Improvement of rate capability of spinel lithium titanate anodes using microwave-assisted zinc nanocoating

In this study, the deposition of microwave-assisted Zn layers onto spinel lithium titanate (Li4Ti5O12) crystals as superior anode materials for Li-ion batteries has been investigated. Microwave heating is capable of rapidly depositing Zn layers over the surface of spinel Li4Ti5O12 within 6 min. The thickness of Zn layer (i.e., 1-10 nm) is an increasing function of zinc nitrate concentration under the microwave irradiation. The charge-discharge curve of Zn-Li4Ti5O12 anode still maintains the plateau at 1.5 V, contributing to the major portion in the overall specific capacity. The presence of Zn coating significantly facilitates the capacity retention (78.1% at 10 C/0.2 C) of the composite anodes with high Coulombic efficiency (>99.9%), indicating an excellent reversibility of insertion/de-insertion of Li ions. This can be ascribed to the fact that well-dispersed Zn layer offers an electronic pathway over the Li4Ti5O12 powder, thus imparting electronic conduction and reducing cell polarization. Accordingly, the deposition of Zn coating, prepared by the rapid microwave heating, shows a positive effect on the rate-capability improvement of Li4Ti5O12 anodes. (C) 2011 Elsevier B. V. All rights reserved.