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Using FFC-Cambridge Process to prepare Si from SiO2 is a promising method to prepare nanostructured and highly pure silicon for solar cells. However, the method still has many problems unsolved and the controlling effect of the cell voltage on silicon product is not clear. Here we report in this article that nano cluster-like silicon product with purity of 99.95% has been prepared by complete conversion of raw material SiO2, quartz glass plate, using constant cell voltage electrolysis FFC-Cambridge Process. By analysis of XRD, EDS, TEM, HRTEM and ICP-AES as well as the discussion from the thermodynamics calculation, the morphology and components of the product based on the change of cell voltage are clarified. It is clear that pure silicon could be prepared at the cell voltage of 1.7–2.1 V in this reaction system. The silicon material have cluster-like structure which are made of silicon nanoparticles in 20–100 nm size. Interestingly, the cluster-like nano structure of the silicon can be tuned by the used cell voltage. The purity, yield and the energy cost of silicon product prepared at the optimized cell voltage are discussed. The purity of the silicon product could be further improved, hence this method is promising for the preparation of solar grade silicon in future.
An efficient and economical route for the synthesis of porous two-dimensional (2D) nanoplates of silicon is developed via the magnesiothermically-induced phase transition of exfoliated clay 2D nanosheets. The magnesiothermic reaction of precursor clay nanosheets prepared by the exfoliation and restacking with Mg2+ cations yields porous 2D nanoplates of elemental silicon. The variation in the Mg:SiO2 ratio has a significant effect on the porosity and connectivity of silicon nanoplates. The porous silicon nanoplates show a high discharge capacity of 2000mAhg−1 after 50 cycles. Of prime importance is that this electrode material still retains a large discharge capacity at higher C-rates, which is unusual for the elemental silicon electrode. This is mainly attributed to the improved diffusion of lithium ions, charge-transfer kinetics, and the preservation of the electrical connection of the porous 2D plate-shaped morphology. This study highlights the usefulness of clay mineral as an economical and scalable precursor of high-performance silicon electrodes with tailorable nanostructures.
Although solid-state Li-ion batteries (SSBs) provide opportunities to simplify safety measures (e.g., sophisticated thermal management systems, overpressure vents, charge interruption devices) currently used in conventional Li-ion batteries (LIBs) with flammable organic liquid electrolytes, the poor interface compatibility (both physically and chemically) between the electrode materials and solid electrolyte strongly hinders the practical application of SSBs. The fabrication of artificial buffer layers (ABLs) was therefore proposed, and it has been an effective approach for overcoming the interface issues of SSBs. In this review paper, we provide a comprehensive summary of recent progress in interface engineering and advanced techniques for characterization of such interfaces in SSBs. First, the critical issues and challenges facing SSBs associated with the stability of the cathode/solid electrolyte and anode/solid electrolyte interfaces are discussed. The latest research approaches and synthetic strategies to improve the performance of SSBs that rely on interface engineering with ABLs are extensively reviewed. The characterization strategies for in situ and ex situ interfacial observation and analysis are comprehensively summarized. Finally, the critical issues associated with electrode–electrolyte interfaces are emphasized, and perspectives regarding the development of high-quality buffer layers are presented.
To the best of our knowledge, this is first report about composite of perovskite materials and reduced graphene oxide as anode material for high performance lithium ion battery (LIB). Here, we report outstanding specific capacities and cyclic stabilities of perovskite BaSnO3 nanoparticles (NPs), decorated on 2D graphene sheets. Electrochemical measurements show that the composite BaSnO3/rGO20 (20wt.%rGO) delivered a highest capacity of 1200mAhg−1 at a current rate of 0.5C (650mAg−1), which is comparatively much higher than individual pristine BaSnO3 and graphene anodes. The BaSnO3/rGO composite anode exhibits a very high rate capability even at the 10C discharge rate (1059mAhg−1) and outstanding long-term stability. Notably, the composite anode material maintains its discharge capacity even after 100 cycles.
