Ammonium ion intercalated hydrated vanadium pentoxide for advanced aqueous rechargeable Zn-ion batteries

Considering many factors, including environmental protection, high cost, and limited resource, aqueous rechargeable Zn-ion batteries (ARZIBs) are expected to be a new next-generation grid to replace Li-ion batteries. The open layered framework of (metal ions intercalated) hydrated vanadium pentoxides is conducive to the transfer and diffusion of zinc ions, making this kind of material a promising cathode material. In this work, ammonium ion (NH4+) intercalated hydrated vanadium pentoxide [(NH4)xV2O5·nH2O, abbreviated as NVOH] is prepared by a comparatively low-temperature synthesis and developed as a cathode material for ARZIBs. The influence of different types and concentrations of zinc salt electrolytes on the electrochemical performance is first studied, demonstrating that 3 M Zn(CF3SO3)2 shows the most excellent performance. The Zn//NVOH battery delivers superior electrochemical reversibility, a high specific capacity (372 mAh·g-1 at 0.1 A·g-1), a preeminent energy density (273 Wh·kg-1 at 155 W·kg-1), and a long lifespan cycling performance (175 mAh·g-1 after 2,000 cycles at 5 A·g-1), which is superior to or comparable to most up-to-the-minute V-based materials applied to ARZIBs. The intercalation reversibility of zinc ion is proved during the electrochemical reaction by various characteristic measurements. This work not only provides a low-temperature hydrothermal synthesis route (100 °C) for NVOH but also demonstrates that it can be a promising supplement for zinc ion batteries or other portable battery devices.