Method for preparing composite polypropylene microporous film by phase conversion method and product and application of composite polypropylene microporous film

Abstract

The invention discloses a method for preparing a composite polypropylene microporous film by a phase conversion method and product and application of the composite polypropylene microporous film. According to the preparation method, a coating layer is introduced to surface(s) of one side or two sides of the film by a first mode (immersion precipitant phase conversion method) or a second mode (dryphase conversion method) during the fabrication process of bidirectionally stretching a polypropylene microporous substrate layer, the coating layer is only stretched in a longitudinal direction and atransverse direction or is only stretched in the transverse direction, and the preparation of the composite polypropylene microporous film is achieved. With the adoption of the method, the productionprocess of the composite polypropylene microporous film is simplified, the fabricated coating layer is high in porosity, the microporous structure is uniform, and the performance of the polypropylenemicroporous substrate layer can be improved very well. The composite polypropylene microporous film is applied into a lithium battery, the coating layer is a polymer or a composition capable for forming gel with an electrolyte, and thus, the cycle property and the safety of the lithium battery can be improved. The invention also provides a lithium battery diaphragm, and the lithium battery diaphragm comprises the composite polypropylene microporous film.

Description

technical field

[0001] The invention belongs to the technical field of microporous membranes, and in particular relates to a method for preparing composite polypropylene microporous membranes by a phase inversion method, as well as products and uses thereof. Background technique

[0002] Polyolefin microporous membrane is a kind of polymer membrane, which is a porous membrane with a pore size between 5nm and 1000nm. It is widely used in breathable materials such as diapers, medical dressings, clothing linings, etc., and materials for liquid separation. , ultrafiltration materials, membrane filtration materials, and supercapacitor and battery diaphragm materials and other fields.

[0003] There are mainly two methods for preparing polyolefin microporous membranes, one is melt extrusion stretching method (dry method), and the other is thermally induced phase separation method (TIPS, wet method). Among them, the dry stretching process can also be divided into a uniaxial stretc...