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EP-4742409-A1 - METHOD FOR MANUFACTURING SEPARATOR, SEPARATOR MANUFACTURED THEREFROM, AND LITHIUM SECONDARY BATTERY INCLUDING SAME

EP4742409A1EP 4742409 A1EP4742409 A1EP 4742409A1EP-4742409-A1

Abstract

The present disclosure provides a method for manufacturing a separator, the method including (S10) preparing a separator coating slurry composition including pore-inducing particles; inorganic particles; a particle-type binder and a solvent; (S20) applying the separator coating slurry composition to at least one surface of a porous polymer substrate to form a porous coating layer; (S30) removing at least some of the pore-inducing particles of the porous coating layer by an etching solution; and (S40) drying the porous coating layer from which the at least some of the pore-inducing particles have been removed.

Inventors

  • KIM, MIN-GYU
  • KA, Kyung-Ryun
  • KIM, MIN-JI
  • KIM, JI-HYEON
  • HWANG, SEON-WOO

Assignees

  • LG Energy Solution, Ltd.

Dates

Publication Date
20260513
Application Date
20250519

Claims (16)

  1. A method for manufacturing a separator, the method comprising: (S10) preparing a separator coating slurry composition including pore-inducing particles; inorganic particles; a particle-type binder and a solvent; (S20) applying the separator coating slurry composition to at least one surface of a porous polymer substrate to form a porous coating layer; (S30) removing at least some of the pore-inducing particles of the porous coating layer by an etching solution; and (S40) drying the porous coating layer from which the at least some pore-inducing particles have been removed.
  2. The method for manufacturing the separator according to claim 1, wherein the pore-inducing particles are a material that reacts with the etching solution.
  3. The method for manufacturing the separator according to claim 1, wherein the pore-inducing particles include silica (SiO 2 ), titania (TiO 2 ), zirconia (ZrO 2 ), or two or more thereof.
  4. The method for manufacturing the separator according to claim 1, wherein the etching solution includes hydrogen fluoride, sodium hydroxide, potassium hydroxide, nitric acid, hydrogen peroxide, carbonic acid, or two or more thereof.
  5. The method for manufacturing the separator according to claim 1, wherein in the (S10), an amount of the pore-inducing particles in the separator coating slurry composition is 20 to 90 parts by weight based on 100 parts by weight of the inorganic particles.
  6. The method for manufacturing the separator according to claim 1, wherein a D 50 of the pore-inducing particles is 20 nm to 500 nm.
  7. The method for manufacturing the separator according to claim 1, wherein the particle-type binder includes an acrylic particle-type binder, a fluorine-based particle-type binder, or a combination thereof.
  8. The method for manufacturing the separator according to claim 1, wherein a glass transition temperature (Tg) of the particle-type binder is 40°C to 80°C.
  9. The method for manufacturing the separator according to claim 1, wherein a D 50 of the particle-type binder is 150 nm to 1 µm.
  10. The method for manufacturing the separator according to claim 1, wherein the porous polymer substrate includes polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, or two or more thereof.
  11. The method for manufacturing the separator according to claim 1, wherein the (S20) further includes (S21) drying the solvent in the separator coating layer slurry composition after applying the slurry composition to the at least one surface of the porous polymer substrate.
  12. The method for manufacturing the separator according to claim 11, after the (S21), further comprising; (S22) applying a pressure of 0.5 MPa to 20 MPa to the separator in a temperature condition of 20°C to 85°C for 1 second to 60 seconds.
  13. The method for manufacturing the separator according to claim 1, after the (S40), further comprising: (S41) applying a pressure of 0.5 MPa to 20 MPa to the separator in a temperature condition of 20°C to 85°C for 1 second to 60 seconds.
  14. A separator manufactured by the method for manufacturing the separator defined in claim 1, the separator comprising: the porous polymer substrate; and the porous coating layer present on the at least one surface of the porous polymer substrate, the porous coating layer including the inorganic particles and the particle-type binder, wherein the porous coating layer includes pores formed by the removal of the at least some of the pore-inducing particles by the etching solution.
  15. The separator according to claim 14, wherein a porosity of the separator is 10 vol% to 50 vol%.
  16. A lithium secondary battery comprising: a positive electrode; a negative electrode; an electrolyte solution; and a separator interposed between the positive electrode and the negative electrode, wherein the separator is defined in claim 14.

