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Nano-sized, semi-crystalline niobium pentoxide (Nb2O5) was synthesized in a single step via a continuous hydrothermal process. The nanomaterial was characterized using a range of analytical techniques including powder X-ray diffraction and transmission electron microscopy. The “as-prepared” Nb2O5 nanomaterial was investigated as negative electrode for a lithium-ion battery and was shown to be stable during electrochemical cycling (98.6 % capacity retention after 800 cycles) and showed promising high rate performance, with a specific capacity of 43mAhg−1 at an applied current of 10,000mAg−1 (in the wide potential range of 0.05 to 3V vs Li/Li+). Scan rate tests were used to investigate the proportion of stored charge from diffusion-limited processes and that from surface effects, which showed that at higher currents, charge storage from the latter was dominant.
An S-doped porous carbon (SPC) with a pillar-supported porous layer structure is prepared by carbonizing petroleum asphalt adsorbed on porous MgO-MgSO4 composite layers. As anode for a half cell, the SPC presents high Li storage capacity and excellent cycling stability (100 cycles without capacity decay), markedly superior to those of the N-doped porous carbon (NPC) and the undoped porous carbon (PC). Coin type full cells with SPC as anode and LiFePO4 (LFP) as cathode (SPC/LFP) are assembled and tested, which afford a high reversible capability (161mAhg−1 at 0.2C based on the mass of cathode) with a capacity retention of 96.8% after 100 cycles at 1C, indicating a superior cycling stability as compared to the previously-reported graphene/LFP cells. State-of-charge estimation with satisfying error tolerance is realized in the SPC/LFP full cell. These unique features of SPC suggest a practical substitution of graphite as a high performance anode material in LIBs and broaden roads to hybrid devices with reliable battery management systems.
For many years, polyaniline films have appeared to be one of the most studied conducting polymers. At the same time, ac-electrogravimetry has been used as a powerful technique for different polymer films but in general for slow perturbation rates. Two reasons for that: on the one hand, high frequency mass transfer responses are not expected and on the other hand, the electronic interfaces dedicated for ac-electrogravimetry are not prepared to follow, without distortion, high rate frequency shifts, faster than a few hertz. This paper shows that high ionic transfer responses can be detected by using a new ac-electrogravimetry concept. The experiments conducted with PANI tried to verify whether high frequency responses in conducting polymers are possible or not. The main interest of the new device is to reach the high frequency values directly and to demonstrate an ionic transfer contribution at 1kHz which was not predicted with old systems.
Fuel cells (FCs) are promising electrochemical devices that convert the chemical energy of fuels directly into electrical energy, as long as the fuel is supplied. This paper describes a room-temperature hydrazine/air direct-liquid fuel cell (DLFC) based on the use of nanostructured copper electrodes. We show that nanostructured copper electrodes function as highly efficient and ultra-long-lasting catalyst for the electro-oxidation of hydrazine. Our Cu/hydrazine anodes show high electrical efficiency for long periods of continuous operation (more than 500h). A hydrazine/air fuel cell prototype was built with a nanostructured Cu/hydrazine anode, combined with a commercial air cathode. The output of this cell is about 0.45W at 1A (0.1Acm−2 corresponds to the anode area), and supplies about 2.3Wh and 1300Whkg−1 hydrazine. The hydrazine discharge efficiency is higher than 85%.
A facile one-step pyrolysis and activation synthesis method is utilized to convert a common biomass of willow catkin into interconnected porous carbon nanosheets (PCNs), and then followed by effective nitrogen and sulfur co-doping. Owing to the unique hollow and multilayered structure of willow catkin fiber, the pore structure of obtained carbons can be controlled by adjusting the mass ratio of raw material to alkali. As a result, the nitrogen and sulfur co-doped PCNs demonstrate a high specific capacitance of 298Fg−1 at 0.5Ag−1 and 233Fg−1 at 50Ag−1, revealing excellent rate performance. In addition, the electrode demonstrates superb cycling stability with only 2% capacitance loss after 10,000 cycles. Furthermore, the assembled symmetric cell with a wide voltage range of 1.8V yields a remarkable specific energy of 21.0Whkg−1 at 180Wkg−1. These exciting results exhibit a green and low-cost design of electrode materials for high performance supercapacitors.
