PROPERTIES AND ELECTRODE PERFORMANCES OF (ZR, A)V0.5NI1.1MN0.2FE0.2 (A=TI, NB AND HF) FOR NICKEL-HYDROGEN RECHARGEABLE BATTERIES

The effect of substitution to the Zr site of ZrM(2) (M(2) equivalent to V0.5Ni1.1Mn0.2Fe0.2) by Ti, Nb, and Hf have been investigated by pressure-composition isotherm measurements, X-ray powder diffraction and electrode performance tests. Quantitative phase analysis has been made by using the Rietveld method. The alloy Zr(0.5)Ti(0.5)M(2) is pure C14 phase, TiM(2) is pure body centered cubic (BCC) and Zr(0.25)Ti(0.75)M(2) is multiphase (74% C14, 26% BCC). All other alloys are a mixture of C14 and C15 phases. The alloy ZrM(2) has the largest capacity at a discharge rate 20mA/g. At the higher discharge rate of 70 mA/g, the alloys having a high proportion of C14 phase show smaller drop in discharge capacity. This indicates that for the present system, the C14 phase is a kinetically favorable phase.