Cylindrical secondary battery to which laser welding is applied, method for manufacturing the same, battery pack including such secondary battery, and motor vehicle

Abstract

A cylindrical secondary battery having an improved electrode terminal structure and a manufacturing method thereof are provided. The cylindrical secondary battery according to the present invention has an improved electrode terminal structure, and a first current collector and the electrode terminal are joined by a laser welding method. A laser weld formed on a contact surface between the first current collector and the electrode terminal is located within an overlapping portion of the first current collector and the electrode terminal in a winding center hole of an electrode assembly.

Description

Technical Field

[0001] The present invention relates to a cylindrical secondary battery and a method for manufacturing the same. The present invention also relates to a battery pack including such a cylindrical secondary battery and a motor vehicle.

[0002] This application claims priority based on Korean Patent Application No. 10-2021-0136997 filed on October 14, 2021, and Korean Patent Application No. 10-2022-0021589 filed on February 18, 2022, and all of the content disclosed in the specifications and drawings of the applications is incorporated into this application.

Background Art

[0003] Secondary batteries that are easy to apply according to product groups and have electrical characteristics such as high energy density are not only applicable to portable devices, but also universally applicable to electric vehicles (EVs), hybrid electric vehicles (HEVs), etc. driven by an electric drive source. Such secondary batteries are attracting attention as a new energy source not only because of the primary advantage of significantly reducing the use of fossil fuels, but also because they are environmentally friendly and can improve energy efficiency in that they do not produce any by-products associated with the use of energy.

[0004] As types of secondary batteries, cylindrical, prismatic, and pouch-type secondary batteries are known. In the case of a cylindrical secondary battery, a separator, which is an insulator, is interposed between a positive electrode and a negative electrode, and it is wound up to form a jelly roll-shaped electrode assembly, and this is inserted into the inside of a battery can together with an electrolyte to constitute a battery. And, strip-shaped electrode tabs may be connected to the non-coated portions of each of the positive electrode and the negative electrode, and the electrode tabs connect the electrode assembly and an electrode terminal exposed to the outside. However, according to a conventional cylindrical secondary battery having such a structure, current concentrates on the strip-shaped electrode tabs that are coupled to the positive electrode non-coated portion and / or the negative electrode non-coated portion, resulting in a problem of high resistance, much heat generation, and poor current collection efficiency.

[0005] Small cylindrical secondary batteries with form factors of 18650 or 21700 do not have significant problems with resistance and heat generation. However, when increasing the form factor for applying cylindrical secondary batteries to electric vehicles, etc., a large amount of heat may be generated around the current collector tab during the rapid charging process, leading to the problem of the cylindrical secondary battery catching fire. Here, the form factor means a value indicating the diameter and height of the battery. In the numerical value indicating the form factor, the first two digits represent the diameter of the cell, the next two digits represent the height of the cell, and the last digit 0 indicates that the cross-section of the cell is circular. When the height of the cell exceeds 100 mm, three digits are required to indicate the height of the cell, so the last digit 0 can be omitted.

[0006] In a cylindrical secondary battery with an increased form factor, in order to solve the problems of resistance and heat generation, a cylindrical secondary battery (so-called Tab-less cylindrical secondary battery) having a structure with improved current collection efficiency using a current collector plate with a larger area than a strip-shaped electrode tab is presented.

[0007] Figures 1 to 3 are diagrams showing the manufacturing process of a conventional Tab-less cylindrical secondary battery. Figure 1 shows the structure of the electrode plate, Figure 2 shows the winding process of the electrode plate, and Figure 3 shows the process of welding the current collector plate to the folded surface of the non-coated part. Figure 4 is a cross-sectional view of a conventional Tab-less cylindrical secondary battery cut in the longitudinal direction (Y direction).

[0008] Referring to Figure 1, the positive electrode plate 10 and the negative electrode plate 11 have a structure in which the active material 21 is coated on the sheet-shaped current collector 20, and include a non-coated part 22 where the active material is not coated on one long side along the winding direction (X direction). In the direction (X direction) along the long side of the current collector 20, one side becomes the core and the other side becomes the outer periphery.

[0009] The electrode assembly A is manufactured by sequentially laminating a positive electrode plate 10 and a negative electrode plate 11 together with two separator membranes 12 as shown in FIG. 2, and then winding them up from the core in one direction (the X direction). At this time, the non-coated portions of the positive electrode plate 10 and the negative electrode plate 11 are arranged in opposite directions in the direction (the Y direction) along the short side of the current collector 20.

[0010] Referring to FIG. 3, a winding center hole 13 is formed in the inner core of the electrode assembly A manufactured by the method of FIG. 2. After the winding process, the non-coated portion 10a of the positive electrode plate 10 and the non-coated portion 11a of the negative electrode plate 11 are bent toward the core side. Then, current collector plates 30 and 31 are connected to the non-coated portions 10a and 11a.

[0011] Another electrode tab is not coupled to each of the non-coated portions 10a and 11a, and the current collector plates 30 and 31 are connected to external electrode terminals, and a current path is formed with a large cross-sectional area along the winding axis direction (refer to the arrow) of the electrode assembly A. Therefore, there is an advantage in that the resistance of the secondary battery can be reduced. This is because the resistance is inversely proportional to the cross-sectional area of the path through which the current flows.

[0012] However, if the form factor of the cylindrical secondary battery increases and the magnitude of the charging current becomes large during rapid charging, a heat generation problem also occurs in the tabless cylindrical secondary battery.

[0013] Specifically, as shown in FIG. 4, a conventional tabless cylindrical secondary battery 40 includes a battery can 41 and a sealing body 42. The sealing body 42 includes a cap plate 42a, a sealing gasket 42b, and a connection plate 42c. The sealing gasket 42b surrounds the periphery of the cap plate 42a and is fixed by a crimping portion 43. Also, the electrode assembly A is fixed in the battery can 41 by a beading portion 44 to prevent up and down movement.

[0014] Generally, the positive electrode terminal is the cap plate 42a of the sealing body 42, and the negative electrode terminal is the battery can 41. Thus, the current collector plate 30 coupled to the non-coated portion 10a of the positive electrode plate 10 is connected to the connection plate 42c attached to the cap plate 42a via the strip-shaped lead 45. Also, the current collector plate 31 coupled to the non-coated portion 11a of the negative electrode plate 11 is connected to the bottom of the battery can 51. The insulator 46 covers the current collector plate 30 to prevent the battery can 51 with a different polarity and the non-coated portion 10a of the positive electrode plate 10 from coming into contact with each other and causing a short circuit.

[0015] In the cylindrical secondary battery 40, when the current collector plate 30 is connected to the connection plate 42c, the strip-shaped lead 45 is used. The lead 45 is separately attached to the current collector plate 30 or is manufactured integrally with the current collector plate 30. However, since the lead 45 is in the form of a thin strip, its cross-sectional area is small, and when a rapid charging current flows, a large amount of heat is generated. Also, the excessive heat generated in the lead 45 is transmitted to the electrode assembly A side, and may cause an internal short circuit, which is a major cause of thermal runaway, by shrinking the separator (12 in FIG. 2).

[0016] Note that the lead 45 occupies a considerable installation space inside the battery can 41. As a result, the cylindrical secondary battery 40 including the lead 45 has low space efficiency and is limited in increasing the energy density. Therefore, in this technical field, it is required to solve the heat generation problem of the cylindrical secondary battery and improve the structure of the electrode terminals to increase the space efficiency inside the battery can.

[0017] On the other hand, the cylindrical secondary battery 40 includes current collector plates 30 and 31, and connection sites between each of the current collector plates 30 and 31 and other components exist in the upper and lower portions of the cylindrical secondary battery 40. Various welding processes can be used for connecting each of the current collector plates 30 and 31 and other components at this position. At this time, it is important to weld with high efficiency and achieve appropriate bonding strength without causing damage to the welded object and surrounding components.

[0018] In the welding process, when resistance welding is used and the workpieces to be welded are made of aluminum materials, an oxide film adheres to the welding rod, making continuous welding impossible. Furthermore, when such an oxide film adheres, heat generation occurs in the welding rod even before heat is generated in the workpieces to be welded. If either of the current collectors 30 or 31 is made of an aluminum material, using resistance welding due to such problems will only reduce the efficiency of the welding process. And if either of the current collectors 30 or 31 is made of a copper material, since the resistance of copper is low and it is difficult to generate resistance heat, there are also problems such as poor welding, such as a decrease in joint strength. Also, since the resistance welding apparatus applies current in a state where the workpieces to be welded are sandwiched between the upper welding rod and the lower welding rod, pressurized and brought into close contact, pressure is essential. If the pressure is insufficient, there is a problem of partial welding, which induces quality variations, and there is also a risk of deforming the parts due to the pressure.

[0019] In addition, in the welding process, when ultrasonic welding is used, the horn must contact and vibrate at the contact part. However, if the vibration direction of the horn is in a linear or zigzag form, there is a high risk of the horn breaking. For example, when ultrasonic welding the current collector 31 to the bottom of the battery can 41 in the cylindrical secondary battery 40, since the horn must be inserted through the winding center hole 13 of the electrode assembly A for welding, the ultrasonic welding horn needs to have a length longer than the length from one end to the other end of the winding center hole 13. Thus, when strong vibration occurs in a linear or zigzag direction, there is a high risk of the horn breaking. Considering this, a method in which the horn rotates can be applied, but in this case as well, there are problems such as a large amount of burrs being generated and it being difficult to confirm the presence or absence of partially unbonded regions. Furthermore, in the case of ultrasonic welding, problems due to foreign matter (slag) generated during welding can also occur. Also, ultrasonic welding has a problem that the joint strength is lower compared to resistance welding.

[0020] Therefore, in the manufacturing method of a tabless cylindrical secondary battery in which there is a connection part between the current collector plate and other components and the connection is to be made by a welding method, it is necessary to apply a welding technique different from the conventional welding methods described above.

Summary of the Invention

Problems to be Solved by the Invention

[0021] The present invention was conceived under the background of the above-described prior art. The problem to be solved by the present invention is to provide a cylindrical secondary battery having an improved electrode terminal structure.

[0022] Another problem to be solved by the present invention is to provide a method for manufacturing a cylindrical secondary battery having an improved electrode terminal structure using a laser welding method.

[0023] Still another problem to be solved by the present invention is to provide a battery pack manufactured using a cylindrical secondary battery having an improved structure and an automobile including the same.

[0024] It should be noted that the technical problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description of the invention.

Means for Solving the Problems

[0025] The cylindrical secondary battery according to the present invention for achieving the above object is a jelly roll type electrode assembly having a structure in which a sheet-like first electrode plate, a second electrode plate, and a separator interposed therebetween are wound in one direction. The first electrode plate includes a non-coated portion exposed outside the separator at a long-side end portion. The second electrode plate includes a non-coated portion exposed outside the separator in a direction opposite to the non-coated portion of the first electrode plate at a long-side end portion. The electrode assembly has a winding center hole in an inner core. A cylindrical battery can that houses the electrode assembly from an opening formed on one side and is connected to the non-coated portion of the second electrode plate. A sealing body that seals the opening of the battery can in an insulating manner. A first current collector plate connected to the non-coated portion of the first electrode plate. An electrode terminal that is riveted through a through hole formed in a bottom portion of the battery can located on the opposite side of the opening of the battery can and is connected to the first current collector plate. A laser welding portion formed on a contact surface between the first current collector plate and the electrode terminal. The laser welding portion is located at a superimposed portion of the first current collector plate and the electrode terminal within the winding center hole.

[0026] Desirably, the converted diameter of the laser welding portion exposed on the surface of the first current collector plate is 0.15D to 0.90D (D: the diameter of the winding center hole).

[0027] Desirably, the electrode terminal may include a main body portion inserted into the through hole, an external flange portion extending along the outer surface from a peripheral edge of one side of the main body portion exposed on the outer surface of the bottom portion of the battery can, an internal flange portion extending toward the inner surface from a peripheral edge of the other side of the main body portion exposed on the inner surface of the bottom portion of the battery can, and a flat portion provided inside the internal flange portion.

[0028] Desirably, in the flat portion, the electrode terminal and the first current collector plate are joined by the laser welding portion.

[0029] In one form, the laser welding part is formed from one surface of the first current collector plate facing the inside of the winding center hole toward the electrode terminal side at the coupling part between the first current collector plate and the electrode terminal.

[0030] The outer surface of the electrode terminal may be a smooth surface.

[0031] In another form, the laser welding part may be an overlap type of welding bead with respect to the center of the winding center hole.

[0032] In still another form, the laser welding part may be composed of a linear shape.

[0033] At this time, the laser welding part may form a continuous closed straight line or closed curve. For example, the laser welding part may be either a circular type centered on the center of the winding center hole or a wobble circle type centered on the center of the winding center hole. Also, the laser welding part may form an open curve. For example, it may be in a form where one sector is open based on a quarter plane. For example, it may be in a C shape or the like.

[0034] In still another form, the laser welding part may be a multi-spot type formed at symmetric positions radially with respect to the center of the winding center hole.

[0035] In still another form, the laser welding part may be any one of an X-type where two lines intersect at the center of the winding center hole, a square frame type centered on the center of the winding center hole, an L-type where two lines touch at a point, and an 8-type where two circles are circumscribed.

[0036] In still another form, the laser welding part may have a center at the center of the winding center hole, have a regular or negative outer periphery in the shape of a polygon, and form a welding bead in a weaving manner to fill the inside of the outer periphery.

[0037] Desirably, the tensile force of the welded portion between the first current collector plate and the electrode terminal by the laser welding portion can be 3 kgf or more and 15 kgf or less.

[0038] In one form, the first current collector plate and the electrode terminal may be made of a material mainly composed of aluminum.

[0039] In another form, the diameter of the winding center hole can be 2 mm or more and 8 mm or less.

[0040] At this time, the equivalent diameter of the laser welding portion exposed on the surface of the first current collector plate can be 2 mm or more.

[0041] Here, the diameter of the flat portion of the electrode terminal can be 3 mm to 14 mm.

[0042] In such a case, the ratio of the area of the laser welding portion exposed on the surface of the first current collector plate to the area of the flat portion of the electrode terminal can be 2.04% to 44.4%.

[0043] In yet another form, the inner surfaces of the flat portion and the bottom portion can be parallel to each other.

[0044] In yet another form, the angle formed by the inner flange portion and the inner surface of the bottom portion can be 0° to 60°.

[0045] Desirably, a recess portion can be provided between the inner flange portion and the flat portion.

[0046] In one form, the recess portion can have a cross-sectional structure of an asymmetric groove.

[0047] In another form, the asymmetric groove can include an inclined surface of the inner flange portion connected to the side wall end portion of the flat portion.

[0048] In yet another form, the side wall can be perpendicular to the inner surface of the bottom portion.

[0049] In still other forms, the side wall may be inclined toward the flat portion.

[0050] Desirably, the thickness of the inner flange portion may decrease as it moves away from the main body portion.

[0051] Desirably, the cylindrical secondary battery further includes a rivet gasket interposed between the electrode terminal and the through hole. The rivet gasket includes an external gasket interposed between the external flange portion and the outer surface of the bottom portion, and an internal gasket interposed between the inner flange portion and the inner surface of the bottom portion. The thickness of the internal gasket may vary depending on the position.

[0052] In one form, in the region of the internal gasket, the thickness of the region interposed between the inner edge of the through hole connected to the inner surface of the bottom portion and the inner flange portion may be relatively smaller than that of other regions.

[0053] In other forms, in the region of the internal gasket, the thickness of the region interposed between the through hole and the main body portion may decrease as it moves away from the external flange portion.

[0054] In still other forms, in the region of the internal gasket, the thickness of the region interposed between the inner surface of the bottom portion and the vicinity of the end of the inner flange portion may be the thinnest.

[0055] In still other forms, the inner edge of the through hole may include an opposing surface facing the inner flange portion.

[0056] In still other forms, the internal gasket may extend longer than the inner flange portion and the end portion may be exposed.

[0057] In still other forms, based on the inner surface of the bottom portion, the height of the flat portion may be the same as or greater than the height of the end portion of the internal gasket.

[0058] In still other forms, based on the inner surface of the bottom portion, the height of the flat portion may be the same as or greater than the height of the inner flange portion.

[0059] In still other forms, the height of the inner flange portion may be 0.5 mm to 3.0 mm based on the inner surface of the bottom of the battery can.

[0060] Desirably, the height of the electrode terminal from the lower surface of the outer flange portion to the surface of the flat portion may be 1.5 mm to 7 mm.

[0061] Desirably, the height of the outer flange portion may be 0.8 mm or more based on the outer surface of the bottom of the battery can.

[0062] Desirably, at least a part of the outer gasket is exposed outside the outer flange portion, and the exposed width of the outer gasket measured in a direction parallel to the outer surface of the bottom of the battery can may be 0.1 mm to 1 mm.

[0063] Desirably, the radius from the center of the main body portion to the periphery of the outer flange portion may be 10% to 70% based on the radius of the bottom of the battery can.

[0064] Desirably, the radius from the center of the main body portion to the periphery of the flat portion may be 4% to 30% based on the radius of the bottom portion.

[0065] Desirably, when the ratio of the change amount of the thickness at the maximum compression point to the thickness of the gasket before compression is defined as the compression rate, the compression rate of the inner gasket may be 30% to 90%.

[0066] More desirably, the inner gasket contains polybutylene terephthalate, polytetrafluoroethylene or polypropylene, and the compression rate of the inner gasket may be 50% to 90%.

[0067] In one form, the first current collector includes an edge portion, a first current collector coupling portion that extends inward from the edge portion and is coupled to the non-coated portion of the first electrode plate, and a terminal coupling portion that is spaced apart from the first current collector coupling portion, and the electrode terminal can be coupled to the terminal coupling portion.

[0068] Desirably, the cylindrical secondary battery further includes an insulator interposed between the battery can and the first current collector, and the electrode terminal can penetrate the insulator and be coupled to the terminal coupling portion.

[0069] More desirably, the cylindrical secondary battery further includes an insulator interposed between the first current collector and the inner peripheral surface of the bottom of the battery can and between the inner peripheral surface of the side wall of the battery can and the electrode assembly.

[0070] The insulator includes a welding hole that exposes the flat portion of the electrode terminal to the first current collector side, and can cover the surface of the first current collector and the peripheral edge of one side of the electrode assembly.

[0071] Desirably, the height from the inner surface of the bottom of the battery can to the flat portion of the electrode terminal can be the same as or smaller than the thickness of the insulator.

[0072] Desirably, the cylindrical secondary battery further includes a rivet gasket interposed between the electrode terminal and the through hole, and the rivet gasket can include an external gasket interposed between the external flange portion and the outer surface of the bottom, and an internal gasket interposed between the internal flange portion and the inner surface of the bottom.

