Method for manufacturing a solid electrolyte layer for lithium metal batteries using solvothermal synthesis and a lithium metal battery comprising the same

Crystalline argyrodite protective layer grown directly on lithium metal via sealed solvothermal synthesis

This technology utilizes a solvothermal synthesis method with a sulfide-based solid electrolyte precursor solution applied to the lithium metal surface, directly forming a crystalline argyrodite-type solid electrolyte thin film at 150–180°C, which is below the melting point of lithium.

Lithium metal anodes are highly reactive, leading to side reactions with liquid electrolytes and unstable SEI layers. Furthermore, dendrite growth during charge/discharge cycles causes short circuits and reduced battery life. Conventional amorphous sulfide coatings suffer from low ionic conductivity, while high-temperature processes required for crystalline solid electrolytes are impractical due to the low melting point of lithium metal (approx. 180°C).

This technology involves immersing a lithium metal substrate in a reaction vessel containing Li2S, P2S5, and LiCl precursor solutions, sealing it completely, and heating it. The increased internal pressure from solvent vapor allows for the direct formation of a Li6PS5Cl crystalline solid electrolyte layer on the lithium surface at 150–180°C. It can be applied to lithium metal anode protective layers, hybrid solid-liquid batteries, and pretreatment processes for all-solid-state battery anodes, offering a distinct advantage by creating a highly ion-conductive crystalline interface without melting the lithium.

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Key Features:

• Dissolving sulfide-based solid electrolyte precursors—lithium sulfide (Li2S), phosphorus pentasulfide (P2S5), and lithium chloride (LiCl)—in a solvent
• Immersing the lithium metal substrate in a reaction vessel containing the precursor solution and sealing it with a lid
• Heating the interior of the reaction vessel to 150–180°C, below the melting point of lithium, to form a Li6PS5Cl solid electrolyte layer
• A stainless steel reaction vessel and lid with an internal Teflon container

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This invention was developed with support from the Ministry of Trade, Industry and Energy’s Advanced Track for Rare Metal Recycling Technology in Urban Mining.

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