Organic and ionic liquid-based phase change materials: Advances in property tailoring and applications

The growing use of intermittent renewable energy sources has increased the need for efficient thermal energy storage (TES), with phase change materials (PCMs) offering high latent heat (LH) storage within a narrow temperature range. This review critically examines conventional organic PCMs, their property-enhancement strategies, emerging ionic liquid (IL)-based PCMs, computational design approaches, and major TES applications. Experimental and computational studies are synthesized to evaluate nanoparticle incorporation, encapsulation, ionic liquids (ILs), functionalized ionic liquids (FILs), deep eutectic solvents (DESs), and computer-aided molecular design (CAMD) methods. The review provides an integrated perspective linking material properties, molecular design, computational screening, and application-specific requirements. The literature shows that nanoparticle incorporation can markedly improve thermal conductivity, although its effects on LH and long-term stability depend on PCM-additive combination and additive loading, while encapsulation helps reduce leakage, protect the PCM from the surrounding environment, and improve heat-transfer performance. ILs, FILs, and DESs exhibit tunable phase-change behavior, with molecular structure, functional groups, and hydrogen-bonding interactions influencing their LH storage capacity. QSPR and machine-learning models enable rapid prediction and screening, but remain limited by scarce high-quality data and validation. Applications in buildings, solar energy storage, and battery thermal management further highlight the need for application-specific PCM design and long-term performance evaluation. Collectively, these findings identify key directions for the rational development and practical deployment of advanced PCMs.