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In this work, carbon nanoparticle-anchored MoS2 nanosheets are synthesized by a supramolecular self-assembly method, through which β-cyclodextrins (β-CDs) are combined with l-cysteine by the hydrogen bond and the electrostatic interaction in the aqueous solution, which are then carbonized to carbon nanoparticles and anchored on the surface of MoS2 nanosheets during the hydrothermal process. The carbon nanoparticles anchored on MoS2 nanosheets effectively inhibit the aggregation and restacking of MoS2, and then enhance the electrical conductivity of the composite. The superior electrochemical performance is exhibited through cyclic voltammetry and galvanostatic charge-discharge, including a high specific capacitance of 394.2 F g−1 at the scan rate of 5 mV s−1 and a high rate retention ratio of 63.3% when the scan rate increases from 5 to 200 mV s−1. The remarkable performance is mainly attributed to the better electrical conductivity and the higher rates of electron migration and ion transport, making the carbon nanoparticle-anchored MoS2 nanosheets a potential candidate material for advanced energy storage systems.
Abstract Superconducting magnetic energy storage (SMES) has been studied since the 1970s. It involves using large magnet(s) to store and then deliver energy. The amount of energy which can be stored is relatively low but the rate of delivery is high. This means that SMES is ideal for applications that require a high power for a relatively short period of time. SMES systems can be built with both low- and high-Tc materials. The systems which have been delivered so far have tended to be constructed from NbTi due to its low cost but as the new coated conductors are improved there is a strong possibility that systems based on YBCO have an attractive future.
Graphene nanoplatelet (GnP), which consists of small stacks of graphene, is used as a reinforcement to enhance the performance of the poly(acrylonitrile-butyl acrylate) (PANBA) binder in a lithium ion battery (LIB). To the best of our knowledge, this is the first time that a conductive nanofiller such as GnP has been used in a conventional water-dispersed polymer and applied as a binder for LIB. Our so-called PANBA/GnP nanocomposites are made with either 0.5 wt%, 1 wt%, or 2 wt% of GnP. The nanocomposites are synthesized via an in situ emulsion polymerization technique and are very well-dispersed, homogeneous, and stable for at least 6 months. The elongation and electrical conductivity of the PANBA/GnP nanocomposites exceed those of the PANBA non-filled polymer, and the PANBA/GnP nanocomposite binder ultimately enhances the electrochemical performance of the high-capacity silicon/graphite mixture anode.
We propose a method to monitor the ageing and damage of capacitors based on their irreversible entropy generation rate. We overstressed several electrolytic capacitors in the range of 33 μF–100 μF and monitored their entropy generation rate S ˙ (t). We found a strong relationship between capacitor degradation and S ˙ (t). Therefore, we proposed a threshold for S ˙ (t) as an indicator of capacitor time-to-failure. This magnitude is related to both capacitor parameters and to a damage indicator such as entropy. Our method goes beyond the typical statistical laws for lifetime prediction provided by manufacturers. We validated the model as a function of capacitance, geometry, and rated voltage. Moreover, we identified different failure modes, such as heating, electrolyte dry-up and gasification from the dependence of S ˙ (T) with temperature, T. Our method was implemented in cheap electrolytic capacitors but can be easily applied to any type of capacitor, supercapacitor, battery, or fuel cell.
This study addresses the lithium insertion performances of amorphous vanadium oxide films, synthesized by atomic layer chemical vapour deposition (ALCVD). AFM and SEM investigations showed that the as-deposited films are amorphous, compact and homogeneous. As revealed by XPS and Raman spectroscopy, the ALCVD oxide films after deposition are mainly composed of V2O5, with V4+ surface content (about 10%). The insertion of Li+ into the lattice was investigated in 1M LiClO4-PC. The results show that the electrochemical performances obtained with amorphous vanadium oxide films, with an optimal thickness of 200nm (455mAhg−1, i.e. composition of Li2.9V2O5), were superior to crystalline V2O5 films. The amorphous films exhibit higher capacity and better cycle ability even for deep lithium insertion ratio compared to crystalline V2O5 films. The chemical diffusion coefficients, deduced from numerical simulation of chronopotentiograms, were comprised between 3×10−12 and 10−13 cm2 s−1 for a lithium insertion ratio comprised between 0 and 2.9. AFM and Raman spectroscopy performed before and after lithiation showed that neither the morphology nor the local order of the amorphous films were significantly affected by the insertion/extraction of lithium. Raman measurements also revealed that a very small amount of lithium are locally trapped in the oxide lattice.
