Secondary battery and manufacturing method therefor

Abstract

Provided is a secondary battery comprising: first group unit cells and second group unit cells stacked in a first direction; first cell tabs extending from one end of the first group unit cells and bonded to each other; second cell tabs extending from one end of the second group unit cells and bonded to each other; and an electrode lead electrically connected to the first cell tabs and the second cell tabs, wherein the first cell tabs comprise a first horizontal portion, a second horizontal portion parallel to the first horizontal portion, and a first connecting portion connecting the first horizontal portion and the second horizontal portion, and the first horizontal portion, the second horizontal portion, and the first connecting portion are connected to form a Z-shaped cross-section.

Description

Secondary battery and its manufacturing method

[0001] The present invention relates to a secondary battery and a method for manufacturing the same, and more particularly, to a high-capacity secondary battery having a high energy density and a method for manufacturing the same.

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0039747, filed March 22, 2024, the entire disclosure of which is incorporated herein by reference.

[0003] Secondary batteries, unlike non-rechargeable primary batteries, are rechargeable and dischargeable. They are widely used in electronic devices such as mobile phones, laptops, and camcorders, as well as electric vehicles. In particular, lithium secondary batteries have a higher capacity than nickel-cadmium or nickel-hydrogen batteries and a higher energy density per unit weight, leading to a rapid increase in their use.

[0004] Various manufacturing methods have been proposed and applied to manufacture secondary batteries, and various efforts are being made to increase energy density.

[0005] The first technical task to be achieved by the present invention is to provide a high-capacity secondary battery with high energy density.

[0006] The second technical task to be achieved by the present invention is to provide a method for manufacturing a high-capacity secondary battery having a high energy density.

[0007] The present invention provides a secondary battery, which comprises a first group of unit cells and a second group of unit cells stacked in a first direction; first cell tabs extending from one end of the unit cells of the first group and joined to each other; second cell tabs extending from one end of the unit cells of the second group and joined to each other; and electrode leads electrically connected to the first cell tabs and the second cell tabs, wherein the first cell tabs include a first horizontal portion, a second horizontal portion parallel to the first horizontal portion, and a first connecting portion connecting the first horizontal portion and the second horizontal portion, and wherein the first horizontal portion, the second horizontal portion, and the first connecting portion are connected in a Z-shaped cross-section shape.

[0008] In some embodiments, the second cell tabs include a third horizontal portion, a fourth horizontal portion parallel to the third horizontal portion, and a second connecting portion connecting the third horizontal portion and the fourth horizontal portion, wherein the first horizontal portion, the second horizontal portion, and the second connecting portion can be connected in a Z-shaped cross-section.

[0009] In some embodiments, in the thickness direction of the secondary battery, the second horizontal portion and the fourth horizontal portion may be positioned at substantially the same level.

[0010] In some embodiments, the device further includes a common electrode portion connected to the second horizontal portion and the fourth horizontal portion, and the first cell tabs and the second cell tabs can be connected to the electrode lead through the common electrode portion.

[0011] In some embodiments, the second horizontal portion and the fourth horizontal portion may be positioned on substantially the same plane, and the common electrode portion may have a flat plate shape disposed on the plane.

[0012] In some embodiments, the electrode lead is coupled to the common electrode portion, and the electrode lead may be positioned to partially overlap the second horizontal portion and the fourth horizontal portion.

[0013] In some embodiments, the inner ends of the second horizontal portion and the fourth horizontal portion may be closer to the unit cells than the outer ends of the first horizontal portion and the third horizontal portion.

[0014] In some embodiments, the first cell tabs and the second cell tabs may be arranged so as not to overlap each other in the thickness direction of the secondary battery.

[0015] In some embodiments, the first cell tabs and the second cell tabs may at least partially overlap in the thickness direction of the secondary battery.

[0016] In some embodiments, the electrode lead may be positioned between the second horizontal portion and the fourth horizontal portion.

[0017] In some embodiments, the electrode lead may be in direct contact with the second horizontal portion and the fourth horizontal portion.

[0018] In some embodiments, the width of the first cell tabs and the width of the second cell tabs may be substantially equal to each other.

[0019] In some embodiments, the angle between the third horizontal portion and the second connecting portion may be less than 90 degrees, and the angle between the fourth horizontal portion and the second connecting portion may be less than 90 degrees.

[0020] In some embodiments, the angle between the first horizontal portion and the first connecting portion may be less than 90 degrees, and the angle between the second horizontal portion and the first connecting portion may be less than 90 degrees.

[0021] The present invention provides a first group of unit cells and a second group of unit cells stacked in a first direction to achieve the second technical task, wherein the first group of unit cells includes first cell tabs extending from one end and joined to each other, the second group of unit cells includes second cell tabs extending from one end and joined to each other, the first cell tabs include a first horizontal portion, a second horizontal portion parallel to the first horizontal portion, and a first connecting portion connecting the first horizontal portion and the second horizontal portion, and the second cell tabs include a third horizontal portion, a fourth horizontal portion parallel to the third horizontal portion, and a second connecting portion connecting the third horizontal portion and the fourth horizontal portion, the first group of unit cells and the second group of unit cells being provided; a step of electrically connecting the second horizontal portion and the fourth horizontal portion with an electrode lead; And, a method for manufacturing a secondary battery is provided, including a step of applying force to the second horizontal portion and the fourth horizontal portion so that the first cell tabs and the second cell tabs each have a Z-shaped cross-sectional shape.

