Optimal Charging Profile for Mechanically Constrained Lithium-Ion Batteries Using Reformulated Pseudo Two Dimensional Models

Abstract

This presentation considers the problem of obtaining the optimal current profile for charging a lithium-ion battery using the reformulated porous electrode pseudo 2D (P2D) model. Our previous efforts (1) in deriving the optimal charging profile considering intercalation-induced stress were limited to single particle level dynamics of an electrode. At higher charge/discharge rates, the dynamics at the sandwich level (anode, separator and cathode) become critical and are considered a natural extension to the previous work. Optimal charging profiles will be derived by incorporating stress into the reformulated P2D model (2). Faster computing and advancement in nonlinear programming algorithms have made it possible to use nonlinear transport and electrochemical engineering-based models (3) to derive optimal charging profiles in real time.When conventional charging profiles for lithium-ion batteries (e.g., constant current followed by constant voltage) are deployed, they do not consider capacity fade mechanisms. These charging profiles are not only inefficient in terms of lifetime usage of the batteries but also slower (4) as they do not exploit the changing dynamics of the system. The progress made in understanding the capacity fade mechanisms (5-8) has paved the way for including that knowledge in deriving optimal control. This work explores the possibilities of using transport and electrochemical-based models in deriving open-loop optimal charging profiles that minimize capacity fade by restricting the development of stresses in the solid phase as well as other capacity fade mechanisms. Acknowledgements The work presented herein was funded in part by the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000275.