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Title: Diffusion and migration in polymer electrolytes

Abstract

Mixtures of neutral polymers and lithium salts have the potential to serve as electrolytes in next-generation rechargeable Li-ion batteries. The purpose of this review is to expose the delicate interplay between polymer-salt interactions at the segmental level and macroscopic ion transport at the battery level. Since complete characterization of this interplay has only been completed in one system: mixtures of poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI), we focus on data obtained from this system. We begin with a discussion of the activity coefficient, followed by a discussion of six different diffusion coefficients: the Rouse motion of polymer segments is quantified by D seg, the self-diffusion of cations and anions is quantified by D self,+ and D self,-, and the build-up of concentration gradients in electrolytes under an applied potential is quantified by Stefan-Maxwell diffusion coefficients, D 0+, D 0-, and D +-. The Stefan-Maxwell diffusion coefficients can be used to predict the velocities of the ions at very early times after an electric field is applied across the electrolyte. The surprising result is that D 0- is negative in certain concentration windows. A consequence of this finding is that at these concentrations, both cations and anions are predicted to migratemore » toward the positive electrode at early times. We describe the controversies that surround this result. Knowledge of the Stefan-Maxwell diffusion coefficients enable prediction of the limiting current. We argue that the limiting current is the most important characteristic of an electrolyte. Excellent agreement between theoretical and experimental limiting current is seen in PEO/LiTFSI mixtures. What sequence of monomers that, when polymerized, will lead to the highest limiting current remains an important unanswered question. It is our hope that the approach presented in this review will guide the development of such polymers.« less

Authors:
 [1];  [1];  [1];  [2];  [2]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1603575
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Progress in Polymer Science
Additional Journal Information:
Journal Volume: 103; Journal ID: ISSN 0079-6700
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; Diffusion Coefficient; Migration; Polymer Electrolytes; Batteries; Ion Transport

Citation Formats

Choo, Youngwoo, Halat, David M., Villaluenga, Irune, Timachova, Ksenia, and Balsara, Nitash P. Diffusion and migration in polymer electrolytes. United States: N. p., 2020. Web. doi:10.1016/j.progpolymsci.2020.101220.
Choo, Youngwoo, Halat, David M., Villaluenga, Irune, Timachova, Ksenia, & Balsara, Nitash P. Diffusion and migration in polymer electrolytes. United States. doi:10.1016/j.progpolymsci.2020.101220.
Choo, Youngwoo, Halat, David M., Villaluenga, Irune, Timachova, Ksenia, and Balsara, Nitash P. Sat . "Diffusion and migration in polymer electrolytes". United States. doi:10.1016/j.progpolymsci.2020.101220.
@article{osti_1603575,
title = {Diffusion and migration in polymer electrolytes},
author = {Choo, Youngwoo and Halat, David M. and Villaluenga, Irune and Timachova, Ksenia and Balsara, Nitash P.},
abstractNote = {Mixtures of neutral polymers and lithium salts have the potential to serve as electrolytes in next-generation rechargeable Li-ion batteries. The purpose of this review is to expose the delicate interplay between polymer-salt interactions at the segmental level and macroscopic ion transport at the battery level. Since complete characterization of this interplay has only been completed in one system: mixtures of poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI), we focus on data obtained from this system. We begin with a discussion of the activity coefficient, followed by a discussion of six different diffusion coefficients: the Rouse motion of polymer segments is quantified by Dseg, the self-diffusion of cations and anions is quantified by Dself,+ and Dself,-, and the build-up of concentration gradients in electrolytes under an applied potential is quantified by Stefan-Maxwell diffusion coefficients, D0+, D0-, and D+-. The Stefan-Maxwell diffusion coefficients can be used to predict the velocities of the ions at very early times after an electric field is applied across the electrolyte. The surprising result is that D0- is negative in certain concentration windows. A consequence of this finding is that at these concentrations, both cations and anions are predicted to migrate toward the positive electrode at early times. We describe the controversies that surround this result. Knowledge of the Stefan-Maxwell diffusion coefficients enable prediction of the limiting current. We argue that the limiting current is the most important characteristic of an electrolyte. Excellent agreement between theoretical and experimental limiting current is seen in PEO/LiTFSI mixtures. What sequence of monomers that, when polymerized, will lead to the highest limiting current remains an important unanswered question. It is our hope that the approach presented in this review will guide the development of such polymers.},
doi = {10.1016/j.progpolymsci.2020.101220},
journal = {Progress in Polymer Science},
issn = {0079-6700},
number = ,
volume = 103,
place = {United States},
year = {2020},
month = {1}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on January 25, 2021
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