Rutile TiO2 mesocrystals with tunable subunits as a long-term cycling performance anode for sodium-ion batteries

A facile, low-temperature hydrothermal synthetic route was designed for fabricating rutile TiO 2 mesocrystals composed of ultra-tiny, rod-like subunits. Mesocrystals with tunable sizes and morphologies of the subunits can be simultaneously achieved through a hydrothermal re-treatment process at different temperatures. A probable mechanism for the formation of the self-assembled giant rutile TiO 2 mesocrystals of various sizes and morphologies is proposed based on the experimental results. The rutile TiO 2 giant mesocrystals as-fabricated were also tested as anode materials for sodium-ion storage, and exhibited a capacity of 129.6 mA h g −1 with a capacity retention of 97% for over 1000 cycles at a charge–discharge rate as high as 5 C and enhanced rate capability up to 30 C (64.5 mA h g −1 at 30 C), effectually demonstrating superior sodium storage properties in terms of long-term cycling stability and rate capability.