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Two nanostructured electrodes were fabricated and used to construct flexible high performance supercapacitors. Hierarchical NiCo2O4 nanostructures (with airy organdy NiCo2O4 nanosheets on vertical NiCo2O4 nanoarrays) were grown on flexible carbon cloth by a facile template-free method while three dimensional (3D) porous graphene papers (PGP) with scaffold-like microstructure were fabricated by freeze-drying. The hierarchical NiCo2O4/carbon cloth (NiCo2O4/CC) and PGP electrodes achieved the maximum specific capacitance of 1768 (based on the mass of NiCo2O4) and 151Fg−1, respectively. The NiCo2O4/CC (as the positive electrode), PGP (as the negative electrode), and PVA–LiOH gel (as both the solid state electrolyte and separator) were assembled into flexible all-solid-state (NiCo2O4/CC//PGP) asymmetric supercapacitor with an exceptional combination of electrochemical properties in terms of working potential (1.8V), maxmum energy density (60.9Whkg−1), maxmium power density (11.36kWkg−1), and cycling stability (96.8% capacitance retention ratio over 5000 cycles under mechanical bending).
Due to the low double-layer capacitance of activated carbons (<20μFcm−2) and to their low density related to their large micro/meso porosity, the volumetric energy density of commercial supercapacitors remains low. Therefore, the use of pseudocapacitive oxides or nitrides as electrode materials can drastically improve the volumetric performance. However, there is currently a lack of reliable tools to extrapolate the performance of a 1cm2 electrode to a real life cell of several thousand farads. In this paper, we provide a calculation tool to extrapolate the cell capacitance and the energy density both from a gravimetric and volumetric point of view in a 399cm3 device. The calculation datasheet indicates that in order to improve the volumetric energy density of supercapacitors, it is crucial to lower the electrodes porosity down to 30–40%. Similarly, the use of high-density pseudocapacitive oxides greatly enhances the volumetric energy density of the related devices. Combining both parameters (porosity of 30%, density of 4.5gcm−3, active material capacitance of 250Fg−1) can lead to a 28000F device compared to only 3000F for a commercial cell of the same volume. The design of asymmetric aqueous devices by combining two high-density pseudocapacitive oxides with reasonable specific capacitance (≈100Fg−1) is also an interesting way to further improve the cell voltage and subsequently the volumetric energy density. Additionally, the use of aqueous electrolytes enhances the safety of the cells. Finally, the provided spreadsheet will help to envision different associations of pseudocapacitive and/or capacitive materials and to predict their performance when used in real life cells.
Neodymium oxide (Nd2O3) nanoparticles were chemically embedded on a state-of-the art carbon felt (CF) by a precipitation method in non-aqueous solution. Different Nd2O3 loadings were chosen and the obtained electrocatalyst-loaded felts tested for application as electrode in all-vanadium redox flow batteries. Cyclic voltammetry (CV) studies confirmed that Nd2O3 has a catalytic effect towards both redox couples, V4+/V5+ at the positive and V2+/V3+ at the negative side. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) demonstrated only minor particle agglomeration and high dispersion of the particles on the fibres. Charge/discharge profiles revealed an enhanced performance with higher discharge capacity and higher energy efficiency for the modified felts when compared to a thermally activated CF. For instance, after 50 consecutive charge/discharge cycles the energy efficiency of the Nd2O3 modified carbon felt (Nd2O3-CF) was reduced only by 3% compared to a 12% irreversible loss observed for the thermally activated CF. After exchanging the electrolyte after 50 cycles, the felts retained their original performance indicating that less degradation occurred in the modified felts than in the industrial standard and that they maintained their oxygen-donating functionalities on the surface as compared to thermally activated CF.
