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Polymer Dynamics in Block Copolymer Electrolytes Detected by Neutron Spin Echo.
Whitney S Loo1, Antonio Faraone2, Lorena S Grundy1
1Department of Chemical and Biomolecular Engineering, University of California-Berkeley, Berkeley, California 94720, United States.
ACS Macro Letters
|June 1, 2022
Summary
Investigating polymer chain dynamics in block copolymer electrolytes reveals how salt concentration affects friction and entanglement. Understanding these ion-polymer interactions is key for advanced battery performance.
Area of Science:
- Materials Science
- Polymer Chemistry
- Electrochemistry
Background:
- Block copolymer electrolytes are crucial for next-generation batteries.
- Understanding ion-polymer interactions is vital for optimizing battery performance.
Purpose of the Study:
- To investigate the polymer chain dynamics of polystyrene-block-poly(ethylene oxide) (SEO) electrolytes with varying lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt concentrations.
- To correlate chain dynamics with salt concentration using established polymer physics models.
Main Methods:
- Neutron spin echo (NSE) spectroscopy was employed to probe dynamics on the 0.1-100 ns timescale.
- The Rouse model was used for short times (≤ 10 ns), and the reptation tube model for long times (≥ 50 ns).
Main Results:
- Monomeric friction coefficient increased with salt concentration in the Rouse regime.
- Tube diameters decreased with salt concentration in the reptation regime, indicating altered entanglement.
- Normalized longest molecular relaxation time increased with salt concentration.
Conclusions:
- Salt concentration significantly influences both friction and entanglement in SEO electrolytes.
- Quantifying ion-polymer chain motion is essential for predicting the behavior of polymer-electrolyte batteries at high currents.
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