Calcium is an attractive negative electrode material for use in secondary cells because of its great abundance, low equivalent weight, and high reaction energy. A number of secondary, molten-salt calcium cells having capacities of up to 20 A-hr were evaluated in terms of their charge-discharge characteristics. The negative electrodes were compounds of calcium and either aluminum or silicon, the electrolytes were mixtures of calcium chloride and alkali halides and the positive electrodes were iron sulfide (FeS). These cells generally exhibited high ampere-hour efficiency, good electrode utilization, and a voltage slightly higher than that of comparable lithium cells.
