Battery pack and battery pack welding method

Abstract

A battery pack and a battery pack welding method are provided. The battery pack may include a first welded portion, a second welded portion, a third welded portion, and a fourth welded portion formed on each of a plurality of battery cell surfaces, each of the first welded portion, the second welded portion, the third welded portion, and the fourth welded portion may include a first curved edge and a second curved edge facing each other, and a first linear edge and a second linear edge connecting the first curved edge and the second curved edge to each other, the first welded portion and the second welded portion may face each other in a diagonal direction, and the third welded portion and the fourth welded portion may face each other in the diagonal direction between the first welded portion and the second welded portion.

Description

[0001] This application claims priority to and the benefit of Korean Patent Application No. 10-2024-0037920 filed in the Korean Intellectual Property Office on March 19, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] One or more embodiments relate to a battery pack and a method of welding a battery pack. Background Art

[0003] Generally, unlike primary batteries, which are not rechargeable, secondary batteries are rechargeable batteries. Secondary batteries can be used as energy sources for mobile devices, electric vehicles, hybrid vehicles, electric bicycles, uninterruptible power supplies, etc. Depending on the type of external device used, secondary batteries can be used in the form of a single battery cell or a battery pack in which multiple battery cells are connected to each other and combined into a single unit.

[0004] Compact mobile devices such as mobile phones can operate for a predetermined period of time using the output and capacity of a single battery. However, for electric or hybrid vehicles that consume large amounts of electricity and require long and high-powered driving, battery packs may be preferable due to output and capacity issues, as these external devices may require greater output and capacity. The output voltage or output current of a battery pack can be increased by the number of built-in battery cells. Summary of the Invention

[0005] One or more embodiments include a battery pack including a plurality of battery cells and a method of welding the battery pack, in which welding strength may be ensured in a resistance welding structure between a battery cell and a cell tab.

[0006] However, the technical objectives to be achieved by the disclosure are not limited to the above objectives, and those skilled in the art will clearly understand other technical objectives not mentioned herein from the disclosed description.

[0007] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments of the disclosure.

[0008] According to one or more embodiments, the battery pack includes a first welding portion, a second welding portion, a third welding portion and a fourth welding portion formed on each of a plurality of battery cell surfaces, wherein: each of the first welding portion, the second welding portion, the third welding portion and the fourth welding portion may include a first curved edge and a second curved edge facing each other and a first straight edge and a second straight edge connecting the first curved edge and the second curved edge to each other, the first welding portion and the second welding portion face each other in a diagonal direction, and the third welding portion and the fourth welding portion face each other in a diagonal direction between the first welding portion and the second welding portion, wherein the portion where the first welding portion and the second welding portion face each other in the diagonal direction and the portion where the third welding portion and the fourth welding portion face each other in the diagonal direction are both formed by the second curved edge, and wherein the portions where the first welding portion, the second welding portion, the third welding portion and the fourth welding portion face each other in the adjacent directions may be formed by the first straight edge and the second straight edge.

[0009] The first welding portion and the second welding portion may be formed symmetrically to each other with respect to a center point on each of the plurality of battery cell surfaces.

[0010] The third welding portion and the fourth welding portion may be formed symmetrically to each other with respect to a center point on each of the plurality of battery cell surfaces.

[0011] The third welding portion may be formed to be separated from the first welding portion by a second distance and from the second welding portion by a first distance, and the fourth welding portion may be formed to be separated from the first welding portion by a first distance and from the second welding portion by a second distance.

[0012] The first distance and the second distance may be the same (eg, the same distance).

[0013] The third welding portion and the fourth welding portion may be formed at positions rotated 90 degrees from the first welding portion and the second welding portion with respect to the center point.

[0014] The first curved edge may be formed as an arc-shaped edge with respect to the first center point, and the second curved edge may be formed as an arc-shaped edge with respect to the second center point.

[0015] The second curved edge may have a smaller radius of curvature than the first curved edge.

[0016] The first straight edge and the second straight edge of each of the first welding portion, the second welding portion, the third welding portion, and the fourth welding portion may extend in directions perpendicular to each other.

[0017] The first straight edge and the second straight edge of each of the first welding portion, the second welding portion, the third welding portion, and the fourth welding portion may extend in adjacent directions.

