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US-20260128467-A1 - SEPARATOR FOR RECHARGEABLE LITHIUM BATTERY AND RECHARGEABLE LITHIUM BATTERY INCLUDING THE SAME

US20260128467A1US 20260128467 A1US20260128467 A1US 20260128467A1US-20260128467-A1

Abstract

A separator for a rechargeable lithium battery includes a porous substrate, and a coating layer located on at least one surface of the porous substrate. The coating layer includes a binder, the binder includes a copolymer including a first structural unit including a unit derived from an aromatic-based unsaturated monomer; a second structural unit derived from a (meth)acrylic monomer containing an alkyl group with 4 or more carbon atoms in the main chain of the ester moiety; and a third structural unit derived from a sulfonic acid group-containing monomer. Based on 100 mol % of the copolymer, the first structural unit is included in an amount of about 5 mol % to about 80 mol %, the second structural unit is included in an amount of about 10 mol % to about 40 mol %, and the third structural unit is included in an amount of about 5 mol % to about 80 mol %.

Inventors

  • Dong Wan Seo
  • Ga In KIM
  • Ja Yeon GU

Assignees

  • SAMSUNG SDI CO., LTD.

Dates

Publication Date
20260507
Application Date
20251106
Priority Date
20241107

Claims (15)

  1. 1 . A separator for a rechargeable lithium battery, the separator comprising: a porous substrate; and a coating layer located on at least one surface of the porous substrate, wherein the coating layer includes a binder, the binder includes a copolymer including a first structural unit comprising a unit derived from an aromatic-based unsaturated monomer; a second structural unit derived from a (meth)acrylic monomer containing an alkyl group with 4 or more carbon atoms in the main chain of the ester moiety; and a third structural unit derived from a sulfonic acid group-containing monomer, and based on 100 mol % of the copolymer, the first structural unit is included in an amount in a range of about 5 mol % to about 80 mol %, the second structural unit is included in an amount in a range of about 10 mol % to about 40 mol %, and the third structural unit is included in an amount in a range of about 5 mol % to about 80 mol %.
  2. 2 . The separator of claim 1 , wherein the copolymer comprises a particulate binder.
  3. 3 . The separator of claim 1 , wherein the copolymer has an average particle size D50 in a range of about 500 nm to about 700 nm.
  4. 4 . The separator of claim 1 , wherein the copolymer is an adhesive binder.
  5. 5 . The separator of claim 1 , wherein the copolymer has a glass transition temperature in a range of about 60° C. to about 80° C.
  6. 6 . The separator of claim 1 , wherein the copolymer is included in an amount in a range of about 1 wt % to about 100 wt % of the coating layer.
  7. 7 . The separator of claim 1 , wherein the sum of the content of the first structural unit, the second structural unit, and the third structural unit is about 95 mol % or more based on the copolymer.
  8. 8 . The separator of claim 1 , wherein the unit derived from the aromatic-based unsaturated monomer is represented by the following Chemical Formula 1: in Chemical Formula 1, R 1 and R 2 each independently comprises hydrogen or a substituted or unsubstituted C 1 to C 5 alkyl group, and Ar comprises a substituted or unsubstituted, monocyclic or polycyclic C 6 to C 20 aryl group, the second structural unit is represented by the following Chemical Formula 4: Chemical Formula 4: in Chemical Formula 4, R 7 and R 8 each independently comprises hydrogen or a methyl group, and L 2 comprises a substituted or unsubstituted, straight or branched C 4 to C 30 alkyl group, and the third structural unit is represented by any one of the following Chemical Formulas 5 to 7: in Chemical Formulas 5 to 7, R 9 , R 10 , R 11 , R 12 , R 13 , and R 14 each independently comprises hydrogen or a C 1 to C 3 alkyl group, L 3 , L 5 , and L 7 each independently comprises —C(═O)—, —C(═O)O—, —OC(═O)—, —O—, or —C(═O)NH—, L 4 , L 6 , and L 8 each independently comprises a substituted or unsubstituted C 1 to C 10 alkylene group, a substituted or unsubstituted C 3 to C 20 cycloalkylene group, a substituted or unsubstituted C 6 to C 20 arylene group, or a substituted or unsubstituted C 3 to C 20 heterocyclic group, a, b, c, d, e and f are each independently an integer in a range from 0 to 2, and in Chemical Formula 6, M comprises an alkali metal.
  9. 9 . The separator of claim 1 , wherein the first structural unit further includes a unit derived from a (meth)acrylic monomer containing an alkyl group having 1 to 3 carbon atoms in the main chain of the ester moiety.
  10. 10 . The separator of claim 9 , wherein the unit derived from the (meth)acrylic monomer is represented by the following Chemical Formula 3: in Chemical Formula 3, R 5 and R 6 each independently comprises hydrogen or a methyl group, and L 1 comprises a substituted or unsubstituted, straight or branched C 1 to C 3 alkyl group.
  11. 11 . The separator of claim 9 , wherein the unit derived from the aromatic-based unsaturated monomer and the unit derived from the (meth)acrylic monomer are included in a molar ratio in a range of about 1:0.5 to about 1:2.
  12. 12 . The separator of claim 9 , wherein based on 100 mol % of the copolymer, the structural unit derived from the aromatic-based unsaturated monomer is included in an amount in a range of about 5 mol % to about 35 mol %, the structural unit derived from the (meth)acrylic monomer containing an alkyl group having 1 to 3 carbon atoms in the main chain of the ester moiety is included in an amount in a range of about 5 mol % to about 35 mol %, the second structural unit is included in an amount in a range of about 20 mol % to about 30 mol %, and the third structural unit is included in an amount in a range of about 10 mol % to about 60 mol %.
