A kind of soluble bisfluorosulfonimide lithium/magnesium lithium silicate coated diaphragm for lithium ion battery and preparation method thereof

Abstract

The invention relates to a soluble bisfluorosulfonimide lithium / magnesium lithium silicate coated separator for lithium batteries and a preparation method thereof, wherein the separator includes a base film and a coating coated on one side of the base film, One side of the base film is the surface of the separator facing the negative electrode, and the coating includes lithium bisfluorosulfonyl imide, lithium magnesium silicate, polymethyl methacrylate and a solvent; the preparation method is specifically to prepare silicon Lithium magnesium oxide / polymethyl methacrylate composite particles, then mixed with lithium bisfluorosulfonimide and dissolved in a solvent to obtain a stable dispersion, and finally spray the prepared stable dispersion on the side facing the negative electrode when winding The surface of the separator substrate and dried. The soluble bisfluorosulfonimide lithium / magnesium lithium silicate coated separator for lithium batteries of the present invention has the characteristics of reducing the deformation of the winding core and increasing the migration number of lithium ions in the electrolyte, and the preparation method of the separator has easy-to-obtain raw materials and is easy to operate , easy to realize industrial operation.

Description

technical field [0001] The invention belongs to the technical field of diaphragms for lithium electronic batteries, and in particular relates to a soluble lithium bisfluorosulfonimide / lithium magnesium silicate coating diaphragm for lithium ion batteries and a preparation method thereof. Background technique [0002] During the use of lithium-ion batteries, the thickness of the electrode sheet will change to a certain extent, especially the graphite negative electrode. According to existing data, after high-temperature storage and cycling of lithium batteries, the expansion rate of the positive electrode is only 4%, and the expansion rate of the negative electrode is more than 20%. The root cause of the deformation of the winding core and the pole piece due to the increase in the thickness of the negative electrode sheet of the lithium battery is graphite, and the negative electrode graphite forms LiCx (LiC 24 , LiC 12 and LiC 6 etc.), the lattice spacing changes, resulti...

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Problems solved by technology

[0006] The Chinese patent with the publication number CN106784532A discloses a preparation method of water-based PVDF and its copolymer composite coating diaphragm, by mixing PVDF and its copolymer and ceramics into a slurry in a certain proportion, and coating according to a certain coating method On one or both sides of the base film, and then dried in a three-stage oven at a temperature of 40°C-90°C to obtain a water-based PVDF and its copolymer composite coated separator, thereby improving the swelling rate of the separator in the electrolyte, The rate discharge performance and cycle performance of lithium-ion batteries, but the use of water-based PVDF and its copolymer composite coating diaphragm in this patent has not fundamentally solved the problem of winding core deformation during the use of lithium-ion batteries, and as the battery As the number of charges and discharges increases, the adhesion of the separator coating gradually weakens or even fails, and the inner winding core and pole piece of the battery gradually deform, which will affect the rate discharge performance and cycle performance of the lithium-ion battery; in addition, the coated separator in this patent The components include PVDF and its copolymers, ceramics, dispersants and ionized water, and the promotion effect of its components on other electrical properties of the battery is not fully considered

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