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Metal-organic frameworks can provide excellent templates for the preparation of nanomaterials for green energy storage. However, it is still a formidable challenge for the synthesis of MOF-templated Sn-based nanomaterials with controllable morphologies and structures. Here, Sn-based MOFs with different morphologies are synthesized by a facial and controllable method, then SnO/C polyhedrons with shapes of cube and stellated octahedron are obtained using the Sn-based MOFs as template by further heat treatment, respectively. Benefited from the composite structures, the SnO/C polyhedrons exhibit excellent electrochemical performances in lithium storage. A high reversible capacity of 950 mA h g−1 is obtained at a current density of 50 mA g−1 after 100 cycles, together with superior cyclic stability and remarkable rate capacity. This paper provides an effective route to prepare high-performance Sn-based anode materials from the morphology-controlled MOFs for lithium-ion batteries.
Jump-landing assessments provide a means to quantify an individual’s ability to attenuate ground reaction forces, generate lower limb explosive power and maintain joint alignment. In order to identify risk factors that can be targeted through appropriate training interventions, it is necessary to establish which (scalar) objective kinetic, kinematic, and performance measures are most associated with lower-extremity injury.
Measurement of impedance is one of well-known methods to experimentally characterize electrochemical properties of Li-ion batteries. The measured impedance responses are generally fitted to an equivalent circuit model that is composed of linear and nonlinear electric components that mimic behaviors of different layers of a battery. However, the parameters do not provide quantitative statements on charge dynamics considering material properties. Therefore, electrochemical models are widely employed to study the charge dynamics, but have not included high frequency responses predominantly determined by double layers. Thus, we have developed models for the double layer and bulk that are integrated into the electrochemical model for a pouch type Li-ion battery. The integrated model is validated against the frequency response obtained from EIS equipment at different temperatures as well as the time response. The results show that the proposed model is capable of representing the responses at charging and discharging in time and frequency domain.
As novel anode materials for lithium-ion batteries (LIBs), ZnO-loaded porous carbons (CMK-3 or CMK-8) are prepared by a two-step method and exhibit better electrochemical properties than pure ZnO particles. ZnO nanoparticles are separated inside the pores of porous carbons, which limit the growth of ZnO crystals and accommodate their volume variation during cycles. Moreover, to further improve their electrochemical performances, these composites are further wrapped by graphene nanosheets through a stepwise heterocoagulation method. Compared to uncoated porous carbon-ZnO, graphene-encapsulated porous carbon-ZnO composites exhibit higher reversible capacities, better cycle performances and rate capabilities. The superior performances of graphene-encapsulated composites may be attributed to graphene encapsulation, which enhances the electrical conductivity of the overall electrode, avoids the aggregation of porous carbon-ZnO particles and even stabilizes the mesostructure of porous carbon during cycles.
Energy is directly related to the most critical social issues which affect sustainable development. Today there is a great incentive for countries to exploit renewable energies in order to slow down the changes in environment and to guard against future trends. This paper presents a review of the assessed potential of renewable resources and practical limitations to their considerable use in the perspective of present scenarios and future projections of the national energy for Oman. Solar and wind are likely to play an important role in the future energy in Oman provided that clear policies are established by the higher authority for using renewable energy resources. Comparison of different solar energy technologies revealed that Concentrator Photovoltaic (CPV) technology may constitute a more appropriate choice for large solar power plants implementation in Oman. Moreover, Oman will not be alone in the region in this regard as similar moves are carried out in other Middle Eastern countries. The status of energy conservation and demand-side management are also discussed in the paper.
