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�� -NMR measurements of molecular-scale lithium-ion dynamics in poly(ethylene oxide)-lithium-salt thin films

Journal Article


Abstract


  • ��-detected NMR (��-NMR) has been used to study the molecular-scale dynamics of lithium ions in thin films of poly(ethylene oxide) (PEO) containing either lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium trifluoroacetate (LiTFA) salts at monomer-to-salt ratios (EO/Li) of 8.3. The results are compared with previous ��-NMR measurements on pure PEO and PEO with lithium triflate (LiOTf) at the same loading [McKenzie et al., J. Am. Chem. Soc. 136, 7833 (2014)]. Activated hopping of 8Li+ was observed in all of the films above ���250 K, with the hopping parameters strongly correlated with the ionicity of the lithium salt rather than the polymer glass transition temperature. The pre-exponential factor increases exponentially with ionicity, while the activation energy for hopping increases approximately linearly, going from 6.3��0.2 kJ mol-1 in PEO:LiTFA to 17.8��0.2 kJ mol-1 in PEO:LiTFSI. The more rapid increase in the pre-exponential factor outweighs the effect of the larger activation energy and results in 8Li+ hopping being fastest in PEO followed by PEO:LiTFSI, PEO:LiOTf, and PEO:LiTFA.

Publication Date


  • 2017

Citation


  • McKenzie, I., Cortie, D. L., Harada, M., Kiefl, R. F., Levy, C. D. P., MacFarlane, W. A., . . . Sugiyama, J. (2017). �� -NMR measurements of molecular-scale lithium-ion dynamics in poly(ethylene oxide)-lithium-salt thin films. Journal of Chemical Physics, 146(24). doi:10.1063/1.4989866

Scopus Eid


  • 2-s2.0-85021655207

Volume


  • 146

Issue


  • 24

Place Of Publication


Abstract


  • ��-detected NMR (��-NMR) has been used to study the molecular-scale dynamics of lithium ions in thin films of poly(ethylene oxide) (PEO) containing either lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium trifluoroacetate (LiTFA) salts at monomer-to-salt ratios (EO/Li) of 8.3. The results are compared with previous ��-NMR measurements on pure PEO and PEO with lithium triflate (LiOTf) at the same loading [McKenzie et al., J. Am. Chem. Soc. 136, 7833 (2014)]. Activated hopping of 8Li+ was observed in all of the films above ���250 K, with the hopping parameters strongly correlated with the ionicity of the lithium salt rather than the polymer glass transition temperature. The pre-exponential factor increases exponentially with ionicity, while the activation energy for hopping increases approximately linearly, going from 6.3��0.2 kJ mol-1 in PEO:LiTFA to 17.8��0.2 kJ mol-1 in PEO:LiTFSI. The more rapid increase in the pre-exponential factor outweighs the effect of the larger activation energy and results in 8Li+ hopping being fastest in PEO followed by PEO:LiTFSI, PEO:LiOTf, and PEO:LiTFA.

Publication Date


  • 2017

Citation


  • McKenzie, I., Cortie, D. L., Harada, M., Kiefl, R. F., Levy, C. D. P., MacFarlane, W. A., . . . Sugiyama, J. (2017). �� -NMR measurements of molecular-scale lithium-ion dynamics in poly(ethylene oxide)-lithium-salt thin films. Journal of Chemical Physics, 146(24). doi:10.1063/1.4989866

Scopus Eid


  • 2-s2.0-85021655207

Volume


  • 146

Issue


  • 24

Place Of Publication