复相La-Mg-Ti-Ni-Co基AB3型储氢合金的相结构与电化学性能衰退机理研究

Study on phase structure and electrochemical performance degradation mechanism of multiphase La-Mg-Ti-Ni-Co based AB3 type hydrogen storage alloy

研究了镧(La)-镁(Mg)-钛(Ti)-镍(Ni)-钴(Co)[La0.7Mg0.3-xTixNi2.5Co0.5(x=0~0.15)]储氢合金的相结构与电化学性能衰退机理。结果显示,合金的主相均为(La,Mg)Ni3相,但随着Ti含量的增加,合金中逐渐产生了TiNi相而形成复相。合金经90次循环后的放电容量保持率从x=0条件下的56.5%增加至x=0.10条件下的62.0%,再下降至x=0.15条件下的60.8%,这与交换电流密度的变化规律一致。Ti对Mg的替代能够提高合金的耐蚀性,但过量的Ti会阻碍电极与电解液之间的界面反应,造成放电容量的衰退。

The phase structures and electrochemical degradation mechanism of La0.7Mg0.3-xTixNi2.5Co0.5(x= 0~0.15)hydrogen storage alloys were studied.The results showed that the main phase of the alloys was(La,Mg)Ni3 phase,but TiNi phase was gradually formed in the alloys with the increase of Ti content.The discharge capacity retention rate of the alloys increased from 56.5%at x=0to 62.0%at x=0.10,and then decreased to 60.8%at x= 0.15after 90cycles,which was consistent with the change rule of exchange current density.The substitution of Ti for Mg could improve the corrosion resistance of the alloys,while excessive Ti hindered the interface reaction between electrodes and electrolyte,resulting in the decline of discharge capacities.