Highly conductive, oriented polymer electrolytes for lithium batteries

In semicrystalline complexes of poly(ethylene oxide) (PEO) with different salts, such as lithium iodide, lithium trifluoromethanesulfonate (LiTF) and lithium trifluoromethanesulfonimide (LiTFSI), stretching induced longitudinal DC conductivity enhancement was observed, in spite of the formation of more ordered polymer electrolyte (PE) structure. It was found that the more amorphous the PE, the less its lengthwise conductivity is influenced by stretching. The results of our investigation suggest that ionic transport occurs preferentially along the PEO helical axis, at least in the crystalline phase, and that the rate-determining step of the lithium ion conduction in LiI:P(EO)20, LiTF:­P(EO)20 polymer electrolytes below Tm is “interchain” hopping. Understanding ion transport processes is clearly a fertile field for research and development in the synthesis of new rigid polymers with ordered channels and composition appropriate for enhanced ionic conductivity. Copyright © 2003 John Wiley & Sons, Ltd.