Influence of Carbonate-Based Additives on the Electrochemical Performance of Si NW Anodes Cycled in an Ionic Liquid Electrolyte

Killian Stokes; Tadhg Kennedy; Guk-Tae Kim; Hugh Geaney; Dylan Storan; Fathima Laffir; Giovanni Battista Appetecchi; Stefano Passerini; Kevin M Ryan

doi:10.1021/acs.nanolett.0c01774

Influence of Carbonate-Based Additives on the Electrochemical Performance of Si NW Anodes Cycled in an Ionic Liquid Electrolyte

Nano Lett. 2020 Oct 14;20(10):7011-7019. doi: 10.1021/acs.nanolett.0c01774. Epub 2020 Sep 2.

Authors

Killian Stokes^{1

2}, Tadhg Kennedy^{1

2}, Guk-Tae Kim^{3

4}, Hugh Geaney^{1

2}, Dylan Storan^{1

2}, Fathima Laffir², Giovanni Battista Appetecchi⁵, Stefano Passerini^{3

4}, Kevin M Ryan^{1

2}

Affiliations

¹ Department of Chemical Sciences, University of Limerick, V94T9PX Limerick, Ireland.
² Bernal Institute, University of Limerick, V94T9PX Limerick, Ireland.
³ Helmholtz Institute Ulm, Karlsruhe Institute of Technology, Helmholtzstrasse 11, 89081 Ulm, Germany.
⁴ Karsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe, Germany.
⁵ Materials and Physicochemical Processes Laboratory, ENEA, Italian National Agency for New Technology, Energy and Sustainable Economic Development, Via Anguillrese 301, 00123 Rome, Italy.

PMID: 32648763
DOI: 10.1021/acs.nanolett.0c01774

Abstract

Addition of electrolyte additives (ethylene or vinylene carbonate) is shown to dramatically improve the cycling stability and capacity retention (1600 mAh g^-1) of Si nanowires (NWs) in a safe ionic liquid (IL) electrolyte (0.1LiTFSI-0.6PYR₁₃FSI-0.3PYR₁₃TFSI). We show, using postmortem SEM and TEM, a distinct difference in morphologies of the active material after cycling in the presence or absence of the additives. The difference in performance is shown by postmortem XPS analysis to arise from a notable increase in irreversible silicate formation in the absence of the carbonate additives. The composition of the solid electrolyte interphase (SEI) formed at the active material surface was further analyzed using XPS as a function of the IL components revealing that the SEI was primarily made up of N-, F-, and S-containing compounds from the degradation of the TFSI and FSI anions.

Keywords: Electrolyte; Ex-situ; Ionic Liquid; SEI; Silicon Nanowires.