Microstructure And Electrochemical Properties Of La-Mg-Ni Based AB_3.8 Hydrogen Storage Alloys

In this paper,the structure and electrochemical properties of La_0.8Mg_0.2Ni_3.3Al_0.2Mo_0.3 type hydrogen storage alloys were studied.The main contents are as follows:The effect of rare earth element substitution for Lanthanum on structure and electrochemical characteristic of La_0.8Mg_0.2Ni_3.3Al_0.2Mo_0.3 hydrogen storage alloys and the effect of the rare earth oxides and metal oxides addition on structure and properties of the La_0.8Mg_0.2Ni_3.3Al_0.2Mo_0.3 alloy.The XRD analysis showed that rare earth elements substitution and addition of rare earth oxides and metal oxides did not change the crystal structure of the alloy and the alloys were composed of La₂Ni₇ and LaNi₅ phase.The cell volume of LaNi₅ is increased,which is the main reason for the increase of the discharge capacity.SEM analysis showed that the gray part was LaNi₅ phase and the black part was La₂Ni₇ phase.The distribution of the two phases of the alloy is uniform and the distribution of the two phases in the alloy is also different with the different elements in the alloy.Electrochemical analysis showed that the rare earth elements Pr substitution increased the maximum discharge capacity and reached the maximum value of 321.7 mAh·g-1,which is 75.6 mAh·g-1 higher than that of base alloy.Y substitution promoted the cyclic durability of the alloy and the S100 reached 63.4%.Nd substitution can improve the high-rate ability?HRD?of the alloy electrodes.The maximum discharge capacity was improved with rare earth oxide Gd₂O₃ addition and reached the maximum value of 310.1 mAh·g-1.Pr₂O₃ addition improved the cycle stability and the S100 can reach 64.7%.The retention rate of alloy with Nd₂O₃ addition was higher than that of the base alloy.The addition of metal oxides NiO improved the maximum discharge capacity of alloy to 304.2mAh·g-1.The retention rates of alloy with ZnO and Ni O addition were S100=77.3% and S100=67.7%,respectively.