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KR-20260062913-A - Electrode assembly, secondary battery, battery pack and vehicle including the same

KR20260062913AKR 20260062913 AKR20260062913 AKR 20260062913AKR-20260062913-A

Abstract

The electrode assembly of the present invention is an electrode assembly in which a core and an outer surface are defined by winding a positive electrode and a negative electrode and a separator interposed between them around a winding axis, wherein the positive or negative electrode is a current collector in the shape of a sheet having a long side and a short side, and the current collector includes a non-defining portion at the end of the long side, wherein the non-defining portion itself includes an electrode tab definition section used as an electrode tab and at least one electrode tab undefining section not used as an electrode tab, and the maximum current path for the at least one electrode tab undefining section includes a width direction current path along the short side of the current collector and a length direction current path along the long side of the current collector, and when the length of the width direction current path and the length direction current path are respectively L1 and L2, the current path ratio (L2/L1) is greater than 0 and less than or equal to 11.

Inventors

  • 이관희
  • 류덕현

Assignees

  • 주식회사 엘지에너지솔루션

Dates

Publication Date
20260507
Application Date
20260409
Priority Date
20210805

Claims (20)

  1. An electrode assembly in which a core and an outer surface are defined by winding an anode and a cathode and a separator interposed between them around a winding axis, The above-mentioned positive or negative electrode comprises a sheet-shaped current collector having a long side and a short side, and a current collector including a non-transferable portion at the end of the long side. The above-mentioned non-defining portion includes an electrode tab definition section that is used as an electrode tab itself and at least one electrode tab undefined section that is not used as an electrode tab, and The maximum current path for at least one undefined section of the electrode tab includes a width-direction current path along the short side of the current collector and a length-direction current path along the long side of the current collector, and when the length of the width-direction current path and the length of the length-direction current path are denoted as L1 and L2, respectively, the current path ratio (L2/L1) is greater than 0 and less than or equal to 11, and An electrode assembly characterized in that the electrode tab definition section includes a folded surface area formed by folding along the radial direction of the electrode assembly.
  2. An electrode assembly according to claim 1, characterized in that the height of the undefined section of the electrode tab is 0 or greater.
  3. In claim 1, the above-mentioned non-removable portion comprises a first portion adjacent to the core, a second portion adjacent to the outer surface, and a third portion between the first portion and the second portion. An electrode assembly characterized in that the length of the second part is shorter than the length of the first part.
  4. An electrode assembly according to claim 1, characterized in that the ratio of the short side to the long side of the current collector is 1.2% to 2.8%.
  5. An electrode assembly according to claim 1, characterized in that an active material layer is formed on at least one surface of the current collector, and an insulating coating layer is formed at the boundary between the active material layer and the uncoated portion.
  6. An electrode assembly according to claim 5, wherein the insulating coating layer comprises a polymer resin and an inorganic filler.
  7. An electrode assembly according to claim 1, characterized in that the height of the undefined section of the electrode tab is smaller than the height of the undefined section of the electrode tab.
  8. In claim 1, the above-mentioned non-removable portion comprises a first portion adjacent to the core, a second portion adjacent to the outer surface, and a third portion between the first portion and the second portion. An electrode assembly characterized in that the first part has a lower height than the third part in the direction of the winding axis.
  9. An electrode assembly according to claim 1, characterized in that the maximum value of the length of the undefined section of the electrode tab is 4% to 23% of the length of the anode and cathode.
  10. An electrode assembly characterized in that, in claim 8, the third portion forms the folded surface area.
  11. An electrode assembly according to claim 8, characterized in that the second part has a height equal to or smaller than the third part in the direction of the winding axis.
  12. An electrode assembly characterized in that, in claim 8, the first portion corresponds to the undefined section of the electrode tab.
  13. An electrode assembly according to claim 8, characterized in that the first portion is not bent along the radial direction of the electrode assembly.
  14. An electrode assembly according to claim 8, characterized in that the second portion is not bent along the radial direction of the electrode assembly.
  15. An electrode assembly according to claim 8, characterized in that, in the winding direction of the electrode assembly, the length of the third part is longer than the length of the first part and the length of the second part.
  16. An electrode assembly according to claim 8, wherein the first portion starts from the core-side short side of the current collector, the height of the first portion is constant along the winding direction, and the first portion is not bent along the radial direction of the electrode assembly.
  17. An electrode assembly according to claim 8, characterized in that at least a portion of the third part is divided into a plurality of segments that can be independently bent.
  18. An electrode assembly according to claim 17, characterized in that the segmented piece is bent and overlapped in the direction of the winding axis.
  19. In claim 17, the electrode assembly comprises, sequentially along the radial direction based on the cross-section along the winding axis direction, a segment omission section where no segments exist and a height uniform section where the height of the segments is uniform, and the plurality of segments are arranged in the height uniform section and form the bending surface area.
  20. An electrode assembly according to claim 19, characterized in that the above-mentioned segment omission section corresponds to the above-mentioned electrode tab undefined section.

