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US-20260128463-A1 - COMPOSITE SEPARATOR AND ELECTROCHEMICAL DEVICE INCLUDING THE SAME

US20260128463A1US 20260128463 A1US20260128463 A1US 20260128463A1US-20260128463-A1

Abstract

Composite separators, methods for manufacturing the composite separators, and electrochemical devices including the composite separators are disclosed. In an embodiment, a composite separator includes: a porous substrate; and a ceramic layer formed on at least one surface of the substrate. Specifically, the ceramic layer includes inorganic particles, a binder, and a particulate fusing agent and satisfies the following Equation 1, and the binder is carboxymethyl cellulose having a weight average molecular weight of 180,000 g/mol to 280,000 g/mol. The composite separator based on the disclosed technology may secure excellent heat resistance, adhesive strength, and fusion strength with an electrode: 0.9 < T × ( W ⁢ 1 + W ⁢ 2 ) W ⁢ 2 × D < 2.4 [ Equation ⁢ 1 ] wherein T, W1, W2, and D are as defined in the specification.

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
20251031
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 porous substrate, wherein the ceramic layer includes inorganic particles; a binder including carboxymethyl cellulose having a weight average molecular weight in a range of 180,000 g/mol to 280,000 g/mol; and a particulate fusing agent, wherein the ceramic layer satisfies the following Equation 1: 0.9 < T × ( W ⁢ 1 + W ⁢ 2 ) W ⁢ 2 × D < 2.4 [ Equation ⁢ 1 ] Wherein: T is a thickness (μm) of the ceramic layer; W1 is a content (wt %) of the binder relative to a total weight of the ceramic layer; W2 is a content (wt %) of the particulate fusing agent relative to the total weight of the ceramic layer; and D is an average particle diameter (μm) of the particulate fusing agent.
  2. 2 . The composite separator of claim 1 , wherein the particulate fusing agent has an average particle diameter (D50) in a range of 1 μm to 10 μm.
  3. 3 . The composite separator of claim 1 , wherein the ceramic layer has a total thickness in a range of 1 μm to 20 μm.
  4. 4 . The composite separator of claim 1 , wherein the carboxymethyl cellulose has a degree of substitution in a range of 0.6 to 1.2.
  5. 5 . The composite separator of claim 1 , wherein the inorganic particles have an average particle diameter (D50) in a range of 0.01 μm to 1 μm.
  6. 6 . The composite separator of claim 1 , 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.
  7. 7 . The composite separator of claim 1 , wherein the inorganic particles are included at 90 to 99 wt % with respect to the total weight of the ceramic layer.
  8. 8 . The composite separator of claim 1 , wherein the binder is included at 0.1 wt % to 10 wt % with respect to the total weight of the ceramic layer.
  9. 9 . The composite separator of claim 1 , wherein the particulate fusing agent is included at 0.1 wt % to 10 wt % with respect to the total weight of the ceramic layer.
  10. 10 . The composite separator of claim 1 , wherein the binder and the particulate fusing agent are included at a weight ratio in a range of 5:5 to 8:2.
  11. 11 . The composite separator of claim 1 , wherein the particulate fusing agent has a glass transition temperature (Tg) in a range of 40° C. to 80° C.
  12. 12 . The composite separator of claim 1 , wherein the porous substrate is hydrophilically surface-treated.
  13. 13 . 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.
  14. 14 . 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.
  15. 15 . An electrochemical device comprising 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 porous substrate, wherein the ceramic layer includes: inorganic particles; a binder including carboxymethyl cellulose having a weight average molecular weight in a range of 180,000 g/mol to 280,000 g/mol; and a particulate fusing agent, wherein the ceramic layer satisfies the following Equation 1: 0.9 < T × ( W ⁢ 1 + W ⁢ 2 ) W ⁢ 2 × D < 2.4 [ Equation ⁢ 1 ] Wherein: T is a thickness (μm) of the ceramic layer; W1 is a content (wt %) of the binder relative to a total weight of the ceramic layer; W2 is a content (wt %) of the particulate fusing agent relative to the total weight of the ceramic layer; and D is an average particle diameter (μm) of the particulate fusing agent.
  16. 16 . The electrochemical device of claim 15 , wherein the particulate fusing agent has an average particle diameter (D50) in a range of 1 μm to 10 μm.
  17. 17 . The electrochemical device of claim 15 , wherein the ceramic layer has a total thickness in a range of 1 μm to 20 μm.
  18. 18 . The electrochemical device of claim 15 , wherein the carboxymethyl cellulose has a degree of substitution in a range of 0.6 to 1.2.
  19. 19 . The electrochemical device of claim 15 , wherein the inorganic particles have an average particle diameter (D50) in a range of 0.01 μm to 1 μm.
  20. 20 . The electrochemical device of claim 15 , wherein the binder and the particulate fusing agent are included at a weight ratio in a range of 5:5 to 8:2.