[0022] In some embodiments, in the step of providing the unit cells of the first group and the unit cells of the second group, the angle between the first horizontal portion and the first connecting portion may be greater than 90 degrees, and the angle between the second horizontal portion and the first connecting portion may be greater than 90 degrees.

[0023] In some embodiments, in the step of providing the unit cells of the first group and the unit cells of the second group, the angle between the third horizontal portion and the second connecting portion may be greater than 90 degrees, and the angle between the fourth horizontal portion and the second connecting portion may be greater than 90 degrees.

[0024] In some embodiments, the step of electrically connecting the second horizontal portion and the fourth horizontal portion with the electrode lead may include the step of providing a common electrode portion connecting the second horizontal portion and the fourth horizontal portion; and the step of connecting the electrode lead to the common electrode portion.

[0025] In some embodiments, the second horizontal portion and the fourth horizontal portion may be bonded side by side on the same surface of the common electrode portion.

[0026] In some embodiments, the step of providing the first group of unit cells and the second group of unit cells may include the step of bending the first cell tabs joined to each other to form the first horizontal portion, the second horizontal portion, and the first connecting portion; and the step of bending the second cell tabs joined to each other to form the third horizontal portion, the fourth horizontal portion, and the second connecting portion.

[0027] The secondary battery according to the embodiments of the present invention has the effect of being able to manufacture a high-capacity secondary battery with a high energy density.

[0028] The effects that can be obtained from the exemplary embodiments of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly derived and understood by those skilled in the art to which the exemplary embodiments of the present disclosure pertain from the following description. In other words, unintended effects resulting from practicing the exemplary embodiments of the present disclosure can also be derived by those skilled in the art from the exemplary embodiments of the present disclosure.

[0029] Figure 1 is a front view showing a secondary battery according to one embodiment of the present invention.

[0030] Figure 2 is a schematic diagram showing the electrode assembly and main components accommodated inside the battery case of the secondary battery of Figure 1.

[0031] Figure 3 is an exploded perspective view of the electrode assembly and main components of Figure 2.

[0032] Fig. 4 is a cross-sectional view showing the electrode assembly and main components illustrated in Fig. 2.

[0033] Figure 5 is an enlarged partial view of part A of Figure 4.

[0034] Figure 6 is a schematic diagram showing an electrode assembly and main components of a secondary battery according to another embodiment of the present invention.

[0035] FIGS. 7A to 11B are schematic diagrams showing a method for manufacturing a secondary battery according to one embodiment of the present invention.

[0036] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments of the present invention may be modified in various different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. It is preferable to interpret that the embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art. Like numbers refer to like elements throughout. Furthermore, various elements and areas in the drawings are schematically drawn. Therefore, the present invention is not limited by the relative sizes or spacings depicted in the accompanying drawings.

[0037] While terms like "first" and "second" may be used to describe various components, these components are not limited by these terms. These terms are used solely to distinguish one component from another. For example, a first component could be referred to as a "second component," and vice versa, without departing from the scope of the present invention.

[0038] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the inventive concept. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the expressions "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, operations, components, parts, or combinations thereof.

[0039] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Furthermore, it is to be understood that commonly used terms, such as those defined in dictionaries, should be interpreted to have a meaning consistent with their meaning within the relevant technical context, and should not be interpreted in an overly formal sense unless explicitly defined herein.

[0040] In some embodiments, where implementations are otherwise feasible, specific process sequences may be performed in a different order than described. For example, two processes described in succession may be performed substantially simultaneously, or in a reverse order from the described order.

[0041] In the accompanying drawings, variations in the shapes depicted may be expected, for example, depending on manufacturing techniques and / or tolerances. Therefore, embodiments of the present invention should not be construed as being limited to the specific shapes of the regions depicted herein, but should include, for example, changes in shapes resulting from the manufacturing process. All terms "and / or" used herein include each and every combination of one or more of the mentioned components. In addition, the term "substrate" used herein may mean the substrate itself, or a laminated structure including the substrate and a predetermined layer or film formed on the surface thereof. In addition, the "surface of the substrate" in this specification may mean the exposed surface of the substrate itself, or the outer surface of a predetermined layer or film formed on the substrate.

[0042]

[0043] (Example 1)

[0044] Figure 1 is a front view showing a secondary battery (100) according to one embodiment of the present invention.

[0045] Referring to FIG. 1, a secondary battery (100) according to one embodiment of the present invention includes an electrode assembly (not shown) including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and a battery case (150) in which the electrode assembly is mounted. Here, the secondary battery (100) may include an electrolyte together with the electrode assembly (not shown) inside the battery case (150).

[0046] For example, the electrolyte refers to a liquid electrolyte, through which ions can move between the positive and negative electrodes, and through this ion exchange between the positive and negative electrodes, the secondary battery can be charged and discharged. Examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0047] In addition, the battery case (150) includes a sealing portion (155) having a structure sealed by heat fusion along the outer periphery. The battery case (150) may be a laminate sheet including a resin layer and a metal layer. In some embodiments, the battery case (150) may be formed of a laminate sheet, and may be formed of an outer resin layer forming the outermost layer, a barrier metal layer preventing penetration of a material, and an inner resin layer for sealing. However, the embodiment of the present invention is not limited to the above-described structure, and may be replaced with a battery case of a secondary battery having another general structure.

