A welded structure between a battery can, a current collector plate, and a cap, and a battery cell to which the welded structure is applied.

Abstract

An embodiment of the present invention includes a can and an electrode assembly housed inside the can. The can includes a bottom member, a side wall member connected to the bottom member and extending upward in the axial direction, and a cap covering an open end provided at the axial end of the side wall member facing the bottom member. The current collector plate is electrically connected to the electrodes of the electrode assembly near the open end. The periphery of the cap is welded together with the periphery of the open end side of the side wall member, the periphery of the cap, and the can connection portion to form a plurality of first welds spaced apart in the outer circumferential direction. Second welds are formed continuously along the outer circumferential direction by welding together the side wall member and the periphery of the cap.

Description

Technical Field

[0001] This application claims priority based on Korean Patent Application No. 10-2023-0074474 filed on June 9, 2023, Korean Patent Application No. 10-2023-0135320 filed on October 11, 2023, and Korean Patent Application No. 10-2024-0070118 filed on May 29, 2024, and all the contents disclosed in the specifications and drawings of the said applications are incorporated into this application.

[0002] The present invention relates to a battery, and more particularly, to a welding structure of a battery can, a current collector plate, and a cap, and a battery cell to which the welding structure is applied.

Background Art

[0003] The process of manufacturing a battery cell using a cylindrical can includes forming a can having a circular bottom member and a circular tubular side wall member connected to the bottom member by deep drawing a metal sheet, accommodating an electrode assembly therein, and then covering and sealing the open end of the side wall member with a cap.

[0004] On the other hand, a current collector plate is provided at one end of the axial direction of both ends of the electrode assembly, which faces the open end, and is electrically connected in contact with at least one electrode tab of the electrode assembly. 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] In the process of welding the current collector plate to the cap or the side wall member, the current collector plate maintains a state of being in close contact with the cap or the side wall member. Therefore, a jig for bringing the current collector plate into close contact with the cap or the side wall member is required, and a mask for exposing the welding portion may also be required.

[0006] To ensure the current collector plates are tightly sealed to the cap and sidewall members using masks and jigs, a space is provided inside the can to accommodate the masks and jigs. However, after the masks and jigs are removed, this space remains empty, resulting in inefficient use of the can's internal volume. This hinders the increase in energy density per unit volume of the can.

[0007] Furthermore, there is a risk that the welding laser beam could directly penetrate the can through the gap between the can, the current collector plate, and the cap. In addition, a large amount of thermal energy can be generated during welding, which may be transmitted through the can to the separation membrane of the electrode assembly, potentially causing deterioration such as decomposition or melting of the separation membrane, or blockage of the pores in the separation membrane.

[0008] Furthermore, when assembling cylindrical cans, the process of electrically connecting the current collector plate to the cap or side wall member and the process of connecting the cap to the side wall member are performed separately. This increase in assembly steps for battery cells reduces the production efficiency of cylindrical battery cells and increases production costs. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The present invention was devised to solve the above-mentioned problems, and aims to provide a welding structure for a battery can, a current collector plate, and a cap, and a battery cell to which this welding structure is applied, which enables a design that increases the energy density per unit volume of the can without wasting the internal space of the can during the process of welding the current collector plate, which is provided on the open end side of the can, to the can, by eliminating the need for a separate welding mask and jig.

[0010] Additionally or alternatively, the present invention aims to improve the production efficiency of cylindrical battery cells and reduce production costs 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] Additionally or alternatively, the present invention aims to improve process stability by providing the functions of a mask and a jig to the can, current collector plate, and cap.

[0012] Additionally or alternatively, the present invention aims to provide a welded structure for a can, a current collector plate, and a cap that minimizes the generation of welding heat, simplifies the assembly process of the current collector plate and the cap, and does not adversely affect the electrode assembly.

[0013] The technical problems of the present invention are not limited to those described above. Other problems and advantages can be understood from the following description and will become even clearer from the embodiments of the present invention. [Means for solving the problem]

[0014] The above-mentioned problems can be solved by forming a first weld by welding the can, current collector plate, and cap together to the extent that the necessary internal resistance can be secured during the temporary welding, pre-welding, or tack welding process to fix the position of the cap on the can before welding, and then forming a second weld by seam welding the can and cap during the main welding process for sealing the can.

[0015] This suppresses the generation of excessive welding heat, maintains a simple welding process, and ensures that the desired internal resistance is achieved, resulting in a securely sealed can.

[0016] According to one aspect of the present invention, a battery cell is provided. The battery cell may include a can, an electrode assembly, a current collector plate, a cap, and the like. The can may have side walls that surround an internal space and define an opening to the internal space at a first end of the can along a central longitudinal axis. The electrode assembly may be housed within the internal space of the can. The cap may cover the opening of the can so as to surround the internal space. The current collector plate may be electrically connected to the electrodes of the electrode assembly. The current collector plate may also include a peripheral portion that contacts the side wall so as to be electrically connected to the can. Triple welding may be performed to join the side wall along the opening, the peripheral portion of the cap, and the peripheral portion of the current collector plate together. Such triple welding may be formed along each of a plurality of first welds. Such a plurality of first welds may be spaced apart from each other along the circumferential direction with respect to a central longitudinal axis. The side wall along the opening and the peripheral portion of the cap may be welded together as a whole along a second weld. Such a second weld may extend substantially continuously along the circumferential direction with respect to the central longitudinal axis.

[0017] Depending on the various configurations of the battery cell, at least a portion of the second weld may overlap with a plurality of the first welds.

[0018] In other embodiments of the battery cell, at least a portion of the second weld may overlap with a plurality of the first welds.

[0019] In yet another form of the battery cell, the cross-sectional area of ​​each of the multiple first welds in each plane is larger than the cross-sectional area of ​​the second weld in each plane. Such cross-sections extend perpendicular to the circumferential direction at the location of each weld.

[0020] In another embodiment of the battery cell, the depth to which the multiple first welds extend axially away from the first end of the can may be greater than the depth to which the second welds extend axially away from the first end of the can. Such an axial direction extends parallel to the central longitudinal axis.

[0021] In other forms of battery cells, the outer diameter of the peripheral edge of the current collector plate may correspond to the outer diameter of the radial outer surface of the cap.

[0022] In some other forms of the battery cell, the periphery of the cap may have a radial outer surface that faces the radial inner surface of the side wall and contacts said inner surface.

[0023] In yet another form of the battery cell, the outer diameter of the peripheral edge of the current collector plate may be larger than the outer diameter of the radial outer surface of the peripheral edge of the cap.

[0024] In some configurations of the battery cell, the periphery of the cap has a radially oriented outer surface toward the radially oriented inner surface of the side wall, and a gap may be defined between them. In some such configurations, the welding area may extend within the gap between the radially oriented outer surface of the cap periphery and the radially oriented inner surface of the side wall.

[0025] In some other embodiments of the battery cell, the periphery of the cap may have a radially oriented outer surface toward the radially oriented inner surface of the side wall. Additionally, at least one first portion of the radially oriented outer surface of the cap periphery may have a first diameter corresponding to the outer diameter of the periphery of the current collector plate. Furthermore, at least one second portion of the radially oriented outer surface of the cap periphery may have a second diameter smaller than the outer diameter of the periphery of the current collector plate. In some of these embodiments, the radially oriented outer surface of the cap periphery may have two or more first portions and two or more second portions that alternate along the circumferential direction with respect to a central longitudinal axis.

[0026] According to still other forms of the battery cell, the periphery of the cap may have a radially outer surface facing the radially inner surface of the side wall. Additionally, the radially outer surface may have a plurality of major diameter portions and a plurality of minor diameter portions alternating along the circumferential direction about the central longitudinal axis. Such a plurality of minor diameter portions may have a diameter smaller than that of the plurality of major diameter portions. According to some of such forms, the major diameter portions of the radially outer surface of the periphery of the cap contact the radially inner surface of the side wall, while the minor diameter portions of the radially outer surface of the periphery of the cap are spaced apart from the radially inner surface of the side wall.

