Water-in-Salt Battery Electrolyte for High-Voltage Supercapacitors: A Fundamental Study on Biomass and Carbon Fiber Electrodes

In this study, we investigated the use of a water-in-salt electrolyte (WiSE) for enhancing the performance of carbon-based supercapacitor electrodes. The all-biomass electrode and a peroxyacetyl nitrate-derived porous carbon fiber electrode (PPCF) were chosen as two examples for evaluating their electrochemical performance. WiSE provides a stable wide voltage window of 3 V, effectively inhibits undesirable water-splitting reactions. The presence of pseudocapacitance behavior, as evidenced by cyclic voltammetry scans, contributed to higher charge storage capacity. As a result, a high areal energy density and power density of 2.2 mWh cm −2 and 11.7 mW cm −2 were achieved for the all-biomass electrode, and a high areal energy density and power density of 0.4 mWh cm −2 and 12.1 mW cm −2 were achieved for the PPCF electrode. Overall, when coupled with carbon-based electrodes WiSE shows great promise for high-voltage supercapacitor applications, providing a balance between charge storage kinetics and interface stability.