Imine‐Based Conjugated Polymers as High‐Performance Organic Cathodes for Rechargeable Magnesium Batteries: Insights from Electronic Structure Design

Rechargeable Mg batteries (RMBs) face challenges of cathode materials due to the high charge density of Mg²⁺ cations. Organic conjugated polymers, with tunable structures and flexible frameworks, offer promising selections for Mg‐storage cathodes. This study compares three nitrogen‐based conjugated polymers, polypyrrole (PPy, amine‐rich), polyaniline (PANI, mixed amine/imine), and poly(o‐phenylenediamine) (PoPD, imine‐rich), to elucidate the advantageous nitrogen‐based Mg‐storage active sites and corresponding materials. Theoretical calculations reveal that PANI and PoPD exhibit lower LUMO energy levels and their imine (N) groups show localized negative electrostatic potential (ESP), favoring Mg²⁺ association via n‐type redox reactions, unlike p‐type amine (NH) groups in PPy. PoPD, with dual imine groups and extended π‐conjugation, demonstrates superior Mg‐storage performance: a high initial capacity of 208 mAh g⁻¹ (0.1 A g⁻¹), exceptional rate capability (72 mAh g⁻¹ at 5 A g⁻¹), and long‐term stability (81.75% retention after 1200 cycles). Mechanism analyses confirm Mg²⁺/MgCl⁺ costorage via N coordination, facilitated by charge delocalization and flexible polymer chains. The work establishes imine‐rich conjugated polymers as high‐performance organic cathodes, highlighting structure–property relationships for advancing RMBs.