An Electrochemical-thermal Coupled Gas Generation and Overcharge-to-thermal-runaway Model for Large-format Lithium Ion Battery

Lithium-ion batteries (LIB) have found a wide range of applications in many consumer products in the last 25 years. The United States Navy and Marine Corps have various applications using LIB, and safe battery technologies are critically needed. While many consumer applications typically utilize smaller high capacity cells, military applications can utilize specialty large-format (>30 Ah) cells in their LIB packs. One of the most important safety considerations for LIB cells is their thermal stability under various abuses such as exposure to heat, nail penetration, external short circuit, crushing, and so on. Several exothermic reactions can occur as the inner cell temperature increases, and if the heat generation is larger than the dissipated heat to the surroundings, this leads to heat accumulation in the cell and acceleration of the chemical reactions, which can then lead to a thermal runaway. To understand and control thermal runaway, many researchers have formulated complex mathematical models and built experimental set-ups for investigating the phenomenon in detail. However, most of the studies focused on the effect of thermal runaway event, while no detailed numerical analysis on the vaporization of the electrolyte and the correlation of electrochemical reactions with overcharge in large-format LIB has been reported yet. So this study reports the recently developed electrochemical-thermal coupled gas generation and overcharge-to-thermal-runaway model for a large-format lithium-ion battery tested at NSWCCD using COMSOL software.