采用中间合金法在感应熔炼炉中制备La 4 MgNi 19?x Co x (x=0~2)合金，研究Co部分替代Ni对合金相结构和电化学性能的影响。XRD测试结果表明：合金主要由La4MgNi19(Ce5Co19+Pr5Co19)相和LaNi5相组成；x的增加有利于促进La 4 MgNi 19相的形成，且晶胞体积随之增大。显微组织观察发现，合金为树枝晶结构，x的增加会使树枝晶变细。电化学测试表明：合金均具有良好的活化性能和高倍率放电性能(HRD 600＞92.57%)；随着x的增加，合金的最大放电容量明显提高(从x=0时的359.23 mA?h/g增大到x=2的380.85 mA?h/g)，而循环寿命则先下降后逐渐提升。高倍率放电性能主要由合金电极的扩散系数控制，而循环稳定性的下降则是由于合金中La4MgNi19相的增加使膨胀率和晶间应力集中增大加速粉化所致。
The La4MgNi19?xCox(x=0?2) alloys were prepared by intermediate alloy method in vacuum levitation melting furnace, and their phase structure and electrochemical properties were investigated systematically. The XRD results show that all alloys consist of LaNi5and La4MgNi19 phases (Ce5Co19+Pr5Co19structure). The increase ofx value can promote the formation of La4MgNi19 phase and increase the cell volume of that phase. The microstructure observation reveals that the microstructures of all alloys are dendritic structure, which becomes fine with the increase ofx value. The electrochemical measurements show that all alloys have good activation performance and high-rate discharge-ability (D600, HR>92.57%). With the increasing ofx value, the maximum discharge capacity of the alloy increases obviously (increasing from 359.23 mA?h/g atx=0 to 380.85 mA?h/g atx=2), and the cycle life first decreases and then increases gradually. The high ratio discharge properties are mainly controlled by the diffusion coefficient of the alloy electrode, and the declination of cycle stability is due to the accelerating pulverization caused by the increase of inter-granular stress concentration and the higher expansion ratio of La4MgNi19phase.
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