Dual-phase TiO₂ hollow microspheres as a superior anode for sodium ion battery

TiO2 is considered as a potential anode with the advantages of stable structure and high safety. However, the large-scale application of TiO2 is restricted due to its low electronic conductivity and sluggish Na+ diffusion. In the present work, anatase and TiO2-B dual-phase TiO2 hollow microspheres (TiO2-MS) were designed through a universal hydrothermal reaction. These microspheres were composed of nanosheets, and the nanosheets were consisted of small nanoparticles. Benefitting from the synergistic effect of dual-phase TiO2 nanoparticles and hierarchical structure, the TiO2-MS can not only buffer the volume changes during Na+ intercalation/deintercalation process, but also provide the contact space for electrolyte - electrode. As a result, the TiO2-MS anode delivered a distinguished sodium storage performance, maintained 240 mA h g(-1) at 2C (1C = 168 mA g(-1)) after 150 cycles. Even the current density was increased to 20C, a capacity of 159.7 mA h g(-1) can still be maintained after 5000 cycles.