Multi-Species, Multi-Reaction Model for Porous Intercalation Electrodes: Part II. Model-Experiment Comparisons for Linear-Sweep Voltammetry of Spinel Lithium Manganese Oxide Electrodes

In Part 1 of this series, we formulated a porous electrode model including multiple lithium-insertion species and associated electrochemical and homogenous reactions. In this paper, the multi-species multi-reaction (MSMR) model is used to simulate linear-sweep voltammetry (LSV) data of a porous electrode of spinel lithium manganese oxide (LMO) at different scan rates, and values of transport, kinetic, and thermodynamic parameters are fit to the measured data. Twenty model parameters are optimized to simultaneously fit the slowest and fastest sweep rates. The optimization is computationally intensive, but the calculation times were reduced by almost one half using a perturbation formula valid at the lowest sweep rate, developed in Part 1, together with numerical solutions at higher sweep rates. A sensitivity analysis determines the importance of different model parameters on the results. The fitting is most sensitive to the values of the Open Circuit Voltage (OCV) and it was necessary include a small amount of hysteresis, so that the OCV is slightly different on forward and backward scans. The next most important fitting parameter was the solid phase diffusion coefficient. Of smaller importance are the kinetic parameters and ohmic losses in the solid and liquid phases of the electrode. (C) The Author(s) 2019. Published by ECS.