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KR-20260065772-A - ELECTRODE, SECONDARY BATTERY COMPRISING THE SAME, AND METHOD FOR MANUFACTURING THE SAME

KR20260065772AKR 20260065772 AKR20260065772 AKR 20260065772AKR-20260065772-A

Abstract

An electrode is provided having an electrode current collector; and an electrode layer located on the electrode current collector and comprising an active material, a conductive material, and a fluorine-containing binder, wherein the degree of crystallization of the fluorine-containing binder is 10% or less and the electrode has a bending resistance of 10 mm Φ or less, a secondary battery including the same, and an energy storage device.

Inventors

  • 이남정
  • 정구승
  • 곽상민
  • 김지현
  • 신동오
  • 이기석
  • 유광호

Assignees

  • 주식회사 엘지에너지솔루션

Dates

Publication Date
20260511
Application Date
20260421
Priority Date
20211005

Claims (20)

  1. Electrode current collector; and The electrode layer is positioned on the electrode current collector and comprises an active material, a conductive material, and a fluorine-containing binder; and The crystallinity of the above fluorine-containing binder is 10% or less, and An electrode having a bending resistance of 10 mm (Φ) or less.
  2. In paragraph 1, An electrode characterized in that the degree of crystallization of the above-mentioned fluorine-containing binder is 0% to 10%.
  3. In paragraph 1, The electrode is characterized by having a bending resistance of 2 to 10 mm (Φ).
  4. In paragraph 1, An electrode characterized in that the flexural strength of the above electrode is evaluated according to the measurement standard JIS K5600-5-1 method.
  5. In paragraph 1, The flexibility of the above electrode, Step of manufacturing a rectangular electrode sample of 100mm x 50mm; A step of preparing measuring rods having diameters of 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 25, and 32 mm, respectively, and using the measuring rod with the largest diameter among them to contact the electrode sample with the measuring rod, and then determining whether a crack occurs in the composite film of the electrode sample when both ends of the electrode sample are lifted; and An electrode characterized by being evaluated through the step of determining the minimum diameter value of the measuring rod at which no crack occurs in the composite film of the electrode sample as the flexural resistance by repeating the step of determining whether a crack occurs in the composite film of the electrode sample in the same manner as the previous step using a measuring rod with a larger diameter if no crack occurs in the previous step.
  6. In paragraph 1, An electrode characterized in that the above-mentioned fluorine-containing binder comprises polytetrafluoroethylene (PTFE).
  7. In paragraph 1, An electrode characterized by having a content of 85 to 98 parts by weight of the active material, a content of 0.5 to 5 parts by weight of the conductive material, and a content of 0.5 to 10 parts by weight of the fluorine-containing binder.
  8. In paragraph 1, The above electrode layer has a QBR (Quantified Binder Ratio) of 1.1 or less, and The above QBR is an electrode characterized by being defined by the following mathematical formula: QBR = Bs/Bf In the above mathematical formula, Bs represents the average value of the fluorine content in the electrode layer surface region from the outermost surface of the electrode layer up to within 15% of the total thickness of the electrode layer, and Bf represents the average value of the fluorine content in the electrode layer bottom region from the electrode layer interface facing the current collector up to within 15% of the total thickness of the electrode layer.
  9. In paragraph 8, An electrode characterized in that the electrode layer has a QBR of 0.95 to 1.05.
  10. In paragraph 1, An electrode characterized in that the above electrode layer is manufactured in a dry manner.
  11. In paragraph 1, An electrode characterized in that the electrode current collector further comprises a conductive primer layer on at least one surface.
  12. A step of preparing a mixture comprising an active material, a conductive material, and a fluorine-containing binder; A step of preparing a mixture mass by kneading the above mixture at a temperature in the range of 70℃ to 200℃ and under a pressure greater than or equal to atmospheric pressure; A step of crushing the above mixture lumps to obtain a mixed powder for electrodes; A step of forming an electrode film by feeding the above electrode mixture powder between a plurality of rolls and calendering it; and A method for manufacturing an electrode of claim 1, characterized by including the step of laminating the electrode film onto a metal current collector.
  13. In Paragraph 12, A method for manufacturing an electrode characterized in that the step of kneading to produce a mass of the mixture is performed in a kneader under a pressure greater than or equal to atmospheric pressure.
  14. In Paragraph 12, A method for manufacturing an electrode characterized in that, in the lamination step, the compression ratio of the electrode film is 30 to 50%.
  15. In Paragraph 12, A method for manufacturing an electrode characterized by the rolling rate of the electrode film being 20% or less.
  16. In Paragraph 12, A method for manufacturing an electrode characterized by an apparent density increase rate of 5 to 30% before and after lamination of the electrode film with a current collector.
  17. In Paragraph 12, A method for manufacturing an electrode characterized in that the above lamination step is performed by a lamination roll at 25 to 250°C.
  18. An electrode characterized by being manufactured by the manufacturing method of any one of claims 12 to 17.
  19. A secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode is an electrode according to any one of claims 1 to 11.
  20. An energy storage device comprising a secondary battery according to paragraph 19 as a unit cell.

