Unraveling the Synergistic Effects of Oxygen Vacancy and Amorphous Structure on TiO2 for High-Performance Lithium Storage

The improved electronic conductivity and ion diffusion efficiency of TiO2-based anode materials have been extensively studied by introducing oxygen vacancies or creating amorphous structure. There has been little exploration of the synergistic effects by combining these two modification strategies into one TiO2-based matrix. In addition, the structure-activity relationship and energy storage mechanism involved remain to be understood. Herein, a facile one-step coreduction method is reported to successfully produce the oxygen vacancy-doped amorphous TiO2 nanoparticles. The oxygen vacancy-doped amorphous TiO2 anode exhibits significantly enhanced electrochemical activity and high-rate stability (up to 87 mAh g(-1) over 10 000 discharge/charge cycles at a current rate of 100 C). This outstanding electrochemical performance is attributable to the synergistic effects of amorphous structure and oxygen vacancies. Density functional theory calculations reveal the enhanced electronic conductivity and thermodynamically favorable lithium insertion architecture due to the introduction of oxygen vacancy and the construction of the amorphous skeleton. Dynamic analysis indicates that the lithium-storage mechanism is a hybrid of surface capacitive storage and enhanced diffusion-controlled ion insertion. This work opens up new pathways in developing novel anode materials for efficient energy storage from the wide spectrum of metal oxides.