| A series of multicomponent Zr_0.8,Ti_0.2Mn_0.4V_0.6Ni_(1-x)Fe_x (x=0.00, 0.08, 0.15, 0.22 and 0.30) alloys are prepared and their crystal structure and P-C-T curves are examined. The electrochemical properties of these alloys such as activation conditions, discharge capacity, cycling performance are also investigated. Zr_0.8,Ti_0.2Mn_0.4V_0.6Ni_(1-x)Fe_x, (x=0.00, 0.08, 0.15, 0.22 and 0.30) have the C14 Laves phase hexagonal structure. The electrode was activated by the hotcharging treatment. The best activation conditions were the current density 120 ㎃/g and the hot-charging time 12h at 80℃ in the case of the alloy with x=0.00. The discharge capacity increased rapidly until the fourth cycle and then decreased. The discharge capacity increased again from the 13th cycle, arriving at 234 mAh/g at the 50th cycle. The discharge capacity just after activation decreases with the increase in the amount of the substituted Fe but the cycling performance is improved. The discharge capacity after activation of the alloy with x=0.00 is 157 ㎃h/g at the current density 60 ㎃/g. Zr_0.8,Ti_0.2Mn_0.4V_0.6Ni_0.85Fe_0.15 shows a medium quantity of discharge capacities but a good cycling performance. Another series of multicomponent Zr_0.8,Ti_0.2Mn_0.4V_0.6Ni_0.85Fe_0.15 (M=Fe, Co, Cu, Mo and Al) alloys are prepared. They also have the C14 Laves phase hexagonal structure. The alloys with M=Co and Fe have relatively larger hydrogen storage capacities. The discharge capacities just after activation are relatively large in the case of the alloys with M=Al and Cu. They are 212 and 170 ㎃h/g, respectively, at the current density 60 ㎃/g. Of the alloys investigated, the Zr_0.8,Ti_0.2Mn_0.4V_0.6Ni_0.85Fe_0.15 alloy is the best one showing a relatively large discharge capacity and a good cycling performance. This alloy contains more Ni as compared with the other alloys, and the small particles of this alloys are the clusters of very fine particles. The ICP analysis of the electrolyte for these electrodes after 50 charge-discharge cycles shows that the concentrations of V and Zr are relatively high. |
|
