Understanding Interfacial Reactions Initiating on Electrode Materials for Energy Storage Technologies

Since the first generation of lithium-ion batteries featured lithium cobalt oxide cathode and carbon anode commercialized in the 1990s, the high-capacity materials with lower cost are in demand to further increase the battery energy density. Lithium metal and silicon anode are promising high-capacity anode materials to achieve next-generation lithium batteries. However, both the materials actively react in electrolytes and suffer from dramatic volume change. Therefore, a reliable passivation layer at the electrolyte/electrode interphase (i.e., solid electrolyte interphase, or “SEI”) is required to support the long-term cycling of both materials. Cetrimonium hydro fluoride (CTAHF2) has been proposed and synthesized as an electrolyte additive, which has the unique advantages of increasing the electrolyte wettability and introducing more LiF content in the electrode surface layer. By incorporating 4 M Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dimethoxyethane (DME) electrolyte, the cycling life has been increased for both lithium metal and silicon anode. To understand the origination and evolution of SEI layers in energy storage systems, an integrated microscopic study has been applied to explore the interfacial reactions initiated on the surfaces of different electrode materials. Specifically, atomic force microscopy (AFM), combined with the scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS), is employed to probe the properties of SEI layers formed on different electrode surfaces. A custom-designed electrochemical cell has been proposed to allow the monitoring of SEI layers by using in situ AFM in a “living” cell. Layered LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising cathode materials for modern lithium-ion batteries with respect to its high reversible capacity. Whereas the redox reactions of Ni2+/Ni3+ and Ni3+/Ni4+ contribute the majority of reversible capacity, the highly reactive Ni-rich surface also encourages the growth of surface impurity species, which causes the irreversible capacity loss and degradation of cycle life. In this work, the residual lithium compounds induced cell failure based on NMC811 was investigated. An acid-base titration method is employed to quantify the carbonate species generated during ambient storage. Finally, a feasible coating method with ethylene carbonate as the coating material has been proposed and helps to maintain the chemical and structural stability of the materials during the ambient environment storage. In comparison to the non-treated extended air-storage samples, the coating treated samples effectively alleviate the initial capacity loss and cycle life degradation. The surface chemical and structural changes and their relevance to electrochemical performances are further discussed in this work

Topological superconductor candidates PdBi2_2Te4_4 and PdBi2_2Te5_5 from a generic ab initio strategy

Superconducting topological metals (SCTMs) have recently emerged as a promising platform of topological superconductivity (TSC) and Majorana zero modes(MZMs) for quantum computation. Despite their importance in both fundamental research and applications, SCTMs are very rare in nature. In addition, some superconductors with topological electronic structures have been reported recently, but a feasible program to determine their TSC properties is still lacking. Here, we propose a new strategy to design SCTMs by intercalating the superconducting units into the topological insulators. A program that characterizes the superconducting BdG Chern number of 2D BdG Hamiltonian from ab initio calculations is also developed. Following this strategy, PdBi$_2$Te$_5$ and PdBi$_2$Te$_4$ are found to be experimentally synthesizable and ideal SCTMs. Chiral TSC could be realized in such SCTMs by incorporating topological surface states with Zeeman effect, which can be realized by an external magnetic field or in proximity to ferromagnetic (FM) insulator. Our strategy provides a new method for identifying the SCTMs and TSC candidates, and the program makes it possible to design and modulate the TSC candidates from ab initio calculations

Three-dimensional Reconstruction of Coronal Mass Ejections by CORAR Technique through Different Stereoscopic Angle of STEREO Twin Spacecraft

Recently, we developed the Correlation-Aided Reconstruction (CORAR) method to reconstruct solar wind inhomogeneous structures, or transients, using dual-view white-light images (Li et al. 2020; Li et al. 2018). This method is proved to be useful for studying the morphological and dynamical properties of transients like blobs and coronal mass ejection (CME), but the accuracy of reconstruction may be affected by the separation angle between the two spacecraft (Lyu et al. 2020). Based on the dual-view CME events from the Heliospheric Imager CME Join Catalogue (HIJoinCAT) in the HELCATS (Heliospheric Cataloguing, Analysis and Techniques Service) project, we study the quality of the CME reconstruction by the CORAR method under different STEREO stereoscopic angles. We find that when the separation angle of spacecraft is around 150{\deg}, most CME events can be well reconstructed. If the collinear effect is considered, the optimal separation angle should locate between 120{\deg} and 150{\deg}. Compared with the CME direction given in the Heliospheric Imager Geometrical Catalogue (HIGeoCAT) from HELCATS, the CME parameters obtained by the CORAR method are reasonable. However, the CORAR-obtained directions have deviations towards the meridian plane in longitude, and towards the equatorial plane in latitude. An empirical formula is proposed to correct these deviations. This study provides the basis for the spacecraft configuration of our recently proposed Solar Ring mission concept (Wang et al. 2020b).Comment: 18 pages, 9 figure

Severe nausea and vomiting in pregnancy: psychiatric and cognitive problems and brain structure in children

Background: Two studies have suggested that severe prolonged nausea and vomiting during pregnancy is associated with emotional and behavioral problems in offspring, with smaller sample size and short-term follow-up. Moreover, little information is available on the role of the brain structure in the associations. Methods: In a US-based cohort, the association was investigated between severe prolonged nausea and vomiting in pregnancy (extending after the second trimester and termed SNVP), psychiatric and cognitive problems, and brain morphology, from the Adolescent Brain Cognitive Development (ABCD) study, from 10,710 children aged 9–11 years. We validated the emotional including psychiatric findings using the Danish National Cohort Study with 2,092,897 participants. Results: SNVP was significantly associated with emotional and psychiatric problems (t = 8.89, Cohen’s d = 0.172, p = 6.9 × 10−19) and reduced global cognitive performance (t = − 4.34, d = − 0.085, p = 1.4 × 10−5) in children. SNVP was associated with low cortical area and volume, especially in the cingulate cortex, precuneus, and superior medial prefrontal cortex. These lower cortical areas and volumes significantly mediated the relation between SNVP and the psychiatric and cognitive problems in children. In the Danish National Cohort, severe nausea and vomiting in pregnancy were significantly associated with increased risks of behavioral and emotional disorders in children (hazard ratio, 1.24; 95% confidence interval, 1.16–1.33). Conclusions: SNVP is strongly associated with psychiatric and cognitive problems in children, with mediation by brain structure. These associations highlight the clinical importance and potential benefits of the treatment of SNVP, which could reduce the risk of psychiatric disorder in the next generation

Alumni Journal: : Remembrance -- One Lucky Guy

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