Chloride Chemistry in Multivalent‐Metal Batteries: From Interphase to Bulk Phase

Abstract Rechargeable magnesium (Mg) batteries are promising candidates for next‐generation energy storage due to their high energy density, intrinsic safety, and earth‐abundant Mg resources. However, their practical application is limited by sluggish desolvation and slow diffusion of divalent Mg 2+ . Here, amine‐hydrochloride‐based Mg electrolytes are designed to form favorable interphases and chloride‐based channels. A ligand exchange strategy is proposed to simultaneously promote fast desolvation on interphases and rapid Mg 2+ diffusion within cathodes. Detailed analysis reveals that the formation of the chloride‐containing cathode–electrolyte interphases and the MgH 2 ‐containing anode–electrolyte interphases are found to facilitate the desolvation process of solvated Mg 2+ . Moreover, the chloride‐based channels significantly reduce the diffusion barriers of Mg 2+ in Mo 6 S 8 from 0.712 to 0.517 eV, demonstrating rapid Mg 2+ diffusion kinetics. Consequently, Mo 6 S 8 ‐based full cells achieve a capacity retention of over 80% after 100 cycles at 1 C. Furthermore, this strategy is compatible with chloride‐free electrolytes, the full‐cells consisted of activated Mo 6 S 8 cathode delivers a high specific capacity exceeding 90 mA h g −1 and 80.3% retention after 900 h of cycling. It is also applicable to organic cathodes and Mo 6 S 8 ‐based calcium‐metal full‐cells. Overall, this work presents a generalizable strategy for designing high‐energy‐density rechargeable multivalent‐metal battery systems.