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US-20260128471-A1 - COMPOSITE SEPARATOR AND ELECTROCHEMICAL DEVICE INCLUDING THE SAME

US20260128471A1US 20260128471 A1US20260128471 A1US 20260128471A1US-20260128471-A1

Abstract

Composite separators and electrochemical devices including the composite separators are disclosed. In an embodiment, a composite separator includes: a porous substrate; and a coating layer disposed on at least one surface of the substrate and including organic particles, wherein the coating layer satisfies the following Equation 1, and the composite separator exhibits excellent heat resistance, adhesive strength, and fusion strength with an electrode even at a small thickness, while suppressing a blocking phenomenon: 4 , 000 ≤ ( A × D 2 ) / T ≤ 5 , 500 [ Equation ⁢ 1 ] wherein A, D, and T are as defined in the specification.

Inventors

  • Dong Jae Kim
  • Cheol Min Yun
  • Soon Bo LEE

Assignees

  • SK INNOVATION CO., LTD.
  • SK IE TECHNOLOGY CO., LTD.

Dates

Publication Date
20260507
Application Date
20251105
Priority Date
20241107

Claims (20)

  1. 1 . A composite separator comprising: a porous substrate; and a coating layer disposed on at least one surface of the substrate and including organic particles, wherein the coating layer satisfies the following Equation 1: 4 , 000 ≤ ( A × D 2 ) / T ≤ 5 , 500 [ Equation ⁢ 1 ] Wherein: A is a number of the organic particles per unit area (/mm 2 ) on a surface of the coating layer; D is an average particle diameter (μm) of the organic particles observed on the surface of the coating layer; and T is a total thickness (μm) of the coating layer.
  2. 2 . The composite separator of claim 1 , wherein the average particle diameter (D) of the organic particles on the surface of the coating layer is in a range of 1 μm to 10 μm.
  3. 3 . The composite separator of claim 1 , wherein the total thickness of the coating layer is in a range of 1 μm to 20 μm.
  4. 4 . The composite separator of claim 1 , wherein the organic particles have a glass transition temperature (T g ) in a range of 40° C. to 80° C.
  5. 5 . The composite separator of claim 1 , wherein the organic particles include at least one of acryl-based polymers, urethane-based polymers, or fluorine-based polymers.
  6. 6 . The composite separator of claim 5 , wherein the acryl-based polymer includes a copolymer including an alkyl (meth)acrylate-based monomer polymerization unit; and at least one of a styrene-based monomer polymerization unit, a butadiene-based monomer polymerization unit, or a vinyl-based monomer polymerization unit.
  7. 7 . The composite separator of claim 1 , wherein the coating layer further includes inorganic particles and a binder.
  8. 8 . The composite separator of claim 7 , wherein the inorganic particles are included at 96 to 99 wt % with respect to a total weight of the coating layer.
  9. 9 . The composite separator of claim 7 , wherein the binder and the organic particles are included at a weight ratio of 5:5 to 7:3.
  10. 10 . The composite separator of claim 7 , wherein the organic particles are included in an amount greater than 1 wt % and less than or equal to 2 wt % with respect to a total weight of the coating layer.
  11. 11 . The composite separator of claim 7 , wherein the inorganic particles have an equivalent spherical diameter (Dv50) in a range of 0.01 μm to 1 μm.
  12. 12 . The composite separator of claim 7 , wherein the inorganic particles include at least one of boehmite, pseudo-boehmite, BaSO 4 , CeO 2 , MgO, Cao, Zno, Al 2 O 3 , SiO 2 , TiO 2 , BaTiO 3 , HfO 2 , SrTiO 3 , SnO 2 , NiO, ZrO 2 , Y 2 O 3 , or Sic.
  13. 13 . The composite separator of claim 7 , wherein the binder includes at least one of (meth)acryl-based polymers, fluorine-based polymers, styrene-based polymers, vinyl alcohol-based polymers, vinyl ester-based polymers, vinylpyrrolidone-based polymers, cellulose-based polymers, polyimide-based polymers, polyamide-based polymers, or polyalkylene glycol.
  14. 14 . The composite separator of claim 7 , wherein the binder includes polyacrylamide, carboxymethyl cellulose, or a combination of polyacrylamide and carboxymethyl cellulose.
  15. 15 . The composite separator of claim 7 , wherein the binder includes carboxymethyl cellulose having a weight average molecular weight of at least 180,000 g/mol and a degree of substitution in a range of 0.6 to 1.2.
  16. 16 . The composite separator of claim 1 , wherein the porous substrate is hydrophilically surface-treated.
  17. 17 . The composite separator of claim 7 , wherein the composite separator is configured such that: when two sheets of the composite separators are placed with the coating layer facing each other, pressed at a temperature of 25° C. and a pressure of 15 kgf/cm 2 for an hour, and peeled apart at an angle of 180° in accordance with ASTM D903, the average number of desorbed organic particles, inorganic particles, or both per unit area, measured via scanning electron microscopy (SEM) at 10 random positions, is less than 10 −4 /μm 2 , or no desorption is observed.
  18. 18 . 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 coating 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.
  19. 19 . An electrochemical device comprising a positive electrode, a negative electrode, and a composite separator, wherein the composite separator includes a porous substrate and a coating layer disposed on at least one surface of the substrate and includes organic particles, and the coating layer satisfies the following Equation 1: 4 , 000 ≤ ( A × D 2 ) / T ≤ 5 , 500 [ Equation ⁢ 1 ] Wherein: A is a number of the organic particles per unit area (/mm 2 ) on a surface of the coating layer; D is an average particle diameter (μm) of the organic particles observed on the surface of the coating layer; and T is a total thickness (μm) of the coating layer.
  20. 20 . The electrochemical device of claim 19 , wherein the coating layer further includes inorganic particles and a binder.

