Electrochemical characterization of polyethylene glycols as solid polymer electrolytes

Abstract

Polymer electrolytes prepared from polyethylene glycol (PEG)-LiClO4 complexes have been characterized at a stainless steel electrode using cyclic voltammetry, chronoamperometry, and ac impedance techniques. The charge transfer process appeared to be affected by the oxide film on the stainless steel electrode surface in the early stages of redox processes. With the electrode surface cleaned off by reduction of oxide films with electrogenerated lithium, very well defined, chemically reversible voltammograms were obtained for Li+ reduction. Different diffusion properties were observed in three different time zones in potentiostatic experiments. An exchange current density has been determined from the Tafel plot for the Li+ reduction using impedance data. The conductivity of the PEG-10000 electrolyte has been determined to be 4.7 x 10(-5) S cm(-1). This value is higher than that of the corresponding polyethylene oxide electrolyte by about two orders of magnitude, which is attributed to the anionic end groups increasing the polarity of the matrix. (C) 1998 Elsevier Science S.A. All rights reserved.