Secondary battery and manufacturing method thereof

Abstract

The secondary battery of the present invention comprises an electrode assembly having a plurality of electrodes, a separator interposed between the plurality of electrodes, and a plurality of electrode tabs each connected to the plurality of electrodes; an electrode lead coupled to the plurality of electrode tabs; and a pouch that accommodates the electrode assembly with the tip of the electrode lead drawn out to the outside. The plurality of electrode tabs each include a connecting portion connected to the plurality of electrodes, a coupling portion coupled to the electrode lead in a combined state, and a bending portion provided between the connecting portion and the coupling portion. The bending portion includes a first bending surface connected to the coupling portion and bent at an angle 1b, a second bending surface connected to the connecting portion and bent at an angle 2b, and a connecting surface connecting the first bending surface and the second bending surface. The angle 1b may have an angle greater than the angle 2b.

Description

Technology Field

[0001] The present invention relates to a secondary battery and a method for manufacturing the same, and in particular to a secondary battery and a method for manufacturing the same in which a margin (i.e., allowance) is secured so that the length of the electrode tab can be increased. Background Technology

[0002] Generally, a secondary battery refers to a battery that can be charged and discharged, unlike a primary battery which cannot be recharged. Such secondary batteries are widely used in phones, laptop computers, camcorders, and electric vehicles.

[0003] The above-described secondary battery is classified into a can-type secondary battery in which an electrode assembly is embedded in a metal can and a pouch-type secondary battery in which an electrode assembly is embedded in a pouch. The pouch-type secondary battery includes an electrode assembly having a structure in which electrodes and separators are alternately stacked, an electrode lead coupled to an electrode tab of the electrode assembly, and a pouch that accommodates the electrode assembly with the tip of the electrode lead drawn out to the outside.

[0004] However, conventional secondary batteries had a problem where, if swelling occurred in the electrode assembly, the electrode tab connecting the electrode assembly and the electrode lead would be stretched, causing a disconnection.

[0005] To solve these problems, conventional secondary batteries prevent electrode tab disconnection by significantly increasing the length between the electrode assembly and the electrode lead to extend the electrode tab length. However, extending the electrode tab length in this manner resulted in an unnecessary increase in the size of the secondary battery. Prior art literature

[0006] Patent Publication No. 10-2016-0094009. The problem to be solved

[0007] The secondary battery and the method for manufacturing the same according to the present invention, which solves the above-mentioned problems, secure a margin rate that allows the length of the electrode tab to be increased, thereby preventing the electrode tab from being disconnected and preventing the length of the secondary battery from increasing even if swelling occurs in the electrode assembly, because the length of the electrode tab is increased. means of solving the problem

[0008] A secondary battery of the present invention for achieving the above-mentioned purpose comprises: an electrode assembly having a plurality of electrodes, a separator interposed between the plurality of electrodes, and a plurality of electrode tabs each connected to the plurality of electrodes; and electrode leads coupled to the plurality of electrode tabs. The apparatus may include a pouch that accommodates the electrode assembly with the tip of the electrode lead drawn out to the outside, and a plurality of electrode tabs, each comprising a connecting portion connected to the plurality of electrodes, a connecting portion coupled to the electrode lead in a combined state, and a bending portion provided between the connecting portion and the connecting portion, wherein the bending portion includes a first bending surface connected to the connecting portion and bent at an angle 1b, a second bending surface connected to the connecting portion and bent at an angle 2b, and a connecting surface connecting the first bending surface and the second bending surface, wherein the angle 1b has an angle greater than the angle 2b, and may include a lead film attached to the electrode lead located in the sealing portion of the pouch, and configured to insert the electrode lead into the interior of the pouch by a first length when inserted into the interior of the pouch with respect to the sealing portion of the pouch.

[0009] The first angle b of the first bending surface can be provided at 100° to 120° relative to the joint.

[0010] The first angle b of the first bending surface can be set to 109° to 116° with respect to the joint.

[0011] The second angle of the second bending surface can be set to 94° to 104° with respect to the connection part.

[0012] The second angle of the second bending surface can be set to 98° to 100° with respect to the connection part.

