Abstract
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 (R b) of the electrolytes, which is inversely proportional to the conductivity (σ DC) of the materials R b ∝ 1 / σ DC $\left({R}_{\mathrm{b}}\propto 1/{\sigma }_{\mathrm{DC}}\right)$ . Several examples and exercises on estimation of quantity R b are supplemented for educational purposes. Comparison was made on estimation of R b 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.
Highlights
IntroductionElectrolyte is an electrically conducting solution when a substance (e.g., ionic compound, dipolar entity etc.) dissolve in a polar matrix (e.g., polar solvent)
Electrolytes and batteriesElectrolyte is an electrically conducting solution when a substance dissolve in a polar matrix
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)
Summary
Electrolyte is an electrically conducting solution when a substance (e.g., ionic compound, dipolar entity etc.) dissolve in a polar matrix (e.g., polar solvent). The redox reaction can be reversed by means of applying an external electric potential (voltage) to produce complementary redox reaction at the electrodes This configuration is a non-spontaneous and energy-dependent process, which can be observed in the rechargeable battery (secondary) that is in the charged state (electrolytic cell) (Learn Engineering, 2019; Ramström, 2019). When a dielectric material (in this case, the SPE) is placed in between two electrodes under an electric field, the randomly oriented dipolar entities will start to align towards the direction of the oppositely charged electrodes. For Nyquist plot, the frequency is hidden and for Bode plot, the frequency is explicit These two plots are the key quantities of the interest in estimation of electric and dielectric properties of the SPEs and non-SPEs and their interfaces with electrodes (Chan & Kammer, 2015, 2018, 2020). The estimation of bulk resistance of SPEs and non-SPEs from Nyquist plots is discussed in Part 1 of this article and the other dielectric response of SPE and non-SPE in the frequency-dependant plot (or Bode plots) will be presented from the phenomenological point of view in the article as Part 2
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