PEO-based polymer electrolytes with ionic liquids and their use in lithium metal-polymer electrolyte batteries

The influence of adding the room-temperature ionic liquid (RTIL) N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR13TFSI) to P(EO)(20)LiTFSI polymer electrolytes and the use of these electrolytes in solid- state Li/V2O5 batteries has been investigated. P(EO)(20)LiTFSI + xPYR(13)TFSI polymer electrolytes with various PYR13+/Li+ mole fractions (x = 0.66, 1.08, 1.73, 1.94, 2.15, and 3.24) were prepared. The addition of up to a 3.24 mole fraction of the RTIL to P(EO)(20)LiTFSI electrolytes, corresponding to a RTIL/ PEO weight fraction of up to 1.5, resulted in freestanding and highly conductive electrolyte films reaching 10(-3) S/cm at 40 degrees C. The electrochemical stability of PYR13TFSI was significantly improved by the addition of LiTFSI. Li/V2O5 cells using the polymer electrolyte with PYR13TFSI showed excellent reversible cyclability with a capacity fading of 0.04% per cycle over several hundreds cycles at 60 degrees C. The incorporation of the RTIL into lithium metal- polymer electrolyte batteries has resulted in a promising improvement in performance at moderate to low temperatures. (c) 2005 The Electrochemical Society.