Welded structure of battery can and cap, and battery cell to which this is applied.

Abstract

The present invention relates to a welded structure for a battery can and a cap, and a battery cell using the same. The battery cell includes a can including a bottom member and a sidewall member connected to the bottom member and extending in an axial direction, an electrode assembly housed inside the can, and a cap covering an open end provided at one axial end of the sidewall member. A terminal connector extending outward in the axial direction is provided on a radially outer edge of a current collector plate connected to an electrode of the electrode assembly and disposed near the open end, and contacting and electrically connecting the inner circumferential surface of the sidewall member. The inner circumferential surface of the sidewall member and the outer circumferential surface of the cap are welded to form a weld, with at least a portion of the terminal connector axially interposed between the inner circumferential surface of the sidewall member and the outer circumferential surface of the cap.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0140254 filed on October 27, 2022, and Korean Patent Application No. 10-2023-0071732 filed on June 2, 2023, and all the contents described in the documents of the patent applications are included as part of this specification.

[0002] The present invention relates to a welding structure of a battery can and a cap, and a battery cell to which the same is applied. [[ID=X]]

Background Art

[0003] In the process of manufacturing a battery cell applying a cylindrical can, a metal sheet is deep-drawn to form a circular bottom member and a circular tubular side wall member connected thereto, and after accommodating an electrode assembly therein, the open end of the side wall member is covered with a cap to finish.

[0004] On the other hand, among both axial ends of the electrode assembly, a current collector plate that contacts the electrode tab of the electrode assembly and is electrically connected thereto is provided at an end facing the open end. The current collector plate is connected to the cap or the side wall member by a method such as welding so as to be in electrical contact with the cap or the side wall member.

[0005] Referring to FIG. 15, in the process of welding the current collector plate 32 to the cap 40 or the side wall member 10, the current collector plate 32 must maintain a state of being in close contact with the cap 40 or the side wall member 10. For this purpose, a jig is required to bring the current collector plate 32 into close contact with the cap 40 or the current collector plate 32 into close contact with the side wall member 10, and a mask is required to expose the welding part.

[0006] [[ID=Y]] In order to ensure that the current collector plate is in close contact with the cap and side wall member via the mask and jig, a space must be provided inside the can to accommodate the mask and jig. However, after the mask and jig are removed, this space remains empty, resulting in the problem that the internal volume of the can cannot be used efficiently. This hinders the design of the can to increase its energy density per unit volume.

[0007] Furthermore, in finishing the open end of the cylindrical can, the process involved connecting the current collector plate to the cap or the side wall member, and connecting the cap to the side wall member. These increased labor costs reduce the production efficiency of cylindrical battery cells and increase the unit cost of production.

[0008] On the other hand, if the welding heat generated when welding the can and cap is transferred to the electrode assembly housed inside the can, it may cause deterioration of the separation membrane, deformation of the internal structure, or disintegration. Therefore, it is necessary to prevent this welding heat from being transferred to the electrode assembly. [Overview of the project] [Problems that the invention aims to solve]

[0009] One aspect of the present invention was devised to solve the above-mentioned problems, and aims to provide a welding structure for a battery can and a cap, and a battery cell to which this structure is applied, which allows for a design that increases the energy density per unit volume of the can without consuming the internal space of the can when welding a current collector plate provided on the open end of the can to the can.

[0010] Furthermore, one aspect of the present invention aims to provide a welded structure for a battery can and a cap, and a battery cell to which this structure is applied, which increases the production efficiency of cylindrical battery cells and lowers the production cost by integrating the process of welding the current collector plate to the can and the process of welding the cap to the side wall member into a single welding process.

[0011] Furthermore, one aspect of the present invention aims to provide a can-cap welding structure and a battery cell to which this structure is applied, by having the cap also function as a jig for pressurizing the current collector plate, thereby eliminating the need for a separate jig to pressurize the current collector plate for welding.

[0012] Furthermore, one aspect of the present invention aims to provide a welded structure for a can and a cap, and a battery cell to which this structure is applied, which minimizes damage to the electrode assembly due to heat by allowing the heat generated when welding the can and the cap to be discharged through a current collector plate.

[0013] The technical problems of the present invention are not limited to the purposes mentioned above. Other purposes and advantages of the present invention not mentioned above will be understood from the following description and will be more clearly understood from the embodiments of the present invention. Furthermore, it will be readily understood that the purposes and advantages of the present invention can be achieved by the means and combinations thereof described in the claims. [Means for solving the problem]

[0014] To solve the above-mentioned problems, one aspect of the present invention can be applied to a battery cell comprising a can including a bottom member, a side wall member connected to the bottom member and extending in the axial direction, an electrode assembly housed inside the can, and a cap covering an open end provided at one axial end of the side wall member.

[0015] The bottom member may be a flat circular plate, and the side wall member may be a circular tube. The can can be formed by deep drawing a metal sheet in which nickel (Ni) is plated on both surfaces of steel.

[0016] The electrode assembly can be manufactured in the form of a jelly roll by sequentially stacking a first electrode, a separation membrane, a second electrode, and a separation membrane and winding them around the circumference of a core shaft.

[0017] The electrode assembly may be cylindrical.

[0018] The cap may be a circular plate made of a metal material.

[0019] A current collector plate connected to the second electrode of the electrode assembly may be provided at one end of the electrode assembly in the axial direction.

[0020] The current collector plate is disposed on the open end side of the can.

[0021] A terminal connection portion that extends axially outward and is in electrical connection by contacting the inner peripheral surface of the side wall member is provided at the outer edge in the radial direction of the current collector plate.

[0022] Since the terminal connection portion extends in the axial direction, a sufficient contact area between the terminal connection portion and the side wall member can be ensured.

[0023] The battery cell includes a welded portion formed by welding the inner peripheral surface of the side wall member and the outer peripheral surface of the cap in a state where at least a part of the terminal connection portion is interposed between the inner peripheral surface of the side wall member and the outer peripheral surface of the cap in the axial direction.

[0024] The current collector plate may be connected to the second electrode of the electrode assembly and include an electrode connection portion that extends in the radial direction.

[0025] The terminal connection portion may be disposed further radially outward than the electrode connection portion.

[0026] The terminal connection portion and the electrode connection portion may be provided at the lower end portion of the terminal connection portion and connected via a bent portion that changes the extending direction of the current collector plate.

[0027] The terminal connection portion may be provided at a portion where the current collector plate extends axially outward from the bent portion.

[0028] The side wall member may extend further axially outward than the terminal connection portion of the current collector plate.

