Battery can filling port sealing structure, battery cell, battery pack and automobile using the same

Abstract

The present invention relates to a structure for sealing a filler hole in a battery can cap. The structure includes a filler hole provided in a metal battery can or cap; a metal plug that closes the filler hole; and a thermal seal portion interposed between the plug and a peripheral portion of the filler hole and thermally seals the plug to the periphery of the filler hole using heat. The thermal seal portion can include a first chromium coating layer coated around the periphery of the filler hole, a second chromium coating layer coated on the plug, and a thermal seal layer containing PP-MAH (polypropylene-maleic anhydride) and formed on one of the two chromium coating layers. The chromium oxide in the chromium coating layer and the PP-MAH can be chemically bonded via the thermal seal layer.

Description

[Technical Field]

[0001] The present invention relates to a structure for sealing a filling port of a battery can, a battery cell to which the structure is applied, a battery pack including the battery cell, and a vehicle equipped with the battery pack. [Background technology]

[0002] Cylindrical battery cells have a structure in which a jelly-roll type electrode assembly is housed inside a cylindrical metal can, and are more resistant to shocks and temperatures than pouch type batteries. For this reason, there is an increasing demand for metal can type cells as battery cells applied to vehicle battery packs.

[0003] The process of manufacturing a battery cell using a cylindrical can includes the steps of deep drawing a metal sheet to form a circular bottom and a circular tubular side wall connected to it, accommodating an electrode assembly therein, and then covering and closing the open end of the side wall with a cap.

[0004] The open end of the battery can is covered with a cap, and the cap and the battery can can be fixed by crimping or seam welding.

[0005] Crimping is a method in which an electrolyte is poured into the battery can through the open end, the open end is covered with a cap, the end of the side wall of the battery can is beaded or crimped, and the edge of the cap is crimped to fix it in place. While this crimping method has the advantage of not generating heat sufficient to cause deterioration or fire of the electrolyte filled inside the battery can during the process, it requires a complex fixing structure, and the fixing structure of the cap occupies the internal volume of the battery can, reducing the energy density.

[0006] 1 to 6, seam welding is a method of butting the periphery of the front end of the side wall 11 of the battery can 10 and the periphery of the edge of the cap 40 together and welding them in the circumferential direction. Because the fixing structure is simple, it is possible to secure a larger volume of the electrode assembly that can be housed inside the battery can. Therefore, the seam welding method is more advantageous in securing a larger electrical capacity for the same volume of the battery can.

[0007] However, when the open end of the battery can is covered with a cap and welded after filling the battery can with electrolyte, the high temperature generated by welding may cause the electrolyte to deteriorate or ignite.

[0008] Therefore, when seam welding the periphery of the open end of the battery can and the cap, a method can be applied in which a battery can 10 having a liquid filling port at the bottom or a cap 40 having a liquid filling port 42 is prepared, an electrode assembly is placed inside the battery can, the battery can 10 and the cap 40 are seam-welded, and then an electrolyte is poured through the liquid filling port 42 at the bottom of the cap or the battery can, and after the pouring is completed, the liquid filling port is sealed with a plug.

[0009] After the electrolyte is poured through the pouring port 42, the pouring port can be closed by seam welding of a metal plug, blind rivet, inserting a metal ball, or the like.

[0010] Referring to FIGS. 1 and 2, seam welding of a metal plug involves covering a filler hole 42 on a battery can 10 with a metal plug 50 and seam-welding the rim of the plug 50 to the cap 40 to form a weld (W). For example, if the battery can and cap are made of stainless steel, the seam welding process can raise the surface temperature to 1,400 degrees Celsius, the melting point of stainless steel. This high temperature can cause the electrolyte to ignite. In other words, the method of sealing the filler hole by seam-welding the metal plug when closing the filler hole completely contradicts the purpose of introducing the filler hole structure, which was to minimize the effect on the electrolyte of heat generated when seam-welding the periphery of the open end of the battery can to the cap. While a structure to prevent electrolyte ignition could be added to prevent this phenomenon, this would simply increase the volume of the battery cell's internal space and be detrimental to maintaining the battery can's electrical capacity.

[0011] The sealing method using blind rivets 58 shown in Figures 3 and 4 involves plastically deforming metal to mechanically seal, which places a large load on the joint. These loads can damage the coatings formed on the surfaces of cap 40 and rivet 58 to prevent leakage. Lowering the load to prevent damage to the coating weakens the sealing function, while increasing the load to improve the sealing function can damage the coating and cause the seal to crack. Furthermore, because the rivet is first inserted into the can before riveting, a space must be secured inside the battery can to accommodate the rivet, which can reduce the soluble volume inside the battery can.

[0012] 5 and 6, the inner circumferential surface of the liquid filling hole 42 must be elongated in the axial direction to secure the metal ball 59. However, this structure is disadvantageous in terms of ensuring the internal volume of the battery can. Furthermore, forcibly inserting the ball 59 into the liquid filling hole 42 applies a large load to the electrode, which may damage the electrode. Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention has been devised to solve the above-mentioned problems, and aims to provide a sealing structure for a liquid filling port in which, during the process of closing the liquid filling port, the plug is strongly chemically bonded to the cap, thereby ensuring a reliable seal, without applying a large load to the cap portion around the liquid filling port or heating it to a high temperature.

[0014] The present invention aims to provide a sealing structure for a cap filling port of a battery can that does not generate high temperatures, does not cause denaturation of the electrolyte solution, or causes the electrolyte solution to ignite, and that performs sealing by generating a chemical bond rather than relying on a mechanical seal, does not apply a large load to the cap and the joint, and can reliably prevent leakage.

[0015] The present invention provides a method for sealing a liquid inlet that does not affect the electrodes or electrolyte contained inside a battery can, and a sealing structure for a liquid inlet to which this method is applied.

[0016] The present invention aims to provide a sealing structure for a liquid filling port that can maximize the internal volume of a battery cell.

[0017] The present invention provides a battery cell to which the above-described sealing structure is applied.

[0018] The present invention provides a battery pack including the battery cell, and a vehicle equipped with the battery pack and driven by the electric energy provided by the battery pack.

[0019] The technical object of the present invention is not limited to the above-mentioned objects, and other unmentioned objects and advantages of the present invention can be understood from the following description and can be more clearly understood from the examples of the present invention. Furthermore, it is clear that the objects and advantages of the present invention can be achieved by the means and combinations thereof set forth in the claims. [Means for solving the problem]

[0020] In order to solve the above-mentioned problems, the present invention provides a sealing structure for a liquid filling port in which a liquid filling port provided in a battery can or cap made of a metal material is completely closed with a metal plug.

[0021] The material of the battery can and cap may include aluminum or steel.

[0022] The plug material may include aluminum or steel.

[0023] The battery can may be cylindrical, and may include a circular tubular sidewall and a bottom connected to one axial end of the sidewall.

