Subcell and manufacturing method thereof, and cylindrical secondary battery, battery pack, and automobile including the subcell

Abstract

A subcell according to one embodiment of the present invention includes a jelly-roll type electrode assembly having electrode tabs; a current collecting plate coupled to one side of the electrode assembly and electrically connected to the electrode tabs; and solder interposed between the electrode tabs and the current collecting plate to couple the electrode tabs and the current collecting plate, the solder having a melting point lower than that of the electrode tabs and the current collecting plate.

Description

[Technical field]

[0001] The present invention relates to a subcell and a manufacturing method thereof, and a battery pack and an automobile including the subcell. More specifically, the present invention relates to a subcell having a structure capable of preventing the generation of welding spatters by performing welding at a temperature lower than the melting point of a base material when performing welding for electrically connecting an uncoated portion of an electrode assembly to a current collecting plate. The present invention also relates to a manufacturing method of the subcell, a cylindrical secondary battery including the subcell, and a battery pack and an automobile including the cylindrical secondary battery.

[0002] This application claims priority to Korean Patent Application No. 10-2021-0007282, filed on January 19, 2021, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings. [Background technology]

[0003] In cylindrical secondary batteries, the uncoated portion (electrode tab) of a jelly-roll type electrode assembly housed in a battery can is connected to a current collecting plate by welding. Laser welding is one example of a welding technique used in manufacturing a subcell including such an electrode assembly and a current collecting plate.

[0004] In order to join the current collecting plate and the uncoated portion by laser welding, welding must be performed at a temperature equal to or higher than the melting point of the base material of the current collecting plate disposed on the electrode assembly so that a portion of the current collecting plate can melt and be joined to the uncoated portion.

[0005] The current collecting plate may be made of, for example, aluminum or copper, but in the case of a welding method in which a typical current collecting plate made of aluminum or copper is directly melted and joined to a non-coated portion, the melting points of aluminum and copper are high, so welding must be performed by irradiating a laser with very high energy.

[0006] In this way, the energy of the laser irradiated for welding is very high, and welding spatter occurs when welding is performed above the melting point of the current collecting plate that is the object of direct laser irradiation. The welding spatter may remain as metallic foreign matter in the electrode assembly and may cause micro-shorts due to unnecessary electrical connections between electrodes. Such micro-shorts can have adverse effects such as a decrease in performance and a safety hazard of cylindrical secondary batteries.

[0007] Therefore, when performing laser welding to join the electrode assembly and current collecting plate that constitute a cylindrical secondary battery, it is necessary to develop a subcell having a structure that prevents the generation of such welding spatter and a manufacturing method thereof. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above problems, and aims to prevent the generation of welding spatter when laser welding is performed to join an electrode assembly and a current collecting plate that constitute a cylindrical secondary battery.

[0009] Another object of the present invention is to ensure a sufficient area for welding electrical connection parts, such as bus bars used to manufacture a battery pack, to the electrode terminals of the cylindrical secondary batteries by utilizing a wide surface of the closing part of the battery can as an electrode terminal when electrically connecting multiple cylindrical secondary batteries in one direction.

[0010] However, the technical problems that the present invention aims to solve are not limited to the problems described above, and other problems not mentioned will be clearly understood by those skilled in the art from the description of the invention described below. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, a subcell according to an embodiment of the present invention includes a jelly-roll type electrode assembly having an electrode tab, a current collecting plate coupled to one side of the electrode assembly and electrically connected to the electrode tab, and a solder interposed between the electrode tab and the current collecting plate to couple the electrode tab and the current collecting plate, the solder having a melting point lower than that of the electrode tab and the current collecting plate.

[0012] The solder may be interposed between adjacent electrode tabs by infiltration due to capillary action when melted by welding.

[0013] The penetration distance of the solder may be shorter than the extension length of the electrode tab.

[0014] The electrode tab may have a shape in which an end portion in the longitudinal direction thereof is bent in a direction parallel to the current collecting plate, and the solder may be interposed between a plane formed by bending the electrode tab and the current collecting plate.

[0015] The distance that the solder penetrates between adjacent electrode tabs may gradually decrease from an outer periphery of the electrode assembly toward a center of the winding.

[0016] The current collecting plate may comprise a plurality of spaced apart sub-plates extending radially from a central portion.

[0017] The sub-plate may have a shape such that its width gradually narrows from an outer circumferential surface of the electrode assembly toward a central portion of the winding.

[0018] The solder may have a shape whose width gradually narrows from the outer circumferential surface of the electrode assembly toward the center of the winding.

[0019] The electrode assembly may have a structure in which a first electrode, a second electrode, and a separator (separation membrane) interposed therebetween are wound in one direction, and the first electrode and the second electrode may each have a first uncoated portion and a second uncoated portion at a long side end portion, respectively, that are not coated with an active material and are exposed to the outside of the separator.

[0020] At least one of the first uncoated portion and the second uncoated portion may function as the electrode tab.

[0021] At least one of the first uncoated portion and the second uncoated portion may include a plurality of segment pieces divided along a winding direction of the electrode assembly, and the plurality of segment pieces may be bent in a radial direction of the electrode assembly.

[0022] The bent segments may be overlapped in multiple layers along the radial direction.

[0023] The electrode assembly may include a welding target region, which is a region where the overlapping number of the segments provided in the uncoated portion is maintained constant along a radial direction of the electrode assembly.

[0024] The current collecting plate may be coupled to the non-coated portion within the weld target area.

