Secondary battery and method for manufacturing same

Abstract

The present invention relates to a secondary battery and a method for manufacturing same. A current collector plate according to the present invention includes a main body portion having a thickness T1 and a stepped portion formed at the end of the main body portion in a bending direction and having a thickness T2. The thickness T1 of the main body portion and the thickness T2 of the stepped portion are different from each other. The thickness of the stepped portion or the output of a welding device can be adjusted for welding the current collector plate to a foil tab. According to the present invention, it is possible to prevent an electrode assembly located below a blank area from being affected during a welding process. Therefore, it is possible to prevent, for example, a separator of the electrode assembly from being damaged during the welding process.

Description

Secondary battery and its manufacturing method

[0001] The present invention relates to a secondary battery and a method for manufacturing the same, and more particularly, to a secondary battery and a method for manufacturing the same in which a step portion is formed on a current collector plate and the output of a welding device is adjusted by taking into account the thickness of the step portion when welding a foil tab and a current collector plate.

[0002] Recently, with the rapid increase in demand for portable electronic products and the full-scale development of electric vehicles, energy storage batteries, robots, satellites, etc., research on high-performance secondary batteries capable of repeated charging and discharging is actively being conducted.

[0003] Secondary batteries can be classified into can-type secondary batteries, in which the electrode assembly is housed in a metal can, and pouch-type secondary batteries, in which the electrode assembly is housed in a pouch made of an aluminum laminate sheet, depending on the shape of the battery case. Can-type secondary batteries can be classified into cylindrical secondary batteries and square secondary batteries, depending on the shape of the metal can.

[0004] Secondary batteries are connected by welding the foil tabs and collector plates of the electrode assembly. Fig. 1 is a drawing showing welding the foil tabs and collector plates by bending them in the bending direction. As shown in Fig. 1, when welding the foil tab (20) and the collector plate (30), in order to increase the contact area between the foil tab (20) and the collector plate (30), the foil tab (20) is bent in the bending direction (BD), and then the collector plate (30) is placed on the upper side of the foil tab (20) and welded. In this case, the upper part of one side of the foil tab (20), not the upper end of the foil tab (20), comes into contact with the collector plate (30), so that stable welding is possible. The welding is performed on the upper side of the collector plate (30) using a laser or ultrasonic welding device (100).

[0005] However, when the foil tab (20) is bent in the bending direction, a blank area (A) is formed between the foil tab (20) located at the outer side in the bending direction and the electrode assembly (10). Since the blank area (A) has a smaller number of overlapping foil tabs (20) than other areas, the layer of the foil tab (20) to be welded becomes thinner than other areas. Therefore, when welding is performed on the upper part of the blank area (A), the heat generated during the welding process may be transferred to the electrode assembly (10), and as a result, a problem may occur in which the separator of the electrode assembly (10) is melted at the lower part of the blank area (A).

[0006] An object of the present invention is to provide a secondary battery and a method for manufacturing the same, which can prevent an electrode assembly from being affected when welding a foil tab and a collector plate.

[0007] According to one embodiment of the present invention, a secondary battery includes an electrode assembly and a current collector. The electrode assembly includes an electrode portion and a plurality of foil tabs formed at one end of the electrode portion. The current collector includes a main body portion and a stepped portion. The main body portion is welded on an upper side of the foil tab while the foil tab is bent in the bending direction, and has a thickness of T1. The stepped portion is formed at an end of the main body portion in the bending direction, and has a thickness of T2. The thickness T1 of the main body portion and the thickness T2 of the stepped portion are different from each other.

[0008] In a secondary battery according to one embodiment of the present invention, the step portion may be formed to correspond to a blank area formed between the electrode portion and the foil tab located at the outermost position in the bending direction when the foil tab is bent in the bending direction.

[0009] In a secondary battery according to one embodiment of the present invention, the thickness T1 of the main body may be greater than the thickness T2 of the step portion. In this case, the thickness T2 of the step portion may be 1 / 3 or more and 2 / 3 or less of the thickness T1 of the main body.

[0010] In a secondary battery according to one embodiment of the present invention, the thickness T1 of the main body may be smaller than the thickness T2 of the step portion. The thickness T2 of the step portion may be determined according to the height of the blank area.

[0011] In a secondary battery according to one embodiment of the present invention, the thickness T2 of the step portion can be changed in a stepwise manner.

[0012] In a secondary battery according to one embodiment of the present invention, the thickness T2 of the step portion can be gradually changed.

[0013] In a secondary battery according to one embodiment of the present invention, a step portion is divided into N regions according to the number of foil tabs located at the bottom, and the thickness T2 of the step portion may be the same thickness in the same region and may be different thicknesses in different regions.

