Superior potassium and zinc storage in K-doped VO₂(B) spheres

The abundant natural resources and low cost benefits of zinc-ion batteries (ZIBs) and potassium-ion batteries (KIBs) offer a better alternative to lithium-ion batteries (LIBs). Nevertheless, the large radius of K⁺ and high charge density of Zn²⁺ lead to sluggish electrochemical kinetics and the development of appropriate electrode materials for KIBs and ZIBs is therefore very important. Herein, hierarchical K-doped brookite vanadium dioxide (K–VO₂(B)) spheres prepared via a simple microwave-assisted hydrothermal approach are proposed. K–VO₂(B) as an anode material for PIBs shows enhanced electrochemical performance in terms of high capacity (∼420 mA h g⁻¹), exceptional rate capability and long-term cycling performance (500 cycles). For ZIBs, it also achieves a high capacity of 350 mA h g⁻¹ at 500 mA g⁻¹ and 122 mA h g⁻¹ at an extremely high rate of 50 A g⁻¹. The outstanding PIB and ZIB performance of the K–VO₂(B) is mainly benefitted from the improved ion diffusion coefficients after K-doping and the occurrence of inherently stable (de)intercalation reactions.