PDF Publication Title:
Text from PDF Page: 141
be seen, i.e. rapid capacity fading during initial cycles followed by rather stable value. Discharge capacity values recorded at 50th cycle are 264, 170 and 161 mAh g-1 for the cells cycled at C/20, C/10 and C/5 respectively. 4.2.7. Strategies for the improvement In the previous sections we saw that by performing the charge to higher voltage limit or using very low currents (C/100), it is possible to reach almost complete theoretical capacity of Li2S (1166 mAh g-1). However, both of these solutions are subjected to some risks, like possible electrolyte degradation (when charging to 4.0 V) or strong shuttle phenomenon (when applying very low C-rates). Moreover, several electrodes exhibited very strong initial polarization and not-reproducible shape of charge voltage (lack of reproducibility of the electrodes). One of the alternative solutions would thus consist in performing the particle size reduction in order to provide better contact between Li2S/carbon. For that purpose, mechanical ball-milling on Li2S powder was performed, and the effect of such treatment was investigated. Even if high charge capacity values could be reached, discharge capacities of ~ 650 ± 50 mAh g-1 could be obtained at most. One of the reason for incomplete discharge capacity might arise from the lack of (i) sufficient conductive and accessible surface area for ‘welcoming’ all solid discharge products and/or (ii) not sufficient accessibility of created polysulfides to the whole conductive surface present in the electrode. In this manner, a proposed solution consists in utilizing a carbon-based current collector paper (NwC) for Li2S positive electrode, which has previously proven to have very beneficial effect, when applied for sulfur positive electrode. 4.2.7.a) The effect of a ball-milling Two ball-milling equipments, different in terms of energy, were used for grinding Li2S powder with SuperP®, aiming for particle size reduction together with providing better contact between both powders. In both cases, the final electrode composition was designed to be 70/20/10 wt% (‘reference’ composition). No additional grinding with SuperP® in a mortar was performed after the ball-milling and prior to electrode preparation. Therefore, the ball-milling containers were filled directly with appropriate amounts of powders inside the glove box, i.e. 0.6 g of Li2S‡ and 0.17 g of SuperP®. The containers were then tightly closed to provide hermetical sealing and avoid any contact of Li2S powder with air during the ball milling process (performed outside the glove box). Planetary ball milling (RETSCH) was done in a 50 mL ‡ Since two ball-milling treatments were not performed in the same interval of time, batch of active material powder was not the same. Li2S purchased from Sigma Aldrich was used for planetary ball milling, while Li2S from Alfa Aesar was used for high energy ball milling. Chapter 4: Li2S electrode 137PDF 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 (Standard Web Page)