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

Abstract

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 (Ia3̅d, No. 230). The ionic conductivities of Li3Na3Al2F12, Li3Na3Sc2F12, and Li3Na3In2F12 are 1.7 × 10–6, 8.2 × 10–6, and 2.4 × 10–6 S/cm at 300 °C and 1.2 × 10–10, 2.6 × 10–9, and 1.8 × 10–10 S/cm at 100 °C, respectively. Even though these fluoride garnets’ conductivity is less, it is still better than those of the oxide analogues Li3Ln3Te2O12 (Ln = Er, Gd, Tb, Nd). Moreover, we explored why garnet-type Li3Na3M2F12 has low ionic conductivity and presented strategies for further improving conductivities.

Defect Strategy in Solid‐State Lithium Batteries

“…Reproduced with permission. [ 104 ] Copyright 2022, American Chemical Society. Reproduced with permission.…”

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Stable Li|LAGP Interface Enabled by Confining Solvate Ionic Liquid in a Hyperbranched Polyanionic Copolymer for NASICON-Based Solid-State Batteries

“…Traditional commercial lithium-ion batteries usually use toxic, flammable, and corrosive liquid (organic) electrolytes, thereby bringing potential safety hazards, such as battery explosion and short circuits caused by thermal runaway behavior and uncontrolled growth of lithium dendrites. − Therefore, safety is one of the most critical issues to be solved in developing large-scale applications for secondary lithium batteries with long cycling life. − Compared with the organic liquid electrolytes, ceramic electrolytes, such as NASICON, perovskites, garnet, and sulfide-type ceramic/glass, have the advantages of non-flammability, a high shear modulus (10–100 GPa) against Li dendrite growth, and a high Li-ion transference number ( t Li+ ≈ 1) at room temperature (R.T.). − Thus, all-solid-state lithium–metal batteries are recognized as the best candidate for next-generation energy storage by replacing the liquid electrolyte with a solid electrolyte (SE). − Unfortunately, these SEs suffer from physicochemical stability issues, including high impedance at solid/solid interfaces and poor chemical stability in contact with Li metal, which hinder the application of solid-state batteries.…”