Performance evaluation of battery thermal management system using anisotropic, shape-stable, flexible composite PCM

Efficient thermal regulation remains a critical challenge in battery thermal management systems (BTMS), especially under high-rate and cyclic operations that risk thermal runaway. Flexible composite phase change materials (FCPCMs) often struggle to provide high latent heat while maintaining thermal conductivity, shape stability, and flexibility. In this study, FCPCM is developed using dry blending method before melt processing. This retains high latent heat while significantly improving thermal conductivity. A notable gap in the literature is whether expanded graphite (EG) or polymeric material (SEBS) has more effect on latent heat reduction. Furthermore, limited attention has been paid to anisotropic thermal conductivity in promoting uniform heat dissipation within cylindrical battery cells. This study analyzes in-plane and through-plane conductivities. The FCPCM is integrated into BTMS with enhanced conductivity, unlike prior studies using pure or randomly mixed PCMs. The FCPCM with 10 wt% EG (S5) achieved anisotropic conductivities of 3.67 W/m·K (in-plane) and 3.06 W/m·K (through-plane), while maintaining latent heat of 206.5 J/g and minimal leakage (0.16%). When used in BTMS, S5 reduced peak surface temperature up to 23.5 °C at a 4C discharge rate and lowered cell temperature difference by 50% compared with the isotropic sample (S2). During repeated 4C discharge and 1C charge cycling, FCPCM integration effectively suppresses the temperature rise relative to the bare battery, with S5 consistently exhibiting lower peak temperatures and reduced temperature non-uniformity than S2. These results highlight that anisotropic FCPCMs offer a promising pathway to enhance thermal safety, mitigate hot-spot formation, and extend the operational limits of batteries.