Student Poster Presentation #16 (Session 2)
Structure and Dynamics of Lithium Polymer Electrolytes
Onyekachi Oparaji 1,2 , Suresh Narayanan 3 , Alec Sandy 3 , and Daniel Hallinan Jr. 1,2
1
2
FAMU-FSU College of Engineering, Tallahassee, Florida 32303
Florida State University, Aero-propulsion, mechatronics, and Energy Center, Tallahassee, Florida 32310
3
Argonne National Laboratory, Argonne, Illinois 60439
Abstract
Polymer electrolytes are promising materials for high energy density rechargeable batteries. They form ion –
polymer complexes with alkali metal salts of low lattice energy through ionic association. The formation of these
charged, associated species affect the ionic conductivity through the change in ionic mobility of the associated
charge carriers. 1 We present a fundamental study of ion association effects and the ion-polymer interactions in
high molecular weight poly(styrene–ethylene oxide) block copolymer (SEO) and complexes with lithium
bis(trifluoromethane sulfonyl) imide salt (LiTFSI) as polymer electrolyte using FTIR-ATR spectroscopy.
Dissolution of the lithium salt in the PEO phase is expected to affect the C-O-C vibrations of the PEO backbone.
The infrared bands observed in the polymer – salt complexes as a function of salt concentration and temperature
show different solvation and degree of ion association behavior. An understanding of the relationship between
ionic conductivity and degree of solvation of lithium salts as a function of ion concentration will be explained
from FTIR-ATR results. Since conductivity is a function of ion concentration and ion mobility, and ion mobility
is coupled to polymer segmental mobility, we investigate the effect of salt concentration on the polymer segment
mobility. We report the influence of lithium salt concentration on the structural relaxation time (XPCS) and stress
relaxation time (rheology) of high molecular weight poly(styrene – ethylene oxide) block copolymer membranes.
Reference
1.
Gray FM, MacCallum JR, Vincent CA. Poly (ethylene oxide)-LiCF3SO3-polystyrene electrolyte systems. Solid State Ionics
18, 282-286 (1986).
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