Battery cell

Abstract

The utility model provides a battery cell. The battery cell includes a can and an electrode assembly accommodated in the can. The can includes a bottom member, a side wall member connected to the bottom member and extending upwardly therefrom in an axial direction, and a cap covering an open end of the can at an axial end opposite the bottom member. The current collector plate is connected to an electrode of the electrode assembly near the open end. An edge of the cover is welded by forming a plurality of first welding portions spaced apart from each other in a circumferential direction, in each of the plurality of first welding portions, the side wall member, the edge of the cover, and the current collector plate are welded together. A second welded portion in which both the side wall member and the edge of the cover are welded together is also continuously formed in the circumferential direction.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present application claims priority based on Korean Patent Application No. 10-2023-0074474 filed on June 9, 2023 and Korean Patent Application No. 10-2023-0135320 filed on October 11, 2023, the entire contents of each application are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the field of batteries, and more particularly to a welding structure of a battery can, a current collector plate and a cover, and a battery cell applying the welding structure. Background Art

[0004] The process of manufacturing a cylindrical unit battery may include deep drawing a metal sheet to form a can having a circular bottom and a cylindrical tubular sidewall member connected to the circular bottom, then accommodating an electrode assembly in the can, and then covering an open end of the sidewall member with a cover.

[0005] In addition, a current collector plate that contacts and is electrically connected to at least one electrode connector of the electrode assembly is disposed at one of the two axial ends of the electrode assembly (i.e., the axial end facing the open end). The current collector plate contacts and is electrically connected to the cover or sidewall member by welding the current collector plate to the cover or sidewall member.

[0006] During welding of the collector plate to the cover or sidewall member, the collector plate can be kept in close contact with the cover or sidewall member. To achieve this, a fixture that keeps the collector plate in close contact with the cover or sidewall member may be required, and a mask that exposes the welding area may also be required.

[0007] In order to hold the collector plate to the cover or sidewall member by a shield or clamp, a space for accommodating the shield or clamp may be provided in the tank. However, after removing the shield or clamp, such a space will remain empty, resulting in a reduced efficiency in the utilization of the internal volume of the tank. This hinders the energy density per unit volume of the tank.

[0008] Due to the tolerances of the area between the can, the current collector plate and the cover, there is a risk that the laser beam used for welding may directly penetrate the can. Additionally, during welding, a large amount of heat energy may be generated, which may be transferred through the can to the separator of the electrode assembly, potentially causing decomposition of the separator or degradation of the separator (such as by melting or sealing the pores of the separator).

[0009] In addition, when the cylindrical can is assembled, the process of electrically connecting the current collector plate to the cover or the side wall member and the process of connecting the cover to the side wall member are performed separately. This increases the man-hours involved in assembling the battery cell components, which reduces the production efficiency of the cylindrical battery cell and increases the production cost. Utility Model Content

[0010] In order to solve at least some of the above-mentioned problems, the present disclosure provides a welding structure of a battery can, a current collector plate and a cover, and a battery cell applying the welding structure, wherein an increased energy density per volume can be obtained without wasting or sacrificing the internal volume of the can (such as by omitting a separate welding shield or clamp during the process of welding the current collector plate to the can).

[0011] Additionally, or alternatively, the present disclosure may include integrating the process of welding the current collector plate to the can and the process of welding the cover to the sidewall member into a single welding process, which may advantageously improve production efficiency and reduce production costs.

[0012] Additionally, or alternatively, cans, current collector plates, and covers according to the present disclosure may function as shields and fixtures, which may advantageously improve process stability.

[0013] Additionally, or alternatively, the welded structure of the battery can, current collector plate, and cover may advantageously simplify the assembly process of the current collector plate and cover, such as by suppressing excessive generation of welding heat, without adversely affecting the electrode assembly.

[0014] However, the technical problems solved by the present disclosure are not limited to the above-mentioned purposes, but other purposes and advantages of the present disclosure that are not described can be understood through the following description and examples.

[0015] According to one aspect of the present disclosure, a battery cell is provided. The battery cell may include a can, an electrode assembly, a current collector plate and a cover. The battery cell may include a can, an electrode assembly, a current collector plate and a cover. The can may have a sidewall member defining an internal volume and define an opening to the internal volume at a first end of the can along a central longitudinal axis. The electrode assembly may be housed within the internal volume of the can. The cover may cover the opening of the can so as to close the internal volume. The current collector plate may be electrically connected to the electrode of the electrode assembly. In addition, the current collector plate may include a peripheral portion that contacts the sidewall member so as to be electrically connected to the can. A triple weld may be provided to join the following parts together: a sidewall member along the opening, an edge of the cover and a peripheral portion of the current collector plate. This triple weld may be formed along each of a plurality of first weld portions. These plurality of first weld portions may be spaced apart from each other along a circumferential direction around the central longitudinal axis. Both the sidewall member along the opening and the edge of the cover may be welded together along a second weld portion. This second weld portion may extend continuously in a circumferential direction to extend substantially completely around the central longitudinal axis.

[0016] According to some aspects of the battery cell, at least a portion of the second weld portion may overlap with a plurality of first weld portions. According to some other aspects of the battery cell, at least a portion of the second weld portion may overlap with a plurality of first weld portions. According to another aspect of the battery cell, each of the plurality of first weld portions has a cross-sectional area in a corresponding plane greater than a cross-sectional area of ​​the second weld portion in a corresponding plane. Such a cross-sectional plane extends perpendicular to the circumferential direction at the position of the corresponding weld portion. According to some other aspects of the battery cell, the depth of the plurality of first weld portions extending away from the first end of the can in the axial direction may be deeper than the depth of the second weld portion extending away from the first end of the can in the axial direction. This axial direction extends parallel to the central longitudinal axis. In other aspects of the battery cell, the outer diameter of the peripheral portion of the collector plate may correspond to the outer diameter of the radial outer surface of the cover. In other aspects of the battery cell, the edge of the cover may have a radial outer surface facing and contacting the radial inner surface of the sidewall member. In some other aspects of the battery cell, the outer diameter of the peripheral portion of the collector plate may be greater than the outer diameter of the radial outer surface of the edge of the cover.

[0017] According to some of the above aspects of the battery cell, the edge of the cover may have a radially outer surface facing the radially inner surface of the sidewall member and defining a gap therebetween. According to some of these aspects, the weld area may extend within the gap between the radially outer surface of the edge of the cover and the radially inner surface of the sidewall member.

[0018] According to some aspects of the battery cell, the edge of the cover may have a radially outer surface facing the radially inner surface of the sidewall member. In addition, at least one first portion of the radially outer surface of the edge of the cover may have a first diameter corresponding to the outer diameter of the peripheral portion of the collector plate. In addition, at least one second portion of the radially outer surface of the edge of the cover may have a second diameter that is smaller than the outer diameter of the peripheral portion of the collector plate. According to some of these aspects, the radially outer surface of the edge of the cover may have two or more first portions and two or more second portions that alternate with each other in the circumferential direction around the central longitudinal axis.

[0019] According to still other aspects of the battery cell, the edge of the cover may have a radially outer surface facing the radially inner surface of the sidewall member. In addition, the radially outer surface may have a plurality of large diameter portions and a plurality of small diameter portions alternating with each other around the central longitudinal axis in the circumferential direction. Such a plurality of small diameter portions may have a smaller diameter than the plurality of large diameter portions. According to some of these aspects, the large diameter portion of the radially outer surface of the edge of the cover may contact the radially inner surface of the sidewall member, while the small diameter portion of the radially outer surface of the edge of the cover is spaced apart from the radially inner surface of the sidewall member.

[0020] According to another aspect of the present disclosure, a method for manufacturing a battery cell is provided. The method may include the following steps: positioning the cover and the current collector plate in an assembly position stacked on each other in the opening of the can. In this assembly position, the current collector plate can be electrically connected to the electrode assembly housed in the internal volume of the can. In addition, in this assembly position, the peripheral portion of the current collector plate can be in contact with the radial inner surface of the side wall member surrounding the opening of the can. In addition, in this assembly position, the cover can be located above the current collector plate along the central longitudinal axis of the can, so that the cover is farther from the electrode assembly than the current collector plate. Preferably, the method also includes the step of forming a plurality of first welded portions, in which the following three parts are welded together to ensure their relative positions to each other: the side wall member of the can along the opening, the edge of the cover, and the peripheral portion of the current collector plate. In addition, the plurality of first welded portions are spaced apart from each other in the circumferential direction around the central longitudinal axis. The method preferably also includes the step of forming a second welded portion, in which the edge of the can along the opening and the edge of the cover are welded together. In order to seal the opening of the can, this second weld portion can extend substantially completely around the central longitudinal axis continuously in the circumferential direction.

