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The hierarchical carbon-coated LiFePO4 nano-grain microspheres are prepared by a chemical co-precipitation method. The microstructure and electrochemical properties of LiFePO4/C composites treated at 950–1025 K are intensively investigated. The rate discharge capability has been obviously enhanced when sample is treated at 1025 K. This attributes to its improved electric conductivity of 0.09 S cm−1 due to the in-situ formation of Fe2P phase. The cycling stabilities are excellent until 300 cycles for all the samples at the rate 1C in discharge, which is very difficult to reach for nano-grains with large specific surface area and high reaction activity. Our samples with hierarchical microstructures exhibit high Li-ion diffusion rate (10−9–10−13 cm2 S−1) with enhanced tap density (1.30 g cm−3). It is considered in our paper that the rate capacities increased by Li-ion diffusion rate are not as obvious as electric conductivity. Therefore, the LiFePO4/FePO4 reaction is a non-diffusional controlled process.
The study of inhomogeneous battery failure processes requires proper tools with high spatial resolving power. Here we describe a simple way to adapt industry-standard coin cells to enable in situ Raman mapping of lithium-ion battery materials. We describe the important cell design parameters and validate that the design achieves a uniform potential distribution within the region probed by Raman. We further validate that the cell yields electrical performance characteristics equivalent to a standard, non-modified coin cell. Using this cell, we probe the local charging profiles of LiNi0.5Mn0.3Co0.2O2 (“NMC”) particles during cycling and demonstrate the ability to achieve spatial maps of the Raman spectra. In order to reduce the effects of local topography, we further analyze these data by numerically extracting the local frequency of the A1g vibrational mode, which is sensitive to the local extent of lithiation, and producing spatial maps of the local frequency of the A1g mode. This work demonstrates a way to collect and analyze high quality in situ spectra with an easy-to-implement cell design that can be applied to a wide range of electrode materials.
Five new copper(II)-based ionic liquids and three crystalline compounds have been synthesized in order to further understand the role of the anion in determining their physicochemical properties. Materials were prepared with combinations of three different anions (2-ethylhexanoate (EHN), tetrafluoroborate (BF4), and triflate (OTf)) and six-coordinate Cu(II) cations. The complexes that contain at least one BF4 anion consistently displayed both the highest specific conductivity and electrochemical reversibility. The presence of one OTf anion (in combination with one EHN or BF4) facilitates the formation of crystalline materials. Single crystal X-ray diffraction studies were completed on two of the mixed anion compounds. The results show that both ethanolamine (EA) and diethanolamine (DEA) chelate to the Cu(II) centers in a highly distorted tetragonal geometry. The properties of the ionic liquid with the overall lowest viscosity and highest conductivity and electrochemical reversibility (Cu{NH2CH2CH2OH}6(BF4)2, 4) were studied as a function of temperature. The viscosity decreases with increasing temperature, but at 45°C (over three hours) there is a loss of two EA ligands to form a more viscous four-coordinate complex. Cyclic voltammetry of 4 reveals a quasi-reversible Cu(II)/Cu(I) reduction wave that shifts to more positive potentials with increasing temperature.
Ever since composite polymeric electrolytes (CPEs) were developed and studied authors publishing their results used to emphasize the role of new materials they used and not the details of the preparation conditions. In this work it is proven that the later can influence markedly the former and shown that the comparison of results obtained for different materials by different authors can be made only in limited number of cases. Herein results of the detailed studies on the composite, PEO-based polymeric electrolytes with surface modified fillers are shown. Extensive studies on the influence of different powders and preparation conditions on the final properties of composite electrolytes are described. The modification of fillers of various type and grain size was studied together with their influence on the functional parameters of electrolytes. Multiple research approaches and analysis methods were utilized in order to obtain as complete image of the materials as possible.
