Heterojunction TiO2@TiOF2 nanosheets as superior anode materials for sodium-ion batteries

Abstract

Anatase TiO₂ is considered as a promising anode material for sodium-ion batteries, but the inherent semiconductor properties and the sluggish Na⁺ diffusion kinetics limit its further development. To overcome these inherent drawbacks, heterojunction TiO₂@TiOF₂ constructed with two-dimensional nanosheets is prepared by the hydrothermal method. When heterojunction TiO₂@TiOF₂ is used as a sodium ion battery material, a stable cycling performance of up to 10 000 cycles can be achieved at a high current density of 5000 mA g⁻¹, probably due to the heterojunction structure, the exposed (0 0 1) facet of TiO₂ and the in situ formed NaF protective layer. Density functional theory (DFT) calculations further reveal that the heterostructure TiO₂@TiOF₂ nanosheets possess better electrical conductivity and lower formation energies of Na⁺ ions than those of the separated TiO₂ and TiOF₂. This work offers a new strategy to design novel heterojunction structures for the electrochemical sodium storage.