[0073] Desirably, the end portion of the internal gasket can be exposed outside the internal flange portion.

[0074] In still another form, the welding hole can expose the flat portion and the internal flange portion of the electrode terminal.

[0075] In yet another form, the welding hole may expose the flat portion and the inner flange portion of the electrode terminal and the inner gasket.

[0076] In yet another form, the ratio of the form factor obtained by dividing the diameter of the cylindrical secondary battery by the height may be greater than 0.4.

[0077] In one form, the edge portion may have a rim form in which at least a part of the inner region is vacant.

[0078] Desirably, the first electrode plate coupling portion and the terminal coupling portion may be connected by the edge portion.

[0079] Also, the terminal coupling portion may be located at the center of the inner space of the edge portion.

[0080] Desirably, a plurality of the first electrode plate coupling portions may be included.

[0081] In this case, the plurality of first electrode plate coupling portions may be arranged at equal intervals along the circumferential direction.

[0082] Subsequently, the extension lengths of each of the plurality of first electrode plate coupling portions may be the same as each other.

[0083] Furthermore, the terminal coupling portion may be arranged so as to be surrounded by the plurality of first electrode plate coupling portions.

[0084] Desirably, the terminal coupling portion may be arranged at a position corresponding to the winding center hole.

[0085] Desirably, at least a partial section of the non-coated portion of the first electrode plate is divided into a plurality of segmented pieces, and the plurality of segmented pieces may be bent along the radial direction of the electrode assembly.

[0086] Desirably, the plurality of segmented pieces may be stacked multiple times along the radial direction of the electrode assembly.

[0087] In one form, the first current collector includes an edge portion, a first current collector coupling portion that extends inward from the edge portion and couples to the non-coated portion of the first electrode plate, and a terminal coupling portion that is spaced apart from the first current collector coupling portion, and the first current collector coupling portion can couple to a region where the plurality of segmented pieces are multiply stacked.

[0088] In another form, the battery can includes a beading portion formed at an end adjacent to the opening portion and press-fitted inward, and the sealing body can include a non-polar cap plate and a sealing gasket interposed between the peripheral edge of the cap plate and the opening portion of the battery can.

[0089] The battery can further includes a crimping portion that extends and is bent inward of the battery can and surrounds and fixes the peripheral edge of the cap plate together with the sealing gasket.

[0090] The cap plate can include a vent notch that ruptures when the pressure inside the battery can exceeds a critical value.

[0091] The vent notch can rupture when the pressure inside the battery can reaches 15 - 35 kgf / cm 2 2.

[0092] In still another form, it further includes a second current collector that couples to the non-coated portion of the second electrode plate, and at least a part of the edge portion of the second current collector that does not contact the non-coated portion of the second electrode plate is interposed between the beading portion and the sealing gasket and can be fixed by the crimping portion.

[0093] At least a part of the edge portion of the second current collector can be fixed to the inner peripheral surface of the beading portion adjacent to the crimping portion by welding.

[0094] In still another form, at least a partial section of the non-coated portion of the second electrode plate is divided into a plurality of segmented pieces, and the plurality of segmented pieces can be bent in the radial direction of the electrode assembly.

[0095] At this time, the plurality of segmented pieces can be superposed multiple times along the radial direction of the electrode assembly.

[0096] In such a case, the second current collector plate includes a second electrode plate coupling portion that couples to the non-coated portion of the second electrode plate, and a can coupling portion that is electrically coupled to the beading portion, and the second electrode plate coupling portion can be coupled to a region where the plurality of segmented pieces are superposed multiple times.

[0097] The second electrode plate coupling portion and the can coupling portion are indirectly connected through the central portion of the second current collector plate and may not be directly connected to each other.

[0098] The second electrode plate coupling portion may include at least one liquid injection hole.

[0099] The second current collector plate may include a circular current collector plate hole at the central portion of the second current collector plate.

[0100] The diameter of the current collector plate hole may be the same as or larger than the diameter of the winding center hole.

[0101] In addition, the present invention also provides a method for manufacturing a cylindrical secondary battery. The method for manufacturing a cylindrical secondary battery according to the present invention is a jelly roll type electrode assembly having a structure in which a sheet-like first electrode plate, a second electrode plate, and a separator interposed therebetween are wound in one direction. The first electrode plate includes an uncoated portion exposed to the outside of the separator at a long side end, and the second electrode plate includes an uncoated portion exposed to the outside of the separator in a direction opposite to the uncoated portion of the first electrode plate at a long side end. Providing an electrode assembly having a winding center hole in the inner core; Connecting a first current collector to the uncoated portion of the first electrode plate; Providing a cylindrical battery can including an electrode terminal riveted through a through hole formed in the bottom of the battery can located on the opposite side of the open portion of the battery can, the electrode terminal being formed on one side; Inserting the electrode assembly into the battery can so that the first current collector faces the bottom of the battery can; Forming a laser welding portion on a contact surface between the first current collector and the electrode terminal using a laser welding device, wherein the laser beam of the laser welding device is irradiated into the winding center hole along the longitudinal direction of the winding center hole.

[0102] In one embodiment, the laser welding device may be one that welds the first current collector to the electrode terminal in a pulse mode or a continuous mode.

[0103] The laser welding device may be one that irradiates a laser beam with a pulse width of 100 ns to 2,000 ns.

[0104] The laser welding device may be one that irradiates a laser beam with an output of 50 W to 4 kW.

[0105] The laser welding device may be one that irradiates a laser beam at a processing speed of 40 mm / s to 1,000 mm / s.

[0106] The spot diameter of the laser beam of the laser welding device may be 10 μm to 200 μm.

[0107] Desirably, a laser beam in a pulsed dot pattern may be superimposed and irradiated on the central portion of the winding center hole to form a superimposed overlay type laser welded portion.

[0108] Desirably, the step of forming the laser welded portion may include inserting a hollow tube into the winding center hole, at least a part of the first current collector being exposed in the inner hollow portion of the hollow tube, and the laser beam emitted from the laser welding apparatus passing through the inner hollow portion of the hollow tube to weld the first current collector to the electrode terminal.

[0109] At this time, the first current collector may be pressed against the electrode terminal by the hollow tube.

[0110] During the welding by the laser, an inert gas for removing the oxygen atmosphere may be supplied using the space between the hollow tube and the inner peripheral surface of the winding center hole.

[0111] The length of the hollow tube is greater than the height of the electrode assembly, and the hollow tube may be a metal hollow tube.

[0112] Also, during the welding by the laser, a step of removing welding fume may be included on one end side of the winding center hole.

[0113] In addition, the method for manufacturing a cylindrical secondary battery according to the present invention is a method for manufacturing a cylindrical secondary battery according to the present invention, characterized in that the step of forming the laser welded portion is a step of irradiating and welding a laser beam using the winding center hole inside the battery can.

[0114] Here, the laser beam can heat from the first current collector.

[0115] A temperature difference may be given between the portion where the laser beam is intensively irradiated and its peripheral portion.

[0116] After being preheated by the laser beam, full melting can be caused to occur.

[0117] The laser beam preferably is a single mode.

[0118] The present invention also provides a battery pack including at least one such cylindrical secondary battery, and a motor vehicle including at least one such battery pack.

Advantages of the Invention

[0119] According to one aspect of the present invention, by improving the electrode terminal structure of the cylindrical secondary battery to increase the space efficiency inside the battery can, the internal resistance of the cylindrical secondary battery can be reduced and the energy density can be increased.

[0120] According to another aspect of the present invention, by improving the electrode terminal structure of the cylindrical secondary battery to expand the cross-sectional area of the current path, the problem of internal heat generation occurring during rapid charging can be improved.

[0121] According to still another aspect of the present invention, it is possible to perform the electrical wiring work for the series and / or parallel connection of the cylindrical secondary batteries on one side of the cylindrical secondary battery. As a result, the space efficiency is high and the efficiency of the electrical wiring is high, so that a significant work improvement effect is achieved in the assembly process of the electric vehicle and the main maintenance of the battery pack.

[0122] According to still another aspect of the present invention, there is provided a cylindrical secondary battery including a first current collector having a structure in which force does not concentrate on the coupling site between components even when external impact and / or vibration is applied during use, and / or a coupling force at the coupling site with the battery can, and a second current collector for improving the energy density of the cylindrical secondary battery. Such a first current collector and a second current collector have a structure that is easy to laser-weld the first current collector to the electrode terminal. Therefore, the mechanical and electrical performance of the cylindrical secondary battery is improved, and it becomes easy to manufacture such a secondary battery by a welding method.

[0123] The manufacturing method according to the present invention is very suitable for large-sized batteries with an increased form factor. Since the jelly roll type electrode assembly included in the large-sized battery has a greater height than before, the length of its winding center hole also becomes greater than before. To connect the first current collector plate to the electrode terminal by welding on the bottom side of the battery can, it is necessary to prevent damage to the electrode assembly during the welding process. In the manufacturing method according to the present invention, a laser beam can be irradiated while preventing damage to the electrode assembly on the first current collector plate portion placed in the long winding center hole. According to the present invention, since the problem of defects that may occur due to laser welding is solved and the first current collector plate can be welded to the electrode terminal, the requirements for high-output low-resistance batteries in the technical field to which the present invention belongs can be satisfied.

[0124] According to the manufacturing method of the present invention, when welding the electrode terminal to the first current collector plate, problems such as damage to the welded body and peripheral components and a decrease in joint strength that may occur when simply following the conventional welding method can be solved, thereby enhancing the processability and efficiency of welding.

[0125] According to the manufacturing method of the present invention, without causing problems due to the material of the current collector plate and without the risk of breaking the horn for welding, the connection and bonding between the current collector plate and other components can be performed. Furthermore, since no welding part is formed on the outer surface of the cylindrical secondary battery, during the electrical wiring work for the series and / or parallel connection of the cylindrical secondary batteries, the connection effect between the cylindrical secondary battery and the bus bar component can be more advantageously ensured.

[0126] The following drawings attached to this specification illustrate desirable embodiments of the present invention and serve to further understand the technical idea of the present invention together with the detailed description of the invention. Therefore, the present invention should not be construed as being limited only to the matters described in the drawings.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0128] Hereinafter, preferred embodiments 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 the claims should not be construed as being limited to ordinary or dictionary meanings. The inventor himself must interpret them in accordance with the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that he can appropriately define the concept of the terms in order to explain the invention in the best way.

[0129] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. At the time of this application, there may be various equivalents and modifications that can replace them.

[0130] In addition, for the purpose of assisting in the understanding of the invention, the attached drawings may show some components exaggerated rather than at actual scale. Note that the same reference numerals may be assigned to the same components in different embodiments.

[0131] FIG. 5 is a cross-sectional view of a cylindrical secondary battery according to an embodiment of the present invention cut along the longitudinal direction (Y direction).

[0132] Referring to FIG. 5, a cylindrical secondary battery 70 according to an embodiment of the present invention includes a jelly roll type electrode assembly 71. The electrode assembly 71 has a structure in which a sheet-like first electrode plate, a second electrode plate, and a separator interposed therebetween are wound in one direction. When illustrating the electrode assembly 71 in FIG. 5, only the non-coated portions 72 and 73 exposed and extending outside the separator are shown in detail, and the illustration of the winding structure of the first electrode plate, the second electrode plate, and the separator is omitted.

[0133] A winding center hole 80 is formed in the inner core of the electrode assembly 71. The winding center hole 80 is a portion where the core that becomes the winding axis is extracted when the electrode plate and the separator are wound. If there is no deformation of the electrode assembly 71 after extracting the core, it can be said that the diameter of the winding center hole 80 is the same as the diameter of the core.

[0134] The method of winding the electrode assembly 71 is substantially the same as the method of winding the electrode assembly used in the manufacture of the tabless cylindrical secondary battery according to the prior art described with reference to FIG. 2.

[0135] The first electrode plate and the second electrode plate have a structure in which an active material layer is coated on one or both surfaces of a sheet-shaped current collector having a long side and a short side, and include non-coated portions 72 and 73 at the ends on one long side along the winding direction X, respectively. The non-coated portions 72 and 73 can be continuously formed along one side end of the current collector. The first electrode plate includes a non-coated portion 73 exposed outside the separator at the long side end, and the second electrode plate includes a non-coated portion 72 exposed outside the separator in the direction opposite to the non-coated portion 73 of the first electrode plate at the long side end. That is, the non-coated portion 72 of the second electrode plate is exposed at the lower part of the electrode assembly 71, and the non-coated portion 73 of the first electrode plate is exposed at the upper part. In the embodiment, the first electrode plate may be a positive electrode plate and the second electrode plate may be a negative electrode plate. Of course, the opposite case is also possible.

[0136] In one embodiment of the present invention, the current collector can be appropriately selected according to the polarity of the electrode plate. As the material, aluminum, copper, nickel, or stainless steel can be used, but it is not necessarily limited to these, and metals and metal alloys used as ordinary current collector materials can be adopted. For example, the current collector for the positive electrode plate may be aluminum or an aluminum alloy, and the current collector for the negative electrode plate may be copper or a copper alloy.

[0137] In one embodiment of the present invention, the active material coated on the current collector can be used without limitation as long as it is a known active material in the industry.

[0138] In one example, the positive electrode active material has the general chemical formula A[A x M y O 2+z(A contains at least one element of Li, Na, and K; M contains at least one element selected from Ni, Co, Mn, Ca, Mg, Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, Mo, Sc, Zr, Ru, and Cr; x≧0, 1≦x + y≦2, -0.1≦z≦2; the stoichiometric coefficients x, y, and z are selected so that the compound maintains electrical neutrality.) may contain an alkali metal compound represented thereby.

[0139] Desirably, the positive electrode active material contains a lithium transition metal oxide. It may contain a nickel-cobalt-manganese-based lithium oxide, among which a high-concentration nickel-cobalt-manganese-based lithium oxide with a high nickel content among the transition metals.

[0140] In other examples, the positive electrode active material is an alkali metal compound xLiM disclosed in US6,677,082, US6,680,143, etc. 1 O2-(1 - x)Li2M 2 O3(M 1 contains at least one element having an average oxidation state of 3; M 2 contains at least one element having an average oxidation state of 4; 0≦x≦1).

[0141] In still other examples, the positive electrode active material has the general chemical formula Li a M 1 x Fe 1‐x M 2 y P 1‐y M 3 z O 4‐z (M 1 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Mg, and Al; M 2 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Mg, Al, As, Sb, Si, Ge, V, and S; M 3contains a halogen group element selectively containing F; 0 < a ≤ 2, 0 ≤ x ≤ 1, 0 ≤ y < 1, 0 ≤ z < 1; the stoichiometric coefficients a, x, y, and z are selected so that the compound maintains electrical neutrality.), or it can be a lithium metal phosphate represented by Li3M2(PO4)3 [M contains at least one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Mg, and Al.].

[0142] Desirably, the positive electrode active material may contain primary particles and / or secondary particles formed by aggregation of primary particles.

[0143] In one example, as the negative electrode active material, a carbon material, a lithium metal or a lithium metal compound, silicon or a silicon compound, tin or a tin compound, etc. can be used. Metal oxides such as TiO2 and SnO2 with a potential of less than 2V can also be used as the negative electrode active material. As the carbon material, both low-crystalline carbon and high-crystalline carbon can be used.

[0144] The separation membrane can be used alone or in a laminated form of a porous polymer film, for example, a porous polymer film made from polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, etc. In another example, the separation membrane can use a normal porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc.

[0145] At least one surface of the separation membrane may include a coating layer of inorganic particles. Also, the separation membrane itself can be composed of a coating layer of inorganic particles. The particles constituting the coating layer may have a structure bonded to a binder so that an interstitial volume exists between adjacent particles.

[0146] The inorganic particles can be made of an inorganic substance with a dielectric constant of 5 or more. As this non-limiting example, the inorganic particles are Pb(Zr,Ti)O3 (PZT), Pb1-x La x Zr 1-y Ti y O3 (PLZT), PB(Mg3Nb 2 / 3 )O3-PbTiO3 (PMN-PT), BaTiO3, HfO2, SrTiO3, TiO2, Al2O3, ZrO2, SnO2, CeO2, MgO, CaO, ZnO, and Y2O3, and may contain at least one substance selected from the group consisting of.

[0147] As shown in the figure, in the electrode assembly 71, the non-coated portions 72 and 73 are arranged in opposite directions to each other. And each non-coated portion 72, 73 is exposed to the outside of the separation membrane. Such an electrode assembly 71 may have at least a part of each non-coated portion 72, 73 used as an electrode tab. For example, the non-coated portion 72 of the second electrode plate may be used as a negative electrode tab, and the non-coated portion 73 of the first electrode plate may be used as a positive electrode tab.

[0148] Further, the cylindrical secondary battery 70 includes a cylindrical battery can 51 that houses the electrode assembly 71 and is connected to the non-coated portion 72 of the second electrode plate. The battery can 51 is made of a conductive metal material. In one example, the battery can 51 may be made of iron, nickel-plated iron, or stainless steel (SUS), but the present invention is not limited thereto.

[0149] Desirably, one side (the lower part in this embodiment) of the battery can 51 is open to form an open portion. The opposite side of the open portion in the battery can 51 becomes a closed portion. In this embodiment, the closed portion is the bottom 52 of the battery can 51. The bottom 52 of the battery can 51 is circular. The side surface (outer peripheral surface) of the battery can 51 and the bottom 52 may be integrally formed. The bottom 52 of the battery can 51 has a generally flat form. The battery can 51 houses the electrode assembly 71 from the open portion and also houses the electrolyte. The side surface of the battery can 51 extends a certain length from the bottom 52.

[0150] The electrolyte serves to make lithium ions generated by an electrochemical reaction at the electrode plates inside the secondary battery during charge and discharge movable. The electrolyte is A+ B - It may be a salt having a structure such as A + is Li + Na + K + and contains ions composed of alkali metal cations such as these or combinations thereof. And B - is F - Cl - Br - I - NO3 - N(CN)2 - BF4 - ClO4 - AlO4 - AlCl4 - PF6 - SbF6 - AsF6 - BF2C2O4 - BC4O8 - (CF3)2PF4 - CF3)3PF3 - CF3)4PF2 - CF3)5PF - CF3)6P - CF3SO3 - C4F9SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN- and (CF3CF2SO2)2N - and contains any one or more anions selected from the group consisting of

[0151] In addition, the electrolyte can be used by being dissolved in an organic solvent. Examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone, or a mixture thereof.

[0152] The bottom 52 of the battery can 51 has a structure in which the electrode terminal 50 is riveted to the through-hole 53 by a caulking process. Further, the cylindrical secondary battery 70 may include a rivet gasket 54 interposed between the electrode terminal 50 and the through-hole 53.