[0024] The cap can cover an open end provided at the other axial end of the battery can.

[0025] The edge of the cap can be thermally bonded to the other axial end of the side wall of the battery can.

[0026] The thermal bonding can be achieved by welding, brazing or soldering.

[0027] The present invention does not exclude the cap being fixed to the battery can by crimping.

[0028] The liquid inlet may be provided in the cap or in the bottom of the battery can.

[0029] The liquid inlet may be provided in the center of the cap or the center of the bottom.

[0030] The plug covering the liquid inlet has a cross section that includes the cross section of the liquid inlet and is larger than the cross section of the liquid inlet.

[0031] The inlet may be circular, and the stopper may be in the form of a circular plate that is concentric with the circular inlet and has a radius that is greater than the radius of the inlet.

[0032] The periphery of the plug surface facing the inlet may surround the inlet and be in close contact with the bottom of the battery can in which the inlet is formed or the periphery of the inlet of the cap.

[0033] A heat-sealed portion is interposed between a first surface of the battery can or cap surrounding the liquid inlet and a second surface of the plug in contact with the first surface.

[0034] That is, the first surface and the second surface refer to the portions where the liquid filling hole and the plug come into contact with each other when the liquid filling hole is completely closed with the plug.

[0035] The heat-sealed portion is fused to at least a partial area of the first surface and the second surface in a closed loop shape surrounding the liquid pouring hole.

[0036] The thermal welding portion includes a first chromium coating layer formed on the first surface; a second chromium coating layer formed on the second surface; and thermal welding layers that contact the first chromium coating layer and the second chromium coating layer on both sides, respectively, and contain PP-MAH (polypropylene-maleic anhydride) that bonds to the first chromium coating layer and the second chromium coating layer by heat.

[0037] The chromium coating layer can be formed by chromate surface treatment.

[0038] The bond may be a chemical bond, including a hydrogen bond.

[0039] That is, the thermal welding portion refers to a region where the first chromium coating layer, the thermal welding layer, and the second chromium coating layer are all stacked in the thickness direction.

[0040] The heat-sealable layer may be a non-substrate layer comprising PP-MAH.

[0041] The area of the first chromium coating layer may correspond to or even be larger than the area of the thermally bonded layer.

[0042] The PP-MAH may be provided by insert injection onto the first chromium coating layer formed on the first surface.

[0043] The first chromium coating layer may constitute a substrate for the PP-MAH of the thermal welding layer.

[0044] The area of the second chromium coating layer may correspond to or even be larger than the area of the thermally bonded layer.

[0045] The PP-MAH may be provided by insert injection onto the second chromium coating layer formed on the second surface.

[0046] The second chromium coating layer can constitute the PP-MAH substrate of the thermally welded layer.

[0047] The stopper may have a central projection that projects toward the inlet at a position facing the inlet.

[0048] The central protrusion may be inserted into the liquid pouring port.

[0049] The central protrusion may be in contact with the inner peripheral surface of the battery can or cap that defines the liquid inlet, so that the centers of the stopper and the liquid inlet are aligned.

[0050] The central protrusion can penetrate the pouring hole in the depth direction.

[0051] The central protrusion may be inserted into only a partial section of the pouring hole in the depth direction.

[0052] The heat-sealed portion may be interposed between the central protrusion and an inner peripheral surface of the battery can or cap defined by the liquid filling hole.

[0053] The heat-sealed portion may not be interposed between the central protrusion and the inner circumferential surface of the battery can or cap defined by the liquid filling hole.

[0054] The central protrusion may not be inserted into the liquid inlet.

[0055] A recess for receiving the stopper may be provided around the inlet.

[0056] A protrusion may be provided around the recess to define the recess.

[0057] The outer circumferential surface of the stopper may contact the inner circumferential surface of the recessed portion, and the centers of the stopper and the filling hole may be aligned.

[0058] The axially outer surface of the plug received in the recess may correspond to the surface of the protrusion in the axial direction or may be located further inward in the axial direction.

[0059] The first surface may include a 1-1 surface facing axially outward of the battery cell, and the second surface may include a 2-1 surface facing axially inward, opposite the 1-1 surface.

[0060] The 1-1 surface may be the bottom of a battery can or the outer surface of a cap, and the 2-1 surface may be the bottom surface of the stopper.

[0061] The heat-sealed portion can be provided between the 1-1 surface and the 2-1 surface.

[0062] The first surface may include a 1-2 surface facing radially inward of the battery cell, and the second surface may include a 2-2 surface facing radially outward opposite the 1-2 surface.

[0063] The first-2 surface may be the inner peripheral surface of the bottom or cap of the battery can that defines the liquid inlet, and the second-2 surface may be the outer peripheral surface of the central protrusion of the stopper.

[0064] The first-2 surface may be the inner peripheral surface of the bottom of the battery can or the protruding portion of the cap that defines the recess, and the second-2 surface may be the outer peripheral surface of the stopper.

[0065] The heat-sealed portion can be provided between the 1-2 surface and the 2-2 surface.

[0066] The heat-sealed portion may be provided between the 1-2 surface and the 2-2 surface.

[0067] The plug and the battery can or cap to which the plug is joined by the heat-sealed portion are electrically connected.

[0068] These electrical connection paths may include contact areas between the first and second surfaces that are not interposed by the thermal weld.

[0069] These electrical connection paths can include heat seals, including the heat seal layer being substrate-free.

[0070] A first electrode terminal may be provided at the center of the bottom.

[0071] The first electrode terminal may be installed on the bottom in a state insulated from the bottom.

[0072] A bottom portion around the first electrode terminal may constitute a second electrode terminal, and a sidewall portion connected to the bottom portion may also constitute a second electrode terminal.

[0073] An electrode assembly including a first electrode and a second electrode may be housed inside the battery can.

[0074] The electrode assembly may be in the form of a jelly roll in which the first electrode and the second electrode with a separator interposed therebetween are wound.

[0075] The electrode assembly may be housed within the battery can in an axially aligned state with the battery can.

[0076] The tab of the first electrode may be located at one axial end of the electrode assembly.

[0077] The tab may be a portion of the metal foil of the first electrode extending to one axial end of the electrode assembly.

[0078] The tab portions of the first electrode may be bent radially to overlap each other, thereby providing a plane that is substantially perpendicular to the axial direction.

[0079] A current collecting plate may be connected to the tab of the first electrode.

[0080] The current collecting plate may be connected to the first electrode terminal.

[0081] This allows the first electrode terminal to have a first polarity.

[0082] The tab of the second electrode may be located at the other axial end of the electrode assembly.

[0083] The tab may be a portion of the metal foil of the second electrode extending to the other axial end of the electrode assembly.

[0084] The tab portions of the second electrode may be bent radially to overlap each other, thereby providing a plane substantially perpendicular to the axial direction.