[0048] Additionally, the electrode assembly (not shown) may be configured in a jelly-roll type (rolled type), stack type (laminated type), or composite type (stack / folded type) structure. More specifically, the electrode assembly (not shown) may include a positive electrode, a negative electrode, and a separator disposed therebetween.

[0049] In addition, in the present embodiment, the battery case (150) may be configured to have a sealed structure in which electrode leads (140) electrically connected to a plurality of electrode tabs (not shown) extending from an electrode assembly (not shown) are exposed to the outside. More specifically, the electrode leads (140) may protrude outwardly of the battery case (150) past the sealing portion (155). In addition, in the present embodiment, a lead film (160) may be positioned between the electrode leads (140) and the sealing portion (155).

[0050] The lead film (160) not only prevents a short circuit from occurring between the electrode lead (140) and the insulating metal layer of the battery case (150), but also improves the sealing property of the battery case (150). When the lead film (160) is provided, the phenomenon of the adhesion being reduced when the electrode lead (140) made of a metal material and the battery case (150) made of a polymer material are thermally bonded can be prevented. In addition, the lead film (160) is preferably made of an insulating material that can block the current from being applied from the electrode lead (140) to the battery case (150). The lead film (160) is made of a film having insulating properties and thermal bonding properties. The lead film (160) may include, for example, one or more material layers selected from polyimide (PI), polypropylene, polyethylene, and polyethylene terephthalate (PET). In some embodiments, the length of the lead film (160) may be increased to prevent short circuiting of the portion of the electrode lead (140) exposed outside the battery case (150).

[0051] In some embodiments, the electrode lead (140) includes an anode lead (141) electrically connected to a cathode tab included in the electrode assembly and a cathode lead (145) electrically connected to a cathode tab included in the electrode assembly.

[0052] In some embodiments, the secondary battery (100) may be a bidirectional pouch battery cell in which a positive electrode lead (141) and a negative electrode lead (145) protrude from each side of a battery case (150). However, the present invention is not limited thereto, and the secondary battery (100) may be a unidirectional pouch battery cell in which a positive electrode lead (141) and a negative electrode lead (145) are arranged together on the same side of the battery case (150). In other embodiments, the secondary battery (100) may be a secondary battery in which an electrode assembly is housed in a square or cylindrical battery case.

[0053] The following description is based on a bidirectional pouch battery cell, but the same or similar description can be applied to a unidirectional pouch battery cell. Those skilled in the art will understand that the following description can also be applied to unidirectional pouch battery cells, prismatic secondary batteries, and cylindrical battery cases.

[0054] Fig. 2 is a schematic diagram showing an electrode assembly (101) and main components accommodated inside a battery case (150) of a secondary battery (100) of Fig. 1. Fig. 3 is an exploded perspective view of the electrode assembly (101) and main components of Fig. 2.

[0055] Referring to FIGS. 2 and 3, the electrode assembly (101) includes a first group of unit cells (111) and a second group of unit cells (112) stacked in a first direction (e.g., thickness direction).

[0056] An electrode assembly (101) is formed by alternately laminating electrodes and separators. First, a slurry containing a mixture of an electrode active material, a binder, and a plasticizer is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and then this is laminated on both sides of a separator, thereby forming an electrode assembly (101) of a predetermined shape.

[0057] Specifically, the electrode assembly (101) includes two types of electrodes, such as a positive electrode and a negative electrode, and a separator interposed between the electrodes to mutually insulate the electrodes. The electrode assembly (101) includes a stack type, a jelly roll type, a cylindrical type, a stack and folding type, etc. The two types of electrodes, i.e., the positive electrode and the negative electrode, have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively. The slurry can be typically formed by stirring a granular active material, an auxiliary conductor, a binder, a plasticizer, etc. in a state in which a solvent is added. The solvent is removed in a subsequent process.

[0058] In this specification, the term "unit cell" or "cell" may refer to an electrode having an active material applied to one or both sides of a current collector, or may refer to a combination of a pair of positive and negative electrodes. Furthermore, the term "unit cell" or "cell" may refer to a combination of multiple positive electrodes and multiple negative electrodes.

[0059] The electrode assembly (101) includes electrode tabs (120), as illustrated in FIGS. 2 and 3. The electrode tabs (120) are connected to the positive and negative electrodes of the electrode assembly (101), respectively, and protrude outward from one side of the electrode assembly (101) to serve as a path through which electrons can move between the inside and the outside of the electrode assembly (101). The current collector of the electrode assembly (101) may include a holding portion and a non-coated portion. The holding portion is a portion on which an electrode active material is applied, and the non-coated portion is a portion on which an electrode active material is not applied. The electrode tabs (120) may be formed by cutting the non-coated portion or by connecting a separate conductive member to the non-coated portion by ultrasonic welding, etc. As illustrated in FIGS. 2 and 3, the electrode tabs (120) may protrude in parallel in the same direction from one side of the electrode assembly (10), but are not limited thereto and may protrude in different directions.

[0060] The electrode tab (120) includes first cell tabs (121) that extend from one end of the unit cells (111) of the first group and are joined to each other, and second cell tabs (122) that extend from one end of the unit cells (112) of the second group and are joined to each other.

