The selected Moutai aromatic microorganisms and their metabolites were applied into the fermentation of tobacco leaves in order to improve the tobacco quality. The results showed that a variety of ...aromatic substances in Moutai, as well as the typical flavor substances commonly used in cigarettes, were detected in the fermented tobacco leaf extract. In view of the GC-MS results as well as the sensory smoking evaluation of tobacco leaf extracts under designed experimental conditions, the optimal parameters of stable single-strain fermentation process was at 40 ℃ for 10-15 days. The results of specific effects of different fermentation conditions on the content of aroma substances in different parts of tobacco leaves after fermentation, as well as the subsequent sensory evaluation, provided basic data for the improvement of tobacco fermentation and aroma flavoring technology, which was conducive to the development of new cigarettes.
The polymer binder is a key constituent of silicon‐based electrode formulation for lithium‐ion batteries. However, its extremely difficult visualization in fresh electrodes becomes completely ...impossible in cycled electrodes. Here, the combination of scanning transmission electron microscopy—valence electron energy‐loss spectroscopy with the use of a specific electrolyte solvent composition (a mixture of dimethyl carbonate and fluoroethylene carbonate, without ethylene carbonate) allows the visualization, for the first time, of the binder in silicon‐based electrodes, even cycled up to 100 cycles. Such an observation is possible as the only solid degradation product of this electrolyte is LiF, as confirmed by quantitative 7Li and 19F magic angle spinning nuclear magnetic resonance. The electrodes, based on a blend of silicon and graphite, have a very high surface capacity, 6.5 mAh cm−2, which makes them meaningful for electric vehicle applications. The performance is appreciable, in particular the first cycle efficiency approaching that of commercial graphite electrodes, as well as the capacity retention in full cell, versus LiNi0.5Mn0.3Co0.2O2, 60% after 100 cycles. This work also illustrates the ultimate state of destructuration of silicon after long cycling, which invites new ways of thinking about the design of this material.
A negative electrode for Li‐ion batteries, made with nanostructured silicon blended with graphite and polyacrylic acid binder, shows good cyclability in fluoroethylene carbonate rich and ethylene carbonate free electrolyte. The absence of lithiated organic electrolyte degradation products allows the visualization of the binder, its distribution at the surface of the active materials in the pristine electrode and its evolution throughout cycling.
Polyacrylic Binders
In article number 2103348, Bernard Lestriez and co‐workers use the combination of STEM‐VEELS with the use of a specific electrolyte solvent composition to visualize, for the first ...time, the binder (polyacrilic acid, in blue) in silicon‐based electrodes, even after up to 100 cycles. Such an observation is possible thanks to the fact that the only solid degradation product of this electrolyte is LiF (in green), as confirmed by NMR.
In the present work, an alternative to the standard ex-situ and destructive focused ion beam scanning electron microscopy (FIB/SEM) analysis procedure is demonstrated for monitoring the morphological ...degradation of a single Si/graphite (1/1 mass ratio) blended electrode for Li-ion batteries. For this purpose, a FIB milled microcavity is created in the pristine electrode, which is observed in FIB- polished cross section by SEM at different cycling periods (pristine, 1st, 9th and 50th cycles). This allows studying the same cycled electrode as for an in-situ method. Its cycling-induced morphological change is characterized at the electrode and particle scales by monitoring the evolution of the electrode thickness, mass and porosity, the Si particle morphology, Si interparticle distance, surface fraction and twisting of the graphite flakes. This is correlated to the evolution of the electrode discharge capacity and impedance. As a result, a more comprehensive view of the degradation phenomena of the Si/graphite blended electrode is established.
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•An investigation technique based on sequential FIB/SEM analysis is demonstrated.•Cycling-induced morphological change of a single Si/Gr electrode is studied.•Morphological changes are correlated with EIS measurements.•The methodology can be extended to other battery systems.
