Carbon-coated spinel-structured Li1-xTi2O4 (0<x<0.5) anode materials with reversible two-stage lithiation potentials

Carbon-coated spinel-structured Li1-xTi2O4 (0<x<0.5) particles with different Ti(III) proportion have been synthesized through a solid-state reaction process. X-ray photoelectron spectroscopy investigation indicates that the Ti(III) proportion in Li1-xTi2O4 is varied by adjusting molar ratio of TiO/C to TiO2 in the starting materials. The electrochemical performance of the carbon-coated Li1-xTi2O4 has been evaluated, which indicates that Li1-xTi2O4 exhibits reversible two-stage lithiation potentials with a voltage plateau at ca. 1.5 V and a voltage slope ranging from ca. 0.7 to 0.45 V during Li ion insertion. Li1-xTi2O4 with higher Ti(III) proportion delivers lower capacity at the voltage plateau but higher capacity at the voltage slope than Li1-xTi2O4 with lower Ti(III) proportion. The Li1-xTi2O4 anode materials with different Ti(III) proportion display excellent cyclic stability and capacity retention. The mechanism of the two-stage lithiation process has been discussed.