A Thermal Management Hybrid Membrane with Both High Thermal Conductivity and Electrical Insulation

Abstract The elevated thermal output of microelectronic devices necessitates efficient thermal management materials to mitigate overheating. However, simultaneously achieving high thermal conductivity and exceptional electrical insulation in polymer‐based composites remains a formidable challenge. Herein, a flexible and scalable aramid nanofiber/expanded graphite (ANF/EG) hybrid membrane is demonstrated, which integrates high thermal conductivity with excellent electrical insulation via a strategy of ANF‐assisted exfoliation and dispersion of EG. Under ultrasound treatment, EG undergoes exfoliation and is subsequently wrapped by ANFs through strong interfacial interactions. This process leads to the formation of a well‐ordered, lamellar structure consisting of nanofiber‐wrapped EG nanosheets. Due to the distinctive microstructure, in which the ANFs block the electron transport between the EG nanosheets, the hybrid membrane maintains exceptional electrical insulation (4.70 × 10 9 Ω·cm) even with the EG content of up to 50 wt.%. Moreover, the high EG content combined with well‐developed heat‐conductive pathways (ANFs serve as the “bridge” to connect adjacent EGs) endows the membrane with an ultrahigh in‐plane thermal conductivity (40.59 W/(m·K)). The cooling experiments with microelectronics reveal that ANF/EG membrane can significantly reduce CPU temperature by 23 °C, outperforming commercial silicone grease by 8 °C, indicating intense heat dissipation performance. This work opens a novel avenue for designing cutting‐edge thermal management materials with high thermal conductivity and electrical insulation, potentially facilitating the modernization and iteration of electronic devices.