The lithium-ion batteries are widely used in rechargeable electronic devices. The current challenges are to improve the capacity and safety of these systems in view of their development to a larger scale, such as for their application in electric and hybrid vehicles. Lithium-ion batteries use organic solvents because of the wide operating voltage. The corresponding electrolytes are usually based on combinations of linear, cyclic alkyl carbonates and a lithium salt such as LiPF6. It has been reported that in abusive thermal conditions, a catalytic effect of the cathode materials lead to the formation fluoro-organics compounds. In order to understand the degradation phenomenon, the study at 240 °C of the interaction between positive electrode materials (LiCoO2, LiNi1/3Mn1/3Co1/3O2, LiMn2O4 and LiFePO4) and electrolyte in dry and wet conditions has been realized by an original method which consists in analyzing by mass spectrometry in real time the volatile molecules produced. The evolution of specific gases channels coupled to the NMR reveal the formation of rarely discussed species such as 2-fluoroethanol and 1,4-dioxane. Furthermore, it appears that the presence of water or other protic impurities greatly influence their formation.
Porous LiMn2O4 thick-film cathodes for Li-ion microbatteries are realized by laser-printing. The porous structure of the printed composite cathode consisting of active powder, binder, carbon black and graphite enables ionic and electronic transport through 50–60 μm thick electrodes due to its high intrinsic active surface area. In order to further improve the cycle stability and capacity retention of the laser-printed thick-film cathodes for discharging rates up to 1 C, laser-printed thick films are first calendered in a press and then structured using ultrafast femtosecond-laser radiation in order to form three-dimensional (3D) cathode architectures. It is shown that calendered/laser structured cathodes in the form of rectangular 3D grids exhibit discharge capacity retention of 68% at a 1 C rate, while calendered but unstructured cathodes retain only about 45% of their initial capacity at the same discharge rate. Overall, the improved discharge capacity retention and reduced degradation during later cycles can be attributed to the combination of increased electrical contact with shortened Li-ion pathways.
This study follows the concept of set cover for proposing a refueling-station-location model using a mixed integer programming method, based on vehicle-routing logics. Its solution uses only the easy-obtain data of the origin-destination distance matrix. A case study that focuses on the siting of refueling stations for achieving multiple origin-destination intercity travel via electric vehicles on Taiwan demonstrates the applicability of the model. Sensitivity analysis shows that greater vehicle range will result in a lower number of refueling stations that need to be sited. Range is crucial in reducing the facility-location costs, and therefore is an important issue in the development of alternative-fuel-vehicle technology.
Fe2O3 microsphere is used as iron source and template to prepare Li2FeSiO4/C nanocomposite by a sol–gel method. The carbon content, structure, and morphology of the sample are characterized by carbon–sulfur inferred analysis (CSI), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM) techniques. The results show that the Li2FeSiO4/C owns pure phase and sphere-like morphology as a result of an agglomeration of nanoparticles with an average particle size of about 50 nm. The Li2FeSiO4/C exhibits stable cycle performance at different rates from 0.1 C to 2 C, and its capacity at 0.1 C rate can reach 160 mAh g−1.
Next Generation Sequencing (NGS) is expected to help find the elusive, causative genetic defects associated with Bipolar Disorder (BD). This article identifies the importance of NGS and further analyses the social and ethical implications of this approach when used in research projects studying BD, as well as other psychiatric ailments, with a view to ensuring the protection of research participants.
T cell maturation into TCRαβ+ or TCRγδ+ cells from common immature CD4−CD8−(DN) precursors occurs in the thymus, and is controlled through ordered regulation of genes. The aryl hydrocarbon receptor (AHR), a latent cytoplasmic transcription factor, affects thymocyte maturation and differentiation at several stages, also including DN cells. We analyzed in murine fetal thymus organ cultures (FTOC) the outcome of AHR-signaling and found a higher frequency of DN TCRγδ+ cells in the presence of the AHR-activating ligand TCDD. We detected a novel population of CD25int/loCD44hi cells associated with preferential emigration and a TCRγδ+ T cell fate of thymocytes. Sorted DN TCRγδ+ emigrants could proliferate if IL-2 was available. Moreover, they suppressed the proliferation of co-cultivated, activated CD4+ T cells. Gene expression profiles of purified DN emigrants from TCDD*FTOC revealed 295 modulated genes, 10% of which are genes of the immune system. For instance, RAG-1, TdT, and Gfi-1 were downregulated, yet genes indicative of mature thymocytes were upregulated. In conclusion, we have detected changes in the differentiation programme of fetal DN thymocytes after ligand-activation of the AHR. In particular, we observed a higher frequency of DN TCRγδ+ cells with high emigration potential, and possible regulatory functions.