A pilot study was conducted in anticipation of implementation of a larger project to assess human immunodeficiency virus (HIV) risk behaviors among older African Americans. A cross-sectional methodology was employed, including 33 African Americans aged more than 50 years in the metropolitan Washington, DC, area. The average age of the participants was 66 years old, with an age range from 51 to 86 years. Data were collected utilizing previously validated instruments that were administered using an audio computer-assisted survey instrument. There was relatively high knowledge regarding HIV, with female participants scoring significantly higher compared to male participants (p =.003). Another specific finding of the preliminary study was the association between higher levels of spirituality and lower levels of HIV sexual risk behaviors (Spearman's correlation =−0.369, p=.035). Results of this pilot study suggest that older African American females may be more knowledgeable regarding HIV than older African American males. This may suggest that educational and behavioral interventions developed for this group may need to be structured based upon the targeted gender of the audience. The association between increased spirituality and decreased risk behaviors may suggest that spiritually-based interventions may provide some benefit regarding reduction of HIV risk behaviors in this population. However, the small sample size in this study warrants caution in the conclusions and highlights the need for further research in this population.
In this paper, the effect of Ge substitution for Nb on Li ion conductivity in the well-known Li5La3Nb2O12(LLN)parents with the cubic garnet framework prepared by using metal Ge is reported. The optimum condition is at 950°C for 8h with 10% excess lithium salt in air. The XPS spectra indicate that the metal Ge is completely transformed into Ge4+ after sintering for 8h. The power XRD patterns reveal that the partial substitutions of Ge for Nb in Li5+xLa3GexNb2-xO12 electrolytes are isostructural. The ionic conductivity of Li5+xLa3GexNb2-xO12 ceramics increases as the molar fractions of Ge increasing for x≤0.75. Among these compounds investigated, the Li5.75La3Ge0.75Nb1.25O12 exhibits the highest ionic conductivity of 1.2×10−4 Scm−1 at room temperature. The result can be regarded as relatively high values among the element substituted LLN garnets reported up to now. The new solid state electrolyte is very stable in potential range of −0.6-6.0V vs. Li/Li+, indicating that Li5.75La3Ge0.75Nb1.25O12 is a promising solid state electrolyte for all-solid-state battery application.
Electrolyte additives are necessary for the application of high potential cathode in high energy density lithium ion batteries, especially at elevated temperature. However, the electrolyte additives that can effectively suppress the dissolution of transition metal ions from cathode have seldom been developed up to date. In this work, we propose a novel electrolyte additive, trimethylsilylcyclopentadiene (SE), for high temperature application of a representative high potential cathode, lithium nickel manganese oxide (LiNi0.5Mn1.5O4). It is found that the dissolution of Mn and Ni from LiNi0.5Mn1.5O4 can be effectively suppressed by applying SE. With applying 0.25% SE, the dissolved amount of Mn and Ni is decreased by 97.4% and 98%, respectively, after 100 cycles at 55 °C. Correspondingly, the cyclic performance of LiNi0.5Mn1.5O4 is significantly improved. Physical characterizations and electrochemical measurements show that SE can be preferentially oxidized and generate a protective film on LiNi0.5Mn1.5O4. The resulting film inhibits the electrolyte decomposition and the transition metal ion dissolution.
Sn2Fe/Al2O3/C nanocomposites are synthesized using a high-energy, mechanical milling method with thermally synthesized Sn2Fe, Al2O3 and carbon (Super P) powders. The effect of Al2O3 addition on the microstructure of the Sn2Fe/Al2O3/C nanocomposites is examined. The electrochemical characteristics of the material as an anode in lithium-ion batteries are also evaluated. High-resolution transmission electron microscopy shows that the crystallite size of active Sn2Fe in the Sn2Fe/Al2O3/C nanocomposite is smaller than that of the Sn2Fe/C nanocomposite without Al2O3. A decrease in the initial irreversible capacity and enhanced cycle performance of the Sn2Fe/Al2O3/C nanocomposite electrode are observed.
