Analysis of impedance spectroscopy of aqueous supercapacitors by evolutionary programming: Finding DFRT from complex capacitance

Abstract

Electrochemical impedance spectroscopy (EIS) of aqueous-electrolyte supercapacitors can shed light on the physical processes occurring within the cell, given a proper analysis technique. Impedance Spectroscopy Genetic Programming (ISGP) is a novel technique to analyze EIS data. ISGP finds a functional form of the distribution of relaxation times utilizing genetic algorithm and offers a detailed quantitative analysis.

In this work, EIS data of aqueous-electrolyte supercapacitors were analyzed by transforming the data to complex capacitance representation. A distribution function of relaxation times (DFRT) model was obtained, comprised of two peaks, each correlated with a different physical process (diffusion and EDLC formation). Two cell configurations were examined and the differences regarding capacitance distribution and diffusion rates are presented.

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