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1
المؤلفون: Umair Gulzar, Alex Lonergan, Vladimir Egorov, Yan Zhang, Alex Grant, Aoife Carroll, Colm O’Dwyer
المصدر: Journal of The Electrochemical Society. 170:030503
مصطلحات موضوعية: Energy storage, Renewable Energy, Sustainability and the Environment, Materials Chemistry, Electrochemistry, Battery, Lithium, Condensed Matter Physics, Materials, Sulfur, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
الوصف: Despite limited commercial success, lithium sulfur technology (LST) is still far from competing existing Li-ion technology. One of the main reasons hindering the success of LST is the complexity of lithium-sulfur chemistry during electrochemical charging and discharging. Dissolution of sulfur species in the electrolyte solution exacerbates the difficulties of this system. Therefore, a comprehensive understanding of sulfur species and their kinetics during charge/discharge process is paramount for a high-performance lithium-sulfur battery. We present a new technique we refer to as Ampero-Coulometry, which takes the chronoamperometric (galvanostatic) charge-discharge curves and mathematically transforms them to a series of curves that reveal the cation diffusional rate inside carbon-sulfur porous electrodes at different states of charge/capacity. This technique allowed us to track the overall Li+ ion diffusional rate inside a Li-S cell over a complete state of discharge. As dissolution of sulfur species and their interplay inside a porous sulfur electrode has a significant role in limiting Li-S battery capacity, and method allows correlation between the known mechanism of polysulfide dissolution, the kinetics of a sulfur electrode, and its response.
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2
المؤلفون: F. J. Günter, J. Keilhofer, V. Böhm, R. Daub, G. Reinhart
المصدر: Journal of The Electrochemical Society. 169:050522
مصطلحات موضوعية: Renewable Energy, Sustainability and the Environment, Batteries and Energy Storage, Batteries-Li-ion, Theory and Modelling, Energy Storage, Electroanalytical Electrochemistry, Materials Chemistry, Electrochemistry, Condensed Matter Physics, ddc, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
الوصف: The wetting of the porous electrodes and the separator is crucial in the production of lithium-ion cells. Electrochemical impedance spectroscopy is able to measure and characterize the wetting. This paper p resents an equivalent circuit for commercial high-capacity cells and shows a method to analyze the wetting of these cells. The equivalent circuit includes an external inductance, a transmission line model (TLM) for the description of the pore impedance and, additionally, a TLM for the impedance of substrate foil inductance and contact resistance. Based on symmetric and full laboratory cells, the superposition of the impedance is discussed. Furthermore, the method to adjust the impedance and analyze the wetting is demonstrated on hard case cells with a capacity of 22 Ah. It is shown that, in addition to inductance for cables and electrode-external contacts, high-capacity lithium-ion cells build up inductance due to the electrode area in combination with the substrate foil. This inductance, together with the contact resistance, result in a characteristic hook in the Nyquist plot. A TLM describes and explains this behavior quite well. Additionally, the impedance of the cell is adjustable so that it corresponds to a laboratory cell in blocking conditions. Thus, the wetting of the separator and the wetting of the electrode become separately evaluable and calculable.
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المؤلفون: Louis Hartmann, Cheuck Hin Ching, Tim Kipfer, Max Koch, Hubert A. Gasteiger
المصدر: Journal of The Electrochemical Society. 169:070516
مصطلحات موضوعية: Renewable Energy, Sustainability and the Environment, Batteries and Energy Storage, Materials Chemistry, Electrochemistry, Condensed Matter Physics, ddc, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
الوصف: Li- and Mn-rich battery active materials like Li1.14(Ni0.26Co0.14Mn0.60)0.86O2 (LMR-NCM) are promising cathode active materials (CAMs) for next-generation Li-Ion batteries, as they combine a higher energy density than state-of-the-art materials at lower materials cost. However, they suffer from high gassing, particularly during formation, and from voltage and capacity fading over their cycle life. While electrolyte additives are known to alleviate these issues, it will be shown that a surface modification of LMR-NCM CAMs can also reduce their gassing during formation and improve their long-term stability. Here, we present a detailed analysis of a water-based post-treatment for LMR-NCMs, which not only lowers their initial gassing by more than 90%, but also avoids the issue of transition metal dissolution observed with conventionally used washing procedures at low ph. We thus utilized a buffered solution to increase the pH into the stability window of LMR-NCM materials (near/above pH 7), while also providing a controlled Li+/H+-exchange that is not possible with unbuffered aqueous solutions like pure H2O, H2O/alcohol mixtures, or acids. TGA-MS experiment showed that heating of Li+/H+-exchanged LMR-NCM leads to the formation of a protective (near-)surface spinel layer, and full-cell cycling displayed a drastic improvement of the capacity retention.
