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Graphite fluorides have become promising electrode materials for lithium batteries while their applications in magnesium batteries are rarely reported. Here we demonstrate for the first time CF0.8 as a cathode material for magnesium batteries with a high discharge capacity of more than 800mAhg−1. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and the charge/discharge measurements are used to characterize its structure and electrochemical performance. SEM indicates that CF0.8 sample is a layered structure with the thickness of approximately 300∼400nm. The CF0.8 cathode exhibits a high discharge capacity of 813.4mAhg−1 after discharging to 0.5V at 20mAg−1 in 0.4M (PhMgCl)2-AlCl3/THF electrolyte (named as APC/THF). Discharge product MgF2 is confirmed by EDX and XPS measurements. Addition of LiCl to APC/THF solution can not only enhance the gravimetric energy densities but also greatly improve the rate performance. The possible function mechanism is proposed and discussed.
We report the electrochemical behaviors of TiO2-B nanowire electrodes exhibiting a high operating potential where they can avoid severe Na plating and a de-sodiation capacity of 196mAhg−1, which is the highest among several types of titanium oxides reported for sodium ion batteries. When TiO2-B nanowires are used as negative electrodes for sodium ion batteries, 1mole of the TiO2-B nanowire can take up approximately 1mole of sodium ions during the sodiation process and reversibly relieve 0.6mole of intercalated sodium during the subsequent de-sodiation process. It has been proved that TiO2-B nanowire electrodes participate in a reversible single-phase Na insertion/desertion reaction during charge and discharge. The electrodes exhibit irreversible capacity, owing to electrolyte decomposition and residual irreversible Na insertion, as determined via in situ XRD, ICP, FE-SEM, XPS, and electrochemical analyses. Further, TiO2-B is a superior material exhibiting long and stable cyclability with a specific capacity of 150mAhg−1 over 50 cycles.
The composite cathode material LiNi1/3Mn1/3Co1/3O2:LiNi0.5Mn0.5O2 (wt. % 75:25) comprising the blend of well characterized LiNi1/3Mn1/3Co1/3O2 and LiNi0.5Mn0.5O2 materials has been synthesized through a facile thermolysis employing mixed hydroxy-carbonate precursor. This composite cathode material yielded impressive charge–discharge profile with a capacity of 213/194 mAh g−1 at 0.1 C and amazing coulombic efficiency of 99.4% at 50th cycle. Notwithstanding impressive initial charge–discharge capacity of the individual LNMC phase 224/187 mAh g−1 attributed to sharp edges of the cathode particles showed large irreversible capacity-hysteresis. Near absence of irreversible capacity observed upon discharging the composite cathode material can be attributed to milled/smoothened cathode particles of the composite cathode material offering little scope for energy loss in contrast to sharp edge-grain boundary induced irreversibility-hysteresis seen in the individual phases (LiNi1/3Mn1/3Co1/3O2 and LiNi0.5Mn0.5O2). The application scope of the high performance composite cathode material has been widened in conjunction with graphitic alloy anode (G0.65Ni0.05Ti0.15Sn0.15) material as demonstrated with the fabrication of W-weaving style design of Li-ion pouch cell (∼500 mAh) at moderate loads 0.12 Wh, 1.1 Wh.
This study uses data from patients with damage to specific parts of the frontal cortex to provide causal evidence for the role of the dorsolateral prefrontal cortex in enabling honest behavior. Damage to this area was associated with decisions that prioritized the decision-maker's own self-interest, at the cost of honesty.
Carbon materials were synthesized by the pyrolysis of acrylonitrile-butadiene-styrene terpolymer (ABS) under different heat treatment conditions. ABS decomposed in a rapid single-step reaction, which was completed around 600°C. X-ray diffraction studies indicated a disordered carbon structure with a large number of single layer carbon sheets. It was found that varying the soak time, pyrolysis temperature and heating rate greatly affected the compositional, structural and electrochemical characteristics of the carbonaceous products. Charge–discharge studies of the product obtained by a 1h pyrolysis at 600°C at a heating rate of 20°C/min exhibited first-cycle lithium insertion and deinsertion capacities of 825 and 564mAh/g, respectively. Subsequent cycles showed a remarkable improvement in cycling efficiency with a 10th cycle efficiency of 100%.
