Quasi-solid-state gel polymer electrolyte for a wide temperature range application of acetonitrile-based supercapacitors

A quasi-solid-state gel polymer electrolyte (GPE) is designed by integrating a free-standing cross-linked film and an injectable polymer electrolyte for applications in acetonitrile-based supercapacitors (SCs) using activated carbon (AC) electrodes. The synthesized GPE exhibits a high ionic conductivity over a wide temperature range (similar to 1.7 x 10(-3) S cm(-1) at similar to 20 degrees C to similar to 7.9 x 10(-3)S cm(-1) at 60 degrees C) as well as thermal stability and flexibility. A quasi-solid-state SC equipped with the GPE exhibits similar to 13% higher specific capacitance (similar to 56% smaller Warburg resistance) at room temperature (RT) than that of an SC containing a corresponding liquid electrolyte. The quasi-solid-state SC also exhibits excellent electrochemical characteristics over a temperature range of -20 to 60 degrees C with only similar to 23% capacitance loss at -20 degrees C compared to that at RT. Furthermore, the quasi-solid-state SC maintains similar to 93% of its initial capacitance (only similar to 4% increase in ESR) after 120-h storage at 85 degrees C (above the boiling point of acetonitrile). This capacitance is superior to an SC equipped with a film-only GPE (similar to 73% capacitance retention and similar to 270% increase in ESR). The proposed strategy provides new insights into the development of GPE designs for practical applications to solid-state SCs operating over a wide temperature range.