[0085] A tab of the second electrode may be located towards the open end.

[0086] The cap may be coupled to a tab of the second electrode.

[0087] The cap may include an electrode connection portion that is thermally bonded to a tab of the second electrode of the electrode assembly.

[0088] The electrode connector may be recessed from a surface of the cap inward in the axial direction.

[0089] The electrode connecting portion may extend flatly in the radial direction.

[0090] The electrode connector may be thermally bonded to a tab of the second electrode of the electrode assembly.

[0091] The thermal joining of the cap and the tab of the second electrode may be performed by any one of welding, brazing, and soldering.

[0092] Thus, the cap, the sidewall connected to the cap, and the bottom connected to the sidewall can have a second polarity.

[0093] A thermal bonding portion between the electrode connecting portion and the tab of the second electrode may be formed along an extending direction of the electrode connecting portion.

[0094] The thermal bonding portion may be a weld (W) formed by irradiating a laser beam onto the surface of the electrode connector in a scanning manner along a radial direction.

[0095] The liquid inlet may be provided in the center of the cap.

[0096] The liquid inlet may be aligned with a hollow core of the electrode assembly.

[0097] The electrode connecting portion may extend radially around the liquid injection port.

[0098] The cap may include a receiving surface extending axially outward from the electrode connecting portion.

[0099] The receiving surface may be disposed further outward in the axial direction than the joint (M) between the cap and the battery can.

[0100] The axially outer surface of the plug may be located further axially inward than the receiving surface.

[0101] The liquid injection port may be provided in a protruding portion that protrudes in the axial direction beyond the electrode connecting portion.

[0102] The cap may include two or more electrode connecting portions each recessed into the inside of the battery can and extending radially, and the number of electrode connecting portions may be four.

[0103] The welded portion may be formed by irradiating a laser onto the surface of the electrode connecting portion along the extending direction of the electrode connecting portion.

[0104] The present invention also provides a method for manufacturing a battery cell to which the sealing structure for the liquid filling port is applied.

[0105] The first embodiment of the manufacturing method includes a battery can preparation step, an electrode assembly preparation step, a cap preparation step, a plug preparation step, an electrode assembly insertion step, a first electrode terminal connection step, a cap connection step, a liquid injection step, and a liquid injection hole closing step.

[0106] The battery can preparation step includes a step of preparing a battery can having a sidewall portion, a bottom portion connected to one axial end portion of the sidewall portion, and an open end portion provided at the other axial end portion of the sidewall portion, and a step of sealingly and insulatedly fixing a first electrode terminal to the center of the bottom portion.

[0107] The step of preparing the electrode assembly includes a step of manufacturing an electrode assembly having a first electrode and a second electrode, with tabs of the first electrode and tabs of the second electrode disposed on both axial sides of each other.

[0108] This may include a step of bending the tab of the first electrode in a radial direction and thermally bonding a current collector plate onto the bent portion.

[0109] The cap preparation step includes a process of manufacturing a cap having an electrode connection part electrically connected to the tab of the second electrode and a liquid injection hole provided at the center of the electrode connection part.

[0110] This may include a step of chromate surface treatment around the pouring hole.

[0111] The plug preparation step includes a step of chromate surface treatment of the plug, and a step of insert-injecting a thermal welding layer containing PP-MAH onto the chromium coating layer formed by the chromate surface treatment.

[0112] The step of accommodating the electrode assembly includes a step of accommodating the electrode assembly in the battery can after the steps of preparing the battery can and preparing the electrode assembly, with the tab of the first electrode facing the bottom of the battery can.

[0113] The connecting step of the first electrode terminal may include connecting a tab of the first electrode or a current collecting plate connected thereto to the first electrode terminal after the electrode assembly is accommodated.

[0114] The connecting step of the cap includes a process of covering the open end of the battery can with the cap and closely contacting the electrode connecting portion with the tab of the second electrode, a process of joining the electrode connecting portion with the tab of the second electrode to electrically connect them, and a process of joining the outer periphery of the cap around the open end of the battery can.

[0115] The liquid injection step includes the steps of connecting the first electrode terminal and injecting an electrolyte into the battery can through the injection hole after connecting the cap.

[0116] The step of closing the inlet includes covering the inlet with the plug and heating the thermal welding layer with a thermal welding machine to chemically bond the PP-MAH to the chromium coating layer, including hydrogen bonding.

[0117] The second embodiment of the manufacturing method includes the steps of preparing a battery can, preparing an electrode assembly, preparing a cap, preparing a plug, connecting a second electrode, housing the electrode assembly and inserting the can, connecting a first electrode terminal and fixing the cap, filling a battery, and closing a filling port.

[0118] The battery can preparation step includes a step of preparing a battery can having a sidewall portion, a bottom portion connected to one axial end portion of the sidewall portion, and an open end portion provided at the other axial end portion of the sidewall portion, and a step of sealingly and insulatedly fixing a first electrode terminal to the center of the bottom portion.

[0119] The step of preparing the electrode assembly includes a step of manufacturing an electrode assembly having a first electrode and a second electrode, with tabs of the first electrode and tabs of the second electrode disposed on both axial sides of each other.

[0120] This may include a step of bending the tab of the first electrode in a radial direction and thermally bonding a current collector plate onto the bent portion.

[0121] The cap preparation step includes a process of manufacturing a cap having an electrode connection part electrically connected to the tab of the second electrode and a liquid injection hole provided at the center of the electrode connection part.

[0122] This may include a step of chromate surface treatment around the pouring hole.

[0123] The plug preparation step includes a step of chromate surface treatment of the plug, and a step of insert-injecting a thermal welding layer containing PP-MAH onto the chromium coating layer formed by the chromate surface treatment.

[0124] The connecting of the second electrode may include, after the electrode assembly preparing step and the cap preparing step, joining an electrode connecting portion of the cap to a tab of the second electrode to electrically connect them.

[0125] The step of placing the electrode assembly and inserting the cap includes, after the step of preparing the battery can and the step of connecting the second electrode, placing the electrode assembly in the battery can so that the tab of the first electrode faces the bottom of the battery can, and inserting the cap into the open end of the battery can.

[0126] The connecting of the first electrode terminal and the fixing of the cap includes, after the accommodating of the electrode assembly and the inserting of the cap, connecting the tab of the first electrode to the first electrode terminal and joining the outer periphery of the cap around the open end of the battery can to electrically connect them.

[0127] The injecting step includes injecting an electrolyte into the battery can through the inlet after the connecting step of the first electrode terminal and the fixing step of the cap.

[0128] The step of closing the inlet includes covering the inlet with the plug and heating the thermal welding layer with a thermal welding machine to chemically bond the PP-MAH to the chromium coating layer, including hydrogen bonding.

[0129] The present invention provides a high energy density battery pack including the above-mentioned battery cell.

[0130] The present invention provides a vehicle equipped with a high-energy density battery pack, reducing the volume and weight occupied by the battery pack. [Effects of the Invention]

[0131] According to the present invention, the inlet is not completely closed with a rivet that applies a load for plastic deformation or a metal ball that applies a load for forced insertion, so there is no concern that the cap will deform or the internal electrode of the battery can will be damaged. There is also no need to secure a space inside the battery can for a rivet to be inserted or a space for a metal ball to be inserted for riveting, so the fusible internal volume of the battery cell can be further secured, thereby increasing the energy density of the battery cell.

[0132] According to the present invention, the filler hole can be closed at a temperature lower than that required for high-temperature joining such as welding or medium-temperature joining methods such as brazing and soldering, and the filler hole does not need to be positioned to protrude from the cap or battery can to prevent heat applied while closing the filler hole from being transferred to the electrolyte or electrode assembly. In other words, the cap to which the filler hole structure is applied can be designed flat, satisfying the same standards and further ensuring the internal volume of the battery can.

[0133] According to the present invention, the plug is joined to the cap at a temperature lower than that required for soldering, without applying an external force strong enough to deform the cap or battery can, and the inlet is closed off. This eliminates the risk of deformation of the cap, damage or deformation of the electrode assembly and related components housed inside the battery can, or deterioration or fire of the electrolyte.

[0134] According to the present invention, when joining a metal cap and a metal plug, the thermal welding layer forms a chemical hydrogen bond with the two metal surfaces to be joined, resulting in excellent sealing strength.

[0135] According to the present invention, since the heat-sealing layer is formed on the plug by insert injection, there is no need to handle a separate heat-sealing layer film, and the sealing operation can be simplified.

[0136] According to the present invention, the PP-MAH in the thermal welding layer chemically bonds with the chrome coating layer on the battery can and plug, ensuring a reliable seal and significantly reducing the possibility of electrolyte leakage.

[0137] The above-mentioned effects and specific effects of the present invention will be described in conjunction with the following description of the preferred embodiment of the invention. [Brief explanation of the drawings]

[0138] [Figure 1] 1 is a diagram showing a conventional method for closing an electrolyte injection port of a battery can. [Figure 2] 1 is a diagram showing a conventional method for closing an electrolyte injection port of a battery can. [Figure 3] 1 is a diagram showing a conventional method for closing an electrolyte injection port of a battery can. [Figure 4] 1 is a diagram showing a conventional method for closing an electrolyte injection port of a battery can. [Figure 5] 1 is a diagram showing a conventional method for closing an electrolyte injection port of a battery can. [Figure 6] 1 is a diagram showing a conventional method for closing an electrolyte injection port of a battery can. [Figure 7] 1 is a view showing a first embodiment of a closing structure and closing method for an electrolyte injection hole of a battery can according to the present invention; [Figure 8] 1 is a view showing a first embodiment of a closing structure and closing method for an electrolyte injection hole of a battery can according to the present invention; [Figure 9] 1 is a view showing a first embodiment of a closing structure and closing method for an electrolyte injection hole of a battery can according to the present invention; [Figure 10] 1 is a diagram showing the chemical bonding structure between chromium oxide and PP-MAH in a chromium coating layer. [Figure 11] 10 is a diagram showing a manufacturing process of the electrolyte plug. [Figure 12] 10 is a diagram showing a manufacturing process of the electrolyte plug. [Figure 13] 10 is a view showing a second embodiment of a closing structure for an electrolyte injection hole of a battery can. [Figure 14] 10 is a view showing a second embodiment of a closing structure for an electrolyte injection hole of a battery can. [Figure 15]10 is a view showing a third embodiment of a closing structure for an electrolyte injection hole of a battery can. [Figure 16] 10 is a view showing a third embodiment of a closing structure for an electrolyte injection hole of a battery can. [Figure 17] 10 is a view showing a fourth embodiment of a closing structure for an electrolyte injection hole of a battery can. [Figure 18] FIG. 2 is a perspective view of a battery cell according to an embodiment. [Figure 19] 1 is a perspective view showing a state before a first electrode, a second electrode, and a separator are stacked to manufacture an electrode assembly to be housed in a battery can. FIG. [Figure 20] 10 is a perspective view showing a state after laminating a first electrode, a second electrode and a separator to manufacture an electrode assembly to be housed in a battery can. FIG. [Figure 21] FIG. 21 is a plan view of the stacked state of FIG. 20. [Figure 22] FIG. 22 is a perspective view of an electrode assembly fabricated by winding the laminate of FIGS. 20 and 21 into a jelly roll shape. [Figure 23] 22 is a side view of an electrode assembly manufactured by winding the laminate of FIGS. 20 and 21 into a jelly roll shape. FIG. [Figure 24] 1 is a perspective view showing a state in which a current collector plate is joined to the upper part of an electrode assembly and a current collector plate is not joined to the lower part of the electrode assembly; [Figure 25] 1 is a perspective view showing a state in which a current collector plate is joined to the upper part of an electrode assembly and a current collector plate is not joined to the lower part of the electrode assembly; [Figure 26] 26 is a multi-faceted view showing the process of housing the electrode assembly of FIG. 24 and FIG. 25 in a battery can. FIG. [Figure 27] 5A to 5C are cross-sectional views showing a process of welding the first electrode terminal and the current collector plate. [Figure 28] 10 is a view showing a process of covering the open end of the battery can with a cap. [Figure 29] 10 is a cross-sectional view showing a process of joining an electrode connecting portion of a cap to a tab of a second electrode of an electrode assembly and joining an edge of the cap around an open end of a battery can. FIG. [Figure 30] 10 is a diagram showing a process of completely closing the inlet with a stopper. [Figure 31] FIG. 10 is a top perspective view of a cap according to a fifth embodiment. [Figure 32] FIG. 10 is a perspective view of the lower part of the cap of the fifth embodiment. [Figure 33] FIG. 10 is a plan view of a cap according to a fifth embodiment. [Figure 34] FIG. 34 is a cross-sectional view of the relevant portion of FIG. 33. [Figure 35] FIG. 34 is a cross-sectional view of the relevant portion of FIG. 33. [Figure 36] 10 is a perspective view showing a state in which a cap is joined to a lower portion of an electrode assembly. FIG. [Figure 37] 1A to 1C are diagrams showing the steps of a first embodiment of a method for manufacturing a battery cell to which a closing structure for a liquid filling port is applied. [Figure 38] 10A to 10C are diagrams showing the steps of a second embodiment of a method for manufacturing a battery cell to which a closing structure for a liquid filling port is applied. [Figure 39] 1 is a diagram showing a battery pack to which a battery cell according to an embodiment of the present invention is applied; [Figure 40] 1 is a diagram showing an automobile equipped with a battery pack to which a battery cell according to an embodiment of the present invention is applied; DETAILED DESCRIPTION OF THE INVENTION

[0139] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0140] The present invention is not limited to the embodiments disclosed below, but may be embodied in various different forms and may be modified in various ways. However, these embodiments are provided to complete the disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art. Therefore, the present invention is not limited to the embodiments disclosed below, and should be understood to include all modifications, equivalents, and alternatives within the technical spirit and scope of the present invention, as well as the substitution or addition of the structure of any embodiment with the structure of another embodiment.

