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Anode materials with high capacity and suitable redox potential are crucial for improving the energy density of aqueous sodium-ion batteries (ASIBs). And organic anode materials play a promising role due to their tunable electrochemical performance. However, the insufficient electroactive sites lead to a low capacity, hindering the elevation of energy density. Thus, it is essential to design organic molecules with multiple redox-active sites. Herein, we propose a strategy to activate redox sites by regulating the spatial distribution of delocalized electrons within the conjugation system, and the quinone rings are successfully activated as new reversible Na-ion storage sites via enhancing the electron density. The obtained 2,5-dihydroxy-1,4-benzoquinonatocobalt (Co-DHBQ) with electroactive quinone rings exhibits a superior capacity of 183 mA h g –1 accompanied by a multiple-electron transfer. Benefiting from the high capacity, the Co-DHBQ||Na 2 MnFe(CN) 6 ·2H 2 O (MnHCF) full cell outputs a ultrahigh energy density of 110 W h kg –1 (based on the total active material mass of the anode and cathode) with a lifespan of 3000 cycles. This work proposes a strategy to activate new redox sites, providing a new impetus for designing high-performance organic electrode materials and developing high energy density ASIBs.
Gou et al. (Thu,) studied this question.