Battery pack and manufacturing method thereof

Abstract

In a vertical coordinate system defined by a first direction, a second direction, and a third direction perpendicular to each other, there is provided a battery pack including: a plurality of battery cells stacked in the first direction; and a pack case that houses the battery cells in an internal space, wherein at least a pair of adjacent battery cells among the battery cells each include an electrode assembly, a cover that surrounds the electrode assembly, and a cell lead that protrudes from one side of the cover in the second direction, the cell lead including a first portion that is relatively close to the cover and a second portion that is relatively farther away from the cover, wherein a maximum dimension of the second portion in the first direction is greater than a maximum dimension of the first portion, and the second portion is configured as a plane perpendicular to the third direction.

Description

[Technical Field]

[0001] The present invention relates to a battery pack and a manufacturing method thereof, and more specifically to a battery pack that can be manufactured inexpensively using a simple number of parts, has excellent productivity, and has little risk of product failure, and a manufacturing method thereof.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0167135, filed December 2, 2022, and Korean Patent Application No. 10-2023-0038211, filed March 23, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference. [Background technology]

[0003] As technological development and demand for various mobile devices, electric vehicles, energy storage systems (ESS), etc. has increased significantly, interest in and demand for secondary batteries as an energy source has been growing rapidly. While nickel-cadmium batteries and nickel-metal hydride batteries have traditionally been widely used as secondary batteries, lithium secondary batteries have recently come into widespread use due to their low memory effect compared to nickel-based secondary batteries, their flexible charging and discharging, extremely low self-discharge rate, and high energy density.

[0004] Such lithium secondary batteries mainly use lithium-based oxides and carbon materials as the positive and negative electrode active materials, respectively, and include an electrode assembly in which positive and negative electrode plates coated with the positive and negative electrode active materials are disposed with a separator between them, and an exterior material, i.e., a battery case, that hermetically houses the electrode assembly together with an electrolyte.

[0005] In recent years, battery packs have been widely used for driving and storing energy in medium- to large-sized devices such as electric vehicles and energy storage systems. A conventional battery pack includes one or more battery modules and a control unit, such as a battery management system (BMS), that controls the charging and discharging of the battery pack inside a pack case. Here, a battery module is configured to include a number of battery cells inside a module case. That is, in the case of a conventional battery pack, a number of battery cells (secondary batteries) are housed inside a module case to form each battery module, and such battery modules are housed inside one or more pack cases to form a battery pack.

[0006] In particular, pouch-type batteries have various advantages, such as being lightweight and leaving little dead space when stacked, but they also have weaknesses, such as being vulnerable to external impacts and somewhat reducing assembly. Therefore, battery packs are generally manufactured by first modularizing a number of cells and then housing them inside a pack case. As a representative example, in the case of a conventional battery pack, a number of pouch-type battery cells are first housed inside a module case to form a battery module, and then the battery module is housed inside one or more pack cases.

[0007] However, such conventional battery packs may be disadvantageous in terms of energy density. Typically, in the process of modularizing a number of battery cells by housing them inside a module case, various components such as the module case or a stacking frame may unnecessarily increase the volume of the battery pack or reduce the space occupied by the battery cells. Furthermore, the space occupied by the components themselves, such as the module case or the stacking frame, may be reduced, as well as the space occupied by the battery cells may be reduced to ensure assembly tolerances for these components. Therefore, in the case of conventional battery packs, there may be limitations on increasing energy density.

[0008] In addition, conventional battery packs can be disadvantageous in terms of assembly. In particular, manufacturing a battery pack requires first modularizing a number of battery cells to form a battery module, and then housing the battery module in a pack case, which complicates the manufacturing process of the battery pack. Furthermore, as disclosed in the above-mentioned prior art, the process and structure of forming a cell stack using a stacking frame, bolts, plates, etc. can be very complicated. Summary of the Invention [Problem to be solved by the invention]

[0009] A first technical problem that the present invention aims to achieve is to provide a battery pack that can be manufactured inexpensively using a simple number of parts, has excellent productivity, and has little risk of product failure.

[0010] The second technical problem that the present invention aims to achieve is to provide a method for manufacturing a battery pack that can be manufactured inexpensively using a simple number of parts, has excellent productivity, and has little risk of product failure.