[0018] The battery pack may further include a fifth welding portion and a sixth welding portion formed on each of the surfaces of the plurality of battery cells, wherein the first welding portion, the second welding portion, the third welding portion, the fourth welding portion, the fifth welding portion, and the sixth welding portion are circularly arranged to be equally spaced from each other relative to a center point.

[0019] According to one or more embodiments, a method for welding a battery pack includes the following steps: forming a first welding portion and a second welding portion separated from each other on the surface of the battery cell by performing welding on the surface of the battery cell using a first welding portion and a second welding portion of the welding rod facing each other; and forming a third welding portion and a fourth welding portion separated from each other and from the first welding portion and the second welding portion on the surface of the battery cell by performing welding on the surface of the battery cell using the first welding portion and the second welding portion of the welding rod facing each other.

[0020] In the step of forming first and second welded portions separated from each other on the battery cell surface by performing welding on the battery cell surface using first and second welded portions of the welding rod facing each other, the first and second welded portions may be formed symmetrically to each other with respect to a center point on the battery cell surface.

[0021] In the step of forming a third welding portion and a fourth welding portion on the surface of the battery cell that are separated from each other and from the first welding portion and the second welding portion by performing welding on the surface of the battery cell using a first welding portion and a second welding portion of a welding rod facing each other, the third welding portion and the fourth welding portion can be formed symmetrically to each other relative to a center point on the surface of the battery cell.

[0022] In the step of forming a third weld portion and a fourth weld portion on the surface of the battery cell that are separated from each other and from the first weld portion and the second weld portion by performing welding on the surface of the battery cell using a first weld portion and a second weld portion of the welding rod facing each other, the third weld portion can be formed to be separated from the first weld portion by a second distance and from the second weld portion by a first distance, and the fourth weld portion can be formed to be separated from the first weld portion by a first distance and from the second weld portion by a second distance.

[0023]

[0011] Further aspects, features, and advantages in addition to those described above will be apparent from the accompanying drawings, claims, and detailed description of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other aspects, features and advantages of some embodiments of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings, in which: Figure 1 is an exploded perspective view of a battery module according to some embodiments; Figure 2 is a perspective view of an assembled battery module according to some embodiments; Figure 3 shows the shape of the welding rod according to the embodiment; Figure 4 is a diagram illustrating the shape of a welding portion formed on a surface of a battery cell according to an embodiment; Figure 5 is a diagram showing an effective view of welding strength according to an embodiment; Figure 6 is a diagram showing a method of forming a Figure 4 A diagram showing the shape of a welded portion on a surface of a battery cell; Figure 7 is a flowchart illustrating a method of welding a battery pack according to an embodiment; and Figure 8 The figure shows the welding sequence according to the embodiment. Figure 4 Figure 1 shows a welded portion formed on the surface of a battery cell. DETAILED DESCRIPTION

[0025] Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the embodiments presented may have different forms and should not be construed as limited to the description set forth herein. Accordingly, the embodiments are described below solely by reference to the accompanying drawings to illustrate aspects of this specification. As used herein, the term "and / or" includes any and all combinations of one or more of the relevant listed items. Expressions such as "at least one of...", when following a list of elements, modify the entire list of elements, not the individual elements of that list.

[0026] Hereinafter, one or more embodiments are described in detail with reference to the accompanying drawings. The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary meanings or dictionary meanings, but must be interpreted as meanings and concepts consistent with the disclosed technical ideas based on the concept that the inventor can appropriately define the terms so as to interpret the disclosed principles in the most appropriate and / or appropriate manner. Therefore, the various embodiments disclosed and the terms used therein are not intended to limit the disclosure to a specific mode of practice, and it will be understood that various modifications, equivalents and / or substitutes that do not depart from the spirit and technical scope of the disclosure are included in the disclosure. In addition, in the disclosure, terms such as "including" or "comprising" may be interpreted to represent a certain characteristic, quantity, step, operation, component or a combination thereof, but may not be interpreted to exclude the possibility of existing or adding one or more other characteristics, quantities, steps, operations, components or a combination thereof. In addition, when describing the disclosed embodiments, "may" or its variations may include "one or more disclosed embodiments".

[0027] In addition, in order to facilitate understanding of the disclosure, the accompanying drawings are not drawn to scale and the sizes of some components may be exaggerated. In addition, in different embodiments, the same reference numerals may be assigned to the same elements.

[0028] When two objects are compared, they are considered "substantially identical." Thus, "substantially identical" can include conditions with a deviation that would be considered low by one of ordinary skill in the art, such as within 5%. Furthermore, "uniformity" of a parameter in a region can mean uniformity from an average perspective.

