Model reduction of fractional impedance spectra for time–frequency analysis of batteries, fuel cells, and supercapacitors

Abstract

Joint time–frequency analysis is an emerging method for interpreting the underlying physics in fuel cells, batteries, and supercapacitors. To increase the reliability of time–frequency analysis, a theoretical correlation between frequency‐domain stationary analysis and time‐domain transient analysis is urgently required. The present work formularizes a thorough model reduction of fractional impedance spectra for electrochemical energy devices involving not only the model reduction from fractional‐order models to integer‐order models and from high‐ to low‐order RC circuits but also insight into the evolution of the characteristic time constants during the whole reduction process. The following work has been carried out: (i) the model‐reduction theory is addressed for typical Warburg elements and RC circuits based on the continued fraction expansion theory and the response error minimization technique, respectively; (ii) the order effect on the model reduction of typical Warburg elements is quantitatively evaluated by time–frequency analysis; (iii) the results of time–frequency analysis are confirmed to be useful to determine the reduction order in terms of the kinetic information needed to be captured; and (iv) the results of time–frequency analysis are validated for the model reduction of fractional impedance spectra for lithium‐ion batteries, supercapacitors, and solid oxide fuel cells. In turn, the numerical validation has demonstrated the powerful function of the joint time–frequency analysis. The thorough model reduction of fractional impedance spectra addressed in the present work not only clarifies the relationship between time‐domain transient analysis and frequency‐domain stationary analysis but also enhances the reliability of the joint time–frequency analysis for electrochemical energy devices.

Electrospinning-derived transition metal/carbon nanofiber composites as electrocatalysts for Zn-air batteries

“…In recent years, there has been a heightened emphasis on environmentally sustainable and renewable energy sources, driven by the depletion and pollution associated with mineral and fossil fuel resources. 1 Among various electrochemical energy conversion and storage technologies, fuel cells have garnered considerable scholarly attention due to their capacity to directly convert chemical energy into electricity, accompanied by notable advantages such as high energy density, cleanliness, safety, and lack of pollution. 2 Zn-air batteries (ZABs), a distinct subclass of fuel cells, have emerged as a promising alternative to lithium-ion batteries owing to their superior theoretical specific capacity, cost-effectiveness, and enhanced energy conversion rates.…”