The exploitation of cathode materials with high capacity as well as high operating voltage is extremely important for the development of aqueous zinc-ion batteries (ZIBs). Yet, the classical high-capacity materials (e.g., vanadium-based materials) provide a low discharge voltage, while organic cathodes with high operating voltage generally suffer from a low capacity. In this work, organic (ethylenediamine)-inorganic (vanadium oxide) hybrid cathodes, that is, EDA-VO, with a dual energy-storage mechanism, are designed for ultrahigh-rate and ultralong-life ZIBs. The embedded ethylenediamine (EDA) can not only increase the layer spacing of the vanadium oxide, with improved mobility of Zn ions in the V-O layered structure, but also act as a bidentate chelating ligand participating in the storage of Zn ions. This hybrid provides a high specific capacity (382.6 mA h g-1 at 0.5 A g-1 ), elevated voltage (0.82 V) and excellent long-term cycle stability (over 10 000 cycles at 5 A g-1 ). Assistant density functional theory (DFT) calculations indicate the cathode has remarkable electronic conductivity, with an ultralow diffusion barrier of 0.78 eV for an optimal Zn-ion diffusion path in the EDA-VO. This interesting idea of building organic-inorganic hybrid cathode materials with a dual energy-storage mechanism opens a new research direction toward high-energy secondary batteries.
Keywords: cathode materials; energy density; organic-inorganic hybrid materials; vanadium-based materials; zinc-ion batteries.
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