Impairments in social communication are a core feature of Autism Spectrum Disorder (ASD). Because the ability to infer other people’s emotions from their facial expressions is critical for many aspects of social communication, deficits in expression recognition are a plausible candidate marker for ASD. However, previous studies on facial expression recognition produced mixed results, which may be due to differences in the sensitivity of the many tests used and/or the heterogeneity among individuals with ASD. To ascertain whether expression recognition may serve as a diagnostic marker (which distinguishes people with ASD from a comparison group) or a stratification marker (which helps to divide ASD into more homogeneous subgroups), a crucial first step is to move beyond identification of mean group differences and to better understand the frequency and severity of impairments.
LiMnPO4 was synthesized using a sol–gel method and tested as a cathode material for lithium ion batteries. After calcination at temperatures between 520 and 600°C, primary particle sizes in the range of 140–220nm were achieved. Subsequent dry ball milling reduced the primary particle diameters from 130 to 90nm, depending on time of ball milling. Reversible capacities of 156mAhg−1 at C/100 and 134mAhg−1 at C/10 were measured. At 92% and 79% of the theoretical values, respectively, these are the highest values reported to date for this material. At faster charging rates, the electrochemical performance was found to be improved when smaller LiMnPO4 particles were used.
We demonstrate that ion transport through polypyrrole doped with dodecylbenzenesulfonate [PPy(DBS)] formed over a pore is regulated by its electrochemical redox state. We refer to this arrangement of PPy(DBS) as an ionic redox transistor owing to its functional similarity to a bipolar junction transistor and chemical physics origins of voltage-regulated transmembrane ion transport. Our results indicate that ionic current across the polymer in its reduced state is facilitated by the affinity of cations to immobile anionic dopant (DBS) and increases with concentration and applied transmembrane potential. We report a maximum conductance of 30 μS cm−1 and a current gain of 60× as the polymer switches between oxidized (Vm > −200 mV) and reduced state (Vm < −600 mV). A demonstration of PPy(DBS) ionic redox transistor as a smart membrane separator in an electrolytic circuit is presented to illustrate its application in electrochemical energy storage devices.
Spinel LiMn2O4 and LiCr x Mn2−x O4 (x=0.00−0.20) have been synthesized by a soft chemistry method using adipic acid as the chelating agent. This technique offers better homogeneity, preferred surface morphology, reduced heat-treatment conditions, sub-micron sized particles, and better crystallinity. The synthesized spinel materials are characterized by X-ray diffraction, scanning electron microscopy, cyclic voltammetry, and charge–discharge testing. It is found that chromium substitution alleviates capacity fading in the 4-V region and improves the structural stability of LiMn2O4 spinel upon repeated cycling.
The effect of added carbon (3, 5 and 10wt.%) on the electronic conductivity and discharge capacity of LiCoPO4 was investigated. It was found after heat-treatment that the samples consisted of a LiCoPO4 majority phase and Co2P second phase. The added carbon was consumed reducing the LiCoPO4 surface layers to Co2P. The electronic conductivity increased as the amount of the Co2P phase increased. It was observed that the discharge capacity increased with increased Co2P content to ∼4–5wt.%, after which the capacity rapidly decreased with increasing Co2P content. The increase in discharge capacity is likely a result of the increase in electronic conductivity. At higher Co2P volume fractions the presence of the electrochemically inert Co2P phase causes decreased capacity by: (1) reducing the amount of LiCoPO4 present and (2) preventing Li+-ions from entering/leaving LiCoPO4, even though the highest values of electronic conductivity were exhibited.
10 mol% Fe- and Ni-substituted Li2MnO3 (Li1+x(Fe0.1Ni0.1Mn0.8)1-xO2, 0 < x < 1/3) samples were prepared under different calcination atmospheres (in air or flowing N2). The N2 calcined sample (sample N) exhibited better cycle performance because sample N had a more homogeneous transition metal (TM) distribution. Through X-ray Rietveld analysis, highly TM-deficient spinel phases were detected with layered rock-salt phase after charging. The highly TM-deficient spinel had unusually low TM occupancy on the 16d site (<40%). At the end of discharging, the spinel phase was diminished. Only TM-disordered layered rock-salt phase was observed. At 34th discharged state, the highly TM-deficient spinel phase appeared as a minor phase because of layer to spinel conversion when upper cut-off voltage was set to 4.6 V. However, the highly TM-deficient spinel phase converted to a normal LiMn2O4-like phase when the upper cut-off voltage was set to 4.8 V. The spinel content after cycling can be reduced by synthesizing homogeneous TM distributed samples.
