Chemistry Teacher International (Mar 2021)
Basics of teaching electrochemical impedance spectroscopy of electrolytes for ion-rechargeable batteries – part 1: a good practice on estimation of bulk resistance of solid polymer electrolytes
Abstract
In this publication, we present the basic to characterize the electrical properties of electrolytes that are widely used in ion-rechargeable batteries using electrochemical impedance spectroscopy (EIS). This simplified yet insightful background provided may be used for educational purposes, especially for beginners or young researchers for both undergraduate and postgraduate students. We start with introduction of electrolytes and electrochemical impedance spectroscopy (EIS) instrumentation, following with the step-by-step guidelines using three different procedures to estimate the bulk resistance (Rb) of the electrolytes, which is inversely proportional to the conductivity (σDC) of the materials Rb∝1/σDC$\left({R}_{\mathrm{b}}\propto 1/{\sigma }_{\mathrm{DC}}\right)$. Several examples and exercises on estimation of quantity Rb are supplemented for educational purposes. Comparison was made on estimation of Rb using manual graphical procedures, mathematical regression procedures using commercial graphical software and equivalent circuit fitting procedures using exclusive EIS software. The results suggest that the manual graphical technique may serves as a useful approach for beginners before venturing to exclusive software. Besides, the instructors may use the procedures to coach the users to extract reliable and reproducible data before data interpretation. Lastly, the phenomenological approach on dielectric relaxation for solid polymer electrolytes [poly(ethylene oxide) (PEO) + lithium salt] and non-solid polymer electrolytes [poly(methyl acrylate) (PMA) + lithium salt], in the classic sense will be addressed in terms of impedance (Z*), permittivity (ε*), tangent loss (tan δ), modulus (M*) and conductivity (σ*) spectra in Part 2.
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