Influence of water-in-salt electrolytes on the electrochemical performance of porous N and S co-doped carbon electrodes in supercapacitors

Abstract

This study demonstrates the impact of water-in-salt (WIS) electrolytes on the performance of a supercapacitor using nitrogen and sulphur co-doped activated carbon as the electrode material, highlighting its potential for enhanced energy storage capabilities. The electrolyte (WIS) used is 12 m NaNO₃ and the electrode material is a previously reported nitrogen and sulphur co-doped activated carbon sourced from mangosteen shells (NS-MSAC). Furthermore, the three-electrode test of NS-MSAC demonstrates a high specific capacitance of 206 F g⁻¹ at a current density of 0.5 A g⁻¹ within a potential window of 0 to −1.0 V. The symmetric supercapacitor built with NS-MSAC achieved a voltage range of 0–2.0 V by exploiting the beneficial electrochemical properties of 12 m NaNO₃, which include a higher potential window, low viscosity, high conductivity, and electrochemical stability. The assembled symmetric device featuring NS-MSAC//NS-MSAC delivered a specific energy of 25 W h kg⁻¹ at a power density of 512 W kg⁻¹. Additionally, after 8000 charge/discharge cycles, approximately 85% of the capacitance was retained. This highly concentrated aqueous electrolyte strategy is promising for achieving remarkable supercapacitor performance.