Recently, a strategy of catalysis is reported to accelerate the chemical kinetics of polysulfide conversion and fundamentally solve shuttle effect of polysulfide. Herein, CoS2 nanoparticles catalyst embedded in porous carbon polyhedron (NC–CoS2) are prepared through in situ method. The CoS2 nanoparticles keep tight connection with carbon, which enable them effectively get electrons through carbon and catalyze the conversion of polysulfide. The porous carbon polyhedron shows high absorption ability to polysulfide and can immobilize polysulfide around CoS2 nanoparticles, which improve the utilization of catalysis sites. With the synergistic effect of porous structure and CoS2 nanoparticles, the Li–S batteries with NC-CoS2 cathode can deliver as high as 1600 and 1150 mAh g−1 at current density of 0.1 and 0.5C, respectively. After cycling 150 times at 0.1C, a capacity of 1050 mAh g−1 is retained. Additionally, the NC-CoS2 cathode shows high initial discharge capacity of 920 mAh g−1 at 2 C, and about 835 mAh g−1 has been reserved after 100 cycles. The results indicate that the CoS2 nanoparticles play a crucial role in improving the performance of batteries owing to their propelling redox reaction of polysulfide.
Layered P2-type Na0.67Fe0.5Mn0.5O2 with economic and environmental friendly metal elements is considered to be a candidate cathode for sodium-ion batteries. However, the poor rate performance and cycling stability of the cathode materials are still the pivotal constraints to the commercial development. To address these concerns, a series of different stoichiometric of Mg2+ substitution samples Na0.67(Fe0.5Mn0.5)1-xMgxO2(x = 0.05, 0.1, 0.15, 0.2, 0.25) are synthesised by solid-state reaction. The results indicate that the introduction of Mg2+ in P2Na0.67Fe0.5Mn0.5O2 cause the transformation of P2 phase to O3 phase with a tremendous influence to the cycling performance. The sample shows P2 phase at x = 0.05. The P2 and O3 phases coexist in the compound while x = 0.1, 0.15, and 0.2. The sample exhibits O3 phase at x = 0.25. The novel composition of P2/O3 biphase Na0.67Fe0.425Mn0.425Mg0.15O2 delivers exceptional rate and cycling performance. Owing to the synergetic effect of P2 and O3 phases, the cathode exhibits excellent capacity retention of 95.7% of its initial capacity after 50 cycles at 1C, and 87.7% after 100 cycles. Therefore, Na0.67Fe0.425Mn0.425Mg0.15O2 with a novel P2/O3 biphase structures may be a promising cathode material for next generation high-performance sodium-ion batteries in the near future.
Repressive adaptation has been conceptualized as one pathway to psychological resilience in children with cancer, but the physiological costs of maintaining a repressive adaptive style are currently unknown. The goal of this study was to examine physiological functioning as a function of adaptive style in children with cancer (N = 120) and healthy controls (N = 120). Children completed self-report measures of state anxiety and defensiveness prior to participating in three verbal stress tasks while monitoring blood pressure, electrocardiogram, and electrodermal response, and rated their anxiety following each task. Findings indicated no consistent differences in baseline indices and physiological reactivity as a function of adaptive style or health status (cancer vs. control). In addition, children identified as having a repressive adaptive style did not exhibit greater verbal-autonomic discrepancy than low-anxious children. In contrast to findings with adults, children with a repressive adaptive style do not appear to experience adverse effects of this coping style in terms of physiological reactivity.
A pyrochlore Fe2F5 ·H2O composite with a much larger cell volume and the interconnected open 3D channel is firstly synthesized by ionic liquid (IL) based precipitation route and used as the cathode material of sodium ion batteries (SIBs). The morphology, structure and physicochemical properties as well as electrochemical performance are characterized by X-ray powder diffraction (XRD), Rietveld refinement of XRD pattern, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and electrochemical tests. It has been found that Fe2F5 ·H2O is a face-centered cubic crystal structure with high crystallinity, and iron in the Fe2F5 ·H2O is in the form of mixed valence states. Moreover, the Fe2F5 ·H2O sample shows the sphere-like morphology with the average particle about 700nm and good dispersity. Besides, the Fe2F5 ·H2O shows a high initial discharge capacity of 253.7mAhg−1 and the reversible capacity of 161.2mAhg−1 at 20mAg−1 in the voltage of 1.0–4.0V. After modification by graphene, the Fe2F5 ·H2O/graphene (abbreviated as Fe2F5 ·H2O/G) composite reveals good cycling stability and high rate performance. Consequently, the Fe2F5 ·H2O may be a potential cathode material for SIBs system.
