Electrolyte Volume Research Articles

Electrochemical Reduction of CO2 into Multicarbon Alcohols on Activated Cu Mesh Catalysts: An Identical Location (IL) Study

Potential-dependent CO2 reduction reactions (CO2RR) were carried out on technical Cu mesh supports that were stepwise modified by (i) electrodeposition of dendritic Cu catalysts under mass transfer control of Cu(II) ions followed by (ii) an extra 3 h thermal annealing at 300 °C in air. The initial electrodeposition of dendritic Cu activates the technical supports for highly efficient formate production at low overpotentials (FEFormate = 49.2% at −0.7 V vs RHE) and in particular for C–C coupling reactions at higher overpotentials (FEC2H4 = 34.3% at −1.1 V vs RHE). The subsequent thermal annealing treatment directs the CO2RR product selectivity toward multicarbon alcohol formation (ethanol/EtOH and n-propanol/n-PrOH) resulting into a total Faradaic yield of FEalcohol = 24.8% at −1.0 V vs RHE (FEEtOH = 13%). Moreover, the EtOH and n-PrOH production rate of 155.2 μMLelectrolyte–1 cmECSA–2 h–1 and 101.4 μMLelectrolyte–1 cmECSA–2 h–1 (normalized with respect to the electrolyte volume and the electrochemically a...

Utilization of a new optical sensor unit to monitor the electrochemical elimination of selected dyes in water

This paper presents results obtained by developed optical sensor, which consist from multi-wavelength LED light source and two photodetectors capable of measuring the change in optical signal along two different optical paths (absorbance and reflectance measurements). Arduino microcomputer was used for light source management and optical signal data measuring and recording. Analytical validation of developed optical sensor is presented in this paper. The performance of the system has been tested with varying water solution of dyes (malachite green, methyl orange, trypan red). These results show strong correlations between the optical signal response and colour change from the dyes. Sensor was used for continual in-situ monitoring of electrochemical elimination of selected dyes (current density 15.7 mA cm-2, electrolyte volume 4 L and NaCl concentration 2 g L-1). Maximum decolorization level varies with each dye. For malachite green was obtain 92,7 % decolorization (25 min); methyl orange 90,8% (8,5 min) and trypan red 84,7% decolorization after 33 min of electrochemical treatment.

Critical Impact of Chloride Containing Reference Electrodes on Electrochemical Measurements

AbstractChloride containing reference electrodes, such as various silver‐silver chloride electrodes, are well established in electrochemical analyses. Usually less attention is paid to the influence of potential chloride contamination of electrochemical measurements. Herein, the impact of the chloride leakage rate is studied by means of experiments concerning the anodic oxidation of aluminum. Based on the results, the authors determine critical leakage rates, depending on typical electrolyte volumes and experimental conditions. The results demonstrate that chloride leakage can significantly influence electrochemical measurements, even at ultra‐low leakage rates. A guideline for the usage of chloride containing reference electrodes is deduced from the experimental results and theoretical considerations.

Understanding Performance Fade in High Energy Density Li Batteries

The desire to develop higher performing batteries can be linked with greater demand for long range electric vehicles, longer lasting consumer electronics, and increased use of energy storage technologies in applications such as grid storage. A key to enhancing battery energy density and specific energy for many of these applications is to reduce battery pack size while maintaining or even increasing total capacity. The first attempts at commercializing secondary Li metal batteries occurred over three decades ago.1,2 However, despite this long history there is still a significant gap between desired high energy density Li metal batteries and what can be effectively achieved. One potential route to enhance energy density is the use of a high energy cathode such as nickel-rich lithium nickel manganese cobalt oxide (NMC) in conjunction with a liquid electrolyte and a Li metal negative electrode. In such a configuration, high theoretical energy densities of at least 500 Wh/kg can be realized with optimal utilization of active materials in both the positive and negative electrodes and minimized electrolyte volume. With increased utilization of active materials, there is a respective decrease in volume of electrolyte and other non-active components such as conductive carbon and binder. Each of these reductions has the potential to shift the equilibrium of degradation processes and alter the accumulation of degradation byproducts in higher energy battery systems. This presentation will discuss some of the implications associated with this shift in degradation as the balance of materials transitions from having multiple components in excess to a more energy dense setting with minimal excesses. 1. Whittingham, M. S. History, Evolution, and Future Status of Energy Storage. Proc. IEEE 100, 1518–1534 (2012). 2. Brandt, K. Historical development of secondary lithium batteries. Solid State Ion. 69, 173–183 (1994).