Description

TECHNICAL FIELD The present disclosure relates to a method for manufacturing a separator, a separator manufactured thereby and a lithium secondary battery including the same. This application is based on and claims priority from Korean Patent Application No. 10-2024-0065882 filed on May 21, 2024 with the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. BACKGROUND ART Non-aqueous secondary batteries including lithium secondary batteries are widely used as power sources for portable electronic devices such as laptop computers, mobile phones, digital cameras or camcorders and electric vehicles. One component of lithium secondary batteries, a separator is basically required to separate and electrically insulate a positive electrode from a negative electrode and increase permeability of ions, for example, lithium ions based on high porosity in order to increase ionic conductivity. The separator does not participate in electrochemical reactions of secondary batteries, but greatly affects performance and safety of secondary batteries due to its physical properties such as electrolyte wetting, porosity or thermal shrinkage. However, the separator using a porous polymer substrate shrinks at high temperature, causing internal short circuits, and in the event of thermal runaway, the polymer separator substrate melts, increasing fire risks. Accordingly, approaches have been proposed to overcome the disadvantage of the porous polymer substrate by adding a porous coating layer to one or two surfaces of the porous polymer substrate, the porous coating layer including inorganic particles for overcoming the disadvantage of the porous polymer substrate and a binder. Meanwhile, the binder included in the porous coating layer may be classified into a particle-type binder and a soluble binder according to whether the binder dissolves in a solvent. In the case of the soluble binder, when applying a slurry for forming the porous coating layer to the surface of the porous substrate, the soluble binder may flow to the surface through the pores of the porous substrate, resulting in the clogged pores of the porous substrate. To prevent this issue, the use of particle-type binders has been proposed. However, in the processes of stacking the negative electrode, the positive electrode and the separator between the negative electrode and the positive electrode and applying heat and pressure, the particle-type binder in the porous coating layer may lose its shape or form a film. In this instance, the binder may block the pores inside the porous coating layer or the pores of the porous polymer substrate, resulting in low porosity of the separator and poor electrolyte wetting. Therefore, there is a need for a method for manufacturing a separator with strong adhesion strength, high ionic conductivity and good electrolyte wetting by using a particle-type binder as a binder, and a separator manufactured thereby. DISCLOSURE Technical Problem The present disclosure is designed to solve the above-described technical problems, and specifically, the present disclosure is directed to providing a method for manufacturing a separator having good electrolyte wetting in the presence of a particle-type binder in a porous coating layer, a separator manufactured thereby and a lithium secondary battery including the same. The present disclosure is further directed to providing a lithium secondary battery having high wettability and permeability by the introduction of pores in various sizes. Technical Solution To achieve the above-described objectives, according to an aspect of the present disclosure, there are provided a separator of the following embodiments, a method for manufacturing the separator, and a lithium secondary battery including the same. According to a first embodiment, there is provided the method for manufacturing the separator, the method including (S10) preparing a separator coating slurry composition including pore-inducing particles; inorganic particles; a particle-type binder and a solvent; (S20) applying the separator coating slurry composition to at least one surface of a porous polymer substrate to form a porous coating layer; (S30) removing at least some of the pore-inducing particles of the porous coating layer by an etching solution; and (S40) drying the porous coating layer from which the at least some pore-inducing particles have been removed. According to a second embodiment, in the first embodiment, the pore-inducing particles may be a material that reacts with the etching solution. According to a third embodiment, in any one of the first and second embodiments, the pore-inducing particles may include silica (SiO2), titania (TiO2), zirconia (ZrO2), or two or more thereof. According to a fourth embodiment, in any one of the first to third embodiments, the etching solution may include hydrogen fluoride, sodium hydroxide, potassium hydroxide, nitric acid, hydrogen