Stationary battery systems have been proposed as plausible alternative for the storage of renewable energy sources in power grid. For this application aqueous electrolytes are preferred, which offer several important advantages compared to organic electrolytes i.e. non-flammability, cost effectiveness, as well as higher ionic conductivity, solubility and thermal capacity. This work was undertaken to investigate the influence of pH on the electrochemical stability window of aqueous electrolytes for metal-ion batteries. The pH was deliberately controlled in the range from pH 2 to 11. Electrochemical chronopotentiometry method served for the electrochemical stability window measurements. It has been observed that the pH critically influenced the measured dynamic stability window, which shows a maximum and almost pH independent value for pH ranging from 5 to 9. The presence of buffering ions and gelling agents strongly affects the dynamic stability window of the electrolyte through the transport overpotential.
RSV infections cause lower respiratory tract infections and result in surges in physician's office, emergency department visits and hospitalizations, especially in infants and toddlers. Point-of-care (POC) testing reduces healthcare costs and permits informed decisions on treatment, however, optimal POC assays must be sensitive, easy to perform and provide rapid results. A prospective study tested 230 patient nasopharyngeal specimens using 4 RSV direct antigen detection assays (Directigen, Quickvue, Sofia and Veritor) and RT-PCR. A RSV dilution study was also performed to evaluate sensitivity. RSV fluorescent antibody testing in 46/230 patients was also evaluated. Sensitivity values obtained for the Sofia, Veritor, Directigen and Quickvue assays (%) were 85, 72.5, 70 and 57.5, respectively. Fluorescent result interpretation may account for Sofia's enhanced sensitivity. Specificity (%) was 97–100 among assays. Sensitivity data were confirmed in the dilution studies. Fluorescent antibody testing demonstrated 64% sensitivity compared with RT-PCR. Objective result reporting, walk away testing and high sensitivity make the Sofia a valuable choice for POC testing. Veritor's sensitivity may also render it acceptable in POC. Lack of objective results by Directigen and the poor sensitivity observed by Quickvue may preclude their value in diagnostic testing.
Increasing focus on sustainability affects all parts of the energy system. The future integration of the power and road transport system due to the introduction of electric drive vehicles influences the economically optimal investments and optimal operation of the power system. This work presents analysis of the optimal configuration and operation of the integrated power and road transport system in Northern Europe, i.e. Denmark, Finland, Germany, Norway, and Sweden using the optimization model, Balmorel, with a transport model extension. A number of scenarios have been set up, including sensitivity on CO2 and oil prices, inclusion/exclusion of electric drive vehicles, and change in investment possibilities in flexible power plants. Plug-in hybrid electric vehicles are shown to be competitive in all scenarios except the low oil scenarios. The increased electricity consumption for the electric vehicles is covered by wind power in Denmark and Norway and by coal production in Finland and Germany. The competition between wind power and coal is dependent on fuel price and CO2 price assumptions. Furthermore, introducing the flexibility of electric drive vehicles helps decrease cycling on the remaining power plants. Finally, the electric drive vehicles can replace the use of both heat storage and electric boilers as well as decrease the use of gas turbines.
It is common in quasi-steady-state models of renewable power systems to use a 1 h time step despite the variability of the load and renewable sources within the hour. The purpose of this study was to examine the efficacy of this level of temporal resolution for a model that includes variable residential loads, wind, solar, diesel generator, and batteries. The component models were analyzed individually and as a complete system to develop an understanding of how each is affected by the temporal resolution. With higher resolution, the wind energy output and the fuel consumption of the genset increased. The PV and battery simulations were unaffected by temporal resolution. Agreement between optimization results was found to greatly depend on system configuration. Systems with only diesel for backup were found to increase in cost with higher temporal resolution. Those with battery backup were much less affected by the time step. For systems with both diesel and battery backup, the optimal system costs were fairly close but the optimal component sizes differed. Because of the many factors that affect the results of these systems, it is not yet possible to determine a general recommendation for choosing a time step prior to a simulation.
This study investigated two strategies for improving facial affect perception in schizophrenia: monetary reinforcement and promoting facial feedback via mimicry of the expressions of target faces. A total of 40 inpatients with schizophrenia were administered the face emotion identification test during four phases: baseline, intervention, immediate post-test, and 1week follow-up. Subjects were randomly assigned to one of four interventions: repeated practice, monetary reinforcement, facial feedback, and a combination of reinforcement and facial feedback. Generalization of the intervention to a test of facial affect discrimination was also examined. The results showed that all groups of subjects, with the exception of those in the repeated practice group, improved in their ability to identify facial affect, with these effects showing some stability over time. There was limited evidence of these effects generalizing to the test of facial affect discrimination.