[0061] The first cell tabs (121) may include a first horizontal portion (1212) and a second horizontal portion (1214) extending in a second direction (e.g., a longitudinal direction), and a first connecting portion (1216) connecting the first horizontal portion (1212) and the second horizontal portion (1214). In some embodiments, the first horizontal portion (1212) and the second horizontal portion (1214) may extend in parallel. The first horizontal portion (1212) and the second horizontal portion (1214) may extend in the second direction while having a predetermined width in a third direction (e.g., a width direction). In some embodiments, the width of the first horizontal portion (1212) and the width of the second horizontal portion (1214) may be substantially equal to each other.

[0062] In some embodiments, the first horizontal portion (1212) may be disposed generally at the center in the thickness direction of the unit cells (111) of the first group. In some embodiments, the second horizontal portion (1214) may be disposed near the boundary between the unit cells (111) of the first group and the unit cells (112) of the second group.

[0063] The first connecting portion (1216) may connect one end of the first horizontal portion (1212) and one end of the second horizontal portion (1214). The end of the first horizontal portion (1212) connected to the first connecting portion (1216) may be an end that is farther from the terrace of the first cell tabs (121) among the ends of the first horizontal portion (1212) in the second direction (e.g., in the length direction). The end of the second horizontal portion (1214) connected to the first connecting portion (1216) may be an end that is closer to the terrace of the first cell tabs (121) among the ends of the second horizontal portion (1214) in the second direction (e.g., in the length direction).

[0064] The second cell tabs (122) may include a third horizontal portion (1222) and a fourth horizontal portion (1224) extending in a second direction (e.g., a longitudinal direction), and a second connecting portion (1226) connecting the third horizontal portion (1222) and the fourth horizontal portion (1224). In some embodiments, the third horizontal portion (1222) and the fourth horizontal portion (1224) may extend in parallel. The third horizontal portion (1222) and the fourth horizontal portion (1224) may extend in the second direction while having a predetermined width in the third direction (e.g., a width direction). In some embodiments, the width of the third horizontal portion (1222) and the width of the fourth horizontal portion (1224) may be substantially equal to each other.

[0065] In some embodiments, the third horizontal portion (1222) may be disposed generally at the center in the thickness direction of the unit cells (112) of the second group. In some embodiments, the fourth horizontal portion (1224) may be disposed near the boundary between the unit cells (111) of the first group and the unit cells (112) of the second group.

[0066] The second connecting portion (1226) may connect one end of the third horizontal portion (1222) and one end of the fourth horizontal portion (1224). The end of the third horizontal portion (1222) connected to the second connecting portion (1226) may be an end that is farther from the terrace of the second cell tabs (122) among the ends of the third horizontal portion (1222) in the second direction (e.g., in the length direction). The end of the fourth horizontal portion (1224) connected to the second connecting portion (1226) may be an end that is closer to the terrace of the second cell tabs (122) among the ends of the fourth horizontal portion (1224) in the second direction (e.g., in the length direction).

[0067] In some embodiments, the width of the second horizontal portion (1214) may be substantially equal to the width of the fourth horizontal portion (1224).

[0068] The first horizontal portion (1212) may be connected to the first connecting portion (1216) at an acute angle. In some embodiments, the angle between the first horizontal portion (1212) and the first connecting portion (1216) may be less than 90 degrees.

[0069] The second horizontal portion (1214) may be connected to the first connecting portion (1216) at an acute angle. In some embodiments, the angle between the second horizontal portion (1214) and the first connecting portion (1216) may be less than 90 degrees.

[0070] The third horizontal portion (1222) may be connected to the second connecting portion (1226) at an acute angle. In some embodiments, the angle between the third horizontal portion (1222) and the second connecting portion (1226) may be less than 90 degrees.

[0071] The fourth horizontal portion (1224) may be connected to the second connecting portion (1226) at an acute angle. In some embodiments, the angle between the fourth horizontal portion (1224) and the second connecting portion (1226) may be less than 90 degrees.

[0072] In some embodiments, the first cell tabs (121) and the second cell tabs (122) may be spaced apart from each other in a third direction (e.g., a width direction) so as not to overlap each other in the first direction (e.g., a thickness direction).

[0073] In some embodiments, the second horizontal portion (1214) and the fourth horizontal portion (1224) may be disposed generally on the same plane. In some embodiments, the second horizontal portion (1214) and the fourth horizontal portion (1224) may be positioned on substantially the same level in the first direction (e.g., thickness direction) of the secondary battery (100). In some embodiments, the second horizontal portion (1214) and the fourth horizontal portion (1224) may be disposed on the plane of the interface between the unit cells of the first group (111) and the unit cells of the second group (112).

[0074] The first cell tabs (121) and the second cell tabs (122) are electrically connected to an electrode lead (140). In some embodiments, the first cell tabs (121) and the second cell tabs (122) are electrically connected to a common electrode lead (140).

[0075] In some embodiments, the first cell tabs (121) and the second cell tabs (122) may be electrically connected to the electrode lead (140) through a common electrode portion (130). In some embodiments, the first cell tabs (121) may be connected to the common electrode portion (130) at a second horizontal portion (1214). In some embodiments, the second cell tabs (122) may be connected to the common electrode portion (130) at a fourth horizontal portion (1224).

[0076] In some embodiments, the common electrode portion (130) may be bonded to the upper surfaces of the second horizontal portion (1214) and the fourth horizontal portion (1224). In some embodiments, the common electrode portion (130) may be bonded to the lower surfaces of the second horizontal portion (1214) and the fourth horizontal portion (1224). Here, the 'upper surface' may refer to the visible surface of the second horizontal portion (1214) and the fourth horizontal portion (1224) illustrated in FIG. 3. In addition, the 'lower surface' here may refer to the opposite surface of the 'upper surface' of the second horizontal portion (1214) and the fourth horizontal portion (1224) illustrated in FIG. 3.