[0014] In a secondary battery according to one embodiment of the present invention, the thickness T2 of the step portion may vary depending on the number of foil tabs positioned at the bottom of the step portion.

[0015] In a secondary battery according to one embodiment of the present invention, a step portion may be formed from the upper portion of a portion where a foil tab located at the outermost side in the bending direction is connected to an electrode portion to an end in the bending direction.

[0016] In a secondary battery according to one embodiment of the present invention, the formation length of the step portion may vary depending on the bending angle at which the foil tab is bent in the bending direction.

[0017] In a secondary battery according to one embodiment of the present invention, a first welding part by welding a main body part and a second welding part by welding a step part can be formed on the current collector plate.

[0018] In a secondary battery according to one embodiment of the present invention, the electrode portion may include a plurality of unit electrode plates each having a foil tab formed at one end thereof, and a separator positioned between each of the plurality of unit electrode plates. The electrode portion may be formed by stacking or winding the plurality of unit electrode plates and the separator.

[0019] A method for manufacturing a secondary battery according to one embodiment of the present invention includes a preparation step, a bending step, a settling step, and a welding step. In the preparation step, an electrode assembly having an electrode part and a plurality of foil tabs formed at one end of the electrode part is prepared. In the bending step, the plurality of foil tabs are bent in a bending direction. In the settling step, a main body part having a thickness T1 and a current collector plate having a step portion formed at an end of the main body part in the bending direction and having a thickness T2 are set on the upper side of the bent foil tab. The thickness T1 of the main body part and the thickness T2 of the step portion are different from each other. In the welding step, the foil tabs and the current collector plate are welded.

[0020] In the bending step of the secondary battery manufacturing method according to one embodiment of the present invention, the bending angle at which the foil tab is bent in the bending direction can be adjusted according to the formation length of the step portion.

[0021] In the settling step of the secondary battery manufacturing method according to one embodiment of the present invention, the step portion can be settling to correspond to the blank area.

[0022] In the welding step of the secondary battery manufacturing method according to one embodiment of the present invention, the output of the welding device can be made different when welding the main body and when welding the step.

[0023] When welding a step portion in a welding step of a secondary battery manufacturing method according to one embodiment of the present invention, the output of the welding device can be adjusted according to the sum of the thicknesses of the foil tabs located on the lower side of the step portion.

[0024] The welding step of the secondary battery manufacturing method according to one embodiment of the present invention may include a first welding step of welding a main body portion and a second welding step of welding a step portion.

[0025] The present invention can adjust the output of a welding device when welding a foil tab and a current collector plate according to the thickness of a step formed on the current collector plate. Accordingly, over-welding or under-welding in a blank area can be prevented.

[0026] In addition, the present invention can prevent damage to the electrode assembly located at the bottom of the blank area during the process of welding the foil tabs and the current collector plate by determining the thickness of the step portion according to the number of foil tabs located at the bottom of the step portion.

[0027] Figure 1 is a drawing showing welding by bending the foil tab in the bending direction when welding the foil tab and the collector plate.

[0028] FIG. 2 is a drawing showing a secondary battery according to one embodiment of the present invention.

[0029] FIG. 3 is a drawing showing an exploded view of a secondary battery according to one embodiment of the present invention.

[0030] FIG. 4 is a drawing showing a state in which a current collector plate and a foil tab are welded in a secondary battery according to one embodiment of the present invention.

[0031] FIG. 5 is a drawing showing a current collecting plate of a secondary battery according to one embodiment of the present invention.

[0032] FIG. 6 is a drawing showing a current collector plate with a step-wise reduced thickness according to one embodiment of the present invention mounted on a foil tab.

[0033] FIG. 7 is a drawing showing a current collector plate having a gradually decreasing thickness of a step portion according to one embodiment of the present invention, mounted on a foil tab.

[0034] Figure 8 is a drawing showing the concept of a bending angle in which a foil tab is bent in the bending direction.

[0035] FIG. 9 is a drawing showing a current collector plate with a step-wise increased thickness according to one embodiment of the present invention mounted on a foil tab.

[0036] FIG. 10 is a drawing showing a current collector plate with a gradually increasing thickness of a step portion according to one embodiment of the present invention being placed on a foil tab.

[0037] FIG. 11a is a drawing conceptually showing a buffer portion formed on a collector plate in which the thickness of the step portion is reduced in a stepwise manner according to one embodiment of the present invention, and FIG. 11b is a drawing conceptually showing a buffer portion formed on a collector plate in which the thickness of the step portion is increased in a stepwise manner according to one embodiment of the present invention.