[0011] The third technical problem that the present invention aims to achieve is to provide a battery cell that can be used in a battery pack that has a simple number of parts, can be manufactured inexpensively, has excellent productivity, and has little risk of product failure. [Means for solving the problem]

[0012] To achieve the first technical object, the present invention provides a battery pack including: a plurality of battery cells stacked in a vertical coordinate system defined by a first direction, a second direction, and a third direction perpendicular to each other; and a pack case accommodating the battery cells in an internal space, wherein at least a pair of adjacent battery cells among the battery cells each include an electrode assembly, a cover surrounding the electrode assembly, and a cell lead protruding from one side of the cover in the second direction, the cell lead including a first portion relatively close to the cover and a second portion relatively farther away from the cover, wherein a maximum dimension of the second portion in the first direction is greater than a maximum dimension of the first portion, and the second portion is configured as a plane perpendicular to the third direction.

[0013] In some embodiments, the corresponding second portions of the pair of adjacent battery cells may be electrically coupled to each other by a bus bar.

[0014] In some embodiments, the bus bar may be electrically coupled to the second portion by welding in the third direction.

[0015] In some embodiments, the dimension of the second portion in the third direction may be 0.5% to 50% of the dimension of the first portion.

[0016] In some embodiments, in the third direction, the center of the first portion can be located between the upper surface of the second portion and the lower surface of the second portion.

[0017] In some embodiments, the upper surface of the second portion can be flush with the upper surface of the first portion, and in some other embodiments, the lower surface of the second portion can be flush with the lower surface of the first portion.

[0018] In some embodiments, the maximum dimension of the second portion in the first direction may be between 2 and 20 times the maximum dimension of the first portion.

[0019] In some embodiments, the area of ​​the second portion may be 2 to 20 times the area of ​​the first portion in a projection onto a plane perpendicular to the third direction.

[0020] To achieve the second technical object, the present invention provides a method for manufacturing a battery pack, including: arranging a plurality of battery cells directly in a pack case in a vertical coordinate system defined by a first direction, a second direction, and a third direction that are perpendicular to each other; and electrically connecting cell leads of at least two adjacent battery cells among the plurality of battery cells, the cell leads protruding in the second direction, using a bus bar, wherein the step of electrically connecting the cell leads using the bus bar includes welding and connecting each of the cell leads to the bus bar in the third direction.

[0021] In some embodiments, the cell lead may include a first portion that is relatively close to the cover and a second portion that is relatively farther away from the cover, wherein the maximum dimension of the second portion in the first direction is greater than the maximum dimension of the first portion, and the second portion may be configured in a plane perpendicular to the third direction.

[0022] In some embodiments, the dimension of the second portion in the third direction may be 0.5% to 50% of the dimension of the first portion.

[0023] In some embodiments, the second portion may not include a through hole.

[0024] In some embodiments, the maximum dimension of the second portion in the first direction may be between 2 and 20 times the maximum dimension of the first portion.

[0025] To achieve the third technical object, the present invention provides a battery cell defined in a vertical coordinate system having a first direction, a second direction, and a third direction that are perpendicular to each other, the battery cell including two parallel main surfaces perpendicular to the first direction, an electrode assembly, a cover surrounding the electrode assembly, and a cell lead protruding from one side of the cover in the second direction, the cell lead including a first portion relatively close to the cover and a second portion relatively farther away from the cover, a maximum dimension of the second portion in the first direction being greater than a maximum dimension of the first portion, the second portion being formed on a plane perpendicular to the third direction, and an area of ​​the second portion being 2 to 20 times the area of ​​the first portion when projected onto the plane perpendicular to the third direction. [Effects of the Invention]

