Thermal management of cylindrical lithium-ion batteries using internal and external phase change material placement

Purpose Thermal management is essential to ensure the performance and safety of lithium-ion batteries, and effective heat dissipation helps prevent excessive temperature rise. This study aims to explore advanced passive thermal management strategies by developing a coupled electrochemical–thermal model to investigate the effectiveness of different phase change material (PCM) configurations: internal (within a hollow mandrel), external (surrounding the cell) and combined internal/external placement. The objective is to contain temperature rise while optimizing battery pack dimensions. In addition, a parametric analysis on the external PCM thickness is carried out to identify optimal design solutions for space-constrained applications. Design/methodology/approach An 18650 lithium cobalt oxide (LCO) battery (3.7 V, 2.6 Ah) is studied, combining a multiscale pseudo-two-dimensional electrochemical model with a two-dimensional axis-symmetric thermal domain. Sodium thiosulfate pentahydrate is selected as PCM and modeled with an enthalpy-based method to account for latent heat effects. Equal PCM volume is used to compare internal and external configurations. Findings The internal/external PCM configuration delays the battery critical temperature of 50 °C by up to 120.5%, compared to the case without PCM. External- and internal-only PCM provide delays of 58.6% and 40.5%, respectively. The parametric study shows that, to maintain a safe operating temperature of 45°C, an optimal PCM thickness of 1.66 mm is required for the internal/external layout versus 1.96 mm for the external-only case, corresponding up to a 5.4% battery pack volume saving. Originality/value This work highlights the benefit of internal PCM integration in lithium-ion batteries, improving both thermal buffering and spatial efficiency. The findings offer guidance for designing compact, passively cooled battery systems.