Independence in activities of daily living (ADL) is important in an aging population. ADL disability is a multifactorial problem, therefore a multifactorial approach is needed in the prediction of ADL disability. Our objective is to identify predictors for the development of ADL disability over a course of ten years in middle-aged and older persons. In a prospective cohort study, 478 middle-aged and older persons (61.2years, range 40–78years) without ADL disability at baseline were included. ADL disability was measured using the Katz-questionnaire. We included the following candidate predictors: number of chronic diseases, MMSE, Short Physical Performance Battery, leg strength, handgrip strength, physical activity, cholesterol/HDL ratio, BMI, pulse wave velocity, the degree of urbanization, age, gender and socioeconomic status. Associations between candidate predictors and ADL disability were examined using Poisson regression analysis. Performance of the prediction model was assessed with calibration and discrimination measures. The number of chronic diseases, muscle strength, age, gender and socioeconomic status were predictors of ADL disability at ten-year follow-up. The model showed a good calibration and discrimination (c-statistic: 0.83) between persons who will and will not develop ADL disability. In conclusion, the present study showed that using a multifactorial prediction model – based on easily and readily available measurements – individuals who are at high risk of developing ADL disability could be identified. The prediction model could be used as a screening tool to identify which persons most likely benefit from preventive strategies and interventions.
At present there are no reliable non-traumatic and non-invasive methods to analyse the healing process and loosening status after total hip replacement. Therefore early as well as late loosening of prosthesis and interface component problems are difficult to be found or diagnosed at any time.
The surface modification of Li powder was attempted in order to enhance the electrochemical properties of the electrodes used in rechargeable batteries. To create a “native” LiF film on Li powder, Li powder was manufactured using a droplet emulsion technique (DET) process by introducing fluoride as a surfactant. The surface modification of the Li powder was confirmed by means of X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDX). Two-electrode cells (Li symmetric cells) were prepared for the purpose of impedance analysis and scanning electron microscope (SEM) observation. From the impedance analysis, the modified surface film was found to have a smaller resistance than the bare Li powder surface. SEM images showed that dendritic formations were more highly suppressed when the compacted Li powder and surface-modified Li powder electrodes were used than when the Li foil electrode was used. Moreover, the surface-modified Li powder electrodes suppressed dendritic formations more effectively than regular Li powder electrodes.
Two lithium oxonitridophosphate materials are computationally examined and found to be promising solid electrolytes for possible use in all solid-state batteries having metallic Li anodes – Li14P2O3N6 and Li7PN4. The first principles simulations are in good agreement with the structural analyses reported in the literature for these materials and the computed total energies indicate that both materials are stable with respect to decomposition into binary and ternary products. The computational results suggest that both materials are likely to form metastable interfaces with Li metal. The simulations also find both materials to have Li ion migration activation energies comparable or smaller than those of related Li ion electrolyte materials. Specifically, for Li7PN4, the experimentally measured activation energy can be explained by the migration of a Li ion vacancy stabilized by a small number of O2− ions substituting for N3− ions. For Li14P2O3N6, the activation energy for Li ion migration has not yet been experimentally measured, but simulations predict it to be smaller than that measured for Li7PN4.
The role of iron sulfide (FeS) in initial cell activation and degradation in Na–NiCl2 battery was investigated in this work. The research focused on identifying the effects of FeS levels on the electrochemical performance and morphological changes in the cathode. The x-ray photoelectron spectroscopy study along with battery tests revealed that FeS plays a critical role in initial battery activation by removing passivation layers on Ni particles. It was also found that the optimum level of FeS in the cathode resulted in suppressing Ni particle growth and improved battery cycling performance. The results of electrochemical characterization indicated that sulfur species generated in situ during initial charging, such as polysulfide and element sulfur, are responsible for removing the passivation layer. Consequently, the cells containing elemental sulfur in the cathode exhibited similar electrochemical behavior during initial charging compared to the cells containing FeS.
This paper describes an investigation into the type of listening test that might serve as an assessment instrument of English language teachers as part of a teacher certification test — the Hong Kong English Language Benchmark Test. The paper first describes the benchmarking initiative in Hong Kong to orient the reader to the nature and purpose of the Listening Test. The paper then describes a case study where groups of pre-service and in-service English language teachers were administered audio and video versions of the same test, after which a survey was conducted of their opinion of the audio/video mode of assessing listening. Scores on the two test modes (as well as on an anchor test) indicated no significant differences between the two scores of the two groups. Further, although some of the test takers from the audio test-taking group said they would have preferred to have taken the test via video, the video test-taking group felt that not only had they gained no advantage from the video mode, they felt they might have done better had they not been distracted by the visual images, and by having to look up and down from question paper to screen. As a high-stakes certification test for English language teachers, the conclusion that is drawn is that the listening comprehension test should be implemented via an audio, and not video, mode.
