batterydata/paper-abstracts huggingface dataset:
Na2Li2Ti6O14 is synthesized by a simple solid state method between 500 and 900°C. It is found that pure Na2Li2Ti6O14 is only formed at 800°C or above. The tap density of as-prepared Na2Li2Ti6O14 is about 1.52gcm−3. Particle morphology analysis shows that the size of Na2Li2Ti6O14 gradually increases with the increase of sintering temperature. Calcined at 900°C, Na2Li2Ti6O14 shows slight particle aggregation and melting. As a result, Na2Li2Ti6O14 formed at 800°C reveals higher electrochemical activity than the sample obtained at 900°C. Therefore, the suitable preparation temperature for Na2Li2Ti6O14 by solid state reaction is 800°C. Charge–discharge results show that Na2Li2Ti6O14 prepared at 800°C can deliver a reversible capacity of 89.9mAhg−1 at 100mA g−1, 81.3mAhg−1 at 200mAg−1, 75.2mAhg−1 at 300mAg−1, 69.6mAhg−1 at 400mAg−1 and 65.5mAhg−1 at 500mAg−1. Besides, the lithium storage mechanism in Na2Li2Ti6O14 is also studied by various in-situ and ex-situ methods, which prove that the structural evolution is highly reversible for Na2Li2Ti6O14 during lithiation/delithiation process.
No consensus based national standard for interhospital transports of critically ill patients exists in Norway. The local hospitals are responsible for funding, organizing and performing these transports, resulting in potentially different level of care for the critically ill patients depending on local hospital resources and not the level of severity in the patient’s condition. The aim of this study was to examine how these transports are executed and to discover challenges during transports and potentials of improvement.
A novel hierarchical network-like Co3O4 are successfully synthesized by hydrothermal method combined with subsequent annealing treatment in air. The evolution process of network-like Co(CO3)0.5(OH)·0.11H2O precursor are characterized by XRD, SEM and FT-IR methods. The as-prepared network-like Co3O4 are tested as an anode material in lithium-ion batteries. The influences of the Co3O4 morphology on the electrochemical performances are investigated. In the specific capability test, the first discharge capacity of 2008mAhg−1 is recorded at current density of 100mAg−1. The excellent electrochemical properties of the Co3O4 electrodes can be attributed to high specific surface area which provides more active area that can react with Li+ ions, leading to outstanding specific capacitance. And the results indicated that the polypyrrole (PPy) as a conductive macromolecule coating on the Co3O4 surface can improve performance of the LIBs obviously.
The electrochemical and rheological properties of composite polymer electrolytes (CPEs) based on fumed silica with tethered crosslinkable groups are reported. These silica nanoparticles are dispersed in electrolytes consisting of poly(ethylene glycol) dimethyl ether (PEGdm)+lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to which various methacrylate monomers, such as methyl (MMA), ethyl (EMA), butyl (BMA), n-hexyl (HMA), and n-dodecyl (DMA) methacrylate, are added. The methacrylate monomer facilitates creation of chemical crosslinks between fumed silica particles and formation of a crosslinked network. In this study, the effects of concentration and alkyl chain length of the monomers on conductivity, dynamic rheology, open-circuit interfacial stability, and cell voltage in lithium–lithium cell cycling are examined. Increasing the length of the monomer alkyl chain enhances both conductivity and elastic modulus of the crosslinked CPE. In contrast, increasing monomer concentration results in higher elastic modulus, but reduced conductivity. Lithium–lithium cell cycling and open-circuit interfacial stability results did not correlate with alkyl chain length. That is, for the lithium–lithium cycling studies, all crosslinked samples exhibit higher half-cycle voltage compared to non-crosslinked samples; however, the open-circuit interfacial stability of CPEs containing BMA and HMA exhibit improved stability compared to the other monomers and the CPE without monomer.