[0141] The accompanying drawings are intended to facilitate understanding of the embodiments disclosed in this specification, and should not be construed as limiting the technical ideas disclosed in this specification, but should be understood to include any modifications, equivalents, or alternatives that fall within the ideas and technical scope of the present invention. The components in the drawings may be exaggerated in size or thickness for ease of understanding, but this should not be interpreted as limiting the scope of protection of the present invention.

[0142] The terms used in this specification are merely used to describe particular embodiments or examples and are not intended to limit the present invention. Furthermore, singular terms include plural terms unless the context clearly dictates otherwise. Terms such as "comprises," "constitutes," and the like in the specification are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification. In other words, terms such as "comprises," "constitutes," and the like in the specification should not be understood to preclude the presence or possibility of adding one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0143] Although terms including ordinal numbers such as first, second, etc. may be used to describe various components, the components are not limited by the terms and are used only to distinguish one component from another.

[0144] When a component is referred to as being "coupled" or "connected" to another component, it should be understood that the component may be directly coupled or connected to the other component, but that there may be other components between them. On the other hand, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that there are no other components between them.

[0145] When a component is referred to as being "on top of" or "under" another component, it should be understood that there may be other components between them, not just directly on top of them.

[0146] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention pertains. Terms commonly used and similar to dictionary definitions should be interpreted to have a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense in this application unless expressly defined.

[0147] In describing the embodiments, the axial direction refers to the direction in which the axis forming the winding center of a jelly roll-type electrode assembly extends or the cylindrical extension direction of a cylindrical battery can, the radial direction refers to the direction toward (centripetal) or away (centrifugal) from the axis, and the circumferential direction refers to the direction surrounding the axis.

[0148] The width direction of the electrode assembly in the unfolded state corresponds to the axial direction of the jelly roll, and the length direction of the electrode assembly in the unfolded state corresponds to the circumferential direction of the jelly roll.

[0149] [First Example] First, referring to Figures 7 to 12, the sealing structure of the liquid filling port of the first embodiment includes a battery can 10 or cap 40 made of a metal material and provided with a liquid filling port 42, and a metal plug 50 that covers and seals the liquid filling port 42.

[0150] In the embodiment, the liquid filling port 42 is shown as being provided in the cap 40. However, it goes without saying that the liquid filling port 42 may also be provided in the can 10. In the case of a cylindrical battery can, the liquid filling port 42 may be provided in the center of the cap 40 or in the center of the bottom of the can 10.

[0151] The material of the battery can 10 and the cap 40 may be aluminum, steel, or an alloy containing these. The material of the plug 50 may also be aluminum, steel, or an alloy containing these. In this embodiment, aluminum is used as the material of the battery can 10 and the cap 40.

[0152] The battery can 10 may be cylindrical. The battery can 10 may include a hollow circular tubular side wall 11 and a bottom 12 connected to one axial end of the side wall 11. However, the shape of the battery can 10 of the present invention is not limited to this, and a rectangular can may also be used.

[0153] The cap 40 may cover an open end provided at the other axial end of the battery can 10. The cap 40 may be circular. However, the shape of the cap 40 of the present invention is not limited thereto, and a polygonal cap may also be used.

[0154] The edge of the cap 40 can be joined in a butt state around the other axial end of the side wall portion 11 of the battery can 10 .

[0155] The plug covering the liquid filling port 42 includes a cross section of the liquid filling port 42 and has a cross section larger than the cross section of the liquid filling port 42. In the embodiment, the liquid filling port 42 is circular, and the plug 50 is a circular plate having a radius larger than the radius of the liquid filling port 42.

[0156] A first chromium coating layer 46 is formed by chromate surface treatment on the outer surface of the cap 40 where the liquid pouring port 42 is provided and on the inner peripheral surface of the hole in the cap 40 that defines the liquid pouring port 42.

[0157] A central protrusion 51 that corresponds to the inner diameter of the pouring port 42 and extends toward the pouring port 42 is provided in the center of the inner surface (bottom surface) of the plug 50.

[0158] When the stopper 50 covers the pouring hole 42 , the central protrusion 51 penetrates the pouring hole 42 and protrudes inward beyond the inner surface of the cap 40 .

[0159] A second chromium coating layer 53 is formed on the inner surface (bottom surface) of the plug 50 and the outer peripheral surface of the central projection 51 by chromate surface treatment.

[0160] When a chromium coating layer is formed on the aluminum cap 40 or plug 50, metal-chromium oxide is coated on the aluminum surface as shown in FIG.

[0161] With the stopper 50 covering the filling hole 42, the outer surface of the cap 40 on which the first chromium coating layer 46 is formed and the inner peripheral surface of the filling hole 42 contact the bottom surface of the stopper 50 on which the second chromium coating layer 53 is formed and the outer peripheral surface of the central protrusion 51, respectively.

[0162] A thermal welding layer 55 is interposed between the first chromium coating layer 46 and the second chromium coating layer 53 that are in contact with each other.

[0163] The thermal welding layer 55 may be a substrate-free layer containing PP-MAH.

[0164] In this manner, with the thermal welding layer 55 interposed, the surface of the plug 50 is pressed against the thermal welding machine 60 and heat is applied. The heating temperature may be lower than the thermal decomposition temperature of the electrolyte injected inside the battery can 10.

[0165] In an embodiment, the thermal decomposition temperature of the electrolyte is, for example, about 200°C, and the heating temperature of the thermal welding layer 55 may be lower than this.

[0166] 10, chemical bonding, including hydrogen bonding, occurs between the PP-MAH of thermally welded layer 55 and the chromium coating layer, forming a thermally welded portion. In this way, when the sealing structure for the liquid filling port of the embodiment is applied, strong external force and high temperature are not applied to cap 40 and stopper 50, and strong chemical bonding occurs between the stopper and the cap, reliably sealing the liquid filling port.

[0167] For convenience of the process, the PP-MAH may be provided in a state where it is insert-injected onto the bottom surface of the plug 50 and laminated thereon to form the thermal welding layer 55 .

[0168] For this purpose, first, the bottom surface of the plug 50 and the outer peripheral surface of the central projection 51 may be coated with a second chromium coating layer 53 as shown in FIG.

[0169] PP-MAH can be insert-injected onto the bottom surface of the plug 50 coated with the second chrome coating layer 53 and the outer circumferential surface of the central protrusion 51 to form a thermal welding layer 55, as shown in FIG.

[0170] The thermally welded layer containing the PP-MAH itself is a non-substrate layer, but since the second chromium coating layer 53 functions as a substrate for the PP-MAH, the thermally welded layer can be laminated to the plug 50 very stably.

[0171] 7, the thermal weld layer 55 can be provided in a state where it is integrally laminated on the bottom surface of the plug 50. Then, the operation of closing the filling port can be easily completed by simply covering the filling port 42 with the plug 50 on which the thermal weld layer 55 has been formed, and then pressurizing and heating the plug 50 in a thermal welding machine 60 so that the thermal weld layer 55 is thermally bonded to the adjacent chromium coating layer through chemical bonding, including hydrogen bonding.

[0172] In the first embodiment, the thermal welding layer 55 is laminated on the second chromium coating layer 53 of the plug 50 as a base material. The plug 50 is not introduced into the battery cell manufacturing process until the filling hole 42 is completely closed, so there is no risk of the thermal welding layer 55 being damaged during the manufacturing process, and handling of the parts becomes easier.

[0173] However, the thermal weld layer 55 can be formed by laminating the first chrome coating layer 46 of the can 10 as a base material. When the stopper 50 is pressurized and heated in the thermal welding machine 60 to form the thermal weld, the heat first reaches the gap between the second chrome coating layer 53 and the thermal weld layer 55, and then reaches the gap between the thermal weld layer 55 and the first chrome coating layer 46. Therefore, when the thermal weld layer 55 is formed by laminating the first chrome coating layer 46 of the can 10 as a base material, there is an advantage in that the chemical bonding between the second chrome coating layer 53 and the thermal weld layer 55 and the chemical bonding between the thermal weld layer 55 and the first chrome coating layer 46 are more balanced.

[0174] In the first embodiment, the thermal welding layer 55 is first laminated onto the plug 50. The thermal welding layer 55 laminated onto the plug 50 is formed by insert injection in a mold, so that the second chromium coating layer 53 and the thermal welding layer 55 can be precisely aligned.

[0175] 9, the radially outer edge of the first chrome coating layer 46 provided on the outer surface of the cap 40 may be coated so as to extend radially further outward than the radially outer edge of the stopper 50. This prevents the first chrome coating layer 46 of the can 10, which is necessary for forming a heat-sealed joint, from leaking from a portion of the outer surface of the can due to manufacturing errors of the stopper 50 or the can 10 or assembly errors in the sealing process.

[0176] For the same reason, central protrusion 51 of plug 50 can be manufactured to extend further than the depth of pouring hole 42. This prevents the risk of second chromium coating layer 53 and heat-sealed layer 55, which are necessary to form the heat-sealed portion, leaking from a portion of the inner circumferential surface of pouring hole 42 due to manufacturing errors in plug 50 or can 10 or assembly errors in the sealing process.

[0177] According to the sealing structure of the filling port of the battery can described above, when the filling port is closed, sealing is performed at a temperature required for the thermal welding layer, so there is no risk of the electrolyte changing quality or catching fire. Furthermore, since the thermal welding layer is performed using a part in which PP-MAH is inserted and injected into the plug, the sealing process is simple, and the PP-MAH chemically bonds with the chrome coating layer, ensuring a reliable seal.

[0178] [Second Example] Next, a sealing structure for a liquid inlet according to a second embodiment will be described with reference to Figures 13 and 14. In describing the second embodiment, explanations that overlap with those of the first embodiment will be omitted. Therefore, when describing any of the embodiments, details that are not specifically described can be understood from the other embodiments. Furthermore, it will be easy to understand that the configuration of any of the embodiments can be substituted, added, omitted, or combined with the configuration of another embodiment.

[0179] The sealing structure of the pouring port of the second embodiment differs from that of the first embodiment in that first chromium coating layer 46 is not provided on the inner peripheral surface of pouring port 42, second chromium coating layer 53 is not provided on the outer peripheral surface of central protrusion 51 of plug 50, and heat-sealed layer 55 is not interposed between the inner peripheral surface of pouring port 42 and the outer peripheral surface of central protrusion 51.

[0180] In order to form a heat-sealed joint between the inner circumferential surface of the pouring hole 42 and the outer circumferential surface of the central protrusion 51, adequate contact must be made between the heat-sealed layer 55 and the chrome coating layer. Furthermore, the plug 50 is axially assembled to the cap 40. Therefore, due to manufacturing errors and assembly tolerances of the various components, the heat-sealed layer 55 and the chrome coating layer may not adequately contact each other to form a heat-sealed joint between the inner circumferential surface of the pouring hole 42 and the outer circumferential surface of the central protrusion 51, which are radially opposed to each other.

[0181] For this reason, in the second embodiment, the structure for forming a thermal fusion joint (first chrome coating layer, second chrome coating layer, and thermal fusion layer) between the inner circumferential surface of the inlet 42 and the outer circumferential surface of the central protrusion 51 is omitted, and a sealing structure is illustrated in which the central protrusion 51 is configured to be in direct contact with the inner circumferential surface of the inlet 42.

[0182] The central protrusion 51 can function to align the centers of the stopper 50 and the pouring hole 42, and the outer diameter of the central protrusion 51 can be configured to be slightly larger than the inner diameter of the pouring hole 42 so that the central protrusion 51 can be pressed into the pouring hole 42.

[0183] According to this, the central protrusion 51 does not need to extend further than the depth of the liquid filling port 42; rather, in order to reduce the pushing force and ensure more internal space in the battery can 10, the length of the central protrusion 51 can be made shorter than the depth of the liquid filling port 42 so that the central protrusion 51 is inserted into only a portion of the liquid filling port 42 in the depth direction.

[0184] The cap 40 can function as an electrode, and it is more preferable that the plug 50 also functions as an electrode, which is why the second embodiment in which the plug 50 and the cap 40 are in direct contact with each other is more advantageous than the first embodiment in which the plug 50 and the cap 40 are connected via a heat-sealed portion. Of course, the heat-sealed portion does not electrically insulate the plug 50 and the cap 40.

[0185] As in the first embodiment, the thermal welding layer 55 of the second embodiment may be laminated by the insert injection method using the second chromium coating layer 53 coated on the plug 50 as a base material.

[0186] [Third Example] Next, the sealing structure of the liquid filling port of the third embodiment will be described with reference to FIGS.

[0187] The sealing structure of the pouring port of the third embodiment differs from that of the second embodiment in that a protrusion 43 that protrudes axially outward is formed radially outward from the pouring port 42 of the can 10, and the pouring port 42 is provided in a recessed portion 47 that is recessed axially inward from the protrusion 43.

