Effects of boron-nitride-based nanomaterials on the thermal properties of composite organic phase change materials: A state-of-the-art review

Utilizing phase change materials (PCMs), which can be tailored to melt or solidify at specific temperatures, as an energy storage medium provides an effective way to store latent thermal heat for diverse applications. However, conventional PCMs exhibit significant disadvantages, such as low thermal conductivity and leakage. Therefore, highly-thermally-conductive composite phase change materials (CPCMs) have received increasing research interest by virtue of integrating nanofillers with high thermal conductivity and thermal stability, such as hexagonal boron nitride (hBN), into the organic PCM matrices. While several nanomaterials-reinforced composites, such as graphene-based CPCMs, have been reviewed extensively, however, there are no critical reviews on the thermal performance of BN-enhanced organic CPCMs in energy storage applications. Therefore, this literature review highlights and comprehensively summarizes the latest research on the thermal improvements of BN-filled organic CPCMs with a focus on different types of BN allotropes, including hBN, BN nanoplatelets, BN nanosheets and BN nanotubes. Moreover, this review provides an extensive discussion on the fabrication processes, effects of functionalization and porous scaffolds, as well as the applications of BN fillers as shell materials. Specifically, the novel theoretical and experimental methodologies for achieving high thermal conductivities are reviewed and compared. Additionally, some other fundamental parameters associated with thermal properties, such as latent heat of fusion, thermal cycle stability, and thermal-to-solar efficiencies are also discussed. Finally, current challenges in the field of BN-incorporated CPCMs are listed/discussed, and recommendations for the future development of BN-enhanced organic CPCMs with better thermal properties to cater the future needs in energy storage are provided.