Lithium sulfide as a promising cathode material not only have a high theoretical specific capacity, but also can be paired with Li-free anode material to avoid potential safety issues. However, how to prepare high electrochemical performance material is still challenge. Herein, we present a facile way to obtain high crystal quality Li2S nanomaterials with average particle size of about 55 nm and coated with Li3PS4 to form the nano-scaled core-shell Li2S@Li3PS4 composite. Then nano-Li2S@Li3PS4/graphene aerogel is prepared by a simple liquid infiltration-evaporation coating process and used directly as a composite cathode without metal substrate for lithium-sulfur batteries. Electrochemical tests demonstrate that the composite delivers a high discharge capacity of 934.4 mAh g−1 in the initial cycle and retains 485.5 mAh g−1 after 100 cycles at 0.1 C rate. In addition, the composite exhibits much lower potential barrier (∼2.40 V) and overpotential compared with previous reports, indicating that Li2S needs only a little energy to be activated. The excellent electrochemical performances could be attributed to the tiny particle size of Li2S and the superionic conducting Li3PS4 coating layer, which can shorten Li-ion and electron diffusion paths, improve the ionic conductivity, as well as retarding polysulfides dissolution into the electrolyte to some extent.
In this paper we study an actual problem proposed by an agricultural cooperative devoted to harvesting corn and grass. The cooperative uses harvesters for harvesting the crop and trucks for carrying it from the smallholdings to the landowners’ silos. The goal is to minimize the total working time of the machinery. Therefore, the cooperative needs to plan both the harvesters and trucks routing. This routing problem simultaneously incorporates the following characteristics: time windows, nested decisions, processing times required to service each facility and the fact that facilities must be visited in clusters. A binary integer linear programming model is proposed to solve this problem. However, since approaches dealing directly with such formulation lead to considerable computation times, we propose a heuristic alternative solution approach for the problem. The heuristic is applied to the case of the cooperative “Os Irmandiños” with a large number of landowners and smallholdings. We report on extensive computational tests to show that the proposed heuristic approach can solve large problems effectively in reasonable computing time.
Layered LiV3O8 as promising cathode material for rechargeable lithium-ion batteries has been efficiently synthesized by an improved spray-drying method followed by heating at different temperatures. Results of X-ray diffraction, scanning electron microscopy, charge–discharge test, cyclic voltammogram and electrochemical impedance spectroscopy indicate that the sample heat-treated at 300°C shows the best electrochemical performance. The LiV3O8 obtained at 300°C displays a maximum discharge capacity of 338.9mAhg−1 at current density of 25mAg−1 and after 20 cycles, a discharge capacity with 330.5mAhg−1 is obtained. Most important is that it displays an excellent cycling stability at large current density. It exhibits high discharge capacity of 251mAg−1 at current density of 125mAg−1 after 50 cycles.
In this study, LiNi0.5Mn1.5O4 (LNMO) nanoparticles were prepared as a 5V cathode material via a rheological phase method and annealed at different temperatures: 680°C, 750°C, and 820°C. The sample annealed at 750°C shows the best performance. A room temperature ionic liquid (RTIL) containing 1M lithium bis(trifluoromethanesulfonyl) imide (LiNTf2) in N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl) imide (C4mpyrNTf2) was used as novel electrolyte in conjunction with the LNMO cathodes and their electrochemical properties have been investigated. The results show that the LNMO using RTIL as electrolyte has better coulombic efficiency and comparable discharge capacities to those of the cells assembled with standard liquid electrolyte (1M LiPF6 in ethylene carbonate/diethyl carbonate). Electrochemical impedance spectroscopy shows that the RTIL is much more stable as the electrolyte for LiNi0.5Mn1.5O4 than the conventional electrolyte.
The simultaneous voltammetric determination of catechol (CC) and hydroquinone (HQ) has been achieved at a mesoporous carbon CMK-3 modified electrode in phosphate buffer solution (pH 7.0). At the electrode both CC and HQ can cause a pair of quasi-reversible and well-defined redox peaks and their peak potential difference increases. In comparison with multi-walled carbon nanotubes (MWCNTs) and Vulcan XC-72 carbon modified electrodes the CMK-3 modified electrode shows larger peak currents and higher adsorbed amounts for the two dihydroxybenzene isomers. This is related to the higher specific surface area of CMK-3. Under the optimized conditions, the linear concentration ranges for CC and HQ are 5×10−7 to 3.5×10−5 M and 1×10−6 to 3×10−5 M, respectively. In the presence of 5μM isomer, the linear concentration range of CC (or HQ) is 5×10−7 to 2.5×10−5 M (or 5×10−7 to 2.0×10−5 M). The sensitivity for CC or HQ is 41AM−1 cm−2 or 52AM−1 cm−2, which is close to that without isomer. The detection limits (S/N=3) for CC and HQ are 1×10−7 M after preconcentration on open circuit for 240s.
This paper deals with the initialization of a non linear identification algorithm used to accurately estimate the physical parameters of Lithium-ion battery. A Randles electric equivalent circuit is used to describe the internal impedance of the battery. The diffusion phenomenon related to this modeling is presented using a fractional order method. The battery model is thus reformulated into a transfer function which can be identified through Levenberg–Marquardt algorithm to ensure the algorithm’s convergence to the physical parameters. An initialization method is proposed in this paper by taking into account previously acquired information about the static and dynamic system behavior. The method is validated using noisy voltage response, while precision of the final identification results is evaluated using Monte-Carlo method.
