![]() ![]() Additionally, the migration of ions across the liquid electrolyte contained in a separator is observed as a high-frequency intercept along the x-axis of the complex impedance plot (also called the Nyquist plot). semi-circles in the complex impedance plots). In the ideal case, the impedance spectrum contains a separate feature for each elementary process that constitute the overall electrochemical mechanism.Īlready a basic EIS measurement of a typical electrochemical energy storage cell, in which the whole system between both cell’s electrodes is probed, may produce a spectrum in which the reaction(s) that occur on the positive and negative electrode are observed as (well) separated features (e.g. By measuring the response (current or potential) of the system to this perturbation, the corresponding transfer function, that is the impedance of the system, can be calculated 2. Both features can be achieved using a small-amplitude potential or current periodic perturbation to excite the electrochemical system at different frequencies. However, the system must remain in a stationary state throughout the EIS measurement. The main strength of EIS is its ability to effectively deconvolute complex electrochemical processes into a series of basic processes based on the different relaxation times. Generally, such processes involve the dynamics of bound or mobile charge in the bulk or interfacial regions of any liquid or solid material: ionic, semiconducting, mixed electronic-ionic and even insulators (dielectrics) 1. Electrochemical impedance spectroscopy (EIS) is a powerful technique for investigating processes occurring in electrochemical systems. ![]()
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