Coating lithium titanate anodes with a mixed ionic-electronic conductor for high-rate lithium-ion batteries

Abstract

Lithium titanate (Li4Ti5O12; LTO) is a promising anode material for fast (dis)charging Li-ion batteries (LIBs). However, its low Li diffusion coefficient and electronic conductivity limit its applications. Here, we uniformly coat the LTO surface with a 1.6 nm layer of partially lithiated titania (LixTiO2, x approximate to 0.5), which is found to be a mixed ionic-electronic conductor (MIEC), using a simple solid-state method. The MIEC layer simultaneously transfers electrons and Li-ions, facilitating efficient charge transfer to (de)lithiate LTO over the entire particle surface. MIEC-nanocoated LTO exhibits highly improved capacity retention and rate capability than pristine LTO; based on electrochemical simulations, MIEC nanocoating causes performance enhancement by maximum surface-area utilization for charge transfer. Furthermore, electrochemical impedance spectroscopy and density functional theory calculations confirm facile ionic transport and high electronic conductivity of LixTiO2 nano -layer. This general strategy of MIEC nanocoating can boost the electrochemical performances of various insu-lating electrodes, maximizing the materials utilization.