[0013] When viewed along the longitudinal direction of the electrode assembly, the distance (α) from one end to the other end of the connecting surface, where the first bending surface and the second bending surface are respectively connected, can be 0.5 mm to 2.0 mm.

[0014] When viewed along the longitudinal direction of the electrode assembly, the distance (β) from the end of the separator facing each other to the end of the coupling part can be 2.0 mm to 4.5 mm.

[0015] Meanwhile, the method for manufacturing a secondary battery according to the present invention comprises: (a) preparing a plurality of electrodes equipped with electrode tabs, and then manufacturing an electrode assembly by alternately arranging the plurality of electrodes and the plurality of separators; (b) folding and joining the plurality of electrode tabs, wherein the folded electrode tab is provided with a connecting portion connected to the electrode, a joining portion joined as a mass and to which an electrode lead is joined, and a folding portion provided between the connecting portion and the joining portion, wherein the folding portion includes a first folding surface connected to the joining portion and bent at an angle 1a, a second folding surface connected to the connecting portion and bent at an angle 2a, and a connecting surface connecting the first folding surface and the second folding surface; (c) joining an electrode lead to the joining portion of the electrode tab; (d) housing the electrode assembly in a pouch with the tip of the electrode lead drawn out to the outside, and then attaching a lead film to the electrode lead located in the sealing portion (310) of the pouch; (e) a step in which, when the lead film is pushed into the pouch by a first length, the electrode lead is inserted into the pouch by the lead film by a first length, and the fold portion is pressed by the electrode lead, thereby adjusting the first angle of the first fold surface to a first angle and the second angle of the second fold surface to a second angle; and (f) a step in which the sealing portion (310) of the pouch where the lead film is located is sealed to manufacture a secondary battery, wherein the first angle may have an angle greater than the second angle.

[0016] In step (e) above, the first angle b of the first bending surface can be set to 100° to 120° with respect to the joint.

[0017] In step (e) above, the second angle 2b of the second bending surface can be set to 94° to 104° with respect to the connection part.

[0018] In step (d) above, the lead film is attached so that it is pulled out further out of the pouch by a first length when attached to the electrode lead, and in step (e), the lead film is pushed into the pouch by a first length, and the first length can be provided as 0.5 to 1.5 mm.

[0019] When step (e) above is completed, the distance (α) from one end to the other end of the connecting surface, where the first bending surface and the second bending surface are respectively connected when viewed in the longitudinal direction of the electrode assembly, can be 0.5 mm to 2.0 mm.

[0020] When step (e) above is completed, the distance (β) between the ends of the separator facing each other and the ends of the coupling part may be 2.0 mm to 4.5 mm.

[0021] Between the above step (e) and the above step (f), there may be an additional step (e1) of checking whether the first angle b of the first bending surface and the second angle b of the second bending surface are included within a preset angle range.

[0022] Step (e1) above may further check whether the distance (α) from one end to the other end of the connecting surface, where the first bending surface and the second bending surface are respectively connected, is 0.5 mm to 2.0 mm when viewed along the longitudinal direction of the electrode assembly. Effects of the invention

[0023] The secondary battery of the present invention comprises an electrode tab having a bend portion, wherein the bend portion includes a first bend surface connected to a coupling portion and bent at an angle 1b, a second bend surface connected to a connecting portion and bent at an angle 2b, and a connecting surface connecting the first bend surface and the second bend surface, wherein the first bend angle is greater than the second bend angle. Due to this feature, the electrode tab can secure a margin (i.e., allowable length) that allows for an increase in length. That is, when swelling occurs in the electrode assembly, the bend portion of the electrode tab straightens out, thereby increasing the length of the electrode tab and preventing the electrode tab from breaking. In particular, it can prevent an increase in the size of the secondary battery, and as a result, improve product quality.

[0024] In addition, the first and second bending surfaces of the secondary battery of the present invention are characterized by being formed as curved surfaces. Due to this characteristic, the first and second bending surfaces can be prevented from folding. Brief explanation of the drawing

[0025] FIG. 1 is a cross-sectional view illustrating a secondary battery according to a first embodiment of the present invention. Figure 2 is a partial enlarged view of Figure 1. FIG. 3 is a side view illustrating an electrode tab of a secondary battery according to a first embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a deformed state of an electrode assembly in a secondary battery according to a first embodiment of the present invention. FIG. 5 is a flowchart illustrating a method for manufacturing a secondary battery according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view showing step (a) of a method for manufacturing a secondary battery according to a second embodiment of the present invention. FIG. 7 is a cross-sectional view showing step (b) of a secondary battery manufacturing method according to a second embodiment of the present invention. FIG. 8 is a side view showing the electrode tab bent in step (b). FIG. 9 is a cross-sectional view showing steps (c) and (d) of a secondary battery manufacturing method according to a second embodiment of the present invention. FIG. 10 is a cross-sectional view showing step (e) of a secondary battery manufacturing method according to a second embodiment of the present invention. FIG. 11 is a side view illustrating the electrode tab deformed in step (e). FIG. 12 is a cross-sectional view showing step (f) of a secondary battery manufacturing method according to a second embodiment of the present invention. FIGS. 13 to 16 are captured images showing experimental examples of the present invention. Specific details for implementing the invention

[0026] Hereinafter, embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0027] [Secondary battery according to the first embodiment of the present invention]

[0028] A secondary battery (1) according to the first embodiment of the present invention comprises, as shown in FIGS. 1 to 4, an electrode assembly (100) having a plurality of electrode tabs, an electrode lead (200) coupled to the plurality of electrode tabs, a pouch (300) that accommodates the electrode assembly (100) with the tip of the electrode lead (200) drawn out to the outside, and a lead film (400) provided on the electrode lead (200) located in the sealing portion (310) of the pouch (300).

[0029] electrode assembly

[0030] The electrode assembly (100) includes a plurality of electrodes (110), a separator (120) disposed between the plurality of electrodes (110), and a plurality of electrode tabs (130) each connected to the plurality of electrodes (110).

[0031] Here, the plurality of electrodes (110) may be positive and negative electrodes, and the plurality of electrode tabs (130) may be a positive tab connected to the positive electrode and a negative tab connected to the negative electrode.

[0032] The electrode assembly (100) having such a configuration has a structure in which a plurality of electrodes (110) are stacked from top to bottom with a separator (120) interposed. At this time, a plurality of electrode tabs (130) are connected to the plurality of electrodes (110) so as to face in the same direction. For example, a plurality of positive electrode tabs are arranged to face the left direction as seen in FIG. 1, and a plurality of negative electrode tabs are arranged to face the right direction as seen in FIG. 1.

[0033] Meanwhile, a plurality of electrode tabs (130) each include a connecting part (131) connected to a plurality of electrodes (110) and a connecting part (132) welded together as one mass and coupled to the electrode lead (200).

[0034] electrode lead

[0035] The electrode lead (200) is for connecting the electrode assembly and an external device and is coupled to the coupling portion (132) of the electrode tab (130).

[0036] pouch

[0037] The pouch (300) is intended to accommodate an electrode assembly with the tip of the electrode lead (200) drawn out to the outside. That is, the pouch (300) includes a receiving portion for accommodating the electrode assembly (100) and a sealing portion (310) for sealing the receiving portion.

[0038] Meanwhile, it further includes a lead film (400) to increase the sealing force between the sealing portion (310) and the electrode lead (200).

[0039] Lid film

[0040] The lead film (400) has a structure that wraps around the outer surface of the electrode lead (200) located in the sealing portion (310). That is, the lead film (400) is bonded to the sealing portion (310) when the sealing portion (310) is heat-fused, thereby increasing the sealing force between the electrode lead and the sealing portion.

[0041] Meanwhile, the secondary battery (1) according to the first embodiment of the present invention has a structure that prevents the electrode tab (130) from breaking even if the thickness or length increases as the electrode assembly (100) swells.

[0042] That is, in the secondary battery (1) according to the first embodiment of the present invention, the electrode tab (130) is provided in a bent state to secure a margin rate, and accordingly, when the electrode assembly (100) swells, the bent electrode tab (130) is flattened and the length of the electrode tab (130) is increased, and as a result, the breakage of the electrode tab (130) can be prevented.

[0043] For example, a plurality of electrode tabs (130) further include a bent portion (133) provided between the connecting portion (131) and the coupling portion (132).