[0029] Terms such as "first" and "second" are used herein only to describe various components, but the components are not limited by the terms. Such terms are used only to distinguish one component from another. For example, unless otherwise specified, a first component may be a second component, and vice versa.

[0030] Throughout the disclosure, unless the context clearly indicates otherwise, expressions used in the singular form in the specification also include expressions in the plural form thereof.

[0031] When a component is described as being disposed on or located “on” or “on top of” another component, the component should be interpreted as being disposed on the upper surface (or lower surface) of the component, but any other components may be placed therebetween.

[0032] In addition, when a component is described as being “connected,” “coupled,” or “linked” to another component, these components may be directly connected or linked to each other, but it can be interpreted that any other component may be “interposed” between these components, or that the corresponding components may be “connected,” “coupled,” or “linked” via a third component. In addition, when a part is electrically coupled to another part, this includes not only a case where they are directly connected to each other, but also a case where they are connected to each other via a third part interposed therebetween.

[0033] Throughout the disclosure, unless specifically stated otherwise, the expression "A and / or B" means A, B, or A and B. In other words, the expression "and / or" includes any combination or combinations of the listed items. Unless specifically stated otherwise, the expression "C to D" means C or greater and D or less.

[0034] In the specification, the terms used herein are used to describe the disclosed embodiments but are not intended to limit the disclosure.

[0035] Figure 1 is an exploded perspective view of a battery module 10 according to some embodiments. Figure 2 is a perspective view of an assembled battery module 10 according to some embodiments. Figure 3 The shape of the welding rod WB according to the embodiment is shown. Figure 4 is a diagram illustrating the shape of a welding portion formed on a battery cell surface 600 a according to an embodiment. Figure 5 is a diagram showing an effective view of welding strength according to an embodiment. Figure 6 is a diagram illustrating the shape of a welding portion formed on a battery cell surface 600 a according to another embodiment.

[0036] The battery module 10 includes a plurality of battery cells 600 and can be applied to large applications such as energy storage systems (ESS) or small and medium-sized applications such as power tools and electronic devices. Alternatively, the battery module 10 can be applied to electric bicycles, electric vehicles, etc. The battery module 10 can be used alone or used with other battery modules 10 to form a battery pack.

[0037] The battery module 10 may include an upper retainer 100 , a lower retainer 200 , bus bars 300 , cell tabs 400 , a connector 500 , and battery cells 600 .

[0038] The upper retainer 100 and the lower retainer 200 may hold and support the battery cell 600. For example, Figure 1 and Figure 2As shown in , the upper retainer 100 and the lower retainer 200 can be located in the upper and lower parts of the battery module 10, respectively, and can accommodate battery cells 600 therein. The upper retainer 100 and the lower retainer 200 can respectively include openings 110, 210 into which the corresponding battery cells 600 are inserted. The openings 110, 210 can have a size and shape corresponding to the battery cells 600. For example, the battery cells 600 can have a cylindrical shape, and the openings 110, 210 can be circular. The number of openings 110, 210 can be the same as the number of battery cells 600. When the battery cells 600 are inserted into the upper retainer 100 and the lower retainer 200, some of the battery cells 600 can be placed with the positive electrodes facing upward, and some other battery cells 600 can be placed with the negative electrodes facing upward.

[0039] The upper retainer 100 may include a connection protrusion 120, and the lower retainer 200 may include a connection hole 220. For example, Figure 1 As shown in , the connecting protrusion 120 can be formed on the side surface of the upper retainer 100, and the connecting hole 220 can be formed in (and / or on) the side surface of the lower retainer 200. The connecting protrusion 120 and the connecting hole 220 can be formed at positions corresponding to each other, and when the connecting protrusion 120 is inserted into / detached from the connecting hole 220, the upper retainer 100 and the lower retainer 200 can be connected to / separated from each other. The connecting protrusion 120 can be formed at one or more (for example, two) positions on at least one of the two side surfaces of the upper retainer 100. The connecting hole 220 can be formed at one or more (for example, two) positions on at least one of the two side surfaces of the lower retainer 200.

[0040] The upper retainer 100 and the lower retainer 200 may have sizes and shapes corresponding to each other. For example, the upper retainer 100 and the lower retainer 200 may each have a length in the length direction of the battery module 10 (eg, Figure 1 The shape of a rectangular cuboid that is long in the X-axis direction.

