Enhancing potential window with ionic liquid/water in salt mixture in co-doped activated carbon electrodes for high-energy supercapacitors

This study presents a novel electrolyte system combining 1-ethyl-3-methylimidazolium dicyanamide (EMIM DCA) with 12 m sodium nitrate (NaNO 3 ) to optimize ionic interactions for advanced supercapacitor performance. Maintaining a constant EMIM DCA concentration, NaNO₃ was varied to yield molar ratios of [EMIM DCA]₁[12 m NaNO₃]₁, [EMIM DCA] 1 [12 m NaNO 3 ] 2 , and [EMIM DCA] 1 [12 m NaNO 3 ] 3 . The resulting mixtures were rigorously characterized for viscosity, density, ionic conductivity, and molecular interactions using Fourier-transform infrared (FTIR) and Raman spectroscopy. Electrochemical evaluation in a three-electrode configuration at 0.5 A g −1 , employing nitrogen and sulfur co-doped activated carbon (N,S-AC) electrodes, revealed a maximum specific capacitance of 257 F g −1 for the [EMIM DCA] 1 [12 m NaNO 3 ] 1 composition, significantly surpassing the performance of pure NaNO 3 . When implemented in a symmetric supercapacitor operating at 2.3 V, this electrolyte achieved a specific energy of 50.22 Wh kg −1 and a power density of 583.97 W kg −1 at 0.5 A g −1 , with 83.33 % capacitance retention after 10,000 charge-discharge cycles. These results underscore the [EMIM DCA] 1 [12 m NaNO 3 ] 1 electrolyte as a high-performance, cost-effective solution for durable supercapacitors, offering substantial potential for applications in renewable energy storage and electric vehicle power systems with further tuning of water in salt-based electrolytes. • A novel hybrid electrolyte combines EMIM DCA with varying concentrations of NaNO 3 • Optimal performance with [EMIM DCA] 1 [12 M NaNO 3 ] 1 composition • Specific capacitance of 257 F g −1 obtained using N,S doped activated carbon electrodes • Symmetric devices supercapacitor delivers 50.22 Wh kg −1 at 2.3 V and 0.5 A g −1 • Excellent cycling stability with 70.46 % capacitance retention after 8000 cycles