Increasing the area specific capacity and reducing the inactive/active material ratio of cathodes and anodes is considered to be a promising approach to improve the energy density of lithium-ion batteries. In principle, this can be achieved by increasing the thickness and the active material mass loading of the electrodes. However, the fabrication of thick electrodes with good electrochemical performance is challenging regarding the drying process, mechanical stability, electronic conductivity, etc. The application of Al-foams as current collector provides a 3D electronic conductive network, which can host high loadings of active material combined with high mechanical stability. Herein, we demonstrate a slurry infiltration process capable to fabricate cathodes with high active material loading. A variety of LiNi1/3Mn1/3Co1/3O2 (NMC111) based cathodes with thicknesses up to 260 μm and area specific capacities high as 7 mAh cm−2 are investigated comprehensively. The electrodes exhibit good cycle life and rate capability performance due to the unique 3D current collector concept. Even at the 2.0C discharge rate, an area specific capacity of 2.3 mAh cm−2 is obtained, which is high in comparison to conventional Al-foil concepts. The design freedom of the presented approach is illustrated by the fabrication of cathodes optimized for high rate capability.
The fading mechanism of Li ion batteries with two different anode materials was discussed in this study. Anode materials were spherical type of meso-phase carbon micro bead (MCMB) and flake type of pitch coated graphite (PCG). This battery used LiMn2O4 as the cathode materials. The LiMn2O4/MCMB battery had higher rate capability than the LiMn2O4/PCG battery. However, the LiMn2O4/PCG battery had only 20% capacity retention after 70 cycling tests, while the LiMn2O4/MCMB battery had 95% capacity retention. The X-ray diffraction (XRD) and X-ray photospectroscopy (XPS) were used to analyze the structure of active materials and the solid electrolyte interface (SEI) films on the electrodes. It was found that structure of PCG anode and LiMn2O4 cathode was maintained as pristine structure by XRD analysis. The carbonate was easier to decompose on PCG surface than on the MCMB surface by XPS analysis. It was suggested that the electrolyte decomposition on PCG surface might be play a major role for the LiMn2O4/PCG battery fading.
Diphenyl disulfide (DPDS) is evaluated as a new bifunctional electrolyte additive to improve the high-voltage performance of LiCoO2/graphite batteries. With the addition of DPDS in the electrolyte, the cell with 2.0 wt% DPDS exhibits enhanced performance in the normal voltage range of 3.0 V–4.2 V. In particular, when the cut-off potential is increased from 4.2 V to 4.4 V, the cell with 1.0 wt% DPDS also exhibits improved discharge capacity and cycle performance. Linear sweep voltammetry and cyclic voltammetry indicate that the DPDS can be reduced prior to the solvent and that the oxidative decomposition of the electrolyte can also be suppressed. In addition, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy analyses demonstrate that the solid electrolyte interface (SEI) film is produced primarily on the graphite anode via the decomposition of DPDS at normal voltage and that the SEI films induced by DPDS can be formed simultaneously on the two electrodes at higher potentials. It is hypothesized that these compact SEI films covering the electrode surface provide protection for the LiCoO2 and graphite materials and accordingly improve the cyclic performance of battery in the voltage range of 3.0 V–4.4 V.
On-board hydrogen storage and production via ammonia electrolysis was evaluated to determine whether the process was feasible using galvanostatic studies between an ammonia electrolytic cell (AEC) and a breathable proton exchange membrane fuel cell (PEMFC). Hydrogen-dense liquid ammonia stored at ambient temperature and pressure is an excellent source for hydrogen storage. This hydrogen is released from ammonia through electrolysis, which theoretically consumes 95% less energy than water electrolysis; 1.55Whg−1 H2 is required for ammonia electrolysis and 33Whg−1 H2 for water electrolysis. An ammonia electrolytic cell (AEC), comprised of carbon fiber paper (CFP) electrodes supported by Ti foil and deposited with Pt–Ir, was designed and constructed for electrolyzing an alkaline ammonia solution. Hydrogen from the cathode compartment of the AEC was fed to a polymer exchange membrane fuel cell (PEMFC). In terms of electric energy, input to the AEC was less than the output from the PEMFC yielding net electrical energies as high as 9.7±1.1Whg−1 H2 while maintaining H2 production equivalent to consumption.
