La0.67Mg0.33Ni3.0-xAlx（x=0.0-0.35）贮氢合金相结构和电化学性能研究

采用X射线衍射、电子探针和电化学测试研究了La0.67Mg0.33Ni3.0-xAlx（x=0.0-0.35）合金的相结构和电化学性能。XRD结果和EPMA观察表明：La0.67Mg0.33Ni3.0合金由LaNi3相和La2Ni7相组成。然而La0.67Mg0.33Ni3.0-xAlx（x=0．1，0．2，0．35）合金不含LaNi3相。研究结果表明Al替代Ni改变了La0．67Mg0．33Ni3.0合金的相结构，Al替代Ni不利于La0．67Mg0．33Ni3.0合金中LaNi3相的形成。此外，随Al含量的增加，La0.67Mg0.33Ni3.0-xAlx（x=0．1，0．2，0．35）合金的相结构也发生了变化。WDS分析表明：随La0.67Mg0.33Ni3.0-xAlx合金中X的增加，Al在LaNis相中的含量增加，但Al在LaNi2相的含量很少并且几乎不随X变化。电化学性能测试表明：Al替代Ni提高了La0.67Mg0.33Ni3.0合金电极的循环稳定性。但La0.67Mg0.33Ni3.0-xAlx合金电极的放电容量却随Al含量的增加而明显降低。

Phase Structures and Electrochemical Performances of La0.67Mg0.33Ni3.0-xAlx (x=0.0～0.35) Hydrogen Storage Alloys

Phase structures and electrochemical performances of La0.67Mg0.33Ni3.0-xAlx(x=0.0～0.35) alloys were investigated by means of X-ray diffraction (XRD), electron probe X-Ray microanalysis (EPMA) and electrochemical measurements. XRD patterns and EPMA analysis show that La0.67Mg0.33Ni3.0 alloy is composed of LaNi3 phase and La2Ni7 phase. But La0.67Mg0.33Ni3.0-xAlx (x=0.1,0.2 and 0.35) alloys do not contain LaNi3 phase. The XRD results indicate that Al substitution for Ni will change phase structure of La0.67Mg0.33Ni3.0 alloy, and Al substitution is not beneficial to form LaNi3 phase in La0.67Mg0.33Ni3.0 alloy. Moreover, phase structures of La0.67Mg0.33Ni3.0-xAlx (x=0.1,0.2 and 0.35) alloys also change with the increase of Al content in the alloys. WDS analysis shows that Al content increase in LaNi5 phase with the increase of x in La0.67Mg0.33Ni3.0-xAlx alloys. But Al content in LaNi2 phase is quite a little and almost keeps constant with the change of x. Electrochemical measurements show that substitution of Ni by Al is effective to enhance the cycle life of La0.67Mg0.33Ni3.0 alloy. However the discharge capacities of La0.67Mg0.33Ni3.0-xAlx alloy electrodes decrease obviously with the Al content x increment in the alloys.