Electrical cycling characteristics of high-entropy energy storage Mg-Y-Ni-Cu alloys with different degrees of amorphization for Ni-MH batteries

Magnesium-rich metal hydride alloys include MgNi, Mg2Ni, REMg12, La2Mg17, etc. Due to their excellent discharge ability, they are promising choices for electrode materials in Ni-MH batteries. However, the high hydrogen adsorption and desorption temperature have seriously hindered crystalline Mg-based alloys from more extensive application. In this study, the element Y was employed as a partial replacement for Mg. To optimize the electroanalytical properties of Mg50-xYxNi45Cu5 (x = 0, 1, 2, 3, 4) + 50 wt% Ni alloys, various mechanical milling techniques with varying durations were employed to synthesize them with a unique small-grained and non-crystalline composition. The electrolytic tests demonstrate that the mechanically alloyed alloys can efficiently Sequester and liberate H at ambient temperature. Furthermore, these alloys exhibit a significant initial discharge capacity without requiring any activation process. The expansion of the milling period prominently boosts the cycling reliability. Specifically, the (x = 2) alloy exhibits a notable increase in discharge efficiency elevated from 407.8 to 546.9 mAh/g, and the capacity retention rate at the 100th cycle (S100 = C100/Cmax) improves from 48 % to 67 % as the milling period is increased from 5 h to 20 h. Moreover, all electrochemical tests demonstrate a significant enhancement within the realm of electrochemistry kinetic behaviors of the alloys with the expansion of the milling period.