[0038] FIG. 12 is a conceptual drawing showing that a step portion according to one embodiment of the present invention is divided into N regions and the step portion changes in a stepwise manner for each region.

[0039] Fig. 13 is a drawing showing a weld formed on the upper side of a current collector plate according to one embodiment of the present invention.

[0040] FIG. 14a is a drawing showing that a first welding portion and a second welding portion are formed on the same line on the upper side of a current collector plate according to another embodiment of the present invention, and FIG. 14b is a drawing showing that a first welding portion and a second welding portion are formed on alternating lines on the upper side of a current collector plate according to another embodiment of the present invention.

[0041] Figure 15 is a drawing showing a method for manufacturing a secondary battery according to one embodiment of the present invention.

[0042] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0043] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In the present invention, it should be understood that the terms "comprise" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0044] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Please note that, where possible, identical components are represented by identical reference numerals throughout the drawings. Furthermore, detailed descriptions of well-known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted.

[0045]

[0046] FIG. 2 is a drawing showing a secondary battery according to one embodiment of the present invention, FIG. 3 is a drawing showing an exploded view of a secondary battery according to one embodiment of the present invention, FIG. 4 is a drawing showing a state in which a current collector plate and a foil tab are welded in a secondary battery according to one embodiment of the present invention, and FIG. 5 is a drawing showing a current collector plate of a secondary battery according to one embodiment of the present invention.

[0047] Referring to FIGS. 2 to 5, a secondary battery (1000) according to one embodiment of the present invention includes a case (1100), an electrode assembly (1200), a collector plate (1300), and a cap assembly (1400).

[0048] The case (1100) forms the exterior of the secondary battery (100). The case (1100) may have a space formed therein to accommodate an electrode assembly (1200), and an opening may be formed on one side. In the present embodiment, the case (1100) has a rectangular parallelepiped shape, but is not limited thereto and may be modified in various ways. The case (1100) may be made of a sturdy material capable of protecting the electrode assembly (1200) accommodated therein. For example, the case (1100) may be made of a metal such as aluminum or stainless steel.

[0049] An electrolyte may be accommodated together with the electrode assembly (1200) inside the case (1100). The electrolyte may be composed of a lithium salt such as LiPF6 or LiBF4 in an organic solvent such as EC, PC, DEC, EMC, or DMC. The electrolyte may be liquid, solid, or gel-like.

[0050] The electrode assembly (1200) is housed inside the case (1100). The electrode assembly (1200) includes an electrode portion (1210) and a plurality of foil tabs (1220, 1220a).

[0051] The electrode part (1210) includes a plurality of unit electrode plates (1211, 1212) and a separator (1213). An active material may be applied to the unit electrode plates (1211, 1212). The plurality of unit electrode plates (1211, 1212) may include a first unit electrode plate (1211) in which an active material such as a transition metal oxide is applied to a metal plate such as aluminum, and a second unit electrode plate (1212) in which an active material such as graphite or carbon is applied to a metal plate such as copper or nickel.

[0052] A separator (1213) is positioned between a plurality of unit electrode plates (1211, 1212) to prevent short circuits between the unit electrode plates (1211, 1212). The material of the separator (316) may be polyethylene, polypropylene, or a composite thereof.

[0053] The electrode portion (1210) can be formed by positioning a separator (1213) between first unit electrode plates (1211) and second unit electrode plates (1212) that are alternately arranged. That is, in one embodiment, the electrode portion (1210) is formed by alternately stacking the first unit electrode plate (1211), the separator (1213), the second unit electrode plate (1212), and the separator (1213) in that order. In another embodiment, the electrode portion (1210) can be formed by arranging the first unit electrode plate (1211), the separator (1213), and the second unit electrode plate (1212) in that order and then winding them.

[0054] In this embodiment, the electrode assembly (1200) has one electrode portion (1210), but in other embodiments, the electrode assembly (1200) may have a plurality of electrode portions (1210). The plurality of electrode portions (1210) may be electrically connected to each other.

[0055] A foil tab (1220, 1220a) on which no active material is applied is formed at one end of a plurality of unit electrode plates (1211, 1212). In one embodiment, the unit electrode plates (1211, 1212) and the foil tab (1220, 1220a) may be formed integrally by cutting a predetermined portion from a single metal plate using a laser or the like to leave the unit electrode plates (1211, 1212) and the foil tab (1220, 1220a).

