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The simple, green, cost-effective and environmental friendly technique used by our south-Indian peoples to make their very favourite and world-famous meal i.e. “Idli” was adopted here to prepare the three-dimensional heteroatom-doped graphene foam. The graphene-Idli was first prepared in a domestic microwave oven using heteroatom-doped (boron, nitrogen, sulphur and phosphorous) graphene and rice flour and calcined to produce graphene foam which was used as a metal-free bifunctional catalyst for oxygen evolution (OER) and oxygen reduction (ORR) reactions. The performance of heteroatom-doped foams (nitrogen, sulphur, boron and phosphorous) was studied and it was found that sulphur-doped graphene foam (s-DGF) shows better performance as electrocatalyst, in terms of high BET surface area (499m2/g), electrochemical surface area (0.271cm2), high roughness factor (0.690) and high porosity. As a bifunctional electrocatalyst, it possess a lowest onset potential (0.29V vs Ag/AgCl), highest current density (497mAcm−2), lowest overpotential (128mV) and lowest Tafel slope (35.71mV/dec) for oxygen evolution reaction and an onset potential of (−0.02V), current density (−125mAcm−2) and Tafel slope (49.83mV/dec) for oxygen reduction reaction. The obtained values are best among other reported metal-free electrocatalyst and superior to several metal-based electrocatalysts. The prepared foams were free from any methanol cross-over effect and show a good stability in all the aspect i.e. performance, storage etc. Being a bifunctional catalyst, the S-DGF was successfully implemented for the fabrication of rechargeable zinc-air battery also. This finding offers a straightforward environment-compatible route for synthesizing attractive bifunctional electrocatalyst material as promising candidates for the large-scale commercialization of regenerative fuel cells and rechargeable metal-air batteries. In addition, the proposed metal-free foam based catalyst are able to overcome the multiple disadvantages of the existing electrocatalyst like high cost, poor stability, low selectivity and detrimental environmental effects.
The research and development of solid polymer electrolyte (SPE) began when Wright found ion conductivity in a PEO-alkaline metal ion complex in 1975. The conductivity then was 1×10−7 S cm−1 at room temperature. A lithium polymer battery has features such as flexibility in the shape of a cell design, leak proof of electrolyte, high safety, etc., but poses the challenge of how close its electrical performance can be made to that of a liquid electrolyte cell. Therefore, various efforts have so far been made to improve the ionic conductivity of the SPE. Recently, such efforts have also included the development of gelled SPE and porous SPE, especially in consideration of its practical application, in particular the use at low temperature. The ionic conductivity of such SPEs now reaches 1×10−3 S cm−1 at room temperature. This paper reviews the history and the present status of the research and development of SPE and the lithium polymer battery, and presents an outlook of the future research and development activities. The paper also introduces the history of the improvement of primary and lithium polymer secondary batteries using SPE at the Yuasa Corporation, with the performance and the applications of its present commercial products, and presents their future outlook.
A straightforward hydrothermal strategy is designed for the fabrication of CoFe2O4-graphene nanocomposites with different graphene contents. Due to the synergetic effect between the conducting graphene nanosheets and CoFe2O4 nanoparticles, the nanocomposites exhibit promising electrochemical performance as anode material for lithium-ion batteries. It is found that the graphene content plays an important role in tuning the electrochemical performance of the nanocomposite. With 20wt% graphene, the CoFe2O4-graphene nanocomposite electrode can deliver a high reversible specific capacity up to 1082mAhg−1 as well as excellent cycling stability and rate capability.
Cobalt oxides are investigated as anode materials for lithium-ion (Li-ion) batteries by means of a variety of electrochemical characterization techniques. The CoO electrode demonstrates a stable reversible lithium storage capacity of about 300mAhg−1, even after 30 cycles. The reactivity of the cobalt oxides is attributed to the fact that the products of lithiation are in the form of nanosized products.
