Mg2Si was synthesized by mechanically activated annealing and evaluated as a negative electrode material A maximum discharge capacity of 830 mAh/g was observed by cycling over a wide voltage window of 5-650 mV versus L-1, but capacity fade was rapid. Cycling over the range 50-225 mV versus Li produced a stable discharge capacity of approximately 100 mAh/g. X-ray diffraction (XRD) experiments showed that lithium insertion converts Mg2Si into Li2MgSi after lithium intercalation into Mg2Si. Electrochemical evidence of Li-Si reactions indicated that the Li2MgSi structure can be converted to binary lithium alloys with extensive charging. Published by Elsevier Science B.V.