[0044] The above-mentioned bending portion (133) includes a first bending surface (133a) connected to the coupling portion (132) and bent at a first angle (1b°) along the thickness direction (approximately 'L' shape) of the electrode assembly (100), a second bending surface (133b) connected to the connecting portion (131) and bent at a second angle (2b°) along a direction parallel to the length direction (approximately 'L' shape) of the electrode assembly (100), and a connecting surface (133c) connecting the first bending surface (133a) and the second bending surface (133b).

[0045] Meanwhile, as shown in FIGS. 3, 8 and 11, a boundary line (---) is indicated to distinguish the positions of the first bending surface (133a), the second bending surface (133b) and the connecting surface (133c).

[0046] Here, the first angle (1b°) has an angle greater than 90° when viewed with respect to the connecting part (131). Accordingly, even if the electrode tab is pressed, the bending part (133) can be induced to fold in a direction that does not face the electrode assembly, and as a result, contact between the electrode tab and an electrode of a different polarity can be prevented.

[0047] Additionally, the 2b angle (2b°) has an angle greater than 90° when viewed from the joint portion (132). Accordingly, even if the electrode tab (130) is compressed in the thickness direction of the electrode assembly, the bend portion (133) can be prevented from folding toward the electrode assembly, and thus, contact between the electrode tab and an electrode of different polarity can be prevented.

[0048] Meanwhile, the first angle (1b°) may have a larger angle than the second angle (2b°). That is, the second angle (2b°) may be formed smaller than the first angle (1b°) to minimize the space between the electrode tab and the electrode assembly, and the first angle (1b°) may be formed larger than the second angle (2b°) to significantly increase the gap between the electrode lead and the electrode assembly. Additionally, by forming the first angle (1b°) larger than the second angle (2b°), a large margin between the electrode tab and the pouch can be secured.

[0049] With a plurality of electrode tabs (130) having such a structure, when the electrode assembly (100) swells as shown in FIG. 4, the thickness or length of the electrode assembly (100) increases, causing the first and second bending surfaces (133a) (133b) of the bending portion (133) to be straightened, thereby preventing the electrode tab (130) from breaking. That is, by having a bent shape, the electrode tab (130) can secure a margin, thereby preventing the electrode tab (130) from breaking.

[0050] In particular, the plurality of electrode tabs (130) are provided with a metal material having restoring force, and accordingly, when the electrode assembly (100) returns to its original shape, the bent portion (133) also returns to its original shape, and as a result, the efficiency of reuse can be increased.

[0051] Accordingly, the electrode assembly (100) includes an electrode tab (130) with a secured margin, thereby preventing the electrode tab (130) from breaking even if the electrode assembly swells, and as a result, safety can be increased.

[0052] Meanwhile, the first bending surface (133a) or the second bending surface (133b) is formed as a curved surface. Accordingly, it is possible to prevent the first and second bending surfaces (133b) from folding at a right angle due to external impact. In particular, when swelling occurs in the electrode assembly (100), it can be straightened more quickly, thereby significantly preventing the disconnection of the electrode tab (130).

[0053] Meanwhile, the distance (β) between the end of the separator (120) facing each other in the electrode assembly (100) and the end of the coupling part (132) is 2.0 mm to 4.5 mm, preferably 3.5 mm. That is, when the electrode tab (130) is bent, the distance (β) between the end of the separator (120) and the end of the coupling part (132) is brought closer to 2.0 mm to 4.5 mm. Accordingly, the size of the secondary battery can be designed to be more compact. Here, if the distance between the end of the separator (120) and the end of the coupling part (132) is 2.0 mm or less, a short circuit may occur as the electrode tab (130) comes into contact with an electrode of the opposite polarity or an electrode lead (200) of the opposite polarity, and if the distance between the end of the separator (120) and the end of the coupling part (132) is 4.5 mm or more, there is a problem that the size of the secondary battery is unnecessarily increased.

[0054] Meanwhile, when viewed in the longitudinal direction of the electrode assembly (100), the distance (α) from one end to the other end of the connecting surface (133c), where the first bending surface (133a) and the second bending surface (133b) are respectively connected, is 0.5mm to 2.0mm, and preferably 1.0mm. Accordingly, the length of the secondary battery can be minimized while the margin rate of the electrode tab (130) can be stably secured. Here, if the distance (α) from one end to the other end of the connecting surface (133c) is 0.5mm or less, there is a problem that the electrode tab (130) and the electrode assembly (100) may come into contact, and if it is 2.0mm or more, there is a problem that the length of the secondary battery increases significantly and product quality decreases.

[0055] Meanwhile, referring to FIG. 3, the first angle (1b°) of the first bending surface (133a) has an inclination angle of 100° to 120°, preferably 109° to 116°, in the thickness direction of the electrode assembly (100) with respect to the coupling part (132), and the second angle (2b°) of the second bending surface (133b) has an inclination angle of 94° to 104°, preferably 98° to 100°, with respect to the connecting part (131). Accordingly, the bending part (133) can secure an increased margin rate of the electrode tab (130) without damaging the pouch or separator by forming the first and second bending surfaces (133a) and (133b) at an inclination angle.

[0056] Accordingly, the secondary battery (1) according to the first embodiment of the present invention includes an electrode tab (130) having first and second folded surfaces, thereby preventing the occurrence of a disconnection of the electrode tab (130) and, as a result, increasing safety.

[0057] Hereinafter, a method for manufacturing a secondary battery according to a second embodiment of the present invention will be described.

[0058] [Method for manufacturing a secondary battery according to the second embodiment of the present invention]

[0059] A method for manufacturing a secondary battery according to a second embodiment of the present invention includes, as illustrated in FIGS. 5 to 12, (a) a step of manufacturing an electrode assembly, (b) a step of combining, (c) a step of combining, (d) a step of attaching, (e) a step of pushing, and (f) a step of sealing.

[0060] (a) Electrode assembly manufacturing step

[0061] (a) Step (a) involves preparing a plurality of electrodes (110) equipped with electrode tabs (130), as illustrated in FIG. 6. Next, a plurality of electrodes (110) and a plurality of separators (120) are alternately arranged to manufacture an electrode assembly (100). Here, the electrode tabs (130) provided on the plurality of electrodes (110) are arranged to face in the same direction.

[0062] (b) Compatibility stage

[0063] (b) Step (b) involves compressing one side of a plurality of electrode tabs (130) using a pair of compression blocks (10) as shown in FIG. 7 to combine the tips of the electrode tabs (130) into one mass.

[0064] At this time, one end of the compressed multiple electrode tabs is bent at an angle 1a (1a°) in the thickness direction of the electrode assembly (100) to form a first bent surface (133a), and the other end is bent at an angle 2a (2a°) in the thickness direction of the electrode assembly (100) to form a second bent surface (133b), and a connecting surface (133c) is formed between the first bent surface (133a) and the second bent surface (133b).

[0065] In summary, the electrode tab (130) is provided with a connecting portion (131) connected to an electrode as shown in FIG. 8, a connecting portion (132) that is combined into a mass and to which an electrode lead (200) is connected, and a bending portion (133) provided between the connecting portion (131) and the connecting portion (132). The bending portion (133) includes a first bending surface (133a) connected to the connecting portion (132) and bent at a first angle (1a°), a second bending surface (133b) connected to the connecting portion (131) and bent at a second angle (2a°), and a connecting surface (133c) connecting the first bending surface (133a) and the second bending surface (133b).

[0066] Here, the corners of the pair of compression blocks (10) are formed as curved surfaces, and accordingly, the first bending surface (133a) compressed by the pair of compression blocks (10) is formed as a curved surface.

[0067] Meanwhile, the first angle (1a°) of the first bending surface (133a) has an inclination angle of 130° to 150°, preferably 148°, in the thickness direction of the electrode assembly (100) with respect to the joint part (132), and the second angle (2a°) of the second bending surface (133b) has an inclination angle of 94° to 104°, preferably 99°, with respect to the connecting part (131).

[0068] (c) Combination step

[0069] (c) Step (c) involves welding the tip of the electrode tab (130), which is combined into one piece as shown in FIG. 9, to form a joint (132), and joining the electrode lead (200) to the joint (132).

