Simultaneously tailoring material structure and surface for robust sodium storage: A case study of TiO2

Abstract

Modulating the atomic structure and surface property represents a pivotal and intriguing approach to tailoring the energy storage performance of battery materials, but their simultaneous modulation via simple processes remains a grand challenge. Taking TiO2 as an example, here we report the structure and surface modulation through a simple two-step operation, hydrogenation and fluorination, which impart high electrical conductivity and robust surface activity to the material. Hydrogenation introduces Ti3+ species in the TiO2 bulk to accelerate electron transport, while surface fluorination speeds up sodium-ion reaction dynamics. This modulated TiO2 exhibits robust Na+ storage, affording 181 mAh g−1 over 2500 cycles at a high rate of 20 C. In addition, when paring with a commercial Na3V2(PO4)2O2F cathode, the designated TiO2 allows the full cell to deliver a remarkable power of 3700 W kg−1, outperforming most sodium-ion batteries. The correlation between the robust performance and the material property is understood through energy band analysis and density functional theory calculations.