Surface diffusion enhancement of titania by surface fluorine modification to boost energy storage capacities

Abstract

Supercapacitors based on environmentally friendly electrode materials have attracted great interest for energy storage devices with wide applications in high-power systems and miniaturized electronic devices, owing to the fast charge/discharge capability and excellent cycling stability. It is highly desired yet challenging to effectively improve the capacitances of TiO2, especially via a facile route. Herein, we demonstrate a surface fluorine modification strategy to greatly improve the capacitance of anatase TiO2 up to 6.4 times. Density functional theory calculations show that the surface F modification can transform the surface storage sites and the diffusion paths for lithium ions. Thus, the diffusion barrier is reduced from 1.46 eV to 0.39 eV, which is confirmed by the experimental results of the significant enhance in diffusion coefficient. This work could provide a new avenue to the design of high-performance electrode materials for electrochemical energy storage and other surface-diffusion-related fields.