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

Abstract

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. [1-3] 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. Li4Ti5O12-carbon composites were built through impregnation of Li4Ti5O12 into the core-shell carbon. These Li4Ti5O12-carbon composites exhibit 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. 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.