The architecture of petal-shaped CoS/CuS nanosphere materials for high-performance magnesium-ion battery cathode materials

Rechargeable magnesium batteries (RMBs) possess the merits of greater theoretical capacity, cheaper magnesium metal and not easily producing branched crystals, and greater safety. Therefore, the current researches mainly concentrate on the exploration of high-performance RMBs in the initial stage, but still face many gigantic challenges. Herein, petal-shaped nanorods CoS/CuS materials are successfully synthesized as RMBs cathode materials through a two-step metal sulfide template-free solvent-thermal synthesis method, which can effectively improve the reaction kinetics due to the petal-like nano-structure and provide rich electrochemically active sites to decrease the transport barrier of Mg²⁺, thus contributing to the enhancement of the reaction kinetics of magnesium storage in RMBs. The electrochemical performance test illustrates that CoS/CuS composite nanomaterials can considerably improve the charging and discharging specific capacity of the batteries as well as the voltage of the batteries due to the existing synergistic effect between them. The specific capacity of CoS/CuS cathode still can still be maintained as high as 62.8 mAh g⁻¹ after 300 cycles at 200 mA g⁻¹. And the specific capacity of this electrode material changes from 180.6 mAh g⁻¹ to 30 mAh g⁻¹ at the current densities from 100 mA g⁻¹ to 1000 mA g⁻¹, and when the current density is restored to 100 mA g⁻¹, the specific capacity gradually recovered to 178.6 mAh g⁻¹, which showed better rate performance and ultra-high cycling stability. This work highlights how the introduction of CuS into CoS nanostructures can benefit the reversibility and cyclicity of the magnesium storage reaction and offers an original and practical route for the modification of RMBs electrode materials with good electrochemical properties.