A simple and highly efficient method toward high density garnet-type LLZTO solid state electrolyte.

Garnet-type Li7La3Zr2O12 (LLZO) is among the most attractive candidates for achieving solid-state lithium batteries. LLZO pellets with high density are preferred because of their potential to prevent dendritic Li growth and penetration. However, the presence of pores inside the LLZO electrolyte is inevitable if it is prepared by a traditional solid-state reaction. Large numbers of pores have an adverse influence on both the ionic conductivity and density of the LLZO pellets. In this work, we studied the origin of pore formation in Li6.4La3Zr1.4Ta0.6O12 (LLZTO) and introduced a fast oxygen-assisted sintering method to eliminate the pores. All of the basic physical properties of the LLZTO sintered in oxygen for only 1 h are better than those of the LLZTO sintered in air. The conductivity and Vickers hardness of the LLZTO increased to 6.13 × 10–4 S cm–1 and 9.82 GPa, corresponding to 12.3% and 62.8% enhancement, respectively, even at a low precalcined temperature of 600 °C. A Li||Li symmetric cell with the LLZTO sintered in oxygen also showed more stable and longer cycling at a higher current density (0.4 mA cm–2).