Improvement in capacity of cobalt-free Mm-based hydrogen storage alloys with good cycling stability

A multi-phase and multicomponent cobalt-free Mm-based hydrogen storage alloy was examined. The phase composition, alloy microstructure, P-C-T and electrochemical properties were investigated. The physical and electrochemical properties of the cobalt-free alloy were compared with a typical AB(5) alloy containing higher cobalt content and with a low-cobalt him-based alloy. The results showed that the cobalt-free alloy had a flatter discharge plateau with electrochemical capacity of 307, mAh/g at 0.2 C rate and good rate capability. The hydrogen storage capacity of the cobalt-Ore alloy was significantly improved as compared with that of the low-cobalt Mm-based alloy (273 mAh/g). The cobalt-free Mm-based hydrogen storage alloy is a promising candidate for development of low-cost NiMH batteries with high capacity, good rate capability and cycling stability. (C) 2000 Elsevier Science S.A. All rights reserved.