AgCuO2 as ultra fast charging cathode material for alkaline secondary batteries is reported in the present paper. The structural characterization shows that the AgCuO2 material is composed of many one-dimension linear crystals arranged in a certain sequence. The experimental results show that the AgCuO2 electrodes have good electrochemical characteristics at ultra fast charging-discharging speed from 5000mAg−1 to 50,000mAg−1. The super high speed ability of charge/discharge makes the charge time of the electrode shorter than 29s. Cyclic voltammetric (CV) and galvanostatic charge–discharge tests reveal that the charge/discharge process is not the single electron transfer for Cu(III) but the fast dual electron transfer for Ag(II) and Cu(III). The characteristics of high cycling capacity and fast charging for AgCuO2 not only increase the specific capacity of batteries considerably but also make it possible to charge the future electric cars instantaneously as fast as refueling the fuel vehicles.
Annealing Nd-only AB3.74 metal hydride alloy was found to effectively increase composition homogeneity, main A2B7 phase abundance, and both gaseous phase and electrochemical hydrogen storage capacities, as well as to facilitate activation, and improve battery high-rate performance, charge retention, and cycle life. As the phase abundance of the main A2B7 phase increases in the alloy with higher annealing temperatures, the general electrochemical performance improves. Extending the annealing period from 5 to 16h further increases the A2B7 phase abundance, but deteriorates the high-rate dischargeability due to the reduction of AB5 catalytic phase.
ABSTRACT In electric vehicles (EVs) the thermal systems (cooling and HVAC) are significantly more complex than conventional vehicles. EV design presents the additional challenge of optimizing electrical energy usage to meet thermal management demands of the cabin and powertrain. An EV is being developed which employs a range of devices to provide heating and cooling for the cabin, powertrain and battery, including an electric compressor and direct air Positive Temperature Coefficient (PTC) heater. This paper discusses the integrated control system developed to balance the complex thermal system demands.
Health planners and managers make decisions based on their appreciation of causality. Social audits question the assumptions behind this and try to improve quality of available evidence. The method has its origin in the follow-up of Bhopal survivors in the 1980s, where “cluster cohorts” tracked health events over time. In social audit, a representative panel of sentinel sites are the framework to follow the impact of health programmes or reforms. The epidemiological backbone of social audit tackles causality in a calculated way, balancing computational aspects with appreciation of the limits of the science.
Co3O4 nanorods are prepared by a facile calcinations of the Co-composites, which is synthesized with the precursors of CoCl2, 1,3,5-Benzenetri carboxylic acid (H3BTC) and phenanthroline (PHEN). The Co-composites nonorods are about 1 um long and 50nm wide. After calcinations, the Co3O4 nanorods are composed of nanoparticles of 20–40nm in queue and possesses a surface area of 23m2 g−1 owning to the release of the organic molecules. The electrochemical properties are examined by cyclic voltammetry, electrochemical impedance spectroscopy and cyclic charge-discharge tests. The results show that the Co3O4 have the highest specific capacity of 262Fg−1 at 5mVs−1 in the range of 0.2–0.7V (vs. Ag/AgCl) and have a good cycle life with nearly no decrease after 500 cycles at 50mVs−1. The asymmetrical Co3O4//AC button cell is also tested by two-electrode system with a large potential testing window of 1.5V and the results show the high energy density with a value of 42.81Whkg−1 at the discharge current of 1.5Ag−1.
