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Enhancement of ion dissociation in polyelectrolyte gels

journal contribution
posted on 30.06.2003, 00:00 authored by Maria ForsythMaria Forsyth, J Sun, F Zhou, D MacFarlane
High conductivity in single ion conducting polymer electrolytes is still the ultimate aim for many electrochemical devices such as secondary lithium batteries. Achieving effective ion dissociation in these cases remains a challenge since the active ion tends to remain in close proximity to the backbone charge as a result of a low degree of ion dissociation. A unique aspect of this dissociation problem in polyelectrolytes is the repulsion between the backbone charges created by dissociation. One way of enhancing ion dissociation in polyelectrolyte systems is to use copolymers in which only a fraction (<20%) of the mer units are charged and where the comonomer is itself chosen to be polar and preferably to be compatible with potential solvents. We have also found that certain dissociation enhancers based on ionic liquids or boroxine ring compounds can lead to high ionic conductivity. In the cases where an ionic liquid is used as the solvent in a polyelectrolyte gel, the viscosity of the ionic liquid and its hydrophilicity are critical to achieving high conductivity. Compounds based on the dicyanamide anion appear to be very effective ionic solvents; polyelectrolyte gels incorporating such ionic liquids exhibit conductivities as high as 10−2 S/cm at room temperature. In the case of boroxine ring dissociation enhancers, gels based on poly(lithium-2-acrylamido-2-methyl-1-propanesulfonate) and ethylene carbonate produce conductivities approaching 10−3 S/cm. This paper will discuss these approaches for achieving higher conductivity in polyelectrolyte materials and suggest future directions to ensure single ion transport.

History

Journal

Electrochimica acta

Volume

48

Issue

14-16

Pagination

2129 - 2136

Publisher

Elsevier Science Pub. Co.

Location

New York, N.Y.

ISSN

0013-4686

eISSN

1873-3859

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2003, Elsevier Science Ltd