[0025] A method for manufacturing a sub-cell according to an embodiment of the present invention includes the steps of: preparing a jelly-roll type electrode assembly (S1); preparing a current collecting plate having solder formed on one surface thereof (S2); placing the current collecting plate on the electrode assembly (S3); and melting the solder to weld the electrode tabs of the electrode assembly and the current collecting plate to each other, the welding being performed at a temperature lower than the melting points of the electrode tabs and the current collecting plate (S4).

[0026] The step (S4) may include melting the solder and allowing the solder to penetrate between the adjacent electrode tabs by capillary action.

[0027] The step (S2) may include a step of adjusting a thickness of the solder formed on one surface of the current collecting plate so that a penetration distance of the solder is smaller than an extension length of the electrode tab.

[0028] The step (S2) The method may include a step of adjusting a thickness of the solder formed on one surface of the collecting plate so that a distance that the solder penetrates between adjacent electrode tabs gradually becomes shorter from the outer circumferential surface of the electrode assembly toward the center of the winding.

[0029] A cylindrical secondary battery according to an embodiment of the present invention includes a subcell according to an embodiment of the present invention, and a battery can that accommodates the subcell through an opening provided on one side and is electrically connected to the electrode assembly.

[0030] The cylindrical secondary battery may further include a terminal electrically connected to the electrode assembly, having a polarity opposite to that of the battery can, and insulated from the battery can.

[0031] The terminal may be exposed to the outside through a closed portion provided on the opposite side to the open portion of the battery can.

[0032] The cylindrical secondary battery may further include a cap plate that seals the open portion.

[0033] The cap plate may be non-polar.

[0034] Meanwhile, a battery pack according to an embodiment of the present invention includes a plurality of cylindrical secondary batteries according to an embodiment of the present invention and a pack housing that accommodates the cylindrical secondary batteries.

[0035] In this case, each of the plurality of cylindrical secondary batteries may include a terminal that is electrically connected to the electrode assembly, has a polarity opposite to that of the battery can, and is insulated from the battery can.

[0036] The outer surface of the closure of the battery can of each of the plurality of cylindrical secondary batteries and the terminal of the battery can may be arranged to face in the same direction.

[0037] The battery pack may include a plurality of bus bars connecting the cylindrical secondary batteries in series and in parallel.

[0038] The plurality of bus bars may be disposed on the upper portion of the plurality of cylindrical secondary batteries. In this case, each of the bus bars may include: a body portion extending between terminals of adjacent cylindrical secondary batteries; a plurality of first bus bar terminals extending in one direction of the body portion and electrically coupled to terminals of cylindrical secondary batteries located in the one direction; and a plurality of second bus bar terminals extending in the other direction of the body portion and electrically coupled to outer surfaces of the closing portions of cylindrical secondary batteries located in the other direction.

[0039] An automobile according to an embodiment of the present invention includes a battery pack according to an embodiment of the present invention. Effect of the Invention

[0040] According to one aspect of the present invention, when performing laser welding to join an electrode assembly and a current collecting plate that constitute a cylindrical secondary battery, welding spatter is not generated, thereby preventing a decrease in performance of the cylindrical secondary battery and preventing a decrease in safety during use of the cylindrical secondary battery.

[0041] According to another aspect of the present invention, electrical wiring for connecting cylindrical secondary batteries in series and / or in parallel may be performed on one side of the cylindrical secondary batteries.

[0042] According to yet another aspect of the present invention, when a plurality of cylindrical secondary batteries are electrically connected in one direction, a wide surface of the closing portion of the battery can can be utilized as an electrode terminal, thereby ensuring a sufficient area for welding an electrical connection component, such as a bus bar used in manufacturing a battery pack, to the electrode terminal of the cylindrical secondary battery. [Brief description of the drawings]

[0043] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical ideas of the present invention. Therefore, the present invention should not be interpreted as being limited only to the matters depicted in such drawings.

[0044] [Figure 1] FIG. 2 illustrates a subcell according to one embodiment of the present invention. [Diagram 2] FIG. 2 illustrates a subcell according to one embodiment of the present invention. [Diagram 3] FIG. 2 illustrates a subcell according to one embodiment of the present invention. [Figure 4] FIG. 2 shows a current collecting plate and solder formed on one side thereof for manufacturing a subcell according to one embodiment of the present invention. [Diagram 5] FIG. 13 illustrates a subcell according to another embodiment of the present invention. [Figure 6] FIG. 13 shows a current collecting plate and solder formed on one side thereof for manufacturing a subcell according to another embodiment of the present invention. [Figure 7] FIG. 13 illustrates a subcell according to yet another embodiment of the present invention. [Figure 8] FIG. 13 is a diagram showing a current collecting plate and solder formed on one surface thereof for manufacturing a subcell according to yet another embodiment of the present invention. [Figure 9] 1 is a plan view illustrating an example of an electrode structure according to a preferred embodiment of the present invention; [Figure 10]4 is a cross-sectional view taken along a longitudinal direction Y of an electrode assembly in which the segmented structure of the uncoated portion of a first electrode is also applied to a second electrode according to an embodiment of the present invention. FIG. [Figure 11] 4 is a cross-sectional view of an electrode assembly in which an uncoated portion is folded in accordance with an embodiment of the present invention, taken along a longitudinal direction Y. FIG. [Figure 12] 1 is a perspective view of an electrode assembly in which a non-coating portion is folded according to an embodiment of the present invention; [Figure 13] 1 is a diagram showing the appearance of a cylindrical secondary battery according to an embodiment of the present invention; [Figure 14] 1 is a cross-sectional view showing an internal structure of a cylindrical secondary battery according to an embodiment of the present invention. [Figure 15] 1 is a top plan view showing a state in which a plurality of cylindrical secondary batteries according to an embodiment of the present invention are connected in series and in parallel using bus bars. [Figure 16] 1 is a schematic diagram illustrating a battery pack according to one embodiment of the present invention. [Figure 17] 1 is a conceptual diagram illustrating a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as being in accordance with the meaning and concept of the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of the term in order to best describe the invention. Therefore, it should be understood that the embodiment described in this specification and the configuration shown in the drawings are merely the most preferred embodiment of the present invention, and do not represent the entire technical idea of ​​the present invention, and therefore there may be various equivalents and modifications that can be substituted for them at the time of this application.

