Effect of AB2 alloy addition on the phase structures and electrochemical characteristics of LaNi5 hydride electrode

Hypo-stoichiometric AB(5-alpha) (alpha > 0) type alloy LaNi5-x%AB(2) (x = 1, 5,10,20) composite alloys were successfully prepared by sintering the powder mixtures of LaNi5 and AB(2)-type Laves phase alloy Zr0.9Ti0.1(Mn0.35Ni0.55V0.15)(2) as addition. The phase structure and electrochemical characteristics of the composite alloys were investigated by means of XRD, EDS and electrochemical measurements. It was shown that LaNi5-x% AB(2) (x = 1, 5, 10, 20) composite alloys have multi-phase structure, the matrix phase is CaCu5 structure of LaNi5 alloy, the second phase is rich-Zr phase which dispersed in the matrix phase as strips. The discharge capacity and rate-discharge capacity of LaNi5 alloy electrodes were greatly improved after composite treated by adding AB(2) alloy. The maximum discharge capacity of the composite alloy electrodes increased from 188 mAh/g for x = 0 to 305 mAh/g for x = 10, and the rate-discharge capacity of the composite alloy for x = 5 at the current density of 300 mA/g and 2040 mA/g was 97% and 55% of that of the alloy at 60 mA/g, respectively. The electrochemical characteristics of LaNi5 alloy at low temperature were also significantly improved by adding AB(2) alloy. The discharge capacity of LaNi-5% AB(2) composite alloy electrode at 233 K was up to 215 mAh/g. (c) 2004 Elsevier B.V. All rights reserved.