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Electrospun SiO2/nylon 6,6 nanofiber membranes were fabricated and their electrochemical performance was evaluated for use as separators in Li-ion batteries. The aim of this study was to design new high-performance separator membranes with enhanced mechanical properties and good thermal stability, as well as superior electrochemical performance compared to microporous polyolefin membranes. It was found that SiO2/nylon 6,6 nanofiber membranes had superior thermal stability and mechanical strength with highly porous structure. Enhanced electrochemical properties were also obtained for these nanofiber membranes due to their high porosity values. Compared with commercial microporous polyolefin membranes, SiO2/nylon 6,6 nanofiber membranes had larger liquid electrolyte uptake, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. SiO2/nylon 6,6 nanofiber membranes with different SiO2 contents (0, 3, 6, 9 and 12%) were assembled into lithium/lithium cobalt oxide and lithium/lithium iron phosphate cells. High cell capacities and good cycling performance were demonstrated at room temperature. In addition, cells using SiO2/nylon 6,6 nanofiber membrane separators showed superior C-rate performance compared to those using commercial microporous polyolefin membrane.
Self-discharge and transition metal dissolution weaknesses bother the application of LiNi0.5Mn1.5O4 cathode material due to the severe oxidation of electrolyte at the high voltage state. A novel additive, 1-propylphosphonic acid cyclic anhydride (PACA), is desirable to prevent this oxidation. CV and charge–discharge results reveal that adding 0.5% PACA can relieve the oxidation of electrolyte. Consequently, the self-discharge and transition metal dissolution are both suppressed effectively, which is validated by self-discharge tests, XPS, and EDX analyses. Moreover, using PACA as an additive enhances the capacity retention capability of LiNi0.5Mn1.5O4 at elevated temperatures significantly.
The main challenges in development of traditional liquid lithium-sulfur batteries are the shuttle effect at the cathode caused by the polysulfide and the safety concern at the Li metal anode arose from the dendrite formation. All-solid-state lithium-sulfur batteries have been proposed to solve the shuttle effect and prevent short circuits. However, solid-solid contacts between the electrodes and the electrolyte increase the interface resistance and stress/strain, which could result in the limited electrochemical performances. In this work, the cathode of all-solid-state lithium-sulfur batteries is prepared by depositing sulfur on the surface of the carbon nanotubes (CNTs@S) and further mixing with Li10GeP2S12 electrolyte and acetylene black agents. At 60 °C, CNTs@S electrode exhibits superior electrochemical performance, delivering the reversible discharge capacities of 1193.3, 959.5, 813.1, 569.6 and 395.5 mAh g−1 at the rate of 0.1, 0.5, 1, 2 and 5 C, respectively. Moreover, the CNTs@S is able to demonstrate superior high-rate capability of 660.3 mAh g−1 and cycling stability of 400 cycles at a high rate of 1.0 C. Such uniform distribution of the CNTs, S and Li10GeP2S12 electrolyte increase the electronic and ionic conductivity between the cathode and the electrolyte hence improves the rate performance and capacity retention.
The latest researches have adopted software technology turning the Nintendo Wii Balance Board into a high performance standing location detector. This study extended Wii Balance Board functionality to assess whether two people with developmental disabilities would be able to actively perform designated physical activities according to simple instructions by controlling their favorite environmental stimulation using Nintendo Wii Balance Boards. This study was carried out according to an A–B–A–B design. Data showed that both participants significantly increased their target response (performing a designated physical activity) by activating the control system to produce their preferred environmental stimulation during the intervention phases.
Graphene nanosheets (GNS)/CoAl-layered double hydroxide (CoAl-LDH) composite with a laminated structure is fabricated by a simple refluxing method. It is found that CoAl-LDH lamellar crystallites gradually self-assemble on the graphene oxide (GO) which is reduced to GNS during the refluxing procedure in the presence of urea. The GNS/CoAl-LDH composite has a higher specific surface area (23.4m2 g−1) and superior electrochemical performance. As electrode material for supercapacitors, the composite shows a maximum specific capacitance of 711.5Fg−1 at low current density of 1Ag−1, and it remains 516.8Fg−1 when the current density increase to 10Ag−1. Furthermore, the capacitance keeps at least about 81% (compare with 64% for that of pure LDH) after 2000 cycles at 10Ag−1, indicating the composite has excellent high-current capacitive behavior.
