Duality of Li2CO3 in Solid-State Batteries

Solid-state batteries (SSBs) have been considered the most promising technology because of their superior energy density and safety. Among all the solid-state electrolytes (SEs), Li7La3Zr2O12 (LLZO) with high ionic conductivity (3 x 10(-4) S/cm) has been widely investigated. However, its large-scale production in ambient air faces a challenge. After air exposure, the generated Li2CO3 layer deteriorates the ionic conductivity and interfacial wettability, thus greatly compromising the electrochemical performance of SSBs. Many works aim to eliminate this layer to recover the pristine LLZO surface. Unfortunately, few articles have emphasized the merits of Li2CO3. In this review, we focus on the two-sidedness of Li2CO3. We discuss the various characteristics of Li2CO3 that can be used and recapitulate the strategies that utilize Li2CO3. Insulating Li2CO3 is no longer an obstacle but an opportunity for realizing intimate interfacial contact, high air stability, and outstanding electrochemical performance. This review aims to offer insightful guidelines for treating air-induced Li2CO3 and lead to developing the enhanced air stability and electrochemical performance of LLZO. [Graphics]