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Cathodic corrosion, a green electrochemical method, has been employed to obtain Sb nanomaterials utilized as anode material for lithium-ion batteries and sodium-ion batteries. Interestingly, two different corrosion mechanisms are found, coming from the impact of electrolyte, resulting in the formation of hexagonal and amorphous Sb in aqueous and organic solution, respectively. With the help of water-soluble carboxymethyl cellulose binder and the electrolyte additive fluoroethylene carbonate, both hexagonal and amorphous Sb electrodes exhibit good cycling stability when utilized as anode materials for lithium-ion batteries and sodium-ion batteries. Additionally, both the hexagonal and amorphous Sb electrodes show very good rate capability in lithium-ion batteries. Even at high current density (2000 mA g−1), the hexagonal and amorphous Sb give reversible capacities of 422 and 379 mA h g−1, respectively. Surprisingly, when used as anode materials for sodium-ion batteries, the hexagonal Sb electrode exhibits a good rate performance of 632, 625, 569, 515 and 426 mA h g−1 at a current density of 100, 200, 500, 1000, and 2000 mA g−1, respectively. However, limited rate performance is observed from the amorphous Sb electrode in case of sodium-ion battery due to the large impedance.
Although significant progress has been made in the identification of youth evidence-based practices, the adoption of these interventions into community-based mental health care remains limited. Dissemination and implementation (DI) research has the potential to bridge this science-practice gap in clinical psychology. The theory of planned behavior (TPB) offers a useful conceptualization of individual behavior change including behavioral intention as defined by attitudes, subjective norms, and perceived behavioral control. To facilitate application of this model to DI efforts, the current study explores perspectives about using evidence-based practice from stakeholders in the field of youth mental health (including clinical supervisors, case managers, administrators at the departments of health and education, and direct service providers in clinic-based, school-based, and intensive in-home settings) within the TPB framework. A set of instrument items was created from this rich qualitative data using a rigorous mixed-method content validation approach. Instrument items are provided for future use in DI research.
We report the synthesis and electrochemical performance of one dimensional NiO nanofibers by simple electrospinning technique and subsequently heat treated at 800 °C to yield single phase material. After the heat treatment, thickness and crystal size electrospun NiO is found ∼1 μm and 100 nm, respectively. The electrospun nanofibers are subjected to various characterizations such as X-ray diffraction with Rietveld refinement, scanning electron microscopy and transmission electron microscopy (TEM). Half-cell assembly is used to evaluate the Li-uptake properties and found maximum reversible capacity of ∼784 mA h g−1 at current density of 80 mA g−1 with operating potential of ∼1.27 V vs. Li. The test cell rendered good cycleability and exhibits capacity retention of over 75% of reversible capacity after 100 cycles. The conversion mechanism of metallic nanoparticles (Ni0) are validated though ex-situ TEM measurements. Rate performance studies are also conducted and delivered good cycling properties under such high current studies.
Polyanionic compounds are regarded as one of the most promising cathode materials for the next generation lithium-ion batteries due to their abundant resource and thermal stability. LiFeBO3 has a relatively higher capacity than olivine LiFePO4, however, moisture sensitivity and low conductivity hinder its further development. Here, we design and synthesize mesoporous LiFeBO3/C (LFB/C) hollow spheres to enhance its structural stability and electric conductivity, two LiFeBO3/C electrodes with different carbon content are prepared and tested. The experimental results show that mesoporous LiFeBO3/C hollow spheres with higher carbon content exhibit superior lithium storage capacity, cycling stability and rate capability. Particularly, the LFB/C electrode with higher carbon content demonstrates good structural stability, which can maintain its original crystal structure and Li storage properties even after three months of air exposure at room temperature. The exceptional structural stability and electrochemical performance may justify their potential use as high-performance cathode materials for advanced lithium-ion batteries. In addition, the synthesis strategy demonstrated herein is simple and versatile for the fabrication of other polyanionic cathode materials with mesoporous hollow spherical structure.
