Synergistic Effect of Aligned Graphene Nanosheets in Graphene Foam for High‐Performance Thermally Conductive Composites

Graphene shows a great potential for high-performance thermally conductive composite applications because of its extremely high thermal conductivity. However, the graphene-based polymer composites reported so far only have a limited thermal conductivity, with the highest thermal conductivity enhancement (TCE) per 1 vol% graphene less than 900%. Here, a continuous network of graphene foam (GF), filled with aligned graphene nanosheets (GNs), is shown to be an ideal filler structure for thermally conductive composite materials. Compared to previous reports, a clear thermal percolation is observed at a low graphene loading fraction. The GNs/GF/natural rubber composite shows the highest TCE of 8100% (6.2 vol% graphene loading) ever reported at room temperature, which gives a record-high TCE per 1 vol% graphene of 1300%. Further analyses reveal a significant synergistic effect between the aligned GNs and 3D interconnected GF, which plays a key role in the formation of a thermal percolation network to remarkably improve the thermal conductivity of the composites. Additionally, the use of this composite for efficient heat dissipation of light-emitting diode (LED) lamps is demonstrated. These findings provide valuable guidance to design high-performance graphene-based thermally conductive materials, and open up the possibility for the use of graphene in high-power electronic devices.