Description

PRIORITY CLAIM AND CROSS-REFERENCE TO RELATED APPLICATIONS This patent document claims the priority and benefits application No. 10-2024-0156960, filed on of Korean Patent Nov. 7, 2024, the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD The disclosed technology relates to a 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 performance requirements for separators, which are key components in ensuring the heat resistance and safety of an electrochemical device, have become more advanced. For example, composite separators comprising an inorganic coating layer that includes inorganic particles such as alumina (Al2O3), silica (SiO2), and zirconia (ZrO2) along with a binder applied to a porous substrate, have emerged as an important technology. SUMMARY An embodiment of the disclosed technology provides a composite separator comprising a coating layer that includes organic particles configured to provide fusion strength with an electrode. The composite separator may exhibit excellent heat resistance, adhesive strength, and fusion strength with an electrode even at a small thickness, and may prevent a blocking phenomenon. Another embodiment of the disclosed technology provides an electrochemical device employing the composite separator. In one general aspect, a composite separator includes: a porous substrate; and a coating layer disposed on at least one surface of the substrate and including organic particles, wherein the coating layer satisfies the following Equation 1: 4,000≤(A × D2)/T≤5,500[Equation⁢ 1] Here, A is the number of the organic particles per unit area (/mm2) on a surface of the coating layer; D is an average particle diameter (μm) of the organic particles observed on the surface of the coating layer; and T is a total thickness (μm) of the coating layer. The average particle diameter (D) of the organic particles on the surface of the coating layer may be in a range of 1 μm to 10 μm. The total thickness of the coating layer may be in a range of 1 μm to 20 μm. The organic particles may have a glass transition temperature (Tg) in a range of 40° C. to 80° C. The organic particles may include at least one of acryl-based polymers, urethane-based polymers, or fluorine-based polymers. The acryl-based polymer may include a copolymer including an alkyl (meth)acrylate-based monomer polymerization unit; and one or two or more polymerization units selected from a styrene-based monomer polymerization unit, a butadiene-based monomer polymerization unit, and a vinyl-based monomer polymerization unit. The coating layer may further include inorganic particles and a binder. The inorganic particles may be included at 96 to 99 wt % with respect to the total weight of the coating layer. The binder and the organic particles may be included at a weight ratio of 5:5 to 7:3. The organic particles may be included an amount greater than 1 wt % and less than or equal to 2 wt % with respect to the total weight of the coating layer. The inorganic particles may have an equivalent spherical diameter (Dv50) in a range of 0.01 μm to 1 μm. The inorganic particles may include at least one of boehmite, pseudo-boehmite, BaSO4, CeO2, MgO, Cao, Zno, Al2O3, SiO2, TiO2, BaTiO3, HfO2, SrTiO3, SnO2, NiO, ZrO2, Y2O3, or Sic. The binder may include at least one of (meth)acryl-based polymers, fluorine-based polymers, styrene-based polymers, vinyl alcohol-based polymers, vinyl ester-based polymers, vinylpyrrolidone-based polymers, cellulose-based polymers, polyimide-based polymers, polyamide-based polymers, or polyalkylene glycol. The binder may include polyacrylamide, carboxymethyl cellulose, or a combination of polyacrylamide and carboxymethyl cellulose. The binder may include carboxymethyl cellulose having a weight average molecular weight of at least 180,000 g/mol and a degree of substitution in a range of 0.6 to 1.2. The porous substrate may be hydrophilically surface-treated. The composite separator based on an embodiment may be configured such that: When two sheets of the composite separators are with the coating layer facing each other, pressed at a temperature of 25° C. and a pressure of 15 kgf/cm2 for an hour, and peeled apart at an angle of 180° in accordance with ASTM D903, the average number of desorbed organic particles, inorganic particles, or both per unit area, measured via scanning electron microscopy (SEM) at 10 random positions, is less than 10−4/μm2, or no desorption is observed. When the composite separator according to an embodiment 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 o