[0056] The foil tabs (1220) of the first unit electrode plate (1211) overlap each other at a first position, and the foil tabs (1220a) of the second unit electrode plate (1212) overlap each other at a second position. In another embodiment, there may be two or more positions where the foil tabs (1220, 1220a) overlap each other on each of the first unit electrode plate (1211) and the second unit electrode plate (1212). A plurality of foil tabs (1220, 1220a) that overlap at the same position may be connected to each other by ultrasonic welding, laser welding, or the like to facilitate the movement of current.

[0057] The current collector plate (1300) electrically connects the foil tabs (1220, 1220a) and the terminals (1420, 1420a) of the cap assembly (1400). Referring to FIG. 5, the current collector plate (1300) has a main body (1310) and a step portion (1320). In the present embodiment, the current collector plate (1300) has a plate shape, but is not limited thereto.

[0058] The main body (1310) of the current collector (1300) is welded to the foil tab (1220, 1220a) on the upper side of the foil tab (1220, 1220a) on the lower side. Welding may be performed using a method such as ultrasonic welding or laser welding. When welding the foil tab (1220, 1220a) and the main body (1310), in order to increase the contact area between the foil tab (1220, 1220a) and the main body (1310) and to ensure stable welding, the foil tab (1220, 1220a) is bent in the bending direction (BD), and then the main body (1310) is placed on the upper side of the foil tab (1220, 1220a) and welding is performed. The welding may be performed while pressing the main body (1310) toward the foil tab (1220, 1220a).

[0059] In this embodiment, the foil tabs (1220, 1220a) joined to each other can be bent in the same bending direction (BD). The foil tab (1220) of the first unit electrode plate (1211) and the foil tab (1220a) of the second unit electrode plate (1212) can be bent in different bending directions (BD).

[0060] The upper surface of the current collector plate (1300) is connected to the terminals (1420, 1420a). The current collector plate (1300) may be provided with a connecting portion (1330) for connection to the terminals (1420, 1420a). In the present embodiment, the connecting portion (1330) is shaped like a rod, but is not limited thereto. In another embodiment, a portion of the current collector plate (1300) may be convexly protruded so that the convex portion is connected to the terminals (1420, 1420a).

[0061] The step portion (1320) is formed at the end of the bending direction (BD) of the main body portion (1310). The thickness T2 of the step portion (1320) is different from the thickness T1 of the main body portion (1310).

[0062] The cap assembly (1400) seals the opening of the case (1100) in which the electrode assembly (1200) is accommodated. The cap assembly (1400) includes a cap plate (1410) and terminals (1420, 1420a).

[0063] The cap plate (1410) may be a plate shape that covers the opening of the case (1100). The cap plate (1410) may have a shape corresponding to the shape of the opening of the case (1100). The cap plate (1410) may be formed of the same material as the case (1100), and the cap plate (1410) may be fixed to the case (1100) by a method such as laser welding.

[0064] An electrolyte injection port (1411) and a vent hole (1412) may be formed in the cap plate (1410). An electrolyte may be injected into the interior of the case (1100) through the electrolyte injection port (1411). The vent hole (1412) is opened when the internal pressure of the case (1100) exceeds a reference value. In the present embodiment, the vent hole (1412) is formed in the cap plate (1410), but in other embodiments, the vent hole (1412) may be formed in the case (1100).

[0065] The terminals (1420, 1420a) may be formed to protrude from the cap plate (1410). The terminals (1420, 1420a) are electrically connected to the foil tabs (1220, 1220a) through the current collector plate (1300). The terminals (1420, 1420a) may be formed in the shape of a circular or rectangular plate.

[0066] A terminal hole (1421, 1421a) may be formed in the terminal (1420, 1420a). A connecting portion (1310) is inserted into the terminal hole (1421, 1421a).

[0067] An insulating member (1430, 1430a) may be positioned between the terminal (1420, 1420a) and the cap plate (1410). The insulating member (1430, 1430a) insulates the terminal (1420, 1420a) and the cap plate (1410) from each other.

[0068]

[0069] FIG. 6 is a drawing showing a current collector plate with a step-wise reduced thickness according to an embodiment of the present invention being mounted on a foil tab, FIG. 7 is a drawing showing a current collector plate with a step-wise reduced thickness according to an embodiment of the present invention being mounted on a foil tab, and FIG. 8 is a drawing showing the concept of a bending angle at which the foil tab is bent in the bending direction.

