Network Former Mixing (NFM) Effects in Ion-Conducting Glasses - Structure/Property Correlations Studied by Modern Solid-State NMR Techniques

Abstract

Glassy solid electrolytes are important integral components for all-solid-state devices for energy storage and conversion. The use of multiple network formers is an important part of their design strategy for specific applications. In many glass systems the interaction between the different network formers results in strongly non-linear variations in physical properties (network former mixing (NFM) effects), requiring a detailed understanding on a structural basis.The issues to be addressed involve both the structural organization and connectivities within the framework, the local environments and spatial distributions of the mobile ions, and the dynamical aspects of ion transport, to be discussed in relation to possible phase separation or nano-segregation effects. Besides Raman and X-ray photoelectron spectroscopies, solid state nuclear magnetic resonance (NMR) methods are particularly useful for providing detailed answers to such issues. The present review introduces the basic principles of modern solid state NMR methods and their applications to glass structure, with a particular focus on the characterization of network-former mixing effects in the most common lithium and sodium conducting oxide and chalcogenide glass systems. Based on the current state of the literature reviewed in the present work, some emerging general principles governing structure/property correlations are identified, to be tested by further experimenteation in the future.