Different Effect of the Atmospheres on the Phase Formation and Performance of Li4Ti5O12 Prepared from Ball-Milling-Assisted Solid-Phase Reaction with Pristine and Carbon-Precoated TiO2 as Starting Materials

Pristine Li4Ti5O12 and Li4Ti5O12/C composite are prepared by high-energy ball-milling (HEBM)-assisted solid-state reaction with TiO2 anatase and Li2CO3 or carbon-precoated TiO2 anatase and Li2CO3 as reactants. The influence of calcination atmosphere on the phase formation and particulate morphology of those two products are systematically investigated by XRD, SEM, TEM, O-2-TPO, and TPR techniques. The optimal calcination atmospheres for the synthesis of Li4Ti5O12 and Li4Ti5O12/C are diluted hydrogen and nitrogen atmospheres, respectively. TPR in various atmospheres demonstrates the difference in optimal atmospheres is due to the suppressing effect of hydrogen for Li2CO3 decomposition, the reducing properties of carbon and hydrogen, and the blocking effect of carbon for the reaction between TiO2 and Li2O. Both the pristine and carbon-coated Li4Ti5O12 show good rate and cycling performance. A near theoretical capacity of 175 mA h g(-1) is achieved for both samples at 0.5 C rate. After a total cycling number of 40 at various rates between 0.5 and 40 C, the capacity retention for Li4Ti5O12 and Li4Ti5O12/C is 97.8 and 98.5%, respectively. The HEBM-assisted solid-state reaction in controlled atmosphere may be a practical way for the economic synthesis of both pristine and carbon-coated Li4Ti5O12 as high-performance electrodes of lithium-ion batteries.