Structure-interface engineering-driven high-performance bidirectional thermally conductive Graphene/PBO composite films for lithium-ion battery thermal management

With the rising integration density of electronic devices, advanced thermal management solutions are urgently needed. Graphene-based materials offer excellent in-plane thermal conductivity but poor through-plane heat transfer due to their intrinsic 2D structure, restricting multi-directional heat dissipation applications. This study fabricated an Ag@AlN-graphene/poly(p-phenylene benzobisoxazole) (PBO) hybrid composite film with a continuous 3D thermal conduction network through a structure-interface engineering. Ag@AlN particles not only regulate the orientation of graphene's heat transfer but also the presence of Ag nanoparticles significantly optimizes the interfaces between graphene and AlN. The film exhibits superior bidirectional thermal conductivity (29.9 W/m·K in-plane; 3.74 W/m·K through-plane), reliable electrothermal performance (217.5 °C at 13 V), excellent mechanical stability (3.2 MPa peak stress, 30% fracture strain), electromagnetic interference (EMI) shielding (up to 50 dB), and photothermal conversion (75.3 °C under 1.5 sun). Lithium-ion battery tests confirm its "low-temperature preheating/high-temperature heat dissipation" dual functions, maintaining ≤50 °C during 2 C charge-discharge. This work overcomes graphene-based thermal interface materials' through-plane thermal conductivity bottleneck, providing a viable thermal management strategy for high-power electronic devices with broad applications in electronics and new energy sectors.