Reconciling Heat Conduction, Energy Storage, and Flexibility in Thermal Interface Materials via Multi-Parameter Optimization

Abstract The rapid advancement of high-power electronic devices has intensified thermal safety issues, such as localized heat accumulation and severe temperature fluctuations. Conventional single-mode heat dissipation or phase-change energy storage materials often fail to simultaneously achieve high thermal conductivity and superior energy storage performance. Therefore, developing integrated thermal management materials that offer efficient heat dissipation, thermal energy storage, and surface conformability is of great practical significance. Herein, boron nitride nanosheets (BNNSs) as thermally conductive fillers and phase-change microcapsules (PCMCs) as energy storage units were coassembled via directional freezing to construct an oriented scaffold. After densification by hot pressing, polydimethylsiloxane (PDMS) was introduced as the flexible matrix through infiltration under reduced pressure, followed by a second hot press to obtain BNNS/PCMC/PDMS composites. In this design, directional freezing induces ordered assembly of BNNSs to form efficient heat conduction pathways; PCMCs are uniformly embedded in the skeleton of the scaffold as heat storage units; and PDMS fills the network voids, endowing the material with favorable flexibility. By systematically regulating the carboxymethyl cellulose sodium content, hot-pressing thickness, and BNNS/PCMC ratio, the continuity of thermal conduction pathways, structural stability of the scaffold, and infiltration effectiveness of PDMS were optimized to achieve a balance among thermal conduction, heat storage capacity, and flexibility. Furthermore, by employing PCMCs with various phase-change temperatures to precisely match the device operating temperature window, a series of composites were fabricated and applied to the thermal management of LED chips, lithium-ion batteries, and 5G smartphones. This work demonstrates that the synergistic integration of an oriented thermally conductive skeleton, a phase-change component, and a flexible matrix can reconcile the trade-off among thermal conduction, heat storage, and mechanical flexibility, offering a structural design for multifunctional thermal management materials.