A dual-acetate synchronous catalysis-activation strategy towards regulable porous graphitic carbon for high-energy supercapacitor with acetate water-in-salt electrolyte

Supercapacitors are one of the most extensively studied energy storage devices due to their many unique advantages. The design of electrode material and electrolyte is the key to building high-performance supercapacitors. In this work, high-energy aqueous supercapacitors are constructed by optimizing these two factors. On the one hand, a dual-acetate (nickel/potassium acetates) synchronous catalysis-activation strategy is developed for the first time to prepare porous graphitic carbon from commercial super absorbent polymer as electrode material. Compared with the porous carbon activated by potassium acetate alone and the graphitic carbon catalyzed by nickel acetate alone, the porous graphitic carbon shows much more remarkable electrochemical performance. On the other hand, the impacts of water-in-salt and salt-in-water electrolytes of aqueous potassium acetate on energy storage properties of supercapacitors are investigated comparatively. The water-in-salt electrolyte of 22 M potassium acetate has a significant effect in broadening voltage window up to 2.95 V. When the operating voltage window is extended from 1.6 to 2.2 V, the energy density can be increased from 17.1 to 40.6 Wh kg−1. Moreover, both the porous graphitic carbon electrode and potassium acetate water-in-salt electrolyte are conducive to the slow self-discharge capability.