Polyimide coating modified polyolefin composite diaphragm and preparation method thereof

Abstract

The invention discloses a polyimide coating modified polyolefin composite diaphragm and a preparation method thereof. The preparation method comprises the following steps: synthesizing a PAA solution with certain intrinsic viscosity through a two-step method, preparing a polyimide film with fiber / microsphere composite morphology by using an electrostatic spinning technology, preparing a polyimide dispersion liquid, adding a polymer adhesive into the polyimide dispersion liquid, stirring at a high speed by using a homogenizer to obtain a polyimide coating slurry, uniformly coating the surface of a polyolefin diaphragm with the polyimide coating slurry, and drying to obtain the polyimide coating modified polyolefin diaphragm with the fiber / microsphere composite morphology. According to the invention, the process is simple and easy to implement, the bonding strength between the polyimide coating and the polyolefin diaphragm layer is high, the thermal dimensional stability and electrolytic solution wettability of the diaphragm can be obviously improved, and the polyolefin diaphragm can play a role in hole closing at a high temperature besides the diaphragm function at a normal temperature, so that short circuit in the battery is prevented, and the safety of the battery is further improved.

Description

technical field [0001] The invention belongs to the technical field of polyolefin diaphragm coating modification, in particular to a polyimide-coated polyolefin diaphragm with fiber / microsphere composite morphology. Background technique [0002] Lithium-ion battery is a new type of green secondary battery, which was successfully developed in 1990. It has the advantages of high energy density, long cycle life, no memory effect, fast charging and discharging, and environmental protection, and has been widely used in 3C products. Lithium-ion batteries are mainly composed of positive / negative electrode materials, electrolytes and separators. Separators are an important part of lithium-ion batteries. Separate the positive and negative electrodes to prevent the battery from short-circuiting and allow the electrolyte ions to pass through freely. The separator plays an important role in improving the overall performance of the battery, and is called the "third electrode" of the b...

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Problems solved by technology

For example, patent CN104993089 reports a lithium-ion battery separator coated with aramid fiber and its preparation method. Aramid fiber slurry is obtained by uniformly mixing aramid fiber solution, emulsifier solution, and polymer adhesive, and then the obtained polymer glue Coating the body fluid on the surface of the polyolefin separator improves the thermal dimensional stability of the separator and improves the safety and reliability of the lithium-ion battery. However, the temperature resistance of the organic polymer is not high in this method, and the thermal dimensional stability is not greatly improved.

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