[0027] According to another aspect of the present invention, a method of manufacturing a battery cell is provided. The method may include positioning a cap and a current collector plate at an assembled position laminated within an opening of a can. In such an assembled position, the current collector plate may be electrically connected to an electrode assembly housed within the internal space of the can. Further, in such an assembled position, the peripheral portion of the current collector plate may contact the radially inner surface of the side wall of the can surrounding the opening. Further, in such an assembled position, the cap may be positioned on the current collector plate along the central longitudinal axis of the can such that the cap is farther away from the electrode assembly than the current collector plate. Preferably, the method also includes forming a plurality of first welded portions where the following three components are welded together to fix their relative positions. That is, the side wall of the can along the opening, the periphery of the cap, and the peripheral portion of the current collector plate are welded together to fix their relative positions with respect to each other. Also, the plurality of first welded portions may be spaced apart from each other along the outer circumferential direction with respect to the central longitudinal axis. The method preferably includes forming a second welded portion where the side wall of the can along the opening and the periphery of the cap are welded together. Such a second welded portion may extend substantially continuously along the outer circumferential direction with respect to the central longitudinal axis to seal the opening of the can.

[0028] According to some forms of the method, the step of forming the plurality of first welded portions may include directing a laser at a region between the radially inner surface of the side wall and the radially outer surface of the periphery of the cap.

[0029] According to some other forms, the step of forming the second weld may include the step of continuously irradiating the area along the radially inner surface of the side wall and the radially outer surface of the periphery of the cap using a laser.

[0030] According to still some other forms, the output or energy density of the laser irradiated when forming the plurality of first welds may be higher than the output or energy density of the laser irradiated when forming the second weld.

[0031] According to still some other forms, the speed of the laser moving along the circumferential direction to form the plurality of first welds may be faster than the speed of the laser forming the second weld.

[0032] According to still some other forms, the step of forming the second weld may include resistance welding using a roller electrode. <​​​​​​​​​​​​​​​​​According to one aspect of the present invention, the side wall member, the cap, and the current collector plate can be welded together, while ensuring weldability, stability, and durability.

[0037] According to one aspect of the present invention, the assembly time required for battery cells can be significantly reduced.

[0038] According to one aspect of the present invention, the volume of the electrode assembly housed inside the can can be maximized, thereby increasing the energy density of the battery cell. [Brief explanation of the drawing]

[0039] [Figure 1] This is a perspective view of a cylindrical battery cell according to one embodiment of the present invention. [Figure 2] Figure 1 is an exploded perspective view of the electrode assembly housed inside the can before winding. [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] Figure 4 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] Figure 4 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 cross-sectional view showing the process of housing the electrode assembly, to which the first and second current collector plates are joined, inside the can. [Figure 8] This is a 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 cross-sectional view showing the process of covering the open end of a can containing an electrode assembly with a cap. [Figure 10] This is a cross-sectional view showing an enlarged view of the open end portion of a battery cell, where the open end of the can is covered with a cap, illustrating the laser welding process. [Figure 11] This is a cross-sectional view showing an enlarged view of the open end portion of a battery cell, where the open end of the can is covered with a cap, illustrating the resistance welding process. [Figure 12] This is a cross-sectional view showing the open end of a battery cell, where the open end of the can is covered with a cap that has a liquid filling port. [Figure 13] Figure 12 is a cross-sectional view showing the liquid injection port of the cap sealed with a stopper. [Figure 14] This is a perspective view of the can with the cap covering the open end. [Figure 15] This figure shows a cross-section along line 15-15 in Figure 14. [Figure 16] Figure 14 is a plan view showing the can and cap with the first weld formed. [Figure 17] This figure shows a cross-section along line 17-17 in Figure 16. [Figure 18] Figure 16 is a plan view showing the can and cap with the second weld formed. [Figure 19] This figure shows a cross-section along line 19-19 in Figure 18. [Figure 20] This figure shows a cross-section along line 20-20 in Figure 18. [Figure 21] This is a perspective view showing a cylindrical battery cell according to another embodiment of the present invention, with a cap covering the open end of the can. [Figure 22] This is a cross-sectional view of Figure 21. [Figure 23] Figure 21 is a perspective view showing the can and cap with the first weld formed. [Figure 24] Figure 23 is a perspective view showing the can and cap with the second weld formed. [Figure 25] This is a photograph of a cross-section along line 25-25 in Figure 24. [Figure 26] This is a photograph of a cross-section along line 26-26 in Figure 24. [Figure 27]This is a plan view of a cap for a cylindrical battery cell according to yet another embodiment of the present invention. [Figure 28] This is a plan view showing the cylindrical battery cell with the cap shown in Figure 27 covering the open end of the can. [Figure 29] This is a flowchart of an example of a battery cell manufacturing method according to the present invention. [Figure 30] This is a flowchart of another example of a battery cell manufacturing method according to the present invention. [Figure 31] This is a perspective view of a battery pack to which a battery cell according to one embodiment of the present invention has been applied. [Figure 32] Figure 31 shows a car equipped with a battery pack. [Modes for carrying out the invention]

[0040] The aforementioned problems, features, and advantages will be described in detail later with reference to the attached drawings. This will enable a person with ordinary skill in the art to which the present invention pertains to be able to easily implement the technical idea of ​​the present invention. In the description of the present invention, if it is determined that a specific description of the relevant prior art may obscure the gist of the present invention, such detailed description will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0041] Furthermore, while terms such as "first," "second," etc., are used to indicate various components, these components are not limited by these terms. These terms are used to distinguish one component from another, and unless otherwise specified, the first component may be the second component.

[0042] Throughout the specification, unless otherwise specified, each component may be singular or plural.

[0043] Furthermore, the placement of any configuration "above (or below)" 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 above (or below) it.

[0044] Furthermore, when one component is described as being "connected," "joined," or "linked" to another component, this includes not only cases where the components are directly connected to or linked to each other, but also cases where other components are "interposed" between each component, or where each component is "connected," "joined," or "linked" through other components.

[0045] As used herein, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0046] Throughout this specification, "A and / or B" means A, B, or A and B unless otherwise specified, and "C-D" means C to D unless otherwise specified.

[0047] In the description of the embodiments, the axial direction refers to the direction in which the central longitudinal axis forming the winding center of the jelly roll-type electrode assembly extends or the direction parallel to the central longitudinal axis; the radial direction refers to the direction that is closer to (centripetal) or further away from (centrifugal) the axis; and the outer circumference (circumferential) direction refers to the direction that surrounds the axis.

[0048] Hereinafter, an embodiment of a battery cell to which the welded structure of the present invention is applied will be described in detail with reference to Figures 1 to 20.

[0049] One embodiment of a battery cell may be a cylindrical battery cell in which the form factor ratio (defined as the ratio of the diameter to the height of a cylindrical battery cell, i.e., the ratio of height (H) to relative diameter (Φ)) is greater than approximately 0.4.

[0050] Here, form factor refers to a value indicating the diameter and height of a cylindrical battery cell. Cylindrical battery cells can be, for example, 46110 cells, 48750 cells, 48110 cells, 48800 cells, or 46800 cells. In the numerical value indicating the form factor, the first two digits indicate the diameter of the cell, the following two digits indicate the height of the cell, and the last digit 0 indicates that the cross-section of the cell is circular.

[0051] The battery cell may be a cylindrical battery cell that is roughly cylindrical in shape, with a diameter of approximately 46 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0052] A battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical, with a diameter of approximately 48 mm, a height of approximately 75 mm, and a form factor ratio of 0.640.

[0053] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical, with a diameter of approximately 48 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0054] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical, with a diameter of approximately 48 mm, a height of approximately 80 mm, and a form factor ratio of 0.600.

[0055] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical in shape, with a diameter of approximately 46 mm, a height of approximately 80 mm, and a form factor ratio of 0.575.

[0056] The present invention can, of course, also 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, the diameter is approximately 18 mm, the height is approximately 65 mm, and the form factor ratio is 0.277. In the case of a 21700 cell, the diameter is approximately 21 mm, the height is approximately 70 mm, and the form factor ratio is 0.300.

[0057] 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.