[0029] The portion of the side wall member extending further outward in the axial direction can melt into the welded portion during welding, increasing the strength and volume of the welded portion.

[0030] The inner diameter of the inner peripheral surface of the section of the side wall member extending further outward in the axial direction than the terminal connection portion of the current collecting plate may be larger than the inner diameter of the inner peripheral surface of the terminal connection portion.

[0031] As a result, the side wall member does not cover the tip surface in the axial direction from the outside in the axial direction of the tip surface provided at the outer end in the axial direction of the terminal connection portion of the current collecting plate.

[0032] This provides a path for the laser irradiated in the axial direction to directly reach the terminal connection portion, making the welding of the cap, the can, and the current collecting plate smoother. Also, this allows the inner peripheral surface of the side wall member of the can to guide the insertion of the cap first, and then the inner peripheral surface of the terminal connection portion of the current collecting plate to guide the insertion of the cap, enabling smooth insertion with the center alignment of the cap.

[0033] The outer peripheral surface of the cap can contact the inner peripheral surface of the terminal connection portion. As a result, the center of the cap with respect to the can can be aligned, and the terminal connection portion may also be electrically connected to the cap.

[0034] A butting portion extending in the axial direction may be provided at the edge of the cap such that its outer peripheral surface faces the inner peripheral surface of the side wall member in the radial direction.

[0035] Since the butting portion extends in the axial direction, a sufficient contact area between the terminal connection portion and the butting portion can be ensured.

[0036] The butting portion may extend further outward in the axial direction than the terminal connection portion of the current collecting plate.

[0037] The portion of the butting portion extending further outward in the axial direction can melt into the welded portion during welding, increasing the strength and volume of the welded portion.

[0038] The outer diameter of the outer surface of the section of the current collector plate that extends further outward in the axial direction than the terminal connection portion at the butt joint may be smaller than the outer diameter of the outer surface of the terminal connection portion.

[0039] As a result, the butt joint does not cover the tip surface provided on the axial outer edge of the terminal connecting portion of the current collector plate from the axial direction outward.

[0040] This provides a path through which the axially irradiated laser can directly reach the terminal connection, making the welding of the cap, can, and current collector plate smoother.

[0041] The axial outer edge of the terminal connecting portion may be positioned further inward in the axial direction than the axial outer edge of the side wall member and the axial outer edge of the butt joint portion.

[0042] As a result, the inner circumferential surface of the side wall member and the outer circumferential surface of the abutting portion may face each other radially with a slight gap between them, on the axial side of the tip surface of the terminal connecting portion.

[0043] The welded portion may be formed by welding at least the axial outer edge of the inner circumferential surface of the side wall member, the axial outer edge of the outer circumferential surface of the butt joint portion, and the axial outer edge of the terminal connecting portion.

[0044] A curved surface portion that is convex inward in the axial direction may be connected to the axial inner end of the abutting portion.

[0045] These curved sections impart an elastic force that allows the butt joint to deform radially. As a result, the curved section of the cap can elastically press the terminal connection portion of the current collector plate against the side wall member.

[0046] The cap can be inserted into the can until the axial inner end of the curved portion interferes with the current collector plate in the axial direction. This allows for limiting the insertion depth of the cap relative to the open end.

[0047] Furthermore, since the cap is forcibly inserted radially inward from the terminal connection portion of the current collector plate, the curved portion can also strongly press the current collector plate in the axial direction.

[0048] In other words, the cap can function as a jig to press and fix the current collector plate in both the axial and radial directions before welding.

[0049] A receiving portion extending radially in a flattened manner may be provided radially inward from the curved portion of the cap.

[0050] The curved portion and the receiving portion may be connected via a first inclined portion that extends outward in the axial direction as it moves inward in the radial direction.

[0051] The first inclined portion further imparts elastic force to the butt joint.

[0052] The axial outer surface of the receiving portion may protrude further outward in the axial direction than the abutting portion with the side wall member. This allows the receiving portion to protect the welded portion and function as a receiving surface for the battery cell.

[0053] A radially extending centering portion is provided in the cap radially inward from the receiving portion, and the receiving portion and the centering portion may be connected via a second inclined portion that extends axially inward as it moves radially inward.

[0054] This further increases the overall rigidity of the cap.

[0055] The second inclined portion may have a gentler incline than the first inclined portion.

[0056] The steep incline of the first inclined section provides radial elastic force, while the gentle incline of the second inclined section is advantageous for ensuring the rigidity of the cap.

[0057] One aspect of the present invention further provides the above-described method for manufacturing a battery cell.

[0058] This includes the steps of: inserting the current collector plate into the can such that the outer circumferential surface of the terminal connecting portion of the current collector plate contacts the inner circumferential surface of the side wall member; inserting the cap into the can such that the outer circumferential surface of the cap contacts the inner circumferential surface of the terminal connecting portion of the current collector plate inserted into the can; and irradiating the region where the outer circumferential surface of the side wall member and the inner circumferential surface of the can face each other with a laser in the axial direction to form a welded portion.

[0059] In one aspect of the present invention, a current collector plate is connected to an electrode tab provided at the end of the electrode assembly facing the open end, among the axial ends of the electrode assembly.

[0060] The current collector plate comprises an electrode connecting portion that extends radially and is electrically connected to the electrode tab by contacting it, and a terminal connecting portion that extends axially outward from the radial outer edge of the second electrode connecting portion and is electrically connected to the inner circumferential surface of the side wall member by contacting it.

[0061] Then, in the axial direction, at least a portion of the second terminal connecting portion is interposed between the inner surface of the side wall member and the outer surface of the cap, and the inner surface of the side wall member and the outer surface of the cap are welded together.

[0062] As a result, in a single step of welding the inner surface of the side wall member to the outer surface of the cap, not only can the can and the cap be seam-welded, but the terminal connecting portion of the current collector plate can also be brought into contact with the side wall member and / or the cap, thereby electrically connecting them.

[0063] The cap may have an axially extending abutting portion such that its outer circumferential surface faces the inner circumferential surface of the side wall member in the radial direction.

[0064] The terminal connection portion of the current collector plate may be interposed between the inner circumferential surface of the side wall member and the outer circumferential surface of the abutting portion.

[0065] The axial outer edge of the inner circumferential surface of the side wall member and the axial outer edge of the outer circumferential surface of the butt joint 4 may be laser-welded with the second terminal connecting portion interposed between them.

[0066] In this case, the axial outer edge of the inner circumferential surface of the side wall member, the axial outer edge of the outer circumferential surface of the butt joint, and the axial outer edge of the second terminal connecting portion may be laser-welded together.