A light-weight and free-standing graphene foam interlayer placed between sulfur cathode and separator is investigated to improve the electrochemical performance of lithium-sulfur batteries. The highly conductive and light-weight porous graphene foam not only increases the electron pathway of cathode, but also adsorbs the dissolved high-order lithium polysulfides during cycles, thus the loss of active materials is greatly avoided with only minimum mass addition approximately 0.3 mg cm−2 on cathodic side. Additionally, the atomic layer deposition method is applied to deposit the zinc oxide nano-scale coating on graphene foam interlayer in order to chemically trap the polysulfides with minimized deterioration on conductivity of graphene foam. Among all the graphene foam, graphene foam@zinc oxide and graphene foam/graphene foam@zinc oxide interlayers, the graphene foam/graphene foam@zinc oxide exhibits the best electrochemical performance, delivering an initial specific capacity of 1051 mAh g−1 at 0.5 C and retaining a reversible capacity of 672 mAh g−1 after 100 cycles, while the cell without interlayer only shows 346 mAh g−1. These results demonstrate the strategy of including a zinc oxide modified graphene foam interlayer as an effective light-weight interlayer for improving Li-S cell performance.
The influence of ZrO2 particles on fluorine-doped lead dioxide electrodeposition process on the glass carbon electrode (GCE) from lead nitrate electrolytes was studied by cyclic voltammetry (CV) and chronoamperometry (CA), coupled with the scanning electron microscope (SEM). Instantaneous nucleation mechanism is found for fluorine-doped lead dioxide electrodeposition in the presence of ZrO2 particles according to Scharifker–Hills’ model with three-dimensional growth. The results show that the addition of ZrO2 particles decrease the active surface area of the GCE, and the growth of the lead dioxide crystallites was obstructed.
The thermal reactions of a lithiated graphite anode with and without 1.3M lithium hexafluorophosphate (LiPF6) in a solvent mixture of ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were investigated by means of differential scanning calorimetry (DSC). The products of the thermal decomposition occurring on the lithiated graphite anode were characterized by Fourier transform infrared (FT-IR) analysis. The lithiated graphite anode showed two broad exothermic peaks at 270 and 325°C, respectively, in the absence of electrolyte. It was demonstrated that the first peak could be assigned to the thermal reactions of PF5 with various linear alkyl carbonates in the solid electrolyte interphase (SEI) and that the second peak was closely related to the thermal decomposition of the polyvinylidene fluoride (PVdF) binder. In the presence of electrolyte, the lithiated graphite anode showed the onset of an additional exothermic peak at 90°C associated with the thermal decomposition reactions of the SEI layer with the organic solvents.
Nonwoven films of composites of thermoplastic polyurethane (TPU) with different proportion of poly(vinylidene fluoride) (PVdF) (80, 50 and 20%, w/w) are prepared by electrospinning 9wt% polymer solution at room temperature. Then the gel polymer electrolytes (GPEs) are prepared by soaking the electrospun TPU–PVdF blending membranes in 1M LiClO4/ethylene carbonate (EC)/propylene carbonate (PC) for 1h. The gel polymer electrolyte (GPE) shows a maximum ionic conductivity of 3.2×10−3 Scm−1 at room temperature and electrochemical stability up to 5.0V versus Li+/Li for the 50:50 blend ratio of TPU:PVdF system. At the first cycle, it shows a first charge–discharge capacity of 168.9mAhg−1 when the gel polymer electrolyte (GPE) is evaluated in a Li/PE/lithium iron phosphate (LiFePO4) cell at 0.1C-rate at 25°C. TPU–PVdF (50:50, w/w) based gel polymer electrolyte is observed much more suitable than the composite films with other ratios for high-performance lithium rechargeable batteries.
Recent epidemiology studies of power-frequency magnetic fields and reproductive health have characterized exposures using data collected from personal exposure monitors over a single day, possibly resulting in exposure misclassification due to temporal variability in daily personal magnetic field exposure metrics, but relevant data in adults are limited. We assessed the temporal variability of daily central tendency (time-weighted average, median) and peak (upper percentiles, maximum) personal magnetic field exposure metrics over 7 consecutive days in 100 pregnant women. When exposure was modeled as a continuous variable, central tendency metrics had substantial reliability, whereas peak metrics had fair (maximum) to moderate (upper percentiles) reliability. The predictive ability of a single-day metric to accurately classify participants into exposure categories based on a weeklong metric depended on the selected exposure threshold, with sensitivity decreasing with increasing exposure threshold. Consistent with the continuous measures analysis, sensitivity was higher for central tendency metrics than for peak metrics. If there is interest in peak metrics, more than 1 day of measurement is needed over the window of disease susceptibility to minimize measurement error, but 1 day may be sufficient for central tendency metrics.
