We have shown that crown ether complexes with the lithium salt, lithium bis-(trifluoromethanesulphonyl) imide (LiTFSI), are plastic crystals as evidenced by DSC and their mechanical properties. The conductivity of the complexes was measured and found to vary as a function of crown ether:salt molar ratio. Our study of the (18-Crown-6)-LiTFSI (1/1) solid complex showed that it has a high conductivity reaching similar to 10(-4) S cm(-1) at 50 degrees C and an electrochemical stability of over 4 V enabling its use in a lithium-metal battery. A lithium battery with 1:1 (18-Crown-6)-LiTFSI as electrolyte was assembled, tested, and found to exhibit reversible Li+ transport. Crown Copyright (C) 2007 Published by Elsevier B.V. All rights reserved.