Synergetic enhancement of heat storage density and heat transport ability of phase change materials inlaid in 3D hierarchical ceramics

Phase change materials (PCMs) based thermal energy storage techniques are promising to bridge the gap between thermal energy demand and intermittent supply. However, the low specific heat capacity (C_p) and thermal conductivity of PCMs preclude the simultaneous realization of high energy density and high power density thermal charging/discharging. Here, concurrent enhancement of C_p and thermal conductivity are demonstrated to be possible based on SiO₂ nanoparticles decorated LiNO₃/NaCl eutectics inlaid in three-dimensional (3D) hierarchical ultralight silicon carbide (SiC) foams. The average C_p is 4.86% higher than that of pure PCMs due to the high surface energy and interfacial thermal resistance induced by weak interaction between SiO₂ nanoparticles and eutectics, as confirmed by molecular dynamics (MD) simulations. The thermal conductivity of composites achieves an ultrahigh value of 2.78 W·m⁻¹·K⁻¹, which is 259% of LiNO₃/NaCl, accompanied with a large phase change enthalpy of 331.9 kJ/kg. Continuous heat transport paths provided by ultralight SiC foams have dominant contributions to the enhancement of thermal conductivity, although the presence of SiO₂ nanoparticles deteriorates it slightly. In addition, the full-spectrum solar absorptance is enhanced from 25.2% to 76.3%. Rapid thermal transport and enhanced solar absorptance of composites enable heat charging rate to rise by 150% compared with SiO₂ nanoparticles decorated eutectics. This work provides a strategy for the realization of high energy density and power density compatible thermal energy storage technology.