ABSTRACT

This chapter considers both circuit-based cell models and physics-based cell models. It focuses on the most common Lithium-ion capacitor (LiC) chemistries and modeling techniques, which means LiCs, use voltage, current, concentration, temperature, and resistance-capacitance as the physical quantities of interest, and can be written as the equivalent impedance equations. In order to use LiC in renewable energy systems, or electric vehicles, dynamic characteristics of LiC have to be identified first of all; therefore appropriate dynamic models are necessary for modeling and simulations of systems containing LiC. A special class of models combine elements of both chemistry and circuit-based modelling techniques. Model parameters including resistances and capacitances are usually determined with the help of electrochemical impedance spectroscopy (EIS) measurements of currents and voltages during charging and discharging processes. The EIS measurements varying with frequency are capable of high precision and are frequently used for the extraction of the frequency dependencies of the circuit components involved in the equivalent circuit.