Solid State Ionics 135 (2000) 283–290 www.elsevier.com / locate / ssi Characterization of the passivation layer at the polymer electrolyte / lithium electrode interface a b b, * Maryline Le Granvalet-Mancini , Tobias Hanrath , Dale Teeters a ´ ´ Institut des Materiaux de Nantes, Laboratoire de Chimie des Solides, UMR CNRS N8 6502-Universite de Nantes, B.P . 32229, 44322 Nantes cedex 3, France b Department of Chemistry and Biochemistry, The University of Tulsa, 600 S. College Ave., Tulsa, OK 74104-3189, USA Abstract This work investigates the formation of a passivation layer at the lithium/poly(ethylene oxide)-lithium triflate electrolyte interface using attenuated total reflection FTIR spectroscopy, atomic force microscopy (AFM) and a.c. impedance spectroscopy. Self-assembled molecular layer technology was used to generate interfaces having no passivation layer so that comparisons could be made between passivated and non-passivated surfaces. AFM data show the formation of a passivation layer composed of what appears to be crystallites and ATR-FTIR data indicate the presence of CF radicals in this 3 passivation layer with possible polymer chain scission. The formation of Li–O–R compounds is also observed.  2000 Elsevier Science B.V. All rights reserved. Keywords: Polymer electrolyte interface; Self-assembled molecular layers; ATR-FTIR; AFM 1. Introduction or lithium alloy anodes in contact with polymer electrolytes that involve complex impedance spec- Lithium polymer electrolyte batteries (LPB) are troscopy or other electrochemical techniques [1–14]. receiving much attention today because they offer a Fauteux [4] investigated Li / solid polymer elec- number of significant advantages both in terms of trolyte / Li symmetric cells and attributed a low high energy density and a large electrochemical frequency semicircle in Nyquist plots to interfacial window. However, these systems are not without resistance from a surface film on the Li electrodes. their technological problems. One problem is the Bruce and Krok [3,11] have shown that interfacial formation of a passivation layer at the lithium / poly- impedance in lithium / polymer electrolyte systems mer electrolyte interface where in many cases this can grow with time until it is significantly larger than layer becomes more and more impervious to ion the bulk resistance, which would have detrimental conduction and results in poor performance of the effects on battery performance. This formation of a battery. There have been various studies of lithium passivation layer at the interface of lithium / polymer electrolyte systems is usually considered similar, from an electrochemical point of view, to lithium in liquid organic electrolytes. These lithium–liquid *Corresponding author. E-mail address: dale-teeters@utulsa.edu (D. Teeters). systems are well characterized [13]; however, the 0167-2738 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0167-2738(00)00448-3