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We report here on the moisture and water stability of the promising Na-ion anode material Na2Ti3O7. Spontaneous Na+/H+ exchange is detected by PXRD after air exposure, forming solid solution compounds of the form Na2−xHxTi3O7 (0 < x < 2). By controlled ion exchange in aqueous solution two mixed compositions are prepared and their composition and structure are characterized with a panel of techniques. Both mixed compositions crystallize in C2/m space group like H2Ti3O7, and therefore Na+/H+ exchange is found to involve a structural transition from AA stacking of [TiO6] layers to AB stacking sequence. The electrochemical behaviour of the mixed compositions vs. Na+/Na is studied as well as that of an electrode of pure Na2Ti3O7 prepared in water media. The water-processed electrode is shown to exhibit a superior cycling stability and therefore the results obtained highlight the potential of Na2Ti3O7 as a green, low cost anode material for NIBs.
Gel polymer electrolytes are prepared using poly(vinylidene fluoride-co-hexafluoropropylene) polymer matrix and 1- propyl-3-methyleimidazolium bis(trifluromethylesulfonyl)-imide ionic liquid and also by adding lithium bis(trifluoromethanesulfonyl)imide salt and plasticizer mixture (ethylene carbonate: propylene carbonate in the ratio 1:1). Thermal and electrical properties of these electrolytes are first investigated. The electrical conductivity of these electrolytes is analyzed over a wide frequency range using a universal power law coupled with modified Poisson-Nernst-Planck model for electrode polarization. All electrolytes show excellent thermal stability up to 340 °C, high ionic conductivity (∼1 × 10−3 S cm−1) and wide potential window (∼4.0 V). Supercapacitors are fabricated with these electrolytes using activated carbon as electrodes and their electrochemical properties are studied. The cyclic voltammetry curves show almost box-like shape corresponding to an ideal and reversible capacitive characteristic. The specific capacitance of supercapacitors increases with the addition of lithium salt and plasticizer mixture. The cycle stability of these supercapacitors up to 4000 cycles confirms their electrochemical stability. A lithium ion coin cell is also fabricated using electrolytes containing plasticizer mixture. At ambient temperature, the fabricated cell delivers high specific discharge capacity (∼165.8 mAh g−1) for the first discharge cycle at a constant current rate C/12.
Different cobalt containing materials obtained from the thermal decomposition of two organic precursors, cobalt–acetylacetonate and cobalt–tetrametoxyphenylporphyrin, and Co3O4 prepared by thermal decomposition of cobalt carbonate have been characterised by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and high resolution transmission microscopy (HRTEM). It has been found that the cobalt precursor, the organic macrocycle and the active carbon are simultaneously needed during the heat treatment in inhert atmosphere. Their contemporaneous presence is useful to obtain a material on which the dispersed metal is able to catalyse reactions that produce pores or tunnels inside the carbon, thus resulting in an enhanced contact area. The organic macrocycle is only partially decomposed and the residual fraction could enhance the conductivity.
Amorphous and nanocrystalline Mg-based alloys (Mg60Ni25)100−x Nd x (x =2, 5, 10, 15) were prepared by rapid solidification. The microstructure of the as-quenched ribbons was characterized by TEM, X-ray and electron diffraction. The electrode properties of these alloys were measured. The experimental results showed that the discharge capacities increased with increasing Nd atomic content and the optimum Nd content is between in 10–15mol%. The highest discharge capacity reached more than 580mAhg−1 at the discharge current densities of 50mAg−1 for (Mg60Ni25)90Nd10 samples. The nanocrystalline (Mg60Ni25)98Nd2 alloy showed the lowest discharge capacity compared to the other Mg–Ni–Nd amorphous alloys. The alloy (Mg60Ni25)90Nd10 displays the broadest discharge potential flat from 1.3 to 1.0V. It was conformed that the increase of discharge capacities is not only a function of the sample composition but strongly influenced by the amorphous phase proportion in the alloys.
