Electropolymerized Bipolar Poly(2,3‐diaminophenazine) Cathode for High‐Performance Aqueous Al‐Ion Batteries with An Extended Temperature Range of −20 to 45 °C

Abstract Achieving reversible insertion/extraction in most cathodes for aqueous aluminum ion batteries (AAIBs) is a significant challenge due to the high charge density of Al³⁺ and strong electrostatic interactions. Organic materials facilitate the hosting of multivalent carriers and rapid ions diffusion through the rearrangement of chemical bonds. Here, a bipolar conjugated poly(2,3‐diaminophenazine) (PDAP) on carbon substrates prepared via a straightforward electropolymerization method is introduced as cathode for AAIBs. The integration of n‐type and p‐type active units endow PDAP with an increased number of sites for ions interaction. The long‐range conjugated skeleton enhances electron delocalization and collaborates with carbon to ensure high conductivity. Moreover, the strong intermolecular interactions including π–π interaction and hydrogen bonding significantly enhance its stability. Consequently, the Al//PDAP battery exhibits a large capacity of 338 mAh g⁻¹ with long lifespan and high‐rate capability. It consistently demonstrates exceptional electrochemical performances even under extreme conditions with capacities of 155 and 348 mAh g⁻¹ at −20 and 45 °C, respectively. In/ex situ spectroscopy comprehensively elucidates its cation/anion (Al³⁺/H₃O⁺ and ClO₄⁻) storage with 3‐electron transfer in dual electroactive centers (C═N and –NH–). This study presents a promising strategy for constructing high‐performance organic cathode for AAIBs over a wide temperature range.