[0067] A curved surface portion may be connected to the axial inner end of the butt joint, which extends radially inward as it moves axially inward, but whose tangent angle to its outer surface gradually decreases.

[0068] The insertion depth of the cap into the open end may be restricted by the axial inner end of the curved portion interfering with the electrode connecting portion of the current collector plate.

[0069] A receiving portion extending radially flattened is provided radially inward from the curved portion of the cap, and a first inclined portion extending axially outward is provided between the curved portion and the receiving portion, with the inward extension in the radial direction increasing.

[0070] As a result, the curved portion and the first inclined portion may have a goose neck shape that allows for easy elastic deformation in the radial direction while maintaining excellent elastic restoring force. Then, when the cap is pressed into the open end, the curved portion elastically deforms, allowing the abutting portion to be displaced radially inward, and the abutting portion to strongly press the terminal connecting portion of the current collector plate radially outward. In other words, the abutting portion can act as a jig to bring the terminal connecting portion into close contact with the side wall member.

[0071] A centering portion extending radially inward from the receiving portion of the cap may be provided, and a second inclined portion may be provided between the receiving portion and the centering portion, which extends axially inward as it moves radially inward.

[0072] The inclination of the first inclined portion may be greater than the inclination of the second inclined portion. This allows the deformation to be more concentrated on the first inclined portion than on the second inclined portion when the cap is subjected to a load radially inward, thereby more reliably performing the jig function of pressing the abutting portion against the terminal connecting portion toward the side wall member.

[0073] The axial outer edge of the terminal connecting portion may be positioned further inward in the axial direction than the axial outer edge of the side wall member and the axial outer edge of the butt joint portion.

[0074] The side wall member and the cap may be made of the same type of metal material, such as aluminum or steel.

[0075] The current collector plate may be made of the same type of metal as the side wall member and the cap.

[0076] In contrast, the current collector plate may be made of a different metal material from the side wall member and the cap, for example, copper.

[0077] As a result, even if they are made of different materials, the axial ends of the side wall member and the cap are welded to each other, and the current collector plate can maintain its position interposed between them. [Effects of the Invention]

[0078] According to one aspect of the present invention, when welding a current collector plate provided at the open end of the can to the can, the cap also acts as a jig, eliminating the need to provide a separate space to accommodate the jig, and thus increasing the energy density relative to the volume of the battery cell without consuming the internal space of the can.

[0079] Furthermore, according to one aspect of the present invention, with the current collector plate interposed between the side wall member and the cap, the axial ends of the side wall member and the cap are welded together, thereby solving the process of welding the current collector plate to the can and welding the cap to the side wall member in a single welding process, thereby increasing the production efficiency of cylindrical battery cells and lowering the production cost per unit.

[0080] Furthermore, according to one aspect of the present invention, since the current collector plate is in close contact with the welded portion of the can and the cap, the heat generated when welding the can and the cap is discharged through the current collector plate, thereby preventing or minimizing the phenomenon of welding heat being conducted through the side wall member and causing thermal damage to the separation membrane of the electrode assembly.

[0081] Furthermore, according to one aspect of the present invention, welding is performed with the current collector plate tightly pressed and interposed between the can and the cap, so the current collector plate acts as a barrier to prevent the welding laser from entering the inside of the cap.

[0082] The effects described above, as well as the specific effects of the present invention, will be explained and described below in conjunction with the descriptions of embodiments for carrying out the invention. [Brief explanation of the drawing]

[0083] [Figure 1] This is a perspective view of the cylindrical battery cell of the embodiment. [Figure 2] Figure 1 is an exploded perspective view of the electrode assembly housed inside the can before it is wound up. [Figure 3] Figure 2 is a perspective view of the electrode assembly in its stacked state before winding. [Figure 4] Figure 3 is a perspective view showing the laminated material wound up to form a cylindrical jelly roll-type electrode assembly. [Figure 5] This is a perspective view showing the state in which the first current collector plate is joined to the electrode tab of the first electrode of the electrode assembly. [Figure 6] This is a perspective view showing the state in which the second current collector plate is joined to the electrode tab of the second electrode of the electrode assembly. [Figure 7]This is a side cross-sectional view showing the process of housing the electrode assembly, to which the current collector plates are joined, inside the can. [Figure 8] This is a side cross-sectional view showing the joining process between the first current collector plate and the first electrode terminal of the electrode assembly housed in a can. [Figure 9] This is a side cross-sectional view showing the process of covering the open end of the can containing the electrode assembly with a cap. [Figure 10] This is a magnified cross-sectional view of the open end portion of a battery cell, where the open end of the can is covered with a cap. [Figure 11] This is a magnified cross-sectional view of the edge of the cap. [Figure 12] This is an enlarged cross-sectional view showing the state in which the cap is inserted into the can. [Figure 13] Figure 10 is a magnified view of the side wall member, current collector plate, and cap portion of the battery cell where welding takes place. [Figure 14] Figure 13 shows the state after the side wall member, current collector plate, and cap portion have been welded together to form the welded joint. [Figure 15] This is a diagram showing the coupling structure between the battery cell casing and the current collector plate of a comparative example. [Figure 16] This is a step diagram illustrating the manufacturing process of a battery cell according to one aspect of the present invention. [Figure 17] This figure shows a battery pack to which the battery cells of the embodiment are applied. [Figure 18] This figure shows an automobile equipped with a battery pack to which the battery cells of the embodiment are applied. [Modes for carrying out the invention]

[0084] The aforementioned objectives, features, and advantages will be described in detail below with reference to the accompanying drawings, so that a person with ordinary skill in the art to which the present invention pertains can easily implement the technical concept of the present invention. In describing the present invention, if a specific description of known technology according to the present invention is deemed to obscure the gist of the present invention, the detailed description will be omitted. Hereafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings are used to indicate the same or similar components.

[0085] Although terms like "first," "second," etc., are used to describe various components, these components are, of course, not limited by these terms. These terms are simply used to distinguish one component from another, and unless otherwise stated, the first component may also be the second component.

[0086] In the entire specification, unless otherwise stated, each component may be singular or plural.

[0087] In the following, the placement of any configuration "above (or below)" a component or "above (or below)" a component means not only that the configuration is placed in contact with the upper (or lower) surface of the component, but also that other configurations may be interposed between the component and any configuration placed on (or below) it.

[0088] Furthermore, where it is stated that one component is “linked,” “joined,” or “connected” to another component, it should be understood that the components may be directly linked or connected to one another, but may also be “interposed” between each component, or each component may be “linked,” “joined,” or “connected” through other components.