The structure design and synthesis of precursors is a key factor to improve the electrochemical properties of Ni-rich cathode materials. However, for the core-shell precursors, the structural evolution in the lithiated process and its effect on the structure and electrochemical properties of the final products has not been clearly elucidated. Herein, three LiNi0.88Co0.12O2 materials are synthesized from three different structured precursors, namely the completely coated 0.88Ni(OH)2@0.12Co(OH)2, the semi-coated & semi-doped 0.94Ni0.936Co0.064(OH)2@0.06Co(OH)2, and the completely doped Ni0.88Co0.12(OH)2, respectively. Unexpectedly, the core-shell structures of the completely coated and semi-coated & semi-doped precursors disappears, and the radial concentration distributions of Ni and Co are almost uniform in spherical LiNi0.88Co0.12O2 particles obtained by sintering with LiOH·H2O, no matter the precursor is coating type or doping type. Even so, the LiNi0.88Co0.12O2 material synthesized from the 0.88Ni(OH)2@0.12Co(OH)2 precursor still has the best electrochemical properties with the specific discharge capacity of 215 mAh g−1 at 0.1 C (20 mA g−1) and the capacity retention of 88.6% after 100 cycles. The reason is that the cobalt hydroxide coating layer on the surface of precursor acts as a barrier to decrease the diffusing rate of lithium ions into the core material, which leaves enough time to make Ni2+ be oxidized to Ni3+ as many as possible. This work not only synthesizes a high-performance LiNi0.88Co0.12O2 material, but also clearly reveals the reaction mechanism and provides valuable references for synthesizing high-performance LiNi1-x-yCo x MnyO2 (NCM) or LiNi0.8Co0.15Al0.05O2 (NCA) materials.
In this study, nano-crystalline LiCoO2 was coated onto the surface of Li1.05Ni0.35Co0.25Mn0.4O2 powders via sol–gel method. The influence of the coating on the electrochemical behavior of Li1.05Ni0.35Co0.25Mn0.4O2 is discussed. The surface morphology was characterized by transmission electron microscopy (TEM). Nano-crystallized LiCoO2 was clearly observed on the surfaces of Li1.05Ni0.35Co0.25Mn0.4O2. The phase and structural changes of the cathode materials before and after coating were revealed by X-ray diffraction spectroscopy (XRD). It was found that LiCoO2 coated Li1.05Ni0.35Co0.25Mn0.4O2 cathode material exhibited distinct surface morphology and lattice constants. Cyclic voltammetry (2.8–4.6V versus Li/Li+) shows that the characteristic voltage transitions on cycling exhibited by the uncoated material are suppressed by the 7wt.% LiCoO2 coating. This behavior implies that LiCoO2 inhibits structural change of Li1.05Ni0.35Co0.25Mn0.4O2 or reaction with the electrolyte on cycling. In addition, the LiCoO2 coating on Li1.05Ni0.35Co0.25Mn0.4O2 significantly improves the rate capability over the range 0.1–4.0C. Comparative data for the coated and uncoated materials are presented and discussed.
Mindfulness-Based Stress Reduction is a secular behavioral medicine program that has roots in meditative spiritual practices. Thus, spirituality may partly explain Mindfulness-Based Stress Reduction outcomes. Participants (N = 279; M (SD) age = 45(12); 75% women) completed an online survey before and after an 8-week Mindfulness-Based Stress Reduction program. Structural equation modeling was used to test the hypothesis that, following Mindfulness-Based Stress Reduction, the relationship between enhanced mindfulness and improved health-related quality of life is mediated by increased daily spiritual experiences. Changes in both spirituality and mindfulness were significantly related to improvement in mental health. Although the initial mediation hypothesis was not supported, an alternate model suggested that enhanced mindfulness partly mediated the association between increased daily spiritual experiences and improved mental health-related quality of life (indirect effect: β = 0.07, P = 0.017). Effects on physical health-related quality of life were not significant. Findings suggest a novel mechanism by which increased daily spiritual experiences following Mindfulness-Based Stress Reduction may partially explain improved mental health as a function of greater mindfulness.
Solid state catalysts play a critical role in peroxide alkali metal–O2 cells. However, the underlying mechanism behind the catalytic activity remains controversial due to the different nature of oxygen reduction and evolutions reactions (ORR, OER) in non-aqueous cells compared to those in classic aqueous based reactions. In the present study, we reveal a detailed spectroscopic and electrochemical picture of the mechanism of catalytic activity in Na– and Li–O2 cells. We demonstrate that ORR and OER catalytic activity in alkali metal–O2 cells primarily originates from the stabilization of O2− intermediates on the catalyst surface during the electrochemical reaction. Monitoring the electronic state of the solid state catalyst during the ORR and OER revealed a dynamic interaction occurring between the catalyst and the discharge product. The morphology and composition of discharge products is also illustrated to be influenced by solid state catalysts. The findings of the present study suggest that catalysts with a higher oxygen-bonding capability may exhibit a higher catalytic activity in alkali metal–O2 cells.
