Diffusion mechanisms of fast lithium-ion conductors

The quest for next-generation energy-storage technologies has pivoted towards all-solid-state batteries, primarily owing to their potential for enhanced safety and energy density. At the centre of this promising technology lie inorganic lithium superionic conductors, which facilitate rapid ion transport comparable to that in their liquid counterparts. Despite their promise, the limited availability of materials that both achieve superionic conductivity and fulfil all practical requirements necessitates the discovery of novel conductors. This Review comprehensively explores the diverse structural and chemical factors that improve ionic conductivity and the atomistic mechanism by which each factor affects it. We emphasize the importance of a dual approach: using structural factors to enable high-conducting prototypes, and chemical factors to further optimize the ionic conductivity. From these insights, we distil over 40 years of conductor development history to the key concepts that paved the way for today’s leading superionic conductors. In detailing the trajectory of ionic conduction advancements, this Review not only charts the progress in the field but also proposes a strategic approach for researchers to efficiently innovate with the ultimate goal of realizing the promise of all-solid-state batteries. Inorganic lithium superionic conductors are central to the development of solid-state batteries, but the availability of practical superionic conductors is still limited. This Review highlights structural and chemical strategies to enhance ionic conductivity and maps a strategic approach to discover, design and optimize fast lithium-ion conductors for safe and high-energy-density all-solid-state batteries.