La_(0.75-x)Pr_xMg_(0.25)Ni_(2.9)Co_(0.4)Al_(0.2)(x=0-0.4)电极合金的微观结构及电化学性能

Microstructures and electrochemical performance of as-cast and quenched La_(0.75-x)Pr_xMg_(0.25)Ni_(2.9)Co_(0.4)Al_(0.2)(x=0-0.4)electrode alloys

为了提高La-Mg-Ni系(PuNi3)型贮氢合金的电化学循环稳定性,用Pr部分替代La,用铸造和快淬工艺制备了La0.75-xPrxMg0.25Ni2.9Co0.4Al0.2(x=0～0.4)贮氢合金。分析测试了铸态及快淬态合金的电化学性能和微观结构、铸态合金的交流阻抗谱,研究了Pr替代对铸态及快淬态合金微观结构及电化学性能的影响。结果表明,铸态及快淬态合金具有多相结构,包括(La,Mg)Ni3相(PuNi3结构),LaNi5相和一定量的LaNi2相。随Pr含量的增加,铸态及快淬态合金中LaNi5相略有增加。Pr的替代提高了铸态及快淬态合金的循环稳定性,但使合金的容量有所下降。铸态及快淬态合金均有优良的活化性能。合金的循环寿命随淬速的增加而增加。

In order to improve the electrochemical cycle stability of La-Mg-Ni system （PuNi3-type） hydrogen storage alloy, the La in the alloy was partially substituted by Pr. La0.75-xPrxMg0.25Ni2.9Co0.4Al0.2 （x=0-0.4） hydrogen storage alloys were prepared by casting and rapid quenching. The electrochemical performance and microstructure of the as-cast and quenched alloys were determined and measured. In the meantime the EIS of the as-cast were measured. The effects of Pr substitution on the microstructure and electrochemical properties of the as-cast and quenched alloys were investigated in detail. The obtained results show that the as-cast and quenched alloys are multi-phase structure and are composed of the （La, Mg）Ni3 phase （PuNi3-type structure） and the LaNi5 phase as well as a certain amount of LaNi2 phase. The amount of the LaNi5 phase slightly increases with the increase of Pr content. The addition of Pr enhances the cycle stability of the as-cast and quenched alloys, but decreases the discharge capacities of the alloys. The as-cast and quenched alloys have an excellent activation performance. The cycle lives of the alloys increase with the increase of the quenching rate.