State of health monitoring by gas generation patterns in commercial 18,650 lithium-ion batteries

Abstract

• Non-disruptive lab made Raman spectroscopic system is applied for gas analysis. • Four distinct phases of gas expulsion were found until commercial LIB’s end of life (EOL). • Mathematical model related to SOH is proposed based on the 4 gas expulsion phases. Because large-scale lithium-ion battery (LIB) packs are compactly constructed using many LIB cells, one battery can cause fire of the other LIB cells when a few cells of them are damaged by accident owing to the latent risk of thermal decomposition reactions. To alleviate this problem, research seeks to provide an understanding of the gas generating mechanisms during cycling, electrolyte decomposition, and electrode material reactions. Understanding gas behaviors can prevent propagation of a battery fire and other hazardous situations. Therefore, in this study, we investigate commercial 18,650 cylindrical cells with long-term cycling. A lab-made in-situ Raman spectroscopic system and comprehensive transient electrochemical analyses are utilized to explore four gas expulsion phases. In addition, gas generation data are assessed for various overcharging voltage cutoffs (4.2–4.6 V). For the first time, furthermore, a simple empircal mathematical model is proposed, based on the distinct gas evolution phases, that can provide the insight into the state of health (SOH) of commercial 18,650 cells.