Mesoporous Lithium Titanate-Carbon Composite (Li4Ti5O12-Carbon) with Controlled Microstructure As Anode in Lithium Ion Batteries for Wide Temperature Range

The high discharge rate performance of lithium titanate (Li₄Ti₅O₁₂) is limited by the low electronic conductivity of the material (< 10^-11 Sm^-1), addition of carbon is one of the effective way in enhancing the rate performance. [1-4]

In this study, carbons with a hollow core and mesoporous shells of controlled dimensions (in terms of diameter of core, thickness of the shell and diameter of the mesopores) were synthesized via silica hard-template method (Fig. 1). Li₄Ti₅O₁₂-carbon composites were built through impregnation of Li₄Ti₅O₁₂ into the core-shell carbon (Fig. 2). These Li₄Ti₅O₁₂-carbon composites demonstrate higher electronic conductivity, and enhanced electrochemical behavior for prolonged cycles at high discharge rate due to increased surface area of the active material, and improved ion transport pathways from possibly the length scale effect.

Cross-section TEM studies have been performed and proved that Li₄Ti₅O₁₂ particles are impregnated within the mesoporous carbon shell structure. (Fig. 3) This Li₄Ti₅O₁₂-carbon composite can achieve superb coulobmic efficiency of 98% and 96%, and superior long-cycling life with remarkably high capacity retention of 99% and 85% over 2,000 cycles at 10C (2.2 Ag^-1) and 20C (4.4 Ag^-1), respectively. Similar electrochemical behavior is observed for low temperature condition.

Acknowledgement

This work was supported by Hong Kong Research Grants Council General Research Fund (HKU 700209P), Strategic Research Theme on Clean Energy, University Development Fund on Initiative on Clean Energy, and Innovation and Technology Fund of the Hong Kong SAR (ITS/076/11).

References

1. C.K. Ho, H. Yung, M. Zhou, C.Y.V. Li, K.Y. Chan, “Mesoporous Lithium Titanate-Carbon Composite with Controlled Microstructure”, Abstract #1148, 224th ECS Meeting, October 2013, San Francisco, U.S.A.
2. S.W. Ting, C.Y.V. Li, H. Yung. C.K. Ho and K.Y. Chan, “Structural and Electrochemical Studies of Mesoporous Li₄Ti₅O₁₂-TiO₂ Composite Spheres as Anode Material  for Lithium ion Batteries, 222nd ECS Meeting, October 2012, Honolulu, Hawaii, U.S.A.
3. C.Y.V. Li, S.W. Ting, Z. Yang, W. Zhuang, X. Lu, H. Yung and K.Y. Chan, “Lithium Titanate Prepared from Mesoporous TiO₂ Fiber as Anode Material for Lithium Ion Batteries, , 222nd ECS Meeting, October 2012, Honolulu, Hawaii, U.S.A.
4. X. Zheng, C. Dong, B. Huang, M. Lu, Int. J. Electrochem. Sci., 7 (2012) 9869 – 9880.