Beyond Electrostatics: Anion‐π ⁺ Orbital Hybridization Underpins High‐Performance Chloride Storage in Poly(arylamine) Organic Cathodes

ABSTRACT 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 ZnCl ₂ ), 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.