High thermal conductivity and high energy density compatible latent heat thermal energy storage enabled by porous AlN ceramics composites

Ceramics embedded phase change materials (PCMs) composites are promising candidates for high-temperature thermal energy storage due to good chemical stability and high thermal shock resistance. However, the energy storage rate is severely restricted by the low thermal conductivity of composites. Here, we successfully achieve high thermal conductivity and high energy density compatible thermal energy storage based on porous AlN-eutectic NaCl/LiNO₃ composites. Designed composites possess a high thermal conductivity ranging from 31.8 to 52.63 W/m-K benefiting from continuous thermal transport channels of densified AlN skeletons. Meanwhile, the phase change enthalpy reaches 140 to 186 kJ/kg since about up to 92% of pores are filled with PCMs. Further decorating AlN skeletons with TiN nanoparticles can significantly increase the solar absorptance from 70% to 90%, enabling proposed composites to be applicable for direct solar thermal energy storage as well. This work provides new routes to achieve high thermal conductivity and energy density compatible thermal energy storage via porous AlN ceramics-based phase change composites.