The study of lithium ion de-insertion/insertion in LiMn2O4 and determination of kinetic parameters in aqueous Li2SO4 solution using electrochemical impedance spectroscopy

In this work, we report a basic study on the mechanism of lithium ion de-insertion/insertion process from/into LiMn2O4 cathode material in aqueous Li2SO4 solution using electrochemical impedance spectroscopy (EIS). An equivalent circuit distinguishing the kinetic parameters of lithium ion de-insertion/insertion is used to simulate the experimental impedance data. The fitting results are in good agreement with the experimental results and the parameters of the kinetic process of Li+ de-insertion and insertion in LiMn2O4 at different potentials during charge and discharge are obtained using the same circuit. The results indicate that the de-insertion/insertion behavior of lithium ions at LiMn2O4 cathode in Li2SO4 aqueous solution is similar to that reported in the organic electrolytes. The charge transfer resistance (R-ct), warburg resistance, double layer capacitance and chemical diffusion coefficient (DLi+) vary with potentials during de-insertion/insertion processes. R-ct is lowest at the CV peak potentials and the important kinetic parameter. DLi+ exhibits two distinct minima at potentials corresponding to CV peaks during de-insertion-insertion and it was found to be between 10(-8) and 10(-1) cm(2) s(-1) during lithium ;de-insertion/insertion processes. (C) 2010 Elsevier Ltd. All rights reserved.