[0153] The electrode terminal 50 is made of a conductive metal material. In one example, the electrode terminal 50 may be made of a material mainly composed of aluminum, but the present invention is not limited thereto. The electrode terminal 50 may be made of a 10-series aluminum alloy that is easy to rivet and has low resistance. A part of the electrode terminal 50 is inserted inside the battery can 51, and the other part is exposed outside the battery can 51.

[0154] The rivet gasket 54 may be made of a polymer resin having insulation and elasticity. In one example, the rivet gasket 54 may be made of polypropylene, polybutylene terephthalate, polyfluorinated ethylene, etc., but the present invention is not limited thereto.

[0155] The cylindrical secondary battery 70 includes a first current collector plate 79 connected to the non-coated portion 73 of the first electrode plate. The connection between the non-coated portion 73 of the first electrode plate and the first current collector plate 79 can be made by a welding method. The first current collector plate 79 is also connected to the electrode terminal 50. The first current collector plate 79 and the electrode terminal 50 are connected by a laser welding method. The first current collector plate 79 can be made of the same metal as the current collector of the first electrode plate and / or the electrode terminal 50, or a material that is easily weldable to them. For example, the first current collector plate 79 can be made of a material mainly composed of aluminum, and can be iron, nickel-plated iron, or SUS, etc. The electrode terminal 50 is connected to the non-coated portion 73 of the first electrode plate via the first current collector plate 79.

[0156] A laser welded portion (not shown) by laser welding is formed on the contact surface between the first current collector plate 79 and the electrode terminal 50. Such a laser welded portion is characterized by being located at the overlapping portion between the first current collector plate 79 and the electrode terminal 50 within the winding center hole 80. The laser welding between the first current collector plate 79 and the electrode terminal 50, the configuration of the laser welded portion and the manufacturing method related thereto, and the specific embodiments of the first current collector plate 79 will be described in detail with reference to FIGS. 14 to 24.

[0157] In addition, the cylindrical secondary battery 70 may include a sealing body 74 that seals the open portion of the battery can 51 in an insulating manner from the battery can 51. Desirably, the sealing body 74 may include a non-polar cap plate 74a and a sealing gasket 74b interposed between the periphery of the cap plate 74a and the open portion of the battery can 51.

[0158] The cap plate 74a can be made of a conductive metal material such as aluminum, iron, nickel-plated iron, or SUS. Further, the sealing gasket 74b can be made of polypropylene, polybutylene terephthalate, polytetrafluoroethylene, etc., which have insulation and elasticity. However, the present invention is not limited by the materials of the cap plate 74a and the sealing gasket 74b. The cap plate 74a can cover the opening of the battery can 51. Even when the cap plate 74a is made of a conductive metal material, it has no polarity. Having no polarity may mean that the cap plate 74a is not connected to the electrode assembly 71. It may also mean that it is electrically insulated from the battery can 51 and the electrode terminal 50. Because it has no polarity, the cap plate 74a does not function as an electrode terminal. The cap plate 74a does not necessarily have to be connected to the electrode assembly 71 and the battery can 51, and its material does not necessarily have to be a conductive metal.

[0159] The cap plate 74a may include a vent notch 77 that ruptures when the pressure inside the battery can 51 exceeds a critical value. The vent notch 77 can be formed on one or both sides of the cap plate 74a. The vent notch 77 can form a continuous or discontinuous circular pattern, linear pattern, or other pattern on the surface of the cap plate 74a. For example, the vent notch 77 can be formed in a substantially annular shape with a certain width. Such an annular vent notch 77 can have the same center as the center of the cap plate 74a and a radius smaller than the radius of the cap plate 74a.

[0160] The breaking pressure of the battery can 51 can be controlled by controlling the depth and width of the vent notch 77. For example, the vent notch 77 is configured such that when the pressure inside the battery can 51 is 15 - 35 kgf / cm 2It can be set to rupture when within a certain range. The vent notch 77 can be formed by notching to partially reduce the thickness of the battery can 51. The vent notch 77 can have a thickness gradient. The thickness gradient means that when the cross-section of the vent notch 77 is examined, it is formed to incline at a certain angle with respect to a predetermined horizontal plane. When it is determined that the pressure inside the battery can 51 has abnormally increased, such a vent notch 77 allows all the internal gas to be discharged to the outside.

[0161] The battery can 51 can include a crimping part 75 that extends and is bent inwardly of the battery can 51 to fix the sealing body 74 and surrounds and fixes the periphery of the cap plate 74a together with the sealing gasket 74b. Desirably, the lower surface of the cap plate 74a can be located above the lower end of the crimping part 75. In such a case, since a vent space is formed below the cap plate 74a, when the vent notch 77 ruptures, gas discharge can be smoothly performed.

[0162] Also, the battery can 51 can further include a beading part 76 that is press-fitted inwardly of the battery can 51 in a region adjacent to the opening part. The beading part 76 is recessed inwardly of the battery can 51. The beading part 76 supports the periphery of the sealing body 74, particularly the outer peripheral surface of the sealing gasket 74b, when the sealing body 74 is fixed by the crimping part 75.

[0163] In addition, the cylindrical secondary battery 70 may further include a second current collector plate 78 that connects to the non-coated portion 72 of the second electrode plate. The connection between the non-coated portion 72 of the second electrode plate and the second current collector plate 78 can be made by a welding method. The second current collector plate 78 can be made of the same metal as the current collector of the second electrode plate or a material that is easily weldable to it. For example, it can be copper or a copper alloy, nickel or a nickel alloy, iron, SUS, or a composite material thereof. Desirably, at least a part 78a of the edge of the second current collector plate 78 that does not contact the non-coated portion 72 of the second electrode plate is interposed between the beading portion 76 and the sealing gasket 74b and fixed by the crimping portion 75. Optionally, at least a part 78a of the edge of the second current collector plate 78 can be fixed to the inner peripheral surface 76a of the beading portion 76 adjacent to the crimping portion 75 by welding. Thereby, the second current collector plate 78 is also connected to the battery can 51, and the battery can 51 is connected to the non-coated portion 72 of the second electrode plate by the second current collector plate 78. Further, the second current collector plate 78 may have a current collector hole (not shown) at its central portion. The current collector hole does not block the winding center hole 80. By including the current collector hole, the second current collector plate 78 allows the laser beam to pass through at the stage of welding the first current collector plate 79 to the electrode terminal 50 so that the laser beam reaches the first current collector plate 79.

[0164] Each of the current collector plates 78 and 79 serves to guide the current generated in each electrode plate of the electrode assembly 71 to the electrode terminal 50 and the battery can 51. Each of the current collector plates 78 and 79 is a component connected to derive the current from the non-coated portions 72 and 73 which are the ends of each electrode plate. Since the current is derived and introduced by directly connecting each of the current collector plates 78 and 79 to each of the non-coated portions 72 and 73 by a welding method or the like, another current collecting tab is not required. Therefore, the step of attaching the current collecting tab is not required, so that the productivity can be improved. Also, since the space for storing the current collecting tab can be reduced, the battery structure becomes overall more compact and the space utilization is improved.

[0165] Further, the cylindrical secondary battery 70 has a structure in which the remaining areas excluding the areas occupied by the electrode terminals 50 on the outer surfaces of the electrode terminals 50 and the battery can 51 can be used as the positive electrode terminal and the negative electrode terminal, respectively. That is, it has a structure in which most of the surface on the opposite side of the open portion of the battery can 51 can be used as the negative electrode terminal. Therefore, it has an advantage that a sufficient area where components for connection such as a bus bar can be welded for electrical wiring can be secured.

[0166] FIG. 6 is a cross-sectional view showing a riveting structure of an electrode terminal according to an embodiment of the present invention. FIG. 7 is an enlarged cross-sectional view of a portion B in FIG. 6. FIGS. 6 and 7 show a state in which the bottom portion 52 of the battery can 51 is located downward.

[0167] Referring to FIGS. 6 and 7, preferably, the electrode terminal 50 includes a main body portion 50a inserted into the through hole 53, an external flange portion 50b extending along the outer surface 52a from the peripheral edge of one side of the main body portion 50a exposed on the outer surface 52a of the bottom portion 52 of the battery can 51, an internal flange portion 50c extending from the peripheral edge of the other side of the main body portion 50a exposed on the inner surface 52b of the bottom portion 52 of the battery can 51 toward the inner surface 52b, and a flat portion 50d provided inside the internal flange portion 50c.

[0168] Preferably, at least a part of the first current collector plate 79, for example, the central portion (79a in FIG. 5), can be laser welded to the flat portion 50d of the electrode terminal 50. Thereby, the electrode terminal 50 and the first current collector plate 79 can be joined by a laser welded portion at the flat portion 50d.

[0169] Preferably, the flat portion 50d and the inner surface 52b of the bottom portion 52 of the battery can 51 can be parallel to each other. Here, "parallel" means substantially parallel when observed visually.

[0170] The flat portion 50d is a surface facing the first current collector plate 79. In the electrode terminal 50, the surface exposed to the outside of the battery can 51 as the surface opposite to this surface can be a flat surface. Furthermore, it can be a smooth surface. "Flat" means flat. "Smooth" means flat and smooth.

[0171] According to one aspect, the angle θ formed between the inner flange portion 50c and the inner surface 52b of the bottom portion 52 of the battery can 51 can be 0° to 60°. The magnitude of the angle is determined by the caulking strength when the electrode terminal 50 is provided in the through hole 53 of the battery can 51 by the caulking method. In one example, the angle θ can decrease to 0° as the caulking strength increases. If the angle exceeds 60°, the sealing effect of the rivet gasket 54 may decrease.

[0172] According to another aspect, a recess portion 55 may be provided between the inner flange portion 50c and the flat portion 50d. The recess portion 55 may have a cross-sectional structure of an asymmetric groove. In one example, the asymmetric groove may be substantially V-shaped. The asymmetric groove may include a side wall 55a of the flat portion 50d and an inclined surface 55b of the inner flange portion 50c connected to an end portion of the side wall 55a. The side wall 55a may be substantially perpendicular to the inner surface 52b of the bottom portion 52 of the battery can 51. "Perpendicular" means substantially perpendicular when observed visually. As will be described later, the side wall 55a may be inclined toward the flat portion 50d. The recess portion 55 is formed by the shape of the caulking jig when the electrode terminal 50 is provided in the through hole 53 of the battery can 51 by the caulking method.

[0173] Desirably, the thickness of the inner flange portion 50c can decrease as it is farther from the main body portion 50a of the electrode terminal 50.

[0174] According to another aspect, the rivet gasket 54 may include an external gasket 54a interposed between the external flange portion 50b and the outer surface 52a of the bottom portion 52 of the battery can 51, and an internal gasket 54b interposed between the inner flange portion 50c and the inner surface 52b of the bottom portion 52 of the battery can 51. Desirably, the external gasket 54a and the internal gasket 54b are separated based on the outer surface 52a of the bottom portion of the battery can 51.

[0175] The outer gasket 54a and the inner gasket 54b may have thicknesses that vary depending on the position. Desirably, even in the region of the inner gasket 54b, the thickness of the region interposed between the inner edge 56 of the through-hole 53 connected to the inner surface 52b of the bottom 52 of the battery can 51 and the inner flange portion 50c may be relatively small. Desirably, a minimum thickness point may exist in the gasket region interposed between the inner edge 56 of the through-hole 53 and the inner flange portion 50c. Also, the inner edge 56 of the through-hole 53 may include a facing surface 57 facing the inner flange portion 50c.

[0176] On the other hand, the upper and lower ends of the inner wall of the through-hole 53 perpendicular to the bottom 52 of the battery can 51 are chamfered (corner cutting) so as to form a tapered surface toward the electrode terminal 50. However, the upper and / or lower ends of the inner wall of the through-hole 53 can be deformed into a soft curved surface having a curvature. In this case, the stress applied to the rivet gasket 54 in the vicinity of the upper and / or lower ends of the inner wall of the through-hole 53 can be more relaxed.

[0177] Desirably, the inner gasket 54b forms an angle of 0° to 60° with the inner surface 52b of the bottom 52 of the battery can 51 and can extend longer than the inner flange portion 50c.

[0178] On the other hand, with reference to the inner surface 52b of the bottom 52 of the battery can 51, the height H1 of the flat portion 50d may be the same as or greater than the height H2 of the end of the inner gasket 54b. Also, with reference to the inner surface 52b of the bottom 52 of the battery can 51, the height H1 of the flat portion 50d may be the same as or greater than the height H3 of the end of the inner flange portion 50c. Here, the height H2 is the maximum height of the end of the inner gasket 54b measured with reference to the inner surface 52b. Also, the height H3 is the maximum height of the end of the inner flange portion 50c measured with reference to the inner surface 52b.

[0179] When the height parameters H1, H2, and H3 satisfy the above conditions, interference between the inner flange portion 50c and the inner gasket 54b with other components can be prevented.

[0180] Desirably, the height H3 of the inner flange portion 50c can be 0.5 mm to 3.0 mm. If the height H3 of the inner flange portion 50c is less than 0.5 mm, it is difficult to sufficiently ensure the sealing property. Further, if the height H3 of the inner flange portion 50c exceeds 3 mm, the internal space of the battery can 51 occupied by the electrode assembly 71 decreases.

[0181] Desirably, the height H4 of the electrode terminal 50 can be 1.5 mm to 7 mm. The height H4 of the electrode terminal 50 is the distance from the lower surface of the outer flange portion 50b to the flat portion 50d. If the height H4 of the electrode terminal 50 is less than 1.5 mm, it is difficult to increase the height of the inner flange portion 50c to such an extent that the sealing property is ensured by the thickness of the bottom portion 52 of the battery can 51. For reference, the thickness of the bottom portion 52 of the battery can 51 is about 0.5 mm to 1 mm. Further, if the height H4 of the electrode terminal 50 exceeds 7 mm, the internal space of the battery can 51 occupied by the electrode assembly 71 decreases, and as the height of the cell increases, the energy density per unit volume decreases accordingly. When H3 and H4 satisfy the above numerical range, the sealing property of the electrode terminal 50 can be sufficiently ensured without reducing the internal space of the battery can 51. Most desirably, the height H4 of the electrode terminal 50 can be 4 mm to 7 mm.

[0182] On the other hand, based on the outer surface 52a of the bottom 52 of the battery can 51, the height H5 of the external flange portion 50b can be 0.8 mm or more. If the height H5 of the external flange portion 50b is less than 0.8 mm, the external flange portion 50b may be deformed when the electrode terminal 50 is riveted. The thickness of the external gasket 54a has a thickness of 0.3 mm or more in consideration of insulation and sealing properties. When considering the thickness of such an external gasket 54a, if the height of the external flange portion 50b is less than 0.8 mm, the thickness of the external flange portion 50b becomes thin to a level where it is difficult to sufficiently ensure mechanical rigidity. This is particularly the case when the electrode terminal 50 is made of aluminum. On the other hand, the height of the external flange portion 50b can be appropriately set in consideration of the space margin at the upper part of the cell. In one example, the height of the external flange portion 50b can be set to 2 mm or less, or 3 mm or less, or 4 mm or less, but the present invention is not limited thereto.

[0183] On the other hand, at least a part of the external gasket 54a can be exposed outside the external flange portion 50b of the electrode terminal 50. The purpose of the exposure of the external gasket 54a is to insulate the outer surface 52a having a polarity opposite to that of the electrode terminal 50 and the electrode terminal 50 from each other. The exposure width G of the external gasket 54a for electrical insulation between the electrode terminal 50 and the outer surface 52a can be 0.1 mm to 1 mm. When the exposure width G is less than 0.1 mm, the electrical insulation between the electrode terminal 50 and the outer surface 52a on the plane may be broken when high-rate charge and discharge of 300 A or more is performed. Also, when the exposure width G is greater than 1 mm, the electrical insulation effect does not increase, and instead, the area of the outer surface 52a used as the negative electrode region decreases, thereby reducing the contact area of the components (e.g., bus bar) used for connection.

[0184] On the other hand, the radius R1 from the center of the main body portion 50a to the periphery of the external flange portion 50b can be 10% to 70% based on the radius R2 of the bottom 52 of the battery can 51.

[0185] When R1 becomes small, there is insufficient welding space when welding the component (bus bar) used for connecting the electrode terminal 50. Also, when R1 becomes large, the welding space decreases when welding the component (bus bar) for connection to the outer surface 52a of the bottom 52 of the battery can 51 excluding the electrode terminal 50.

[0186] When adjusting the ratio R1 / R2 between 10% and 70%, an appropriate welding space can be ensured for the electrode terminal 50 and the outer surface 52a of the bottom 52 of the battery can 51.

[0187] Also, the radius R3 from the center of the main body portion 50a of the electrode terminal 50 to the periphery of the flat portion 50d can be 4% to 30% based on the radius R2 of the bottom 52 of the battery can 51.

[0188] When R3 becomes small, there is insufficient welding space when laser-welding the first current collector plate 79 to the flat portion 50d of the electrode terminal 50, the welding area of the electrode terminal 50 may decrease, and the contact resistance may increase. Also, R3 needs to be smaller than R1. When R3 becomes large, the thickness of the inner flange portion 50c becomes thin, the force with which the inner flange portion 50c crimps the rivet gasket 54 becomes weak, and the sealing force of the rivet gasket 54 may decrease.

[0189] When adjusting R3 / R2 between 4% and 30%, not only can the welding process be easily performed by sufficiently ensuring the welding area between the flat portion 50d of the electrode terminal 50 and the first current collector plate 79, but also the contact resistance in the welding region can be decreased, and a decrease in the sealing force of the rivet gasket 54 can be prevented.

[0190] According to an embodiment of the present invention, the riveting structure of the electrode terminal 50 can be formed using a caulking jig that moves up and down. First, a preform (not shown) of the electrode terminal 50 is inserted through the through-hole 53 formed in the bottom 52 of the battery can 51 with a rivet gasket 54 interposed therebetween. The preform refers to the electrode terminal before riveting.

[0191] Next, insert the caulking jig into the inner space of the battery can 51. The caulking jig has grooves and protrusions corresponding to the final shape of the electrode terminal 50 on the surface facing the preform in order to rebate the preform and form the electrode terminal 50.

[0192] Thereafter, move the caulking jig downward to press-mold the upper part of the preform and deform the preform into the rebated electrode terminal 50.

[0193] While the preform is being pressed by the caulking jig, the external gasket 54a interposed between the external flange portion 50b and the outer surface 52a of the bottom 52 of the battery can 51 is elastically compressed and its thickness decreases. Also, the portion of the internal gasket 54b interposed between the inner edge 56 of the through-hole 53 and the preform is elastically compressed by the internal flange portion 50c and its thickness decreases more than other regions. In particular, the region where the thickness of the internal gasket 54b decreases intensively is the portion indicated by the dotted circle in FIG. 7. As a result, the sealing property and airtightness between the rebated electrode terminal 50 and the battery can 51 are significantly improved.

