Plasma-Induced Oxygen Vacancies in Urchin-Like Anatase Titania Coated by Carbon for Excellent Sodium-Ion Battery Anodes

Abstract

The incorporation of oxygen vacancies in anatase TiO₂ has been studied as a promising way to accelerate the transport of electrons and Na⁺ ions, which is important for achieving excellent electrochemical properties for anatase TiO₂. However, wittingly introducing oxygen vacancies in anatase TiO₂ for sodium-ion anodes by a facile and effective method is still a challenge. In this work, we report an innovative method to introduce oxygen vacancies into the urchin-like N-doped carbon coated anatase TiO₂ (NC-DTO) by a facile plasma treatment. The superiorities of the oxygen vacancies combined with the conductive N-doped carbon coating enable the obtained NC-DTO of greatly improved sodium storage performance. When served as the anode for sodium-ion batteries, the NC-DTO electrode shows superior electrochemical performance (capacity: 272 mA h g^-1 at 0.25 C, capacity retention: 98.8% after 5000 cycles at 10 C, as well as ultrahigh capacity: 150 mA h g^-1 at 15 C). Density functional theory calculations combined with experimental results suggest that considerably improved sodium storage performance of NC-DTO is due to the enhanced electronic conductivity from the N-doped carbon layer as well as narrowed band gap and lowered sodiation energy barrier from the introduction of oxygen vacancies. This work highlights that introducing oxygen vacancies into TiO₂ by plasma is a promising method to enhance the electrochemical property of TiO₂, which also can be applied to different metal oxides for energy storage devices.