[0041] The upper retainer 100 may include an embedding hole 130. For example, Figure 1 As shown in FIG, the embedding holes 130 may be formed at one or more locations on the upper surface of the upper retainer 100. The first protruding portion 310 of the bus bar 300 and the second protruding portion 410 of the cell tab 400 may be located in each embedding hole 130 to correspond to each other. In addition, the connector 500 may be inserted into each embedding hole 130. When a connecting member such as a bolt is inserted into the connector 500, the upper retainer 100, the bus bar 300, and the cell tab 400 may be electrically connected to each other.

[0042] The upper holder 100 may be molded with the connector 500 therein. For example, before molding the upper holder 100, the upper holder 100 may be molded with the connector 500 positioned at a position corresponding to the insertion hole 130. In other words, the connector 500 may be insert-molded in the upper holder 100.

[0043] In some examples, the upper retainer 100 and the lower retainer 200 may include a plastic material.

[0044] The bus bar 300 can electrically connect the battery cells 600 to an external device such as a battery monitoring system (BMS). For example, when the battery cells 600 are electrically connected to each other via the cell tabs 400, the cell tabs 400 can be connected to the bus bar 300. The bus bar 300 can be in direct contact with the cell tabs 400, or can be electrically connected to the cell tabs 400 via the connector 500. The bus bar 300 can include a conductive material such as metal.

[0045] The bus bar 300 may include a first protruding portion 310. For example, Figure 1 As shown in FIG, the bus bar 300 may include one or more first protruding portions 310 protruding toward the interior of the battery module 10. The one or more first protruding portions 310 may be provided in the length direction of the bus bar 300 (eg, Figure 1 The first protruding portion 310 may be positioned to correspond to the second protruding portion 410 and the embedding hole 130 (eg, may overlap with these elements).

[0046] The cell tabs 400 can electrically connect the battery cells 600 to each other. For example, the cell tabs 400 may include a plurality of cell tabs, and each of the cell tabs 400 can electrically connect battery cells 600 having the same polarity. A portion of the cell tabs 400 may extend toward the opening 110 of the upper retainer 100 to contact the electrodes of the battery cells 600 inserted into the opening 110. The cell tabs 400 may include a conductive material such as metal.

[0047] The cell tab 400 may be in contact with the bus bar 300. For example, Figure 1, any one of the cell tabs 400 may be located at an edge of the upper retainer 100 adjacent to the bus bar 300. The cell tab 400 at the edge of the upper retainer 100 may be located on the upper retainer 100 with a portion of the cell tab 400 located on the upper surface of the upper retainer 100 and another portion of the cell tab 400 extending downward to cover the edge of the upper retainer 100. In this state, the bus bar 300 may be located on and in contact with its corresponding cell tab 400.

[0048] The single terminal piece 400 may include a second protruding portion 410. For example, Figure 1 As shown in FIG, the cell tab 400 may include one or more second protruding portions 410 protruding toward the interior of the battery module 10. The one or more second protruding portions 410 may be provided in the length direction of the bus bar 300 (eg, Figure 1 The second protruding portion 410 may be positioned to correspond to the first protruding portion 310 and the embedding hole 130.

[0049] The connector 500 may be located on the upper retainer 100, may physically and / or electrically connect the bus bar 300 and the cell tab 400 to each other, and may fix the bus bar 300 and the cell tab 400 to the upper retainer 100. The connector 500 may be at least partially embedded in the upper surface of the upper retainer 100 and at least partially exposed from the upper surface of the upper retainer 100. Whether the connector 500 is embedded in a normal (e.g., desired) position of the upper retainer 100 may be checked based on a state in which the connector 500 is exposed to the outside (e.g., rotation or tilt of the connector 500 and / or the degree of rotation or tilt, the amount of exposure of the connector 500, etc.).

[0050] The connector 500 can be embedded in the embedding hole 130 and can be connected to the first protruding portion 310 of the busbar 300 and the second protruding portion 410 of the cell tab 400 via a fastening member such as a bolt. In some embodiments, the connector may include a fastening member. The connector 500 and the fastening member may include a conductive material such as metal. Therefore, when the fastening member is inserted into the first protruding portion 310, the second protruding portion 410, and the connector 500, the connector 500, the busbar 300, and the cell tab 400 can be electrically connected to each other. In addition, when the fastening member is inserted into the connector 500, the busbar 300 and the cell tab 400 can be physically connected to each other.

