Post‐Compaction Strategy for Unlocking the Inherent High Thermal Conductivity of Aligned Composite Phase Change Materials Toward Efficient Photothermal Conversion and Battery Thermal Management

ABSTRACT This study presents a multidimensional assembly and post‐compression strategy. It unlocks the inherent high thermal conductivity of aligned composite phase change materials. Expanded graphite (EG) has poor aqueous processability for ordered frameworks. This limitation is overcome via synergistic intercalation and dispersion of graphene oxide (GO) and a dispersant. This produces a multidimensional oriented aerogel (ECGA) reinforced with EG, GO, aramid nanofibers, and carbon nanotubes. The key innovation is subsequent hot‐pressing. It consolidates the composite and induces secondary orientation‐reconstruction of the 3D thermally conductive network, forming continuous dense phonon pathways. The resulting ECGA/PW‐HP (HP denotes hot pressing) with paraffin wax maintains a high phase‐change enthalpy of 181.0 J/g. Axial and radial thermal conductivities reach 4.050 and 6.367 W/(m·K), respectively, a 19.9‐fold enhancement over the non‐compressed counterpart. The material shows a photothermal conversion efficiency of 91.4% and a thermoelectric output of 231.4 mV under 300 mW/cm 2 simulated sunlight. It also lowers the maximum surface temperature of an 18650 battery under 3C cycling by 10.4°C. This work offers a new paradigm for designing advanced thermal management materials with high energy density, superior thermal conductivity, and excellent reliability.