A General Mechanism to Increase Ionic Conductivity by High Entropy

There is increasing interest in high-entropy ceramics due to their successful use to enhance properties in Li-ion cathodes, catalysts, thermal barrier coatings, and thermoelectrics. Attractive because of their good synthesizability and reduced reliance on specific chemistries, it has been unclear whether and how a high-entropy design would be beneficial for developing new and better ion alkali-ion conductors for all-solid-state batteries. In this work, we combine first-principles modeling and experiments to demonstrate the mechanism by which a mixture of multiple principal elements boosts ionic conductivity, regardless of the alkali metal content and crystal framework. We validated our conceptual models and first principles results with experiments that show several orders of magnitude enhancement in the ionic conductivity in oxide materials when the mixing entropy of the metals is increased. This work unveils new opportunities in the vast design space of high-entropy materials and adds a new strategy to the development of novel superionic conductors.