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EP-4131549-B1 - CAPSULE FOR LITHIUM-SULFUR SECONDARY BATTERY, AND LITHIUM-SULFUR SECONDARY BATTERY COMPRISING SAME

EP4131549B1EP 4131549 B1EP4131549 B1EP 4131549B1EP-4131549-B1

Inventors

  • KIM, KIHYUN
  • LEE, Sangryeo
  • KIM, LUCIA
  • HAN, DONG HYEOP
  • KIM, JEE SEON

Dates

Publication Date
20260513
Application Date
20210907

Claims (13)

  1. A capsule for a lithium-sulfur secondary battery, the capsule comprising: a core containing a material capable of forming and restoring a solid electrolyte interface layer, and a hydrogel; and a shell formed of a polymer and surrounding the core, wherein the material capable of forming and restoring the solid electrolyte interface layer is at least one selected from the group consisting of LiNO 3 , Be(NO 3 ) 2 , NaNO 3 , Mg (NO 3 ) 2 , Al(NO 3 ) 3 , KNO 3 , Ca (NO 3 ) 2 , Sc (NO 3 ) 3 , Ti (NO 3 ) 4 , VO (NO 3 ) 3 , Cr (NO 3 ) 3 , Mn (NO 3 ) 2 , Fe (NO 3 ) 3 , Fe (NO 3 ) 2 , Co (NO 3 ) 2 , Co (NO 3 ) 3 , Ni (NO 3 ) 2 , Cu (NO 3 ) 2 , Zn (NO 3 ) 2 , Ga (NO 3 ) 3 , RbNO 3 , Sr (NO 3 ) 2 , Y (NO 3 ) 3 , Zr (NO 3 ) 4 , Pd(NO 3 ) 2 , AgNO 3 , Cd(NO 3 ) 2 , Sb (NO 3 ) 3 , Xe (NO 3 ) 2 , CsNO 3 , Ba (NO 3 ) 2 , Hg 2 (NO 3 ) 2 , Hg (NO 3 ) 2 , Tl(NO 3 ) 3 , TlNO 3 , Pb (NO 3 ) 2 , Bi (NO 3 ) 3 , BiO (NO 3 ), FrNO 3 , Ra (NO 3 ) 2 , La (NO 3 ) 3 , Ce (NO 3 ) 3 , Ce(NO 3 ) 4 , Nd (NO 3 ) 3 , Eu(NO 3 ) 3 , Gd (NO 3 ) 3 , and Tb(NO 3 ) 3 .
  2. The capsule according to claim 1, wherein the hydrogel is selected from the group consisting of acrylate-based polymers, polysaccharides, poly amino acids, and combinations thereof, and the acrylate-based polymer includes a monomer-derived unit having two or more acrylate groups and an ethylene glycol group.
  3. The capsule according to claim 1, wherein the polymer is formed by crosslinking an epoxy compound having two or more epoxy groups and a crosslinking agent having two or more amino groups.
  4. The capsule according to claim 3, wherein the epoxy compound having two or more epoxy groups is at least one selected from the group consisting of 1,4-butanediol diglycidyl ether (BDDE), ethylene glycol diglycidyl ether (EGDGE), 1,6-hexanediol diglycidyl ether, propylene glycol diglycidyl ether, poly(propylene glycol)diglycidyl ether, poly(tetramethylene glycol)diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, polyglycerol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, 1,2-(bis(2,3-epoxypropoxy)ethylene, pentaerythritol polyglycidyl ether, and sorbitol polyglycidyl ether.
  5. The capsule according to claim 3, wherein the crosslinking agent having two or more amino groups is at least one selected from the group consisting of ethylene diamine, diethylene triamine, dipropylene triamine, triethylene tetramine, tetraethylene pentaamine, 1,3-diamino propane, 1,4-diamino butane, 1,6-diamino hexane, 1,8-diamino octane, 1,10-diamino decane, 1,12-diamino dodecane, isophoronediamine, 1,2-cyclohexane diamine, piperazine, 2,5-diamino pyridine, 4,4'-diamino dicyclohexyl methane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 1,3-bis(aminoethyl)cyclohexane, xylylene diamine, methaphenylene diamine, and diamino diphenyl methane.