Charge–discharge properties of a new type of all solid-state lithium cell are presented, which comprises a conductive nano-sulfur composite (NSC) cathode, composite polymer electrolyte based on poly(ethylene oxide), LiN(CF3SO2)2 and nano-sized TiO2 filler and lithium anode. The cell exhibits high discharge capacity up to 600mAhg−1 (referred to the NSC active material, EO/Li=8 for polymer electrolyte) at the second cycle and about 385mAhg−1 at the 40th cycle at operation temperature of 70°C. The electrochemical characteristics of the nano-composite polymer electrolyte, related to the performance of cells, are also examined in detail.
A graphene-like nanomaterial, carbon nano-fragments (CNFs), is obtained using the graphite anodes of spent lithium-ion batteries (LIBs) as carbon source, and its morphology, structure, functional groups, and reactivity are characterized to evaluate the properties and potential applications. The interlayer space increase, layer distortion, and remnant lithium of the waste lithium-intercalated graphite are utilized to prepare the oxidized CNFs (ox-CNFs) through a chemical oxidation and ultrasonic crushing process. These ox-CNFs exhibit a size distribution of 15nm to 2μm and excellent hydrophilicity, and disperse well in an aqueous suspension. Under the hydrothermal condition at 180°C for 12h, the ox-CNFs are converted into a suspension of reduced CNFs (re-CNFs), or a cylindrical aggregate when the concentration exceeds 2 mg·mL−1. The spectroscopic results demonstrate that there are abundant edges, defects, and functional groups existing on the CNFs, which affect their reactive, electronic, and electrochemical properties. Thereinto, the vacuum-dried ox-CNFs film can be converted from an insulator to a conductor after a chemical reduction by hydroiodic acid. And the re-CNFs modified glass carbon electrode (re-CNFs/GCE) exhibits enhanced electrocatalytic activity of about 8 times than the GCE to the oxidation reaction of dopamine. Furthermore, with the addition of the carboxylic ox-CNFs in aniline, the CNFs/polyaniline composite discharges a capacitance of 356.4 F·g−1 at 2 mV·s−1, an increase of 80.5% compared to the polyaniline. This preparation entails not only novel carbon nanomaterials but also an excellent disposal method of spent graphite, showing special significance in materials innovation and environmental science.
Choosing between different scenarios commonly requires decision making based on multiple criteria. For example finding the most sustainable agricultural production system requires evaluation of many indicators in fields as diverse as environment, animal welfare and economics. A new and transparent method to such problems based on piecewise linear functions is described, and compared to other approaches. This paper presents a decision support tool which allows to (1) group indicators in a hierarchy, (2) define the acceptability of indicator values between unacceptable and desirable values, (3) define the relative importance of indicators, and (4) combine the individual indicators’ acceptabilities using various degrees of compromising into a final acceptability score for each of the investigated scenarios. The tool contains a visual module to study the comparison of scenarios in the bivariate case, which allows to get familiar with the concepts behind the balancing of indicators. The developed method and software tool are useful for decision support in processes where policy makers and scientists are interacting to arrive at optimal decisions.
The cubic ZnFe2O4 with the spinel structure is prepared by the urea combustion method. Powder X-ray diffraction and HR-TEM studies confirm the single-phase nature with particle size in the range, 100–300nm. A stable and reversible capacity, 615(±10)mAhg−1 (5.5moles of Li per mole of ZnFe2O4) when cycled in the range, 0.005–3.0V vs. Li at a current of 60mAg−1(0.1C) has been achieved between 15 and 50 cycles. The underlying reaction mechanism contributing to the observed capacity is the combination of ‘de-alloying–alloying’ and ‘conversion’ reactions of ‘LiZn–Fe–Li2O composite’. Ex situ HR-TEM and SAED data on the charged-electrode confirmed the proposed reaction mechanism.