[0046] 1 to 3, 13 and 14, a subcell 1 according to an embodiment of the present invention includes an electrode assembly, a current collecting plate (first current collecting plate), and solder S that connects the electrode assembly 10 and the current collecting plate 20. The subcell 1 may further include a current collecting plate (second current collecting plate) 60 in addition to the current collecting plate (first current collecting plate).

[0047] The electrode assembly 10 includes a first electrode having a first polarity, a second electrode having a second polarity, and a separator interposed between the first electrode and the second electrode. The electrode assembly 10 may be a jelly-roll type electrode assembly. That is, the electrode assembly 10 may be manufactured by winding a laminate formed by sequentially stacking a first electrode, a separator, and a second electrode at least once, based on a winding center C. In this case, a separator for insulating the electrode assembly 10 from a battery can (see FIGS. 13 and 14) may be provided on the outer circumferential surface of the electrode assembly 10. The first electrode is a positive electrode or a negative electrode, and the second electrode has a polarity opposite to that of the first electrode.

[0048] The first electrode includes a first electrode collector and a first electrode active material applied to one or both sides of the first electrode collector. An uncoated portion where the first electrode active material is not applied exists at one end in the width direction (direction parallel to the Z axis) of the first electrode collector. The uncoated portion functions as a first electrode tab. The first electrode tab 11 can also be a positive electrode tab or a negative electrode tab.

[0049] The second electrode includes a second electrode collector and a second electrode active material applied to one or both sides of the second electrode collector. An uncoated portion where the second electrode active material is not applied exists at the other end of the second electrode collector in the width direction (direction parallel to the Z axis). The uncoated portion functions as a second electrode tab. The second electrode tab 12 has a polarity opposite to that of the first electrode tab 11.

[0050] The first electrode tab and the second electrode tab 12 may extend in opposite directions. Although the drawings of the present invention show that all of the first current collecting plate 20, the second current collecting plate 60, and the second electrode tab 12 are provided, the present invention is not limited thereto. That is, either one of the first current collecting plate and the second current collecting plate may not be provided. In addition, although only the coupling structure between the first current collecting plate 20 and the first electrode tab 11 is shown in Figs. 1 to 3 and 7 of the present invention, this is merely an example and for the convenience of explanation, and the coupling structure shown in these drawings may be applied to the coupling between the first current collecting plate 20 and the first electrode tab 11 and / or the coupling between the second current collecting plate 60 and the second electrode tab 12.

[0051] 1 and 14, the current collecting plate 20 is coupled to one side of the electrode assembly 10 in a height direction (parallel to the Z-axis). The current collecting plate 20 is made of a conductive metal material and is electrically connected to the first electrode tab 11. The current collecting plate 20 may include a tab coupling portion coupled to the first electrode tab 11. In addition, the current collecting plate 20 may include a terminal coupling portion coupled to a component capable of functioning as an electrode terminal of a cylindrical secondary battery.

[0052] The current collecting plate (first current collecting plate) 20 may include, for example, a plurality of sub-plates 20 extending radially from its center. In this case, the sub-plates may function as tap joints. The sub-plates 20 may be spaced apart from one another. This is because when the current collecting plate 20 is joined to the upper or lower part of the electrode assembly, the current collecting plate 20 only partially covers the upper or lower surface of the electrode assembly 10, thereby improving impregnation when an electrolyte is injected and ensuring ease of gas discharge when gas is generated inside the electrode assembly 10.

[0053] The current collecting plate 20 may further include a lead plate 22. The lead plate 22 may function as a terminal coupling portion. Alternatively, the current collecting plate 20 may not include the lead plate 22. In this case, for example, the center of the current collecting plate 20 may function as the terminal coupling portion.

[0054] The current collecting plate (second current collecting plate) 60 is coupled to the other side of the electrode assembly 10 in the height direction (direction parallel to the Z-axis). The current collecting plate 60 is made of a conductive metal material and is electrically connected to the second electrode tab 12. The current collecting plate (second current collecting plate) 60 may include a tab coupling portion coupled to the second electrode tab 12. In addition, the current collecting plate 20 may include a terminal coupling portion coupled to a component capable of functioning as an electrode terminal in a cylindrical secondary battery.

[0055] 2 and 3, the solder S is interposed between the electrode tab 11 and the current collecting plate to connect the electrode tab 11 and the current collecting plate 20. The solder S is made of a metal material having a lower melting point than the electrode tab and the current collecting plate. This is to lower the melting point of the solder S below the melting point of the base material to lower the welding temperature and thereby prevent the occurrence of welding spatters during welding.

[0056] The solder S may be provided by a soldering type or a brazing type. Here, the soldering type means that the solder S is provided by applying a low melting point solder paste to one side of the current collecting plate 20. Also, the brazing type means that the current collecting plate 20 and the solder S are provided integrally by cladding one side of the current collecting plate 20 with a low melting point alloy layer.

