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The electrochemical stability window (EW) of polyether based salt-in-polymer electrolytes was investigated using density functional theory (DFT) calculations. The electrolyte systems investigated consisted of polyethylene oxide (PEO) in either lithium-bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium-hexafluorophosphate (LiPF6) salt and the EW was determined by performing calculations of reduction and oxidation potentials of isolated ethylene oxide (EO) oligomer and the respective salt species in a continuum solvent. The simulations suggest that the cathodic limit of the polymer-salt system is defined by the reduction potential of the salt anion and that both salt anions considered are unstable against Li anode. The anodic limit is defined by EO and it is stable against most commercial cathodes. Including explicit salt molecules in the calculations shows that the predicted EW is changed by ∼0.4 V. The calculations further reveal that the EW is dependent on the type of the salt molecule. Perfluoropolyether, a perfluorinated analog of PEO that has lower reduction potential and higher oxidation potential in isolation as compared to PEO, improved both oxidation and reduction stability of the polymer-salt system. Substitution of other functional groups to PEO improved the electrochemical stability to potentially accommodate higher voltage window requirements.
Novel polymer electrolyte based on low-molecular weight poly(carbonate-ether) and lithium tetrafluoroborate has been prepared and used in lithium–oxygen battery for the first time, the electrolyte with approximate 17% of LiBF4 showed ionic conductivity of 1.57 mS cm−1. Infrared spectra analysis indicates that obvious interaction between the lithium ions and partial oxygen atoms in the host polymer exists, and the lithium salt and the host polymer have good miscibility. The lithium–oxygen battery from this polymer electrolyte shows similar cyclic stability to traditional liquid electrolyte observed by FT-IR, AFM and electrochemical measurements, which may provide a new choice for fabrication of all-solid-state high-capacity rechargeable lithium–oxygen battery with better safety.
In this paper we report density-functional theory (DFT) calculations at various levels of accuracy to compare the electrochemical properties of several silicate compounds as possible cathode materials in Li-ion batteries. We have tested the already known olivine-like structure (LiMSiO4, M=Mn, Fe, Co, and Ni) and the more recently discovered tetrahedral Pmn21 Li2MSiO4 (M=Mn, Fe, Co, and Ni). Our calculations show the influence of exchange and correlation potentials used to compute the redox potentials, electronic band gaps and other properties of these materials. A detailed study of the multicomponent effect on those characteristics gives us useful insight about how to improve the electrochemical performance of the cathode and its efficiency in the Li-ion battery.
Hydrogen peroxide features in many biological oxidative processes and must be continuously degraded enzymatically either via a catalatic or a peroxidatic mechanism. For this purpose ancestral bacteria evolved a battery of different heme and non-heme enzymes, among which heme-containing catalase-peroxidases (CP) are one of the most widespread representatives. They are unique since they can follow both H2O2-degrading mechanisms, the catalase activity being clearly dominant. With the fast increasing amount of genomic data available, we were able to perform an extensive search for CP and found almost 300 sequences covering a large range of microorganisms. Most of them were encoded by bacterial genomes, but we could also find some in eukaryotic organisms other than fungi, which has never been shown until now. Our screen also reveals that approximately 60% of the bacteria do not possess CP genes. Chaotic distribution among species and incongruous phylogenetic reconstruction indicated existence of numerous lateral gene transfers in addition to duplication events and regular speciation. The results obtained show an impressively complex gene transmission pattern, and give some new insights about the role of CP and the origin of life on earth. Finally, we propose for the first time bacterial candidates that may have participated in the transfer of CP from bacteria to eukaryotes.
A metal film of Cu or Sn was vacuum-deposited on the surface of mesoporous anatase TiO2 electrodes, and the Li insertion/extraction behaviour was investigated by cyclic voltammetry and galvanostatic cycling. The morphological and structural characterization of metal-coated electrodes showed that the metallic layers do not alter the structure of anatase. The electrode surface modification made by thin-film deposition improves the kinetics of Li insertion/extraction and remarkably enhances the electrochemical performances in terms of capacity and stability, especially at high charge/discharge rates.