[0021] According to some aspects of the method, the step of forming a plurality of first weld portions may include: directing a laser on an area between a radial inner surface of the sidewall member and a radial outer surface of an edge of the cover. According to other of these aspects, the step of forming a second weld portion may include: continuously irradiating an area along a radial inner surface of the sidewall member and a radial outer surface of an edge of the cover with a laser. According to other of these aspects, the power or energy density of the laser irradiation when forming the plurality of first weld portions may be higher than the corresponding power or energy density of the laser irradiation when forming the second weld portion. According to even further aspects of the present disclosure, the speed at which the laser moves in a circumferential direction to form the plurality of first weld portions may be faster than the speed at which the laser moves when forming the second weld portion.

[0022] According to some aspects of the method, the step of forming the second weld portion may include resistance welding using a roller electrode.

[0023] According to some other aspects of the method, the steps of forming the plurality of first weld portions and forming the second weld portion may include: melting material of an extension portion of the sidewall member that protrudes above the cover in an axial direction, the axial direction extending parallel to the central longitudinal axis. As a result, the material of the extension portion preferably flows between a radial inner surface of the sidewall member and a radial outer surface of the edge of the cover.

[0024] The above problem can be solved by forming a first welding portion in which the can, the current collector plate and the cover are welded together in such a manner that the desired battery internal resistance is obtained through a temporary welding process, a preliminary welding process or a positioning welding process, wherein the cover becomes attached to the can. Then, a second welding portion for sealing the can can be formed by welding the seam between the can and the cover.

[0025] Advantageously, a desired internal resistance can be obtained and the can can be reliably sealed while suppressing excessive welding heat and maintaining simplicity of the welding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a perspective view of a cylindrical battery cell according to one aspect of the present disclosure.

[0027] Figure 2 The electrode assembly is wound and housed in Figure 1 Exploded perspective view of the tank before it was put into use.

[0028] Figure 3 yes Figure 2 A perspective view of an electrode assembly in a laminated state before winding.

[0029] Figure 4 By winding Figure 3 A perspective view of a cylindrical jellyroll-type electrode assembly assembled by using a laminate of the present invention.

[0030] Figure 5 is shown in conjunction with Figure 4 A perspective view of a first current collector plate of an electrode tap of a first electrode of an electrode assembly.

[0031] Figure 6 is shown in conjunction with Figure 4 A perspective view of a second current collector plate of an electrode tap of a second electrode of an electrode assembly.

[0032] Figure 7 is a side sectional view illustrating a process of positioning an electrode assembly coupled to a first current collector plate and a second current collector plate into a can.

[0033] Figure 8 is a side sectional view illustrating a process of combining a first current collector plate and a first electrode terminal of an electrode assembly accommodated in a can.

[0034] Fig. 9 is a side cross-sectional view showing the process of positioning a cover to cover the open end of a can containing an electrode assembly therein.

[0035] Fig.10 is an enlarged side cross-sectional view of the open end of a can covered with a cover subjected to a laser welding process.

[0036] Fig.11 is an enlarged cross-sectional view of the open end of the can covered with a cover subjected to a resistance welding process.

[0037] Fig.12 is a cross-sectional view of the open end of a can covered with a cap having a liquid injection port.

[0038] Fig.13 is shown closed with a stopper Fig.12 A cross-sectional view of the liquid injection port of the cover.

[0039] Fig.14 is a perspective view of the open end of a can with a lid.

[0040] Fig.15 is along Fig.14 Enlarged cross-sectional view of line .15.--.15.

[0041] Fig.16 It is shown that the Fig.14 A plan view of the first welded portion between the can and the cover.

[0042] Fig.17 is along Fig.16 Enlarged cross-sectional view of line .17.-.17.

[0043] Fig.18 It is shown that the Fig.16A plan view of the second welded portion between the can and the cover.

[0044] Fig.19 is along Fig.18 Enlarged cross-sectional view of line .19.-.19.

[0045] Fig. 20 is along Fig.18 Enlarged cross-sectional view of line .20.--.20.

[0046] Fig.21 is a perspective view of an open end of a can with a cover according to a second aspect of the present disclosure.

[0047] Fig. 22 is along Fig.21 An enlarged cross-sectional view of line .22.--.22.

[0048] Fig.23 It is shown that the Fig.21 A perspective view of the first welded portion between the can and the cover.

[0049] Fig.24 It is shown that the Fig.23 A perspective view of the second welded portion between the can and the cover.

[0050] Fig.25 is along Fig.24 A photograph of a cut cross section of a battery cell cut along line .25.--.25.

[0051] Fig.26 is along Fig.24 A photograph of a cut cross section of a battery cell cut along line .26.--.26.

[0052] Fig. 27 is a plan view of a cover of a cylindrical battery cell according to a third aspect of the present disclosure.

[0053] Fig.28 Is has Fig. 27 A plan view of the open end of the can of a cylindrical battery cell.

[0054] Fig.29 is a flowchart illustrating an example of a manufacturing process of a battery cell according to the present disclosure.

[0055] Fig.30 is a flow chart showing another example of a manufacturing process of a battery cell according to the present disclosure.

[0056] Fig.31 is a perspective view of a battery pack including a plurality of battery cells according to various aspects of the present disclosure.

[0057] Fig.32 Is equipped with Fig.31 Diagram of the battery pack of a car. DETAILED DESCRIPTION

[0058] 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 will be able to implement the technical concept of the present disclosure. When describing the present disclosure, when it is determined that the detailed description of the prior art related to the present disclosure unnecessarily obscures the main idea of ​​the present disclosure, its detailed description will be omitted. Hereinafter, each scheme of the present disclosure will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals are used to represent the same or similar parts.

[0059] Although "first", "second", etc. are used to describe various elements, these elements are not limited by these terms. Instead, these terms are only used to distinguish one element from another element, and unless otherwise specifically stated, a component identified as a first element may also be a second element, and vice versa.

[0060] Throughout the specification, unless otherwise specified, each element may be in the singular or in the plural.

[0061] Hereinafter, “arranging an element at the upper (or lower) part of a component” or “arranging an element at the top (or bottom) of a component” means not only arranging the element to be in contact with the upper surface (or lower surface) of the component, but also arranging the element above the upper surface (or below the lower surface) with another element interposed therebetween.

[0062] In addition, when an element is described as being “connected to,” “coupled to,” or “contacting” a component, it should be understood that the element may be directly connected to, directly coupled to, or directly contact the component, or the element may be connected to, coupled to, or contact the component with one or more other elements interposed therebetween.

[0063] Unless the context clearly dictates otherwise, an expression in the singular form herein includes the expression in the plural form.

[0064] Throughout the specification, unless specifically stated otherwise, "A and / or B" means A, B, or A and B, and "C to D" includes both endpoints and all intervening values.

[0065] In the description of the implementation scheme, the "axial direction" refers to the direction in which the central longitudinal axis of the winding center constituting the core-type electrode assembly extends (i.e., the direction parallel to the central longitudinal axis), while the "radial direction" refers to the direction toward (centripetal) or away from (eccentric) the axis, and the circumferential direction refers to the direction around the axis.

[0066] In the following, reference will be made to Figures 1 to 20 A first aspect of a battery cell to which the welding structure of the present disclosure is applied is described in detail.

[0067] The battery cell of this aspect of the present disclosure may be, for example, a cylindrical battery cell having a shape factor ratio (defined as the diameter of the cylindrical battery cell divided by the height, ie, the ratio of the diameter Φ to the height H) greater than about 0.4.

[0068] The shape factor refers to a value representing the diameter and height of a cylindrical battery cell. A 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 value representing the shape factor, the first two digits represent the diameter of the cell, the next two digits represent the height of the cell, and the last digit 0 represents that the cross section of the cell is circular.

[0069] The battery cell may be a generally cylindrical cell having a diameter of approximately 46 mm, a height of approximately 110 mm, and an aspect ratio of 0.418.

[0070] A battery cell according to another aspect may be a generally cylindrical cell having a diameter of approximately 48 mm, a height of approximately 75 mm, and an aspect ratio of 0.640.

[0071] A battery cell according to another aspect may be a substantially cylindrical cell having a diameter of about 48 mm, a height of about 110 mm, and an aspect ratio of 0.436.

[0072] A battery cell according to yet another aspect may be a generally cylindrical cell having a diameter of approximately 48 mm, a height of approximately 80 mm, and an aspect ratio of 0.600.

[0073] A battery cell according to another aspect may be a generally cylindrical cell having a diameter of approximately 46 mm, a height of approximately 80 mm, and an aspect ratio of 0.575.

[0074] The present disclosure can be applied in the context of battery cells having a shape factor ratio of about 0.4 or less, such as 18650 cells, 21700 cells, etc. For 18650 cells, the diameter is about 18 mm, the height is about 65 mm, and the shape factor ratio is 0.277. For 21700 cells, the diameter is about 21 mm, the height is about 70 mm, and the shape factor ratio is 0.300.

[0075] The battery cell of the present disclosure includes an electrode assembly 20 , current collector plates 31 and 32 electrically connected to the electrode assembly 20 , and a can 10 accommodating the electrode assembly 20 and the current collector plates 31 and 32 .

[0076] The tank 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 cover 16 covering an open end provided at one axial end of the side wall member 11, i.e., an upper end 30 (or "first end") of the side wall member 11.

[0077] The bottom member 12 may have a disk shape in which a hole is centrally provided, and the sidewall member 11 may have a cylindrical shape defining an inner volume of the can 10 .

[0078] The bottom member 12 and the side wall member 11 may be manufactured by performing a deep drawing process on a metal sheet having a nickel-plated steel surface (although the material is not limited thereto), and then trimming the side wall member 11 with a punch while holding the front end of the side wall member with a blank holder.

[0079] The first electrode terminal 13 may be fitted into the hole and coupled to the hole. The first electrode terminal 13 may be riveted and fixed to the bottom member 12, and the gasket 14 is interposed therebetween. Specifically, 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, thereby preventing electrolyte leakage, and electrically insulating the first electrode terminal 13 from the bottom member 12.

[0080] However, the connection method between the first electrode terminal 13 and the bottom member 12 is not limited thereto. For example, if the resulting structure is capable of creating a seal between the first electrode terminal 13 and the bottom member 12 and electrically insulating the first electrode terminal 13 from the bottom member 12, various other fixing methods such as a bolt and nut connection method, a glass sealing method, or a chrome coating-and-PP-MAH (maleic anhydride grafted polypropylene or maleated polypropylene) thermal bonding method may be used.

[0081] 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 sidewall member 11 connected thereto, and the cover 16 (described later) connected to the sidewall member 11 may all have the second polarity.

[0082] Therefore, the battery cell may have both the first electrode terminal 13 and the second electrode terminal 15, which are disposed at the axial end where the bottom member 12 is disposed (i.e., disposed at the closed end of the can 10). As a result, the battery cell may have a bus bar connected to the first electrode terminal 13 and another bus bar connected to the second electrode terminal 15, both of which are located at the top of the battery cell.

[0083] In one example, the first electrode terminal 13 may be a positive terminal and the second electrode terminal 15 may be a negative terminal, although they may be reversed in different examples.

[0084] The electrode assembly 20 is housed in the inner volume of the can 10. The electrode assembly 20 is manufactured in the following manner: Figure 2 As shown in FIG. 1 , a first electrode 21, a second electrode 22 and a separator 28 extending in the length direction with a predetermined width are prepared; then as shown in FIG. Figure 3 As shown, a laminate is formed by sequentially stacking a first electrode 21, a separator 28, a second electrode 22, and a separator 28; Figure 4 As shown, the laminate is wound into a shape having a core wound around a mandrel.

[0085] The first electrode 21 may be a positive electrode, and the second electrode 22 may be a negative electrode. However, the first electrode 21 and the second electrode 22 may be reversed.

[0086] The first electrode 21 and the second electrode 22 are manufactured in the form of sheets. The electrode sheet is manufactured by applying an active material layer 24 to the surface of a metal foil 23. The electrode sheet includes a coated area 25 coated with the active material layer 24 and an uncoated area 26 not coated with the active material layer 24. The positive electrode sheet is provided with the uncoated area 26 on one side in the width direction, and the negative electrode sheet is provided with the non-coated area 26 on the other side in the width direction.

[0087] The first electrode 21 and the second electrode 22 are arranged in the laminate so that their uncoated regions 26 are exposed or protruded from the laminate in the width direction, wherein the uncoated region 26 of the first electrode 21 protrudes at one axial end of the wound core, and the uncoated region 26 of the second electrode 22 protrudes at the opposite axial end of the core. The uncoated region 26 itself functions as at least one notched joint 27.

[0088] Notches may be formed at predetermined intervals along the uncoated region 26 to define notch joints 27 .

[0089] Each of the notched joints 27 can be formed in the form of a flag. In the illustrated embodiment, the notched joints 27 have the shape of an equilateral trapezoid. However, the notched joints 27 can have various shapes, such as a semicircle, a semi-ellipse, a triangle, a rectangle, a parallelogram, etc. In addition, in the illustrated embodiment, the notched joints 27 each have the same width along the length direction of the electrode. However, in another embodiment, the width of the notched joints along the length direction can gradually widen from the core side to the peripheral side.

[0090] In addition, if Figure 2 and Figure 3 As shown, the height of the notched joint 27 gradually increases from the core side to the peripheral side. However, in an alternative, the height of the notched joint may be constant or may gradually decrease.

[0091] In addition, according to this scheme, at both opposite ends of the first electrode 21 and the second electrode 22 in the length direction, the notched joint 27 may be removed from the uncoated region 26 or may not exist. However, in some schemes, when the electrode assembly 20 is wound into a core structure, the notched joints may not be removed from either end, or they may be removed only from the uncoated region at the radially inner end or the radially outer end.

[0092] In the jelly-roll type electrode assembly 20, the notched tab 27 may be bent and flattened in the radial direction, as shown in FIG. Figure 4 That is, the notched joint 27 can be bent inwardly or outwardly in the radial direction. Although according to various embodiments of the present disclosure, the notched joint 27 is bent inwardly in the radial direction as shown in the figure.

[0093] The notched tabs 27 may be bent one by one in the process of winding the laminate to form the jellyroll type electrode assembly 20. Alternatively, the notched tabs 27 may be formed by bending all the notched tabs 27 at once after the laminate has been wound to form the jellyroll type electrode assembly.

[0094] The notched joint 27 of the first electrode 21 and the notched joint 27 of the second electrode 22 , which have been bent in the radial direction and overlapped with each other, may provide a plane substantially perpendicular to the axial direction at each of two opposite axial ends of the electrode assembly 20 .

[0095] The first current collector plate 31 and the second current collector plate 32 may be bonded to a substantially flat surface provided by the bent notched tabs 27 exposed at both axial ends of the electrode assembly 20, as shown in FIG. Figure 5 and Figure 6 shown.

[0096] In one embodiment, the first current collector plate 31 is a positive current collector plate, and the second current collector plate 32 is a negative 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. The current collector plates 31 and 32 may be manufactured by stamping, trimming, piercing, and / or bending metal sheets.

[0097] Reference Figure 5 The first current collector plate 31 includes a terminal connection portion 312 extending radially outward from the center, a ring portion 313 connecting the radial outer ends of the terminal connection portion 312 and extending in the circumferential direction, and an electrode connection portion 314 extending radially inward from the ring portion 313 and not connected to the terminal connection portion 312. The center of the terminal connection portion 312 covers at least a portion of the core hollow portion along the central longitudinal axis of the electrode assembly 20.

[0098] Before the electrode assembly 20 is inserted into the can 10, the electrode connection portion 314 is bonded to the notched tab 27 of the first electrode 21 of the electrode assembly 20 using a method such as laser welding. The welding line of the laser may extend radially.