Low-cost lithium ion batteries with LiFePO4 and natural graphite were cycled in 1M LiBF4+EC/DEC at 100% depth of discharge and 25°C in order to investigate cycle performance and diagnostics for capacity fading. The 12cm2 pouch cell showed 65% of capacity retention at 5C compared to that at C/25. The cell showed 80% of initial capacity after 80 cycles and its capacity fade rate was 11.3μAh/cycle during constant C/2 cycling. In hybrid pulse power characterization, the discharge resistance of this cell was higher than commercial graphite/LiCoO2 cell because of low lithium diffusivity in LiFePO4. Slow rate cycling in pouch full cell showed almost 40% of capacity fade after 100 cycles. However, the 100-cycled cathode and anode did not show any capacity fading in half-cell test after disassembling full cell, suggesting that capacity fade in the full cell is caused by loss of cycleable Li.
Binary metal oxides have been proved to possess better pseudocapacitive performance than single metal oxide analogies. Substitution of toxic and high-cost ions (Co and Mo) in binary metal oxides with low-cost and environmentally-friendly ions (Ni and Mn) is of great economic and environmental importance. In this paper, murdochite-type binary metal oxides (i.e., Ni6MnO8) and binary metal oxides@carbon nanotubes (i.e., Ni6MnO8@CNTs) core-shell structure were synthesized via a facile hydrothermal approach followed by a calcination process. Electrochemical measurement results indicated that the synthesized Ni6MnO8@CNT core-shell structure showed a high specific capacitance of 1213 F g−1 at 1 A g−1 with two times capacitance value of Ni6MnO8 at same current density. Even at the high current density of 20 A g−1, the Ni6MnO8@CNT core-shell structure can still deliver a high capacitance value of 711 F g−1, which value is also much higher than that of Ni6MnO8 at the current density of 1 A g−1. With the prepared Ni6MnO8@CNT hybrid as positive electrode and activated-polyaniline-derived-carbon as negative electrode, an asymmetric supercapacitor cell (ASC) was successfully assembled. The assembled ASC device exhibited excellent pseudocapacitive performance with a high specific capacitance of 154 F g−1 at 1 A g−1 and a high energy density of 58.2 Wh kg−1 at a power density of 831.4 W kg−1. Even at a high power density of 16.6 kW kg−1, the ASC device can still deliver a high energy density of 23.1 Wh kg−1, suggesting the promising applications of Ni6MnO8@CNT hybrid in supercapacitors.
Indeed, intracerebral hemorrhage (ICH) account for only 15% of all strokes but it is one of the most devastating subtype of stroke associated with behavioral, cognitive and neurological deficits. The primary cause of neurological deficits in ICH is the hematoma growth, generation of free radicals, inflammatory cytokines and exhausting endogenous anti-oxidant machinery. It has been found that neuroinflammation following ICH leads to exaggeration of hallmarks of ICH. With this background, the study was aimed to evaluate the protective effect of resveratrol (RSV) in intracerebroventricular (ICV) collagenase (COL) induced neurological deficits in rats.
Lithium-rich layered electrode materials are of interest as a promising candidate of cathodes for lithium-ion batteries because of their excellent electrochemical properties. The electrochemical performance of these materials is mainly regulated by preparation conditions during synthesis and calcination process. Here, microspherical Li1.2Mn0.54Co0.13Ni0.13O2 (LMNCO) particles are synthesized through steady pH value control with carbon dioxides bubbling method in co-precipitation process using a simple reactor. SEM images present that CP-LMNCO sample prepared through the assistance of carbon dioxides has spherical particle morphology, while sample (TP-LMNCO) without carbon dioxides assistance shows large nanoparticles agglomeration. The CP-LMNCO electrode demonstrates superior electrochemical performance, which exhibits capacity retention of 97.76% after 100 cycles compared with only 81.94% for TP-LMNCO electrode at 1C (250mAg−1). Even at a higher current density (5C), the CP-LMNCO electrode shows reversible capacity up to 105.4mA h g−1. The remarkably improved electrochemical performance of CP-LMNCO electrode is ascribed to spherical morphology with small surface area which decreases side reactions with electrolyte during cycling and smaller primary sizes which reduce lithium ion (Li+) diffusion distance. Furthermore, the synthesis of spherical materials using metal sulfate with high concentration (up to 5M) as starting agents are attempted under carbon dioxides assisted conditions, and as-prepared materials also show improved performance.
