ABSTRACT Directional thermal control is a critical requirement in adaptive thermal management, with applications spanning from spacecraft to self‐heating devices. Herein, an anisotropic coating is introduced that enables passive, thermal conductivity difference‐based directional heat transfer on device surfaces without external energy input. The thermal conductivity contrast between the phase change cooling layer and a graphene‐based conductive layer produces a pronounced thermal rectification effect, yielding a maximum rectification coefficient of 3.96. The anisotropic coating further enhances heat dissipation, blocks external heat influx, and improves thermal utilization via synergy with phase‐change. Furthermore, this structure achieves a solar reflectance of 95.13% and a mid‐infrared emissivity of 95.56% by integrating hollow scatterers with a broadband infrared‐radiative polyurea matrix. During the daytime, the anisotropic coating reduces internal and external temperatures by up to 13.1°C and 7.4°C, respectively, compared to commercial white coating. Even with an internal heat source (50°C), temperature reductions of 3.9°C and 1.6°C are maintained. The cooling power of the composite coating is enhanced by 71.6%, highlighting the roles of thermal rectification. In addition, the anisotropic coating exhibits robust adhesion and hydrophobicity on various substrates. Ultimately, this design effectively mitigates critical thermal hazards‐overheating and fire—in high‐power‐density electrical equipment.
Qi et al. (Wed,) studied this question.