Welded structure of battery can, current collector plate, and cap, and battery cell using the same

Abstract

A battery cell according to an embodiment of the present invention includes a can having an electrode assembly housed therein, and a cap. The can includes a bottom member and a sidewall member connected to the bottom member and extending axially upward. The cap covers an open end of the can, which is provided at an axially opposite end of the bottom member. A current collector plate is connected to an electrode tab of the electrode assembly near the open end. The current collector plate has a central portion electrically connected to the electrode tab and a peripheral portion electrically connected to a radially inner surface of the sidewall of the can. The peripheral portion also contacts the bottom surface of the cap. The radially inner surface of the sidewall member, the radially outer surface of the cap, and the peripheral portion of the current collector plate are all welded to each other.

Description

[Technical Field]

[0001] This application claims priority based on Korean Patent Application No. 10-2023-0059345 filed on May 8, 2023, and Korean Patent Application No. 10-2023-0135319 filed on October 11, 2023, and the contents disclosed in the specifications and drawings of said applications are incorporated herein in their entirety.

[0002] The present invention relates to the field of batteries, and more particularly to 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. [Background technology]

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

[0004] Meanwhile, a current collecting plate is provided at one of both axial ends of the electrode assembly opposite the open end, and is in contact with and electrically connected to at least one electrode tab of the electrode assembly. The current collecting plate is connected to the cap or the side wall member by welding or the like so as to be in contact with and electrically connected to the cap or the side wall member.

[0005] In the process of welding the current collecting plate to the cap or the side wall member, the current collecting plate maintains a state of close contact with the cap or the side wall member, so a jig is required to closely contact the current collecting plate and the cap or the current collecting plate and the side wall member, and a mask may also be required to expose the welding area.

[0006] Since the current collector plate is tightly attached to the cap and sidewall member using the mask and jig, a space is provided inside the can to accommodate the mask and jig. However, this space remains empty after the mask and jig are removed, resulting in inefficient use of the internal volume of the can. This is a factor that hinders designs that increase the energy density per unit volume of the can.

[0007] In addition, when sealing the open end of the cylindrical can, a process of connecting the current collector plate to the cap or the sidewall member and a process of connecting the cap to the sidewall member are performed separately. Such an increase in the number of steps required for assembling the battery cell reduces production efficiency of cylindrical battery cells and increases production costs. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been invented to solve the above-mentioned problems, and an object of the present invention is to provide a welding structure between a battery can, a current collector plate, and a cap, which enables a design that increases the energy density per unit volume of the can without wasting or sacrificing the internal space of the can in the process of welding a current collector plate provided on the open end side of the can to the can by eliminating the need for a separate welding mask or jig, and a battery cell using the welding structure.

[0009] Additionally or alternatively, the present invention aims to improve production efficiency and reduce production costs of cylindrical battery cells 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.

[0010] Additionally or alternatively, the present invention aims to improve process stability by providing the can, current collector plate, and cap with mask and jig functions.

[0011] Another object of the present invention is to provide shapes of a can, a current collecting plate, and a cap, as well as an engagement relationship between the can, the current collecting plate, and the cap, that ensure weldability, increase process stability, and guarantee the durability of the weld.

[0012] The technical object of the present invention is not limited to the above-mentioned object, and other objects and advantages can be understood from the following description and can be more clearly understood by the embodiments of the present invention. [Means for solving the problem]

[0013] According to one aspect of the present invention, there is provided a battery cell, the battery cell including an electrode assembly, a current collector plate, and a can.

[0014] The can may include a sidewall member (sidewall) surrounding the interior space and extending along a central longitudinal axis thereof, the sidewall member defining an opening to the interior space of the can at the first longitudinal end.

[0015] The electrode assembly may be housed in the interior space of the can.

[0016] The opening of the can may be closed by a cap.

[0017] The cap may cover the opening of the can to enclose the interior space.

[0018] The current collector may be electrically connected to the electrode assembly.

[0019] The current collector plate may include a central portion and a peripheral portion, the peripheral portion being positioned around the central portion and being disposed farther away from the central longitudinal axis than the central portion.

[0020] The central portion may be electrically connected to an electrode tab of the electrode assembly.

[0021] The peripheral edge may contact the radially inner surface of the sidewall member to electrically connect with the can.

[0022] The peripheral edge may be in contact with a bottom surface of the cap, and the bottom surface of the cap may be arranged to face the interior space of the can in the longitudinal direction of the axis.

[0023] Preferably, the radially inner surface of the side wall member, the radially outer surface of the cap, and the peripheral edge of the current collector plate are welded to one another.

[0024] According to one embodiment of the battery cell, the radially inner surface of the sidewall member may include a side step extending in a direction transverse to the longitudinal direction of the axis.

[0025] A first inner surface of the sidewall member located on a first side of the side step in the longitudinal direction of the axis may have a first diameter. A second inner surface of the sidewall member located on a second side of the side step in the longitudinal direction of the axis may have a second diameter. The second side may be located closer to the open end of the can than the first side. The second diameter may be larger than the first diameter.

[0026] The radially outer surface of the cap and the peripheral edge of the current collector plate may contact the second inner surface.

[0027] According to one aspect of the battery cell, an outer diameter of a peripheral edge portion of the current collector plate may be larger than a first diameter of a first inner surface of the sidewall member of the can.

[0028] According to one aspect of the battery cell, a peripheral edge of the current collector plate may be in contact with the side step.

[0029] According to another aspect of the battery cell, the side step may be defined by a slope extending from a first diameter of the first inner surface to a second diameter of the second inner surface.

[0030] According to another aspect of the battery cell, a first thickness of the cap measured in the longitudinal direction of the axis along a radial outer surface of the cap may be greater than a second thickness of the sidewall member measured in a radial direction perpendicular to the longitudinal direction of the axis along a second inner surface of the sidewall member.

[0031] In an additional embodiment, the first thickness may be at least one to two times thicker than the second thickness.

[0032] According to one aspect of the battery cell, a diameter of the radially outer surface of the cap may be smaller than a diameter of an adjacent portion of the radially inner surface of the adjacent sidewall member, and a weld region may extend from the adjacent portion of the radially inner surface of the sidewall member to the radially outer surface of the cap.

[0033] According to one aspect of the battery cell, the cap may include an annular region extending along a radially outer surface thereof, and a thickness of the annular region of the cap along the axial longitudinal direction may be less than a thickness of a central region of the cap located along a central longitudinal axis.

[0034] In one form, a bevel along the bottom surface of the cap may connect the annular region and the central region.

[0035] In one embodiment, the beveled surface may contact the current collector plate.

[0036] According to one aspect of the battery cell, the current collector plate may include an axial step between the central portion and the peripheral portion, and the peripheral portion may be offset relative to the central portion toward the open end of the can.

[0037] According to one aspect of the battery cell, the longitudinal dimension of the central portion of the current collector plate extends transverse to the axial direction, and the longitudinal dimension of the peripheral portion of the current collector plate extends parallel to the axial direction. Thus, the peripheral portion may extend along the radially inner surface of the can sidewall member to a peripheral tip portion that contacts the bottom surface of the cap.

