Journal of Applied Electrochemistry, Vol.40, No.9, 1619-1624, 2010
LiFePO4 cathode in N-methyl-N-propylpiperidinium and N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide
Ternary [Li+][MePrPip(+)][NTf (2) (-) ] and [Li+][MePrPyrr(+)][NTf (2) (-) ] room temperature ionic liquids (ILs) were obtained by dissolution of solid lithium bis(trifluoromethanesulfonyl)imide (LiNTf2) in liquid N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide and N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, respectively, and studied as electrolytes for the use in Li/LiFePO4 or C(Li)/LiFePO4 batteries. The cell worked properly in the presence of 10 wt% of vinylene carbonate (VC). Impedance-spectroscopy studies showed that the additive (VC) forms a protective coating on the anode. The LiFePO4 cathode shows good efficiency (135 mAh g(-1)) working together with [Li+][MePrPip(+)][NTf (2) (-) ] + VC and [Li+][MePrPyrr(+)][NTf (2) (-) ] + VC ionic liquid electrolytes. The flash point of ionic liquid electrolytes containing 10 wt% of VC is above 300 A degrees C, which makes them practically non-flammable.