Pr. Janusz Smulko

Gdańsk University of Technology, Poland

 

Talk Title
State-of-Health Assessment of Electric Double-Layer Capacitors (EDLCs) by Random Fluctuations
Talk Abstract

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Electrostatic double-layer capacitors (EDLCs) comprise of porous carbon electrodes and electrolyte achieving high capacitance which may be used for rapid charging and discharging. This feature is vital for numerous applications where fast energy delivery is a request. This ability is due to a large active area of porous electrodes and ions penetrating inside the pores. Mechanisms of ions penetrations are still under investigation and require more in-depth studies for various electrolytes and electrodes of different pores dimensions. These mechanisms determine the ability of charge storage and fast energy delivery, and therefore are worthy of detailed investigation. We know that flicker (1/f-like) noise phenomena depends on any structural changes in numerous electronic devices (e.g., semiconductor materials, porous gas sensing layers). Corrosion events generate low-frequency noise as well. This nose is called electrochemical noise and is induced by pitting corrosion events. Therefore, we may expect similar dependence between the state of the electrode-electrolyte interface and 1/f-like noise generation. Additionally, white noise component may also shed light on the state of the electrode-electrolyte interface in a similar way as used for determination of uniform corrosion rate. In our experimental studies, we consider both noise components and propose how to utilize the observed results for determining the state-of-health of the EDLC structure.

Random fluctuations can be observed in the EDLCs structures at low-frequency range only due to high RC values. The EDLC is characterized by a capacitance C of at least a few or even more Farads and equivalent serial resistance R of about a few tenths of Ohm. These conditions require a stable measurement set-up to observe such slowly changing random phenomena and of low intensity, close to inherent noise of the set-up. We were able to identify noise generated in the EDLCs structures during discharging when DC voltage between the terminals reached tens of mV only. Observed noise comprised of 1/f-like noise component at low frequencies below 1 Hz and white noise above. The estimated power spectral densities required a few hours of voltage samples recording in our experimental studies to observe noise at the frequencies of tens of mHz. Both components changed their levels when the EDLC was aged by floating (kept at constant voltage when charged). We explain how the aging processes determined changes of noise levels. White noise intensified because the charge transfer resistance increased by aging.  Flicker noise increased due to pores blocking and local delamination of porous electrodes.

We propose to utilize the observed results to determine the state-of-health of the studied EDLCs by the simplified measurement method. The method may be applied to monitor the EDLC when working by limiting measurement time and requirements for low-level voltage measurements. Moreover, the technique requires cheap electronics to estimate noise intensity at selected frequency bandwidth.

Short Biography

Janusz Smulko (born April 25, 1964 in Kolno, Poland) - Polish electronics, full professor of Gdańsk University of Technology. Research Interests: reliability assessment of electronic devices (electrochromic materials, supercapacitorsvaristors, thin metal foil capacitors), fluctuation-enhanced sensing (various systems and sensors), gas sensingRaman spectroscopy, noise in biological systems, signal processing. Since September 2016 – Vice-Rector for Scientific Research, Gdańsk University of Technology, Poland.

 
Talk Keywords
Noise, state-of-health, supercapacitor, low-voltage measurements.
 
Target Audience
Students, Post doctoral, Industry, Doctors and professors
 
Speaker-intro video
TBA
 

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