[0038] According to another aspect of the present invention, a method for manufacturing a battery cell is provided.

[0039] The method may include positioning a cap and a current collector plate in a stacked assembly position within the opening of the can, where the current collector plate may be electrically connected to an electrode assembly contained within the interior space of the can.

[0040] Furthermore, in such an assembled position, the peripheral edge of the current collector plate may contact the radially inner surface of the sidewall member surrounding the opening of the can.

[0041] Furthermore, in such an assembled position, the cap may be positioned on the current collector plate along the central longitudinal axis of the can, and may be positioned farther from the electrode assembly than the current collector plate.

[0042] Preferably, the method includes welding together the radially inner surface of the side wall member, the radially outer surface of the cap, and the peripheral edge of the current collector plate.

[0043] According to one aspect of the method, positioning the cap and the current collector plate in an assembled position may include contacting a peripheral edge of the current collector plate with a side step defined in a radially inner surface of the side wall member of the can.

[0044] According to one form of the method, positioning the cap and the current collector plate in an assembled position may include contacting a beveled surface located along a bottom surface of the cap with an annular portion of the current collector plate extending along a peripheral edge thereof.

[0045] According to one aspect of the method, welding the radially inner surface of the sidewall member of the can may include melting material of the extension of the sidewall member that projects upwardly of the cap along an axial direction extending parallel to the central longitudinal axis, such that material of the extension flows between the radially inner surface of the sidewall member and the radially outer surface of the cap, bonding the radially inner surface of the sidewall member and the radially outer surface of the cap.

[0046] According to one aspect of the method, welding the radially inner surface of the sidewall member may include tack welds at a plurality of discrete locations spaced circumferentially along the sidewall member about a central longitudinal axis.

[0047] The method may further include performing a continuous weld along the sidewall member to form a weld that substantially circumferentially surrounds the cap.

[0048] According to one aspect of the method, the step of positioning the cap and the current collector plate in the assembly position may include inserting the electrode assembly to which the current collector plate is joined into an internal space of a can.

[0049] According to a further aspect, the step of positioning the cap and the current collecting plate in the assembly position may further include inserting the cap into an opening of the can to contact the current collecting plate. Furthermore, after inserting the electrode assembly with the current collecting plate attached into the can, the cap may be inserted into the opening to contact the current collecting plate. [Effects of the Invention]

[0050] According to one aspect of the present invention, the side wall member, the cap, and the current collector plate can be welded together, improving welding performance.

[0051] Furthermore, since the side wall member, the cap, and the current collector plate can be welded together, process stability can be improved.

[0052] Furthermore, the durability of the welded portion between the side wall member and the cap can be ensured.

[0053] Additionally, by welding the sidewall members, caps, and current collector plates together as at least part of the same welding process, the number of steps and time required to assemble the battery cell can be significantly reduced. [Brief explanation of the drawings]

[0054] [Figure 1] FIG. 1 is a perspective view of a cylindrical battery cell according to one embodiment of the present invention. [Figure 2] 2 is an exploded perspective view of the electrode assembly housed inside the can of FIG. 1 before being wound up. FIG. [Figure 3] FIG. 3 is a perspective view of the electrode assembly of FIG. 2 in a stacked state before being wound up. [Figure 4] 4 is a perspective view of the laminate of FIG. 3 wound up to form a cylindrical jelly-roll type electrode assembly. FIG. [Figure 5] 5 is a perspective view showing a state in which a first current collecting plate is joined to an electrode tab of a first electrode of the electrode assembly of FIG. 4. FIG. [Figure 6] 5 is a perspective view showing a state in which a second current collecting plate is joined to an electrode tab of a second electrode of the electrode assembly of FIG. 4. FIG. [Figure 7] 10 is a cross-sectional view showing a process of placing an electrode assembly to which a current collector plate is joined inside a can. FIG. [Figure 8] 5A to 5C are cross-sectional views illustrating a process of joining a first current collector plate and a first electrode terminal of an electrode assembly housed in a can. [Figure 9] 10A and 10B are cross-sectional views showing a process of placing a cap to cover an open end of a can containing an electrode assembly. [Figure 10] 10 is an enlarged cross-sectional view showing an open end portion of a battery cell in which the open end of the can is covered with a cap. FIG. [Figure 11]11 is an enlarged view showing the side wall member, current collector plate, and cap to be welded in the battery cell of FIG. 10. FIG. [Figure 12] FIG. 12 is a view showing the state in which the side wall member, the current collecting plate, and the cap are welded together in FIG. [Figure 13] 12 is a cross-sectional enlarged photograph of the welded portion corresponding to FIG. 11. [Figure 14] 12 is an enlarged view of a side wall member, a current collector plate, and a cap corresponding to FIG. 11 in a battery cell according to another embodiment. FIG. [Figure 15] 1 is a diagram showing the position and magnitude of stress concentration that changes depending on the welding length on the outer peripheral surface of the cap. [Figure 16] FIG. 2 is a flow diagram of a manufacturing process for a battery cell according to one embodiment of the present invention. [Figure 17] 1 is a perspective view of a battery pack including a plurality of battery cells according to one embodiment of the present invention. [Figure 18] FIG. 18 is a diagram showing a car equipped with the battery pack of FIG. 17. DETAILED DESCRIPTION OF THE INVENTION

[0055] The above-mentioned objects, features, and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily implement the technical concept of the present invention. In the description of the present invention, if a detailed description of related known technology is deemed to 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 accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0056] Furthermore, although terms such as "first" and "second" 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.

[0057] Throughout the specification, unless otherwise stated, each element may be singular or plural.

[0058] Furthermore, when an arbitrary structure is placed on the "top (or bottom)" of a component or "above (or below)" a component, it does not only mean that the arbitrary structure is placed in contact with the top surface (or bottom surface) of the component, but also means that other structures may be interposed between the component and the arbitrary structure placed above (or below) the component.

[0059] Furthermore, when a component is said to be "coupled," "coupled," or "connected" to another component, this includes not only the cases where the components are directly coupled or connected to each other, but also the cases where other components are "interposed" between each component, or the cases where each component is "coupled," "coupled," or "connected" through other components.

[0060] As used herein, singular expressions include plural expressions unless the context clearly dictates otherwise.

[0061] Throughout the specification, unless otherwise specified, "A and / or B" means A, B, or A and B, and "C to D" means C or more and D or less, unless otherwise specified.

[0062] In the description of the embodiments, the axial direction refers to the direction along which the central longitudinal axis of the jelly roll electrode assembly extends, e.g., the direction parallel to the central longitudinal axis, the radial direction refers to the direction toward (centripetal) or away (centrifugal) from the axis, and the circumferential direction refers to the direction surrounding the axis.

[0063] Hereinafter, an embodiment of a battery cell to which the welding structure of the present invention is applied will be described in detail with reference to FIGS.

[0064] In one embodiment, the battery cell may be, for example, a cylindrical battery cell having a form factor ratio (defined as the diameter divided by the height of a cylindrical battery cell, i.e., the ratio of height (H) to diameter (Φ)) greater than about 0.4.

[0065] Here, the 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 form factor value, the first two digits indicate the diameter of the cell, the next two digits indicate the height of the cell, and the final digit 0 indicates that the cross section of the cell is circular.