Lithium intercalation hosts are a key point to the energy density of the largely used LiCoO2 (even if of high cost and toxicity) as well as of manganese oxides which have been investigated most extensively. Iron oxides are attractive electrode materials for low-voltage rechargeable lithium batteries from both cost and environmental standpoints. However, search for iron oxides of conventional crystalline structures and micrometer particle sizes as lithium intercalation cathodes, has been greeted with disappointing results. Here we report on the synthesis, characterizations, electrochemical study and electrochemical impedance spectroscopy (EIS) of a nanocrystalline γ-Fe2O3 that simultaneously exhibits high lithium insertion capacity and good capacity retention upon cycling. These properties reveal thermodynamics of the nanocrystalline material inherently different from those of its microcrystalline counterpart. Moreover, EIS showed that the intercalation process of the lithium ion occurs according to two processes involving first the reduction of the surface Fe3+ with concomitant charge neutralization by Li+ ions onto the surface defects of the nanoparticle followed by the reduction of the core Fe3+ with insertion of the Li+ deeper in the particle.
A gradient boracic polyanion-doping method is applied to Ni-rich LiNi0.8Co0.15Al0.05O2 (NCA) cathode material in this study to suppress the capacity/potential fade during charge-discharge cycling. Scanning electron microscope (SEM) results show that all samples present spherical morphology and the secondary particle size increases with increasing boron content. X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) results demonstrate that boracic polyanions are successfully introduced into the bulk material and more enriched in the outer layer. XPS analysis further reveals that the valence state of Ni3+ is partly reduced to Ni2+ at the surface due to the incorporation of boracic polyanions. From the electrochemical measurements, B0.015-NCA electrode exhibits excellent cycling performance, even at high potential and elevated temperature. Moreover, the SEM images illustrate the presence of cracks and a thick SEI layer on pristine particles after 100 cycles at high temperature, while the B0.015-NCA particles show an intact structure and thin SEI layer. Electrochemical impedance spectroscopy confirms that the boracic polyanion doping could hinder the impedance increase during cycling at elevated temperature. These results clearly indicate that the gradient boracic polyanion-doping contributes to the remarkable enhancement of structure stability and cycling performance of NCA.
Tunnel-structured Na0.5Mn0.5Ti0.5O2 has been synthesized with a simple solid-phase reaction route as highly stable Na-storage cathode for aqueous sodium-ion batteries (SIBs). Combined chracterizations of X-ray diffraction, scanning electron microscope and electrochemical measurements reveal that the material is mainly composed of rod-shaped particles with a diameter of 500nm and a length of ~5μm. During Na extraction/insertion process, it undergoes a single-phase reaction mechanism in the potential range of 0–1.0V(vs Ag/AgCl), showing a reversible capacity of 46mAhg−1 at a current density of 30mAg−1 and an average operating potential of 0.41V. In particular, excellent cycling performance is achieved owing to the favorable tunnel channel and robust structural framework, with a capacity retention of 95% after 100cycles. The finding in this study demonstrates application potential of the Na0.5Mn0.5Ti0.5O2 material as cathode for low-cost, long-cycling aqueous SIBs.
In this study, mesoporous carbon materials were prepared through the hard template method with attapulgite and citric acid as the template and the carbon source, respectively. The morphology and structure of the as-prepared carbon materials were investigated via scanning electron microscopy, transmission electron microscopy, N2 adsorption/desorption technique, and powder X-ray diffraction. The as-prepared carbon materials replicated the nanorod structure of attapulgite. Furthermore, high-density mesopores were distributed on the surface of the as-prepared carbon materials. The carbon material ACA-700-3 exhibited a maximum specific surface area and total pore volume of 707 m2 g−1 and 1.22 cm3 g−1, respectively. The electrochemical performance and energy storage capacity of the carbon materials were evaluated using electrochemical tests. The maximum specific capacitance reached 182 F g−1 when the current density was 2 mA cm−2.
