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This content will become publicly available on March 23, 2019

Title: Structural Dynamics of Strongly Segregated Block Copolymer Electrolytes

Polymer electrolytes are promising materials for high energy density rechargeable batteries. However, they have low ion transport rates and gradually lose electrode adhesion during cycling. These effects are dependent on polymer structure and dynamics. This motivates an investigation of diblock copolymer electrolyte dynamics. Structural and stress relaxations have been measured with X-ray photon correlation spectroscopy (XPCS) and rheology, respectively, as a function of salt concentration and temperature. The polymer electrolyte studied in this work is a mixture of poly(styrene-b-ethylene oxide), SEO, and lithium bistrifluoromethanesulfonimide (LiTFSI). Results from XPCS experiments showed hyperdiffusive motion for various lithium salt concentrations and at varying temperatures, which is indicative of soft glassy materials. This behavior is attributed to cooperative dynamics. The decay time was a weak, nonmonotonic function of salt concentration and decreased with increasing temperature, in an Arrhenius fashion. In contrast, the shear modulus decreased with increasing salt concentration and increasing temperature. The entanglement relaxation from rheological measurements followed Vogel-Fulcher-Tammann behavior. The structural decay time was slower than the entanglement relaxation time at temperatures above the glass transition temperature, but they were approximately equal at T g regardless of salt concentration. This may indicate a fundamental connection between cooperative structural motion and polymer chainmore » motion in this material.« less
Authors:
ORCiD logo [1] ;  [2] ;  [2] ;  [1] ; ORCiD logo [1]
  1. Florida A&M Univ. and Florida State Univ., Tallahassee, FL (United States). FAMU-FSU College of Engineering; Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Macromolecules
Additional Journal Information:
Journal Volume: 51; Journal Issue: 7; Journal ID: ISSN 0024-9297
Publisher:
American Chemical Society
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; 36 MATERIALS SCIENCE
OSTI Identifier:
1461494