Studies of the interface between V₆O₁₃ and poly(ethylene oxide) based electrolytes

ac impedance measurements have been carried out on the V₆O₁₃/poly(ethylene oxide)-LiX interface, where X = CF₃SO₃ or ClO₄. The reveal the existence of two semicircles one of which is associated with capacitances which range from, 8 × 10^-8 to 3 × 10^-7 F cm^-2. The magnitude of this capacitance decreases with time whereas the associated resistance increases, however the time constant t (t = RC) is virtually invariant. The temperature dependence of this resistance and that of the bulk electrolyte exhibit a similar discontinuity. Similar ac impedance plots are obtained for both high molecular weight (solid) electrolytes and low molecular weight (liquid) electrolytes. The electrochemical measurements suggest that a lithium ion conducting layer is present on the surface of the V₆O₁₃ electrode. The second semicircle present in the impedance plots is assumed to arise from charge transfer at the electrode. The total interfacial resistance is generally many times that of the bulk electrolyte. © 1988.