Showing papers on "Anode published in 2004"
TL;DR: This paper will describe lithium batteries in more detail, building an overall foundation for the papers that follow which describe specific components in some depth and usually with an emphasis on the materials behavior.
Abstract: In the previous paper Ralph Brodd and Martin Winter described the different kinds of batteries and fuel cells. In this paper I will describe lithium batteries in more detail, building an overall foundation for the papers that follow which describe specific components in some depth and usually with an emphasis on the materials behavior. The lithium battery industry is undergoing rapid expansion, now representing the largest segment of the portable battery industry and dominating the computer, cell phone, and camera power source industry. However, the present secondary batteries use expensive components, which are not in sufficient supply to allow the industry to grow at the same rate in the next decade. Moreover, the safety of the system is questionable for the large-scale batteries needed for hybrid electric vehicles (HEV). Another battery need is for a high-power system that can be used for power tools, where only the environmentally hazardous Ni/ Cd battery presently meets the requirements. A battery is a transducer that converts chemical energy into electrical energy and vice versa. It contains an anode, a cathode, and an electrolyte. The anode, in the case of a lithium battery, is the source of lithium ions. The cathode is the sink for the lithium ions and is chosen to optimize a number of parameters, discussed below. The electrolyte provides for the separation of ionic transport and electronic transport, and in a perfect battery the lithium ion transport number will be unity in the electrolyte. The cell potential is determined by the difference between the chemical potential of the lithium in the anode and cathode, ∆G ) -EF. As noted above, the lithium ions flow through the electrolyte whereas the electrons generated from the reaction, Li ) Li+ + e-, go through the external circuit to do work. Thus, the electrode system must allow for the flow of both lithium ions and electrons. That is, it must be both a good ionic conductor and an electronic conductor. As discussed below, many electrochemically active materials are not good electronic conductors, so it is necessary to add an electronically conductive material such as carbon * To whom correspondence should be addressed. Phone and fax: (607) 777-4623. E-mail: stanwhit@binghamton.edu. 4271 Chem. Rev. 2004, 104, 4271−4301
6,063 citations
TL;DR: BSCF is presented as a new cathode material for reduced-temperature SOFC operation and demonstrated that BSCF is ideally suited to ‘single-chamber’ fuel-cell operation, where anode and cathode reactions take place within the same physical chamber.
Abstract: Fuel cells directly and efficiently convert chemical energy to electrical energy. Of the various fuel cell types, solid-oxide fuel cells (SOFCs) combine the benefits of environmentally benign power generation with fuel flexibility. However, the necessity for high operating temperatures (800–1,000 °C) has resulted in high costs and materials compatibility challenges. As a consequence, significant effort has been devoted to the development of intermediate-temperature (500–700 °C) SOFCs. A key obstacle to reduced-temperature operation of SOFCs is the poor activity of traditional cathode materials for electrochemical reduction of oxygen in this temperature regime2. Here we present Ba_(0.5_Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-delta) (BSCF) as a new cathode material for reduced-temperature SOFC operation. BSCF, incorporated into a thin-film doped ceria fuel cell, exhibits high power densities (1,010 mW cm^(-2) and 402 mW cm^(-2) at 600 °C and 500 °C, respectively) when operated with humidified hydrogen as the fuel and air as the cathode gas. We further demonstrate that BSCF is ideally suited to 'single-chamber' fuel-cell operation, where anode and cathode reactions take place within the same physical chamber. The high power output of BSCF cathodes results from the high rate of oxygen diffusion through the material. By enabling operation at reduced temperatures, BSCF cathodes may result in widespread practical implementation of SOFCs.
2,998 citations
TL;DR: The primary issues in direct hydrocarbon anode development are reviewed and the new materials and composites that have been developed to meet this challenge are discussed.
Abstract: Solid Oxide Fuel Cells (SOFCs) are one of the most promising technologies for future efficient conversion of the chemical energy stored in fuels to electrical energy. One of the primary advantages of SOFCs is the potential to operate with a wide variety of fuels. While H2 is the fuel of choice for most fuel cells, operation with fossil-derived and bio-derived hydrocarbon fuels would bypass the costly requirement of a new H2 infrastructure, and accelerate adoption of fuel cell technology. This is feasible as SOFCs transport oxygen anions from the air electrode (cathode) to the fuel electrode (anode). The primary barrier to the realization of fuel flexible SOFCs is the anode material set. Traditional SOFC anodes are based on Ni composites. While these are very efficient for H2 and CO fuels, Ni catalyzes graphite formation from dry hydrocarbons, leading to rapid degradation of cell performance and possible mechanical failure. This motivates the development of new anode materials and composites. The principle requirements of an anode are oxygen anion conductivity, electronic conductivity, and electrocatalytic activity toward the desired reaction. This entry reviews the primary issues in direct hydrocarbon anode development and discusses the new materials and composites that have been developed to meet this challenge.
