Flexible, high-wettability and thermostable separator based on fluorinated polyimide for lithium-ion battery

To meet the booming demands for lithium-ion battery (LIB), it is practically significant to promote its electrochemical performance and safety. In our work, a novel kind of flexible membrane as separator for LIB is prepared via phase inversion method with soluble polyimide (SPI) containing trifluoromethyl substituent, which is synthesized from 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) and 4,4'-oxydiphthalic anhydride (ODPA). The SPI separator shows 5% weight loss temperature (T-d5%) of 535 degrees C and maintains intrinsic dimension even after heating at 200 degrees C. The SPI membrane depicts a sponge-like structure with abundant interconnected pores and delivers a dominant porosity (67%). The SPI membrane displays desired electrolyte wettability, validated by contact angle tests (16.2 degrees and 46.8 degrees for SPI membrane and PE separator, respectively) and electrolyte uptake tests (420 and 132% for SPI membrane and PE separator, respectively). The LIB with SPI membrane as separator exhibits nice ionic conductivity (0.92 mS cm(-1)) than that with PE separator (0.30 mS cm(-1)), and therefore affords better electrochemical performance, such as cycling stability and rate capability.