[0070] Meanwhile, after step (c) above, when viewed in the longitudinal direction of the electrode assembly, the distance (α) from one end to the other end of the connecting surface (133c), where the first bending surface (133a) and the second bending surface (133b) are respectively connected, is 2.0mm to 3.0mm, preferably 2.0mm. That is, the distance (α) from one end to the other end of the connecting surface (133c) is secured so that the bending portion (133) can be pressed.

[0071] (d) Attachment step

[0072] (d) Step (d) involves receiving the electrode assembly in the pouch (300) with the tip of the electrode lead (200) extended outward, and then attaching a lead film (400) to the electrode lead (200) located in the sealing portion (310) of the pouch (300). At this time, the lead film (400) is attached so that it extends further outward from the sealing portion (310) of the pouch (300) by a first length (B).

[0073] That is, referring to FIG. 9, the lead film (400) is drawn out to the outside of the sealing portion (310) by a length A, and the present application further draws out to the outside of the sealing portion of the pouch (300) by a first length (B).

[0074] Here, the first length (B) may be 1 to 2 mm, and preferably 1 mm.

[0075] (e) Pushing stage

[0076] (e) Step (e) is to push the lead film (400) into the pouch (300) by a first length (B) based on the sealing portion (310) of the pouch (300) as shown in FIG. 10. Then, the electrode lead (200) is inserted into the pouch (300) by a first length (B) by the lead film (400), and the fold portion (133) is deformed by being pressed in the direction of the electrode assembly (100) by the electrode lead (200). At this time, the first angle of the first fold surface (133a) is adjusted to become smaller to the first angle (1b), and the second angle of the second fold surface (133b) is adjusted to become smaller to the second angle (2b). Here, the first angle of the first bending surface (133a) is connected to a joint that is combined into one piece, so the angle adjustment is large, and the second angle of the second bending surface (133b) is connected to a plurality of joints, so the angle adjustment is small or non-existent. Accordingly, the first angle has a larger angle than the second angle because the angle change is greater than that of the first angle.

[0077] At this time, the lead film (400) and the sealing part (310) are not sealed and remain separated.

[0078] Here, the first angle (1b°) of the first bending surface (133a) has an inclination angle of 100° to 120°, preferably 109° to 116°, in the thickness direction of the electrode assembly (100) with respect to the joint part (132), and optimally has 111°. The second angle (2b°) of the second bending surface (133b) has an angle of 94° to 104°, preferably 98° to 100°, with respect to the connecting part (131), and optimally has 99°.

[0079] Meanwhile, after step (e) above, the distance between the end of the separator (120) and the end of the connecting part (132) facing each other is 2.0mm to 4.5mm, preferably 3.5mm.

[0080] That is, before step (e), the distance between the end of the separator (120) and the end of the connecting part (132) facing each other is formed to be 4.5 mm, and after step (e), the distance between the end of the separator (120) and the end of the connecting part (132) is reduced to 3.5 mm.

[0081] And after step (e) above, when viewed in the longitudinal direction of the electrode assembly, the distance from one end of the bent surface connected to the first bent surface to the other end of the bent surface connected to the second bent surface (133b) is 0.5 mm to 2.0 mm, preferably 1.0 mm. Accordingly, the length in the longitudinal direction of the secondary battery can be minimized, and as a result, the increase in the size of the secondary battery can be prevented.

[0082] (f) Sealing step

[0083] (f) Step (f) seals the sealing portion (310) of the pouch (300) using a sealing block (20). Accordingly, the electrode assembly (100) can be sealed and accommodated inside the pouch (300).

[0084] Once the above steps are completed, a finished secondary battery (1) can be manufactured.

[0085] Meanwhile, between the above step (e) and the above step (f), there is further a step (e1) of checking whether the first angle b of the first bending surface (133a) and the second angle b of the second bending surface (133b) are included within a preset angle range.

[0086] (e1) Inspection stage

[0087] (e1) Step (e1) involves taking a vision image of the secondary battery (1), outputting an image of the electrode assembly from the captured image, measuring the first angle b of the first bending surface (133a) and the second angle b of the second bending surface (133b) from the captured image of the electrode assembly, and checking for defects by comparing the measured first angle b of the first bending surface (133a) and the second angle b of the second bending surface (133b) with a preset angle.

