High-rate aqueous zinc-organic battery achieved by lowering HOMO/LUMO of organic cathode

Despite the development of quinone as the potential cathode material for Zn-organic batteries, there are undesired behaviors for the rate and cycling performances. To achieve high-performance Zn-organic batteries, intentional organic molecular design and a deep understanding of the mechanism of Zn-organic batteries are highly essential. Herein, strong electron-withdrawing and conjugating groups (-CN) were introduced to lower the highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energy on an aromatic Schiff base (Hexaazatrinnphthalene, denoted as HATN). With such a decoration, HATN-3CN exhibits an outstanding rate capacity with retention of 60.7% of the initial capacity at 400 times the initial current density and long cycle life of over 5800 cycles. Besides, the charge storage mechanism was systematically investigated through experiments and density functional theory calculation, showing that CN moieties are the active site for the storage of H+/Zn2+. This strategy and insight provided by molecular orbital theory and kinetics-controlled process offer a feasible pathway of molecular-level design for constructing high-performance Zn-organic batteries.