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المؤلفون: Maximilian Möckl, Matthias F. Ernst, Matthias Kornherr, Frank Allebrod, Maximilian Bernt, Jan Byrknes, Christian Eickes, Christian Gebauer, Antonina Moskovtseva, Hubert A. Gasteiger
المصدر: Journal of The Electrochemical Society. 169:064505
مصطلحات موضوعية: Fuel Cells, Electrolyzers, and Energy Conversion, Focus Issue on Advanced Electrolysis for Renewable Energy Storage, Proton exchange membrane water electrolysis (PEMWE), PEMWE short stack durability testing, low iridium loading OER catalyst, Renewable Energy, Sustainability and the Environment, Materials Chemistry, Electrochemistry, Condensed Matter Physics, ddc, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
الوصف: Lowering the iridium loading at the anode of proton exchange membrane (PEM) water electrolyzers is crucial for the envisaged GW-scale deployment of PEM water electrolysis. Here, the durability of a novel iridium catalyst with a low iridium packing density, allowing for low iridium loadings without decreasing the electrode thickness, is being investigated in a 10-cell PEM water electrolyzer short stack. The anodes of the membrane electrode assemblies (MEAs) of the first five cells utilize a conventional iridium catalyst, at loadings that serve as benchmark for today's industry standard (2 mgIr cm−2). The last five cells utilize the novel catalyst at 8-fold lower loadings (0.25 mgIr cm−2). The MEAs are based on Nafion® 117 and are tested for 3700 h by load cycling between 0.2 and 2.0 A cm−2, with weekly polarization curves and impedance diagnostics. For both catalysts, the performance degradation at low current densities is dominated by an increase of the overpotential for the oxygen evolution reaction (OER), whereby the OER mass activity of the novel catalyst remains ≈4-fold higher after 3700 h. The temporal evolution of the OER mass activities of the two catalysts will be analyzed in order to assess the suitability of the novel catalyst for industrial application.
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المؤلفون: Menghsuan Sam Pan, Liang Su, Stephanie L. Eiler, Linda W. Jing, Andres F. Badel, Zheng Li, Fikile R. Brushett, Yet-Ming Chiang
المصدر: Journal of The Electrochemical Society. 169:060524
مصطلحات موضوعية: sulfide solutions, optical-spectra, batteries, constant, kinetics, Renewable Energy, Sustainability and the Environment, ions, Materials Chemistry, Electrochemistry, energy-storage, Condensed Matter Physics, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
الوصف: Batteries which use dissolved redox-active species, such as redox flow batteries (RFBs), are often considered to be constrained in their operation and energy density by the solubility limit of the redox species. Here, we show that soluble redox active electrolytes can be reversibly cycled deeply into the precipitation regime, permitting higher effective concentrations, energy densities, and lower costs. Using aqueous sodium polysulfide negative electrolytes cycled in the nominal Na2S2 to Na2S4 capacity range as an example, we show that the effective solubility can be increased from 5 M in the fully-dissolved state to as much as 10 M using the precipitation strategy. Stable cycling was observed at 8 M concentration over more than 1600h at room temperature. We also analyze the range of polysulfide electrochemical stability, and characterize the precipitate composition. This enhanced effective concentration approach may be generalized to other redox chemistries that utilize solubilized reactants, and may be especially useful for long-duration storage applications where slow charge-discharge rates allow equilibration of precipitated species with the redox-active solution. Joint Center for Energy Storage Research, an Energy Innovation Hub - U.S. Department of Energy, Office of Science, Basic Energy Sciences; National Science Foundation [DMR-1419807] Published version 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, Basic Energy Sciences. This work made use of the MRSEC Shared Experimental Facilities at MIT, supported by the National Science Foundation under award number DMR-1419807.
