High-Temperature and All-Solid-State Flexible Supercapacitors with Excellent Long-Term Stability Based on Porous Polybenzimidazole/Functional Ionic Liquid Electrolyte

A high-performance solid-state electrolyte was obtained using porous polybenzimidazole (pPBI) and ionic liquid (IL) (i.e., (1-(3-trimethoxysilylpropyl)-3-methylimidazolium chloride). IL is hydrolyzed to form Si–O–Si networks under acidic conditions, which guarantee the enhanced mechanical properties. The porous structure and Si–O–Si networks improve the acid retention capacity and conductivity simultaneously. The prepared porous composite film exhibits a proton conductivity as high as 0.103 S cm–1 at 170 °C. Then, an all-solid-state supercapacitor (ASSC) was assembled using the obtained film electrolyte and activated carbon electrodes. The electrochemical performance was evaluated at different temperatures (30, 60, 90, 120, and 150 °C). The prepared ASSC displayed a specific capacitance of 85.5 F g–1 at 120 °C, which is 3 times higher than that at 30 °C. Meanwhile, the ASSC displayed excellent long-term cycle stability after 10？000 constant current charge and discharge tests, 91.0% capacitance retention, and 95.8% coulomb efficiency. All the results indicate that the porous polymer electrolyte is promising for application in high-temperature energy-storage devices