3D nitrogen-doped graphene foams embedded with ultrafine TiO2 nanoparticles for high-performance lithium-ion batteries†
A three-dimensional (3D) foam architecture of ultrafine TiO2 nanoparticles embedded in N-doped graphene networks (denoted as UTO/NGF) is prepared via a facile hydrothermal self-assembly and a subsequent freeze-drying scheme. The obtained UTO/NGF possesses a large surface area, macro/mesoporous structure, and high-level nitrogen content (7.34%). Such a unique hierarchical architecture provides multidimensional electronic network, enlarged contact area between electrolyte and electrode, and numerous open channels for the access of the electrolyte, thus favoring diffusion kinetics for both electrons and lithium ions. Meanwhile, nitrogen doping can further improve the electrical conductivity and electrochemical activity of the obtained composite during electrochemical processes. As a consequence, the UTO/NGF exhibits high reversible capacities with remarkable cyclic retention at different current rates (165 mA h g−1 after 200 cycles at 1 C rate, 143 mA h g−1 after 200 cycles at 5 C rate) and excellent rate performance (96 mA h g−1 at 20 C) as anodes in lithium ion batteries.