Patients with anterior cruciate ligament (ACL) injury often exhibit reduced movement quality during functional tasks in the form of a knee-medial-to-foot position (KMFP). This movement pattern is suggested to be more common in women than in men, but the possible contributing sensorimotor factors for this altered knee position are poorly studied in these patients. The aim of this study was to evaluate the association between sensory function and medio-lateral knee position during functional tasks in men and women with ACL injury.
Batteries with lithium iron phosphate (LFP) cathode and carbon anode have shown various advantages over those with other chemistries, but the plateau and path dependence caused by the two-phase transition taking place during charging and discharging make it difficult to estimate the states of battery. Thus, based on electrochemical principles we propose a new reduced order model that has been validated against experimental data obtained during galvanostatic charging/discharging. The mechanism of the two-phase transition during lithiation and delithiation in LFP particles is approximated using a shrinking corewith a moving interface between the two phases and is described by modified diffusion equations that take into account multiple layers formed within LFP particles. The shrinking core model is integrated into a cell model developed previously, which is used to analyze the path dependence at different load profiles. The results show that the model is capable of representing the characteristics of the plateau and path dependence. Particularly, the available charge at a certain State of Charge (SOC) varies dependent upon paths to reach the SOC. When an initial SOC is reached by discharging, the cell can accept more charges during charging, while when an initial SOC is reached by charging, more charge will be available during discharging.
The ability of alkali-substituted binders for composite Si and graphite negative electrodes to minimize capacity fade for lithium ion batteries is investigated. Polymer films and electrodes are described and characterized by FTIR following immersion in electrolyte (1:2 EC:DMC) for 24 h. FTIR analysis following electrode formation displayed similar alkali-ion-dependent shifts in peak location suggesting that changes in the vibrational structure of the binder are maintained after electrode formation. The Si and graphite composite electrodes prepared using the alkali-substituted polyacrylates were also exposed to electrochemical cycling and it has been found that the performance of the Na-substituted binder is superior to a comparable density K-substituted system. However, in comparing performance across many different electrode densities, attention needs to be placed on making comparisons at similar densities, as low-density electrodes tend to exhibit lower capacity fade over cycling. This is highlighted by a 6 % difference between a low-density K-substituted electrode and a high-density Na-substituted sample. This low variance between the two systems makes it difficult to quickly make a direct evaluation of binder performance unless electrode density is tightly controlled.
Crystalline hausmannite nanocrystals/reduced graphene oxide composites (denoted as Mn3O4/RGO) are synthesized by means of the microwave-assisted hydrothermal synthesis (MAHS) route for the application of symmetric and asymmetric supercapacitors. Effects of the Mn3O4 content on the microstructure and electrochemical performances of nanocomposites are systematically investigated. The morphology and crystalline structure of composites are examined by scanning electron microscopic (SEM) and X-ray diffraction (XRD) analyses. Thermogravimetric analysis (TGA) is used to determine the mass content of RGO in the Mn3O4/RGO composites. The results indicate that the composite with about 82.4 weight percents (wt%) Mn3O4 (denoted as GMn80) shows the largest total specific capacitance (∼193 F g−1), which is employed for the tests of supercapacitors of both symmetric and asymmetric types. An aqueous asymmetric supercapacitor, consisting of a GMn80 cathode and an N-doped RGO anode (reduced from a GO-NH4OH solution through the MAHS method), with a cell voltage of 2 V is demonstrated in this work, which shows the device energy and power densities of 11.11 Wh kg−1 and 23.5 kW kg−1, respectively.
Understanding the electrode/electrolyte interfaces is an essential issue when describing a lithium ion battery. This work reports the application of electrochemical impedance and infrared spectroscopies on the study of interfacial properties of two novel kinds of lithium reservoirs: an electrodeposited Li film onto magnesium foil and an electroformed Li–Al alloy onto aluminium foil. LiFePO4-based lithium ion cells with both electrodes showed high values of energy densities. However, LiAl(Al) failed in guaranteeing capacity retention due to irreversible crumbling. Nevertheless, optimization of its practical cycling life can be envisaged. We observed that the impedance of a LiFePO4-battery built with LiAl(Al) in 1M LiPF6 (EC/DMC) solution, is quite smaller than for a Li(Mg)-based system by virtue of an attenuated formation of surface films on the former. It was also evidenced that electrolyte degradation products migrate from the negative electrode towards the positive one. This phenomenon proceeds in a major extent for LiAl(Al) but results in the formation of a thinner and more conductive film onto the positive electrode than when Li(Mg) acts as negative electrode. The major interfacial drawback of LiAl(Al) is the lack of its passivation since a corrosion process is still observed after 10 cycles.
