• A water molecule coordination model based on unit cell cluster structures was established to theoretically determine that a minimum of 10.67 wt% excess water is required to completely suppress phase separation in SAT. • EDTA was introduced as a synergistic additive to develop SAT-H 2 O-EDTA composite phase change materials, which effectively reduces the demand for excess water. When the added EDTA was increased from 0 to 0.5 wt%, the excess water was decreased from 12 wt% to 8 wt%. • The SAT-H 2 O-EDTA composite exhibits long-term stable supercooling capability (>400 h at 30–35 K undercooling) and maintains unchanged chemical composition and crystal structure after 100 heating–cooling cycles, demonstrating excellent long-term usability. To address the defects of SAT, such as phase separation and supercooling instability during service, this study systematically analyzes phase separation suppression methods and their effectiveness via theoretical analysis and experimental research. Based on typical unit cell cluster structures, a water molecule coordination model was established to theoretically calculate the minimum required excess water content for suppressing SAT phase separation. EDTA was introduced as a synergistic additive to develop an SAT-H 2 O-EDTA composite PCM. Experimental tests were conducted to verify its phase separation suppression effect and material stability. The results show that at least 10.67 wt% excess water is required to completely suppress SAT phase separation in SAT. EDTA is an effective additive for inhibiting SAT phase separation and can reduce the demand for water. For SAT samples with 8 wt% water content, adding 0.5 wt% EDTA fully suppresses phase separation, while for those with 10 wt% water content, only 0.1 wt% EDTA is needed. The developed SAT-H 2 O-EDTA composite exhibits long-term stable supercooling capability (>400 h) at 30–35 K undercooling, with no degradation in chemical composition or crystal structure after 100 thermal cycles, demonstrating long-term usability. Through theoretical modeling and experimental optimization, this study successfully prepares an SAT-H 2 O-EDTA composite PCM with high latent heat, strong phase separation suppression, and long-term stable supercooling properties, providing a reliable solution for long-term thermal energy storage applications.
Zhang et al. (Thu,) studied this question.