FRG: Collaborative Research: Mathematical Modeling of Rechargeable Batteries

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The project will develop a new framework for mathematical modeling of rechargeable batteries, taking into account statistical thermodynamics, concentrated-solution reaction rates, elasticity, crystal anisotropy, stochastic effects, and composite microstructures. Existing engineering models simply fit the open circuit voltage empirically and postulate dynamics by linear diffusion of intercalated lithium, but recent experiments contradict this picture for phase-separating materials. In contrast, the team will develop robust mathematical models to predict the voltage and current response over the full range of operating conditions. The basis for modeling at the single-crystal level will be Cahn-Hilliard partial differential equations with nonlinear boundary conditions, expressing chemical-potential dependent reaction reactions. The goal will be to provide the first mathematical description of emerging high-rate materials, where phase transformations occur via nonlinear intercalation waves, coupling anisotropic diffusion and electrochemical reactions. This effort will also raise basic mathematical questions in linear and nonlinear stability, degenerate wave solutions, and numerical methods.In spite of extensive engineering over the past few decades, the performance of rechargeable batteries has improved only incrementally. Power density (charge/discharge rate per unit mass) and cycle life must still improve drastically for applications such as electric vehicles and renewable energy storage, and this will require a better fundamental understanding of how ions are inserted and extracted from porous electrodes. To meet this need, the project creates a Focused Research Group from mathematics, chemical engineering, and materials science to develop a new theoretical paradigm for Li-ion batteries. The group will guide the engineering of new ultrafast Li-ion batteries, capable of charging and discharging in seconds rather than hours, while opening fruitful directions for applied mathematics. The group will train graduate and undergraduate students and postdocs, organize annual workshops, and develop a course on mathematical modeling of electrochemical energy systems.