The interface between electrode and poly(ethylene oxide) electrolytes

Impedance spectroscopy has been used for characterization of the interface between an ideally polarizable electrode and poly(ethylene oxide) electrolytes containing lithium salts. The solvent contribution to the inner layer capacitance, Cs, for CH3O(CH2CH2O)nCH3 for (n = 4, 8, 10) and oxymethylene-linked poly(oxyethylene), PMEO was evaluated by subtracting the contribution of the metal (Cm) from the inner layer capacitance. The position of the maximum in the bell-shaped curves Cs(σ) depends on the molecular mass of the solvent. The influence of the external electric field on the condition of the solvent molecules at the inner layer has been characterized by a dipolar capacitance as a function of effective charge density, Cdip(σ*) for PEO(n = 4, 8, 10) and solid PMEO. Polyethers with shorter chain have been found to be more sensitive to the external electric field for a negative electrode charge, the slopes of the Cdip(σ*) curves are changing in sequence: PEO(n = 4) > PEO(n = 8, n = 10) > PMEO.