Mechanism of ion transport in perfluoropolyether electrolytes with a lithium salt
[1];
- Univ. of California, Berkeley, CA (United States). Dept. of Chemical and Biomolecular Engineering; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Engineering
- Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry
- Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry; North Carolina State Univ., Raleigh, NC (United States). Dept. of Chemical and Biomolecular Engineering
- Univ. of California, Berkeley, CA (United States). Dept. of Chemical and Biomolecular Engineering; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division. Environmental Energy Technologies Division
Perfluoropolyethers (PFPEs) are polymer electrolytes with fluorinated carbon backbones that have high flash points and have been shown to exhibit moderate conductivities and high cation transference numbers when mixed with lithium salts. Ion transport in four PFPE electrolytes with different endgroups was characterized by differential scanning calorimetry (DSC), ac impedance, and pulsed-field gradient NMR (PFG-NMR) as a function of salt concentration and temperature. In spite of the chemical similarity of the electrolytes, salt diffusion coefficients measured by PFG-NMR and the glass transition temperature measured by DSC appear to be uncorrelated to ionic conductivity measured by ac impedance. We calculate a non-dimensional parameter, β, that depends on the salt diffusion coefficients and ionic conductivity. We also use the Vogel–Tammann–Fulcher relationship to fit the temperature dependence of conductivity. We present a linear relationship between the prefactor in the VTF fit and β; both parameters vary by four orders of magnitude in our experimental window. Finally, our analysis suggests that transport in electrolytes with low dielectric constants (low β) is dictated by ion hopping between clusters.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- DOE Contract Number:
- AC02-05CH11231; SC0012673
- OSTI ID:
- 1475011
- Journal Information:
- Soft Matter, Vol. 13, Issue 32; ISSN 1744-683X
- Publisher:
- Royal Society of Chemistry
- Country of Publication:
- United States
- Language:
- English
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