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EP-4738451-A1 - ANODE FOR LITHIUM SECONDARY BATTERY, MANUFACTURING METHOD THEREFOR AND LITHIUM SECONDARY BATTERY COMPRISING SAME

EP4738451A1EP 4738451 A1EP4738451 A1EP 4738451A1EP-4738451-A1

Abstract

The present invention relates to a negative electrode for a lithium secondary battery, including: a metal current collector; a coating layer formed on at least one surface of the metal current collector and including a first binder and a first conductive material; and a negative electrode active material layer formed on the coating layer and including a negative electrode active material, a second conductive material, and a second binder, as well as a method for producing the same and a lithium secondary battery including the same.

Inventors

  • YI, Yeonhui
  • KO, KYUNG MOON
  • JUNG, SOONHWA
  • HONG, Ja Min

Assignees

  • LG Chem, Ltd.

Dates

Publication Date
20260506
Application Date
20240807

Claims (15)

  1. A negative electrode for a lithium secondary battery, comprising: a metal current collector; a coating layer formed on at least one surface of the metal current collector and comprising a first binder and a first conductive material; and a negative electrode active material layer formed on the coating layer and comprising a negative electrode active material, a second conductive material, and a second binder, wherein the first conductive material comprises multi-walled carbon nanotubes, the coating layer comprises the first binder in an amount of 400 parts by weight to 2,000 parts by weight based on 100 parts by weight of the multi-walled carbon nanotubes, and a ratio of a thickness of the coating layer to a thickness of the negative electrode active material layer is 0.005 to 0.2.
  2. The negative electrode according to claim 1, wherein the multi-walled carbon nanotubes have a specific surface area of 100 m 2 /g to 400 m 2 /g.
  3. The negative electrode according to claim 1, wherein the multi-walled carbon nanotubes have a diameter of 1 nm to 40 nm and a length of 10 µm to 30 µm.
  4. The negative electrode according to claim 1, wherein the multi-walled carbon nanotubes have a bulk density of 20 kg/m 3 to 200 kg/m 3 .
  5. The negative electrode according to claim 1, wherein the negative electrode active material comprises at least one graphite-based active material selected from the group consisting of natural graphite, artificial graphite, fibrous artificial graphite, graphitized black, and graphitized nanofibers.
  6. The negative electrode according to claim 1, wherein the second conductive material comprises at least one selected from the group consisting of carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black.
  7. The negative electrode according to claim 1, wherein the first binder and the second binder each independently comprise at least one selected from the group consisting of a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, and styrene butadiene rubber (SBR).
  8. The negative electrode according to claim 1, wherein the coating layer comprises the multi-walled carbon nanotubes in an amount of 40 wt% to 100 wt% based on the total weight of the first conductive material.
  9. The negative electrode according to claim 1, wherein the coating layer has a thickness of 0.1 µm to 5.0 µm.
  10. The negative electrode according to claim 1, wherein the negative electrode active material layer has a thickness of 100 µm to 200 µm.
  11. The negative electrode according to claim 1, wherein the metal current collector comprises at least one metal selected from the group consisting of copper, stainless steel, aluminum, nickel, and titanium.
  12. The negative electrode according to claim 1, wherein the negative electrode active material layer is attached onto the coating layer with an adhesion of 30 gf/20 mm to 50 gf/20 mm.
  13. A method for producing a negative electrode for a lithium secondary battery, comprising steps of: applying a slurry composition for forming a coating layer, which comprises a first binder, a first conductive material, and a solvent, onto a metal current collector, followed by drying to form a coating layer; applying a negative electrode slurry composition, which comprises a negative electrode active material, a second binder, a second conductive material, and a solvent, onto the coating layer; and pressing the negative electrode slurry composition, wherein the first conductive material comprises multi-walled carbon nanotubes, and the slurry composition for forming a coating layer comprises the first binder in an amount of 400 parts by weight to 2,000 parts by weight based on 100 parts by weight of the multi-walled carbon nanotubes.
  14. The method according to claim 13, further comprising, after the step of pressing the negative electrode slurry composition, a step of drying the negative electrode slurry composition to remove the solvent.
  15. A lithium secondary battery, comprising: a positive electrode for a lithium secondary battery; the negative electrode for a lithium secondary battery according to claim 1; and a separator interposed between the positive electrode and the negative electrode.