The electrodeposited Sn–O–C composite anode cycling with LiClO4 delivered stable cycle performances showing discharge capacity of 473 mA h g of Sn −1 with 95% of coulombic efficiency at 100th cycle. However, the anode showed poor cycle performances with LiPF6 delivering discharge capacity of 69 mA h g of Sn −1 at 100th cycle with 70% of coulombic efficiency. Electrochemical investigation performed by cyclic voltammetry and differential capacity plots revealed that the Sn–O–C composite cycling with LiPF6 suffered from retarded phase transition reaction between Li and Sn during charge/discharge process. X-ray photoelectron spectroscopy declared the existence of fluorinated-Sn and LiF. Moreover, energy dispersive X-ray spectroscopy found increase in their amount with repeated cycles. The morphologies of the Sn–O–C composite cycled with LiPF6 showed aggregated particles containing the chemical state of fluorinated-Sn and LiF on its surface. Furthermore, the significant pulverization and aggregation of the active material were observed from the Sn–O–C composite cycled by LiPF6 rather than that of LiClO4, which was probably promoted by the generated HF strongly corroding metallic component.
The electrochemical overoxidation of conducting polypyrrole nitrate film in aqueous solutions was studied by cyclic voltammetry, in-situ spectro-electrochemical measurement and FTIR spectroscopy. The overoxidation, which is entirely irreversible, results in the dedoping of conducting polypyrrole and the formation of carboxyl group. The potentials at which the overoxidation occurs depends on the pH values of the aqueous solutions. The higher the pH value, the lower the overoxidation potential will be, i.e. the easier the occurrence of the overoxidation, which is coincident with the electrolysis reaction of water to give out oxygen. It was supposed that the oxygen produced in the electrolysis of water results in the overoxidation of the conducting polypyrrole films.
Molybdenum disulfide (MoS2), as an extremely intriguing two-dimensional (2D) material with excellent electrocatalyst, has attracted more and more attentions in recent years. However, the lack of precisely engineered rich-edge S-vacancy MoS2 constitutes a major obstacle for in-depth studying of structure-activity relationship of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, based on Lewis acid-base theory, we prepared rich-edge S-vacancy MoS2 quantum dots (MoS2 QDs) via top-down strategy using lithium bis(trifluoromethylsulphonyl)imide as a stripper and clipper. It is demonstrated for the first time that the rich-edge S-vacancy MoS2 QDs exhibit an extraordinary ORR/OER catalytic performance in Li-O2 batteries system by a joint experimental and theoretical study. Importantly, the rich-edge S-vacancy MoS2 QDs can run more than 230 cycles at high current density, which was almost 9 times longer than the cycle stability of bulk MoS2. The excellent activity arises primarily due to that the MoS2 QDs facilitate conformal growth of amorphous Li2O2 film on the cathode, originating from the significant differences of adsorption energies between Li+ and O2, which could significantly enhanced Li2O2 formation/decomposition kinetics. This work provides a novel way for controllable synthesis of rich-edge S-vacancy MoS2 QDs, establishes the underlying mechanisms for the high OER/ORR activity, and suggests high translatability to apply other TMDs.
Silicon/lithium titanate (Si/Li2TiO3) nanocomposite is successfully prepared through the combination of a sol–gel approach with a high-temperature treatment as well as a high energy ball milling process. The structure and morphology of the composite are characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) analysis reveals Si particles are coated by the uniform disordered Li2TiO3 layer with a thickness of about 5nm. The investigation in cycling performances demonstrates that Si/Li2TiO3 exhibits the improved cycling stability, with specific capacity of 471.0mAhg−1 after 50 cycles and the capacity retention is 31.5%, much higher than pure Si. Compared with pure Si, Si/Li2TiO3 shows better rate-capability, a reversible capacity of 315.2mAhg−1 at 0.8Ag−1 is maintained. The higher ionic conductivity of Li2TiO3 is responsible for the improved rate performance. In addition, the results derived from XRD, the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicate that lithium ions could react reversibly with Si, and electrochemically less active Li2TiO3 turns into the Li–Ti–O ternary phase, which acts as a buffer matrix in the Si/Li2TiO3 composite, thus improving the reversibility of electrode.
