CuCo₂S₄/CuS@MWCNTs Composite as a Cathode for Rechargeable Magnesium-Ion Batteries with Long Cycle Life

Rechargeable magnesium batteries (RMBs) have been considered as promising candidates for large-scale energy storage devices due to their high safety and high energy density. However, searching for cathode materials with excellent cycling stability remains a major challenge hindering their development. In this work, we investigated, for the first time, the effects of different solvent systems on the composition and electrochemical performance of a material. The results showed that the final product is a CuCo₂S₄/CuS composite when deionized water is used as the solvent, in which CuCo₂S₄ appears as sheets and CuS has a bulk morphology. CuCo₂S₄/CuS had the highest first discharge specific capacity, while its cycling performance was poor. Therefore, we successfully synthesized a CuCo₂S₄/CuS@MWCNTs composite as a cathode material for RMBs with the addition of an appropriate amount of MWCNTs to enhance the cycling stability. The electrochemical results showed that CuCo₂S₄/CuS@MWCNTs (15 wt %) exhibits a high initial discharge specific capacity of 214.79 mAh g^–1 at 10 mA g^–1 and 118.29 mAh g^–1 at 300 mA g^–1, excellent rate performance, and long cycle stability over 1000 cycles at 300 mA g^–1. These results demonstrated that the CuCo₂S₄/CuS@MWCNTs composite is a promising cathode for RMBs with long cycle life.