The electrochemical impedance spectroscopy, cyclic voltammetry, constant current charge/discharge and the constant power discharge methods have been applied to establish the electrochemical characteristics of the electrical double–layer capacitor (EDLC) consisting of the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) ionic liquid and microporous carbon electrodes. Microporous carbon material used for preparation of electrodes (GDAC – glucose derived activated carbon), has been synthesised from D-(+)-glucose by the hydrothermal carbonization method, including subsequent pyrolysis, carbon dioxide activation and surface cleaning step with hydrogen. The Brunauer-Emmett-Teller specific surface area (S BET = 1540 m2 g−1), specific surface area calculated using the non–local density functional theory in conjunction with stable adsorption integral equation using splines (SAIEUS) model S SAIEUS = 1820 m2 g−1, micropore surface area (S micro = 1535 m2 g−1), total pore volume (V tot = 0.695 cm3 g−1) and the pore size distribution were obtained from the N2 sorption data. The S BET, S micro and V tot values have been correlated with the electrochemical characteristics strongly dependent on the carbon activation conditions applied for EDLCs. Wide region of ideal polarizability (ΔV ≤ 3.2 V), very short charging/discharging time constant (2.7 s), and high specific series capacitance (158 F g−1) have been calculated for the optimized carbon material GDAC-10h (activation of GDAC with CO2 during 10 h) in EMImBF4 demonstrating that this system can be used for completing the EDLC with high energy- and power densities.
A systematic first-principles calculation based on density functional theory is carried out to discuss the redox mechanism of Li2MnO3. The lattices of structural models having C2/m- and C2/c-type stacking sequences can be regarded as hexagonal, while their symmetry is monoclinic. Different stacking sequences of [Mn2/3Li1/3] layers do not cause differences in the energy or crystallographic structure, suggesting a disordered stacking sequence. A calculation for Li2−x MnO3 assuming topotactic lithium removal indicates that lithium removal can occur at a potential of about 4.6V with a wide potential plateau. The electronic structure of Li2−x MnO3 shows that the manganese ions remain in the charge state of Mn4+ and the charge of the removed lithium ions is compensated by the oxidation of oxygen.
Word learning is a multifaceted perceptual and cognitive task that is omnipresent in everyday life. Currently, it is unclear whether this ability is influenced by age, musical expertise or both variables. Accordingly, we used EEG and compared behavioral and electrophysiological indices of word learning between older adults with and without musical expertise (older adults’ perspective) as well as between musically trained and untrained children, young adults, and older adults (lifespan perspective). Results of the older adults’ perspective showed that the ability to learn new words is preserved in elderly, however, without a beneficial influence of musical expertise. Otherwise, results of the lifespan perspective revealed lower error rates and faster reaction times in young adults compared to children and older adults. Furthermore, musically trained children and young adults outperformed participants without musical expertise, and this advantage was accompanied by EEG manifestations reflecting faster learning and neural facilitation in accessing lexical-semantic representations.
Diatoms and the large, fast-sinking aggregates they form during blooms play an important role in downward flux of particles in the ocean. To study how the aggregation process operates on particle dynamics, diatom blooms were generated and followed under controlled conditions in nutrient-enriched laboratory mesocosm where a homogeneous mixed surface layer was emulated. The size spectrum of particles (from 12μm to several mm) was recorded each hour during the 1 month span of the experiment by a non-intrusive image analysis system with two CCD cameras. Beam attenuation was continuously recorded as an additional estimator for particle abundance. The high time resolution and wide size range of the records obtained with this design were able to resolve the time scale for coagulation as well as to determine the lowest time resolution needed to sample any experiment aimed to study aggregation of diatoms. Our results narrow previous theoretical time scales to the order of hours to days for the process of mass transfer from small particles to marine snow. Also, daily analyses of a broad range of biological and chemical variables permitted to link phytoplankton succession to the aggregation process. Finally, the evaluated role of different copious exopolymers suggested a lower implication of Coomassie stained particles (CSP) than transparent exopolymeric particles (TEP) in the formation of marine aggregates.
