Development of new inorganic shape stabilized phase change materials with LiNO3 and LiCl salts by sol-gel method

Abstract

Latent heat storage with inorganic salts as phase change materials (PCM) is very attractive as these compounds can store a large amount of heat within a small temperature range in a small volume. However, subcooling, phase segregation, and low cycling stability are present in these materials, affecting its applications. One of the ways to reduce or eliminate these disadvantages is to encapsulate or stabilize the inorganic salts. In this work, one-step sol–gel technique was used to create new shape stabilized PCM (SS-PCM) with SiO2 as support material. Four pure salts, LiCl, LiNO3, LiCO3, and CH3COOLi·2H2O, were investigated to evaluate the potential of this sol–gel method, usually used with organic PCM, to obtain inorganic SS-PCM. IR spectroscopy confirmed the polymerization process during the sol–gel process, and show that no chemical reaction occurs between PCM and SiO2 support material, except for Li2CO3. XRD patterns for high salt content (60%) samples show occurrence of salt agglomerations. In addition, the water molecules loss for CH3COOLi·H2O during sol–gel process was observed in SS-PCM. The thermophysical characterization by DSC show that LiCl and LiNO3 properties were improved due to sol gel process, exhibiting higher cycling stability and lower subcooling value than the pure salts. The LiNO3 and LiCl SS-PCM present potential thermal energy storage applications. However, CH3COOLi·H2O and Li2CO3 did not demonstrate potential to be used as PCM under the studied condition.