Excellent performance of carbon-coated TiO2/Li4Ti5O12 composites with low Li/Ti ratio for Li-ion storage

Abstract

TiO₂/Li₄Ti₅O₁₂ composites with different Li : Ti molar ratios were fabricated by simply hydrolyzing tetrabutyl titanate in a water solution of LiNO₃ and calcining the dried mixture at 600 °C, and the carbon-coated composites were prepared at 600 °C employing glucose as a carbon precursor. Compared to the carbon-coated TiO₂ and Li₄Ti₅O₁₂ prepared under the similar conditions, the carbon-coated TiO₂/Li₄Ti₅O₁₂ composite with Li : Ti = 4 : 8 exhibits a stable capacity of 227.2 mA h g⁻¹ when cycled 100 times at a current density of 100 mA g⁻¹, and when cycled at 200, 400, 800 and 1600 mA g⁻¹, the corresponding capacities are 206.1, 183.0, 152.4 and 119.4 mA h g⁻¹ with the coulombic efficiency close to 100%. The composite also reveals outstanding long-term cycling stability at 500 mA g⁻¹ with a reversible capacity of 177.6 mA h g⁻¹ after 850 cycles. The enhanced electrochemical performance is ascribed to the synergistic effect of the two phases of TiO₂ and Li₄Ti₅O₁₂ with the carbon coating.