A review of challenges and issues concerning interfaces for garnet-type all-solid-state batteries

The rapid surge in sales of electronic devices and electric vehicles has created an ever-increasing demand for batteries that excel in terms of both safety and energy density. Solid-state batteries (SSBs), as compared to conventional liquid electrolyte-based lithium-ion batteries, have emerged as pioneers at the forefront of the transformation of lithium-ion battery technology, distinguished by their exceptional safety features and elevated energy density. Among the numerous candidate materials in the realm of solid-state electrolytes (SSEs), the garnet-type Li7La3Zr2O12 (LLZO) stands out due to its exceptional ionic conductivity, shear modulus, and chemical stability. However, inadequate contact between LLZO and the cathode, anode, and even within LLZO itself have been a substantial impediment to the practical application of solid-state batteries. In this review, we delve deeply into the diverse types of interfaces and the associated challenges they present, providing a meticulous analysis of improvement strategies tailored to each specific issue. Finally, we offer an extensive discussion on the challenges and prospective future developments of LLZO in the realm of SSBs, with the aim of contributing to the sustainable advancement of energy storage technologies.