Amorphization model of nanostructured composite solid electrolytes

Abstract

In the last decades, extensive research has been undertaken to find solid electrolytes that might increase the power and safety of promising electrochemical devices such as lithium batteries, supercapacitors, and solid oxide fuel cells. It is mainly based on the screening of advanced functional suprastructures and developing special synthesis procedures to obtain nanosized materials, allowing one to increase ionic conductivity. That’s why special attention is paid to composite solid electrolytes. In this work we use the accumulated knowledge on the physical chemistry of metals and alloys to describe the amorphization effects. It is known that amorphization at the interphase boundaries (interfaces) and grain boundaries noticeably increases (sometimes by orders of magnitude) the ionic transfer rate and, therefore, affects the functional properties of nanostructured composite solid electrolytes. In the theoretical model proposed, we have attempted to elucidate the reasons, inducing the amorphization effects which are observed upon the crystallization of inorganic eutectics and composite formation. We have especially used the approximation of rigid discs, considered, unit-cell volumes. In the context of the theory, describing the amorphization as an excess molar volume arising upon the crystallization of metals and alloys, we have established that the degree of amorphization depends not only on the synthesis conditions, but also on the incommensurability of crystal unit cells in the components. The findings can be useful in the elaboration of novel inorganic materials for various applications.