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المصدر: Journal of The Electrochemical Society. 169:060521
مصطلحات موضوعية: Renewable Energy, Sustainability and the Environment, Batteries and Energy Storage, Materials Chemistry, Electrochemistry, Condensed Matter Physics, ddc, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
الوصف: Li- and Mn-rich layered oxides are a promising next-generation cathode active material (CAM) for automotive applications. Beyond well-known challenges such as voltage fading and oxygen release, their commercialization also depends on practical considerations including cost and energy density. While the cost requirement for these materials could be satisfied by eliminating cobalt, the volumetric energy density requirement might imply the transition from the most widely used porous structure to a more densely packed structure. Here, we investigated five Li- and Mn-rich layered oxides which were synthesized by various routes to obtain CAMs with different morphologies (porous vs dense), transition-metal compositions (Co-containing vs Co-free), and agglomerates sizes (≈6−12 μm). The as-received materials were characterized, e.g., by gas physisorption, Hg intrusion porosimetry, as well as X-ray powder diffraction, and were electrochemically tested by a discharge rate test. Thus, we identified two important material metrics which determine the initial electrochemical performance of Li- and Mn-rich CAMs, and which might be used as performance predictors: (i) the surface area in contact with the electrolyte that defines the effective current density which is applied to the surface of the CAMs, and (ii) the microstrain in the bulk that affects distinct redox features during cycling.
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7
المؤلفون: Stefan Oswald, Hubert Gasteiger, Moritz Bock
المصدر: Journal of The Electrochemical Society. 169:050501
مصطلحات موضوعية: A Centenarian Milestone [Batteries and Energy Storage, Focus Issue In Honor of John Goodenough], Renewable Energy, Sustainability and the Environment, Materials Chemistry, Electrochemistry, Condensed Matter Physics, ddc, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
الوصف: Nickel-rich NCM (LiMO2, with M = Ni, Co, and Mn) cathode active materials for lithium-ion batteries are being increasingly commercialized due to their high specific capacity. Since the particle cracking of conventional polycrystalline NCMs is reported to be a major failure mechanism, the demand for single-crystalline materials is rising, as they are believed to provide superior cycle life. To gain comprehensive insights into the implications of NCM particle morphology on the electrochemical performance, the fundamental properties of these two material classes will be examined in this study. Krypton physisorption experiments and capacitance measurements reveal considerable differences in the change of the NCM surface area upon compression, delithiation, and charge/discharge cycling, depending on the material’s morphology. Here, a polycrystalline NCM622 exhibits changes of its specific surface area of up to 650 % when cycled to a high state of charge, while the one of a single-crystalline NCM622 remains essentially unaffected. Consequently, the difference in morphology and, therefore, in exposed NCM surface area leads to differences in the extent of gassing at high degrees of delithiation (determined via on-line electrochemical mass spectrometry), in the rate capability (evaluated in half-cell discharge rate tests), and in the thermal stability (assessed by thermogravimetric analysis).
