| 摘要 |
PROBLEM TO BE SOLVED: To prevent discharging characteristics of a battery from lowering even in a low temperature by setting the mean grain size of a rare earth-based hydrogen storage alloy having CaCu5 type crystal structure, treating the alloy with an alkaline solution, and coating the alloy surface with an antioxidant. SOLUTION: A hydrogen storage alloy with a mean grain size 10-25μm at D50 is treated with an alkaline solution, washed, and surface treated with an antioxidant. This process can provide it with the alloy surface of fine particles and the use of the treated alloy for the negative electrode can improve the initial characteristics and the low-temperature characteristics. In this case, pulverized alloy powder is necessary to be pretreated with sodium hydroxide, potassium hydroxide, lithium hydroxide, etc., at 150 deg.C, preferably at 100-130 deg.C for 0.5-20 hours. The alkali concentration of 1.0-10.0 N is used. Condensation phosphoric acid, phytic acid, etc., are used for an antioxidant.
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