Unveiling the potential of two morphological Ni0.85Se nanostructures as cathode materials for rechargeable magnesium batteries

In this work, two different types of Ni_0.85Se nanostructures (A-Ni_0.85Se and B-Ni_0.85Se) were prepared by a simple solvothermal strategy using hydrazine hydrate and sodium borohydride as reductants, respectively, and then applied as the cathode materials for rechargeable magnesium batteries (RMBs). Compared to the B-Ni_0.85Se nanocrystals, the A-Ni_0.85Se cathode with the nanosheet structure shows higher initial discharge specific capacity of 338.0 mAh g⁻¹ at 50 mA g⁻¹, higher reversible specific capacity of 124.1 mAh g⁻¹ after 100 cycles at 50 mA g⁻¹, better rate capacity of 80.6 mAh g⁻¹ at 250 mA g⁻¹, and better cycling performance over 500 cycles. Such a performance enhancement is ascribed to the unique sheet-like nanostructure of A-Ni_0.85Se, providing more convenient diffusion pathways for Mg²⁺ ions. Furthermore, the Mg-storage mechanism was also proposed. This study unveils the potential of Ni_0.85Se nanostructures with different morphologies as the cathode materials of RMBs.