Metal Hydride Electrodes Applied to Ni-MH Battery Using Mg-Y-Ni-Cu-Based Alloys

To improve the electrochemical properties of the Mg-Ni-based alloys, mechanical ball milling was used to create the nanocrystalline and amorphous Mg_50−xY_xNi₄₅Cu₅ (x = 0, 1, 2, 3, 4) + 50 wt%Ni (named Mg_50−xY_xNi₄₅Cu₅ (x = 0, 1, 2, 3, 4) + 50Ni) alloys. The effects of Y content and ball milling time on the microstructure and electrochemical hydrogen storage properties of the alloy are investigated. The results show that the as-milled alloys can electrochemical hydrogen absorption and desorption effectively at room temperature. The as-milled alloys can reach their maximal discharge capability without activation in the initial cycle. The maximum discharge capacities of the 5 h- and 30 h-milled alloys are 407.8 and 600.6 mAh g⁻¹, respectively. With the increase of Y content, the alloys exhibit a noticeable enhancement in cycle stability. With Y content increasing from 0 to 4, the retention rate of capacity increases from 36% to 63% at 100th cycles for the 5 h-milled alloy, and the retention rate of capacity increases from 55% to 79% for the 30 h-milled alloy. Furthermore, Y addition effectively enhances the electrochemical kinetic characteristics of the alloys.