A typical inorganic electrolyte or an additive to electrolytes contain ions that can change their oxidation state within a suitable potential window. The addition of potassium iodide to an aqueous electrolyte increased the capacitance of the high SSA carbon electrode by an order of magnitude: from 100 F g−1 to 1,200 F g−1. The reason is that an iodide ion reversibly loses up to 6e− following the electrochemical reaction (equation (1)),