为开发出高能量密度镍氢电池负极材料,采用真空感应熔炼的方法制备了La_0.79Mg_0.21Ni_3.95储氢合金,对比分析了铸态和退火态储氢合金的物相组成、显微形貌和电化学性能。结果表明,铸态和800 ℃/24 h退火态La_0.79Mg_0.21Ni_3.95储氢合金中都只含有LaNi₅和（La,Mg）₂Ni₇相;升高温度至900 ℃及以上时,储氢合金中形成了不同含量的（La,Mg）₅Ni₁₉和（La,Mg）₆Ni₂₄相。900 ℃/24 h退火态储氢合金的可逆吸放氢性能要高于950 ℃/48 h退火态储氢合金。铸态和退火态储氢合金都在前3周循环过程中到达了最大放电比容量,950 ℃/48 h退火态储氢合金中主要为（La,Mg）₆Ni₂₄相,其具有较高的循环稳定性。铸态和退火态La_0.79Mg_0.21Ni_3.95储氢合金具有良好的电化学活化性能,高倍率放电性能（HRD₁₅₀₀）从高至低的顺序依次为950 ℃/48 h、950 ℃/24 h、900 ℃/24 h、 800 ℃/24 h、铸态;储氢合金的HRD₁₅₀₀与氢扩散速率（D）和交换电流密度（I₀）的变化趋势相同,950 ℃/48 h退火态储氢合金具有最大的HRD₁₅₀₀,这主要与合金电极中含有61.8%（质量分数）的（La,Mg）₆Ni₂₄相、具有较高的D和I₀有关。

In order to develop cathode materials for Ni-MH batteries with high energy density,La_0.79Mg_0.21Ni_3.95 hydrogen storage alloy was prepared by vacuum induction melting,and the phase composition,microstructure and electrochemical properties of as cast and annealed hydrogen storage alloys were compared and analyzed.The results showed that there were only LaNi₅ and（La,Mg）₂Ni₇ phases in as cast and 800 ℃/24 h annealed La_0.79Mg_0.21Ni_3.95 hydrogen storage alloys.When the tem-perature was raised to 900 ℃ or above,different contents of（La,Mg）₅Ni₁₉ phase and（La,Mg）₆Ni₂₄ phase were formed in the hydrogen storage alloy.The reversible hydrogen absorption and desorption performance of 900 ℃/24 h annealed hydrogen storage alloy was higher than that of 950 ℃/48 h annealed hydrogen storage alloy.The maximum discharge capacity of as cast and annealed hydrogen storage alloys reached the maximum in the first three cycles,and the hydrogen storage alloy annealed at 950 ℃/48 h mainly consisted of（La,Mg）₆Ni₂₄ phase,which had high cycle stability.As cast and annealed La_0.79Mg_0.21Ni_3.95 hy-drogen storage alloys had good electrochemical activation properties.The order of HRD₁₅₀₀ from high to low was: 950 ℃/48 h>950 ℃/24 h>900 ℃/24 h>800 ℃/24 h>as cast,the results showed that the HRD₁₅₀₀ of hydrogen storage alloy had the same trend with that of hydrogen diffusion rate（D） and exchange current density（I₀）.The maximum HRD₁₅₀₀ of hydrogen storage alloy annealed at 950 ℃/48 h was mainly due to the fact that the alloy electrode contained 61.8% of（La,Mg）₆Ni₂₄ phase and had higher D and I₀.