Ionic conductivity in the solid glyme complexes [CH3O(CH2CH2O)(n)CH3]: LiAsF6 (n=3,4)

We have shown that two small molecule solid electrolytes, [CH3O(CH2CH2O)(3)CH3]:LiAsF6 and [CH3O(CH2CH2O)(4)CH3]:LiAsF6, differing by only one ethylene oxide unit exhibit markedly different transport numbers, t(+)= 0.8 and 0.1, respectively. Such differences are related, on the one hand, to the presence of tunnels for Li+ migration in the crystal structure of the G3 complex, but not G4, and, on the other hand, to the weaker binding of AsF6- in the structure of G4 than in G3. Learning how to construct solid electrolytes that exhibit high Li+ transport numbers is important in minimizing polarization when such electrolytes are used in all-solid-state cells, such as lithium batteries.