Origin of O<sub>2</sub> Generation in Sulfide‐Based All‐Solid‐State Batteries and its Impact on High Energy Density
Keisuke Yoshikawa, Takeshi Kato, Yasuhíro Suzuki, Akihiro Shiota, Tsuyoshi Ohnishi, Koji Amezawa, Aiko Nakao, Takeshi Yajima, Yasutoshi Iriyama
Abstract
Abstract The cathode surface of sulfide‐based all‐solid‐state batteries (SBs) is commonly coated with amorphous‐LiNbO 3 in order to stabilize charge–discharge reactions. However, high‐voltage charging diminishes the advantages, which is caused by problems with the amorphous‐LiNbO 3 coating layer. This study has investigated the degradation of amorphous‐LiNbO 3 coating layer directly during the high‐voltage charging of SBs. O 2 generation via Li extraction from the amorphous‐LiNbO 3 coating layer is observed using electrochemical gas analysis and electrochemical X‐ray photoelectron spectroscopy. This O 2 leads to the formation of an oxidative solid electrolyte (SE) around the coating layer and degrades the battery performance. On the other hand, elemental substitution (i.e., amorphous‐LiNb x P 1‐ x O 3 ) reduces O 2 release, leading to stable high‐voltage charge–discharge reactions of SBs. The results have emphasized that the suppression of O 2 generation is a key factor in improving the energy density of SBs.