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.