Enhancing thermal properties and moisture resistance of eutectic molten salts via nanoencapsulation for medium-temperature thermal energy storage

Abstract

A nanoencapsulation strategy was developed to addresses the limitations of molten salts as phase change materials (PCMs), including leakage and high hygroscopicity, which hinder their practical application in thermal energy storage. An eutectic molten salt LiNO3-NaNO3-KCl (LNK) was first prepared via aqueous solution evaporation, followed by SiO2 nanoencapsulation using a sol-gel process with methyltriethoxysilane (MTES) and tetraethyl orthosilicate (TEOS) as co-precursors, resulting in nanoencapsulated LNK (NELNK). Characterization results revealed a phase change temperature of 174.7 °C, a supercooling degree of approximately 0 °C, a latent heat of 128.8 kJ/kg, and an encapsulation ratio of 66.2 %. NELNK also exhibited excellent thermal cycling stability, retaining 98.3 % of its energy storage efficiency after thermal cycles. Moisture absorption tests demonstrated significantly improved moisture resistance compared to the pristine LNK. This work successfully enhances the performance of LNK through modification of the SiO2 shell, offering a promising solution for medium-temperature thermal energy storage applications