Improved Poly(vinyl alcohol) (PVA) based matrix as a potential solid electrolyte for electrochemical energy conversion devices, obtained by gamma irradiation

Abstract

PVA (Poly(vinyl alcohol)) matrixes were developed for potential application in electrochemical energy conversion devices, like batteries, alkaline fuel cells and electrolyzers. They were prepared by γ{phonetic}-irradiation of aqueous PVA solutions, followed by different post irradiation treatments. By immersion in an electrolyte they become membranes with high ionic conductivities. The treatments were shown as the key factor determining the conductivity, through affecting their structure. An improved structure has large fractional free volume, and allows high electrolyte uptake and thus high conductivity (0.30 S cm-1-0.34 S cm-1). The structure, as well as the conductivity, has not been changed even after a period of 14 months, although the membranes have been exposed to strong alkaline medium. Besides high and long-term conductivity of the KOH doped membranes, other important properties for application in the devices were investigated, like thermal stability and gas crossover through the membranes. The 10%PVA25kGy membrane doped with saturated LiNO3 solution was tested in a rechargeable aqueous Li-ion battery. Due to its high conductivity it allowed an electrode material to have the same coulombic efficiency as it would have in liquid LiNO3, showing good compatibility with the material. All these properties make the memebranes attractive candidates for possible application in the electrochemical devices.