Description

Electrode assembly, secondary battery, battery pack including the same, and vehicle including the same The present invention relates to an electrode assembly, a secondary battery, a battery pack including the same, and an automobile. More specifically, it relates to a jelly-roll type electrode assembly that enables low resistance, a cylindrical secondary battery including the same, a battery pack including the same, and an automobile. Secondary batteries, which possess electrical characteristics such as high energy density and high applicability across product groups, are widely applied not only to portable devices but also to electric vehicles (EVs) or hybrid electric vehicles (HEVs) powered by electric sources. These secondary batteries are attracting attention as a new energy source for enhancing eco-friendliness and energy efficiency, as they possess not only the primary advantage of drastically reducing the use of fossil fuels but also the advantage of generating no by-products from energy use. Cylindrical, prismatic, and pouch-type secondary batteries are known as types of secondary batteries. In the case of cylindrical secondary batteries, an insulating separator is interposed between the positive and negative electrodes, and this is wound to form a jelly-roll type electrode assembly, which is then inserted into a battery can to constitute the battery. Additionally, strip-shaped electrode tabs can be connected to the uninsulated portions of the positive and negative electrodes, and these electrode tabs electrically connect the electrode assembly with the externally exposed electrode terminals. Cylindrical secondary batteries can increase capacity by increasing the cell size. In this case, a low-resistance cell design is required that can demonstrate superior quality in terms of energy loss and heat generation even at high current densities. Ultimately, minimizing the current path is crucial for designing such a low-resistance cell. Figure 1 is a diagram showing the positive and negative electrodes applied to a conventional cylindrical secondary battery in an unfolded state. Referring to FIG. 1, a positive electrode (1) and a negative electrode (2) are shown as electrodes applied to a conventional cylindrical secondary battery. A strip-shaped positive electrode tab (1b) is connected to a non-bordered portion (1a) formed in the middle of the length direction of the positive electrode (1) so as to protrude upward along the width direction, and a strip-shaped negative electrode tab (2b) is connected to a non-bordered portion (2a) formed at both ends of the length direction of the negative electrode (2) so as to protrude downward along the width direction. FIG. 1 (a) is the case where there is one positive electrode tab (1b) and one negative electrode tab (2b), and (b) is the case where there is one positive electrode tab (1b) and two negative electrode tabs (2b). FIG. 2 is a schematic diagram showing the flow of current or electrons outside the secondary battery in a conventional cylindrical secondary battery. FIG. 3 is a schematic diagram showing the flow of current or electrons in the positive and negative electrodes constituting the electrode assembly in a conventional cylindrical secondary battery. Referring to FIGS. 2 and FIGS. 3, the current path can be broadly divided into two paths: a path from the module busbar welding location to the electrode tabs (1b, 2b) of each electrode (1, 2) (hereinafter, the first path), and a path from the electrode tabs (1b, 2b) of each electrode (1, 2) to the electrode end point. In FIG. 2, a first path is illustrated, where the current starting point (indicated by a circle) in FIG. 2 is located at the positive terminal (1c) and the negative terminal (2c). The positive terminal (1c) is the cap of a sealing body that seals the opening of the battery can (3), and the negative terminal (2c) is the battery can (3). An example is given where the module busbar welding position is located at the top of the cylindrical secondary battery. A current path is formed starting from the positive terminal (1c) and connected to the positive tab (1b), and a current path is formed starting from the negative terminal (2c) and connected to the negative tab (2b) (the connection position is indicated by a triangle). As such, the first path is determined by the cell exterior. When an electrochemical oxidation reaction occurs in the active material layer of the electrode, electrons are generated as metal atoms (Li) are converted into metal cations (Li + ) throughout the entire active material layer. The electrons move through the current collector (foil) constituting the electrode to the electrode tab and then flow outward through the first path. At this time, the current flows in the opposite direction to the flow of electrons. On the other hand, when an electrochemical reduction reaction occurs at the electrode, electrons flow from the first path through the electrode tab to the current co