Molecular electronic structure regulation toward high-voltage organic cathodes via redox-site reconstruction for aqueous zinc-ion batteries.

Abstract

N-type organic cathode materials with abundant redox-active sites and tunable molecular frameworks are promising candidates for aqueous zinc-ion batteries (AZIBs), yet their practical application is hindered by poor conductivity, active-material dissolution, and limited redox potentials. Herein, an active-site reconstruction strategy is developed to design benzo[f]quinoxalino [2,3-b] quinoxaline (BQQ) as a high-voltage small-molecule cathode for AZIBs. Incorporating electron-deficient conjugated units into the aromatic framework regulates molecular electronic structures, enhances π-electron delocalization, and increases accessible redox-active sites. These molecular-level modifications optimize interfacial charge-transfer kinetics, stabilize redox centers, and suppress dissolution. Consequently, the BQQ cathode achieves an average discharge voltage of 0.93 V (vs. Zn2+/Zn), nearly doubling that of the reference molecule (0.52 V), together with a high energy density of 190.6 Wh kg-1 and excellent cycling stability (86.6% retention after 10,000 cycles at 10 A g-1). Combined experimental analyses and theoretical calculations reveal a reversible Zn2+/H+ co-storage mechanism dominated by CN-centered redox reactions. This work establishes a molecular-level correlation between electronic structure regulation, interfacial reaction chemistry, and electrochemical performance, offering a rational design strategy for high-energy and durable organic cathodes in aqueous energy-storage systems.

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