Solid–solid phase‐change materials cross‐linked by carbon quantum dots: Address leakage and high super‐cooling degree simultaneously

Abstract Leakage and super‐cooling are two main disadvantages of polyethylene glycol (PEG) when used as phase‐change materials (PCMs) for thermal energy storage, which seriously restrict the practical applications of the materials. In this study, we employ carbon quantum dots (CQDs) as cross‐linkers to fabricate PEG‐based solid–solid PCMs, which not only address the leakage issue of PEG during melting process, but also have much lower super‐cooling degree compared with PEG, exhibiting extraordinary thermal energy storage performance. CQDs serve as a heterogeneous nucleating agent in the crystal domains of these PEG‐based PCMs according to the characterizations. Additionally, CQDs are also beneficial to the thermal stability of the PCMs. And these PEG‐based PCMs have high phase‐change enthalpies (94.4 J/g) and applicable phase‐change temperatures (25–37°C), showing potential for thermal energy storage.