Construction of symmetric supercapacitors using anhydrous electrolytes containing heterocyclic oligomeric structures

Summary The anhydrous electrolytes have become an important part of supercapacitors, which provide temperature‐tolerant applications in various electronic devices. This work reports on the fabrication of a wide‐temperature‐range supercapacitor using 3‐amino‐1 H ‐1,2,4‐triazole (Atri)/1,4‐butanediol diglycidyl ether (BG) and imidazole (Imi)/BG–based electrolytes in active carbon‐based electrodes. The triazole‐terminated BG (BG(Atri) 2 ) and Imi‐terminated BG (BG(Imi) 2 ) were initially synthesized, and then anhydrous electrolytes were produced by doping BG(Atri) 2 and BG(Imi) 2 with phosphoric acid (H 3 PO 4 ) and ionic liquid (IL) at different molar fractions. The supercapacitors constructed with the anhydrous BG(Atri) 2 /H 3 PO 4 /0.1IL and BG(Imi) 2 /H 3 PO 4 /0.1IL electrolytes provided maximum specific capacitances ( C s) of 114 and 191 F g −1 at 1 A g −1 , respectively. The corresponding electrolytes yielded the highest energy densities of 15.8 and 26.7 Wh kg −1 at the power densities of 1150 and 1225 W kg −1 , respectively. The Imi‐terminated electrolyte‐based supercapacitor indicated superior performance and efficiency even after 2300 charge‐discharge cycles by holding 20% of its original capacitance. The temperature dependence of the supercapacitors' capacitances was studied, and they increased from 191 to 266 F g −1 for BG(Imi) 2 /H 3 PO 4 /0.1IL and from 114 to 148 F g −1 for BG(Tri) 2 /H 3 PO 4 /0.1IL as the temperature increased from 25°C to 75°C.