File(s) under permanent embargo

Stable cycling of NaFePO4 cathodes in high salt concentration ionic liquid electrolytes

journal contribution
posted on 01.12.2018, 00:00 authored by Matthias HilderMatthias Hilder, Patrick HowlettPatrick Howlett, D Saurel, H Anne, M Casas Cabanas, M Armand, T Rojo, D R MacFarlane, Maria ForsythMaria Forsyth
© 2018 Elsevier B.V. Highly concentrated solutions of sodium bis(fluorosulfonyl)imide (NaFSI) with a series of bis(fluorosulfonyl)imide-based ionic liquids incorporating either alkyl phosphonium or alkoxy ammonium cations (P111i4FSI:NaFSI, P1i4i4i4FSI:NaFSI), N2(2O2O1)3FSI:NaFSI) are combined with NaFePO4 cathodes to demonstrate excellent cycling performance with respect to potential range, rate capability, cycle life and elevated temperature stability. With a capacity of 85 mAhg−1 and a capacity retention of 95% over 100 cycles (50 °C, C/2) P111i4FSI:NaFSI matches or outperforms conventional organic solvent based electrolytes as well as other ionic liquid electrolytes in terms of capacity, elevated temperature performance and cycle stability. The electrolyte conductivity does not correlate with the capacity, suggesting that this is not the primary factor determining the cell performance. The solid electrolyte interphase determines the cycle stability with SEM and XPS techniques suggesting the presence of NaOH, Na2S and NaF on the Na metal surface post cycling.

History

Journal

Journal of Power Sources

Volume

406

Pagination

70 - 80

Publisher

Elsevier

Location

Amsterdam, The Netherlands

ISSN

0378-7753

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2018, Elsevier