Tailored design the redox chemistry and microstructures of bronze-type VO2(B) via Co/Zn doping towards enhanced sodium storage

Bronze-type vanadium dioxide (VO2(B)) is a promising intercalation pseudocapacitive material due to its stable bilayered structure, however, the low electronic/ionic conductivity greatly limit its charge storage capability. Herein, a Co/Zn-mediated strategy has been proposed to optimize the electronic/micro structures of VO2(B) and thus achieve enhanced Na+ storage. Both the experimental results and theoretical calculations have revealed that the introduction of appropriate amount Co ions can effectively promote ion diffusion, charge transfer, and provide multiple redox-active sites, thus leading to enhanced electrochemical properties. The effects of Zn dopants are resulted from the synergistic effect between electronic and microstructure variations of VO2(B). Increasing the Zn doping content leading to distorted local structure that impede ion diffusion, however, the enhanced V redox activity and increased electrical conductivity are beneficial to promote charge transfer and Na+ storage (for example, 5 mol% Zn incorporation leads to 2 × increased capacitance, and 10 mol% Zn substitution results in 2 × improvement of the rate performance). In general, this work provides valuable insights in understanding the relationship between heteroatom doping induced electronic/micro structure variations of VO2(B) and its Na+ storage properties, which will enable rational design of more layered oxides with excellent charge storage properties or extend to other applications.