Carbon-coated Li4Ti5O12 and lithiated Li4+xTi5O12 anode materials have been synthesized using nanosized anatase TiO2 and commercial TiO2 with mixed structure as Ti sources, respectively. Microstructural investigation indicates that Li4Ti5O12 and Li4+xTi5O12 are covered by amorphous carbon layers with thickness of 2-3 nm. Their electrochemical performance has been evaluated, which indicates that an amount of active Li ions have been pre-stored in the Li4+xTi5O12 lattice during solid-state synthesis, resulting in its first-cycle coulombic efficiency over 100%. Further, Li4+xTi5O12/C exhibits higher cyclic capacities than Li4Ti5O012/C at different current density. The reversible charge capacity retention of Li4+xTi5O12/C reaches 98.5% after 100 cycles, which indicates that Li4+xTi5O12/C is promising candidate anode material for long lifetime lithium-ion batteries. The formation mechanism of Li4+xTi5O12/C has been discussed, in which the nanosized anatase TiO2 with high chemical activity and the carbon coating play key roles for the formation of Li4+xTi5O12/C. (C) 2015 Elsevier Ltd. All rights reserved.