention capacity of polyolefin films, as well as the resistance of polyolefin films. shrinkage ability, the present invention provides the following technical solutions