[0099] Reference Figure 6 , the second current collector plate 32 defines a hole 322 corresponding to the core hollow portion of the electrode assembly 20. The second current collector plate 32 includes an inner ring portion 321 surrounding the core hollow portion and an electrode joint connection portion 323 extending radially from the inner ring portion 321. The electrode joint connection portion 323 may be in the form of a plurality of spokes extending radially outward from the inner ring portion, wherein one or more of the spokes have a radially outer end connected to a peripheral portion (referred to as a can connection portion 324) of the current collector plate 32. In addition, one or more spokes of the electrode joint connection portion 323 may have a radially outer end that does not reach the can connection portion 324. The can connection portion 324 has an outer ring shape surrounding the electrode joint connection portion 323, and the can connection portion 324 may include a step away from the electrode assembly 20 in the axial direction, so that at least the outermost periphery of the can connection portion 324 is spaced farther from the electrode assembly 20 than other portions of the can connection portion 324 (including the electrode joint connection portion 323 and the inner ring portion 321).

[0100] Before the electrode assembly 20 is inserted into the can 10, the electrode tab connection portion 323 is bonded to the notched tab 27 of the second electrode 22 of the electrode assembly 20 by laser welding or the like. The welding line of the laser may extend radially.

[0101] like Figure 7 and Figure 8 As shown, the electrode assembly 20 is accommodated in the can 10, and the first current collector plate 31 is aligned to face the bottom member 12 of the can 10. The 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.

[0102] The terminal connection portion 312 of the first current collector plate 31 is bonded to the first electrode terminal 13 by resistance welding, ultrasonic welding, laser welding, etc. The welding device for welding the first current collector plate 31 and the first electrode terminal 13 can perform welding by entering the inner side of the center of the terminal connection portion 312 of the first current collector plate 31 (that is, the side of the terminal connection portion 312 facing the electrode assembly 20). Specifically, the welding device can enter the position of the first current collector plate 31 from the open end of the can 10 through the core hollow portion of the electrode assembly 20, as shown in FIG. Figure 8As an alternative to the above-mentioned welding method, the first current collector plate 31 and the first electrode terminal 13 may be combined with each other by brazing or soldering. That is, various combining methods may be used as long as both the first current collector plate 31 and the first electrode terminal 13 are fixed to each other and electrically connected to each other.

[0103] In the case where the electrode assembly 20 is housed inside the can 10 , the notched tab 27 of the second electrode 22 and the second current collector plate 32 will be arranged to face the open end of the sidewall member 11 .

[0104] After the first current collector plate 31 and the first electrode terminal 13 are combined, an electrolyte solution may be injected into the can 10. After the electrolyte solution is injected, the open end of the sidewall member 11 may be covered and closed with a cover 16, such as Fig. 9 Due to the connection between the bottom member 12 and the side wall member 11 of the can 10, the internal volume of the can 10 is closed by covering the open end with a cover 16.

[0105] like Fig.10 As shown, the edge of the cover 16 is bonded to the edge of the side wall member 11 by seam welding using a laser, so that the can 10 can be sealed thereby.

[0106] In addition to the above methods, Fig.11 As shown, it is also feasible to perform bonding by resistance seam welding (for example, by using a roller electrode R). The roller electrode R may have a tapered shape. The method involves rotating the can 10 with the circumferential surface of the roller electrode R in contact with the upper end 30 of the side wall member 11, and the roller electrode R also rotates with the rotation of the can 10. By applying a positive voltage to one of the two electrodes and a negative voltage to the other during rotation, current flows as desired, so that resistance heat can be generated in the contact area between the cover 16 and the side wall member 11 adjacent to the electrode R. As a result, welding can be performed in these contact areas.

[0107] The welding structure and welding method of the present disclosure may be used in combination with a method in which, after first covering the open end of the can 10 with the cover 16 and then welding (W) the side wall member 11, an electrolyte solution is injected into the can 10 through the liquid injection port 18 (e.g., Fig.12 Then, the liquid injection port 18 of the cover 16 is closed with a plug 40 (as shown in Fig.13). The liquid injection port 18 may have a circular hole shape provided in the center of the cover 16, and the plug 40 may be a round cap including a surface portion and an insertion portion, wherein the surface portion has a larger diameter than the liquid injection port 18, and the insertion portion protrudes from the surface portion to fit into the liquid injection port 18. The outer periphery of the plug 40 is welded to the cover 16, and thus the liquid injection port 18 can be sealed. However, the bonding method between the plug 40 and the cover 16 is not limited to welding, as various bonding methods capable of sealing, such as soldering, O-ring compression, and screw fastening, may be utilized.

[0108] Reference Fig.10 , Fig.14 and Fig.15 , an inner diameter expansion portion 113 may be provided at the open end of the sidewall member 11. The inner diameter expansion portion 113 may be in the form of a transverse step extending across the central longitudinal axis and positioned along the radial inner surface of the sidewall member 11. Therefore, the radial inner surface of the sidewall member 11 may include: a first inner surface 111, which is located axially below the inner diameter expansion portion 113 (i.e., farther away from the opening of the open end of the sidewall member 11 than the inner diameter expansion portion 113); and a second inner surface 115, which is arranged axially more outward than the inner diameter expansion portion 113. The second inner surface 115 may have a larger inner diameter than the first inner surface 111. Therefore, the second thickness t2 of the sidewall member 11 measured in the radial direction at the portion where the second inner surface 115 is located is less than the first thickness t1 of the sidewall member 11 at the portion where the first inner surface 111 is located.

[0109] The tank connection portion 324 provided at the edge of the second current collector plate 32 and electrically connected to the tank 10 includes a first portion contacting the second inner surface 115 of the sidewall member 11. In the first portion, a circumferential contact surface 325 facing and contacting the second inner surface 115 of the sidewall member 11 in the radial direction is provided.

[0110] The tank connection portion 324 includes a second portion that contacts the cover 16. In the second portion, a cover contact surface 326 that is an inner surface facing and contacting the cover 16 in the axial direction (ie, the lower side of the cover 16) is provided.

[0111] The diameter of the circumferential contact surface 325 of the tank connection portion 324 is set to be larger than the inner diameter of the first inner surface 111. Therefore, the tank connection portion 324 includes a third portion that contacts the inner diameter expansion portion 113. The third portion is positioned on the opposite side of the cover contact surface 326 in the axial direction. The third portion contacts the inner diameter expansion portion 113, thereby limiting the depth of insertion of the second collector plate 32 into the tank 10.

[0112] The second current collector plate 32 also includes a first bend 327 and a second bend 328, thereby defining a step in the axial direction. The first bend 327 provides a shape in which the second current collector plate 32 extending outward in the radial direction is bent upward in the axial direction. The second bend 328 provides a shape in which the upwardly bent portion of the second current collector plate 32 is bent back outward in the radial direction. Due to the axial step between the first bend 327 and the second bend 328, the peripheral portion (or tank connection portion 324) of the current collector plate 32 is offset in the axial direction toward the open end of the tank 10 relative to the central portion of the current collector plate 32. The tank connection portion 324 is connected to the electrode joint connection portion 323 through the first bend 327 and the second bend 328 and through the above-mentioned inner ring portion 321. The tank connection portion 324 is connected to the outer side of the second bend 328 in the radial direction and extends outward from the second bend 328 in the radial direction, thereby providing the cover contact surface 326 of the second current collector plate 32.

[0113] The material of the second current collector plate 32 is desirably softer than the material of the sidewall member 11, and therefore, the first bent portion 327 and the second bent portion 328 are elastically deformed during the insertion of the second current collector plate 32 into the open end of the sidewall member 11. Therefore, when the outer diameter of the circumferential contact surface 325 is set to be slightly larger than the inner diameter of the second inner surface 115, the circumferential contact surface 325 is press-fitted into the second inner surface 115.

[0114] The cover 16 includes, in order from the center toward the outside in the radial direction: a cover body 160, a reduced thickness portion 161 (a portion where the thickness of the cover changes), and a joint portion 17. That is, the cover body 160 is centered on the central area of ​​the cover 16, and the reduced thickness portion 161 is provided around the outside of the cover body 160 in the radial direction. The joint portion 17 is positioned along the radial outside of the reduced thickness portion 161 to define an annular region of the cover 16 where the thickness is reduced relative to the cover body 160. That is, the third thickness t3 of the joint portion 17 measured in the axial direction is less than the fourth thickness t4 of the cover body 160 measured in the axial direction.