[0057] In the case of the soldering type, for example, a ternary alloy containing Sn, Ag, and Bi can be used as the solder S. In this case, the solder S can have a melting point of about 290°C. In the case of the brazing type, for example, an alloy of the Al40 series (in which silicon is added to Al to lower the melting point) can be used as the solder S. In this case, the solder S can have a melting point of about 510°C.

[0058] The electrode tab 11 corresponds to a region of the electrode current collector made of foil where the electrode active material is not applied. Therefore, the electrode tab 11 may be made of copper or aluminum. The current collector plate may also be a plate made of aluminum or copper. In both the soldering type and brazing type, the alloy constituting the solder S has a melting point that is sufficiently lower than that of aluminum or copper, which are metals commonly used for the electrode tab and current collector plate 20.

[0059] 2, a plurality of electrode tabs spaced apart from one another extend side by side on one side of the electrode assembly 10, and solder S is interposed between adjacent electrode tabs by infiltration due to capillary action during melting by welding. In the figures of the present invention, a sufficient gap is shown between adjacent electrode tabs to show the manner in which the solder S is interposed, but in reality, in a jelly roll type electrode assembly, there are only very fine gaps between adjacent electrodes and between adjacent electrode tabs. Therefore, the solder S temporarily melted by welding penetrates into the gaps between adjacent electrode tabs by capillary action.

[0060] If the penetration distance D of the solder S is longer than the extension length L of the electrode tab 11, the solder S will come into contact with the electrode active material formed on the electrode current collector. If this phenomenon occurs, the electrode active material may be damaged, and adjacent electrodes of opposite polarity may be electrically connected to each other, causing a short circuit. Therefore, the distance D that the solder S penetrates between adjacent electrode tabs is shorter than the extension length L of the electrode tab 11.

[0061] Referring to FIG. 4, the thickness T of the solder S formed on the current collecting plate is adjusted so that the distance D over which the solder S penetrates between adjacent electrode tabs by welding is shorter than the extension length L of the electrode tabs 11.

[0062] 3, the longitudinal end of the electrode tab 11 is bent in a direction parallel to the current collecting plate 20 (parallel to the X-axis). In this case, the solder S is interposed between the current collecting plate and a plane formed by bending the electrode tab 11. When the electrode tab 11 has a bent shape in this manner, the space occupied by the electrode tab 11 is reduced, thereby improving the energy density.

[0063] A subcell 1 according to another embodiment of the present invention shown in Fig. 5 is substantially the same as the embodiment shown in Fig. 2, except for the difference in the infiltration form of the solder S. Therefore, in the description of the subcell 1 according to the other embodiment of the present invention, the description will be focused on the infiltration form of the solder S, and descriptions overlapping with the above-mentioned embodiment will be omitted.

[0064] 5, the solder S permeates between the adjacent electrode tabs due to capillary action. At this time, the permeation distances D1 and D2 of the solder S gradually become shorter from the outer circumferential surface of the electrode assembly 10 toward the winding center C. That is, the distance D1 is longer than the distance D2, and the permeation distance of the solder S decreases substantially uniformly from D1 to D2. As such, the permeation distances of the solder S are formed differently, so that the variation (deviation) in electrical resistance and heat generation can be minimized throughout the entire joint area between the electrode tabs 11 and the solder S.

[0065] 1, when the jelly-roll type electrode assembly 10 is viewed from above, the area of ​​the electrode wound in a circle increases as it moves away from the winding center C. The area of ​​the electrode contacting the solder S area located farther from the winding center C is larger than the area of ​​the electrode contacting the solder S area located closer to the winding center C. Therefore, advantageously, the solder S area located farther from the winding center C has a relatively larger area in contact with the electrode compared to the solder S area located closer to the winding center C.

[0066] 5 and 6, the thicknesses T1, T2 of the solder S formed on the current collecting plate are adjusted so that the distances D1, D2 by which the solder S penetrates between the electrode tabs by welding gradually decrease from the outer circumferential surface of the electrode assembly 10 toward the winding center C. That is, the thicknesses T1, T2 of the solder S formed on one surface of the current collecting plate 20 before welding gradually decrease from the outer periphery toward the center of the current collecting plate 20. That is, the thickness T1 is formed to be larger than the thickness T2, and the thickness of the solder S decreases almost constantly from T1 to T2.

[0067] 7 is substantially the same as the above-described embodiment, except for the shape of the current collecting plate 20. Therefore, in the description of the subcell 1 according to the further embodiment of the present invention, the description will be omitted to focus on the shape of the current collecting plate 20 and the resulting shape of the solder S.

[0068] 7 and 8, the sub-plate 21 of the current collecting plate 20 has a shape in which the width gradually narrows from the outer circumferential surface of the electrode assembly 10 toward the winding center. As a result, the solder S formed on one surface of the sub-plate 21 also has a shape in which the width gradually narrows from the outer circumferential surface of the electrode assembly 10 toward the winding center. This structure is intended to obtain the same advantages as the structure shown in FIG. 5. In addition, the structure of the sub-cell 1 shown in FIGS. 7 and 8 can be combined with the structure of the sub-cell 1 shown in FIGS. 5 and 6, thereby further reducing the variation (deviation) in electrical resistance and heat generation over the entire joint area between the electrode tab 11 and the solder S.

[0069] 9 to 12, a specific structure of an electrode assembly 10 according to an embodiment of the present invention is shown. In the following description, the first electrode of the above-mentioned first and second electrodes will be described as an example, but the structure of the first electrode can be similarly applied to the second electrode.

