Quasi 3D electrochemical and thermal modeling of lithium ion polymer battery in time and frequency domain and its validation
Type of Degreedissertation
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A dynamic model for a pouch type Li-polymer battery based on electrochemical, thermal, and double layer principles is developed to analyze static and dynamic performances of a single cell. The model is built in three steps: Firstly, the model for the single cell is a quasi-three-dimensional, constructed by connecting one-dimensional models for micro cells using current collectors. The developed model can represent distributions of temperature, potentials, and current flows along with distribution of lithium ions through the plane. The model is coded using MATLAB and validated against a LiMn2O4/Carbon pouch type power cell. Secondly, by theoretically analyzing the heat source terms, a new heat generation equation considering heat of mixing and enthalpy is proposed based on energy conservation and integrated into the electrochemical model. A specially designed calorimeter with high accuracy and fast response is used to validate the hypothesis. Finally, potential and ion transport governing equations for double layers and bulk are used to replace the Butler-Volmer and ion transport equation used in electrochemical model, which enables representation of high frequency behavior of a cell. The behaviors of the sub-models are analyzed. The sub-models are integrated into the microcell model that is validated against experiment data collected by EIS.