829 citations
TL;DR: In this paper, a dynamic anode-supported intermediate temperature direct internal reforming planar solid oxide fuel cell stack model was developed for both co-flow and counter-flow operation, and the electrochemical performance of the cell was analyzed for several temperatures and fuel utilisations, by means of the voltage and power density versus current density curves.
762 citations
TL;DR: A cathode potential of 804 mV (NHE basis) is theoretically possible using dissolved oxygen, indicating that further improvements in cathode performance with oxygen as the electron acceptor are possible that could lead to increased power densities in this type of MFC.
Abstract: Although microbial fuel cells (MFCs) generate much lower power densities than hydrogen fuel cells, the characteristics of the cathode can also substantially affect electricity generation. Cathodes used for MFCs are often either Pt-coated carbon electrodes immersed in water that use dissolved oxygen as the electron acceptor or they are plain carbon electrodes in a ferricyanide solution. The characteristics and performance of these two cathodes were compared using a two-chambered MFC. Power generation using the Pt-carbon cathode and dissolved oxygen (saturated) reached a maximum of 0.097 mW within 120 h after inoculation (wastewater sludge and 20 mM acetate) when the cathode was equal size to the anode (2.5 × 4.5 cm). Once stable power was generated after replacing the MFC with fresh medium (no sludge), the Coulombic efficiency ranged from 63 to 78%. Power was proportional to the dissolved oxygen concentration in a manner consistent with Monod-type kinetics, with a half saturation constant of KDO = 1.74 mg ...
677 citations
TL;DR: In this paper, a determination of the cell voltage losses observed for Pt and PtRu loading reductions in H2/air and reformate/air polymer/electrolyte-membrane fuel cells (PEMFC) is presented.
672 citations
TL;DR: In this paper, the development and achievement in the Ni/Y2O3-ZrO2 (Ni/YSZ) cermet anodes, alternative and conducting oxide anodes and anode-supported substrate materials are presented.
Abstract: High temperature solid oxide fuel cell (SOFC) has prospect and potential to generate electricity from fossil fuels with high efficiency and very low greenhouse gas emissions as compared to traditional thermal power plants. In the last 10 years, there has been significant progress in the materials development and stack technologies in SOFC. The objective of this paper is to review the development of anode materials in SOFC from the viewpoint of materials microstructure and performance associated with the fabrication and optimization processes. Latest development and achievement in the Ni/Y2O3-ZrO2 (Ni/YSZ) cermet anodes, alternative and conducting oxide anodes and anode-supported substrate materials are presented. Challenges and research trends based on the fundamental understanding of the materials science and engineering for the anode development for the commercially viable SOFC technologies are discussed.
641 citations
TL;DR: In this article, double-heterostructure copper phthalocyanine/C60 organic photovoltaic cells with series resistances as low as 0.1 µm2 were demonstrated.
Abstract: We demonstrate double-heterostructure copper phthalocyanine/C60 organic photovoltaic cells with series resistances as low as 0.1 Ω cm2. A high fill factor of ∼0.6 is achieved, which is only slightly reduced at very intense illumination. As a result, the power conversion efficiency increases with the incident optical power density, reaching a maximum of (4.2±0.2)% under 4–12 suns simulated AM1.5G illumination. The cell performance is accurately described employing an analysis based on conventional semiconductor p–n junction diodes. The dependence of the series resistance on the device area suggests the dominance of the bulk resistance of the indium-tin-oxide anode as a limiting factor in practical cell efficiencies.
601 citations
TL;DR: In this article, a simple and efficient approach is developed for the synthesis of copper oxide nanorods with different morphology and crystallographic structure, and the correlation between the structural features of the nanorod and their electrode performance is discussed in detail.
Abstract: A simple and efficient approach is developed for the synthesis of copper oxide nanorods with different morphology and crystallographic structure. Polycrystalline fine rods 10−20 nm thick and several hundred nanometers long and single crystalline thick rods 60−100 nm thick and up to 1 μm long were obtained from the reactions of copper hydrate with caustic soda solution at room temperature and 100 °C, respectively. The fine CuO nanorods as anode materials for Li ion battery exhibit a high electrochemical capacity of 766 mA h/g and relatively poor capacity retention as compared to thick nanorods with the single crystalline structure. The correlation between the structural features of the nanorods and their electrode performance is discussed in detail.
