汽车电池用La-Mg-Ni基储氢合金的元素替代及电化学性能

Element Substitution and Electrochemical Performance of La-Mg-Ni Based Hydrogen Storage Alloys for Automotive Batteries

采用感应熔炼方法制备了La_(0.7)R_(0.1)Mg_(0.2)Ni_(3.35)Al_(0.15)(R=La/Nd/Sm)储氢合金,研究了稀土元素Nd/Sm替代La对储氢合金相结构和电化学性能的影响。结果表明,采用Nd或Sm替代La时,储氢合金物相组成未发生改变,仍由LaNi_(5)、(LaMg)_(2)Ni_(7)和(LaMg)_(5)Ni_(19)相组成,但储氢合金中LaNi_(5)相和(LaMg)_(5)Ni_(19)相丰度会增加、(LaMg)_(2)Ni_(7)相丰度减小。R为La、Nd和Sm时储氢合金的最大放电比容量均在第2次充放电循环时获得,分别为377 mAh/g、382 mAh/g和376 mAh/g;采用Nd或Sm替代La,储氢合金高倍率放电性能、24 h荷电保持率和充放电循环100次时的容量保持率都不同程度地增加,且R为Nd时储氢合金的相应值最大。采用Nd或Sm替代La会使得储氢合金的交换电流密度、氢扩散系数增加,储氢合金电极的高倍率放电性能与交换电流密度和氢扩散系数变化趋势一致,表明储氢合金电极的高倍率放电性能由交换电流密度和氢扩散系数共同决定。

A kind of hydrogen storage alloy of La_(0.7)R_(0.1)Mg_(0.2)Ni_(3.35)Al_(0.15)(R=La/Nd/Sm)was synthesized with induction melting method,and the effect of La substituted with rare earth element Nd/Sm on the phase structure,microstructure,and electrochemical performance of the hydrogen storage alloy was explored.The results show that the substitution of Nd or Sm for La doesn′t change the phase composition of the hydrogen storage alloy,which is still composed of LaNi_(5),(LaMg)_(2)Ni_(7),and(LaMg)_(5)Ni_(19)phases,but leads to higher abundance of LaNi_(5)and(LaMg)_(5)Ni_(19)phases,and lower abundance of(LaMg)_(2)Ni_(7)phase in the hydrogen storage alloy.The hydrogen storage alloy,with La,Nd and Sm as R,deliver the maximum discharge capacities of 377 mAh/g,382 mAh/g and 376 mAh/g,respectively,after the second charge-discharge cycle.With La substituted with Nd or Sm,the hydrogen storage alloy has its high-rate discharge capacity,the charge retention rate after 24 hours,and capacity retention rate after 100 cycles all improved to some extent,among which the hydrogen storage alloy with Nd as R is the best in all corresponding performance.Moreover,the substitution of La with Nd or Sm can make the hydrogen storage alloy with higher exchange current density and higher coefficient of hydrogen diffusion.Its high-rate discharge performance,exchange current density and hydrogen diffusion coefficient are all in in the same trend,indicating that high-rate discharge performance of the hydrogen storage depends on both exchange current density and hydrogen diffusion coefficient.