An iron-vanadium redox flow battery utilizing 15 μm thick HCl doped meta-polybenzimidazole (m-PBI) membranes is used. Ex-situ tests for m-PBI membranes show a much lower permeability for Fe2+ and V3+ ions than when using Nafion 212. Specifically, cells utilizing 50 μm thick Nafion 212 show a strong electrolyte imbalance (catholyte moving to anolyte), a low charge efficiency (CE) of 90%, and a high capacity loss rate (CLR) of 0.63 Ahr∙L−1 per cycle, indicating low energy efficiency and stability. In contrast to this, cells utilizing m-PBI reveal a CE of 99% and a CLR of just 0.11 Ahr∙L−1 per cycle. After 20 cycles, the discharge capacity is three times higher than for the cell with Nafion 212. Since the polymer needed for a 15 μm thick m-PBI membrane costs 97% less than for a 50 μm thick Nafion membrane, the utilization of m-PBI membranes is also economically advantageous.
Electroactive copolymers of o-toluidine (OT) and o-phenylenediamine (OPD) were electrosynthesized in aqueous sulfuric acid. Cyclic voltammetry was used both for the electrochemical synthesis and characterization of the copolymers deposited on a gold electrode. The voltammograms exhibited different behavior for different concentrations of OPD in the feed. At optimum conditions the rate of copolymerization was found to be between the rates of homopolymerizations. The resulting poly(OPD-co-OT) shows an extended useful potential range of the redox activity as compared to the corresponding homopolymers. The effect of scan rate and pH on the electrochemical activity was studied. The copolymer was electrochemically active even at pH 9.0. In situ conductivity measurements further support the formation of a copolymer because the copolymers have a potential region of maximum conductivity completely different from that of POT. However, conductivities of the copolymers were lower by 2–2.7 orders of magnitude than of POT.
CeO2-coated LiCoO2 particles were successfully synthesized by a sol–gel coating of CeO2 on the surface of the LiCoO2 powder and subsequent heat treatment at 700°C for 5h. The surface-modified and pristine LiCoO2 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Auger electron spectroscopy (AES), slow rate cyclic voltammogram (CV), and differential scanning calorimetry (DSC). Cyclic voltammetry curves suggested that the CeO2 coating suppressed the phase transitions. Unlike pristine LiCoO2, the CeO2-coated LiCoO2 cathode exhibited better capacity retention than the pristine LiCoO2 electrode in the higher cutoff voltage. Differential scanning calorimetric data revealed the higher thermal stability of the CeO2-coated LiCoO2 electrode.
New Cu x Zn3−x V2O7(OH)2·yH2O (0< x ≤1.5) isostructural to zinc pyrovanadate Zn3V2O7(OH)2·2H2O, were successfully prepared by using a chimie douce technique. The method consists in mixing zinc nitrate and copper nitrate with a boiling solution of vanadium oxide (obtained by reacting V2O5 with few millilitres of 30vol.% H2O2 followed by addition of distilled water). When ammonium hydroxide NH4OH 10% was added (pH≈6), a precipitate was obtained. Using powder X-ray diffraction data, the crystal structures of as-prepared samples were determined by Rietveld refinement. Copper substitutes zinc in the zinc pyrovanadate lattice and is found to introduce distortion in the structure, which is mainly due to the Jahn–Teller effect. Distortion becomes more pronounced when the amount of copper is increased. This restricts the amount of copper which can be incorporated in the hexagonal zinc pyrovanadate lattice.