LiFe1−x MII x PO4/C (MII =Co, Ni, Mg) composites had been obtained by sol–gel method. Structure and morphology of the obtained materials have been studied with the use of the XRD-analysis, SEM and Mössbauer spectroscopy. Their electrochemical behavior has been investigated with the use of charge/discharge tests. The materials doped by cobalt and nickel were shown to be characterized by an increased lithium intercalation and deintercalation rates, and retain a high capacity during charge and discharge the battery at high currents densities (LiFe0.9Ni0.1PO4 capacity amounts to 145 and 62mAh/g at a discharge current 50 and 3000mA/g). Mg2+ incorporation into LiFePO4/C cathode material results in the slight increase of charge/discharge rate and significant capacity decrease. Mössbauer spectroscopy has shown that MII ions in the LiFe1−x MII x PO4/C (MII =Co, Ni) materials are orderly distributed both in charged and discharged states, each iron ion has no more than one MII ion in the nearest environment. In the case of Ni-doped samples the ordering is less pronounced. The reasons of the changes observed in the electrochemical performances and charge/discharge rate have been discussed on the base of Mössbauer spectroscopy and XRD data.
A series of LiMn2−x Cr x O4 (x=0, 0.01, 0.05, 0.1, 0.2) has been synthesized by a modified citrate route with combustion. The influence of the substitution of Cr for Mn on the electrochemical performances was investigated and compared. The results show that Cr substitution in spinel LiMn2O4 can effectively depress the capacity fading over 4V and improve the cycleability.
The electrochemical behaviour of electrodes modified with a Co/Al-NO3 hydrotalcite-like compound was investigated by voltammetric techniques and electrochemical impedance spectroscopy in aqueous solution. The latter technique was used in order to study the electronic and ionic transport, both inside and on the surface of the material. The behaviour of the modified electrode was studied at different OH− concentrations (pH 11–12.8) and at different temperatures, with the aim to calculate the activation energies of the electronic conduction and charge-transfer processes. The electronic conductivity of the bulk material is dependent on the CoIII/CoII ratio and results the limiting parameter of the overall redox process. The same result was previously obtained for the Ni based hydrotalcite, but the latter material showed a better electrical conductivity.
Rechargeable aqueous zinc ion batteries are particularly attractive for large-scale application due to their features including low cost, environmental friendliness, and safety. Herein, we report the use of defect engineering to generate oxygen vacancies in tunneled α-MnO2 through surface gradient Ti doping for long-life ZnMnO2 battery. Interestingly, the introduction of surface gradient Ti doping leads to shrinkage of the interlayer, but simultaneously generates oxygen vacancies as compensated by electron due to the decreased valence state of Mn. Moreover, Ti substitution as well as the created oxygen vacancies open the [MnO6] octahedral walls and result in imbalanced charge distribution and local electric field in the crystal structure, accelerating ion/electron migration rates. Thus, diffusion coefficients of both Zn2+ and H+ ions in TiMnO2 nanowires are improved. Consequently, the TiMnO2 nanowires show improved both H+ and Zn2+ ions storage capacity in Zn/MnO2 battery and achieved excellent high-rate capability and ultralong cycling stability with a low capacity decay rate of 0.005% per cycle at high rate of 1 A g−1. It is believed that the intentionally created vacancies in this work opens up approaches to enhance existing materials that may have applications in more efficient and durable multi-valent ion battery and other technologies.