[0115] The outer peripheral joint surface 171 facing the second inner surface 115 of the side wall member 11 in the radial direction is provided along the radial outer surface of the cover 16, and specifically, along the radial outer surface of the joint 17. According to the first aspect of the present disclosure, the outer peripheral joint surface 171 is in contact with the second inner surface 115 of the side wall member 11. In addition, the lower side of the cover 16 along the joint 17 includes a collector plate contact surface 173, which faces downward in the axial direction so as to contact the cover contact surface 326 of the tank connection portion 324 of the second collector plate 32.

[0116] The position of the reduced thickness portion 161 is selected so that at least a portion of the reduced thickness portion 161 contacts the second current collector plate 32. In the process of inserting the cover 16 into the open end of the side wall member 11, when the reduced thickness portion 161 of the cover 16 contacts the second current collector plate 32, such contact beneficially achieves the effect of aligning the center of the cover 16 relative to the second current collector plate 32 and the central longitudinal axis. In the first scheme shown, the alignment effect can be achieved by placing the reduced thickness portion 161 at a position corresponding to the position where the second bend 328 of the second current collector plate 32 is formed in the radial direction. In order to improve the alignment effect, the reduced thickness portion 161 is desirably in the form of an inclined surface that extends upward in the axial direction as it approaches the outside in the radial direction. In addition, in order to improve the alignment effect, an inclined surface shape is desirably provided on the second current collector plate 32 by means of the surface shape of the second bend 328 of the second current collector plate 32.

[0117] The outer peripheral joint surface 171 of the cover 16 and the circumferential contact surface 325 of the second current collector plate 32 are each in contact with the second inner surface 115 of the side wall member 11 in the radial direction. In addition, in the axial direction, the lower side of the second current collector plate 32 is in contact with the inner diameter expansion portion 113 of the side wall member 11 along at least a portion of its peripheral portion. The cover contact surface 326 provided on the upper side of the second current collector plate 32 is in contact with the collector plate contact surface 173 provided on the lower side of the joint portion 17 of the cover 16.

[0118] With the second current collector plate 32 and the cover 16 inserted, the position of the upper end 30 of the sidewall member 11 in the axial direction may correspond to the position of the upper surface of the cover 16 .

[0119] like Fig.15 As shown, a first height h1 of the area extending upward from the inner diameter expansion portion 113 may correspond to the sum of a third thickness t3 of the coupling portion 17 of the cover 16 and a fifth thickness t5 of the tank connection portion 324 of the second current collector plate 32 .

[0120] As shown in the drawings, the upper axial end of the outer peripheral joint surface 171 of the cover 16 and the radial inner surface of the side wall member 11 , which are in contact with each other in the radial direction, are exposed along the outer side of the battery cell.

[0121] The cover 16 may be welded to the can 10 by laser irradiated in the axial direction from the outside of the battery cell and directed toward the second inner surface 115 of the sidewall member 11 and the axial end of the outer peripheral joint surface 171 of the cover 16 .

[0122] Since the circumferential contact surface 3255 of the second current collector plate 32 is axially disposed below the cover 16 and in contact with the radial inner surface of the side wall member 11, it is possible to prevent the laser from being irradiated into the inner volume of the tank through any gap that may exist between the side wall member 11 and the cover 16. In addition, the inner diameter expansion portion 113 of the side wall member 11 also prevents the laser from being irradiated and penetrating the gap between the side wall member 11 and the cover 16 or the gap between the side wall member 11 and the second current collector plate 32.

[0123] The second current collector plate 32 may be made of a material having a higher thermal conductivity than the sidewall member 11. In addition, the second current collector plate 32 is in contact with the sidewall member 11. Therefore, when the welding heat generated in the sidewall member 11 by the laser is conducted in the axial direction of the sidewall member 11, the welding heat is dispersed to the top of the electrode assembly 20 through the second current collector plate 32 and passes through the top of the electrode assembly 20, so that damage to the separator caused by the welding heat can be prevented.

[0124] The second current collector plate 32 is also in contact with the cover 16. Therefore, heat generated in the cover 16 by laser welding or resistance welding is dispersed and transferred through the second current collector plate 32. As a result, when the contact area between the cover 16 and the sidewall member 11 is heated by laser, the sidewall member 11 may be first heated and then melted.

[0125] Therefore, when the side wall member 11 is too thin, the side wall member 11 may melt before the cover 16, and welding may not be performed smoothly. Therefore, the second thickness t2 of the side wall member 11 is preferably 0.25 mm or more. For example, the second thickness t2 may be 0.35 mm.

[0126] It is also important that the cover 16 has sufficient strength to withstand the expected increase in internal pressure within the can 10. When the cover 16 is too thin, excessive bulging may occur, in which the cover 16 expands into a spherical surface profile under the high internal pressure within the can 10, thereby deteriorating the durability of the battery cell. In order to resist such bulging deformation, it is important that the cover 16 has a certain thickness. On the other hand, when the thickness of the cover 16 is too thick relative to the side wall member 11, only the side wall member 11 can be initially melted during laser welding, thereby greatly weakening the welding process. In addition, as the thickness of the cover 16 increases, the axial length of the peripheral joint surface 171 of the cover 16 where welding can be performed also increases. In addition, in order to ensure the durability of the can 10, it is preferably welded The entire section of the peripheral joint surface 171 of the cover 16 in the axial direction.

[0127] The illustrated scheme relates to a structure in which the third thickness t3 of the joint portion 17 welded to the side wall member 11 is different from the fourth thickness t4 of the cover body 160. The thicker the fourth thickness t4, the higher the anti-bulging property, but the internal space of the can occupied by it also increases. In order to improve the anti-bulging property while minimizing the space occupation and weight, the fourth thickness t4 is preferably as small as possible within the required anti-bulging property range.

[0128] As a result, the fourth thickness t4 of the cover body 160, which occupies most of the cover 16, is desirably greater than the third thickness t3, so as to minimize the deformation of the cover 16 due to the internal pressure in the tank 10, while minimizing the thickness of the welded portion along the axial dimension, so as to ensure that the welded portion W is formed along the entire axial dimension of the peripheral joint surface 171, thereby improving the strength of the cover 16 itself and the bonding strength of the cover 16 with the side wall member 11. 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. When the ratio is less than this range, the cover body 160 becomes too thick without increasing the anti-bulging property and / or the strength of the welded portion becomes insufficient. When the ratio is greater than this range, the anti-bulging property of the cover body 160 becomes insufficient and / or it becomes difficult to weld the peripheral joint surface 171 of the cover 16 along the entire axial direction of the peripheral joint surface 171 of the cover 16.

[0129] According to the illustrated embodiment, the reduced thickness portion 161 can be positioned as close to the welding area as possible in the radial direction so that the maximum area of ​​the cover body 160 that resists bulging can be obtained. In addition, by selecting the position of the reduced thickness portion 161, a guiding function for aligning the center of the cover 16 while contacting the second collector plate 32 can also be provided.

[0130] The third thickness t3 of the joint portion 17 of the cover 16 can be set to be greater than the second thickness t2 of the side wall member 11. The third thickness t3 can be between one and two times the second thickness t2. For example, when the second thickness t2 is 0.35 mm, the third thickness t3 can be 0.5 mm or in the range of 0.5 mm to 0.7 mm.

[0131] When the third thickness t3 is greater than twice the second thickness t2, there is a risk that the side wall member 11 may be excessively melted before the cover 16 is melted during the formation of the welded portion. In addition, when the third thickness t3 is greater than twice the second thickness t2, there is a risk that the welded portion will not be formed along the entire peripheral bonding surface 171 of the cover 16 in the axial direction.

[0132] When the third thickness t3 is less than the second thickness t2 (i.e., when the second thickness t2 is greater than the third thickness t3), it may be difficult to ensure the strength of the edge region of the cover 16. It may also be difficult to provide a sufficient lateral step size of the inner diameter expansion portion 113 of the side wall member 11 without making the overall thickness t1 of the side wall member 11 too large.

[0133] The process of welding the cover 16 and the second current collector plate 32 to the open end of the side wall member 11 may be completed in two steps, thereby obtaining the battery cell according to the first aspect of the present disclosure including the first welding portion W1 and the second welding portion W2 .

[0134] First, in Fig.15 As shown, when the cover 16 is inserted into the open end of the side wall member 11, positioning welding can be performed to fix the position of the cover 16 relative to the side wall member 11, as shown in FIG. Fig.16 and 17 The tack welding process desirably results in the formation of first weld portions W1 at a plurality of locations spaced apart in the circumferential direction of the outer peripheral joining surface 171 of the cover 16 and the second inner surface 115 of the sidewall member 11 .

