Abstract:Compositions of MgNi-based amorphous-monocrystalline thin films produced by radio frequency (RF) sputtering with a varying composition target have been optimized. The composition Mg 52 Ni 39 Co 3 Mn 6 is identified to possess the highest initial discharge capacity of 640 mAh·g −1 with a 50 mA·g −1 discharge current density. Reproduction in bulk form of Mg 52 Ni 39 Co 3 Mn 6 alloy composition was prepared through a combination of melt spinning (MS) and mechanical alloying (MA), shows a sponge-like microstructure with >95% amorphous content, and is chosen as the metal hydride (MH) alloy for a sequence of electrolyte experiments with various hydroxides including LiOH, NaOH, KOH, RbOH, CsOH, and (C 2 H 5 ) 4 N(OH). The electrolyte conductivity is found to be closely related to cation size in the hydroxide compound used as 1 M additive to the 4 M KOH aqueous solution. The degradation performance of Mg 52 Ni 39 Co 3 Mn 6 alloy through cycling demonstrates a strong correlation with the redox potential of the cation in the alkali hydroxide compound used as 1 M additive to the 5 M KOH aqueous solution. NaOH, CsOH, and (C 2 H 5 ) 4 N(OH) additions are found to achieve a good balance between corrosion and conductivity performances.