Preparation of thermal stable porous polyimide membranes by phase inversion process for lithium-ion battery

The porous polyimide membranes were prepared by a wet phase inversion process based on the organo-soluble polyimide. The influence of coagulation bath composition and casting polymer solution concentration on the morphology of membranes was investigated. A series of spongy-like porous polyimide membranes with different porosity were obtained and characterized. These porous polyimide membranes exhibited excellent thermal stability and dimensional stability with the glass transition temperature of 274 °C and thermal shrinkage less than 1% after stored at 200 °C. All the porous polyimide membranes exhibited good wettability with electrolyte uptake of 190–378% due to their high surface polarity and high porosity. The discharge curves for the lithium-ion cells using porous polyimide membranes as separator displayed relatively flatter voltage plateaus than that for Celgard 2400 membrane and gave the discharge capacity of 129–131 mAh/g. The thermal stable porous polyimide membranes are favorable to be applied as separator in the lithium-ion cell and can be expected to provide excellent battery performance at elevated temperature.