[0026] The battery pack according to the embodiment of the present invention has a simple number of parts, can be manufactured inexpensively, has excellent productivity, and has little risk of product failure. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is an exploded perspective view showing a main part of a battery pack according to an embodiment of the present invention; [Figure 2] 1 is a perspective view showing a main part of a battery cell according to an embodiment of the present invention. [Figure 3] 3 is a partially enlarged view showing a part of the battery cell, focusing on a cell lead portion of the battery cell according to an embodiment of the present invention; FIG. [Figure 4] 3 is a partially enlarged view of a part of the battery cell viewed from the x direction, with a cell lead portion of the battery cell at the center. FIG. [Figure 5]4 is a partially enlarged view of a part of the battery cell viewed from the y direction, with a cell lead portion of the battery cell at the center. FIG. [Figure 6] 3 is a partially enlarged view of a part of the battery cell viewed from the z direction, with a cell lead portion of the battery cell at the center. FIG. [Figure 7a] 10 is a partially enlarged view illustrating a part of a battery cell, focusing on a cell lead portion of the battery cell according to another embodiment of the present invention. FIG. [Figure 7b] FIG. 10 is a partially enlarged view showing a part of the battery cell, focusing on a cell lead portion of the battery cell according to another embodiment of the present invention. [Figure 8] FIG. 2 is a perspective view showing a pair of adjacent battery cells electrically connected by a bus bar. [Figure 9] 9 is a cross-sectional view showing a cross section of the second portion and the bus bar of FIG. 8 taken along line IX-IX′. [Figure 10] 3 is a flowchart illustrating a method for manufacturing a battery pack according to an embodiment of the present invention. [Figure 11a] 1 is a perspective view illustrating a method for manufacturing a battery pack according to an embodiment of the present invention. [Figure 11b] 1 is a perspective view illustrating a method for manufacturing a battery pack according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] Preferred embodiments of the inventive concept will now be described in detail with reference to the accompanying drawings. However, the embodiments of the inventive concept may be modified in various different forms, and the scope of the inventive concept should not be construed as being limited by the embodiments described below. The embodiments of the inventive concept are preferably construed as being provided to more completely explain the inventive concept to those of ordinary skill in the art. The same reference numerals refer to the same elements throughout. Furthermore, various elements and regions in the drawings are depicted schematically. Therefore, the inventive concept is not limited by the relative sizes or spacings depicted in the accompanying drawings.

[0029] Terms such as "first," "second," etc. may be used to describe various components, but the components are not limited by these terms. These terms are used only to distinguish one component from another. For example, a first component may be designated a second component, and vice versa, without departing from the scope of the inventive concept.

[0030] The terms used in this application are merely used to describe specific embodiments and are not intended to limit the concept of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, expressions such as "comprise" and "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, and are understood not to preclude the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0031] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the concept of the present invention belongs. Furthermore, it is understood that terms defined in commonly used dictionaries should be interpreted to have a meaning consistent with what they mean in the context of the relevant art, and should not be interpreted as overly formal unless explicitly defined herein.

[0032] In other embodiments, the order of certain steps may be different from that described, for example, two steps described in succession may be performed substantially simultaneously or may be performed in the reverse order from that described.

[0033] In the accompanying drawings, variations in the shapes illustrated may be expected due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the present invention should not be construed as limited to the specific shapes of regions illustrated herein and may include, for example, variations in shapes resulting from the manufacturing process. As used herein, the term "and / or" includes each and every combination of one or more of the listed elements. Furthermore, the term "substrate" as used herein may refer to the substrate itself or a laminated structure including the substrate and a predetermined layer or film formed on its surface. Furthermore, as used herein, the term "surface of the substrate" may refer to the exposed surface of the substrate itself or the outer surface of a predetermined layer or film formed on the substrate.

[0034] 1 is an exploded perspective view showing a main part of a battery pack 10 according to one embodiment of the present invention. In FIG. 1, the battery pack 10 is shown as being defined in a vertical coordinate system in which a first direction is perpendicular to one another and is along the x-axis, a second direction is along the y-axis, and a third direction is along the z-axis. However, the first, second, and third directions are not particularly limited as long as they are relatively perpendicular to one another.

[0035] Referring to FIG. 1, the battery pack 10 includes a plurality of battery cells 100 stacked in a first direction (eg, an x-direction) and a pack case 300 that houses the plurality of battery cells 100.

[0036] The pack case 300 has an interior space 330 that can accommodate the plurality of battery cells 100. In some embodiments, the pack case 300 can include an upper case 310 and a lower case 320 that define the interior space 330.

[0037] Although not explicitly shown in FIG. 1, the pack case 300 may be provided with conductors that electrically connect the plurality of battery cells 100 to an external electric load.

[0038] In some embodiments, the lower case 320 may have a box shape with an open top, and may accommodate a number of battery cells in the internal space 330. The upper case 310 may be configured as a lid that covers the open top of the lower case 320. In this case, the upper case 310 may be configured as a box shape with an open bottom.

[0039] The pack case 300 may include a plastic or metal material, or may be made of various exterior materials of battery packs known at the time of filing of the present invention.