[0135] The first welding portion W1 may be a portion where the side wall member 11, the cover 16, and the second current collector plate 32 are melted together. That is, unlike the general tack welding process that may be used as the main welding process herein, the tack welding process of the first scheme temporarily fixes the position of the cover 16 before performing the main welding. In addition, because the cover 16, the side wall member 11, and the second current collector plate 32 are welded at the same time, the tack welding process of the first scheme also allows the process of separately welding the second current collector plate 32 to the side wall member 11 before covering the open end of the side wall member 11 with the cover 16 to be omitted.

[0136] The first welding portions W1 may be positioned at equal intervals in the circumferential direction. In order to ensure the position of the cover 16 relative to the side wall member 11 and reduce the internal resistance by obtaining a desired cross-sectional area of ​​the combination between the second collector plate 32 and the tank 10, the first welding portions W1 may be disposed at three or more locations. Preferably, the first welding portions W1 may be disposed at four locations.

[0137] The first weld portion W1 can be formed by a spot welding method in which the laser is directed to a specific area instead of scanning as in conventional tack welding. However, in order to ensure that not only the side wall member 11 and the cover 16 are melted, but also the tank connection portion 324 of the second current collector plate 32 is melted and bonded, a scanning welding method in which the laser is scanned at a predetermined distance in a circumferential direction can be used to form the first weld portion W1. This laser scanning distance for forming the first weld portion W1 can be between 0.5 mm and 5 mm. Preferably, the scanning distance can be 4 mm. When the scanning distance is less than 0.5 mm, it may be difficult to ensure that the second current collector plate 32 is reliably melted. On the other hand, when the scanning distance is greater than 5 mm, excessive welding heat may be generated, which may cause thermal damage to the diaphragm 28 of the electrode assembly 20.

[0138] The first welded portion W1 of the first aspect can be formed by scanning welding using a laser having a higher output than a laser used for general tack welding using spot welding.

[0139] The output of the laser can be adjusted by adjusting the focal length of the laser, thereby adjusting the size of the irradiation area. For example, even if the output of the laser oscillator is the same, for a smaller irradiation area, the output per unit area may be higher, resulting in a higher energy density. On the other hand, for a larger irradiation area, the output per unit area may be lower, resulting in a lower energy density.

[0140] As an example, the first weld portion can be formed by reducing the size of the irradiated area to have a high energy density (output per unit area). The scanning speed of the laser used to form the first weld portion W1 can be set to be relatively fast to prevent damage to the separator due to high heat concentrated at a specific point. Therefore, instead of simply temporarily bonding the cover 16 to the side wall member 11, triple welding is performed by also melting and bonding the second current collector plate 32, while preventing damage to the electrode assembly 20 by sufficiently reducing the internal resistance and minimizing the heat generation caused by triple welding.

[0141] Next, if Figures 18 to 20 As shown, the main welding may be performed by seam welding of welding the second inner surface 115 of the side wall member 11 and the outer peripheral joint surface 171 of the cover 16. This main welding process may be a process of forming the welded portion W2, in which the can 10 is sealed by substantially entirely and firmly welding the second inner surface 115 of the side wall member 11 and the outer peripheral joint surface 171 of the cover 16 in the circumferential direction.

[0142] The second weld portion W2 may be formed using a laser having a lower output than the laser used to form the first weld portion W1. For example, the second weld portion may be formed by expanding the size of the irradiation region to have a relatively low energy density (output per unit area).

[0143] The scanning speed of the laser used to form the second welding portion W2 can be set relatively slow so as to stably form the welding pool. Even in the case of a slow scanning speed, the heat generated when forming the second welding portion W2 can be dispersed through the second current collector plate 32 made of a high thermal conductivity material, thereby reducing the possibility of damaging the diaphragm.

[0144] The power and scanning speed of the laser used to form the second welding portion W2 should be determined in such a manner that substantially the entire section of the outer peripheral bonding surface 171 of the cover 16 in the axial direction can be bonded to the second inner surface 115 of the sidewall member 11. Additional bonding of the second current collector plate 32 to the can 10 can be achieved by melting and bonding a portion of the second current collector plate 32 through additional welding heat.

[0145] Since the amount of welding heat generated in forming the second weld portion W2 is desirably significantly smaller than the amount of welding heat generated in forming the first weld portion W1 , damage to the electrode assembly 20 may be desirably prevented.

[0146] The second welding portion W2 may be formed continuously in the circumferential direction. Therefore, in the section where the first welding portion W1 has been formed, the second welding portion W2 may be formed by overlapping with the first welding portion W1, such as Fig. 20 That is, as shown in this figure, the shape of the first welding portion W1 can be combined with the shape of the second welding portion W2 to provide the same overall appearance as a single welding. Fig. 20 As shown, the depth (i.e., distance) of the first weld portion W1 extending away from the first end or upper end 30 of the tank 10 in the axial direction may be deeper than the depth / distance of the second weld portion W2 extending away from the first end or upper end 30 of the tank 10. Fig. 20 As shown, the cross-sectional area of ​​the first welding portion W1 may be different from the cross-sectional area of ​​the second welding portion W2, especially along a line similar to Fig. 20 A section wherein the plane of the section extends perpendicular to the circumferential direction at the position where the plane intersects the relevant welding portion W1 or W2. The plane of such a section extends parallel to the central longitudinal axis.

[0147] In the following, reference is made to Figure 21 to Figure 26, a second scheme of the welding structure of the battery cell will be described. When describing the second scheme, in order to avoid redundant description, the differences from the first scheme will be mainly described. Therefore, it should be understood that in view of the description of the first scheme, matters not described in conjunction with the second scheme can be fully understood. In addition, it should be understood that the various elements of the first scheme described above and the second scheme described below can be replaced or omitted with each other, as long as there is no conflict with the spirit of the present disclosure.

[0148] Reference Fig.21 and Fig. 22 The outer diameter of the outer peripheral joint surface 171 of the cover 16 of the second embodiment is slightly smaller than the outer diameter of the outer peripheral joint surface 171 of the cover 16 of the first embodiment. Therefore, a small gap G exists between the second inner surface 115 of the side wall member 11 and the outer peripheral joint surface 171 of the cover 16 in the radial direction.

[0149] The gap G serves as a path through which the laser for welding can directly reach the second current collector plate 32. Therefore, even if the laser power is lower than that in the first embodiment, the first welded portion W1 in which triple welding is performed can be formed, and the second welded portion W2 in which seam welding is performed can also be formed.

[0150] Even when the gap G exists in the entire circumferential direction, the second bent portion 328 of the second current collector plate 32 and the reduced thickness portion 161 of the cover 16 preferably contact so that the center of the cover 16 is aligned so that the width of the gap G is uniform in the circumferential direction.

[0151] The side wall member 11 of the second embodiment can be extended longer than the side wall member 11 of the first embodiment. Fig.21 and Fig. 22 As shown, when the second current collector plate 32 and the cover 16 are inserted, an overhang 117 is provided at the open end of the side wall member 11, and the overhang 117 protrudes further upward in the axial direction than the cover 16. The overhang 117 can also be called an "extension" of the side wall member 11.

[0152] The first height h1 of the section of the side wall member 11 located above the inner diameter expansion portion 113 in the axial direction may be greater than the sum of the third thickness t3 of the joint portion 17 of the cover 16 and the fifth thickness t5 of the tank connection portion 324 of the collector plate 32. The second height h2 of the overhang portion 117 (or the extension of the side wall) may be a length obtained by subtracting the third thickness t3 and the fifth thickness t5 from the first height h1.