A simple circuit model is developed to describe supercapacitor behavior, which uses two resistor–capacitor branches with different time constants to characterize the charging and redistribution processes, and a variable leakage resistance to characterize the self-discharge process. The parameter values of a supercapacitor can be determined by a charging-redistribution experiment and a self-discharge experiment. The modeling and characterization procedures are illustrated using a 22F supercapacitor. The accuracy of the model is compared with that of other models often used in power electronics applications. The results show that the proposed model has better accuracy in characterizing the self-discharge process while maintaining similar performance as other models during charging and redistribution processes. Additionally, the proposed model is evaluated in a simplified energy storage system for self-powered wireless sensors. The model performance is compared with that of a commonly used energy recursive equation (ERE) model. The results demonstrate that the proposed model can predict the evolution profile of voltage across the supercapacitor more accurately than the ERE model, and therefore provides a better alternative for supporting research on storage system design and power management for wireless sensor networks.
While attachment research has demonstrated that parents’ internal working models of attachment relationships tend to be transmitted to their children, affecting children’s developmental trajectories, this study specifically examines associations between adult attachment status and observable parent, child, and dyadic behaviors among children with autism and associated neurodevelopmental disorders of relating and communicating. The Adult Attachment Interview (AAI) was employed to derive parental working models of attachment relationships. The Functional Emotional Assessment Scale (FEAS) was used to determine the quality of relational and functional behaviors in parents and their children. The sample included parents and their 4- to 16-year-old children with autism and associated neurodevelopmental disorders. Hypothesized relationships between AAI classifications and FEAS scores were supported. Significant correlations were found between AAI classification and FEAS scores, indicating that children with autism spectrum disorders whose parents demonstrated secure attachment representations were better able to initiate and respond in two-way pre-symbolic gestural communication; organize two-way social problem-solving communication; and engage in imaginative thinking, symbolic play, and verbal communication. These findings lend support to the relevance of the parent’s state of mind pertaining to attachment status to child and parent relational behavior in cases wherein the child has been diagnosed with autism or an associated neurodevelopmental disorder of relating and communicating. A model emerges from these findings of conceptualizing relationships between parental internal models of attachment relationships and parent-child relational and functional levels that may aid in differentiating interventions.
Exploring high performance and environment-friendly electrode materials is highly desirable for the sustainable Li-ion batteries (LIBs) system. In this study, a facile approach of the modified Hummers’ method combining with special thermal reduction was proposed to synthesize nanostructured reduced graphene oxide (RGO) with abundant oxygen-containing functional groups. The resultant RGO showed high specific capacity and excellent cyclability as cathode materials for LIBs. The specific capacity of about 220mAhg−1 at a current density of 50mAg−1 was achieved after 100 cycles. More importantly, it was demonstrated that the capacity increased with the increase of the amount of oxygen functional groups, highlighting the significant effects of oxygen-containing functional groups of RGO on high lithium storage performance.
Exhibiting a very high surface area, a good electrical conductivity and a high density of active sites, nitrogen-doped graphenic materials are considered as promising catalysts for the oxygen reduction reaction (ORR). Seldom studied in acidic media, N-doped graphenic foams were tested here as the cathode catalysts of a polymer electrolyte membrane fuel cell (PEMFC). The materials were prepared via a solvothermal-based process, by reacting either cyclohexanol and ethanolamine or 1-(2-hydroxyethylethyl) piperidine with metallic sodium, under high pressure and temperature. Membrane electrode assemblies were prepared with a Pt/C anode, 212 Nafion membrane, and an 8 mm disk cathode based on the graphenic materials. The performance exhibited by the PEMFC was evaluated using chronopotentiometry and impedance spectroscopy, depending on the synthesis conditions. The kinetic parameters of the ORR were estimated by interpretation of the experimental data: the high Tafel slope found might express the partial control of oxygen diffusion through the graphenic microporous structure. Relationships between the electrochemical behavior of the materials and their structural properties are discussed. Moderately crystallized materials with a low oxygen content showed the highest catalytic properties, with a current density larger than 30 mA cm−2 and a maximum power density at 2.3 mW cm−2.
