Three‐Dimensional Highly Thermally Conductive Graphene Blocks by Multiscale Blending and Multistage Pressure Induction

The thermal conductivity of graphene materials rapidly decreases with the increase of thickness, seriously hindering its application potential in high heat flow scenarios. Here, a novel strategy for synthesizing expandable‐thickness graphene block (GPB) with high thermal conductivity is proposed via multiscale blending and multistage pressure induction (MBP). The reduction of the in‐plane thermal conductivity with the increase of thickness of the proposed GPB‐MBP is lowered by more than 94% compared to existing graphene materials, and the maximum thickness of GPB‐MBP reaches 12.1 mm, which is more than 10 times that of the existing graphene materials. Compared with the thickest existing graphene material of 1.05 mm, the in‐plane thermal conductivity and cross‐plane thermal conductivity of GPB‐MBP are 4.7–7.4 times and 6.2–6.6 times higher, respectively. The maximum thermal diffusion ability of GPB‐MBP reaches 6.3 W/K, which is 8–53 times higher than that of existing graphene materials. Furthermore, the proportional relationship between in‐plane thermal conductivity and the logarithm of length was discovered on macroscopic graphene materials for the first time. The new strategy for synthesizing expandable‐thickness GPB offers a new approach for high‐heat‐flux thermal management.