Simultaneously Coupled Mechanical-Electrochemical-Thermal Simulation of Lithium-Ion Cells

Abstract

Understanding the combined electrochemical-thermal and mechanical response of a system has a variety of applications. For instance, such behavior is characterized routinely in reactor design to understand structural failure of components from electrochemical fatigue. In energy storage, the potential induced changes to properties of materials (e.g., swelling or surface oxidation induced fracture) have often been categorized as reliability concerns. For lithium ion batteries, there is the added concern over safety of the system in the event of mechanical failure of the cell components. In this work, we study different mechanical test conditions and examine the interaction between mechanical failure and electrochemical-thermal responses, by developing a simultaneously coupled model. We begin with a model system to demonstrate the steps involved in building the coupling framework and proceed to model a pouch-format cell with explicit representations for each individual component such as the active material, current collector, separator, etc. Anisotropic constitutive material models are presented to describe the mechanical properties of active materials and separator. Some initial results are shown in Figure 1. The model predicts accurately the force-strain response and fracture of battery structure, simulates the local failure of separator layer, and captures the onset of short circuit for lithium-ion battery cell under different test conditions. The difference in the electrochemical response and the implications for follow on chemical reactions under these test conditions are discussed. Acknowledgement This study was supported by Computer Aided Engineering for Batteries (CAEBAT) project of the Vehicle Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy. The research was performed using computational resources sponsored by the Department of Energy's Office of Energy Efficiency and Renewable Energy, located at the National Renewable Energy Laboratory. Figure 1