  13. 13 . The separator of claim 9 , wherein the copolymer comprises: the structural unit derived from the aromatic-based unsaturated monomer derived from one or more of styrene, alpha-methyl styrene, 4-butyl styrene, 4-butoxy styrene, halo styrene, vinyl toluene, and vinyl naphthalene; the structural unit derived from the (meth)acrylic monomer containing an alkyl group having 1 to 3 carbon atoms in the main chain of the ester moiety, which is derived from one or more of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and iso-propyl (meth)acrylate; the second structural unit derived from one or more of 2-ethylhexyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, and isodecyl (meth)acrylate; and the third structural unit derived from at least one of vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, anethole sulfonic acid, (meth)acrylamidoalkane sulfonic acid, sulfoalkyl (meth)acrylate, and a salt thereof.
  14. 14 . The separator of claim 1 , wherein the coating layer has a thickness in a range of about 0.1 μm to about 1.5 μm.
  15. 15 . A rechargeable lithium battery comprising: a positive electrode; a negative electrode; and the separator for a rechargeable lithium battery according to claim 1 interposed between the positive electrode and the negative electrode.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application claims priority to Korean Patent Application No. 10-2024-0157089, filed on Nov. 7, 2024 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. BACKGROUND 1. Field of the Disclosure The present disclosure relates to a separator for a rechargeable lithium battery, and to a rechargeable lithium battery including the separator. 2. Discussion of Related Art With increasing use of electronic devices using batteries such as, e.g., mobile phones, notebook computers, electric vehicles, and the like, the demand for secondary batteries having high energy density and high capacity is increasing. Therefore, improving the performance of rechargeable lithium batteries may be advantageous. A rechargeable lithium battery typically includes a positive electrode and a negative electrode that contain an active material capable of the intercalation and deintercalation of lithium ions, and produces electrical energy by oxidation and reduction reactions when the lithium ions are intercalated into and deintercalated from the positive electrode and the negative electrode. SUMMARY The present disclosure describes a separator for a rechargeable lithium battery that improves the capacity of a rechargeable lithium battery due to the low membrane resistance thereof. The present also describes a separator for a rechargeable lithium battery that improves the safety and lifespan of a rechargeable lithium battery due to the high adhesion thereof. The present also describes a separator for a rechargeable lithium battery that improves resistance due to the high electrolyte wettability and improved flexibility thereof. The present also describes a separator for a rechargeable lithium battery that has high capacity retention rates and low direct current internal resistance (DC-IR) change rates at both room temperature and high temperature. The present also describes a rechargeable lithium battery including the above-described separator for a rechargeable lithium battery. According to an aspect of the present disclosure, a separator for a rechargeable lithium battery is described. The separator for a rechargeable lithium battery includes a porous substrate and a coating layer located on at least one surface of the porous substrate. The coating layer includes a binder, the binder includes a copolymer including a first structural unit including a unit derived from an aromatic-based unsaturated monomer; a second structural unit derived from a (meth)acrylic monomer containing an alkyl group with 4 or more carbon atoms in the main chain of the ester moiety; and a third structural unit derived from a sulfonic acid group-containing monomer. Based on 100 mol % of the copolymer, the first structural unit is included in an amount in a range of about 5 mol % to about 80 mol %, the second structural unit is included in an amount in a range of about 10 mol % to about 40 mol %, and the third structural unit is included in an amount in a range of about 5 mol % to 80 about mol %. According to another aspect of the present disclosure, a rechargeable lithium battery is described. The rechargeable lithium battery includes a positive electrode, a negative electrode, and the separator for a rechargeable lithium battery interposed between the positive electrode and the negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present disclosure are more apparent to those of ordinary skill in the art by describing example embodiments thereof in detail with reference to the accompanying drawings, in which: FIG. 1 to FIG. 4 are cross-sectional views schematically illustrating rechargeable lithium batteries according to example embodiments of the present disclosure. FIG. 5 is a cross-sectional view illustrating a separator for a rechargeable lithium battery according to one example embodiment. DETAILED DESCRIPTION Hereinafter, example embodiments of the present disclosure are described in detail. However, the embodiments are presented as examples, and the present disclosure is not limited thereto, and the present disclosure is only defined by the scope of the appended claims. Unless otherwise stated herein, when a part such as a layer, a membrane, an area, a plate, and the like, is described as being disposed “on” another part, it includes not only a case where the part is “directly on” another part, but also a case where there are other parts therebetween. Unless otherwise stated herein, the singular may also include the plural. In addition, unless otherwise stated, the term “A or B” may mean “including A, including B, or including A and B.” In the present specification, “a combination thereof” may mean a mixture, stack, composite, copolymer, alloy, blend, or reaction product of constituents. Unless otherwise defined herein, “particle size D100” refers to a size of a particle with a cumulative vol