[0070] Referring to FIG. 6, a current collector plate (1300) according to one embodiment of the present invention has a main body (1310) and a step portion (1320). The step portion (1320) is positioned to correspond to a blank area (A) formed between the foil tab (1220) located at the outermost position in the bending direction (BD) and the electrode portion (1210) when the foil tab (1220) is bent in the bending direction (BD). Corresponding to the blank area means that the blank area (A) does not extend beyond the step portion (1320) when viewed from above. In the present embodiment, the step portion (1320) is formed from the upper portion (R) of the portion where the foil tab (1220) located at the outermost position in the bending direction (BD) is connected to the electrode portion (1210) to the end in the bending direction (BD). In another embodiment, the step portion (1320) may be formed from a point where the outermost foil tab (1220) is moved further in the opposite direction of the bending direction (BD) than the upper portion (R) of the portion connected to the electrode portion (1210).

[0071] In this way, when the step portion (1320) is positioned to correspond to the blank area (A), the thickness adjustment of the step portion (1320) and the output adjustment of the welding device affect the welding of the blank area. Therefore, through such adjustment, it is possible to prevent the welding of the foil tab (1220) and the collector plate (1300) from affecting the electrode assembly below the blank area.

[0072] The formation length (L) of the step portion (1320) may vary depending on the bending angle at which the foil tab (1220) is bent in the bending direction (BD). Referring to FIG. 8, the bending angle (θ) is the angle formed by the foil tab (1220) with a plane perpendicular to the upper surface of the electrode portion (1210) when the foil tab (1220) is bent in the bending direction (BD). When the bending angle (θ) is large, the formation length (L) of the step portion (1320) becomes longer, and when the bending angle (θ) is small, the formation length (L) of the step portion (1320) becomes shorter.

[0073] In this embodiment, the thickness T1 of the main body (1310) is greater than the thickness T2 of the step portion (1320). Therefore, when welding the foil tab (1220) and the collector plate (1300), the output of the welding device can be set lower when welding the step portion (1320) than when welding the main body (1310), thereby preventing overwelding.

[0074] More specifically, the thickness T2 of the step portion (1320) may be 1 / 3 or more and 2 / 3 or less of the thickness T1 of the main body portion (1310). If the thickness T2 of the step portion (1320) is 1 / 3 or less compared to the thickness T1 of the main body portion (1310), overwelding may occur at the step portion (1320) when welding the foil tab (1220) and the collector plate (1300). If the thickness T2 of the step portion (1320) is 2 / 3 or more compared to the thickness T1 of the main body portion (1310), the output of the welding device must be finely adjusted when welding the foil tab (1220) and the collector plate (1300), making the adjustment difficult.

[0075] The thickness T2 of the step portion (1320) can be determined according to the height of the blank area (A). If the height of the blank area (A) is high, the thickness T2 of the step portion (1320) becomes thicker, and if the height of the blank area (A) is low, the thickness T2 of the step portion (1320) becomes thinner.

[0076] The thickness T2 of the step portion (1320) can be gradually changed, as shown in FIG. 7. In this embodiment, the thickness T2 of the step portion (1320) gradually decreases. As the thickness of the step portion (1320) is gradually changed in this way, the output of the welding device can be gradually adjusted when welding the foil tab (1220) and the current collector plate (1300), so that the main body (1310) and the step portion (1320) can be welded continuously.

[0077]

[0078] FIG. 9 is a drawing showing a current collector plate with a stepwise increased thickness according to one embodiment of the present invention mounted on a foil tab, and FIG. 10 is a drawing showing a current collector plate with a stepwise increased thickness according to one embodiment of the present invention mounted on a foil tab.

[0079] Referring to FIG. 9, the thickness T1 of the main body (1310) of the current collector plate (1300) according to one embodiment of the present invention is smaller than the thickness T2 of the step portion (1320). Therefore, when welding the foil tab (1220) and the current collector plate (1300), the output of the welding device can be set higher when welding the step portion (1320) than when welding the main body (1310), thereby preventing weak welding.

[0080] The thickness T2 of the step portion (1320) may vary depending on the number of foil tabs (1220) positioned at the bottom of the step portion (1320). If the number of foil tabs (1220) positioned at the bottom of the step portion (1320) is large, the thickness T2 of the step portion (1320) becomes thinner, and if the number of foil tabs (1220) positioned at the bottom of the step portion (1320) is small, the thickness T2 of the step portion (1320) becomes thicker.

[0081] In one embodiment, the thickness T2 of the step portion (1320) may be set so that the sum of the thickness T1 of the main body portion (1310) and the thickness of the foil tab (1220) located at the lower portion of the main body portion, and the sum of the thickness T2 of the step portion (1320) and the thickness of the foil tab (1220) located at the lower portion of the step portion (1320) are equal. In this case, the output of the welding device can be made constant when welding the foil tab (1220) and the current collector (1300).

