Hierarchical TiO2 microspheres with enlarged lattice spacing for rapid and ultrastable sodium storage

Abstract

Intercalation-type TiO2 anode materials have garnered extensive interest for use in Na-ion batteries owing to their low cost and excellent stability. However, such materials are limited by their unsatisfactory specific capacity, particularly at high rates. Herein, we demonstrated the synthesis of hierarchical anatase TiO2 microspheres with enlarged lattice spacings using a simple salt template-assisted spray pyrolysis technique. The broad lattice distance can not only promote ionic transfer but also reduce the band gap with locally enhanced differential charge density, according to density functional theory calculations. Consequently, the resultant sample exhibited reversible specific capacities as high as 362 and 141.8 mA h g−1 at 50 and 5 A g−1, respectively. Impressively, the sample retained specific capacities of 154 mA h g−1 at 1.0 A g−1 after 1600 cycles and of 93.4 mA h g−1 at 5 A g−1 after 7700 cycles. To the best of our knowledge, the Na storage performance of the prepared sample is one of the best among that of TiO2-dominated anode materials. These findings provide new insight into the preparation of novel anode materials for Na-ion batteries with high ionic and electronic conductivities.