Wheat is the world’s second largest crop, supplies 19% of human calories, and is the largest volume crop traded internationally. Its uniquely malleable physical properties make it a valued industrial substance, albeit often an invisible one, as well as a food. This combination of transformation, invisibility and mobility demands new ways of thinking about wheat geographies. In this paper we document and analyse several ‘moments’ in the life of Australian wheat; at the supermarket, in the lives of coeliac sufferers, in laboratories, industrial factories and on the farm. We illustrate diverse patterns of interaction with wheat. The major plane of differentiation is between wheat as food and wheat as industrial substance. The explicit connection of food to the human body tends to fix the identity of wheat, whether as healthy staple of the nation, or harmful poison to coeliacs who must negotiate its presence using the regulatory regime of food labelling. This is no small task given the ubiquity of wheat; our survey of 10,235 supermarket items found it in 29.5% of labelled food items. In contrast, when wheat is physically and chemically disassembled to become an industrial substance, its presence and identity become mutable, hidden and often invisible.
A nanostructured ternary transition metal oxide, ZnFe2O4, is synthesized via the simple polymer pyrolysis method. The characteristics of the material are examined by thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical test results show that this method of ZnFe2O4 synthesis produces high specific capacities and good cycling performance, with an initial specific capacity as high as 1419.6mAhg−1 at first discharge that is maintained at over 800mAhg−1 even after 50 charge–discharge cycles. The electrode also presents a good rate capability, with a high rate of 4C (1C =928mAg−1), a reversible specific capacity that can be as high as 400mAhg−1. ZnFe2O4 is a potential alternative to high-performance nanostructured anode material in lithium ion batteries.
Metallic sodium is regarded as a promising anode material for sodium rechargeable batteries. However, sodium dendrite growth and exhaustive electrolyte decomposition cause the poor reversibility of the sodium metal electrode. Here, we present that, by forming a mixed surface of carbon and sodium metal, the sodium electrodeposition mode and stripping mechanism can be tuned. In order to systematically investigate sodium plating/stripping behavior on a mixed surface of carbon and sodium, we fabricate a carbon nanotube-sodium composite electrode with a simple rolling and folding method. As the carbon nanotube content is increased, the overpotentials for sodium nucleation and pit-formation are remarkably reduced. Postmortem and chronoamperometry analysis elucidate that sodium and sodiated carbon nanotube have a different sodium nucleation mode, and sodium nucleation is preferred on the sodiated carbon nanotube surface with lower nucleation energy, inducing a more uniform sodium deposition. Furthermore, the embedded carbon nanotube appears to help sodium stripping by providing a channel for a more facile sodium ion transport. As a result, the carbon nanotube-sodium composite electrode exhibites a 5 times higher cycling stability. The tuning of the nucleation and stripping behaviors by forming a mixed surface can be a viable approach for enhancing the reversibility of metal electrode.
Cu Foil, a thin sheet of Cu, is the common anode current collector in commercial lithium ion batteries (LIBs) which accounts for ∼ 10 wt% of the total cell weight. However, thickness reduction of LIB-based Cu foils below 6 μm has been limited by the incapability of conventional rolling annealing or electrodeposition process. We here report a new type of Cu foil, so called Cu nanowire foil (CuNW foil), for use as an LIB anode current collector. We fabricate Cu NW foils by rolling press Cu nanowire fabric to reduce the thickness down to ∼1.5 μm with an areal weight down to ∼1.2 mg cm−2 and a density approximately 96% to that of bulk Cu. The rough surface and porous structure of CuNW foil enable better wetting and adhering properties of graphite slurry on foil. In full cell examination, a cell of a areal capacity of 3 mAh cm−2 exhibits 83.6% capacity retention for 600 cycles at 0.6 C that meets the standard specification of most commercial LIBs. As a proof-of-concept of demonstration, we fabricate a 700 mA pouch-type battery implemented with graphite-Cu NWs foil anodes to serve as energy supply to operate electronic devices.