Use of Microelectrode Arrays to Directly Measure Diffusion of Ions in Solid Electrolytes: Proof of Concept Experiments Involving Ag+ in a Solid Polymer Electrolyte

摘要

We report proof of concept experiments demonstrating a new methodology for direct measurement of molecular or ionic species in electrolyte media. A microelectrode array of closely spaced Platinum microelectrodes allows direct measurement of the movement of Silver cations in aqueous electrolyte and in the solid polymer electrolytes, LiCF3SO3/MEEP (MEEP = poly (bis(2-(2-methoxyethoxy) ethoxy)phosphazene) at 298 K with a molar ratio of LiCF3SO3 to polymer repeat unit of 1 to 4 and LiCF3SO3/PEO (PEO = poly(ethylene oxide)) at 352 K and a molar ratio of LiCF3SO3 to polymer repeat unit of 1 to 8. The crucial experiments involve anodically stripping Ag from a Ag-coated Pt microelectrode (generator) and electrochemically detecting the resulting Ag(+) at nearby Pt electrodes (collectors) by reducing the Ag(+) back to Ag. The time dependence of the collector current corresponding to Ag(+) to Ag reduction after the generation step allows evaluation of the diffusion coefficient, D, for the Ag(+) in the various media and conditions used. Keywords: Lithium methafluorosulfite. (AW)