A Lithium-Ion Capacitor electrical model considering pore size dispersion

Since Energy Storage Systems (ESSs) are electrochemical devices, they are often modeled using equivalent circuit models in order to monitor and control their behaviors. Several models had been developed for Lithium-Ion Batteries (LIBs) and Supercapacitors (SCs) based on time or frequency domain measurements. One of the frequently used modeling methods consists on measuring the impedance of the cells using Electrochemical Impedance Spectroscopy (EIS) and then fitting an impedance model to the data. Recent research applied this method to Lithium-Ion Capacitors (LICs), which belong to a new series of hybrid SCs. However, the applied models do not accurately describe the impedance of LICs at low frequencies. This results from considering the size of the pores of their positive electrode, made of activated carbon, identical. Therefore, this paper introduces a new model of LICs taking into account the dispersion of pores of the positive electrode. A dispersion factor was added to a previous model using a Constant Phase Element (CPE). A good agreement between measured and predicted values of the impedance was found, especially at low frequencies.