Heat resistant microporous membranes based on soluble poly(aryl ether ketone) copolymers for lithium ion battery separator

To improve the safety and electrochemical properties of lithium ion batterie (LIB), a series of novel organic soluble poly(aryl ether ketone) (PAEK) copolymers were synthesized and used to fabricate LIB separators. The PAEK copolymers exhibited superior structural thermal stability and flame retardant, with glass transition temperature ( T g ) above 150°C, oxygen index above 30 and no thermal decomposition before 500°C. Accordingly, the fabricated separators exhibited superior dimensional stability. The mechanical properties and electrolyte uptakes of the separators, as well as the electrochemical properties of the cells assembled with the separators were affected by the morphology and porosity of the separators. The separators with sponge-like structure exhibited less electrolyte uptakes but better mechanical properties than that of the ones with finger-like structure. The cell with finger-like structure separator exhibited poorer electrochemical properties than sponge-like structure separator, which might be caused by the collapse of some finger hole during the assemble process due to its poor mechanical properties. The charge–discharge performances of the cells after treated at 150°C demonstrates that the PAEK separators could be promising candidates for high-safety LIB.