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 CuCo2S4/Cu7.2S4 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 CuCo2S4/Cu7.2S4 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 CuCo2S4/Cu7.2S4 cathode is mainly driven by strong pseudocapacitive effects.