The role of the physicochemical properties of the water-soluble polyacrylic acid (PAA) binder in the electrochemical performance of highly loaded silicon/graphite 50/50 wt % negative electrodes has ...been examined as a function of the neutralization degree x in PAAH1–x Li x at the initial cycle in an electrolyte not containing ethylene carbonate. Electrode processing in the acidic PAAH binder at pH 2.5 leads to a deep copper corrosion, resulting in a significant electrode cohesion and adhesion to the current collector surface, but the strong binder rigidity may explain the big cracks occurring on the electrode surface at the first cycle. The nonuniform binder coating on the material surface leads to an important degradation of the electrolyte, explaining the lowest initial Coulombic efficiency and the lowest reversible capacity among the studied electrodes. When processed in neutral pH, the PAAH0.22Li0.78 binder forms a conformal artificial solid electrolyte interphase layer on the material surface, which minimizes the electrolyte reduction at the first cycle and then maximizes the initial Coulombic efficiency. However, the low mechanical resistance of the electrode and its strong cracking explain its low reversible capacity. Electrodes prepared at intermediate pH 4 combine the positive assets of electrodes prepared at acidic and neutral pH. They lead to the best initial performance with a notable areal capacity of 7.2 mA h cm–2 and the highest initial Coulombic efficiency of around 90%, a value much larger than the usual range reported for silicon/graphite anodes. All data obtained with complementary characterization techniques were discussed as a function of the PAA polymeric chain molecular conformation, microstructure, and surface adsorption or grafting, emphasizing the tremendous role of the binder in the electrode initial performance.
In need of increasing automotive applications, it is necessary to find both higher capacity and higher-capacity retention electrode materials for Li-ion batteries. Among the candidates for negative ...electrode 1, silicon appears as an attractive alternative to graphite due to its natural abundance, high specific gravimetric capacity (3579 mAh.g
-1
vs. 372mAh.g
-1
for graphite) and a large volumetric capacity (2081 mAh.cm
-3
vs. 779 mAh.cm
-3
). Silicon based electrodes nevertheless suffer from poor cyclability usually due to dramatic volume expansion of the electrode during the cycling and electrolyte reduction 2. As a consequence, irreversible capacity losses are not limited to the first few cycles, but may continue to deteriorate cell performance and life 3, 4.
On one hand, previous studies demonstrated that the formulation 5, the processing 6 of the composite electrode and the adhesion to the current collector are critical for Si with respect to the electrochemical performance. The design of a flexible network of shaped conductive additives bonded with an aqueous binder to silicon particles through an optimized ratio of covalent and hydrogen bonds greatly help in facilitating a homogeneous functioning of the electrode that minimizes electrolyte reduction and keep the mechanical integrity of the electrode. On the other hand, using a combined silicon/graphite material also help in mitigating volume variations expected to occur upon cycling, especially for high mass loading electrodes (>3-4 mg).
In this study, we use both approaches by tuning the binder incorporation in the case of a 50/50 %wt Silicon/Graphite composite electrodes. We focus here in particular on the electrode formulation, using a polyacrylic acid polymer binder thanks to its grafting mechanism to silicon particles enabling a strong mechanical cohesion even in the case of high-loaded electrodes. 7 pH and viscosity adjustments of the electrode slurry will be discussed, as they seem to have a remarkable effect at the interface between electrode and current collector. In fact, the longer drying process (due to thicker coating) exacerbate different corrosion mechanisms and migration phenomena that were not observed previously for thin electrodes usually studied. Characterizations on this interface were carried out, combining XPS and SEM, in order to offer a further comprehension of Si/Gr cycling performance as a function of electrode preparation.
Reference :
1) Kasavajjula, U., Wang, C. & Appleby, A. J. Nano- and bulk-silicon-based insertion anodes for lithium-ion secondary cells.
163,
1003–1039 (2007).
2) Obrovac, M. N. & Chevrier, V. L. Alloy negative electrodes for Li-ion batteries.
Chem. Rev.
114,
11444–11502 (2014).
3) Ryu, J. H., Kim, J. W., Sung, Y. & Oh, S. M. Failure Modes of Silicon Powder Negative Electrode in Lithium Secondary Batteries.
Electrochem. Solid-State Lett.
7,
306–309 (2004).
4) Beaulieu, L. Y.
et al.
Colossal Reversible Volume Changes in Lithium Alloys service Colossal Reversible Volume Changes in Lithium Alloys.
Electrochem. Solid-State Lett.
4,
A137 (2001).
5) Mazouzi, D.
et al.
Critical roles of binders and formulation at multiscales of silicon-based composite electrodes.
J. Power Sources
280,
533–549 (2015).
6) Nguyen, B. P. N., Chazelle, S., Cerbelaud, M., Porcher, W. & Lestriez, B. Manufacturing of industry-relevant silicon negative composite electrodes for lithium ion-cells.
J. Power Sources
262,
112–122 (2014).
7) Mazouzi, D., Lestriez, B., Roué, L. & Guyomard, D. Silicon Composite Electrode with High Capacity and Long Cycle Life.
Electrochem. Solid-State Lett.
12,
A215 (2009).
