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Full-Text Articles in Chemical Engineering
Analytical Solution For The Impedance Of A Porous Electrode, Sheba Devan, Venkat R. Subramanian, Ralph E. White
Analytical Solution For The Impedance Of A Porous Electrode, Sheba Devan, Venkat R. Subramanian, Ralph E. White
Faculty Publications
A macrohomogeneous model is presented for a porous electrode that includes coupled potential and concentration gradients with linear kinetics. The equations are solved to obtain an analytical expression for the impedance of a porous electrode. Complex plane plots are presented that illustrate two well-defined arcs: a kinetic arc and a diffusion arc with their time constants far apart. The effects of parameters such as exchange current density, porosity, diffusion coefficient, thickness, and interfacial area on the impedance spectra are presented. The usefulness of the analytical solution in investigating the effect of solution phase diffusion is also presented.
Solvent Diffusion Model For Aging Of Lithium-Ion Battery Cells, Harry J. Ploehn, Premanand Ramadass, Ralph E. White
Solvent Diffusion Model For Aging Of Lithium-Ion Battery Cells, Harry J. Ploehn, Premanand Ramadass, Ralph E. White
Faculty Publications
This work presents a rigorous continuum mechanics model of solvent diffusion describing the growth of solid-electrolyte interfaces (SEIs) in Li-ion cells incorporating carbon anodes. The model assumes that a reactive solvent component diffuses through the SEI and undergoes two-electron reduction at the carbon-SEI interface. Solvent reduction produces an insoluble product, resulting in increasing SEI thickness. The model predicts that the SEI thickness increases linearly with the square root of time. Experimental data from the literature for capacity loss in two types of prototype Li-ion cells validates the solvent diffusion model. We use the model to estimate SEI thickness and extract …
Series Solution To The Transient Convective Diffusion Equation For A Rotating Disk Electrode, Shiriram Santhanagopalan, Ralph E. White
Series Solution To The Transient Convective Diffusion Equation For A Rotating Disk Electrode, Shiriram Santhanagopalan, Ralph E. White
Faculty Publications
A series solution to the transient convective diffusion equation for the rotating disc electrode system is presented and compared to previously reported solutions. The solution presented here is for the entire time domain and agrees well with both the short and long time solutions presented earlier in the literature.
Parameter Estimates For A Pemfc Cathode, Qingzhi Guo, Vijay A. Sethuraman, Ralph E. White
Parameter Estimates For A Pemfc Cathode, Qingzhi Guo, Vijay A. Sethuraman, Ralph E. White
Faculty Publications
Five parameters of a model of a polymer electrolyte membrane fuel cell (PEMFC) cathode (the volume fraction of gas pores in the gas diffusion layer, the volume fraction of gas pores in the catalyst layer, the exchange current density of the oxygen reduction reaction, the effective ionic conductivity of the electrolyte, and the ratio of the effective diffusion coefficient of oxygen in a flooded spherical agglomerate particle to the square of that particle radius) were determined by least-squares fitting of experimental polarization curves. The values of parameters obtained in this work indicate that ionic conduction and gas-phase transport are two …
A Steady-State Impedance Model For A Pemfc Cathode, Qingzhi Guo, Ralph E. White
A Steady-State Impedance Model For A Pemfc Cathode, Qingzhi Guo, Ralph E. White
Faculty Publications
A model for the simulation of the steady-state impedance response of a polymer electrolyte membrane fuel cell (PEMFC) cathode is presented. The catalyst layer of the electrode is assumed to consist of many flooded spherical agglomerate particles surrounded by a small volume fraction of gas pores. Stefan-Maxwell equations are used to describe the multicomponent gas-phase transport occurring in both the gas diffusion layer and the catalyst layer of the electrode. Liquid-phase diffusion of O2 is assumed to take place in the flooded agglomerate particles. Newman’s porous electrode theory is applied to determine over-potential distributions. © 2004 The Electrochemical Society. All …