[0066] The battery cell may be a cylindrical battery cell that is a substantially cylindrical cell, having a diameter of about 46 mm, a height of about 110 mm, and a form factor ratio of 0.418.

[0067] A battery cell according to another embodiment may be a cylindrical battery cell that is generally cylindrical, having a diameter of about 48 mm, a height of about 75 mm, and a form factor ratio of 0.640.

[0068] A battery cell according to yet another embodiment may be a cylindrical battery cell that is generally cylindrical, having a diameter of about 48 mm, a height of about 110 mm, and a form factor ratio of 0.418.

[0069] A battery cell according to yet another embodiment may be a cylindrical battery cell that is generally cylindrical, having a diameter of about 48 mm, a height of about 80 mm, and a form factor ratio of 0.600.

[0070] A battery cell according to yet another embodiment may be a cylindrical battery cell that is generally cylindrical, having a diameter of about 46 mm, a height of about 80 mm, and a form factor ratio of 0.575.

[0071] Of course, the present invention can also be applied to battery cells with a form factor ratio of approximately 0.4 or less, such as 18650 cells and 21700 cells. 18650 cells have a diameter of approximately 18 mm, a height of approximately 65 mm, and a form factor ratio of 0.277. 21700 cells have a diameter of approximately 21 mm, a height of approximately 70 mm, and a form factor ratio of 0.300.

[0072] 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.

[0073] 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.

[0074] The bottom member 12 may be in the form of a disk with a hole formed in the center, and the side wall member 11 may be in the form of a circular tube that surrounds the inner space of the can 10 .

[0075] The bottom member 12 and the side wall member 11 may be manufactured by forming a metal sheet, the surface of which is nickel-plated, using a deep drawing process, and then trimming the leading end 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.

[0076] A first electrode terminal 13 may be fitted into the hole. The first electrode terminal 13 may be riveted to the bottom member 12 with a gasket 14 interposed therebetween. 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.

[0077] However, the method of connecting the first electrode terminal 13 and the bottom member 12 is not limited thereto. For example, as long as the first electrode terminal 13 and the bottom member 12 can be sealed and electrically insulated from each other, various other fixing methods, such as i) a bolt and nut connection method, ii) a glass seal method, or iii) a chrome coating and PP-MAH thermal bonding method, may also be used.

[0078] The first electrode terminal 13 may have 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 connected to the side wall member 11 (described later) may all have the second polarity.

[0079] As a result, the first electrode terminal 13 and the second electrode terminal 15 of the battery cell may all be disposed at the axial end, i.e., the closed end, where the bottom member 12 is provided. Then, the bus bar connected to the first electrode terminal 13 and the bus bar connected to the second electrode terminal 15 of the battery cell may all be located on one side (top) of the battery cell.

[0080] For example, the first electrode terminal 13 may be a positive terminal and the second electrode terminal 15 may be a negative terminal, or vice versa.

[0081] An electrode assembly 20 is accommodated inside the can 10. The electrode assembly 20 is manufactured by preparing a first electrode 21, a second electrode 22, and a separator 28 that are longitudinally extended and have a predetermined width as shown in Fig. 2, stacking the first electrode 21, the separator 28, the second electrode 22, and the separator 28 in this order as shown in Fig. 3, and then winding the stack around a core shaft to form a jelly roll as shown in Fig. 4.

[0082] The first electrode 21 may be a positive electrode and the second electrode 22 may be a negative electrode, or vice versa.

[0083] The first electrode 21 and the second electrode 22 are fabricated in a sheet shape. The electrode sheets are fabricated by coating an active material layer 24 on the surface of a metal foil 23. The electrode sheets have a coated region 25 where the active material layer 24 is coated and an uncoated region 26 where the active material layer 24 is not coated. The uncoated region 26 is provided on one side of the positive electrode sheet in the width direction, and the uncoated region 26 is provided on the other side of the negative electrode sheet in the width direction.

[0084] The first electrode 21 and the second electrode 22 are laminated such that their uncoated regions 26 are exposed or protrude in the width direction from the laminate. The uncoated region 26 of the first electrode 21 protrudes from one axial end of the wound jelly roll, and the uncoated region 26 of the second electrode 22 protrudes from the opposite axial end of the jelly roll. The uncoated region 26 itself functions as at least one electrode tab 27.

[0085] Notches may be formed at predetermined intervals in the uncoated portion 26 to form a plurality of flag-shaped notched tabs 27.

[0086] In the embodiment, the notching tabs 27 are shaped like an equilateral trapezoid, but may be shaped in various other ways, such as a semicircle, a semi-ellipse, a triangle, a rectangle, or a parallelogram.

[0087] In the embodiment, the notching tabs 27 arranged along the longitudinal direction have the same width. However, the width of the notching tabs may be gradually or stepwise increased from the core side toward the outer periphery.

[0088] 2 and 3, the height of the notching tabs 27 increases stepwise from the core side toward the outer periphery. However, the height of the notching tabs may be constant or may decrease gradually.

[0089] In addition, in the embodiment, a structure is exemplified in which the notching tabs 27 are removed from a predetermined section of the centripetal end and a predetermined section of the distal end of the non-coated portion 26. However, alternatively, the notching tabs may not be removed from the centripetal end of the non-coated portion, the notching tabs may not be removed from the distal end of the non-coated portion, or the notching tabs may not be removed from either side.

[0090] In the jelly-roll type electrode assembly 20, the notching tabs 27 may be bent radially inward and flattened as shown in Fig. 4. The notching tabs 27 may be bent radially inward or outward. In the embodiment, a structure in which the notching tabs 27 are bent radially inward is illustrated.

[0091] The notching tabs 27 may 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 winding the laminate to form the jelly roll type electrode assembly.

[0092] The multiple notching tabs 27 of the first electrode 21 and the multiple notching tabs 27 of the second electrode 22, which are folded radially and stacked in this manner, can each provide a plane substantially perpendicular to the axial direction at both axial ends of the electrode assembly 20.

[0093] As shown in Figures 5 and 6, a first current collecting plate 31 and a second current collecting plate 32 may be bonded to substantially flat surfaces formed by bending the notching tabs 27 exposed at both axial ends of the electrode assembly 20.

[0094] In the embodiment, the first current collector 31 is a positive current collector, and the second current collector 32 is a negative current collector. The first current collector 31 may be made of an aluminum material, and the second current collector 32 may be made of a copper material.

[0095] The current collecting plates 31 and 32 may be manufactured by punching, trimming, piercing, and / or bending a metal sheet.

[0096] 5, the first current collector plate 31 includes a terminal connection portion 312 extending radially from a center portion, a ring portion 313 circumferentially connecting the periphery of the terminal connection portion 312 on the distal side, and an electrode connection portion 314 extending centripetally from the ring portion 313 and not connected to the terminal connection portion 312. The center portion of the terminal connection portion 312 covers at least a portion of the hollow portion of the winding core of the electrode assembly 20.

[0097] The electrode connector 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 housed in the can 10. The laser welding lines may extend radially.

