A Control-Oriented Single Particle Model with Electrolyte Dynamics and Stress-Diffusion Coupling

Abstract

Full electrochemical models are well-established as the standards for accurately predicting battery behavior. These are especially useful for cell design since performance can be evaluated based on various model parameters. Conventional models can be coupled with additional physics such as diffusion-induced stress, crack propagation, and battery degradation mechanisms to test different physical phenomena. However, these models are too computationally intensive to implement in battery management systems (BMSs), which utilize control and estimation algorithms to monitor performance and ensure safety. Single particle models (SPMs), which are computationally efficient approximations of pseudo-two-dimensional (P2D) models, are often used instead. However, most SPMs are only valid for low C-rates. In this paper, a new ODE-based SPM is proposed that captures high C-rate effects by including electrolyte physics and stress-diffusion coupling. Models describing these physics are validated by comparing simulation results to the P2D model at several C-rates. A single lumped parameter is used to quantify the intensity of the stress-diffusion coupling in an electrode. Simulation results are presented to show how variation of this parameter affects charge-discharge cycle times at different C-rates. Next, the improved SPM is linearized and presented as both state space and transfer function models. The frequency responses of the linearized SPM and P2D model are compared with and without stress-diffusion coupling. Further, the effects of varying the stress-diffusion coupling intensity on the frequency response are discussed. The proposed linearized model is more computationally efficient than full electrochemical and P2D models, and includes key physics that are missing in most low-order battery models. As a result, the proposed model is well-suited for a wide variety of BMS applications and offers improvements at high C-rates that are necessary for fast charging applications.