In-situ synthesis Fe3C@C/rGO as matrix for high performance lithium-sulfur batteries at room and low temperatures

People have been focusing on how to improve the specific capacity and cycling stability of lithium-sulfur batteries at room temperature, however, on some special occasions such as cold cities and aerospace fields, the operating temperature is low, which dramatically hinders the performance of batteries. Here, we report an iron carbide (Fe3C)/rGO composite as electrode host, the Fe3C nanoparticles in the composite have strong adsorption and high catalytic ability for polysulfide. The rGO makes the distribution of Fe3C nanoparticles more disperse, and this specific structure makes the deposition of Li2S more uniform. Therefore, it realizes the rapid transformation and high performance of lithium-sulfur batteries at both room and low temperatures. At room temperature, after 100 cycles at 1C current density, the reversible specific capacity of the battery can be stabilized at 889 ± 7.1 mAh/g. Even at -40 °C, in the first cycle battery still emits 542.9 ± 3.7 mAh/g specific capacity. This broadens the operating temperature for lithium-sulfur batteries and also provides a new idea for the selection of host materials for sulfur in low-temperature lithium-sulfur batteries.

Synthesis of Low-Cost and High-Performance Dual-Atom Doped Carbon-Based Materials with a Simple Green Route as Anodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are promising alternatives to replace lithium-ion batteries as future energy storage batteries because of their abundant sodium resources, low cost, and high charging efficiency. In order to match the high energy capacity and density, designing an atomically doped carbonous material as the anode is presently one of the important strategies to commercialize SIBs. In this work, we report the preparation of high-performance dual-atom-doped carbon (C) materials using low-cost corn starch and thiourea (CH4N2S) as the precursors. The electronegativity and radii of the doped atoms and C are different, which can vary the embedding properties of sodium ions (Na+) into/on C. As sulfur (S) can effectively expand the layer spacing, it provides more channels for embedding and de-embedding Na+. The synergistic effect of N and S co-doping can remarkably boost the performance of SIBs. The capacity is preserved at 400 mAh g -1 after 200 cycles at 500 mA g-1; more notably, the initial Coulombic efficiency is 81%. Even at a high rate of high current of 10 A g-1, the cell capacity can still reach 170 mAh g-1. More importantly, after 3000 cycles at 1 A g-1, the capacity decay is less than 0.003% per cycle, which demonstrates its excellent electrochemical performance. These results indicate that high-performance carbon materials can be prepared using low-cost corn starch and thiourea.

Thin Nano Cages with Limited Hollow Space for Ultrahigh Sulfur Loading Lithium-Sulfur Batteries

Owning to its various advantages, the lithium-sulfur battery is one of the research hot spots for new energy storage systems. Diverse hollow structures with specific morphologies have been used as the sulfur host materials to adsorb or/and catalyze the polysulfides, and can in particular concurrently inhibit the volume expansion during electrochemical processes in lithium-sulfur batteries. However, hollow space with a large volume will restrict the performance of the cell under high sulfur area loading, which is a very important indicator for the practical applications of the lithium-sulfur battery. Here, we report a nano thin cage cobalt acid zinc (ZnCo₂O₄) with limited hollow space as the cathode catalyst for lithium-sulfur batteries, which greatly reduces the electrode volume occupied by the hollow structure. The hollow volume of these thin cages is much smaller than those of the normally reported hollow materials in the literatue. The electrochemical performance of lithium-sulfur batteries with ZnCo₂O₄ thin cages could greatly improve due to the unique structure and the synergistic adsorption/catalytic effect of Zn/Co sites, especially at an ultrahigh S area load. Under a high S loading of 8 mg cm^-2, the cell could keep a reversible capacity of 600 mAh g^-1 after 500 cycles. Even at a sulfur loading of 10 mg cm^-2, the cell still releases a discharge capacity of 1000 mAh g^-1 which is equivalent of an area capacity of 10 mAh cm^-2. This work provides a feasible way to develop lithium sulfur batteries with a high area sulfur load. This idea provides a possible solution to develop a Li-S battery at high area S loading and move one step closer to the practical applications.

An 8-week brain MRI follow-up analysis of rat eosinophilic meningitis caused by Angiostrongylus cantonensis infection

Early differential diagnosis and timely follow-up are advantageous in the management of Angiostrongylus cantonensis infection. This study aimed to characterize angiostrongyliasis in the rat brain for an 8-week period using magnetic resonance imaging (MRI) with contrast-enhanced T1-weighted images (T1WI), T2-weighted imaging (T2WI), fluid attenuation inversion recovery (FLAIR) and R2 mapping sequences. The data were analysed with Mathematica and Matlab software programs for weekly changes in each brain following the infection of 20, 50, 100 and 300 third-stage larvae (L3), respectively. The results showed that the average subarachnoid space detected by T2WI technique was peaked up to 10% increase of original size on day 35 after 100 or 300 larvae infection, while those infected with 20 or 50 larvae showed less than 4% increase during the entire course of observation. This increase was relevant to the mortality of the infected rats, because those with 100 or 300 larvae infections showed a sharp decrease in survival rate before day 40. After day 40, the average subarachnoid space was decreased, but the average ventricle size was persistently increased, with the highest increase observed in the group infected with 300 larvae on day 56. Furthermore, the R2 mapping mean and R2 mapping size were significantly different between the brains with severe infection (100 and 300 larvae groups together) and those with mild infection (20 and 50 larvae groups together) on day 49, but not on day 35. Our results showed that diagnosis for different quantity of larvae infection using MRI is possible and follow-up characterization is informative in revealing the effects of angiostrongyliasis on different brain areas. In conclusion, our results support the use of MRI as a non-invasive diagnostic technique for eosinophilic meningitis caused by A. cantonensis infection.

Carbon dioxide laser surgery for snoring: results in 192 patients

Laser-assisted uvulopalatoplasty has been introduced as an alternative to uvulopalatopharyngoplasty for treatment of snoring and potentially of obstructive sleep apnea syndrome. Between July 1994 and June 1996, 192 patients underwent 227 laser-assisted uvulopalatoplasty procedures. Loud habitual snoring was evaluated in 42 women (21.8%) and 150 men (78.2%), who were then treated with laser-assisted uvulopalatoplasty. Among the 192 patients (227 procedures), with ages from 18 to 81 years (mean 42.6 years), 15.6% (30 patients) had more than one laser-assisted uvulopalatoplasty treatment. In our series, 80 patients (42.1%) had a history of obstructive sleep apnea syndrome in addition to snoring. Laser-assisted uvulopalatoplasty treatment in patients with loud snoring resulted in elimination of snoring in 61%, partial improvement of snoring in 26%, and no improvement in 13%. The overall success rate was 87%. The mean body mass index was significantly higher in the patients with no response after the operation (27.9 kg/m2) compared with that in the patients with a good response (25.9 kg/m2). Obese (body mass index >30 kg/m2) patients were more likely to have no response to laser-assisted uvulopalatoplasty treatment of snoring than patients with an ideal body weight (body mass index <25 kg/m2) (p < 0.01). We conclude that the body mass index may be of significant value in the postoperative success rate of laser-assisted uvulopalatoplasty for the treatment of snoring.