The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Ralph E. White - One of the best experts on this subject based on the ideXlab platform.
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Current Distribution in a HORIZON ® Lead-Acid Battery during Discharge
2016Co-Authors: Scholar Commons, Ralph E. White, Z. Mao, B. JayAbstract:The displacement ofthis horizontal line also reflects the ef-fect of curvature on the system behavior. Since in the recti-linear case the voltage drop is proportional to the separa-tion distance between the two interfaces, but is only proportional to the natural logarithm of that distance in the cylindrical cases, curvature results in a reduction of polarization. The value of the asymptote for the rectilinear Porous Electrode case is log [crK/( ~ + K)2]. Consider a third situation: Suppose 5 is large, but ~ = 0. The reaction zone is confined only to a thin region near the Electrode/separator interface. In this case, Eq. [23] be-comes e ~ ~ Since as ~ becomes large and [33
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an approximate solution for solid phase diffusion in a spherical particle in physics based li ion cell models
Journal of Power Sources, 2012Co-Authors: Ralph E. WhiteAbstract:Abstract An approximate solution is presented for the spherical diffusion equation for the spherical particles in a physics-based lithium-ion battery model. This approximate solution is compared to different numerical and analytic solutions for various boundary conditions. These comparisons reveal that our approximate solution can provide accuracy and time-efficiency in simulation. This approximate solution is much faster than the numerical and truncated analytical solutions at high current rate, and shows better long-time accuracy than the short-time analytical solution. This approximate solution can also be used as the Porous Electrode model.
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moving boundary model for the discharge of a licoo2 Electrode
Journal of The Electrochemical Society, 2007Co-Authors: Qi Zhang, Ralph E. WhiteAbstract:A moving boundary model in a spherical LiCoO 2 particle is presented to account for the diffusion controlled phase transition in LiCoO 2 solid particles, and this model is incorporated into a Porous Electrode model for the LiCoO 2 Electrode. The simulation results agree well with the experimental data of a LiCoO 2 Electrode. A study of the flux distribution in the Porous Electrode shows that the phase transition phenomenon in the LiCoO 2 particles has a significant effect on the flux distribution by changing the solid phase diffusion resistance in the particles.
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comparison of approximate solution methods for the solid phase diffusion equation in a Porous Electrode model
Journal of Power Sources, 2007Co-Authors: Qi Zhang, Ralph E. WhiteAbstract:Abstract Approximation methods are often used in Porous Electrode models to eliminate the need to solve the local solid phase diffusion equation. These methods include Duhamel's superposition method, a diffusion length method and a polynomial approximation method which have long been used in the literature. The pseudo steady state (PSS) method is a method that has been used recently to develop a solution to the diffusion equation in a spherical particle with time dependent boundary conditions, but the PSS method has not been used in a Porous Electrode model. These methods are compared to each other in a dimensionless analysis study, and they are used in a Porous Electrode model to predict the discharge curves for a LiCoO2 Electrode. Simulation results presented here indicate that the PSS method or the high order polynomial method should be used in a Porous Electrode model to obtain accuracy and save computation time.
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Analytical Expression for the Impedance Response of an Insertion Electrode Cell
Journal of The Electrochemical Society, 2007Co-Authors: Godfrey Sikha, Ralph E. WhiteAbstract:An analytical expression for the impedance response of an insertion cathode/separator/foil anode cell sandwich is presented. The analytical expression includes the impedance contributions from interfacial kinetics, double-layer adsorption, and solution-phase and solid-phase diffusion processes. The validity of the analytical solution is ascertained by comparison with the numerical solution obtained for a LiCoO2/polypropylene/lithium metal cell. The flexibility of the analytical solution is utilized to analyze various limiting conditions. An expression to estimate solid-phase diffusion coefficient of insertion species in a Porous Electrode
Lei Wei - One of the best experts on this subject based on the ideXlab platform.