Study of an Organic Alkaline Redox Flow Battery By Means of a Segmented Cell

Reducing the carbon footprint of electricity generation is becoming a major concern. With the development of renewable sources (solar, wind), there is a growing interest for grid-connected storage systems, because they can buffer the intermittency of renewable energy. Among the conceivable storage solutions, the redox flow battery (RFB) is one of the most promising. Its flexibility is very advantageous: power and energy capacity can be tailored independently by stack design and electrolyte volume, respectively. The most popular technology is the all-vanadium redox flow battery, but the French startup Kemwatt is developing an attractive alternative: an alkaline organic redox flow battery. Lots of research papers about RFB are already available but many of them deal with the vanadium technology and are based on modelling [1-2]. Moreover, industrial development has prevailed over laboratory research at this point. But to optimize RFBs and solve the remaining roadblocks to mass production, scientific work is still required for fundamental understanding. In the present work, an instrumented and segmented cell is developed based on Kemwatt’s RFB technology. It is used to perform a fine analysis of the system, by following at the same time the local current density and the potential evolutions inside the cell, as it was already done for hydrogen fuel cells [3-4]. The operating parameters are controlled and local electrochemical characterizations such as polarization curve and impedance spectroscopy are realized. The two electrolytes used in Kemwatt’s system are first characterized separately thanks to a symmetric cell set-up, both sides of the cell being filled with the same electrolyte. The State Of Charge (SOC) of each side is modified as needed by applying a constant current and the impedance variation is measured. It reveals that the resistance is quite constant during a cycle, but increases sharply when the electrolyte composition gets close to 0 or 100% SOC. As shown in the figure, the resistance variation follows the same trend for both electrolytes. However, the study points out the complexity of the electrochemical behavior of the anolyte, which needs to be investigated further. It is also observed that the pressure drops vary with the SOC of the anolyte; an ex-situ rheological study confirms that the fluid properties depend on both its SOC and its age in the process. The catholyte, however, has constant flow properties. These two independent studies inform on the limiting components of the system. A 1D-model is developed and compared to experimental data. By inverse problem method, the membrane resistance and the reaction rate constant are estimated for both electrolytes. The membrane appears as the major resistive contribution; its ionic conductivity is lower than when measured by an ex-situ method. It implies an adverse interaction between the membrane and the electrolytes in the battery. Afterwards, the segmented cell is used to study the whole system. It highlights significant current gradients along the cell at low SOC and pinpoints a mass transport limitation at the channel outlet. These heterogeneities appear earlier during discharge with a lower flow rate, preventing from discharging the electrolytes completely. The results matches the ones obtained with the symmetric cell. References : Xu, Q. et al. Fundamental models for flow batteries. Prog. Energy Combust. Sci. 49, 40–58 (2015).Weber, A. Z. et al. Redox flow batteries: A review. J. Appl. Electrochem. 41, 1137–1164 (2011).Abbou, S. et al. Time Evolution of Local Potentials during PEM Fuel Cell Operation with Dead-Ended Anode. ECS Trans. 58, 1631–1642 (2013).Dillet, J. et al. Impact of flow rates and electrode specifications on degradations during repeated startups and shutdowns in polymer-electrolyte membrane fuel cells. J. Power Sources 250, 68–79 (2014). Figure 1