Hollow carbon fibers with diameters on the order of 30 nm were grown on a ceramic porous substrate, which was used as the oxygen electrode in lithium-oxygen (Li–O2) batteries. These all-carbon-fiber (binder-free) electrodes were found to yield high gravimetric energies (up to 2500 W h kgdischarged−1) in Li–O2cells, translating to an energy enhancement ∼4 times greater than the state-of-the-art lithium intercalation compounds such as LiCoO2 (∼600 W h kgelectrode−1). The high gravimetric energy achieved in this study can be attributed to low carbon packing in the grown carbon-fiber electrodes and highly efficient utilization of the available carbon mass and void volume for Li2O2 formation. The nanofiber structure allowed for the clear visualization of Li2O2 formation and morphological evolution during discharge and its disappearance upon charge, where Li2O2 particles grown on the sidewalls of the aligned carbon fibers were found to be toroids, having particle sizes increasing (up to ∼1 μm) with increasing depth-of-discharge. The visualization of Li2O2 morphologies upon discharge and disappearance upon charge represents a critical step toward understanding key processes that limit the rate capability and low round-trip efficiencies of Li–O2 batteries, which are not currently understood within the field.
Innocuous hydrogels with the characteristics of high conductivity, stretchability and air-stability have potential applications for emerging wearable and bio-related electronic devices. In this study, we develop a rapid and green method for stretchable supercapcitors using safer chemicals to produce hygroscopic conductive polymer hydrogels, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)/poly(vinyl alcohol)/poly(methacrylic acid) (PEDOT:PSS/PVA/PMAA). The as-fabricated conductive polymer hydrogels show a high stretchability as well as a high conductivity (3.1 S cm−1) after absorbing water moisture as the plasticizer, which are used as current collectors and electrode materials to assemble the supercapacitor. By modulating the PEDOT: PSS composition in the hydrogel, the fabricated supercapacitor exhibits fascinating mechanical properties and excellent electrochemical characteristics. The supercapacitor has a maximum specific capacitance of 7.38 mF cm−2 at 10 mV/s, and shows 82% capacitance retention over 2000 charge-discharge electrochemical cycling testing at a current density of 10 mA cm−2. More importantly, the device could be stretched up to 100% strain without affecting the electrochemical performance and is well conserved after stretching 1000 times under 30% tensile strain.
Recent developments in solid-oxide fuel cells (SOFC) that electrochemically oxidize hydrocarbon fuels to produce electrical power without first reforming them to H2 are described. First, the operating principles of SOFCs are reviewed, along with a description of state-of-the-art SOFC designs. This is followed by a discussion of the concepts and procedures used in the synthesis of direct-oxidation fuel cells with anodes based on composites of Cu, ceria, and yttria-stabilized zirconia. The discussion focuses on how heterogeneous catalysis has an important role to play in the development of SOFCs that directly oxidize hydrocarbon fuels.
This paper reports an amorphous carbon-coated SnO2-graphene composite (C@SnO2-Gr) which shows excellent cyclability and a high specific capacity used as an anode for the Li-ion batteries. The C@SnO2-Gr maintained a specific capacity of 879mAhg−1 after 50 cycles at a current density of 100mAg−1. After 350 cycles at a high current density of 1200mAg−1, the specific capacity was resumed to around 860mAhg−1 when the current density dropped to 100mAg−1. It is proved that the excellent electrochemical performance is mainly related to the unique ‘core-shell’ structure induced by the carbon coating. This structure significantly alleviated the pulverization problems of the electrode materials, maintained the microstructure of electrodes and stabilized Sn nanoparticles in the form of nanocrystallites. Graphene and amorphous carbon also provide good conductivity to the active materials. This work suggests that carbon coating is an effective way to improve the electrochemical performance of graphene-metal oxide as anode for Li-ion batteries by means of improving the stability of the nanocrystalline structure.
