Fast ion conducting glasses have long been considered as alternatives to flammable liquid electrolytes in Li and Na batteries. However, for such glassy solid electrolytes (GSEs) studied so far, they have lacked the unique combination of required electrochemical properties for use as a solid electrolyte with the equally important requirements of viscoelastic behavior to form them into thin films suitable for high ion conductivity separators. Indeed, to date, most GSEs are considered as “invert” glasses where the high viscosity promoting glass formers in the compositions, such as SiO2, B2O3, or P2O5 are not the dominant component, but rather are the minor component and the alkali salt, such as Li2O or Na2O is the majority component. This has led to the general observation that such high alkali content invert glasses are rather poor glass formers that crystallize rapidly upon heating above their glass transition temperature into the viscoelastic supercooled liquid regime. This has forced most workers in this field to consider only fully crystallized polycrystalline ceramic versions of these compositions or at most glass ceramics where the crystalline phase is dominant, > 90 v/v%. In this first-ever report of thin film fast ion conducting glasses made by viscoelastic deformation processing of redrawing glass preforms, we report new compositions where we have broken this long-standing paradigm of high conductivity combined with high alkali salt concentration but poor glass formability and will summarize our efforts to produce thin films of Li and Na ion conducting glasses and test in them in symmetric and asymmetric cells.
Steve W. Martin received his B.S. in Chemistry from Capital University in 1980 and his Ph.D. in Physical Chemistry from Purdue University in 1986. From Purdue, he directly joined the faculty of Materials Science & Engineering in 1986 and was promoted to Associate Professor in 1991 and Full Professor in 1996. He has since been promoted to the ranks of University Professor in 2006 and the rank of Anson Marston Distinguished Professor in Engineering in 2009. He has been awarded the George W. Morey Award in Glass Science from the Glass and Optical Materials Division of the American Ceramic Society, where he is also a named Fellow of the society. He has been a visiting professor on eight different occasions at universities around the world. His core research specialization is the preparation, characterization and study of ionically conducting glasses for all solid-state lithium and sodium batteries. His broader research interests include glass and amorphous materials, solid electrolytes for batteries and fuel cells, optical materials and fibers and the characterization of materials. He has published more than 200 refereed articles, given more than 225 invited talks around the world, and has consulted for more than 50 companies worldwide.