Capsule for lithium-sulfur secondary battery and lithium-sulfur secondary battery comprising same

The lithium-sulfur secondary battery comprising:

• a capsule for the lithium-sulfur secondary battery comprising:
• a core comprising a material required for formation and restoration of a solid electrolyte interface layer (SEI layer);
• and
• a shell comprising a polymer surrounding the core;
• a positive electrode;
• a negative electrode;
• a separator;
• and
• an electrolyte solution.

A method for preparing a capsule for a lithium-sulfur secondary battery, comprising the steps of:

• dissolving a material required for formation and restoration of a solid electrolyte interface layer (SEI layer) and a crosslinking agent having two or more amino groups in water to prepare an aqueous phase portion,
• mixing the aqueous phase portion into an oil phase portion comprising an oil phase component and a surfactant to prepare a water-in-oil emulsion solution,
• adding an epoxy compound having two or more epoxy groups to the water-in-oil emulsion solution to form an amine-epoxy crosslink, and
• removing the oil phase component from the water-in-oil emulsion solution and drying the emulsion solution to obtain capsules.