[0077] As previously described, the second horizontal portion (1214) and the fourth horizontal portion (1224) may be arranged on a common plane. Furthermore, the common electrode portion (130) may have a flat plate shape and may be arranged on the common plane.

[0078] In some embodiments, the common electrode portion (130) may at least partially overlap the second horizontal portion (1214) in the first direction (e.g., in the thickness direction). Additionally, the common electrode portion (130) may at least partially overlap the fourth horizontal portion (1224) in the first direction (e.g., in the thickness direction).

[0079] Fig. 4 is a cross-sectional view showing the electrode assembly (101) and its main components illustrated in Fig. 2. Fig. 5 is an enlarged partial view showing part A of Fig. 4.

[0080] Referring to FIGS. 4 and 5, the cross-section of the first cell tabs (121) may have a Z-shaped cross-section. That is, the first horizontal portion (1212), the second horizontal portion (1214), and the first connecting portion (1216) of the first cell tabs (121) may be connected to each other so that the first cell tabs (121) have a Z-shaped cross-section.

[0081] Additionally, the cross-section of the second cell tabs (122) may have a Z-shaped cross-section. That is, the third horizontal portion (1222), the fourth horizontal portion (1224), and the second connecting portion (1226) of the second cell tabs (122) may be connected to each other so that the second cell tabs (122) have a Z-shaped cross-section.

[0082] The first connecting portion (1216) may be a plane, but may include a curved surface having a predetermined curvature. The second connecting portion (1226) may be a plane, but may include a curved surface having a predetermined curvature.

[0083] The inner end of the second horizontal portion (1214) may be positioned further inward than the outer end of the first horizontal portion (1212). Here, 'inward' means the side closer to the unit cells in the second direction (e.g., lengthwise direction). In addition, the inner end of the fourth horizontal portion (1224) may be positioned further inward than the outer end of the third horizontal portion (1222).

[0084] In FIG. 5, a common electrode portion (130) is shown interposed between the second horizontal portion (1214) and the fourth horizontal portion (1224) and the electrode lead (140), but in some embodiments, the common electrode portion (130) may be omitted.

[0085] As demand for higher capacity secondary batteries grows, multiple unit cells are stacked, increasing the thickness of the electrode assembly. If the cell tabs of unit cells located near the ends along the thickness direction are bent abruptly, mechanical properties may deteriorate. Therefore, bending at the same angle as before increases lateral dead space.

[0086] As described with reference to FIGS. 2 to 5, by making the cell tabs have a Z-shaped cross-section and connecting the electrode leads to the terminal portions of the Z-shaped cross-sections of the cell tabs, the lateral dead space of the secondary battery can be significantly reduced, thereby improving the energy density.

[0087]

[0088] (Example 2)

[0089] FIG. 6 is a schematic diagram showing an electrode assembly (101) and main components of a secondary battery (100) according to another embodiment of the present invention. The embodiment illustrated in FIG. 6 differs from the embodiments illustrated in FIGS. 2 and 3 in the relative positions of the first cell tabs (121) and the second cell tabs (122). Therefore, the embodiment illustrated in FIG. 6 will be described below focusing on these differences, and descriptions of overlapping parts will be omitted.

[0090] Referring to FIG. 6, the first cell tabs (121) and the second cell tabs (122) may be arranged to at least partially overlap each other in a first direction (e.g., thickness direction) of the secondary battery (100). That is, in a third direction (e.g., width direction) of the secondary battery (100), the width direction positions of the first cell tabs (121) and the width direction positions of the second cell tabs (122) may at least partially overlap each other.

[0091] In some embodiments, the widthwise positions of the first cell tabs (121) and the widthwise positions of the second cell tabs (122) may be substantially the same. FIG. 6 illustrates an example in which the widthwise positions of the first cell tabs (121) and the widthwise positions of the second cell tabs (122) are the same.

[0092] In some embodiments, the first horizontal portion (1212) and the third horizontal portion (1222) may be arranged to at least partially overlap each other in the first direction (e.g., thickness direction) of the secondary battery (100). That is, in the third direction (e.g., width direction) of the secondary battery (100), the width direction position of the first horizontal portion (1212) and the width direction position of the third horizontal portion (1222) may at least partially overlap each other.

[0093] In some embodiments, the second horizontal portion (1214) and the fourth horizontal portion (1224) may be arranged to at least partially overlap each other in the first direction (e.g., thickness direction) of the secondary battery (100). That is, in the third direction (e.g., width direction) of the secondary battery (100), the width direction position of the second horizontal portion (1214) and the width direction position of the fourth horizontal portion (1224) may at least partially overlap each other.

[0094] In some embodiments, the electrode lead (140) may be positioned between an end of the first cell tabs (121) and an end of the second cell tabs (122). In some embodiments, the electrode lead (140) may be positioned between the second horizontal portion (1214) and the fourth horizontal portion (1224).

[0095] In some embodiments, the electrode lead (140) may be in direct contact with the second horizontal portion (1214) and the fourth horizontal portion (1224). In some embodiments, the electrode lead (140) may be bonded to the lower surface of the second horizontal portion (1214) and the upper surface of the fourth horizontal portion (1224).