The lithium-sulfur flow battery (LSFB) is a new addition to the rechargeable lithium flow batteries (LFBs) where sulfur or a sulfur compound is used as the cathode material against the lithium anode. We report here our evaluation of an organic sulfide - dimethyl trisulfide (DMTS), as 1) a catholyte of a LFB and 2) a multi-electron redox mediator for discharging and charging a solid sulfur cathode without any conductive additives. The latter configuration is also known as the redox-targeting lithium-sulfur flow battery (RTLSFB). The LFB provides an initial discharge capacity of 131.5 mAh g−1 DMTS (1.66 A h L−1), which decreases to 59 mAh g−1 DMTS (0.75 A h L−1) after 40 cycles. The RTLSFB delivers a significantly higher application performance - initial discharge capacity of 1225.3 mAh g−1 sulfur (3.83 A h L−1), for which 1030.9 mAh g−1 sulfur (3.23 A h L−1) is still available after 40 cycles. The significant increase in the discharge and charge duration of the LFB after sulfur addition indicates that DMTS is better used as a redox mediator in a RTLSFB than as a catholyte in a LFB.
A simplified, miniaturized polymer electrolyte fuel cell without gas diffusion layers was investigated under operation by neutron radiography. By visualizing liquid water, it was possible to identify limiting effects, which are directly related to the simplified construction principle. Depending on the operation conditions, undesired water accumulation either in particular micro-channels or on the cathode catalyst layer as well as drying of the anode catalyst layer was observed. As a consequence, the design of a fuel cell without gas diffusion layers must take into account these limitations visualized by neutron radiography.
Carbon coating technologies for olivine-structured LiFePO4 have been successfully commercialized in lithium ion industries. However, up to today, there are still many challenges overcoming the low intrinsic ionic conductivity and surface instability limitations. Herein, we propose a lithium ion conductive organic-skinned secondary coating technique by applying sodium maleate onto the surface of a commercial carbon-coated LiFePO4 cathode. Very distinctive features of the organic skin secondary coating are highly uniform and continuous. More importantly, the abundant carbonyl groups on the LFP surface facilitates facial Li ion transport. The nanostructure tuned organic layer is able to effectively suppress the undesired side reactions at the electrode/electrolyte interface. With 6.0 wt% of the sodium maleate coating, rate capability and long-term cycling behavior of the LiFePO4 cathode at different temperatures are significantly improved. Notably, the well-known impedance rise of LFP cathode with increasing electrochemical cycles is effectively suppressed. An insight into the mechanisms of the secondary sodium maleate coating on the carbon-coated LiFePO4 cathode is discussed.
Net primary production (NPP) is a critical ecosystem property that researchers and land managers attempt to quantify across ecosystems globally. Although the belowground NPP (BNPP) component of total NPP often contributes 50% or more to total NPP, it is infrequently measured due to the amount of labor involved. Here, I present a rapid method to estimate BNPP or fine root production in rangelands using sequential or root ingrowth cores and modifications to existing root-washing methods. The details provided should allow anyone to estimate BNPP in rangelands worldwide with minimal investment in materials and labor.
The thermal shrinkage of the widely adopted polyethylene (PE) separators has become a very critical issue for safety in lithium ion batteries, especially for electrical vehicle applications. As an effort to minimize the thermal shrinkage of PE separators, in this study, we coat PE separators with a substance from the polyimide family by engaging a simple dipping method. A polymer coating at the optimal concentration endows PE separators with improved mechanical strength and thus remarkably increased resistance against thermal shrinkage at elevated temperatures. Despite the coating layers, the cells with the polyimide-coated separators exhibit almost identical electrochemical properties to those of the cells with the bare PE separators, thus proving that the polymer coating does not affect the battery performance. The preserved electrochemical properties can be explained by morphology and porosity characterization.