[0194] Desirably, the rivet gasket 54 is sufficiently compressed so that the desired sealing strength is ensured without being physically damaged during the process of rebating the preform.

[0195] Desirably, the compression ratio of the rivet gasket 54 can be 30% - 90%. The minimum compression ratio is the minimum level of compression ratio for ensuring the sealing property (airtightness) of the electrode terminal 50. The maximum compression ratio is the maximum level of compression ratio that can be achieved without physically damaging the rivet gasket 54.

[0196] In one example, when the rivet gasket 54 is made of polybutylene terephthalate, it is desirable that the compression ratio of the rivet gasket 54 is 50% or more at the point where it is compressed to the minimum thickness. The compression ratio is the ratio of the change in thickness before and after compression to the thickness before compression.

[0197] Desirably, the compression ratio is determined for the internal gasket 54b. That is, the compression ratio can be defined as the ratio of the amount of thickness change at the maximum compression point to the thickness before compression of the internal gasket 54b. Hereinafter, it is the same. The thickness before compression of the internal gasket 54b is uniform, and the maximum compression point may exist in the vicinity of the inner edge 56 portion.

[0198] In another example, when the rivet gasket 54 is made of polytetrafluoroethylene, it is desirable that the compression ratio of the rivet gasket 54 is 60% or more at the point where it is compressed to the minimum thickness. Desirably, the compression ratio is determined for the internal gasket 54b.

[0199] In still another example, when the rivet gasket 54 is made of polypropylene, it is desirable that the compression ratio of the rivet gasket 54 is 60% or more at the point where it is compressed to the minimum thickness. Desirably, the compression ratio is determined for the internal gasket 54b.

[0200] Desirably, the vertical movement of the caulking jig can be performed at least two or more times to perform the pressure molding of the upper part of the preform step by step. That is, the preform can be pressure molded step by step and deformed in several times. At this time, the pressure applied to the caulking jig can be increased step by step. By doing so, it is possible to prevent the rivet gasket 54 from being damaged during the caulking process by dispersing the stress applied to the preform in several times. In particular, when the portion of the internal gasket 54b interposed between the inner edge 56 of the through hole 53 and the preform is intensively compressed by the internal flange portion 50c, the damage of the rivet gasket 54 is minimized.

[0201] After the pressure molding of the preform using the caulking jig is completed, when the caulking jig is separated from the battery can 51, the riveting structure of the electrode terminal 50 according to the embodiment of the present invention as shown in FIGS. 6 and 7 can be obtained.

[0202] According to the above-described embodiments, the coking jig pressurizes and forms the upper portion of the preform by vertical movement inside the battery can 51. In some cases, a rotary rotating jig used in the prior art may be used for pressurizing and forming the preform.

[0203] However, the rotary rotating jig rotates at a predetermined angle with respect to the central axis of the battery can 51. Therefore, a rotary rotating jig with a large rotation radius may interfere with the inner wall of the battery can 51. Also, when the depth of the battery can 51 is large, the length of the rotary rotating jig also becomes correspondingly long. In this case, the rotation radius of the end of the rotary rotating jig becomes large, and there is a risk that the pressurizing and forming of the preform may not be properly performed. Therefore, the pressurizing and forming using the coking jig is more effective than the method using the rotary rotating jig.

[0204] On the other hand, the structure of the electrode terminal 50 can have various structures depending on the design of the preform and / or the coking jig and / or the rivet gasket 54, and the magnitude of the pressure applied to the preform during the coking process.

[0205] FIG. 8 is a partially enlarged cross-sectional view showing the structure of the electrode terminal 50' according to another embodiment of the present invention.

[0206] Referring to FIG. 8, the electrode terminal 50' according to another embodiment has a structure in which the inner flange portion 50c is riveted substantially parallel to the inner surface 52b of the bottom portion 52 of the battery can 51. Therefore, the angle formed by the surface of the inner flange portion 50c facing the inner surface 52b of the bottom portion 52 of the battery can 51 and the inner surface 52b is substantially close to 0, and the height H3 of the inner flange portion 53c is larger than the height H2 of the inner gasket 54b. Also, the inner edge 56 of the through hole 53 is in the shape of an arc having a predetermined curvature (arc: a portion limited by two points on a circumference or other curve). Further, the side wall 55a of the flat portion 50d has a structure inclined toward the flat portion 50d.

[0207] Desirably, the thickness of the internal gasket 54b gradually decreases as it goes upward, then decreases to the minimum thickness near the end of the internal flange portion 53c, and may slightly increase as it goes to the uppermost end. Such a compression structure of the internal gasket 54b further improves the sealing property of the electrode terminal 50'. The compression rate of the internal gasket 54b can be calculated at the point of the minimum thickness near the end of the internal flange portion 53c.

[0208] In the cylindrical secondary battery 70 shown in FIG. 5, the electrode terminal 50 can be replaced with the structure of the electrode terminal 50' shown in FIG. 8. With the electrode terminals 50 and 50' described above, the space efficiency inside the battery can 51 can be increased. Thereby, the internal resistance of the cylindrical secondary battery 70 including it can be lowered, and the energy density can be increased. The electrode terminals 50 and 50' are improved so that the cross-sectional area of the current path is enlarged. Thereby, the problem of internal heat generation occurring during rapid charging of the cylindrical secondary battery 70 including it is improved.

[0209] Further, the cylindrical secondary battery 70 to which the riveting structure of the electrode terminals 50 and 50' is applied can perform electrical wiring in one direction. As described with reference to FIG. 5, in the cylindrical secondary battery 70 according to the embodiment of the present invention, the cap plate 74a of the sealing body 74 has no polarity. Instead, since the second current collector plate 78 is connected to the battery can 51, the outer surface 52a of the bottom 52 of the battery can 51 has the opposite polarity to the electrode terminal 50. Thereby, when connecting a plurality of cylindrical secondary batteries 70, since the positive electrode / negative electrode can be connected together in one direction, the connection structure can be simplified. Thereby, when trying to connect a plurality of cylindrical secondary batteries 70 in series and / or in parallel for the manufacture of a battery pack, wiring such as bus bar connection can be performed at the upper part of the cylindrical secondary battery 70 using the outer surface 52a of the bottom 52 of the battery can 51 and the electrode terminal 50. Thereby, the number of secondary batteries that can be mounted in the same space can be increased to improve the energy density, and the electrical wiring work can be easily performed. Therefore, since the space efficiency is good and the efficiency of electrical wiring is high, it has a significant effect of improving the work during the assembly process of an electric vehicle and the assembly and maintenance of a battery pack.

[0210] Furthermore, the electrical wiring is performed on the outer surface 52a of the bottom 52 of the battery can 51 on the side where the electrode terminals 50 are located, and it is not necessary to provide electrical wiring on the cap plate 74a located on the opposite side. Therefore, the effect of the vent notch 77 formed in the cap plate 74a can be maximized. Also, if a heat sink, a cooling plate, a tray, or the like is disposed on the cap plate 74a side, the purposes such as assembly and cooling can be effectively achieved regardless of the electrical wiring connection part. Further, by assembling the vent notch 77 so as to be located downward, the gas discharged from the inside of the secondary battery is discharged downward. Usually, since the secondary battery is mounted at a position lower than that of the vehicle occupants such as in an EV, if gas is discharged upward from the secondary battery, there is a risk of harming the occupants. However, the cylindrical secondary battery 70 according to an embodiment of the present invention can not only effectively discharge the high-pressure gas inside the secondary battery, but also is safe regardless of the electrical wiring connection part at the upper part. Thus, when gas is discharged due to the breakage of the vent notch 77, the gas is discharged downward, so that it does not harm the occupants and the safety is greatly improved.

[0211] Desirably, the riveting structure of the electrode terminals 50, 50' according to the embodiment of the present invention described above can be applied to a cylindrical secondary battery having a form factor larger than 21700. Recently, with the application of cylindrical secondary batteries to electric vehicles, the form factor of cylindrical secondary batteries is increasing compared to the conventional 18650, 21700, etc. The increase in the form factor brings an increase in energy density, an increase in safety against thermal runaway, and an improvement in cooling efficiency.

[0212] Desirably, the cylindrical secondary battery 70 can be, for example, a cylindrical secondary battery having a form factor ratio (a value obtained by dividing the diameter of the cylindrical secondary battery by the height, that is, a ratio of the diameter Φ to the height H) greater than about 0.4. Such a secondary battery is suitable for, for example, a high-output and large-capacity secondary battery of an HEV.

[0213] The cylindrical secondary battery according to an embodiment of the present invention can be, for example, 46110 cells, 48750 cells, 48110 cells, 48800 cells, or 46800 cells.

[0214] The secondary battery according to an embodiment of the present invention can be a cylindrical secondary battery that is a substantially cylindrical cell, has a diameter of about 46 mm, a height of about 110 mm, and a form factor ratio of 0.418.

[0215] The secondary battery according to another embodiment can be a cylindrical secondary battery that is a substantially cylindrical cell, has a diameter of about 48 mm, a height of about 75 mm, and a form factor ratio of 0.640.

[0216] The secondary battery according to still another embodiment can be a cylindrical secondary battery that is a substantially cylindrical cell, has a diameter of about 48 mm, a height of about 110 mm, and a form factor ratio of 0.436.

[0217] The secondary battery according to still another embodiment can be a cylindrical secondary battery that is a substantially cylindrical cell, has a diameter of about 48 mm, a height of about 80 mm, and a form factor ratio of 0.600.

[0218] The secondary battery according to still another embodiment can be a cylindrical secondary battery that is a substantially cylindrical cell, has a diameter of about 46 mm, a height of about 80 mm, and a form factor ratio of 0.575.

[0219] Conventionally, secondary batteries with a form factor ratio of about 0.4 or less have been used. That is, conventionally, for example, 18650 cells, 21700 cells, etc. have been used. In the case of 18650 cells, the diameter is about 18 mm, the height is about 65 mm, and the form factor ratio is 0.277. In the case of 21700 cells, the diameter is about 21 mm, the height is about 70 mm, and the form factor ratio is 0.300.

[0220] As described above, the cylindrical secondary battery 70 according to an embodiment of the present invention has an improved electrode terminal structure (riveting) and current collecting structure (connection between the non-coated portion and the current collecting plate). In addition to embodying such a structure, as will be described below, it also includes specific means for providing more improved functions (a current collector segmentation structure for bending the non-coated portion, an insulator designed to enable laser welding of the first current collecting plate and the electrode terminal while being coupled to the electrode assembly, components such as the second current collecting plate, etc.). This enables the production of a cylindrical secondary battery with a form factor larger than 21700.

[0221] Referring further to FIG. 5, the cylindrical secondary battery 70 may further include an insulator 85 interposed between the closed portion of the battery can 51 and the first current collecting plate 79. The insulator 85 may be interposed between the first current collecting plate 79 and the inner surface 52b of the bottom 52 of the battery can 51, and between the inner peripheral surface 51a of the side wall of the battery can 51 and the electrode assembly 71.

[0222] Desirably, the insulator 85 may include a welding hole 85a that exposes the flat portion 50d of the electrode terminal 50 to the side of the first current collecting plate 79. Further, the welding hole 85a may expose the inner flange portion 50c and the inner gasket 54b together with the flat portion 50d of the electrode terminal. Desirably, the welding hole 85a does not block the winding center hole 80. Thus, when a large amount of gas is generated due to an abnormality in the secondary battery, it does not obstruct the movement of the gas attempting to move to the cap plate 74a side through the winding center hole 80. Therefore, when a large amount of gas is generated, it can smooth the pressure control action of the vent notch 77 on the internal pressure of the battery. Also, by including the welding hole 85a in the cap plate 74a, a laser beam is passed through at the stage of welding the first current collecting plate 79 to the electrode terminal 50, allowing the laser beam to reach the first current collecting plate 79.

[0223] Desirably, the insulator 85 may cover at least the surface of the first current collecting plate 79 and the periphery of one side (upper part) of the electrode assembly 71. Thereby, it is possible to prevent the first current collecting plate 79 having a different polarity from the battery can 51 and the non-coated portion 73 of the first electrode plate from contacting each other.

[0224] Desirably, the insulator 85 is made of an insulating resin and may include an upper plate 85b and a side sleeve 85c. In one example, the upper plate 85b and the side sleeve 85c may be an integrally molded injection-molded product. Alternatively, the side sleeve 85c may be replaced with an insulating tape or the like. The insulating tape may cover the outer peripheral edge of the first current collector plate 79 together with the non-coated portion 73 of the first electrode plate exposed on the outer peripheral surface of the electrode assembly 71.

[0225] Desirably, the insulator 85 and the inner surface 52b of the bottom 52 of the battery can 51 can be in close contact with each other as shown in FIG. 9. FIG. 9 is a cross-sectional view of a cylindrical secondary battery cut along the longitudinal direction (Y direction) according to another embodiment of the present invention.

[0226] Here, "close contact" means that there is no visually confirmed space (gap). In order to eliminate the space (gap), the distance from the inner surface 52b of the bottom 52 of the battery can 51 to the flat portion 50d of the electrode terminal 50 may be the same as the thickness of the insulator 85 or a value slightly smaller than that.

[0227] Referring further to FIG. 5, desirably, the non-coated portions 72, 73 of the first electrode plate and / or the second electrode plate can form bent surfaces at the upper and lower portions of the electrode assembly 71 by being bent in the radial direction of the electrode assembly 71, for example, from the outer peripheral side to the core side. Further, the second current collector plate 78 can be welded to the bent surface formed by bending the non-coated portion 72 of the second electrode plate, and the first current collector plate 79 can be welded to the bent surface formed by bending the non-coated portion 73 of the first electrode plate. By bending each non-coated portion 72, 73, the space occupied by them can be reduced and the energy density can be improved. Further, by increasing the bonding area between each non-coated portion 72, 73 and each current collector plate 78, 79, the bonding force can be improved and the resistance can be reduced. Such a structure is particularly suitable for a high-output secondary battery.

[0228] In addition, in order to relieve the stress generated when the non-coated portions 72 and 73 are bent, the first electrode plate and / or the second electrode plate may have an improved structure different from that of a conventional electrode plate (see FIG. 1).

[0229] FIG. 10 is a plan view showing the structure of an electrode plate 90 according to a preferred embodiment of the present invention.

[0230] Referring to FIG. 10, the electrode plate 90 includes a sheet-like current collector 91 made of a foil of a conductive material, an active material layer 92 formed on at least one surface of the current collector 91, and a non-coated portion 93 at a long-side end of the current collector 91 where the active material is not coated.

[0231] Preferably, the non-coated portion 93 may include a plurality of segmented pieces 93a obtained by notch processing. At least a partial section of the non-coated portion 93 is divided into a plurality of segmented pieces 93a. The plurality of segmented pieces 93a form a plurality of groups, and the segmented pieces 93a belonging to each group may have the same height (length in the Y direction) and / or width (length in the X direction) and / or separation pitch. The number of segmented pieces 93a belonging to each group may be increased or decreased compared to that shown. The segmented piece 93a has a shape of a geometric figure combined with at least one straight line and / or at least one curve. Preferably, the segmented piece 93a may be trapezoidal, but can be deformed into various shapes such as a quadrilateral, a parallelogram, a semi-circular shape, or an oval shape.

[0232] Preferably, the height of the segmented piece 93a may increase stepwise along a direction parallel to the winding direction of the electrode assembly, for example, as it progresses from the core side to the outer peripheral side. Also, the non-coated portion 93' on the core side adjacent to the core side may not include the segmented piece 93a, and the height of the non-coated portion 93' on the core side may be smaller than the regions of other non-coated portions. Also, the non-coated portion 93'' on the outer peripheral side adjacent to the outer peripheral side may not include the segmented piece 93a, and the height of the non-coated portion 93'' on the outer peripheral side may be smaller than the regions of other non-coated portions.

[0233] Optionally, the electrode plate 90 may include an insulating coating layer 94 that covers the boundary between the active material layer 92 and the non - coating portion 93. The insulating coating layer 94 includes an insulating polymer resin and may optionally further include an inorganic filler. The insulating coating layer 94 prevents the end of the active material layer 92 from contacting the active material layer of the opposite polarity that faces through the separator, and plays a role in structurally supporting the bending of the segmented piece 93a. For this purpose, when the electrode plate 90 is wound into the electrode assembly, it is desirable that at least a part of the insulating coating layer 94 is exposed to the outside from the separator.

[0234] FIG. 11 is a cross - sectional view taken along the longitudinal direction (Y - direction) of an electrode assembly 100 in which the segmented structure of the non - coating portion of the electrode plate 90 according to an embodiment of the present invention is applied to the first electrode plate and the second electrode plate.

[0235] Referring to FIG. 11, the electrode assembly 100 can be manufactured by the winding method described in FIG. 2. For the sake of convenience of explanation, the protruding structures of the non - coating portions 72, 73 extending to the outside of the separator are shown in detail, and the illustration of the winding structure of the first electrode plate, the second electrode plate, and the separator is omitted. The non - coating portion 72 protruding downward extends from the second electrode plate, and the non - coating portion 73 protruding upward extends from the first electrode plate.

[0236] The pattern in which the heights of the non - coating portions 72, 73 change is schematically shown. That is, the heights of the non - coating portions 72, 73 may change irregularly depending on the position where the cross - section is cut. In one example, when the side portion of the trapezoidal segmented piece (93a in FIG. 10) is cut, the height of the non - coating portion in the cross - section becomes lower than the height of the segmented piece 93a. Therefore, it should be understood that the heights of the non - coating portions 72, 73 shown in the drawing showing the cross - section of the electrode assembly 100 correspond to the average of the heights of the non - coating portions included in each winding turn.

[0237] The non-coated portions 72 and 73 can be bent. The portion 101 to be bent in FIG. 11 is indicated by a dotted box. For example, the non-coated portions 72 and 73 can be bent from the outer peripheral side to the core side along the direction of the arrow in FIG. 11. FIGS. 12 and 13 show the electrode assembly 100 in which the non-coated portions 72 and 73 are bent from the outer peripheral side to the core side along the radial direction of the electrode assembly 100 in this way.

[0238] Referring to FIGS. 11 and 12, when the non-coated portions 72 and 73 are bent, the segmented pieces (93a in FIG. 10) adjacent to each other in the radial direction are superposed on each other multiple times along the radial direction, and bending surfaces 101a are formed on the upper and lower portions of the electrode assembly 100. At this time, the non-coated portion on the core side (93' in FIG. 10) is not bent because its height is low, and the height h of the segmented piece bent at the innermost side is the same as or smaller than the radial length r of the winding region formed by the non-coated portion 93' on the core side that does not have the structure of the segmented piece. As a result, the winding center hole 80 of the electrode assembly 100 is not closed by the bent segmented piece. If the winding center hole 80 is not closed, the electrolyte injection process becomes easy, and the electrolyte injection efficiency is improved. Also, when laser welding is performed using the winding center hole 80, the path irradiated by the laser beam is not blocked, so that the welding of the electrode terminal 50 and the first current collector plate 79 can be easily performed.

