A phenazine-derived organic anode for ultrafast and long-life aqueous potassium-ion full cells

Organic electrode materials hold great promise for advancing the development of aqueous potassium-ion batteries (AKIBs) due to their structural diversity and sustainability. However, they still encounter challenges such as low electroactive mass contribution and undesirable cycling performance resulting from intrinsic poor electronic conductivity and severe solubility issues. Herein, tricyano-substituted hexaazatrinnphthalene (3CN-HATN) was designed by enlarging the conjugated N-heteroaromatic structure and introducing cyano (C≡N) moieties as additional redox centers. Compared with the typical phenazine anode, the decrease in the lowest unoccupied molecular orbital energy level endows 3CN-HATN with a preferable reduction reaction. The narrower band gap ensures higher utilization of 3CN-HATN, while the elongation of π-conjugated structure effectively inhibits the dissolution in aqueous electrolytes. As a result, the 3CN-HATN anode achieves a remarkable capacity of 233.8 mA h g−1 at an ultrahigh rate of 80 C (1 C = 350 mA g−1), retaining an impressive 87.5% of the capacity at 2 C. When coupled with commercial Ni(OH)2 cathode, the as-assembled full cells exhibit outstanding cycling stability, maintaining a capacity retention of 81.5% after 10,000 cycles at 30 C. This work underscores the significance of molecular engineering in the development of redox-active organic materials for constructing high-performance AKIBs.