Localizing Oxygen Lattice Evolutions Eliminates Oxygen Release and Voltage Decay in All-Mn-Based Li-Rich Cathodes.

All-Mn-based Li-rich cathodes Li2 MnO3 have attracted extensive attention because of their cost advantage and ultrahigh theoretical capacity. However, the unstable anionic redox reaction (ARR), which involves irreversible oxygen releases, causes declines in cycling capacity and intercalation potential, thus hindering their practical applications. Here, it is proposed that introducing stacking-fault defects into the Li2 MnO3 can localize oxygen lattice evolutions and stabilize the ARR, eliminating oxygen releases. The thus-made cathode has a highly reversible capacity (320 mA h g-1 ) and achieves excellent cycling stability. After 100 cycles, the capacity retention rate is 86% and the voltage decay is practically eliminated at 0.19 mV per cycle. Attributing to the stable ARR, samples show reduced stress-strain and phase transitions. Neutron pair distribution function (nPDF) measurements indicate that there is a structure response of localized oxygen lattice distortion to the ARR and the average oxygen lattice framework is well-preserved which is a prerequisite for the high cycle reversibility.

Anomalous Ferromagnetic Behavior in Orthorhombic Li3Co2SbO6.

Monoclinic Li3Co2SbO6 has been proposed as a Kitaev spin liquid candidate and investigated intensively, whereas the properties of its polymorph, the orthorhombic phase, are less known. Here we report the magnetic properties of orthorhombic Li3Co2SbO6 as revealed by dc and ac magnetic susceptibility, muon spin relaxation (µSR), and neutron diffraction measurements. Successive magnetic transitions at 115, 89, and 71 K were observed in the low-field dc susceptibility measurements. The transitions below TN (115 K) are suppressed at higher applied fields. However, zero-field ac susceptibility measurements reveal distinct frequency-independent transitions at about 114, 107, 97, 79, and 71 K. A long-range magnetic ordered state was confirmed by specific heat, µSR, and neutron diffraction measurements, all indicating a single transition at about 115 K. The discrepancy between different measurements is attributed to possible stacking faults and/or local disorders of the ferromagnetic zigzag chains, resulting in ferromagnetic boundaries within the overall antiferromagnetic matrix.

[Difference analysis of muscle fatigue during the exercises of core stability training].

The present study was carried out with the surface electromyography signal of subjects during the time when subjects did the exercises of the 6 core stability trainings. We analyzed the different activity level of surface electromyography signal, and finally got various fatigue states of muscles in different exercises. Thirty subjects completed exercises of 6 core stability trainings, which were prone bridge, supine bridge, unilateral bridge (divided into two trainings, i.e. the left and right sides alternatively) and bird-dog (divided into two trainings, i.e. the left and right sides alternatively), respectively. Each exercise was held on for 1 minute and 2 minutes were given to relax between two exercises in this test. We measured both left and right sides of the body's muscles, which included erector spina, external oblique, rectus abdominis, rectus femoris, biceps femoris, anterior tibial and gastrocnemius muscles. We adopted the frequency domain characteristic value of the surface electromyography signal, i.e. median frequency slope to analyze the muscle fatigue in this study. In the present paper, the results exhibit different fatigue degrees of the above muscles during the time when they did the core stability rehabilitation exercises. It could be concluded that supine bridge and unilateral bridge can cause more fatigue on erector spina muscle, prone bridge caused Gastrocnemius muscle much fatigue and there were statistical significant differences ( P<0.05) between prone bridge and other five rehabilitation exercises in the degree of rectus abdominis muscle fatigue. There were no statistical significant differences ( P>0.05) between all the left and right sides of the same-named muscles in the median frequency slope during all the exercises of the six core stability trainings, i.e. the degree which the various kinds of rehabilitation exercises effected the left and right side of the same-named muscle had no statistical significant difference ( P>0.05). In this research, the conclusion presents quantized guidelines on the effects of core stability trainings on different muscles.