583 citations
TL;DR: In this article, a potassium secondary cell was designed employing a potassium anode and a Prussian blue (PB)-based cathode, and the electrolyte solution for the nonaqueous battery was 1M KBF4 in 3:7 EC/EMC. The cell design is simple and both the material used and the procedure needed for the cell fabrication are cheaper.
581 citations
TL;DR: In this paper, a first-principles-based charge-discharge model was developed to simulate the capacity fade of Li-ion batteries, based on the loss of active lithium ions due to solvent reduction reaction and on the rise of the anode film resistance.
Abstract: A first-principles-based charge-discharge model was developed to simulate the capacity fade of Li-ion batteries. The model is based on the loss of active lithium ions due to solvent reduction reaction and on the rise of the anode film resistance. The effect of parameters such as exchange current density, depth of discharge (DOD), end of charge voltage, film resistance, and the overvoltage of parasitic reaction were studied quantitatively. The model controls the required DOD by controlling the discharge time and estimates the end of discharge voltages as a function of cycle number. © 2004 The Electrochemical Society. All rights reserved.
TL;DR: In this paper, basic electrochemical processes (such as oxide film growth, anodic dissolution and oxygen liberation) on an aluminium anode in a model alkaline solution are considered under conditions of galvanostatic DC plasma electrolytic oxidation (PEO).
TL;DR: In this paper, the anode of the solid oxide fuel cells (SOFCs) was shown to be chemically compatible with yttria-stabilized zirconia (YSZ) to at least 1300°C.
Abstract: Perovskite-related materials, (La 0.75 Sr 0.25 ) 1-x Cr 0.5 Mn 0.5 O 3-δ (0 ≤ x ≤ 0.1) (LSCM), have been synthesised and examined as potential anode materials for solid oxide fuel cells (SOFCs). La 0.75 Sr 0.25 Cr 0.5 Mn 0.5 O 3 exhibits a rhombohedral structure. It appears to be chemically compatible with yttria-stabilized zirconia (YSZ) to at least 1300°C. At 900°C, its electrical conductivity is about 38 S/cm in air and 1.5 S/cm in 5% H 2 (p O , 10 -21 atm). Good performance was achieved using LSCM as anode with a polarization resistance 0.9 and 0.47 Ω cm 2 in wet 5% H 2 /Ar and wet H 2 , respectively. The anode polarization was further reduced to 0.6 and 0.25 Ω cm 2 in wet 5% H 2 /Ar and wet H 2 when a thin layer of Ce 0.8 Gd 0.2 O 2-δ (CGO) layer was coated between YSZ and LSCM anode. Stable performance was sustained for at least for 4 h operating in wet methane. By improving the electrode microstructure the electrode polarization resistance approaches 0.2 Ω cm 2 at 900°C in 97% H 2 /3% H 2 O for LSCM containing a small amount of YSZ to improve adherence but without CGO. Very good performance is achieved for methane without using excess steam. Using ambient humidification (i.e., 3% H 2 O), the same performance is achieved with methane at 950°C as for hydrogen at 850°C. The anode is stable in both fuel and air conditions and shows stable electrode performance in methane. Thus, both redox stability and operation in low-steam hydrocarbons have been demonstrated, overcoming two of the major limitations of the current generation of nickel zirconia cermet SOFC anodes. LSCM and other complex perovskites are promising anode materials for SOFCs.
TL;DR: In this article, critical properties of five commercial and one in-house gas diffusion layers have been characterized and compared to determine factors limiting the oxygen transport in the cathode gas diffusion layer where there is no oxygen consumption.
Abstract: In proton-exchange membrane fuel cells (PEMFC), gas diffusion layers serve as current collectors that allow ready access of fuel and oxidant to the anode and the cathode catalyst surfaces, respectively. Critical properties of five commercial and one in-house gas diffusion layers have been characterized and compared to determine factors limiting the oxygen transport in the cathode gas diffusion layer where there is no oxygen consumption. These properties are the limiting current, electronic resistivity, fraction of hydrophobic pores, gas permeability, pore size distribution, and surface morphology. Polarization curves using air and neat oxygen were collected to determine the air-limiting currents at three operating conditions: 80°C/75% relative humidity (RH) cathode inlet, 100°C/70% RH cathode inlet, and 120°C/35% RH cathode inlet, all at atmospheric pressure. Linear empirical relationships for permeability coefficient vs. limiting current were found at all three conditions. Characterization of the gas diffusion layers by porosimetry measurement provides the pore size distribution for the gas diffusion layers, which helps in understanding the correlation between the permeability coefficient and the limiting current at the temperatures and relative humidity tested. © 2004 The Electrochemical Society. All rights reserved.
