XPS STUDIES ON (PEO)(N)LICLO4 AND (PEO)(N)CU(CLO4)(2) POLYMER ELECTROLYTES

The usefulness of x-ray photoelectron spectroscopy to study surface st ructural aspects of polymer electrolytes has been demonstrated by its application to complexes of poly(ethylene oxide) with lithium perchlor ate or copper perchlorate in various molar ratios. The binding energie s for various core level electrons of the different elements present i n these electrolytes have been determined. The shifts in observed bind ing energies with respect to the elemental values are interpreted by c onsidering the effect of the surrounding ions' electronegativity on th e core electrons. These results present direct evidence for the intera ction between PEO and the cation/anion of the salt, caused by the comp lexation between the oxygen of the -CH2-CH2-O- repeating units and the cations of the salt as well as the effective cross-linking between th e polymer chains of PEO through the anions of the salt. While in neat PEO there is only one type of carbon atom, the above interactions with the salt lead to the formation of nonequivalent carbons. These intera ctions are described by the varying cation environment and the unchang ed anion environment for the different PEO-salt complexes.