熔体快淬对La_(0.75-x)Zr_xMg_(0.25)Ni_(3.2)Co_(0.2)Al_(0.1)(x=0～0.2)电极合金循环稳定性的影响

Influence of melt spinning on the cycle stability of La_(0.75-x)Zr_xMg_(0.25)Ni_(3.2)Co_(0.2)Al_(0.1)(x=0～0.2) electrode alloys

为了改善La-Mg-Ni系A2B7型电极合金的电化学循环稳定性,用Zr部分替代合金中的La,并用熔体快淬工艺制备了La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0、0.05、0.1、0.15、0.2)电极合金。用XRD、SEM、TEM分析了铸态及快淬态合金的微观结构,测试了铸态及快淬态合金的电化学循环稳定性,研究了快淬工艺及Zr替代La对合金循环稳定性的影响,探讨了电极合金的失效机理。结果表明,铸态及快淬态合金均具有多相结构,包括两个主相(La,Mg)Ni3及LaNi5和一个残余相LaNi2。快淬处理及Zr替代La可以显著的改善合金的电化学循环稳定性。导致合金失效的主要原因是电极表面被电解液剧烈腐蚀以及合金电极在电化学循环过程中的粉化。

In order to improve the electrochemical cycle stability of La-Mg-Ni system A2B7-type electrode alloy, La in the alloy was partly substituted by Zr, and the electrode alloys La0.75-x Zrx Mg0.25 Ni3.2 Co0.2Al0.1 （x=0, 0.05, 0.1, 0.15, 0.2） were prepared by melt spinning technology. The structures of the as-cast and spun alloys were analyzed by XRD, SEM and TEM. The electrochemical cycle stability of the alloys was measured. The influences of the melt spinning and substituting La with Zr on the cycle stability of the alloys were investigated in detail. The failure mechanism of the alloy electrodes was investigated. The obtained results indicated that the as-cast and spun alloys have multiphase structure, including two major phases （La, Mg）Ni3 and LaNi5 as well as a residual phase LaNi2. Both the melt spinning and substituting La with Zr significantly improved the electrochemical cycle stability. The fundamental reasons of which cause lose efficacy of the alloy electrodes are that the surface of the alloy electrodes is severely corroded by electrolyte and that the alloy electrodes are pulverized in process of the electrochemical charge-discharge cycle.