The kinetics and the processes governing the electrochemical reactions of various types of iron oxide nanostructures (i.e., nanopowders, nanowires and thin-films) have been studied via cyclic voltammetry in parallel with Li- and Na-half cells containing analogous electrolytes (Li+/Na+, ClO4 − in EC:DEC). The particular features arising from each electrode architecture are discussed and compared to shed light on the associated behaviour of the reacting nanostructured active materials. The influence of their characteristic structure, texture and electrical wiring on the overall conversion reaction upon their respective lithiation and sodiation has been analyzed carefully. The limiting factors existing for this reaction upon uptake of Li+ and Na+ ions are highlighted and the related issues in both systems are addressed. The results of this investigation clearly prove that the conversion of iron oxide into metallic Fe and Na2O is severely impeded compared to its analogous process upon lithiation, independently of the type of nanostructure involved in such reaction. The diffusion mechanisms of the different ions (i.e., Li+ vs. Na+) through the phases formed upon conversion, as well as the influence of various interfaces on the resulting reaction, appear to pose further constraints on an efficient use of these compounds.
In this work we disclose a new, lithium metal-free, silicon–sulfur, lithium ion battery based on a high-rate sulfur–carbon composite cathode, formed by trapping sulfur in highly porous and hard carbon spherules, combined with a lithiated, silicon–carbon nanocomposite anode, separated by a glycol-based electrolyte. This 2V battery shows an average specific capacity of 300mAhg−1 (S), a long cycle life, an expected low cost and high safety. Due to these properties, this new battery is expected to be a very valid power source for efficient electric vehicles.
Laccases are multi-copper containing oxidases (EC 1.10.3.2), widely distributed in fungi, higher plants and bacteria. Laccase catalyses the oxidation of phenols, polyphenols and anilines by one-electron abstraction, with the concomitant reduction of oxygen to water in a four-electron transfer process. In the presence of small redox mediators, laccase offers a broader repertory of oxidations including non-phenolic substrates. Hence, fungal laccases are considered as ideal green catalysts of great biotechnological impact due to their few requirements (they only require air, and they produce water as the only by-product) and their broad substrate specificity, including direct bioelectrocatalysis.
The importance of the choice of solvent in a non-aqueous redox flow battery (NARFB) cannot be overemphasized. Several studies demonstrated the influence of the solvent on electrolyte performance in terms of reaction rates, energy/power densities, and efficiencies. In this work, we investigate capacity decay as a direct consequence of varying reactant crossover rates through membranes in different solvent environments. Specifically, we demonstrate the superiority of an 84/16 vol% acetonitrile/1,3 dioxolane solvent mixture over pure acetonitrile in terms of energy efficiency (up to 89%) and capacity retention for vanadium NARFBs - while incorporating a Nafion 115 membrane. The permeability of Nafion to the vanadium acetylacetonate active species is an order of magnitude lower when pure acetonitrile is replaced by the solvent mixture. A method to estimate relative membrane permeability is formulated from numerical analysis of self-discharge experimental data. Furthermore, tests on a modified Nafion/SiO2 membrane, which generally offered low species permeability, also show that different solvents alter membrane permeability. Elemental and morphological analyses of cycled Nafion and NafionSi membranes in different solvent environments indicate that different crossover rates induced by the choice of solvent during cycling are due to changes in the membrane microstructure, intrinsic permeability, swelling rates, and chemical stability.
