Comparison of EDLC impedance models used for ageing monitoring

Electrochemical double layer capacitors (EDLC) electrodes are made with pores of different geometric characteristics. This particularity is called pore size distribution. During EDLC ageing monitoring, it is necessary to know precisely the evolution of impedance. Firstly, this article deals with classical impedance models like single pore or constant phase element (CPE) for EDLC and exposes their strengths and their drawbacks. Then a more recent model grouping pores of the same geometric capacities is presented. Each group can be modeled by an electrical branch and has its own impedance expression. The resulting electrode impedance is obtained by putting n branches in parallel. This new model, called multi-pores model (MP), has been recently presented by A. Hammar [3] and is highly hoped to be used for more precise health monitoring of EDLC. The physical advantage is to take into account the pore heterogeneity. The models precision is finally compared using experimental results.