Poly(ethylene oxide) (PEO) – Poly(vinyl pyrrolidone) (PVP) blend polymer based solid electrolyte membranes for developing solid state magnesium ion cells

Abstract

The present work is an attempt to find the suitability of Poly(ethylene oxide) (PEO) - Poly(vinyl pyrrolidone) (PVP) blend polymer based solid electrolyte membranes for applications in all solid state magnesium ion cells. On solvating the PEO-PVP blend with different concentrations of Mg(NO3)2 salt, the PEO-PVP-Mg(NO3)2 complex electrolyte, termed as the solid polymer electrolyte (SPE) is formed. Flexible free-standing membranes of this SPE of thickness around 100µm are obtained by solution casting technique. The amorphous nature of the semi-crystalline polymer PEO is enhanced by the addition of the Mg salt, as revealed by XRD, FE-SEM and Raman studies. The ionic conductivity evaluated for this SPE membrane is four orders higher than that of pure PEO and close to that of liquid electrolytes used in Mg ion cells. The highest Mg ion conductivity observed for the SPE membrane, in the present work is 5.8×10−4Scm−1 at room temperature and is higher than previously reported ionic conductivity for Mg salt complexed solid polymer electrolytes. The Cyclic Voltammetry (CV) curve of the SPE with stainless steel (SS) blocking electrodes shows wide electrochemical window of 4V. The Mg ion cells assembled using this SPE as the electrolyte, without the need for any additional separator show an open circuit voltage around 1.46V and are electrochemically active.