Numerical thermal management of Li-ion batteries using phase change materials: A transient 2D-axisymmetric study

Efficient battery thermal management systems (BTMS) are critical for maintaining safe operating temperatures and preventing thermal runaway in lithium-ion batteries. This study presents a rigorous two-dimensional (2D) axisymmetric transient numerical model using the enthalpy-porosity method in COMSOL Multiphysics to evaluate the thermal performance of a phase change material (PCM) sleeve (3–4 mm thickness) encasing an 18650 Li-ion battery. The model comprehensively captures the solid-liquid phase change progression, latent heat absorption, and the transition from conduction-dominated heat transfer to buoyancy-driven natural convection within the PCM domain. The numerical results indicate that an optimized 3–4 mm PCM sleeve effectively regulates the maximum cell temperature below the critical threshold (50" " ^∘ "C" ) under transient high-rate discharge conditions. Furthermore, the analysis elucidates the spatial distribution of the melting front, liquid volume fraction evolution, and local energy flux variations during continuous operation. These findings provide valuable design guidelines for optimizing compact, passive BTMS configurations in cylindrical battery packs, contributing to enhanced thermal safety and extended service life in electric vehicle applications.