The Br2/H2 redox flow cell shows promise as a high-power, low-cost energy storage device. In this paper, the effect of various aspects of material selection and processing of proton exchange membranes on the operation of the Br2/H2 redox flow cell is determined. Membrane properties have a significant impact on the performance and efficiency of the system. In particular, there is a tradeoff between conductivity and crossover, where conductivity limits system efficiency at high current density and crossover limits efficiency at low current density. The impact of thickness, pretreatment procedure, swelling state during cell assembly, equivalent weight, membrane reinforcement, and addition of a microporous separator layer on this tradeoff is assessed. NR212 (50 μm) pretreated by soaking in 70 °C water is found to be optimal for the studied operating conditions. For this case, an energy efficiency of greater than 75% is achieved for current density up to 400 mA cm−2, with a maximum obtainable energy efficiency of 88%. A cell with this membrane was cycled continuously for 3164 h. Membrane transport properties, including conductivity and bromine and water crossover, were found to decrease moderately upon cycling but remained higher than those for the as-received membrane.
LiCo1/3Ni1/3Mn1/3O2 cathode electrodes were prepared onto Al current collectors with different surface morphologies through usual doctor blade technique. Their electrochemical performances, especially at high current rate, were influenced by the surface morphology of the current collector:. These implied the less polarization for the electrode prepared on the surface roughened current collector. In addition, the AC complex impedance analysis exhibited that the interface resistance between the film electrode and the current collector as well as the interface resistance between the electrode and the electrolyte was reduced in the case of the surface-roughened current collector, but that the Ohmic resistance was enlarged.
Dendritic Li deposition on graphite anodes of Li-ion batteries (LIBs) not only deteriorates the anode performance but also causes safety concerns. We demonstrate here a proof-of-concept graphite anode containing a polymer coating that effectively mitigates Li dendrite formation under harsh lithiation conditions. It is shown that Li dendrites with dimensions ranging from a few tens nanometers to microns occur readily on granular graphite electrodes either under 20% over-lithiation at 0.2C or fast lithiation up to 10C rate. In contrast, the graphite anode with a conformal thin coating of high-polarity β-phase polyvinylidene difluoride (PVDF) on graphite particles exhibits dendrite-free Li plating under either condition. Moreover, the PVDF coated graphite anode exhibits substantially improved cycling stability with high Coulombic efficiencies under the Li-plating conditions. The rise of charge-transfer resistance due to over-lithiation is reduced. The proof of concept for adopting a dendrite-suppressing polymer coating on graphite anodes offers a new strategy for improving battery safety and renders more options for cell design in enhancing energy and power performances for the state-of-the-art LIBs.
This review presents neuroimaging studies that have explored the cerebral substrates of executive functioning. These studies have demonstrated that different executive functions not only recruit various frontal areas but also depend upon posterior (mainly parietal) regions. These results are in accordance with the hypothesis that executive functioning relies on a distributed cerebral network that is not restricted to anterior cerebral areas. However, there exists an important heterogeneity in the cerebral areas associated with these different processes, and also between different tasks assessing the same process. Since these discrepant results could be due to the paradigms used (subtraction designs), recent results obtained with conjunction and interaction analyses are presented, which confirm the role of parietal areas in executive functioning and also demonstrate the existence of some specificity in the neural substrates of the executive processes of updating, shifting and inhibition. Finally, functional magnetic resonance imaging studies show that the activity in cerebral areas involved in executive tasks can be transient or sustained. Consequently, to better characterize the functional role of areas associated with executive functioning, it is important to take into account not only the localization of cerebral activity but also the temporal pattern of this activity.
The electrochemical properties of amorphous MgNi-based hydrogen storage alloys synthesized by mechanical alloying (MA) were evaluated. The results show that these amorphous Mg50Ni50 alloys exhibit a higher discharge capacity and relatively good rate capacity at a suitable grinding time while their cycle life is very poor. In order to improve the cycle life, the surface of the amorphous Mg50Ni50 alloy was coated with Ti, Al and Zr in Spex 8000 mill/mixer and the coating effects were further investigated. Based on experimental results, two kinds of MgNi-based amorphous alloys are designed by substituting part of Mg in MgNi-based alloys by suitable elements. These alloys are then composed of four components. Thus, the cycle life of electrodes consisting of these quaternary amorphous alloys is greatly improved.