[0058] The can 10 includes a bottom member 12, a side wall member 11 connected to the bottom member 12 and extending in the axial direction, and a cap 16 that covers an open end provided at one axial end of the side wall member 11, i.e., the upper end 30 or first end of the side wall member 11.

[0059] The bottom member 12 is a disc shape with a hole formed in the center, and the side wall member 11 may be a circular tube surrounding the internal space of the can 10.

[0060] 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 in a blank holder. Of course, the material of the can 10 is not limited to this.

[0061] A first electrode terminal 13 can be fitted into the hole. The first electrode terminal 13 can be fixed to the bottom member 12 by riveting with a gasket 14 in between. 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 leakage of the electrolyte, and electrically insulate the first electrode terminal 13 from the bottom member 12.

[0062] However, the method of connecting the first electrode terminal 13 and the bottom member 12 is not limited to this. For example, as long as the structure can seal the space between the first electrode terminal 13 and the bottom member 12 and electrically insulate the first electrode terminal 13 and the bottom member 12, a variety of other fixing methods can be applied, such as a bolt-nut connection method, a glass seal method, or a chrome coating & PP-MAH thermal bonding method.

[0063] The first electrode terminal 13 has a first polarity, and the can 10 may have a second polarity. That is, the bottom member 12 of the can 10, the side wall member 11 connected to the bottom member 12, and the cap 16, which will be described later and connected to the side wall member 11, may all have a second polarity.

[0064] As a result, the battery cell can have both the first electrode terminal 13 and the second electrode terminal 15 positioned at the axial end, i.e., the closed end, of the can 10 where the bottom member 12 is provided. Then, the battery cell can have both the busbar connected to the first electrode terminal 13 and the busbar connected to the second electrode terminal 15 positioned at the top of the battery cell.

[0065] For example, the first electrode terminal 13 may be the positive terminal and the second electrode terminal 15 may be the negative terminal. Of course, the opposite may also be true.

[0066] The electrode assembly 20 is housed in the internal space of the 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 that have a predetermined width and extend 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 a core shaft.

[0067] The first electrode 21 can be the positive electrode, and the second electrode 22 can be the negative electrode. Of course, the opposite is also possible.

[0068] 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 has 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.

[0069] The first electrode 21 and the second electrode 22 are arranged such that their plain areas 26 are exposed or protrude from the laminate in the width direction. The plain area 26 of the first electrode 21 protrudes from one axial end of the jelly roll, and the plain area 26 of the second electrode 22 protrudes from the other axial end of the jelly roll. The plain area 26 itself functions as at least one electrode tab 27.

[0070] The plain portion 26 can be formed with notches at predetermined intervals to create a plurality of notched tabs 27.

[0071] Each notching tab 27 can be flag-shaped. In the embodiment, multiple notching tabs 27 are shown to be isosceles trapezoidal. However, these shapes may be a variety of shapes such as semicircular, semielliptical, triangular, rectangular, or parallelogram.

[0072] Furthermore, in the embodiment, an example is shown in which the notching tabs 27 arranged along the longitudinal direction have the same width. However, the width of the multiple notching tabs may be such that they gradually or stepwise increase from the core side to the outer circumference side.

[0073] Furthermore, as shown in Figures 2 and 3, the embodiment illustrates a configuration in which the height of the notching tab 27 gradually increases from the core side to the outer circumference side. However, the height of the multiple notching tabs may be constant or gradually decrease.

[0074] Furthermore, in the embodiment, a structure is exemplified in which the notching tab 27 is removed from a predetermined section at the centripetal end and a predetermined section at the centrifugal end of the plain portion 26. However, in contrast to this, the notching tab may not be removed from the centripetal end of the plain portion, or from the centrifugal end of the plain portion, or the notching tab may not be removed from both sides.

[0075] In the jelly roll-type electrode assembly 20, the notching tab 27 can be bent radially and flattened, as shown in Figure 4. The notching tab 27 can be bent radially inward or outward. In this embodiment, a structure in which the notching tab 27 is bent radially inward is illustrated.

[0076] The notching tabs 27 can be bent one by one during the process of winding the laminate to form the jelly roll-type electrode assembly 20. Alternatively, the notching tabs 27 may be bent all at once after the laminate has been wound to form the jelly roll-type electrode assembly.

[0077] The multiple notched tabs 27 of the first electrode 21 and the multiple notched tabs 27 of the second electrode 22, which are folded radially and overlapped in this manner, can each provide a plane substantially perpendicular to the axial direction at both axial ends of the electrode assembly 20.

[0078] The notched tabs 27 exposed at both axial ends of the electrode assembly 20 are bent to provide a substantially flat surface, which can then be bonded to the first current collector plate 31 and the second current collector plate 32, respectively, as shown in Figures 5 and 6.

[0079] 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.

[0080] The current collector plates 31 and 32 may be manufactured by punching, trimming, piercing, and / or bending a metal sheet.

[0081] Referring to Figure 5, the first current collector plate 31 includes terminal connecting portions 312 extending radially from the center, a ring portion 313 connecting the centrifugal periphery of the terminal connecting portions 312 in the circumferential direction, and an electrode connecting portion 314 extending centripetally from the ring portion 313 and not connected to the terminal connecting portions 312. The central part of the terminal connecting portion 312 covers at least a portion of the hollow core along the central longitudinal axis of the electrode assembly 20.

[0082] The electrode connecting portion 314 is joined to the notched tab 27 of the first electrode 21 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.

[0083] 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, and an electrode tab connecting portion 323 that extends radially from the inner ring portion 321. The electrode tab connecting portion 323 may be in the form of a plurality of spokes that extend radially outward from the inner ring portion. Here, one or more of the spokes may have a radially outer end that is connected to the peripheral edge of the second current collector plate 32, which is called a can connecting portion 324. In addition, one or more of the spokes of the electrode tab connecting portion 323 may have a radially outer end that does not reach the can connecting portion 324. The can connecting portion 324 is an outer ring shape that surrounds the electrode tab connecting portion 323 and may include a step that moves away from the electrode assembly 20 in the axial direction. As a result, at least the outermost peripheral edge of the can connector 324 can be positioned further away from the electrode assembly 20 than the electrode tab connector 323, the inner ring 321, and other parts of the can connector 324.

[0084] The electrode tab connecting portion 323 may be joined to the notched tab 27 of the second electrode 22 of the electrode assembly 20 by methods such as laser welding before the electrode assembly 20 is placed in the can 10. The laser welding line may extend radially.

[0085] 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.

[0086] The terminal connection portion 312 of the first current collector plate 31 is joined to the first electrode terminal 13 fixed to the can 10 by resistance welding, ultrasonic welding, or laser welding. As shown in Figure 8, the welding apparatus for welding the first current collector plate 31 and the first electrode terminal 13 can be brought in from the open end of the can 10, through the hollow core of the electrode assembly 20, and approach the back surface of the center of the terminal connection portion 312 of the first current collector plate 31 (the surface facing the electrode assembly 20) to perform the welding. Of course, the first current collector plate 31 and the first electrode terminal 13 may also be joined by other methods such as brazing or soldering. In other words, a variety of methods can be applied as long as the coupling method allows the first current collector plate 31 and the first electrode terminal 13 to be electrically connected and fixed to each other.

[0087] With the electrode assembly 20 housed inside the can 10, the electrode tab 27 and the second current collector plate 32 of the second electrode 22 are positioned to face the open end of the side wall member 11.

[0088] After the first current collector plate 31 and the first electrode terminal 13 are joined, electrolyte can be injected into the can 10. After the electrolyte is injected, the open end of the side wall member 11 is covered and sealed by the cap 16 as shown in Figure 9. The connection between the side wall member 11 and the bottom member 12 of the can 10 closes the internal space of the can 10 by covering the open end of the cap 16.

[0089] The periphery of the cap 16 is joined to the periphery of the side wall member 11 by laser seam welding, as shown in Figure 10, thereby enabling the can 10 to be sealed.

