Lithium ion battery diaphragm with high heat resistance and high adhesion and preparation method thereof

Abstract

The invention discloses a lithium ion battery diaphragm with high heat resistance and high adhesion and a preparation method of the lithium ion battery diaphragm. The lithium ion battery diaphragm comprises a polyolefin porous base material and a porous composite coating coated on one side surface or two side surfaces of the base material, wherein the thickness of the porous composite coating accounts for greater than 20% of the total thickness of the diaphragm, the bonding strength is greater than or equal to 0.3 N / m, after the diaphragm is soaked in electrolyte at 55 DEG C for 7 days, the permeability increase rate of the coating thickness per micron is less than or equal to 5%, and the thermal shrinkage at 130 DEG C is less than or equal to 4% after 1h. The surface of at least one side of the polyolefin porous base material is coated with the porous composite layer, so the heat resistance and the adhesion of the diaphragm are improved, the flatness and the safety of the lithium ion battery are effectively improved, and the problems of fire and explosion caused by thermal shock, deformation and lithium precipitation in the later period of circulation and the like are prevented; meanwhile, through material screening and formula design, the surface of the polyolefin base material is coated with the inorganic filler and the high-molecular polymer at a time, the production cost is greatly reduced, the obtained diaphragm has heat resistance and adhesion, and the heat resistance is remarkably improved.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion battery separators, and relates to a lithium-ion battery separator with high heat resistance and high adhesion and a preparation method thereof. Background technique [0002] With the continuous improvement of the energy density of lithium-ion batteries, the safety performance requirements of the separator continue to increase. Conventional lithium-ion battery coated separators are ceramic coated separators coated with polyolefins, inorganic fillers coated with polyolefins, rubberized separators coated with polymers, and multi-layer adhesives coated with polymers after polyolefins are coated with inorganic fillers. diaphragm. The thermal stability of the rubber-coated separator is poor, and it is easy to cause a short circuit between the positive and negative electrodes of the lithium-ion battery, resulting in thermal runaway, resulting in fire or explosion, and is rarely used in the field of...

AI Technical Summary

Problems solved by technology

The thermal stability of the rubber-coated separator is poor, and it is easy to cause a short circuit between the positive and negative electrodes of the lithium-ion battery, resulting in thermal runaway, resulting in fire or explosion, and is rarely used in the field of power batteries

The ceramic coated separator has good heat resistance but has no adhesiveness, which cannot improve the bonding force between the separator and the pole piece. During the long cycle process, the pole piece expands and deforms, and problems such as lithium precipitation are prone to occur, and the battery safety is poor.

The multi-layer rubber-coated separator can balance the heat resistance and adhesiveness of the separator, but it needs to be coated twice, and the cost is high

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