HYDROGEN-ABSORBING ALLOY POWDER, NEGATIVE ELECTRODE, AND NICKEL HYDROGEN SECONDARY BATTERY

摘要

Provided are: a hydrogen-absorbing alloy powder, whereby it becomes possible to achieve all of excellent initial activity, excellent discharge capacity and excellent cycle properties which have a trade-off relationship with one another in a nickel hydrogen secondary battery; a negative electrode for nickel hydrogen secondary batteries, which is produced using the hydrogen-absorbing alloy powder; and a nickel hydrogen secondary battery. The hydrogen-absorbing alloy has a specific chemical composition represented by formula (1): R1-aMgaNibAlcMd, and has an Mg-rich Ni-poor region on the outermost surface thereof and an Mg-Ni-containing region in the inside thereof, wherein the Mg-rich Ni-poor region contains Mg at a larger molar ratio than the molar ratio of Mg in formula (1) and contains Ni at a smaller molar ratio than the molar ratio of Ni in formula (1), and wherein the Mg-Ni-containing region contains Mg in a smaller molar ratio than the molar ratio of Mg in the Mg-rich Ni-poor region and contains Ni at a larger molar ratio than the molar ratio of Ni in the Mg-rich Ni-poor region.