Dual-Redox Conjugated Bipolar Covalent Organic Framework Enables High-Voltage Symmetric Proton Batteries

Symmetric all-organic proton batteries (SAOPBs) attract increasing attention for large-scale energy storage due to their safe and superior rate performance, which is severely limited by the lack of suitable bipolar electrode materials that integrate reversible dual-redox activity and high operating voltage within a single structure. Herein, we report a bipolar covalent organic framework (TAPT-HAT-COF) as both cathode and anode in symmetric proton battery. In this COF, the electron-deficient pyrazine/carbonyl units and electron-rich phenylimine groups establish two independent and reversible redox couples, achieving a high operating voltage of up to 0.83 V. Combined with in situ FTIR spectroscopy and theoretical calculations, TAPT-HAT-COF shows bipolar charge storage mechanism with the C═N and C═O groups served as reversible redox centers. Benefiting from the fully conjugated structure and abundant active sites, the assembled SAOPB exhibits high specific capacity of 108.5 mAh g^-1 under 5 A g^-1 with stable cycling over 3000 cycles. Moreover, when applied in a practical pouch cell, which delivers a specific capacity of 145.8 mAh g^-1 at 0.5 A g^-1, confirming the material's potential for practical applications. The work can provide viable design strategy and model of bipolar COF materials for symmetric energy storage systems.