In the development of hydrogen storage alloys for Ni MH battery,multicomponent AB 5 type of
mischmetal nickel based hydrogen
storage alloys were mostly investigated not only on B side of nickel and nickel substitute element, i.e.,multicomponent alloy of B-side, but also on A(RE) side (RE=La 1-x-y-z Ce xNd yPr z) with different La, Ce, Nd and Pr compositions in order to optimize the hydride electrode alloy. The results showed that La,Ce,Nd,and Pr had great effects on the electrode performance.Due to the high price of pure La, Ce, Nd and Pr,the REB 5 type electrode material for mass production should not be pure rare earths.The use of unrefined rare earth mixture (
mischmetal—a mixture of different composition of lanthanum, cerium, neodymium, preseodymium, etc) was very economical. Generally, they are categorized as lanthanum rich mischmetal (denoted as Ml), cerium rich mischmetal (denoted as Mm) and high lanthanum mischmetal (denoted as Lm) owing to different mineral resources and extractive metallurgical methods. Therefore, good electrochemical properties of RENi 5 alloys could be obtained by choosing a proper Mm:Ml ratio. In this paper, the electrochemical properties Ml βMm 1 β (NiCoMnTi) 5 hydrogen storage alloys with different composition of rare earth components were systematically examined. By the optimization of the Ml:Mm ratio, the alloy Ml 0.85 Mm 0.15 (NiCoMnTi) 5 showed a maximum capacity 280 mAhg -1 and good cycling stability. The basic structure of Ml βMm 1-β (NiCoMnTi) 5 was revealed by the Rietveld refinement analysis method.