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It is highly desired to design and develop highly efficient and durable electrocatalysts for hydrogen evolution reaction and oxygen evolution reaction under alkaline condition. In this study, three dimensional freestanding porous Cu foam in situ armored CoNi alloy nanosheet arrays with tunable compositions is synthesized via a facile and cost-efficient electrodeposition strategy. With the optimal nanosheet composition (Co81Ni19), highly exposed active surface, improved electrical conductivity, the as-fabricated composite exhibits intriguing properties for efficient overall water splitting in alkaline media. Such freestanding Co81Ni19 alloy nanosheet arrays demonstrate superior electrocatalytic performances with the overpotentials of only 132 and 240 mV for hydrogen evolution and oxygen evolution to reach a catalytic current density of 10 mA cm−2 in 1.0 M KOH. Meanwhile, the Co81Ni19 exhibits high electrochemical stability with almost no detectable activity decay after 36,000 s of continuous operation. Remarkably, this study paves the way to design high-performance and easy-accessible transition metal alloy-based bifunctional catalysts for overall water splitting. Meanwhile, these transition metal-based macroscopic assemblies may be attractive candidates for a wide range of practical energy conversion and storage applications.
A comparative study of the impedance response measured with composite electrodes and thin film electrodes of LiMn2O4 was conducted. The electrodes were prepared on different current collectors (i.e. aluminium, carbonised aluminium and gold) and the experiments were run at various state-of-discharge (SOD) and liquid electrolyte compositions. The impedance response was shown to be strongly dependent on the current collector used. It was demonstrated that the high-to-medium frequency semicircle can be attributed to the contact resistance between the current collector and the active electrode material and that the medium-to-low frequency semicircle can be ascribed to the active electrode material. For the analysis, a mathematical model based on a resistance between the current collector and the active electrode material, interfacial-charge transfer coupled to the double-layer charging and solid-phase diffusion was developed. Potential distribution due to porous electrode effects was also considered. Fitting the model to experimental data enabled reasonable values of the exchange-current density, the double-layer capacitance and the solid-phase diffusion coefficient. However, the very low fitted value of the effective conductivity in the liquid phase indicates that this model does not give a satisfying description of the intercalation process of LiMn2O4.
An electrochemical device for the reduction of CO2 back to liquid fuels is here presented. The key of this novel electrocatalytic approach is the design and development of the gas diffusion membrane (GDM), which is obtained by assembling (i) a proton selective membrane (Nafion), (ii) a nanocomposite electrocatalyst based on metal-doped conjugated microporous polymer (CMP) and (iii) a C-based support working as the gas diffusion layer. CMP is a very attractive material able to adsorb CO2 selectively with respect to other gases (such as H2, O2, N2, etc.), also in mild conditions (r.t. and atmospheric pressure). Particularly, tetrakis-phenylethene conjugated microporous polymer (TPE-CMP) was synthesized through Yamamoto homo-coupling reaction. TPE-CMP was modified by depositing noble (Pt) and non-noble (Fe) metal nanoparticles to create the active catalytic sites for the process of CO2 reduction directly on the polymer surface where CO2 is adsorbed. The metal-doped TPE-CMP electrocatalysts were fully characterized by infrared spectroscopy (IR), thermo-gravimetric analysis (TGA) and transmission electron microscopy (TEM). Then, the as-assembled GDM was tested in our homemade semi-continuous three-electrode electrochemical cell working in gas phase at 60 °C, coupled with a cold trap for the accumulation of the liquid products. Results showed the better performances of the metal-doped TPE-CMP in terms of total productivity (C1–C8 oxygenates) with respect to other kinds of materials that do not show high CO2 adsorption capacity.