[0070] 9 and 10, the first electrode 110 includes a substantially sheet-shaped first electrode collector 111 made of a conductive foil, a first active material layer 112 formed on at least one surface of the first electrode collector 111, and a first uncoated portion (first electrode tab) 11 at a long side end of the first electrode collector 111 where no active material is coated.

[0071] Preferably, the first plain portion 11 may include a plurality of notched segments 11a. The plurality of segments 11a may form a plurality of groups, and the segment pieces 11a belonging to each group may have the same height (length in the Z direction) and / or width (length in the X direction) and / or spacing pitch. The number of segment pieces 11a belonging to each group may be increased or decreased compared to the number shown in the figure. The segment pieces 11a have a geometric shape in which at least one straight line and / or at least one curved line are combined. Preferably, the segment pieces 11a may have a trapezoidal shape, and may be deformed into a rectangle, a parallelogram, a semicircle, a semiellipse, or the like.

[0072] Preferably, the height of the segment piece 11a may increase stepwise, for example, from the core side toward the outer periphery side, along one direction parallel to the winding direction of the electrode assembly 10. Also, the core-side uncoated portion 11-1 adjacent to the core side of the electrode assembly 10 may not include a segment piece 11a, and the height of the core-side uncoated portion 11-1 may be lower than the height of the uncoated portions in other regions. Also, the outer periphery-side uncoated portion 11-2 adjacent to the outer periphery side of the electrode assembly 10 may not include a segment piece 11a, and the height of the outer periphery-side uncoated portion 11-2 may be lower than the height of the uncoated portions in other regions.

[0073] Optionally, the first electrode 110 may include an insulating coating layer E covering the boundary between the active material layer 112 and the first uncoated portion. The insulating coating layer E includes an insulating polymer resin, and may optionally further include an inorganic filler. The insulating coating layer E may prevent the end of the active material layer 112 from contacting the active material layer of the opposite polarity facing the separator therebetween, and may help structurally support the folding of the segment piece 11a. For this reason, it is preferable that at least a portion of the insulating coating layer E is exposed to the outside from the separator when the first electrode 110 is wound to form the electrode assembly 10.

[0074] The pattern in which the height of the uncoated portions 11, 12 varies is shown diagrammatically. That is, the height of the uncoated portions 11, 12 may vary irregularly depending on the position where the cross section is cut. For example, when a side portion of the trapezoidal segment 11a is cut, the height of the uncoated portions in the cross section becomes lower than the height of the segment 11a. Therefore, it should be understood that the height of the uncoated portions 11, 12 shown in the cross section of the electrode assembly 10 corresponds to the average height of the uncoated portions included in each winding turn.

[0075] 9 to 12, the uncoated portions 11 and 12 may be folded radially of the electrode assembly 10, for example, from the outer periphery toward the core. The portion where the uncoated portions 11 and 12 are folded is indicated by a dotted box in FIG. 10. When the uncoated portions 11 and 12 are folded, the segments adjacent in the radial direction are overlapped in multiple layers to form a folded surface 102 at the top and bottom of the electrode assembly 10. At this time, the core-side uncoated portion (11-1 in FIG. 9) is not folded due to its low height, and the height h of the segment piece 11a that is folded at the innermost side is equal to or smaller than the radial length r of the winding region formed by the core-side uncoated portion 11-1 without a segment piece structure. Therefore, the hole formed in the core of the electrode assembly 10, i.e., the winding center C, is not closed. If the hole is not closed, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency can be improved. Also, by inserting a welding tool through the hole, the terminal (40) and the current collecting plate (see FIG. 14) can be easily welded together.

[0076] On the other hand, referring to Figures 9 to 12 and 14, as described above, when the first electrode tab (first uncoated portion) and / or the second electrode tab (second uncoated portion) 12 each have a segment piece, and the segment piece has a structure in which it is folded inward or outward approximately along the radial direction of the electrode assembly 10 and overlapped in multiple layers, the electrode assembly 10 may have a welding target region, which is a region in which the number of overlapping layers of the segment pieces is maintained approximately constant along the radial direction. In this region, the number of overlapping layers is maintained at approximately the maximum. Therefore, it may be advantageous to perform welding between the current collecting plates 20, 60 and the electrode tabs 11, 12 in this region. This is to prevent the laser beam from penetrating the electrode tabs 11, 12 and damaging the electrode assembly 10 when the laser output is increased to improve the welding quality, for example, when applying laser welding. Also, this is to effectively prevent foreign matter such as welding spatter from flowing into the inside of the electrode assembly 10.

[0077] 1 to 8, the method for manufacturing the subcell 1 of the present invention includes the steps of preparing an electrode assembly 10 (S1), preparing a current collecting plate 20 (S2), placing the current collecting plate 20 on the electrode assembly (S3), and welding (S4). Either step (S1) or step (S2) may be performed first, or both steps may be performed simultaneously.

[0078] The step (S1) is a step of preparing a jelly roll type electrode assembly 10 by winding up a laminate including electrodes and a separator.

[0079] The step (S2) is a step of preparing a current collecting plate 20 having solder S formed on one surface thereof. The step (S2) includes a step of applying a solder paste onto the current collecting plate 20, or a step of cladding an alloy layer on one surface of the current collecting plate 20.