Modified Electrodes for Improved Performance of Redox Flow Batteries

Redox Flow Batteries (RFBs) are an emerging electrochemical energy storage technology well-suited for intermittent energy sources, such as wind and solar. Integrated RFBs into grid-level energy systems would provide the storage necessary for alternative energy with only slight infrastructure changes. Currently, RFBs are limited by high material costs – from the use of precious metals – and/or low electrochemical activity. This work aims at improving power and energy of low-cost RFB electrolyte systems by doping carbon electrodes to facilitate Faradaic charge transfer at the interface, thereby decreasing costs and increasing accessibility of RFB systems. Carbon electrodes are modified with redox mediators to decrease the voltage drop and to increase charge transfer. Simulated half-cell experiments are conducted using carbon modified electrodes soaked with redox electrolytes s that are separated from pure base electrolytes by alkaline modified Nafion. Full cell testing is performed with modified Nafion separating the catholyte (0.7M Fe(CN)6 •3H2O and 1M NaOH) and the anolyte (0.35M Fe2SO4, 0.4M NaCl, Triethanolamine, and 3M NaOH). These electrolytes provide a test bed for evaluating all Iron RFBs as a cheaper alternative to Vanadium, therefore decreasing raw material cost and environmental impact. Incorporating redox mediators into carbon electrodes improves kinetics elevating voltage efficiency and allowing higher current densities without ebbing discharge voltage. Power is modeled with current and voltage by Ohm’s Law (P=IE). Electrolytes with low inherit voltage efficiency display increased energy density due to fully capturing the redox behavior at raised current densities. Our alkaline discharge voltage difference has a maximum of 1.5 V with our modified electrodes. These electrodes showed a ~10x increase in power with catholyte half-cell testing (305 to 32W/Kg) and a ~4x increase in power with the anolyte (990 to 227Wh/Kg). Energy density improvements were observed for the catholyte (232%) and the anolyte (41%), lowering the volume of electrolyte needed. Long term stability experimentation revealed consistent, coulombic and voltage efficiencies for 1400 cycles (~4 years of daily use). These adaptations to RFB electrodes could also be applied to current RFBs to increase their performance, thereby decreasing material costs and improving cheaper alternatives. Figure 1

(Keynote) Electrolyte Design for High Energy Density Li-S Batteries

Creating a cost effective, high energy density, long cycle life transportation battery based on the lithium – sulfur electrochemical couple requires overcoming a series of scientific and technical challenges (1). These challenges include reducing the electrolyte volume fraction within the cell, increasing the sulfur loading in the cathode, reducing sulfur loss from the cathode and the subsequent redox shuttle of lithium polysulfides, and reducing excess lithium in the anode, all while maintaining the necessary kinetics to support facile charge transport. The Joint Center for Energy Storage Research (JCESR) is redesigning the lithium-sulfur battery using a combination of novel materials concepts to address these challenges. An example is the use of electrolytes that are sparingly solvating of the polysulfide reaction intermediates and that constrain sulfur at the cathode, reducing the quantity of electrolyte necessary within the cell (2). Focus will be placed on the design of a select class of sparingly solvating electrolytes, their structure-function relationship, and their impact on cell performance. Solvent-in-salt electrolytes, loosely referred to as solvates, represent a class of electrolytes in which the saturated lithium polysufide concentration can be tailored to greatly reduce redox shuttling between cathode and anode. Polysulfide solubility restriction has been demonstrated to redirect sulfur reduction from a solution mediated to a semi-solid state path. A number of solvates are shown to exhibit this behavior. Experimental methods are developed to describe the extent of the solvate regime (solvent-to-salt ratio) in these electrolytes using NMR, Raman spectroscopy, and conductivity measurements. Solvates are found to function below target compositions expected for the standard coordination of the lithium cation, raising questions as to details of the local structure and impact on kinetics. Experimental data is complemented by molecular dynamics simulations to gain insight into electrolyte structure at low solvent levels. The benefit of a semi-solid reaction pathway is the possibility of using the electrolyte in concert with the cathode structure to regulate how lithium sulfide is redistributed. The challenge of integrating both electrolyte and cathode design to take advantage of the unique properties of these electrolytes will be discussed. The author acknowledges the contribution of the Joint Center for Energy Storage Research Li-S team in this presentation. This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science. Sandia is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE’s NNSA under contract DE-AC04-94AL85000. 1. Eroglu, D.; Zavadil, K. R.; Gallagher, K. G., J Electrochem Soc 2015, 162, A982-A990. 2. Cheng, L.; Curtiss, L. A.; Zavadil, K. R.; Gewirth, A. A.; Shao, Y.; Gallagher, K. G. ACS Energy Lett. 2016, 1, 503−509.