[0089] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise. Terms such as “composed of” or “including” in this application should not be construed as necessarily including all of the multiple components or stages described in the specification, and some of them may not be included, or may include further components or stages.

[0090] Where "A and / or B" is used throughout the specification, it means A, B, or A and B unless otherwise specified. Where "C~D" is used, it means C or greater and D or less unless otherwise specified.

[0091] In describing the embodiment, the axial direction refers to the direction in which the axis forming the winding center of the jelly roll type electrode assembly extends, the radial direction refers to the direction that is closer to (centripetal) or further away from (centrifugal) the axis, and the circumferential direction refers to the direction that surrounds the axis.

[0092] In the following, with reference to Figures 1 to 13, an example of a battery cell to which a welded structure according to an embodiment of the present invention is applied will be described in detail.

[0093] The battery cell in the embodiment may be, for example, a cylindrical battery cell with a form factor ratio (defined as the ratio of diameter to height of a cylindrical battery cell, i.e., the ratio of diameter (Φ) to height (H)) greater than approximately 0.4.

[0094] Here, form factor refers to a value indicating the diameter and height of a cylindrical battery cell. The cylindrical battery cell may be, for example, a 46110 cell, a 48750 cell, a 48110 cell, a 48800 cell, or a 46800 cell. In the numerical value indicating the form factor, the first two digits indicate the diameter of the cell, the next two digits indicate the height of the cell, and the last zero indicates that the cross-section of the cell is circular.

[0095] The aforementioned battery cell may be a cylindrical battery cell that is substantially cylindrical in shape, with a diameter of approximately 46 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0096] The battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical in shape, with a diameter of substantially 48 mm, a height of substantially 75 mm, and a form factor ratio of 0.640.

[0097] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical in shape, with a diameter of substantially 48 mm, a height of substantially 110 mm, and a form factor ratio of 0.418.

[0098] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical in shape, with a diameter of substantially 48 mm, a height of substantially 80 mm, and a form factor ratio of 0.600.

[0099] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical in shape, with a diameter of substantially 46 mm, a height of substantially 80 mm, and a form factor ratio of 0.575.

[0100] One aspect of the present invention can, of course, be applied to battery cells with a form factor ratio of approximately 0.4 or less, such as 18650 cells and 21700 cells. In the case of an 18650 cell, its diameter is approximately 18 mm, its height is approximately 65 mm, and its form factor ratio is 0.277. In the case of a 21700 cell, its diameter is approximately 21 mm, its height is approximately 70 mm, and its form factor ratio is 0.300.

[0101] The battery cell of the embodiment includes an electrode assembly 20, current collector plates 31 and 32 electrically connected to the electrode assembly 20, and a can 10 that houses the electrode assembly 20 and the current collector plates 31 and 32.

[0102] The can 10 includes a bottom member 12 and a side wall member 11 connected to the bottom member 12 and extending in the axial direction.

[0103] The open end provided at one axial end of the side wall member 11 is covered and sealed with the cap 16 after the electrode assembly 20 is housed in the can 10.

[0104] The bottom member 12 may be disc-shaped with a hole in the center, and the side wall member 11 may be circular tubular.

[0105] The bottom member 12 and the side wall member 11 can be manufactured by forming a metal sheet with nickel plating on the surface of steel using a deep drawing process, and then trimming the tip of the side wall member 11 with a punch while holding it with a blank holder. Of course, the material of the can 10 is not limited to this.

[0106] The first electrode terminal 13 may be inserted and coupled into the hole. The first electrode terminal 13 may be fixed to the bottom member 12 by riveting with a gasket 14 interposed between them. The gasket 14 is interposed between the first electrode terminal 13 and the bottom member 12 to seal the inside and outside of the can 10, prevent electrolyte leakage, and electrically insulate the first electrode terminal 13 and the bottom member 12.

[0107] However, the method of connecting the first electrode terminal 13 and the bottom member 12 is not limited to this. For example, any other fixing method that can be used to electrically insulate the first electrode terminal 13 and the bottom member 12 by sealing the space between them is also applicable, such as a bolt-nut connection method, a glass seal method, or a chrome coating & PP-MAH heat bonding method.

[0108] The first electrode terminal 13 has a first polarity, and the battery can 10 can have a second polarity. That is, the bottom member 12 of the battery can 10, the side wall portion 11 connected thereto, and the cap 16, which will be described later and connected to the side wall portion 11, can all have a second polarity.

[0109] As a result, the battery cell may have both the first electrode terminal 13 and the second electrode terminal 15 positioned at the axial end, i.e., the closed end, where the bottom member 12 is located. In this case, the busbar connected to the first electrode terminal 13 and the busbar connected to the second electrode terminal 15 may both be located at the top of the battery cell.

[0110] In one example, the first electrode terminal 13 may be a positive terminal, and the second electrode terminal 15 may be a negative terminal. Of course, the reverse may also be true.

[0111] An electrode assembly 20 is housed inside the battery can 10. As shown in Figure 2, the electrode assembly 20 is prepared by preparing a first electrode 21, a second electrode 22, and a separation membrane 28 having a predetermined width and extending in the longitudinal direction. As shown in Figure 3, a laminate is formed by stacking the first electrode 21, separation membrane 28, second electrode 22, and separation membrane 28 in that order, and then, as shown in Figure 4, it is manufactured in the form of a jelly roll by winding it around the circumference of a winding core.

[0112] The first electrode 21 may be a positive electrode, and the second electrode 22 may be a negative electrode. Of course, the reverse may also be true.

[0113] The first electrode 21 and the second electrode 22 are manufactured in sheet form. The electrode sheet is manufactured in a form in which an active material layer 24 is coated on the surface of a metal foil 23. The electrode sheet comprises a textured area 25 on which the active material layer 24 is coated and a plain area 26 on which the active material layer 24 is not coated. The positive electrode sheet has a plain area 26 on one side in the width direction, and the negative electrode sheet has a plain area 26 on the other side in the width direction.

[0114] The plain area 26 is exposed or protrudes in the width direction of the laminate. The plain area 26 itself functions as an electrode tab 27.

[0115] Notches can be formed in the plain portion 26 at predetermined intervals to create flag-shaped notched tabs 27.

[0116] In the embodiment, the notched tab 27 is exemplified as being in the shape of an equilateral trapezoid. However, these shapes may be of various forms, such as semicircular, inverted elliptical, triangular, rectangular, or parallelogram shapes.

