Battery cells and bonding apparatus for manufacturing them

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 of related applications This application claims the benefit of priority based on 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, and all the contents disclosed in the Korean patent applications are included as part of this specification.

[0002] The present invention relates to an electrode assembly including an electrode tab in which generation of disconnection of the electrode tab is minimized and a bonding device for manufacturing the same, and specifically provides a pattern of a welding part for minimizing generation of disconnection of the electrode tab and an electrode tab bonding device for manufacturing the same.

Background Art

[0003] The demand for secondary batteries as an energy source for electronic devices such as mobile phones, notebook computers, wearable devices, etc. or electric vehicles has been increasing. Secondary batteries are classified into nickel-cadmium secondary batteries, nickel-metal hydride secondary batteries, lithium secondary batteries, etc. depending on the type of electrode, but research and development on lithium secondary batteries having advantages such as a high operating voltage and a high energy density per unit weight have been actively promoted.

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

[0005] The electrode assembly may have a stack-type electrode assembly shape in which plate-shaped electrodes with electrode tabs protruding in one or both side directions are laminated, and in a state where the laminated electrode tabs form an electrode tab bundle, they are combined with an electrode lead to become an electrode terminal.

[0006] To achieve this, first, multiple layers of electrode tabs are connected, and then the bonded electrode tabs are joined to the electrode leads. Generally, ultrasonic welding or laser welding is used as the joining method. When ultrasonic welding is used, the protruding pattern shapes of the horn and anvil create a bonding area between the electrode tabs and / or between the electrode tabs and electrode leads.

[0007] On the other hand, tensile forces are applied to the electrode leads and electrode tabs during processes such as connecting the electrode tabs and electrode leads, connecting and fixing the electrode leads to the external frame, and periodic charging and discharging, vibration, or shock, which can cause the relatively weaker electrode tabs to physically break. When electrode tabs break, there is a high possibility of safety problems such as a decrease in battery cell capacity and overheating.

[0008] To prevent such problems, there is a high need for technologies that can minimize the risk of wire breakage by improving the joints between electrode tabs or between electrode tabs and electrode leads. [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention aims to solve the above-mentioned problems and to provide a battery cell that can prevent the disconnection of electrode tabs at the electrode tab welding portion, and a battery cell joining apparatus for manufacturing the same. [Means for solving the problem]

[0010] A battery cell according to one embodiment of the present invention includes an electrode assembly containing a plurality of electrodes stacked with a separator membrane in between, 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 and formed thereon, the plurality of electrode tabs including an electrode tab bundle portion coupled between those of the same polarity, and the electrode tab bundle portion includes a pattern portion on at least one surface, the pattern portion includes a plurality of subpatterns arranged in a row along the lateral and vertical directions of the electrode tabs, the subpatterns have a shape that is recessed in the height direction of the electrode tab bundle portion, and the corners of the pattern portion may include chamfered portions.

[0011] Of the aforementioned subpatterns, at least the subpatterns located at the outermost ends in both the horizontal and vertical directions may include right-angled triangles or chamfered portions.

[0012] The vertical length (H) / horizontal length (W) value of the right-angled triangle or chamfered portion of the subpattern located at the very end may be 0.4 to 0.82.

[0013] The vertical length (H) / horizontal length (W) of the right-angled triangle or chamfered portion of the subpattern located at the very end may be 0.7.

[0014] Each of the remaining subpatterns has a rectangular or square shape, and each side of the rectangular or square subpattern is positioned parallel to the periphery of the electrode tab.

[0015] The pattern portion is positioned at a distance from the periphery of the electrode tab and at a distance from the sub-patterns.

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

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

[0018] The pattern portion is generally rectangular in shape, and may include chamfered portions at two of its four corners that face away from the electrode leads.

[0019] The outermost subpattern is a right triangle, and the subpattern adjacent to the outermost subpattern includes a chamfered portion, and the hypotenuse of the right triangle of the outermost subpattern and the hypotenuse of the chamfered portion of the adjacent subpattern lie on the same extension line.

