Ni-MH电池用Mg-Y-Ni纳米晶和非晶合金的电化学性能

摘要

The as-cast Mg2Ni-type Mg20–xYxNi10 (x=0, 1, 2, 3 and 4) electrode alloys were prepared by vacuum induction melting. Subsequently, the as-cast alloys were mechanically milled in a planetary-type ball mill. The analyses of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) reveal that nanocrystalline and amorphous structure can be obtained by mechanical milling, and the amount of amorphous phase increases with milling time prolonging. The electrochemical measurements show that the discharge capacity of Y0 alloy increases with milling time prolonging, while that of the Y-substituted alloys has a maximum value in the same condition. The cycle stabilities of the alloys decrease with milling time prolonging. The effect of milling time on the electrochemical kinetics of the alloys is related to Y content. Whenx=0, the high rate discharge ability, diffusion coefficient of hydrogen atom, limiting current density and charge transfer rate all increase with milling time prolonging, but the results are exactly opposite whenx=3.%采用真空感应熔炼在高纯氦气气氛保护下制备Mg2Ni型Mg20–xYxNi10(x=0,1,2,3,4)铸态电极合金，然后将铸态合金置于行星式球磨机中进行机械球磨得到球磨合金。SEM、XRD以及TEM测试结果表明，通过球磨可以得到纳米晶和非晶结构，非晶相含量随着球磨时间的延长而增加。电化学测试表明，Y0合金的放电容量随着球磨时间的延长而增大，而Y替代合金的放电容量随球磨时间的延长出现最大值。循环稳定性随着球磨时间的延长均有所降低，表明球磨对循环稳定性不利。球磨时间对电化学动力学的影响与Y含量有关。当x=0时，合金电极的高倍率放电性能、氢扩散系数、极限电流密度以及电荷转移率都随着球磨时间的延长而增大，而x=3时结果却相反。