Variable-Temperature 7Li Solid-State NMR Investigation of Li-Ion Mobility and Its Correlation with Conductivity in Pore-Filling Polymer Electrolytes for Secondary Batteries

Abstract

We have attempted to combine a gel and a solvent-free polymer electrolyte through the concept of the pore-filling polymer electrolyte; instead of using organic solvents, a viscous poly(ethylene oxide-co-ethylene carbonate) (P(EO−EC)) complexed with a LiCF3SO3 is filled into the pores of a porous poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF−HFP))/P(EO−EC)) blend membrane. Our results indicated that the ionic conductivity of the pore-filling polymer electrolytes showing Arrhenius temperature dependence reached a maximum value of 3.7 × 10-5 S cm-1 at 298 K for E-V6E4, where “E-VxEy” denotes the Electrolyte of P(VdF−HFP)/P(EO−EC) porous matrix (x/y by wt %) filled with the P(EO−EC)/LiCF3SO3 (in the case of E-V6E4, ca. 61 wt %). In this study, the Li-ion mobilities of a series of pore-filling E-VxEy polymer electrolytes were determined from 7Li solid-state NMR line width and spin−lattice relaxation time measurements and were correlated with their ionic conductivities in conjunction with the effect a...