Thermal analysis and NMR study of a poly(ethylene oxide) complex electrolyte : PEO(LiCF3SO3)x

M. Minier , C. Berthier , W. Gorecki

We have determined the equilibrium diagram between the different phases which coexist in the complexes between the poly(ethylene oxide) PEO and the salt LiCF3SO 3, by using DSC and NMR techniques. We have also measured the variation of the glass transition temperature as a function of the salt concentration dTg/dx = 280 K/(mole of salt per mole of monomer unit). We show that in the temperature range 340-420 K the ionic conduction σ only takes place in the amorphous phase. The thermal dependence of σ, previously interpreted in term of Arrhenius law, indeed results from that of three terms : the salt concentration in the amorphous phase (number of carriers), the local dynamics of the polymer chains (diffusion coefficient) and the respective amounts of crystalline and amorphous phases. The temperature dependence of each of these parameters has been estimated from experiments in the sample x-1 = 8 and they combine to give a fair description of σ(T). A striking result is the small temperature dependence of the diffusion coefficient (Dσ ≅ 6 x 10 -8 cm2 s-1 at 375 K). Taking into account these parameters also provides a satisfactory interpretation of the ionic conductivity behaviour in most of complexes formed between PEO and the alkali metals salts.

Mots clés: electrolytes; glass transition polymers; ionic conduction in solids; nuclear magnetic resonance; phase diagrams; polymers; self diffusion in solids; thermal analysis

Domaines: Articles anciens

M. Minier, C. Berthier, W. Gorecki. Thermal analysis and NMR study of a poly(ethylene oxide) complex electrolyte : PEO(LiCF3SO3)x. Journal de Physique, 1984, 45 (4), pp.739-744. ⟨10.1051/jphys:01984004504073900⟩. ⟨jpa-00209805⟩