Advanced phase change gel featuring tunable low-temperature transition for cold energy storage

Phase change materials (PCMs) are crucial in cold storage technology, yet their application in low-temperature environments remains underexplored due to the limited availability of suitable materials. Most existing studies focus solely on either inorganic or organic PCMs, inorganic PCMs often face issues such as phase separation, supercooling, and poor cycling stability, while organic PCMs face challenges such as low thermal conductivity, flammability, and high costs. Additionally, the incompatibility between organic and inorganic PCMs has long posed a fundamental challenge, preventing the integration of their respective advantages. This study addresses these challenges by developing an innovative organic-inorganic composite PCM through interfacial modifications. Mechanistically, the modulation of interfacial forces enhances compatibility, suppresses phase separation, and provides nucleation sites to eliminate supercooling. A significant breakthrough was realized in precisely tuning phase change temperature (PCT) to 4.9 °C, while maintaining a high latent heat of 157.9 J g⁻¹ and achieving a thermal conductivity of 0.198 W m⁻¹ K⁻¹. The optimized HTG₅ formulation, with a modified eutectic salt-to-tetradecane ratio of 5:5, exhibited a 33 % enhancement in cold storage density compared to conventional inorganic PCMs at the same PCT, while effectively eliminating phase separation and supercooling. Cycling stability tests further demonstrated that the phase change properties remained stable even after 50 thermal cycles. Beyond thermal performance, the composite formulation effectively mitigated the flammability concerns associated with pure organic PCMs and significantly reduced costs by incorporating low-cost inorganic components. Application experiments validated its ability to delay internal temperature fluctuations, highlighting its potential as an efficient cold energy storage medium. By successfully integrating organic and inorganic PCMs for low-temperature applications, this study paves the way for next-generation cold storage PCMs with enhanced performance and reliability.