[0098] 6 , the second current collecting plate 32 includes an inner ring portion 321 surrounding the core hollow portion of the electrode assembly 20 and defining a hole 322 corresponding to the core hollow portion, and an electrode tab connecting portion 323 extending radially from the inner ring portion 321. The electrode tab connecting portion 323 may have a plurality of spokes extending radially outward from the inner ring portion. One or more of the spokes may have a radially outer end, referred to as a can connecting portion 324, that connects to the periphery of the second current collecting plate 32. 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 has an outer ring shape surrounding the electrode tab connecting portion 323 and may include a step extending away from the electrode assembly 20 in the axial direction. As a result, at least the outermost periphery of the can connecting portion 324 may be positioned farther away from the electrode assembly 20 than the electrode tab connecting portion 323, the inner ring portion 321, and other portions of the can connecting portion 324.

[0099] The electrode tab connector 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 housed in the can 10. The laser welding lines may extend radially.

[0100] 7 and 8, the electrode assembly 20 is accommodated in the can 10 with the first current collecting plate 31 aligned toward the bottom member 12 of the can 10. At this time, an insulator 19 is interposed between the first current collecting plate 31 and the bottom member 12 of the can 10 to electrically insulate the first current collecting plate 31 from the bottom member 12.

[0101] The terminal connection portion 312 of the first current collecting plate 31 is joined to the first electrode terminal 13 fixed to the can 10 by resistance welding, ultrasonic welding, laser welding, or the like. A welding device for welding the first current collecting plate 31 to the first electrode terminal 13 may be positioned from the open end of the can 10, pass through the hollow portion of the core of the electrode assembly 20, and approach the rear surface (the surface facing the electrode assembly 20) of the center of the terminal connection portion 312 of the first current collecting plate 31 to perform welding. Of course, the first current collecting plate 31 and the first electrode terminal 13 may also be joined by brazing, soldering, or the like. That is, various joining methods are applicable as long as they can electrically connect and fix the first current collecting plate 31 and the first electrode terminal 13 to each other.

[0102] When the electrode assembly 20 is housed inside the can 10 , the electrode tab 27 of the second electrode 22 and the second current collector plate 32 may be disposed facing the open end of the side wall member 11 .

[0103] After the first current collector plate 31 and the first electrode terminal 13 are joined, an electrolyte may be injected into the can 10. After the electrolyte is injected, the open end of the side wall member 11 may be covered and sealed with a cap 16 as shown in FIG.

[0104] Of course, the welding method of the present invention may also be applied in a manner in which the cap 16 is first covered, the electrolyte is then poured through the pouring port of the cap 16, and the pouring port of the cap 16 is then sealed.

[0105] As shown in FIG. 10, the periphery of the cap 16 is joined to the periphery of the side wall member 11 by laser seam welding, thereby sealing the can 10.

[0106] 10 and 11, the open end of the sidewall member 11 may be provided with an inner diameter expansion 113. The inner diameter expansion 113 may be in the form of a lateral step extending transversely to the central longitudinal axis and disposed along the radially inner surface of the sidewall member 11.

[0107] As a result, the radial inner surface of the side wall member 11 may include a first inner surface 111 that is positioned axially inward from the inner diameter expansion portion 113, i.e., farther from the opening of the open end of the side wall member 11, and a second inner surface 115 that is 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.

[0108] The second inner surface 115 may have a larger inner diameter than the first inner surface 111. As a result, the sidewall member 11 may have a second thickness t2 measured in the radial direction at a portion where the second inner surface 115 is provided that is thinner than a first thickness t1 measured in the radial direction at a portion where the first inner surface 111 is provided.

[0109] A can connecting portion 324, which is provided on the periphery of the second current collecting plate 32 and contacts and is electrically connected to the can 10, includes a first portion that contacts the second inner surface 115 of the side wall member 11. The first portion is provided with an abutting outer peripheral surface 325 that faces and contacts the second inner surface 115 of the side wall member 11 in the radial direction.

[0110] The can connecting portion 324 includes a second portion that contacts the cap 16. The second portion is provided with a cap abutment 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.

[0111] The outer diameter of the abutting outer peripheral surface 325 of the can connecting portion 324 is set larger than the inner diameter of the first inner 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 provided on the opposite side of the cap abutting surface 326 in the axial direction. The third portion abuts against the inner diameter expansion portion 113 to regulate the insertion depth of the second current collecting plate 32 into the can 10.

[0112] The second current collecting plate 32 further includes a first bent portion 327 and a second bent portion 328, thereby defining a step in the axial direction of the second current collecting plate 32. The first bent portion 327 is formed by bending the second current collecting plate 32, which extends radially outward, outward in the axial direction. The second bent portion 328 is formed by bending the second current collecting plate 32, which extends axially outward, outward in the radial direction. Due to the axial step between the first bent portion 327 and the second bent portion 328, the peripheral portion or can connecting portion 324 of the second current collecting plate 32 is axially offset toward the open end of the can 10 relative to the center of the second current collecting plate 32.

[0113] The can connector 324 is connected to the electrode tab connector 323 through the first bent portion 327 and the second bent portion 328 and the inner ring portion 321 .

[0114] The can connecting portion 324 is connected to the radially outer side of the second bent portion 328 and extends radially from the second bent portion 328. This allows the area of ​​the cap abutting surface 326 of the second current collecting plate 32 to be further increased.

[0115] Preferably, the material of the second current collecting plate 32 is softer than the material of the side wall member 11. Therefore, the first bent portion 327 and the second bent portion 328 are elastically deformed during the process of inserting the second current collecting plate 32 into the open end of the side wall member 11. Therefore, if the outer diameter of the contact outer peripheral surface 325 is set slightly larger than the inner diameter of the second inner surface 115, the contact outer peripheral surface 325 is pressed into the second inner surface 115.

[0116] The cap 16 includes, from the radial center outward, a cap body 160, a reduced thickness portion 161 where the thickness of the cap changes, and a joint portion 17, in that order. That is, the cap body 160 is centered in the central region of the cap 16, and the reduced thickness portion 161 is provided radially outward of the cap body 160. The joint portion 17 is provided radially outward of the reduced thickness portion 161 and defines an annular region of the cap 16 having a reduced thickness relative to the cap body 160. That is, a third thickness t3 of the joint portion 17 measured in the axial direction is thinner than a fourth thickness t4 of the cap body 160 measured in the axial direction.

[0117] An outer joint surface 171 is provided along the radially outer side surface of the cap 16, specifically along the radially outer side surface of the joint portion 17, and is in radially facing contact with the second inner side surface 115 of the side wall member 11. In addition, a current collector abutment surface 173 is provided on the bottom surface of the joint portion 17 of the cap 16, and faces inward in the axial direction so as to be in contact with the cap abutment surface 326 of the can connecting portion 324 of the second current collector plate 32.

[0118] By appropriately selecting the position where the reduced thickness portion 161 is provided, it is possible to make at least a portion of the reduced thickness portion 161 contact the second current collecting plate 32. Then, during the process of inserting the cap 16 into the open end of the side wall member 11, the reduced thickness portion 161 of the cap 16 abuts against the second current collecting plate 32, thereby achieving the effect of aligning the center of the cap 16 with the central longitudinal axis of the second current collecting plate 32.