TL;DR: A thin film of Si was vacuum-deposited onto a 30μm thick Ni foil from a source of n-type of Si, the film thickness examined being 200-1500
TL;DR: AISI 316 austenitic stainless steel has been plasma nitrided using the active screen plasminarizing (ASPN) technique as mentioned in this paper, and the results showed that the untreated 316 stainless steel suffered severe localised pitting and crevice corrosion.
TL;DR: In this paper, both interfacial contact resistance (ICR) measurements and electrochemical corrosion techniques were applied to ferritic stainless steels in a solution simulating the environment of a bipolar plate in a polymer electrolyte membrane fuel cell (PEMFC).
TL;DR: XAS as a Characterization Method: Pt/C 4.1.
Abstract: 1.Introduction
2.X-ray Absorption Spectroscopy
2.1. XANES
2.2. EXAFS
3.Data Collection and In Situ Cells
4.XAS as a Characterization Method: Pt/C
4.1. Particle Size
4.2. Potential Dependence
4.3. Adsorbates
5.Pt Containing Alloy Catalysts
5.1. PtRu Alloys
5.1.1. Compositional Analysis
5.1.2. Potential Dependence
5.1.3. Adsorbates
5.2. Other Pt Containing Alloy Anode Catalysts
5.3. Pt Containing Alloy Cathode Catalysts
6.Non-Pt Catalysts
7.Conclusion
8.References
TL;DR: In this paper, LiNi 0.8 Co 0.2 O 2 cathodes from three industrial developers coupled with graphite anodes were made into lithium-ion cells for high-power applications.
TL;DR: In this article, the authors provide electrochemical and X-ray fluorescence evidence of ruthenium crossover in direct methanol fuel cells using a state-of-the-art Pt-Ru alloy catalyst at the anode.
Abstract: In this study, we provide electrochemical and X-ray fluorescence evidence of ruthenium crossover in direct methanol fuel cells using a state-of-the-art Pt-Ru alloy catalyst at the anode. We find ruthenium susceptible to leaching out from the highly active Pt-Ru black catalyst, crossing the proton-conducting Nafion membrane and redepositing at the Pt cathode on the opposite side of the fuel cell. After first detecting this phenomenon in a direct methanol fuel cell (DMFC) stack with a history of cell-voltage reversal, we have since observed ruthenium crossover under virtually all DMFC operating conditions, from single cell break-in (humidification) to stack life testing. The degree of cathode contamination by ruthenium species (of chemical form yet unknown) depends on, among other factors, the DMFC anode potential and the cell operating time. Once deposited at the cathode, ruthenium inhibits oxygen reduction kinetics and the catalyst's ability to handle methanol crossover. Depending on the degree of cathode contamination, the overall effect of ruthenium crossover on cell performance may be from as little as ∼40mV up to 200 mV.
Patent•
18 May 2004TL;DR: In this paper, an organic light emitting device with an anode, a cathode, and an organic layer disposed between the anode and the cathode is described, where the organic layer comprises a compound further comprising one or more carbene ligands coordinated to a metal center.
Abstract: An organic light emitting device is provided. The device has an anode, a cathode and an organic layer disposed between the anode and the cathode. The organic layer comprises a compound further comprising one or more carbene ligands coordinated to a metal center.
Patent•
8 Oct 2004
TL;DR: Active metal and active metal intercalation electrode structures and battery cells having ionically conductive protective architecture including an active metal (e.g., lithium) conductive impervious layer separated from the electrode (anode) by a porous separator impregnated with a non-aqueous electrolyte (anolyte) are discussed in this article.
Abstract: Active metal and active metal intercalation electrode structures and battery cells having ionically conductive protective architecture including an active metal (e.g., lithium) conductive impervious layer separated from the electrode (anode) by a porous separator impregnated with a non-aqueous electrolyte (anolyte). This protective architecture prevents the active metal from deleterious reaction with the environment on the other (cathode) side of the impervious layer, which may include aqueous or non-aqueous liquid electrolytes (catholytes) and/or a variety electrochemically active materials, including liquid, solid and gaseous oxidizers. Safety additives and designs that facilitate manufacture are also provided.
TL;DR: In this article, a micro direct methanol fuel cell (DMFC) for portable applications has been developed and its electrochemical characterization carried out in this study, where anode and cathode flowfields with channel and rib width of 750 m and channel depth of 400m were fabricated on Si wafers using the microelectromechanical system (MEMS) technology.
TL;DR: In this article, the performance of carbon-coated spherical graphite has been investigated in terms of high rate capacity, reversible capacity, high coulombic efficiency and low irreversible capacity.