This paper provides an insight into the specifications for electric double layer capacitor systems (EDLCs), design issues and production technology. It focuses on systems with power ratings far in excess of 100 kW and with short cycle times. As a result, a major topic of interest is EDLC cooling. Several cooling concepts are compared with each other based on experimental data. This is done for four EDLC configuration types. Mechanical aspects and diagnostics of the electric and thermal system are also covered.
Capsaicin is the active substance responsible for the pungent sensation produced by red pepper. In order to approach the underlying genetic mechanism for preference of red pepper, we conducted a 12-h, 1-bottle intake test of capsaicin solution using both male and female animals from the Mishima battery of mouse strains: 10 wild-derived inbred strains (PGN2, BFM/2, HMI, CAST/Ei, NJL, BLG2, CHD, SWN, KJR, MSM), 1 strain derived from the so-called fancy mouse (JF1), and 3 widely used laboratory strains (C57BL/6J, DBA/1J and BALB/cAnN). The concentration of capsaicin was increased from 0.5 to 15 μM successively. Gender differences were not observed in this test, but we found striking strain differences in capsaicin intake. Relative to baseline water intake, C57BL/6J and DBA/1J consumed 10%, whereas two wild strains, KJR and MSM, ingested approximately 60% of the 15-μM capsaicin solution. In a 2-bottle fluid preference test, both C57BL/6J and MSM strains reject capsaicin fluid even at the 0.5-μM concentration, which indicates that the receptors for capsaicin in these strains recognize capsaicin at a similar level. Thus, the strain differences at higher capsaicin concentrations in the 1-bottle test may reflect differences in central nervous system response to the capsaicin solution. The genetic difference in intake of capsaicin observed in these strains may provide a useful tool for identifying genes underlying response to red pepper in mice and other mammalian species.
Poly(hexyl viologen dichloride) (PHV-Cl) is described as a high energy density (ED) material in magnesium-based electrolytes. When coupled with Mg metal in all phenyl complex (APC) electrolytes, PHV-Cl cathodes demonstrate anion-transport behaviors with the reduction/oxidation of viologen units. This dual-ion type cell delivers a relatively high ED with reasonable stability during repeated charge/discharge (C/D) when compared with previously reported inorganic/organic cathodes in magnesium-ion batteries (MIBs). PHV-Cl shows a capacity of 171 mAh g−1 at an average discharge potential of 1.33 V vs. Mg/Mg2+, resulting in a significantly high ED (227 mWh g−1). The high ED characteristics of PHV-Cl are retained during repeated C/D cycles (201 mWh g−1 after 50 C/D) in contrast to the relative instability of other previously reported organic cathodes. Herein, the electrochemical performance of PHV-Cl in various types of electrolytes is also described. This work suggests that viologen-based cathodes with anion-transport properties could be implemented to achieve high levels of ED and stability via a dual-ion mode in MIBs, particularly with currently available electrolytes that are compatible with magnesium metal.
Objective Verify whether Percutaneous Transluminal Angioplasty (PTA) may affect neural conduction properties in Multiple Sclerosis (MS) patients, thereby modifying patients’ disability, with prospective neurophysiological, urodynamic, clinical and subjective well-being evaluations. Methods In 55 out of 72 consecutively screened MS patients, the following procedures were carried out before (T0), at 2–6 months (T1) and at 6–15 months (T2) after a diagnostic phlebography, eventually followed by the PTA intervention if chronic cerebrospinal venous insufficiency (CCSVI) was diagnosed: clinical/objective evaluation (Expanded Disability Status Scale, EDSS), ratings of subjective well-being, evaluation of urodynamic functions and multimodal EPs (visual, acoustic, upper and lower limbs somatosensory and motor evoked potentials). Results The number of dropouts was relatively high, and a complete set of neurophysiological and clinical data remained available for 37 patients (19 for urological investigations). The subjective well-being score significantly increased at T1 and returned close to basal values at T2, but their degree of objective disability did not change. Nevertheless, global EP-scores (indexing the impairment in conductivity of central pathways in multiple functional domains) significantly increased from T0 (7.9 ± 6.0) to T1 (9.2 ± 6.3) and from T0 to T2 (9.8 ± 6.3), but not from T1 and T2 (p > 0.05). Neurogenic urological lower tract dysfunctions slightly increased throughout the study. Conclusions The PTA intervention did not induce significant changes in disability in the present cohort of MS patients, in line with recent evidence of clinical inefficacy of this procedure. Significance Absence of multimodal neurophysiological and functional testing changes in the first 15 months following PTA suggests that conduction properties of neural pathways are unaffected by PTA. Current findings suggest that the short-lived (2–6 months), post-PTA, beneficial effect on subjective well-being measures experienced by MS patients is likely related to a placebo effect.
