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US-20260128472-A1 - COMPOSITE SEPARATOR AND ELECTROCHEMICAL DEVICE INCLUDING THE SAME

US20260128472A1US 20260128472 A1US20260128472 A1US 20260128472A1US-20260128472-A1

Abstract

Composite separators and electrochemical devices including the composite separators are disclosed. In an embodiment, a composite separator include: a porous substrate; and a ceramic layer disposed on at least one surface of the substrate, the ceramic layer including inorganic particles and a binder, wherein the inorganic particles have an average particle diameter (D50) in a range of 0.20 μm to 0.40 μm and a ratio (A/B) of at least of 1.05, the ratio (A/B) being calculated between an area (A) on a small particle diameter side and an area (B) on a large particle diameter side based on a maximum peak in a particle size distribution diagram of the inorganic particles. The composite separator may exhibit excellent mechanical and thermal stability and excellent ion conduction properties.

Inventors

  • Cheol Min Yun
  • Dong Jae Kim
  • Eun Ji Oh
  • Hee Joon Jung

Assignees

  • SK IE TECHNOLOGY CO., LTD.

Dates

Publication Date
20260507
Application Date
20251106
Priority Date
20241107

Claims (20)

  1. 1 . A composite separator comprising: a porous substrate; and a ceramic layer disposed on at least one surface of the substrate, the ceramic layer including inorganic particles and a binder, wherein the inorganic particles have an average particle diameter (D50) in a range of 0.20 μm to 0.40 μm, and a ratio (A/B) of at least of 1.05, the ratio (A/B) being calculated between an area (A) on a small particle diameter side and an area (B) on a large particle diameter side based on a maximum peak in a particle size distribution diagram of the inorganic particles.
  2. 2 . The composite separator of claim 1 , wherein the inorganic particles have a (D95−D50)/D50 value in a range of 1.8 to 2.5 in the particle size distribution diagram.
  3. 3 . The composite separator of claim 1 , wherein the ratio (A/B) is in a range of 1.05 to 1.3 based on the maximum peak in the particle size distribution diagram of the inorganic particles.
  4. 4 . The composite separator of claim 1 , wherein the binder is included in an amount of 0.1 to 10 parts by weight relative to 100 parts by weight of the inorganic particles.
  5. 5 . The composite separator of claim 1 , wherein the inorganic particles include at least one of boehmite, BaSO 4 , CeO 2 , MgO, CaO, ZnO, Al 2 O 3 , TiO 2 , BaTiO 3 , HfO 2 , SrTiO 3 , SnO 2 , NiO, ZrO 2 , Y 2 O 3 , or SiC.
  6. 6 . The composite separator of claim 1 , wherein the binder includes at least one of (meth)acryl-based polymers, fluorine-based polymers, styrene-based polymers, vinylalcohol-based polymers, vinylester-based polymers, vinylpyrrolidone-based polymers, cellulose-based polymers, polyimide-based polymers, polyamide-based polymers, polyalkylene glycol, or copolymers thereof.
  7. 7 . The composite separator of claim 1 , wherein the binder includes polyacrylamide, carboxylmethyl cellulose, or a combination thereof.
  8. 8 . The composite separator of claim 1 , wherein the binder includes carboxymethyl cellulose having a weight-average molecular weight of at least 180,000 and a degree of substitution in a range of 0.6 to 1.2.
  9. 9 . The composite separator of claim 1 , wherein the porous substrate is hydrophilically surface-treated to be hydrophilic.
  10. 10 . The composite separator of claim 1 , wherein the ceramic layer has a coating density in a range of 1.2 to 1.8 g/cm 3 .
  11. 11 . The composite separator of claim 1 , wherein the ceramic layer has a total thickness in a range of 0.5 μm to 10 μm.
  12. 12 . The composite separator of claim 1 , wherein the composite separator has a thickness in a range of 1 to 100 μm.
  13. 13 . The composite separator of claim 1 , wherein, when the composite separator is subjected to a cardboard test, a ratio of an area occupied by foreign matter smeared on a surface of a cardboard to a total area of the cardboard is 5% or less, wherein the cardboard test comprises: placing a black cardboard and a rubber pad having a size of 2 cm×10 cm sequentially on a ceramic layer of a composite separator specimen having a size of 5 cm×10 cm; pulling the cardboard horizontally at a speed of 0.1 m/s while applying a force of 10 N to the rubber pad using a pressing device; and evaluating a degree of foreign matter smeared on the surface of the cardboard.
  14. 14 . The composite separator of claim 1 , wherein the composite separator exhibits heat shrinkage rates in machine direction (MD) and transverse direction (TD) of 4% or less, wherein the heat shrinkage rates in MD and TD are measured after the composite separator is allowed to stand at 150° C. for 60 minutes.
  15. 15 . An electrochemical device comprising a positive electrode, a negative electrode, and a composite separator between the positive and negative electrodes, wherein the composite separator includes: a porous substrate; and a ceramic layer disposed on at least one surface of the substrate, the ceramic layer including inorganic particles and a binder, wherein the inorganic particles have an average particle diameter (D50) in a range of 0.2 μm to 0.4 μm, and a ratio (A/B) of at least of 1.05, the ratio (A/B) being calculated between an area (A) on a small particle diameter side and an area (B) on a large particle diameter side based on a maximum peak in a particle size distribution diagram of the inorganic particles.
  16. 16 . The composite separator of claim 15 , wherein the inorganic particles have a (D95−D50)/D50 value in a range of 1.8 to 2.5 in the particle size distribution diagram.
  17. 17 . The composite separator of claim 15 , wherein the ratio (A/B) is in a range of 1.05 to 1.3 based on the maximum peak in the particle size distribution diagram of the inorganic particles.
  18. 18 . The composite separator of claim 15 , wherein the ceramic layer has a coating density in a range of 1.2 to 1.8 g/cm 3 .
  19. 19 . The composite separator of claim 15 , wherein the composite separator exhibits heat shrinkage rates in machine direction (MD) and transverse direction (TD) of 4% or less, wherein the heat shrinkage rates in MD and TD are measured after the composite separator is allowed to stand at 150° C. for 60 minutes.
  20. 20 . The composite separator of claim 15 , wherein the binder includes carboxymethyl cellulose having a weight-average molecular weight of at least 180,000 and a degree of substitution in a range of 0.6 to 1.2.

