Beyond Electrostatics: Anion-π⁺ Orbital Hybridization Underpins High-Performance Chloride Storage in Poly(arylamine)...

The interactions between ionic charge carriers and host framework critically govern electrochemical reactions and ion-storing performance, serving as a pivotal design consideration for energy storage devices. However, the fundamental understanding of the covalent-ionic interactions between anion and oxidized π⁺-framework remains limited thus far. Here we reveal the covalent-ionic nature of anion-π⁺ interactions between poly(arylamine)s (PAAs) and Cl^- anions. Cl^--π⁺ complexes bearing rigid polymeric aryl-substituted dihydrophenazine (PDPZ) exhibit both electrostatic interaction and distinct Cl^-→π⁺ charge-transfer orbital contribution, confirming the underlying hybrid covalent-ionic nature of Cl^--π⁺ interaction. The synergistic effect of Cl^--π⁺ interaction and high electron delocalization capability of PDPZ^x+ framework enables reversible Cl^- intercalation/deintercalation during multi-electron redox, achieving a high anion storage capacity of 236 mAh g^-1 and remarkable energy densities of 175 Wh kg^-1 (Zn||PDPZ cell, in 30 m ZnCl₂), alongside long calendar life as cathodes for Cl^--based dual-ion batteries (Cl-DIBs). Spectroscopic evidence reveals dynamic evolution of vibrational modes and electronic structures from PDPZ to PDPZ^x+·xCl^- complexes, demonstrating the entire π⁺-framework participation and anion-to-π⁺ charge transfer during chloride storage. Our mechanistic insights into anion-π⁺ interactions in Cl-DIBs provide theoretical guidance for designing advanced anion-storage organic cathodes and advance anion coordination chemistry.