Preparation method of polyamide-imide lithium battery membrane

Abstract

The invention provides a preparation method of polyamide-imide lithium battery membrane, comprising following steps: dissolving polyamide-imide in a non-protonic polar solvent to obtain polyamide-imide solution, adding a pore-forming agent in the polyamide-imide solution, stirring and mixing to obtain film coating solution, deforming, carrying out knife coating on a substrate through a knife to form a primary membrane, carrying out gradient coagulating bath on the primary membrane, gradually coagulating to form a coagulating membrane, washing the coagulating membrane by water so as to remove the pore-forming agent in the coagulating membrane, thus obtaining a pore-forming membrane, drying, stretching, sizing, thus obtaining the polyamide-imide lithium battery membrane. The polyamide-imide lithium battery membrane prepared by the method provided by the invention has various performances demanded by the lithium battery membrane field; particularly, the temperature tolerance of the membrane is excellent and reaches 280 degrees centigrade or more.

Description

technical field [0001] The invention belongs to the application field of lithium batteries, and in particular relates to the preparation of a polyamide-imide lithium battery diaphragm. Background technique [0002] Due to the advantages of high power density, low self-discharge rate, long cycle life, no memory effect, stable discharge voltage and fast charge and discharge, lithium-ion batteries have gradually replaced traditional lead-acid batteries and nickel-cadmium batteries and become the main power battery. choose. The separator is a key component of the lithium-ion battery. It plays an important role in blocking the electronic conductance of the positive and negative electrodes in the battery and allowing the electrolyte ions to pass through freely to achieve ion conduction. It is an important determinant of battery capacity, cycle capacity and safety performance. [0003] At present, the demand for high power output performance and safety of power batteries poses a m...

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Problems solved by technology

[0004] CN104752665A discloses a preparation method of a polyimide porous nanofiber electrode diaphragm. The obtained polyimide nanoporous fiber membrane is an ideal material for a lithium ion battery diaphragm in terms of temperature resistance and charge-discharge rate, but the nanometer The puncture strength of the fiber separator is not high, and it is easy to be pierced by lithium dendrites in the electrolyte, causing the battery to short-circuit the danger

JP11310658A2 discloses a polyimide and porous polyolefin film composite film to improve the heat resistance of the battery separator, however, when the temperature exceeds the melting point of the polyolefin material (about 180 ° C), the polyimide composite film There is still a risk of a short circuit in the diaphragm

CN101000951A discloses a polyimide solution mixed with a pore-forming agent to form a film, and removes the pore-forming agent below the polyimide glass transition temperature, the pore-forming agent is generally a non-volatile organic solvent, Such as nonane, liquid paraffin, etc. Although the above substances can obtain polyimide micropores through the escape of pore-forming substances, it is difficult to completely remove the pore-forming substances by this method.

CN101645497A discloses a polyimide acid film formed from a mixture of polyimide acid, solvent and pore-forming substance, and then the film is placed in a coagulation solution that can dissolve or react the pore-forming agent to remove the pore-forming agent, Then the polyimide acid film is imidized, the polyimide acid film of this method is more likely to be degraded in the coagulation bath, and directly entering the coagulation bath will easily cause the surface of the film to react rapidly, and the interior will not be able to react in time in the future. Reaction occurs, so it is easy to form a leather core structure, which affects mechanical properties such as puncture strength

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