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Chapter 3: Porous 3D carbon current collector - a potential way for the electrode improvements In the previous paragraph we saw the performances of a simply prepared positive electrodes, coated on aluminum foil – a current collector mostly used for cathodes fabrication. It was indeed shown that very high loadings of sulfur (even 5.7 mg cm-2) can be prepared, with relatively good discharge capacities obtained at slow (C/20) rates. However, after the active material leaves the electrode and dissolves in the electrolyte, strong pulverization could appear, thus the carbon/binder matrix and the conductive network through the whole electrode thickness may be strongly affected. When applying higher currents (C/5) for such highly loaded electrodes, high polarization occurs, resulting in much lower capacities and probably not complete sulfur utilization. Another way to increase the electrode loading and to improve the mechanical integrity of the global electrode, without sacrificing capacity values, is to use a 3D type porous current collector. Indeed, a 3D collectors provide cohesive conductive network along with a stable surface area during cycling for the deposition of solid reaction products. A non-woven carbon tissue (NwC) has already been applied to the Li/S batteries by the former PhD student in our groups, mainly as a current collector in a ‘catholyte’ cell architecture (semi-liquid cell)45,126. The literature also presents electrodes with porous carbon collectors128,104,129-133, with successfully improved electrochemical performances, as demonstrated in the state of the art review (section 1.3.1.d). Therefore, we applied such NwC collector in our simply prepared electrodes. We mostly focused on understanding how the electrode’s performances may get improved when using such type of collector. Different aspects were taken into consideration, i.e. surface area, electrolyte amount, porosity, etc. Apart from aiming to obtain better cycling performances, the point of view of going deeper into understanding the Li/S system, its functioning and limitations, was always kept in mind. 3.1. Non-woven carbon felt (NwC) - physical and structural properties Non-woven carbon tissue used in this work is a GDL felt (gas diffusion layer), produced by Freudenberg under its commercial name H2315. It is an electronically conductive and porous material composed of randomly dispersed carbon fibers of ~ Ø 10 μm approximately. It 71 Chapter 3: S8 electrode on NwCPDF 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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