<p>Solid magnesium-based alloys are referred to as “breathing” metal hydrogen storage alloys due to their high hydrogen storage capacity, ease of activation, and robust discharge ability. This study focuses on the preparation of the Mg-Ni-Nd hydrogen storage alloy using a constant potential electrodeposition method within a low-temperature molten salt system composed of urea, acetamide, sodium bromide, and potassium bromide. The research aims to determine the optimal Mg-Ni ratio and the concentration of Nd³⁺. Electrochemical methods were employed to evaluate the charging and discharging performance of both Mg-Ni and Mg-Ni-Nd hydrogen storage alloys, as well as the electrochemical behaviors of Mg²⁺ and Ni²⁺ in the low-temperature molten salt system. The findings indicate that the reduction processes of Mg²⁺ and Ni²⁺ in this system are irreversible and are controlled by ion diffusion. The maximum discharge capacity of the Mg-Ni hydrogen storage alloy, with a Mg-Ni ratio of 2:1, is 755.5 mAh/g and the capacity retention rate is 90.33%. Conversely, for the Mg-Ni-Nd hydrogen storage alloy with an Nd³⁺ concentration of 0.02&#xa0;mol/L, the maximum discharge capacity reaches 884.5 mAh/g with a capacity retention rate of 95.62%. The incorporation of the Nd element significantly enhances the electrochemical energy storage properties of the Mg-Ni hydrogen storage alloy.</p>