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High-capacity retention of Si anodes using a mixed lithium/phosphonium bis(fluorosulfonyl)imide ionic liquid electrolyte

journal contribution
posted on 11.08.2017, 00:00 authored by Robert KerrRobert Kerr, D Mazouzi, Mojtaba EftekharniaMojtaba Eftekharnia, B Lestriez, N Dupré, Maria ForsythMaria Forsyth, D Guyomard, Patrick HowlettPatrick Howlett
The commercialization of high-capacity Si electrodes for lithium batteries has stalled due to the inability to overcome the mechanical degradation and electrolyte consumption that occur as a result of the inherent volume expansion upon charging. Using an ionic liquid (IL) electrolyte, trimethylisobutylphosphonium bis(fluorosulfonyl)imide (P1,1,1,i4FSI) containing a high lithium bis(fluorosulfonyl)imide (LiFSI) salt content of 3.2 mol per kg of IL (50 mol %), inexpensive and high-capacity Si electrodes made from a facile and ball-milling process demonstrated outstanding capacity retention of around 3.5 mAh/cm2after 300 cycles when cycled at current densities of 1500 mA/g (C/2.5) at room temperature. Moreover, high-capacity retention was maintained for 60 cycles at elevated temperatures up to 80 °C, where traditional electrolytes are unable to operate. SEM images suggest that the use of this highly concentrated IL electrolyte promotes the formation of a stable surface layer that accommodates the volume expansion of the Si electrode. This benchmark result suggests that tailoring of the electrolyte for advantageous solid-electrolyte interphase properties is a very promising route of premium interest.

History

Journal

ACS energy letters

Volume

2

Issue

8

Pagination

1804 - 1809

Publisher

American Chemical Society

Location

Washington, D.C.

eISSN

2380-8195

Language

eng

Publication classification

C Journal article; C1 Refereed article in a scholarly journal

Copyright notice

2017, American Chemical Society