[0096]

[0097] (Example 3)

[0098] Figures 7a to 11b are schematic diagrams illustrating a method for manufacturing a secondary battery (100) according to one embodiment of the present invention. In particular, Figures 7a, 8a, 9a, 10a, and 11a are perspective views illustrating a manufacturing process of one end portion of an electrode assembly (101). Figures 7b, 8b, 9b, 10b, and 11b are cross-sectional side views illustrating a manufacturing process of one end portion of an electrode assembly (101).

[0099] Referring to FIGS. 7a and 7b, a first group of unit cells (111) and a second group of unit cells (112) stacked in a first direction (e.g., thickness direction) can be provided.

[0100] The unit cells (111) of the first group may be bi-cells and / or mono-cells having generally the same structure. The unit cells (111) of the first group, which are aligned and stacked in a first direction (e.g., a thickness direction), may have first cell tabs (121) at the same positions in a third direction (e.g., a width direction). The first cell tabs (121) may extend from one end of the unit cells (111) of the first group and be joined to each other.

[0101] The unit cells (112) of the second group may be bi-cells and / or mono-cells having a generally identical structure. The unit cells (112) of the second group, which are aligned and stacked in a first direction (e.g., a thickness direction), may have second cell tabs (122) at the same positions in a third direction (e.g., a width direction). The second cell tabs (122) may extend from one end of the unit cells (112) of the second group and be joined to each other.

[0102] The unit cells (111) of the first group and the unit cells (112) of the second group can be aligned and stacked in the first direction (e.g., the thickness direction).

[0103] Although only one side of the electrode assembly (101) is shown in FIG. 7a, a person skilled in the art will understand that the opposite side of the electrode assembly (101) can be configured in the same manner.

[0104]

[0105] Referring to FIGS. 8A and 8B, the first cell tabs (121) joined to each other can be bent to form a first horizontal portion (1212), a second horizontal portion (1214), and a first connecting portion (1216). At this time, the angle between the first horizontal portion (1212) and the first connecting portion (1216) can be greater than 90 degrees. For example, the angle between the first horizontal portion (1212) and the first connecting portion (1216) can be about 95 degrees to about 140 degrees. In addition, the angle between the second horizontal portion (1214) and the first connecting portion (1216) can be greater than 90 degrees. For example, the angle between the second horizontal portion (1214) and the first connecting portion (1216) can be about 95 degrees to about 140 degrees.

[0106] In addition, the second cell tabs (122) joined to each other can be bent to form a third horizontal portion (1222), a fourth horizontal portion (1224), and a second connecting portion (1226). At this time, the angle between the third horizontal portion (1222) and the second connecting portion (1226) can be greater than 90 degrees. For example, the angle between the third horizontal portion (1222) and the second connecting portion (1226) can be about 95 degrees to about 140 degrees. In addition, the angle between the fourth horizontal portion (1224) and the second connecting portion (1226) can be greater than 90 degrees. For example, the angle between the fourth horizontal portion (1224) and the second connecting portion (1226) can be about 95 degrees to about 140 degrees.

[0107] In some embodiments, the first cell tabs (121) and the second cell tabs (122) may be bent simultaneously. In some embodiments, the first cell tabs (121) and the second cell tabs (122) may be bent sequentially. In this case, the first cell tabs (121) may be bent first and then the second cell tabs (122) may be bent. Alternatively, the second cell tabs (122) may be bent first and then the first cell tabs (121) may be bent.

[0108] The interface between the unit cells (111) of the first group and the unit cells (112) of the second group may be a part of a virtual plane (IP). In some embodiments, the first cell tabs (121) may be bent so that the second horizontal portion (1214) is positioned on the virtual plane (IP). In some embodiments, the second cell tabs (122) may be bent so that the fourth horizontal portion (1224) is positioned on the virtual plane (IP).

[0109] In the above, an example of folding the first cell tabs (121) and the second cell tabs (122) after stacking the first group of unit cells (111) and the second group of unit cells (112) has been described, but a person skilled in the art will understand that it is also possible to prepare the first group of unit cells (111) having the folded first cell tabs (121) and the second group of unit cells (121) having the folded second cell tabs (122) and stack the first group of unit cells (111) and the second group of unit cells (121).

[0110]

[0111] Referring to FIGS. 9a and 9b, a common electrode portion (130) connecting the first cell tabs (121) and the second cell tabs (122) can be provided.

[0112] The common electrode portion (130) may include an electrical conductor that electrically connects the first cell tabs (121) and the second cell tabs (122). In some embodiments, the common electrode portion (130) may include copper (Cu), aluminum (Al), iron (Fe), nickel (Ni), tin (Sn), gold (Au), silver (Ag), platinum (Pt), or an alloy including one or more of these.

[0113] In some embodiments, the common electrode portion (130) may have a strip shape extending in a third direction (e.g., width direction). The common electrode portion (130) may be connected to the second horizontal portion (1214) of the first cell tabs (121) and the fourth horizontal portion (1224) of the second cell tabs.

[0114] In some embodiments, the common electrode portion (130) may be connected to the second horizontal portion (1214) and the fourth horizontal portion (1224) by welding. In some embodiments, the common electrode portion (130) may be simultaneously connected to the second horizontal portion (1214) and the fourth horizontal portion (1224). In some embodiments, the common electrode portion (130) may be sequentially connected to the second horizontal portion (1214) and the fourth horizontal portion (1224).