[0090] Of course, in addition to this method, the can may also be joined by seam welding through a resistance welding method with a roll electrode R, as shown in Figure 11. The roll electrode R may be tapered roll in shape. If the can 10 is rotated with the outer surface of the roll electrode R in contact with the tip of the side wall member 11, the roll electrode R will also rotate as the can 10 rotates. If a positive voltage (+) is applied to one of the two electrodes and a negative voltage (-) is applied to the other while it is rotating in this way, current will flow and resistance heating will occur at the contact point between the side wall member 11 adjacent to the roll electrode R and the cap 16, and welding will be performed at these contact points.

[0091] Furthermore, the welded structure of the present invention can also be applied to a method in which, as shown in Figure 12, the cap 16 is first placed over the open end of the can 10 and welded W to the side wall member 11, then the electrolyte is injected into the can 10 through the liquid injection port 18 provided on the cap 16, and as shown in Figure 13, the liquid injection port 18 of the cap 16 is sealed with a stopper 40. The liquid injection port 18 may be a circular hole provided in the center of the cap 16, and the stopper 40 may be a circular stopper having a surface portion having a larger diameter than the liquid injection port 18 and an insertion portion that protrudes from the surface portion and is fitted into the liquid injection port 18. The outer edge of the stopper 40 is welded to the cap 16, thereby sealing the liquid injection port 18. Of course, the method of joining the stopper 40 and the cap 16 is not limited to welding, and various sealing joining methods such as soldering, O-ring compression, and screw joining can be applied.

[0092] Referring to Figures 10, 14, and 15, an inner diameter expansion portion 113 may be provided on the open end side of the side wall member 11. The inner diameter expansion portion 113 may be a lateral step shape that extends across the central longitudinal axis and is positioned along the radial inner surface of the side wall member 11.

[0093] As a result, the radial inner surface of the side wall member 11 may include a first inner circumferential surface 111 located axially inward from the inner diameter expansion portion 113, i.e., further away from the opening of the open end of the side wall member 11, and a second inner circumferential surface 115 located axially outward from the inner diameter expansion portion 113, i.e., closer to the opening of the open end of the side wall member 11.

[0094] The second inner circumferential surface 115 may have a larger inner diameter than the first inner circumferential surface 111. As a result, the side wall member 11 may have a second thickness t2 measured radially in the portion where the second inner circumferential surface 115 is provided that is thinner than the first thickness t1 measured radially in the portion where the first inner circumferential surface 111 is provided.

[0095] The can connecting portion 324, which is provided on the periphery of the second current collector plate 32 and contacts the can 10 to be electrically connected, includes a first portion that contacts the second inner circumferential surface 115 of the side wall member 11. The first portion is provided with a contact outer circumferential surface 325 that faces and contacts the second inner circumferential surface 115 of the side wall member 11 in the radial direction.

[0096] The can connecting portion 324 includes a second portion that contacts the cap 16. The second portion is provided with a cap contact surface 326 that faces and contacts the inner surface of the cap 16, i.e., the bottom surface of the cap 16, in the axial direction.

[0097] The outer diameter of the contact outer peripheral surface 325 of the can connecting portion 324 is set to be larger than the inner diameter of the first inner peripheral surface 111. As a result, the can connecting portion 324 includes a third portion that contacts the inner diameter expansion portion 113. The third portion is located on the opposite side of the cap contact surface 326 in the axial direction. The third portion contacts the inner diameter expansion portion 113 and restricts the insertion depth of the second current collector plate 32 into the can 10.

[0098] The second current collector plate 32 further includes a first bent portion 327 and a second bent portion 328, thereby defining an axial step in the second current collector plate 32. The first bent portion 327 is shaped by bending the second current collector plate 32, which extends radially outward, outward in the axial direction. The second bent portion 328 is also shaped by bending the second current collector plate 32, which extends axially outward, outward in the axial direction. Due to the axial step between the first bent portion 327 and the second bent portion 328, the peripheral edge of the second current collector plate 32 or the can connecting portion 324 is axially offset from the central portion of the second current collector plate 32 toward the open end of the can 10.

[0099] The can connecting portion 324 is connected to the electrode tab connecting portion 323 through the first bent portion 327 and the second bent portion 328, and also through the inner ring portion 321 described above.

[0100] The can connecting portion 324 is connected to the radially outer side of the second bent portion 328 and has a configuration that extends radially from the second bent portion 328. This makes it possible to further secure the area of ​​the cap contact surface 326 of the second current collector plate 32.

[0101] Preferably, the material of the second current collector plate 32 may be softer than the material of the side wall member 11. Therefore, during the process of inserting the second current collector plate 32 into the open end of the side wall member 11, the first bent portion 327 and the second bent portion 328 are elastically deformed. As a result, if the outer diameter of the contact outer peripheral surface 325 is set to be slightly larger than the inner diameter of the second inner peripheral surface 115, the contact outer peripheral surface 325 will be pressed into the second inner peripheral surface 115.

[0102] The cap 16 comprises, in order from the radial center outward, a cap body 160, a thickness reduction section 161 in which the thickness of the cap changes, and a joint section 17. That is, the cap body 160 has its center in the central region of the cap 16, and the thickness reduction section 161 is provided on the radially outer side of the cap body 160. The joint section 17 is provided on the radially outer side of the thickness reduction section 161 and defines an annular region of the cap 16 having a thickness that is relatively reduced with respect to the cap body 160.

[0103] In other words, the third thickness t3 of the joint 17, measured in the axial direction, is thinner than the fourth thickness t4 of the cap body 160, also measured in the axial direction.

[0104] Along the radial outer surface of the cap 16, specifically along the radial outer surface of the joint portion 17, a joint outer surface 171 is provided that faces the second inner circumferential surface 115 of the side wall member 11 in the radial direction. In one embodiment, the joint outer surface 171 contacts the second inner circumferential surface 115 of the side wall member 11 in the radial direction. In addition, the bottom surface of the joint portion 17 of the cap 16 is provided with a current collector plate contact surface 173 that faces and contacts the cap contact surface 326 of the can connecting portion 324 of the second current collector plate 32 in the axial downward direction.

[0105] By appropriately selecting the position where the thickness reduction portion 161 is provided, it is possible to bring at least a part of the thickness reduction portion 161 into contact with the second current collector plate 32. Then, in the process of inserting the cap 16 into the open end of the side wall member 11, the thickness reduction portion 161 of the cap 16 comes into contact with the second current collector plate 32, and the center of the cap 16 is aligned with the central longitudinal axis of the second current collector plate 32.

[0106] In one embodiment, the thickness reduction portion 161 is positioned at a location in the radial direction corresponding to the position where the second bent portion 328 of the second current collector plate 32 is formed, thereby achieving this alignment effect.

[0107] Preferably, in one embodiment, in order to enhance the alignment effect, the thickness reduction portion 161 is realized in the form of a slope that extends outward in the axial direction as it extends outward in the radial direction.

[0108] Preferably, in one embodiment, in order to enhance the alignment effect, the second current collector plate 32 is also given a slanted shape through the surface shape of the second bent portion 328 of the second current collector plate 32.

[0109] In the radial direction, the joining outer peripheral surface 171 of the cap 16 and the contact outer peripheral surface 325 of the second current collector plate 32 each contact the second inner peripheral surface 115 of the side wall member 11.

[0110] In addition, in the axial direction, at least a portion of the lower part of the second current collector plate 32 along its peripheral edge contacts the inner diameter expansion portion 113 of the side wall member 11. In the axial direction, the cap contact surface 326 provided on the upper part of the second current collector plate 32 contacts the current collector plate contact surface 173 provided on the lower part of the joint portion 17 of the cap 16.

[0111] With the second current collector plate 32 and the cap 16 inserted in this manner, the axial position of the upper end of the side wall member 11 can correspond to the axial position of the upper surface of the cap 16.

[0112] As shown in Figure 15, that is, in the side wall member 11, the first height h1 of the section located axially outward from the inner diameter expansion portion 113 can correspond to the sum of the third thickness t3 of the joint portion 17 of the cap 16 and the fifth thickness t5 of the can connecting portion 324 of the second current collector plate 32.

[0113] As shown in the diagram, the joint outer surface 171 of the cap 16 and the axial end of the inner surface of the side wall member 11, which are in contact with each other in the radial direction, are exposed to the outside of the battery cell.