Abstract: Natural graphite is a promising candidate for the anode material in lithium-ion batteries. To enhance its electrochemical performance, raw natural graphite flakes have been rolled into spheres by impact milling and then coated with carbon by thermal vapor decomposition (TVD). The obtained spherical graphite samples show excellent performance in terms of high rate capacity, high reversible capacity, high coulombic efficiency and low irreversible capacity. The improvements in performance have been mainly correlated with the morphologies of carbon-coated spherical graphite.
TL;DR: In this article, a simple model based on Butler-Volmer kinetics for electrodes and transport resistance in the polymer electrolyte is analyzed for water electrolysis by using a simple circuit analogy for the sequential kinetic and transport resistances.
TL;DR: In this article, a two-phase, one-dimensional steady-state, isothermal model of a fuel cell region consisting of the catalyst and gas diffusion layers bonded to a proton exchange membrane (PEM) was used to model the catalyst layer.
Abstract: This paper describes a two-phase, one-dimensional steady-state, isothermal model of a fuel cell region consisting of the catalyst and gas diffusion layers bonded to a proton exchange membrane (PEM). A thin film-agglomerate approach is used to model the catalyst layer. The effect of water flooding in the gas diffusion layer and catalyst layer of the cathode on the overall cell performance was investigated. The simulation results confirmed that the water-flooding situation in the catalyst layer is more severe than that in the backing layer since water is first produced in the catalyst layer. The catalyst layer should be considered as an individual domain. The effect of operating parameters that affect the water generation and removal process, such as the inlet relative humidity of the cathode and anode streams and operating temperature was studied. The results show good agreement with the experimental observations.
TL;DR: In this article, formic acid was used as an anode fuel for polymer electrolyte fuel cells and the electro-oxidation process was investigated on Pt/C. The effect of the electrode potential on the impedance pattern was revealed and an impedance model incorporating reaction kinetics information was developed to simulate the experimental impedance response.
TL;DR: In this article, the sulfur tolerance of the various perovskite-based anodes was examined at 1273 K in a H 2 /H 2 O fuel and showed no degradation when the fuel was switched back to hydrogen.
Abstract: Solid oxide fuel cells (SOFCs) using yttria-stabilized zirconia (YSZ) electrolytes, lanthanum strontium manganate cathodes, and La 1 - x Sr x BO 3 /YSZ anodes (where B = Mn, Cr, and Ti) were fabricated. The sulfur tolerance of the various perovskite-based anodes was examined at 1273 K in a H 2 /H 2 O fuel. The Sr 0 . 6 La 0 . 4 TiO 3 /YSZ (50/50 wt %) anode showed no degradation in the presence of up to 5000 ppm of H 2 S in a hydrogen fuel. This anode was also able to operate for 8 h with 1% H 2 S as a fuel and showed no degradation when the fuel was switched back to hydrogen.
TL;DR: In this article, two types of membrane-electrode assembly (MEA) based on Nafion ® 112 were used to investigate effects of backing pore structure and wettability on cell polarization characteristics and two-phase flow dynamics.
TL;DR: In this article, a three-dimensional, single-phase, isothermal numerical model of polymer electrolyte fuel cell was employed to investigate effects of electron transport through the gas diffusion layer.
Abstract: A three-dimensional, single-phase, isothermal numerical model of polymer electrolyte fuel cell ~PEFC! was employed to investigate effects of electron transport through the gas diffusion layer ~GDL! for the first time. An electron transport equation was additionally solved in the catalyst and gas diffusion layers, as well as in the current collector. It was found that the lateral electronic resistance of GDL, which is affected by the electronic conductivity, GDL thickness, and gas channel width, played a critical role in determining the current distribution and cell performance. Under fully-humidified gas feed in the anode and cathode, both oxygen and lateral electron transport in GDL dictated the current distribution. The lateral electronic resistance dominated the current distribution at high cell voltages, while the oxygen concentration played a more decisive role at low cell voltages. With reduced GDL thickness, the effect of the lateral electronic resistance on the current distribution and cell performance became even stronger, because the cross-sectional area of GDL for lateral electron transport was smaller. Inclusion of GDL electron transport enabled the thickness of GDL and widths of the gas channel and current collecting land to be optimized for better current distribution and cell performance. In addition, the present model enables: ~i! direct incorporation of contact resistances emerging from GDL/catalyzed membrane or GDL/land interface, ~ii! implementation of the total current as a more useful boundary condition than the constant cell voltage, and ~iii! stack modeling with cells connected in series and hence having the identical total current.