Modeling Thermal Runaway of Large Format All-Solid-State Lithium Metal Cells during a Thermal Ramp Test and Short Circuit: Sensitivity Analysis and Reaction Pathways

Abstract

While high-energy batteries with an inorganic solid electrolyte may offer improved safety compared with current Li-ion cells because of the lack of a flammable liquid electrolyte, this is a topic that requires careful analysis. In our past work we modeled an LiyCoO2|LLZO|Li large format cell in a thermal ramp test and with a short circuit in a portion of the cell that led to thermal runaway of the entire cell.1 In the present talk we explore several key sensitivities and limitations in our large-format solid state cell model, those sensitivities include the specific energy, electrode capacity ratio, heat transfer to the surroundings, kinetic parameters for key exothermic reactions (e.g., Li2O formation), and others. Our previous modeling work also only considered the potential reaction of lithium metal with oxygen released from the cathode, as the differential scanning calorimetry (DSC) data on which our model was built did not include other cell reactions.2 In the present talk we also present results with an expanded kinetic model to include processes such as lithium/current collector alloying, oxidation of binder, oxidation of conductive carbon, and reaction of lithium with other gaseous products. The impact of modifying our baseline model parameters, and adding additional reactions, on the onset temperature for thermal runaway, the maximum heating rate, and the maximum temperature reached during thermal runaway.