An azo-spiro mixed ionic liquid electrolyte for lithium metal- LiFePO 4 batteries

George Hamilton Lane, Adam Samuel Best, Douglas Robert Macfarlane, Anthony F Hollenkamp, Maria Forsyth

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Using a binary ionic liquid (IL) electrolyte composed of N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide and 2-oxo-3,9-dioxa-6-azonia-spiro[5.5]undecane bis(trifluoromethanesulfonyl)imide at an optimized ratio, we investigated battery cycling behavior at temperatures of 50 degrees C and above. We achieved an extended cycle life using the binary electrolyte system as the problem of cell short-circuiting (stemming from lithium dendrite growth) was significantly reduced. We provide evidence that 2-oxo-3,9-dioxa-6-azonia-spiro[5.5]undecane bis(trifluoromethanesulfonyl)imide assists in short-circuit prevention through the suppression of lithium dendrites. For batteries employing a lithium metal anode and a LiFePO4 cathode, we report capacities in excess of 120 mAh g(-1), and by utilizing a pulse charging technique we were able to charge a cell at a current density (0.1 mA cm(-2)), which we were not able to achieve using a normal charging regime. We also present lithium cycling data for 2-oxo-3,9-dioxa-6-azonia-spiro[5.5]undecane bis(trifluoromethanesulfonyl)imide in the absence of another IL. We show that poor capacity and a necessarily high operating temperature make this system undesirable although we observed no short-circuiting. We conclude that the structure of the components of the IL and the nature of the charging regime employed can cause a significant reduction in dendrite-induced short-circuiting. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3429138] All rights reserved.
Original languageEnglish
Pages (from-to)876 - 884
Number of pages9
JournalJournal of the Electrochemical Society
Issue number7
Publication statusPublished - 2010

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