Engineering polymer electrolytes with enhanced ionic conduction

This paper describes our strategies to engineer amorphous polymer–salt complexes and investigate their electrical behavior. In the first approach, semicrystalline polymer polyoxyethylene (POE) was plasticised using amorphous polyoxypropyleneglycol (POPG) in the presence of sodium salts. In the second approach, amorphous polymers, poly(bis(methoxyethoxyethoxy phosphazene)) (MEEP) and polysiloxane, were used to synthesise electrolytes. These were complexed with sodium salts and a small amount of polyoxyethylene. The nature of each complex was ascertained from optical microscopy, X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC) in these systems. The polymer–salt complexes, in the first approach, revealed a well-defined glass formation region in which all the compositions were amorphous and showed unusually high ionic conductivity ∼10−4 (Ω cm)−1 at ambient temperature. The electrolytes in the second approach showed a maximum conductivity of ∼10−5 (Ω cm)−1. However, truly amorphous compositions could not be obtained. The first approach of engineering reduction in crystalline phases appeared more effective in enhancing ionic conductivity.