Oxygen defect enriched (NH4)2V10O25·8H2O nanosheets for superior aqueous zinc‐ion batteries

Aqueous zinc-ion batteries (ZIBs) are recognized as a highly competitive electrochemical energy storage systems due to the high safety and low cost, however, rational design of advanced cathodes with stable internal structures and fast Zn2+ diffusion channel remains challenging. Herein, we reported an advanced cathode of oxygen defect enriched (NH4)2V10O25·8H2O (NVOD) nanosheets with expanded tunnel structure, exceptional conductivity and superior structural stability for aqueous ZIBs, showing fast Zn2+ diffusion and excellent performance. The resulted ZIBs afford a remarkably high capacity (408 mAh g−1 at 0.1 A g−1), ultrahigh stability (94.1% retention over 4000 cycles), and exceptional energy density (287 Wh kg−1), outperforming many cathodes of ZIBs. Furthermore, it is revealed that from theoretical and experimental studies the oxygen defects intrinsically contribute to the narrow bandgap and high electrical conductivity of NVOD to greatly boost the performance. The reversible storage of Zn2+ in NVOD is further illustrated via different in-situ characterization techniques. Moreover, the flexible soft-packaged batteries also demonstrate superior capacity retention of 91% after 200 cycles. Therefore, the exploration in NVOD materials with rich oxygen defects will supply an attractive approach for designing high-performance and flexible ZIBs.