稀土含量对MmNi_5基储氢合金性能的影响

测试了ＭｍｘＮｉ３．８Ｃｏ０．６Ｍｎ０．５５Ｔｉ０．０５（ｘ＝１．０５，１，０．９５）合金的充放电特性及循环寿命。当ｘ＝１．０５时，合金有较高的放电容量而循环寿命略有降低，这主要归因于稀土元素有较好的吸氢特性且易在晶界处偏析，形成ＭｍＮｉ相。当ｘ＝０．９５时，合金的放电容量及循环寿命显著降低，这是由于合金中的Ｍｎ向晶界处偏析，且极易溶于６ＭＫＯＨ中，破坏了合金表面，降低了放电容量和循环寿命。

Effect of the Rare Earth Content on the Characteristics of the MmNi 5 Based Hydrogen Storage Alloys

The charge-discharge properties and cycle lifetime of Mm xNi 3.8 Co 0.6 Mn 0.55 Ti 0.05 compound are studied. It is found that the compound has higher electrochemical capacity and lower cycle lifetime when x=1.05. The lower cycle lifetime is due to precipitate MmNi phase at the grain boundaries during the charge-discharge cycle. The capacity and cycle lifetime decrease obviously when the Mm content x=0.95, owing to the precipitation of Mn element toward the grain boundary and dissolve in the KOH alkali solution. This dissolve destroys the grain surface, and thus results in the decrease of the cycle lifetime of the compound.