Lithium transportation across the interface of LiMn2O4/LiPF6-based electrolyte was studied by 6/7Li solid-state NMR with 6Li-enriched LiPF6. For almost stoichiometric LiMn2O4, we show that exchange of lithium ions occurs across an electrolyte/electrode interface just by immersing LiMn2O4 powder into LiPF6-based electrolyte, while such transportation is suppressed in Li-excess LiMn2O4. The exchange was approximated by the 1st-order reaction, and the rate was estimated from the 6Li/7Li intensities to be 0.024min−1 at room temperature. The lithium ions penetrated into the surface of a LiMn2O4 particle reach to the core with a time scale of a few hours at room temperature. The suppression of the exchange in Li-excess LiMn2O4 was ascribed to the presence of excess amount of Mn4+.
Carbon aerogel was prepared by the polycondensation of resorcinol (R) with formaldehyde (F), and sodium carbonate was added as a catalyst (C). Physical properties of carbon aerogel were characterized by infrared spectrometer (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that carbon aerogel is an amorphous material with a pearly network structure, and it consists of one or two diffuse X-ray peaks. The results of cyclic voltammetry indicated that the specific capacitance of a carbon aerogel electrode in 6M KOH electrolyte was approximately 110.06Fg−1. Through the galvanostatic charge/discharge measurement, it was found that the electrode is stable in KOH electrolyte, the maximum capacitance of the supercapacitor with carbon aerogel as the electrode active material was 28Fg−1. Besides, the supercapacitor has long cycle life. Thus, it was thought that the carbon aerogel is an excellent electrode material for a supercapcitor.
The composite material was obtained by the polymerization of aniline in the presence of graphene oxide nanosheets. The resulting composite containing polyaniline (72%) and graphene oxide nanosheets (28%) was investigated by XPS, TGA, Raman and IR spectroscopy. A partial reduction of graphene oxide was observed in the process of polymerization. The specific capacitance of the polyaniline/graphene oxide composite electrode in H2SO4 (1 M concentration), corresponding to its discharge from 0.700 to 0.052 V, was found to be 547 F g−1.
Hot topic of research today is to overcome the irreversible capacity loss (ICL) in high capacity anodes used in Li-ion battery. Several attempts have been exploited to overcome the ICL issue, but all of them involved time consuming and inevitable electrolyte decomposition. Here, we attempted to utilize the octahedral site of spinel cathode (ex. LiMn2O4) for the compensation of ICL when paired with conversion type anode, α-Fe2O3 nanorods. The performance of Li1.26Mn2O4/α-Fe2O3 nanorods cell is compared with similar configurations fabricated without any electrode treatment and α-Fe2O3 treated one. Amongst, LiMn2O4 treated assembly showed promising results as compared with anode treated configuration.
High power, phase-pure Nb-doped LiFePO4 (LFP) nanoparticles are synthesised using a pilot-scale continuous hydrothermal flow synthesis process (production rate of 6 kg per day) in the range 0.01–2.00 at% Nb with respect to total transition metal content. EDS analysis suggests that Nb is homogeneously distributed throughout the structure. The addition of fructose as a reagent in the hydrothermal flow process, followed by a post synthesis heat-treatment, affords a continuous graphitic carbon coating on the particle surfaces. Electrochemical testing reveals that cycling performance improves with increasing dopant concentration, up to a maximum of 1.0 at% Nb, for which point a specific capacity of 110 mAh g−1 is obtained at 10 C (6 min for the charge or discharge). This is an excellent result for a high power cathode LFP based material, particularly when considering the synthesis was performed on a large pilot-scale apparatus.
The development of small-scale, decentralized reactors for H2O2 production that can couple to renewable energy sources would be of great benefit, particularly for water purification in the developing world. Herein, we describe our efforts to develop electrochemical reactors for H2O2 generation with high Faradaic efficiencies of >90%, requiring cell voltages of only ∼1.6 V. The reactor employs a carbon-based catalyst that demonstrates excellent performance for H2O2 production under alkaline conditions, as demonstrated by fundamental studies involving rotating-ring disk electrode methods. The low-cost, membrane-free reactor design represents a step towards a continuous, modular-scale, de-centralized production of H2O2.