The aging behavior of electrochemical double layer capacitors (EDLCs) based on activated carbon electrodes bound with poly(tetrafluoroethylene) (PTFE) was tested in electrolyte solutions based on acetonitrile (AN) and propylene carbonate (PC) at a constant elevated cell voltage of 3.5V. The aging was quantified in terms of capacitance loss and resistance increase for the full cell and the individual electrodes. It is shown that the enhanced aging rate of symmetric EDLCs in either solvent at elevated voltages is dominated by the aging of a single electrode, and that the polarity of this limiting electrode depends directly on the solvent. In AN, the positive electrode ages much more rapidly than the negative, while in PC the negative electrode exhibits faster aging than the positive. After aging, the electrodes were investigated by nitrogen adsorption and X-ray photoelectron spectroscopy, revealing significant modifications of the electrode surface and providing clear evidence for the deposition of electrolyte degradation products on the electrodes.
Hydrogen peroxide was used as oxidizing agent in the preparation of graphite oxide to improve the Hummers method. The aim is to support and increase the reactivity without affecting the yield product. The graphite oxide was exposed to microwave to get a microwave reduced graphite oxide (MrGO) usually contains some functional groups containing oxygen. Both cyclic voltammetry and galvanostatic charge/discharge tests were carried out to investigate the electrochemical properties. Results show a maximum specific capacitance of 302F/g at scan rate of 1mV/s and exhibit excellent cycling retention 120.8% after 1000 cycles at 200mV/s by using aqueous electrolyte (1M H2SO4) at room temperature. In addition, the energy density could reach 25.94Wh/kg and power density 1.734kW/kg at a current density of 3A/g. The supercapacitor electrode prepared from MrGO material shows a pseudocapactive performance attributed to the redox reactions between the protons form the acidic electrolyte and the remaining oxygen-functional groups.
In Li-ion batteries, the solid electrolyte interface (SEI) plays a crucial role in transferring Li ions into active materials through an electrochemical driving force. SEI is a composite layer containing of inorganic and organic components, which are fabricated by the salt degradation products and partial or complete reduction products of the solvent of the electrolyte at the battery's initial charge-discharge cycle. The chemical properties of SEI and the electrochemical driving force must be mutually optimized so as to strengthen its integrity, while minimizing irreversible SEI formation; thereby suppressing the decomposition at high temperatures. In this study, we investigated a new method of creating the SEI, i.e. the forward and reverse differential-pulse (FRDP) method, which balances the reaction kinetics of SEI formation. Furthermore, the use of the FRDP method also creates a SEI with a modified kinetic reaction route that affects battery performance. Here, we present data from the first charge-discharge and cycle performance at a high rate and a high temperature, obtained using scanning electron microscopy, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and Li+-diffusion kinetics analysis. Our findings indicate that the use of the FRDP method for generating the SEI results in a 58% reduction in the SEI's ionic diffusion activation energy and a 4.5% increase in battery capacity at room temperature, while increasing battery performance at 60°C stability compared to batteries in which the SEI is formed using the constant-current method.
Nitrogen-doped carbon matrix (Co/NC) has been synthesized with NaCl as a template and peptone as a carbon/nitrogen source. Subsequently, mesoporous nitrogen-doped CoSe/NC was prepared by solvothermal selenization. The obtained CoSe/NC is useful as highly efficient bifunctional electrocatalyst for hydrogen evolution and oxygen reduction reactions. Structures of the CoSe/NC material have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption desorption analysis and X-ray photoelectron spectroscopy. Results demonstrate the role of NaCl as efficient low cost template to form mesoporous nitrogen doped carbon, which could significantly simplify and reduce the cost of the synthetic procedure. During hydrogen evolution reaction in a 1 M KOH electrolyte, the best performing sample with formula Co0.88Se/NC produces an overpotential of 72 ± 0.1 mV at a current density of 10 mA cm−2. This material also shows excellent electrocatalytic activity and stability in oxygen reduction reaction, superior even to a commercial Pt/C catalyst. A primary zinc-air battery containing Co0.88Se/NC as a oxygen reduction reaction catalyst reaches an open circuit voltage of 1.44 ± 0.02 V, higher than that of a Pt/C containing zinc-air battery and delivers superior power and current density combination.
