Enhanced high-rate performance of Li4Ti5O12 microspheres/multiwalled carbon nanotubes composites prepared by electrostatic self-assembly

Abstract

Li4Ti5O12 microspheres (LTOS)/multiwalled carbon nanotubes (MWCNTs) composites with different contents of MWCNTs have been prepared by electrostatic self-assembly. In the preparation, the surface charge of cetyltrimethylammonium bromide (CTAB)-functionalized HNO3-treated MWCNTs (CTAB-functionalized MWCNTs) in aqueous solution is positive because of the hydrophobic force between MWCNTs and the long alkane chain of CTAB, while that of LTOS is negative. Therefore, electrostatic attraction occurs between LTOS and CTAB-functionalized MWCNTs when they approach, and LTOS/MWCNTs composites are obtained after removing CTAB by calcination. Notably, LTOS/MWCNTs composites with 10 wt.% MWCNTs exhibit superior rate performance and cyclic stability. Their specific capacities at 5C, 10C, 20C, 40C and 60C are 170, 168, 167, 165 and 160 mAh·g−1, respectively. Even at 80C and 90C, the specific capacities are still as high as 154 and 152 mAh·g−1. Moreover, the specific capacity retains 140 mAh g−1 after 2000 cycles at 10C. The excellent performance of LTOS/MWCNTs composites is mainly owing to the conductive network forming by MWCNTs connecting different LTOS, acting as highway for the fast transmission of electrons and ions during charge-discharge process.