The effect of F127 addition on the properties of PEGDA/PVdF cross-linked gel polymer electrolytes

The ternary polymer membranes consisting of poly(ethylene glycol) diacrylate (PEGDA), poly(vinylidene fluoride) (PVdF), and polyethylene oxide-co-polypropylene oxide-co-polyethylene oxide (PEO-PPO-PEO, F127) were prepared as the matrix of gel polymer electrolytes (GPEs) by a solvent controlled evaporation procedure. In the ternary system, the unraveled PVdF polymer chains are randomly mixed with the liquid PEGDA oligomer, which are entangled with themselves and the PEGDA network after curing, while F127 acts as a plasticizer. Infrared (IR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and potentiostat/galvanostat measurements were carried out to check the characteristics of the polymer membranes. It was found that the interpenetrating polymer network (IPN) structure influenced the porous structure, pore size and mechanical properties to a great extent, and that F127 had a plasticization effect which resulted in a decrease of the crystallinity and mechanical strength. The highest electrolyte uptake and the maximum room temperature ionic conductivity were obtained in the blended membrane with a PEGDA/PVdF/F127 ratio of 0/4/4. The PEGDA/PVdF/F127 GPEs assured electrochemical stability up to 4.5 V.