Exploiting the Mixed Entropy Strategy for the Design of Fast Ion Conductors

Abstract The inorganic solid‐state electrolytes play a crucial role in all‐solid‐state batteries. The entropy of solid‐state electrolytes has a significant impact on ion transport. It has been reported that ionic conductivity can be enhanced by increasing the entropy by adding multiple atoms to the materials. However, there is a lack of understanding regarding the potential mechanism between entropy and ion transport in the atomic‐level microstructure of materials. Herein, a new point of view is brought up to understand the influence of entropy on lithium ionic conductivity at an atomic level only by adding one element at a time inspired by the diagonal relationship. A series of materials is designed, including Li 1.75 Zr 0.75 Ta 0.25 Cl 6 , Li 1.75 Zr 0.75 Nb 0.25 Cl 6 , Li 1.75 Zr 0.75 Mo 0.25 Cl 6 , and Li 1.75 Zr 0.75 W 0.25 Cl 6 , with various mixed entropy, directed by diagonal relationship. It reveals that the substitution increases the mixed entropy, alters the disorder degree of cations around lithium ions, and improves ionic conductivity. Highlighting the importance of mixed entropy in ion migration and establishing the close connection between mixed entropy and ion conduction could provide new insights into the design and development of solid‐state electrolytes.