Flexible anisotropically heat-conductive phase-change composites based on maleic anhydride-grafted SEBS matrix for battery thermal management.

Phase change materials (PCMs) are promising for battery thermal management because they absorb latent heat to maintain battery temperature within a safe range. However, simultaneously achieving high thermal conductivity, high latent heat, leakage resistance, and electrical insulation remains challenging, because increasing polymer content to suppress leakage and filler content to enhance heat conduction inevitably reduces PCM loading and compromises latent heat and flexibility. Here, we introduce a coordinated multiscale design that integrates reinforced molecular confinement with directional thermal pathways in a flexible, electrically insulating, anisotropically heat-conductive phase-change composite based on a maleic anhydride-grafted styrene-ethylene-butylene-styrene (SEBS-g-MAH) matrix for battery thermal management (MA-SEBS-AHPCC). Within the SEBS-g-MAH matrix, paraffin wax is accommodated by the ethylene-butylene soft segments through alkyl-chain affinity and van der Waals interactions, while polystyrene hard domains provide physical crosslinking points and the grafted maleic anhydride groups reinforce interchain interactions through local dipole-dipole interactions. This strengthened elastomeric network enables effective confinement of molten paraffin at reduced polymer content. Meanwhile, the aligned boron nitride (BN) pathways provide efficient through-plane heat conduction with reduced filler content, thereby preserving sufficient space for PCM incorporation. As a result, MA-SEBS-AHPCC achieves a through-plane thermal conductivity of 3.658 W m-1 K-1 with only 25 wt% BN, while retaining a high latent heat of 138.934 J g-1. It also exhibits good mechanical flexibility, electrical insulation, leakage resistance and cycling stability. When conformally wrapped around an 18 650 cell, MA-SEBS-AHPCC reduces the peak surface temperature by 8.91 °C during 2C discharge. These results shift FPCM design from the independent optimization of polymer and filler contents toward coordinated control of confinement chemistry and directional heat-transfer pathways.