Mg-Ni thin films for nickel-metal hydride batteries electrodes were prepared by direct current magnetron sputtering from a Mg-Ni alloy target on three substrates (glass, Ni foil, and foam Ni substrates) and characterized by differential scanning calorimetry, x-ray fluorescence measurement, energy dispersive spectroscopy, x-ray diffraction, and transmission electron microscopy. The microstructure of the Mg-Ni thin films as found to be composed of an amorphous Mg-Ni phase and Mg2Ni nanocrystalline, regardless the substrates. The amorphous phase is crystallized into Mg2Ni at about 360 degreesC. The maximal discharge capacity of Mg-Ni thin film being 557 mA h/g was achieved in an alkaline solution. (C) 2003 American Vacuum Society.