Abstract
Step potential electrochemical spectroscopy (SPECS) or current transient technique for determining the mechanisms by which lithium ion transport through spinel LiMn2O4 positive electrode material during intercalation/de-intercalation was investigated. In this work, step potential electrochemical spectroscopy (SPECS) in three electrode systems have been conducted on spinel prepared by solid state and sol-gel methods. Based on the data obtained from the SPECS experiment the data has been fitted with planar, double planar and a spherical diffusional model, to better understand the diffusional mechanism and to obtain an accurate diffusional parameter for these materials. Theoretical models clearly illustrate that both spherical and double plane diffusion models are in excellent agreement with experimental data from beginning short time of the potential step till the end for long time 3600s. This work aims to develop a more comprehensive analysis technique for future work. By using SPECS technique, the various curves for Cottrellian type behaviour were also investigated, such as I(t)*sqrt(t) vs decimal logarithm as Li-ion insertion/de-insertion into the spinel. The crystal structure, materials morphology and elemental composition were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive x-ray spectroscopy (EDS), and high-resolution transmission electron microscopy (HR-TEM). These experiments reveal the potential benefits of understanding Li-ion diffusion of spinel LiMn2O4 for high-power lithium-ion batteries (LIBs) storage performance.