Porous Carbons Activated by Different Methods as Positive Electrode Materials for Zn-Carbon Capacitors

Porous carbon materials prepared with different activation methods were evaluated as positive electrodes for zinc-ion capacitors. Higher capacities were obtained with chemically activated carbons than with steam-activated carbons, with KOH-activated carbon showing the highest capacity. Furthermore, the dependence of charge–discharge characteristics on electrolyte was explored using seven different electrolyte types. Gas evolution was observed during the charging reaction in alkaline electrolytes such as potassium hydroxide and tetraethylammonium hydroxide, but no gas generation was observed in acidic electrolytes. In addition, the discharge capacity tended to be higher for chlorine- ion-containing electrolytes such as zinc chloride and ammonium chloride.