[0117] Furthermore, in the embodiment, a configuration is shown in which the notched tabs 27 arranged along the length direction have the same width. However, the width of the notched tabs may be gradually or stepwise wider from the core side to the outer circumference side.

[0118] Furthermore, in the embodiment, a configuration is shown in which the height of the notched tab 27 gradually increases from the core side to the outer circumference side. However, the height of these notched tabs can also be constant or gradually decrease.

[0119] Furthermore, in the embodiment, a structure is shown in which the notched tabs 27 are removed from predetermined sections of the centripetal end and the centrifugal end of the plain portion 26. However, it goes without saying that the notched tabs at the centripetal end of the plain portion do not have to be removed, nor do the notched tabs at the centrifugal end of the plain portion.

[0120] In the jelly roll type electrode assembly 20, the notched tab 27 can be bent radially and flattened, as shown in Figure 4. The notched tab 27 may be bent radially inward or outward. In this embodiment, a structure in which the notched tab 27 is bent radially inward is exemplified.

[0121] The notched tabs 27 can be bent one by one during the process of winding up the laminate to form the jelly roll-type electrode assembly 20. Alternatively, the notched tabs 27 can also be bent all at once after winding up the laminate to form the jelly roll-type electrode assembly.

[0122] In this way, the notched tabs 27 of the first electrode 21 and the second electrode 22, which are folded radially and overlapping, can each provide a plane substantially perpendicular to the axial direction at both axial ends of the electrode assembly 20.

[0123] The notched tabs 27 exposed at both axial ends of the electrode assembly 20 are bent to provide a substantially flat surface, to which the first current collector plate 31 and the second current collector plate 32 may be bonded, as shown in Figures 5 and 6.

[0124] In the embodiment, the first current collector plate 31 is a positive electrode current collector plate, and the second current collector plate 32 is a negative electrode current collector plate. The first current collector plate 31 may be made of aluminum, and the second current collector plate 32 may be made of copper.

[0125] The current collector plates 31 and 32 can be manufactured by punching, trimming, piercing, and bending metal sheets.

[0126] Referring to Figure 5, the current collector plate 31 comprises a terminal connecting portion 312 extending radially from the center, a ring portion 313 connecting the centrifugal edge of the first terminal connecting portion 312 in the circumferential direction, and a first electrode connecting portion 314 extending centripetally from the ring portion 313 but not connected to the first terminal connecting portion 312. The central part of the first terminal connecting portion 312 covers at least a portion of the hollow core of the electrode assembly 20.

[0127] The first electrode connecting portion 314 is joined to the notched tab 27 of the first electrode 21 of the electrode assembly 20 by laser welding or the like before the electrode assembly 20 is placed in the can 10. The laser welding line may extend radially.

[0128] Referring to Figure 6, the second current collector plate 32 includes an inner ring portion 321 that defines a hole 322 corresponding to the hollow portion of the core of the electrode assembly 20 and is provided in a manner that surrounds the hollow portion of the core, a second electrode connecting portion 323 that extends radially from the inner ring portion 321, and a second terminal connecting portion 324 that is positioned centrifugal to the second electrode connecting portion 323 and is connected to the inner ring portion 321. The second terminal connecting portion 324 has an outer ring shape that surrounds the edge of the second current collector plate 32.

[0129] The second electrode connecting portion 323 may be joined to the notched tab 27 of the second electrode 22 of the electrode assembly 20 by a method such as laser welding before the electrode assembly 20 is placed in the can 10. The laser welding line may extend radially.

[0130] As shown in Figures 7 and 8, the electrode assembly 20 is housed in the can 10 with the first current collector plate 31 aligned toward the bottom member 12 of the can 10. At this time, an insulator 19 is interposed between the first current collector plate 31 and the bottom member 12 of the can 10 to electrically insulate the first current collector plate 31 from the bottom member 12.

[0131] The terminal connection portion 312 of the current collector plate 31 is joined to the first electrode terminal 13 fixed to the battery can 10 by resistance welding, ultrasonic welding, or laser welding. For welding the current collector plate 31 and the first electrode terminal 13, the welding apparatus can approach the back surface of the center of the first terminal connection portion 312 of the first current collector plate 31 from the open end of the can 10 through the hollow core portion of the electrode assembly 20 and perform the welding. Of course, the current collector plate 31 and the first electrode terminal 13 can also be joined by other methods such as brazing or soldering. In other words, various methods can be applied to the current collector plate 31 and the first electrode terminal 13 as long as they can be electrically connected and fixed to each other.

[0132] However, the present invention does not exclude a structure in which the positive electrode tab is electrically directly connected to the positive electrode terminal, even when the positive electrode current collector plate is omitted.

[0133] With the electrode assembly 20 housed inside the can 10, the electrode tab 27 of the second electrode 22 and the second current collector plate 32 are positioned to face the open end of the side wall member 11.

[0134] After the first current collector plate 31 and the first electrode terminal 13 are joined, the electrolyte can be injected into the can 10. After the electrolyte is injected, the open end of the side wall member 11 is covered with a cap 16, as shown in Figure 9.

[0135] Of course, the welded structure according to the embodiment of the present invention can also be applied to a method in which the cap 16 is covered first, and then the electrolyte is injected to finish the injection port of the cap 16.

[0136] As shown in Figure 10, the edge of the cap 16 is joined to the edge of the side wall member 11 by laser seam welding, thereby enabling the can 10 to be sealed.

[0137] In the following, with reference to Figures 10 to 14, a welded structure of a can and cap according to one aspect of the present invention will be described in detail.

[0138] The second current collector plate 32 comprises a second electrode connecting portion 323 that contacts and electrically connects to the electrode tab 27 of the second electrode 22 of the electrode assembly 20, and a second terminal connecting portion 324 that contacts and electrically connects to the inner circumferential surface of the side wall member 11.

[0139] The second electrode connecting portion 323 may have a circular flat plate structure extending in the radial direction. The bottom surface of the second electrode connecting portion 323 may be welded to the surface of the second electrode tab 27 by a method such as laser welding.

[0140] The second terminal connecting portion 324 extends axially outward from the bent portion 328 provided on the radial outer edge of the second electrode connecting portion 323.

[0141] The material of the second current collector plate 32 may be softer than the material of the side wall member 11.

[0142] If the outer diameter of the second terminal connecting portion 324 is set to be significantly larger than the inner diameter of the inner surface of the side wall member 11, the bent portion 328 will elastically deform during the process of inserting the second current collector plate 32, causing the second terminal connecting portion 324 to press into the inner surface of the side wall member 11, and the second terminal connecting portion 324 and the side wall member 11 to be in close contact in the radial direction. As a result, with the second current collector plate 32 inserted, the outer diameter of the second terminal connecting portion 324 can correspond to the inner diameter of the side wall member 11.