Objective: To prospectively evaluate the intraoperative and post-operative utility of the Cook–Swartz Doppler flow monitoring system for free flap monitoring of arterial and venous anastomosis in head and neck reconstruction of oral cavity defects. Study design and setting: A cohort of consecutive patients with oral cavity defects requiring free-tissue transfer flap reconstruction by the Division of Otolaryngology-Head and Neck surgery at the University of Alberta Hospital were followed prospectively. The intervention in all patients was the use of implantable Cook–Swartz Doppler probe systems for monitoring both the arterial and venous microvascular anastomoses while concurrently collecting a battery of traditional clinical markers for free flap viability. These patients were group matched by flap type, age and gender to a cohort of patients who underwent free-tissue transfer flap reconstruction with single vessel implantable Doppler monitors. Data were collected at the time of surgery and for the ten post-operative days while the Doppler system was in situ regarding flap compromise, salvage, impaired flow as determined by the Doppler monitoring system and any intervention or re-operative findings. Results: When compared with the matched single Doppler cohort, the double Doppler group had an increased rate of intraoperative modifications but a significantly lower rate of surgical re-explorations, a lower need for revising the anastomosis and a lower rate of flap failure. Conclusions: This study supports the utility of a two-vessel monitoring system for intraoperative detecting in adequacy of vascular anastomosis. In the post-operative period, while the Doppler system was associated with false positives, reassuring Doppler signals were often used to prevent unnecessary surgical re-exploration in addition to earlier detection of compromise leading to improved rates of salvage.
Rutile-type FeOF is a promising cathode for lithium-ion batteries, because it has a relatively large theoretical capacity of 885 mAh g−1 in eco-friendly iron-based cathodes. Although it is difficult to synthesize by conventional solid-state synthesis methods, it can be quickly synthesized by the roll-quenching method. The quick synthesis method is suitable to reduce the produce cost, but also to avoid the fluorine gas release during synthesis procedure. The obtained FeOF by roll-quenching method has kept some crystallinities, and provides a large discharge capacity (900 mAh g−1) between 0.7 and 4.0 V. The charge and discharge reaction mechanism was investigated by structural analyses.
The Equotip hardness tester (EHT) is a portable and non-destructive instrument used mainly for the dynamic rebound hardness testing of metals. Although various versions of the ‘single impacts’ and ‘repeated impacts’ testing procedures have been employed by different authors for different applications, it is not yet known whether a particular testing procedure is more relevant for a specific application in rock engineering. To be able to contribute to the subject, the present study was carried out to determine the suitability of different rebound testing procedures with this instrument for uniaxial compressive strength (UCS) estimations of some selected carbonate rocks. To achieve this goal, as well as four different existing rebound testing procedures, a newly proposed testing methodology involving the parameter hybrid dynamic hardness (HDH) was also employed. The statistical analyses performed on the experimental data, on the whole, showed that the test procedures which are based on single impacts test procedures outperformed the repeated impacts test procedures in terms of UCS prediction accuracy. The prediction capability of the newly introduced testing methodology was found to be superior to those of other procedures considered in this work, suggesting that it could be an efficient tool in practice for preliminary estimates of rock strength. The statistical analyses also indicated that, in practical applications of the EHT using different test procedures, it may be possible to predict the UCS more accurately when apparent density data is available. For the range of specimen sizes considered, no clear evidence of size effect was observed in the mean rebound values. The argument raised by some other authors that the EHT might not be a convenient instrument for the dynamic rebound hardness determination of relatively high-porosity rocks was not confirmed in this study.
This study develops two novel charging strategies for lithium-ion batteries, designed to prevent the onset of lithium plating when the cells are charged at low ambient temperatures. Commercially available 3.1 Ah 18650-type cells with NCA and graphite electrodes have been selected for this study. Experimental results highlight that for these cells, lithium plating can be detected when the cells are charged with a traditional constant-current constant-voltage (CC-CV) profile at an ambient temperature of 5 °C and a charge rate of 1C. The occurrence of lithium plating is known to lead to a considerable capacity reduction. To avoid the onset of lithium plating with minimum impact on the charge time, two optimal charging strategies are proposed. The first is based on detecting the onset of lithium plating through the online analysis of the voltage relaxation profile (VRP). The second is to manage the cell charging process to achieve a pre-defined rate of battery degradation per charge cycle. Experimental results highlight that the capacity fade of cells using the proposed charging strategies can be significantly reduced compared to when charged using the conventional CC-CV approach by 45% and 70% respectively while minimizing their impact on the charging speed.
