Regulating the Double‐Way Traffic of Cations and Anions in Ambipolar Polymer Cathodes for High‐Performing Aluminum Dual‐Ion Batteries

Abstract The strong Coulombic interactions between Al³⁺ and traditional inorganic crystalline cathodes present a significant obstacle in developing high‐performance rechargeable aluminum batteries (RABs) that hold promise for safe and sustainable stationary energy storage. While accommodating chloroaluminate ions (AlCl₄⁻, AlCl²⁺, etc.) in redox‐active organic compounds offers a promising solution for RABs, the issues of dissolution and low ionic/electronic conductivities plague the development of organic cathodes. Herein, electron donors are synthetically connected with acceptors to create crosslinked, bipolar‐conjugated polymer cathodes. These cathodes exhibit overlapped redox potential ranges for both donors and acceptors in highly concentrated AlCl₃‐based ionic liquid electrolytes. This approach strategically enables on‐site doping of the polymer backbones during redox reactions involving both donor and acceptor units, thereby enhancing the electron/ion transfer kinetics within the resultant polymer cathodes. Based on the optimal donor/acceptor combination, the bipolar polymer cathodes can deliver a high specific capacity of 205 mAh g⁻¹ by leveraging the co‐storage of AlCl₄⁻ and AlCl²⁺. The electrodes exhibit excellent rate performance, a stable cycle life of 60 000 cycles, and function efficiently at high mass loadings, i.e., 100 mg cm⁻², and at low temperatures, i.e., −30 °C. The findings exemplify the exploration of high‐performing conjugated polymer cathodes for RABs through rational structural design.