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KR-20260066037-A - Current collecting plate for secondary battery and cylindrical battery cell comprising the same

KR20260066037AKR 20260066037 AKR20260066037 AKR 20260066037AKR-20260066037-A

Abstract

The present invention discloses a current collector for a secondary battery. The current collector for a secondary battery is characterized by having an elongation of 1.5-3.0% and a tensile strength of 25-35 kgf/ mm² . According to the present invention, by optimally setting the elongation and tensile strength of the current collector, the camber length is reduced to less than 20 mm during the manufacture of an electrode plate, and no skewness or wire breakage occurs during the jelly roll winding process.

Inventors

  • 이윤주
  • 류덕현
  • 이관희
  • 김수진
  • 박근호
  • 손승연
  • 장진수

Assignees

  • 주식회사 엘지에너지솔루션

Dates

Publication Date
20260512
Application Date
20260504
Priority Date
20211108

Claims (20)

  1. A current collector for a secondary battery characterized by an elongation of 1.5-3.0% and a tensile strength of 25-35 kgf/ mm² .
  2. A current collector for a secondary battery, characterized in that, in claim 1, the current collector is an aluminum current collector.
  3. A current collector for a secondary battery having an elongation of 1.5-3.0% and a tensile strength of 25-35 kgf/ mm² ; and An electrode plate for a secondary battery characterized by including an active material layer formed on the above-mentioned current collector.
  4. An electrode plate for a secondary battery, characterized in that, in paragraph 3, the current collector is an aluminum current collector.
  5. An electrode plate for a secondary battery according to claim 3, wherein the current collector is in the shape of a sheet having a short side and a long side, and the long side end of the current collector includes a blank portion where the active material layer is not formed.
  6. An electrode plate for a secondary battery according to claim 5, characterized in that the width in the direction along the short side of the current collector on the electrode plate is 60-110 mm, the length in the direction along the long side of the current collector is 3-5 m, and the camber length is less than 20 mm.
  7. An electrode plate for a secondary battery according to claim 6, characterized in that the length of the unseen portion measured along the short side of the current collector is 2-20 mm.
  8. An electrode plate for a secondary battery according to claim 5, characterized in that at least a portion of the above-mentioned unused portion is divided into a plurality of segments.
  9. An electrode plate for a secondary battery according to claim 8, characterized in that the above-mentioned non-removable portion is notched along the direction following the short side of the above-mentioned current collector.
  10. An electrode plate for a secondary battery according to claim 9, characterized in that it does not contain a broken wire or a crack in the unseen portion of the notched area.
  11. An electrode plate for a secondary battery according to claim 3, characterized in that the energy density per unit area of the active material layer is 1 to 6 mAh/ cm² .
  12. An electrode plate for a secondary battery according to paragraph 3, characterized in that the current collector is an aluminum current collector and the active material comprises a lithium transition metal oxide.
  13. In a jellyroll type electrode assembly having a structure in which a first electrode plate and a second electrode plate having a sheet shape and a separator interposed between them are wound in one direction, At least one of the first electrode plate and the second electrode plate comprises a current collector and an uncoated portion at the long end of the current collector in which an active material layer is not coated. At least a portion of the above-mentioned non-removable portion is exposed to the outside of the separator and is used as an electrode tab itself, and The above electrode assembly is characterized by having an elongation of 1.5-3.0% and a tensile strength of 25-35 kgf/ mm² .
  14. An electrode assembly characterized in that, in paragraph 13, the current collector is an aluminum current collector.
  15. An electrode assembly according to claim 13, characterized in that the width in the direction along the short side of the current collector on the first electrode plate or the second electrode plate is 60-110 mm, the length in the direction along the long side of the current collector is 3-5 m, and the camber length is less than 20 mm.
  16. In paragraph 13, the above-mentioned blank portion comprises a core-side blank portion adjacent to the core of the electrode assembly, an outer-side blank portion adjacent to the outer surface of the electrode assembly, and an intermediate blank portion interposed between the core-side blank portion and the outer-side blank portion. An electrode assembly characterized in that at least a portion of the above-mentioned intermediate non-removable part is divided into a plurality of segments.
  17. In claim 16, the electrode assembly is characterized in that the shape of the segment is such that the upper width is smaller than the lower width.
  18. An electrode assembly according to claim 16, wherein each of the plurality of segments has a structure of a square, trapezoid, triangle, parallelogram, semicircle, or semi-ellipse.
  19. An electrode assembly characterized in that, in claim 16, the outer circumference side unoccupied portion and the core side unoccupied portion do not have a segmented structure of the unoccupied portion.
  20. An electrode assembly according to claim 16, characterized in that the plurality of segments are folded in the radial direction of the electrode assembly and overlapped in multiple layers.

