Strain-Stabilized Ceramic-Sulfide Electrolytes.

ABSTRACT

Ceramic-sulfide solid electrolytes are a promising material system for enabling solid-state batteries. However, one challenge that remains is the discrepancy in the reported electrochemical stability. Recent work has suggested that it may be due to the sensitivity of ceramic sulfides to mechanically induced stability. Small changes in ceramic-sulfide microstructure, for example, have been shown to cause substantial differences in the electrochemical stability. In this work, a rigorous theoretical framework is constructed to enable the simulation of such mechanically induced stability for a generalized constraint mechanism. It is shown that the susceptibility for voltage widening in ceramic sulfides can be significantly influenced by the choice of different decay morphology models. This results in a less intrusive microstructure requirement for improved stability, which stems from the tendency of sulfides to decay via inclusions rather than homogeneously. This predicted decay morphology is experimentally confirmed. Li10 GeP2 S12 is stabilized by a thin amorphous shell, which prior models predict is too thin for stabilization. The generality of this framework is discussed in light of stabilization methods beyond microstructure, such as on the battery cell level. The relation of our picture to the observed lithium metal formation in ceramic sulfides is also discussed.