[0188] When the plug 50 covers the inlet 42 , the height of the axially outer surface of the plug 50 may correspond to or be lower than the height of the surface of the protrusion 43 .

[0189] As a result, the plug 50 does not protrude from the surface of the cap 40 at all, and there is no risk of the protruding portion of the plug 50 from the surface of the cap 40 being subjected to external force or impact from the outside, causing damage to the seal.

[0190] The inner circumferential surface of the protrusion 43 defined by the depression 47 can come into contact with the outer circumferential surface of the plug 50. Thus, when the plug 50 covers the filling hole 42, the inner circumferential surface of the protrusion 43 guides the alignment of the plug 50 and the filling hole 42.

[0191] Therefore, the upper end of the inner peripheral surface of the protrusion 43 can be provided with a tapered surface such that the diameter gradually decreases axially inward from the boundary between the protrusion 43 and the depression 47. This tapered shape can be formed naturally when the protrusion 43 and the depression 47 are formed by pressing the cap 40.

[0192] No heat-sealed portion is provided between the inner circumferential surface of the protrusion 43 and the outer circumferential surface of the plug 50. As a result, the inner circumferential surface of the protrusion 43 and the outer circumferential surface of the plug 50 can be in direct contact with each other, and the plug 50 can be electrically connected to the protrusion 43.

[0193] Therefore, when the height of the protrusion 43 and the height of the plug 50 are made to correspond to each other, the protrusion 43 and the plug 50 themselves can function as electrode terminals protruding from the surface of the cap 40. The polarity of these electrode terminals can correspond to the polarity of the cap 40.

[0194] According to the third embodiment, the outer diameter of the plug 50 may be made to correspond to or slightly larger than the inner diameter of the protrusion 43 so that the plug 50 can be pushed into the recess 47 .

[0195] On the other hand, according to the third embodiment, the structure of the protrusion 43 and the recess 47 guides the alignment of the filling hole 42 and the plug 50, so there is no need for the central protrusion 51 and the filling hole 42 to overlap and guide them. If they overlap, it may be difficult to fit the plug 50 if there is a positional error in either one.

[0196] Therefore, in the third embodiment, unlike the second embodiment, the central protrusion 51 protrudes low enough that it cannot fit into the liquid inlet 42, and when the layers 53, 55, and 46 of the heat-sealed portion are stacked so that they are in contact with each other, the central protrusion 51 cannot be inserted into the liquid inlet 42.

[0197] Therefore, as shown in FIG. 16, the height of the central protrusion 51 can be formed to be longer than the sum of the thicknesses of the second chrome coating layer 53 and the thermal welding layer 55, but shorter than the sum of the thicknesses of the second chrome coating layer 53, the thermal welding layer 55, and the first chrome coating layer 46.

[0198] In this case, the diameter of the central protrusion 51 may be the same as or slightly smaller than the diameter of the filling hole 42. The central protrusion 51 can define the radial inner boundary of the thermally welded layer 55 during the process of insert injection molding the thermally welded layer 55 into the plug 50.

[0199] According to the third embodiment, the plug 50 covering the inlet 42 of the cap 40 is protected by the protrusion 43 and the recess 47, and can reliably function as an electrode terminal together with the protrusion 43.

[0200] [Fourth Example] Next, with reference to FIG. 17, the sealing structure of the liquid filling port of the fourth embodiment will be described.

[0201] The sealing structure of the liquid filling port of the fourth embodiment differs from that of the third embodiment in that a plug 50 from which the central projection 51 is omitted is used.

[0202] The sealing structure of the filling hole of the fourth embodiment is also different in that the thermal welding layer 55 is laminated by insert injection using the first chromium coating layer 46 formed on the bottom of the recess 47 of the cap 40 as the base material.

[0203] During the insert injection process of the thermal welding layer 55 of the cap 40, the inner peripheral surface of the recessed portion 47 defines the boundary of the outer peripheral surface of the thermal welding layer 55, so it is very easy to laminate the thermal welding layer 55 on the bottom, i.e., the surface, of the recessed portion 47 of the cap 40 by insert injection.

[0204] Furthermore, the second chromium coating layer 53 coated on the bottom surface of the plug 50 of the fourth embodiment can be formed to have an inner diameter smaller than the filling hole 42 of the cap 40. This ensures that even if manufacturing errors or assembly tolerances occur, when the plug 50 covers the filling hole 42 and the bottom surface of the plug 50 comes into contact with the thermally welded layer 55 laminated on the cap 40, the second chromium coating layer 53 is present over the entire surface of the thermally welded layer 55. This ensures a sufficient area for the thermally welded portion.

[0205] In contrast to the third embodiment, the fourth embodiment does not require precise machining of the height of the central protrusion 51, and the thermal welding layer 55 is provided by being laminated on the surface of the recessed portion 47 of the cap 40. Therefore, there is no risk of the thermal welding layer 55 being damaged during handling of the cap 40 to assemble the battery cell.

[0206] [Fifth Example] Hereinafter, a method for manufacturing a battery cell to which the above-described sealing structure for the liquid filling port is applied, and the structure of these battery cells will be described with reference to FIGS.

[0207] FIG. 18 discloses a cylindrical battery cell.

[0208] The battery cell of the embodiment may be, for example, a cylindrical battery cell having a form factor ratio (defined as the diameter of a cylindrical battery cell divided by its height, i.e., the ratio of the diameter (Φ) to the height (H)) greater than approximately 0.4.

[0209] Here, the form factor refers to a value indicating the diameter and height of a cylindrical battery cell. Cylindrical battery cells applicable to pressure testers may be, for example, 46110 cells, 48750 cells, 48110 cells, 48800 cells, or 46800 cells. In the form factor value, the first two digits indicate the diameter of the cell, the next two digits indicate the height of the cell, and the final digit 0 indicates that the cell has a circular cross section.

[0210] The battery cell applied to the pressure tester may be a cylindrical battery cell having a diameter of approximately 46 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0211] Another embodiment of the battery cell may be a cylindrical battery cell having a diameter of approximately 48 mm, a height of approximately 75 mm, and a form factor ratio of 0.640.

[0212] In yet another embodiment, the battery cell may be a substantially cylindrical cell having a diameter of approximately 48 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0213] In yet another embodiment, the battery cell may be a substantially cylindrical cell having a diameter of approximately 48 mm, a height of approximately 80 mm, and a form factor ratio of 0.600.

[0214] In yet another embodiment, the battery cell may be a substantially cylindrical cell having a diameter of approximately 46 mm, a height of approximately 80 mm, and a form factor ratio of 0.575.

[0215] The pressure tester of the present invention can of course be applied to battery cells with a form factor ratio of approximately 0.4 or less, such as 18650 cells and 21700 cells. For 18650 cells, the diameter is approximately 18 mm, the height is approximately 65 mm, and the form factor ratio is 0.277. For 21700 cells, the diameter is approximately 21 mm, the height is approximately 70 mm, and the form factor ratio is 0.300.