Diffusion-Optimized Long Lifespan 4.6 V LiCoO2: Homogenizing Cycled Bulk-To-Surface Li Concentration with Reduced Structure Stress.

Increasing the charging cut-off voltage (e.g., 4.6 V) to extract more Li ions are pushing the LiCoO2 (LCO) cathode to achieve a higher energy density. However, an inhomogeneous cycled bulk-to-surface Li distribution, which is closely associated with the enhanced extracted Li ions, is usually ignored, and severely restricts the design of long lifespan high voltage LCO. Here, a strategy by constructing an artificial solid-solid Li diffusion environment on LCO's surface is proposed to achieve a homogeneous bulk-to-surface Li distribution upon cycling. The diffusion optimized LCO not only shows a highly reversible capacity of 212 mA h g-1 but also an ultrahigh capacity retention of 80% over 600 cycles at 4.6 V. Combined in situ X-ray diffraction measurements and stress-evolution simulation analysis, it is revealed that the superior 4.6 V long-cycled stability is ascribed to a reduced structure stress leaded by the homogeneous bulk-to-surface Li diffusion. This work broadens approaches for the design of highly stable layered oxide cathodes with low ion-storage structure stress.

Suppressing Surface Ligand-to-Metal Charge Transfer toward Stable High-Voltage LiCoO2.

Increasing the charging cutoff voltage is a viable approach to push the energy density limits of LiCoO2 and meet the requirements of the rapid development of 3C electronics. However, an irreversible oxygen redox is readily triggered by the high charging voltage, which severely restricts practical applications of high-voltage LiCoO2. In this study, we propose a modification strategy via suppressing surface ligand-to-metal charge transfer to inhibit the oxygen redox-induced structure instability. A d0 electronic structure Zr4+ is selected as the charge transfer insulator and successfully doped into the surface lattice of LiCoO2. Using a combination of theoretical calculations, ex situ X-ray absorption spectra, and in situ differential electrochemical mass spectrometry analysis, our results show that the modified LiCoO2 exhibits suppressed oxygen redox activity and stable redox electrochemistry. As a result, it demonstrates a robust long-cycle lattice structure with a practically eliminated voltage decay (0.17 mV/cycle) and an excellent capacity retention of 89.4% after 100 cycles at 4.6 V. More broadly, this work provides a new perspective on suppressing the oxygen redox activity through modulating surface ligand-to-metal charge transfer for achieving a stable high-voltage ion storage structure.

Open conformation of ezrin bound to phosphatidylinositol 4,5-bisphosphate and to F-actin revealed by neutron scattering.

Ezrin is a member of the ezrin-radixin-moesin family (ERM) of adapter proteins that are localized at the interface between the cell membrane and the cortical actin cytoskeleton, and they regulate a variety of cellular functions. The structure representing a dormant and closed conformation of an ERM protein has previously been determined by x-ray crystallography. Here, using contrast variation small angle neutron scattering, we reveal the structural changes of the full-length ezrin upon binding to the signaling lipid phosphatidylinositol 4,5-bisphosphate (PIP(2)) and to F-actin. Ezrin binding to F-actin requires the simultaneous binding of ezrin to PIP(2). Once bound to F-actin, the opened ezrin forms more extensive contacts with F-actin than generally depicted, suggesting a possible role of ezrin in regulating the interfacial structure and dynamics between the cell membrane and the underlying actin cytoskeleton. In addition, using gel filtration, we find that the conformational opening of ezrin in response to PIP(2) binding is cooperative, but the cooperativity is disrupted by a phospho-mimic mutation S249D in the 4.1-ezrin/radixin/moesin (FERM) domain of ezrin. Using surface plasmon resonance, we show that the S249D mutation weakens the binding affinity and changes the kinetics of 4.1-ERM to PIP(2) binding. The study provides the first structural view of the activated ezrin bound to PIP(2) and to F-actin.

Exponential Signal Reconstruction With Deep Hankel Matrix Factorization.

