High-performance cellulose nanofiber-derived composite films for efficient thermal management of flexible electronic devices

Heat dissipation material shows great promise as a thermal management tool for high-power-density flexible electronic devices. However, conventional materials (e.g., metals, carbon materials, and polymer-based composites) typically are difficult to meet the required thermal conductivity and mechanical properties at the same time. Additionally, performance enhancement of the heat-dissipating materials generally requires complicated procedures with high manufacturing costs. Here, we design a facile and robust synthesis procedure by processing all-natural cellulose nanofiber (CNF) and graphite nanoplatelet (GNP) to generate a high-performance sustainable thermal management material. The obtained CNF-GNP composite film contains extensive heat transfer highways and highly aligned hydrogen bonds in its brick-and-mortar microstructure. Consequently, the CNF-GNP-40 film exhibits high thermal conductivity (21.42 W m- 1 K-1), high strength (115.8 MPa), high toughness (4.19 MJ m(-3)), low density (similar to 1.3 g cm(-3)), and super flexibility simultaneously. Besides, the composite film possesses excellent stability after multiple cycles of mechanical deformation and exposure to various environments. Taking the thermal management of wearable devices as an example, experimental results reveal that applying the composite film can effectively reduce the temperature of both device and skin by about 8 degrees C on average, making it a prospective thermal management material for flexible electronic devices.