Examples of previous design competitions are listed with all of the steps from problem assignment to problem completion. Key Words: Design competition example, official rules, objective, constraints, scoring, performance testing, design report, additional supplies
Some evidence suggests that patients with bipolar disorder (BD) have better Theory of Mind (ToM) skills than patients with schizophrenia/schizoaffective disorder (SCH). However, this difference is not consistently reported across studies, so rather than being global, it may be restricted to specific aspects of ToM. Our primary objective was to compare higher order ToM performance between BD and SCH patients using the Hinting Task (HT). Ninety-four remitted patients were recruited (BD = 47, SCH = 47). Intelligence quotient (IQ), attention, memory, executive functions, and processing speed were also assessed. Patients with BD performed better on the HT than patients with SCH, even when the analysis was adjusted for IQ and neurocognition (p < 0.001, ηp2
“Theory of Mind” (ToM) encompasses the ability to understand the cognitive and affective mental states of oneself and others and the ability to use this knowledge to predict and anticipate people’s behavior [1]. Patients with bipolar disorder (BD) and schizophrenia/schizoaffective disorder (SCH) show mild-to-severe deficits in ToM throughout the course of the disease, including the prodromal, acute, and remitted phases [2, 3]. Although less severe, similar difficulties have been observed in their unaffected first-degree relatives, suggesting some degree of heritability and that ToM difficulties are a vulnerability marker for BD and SCH [4, 5].
By dissolving plasticizing lithium borate (Salt A) and LiN(SO2CF3)2 (LiTFSI) at different ratios in poly(ethylene oxide) (PEO), a series of solid-state mix-salt polymer electrolytes were prepared. Higher ionic conductivities were determined for the mix-salt polymer electrolytes than for the pure-salt counterparts. The optimum mixing ratio of the two salts was explored. The electrochemical stability and interfacial performance of the mix-salt polymer electrolytes were also investigated. A battery testing using LiNi0.8Co0.2O2 as cathode material and lithium as anode material was executed to assess the cyclic performance of the electrolyte.
Lithium vanadium bronze LiV3O8 was synthesized by the method of aqueous solution and by solid state method. The synthesized materials were characterized using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). Thermal stability and temperature dependences of conductivity for the bronze samples synthesized by both methods were studied. At room temperature the conductivity of the bronze obtained by solid state method is three times higher. LiV3O8| Li3.4Si0.4P0.6O4 |LiV3O8 solid state cell was analysed by pulse potentiometry and voltammetry at 320°С. It is shown that lithium vanadium bronze has a good adhesion to Li+ solid electrolyte, does not react with it below 330 оС and does not degrade with cycling. It was established that the microstructure of the active material of the cathode, which determines the kinetics of Li+ intercalation/deintercalation, dominates the characteristics of the investigated cell.
Strain and temperature are critical parameters to monitor in Li-ion batteries (LIBs) to improve their safety and long-term cycling stability. High local current densities can result in a massive heat release, decomposition of the electrolyte, gas evolution and even explosion of the battery cell, known as thermal runaway. However, the corrosive chemical environment in the batteries is a challenge to monitor strain and temperature. Optical fiber sensors, due to their high chemical stability and small diameter, can be embedded within the LIBs, thus becoming an interesting solution for operando and in situ measurements. In this work, a hybrid sensing network constituted by fiber Bragg gratings and Fabry-Perot cavities is proposed for the discrimination of strain and temperature. The proof-of-concept was performed by attaching the sensing network to the surface of a smartphone battery. Afterwards, it was embedded in a Li-ion pouch cell to monitor and simultaneously discriminate internal strain and temperature variations in three different locations. Higher thermal and strain variations are observed in the middle position. The methodology presented proves to be a feasible and non-invasive solution for internal, real-time, multipoint and operando temperature and strain monitoring of LIBs, which is crucial for their safety.
Owing to their high theoretical capacity, metal fluorides have attracted significant interest as materials for fabricating the cathode of lithium secondary batteries. In the present study, a nanocomposite of LiF and FeF2 is prepared by a fluorolytic sol–gel method in an ethanol solution, for use as the cathode material of a lithium secondary battery. The produced LiF/FeF2 composite is characterized by broad X-ray diffraction peaks attributed to the nanosized (∼10 nm) LiF and FeF2 crystals, a large Brunauer–Emmett–Teller surface area of 119 m2 g-1, and adsorption–desorption hysteresis, attributed to the presence of mesopores. The results of charge–discharge tests indicates an initial discharge capacity of 225 mAh (g-LiF/FeF2)−1 through reversal conversion at a current rate of 10 mA (g-LiF/FeF2)−1. Based on a combination of galvanostatic intermittent titration, X-ray absorption, and X-ray diffraction investigations, a new reaction mechanism is developed, namely, the conversion of the local environment of an Fe atom from a rutile-type FeF2 structure to a rhenium trioxide-type FeF3 structure during charging, with the subsequent discharge resulting in the insertion of Li+ into the rhenium trioxide-type FeF3 structure, followed by the conversion reaction to LiF and FeF2.