[0119] In the embodiment, the thickness-reducing portion 161 is disposed at a position corresponding to the position where the second bent portion 328 of the second current collecting plate 32 is formed in the radial direction, thereby achieving such an alignment effect.

[0120] Preferably, in this embodiment, the thickness-reducing portion 161 is realized in the form of a slope that extends more axially outward as it goes radially outward to enhance the alignment effect.

[0121] Preferably, in the embodiment, the second current collector plate 32 is also provided with a sloped surface shape through the surface shape of the second bent portion 328 of the second current collector plate 32 in order to enhance the alignment effect.

[0122] In the radial direction, the joining outer peripheral surface 171 of the cap 16 and the abutting outer peripheral surface 325 of the second current collector plate 32 contact the second inner surface 115 of the side wall member 11, respectively.

[0123] In addition, in the axial direction, at least a part of the lower portion along the peripheral edge of the second current collector plate 32 contacts the expanded inner diameter portion 113 of the side wall member 11. In the axial direction, a cap abutment surface 326 provided on the upper portion of the second current collector plate 32 contacts a current collector abutment surface 173 provided on the lower portion of the joint portion 17 of the cap 16.

[0124] With the second current collector plate 32 and the cap 16 inserted in this manner, an overhang portion 117 that protrudes further outward in the axial direction than the cap 16 may be provided at the open end of the side wall member 11 .

[0125] A first height h1 of a section of the side wall member 11 located axially outward of the inner diameter expansion portion 113 is greater than the sum of a third thickness t3 of the joint portion 17 of the cap 16 and a fifth thickness t5 of the can connecting portion 324 of the second current collector plate 32. A second height h2 of the overhang portion 117 may be a length obtained by subtracting the third thickness t3 and the fifth thickness t5 from the first height h1. For example, the first height h1 may be 1 mm, the second height h2 may be 0.2 mm, the third thickness t3 may be 0.5 mm, and the fifth thickness t5 may be 0.3 mm.

[0126] In the battery cell, a welded portion W is formed at the contact portion between the side wall member 11, the cap 16, and the second current collector plate 32, where the second inner surface 115 portion of the side wall member 11, the joint outer peripheral surface 171 portion of the cap 16, and the can connecting portion 324 portion of the second current collector plate 32 are welded together.

[0127] In the embodiment, the welded portion W is formed over substantially the entire circumferential length of the cap 16. In this way, the welded portion W can also function as a sealing portion S that seals the contact portion between the can 10 and the cap 16.

[0128] However, unlike the embodiment, the welded portion W may be formed only in a portion that is discontinuously spaced apart from one another in the circumferential direction, and thus the welded portion W may constitute a portion of the sealing portion S that seals the contact portion between the can 10 and the cap 16.

[0129] The welded portion W may be formed by laser welding, in which a laser is applied to the contact portion between the can 10 and the cap 16 along the circumferential direction, and the can connecting portion 324 of the second current collecting plate 32 is also welded together.

[0130] The sealing portion S can also be formed by laser welding, which continuously irradiates the contact portion between the can 10 and the cap 16 along the circumferential direction.

[0131] For example, the weld W may be formed in a preliminary welding process or in a subsequent main welding process.

[0132] The sealed portion S can be formed during this welding process.

[0133] The weld W and the seal S may be formed together during the welding process.

[0134] In this embodiment, in this welding process, a laser is continuously irradiated to the contact portion between the can 10 and the cap 16 along the circumferential direction, and at this time, the laser energy density and scanning speed are kept constant so that the can connecting portion 324 of the second current collecting plate 32 is welded together, thereby forming a welded portion W over the entire circumferential section and also forming a sealed portion S.

[0135] However, in this welding process, it is also possible to continuously irradiate the contact area between the can 10 and the cap 16 along the circumferential direction with a laser, and at this time, increase the energy density of the laser or decrease the scanning speed only in specific discontinuous sections so that the laser penetrates deeper and welds the can 10 up to the can connecting portion 324 of the second current collecting plate 32 together, thereby forming a sealed portion S in the entire section of the side wall member along the circumferential direction and a welded portion W in the specific section.

[0136] The discontinuous weld W formed between the second current collector plate 32 and the can 10 is similar to a "tack weld" that secures the two components together, while the continuous seal S forms a seal along substantially the entire exposed area between the can 10 and the cap 16.

[0137] Indeed, similar to tack welding, the welding method may involve first forming a plurality of discontinuous welds W between the second current collector plate 32 and the can 10 and between the cap 16 and the can 10 (e.g., by applying the laser at a slower speed and / or a higher energy density at discrete locations along the circumference), followed by applying the laser continuously along the entire exposed joint between the can 10 and the cap 16. Such an approach has the advantage that the discontinuous welds can at least temporarily fix the position of the second current collector plate 32 and the cap 16 relative to the can 10 while the subsequent process of forming and sealing a continuous seal S is carried out.

[0138] As shown in the drawing, the joining outer peripheral surface 171 of the cap 16 and the axial upper 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.

[0139] The welded portion W is formed by a laser irradiated from the axial outside of the battery cell toward the joining outer peripheral surface 171 of the cap 16 and the axial end of the second inner surface 115 of the side wall member 11.

[0140] At this time, the abutting outer surface 325 of the second current collector plate 32, which is arranged axially lower than the cap 16, faces and contacts the radially 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.

[0141] In addition, the expanded inner diameter portion 113 of the side wall member 11 also prevents the laser irradiated through the gap between the side wall member 11 and the cap 16 or the gap between the side wall member 11 and the second current collector plate 32 from penetrating inside.

[0142] The second current collecting plate 32 may include a material having a higher thermal conductivity than the side wall member 11. In addition, the second current collecting plate 32 is in contact with the side wall member 11. Therefore, when welding heat generated in the side wall member 11 by a laser is conducted along the axial direction of the side wall member 11, the welding heat is dispersed while crossing the upper part of the electrode assembly 20 through the second current collecting plate 32, thereby preventing the welding heat from being transmitted to the separator portion of the electrode assembly 20 and damaging the separator.

[0143] The second current collecting plate 32 is also in contact with the cap 16. As a result, heat generated in the cap 16 by the laser is dispersed and transferred through the second current collecting plate 32. As a result, when the contact portion between the cap 16 and the side wall member 11 is heated by the laser, the side wall member 11 may heat up first and melt.

[0144] Therefore, if the side wall member 11 is too thin, the side wall member 11 may melt before the cap 16, which may prevent smooth welding. Preferably, the second thickness t2 of the side wall member 11 may be 0.25 mm or more. For example, the second thickness t2 may be 0.35 mm.

[0145] It is also important that the cap 16 has the strength to support the pressure when the pressure in the internal space of the can 10 increases. If the cap 16 is too thin, excessive bulging occurs, in which the cap 16 expands into a spherical surface profile when the internal pressure of the can 10 increases, which deteriorates the durability of the battery cell. It is important that the cap 16 has a certain thickness to withstand such bulging deformation.

[0146] 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 where welding is performed.

