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Ionic liquid electrolyte for lithium metal batteries : physical, electrochemical, and interfacial studies of N-Methyl-N-butylmorpholinium Bis(fluorosulfonyl)imide

journal contribution
posted on 01.01.2010, 00:00 authored by G Lane, Paul Bayley, B Clare, A Best, D MacFarlane, Maria ForsythMaria Forsyth, A Hollenkamp
The ionic liquid (IL) N-methyl-N-butylmorpholinium bis(fluorosulfonyl)imide (C4mmor FSI) is examined from physical and electrochemical perspectives. Pulsed field gradient NMR spectroscopy shows that ion diffusivities are low compared with similar, non-ethereal ILs. Ionicity values indicate that above room temperature, less than 50% of ions contribute to conductivity.

Lithium cycling in symmetrical cells using a C4mmor FSI-based electrolyte is best demonstrated at elevated temperatures. Specific capacities of 130 mAh g−1 are achieved in a Li−LiFePO4 battery at 85 °C. FT-IR spectroscopic investigations of lithium electrodes suggest the presence of alkoxide species in the solid electrolyte interphase (SEI), implying a ring-opening reaction of C4mmor with lithium metal. In contrast, the SEI derived from N-methyl-N-propylpiperidinium FSI lacks the alkoxide signature but shows signs of alkyl unsaturation, and the activation energy for Li+ transport through this SEI is slightly lower than that for the C4mmor-derived SEI. Our detailed findings give insight into the capabilities and limitations of rechargeable lithium metal batteries utilizing a C4mmor FSI electrolyte.

History

Journal

Journal of physical chemistry part c : nanomaterials and interfaces

Volume

114

Issue

49

Pagination

21775 - 21785

Publisher

American Chemical Society

Location

Washington, D.C.

ISSN

1932-7447

eISSN

1932-7455

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2010 American Chemical Society