Physics-Based and Control-Oriented Modeling of Diffusion-Induced Stress in Li-Ion Batteries

Advanced battery management systems must take into account all key factors that contribute to significant degradation in order to ensure safe operation and to prolong battery useful life. One of the most important battery degradation mechanisms is the stress induced fracture. This has been observed on cathode electrodes during experiments, and may lead to partial or complete electrical isolation of the particles from the electrode. A physics-based stress model considering the nonlinear variation of lattice constant is presented and validated against experimental data. The effect of stress on diffusion dynamics is investigated. Stresses under the linear lattice constant and nonlinear lattice constant are compared. Stresses at different SOCs are also studied. SOC operating window which avoids the maximum stresses are determined. A physics-based, control-oriented, and highly computationally efficient model is also developed to predict the particle level stress in lithium ion batteries. This physics-based control-oriented model enables accurate estimation of stress levels inside the cathode particles while being computationally efficient enough to be implemented on an inexpensive micro-controller. With the accurate prediction of the stress level in the electrode particles, vehicles can be optimized to operate more efficiently with the aim of protecting battery health and prolonging battery life. (C) 2018 The Electrochemical Society.