Activated carbon electrode with promising specific capacitance based on potassium bromide redox additive electrolyte for supercapacitor application

Halogenated Bromide (Br −) was subsequently dosed to aqueous electrolyte solution to enforce the capacitance features of activated carbon (AC) electrodes in electric double-layer supercapacitor devices for electrical energy storage. Physicochemical properties for AC with sodium sulfate (Na2SO4) and KBr redox additive were assessed by different characterization tools such as XRD, SEM, EDS, surface roughness, and BET techniques. Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS), and the stability after 1000 cycles have been used to monitor the electrochemical behaviors of the prepared electrodes. The presence of halogen atom exhibited large faradaic resembling battery like-type in charge–discharge curves. In the aqueous solution, the investigated electrode showed a high specific capacitance of 957.8 F g−1 at a specific current of 0.46 A g−1 using a certain concentration of KBr added to Na2SO4. The single AC electrode showed specific energy of 133 Wh kg−1 and specific power of 859.6 W kg−1. Besides, the AC electrode displayed excellent long-term stability in Na2SO4@KBr electrolyte, preserving retention capacitance of 174%. AC/AC symmetric supercapacitor cell demonstrated excellent electrochemical performance, including specific energy of 57.15 Wh kg−1, specific capacitance of 127 F g−1, specific power of 5262 W kg−1 at a specific current of 3.8 A g−1, and 82.8% capacitance retention after 10,000 cycles.