Stannous sulfide@reduced graphene oxide (SnS@RGO) composite is successfully synthesized via a facile precipitation route. The structural and morphological characterizations reveal SnS@RGO composites are composed of SnS nanoparticles of the size 5–10 nm, which are uniformly anchored on the surface of RGO. The electrochemical measurements demonstrate the reversible capacity of the SnS@RGO composite – that includes contributions from the conversion reaction of SnS to Sn and NaxS and the alloying reaction of Sn to NaxSn. The SnS@RGO electrode exhibits a reversible capacity of 457 mAh g−1 at 20 mA g−1, superior cycling stability (94% capacity retention over 100 cycles at 100 mA g−1) and adequate rate performance. Compared to the neat SnS nanoparticles, the enhanced electrochemical performance of the SnS@RGO composite is primarily due to the incorporation of RGO as a highly conductive, flexible component as well as possessing a large available surface area, which provides desirable properties such as improved electronic contact between active materials, aggregation suppression of intermediate products, and alleviation of the volume change during sodiation and desodiation. Encouraging experimental results suggest that the SnS@RGO composite is a promising material to achieve a high-capacity and stable anode for NIBs.
Ti3+ self-doped spinel Li4Ti5O12 (LTO) particles were synthesized through a facile electrochemical modification route in NaCl-KCl molten salt electrolysis, and the formation mechanism is explored. Alternating Ti3+ self-doping significantly improves the electrochemical performance of the spinel Li4Ti5O12 (LTO) particle, especially at high charge/discharge rates. According to the report, LTO, once introduced with oxygen vacancies or Ti3+, will decrease the band gap about to 1.54 eV, which can dramatically improve the inherent electronic conductivity. Through the molten salt electrochemical modification technique, the Ti3+ species will be doped onto the surface of LTO, which was confirmed through transmission electron microscopy with EPR (namely electron spin resonance) spectra, X-ray photoelectron spectroscopy, X-ray analysis. As anodes in lithium-ion batteries (LIBs), the spinel Li4Ti5O12 (LTO) particle electrode with self-doped Ti3+ can deliver stable discharge capacities of 168, 152, 131, 120, 102, 93 and 78 mAh g−1 at different rates of 0.5, 1, 5, 10, 15 and 20C, respectively. Meanwhile, like pure spinel LTO, they also carry strong cycling stability and demonstrate the capacity retention of 92.0%, though after 900 cycles under 5C. Our results indicate that pure-phase LTO is prepared by a molten salt method, and it is then electrochemically modified by a constant current to obtain conductive Ti3+. Self-doped spinel Li4Ti5O12 particles are a good alternative to facilitate the transfer of electrons, especially under high-rate conditions, because it shows good electronic and ionic conductivities. In addition, the molten salt synthesis and the electrochemical modification steps of this method are conducted in the same reactor with a simple process, strong operability and environmental friendly process.
A pure SnO2 film consisting of SnO2 nanocrystals with a size of ~ 15nm can deliver a stable and high capacity > 900 mAhg−1 for 100 cycles. Unlike the previous perception, the capacity decay in the initial cycles of the SnO2 anode is mainly induced by the gradual degradation of the reversible conversion reaction (Sn + Li2O←→SnO2) at a potential > 1.0 V due to Sn coarsening with cycling. The coarsening of Sn has a significant impact on the reversible capacity, Coulombic efficiency, energy efficiency and Li+ ion diffusion kinetics of the SnO2 electrode. The grain size of coarsening Sn and the degree of irreversibility monotonically increase with cycling, which is quantitatively expressed with a linear equation. It is extrapolated that if the Sn grains remain with diameters < 11nm, the fast interdiffusion kinetics among the interfaces of Sn/Li2O will enable complete reversible conversion reactions in lithiated SnO2 electrodes. Since the stability of nanostructured interfaces in metal (M)/LinX (X = O, F, S) compounds is also crucial for the reversible conversion reactions in binary M-X compounds, we firmly believe that these results will provide valuable insight into the design of new conversion-type electrode materials with high and stable capacities for next-generation rechargeable batteries.
