Battery cell and joining device for manufacturing same

Abstract

According to an embodiment of the present invention, there is provided a battery cell comprising: an electrode assembly including a plurality of electrodes stacked with a separator interposed therebetween; and a battery case housing the electrode assembly, wherein the electrode assembly includes a plurality of electrode tabs each extending from the plurality of electrodes, the electrode tabs including an electrode tab bundle portion coupled between electrodes of the same polarity; and a pattern portion on at least one surface of the electrode tab bundle portion, the pattern portion including a plurality of sub-patterns respectively arranged in a row along horizontal and vertical directions of the electrode tabs, the sub-patterns having a shape recessed in a height direction of the electrode tab bundle portion, and corners of the pattern portion including chamfered portions.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to Korean Patent Application No. 10-2022-0121832 filed on September 26, 2022 and Korean Patent Application No. 10-2023-0126956 filed on September 22, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly including an electrode tab that minimizes the occurrence of breakage of the electrode tab and a joining apparatus for manufacturing the same, and more particularly, to a weld pattern for minimizing the occurrence of breakage of the electrode tab and an electrode tab joining apparatus for manufacturing the same. [Background technology]

[0003] Demand for secondary batteries as energy sources for electronic devices such as mobile phones, laptops, and wearable devices, as well as electric vehicles, is increasing. Secondary batteries are classified into nickel-cadmium secondary batteries, nickel-hydrogen secondary batteries, lithium secondary batteries, etc. depending on the type of electrode, and research and development into lithium secondary batteries, which have advantages such as high operating voltage and high energy density per unit weight, is actively underway.

[0004] Depending on the shape of the battery case, the lithium secondary batteries are classified into prismatic secondary batteries and cylindrical secondary batteries in which an electrode assembly is housed in a metal can, and pouch-type secondary batteries in which an electrode assembly is housed in a pouch case made of an aluminum laminate sheet.

[0005] The electrode assembly may be a stack-type electrode assembly in which plate-shaped electrodes having electrode tabs protruding from one or both sides are stacked, and the stacked electrode tabs form an electrode tab bundle and are coupled to an electrode lead to form an electrode terminal.

[0006] For this purpose, first, the electrode tabs in the multiple layers are connected, and then the joined electrode tabs and the electrode lead are joined. Generally, ultrasonic welding or laser welding is applied as the joining method. When ultrasonic welding is used as the joining method, a joining area is formed between the electrode tabs and / or between the electrode tab and the electrode lead by the protruding pattern shape of a horn and anvil.

[0007] Meanwhile, a phenomenon occurs in which the electrode tab, which has a relatively weak strength, is physically broken when tensile forces are applied to the electrode lead and the electrode tab during a process for connecting the electrode tab and the electrode lead, connecting and fixing the electrode lead to an external frame, and cyclic charging and discharging, vibration, impact, etc. When the electrode tab is broken, there is a high possibility that safety issues such as a decrease in battery cell capacity and heat generation may occur.

[0008] In order to prevent such problems, there is currently a strong need for a technique that can improve the joints between electrode tabs or the joints between the electrode tabs and the electrode leads to minimize the risk of disconnection. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention is devised to solve the above problems, and has an object to provide a battery cell that can prevent breakage of the electrode tabs at the electrode tab welded portions, and a battery cell joining device for manufacturing the same. [Means for solving the problem]

[0010] According to an embodiment of the present invention, there is provided a battery cell comprising: an electrode assembly including a plurality of electrodes stacked with a separator interposed therebetween; and a battery case housing the electrode assembly, wherein the electrode assembly includes a plurality of electrode tabs each extending from the plurality of electrodes, the electrode tabs including an electrode tab bundle portion coupled between electrodes of the same polarity; and a pattern portion on at least one surface of the electrode tab bundle portion, the pattern portion including a plurality of sub-patterns respectively arranged in a row along horizontal and vertical directions of the electrode tabs, the sub-patterns having a shape recessed in a height direction of the electrode tab bundle portion, and corners of the pattern portion including chamfered portions.

[0011] At least one of the sub-patterns located at the most distal end in each of the horizontal and vertical directions may include a right triangle or a chamfered portion.

[0012] The right triangle or the chamfered portion of the sub-pattern located at the end may have a height (H) / width (W) ratio of 0.4 to 0.82.

[0013] The right triangle or the chamfered portion of the subpattern located at the extreme end may have a height (H) / width (W) ratio of 0.7.

[0014] Each of the remaining sub-patterns has a rectangular or square shape, and each side of the rectangular or square sub-pattern is arranged parallel to a periphery of the electrode tab.

[0015] The pattern portion is spaced apart from a periphery of the electrode tab and is spaced apart between the sub-patterns.

