Synthesis and characterization of ion transport behavior in Cu2+-conducting nano composite polymer electrolyte membranes

Abstract

Synthesis and characterization of ion transport behavior in Cu2+-conducting nano composite polymer electrolyte (NCPE) films: [90PEO: 10Cu(CF3SO3)2] + x CuO have been reported. NCPE films have been formed by hot-press casting technique using solid polymer electrolyte (SPE) film composition: [90PEO: 10Cu(CF3SO3)2] as 1st-phase host and nanoparticles of CuO in varying wt.(%) as 2nd-phase active filler. SPE: [90PEO: 10Cu(CF3SO3)2] was identified earlier as highest conducting film with room temperature conductivity (σrt) ~ 3.0 x 10−6 S cm−1, which is three orders of magnitude higher than that of pure polymer host PEO with σrt ~ 3.2 × 10−9 S cm−1. Filler particle concentration dependent conductivity study revealed NCPE film: [90PEO: 10Cu(CF3SO3)2] + 3%CuO as optimum conducting composition (OCC) exhibiting σrt ~ 1.14 × 10−5 S cm−1. Hence, by the fractional dispersal of 2nd-phase active filler into 1st-phase SPE host, σ-enhancement of approximately an order of magnitude has further been obtained. Ion transport behavior in NCPE OCC film has been characterized in terms of basic ionic parameters viz. ionic conductivity (σ), total ionic transference (tion)/cationic (t+) numbers. Temperature dependent conductivity measurement has also been done to explain the mechanism of ion transport and to compute activation energy (Ea). Materials characterization and hence, confirmation of complexation of salt in polymeric host and/or dispersal of filler particles in SPE host have been done by scanning electron microscopy (SEM), energy dispersive x-ray spectrometer (EDS), x-ray diffraction (XRD), Fourier transform infra-red (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). All-solid-state battery in the cell configuration: Cu (Anode) || SPE host/NCPE OCC film || C + I2 + Electrolyte) (Cathode) has been fabricated and cell performance has been studied under two load resistances viz. 60 and 100 kΩ. Each NCPE cell gave on an open circuit voltage (OCV) ~ 0.68 V. Some important battery parameters have also been evaluated from the plateau regions of cell potential discharge profiles.