[0114] The cap 16 can be welded to the can 10 by a laser irradiated from the axial outside of the battery cell toward the axial end of the joining outer surface 171 of the cap 16 and the second inner surface 115 of the side wall member 11.

[0115] In this case, the contact outer peripheral surface 325 of the second current collector plate 32, which is located axially lower than the cap 16, is in contact with the inner surface of the side wall member 11, thereby preventing the laser from being irradiated into the internal space of the can through any gap that may exist between the side wall member 11 and the cap 16.

[0116] Furthermore, the inner diameter expansion portion 113 of the side wall member 11 can also prevent the laser from penetrating inside the gap between the side wall member 11 and the cap 16, or between the side wall member 11 and the second current collector plate 32.

[0117] The second current collector plate 32 may contain a material with a higher thermal conductivity than the side wall member 11. Furthermore, the second current collector plate 32 is in contact with the side wall member 11. Therefore, when the welding heat generated on the side wall member 11 by the laser is conducted along the axial direction of the side wall member 11, the welding heat is dispersed across the upper end of the electrode assembly 20 through the second current collector plate 32, preventing the welding heat from being transmitted to the separation membrane portion of the electrode assembly 20 and damaging the separation membrane.

[0118] The second current collector plate 32 is also in contact with the cap 16. As a result, the heat generated in the cap 16 by laser or resistance welding is dispersed and transmitted through the second current collector plate 32. Consequently, when the contact area between the cap 16 and the side wall member 11 is heated with a laser, the side wall member 11 may heat up and melt first.

[0119] Therefore, if the side wall member 11 is too thin, it may melt before the cap 16, potentially hindering smooth welding. Consequently, the second thickness t2 of the side wall member 11 can be 0.25 mm or more. For example, the second thickness t2 can be 0.35 mm.

[0120] Furthermore, it is important that the cap 16 has sufficient strength to withstand the pressure inside the can 10 when the internal pressure increases. If the cap 16 is too thin, excessive bulging will occur when the internal pressure of the can 10 is high, causing the cap 16 to bulge into a spherical surface profile, which will worsen the durability of the battery cells. To withstand such bulging deformation, it is important that the cap 16 has a certain thickness.

[0121] On the other hand, if the thickness of the cap 16 is too thick compared to the side wall member 11, only the side wall member 11 will melt first during laser welding, significantly reducing weldability. Also, the thicker the cap 16, the longer the axial length of the joining outer peripheral surface 171 of the cap 16 that is welded. To ensure the durability of the can 10, it is preferable that the entire axial section of the joining outer peripheral surface 171 of the cap 16 is welded.

[0122] Therefore, in this embodiment, a cap 16 is disclosed in which the third thickness t3 of the joint 17 to which the side wall member 11 is welded and the fourth thickness t4 of the cap body 160 that withstands bulging are made different. The thicker the fourth thickness t4, the higher the resistance to bulging, but the larger the space it occupies inside the can. In order to increase resistance to bulging while minimizing space occupancy and weight, it is preferable that the fourth thickness t4 be as small as possible within the range of required bulging resistance.

[0123] Ultimately, the fourth thickness t4 of the cap body 160, which makes up most of the cap 16, is preferably greater than the third thickness t3 in order to minimize deformation of the cap 16 due to the internal pressure of the can 10. Furthermore, the thickness dimension of the weld along the axial direction is minimized so that the weld W is reliably formed over the entire axial direction of the joint outer surface 171. This increases the strength of the cap 16 itself and also increases the joint strength of the cap 16 to the side wall member 11.

[0124] The ratio of the third thickness t3 to the fourth thickness t4 is preferably 0.4 to 0.8, and more preferably 0.5 to 0.75. If the ratio is less than the above range, the cap body 160 may become excessively thick without an increase in bulging resistance, and / or the strength of the weld may become insufficient. If the ratio exceeds the above range, the bulging resistance of the cap body 160 will become insufficient, and / or the joining outer peripheral surface 171 of the cap 16 will become difficult to weld along the entire axial direction.

[0125] According to the cap 16 of this embodiment, by positioning the radial position of the thickness reduction portion 161 as close as possible to the welding area, the area of ​​the cap body 160 that resists bulging can be maximized. Furthermore, by selecting the position of the thickness reduction portion 161 in this way, a guide function that aligns the center of the cap 16 by contacting the second current collector plate 32 can also be provided.

[0126] The third thickness t3 of the joint 17 of the cap 16 may be set to be greater than the second thickness t2 of the side wall member 11. The third thickness t3 may be between 1 and 2 times the second thickness t2. For example, when the second thickness t2 is 0.35 mm, the third thickness t3 may be 0.5 mm or in the range of 0.5 to 0.7 mm.

[0127] If the third thickness t3 exceeds twice the second thickness t2, there is a risk that the side wall member 11 will melt excessively before the cap 16 melts during the process of forming the weld. Also, if the third thickness t3 exceeds twice the second thickness t2, there is a risk that the weld will not be formed over the entire axial direction of the joining outer peripheral surface 171 of the cap 16.

[0128] If the third thickness t3 is less than one times the second thickness t2, that is, if the second thickness t2 is greater than the third thickness t3, it is difficult to ensure the strength of the peripheral portion of the cap 16, and it is also difficult to ensure sufficient dimensions for the side step of the inner diameter expansion portion 113 of the side wall member 11 without increasing the overall first thickness t1 of the side wall member 11.

[0129] The process of welding the cap 16 and the second current collector plate 32 to the open end of the side wall member 11 can be carried out in two stages. As a result, a battery cell according to one embodiment may have a first welded part W1 and a second welded part W2.

[0130] First, as shown in Figure 15, with the cap 16 inserted into the open end of the side wall member 11, tack welding may be performed to fix the position of the can 10 relative to the side wall member 11, as shown in Figures 16 and 17. Preferably, the tack welding process can form first welds W1 at multiple locations spaced apart along the outer circumference direction of the joining outer circumferential surface 171 of the cap 16 and the second inner circumferential surface 115 of the side wall member 11.

[0131] The first welded joint W1 may be a portion where the side wall member 11, the cap 16, and the second current collector plate 32 are melted and joined together. In other words, unlike the general tack welding-main welding process, the tack welding process in one embodiment not only temporarily fixes the position of the cap 16 before main welding, but also welds the cap 16, the side wall member 11, and the second current collector plate 32 all at once during the tack welding process. This has the effect of eliminating the need to separately weld the second current collector plate 32 to the side wall member 11 before the cap 16 covers the open end of the side wall member 11.

[0132] The first welded joints W1 may be arranged at equal intervals along the outer circumference.

[0133] Before the main welding, in order to securely fix the position of the cap 16 relative to the side wall member 11, and to ensure a sufficient cross-sectional area for joining the second current collector plate 32 to the can 10 to reduce internal resistance, three or more first welds W1 may be provided. Preferably, four first welds W1 may be provided.

[0134] The first weld W1 may be formed using a spot welding method, similar to conventional tack welding, where the laser is directed to a single point without scanning.

[0135] However, in one embodiment, in order to ensure that not only the side wall member 11 and the cap 16 are melted, but also the can connecting portion 324 of the second current collector plate 32 is melted and joined, the first welded portion W1 is formed by a scan welding method in which a laser is scanned along the outer circumference for a predetermined distance and then welded.

[0136] The laser scan distance for forming the first weld W1 may be between 0.5 mm and 5 mm. Preferably, the scan distance may be 4 mm. If the scan distance is less than 0.5 mm, it is difficult to guarantee reliable melting of the second current collector plate 32. On the other hand, if the scan distance is greater than 5 mm, excessive welding heat may be generated, potentially damaging the separation film 28 of the electrode assembly 20 due to the heat.

[0137] In other words, the first weld W1 of one embodiment can be formed in the tack welding process by increasing the laser output and performing scan welding, unlike general tack welding which involves spot welding.

[0138] The output of such lasers can be adjusted by changing the focal length of the laser to control the size of the irradiated area. For example, even if the output of the laser oscillator is the same, if the area of ​​the irradiated area is small, the output per unit area will be higher and the energy density will be higher. Conversely, if the area of ​​the irradiated area is large, the output per unit area will be lower and the energy density will be lower.

