P-P Orbital Interaction Enables Single-Crystalline Semimetallic ß-MoTe2 Nanosheets as Efficient Electrocatalysts for Lithium-Sulfur Batteries.

The practical implementation of lithium-sulfur batteries (LSBs) has been impeded by the sluggish redox kinetics of lithium polysulfides (LiPSs) and shuttle effect of soluble LiPSs during charge/discharge. It is desirable to exploit materials combining superior electrical conductivity with excellent catalytic activity for use as electrocatalysts in LSBs. Herein, we report the employment of chemical vapor transport (CVT) method followed by an electrochemical intercalation process to fabricate high-quality single-crystalline semimetallic ß-MoTe2 nanosheets, which are utilized to manipulate the LiPSs conversion kinetics. The first-principles calculations prove that ß-MoTe2 could lower the Gibbs free-energy barrier for Li2S2 transformation to Li2S. The wavefunction analysis demonstrates that the p-p orbital interaction between Te p and S p orbitals accounts for the strong electronic interaction between the ß-MoTe2 surface and Li2S2/Li2S, making bonding and electron transfer more efficient. As a result, a ß-MoTe2/CNT@S-based LSB cell can deliver an excellent cycling performance with a low capacity fade rate of 0.11% per cycle over 300 cycles at 1C. Our work might not only provide a universal route to prepare high-quality single-crystalline transition-metal dichalcogenides (TMDs) nanosheets for use as electrocatalysts in LSBs, but also suggest a different viewpoint for the rational design of LiPSs conversion electrocatalysts.

Polyacrylonitrile Porous Membrane-Based Gel Polymer Electrolyte by In Situ Free-Radical Polymerization for Stable Li Metal Batteries.

Because of their high ionic conductivity, utilizing gel polymer electrolytes (GPEs) is thought to be an effective way to accomplish high-energy-density batteries. Nevertheless, most GPEs have poor adaptability to Ni-rich cathodes to alleviate the problem of inevitable rapid capacity decay during cycling. Therefore, to match LiNi0.8Co0.1Mn0.1O2 (NCM811), we applied pentaerythritol tetraacrylate (PETEA) monomers to polymerize in situ in a polyacrylonitrile (PAN) membrane to obtain GPEs (PETEA-TCGG-PAN). The impedance variations and key groups during the in situ polymerization of PETEA-TCGG-PAN are investigated in detail. PETEA-TCGG-PAN with a high lithium-ion transference number (0.77) exhibits an electrochemical decomposition voltage of 5.15 V. Noticeably, the NCM811|PETEA-TCGG-PAN|Li battery can cycle at 2C for 120 cycles with a capacity retention rate of 89%. Even at 6C, the discharge specific capacity is able to reach 101.47 mAh g-1. The combination of LiF and Li2CO3 at the CEI interface is the reason for the improved rate performance. Moreover, when commercialized LFP is used as the cathode, the battery can also cycle stably for 150 cycles at 0.5C. PETEA and PAN can together foster the transportation of Li+ with the construction of a fast ion transport channel, making a contribution to stable charge-discharge of the above batteries. This study provides an innovative design philosophy for designing in situ GPEs in high-energy-density lithium metal batteries.

Flame Retardancy, Fire Behavior, and Flame Retardant Mechanism of Intumescent Flame Retardant EPDM Containing Ammonium Polyphosphate/Pentaerythrotol and Expandable Graphite.

The intumescent flame retardant ethylene-propylene-diene rubber (EPDM) was prepared using intumescent flame retardant (IFR), including ammonium polyphosphate (APP) /pentaerythrotol (PER) and expandable graphite (EG), as the flame retardant agent. The effects of IFR and EG on the flame retardancy, fire behavior, and thermal stability of the EPDM were investigated. The results show that IFR and EG have excellent synergistic flame retardant effects. When the mass ratio of IFR to EG is 3:1 and the total addition content is 40 phr, the limiting oxygen index (LOI) value of the EPDM material (EPDM/IFR/EG) can reach 30.4%, and it can pass a V-0 rating in the vertical combustion (UL-94) test. Meanwhile, during the cone calorimetry test, the heat release rate and total heat release of EPDM/IFR/EG are 69.0% and 33.3% lower than that of the pure EPDM, respectively, and the smoke release of the material also decreases significantly, suggesting that the sample shows good fire safety. In addition, the flame retardant mechanism of IFR and EG is systematically investigated by thermogravimetric analysis/infrared spectrometry (TG-IR), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), and the results indicate that IFR and EG have only physical interaction. Moreover, the reason why IFR exhibits a poor flame retardant effect in EPDM materials is explained.

[Application of narrow band imaging in early diagnosis of pharyngolaryngeal tumors].

OBJECTIVE: To investigate the application value of narrow band imaging (NBI) in early diagnosis of pharyngolaryngeal tumors. METHOD: A total of 106 patients received NBI endoscopy in the endoscopic diagnosis. Lesions found under the white-light endoscopy mode and NBI endoscopy mode were compared in the morphology of capillaries on lesiorn surface and the clarity of lesion rim. Biopsy was performed in suspected areas with those two endoscopies for the lesions found under white-light endoscopy and NBI endoscopy, the morphology of capillaries on the surface of lesion and the clarity of lesion boundary were compared between both. Biopsy was performed for suspected areas under two modes, and specimens were preserved in 10% formaldehyde for pathological examination. The characteristic, position and endoscopic diagnosis under two modes were recorded. All the patients underwent corresponding laryngeal tumor resection according to the histopathological result of biopsy, and the histopathological result of resected tissues was taken as the gold standard for diagnosis. The biopsy detection rate and biopsy correct detection rate of malignant lesions in two groups were calculated and statistical compared. RESULT: The diagnostic accuracy under white-light mode was 75.47%, while that under NBI mode was 96.23%, and the difference between them was statistically significant (χ² = 18.375, P < 0.01). The biopsy correct detection rate under white-light mode was 82.08%, while that under NBI mode was 95.28%, and the difference between them was statistically significant (χ² = 12.071, P < 0.01). The correct detection rate of malignant tumor under white-light mode was 48.15%, while that under NBI mode was 92.59%, and the difference between them was statistically significant (χ² = 10.083, P < 0.01). CONCLUSION: Using NBI endoscopy to observe the morphological changes of capillaries on the pharyngolaryneal mucosa surface can increase the detection rate of early pharyngolaryngeal tumors, so it is worth to be widely applied.