Ionic Conductivity of Ruddlesden-Popper Layered Perovskites (Li2SrTa2O7, Li2SrNb2O7, and Li2CaTa2O7) with Poly (ethylene oxide) as a Composite Solid Electrolyte

Abstract

We report the ionic conductivity studies of three different Ruddlesden-Popper layered perovskite (RP-LP) materials (Li2SrTa2O7, Li2SrNb2O7, and Li2CaTa2O7) in composites with poly (ethylene oxide) (PEO). For the first time, the lithium-ion conduction pathway in the RP-LP materials, of n=2 in AnA'BnO3n+1 general crystal structure, have been studied by using bond valence sum mapping. The results show a two-dimensional lithium-ion pathway. The temperature dependence of the conductivity is modelled by using a Vogel-Tamman-Fulcher (VTF)-type relationship for PEO RP-LP and pure PEO samples. The PEO RP-LP composites deliver ionic conductivities in the range of 3.32 to 4.09×10-06σcm-2 at 80°C, and their corresponding activation energies range from 6.37 to 7.01kJmol-1 at the calculated temperature slope range of 50 to 80°C. They also deliver appreciable lithium transference numbers in the range of 0.20 to 0.58 at 30°C and an excellent wide potential window stability of 4V. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.