Al2O3-coated layered oxide Li1.2Mn0.54Ni0.13Co0.13O2 (AO-LMNCO) is synthesized by a facile sol-gel reaction to prepare a preliminary formation of Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO), and then coating process with Al2O3 nano layer is followed via a chemical deposition route. Galvanostatic charge-discharge tests show that 1.5wt% Al2O3 coated sample presents the optimum electrochemical performance. It delivers a discharge capacity 285mAhg−1 in the potential window of 2.0–4.8V at 0.2C, which is superior to that 274mAhg−1 for the pristine one. The initial columbic efficiency is significantly enhanced from 80.60% to 87.40% after the coating process. Moreover, the optimal sample presents a superior high-rate capacity of 120mAhg−1 at 10C, and the value is much greater than the pristine one. Physical characterization results show that the as-prepared Li-rich oxide has a typical layered structure, and the Al2O3 nano layer (~4nm thick) is coated on the surface of the cathode grains. We could ascribe the remarkably enhancement of cycling stability and high-rate capability to the Al2O3 protective coat, which could obstruct the electrolyte from the close contact with the active material. Thus the corrosion of the electrode structure effectively decreases and the dissolution of Mn from the pristine material greatly suppresses.
Impedance measurements of both electrodes of a flooded OEM SLI battery at various SOC and with various direct currents have been measured. For each part of the impedance spectra, an electrochemical process is proposed and implemented in a simulation model. By simulation of impedance spectroscopy, spectra of the model are obtained and compared with the measurement. In this first part, the focus is put on inductive semicircles in impedance spectra.
In vitro alkaline elution is a sensitive and specific short term assay which measures DNA strand breakage in a mammalian test system (primary rat hepatocytes). This lab has previously demonstrated the performance of the assay with known genotoxic and non-genotoxic compounds. The methodology employed has relatively low sample throughput and is labor-intensive, requiring a great deal of manual processing of samples in a format that is not amenable to automation. Here, we present an automated version of the assay. This high-throughput alkaline elution assay (HT-AE) was made possible through 3 key developments: (1) DNA quantitation using PicoGreen® and OliGreen® fluorescent DNA binding dyes; (2) design and implementation of a custom automation system; and (3) reducing the assay to a 96-well plate format. The assay can now be run with 5–50mg of test compound. HT-AE was validated in a similar manner as the original assay, including assessment of non-genotoxic and non-carcinogenic compounds and evaluation of cytotoxicity to avoid confounding effects of toxicity-associated DNA degradation. The validation test results from compounds of known genotoxic potential were used to set appropriate criteria to classify alkaline elution results for genotoxicity.
Efficient and stable operation of a lithium metal anode has become the enabling factor for next-generation high energy density storage system. Here, vertical graphene (VG) arrays are used as the scaffold structure for high performance Li metal batteries. The melt infusion method is employed to encapsulate Li inside the VG scaffold structure, and the lithiophilic Si layer is coated onto the array surface by magnetron sputtering to assist this melt-infusion process. The porous scaffold structure can control the volume expansion and inhibit the formation of dendritic lithium significantly, leading to the excellent electrochemical performance of the Li composite anode. In addition, the Li-S full batteries with the composite anode display enhanced cycling reversibility.
In this work we demonstrate that the thermal treatment of CF x cathode material just below the decomposition temperature can enhance discharge performance of Li/CF x cells. The performance enhancement becomes more effective when heating a mixture of CF x and citric acid (CA) since CA serves as an extra carbon source. Discharge experiments show that the thermal treatment not only reduces initial voltage delay, but also raises discharge voltage. Whereas the measurement of powder impedance indicates the thermal treatment does not increase electronic conductivity of CF x material. Based on these facts, we propose that the thermal treatment results in a limited decomposition of CF x , which yields a subfluorinated carbon (CF x−δ ), instead of a highly conductive carbon. In the case of CF x /AC mixture, the AC provides extra carbon that reacts with F2 and fluorocarbon radicals generated by the thermal decomposition of CF x to form subfluorinated carbon. The process of thermal treatment is studied by thermogravimetric analysis and X-ray diffraction, and the effect of treatment conditions such as heating temperature, heating time and CF x /CA ratio on the discharge performance of CF x cathode is discussed. As an example, a Li/CF x cell using CF x treated with CA at 500°C under nitrogen for 2h achieved theretical specific capacity when being discharged at C/5. Impedance analysis indicates that the enhanced performance is attributed to a significant reduction in the cell reaction resistance.
