Electrochemical properties of the polyethylene oxide-Li(CF3SO2)2N and ionic liquid composite electrolyte

► The electrical conductivity of PEO18LiTFSI-xPP13FSI increased with x. ► The lowest interface resistance of lithium electrode was observed in the range of x = 1.2-1.44. ► Lithium dendrite formation was suppressed by the addition of PP13FSI into PEO18LiTFSI.