[0082] The thickness T2 of the step portion (1320) can be gradually changed, as illustrated in FIG. 10. In the present embodiment, the thickness T2 of the step portion (1320) gradually increases. As the thickness of the step portion (1320) is gradually changed in this way, the output of the welding device can be gradually adjusted when welding the foil tab (1220) and the current collector plate (1300), so that the main body (1310) and the step portion (1320) can be welded continuously.

[0083]

[0084] FIG. 11a is a drawing conceptually showing a buffer portion formed on a collector plate in which the thickness of the step portion is reduced in a stepwise manner according to one embodiment of the present invention, and FIG. 11b is a drawing conceptually showing a buffer portion formed on a collector plate in which the thickness of the step portion is increased in a stepwise manner according to one embodiment of the present invention.

[0085] Referring to FIGS. 11A and 11B, the current collector plate (1300) according to one embodiment of the present invention may have thicknesses T1 and T2 of the main body (1310) and the step portion (1320) that change in a stepwise manner. When the thicknesses T1 and T2 of the main body (1310) and the step portion (1320) change in a stepwise manner, it is difficult to weld the main body (1310) and the step portion (1320) at the same time when welding the foil tab (1220) and the current collector plate (1300).

[0086] To solve this problem, a buffer portion (1340) can be formed at the boundary between the main body portion (1310) and the step portion (1320). The buffer portion (1340) makes the boundary between the main body portion (1310) and the step portion (1320) gentle. Therefore, there is no need to stop the welding device at the boundary between the main body portion (1310) and the step portion (1320) during welding.

[0087]

[0088] FIG. 12 is a conceptual drawing showing that a step portion according to one embodiment of the present invention is divided into N regions and the step portion changes in a stepwise manner for each region.

[0089] Referring to FIG. 12, the current collector (1300) according to the present embodiment has a thickness T1 of the main body (1310) that is smaller than the thickness T2 of the step portion (1320). The step portion (1320) can be divided into N regions according to the number of foil tabs (1220) located thereunder. In the present embodiment, the step portion (1320) is divided into three regions (A1, A2, A3), but in other embodiments, it can be divided into two or four or more regions.

[0090] In the A1 region, one foil tab (1220) is positioned at the bottom of the step portion (1320), in the A2 region, two foil tabs (1220) are positioned at the bottom of the step portion (1320), and in the A3 region, three foil tabs (1220) are positioned at the bottom of the step portion (1320). Therefore, the thickness of the overlapping foil tabs (1220) in the A2 region is twice that of the A1 region, and in the A3 region, three times that of the A1 region. In this case, if the output of the welding device is set and welding is performed so as to prevent overwelding in the A1 region, weak welding may occur not only in the A2 and A3 regions but also in the main body portion (1310). Therefore, it is necessary to set the output of the welding device so that proper welding can be performed in the main body portion (1310), and to adjust the thickness of the step portion (1320) so as to prevent overwelding in the step portion (1320). In this case, the step portion (1320) may be formed with the same thickness in the same area, and may be formed with different thicknesses in different areas. For example, the step portion (1320) may have the same thickness in area A1 and also have the same thickness in area A2, but may have different thicknesses in areas A1 and A2.

[0091] In this embodiment, the thickness of the step portion (1320) may be increased in the order of the A1, A2, and A3 regions. However, the thickness of the receiving portion (1320) may be made the same within each region. That is, the thickness of the receiving portion (1320) changes in a stepwise manner. This can prevent overwelding from occurring in the blank region.

[0092]

[0093] FIG. 13 is a drawing showing that a weld is formed on the upper side of a current collector plate according to one embodiment of the present invention, FIG. 14a is a drawing showing that a first weld and a second weld are formed on the same line on the upper side of a current collector plate according to another embodiment of the present invention, and FIG. 14b is a drawing showing that a first weld and a second weld are formed on intersecting lines on the upper side of a current collector plate according to another embodiment of the present invention.

[0094] Referring to Fig. 13, the current collector plate (1300) can be welded on the upper side of the main body (1310) and the step portion (1320). The welding can be performed using a laser welding device or an ultrasonic welding device, etc. The welding method can be line welding that is performed along the bending direction.

[0095] In this embodiment, the main body (1310) and the step portion (1320) may be welded in a continuous line to form a continuous weld portion (1500) on the current collector plate (1300). In order to weld in a continuous line like this, the thickness of the step portion (1320) may be gradually changed, or a buffer portion may be formed at the boundary between the main body (1310) and the step portion (1320). In this embodiment, three weld portions (1500) are formed, but this is not limited thereto.