This study combined the experimental and modeling methods to investigate effects of different factors on the performance of the micro-PEM fuel cell (μ-PEMFC). The results showed that species transport and contact resistance determined the performance of the μ-PEMFC. Contact resistance in the μ-PEMFC contributed to 19.4% of the total inner resistance in this study. The contact resistance changed significantly the distribution of overpotential in the μ-PEMFC and decreased the current output. Small dimensions of the μ-channel drastically affected the species transport and resulted in a non-uniform current distribution along channel direction at low cell potential (high current). Therefore, the designs of new flow field configurations and assembling modes of μ-PEMFCs are very important in improving the performance of μ-PEMFCs. These designs including flow field and assembling mode of μ-PEMFCs should improve species transport through μ-channels and decrease the contact resistance between gas diffusion layers (GDLs) and current collectors.
This paper is the introductory presentation given at the pre conference seminar devoted to a discussion of the oxygen-cycle in valve-regulated lead-acid batteries.
Nanoparticle-dispersed polymer electrolytes have been prepared by stirring or high-energy ball milling of polyethylene oxide (PEO), lithium salt (LiCF3SO3, LiClO4 and LiPF6), and nanometer-size ceramic powder (TiO2, SiO2 and Al2O3). The smaller the size of ceramic particles, the better they influence the crystallization kinetics of the PEO polymer chains. High-energy ball milling lowers the glass transition temperature of the composite polymers, and thus increases the ionic conductivity greater than the order of the magnitude compared with the un-milled samples. The highest ionic conductivity was reported when using LiPF6 as added lithium salt and Al2O3 as dispersed particle. Cyclic voltametric measurements showed that the PEO-system is electrochemically stable in the range of 2–5V.
An investigation is made on the interfacial phenomena of commercially available mesocarbon microbeads (MCMB) as the carbon lithium electrode in an electrolyte, which consists of 1 M LiPF6 dissolved in an equal mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). Once the charge–discharge of lithium (Li) proceeds, a surface film is formed on the MCMB carbon electrode, and its thickness increases with cycle number. The growth of the surface film with cycle number is observed by a scanning electron microscope and the surface resistance by means of AC impedance measurements. A continuous decrease in the charge capacity with cycle number is found and is related to film growth. The surface films are composed of solvated Li compounds, as shown by surface-sensitive Fourier transform infrared (FT-IR) spectroscopy.
The promising lithium-oxygen battery chemistry presents a set of challenges that need to be solved if commercialization is ever to be realized. This study focuses on how the O2 reaction path is effected by the O2 concentration in the electrolyte. An electrochemical quartz crystal microbalance system was used to measure current, potential, and change in electrode mass simultaneously. It is concluded that the mass reversibility is O2 concentration dependent while the coulombic efficiency is not. The mass reversibility is higher at low O2 concentration meaning that more of the deposited Li2O2 is removed during oxidation in relation to the amount deposited during reduction. The first step of the reduction is the formation of soluble LiO2, which is then either reacting further at the electrode or being transported away from the electrode resulting in low current efficiency and low deposited mass per electrons transferred. During the oxidation, the first step involves de-lithiation of Li2O2 at low potential followed by bulk oxidation. The oxidation behavior is O2 concentration dependent, and this dependence is likely indirect as the O2 concentration effects the amount of discharge product formed during the reduction. The O2 concentration at different saturation pressures was determined using a mass spectrometer. It was found that the electrolyte follows Henry's law at the pressures used in the study. In conclusion, this study provides insight to the O2 concentration dependence and the preferred path of the O2 electrochemical reactions in lithium-oxygen batteries.
