Silver Imidazolium Moiety Electrode for High‐Performance Supercapacitors in Ionic Liquid Electrolytes

ABSTRACT

This report presents the synthesis and electrochemical evaluation of three novel imidazolium compounds‐ 1,1'‐diethyl‐3,3'‐methylenediimidazolium diiodide (compound 1 ), 1,1'‐diethyl‐3,3'‐methylenediimidazolium bis(tetrafluoroborate) (compound 2 ), and 1,1'‐diethyl‐3,3'‐methylenediimidazolium silver(I) triiodide (compound 3 ) for supercapacitor applications. Compound 1 was synthesized via alkylation, compound 2 through anion exchange with AgBF ₄ , and compound 3 via complexation with Ag ₂ O. Compound 2 outperformed benchmark BMIMCl electrolyte, delivering a higher specific capacitance (35.53 F/g vs.16.78 F/g) when paired with a MoS ₂ electrode. Compound 3 , used as an electrode material and tested in 1 M H ₂ SO ₄ and 1 M BMIMCl, demonstrated the highest specific capacitance (i.e., 11.54 F/g) in BMIMCl, indicating superior compatibility. Cyclic voltammetry in BMIMCl yielded b‐values of 0.6 (charging) and 0.53 (discharging), suggesting a mixed charge storage mechanism dominated by pseudocapacitance. Galvanostatic charge–discharge (GCD) of compound 3 in 1 M BMIMCl showed a specific capacitance of 55.68 F/g at 2 A/g, with capacitance retention of 98.14 % after 6200 cycles and a high coulombic efficiency of 96.82 %. The device delivered power densities of 150.06–748.36 Wh/kg, while energy density decreased from 11.4 to 1.9 Wh/kg with increasing current density. MoS ₂ electrode in 0.05 M compound 2 electrolyte achieved a specific capacitance of 15.63 F/g at 8 A/g, outperforming BMIMCl (11.02 F/g).