[0088] Here, the preset angle range of the first angle is 109° to 116°, and the preset angle range of the second angle is 94° to 104°.

[0089] Accordingly, step (e1) can inspect the bending state of the electrode tab (130).

[0090] Meanwhile, the above step (e1) may further check whether the distance (α) from one end to the other end of the connecting surface (133c), where the first bending surface (133a) and the second bending surface (133b) are respectively connected when viewed in the longitudinal direction of the electrode assembly, is 0.5mm to 2.0mm, preferably 1.0mm.

[0091] Therefore, the secondary battery manufacturing method according to the second embodiment of the present invention can manufacture a secondary battery (1) with a secured margin.

[0092] [Experimental Example]

[0093] In the method for manufacturing a secondary battery according to the second embodiment of the present application, four secondary batteries manufactured up to the (d) attachment step are prepared. The four secondary batteries have the same structure and are referred to as the first to fourth experimental specimens.

[0094] Experimental Example 1 (e) photographs the first experimental specimen before the pushing step. As a result, a photographic image as shown in Fig. 13 can be obtained.

[0095] Experimental Example 2 (e) pushes the lead film (400) of the second experimental specimen by 0.5 mm during the pushing step, and then photographs the second experimental specimen. As a result, a photographic image as shown in FIG. 14 can be obtained. That is, it can be confirmed that the bent angle of the electrode tab (130) of the second experimental specimen has changed compared to the first experimental specimen, and that no phenomenon such as the electrode and the separator separating occurs.

[0096] In Experimental Example 3, (e) in the pushing step, the lead film (400) of the third experimental specimen is pushed by 1.0 mm, and then the third experimental specimen is photographed. As a result, a photographic image as shown in FIG. 15 can be obtained. That is, it can be confirmed that the bent angle of the electrode tab (130) of the third experimental specimen has changed significantly compared to the second experimental specimen, and that no phenomenon such as the electrode and the separator separating occurs.

[0097] In Experimental Example 4, the lead film (400) of the fourth experimental specimen is pushed 1.2 mm in the pushing step (e), and then the fourth experimental specimen is photographed. As a result, a photographic image as shown in FIG. 16 can be obtained. That is, it can be confirmed that the bent angle of the electrode tab (130) of the fourth experimental specimen has changed significantly compared to the third experimental specimen. However, it can be confirmed that a defect occurs in which the electrode and the separator are separated.

[0098] Therefore, as a result of the experiment as described above, in order to prevent defects, the lead film (400) must be pushed 0.5 to 1.5 mm, preferably 1.0 mm, during the pushing step (e), and it can be confirmed that if pushed more than that, a defect occurs as the electrode and the separator separate.

[0099] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and various embodiments derived from the meaning and scope of the claims and equivalent concepts are possible. Explanation of the symbols

[0100] 1: Secondary battery 100: Electrode assembly 110: Electrode 120: Separator 130: Electrode tab 131: Connection 132: Joint 133: Bending part 133a: First bend surface 133b: Second bend surface 133c: Connection surface 200: Electrode lead 300: Pouch 400: Lead film

