Conduction Mechanisms in Concentrated Lu-Polyethylene Oxide-A1203-Based Solid Electrolytes

The ionic conductivity of concentrated Lu-polyethylene oxide P(E0) high surface area oxide composite polymer electrolytes has been investigated. Two different Arrhenius dependences for concentrated composite polymer electrolytes(CPEs) have been identified. The first one is characterized by an inflection point at about 80°C, and the second, by a con.. ductivity jump. We have suggested that in CPEs, where 3 <n < 9, the solid phase is major contributor to the overall ionic conductivity at temperatures above, but close to the melting point of the eutectic (T,,, < T < Tk), where Tk is the knee tem-perature. It is important to note that at T < Tk the apparent activation energy of conduction (Ea) for composite solid elec-. trolytes (CSEs, a 3), is about 40 % of that for CPEs. We believe that the preferred conduction path in even more con-centrated CPEs, which are defined as CSEs, is interfacial conduction. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and x-ray data, presented in this communication, are evidence supporting our view. The effects of several parameters including type and content of oxide matrix, Li salt to ethylene oxide (E0) ratio, copolymers, and solvents on polymer electrolyte conductivity (especially at T> Tk or and on Ea have been studied (Tjump is a tem-perature of the conductivity jump). The addition of small quantities of ethylene carbonate (EC), poly(methyl methacry-late), and polyacrylonitrile were found to be beneficial while poly(methyl acrylate), poly(butyl acrylate), and poly(vinyli-dene fluoride) additions made the polymer electrolyte stiffer and less conductive. Mg0, A1203, and potassium aluminosilicate muscovite mica based CSEs have similar conductivity. DSC and SEM results clearly demonstrated th