Improved Poly(vinyl alcohol) (PVA) based matrix as a potential solid electrolyte for electrochemical energy conversion devices, obtained by gamma irradiation Ivan Sto  sevski a , Jelena Krsti  c b , Nikola Voki  c a , Miljan Radosavljevi  c a , Zorica Ka  carevi  c Popovi  c b ,  S  cepan Miljani  c a, * a University of Belgrade, Faculty of Physical Chemistry, P.O. Box 47,11158 Belgrade 118, Serbia b University of Belgrade, Vin ca Institute of Nuclear Sciences, Laboratory for Radiation Chemistry and Physics, P.O. Box 522,11001 Belgrade, Serbia article info Article history: Received 6 May 2015 Received in revised form 17 July 2015 Accepted 18 July 2015 Available online xxx Keywords: Energy conversion Electrochemical devices Membrane Poly(vinyl alcohol) (PVA) matrix Gamma radiation Ionic conductivity 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 ɣ-irradi- ation 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 e0.34 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 de- vices were investigated, like thermal stability and gas crossover through the membranes. The 10% PVA 25kGy membrane doped with saturated LiNO 3 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 effi- ciency as it would have in liquid LiNO 3 , showing good compatibility with the material. All these prop- erties make the memebranes attractive candidates for possible application in the electrochemical devices. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Energy is an everlasting need of mankind and the absolute ne- cessity for its existence. Energy supply is one of the main objectives of the modern society. One of the main ‘energy magic’ words now is so-called energy efficiency, whose important part is the energy management. It is a system of measures to be undertaken within the energy production-storage-transportation-consumption chain, to keep energy consumption at a lowest possible level (to save re- sources), to have low-priced energy, and to protect environment at the same time, while consumers must have enough energy at any moment. In that sense manipulation with energy, especially energy conversion from one form to another plays a very important role. This article considers in a way one possible aspect of the energy conversion. That is development of different electrochemical de- vices to be used for that purpose. Hydrogen or direct methanol fuel cells, batteries and electrolyzers are here of special interest. Actu- ally, the aim of this work is development of matrix-type mem- branes to be used as solid electrolytes in such devices. EECDs (Electrochemical energy conversion devices) are expected to become more efficient and thus price competitive alternatives to fossil fuel-based technologies. They are more environmentally friendly, and if use renewable fuels, like hydrogen obtained from water electrolysis, they can be considered as a part of sustainable energy conversion technologies. Many efforts are made in a development of these technologies [1e4]. One of the limiting factors that prevents widespread commer- cialization of EECDs is their high cost. For example, fuel cells, particularly PEMFCs (proton exchange membrane fuel cells) already possess relatively high efficiency, however they use precious metals as catalysts and expensive polymeric membrane * Corresponding author. Tel.: þ381 11 2635545; fax: þ381 11 2187133. E-mail address: epan@ffh.bg.ac.rs (  S. Miljani c). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2015.07.096 0360-5442/© 2015 Elsevier Ltd. All rights reserved. Energy xxx (2015) 1e10 Please cite this article in press as: Sto sevski I, et al., Improved Poly(vinyl alcohol) (PVA) based matrix as a potential solid electrolyte for electrochemical energy conversion devices, obtained by gamma irradiation, Energy (2015), http://dx.doi.org/10.1016/j.energy.2015.07.096