Super-liquid-repellent thin film materials for low temperature latent heat thermal energy storage: A comprehensive review of materials for dip-coating

When discharging latent heat thermal energy storage (LHTES) systems, performance is influenced by the formation and adherence of a solid layer of phase change material (PCM) on heat eXchange (HX) surfaces. Super-liquid-repellent thin films (STFs) may be able to reduce solidifying PCM adhesion on HX surfaces during discharging, delay PCM solidification to lower temperatures, and by modifying nucleation sites potentially enable long-term seasonal thermal storage. Techniques employed previously to fabricate sintered polymeric STF coatings include chemical vapour deposition, dip-coating, spray-coating, spin-coating, layer-by-layer (LbL) assembly, sol-gel, anodizing, electrodeposition, electrospinning, so on. Dip-coating is considered attractive for fabricating thin films on simple and complex surface geometries due to process maturity, scalability, flexibility and cost-effectiveness. To identify suitable materials for preparing STFs on metal HX surfaces using the dip-coating process, more than 200 journal articles published in English during the period 2010 to 2022 were reviewed and the potential role of STFs in LHTES applications was assessed. The review identified key areas and applications stimulating STF material developments and formulations. The dip-coating of potential STF materials was classified under three major themes driving current research and development (R&D) activities, that is, high performance thin films, eco-friendly thin films and fundamental research formulations. This review provides a platform from which to develop coatings and HX systems to enable the cost-effective implementation of STFs for improved heat transfer in future mobile/stationery LHTES systems.