The formation of a stable and ionically conductive interface between solid electrolyte and electrode is critical to achieving functional solid-state batteries [29,30]. To alleviate the influence of Li2CO3, Li and coworkers proposed that the incorporation of a small amount LiF into the garnet LLZO electrolyte could effectively decrease the interface resistance from 1260 Ω cm−2 to 345 Ω cm−2 [29].