Modeling Impedance in the Lithium-Ion Battery

Application ID: 17809

The impedance of a lithium-ion battery cell with a negative LTO and positive NCA electrode is modeled for harmonic perturbations between 10 mHz to 1000 Hz. The model incorporates an additional double-layer current at the conductive material in the positive electrode. The impedance of each electrode is also possible to investigate versus a reference electrode located in the middle of the separator.

The model is fitted to experimental data in literature using an optimization interface. Four control variables are used and can be extracted using the optimization procedure. The best fit is achieved using the SNOPT method with a numeric gradient method.

The application takes experimental data from EIS measurements as input, simulates these measurements, and then runs a parameter estimation based on the experimental data.

The control parameters are the exchange current density, the resistivity of the resistive layer on the particles, the double-layer capacitance of NCA, and the double-layer capacitance of the carbon support in the positive electrode. The fitting is done to the measured impedance of the positive electrode at frequencies ranging from 10 mHz to 1 kHz.

This application example illustrates applications of this type that would nominally be built using the following products: