Battery cell and manufacturing method thereof

Abstract

A battery cell according to one embodiment of the present invention includes a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, an electrode tab extending from the positive electrode or the negative electrode of the laminate, and an electrode lead connected to the electrode tab, the electrode tab having a pre-welding portion connecting the respective electrode tabs and a main welding portion connecting the electrode tab and the electrode lead, the pre-welding portion having an inner periphery and an outer periphery, at least one welding spot of the main welding portion overlaps with the inner periphery of the pre-welding portion, and the inner periphery of the pre-welding portion is located closer to the laminate in the longitudinal direction of the electrode tab than the outer periphery of the pre-welding portion.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0013633, filed January 28, 2022, and Korean Patent Application No. 10-2023-0010154, filed January 26, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a battery cell and a manufacturing method thereof, and more particularly to a battery cell in which cracks in electrode tabs are prevented and a manufacturing method thereof. [Background technology]

[0003] In modern society, as the use of portable devices such as mobile phones, laptops, video cameras, and digital cameras has become commonplace, technological development in fields related to these mobile devices is accelerating. Furthermore, rechargeable secondary batteries are being used as the power source for electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (P-HEVs), and other vehicles as a way to solve problems such as air pollution caused by existing gasoline-powered vehicles that use fossil fuels, and so there is an increasing need for the development of secondary batteries.

[0004] Currently commercially available secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Of these, lithium secondary batteries are attracting the most attention due to their advantages of being freely chargeable and dischargeable, having a low self-discharge rate, and having a high energy density.

[0005] Secondary batteries are classified according to the shape of the battery case into cylindrical batteries and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal can, and pouch batteries, in which the electrode assembly is housed in a pouch-shaped case made of an aluminum laminate sheet.

[0006] Secondary batteries are also classified according to the structure of the electrode assembly, which is a stack of positive and negative electrodes and a separator between them. Representative examples include a jelly-roll (wound) electrode assembly in which long sheet-like positive and negative electrodes are wound with a separator between them, and a stack (layered) electrode assembly in which multiple positive and negative electrodes cut into predetermined sizes are stacked in sequence with a separator between them.

[0007] FIG. 1 is a diagram showing electrode tabs and electrode leads included in a conventional battery cell.

[0008] 1, the battery cell 10 may be a pouch-type battery in which a stacked electrode assembly is housed in a cell case. The battery cell 10 may include a stack 11 including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, an electrode tab 12 extending from the positive electrode or the negative electrode, and an electrode lead 13 connected to the electrode tab 12.

[0009] In a pouch-type battery, a plurality of electrode tabs 12 extending from each electrode of a laminate 11 are pre-welded by a welding machine to gather at one point and then connected to an electrode lead 13. Here, the welding portion connecting the plurality of electrode tabs 12 is referred to as a pre-welding portion 20, and the welding portion connecting the electrode tabs 12 and the electrode lead 13 is referred to as a main welding portion 30. Thereafter, the laminate 11, the electrode tabs 12, and the electrode lead 13 are incorporated into a cell case to manufacture a battery cell 10, and at this time, one end of the electrode lead 13 may be positioned to protrude outside the cell case to be connected to an external bus bar.

[0010] Meanwhile, when the battery cell 10 is mounted in a module or pack, the electrode leads 13 and bus bars are also connected by a welding process, but if high energy is applied to the electrode leads 13 due to welding conditions, the electrode leads 13 and electrode tabs 12 inside the battery cell 10 may become separated. Furthermore, if excessive welding energy or pressure is applied to the electrode tabs 12 in an attempt to strengthen the welding conditions of the main welding parts 30 during the manufacture of the battery cell 10 in order to prevent separation of the electrode leads 13 and electrode tabs 12, cracks may occur in the electrode tabs 12, or existing cracks may grow. Summary of the Invention [Problem to be solved by the invention]

[0011] The problem to be solved by the present invention is to provide a battery cell and a manufacturing method thereof that reduce the risk of disconnection of electrode tabs.

[0012] However, the problems to be solved by the embodiments of the present invention are not limited to the above problems, and can be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0013] A battery cell according to one embodiment of the present invention includes a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; electrode tabs extending from the positive electrode or the negative electrode of the laminate; and electrode leads connected to the electrode tabs. The electrode tabs have pre-welding portions connecting the electrode tabs and main welding portions connecting the electrode tabs to the electrode leads. The pre-welding portions have inner and outer peripheries, and at least one welding spot of the main welding portion overlaps the inner periphery of the pre-welding portion. In the longitudinal direction of the electrode tabs, the inner periphery of the pre-welding portion is located closer to the laminate than the outer periphery of the pre-welding portion.

[0014] The main welding portion includes a first welding line, a second welding line, and a third welding line arranged side by side, the first welding line being arranged between the second welding line and the third welding line, the second welding line overlapping the pre-welding portion, and the third welding line not overlapping the pre-welding portion.

[0015] The second welding line may form a periphery of the main welding portion, and an outer periphery of the pre-welding portion may be located outside the second welding line in a longitudinal direction of the electrode tab away from the laminate.

[0016] The third welding line may be located outside an inner periphery of the pre-welding portion in a longitudinal direction of the electrode tab in a direction approaching the laminate.

[0017] At least one of the welding spots of the main welding portion may be located inside the pre-welding portion.

[0018] The pre-welding portion is formed to be spaced apart from the periphery of the electrode tab in the width direction of the electrode tab.

[0019] The length of the pre-welding portion in the width direction of the electrode tab is smaller than the width of the electrode tab.

[0020] A part of the main welding portion is formed on the outer side of the peripheral edge of the pre-welding portion in the width direction of the electrode tab.

[0021] The pre-welding portion is formed in a pyramidal pattern.

[0022] The pre-welding portion is formed in a straight line pattern.

[0023] The corners of the electrode leads are formed in a rounded shape.

[0024] The electrode lead may be located on one side of the electrode tab, and a back plate may be located on the other side of the electrode tab opposite to the one side of the electrode tab.

[0025] An additional weld is formed between the back plate and the electrode tab.

[0026] According to another embodiment of the present invention, a battery cell includes a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; electrode tabs extending from the positive electrode or the negative electrode of the laminate; and pre-welding portions connecting the electrode tabs to form a tab bundle, the pre-welding portions being spaced apart from the peripheries of the electrode tabs in the width direction of the electrode tabs.

[0027] The battery cell may further include an electrode lead coupled to the electrode tab and a main welding portion coupling the electrode tab and the electrode lead, the pre-welding portion having an inner periphery and an outer periphery, and at least one welding spot of the main welding portion may overlap the inner periphery of the pre-welding portion.

[0028] A method for manufacturing a battery cell according to yet another embodiment of the present invention includes forming a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; forming a pre-welding portion on an electrode tab extending from the positive electrode or the negative electrode; and forming a main welding portion on one surface of the electrode tab for connecting an electrode lead, wherein at least a portion of the pre-welding portion and the main welding portion overlap each other, and the main welding portion is located closer to the laminate than the pre-welding portion in the longitudinal direction of the electrode tab.

[0029] The method may further include removing the unwelded electrode tabs after the forming of the pre-welding portion.

[0030] The method may further include forming corners of the electrode leads into round shapes before forming the main welding portions.

[0031] The forming of the main welding portion may include disposing an electrode lead on one side of the electrode tab, and disposing a back plate on the other side of the electrode tab. [Effects of the Invention]

[0032] According to the embodiment, when manufacturing a battery cell of the present invention, the risk of disconnection of the electrode tab can be reduced by adjusting the position and size of the welding portion formed on the electrode lead and the electrode tab.

[0033] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. [Brief explanation of the drawings]

[0034] [Figure 1] 1A and 1B are diagrams showing electrode tabs and electrode leads included in a conventional battery cell. [Figure 2] 2A and 2B are diagrams showing electrode tabs and electrode leads included in a battery cell according to an embodiment of the present invention. [Figure 3] FIG. 3 is a partial enlarged view of region A in FIG. 2. [Figure 4] 10A and 10B are diagrams for explaining stress that may occur in an electrode tab. [Figure 5] 10A and 10B are diagrams illustrating changes in stress depending on the size and position of a pre-welded portion formed on an electrode tab. [Figure 6] 3 is an example of a pre-welding portion formed on the electrode tab of FIG. 2. [Figure 7]3A to 3C are diagrams showing a process of forming corners of the electrode lead of FIG. 2. [Figure 8] 3 shows an example in which the battery cell of FIG. 2 is provided with a back plate. DETAILED DESCRIPTION OF THE INVENTION

[0035]

[0023] Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the embodiments. The present invention can be realized in various different forms other than those described below, and the scope of the present invention is not limited to the embodiments described herein.

[0036] In order to clearly explain the present invention, parts that are not necessary for the explanation will be omitted, and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0037] Furthermore, the size and thickness of each component shown in the drawings are arbitrarily enlarged or reduced for the sake of convenience, and it is obvious that the content of the present invention is not limited to those shown in the drawings. In the following drawings, the thickness of each layer is enlarged to clearly show various layers and regions. In the following drawings, the thickness of some layers and regions is exaggerated for the sake of convenience.

[0038] Furthermore, when a layer, film, region, plate, or other portion is described as being "on" another portion, this should be interpreted as including not only the case where the layer, film, region, plate, or other portion is "directly on" the other portion, but also the case where there is another portion between them. Conversely, when a layer, film, region, plate, or other portion is described as being "directly on" the other portion, it can mean that there is no other portion between them. Furthermore, being "on" a reference portion means being located above or below the reference portion, and does not necessarily mean being located "on" in the opposite direction of gravity. Meanwhile, the description of being "on" another portion, as well as the description of being "under" another portion, can be understood by referring to the above content.

[0039] Furthermore, throughout the specification, when a part is described as "comprising" a certain element, this means that it can further include other elements, rather than excluding other elements, unless otherwise specified.

[0040] Furthermore, throughout the specification, "in a plane" means the part is viewed from above, and "in cross section" means the part is viewed from the side through a vertical cross section.

[0041] Fig. 2 is a diagram showing electrode tabs and electrode leads included in a battery cell according to an embodiment of the present invention, and Fig. 3 is a partial enlarged view of area A in Fig. 2.

[0042] 2 and 3, the battery cell 100 of this embodiment may include a laminate 110 including a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, an electrode tab 120 extending from the positive or negative electrode of the laminate 110, and an electrode lead 130 connected to the electrode tab 120. The laminate 110, the electrode tab 120, and the electrode lead 130 are sealed together with an electrolyte in a cell case with one end of the electrode lead 130 protruding to form the battery cell 100. FIGS. 2 and 3 show the battery cell 100 without the cell case.

[0043] The laminate 110 may be a chargeable and dischargeable power generating element. The electrodes included in the laminate 110 may include a positive electrode and a negative electrode, and a separator may be interposed between each electrode, so that the laminate 110 may have a structure in which a positive electrode / separator / negative electrode are alternately stacked. The positive electrode or negative electrode may be a current collector coated with a positive electrode active material or a negative electrode active material, and the separator may be made of an insulating material to electrically insulate the positive electrode from the negative electrode.

[0044] In addition, the stack 110 may be formed by stacking a plurality of mono-cells, each having a separator / positive electrode / separator / negative electrode or a separator / negative electrode / separator / positive electrode stacked from the bottom up, manufactured as a unit cell, and stacking the mono-cells together, and a half-cell, each having a separator / negative electrode / separator or a separator / positive electrode / separator stacked in that order, as the outermost layer.

[0045] An electrode tab 120 may be located at one end of the laminate 110 or at one end of an electrode included in the laminate 110. The electrode tab 120 may be a portion extending in one or two directions from each electrode. The electrode tab 120 may be a portion to which an electrode active material is not applied. Among the electrode tabs 120, the electrode tab 120 connected to the positive electrode is called a positive electrode tab, and the electrode tab 120 connected to the negative electrode is called a negative electrode tab. In this case, the positive electrode tab may be located at one end of the laminate 110, and the negative electrode tab may be located at the other end of the laminate 110.

[0046] The electrode lead 130 may be used to form an electrical connection between the laminate 110 inside the cell casing and an external member of the cell casing. One end of the electrode lead 130 may be drawn out to the outside of the cell casing, and the other end of the electrode lead 130 may be connected to the electrode tab 120 inside the cell casing. Here, the electrode lead 130 and the electrode tab 120 may be connected by welding.

[0047] Meanwhile, the electrode tabs 120 extending from the electrode may be interconnected by a welding device to form an electrode tab bundle before being connected to the electrode lead 130. A pre-weld portion 200 for connecting the electrode tabs 120 is formed on the electrode tabs 120. The pre-weld portion 200 may be formed by forming a joint between the electrode tabs 120 using a welding device. The electrode tabs 120 may be gathered together by applying pressure to a tab guide or the like, and may be joined in a liquid or solid state by the welding device. The welding device used to form the pre-weld portion 200 may be an ultrasonic welding device. In this case, the welding device may include a horn, an anvil, and / or an actuator that vibrates the horn. The electrode tabs 120 of the workpiece may be inserted between the horn and the anvil and then joined to each other by ultrasonic welding.

[0048] Furthermore, to connect the electrode tab 120 and the electrode lead 130, a main welding portion 300 is formed in the electrode tab 120 and the electrode lead 130. The main welding portion 300 is formed using a welding machine. The electrode tab 120 and the electrode lead 130 are partially heated by the welding machine, and the heated portions are joined together to connect them to each other. The welding machine used to form the main welding portion 300 may be a machine that uses a laser welding method. When using a laser welding method, the main welding portion 300 may include a plurality of welding spots 302 formed by an irradiated laser.

[0049] Here, it has been explained that the laser welding method is used to form the main welding portion 300 and the ultrasonic welding method is used to form the pre-welding portion 200, but this is not necessarily limited thereto, and it would also be possible for laser welding to be used to form the pre-welding portion 200 and the ultrasonic welding method to be used to form the main welding portion 300.

[0050] 2 and 3, at least a portion of the pre-welding portion 200 and the main welding portion 300 formed on one surface of the electrode tab 120 may overlap each other. The main welding portion 300 is formed outside the pre-welding portion 200 in the width direction (X-axis direction) of the electrode tab 120 and / or the length direction (Y-axis direction) of the electrode tab 120. In addition, there is an area outside the area occupied by the pre-welding portion 200 where the main welding portion 300 is not formed.

[0051] At least one of the welding spots 302 included in the main welding portion 300 may overlap a periphery located on one side of the pre-welding portion 200. At least one of the welding spots 302 included in the main welding portion 300 may overlap an inner periphery 210 of the pre-welding portion 200. Here, the inner periphery 210 may be a portion of the region of the pre-welding portion 200 that is located relatively closer to the laminate 110 than an outer periphery 220 described below.

[0052] Specifically, the pre-welding portion 200 includes an inner periphery 210 and an outer periphery 220, and at least one of the welding spots 302 of the main welding portion 300 may overlap the inner periphery 210 of the pre-welding portion 200. In this case, the inner periphery 210 of the pre-welding portion 200 may be positioned closer to the laminate 110 than the outer periphery 220 of the pre-welding portion 200 in the longitudinal direction of the electrode tab.

[0053] 3, the main welding portion 300 may include a first welding line 310, a second welding line 320, and a third welding line 330 arranged side by side. Each of the first welding line 310, the second welding line 320, and the third welding line 330 may include a plurality of welding spots 302 of the main welding portion 300 arranged in the width direction (X-axis direction) of the electrode tab 120.

[0054] 3 shows one each of second welding line 320 and third welding line 330, there may be two or more of each of second welding line 320 and third welding line 330. First welding line 310 is disposed between second welding line 320 and third welding line 330, and second welding line 320 overlaps pre-welded portion 200, while third welding line 330 does not overlap pre-welded portion 200.

[0055] The second welding line 320 forms the periphery of the main welding portion 300, and the outer periphery 220 of the pre-welding portion may be located outside the second welding line 320 in the longitudinal direction (Y-axis direction) of the electrode tab 120, away from the laminate 110. In addition, the third welding line 320 may be located outside the inner periphery 210 of the pre-welding portion 200 in the longitudinal direction (Y-axis direction) of the electrode tab 120, towards the laminate 110.

[0056] 1, cracks may occur in the electrode tab 120 when the main welding portion 300 is formed, but in this embodiment, by forming the welding spot 302 on the inner periphery 210 of the pre-welding portion 200, the formation of cracks at the inner periphery 210 of the pre-welding portion 200 or the propagation of the cracks that occur at the inner periphery 210 of the pre-welding portion 200 can be minimized. The inner periphery 210 of the pre-welding portion 200 can correspond to the point where cracks start when the main welding portion 300 is formed.

[0057] Here, the inside of the electrode tab 120 refers to the direction from the electrode tab 120 toward the laminate 110 (-Y axis direction), and may be the direction toward the inside of the cell case in the longitudinal direction of the battery cell 100. Additionally, the outside refers to the direction from the electrode tab 120 toward the electrode lead 130, and may be the direction toward the outside of the cell case in the longitudinal direction of the battery cell 100.

[0058] In the electrode tab 120, the main welding portion 300 may be located more inward than the pre-welding portion 200. A peripheral edge located on one side of the pre-welding portion 200 may be located within the main welding portion 300. The inner peripheral edge 210 of the pre-welding portion 200 may be located overlapping the main welding portion 300. In the longitudinal direction of the electrode tab 120, the main welding portion 300 may be located closer to the laminate 110 than the pre-welding portion 200. One or more of the welding spots 302 included in the main welding portion 300 may be located closer to the laminate 110 than the pre-welding portion 200. When the main welding portion 300 is formed extending more inward than the pre-welding portion 200, a mechanical constraint region is formed around the inner peripheral edge 210 of the pre-welding portion 200 due to welding of the main welding portion 300, and cracks occurring in this region can be prevented by the welding spots 302 of the main welding portion 300. Also, when the main welding portion 300 is formed, the inner periphery 210 of the pre-welding portion 200 may be remelted, thereby removing cracks.

[0059] Furthermore, as will be described later, the electrode tab 120 may be subjected to tensile force due to volume expansion caused by cell swelling that occurs during the manufacturing process or while the battery cell is in operation, which causes contraction due to stress. However, since a portion of the welding spot 302 included in the main welding portion 300 is formed inside the pre-welding portion 200, the rigidity of the electrode tab 120 is supplemented, and damage to the electrode tab 120 due to tensile force and stress can be prevented.

[0060] 2 and 3, according to another embodiment of the present invention, the pre-welding portion 200 formed on one surface of the electrode tab 120 is spaced apart from the periphery of the electrode tab 120 in the width direction of the electrode tab 120. Alternatively, the length of the pre-welding portion 200 in the width direction of the electrode tab 120 is smaller than the width of the electrode tab 120. This will be described in more detail with reference to FIGS. 4 and 5.

[0061] FIG. 4 is a diagram illustrating stress that may occur in an electrode tab. FIG. 5 is a diagram illustrating changes in stress depending on the size and position of a pre-welded portion formed on the electrode tab. Here, "tension" refers to pulling the electrode tab toward both ends in the longitudinal direction, and the tensile direction is indicated by arrows pointing up and down in FIGS. 4 and 5. Furthermore, stress due to tension is indicated by arrows pointing left and right in FIGS. 4 and 5.

[0062] Referring to FIG. 4, stress generated when the electrode tab 12 is pulled can cause the electrode tab 12 to shrink in the width direction. However, as shown in FIG. 5, when a pre-welding portion 20 is formed on the electrode tab 12, the stress and the resulting shrinkage can change slightly. In a conventional electrode tab 12 in which the pre-welding portion 200 is formed up to the upper periphery in the width direction of the electrode tab 12 as shown in FIG. 5(a), the pre-welding portion 200 fixes a portion of the length of the electrode tab 12 as a whole, so that when the electrode tab 12 is pulled, stress tends to concentrate around the inner periphery 21 of the pre-welding portion 20. When stress concentrates on the inner periphery 21 of the pre-welding portion 20, cracks are likely to form around the inner periphery 21 of the pre-welding portion 20, and small cracks can grow larger.

[0063] In contrast, in this embodiment, to solve the above-mentioned problems, the pre-welding portion 200 is formed so as to be spaced apart from the periphery of the electrode tab 120 in the width direction of the electrode tab 120. Specifically, as shown in Fig. 5(b), a portion of the main welding portion 300 is formed outside the periphery of the pre-welding portion 200 in the width direction (X-axis direction) of the electrode tab 120. As an example, as shown in Fig. 3, the welding spot 302 of the main welding portion 300 is formed outside the periphery of the pre-welding portion 200.

[0064] 5(b), when the pre-welding portion 200 is formed so as to be spaced apart from the periphery of the electrode tab 120 in the width direction of the electrode tab 120, the pre-welding portion 200 partially fixes a portion of the length of the electrode tab 120, so that contraction due to stress when the electrode tab 120 is pulled does not concentrate on the inner periphery 210 of the pre-welding portion 200. Contraction of the electrode tab 120 due to stress occurs over a wider range, including the pre-welding portion 200, thereby minimizing the occurrence and growth of cracks around the inner periphery 210. Therefore, by forming the pre-welding portion 200 as in this embodiment, the occurrence and growth of cracks that may occur in the electrode tab 120 can be mitigated.

[0065] In the embodiments described with reference to Figures 2 and 3, an embodiment in which the pre-welding portion 200 is formed so as to be spaced apart from the periphery in the width direction of the electrode tab 120 and an embodiment in which at least a portion of the pre-welding portion 200 and the main welding portion 300 overlap each other are shown in the same drawing, but this is not limited to this, and the embodiment in which the pre-welding portion 200 described in Figures 4 and 5 is formed so as to be spaced apart from the upper periphery in the width direction of the electrode tab 120 can be implemented without being limited to a specific structure of the main welding portion 300.

[0066] FIG. 6 is an example of a pre-welded portion formed on the electrode tab of FIG.

[0067] 6, the pre-weld portion 200 of this embodiment is formed in various patterns. The pattern of the pre-weld portion 200 varies depending on the specifications of the horn included in the welding equipment. The pattern of the pre-weld portion 200 varies depending on the knurl pattern of the horn.

[0068] For example, the pattern of the pre-welding portion 200 may be formed in a pyramidal shape as shown in Figure 6(a), or in a linear or window shape as shown in Figures 6(b) and 6(c). In the case of a pyramidal shape as shown in Figure 6(a), the pressure applied to the electrode tab 120 per knurl is greater than in the linear shape as shown in Figures 6(b) and 6(c), which may damage the electrode tab 120. Therefore, in order to distribute the pressure applied to the electrode tab 120, it is preferable to form the pre-welding portion 200 in a linear shape as shown in Figure 6(b) or 6(c).

[0069] 7A to 7C are diagrams showing a process for forming the corners of the electrode lead of FIG.

[0070] 7, the corners 132 of the electrode lead 130 in this embodiment may have a rounded shape. The corners 132 of the electrode lead 130 may come into contact with the electrode tab 120 during the manufacturing process or use of the battery cell 100. If burrs are formed on the corners 132, they may pierce and damage the electrode tab 120. Therefore, to prevent breakage of the electrode tab 120, it is preferable that the corners 132 of the electrode lead 130 be processed to have a rounded shape. To remove burrs formed on the corners 132, a laser tool is used, as shown in FIG. 7.

[0071] FIG. 8 shows an example in which the battery cell of FIG. 2 is provided with a back plate.

[0072] 8, the battery cell 100 of this embodiment is provided with a back plate 140. The back plate 140 is provided on one side of the electrode tab 120. The back plate 140 may be positioned to face the electrode lead 130 with the electrode tab 120 sandwiched between them. By providing the back plate 140 on one side of the electrode tab 120, breakage during welding can be prevented and pressure applied to the electrode tab 120 can be dispersed. In addition, the back plate 140 can strengthen the resistance of the electrode tab 120 to tension and resulting stress that may occur during the manufacturing process.

[0073] Therefore, the main welding portion 300 of the battery cell 100 of this embodiment is formed by disposing the electrode lead 130 on one side of the electrode tab 120, disposing the back plate 140 on the other side opposite the one side of the electrode tab 120, and joining the electrode lead 130, the electrode tab 120, and the back plate 140 using a welding device. In this case, the battery cell 100 according to this embodiment may include an additional welding portion 300' formed between the back plate 140 and the electrode tab 120. The additional welding portion 300' may be a welding portion formed between the back plate 140 and the electrode tab 120 by adding the back plate 140 to strengthen the welding portion of the main welding portion 300 when forming the main welding portion 300 between the electrode tab 120 and the electrode lead 130. The additional welding portion 300' can strengthen the welding strength between the electrode tabs 120 and between the electrode tabs 120 and the electrode lead 130, thereby increasing the ability of the bonded portions of the electrode tabs 120 and the electrode tabs 120 and the electrode lead 130 to withstand shear forces.

[0074] In this case, the area of ​​the additional welding portion 300' may overlap with the main welding portion 300, and the area of ​​the additional welding portion 300' may be substantially the same as the area of ​​the main welding portion 300. In order to ensure that the area of ​​the additional welding portion 300' is substantially the same as the area of ​​the main welding portion 300, the back plate 140 may have the same area as the area of ​​the portion where the electrode lead 130 overlaps with the electrode tab 120. In addition, the back plate 140 may be formed using the same material as the electrode lead 130, for example, aluminum or copper.

[0075] A method for manufacturing a battery cell according to another embodiment of the present invention will now be described. The manufacturing method described below includes all of the content of the above-described embodiment, and to avoid repetition, the same content as the above-described embodiment will be omitted. Furthermore, in describing the method for manufacturing a battery cell according to this embodiment, reference numerals such as S100 are merely used to distinguish between steps and are not shown in the drawings.

[0076] The method S100 for manufacturing a battery cell according to this embodiment may include step S110 of forming a laminate 110 including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, step S120 of forming a pre-welding portion 200 on an electrode tab 120 extending from the positive electrode or the negative electrode, and step S130 of forming a main welding portion 300 on one side of the electrode tab 120 to connect the electrode tab 120 to an electrode lead 130.

[0077] Step S110 of forming the stack 110 can be explained using a known method for forming a stacked electrode assembly. For example, the stack 110 can be formed by stacking a plurality of mono-cells and stacking half-cells on the outermost layer of the stacked mono-cells.

[0078] Step S120 of forming the pre-welded portion 200 may be for forming connections between the plurality of electrode tabs 120. Although ultrasonic welding is used to form the pre-welded portion 200 as described above, the pre-welded portion 200 may also be formed by other known welding methods such as resistance welding.

[0079] 2 to 5, the pre-welding portion 200 is formed to be spaced apart from the periphery in the width direction of the electrode tab 120. Also, the pre-welding portion 200 is formed in various patterns as described in FIG.

[0080] On the other hand, if an unwelded section remains on the electrode tab 120, the main welding portion 300 must be formed larger when the electrode lead 130 and the electrode tab 120 are coupled. Therefore, the method of manufacturing a battery cell (S100) according to this embodiment may further include a step of removing the unwelded electrode tab 120 after the step of forming the pre-welding portion 200 (S120) and before the step of forming the main welding portion 300 (S130). The unwelded section can be removed from the electrode tab 120 by cutting around the outer periphery of the pre-welding portion 200. In this case, the cutting position may be a position spaced a predetermined distance inward from the outer periphery of the pre-welding portion 200. In this way, the step of cutting the unwelded electrode tab 120 prevents an unwelded portion from being positioned at the outer end of the electrode tab 120, and the outer end of the electrode tab 120 is welded. As a result, the size of the main welding portion 300 or the number of welding spots 302 can be reduced.

[0081] Step S130 of forming the main welding portion 300 may be for forming a connection between the electrode tab 120 and the electrode lead 130. Although laser welding is used to form the main welding portion 300 as described above, the main welding portion 300 may also be formed by other known welding methods such as resistance welding. Also, although not specifically shown, a lead film may be attached to one surface of the electrode lead 130, and the lead film may be used to form an adhesion between the cell casing and the electrode lead 130 or to prevent damage to the cell casing.

[0082] Here, the corners 132 of the electrode leads 130 are processed to have a rounded shape as described in Fig. 7. Therefore, the method S100 for manufacturing a battery cell according to this embodiment may further include a step of forming the corners 132 of the electrode leads 130 into a rounded shape before the step S130 for forming the main welding portion 300.

[0083] 8, the electrode tab 120 is provided with a back plate 140. Therefore, step S130 of forming the main welding portion 300 is realized by arranging one surface of the electrode lead 130 so that at least a portion of one surface of the electrode tab 120 overlaps with the electrode lead 130, arranging the back plate 140 on the other surface of the electrode tab 120, and joining the electrode tab 120, the electrode lead 130, and the back plate 140 with a welding device. At this time, an additional welding portion 300' is formed between the back plate 140 and the electrode tab 120.

[0084] Meanwhile, the above-described battery cells may be stacked in one direction to form a battery cell stack, which may then be housed inside a module case that houses the battery cell stack, thereby modularizing it into a battery module. The battery module may also form a battery pack together with a Battery Management System (BMS) that manages the temperature and voltage of the batteries and / or a cooling device. The battery pack may be applied to a variety of devices. For example, the device to which the battery pack is applied may be a means of transportation such as an electric bicycle, an electric vehicle, or a hybrid vehicle. However, the above-described devices are not limited thereto, and the battery pack according to this embodiment may be used in various devices other than those illustrated above, which also fall within the scope of the present invention.

[0085] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0086] 100: Battery cell 110: Laminate 120: Electrode tab 130: Electrode lead 140: Back plate 200: Pre-welding section 210: Inner periphery 220:Outer periphery 300: Main welding section 300': Additional welding section 310, 320, 330: 1st, 2nd, 3rd welding lines

Claims

1. a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; an electrode tab extending from the positive electrode or the negative electrode of the laminate; an electrode lead coupled to the electrode tab; The electrode tabs are formed with pre-welding portions connecting the electrode tabs and main welding portions connecting the electrode tabs to the electrode leads, The pre-weld portion includes an inner periphery and an outer periphery, The main welding portion includes a plurality of welding spots, At least one of the welding spots of the main welding portion overlaps with the inner periphery of the pre-welding portion; In the longitudinal direction of the electrode tab, an inner peripheral edge of the pre-welding portion is located closer to the laminate than an outer peripheral edge of the pre-welding portion, A battery cell, wherein at least one of the welding spots of the main welding portion is located closer to the stack than an inner periphery of the pre-welding portion and does not overlap with the pre-welding portion.

2. The main welding portion includes a first welding line, a second welding line, and a third welding line arranged side by side, 2. The battery cell of claim 1, wherein the first welding line is disposed between the second welding line and the third welding line, the second welding line overlaps the pre-welding portion, and the third welding line does not overlap the pre-welding portion.

3. the second welding line forms a periphery of the main welding portion; The battery cell according to claim 2 , wherein an outer peripheral edge of the pre-welding portion is located outside the second welding line in the longitudinal direction of the electrode tab, in a direction away from the laminate.

4. The battery cell according to claim 2 , wherein the third welding line is located outside an inner periphery of the pre-welded portion in the longitudinal direction of the electrode tab in a direction approaching the laminate.

5. The battery cell according to claim 1 , wherein at least one of the welding spots of the main welding portion is located more inward than the pre-welding portion.

6. The battery cell according to claim 1 , wherein the pre-welding portion is formed so as to be spaced apart from a peripheral edge of the electrode tab in a width direction of the electrode tab.

7. The battery cell according to claim 6 , wherein a length of the pre-welded portion in the width direction of the electrode tab is smaller than a width of the electrode tab.

8. The battery cell according to claim 6 , wherein a portion of the main welding portion is formed outside a periphery of the pre-welding portion in the width direction of the electrode tab.

9. The battery cell of claim 1 , wherein the pre-welding portion is formed in a pyramidal pattern.

10. The battery cell according to claim 1 , wherein the pre-welding portion is formed in a straight line pattern.

11. The battery cell according to claim 1 , wherein corners of the electrode leads are formed in a rounded shape.

12. The electrode lead is located on one surface of the electrode tab, The battery cell according to claim 1 , wherein a back plate is located on the other side of the electrode tab opposite to the one side of the electrode tab.

13. The battery cell of claim 12 , wherein an additional weld is formed between the back plate and the electrode tab.

14. a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; an electrode tab extending from the positive electrode or the negative electrode of the laminate; an electrode lead, one end of which is connected to the electrode tab and the other end of which protrudes outside the cell casing; The electrode tabs each include a pre-welding portion that connects the electrode tabs to form a tab bundle, the pre-welding portion is formed to be spaced apart from the periphery of the electrode tab in the width direction of the electrode tab, a main welding portion connecting the electrode tab and the electrode lead, The pre-weld portion includes an inner periphery and an outer periphery, At least one of the welding spots of the main welding portion overlaps with the inner periphery of the pre-welding portion; In the longitudinal direction of the electrode tab, an inner peripheral edge of the pre-welding portion is located closer to the laminate than an outer peripheral edge of the pre-welding portion, The main welding portion includes a first welding line, a second welding line, and a third welding line arranged side by side, A battery cell, wherein the first welding line is disposed between the second welding line and the third welding line, the second welding line overlaps the pre-welding portion, and the third welding line does not overlap the pre-welding portion.

15. The battery cell according to claim 14 , wherein a part of the main welding portion is formed outside the periphery of the pre-welding portion in the width direction of the electrode tab.

16. forming a laminate including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; forming a pre-welding portion on an electrode tab extending from the positive electrode or the negative electrode; forming a main welding portion for connecting an electrode lead on one surface of the electrode tab; The pre-weld portion includes an inner periphery and an outer periphery, The main welding portion includes a plurality of welding spots, At least one of the welding spots of the main welding portion overlaps with the inner periphery of the pre-welding portion; In the longitudinal direction of the electrode tab, an inner peripheral edge of the pre-welding portion is located closer to the laminate than an outer peripheral edge of the pre-welding portion, A method for manufacturing a battery cell, wherein at least one of the welding spots of the main welding portion is located closer to the stack than an inner periphery of the pre-welding portion and does not overlap with the pre-welding portion.

17. The method of claim 16 , further comprising removing the unwelded electrode tabs after forming the pre-welding portion.

18. The method of claim 16 , further comprising the step of forming a corner of the electrode lead into a rounded shape before the step of forming the main welding portion.

19. The method of claim 16 , wherein forming the main welding portion comprises disposing an electrode lead on one side of the electrode tab and disposing a back plate on the other side of the electrode tab.

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