[0139] For example, the first weld can be formed by narrowing the irradiated area and applying a high energy density (output per unit area).

[0140] By setting the laser scanning speed for forming the first weld W1 to be relatively fast, it is possible to prevent high heat from concentrating at specific points and damaging the separation membrane, etc.

[0141] This allows for triple welding by melting and joining the cap 16 to the side wall member 11, as well as the second current collector plate 32, while simultaneously reducing internal resistance and minimizing heat generation due to triple welding, thereby preventing damage to the electrode assembly 20.

[0142] Next, as shown in Figures 18 to 20, main welding may be performed to seam weld the second inner circumferential surface 115 of the side wall member 11 and the joining outer circumferential surface 171 of the cap 16. This main welding step may be a step in which the second inner circumferential surface 115 of the side wall member 11 and the joining outer circumferential surface 171 of the cap 16 are reliably welded over the entire outer circumference to form a second welded joint W2 that seals the can 10.

[0143] The second weld W2 can be formed by using a laser with a lower output than the laser used to weld the first weld W1. For example, the second weld can be formed by widening the irradiated area and applying a relatively lower energy density (output per unit area).

[0144] By setting the laser scan speed for forming the second weld W2 to a relatively slow setting, a weld pool can be formed stably. Even with a slow scan speed, the heat generated when forming the second weld W2 is dispersed through the second current collector plate 32, which is made of a highly thermally conductive material, thus reducing the likelihood of problems such as damage to the separation membrane.

[0145] The laser output and scanning speed for forming the second weld W2 can be determined to such an extent that at least the entire axial section of the joining outer surface 171 of the cap 16 is joined to the second inner surface 115 of the side wall member 11. This allows for additional joining of the second current collector plate 32 to the can 10, as even if some additional welding heat is generated, this heat can also melt and join a portion of the second current collector plate 32. Furthermore, since the amount of welding heat generated is significantly less compared to when forming the first weld W1, damage to the electrode assembly 20 can be reliably prevented.

[0146] The second weld W2 may be formed continuously along the outer circumference. This allows the second weld W2 to be formed superimposed on the first weld W1 in sections where the first weld W1 has already been formed, as shown in Figure 20. This allows the shape of the first weld W1 to be matched with that of the second weld W2, providing an overall appearance similar to that of a single weld. As shown in Figure 20, the depth (i.e., distance) of the first weld W1 extending axially away from the first end or upper end 30 of the can 10 may be greater than the depth / distance of the second weld W2 extending away from the first end or upper end 30 of the can 10. Also, as shown in Figure 20, the cross-sectional area of ​​the first weld W1 may differ from that of the second weld W2, particularly along the same cross-section as shown. In Figure 20, the plane defining the cross-section extends perpendicular to the circumferential direction at the point where it intersects with the weld (first weld W1 or second weld W2). Such planes extend parallel to the central longitudinal axis.

[0147] Hereinafter, other embodiments of the battery cell welding structure will be described with reference to Figures 21 to 26. In describing the other embodiments, in order to avoid redundant explanations, the differences from the embodiment described above will be mainly described. Therefore, matters not described in the other embodiments can be fully understood through the description of the embodiment described above, and each component of these embodiments can be substituted or omitted as long as they do not depart from the spirit of the invention.

[0148] Referring to Figures 21 and 22, the cap 16 of the other embodiment has a slightly smaller outer diameter of the joining outer peripheral surface 171 of the cap 16 compared to the cap 16 of the first embodiment. As a result, a small radial gap G exists between the second inner peripheral surface 115 of the side wall member 11 and the joining outer peripheral surface 171 of the cap 16.

[0149] Such a gap G provides a path through which the laser for welding can directly reach the second current collector plate 32. Therefore, even with a lower laser output than in the embodiment described above, it is possible to form the first weld W1 where triple welding is performed and the second weld W2 where seam welding is performed.

[0150] Even if the gap G exists throughout the outer circumference, the second bent portion 328 of the second current collector plate 32 and the thickness reduction portion 161 of the cap 16 are in contact and guide the center alignment of the cap 16, so the width of the gap G can be provided uniformly throughout the outer circumference.

[0151] On the other hand, the side wall member 11 of other embodiments may extend longer than the side wall member 11 of one embodiment. As a result, as shown in Figures 21 and 22, with the second current collector plate 32 and the cap 16 inserted, the open end of the side wall member 11 is provided with an overhang portion 117 that protrudes further axially outward than the cap 16. The overhang portion 117 may also be referred to as the extended portion of the side wall member 11.

[0152] In the side wall member 11, the first height h1 of the section located axially outward from the inner diameter expansion portion 113 is greater than the sum of the third thickness t3 of the joint portion 17 of the cap 16 and the fifth thickness t5 of the can connecting portion 324 of the second current collector plate 32. The second height h2 of the overhang portion 117 or the extended portion of the side wall member may be the length obtained by subtracting the third thickness t3 and the fifth thickness t5 from the first height h1.

[0153] The overhang portion 117 delays the melting point of the relatively thin sidewall member 11, reducing the difference in melting points between the sidewall member 11 and the cap 16, and can be melted into the weld area between the second inner surface 115 of the sidewall member 11 and the joining outer surface 171 of the cap 16 during the welding process.

[0154] Therefore, the diameter of the joining outer circumferential surface 171 of the cap 16 can be slightly smaller than the diameter of the second inner circumferential surface 115 of the side wall member 11 adjacent to the joining outer circumferential surface 171. Here, the concept of two objects being "adjacent" means that the two objects are spaced relatively close to each other relative to their external dimensions, and that there are no other intervening objects between the two objects in the related plane (i.e., the radial plane perpendicular to the central longitudinal axis). Because the diameter of the joining outer circumferential surface 171 of the cap 16 is slightly smaller than the diameter of the second inner circumferential surface 115 of the side wall member 11, a small gap is defined between these two components.

[0155] Such gaps can serve as passages through which the welding laser can be directly irradiated onto the second current collector plate 32.

[0156] Preferably, such a gap may have a uniform radial width along the circumference of the cap 16, as described above, by aligning the center of the cap 16 through interaction between at least the thickness reduction portion 161 of the cap 16 and the second current collector plate 32.

[0157] Furthermore, during the welding process, it is preferable that the material of the overhang portion 117 melts into the gap between the joining outer peripheral surface 171 of the cap 16 and the second inner peripheral surface 115 of the side wall member 11, thereby joining the cap 16 and the side wall member 11.

[0158] For example, the height of the overhang portion 117 (second height h2) is 0.2 mm, and the thickness of the joint portion 17 of the cap 16 (third thickness t3) is 0.5 mm. If the thickness of the overhang portion 117 (second thickness t2) is 0.35 mm, sufficient molten material is provided during the welding process, and the cap 16 and the side wall member 11 can be strongly joined. For example, the ratio of the height of the overhang portion (second height h2) to the thickness of the joint portion 17 (third thickness t3) may preferably be in the range of 0.2 to 1.

[0159] Referring to Figure 23, the first welded joint W1 is formed by intermittently welding the second inner circumferential surface 115 portion of the side wall member 11, the joining outer circumferential surface 171 portion of the cap 16, and the can connecting portion 324 portion of the second current collector plate 32 together along the outer circumference.

[0160] In the section where the first weld W1 is formed, the overhang portion 117 may completely melt and melt into the contact area between the second inner circumferential surface 115 portion of the side wall member 11, the joining outer circumferential surface 171 portion of the cap 16, and the can connecting portion 324 portion of the second current collector plate 32, so as shown in Figure 25, that it fills at least the gap G.

[0161] Next, referring to Figure 24, the second weld W2 is formed by melting at least the second inner circumferential surface 115 portion of the side wall member 11 and the joining outer circumferential surface 171 portion of the cap 16 over its entire outer circumference.

[0162] When the second weld W2 is formed, the overhang portion 117 may completely melt and be incorporated into the contact area between the second inner surface 115 portion of the side wall member 11 and the joining outer surface 171 portion of the cap 16, and into the gap G, as shown in Figure 26. As a result, the height of the battery cell can be defined by the outer surface of the cap 16. In other words, according to another embodiment, the overhang portion 117 and the weld do not restrict the height of the battery cell, and as a result, the height dimension of the battery cell can be controlled to be constant.

