Effect of Postannealing on the Properties of a Ta-Doped Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> Solid Electrolyte Degraded by Li Dendrite Penetration
Ryoji Inada, Atsuto Takeda, Yusuke Yamazaki, Shotaro Miyake, Yoji Sakurai, Venkataraman Thangadurai
Abstract
In this study, we investigated the effect of postannealing on the properties of a garnet-type Ta-doped Li6.55La3Zr1.55Ta0.45O12 (Ta-LLZO) ceramic solid electrolyte degraded by lithium (Li) dendrite penetration during electrochemical Li plating and stripping testing in a Li/Ta-LLZO/Li symmetric cell. After the electrochemical testing in the symmetric cell, the Ta-LLZO pellet was taken out of the cell and then annealed at 800 or 900 °C for 4 h in air. It was confirmed that locally discolored spots on the Ta-LLZO surface at which Li dendrite penetrated disappeared after postannealing. The total conductivity of the annealed Ta-LLZO pellet was lower than the initial one but was retained above 10–4 S cm–1 at room temperature. When the soft-shorted or degraded area size by Li dendrite penetration is localized and smaller than the area size for Ta-LLZO, it is expected that the degradation of the conductivity of annealed Ta-LLZO becomes smaller. Obtained electrochemical results indicate the possibility of reusing the degraded garnet-type solid electrolyte by Li dendrite penetration in another all-solid-state Li battery.