[0080] The step (S2) may further include a step of adjusting the thickness of the solder S formed on one surface of the current collecting plate 20 so that the penetration distance of the solder S is shorter than the extension length of the electrode tabs 11 when performing the step (S4) (see FIGS. 2 and 4). The step (S2) may further include a step of adjusting the thickness of the solder S formed on one surface of the current collecting plate 20 so that the penetration distance of the solder S between adjacent electrode tabs gradually becomes shorter from the outer peripheral surface of the electrode assembly (10) toward the winding center C (see FIGS. 5 and 6).

[0081] The step (S4) is a step of performing welding by melting the solder S to join the electrode tab 11 and the current collecting plate 20 of the electrode assembly 10. The step (S4) is a step of performing welding at a temperature lower than the melting points of the current collecting plate 20 and the electrode tab 11. The welding may be, for example, laser welding. The step (S4) is a step of melting the solder S and allowing it to penetrate between the adjacent electrode tabs by capillary action (see FIGS. 2 and 5).

[0082] 13 and 14, an exemplary embodiment of a cylindrical secondary battery 2 of the present invention is shown. The cylindrical secondary battery 2 according to an embodiment of the present invention includes a subcell according to an embodiment of the present invention and a battery can 30 that houses the subcell. In addition to the above, the cylindrical secondary battery 2 may further include a terminal electrically connected to the electrode assembly 10 and / or a cap 50 that covers an opening formed on one side of the battery can 30.

[0083] The battery can 30 is a substantially cylindrical container having an open portion on one side, and is made of a conductive material such as metal. The battery can 30 may have a closed portion located on the opposite side of the open portion, and an outer surface 30a of the closed portion may have a substantially flat shape. The battery can 30 accommodates the electrode assembly 10 through the open portion, and also accommodates an electrolyte. The battery can 30 may have a beading portion 31 and a crimping portion 32 formed adjacent to the open portion. The beading portion 31 is formed by pressing around the outer circumferential surface of the battery can 30. The beading portion 31 may function as a fixing portion that prevents the electrode assembly 10 accommodated in the battery can 30 from being removed to the open portion side. The crimping portion 32 is formed below the beading portion 31, as shown in FIG. 13 and FIG. 14. The crimping portion 32 has a shape that extends from the beading portion and is bent to surround the outer circumferential surface of the cap 50 and a part of the lower surface of the cap 50. In this case, a sealing gasket G2 may be provided in the area where the crimping portion 32 is formed. The sealing gasket G2 may be interposed between the inner surface of the battery can 30 and the cap.

[0084] The battery can 30 may be electrically connected to the second electrode tab 12 of the electrode assembly 10. The electrical connection between the battery can 30 and the second electrode tab may be made via a current collecting plate (second current collecting plate) 60. In this case, a terminal coupling portion of the current collecting plate 60 may be electrically coupled to, for example, a side wall of the battery can 30. However, the present invention is not limited thereto, and the second electrode tab 12 may be directly coupled to the battery can 30.

[0085] The terminal 40 is electrically connected to the first electrode tab 11. The terminal 40 and the first electrode tab may be coupled via a current collecting plate (first current collecting plate) 20. The terminal 40 may be coupled to a terminal coupling portion of the current collecting plate 20, or may be exposed to the outside through approximately the center of the closed portion of the battery can 30. In this case, since the polarities of the terminal 40 and the battery can 30 are different, an insulating gasket G1 may be interposed between the battery can 30 and the terminal 40 to prevent contact between them and to enhance the sealing of the exposed portion of the terminal 40.

[0086] The cap 50 seals an opening formed on one side of the battery can 30. When the cylindrical secondary battery 2 of the present invention has the shape shown in Figs. 13 and 14, the cap 50 may be made of a conductive metal material and may not have polarity. The cap 50 having no polarity means that the cap 50 is not electrically connected to the electrode assembly 10. Thus, when the cap 50 is not electrically connected to the electrode assembly 10, the cap 50 does not function as an electrode terminal. That is, in the present invention, the cap 50 does not necessarily have to be electrically connected to the electrode assembly and the battery can 30, and the material thereof does not necessarily have to be a conductive metal.

[0087] 13 and 14, the terminal 40, which is electrically connected to the first electrode tab 11 and can function as a first electrode terminal, and the outer surface 30a of the closing part of the battery can 30, which is electrically connected to the second electrode tab 12 and can function as a second electrode terminal, are located in the same direction. This structure makes it easy to electrically connect the cylindrical secondary battery using a bus bar.

[0088] 15, there is shown an example of a structure in which a plurality of cylindrical secondary batteries 2 are electrically connected when the first electrode terminal and the second electrode terminal of the cylindrical secondary battery 2 are positioned in the same direction as described above. The plurality of cylindrical secondary batteries 2 may be connected in series and parallel at the top of the cylindrical secondary batteries 2 using a bus bar 150. The number of cylindrical secondary batteries 2 may be increased or decreased taking into account the capacity of the battery pack.

[0089] In each cylindrical secondary battery 2, for example, the terminal 40 may have a positive polarity, and the outer surface 30a of the closure of the battery can 30 may have a negative polarity. Of course, the reverse is also possible.

[0090] Preferably, a plurality of cylindrical secondary batteries 2 may be arranged in a plurality of columns and rows. As shown in FIG. 15, the columns are in the vertical direction, and the rows are in the horizontal direction. In order to maximize space efficiency, the cylindrical secondary batteries 2 may be arranged in a closest packing structure. The closest packing structure is formed when an equilateral triangle is formed when the centers of the upper surfaces of the terminals 40 exposed to the outside of the battery can 30 are connected to each other. Preferably, the bus bar 150 may be arranged on top of the plurality of cylindrical secondary batteries 2, more preferably between adjacent columns. Alternatively, the bus bar 150 may be arranged between adjacent rows.

