All-solid-state lithium-ion batteries that use ionconducting ceramics as electrolytes have the potential to replace commercial lithium-ion cells that use liquid electrolytes, offering improved energy densities and reliability . A practical solid electrolyte should have a high ionic conductivity to allow fast charge and discharge rates and high power output. To achieve this goal, considerable research effort has been directed towards both the discovery of new materials with intrinsically high ionic mobilities and to deriving general principles that can explain how chemical or structural variations within solid electrolytes modulate lithium transport .