Synthesis of pristine and carbon-coated Li₄Ti₅O₁₂ and their low-temperature electrochemical performance

Pristine and carbon-coated Li₄Ti₅O₁₂ oxide electrodes are synthesized by a cellulose-assisted combustion technique with sucrose as organic carbon source and their low-temperature electrochemical performance as anodes for lithium-ion batteries are investigated. X-ray diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) are applied to characterize the phase structure, composition, and morphology of the composites. It is found that the sequence of sucrose addition has significant effect on the phase formation of Li₄Ti₅O₁₂. Carbon-coated Li₄Ti₅O₁₂ is successfully prepared by coating the pre-crystallized Li₄Ti₅O₁₂ phase with sucrose followed by thermal treatment. Electrochemical lithium insertion/extraction performance is evaluated by the galvanostatic charge/discharge tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), from room temperature (25 °C) to -20 °C. The carbon-coated composite anode materials show improved lithium insertion/extraction capacity and electrode kinetics, especially at high rates and low temperature. Both of the two samples show fairly stable cycling performance at various temperatures, which is highly promising for practical applications in power sources of electric or electric-hybrid vehicles.