US-20260128468-A1 - COMPOSITE SEPARATOR AND ELECTROCHEMICAL DEVICE INCLUDING THE SAME

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 disposed on at least one surface of the substrate and including inorganic particles and a binder, wherein the binder includes carboxymethyl cellulose having a weight-average molecular weight in a range of 180,000 to 280,000 g/mol and a degree of substitution in a range of 0.6 to 1.2. The composite separator may exhibit excellent mechanical and thermal stability and 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

20251009

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 binder includes carboxymethyl cellulose having a weight-average molecular weight in a range of 180,000 to 280,000 g/mol and a degree of substitution in a range of 0.6 to 1.2.
2. 2 . The composite separator of claim 1 , wherein the weight-average molecular weight of the carboxymethyl cellulose is in a range of 200,000 to 250,000 g/mol.
3. 3 . The composite separator of claim 1 , wherein the degree of substitution of the carboxymethyl cellulose is in a range of 0.7 to 1.0.
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 binder includes at least 70 wt % of the carboxymethyl cellulose with respect to a total weight of the binder.
6. 6 . The composite separator of claim 1 , wherein the binder consists of the carboxymethyl cellulose.
7. 7 . 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.
8. 8 . The composite separator of claim 1 , wherein the inorganic particles have an average particle diameter in a range of 0.1 μm to 1.0 μm.
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 total thickness in a range of 0.5 μm to 10 μm.
11. 11 . 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.
12. 12 . 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 pressure 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.
13. 13 . A method for manufacturing a composite separator, the method comprising: applying a composition for forming a ceramic layer including a binder and inorganic particles to at least one surface of a porous substrate; and drying the composition to form a ceramic layer, wherein the binder includes carboxymethyl cellulose having a weight-average molecular weight in a range of 180,000 to 280,000 g/mol and a degree of substitution in a range of 0.6 to 1.2.
14. 14 . The method of claim 13 , wherein the weight-average molecular weight of the carboxymethyl cellulose is in a range of 200,000 to 250,000 g/mol.
15. 15 . The method of claim 13 , wherein the degree of substitution of the carboxymethyl cellulose is in a range of 0.7 to 1.0.
16. 16 . The method of claim 13 , wherein the inorganic particles have an average particle diameter in a range of 0.1 μm to 1.0 μm.
17. 17 . 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 binder includes carboxymethyl cellulose having a weight-average molecular weight in a range of 180,000 to 280,000 g/mol and a degree of substitution in a range of 0.6 to 1.2.
18. 18 . The electrochemical device of claim 17 , wherein the weight-average molecular weight of the carboxymethyl cellulose is in a range of 200,000 to 250,000 g/mol.
19. 19 . The electrochemical device of claim 17 , wherein the degree of substitution of the carboxymethyl cellulose is in a range of 0.7 to 1.0.
20. 20 . The electrochemical device of claim 17 , wherein the inorganic particles have an average particle diameter in a range of 0.1 μm to 1.0 μm.

Description

PRIORITY CLAIM AND CROSS-REFERENCE TO RELATED APPLICATIONS This patent document claims the priority and benefits of Korean Patent Application No. 10-2024-0156748, 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 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 composite separator 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 and including inorganic particles and a binder, wherein the binder includes carboxymethyl cellulose having a weight-average molecular weight in a range of 180,000 to 280,000 g/mol and a degree of substitution in a range of 0.6 to 1.2. In some embodiments, the weight-average molecular weight of the carboxymethyl cellulose may be in a range of 200,000 to 250,000 g/mol. In some embodiments, the degree of substitution of the carboxymethyl cellulose may be in a range of 0.7 to 1.0. 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 binder may include at least 70 wt % of the carboxymethyl cellulose with respect to a total weight of the binder. In some embodiments, the binder may consist of the carboxymethyl cellulose. 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 inorganic particles may have an average particle diameter in a range of 0.1 μm to 1.0 μm. In some embodiments, the porous substrate may be hydrophilically surface-treated to be hydrophilic. 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 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 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 while applying a pressure 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 another general aspect, a method for manufacturing a composite separator includes: applying a composition for forming a ceramic layer including a binder and inorganic particles to at least one surface of a porous substrate; and drying the composition to form a ceramic layer, wherein the binder includes carboxymethyl cellulose having a weight-average molecular weight in a range of 180,000 to 280,000 g/mol and a degree of substitution in a range of 0.6 to 1.2. In still another general aspect, an electrochemical device includes 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 and includes inorganic particles and a binder, wherein the binder includes carboxymethyl cellulose having a weight-average molecular weight of in a range 180,000 to 280,000 g/mol and a degree of substitution in a range of 0.6 to 1.2. Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cross section of an example of a composite separator based on an example embodiment. DETAILED DESCRIPTION The numerical range used in some embodiments includes all va