Claims

Claim 1 An electrode assembly comprising a plurality of electrodes, a separator interposed between the plurality of electrodes, and a plurality of electrode tabs each connected to the plurality of electrodes; an electrode lead coupled to the plurality of electrode tabs; and a pouch accommodating the electrode assembly with the tip of the electrode lead drawn out to the outside, wherein the plurality of electrode tabs each comprise a connecting portion connected to the plurality of electrodes, a connecting portion coupled to the electrode lead in a combined state, and a bending portion provided between the connecting portion and the connecting portion, wherein the bending portion includes a first bending surface connected to the connecting portion and bent at a firstb angle, a second bending surface connected to the connecting portion and bent at a secondb angle, and a connecting surface connecting the first bending surface and the second bending surface, wherein the firstb angle is greater than the secondb angle, and a lead film attached to the electrode lead located at the sealing portion of the pouch, and configured to insert the electrode lead into the pouch by a first length when inserted into the interior of the pouch by a first length relative to the sealing portion of the pouch. Secondary battery. Claim 2 A secondary battery according to claim 1, wherein the first angle b of the first bending surface is provided at 100° to 120° with respect to the joining portion. Claim 3 A secondary battery according to claim 2, wherein the first angle b of the first bending surface is provided as 109° to 116° with respect to the joint portion. Claim 4 A secondary battery according to claim 1, wherein the angle 2b of the second bending surface is provided as 94° to 104° with respect to the connecting portion. Claim 5 A secondary battery according to claim 4, wherein the angle 2b of the second bending surface is provided at 98° to 100° with respect to the connecting portion. Claim 6 A secondary battery according to claim 1, wherein the distance (α) from one end to the other end of the connecting surface, where the first bending surface and the second bending surface are respectively connected when viewed in the longitudinal direction of the electrode assembly, is 0.5 mm to 2.0 mm. Claim 7 A secondary battery according to claim 1, wherein the distance (β) from the end of the separator facing each other when viewed in the longitudinal direction of the electrode assembly to the end of the coupling portion is 2.0 mm to 4.5 mm. Claim 8 (a) a step of preparing a plurality of electrodes equipped with electrode tabs, and then manufacturing an electrode assembly by alternately arranging the plurality of electrodes and the plurality of separators; (b) a step of folding and joining the plurality of electrode tabs, wherein the folded electrode tab is provided with a connecting portion connected to the electrode, a joining portion joined as a mass and to which an electrode lead is joined, and a folding portion provided between the connecting portion and the joining portion, wherein the folding portion includes a first folding surface connected to the joining portion and folded at an angle 1a, a second folding surface connected to the connecting portion and folded at an angle 2a, and a connecting surface connecting the first folding surface and the second folding surface; (c) a step of joining an electrode lead to the joining portion of the electrode tab; (d) a step of housing the electrode assembly in a pouch with the tip of the electrode lead drawn out to the outside, and then attaching a lead film to the electrode lead located in the sealing portion of the pouch; (e) a step of pushing the lead film into the pouch by a first length, thereby inserting the electrode lead into the pouch by the lead film by a first length, and pressing the fold portion by the electrode lead so that the first angle of the first fold surface is adjusted to a smaller angle of 1a and the second angle of the second fold surface is adjusted to a smaller angle of 2b; and (f) a step of manufacturing a secondary battery by sealing the sealing portion (310) of the pouch where the lead film is located, wherein the first angle of 1b has an angle greater than the second angle of 2b. Claim 9 A method for manufacturing a secondary battery according to claim 8, wherein in step (e), the first angle b of the first bending surface is provided at 100° to 120° with respect to the joint portion. Claim 10 A method for manufacturing a secondary battery according to claim 8, wherein in step (e), the angle 2b of the second bending surface is provided as 94° to 104° with respect to the connecting part. Claim 11 A method for manufacturing a secondary battery according to claim 8, wherein in step (d), the lead film is attached so as to be drawn out further outside the pouch by a first length when attached to the electrode lead, and in step (e), the lead film is pushed into the pouch by a first length, and the first length is provided to be 0.5 to 1.5 mm. Claim 12 A method for manufacturing a secondary battery according to claim 8, wherein when step (e) is completed, the distance (α) from one end to the other end of the connecting surface, where the first bending surface and the second bending surface are respectively connected, when viewed in the longitudinal direction of the electrode assembly, is 0.5 mm to 2.0 mm. Claim 13 A method for manufacturing a secondary battery according to claim 8, wherein, when step (e) is completed, the distance (β) between the mutually facing ends of the separator and the ends of the coupling portion is 2.0 mm to 4.5 mm. Claim 14 A method for manufacturing a secondary battery according to claim 8, wherein between step (e) and step (f), (e1) a step of inspecting whether the first angle b of the first bending surface and the second angle b of the second bending surface are included within a preset angle range. Claim 15 A method for manufacturing a secondary battery according to claim 8, wherein step (e1) further inspects whether the distance (α) from one end to the other end of the connecting surface, where the first bending surface and the second bending surface are respectively connected, is 0.5 mm to 2.0 mm when viewed in the longitudinal direction of the electrode assembly.

Images