Mesoporous TiO₂@N-doped carbon composite nanospheres synthesized by the direct carbonization of surfactants after sol–gel process for superior lithium storage

Abstract

Here, we report mesoporous TiO₂@N-doped carbon composite nanospheres synthesized via a double-surfactant-assisted assembly sol-gel process followed by sequential carbonization of surfactants under a N₂ atmosphere. The resulting TiO₂@N-doped C composite nanospheres are composed of uniformly distributed TiO₂ nanocrystals with a diameter of ∼8 nm coated by a N-doped carbon layer that was formed by surfactants. Moreover, a large number of connected mesopores were observed in the nanospheres after high-temperature carbonization treatment. The synthesized nanospheres possess a large specific surface area (∼120 m² g^-1) and a large pore size (4-40 nm), with a well-defined spherical structure and a diameter in the nanoscale range. As an anode material for lithium-ion batteries (LIB), the mesoporous composite nanospheres delivered a reversible capacity of ∼117 mA h g^-1 after 2000 cycles at a current rate as high as 10 C, as well as superior rate capability. The N-doped carbon layers greatly improved the overall electrical conductivity of the mesoporous TiO₂ nanospheres. This study provides a remarkable synthetic route for the preparation of mesoporous TiO₂-based N-doped carbon composite materials as high-performance anode materials in LIBs.