Description

Current collecting plate for secondary battery and cylindrical battery cell comprising the same The present invention relates to a current collector used in a secondary battery and a battery cell including the same. The present invention is also related to a battery pack including such a battery cell and an automobile. As technology development and demand for mobile devices and electric vehicles increase, the demand for secondary batteries as an energy source is rapidly increasing. Currently, the widely used secondary battery is the lithium-ion battery, and the operating voltage of a unit battery cell is approximately 2.5V-4.5V. If a higher output voltage is required, multiple battery cells are connected in series to form a battery pack, or multiple battery cells are connected in parallel to form a battery pack depending on the charge/discharge capacity required for the battery pack. Cylindrical, prismatic, and pouch types are known as types of unit battery cells. Cylindrical battery cells include a jellyroll-type electrode assembly. The jellyroll-type electrode assembly has a structure in which a positive plate and a negative plate, which have a sheet shape, are wound with a separator interposed therein. FIG. 1 is a plan view illustrating the structure of an electrode plate, and FIG. 2 is a drawing showing the electrode plate winding process for manufacturing a jelly roll type electrode assembly. Referring to FIGS. 1 and 2, the positive plate (10) and the negative plate (11) have a structure in which an active material layer (21) is coated on a sheet-shaped current collector (20), and may include a non-solid portion (22) on one long side along the winding direction (X). The electrode assembly is manufactured by sequentially stacking the positive plate (10) and the negative plate (11) together with two separators (12) as shown in FIG. 2, and then winding them in one direction (X) around the core. At this time, the non-solid portions (22) of the positive plate (10) and the negative plate (11) may be arranged in opposite directions. The positive plate (10) and the negative plate (11) may include a current collector (20) that is extended in the winding direction (X) and an active material layer (21) coated on the upper surface and/or lower surface of the current collector (20). The end portion of the current collector (20) is not coated with the active material layer (21) for a predetermined width. In the art, the area where the active material layer (21) is not coated is called the uncoated portion (22), and the area where the active material layer (21) is coated is called the coated portion. The electrode plate manufacturing process includes the steps of coating an active material layer (21) on a current collector (20) to a designed thickness, drying the coated active material layer (21), and compressing the active material layer (21) to a desired density through a rolling process using a roller. Figure 3 is a schematic diagram illustrating the process of rolling an electrode plate using a roller. Referring to FIG. 3, an electrode plate (1) coated with an active material layer (21) on the upper and lower surfaces of a current collector (20) is rolled as it passes between a pair of rollers (30). Therefore, the deformation force that substantially stretches the electrode plate (1) can be seen as acting along the longitudinal direction of the electrode plate (1) (same as the X direction in FIG. 1). When the active material layer (21) is compressed, the amount of stretching differs between the retaining portion and the unretained portion (22). Accordingly, the actual electrode plate (1) deviates from the ideal shape as shown in FIG. 1. As shown in FIG. 4, unlike the state before compression in (a), after the rolling process proceeds and compression is performed as in (b), ripples form in the longitudinal direction of the electrode plate (1) (the direction of travel of the roller (30)), and thus a camber phenomenon as shown in FIG. 5 occurs. The camber phenomenon refers to the phenomenon in which the electrode plate (1) bends toward the unsupported portion (22) when unfolded, due to the difference in elongation between the unsupported portion (22) and the supporting portion. Elongation is defined as shown in the following mathematical formula 1. In other words, elongation is expressed as a percentage of the degree to which an object of length L is stretched when deformed to length L'. Elongation refers to the rate at which a material elongates during a tensile test; the higher the elongation, the greater the property of the material to stretch without breaking under external impact. That is, elongation is used as a measure of a material's fracture performance. Therefore, materials with lower elongation have a greater tendency to fracture under external impact, while materials with higher elongation have a greater tendency to stretch without fracturing under external impact. For reference, the camber length is def