Li₂CO₃: A Critical Issue for Developing Solid Garnet Batteries

Solid garnet electrolytes are promising solid-state electrolytes because of their favorable ionic conductivity and high stability against Li metal anodes. However, their special surface chemistry greatly affects the practical applications whether in the form of garnet ceramic electrolytes (GCEs) or polymer/garnet electrolytes (PGEs). Even though large-scale production of garnet in an ambient atmosphere is possible, the passivated surface due to air exposure can lead to poor interfacial properties of GCEs with electrodes and low ionic conductivities of PGEs. Understanding the effects of air exposure on garnet structure stability, ion mobility, and interfacial configuration is crucial for better applications of solid garnet electrolytes. In this Perspective, we comprehensively recapitulate the reaction mechanisms and influencing factors of air-induced contaminations. Various surface engineering strategies tailoring garnet particles and/or pellets are reviewed. This Perspective provides insightful guidelines for better storage of garnet electrolytes and construction of solid garnet batteries with enhanced electrochemical performance.