Thermal-Runaway Investigation for a Cylindrical LiFePO4 Cell in Battery Energy Storage Systems (BESS): A Fully Coupled Electro-Chemo-Thermo-Mechanical (ECTM) Perspective

This study presents a reduced-order electro-chemo-thermo-mechanical (ECTM) model for an 18650-format LiFePO4 (LFP)/graphite cell under normal charging. A one-dimensional Doyle–Fuller–Newman electrochemical model is coupled to a two-dimensional axisymmetric equivalent-continuum thermal–mechanical model. Three controlled cases are compared over the first 100 s of a 1C charge: (1) the COMSOL material-default positive-electrode equilibrium potential, (2) a literature-derived LFP equilibrium-potential function that represents the plateau thermodynamics without explicitly resolving a phase field, and (3) Case 2 with a phenomenological stress-feedback term. At 100 s, the terminal voltage is approximately 3.360 V in Case 1 and 3.368 V in Cases 2 and 3. The corresponding average volumetric heat-generation rates are approximately 2.83 × 103 and 3.05 × 103 W m−3, and the average temperature rises are approximately 0.133 and 0.145 K. The maximum equivalent-continuum von Mises stresses are only about 0.21 and 0.23 kPa, respectively; these values are not interpreted as electrode- or particle-scale stress. Cases 2 and 3 are practically indistinguishable at the plotted resolution, so the feedback coefficient is treated only as an uncalibrated sensitivity parameter. The model is therefore a short-time operational framework demonstration, not a thermal-runaway or experimentally validated safety model.