[0040] 1, the battery pack 10 may further include a battery management system 400. The battery management system (BMS) 400 may be mounted in the internal space of the pack case 300 and configured to generally control the charging and discharging operations and data transmission and reception operations of the battery cells 100. The battery management system 400 may be provided on a pack basis rather than on a module basis. More specifically, the battery management system 400 may be configured to control the charging and discharging state, power state, performance state, etc. of the battery cells 100 via the pack voltage and pack current.

[0041] 1, the battery pack 10 may further include a battery disconnect unit 500. The battery disconnect unit (BDU) 500 may be configured to control electrical connection of battery cells to manage the power capacity and functions of the battery pack 10. To this end, the battery disconnect unit 500 may include a power relay, a current sensor, a fuse, etc. The battery disconnect unit 500 is also configured to be provided on a pack-by-pack basis rather than on a module-by-module basis, and various disconnection units known at the time of filing of the present invention may be used.

[0042] In addition, the battery pack 10 may further include various battery pack components known at the time of filing of the present invention. For example, the battery pack 10 according to an embodiment of the present invention may further include a manual service disconnector (MSD) that allows an operator to manually disconnect the service plug to cut off the power supply.

[0043] FIG. 2 is a perspective view showing a main part of a battery cell 100 according to one embodiment of the present invention.

[0044] Referring to FIG. 2, the battery cell 100 includes an electrode assembly 101, a cover 105 surrounding the electrode assembly 101, and a cell lead 110 protruding from one side of the cover 105 in the second direction (e.g., the y direction).

[0045] In some embodiments, the battery cell 100 may be a pouch-type battery cell, but the present invention is not limited thereto. In some embodiments, the battery cell 100 may be a prismatic battery cell.

[0046] In some embodiments, the battery cell 100 has a thin plate-like body, preferably a pouch cell. The pouch cell may have a structure in which a positive electrode, a separator, and a negative electrode are alternately stacked to form the electrode assembly 101, with an electrode tab extending from at least one side and connected to the cell lead 110. The positive and negative electrodes may be fabricated by coating at least one surface of a current collector with a slurry containing an electrode active material, a binder resin, a conductive material, and other additives. The positive electrode may use a conventional positive electrode active material, such as a lithium-containing transition metal oxide, while the negative electrode may use a conventional negative electrode active material, such as lithium metal, a carbon material, a metal compound, or a mixture thereof, capable of absorbing and releasing lithium ions. The separator may be a conventional porous polymer film used in lithium secondary batteries.

[0047] A typical electrolyte for lithium secondary batteries may be used as the electrolyte housed in the cover 105 together with the electrode assembly 101. The cover 105 is made of a sheet material and includes a housing for housing the electrode assembly 101. Preferably, the cover 105 is formed by combining a first case and a second case, each of which is formed by processing the sheet material into a predetermined shape. The sheet material constituting the cover 105 has a multilayer structure including an outermost resin layer made of an insulating material such as polyethylene terephthalate (PET) or nylon, a metal layer made of aluminum that maintains mechanical strength and prevents penetration of moisture and oxygen, and an inner resin layer made of a polyolefin-based material that has thermal adhesive properties and serves as a sealant.

[0048] The sheet material forming the cover 105 may have a predetermined adhesive resin layer interposed between the inner resin layer and the metal layer, and between the outer resin layer and the metal layer, as needed. The adhesive resin layer is formed as a single layer or multiple layers to facilitate smooth adhesion between different materials. Polyolefin resins are typically used as the material, or polyurethane resins for easy processing, and mixtures thereof may also be used.

[0049] 2, the battery cell 100 has two major surfaces S1 and S2 perpendicular to the first direction (e.g., the x direction). That is, the battery cell 100 may have a first major surface S1 and a second major surface S2 extending along a yz plane in FIG. 2 and parallel to each other.

[0050] FIG. 3 is a partially enlarged view showing a part of the battery cell 100, focusing on the cell lead 110 of the battery cell 100 according to one embodiment of the present invention.

[0051] 3, the cell lead 110 protrudes from one side of the cover 105 in the second direction (e.g., the y-axis direction) and includes a first portion 111 and a second portion 112. The first portion 111 may be located closer to the cover 105 than the second portion 112. The second portion 112 may be the tip of the cell lead 110 in the second direction.

