Modeling of Equivalent Circuit Analysis of Degraded Electric Double-Layer Capacitors

Tomoki Omori,Daisuke Tashima,Masahiro Nakanishi

doi:10.3390/ma14020435

Tomoki Omori, Daisuke Tashima + Show 1 more

Open Access

https://doi.org/10.3390/ma14020435

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Journal: Materials	Publication Date: Jan 17, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: Fukuoka Institute of Technology

Abstract

The demand for electric double-layer capacitors (EDLCs) has recently increased, especially for regenerative braking systems in electric or hybrid vehicles. However, using EDLCs under high temperature often enhances their degradation. Continuously monitoring EDLC degradation is important to prevent sudden malfunction and rapid drops in efficiency. Therefore, it is useful to diagnose the degradation at a lower frequency than that used in charge/discharge. Unused and degraded EDLCs were analyzed using the alternating current impedance method for measurements over a wide frequency range. Each result had a different spectrum up to 1 kHz. In addition, we show the basic inside condition of EDLCs with equivalent circuit analysis. This paper explores the possibility of degradation diagnosis at a high frequency and the basic physical mechanism.

Highlights

Electric double-layer capacitors (EDLCs) are energy storage devices that store energy by forming an electric double layer between a porous electrode and an electrolyte [1,2].EDLCs are characterized by their ability to rapidly charge and discharge
EDLCs are increasingly used as energy storage devices for electric vehicles, wind turbines, and solar power generators [4–8]
The degradation of EDLCs is enhanced by harsh environments, such as high temperature and voltage [9–15], and EDLCs are exposed to such environments in vehicles

Summary

Introduction

Electric double-layer capacitors (EDLCs) are energy storage devices that store energy by forming an electric double layer between a porous electrode and an electrolyte [1,2]. EDLCs are characterized by their ability to rapidly charge and discharge They have a long life and are virtually maintenance-free owing to no chemical changes [3–6]. Due to these advantages, EDLCs are increasingly used as energy storage devices for electric vehicles, wind turbines, and solar power generators [4–8]. We especially focus on a higher-frequency impedance rather than the timescale of charge and discharge. A diagnosis circuit at a higher frequency has the advantage of a high diagnostic speed. EDLCs over ried out alternating current impedance measurements on unused and degraded. EDLCs ried out alternating current impedance measurements ontheir unused and spectra degraded.

Materials and

Equivalent of an EDLCresults for the unused and degraded EDLCs using

Capacitance impedance measurements of the unused degraded

Hz was the cause

Internal Model of EDLC Degradation

Conclusions