SGER: Exploratory Research -- A Novel AC Impedance Model for Understanding Transport and Kinetic Limitations of Electrochemical Devices

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ABSTRACTPI: Venkat Subramanian Institution: Tennessee Technological UniversityProposal Number: 0609914Title: (SGER) Exploratory Research A Novel AC Impedance Model for Understanding Transport and Kinetic Limitations of Electrochemical DevicesImproving the design, economy and operating range of electrochemical devices (batteries, fuel cells, super capacitors, sensors) is presently a high priority area as they are expected to play a vital role in the future for automobiles, power storage, military, mobile-station and space applications. Lithium-ion batteries (and similarly other batteries) lose their capacity with cycles. Various transport and reaction limitations restrict the cost effectiveness and utilization of Li-ion batteries and other electrochemical devices. AC impedance is a technique used by various researchers to understand electrochemical systems.Understanding and extracting useful information from AC impedance data can be a complex task. Typically circuit based models have been used by researchers to obtain effective resistance and capacitance of electrochemical systems. The main drawback with using the circuit approach is that it only gives lumped-parameters for the system of interest and does not involve all the meaningful quantitative system parameters (diffusion coefficient, rate constants, etc.). Rigorous physics based models for simulating AC impedance response involves solving multiple partial differential equations (PDEs) in multiple domains making the models prohibitive because of numerical and computation constraints. Though modeling Lithium-ion batteries involve multiple PDEs in multiple domains, this exploratory research proposal explores the possibility of developing PIs novel scheme for two PDEs to solve such systems. The research builds on the PIs past results in the area of mathematical modeling and computational methods for electrochemical systems and is an integrated effort to develop the next generation of high-efficient novel closed-form solutions to better understand electrochemical devices using AC impedance technique.Intellectual Merit - The PIs Numeric Symbolic Solution (NSS) is numerical in the spatial coordinate and closed-form in all the system parameters. The proposed schemes will help bridge the gap between a purely numerical solution and a rigorous analytical solution. Broader Impacts If the exploratory research is successful, then the mathematical solution scheme can be extended to multiple partial differential equations in multiple domains that govern the electrochemical behavior of various devices. These schemes could help predict transport and kinetic parameters and understand the limitations of Lithium-ion batteries, whose use in automobiles, power storage, etc. applications have potential benefits for the environment.