A2B7型贮氢合金相结构及电化学性能研究

采用感应熔炼方法制备La0.75Mg0.25Ni3.5-xMnx(x=0,0.05,0.1,0.15,0.2)四元贮氢合金,系统地研究合金B侧Mn对Ni部分替代对合金相结构及电化学性能的影响。XRD分析表明,La0.75Mg0.25Ni3.5-xMnx由La2Ni7相(包括Gd2Co7型高温相和Ce2Ni7型低温相)组成。此外,Mn的加入,使该类合金中出现LaNi5相,但是在含Mn量较高(x=0.15,0.2)的合金中LaNi5相消失。电化学测试表明,随Mn含量的增加,合金电极活化次数变化不大,合金电极的最大放电容量减小,高倍率放电性能、交换电流密度变差,循环稳定性、极限电流密度均得到明显的改善。

Phase Structure and Electrochemical Characteristics of A2B7 Type Hydrogen Storage Alloy

La0.75Mg0..25Ni3.5-xMnx (x=0,0.05,0.1,0.15,0.2) alloy ingots were prepared by induction melting. The effect of Mn substitution for Ni on the phase structure and the electrochemical characteristics of hydrogen storage alloys was studied. XRD analysis shows that the La0.75Mg0.25Ni3.5-xMnx consists of La2Ni7 phase, and LaNi5 phase with CaCu5 type appears when Mn is added. LaNi5 phase disappears with Mn higher content from x=0.15 to x=0.2. The electrochemical analysis shows that the substitutions lower the maximum electrochemical discharge capacity, the high rate dischargeability, and the exchange current density and have a little effect on the activation property. The replacements of Ni by Mn have a little effect on the cyclic stability and limiting current density (IL).