[0115] In some embodiments, the second horizontal portion (1214) and the fourth horizontal portion (1224) may be bonded side by side on the same surface of the common electrode portion (130). In some embodiments, the common electrode portion (130) may be bonded to an upper surface of the second horizontal portion (1214) and an upper surface of the fourth horizontal portion (1224). In some embodiments, the common electrode portion (130) may be bonded to a lower surface of the second horizontal portion (1214) and a lower surface of the fourth horizontal portion (1224).

[0116] In some embodiments, the second horizontal portion (1214) and the fourth horizontal portion (1224) may be bonded side by side on different surfaces of the common electrode portion (130). In some embodiments, the common electrode portion (130) may be bonded to an upper surface of the second horizontal portion (1214) and a lower surface of the fourth horizontal portion (1224). In some embodiments, the common electrode portion (130) may be bonded to a lower surface of the second horizontal portion (1214) and an upper surface of the fourth horizontal portion (1224).

[0117] In some embodiments, the step of providing the common electrode portion (130) may be omitted. For example, the first cell tabs (121) and the second cell tabs (122) may at least partially overlap in the thickness direction of the electrode assembly (101), in which case the common electrode portion (130) may be omitted.

[0118]

[0119] Referring to FIGS. 10A and 10B, an electrode lead (140) is connected to the common electrode portion (130). The electrode lead (140) may be a conventional electrode lead known in the art and is not particularly limited.

[0120] The electrode lead (140) may be electrically connected to the first cell tabs (121) and the second cell tabs (122). In some embodiments, the electrode lead (140) may be electrically connected to the second horizontal portion (1214) through the common electrode portion (130). In some embodiments, the electrode lead (140) may be electrically connected to the fourth horizontal portion (1224) through the common electrode portion (130).

[0121] The electrode lead (140) may be connected to the common electrode portion (130), for example, by welding. If the dimension of the electrode lead (140) in the first direction (e.g., width direction) is sufficiently large, the electrode lead (140) may be directly connected to the first cell tabs (121) and the second cell tabs (122) without the common electrode portion (130).

[0122] In some embodiments, the first cell tabs (121) and the second cell tabs (122) may at least partially overlap in a first direction (e.g., a thickness direction) of the electrode assembly (101). That is, when the first cell tabs (121) and the second cell tabs (122) are projected in the first direction (e.g., a thickness direction), the first cell tabs (121) and the second cell tabs (122) may overlap each other. In this case, the electrode lead (140) may be inserted between the first cell tabs (121) and the second cell tabs (122). That is, the electrode lead (140) may be inserted between the second horizontal portion (1214) of the first cell tabs (121) and the fourth horizontal portion (1224) of the second cell tabs (122). In some embodiments, the electrode lead (140) may be directly bonded to the lower surface of the second horizontal portion (1214) and the upper surface of the fourth horizontal portion (1224).

[0123]

[0124] Referring to FIGS. 11A and 11B, a force (F) may be applied to the second horizontal portion (1214) and the fourth horizontal portion (1224) in a second direction (e.g., in the longitudinal direction) to push the second horizontal portion (1214) and the fourth horizontal portion (1224) toward the electrode assembly (101). To this end, a force (F) may be applied to the electrode lead (140) in a second direction (e.g., in the longitudinal direction). However, the present invention is not limited thereto, and a force (F) may be applied directly to the second horizontal portion (1214) and the fourth horizontal portion (1224).

[0125] A person skilled in the art will be able to determine the magnitude of the force (F) by considering the mechanical properties of the first cell tabs (121) and the second cell tabs (122).

[0126] In some embodiments, the step of applying the force (F) to the second horizontal portion (1214) and the fourth horizontal portion (1224) may be performed after electrically connecting the second horizontal portion (1214) and the fourth horizontal portion (1224) to the electrode lead (140).

[0127] By pushing in the second horizontal portion (1214) and the fourth horizontal portion (1224), the angle between the second horizontal portion (1214) and the first connecting portion (1216) and the angle between the fourth horizontal portion (1224) and the second connecting portion (1226) can each be less than 90 degrees. In addition, by pushing in the second horizontal portion (1214) and the fourth horizontal portion (1224), the angle between the first horizontal portion (1212) and the first connecting portion (1216) and the angle between the third horizontal portion (1222) and the second connecting portion (1226) can each be less than 90 degrees.

[0128] As a result, the first cell tabs (121) and the second cell tabs (122) each have a Z-shaped cross-sectional shape.

[0129] While the embodiments of the present invention have been described in detail above, those skilled in the art will appreciate that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention as defined in the appended claims. Therefore, modifications to future embodiments of the present invention will not depart from the scope of the invention.

[0130] <Explanation of symbols>

[0131] 100: Secondary battery

[0132] 101: Electrode Assembly

[0133] 111: Unit cells of the 1st Army

[0134] 112: Unit cells of the 2nd Army

[0135] 121: First cell tabs

[0136] 122: Second cell tabs

[0137] 130: Common electrode section

[0138] 140: Electrode lead

[0139] 141: Positive lead

[0140] 145: Negative lead

[0141] 150: Battery case

[0142] 155: Sealing part

[0143] 160: Lead Film

[0144] 1212: First horizontal section

[0145] 1214: Second horizontal section

[0146] 1216: First connector

[0147] 1222: Third horizontal section

[0148] 1224: 4th horizontal section

[0149] 1226: Second connector

Claims

1. Unit cells of the first group and unit cells of the second group stacked in the first direction; First cell tabs extending from one end of the unit cells of the first group and joined to each other; Second cell tabs extending from one end of the unit cells of the second group and joined to each other; and Electrode leads electrically connected to the first cell tabs and the second cell tabs; Including, A secondary battery in which the first cell tabs include a first horizontal portion, a second horizontal portion parallel to the first horizontal portion, and a first connecting portion connecting the first horizontal portion and the second horizontal portion, wherein the first horizontal portion, the second horizontal portion, and the first connecting portion are connected in a Z-shaped cross-section shape.

