Facile Preparation of CuCo 2 S 4 /Cu 7.2 S 4 Nanocomposites as High‐Performance Cathode Materials for Rechargeable Magnesium Batteries **

Rechargeable magnesium batteries (RMBs) have been considered a promising energy‐storage device due to their high energy density and high safety, but they still suffer from a lack of high‐rate performance and cycle performance of the cathode. Nanosized CuCo 2 S 4 /Cu 7.2 S 4 composites have been synthesized for the first time by a facile solvothermal method. Herein, the magnesium ion storage behavior when applied in the cathode for RMBs is discussed. Electrochemical results demonstrated that the CuCo 2 S 4 /Cu 7.2 S 4 composites exhibit a high initial discharge capacity of 256 mAh g −1 at 10 mA g −1 and 123 mAh g −1 at 300 mA g −1 at room temperature and an outstanding long‐term cyclic stability over 300 cycles at 300 mA g −1 . Furthermore, the electrochemical storage mechanism demonstrated that the storage process of magnesium ion in the CuCo 2 S 4 /Cu 7.2 S 4 cathode is mainly driven by strong pseudocapacitive effects.