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a highly permeable and enhanced surface area carbon cloth Electrode for vanadium redox flow batteries
Journal of Power Sources, 2016Co-Authors: Xuelong Zhou, Yikai Zeng, Tianshou Zhao, Lei WeiAbstract:Abstract In this work, a high-performance Porous Electrode, made of KOH-activated carbon-cloth, is developed for vanadium redox flow batteries (VRFBs). The macro-scale Porous structure in the carbon cloth formed by weaving the carbon fibers in an ordered manner offers a low tortuosity (∼1.1) and a broad pore distribution from 5 μm to 100 μm, rendering the Electrode a high hydraulic permeability and high effective ionic conductivity, which are beneficial for the electrolyte flow and ion transport through the Porous Electrode. The use of KOH activation method to create nano-scale pores on the carbon-fiber surfaces leads to a significant increase in the surface area for redox reactions from 2.39 m 2 g −1 to 15.4 m 2 g −1 . The battery assembled with the present Electrode delivers an energy efficiency of 80.1% and an electrolyte utilization of 74.6% at a current density of 400 mA cm −2 , as opposed to an electrolyte utilization of 61.1% achieved by using a conventional carbon-paper Electrode. Such a high performance is mainly attributed to the combination of the excellent mass/ion transport properties and the high surface area rendered by the present Electrode. It is suggested that the KOH-activated carbon-cloth Electrode is a promising candidate in redox flow batteries.
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a high performance dual scale Porous Electrode for vanadium redox flow batteries
Journal of Power Sources, 2016Co-Authors: Xuelong Zhou, Yikai Zeng, Xingbao Zhu, Lei Wei, Tianshou ZhaoAbstract:Abstract In this work, we present a simple and cost-effective method to form a dual-scale Porous Electrode by KOH activation of the fibers of carbon papers. The large pores (∼10 μm), formed between carbon fibers, serve as the macroscopic pathways for high electrolyte flow rates, while the small pores (∼5 nm), formed on carbon fiber surfaces, act as active sites for rapid electrochemical reactions. It is shown that the Brunauer-Emmett-Teller specific surface area of the carbon paper is increased by a factor of 16 while maintaining the same hydraulic permeability as that of the original carbon paper Electrode. We then apply the dual-scale Electrode to a vanadium redox flow battery (VRFB) and demonstrate an energy efficiency ranging from 82% to 88% at current densities of 200–400 mA cm−2, which is record breaking as the highest performance of VRFB in the open literature.
Lianwei Wang - One of the best experts on this subject based on the ideXlab platform.
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core shell comoo4 ni oh 2 on ordered macro Porous Electrode plate for high performance supercapacitor
Electrochimica Acta, 2018Co-Authors: Hongxing Yang, Yuanhao Wang, Lianwei Wang, Paul K ChuAbstract:Abstract Multidimensional CoMoO4@Ni(OH)2 nanocomposite materials are fabricated on the nickel modified surface and channels of an ordered macro-Porous Electrode plate (OMEP) by a multistep high temperature hydrothermal method as the supercapacitor Electrode in a high power density energy storage device. The effects, morphology, capacitive properties, and formation mechanism of the CoMoO4@Ni(OH)2 composite materials are systematically investigated. Compared to nanostructured nickel grown on the OMEP or CoMoO4@Ni(OH)2 on nickel plate with the same area, the CoMoO4@Ni(OH)2/OMEP shows enhanced electrochemical energy storage properties such as high energy capacitance of 8.55 F cm−2 (1812.42 F g−1) at 2 mA cm−2 and good cycling stability of 87.42% capacity retention after 5000 cycles. An asymmetrical supercapacitor (ASC) device is assembled with a polyethylene (PE) membrane, CoMoO4@Ni(OH)2/OMEP, and active carbon covered nickel foam. The ASC with the CoMoO4@Ni(OH)2/OMEP has an energy density of 9.66 Wh Kg−1 even at a power density of 3000 W Kg−1 as well as stable power characteristics with 86.5% retention after 10,000 cycles at a current of 0.06 A. The device produces large instantaneous power after charging at 2.8 V for 10 s one ASC can power a 5 mm red LED with high efficiency.