[0052] The first portion 111 and the second portion 112 may be electrically connected to each other. In some embodiments, the first portion 111 and the second portion 112 may be in direct contact with each other, but the present invention is not limited thereto. In some embodiments, the first portion 111 and the second portion 112 may be integrally formed (integrated).

[0053] In some embodiments, the first portion 111 may have the form of a flat plate having a plane perpendicular to the first direction (e.g., the x-axis direction) as a main plane. In some embodiments, the second portion 112 may be configured as a plane perpendicular to the third direction (e.g., the z-axis direction). Here, the second portion 112 being configured as a plane perpendicular to the third direction means that the upper and lower surfaces of the second portion 112 are perpendicular to the third direction but do not include through-holes therein. In some embodiments, the upper and lower surfaces of the second portion 112 may be perpendicular to the third direction but may not include through-holes therein. In some embodiments, the upper and lower surfaces of the second portion 112 may be perpendicular to the third direction but may include through-holes therein.

[0054] FIG. 4 is a partially enlarged view of a part of the battery cell 100 viewed from the x direction, with the cell lead 110 of the battery cell 100 at the center.

[0055] 4, the first portion 111 of the cell lead 110 has a first upper surface 111a and a first lower surface 111b. The second portion 112 of the cell lead 110 has a second upper surface 112a and a second lower surface 112b. Here, the terms "upper surface" and "lower surface" are relative concepts, and one that is relatively higher can be defined as the "upper surface" and one that is relatively lower can be defined as the "lower surface," or one of the two can be defined as the "upper surface" and the other as the "lower surface."

[0056] A center line CL may be defined for the first portion 111. The center line CL is a straight line in a second direction (for example, the y-axis direction) that divides the first portion 111 into two equal parts in a third direction (for example, the z-axis direction).

[0057] In the third direction, the center line CL may be located between the second upper surface 112a and the second lower surface 112b of the second portion 112.

[0058] In the third direction, the first portion 111 has a first dimension H1, and the second portion 112 has a second dimension H2 that is smaller than the first dimension H1. The second dimension H2 may be, for example, about 0.5% to about 50% of the first dimension H1. In some embodiments, the second dimension H2 may be approximately 0.5% to approximately 50%, approximately 1% to approximately 48%, approximately 1.5% to approximately 45%, approximately 2% to approximately 43%, approximately 2.5% to approximately 40%, approximately 3% to approximately 38%, approximately 3.5% to approximately 35%, approximately 4% to approximately 33%, approximately 4.5% to approximately 30%, approximately 5% to approximately 28%, approximately 5.5% to approximately 25%, approximately 6% to approximately 23%, approximately 6.5% to approximately 20%, approximately 7% to approximately 18%, approximately 7.5% to approximately 15%, approximately 8% to approximately 13%, approximately 8.5% to approximately 10% of the first dimension H1, or a range between any two of these values.

[0059] If the second dimension H2 is too small compared to the first dimension H1, the second portion 112 may have insufficient mechanical strength and may be easily damaged. If the second dimension H2 is too large compared to the first dimension H1, the weight of the battery cell 100 may increase unnecessarily.

[0060] FIG. 5 is a partially enlarged view of a part of the battery cell 100 viewed from the y direction, with the cell lead 110 of the battery cell 100 at the center.

[0061] 5, in a first direction (e.g., the x-axis direction), the first portion 111 of the cell lead 110 has a first maximum dimension d1, and the second portion 112 of the cell lead 110 has a second maximum dimension d2. The second maximum dimension d2 is greater than the first maximum dimension d1. For example, the second maximum dimension d2 may be about 2 to 20 times the first maximum dimension d1. In some embodiments, the second maximum dimension d2 may be about 2 to about 20 times, about 2.5 to about 19.5 times, about 3 to about 19 times, about 3.5 to about 18.5 times, about 4 to about 18 times, about 4.5 to about 17.5 times, about 5 to about 17 times, about 5.5 to about 16.5 times, about 6 to about 16 times, about 6.5 to about 15.5 times, about 7 to about 15 times, about 7.5 to about 14.5 times, about 8 to about 14 times, about 8.5 to about 13.5 times, about 9 to about 13 times, about 9.5 to about 12.5 times, about 10 to about 12 times, or about 10.5 to about 11.5 times the first maximum dimension d1, or may be in a range between any two of these values.

