High Ionic Conductivity of Flexible Polymer-Based Electrolyte with Low Porosity

Solid or polymer based electrolytes have attracted many interests with growing need for high-density power sources due to safety concerns. Among these ‘dry’ electrolytes, polymer-based electrolytes can be used widely in portable electronics or large scale industry energy storage thanks to its flexibility. However, low ionic conductivity of polymer is a drawback of these polymer-based electrolytes, especially for poreless membranes. In this work, various polymer-based membranes, e.g. polyvinylidene fluoride (PVdF) membranes, sulfonated poly(ether ether ketone) (SPEEK) membrane, were fabricated via various methods. We explored various methods to reduce porosity of membranes without decreasing their ionic conductivity. For example, hot pressing with poly 2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS) can significantly decrease the porosity of membranes while ionic conductivity of membranes remained the same. Filling pores with succinonitrile (SN) was even able to increase ionic conductivity as well as decreasing porosity. High ionic conductivity of ~10^-4 S/cm was obtained on PVdF/SN membranes. SPEEK membranes without pores were also fabricated, achieving a high ionic conductivity of ~10^-4 S/cm, which is suitable for applications such as flow battery electrolyte.