[0051] Reference Figure 2, the cell tab 400 may include a first tab 400a and a second tab 400b. The first tab 400a and the second tab 400b may be bonded to and / or connected to the battery cell surface 600a by welding. In this state, the first tab 400a and the second tab 400b may be connected to the positive electrode and the negative electrode of the battery cell 600, respectively.

[0052] The first and second tabs 400a and 400b may be connected to the positive and negative electrodes of the battery cell 600 by welding portions of the battery cell surface 600a that are formed apart from each other. In this state, the welded portions respectively connected to the first and second tabs 400a and 400b are formed to be separated from each other to prevent electrical connection between the welded portions.

[0053] Reference Figure 3 The welding rods WB used to form the welded portion on the battery cell surface 600a may have a structure in which two welding rods are formed into a set. In this state, the welding rods WB may be made of a material obtained by cylindrically processing a copper (Cu) alloy. Welding the battery cell surface 600a using the welding rods WB may include resistance welding. The battery cell surface 600a may be formed of nickel, nickel-plated steel, aluminum, or copper.

[0054] A plurality of weld portions may be formed on the battery cell surface 600a by using two welding portions WBS1, WBS2 of the welding rod WB. In this state, the shape of the weld portion may be determined based on the shape of the two welding portions WBS1, WBS2.

[0055] Reference Figure 4 , the battery pack according to the embodiment includes first, second, third, and fourth welding portions (eg, first, second, third, and fourth welding portions S1, S2, S3, and S4) formed on each of a plurality of battery cell surfaces 600a.

[0056] In this state, the first to fourth welding portions S1, S2, S3, and S4 include first and second curved edges A1 and A2 facing each other and first and second straight edges T1 and T2 connecting the first and second curved edges A1 and A2 to each other.

[0057] The first weld portion S1 and the second weld portion S2 may face each other in a diagonal direction, and the third weld portion S3 and the fourth weld portion S4 may face each other in a diagonal direction (for example, between the first weld portion S1 and the second weld portion S2). In addition, the portion where the first weld portion S1 and the second weld portion S2 face each other in a diagonal direction and the portion where the third weld portion S3 and the fourth weld portion S4 face each other in a diagonal direction are both formed by the second curved edge A2, and the portions where the first weld portion S1, the second weld portion S2, the third weld portion S3, and the fourth weld portion S4 face each other in adjacent directions are both formed by the first straight edge T1 and the second straight edge T2.

[0058] The first weld portion S1 and the second weld portion S2 may be formed symmetrically with respect to the center point C on the battery cell surface 600a. In this state, the center point C may not be the center point of the battery cell surface 600a, but may be a specific point on the battery cell surface 600a. The center point C may be any portion of the central space on the battery cell surface 600a, and the space may be between the weld portions facing each other.

[0059] In addition, the third welding portion S3 and the fourth welding portion S4 may be formed symmetrically to each other with respect to the center point C on the battery cell surface 600 a .

[0060] Figure 4 The third weld portion S3 shown in FIG is formed to be separated from the first weld portion S1 by a second distance G2 and separated from the second weld portion S2 by a first distance G1, and the fourth weld portion S4 is formed to be separated from the first weld portion S1 by a first distance G1 and separated from the second weld portion S2 by a second distance G2. In some embodiments, the first distance G1 can be the same as (e.g., the same distance as) the second distance G2.

[0061] The third welding portion S3 and the fourth welding portion S4 may be formed at positions rotated 90 degrees from the first welding portion S1 and the second welding portion S2 relative to the center point C. Therefore, the first welding portion S1, the second welding portion S2, the third welding portion S3, and the fourth welding portion S4 may be disposed at the same intervals in the rotation direction relative to the center point C.

[0062] The first curved edge A1 may be formed as an arc edge relative to the first center point C1, and the second curved edge A2 may be formed as an arc edge relative to the second center point C2. In this state, the curvature radius R2 of the second curved edge A2 may be smaller than the curvature radius R1 of the first curved edge A1.

[0063] In addition, the first straight edge T1 and the second straight edge T2 of each of the first welding portion S1, the second welding portion S2, the third welding portion S3, and the fourth welding portion S4 may extend in directions perpendicular to each other. In addition, the first straight edge T1 and the second straight edge T2 of each of the first welding portion S1, the second welding portion S2, the third welding portion S3, and the fourth welding portion S4 may extend in adjacent directions, respectively. In some embodiments, the adjacent directions may be parallel directions.