[0062] If the second maximum dimension d2 is too small compared to the first maximum dimension d1, it may not be easy to weld a bus bar (described later) to the second portion 112. If the second maximum dimension d2 is too large compared to the first maximum dimension d1, the thickness of the battery cell 100 in a first direction (e.g., the x-axis direction) may increase excessively, and the energy density may decrease.

[0063] In some embodiments, a second maximum dimension d2 of the second portion 112 in a first direction (e.g., the x-axis direction) may be greater than a cell thickness d3 defined between the first major surface S1 and the second major surface S2 of the battery cell 100. In other embodiments, the second maximum dimension d2 of the second portion 112 in the first direction (e.g., the x-axis direction) may be smaller than a cell thickness d3 defined between the first major surface S1 and the second major surface S2 of the battery cell 100.

[0064] FIG. 6 is a partially enlarged view of a part of the battery cell 100 viewed from the z direction, with the cell lead 110 of the battery cell 100 at the center.

[0065] 6, a projection of the second portion 112 on a plane (e.g., an xy plane) perpendicular to the third direction (e.g., the z-axis direction) may have a circular shape. In some embodiments, the projection of the second portion 112 on the xy plane may have any shape other than a circle, such as an ellipse, a polygon (e.g., a square, a pentagon, a hexagon, etc.), or any other shape. However, it may be advantageous for the projection to have a circular shape in terms of the versatility of welding methods that can be used for subsequent welding to a bus bar, structural stability, ease of handling, etc.

[0066] In some embodiments, when the projection is circular, the second portion 112 may have the form of a cylinder or a truncated cone. When the projection is polygonal, the second portion 112 may have the form of a polygonal prism or a truncated pyramid.

[0067] The projected area of ​​the second portion 112 may be about 2 to about 20 times the projected area of ​​the first portion 111. In some embodiments, the projected area of ​​the second portion 112 may be about 2 to about 20 times, about 2.5 to about 19 times, about 3 to about 18 times, about 3.5 to about 17 times, about 4 to about 16 times, about 4.5 to about 15 times, about 5 to about 14 times, about 5.5 to about 13 times, about 6 to about 12 times, about 6.5 to about 11 times, about 7 to about 10 times, about 7.5 to about 9 times the projected area of ​​the first portion 111, or a range between any two of these values.

[0068] If the projected area of ​​the second portion 112 is too small compared to the projected area of ​​the first portion 111, it may not be easy to weld a bus bar (to be described later) to the second portion 112. If the projected area of ​​the second portion 112 is too large compared to the projected area of ​​the first portion 111, the weight of the battery cell 100 may increase unnecessarily.

[0069] The second portions 112 of the cell leads 110 of the battery cells 100 have a planar shape perpendicular to the third direction (e.g., the z-axis direction), and therefore, the battery cells 100 can be electrically interconnected after being coupled to the pack case 300. Therefore, the battery pack according to the embodiment of the present invention has a simple number of parts, can be manufactured at low cost, has excellent productivity, and has little risk of product failure.

[0070] FIG. 7a is a partially enlarged view showing a part of the battery cell 100, focusing on the cell lead 110 of the battery cell 100 according to another embodiment of the present invention.

[0071] Referring to FIG. 7 a, the second portion 112 may be configured such that a second top surface 112 a of the second portion 112 is substantially coplanar with the first top surface 111 a of the first portion 111 .

[0072] FIG. 7b is a partially enlarged view showing a part of the battery cell 100, focusing on the cell lead 110 of the battery cell 100 according to another embodiment of the present invention.

[0073] Referring to FIG. 7 b, the second portion 112 may be configured such that a second lower surface 112 b of the second portion 112 is substantially coplanar with the first lower surface 111 b of the first portion 111 .

[0074] By configuring the second portion 112 as shown in FIG. 7a or 7b, it is possible to ensure an error margin for the positioning of the bus bar when the second portion 112 and the bus bar are later welded together.

[0075] FIG. 8 is a perspective view showing a pair of adjacent battery cells 100_1 and 100_2 electrically connected by a bus bar 200. As shown in FIG.

[0076] Referring to FIG. 8, the cell lead 110_1 of the first battery cell 100_1 includes a first portion 111_1 and a second portion 112_1, and the cell lead 110_2 of the second battery cell 100_2 includes a first portion 111_2 and a second portion 112_2.