[0091] Preferably, the bus bars 150 connect the cylindrical secondary batteries 2 arranged in the same row in parallel to each other, and connect the cylindrical secondary batteries 2 arranged in two adjacent rows in series to each other.

[0092] Preferably, bus bar 150 may include a body portion 151, a plurality of first bus bar terminals 152 and a plurality of second bus bar terminals 153 for series and parallel connections.

[0093] The body portion 151 may extend between the terminals 40 of adjacent cylindrical secondary batteries 2, preferably between rows of cylindrical secondary batteries 2. Alternatively, the body portion 151 may extend along the row of cylindrical secondary batteries 2, and in this case, may be folded in a regular zigzag pattern.

[0094] The plurality of first bus bar terminals 152 may protrude and extend from one side of the body portion 151 toward the terminals 40 of the respective cylindrical secondary batteries 2 and may be electrically coupled to the terminals 40. The electrical coupling between the first bus bar terminals 152 and the terminals 40 may be performed by laser welding, ultrasonic welding, or the like. Also, the plurality of second bus bar terminals 153 may be electrically coupled to the outer surface 20a of each cylindrical secondary battery 2 from the other side of the body portion 151. The electrical coupling between the second bus bar terminals 153 and the outer surface 20a may be performed by laser welding, ultrasonic welding, or the like.

[0095] Preferably, the body portion 151, the plurality of first busbar terminals 152, and the plurality of second busbar terminals 153 may be made of a single conductive metal plate. The metal plate may be, for example, an aluminum plate or a copper plate, but the present invention is not limited thereto. In a modified example, the body portion 151, the plurality of first busbar terminals 152, and the second busbar terminals 153 may be manufactured as individual pieces and then joined together by welding or the like.

[0096] In the cylindrical secondary battery 2 according to the present invention, the terminal 40 having a positive polarity and the outer surface 20a of the closing part of the battery can 30 having a negative polarity are positioned in the same direction, so that the cylindrical secondary batteries 2 can be easily electrically connected to each other using the bus bar 150.

[0097] In addition, since the area of ​​the terminal 40 of the cylindrical secondary battery 2 and the outer surface 20a of the closing part of the battery can 30 are large, a sufficient bonding area for the bus bar 150 can be secured, thereby sufficiently reducing the resistance of the battery pack including the cylindrical secondary battery 2.

[0098] 16, a battery pack 4 according to an embodiment of the present invention includes a secondary battery assembly in which a plurality of cylindrical secondary batteries 2 according to an embodiment of the present invention are electrically connected as described above, and a pack housing 3 that accommodates the secondary battery assembly. For convenience of illustration, components such as bus bars and power terminals for electrical connection are omitted in FIG. 16 of the present invention. A specific example of the electrical connection structure of the plurality of cylindrical secondary batteries 2 is similar to that described with reference to FIG. 15 above.

[0099] 17, an automobile 5 according to an embodiment of the present invention may be, for example, an electric vehicle, and includes a battery pack 4 according to an embodiment of the present invention. The automobile 5 operates by receiving power from the battery pack according to an embodiment of the present invention.

[0100] Although the present invention has been described above using limited embodiments and drawings, the present invention is not limited thereto, and it goes without saying that various modifications and variations can be made by a person having ordinary knowledge in the technical field to which the present invention pertains within the scope of the technical concept of the present invention and the scope of the claims.

Claims

1. a jelly-roll type electrode assembly having a plurality of spaced apart electrode tabs; a current collecting plate coupled to one side of the jelly roll type electrode assembly and electrically connected to the plurality of electrode tabs extending side by side on the one side; a solder that is confined within a space formed by the adjacent electrode tabs and one surface of the current collecting plate to join the electrode tabs and the current collecting plate and to join adjacent electrode tabs to each other, the solder having a melting point lower than that of the electrode tabs and the current collecting plate; Including, The solder is When melted by welding, the metal particles penetrate between the adjacent electrode tabs due to capillary action. The penetration distance of the solder is A subcell having an extension length shorter than that of the electrode tab.

2. a jelly-roll type electrode assembly having electrode tabs; a current collecting plate coupled to one side of the jelly-roll type electrode assembly and electrically connected to the electrode tab; a solder interposed between the electrode tab and the current collecting plate to connect the electrode tab and the current collecting plate, the solder having a melting point lower than that of the electrode tab and the current collecting plate; A subcell comprising: The solder is When melted by welding, the metal particles penetrate between the adjacent electrode tabs due to capillary action. The penetration distance of the solder is The extension length of the electrode tab is shorter than the extension length of the electrode tab. A subcell, wherein the distance that the solder penetrates between adjacent electrode tabs gradually decreases from the outer periphery of the jelly roll type electrode assembly toward the center of the roll.

3. The current collecting plate is 3. The subcell of claim 1 or 2, comprising a plurality of spaced apart subplates extending radially from a central portion.

4. The subplate is 4. The subcell of claim 3, wherein the width of the jelly roll-type electrode assembly is gradually narrowed from the outer periphery toward the center of the jelly roll-type electrode assembly.