2. In paragraph 1, A secondary battery characterized in that the second cell tabs include a third horizontal portion, a fourth horizontal portion parallel to the third horizontal portion, and a second connecting portion connecting the third horizontal portion and the fourth horizontal portion, and the first horizontal portion, the second horizontal portion, and the second connecting portion are connected in a Z-shaped cross-section shape.

3. In paragraph 2, A secondary battery, characterized in that, in the thickness direction of the secondary battery, the second horizontal portion and the fourth horizontal portion are positioned at substantially the same level.

4. In paragraph 2, Further comprising a common electrode portion connected to the second horizontal portion and the fourth horizontal portion, A secondary battery characterized in that the first cell tabs and the second cell tabs are connected to the electrode lead through the common electrode portion.

5. In paragraph 4, A secondary battery characterized in that the second horizontal portion and the fourth horizontal portion are positioned on substantially the same plane, and the common electrode portion has a flat plate shape arranged on the plane.

6. In paragraph 5, The above electrode lead is coupled to the common electrode portion, A secondary battery characterized in that the electrode leads are arranged to partially overlap the second horizontal portion and the fourth horizontal portion.

7. In paragraph 2, A secondary battery characterized in that the inner ends of the second horizontal portion and the fourth horizontal portion are closer to the unit cells than the outer ends of the first horizontal portion and the third horizontal portion.

8. In paragraph 2, A secondary battery characterized in that the first cell tabs and the second cell tabs are arranged so as not to overlap each other in the thickness direction of the secondary battery.

9. In paragraph 2, A secondary battery, characterized in that the first cell tabs and the second cell tabs at least partially overlap in the thickness direction of the secondary battery.

10. In paragraph 9, A secondary battery characterized in that the electrode lead is positioned between the second horizontal portion and the fourth horizontal portion.

11. In paragraph 9, A secondary battery characterized in that the electrode lead is in direct contact with the second horizontal portion and the fourth horizontal portion.

12. In paragraph 9, A secondary battery characterized in that the widths of the first cell tabs and the widths of the second cell tabs are substantially the same.

13. In paragraph 2, The angle between the third horizontal portion and the second connecting portion is less than 90 degrees, A secondary battery characterized in that the angle between the fourth horizontal portion and the second connecting portion is less than 90 degrees.

14. In paragraph 1, The angle between the first horizontal portion and the first connecting portion is less than 90 degrees, A secondary battery characterized in that the angle between the second horizontal portion and the first connecting portion is less than 90 degrees.

15. A step of providing a first group of unit cells and a second group of unit cells stacked in a first direction, wherein the unit cells of the first group include first cell tabs extending from one end and joined to each other, the unit cells of the second group include second cell tabs extending from one end and joined to each other, the first cell tabs include a first horizontal portion, a second horizontal portion parallel to the first horizontal portion, and a first connecting portion connecting the first horizontal portion and the second horizontal portion, and the second cell tabs include a third horizontal portion, a fourth horizontal portion parallel to the third horizontal portion, and a second connecting portion connecting the third horizontal portion and the fourth horizontal portion, the step of providing the unit cells of the first group and the unit cells of the second group; A step of electrically connecting the second horizontal portion and the fourth horizontal portion to the electrode lead; and A step of applying force to the second horizontal portion and the fourth horizontal portion so that the first cell tabs and the second cell tabs each have a Z-shaped cross-section; A method for manufacturing a secondary battery comprising:

16. In paragraph 15, A method for manufacturing a secondary battery, characterized in that, in the step of providing the unit cells of the first group and the unit cells of the second group, an angle between the first horizontal portion and the first connecting portion is greater than 90 degrees, and an angle between the second horizontal portion and the first connecting portion is greater than 90 degrees.

17. In paragraph 16, A method for manufacturing a secondary battery, characterized in that, in the step of providing the unit cells of the first group and the unit cells of the second group, the angle between the third horizontal portion and the second connecting portion is greater than 90 degrees, and the angle between the fourth horizontal portion and the second connecting portion is greater than 90 degrees.

18. In paragraph 15, The step of electrically connecting the second horizontal portion and the fourth horizontal portion to the electrode lead is: A step of providing a common electrode portion connecting the second horizontal portion and the fourth horizontal portion; and A step of connecting the electrode lead to the common electrode portion; A method for manufacturing a secondary battery, characterized in that it includes:

19. In paragraph 18, A method for manufacturing a secondary battery, characterized in that the second horizontal portion and the fourth horizontal portion are joined side by side on the same surface of the common electrode portion.

20. In paragraph 15, The step of providing the unit cells of the first group and the unit cells of the second group is: A step of bending the first cell tabs joined to each other to form the first horizontal portion, the second horizontal portion, and the first connecting portion; and A step of bending the second cell tabs joined to each other to form the third horizontal portion, the fourth horizontal portion, and the second connecting portion; A method for manufacturing a secondary battery, characterized in that it includes:

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