Electrolyte-Centric Thermal Model of Li-Ion Battery Under Abuse Conditions

Abstract

Safety is an important concern in Li-ion battery operation and storage. As both energy stored per unit volume and current densities have increased in these batteries, energy dissipation in the form of heat has become one of the main issues for proper battery operation. As temperature increases, secondary chemical reactions may be initiated. These reactions release more heat and undesired products, triggering an auto-catalytic feedback process, commonly classified as thermal-runaway mechanisms. This can potentially lead to a complete degradation of the battery and possible explosion or combustion of the battery components. Several researchers have worked on developing models to predict thermal behavior under conditions with potential thermal runaway outcomes on Li-ion batteries. The first studies proposed a model that emulates the solid electrolyte interface (SEI) decomposition and regeneration reactions on a standard 18650 cylindrical cell. Later works extended these models and included the reactions of cathode decomposition and electrolyte decomposition with potential combustion. Although macroscopic level energy balance helps predict potential thermal behavior in a battery of multiple layers, the study of all the different transport mechanisms that happen inside a single layer battery is essential for a better understanding of the process taking place when temperature begins to rise. With the aim of improving heat dissipation inside a battery, the electrolyte is a key component to consider as it can potentially handle heat flux easier through convection within the solution. Our work investigates spatially dependent electrolyte conditions in the presence of a thermal gradient to produce an electrolyte-centric thermal runaway model. Non-current conditions are considered for emulating oven-test experiments or storage conditions. Furthermore, this specific case study aims to extend our previous model by accounting for the influence of the Joule effect on simulating a battery's operational conditions. The purpose of the study is to model transport mechanisms that can potentially lead to thermal degradation of the battery. Li-ions, momentum, and thermal flux are the main components of the analysis. This objective is achieved by using numerical simulation techniques. A detailed understanding of the transport processes taking place inside the battery will contribute towards mitigating damage induced due to thermal abuse conditions. Figure 1