Understanding the Knee Point of Aged Lithium-Ion Batteries: A Physics-Based Modeling of Electrolyte Dry-Out and Gas Bubble Entrapment

Abstract

This research addresses the performance and degradation characteristics of lithium-ion batteries (LIBs), focusing on the implications of electrolyte depletion and gas bubble entrapment within the cell. Using a comprehensive electrochemical-thermal model, this study provides simulation results of electrolyte depletion and gas bubble entrapment and their influence on the lifespan of lithium-ion batteries (LIBs). Th study notably explores the battery life beyond the critical “knee-point” - a transition point marking the shift from linear to accelerated capacity decline. An intricate exploration of the relationship between electrolyte saturation levels and various battery parameters, including performance, thermal behavior, and transport properties, is carried out through a detailed mathematical model. The findings highlight the critical impact of electrolyte levels on LIB performance and thermal behavior. It also shows that electrolyte depletion can facilitate lithium plating. Providing insights into electrolyte depletion and gas production processes paves the way for strategies to enhance battery life, safety, and performance, ultimately fostering a deeper understanding of LIB degradation mechanisms. An electrochemical-thermal model demonstrated the crucial influence of electrolyte depletion on the rapid decline in the lifespan of lithium-ion batteries. Undershooting and overshooting phenomena were observed at low electrolyte saturation levels. The model results indicated that electrolyte depletion can promote lithium plating at the anode.