Review-Knees in Lithium-Ion Battery Aging Trajectories

Lithium-ion batteries can last many years but sometimes exhibit rapid, nonlinear degradation that severely limits battery lifetime. In this work, we review prior work on knees in lithium-ion battery aging trajectories. We first review definitions for knees and three classes of internal state trajectories (termed snowball, hidden, and threshold trajectories) that can cause a knee. We then discuss six knee pathways, including lithium plating, electrode saturation, resistance growth, electrolyte and additive depletion, percolation-limited connectivity, and mechanical deformation-some of which have internal state trajectories with signals that are electrochemically undetectable. We also identify key design and usage sensitivities for knees. Finally, we discuss challenges and opportunities for knee modeling and prediction. Our findings illustrate the complexity and subtlety of lithium-ion battery degradation and can aid both academic and industrial efforts to improve battery lifetime. (c) 2022 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/ by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.

Automated summary

This article reviews the phenomenon of "knees" in the aging trajectories of lithium-ion batteries and discusses their pathways, key design and usage sensitivities, as well as the challenges and opportunities for knee modeling and prediction.