Electrochemical Kinetics Investigation of Li4Ti5O12/Reduced Graphene Oxide Nanocomposite Using Voltammetric Charge Analysis

The electrochemical kinetic properties of a Li4Ti5O12 (LTO)/reduced graphene oxide (RGO) nanocomposite were systematically investigated using cyclic voltammetry (CV). Since there are several factors that influence the electrochemical kinetics of LTO depending on the potential scan rate, the kinetic properties of LTO in the nanocomposite were evaluated by analyzing the scan rate dependence of the voltammetric charge, as measured by CV. When we formed a nanocomposite of LTO and electrically conductive RGO, the number of surface electrochemical reaction sites increased and that of the bulk electrochemical reaction sites decreased. This led to an improvement in the kinetics related to Li+ ion diffusion in LTO. The range of scan rates for which the voltammetric charge was decreased by the kinetic limitations ascribed to diffusion was reduced because of the decrease in the effective diffusion length and the increase in the diffusion area, compared to commercial LTO particles. Thus, unlike previous studies, we report that the improved rate capability of the composite with RGO is ascribed to enhanced diffusion properties in the bulk electrochemical reaction sites rather than an increase in the electrical conductivity, which is a surface property. (C) 2015 The Electrochemical Society. All rights reserved.