Spontaneous formation of a core–shell structure by a lithium ion conductive garnet-type oxide electrolyte for co-sintering with the cathode

Abstract

Solid-state batteries (SSBs) that use a lithium ion, conducting garnet-type oxide electrolyte, Li₇La₃Zr₂O₁₂ (LLZ), are currently gaining a lot of attention. As they are very safe and reliable, these batteries can be used in a range of wireless devices and sensors as part of the future internet of things. The major issue for realizing oxide-based SSBs is the chemical reaction between the cathode and electrolyte during the ceramic fabrication process. We developed an Sr-substituted LLZ that spontaneously formed a core–shell structure that suppressed the chemical reaction during high-temperature sintering. The formation of this core–shell structure was confirmed using substitution by Sr only. A model battery using Sr-substituted LLZ significantly improved the battery capacity from ∼10% to ∼85% of the theoretical capacity.