A simple, fast and accurate in-situ method to measure the rate of transport of redox species through membranes for lithium batteries

Lithium ion conducting membranes are important to protect the lithium metal electrode and act as a barrier to crossover species such as polysulphides in Li-S systems, redox mediators in Li-O2 cells or dissolved cathode species or electrolyte oxidation products in high voltage Li-ion batteries. We present an in-situ method for measuring permeability of membranes to crossover redox species. The method employs a ‘Swagelok’ cell design equipped with a glassy carbon working electrode, in which redox species are placed initially in the counter electrode compartment only. Permeability through the membrane, which separates working and counter electrodes, is determined using a square wave voltammetry technique that allows the concentration of crossover redox species to be evaluated over time with very high precision. We test the method using a model and well-behaved electrochemical system to demonstrate its sensitivity, reproducibility and reliability relative to alternative approaches. This new method offers advantages in terms of small electrolyte volume, and simple, fast, quantitative and in-situ measurement.

Synthesis and electrochemical performances of LiV3O8/poly (3, 4-ethylenedioxythiophene) composites as cathode materials for rechargeable lithium batteries

LiV3O8/poly (3, 4-ethylenedioxythiophene) (LVO/PEDOT) composites were synthesized via an in-situ oxidative polymerization process. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, galvanostatic discharge/charge tests, and electrochemical impedance spectroscopy techniques are used to characterize the as-prepared samples. The results demonstrated that the electrochemical performances of LVO/PEDOT composites have greatly improved in comparison with bare LVO. The discharge capacities of 20wt% LVO/PEDOT composite are 270, 265, 252, 240, and 229mAhg−1 and ˃95% capacity retention is maintained after the charge-discharge 50cycles at the current densities of 60, 90, 120, 180, and 240mAg−1, respectively. A high reversible capacity of 176mAhg−1 (only 58mAhg−1 for the bare LVO) can be maintained after 50cycles at a very high current rate of 2000mAg−1. Electrochemical impedance spectra results implied that the 20wt% LVO/PEDOT composite revealed a decreased charge transfer resistance and increased Li+ ions diffusion ability. This noteworthy improvement is ascribed to the combination of PEDOT, which can act just as a defending layer to inhibit the LVO from direct contact with electrolyte and buffer volume change, and act just as a conductive network to improve the electronic conductivity, thus cycling stability and rate capability are improved.

Evaluation of in Vivo Diuretic Activity of Methanolic Extracts of Clutia Abyssinica (Euphorbiaceae) Roots in Wistar Albino Rats

Introduction: Most parts of the plant Clutia abyssinica is traditionally used in different diseases because of their medicinal properties. The roots are widely used traditionally, as diuretic purpose, liver problems, enlarged spleen and kidney problems. The present study was carried out to evaluate the diuretic effect of methanolic extracts of Clutia abyssinica roots in rats in comparison with standard drug furosemide. Methodology: Thirty rats of either sex were randomly allocated into five groups of six each. The rats were pretreated with physiological saline (0.9% NaCl, po) at a dose of 25 ml/kg, to impose uniform water and salt load. The control group received normal saline (20 ml/kg po), the standard group received furosemide (10mg/kg, po) and the test groups were administered different doses of the crude methanolic extract (100, 200 and 400mg/kg, po) respectively and urine was collected from individual rat for a period of 24 hrs. The urine volume and concentration of urine electrolytes were measured. Result: At medium (M200) and maximum (M400) doses of Clutia abyssinica had a significant urine output at the end of 6 hr (p<0.001) and 24hr (p<0.05) when compared with control group. Effect on electrolyte excretion showed in both 6hr and 24hr had an increased natriuresis (p<0.001 for both time of collection) and kaliuresis (p<0.05 for 6hr and p<0.001 for 24hr urine) at M400 dose, while the kaliuresis effect was smaller at M100 doses when compared with standard. The plant was also found to be safe at a maximum dose of 2000 mg/kg for methanolic extracts. Conclusions: These findings indicate that crude extract of Clutia abyssinica roots has good diuretic activity on rat model. However, future studies should focus on its exact mechanisms of action and isolating the phytochemical component(s) responsible for diuresis. Keywords: Diuretics, Clutia abyssinica, natriuretic index, saluretic index

Porous cobalt chalcogenide nanostructures as high performance pseudo-capacitor electrodes