In this study, the effect of utilization of a nanostructured nickel based material as a negative electrode on the performance of microfluidic microbial fuel cell (MFC) with Escherichia coli as biocatalyst has been investigated. Designing the microfluidic MFC with nickel nanostructure resulted in a higher volumetric power density of 343 W m−3 compared to the previously published results. The assessment of effective parameters on the electrochemical performance of cell was investigated. The investigation of the hydraulic diameter impact on the power generation proves that reducing the microchannel hydraulic diameter from 1000 to 350 μm minimized the internal mass-transfer resistance, and consequently 32% increase in the maximum surface power density is observed. Replacing the nickel foil with nickel nanostructures resulted in an additional improvement of 67% in the maximum surface power density. The maximum volumetric power density of 343 W m−3 has been obtained for the fabricated MFC with 350 μm hydraulic diameter associating nanostructured morphology. To assess the capability of the microfluidic MFC as a power source of the energy storage devices, the obtained results show that the microfluidic MFC with nickel nanostructure is able to provide about 76% of the total power needed for manganese rechargeable lithium battery.
Graphene oxide/polypyrrole (GO/PPy) composite is synthesized by in situ oxidation polymerization of pyrrole (Py) in the presence of GO and used for supercapacitor electrode. The scanning electron microscope (SEM) observes that PPy nanoparticles are uniformly grown on the surfaces of GO sheets, leading to increase both the specific surface area and the electrical conductivity of material. GO/PPy composite exhibits better electrochemical performances than the pure individual components. When the mass ratio of GO to Py is 10:100, the GO/PPy composite electrode shows the highest capacitance of 332.6 F g−1, and presents high rate capability. An asymmetric supercapacitor is fabricated by using the optimized GO/PPy composite as positive electrode and activated carbon (AC) as negative electrode. The asymmetric supercapacitor can be cycled reversibly in the voltage range of 0–1.6V, and exhibits the maximum energy density of 21.4 Wh kg−1 at a power density of 453.9Wkg−1. Furthermore, the GO/PPy//AC asymmetric supercapacitor displays good rate capability and excellent cyclic durability.
Mesophase pitch AR24 was directly activated with KOH using different proportions of the activating agent and activation temperatures, to study the effect on the textural characteristics of the resultant activated carbons and how these characteristics influence their behaviour as electrodes in supercapacitors. The textural properties of the activated carbons were studied by gas adsorption and immersion calorimetry. The results indicate that all the carbons produced were mainly microporous, with pore size around 1nm. The behaviour of these carbons as electrodes in supercapacitors was studied from galvanostatic charge–discharge cycles. The specific capacitance values obtained were very high, reaching 400 and 200Fg−1 at low and high current densities respectively, for the sample activated with (5:1) KOH to mesophase ratio. Nevertheless, the reasons for this high capacitance values cannot be explained only on the basis of the textural characteristics of the activated carbons, as the results indicated that other factors might be also playing a significant role in their electrochemical behaviour.
Lithium manganese oxide (LiMn2O4) of spinel structure is a very attractive and widely applied active material for lithium ion cells because of high potential vs. metallic lithium content, non-toxicity and low cost of production. Unfortunately, the capacity fading at higher current densities limits its application in fast charging batteries. One of the solutions to this problem is modification of the interface between the current collector and the cathode mass. In this paper we proposed a modification of aluminum current collector by coating it with a thin film of multiwalled carbon nanotubes. Two variants of Langmuir-Schaefer method have been used for the first time to produce the film modifying the interface between the collector and the active material. The proposed modification of the current collector resulted in reduction of charge-transfer resistance and consequently in increasing cells capacity at high current densities.
