Investigations on ion transport properties of and battery discharge characteristic studies on hot-pressed Ag+-ion-conducting nano-composite polymer electrolytes: (1–x) [90PEO : 10AgNO3] : xSiO2

Abstract

Investigations on the ion transport properties of Ag+-ion-conducting nano-composite polymeric electrolytes (NCPEs): (1−x)[90PEO : 10AgNO3] : xSiO2, where x = 0, 1, 2, 3, 5, 10 or 15 (wt%) and PEO is poly(ethylene oxide), are reported here. Films of NCPEs were cast using a novel hot-press/solvent-free/dry technique instead of the usual solution cast method. Nano-size (∼8 nm) SiO2 particles, as the second dispersoid phase, were dispersed into the first-phase conventional solid polymer electrolyte (SPE) host: (90PEO : 10AgNO3). The SPE host, also prepared by hot-pressing the homogeneously mixed composition: PEO : AgNO3 :: 90 : 10 (wt%), has been identified as the film with the highest room temperature conductivity σ∼4×10-6 S cm-1, exhibiting a σ increase of more than three orders of magnitude from that of the pure PEO. Dispersal of SiO2 nano-particles in the SPE host resulted in a 2-fold conductivity enhancement in the NCPE film: 95(90PEO : 10AgNO3) : 5SiO2 (wt%). This has been referred to as the ‘optimum conducting composition (OCC)’. The ion transport behavior in NCPE has been characterized on the basis of experimental studies on some basic ionic parameters, viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n), ionic transference number (tion), etc. The temperature-dependent measurements on σ, μ and n in the NCPE OCC film provided quantitative information on the energies involved in different thermally activated processes. A thin-film solid-state battery has been fabricated using the NCPE OCC membrane as the electrolyte to test the cell performance under a fixed load condition at temperatures below/above room temperature.