High-capacity organic cathode boosted by coordination chemistry for energy-dense aqueous zinc-organic batteries.

N-type organic cathode materials containing carbonyl and imine groups have emerged as promising candidates for zinc-ion batteries due to their excellent charge storage capability, which arise from the synergic storage of both Zn and H. However, an increase in active sites also complicates the synthesis, introduces complex multi-electron reactions, and hinders comprehensive understanding of the charge storage mechanism and the evolution of molecular configuration during the electrochemical process. Herein, a 10-electron transfer organic cathode material, featuring imine and quinone groups that are spaced apart, was synthesized in one-step. Its highly conjugated molecular structure promotes electron delocalization, thereby enhancing the stability. The competitive storage mechanism of Zn and H was unveiled through multiple quasi spectroscopy techniques and calculations, revealing that Zn are initially coordinated to form O-Zn-N, followed by the co-insertion of H/Zn during the reduction of the carbonyl groups. Thanks to the Zn/H co-insertion and coordination stabilization, an ultra-high capacity of 445 mA h g at a current density of 0.2 A g and a retained capacity of 200 mA h g (>80% capacity retention) at 10 A g after 15 000 cycles can be achieved. The molecular structure-related charge storage mechanism revealed in this study can provide useful design considerations for realizing high-capacity, fast-charging and long-duration organic cathodes for various energy storage systems.