[0016] The pattern portion is formed at a joint between the electrode tab bundle and the electrode lead.

[0017] The pattern portion may be generally rectangular, and each of four corners of the pattern portion may include a chamfered portion.

[0018] The pattern portion may be generally rectangular, and may include chamfered portions at two of four corners of the pattern portion that face away from the electrode lead.

[0019] The subpattern located at the end is a right-angled triangle, and a subpattern adjacent to the subpattern located at the end includes a chamfered portion, and the hypotenuse of the right-angled triangle of the subpattern located at the end and the hypotenuse of the chamfered portion of the adjacent subpattern are on the same extension line of each other.

[0020] One vertex of a subpattern adjacent to the subpattern located at the most end may be located on an extension line of the hypotenuse of the right-angled triangle of the subpattern located at the most end.

[0021] A battery cell joining apparatus for manufacturing a battery cell including an electrode assembly including a plurality of electrodes stacked with a separator interposed therebetween according to the above-mentioned embodiment and a battery case housing the electrode assembly may include a horn and an anvil, the horn including a welding portion including a plurality of horn protrusions, the welding portion including a plurality of horn protrusions respectively arranged in a row along the horizontal and vertical directions of the horn, and a corner of the welding portion may include a chamfered portion.

[0022] At least one of the horn protrusions located at the most distal end in each of the horizontal and vertical directions among the plurality of horn protrusions may have a right-angled triangular or chamfered portion.

[0023] The right triangle or the chamfered portion of the top surface of the most distal horn protrusion may have a vertical length (H) / horizontal length (W) ratio of 0.42 to 0.8.

[0024] The right triangle or the chamfered portion of the top surface of the most distal horn protrusion may have a height (H) / width (W) ratio of 0.7.

[0025] The top surface of each of the remaining horn projections has a rectangular or square shape, and each side of the rectangular or square shape of the horn projection is disposed parallel to a periphery of the electrode tab.

[0026] The electrode assembly includes a plurality of electrode tabs formed by extending from the plurality of electrodes, respectively, the plurality of electrode tabs including an electrode tab bundle portion that is joined between electrodes of the same polarity, and the battery cell joining device can join the plurality of electrode tabs to form the electrode tab bundle portion.

[0027] The electrode assembly includes a plurality of electrode tabs formed by extending from the plurality of electrodes, respectively, the plurality of electrode tabs including an electrode tab bundle portion that is coupled between electrodes of the same polarity, and the battery cell joining device can join the electrode tab bundle portion and an electrode lead.

[0028] When viewed from above, the weld may have a generally rectangular shape and may include a chamfered portion at each of four corners of the weld.

[0029] When viewed from above, the weld may have a generally rectangular shape and may include chamfered portions at two of the four corners of the weld.

[0030] The top surface of the most distal horn protrusion is a right-angled triangle, and the horn protrusion adjacent to the most distal horn protrusion includes a chamfered portion, and the hypotenuse of the right-angled triangle of the most distal horn protrusion and the hypotenuse of the chamfered portion of the adjacent horn protrusion are on the same extension line.

[0031] One apex of a horn protrusion adjacent to the horn protrusion located at the most end may be located on an extension line of the hypotenuse of the right-angled triangle of the horn protrusion located at the most end.

[0032] The battery cell bonding device may be an ultrasonic welding device or a laser welding device. Effect of the Invention

[0033] As described above, the present invention has an effect of preventing disconnection that may occur when welding electrode tabs, thereby reducing the rate of welding defects during battery cell manufacturing and reducing the manufacturing cost of the battery cells. [Brief description of the drawings]

[0034] [Figure 1] 1 is a perspective view of an electrode assembly according to an embodiment of the present invention; [Diagram 2] 1 is a side view showing a state in which an electrode tab is positioned between a horn and an anvil of a bonding apparatus according to an embodiment of the present invention. FIG. [Diagram 3] 3 shows a plan view of the horn of FIG. 2. [Figure 4] FIG. 4 is a plan view showing a partially modified horn of FIG. [Diagram 5] 4 is a partially enlarged perspective view of a horn of the joining device of FIG. 3. FIG. [Figure 6] FIG. 4 is a partially enlarged plan view of the horn of the joining device of FIG. 3. [Figure 7] As another embodiment of the present invention, modified examples of Figs. 5 and 6 are shown. [Figure 8] A further embodiment of the present invention will now be described. [Figure 9] 4 shows a weld pattern formed on an electrode tab when the electrode tab is welded with the horn of FIG. 3. [Figure 10] 4 shows a weld pattern formed on an electrode tab when the electrode tab is welded with the horn of FIG. 3. [Figure 11] 5 shows the weld pattern formed on the electrode tab when the electrode tab is welded with the horn of FIG. 4. [Figure 12] 6 is a graph showing the tensile strength of an electrode tab joined by the horn according to the ratio between the vertical length (H) and horizontal length (W) of a horn protrusion located at the most end of the horn of FIG. 5. [Figure 13] FIG. 5 shows a stress distribution diagram of an electrode tab joined by a horn according to the ratio between the vertical length (H) and horizontal length (W) of a horn protrusion located at the end of the horn. [Figure 14] The tensile strength and stress distribution diagrams of the comparative example and the example (Example 1) of the present invention are shown for comparison. [Figure 15] 10 is a schematic enlarged view of a portion of the welding pattern of the electrode tab of FIG. 9; [Figure 16] FIG. 2 is a perspective view of an anvil according to one embodiment of the present invention. [Figure 17] FIG. 2 is a perspective view of an anvil according to one embodiment of the present invention. [Figure 18] FIG. 2 is a perspective view of an anvil according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of an embodiment of the present invention that enables a person having ordinary skill in the art to which the present invention pertains to easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, if it is determined that the detailed description of such well-known functions or configurations may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

[0036] In addition, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes not only the case where the part is directly connected to another part, but also the case where the part is indirectly connected to another part through another element therebetween. In addition, the term "including a certain component" does not mean to exclude other components, but means that other components can be further included, unless otherwise specified.

[0037] The electrode assembly according to the present invention includes a shape in which plate-shaped electrode plates 104 having electrode tabs protruding from one or both sides are stacked with a separator sandwiched therebetween, and may be a stack-type electrode assembly in which a plurality of positive electrode plates and a plurality of negative electrode plates are stacked with a separator interposed therebetween, a stack / folding type electrode assembly in which stack-type unit cells including two or three electrodes are wound up with a certain distance between them positioned on a separator film, or a lamination / stack type electrode assembly in which a plurality of the unit cells are stacked vertically and joined.

[0038] The electrode tabs protruding from the electrode assembly are welded to form a positive electrode tab bundle and a negative electrode tab bundle, and are then connected to a positive electrode lead and a negative electrode lead, respectively, to serve as electrode terminals.

[0039] In this regard, FIG. 1 shows a perspective view of an electrode assembly according to the present invention.

[0040] Referring to FIG. 1, the electrode assembly 10 is a stack-type electrode assembly having a structure in which, for example, plate-shaped electrode plates 104 are stacked, and the electrode tabs 100 include an electrode tab bundle 100a formed by combining a plurality of electrode tabs 100 in a state of protruding to one side. The electrode tab bundle 100a is combined with an electrode lead 102 and extends to the outside of a battery case to become an electrode terminal. Although FIG. 1 shows that the positive electrode tab 100 and the negative electrode tab 100 protrude to one side, the present invention is not limited to the illustrated example, and various modifications and alterations are possible, including cases in which the positive electrode tab 100 and the negative electrode tab 100 protrude to both sides of the electrode assembly 10. Meanwhile, the electrode tab bundle 100a is combined with the electrode lead 102 on the outer surface of the uppermost electrode tab or the outer surface of the lowermost electrode tab.

[0041] 2 to 6 show a joining device including a horn according to an embodiment of the present invention. The joining device 200 according to an embodiment of the present invention may be an ultrasonic welding device, a laser welding device, or a welding device that performs both ultrasonic and laser welding.

[0042] 2 is a side view showing a state where electrode tabs are positioned between a horn and an anvil of a bonding apparatus according to an embodiment of the present invention. Referring to FIG. 2, a bonding apparatus 200 includes a horn 210 and an anvil 220. After the electrode tabs 100 in a stacked state are positioned between the horn 210 and the anvil 220, ultrasonic waves or laser irradiation are applied to bond the electrode tabs 100 to form an electrode tab bundle 100a.

[0043] Alternatively, the electrode tab bundle 100a of the electrode tab 100 and the electrode lead 102 are stacked so as to overlap each other, and this is positioned between the horn 210 and the anvil 220, and then ultrasonic waves are applied or a laser is irradiated to bond the electrode tab bundle 100a of the electrode tab 100 and the electrode lead 102.

[0044] When the joining device 200 is an ultrasonic welding device, it includes an ultrasonic generator, an ultrasonic transducer, a booster, a horn, and an anvil. The ultrasonic generator converts 60 Hz AC current into a high-frequency current of 20 kHz or more and supplies it to the ultrasonic transducer. The ultrasonic transducer serves to convert electrical energy into mechanical energy and is also called an ultrasonic piezoelectric transducer. That is, the high-frequency current generated by the ultrasonic generator is converted into ultrasonic waves by the ultrasonic transducer, and the converted ultrasonic waves are transmitted to the booster. The booster amplifies the transmitted ultrasonic waves and transmits them to the horn. The horn presses the surface of the electrode tab placed on the anvil with a certain load, and at the same time, applies the amplified ultrasonic waves transmitted from the booster to the electrode tab, thereby welding the multiple positive electrode tabs and the multiple negative electrode tabs, respectively.

[0045] When the joining device 200 is a laser welding device or includes a laser welding device, it includes a laser oscillator, a head unit including an optical system, a welding mask jig, etc. The laser beam amplified by the oscillator is irradiated via the head unit to a plurality of positive or negative electrode tabs or electrode leads fixed to the mask jig, and melts and joins them. At this time, the mask jig may have a shape in which the convex or concave portions of the protrusions of the horn and anvil are partially penetrated so that the laser beam can reach the tab bundle or the joint between the tab and the lead.

[0046] According to an embodiment of the present invention, the horn 210 of FIG. 2 is formed with a plurality of horn protrusions 211 having a trapezoidal or rectangular shape in vertical cross section, and the anvil 220 is also formed with a plurality of anvil protrusions 221 having a trapezoidal or rectangular shape in vertical cross section. In some cases, the horn protrusions 211 and the anvil protrusions 221 may be fully or partially engaged with each other. That is, each of the convex protrusions of the plurality of horn protrusions 211 may correspond only to the convex portion between the plurality of anvil protrusions 221. Also, the convex protrusions of each of the plurality of horn protrusions 211 may correspond to the concave portion between the plurality of anvil protrusions 221, and the concave portion between the plurality of horn protrusions 211 may correspond to the convex protrusions of each of the plurality of anvil protrusions 221. In this case, for example, the size of the welding surface 221a of the anvil protrusion 221 formed on the anvil 220 may be smaller than or the same as the size of the welding surface 211a of the horn protrusion 211 formed on the horn 210. When the centers of the horn protrusions 211 and the anvil protrusions 221 are all aligned, the spacing between the anvil protrusions 221 is greater than or equal to the spacing between the horn protrusions 211. When the centers of the horn protrusions 211 and the anvil protrusions 221 are only partially aligned or not aligned at all, the spacing between the anvil protrusions 221 is smaller than or equal to the spacing between the horn protrusions 211. For reference, Figs. 16 to 18 show one embodiment of the anvil 220, but the present invention is not limited thereto and various modifications and variations are possible.

[0047] Figure 3 shows a plan view of a horn 210 of a splicing apparatus according to an embodiment of the present invention. Figure 4 shows a modification of Figure 3. Figures 5 and 6 are partially enlarged views of the horn 210 of Figure 3, showing a perspective view and a plan view, respectively. Figure 7 shows another modification of Figures 5 and 6. Figure 8 shows yet another modification of Figures 5 and 6.

[0048] 9 and 10 show a welding pattern portion 110 formed on at least one surface (e.g., the top surface) of the electrode tab 100 when the electrode tab 100 is welded with the horn 210 of FIG. 3, and FIG. 11 shows a welding pattern portion 110' formed on the electrode tab 100 when the electrode tab 100 is welded with the horn 210' of FIG. 4.

[0049] Referring to FIG. 3, a horn 210 of a bonding apparatus according to an embodiment of the present invention includes a welding portion 210a that contacts a portion to be bonded (e.g., an electrode tab bundle or a bonding portion between an electrode tab bundle and an electrode lead) and applies pressure thereto. The welding portion 210a of the horn 210 is composed of a plurality of horn protrusions 211. More specifically, the welding portion 210a of the horn 210 has a lattice structure in which a plurality of horn protrusions 211 are arranged in a row in the horizontal and vertical directions. In the embodiment of FIG. 3, the horn protrusions 211 have a square top surface and a trapezoidal vertical cross section. In the present specification, the case where the top surface of the horn protrusions 211 is square is described as an example, but the present invention is not limited to the illustrated example, and the horn protrusions 211 may have various modifications and variations, such as a rectangular top surface and a rectangular vertical cross section.

[0050] 3, 9 and 10, when the electrode tab 100 is welded, the periphery of the welding portion 210a of the horn 210 of the joining device is spaced a predetermined distance from the periphery of the electrode tab 100 and is arranged to be parallel to the periphery of the electrode tab 100. In addition, each side of the square of the horn protrusion 211 is also arranged parallel to the periphery of the electrode tab 100. As a result, the periphery of the welding pattern portion 110 formed on the electrode tab 100 is arranged parallel to the periphery of the electrode tab 100. Each side of the square sub-pattern 111 formed on the electrode tab 100 is also arranged parallel to the periphery of the electrode tab 100. In other words, the welding pattern portion 110 has a lattice structure in which a plurality of square sub-patterns 111 are arranged in a row along the horizontal and vertical directions of the electrode tab 100. Meanwhile, when the top surface of the horn protrusion 211 is rectangular as described above, the sub-pattern 111 of the welding pattern portion 110 formed on the electrode tab 100 also has a rectangular shape.

[0051] In addition, the sub-pattern 111 formed on the upper surface of the electrode tab 100 is formed by the horn protrusion 211 of the horn 210 of the bonding device, and therefore has a recessed shape corresponding to the protruding shape of the horn protrusion 211.

[0052] For reference, in a comparative example described later (see FIG. 14), the welding pattern portion formed on the electrode tab has a shape in which a plurality of diamonds are arranged in a row along both the horizontal and vertical directions of the electrode tab.

[0053] According to one embodiment of the present invention, the weld pattern portion 110 is formed on the electrode tab 100. More specifically, the weld pattern portion 110 is formed on the electrode tab bundle 100a so as to join a plurality of electrode tabs 100. Alternatively, the weld pattern portion 110 may be formed across the electrode tab 100 and the electrode lead 102 so as to join the electrode tab 100 and the electrode lead 102.

[0054] According to one embodiment of the present invention, the welded portion 210a of the horn 210 has an overall rectangular shape when viewed from above, and specifically, the corners of the welded portion 210a of the horn 210 include chamfered portions. Referring to Fig. 3, all four corners of the welded portion 210a of the horn 210 may include chamfered portions, and referring to Fig. 4, which is a modification of Fig. 3, only two of the four corners of the welded portion 210a of the horn 210 that face the main body side of the battery cell, i.e., the side opposite the electrode lead 102, may include chamfered portions. In the case of Fig. 4, the description of the portions that overlap with the description of the horn 210 in Fig. 3 will be omitted, so please refer to Fig. 3 and the description of Figs. 5 to 10 which describe Fig. 3 in detail.

[0055] According to an embodiment of the present invention, at least the top surface of the horn projection 211-1 located at the most distal end may include a right-angled triangle or a chamfered portion. With reference to Fig. 5 and Fig. 6, the case where the top surface of the horn projection 211-1 is a right-angled triangle is shown. That is, in Fig. 5 and Fig. 6, as an embodiment, the top surface of the horn projection 211-1 located at the corner of the welded portion 210a of the horn 210, that is, the horn projection 211-1 located at the most distal end in each of the horizontal and vertical directions of the horn 210, has a right-angled triangle shape. At this time, the ratio between the vertical length (H) and the horizontal length (W) of the right-angled top surface of the horn projection 211-1 located at the most distal end, that is, the vertical length (H) / horizontal length (W) value, is 0.42 to 0.8, preferably 0.5 to 0.75, more preferably 0.59 to 0.73, and more preferably 0.7. When the top surface of the horn projection 211-1 includes a chamfered portion, the vertical length (H) / horizontal length (W) ratio of the chamfered portion may be 0.42 to 0.8, preferably 0.5 to 0.75, more preferably 0.59 to 0.73, and more preferably 0.7. Similarly, the sub-pattern 111-1 at the extreme end of the welding pattern portion 110 formed on the electrode tab 100 also has a right-angled triangular shape or includes a chamfered portion as a shape corresponding to the top surface of the horn projection 211-1.

[0056] Similarly, the ratio between the vertical length (H) and horizontal length (W) of the most distal sub-pattern 111-1, i.e., the vertical length (H) / horizontal length (W) value, is 0.4 to 0.82, preferably 0.48 to 0.78, more preferably 0.57 to 0.75, and more preferably 0.7. The sub-pattern 111-1 may have a wider range than the horn protrusion 211-1. This is because, when the sub-pattern 111-1 is ultrasonically welded, the ultrasonic vibration may cause the mark after welding to be longer in vertical length than the horn. In addition, the horizontal interval (I) between the periphery of the electrode tab 100 and the periphery of the welded pattern portion 110 is 0.011 to 0.1 times the horizontal length of the electrode tab 100.

[0057] In this regard, referring to FIG. 10, the lateral length (W T The horizontal length (W P ) is 19.75mm~99.75mm, and the vertical length (H P ) may be 1 mm to 10 mm. The horizontal length of the subpattern 111 may be 0.3 mm to 1.8 mm and the vertical length may be 0.3 mm to 1.8 mm, or the horizontal length and vertical length of the subpattern 111 may be the same.

[0058] Meanwhile, the side of the horn protrusion 211-1 located at the end may also have an inclination so that the horn 210 can be easily separated from the electrode tab 100 without being attached thereto after welding. Fig. 5 shows an example in which the inclination is 45 degrees. However, the present invention is not limited to the illustrated example, and the inclination of the side of the horn protrusion 211-1 located at the end may be 90 degrees as shown in Fig. 7.

[0059] 8, in another embodiment, the top surface of the horn protrusion 211-1 located at the end of the horn 210 is a right triangle, and the top surface of the adjacent horn protrusion 211-2 includes a chamfered portion. The hypotenuse of the top surface of the right triangle of the horn protrusion 211-1 located at the end and the hypotenuse of the chamfered portion of the top surface of the adjacent horn protrusion 211-2 are on the same extension line. In conclusion, in the case of FIG. 8, the corner of the welded portion 210a of the horn 210 also has a chamfered shape as described above.

[0060] As a result, the subpattern 111-1 located at the end of the welding pattern portion 110 of the electrode tab 100 is a right triangle, and the subpattern 111-2 adjacent thereto includes a chamfered portion. The hypotenuse of the right triangle of the subpattern 111-1 located at the end and the hypotenuse of the chamfered portion of the adjacent subpattern 111-2 are on the same extension line. The corners of the welding pattern portion 110 of the electrode tab 100 have a chamfered shape.

[0061] FIG. 12 is a graph showing the tensile strength of the electrode tab 100 according to the ratio between the vertical length (H) and horizontal length (W) of the horn projection 211-1 located at the end of the horn 210 in FIG. 5 (i.e., the ratio between the vertical length (H) and horizontal length (W) of the sub-pattern 111-1 located at the end of the welding pattern portion 110). The tensile strength of the electrode tab 100 can be expressed, for example, as the force (hereinafter referred to as "tensile force") applied to the electrode tab just before a crack occurs while increasing the length of the opposite side in the longitudinal direction with one side of the electrode tab fixed. The graph in FIG. 12 was derived using a UTM (LS5 model of LLOYD) device, with the test piece size being 45 mm x 50 mm (width x height), the welding pattern portion size being 43.5 mm x 7.5 mm, and the fixed grip interval being 15 mm.

[0062] In other words, the x-axis of the graph in FIG. 12 represents the ratio between the vertical length (H) and horizontal length (W) of the horn protrusion 211-1 located at the very end of the horn 210 (i.e., the ratio between the vertical length (H) and horizontal length (W) of the sub-pattern 111-1 located at the very end of the welding pattern portion 110), and the y-axis represents the tensile force applied immediately before the occurrence of a crack in the electrode tab 100.

[0063] Specifically, the tensile strength of the electrode tab varies depending on the ratio between the vertical length (H) and horizontal length (W) of the sub-pattern 111-1 located at the end of the welding pattern unit 110. According to the graph of Fig. 12, as the ratio between the vertical length (H) and horizontal length (W), i.e., the vertical length (H) / horizontal length (W) value, increases from 0 to 0.7, the tensile strength gradually increases, and the tensile strength of the electrode tab is highest when the vertical length (H) / horizontal length (W)=0.7. It can also be seen that the tensile strength of the electrode tab decreases as the vertical length (H) / horizontal length (W) value changes from 0.7 to 1.

[0064] FIG. 13 shows a stress distribution diagram of the electrode tab 100 according to the ratio between the vertical length (H) and horizontal length (W) of the horn protrusion 211-1 located at the very end of the horn 210 in FIG. 5 (i.e., the ratio between the vertical length (H) and horizontal length (W) of the sub-pattern 111-1 located at the very end of the welding pattern part 110). In the case of FIG. 13, as in FIG. 12, a stress distribution diagram measured immediately before the occurrence of a crack is shown. First, a part where the stress concentration is particularly high relatively to the peripheral part (hereinafter referred to as "stress concentration part") is indicated by an arrow for reference. As shown in FIG. 13, this is mainly formed at the corner of the sub-pattern 111-1 located at the very end of the welding pattern part 110 of the electrode tab 100, and in some cases, it is also formed at the corner of the sub-pattern 111-2 adjacent to the very end sub-pattern 111-1.

[0065] In the stress distribution diagram images when the vertical length (H) / horizontal length (W) is 0.2 and 0.4, there are two stress concentration areas indicated by arrows, and in the stress distribution diagram image when the vertical length (H) / horizontal length (W) is 1.0, there is one stress concentration area indicated by an arrow.

[0066] In contrast, in the stress distribution diagram image when the vertical length (H) / horizontal length (W) is 0.7, there are four stress concentration areas indicated by arrows, and it can be seen that the areas where stress is concentrated are more evenly distributed than in the former case (i.e., when the vertical length (H) / horizontal length (W) is 0.2, 0.4, or 1.0). In other words, it can be seen that the degree of stress dispersion is higher than in the former case. This shows that as the areas with high stress concentration in the electrode tab 100 are relatively evenly distributed, the possibility of cracks or breakage due to impacts or forces applied to the electrode tab 100 is lower. In other words, it can also be seen from the stress distribution diagram image of Figure 13 that the tensile strength of the electrode tab 100 is best when the vertical length (H) / horizontal length (W) is 0.7.

