化学计量比对AB_5型贮氢合金相结构及电化学性能的影响

Effect of Stoichiometric Ratio on Structure and Electrochemical Properties of AB_5-type Hydrogen Storage Alloys

对低钴稀土系贮氢合金Ml（Ni0.78Co0.08Al0.05Mn0.08）x（4．8≤x≤5．4）的相结构及电化学性能进行了研究。结果表明：在4．8≤x≤5．2的合金中除CaCu5型结构的主相之外，还出现LaNi3第二相，而且合金中第二相（LaNi3）的析出量随着x值的增大而减少，化学计量比x=5．4的合金则有富镍相析出，B侧合金化使低钴贮氢合金形成单相AB；型合金的化学计量比由x=5．0增大至5．2～5．4之间。四种不同化学计量比合金的活化性能都较好，合金的最大放电容量随化学计量比x的增大而增加，过化学计量比（x=5．4）合金具有最大的放电容量，最优的放电电压特性及最佳的循环稳定性，且其高倍率放电性能也较好。

Phase structure, microstructure and electrochemical properties of low Co hydrogen storage alloys Ml（Ni0.78Co0.08Al0.05Mn0.08）x （4.8≤x≤5.44） have been studied. The results show that alloys consisted of a main phase with CaCu5-type structure and a LaNi3 secondary phase, and the amount of the second phase （LaNi3） decreased with the increase of stoichiometric ratio x,the alloy, with x=5.4 segregated rich--Ni phase, alloying made stoichiometric ratio x formed single phase AB5 type alloys of low Co hydrogen storage alloys increase from 5.0 to 5.2～5.4. The different stoichiometric alloys have fa- vorable activation behavior. The electrochemical capacity of hydrogen storage alloys increased with the increase of stoichiometric ratio x. The alloy with x= 5.4 has the highest electrochemical capacity,the best discharge voltage character,the best cycling stability and favorable high--rate discharge capacity among the studied alloys.