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core shell comoo4 ni oh 2 on ordered macro Porous Electrode plate for high performance supercapacitor
Electrochimica Acta, 2018Co-Authors: Mai Li, Hongxing Yang, Yuanhao Wang, Lianwei WangAbstract:Abstract Multidimensional CoMoO4@Ni(OH)2 nanocomposite materials are fabricated on the nickel modified surface and channels of an ordered macro-Porous Electrode plate (OMEP) by a multistep high temperature hydrothermal method as the supercapacitor Electrode in a high power density energy storage device. The effects, morphology, capacitive properties, and formation mechanism of the CoMoO4@Ni(OH)2 composite materials are systematically investigated. Compared to nanostructured nickel grown on the OMEP or CoMoO4@Ni(OH)2 on nickel plate with the same area, the CoMoO4@Ni(OH)2/OMEP shows enhanced electrochemical energy storage properties such as high energy capacitance of 8.55 F cm−2 (1812.42 F g−1) at 2 mA cm−2 and good cycling stability of 87.42% capacity retention after 5000 cycles. An asymmetrical supercapacitor (ASC) device is assembled with a polyethylene (PE) membrane, CoMoO4@Ni(OH)2/OMEP, and active carbon covered nickel foam. The ASC with the CoMoO4@Ni(OH)2/OMEP has an energy density of 9.66 Wh Kg−1 even at a power density of 3000 W Kg−1 as well as stable power characteristics with 86.5% retention after 10,000 cycles at a current of 0.06 A. The device produces large instantaneous power after charging at 2.8 V for 10 s one ASC can power a 5 mm red LED with high efficiency.
Juan G Santiago - One of the best experts on this subject based on the ideXlab platform.
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tailored Porous Electrode resistance for controlling electrolyte depletion and improving charging response in electrochemical systems
Journal of Power Sources, 2018Co-Authors: James W Palko, Ali Hemmatifar, Juan G SantiagoAbstract:Abstract The rapid charging and/or discharging of electrochemical cells can lead to localized depletion of electrolyte concentration. This depletion can significantly impact the system's time dependent resistance. For systems with Porous Electrodes, electrolyte depletion can limit the rate of charging and increase energy dissipation. Here we propose a theory to control and avoid electrolyte depletion by tailoring the value and spatial distribution of resistance in a Porous Electrode. We explore the somewhat counterintuitive idea that increasing local spatial resistances of the solid Electrode itself leads to improved charging rate and minimal change in energy loss. We analytically derive a simple expression for an Electrode matrix resistance profile that leads to highly uniform electrolyte depletion. We use numerical simulations to explore this theory and simulate spatiotemporal dynamics of electrolyte concentration in the case of a supercapacitor with various tailored Electrode matrix resistance profiles which avoid localized depletion. This increases charging rate up to ∼ 2 -fold with minimal effect on overall dissipated energy in the system.
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two dimensional Porous Electrode model for capacitive deionization
Journal of Physical Chemistry C, 2015Co-Authors: Ali Hemmatifar, Michael Stadermann, Juan G SantiagoAbstract:Ion transport in Porous conductive materials is of great importance in a variety of electrochemical systems including batteries and supercapacitors. We here analyze the coupling of flow and charge transport and charge capacitance in capacitive deionization (CDI). In CDI, a pair of Porous carbon Electrodes is employed to electrostatically retain and remove ionic species from aqueous solutions. We here develop and solve a novel unsteady two-dimensional model for capturing the ion adsorption/desorption dynamics in a flow-between CDI system. We use this model to study the complex, nonlinear coupling between electromigration, diffusion, and advection of ions. We also fabricated a laboratory-scale CDI cell which we use to measure the near-equilibrium, cumulative adsorbed salt, and electric charge as a function of applied external voltage. We use these integral measures to validate and calibrate this model. We further present a detailed computational study of the spatiotemporal adsorption/desorption dynamics und...