[0064] In detail, the first welding portion S1 may be formed symmetrically with the second welding portion S2 with respect to the center point C, and also formed mirror-symmetrically with the third welding portion S3 and the fourth welding portion S4 (eg, have mirror symmetry).

[0065] The first weld portion S1 may include a first-1 curved edge A11 relative to the first-1 center point C11, a second-1 curved edge A21 relative to the second-1 center point C21, and a first-1 straight edge T11 and a second-1 straight edge T21 connecting the first-1 curved edge A11 and the second-1 curved edge A21. In this state, the curvature radius R21 of the second-1 curved edge A21 may be smaller than the curvature radius R11 of the first-1 curved edge A11.

[0066] The first-1 straight edge T11 may be positioned to correspond to the second-4 straight edge T24 of the fourth weld portion S4, with a first distance G1 between the first-1 straight edge T11 and the second-4 straight edge T24 of the fourth weld portion S4. The second-1 straight edge T21 may be positioned to correspond to the first-3 straight edge T13 of the third weld portion S3, with a second distance G2 between the second-1 straight edge T21 and the first-3 straight edge T13 of the third weld portion S3.

[0067] The second welding portion S2 may be formed symmetrically to the first welding portion S1 with respect to the center point C, and also formed in mirror symmetry with the third welding portion S3 and the fourth welding portion S4.

[0068] The second weld portion S2 may include a first-2 curved edge A12 relative to the first-2 center point C12, a second-2 curved edge A22 relative to the second-2 center point C22, and first-2 straight edges T12 and second-2 straight edges T22 connecting the first-2 curved edge A12 and the second-2 curved edge A22. In this state, the curvature radius R22 of the second-2 curved edge A22 may be smaller than the curvature radius R12 of the first-2 curved edge A12.

[0069] The first-second straight edge T12 may be positioned to correspond to the second-third straight edge T23 of the third weld portion S3, with a first distance G1 between the first-second straight edge T12 and the second-third straight edge T23 of the third weld portion S3. The second-second straight edge T22 may be positioned to correspond to the first-fourth straight edge T14 of the fourth weld portion S4, with a second distance G2 between the second-second straight edge T22 and the first-fourth straight edge T14 of the fourth weld portion S4.

[0070] The third welding portion S3 may be formed symmetrically with the fourth welding portion S4 with respect to the center point C, and also formed in mirror symmetry with the first welding portion S1 and the second welding portion S2.

[0071] The third weld portion S3 may include a first-3D curved edge A13 relative to the first-3D center point C13, a second-3D curved edge A23 relative to the second-3D center point C23, and first-3D straight edges T13 and second-3D straight edges T23 connecting the first-3D curved edge A13 and the second-3D curved edge A23. In this state, the curvature radius R23 of the second-3D curved edge A23 may be smaller than the curvature radius R13 of the first-3D curved edge A13.

[0072] The first-3 straight edge T13 may be positioned to correspond to the second-1 straight edge T21 of the first weld portion S1, with a second distance G2 between the first-3 straight edge T13 and the second-1 straight edge T21 of the first weld portion S1. The second-3 straight edge T23 may be positioned to correspond to the first-2 straight edge T12 of the second weld portion S2, with a first distance G1 between the second-3 straight edge T23 and the first-2 straight edge T12 of the second weld portion S2.

[0073] The fourth welding portion S4 may be formed symmetrically to the third welding portion S3 with respect to the center point C, and also formed in mirror symmetry with the first welding portion S1 and the second welding portion S2.

[0074] The fourth weld portion S4 may include a first-A curved edge A14 relative to the first-A center point C14, a second-A curved edge A24 relative to the second-A center point C24, and first-A straight edges T14 and second-A straight edges T24 connecting the first-A curved edge A14 and the second-A curved edge A24. In this state, the curvature radius R24 of the second-A curved edge A24 may be smaller than the curvature radius R14 of the first-A curved edge A14.

[0075] The first-fourth straight edge T14 may be positioned to correspond to the second-second straight edge T22 of the second weld portion S2, with a second distance G2 between the first-fourth straight edge T14 and the second-second straight edge T22 of the second weld portion S2. The second-fourth straight edge T24 may be positioned to correspond to the first-first straight edge T11 of the first weld portion S1, with a first distance G1 between the first-fourth straight edge T24 and the first-first straight edge T11 of the first weld portion S1.