[0067] In the stress distribution diagram image when the vertical length (H) / horizontal length (W) is 0.8, there are three stress concentration areas indicated by arrows, and it can be seen that the degree of stress dispersion is higher than when the vertical length (H) / horizontal length (W) is 0.2, 0.4, 0.9, or 1.0, and the tensile strength of the electrode tab 100 is excellent. In the stress distribution diagram image when the vertical length (H) / horizontal length (W) is 0.9, there are two stress concentration areas indicated by arrows, but it can be seen that the stress is also slightly higher at the corner of the subpattern 111-2 adjacent to the endmost subpattern 111-1 than at the peripheral areas.

[0068] 14, in Example 1 where vertical length (H) / horizontal length (W)=0.7, the tensile force just before cracks occur in the electrode tab 100 is 44.4 N. This is greater than the tensile force value of 36.8 N just before cracks occur measured in the comparative example, and therefore it can be confirmed that the tensile strength of the electrode tab 100 of the present invention is superior to that of the comparative example.

[0069] Fig. 15 is a schematic diagram showing a partial enlarged view of the welding pattern portion 110 of the electrode tab 100 of Fig. 9. For example, the welding pattern portion 110 of Fig. 15 may correspond to a partial enlarged view of the horn 210 of Fig. 5. In one embodiment of the present invention, the vertex (C) of the sub-pattern 111-2 may be located on the extension line of both vertices (A, B) of the sub-pattern 111-1 located at the extreme end, i.e., the hypotenuse of a right-angled triangle. In this case, the degree of stress dispersion is also increased.

[0070] 16 to 18 are perspective views of an anvil applicable to the joining device according to the present invention.

[0071] As shown in Figures 16 to 18, the size of one welding surface 221a of the anvil protrusion 221 formed on the anvil 220 is formed to be smaller than the size of one welding surface 211a (see Figure 2) of the horn protrusion 211 formed on the horn 210, or the size of one welding surface 221a of the anvil protrusion 221 may be the same as the size of one welding surface 211a of the horn protrusion 211.

[0072] According to the present invention, although not shown here, the corners of the welds of the anvil 220 corresponding to the corners of the welds 210a of the horn 210 can also have a chamfered shape. When all four corners of the welds 210a of the horn 210 have a chamfered shape as in Fig. 3, all four corners of the welds of the anvil 220 can also have a chamfered shape. Similarly, when only two corners of the four corners of the welds 210a of the horn 210 facing the main body of the battery cell, i.e., the opposite side of the electrode lead 102, have a chamfered shape as in Fig. 4, which is a modification of Fig. 3, only two corners of the corresponding welds of the anvil 220 can also have a chamfered shape.

[0073] 16 to 18 show examples of the shape of the anvil projection 221, but the combination of the anvil and the horn is not limited to those shown here.

[0074] Meanwhile, the present invention provides a battery module including two or more of the above-mentioned battery cells electrically connected (in series or parallel). Of course, the number of lithium secondary batteries included in the battery module can be variously adjusted in consideration of the use and capacity of the battery module. Furthermore, the present invention provides a battery pack in which the above-mentioned battery modules are electrically connected according to conventional techniques in the art.

[0075] Such battery modules and battery packs may be used as a power source for one or more medium to large devices, including, but not limited to, power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric trucks; electric commercial vehicles; or power storage systems.

[0076] The above-described embodiments are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical idea of ​​the present invention. Naturally, such changes and modifications also fall within the scope of the appended claims. [Explanation of symbols]

[0077] 10: Electrode assembly 100: Electrode tab 100a: Electrode tab bundle 102: Electrode lead 104: Electrode plate 110, 110': Welding pattern section 111:Subpattern 111-1: The most distal subpattern 200:Joining equipment 210: Horn 210a: Welded parts 211: Horn protrusion 211-1: Horn protrusion located at the very end 220: Anvil 221: Anvil protrusion

Claims

1. an electrode assembly including a plurality of electrodes stacked with a separator interposed therebetween; a battery case that houses the electrode assembly, the electrode assembly includes a plurality of electrode tabs extending from the plurality of electrodes, the plurality of electrode tabs including an electrode tab bundle portion that is coupled between electrodes of the same polarity; a pattern portion on at least one surface of the electrode tab bundle portion, the pattern portion including a plurality of sub-patterns respectively aligned in a row along a horizontal direction and a vertical direction of the electrode tabs, the sub-patterns having a shape recessed in a height direction of the electrode tab bundle portion, and corners of the pattern portion including chamfered portions.

