The effect of Zr substitution for Ti on the microstructures and electrochemical properties of electrode alloys Ti_1-xZr_xV_1.6Mn_0.32 Cr_0.48Ni_0.6

The effect of Zr substitution for Ti on the microstructures and electrochemical properties of the electrode alloys Ti_1-xZr_xV_1.6Mn_0.32 Cr_0.48Ni_0.6 (x=0.2,0.3,0.4,0.5) has been studied. It is found by X-ray powder diffraction and energy dispersive X-ray spectroscope analyses that all the alloys consist of a C14 Laves main phase with hexagonal structure and a V-based solid solution secondary phase with b.c.c. structure. A small amount of TiNi-based third phase with b.c.c. structure has been found precipitated in the C14 Laves main phase in addition. With the increase in the amount of Zr substitution, the lattice parameters of the main phase and secondary phase are found increased and decreased, respectively. The electrochemical PCT curves indicate that the maximum hydrogen absorption capacity [H/M]_max decreases with increasing Zr substitution, which may be attributed to the decrease in the content of V-based solid solution. The maximum discharge capacity and high rate dischargeability of the alloy electrodes both decrease, while the cyclic durability increases with the increasing amount of Zr substitution.