V6O13 nanosheets were successfully synthesized via a facile hydrothermal synthesis combined with an appropriate heat treatment. The evolutions in crystallization, chemical composition, structure, and consequent electrochemical performances upon different hydrothermal routes were briefly discussed. The lithium battery using VO2(B), V6O13 or V6O12.3 compound as the positive electrode exhibited a high discharge capacity. It enabled us to further demonstrate the differences and resemblance between V6O13 and V6O12.3 cells.
Dense β″-alumina electrolyte tubes with thickness less than 50μm were slip cast on a porous substrate of β″-alumina. The resistance of the composite electrolyte was measured by a DC method. The area specific resistance of a thin layer electrolyte versus the full thickness electrolyte was lower by a factor of 1.6. The components of cell resistance were determined. It was concluded that interfacial resistance is a dominant factor in the electrolyte resistance.
Hypoxia is defined as a decrease in available oxygen reaching the tissues of the body. It is linked to the pathology of cancer, cardiovascular disease, and stroke, the leading causes of death in the United States. Cells under hypoxic stress either induce an adaptive response that includes increasing the rates of glycolysis and angiogenesis or undergo cell death by promoting apoptosis or necrosis. The ability of cells to maintain a balance between adaptation and cell death is regulated by a family of transcription factors called the hypoxia inducible factors (HIF). HIF1, the most widely studied HIF, is essential for regulating the expression of a battery of hypoxia-responsive genes involved in the adaptive and cell death responses. The ability of HIF1 to balance these 2 responses likely lies in the regulation of HIF1α stability and transcriptional activity by post-translational hydroxylation and its ability to respond to other cellular factors including key metabolites and growth factors. Targeting HIF1 signaling for therapeutics, therefore, requires an understanding of how these various signals converge upon HIF1 and regulate its role in maintaining the balance between adaptation and cell death. In addition, one must understand how this balance can be perturbed during toxicant-induced tissue damage. This review will summarize our current understanding of hypoxia signaling as it applies to drug therapy and toxicity and describe how these processes can influence the HIF-mediated balance between adaptation and cell death.
Safety issues along with the substantially reduced energy and power capabilities of Li-ion cells, operated at low temperatures, pose a technical barrier limiting their use in electric vehicles and aerospace applications. A combined in situ high-resolution neutron powder diffraction and electrochemical study on Li-ion cells of the 18650-type over a temperature range from 230 K to 320 K is reported with a focus on the graphite anode and the low temperature performance of the cell. Instead of a quasi-continuous behavior as observed at ambient temperatures, an anomalous behavior occurs upon discharge at low temperature, primarily reflected in the abrupt character of the LiC12 – to – graphite phase transformation and the unusual temperature dependence of the amount of LiC6. An instability of lithiated graphite phases at temperatures below 250 K is observed, which affects the performance of Li-ion batteries at low temperatures.
Prior research provides evidence for aberrant cognition-emotion interactions in schizophrenia. In the current study, we aimed to extend these findings by administering the “distractor devaluation” task to 40 individuals with schizophrenia and 32 demographically matched healthy controls. The task consisted of a simple visual search task for neutral faces, followed by an evaluative response made for one of the search items (or a novel item) to determine whether prior attentional selection results in a devaluation of a previously unattended stimulus. We also manipulated working memory demands by preceding the search array with a memory array that required subjects to hold 0, 1, or 2 items in working memory while performing the search array and devaluation task, to determine whether the normative process by which attentional states influence evaluative response is limited by working memory capacity. Results indicated that individuals with schizophrenia demonstrated the typical distractor devaluation effect at working memory load 0, suggesting intact evaluative response. However, the devaluation effect was absent at working memory loads of 1 and 2, suggesting that normal evaluative responses can be abolished in people with schizophrenia when working memory capacity is exceeded. Thus, findings provide further evidence for normal evaluative response in schizophrenia, but clarify that these normal experiences may not hold when working memory demands are too high.