[0147] 15 is a diagram showing the results of stress analysis when the internal pressure of the can 10 increases in the following cases: (a) the outer peripheral joining surface 171 of the cap 16 is welded over the entire length in the axial direction to form a sealed portion S and / or a welded portion W, (b) the outer peripheral joining surface 171 of the cap 16 is welded over 75% of the length in the axial direction to form a sealed portion S and / or a welded portion W, and (c) the outer peripheral joining surface 171 of the cap 16 is welded over 25% of the length in the axial direction to form a sealed portion S and / or a welded portion W. Referring to FIG. 15, it can be seen that when the outer peripheral joining surface 171 of the cap 16 is not welded over the entire length in the axial direction, a weak portion exists at the welded portion between the side wall member 11 and the cap 16.

[0148] Therefore, in the embodiment, a cap 16 is disclosed in which the third thickness t3 of the joint 17 where the side wall member 11 is welded is different from the fourth thickness t4 of the cap body 160. The greater the fourth thickness t4, the higher the resistance to bulging, but the greater the space it occupies inside the can. To increase the resistance to bulging while minimizing the space and weight, it is preferable that the fourth thickness t4 be as small as possible within the range of the required bulging resistance.

[0149] Consequently, the fourth thickness t4 of the cap body 160, which accounts for 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 welded portion along the axial direction is minimized to ensure that the sealing portion S and / or the welded portion W are formed over the entire axial length of the joining outer peripheral surface 171. This increases the strength of the cap 16 itself and also increases the joining strength of the cap 16 to the side wall member 11.

[0150] 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 below the above range, the cap body 160 may become excessively thick without increasing bulging resistance, or the strength of the welded portion may be insufficient. If the ratio exceeds the above range, the bulging resistance of the cap body 160 may become insufficient, or the outer peripheral joining surface 171 of the cap 16 may be difficult to weld along the entire axial direction.

[0151] Therefore, by increasing the fourth thickness t4 of the cap body 160, which accounts for the overall shape of the cap 16, and minimizing deformation of the cap 16 due to the internal pressure of the can 10, the welded portion to the side wall member 11, i.e., the axial dimension of the outer peripheral joining surface 171, is reduced so that the sealing portion S and / or the welded portion W are formed over the entire outer peripheral joining surface 171 in the axial direction, thereby increasing both the strength of the cap 16 itself and the bonding strength of the cap 16 to the side wall member 11.

[0152] According to the cap 16 of the embodiment, the reduced thickness portion 161 is positioned as close as possible to the welded portion in the radial direction, thereby maximizing the area of ​​the cap body 160 that resists bulging. In addition, the selected position of the reduced thickness portion 161 can also provide a guide function for aligning the center of the cap 16 by contacting the second current collecting plate 32.

[0153] The third thickness t3 of the joint portion 17 of the cap 16 may be set to be larger than the second thickness t2 of the side wall member 11. The third thickness t3 may be equal to or greater than one time and equal to or less than two 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 may be in the range of 0.5 mm to 0.7 mm.

[0154] If the third thickness t3 is more than 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 sealed portion and / or welded portion. Also, if the third thickness t3 is more than twice the second thickness t2, there is a risk that the sealed portion and / or welded portion will not be formed over the entire axial length of the joining outer peripheral surface 171 of the cap 16.

[0155] If the third thickness t3 is less than one time the second thickness t2, i.e., 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.

[0156] Next, the overhang portion 117 delays the melting point of the relatively thin sidewall member 11, thereby reducing the difference in melting point between the sidewall member 11 and the cap 16, and can be melted into the welding portion between the radially inner surface of the sidewall member 11 and the joining outer peripheral surface 171 of the cap 16 during the welding process.

[0157] Therefore, the diameter of the outer mating surface 171 of the cap 16 can be slightly smaller than the diameter of the second inner surface 115 of the sidewall member 11 adjacent to the outer mating surface 171. Here, the concept of two objects being "adjacent" means that the two objects are closely spaced from each other compared to their outer dimensions and that there is no intervening object between the two objects in the relevant plane (i.e., a radial plane perpendicular to the central longitudinal axis). Because the diameter of the outer mating surface 171 of the cap 16 is slightly smaller than the diameter of the second inner surface 115 of the sidewall member 11, a small gap is defined between these two components, i.e., between the second inner surface 115 of the sidewall member 11 and the outer mating surface 171 of the cap 16.

[0158] Such a gap can serve as a passage through which the welding laser can be irradiated directly onto the second current collector plate 32 .

[0159] Preferably, such gaps can have a generally uniform radial width along the circumference of the cap 16, with the center of the cap 16 being aligned by the interaction between at least the reduced thickness portion 161 of the cap 16 and the second current collector plate 32, as described above.

[0160] In addition, 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 surface 115 of the side wall member 11 to join the cap 16 and the side wall member 11.

[0161] As an example, the height (second height h2) of the overhang portion 117 is 0.2 mm, and the thickness (third thickness t3) of the joint portion 17 of the cap 16 is 0.5 mm. When the thickness (second thickness t2) of the overhang portion 117 is 0.35 mm, a sufficient amount of molten material is provided during the welding process, and a strong bond can be formed between the cap 16 and the side wall member 11. For example, the ratio of the height (second height h2) of the overhang portion to the thickness (third thickness t3) of the joint portion 17 can preferably be in the range of 0.2 to 1.

[0162] 11 may melt as shown in FIGS. 12 and 13 during the process of forming the sealing portion S and / or the welded portion W. As a result, the height of the battery cell may be determined by the outer surface of the cap 16. That is, according to the embodiment, the sealing portion S and / or the welded portion W does not restrict the height of the battery cell, and as a result, the height dimension of the battery cell can be maintained constant.

[0163] Hereinafter, a modified embodiment of the welding structure according to the present invention will be described with reference to Fig. 14. In the description of the modified embodiment, differences from the above-described embodiment will be mainly described to avoid repetition. Therefore, matters not described in the modified embodiment can be fully understood through the description of the above-described embodiment, and it is self-evident that each configuration of the above-described embodiment and the following modified embodiment can be replaced or omitted as long as it does not go against the spirit of the invention.

[0164] The sidewall member 11 has an expanded inner diameter portion 113 on the open end side. The expanded inner diameter portion 113 has an inclined or oblique surface shape provided on the inner peripheral surface of the sidewall member 11 so as to expand the inner diameter of the sidewall member 11 toward the axially outward direction. That is, the expanded inner diameter portion 113 is provided on the inner surface of the sidewall member 11 and has a sloped shape that is oblique relative to the central longitudinal axis, extending radially outward toward the axially upper end of the sidewall member 11.

[0165] The second current collector plate 32 includes a first bent portion 327. The first bent portion 327 bends the radially outwardly extending second current collector plate 32 axially outward to provide an axially extending shape. Therefore, the peripheral edge of the second current collector plate (i.e., the can connecting portion 324) extends axially rather than radially as in the previously described embodiments. As a result, the abutment outer peripheral surface 325 that contacts the second inner surface 115 of the sidewall member 11 extends along the longitudinal dimension of the peripheral edge rather than being defined by the leading edge of the peripheral edge. Instead, the leading edge of the peripheral edge in the embodiment of FIG. 14 becomes a cap abutment surface 326 that abuts against the current collector abutment surface 173 at the bottom of the cap 16 along the joint 17.