Description

Electrode, secondary battery comprising the same, and method for manufacturing the same The present invention relates to an electrode, a secondary battery including the same, and a method for manufacturing the same. Specifically, the invention relates to an electrode having a uniform binder distribution in the thickness direction of the electrode layer, a secondary battery including the same, and a method for manufacturing the same. Due to the rapid increase in the use of fossil fuels, there is a growing demand for alternative and clean energy. As part of this trend, the fields of power generation and energy storage utilizing electrochemistry are among the most actively researched. Currently, secondary batteries are a representative example of electrochemical devices that utilize such electrochemical energy, and their scope of application is steadily expanding. Among these secondary batteries, lithium-ion batteries serve not only as an energy source for mobile devices but are also being realized as power sources for electric and hybrid electric vehicles that can replace fossil fuel-using vehicles, such as gasoline and diesel cars—which are major causes of air pollution. Furthermore, their application is expanding to include auxiliary power sources for grid integration. The manufacturing process of such lithium secondary batteries is broadly divided into three stages: electrode manufacturing process, electrode assembly manufacturing process, and formation process. The electrode manufacturing process is further divided into electrode composite mixing process, electrode coating process, drying process, rolling process, slitting process, and winding process. Among these, the electrode mixture mixing process is a process for mixing components for forming an electrode active layer where actual electrochemical reactions occur at the electrode, and more specifically, it involves mixing an electrode active material, which is an essential element of the electrode, other additives such as a conductive material and a filler, a binder for binding between powders and adhesion to a current collector, and a solvent for imparting viscosity and dispersing powders, to produce a fluid slurry. An electrode coating process is performed to apply such a slurry onto an electrically conductive current collector, and a drying process is performed to remove the solvent contained in the electrode mixture slurry, and additionally, the electrode is rolled to manufacture an electrode of a predetermined thickness. In this electrode manufacturing process, the slurry liquid is coated and dried in a drying oven in a short time, so the binder migrates to the electrode surface, resulting in an uneven distribution of the binder in the direction of the electrode layer thickness, which causes a problem of reduced adhesion to the current collector. The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the aforementioned description; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. FIG. 1 is a schematic diagram of an electrode according to one embodiment of the present invention. Figure 2 is a schematic diagram for calculating the QBR value of the electrode layer. FIG. 3 is a schematic diagram of a manufacturing process for an electrode film according to one embodiment of the present invention. FIG. 4 is a schematic diagram of an electrode lamination process according to one embodiment of the present invention. Figure 5 is a graph showing the change in the normalized intensity of the fluorine component of the electrode layer extracted and analyzed from EDS mapping at a distance from the surface of the electrode layer to the current collector for the electrode of Example 1. Figure 6 is a graph showing the change in the normalized intensity of the fluorine component of the electrode layer extracted and analyzed from EDS mapping at a distance from the surface of the electrode layer to the current collector for the electrode of Comparative Example 1. Figure 7 is a graph showing the percentage values of discharge capacities of 0.33C, 0.5C, 1C, 2C, 2.5C, and 3C based on the discharge capacity of 0.1C of a secondary battery equipped with electrodes prepared in Example 1 and Comparative Example 1. Hereinafter, the present invention will be described in more detail to aid in understanding the invention. Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. The terms used in this specification are used merely to des