[0163] Further embodiments of the battery cell welding structure will be described below with reference to Figures 27 and 28. In describing these further embodiments, in order to avoid repetition, the differences from the embodiments described above will be the main focus. Therefore, matters not described in these further embodiments can be fully understood through the descriptions of the embodiments described above, and each component of these embodiments can be substituted or omitted as long as it does not depart from the spirit of the invention.

[0164] Referring to Figure 27, in yet another embodiment, the joining outer peripheral surface 171 of the cap 16 may have alternating large-diameter sections 171a and small-diameter sections 171b with a smaller diameter than the large-diameter sections 171a in the outer peripheral direction.

[0165] As a result, as shown in Figure 28, the large-diameter section 171a of the joint outer peripheral surface 171 can face and contact the second inner peripheral surface 115 of the side wall member 11 in the radial direction, while the small-diameter section 171b can face the second inner peripheral surface 115 of the side wall member 11 with a gap G between them in the radial direction.

[0166] In other words, the outer diameter of the joining outer peripheral surface 171 of the cap 16 is arranged alternately in the outer peripheral direction between sections corresponding to the outer diameter of the contact outer peripheral surface 325 of the second current collector plate 32 and sections smaller than the outer diameter of the contact outer peripheral surface 325 of the second current collector plate 32.

[0167] The large-diameter section 171a aligns the center position of the cap 16 with respect to the side wall member 11 during the insertion process and while the cap 16 is inserted. The small-diameter section 171b has a gap G with respect to the side wall member 11. In other words, if the cap 16 is manufactured as in another embodiment, it is easier to align the center of the cap 16, and welding is possible even with a relatively low-power laser compared to one embodiment.

[0168] Furthermore, when forming the first weld W1, if the first weld W1 is formed in the gap G region where the small-diameter section 171b is formed, triple welding can be performed even with a lower-power laser, and the amount of heat generated by triple welding can be suppressed.

[0169] According to the embodiment described above, the generation of welding heat can be minimized even while performing triple welding including the second current collector plate, there is no increase in man-hours by performing triple welding during the tack welding process, internal resistance can be sufficiently reduced, and seam welding can be reliably performed as the main welding with the cap position precisely fixed by tack welding. As a result, sealing force can be ensured without perforation or leakage despite the wide welding area, improving weldability, preventing thermal damage to cell components and separation membranes due to welding heat, improving process stability, and suppressing dimensional deformation due to internal pressure to ensure dimensional stability and bulging resistance, thereby improving durability.

[0170] An example of the battery cell manufacturing method described above will be explained below with reference to Figure 29.

[0171] According to the battery cell manufacturing method, first, a can 10 is prepared with a first electrode terminal 13 fixed to a bottom member 12, and an electrode assembly 20 is prepared by joining a first current collector plate 31 and a second current collector plate 32 to both ends in the axial direction, respectively.

[0172] Then, the electrode assembly 20 is inserted and housed in the can 10 so that the first current collector plate 31 faces the bottom member 12. As a result, the second current collector plate 32 is positioned on the open end side of the can 10. In this process of housing the electrode assembly 20 in the can 10, the contact outer peripheral surface 325 of the can connecting portion 324 provided at the radial outer end of the second current collector plate 32 is brought into contact with the second inner peripheral surface 115 of the side wall member 11.

[0173] At this time, the can-connecting portion 324 of the second current collector plate 32 is brought into contact with the inner diameter expansion portion 113 of the side wall member 11, thereby ensuring the adhesion force of the second current collector plate 32 to the inner surface of the side wall member 11 and regulating the insertion depth of the second current collector plate 32.

[0174] Next, the first current collector plate 31 and the first electrode terminal 13 are joined together.

[0175] Then, pour the electrolyte into can 10.

[0176] After the electrolyte injection is complete, the open end of the side wall member 11 is covered with the cap 16, and the joining outer peripheral surface 171 and the current collector plate contact surface 173 provided on the periphery of the cap 16 are brought to face or in contact with the second inner peripheral surface 115 of the side wall member 11 and the cap contact surface 326 of the second current collector plate 32, respectively.

[0177] At this time, the center of the cap 16 can be aligned by bringing the inclined thickness reduction portion 161 provided on the axial inner surface of the cap 16 into contact with the second current collector plate 32.

[0178] Next, a laser is irradiated from the outside in the axial direction of the battery cell to the contact area between the second inner circumferential surface 115 of the side wall member 11 and the joining outer circumferential surface 171 of the cap 16, thereby welding.

[0179] During the welding process, the overhang portion 117 of the side wall member 11, which protrudes further outward in the axial direction than the cap 16, can be melted into the weld area between the inner surface of the side wall member 11 and the joining outer peripheral surface 171 of the cap 16.

[0180] During welding, a tack welding process is performed first, followed by the final welding.

[0181] In the tack welding process, a laser is irradiated from the outside in the axial direction to the contact area between the inner surface of the side wall member 11 and the joining outer surface 171 of the cap 16 at multiple locations spaced apart along the outer circumference, forming first welds W1 at multiple locations where the inner surface of the side wall member 11, the joining outer surface 171 of the cap 16, and the can connecting portion 324 of the second current collector plate 32 are welded together.

[0182] The laser used in the tack welding process scans and irradiates a predetermined section at a first output intensity or a first density energy density and a first velocity.

[0183] Next, in this welding process, a laser is continuously irradiated in the axial direction from the outside in the axial direction to the contact area between the inner surface of the side wall member 11 and the joining outer surface 171 of the cap 16, thereby forming a second welded joint W2 in which at least the inner surface of the side wall member 11 and the joining outer surface 171 of the cap 16 are welded together.

[0184] The laser used in this welding process may have a second power intensity lower than the first power intensity, or an energy density lower than the first density.

[0185] The laser used in this welding process scans along the entire outer circumference at a second speed, which is slower than the first speed.

[0186] While tack welding only requires the formation of a joint for electrical connection, main welding requires sealing, and thus allows for the formation of a uniform weld pool to ensure stability. As a result, the second velocity relative to the second laser output in the main welding process may be slower than the first velocity relative to the first laser output in the tack welding process.

[0187] The following describes another example of the battery cell manufacturing method described above, with reference to Figure 30. This is a battery cell manufacturing method that uses a cap with an electrolyte injection port, and differs from Figure 29 described above in that the order is different in that the tack welding of the side wall member, the cap and the second current collector plate and the final welding of the side wall member and the cap are performed first before the electrolyte is injected into the can, and after the electrolyte is injected into the electrolyte injection port of the cap, the injection port is sealed with a stopper.

[0188] According to this method, the cap is welded to the can before the electrolyte is poured into the can, so the welding heat does not affect the electrolyte.

[0189] The battery cells 72 produced through the welded structure and welding process described above can be housed in the housing 71 of the battery pack 70, as shown in Figure 31. The battery pack 70 may be constructed using battery modules, which are an intermediate form of assembly, or the battery pack 70 may be constructed directly without battery modules, as shown.

[0190] Because the aforementioned battery cell 72 has a large volume, the battery pack 70 can be easily realized 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 battery pack 70 equipped with the battery cell 72 can achieve an even higher energy density.

[0191] By increasing the energy density in this way, the battery pack 70 can reduce its volume and weight while storing the same amount of energy. Therefore, if a battery pack 70 incorporating such battery cells 72 is installed in a vehicle such as the electric vehicle 80 shown in Figure 32, the vehicle's driving range relative to its energy can be further expanded.

[0192] While the seam welding structures and methods described above are disclosed in relation to cylindrical battery cans, it should be understood that within the scope of this disclosure, such techniques can be similarly applied to other battery form factors. For example, the relevant battery cells do not need to have a circular cross-sectional profile perpendicular to the central longitudinal axis, and may use other cross-sectional shapes, including elliptical, square, rectangular, and partially circular shapes. Furthermore, the longitudinal axis does not need to be oriented perpendicular to the bottom member and / or the caps at each end. For example, the side wall members of the can (along with the internal components of the can) may form tubes extending along axes oriented obliquely to the plane defined by the bottom member and / or caps. Also, the welding techniques disclosed herein can be used outside the scope of cylindrical battery cans and can be applied to batteries having, for example, rectangular and pouch-type form factors.

