Microscopic Model for Cyclic Voltammetry of Porous Electrodes

Cyclic voltammetry (CV) is a widespread experimental technique for characterizing electrochemical devices such as supercapacitors. Despite its wide use, a quantitative relation between CV and microscopic properties of supercapacitors is still lacking. In this Letter, we use both the microscopic stack-electrode model and its equivalent circuit for predicting the cyclic voltammetry of electric double-layer formation in porous electrodes. We find that the dimensionless combination omega tau(n), with omega the scan frequency of the time-dependent potential and tau(n) the relaxation timescale of the stack-electrode model, governs the CV curves and capacitance: the capacitance is scan-rate independent for omega tau(n) << 1 and scan-rate dependent for omega tau(n) >> 1. With a single fit parameter and all other model parameters dictated by experiments, our model reproduces experimental CV curves over a wide range of omega. Meanwhile, the influence of the pore size distribution on the charging dynamics is investigated to explain the experimental data.

Automated summary

In this Letter, a microscopic stack-electrode model and its equivalent circuit are used to predict the cyclic voltammetry (CV) of electric double-layer formation in porous electrodes. It is found that the dimensionless combination of ωτ(n) governs the CV curves and capacitance. The model reproduces experimental CV curves with a single fit parameter and investigates the influence of pore size distribution on the charging dynamics to explain the experimental data.