Electrochemical supercapacitor is an essential technology that is pivotal for the development of reliable energy storage devices. Herein, we report the fabrication of supercapacitor electrodes using nanostructured porous cobalt chalcogenide (CoTe2 and CoSe2) electrodes, anticipating an enhanced performance owing to their higher contact area with electrolyte and large pore volume enabling shorter diffusion paths for ion exchange. In this regard, we synthesized CoTe2 and CoSe2 nanostructures via an anion-exchange-reaction between pre-synthesized Co(OH)2 hexagonal nanosheets and chalcogen (tellurium and selenium) ions under hydrothermal conditions. Structural, morphological and compositional properties of the as-synthesized materials are examined using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. Pseudo-capacitive properties of CoTe2 and CoSe2 nanostructures as working electrodes are studied through cyclic voltammetry and galvanostatic charge-discharge methods using an electrochemical workstation. CoSe2 electrode delivered a specific capacitance of 951Fg−1 at a scan rate of 5mVs−1, which surprisingly is almost three times higher in comparison to CoTe2 electrode (360Fg−1). Both CoTe2 and CoSe2 electrodes exhibited good capacitance retention capability for 2500 CV cycles. The superior electrochemical performance of the nanoporous CoSe2 electrode indicate their applicability for high-performance energy storage device applications.

The Oxidative Destruction of Substandard Tributyl Phosphate Organic Solutions under Mild Conditions

The liquid-phase oxidative destruction of 30% solution of tributyl рhosphate in kerosene has been carried out under the action of oxidants generated by the electrical current which has been passed through 40% aqueous solutions of the sulfuric acid under atmospheric pressure and at temperature of 50 °C. Tributyl phosphate and its solvent have been partly destroyed due to the electrochemical processes on the lead electrodes, however, a large part of components has been subjected to deep oxidation in the volume of electrolyte. As a result of oxidation, the following final products have been formed: phosphoric acid, mono- and dicarboxylic acids, carbon dioxide and water.

Gold Electrowinning from Cyanide Solutions Using Three-Dimensional Cathodes

Work is devoted to studying electrowinning of precious metals, in particular gold, in rich cyanide solutions on three-dimensional cathodes of electronegative metals. The object studied is production solution obtained during cyanide leaching of gravitation concentrates containing about 95 g/m3 of gold, 30 g/m3 of silver, and 6.5 g/dm3 CN–. The effect of current density, electrolyte volume consumption, and cathode material on the degree of gold extraction are studied. An operating regime is established making it possible to extract more than 99% gold with a residual concentration below 0.1 g/m3.

Diuretic activity of the aqueous crude extract and hot tea infusion of Moringa stenopetala (Baker f.) Cufod. leaves in rats.

Moringa stenopetala (Baker f.) Cufod. is a medicinal plant that has been used for the treatment of different ailments such as hypertension and diabetes in Ethiopia. This study aims to assess the diuretic activity of the aqueous crude extract and hot tea infusion of M. stenopetala leaves in saline-loaded rats. Male Wistar rats were divided into ten groups (n = 5). The control group received distilled water (5 mL/kg), whereas the reference group received Furosemide (10 mg/kg). Groups III–X orally received different doses of aqueous crude extract (62.5, 125, 250, and 500 mg/kg) and hot tea infusion (1, 2, 4, and 6 teaspoons [Tsp]) based on community use. Urine volume was recorded every hour until the end of the 5th hour, and total urine volume of each animal was calculated. The diuretic activity and diuretic action were determined based on the urine output. Additionally, concentration of urinary sodium, chloride, and potassium ions was determined. The urinary Na+/K+ ratio and carbonyl anhydrase activity (Cl−/(Na+/K+)) were also assessed. The findings verified that the aqueous crude extract as well as the hot tea infusion of the leaves of M. stenopetala possesses significant (P < 0.01) diuretic, natriuretic, and kaliuretic effects. The aqueous crude extract (125 mg/kg) and hot tea infusion (2 Tsp) displayed the highest diuretic activity (101% and 96%, respectively) comparable to the reference drug, Furosemide (10 mg/kg). They also displayed a good natriuretic activity. The aqueous crude extract and hot tea infusion revealed a significant Na+ urinary excretion (P < 0.001) and Na+/K+ ratio (P < 0.05) at all test doses. There was also a significant (P < 0.01) Cl− urinary excretion at all test doses of aqueous crude extract except 62.5 mg/kg and all test doses of hot tea infusion except higher doses (4 and 6 Tsp). Thus, the aqueous crude extract as well as the hot tea infusion of the leaves of M. stenopetala causes a plausible increase in the urine volume and concentration of urinary electrolytes in rats.

Electrolyte Volume Effects on Electrochemical Performance and Solid Electrolyte Interphase in Si-Graphite/NMC Lithium-Ion Pouch Cells.

