Carbon-coated Li4Ti5O12 as a high rate electrode material for Li-ion intercalation

Li4Ti5O12 is a promising electrode material for high power density lithium-ion batteries and hybrid supercapacitors, but has the drawback of low electrical conductivity. We report a thermal vapor decomposition method to coat a uniform nanothickness graphitized-carbon on the Li4Ti5O12 particle surface. The resulting product coated at 800 degrees C has a 5 nm thick carbon layer and a electrical conductivity of 2.05 S/cm, which is much higher than that of raw Li4Ti5O12 (< 10(-13) S/cm). As a result, it shows much better rate capability when used as a negative electrode for electrochemical supercapacitors. AC impedance measurements reveal that the carbon-coated Li4Ti5O12 has smaller charge-transfer resistance due to large effective interface reaction area. (C) 2007 The Electrochemical Society.