| 摘要 |
PROBLEM TO BE SOLVED: To enhance initial discharge capacity of a secondary battery and to suppress lowering of discharge capacity when it is subjected to repeated charging and discharging by using a material which is comprised of rare earth elements or misch-metal, Ni, Mn, and at least one of Co, Al, Cu in a specified composition and in which the alloy has a mixed structure of two phases, each having a specified crystal structure. SOLUTION: The hydrogen occluding material is expressed by the general formula: R2(Ni7-x-yMnxAy)n, wherein R is a rare earth element or misch metal; A is at least one selected from Co, Al and Cu; 0.3<=x<=3.0, 0<=y<=1.0, and 0.9<=n<=1.3. The alloy has a two-phase mixed structure comprised of a crystal having hexagonal P63/mmc structure and a crystal having P6/mmm structure. In this structure, the crystals having P6/mmm structure are dispersed in the mother phase having P63/mmc structure, thereby the material is excellent in resistance to macroscopic pulverization. Accordingly, the characteristics excellent in discharge capacity and durability are obtained. It is preferable that the volume ratio of the phase having P63/mmc structure is to less than 40 vol.%, for realizing such characteristics.
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