Dissolution-Equilibrium-Driven Continuous Regeneration of a Dynamic Mg ₃ Bi ₂ /Bi Magnesiophilic Interphase for Efficient Mg Plating/Stripping

Magnesium metal batteries (MMBs) are promising candidates for sustainable energy storage, yet their development is severely hindered by the formation of passivation layers on the Mg anode. Conventional artificial interphase layers often suffer from progressive defunctionalization during prolonged cycling. Herein, we propose a chemical-dissolution-equilibrium-driven strategy that continuously supplies Bi³⁺ species to spontaneously construct an in situ Mg₃Bi₂/Bi protective layer on the Mg electrode surface. This self-sustaining interphase not only enables continuous interfacial repair but also provides abundant magnesiophilic nucleation sites, thereby facilitating highly efficient Mg plating/stripping. As a result, the Mg||Mg symmetric cell exhibits an ultralong cycling life exceeding 1500 h with an ultralow overpotential of 30 mV at 0.5 mA cm^-2 and 0.25 mAh cm^-2. Moreover, the preferential reduction of Bi³⁺ on various current collectors creates favorable nucleation sites for Mg deposition, leading to high Coulombic efficiencies in Mg||Cu, Mg||SS, and Mg||Mo asymmetric cells. Remarkably, the Mg||SS cell achieves a cycling life exceeding 1400 h with an average Coulombic efficiency of ∼99.84% and a low polarization voltage of 90 mV. This work underscores the critical role of a sustained dynamic interphase and establishes a new paradigm for designing nonaqueous, all-inorganic electrolytes for high-performance MMBs.