Garnet-Type Lithium Metal Fluorides: A Potential Solid Electrolyte for Solid-State Batteries

In this work, we introduced a garnet-type lithium metal fluoride, Li3Na3M2F12 (M = Al, Sc, In), as solid-state lithium-ion conductors for the first time. The mechanically milled Li3Na3M2F12 compounds crystallized in a cubic garnet-like structure (Ia (3) over bard, No. 230). The ionic conductivities of Li3Na3Al2F12, Li3Na3Sc2F12, and Li3Na3In2F12 are 1.7 X 10(-6), 8.2 X 10(-6), and 2.4 X 10(-6) S/cm at 300 degrees C and 1.2 X 10(-10), 2.6 X 10(-9), and 1.8 X 10(-10) S/cm at 100 degrees C, respectively. Even though these fluoride garnets' conductivity is less, it is still better than those of the oxide analogues Li(3)Ln(3)Te(2)O(12) (Ln = Er, Gd, Tb, Nd). Moreover, we explored why garnet-type Li3Na3M2F12 has low ionic conductivity and presented strategies for further improving conductivities.

Automated summary

We introduced a garnet-type lithium metal fluoride, Li3Na3M2F12 (M = Al, Sc, In), as solid-state lithium-ion conductors for the first time. The mechanically milled Li3Na3M2F12 compounds crystallized in a cubic garnet-like structure. The ionic conductivities of Li3Na3Al2F12, Li3Na3Sc2F12, and Li3Na3In2F12 are relatively low, but still better than the oxide analogues Li(3)Ln(3)Te(2)O(12) (Ln = Er, Gd, Tb, Nd). Strategies for further improving conductivities of garnet-type Li3Na3M2F12 were also presented.