In this study, we described a novel impedance biosensor combining immunomagnetic separation with urease catalysis for sensitive detection of foodborne bacteria using Listeria monocytogenes as model ...and an immobilization-free microelectrode as detector. The monoclonal antibodies (MAbs) were immobilized on the surface of the magnetic nanoparticles (MNPs) with the diameter of 180nm by biotin–streptavidin system for specifically and efficiently separating Listeria cells from sample background. The polyclonal antibodies (PAbs) and the urease were modified onto the surface of the gold nanoparticles (AuNPs) with the diameter of 20nm and the modified AuNPs were used to react with Listera to form the MNP–MAb–Listeria–PAb–AuNP–urease sandwich complexes. The urease in the complexes could catalyze the hydrolysis of the urea into ammonium carbonate and this led to an increase in the ionic strength of the media, which could be detected by the microelectrode. The magnetic separation efficiencies for L. monocytogenes at the concentrations ranging from 3.0×101 to 3.0×104CFU/mL were over 95% for the pure cultures and over 85% for the spiked lettuce samples. The lower detection limit of this biosensor for L. monocytogenes was found to be 300CFU/mL in both the pure cultures and the spiked lettuce samples. The microelectrode was demonstrated to be reusable for over 50 times with thorough cleaning by deionized water. This biosensor showed its potential to provide a simple, low-cost and sensitive method for rapid screening of foodborne pathogens and could be extended for detection of other biological or chemical targets.
•The detection limit of this biosensor was 30CFU/mL for Listeria monocytogenes.•The microelectrode was free of immobilization and could be reused for >50 times.•Urease catalysis was successfully used to amplify the detection signal.•The separation efficiency of Listeria was ~90% for pure culture and spiked samples.
Early screening of pathogenic bacteria is a key to prevent and control of foodborne diseases. In this study, we developed a fast and sensitive bacteria detection method integrating electrochemical ...impedance analysis, urease catalysis with microfluidics and using Listeria as model. The Listeria cells, the anti-Listeria monoclonal antibodies modified magnetic nanoparticles (MNPs), and the anti-Listeria polyclonal antibodies and urease modified gold nanoparticles (AuNPs) were incubated in a fluidic separation chip with active mixing to form the MNP-Listeria-AuNP-urease sandwich complexes. The complexes were captured in the separation chip by applying a high gradient magnetic field, and the urea was injected to resuspend the complexes and hydrolyzed under the catalysis of the urease on the complexes into ammonium ions and carbonate ions, which were transported into a microfluidic detection chip with an interdigitated microelectrode for impedance measurement to determine the amount of the Listeria cells. The capture efficiency of the Listeria cells in the separation chip was ∼93% with a shorter time of 30min due to the faster immuno-reaction using the active magnetic mixing. The changes on both impedance magnitude and phase angle were demonstrated to be able to detect the Listeria cells as low as 1.6×102CFU/mL. The detection time was reduced from original ∼2h to current ∼1h. The recoveries of the spiked lettuce samples ranged from 82.1% to 89.6%, indicating the applicability of this proposed biosensor. This microfluidic impedance biosensor has shown the potential for online, automatic and sensitive bacteria separation and detection.
•Phase angle shift was successfully used for determination of Listeria.•The detection limit of this biosensor was 102CFU/mL for Listeria.•The detection time was reduced to 1h due to on-chip passive mixing.•The recoveries of Listeria cells in the spiked samples was ∼85%.
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•The impact of flue gas on the toluene oxidation was researched for the first time.•By-products of toluene oxidation induced reduction of the COx selectivity.•NH3 was the key ...component responsible for reducing the COx selectivity.•NH3 promoted the formation of nitriles and inhibited the generation of maleic acid.
The impact of the complex flue gas (containing SO2, NO, NH3, O2 and H2O) on the synergistic elimination of toluene and NOx over over V2O5-MoO3(WO3)/TiO2 in the SCR section was systematic researched for the first time. NO and SO2 proved to be mutually repressive in reaction and competitive in absorption. Moreover, NH3 was identified as the key factor responsible for reducing the COx selectivity in the catalytic oxidation of toluene. It promoted the generation of nitriles and indirectly inhibited the generation of benzoic acid, nitrobenzene, and maleic acid (the product of benzene ring opening). In addition, 16 types of polycyclic aromatic hydrocarbons (PAHs) were detected in the exhaust emissions from the flue gas, among which the content of naphthalene was the highest. The V2O5-MoO3(WO3)/TiO2 catalysts displayed low selectivity and generated a lot of by-products with high environmental risk, even though it had a high VOCs removal rate.
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