[0193] It should be understood that the embodiments described above are illustrative in all respects and not limiting. The scope of the present invention is indicated more by the claims described below than by the detailed description above. Furthermore, the meaning and scope of the claims described below, as well as all modifiable forms derived from their equivalent concepts, are to be interpreted as being included within the scope of the present invention.

[0194] As described above, the present invention has been explained with reference to the embodiments and drawings, but it is obvious that the present invention is not limited to the embodiments and drawings disclosed herein, and that various modifications are possible by an ordinary person within the scope of the technical concept of the present invention. Furthermore, it goes without saying that even if the effects of the configuration of the present invention are not explicitly stated in the description of the embodiments of the present invention, the effects that can be predicted by such configuration should also be recognized. [Explanation of Symbols]

[0195] 10: Can, 11: Side wall member, 111: First inner surface, 113: Inner diameter expansion section, 115: Second inner surface, 117: Overhang section, 12: Bottom member, 13: First electrode terminal, 14: Gasket, 15: Second electrode terminal, 16: Cap, 160: Cap body, 161: Thickness reduction section, 17: Joint section, 171: Joint outer surface, 171a: Large diameter section, 171b: Small diameter section, 173: Current collector plate contact surface, 18: Liquid injection port, 19: Insulator, 20: Electrode assembly, 21: First electrode (positive electrode), 22: Second electrode (negative electrode), 23: Metal foil, 24: Active material layer, 25: Surfaced section, 26: Unskinned section Ground part, 27: Electrode tab (notching tab), 28: Separation membrane, 31: First current collector plate (positive electrode current collector plate), 312: Terminal connection part, 313: Ring part, 314: Electrode connection part, 32: Second current collector plate (negative electrode current collector plate), t5: Fifth thickness, 321: Inner ring part, 322: Hole, 323: Electrode tab connection part, 324: Can connection part, 325: Contact outer peripheral surface, 326: Cap contact surface, 327: First bend part, 328: Second bend part, 40: Stopper, G: Gap, R: Roll electrode, W1: First weld part, W2: Second weld part, 70: Battery pack, 71: Housing, 72: Battery cell, 80: Automobile

Claims

1. A can having side walls that surround the internal space and define an opening to the internal space at a first end along the central longitudinal axis, An electrode assembly housed in the internal space of the can, A current collector plate electrically connected to the electrodes of the electrode assembly, Includes a cap that covers the opening of the can so as to surround the internal space, The current collector plate has a peripheral edge that contacts the side wall so as to be electrically connected to the can, A battery cell in which the side wall along the opening, the periphery of the cap, and the periphery of the current collector plate are welded together along each of a plurality of first welds, the plurality of first welds being spaced apart from each other along the outer circumference with respect to the central longitudinal axis, and the side wall along the opening and the periphery of the cap are welded together along a second weld that extends substantially continuously along the entire outer circumference with respect to the central longitudinal axis.

2. The battery cell according to claim 1, wherein at least a portion of the second weld overlaps with the plurality of first welds.

3. The battery cell according to claim 1, wherein the cross-section of each of the plurality of first welds defined by each plane extending perpendicular to the outer circumference is wider than the cross-section of the second weld defined by each of the planes.

4. The battery cell according to claim 1, wherein the depth of the plurality of first welds extending in an axial direction parallel to the central longitudinal axis, such that they are further away from the first end of the can in the axial direction, is greater than the depth of the second welds extending in an axial direction further away from the first end of the can in the axial direction.

5. The battery cell according to any one of claims 1 to 4, wherein the outer diameter of the peripheral edge of the current collector plate corresponds to the outer diameter of the radial outer surface of the cap.

6. The battery cell according to any one of claims 1 to 4, wherein the periphery of the cap has a bonding outer surface that faces and contacts the radial inner surface of the side wall in the radial direction.

7. The battery cell according to any one of claims 1 to 4, wherein the outer diameter of the peripheral edge of the current collector plate is larger than the outer diameter of the radial outer surface of the peripheral edge of the cap.

8. The battery cell according to any one of claims 1 to 4, wherein the periphery of the cap has a joining outer surface that faces radially with a gap from the inner surface of the side wall.

9. The battery cell according to claim 8, wherein the welding area extends within the gap between the radial outer surface of the periphery of the cap and the radial inner surface of the side wall.

10. The battery cell according to any one of claims 1 to 4, wherein the periphery of the cap has a radial outer surface facing the radial inner surface of the side wall, at least a first portion of the radial outer surface of the periphery of the cap has a first diameter corresponding to the outer diameter of the periphery of the current collector plate, and at least a second portion of the radial outer surface of the periphery of the cap has a second diameter smaller than the outer diameter of the periphery of the current collector plate.

11. The battery cell according to claim 10, wherein the radial outer surface of the periphery of the cap comprises two or more first portions and two or more second portions arranged alternately along the outer circumference with respect to the central longitudinal axis.

12. The battery cell according to any one of claims 1 to 4, wherein the periphery of the cap has a radial outer surface facing the radial inner surface of the side wall, and the radial outer surface has a plurality of large-diameter portions and a plurality of small-diameter portions that are alternately arranged in the outer peripheral direction with respect to the central longitudinal axis, and the plurality of small-diameter portions have a smaller diameter than the plurality of large-diameter portions.

13. The battery cell according to claim 12, wherein the large-diameter portion of the radial outer surface of the periphery of the cap is in contact with the radial inner surface of the side wall, and the small-diameter portion of the radial outer surface of the periphery of the cap is separated from the radial inner surface of the side wall.

14. A step of positioning the cap and the current collector plate at assembly positions where they are stacked on top of each other within the opening of the can, wherein at the assembly positions, the current collector plate is electrically connected to an electrode assembly housed in the internal space of the can, the peripheral edge of the current collector plate contacts the radial inner surface of the side wall of the can surrounding the opening, and the cap is positioned on the current collector plate along the longitudinal axis of the center of the can such that it is positioned further away from the electrode assembly than the current collector plate; A step of forming a plurality of first welds such that the side wall of the can along the opening, the periphery of the cap, and the periphery of the current collector plate are welded together to maintain their relative positions, wherein the plurality of first welds are formed to be spaced apart from each other along the outer circumference direction with respect to the central longitudinal axis, A method for manufacturing a battery cell, comprising the step of forming a second weld such that the side wall of the can and the periphery of the cap are welded together along the opening, the second weld extending substantially continuously along the entire outer circumference with respect to the central longitudinal axis so as to seal the opening of the can.

15. The method for manufacturing a battery cell according to claim 14, wherein the step of forming the plurality of first welds includes irradiating a laser between the radial inner surface of the side wall and the radial outer surface of the periphery of the cap.

16. The method for manufacturing a battery cell according to claim 15, wherein the step of forming the second welded portion includes continuously irradiating the radial inner surface of the side wall and the radial outer surface of the periphery of the cap with a laser.

17. The method for manufacturing a battery cell according to claim 16, wherein the output power or energy density of the laser irradiated when forming the plurality of first welds is higher than the output power or energy density of the laser irradiated when forming the second weld.

18. The method for manufacturing a battery cell according to claim 16 or 17, wherein the speed at which the laser moves along the outer peripheral direction when forming the plurality of first welds is faster than the speed at which the laser moves along the outer peripheral direction when forming the second weld.

19. The method for manufacturing a battery cell according to claim 14 or 15, wherein the step of forming the second welded portion includes resistance welding using a roller electrode.

20. A method for manufacturing a battery cell according to any one of claims 14 to 17, wherein the formation of the plurality of first welds and the second welds includes melting the material of the extended portion of the side wall that protrudes above the cap along an axial direction parallel to the central longitudinal axis, and allowing the material to melt between the radial inner surface of the side wall and the radial outer surface of the periphery of the cap.

Images