This study aims to explore the correlations between electrolyte volume, electrochemical performance, and properties of the solid electrolyte interphase in pouch cells with Si-graphite composite anodes. The electrolyte is 1.2 M LiPF6 in ethylene carbonate:ethylmethyl carbonate with 10 wt % fluoroethylene carbonate. Single layer pouch cells (100 mA h) were constructed with 15 wt % Si-graphite/LiNi0.5Mn0.3CO0.2O2 electrodes. It is found that a minimum electrolyte volume factor of 3.1 times to the total pore volume of cell components (cathode, anode, and separator) is needed for better cycling stability. Less electrolyte causes increases in ohmic and charge transfer resistances. Lithium dendrites are observed when the electrolyte volume factor is low. The resistances from the anodes become significant as the cells are discharged. Solid electrolyte interphase thickness grows as the electrolyte volume factor increases and is nonuniform after cycling.

Ethnopharmacological investigations of the cardio-renal properties of a native species from the region of Pantanal, state of Mato Grosso do Sul, Brazil

Ethnopharmacological relevanceAcanthospermum hispidum DC. is an important medicinal herb that belongs to family Asteraceae, popularly used as a diuretic and hypotensive in the region of Pantanal, state of Mato Grosso do Sul, Brazil. Despite the relevance of this species throughout the country, there are no detailed studies about its possible ethnobotanical indication. AimTo carry out a detailed ethnopharmacological investigation of the cardio-renal properties of A. hispidum. Materials and methodsFirst, a detailed morpho-anatomical study with the purpose of characterizing and providing quality control parameters for the species was carried out. Then, purified aqueous extract (ESAH) was obtained and a detailed phytochemical investigation about its main secondary metabolites was performed. In addition, a thorough acute toxicological study was conducted to evaluate the actual toxic effects of this preparation. Finally, the possible diuretic and hypotensive effects of ESAH on male Wistar rats (30, 100, 300mg/kg; intraduodenally) were evaluated, and using pharmacological antagonists or inhibitors, the involvement of prostaglandin/cAMP and nitric oxide/cGMP pathway and potassium channels in ESAH-induced hypotension was investigated. ResultsThe analyses performed by liquid chromatography–mass spectrometry showed that the main secondary metabolites present in ESAH were phenolic compounds, such as caffeoylquinic acids (chlorogenic acid), dicaffeoylquinic acids and glycosylated flavonoids (quercetin glucoside and galactoside). ESAH did not induce any acute toxic effects and did not affect the urinary volume or renal excretion of electrolytes in Wistar rats. On the other hand, intraduodenal administration of ESAH induces a significant acute hypotensive effect. Previous treatment with N(G)-nitro-L-arginine methyl ester, methylene blue, or tetraethylammonium fully avoided the hypotensive effect of ESAH. All other parameters were not affected by treatment with ESAH. ConclusionData obtained in this study allow us to suggest that ESAH obtained from A. hispidum presents an important acute hypotensive effect, which appears to be dependent on the nitric oxide/cGMP pathway. This study presents new evidences about the therapeutic potential of this species when acute hypotensive response is required.

Influence of the Electrolyte on the Internal Resistance of Lithium−Sulfur Batteries Studied with an Intermittent Current Interruption Method

AbstractGalvanostatic cycling combined with a modified intermittent current interruption resistance determination method is presented as a fast, accurate, and comparatively simple analytical tool for following internal resistance changes in batteries over long‐term cycling. The technique is demonstrated here to study the influence of electrolyte composition and volume on the internal resistance of lithium−sulfur (Li−S) batteries. This approach is found to be particularly useful for the study of the Li−S system, where resistance changes considerably during charge and discharge as a result of compositional changes to the positive electrode and the electrolyte, but may also be valuable in the study of other battery systems.

Electrochemical drilling of multiple small holes with optimized electrolyte dividing manifolds

Structures with multiple small holes have been widely used to aid cooling in aeronautical engine components. Electrochemical drilling uses a side-insulated tube as the tool cathode and removes anodic material via controlled electrochemical reactions in a cell. The flexibility for simultaneous drilling makes electrochemical drilling a feasible technique for producing multiple small holes. In multiple hole electrochemical drilling, uneven electrolyte volume divided to each tube electrode would cause each hole machining status different. This paper addresses the design of an electrolyte dividing manifold for use in electrochemical drilling of multiple holes. Structural parameters such as the distance from the manifold inlet to the first tube electrode, the manifold inlet diameter and the tube electrode length have obvious effects on the electrolyte distribution along the electrode array. Experiments illustrate an optimized manifold structure is feasible for practical fabrication. Finally, two types of hole arrays are successfully fabricated.

