Construction of symmetric supercapacitors using anhydrous electrolytes containing heterocyclic oligomeric structures

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-1H-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 (H₃PO₄) and ionic liquid (IL) at different molar fractions. The supercapacitors constructed with the anhydrous BG(Atri)₂/H₃PO₄/0.1IL and BG(Imi)₂/H₃PO₄/0.1IL electrolytes provided maximum specific capacitances (Cs) 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/H₃PO₄/0.1IL and from 114 to 148 F g⁻¹ for BG(Tri)₂/H₃PO₄/0.1IL as the temperature increased from 25°C to 75°C.