Polymer-Intercalated Vanadium Oxide as A Near-Zero-Strain, Dual Mechanism Cathode for Rechargeable Magnesium-Metal Batteries

Abstract

The development of high-performance cathodes for rechargeable magnesium-metal batteries (RMBs) is hindered by sluggish Mg2+ solid-state diffusion and severe structural instability during cycling. While organic-inorganic hybrid materials offer a promising avenue as they can potentially decouple ion transport from structural constraints, the deep understanding of how polymeric components modulate the intrinsic structure and storage mechanisms of inorganic hosts is still limited. Here, we demonstrate the strategic design of a polymer-intercalated V2O5 (P-VOx) hybrid. The intercalated polymer interacts with VOx layers through robust V-N coordination bonds, acting as structural pillars that not only substantially expand the interlayer spacing, effectively reducing the migration barrier of Mg2+ ions, but also modulate the electronic structure of the crystal, enhancing bulk electronic conductivity. More importantly, we unveil a novel dual storage mechanism for magnesium, involving concurrent Mg2+ intercalation within the expanded VOx interlayers and the reversible binding of Mg2+ with deprotonated sites of the intercalated polymer. Furthermore, operando X-ray diffraction reveals a near-zero-strain characteristic upon Mg2+ insertion/extraction in P-VOx. Consequently, the P-VOx cathode exhibits outstanding rate performance and long-term cyclability in RMBs. This work provides atomic-scale insights into the role of polymer intercalation in stabilizing structure and enabling novel multimechanistic energy storage.