Towards a calcium-based rechargeable battery.

The development of a rechargeable battery technology using light electropositive metal anodes would result in a breakthrough in energy density. For multivalent charge carriers (M(n+)), the number of ions that must react to achieve a certain electrochemical capacity is diminished by two (n = 2) or three (n = 3) when compared with Li(+) (ref. ). Whereas proof of concept has been achieved for magnesium, the electrodeposition of calcium has so far been thought to be impossible and research has been restricted to non-rechargeable systems. Here we demonstrate the feasibility of calcium plating at moderate temperatures using conventional organic electrolytes, such as those used for the Li-ion technology. The reversibility of the process on cycling has been ascertained and thus the results presented here constitute the first step towards the development of a new rechargeable battery technology using calcium anodes.