Facile and fast synthesis of porous TiO₂ spheres for use in lithium ion batteries

Porous anatase TiO₂ spheres have been synthesized by a microwave-assisted hydrothermal reaction of spherical particle precursors followed by annealing in air. The synthesized TiO₂ spheres are formed by interconnected nanocrystals with size of 8.7nm in average and have grain diameters of 250-400nm. After annealing at 500°C, the TiO₂ samples maintain spherical shape and develop highly mesoporous characteristics with a specific surface area of 151m²g^-1. The TiO₂ samples annealed at 750°C consist of larger aggregated particles with diameters of 500-900nm and still retain mesoporous anatase structure, but with a reduced specific surface area of 25.6m²g^-1. Electrochemical studies reveal that the porous TiO₂ spheres annealed at 500°C own very high and stable lithium ion (Li⁺) storage capacities of 207, 184, 166, and 119mAhg^-1 at 0.5, 1, 2, and 5C (850mAg^-1) rates, respectively, owing to their highly porous nanostructures and fine spherical morphology. In contrast, the TiO₂ spheres annealed at 700°C exhibit modest electrochemical performance due to their reduced pore structures and larger crystallite size. The prepared porous TiO₂ spherical particles show great promise for use as high performance anode materials for lithium ion batteries (LIBs).