Microstructure and Electrochemical Properties of V2.1TiNi0.4Zr0.06Cu0.03M0.10 (M=Cr, Co, Fe, Nb, Ta) Hydrogen Storage Alloys

V2.1TiNi0.4Zr0.06Cu0.03M0.10(M=Cr, Co, Fe, Nb, Ta) hydrogen storage alloys were prepared by induction melting with magnetic levitation. The effects of an additive element M on the microstructure and electrochemical properties of these alloys were investigated by means of X-ray diffractiuon (XRD), scanning electron midroscopy( SEM), electron diffraction spectroscopy (EDS) analyses and electrochemical measurements. The results show that all these alloys consist of a V-based solid solution main phase with bee structure and a C14-type Laves secondary phase in the form of a three-dimensional network, Cr, Nb or Ta predominantly exist in the main phase and Co or Fe is mainly distributed in the secondary phase. Adding Cr, Co, Fe, Nb or Ta into the V2.1TiNi0.4Zr0.06Cu0.03 alloy can effectively restrict the dissolution of vanadium and titanium as well as improve the corrosion resistance and cycling stability of the alloy electrode. The maximum discharge capacity of the alloy, however, decreases to some extent. Doping with Cr, Co, Nb or Ta increases the high-rate dischargeability of the alloy. Among the alloy samples studied, the V2.1TiNi0.4Zr0.03Cu0.03Cr0.10 alloy possessed the best overall electrochemical properties.