Effect of substitution of chromium for manganese on structure discharge characteristics of Ti-Zr-V-Mn-Ni-type muti-phase hydrogen storage electrode alloys

In this paper the structure and discharge characteristics of Ti0.8Zr0.2V1.6Mn0.8−xCrxNi0.6 (0⩽x⩽0.64) hydrogen storage annealed electrodes are studied by the use of electrochemical techniques, XPS, XRD and EDS in detail. The results have shown that the organization of alloys is made up of dispersed branch crystals and continuous base body structure. With increase of the quantity of substitution of chromium for manganese, the branch crystals become coarser. Their phase structures are the compound phases of C14 Laves phase and b.c.c. phase, rich in vanadium. Substitution influences the parameters of lattice of the alloys. The quantity of vanadium in b.c.c. phase is the highest. The maximal capacity of the alloy is 545 mAh/g. The activation of alloys is very easy but the cycle property is rather poor. With increase of the quantity of substitution of chromium for manganese, the property deterioration decreases clearly but the maximal capacity decreases apparently too. Further, the studies of XPS have shown that the restrain effect of chromium substitution on property deterioration of alloys is due to the decrease of oxygenation and surface segregation of titanium, zirconium and vanadium.