Small-scale pyrotechnic igniter output has been characterized using a high-speed schlieren imaging system for observing critical features of the post-combustion flow. The diagnostic, with laser illumination, was successfully applied towards the quantitative characterization of the output from
The breakdown of the protective solid electrolyte interface (SEI) layer formed on lithium ion battery anodes can initiate further electrolyte decomposition and the formation of non-uniform and electronically insulating reaction products on the surface of the graphite particles. The results from this study indicate that raising both the lower and upper ends of the state of charge (SOC) increased the rate of the electrolyte decomposition side reaction to form a thick deposit surface film. This deposit layer contained lithium that can no longer participate in the reversible electrochemical reaction. In addition, the high cycling potential coupled with high charge rate created a large lithium concentration gradient that led to some particles detachment from the current collector and isolation in the electrochemical process.
Xenon (Xe) is a noble gas that has been used for the last several decades as an anesthetic during surgery. Its antagonistic effect on glutamate subtype of NMDA (N-methyl-d-aspartate) receptors resulted in evaluation of this gas for treatment of CNS pathologies, including psychoemotional disorders. The aim of this study was to assess the behavioral effects of acute inhalation of subanesthetic concentrations of Xe and to study the outcomes of Xe exposure in valproic acid (VPA)-induced rodent model of autism.
Exploring anode materials with excellent safety, high capacities and superior rate performance for lithium ion batteries remains a persistent objective. Herein, TiO2-bronze/anatase TiO2 hybrid nanowires are successfully prepared through a facile stirring hydrothermal method, which have elongated bending wire morphology and a heterojunction structure with TiO2-bronze and anatase TiO2 nanocrystal. The ratio of the two constituents can be easily adjusted by controlling the hydrothermal time, of which the growing orientation of the major TiO2-bronze is along <110> direction that facilitates the transport of Li+ ions. More importantly, the optimized hybrid material with 8.21% of anatase has superior electrochemical performances in terms of specific capacities, rate capability and cycling stability. Typically, the material shows a discharge capacity of 230.6m Ah g−1 at 1C rate with a capacity retention of 99% after 80 cycles, and also displays a discharge capacity of 145.7mAhg−1 even at a higher rate of 30C, which make it as promising anode material for high power rechargeable batteries.
FIB-SEM, XPS and gas adsorption methods have been used for the characterisation of physical properties of microporous carbide derived carbon electrodes prepared from Mo2C at 600°C (noted as CDC-Mo2C). Cyclic voltammetry, constant current charge/discharge, and electrochemical impedance spectroscopy have been applied to establish the electrochemical characteristics for supercapacitors consisting of the 1M Na2SO4, KOH, tetraethyl ammonium iodide or 6M KOH aqueous electrolyte and CDC-Mo2C electrodes. The N2 sorption values obtained have been correlated with electrochemical characteristics for supercapacitors in various aqueous electrolytes. The maximum gravimetric energy, E max, and gravimetric power, P max, for supercapacitors (taking into consideration the active material weight) have been obtained at cell voltage 0.9V for 6M KOH aqueous supercapacitor (E max =5.7Whkg−1 and P max =43kWkg−1). For 1M TEAI based SC somewhat higher E max (6.2Whkg−1) and comparatively low P max (7.0kWkg−1) have been calculated.
Criterion validity and test-retest reliability of the Scale of Psychomotor Development (SPMD) was studied on groups of children of 4–6 years old. A conclusion about developmental delay or delayed speech development was used as a criterion of external validity. To examine the accuracy of the differential diagnostics of the three groups (the norm and two groups with the above diagnoses) a discriminant analysis was used. The results showed high accuracy in predicting the subject's belonging to the norm group or developmental delay group, and lower prediction accuracy for the group with delayed speech development in differentiation with the norm and developmental delay.