Suspended particle device (SPD) glazing is an electrically actuated switchable glazing. It requires alternate current (AC) power supply to switch from opaque to transparent state. To power this glazing using PV device requires inverter. Optimization of AC powered switchable SPD glazing using photovoltaic (PV) device has been evaluated using loss of power supply probability (LPSP). Electrically switchable direct current (DC) powered electrochromic glazing was also considered in this investigation as it doesn't need any inverter to couple with PV. It is concluded that behaviour of these glazings is the dominant factor in performance optimization outweighting than azimuthal orientation and inclination of PV.
3-Aminopropylphosphonic acid (3APPA) and sodium 3-phosphonopropionate (3PPA-Na) are investigated as organophosphorus compound additives in a positive electrolyte of a vanadium redox flow battery (VRFB) to improve its thermal stability. The precipitation-inhibiting effects of 2 M vanadium electrolytes, including the above additives, are studied by UV–Vis spectroscopy, Raman spectrophotometry, cyclic voltammetry (CV), and charge–discharge cycling test in the redox flow battery. The UV–Vis spectroscopy and Raman spectrophotometry show that no new substances formed in both the V(IV) and V(V) electrolytes with 3APPA and 3PPA-Na additives. Cyclic voltammetry (CV) shows the electrochemical activity and reversibility of the electrolytes with and without the additives. In the flow cell, the discharge capacity retention values in the positive electrolyte after 100 cycles at 45 °C are 56.7, 64.7, and 48.4% in 3PPA-Na, 3APPA, and without the additives, respectively. These results indicate that the 3APPA additive increases the discharge capacity retention to more than 16% compared to the electrolyte without the additive due to the retardation of precipitation at the high temperature.
To enhance the safety of lithium ion battery, cresyl diphenyl phosphate (CDP) is explored as an additive in 1.0M LiPF6/ethylene carbonate (EC)+diethyl carbonate (DEC) (1:1wt.). The electrochemical performances of LiCoO2/CDP-electrolyte/C cells are tested. At the thermal aspect, the thermal stability of the electrolyte with CDP is detected firstly by using a C80 micro-calorimeter, and then the charged LiCoO2/CDP-electrolyte/C cells are disassembled and wrapped to detect the thermal behaviors. The results indicate that CDP-containing electrolyte enhances the thermal stabilities of electrolyte and lithium ion battery, and the electrochemical performances of LiCoO2/CDP-electrolyte/C cell become slightly worse by using CDP in the electrolyte. Furthermore, the cell with 10% (wt.) CDP-containing electrolyte shows better cycle efficiency than that of other CDP-containing electrolyte, such as containing 5% (wt.) CDP and 15% (wt.) CDP. This maybe because that the mass ratio between CDP and electrolyte is close to the reaction stoichiometric ratio in the 10% (wt.) CDP-containing electrolyte, where stable solid electrolyte interphase (SEI) is formed. Therefore, 10% CDP-containing electrolyte improves the safety of lithium ion battery and keeps its electrochemical performance.
A dissociation between short- and long-term memory (LTM) and between the episodic and the semantic component of LTM is reported in a young girl who became amnesic at the age of 6 after an episode of acute encephalopathy resulting in bilateral frontal, insular, thalamic, ponto-mesencephalic, hippocampal and temporal lesions, as documented by MRI. The girl became amnesic a few months after starting school. A follow-up investigation showed that she was able to learn to read, write and acquire number facts and procedures and to improve her semantic knowledge. Our results show that the features of adult amnesia can also be found in children and that new semantic knowledge can be acquired in spite of an anterograde memory deficit. This dissociation does not agree with theories viewing long- term declarative memory as a unitary process mediated by the hippocampal system, but supports recent hypotheses that the acquisition of semantic knowledge is independent from episodic memory processes, and takes place through spared cortical regions subjacent to the hippocampi (Vargha-Khadem et al., 1997).