[0020] One vertex of a subpattern adjacent to the subpattern located at the very end can be located on the extension of the hypotenuse of the right triangle of the subpattern located at the very end.

[0021] A battery cell bonding apparatus for manufacturing a battery cell comprising an electrode assembly including a plurality of electrodes stacked with a separation membrane interposed therebetween, and a battery case housing the electrode assembly, includes a horn and an anvil, wherein the horn includes a welded portion including a plurality of horn protrusions, the welded portion includes a plurality of horn protrusions arranged in a row along the lateral and longitudinal directions of the horn, and the corners of the welded portion may include chamfered portions.

[0022] The uppermost surface of at least the outermost horn projection in both the lateral and longitudinal directions among the plurality of horn projections may include a right-angled triangle or a chamfered portion.

[0023] The vertical length (H) / horizontal length (W) of the right-angled triangle or chamfered portion on the uppermost surface of the horn projection located at the very end may be between 0.42 and 0.8.

[0024] The vertical length (H) / horizontal length (W) of the right-angled triangle or chamfered portion on the uppermost surface of the horn projection located at the very end may be 0.7.

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

[0026] The electrode assembly includes the plurality of electrode tabs including electrode tab bundles joined between the same polarities as a plurality of electrode tabs respectively extending from the plurality of electrodes, and the battery cell joining device can join the plurality of electrode tabs so as to form the electrode tab bundles.

[0027] The electrode assembly includes the plurality of electrode tabs including electrode tab bundles joined between the same polarities as a plurality of electrode tabs respectively extending from the plurality of electrodes, and the battery cell joining device can join the electrode tab bundle and the electrode lead.

[0028] When viewed from above, the welded portion can be entirely rectangular and include portions where each of the four corners of the welded portion is chamfered.

[0029] When viewed from above, the welded portion can be entirely rectangular and include portions where each of two of the four corners of the welded portion is chamfered.

[0030] The top surface of the horn projection located at the outermost end is a right triangle, the horn projection adjacent to the horn projection located at the outermost end includes a chamfered portion, and the hypotenuse of the right triangle of the horn projection located at the outermost end and the hypotenuse of the chamfered portion of the adjacent horn projection are on the same extension line.

[0031] One vertex of the horn projection adjacent to the horn projection located at the outermost end can be located on the extension line of the hypotenuse of the right triangle of the horn projection located at the outermost end.

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

[0033] As described above, the present invention has the effect of eliminating wire breakage that can occur during welding of electrode tabs. This reduces the welding defect rate during battery cell manufacturing and thus reduces the unit cost of manufacturing battery cells. [Brief explanation of the drawing]

[0034] [Figure 1] This is a perspective view of an electrode assembly according to one embodiment of the present invention. [Figure 2] This is a side view showing the state in which the electrode tab is positioned between the horn and the anvil of a bonding apparatus according to one embodiment of the present invention. [Figure 3] Figure 2 shows a plan view of the horn. [Figure 4] Figure 3 shows a plan view of the horn after it has been partially deformed. [Figure 5] Figure 3 is a partially enlarged view of the horn of the bonding device, and is shown in a perspective view. [Figure 6] Figure 3 is a magnified view of a section of the horn of the bonding device, showing a plan view. [Figure 7] As another embodiment of the present invention, modifications of Figures 5 and 6 are shown. [Figure 8] Further embodiments of the present invention are shown below. [Figure 9] Figure 3 shows the weld pattern formed on the electrode tab when the electrode tab is welded using the horn. [Figure 10] Figure 3 shows the weld pattern formed on the electrode tab when the electrode tab is welded using the horn. [Figure 11] Figure 4 shows the weld pattern formed on the electrode tab when the electrode tab is welded using the horn. [Figure 12] Figure 5 is a graph showing the tensile strength of the electrode tab joined to the horn, according to the ratio between the vertical length (H) and horizontal length (W) of the horn projection located at the very end of the horn. [Figure 13] Figure 5 shows the stress distribution diagram of the electrode tab joined by the horn, according to the ratio between the vertical length (H) and horizontal length (W) of the horn projection located at the very end of the horn. [Figure 14] The tensile strength and stress distribution diagrams for the comparative example and the example of the present invention (Example 1) are shown for comparison. [Figure 15] Figure 9 shows a schematic magnified view of the welding pattern area of ​​the electrode tab. [Figure 16] This is a perspective view of an anvil according to one embodiment of the present invention. [Figure 17] This is a perspective view of an anvil according to one embodiment of the present invention. [Figure 18] This is a perspective view of an anvil according to one embodiment of the present invention. [Modes for carrying out the invention]

[0035] Hereinafter, with reference to the attached drawings, embodiments that allow a person with ordinary skill in the art to which the present invention pertains to be easily implemented will be described in detail. However, in describing the operating principles of preferred embodiments of the present invention in detail, if it is determined that a specific description of such known functions or configurations may unnecessarily obscure the gist of the present invention, such detailed description will be omitted.

[0036] Furthermore, the same reference numerals shall be used for parts that have similar functions and operations throughout the entire drawing. Throughout the specification, when a part is described as being connected to another part, this includes not only direct connections but also indirect connections through other elements in between. Note that "including" a component means that other components may be further included, rather than excluding other components, unless otherwise stated.

[0037] The electrode assembly according to the present invention includes a shape in which plate-shaped electrode plates 104, each having electrode tabs protruding from one or both sides, are stacked with a separation film in between. However, it may also 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 separation film in between, a stack / folding-type electrode assembly in which stack-type unit cells containing two or three electrodes are wound up while being isolated from a separation film for a certain period of time, or a lamination / stack-type electrode assembly in which a plurality of the unit cells are stacked vertically and joined together.

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

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

[0040] Referring to Figure 1, the electrode assembly 10 is a stacked electrode assembly consisting of, for example, plate-shaped electrode plates 104 stacked on top of each other, and the electrode tab 100 includes an electrode tab bundle 100a formed by joining multiple electrode tabs 100 with each tab protruding to one side. The electrode tab bundle 100a is joined to the electrode lead 102 and extends to the outside of the battery case to become an electrode terminal. Figure 1 shows the positive electrode tab 100 and the negative electrode tab 100 protruding to one side, but the present invention is not limited to the illustrated configuration, and various modifications and changes are possible, including cases where the positive electrode tab 100 and the negative electrode tab 100 protrude to both sides of the electrode assembly 10, respectively. On the other hand, the electrode tab bundle 100a is joined to the electrode lead 102 at the outer surface of the uppermost electrode tab or the outer surface of the lowermost electrode tab.

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

[0042] Figure 2 shows a side view of a bonding apparatus according to one embodiment of the present invention, in which electrode tabs are positioned between a horn and an anvil. Referring to Figure 2, the bonding apparatus 200 includes a horn 210 and an anvil 220. After positioning the stacked electrode tabs 100 between the horn 210 and anvil 220, ultrasonic waves are applied or a laser is irradiated to bond the electrode tabs 100 and 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 that they partially overlap each other, and after positioning this between the horn 210 and the anvil 220, ultrasound is applied or a laser is irradiated to bond the electrode tab bundle 100a of the electrode tab 100 and the electrode lead 102.

[0044] If the joining apparatus 200 is an ultrasonic welding apparatus, it includes an ultrasonic oscillator, an ultrasonic transducer, a booster, a horn, and an anvil. The ultrasonic oscillator converts a 60 Hz AC current into a high-frequency current of 20 kHz or higher and supplies it to the ultrasonic transducer. The ultrasonic transducer plays the role of converting electrical energy into mechanical energy and is also called ultrasonic pressure electrons. In other words, the high-frequency current generated by the ultrasonic oscillator is converted into ultrasound by the ultrasonic transducer, and this converted ultrasound is transmitted to the booster. The booster amplifies the transmitted ultrasound and transmits it to the horn. The horn applies a constant load to the surface of the electrode tabs placed on the anvil, and at the same time applies the amplified ultrasound transmitted from the booster to the electrode tabs, thereby welding multiple positive electrode tabs and multiple negative electrode tabs, respectively.

[0045] If 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 through the head unit onto a plurality of positive or negative electrode tabs or electrode leads fixed to the mask jig, melting and joining them. At this time, the mask jig may have a configuration in which the convex and concave portions of the projections of the horn and anvil partially penetrate so that the laser beam can reach the tab bundle or the joint between the tabs and leads.

[0046] According to one embodiment of the present invention, the horn 210 in Figure 2 has a plurality of horn protrusions 211 with a vertical cross-section that is trapezoidal or rectangular, and the anvil 220 also has a plurality of anvil protrusions 221 with a vertical cross-section that is trapezoidal or rectangular. In some cases, the horn protrusions 211 and the anvil protrusions 221 may interlock completely or partially. That is, each of the protruding parts of the plurality of horn protrusions 211 can correspond only to the protruding parts between the plurality of anvil protrusions 221. Also, each of the protruding parts of the plurality of horn protrusions 211 can correspond to the recessed parts between the plurality of anvil protrusions 221, and the recessed parts between the plurality of horn protrusions 211 can correspond to each of the protruding parts of the plurality of anvil protrusions 221. In this case, for example, the size of the welded surface 221a of the anvil protrusion 221 formed on the anvil 220 may be smaller than or the same as the size of the welded surface 211a of the horn protrusion 211 formed on the horn 210. If all centers of the horn projections 211 and anvil projections 221 coincide, the spacing of the anvil projections 221 is greater than or equal to the spacing of the horn projections 211. If only some centers of the horn projections 211 and anvil projections 221 coincide, or do not coincide at all, the spacing of the anvil projections 221 is smaller than or equal to the spacing of the horn projections 211. For reference, Figures 16 to 18 show one embodiment of the anvil 220, but the present invention is not limited thereto, and various modifications and changes are possible.

[0047] Figure 3 shows a plan view of the horn 210 of a bonding device according to one embodiment of the present invention. Figure 4 shows a modified example 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 modified example of Figures 5 and 6. Figure 8 shows yet another modified example of Figures 5 and 6.

[0048] Figures 9 and 10 show the weld 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 Figure 3, and Figure 11 shows the weld pattern portion 110' formed on the electrode tab 100 when the electrode tab 100 is welded with the horn 210' of Figure 4.

[0049] Referring to Figure 3, the horn 210 of a joining device according to one embodiment of the present invention includes a welded portion 210a that contacts and pressurizes the part to be joined (for example, an electrode tab bundle or the joint between an electrode tab bundle and an electrode lead). The welded portion 210a of the horn 210 consists of a plurality of horn protrusions 211. More specifically, the welded 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 lateral and vertical directions, respectively. In the embodiment of Figure 3, the uppermost surface of the horn protrusion 211 is, for example, square and has a trapezoidal shape in the vertical cross-section. In the specification of the present invention, the case in which the uppermost surface of the horn protrusion 211 is square is described as an example, but the present invention is not limited to the illustrated example, and the horn protrusion 211 can be modified in various ways, such as having a rectangular uppermost surface and a rectangular shape in the vertical cross-section.

[0050] Referring to Figures 3, 9, and 10, during welding of the electrode tab 100, the periphery of the weld portion 210a of the horn 210 of the joining device is positioned at a predetermined distance from the periphery of the electrode tab 100 and parallel to the periphery of the electrode tab 100. Furthermore, each side of the square of the horn projection 211 is also positioned 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 positioned 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 positioned parallel to the periphery of the electrode tab 100. In other words, the welding pattern portion 110 has a lattice structure in which multiple square sub-patterns 111 are arranged in a row along the horizontal and vertical directions of the electrode tab 100, respectively. On the other hand, as described above, if the uppermost surface of the horn projection 211 is rectangular, the sub-pattern 111 of the welding pattern portion 110 formed on the electrode tab 100 also has a rectangular shape.

[0051] Furthermore, since the subpattern 111 formed on the upper surface of the electrode tab 100 is formed by the horn projection 211 of the horn 210 of the bonding device, it has a recessed shape corresponding to the protruding shape of the horn projection 211.

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

[0053] According to one embodiment of the present invention, the welding pattern portion 110 is formed on the electrode tab 100. More specifically, it is formed on an electrode tab bundle 100a so as to join a plurality of electrode tabs 100. Alternatively, it 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, when viewed from above, the welded portion 210a of the horn 210 has an overall rectangular shape, and specifically, the corners of the welded portion 210a of the horn 210 include chamfered portions. Referring to Figure 3, all four corners of the welded portion 210a of the horn 210 may include chamfered portions, and referring to Figure 4, a modified example of Figure 3, only the two corners of the welded portion 210a of the horn 210 that face the main body side of the battery cell, that is, the opposite side of the electrode lead 102, may include chamfered portions. In the case of Figure 4, the part that overlaps with the description of the horn 210 in Figure 3 is omitted, so please refer to the description of Figure 3 and Figures 5 to 10 which elaborate on Figure 3.

[0055] According to embodiments of the present invention, the uppermost surface of at least the outermost horn projection 211-1 may include a right triangle or a chamfered portion. Figures 5 and 6 show the case where the uppermost surface of the horn projection 211-1 is a right triangle. That is, in one embodiment, Figures 5 and 6 show the uppermost surface of the horn projection 211-1 located at the corner of the welded portion 210a of the horn 210, i.e., the horn projection 211-1 located at the outermost end in both the lateral and longitudinal directions of the horn 210, having a right triangle shape. In this case, the ratio between the vertical length (H) and horizontal length (W) of the right triangle uppermost surface of the outermost horn projection 211-1, i.e., 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. If the uppermost surface of the horn projection 211-1 includes a chamfered portion, the vertical length (H) / horizontal length (W) value of the chamfered portion is 0.42 to 0.8, preferably 0.5 to 0.75, more preferably 0.59 to 0.73, and may also be more preferably 0.7. Similarly, the outermost sub-pattern 111-1 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 uppermost surface of the horn projection 211-1.

[0056] Similarly, the ratio of the vertical length (H) to the horizontal length (W) of the outermost subpattern 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 even more preferably 0.7. The range of the subpattern 111-1 may be wider than that of the horn projection 211-1. This is because, in the case of ultrasonic welding of the subpattern 111-1, the ultrasonic vibration may cause the welded trace to be longer vertically than that of the horn. Also, the lateral spacing (I) between the periphery of the electrode tab 100 and the periphery of the weld pattern portion 110 has a length of 0.011 to 0.1 times the horizontal length of the electrode tab 100.

[0057] In relation to this, referring to Figure 10, the lateral length (W) of the electrode tab 100 is... T ) may be 20mm to 100mm. In this case, the lateral length (W) of the welding pattern portion 110 P ) is 19.75mm to 99.75mm, and the length in the vertical direction (H P The length of the subpattern 111 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, and the horizontal and vertical lengths of the subpattern 111 may be the same.

[0058] On the other hand, the side surface of the horn projection 211-1 located at the very end can also have an inclination so that the horn 210 can be more easily separated from the electrode tab 100 without adhering to it after welding. Figure 5 shows an example where the inclination is 45 degrees. However, the present invention is not limited to the illustrated example, and as shown in Figure 7, the inclination of the side surface of the horn projection 211-1 located at the very end may be 90 degrees.

[0059] Referring to Figure 8, in another embodiment, the uppermost surface of the horn projection 211-1 located at the very end of the horn 210 is a right triangle, and the uppermost surface of the adjacent horn projection 211-2 includes a chamfered portion. The hypotenuse of the right triangle uppermost surface of the horn projection 211-1 located at the very end and the hypotenuse of the chamfered portion of the uppermost surface of the adjacent horn projection 211-2 lie on the same extension line. In conclusion, in the case of Figure 8 as well, the corners of the welded portion 210a of the horn 210 have a chamfered shape as described above.

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

[0061] Figure 12 is a graph showing the tensile strength of the electrode tab 100 according to the ratio of the vertical length (H) to the horizontal length (W) of the horn projection 211-1 located at the very end of the horn 210 in Figure 5 (i.e., the ratio of the vertical length (H) to the horizontal length (W) of the sub-pattern 111-1 located at the very end of the weld pattern section 110). The tensile strength of the electrode tab 100 can be expressed, for example, as the force applied to the electrode tab just before cracking occurs, while increasing the force on the opposite side in the longitudinal direction with one side of the electrode tab fixed (hereinafter referred to as "tensile force"). The graph in Figure 12 was derived using a UTM (LLOYD LS5 model) apparatus, with a test specimen size of 45 mm × 50 mm (Width × Height), a weld pattern section size of 43.5 mm × 7.5 mm, and a fixing grip spacing of 15 mm.

[0062] In other words, the x-axis of the graph in Figure 12 represents the ratio of the vertical length (H) to the horizontal length (W) of the horn projection 211-1 located at the very end of the horn 210 (i.e., the ratio of the vertical length (H) to the horizontal length (W) of the sub-pattern 111-1 located at the very end of the weld pattern section 110), and the y-axis represents the tensile force applied immediately before the crack occurred in the electrode tab 100.

[0063] Specifically, the tensile strength of the electrode tab differs depending on the ratio between the vertical length (H) and horizontal length (W) of the sub-pattern 111-1 located at the very end of the weld pattern section 110. According to the graph in Figure 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 of the electrode tab gradually increases, with the highest tensile strength occurring when vertical length (H) / horizontal length (W) = 0.7. Furthermore, it can be confirmed that the tensile strength of the electrode tab decreases as the vertical length (H) / horizontal length (W) value decreases from 0.7 to 1.

[0064] Figure 13 shows the stress distribution diagram 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 very end of the horn 210 in Figure 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 section 110). In the case of Figure 13, as with Figure 12, the stress distribution diagram is shown as measured immediately before crack initiation. First, areas with particularly high stress concentration relative to the surrounding areas (hereinafter referred to as "stress concentration areas") are indicated by arrows for reference. As shown in Figure 13, these are mainly formed at the corners of the sub-pattern 111-1 located at the end of the welding pattern section 110 of the electrode tab 100, and in some cases, also at the corners of the sub-pattern 111-2 adjacent to the very end sub-pattern 111-1.

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

[0066] In contrast, the stress distribution diagram image for the case where the vertical length (H) / horizontal length (W) is 0.7 shows that there are four stress concentration points indicated by arrows, indicating that the stress concentration is 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, the degree of stress distribution is higher than in the former case. This indicates that the high stress concentration points on the electrode tab 100 are relatively evenly distributed, making it less likely for cracks or fractures to occur due to impacts or forces applied to the electrode tab 100. In other words, the stress distribution diagram image in Figure 13 shows 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 for the case where the vertical length (H) / horizontal length (W) is 0.8, there are three stress concentration points indicated by arrows, and the degree of stress distribution is higher than in the cases where the vertical length (H) / horizontal length (W) is 0.2, 0.4, 0.9, or 1.0, indicating superior tensile strength of the electrode tab 100. In the stress distribution diagram image for the case where the vertical length (H) / horizontal length (W) is 0.9, although there are two stress concentration points indicated by arrows, it can be seen that the stress is slightly higher than in the surrounding area even at the corner of sub-pattern 111-2 adjacent to the outermost sub-pattern 111-1.

[0068] Referring to Figure 14, in Example 1, where the vertical length (H) / horizontal length (W) = 0.7, the tensile force immediately before cracking occurs in the electrode tab 100 is 44.4 N. This is greater than the tensile force value of 36.8 N measured immediately before cracking in the comparative example, confirming that in the present invention, the tensile strength of the electrode tab 100 is superior to that of the comparative example.

[0069] Figure 15 schematically shows a partially enlarged view of the welding pattern portion 110 of the electrode tab 100 in Figure 9. For example, the welding pattern portion 110 in Figure 15 may correspond to a partially enlarged view of the horn 210 in Figure 5. In one embodiment of the present invention, the vertex (C) of sub-pattern 111-2 may be located on the extension of the hypotenuse of the right triangle, i.e., both vertices (A, B) of sub-pattern 111-1 located at the very end. In this case as well, the degree of stress distribution is increased.

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

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

[0072] According to the present invention, although not shown herein, the corners of the welded portion of the anvil 220 corresponding to the corners of the welded portion 210a of the horn 210 can also have a chamfered shape. As shown in Figure 3, if all four corners of the welded portion 210a of the horn 210 have a chamfered shape, then all four corners of the welded portion of the anvil 220 can also have a chamfered shape. Similarly, as shown in Figure 4, a modified example of Figure 3, if only the two corners of the welded portion 210a of the horn 210 that face the main body side of the battery cell, i.e., the opposite side of the electrode lead 102, have a chamfered shape, then only the two corresponding corners of the welded portion of the anvil 220 can also have a chamfered shape.

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

[0074] On the other hand, the present invention provides a battery module containing two or more of the above-mentioned battery cells electrically connected (in series or parallel). The number of lithium secondary batteries included in the battery module can, of course, be adjusted in various ways, taking into account the application and capacity of the battery module. Furthermore, the present invention provides a battery pack in which the above-mentioned battery modules are electrically connected using conventional art techniques.

[0075] Such battery modules and battery packs can be used as power sources for one or more medium-to-large devices, including power tools; 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 embodiments described above are merely illustrative of the present invention, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the technical concept, and that such changes and modifications naturally fall within the scope of the attached claims. [Explanation of Symbols]

[0077] 10: Electrode assembly 100: Electrode Tab 100a: Electrode tab bundle 102: Electrode Leads 104: Electrode plate 110, 110': Weld pattern section 111: Subpattern 111-1: Subpattern located at the very end 200:Joining equipment 210: Horn 210a: Welded section 211: Horn protrusion 211-1: Horn projection located at the very end 220: Anvil 221: Anvil protrusion

Claims

1. An electrode assembly including multiple electrodes stacked with a separation membrane in between, The battery case includes the electrode assembly, The electrode assembly includes a plurality of electrode tabs, each extending from the plurality of electrodes and formed thereon, the plurality of electrode tabs including an electrode tab bundle portion coupled between those of the same polarity. The electrode tab bundle includes a patterned portion on at least one surface, the patterned portion includes a plurality of sub-patterns arranged in a row along the lateral and vertical directions of the electrode tabs, the sub-patterns have a shape that is recessed in the height direction of the electrode tab bundle, and the corners of the patterned portion include chamfered portions. The aforementioned vertical direction is parallel to the direction in which the electrode tab extends, and the aforementioned horizontal direction is perpendicular to the aforementioned vertical direction. A battery cell in which at least a portion of the subpatterns located at the outermost ends in the lateral and vertical directions, respectively, of the plurality of subpatterns, the bottom surface of the recessed shape includes a right-angled triangle or a portion beveled into a right-angled triangle.

2. The battery cell according to claim 1, wherein the vertical length (H) / horizontal length (W) value of the right-angled triangle of the subpattern located at the outermost end is 0.4 to 0.

82.

3. The battery cell according to claim 2, wherein the vertical length (H) / horizontal length (W) value of the right-angled triangle of the subpattern located at the outermost end is 0.

7.

4. Each of the remaining subpatterns has a rectangular or square shape. The battery cell according to any one of claims 1 to 3, wherein each side of the rectangular or square subpattern is arranged to be parallel to the periphery of the electrode tab.

5. The battery cell according to claim 4, wherein the pattern portion is arranged at a distance from the periphery of the electrode tab.

6. The battery cell according to claim 1, wherein the pattern portion is formed at the junction between the electrode tab bundle portion and the electrode lead portion.

7. The battery cell according to claim 1, wherein the pattern portion is rectangular in shape overall, and each of the four corners of the pattern portion includes a chamfered portion.

