PEO-Based Polymer Electrolytes with Ionic Liquids and Their Use in Lithium Metal-Polymer Electrolyte Batteries

Abstract

The influence of adding the room-temperature ionic liquid (RTIL) NN -methyl- NN -propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13TFSI)(PYR13TFSI) to P(EO)20LiTFSIP(EO)20LiTFSI polymer electrolytes and the use of these electrolytes in solid-state Li∕V2O5Li∕V2O5 batteries has been investigated. P(EO)20LiTFSI+xPYR13TFSIP(EO)20LiTFSI+xPYR13TFSI polymer electrolytes with various PYR13+∕Li+PYR13+∕Li+ mole fractions ( x=0.66x=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)20LiTFSIP(EO)20LiTFSI electrolytes, corresponding to a RTIL/PEO weight fraction of up to 1.5, resulted in freestanding and highly conductive electrolyte films reaching 10−3S∕cm10−3S∕cm at 40°C40°C . The electrochemical stability of PYR13TFSIPYR13TFSI was significantly improved by the addition of LiTFSI. Li∕V2O5Li∕V2O5 cells using the polymer electrolyte with PYR13TFSIPYR13TFSI showed excellent reversible cyclability with a capacity fading of 0.04% per cycle over several hundreds cycles at 60°C60°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.