Electrochemical Impedance Spectroscopy Part 2: Applications (Presentation File and EIS Calculation Sheet)

 This supplementary material is a part of the presentation handout, pages 155–180, for the 51st Electrochemistry Workshop entitled “Fundamentals and New Approaches to Electrochemistry” organized by Kansai Branch of the Electrochemical Society of Japan on November 14–18, 2022 to be distributed at the workshop. / Electrochemical impedance spectroscopy (EIS) is widely used for the analysis of various electrochemical devices, as it can quantitatively evaluate the main kinetic parameters related to electrochemical phenomena by analysis using equivalent circuits. This paper describes practical applications of EIS, along with EIS measurement and analysis methods for solid electrolytes, Li-ion batteries (LIBs), and electric double-layer capacitors (EDLCs). In all applications, it is necessary to properly measure the impedance data for an adequate equivalent circuit analysis. Therefore, after presenting the backgrounds of EIS applications in the Section 1 (Introduction), the experimental cautions in the measurements are discussed in detail in Sections 2–4. Section 2 (“EIS for Solid Electrolytes”) presents practical examples of measurements for accurate data, as the EIS analysis of solid electrolytes requires impedance data in the high-frequency range above 1 MHz. Section 3 (“EIS for Lithium-Ion Batteries”) describes a method of separating the internal resistance into the resistances of the positive and negative electrodes and electrolyte resistance, as the output power capabilities of LIBs are frequently evaluated based on an internal resistance. In particular, a symmetrical cell technique enabling measurements of the impedance data only for the positive or negative electrode is demonstrated. As described in Section 4 (“EIS for Electric Double-Layer Capacitors”), the excessive and unwanted impedances arising from instruments and cells must be suppressed as much as possible for appropriately measuring the correct EIS of EDLCs, because the resistance of EDLCs is very small. Therefore, the experimental setup that should be considered in EIS measurements for EDLCs leading to disturbed impedance data is discussed, along with the effects of this scenario on the impedance data. Finally, we summarize our conclusions in Section 5 (Summary).