Novel three-dimensional (3D) hierarchical Co3O4/CuO nanowire (NW) arrays on nickel foam composed of CuO NW stems and Co3O4 nanosheet branches are synthesized by combining a facile, scalable, and cost-effective thermal oxidation method with a simple but powerful chemical bath deposition followed by a calcination process. These arrays are further investigated as binder- and conductive-agent-free anodes for lithium-ion batteries (LIBs). The smart hybridization of CuO NWs and Co3O4 nanosheets into hierarchical core/shell array configuration results in remarkably enhanced electrochemical performances with good cycle performance, high reversible capacity, and excellent rate capability compared with pure CuO NW and single net-like Co3O4 nanosheets. A high reversible capacity of 1191mAhg−1 with 90.9% capacity retention after 200 cycles at a current density of 200mAg−1, and reversible capacity up to 810mAhg−1 even after 500 cycles at a current density as high as 1000mAg−1 can be maintained. The superior electrochemical performances of electrodes composed of hierarchical Co3O4/CuO NW arrays connected directly on nickel foam make them potential anode materials for high-performance LIBs.
The principal inhibitor of fast charging lithium ion cells is the graphite negative electrode, where favorable conditions for lithium plating occur at high charge rates, causing accelerated degradation and safety concerns. The local response of graphite, both at the electrode and particle level, when exposed to fast charging conditions of around 6C is not well understood. Consequently, the conditions that lead to the onset of lithium plating, as well as the local dynamics of lithium plating and stripping, have also remained elusive. Here, we use high-speed (100 Hz) pencil-beam X-ray diffraction to repeatedly raster along the depth of a 101 μm thick graphite electrode in 3 μm steps during fast (up to 6C) charge and discharge conditions. Consecutive depth profiles from separator to current collector were each captured in 0.5 seconds, giving an unprecedented spatial and temporal description of the state of the electrode and graphite's staging dynamics during high rate conditions. The electrode is preferentially activated near the separator, and the non-uniformity increases with rate and is influenced by free-energy barriers between graphite's lithiation stages. The onset of lithium plating and stripping was quantified, occurring only within the first 15 μm from the separator. The presence of lithium plating changed the behavior of the underlying graphite, such as causing co-existence of LiC6 and graphite in the fully discharged state. Finally, the staging behavior of graphite at different rates was quantified, revealing a high dependency on rate and drastic hysteresis between lithiation and delithiation.
A special Fe-boosting strategy based on the thermal conversion of new covalent porphyrin frameworks (CPFs) was developed to construct Sn-based core-dual shell nanostructures for efficiently catalyzing oxygen electroreduction (ORR). Fe-boosting carbonization of CPFs with abundant Sn species (Sn-CPFs) resulted into the formation of FeSn2@FeSnOx nanoparticles encapsulated in thin sulphur and nitrogen doped carbon shells (FeSn2@FeSnOx@S–N–C). These unique dual-shell nanostructures embedding in S–N-doped porous carbons were among the best Sn-based ORR electro catalysts in both alkaline and acidic media. Its ORR half-wave potentials reached 0.88 V in 0.1 M KOH and 0.79 V in HClO4 electrolytes, together with long-time ORR durability. Moreover, FeSn2@FeSnOx@S–N–C-900 catalyst demonstrated a peak power density of 64.5 mW cm−2 in the Zn-air batteries, comparable to the Pt/C-based counterpart (about 61.0 mW cm−2). The special Fe-boosting Sn-based dual-shell nanostructures greatly contributed to high ORR performance of this catalyst. The reported synthesis opens up a feasible route to obtain high-efficiency ORR cathode materials from p-block metals.
Design and first results of a newly constructed autonomous deep sea profiler for CTD measurements are described. The profiler differs substantially from previous attempts, as its energy concept uses potential energy for the movement of the vehicle. The vehicle is buoyant and its compressibility is adjusted to that of sea water. A 1 year time series is used to illustrate the performance of the profiler.
Polycrystalline metal-organic frameworks Zn4O(1,3,5-benzenetribenzoate)2 (named as MOF-177) with different morphologies have been controlled synthesized through a solvothermal route. MOF-177 electrodes for lithium storage exhibit a relatively high irreversible capacity in the first discharge process and a much lower reversible discharge–charge capacity in the following electrochemical cycles. The performance of MOF-177 is found not impressive for application in reversible lithium storage. A preliminary reaction mechanism on the basis of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) is proposed to understand the chemical behaviors of the electrode.