The carbon-coated Li3VO4 (Li3VO4/C) sample was synthesized by simple solid-state reaction method using glucose as carbon source. Rietveld refinement, XPS and element analysis results show that, though it is synthesized in the presence of carbon and reducing atmosphere, both the single-phase Li3VO4/C and the valence of vanadium of +5 can be retained. The SEM and TEM images reveal that Li3VO4/C composite has uniform particles with size less than 1μm. Electrochemical testing results show that Li3VO4/C at high operation temperatures holds both higher specific capacity and cyclic performance than that of low temperatures. The initial discharge capacities for the Li3VO4/C electrodes at temperatures of −20, 0, 25 and 50°C are 312, 600, 760 and 721mAhg−1 with the coulombic efficiency of 40.45%, 72.09%, 74.34% and 73.41%, respectively. Even at a high discharge/charge rate of 15C, the capacities of the Li3VO4/C electrodes at −20, 0, 25 and 50°C still can retain about 20, 120, 370 and 450mAhg−1, respectively. The CV results demonstrate that the higher operation temperature can decrease the voltage polarization of the electrode, thus benefit the electrochemical performance of the Li3VO4/C electrode. In addition, the EIS results indicate that larger charge-transfer resistance and smaller lithium diffusion coefficient can be obtained at low operation temperatures, which should be one of the major reasons for its poor low-temperature performance of the Li3VO4/C electrode.
This paper presents an original model capable of simulating the thermal behavior of a vanadium redox flow battery stack in standby condition, i.e. without power and reactant flow, where the temperature distribution in the cells evolves because of ions crossover through the membrane, Joule losses due to shunt currents and inherent self-discharge effects. For the first time, a model is presented that is capable of simulating the cell temperature distribution in the stack and its time evolution considering all above effects. The model is applied to a 9 kW/40-cell stack and validated against measurements from a thermal imager. Numerical results show that shunt currents affect the temperature in the stack and can be responsible for local increases of cell temperatures up to 10 °C if the solutions are initially at high state of charge. This effect can be critical if standby occurs after a period of operation, with the electrolyte stack temperature markedly higher than air temperature. In addition, results show that shunt currents can play a major role in the thermal behavior of compact stacks, based on new materials capable of high power density and low ion crossover. The model presented here can constitute the basis for advanced cooling strategies.
In order to improve the discharge capacity in lithium ion microbatteries, a thick-film cathode was fabricated by a screen printing using LiCoO2 pastes. The printed cathode showed a different discharge curves when the cell was tested using various (liquid, gel and solid-state) electrolytes. When a cell test was performed with organic liquid electrolyte, the maximum discharge capacity was 200μAhcm−2, which corresponded to approximately 133mAhg−1 when the loading weight of LiCoO2 was calculated. An all-solid-state microbattery could be assembled using sputtered LiPON electrolyte, an evaporated Li anode, and printed LiCoO2 cathode films without delamination or electrical problems. However, the highest discharge capacity showed a very small value (7μAhcm−2). This problem could be improved using a poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) gel electrolyte, which enhanced the contact area and adhesion force between cathode and electrolyte. The discharge value of this cell was measured as approximately 164μAhcm−2 (≈110mAhg−1). As the PVDF-HFP electrolyte had a relatively soft contact property with higher ionic conductance, the cell performance was improved. In addition, the cell can be fabricated in a leakage-free process, which can resolve many safety problems. According to these results, there is a significant possibility that a film prepared using the aforementioned paste with screen printing and PVDF-HFP gel electrolyte is feasible for a microbattery.
In cooperation with the industrial project partners ACCUREC Recycling and UVR-FIA a recycling process specially dedicated to portable Li-ion batteries was developed combining a mechanical pretreatment with hydro- and pyrometallurgical process steps. Therefore not only the recovery of cobalt but also the recovery of all other battery components, especially of lithium was of interest. Besides the characterization and evaluation of all generated metallic material fractions, the focus of the research work was the development of a pyrometallurgical process step in an electric arc furnace for the carbo-reductive melting of the fine fraction extracted from spent Li-ion batteries. This fine fraction mainly consists of the cobalt and lithium containing electrode material. Since a selective pyrometallurgical treatment of the fine fraction for producing a cobalt alloy has not been done before, the proof of feasibility was the main aim.
