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Enhanced Li+ Transport in Ionic Liquid-Based Electrolytes Aided by Fluorinated Ethers for Highly Efficient Lithium Metal Batteries with Improved Rate Capability

Liu, Xu 1; Zarrabeitia, Maider 1; Mariani, Alessandro 1; Gao, Xinpei 1; Schütz, Hanno Maria 1; Fang, Shan 1; Bizien, Thomas; Elia, Giuseppe Antonio 1; Passerini, Stefano 1
1 Karlsruher Institut für Technologie (KIT)


FSI$^{-}$-based ionic liquids (ILs) are promising electrolyte candidates for long-life and safe lithium metal batteries (LMBs). However, their practical application is hindered by sluggish Li$^{+}$ transport at room temperature. Herein, it is shown that additions of bis(2,2,2-trifluoroethyl) ether (BTFE) to LiFSI-Pyr$_{14}$FSI ILs can effectively mitigate this shortcoming, while maintaining ILs′ high compatibility with lithium metal. Raman spectroscopy and small-angle X-ray scattering indicate that the promoted Li+ transport in the optimized electrolyte, [LiFSI]$_{3}$[Pyr$_{14}$FSI]$_{4}$[BTFE]$_{4}$ (Li$_{3}$Py$_{4}$BT$_{4}$), originates from the reduced solution viscosity and increased formation of Li$^{+}$-FSI$^{-}$ complexes, which are associated with the low viscosity and non-coordinating character of BTFE. As a result, Li/LiFePO$_{4}$ (LFP) cells using Li$_{3}$Py$_{4}$BT$_{4}$ electrolyte reach 150 mAh g$^{-1}$ at 1 C rate (1 mA cm$^{-2}$) and a capacity retention of 94.6% after 400 cycles, revealing better characteristics with respect to the cells employing the LiFSI-Pyr$_{14}$FSI (operate only a few cycles) and commercial carbonate (80% retention after only 218 cycles) electrolytes. ... mehr

Verlagsausgabe §
DOI: 10.5445/IR/1000134001
Veröffentlicht am 20.09.2021
DOI: 10.1002/smtd.202100168
Zitationen: 22
Web of Science
Zitationen: 21
Zitationen: 24
Cover der Publikation
Zugehörige Institution(en) am KIT Helmholtz-Institut Ulm (HIU)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2021
Sprache Englisch
Identifikator ISSN: 2366-9608
KITopen-ID: 1000134001
HGF-Programm 38.02.01 (POF IV, LK 01) Fundamentals and Materials
Erschienen in Small Methods
Verlag Wiley-VCH Verlag
Band 5
Heft 7
Seiten 2100168
Nachgewiesen in Scopus
Web of Science
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