Abstract
The interfacial region where ion-transporting polymer chains are anchored to a hard, insulating phase is a major factor dictating the limits of ion-conduction in nanostructure-forming electrolytes. In this work, we investigate the effect of an end-grafted poly(ethylene oxide) (20 kg mol-1) surface on the ionic conductivity σ of PEO and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt mixtures. Specifically, we characterize nanothin films in the range of ca. 10 to 250 nm, which amplify the contributions from the polymer/substrate interface that dictate any deviations from expected bulk conductivity σbulk values. Conductivity measurements reveal a monotonic decrease in σ upon decreasing film thickness at all values of r (r = molar ratio of Li+ to EO units). The reduction from bulk-like σ occurs for film thicknesses approximately 100 nm and below for all values of r. This trend in conductivity arises from the presence of the underlying grafted-PEO layer. Through a thickness dependence normalized conductivity study, we observe nanoscale constraints leading to deviation from intrinsic conductivity of bulk PEO-LiTFSI electrolytes. These nanoscale constraints correspond to an immobile interfacial zone whose thickness hint ranges from 9.5 ± 1.4 nm at r = 0.01 to 2.9 ± 1.5 nm at r = 0.15 in our nanothin films that impedes ion transport. Overall, we have presented a robust platform that facilitates probing the role of polymer-grafted surfaces on the σ of polymer electrolytes.
Original language | English |
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Pages (from-to) | 597-608 |
Number of pages | 12 |
Journal | Molecular Systems Design and Engineering |
Volume | 4 |
Issue number | 3 |
DOIs | |
State | Published - Jun 2019 |
Externally published | Yes |
Bibliographical note
Publisher Copyright:© 2019 The Royal Society of Chemistry.
Funding
We gratefully acknowledge support by the U.S. Department of Energy (DOE), Basic Energy Sciences, Materials Science and Engineering Division. This work made use of the Pritzker Nanofabrication Facility of the Institute for Molecular Engineering at the University of Chicago, which receives support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), a node of the National Science Foundation's National Nanotechnology Coordinated Infrastructure. We acknowledge the MRSEC Shared User Facilities at the University of Chicago (NSF DMR-1420709). Parts of this work were carried out at the Soft Matter Characterization Facility of the University of Chicago. B. X. D acknowledged useful comments from Phillip Griffin. This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
Funders | Funder number |
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Materials Science and Engineering Division | |
Soft and Hybrid Nanotechnology Experimental | |
National Science Foundation | ECCS-1542205 |
U.S. Department of Energy | |
Office of Science | |
Basic Energy Sciences | |
Argonne National Laboratory | |
University of Chicago |