Effect of Li 3+ Ion Irradiation on Ionic Transport Properties of Complexed Polymer Electrolytes
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1269-FF03-02
Effect of Li 3+ Ion Irradiation on Ionic Transport Properties of Complexed Polymer Electrolytes
P.N. Gupta, G.K. Prajapati and R. Roshan Physics Department, Banaras Hindu University, Varanasi-221005 (U.P.) INDIA
ABSTRACT Swift heavy ion (SHI) irradiation effects on ionic conduction in the PVA-H3PO4 polymer electrolyte films have been investigated due to its variety of applications in electrochemical devices. Polymer electrolytes films are irradiated with 50 MeV Li3+ ions having five different fluences viz. 5x1010, 1011, 5x1011, 1012 and 5x1012 ions/cm2. It is observed that irradiation of the polymer electrolyte films with swift heavy ions shows enhancement in conductivity at lower fluences and decrease in conductivity at higher fluences. It appears that below the critical fluence, swift heavy ion irradiation increases the diffusivity of Li+ ion in the polymer electrolyte which provides larger pathways for ionic transport throughout the system. The temperature dependence of electrical conductivity variation has been used to compute the activation energy involved in conduction process.
INTRODUCTION Ion conducting polymers have been recognized as an effective solid state material widely used in batteries, supercapacitors, fuel cells, ECD’s etc [1-3]. However, to this date, researchers have not succeeded much in enhancing the ionic conductivity of the polymer to have their application on commercial scale. Moreover, good electrochemical and mechanical stability of these polymer electrolytes are not found. In order to increase the ionic conductivity in desirable manner and improving other film properties various methods like doping of salts/acids/alkali and/or irradiation are adopted. Both methods are based on bringing microscopic physical and structural changes that may bring wishful changes. It has been reported that doping of acids/salts/alkalis increases the amorphicity of the film by creating more free spaces for ions to move in the polymer matrix [4, 5]. On the other hand, high energy ion-irradiation and γirradiation on polymers causes some physical and structural changes initiating the chemical reactions. These chemical reactions bring either chain scission and/or cross linking in the polymer chains depending upon the radiation dose and/or dose rate. Unlike doping, high energy irradiation has the advantage that it can penetrate and induce reactions in the solid state over a wide range of temperatures and environments. Ionic conductivity has been found to be increased appreciably when samples are irradiated with ions of suitable energy and dose [6, 7]. In the present work, the effect of 50 MeV, Li3+ ions irradiation for five different doses (5x1010, 1011, 5x1011, 1012 and 5x1012 ions/cm2) on PVA:H3PO4 (80:20) polymer electrolytes has been studied and the results has been compared to their corresponding un-irradiated samples.
EXPERIMENTAL DETAILS Thin film preparation Poly vinyl alcohol (PVA) (Mw. ≈ 1, 25,000 AR grade, Sd. Fine chem. make), ortho phosphoric acid (H3PO4) (88-93%, Ranbaxy Lab Ltd.) a
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