A novel composite polymer electrolyte:: Effect of mesoporous SiO2 on ionic conduction in poly(ethylene oxide)-LiCF3SO3 complex

Internal modified-mesoporous SiO2 using ionic liquid (IL-MPSi) as one of the additives has been prepared and added to the poly(ethylene oxide) (PEO)-based solid electrolytes for improving the ionic conductivity. In this study, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) has been used as an ionic liquid. The conductivity was significantly improved by the addition of IL-MPSi, to be more than 10(-5) S cm(-1) at room temperature and at the filler contents of 15 wt.%, in the solid state. From the combination of dc polarization and ac impedance measurement for lithium cells, it was revealed that the addition of IL-MPSi increased the Li+ transference number (t(+)), because the EMImBF4 used in this study possesses higher t(+) (approximately 0.5) than the PEO-salt simple mixture. This means that the MPSi domains can act as bypass for transport of carrier ions to the PEO matrix through the inside IL phase. (c) 2005 Elsevier B.V. All rights reserved.