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المؤلفون: Michel Suermann, Patrick Trinke, Christoph Immerz, Richard Hanke-Rauschenbach, Boris Bensmann
المصدر: Journal of the Electrochemical Society 165 (2018), Nr. 16
مصطلحات موضوعية: Materials science, 020209 energy, Dewey Decimal Classification::600 | Technik::620 | Ingenieurwissenschaften und Maschinenbau, Electrochemical Engineering, Electrochemical engineering, Dewey Decimal Classification::100 | Philosophie, 02 engineering and technology, Electrochemistry, Energy storage, 0202 electrical engineering, electronic engineering, information engineering, Materials Chemistry, Energy transformation, Spatially resolved cell, Electrical impedance, Energy Conversion, Renewable Energy, Sustainability and the Environment, business.industry, Proton exchange membrane water electrolysis, Energy Storage, Condensed Matter Physics, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Dielectric spectroscopy, ddc:100, Optoelectronics, ddc:620, business, Electrochemical impedance spectroscopy, Polymer electrolyte membrane electrolysis, Communication channel
الوصف: The present analysis shows the local distribution of current density and EIS measurements along a 50 cm single-channel proton exchange membrane water electrolysis (PEMWE) cell. Measurements for operating modes with one sufficiently high and one insufficiently low stoichiometric water ratio (lambda) were carried out to observe effects on the current density distribution. Furthermore, global and local EIS measurements were performed to distinguish between the cell voltage loss differences in the two cases. The mass transport losses.mtx and the Ohmic voltage losses eta Omega show a strong increase, when the stoichiometric water ratio falls below a level of lambda approximate to 5. The reduction of the inlet water flux of the anode reduces both the proton conductivity of the ionomer within the catalyst layer and the membrane, increasing transport and Ohmic resistances, respectively. The local analysis has shown that the level of membrane and catalyst hydration under low stoichiometric conditions can be distributed highly non-homogeneous in along-the-channel direction, with the most pronounced dehydration toward the end of the channel.
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المؤلفون: Rajesh K. Ahluwalia, Andrew Shum, Firat C. Cetinbas, Iryna V. Zenyuk
المصدر: Journal of The Electrochemical Society. 166:F3001-F3008
مصطلحات موضوعية: Water transport, Materials science, Renewable Energy, Sustainability and the Environment, Chemical physics, Pore scale, Materials Chemistry, Electrochemistry, Diffusion (business), Condensed Matter Physics, Energy storage, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
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المؤلفون: John T. S. Irvine, Richard K. B. Gover, Julia D. Percival, George M. Carins, Kyriakos Giagloglou, Christina J. Crouch, Julia L. Payne, Ronald I. Smith
المساهمون: EPSRC, The Royal Society, University of St Andrews. School of Chemistry, University of St Andrews. Centre for Designer Quantum Materials, University of St Andrews. EaSTCHEM
المصدر: Journal of The Electrochemical Society. 166:A2660-A2664
مصطلحات موضوعية: In situ, Energy storage, Materials science, Renewable Energy, Sustainability and the Environment, DAS, QD Chemistry, Condensed Matter Physics, High temperature batteries, Neutron diffraction, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Batteries, Cathode material, Materials Chemistry, Electrochemistry, QD, SDG 7 - Affordable and Clean Energy, Composite material, Thermal Battery
الوصف: Authors thank AWE and the EPSRC (EP/K015540/1) for funding. JTSI acknowledges a Royal Society Wolfson Research Merit award. We thank the STFC for beam-time. Thermal batteries are an established primary battery technology and the most commonly used cathodes in these batteries are transition metal disulfides MS2 (where M = Co, Ni and Fe). However, understanding the evolution of crystalline phases upon battery discharge has been hindered due to the high temperature operation of these batteries. Here we report an experiment that simultaneously collects powder neutron diffraction and electrochemical data as the battery is discharged. Four regions are observed in the diffraction data and four different cobalt containing phases are observed. Multi-phase Rietveld refinement has been used to monitor the evolution of phases during discharge and this is linked to the battery discharge profile. A new discharge mechanism has been proposed which involves hexagonal CoS instead of Co3S4, and the increase in unit cell parameters on discharge suggests the formation of a sulfur deficient solid solution before transformation to Co9S8. This behavior seems reminiscent of that of NiS2 suggesting that the discharge mechanisms of transition metal disulfides may have more similarities than originally thought. Publisher PDF
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