Graphene nanoplatelets were chemically modified by polyethylene glycol (PEG), via an amidation reaction. Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX) and thermo-gravimetric analysis (TGA) revealed the successful accomplishment of reaction. Functionalized graphene (FGnP) were incorporated into poly(ethylene oxide) (PEO) and solid polymer electrolytes (SPE) based on PEO and lithium perchlorate salt (LiClO4). The non-isothermal crystallization kinetics of samples were studied using differential scanning calorimetry (DSC). Modified Avrami and combined Avrami-Ozawa equations were used to analyze the non-isothermal crystallization. The Avrami exponent values showed that FGnP did not change the nucleation mechanism and crystal growth in neither PEO nor PEO:LiClO4. However, the half-time of crystallization increased by addition of FGnP in both PEO and PEO: LiClO4 systems. A more considerable effect of FGnP on the crystallization behavior of SPE/FGnP electrolytes was found in comparison to PEO/FGnP nanocomposites, which can be related to the FGnP induced dissociation of lithium salt. (C) 2016 Elsevier Ltd. All rights reserved.