Progress and perspective of interface design in garnet electrolyte‐based all‐solid‐state batteries

Abstract Inorganic solid‐state electrolytes (SSEs) are nonflammable alternatives to the commercial liquid‐phase electrolytes. This enables the use of lithium (Li) metal as an anode, providing high‐energy density and improved stability by avoiding unwanted liquid‐phase chemical reactions. Among the different types of SSEs, the garnet‐type electrolytes witness a rapid development and are considered as one of the top candidates to pair with Li metal due to their high ionic conductivity, thermal, and electrochemical stability. However, the large resistances at the interface between garnet‐type electrolytes and cathode/anode are the major bottlenecks for delivering desirable electrochemical performances of all‐solid‐state batteries (SSBs). The electrolyte/anode interface also suffers from metallic dendrite formation, leading to rapid performance degradation. This is a fundamental material challenge due to the poor contact and wettability between garnet‐type electrolytes with electrode materials. Here, we summarize and analyze the recent contributions in mitigating such materials challenges at the interface. Strategies used to address these challenges are divided into different categories with regard to their working principles. On one hand, progress has been made in the anode/garnet interface, such as the successful application of Li‐alloy anode and different artificial interlayers, significantly improving interfacial performance. On the other hand, the desired cathode/garnet interface is still hard to reach due to the complex chemical and physical structure at the cathode. The common methods used are nanostructured cathode host and sintering additives for increasing the contact area. On the basis of this information, we present our views on the remaining challenges and future research of electrode/garnet interface. This review not only motivates the need for further understanding of the fundamentals, stability, and modifications of the garnet/electrode interfaces but also provides guidelines for the future design of the interface for SSB.