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)(2)V4O9 cathode material at the voltage of above 1.3 V. After the initial Zn2+ insertion/extraction process, bilayer V2O5 center dot nH(2)O 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 and stable cycling performance (259 mAh g(-1) after 1000 cycles at 10 A g(-1), with 98.2% capacity retention). Moreover, the (NH4)(2)V4O9 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.