Description

PRIORITY CLAIM AND CROSS-REFERENCE TO RELATED APPLICATIONS This patent document claims the priority and benefits of Korean Patent Application No. 10-2024-0156847 filed in the Korean Intellectual Property Office on 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 play an important role in ensuring heat resistance and safety of the electrochemical devices, 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 that includes a particulate fusing agent along with a ceramic layer, thereby exhibiting excellent heat resistance, adhesive strength, and fusion strength with an electrode even at a small thickness, which minimizing the occurrence of a blocking phenomenon. Another embodiment of the disclosed technology provides an electrochemical device that includes the composite separator. In one general aspect, a composite separator includes: a porous substrate; and a ceramic layer disposed on at least one surface of the substrate, wherein the ceramic layer includes inorganic particles, a binder including carboxymethyl cellulose having a weight average molecular weight in a range of 180,000 g/mol to 280,000 g/mol, and a particulate fusing agent, wherein the ceramic layer satisfies the following Equation 1: 0.9<T×(W⁢1+W⁢2)W⁢2×D<2.4[Equation⁢ 1] Wherein: T is a thickness (μm) of the ceramic layer;W1 is a content (wt %) of the binder relative to a total weight of the ceramic layer;W2 is a content (wt %) of the particulate fusing agent relative to the total weight of the ceramic layer; andD is an average particle diameter (μm) of the particulate fusing agent. The particulate fusing agent may have an average particle diameter (D50) in a range of 1 μm to 10 μm. The ceramic layer may have a total thickness in a range of 1 μm to 20 μm. The carboxymethyl cellulose may have a degree of substitution in a range of 0.6 to 1.2. The inorganic particles may have an average particle diameter (D50) 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 inorganic particles may be included at 90 to 99 wt % with respect to the total weight of the ceramic layer. The binder may be included at 0.1 wt % to 10 wt % with respect to the total weight of the ceramic layer. The particulate fusing agent may be included at 0.1 wt % to 10 wt % with respect to the total weight of the ceramic layer. The binder and the particulate fusing agent may be included at a weight ratio of 5:5 to 8:2. The particulate fusing agent may have a glass transition temperature (Tg) in a range of 40° C. to 80° C. The porous substrate may be hydrophilically surface-treated. The composite separator implemented based on an example embodiment 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. The heat shrinkage rate of the composite separator was measured based on the ASTM D1204 standard, but the following method was used. Lattice points were marked at 2 cm intervals on a square with one side of 10 cm on the composite separator specimen, and one side of the square was the transverse direction (TD) and the other one was the machine direction (MD). The specimen was placed right in the center, 5 sheets of paper were placed on and under the specimen, respectively, the four sides of the paper were taped, and the taped specimen was allowed to stand in a hot air drying oven at 150° C. for 60 minutes. Thereafter, the specimen was taken out, and the separator was observed with a camera to calculate the shrinkage rate in the machine direction (MD) and the shrinkage rate in the transverse direction (MD) at an ambient temperature. When the composite separator implemented based on an example embodiment is subjected to a cardboard test, a ratio of an area occupied by foreign matter smeared on a surface of a cardboard to at total area of the cardboard may be 5% or less. Here, the cardboard test may comprise: 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 o