An Energy‐Dense Aqueous All‐Polymer Battery Enabled by Unique Cross‐Conjugated Dual‐Active‐Center Design in Organic Redox Chemistry

ABSTRACT The emergence of aqueous all‐organic batteries (AAOBs) has attracted surging attention, yet their progress is hindered by the limited energy density due to the scarcity of large‐capacity and high‐potential positive electrode materials. Herein, we develop a cross‐conjugated dual‐active‐center design strategy to modulate the electron distribution and frontier orbitals of 2D redox polymers (2DRPs) for attaining energy‐dense AAOBs. Theoretical studies reveal that simply embedding more pyrazine units in the polymer skeleton can elevate capacity and potential but at the expense of reduced activity, while introducing quinone units can form a cross‐conjugated donor–acceptor (D–A) structure that improves all above metrics. Accordingly, we synthesized 2DRP with alternating pyrazine‐quinone units (PQ) and its analogues with pure pyrazine units (P1 and P3). All predicted advantages over its analogues are realized by PQ in acidic electrolytes, presenting fast Grotthuss‐type proton transport, a larger capacity (251 mAh g −1 ) and a higher average reduction potential (0.46 V vs. SHE), surpassing most reported polymer electrodes, along with an ultralong low‐temperature lifespan (83.8%@12000 cycles, −20°C). Finally, pairing PQ with a 2DRP negative electrode (PD) in hybrid electrolytes affords a PD//PQ all‐polymer battery with an average output voltage of 1.31 V and a maximum specific energy of 111.7 Wh kg −1 , exceeding most AAOBs.