[0077] The cell lead 110_1 of the first battery cell 100_1 and the cell lead 110_2 of the second battery cell 100_2 may be electrically connected by a bus bar 200. Specifically, the second portion 112_1 of the first battery cell 100_1 and the second portion 112_2 of the second battery cell 100_2 may be electrically connected by the bus bar 200.

[0078] The cell lead 110_1 of the first battery cell 100_1 and the cell lead 110_2 of the second battery cell 100_2, which are electrically connected by the bus bar 200, may have the same polarity or different polarities.

[0079] The bus bar 200 may be disposed to extend in a first direction (e.g., the x-axis direction) and may be configured to contact the lower surfaces of the second portion 112_1 of the first battery cell 100_1 and the second portion 112_2 of the second battery cell 100_2. In some embodiments, the bus bar 200 may have a strip shape extending in the first direction. In this case, a flat surface of the bus bar 200 may face the second portion 112_1 of the first battery cell 100_1 and the second portion 112_2 of the second battery cell 100_2 in a third direction (e.g., the z-axis direction).

[0080] FIG. 9 is a cross-sectional view showing a cross section of second portions 112_1 and 112_2 and bus bar 200 taken along line IX-IX' in FIG.

[0081] 9, the bus bar 200 may have a recess R recessed in a third direction (e.g., the z-axis direction) at a portion overlapping with the second portions 112_1 and 112_2. In some embodiments, the recess R may be generated as a result of welding the bus bar 200 and the second portions 112_1 and 112_2 in the third direction. However, since the recess R is a result of partial melting and solidification of contact portions between the bus bar 200 and the second portions 112_1 and 112_2 due to welding, it may appear as a trace of melting and solidification in some cases.

[0082] In FIG. 9, the recess R is shown as being formed continuously with the flat surface of the bus bar 200, but in some cases, a slight protrusion may be formed around the recess R.

[0083] In some embodiments, due to the welding method, the recess R may not be observed as a clear interface.

[0084] Fig. 10 is a flowchart showing a method for manufacturing a battery pack 10 according to an embodiment of the present invention. Fig. 11a and Fig. 11b are perspective views showing a method for manufacturing a battery pack 10 according to an embodiment of the present invention.

[0085] 10 and 11a, a plurality of battery cells 100 may be directly disposed in a pack case 300 (S10). Here, disposing the plurality of battery cells 100 directly in the pack case 300 means disposing the plurality of battery cells 100 in the pack case 300 without configuring them as a module.

[0086] In some embodiments, the plurality of battery cells 100 may be individually disposed one by one in the pack case 300. In other embodiments, the plurality of battery cells 100 may be disposed in the pack case 300 after being stacked two or more times.

[0087] The method of arranging the battery cells 100 in the pack case 300 is not particularly limited, and any known method may be used to arrange the battery cells 100 in the pack case 300. The specific configuration of each battery cell 100 has been described with reference to FIGS. 1 to 7b, and therefore detailed description thereof will be omitted here.

[0088] 10 and 11b, the cell leads 110_1 and 110_2 protruding in a second direction (e.g., the y-axis direction) of two adjacent battery cells 100 may be electrically connected to the bus bar 200 (S20). The cell leads 110_1 and 110_2 may be connected to the bus bar 200 by welding in a third direction (e.g., the z-axis direction).

[0089] In some embodiments, the bus bar 200 may be disposed in the pack case 300 before the plurality of battery cells 100 are disposed in the pack case 300. In some embodiments, the bus bar 200 may be disposed on the cell leads 110_1, 110_2 after the plurality of battery cells 100 are disposed in the pack case 300. Thereafter, the bus bar 200 may be welded to the cell leads 110_1, 110_2. The welding method may be any known method and is not particularly limited.

[0090] The second portions 112 of the cell leads 110 of the battery cells 100 have a planar shape perpendicular to the third direction (e.g., the z-axis direction), and therefore, the battery cells 100 can be electrically interconnected after being coupled to the pack case 300. Therefore, the battery pack according to the embodiment of the present invention has a simple number of parts, can be manufactured at low cost, has excellent productivity, and has little risk of product failure.