8. The battery cell according to claim 1, wherein the pattern portion is rectangular in shape overall, and each of the two corners of the pattern portion that face away from the electrode leads has a chamfered portion.

9. The battery cell according to claim 1, wherein the bottom surface of the recessed shape of the outermost subpattern is a right triangle, the bottom surface of the recessed shape of the subpattern adjacent to the outermost subpattern includes a chamfered portion of the right triangle, and the hypotenuse of the right triangle of the outermost subpattern and the hypotenuse of the chamfered portion of the adjacent subpattern are on the same extension line.

10. The battery cell according to claim 1, wherein one vertex of a subpattern adjacent to the outermost subpattern is located on the extension of the hypotenuse of the right triangle of the outermost subpattern.

11. A bonding apparatus including a horn and an anvil for manufacturing a battery cell, which includes an electrode assembly containing a plurality of electrodes stacked with a separation membrane interposed therebetween, and a battery case for housing the electrode assembly, The horn includes a welded portion containing a plurality of horn protrusions, The welded portion includes a plurality of horn protrusions arranged in a row along the lateral and longitudinal directions of the horn, and the corners of the welded portion include chamfered portions. The aforementioned vertical direction is parallel to the direction in which the plurality of electrode tabs, each extending from the plurality of electrodes, extend, and the aforementioned horizontal direction is perpendicular to the aforementioned vertical direction. A battery cell bonding device wherein the uppermost surface of at least some of the horn protrusions located at the outermost ends in the lateral and vertical directions of the plurality of horn protrusions includes a right-angled triangle or a portion beveled into a right-angled triangle.

12. The battery cell bonding device according to claim 11, wherein the vertical length (H) / horizontal length (W) of the right-angled triangle on the uppermost surface of the horn projection located at the outermost end is 0.42 to 0.

8.

13. The battery cell bonding device according to claim 12, wherein the vertical length (H) / horizontal length (W) of the right-angled triangle on the uppermost surface of the horn projection located at the very end is 0.

7.

14. The uppermost surface of each of the remaining horn protrusions has a rectangular or square shape. The battery cell bonding apparatus according to any one of claims 11 to 13, wherein each side of the rectangular or square of the horn projection is arranged to be parallel to the periphery of the electrode tab.

15. The electrode assembly includes a plurality of electrode tabs, each extending from the plurality of electrodes and formed thereon, the plurality of electrode tabs including an electrode tab bundle portion coupled between those of the same polarity. The battery cell bonding apparatus according to claim 11, wherein the battery cell bonding apparatus bonds the plurality of electrode tabs to form the electrode tab bundle.

16. The electrode assembly includes a plurality of electrode tabs, each extending from the plurality of electrodes and formed thereon, the plurality of electrode tabs including an electrode tab bundle portion coupled between those of the same polarity. The battery cell bonding apparatus according to claim 11, wherein the battery cell bonding apparatus bonds the electrode tab bundle and the electrode lead.

17. The battery cell joining device according to claim 11, wherein, when viewed from above, the welded portion is rectangular in shape overall, and each of the four corners of the welded portion includes a chamfered portion.

18. The battery cell joining device according to claim 11, wherein, when viewed from above, the welded portion is rectangular in shape overall, and each of the four corners of the welded portion includes a chamfered portion.

19. The battery cell bonding device according to claim 11, wherein the uppermost surface of the horn projection located at the very end is a right triangle, the horn projection adjacent to the horn projection located at the very end includes a portion that is chamfered into a right triangle, and the hypotenuse of the right triangle of the horn projection located at the very end and the hypotenuse of the chamfered portion of the adjacent horn projection are on the same extension line.

20. The battery cell bonding device according to claim 11, wherein one vertex of a horn projection adjacent to the horn projection located at the outermost end is located on the extension of the hypotenuse of the right-angled triangle of the horn projection located at the outermost end.

21. The battery cell bonding apparatus according to claim 11, wherein the battery cell bonding apparatus is an ultrasonic welding apparatus.

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