An electrolysis technique at a constant potential was used to develop a highly reproducible and fast elaboration method of adherent manganese dioxide thin films on a glassy carbon electrode from aqueous solutions containing sulfuric acid and manganese sulfate. The resulting films were found to have a nanostructured character presumably due rather to birnessite (δ-MnO2) than to γ-MnO2, as suggested by their Raman and XRD signatures. They lead to modified electrodes that present an obvious although complex pH dependent potentiometric response. This sensor indeed showed a single slope non-Nernstian linear behaviour over the 1.5–12 pH range for increasing pH direction (“trace”), whereas a Nernstian two slopes linear behaviour was observed for decreasing pH direction (“re-trace”). Preliminary EIS experiments carried out at a pH value of 1.8 seem to reveal a sensitivity mechanism based on proton insertion process at least at highly acidic pH values.
A facile one-step pyrolysis route for the synthesis of hierarchically porous carbon nanosheets (PCNSs) derived from Moringa oleifera stems (MOSs) is reported, in which no post-activation-process in needed. The as-prepared PCNSs possesses unique porous nanosheet morphology with high specific surface area of ca. 2250 m2 g−1, large pore volume of ca. 2.3 cm3 g−1, appropriate porosity as well as heteroatom doping (N and O), endowing outstanding electrochemical properties as electrode material for high-performance supercapacitors. The PCNS-based electrodes are investigated in various aqueous electrolytes including 1.0 M Na2SO4, 1.0 M H2SO4, and 6.0 M KOH. The PCNSs exhibit a maximum specific capacitance of ca. 283 F g−1 (0.5 A g−1), excellent rate capability (ca. 72% of capacitance retention even at an ultrahigh current density of 50 A g−1), and a tremendous long-term cycling stability in the three-electrode system. Moreover, the as-assembled PCNS-based symmetric supercapacitor shows a high energy density of ca. 25.8 Wh kg−1 (in 1.0 M Na2SO4 electrolyte) and remarkable long-term cycling stability (almost no capacitance fade in aqueous electrolytes), indicating the promising of the as-prepared PCNSs for electrochemical energy storage and conversion.
V2O5 micro/nanorods are produced through the heat treatment for the electrospun composite fibers which are prepared by using inexpensive NH4VO3 and H2C2O4 as starting materials at room temperature. Powder X-ray diffraction analysis reveals that the micro/nanorods are orthorhombic V2O5 (space group Pmmn (59), a =1.1516, b =0.3566, c =0.4373nm), and the results of field emission scanning electron microscopy indicate that the V2O5 micro/nanorods have a diameter of roughly 300nm and a length-to-diameter ratio of 5–10. Meanwhile, the V2O5 micro/nanorod cathodes show a high lithium storage performance with the first discharge capacity of 418.8mAhg−1 and the 50th discharge capacity of 180.5mAh g−1 when the half cell is cycled between 2.0 and 4.0V at a current density of 50mAg−1. This is possibly attributed to the fact that the micro/nanostructure samples are well dispersive and they have high structural stability and efficient electron/ion transport in the charging and discharging processes.
The Li/PVdF/S cell showed the first discharge capacity of 1268mAhg−1, which was about 78% utilization of theoretical value. There were two plateau regions at the first discharge curve. From the XRD, DSC results of the sulfur electrode, elemental sulfur disappeared at the upper plateau region and Li2S was formed at the low plateau region. We suggested the discharge process of Li/polymer electrolyte/S cell. The elemental sulfur changed into Li2S n (n >4) and subsequently changed into Li2S at a lower plateau potential region.
Animal movements, residence times, and subsequently foraging strategies, should vary with habitat quality. We used acoustic and satellite telemetry, as well as stable isotopes, to look at movement patterns, macro-scale habitat use, and trophic ecology of blacktip reef sharks, Carcharhinus melanopterus, between two lagoons (eastern and western) at Palmyra Atoll, a US National Wildlife Refuge in the central Pacific. Sharks in the Palmyra lagoons have relatively small home ranges and appear to obtain most of their energy from the lagoon ecosystem. Sharks showed low levels of migration between lagoons over periods of several years, and individuals in the larger western lagoon tended to have longer residence times than those in the smaller eastern lagoon. Furthermore, for sharks in the western lagoon, there was no relationship between total length (TL) and δ15N, 13C relative isotope concentrations, or a Body Condition index (BC). For sharks in the eastern lagoon, TL was positively related to δ15N and negatively related to δ13C and BC. These results suggest that there are low levels of mixing of sharks between lagoons, and these are leading to differences in trophic ecology and potentially foraging success. Although the causative factors behind these differences are unknown, shark home range location can potentially lead to variation in trophic ecology, even over small spatial scales.
