Carbon-coated Vanadium Oxide Nanoflowers with K+ Ions Pre-embedment as a High-rate Cathode for Zinc-Ion Batteries

Graphical Carbon-coated vanadium oxides with K + ion pre-embedded (KVO-C3) were hydrothermally synthesized by reducing glucose as a carbon source. The improved crystallinity of KVO-C3 facilitates Zn 2+ intercalation/extraction, which delivers a superior specific capacity of 389.2 mAh g −1 at 0.1 A g −1 and retains 83.5% capacity as current density increases 50 times. The KVO-C3 battery shows a high energy density of 209 Wh kg −1 at a power density of 3500 W kg −1 . Recently, aqueous zinc-ion batteries have become a promising candidate for energy storage devices due to their low cost, high capacity, and environmental friendliness. However, the low electrical conductivity and irreversible Zn 2+ intercalation/extraction of cathode materials limit the rate performance and cycling stability of Zn-ion batteries. Herein, carbon-coated V 2 O 5 nanoflowers with K + pre-embedment (KVO-C) were synthesized by hydrothermal and high-temperature annealing methods, showing enhanced electrical conductivity and crystallinity. Assembled with Zn anode and 2 M Zn(CF 3 SO 3 ) 2 electrolyte, the optimized KVO-C3 battery achieves a high specific capacity of 389.2 mAh g −1 at a current density of 0.1 A g −1 and retains 85% even with a 50-fold increase in current density and cycling back to 0.1 A g −1 . KVO-C3 also shows excellent capacity retention of 77% and coulomb efficiency of nearly 100% after 2000 cycles and delivers a high energy density of 209 Wh kg −1 at a power density of 3500 W kg −1 .