In this paper, the effectiveness of support schemes for micro fuel cells in Germany is analyzed with regard to the latest market conditions, technical characteristics, and legislative changes. To this end, a dynamic model is used and applied to high-resolution household demand data. Specifically, we scrutinize whether polymer electrolyte membrane fuel cells are now a feasible investment option for residential usage in Germany or are likely to become so soon. Furthermore, we investigate whether electric energy storage could be a useful extension to the domestic fuel cell system by supplying short-term peak demand, and thus increasing self-consumption and potentially the overall economic merit. We find that the fuel cell technology analyzed is unlikely to become cost-competitive by 2020, and it may take quite some time to achieve a substantial market diffusion. We conclude that for the time being, electric energy storage in combination with a fuel cell system is not a worthwhile investment in a scenario where grid connection is assumed.
Recently, there have been many reports on efforts to improve the rate capability and discharge capacity of lithium secondary batteries in order to facilitate their use for hybrid electric vehicles and electric power tools. In the present work, we present a ZrO2-coated Li[Li1/6Mn1/2Co1/6Ni1/6]O2. The bare Li[Li1/6Mn1/2Co1/6Ni1/6]O2 shows a high initial discharge capacity of 224 mAh g−1 at a 0.2 C rate. Owing to the stability of ZrO2, it was possible to enhance the rate capability and cyclability. After 1 wt% ZrO2 coating, the ZrO2-coated Li[Li1/6Mn1/2Co1/6Ni1/6]O2 showed a high discharge capacity of 115 mAh g−1 after 50 cycles under a 6 C rate, whereas the bare Li[Li1/6Mn1/2Co1/6Ni1/6]O2 showed a discharge capacity of only 40 mAh g−1 and very poor cyclability under the same conditions. Based on results of XRD and EIS measurements, it was found that the ZrO2 suppressed impedance growth at the interface between the electrodes and electrolyte and prevented collapse of the layered hexagonal structure.
Nickel-based layered rock-salt cathode materials for lithium-ion secondary batteries have drawn considerable attention due to their high energy capacity, lower cost, and better environmental compatibility than other current potential materials. As the nickel content increases, however, these materials suffer from significant capacity fading during charge-discharge cycles at elevated temperatures. While the capacity deterioration and poor cycling stability are mainly because of the formation of NiO-like rock-salt structures at the surface of active materials, the degradation mechanisms have not been fully investigated. In this study, to clarify the process of formation of inactive NiO-like structures, the degradation mechanism of a cathode-active material, namely, LiNi0.80Co0.15Al0.05O2 (NCA) is studied after a single charge–discharge cycle, by using site-selective energy-dispersive X-ray spectroscopy associated with transmission electron microscopy. It is confirmed that cation mixing occurs between the lithium- and transition metal-sites of the LiMO2 (M = transition metals) layered rock-salt structures during the transition to partially ordered transition states and then to the final NiO-like disordered rock-salt structures. Further, the volume fractions of the partially/fully disordered phases in the NCA primary particles are quantitatively estimated.
Child externalising symptoms are associated with a bias towards attributing hostile intent to others. We examined the role of parental attributions in the development of this hostile attribution bias in children. The parents of 134 children aged 5–7 years responded to hypothetical social scenarios examining a) their general tendency to attribute hostile intent to the ambiguous behaviour of others, and b) hostile attributions made specifically to their child. Children's own attributions of hostile intent and levels of externalising symptomatology were assessed. The results indicated that child externalising symptoms were positively associated with both a generalised tendency towards the attribution of hostile intent and child-specific hostile attributions in parents. Child externalising symptoms were themselves associated with hostile attributions made by the child. However, no direct associations were observed between parental and child attributions of hostile intent. Thus, although the results suggest a role for parental social information processing biases in the development of child externalising symptoms, a direct transmission of such biases from parent to child was not supported.