Boilers, the most troublesome components of electric-power generation plants, cost the US utility industry over $5 billion per year in unscheduled shutdowns, repairs and power replacements. The non-destructive testing technique is an important tool for predicting the life of boiler tubes. A standard ultrasonic technique is used for measuring their wall thicknesses and determining the degree of corrosion. Such a test requires clean, rust-free surface and all tubes must be sandblasted prior to the inspection. This adds precious hours to the boiler's outage-time. This paper presents the application of the electromagnetic-acoustic transducer (EMAT) process that accurately measures the tube's wall thickness through thick layers of crusty scale—the kind most often found in aging fossil-fired boilers. Laboratory and field trials were carried out during the last outage season. Back-to-back tests showed that good agreement between the results of the EMAT technique and the classic ultrasonic thickness gauge measurement process.
The optical efficacy of light emitting diode (LED) has exceeded 72lm/W in 2006. This implies that energy can be saved about 75%, as compared to mercury lamps widely used in roadway lighting. In some remote areas where the grid power cannot reach, independent solar-powered lighting using high-power LED provides a promising solution. However, the cost of solar photovoltaic device may cause the application of solar-powered LED roadway lighting to be not economically feasible. The present study investigates the design of the solar-powered LED roadway lighting using high-power LED luminaire (100W) and estimates the installation cost for a 10km highway with 2 lanes. LED luminaries are installed on both side of the road with staggered arrangement. The pole distance is 30m. The cost comparison of LED lighting using grid and solar power with the conventional mercury lamps was carried out. It shows that the installation cost is 22 million USD for LED powered by grid power and 26 million USD for solar-powered. The total installation cost of conventional mercury lighting is 18 million USD. The excess cost of LED mainly comes from the cost of LED lamp and solar PV. But, the cost of power generation and electrical transmission line can be greatly reduced since about 75% energy was saved for LED. This permits the use of smaller copper wire and shorter line length for solar-powered system which in turn saves installation cost. The payback time for the excess investment of LED is 2.2 years for LED using grid power and 3.3 years for LED using solar power.
We investigated additive effect of five kinds of ionic liquids, such as 1-ethyl-3-methyl-imidazolium bis(trifluoromethane-sulfonyl)imide [EMI][TFSI], 1-ethyl-3-methyl-imidazolium tetrafluoroborate [EMI][BF4], 1-buthyl-3-methyl-imidazolium bis(trifluoromethane- sulfonyl) imide [BMI][TFSI], 1-buthyl-3-methyl-imidazolium tetrafluoroborate [BMI][BF4], and/or 1-buthyl-3-methyl-imidazolium iodide [BMI][I], on electrochemical properties of the sulfur composite electrode for all-solid-state lithium–sulfur batteries. The sulfur composite electrode that was composed of sulfur (29.9 wt%), vapor-grown carbon fiber (VGCF, 9.9 wt%), solid electrolyte (amorphous Li3PS4, 60.0 wt%), and [EMI][TFSI] (0.2 wt%) showed high initial specific capacity of 1270 mAh g−1 at 25 °C, which was calculated on the base of the weight of sulfur. To construct a laboratory-scale all-solid-state battery, amorphous Li3PS4 and meta-stable Li4.4Si alloy were used as solid electrolyte and as negative electrode materials, respectively. The laboratory-scale all-solid-state battery showed good discharge–charge cycle performance under a constant current density of 0.1 mA cm−2 (24 mA g−1) at room temperature and retained the large specific capacity more than 1230 mAh g−1 even after 50 cycles at 25 °C. The capacity after 50 cycles was about 97% of the initial capacity of the test cell.