A Fernicola

B Scrosati

C Sirisopanaporn

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LiTFSI-Py24TFSI: a novel electrolyte for rechargeable 
lithium batteries 
 
A. Fernicola, C. Sirisopanaporn and B. Scrosati, 
 Department of Chemistry, Sapienza University of Rome, 
P.le Aldo Moro, 5 00185 Rome, Italy 
  
 Lithium batteries are appealing power sources 
for electronic portable devices (e.g. laptops and mobile 
phones) and electric or hybrid vehicles. One of the main 
drawbacks of the systems actually available in commerce 
is the use of volatile organic solvents as electrolyte 
components. Their accidental vaporization, in case of a 
local overheating, or their electrochemical decomposition 
would generate gaseous products.[1] The consequent 
increase of the internal pressure may provoke the cell 
rupture and the gases leakage, but even violent side 
reactions which may lead to fire. The development of 
new-generation batteries is directed to achieve 
performances higher than those of actual devices, in terms 
of safety, cost, cycle life and environmental compatibility.  
In this concern, ionic liquids, ILs are of great 
interest due to their specific properties,[2, 3] such as the 
high ionic conductivity and the non-volatility, the latter 
leading to thermal stability and non-flammability.  
In this work, we present some of the results 
obtained in our laboratory for the application of ILs in 
lithium metal batteries.  
The comparison of the intrinsic characteristics of 
different ILs led to the choice of the N-n-butyl-N-
ethylpyrrolidinium N,N-
bis(trifluoromethanesulfonyl)imide, Py24TFSI as the 
sample to be tested.[4] The synthesis of this salt, whose 
structure is reported in Figure 1, has been optimized in 
our laboratory in order to obtain high purity and low 
water content samples, as required by the use in batteries. 
The IL has been used as the solvent of a LiTFSI salt, and 
the resulting solution has been characterized in terms of 
thermal behavior, conductivity and electrochemical 
stability. LiTFSI-Py24TFSI showed an improved stability 
towards lithium metal electrode, with respect to the most 
commonly studied imidazolium-based ILs. This stability 
allowed further electrochemical tests, including the 
assembling of a lithium battery prototype using lithium 
iron phosphate as the cathode. In Figure 2, the voltage 
profile in charge and discharge of the cell Li / LiTFSI 
(Py24TFSI) / LiFePO4, is reported. The results obtained 
within this work are, although preliminary, encouraging 
in promoting the study of this LiTFSI-Py24TFSI solution 
as a lithium conducting electrolyte, either in the liquid and 
in membrane configuration.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
References 
[1] A.S. Aricò, P. Bruce, B. Scrosati, J.M. Tarascon, W. 
Van Schalkwijk, Nature Mater. 4 366 (2005) 
[2] A. Fernicola, B.Scrosati, H. Ohno, Ionics, 12, 95 
(2006) 
[3] H. Ohno, Electrochemical aspects of ionic liquids, 
Wiley, Hoboken NJ (2005) 
[4] A. Fernicola, F. Croce, B. Scrosati, T. Watanabe, H. 
Ohno, J. Power Sources 174 342 (2007) 
 
Fig. 1. Structure of the Py24TFSI IL 
studied in this work. 
Fig. 2. Charge-discharge profile of the 
battery Li / LiTFSI (Py24TFSI) / LiFePO4 
cycled at different rates.  
0 20 40 60 80 100 120 140 160 180 200
2,4
2,6
2,8
3,0
3,2
3,4
3,6
3,8
4,0
4,2
C/3 C/5C/21C
V
ol
ta
ge
 / 
V
Specific capacity /mAhg-1
214th ECS Meeting, Abstract #717, © The Electrochemical Society
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LiTFSI-Py 24 TFSI: a novel electrolyte for rechargeable lithium batteries

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LiTFSI-Py 24 TFSI: a novel electrolyte for rechargeable lithium batteries

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