The recycling of spent commercial lithium-ion batteries (LIBs) generates numerous environmental and economic benefits. In this research, a thermal treatment-ammoniacal leaching process is proposed to recover valuable metals from cathode active powder. Based on the thermal behavior by TG-DSC analysis, the cathode active powder is calcined at 300 °C and 550 °C in air atmosphere, and the crystalline phase characterization indicates that a new phase of Co3O4 appears in the cathode active powder calcined at 550 °C, which signifies that the layer structure of LiCoO2 collapses. The valence of manganese increases to form Li4Mn5O12 in spinel structure of LiMn2O4. Using calcined cathode powder as feed material, ammoniacal leaching is carried out in (NH4)2SO4 -(NH4)2SO3 solution. Under the optimum conditions, Ni, Co, Mn and Li can be completely leached out with efficiencies of 98%, 81%, 92% and 98%, respectively. However, with the increase of ammonia concentration, the leaching efficiency of Mn decreases dramatically to 4% due to the formation of double salts. It is found that Co and Mn can be precipitated into residues in the form of (NH4)2Co(SO4)2·H2O, (NH4)2Mn(SO3)2·H2O and (NH4)2Mn(SO4)2·6H2O under different leaching parameters. Based on the corresponding relationship between the leaching efficiency and phase evolution of object element, selective leaching can be achieved by controlling the formation of double salts.
Li2NiSi x Ti1−x O4 was obtained by the sol–gel method under ambient pressure in the whole 0 ≤ x ≤ 0.2 regions. The lattice constant did not change, but the crystallinity decreased by increasing the Si doping level. The discharge capacities at the rate of 0.32 mA g−1 for the obtained Li2NiTiO4 and Li2NiSi0.1Ti0.9O4 were 153.4 mAh g−1 and 145.5 mAh g−1, respectively. The energy densities of the Li2NiTiO4 (598 mWh g−1) and Li2NiSi0.1Ti0.9O4 (567 mWh g−1) obtained at the rate of 0.32 mA g−1 were equivalent to that of LiCoO2. Moreover, the discharge capacities of Li2NiTiO4 and Li2NiSi0.1Ti0.9TiO4 remained at 57.1 mAh g−1 and 75.6 mAh g−1 even after 20 cycles, respectively. In addition, the framework of Li2NiTiO4 and Li2NiSi x Ti1−x O4 was stable enough to maintain its charge–discharge processes at the first cycle by expansion and contraction of the lattice accompanying the extraction/insertion of lithium.
The use of internal telemetry has greatly advanced fisheries research in the past two decades, permitting researchers to observe movements and distributions of organisms in their natural environment. For many years, the prevailing opinion has been that internal tags should not weigh more than 2% of the dry body weight of a fish. Some studies indicate that tags weighing up to 12% dry body weight do not have a negative effect on swimming performance, but few authors have examined impacts to fish physiology and health. This study investigated how tags greater than 2% body mass affected the mortality, tag retention, swimming performance, and physiological indicators of stress in brook trout (Salvelinus fontinalis Mitchill).
Piezoelectric nanogenerators have been intensively developed in terms of their materials and applications; however, only modest structural progress has been made due to limitations in the growth mechanisms of nano-materials. In this work, a piezoelectric nanogenerator based on a nanoforest structure is introduced. Through a metal-assisted chemical etching (mac-etch) process, densely packed vertical nanowires and nanovoids are fabricated. The nanoforest structure serves as a bottom electrode, which increases the interfacial area with a subsequently deposited piezoelectric material, in this case barium titanate (BaTiO3). In the proposed fabrication method, more various piezoelectric materials can be used for a piezoelectric device compared to previously reported methods because the process relies not on the growth mechanism but on the deposition technique. The proposed nanoforest structured nanogenerator produces a 4.2 times enhanced power density compared to the control generator, which uses the same material but has a flat topology. The strong relationship between the enhancement ratio and the nanoforest height is found. Both the experiment and the simulation data present a consistent trend of a gradual increase with a short height and saturation at a tall height.
In this article, studies on coordinative properties of 5,11,17,23-tetra-p-tert-butyl-25,27-bis(N-p-nitrophenylureido-butoxy)-26,28-dipropoxycalix[4]arene (Cx2) are presented. Since this anion-receptor was previously used as an additive to solid polymer electrolytes, the correlation of the data presented here and the role of anion-receptors in this type of electrolytes is discussed. The formation constants of salt–receptor complexes and receptor self-complexation (dimer formation) are estimated in the solution in the non-interacting solvent using 1H and 19F NMR titration. Independently, the affinity of the Cx2 to low molecular weight analogs of PEO and some other organic solvents in this system was tested using the same technique. The estimated values of the formation constants are used in the discussion the role of the anion-receptor in the changes of concentration of ions, ionic agglomerates and complexes of Cx2 in the system comprising salt, solid or liquid matrix and anion-receptor.
