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The redox flow battery using uranium as the negative and the positive active materials in polar aprotic solvents was proposed. In order to establish the guiding principle for the uranium compounds as the active materials, the investigation of uranium β-diketonate complexes was conducted on (i) the solubility of active materials, (ii) the electrode reaction of U(VI) and U(IV) β-diketonate complexes and (iii) the estimation of the open circuit voltage of the battery. The solubilities of higher than 0.8 mol dm−3 of U(VI) complexes and higher than 0.4 mol dm−3 of a U(IV) complex were obtained in the solvents. The electrode reactions of U(pta)4, UO2(dpm)2, UO2(fod)2 and UO2(pta)2 were first studied and the redox potentials of uranium β-diketonates were thermodynamically discussed. The open circuit voltage is estimated more than 1 V by using Hacac or Hdpm. The larger open circuit voltage is expected when a ligand with the larger basicity is used.
A new family of hydrophobic ionic liquids (ILs) based on a super-delocalized perfluorinated sulfonimide anion, namely (trifluoromethyl(S-trifluoromethylsulfonylimino)sulfonyl)(trifluoromethylsulfonyl)imide ([CF3SO(NSO2CF3)2]−, [sTFSI]−), with various oniums, including imidazolium, quaternary ammonium, pyrrolidinium and piperidinium, have been prepared and characterized. Their physical and electrochemical properties are extensively characterized, and comparatively studied with those based on a lesser delocalized analogue, bis(trifluoromethanesulfonyl) imide ([(CF3SO2)2N]−, [TFSI]−), in terms of thermal properties, density, viscosity, ionic conductivity, and electrochemical stability. These new [sTFSI]-based ILs show low glass transitions (between −95 and −81°C), relatively low viscosities (36–120 cP at 25°C), good thermal stabilities (T d >400°C), and wide electrochemical windows. Particularly, the viscosities are generally lower for the [sTFSI]-based ILs than for the corresponding [TFSI]-based ones, due to better charge delocalization and higher degrees of freedoms for [sTFSI]− vs. [TFSI]−. It is found that the [sTFSI]− anion is more resistant toward oxidation, but less resistant toward reduction than the [TFSI]− one, suggesting that replacement of a O group in [TFSI]− with a strong electron-withdrawning CF3SO2N=group increase both the reductive and oxidative potential. The coulombic efficiencies of Li deposition/stripping on Ni electrode are comparable in the [sTFSI]- and [TFSI]-based ionic liquid electrolytes; however, Li/LiFePO4 cell using the [sTFSI]-based ionic liquid electrolyte shows more stable cycling performance than that using the [TFSI]-based one, which would be attributable to the improved anodic stability of the [sTFSI]− anion and stable electrode/electrolyte interphases formed on Li anode.
Rechargeable Li–CO2 batteries recently have gained an increasing popularity because they can directly reduce fossil fuel consumption and convert chemical energy of greenhouse gas CO2 into electric energy. However, Li–CO2 batteries still suffer from great challenges to realize long-term cycling due to a high charging voltage to drive the electrochemical decomposition of discharge products Li2CO3. Herein, porous NiO nanofibers obtained by electrospining technique are firstly served as a high-efficient cathode catalyst in Li–CO2 batteries. The addition of NiO not only improves the catalytic performance of batteries but also tailors the cathode structure. Experimental results and theoretical calculation show the existence of NiO facilitates a conformal growth of Li2CO3 on the NiO surface with large contact areas, which promotes the decomposition of Li2CO3 among charging process. Owing to these synchronous advantages, enhanced electrochemical performances including high capacity, superior round-trip efficiency and especially the long cycling-life are achieved.
Hollow carbon@SnO2@graphene composite was fabricated by hard template method combined with layer by layer self assembly modification method based on internal-external double protection strategy. The ∼45nm thick active SnO2 existed uniformly between the ∼20nm thick carbon layer and graphene layer to form a three-dimensional porous composite structure. The prepared composite electrode exhibited stable and high capacity of 1015mAhg−1 over 600 cycles at 500mAg−1.
