Study on advanced electrolyte for improving electrochemical performance of lithium-sulfur batteries

Battery Science & TechnologyLithium-sulfur (Li-S) batteries have been drawing attention as one of the high density energy storage devices due to their high theoretical capacity (1,672mAhr g-1), high theoretical energy density (2600Wh kg-1), which is 3 to 5 times higher than that of Li ion batteries based on intercalation reactions, eco-friendliness and low cost. In spite of these advantages, there are many problems that hinder practical applications. The challenges are attributed to the solubility of the polysulfide ions (Sn2-) formed on electrochemical reduction of S8 or on electrochemical oxidation of insoluble sulfides. In the first discharge step, electrochemical conversion of S8 to form S42- occurs through a sequence of soluble molecular poly-sulfides. The formation of insoluble Li2S2 is hindered and conversion of Li2S2 to Li2S as the last discharge step is the most difficult. In addition, Li metal as an anode in Li-S batteries is problematic when it is contact with any kind of liquid electrolyte solution, because of it`s high reactivity. Li metal would result in poor cycling efficiencies due to the severe growth of the SEI layer and Li dendrite formation. Moreover, insulating products layer such as Li2S and Li2S2 on Li anode can be formed by the reaction of Li and soluble polysulfide intermediates Li2Sn (4≤n≤6), which are diffused from the cathode. This study is concerned with the understanding and the improvement of Li-S battery. In order to understand basic operation mechanism of Li-S battery, structural evolution of sulfur cathode and lithium anode was investigated by using Raman spectroscopy and X-ray diffraction during discharge and charge. With based on such understanding, the improvement of Li-S battery was also performed by using protection layer with FEC based electrolytes . The effect of solvents on the discharge behavior of Li-S cells was investigated by ex situ Raman spectroscopy and X-ray diffraction. Lithium polysulfide species formed in a sulfur cathode during cycling are characterized by Raman experiments for the first time and their structures are examined with regard to three different electrolytes at fully charged and discharged states. Moreover, ex-situ Raman studies give the evidence for the formation of lithium polysulfide on a Li metal anode by shuttle phenomena and the coexistence of soluble lithium polysulfide with elemental sulfur even after full charge. It was found that 1,3-dioxolane (DOX)/1M LiTFSI facilitates the migration of soluble lithium polysulfide toward a lithium anode and initiates a polysulfide shuttle causing a considerable capacity loss in Li-S cells. Raman results and cycling tests using an air-tight cell demonstrated that tetra(ethylene glycol) dimethyl ether (TEGDME)-based electrolytes hindered the significant overcharge and led to the formation of Li2S2 contributing to high discharge capacity through further electrochemical reduction to Li2S. In addition, the impact of a fluoroethylene carbonate (FEC) solvent on the electrochemical performance of Li-Li and Li-S cells was investigated. To confirm the effects of FEC on electrolyte decomposition and cell resistance, the surface chemistry and impedance of a Li electrode cycled in electrolytes with and without a FEC solvent were investigated using attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (ToF-SIMS), and electrochemical impedance spectroscopy. It is found that the protective layer with FEC hinders the migration of soluble lithium polysulfides toward a Li metal electrode and results in the suppression of overcharging of Li-S cells.ope

Intra-arterial delivery of triolein emulsion increases vascular permeability in skeletal muscles of rabbits

<p>Abstract</p> <p>Background</p> <p>To test the hypothesis that triolein emulsion will increase vascular permeability of skeletal muscle.</p> <p>Methods</p> <p>Triolein emulsion was infused into the superficial femoral artery in rabbits (triolein group, n = 12). As a control, saline was infused (saline group, n = 18). Pre- and post-contrast T1-weighted MR images were obtained two hours after infusion. The MR images were qualitatively and quantitatively evaluated by assessing the contrast enhancement of the ipsilateral muscles. Histologic examination was performed in all rabbits.</p> <p>Results</p> <p>The ipsilateral muscles of the rabbits in the triolein group showed contrast enhancement, as opposed to in the ipsilateral muscles of the rabbits in the saline group. The contrast enhancement of the lesions was statistically significant (p < 0.001). Histologic findings showed that most examination areas of the triolein and saline groups had a normal appearance.</p> <p>Conclusion</p> <p>Rabbit thigh muscle revealed significantly increased vascular permeability with triolein emulsion; this was clearly demonstrated on the postcontrast MR images.</p

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Wintertime marine extreme temperature events modulate phytoplankton blooms in the North Pacific through subtropical mode water

Marine extreme temperature events (METs), including marine heatwaves (MHWs) and cold spells, have recently gained much attention owing to their vital influence on the marine ecosystem and social economy. Since METs can alter the upper ocean stratification and wintertime convective mixing in the northwestern North Pacific subtropical gyre (NPSG), their activities may modulate phytoplankton blooms by regulating entrainment of the subtropical mode water (STMW) with high NO $_{3}^{-}$ . Furthermore, because STMW formed in the previous winter reemerges east of its formation site in the following winter, the METs activities imprinted in STMW affect phytoplankton blooms remote from its formation site. Here, we examined the relationship between the MET activities, STMW volume, and phytoplankton blooms using satellite observations and a data-assimilative coupled physical-biogeochemical model dataset. MET activities appearing in the STMW formation region during winter regulate the formation of STMW and the supply of NO $_{3}^{-}$ from the subsurface, with the latter controlling the spring/autumn blooms in that region under NO $_{3}^{-}$ -limited conditions. Subsequently, this water mass is transported eastward in the subsurface within the northern flank of the NPSG before reemerging east of the STMW formation site the following spring. This process results in a negative lag-correlation between MET activities and surface chlorophyll in the reemergence region; for example, MHWs in winter at the STMW formation site tend to lower the surface chlorophyll concentration one year later in the reemergence region. Our study suggests that the oceanic processes allow one year of predictability of the marine ecosystems by monitoring METs in the STMW formation site