[0143] With the electrode assembly 20 housed inside the can 10, the second electrode tab 27 and the second current collector plate 32 are positioned to face the open end of the side wall member 11.

[0144] The side wall member 11 extends further outward in the axial direction than the second terminal connecting portion 324 of the second current collector plate 32. As shown in Figure 12, the inner circumferential surface of the side wall member 11 of the can 10 first guides the insertion of the cap 40, and then the inner circumferential surface of the second terminal connecting portion 324 of the second current collector plate 32 can guide the insertion of the cap 40. In other words, the above structure is not only advantageous for welding, which will be described later, but also guides the insertion of the cap 40, making it easier to center the cap when inserting it.

[0145] The open end of the side wall member 11 is covered and finished with a cap 40. The cap 40 is a cover for the open end that is substantially disc-shaped. Referring to Figure 11, the cap 40 includes, in this order from the radially outer to the inner side, a butt portion 49, a curved portion 48, a first inclined portion 47, a receiving portion 45, a second inclined portion 43, and a centering portion 41.

[0146] The radial outer edge of the cap 40 is provided with an axially extending abutting portion 49 such that its outer peripheral surface faces radially with the inner peripheral surface of the side wall member 11 of the can 10.

[0147] With the cap 40 inserted into the can 10, the axial outer edge of the inner circumferential surface of the side wall member 11 and the axial outer edge of the outer circumferential surface of the abutment portion 49 may be positioned so that their heights correspond to each other.

[0148] At least a portion of the second terminal connecting portion 324 in the axial direction is interposed between the side wall member 11 and the abutting portion 49 in the radial direction, by being pressed together radially by them.

[0149] In one embodiment, the axial outer edge of the second terminal connecting portion 324 is positioned further inward in the axial direction than the axial outer edge of the side wall member 11 and the axial outer edge of the abutting portion 49.

[0150] However, the present invention is not necessarily limited to these height relationships. For example, the height of the axial outer edge of the second terminal connecting portion 324 can correspond to the height of the axial outer edge of the side wall member 11 and / or the axial outer edge of the abutting portion 49, and may, of course, protrude even higher if necessary.

[0151] However, if the height of the axial outer edge of the second terminal connecting portion 324 is slightly lower than the height of the axial outer edge of the side wall member 11 and the axial outer edge of the butt portion 49, a groove is provided between the axial outer edge of the side wall member 11 and the axial outer edge of the butt portion 49. The molten metal of the axial outer edge of the side wall member 11 and the axial outer edge of the butt portion 49 melts into these grooves and welds them together, so that the axial outer edge of the second terminal connecting portion 324 is not exposed to the outside after welding.

[0152] A curved surface portion 48 is connected to the axial inner end of the butt joint portion 49, extending radially inward as it moves axially inward.

[0153] The curved portion 48 may be convex downwards, that is, the angle of the tangent to its outer surface gradually decreases as it moves further away from the abutment portion 49. Since the abutment portion 49 extends perpendicular to the axial direction, the angle of the tangent to the outer surface of the curved portion 48 may gradually decrease from 90 degrees as it moves further away from the abutment portion 49.

[0154] The curved portion 48 may extend to a point where the inclination of the tangent is 0 degrees. More preferably, the curved portion 48 may extend beyond 0 degrees to an angle where the inclination of the tangent corresponds to the first inclination of the first inclined portion 47, which will be described later.

[0155] The point where the inclination of the tangent line in the curved surface portion 48 becomes 0 degrees may be the part of the curved surface portion 48 that extends furthest inward in the axial direction.

[0156] The insertion depth of the cap 40 into the open end may be restricted by interference between the axial inner end of the curved portion 48, that is, the point where the tangent inclination is 0 degrees, and the surface of the second electrode connecting portion 323 of the current collector plate 32.

[0157] The cap 40 presses the second terminal connecting portion 324 of the second current collector plate 32 in the centrifugal direction and also presses the area near the centrifugal edge of the second electrode connecting portion 323 of the second current collector plate 32 in the axial direction. As a result, the second terminal connecting portion 324 of the second current collector plate 32 is firmly fixed in close contact with the side wall member 11 and the cap 40.

[0158] Unlike the cap 40, the second current collector plate 32 itself does not need to have enough rigidity to exert elastic force to strongly press its own second terminal connecting portion 324 against the side wall member 11.

[0159] Therefore, if the shape of the cap 40, which has higher rigidity than the second current collector plate 32, is designed to have elastic force, then not only will the cap 40 be strongly pressed against the side wall member 11, but the second current collector plate 32, which must be strongly pressed against the side wall member 11 in order to be welded to the side wall member 11, will also be strongly pressed against the side wall member 11 by the cap 40, so that the cap 40 can also function as a jig for welding the second current collector plate 32 to the side wall member 11.

[0160] A receiving portion 45 is provided radially inward from the curved portion 48 of the cap 40, extending horizontally in the radial direction. The surface of the receiving portion 45 has a flat ring shape, so when the battery cell shown in Figure 1 is turned upside down, it acts as the legs of the battery cell.

[0161] As shown in the figure, the axial outer surface of the receiving portion 45 is positioned at the same height as the axial outer edge of the butt joint portion 49, or further outward in the axial direction. Therefore, even if the battery cell shown in Figure 1 is turned upside down so that the cap 40 is in contact with the bottom and the battery cell is placed on top, the welded portion of the cap 40 and the can 10 does not directly support the load of the battery cell, thereby protecting the welded portion.

[0162] Between the curved surface portion 48 and the receiving portion 45, a constant first inclined portion 47 is provided, which extends outward in the axial direction as it moves inward in the radial direction, but whose inclination is substantially a first inclination. In the embodiment, the first inclination is exemplified as being about 45 degrees. Then, the angle between the first inclined portion 47 and the abutting portion 49 can be about 45 degrees.

[0163] A centering portion 41 is provided radially inward from the receiving portion 45 of the cap 40, extending horizontally in the radial direction. The axial inner surface of the centering portion 41 is positioned further outward in the axial direction than the axial inner end of the curved portion 48.

[0164] As a result, when the cap 40 is pressed in, the curved portion 48 may come into contact with the second current collector plate 32 before the axial inner surface of the centering portion 41 comes into contact with the second current collector plate 32. In other words, according to the embodiment, the depth to which the cap 40 is pressed in may be restricted by interference between the curved portion 48 and the second electrode connecting portion 323 of the second current collector plate 32.