[0166] The can connecting portion 324 of the second current collecting plate 32 is connected to the electrode tab connecting portion 323 through the first bent portion 327 and the inner ring portion 321 .

[0167] Since the material of the second current collecting plate 32 is softer than the material of the side wall member 11, the first bent portion 327 is elastically deformed in the process of inserting the second current collecting plate 32 into the open end of the side wall member 11. Therefore, if the outer diameter of the abutting outer peripheral surface 325 is set slightly larger than the inner diameter of the second inner surface 115, the abutting outer peripheral surface 325 is pressed into the second inner surface 115, and the abutting outer peripheral surface 325 and the second inner surface 115 come into close contact with each other in the radial direction.

[0168] In terms of dimensions, the outer peripheral surface of the first bent portion 327 of the second current collecting plate 32 partially overlaps with the portion of the expanded inner diameter portion 113 of the side wall member 11. As a result, even if there is a tolerance in the dimensions of the second current collecting plate 32 or the side wall member 11, the outer peripheral surface of the second current collecting plate 32 can be firmly attached to the radially inner surface of the side wall member 11.

[0169] Therefore, according to the modified structure of the second current collector 32, the cap abutment surface 326 provided at the axial outer end of the can connecting portion 324 of the second current collector 32 has a radial width that substantially corresponds to the fifth thickness t5. In other words, the area of ​​the portion of the second current collector 32 that contacts the side wall member 11 can be larger than the area of ​​the portion of the second current collector 32 that contacts the cap 16.

[0170] As a result, compared to the above-described embodiment, heat generated in the side wall member 11 by the laser can be dispersed and conducted more quickly through the second current collecting plate 32, while heat generated in the cap 16 by the laser can be dispersed and conducted somewhat more slowly through the second current collecting plate 32. This can further delay the melting point of the side wall member 11, which is relatively thinner than the joint portion 17 of the cap 16.

[0171] In addition, since most of the welding heat transferred through the side wall member 11 is dispersed through the second current collecting plate 32, heat transfer to the separator 28 side of the electrode assembly 20 in contact with the first inner surface 111 of the side wall member 11 can be further reduced.

[0172] Next, the reduced thickness portion 161 of the cap 16 of the modified embodiment is disposed radially further outward than the reduced thickness portion 161 of the cap 16 of the above-described embodiment, thereby ensuring a larger area for the cap body 160. In addition, the reduced thickness portion 161 is also provided in a sloped shape, and can guide the center alignment of the cap 16 while contacting the second current collecting plate 32 during the insertion process of the cap 16.

[0173] According to the above-described embodiments and modified embodiments, despite the wide range of welding processes, it is possible to ensure sealing strength without perforation or leakage, thereby improving weldability; it is possible to prevent thermal damage to cell components and separators due to welding heat, thereby improving process stability; and it is possible to suppress dimensional deformation due to internal pressure, thereby ensuring dimensional stability and resistance to bulging, thereby improving durability.

[0174] Hereinafter, a method for manufacturing the above-described battery cell will be described with reference to FIGS.

[0175] According to the manufacturing method of the battery cell, first, a can 10 having a first electrode terminal 13 fixed to a bottom member 12 is prepared, and an electrode assembly 20 having a first current collector plate 31 and a second current collector plate 32 joined to both axial ends thereof is prepared.

[0176] The electrode assembly 20 is inserted into the can 10 with the first current collecting plate 31 facing the bottom member 12. Then, the second current collecting plate 32 is positioned at the open end of the can 10. During the process of inserting the electrode assembly 20 into the can 10, the abutting outer peripheral surface 325 of a can connecting portion 324 provided on the radially outer edge of the second current collecting plate 32 is brought into contact with the second inner surface 115 of the side wall member 11.

[0177] At this time, the can connecting portion 324 of the second current collecting plate 32 is brought into contact with the inner diameter expansion portion 113 of the side wall member 11, thereby ensuring the adhesion of the second current collecting plate 32 to the inner surface of the side wall member 11 and regulating the insertion depth of the second current collecting plate 32.

[0178] Next, the first current collector plate 31 and the first electrode terminal 13 are joined together.

[0179] Then, an electrolyte is poured into the can 10 .

[0180] After completing the injection of the electrolyte, the open end of the side wall member 11 is covered with the cap 16, and the outer circumferential joint surface 171 and the current collector abutting surface 173 on the periphery of the cap 16 are brought into contact with the second inner surface 115 of the side wall member 11 and the cap abutting surface 326 of the second current collector 32, respectively. At this time, the thickness-reducing portion 161, which is formed in a sloped shape on the inner surface of the cap 16 in the axial direction, is brought into contact with the second current collector 32, so that the center of the cap 16 can be aligned.

[0181] Next, a laser is irradiated from the outside in the axial direction to the contact portion between the second inner surface 115 of the side wall member 11 and the outer joint surface 171 of the cap 16, thereby welding together the inner surface of the side wall member 11, the outer joint surface 171 of the cap 16, and the can connecting portion 324 of the second current collecting plate 32. As a result, the welded portion W joins together the side wall member 11, the cap 16, and the second current collecting plate 32.

[0182] At this time, the overhang portion 117 of the side wall member 11, which protrudes further axially outward than the cap 16, can be melted into the welded portion between the inner surface of the side wall member 11 and the joining outer peripheral surface 171 of the cap 16.

[0183] The battery cells 72 manufactured through the above-described welding structure and welding process may be housed in a housing 71 of a battery pack 70 as shown in Fig. 17. The battery pack 70 may be constructed using a battery module which is an intermediate form of assembly, or the battery pack 70 may be constructed directly without a battery module as shown in the figure.

[0184] The battery cells 72 themselves have a large volume, so the battery pack 70 can be easily realized without using an intermediate structure such as a battery module. In addition, the battery cells 72 have low internal resistance and a high energy density. As a result, the battery pack 70 including the battery cells 72 can achieve a higher energy density.

[0185] The battery pack 70 with increased energy density can store the same amount of energy while reducing its volume and weight. Therefore, if the battery pack 70 using such battery cells 72 is installed in a vehicle such as an automobile 80 that uses electricity as its energy source as shown in Fig. 18, the driving range of the vehicle relative to the energy can be further extended.

[0186] While the seam welding structures and methods described above have been disclosed with respect to cylindrical battery cans, it should be understood within the scope of this disclosure that such techniques may be similarly applied to other battery form factors. For example, the associated battery cells need not have a circular cross-sectional profile perpendicular to the central longitudinal axis, but may use other cross-sectional shapes, including oval, square, rectangular, partial circular, etc. Furthermore, the central longitudinal axis need not be oriented perpendicular to the bottom member and / or cap at each opposing end. For example, the sidewall members of the can (together with the can's internal components) may form a tube extending along an axis oriented obliquely relative to a plane defined by the bottom member and / or cap. Furthermore, the welding techniques disclosed herein may also be used outside of cylindrical battery cans, and may be applied to batteries having, for example, prismatic and pouch-type form factors.

