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系统研究了Mg元素对退火态A2B7型储氢合金La0.7-xY0.1Gd0.2MgxNi3.35Al0.15(x=0～0.4)电极自放电性能的影响。结果表明,退火态合金主要由Ce2Ni7(或Gd2Co7)型、Pr5Co19型、CaCu5型和PuNi3型相组成,Mg含量对合金组成和相结构有重要的影响,低镁含量有利于提高合金组织中Ce2Ni7型相的丰度,高镁含量易出现大量的CaCu5型和PuNi3型相。电化学测试表明,循环稳定性及电化学放电容量随Mg含量的增加而呈现先降低后升高的趋势,x=0.15,0.17合金电极具有最高的循环稳定性(S100=90%)和最大的电化学放电容量(368mAh.g-1)。Mg含量对合金电极的荷电保持率和开路电位影响显著,搁置7 d后的电极荷电保持率从7.9%(x=0)增加到59.7%(x=0.17),然后又降低到1.8%(x=0.4),表明适量的Mg含量可以改善合金的自放电性能,其中合金电极自放电时的可逆容量损失占97.5%以上,不可逆损失仅占0.4%～2.5%。合金电极的荷电保持率随合金PCT曲线放氢平台压力的升高而减小,其中氢致非晶态(x=0)和具有较高放氢平台压力的多相组织合金电极(x=0.4)的自放电率较大,荷电保持率最小。合金的腐蚀电流Icorr与电极的不可逆容量损失存在一定对应关系,当x=0.15～0.17时,合金的耐腐电流较小,其自放电时的不可逆容量损失最低,循环寿命也较佳。
The effect of Mg on the self-discharge of La0.7-xY0.1Gd0.2MgxNi3.35Al0.15 (x = 0 ~ 0.4) annealed A2B7 hydrogen storage alloy was studied systematically. The results show that the annealed alloys mainly consist of Ce2Ni7 (or Gd2Co7), Pr5Co19, CaCu5 and PuNi3 phases. The Mg content has an important influence on the composition and phase structure of the alloy. The low Mg content is beneficial to improve the Ce2Ni7 Phase abundance, high content of magnesium prone to a large number of CaCu5 and PuNi3 phase. The results of electrochemical tests showed that the cyclic stability and electrochemical discharge capacity first decreased and then increased with the increase of Mg content. The highest cycle stability (S100 = 90%) and the largest Electrochemical discharge capacity (368mAh.g-1). The effect of Mg content on the charge retention rate and open circuit potential of the alloy electrode is significant. The retention of electrode charge after 7 days rests from 7.9% (x = 0) to 59.7% (x = 0.17) and then decreases to 1.8% (x = 0.4), indicating that the proper Mg content can improve the self-discharge properties of the alloy. The reversible capacity loss of the alloy electrode accounts for more than 97.5% and the irreversible loss only accounts for 0.4% -2.5%. The charge holding rate of the alloy electrode decreases with the increase of the pressure on the desorption platform of the alloy PCT curves, in which the hydrogen is amorphous (x = 0) and the multiphase alloy electrode with higher hydrogen release platform pressure (x = 0.4) self-discharge rate is larger, the charge retention rate of the smallest. The corrosion current of the alloy Icorr is related to the irreversible capacity loss of the electrode. When x = 0.15 ~ 0.17, the corrosion current of the alloy is small, the loss of irreversible capacity of the alloy is the lowest, and the cycle life is also better.