Ultrahigh Thermal Conductive yet Superflexible Graphene Films

Electrical devices generate heat at work. The heat should be transferred away immediately by a thermal manager to keep proper functions, especially for high‐frequency apparatuses. Besides high thermal conductivity (K), the thermal manager material requires good foldability for the next generation flexible electronics. Unfortunately, metals have satisfactory ductility but inferior K (≤429 W m−1 K−1), and highly thermal‐conductive nonmetallic materials are generally brittle. Therefore, fabricating a foldable macroscopic material with a prominent K is still under challenge. This study solves the problem by folding atomic thin graphene into microfolds. The debris‐free giant graphene sheets endow graphene film (GF) with a high K of 1940 ± 113 W m−1 K−1. Simultaneously, the microfolds render GF superflexible with a high fracture elongation up to 16%, enabling it more than 6000 cycles of ultimate folding. The large‐area multifunctional GFs can be easily integrated into high‐power flexible devices for highly efficient thermal management. An atomic crystal‐folding principle is proposed for designing highly thermal‐conductive yet superflexible graphene film. Debris‐free, giant graphene sheets and folded atomic thin crystals afford macroscopic assembled graphene film a high thermal conductivity 1940 W m−1 K−1 and fracture elongation 16%, respectively. This principle opens the door for high‐performance yet flexible inorganic/ceramic macroscopic materials and devices.