Ionic conduction in solid polymer electrolytes using carbon dioxide as solvent

Abstract

Solid polymer electrolytes (SPEs) such as poly (ethylene oxide)-metal salt complexes have been proposed as solid-state alternatives to liquid electrolytes in electrochemical device applications such as all-polymer lithium batteries, However, SPEs suffer from relatively low ionic conductivity in the solid state compared with most liquid, gel and ceramic electrolytes. For increase in the migration of ions, we have been focusing on compressed carbon dioxide, especially supercritical carbon dioxide (scCO2) as a unique solvent for SPEs. The treatment of SPEs with scCO2 gave rise to a large increase in the conductivity of polyether-Li salt complexes. Moreover, we measured the conductivity directly in pressurized CO2. The SPEs revealed a significant increase in the conductivity in the high-pressure conditions. It was found that CO2 plays an important role for adsorption, plasticization f or polymers and dissociation of aggregated ions. CO2 is able to cause a dramatic decrease in the Tg of SPEs leading to an increase in the conductivity in solid state. © 2008, The Society of Polymer Science, Japan.