Lithium-air batteries are considered to be a potential alternative to lithium-ion batteries for transportation applications, owing to their high theoretical specific energy. So far, however, such systems have been largely restricted to pure oxygen environments (lithium-oxygen batteries) and have a limited cycle life owing to side reactions involving the cathode, anode and electrolyte. In the presence of nitrogen, carbon dioxide and water vapour, these side reactions can become even more complex. Moreover, because of the need to store oxygen, the volumetric energy densities of lithium-oxygen systems may be too small for practical applications. Here we report a system comprising a lithium carbonate-based protected anode, a molybdenum disulfide cathode and an ionic liquid/dimethyl sulfoxide electrolyte that operates as a lithium-air battery in a simulated air atmosphere with a long cycle life of up to 700 cycles. We perform computational studies to provide insight into the operation of the system in this environment. This demonstration of a lithium-oxygen battery with a long cycle life in an air-like atmosphere is an important step towards the development of this field beyond lithium-ion technology, with a possibility to obtain much higher specific energy densities than for conventional lithium-ion batteries.

Two-dimensional materials, including graphene, transition metal dichalcogenides and their heterostructures, exhibit great potential for a variety of applications, such as transistors, spintronics, and photovoltaics. While the miniaturization offers remarkable improvements in electrical performance, heat dissipation and thermal mismatch can be a problem in designing electronic devices based on two-dimensional materials. Quantifying the thermal expansion coefficient of 2D materials requires temperature measurements at nanometer scale. Here, we introduce a novel nanometer-scale thermometry approach to measure temperature and quantify the thermal expansion coefficients in 2D materials based on scanning transmission electron microscopy combined with electron energy-loss spectroscopy to determine the energy shift of the plasmon resonance peak of 2D materials as a function of sample temperature. By combining these measurements with first-principles modeling, the thermal expansion coefficients (TECs) of single-layer and freestanding graphene and bulk, as well as monolayer MoS_{2}, MoSe_{2}, WS_{2}, or WSe_{2}, are directly determined and mapped.

electrochemical reactions. [1][2][3][4][5][6][7][8][9][10][11] In particular, molybdenum disulfide (MoS 2 ) and a few members of transition metal dichalcogenides (TMDCs) in contact with ionic-liquid (IL) electrolyte have recently shown a great promise to overcome fundamental electronic and thermokinetic limitations for CO 2 reduction reaction, as well as the oxygen reduction and evolution reactions (ORR/OER). [7][8][9][10] These studies have been conducted on a limited number of TMDCs, and the majority of other TMDCs with a wide range of electronic and potentially catalytic properties have not been investigated. In this study, we report synthesis and characterization of a wide range of TMDCs including sulfides, selenides, and tellurides of group V and VI transition metals and study their electrochemical performance in aprotic medium with Li salts. We employ a wide suite of characterization techniques, such as scanning transmission electron microscopy (STEM), energy dispersive spectroscopy (EDS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), dynamic light scattering (DLS), and atomic forceThe optimization of traditional electrocatalysts has reached a point where progress is impeded by fundamental physical factors including inherent scaling relations among thermokinetic characteristics of different elementary reaction steps, non-Nernstian behavior, and electronic structure of the catalyst. This indicates that the currently utilized classes of electrocatalysts may not be adequate for future needs. This study reports on synthesis and characterization of a new class of materials based on 2D transition metal dichalcogenides including sulfides, selenides, and tellurides of group V and VI transition metals that exhibit excellent catalytic performance for both oxygen reduction and evolution reactions in an aprotic medium with Li salts. The reaction rates are much higher for these materials than previously reported catalysts for these reactions. The reasons for the high activity are found to be the metal edges with adiabatic electron transfer capability and a cocatalyst effect involving an ionic-liquid electrolyte. These new materials are expected to have high activity for other core electrocatalytic reactions and open the way for advances in energy storage and catalysis. ElectrocatalystsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

The ability to examine the vibrational spectra of liquids with nanometer spatial resolution will greatly expand the potential to study liquids and liquid interfaces. In fact, the fundamental properties of water, including complexities in its phase diagram, electrochemistry, and bonding due to nanoscale confinement are current research topics. For any liquid, direct investigation of ordered liquid structures, interfacial double layers, and adsorbed species at liquid-solid interfaces are of interest. Here, a novel way of characterizing the vibrational properties of liquid water with high spatial resolution using transmission electron microscopy is reported. By encapsulating water between two sheets of boron nitride, the ability to capture vibrational spectra to quantify the structure of the liquid, its interaction with the liquid-cell surfaces, and the ability to identify isotopes including H O and D O using electron energy-loss spectroscopy is demonstrated. The electron microscope used here, equipped with a high-energy-resolution monochromator, is able to record vibrational spectra of liquids and molecules and is sensitive to surface and bulk morphological properties both at the nano- and micrometer scales. These results represent an important milestone for liquid and isotope-labeled materials characterization with high spatial resolution, combining nanoscale imaging with vibrational spectroscopy.

The present study aimed to investigate the prevalence of fatigue and determine factors associated with fatigue in female medical personnel. Based on a cross-sectional study, a total of 1608 female medical personnel at 54 hospitals in Zhuhai, China were recruited by a multistage stratified cluster sampling method. The Symptoms Checklist-90-Revised and Chalder Fatigue Scale were used to assess psychiatric symptoms and fatigue, respectively. Data regarding demographic, health, and work related variables were also collected. Multivariate logistic regression model was constructed to determine the influencing factors of fatigue. Approximately 83% of participants had experienced fatigue in the past week. The risk of fatigue was higher in aged 30-39 years old than older or younger participants; Longer sleeping time predicted a lower prevalence of fatigue (OR = .35), while tense physician-patient relationship predicted a higher prevalence of fatigue (OR = 1.77). Depression (OR = 1.76) and anxiety (OR = 1.96) were found related to fatigue. Additionally, fatigue was associated with marital status, occupation, health related factors (exercise, regular diet, and health status), and work related factors (hospital rank and turnover intention). These study findings might facilitate development and implementation of targeted interventions and preventive measures.