Local Li cation coordination and dynamics in novel solid electrolytes

Abstract

Research on solid ionic conductors for use as electrolytes in all solid state batteriesstill constitutes a rather vivid branch of today's materials science. Despite enormousefforts, neither the development of a solid electrolyte fulfilling the key requirementssuch as mechanical stability and high ionic conductivity at ambient temperature has beensuccessful nor has an extended understanding of the local Li coordination motifs in theoften amorphous systems been obtained. In this contribution, recent progress both in thedevelopment of novel solid state electrolytes with high ionic conductivity and mechanicalstability and in the characterization of the local Li coordination motifs in these electrolytesfrom our laboratory is presented. The work was performed as a project within theframework of the Collaborative Research Centre SFB 458 "Ionic Motion in Materials withDisordered Structures - From Elementary Steps to Macroscopic Transport". Results willbe given for polymer electrolytes based on polyethylene oxide (PEO), polyphosphazene(PPZ) and polyacrylonitrile (PAN) with various Li salts, nano-composites of these polymerelectrolytes and Al2O3 as a ceramic filler, novel inorganic/organic hybrid electrolytes,in which a mixture of an ionic liquid and Li salt is confined within the pore systemof a SiO3 glass, and a crystalline electrolyte, Li5La3Nb2O 12. Employing a range ofadvanced solid state NMR methodologies including dipolar based NMR techniques andpulsed field gradient (PFG) NMR and impedance spectroscopy we were able to obtaina detailed knowledge about the local Li cation coordination motifs and the mechanism ofLi transport in these electrolytes. Especially the hybrid electrolytes and the salt rich PANbased polymer electrolytes were identified as rather promising materials which combinea high ionic conductivity and mechanical stability.1. © by Oldenbourg Wissenschaftsverlag, München.