Description

PRIORITY CLAIM AND CROSS-REFERENCE TO RELATED APPLICATIONS This patent document claims the priority and benefits of Korean Patent Application No. 10-2024-0156768, filed on Nov. 7, 2024, the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD The disclosed technology relates to a composite separator and an electrochemical device including the same. BACKGROUND In recent years, as electrochemical devices have gained greater capacity and output, there has been a growing demand for improved heat resistance and safety. In particular, the required performance of the separator, which is a very important component of electrochemical devices, has been advancing to meet these needs. SUMMARY An embodiment of the disclosed technology provides a ceramic layer including: a porous substrate; and a ceramic layer disposed on at least one surface of the porous substrate and including pores formed between inorganic particles that are connected and fixed by a binder. The composite separator exhibits both excellent heat resistance and adhesive strength. Another embodiment of the disclosed technology provides an electrochemical device that includes the composite separator to provide excellent battery performance and safety. In one general aspect, a composite separator includes: a porous substrate; and a ceramic layer disposed on at least one surface of the substrate, the ceramic layer including inorganic particles and a binder, wherein the inorganic particles have an average particle diameter (D50) in a range of 0.20 μm to 0.40 μm, and a ratio (A/B) of at least of 1.05, the ratio (A/B) being calculated between an area (A) on a small particle diameter side and an area (B) on a large particle diameter side based on a maximum peak in a particle size distribution diagram of the inorganic particles. In some embodiments, the inorganic particles may have a (D95−D50)/D50 value in a range of 1.8 to 2.5 in the particle size distribution diagram. In some embodiments, the ratio (A/B) between the area (A) on the small particle diameter side and the area (B) on the large particle diameter may be in a range of 1.05 to 1.3 based on the maximum peak in the particle size distribution diagram of the inorganic particles. In some embodiments, the binder may be included in an amount of 0.1 to 10 parts by weight relative to 100 parts by weight of the inorganic particles. In some embodiments, the inorganic particles may include at least one of boehmite, BaSO4, CeO2, MgO, CaO, ZnO, Al2O3, TiO2, BaTiO3, HfO2, SrTiO3, SnO2, NiO, ZrO2, Y2O3, or SiC. In some embodiments, the binder may include at least one of (meth)acryl-based polymers, fluorine-based polymers, styrene-based polymers, vinylalcohol-based polymers, vinylester-based polymers, vinylpyrrolidone-based polymers, cellulose-based polymers, polyimide-based polymers, polyamide-based polymers, polyalkylene glycol, or copolymers thereof. In some embodiments, the binder may include polyacrylamide, carboxylmethyl cellulose, or a combination thereof. In some embodiments, the binder may include carboxymethyl cellulose having a weight-average molecular weight of at least 180,000 and a degree of substitution in a range of 0.6 to 1.2. In some embodiments, the porous substrate may be hydrophilically surface-treated to be hydrophilic. In some embodiments, the ceramic layer may have a coating density in a range of 1.2 to 1.8 g/cm3. In some embodiments, the ceramic layer may have a total thickness in a range of 0.5 μm to 10 μm. In some embodiments, the composite separator may have a thickness in a range of 1 to 100 μm. In some embodiments, when the composite separator is subjected to a cardboard test, a ratio of an area occupied by foreign matter smeared on a surface of a cardboard to a total area of the cardboard may be 5% or less: Here, the cardboard test comprises: placing a black cardboard and a rubber pad having a size of 2 cm×10 cm sequentially on a ceramic layer of a composite separator specimen having a size of 5 cm×10 cm; pulling the cardboard horizontally at a speed of 0.1 m/s for a distance of 60 mm while applying a force of 10 N to the rubber pad using a pressing device; and evaluating a degree of foreign matter smeared on the surface of the cardboard. In some embodiments, the composite separator may exhibit heat shrinkage rates in machine direction (MD) and transverse direction (TD) of 4% or less, wherein the heat shrinkage rates in MD and TD are measured after the composite separator is allowed to stand at 150° C. for 60 minutes. In another general aspect, an electrochemical device includes: a positive electrode, a negative electrode, and a composite separator, wherein the composite separator includes: a porous substrate, and a ceramic layer disposed on at least one surface of the substrate, the ceramic layer including inorganic particles and a binder, wherein the inorganic particles have an average particle diameter (D50) in a range of 0.2 μm to 0.4 μm, and a rati