Sputtered Pb films have been found to reversibly alloy electrochemically with magnesium in Grignard based electrolytes. The voltage curve shows a single plateau at about 125 mV vs. Mg, corresponding to the formation of Mg2Pb, as confirmed by ex-situ X-ray diffraction. Pb was found to be the highest energy density Mg alloy yet reported, with the lowest voltage and highest volumetric capacity of any Mg alloy. (C) 2015 Elsevier Ltd. All rights reserved.