Description

Technical Field This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0107173 filed with the Korean Intellectual Property Office on August 16, 2023, the entire contents of which are incorporated herein by reference. The present invention relates to a negative electrode for a lithium secondary battery, which has improved peeling resistance and adhesion of a negative electrode active material layer, which may improve the life characteristics of the negative electrode and the lithium secondary battery, a method for producing the same, and a lithium secondary battery including the same. Background Art Technological development and increased demand for mobile devices and electric vehicles have led to a rapid increase in the demand for lithium secondary batteries as an energy source. Among these lithium secondary batteries, lithium secondary batteries with high energy density and voltage, long cycle life, and low discharge rate have been commercialized and widely used. In general, a lithium secondary battery has a structure in which an electrode assembly including a positive electrode including an active material applied onto a metal current collector, a negative electrode including an active material applied onto a metal current collector, and a porous separator interposed between the positive electrode and the negative electrode is impregnated with an electrolyte containing a lithium salt. Here, each of the electrodes is produced by applying onto the metal current collector a slurry composition in which an active material, a binder, and a conductive material are dispersed in a solvent, followed by pressing and drying. Therefore, the life characteristics of the lithium secondary battery may be mainly determined depending on how long the electrochemical characteristics of the electrode, particularly, the active material layer, are maintained. However, in the case of a conventional lithium secondary battery, there have been many cases where the active material layer is peeled off from the metal current collector in the negative electrode as the period of use elapses, resulting in deterioration in the life characteristics of the lithium secondary battery. This appears to be because the active material layer of the negative electrode contains, as a main component, a graphite-based negative electrode active material having properties different from those of metals, and thus it is difficult to ensure sufficient adhesion, close adhesion and peeling resistance of the active material layer to the metal current collector. Due to this poor adhesion of the active material layer of the negative electrode, there is a disadvantage in that the active material layer is easily peeled off from the metal current collector as the lithium secondary battery is used for an extended period of time. In addition, a problem arises in that the peeled active material layer can no longer function as an active region of the lithium secondary battery, and thus the charge/discharge cycle characteristics of the lithium secondary battery rapidly deteriorate. Due to these problems, there is a continuous demand for the development of technology that may improve the life characteristics of the lithium secondary battery by further improving the adhesion and the like of the active material layer included in the negative electrode. DISCLOSURE Technical Problem Accordingly, the present invention is intended to provide a negative electrode for a lithium secondary battery, which has improved peeling resistance and adhesion of a negative electrode active material layer, which may improve the life characteristics of the negative electrode and the lithium secondary battery, and a method for producing the same. The present invention is also intended to provide a lithium secondary battery that exhibits improved life characteristics by including the negative electrode for a lithium secondary battery. Technical Solution The present invention provides a negative electrode for a lithium secondary battery, including: a metal current collector; a coating layer formed on at least one surface of the metal current collector and including a first binder and a first conductive material; and a negative electrode active material layer formed on the coating layer and including a negative electrode active material, a second conductive material and a second binder, wherein the first conductive material includes multi-walled carbon nanotubes, the coating layer includes the first binder in an amount of 400 parts by weight to 2,000 parts by weight based on 100 parts by weight of the multi-walled carbon nanotubes, and the ratio of the thickness of the coating layer to the thickness of the negative electrode active material layer is 0.005 to 0.2. The present invention also provides a method for producing a negative electrode for a lithium secondary battery, including steps of: applying a slurry composition for forming a coating layer, which