[0239] Next, with reference to both FIGS. 5 and 14, the manufacturing method of the cylindrical secondary battery 70 will be described in detail. FIG. 14 is a diagram showing a step of joining the electrode terminal and the first current collector plate of the cylindrical secondary battery by laser welding according to an embodiment of the present invention. FIG. 15 is an enlarged view of the dotted box portion in FIG. 14 and is also a cross-sectional view of the laser-welded electrode terminal and the first current collector plate.

[0240] First, an electrode assembly 71 is provided as described above with reference to FIG. 5 and the like. The electrode assembly 71 can be the electrode assembly 100 described with reference to FIG. 13 and the like.

[0241] Next, a first current collector plate 79 is connected to the non-coated portion 73 of the first electrode plate of the electrode assembly 71. For example, it can be connected by a welding method. As a method of welding the first current collector plate 79 to the non-coated portion 73 of the first electrode plate, laser welding, resistance welding, ultrasonic welding, etc. are possible. When the first current collector plate 79 is made of an aluminum material, laser welding or ultrasonic welding is desirable. An insulator 85 can be added on top of the first current collector plate 79 connected to the non-coated portion 73 of the first electrode plate.

[0242] A second current collector plate 78 is connected to the non-coated portion 72 of the second electrode plate of the electrode assembly 71. For example, it can be connected by a welding method. As a method of welding the second current collector plate 78 to the non-coated portion 72 of the second electrode plate, laser welding, resistance welding, ultrasonic welding, etc. are possible.

[0243] Next, as described above in the method and structure, an electrode terminal 50 is formed on the battery can 51 and prepared. The electrode assembly 71 is inserted into the battery can 51 from the open portion of the battery can 51 so that the first current collector plate 79 connected to the non-coated portion 73 of the first electrode plate of the electrode assembly 71 faces the bottom 52 of the battery can 51.

[0244] Next, as shown in FIG. 14, the first current collector plate 79 is laser-welded to the electrode terminal 50 using a laser welding apparatus 102. In FIG. 14, for the sake of illustration, the form of the electrode terminal 50 is schematically shown, and the illustration of the peripheral components of the electrode terminal 50, for example, other components such as a rivet gasket 54 and an insulator 85, is omitted. The laser welding apparatus 102 is also schematically shown.

[0245] Desirably, after the first current collector plate 79 is connected to the non-coated portion 73 of the first electrode plate, it is inserted into the battery can 51 from above to below with the bottom 52 placed at the lower part and an open portion at the upper part, and is connected to the inner surface of the electrode terminal 50 formed on the bottom 52 of the battery can 51 by laser welding with a laser beam 103 irradiated from above. The laser beam 103 is irradiated into the winding center hole 80 along the longitudinal direction of the winding center hole 80.

[0246] Thus, in one embodiment of the present invention, it is characterized in that laser welding is performed while the opening of the battery can 51 remains open with the electrode assembly 71 inserted from the opening of the battery can 51. Laser welding is used to connect the first current collector plate 79 and the electrode terminal 50. During laser welding, the laser beam 103 can reach the welding area of the first current collector plate 79 through the winding center hole 80 of the electrode assembly 71. When the first current collector plate 79 is welded to the flat portion 50d of the electrode terminal 50, the electrode terminal 50 can support the welding area of the first current collector plate 79. Also, since the flat portion 50d of the electrode terminal 50 has a large area, a wide welding area can be secured. Thereby, the internal resistance of the cylindrical secondary battery 70 can be reduced by reducing the contact resistance of the welding area. The face-to-face welding structure of the riveted electrode terminal 50 and the first current collector plate 79 is very useful for rapid charging. This is because in the cross-section in the direction in which current flows, the current density per unit area can be reduced, so that the amount of heat generated in the current path can be made lower than before.

[0247] The laser beam 103 directly reaches the surface of the first current collector plate 79, which is the object to be welded, downward through the winding center hole 80 of the electrode assembly 71 above the electrode assembly 71 and the battery can 51. The laser welding apparatus 102 may include an optical system including a laser light source (laser beam source) and optical components such as a collimator, a lens, and a mirror for converging the laser from the laser light source into a laser beam 103 having a predetermined spot diameter and irradiating the object to be welded, and a system for introducing the welding atmosphere gas and discharging by-products. The spot diameter indicates the diameter at the positive focal position. Although welding can be performed in air, it is desirable to introduce an inert gas such as nitrogen gas (N2) or argon gas (Ar), even partially, so it is desirable to include a welding atmosphere gas introduction system including an inert gas supply section. And it is desirable to include a by-product discharge system including a dust collection section that sucks in and removes welding fumes so that the welding fumes can be removed.

[0248] Referring to FIG. 15, a laser beam 103 is used to form a laser welded portion 104 in a welding region including the contact surface between the first current collector 79 and the electrode terminal 50, thereby welding the first current collector 79 to the electrode terminal 50. Of course, the bottom 52 of the battery can 51 may be covered so as to face upward, and the laser beam 103 may be irradiated upward from the open portion of the battery can 51. Also in this case, the key is to irradiate the laser beam 103 so as to pass through the winding center hole 80. Since the laser beam 103 does not pass through the outer surface side of the battery can 51 or the electrode terminal 50 formed on the battery can 51, welding beads, welding spots, etc. are not formed on the outer surface of the cylindrical secondary battery 70, so the outer surface is not uneven. This is advantageous for ensuring the connection effect between the cylindrical secondary battery 70 and the bus bar component during the electrical wiring operation for the series and / or parallel connection of the cylindrical secondary batteries 70.

[0249] Since the laser beam 103 is incident from the surface of the first current collector 79 where it is exposed inside the winding center hole 80 toward the electrode terminal 50 side below it, the laser welded portion 104 is formed from one surface of the first current collector 79 facing toward the inside of the winding center hole 80 toward the electrode terminal 50 side at the coupling portion between the first current collector 79 and the electrode terminal 50 as shown in FIG. 15. The width WS of the portion of the laser welded portion 104 that appears on the surface of the first current collector 79, the depth WD of the laser welded portion 104, and the aspect ratio which is the ratio of these can be managed as design factors.

[0250] In the manufacturing method according to an embodiment of the present invention, it is desirable that the laser beam 103 does not deviate from the winding center hole 80. Thereby, the laser welding part 104 can be located at the overlapping part of the first current collector plate 79 and the electrode terminal 50 within the winding center hole 80. When the laser beam 103 does not deviate from the winding center hole 80, damage to peripheral components of the workpiece to be welded, for example, a separation film located near the winding center hole 80 of the electrode assembly 71, can be prevented. On the other hand, even when the laser beam 103 does not deviate from the winding center hole 80, if the heat transmitted to the workpiece to be welded spreads to the peripheral part and reaches the separation film, damage to the separation film will occur. Also, damage to the separation film will occur when by-products and metal fragments generated by laser welding scatter onto the separation film. Therefore, the welding process is controlled so that such damage to the separation film does not occur.

[0251] A laser welding part 104 is formed in the welding area of the first current collector plate 79. By adjusting the depth WD of the laser welding part 104, the laser welding part 104 can be made not to penetrate the electrode terminal 50 and be exposed to the outside. Thereby, the outer surface of the welding area of the electrode terminal 50, that is, the surface where components such as a bus bar are further connected, like the uppermost end of the part of the electrode terminal 50 exposed outside the battery can 51, can be made a smooth surface. By maintaining good contact with the bus bar when connecting to the bus bar, the connection effect and energy transfer efficiency are ensured.

[0252] In a secondary battery 70 manufactured by the manufacturing method according to an embodiment of the present invention, the first current collector plate 79 is welded to the electrode terminal 50 by a laser welding method. A laser welding portion 104 is provided on the contact surface between the first current collector plate 79 and the electrode terminal 50. Such a laser welding portion 104 is located within a superimposed portion where the winding center hole 80, the first current collector plate 79, and the electrode terminal 50 are superimposed on each other. The outer surface of the welding region of the electrode terminal 50 can be a smooth surface. The fact that the outer surface of the welding region is a smooth surface indicates that when the first current collector plate 79 and the electrode terminal 50 are welded together with the laser beam 103, the laser welding portion 104 is formed only on the inner surface of the bottom 52 of the battery can 51. That is, the laser welding portion 104 can be observed only inside the battery can 51, that is, only inside the cylindrical secondary battery 70, and the laser welding portion 104 does not penetrate the inner surface of the bottom 52 of the battery can 51 and expose to the outer surface of the electrode terminal 50. The outer surface of the electrode terminal 50 can maintain the state before the first current collector plate 79 is welded, that is, a smooth surface state, without change.

[0253] The diameter D of the winding center hole 80 can be 2 mm or more and 8 mm or less. The smaller the diameter D of the winding center hole 80, the more advantageous it is to utilize the internal space of the battery can 51. However, since a winding core is used, the diameter D of the winding center hole 80 cannot be set to 0. In addition, since the winding center hole 80 serves as a movement path for the electrolyte during electrolyte injection, in order to smoothly achieve the impregnation of the electrolyte, it must be larger than a predetermined size. Therefore, at the level of the allowable winding process, it is desirable to make the diameter D of the winding center hole 80 2 mm or more as much as possible. When the diameter D of the winding center hole 80 exceeds 8 mm, the utilization of the internal space of the battery can 51 becomes inefficient, which is not desirable from the viewpoint of energy density.

[0254] The optical system of the laser welding apparatus 102 is configured so that the laser beam 103 does not deviate from the winding center hole 80. The jelly roll type electrode assembly included in the large-sized battery has a longer winding center hole. For example, when manufacturing the cylindrical secondary battery 70 to be larger than the form factor 21700, the height of the cylindrical secondary battery 70 is 70 mm or more, about 75 mm or more. In such a case, the length of the winding center hole 80 is also 60 mm or more, which is longer than that of the conventional small-sized cylindrical secondary battery. To connect the first current collector 79 to the electrode terminal 50 by welding on the bottom 52 side of the battery can 51, it is necessary to easily perform focusing on the first current collector 79, and damage to the electrode assembly 71 must be prevented during the welding process. The laser beam 103 has the advantages of monochromaticity, straightness, high brightness, high focusing degree, and high energy intensity. However, a process margin is required to align the laser beam 103 with the winding center hole 80. Also, even after alignment, the position of the winding center hole 80 can be changed due to fine vibrations or the like. Further, the diameter of the laser beam at one end of the winding center hole 80 where the laser beam 103 arrives first is different from the diameter of the laser beam at the other end of the winding center hole 80 near where the laser beam 103 is incident on the first current collector 79. Therefore, in order for the laser beam 103 not to deviate from the winding center hole 80 while passing through the winding center hole 80, it is necessary to ensure a predetermined interference margin between the laser beam 103 and the winding center hole 80 and irradiate the laser beam 103.

[0255] Also, in the case of emitting and irradiating the laser beam 103 using a focusing lens that focuses the laser beam 103 on the first current collector 79, the depth of focus of the focusing lens must be larger than the length of the winding center hole 80. The laser light focused by the focusing lens has the smallest diameter at the focal position, and the diameter increases as it moves away from the focal point. The depth of focus means the length of the region where the diameter of the laser beam does not deviate significantly from the focal diameter before and after the focal plane (the first current collector 79). Desirably, the depth of focus of the focusing lens must be larger than the height of the electrode assembly 71. More desirably, the depth of focus of the focusing lens must be larger than the height of the battery can 51.

[0256] When the depth of focus has a value smaller than the height of the electrode assembly 71, the diameter may be enlarged before the laser beam reaches the welding position and the electrode assembly 71 may be irradiated outside the winding center hole 80, which may cause problems of interference and damage to the electrode assembly 71. Since the height of the cylindrical secondary battery 70 can be about 75 mm, 80 mm, 110 mm or more, it is desirable that the depth of focus of the focusing lens is about 60 mm or more. The depth of focus varies depending on the focal length (distance from the focusing lens to the welding position), the wavelength of the laser beam, the diameter of the laser beam incident on the focusing lens, the quality factor of light, etc. Since the working space must be secured by irradiating the laser beam 103 at a position separated from the upper end of the battery can 51 as much as possible, the longer the depth of focus of the focusing lens, the better. For example, the depth of focus of the focusing lens can be 2 to 3 times the height of the electrode assembly 71. Therefore, the laser welding apparatus 102 may include a focusing lens with a long depth of focus. Most desirably, by making the depth of focus larger than the height of the battery can 51, the diameter is not enlarged before the laser beam reaches the first current collector plate 79, so that irradiation and interference with the peripheral components of the winding center hole 80 can be prevented.

[0257] In one embodiment of the present invention, by using the laser welding apparatus 102 with an improved optical system, the laser beam 103 can be irradiated to the portion of the first current collector plate 79 exposed inside the winding center hole 80 at the lower end of the winding center hole 80, which has become longer than before, while preventing damage to the electrode assembly 71. According to one embodiment of the present invention, since the problem of defects that may occur during laser welding is solved and the first current collector plate 79 can be welded to the electrode terminal 50, the requirements for high-output and low-resistance batteries in the technical field to which the present invention belongs can be satisfied.

[0258] In a laser welding method used in an embodiment of the present invention, the laser beam 103 emitted from the laser welding apparatus 102 irradiates the first current collector 79 without directly contacting the laser welding apparatus 102 with the first current collector 79, thereby realizing welding of the first current collector 79 and the electrode terminal 50. Therefore, component deformation due to contact pressure welding or the like can be prevented, which is not only advantageous for ensuring the quality and performance of the cylindrical secondary battery 70, but also advantageous for improving the product yield.

[0259] When the first current collector 79 and the electrode terminal 50 are made of aluminum material, the welding using a welding rod is less efficient. Since the welding wear is fast, it is necessary to frequently replace the welding rod, and adjustment of the welding apparatus is also required. This not only affects the production efficiency, but also increases the cost of the welding rod. Since using a welding rod is a pressurizing method, it not only causes deformation of the battery can 51 and the welded object, affecting the quality and performance, but also affects the product yield. It is also not desirable to weld the first current collector 79 and the electrode terminal 50 by ultrasonic welding. At this time, a long horn that can be inserted into the winding center hole 80 is required. The horn is easily broken and generates a lot of burrs, and it is difficult to confirm the presence or absence of an unbonded region. Problems due to foreign matter generated during welding also occur.

[0260] In an embodiment of the present invention, by applying laser welding, deformation due to contact pressure welding such as resistance welding can be prevented, which is not only advantageous for ensuring quality and performance, but also advantageous for improving the product yield. Since the laser welding portion 104 is formed inside the secondary battery 70 and not on the outer surface, making the outer surface of the electrode terminal 50 that connects to a bus bar or the like a smooth surface is advantageous for ensuring the connection effect with other components and the energy transfer efficiency. Also, since it is not necessary to replace the welding rod or the horn, it is advantageous for improving production efficiency and reducing production costs, and the manufacturing process time can be shortened. The bonding strength is higher than that of ultrasonic welding, and the welding performance and quality uniformity can also be ensured compared to resistance welding.

[0261] The laser welding portion 104 may include one or more weld beads. A weld bead indicates the welded metal created by one welding (one pass of the laser beam 103), and can also be called a welding spot. The size, shape, position, and degree of overlap of the weld beads can vary depending on the welding conditions. The laser welding portion 104 is formed separately one by one, including not only the weld beads that are distinguishable from each other, but also all cases where the weld beads are partially overlapped and become one mass. Welding methods using the laser beam 103 can include wobble welding, spot welding, weaving (hatching) welding, scanning method welding, etc., and those with ordinary knowledge in the technical field to which the present invention belongs can select and apply them as needed.

[0262] Figures 16 and 17 are diagrams showing various surface forms of the laser welding portion according to an embodiment of the present invention. The shape of the laser welding portion 104 is not particularly limited as long as the joint strength can be maintained. However, since the laser welding portion 104 must be formed inside the winding center hole 80 with a diameter D of 2 mm or more and 8 mm or less, it can be formed at a position that does not deviate from the winding center hole 80 and in a size that does not deviate from the winding center hole 80, and it is desirable to select a shape that is advantageous for showing the intended joint strength. The winding center hole 80 and its diameter D are also shown for reference in Figures 16 and 17. D can be the diameter of the winding center.

[0263] First, referring to FIG. 16, the laser welding portion 104 can be of an overlapping overlay type with respect to the center of the winding center hole 80. For example, the welding bead is circular in shape by spot welding. Forming and overlapping a plurality of such welding beads at the same point is the overlapping overlay type. The circular welding beads can have the same or different diameters from each other. That is, it can be a shape in which a plurality of concentric circles with the same or different diameters are stacked. The overlapping overlay type can be realized by irradiating the laser beam 103 at the same position in a low-power pulse mode. If a high-power laser beam is irradiated at once, overwelding may occur. For example, the workpiece to be welded may be perforated, or a back bead may occur. Here, the back bead means a phenomenon in which a hue change or a welding bead occurs on the opposite surface of the surface where laser welding is performed. By safely using a low-power laser beam 103, such problems can be prevented. There is also an advantage that the joining strength can be adjusted by adjusting the number of irradiations of the laser beam 103. Since it is not necessary to move the laser beam 103, there is little risk that the laser beam 103 will deviate from the narrow winding center hole 80, and the laser welding portion 104 can be stably formed at the center of the winding center hole 80. Therefore, the welding portion can be formed with ideal accuracy and high reliability, and welding defects can be minimized.

[0264] The circular welding beads by spot welding can be overlapped to form a single continuous line. Exemplarily, when the laser beam 103 emitted from the laser welding device 102 is irradiated while moving along a linear path on the first current collector 79 in the winding center hole 80, the laser welding portion 104 can be configured linearly. The line can be a straight line, a curve, a bent line, a spiral (e.g., a spiral, a helix, a vortex, etc.). The movement of the laser beam 103 can be realized by fixing the first current collector 79 and moving the laser beam 103, or by fixing the laser beam 103 and setting the work table on which the battery can 51 provided with the first current collector 79 is placed, for example, on an NC-controlled X-Y table and moving the battery can 51 side to relatively move the laser beam 103.

[0265] The laser welding part 104 can form a continuous closed straight line or closed curve with the start point and end point of the irradiation of the laser beam 103 coinciding. Also, the start point and end point of the irradiation of the laser beam 103 of the laser welding part 104 do not have to coincide. Further, the laser welding part 104 can form an open curve. For example, it can be in the form of a structure with one facet open based on the four-facet reference. For example, it can be in a C shape or the like.