5. A jelly-roll type electrode assembly having a plurality of spaced apart electrode tabs; a current collecting plate coupled to one side of the jelly roll type electrode assembly and electrically connected to the plurality of electrode tabs extending side by side on the one side; a solder that is confined within a space formed by the adjacent electrode tabs and one surface of the current collecting plate to join the electrode tabs and the current collecting plate and to join adjacent electrode tabs to each other, the solder having a melting point lower than that of the electrode tabs and the current collecting plate; Including, The current collecting plate is a plurality of spaced apart sub-plates extending radially from a central portion; The subplate is The jelly roll type electrode assembly has a shape in which its width gradually narrows from its outer circumferential surface toward its winding center, The solder is The subcell has a shape in which the width gradually narrows from the outer circumferential surface of the jelly roll type electrode assembly toward the center of the winding.

6. The jelly roll type electrode assembly has a structure in which a first electrode, a second electrode, and a separator interposed therebetween are wound in one direction, 6. The subcell according to claim 1 , wherein the first electrode and the second electrode each have a first uncoated portion and a second uncoated portion at a long side end portion, respectively, that are not coated with an active material and are exposed to the outside of the separator.

7. The subcell of claim 6 , wherein at least one of the first uncoated portion and the second uncoated portion functions as the electrode tab.

8. At least one of the first uncoated portion and the second uncoated portion includes a plurality of segments divided along a winding direction of the jelly-roll type electrode assembly, The subcell of claim 6 , wherein the plurality of segments are bent in a radial direction of the jelly-roll type electrode assembly.

9. The bent segments are The subcells of claim 8 , which are multiply stacked along the radial direction.

10. The jelly roll type electrode assembly is 10. The subcell of claim 9, further comprising a welding target area, the welding target area being an area where a number of overlapping segments provided in at least one of the first uncoated area and the second uncoated area is maintained constant along a radial direction of the jelly roll type electrode assembly.

11. The current collecting plate is The subcell of claim 10 , wherein the subcell is coupled to at least one of the first and second non-coated portions within the weld target area.

12. A subcell according to any one of claims 1 to 11; a battery can that houses the subcell through an opening on one side and is electrically connected to the jelly-roll type electrode assembly; A cylindrical secondary battery comprising:

13. The cylindrical secondary battery according to claim 12 , further comprising a terminal electrically connected to the jelly-roll type electrode assembly, having a polarity opposite to that of the battery can, and insulated from the battery can.

14. The terminal is The cylindrical secondary battery according to claim 13 , wherein the battery can is exposed to the outside through a closed part provided on the opposite side to the open part of the battery can.

15. The cylindrical secondary battery according to any one of claims 12 to 14, further comprising a cap plate that seals the open portion.

16. The cap plate is The cylindrical secondary battery according to claim 15 , which has no polarity.

17. A plurality of cylindrical secondary batteries according to any one of claims 12 to 16; a pack housing that houses a plurality of the cylindrical secondary batteries; Including the battery pack.

18. Each of the plurality of cylindrical secondary batteries is 18. The battery pack according to claim 17, comprising a terminal electrically connected to the jelly roll type electrode assembly, having a polarity opposite to that of the battery can, and insulated from the battery can.

19. 19 . The battery pack according to claim 18 , wherein an outer surface of the closure of the battery can of each of the plurality of cylindrical secondary batteries and the terminal of the battery can are arranged to face in the same direction.

20. The battery pack according to claim 19 , comprising a plurality of bus bars connecting a plurality of the cylindrical secondary batteries in series and in parallel.

21. the bus bars are disposed on top of the cylindrical secondary batteries, Each of the bus bars is a body portion extending between terminals of adjacent cylindrical secondary batteries; a plurality of first bus bar terminals extending in one direction of the body portion and electrically coupled to terminals of cylindrical secondary batteries located in the one direction; a plurality of second bus bar terminals extending in another direction of the body portion and electrically coupled to outer surfaces of the closing portions of cylindrical secondary batteries located in the other direction; 21. The battery pack of claim 20, comprising:

22. A motor vehicle comprising a battery pack according to any one of claims 17 to 21.

23. A step of preparing a jelly roll type electrode assembly (S1); A step (S2) of preparing a current collecting plate having solder formed on one surface thereof; placing the current collecting plate on the jelly roll type electrode assembly (S3); S4: melting the solder to weld the electrode tabs of the jelly-roll type electrode assembly to the current collecting plate and to weld the solder into the gaps between the adjacent electrode tabs, the welding being performed at a temperature lower than the melting points of the electrode tabs and the current collecting plate; Including, The solder is When melted by welding, the metal particles penetrate between the adjacent electrode tabs due to capillary action. The penetration distance of the solder is A method for manufacturing a subcell, the length of which is shorter than the extension length of the electrode tab.

24. A step of preparing a jelly roll type electrode assembly (S1); A step (S2) of preparing a current collecting plate having solder formed on one surface thereof; placing the current collecting plate on the jelly roll type electrode assembly (S3); (S4) performing welding to connect the electrode tabs and the current collecting plate of the jelly-roll type electrode assembly to each other by melting the solder, the welding being performed at a temperature lower than the melting points of the electrode tabs and the current collecting plate; A method for producing a subcell comprising: The step (S4) a step of melting the solder and allowing the solder to penetrate between adjacent electrode tabs by capillary action; The step (S2) A method for manufacturing a subcell, comprising: adjusting a thickness of the solder formed on one surface of the current collecting plate so that a penetration distance of the solder is smaller than an extension length of the electrode tab.

25. The step (S2) 25. The method for manufacturing a subcell according to claim 24, further comprising adjusting a thickness of the solder formed on one surface of the current collecting plate such that a distance by which the solder penetrates between adjacent electrode tabs gradually decreases from an outer circumferential surface toward a center of the jelly roll type electrode assembly.

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