Rechargeable aqueous zinc-ion batteries (ZIBs) featured with environmental friendliness, low cost, and high safety have attracted great interest but still suffer from the lack of high-performance electrodes. Herein, a facile in situ approach is developed to simultaneously introduce multivalence, increase the interlayer water content, and expand the interlayer distance in hydrated V2O5. These structural modulations endow the as-obtained layer-expanded V2O5 2.2H2O (E-VO) nanosheets with faster charge transfer kinetics, more Zn2+ storage space, and higher structural stability than precursor V2O5. Besides, a unique flexible Zn/stainless steel (Zn/SS) mesh composite anode with low polarization and uniform Zn stripping/plating behavior is fabricated, which alleviates the Zn dendrite growth. As cathode for aqueous ZIBs, E-VO exhibits high reversible capacity (450 mAh g−1 at 0.1 A g−1), good rate capability (222 mAh g−1 at 10 A g−1) and long stability (72% capacity retention for 3000 cycles at 5 A g−1). Moreover, the flexibility and large lateral size make E-VO a high-performance binder-free cathode for flexible quasi-solid-state Zn/E-VO battery, i.e. high capacity under different bending states (361 mAh g−1 at 0.1 A g−1), good rate capability (115 mAh g−1 at 2 A g−1), and long stability (85% capacity retention for 300 cycles at 1 A g−1). The achievements of this study can be considered as an important step toward the development of aqueous-based ZIBs.
This paper develops a new framework for the interpretation of impedance or capacitance spectroscopy of ion insertion processes in thin film electrodes, with a particular emphasis in electrochromic materials. The model distinguishes types of inserted ion charge regarding the energetics and kinetics properties of ion storage sites. The ion charge in a connected network of sites moves rapidly (fast sites) and is distributed according to equilibrium thermodynamic properties, while slower sites trap the ions and provide a variety of kinetic behaviors that dominate the response in the long time scale. We show that the assumption that a fraction of the intercalated ions have been immobilized at certain sites, and do not participate in diffusion, provides a suitable explanation for the observation of different capacitive components in the faradaic impedance of homogeneous systems (fast and slow charging modes). Moreover, ion trapping contributes a resistive component to the impedance, related to homogeneous charge-transfer between different types of sites (trap resistance). The model predicts an arc in the complex capacitance representation associated to the solid-state reduction step involved in the coloration by electroinsertion. The characteristic features of the relaxation in structurally disordered materials are studied in the kinetic framework of a multiple trapping scheme. We show that a wide distribution of trapping times provides a power law of frequency, which relates to the frequent observation of a constant phase element (CPE) impedance.
In this work, well-aligned and ordered NiSi nano columnar arrays were fabricated using an ion assisted oblique angle deposition technique based on electron beam co-evaporation. It was demonstrated that these NiSi nano columnar arrays were promising high-capacity anode material for next generation lithium-ion batteries. Nano-structured Si films were also deposited and evaluated as anode material under the same experimental conditions for comparison. It was found that the dopant of about 9% wt. Ni in Si nano columns helped to improve the electrical conductivity and the electrochemical performance of the material. The electrochemical characterization showed that the well-aligned nano-columnar porous NiSi thin film delivered a very high reversible capacity (~1100mAhg−1) with almost no capacity fade for up to 100 cycles.