[0153] The overhang 117 can reduce the melting time difference between the sidewall member 11 and the cover 16 by delaying the melting time of the relatively thin sidewall member 11. In addition, during the welding process, the overhang 117 can be expected to melt and flow into the welding area between the second inner surface 115 of the sidewall member 11 and the outer peripheral joint surface 171 of the cover 16. In this regard, the diameter of the outer peripheral joint surface 171 of the cover 16 can be slightly smaller than the diameter of the second inner surface 115 of the sidewall member 11 adjacent to the outer peripheral joint surface 171. In this context, when two objects are closely spaced relative to their outer dimensions and there is no separate intervening object between the two objects in the relevant plane (i.e., the radial plane orthogonal to the central longitudinal axis), the two objects are "adjacent". The diameter of the outer peripheral joint surface 171 of the cover 16 is slightly smaller than the diameter of the second inner surface 115 of the sidewall member 11, resulting in a small gap defined between the two components. Such a gap can be used as a path for the laser used for welding to directly irradiate the second collector plate 32. As discussed above, at least due to the interaction between the reduced thickness portion 161 of the cover 16 and the second collector plate 32, the cover 16 is located in the center, and such a gap is desirably of uniform width in the radial direction along the entire circumferential direction of the cover 16. In addition, during the welding process, the material of the overhang 117 desirably flows into the gap between the outer peripheral joint surface 171 of the cover 16 and the second inner surface 115 of the sidewall member 11 so as to join the cover 16 and the sidewall member 11 together. In an exemplary embodiment, the height h2 of the overhang 117 is 0.2 mm, and the thickness t3 of the joint portion 17 of the cover 16 is 0.5 mm. When the thickness t2 of the overhang 117 is 0.35 mm, it can provide sufficient material when it melts during welding, thereby creating a strong joint between the cover 16 and the sidewall member 11. For example, the ratio of the overhang height h2 to the thickness t3 of the joint portion 17 can be desirably in the range of 0.2 to 1.

[0154] Reference Fig.23 , a first welded portion W1 may be formed by welding together at discrete positions in the circumferential direction the following segments: a segment of the second inner surface 115 of the side wall member 11 , a segment of the peripheral joint surface 171 of the cover 16 , and a segment of the tank connection portion 324 of the second current collector plate 32 .

[0155] In those portions where the first weld portion W1 is formed, the overhang 117 is desirably completely melted so that the overhang 117 in its molten state can penetrate into the contact area among the section of the second inner surface 115 of the side wall member 11, the section of the outer peripheral joint surface 171 of the cover 16, and the section of the tank connecting portion 324 of the second current collector plate 32 to fill at least a portion of the gap G, as shown in FIG. Fig.25 shown.

[0156] Next, refer to Fig.24 The second weld portion W2 may be formed by melting at least a portion of the second inner surface 115 of the side wall member 11 and a portion of the outer peripheral joining surface 171 of the cover 16 along substantially the entire circumferential direction.

[0157] When forming the second welding portion W2, the overhang 117 is preferably completely melted so that the melted overhang 117 can penetrate into the contact area between the section of the second inner surface 115 of the side wall member 11 and the section of the outer peripheral joint surface 171 of the cover 16, as well as Fig.26 As a result, the final overall height of the battery cell can be defined by the outer surface of the cover 16. That is, as shown in the illustrated second scheme, the overhang 117 and the welded portion W do not contribute to the height of the battery cell, so that the height dimension of the battery cell can be consistently managed.

[0158] In the following, reference will be made to Fig. 27 and 28 A third scheme of the welding structure of the battery cell according to the present disclosure is described. In this description, in order to avoid redundant description, the differences from the aforementioned scheme will be mainly described. Therefore, it should be understood that matters not described in conjunction with the third scheme can be fully understood in view of the description of other schemes. In addition, it should be understood that the various elements of the preceding scheme described above and the third scheme described below can be replaced or omitted with each other, as long as there is no conflict with the spirit of the present disclosure.

[0159] Reference Fig. 27 The outer peripheral joint surface 171 of the cover 16 of the third embodiment may be provided with a large diameter section 171a and a small diameter section 171b having a smaller diameter than the large diameter section 171a. The large diameter section 171a and the small diameter section 171b may be alternately arranged with each other in the circumferential direction.

[0160] like Fig.28 As shown, the large diameter section 171a of the outer peripheral joint surface 171 may face and contact the second inner surface 115 of the sidewall member 11 in the radial direction, while the small diameter section 171b may face the second inner surface 115 of the sidewall member 11 in the radial direction with a gap G provided therebetween. That is, the outer diameter of the outer peripheral joint surface 171 of the cover 16 in the large diameter section 171a may correspond to the outer diameter of the circumferential contact surface 325 of the second current collector plate 32. In addition, the outer diameter of the outer peripheral joint surface 171 of the cover 16 in the small diameter section 171b may be smaller than the outer diameter of the circumferential contact surface 325 of the second current collector plate 32.

[0161] During and after the insertion of the cover 16, the large diameter section 171a preferably aligns the central position of the cover 16 relative to the side wall member 11. In addition, the small diameter section 171b defines a gap G relative to the side wall member 11. Therefore, when the cover 16 is manufactured according to the third scheme, the alignment of the central position of the cover 16 can be promoted, and welding can be performed even with a relatively low-power laser compared to the first scheme. In addition, when the first welding portion W1 is formed in the region of the gap G formed with the small diameter section 171b, triple welding can be performed even with a relatively low-power laser, and the amount of heat generated due to triple welding can also be suppressed.

[0162] According to the aforementioned scheme of the present disclosure, when performing triple welding including the second current collector plate, the generation of welding heat can be minimized. In addition, even when triple welding is performed in combination with a positioning welding process, the number of working hours is preferably not increased. The internal resistance can also be advantageously reduced. By utilizing positioning welding before the main seam welding process, the position of the cover can be accurately fixed before performing seam welding. Therefore, although different welding processes are involved, sufficient sealing (i.e., no perforation or liquid leakage) can be obtained, and the welding performance can be improved. In addition, the process stability can be improved by preventing the welding heat from causing thermal damage to the unit components or the diaphragm, and the durability can also be improved by suppressing the dimensional deformation caused by the internal pressure to obtain dimensional stability and anti-uplift properties.

[0163] In the following, reference will be made to Fig.29 An example of a method of manufacturing the above-mentioned battery cell is described.

[0164] According to the manufacturing method of the battery cell, the can 10 having the first electrode terminal 13 fixed to the bottom member 12 is prepared, and then the electrode assembly 20 having both ends respectively coupled to the first and second current collector plates 31 and 32 in the axial direction is prepared.

[0165] Thereafter, the electrode assembly 20 is accommodated in the can 10 with the first current collector plate 31 facing the bottom member 12. As a result, the second current collector plate 32 is located on the open end side of the can 10. In the process of accommodating the electrode assembly 20 in the can 10, the circumferential contact surface 325 of the can connection portion 324 provided at the outer edge of the second current collector plate 32 in the radial direction comes into contact with the second inner surface 115 of the sidewall member 11.

[0166] Here, the tank connection portion 324 of the second current collector plate 32 contacts the inner diameter expansion portion 113 of the sidewall member 11 , so that adhesion strength of the current collector plate 32 to the radial inner surface of the sidewall member 11 is improved and an insertion depth of the second current collector plate 32 is adjusted.

[0167] Next, the first current collector plate 31 and the first electrode terminal 13 are combined.

[0168] Then, an electrolyte solution is injected into the can 10 .

[0169] After the electrolyte injection is completed, in the case where the open end of the side wall member 11 is covered with the cover 16, the peripheral joint surface 171 and the current collector plate contact surface 173 provided at the edge of the cover 16 are respectively in contact with or face the second inner surface 115 of the side wall member 11 and the cover contact surface 326 of the second current collector plate 32. In this way, the thickness reduction portion 161 in the form of an inclined surface provided on the lower side of the cover 16 in the axial direction can contact the second current collector plate 32 to align with the center of the cover 16.

[0170] Thereafter, welding is performed by irradiating laser on a contact area between the second inner surface 115 of the side wall member 11 and the outer peripheral joint surface 171 of the cover 16 in the axial direction from the outside of the battery cell.

[0171] During the welding process, the overhang portion 117 of the sidewall member 11 that protrudes further outward in the axial direction than the cover 16 may melt and flow into the welding area between the radial inner surface of the sidewall member 11 and the outer peripheral joint surface 171 of the cover 16 .

[0172] When performing the above welding, positioning welding can be performed first, and then main welding can be performed.

[0173] During the positioning welding process, a plurality of first welding portions W1 can be formed by irradiating a laser on the contact area between the inner peripheral surface of the side wall member 11 and the outer peripheral joint surface 171 of the cover 16 at positions spaced apart in the circumferential direction (from the outer side of the battery cell in the axial direction) to weld the inner peripheral surface of the side wall member 11, the outer peripheral joint surface 171 of the cover 16, and the tank connection portion 324 of the collector plate 32 together.