Operando Spectromicroscopy of Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are a “beyond Li-ion” technology that provides high capacity (1675 mAh g-1) while also being low cost, earth-abundant, and lightweight. Li-S batteries have a unique chemistry that achieves high capacity via chemical transformation rather than Li intercalation as in Li-ion. Elemental sulfur S8 is reduced through a series of soluble Li polysulfides (Li2Sx, 2 ≤ x ≤ 8) to a final solid discharge product Li2S, and the process is reversed upon charging. However, Li-S suffers from unrealized theoretical capacity and rapid capacity fade due to loss processes that are not well-understood. Batteries are spatially and chemically heterogeneous. Deciphering the chemical states of sulfur and the distribution of dissolved polysulfides in the anode, cathode, and especially the electrolyte during cycling is critical for realizing the potential of Li-S. We present operando characterization using sulfur K-edge X-ray absorption spectromicroscopy performed at the Stanford Synchrotron Radiation Lightsource (SSRL, BL 14-3). Synchrotron radiation provides the high energy resolution and micron-scale beam size needed to distinguish complicated polysulfide spectral features in the tender X-ray regime. From this information, we can observe a spatially and chemically varied system to gain insight into how sulfur speciation and spatial distribution contribute to capacity fade. Typically, operando X-ray characterization is conducted perpendicular to battery electrodes, providing an average of the chemistry throughout the entire stack. The cross-sectional pouch cell geometry presented here provides a spatially resolved picture of sulfur diffusion between the cathode and anode, which cannot be achieved by typical characterization methods. Cells consisting of a sulfur/carbon cathode, Li anode, and 1 M LiClO4 + 0.5 LiNO3 in 1,3-dioxolane/1,2-dimethoxyethane (DOL/DME) were discharged, and maps were collected at energies sensitive to the sulfur and Li polysulfide species. Tuning the incident X-ray energy allows for targeted observations of species such as polysulfides, sulfates, elemental sulfur, and lithium sulfide during cycling. A novel electrochemical cell with well-defined electrode geometry, electrolyte volume, and current collection has been designed at SSRL to map the battery cross-section in fluorescence mode. This cell will mitigate the challenges of using pouch cells for X-ray experiments such as water and oxygen contamination and sample-to-sample variation. It will also provide more robust, longer-term cycling that better replicates the offline electrochemistry of a typical coin or pouch cell. Because the new cell will increase reproducibility, we can alter electrode architecture and electrolyte composition to directly compare polysulfide and sulfur distributions, illuminating the direct influence that these parameters have on battery chemistry. Using this new design, changes in sulfur and polysulfide chemistry are systematically correlated to structure and performance.

Analysis of prognostic factors for acute kidney injury with continuous renal replacement therapy in severely burned patients

Acute kidney injury (AKI) is a critical complications in severely burned patients associated with high morbidity and mortality. The purpose of this study was to investigate the impact of severity of AKI at the time of continuous renal replacement therapy (CRRT) start on patient outcome and to identify the prognostic factors in severely burned patients with CRRT application. From January 2007 to June 2010, 84 burn patients with more than 40% of total body surface area (TBSA) burned who treated with continuous renal replacement therapy for acute kidney injury were analyzed retrospectively. There was no significant difference of mortality by the severity of AKI at the time of CRRT start. However, the mean TBSA burned, abbreviated burn severity index, arterial pH, partial pressure of carbon dioxide (PaCO2) and blood urea nitrogen (BUN)/creatinine (Cr) ratio had a statistical significance to predict mortality in receiver operation characteristic curve. In a multivariate logistic regression analysis, only sepsis had an independent association with mortality. The severity of the AKI at the time of CRRT start did not have significant relationship with patient outcome. CRRT can be applied to minimize the complication of AKI including electrolyte imbalance and volume overload. Because only the presence of sepsis was independently associated with mortality, treatment for sepsis should be focused to improve the survival of the severely burned patients with CRRT.