Spray-pyrolysis-assisted synthesis of yolk@shell anatase with rich oxygen vacancies for efficient sodium storage

Herein, yolk@shell structured anatase TiO₂ microspheres are produced by a facile spray-pyrolysis-assisted method. Through introducing oxygen vacancies by hydrogen treatment, yolk@shell structured TiO_2-x microspheres are also obtained. The as-synthesized yolk@shell TiO_2-x demonstrates a high reversible capacity (230.7 mA h g^-1 after 200 cycles at 0.05 A g^-1) and remarkable long-term cycling stability (capacity retention of 91.7% after 1000 cycles at 1 A g^-1). DFT calculations reveal that introducing oxygen vacancies into TiO₂ enhances the electrical conductivity, lowers the sodiation energy barrier, and facilitates Na⁺ diffusion kinetics. This work sheds light on the rational design of high-performance electrode materials through integrating the yolk@shell structure and oxygen vacancies.