Health literacy is a significant public health concern, particularly given the increased complexity of chronic disease health management and health system navigation, and documented associations between low health literacy and poor health outcomes. This study therefore aimed to identify the proportion and characteristics of outpatients visiting a specialist cancer hospital who report low health literacy and/or low cancer health literacy.
Li2FeSiO4/C nanocomposites were synthesized by a novel synthesis route, i.e., a combination of spray pyrolysis and wet ball-milling followed by annealing. The effect of process parameters such as spray pyrolysis temperature, ball-milling time, carbon content in the wet ball-milling process and annealing temperature on the physical and electrochemical properties of Li2FeSiO4/C nanocomposites was investigated. The final sample was identified as Li2FeSiO4 with a P2 1 monoclinic structure by X-ray diffraction analysis. Field-emission scanning electron microscopy and transmission electron microscopy with energy-dispersive spectroscopy verified that the Li2FeSiO4/C nanocomposites are agglomerates of Li2FeSiO4 primary particles with a geometric mean diameter of 65nm and that the carbon was well-distributed on the surface of the agglomerates. A Li2FeSiO4/C nanocomposite sample was used as an electrode material for rechargeable lithium batteries, and electrochemical measurements were carried out by using Li|1M LiPF6 in EC: DMC=1:1| Li2FeSiO4/C cells at room temperature. The Li2FeSiO4/C nanocomposite electrode delivered a first discharge capacity of 154mAhg−1 at 0.05C, corresponding to 93% of the theoretical value. Furthermore, the cycleability and rate capability of the cells were good.
The nature and extent of the neuropsychological difficulties associated with childhood absence epilepsy (CAE) remain unclear. Because aberrant thalamocortical rhythms have been implicated in the pathogenesis of CAE, it was hypothesized that children with CAE would show greater difficulties in neuropsychological domains that are thought to be subserved by basal ganglia–thalamocortical circuits. Multivariate analysis of variance was used to compare the neuropsychological functioning of 16 children with CAE with that of 14 children with type 1 diabetes mellitus and 15 healthy children. The CAE group did not perform differently from the other groups on measures of intellectual functioning, memory, academic achievement, fine motor speed, or processing speed. In contrast, significant differences were found in problem solving, letter fluency, complex motor control, attention/behavioral inhibition, and psychosocial functioning. These results suggest that children with CAE show difficulties in neuropsychological functions thought to be subserved by the same regions implicated in the pathogenesis of the disorder.
Ingredients have been used in industrial manufacture of tobacco products since the early part of the 20th century. However, unlike other consumer goods, until now no regulatory authority has determined how tobacco ingredients should be assessed. Although there is currently no consensus on how added cigarette ingredients should be evaluated, this paper reviews some of the institutional guidance alongside published literature with a view to determining if there is a generally accepted approach in the absence of any strict regulation. Our aim was to review the recommendations, to compare them to the working practices as demonstrated from published studies, and to draw conclusions on currently used methodologies for testing ingredients added to cigarettes. The extent of testing is discussed in the light of practical and theoretical constraints and an example of an industry testing program is presented.
The flexible supercapacitors (FSCs) have attracted much attention with the development of personal electronics. Here, the polyethylene-polypropylene fibrous membranes (PE-PPFMs) are used as the substrate to prepare conductively metallized organic films (Ni/PE-PPFMs) by employing electroless nickel plating method. After graphene oxide (GO) dispersion is coated on the substrate of Ni/PE-PPFMs, electrochemical reduction is carried out to reduce GO and the electrodes of ErGO/Ni/PE-PPFMs have been obtained. The preparation conditions have been optimized and the electrodes have also been characterized in detail. The capacitive performances of the electrodes are evaluated by assembling the FSCs with the NaOH/polyvinyl alcohol (NaOH/PVA) as the gel electrolyte. The specific capacitance of the optimized electrode can reach 368.2 mF cm−2 (147.3 F g−1 based on the active materials), and the maximum energy density of the cell can reach 16.2 μWh cm−2 (or 3.2 Wh kg−1) when the power density is 0.24 mW cm−2 (48 W kg−1). Meanwhile, the cell exhibits excellent cyclic stability (the capacitance retention can still keep at 89.5% after 10,000 cycles) and flexibility (84.4% capacitance retention after 5500 bending cycles). This strategy provides a simple and environmentally friendly method to prepare flexible rGO-based electrodes.
