Covalent Bridges Enabling Layered C 60 as an Exceptionally Stable Anode in Lithium-Ion Batteries

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Fullerene (C 60 ) exhibits rich redox chemistry but suffers from severe dissolution of reduced fulleride species in carbonate electrolytes, leading to poor reversibility and rapid capacity fading. Here, we demonstrate covalent bridging as a general strategy to stabilize the fullerene framework using Mg 4 C 60 . Mg atoms promote intercage covalent connections through C–C single bonds and [2 + 2] cycloaddition bonds, transforming a van der Waals molecular solid into a layered polymeric framework. Comprehensive characterizations reveal that such bridging effectively suppresses dissolution, preserves structural integrity, and enables a reversible Li + storage process. Interestingly, unlike pristine C 60 that undergoes multiple phase transitions, Mg 4 C 60 exhibits slope-type electrochemical profiles reminiscent of soft carbon yet originates from an ordered two-dimensional framework. Comprehensive mechanistic studies reveal reversible fullerene cage distortions accompanied by the dynamic reconstruction of sp 2 electronic states, while the covalently bridged scaffold remains intact. This work establishes covalently bridged fullerenes as a new class of durable carbonaceous anodes and provides a general pathway for designing ordered carbon frameworks with enhanced stability for next-generation rechargeable batteries.

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