Exponential function is a basic form of temporal signals, and how to fast acquire this signal is one of the fundamental problems and frontiers in signal processing. To achieve this goal, partial data may be acquired but result in severe artifacts in its spectrum, which is the Fourier transform of exponentials. Thus, reliable spectrum reconstruction is highly expected in the fast data acquisition in many applications, such as chemistry, biology, and medical imaging. In this work, we propose a deep learning method whose neural network structure is designed by imitating the iterative process in the model-based state-of-the-art exponentials' reconstruction method with the low-rank Hankel matrix factorization. With the experiments on synthetic data and realistic biological magnetic resonance signals, we demonstrate that the new method yields much lower reconstruction errors and preserves the low-intensity signals much better than compared methods.

Exploitation of Schottky-Junction-based Sensors for Specifically Detecting ppt-Concentration Gases.

Gas species and concentrations of human-exhaled breath correlate with health, wherein disease markers contain volatile organic compounds (VOCs) of concentrations in parts per billion. It is expected that a gas-sensing strategy possesses a gas specificity and detection limit in the parts per trillion (ppt) range; however, it is still a challenge. This investigation has exploited the Schottky junction of gas sensors for detecting the reactance signal of ppt VOC, aiming for a specific and rapid detection toward disease marker acetone. In this new sensing paradigm, formed by the engineered energy band between metal-semiconductor contact, the Schottky junction is accessed to specific modulation of different adsorbate dopings and the corresponding reactance signal is measured. Regarding the detection toward ppt concentration of acetone, this sensing paradigm possesses rapid (∼100 s) and room-temperature response, molecular specificity, and 34 ppt of detection limit. The proposed detection paradigm is demonstrated to show a high feasibility toward detection of disease marker acetone.

Quantifying the Anomalous Local and Nanostructure Evolutions Induced by Lattice Oxygen Redox in Lithium-Rich Cathodes.

Due to their accessible lattice oxygen redox (l-OR) at high voltages, Li-rich layered transition metal (TM) oxides have shown promising potential as candidate cathodes for high-energy-density Li-ion batteries. However, this l-OR process is also associated with unusual electrochemical issues such as voltage hysteresis and long-term voltage decay. The structure response mechanism to the l-OR behavior also remains unclear, hindering rational structure optimizations that would enable practical Li-rich cathodes. Here, this study reveals a strong coupling between l-OR and structure dynamic evolutions, as well as their effects on the electrochemical properties. Using the technique of neutron total scattering with pair distribution function analysis and small-angle neutron scattering, this study quantifies the local TM migration and formation of nanopores that accompany the l-OR. These experiments demonstrate the causal relationships among l-OR, the local/nanostructure evolutions, and the unusual electrochemistry. The TM migration triggered by the l-OR can change local oxygen coordination environments, which results in voltage hysteresis. Coupled with formed oxygen vacancies, it will accelerate the formation of nanopores, inducing a phase transition, and leading to irreversible capacity and long-cycling voltage fade.

New insights into Li distribution in the superionic argyrodite Li6PS5Cl.

By using temperature-dependent neutron powder diffraction combined with maximum entropy method analysis, a previously unreported Li lattice site was discovered in the argyrodite Li6PS5Cl solid-state electrolyte. This new finding enables a more complete description of the Li diffusion model in argyrodites, providing structural guidance for designing novel high-conductivity solid-state electrolytes.

Dynamic nuclear polarization enhanced neutron crystallography: Amplifying hydrogen in biological crystals.

Dynamic nuclear polarization (DNP) can provide a powerful means to amplify neutron diffraction from biological crystals by 10-100-fold, while simultaneously enhancing the visibility of hydrogen by an order of magnitude. Polarizing the neutron beam and aligning the proton spins in a polarized sample modulates the coherent and incoherent neutron scattering cross-sections of hydrogen, in ideal cases amplifying the coherent scattering by almost an order of magnitude and suppressing the incoherent background to zero. This chapter describes current efforts to develop and apply DNP techniques for spin polarized neutron protein crystallography, highlighting concepts, experimental design, labeling strategies and recent results, as well as considering new strategies for data collection and analysis that these techniques could enable.