We use data from the 2002 wave of the National Survey of America’s Families to develop and validate discrete measures of material hardship that can be used to examine the difficulties that vulnerable populations such as people with disabilities have in making ends meet. Using latent class analysis, we estimate two measurement models: multidimensional and omnibus. The multidimensional model provides separate estimates for food, medical, and housing and utilities hardship. The omnibus model is a single model of 11 hardship indicators. Results show three distinct classes of food hardship, three classes of medical hardship, and two classes of housing/utilities hardship. The omnibus model reveals eight classes. Both the multidimensional and omnibus models are largely invariant between women with disabilities and women without disabilities, indicating that valid comparisons can be made between these populations using these classes of hardship. These classes can be utilized in further research on the hardship of women with disabilities to inform the development of policies targeted to alleviate the specific forms of hardship experienced by disabled women.
The authors regret that the following errors were present within their article:1.In equation 10 and 11, the rate constant “k” should be in lowercase; the same problem existed within table 2 and 3 and also in the ‘List of symbols’.2.In table 2 and 3, “k6/m4(mols)-1” should have been “ke/m4(mols)-1” In equation 10 and 11, the rate constant “k” should be in lowercase; the same problem existed within table 2 and 3 and also in the ‘List of symbols’. In table 2 and 3, “k6/m4(mols)-1” should have been “ke/m4(mols)-1” The authors would like to apologise for any inconvenience caused.
Cell components in lithium ion cells have been studied to check their effects to reduce the charge time. Factors including various separator thickness, tab width, LiPF6 concentration and solvent composition in electrolytes, cathode thickness, anode thickness and cathode active materials were studied. In addition, charge time of lithium ion cells was studied based on the charge voltage of cell. The most important variable in reducing the charge time of lithium ion cells was found to be the thickness of the cathode. The charge time of the lithium ion cells was reduced with thinner cathode. Other variables such as the separator thickness, LiPF6 concentration and solvent composition in electrolytes, anode thickness and charge voltage of lithium ion cells were also effective in reducing the charge time of the cells, but with fewer impacts.
The aim of the study was to analyse the characteristics of domestic violence by comparing a sample of children who witnessed abuse against a sample of children who suffered from it, and to outline how the traumatic experience could influence the child's emotional, cognitive and psychopathological development. Thirty-three school-age children (14 girls and 19 boys) aged between 6 and 11 years of age were studied; 17 out of 33 were witnesses of violence (WA; age Mean (M) 8.8; Standard Deviation (SD) 1.4), and 16 out of 33 suffered from sexual abuse or physical maltreatment (SPA; age M 8.7; DS 1.4). All children have been assessed by the K-SADS-PL (Schedule for Affective Disorders and Schizophrenia for School-age Children – Present and Lifetime Version) interview, the projective test of Duss Fables and the Promea battery of tests, which investigate the cognitive function of memory. The presence of behavioural disorders (WA > SPA), post-traumatic stress disorder (WA < SPA) and also anxiety disorders (WA = SPA) emerged from the study. The Duss Fables method highlighted areas of conflict. The Promea test draws attention to the performance of all abused children being average, but different learning styles emerged from implicit learning (WA > SPA) and implicit and explicit visual learning (WA > SPA). The comparison between the two samples has shed light on areas of specific vulnerability concerning psychopathological, emotional and cognitive aspects of development.
High ionic conductivity and superior interfacial stability of solid electrolytes at the electrodes are crucial factors for high-performance all-solid-state sodium batteries. Herein, a composite solid electrolyte Na3PS4-polyethylene oxide is synthesized by the solution-phase reaction method with an improved ionic conductivity up to 9.4 × 10− 5 S/cm at room temperature. Moreover, polyethylene oxide polymer layer is wrapped homogeneously on the surface of Na3PS4 particles, which could effectively avoid the direct contact between Na3PS4 electrolyte and sodium metal, thus alleviate their side reactions. We demonstrate that all-solid-state battery SnS2/Na with the composite solid electrolyte Na3PS4-polyethylene oxide delivers an enhanced electrochemical performance with 230 mAh/g after 40 cycles.