High-Rate and Ultra-Stable aqueous Zinc-Ion batteries enabled by Potassium-Infused ammonium vanadate nanosheets.

ABSTRACT

Aqueous zinc-ion batteries (AZIBs), defined by low expenses, superior safety, and plentiful reserves, demonstrate tremendous development potential in energy storage systems at the grid scale. Whereas the cathode instability and the limited diffusion of Zn2+ have impeded the development of AZIBs. Herein, a high-performance K-NH4V4O10 (K-NVO) cathode with K+ doping synthesized successfully through one-step hydrothermal approach. Experiments and density functional theory (DFT) calculations indicate that K-NVO has Zn2+ diffusion pathways with lower barriers for smoother transport, and lower formation energy. The combination of the rapid Zn2+ diffusion and the stable structure results in outstanding electrochemical performance of K-NVO as demonstrated in tests. K-NVO cathode achieves a specific capacity of 406 mAh g-1 at 0.2 A g-1, maintains satisfactory cyclic stability with 81.6 % capacity retention after 1000 cycles at 5 A g-1, and possesses a high energy density of 350.9 Wh kg-1. Furthermore, confirmation of the zinc storage mechanism in K-NVO was carried out through Ex situ tests, such as XRD and XPS. This research contributes a unique perspective to the formulation of high-performance cathode materials for AZIBs.