High-Energy-Density Rechargeable Mg Battery Enabled by a Displacement Reaction.

Because of its high theoretical volumetric capacity and dendrite-free stripping/plating of Mg, rechargeable magnesium batteries (RMBs) hold great promise for high energy density in consumer electronics. However, the lack of high-energy-density cathodes severely constrains their practical applications. Herein, for the first time, we report that a CuS cathode can fully reversibly work through a displacement reaction in CuS/Mg pouch cells at room temperature and provide a high capacity of ∼400 mA h/g in a MACC electrolyte, corresponding to the gravimetric and volumetric energy density of 608 W h/kg and1042 W h/L, respectively. Even after 80 cycles, CuS/Mg pouch cells can maintain a high capacity of 335 mA h/g. Detailed mechanistic studies reveal that CuS undergoes a displacement reaction route rather than a typical conversion mechanism. This work will provide a guide for more discovery of high-performance cathode candidates for RMBs.