Lithium halide solid electrolyte, method for manufacturing the same, and all-solid-state battery comprising said lithium halide solid electrolyte

High-Conductivity Lithium Halide Electrolyte with Phase Transition via Aliovalent Substitution of Hf/Zr at Yb Sites

This technology improves lithium-ion conductivity in a lithium halide (Li3-xM11-xM2xX6) structure by performing aliovalent substitution of a +3 metal (M1) with a +4 metal (M2), inducing a phase transition to monoclinic and orthorhombic II crystal structures.

Existing oxide, sulfide, and borohydride solid electrolytes suffer from low ionic conductivity, high interfacial resistance, and electrochemical instability. Some also generate toxic gases or require complex synthesis processes, limiting their potential for mass production.

This technology involves mixing Yb (M1) with Hf or Zr (M2) in a specific molar ratio, followed by heat treatment at 400–500°C to control the crystal structure. By creating a hybrid structure of monoclinic and orthorhombic II phases, it achieves ionic conductivity of 1–3 mS/cm and a low activation energy of 0.1–0.5 eV. It can be applied to cathode composite layers in all-solid-state batteries, high-safety EV cells, and dry-milling-based mass production, enabling high-conductivity room-temperature electrolytes without the risk of hydrogen sulfide generation.

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Key Features:

• Lithium halide solid electrolyte represented by Li3-xM11-xM2xX6, where x is 0.4–0.5, M1 is Yb, M2 is Hf or Zr, and X is Cl
• Mixed crystal structure of monoclinic and orthorhombic II phases formed by heat treatment of precursor mixtures and aliovalent substitution
• Step of preparing a precursor mixture by solid-state mixing of lithium halide, M1 metal halide, and M2 metal halide in an inert gas atmosphere
• Step of heat-treating the precursor mixture at 300–600°C for 3–8 hours to produce a lithium halide solid electrolyte with 1–3 mS/cm ionic conductivity

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This invention was developed with support from the Ministry of Science and ICT for the development of core technologies for R2R-type high-ionic-conductivity solid electrolyte membranes.

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