PDF Publication Title:
Text from PDF Page: 197
6.3. Impedance response – Nyquist plot features Nyquist plot of two-electrode Li/S response is shown on Figure 6-1. Three regions with different time constants can be clearly distinguished and are separated by vertical dot lines for easier visualization. (a) (b) Figure 6-1. Nyquist plot of a Li/S cell at the initial state (a) and corresponding equivalent circuit (b). As previously described in section 2.3.3, (where symmetric coin cells tests were discussed), high frequency (HF) region can be attributed to the ohmic resistance of the cell, resulting from electrolyte resistance, coin cells casing, sample holder, leads and terminals and is represented by a pure resistor (R). A depressed semicircle in the middle frequency (MF) part is usually modeled with a resistor (R) in parallel with a constant phase element (CPE). A straight vertical line in the very low frequency region (LF) indicates blocking character of the system vs. electrochemical reaction. However, the porous character of the electrode leads to a distribution of the local interfacial capacity observed at the beginning of the low frequency straight line228. A CPE can be also proposed for modeling this part of the spectra212 in the situations when the inclined line (due to local interfacial capacity distribution) and the blocking part (a purely vertical straight line) are not well-separated in frequency. While the literature data are in agreement when it comes to the HF and LF regions interpretation, the origin of the MF semicircle is still controversial. Proposed interpretations are: charge transfer resistance (often attributed to the positive electrode solely) and its relevant capacitance132, electronic contact resistance in the bulk electrode212. To our best knowledge, most of the existing reports about EIS applied to Li/S batteries were based on two-electrode cells, very often without deeper discussion concerning the separation of each electrode contribution. Therefore, the first step of our studies, before moving to in situ methodology, was Chapter 6: EIS and low temperature studies 193PDF Image | Accumulateur Lithium Soufre
PDF Search Title:
Accumulateur Lithium SoufreOriginal File Name Searched:
WALUS_2015_archivage.pdfDIY PDF Search: Google It | Yahoo | Bing
Sulfur Deposition on Carbon Nanofibers using Supercritical CO2 Sulfur Deposition on Carbon Nanofibers using Supercritical CO2. Gamma sulfur also known as mother of pearl sulfur and nacreous sulfur... More Info
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |