화학공학소재연구정보센터
Journal of the Electrochemical Society, Vol.148, No.9, A1041-A1044, 2001
Development of AB(2)-Type Zr-Ti-Mn-V-Ni-M hydride electrode for Ni-MH secondary battery
A series of multicomponent Zr0.5Ti0.5Mn0.4V0.6Ni0.85M0.15 (M = Fe, Co, Cu, Mo, and AI) alloys are prepared and their crystal structure and pressure-composition-temperature curves are examined. The electrochemical properties of these alloys such as discharge capacity, cycling performance, and rate capability are also investigated. Zr0.5Ti0.5Mn0.4V0.6Ni0.85M0.15 (M = Fe, Co, Cu, Mo, and Al) alloys have predominantly C14 Laves phases multiple phase 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 = Co and Fe. They are 226 and 225 mAh/g, respectively, at the current density 60 mA/g. The Zr0.5Ti0.5Mn0.4V0.6Ni0.85Co0.15 alloy is the best one with a relatively large discharge capacity and good cycling performance. The gradual increases in the discharge capacities of the alloys with the increase in the current density (from 60 to 250 mA/g) are considered to result from the spontaneous hydrogen evolution due to an insufficient hydrogen overvoltage. During activation Ni-rich and Fe-rich regions form on the surface of the Zr0.5Ti0.5Mn0.4V0.6Ni0.85Fe0.15 alloy. They may act as active sites for the electrochemical reaction. With the increase in the number of charge/discharge cycles for the Zr0.5Ti0.5Mn0.4V0.6Ni0.85Fe0.15 alloy, the quantities of the zirconium and iron dissolved in the solution increase.