AB_5-AB_2复合合金电极的微观结构和活化性能

Microstructure and Activation Characteristics of AB_5-AB_2 Composite Alloy Electrode

根据AB5型稀土基合金的活化性能优良及对氢化和氢化物分解过程具有催化作用的特点 ,将Zr0 .9Ti0 .1 (Mn0 .35Ni0 .6 5) 2 AB2 型Laves相合金与AB5型混合稀土合金进行机械球磨处理 ,制备了AB5 AB2 复合合金。研究了复合合金的微观结构和电化学性能 ,结果表明 :在AB5 AB2复合合金中 ,AB5粒子与AB2 粒子在表面处相互镶嵌在一起 ,并仍保持原来的晶体结构。复合合金电极的活化周期从AB2 合金的 11周减少到 4周 ,最大放电容量从 14 1mAh·g- 1 增加到 2 18mAh·g- 1 ,而且在活化初期表现出协同效应。

Rare earths based AB 5 type alloys (represented as AB 5) not only have a good activation behavior and high rate discharge ability, but also catalyse the hydriding and dehydriding. A kind of composite alloy with AB 5 and Zr 0.9 Ti 0.1 (Mn 0.35 Ni 0.65 ) 2 Laves phase alloy (represented as AB 2) was successfully prepared by means of mechanical ball milling. XRD showed that after milling mixed AB 5 and AB 2 (1∶1 in weight ratio) for 10 min, AB 5 and AB 2 maintain their crystalline state. Further SEM and EDS analysis revealed that some AB 5 and AB 2 particles are decorated on the surface each other, and in the meantime some fresh surface are simultaneously formed. It was found that AB 5 AB 2 composite alloy shorts the active cycles from 11 to 4 and increases the maximum discharge capacity from 141 mAh·g -1 to 218 mAh·g -1 compared to AB 2 alloy. In particular, the discharge capacity for AB 5 AB 2 composite alloy positively deviates from the estimated values based on the discharge capacity for both alloys and their contents, suggesting that the AB 5 alloy can work as a catalyst for dehydriding the AB 2 alloy hydride besides as a hydrogen reservoir, a synergistic effect appeares by the mixing.