Lithium recovery system including a solid electrolyte membrane and a method for manufacturing said solid electrolyte membrane

Electrochemical waste solution lithium recovery system preventing solid electrolyte reduction using a cation exchange membrane

This technology is an electrochemical cell structure for recovering lithium from waste solutions, featuring a cation exchange membrane placed between a metalloid or transition metal-based solid electrolyte membrane and the anode. This prevents the reduction and discoloration of metal ions on the surface of the solid electrolyte.

Conventional electrochemical cells for lithium recovery have faced issues where electrons moving to the anode during operation are injected into the solid electrolyte membrane. This causes Ge4+ and Ti4+ ions to reduce to Ge2+ and Ti3+, leading to discoloration of the electrolyte membrane and degradation of performance.

This technology physically blocks electron movement by placing an electrically insulating cation exchange membrane between the anode and the solid electrolyte membrane. It also utilizes a solid electrolyte membrane manufactured at a quenching temperature of 350–400°C, which is free of (Ge, Si)O2 secondary phases, thereby improving both ionic conductivity and mechanical strength. Applicable to waste battery recycling plants and LAS circular resource processing, it allows for the direct recovery of lithium as LiOH and Li2CO3 while extending the replacement cycle of the electrolyte membrane.

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Key Features:

• A solid electrolyte membrane positioned between the anode and cathode, containing a main crystalline phase and an AlPO4 secondary phase without the (Ge, Si)O2 secondary phase
• A separator positioned between the cathode and the solid electrolyte membrane, composed of a polyethylene film laminate or non-woven fabric impregnated with an organic electrolyte
• A cation exchange membrane placed in contact between the anode and the solid electrolyte membrane to prevent the reduction of Ge4+ and Ti4+ ions
• A step of filling the reservoir with waste solution to precipitate lithium metal at the cathode, followed by adding water and discharging to obtain lithium salts

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This invention was developed with support from the Ministry of Trade, Industry and Energy for the development of core technologies and key materials for an eco-friendly electrochemical recovery system to produce high-purity lithium and lithium compounds for lithium-ion batteries from LAS circular resources.

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