Sulfone-functionalized imidazolium ionic liquids were synthesized from direct nucleophilic substitution for the first time. Detailed NMR analysis of the products revealed the competition pathways of classic SN2 substitution and E2 elimination in the synthesis reaction. Impurities from E2 elimination can easily be overlooked during the conventional method of ionic liquid preparation via SN2 substitution. Initial electrochemical examination of the synthesized ionic liquids shows good compatibility with Li1.1(Ni1/3Co1/3Mn1/3)0.9O2 cathode material.
Phosphorus is a promising material for the electrode in sodium ion batteries (NIBs). In this study, the states of NaxPy compounds synthesized by thermochemical reaction and electrochemical sodiation were compared using solid state 23Na magic angle spinning (MAS) NMR, 23Na multiple quantum (MQ) MAS NMR, and 31P MAS NMR. The NMR signals in thermochemically synthesized NaxPy compounds (Na3P, NaP, Na3P7, Na3P11, NaP7) are assigned in reference to theoretical chemical shifts, based on first-principles calculations. Furthermore, the NMR signals in electrochemically prepared NaxPy compounds after two sodiation/desodiation cycles are ascribed to Na3P compounds and three amorphous compositions. The amorphous compounds ascribed to Na1−αP (0 < α < 1), Na2−βP (0 < β < 1), and Na3−γP (0 < γ < 1) are formed below 0.58 V in the charge and discharge process. These Na3P and the amorphous phases overlapped in the range from 0.20 V (sodiation process) to 0.58 V (desodiation process). 23Na and 31P NMR spectra reveal reversible sodiation and desodiation processes in the third cycle.
A redox flow battery utilizing two, three-electron polyoxometalate redox couples (SiVV 3WVI 9O40 7–/SiVIV 3WVI 9O40 10− and SiVIV 3WVI 9O40 10−/SiVIV 3WV 3WVI 6O40 13−) was investigated for use in stationary storage in either aqueous or non-aqueous conditions. The aqueous battery had coulombic efficiencies greater than 95% with relatively low capacity fading over 100 cycles. Infrared studies showed there was no decomposition of the compound under these conditions. The non-aqueous analog had a higher operating voltage but at the expense of coulombic efficiency. The spontaneous formation of these clusters by self-assembly facilitates recovery of the battery after being subjected to reversed polarity. Polyoxometalates offer a new approach to stationary storage materials because they are capable of undergoing multi-electron reactions and are stable over a wide range of pH values and temperatures.
The inorganic–organic hybrid maghemite (γ-Fe2O3)/polypyrrole (PPy) was synthesized and evaluated as cathode-active material for room temperature lithium batteries. The nanometer-sized core–shell structure of the hybrid consisting of the maghemite core with surface modified by PPy was evidenced from the morphological examination. The cathode fabricated with the as-prepared hybrid material delivered an initial discharge capacity of 233mAhg−1 and a reversible capacity of ∼62mAhg−1 after 50 charge–discharge cycles. A much higher performance with an initial discharge capacity of 378mAhg−1 and a reversible capacity of ∼100mAhg−1 was achieved with the cathode based on the segregated active material, which was obtained by subjecting the as-prepared hybrid material to an additional ball-milling process. The study demonstrates the promising lithium insertion characteristics of the nanometer-sized core–shell maghemite/PPy particles prepared under optimized conditions for application in secondary batteries.
The electrochemical performance of thermal-vapor-decomposition carbon-coated natural graphite was studied in both propylene carbonate (PC)-based electrolytes and ethylene carbonate (EC)-based electrolytes. In the cyclic votammograms of carbon-coated natural graphite, the hump in the range of 1.3–0.7V versus Li+/Li can be observed when the potential was swept at higher scan rates. This hump was investigated with reference of carbon black. The effect of electrode-fabrication pressure on the electrochemical performance of carbon-coated in the PC-based electrolyte has also been studied.