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

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 TiO 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 Ti species in the TiO bulk to accelerate electron transport, while surface fluorination speeds up sodium-ion reaction dynamics. This modulated TiO exhibits robust Na storage, affording 181 mAh g over 2500 cycles at a high rate of 20 C. In addition, when paring with a commercial NaV(PO)OF cathode, the designated TiO allows the full cell to deliver a remarkable power of 3700 W kg, 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.