[0091] Although the embodiments of the present invention have been described in detail as described above, those skilled in the art can implement the present invention in various modifications without departing from the spirit and scope of the present invention as defined in the appended claims. Therefore, future changes to the embodiments of the present invention will not depart from the technology of the present invention. [Explanation of symbols]

[0092] 10 Battery Pack 100 battery cells 100_1, 100_2 battery cells 100_1 Battery cell 100_1 1st battery cell 100_2 Battery cell 100_2 Second battery cell 101 Electrode assembly 105 Cover 110 Cell Read 110_1, 110_2 Cell Read 110_1 Cell Read 110_2 Cell Read 111 Part 1 111_1 Part 1 111_2 Part 1 111a 1st top surface 111b 1st bottom surface 112 Part 2 112_1, 112_2 2nd part 112_1 2nd part 112_2 2nd part 112a 2nd top surface 112b 2nd bottom surface 200 Busbar 300 pack case 300 direct pack cases 310 Upper Case 320 Lower Case 330 Interior Space 400 Battery Management System 500 Battery Disconnect Unit CL center line d1 First maximum dimension d2 Second largest dimension H1 First dimension H2 Second dimension R recess S1 main surface, 1st main surface S2 main surface, 2nd main surface

Claims

1. In a vertical coordinate system defined by a first direction, a second direction, and a third direction that are perpendicular to each other, a plurality of battery cells stacked in the first direction; a pack case that houses the battery cell in an internal space, Each of at least a pair of adjacent battery cells among the battery cells includes an electrode assembly, a cover surrounding the electrode assembly, and a cell lead protruding from one side of the cover in the second direction, the cell lead includes a first portion relatively close to the cover and a second portion relatively farther away from the cover; a maximum dimension of the second portion in the first direction being greater than a maximum dimension of the first portion, and the second portion being configured as a plane perpendicular to the third direction.

2. The battery pack according to claim 1 , wherein the corresponding second portions of the pair of adjacent battery cells are electrically connected to each other by a bus bar.

3. The battery pack according to claim 2 , wherein the bus bar is electrically connected to the second portion by welding in the third direction.

4. 3. The battery pack according to claim 1, wherein the dimension of the second portion in the third direction is 0.5% to 50% of the dimension of the first portion.

5. The battery pack according to claim 4 , wherein a center of the first portion is located between an upper surface of the second portion and a lower surface of the second portion in the third direction.

6. 3. The battery pack according to claim 1, wherein an upper surface of the second portion is flush with an upper surface of the first portion.

7. 3. The battery pack according to claim 1, wherein a lower surface of the second portion is flush with a lower surface of the first portion.

8. 3. The battery pack according to claim 1, wherein the maximum dimension of the second portion in the first direction is 2 to 20 times the maximum dimension of the first portion.

9. 3. The battery pack according to claim 1, wherein the area of ​​the second portion is 2 to 20 times the area of ​​the first portion in a projection onto a plane perpendicular to the third direction.

10. In a vertical coordinate system defined by a first direction, a second direction, and a third direction that are perpendicular to each other, placing a plurality of battery cells directly within a pack case; electrically connecting cell leads protruding in the second direction of at least two adjacent battery cells among the plurality of battery cells using a bus bar; the step of electrically connecting the cell leads to each other using the bus bar includes the step of welding each of the cell leads to the bus bar in the third direction to connect them.

11. the cell lead includes a first portion that is relatively close to a cover of the battery cell and a second portion that is relatively farther away from the cover; 11. The method of manufacturing a battery pack according to claim 10, wherein a maximum dimension of the second portion in the first direction is greater than a maximum dimension of the first portion, and the second portion is configured as a plane perpendicular to the third direction.

12. The method for manufacturing a battery pack according to claim 11, wherein a dimension of the second portion in the third direction is 0.5% to 50% of a dimension of the first portion.

13. The method for manufacturing a battery pack according to claim 11 or 12, wherein the second portion does not include a through-hole.

14. The method for manufacturing a battery pack according to claim 11 or 12, wherein the second portion includes a through hole.

15. A battery cell defined in a vertical coordinate system having a first direction, a second direction, and a third direction that are perpendicular to each other, The battery cell includes two parallel main surfaces perpendicular to the first direction, the battery cell includes an electrode assembly, a cover surrounding the electrode assembly, and a cell lead protruding from one side of the cover in the second direction; the cell lead includes a first portion relatively close to the cover and a second portion relatively farther away from the cover; In the first direction, a maximum dimension of the second portion is greater than a maximum dimension of the first portion, and the second portion is configured with a plane perpendicular to the third direction; In a projection onto a plane perpendicular to the third direction, the area of ​​the second portion is 2 to 20 times the area of ​​the first portion.

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