  6. The capsule according to claim 1, wherein the capsule has a particle diameter of 0.1 to 5.0 µm, wherein the particle diameter is measured by SEM.
  7. The capsule according to claim 1, wherein a content of the material capable of forming and restoring the solid electrolyte interface layer is 10% by weight to 70% by weight based on the total weight of the capsule.
  8. A lithium-sulfur secondary battery comprising: the capsule according to claim 1; a positive electrode; a negative electrode; a separator; and an electrolyte solution, wherein the lithium-sulfur secondary battery additionally includes the material capable of forming and restoring the solid electrolyte interface layer.
  9. The lithium-sulfur secondary battery according to claim 8, wherein a content of the capsule is 0.1% by weight to 6.0% by weight based on the total weight of the electrolyte solution.
  10. The lithium-sulfur secondary battery according to claim 8, wherein the total amount of the material capable of forming and restoring the solid electrolyte interface layer included in the capsule and the additionally included material capable of forming and restoring the solid electrolyte interface layer is 0.1% by weight to 10% by weight based on the total weight of the electrolyte solution.
  11. A method for preparing a capsule for a lithium-sulfur secondary battery, the method comprising: dissolving a material capable of forming and restoring a solid electrolyte interface layer, a monomer capable of forming a hydrogel, and a crosslinking agent having two or more amino groups in water to prepare an aqueous phase portion; preparing a water-in-oil emulsion solution by mixing the aqueous phase portion with an oil phase portion containing an oil phase component and a surfactant; adding an epoxy compound having two or more epoxy groups to the emulsion solution to form a shell; forming a hydrogel core by radical polymerization; and removing the oil phase component from the emulsion solution and drying the resulting product, wherein the material capable of forming and restoring the solid electrolyte interface layer is at least one selected from the group consisting of LiNO 3 , Be(NO 3 ) 2 , NaNO 3 , Mg (NO 3 ) 2 , Al(NO 3 ) 3 , KNO 3 , Ca (NO 3 ) 2 , Sc (NO 3 ) 3 , Ti (NO 3 ) 4 , VO (NO 3 ) 3 , Cr (NO 3 ) 3 , Mn (NO 3 ) 2 , Fe (NO 3 ) 3 , Fe (NO 3 ) 2 , Co (NO 3 ) 2 , Co (NO 3 ) 3 , Ni (NO 3 ) 2 , Cu (NO 3 ) 2 , Zn (NO 3 ) 2 , Ga (NO 3 ) 3 , RbNO 3 , Sr (NO 3 ) 2 , Y (NO 3 ) 3 , Zr (NO 3 ) 4 , Pd(NO 3 ) 2 , AgNO 3 , Cd(NO 3 ) 2 , Sb (NO 3 ) 3 , Xe (NO 3 ) 2 , CsNO 3 , Ba (NO 3 ) 2 , Hg 2 (NO 3 ) 2 , Hg (NO 3 ) 2 , Tl(NO 3 ) 3 , TlNO 3 , Pb (NO 3 ) 2 , Bi (NO 3 ) 3 , BiO (NO 3 ), FrNO 3 , Ra (NO 3 ) 2 , La (NO 3 ) 3 , Ce (NO 3 ) 3 , Ce(NO 3 ) 4 , Nd (NO 3 ) 3 , Eu(NO 3 ) 3 , Gd (NO 3 ) 3 , and Tb(NO 3 ) 3 .
  12. The method according to claim 11, wherein the hydrogel is selected from the group consisting of acrylate-based polymers, polysaccharides, poly amino acids, and combinations thereof, and the acrylate-based polymer includes a monomer-derived unit having two or more acrylate groups and an ethylene glycol group.
  13. The method according to claim 11, wherein the surfactant has a hydrophilic/lipophilic balance value of 1 to 6.