The electrochemical fabrication of alumina membranes by anodizing of aluminium in phosphoric acid and oxalic acid solutions, in the temperature interval from −1 to 16°C, was investigated in order to study the influence of different parameters (initial treatment of aluminium surface, nature and composition of electrolyte, temperature) on the final characteristics of the membranes. Porous layers were grown using a linear potential scan at 0.2 V s−1 up to 160 V in H3PO4 solution and 70 V in oxalic acid solution. The efficiency of porous layer formation was calculated by using Faraday's law and weight measurements. Pore size distribution and porosity of membranes prepared in 0.4 M H3PO4 were found to be dependent on temperature, while in 0.04 M smaller pore size and lower porosity were obtained, independent of temperature. Highly ordered structures were formed by aluminium anodizing in 0.15 M oxalic acid solution at 70 V. A uniform pore diameter of about 90 nm was found, independent of temperature. A porosity value of about 26% was achieved and it was found to be independent of temperature for membranes prepared in oxalic acid. Porous layers grown either in H3PO4 or oxalic acid solution crystallized at temperatures around 870–890°C. For membranes formed in oxalic acid the pyrolysis of oxalate anions also occurs.
Publisher Summary This chapter discusses magnesium perchlorate primary batteries. Magnesium dry batteries are now finding widespread use in military communications equipment. With increasing use and production, the cost of these batteries has dropped significantly. There are two main types of primary battery: the non-reserve type, which is ready for use off the shelf and requires no activation or pre-use conditioning, and the reserve type, which usually contains the active electrode materials but requires the addition of water or an electrolyte just before use. The advantage of reserve manganese dioxide- magnesium perchlorate batteries is that they can be stored for years in an inactivated condition and require activation with the electrolyte before use. However, unlike the non-reserve type, it is necessary, once they are activated, to use reserve batteries fairly soon, as they undergo self-discharge. Reserve batteries are recommended for use in portable transceivers, locator beacons, electronic counter measures, and expendable electronic equipment. Further, applications for non-reserve batteries include fire and burglar alarm systems, barricade lights light packs for emergency slide crates in commercial aircraft, and emergency location transmitters on aircraft.
Herein we report early results on efforts to optimize the electrochemical performance of a cathode composed of a lithium- and manganese-rich “layered-layered-spinel” (LLS) material for lithium-ion battery applications. Pre-pilot scale synthesis leads to improved particle properties compared with lab-scale efforts, resulting in high capacities (∼200 mAh g−1) and good energy densities (>700 Wh kgoxide −1) in tests with lithium-ion cells. Subsequent surface modifications give further improvements in rate capabilities and high-voltage stability. These results bode well for advances in the performance of this class of lithium- and manganese-rich cathode materials.
The olivine-structured LiMPO4 (M=Fe, Mn, Co and Ni), particularly LiFePO4, is one of the most viable and promising candidates of cathode material for the sustainable lithium ion batteries (LIBs) as reversible electrochemical energy storage (EES) devices. Usually, LiMPO4 can be synthesized via solid phase thermal (SPT) route, which is considered as a crucial process for improving the crystallinity of LiMPO4. However, in the conventional SPT process, e.g., common calcination, energy is generally transferred through heat convection, heat conduction and heat radiation from the surfaces to inners, which entail prolonged exposure to high calcination temperature (e.g. 700°C for 12h). Different from the heat treatment route of calcinaiton, microwave irradiation can provide “inert and instant heating” of LiMPO4 precursors and synthesize even crystallite LiMPO4 cathode materials. This microwave-assisted SPT (MW-SPT) method is not only energy- and time-saving (e.g., 700W, 4min), but also exhibits superiority in optimizing physical characters, improving Li-ion diffusion kinetics and enhancing high rate performance. Furthermore, the microwave-assisted liquid phase thermal (MW-LPT) method has been also employed to prepare LiMPO4 cathode materials. Recently, both MW-SPT and MW-LPT routes have led to increased interest in the development of LiMPO4 cathode materials and processing capabilities to enable high electrochemical performance. In this review, we focus on the LiMPO4 cathode materials synthesized by microwave irradiation assisted synthesis (MIAS) route, which conclude mainly two parts, MW-SPT and MW-LPT routes. The major goal is to highlight the reaction mechanism and current developments of LiMPO4 synthesized via MW-SPT and MW-LPT methods. The structural, morphological and electrochemical performance of LiMPO4 cathode materials prepared by MIAS has also been discussed.