Investigation of ionic conduction and mechanical properties of PMMA–PVdF blend-based polymer electrolytes ☆ Isabella Nicotera a, ⁎ , Luigi Coppola a , Cesare Oliviero a , Marco Castriota b , Enzo Cazzanelli b a Department of Chemistry, University of Calabria, 87036, Arcavacata di Rende, Cosenza, Italy b LICRYL-INFM (Liquid Crystal Regional Center) c/o Department of Physics, University of Calabria, Via P. Bucci Cubo 33/b, I-87036 Arcavacata di Rende (CS), Italy Received 23 June 2005; received in revised form 29 December 2005; accepted 31 December 2005 Abstract Polymeric gel electrolytes, based on a blend of poly(methylmethacrylate)/poly(vinylidene fluoride) (PMMA/PVdF), ethylene carbonate/ propylene carbonate (EC/PC) as plasticizer and lithium perchlorate as electrolyte, have been studied as a function of the different polymeric ratios to obtain the best compromise between ionic conduction and mechanical properties of the systems involved. Ionic conductivity and the lithium self-diffusion coefficient were measured by the PFG–NMR method, which revealed a maximum of lithium mobility for the composition PMMA 60%–PVdF 40%. The Raman spectroscopic study revealed a change of the interaction between that of the lithium cations and the plasticizer molecules for different PMMA / PVdF ratios. Oscillatory rheological tests have shown better mechanical properties for the intermediate compositions of the blend. © 2006 Elsevier B.V. All rights reserved. Keywords: Polymer blend electrolyte; Ionic conductivity; Raman spectroscopy; Rheology; NMR self-diffusion coefficients; SEM 1. Introduction Gel polymer electrolytes [1,2] are promising materials as electrolytes in advanced electrochemical applications, particu- larly lithium-battery technology. By replacing the liquid electrolyte currently in use, the gel polymer electrolyte yields several advantages including high energy density, structural stability and low volatility [3–5]. A gel-type membrane is achieved by immobilizing a liquid solution (for instance, pro- pylene carbonate and/or ethylene carbonate solutions of a li- thium salt) into a polymeric matrix. The polymers generally used for these systems are poly(methylmetacrylate) (PMMA) [6–8], poly(acrylonitrile) (PAN) [8], poly(vinilicloride) (PVC) [9,10] and poly(vinilidenefluoride) (PVdF) [11,12]. The lithium mobility, as well as the general performance of the material, will strongly depend on the interactions between the various components of the electrolyte. Recent investigations [13] of PAN-based systems have shown, for example, a clear tem- perature dependence of the solvation of the lithium cations with the plasticizer molecules (EC) and with the PAN cyanide group. These gel electrolytes exhibit sufficient mechanical strength and ionic conductivities on the order of 10 - 3 S cm - 1 [9]. Never- theless, the leakage problem remains, which is due to a phase separation between the polymer matrix and the encapsulated electrolyte solution. The solvent loss may also result in a failing of the electrode/electrolyte contact as well as a reduction of ionic conductivity. To bypass this limitation, one of the approaches undertaken is the blending method [14–16]. The polymer blend electrolyte is composed of at least two polymers: one that absorbs the electrolyte's active species and one that is tougher and sometimes, substantially inert, which enhances the mechanical integrity of the polymer blend. Recently, the inherent merits of using blend-based electrolytes have been shown by several research groups [15–17] since this method seems to give the Solid State Ionics 177 (2006) 581 – 588 www.elsevier.com/locate/ssi ☆ This work was financially supported by MIUR within the project CIPE Cluster 26-P4. ⁎ Corresponding author. Tel.: +39 0984 492021; fax: +39 0984 492044. E-mail address: isabella.nicotera@unical.it (I. Nicotera). 0167-2738/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.ssi.2005.12.028