[0165] Between the receiving portion 45 and the centering portion 41, a constant second inclined portion 43 is provided, which extends inward in the axial direction as it moves radially inward, but whose inclination is substantially a second inclination. In the embodiment, the second inclination is exemplified to be approximately 22.5 degrees.

[0166] The second inclination may be smaller than the first inclination. This allows the radial ends of the first inclined portion 47 to deform more effectively than the radial ends of the second inclined portion 43 when the cap 40 is subjected to a radial load. The difference in these inclinations further ensures that the abutting portion 49 of the cap 40 acts as a jig to press against the second terminal connecting portion 324 of the second current collector plate 32.

[0167] The radial length of the receiving portion 45 may be at least twice as long as the length of the section occupied radially by the abutting portion 49, the curved surface portion 48, and the first inclined portion 47. In this case, the receiving portion 45 will have relatively higher rigidity in the radial direction, and the radial load applied to the cap 40 on the outer circumferential surface of the cap 40 will be concentrated in the section radially outside the receiving portion 45. These differences in length also further ensure that the abutting portion 49 of the cap 40 functions as a jig that pressurizes the second terminal connecting portion 324 of the second current collector plate 32.

[0168] Referring to Figure 12, when a load is applied to the abutting portion 49 radially inward, the curved portion 48 mainly undergoes elastic deformation, and the connection portion between the first inclined portion 47 and the receiving portion 45 can mainly undergo elastic deformation. Furthermore, due to the large elastic deformation section in these neck structures, a large elastic force acts on the abutting portion 49 in the direction of returning it to its radially outward position.

[0169] As a result, when the cap 40 is pressed into the open portion of the can 10, the elastic force of the cap 40 acts in a direction that repairs the abutment portion 49 radially outward, and the second terminal connecting portion 324 of the second current collector plate 32 is strongly pressed against the side wall member 11 and the abutment portion 49, as shown in Figure 13.

[0170] In this state, the axial end of the side wall member 11 and the axial end of the butt joint 49 are welded together by a laser (L) irradiated in the axial direction, as shown in Figure 13. The direction of irradiation of the laser may be aligned with the axial direction.

[0171] As a result, at least a portion of the second terminal connecting portion 324 is interposed between the inner surface of the side wall member 11 and the outer surface of the cap 40 in the axial direction, and the inner surface of the side wall member 11 and the outer surface of the cap 40 are welded together to form a welded portion (W). A portion of the second terminal connecting portion 324 may also be melted into these welded portions (W).

[0172] The portion of the side wall member 11 that extends further outward in the axial direction and the portion of the abutting section 49 are separated by a slight gap, facing each other radially, and providing a path for the axially irradiated laser to directly reach the second terminal connecting section 324. This allows the second current collector plate 32 to be heated before excessive heat is generated, making the triple welding of the cap 40, the can 10, and the second current collector plate 32 smoother.

[0173] Furthermore, the portion of the side wall member 11 that extends further outward in the axial direction and the portion of the abutting joint 49 melt into the weld (W) during welding, increasing the strength and volume of the weld (W).

[0174] The side wall member 11 and the cap 40 may be made of the same type of metal material, for example, aluminum or steel.

[0175] The second current collector plate 32 may be made of the same type of metal as the side wall member 11 and the cap 40. In that case, the second current collector plate 32 may be welded together with the side wall member 11 and the cap 40 in the welding process.

[0176] In contrast, the second current collector plate 32 may be made of a different metal material from the side wall member 11 and the cap 40, for example, copper.

[0177] As a result, even if the materials are different, the second current collector plate 32 can be welded together with the side wall member 11 and the cap 40 in the welding process, and even if the welding of the second current collector plate 32 is somewhat insufficient due to the materials being different, the axial ends of the side wall member 11 and the cap 40 are welded to each other, and the current collector plate can be maintained interposed between them, so there is no problem with the electrical connection between the current collector plate and the can.

[0178] Below, with reference to Figure 16, an example of a method for manufacturing a battery cell according to one aspect of the present invention will be described.

[0179] First, the first electrode terminal 13 is fixed to a hole provided in the bottom member 12 of the can 10. At this time, a gasket 14 is interposed between the bottom member 12 and the electrode terminal 13 to provide electrical insulation and sealing between them. In this embodiment, a configuration in which the first electrode terminal 13 is fixed with a rivet with a gasket 14 interposed is shown as an example, but of course, various other known methods can be applied to fix the first electrode terminal 13 to the bottom member 12 while providing insulation and sealing.

[0180] Next, an electrode assembly 20, with current collector plates 31 and 32 welded to both ends, is inserted into the can. The first current collector plate 31 then faces and contacts the first electrode terminal 13, the second electrode connecting portion 323 of the second current collector plate 32 faces the open end, and the second terminal connecting portion 324 of the second current collector plate 32 contacts the inner circumferential surface of the side wall member 11 of the can 10. In this state, the first current collector plate 31 and the first electrode terminal 13 are welded together.

[0181] Next, the cap 40 is pressed onto the open end of the can 10. The outer surface of the cap 40 is provided with a curved portion 48 in which the outer diameter gradually decreases as it moves inward in the axial direction. As a result, the inner edge of the axial outer end of the second terminal connecting portion 324 of the second current collector plate 32 is naturally pressed by the curved portion 48, and the second terminal connecting portion 324 comes into contact with the abutting portion 49 of the cap 40 and is pressed radially outward. The insertion of the cap 40 may be continued until the curved portion 48 of the cap 40 interferes with the second electrode connecting portion 323 in the axial direction.

[0182] Next, the axial end of the side wall member 11 of the can 10 and the axial end of the butt joint 49 of the cap 40 are welded together.

[0183] Unlike the comparative example battery cell shown in Figure 15, in this embodiment, the cap 40 also acts as a jig when welding the second current collector plate 32 to the can 10, eliminating the need to provide separate space inside the can to house the jig. Therefore, the energy density relative to the volume of the battery cell can be increased without consuming the internal space of the can 10.

[0184] Furthermore, unlike the comparative example battery cell shown in Figure 15, the battery cell of this embodiment has the second current collector plate 32 interposed between the side wall member 11 and the cap 40. The axial ends of the side wall member and the cap are welded together, and the process of welding the second current collector plate 32 to the can 10 and the process of welding the cap 40 to the side wall member 11 are combined into a single welding process. Therefore, the production efficiency of cylindrical battery cells can be increased and the production cost can be reduced.