[0076] Reference Figure 5 , shows the effective range WP of welding strength including four welding parts. Figure 5 As shown in , the welding portion may be formed by using a welding rod WB. In this state, as the area of ​​the welding portion increases, the welding strength between the cell tab 400 and the battery cell 600 may be improved.

[0077] When the respective welded portions are connected to each other, interference between the electrodes may occur, and therefore, the inventors have recognized that it is necessary to make the intervals between the welded portions and the Figure 5 The area of ​​the dead space (DS) in the weld is minimized while the area of ​​the weld portion is maximized within the effective range WP of weld strength.

[0078] Therefore, according to this embodiment, without making the shape of the welded portion substantially circular, as shown in FIG. Figure 5 As shown in FIG, in order to minimize the area of ​​the dead space DS, which is the intermediate space of the welded portion and in which no welded portion is formed, the second curved edge having a smaller curvature radius than the first curved edge is formed to face the center point. In this state, the first distance G1 and the second distance G2 can be set to the minimum distance at which no interference occurs between the two welded portions during welding.

[0079] Reference Figure 6 The battery pack according to another embodiment further includes a fifth weld portion S5' and a sixth weld portion S6' formed on each of the plurality of battery cell surfaces 600a', and the first to sixth weld portions (e.g., the first weld portion S1', the second weld portion S2', the third weld portion S3', the fourth weld portion S4', the fifth weld portion S5', and the sixth weld portion S6') may be circularly arranged to be equally spaced apart from each other (e.g., may be radially arranged in a circle) relative to the center point C. However, the number of weld portions is not limited thereto, and because the positive electrode and the negative electrode are connected to each other (e.g., one of the weld portions is connected to the negative electrode, and the other is connected to the positive electrode), various numbers may be possible if the number is an even number, e.g., two, four, six, etc.

[0080] Figure 7is a flowchart illustrating a method of welding a battery pack according to an embodiment. Figure 8 is a diagram illustrating forming welding portions on surfaces of battery cells in a welding sequence according to an embodiment.

[0081] Reference Figure 7 and Figure 8 The method of welding a battery pack according to an embodiment includes performing welding on a battery cell surface 600a using first and second welding rod portions WBS1 and WBS2 of a welding rod facing each other to form first and second welding portions S1 and S2 separated from each other on the battery cell surface (S100). The method may further include performing welding again on the battery cell surface 600a using first and second welding rod portions WBS1 and WBS2 of a welding rod facing each other to form third and fourth welding portions S3 and S4 separated from each other and from the first and second welding portions S1 and S2 on the battery cell surface 600a (S200).

[0082] In this state, when welding is performed again on the battery cell surface 600a using the first and second welding rod portions WBS1 and WBS2, welding may be performed again by rotating the welding rod WB 90 degrees relative to the center point C compared to previous welding.

[0083] When welding is performed on the battery cell surface 600a using the first and second welding rod welding portions WBS1 and WBS2 of the welding rod facing each other to form first and second welding portions S1 and S2 separated from each other on the battery cell surface, the first and second welding portions S1 and S2 may be formed symmetrically with respect to the center point C on the battery cell surface 600a.

[0084] In addition, when welding is performed again on the battery cell surface 600a using the first welding portion WBS1 and the second welding portion WBS2 of the welding rod facing each other to form the third welding portion S3 and the fourth welding portion S4 on the battery cell surface 600a, which are separated from each other and from the first welding portion S1 and the second welding portion S2, the third welding portion S3 and the fourth welding portion S4 can be formed symmetrically with respect to the center point C on the battery cell surface 600a.

[0085] In this state, the third welding portion S3 can be formed to be separated from the first welding portion S1 by the second distance G2 and also separated from the second welding portion S2 by the first distance G1, and the fourth welding portion S4 can be formed to be separated from the first welding portion S1 by the first distance G1 and also separated from the second welding portion S2 by the second distance G2.

[0086] According to one or more embodiments, a battery pack with improved welding strength can be provided by maximizing welding strength by utilizing dead space within an effective range of welding strength, and maintaining the distance between corresponding electrodes of cell tabs, which can be a major factor in process management, while ensuring maximum area resistance welding.

[0087] However, the effects of the present disclosure are not limited to the above-mentioned effects, and other various effects that are not described in the specification can be clearly understood from the foregoing description by those skilled in the art to which the present disclosure pertains.