A study has been made of the electrical and electrochemical characteristics of polyvinylidene fluoride (PVDF)-based polymer electrolytes. The room-temperature ionic conductivity of PVDF increases by up to four orders of magnitude on addition of trifluoromethane sulfone (LiCF3SO3), and a further increase is observed with the incorporation of an ethylene carbonate (EC) plasticizer. The conductive behavior of the electrolytes over a wide temperature range (−100 to 100°C) is examined. An electrochemical cell has been fabricated using the film that gives the highest ionic conductivity at room temperature. The discharge characteristics of cells stored/heated at different temperatures have been studied in the 4.2–2.5V voltage range. A greater discharge capacity is delivered on heating. In general, the discharge capacity and the capacity retention increase with the increase in temperature. This can be attributed to a reduction in the interfacial resistance due to an improvement in the electrolyte|electrode interfacial adhesion.
At low levels, carbon monoxide (CO) has physiological roles as a second messenger and neuromodulator1,2. Here we assess the effects of CO in a mouse model of traumatic brain injury (TBI). Treatment with CO-releasing molecule (CORM)-3 reduced pericyte death and ameliorated the progression of neurological deficits. In contrast, although treatment with the radical scavenger N-tert-butyl-a-phenylnitrone (PBN) also reduced pericyte death, neurological outcomes were not rescued. As compared to vehicle-treated control and PBN-treated mice, CORM-3-treated mice showed higher levels of phosphorylated neural nitric oxide synthase within neural stem cells (NSCs). Inhibition of nitric oxide synthase diminished the CORM-3-mediated increase in the number of cells that stained positive for both the neuronal marker NeuN and 5-bromo-2′-deoxyuridine (BrdU; a marker for proliferating cells) in vivo, consequently interfering with neurological recovery after TBI. Because NSCs seemed to be in close proximity to pericytes, we asked whether cross-talk between pericytes and NSCs was induced by CORM-3, thereby promoting neurogenesis. In pericyte cultures that were undergoing oxygen and glucose deprivation, conditioned cell culture medium collected after CORM-3 treatment enhanced the in vitro differentiation of NSCs into mature neurons. Taken together, these findings suggest that CO treatment may provide a therapeutic approach for TBI by preventing pericyte death, rescuing cross-talk with NSCs and promoting neurogenesis.
For the last 5a, the authors have been investigating the transport, fate, natural attenuation and ecosystem impacts of inorganic and organic compounds in releases of produced water and associated hydrocarbons at the Osage-Skiatook Petroleum Environmental Research (OSPER) “A” and “B” sites, located in NE Oklahoma. Approximately 1.0ha of land at OSPER “B”, located within the active Branstetter lease, is visibly affected by salt scarring, tree kills, soil salinization, and brine and petroleum contamination. Site “B” includes an active production tank battery and adjacent large brine pit, two injection well sites, one with an adjacent small pit, and an abandoned brine pit and tank battery site. Oil production in this lease started in 1938, and currently there are 10 wells that produce 0.2–0.5m3/d (1–3bbl/d) oil, and 8–16m3/d (50–100bbl/d) brine. Geochemical data from nearby oil wells show that the produced water source is a Na–Ca–Cl brine (∼150,000mg/L TDS), with high Mg, but low SO4 and dissolved organic concentrations. Groundwater impacts are being investigated by detailed chemical analyses of water from repeated sampling of 41 boreholes, 1–71m deep. The most important results at OSPER “B” are: (1) significant amounts of produced water from the two active brine pits percolate into the surficial rocks and flow towards the adjacent Skiatook reservoir, but only minor amounts of liquid petroleum leave the brine pits; (2) produced-water brine and minor dissolved organics have penetrated the thick (3–7m) shale and siltstone units resulting in the formation of three interconnected plumes of high-salinity water (5000–30,000mg/L TDS) that extend towards the Skiatook reservoir from the two active and one abandoned brine pits; and (3) groundwater from the deep section of only one well, BR-01 located 330m upslope and west of the site, appear not to be impacted by petroleum operations.
