Effect of monomer structure on ionic conductivity in a systematic set of polyester electrolytes
Abstract
Polymer electrolytes may enable the next generation of lithium ion batteries with improved energy density and safety. Predicting the performance of new ion-conducting polymers is difficult because ion transport depends on a variety of interconnected factors which are affected by monomer structure: interactions between the polymer chains and the salt, extent of dissociation of the salt, and dynamics in the vicinity of ions. In an attempt to unravel these factors, we have conducted a systematic study of the dependence of monomer structure on ionic conductivity, σ, and glass transition temperature, T_g, using electrolytes composed of aliphatic polyesters and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt. The properties of these electrolytes were compared to those of poly(ethylene oxide) (PEO), a standard polymer electrolyte for lithium batteries. We define a new measure of salt concentration, ρ, the number of lithium ions per unit length of the monomer backbone. This measure enables collapse of the dependence of both the σ and T_g on salt concentration for all polymers (polyesters and PEO). Analysis based on the Vogel–Tammann–Fulcher (VTF) equation reveals the effect of different oxygen atoms on ion transport. The VTF fits were used to factor out the effect of segmental motion in order to clarify the relationship between molecular structure and ionic conductivity. While the conductivity of the newly-developed polyesters was lower than that of PEO, our study provides new insight into the relationship between ion transport and monomer structure in polymer electrolytes.
Additional Information
© 2016 Elsevier B.V. Received 8 October 2015. Received in revised form 23 February 2016. Accepted 24 February 2016. Available online 18 March 2016. This research was supported by the National Science Foundation under DMREF award number NSF-CHE-1335486. DSC experiments were performed at the Molecular Foundry user facilities at Lawrence Berkeley National Laboratory supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The authors declare no competing financial interest.Attached Files
Supplemental Material - mmc1.docx
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Additional details
- Eprint ID
- 68669
- DOI
- 10.1016/j.ssi.2016.02.020
- Resolver ID
- CaltechAUTHORS:20160624-153416230
- CHE-1335486
- NSF
- DE-AC02-05CH11231
- Department of Energy (DOE)
- Created
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2016-06-26Created from EPrint's datestamp field
- Updated
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2021-11-11Created from EPrint's last_modified field