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in situ spatially and temporally resolved measurements of salt concentration between charging Porous Electrodes for desalination by capacitive deionization
Environmental Science & Technology, 2014Co-Authors: Matthew E Suss, P. Maarten Biesheuvel, Michael Stadermann, Theodore F Baumann, Juan G SantiagoAbstract:Capacitive deionization (CDI) is an emerging water desalination technique. In CDI, pairs of Porous Electrode capacitors are electrically charged to remove salt from brackish water present between the Electrodes. We here present a novel experimental technique allowing measurement of spatially and temporally resolved salt concentration between the CDI Electrodes. Our technique measures the local fluorescence intensity of a neutrally charged fluorescent probe which is collisionally quenched by chloride ions. To our knowledge, our system is the first to measure in situ and spatially resolved chloride concentration in a laboratory CDI cell. We here demonstrate good agreement between our dynamic measurements of salt concentration in a charging, millimeter-scale CDI system to the results of a modified Donnan Porous Electrode transport model. Further, we utilize our dynamic measurements to demonstrate that salt removal between our charging CDI Electrodes occurs on a longer time scale than the capacitive charging ...
Tianshou Zhao - One of the best experts on this subject based on the ideXlab platform.
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a highly permeable and enhanced surface area carbon cloth Electrode for vanadium redox flow batteries
Journal of Power Sources, 2016Co-Authors: Xuelong Zhou, Yikai Zeng, Tianshou Zhao, Lei WeiAbstract:Abstract In this work, a high-performance Porous Electrode, made of KOH-activated carbon-cloth, is developed for vanadium redox flow batteries (VRFBs). The macro-scale Porous structure in the carbon cloth formed by weaving the carbon fibers in an ordered manner offers a low tortuosity (∼1.1) and a broad pore distribution from 5 μm to 100 μm, rendering the Electrode a high hydraulic permeability and high effective ionic conductivity, which are beneficial for the electrolyte flow and ion transport through the Porous Electrode. The use of KOH activation method to create nano-scale pores on the carbon-fiber surfaces leads to a significant increase in the surface area for redox reactions from 2.39 m 2 g −1 to 15.4 m 2 g −1 . The battery assembled with the present Electrode delivers an energy efficiency of 80.1% and an electrolyte utilization of 74.6% at a current density of 400 mA cm −2 , as opposed to an electrolyte utilization of 61.1% achieved by using a conventional carbon-paper Electrode. Such a high performance is mainly attributed to the combination of the excellent mass/ion transport properties and the high surface area rendered by the present Electrode. It is suggested that the KOH-activated carbon-cloth Electrode is a promising candidate in redox flow batteries.
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a high performance dual scale Porous Electrode for vanadium redox flow batteries
Journal of Power Sources, 2016Co-Authors: Xuelong Zhou, Yikai Zeng, Xingbao Zhu, Lei Wei, Tianshou ZhaoAbstract:Abstract In this work, we present a simple and cost-effective method to form a dual-scale Porous Electrode by KOH activation of the fibers of carbon papers. The large pores (∼10 μm), formed between carbon fibers, serve as the macroscopic pathways for high electrolyte flow rates, while the small pores (∼5 nm), formed on carbon fiber surfaces, act as active sites for rapid electrochemical reactions. It is shown that the Brunauer-Emmett-Teller specific surface area of the carbon paper is increased by a factor of 16 while maintaining the same hydraulic permeability as that of the original carbon paper Electrode. We then apply the dual-scale Electrode to a vanadium redox flow battery (VRFB) and demonstrate an energy efficiency ranging from 82% to 88% at current densities of 200–400 mA cm−2, which is record breaking as the highest performance of VRFB in the open literature.
