Healing Broken S─S Bonds via d-p Orbital Coupling for Durable Magnesium Batteries

Rechargeable Mg batteries hold great promise for large-scale energy storage due to the abundance, safety, and high theoretical capacity of the metallic Mg anode. However, their development is hampered by the irreversible structural evolution of chalcogenide cathodes, which originates from the inability to reform broken S─S bonds during charging. Here, we identify this irreversibility mechanism and propose an innovative d-p orbital coupling strategy to address it. Using CuS as a model system, we demonstrate that introducing high-covalency Mo─S bonds via Mo 4d-S 3p coupling enables precise regulation of the electronic structure, thereby facilitating the reversible breaking and reconstruction of S─S bonds. This orbital-level optimization yields a breakthrough in Mg-storage performance, including a high reversible capacity (356 mAh g^-1 at 100 mA g^-1), exceptional rate capability (166 mAh g^-1 at 1 A g^-1), and outstanding cycling stability (84.6% capacity retention after 3000 cycles). The material also exhibits remarkable performance under high loadings, across a wide temperature range (-20 to 60°C), and in durable pouch cells. Crucially, this d-p orbital coupling strategy is universally applicable to various transition metals, providing a general design paradigm for high-energy-density rechargeable Mg battery cathodes.