High-temperature composite phase change materials with superior thermal storage performance enabled by hierarchical AlN aerogel ceramics

High-temperature phase change materials (HT-PCMs) play a crucial role in latent heat storage systems for renewable power generation. Integrating HT-PCMs with high-thermal-conductivity porous ceramic skeletons to form composite PCMs (CPCMs) effectively mitigates limitations such as low thermal conductivity, leakage, and supercooling. However, most skeletons fail to achieve both high thermal conductivity and ideal porosity (>85 %) simultaneously, resulting in a trade-off in CPCMs between high latent heat (>300 J/g) and fast thermal response (>10 W/(m·K)). Herein, we developed high-performance CPCMs through the synergistic integration of a tailored AlN aerogel ceramic (AlN-AC) and two distinct HT-PCMs, enabling efficient thermal storage performance from 500 to 900 °C. The hierarchical AlN-AC was fabricated via the spontaneous coagulation casting method, exhibiting 90 % porosity and a thermal conductivity of approximately 10 W/(m·K). Leveraging its exceptional infiltration capacity and highly conductive network, two CPCMs were developed by incorporating Al Si alloy (CPCM-AlSi) and NaCl (CPCM-NaCl), respectively. The resulting composites achieved a maximum latent heat of 402 J/g with CPCM-NaCl and a maximum thermal conductivity of 22 W/(m·K) with CPCM-AlSi. Meanwhile, the CPCMs also achieved a high total energy storage density of 625 J/g and 1791 J/cm 3 within a narrow 200 °C range, with reliable performance over 800 thermal cycles. The CPCMs successfully combine high thermal energy density with efficient heat transfer, outperforming the overall performance of previously reported CPCMs. Additionally, a novel micro-CT-based method was developed for predicting thermal storage performance, offering significantly improved accuracy over conventional approaches. This study presents an integrated strategy from material design to performance prediction for advanced high-temperature CPCMs.