Mitigation strategies for Li₂CO₃ contamination in garnet-type solid-state electrolytes: formation mechanisms and...

Garnet-type solid-state electrolytes (SSEs) are promising candidates for next-generation solid-state batteries (SSBs) owing to their high ionic conductivity, robust mechanical strength, and broad electrochemical stability window. However, exposure to ambient air results in the formation of a Li₂CO₃ passivation layer on the surface, significantly reducing ionic conductivity and deteriorating interfacial wettability, thereby severely impairing the electrochemical performance of SSBs. This review systematically analyzes the formation mechanisms and influencing factors of Li₂CO₃ contamination on garnet-type SSE surfaces. It summarizes recent strategies for suppressing Li₂CO₃ formation, including sintering process optimization, elemental doping, and grain boundary/interface engineering. Among these approaches, interfacial treatments have attracted considerable attention owing to their cost-effectiveness and operational efficiency. This review focuses on categorizing diverse treatment strategies for improving electrode/electrolyte interfacial contact, including physical cleaning, chemical treatment and conversion, and modification with interfacial interlayers-specifically detailing types such as inorganic, organic, and organic-inorganic composite interlayers. Finally, the future prospects of garnet-type SSEs in high-performance SSBs are discussed, pointing out the need for in-depth research into the formation and evolution mechanisms of Li₂CO₃ and the development of more efficient interface control strategies. This review systematically examines interfacial challenges in garnet-type SSEs, with the ultimate goal of facilitating the development of stable all-solid-state lithium metal batteries and accelerating their commercialization.