[0174] The laser in the tack welding process may have a first output power or a first energy density, and the laser may scan along a predetermined area at a first speed.

[0175] Next, during the main welding process, a second welding portion W2 is formed by continuously irradiating the laser on the contact area between the inner peripheral surface of the side wall member 11 and the outer peripheral joint surface 171 of the cover 16 and moving the laser along the contact area to weld at least the inner peripheral surface of the side wall member 11 and the outer peripheral joint surface 171 of the cover 16 together.

[0176] The laser of the main welding process may have a second output power lower than the first output power, or may have a second energy density lower than the first energy density.

[0177] The laser in the main welding process may scan and irradiate along substantially the entire circumferential section at a second speed that is slower than the first speed.

[0178] It may be sufficient to create the desired electrical connection area for the tack weld, but it is important to securely seal the can during the main weld (such as by forming a uniform weld pool). Therefore, the second speed relative to the second output power of the laser during the main weld may be slower than the first speed relative to the first output power of the laser during the tack weld.

[0179] In the following, reference is made to Fig.30 , another example of the manufacturing method of the above-mentioned battery cell will be described. This example involves using a cover having a liquid injection port. Fig.29 Compared to the example, Fig.30 An example may involve performing tack welding and main welding processes before injecting the electrolyte solution into the tank via the liquid injection port of the cover, after which the liquid injection port may be sealed with a plug. Therefore, since the cover is welded to the tank before injecting the electrolyte solution into the tank, welding heat may not affect the electrolyte solution.

[0180] The battery cell 72 manufactured by the above-mentioned welding structure and welding process can be accommodated in the housing 71 of the battery pack 70, as shown in FIG. Fig.31 The battery pack 70 may be constructed using one or more battery modules, each of which is an intermediate assembly form including a plurality of battery cells 72. Alternatively, as shown, the battery pack 70 may be constructed directly from a plurality of battery cells 72 without any intervening battery modules.

[0181] Since the battery cell 72 has a large volume, there is no particular difficulty in realizing the battery pack 70 even without using an intermediate structure such as a battery module. In addition, the battery cell 72 has a smaller internal resistance and a higher energy density than a conventional battery cell. Therefore, the energy density of the battery pack 70 including the battery cell 72 can be higher.

[0182] The battery pack 70 with this increased energy density can store the same amount of energy while reducing its volume and weight. Fig.32 As shown, when the battery pack 70 to which the battery cell 72 is applied is mounted on a vehicle (such as a car 80) that uses electricity as an energy source, the energy mileage of the vehicle can be further extended.

[0183] Although the above seam welding structures and methods are disclosed in the context of cylindrical battery cans, it should be appreciated that these techniques can be similarly applied to other battery form factors within the scope of the present disclosure. For example, the associated battery cells do not need to have a circular cross-sectional profile that is orthogonal to the central longitudinal axis, but other cross-sectional shapes (including elliptical, square, rectangular, partially circular, etc.) can be used. In addition, the central longitudinal axis does not need to be oriented perpendicular to the bottom member and / or cover at the corresponding opposite ends. As an example, the side wall member of the can (together with the internal components of the can) can form a tube extending along an axis that is oriented obliquely relative to the plane defined by the bottom member and / or cover. In addition, the welding techniques disclosed herein can also be used outside the context of cylindrical battery cans, and can also be applied to batteries having square and pouch-type form factors, for example.

[0184] A non-limiting benefit that some or all of the embodiments of the present disclosure may provide is that (especially compared to methods involving welding the entire perimeter of the tank in a single process) the generation of welding heat may be reduced while ensuring the electrical connection of the collector plate and the sealing of the tank. In addition, the desired internal resistance may be fully achieved while reliably sealing the tank. While welding the sidewall members, the cover, and the collector plate together, welding performance, stability, and durability may also be ensured. In addition, the assembly time of the battery cell may be greatly shortened. The volume of the electrode assembly contained in the tank may also be maximized to increase the energy density of the battery cell.

[0185] The above scheme should be understood as illustrative and not restrictive in all aspects, and the scope of the present disclosure will be presented by the claims rather than the detailed description given above. In addition, all variations and modifications derived from the meaning and scope of equivalent concepts and patent claims will be interpreted as being included in the scope of the present disclosure.

[0186] As described above, the present disclosure has been described with reference to the accompanying drawings, but the present disclosure is not limited to any aspect or drawings disclosed herein, and those skilled in the art may make various modifications within the scope of the technical concept of the present disclosure. In addition, when explaining the scheme of the present disclosure, not all operational effects produced by the present disclosure have been explicitly described and explained herein, but those of ordinary skill in the art will recognize these predictable effects.

Claims

1. A battery cell, characterized in that: The battery unit includes: a can having a sidewall member defining an interior volume and defining an opening to the interior volume at a first end of the can along a central longitudinal axis; an electrode assembly received within the interior volume of the can; a current collector plate electrically connected to the electrodes of the electrode assembly; and a lid covering the opening of the can so as to close the interior volume, wherein the current collector plate includes a peripheral portion that contacts the side wall member so as to be electrically connected to the tank, wherein the side wall members along the opening, the edge of the cover and the peripheral portion of the collector plate are all welded together along each of a plurality of first weld portions, the plurality of first weld portions are spaced apart from each other along a circumferential direction around the central longitudinal axis, and wherein both the side wall members along the opening and the edge of the cover are welded together along a second weld portion, the second weld portion continuously extending along the circumferential direction to extend completely around the central longitudinal axis.

2. The battery cell according to claim 1, characterized in that: At least a portion of the second welding portion overlaps the plurality of first welding portions.

3. The battery cell according to claim 1, characterized in that A cross-sectional area of ​​each of the plurality of first weld portions in a corresponding plane is greater than a cross-sectional area of ​​the second weld portion in the corresponding plane, the corresponding plane extending perpendicularly to the circumferential direction at a position of the corresponding first weld portion.

4. The battery cell according to claim 1, characterized in that: The plurality of first weld portions extend to a greater depth away from the first end of the tank in an axial direction than the second weld portions extend to a greater depth away from the first end of the tank in the axial direction, the axial direction extending parallel to the central longitudinal axis.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The outer diameter of the peripheral portion of the current collector plate corresponds to the outer diameter of the radially outer surface of the cover.

6. The battery cell according to any one of claims 1 to 4, characterized in that: The edge of the cover has a radially outer surface facing and contacting the radially inner surface of the sidewall member.

7. The battery cell according to any one of claims 1 to 4, characterized in that: The outer diameter of the peripheral portion of the current collector plate is greater than the outer diameter of the radially outer surface of the rim of the cover.

8. The battery cell according to any one of claims 1 to 4, characterized in that: The edge of the cover has a radially outer surface facing the radially inner surface of the sidewall member, and a gap is defined between the radially outer surface of the edge of the cover and the radially inner surface of the sidewall member.

9. The battery cell according to claim 8, characterized in that: The weld region extends within the gap.

10. The battery cell according to any one of claims 1 to 4, characterized in that: The edge of the cover has a radially outer surface facing the radially inner surface of the side wall member, at least one first portion of the radially outer surface of the edge of the cover has a first diameter corresponding to the outer diameter of the peripheral portion of the collector plate, and at least one second portion of the radially outer surface of the edge of the cover has a second diameter smaller than the outer diameter of the peripheral portion of the collector plate.

11. The battery cell according to claim 10, characterized in that: The radially outer surface of the edge of the cover has two or more first portions and two or more second portions alternating with each other in the circumferential direction around the central longitudinal axis.

12. The battery cell according to any one of claims 1 to 4, characterized in that: The edge of the cover has a radial outer surface facing the radial inner surface of the side wall member, and the radial outer surface has a plurality of large diameter portions and a plurality of small diameter portions alternating with each other around the central longitudinal axis in the circumferential direction, each of the plurality of small diameter portions having a smaller diameter than each of the plurality of large diameter portions.

13. The battery cell according to claim 12, characterized in that: The large diameter portion of the radially outer surface of the rim of the cover contacts the radially inner surface of the sidewall member, while the small diameter portion of the radially outer surface of the rim of the cover is spaced apart from the radially inner surface of the sidewall member.

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