Mo-doped NH4V4O10 with enhanced electrochemical performance in aqueous Zn-ion batteries

Abstract Ammonium vanadium bronze (NH4V4O10) has garnered increasing attention due to its extensive electrochemical applications. The development of NH4V4O10 with high conductivity and fast ion diffusion ability remains to be a significant challenge. In this work, we report a facile synthesis of Mo-doped NH4V4O10 via a one-step hydrothermal reaction. The morphology evolution process and phase transformation of Mo-doped NH4V4O10 are investigated by controlling the Mo concentration. When investigated as an aqueous Zn-ion battery cathode material, the as-optimized Mo-doped NH4V4O10 exhibits a high capacity of 335.0 mAh g-1 at a current density of 0.1 A g-1, and it is also able to demonstrate superior capacity retention and better cycle performance than the undoped NH4V4O10. The enhanced electrochemical performance is mainly due to the expansion of the (001) interlayer spacing of NH4V4O10 caused by the intercalation of Mo into the framework, which provides more space for Zn ion intercalation. Moreover, the doping of Mo decreases the band gap of NH4V4O10, which is verified by the UV-Vis (Ultraviolet-visible spectroscopy) spectrum and DFT (density-functional theory) calculations. The reduced band gap leads to a higher intrinsic carrier concentration, which in turn improves the electrical conductivity and the Zn ion diffusion coefficient of the material. Thus, based on these results, this work may present a new strategy in designing potential cathode for Zn-ion battery.