The application of thermal energy storage (TES) system with phase change material (PCM) is an effective way for energy conservation and greenhouse gas (GHG) emission reduction. Global warming is increasing along with the energy consumption. Many researchers are concerned about this present global environmental problem for fossil-fuel burning. Thermal energy storage system with phase change material is observed as a potential candidate for mitigating this problem. This paper emphasizes the opportunities for energy savings and greenhouse-gas emissions reduction with the implementation of PCM in TES systems. For instance, about 3.43% of CO2 emission by 2020 could be reduced through the application of PCM in building and solar thermal power systems. Similarly, energy conservation and GHGs emission reduction by other PCM applications for thermal comfort of vehicles, transport refrigeration, engine cold start, greenhouse and waste heat management are also presented. In addition, some present investigations on the performance improvement of the phase change materials are addressed.
In this work, we have achieved all-climate high-rate performance of sodium ion batteries by utilizing electrode materials with Na Super Ionic Conductor (NASICON) crystalline structure. A designed NASICON-structured carbon-coated Na3V2(PO4)3 (NVP@C) nanocomposite exhibits an excellent performance at high rates in a wide temperature range (i.e., from −20 to 55°C). Even at a low temperature of −20°C, the NVP@C cathode can still maintain a discharge capacity of 91.3mAhg−1 or 85.2% of the room performance at 10C, and secure an average output voltage of 2.86V (vs. Na+/Na). These excellent wide-temperature accomplishments can be ascribed to fast three-dimensional Na+ hopping transportation mechanism in the NASICON structure. The finding in this work offers a promising strategy to address the long-standing inherent wide-temperature issues of rechargeable batteries and extends the potential application of sodium ion batteries.
One of the most important constraints in traditional wireless sensor networks is the limited amount of energy available at each sensor node. The energy consumption is mainly determined by the choice of media access mechanism. SMAC is a typical access mechanism that has drawn much attention in recent years. In WSNs, sensors are usually equipped with capacity-limited battery sources that can sustain longer or shorter period, depending on the energy usage pattern and the activeness level of sensor nodes. To extend the lifetime of the sensor networks, ambient energy resources have been recently exploited in WSNs. Even though solar radiation is known as the superior candidate, its density varies over time depending on many factors such as solar intensity and cloud states, which makes it difficult to predict and utilize the energy efficiently. As a result, how to design an efficient MAC in a solar energy harvesting based WSN becomes a challenging problem. In this paper, we first incorporate a solar energy-harvesting model into SMAC and conduct its performance analysis from a theoretical aspect. Our research works provide a fundamental guideline to design efficient MAC for energy harvesting based WSNs. Our major contribution includes three folders: firstly, we model solar energy harvesting in a photovoltaic cell and then derive the throughput of SMAC in the energy-harvesting based WSNs. Second, we develop a new model based on queuing theory to calculate the average number of energy packets in battery in terms of both duty cycle and throughput. Finally, we form an optimization problem to find a suitable range for the duty cycle to satisfy both quality of service (QoS) and network lifetime requirements.
Abstract Energy plays a very important role in society. It has been one of the main drivers in the organization of civilization and, before that, in evolution. The availability of relatively inexpensive energy could solve many other problems, for example supplying fresh water through desalination. An economy based on solar energy has been the dream of many for many years. It would be great to only depend on the freely distributed energy of the sun, which is available everywhere. While solar energy might include a wide range of potential energy sources, the solar energy considered here is restricted to solar concentrators, solar photovoltaics, and artificial solar chemical processes. After these are considered, both the related uncertainties and the possible range of climate variability are explored. Characteristics of the various technologies, uncertainties, and potential climate effects are also identified. An analysis explores the solar energy technologies, uncertainties, and vulnerabilities related to climate. Finally, an integrated analysis method of real options analysis provides a potential semiquantitative framework for discussion and interpretation.
Fundamentals of classical thermodynamics and chemical species mole balances have been applied to formulate the mathematical equations to compute lithium/air cell reversible reaction voltages, heat transfer rate between the cell and its surroundings, theoretical discharge capacity, and thermal efficiency. The developed formulation also provides a set of mathematical equations to compute the total cathode volume for a desired maximum discharge capacity of a lithium/air cell or battery.
An extensive study of various properties of gel electrolyte systems based on 2-ethoxyethyl methacrylate (EOEMA) was conducted with several experimental techniques in order to clarify the influence of varying composition of the samples. The addition of 3-(trimethoxysilyl) propyl methacrylate (SPMA), used here with the aim of decreasing flammability of the ether-oxygen rich system, was investigated in terms of resulting mechanical, thermal and electrochemical properties. Furthermore, changes in these properties based on the use of different cross-linker monomers, salt and its solvent were studied.