[0185] The battery cells 72 manufactured by the aforementioned welded structure and welding process can be housed in the housing 71 of the battery pack 70, as shown in Figure 17. The battery pack 70 can also be constructed using battery modules, which are an intermediate assembly form, or the battery pack 70 can be constructed directly without battery modules, as shown in the figure.

[0186] As described above, the battery cell 72 has a large volume on its own, so it is not particularly difficult to realize the battery pack 70 without using an intermediate structure such as a battery module. Furthermore, the battery cell 72 has low internal resistance and an even higher energy density. As a result, the energy density of the battery pack 70 equipped with the battery cell 72 can be realized to be even higher.

[0187] Thus, a battery pack 70 with increased energy density can store the same amount of energy while reducing its volume and weight. Therefore, when a battery pack 70 to which these battery cells 72 are applied is installed in a vehicle such as an electric automobile 80, as shown in Figure 18, the vehicle's energy mileage can be further extended.

[0188] The embodiments described above should be understood to be illustrative and not limiting in all respects, and the scope of the present invention is indicated more by the claims described below than by the detailed description above. The meaning and scope of the claims described below, as well as any modifications and deformable forms conceived from their equivalent concepts, should be interpreted as being included within the scope of the present invention.

[0189] As described above, the present invention has been explained with reference to the illustrative drawings. However, the present invention is not limited to the embodiments and drawings disclosed herein, and it is obvious to an ordinary person skilled in the art that various modifications can be made within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention are not explicitly described and explained while embodiments of the present invention are described above, it is natural to acknowledge that predictable effects can be obtained from such configuration. [Explanation of symbols]

[0190] 10 cans 11 Side wall member 12 Bottom member 13 1st electrode terminal 14 Gasket 15 2nd electrode terminal 19 Insulators 20 Electrode assembly 21 1st electrode 22 2nd electrode 23 Metal foil 24 Active material layer 25 Maintenance Department 26 Ignorance 27 Electrode tabs (notched tabs) 28 Separation membrane 31. First current collector plate (positive electrode current collector plate) 312 1st terminal connection part 313 Ring section 314 1st electrode connection part 32. Second current collector plate 321 Inner ring section 322 holes 323 2nd electrode connection part 324 2nd terminal connection part 328 Bend section 40 caps 41 Centrifugal part 43 2nd slope part 45 Receiving part 47 1st slope part 48 Curved part 49 Butt joint 70 Battery Packs 71 Housing 72 battery cells 80 vehicles W Weld

Claims

1. A battery cell comprising a can including a side wall member extending in the axial direction, an electrode assembly housed inside the can, and a cap covering an open end provided at one axial end of the side wall member, A terminal connecting portion is provided on the radial outer edge of the current collector plate, which is connected to the electrode of the electrode assembly and positioned on the open end side. This terminal connecting portion extends outward in the axial direction in the shape of an outer ring surrounding the outer peripheral edge of the current collector plate and contacts the inner circumferential surface of the side wall member to provide an electrical connection. A welded portion is formed where the inner surface of the side wall member and the outer surface of the cap are welded together, with at least a portion of the terminal connecting portion in the axial direction interposed between the inner surface of the side wall member and the outer surface of the cap, along the outer edge of the current collector plate. Battery cell.

2. The current collector plate is connected to the electrodes of the electrode assembly and has an electrode connecting portion that extends radially, The terminal connecting portion is positioned further outward in the radial direction than the electrode connecting portion. The terminal connecting portion and the electrode connecting portion are connected via a bent portion provided at the lower end of the terminal connecting portion, which changes the extending direction of the current collector plate. The battery cell according to claim 1.

3. The side wall member extends further outward in the axial direction than the terminal connection portion of the current collector plate. The battery cell according to claim 1 or 2.

4. The inner diameter of the inner surface of the section of the side wall member that extends further outward in the axial direction than the terminal connection portion of the current collector plate is larger than the inner diameter of the inner surface of the terminal connection portion. The battery cell according to claim 3.

5. The outer circumferential surface of the cap is in contact with the inner circumferential surface of the terminal connecting portion. The battery cell according to claim 1 or 2.

6. The edge of the cap is provided with a butt joint extending in the axial direction such that its outer circumferential surface faces the inner circumferential surface of the side wall member in the radial direction. The battery cell according to claim 5.

7. The aforementioned butt joint extends further outward in the axial direction than the terminal connection portion of the current collector plate. The battery cell according to claim 6.

8. The outer diameter of the outer surface of the section of the current collector plate that extends further outward in the axial direction than the terminal connection portion at the abutting portion is smaller than the outer diameter of the outer surface of the terminal connection portion. The battery cell according to claim 6.

9. The welded portion is formed by welding at least the axial outer edge of the inner circumferential surface of the side wall member, the axial outer edge of the outer circumferential surface of the butt joint portion, and the axial outer edge of the terminal connecting portion. The battery cell according to claim 6.

10. A curved surface portion with a convex curved shape on the axial side is connected to the axial inner end of the aforementioned butt joint portion. The axial inner end of the curved portion interferes with the current collector plate in the axial direction, thereby restricting the insertion depth of the cap into the open end. The battery cell according to claim 6.

11. A receiving portion is provided radially inward from the curved portion of the cap, which extends in a radially flattened manner. The curved portion and the receiving portion are connected via a first inclined portion that extends outward in the axial direction as it moves inward in the radial direction. The battery cell according to claim 10.

12. The axial outer surface of the receiving portion protrudes further outward in the axial direction than the abutting portion with the side wall member. The battery cell according to claim 11.

13. A radially extending centering portion is provided radially inward from the receiving portion of the cap. The receiving portion and the centering portion are connected via a second inclined portion that extends inward in the axial direction as it moves inward in the radial direction. The battery cell according to claim 11.

14. The second inclined portion has a gentler incline than the first inclined portion. The battery cell according to claim 13.

15. The axial outer edge of the terminal connecting portion is positioned further inward in the axial direction than the axial outer edge of the side wall member and the axial outer edge of the butt joint portion. The battery cell according to claim 6.

16. A method for manufacturing a battery cell according to claim 1 or 2, During the stage of inserting the current collector plate into the can, the outer circumferential surface of the terminal connecting portion of the current collector plate contacts the inner circumferential surface of the side wall member; The step of inserting the cap into the can such that the outer surface of the cap contacts the inner surface of the terminal connecting portion of the current collector plate inserted into the can; and The step includes irradiating a laser in the axial direction into the region where the outer circumferential surface of the side wall member and the inner circumferential surface of the can face each other to form a welded portion; A method for manufacturing battery cells.

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