Investigation of the inherent electrical potential of PEO electrolyte films

Measurement of the through-plane potential of PEO–lithium triflate electrolyte films has demonstrated that they possess an inherent potential as cast from an acetonitrile solution onto a Teflon substrate. These films have an inherent potential of around 0.2 V and the cast films display a discharge behavior similar to a double layer capacitor system with a small discharge capacitance of 80 nF cm−2. It is postulated that electrochemical properties of the films can be attributed to different salt concentration at the two surfaces. This difference in concentration may result from a matching of the surface-free energy of the Teflon substrate side of the film and the side of the film where evaporation occurs with the lithium triflate species in the polymer. Different spherulite morphologies were also observed for each surface. These morphologies can be assigned to spherulites having much different ion concentrations. Attenuated total reflection (ATR) IR spectroscopy was used to investigate the surface concentrations of free ions, ion pairs and ion multiples of both surfaces of the films. AC impedance spectroscopy of the surfaces of the film was also conducted. These data indicated that there is a difference in the surface concentration of each side. The ability of electrolyte films to exhibit a potential as fabricated may have potential applications as an easily manufactured power source for micro and nanodevices.