The impact of two aqueous electrolytes (1 M Na 2 SO 4 and 1 M KOH) and one water‐in‐salt electrolyte (WiSE) (17m NaClO 4 ) on the electrochemical performance is analyzed in conjunction with Ni‐doped FeS 2 /WS 2 hybrid nanocomposite electrodes. The Ni‐doped FeS 2 /WS 2 nanocomposite reveals pseudocapacitive behavior with a high specific capacitance of 474.19 F/g in the 17 m NaClO 4 electrolyte at a low discharge current density of 3.5 mA/g, which is much higher than in 1 M Na 2 SO 4 and 1 M KOH electrolytes. Furthermore, cyclic voltammetry tests show a large potential window of ∼3.0 V for 17 m NaClO 4 electrolyte, which is much wider as compared to only 1.4 V and 1.1 V for the 1 M Na 2 SO 4 and 1 M KOH electrolytes, respectively. Additionally, these high capacitances combine with the large voltage window, leading to the highest energy density of 129.08 Wh/Kg and power density of 680.56 W/Kg, along with the better capacity retention of 87% even following 5000 constructive charge–discharge cycles. The low cost and excellent electrochemical performances suggest that the Ni‐doped FeS 2 /WS 2 nanocomposite employing with WiSE electrolyte, that is, 17 m NaClO 4 may be the best combined effective pair to improve the electrochemical performances of supercapacitors as well as other advanced energy storage and portable energy devices.
Kumar et al. (Sun,) studied this question.