We examined the use of two conductive additives (C and Au) to boost the performance of lithium iron phosphate as a positive electrode material for lithium ion batteries. The phosphate was prepared by using a new, fast synthetic method that provides nanosized particles. Carbon and gold were sputtered on LiFePO4. Additional sample was an intimate mixture of carbon and phosphate by mechanochemical–pyrolitical synthesis. Although the voltammetric tests revealed that the addition of these conductive materials expedited electron transfer kinetics, the effect on galvanostatic cycled cells was found to depend largely on the nature and way of introduction of the additive (carbon or metal). Surface analysis and electrochemical impedance spectroscopy on cycled electrodes provided a better understanding of the special behaviour of the carbon and gold composites obtained by sputtering.
Triphenyl phosphite (TPPi) was investigated as an electrolyte additive for high-voltage lithium-ion batteries using lithium-rich layered oxide cathode in this paper. The cyclic stability of Li1.16Ni0.2Co0.1Mn0.54O2 was improved significantly with the adoption of 0.2wt. % TPPi. The capacity retention of Li1.16Ni0.2Co0.1Mn0.54O2 was improved significantly, especially at elevated temperature, from 69.0% to 89.6% after 90 cycles. Electrochemical and physical characterizations indicated that TPPi was oxidized at 4.2V (vs. Li/Li+), which was lower than that of the solvents and lithium extraction from Li1.16Ni0.2Co0.1Mn0.54O2, and the oxidization resulting in an artificial cathode interface film, which effectively inhibited the decomposition of traditional electrolyte and protected Li1.16Ni0.2Co0.1Mn0.54O2 material from destruction.
Drought and fire are common disturbances to grassland ecosystems. We report two years of eddy covariance ecosystem–atmosphere fluxes and biometric variables measured in nearby burned and unburned pastures in the US Southern Great Plains. Over the course of the experiment, annual precipitation (∼600mmyr−1) was lower than the long term mean (∼860mmyr−1). Soil moisture decreased from productive conditions in March 2005 dry, unproductive conditions during the growing season starting in March 2006. Just prior to the burn in early March 2005, burned and unburned pastures contained 520±60 and 360±40gCm−2 of total above ground biomass (AGB) and litter, respectively. The fire removed approximately 200gCm−2 of litter and biomass. In the 2005 growing season following the burn, maximum green AGB was 450±60 and 270±40gCm−2, with corresponding cumulative annual net ecosystem carbon exchange (NEE) of −330 and −150gCm−2 for the burned and unburned pastures, respectively. In contrast to NEE, cumulative mean sensible heat and water fluxes were approximately equal in both pastures during the growing season, suggesting either an increase in water use efficiency or a decrease in evaporation in the burned relative to the unburned pasture. In the 2006 growing season, dry conditions decreased carbon uptake and latent heat, and increased sensible heat fluxes. Peak AGB was reduced to 210±30gCm−2 and 140±30gCm−2 in the burned and unburned pastures, respectively, while NEE was near zero. These results suggest that the lack of precipitation was responsible for most of the interannual variation in carbon exchange for these un-irrigated prairie pastures.
Objectives Social cognition plays an important role in the functioning of individuals with psychosis. In this study, we explored two areas of social cognition not previously investigated early in the course of psychosis. Method Eighty-eight clinical high risk participants, 26 participants diagnosed with schizophrenia for less than 5 years, and 41 non-clinical control participants completed two measures of social cognition. Results Clinical high risk participants demonstrated biased responses to untrustworthy faces compared to both of the other groups. Early schizophrenia participants performed more poorly on an advanced theory of mind task compared to the clinical high risk and control groups. Conclusions There are different patterns of performance on social cognitive tasks in these groups, which require further examination in longitudinal studies.