Description

Field of Disclosure The present disclosure relates to a capsule for a lithium-sulfur secondary battery. Background Recently, as the miniaturization, weight reduction and high performance of electronic devices and communication devices are rapidly progressing and the need for electric vehicles has been greatly increased in relation to environmental problems, there is a growing demand for performance improvements in secondary batteries used as energy sources for these products. For a secondary battery to satisfy these requirements, a lot of research on a lithium-sulfur battery using sulfur-based materials as a positive electrode active material is being conducted. The lithium-sulfur battery is a secondary battery that uses, as a positive electrode active material, sulfur-based compounds containing sulfur-sulfur bonds and uses, as a negative electrode active material, an alkali metal such as lithium or a carbon-based material in which intercalation/deintercalation of metal ions such as lithium ions occur. In particular, the theoretical discharging capacity of the lithium-sulfur battery is 1,675 mAh/g, and the theoretical energy density is 2,600 Wh/kg, which is about 5 times higher than that of the lithium-ion battery currently being studied (about 570 Wh/kg). Accordingly, the lithium-sulfur battery is a battery that can realize high capacity, high energy density and long lifetime. In addition, since sulfur, which is the main material of the positive electrode active material, has a low atomic weight, is very rich in resources and thus easy to supply and receive, and is cheap, non-toxic and environmentally friendly, the lithium-sulfur battery is attracting attention as an energy source for medium to large-sized devices such as electric vehicles as well as portable electronic devices. This lithium-sulfur secondary battery uses lithium metal as a negative electrode, and thus in order to protect the lithium metal negative electrode, an additive is added to the electrolyte solution, and accordingly, a solid electrolyte interface (SEI) layer is formed by the reaction of the additive with the lithium metal. However, in such a lithium-sulfur secondary battery, when charging and discharging are repeated, the solid electrolyte interface (SEI) layer on the negative electrode is damaged, and lithium metal is exposed, and as a result, the efficiency of the battery is sharply reduced, and the discharging capacity is lowered, leading to deterioration of the battery. In order to prevent such damage to the solid electrolyte interface (SEI) layer of the negative electrode, if the content of a material (additive) that can simply form and recover the solid electrolyte interface (SEI) layer as a component of the battery is increased, the additive may act as a resistor in the battery, and thus cause a decrease in energy density and a shortened lifetime. Therefore, in order to prevent damage to the solid electrolyte interface layer and maintain a constant level of the solid electrolyte interface (SEI) layer, there is a need for a method to maintain the content of a material, which is capable of forming and recovering the solid electrolyte interface (SEI) layer even during operation of the lithium-sulfur secondary battery, at a constant level. Related Art Korean Laid-open Patent Publication No. 10-2007-0008405 (January 17, 2007), "Lithium Secondary Battery Containing Capsule for Controlled-release of Additives"Nature Communications, Vol. 9, No. 1, 2018, pages 1-10, discloses a lithium nitrate-sustained release film, in which LiNO3, which is a material for forming a solid electrolyte interface, is dispersed on a polymer matrix; and a lithium secondary battery including same. Summary Therefore, in the present disclosure, it was found that with regard to a negative electrode of a lithium-sulfur secondary battery, when a capsule comprising a core containing a hydrogel and a material capable of forming and restoring a solid electrolyte interface (SEI) layer, and a shell formed of a polymer and surrounding the core is used as an additive for the lithium-sulfur secondary battery to maintain a constant level of a material (additive) that can react with lithium metal to form and restore the solid electrolyte interface (SEI) layer on the negative electrode even during operation of the lithium-sulfur secondary battery, it is possible to suppress the abrupt decrease in the efficiency of the battery and the decrease in the discharging capacity by preventing damage to the solid electrolyte interface (SEI) layer on the negative electrode even during operation of the lithium-sulfur secondary battery and thus preventing the lithium metal from being exposed to the electrolyte solution, and thus the present disclosure has been completed. Therefore, it is an object of the present disclosure to provide a capsule for a lithium-sulfur secondary battery, which can prevent damage to the solid electrolyte interface (SEI) layer formed on the negative electrode