Effect of Ti-Al substitution on the electrochemical properties of amorphous MgNi-based secondary hydride electrodes

A new amorphous Mg-0.(Ti0.225Al0.075Ni)-Ti-.. alloy was prepared by means of mechanical alloying (NIA), its discharge capacity reached 218.32 mAh g(-1) after 50 cycles, which retains 63.57% of the initial capacity of 343.44 mAh g(-1). On the surface of the alloy during cycling in the electrolyte of 5 M KOH, the X-ray photoelectron spectroscopy (XPS) shows that the majority of magnesium and aluminum in the alloy exist in metallic state; Ti exists in the +3 oxidation state. Electrochemical impedance spectroscopy (EIS) shows that the aluminum lowered the charge transfer resistance. The structure of the alloy was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). And the improvement of cycle life of the electrode can be related to the formation of MgTi2O4. A study on the anti-corrosion properties in alkaline solution of the alloy electrode has been done, and it is shown that Ti and Al substitution of Mg improves the anti-corrosion properties significantly. It is found that Ti and Al substitution of Mg could improve the electrochemical behavior of MgNi-based electrodes. (c) 2004 Elsevier B.V. All rights reserved.