Understanding How Degree of Crystallinity Affects Electrochemical Kinetics of Sodium-Ion in Brown TiO2 Nanotubes

Sodium-ion batteries (SIBs) have attracted significant attention as an emerging alternative to lithium-ion batteries (LIBs). The charge and discharge performance of the electrode material are affected by various intrinsic parameters, including Na-ion diffusion coefficient, ionic conductivity, concentration, etc., which are further related to the structure and crystallinity of the material. Herein, the kinetics of Na-ion intercalation into low and high crystalline brown TiO2 nanotubes are studied by using galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) techniques. Various parameters such as intercalation capacity, partial sodium ion conductivity sigma Na+, diffusion time constant (tau), characteristic diffusion length (L), etc., are analyzed during sodiation/de-sodiation, and the dependence of these parameters with the degree of crystallinity of the material is discussed. The chemical diffusion coefficients (Dchem) are determined at different intercalation and de-intercalation potentials, which showed similar behaviour within a range of 10(-15)-10(-18) cm(2) s(-1), with a slightly higher value for high crystalline brown TiO2. The correlation between the diffusion behavior of Na-ions in high and low crystalline brown TiO2 nanotubes and their degree of crystallinity provides insights into the electrochemical performance of TiO2 anodes.

Automated summary

This study investigates the kinetics of Na-ion intercalation into low and high crystalline brown TiO2 nanotubes, analyzing various parameters and their relationship with the material's crystallinity. The chemical diffusion coefficients exhibit similar behavior at different crystallinities, providing insights into the electrochemical performance of TiO2 anodes.