[0266] Referring to Fig. 17(a), the laser welding part 104 can be a ring type centered on the center of the winding center hole 80. Since it is circular, it is desirable because even when forces are applied from multiple directions, the force can be evenly dispersed.

[0267] Referring to Fig. 17(b), the laser welding part 104 can be a wobble circle type centered on the center of the winding center hole 80. This type is also desirable because even when forces are applied from multiple directions, the force can be evenly dispersed.

[0268] Referring to Fig. 17(c), the laser welding part 104 can be an 8-type where two circles are circumscribed.

[0269] Figs. 17(a) and (c) are examples of closed curves, and Fig. 17(b) includes a closed curve but is an example where the start point and end point of the irradiation of the laser beam 103 do not coincide.

[0270] Referring to Fig. 17(d), the laser welding part 104 can be a square frame type centered on the center of the winding center hole 80. Fig. 17(d) is an example of a closed straight line.

[0271] In addition to the square frame, frame types of polygons such as triangles and pentagons are also possible. When forming a circular or polygonal laser welding part, if there is a problem that a welding bead slightly deeper than the periphery is formed at the part where the start point and end point of the laser beam irradiation coincide, the start point and end point do not have to be made to coincide completely, and it can be made to have an incomplete circular or polygonal shape.

[0272] The laser welding part 104 can be arc-shaped as shown in Fig. 17(e). The arc can be formed radially and symmetrically with respect to the center of the winding center hole 80. When formed symmetrically, it is desirable because force can be evenly distributed even when force is applied from multiple directions. The number of arcs is not particularly limited and can desirably be 2 to 4. For example, three arcs can be formed in an arc shape with a length corresponding to an angular range of 50° to 80° with respect to the center of the winding center hole 80 and arranged at the same interval from each other.

[0273] The laser welding part 104 can be of an X-type in which two lines intersect at the center of the winding center hole 80 as shown in Fig. 17(f), or an L-type in which two lines touch at one point as shown in Fig. 17(g).

[0274] A plurality of circular welding beads by spot welding can be formed separately in a state where they do not overlap with other welding beads. In such a case, the laser welding part 104 can be of a multi-spot type formed at symmetric positions radially with respect to the center of the winding center hole 80 as shown in Fig. 17(h). When formed symmetrically, it is desirable because force can be evenly distributed even when force is applied from multiple directions. The number of circular spot welding beads can be two or more. For example, the quantity can be 2, 3, 4, 5, 6, or 8, or can be set to any quantity not less than 2 according to actual demand. In the illustrated example, the quantity is 3. These can be arranged at the same interval from each other. For example, each welding bead can be arranged every 120° with respect to the center of the winding center hole 80.

[0275] The laser beam 103 does not pass through a point only once, but can pass through a point two or more times while moving in a weaving manner. In such a case, the laser welding part 104 can be shaped as shown in Figs. 17(i) and (j), having a center at the center of the winding center hole 80, a regular or irregular outer peripheral part in a polygon shape, and the welding bead filling the inside of the outer peripheral part.

[0276] Thus, as long as the joining strength can be maintained, the shape of the laser welded portion 104 is not particularly limited and may include various shapes that can be realized by the laser beam 103 within the winding center hole 80.

[0277] Regarding the joining strength, the tensile force of the joint between the first current collector plate 79 and the electrode terminal 50 by the laser welded portion 104 is preferably 2 kgf or more, more preferably 3 kgf or more and 15 kgf or less, and even more preferably 5 kgf or more and 15 kgf or less. The tensile force is a force applied perpendicular to the joint surface. It can be converted to tensile strength by multiplying the area of the surface on which the force acts. If the tensile force is 2 kgf or more, preferably 3 kgf or more, when using the cylindrical secondary battery 70, the first current collector plate 79 will not detach from the electrode terminal 50 due to vibrations or pressure of the equipment generated during the process without affecting the performance of the secondary battery. The tensile force of the joint between the first current collector plate 79 and the electrode terminal 50 can be at least 2 kgf or more, or 3 kgf or more, or 5 kgf or more, or 6 kgf or more, or 7 kgf or more, or 8 kgf or more, or 9 kgf or more, or 10 kgf or more. It is desirable to increase the tensile force to the maximum within the allowable range by optimally selecting the welding method.

[0278] Since the joint strength in terms of tensile strength is also related to the area and depth (WD in FIG. 15) of the laser welded portion 104, the joint strength can be adjusted by adjusting the area and depth WD of the laser welded portion 104. As shown in the cross section of FIG. 15, the weld bead should not exist only on the surface, but should be formed on the contact surface of the two members joined by welding and have a three-dimensional shape with a thickness. The depth WD of the laser welded portion 104 includes the thickness of such a weld bead. The depth WD of the laser welded portion 104 can be adjusted by the output of the laser beam 103, the irradiation time, etc. The depth increases as the output of the laser beam 103 increases and also as the irradiation time becomes longer. The output of the laser beam 103, the irradiation time, etc. can be adjusted so that the weld bead extends to the outer surface of the electrode terminal 50 while having an appropriate joint strength and is not formed too deeply. In the actual process, since the thickness ranges of the first current collector 79 and the electrode terminal 50 are determined, the depth WD of the laser beam 103 that can be adjusted to prevent overwelding is somewhat limited. Adjusting the area of the laser welded portion 104 has a wider process window. The area of the laser welded portion 104 is also related to the width WS of the laser welded portion 104, but as proposed in the present invention, it can be managed using the design factor of the equivalent diameter D' of the laser welded portion 104.

[0279] The equivalent diameter D' of the laser welded portion 104 is the diameter of the virtual circle circumscribing the laser welded portion 104 on the surface of the welded body, that is, the laser welded portion 104 exposed on the surface of the first current collector 79. Therefore, the equivalent diameter D' can indicate the distance between a pair of welding points located at the farthest distance from each other among the respective laser welding points forming the weld bead included in the laser welded portion 104. The equivalent diameter D' proposed for management in the present invention is obtained by converting the area SA of the welded portion shown on the surface of the welded body into the area of a circle πr 2 When converted to, the diameter of the circle (D = 2×(SA / π) 0.5) is different from that represented by. The latter indicates information regarding the size of the welded portion or the area occupied by the welded portion on a plane, and is a control factor regarding what fraction of the total area of a given region the welded portion occupies. On the other hand, although the equivalent diameter D’ is also related to the size of the welded portion, it also includes information regarding the shape of the welded portion. Therefore, even for welded portions with the same area, it takes into account how far apart the welding points in the welded portion are from each other, that is, it can indicate how widely the welded portion spreads within a given region, and is a control factor. In an embodiment of the present invention, since a laser welded portion 104 is formed in the winding center hole 80 and it must be controlled so that the laser welded portion 104 does not deviate from the winding center hole 80, even if it is a welded portion having a narrow area, it should not spread widely. Therefore, it is desirable to control it as the equivalent diameter D’.

[0280] FIG. 18 is a diagram for explaining a method of calculating the equivalent diameter of a laser welded portion in the case of spot welding.

[0281] Laser welding forms a laser welded portion 104 in a multi-spot method as shown in (h) among the various forms shown in FIG. 17. For example, in the case of a spot welding type, the equivalent diameter D’ of the laser welded portion 104 is the diameter of a virtual circle 104b circumscribing the three welding points 104a.

[0282] To assist in understanding the equivalent diameter D’, the equivalent diameter D’ of the laser welded portion 104 is also shown in FIGS. 16 and 17(a), (b), (d), (g).

[0283] In one embodiment of the present invention, the equivalent diameter D' of the laser welding part 104 can be 0.15D to 0.90D. That is, the equivalent diameter of the laser welding part 104 can be formed in the range of about 15% to 90% of the diameter D of the winding center hole 80. It is very difficult to realize an equivalent diameter D' of 0.4D or more using a conventionally known laser welding method. This is because it is very difficult to focus and reach the laser beam without affecting the periphery of the winding center hole 80 on the bottom side of the winding center hole 80, which has become longer than before. That is, in the manufacture of large batteries, when the laser beam has a length of 60 mm or more, an improved optical system is required to prevent deviation from the winding center hole 80 with a diameter D of 2 mm or more and 8 mm or less when passing through the winding center hole 80, or other means of implementation are essentially required. The laser welding apparatus 102 according to one embodiment of the present invention includes an improved optical system that takes precedence in considering the narrow and long winding center hole 80, and thus the equivalent diameter D' can be realized to be 0.4D or more. Although the larger the equivalent diameter D' is, the more advantageous it is in terms of bonding strength, when the equivalent diameter D' is 0.9D or more, there is a risk of damaging the peripheral components of the winding center hole 80 due to fine vibrations, movements, and other accidents during the process. Therefore, although it is possible to make it even larger, it is desirable to make the equivalent diameter D' 0.9D or less. If the equivalent diameter D' is small, sufficient bonding strength cannot be obtained. Therefore, it is desirable to make the equivalent diameter D' at least 0.15D.

[0284] As described above, the diameter D of the winding center hole 80 can be 2 mm or more and 8 mm or less. The equivalent diameter D' of the laser welding part 104 exposed on the surface of the first current collector 79 can be 2 mm or more. The area SA of the laser welding part 104 exposed on the surface of the first current collector 79 is regarded as the area of a circle having the equivalent diameter D' (π(D' / 2) 2 )

[0285] The diameter of the flat portion 50d of the electrode terminal 50 can be determined in consideration of the bonding strength between the first current collector plate 79 and the electrode terminal 50. The diameter of the flat portion 50d of the electrode terminal 50 is twice the radius R3 from the center of the main body portion 50a of the electrode terminal 50 described with reference to FIG. 8 to the periphery of the flat portion 50d, and can be 3 mm to 14 mm.

[0286] The flat portion 50d of the electrode terminal 50 becomes an area where welding is possible. Accordingly, the diameter of the area where welding is possible in the electrode terminal 50 can be 3 mm to 14 mm. If the diameter of the area where welding is possible is less than 3 mm, it is difficult to secure a laser welded portion having a converted diameter D' of 2 mm or more. If the diameter of the area where welding is possible exceeds 14 mm, the diameter of the outer flange portion 50b of the electrode terminal 50 becomes excessively large, and it is difficult to sufficiently secure the area of the outer surface 52a of the bottom portion 52 of the battery can used as the negative electrode terminal.

[0287] Considering the converted diameter D' of the laser welded portion 104 and the diameter condition of the area where welding is possible of the electrode terminal 50, the ratio of the area of the laser welded portion 104 exposed on the surface of the first current collector plate 79 to the area of the flat portion 50d of the electrode terminal 50 necessary to secure a tensile force of the welded portion of at least 2 kgf or more, preferably 3 kgf or more, is 2.04% (π1 2 / π7 2 ) to 44.4% (π1 2 / π1.5 2 ) is desirable.

[0288] Referring further to FIG. 14, the step of forming the laser welded portion 104 may include inserting the hollow tube 105 into the winding center hole 80 and exposing at least a part of the first current collector plate 79 into the inner hollow portion of the hollow tube 105.

[0289] At this time, the first current collector plate 79 can be pressed against the electrode terminal 50 by the hollow tube 105. The laser beam 103 emitted from the laser welding apparatus 102 can pass through the inner hollow portion of the hollow tube 105 and weld the first current collector plate 79 to the electrode terminal 50.

[0290] The laser beam 103 is focused onto the first current collector 79 through an optical system such as expansion, reflection, and focusing. The laser beam 103 irradiated on the first current collector 79 can heat the first current collector 79, which is the object to be welded. The heat on the surface diffuses into the interior by heat conduction, and the pulse width, energy, peak power, repetition frequency (pulse cycle), etc. of the laser beam 103 are precisely controlled as preset. By the irradiation of the laser beam 103, the material at the irradiated site melts, vaporizes, and evaporates, and the molten site solidifies behind the passage of the laser beam 103 to form a weld bead. The laser beam 103 can be controlled to move to a predetermined locus or position.

[0291] The joint quality can be improved only by preventing joint defects such as cracks and back beads and suppressing the occurrence of thermal deformation and spatter at the joint site. Such defects can be caused by the incidence of excessive heat. In one embodiment of the present invention, when heating the first current collector 79 with the laser beam 103, the mode of the laser beam 103 can be adjusted, or the output of the laser beam 103 can be adjusted over time to change the heating site and heating temperature, creating a temperature difference between the portion where the laser beam 103 is intensively irradiated and its periphery, or causing full melting to occur after preheating, thereby preventing the occurrence of spatter. If a deep-depth weld bead is formed with high energy from the beginning at the portion where the laser beam 103 is intensively irradiated, there is a risk that pores will occur in the first current collector 79 due to high welding heat, or scattered materials such as spatter will be formed. Therefore, the occurrence of spatter can be prevented by having a process of managing the welding heat, such as having a preheating process. Also, even if scattered materials on the surface such as spatter occur, a method of melting them, maintaining them in a molten state, and then solidifying them to form a part of the weld bead on the first current collector 79 by creating the temperature difference can also be carried out.

[0292] On the one hand, when the first current collector plate 79 is pressed against the electrode terminal 50 using the hollow tube 105, the quality and performance of the cylindrical secondary battery 70 are improved by preventing welding defects caused by the lack of close contact between the first current collector plate 79 and the electrode terminal 50. On the other hand, not only is it possible to prevent the laser beam 103 from damaging the electrode assembly 71 by isolating the laser beam 103 and guiding it, but the mask can also play a role in preventing the laser beam 103 from being irradiated to other positions outside the welding area. Thus, when the first current collector plate 79 is pressed using the hollow tube 105, the welding quality can be improved by applying a stronger pressure to the welding area.

[0293] The hollow tube 105 is a selectable element. Also, optionally, by making the length of the hollow tube 105 larger than the height of the electrode assembly 71, the separation between the electrode assembly 71 and the laser beam 103 can be ensured using the hollow tube 105. For example, the length of the hollow tube 105 is greater than 60 mm. The outer diameter of the hollow tube 105 is smaller than the diameter D of the winding center hole 80. For example, the diameter D of the winding center hole 80 is 80 mm, and the outer diameter of the hollow tube 105 can be 60 mm. The inner diameter DI of the hollow tube 105 has a value obtained by subtracting twice the wall thickness of the hollow tube 105 from the outer diameter. The wall thickness of the hollow tube 105 can be, for example, 0.1 mm to 1 mm.

[0294] The hollow tube 105 is, for example, a metal hollow tube. For example, the hollow tube 105 can be made of iron, nickel-plated iron, SUS, or an aluminum alloy material. In another example, the hollow tube 105 can be a non-metallic material resistant to high temperatures. For example, it can be ceramic. Also, the hollow tube 105 can effectively prevent problems such as the melt generated during the laser welding process, that is, spatter, from flowing into the electrode assembly 71 and causing a short circuit.

[0295] While welding is being performed by the laser beam 103, a step of supplying an inert gas such as nitrogen gas or argon gas for removing the oxygen atmosphere into the space between the hollow tube 105 and the inner peripheral surface of the winding center hole 80 can be carried out. In order to more smoothly guide the inert gas onto the first current collector plate 79, the bottom of the hollow tube 105 can be separated so as to be positioned above the upper surface of the first current collector plate 79. In another example, at least one hole for the entry and exit of gas can be formed in the wall of the hollow tube 105 at a portion adjacent to the first current collector plate 79.

[0296] When the inert gas is supplied, the internal space of the inner hollow portion of the hollow tube 105 can be converted into an inert gas atmosphere. Thereby, when the first current collector plate 79 and the electrode terminal 50 are made of an aluminum material, it is possible to prevent the aluminum melted by laser irradiation from reacting with oxygen to form welding fumes in the form of fine dust.

[0297] Also, while welding is being performed by the laser beam 103, a step of removing welding fumes can be carried out at one end side of the winding center hole 80, which is on the opposite side of the portion where welding is being performed. The inflow of welding fumes into the electrode assembly 71 can be primarily prevented by the hollow tube 105, and furthermore, when an inert gas atmosphere is formed when supplying and welding the inert gas, the generation of welding fumes can be prevented. However, when welding fumes are generated despite such a configuration, product defects can be more reliably prevented by inhaling / removing them. Thereby, the welding quality is further improved.

[0298] The laser welding device 102 can weld the first current collector plate 79 to the electrode terminal 50 in a pulse mode or a continuous mode. In the continuous mode of operation, the laser medium of the laser light source is continuously excited to generate a continuous laser beam. In the pulse mode, the laser medium is excited in the form of pulses rather than continuously. In this mode, a laser beam that is cut in time (pulse beam) is generated. The period, energy, and pulse cycle of this laser pulse can be adjusted. It can be determined in advance during the design of the laser welding device 102 to have a specific operation mode. For example, the laser welding device 102 can irradiate the laser beam 103 with a pulse width of 100 ns to 2000 ns. When the first current collector plate 79 and the electrode terminal 50 are made of aluminum or an aluminum alloy agent, since its thermal conductivity is high, it is desirable to irradiate a beam with a large output to the welding area. Therefore, it is desirable to perform welding with a pulse beam. When performing welding with a pulse beam, conditions such as the pulse width and pulse cycle can be appropriately set considering the type of material, penetration depth, etc. Other welding conditions, such as the spot diameter and processing speed, can also be appropriately set according to the materials of the first current collector plate 79 and the electrode terminal 50 to be joined, and the welding design such as the width WS, depth WD, and aspect ratio of the laser welding portion 104.

[0299] Laser light sources include carbon dioxide lasers, argon lasers, ruby lasers, YAG lasers, fiber lasers, etc., which are a type of solid laser. An appropriate one can be selected according to the material and thickness of the object to be welded. Also, the output can be appropriately determined according to these. For example, a YAG laser with high bonding efficiency with metals and excellent processing performance is desirable. The laser beam 103 is selected so that the thermal deformation of the object to be welded and the deterioration of material properties are reduced.

[0300] The wavelength of the laser beam 103 is not particularly limited as long as efficient welding is possible. When using a green laser light source (515 nm), it is desirable because the weldable output range is high. When using a green laser light source, the optical system can be configured by changing a lens or the like for reducing the beam size (spot diameter). When the beam size is large, the influence on corrosion increases, the aspect ratio of the laser welded portion 104 decreases, and the welding efficiency may be inferior. Note that an IR laser light source (1070 nm) may be used. Even if the weldable output range is smaller than that of the green laser light source, an overlapping overlay type weld bead may be formed with a low-output laser beam. Desirably, a pulsed dot type laser beam can be overlapped and irradiated on the center portion of the take-up center hole 80 to form an overlapping overlay type laser welded portion 104 as shown in FIG. 6.

