Zr替代La对快淬态A2B7型电极合金结构及电化学性能的影响

Influences of Substitution of Zr for La on Structures and Electrochemical Performances of A2B7-Type Electrode Alloys by Melt-Spinning

摘要:

用铸造及快淬工艺制备了A2B7型电极合金，合金的名义成分为La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1 (x = 0, 0.05, 0.1, 0.15, 0.2)。深入研究了Zr替代La对合金微观结构及电化学性能的影响。用XRD、SEM、TEM分析了合金的结构。结果表明，铸态及快淬态合金均具有多相结构，含有两个主相(La,Mg)Ni3和LaNi5以及一个残余相LaNi2。Zr替代La使合金中LaNi5相明显增加，并促进快淬态合金中形成非晶相。电化学测试的结果表明，Zr替代La明显降低合金的放电容量，但显著改善合金的电化学循环稳定性。当Zr含量小于0.1时，合金的放电容量随淬速的增加而先增加后减小，合金的循环稳定性随淬速的增加而单调增加。

Abstract:

A2B7-type electrode alloys with a nominal composition of La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1 (x = 0, 0.05, 0.1, 0.15, 0.2) were prepared by casting and melt-spinning. The influences of the substitution of Zr for La on the structures as well as the electrochemical performances of the alloys were investigated. The results obtained by XRD, SEM and TEM show that the as-cast and spun alloys have a multiphase structure, consisting of two main phases (La,Mg)Ni3 and LaNi5 as well as a residual phase LaNi2. The substitution of Zr for La leads to an obvious increase of the LaNi5 phase in the alloys, and it also helps the formation of a like amorphous structure in the as-spun alloy. The results of the electrochemical measurements indicate that the substitution of Zr for La obviously decreases the discharge capacity of the as-cast and spun alloys, but significantly improves their cycle stability. With increasing the spinning rate, the discharge capacity of the alloys (x≤0.1) first increases and then decreases, while the cycle stability monotonously rises.