FeF2-reduced graphene oxide nanocomposite is in-situ synthesized and assembled into electrode with poly (acrylic acid) binder as a novel sodium ion cathode, which exhibits greatly improved electrochemical performance. The mechanism for the improved performance of the electrode is studied by ex-situ morphology and phase analysis, before and after cycling. The results show that poly (acrylic acid) binder with high adhesion ability can stabilize the electrode structure, thus increase the utilization of active materials. The in-situ hybridization of FeF2 nanoparticles with reduced graphene oxide can confine the sizes of particles, and restrain the particles agglomeration. As a result, the electrode can attain high capacity and stability. The electrode exhibits superior electrochemical performance: high capacity of 175 mAh g−1 at 0.2 A g−1, high rate capability of 78 mAh g−1 at 10 A g−1, and good cycling stability. The results demonstrate the electrochemical performance of metal fluoride electrode can be enhanced by using highly adhesive materials as binders and the nanostructure construction.
Recently, sodium-ion batteries (SIBs) have been considered as the promising alternative for lithium-ion batteries. Although layered P2-type transition metal oxides are an important class of cathode materials for SIBs, there are still some hurdles for the practical applications, including low specific capacity as well as poor cycling and rate properties. In this study, the electrochemical properties of layered Mn-based oxides have been effectively improved via Al doping, which cannot only promote the formation of layered P2-type structure in the preparation processes but also stabilize the lattice during the successive Na-intercalation/deintercalation due to suppression of the Jahn-Teller distortion of Mn3+. Among the as-prepared series of Na2/3Mn1-x Al x O2 (x = 0, 1/18, 1/9, and 2/9), Na2/3Mn8/9Al1/9O2 with x = 1/9 exhibits the optimal doping effect with the best electrochemical properties, in terms of the highest specific capacity of 162.3 mA h g−1 at 0.1 C, the highest rate capability, and the best cycling stability in comparison to the undoped Na2/3MnO2 and the other two materials with different Al-doped contents. Both cyclic voltammetry at varied scan rates and galvanostatic intermittent titration technique disclose the optimal electrode kinetics (the highest Na-diffusion coefficient) of the best Na2/3Mn8/9Al1/9O2.
Objective To examine the effects of online Cognitive Behavior Therapy for Insomnia (CBTI) on adolescents' sleep and cognitive functioning. Methods 32 adolescents (13–19 years, M = 15.9, SD = 1.6) with DSM-5 insomnia disorder, were randomly assigned to a treatment group (n = 18) or a waiting list (n = 14). Treatment consisted of six guided self-help online CBTI sessions. Both groups were assessed at baseline and post-treatment. Sleep was measured with actigraphy, sleep logs, and questionnaires. Cognitive functioning was assessed with a battery of standard cognitive tests. Results After CBTI the treatment group showed significant improvements compared to the waiting list group in sleep efficiency from actigraphy and sleep logs. This finding was confirmed by improvements in other sleep variables from sleep logs, and in symptoms of chronic sleep reduction and insomnia. Most participants from the treatment group improved to sub clinical levels of insomnia. Cognitive functioning of the treatment group showed more improvement compared to the waiting list in visuospatial processing, selective attention and phonological working memory, and a trend of improvement in response inhibition and set shifting, letter fluency and sustained attention, but not in declarative memory, visuospatial working memory, category fluency, and general cognitive speed. Changes in sleep appeared to be related to changes in cognitive functioning. Conclusions These results indicate that CBTI can have positive effects on cognitive functions in adolescents, with notable improvements in visuospatial processing and phonological working memory but not in visuospatial working memory.
Current lithium ion battery (LIB) technologies are all based on inorganic electrodes though organic materials have been hyped as electrodes for years. Disadvantages such as low specific capacity and poor rate performance hinder their applications. Here we report a novel high-performance organometallic lithium-storage material, a polypyrrole-iron-oxygen (PPy-Fe-O) coordination complex. Extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) calculations indicate that this complex has a multilayer structure. The strong and stable intralayer Fe–N coordination permits the material to possess high specific capacity, the high reversibility of its interlayer Fe–O–Fe interaction during cycling ensures its high cycling stability and the conducting PPy matrix endows it with outstanding rate performance. These findings pave the way to constructing a new type of high-performance organic anode materials for LIBs.