[0301] The wavelength of the laser beam 103 can be 1,000 to 1,500 nm, desirably 900 to 1,350 nm, more desirably 1,060 to 1,080 nm, considering the materials of the metal terminal 50 and the first current collector plate 79 to be welded. When the wavelength of the laser beam 103 is less than the above range, the weldable output range can be widened, but there is a problem that it is difficult to reduce the size of the laser beam 103. When the wavelength of the laser beam 103 exceeds the above range, the weldable output range is narrow and there is a high possibility of welding failure. Therefore, it is desirable that the wavelength of the laser beam 103 satisfies the above range. In addition, a laser beam 103 having a wavelength of 400 nm to 600 nm can also be used.

[0302] The laser welding apparatus 102 can irradiate a laser beam 103 at a processing speed of 40 mm / s to 1,000 mm / s. The processing speed indicates the moving speed of the laser beam 103 on the first current collector 79. Since the shape of the weld bead changes depending on the processing speed, the processing speed of the laser beam 103 is important. In the laser welding step according to an embodiment of the present invention, the processing speed of the laser beam 103 is 40 mm / s to 1,000 mm / s, desirably 100 mm / s to 500 mm / s, and more desirably 200 mm / s to 300 mm / s. If the processing speed of the laser beam 103 is less than the above range, there is a risk of back bead generation, and if it exceeds the above range, there is a problem that the joining strength decreases. Therefore, it is desirable that the processing speed of the laser beam 103 satisfies the above range.

[0303] The laser welding apparatus 102 can irradiate a laser beam 103 with an output of 50 W to 4 kW. The output of the laser beam 103 can be converted into "line energy", which is the output value of the laser beam 103 with respect to the processing speed of the laser beam 103, and managed as a design factor. If the output of the laser beam 103 is less than the above range, there may be a problem that the joining strength decreases, and if it exceeds the above range, there is a risk of back bead generation. Therefore, it is desirable that the output of the laser beam 103 satisfies the above range. The output of the laser beam 103 can be 300 W to 500 W.

[0304] The spot diameter of the laser beam 103 can be 10 μm to 200 μm. If the spot diameter of the laser beam 103 exceeds 200 μm, the influence on corrosion increases, and there is a disadvantage that the aspect ratio of the laser welded portion 104 decreases and the welding efficiency may drop. Also, if the size of the laser beam 103 is less than 10 μm, there is a disadvantage that the welding area is small and sufficient joining strength cannot be ensured by one welding. Therefore, it is desirable that the spot diameter of the laser beam 103 satisfies the above range. Desirably, the spot diameter of the laser beam 103 can be around 50 μm.

[0305] When irradiating in a pulsed dot manner with the laser beam 103 having a spot diameter within such a range, one weld bead can be formed in a circular shape by spot welding as shown in Fig. 17(h). The width (WS in Fig. 15) of the circular spot weld bead is not less than 50μm, for example, 50μm, 60μm, 70μm, 80μm or 100μm, or can be set to any value not less than 50μm according to actual requirements. By forming the width not less than 50μm, the welding effect between the first current collector plate 79 and the electrode terminal 50 can be well ensured, and the influence on the welding effect between the first current collector plate 79 and the electrode terminal 50 due to the width of the circular spot weld bead being excessively small can be prevented.

[0306] The laser beam 103 can be a single mode or a multi - mode. The laser beam mode refers to showing the energy distribution within the cross - section of the laser beam. The laser welding apparatus 102 can be pre - determined at the design stage to have a specific mode. The output energy and application fields vary depending on the laser beam mode, and it is distinguishable to the extent that it can be known which mode was used from the shape of the weld bead. The spot diameter of the single - mode laser beam 103 can be 50μm or less. The spot diameter of the multi - mode laser beam 103 can be 50μm or more.

[0307] In the single mode, the energy distribution follows a Gaussian distribution and there is one energy peak. To obtain the single mode, although the output of the laser may be lost, it is advantageous for high - precision processing. In one embodiment of the present invention, when it is required to finely form the laser welding part 104, a single - mode laser beam can be used.

[0308] In multimode, there are two or more energy peaks in the energy distribution. Many high-power lasers come to have multimode beams. In order to obtain a single-mode beam from such a multimode beam, the output energy is reduced by about half. Multimode has a larger spot diameter than single mode when connected. Also, in multimode, the portion that contacts and heats the workpiece is different from that in single mode. Using such characteristics, the welding quality and work efficiency can be further improved.

[0309] The laser welding apparatus 102 can use a fiber laser. The wavelength of the laser beam 103 is 1,070 nm, and welding by a scanning method may be possible. A commercialized laser apparatus with a maximum output of about 200 W in the pulse mode and a maximum output of about 700 W in the continuous mode can be used. The commercialized laser apparatus has a beam size of about 30 μm and can easily form a welded portion with a narrow area. A laser welding apparatus 102 that can have a larger maximum output and can make the size of the beam smaller or larger than that may be configured to perform the manufacturing method according to an embodiment of the present invention.

[0310] Laser welding is advantageous for increasing the capacity of a secondary battery by further reducing the diameter D of the winding center hole 80 and increasing the height of the electrode assembly 71 because it enables processing of a narrower area compared to resistance welding. Also, laser welding has no restrictions on the material of the workpiece compared to resistance welding. The present invention does not arbitrarily select and apply laser welding among known resistance welding, ultrasonic welding, and laser welding. The present invention is an improved positive electrode terminal 50. For the electrode assembly 71 having the long winding center hole 80, there was no known technical problem before the present invention that the first current collector plate 79 made mainly of aluminum and the positive electrode terminal 50 had to be connected inside the battery can 51. Thus, even for a person with ordinary knowledge, it is not easy to arrive at connecting the first current collector plate 79 and the positive electrode terminal 50 using laser welding. Even if laser welding is used, while preventing damage to the peripheral components of the long winding center hole 80, preventing the occurrence of spatter, etc., and having an appropriate bonding strength, it is not possible to laser-weld the first current collector plate 79 and the positive electrode terminal 50 within the portion overlapping the winding center hole 80.

[0311] Hereinafter, an experimental example of the welding step in the manufacturing method according to an embodiment of the present invention will be described.

[0312] FIG. 19 is a diagram showing the appearance of the laser-welded portion and comparing the converted diameter D' with the diameter of the winding center hole 80 of the electrode assembly 71. FIG. 20 is a diagram showing the appearance of the laser-welded portion and comparing the converted diameter D' with the diameter of the hollow tube 105 inserted into the winding center hole 80 of the electrode assembly 71.

[0313] The diameter D of the winding center hole 80 was 8 mm. According to the manufacturing method of an embodiment of the present invention, the surface appearance of the laser welding part 104 formed on the first current collector plate 79 inside such a winding center hole 80 was the same as that shown in FIG. 19. According to the manufacturing method of an embodiment of the present invention, the laser welding part 104 could be successfully formed. The numbers #1, #2, #4, #5 of the experimental examples were the same circle type as those exemplified in FIG. 17(a), and #3 was the overlapping overlay type. In each experimental example, it was confirmed that the laser welding part 104 was not exposed on the outer surface of the electrode terminal below the first current collector plate 79, and the first current collector plate 79 and the electrode terminal were firmly welded. In #1 to #5, since the converted diameter D' of the laser welding part 104 was 3.8 mm, 4.1 mm, 2.6 mm, 3.5 mm, and 3.6 mm respectively, the converted diameter D' was 0.325D to 0.5125D, and the condition that D' was 0.15D to 0.90D was satisfied. Also, it was confirmed that according to the manufacturing method of an embodiment of the present invention, a laser welding part 104 with a converted diameter D' of 2 mm or more could be successfully formed.

[0314] The diameter D of the winding center hole 80 can vary. The outer diameter and inner diameter of the hollow tube 105 can also vary according to the winding center holes 80 with various diameters D. The results of laser welding performed using various hollow tubes 105 are shown in FIG. 20.

[0315] Referring to FIG. 20, the laser welding part 104 was well formed in the inner hollow part of the hollow tube 105 to a size smaller than the inner diameter DI of the hollow tube 105. The converted diameters D' of the laser welding part 104 were arranged in ascending order from 2.6 mm in #6 to 4.9 mm in #13. In each experimental example, the inner diameter DI of the hollow tube 105 was different. In each experimental example, the ratio of the converted diameter D' to the inner diameter DI of the hollow tube 105 was also arranged in ascending order from 27% to 96%. The inner diameter DI of the hollow tube 105 in #6 was 9.6 mm. The inner diameter DI of the hollow tube 105 in #13 was 5.1 mm.

[0316] Since the inner diameter DI of the hollow tube 105 is smaller than the diameter D of the winding center hole 80, in the experimental examples #6 to #13 having a range where D’ / DI is 27% to 96%, D’ / D shows a range where the upper and lower limits are changed to smaller values. For example, D’ / D can show a range of 30% to 94%. In this way, while forming the laser welded part 104 with various converted diameters D’ using various hollow tubes 105, it was possible to satisfy the condition that D’ is 0.15D to 0.90D.

[0317] In particular, as in #13, when D’ / DI is 96%, it indicates that the laser welded part 104 is formed very close to the wall of the hollow tube 105. It is necessary to note that even in such a case, the laser welded part could be formed without damaging the electrode assembly part around the winding center hole 80. Also in the case of using the hollow tube 105 in this way, the condition that D’ is 0.15D to 0.90D, that is, the range where D’ / D is 15% to 90% could be sufficiently achieved.

[0318] After the laser welding step is completed as described above, further steps such as the assembly, beading, crimping, electrolyte injection, and sizing of the sealing body 74 can be performed. The order of the steps can be changed as necessary. For example, depending on the structure of the second current collector 78, the step of welding the second current collector 78 to the battery can 51 can also be performed.

[0319] The cylindrical secondary battery 70 according to an embodiment of the present invention includes a first current collector 79 and a second current collector 78. The first current collector 79 may have a structure that prevents force from concentrating on the joint part between components even when external impact and / or vibration is applied during use. The second current collector 78 not only has a structure that improves the bonding force of the joint part with the battery can 51, but also improves the energy density of the cylindrical secondary battery 70. Such a first current collector 79 and second current collector 78 also have a structure that is easy to laser weld the first current collector 79 to the electrode terminal 50.

[0320] Hereinafter, various embodiments of the first current collector 79 and the second current collector 78 will be described.

[0321] Figures 21 to 24 are diagrams showing various surface forms of the first current collector.

[0322] Referring to Figures 21 to 24, the first current collector 120 includes an edge portion 121, a first electrode tab coupling portion 122, and a terminal coupling portion 123. The edge portion 121, the first electrode tab coupling portion 122, and the terminal coupling portion 123 can all be in the same plane. That is, the first current collector 120 is a substantially plate-shaped member having a thickness smaller than the horizontal or vertical length of the portion having a large area, and when the portion having a large area in the first current collector 120 is placed at the upper end or the lower end of the electrode assembly 71, the entire first current collector 120 has a shape extending parallel to the upper end surface or the lower end surface of the electrode assembly 71, and there is no height difference among the edge portion 121, the first electrode tab coupling portion 122, and the terminal coupling portion 123 within the first current collector 120. Such a planar structure does not occupy volume within the battery can 51, so the space utilization is good.

[0323] The edge portion 121 can have a substantially rim form in which a space S is formed in at least a part of the inner region. In the drawings, only the case where the edge portion 121 has a substantially circular rim form is shown, but the present invention is not limited thereby. The edge portion 121 can have a substantially square rim form or other forms different from those shown.

[0324] The first electrode tab coupling portion 122 extends inward from the edge portion 121 and can be coupled to the non-coated portion 73 of the first electrode plate by welding. The terminal coupling portion 123 is located inside the edge portion 121 at a distance from the first electrode tab coupling portion 122. The terminal coupling portion 123 can be a portion that is coupled to the positive electrode terminal 50 by laser welding as described above. The terminal coupling portion 123 can be located, for example, at the center of the inner space of the edge portion 121. The terminal coupling portion 123 can be arranged at a position corresponding to the winding center hole 80 of the electrode assembly 71. The size of the terminal coupling portion 123 may be larger than the diameter of the winding center hole 80. A laser welding portion 104 as described above can be formed on the terminal coupling portion 123.

[0325] The first electrode tab connection part 122 and the terminal connection part 123 are not directly connected to each other, but are arranged to be separated from each other and are connected by the edge part 121. In this way, the first current collector plate 120 has a structure in which the first electrode tab connection part 122 and the terminal connection part 123 are not directly connected to each other but are connected via the edge part 121. When impact and / or vibration occur in the cylindrical secondary battery 70, the impact applied to the connection site between the first electrode tab connection part 122 and the non-coated part 73 of the first electrode plate and the connection site between the terminal connection part 123 and the positive electrode terminal 50 can be dispersed. As a result, the first current collector plate 120 also has the effect of minimizing or preventing damage to the welding site due to external impact. When an external impact is applied, the first current collector plate 120 has a structure in which stress can concentrate at the connection site between the edge part 121 and the terminal connection part 123. Since such a connection site is not a site where a welding part for connecting parts is formed, the occurrence of product defects due to damage to the welding part caused by external impact can be prevented. In this way, since the first current collector plate 120 has a structure in which force does not concentrate on the connection site between parts even when external impact and / or vibration is applied during the use process, the performance of the cylindrical secondary battery 70 including the same is improved.

[0326] The first battery 120 may further include a connection part 124 that extends inward from the edge part 121 and is connected to the terminal connection part 123. At least a part of the connection part 124 may be formed to have a smaller width than that of the first electrode tab connection part 122. In this case, when the electrical resistance increases at the connection part 124 and current flows through the connection part 124, a larger resistance is generated than in other parts, so that a part of the connection part 124 breaks when an overcurrent occurs, thereby interrupting the overcurrent. The width of the connection part 124 may be adjusted to an appropriate level in consideration of such an overcurrent interruption function. At least a part of the connection part 124 may have a relatively narrow width to enhance the current interruption function. For example, both sides of the connection part 124 may be provided with notch parts that are cut inward so that the width of the connection part 124 is partially reduced. When the notch parts are provided, the electrical resistance in the region where the notch parts are formed further increases, and the current conduction becomes impossible by melting and breaking due to resistance heating. Thereby, rapid current interruption is possible when an overcurrent occurs.

[0327] The connection part 124 may include a tapered part 124a whose width gradually becomes narrower along the direction from the inner end of the edge part 121 toward the terminal connection part 123. When the tapered part 124a is included, the rigidity of the component can be improved at the connection site between the connection part 124 and the edge part 121. If the notch part is provided, the notch part may be located closer to the tapered part 124a than the terminal connection part 123. In this case, due to the structure of the edge part 124a whose width gradually becomes narrower, the notch part is located in a region adjacent to a region with a large heat generation amount, so that more rapid overcurrent interruption is possible.

[0328] In the first battery plate 120, a plurality of first electrode tab connection parts 122 may be included. The plurality of first electrode tab connection parts 122 may be arranged at equal intervals from each other along the circumferential direction. The extension lengths of each of the plurality of first electrode tab connection parts 122 may be the same as each other. The terminal connection part 123 may be arranged so as to be surrounded by the plurality of first electrode tab connection parts 122. The connection part 124 may be located between a pair of adjacent first electrode tab connection parts 122. In this case, the distance from the connection part 124 to any one of the pair of first electrode tab connection parts 122 in the direction along the edge part 121 may be the same as the distance from the connection part 124 to the remaining one of the pair of first electrode tab connection parts 122 in the direction along the edge part 121.

[0329] A plurality of connection parts 124 may be included. Each of the plurality of connection parts 124 may be arranged between a pair of adjacent first electrode tab connection parts 122. The plurality of connection parts 124 may be arranged at equal intervals from each other along the circumferential direction.

[0330] When a plurality of first electrode tab connection parts 122 and / or connection parts 124 are included as described above, if the distances between the first electrode tab connection parts 122 and / or the distances between the connection parts 124 and / or the distance between the first electrode tab connection parts 122 and the connection parts 124 are formed to be constant, the flow of current from the first electrode tab connection parts 122 toward the connection parts 124 or the flow of current from the connection parts 124 toward the first electrode tab connection parts 122 can be formed smoothly.

[0331] The first electrode tab connection part 122 may be welded to a certain area in a state of being placed on the folded surface of the non-coated part 73 of the first electrode plate in the electrode assembly 71. That is, the first electrode tab connection part 122 may be joined to a region where a plurality of segmented pieces (93a in FIG. 12) are superposed multiple times. A welding part may be formed for each of the first electrode tab connection parts 122. The welding part may be formed to extend along the extension direction of the first electrode tab connection part 122.

[0332] When a cylindrical secondary battery is applied to a device such as an automobile, external shocks and vibrations may be frequently applied during use, which may cause damage to the bonding sites for connection between components. Such damage to the bonding sites causes product defects. Or, even if the bonding site for connection is damaged and the connection is not completely interrupted, when the welding site is partially damaged and the bonding area between components is reduced, there may be problems such as excessive heat generation due to increased resistance and internal short circuit due to deformation of the component form. The cylindrical secondary battery 70 according to an embodiment of the present invention can solve such problems by including the first current collector plate 120 as described above.

[0333] FIGS. 25 to 28 are views showing various surface forms of the second current collector plate.

[0334] Referring to FIG. 25, the second current collector plate 140 includes at least one second electrode tab coupling portion 142 that couples with the non-coated portion 72 of the second electrode plate and at least one can coupling portion 143 that is electrically coupled to the beading portion 76 on the inner surface of the battery can 51. The second electrode tab coupling portion 142 and the can coupling portion 143 do not have to be in the same plane. That is, the second current collector plate 140 is a substantially plate-shaped member having a thickness thinner than the horizontal or vertical length of the portion having a large area. When the portion having a large area in the second current collector plate 140 is placed at the lower end of the electrode assembly 71, the second electrode tab coupling portion 142 and the can coupling portion 143 in the second current collector plate 140 have a height difference. Such a three-dimensional structure can improve the bonding force of the bonding site with the battery can 51 by ensuring the contact area between the second electrode tab coupling portion 142 and the non-coated portion 72 of the second electrode plate while lowering the can coupling portion 143 and fixing it to the beading portion 76 of the battery can 51.

[0335] The central portion 141 of the second current collector plate 140 may be in a substantially circular plate shape. The central portion 141 may selectively couple with the non-coated portion 72 of the second electrode plate. The central portion 141 may be in a ring-shaped plate form provided with a current collector plate hole 145 at its center.

[0336] The current collector plate hole 145 is formed at a position corresponding to the winding center hole 80 of the electrode assembly 71 and may be circular. The winding center hole 80 and the current collector plate hole 145 that communicate with each other can function as a passage for irradiating the laser beam 103 for welding the electrode terminal 50 and the positive current collector plate 120. Further, when a large amount of gas is generated due to an abnormality in the secondary battery, the current collector plate hole 145 can also serve to allow the gas to quickly move downward through the winding center hole 80.

