A Low‐Thermal‐Resistance and Oriented Assembly Strategy Enabling Ultrahigh Thermal Conductivity Phase Change Composites for Efficient Thermal Management

Phase change materials (PCMs) with high thermal conductivity are highly desired for fast-response thermal management and high-power-density thermal storage. Although graphite/PCM composites have been intensively studied for decades, achieving a high-performance yet low-cost graphite-based phase-change composites (PCCs) remains challenging. In this work, a novel strategy for synthesizing ultrahigh thermal conductivity PCCs is proposed by the low-thermal-resistance and oriented assembly of PCM-filled expanded graphite particles. The alignment of large-size graphite sheets and suppression of the thermal resistance between them are realized inside the PCC blocks by a facile compression-induced assembly and local heating treatment. The resultant PCCs present remarkable thermal conductivity of 8.7-44.7 W m^-1 K^-1 at graphite contents of 5-17 vol.%, two orders of magnitude higher than that of pure PCM. Besides, the PCC blocks also demonstrate superior overall thermal effusivity and excellent mechanical stability, enabling them to be easily engineered into efficient thermal management devices by coordinating the graphite sheet orientation with the overall thermal transfer direction. Experimental results show an optimized PCC device can lower the peak cooling power by ≈35% through the peak load shifting. The methods presented offers a promising route to preparing high-performance yet cost-effective thermal storage materials for various heat-related applications.