A study of low-temperature solid-state supercapacitors based on Al-ion conducting polymer electrolyte and graphene electrodes

Abstract

Abstract Gel electrolytes currently draw considerable interest for flexible supercapacitors. Conventional hydrogel electrolytes find limited suitability at low/high temperatures as they contain immense water. This hinders their application in supercapacitors under a harsh environment. Herein, a novel gel polymer electrolyte (GPE) membrane based on the PVdF-HFP/EMITf/Al(Tf)3 system is prepared. The optimized GPE membrane exhibits a high ionic conductivity of ~1.6\xa0×\xa010−3\xa0S cm−1 at room-temperature with a high value of ~0.8\xa0×\xa010−3\xa0S cm−1 retained at a freezing temperature of −20\xa0°C. The prepared GPE membrane also offers a wide electrochemical stability window (~5.6–4.2\xa0V) in the temperature range of −20 to 60\xa0°C. The supercapacitor cells designed with GPE membrane and graphene nano-platelet electrode display excellent capacitive performance (323.9\xa0F g−1 at 2\xa0V) and cycling stability (over 50000 cycles) at room-temperature. At −20\xa0°C, the supercapacitor cells still maintain promising capacitive performance and outstanding cycling stability. Moreover, the designed flexible supercapacitors also offer remarkable performance under various bending conditions and maintain low-temperature tolerance. Consequently, it is believed that the low-temperature tolerance GPE membrane based on the PVdF-HFP/EMITf/Al(Tf)3 system possesses potential applications in flexible supercapacitors under harsh environments.