Effect of particle size on the performance of rare earth–Mg–Ni-based hydrogen storage alloy electrode

Rare earth–Mg–Ni-based hydrogen storage alloy has been synthesized by vacuum induction levitation melting and sieved into five particle size fractions from 120 mesh to below 800 mesh. The effect of particle size on the electrochemical behaviors has been investigated. It was found that the alloy electrode with the particle size of 220–325 mesh exhibited better cyclic stability and high rate dischargeability than the larger or smaller alloy powders. The pulverization and the surface oxidation/corrosion have been studied by SEM, AES, and XPS methods. The results showed that the pulverization rate became faster with the increase of the particle size. The formation of an oxide layer with proper thickness during cycling can effectively improve the cyclic stability for the 220–325 mesh alloy electrode. The capacity degradation and the electrochemical kinetics of the alloy electrodes of different particle sizes are determined by the pulverization rate and the oxidation of active components on the alloy surface during cycling in the alkaline electrolyte.