Charge transfer at polymer electrolytes

Abstract

Polymer electrolytes (PEs) are ion-conducting complexes formed between a metal salt and a solvating polymer, usually a polyether like poly(ethylene oxide). Electrochemical reactions at PEs/electrode interfaces are reviewed and compared with those of liquid electrolytes. One characteristic of these materials is their exceptional inertness which spans the 0–4.6 V/Li⁺:Li° stability window. Nevertheless, the conduction mechanism, a solvation–desolvation of the cation along the chain, governs the kinetics: only cations with fast ligand exchange are electroactive, irrespective of thermodynamics; anions, which are not solvated are always mobile. Transfer of ions into intercalation compounds is usually well defined, with no solvent co-intercalation. The possibility is discussed that some level of redox conduction appears in PEs at potentials either cathodic (metal solubility) or anodic beyond the stability window (oxonium radical).