Bimetallic sulfide CoNi2S4 hollow nanospheres as a high-performance cathode material for Mg-ion batteries

Mg-ion batteries (MIBs), as a next-generation battery, are drawing considerable attention due to abundant and well-distributed magnesium sources available. The construction of structurally ideal bimetallic sulfides can effectively alleviate the poor cycling stability of MIBs. Herein, we report for the first time, the synthesis of bimetallic sulfide CoNi2S4 hollow nanospheres (CoNi2S4 HSs) via a one-step solvothermal method and their application as a cathode material for MIBs. Compared with common unary transition metal sulfides, CoNi2S4 HSs have more electrochemically active sites and higher electronic conductivity. Meanwhile, the distinct morphology of CoNi2S4 HSs exhibits higher surface area, smaller charge-transfer resistance, and higher magnesium diffusion coefficient. Further, CoNi2S4 HSs deliver a considerable reversible capacity of 290.1 mAh g-1 at 50 mA g-1, and a high capacity of 97.8 mAh g-1 can be achieved at 1000 mA g-1, demonstrating excellent rate performance. The structural integrity, high specific capacity, good rate capability and cycling stability of CoNi2S4 HSs render it a promising cathode material for advanced MIBs.