Pre-Activated Cascade Redox Enables High-Voltage Multi-Electron Anion Storage in Graphite

Graphite cathodes enable high-voltage operation in dual-ion batteries but are intrinsically constrained by a single-electron chemistry and sluggish anion intercalation. Here, an iron-chloride-intercalated graphite stabilized by oxygen functional groups is shown to establish a pre-activated, cascade multi-electron redox pathway. Sequential oxidation of iron and chlorine at intermediate potentials simultaneously expands interlayer spacing and redistributes electronic density, creating a favorable host for high-voltage PF₆⁻ intercalation. This synergistic activation enables an average transfer of 2.61 electrons per redox event, breaking the intrinsic one-electron limit of graphite. As a result, the cathode delivers up to 5 V (vs. Na/Na⁺) with a stable capacity of 52 mAh g⁻¹ at 3 A g⁻¹, significantly outperforming conventional graphite cathodes (15 mAh g⁻¹). By integrating multi-electron redox chemistry with anion storage, this approach unlocks a new direction for high-power electrochemical energy storage.