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(a) (b) Chapter 2: S8 electrode on Aluminum Figure 2-19. Galvanostatic cycling results of sulfur electrodes (S/SuperP®/binder = 80/10/10 wt%) with different binders, in regard to binder type, i.e. CMC and PVdF, and the way it was incorporated: PVdFmanual (in black), PVdFdispermat (in red) and CMCdispermat (in blue). Three cells were of relatively high and similar sulfur loading ~ 4.5 mgsulfur cm-2. Initial cycle voltage profile recorded at C/5 (a) and corresponding capacity retention upon 100 cycles (b). We can see that the polarization of PVdFmanual electrode is the highest, especially during the second plateau, while CMC one displays the lowest overpotential. Consequently, initial discharge capacities were 621, 529 and 406 mAh g-1, obtained for CMC, PVdFdispermat and PVdFmanual respectively. The difference could directly be associated with the polarization effect. Indeed, the amounts of sulfur oxidized in the three cells are very close (same length of high voltage plateau upon discharge, of ~ 280 mAh g-1), while the capacity decrease is mainly due to the reduction of the lower discharge plateau. This observation may relate to the fact that the low voltage plateau is definitely linked to the electrode morphology, its homogeneity and conductivity, and it could be expected to be linked to the way the electrode was fabricated. One should, however, note that the capacity retention over 100 cycles was proportional to the initial values. Figure 2-20 presents the capacity evolution versus C-rate for the three formulated electrodes. The compared electrodes are of high sulfur loadings (~ 5.6 – 7.5 mgSulfur cm-2). However, due to not exactly the same loadings, direct quantitative comparison of the capacity values is difficult, and large dispersions of the data can be obtained. Nevertheless, the evolution of the capacity vs. C-rate could give some information about the limiting processes. Rather stable capacity value is obtained up to C/5 rate, with the exception for PVdFmanual, which starts to slowly loose its capacity at this rate. However, limiting processes start to be visible already at C/2 or 1C rates, and these are much lower C-rates values than what is generally observed in classical Li-ion cells11,230. Such behavior may be associated with the solubility of the active species, i.e. electrochemical reaction requires mass transport through the electrolyte and to the electrode. Furthermore, the fact of using very thick separators (Viledon® + Celgard®2400 with 67PDF Image | Accumulateur Lithium Soufre
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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
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