Low-Temperature Sintering of a Garnet-Type Li_6.5La₃Zr_1.5Ta_0.5O₁₂ Solid Electrolyte and an All-Solid-State Lithium-Ion...

Garnet-type Ta-substituted Li₇La₃Zr₂O₁₂ materials attract considerable attention as solid electrolytes for use in future oxide-based all-solid-state lithium-ion batteries owing to their superior ionic conductivity and chemical and electrochemical stabilities. However, high-temperature sintering above 1000 °C, which is needed to realize high lithium-ion conductivity, results in the formation of insulating interface impurities at the electrode-electrolyte interface. Herein, the low-temperature sintering of the Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZT) solid electrolyte at a remarkably low temperature of 400 °C was demonstrated using the submicrometer-sized garnet-type LLZT fine powder sample prepared at 600 °C through a reaction of Li₂O and La_2.4Zr_1.2Ta_0.4O₇. The lithium-ion conductivity at 25 °C was 4.54 × 10^-5 S cm^-1 without any additives through low-temperature sintering at 400 °C. In addition, the preliminary battery performance of the oxide-based all-solid-state LiNi_1/3Co_1/3Mn_1/3O₂-Li₄Ti₅O₁₂ full-battery cell fabricated at 400 °C using the present LLZT fine powder sample as the solid electrolyte was demonstrated.