β-Alanine (BA) supplementation may be ergogenic during high-intensity exercise, primarily due to the buffering of hydrogen cations, although the effects of beta-alanine supplementation on strength endurance are equivocal. The aim of the study was to determine the effects of 4 weeks of beta-alanine supplementation on skeletal muscle endurance using a battery of performance tests. This study employed a parallel group, repeated measures, randomised, double-blinded and placebo-controlled design. Twenty recreationally strength-trained healthy males completed tests of isotonic strength endurance (repeated bench and leg press), along with tests of isometric and isokinetic endurance conducted using an isokinetic dynamometer. Tests were performed before and after a 4 week intervention, comprising an intake of 6.4 g day−1 of BA (n = 9) or placebo (maltodextrin, n = 11). Time-to-exhaustion during the isometric endurance test improved by ~ 17% in the BA group (p < 0.01), while PL remained unchanged. No significant within-group differences (p > 0.1) were shown for any of the performance variables in the isokinetic test (peak torque, fatigue index, total work) nor for the total number of repetitions performed in the isotonic endurance tests (leg or bench press). Four weeks of BA supplementation (6.4 g day−1) improved isometric, but not isokinetic or isotonic endurance performance.
Hierarchical sea urchin-like structured carbon–Fe3O4 nanocomposite particles composed of a nanoporous interior and a carbon-coated surface have been prepared by a simple, economical and scalable synthetic process. When the nanocomposite particles were tested as lithium ion battery anodes, they exhibited high capacity, excellent cycle stability and rate performance due to their unique hierarchical nanoporous structure and carbon shell.
LiBF3Cl was synthesized by reacting BF3 etherate and LiCl in an organic media, and evaluated as a salt for the electrolyte of Li-ion batteries. XRD results showed that LiBF3Cl has the same crystallographic structure as LiBF4 except for little difference in the lattice parameter. With a 3:7 (w/w) solvent blend of ethylene carbonate and ethyl methyl carbonate, LiBF3Cl electrolyte was found to have lower liquidus temperature than LiBF4 analogue either due to its higher solubility or due to its higher tendency in forming a super-cooling solution, which was related to the less symmetry of BF3Cl− anion. Meanwhile, LiBF3Cl electrolyte displayed excellent ability in passivating Al at high potentials due to the similar chemical composition of LiBF3Cl and LiBF4. Most importantly, the LiBF3Cl electrolyte was superior to the LiBF4 electrolyte in facilitating the formation of solid electrolyte interphase (SEI) on graphite electrode, which not only increased Coulombic efficiencies of the SEI formation, but also prolonged cycle life of the Li-ion batteries. The merits above make LiBF3Cl very promising as an alternative lithium salt for the electrolyte of Li-ion batteries.
Different forms of anomia are observed in aphasia, which can be related to impaired semantic, lexical or phonological processes. In the present study, we analysed electrophysiological correlates of different patterns of anomia in six aphasic speakers. Event-related potentials (ERPs) were recorded during picture naming in each anomic speaker and in 15 healthy controls. Waveform analysis and temporal segmentation indicated a difference between high and low frequency words in the control group between 270 and 330msec after picture onset. The ERPs recorded in the patients were compared to the control group. The time-windows of divergent ERP correlates were very similar between successful and erroneous naming, but they were differently distributed in the 6 patients. Two patients with conduction aphasia and impaired phonological encoding had normal electro-cortical activity during the first 300msec and abnormal patterns between 300 and 450msec. Two patients with lexical-semantic impairment had earlier ERP abnormalities starting immediately after visual processes. The two patients with less severe anomia and preponderance of omission errors displayed abnormal ERPs between 280 and 350msec. These results indicate that abnormal electro-cortical correlates of anomic profiles can be observed in different time-windows, which seem to correspond to the time course of the impaired encoding processes.