[0187] It should be understood that the above-described embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the following claims rather than the above detailed description. Furthermore, it is intended that the meaning and scope of the following claims, as well as all modifications and variations derived from the equivalent concepts thereof, are included within the scope of the present invention.

[0188] Although the present invention has been described above with reference to exemplary embodiments and drawings, it is obvious that the present invention is not limited to the embodiments and drawings disclosed in this specification, and various modifications can be made by those skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the operational effects of the configurations of the present invention are not explicitly stated in the description of the embodiments of the present invention, it goes without saying that the effects that can be predicted by the configurations should also be recognized. [Explanation of symbols]

[0189] 10: can, 11: side wall member, 111: first inner surface, 113: inner diameter expansion portion, 115: second inner surface, 117: overhang portion, t1: first thickness, t2: second thickness, h1: first height, h2: second height, 12: bottom member, 13: first electrode terminal, 14: gasket, 15: second electrode terminal, 16: cap, 160: cap body, 161: thickness reduction portion, 17: joint portion, 171: joint outer peripheral surface, 173: current collector plate abutment surface, t3: third thickness (periphery), t4: fourth thickness (cap body), 19: insulator, 20: electrode assembly, 21: first electrode (positive electrode), 22: second electrode (negative electrode) electrode), 23: metal foil, 24: active material layer, 25: coated portion, 26: uncoated portion, 27: electrode tab (notched tab), 28: separation membrane, 31: first current collector (positive current collector), 312: terminal connecting portion, 313: ring portion, 314: electrode connecting portion, 32: second current collector (negative current collector), t5: fifth thickness, 321: inner ring portion, 322: hole, 323: electrode tab connecting portion, 324: can connecting portion, 325: abutting outer peripheral surface, 326: cap abutting surface, 327: first bent portion, 328: second bent portion, W: welded portion, S: sealed portion, 70: battery pack, 71: housing, 72: battery cell, 80: automobile

Claims

1. a can having a sidewall surrounding an interior space and defining an opening to said interior space at a first end along a central longitudinal axis; an electrode assembly housed within the interior space of the can; a current collector plate electrically connected to the electrode assembly; a cap that covers the opening of the can so as to surround the internal space; In a battery cell comprising: the current collector plate includes a central portion and a peripheral portion; the central portion is electrically connected to an electrode tab of the electrode assembly; The peripheral portion is located at the periphery of the central portion so as to be positioned farther from the central longitudinal axis than the central portion; contacting a radially inner surface of the side wall so as to be in electrical communication with the can; contacting a bottom surface of the cap facing the interior space along an axial direction extending parallel to the central longitudinal axis; The side wall, the radially outer surface of the cap, and the peripheral edge of the current collector plate are welded to one another.

2. a radially inner surface of the sidewall including a side step extending transversely to the central longitudinal axis, a first inner surface of the sidewall axially disposed on a first side of the side step having a first diameter, a second inner surface of the sidewall axially disposed on a second side of the side step having a second diameter, the second side of the side step being disposed closer to the opening than the first side, and the second diameter being greater than the first diameter; The battery cell according to claim 1 , wherein a radially outer surface of the cap and a peripheral edge of the current collector plate contact the second inner surface.

3. The battery cell according to claim 2 , wherein an outer diameter of the peripheral edge of the current collector plate is larger than a first diameter of the first inner surface.

4. The battery cell according to claim 2 , wherein a peripheral edge of the current collector plate is in contact with the side step.

5. The battery cell of claim 2 , wherein the side step extends diagonally from a first diameter of the first interior surface to a second diameter of the second interior surface.

6. 3. The battery cell of claim 2, wherein a first thickness of the cap in an axial direction along the radially outer surface is greater than a second thickness of the sidewall in a radial direction along the second inner surface, the radial direction being perpendicular to the central longitudinal axis.

7. The battery cell of claim 6 , wherein the first thickness is between one and two times thicker than the second thickness.

8. a diameter of the radially outer surface of the cap that is smaller than a diameter of an adjacent portion of the radially inner surface of the sidewall; The battery cell of claim 1 , wherein a weld area extends from the adjacent portion of the radially inner surface of the side wall to the radially outer surface of the cap.

9. the cap includes an annular region extending along a radially outer surface; 8. The battery cell of claim 1, wherein a thickness of the annular region of the cap along the axial direction is less than a thickness of a central region of the cap disposed along the central longitudinal axis.

10. The battery cell of claim 9 , wherein a beveled surface along the bottom surface of the cap connects the annular region and the central region.

11. The battery cell of claim 10 , wherein the beveled surface is in contact with the current collector plate.

12. 8. The battery cell of claim 1, wherein the current collector plate includes an axial step between the central portion and the peripheral portion, such that the peripheral portion is offset toward the opening of the can relative to the central portion.

13. The longitudinal dimension of the central portion of the current collector plate extends transversely to the axial direction, The longitudinal dimension of the peripheral edge of the current collector plate extends parallel to the axial direction, 8. The battery cell of claim 1, wherein the peripheral edge extends along a radially inner surface of the side wall of the can to a tip of the peripheral edge that abuts a bottom surface of the cap.

14. placing a cap and a current collector plate in an assembly position within an opening of the can, wherein in the assembly position, the current collector plate is electrically connected to an electrode assembly contained within an interior space of the can, a peripheral edge of the current collector plate contacts a radially inner surface of a side wall of the can surrounding the opening, and the cap is positioned on the current collector plate along a central longitudinal axis of the can such that the cap is positioned further from the electrode assembly than the current collector plate; welding the radially inner surface of the side wall, the radially outer surface of the cap, and the peripheral edge of the current collector plate to one another.

15. 15. The method of fabricating a battery cell of claim 14, wherein placing the cap and the current collector plate in the assembly position includes contacting a peripheral edge of the current collector plate with a side step defined on the radially inner surface of the side wall of the can.

16. 15. The method of fabricating a battery cell according to claim 14, wherein the step of placing the cap and the current collector plate in the assembly position includes contacting a beveled surface disposed along a bottom surface of the cap with an annular region of the current collector plate extending along the periphery.

17. 17. The method of fabricating a battery cell of claim 14, wherein welding the radially inner surface of the can sidewall comprises melting material of an extension of the sidewall that projects above the cap along an axial direction extending parallel to the central longitudinal axis, such that material of the extension flows between the radially inner surface of the sidewall and the radially outer surface of the cap to join the radially inner surface of the sidewall and the radially outer surface of the cap together.

18. 17. The method of fabricating a battery cell of claim 14, wherein welding the radially inner surface of the side wall includes applying tack welds at a plurality of discrete spaced apart locations along the side wall in a circumferential direction relative to the central longitudinal axis, and then continuously welding along the side wall to form a weld that substantially circumferentially circumscribes the cap.

19. 17. The method of manufacturing a battery cell according to claim 14, wherein the step of disposing the cap and the current collector plate in the assembly position comprises inserting the electrode assembly to which the current collector plate is joined into an internal space of the can.

20. 20. The method of claim 19, wherein the disposing the cap and the current collector plate in the assembly position further comprises inserting the electrode assembly having the current collector plate joined thereto, and then inserting the cap into the opening of the can to contact the current collector plate.

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