The electrochemical characteristics of Mg and several Mg-Ni alloys were studied as alternatives to anode materials for secondary Li batteries. Li was alloyed and dealloyed reversibly with Mg at very low voltage region (below 100 mV vs. Li/Li+), and the initial capacity obtained was approximately 3070 mA h/g. Alloys of Mg,,Ni,,, Mg,,Ni,, and Mg,,Ni,, were prepared by mechanical alloying and characterized using X-ray diffraction (XRD) and Auger electron spectroscopy (AES). Mg50Ni50 and Mg67Ni33 were found amorphous and crystalline, respectively, while Mg,,Ni, was a mixture of Mg and Mg,Ni phases. Electrochemical tests with these Mg-Ni alloys demonstrated that only Mg,,Ni,, reacted significantly with Li at room temperature while Mg,,Ni,, reacted with Li at high temperature. Mg75Ni25 showed enhanced cycle performance compared to that of pure Mg.