2. The battery cell according to claim 1 , wherein at least one of the sub-patterns located at the most terminal end in each of the horizontal and vertical directions includes a right triangle or a chamfered portion.

3. The battery cell according to claim 2 , wherein the vertical length (H) / horizontal length (W) value of the right triangle or the chamfered portion of the subpattern located at the most end is 0.4 to 0.

82.

4. The battery cell of claim 3 , wherein the height (H) / width (W) value of the right triangle or the chamfered portion of the subpattern located at the extreme end is 0.

7.

5. each of the remaining sub-patterns has a rectangular or square shape; The battery cell according to any one of claims 2 to 4, wherein each side of the rectangular or square sub-pattern is arranged so as to be parallel to a periphery of the electrode tab.

6. The battery cell according to claim 5 , wherein the pattern portion is spaced apart from a periphery of the electrode tab and spaced apart between the sub-patterns.

7. The battery cell according to claim 1 , wherein the pattern portion is formed at a joint between the electrode tab bundle portion and an electrode lead.

8. The battery cell according to claim 1 , wherein the pattern portion is generally rectangular, and each of four corners of the pattern portion includes a chamfered portion.

9. The battery cell according to claim 1 , wherein the pattern portion is generally rectangular, and each of two of the four corners of the pattern portion that face away from the electrode lead includes a chamfered portion.

10. 3. The battery cell of claim 2, wherein the subpattern located at the most end is a right-angled triangle, and a subpattern adjacent to the subpattern located at the most end includes a chamfered portion, and a hypotenuse of the right-angled triangle of the subpattern located at the most end and a hypotenuse of the chamfered portion of the adjacent subpattern are on the same extension line of each other.

11. The battery cell according to claim 2 , wherein one vertex of a subpattern adjacent to the subpattern located at the most end is located on an extension line of the hypotenuse of the right-angled triangle of the subpattern located at the most end.

12. A joining apparatus for manufacturing a battery cell including an electrode assembly including a plurality of electrodes stacked with a separator interposed therebetween and a battery case for accommodating the electrode assembly, the joining apparatus including a horn and an anvil, the horn includes a weld including a plurality of horn projections; The weld portion includes a plurality of horn protrusions aligned in a row along the horizontal and vertical directions of the horn, and corners of the weld portion include chamfered portions.

13. The battery cell joining device of claim 12 , wherein a top surface of at least one of the horn protrusions located at the most distal end in each of the horizontal and vertical directions among the plurality of horn protrusions includes a right-angled triangle or a chamfered portion.

14. 14. The battery cell joining device of claim 13, wherein the right triangle or the chamfered portion of the top surface of the most distal horn protrusion has a vertical length (H) / horizontal length (W) ratio of 0.42 to 0.

8.

15. 15. The battery cell joining device of claim 14, wherein the right triangle or the chamfered portion of the top surface of the most distal horn protrusion has a height (H) / width (W) ratio of 0.

7.

16. a top surface of each of the remaining horn projections has a rectangular or square shape; The battery cell joining device according to claim 13 , wherein each side of the rectangular or square shape of the horn protrusion is arranged so as to be parallel to a peripheral edge of an electrode tab.

17. the electrode assembly includes a plurality of electrode tabs extending from the plurality of electrodes, the plurality of electrode tabs including an electrode tab bundle portion that is coupled between electrodes of the same polarity; The battery cell joining device according to claim 12 , wherein the battery cell joining device joins the plurality of electrode tabs to form the electrode tab bundle.

18. the electrode assembly includes a plurality of electrode tabs extending from the plurality of electrodes, the plurality of electrode tabs including an electrode tab bundle portion that is coupled between electrodes of the same polarity; The battery cell joining device according to claim 12 , wherein the battery cell joining device joins the electrode tab bundle portion and an electrode lead.

19. The battery cell joining apparatus of claim 12 , wherein when viewed from above, the weld has a generally rectangular shape and each of four corners of the weld includes a chamfered portion.

20. The battery cell joining device of claim 12 , wherein when viewed from above, the weld has a generally rectangular shape, and two of four corners of the weld each include a chamfered portion.

21. 14. The battery cell joining device of claim 13, wherein a top surface of the most distal horn protrusion is a right-angled triangle, a horn protrusion adjacent to the most distal horn protrusion includes a chamfered portion, and a hypotenuse of the right-angled triangle of the most distal horn protrusion and a hypotenuse of the chamfered portion of the adjacent horn protrusion are on the same extension line.

22. 14. The battery cell joining device according to claim 13, wherein one vertex of a horn protrusion adjacent to the horn protrusion located at the most end is located on an extension of the hypotenuse of the right-angled triangle of the horn protrusion located at the most end.

23. The battery cell joining device according to claim 12 , wherein the battery cell joining device is an ultrasonic welding device or a laser welding device.

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