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对La1.7+xMg1.3-x(NiCoMn)9.3(x=0~0.4)贮氢合金相结构和电化学性能进行研究。结构分析表明,合金主要由LaNi5相(CaCu5结构)和其他相组成,如LaMg2Ni9相(PuNi3结构)或La4MgNi19相(Ce5Co19+Pr5Co19结构)。随着x的增加,LaMg2Ni9相消失并出现La4MgNi19相,而LaNi5相的含量则先增加后减小,且晶胞体积下降。电化学分析表明,合金电极只需4、5次循环即可活化;随着x的增加,最大放电容量逐渐增大,从x=0的330.9mA·h/g增加到x=0.4的366.8mA·h/g,但高倍率放电性能(HRD)和循环稳定性(S)则有所下降(x=0.4,HRD600=82.32%,S100=73.8%)。研究认为,HRD主要由合金电极表面的电催化活性控制,而循环稳定性的下降则是由于x=0.4合金中出现了具有较大吸氢量的Ce5Co19和Pr5Co19型结构相,导致吸氢膨胀率和晶间应力增大,使合金颗粒在吸放氢过程中较易粉化所致。
The phase structure and electrochemical properties of La1.7 + xMg1.3-x (NiCoMn) 9.3 (x = 0 ~ 0.4) hydrogen storage alloys were studied. Structural analysis shows that the alloy mainly consists of LaNi5 phase (CaCu5 structure) and other phases, such as LaMg2Ni9 phase (PuNi3 structure) or La4MgNi19 phase (Ce5Co19 + Pr5Co19 structure). With the increase of x, LaMg2Ni9 phase disappeared and La4MgNi19 phase appeared, while the content of LaNi5 phase first increased and then decreased, and the unit cell volume decreased. Electrochemical analysis shows that the alloy electrode can be activated only in 4, 5 cycles. With the increase of x, the maximum discharge capacity increases from 330.9mA · h / g at x = 0 to 366.8mA at x = 0.4 · H / g, but the HRD and S decreased (x = 0.4, HRD600 = 82.32%, S100 = 73.8%). It is considered that the HRD is mainly controlled by the electrocatalytic activity of the electrode surface of the alloy, while the decrease of the cycle stability is due to the appearance of the Ce5Co19 and Pr5Co19-type structural phases with large hydrogen uptake in the x = 0.4 alloy, resulting in hydrogen absorption expansion And the intergranular stress increases, the alloy particles in the process of absorbing and discharging hydrogen easier due to powder.