Synergistic Thermal Management and Electromagnetic Wave Absorption in Core‐Sheath Phase Change Composites

Abstract The relentless pursuit of ultra‐compact, high‐power electronics has intensified the urgent demand for advanced functional materials capable of simultaneously mitigating Joule heating and electromagnetic interference, a longstanding challenge arising from the inherent conflict between thermal and electromagnetic behaviors. Herein, an innovative 3D continuously interconnected carbon fiber network, functionalized with magneto‐dielectric heterointerfaces and enveloped within phase‐change paraffin medium is modulated, to achieve concurrent thermal regulation and efficient electromagnetic dissipation. This pioneering core‐sheath architecture delivers high latent heat storage and highway‐like phonon transport, while maintaining structural integrity without statistically significant degradation in key metrics even under harsh long‐term thermal shock. More strikingly, core‐sheath heterostructures synergistically integrate a conductive framework with a magnetic coupling network, generating abundant heterojunction interfaces and tailored electron transport pathways that enable an ultralow reflection loss and a broad effective absorption bandwidth. Through cutting‐edge off‐axis electron holography, the magnetic–dielectric coupling interactions are directly visualized and unravel the nanoscale electromagnetic wave absorption mechanism. Real‐world demonstrations confirm the great potential of this solution in enabling co‐optimized thermal management and electromagnetic compatibility for next‐generation high‐power electronic devices.