Materials for all-solid-state lithium ion batteries

Garnet-type electrolytes are currently receiving much attention for applications in Li-ion batteries, as they possess high ionic conductivity and chemical stability. Doping the garnet structure has proved to be a good way to improve the Li ion conductivity and stability. The present study includes effects of Y- doping in Li₅La₃Nb₂O₁₂ on Li ion conductivity and stability of"Li_5-2xLa ₃Nb_2-xY_xO₁₂" (0.05 ≤x≤0.75) under various environments, as well as chemical stability studies of Li_5-xBa_xLa_3-xM₂O₁₂ (M = Nb, Ta) in water. "Li_6.5La₃Nb_1.25Y _0.75O₁₂" showed a very high ionic conductivity of 2.7 x 10^-4Scm^-1at 25 °C, which is comparable to the highest value reported for garnet-type compounds, e.g., Li₇La ₃Zr₂O₁₂. The selected members show very good stability against high temperatures, water, Li battery cathode Li ₂CoMn₃O₈ and carbon. The Li _5-xBa_xLa_3-xNb₂O₁₂ garnets have shown to readily undergo an ion-exchange (proton) reaction under water treatment at room temperature; however, the Ta-based garnet appears to exhibit considerably higher stability under the same conditions.