(Invited) Theoretical Analysis of Reaction Inhomogeneity and Lithium Plating Onset at Fast Charge Rates for Lithium Ion Batteries

Abstract

Inhomogeneous reactions in porous anodes may lead to lithium plating at high C-rates. Inhomogeneous lithium intercalation behavior in cathodes and anodes has been studied on particle and macroscale (i.e., cell) length scales. The effects of various physical and electrochemical phenomena (e.g., ionic transport, mass transport, interface reaction kinetics, and electrode thermodynamic behavior) have been studied in the context of reaction inhomogeneity. However, an accurate theoretical understanding of how these accelerate lithium metal plating has not been established in fast charging applications. Here, analytical and numerical modeling is used to develop a more complete understanding of how these coupled, nonlinear electrochemical and physical effects interplay to cause lithium plating. Specifically, it is shown that simple analytical solutions (which are functions of one or several nondimensional numbers) can with surprising accuracy approximate the onset of lithium plating predicted by calibrated numerical models of graphite half-cells. These analytical and numerical results are compared against in situ experimental observations of lithium plating onset during fast charging. This work attempts to use simplified analytical analysis to clarify and unify findings in more complex numerical models, which can ultimately provide strategies for mitigating Li metal plating during fast charging. Application of this theory for design and optimization of electrodes with engineered architectures is discussed.