In this work, we demonstrated a novel and facile approach to synthesising anode materials for sodium-ion batteries (SIBs). Briefly, 1,3,5-tris(4-aminophenyl)benzene and terephthalaldehyde were used to form porous covalent-organic frameworks (COFs) as precursors for the anodic materials. A simple carbonisation of the COFs at elevated temperatures produced nitrogen-doped, carbon-based materials with interconnected, highly-porous network structures. Of all the carbonisation temperatures experimented, the carbonisation temperature of 800 °C resulted in the best-performing material. This material had a reversible capacity of 303 mA h g−1 at 100 mA g−1 and exhibited excellent stability over 1000 cycles at 100 and 1000 mA g−1 respectively without the aid of any conductive additives. These results offer new possibilities to the field of disordered carbons used in SIBs.
In this work, a novel composite consisting of nanosized silicon highly dispersed within the porous, elastic and conductive oxide/carbon matrix has been developed as an anode candidate for lithium ion batteries. The composite was prepared by a mechanochemical reaction between SiO and Li under ball milling followed by a carbon coating using the pyrolysis of poly(vinyl chloride)–co-vinyl acetate. The porous structure can effectively suppress the volume change of silicon during the electrochemically Li-alloying process. No obvious capacity fading was observed up to 100 cycles with a stable capacity of 620mAhg−1. The factors influencing the microstructure and the electrochemical behavior of the composite were discussed.
Chiral carbon-based nanomaterials possess many superior properties originated both from their nano-sized structure and their chirality. We presented a facile way to synthesize chiral mesoporous carbonaceous nanofibers (chiral MCNFs) through a supramolecular templating method, using a pair of chiral low-molecular-weight gelators as the templates, resorcinol, formaldehyde and tetraethyl orthosilicate as the precursors, respectively. Besides, the chiral MCNFs exhibited optical activity; the electrochemical measurements implied that they also showed good capacitance and lithium-ion storage performances.
A novel methodology to create covalently linked polypeptide-siloxane hybrid materials by controlled n-carboxyanhydride ring opening polymerisation is disclosed. Poly-
The electrochemical properties of β-Zn4Sb3 and Zn4Sb3C7 as new lithium-ion anode materials were investigated. The reversible capacities of the pure Zn4Sb3 alloy electrode and 100h milled Zn4Sb3 in the first cycle reached 503 and 566mAh/g, respectively, but the cycle stability of Zn4Sb3 whether milled or not were obviously bad. It was demonstrated that cycle stability of Zn4Sb3 could be largely improved by milling after mixing with graphite. It was shown that Zn4Sb3C7 composite has a lithium-ion extraction capacity of 581mAh/g at the first cycle and 402mAh/g at 10th cycle.
Thermal traits likely mediate organismal responses to changing thermal environments. As temperatures increase, predicting species responses will depend on understanding how thermal traits vary within and among individuals and across time and space.
Several TIMREX® synthetic and natural graphite negative electrode materials with different particle size distributions were tested with regard to their compatibility with propylene carbonate used as electrolyte component in lithium-ion cells. The first lithium insertion properties of these graphite materials were characterised in electrochemical lithium half-cells containing 1M LiPF6 in ethylene carbonate/propylene carbonate as electrolyte system. Post mortem scanning electron microscopy was applied to study the exfoliation process observed for some of these graphite materials especially with coarser particle sizes. X-ray diffraction, Raman spectroscopy and nitrogen gas adsorption were used to characterise and correlate the material bulk and surface properties of the graphite materials with their electrochemical performance. Differential electrochemical mass spectrometry was applied to study the passivation process of the graphite material surface during the first electrochemical reduction. Non-exfoliating graphite materials indicate the formation of an efficient solid electrolyte interphase, which seems to be kinetically controlled by intrinsic properties of the graphite material bulk and surface.
