TiO2-rGO nanocomposite hollow spheres: large scale synthesis and application as an efficient anode material for lithium-ion batteries

Abstract

We report here a controllable large-scale synthesis protocol for TiO₂-rGO nanocomposites with a hollow spherical morphology by a novel aerosol-assisted spray drying method followed by calcination. The developed strategy is easy to scale-up without significant change in morphology. The precursors used for the synthesis are aqueous titanium ammonium peroxo-carbonate complex (TAPCC) solution, being decomposable at low temperatures, and an aqueous graphene oxide (GO) suspension; no additive or structure-directing agent is required. Both the precursors play vital roles in hollow sphere formation. The enhanced internal pressure inside the atomized droplets built-up in situ through decomposition of TAPCC forming gaseous CO₂, NH₃, O₂ and H₂O vapour, helps overcome the crumpling effect of GO. The sheet structure of GO provides sufficient mechanical strength to prevent bursting of the expanded droplets. The synthesized TiO₂-rGO hollow spheres are porous, composed of 10–20 nm TiO₂ particles dispersed on the surfaces of rGO with a surface area of 86 m² g⁻¹. The synthesized TiO₂-rGO composites showed superior electrochemical performance as lithium-ion battery (LIB) anode with capacity values of 265 mA h g⁻¹ (10 wt% rGO) and 274 mA h g⁻¹ (20 wt% rGO) at 18.8 mA g⁻¹ as compared to 236 mA h g⁻¹ for the pristine sample with a 2D flake-like morphology. This is due to the unique thin-walled hollow-spherical structure of TiO₂-rGO composites, which provides a large number of electrochemically accessible active sites, favorable diffusion paths for Li⁺ ions and enhanced charge transport. Thus, the present synthetic method has great potential for large scale production of TiO₂-rGO hollow spheres for application as anode in practical high-rate lithium-ion batteries.