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.