Physical properties of solid polymer electrolyte PEO(LiTFSI) complexes

The physical properties of the ionic conductor, obtained by dissolution of lithium trifluoromethanesulphonylimide in polyethylene oxide, (PEO)_nLi⁺((CF₃SO₂)₂N)^- have been investigated for several values of n. The phase diagram has been established from both DSC and NMR techniques. The diffusion coefficients of ⁷Li and ¹⁹F containing Species, determined by the pulsed magnetic field gradient (PMFG) technique, are interpreted as the measures of the cationic and anionic transport numbers, which are concentration dependent, and t₊ reaches a value close to 0.3. This study is complemented by a systematic analysis of the behaviour of the ⁷Li relaxation time T₁ versus temperature and concentration which is correlated to the glass temperature T_g.