The Effects Of Ball Milling And Catalyst On The Electroche-Ical Performance Of Mg_2-xNd_xNi （x=0.1-0.4） Hydrogen Storage Alloy

Mg-based hydrogen storage alloy with high capacity and rich sorces is considered as oneof the most valuable hydrogen storage materials. However, the poor electrochemical cycle lifeand hydriding-dehydriding kinetics performance is the main problem in its application. In orderto improve the performance of Mg₂Ni type hydrogen storage alloy, Mg_2-xNd_xNi（x=0.1，0.2，0.3，0.4）alloy were prepared by vacuum melting. The effects of partial substitution of Nd forMg on the performance of Mg₂Ni type hydrogen storage alloy have been investigated. And theinfluence of different ball milling time and catalyst Fe on Mg_2-xNd_xNi（x=0.1-0.4）alloy havebeen also researched in this paper. Microstructure XRD test, electrochemical measurement andkinetics performance test show the result as follows:Based on the reaserch of Mg_2-xNd_xNi（x=0，0.1，0.2，0.3，0.4）as-cast alloy,theresults show that the alloy changed single-phase structure with Mg₂Ni into the multiphasestructure containing Mg₂Ni phase、NdNi phase、NdMgNi₄phase and Nd phase.when the Ndcontent was0.3, The maximum discharge capacity and capacity retention rate are128.8mAh/gand56.67%, it has a good electrochemical and kinetics performance. This indicates that theamout of Nd substitution apparently increased the electrochemical capacity of alloy andeffectively improve the cycle stability and kinetics performance of Mg₂Ni hydrogen storagealloy.The research of Mg_2-xNd_xNi（x=0.1-0.4）alloy in different ball milling time shows thatthe paase structure of alloy hasn’t significantly changged by ball milling, but the alloy guaduallychanged into amorphous structture because of the ball milling. When the milling time increasedfrom0to72h, the maximum discharge capacity of Mg_2-xNd_xNi（x=0.1）alloy were58.6mAh/g、170.1mAh/g、118.6mAh/g、131.1mAh/g, it state clearly that ball milling observablyincrease maximum discharge capacity of alloy. The capacity retention rate of Mg_2-xNd_xNi（x=0.1）alloy have improved by the ball milling. When the Nd content were0.1and0.2, T=72h has show the good kinetics performance.When x=0.3and0.4, the as-cast alloy has thebest kinetics performance.The phase structure of alloy hasn’t changed by adding catalyst Fe in different milling time,however, the Fe increase the amorphization process of alloy. The maximum discharge capacityof Mg_2-xNd_xNi（x=0.1，0.2）alloy increased by adding catalyst Fe in24h milling time. Thecapacity retention rate of this alloy improved by adding Fe in72h. For Mg_2-xNd_xNi（x=0.3，0.4）alloy with different milling time, the catalyst Fe enhanced its capacity retention rate.Appropriate milling time to add catalyst Fe played a positive role in the kinetics performance ofalloy with different Nd content.