The aim of this study was to get an overview about the occurrence of bacteria from the genus Ehrlichia and Rickettsia in ixodid ticks with medical importance in Argentina. Therefore, in 2013 and 2014, free-living ticks were collected in different provinces of northern Argentina. These ticks were determined as Amblyomma sculptum, Amblyomma neumanni, Amblyomma parvum, Amblyomma triste, Amblyomma ovale, Amblyomma tonelliae and Haemaphysalis juxtakochi. All samples were tested to determine the infection with Ehrlichia spp. and Rickettsia spp. by PCR assays. Rickettsial DNA was detected in all tested tick species, with the exception of A. tonelliae. ‘Candidatus Rickettsia amblyommii’, ‘Candidatus Rickettsia andeanae’, and Rickettsia parkeri were found in A. neumanni, A. parvum, and A. triste, respectively. Another rickettsial species, Rickettsia bellii, was found in A. sculptum, A. ovale and H. juxtakochi. None of the tested ticks showed infection with Ehrlichia. The results of the study demonstrate that Rickettsia species belonging to the spotted fever group are associated with various species of Amblyomma throughout a wide area of northern Argentina, where cases of Amblyomma ticks biting humans are common.
In an assessment of the performance of a Li|LiCl–LiF|Bi liquid metal battery, increasing the current density from 200 to 1250 mA cm−2 results in a less than 30% loss in specific discharge capacity at 550 °C. The charge and discharge voltage profiles exhibit two distinct regions: one corresponding to a Li–Bi liquid alloy and one corresponding to the two-phase mixture of Li–Bi liquid alloy and the intermetallic solid compound, Li3Bi. Full cell prototypes of 0.1 Ah nameplate capacity have been assembled and cycled at 3 C rate for over a 1000 cycles with only 0.004% capacity fade per cycle. This is tantamount to retention of over 85% of original capacity after 10 years of daily cycling. With minimal changes in design, cells of 44.8 Ah and 134 Ah capacity have been fabricated and cycled at C/3 rate. After a hundred cycles and over a month of testing, no capacity fade is observed. The coulombic efficiency of 99% and energy efficiency of 70% validate the ease of scalability of this battery chemistry. Post mortem cross sections of the cells in various states of charge demonstrate the total reversibility of the Li3Bi solid phase formed at high degrees of lithiation.
The application of silicon as ultrahigh capacity electrodes in lithium-ion batteries has been limited by a number of mechanical degradation mechanisms including fracture, delamination and plastic ratcheting, as a result of its large volumetric change during lithiation and delithiation. Graphene coating is one feasible technique to mitigate the mechanical degradation of Si anode and improve its conductivity. In this paper, first-principles calculations are performed to study the atomic structure, charge transfer and sliding strength of the interface between lithiated silicon and graphene. Our results show that Li atoms segregate at the (lithiated) Si-graphene interface preferentially, donating electrons to graphene and enhancing the interfacial sliding resistance. Moreover, the interfacial cohesion and sliding strength can be further enhanced by introducing single-vacancy defects into graphene. These findings provide insights that can guide the design of stable and efficient anodes of silicon/graphene hybrids for energy storage applications.
Two-dimensional MoS2 is a promising anode material for Li-ion batteries, but suffers from poor electrochemical activity and stability. Herein, a facile approach for the controlled synthesis of onion-like nanospheres organized by carbon encapsulated MoS2 nanosheets is developed through a simple polymerization and sulfidation/carbonation process. Mo-containing polyoxometalate is demonstrated to enable polymerization of polypyrrole accompanying with uniform encapsulation of Mo-nanoclusters. The hybrid precursor confines the growth of few-layer MoS2 nanosheets (≤5 layers) into N-doped carbon framework, which is of great benefit in enhancing the electrical conductivity and structural integrity. As a result, the nanospherical MoS2@C hybrid electrode manifests high Li-ion storage capacity (1119 mAh g−1 at 0.1 A g−1), excellent rate capability (616 mAh g−1 at 2 A g−1), and long cycling stability. The substantial improvement is rationalized by fast electrode kinetics and great pseudocapacitive contribution. The present work may offer a powerful engineering strategy of MoS2@C nanomaterials for Li/Na-ion batteries and electrocatalysts.