Benzoquinone-Pyrrole Polymers as Cost-Effective Cathodes toward Practical Organic Batteries

Organic cathode materials (OCMs) for rechargeable Li and Na batteries show great advantages in resource sustainability and huge potential in electrochemical performance but suffer from dissolution problems and costly synthesis. Herein, for the first time, we investigated the copolymer of benzoquinone (BQ) and pyrrole (Py), namely, poly(benzoquinone-pyrrole) (PBQPy), as an OCM for Li batteries. The low-cost raw materials and solvent-free synthesis provide PBQPy much brighter prospects in large-scale production compared to other carbonyl-based polymer cathode materials. Nevertheless, PBQPy showed one of the best electrochemical performances among all OCMs, including excellent energy density (2.32 V × 255 mAh g^-1 = 592 Wh kg^-1), rate capability (79%@2000 mA g^-1), and cycling stability (81%@1000th cycle). By introducing poly(benzoquinone-methyl pyrrole) for comparison, as well as employing density functional theory calculations and various characterizations for in-depth understanding, the synthesis mechanism, polymer structure, electrochemical behavior, and redox mechanism were clearly clarified. It is believed that this work will encourage more efforts to develop cost-effective OCMs toward practical organic batteries.