polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) were used as passivators to prepare PVP/PEG/Cu composite nanoaggregates (CuNP) by in-situ coating copper nanoparticles. Then, CuNP, as a thermal conductivity enhancer, were introduced into the phase change system to prepare CuNP/PEG solid-liquid phase change materials (CuNP/PEG PCMs). FT-IR, XRD, DSC and TGA were used to investigate the interaction and thermal properties of the PCMs. The physical interaction between the PVP coated on the nanoaggregate and the working material PEG, and the protective effect of PVP ensured that the PCMs exhibit stable performance, good thermal cycle stability and service life. The results showed that the introduction of CuNP significantly improved the thermal conductivity of the PCMs and accelerated the crystallization of the working material as a crystal nucleus. When the mass fraction of CuNP was 5%, the phase change enthalpy of the solid-liquid PCMs was 157.0 J/g, and the material also exhibited strong thermal stability under 370°C. The heat accumulation rate, heat release rate, and crystallization rate were increased 34.09%, 31.45%, and 55.33%, respectively, when comparing with the pure PEG.