Extending a Thermal Runaway Modeling Framework to Cells of Different Formats, Sizes, and Chemistries

Simplified staged thermal runaway (TR) models are attractive for early-stage battery safety assessment, but they are usually parameterized for a single cell type and rely on internal temperature measurements that are impractical in sealed cylindrical and pouch cells. This work extends a four-stage TR modeling framework so it can be applied to cylindrical and pouch cells of different sizes with nickel-rich layered-oxide cathodes using surface-temperature data from accelerating rate calorimetry (ARC) alone. Four modifications are introduced: an objective segmentation of the temperature-rate curve by three-segment piecewise regression with free breakpoints; a regularized extraction of the Arrhenius parameters that removes the ill-conditioned data at each stage end; a stage-dependent mass-loss function, including a two-step venting formulation for cells with delayed vent opening; and format-specific non-adiabatic boundary conditions for the severe and cooling phases. Adiabatic TR experiments were performed on three samples each of a 4.5 Ah 21700 NMC cylindrical cell, a 33 Ah 4695 NCMA cylindrical cell, and a 65 Ah NMC pouch cell. The model reproduces the measured temperature and temperature-rise rate for all three formats. The results quantify how strongly cell format governs TR severity and indicate that TR in large-format pouch cells can be accurately described without internal instrumentation. Applicability to prismatic cells and to other cathode chemistries, such as LFP, has not been demonstrated.