A comprehensive study is reported entailing optimization of sodium ion electrolyte formulation and compatibility studies with positive and negative electrode materials. EC:PC:DMC and EC:PC:DME were found to exhibit optimum ionic conductivities and lower viscosities. Yet, hard carbon negative electrode materials tested in such electrolytes exhibit significant differences in performance, rooted in the different resistivity of the SEI, which results in too large polarization and concomitant loss of capacity at low potentials when DME is used as a co-solvent. EC0.45:PC0.45:DMC0.1 was found to be the optimum composition resulting in good rate capability and high capacity upon sustained cycling for hard carbon electrodes. Its compatibility with positive Na3V2(PO4)2F3 (NVPF) electrodes was also confirmed, which led to the assembly of full Na-ion cells displaying an operation voltage of 3.65 V, very low polarisation and excellent capacity retention upon cycling with ca. 97 mA h g−1 of NVPF after more than 120 cycles together with satisfactory coulombic efficiency (>98.5%) and very good power performance. Such values lead to energy densities comparable to those of the current state-of-the-art lithium-ion technology.
Activated Carbon (AC) and multi-walled carbon nanotubes (CNT) are investigated as components of LiFePO4 (LFP)-based bi-material electrodes for hybrid devices. Firstly, the influence of their different morphological and porosimetric characteristics is correlated to the electrochemical performance. Furthermore, kinetic aspects are carefully studied (by means of galvanostatic cycling and cyclic voltammetry), in order to address the processes which determine the power performance. The results indicate that, independently from the carbon, under high current loads the electrode kinetics are limited by the transport of reactant to the LFP particles. In such conditions CNT allow, better than AC, rapid electrons and Li+ ions flow through the open network established in the electrode, thus enabling superior high rate performance, especially during pulsed operation.
Augmentative and alternative communication (AAC) includes a range of approaches aimed at supporting or replacing speech for children and others for whom natural speech is not sufficient to meet their needs. For some children it also offers a support to the process of language learning. A wide range of medical conditions may lead to a child requiring AAC, either temporarily or on a more permanent basis. AAC systems may be unaided or aided, in the sense of requiring some form of equipment. They vary on the level of technology required from none to specialized computer-based devices offering synthesized speech output. Management of children requiring AAC must involve parents and a multidisciplinary team of health and education professionals, in addition to active involvement on the part of the child.
A novel approach to large bandgap semiconductor materials design is demonstrated. Based on a thermodynamical growth control concept, a low temperature aqueous thin film growth technique is presented to produce, at large scale and low cost, novel metal oxide-based nano- to micro-structures. Three-dimensional arrays consisting of building blocks of controlled morphologies, sizes and orientations, engineered from molecular to nano-, meso- or microscopic scales are generated onto various substrates. Semiconductor technology and in particular, photovoltaics and photocatalysis, shall be beneficiary of such designed arrays. Promising improvements in terms of overall efficiency and manufacturing costs as well as better fundamental understandings of their electronic structure are foreseen with the use of such purpose-built materials. To cite this article: L. Vayssieres, C. R. Chimie 9 (2006) .
Lithium transport through Li1−δ Mn2O4 electrode during the lithium intercalation involving the disorder to order phase transition was investigated by numerical analysis of the current transient. All the measured current transients showed non-Cottrell behaviour during the whole lithium intercalation, and the relationship between the initial current level and the applied potential drop followed Ohm’s law. The current transient was numerically simulated based upon the ‘cell-impedance controlled’ lithium transport at various applied potential steps. The current transient theoretically calculated well coincided with that transient experimentally measured in value and shape. The typical current transient showed two ‘quasi-current plateaux’ separated by a steep current drop in value, indicating the coexistence of the disordered and ordered phases, as confirmed from the concentration profile across the electrode. From the experimental and theoretical results, it was strongly inferred that lithium transport through the Li1−δ Mn2O4 electrode is governed by the ‘cell-impedance controlled’ constraint during the whole lithium intercalation involving the ordering of lithium ion.