Characterization and electrochemical properties of carbon-coated Li4Ti5O12 prepared by a citric acid sol–gel method

Since carbon coating can effectively improve electrical wiring of Li4Ti5O12 and thus enhance its high rate performance, a novel and simple citric acid sol–gel method for in situ carbon coating is employed in this study. The effects of the amount of the carbon source in the starting xerogel on the particle size, the resistance and the electrochemical performance of the synthesized Li4Ti5O12 samples are systematically studied. The physical and electrochemical properties of the obtained samples have been characterized by XRD, TG-DSC, SEM, TEM, BET, A.C. impedance, galvanostatically charge–discharge and cyclic voltammetry tests. The results show that the initial amount of the carbon source in the starting xerogel is a critical factor which determines the content of the coated carbon and the pore volume, therefore governs the high rate performance of the Li4Ti5O12/C composites. The Li4Ti5O12/C composite with in situ carbon coating of 3.5 wt% exhibits the best electrochemical performance which delivers delithiation capacities of 143.6 and 133.5 mAh g−1 with fairly stable cycling performance even after 50 cycles at 0.5C and 1C rate, respectively.

Research highlights▶ Since carbon coating can effectively increase the conductivity of Li4Ti5O12 and thus improving its high rate performance, a novel and simple citric acid sol–gel method for in situ carbon coating is employed in this study. In this study, the effects of the amount of the carbon source in the starting xerogel on the particle size, the resistance and the electrochemical performance of the synthesized Li4Ti5O12 samples are systematically studied. For the first time, we systematically demonstrate the impact of the carbon content on the electrochemical performance of the electrodes. The Li4Ti5O12/C composite with in situ surface carbon coating of 2.2 wt% exhibits the best electrochemical performance which delivers delithiation capacities of 143.6 and 133.5 mAh g−1 with fairly stable cycling performance even after 50 cycles at 0.5C and 1C rate, respectively.