A stoichiometric mixture of potassium chloride (KCl) and tin chloride pentahydrate (SnCl4.5H2O) was ball milled for 12 h, at 400 rpm using a planetary ball mill with a ball-tomaterial weight ratio of 20:1. The filling and emptying of the grinding jars took place in a glovebox with a dry Ar environment to prevent any contact with O2 or moisture. The milled powder was then dried at 150 °C for 4 h in a vacuum oven to remove the residual moisture. This dried sample is used as an active material for the electrode.