Anderson Localization of Phonons in Thermally Superinsulating Graphene Aerogels with Metal‐Like Electrical Conductivity

Abstract In the quest to improve energy efficiency and design better thermal insulators, various engineering strategies have been extensively investigated to minimize heat transfer through a material. Yet, the suppression of thermal transport in a material remains elusive because heat can be transferred by multiple energy carriers. Here, the realization of Anderson localization of phonons in a random 3D elastic network of graphene is reported. It is shown that thermal conductivity in a cellular graphene aerogel can be drastically reduced to 0.9 mW m −1 K −1 by the application of compressive strain while keeping a high metal‐like electrical conductivity of 120 S m −1 and ampacity of 0.9 A. The experiments reveal that the strain can cause phonon localization over a broad compression range. The remaining heat flow in the material is dominated by charge transport. Conversely, electrical conductivity exhibits a gradual increase with increasing compressive strain, opposite to the thermal conductivity. These results imply that strain engineering provides the ability to independently tune charge and heat transport, establishing a new paradigm for controlling phonon and charge conduction in solids. This approach will enable the development of a new type of high‐performance insulation solutions and thermally superinsulating materials with metal‐like electrical conductivity.