Synergistic Dual Electrolyte Additives for Long‐Cycle Rechargeable Magnesium Batteries

ABSTRACT The interfacial kinetics of magnesium ions at the electrolyte‐magnesium anode interface remains a critical challenge for rechargeable magnesium batteries (RMBs). Developing advanced electrolyte additives represents one of the most promising strategies to mitigate this issue. This work systematically investigates the interfacial chemistry of a Mg(OTf) 2 /G2 electrolyte enhanced by InBr 3 and Tris(hexafluoroisopropyl) Borate (BHFP) as dual additives at the Mg metal anode for RMBs. The in situ‐formed organic–inorganic hybrid interphase derived from the dual‐additive electrolyte improves the magnesiophilicity and lowers the Mg 2+ diffusion energy barrier. Furthermore, the chain reaction between the additives and the anode yields weakly coordinating B(HFIP) 4 − anions and highly migrating Mg(Br)(G2) 2 + cations. As a result, the dual‐additive electrolyte demonstrated superior electrochemical performance, characterized by high rate performance and cycling stability of 1000 h at 0.5 mA cm −2 . Furthermore, the Mg//MIB//Mo 6 S 8 full cell exhibited a capacity retention of 83.7% even after 1700 cycles at a high current density of 500 mA g −1 . Crucially, the study proved that the reaction of the metal halide and BHFP with the metal anode provides a vital pathway for the optimization of both the electrolyte and the interface in multivalent metal batteries.