Microstructures and electrochemical properties of Mg49Ti6Ni(45-x)Mx (M=Pd and Pt) alloy electrodes

Magnesium nickel alloys have been considered an alternative for AB5 and AB2-type alloys in nickelmetal hydride batteries due to their larger maximum discharge capacities, but their low stability in alkaline solution has hindered their use in commercial cells. Aiming to improve the electrode performance of the Mg55Ni45 alloy, we investigated the simultaneous addition of Ti and a noble metal (Pd and Pt) as alloying elements. The investigated system has general composition Mg49Ti6Ni(45-x)Mx, where M is Pd or Pt, and x assumed values of 0, 2.0 and 4.0 at.%. The electrochemical measurements showed that the Mg49Ti6Ni41Pd4 alloy has the best electrode performance among the studied alloys, reaching 431 mA h g1 of maximum discharge capacity at the first cycle of charge/discharge. After 10 and 20 cycles, this alloy presented relative discharge capacities of 84 and 77% of the initial one, respectively. The electrode performance of the investigated alloys is discussed in light of results of structural characterization by transmission electron microscopy and X-ray diffraction. Copyright (c) 2013 John Wiley & Sons, Ltd.