Solid solutions between Li[Li1/3Mn2/3]O2 and LiMO2 (M=Ni1/3Mn1/3Co1/3, Ni0.4Mn0.4Co0.2, Ni0.45Mn0.45Co0.1, Ni0.5Mn0.2Co0.3, and Ni0.5Mn0.3Co0.2) have been synthesized by a solid-state reaction method. The as-prepared Li1.2Ni0.13Mn0.54Co0.13O2, Li1.2Ni0.16Mn0.56Co0.08O2, Li1.2Ni0.18Mn0.58Co0.04O2, Li1.2Ni0.2Mn0.48Co0.12O2, and Li1.2Ni0.2Mn0.52Co0.08O2 solid solutions cathode materials can deliver discharge capacities of 267, 262, 253, 235, and 238mAhg−1, respectively, at a charge/discharge current density of 25 mA g−1 in the voltage range of 2.5–4.7 V. These cathodes all have initial coulombic efficiencies larger than 80%, and show capacity loss less than 0.13% per cycle while cycling at 125 mA g−1 for 50 cycles. From Rietveld refinement results and electrochemical impedance spectra (EIS) analysis, it is found that the highest charge/discharge capacity values of Li1.2Ni0.13Mn0.54Co0.13O2 cathode with the lowest Ni content among them are attributed to the lowest cation mixing. While both the Li1.2Ni0.2Mn0.48Co0.12O2 and Li1.2Ni0.2Mn0.52Co0.08O2 cathode materials with higher Ni content exhibit better rate capabilities due to their lower charge transfer resistances and higher electrical conductivities than those of other samples.
Fluoroethylene carbonate (FEC) has been proposed as an effective electrolyte additive that enhances the stability and elasticity of the solid electrolyte interphase (SEI) of emerging Si and Li metal anodes. However, uncertainties still remain on the exact mechanism through which FEC alters the electrolyte decomposition and SEI formation process. Herein, the influence of FEC on LiPF6/ethylene carbonate (EC) electrolytes for Si anodes is investigated through classical molecular dynamics, Fourier-transform infrared spectroscopy, and quantum chemical calculations. Albeit a minority species, FEC is found to significantly modify the solvation structure and reduction behavior of the electrolyte while being innocuous to transport properties. Even with limited 10% of FEC, the Li+ solvation structure exhibits a notably higher contact-ion pair ratio (14%) than the parent EC electrolyte (6%). Moreover, FEC itself, as a new fluorine-containing species, appears in 1/5 of the Li+ solvation shells. The Li+-coordinated FEC is found to reduce prior to EC and uncoordinated FEC which will passivate the anode surface at an early onset (ca. 0.3 V higher than EC) by forming LiF. The critical role of FEC in tailoring the Li+ solvation structure and as-formed protective SEI composition provides mechanistic insight that will aid in the rational design of novel electrolytes.
Li3V2(PO4)3, Li3V2(PO4)3/C and Li3V2(PO4)3/(Ag+C) composites as cathodes for Li ion batteries are synthesized by carbon-thermal reduction (CTR) method and chemical plating reactions. The microstructure and morphology of the compounds are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Li3V2(PO4)3/(Ag+C) particles are 0.5–1μm in diameters. As compared to Li3V2(PO4)3, Li3V2(PO4)3/C, the Li3V2(PO4)3/(Ag+C) composite cathode exhibits high discharge capacity, good cycle performance (140.5mAhg−1 at 50th cycle at 1C, 97.3% of initial discharge capacity) and rate behavior (120.5mAhg−1 for initial discharge at 5C) for the fully delithiated (3.0–4.8V) state. Electrochemical impedance spectroscopy (EIS) measurements show that the carbon and silver co-modification decreases the charge transfer resistance of Li3V2(PO4)3/(Ag+C) cathode, and improves the conductivity and boosts the electrochemical performance of the electrode.
Electroreduction of trans(Cl) and cis(Cl)Ru(L)(CO)2Cl2 (L=bpy=2,2′-bipyridine, dmbpy=4,4′-dimethyl-2,2′-bipyridine) in CH3CN and DMSO resulted in electrode-adhering films and the reactions were studied by voltammetry and the electrochemical quartz crystal microbalance. These methods were complemented by hydrodynamic rotating ring-disc and quartz crystal impedance methods. The deposition was strongly influenced by the type of solvent, polarisation mode and electrolyte stirring, but for all compounds, rapid charge transfer was found. For monomers with trans(Cl)Ru(bpy)(CO)2Cl2, the two-electron reduction and Ru0Ru0 polymerisation process suggested in the literature was confirmed. Some adsorption of CH3CN was also indicated and for potentiostatic deposition in static solution the impedance measurements indicated increased film viscoelasticity. Depositions with cis(Cl)Ru(bpy)(CO)2Cl2 were more complex and the rate declined gradually in static solution. In stirred solution a straightforward polymer formation took place. For trans(Cl)Ru(dmbpy)(CO)2Cl2 the literature mechanism could not be confirmed and large deviations were observed during the early stages of deposition. The trans(Cl) dimer, [Ru(bpy)(CO)2Cl]2 displayed a lower current efficiency during film formation than the monomer and no simple deposition mechanism could be suggested. For the trans(Cl)[Ru(dmbpy)(CO)2Cl]2 dimer a straightforward deposition was found. The films could be removed by electrooxidation and mass/charge data show that the films break up in large fragments. The reduction and deposition process for trans(Cl) monomers (L=bpy, dmbpy) was light sensitive and the mass of films deposited during cyclic voltammetry (CV) was doubled when the electrode was irradiated.
