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 Li 4 Ti 5 O 12 and Li 4 Ti 5 O 12 /C composite are prepared by high-energy ball-milling (HEBM)-assisted solid-state reaction with TiO 2 anatase and Li 2 CO 3 or carbon-precoated TiO 2 anatase and Li 2 CO 3 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 Li 4 Ti 5 O 12 and Li 4 Ti 5 O 12 /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 Li 2 CO 3 decomposition, the reducing properties of carbon and hydrogen, and the blocking effect of carbon for the reaction between TiO 2 and Li 2 O. Both the pristine and carbon-coated Li 4 Ti 5 O 12 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 Li 4 Ti 5 O 12 and Li 4 Ti 5 O 12 /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 Li 4 Ti 5 O 12 as high-performance electrodes of lithium-ion batteries.