In-situ tuning the NH4+ extraction in (NH4)2V4O9 nanosheets towards high performance aqueous zinc ion batteries

Aqueous rechargeable Zn ion batteries (ARZIBs) are investigated as a capable alternative battery technology for a large-scale energy storage system. Exploring and understanding the Zn ions storage mechanism is a significant method to adjust the Zn ion storage behavior of electrode materials. Herein, we demonstrate a phase transition of the (NH4)2V4O9 cathode material at the voltage of above 1.3 V. After the initial Zn2+ insertion/extraction process, bilayer V2O5·nH2O is observed and the interlayer spacing is enlarged, boosting the electrochemical performance of the electrode. The cathode materials show an enhanced capacity of 508 mAh g−1 at 100 mA g−1 and stable cycling performance (259 mAh g−1 after 1000 cycles at 10 A g−1, with 98.2% capacity retention). Moreover, the (NH4)2V4O9 nanosheets exhibited a remarkable specific energy density of 373.2 Wh kg−1 at a power density of 74.6 W kg−1, suggesting its potential application for the high-performance ARZIBs.