Abstract Regenerative braking systems for electric vehicles enable the range of the vehicle to be extended, but experience has indicated that the benefits are not always as great as might be expected because of inefficiencies in the power conversion processes. Extra mass and cost can often combine to limit the financial viability of a regenerative braking system. To measure the efficiency of a regenerative braking system, the Tata Ace Electric Vehicle has been tested on a hub-mounted chassis dynamometer, and instrumented to enable calculations for plug-to-wheel efficiency and total range (compared to the same vehicle with little or no regenerative braking). Previously the Tata Ace EV has been tested on the road to optimise the regenerative braking settings for energy recovery. The vehicle’s motor controller allows the field map of the motor to be adjusted, giving full control over the deceleration of the vehicle when the accelerator pedal is released (and subsequent levels of recovered energy). By mounting the vehicle to a calibrated dynamometer, these settings can be validated by monitoring range and efficiency under controlled conditions. The vehicle has been driven at constant speeds and also on the urban section of the New European Drive Cycle, with results presented here.
A facile synthesis of SnO2/corncob-derived activated carbon (CAC) composite was proposed, and the CAC used here has high specific surface area (over 3000 m2/g) and ample oxygen-containing functional groups. The microstructures and morphology as well as electrochemical performance of the SnO2/CAC composites were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and relevant electrochemical characterization. The results show that the mass ratios of SnO2 to CAC have a significant effect on the structures and properties of the composites. The sample with 34% SnO2 delivered a capacity of 879.8 mAh/g in the first reversible cycle and maintained at 634.0 mAh/g (72.1% retention of the initial reversible capacity) after 100 cycles at a current density of 200 mA/g. After 60 cycles at different specific currents from 200 to 2000 mA/g, the reversible specific capacity was still maintained at 632.8 mAh/g at a current density of 200 mA/g. These results indicate that SnO2/CAC can be a desirable alternative anode material for lithium ion batteries.
Abstract Surgical instruments were the earliest products of biomedical engineering. Principal knowledge of the surgical tools used in classical (open) surgery is a precondition to understand the mode of action and design of even more sophisticated instruments as used in flexible endoscopy, laparoscopy, or NOTES. In this chapter, the most important items, such as forceps, clamps, scissors, retractors, and needle holders are explained. The therapeutic use of electrosurgery is described as well as new tissue dissection techniques like ultrasound and water jet dissection. A detailed description of stapling devices is followed by an overview upon suture materials and meshes.
The mechanical condition in stack assembly can impose a significant influence in performance and reliability of the vanadium flow battery. In order to analyze the influence and optimize the overall performance, the effect of clamping force on electrode morphology, mass transfer and polarizations is investigated in this study by measurement of contact resistance and development of a coupled mechanical-electrochemical model. The experimental results indicate that the contact resistance and ohmic polarization decreases with an increase in clamping force, while the simulation results demonstrate that the clamping force can significantly impact on the electrode morphology and mass transport phenomena, and subsequently affect the distributions of activation and concentration polarizations. Despite the concentration polarization presenting to rise at a large clamping force, the overall polarization is proved to be decreased demonstrating that an increased clamping force can offer high voltage efficiency and power density. By further considering the mechanical failure probability and trading off the cell performance and reliability, an optimal clamping force is successfully determined. Such an analysis focusing on assembling condition is vital for understanding the effect of mechanical condition on the battery performance, while also highlighting the significance of rational mechanical design and assembly in flow battery manufacture.
Metal oxide coating on positive active materials in lithium-ion batteries is an effective way to improve its cycleability. However, coating state of the metal oxide layer and the mechanism of the improvement have not been fully understood. In this paper, the coated state of ZrO2 on a LiCoO2 thin-film electrode was investigated using a ferrocene redox reaction, and the role of the ZrO2-coating on the degradation phenomena of the LiCoO2 was investigated. The redox behavior of ferrocene revealed that the ZrO2 layer did not cover the entire surface area of LiCoO2, that is, the ZrO2 layer was not compact and contained cracks. In addition, a lithium-ion deficit phase (Li1−xCoO2) was irreversibly formed on the uncovered LiCoO2 areas. In spite of the imperfect ZrO2 layer, the formation of the lithium-ion deficit phase inside the bulk was suppressed. It is clarified that a partial ZrO2 coating on the LiCoO2 is sufficient to suppress the growth of the lithium-ion deficit phase inside the bulk of LiCoO2.