[0096] In another embodiment, referring to FIGS. 14A and 14B, the main body portion (1310) and the step portion (1320) may be welded separately. Accordingly, a first welding portion (1500-1) in which the main body portion is welded and a second welding portion (1500-2) in which the step portion (1320) is welded are formed on the current collector plate (1300). In this case, the welding of the main body portion (1310) may be performed first, followed by the welding of the step portion (1320). In another embodiment, the welding order may be changed.

[0097] The first weld (1500-1) and the second weld (1500-2) may be formed to be positioned on the same line, as illustrated in FIG. 14a. In another embodiment, the first weld (1500-1) and the second weld (1500-2) may be formed on the same line, as illustrated in FIG. 14b.

[0098] In this embodiment, when welding the current collector (1300) and the foil tab (1220), the output of the welding device can be adjusted differently depending on the thickness of the step portion (1320). In addition, the output of the welding device can be adjusted differently when welding the main body (1310) and when welding the step portion (1320).

[0099]

[0100] Figure 15 is a drawing showing a method for manufacturing a secondary battery according to one embodiment of the present invention.

[0101] Referring to FIG. 15, a method for manufacturing a secondary battery according to one embodiment of the present invention includes a preparation step (S2100), a bending step (S2200), a settling step (S2300), and a welding step (S2400).

[0102] In the preparation step (S2100), an electrode assembly is prepared. The electrode assembly includes an electrode portion and a plurality of foil tabs formed at one end of the electrode portion. The electrode portion includes a plurality of unit electrode plates coated with an active material, and a separator that prevents short circuits between the plurality of unit electrode plates. The foil tabs are formed at one end of the plurality of unit electrode plates and are not coated with an active material.

[0103] The electrode portion may be formed by positioning a separator between alternately arranged unit electrode plates. In one embodiment, the electrode portion is formed by alternately stacking unit electrode plates, separators, and unit electrode plates in that order. In another embodiment, the electrode portion may be formed by sequentially arranging unit electrode plates, separators, and unit electrode plates and then winding them.

[0104] In the bending step (S2200), multiple foil tabs are bent in the bending direction. This allows the foil tabs and the main body of the current collector to contact a wide area during welding, enabling stable welding.

[0105] In the settling step (S2300), the collector plate is set on the upper side of the bent foil tab. The collector plate has a main body having a thickness of T1 and a step portion having a thickness of T2 formed at an end in the bending direction of the main body. The thickness T1 of the main body and the thickness T2 of the step portion are different from each other.

[0106] In the welding step (S2400), the foil tab and the current collector are welded. Welding is performed using a welding device. In the present invention, methods such as laser welding and ultrasonic welding can be applied.

[0107] In one embodiment, the step (S2300) may be set so that the step corresponds to the blank area. This allows the adjustment of the step to prevent the welding of the foil tab and the collector plate from affecting the electrode assembly below the blank area.

[0108] In another embodiment, the bending angle in the bending step (S2200) can be adjusted according to the formation length of the step portion. If the formation length of the step portion is long, the bending angle is increased, and if the formation length of the step portion is short, the bending angle is decreased. This facilitates the installation of the step portion corresponding to the blank area.

[0109] In one embodiment of the present invention, the output of the welding device can be set differently when welding the main body and when welding the step portion in the welding step (S2400). This can prevent over-welding or under-welding when welding the step portion.

[0110] In another embodiment, when welding a stepped portion in the welding step (S2400), the output of the welding device can be adjusted according to the sum of the thicknesses of the foil tabs located below the stepped portion. The larger the sum of the thicknesses of the foil tabs, the lower the output of the welding device. The smaller the sum of the thicknesses of the foil tabs, the higher the output of the welding device. This adjustment can prevent over-welding or under-welding when welding a stepped portion.

[0111] In one embodiment of the present invention, the welding step (S2400) may include a first welding step for welding the main body and a second welding step for welding the step. That is, in this embodiment, the welding of the main body and the welding of the step may be performed separately. Accordingly, a first welding part for welding the main body and a second welding part for welding the step are formed on the current collector plate.

[0112] In one embodiment, the first welding step may be performed first, followed by the second welding step. In another embodiment, the second welding step may be performed first, followed by the first welding step. The first and second welding steps may be performed on the same line, but this is not limited thereto, and the first and second welding steps may be performed on different lines.

[0113]

[0114] Above, one embodiment of the present invention has been described, but a person having ordinary skill in the art will be able to modify and change the present invention in various ways by adding, changing, deleting or adding components, etc., within the scope that does not depart from the spirit of the present invention described in the claims, and this will also be considered to be included within the scope of the rights of the present invention.

[0115]

[0116] [Explanation of symbols]

[0117] 1000: Secondary battery 1100: Case

[0118] 1200: Electrode assembly 1210: Electrode body

[0119] 1211, 1212: Unit electrode plate 1213: Separator

[0120] 1220, 1220a: Foil tab 1300: Current collector plate

[0121] 1310: Main body 1320: Stepped part

[0122] 1330: Connection part 1340: Buffer part

[0123] 1400: Cap assembly 1410: Cap plate

[0124] 1420, 1420a: Terminal 1411: Electrolyte inlet

[0125] 1412: Vent Hall

Claims

1. An electrode assembly having an electrode part and a plurality of foil tabs formed at one end of the electrode part; and A current collector plate having a main body portion having a thickness of T1 and welded on the upper side of the foil tab while the foil tab is bent in the bending direction, and a step portion having a thickness of T2 formed at an end of the main body portion in the bending direction; A secondary battery in which the thickness T1 of the main body and the thickness T2 of the step are different from each other.

2. In paragraph 1, A secondary battery, wherein the step portion is formed to correspond to a blank area formed between the electrode portion and the foil tab located at the outermost position in the bending direction when the foil tab is bent in the bending direction.

3. In paragraph 1, A secondary battery, wherein the thickness T1 of the main body portion is greater than the thickness T2 of the step portion.

4. In paragraph 3, A secondary battery in which the thickness T2 of the above-mentioned step portion is 1 / 3 or more and 2 / 3 or less of the thickness T1 of the above-mentioned main body portion.

5. In paragraph 1, A secondary battery, wherein the thickness T1 of the main body portion is smaller than the thickness T2 of the step portion.

6. In paragraph 5, A secondary battery, wherein the thickness T2 of the step portion is determined by the height of the blank area formed between the outermost foil tab in the bending direction and the electrode portion when the foil tab is bent in the bending direction.

7. In paragraph 1, A secondary battery in which the thickness T2 of the above-mentioned step portion changes in a stepwise manner.

8. In paragraph 1, A secondary battery in which the thickness T2 of the above-mentioned step portion gradually changes.

9. In paragraph 1, The above step portion is divided into N areas according to the number of foil tabs located at the bottom. A secondary battery in which the thickness T2 of the above-mentioned step portion is the same thickness in the same area and different thickness in different areas.

10. In paragraph 9, A secondary battery, wherein the thickness T2 of the above-mentioned step portion varies depending on the number of foil tabs located at the lower portion of the above-mentioned step portion.

11. In paragraph 1, A secondary battery in which the above-mentioned step portion is formed from the upper portion of the portion where the foil tab, which is located at the outermost position in the bending direction, is connected to the electrode portion to the end in the bending direction.

12. In paragraph 1, A secondary battery, wherein the formation length of the above-mentioned step portion varies depending on the bending angle at which the foil tab is bent in the bending direction.

13. In paragraph 1, A secondary battery, wherein a first welding part that welds the main body part and a second welding part that welds the step part are formed on the above current collector plate.

14. In paragraph 1, The above electrode part It comprises a plurality of unit electrode plates on which foil tabs are formed, and a separator positioned between each of the plurality of unit electrode plates. A secondary battery formed by stacking or winding the plurality of unit electrode plates and the separator.

15. A preparatory step in which an electrode assembly having an electrode part and a plurality of foil tabs formed on one end of the electrode part is prepared; A bending step in which the plurality of foil tabs are bent in the bending direction; A mounting step in which a main body having a thickness of T1 and a current collector plate having a step portion having a thickness of T2 formed at an end of the main body in the bending direction are mounted on the upper side of the bent foil tab; and A welding step in which the above foil tab and the above collector plate are welded; A method for manufacturing a secondary battery, wherein the thickness T1 of the main body and the thickness T2 of the step portion are different from each other.

16. In paragraph 15, In the above bending step A secondary battery manufacturing method, wherein the bending angle at which the above foil tab is bent in the bending direction is adjusted according to the formation length of the step portion.

17. In paragraph 15, In the above settling stage A method for manufacturing a secondary battery, wherein the step portion is positioned so as to correspond to a blank area formed between the electrode portion and the foil tab located at the outermost position in the bending direction when the foil tab is bent in the bending direction.

18. In paragraph 15, In the above welding step A secondary battery manufacturing method in which the output of the welding device is different when welding the main body and when welding the step portion.

19. In paragraph 15, In the above welding step A method for manufacturing a secondary battery, wherein when welding the above-mentioned step portion, the output of the welding device is adjusted according to the sum of the thicknesses of the foil tabs located on the lower side of the step portion.

20. In paragraph 15, The above welding step A method for manufacturing a secondary battery, comprising a first welding step of welding the main body portion and a second welding step of welding the step portion.

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