High‐Energy Interlayer‐Expanded Copper Sulfide Cathode Material in Non‐Corrosive Electrolyte for Rechargeable Magnesium Batteries

Abstract Rechargeable magnesium batteries (RMB) have been regarded as an alternative to lithium‐based batteries because of their abundant elemental resource, high theoretical volumetric capacity, and multi‐electron redox reaction without the dendrite formation of magnesium metal anode. However, their development is impeded by their poor electrode/electrolyte compatibility and the strong Coulombic effect of the multivalent Mg 2+ ions in cathode materials. Herein, copper sulfide material is developed as a high‐energy cathode for RMBs with a non‐corrosive Mg‐ion electrolyte. Given the benefit of its optimized interlayer structure, good compatibility with the electrolyte, and enhanced surface area, the as‐prepared copper sulfide cathode exhibits unprecedented electrochemical Mg‐ion storage properties, with the highest specific capacity of 477 mAh g −1 and gravimetric energy density of 415 Wh kg −1 at 50 mA g −1 , among the reported cathode materials of metal oxides, metal chalcogenides, and polyanion‐type compounds for RMBs. Notably, an impressive long‐term cycling performance with a stable capacity of 111 mAh g −1 at 1 C (560 mA g −1 ) is achieved over 1000 cycles. The results of the present study offer an avenue for designing high‐performance cathode materials for RMBs and other multivalent batteries.