[0088] It should be understood that the embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should generally be considered applicable to other similar features or aspects in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims.

Claims

1. A battery pack, comprising: a first welding portion, a second welding portion, a third welding portion, and a fourth welding portion formed on each of the plurality of battery cell surfaces; in: Each of the first welding portion, the second welding portion, the third welding portion, and the fourth welding portion includes a first curved edge and a second curved edge facing each other and a first straight edge and a second straight edge connecting the first curved edge and the second curved edge to each other, The first welding portion and the second welding portion face each other in a diagonal direction, The third welding portion and the fourth welding portion face each other in a diagonal direction between the first welding portion and the second welding portion, The portions of the first welding portion and the second welding portion facing each other in the diagonal direction and the portions of the third welding portion and the fourth welding portion facing each other in the diagonal direction are both formed by the second bent edge, and Portions of the first welding portion, the second welding portion, the third welding portion, and the fourth welding portion facing each other in adjacent directions are formed by the first straight edge and the second straight edge.

2. The battery pack according to claim 1, wherein: The first welding portion and the second welding portion are formed symmetrically to each other with respect to a center point on each of surfaces of the plurality of battery cells.

3. The battery pack according to claim 1, wherein: The third welding portion and the fourth welding portion are formed symmetrically to each other with respect to a center point on each of surfaces of the plurality of battery cells.

4. The battery pack according to claim 1, wherein The third welding portion is formed to be separated from the first welding portion by a second distance and to be separated from the second welding portion by a first distance, and The fourth welding portion is formed to be separated from the first welding portion by the first distance and to be separated from the second welding portion by the second distance.

5. The battery pack according to claim 4, wherein: The first distance and the second distance are the same distance.

6. The battery pack according to claim 1, wherein: The third welding portion and the fourth welding portion are formed at positions rotated 90 degrees from the first welding portion and the second welding portion with respect to a center point on each of the plurality of battery cell surfaces.

7. The battery pack according to claim 1, wherein: The first curved edge is formed as an arc-shaped edge relative to the first center point, and The second curved edge is formed as an arc-shaped edge relative to the second center point.

8. The battery pack according to claim 7, wherein: A curvature radius of the second curved edge is smaller than a curvature radius of the first curved edge.

9. The battery pack according to claim 1, wherein: The first straight edge and the second straight edge of each of the first welding portion, the second welding portion, the third welding portion, and the fourth welding portion extend in directions perpendicular to each other.

10. The battery pack according to claim 1, wherein The first straight edge and the second straight edge of each of the first welding portion, the second welding portion, the third welding portion, and the fourth welding portion extend in adjacent directions.

11. The battery pack according to claim 1 , further comprising a fifth welding portion and a sixth welding portion formed on each of surfaces of the plurality of battery cells, in, The first, second, third, fourth, fifth, and sixth welding portions are circularly disposed to be equally spaced apart from one another with respect to a center point on each of the plurality of battery cell surfaces.

12. A method for welding a battery pack, the method comprising the following steps: forming first and second welded portions separated from each other on the battery cell surface by performing welding on the battery cell surface using first and second welded portions of the welding rod facing each other; as well as Third and fourth welding portions separated from each other and from the first and second welding portions are formed on the battery cell surface by welding the battery cell surface using the first and second welding portions of the welding rod facing each other.

13. The method according to claim 12, wherein: In the step of forming the first welding portion and the second welding portion separated from each other on the battery cell surface by performing welding on the battery cell surface using the first welding portion and the second welding portion of the welding rod facing each other, The first welding portion and the second welding portion are formed symmetrically to each other with respect to a center point on a surface of the battery cell.

14. The method according to claim 12, wherein: In the step of forming the third and fourth welded portions separated from each other and from the first and second welded portions on the battery cell surface by performing welding on the battery cell surface using the first and second welded portions of the welding rod facing each other, The third welding portion and the fourth welding portion are formed symmetrically to each other with respect to a center point on the surface of the battery cell.

15. The method according to claim 12, wherein: In the step of forming the third and fourth welded portions separated from each other and from the first and second welded portions on the battery cell surface by performing welding on the battery cell surface using the first and second welded portions of the welding rod facing each other, The third welding portion is formed to be separated from the first welding portion by a second distance and to be separated from the second welding portion by a first distance, and The fourth welding portion is formed to be separated from the first welding portion by the first distance and to be separated from the second welding portion by the second distance.

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