Sulfur and metal sulfides have been the materials of choice for the cathodes to achieve high energy density from lithium based batteries. Among several metal sulfides, copper sulfide has been widely investigated as a positive electrode material for Li-ion batteries. In the present study, in situ preparation of copper sulfide by reaction of sulfur coated on copper foil current collector is investigated. Sulfur is blended with either acetylene black as a conducting agent or TiO2 nanotubes as porous and non-conducting additive and electrodes are prepared on Cu foil. Electrodes are also prepared without any additive. Copper reacts with sulfur forming copper sulfide which has been confirmed by X-ray diffraction studies. Formation of sulfides with platelet like morphology has been observed in all the coatings. Specific discharge capacity of 282mAhg−1 has been obtained from S-TiO2 electrode based cell as compared to 317mAhg−1 from S-C electrode based cell. Discharge capacity of 230mAhg−1 has been obtained from the cells with S electrode without any additive. This is attributed to the higher conductivity of copper sulfide than sulfur and also to the formation of conducting copper particles on discharge. On subjecting the cells to 100 discharge-charge cycles, almost stable performance has been observed with S-TiO2 electrode based cell. Furthermore, the discharge capacity of S-TiO2 based cell is greater than S-C based cell and it increases on repeated cycling.
With data drawn from the second public release version of the “Survey of Health, Aging and Retirement in Europe” (SHARE), we scrutinize individual and contextual (regional) correlates of economic difficulties among older Europeans, aged 65 or more. A logistic multi-level regression model with random intercept shows that the risk of being relatively poor varies considerably among the aged. We verified that the factors affecting poverty in each area are not merely the weighted sum of the effect of the more disadvantaged people within the same area, which also exists: poverty appears also significantly influenced by the specific context of residence.
The electrochemical methods with the advantages of sensitivity, accuracy, low-cost, simplicity and real-time online determination are expected to detect organic dyes, Methyl Orange (MO) and Rhodamine B (RhB), which are harmful to human beings extensively. In this work, Fe3O4 and single-walled carbon nanotubes (SWNTs) hybrid, as a non-noble metal electrocatalyst, was synthesized by hydrothermal method and modified on the electrode to prepare an electro-sensor for monitoring MO and RhB. Due to the synergistic effects between Fe3O4 and SWNTs, the magnified surface area and good dispersion of SWNTs, the Fe3O4/SWNTs hybrid, has the outstanding superiority of higher-conductivity and catalytical activity with a wide linear concentration range of 0.025–4000μM, 0.1–250μM and a calculated low detection limit (LOD) of 4nM, 25nM for MO and RhB respectively. Furthermore, it's the first time that the proposed electrode achieves the simultaneous determination of both dyes. Then, from the investigation of kinetics and pH value, it's found that both oxidation reactions involve two electrons and one proton participating. The modified electrode also exhibited good selectivity, high reproducibility and promising feasibility in practical sample analysis.
A new series of electrolytes composed of LiI and acetamide have been investigated in dye-sensitized solar cells (DSSCs). These electrolytes melt at about 50°C and their ionic conductivities vary drastically below and above the melting points (T m). They tend to form large crystals at low temperature, leading to poor penetration and contact within porous TiO2 anode film. This shortage is improved by introducing nano-SiO2 particles into the electrolyte. A total conversion efficiencies (η) of 0.3% at 35°C and 4.2% at 75°C are achieved respectively under AM 1.5 simulated solar light illumination when a LiI/acetamide (1:16) electrolyte with 8wt% nano-SiO2 is used. It is expected that the DSSC using phase transition electrolyte could show high efficiency for operation at high temperature and high stability for storage at low temperature.