[0337] The diameter of the current collector plate hole 145 can be 0.5D or more, desirably 0.7D or more, and more desirably 1.0D or more, based on the diameter D of the winding center hole 80 of the electrode assembly 71. When the diameter of the current collector plate hole 145 is 0.5D or more and less than 1.0D, in a situation where the cell is vented, the phenomenon of the separator or the electrode plate being pushed out from the winding center hole 80 can be prevented. Desirably, when the diameter of the current collector plate hole 145 is set larger than the diameter D of the winding center hole 80 of the electrode assembly 71, it becomes easier to secure a space by inserting the hollow tube 105 when irradiating the laser beam 103 for welding the electrode terminal 50 and the positive current collector plate 120.

[0338] The second current collector plate 140 may be provided with a plurality of second electrode tab coupling portions 142 and can coupling portions 143. At this time, although not shown, the plurality of can coupling portions 143 can be connected to each other and integrally formed.

[0339] The second electrode tab coupling portion 142 may have a form that extends substantially radially from the central portion 141 of the second current collector plate 140 toward the side wall of the battery can 51. The plurality of second electrode tab coupling portions 142 can be positioned separately from each other along the circumference of the central portion 141. By providing the plurality of second electrode tab coupling portions 142, the bonding area with the non-coated portion 72 of the second electrode plate can be increased. Thereby, the bonding force between the non-coated portion 72 of the second electrode plate and the second electrode tab coupling portion 142 is ensured, and the electrical resistance can be reduced.

[0340] The second electrode tab coupling portion 142 can be welded to the non-coated portion 72 of the second electrode plate. The second electrode tab coupling portion 142 can be welded to a certain region while being placed on the bent surface of the non-coated portion 72 of the second electrode plate in the electrode assembly 71. That is, the second electrode tab coupling portion 142 can be coupled to a region where a plurality of segmented pieces (93a in FIG. 12) are multiply stacked. A welding portion can be formed for each second electrode tab coupling portion 142. The welding portion can be formed to extend along the extending direction of the second electrode tab coupling portion 142.

[0341] The plurality of can coupling portions 143 can be positioned separately from each other along the periphery of the central portion 141. The can coupling portion 143 can be coupled to the beading portion 76 on the inner surface of the battery can 51. With such a structure in which the second current collector plate 140 is coupled to the beading portion 76 of the battery can 51 instead of the inner surface of the cylindrical portion of the battery can 51, the distance between the second current collector plate 140 and the beading portion 76 can be reduced. Thereby, the dead space inside the battery can 51 is minimized, and the energy density of the cylindrical secondary battery 70 can be improved.

[0342] The can coupling portion 143 can be fixed by being crimped by the crimping portion 114 of the battery can 51. The can coupling portion 143 can include a contact portion 143a that couples to the beading portion 76 on the inner surface of the battery can 51, and a connecting portion 143b that connects the second electrode tab coupling portion 142 and the contact portion 143a.

[0343] The contact portion 143a couples to the inner surface of the battery can 51. When the beading portion 76 is formed on the battery can 51, the contact portion 143a can couple to the beading portion 76. In this case, as described above, for stable contact and coupling, both the beading portion 76 and the contact portion 143a can have a form extending along a direction substantially parallel to the lower surface of the battery can 51, that is, a direction substantially perpendicular to the side wall of the battery can 51. That is, the contact portion 143a includes at least a part of a flat portion substantially parallel to the lower surface of the battery can 51.

[0344] As shown in FIG. 25, the connecting portion 143b may include at least one bending portion BD whose extending direction is converted at least once between the central portion 141 and the contact portion 143a. That is, the connecting portion 143b may have a structure similar to a spring or a bellows structure that can contract and expand within a certain range. On the other hand, the connecting portion 143b may be elastically biased upward by the bending portion BD. Such a structure of the connecting portion 143b enables the contact portion 143a to closely adhere to the beading portion 76 during the process of accommodating the electrode assembly 71 to which the second current collector plate 140 is coupled into the battery can 51, even if there is a variation in the height of the electrode assembly 71 within a certain range. Also, according to such a structure of the connecting portion 143b, the shape can be more stably realized during the sizing process. The sizing process is a compression process for reducing the height occupied by the region of the beading portion 76 of the battery can 51 in order to reduce the total height of the cylindrical secondary battery 70 when manufacturing the cylindrical secondary battery 70. Further, according to the structure of the connecting portion 143b that can contract and expand, even if vibrations and / or impacts occur during the use of the cylindrical secondary battery 70 and the electrode assembly 71 moves up and down, the impact caused by the movement of the electrode assembly 71 can be mitigated within a certain range.

[0345] The forms of the contact portion 143a and the connecting portion 143b can be variously changed. The second current collector plate 140 in FIG. 25 and the second current collector plate 140 in FIG. 26 only differ in the form of the contact portion 143a, and the structure of the second current collector plate 140 described above can be substantially identically applied otherwise.

[0346] Referring to FIG. 26, the contact portion 143a may have a form in which at least a part thereof extends along the inner circumferential surface of the battery can 51. For example, the contact portion 143a may be arc-shaped extending along the beading portion of the battery can 51. Also, although not shown, for maximizing the contact area, the second current collector plate 140 may be configured such that the sum of the extended lengths of the contact portions 143a of each of at least one can coupling portion 143 is substantially the same as the inner circumference of the battery can 51. In such an embodiment, the effects of improving the bonding force and reducing the electrical resistance due to maximizing the bonding area can be achieved.

[0347] The contact portion 143a can be interposed and fixed between the beading portion 76 of the battery can 51 and the sealing gasket 180. That is, the contact portion 143a can be fixed by the crimping force of the crimping portion 114 in a state where the contact portion 143a is interposed between the beading portion 76 of the battery can 51 and the sealing gasket 180.

[0348] Referring to FIG. 27, the second current collector 140 in FIG. 27 is different in that it further includes an additional can coupling portion 144 as compared with the second current collector 140 described with reference to FIG. 25. Otherwise, the structure of the second current collector 140 in FIGS. 25 and 26 described above can be substantially identically applied.

[0349] The additional can coupling portion 144 extends from the end of the second electrode tab coupling portion 142 and is coupled to the inner surface of the battery can 51. Such an additional can coupling portion 144 is provided at least at one end of the plurality of second electrode tab coupling portions 142. The additional can coupling portion 144 includes an additional contact portion 144a that is coupled to the inner surface of the battery can 51, and an additional connecting portion 144b that connects the end of the second electrode tab coupling portion 142 and the additional contact portion 144a.

[0350] The additional contact portion 144a is coupled to the inner surface of the battery can 51. When the beading portion 76 is formed on the battery can 51, the additional contact portion 144a can be coupled to the beading portion 76 in the same manner as the contact portion 143a. Also, like the form of the contact portion 143a shown in FIG. 26, the additional contact portion 144a may also have a form in which at least a part thereof extends along the inner circumferential surface of the battery can 51.

[0351] Similar to the connecting portion 143b described with reference to FIG. 25, the additional connecting portion 144b may include at least one bent portion whose extending direction is changed at least once between the second electrode tab coupling portion 142 and the additional contact portion 144a. By forming the bent portion, the additional connecting portion 144b has a structure that can contract and expand, and thus has advantages and a buffering effect in the assembling process of the cylindrical secondary battery 70 as described above.

[0352] Referring to FIG. 28, the second current collector 140 may include at least one electrolyte injection hole 146. The electrolyte injection hole 146 may be provided, for example, in the second electrode tab coupling portion 142. When a plurality of second electrode tab coupling portions 142 are provided, the electrolyte injection hole 146 may be provided in at least one of the second electrode tab coupling portions 142. The electrolyte injection hole 146 may be provided, for example, on one side or both sides of a welding portion W formed in the second electrode tab coupling portion 142. When manufacturing the cylindrical secondary battery 70, after accommodating the combined body including the electrode assembly 71 and the second current collector 140 in the battery can 51, an electrolyte may be injected. At this time, the electrolyte can rapidly flow into the electrode assembly 71 through the electrolyte injection hole 146, improving the injectability.

[0353] A plurality of electrolyte injection holes 146 may be provided. The plurality of electrolyte injection holes 146 may be arranged to be substantially symmetric about the center in the width direction of the second electrode tab coupling portion 142. A welding portion W for coupling the second electrode tab coupling portion 142 and the non-coated portion 72 of the second current collector may be formed between the electrolyte injection holes 146 arranged substantially symmetrically in this way.

[0354] The second electrode tab coupling portion 142 may be formed such that the width at a position separated by a predetermined distance from the connection portion between the second electrode tab coupling portion 142 and the central portion 141 toward the longitudinal end of the tab coupling portion is further larger than the width at the connection portion. At least a part of the region where the electrolyte injection hole 146 is formed may be included in the region where the width increases by increasing the width at a position separated by a predetermined distance from the connection portion toward the end of the second electrode tab coupling portion 142 as compared with the width at the connection portion between the second electrode tab coupling portion 142 and the central portion 141. On the other hand, the longitudinal end of the second electrode tab coupling portion 142 may be substantially arc-shaped so as to correspond to the inner peripheral surface of the battery can 51. In addition, the description of the structure of the second current collector 140 in FIG. 28 may be replaced with the description of the second current collector 140 described with reference to FIGS. 25 to 27.

[0355] As described above, the current collectors 120 and 140 have a structure suitable for the electrode assembly 71 having a low-resistance structure. Thereby, the mechanical and electrical performance of the cylindrical secondary battery 70 including the same is improved. Further, such a cylindrical secondary battery 70 is easy to manufacture by a welding method.

[0356] The cylindrical secondary battery 70 according to the above-described embodiment can be used to manufacture a battery pack.

[0357] FIG. 29 is a diagram schematically showing the configuration of a battery pack according to an embodiment of the present invention.

[0358] Referring to FIG. 29, the battery pack 200 according to an embodiment of the present invention includes an assembly to which a cylindrical secondary battery 201 is connected and a pack housing 202 that houses the same. The cylindrical secondary battery 201 can be the secondary battery 70 according to the above-described embodiment. In the drawing, for the sake of illustration, illustration of components such as a bus bar, a cooling unit, and an external terminal for connecting the cylindrical secondary battery 201 is omitted.

[0359] The battery pack 200 can be mounted on an automobile. The automobile can be, for example, an EV, an HEV, or a plug-in hybrid vehicle (PHEV). The automobile includes a four-wheel vehicle or a two-wheel vehicle.

[0360] FIG. 30 is a diagram for explaining an automobile including the battery pack 200 of FIG. 29.

[0361] Referring to FIG. 30, an automobile 300 according to an embodiment of the present invention includes a battery pack 200 according to an embodiment of the present invention. The automobile 300 operates by receiving power from the battery pack 200 according to an embodiment of the present invention.

[0362] In the base material according to the present invention, unless otherwise specifically defined and limited, terms such as "installation", "connection", "connection", "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection, a mechanical connection, an electrical connection, a direct connection or an indirect connection through a medium, or an internal communication between two components. Those with ordinary knowledge in the technical field to which the present invention pertains will be able to understand the specific meaning of the above terms in the present invention according to the specific situation.

[0363] In describing the present invention, "first", "second" are only for distinguishing similar structures and do not describe a specific order or sequence. Such numbers can be exchanged with each other in appropriate situations or can also be alternated with other numbers.

[0364] As described above, the present invention has been described with reference to the limited embodiments and drawings, but the present invention is not limited thereto. Of course, various modifications and variations are possible within the equivalent scope of the technical idea of the present invention and the scope of the claims by those with ordinary knowledge in the technical field to which the present invention pertains.

Explanation of Reference Numerals

[0365] 10 Positive electrode plate 10a Non-coated portion 11 Negative electrode plate 11a Non-coated portion 12 Separator 13 Winding center hole 20 Current collector 21 Active material 22 Non-coated portion 30 Current collecting plate 31 Current collecting plate 40 Cylindrical secondary battery 41 Battery can 42 Sealing body 42a Cap plate 42b Sealing gasket 42c Connection plate 43 Crimping part 44 Beading part 45 Lead 46 Insulator 50 Electrode terminal 50’ Electrode terminal 50a Body part 50b Outer flange part 50c Inner flange part 50d Flat part 51 Battery can 52 Bottom 53 Through hole 54 Rivet gasket 54a Outer gasket 54b Inner gasket 55 Recess part 56 Inner edge 70 Secondary battery 71 Electrode assembly 72 Non - coating part 73 Non - coating part 74 Sealing body 74a Cap plate 74b Sealing gasket 75 Crimping part 76 Beading part 77 Vent notch 78 Second current collector 79 First current collector 80 Winding center hole 85 Insulator 85a Welding hole 85b Upper plate 85c Side sleeve 90 Electrode plate 91 Current collector 92 Active material layer 93 Non - coating part 93’ Non - coating part 93a Section piece 94 Insulating coating layer 100 Electrode assembly 102 Laser welding device 103 Laser beam 104 Laser welding part 114 Crimping part 120 First current collector 122 First electrode tab connection part 123 Terminal connection part 124 Connection part 140 Second current collector 142 Second electrode tab connection part 143 Can connection part 144 Additional can connection part 145 Current collector hole 146 Liquid injection hole 180 Sealing gasket 200 Battery pack 201 Cylindrical secondary battery 202 Pack housing 300 Automobile

Claims

1. A jelly roll type electrode assembly having a structure in which a sheet-like first electrode plate, a second electrode plate, and a separator interposed therebetween are wound in one direction, wherein the first electrode plate includes an uncoated portion exposed outside the separator at a long side end, and the second electrode plate includes an uncoated portion exposed outside the separator in a direction opposite to the uncoated portion of the first electrode plate at a long side end, and an electrode assembly having a winding center hole in an inner core, A cylindrical battery can that houses the electrode assembly from an open portion formed on one side and is connected to the uncoated portion of the second electrode plate, A sealing body that seals the open portion of the battery can in an insulating manner, A first current collector plate connected to the uncoated portion of the first electrode plate, An electrode terminal that is riveted through a through hole formed in the bottom of the battery can located on the opposite side of the open portion of the battery can and is connected to the first current collector plate, A laser welding portion formed on a contact surface between the first current collector plate and the electrode terminal, and including, The laser welding portion is located at a superimposed portion of the first current collector plate and the electrode terminal within the winding center hole, a cylindrical secondary battery.

2. The cylindrical secondary battery according to claim 1, wherein a converted diameter of the laser welding portion exposed on a surface of the first current collector plate is 0.15D to 0.90D (D: a diameter of the winding center hole).

3. The electrode terminal is, A main body portion inserted into the through hole, An external flange portion extending along the outer surface from a peripheral edge of one side of the main body portion exposed on an outer surface of the bottom of the battery can, An internal flange portion extending toward the inner surface from a peripheral edge of the other side of the main body portion exposed on an inner surface of the bottom of the battery can, The cylindrical secondary battery according to claim 1 or 2, further including a flat portion provided inside the internal flange portion.

4. The cylindrical secondary battery according to claim 3, wherein in the flat portion, the electrode terminal and the first current collector are joined by the laser welding portion.

5. The cylindrical secondary battery according to claim 1 or 2, wherein the laser welding portion is formed from one surface of the first current collector toward the electrode terminal side inside the winding center hole at a joining portion between the first current collector and the electrode terminal.

6. The cylindrical secondary battery according to claim 1 or 2, wherein the laser welding portion is an overlapping overlay type of welding bead with respect to the center of the winding center hole.

7. The first current collector is an edge portion, a first electrode plate joining portion that extends inward from the edge portion and joins the non-coated portion of the first electrode plate, and a terminal joining portion that is located apart from the first electrode plate joining portion, and the cylindrical secondary battery according to claim 1 or 2, wherein the electrode terminal is joined to the terminal joining portion.

8. A jelly roll type electrode assembly having a structure in which a sheet-like first electrode plate and a second electrode plate and a separator interposed therebetween are wound in one direction, wherein the first electrode plate includes a first non-coated portion exposed outside the separator at a long side end portion, the second electrode plate includes a non-coated portion exposed outside the separator in a direction opposite to the non-coated portion of the first electrode plate at a long side end portion, and providing an electrode assembly having a winding center hole in an inner core; connecting a first current collector to the non-coated portion of the first electrode plate; providing a cylindrical battery can including an electrode terminal riveted through a through hole formed in a bottom portion of the battery can located on the opposite side of the open portion of the battery can, the battery can including an open portion formed on one side; inserting the electrode assembly into the battery can so that the first current collector faces the bottom portion of the battery can; Forming a laser welding part on the contact surface between the first current collector and the electrode terminal using a laser welding apparatus, A method for manufacturing a cylindrical secondary battery, wherein the laser beam of the laser welding apparatus is irradiated into the winding center hole along the longitudinal direction of the winding center hole.

9. The method for manufacturing a cylindrical secondary battery according to claim 8, wherein the laser welding part is located at an overlapping part of the first current collector and the electrode terminal in the winding center hole.

10. The method for manufacturing a cylindrical secondary battery according to claim 8 or 9, wherein the converted diameter of the laser welding part exposed on the surface of the first current collector is 0.15D to 0.90D (D: the diameter of the winding center hole).

11. The step of forming the laser welding part Inserting a hollow tube into the winding center hole, and at least a part of the first current collector is exposed in the inner hollow part of the hollow tube, The method for manufacturing a cylindrical secondary battery according to claim 8 or 9, characterized by including the step of welding the first current collector to the electrode terminal by passing a laser beam emitted from the laser welding apparatus through the inner hollow part of the hollow tube.

12. The method for manufacturing a cylindrical secondary battery according to claim 11, wherein the first current collector is pressed against the electrode terminal by the hollow tube.

13. The method for manufacturing a cylindrical secondary battery according to claim 11, characterized by including the step of supplying an inert gas for removing an oxygen atmosphere using a space between the hollow tube and the inner peripheral surface of the winding center hole while welding is performed by the laser beam.

14. The method for manufacturing a cylindrical secondary battery according to claim 11, wherein the length of the hollow tube is greater than the height of the electrode assembly, and the hollow tube is a metal hollow tube.

15. The method for manufacturing a cylindrical secondary battery according to claim 11, comprising the step of removing welding fumes on one end side of the winding center hole while the welding by the laser beam is being performed.

16. A method for manufacturing a cylindrical secondary battery according to claim 1 or 2, wherein the step of forming the laser welded portion is a step of irradiating a laser beam using the winding center hole inside the battery can and performing welding.

17. The method for manufacturing a cylindrical secondary battery according to claim 16, wherein the laser beam is heated from the first current collector plate.

18. The method for manufacturing a cylindrical secondary battery according to claim 17, wherein a temperature difference is provided between a portion where the laser beam is intensively irradiated and its peripheral portion.

19. The method for manufacturing a cylindrical secondary battery according to claim 17, wherein after being preheated by the laser beam, melting occurs in earnest.

20. A battery pack including the cylindrical secondary battery according to claim 1 or 2.

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