[0216] The battery can 10 includes a cylindrical side wall 11 and a bottom 12 connected to one axial end of the side wall 11. Here, the term "bottom" is used because the bottom 12 is placed on the floor in the process of assembling the battery cell, with the open end of the battery can 10 facing upward as shown in Figs. 26 to 30. It should be understood that the bottom 12 may actually be located at the top together with the first electrode terminal 13 as shown in Fig. 18 in the process of using the battery cell.

[0217] The bottom 12 and the side wall 11 of the battery can 10 may be integral. For example, the battery can 10 may be manufactured by drawing a steel or aluminum sheet material. The opposite end of the side wall 11, which is not connected to the bottom 12, may form an open end that is open in the axial direction.

[0218] A hole may be formed in the center of the bottom 12, and a first electrode terminal 13 may be fitted into the hole. The first electrode terminal 13 may be riveted to the bottom 12 with a terminal gasket 14 interposed therebetween. The terminal gasket 14 is interposed between the first electrode terminal 13 and the bottom 12 to seal the inside and outside of the battery can 10, prevent leakage of the electrolyte, and electrically insulate the first electrode terminal 13 from the bottom 12.

[0219] However, the method of connecting the first electrode terminal 13 and the bottom 12 is not limited thereto. For example, as long as the first electrode terminal 13 and the bottom 12 can be sealed and electrically insulated from each other, various other fixing methods, such as a bolt and nut connection method, a glass seal method, and a thermal bonding method of a PP-MAH insulating gasket using an insulating film such as PP (polypropylene) as a substrate, may also be applied.

[0220] In the embodiment, the first electrode terminal 13 may have a first polarity, and the battery can 10 may have a second polarity, so that the bottom 12 of the battery can 10 and the side wall 11 connected thereto may both have the second polarity.

[0221] In this case, the first electrode terminal 13 and the second electrode terminal 15 may both be disposed at one axial end of the battery can 10. Accordingly, in the battery can 10, the bus bar connected to the first electrode terminal 13 and the bus bar connected to the second electrode terminal 15 may both be located at one axial end of the battery can 10, i.e., at the top.

[0222] In one example, the first electrode terminal 13 may be a positive terminal and the second electrode terminal 15 may be a negative terminal, or vice versa.

[0223] An electrode assembly 20 is accommodated within the battery can 10. The electrode assembly 20 is manufactured in a jelly roll shape by preparing a first electrode 21, a second electrode 22, and a separator 28 that have a predetermined width and extend in the length direction as shown in Fig. 19, stacking the first electrode 21, the separator 28, the second electrode 22, and the separator 28 in this order as shown in Figs. 20 and 21, and then winding the stack around a core shaft.

[0224] The first electrode 21 may be a positive electrode and the second electrode 22 may be a negative electrode, or vice versa.

[0225] The first electrode 21 and the second electrode 22 are fabricated in the form of sheets. The electrode sheets are fabricated by coating an active material layer 24 on the surface of a metal foil 23. The electrode sheets have a coated portion 25 where the active material layer 24 is coated and an uncoated portion 26 where the active material layer 24 is not coated. The positive electrode sheet has the uncoated portion 26 on one side in the width direction, and the negative electrode sheet has the uncoated portion 26 on the other side in the width direction.

[0226] The uncoated area 26 is exposed or protrudes in the width direction of the laminate, and the uncoated area 26 itself functions as an electrode tab.

[0227] Notches may be formed at predetermined intervals in the plain portion 26 to form flag-shaped notched tabs 27.

[0228] In this embodiment, the notched tab 27 is shaped like an equilateral trapezoid, but may have various other shapes such as a semicircle, a semi-ellipse, a triangle, a rectangle, a parallelogram, and the like.

[0229] In addition, in the embodiment, the notched tabs 27 arranged along the length direction have the same width, but the width of the notched tabs may be gradually or stepwise increased from the winding core side to the outer periphery side.

[0230] In the embodiment, the height of the notched tabs 27 increases stepwise from the core side to the outer periphery side, but the height of the notched tabs may be constant or may decrease gradually.

[0231] In the embodiment, the notched tabs 27 are omitted from a predetermined section of the centripetal end and a predetermined section of the distal end of the non-coated portion 26. However, it goes without saying that the notched tabs at the centripetal end of the non-coated portion do not have to be omitted, and the notched tabs at the distal end of the non-coated portion do not have to be omitted.

[0232] In the jelly roll type electrode assembly 20, the notched tabs 27 may be flattened by bending them radially. The notched tabs 27 may be bent radially inward or outward. In the embodiment, as shown in Figures 22 and 23, a structure in which the notched tabs 27 are bent radially inward is illustrated.

[0233] The notched tabs 27 may be bent one by one during the process of winding the laminate to form the jelly roll type electrode assembly 20. Alternatively, the notched tabs 27 may be bent all at once after winding the laminate to form the jelly roll type electrode assembly.

[0234] In this way, the notched tabs 27 of the first electrode 21 and the notched tabs 27 of the second electrode 22, which are bent radially and overlapped, can provide planes substantially perpendicular to the axial direction at both axial ends of the electrode assembly 20, as shown in Figure 23.

[0235] As shown in FIG. 24, a current collector plate 31 may be bonded to a substantially flat surface formed by bending the notched tabs 27 exposed at both axial ends of the electrode assembly 20.

[0236] The current collecting plate 31 can be made by stamping, trimming, piercing and bending a metal sheet.

[0237] 24, the current collecting plate 31 includes terminal connecting portions 32 extending radially from a center portion, ring portions 33 connecting the distal side edges of the terminal connecting portions 32 in the circumferential direction, and an electrode connecting portion 34 extending centripetally from the ring portions 33 but not connected to the terminal connecting portions 32. The center portion of the terminal connecting portion 32 covers at least a portion of the hollow portion of the winding core of the electrode assembly 20.

[0238] Before the electrode assembly 20 is placed in the battery can 10, the electrode connector 34 is joined to the notched tab 27 of the first electrode 21 of the electrode assembly 20 by a method such as laser welding.

[0239] Unlike the embodiments, in the case of a battery cell having a different structure, for example, the notched tab 27 of the first electrode 21 or the current collector plate 31 can be joined to the bottom 12 of the battery can 10 by a method such as welding, and can be electrically connected. That is, it should be understood that the fifth embodiment is an example of a battery cell to which the above-described sealing structure of the filler hole can be applied. That is, it is clear that the sealing structure of the filler hole disclosed above is not a technology that can be applied only to the battery cell structure disclosed in the fifth embodiment.

[0240] 25, a current collecting plate does not have to be connected to the notched tab 27 of the second electrode 22 of the electrode assembly 20. It can be electrically connected by directly joining it to a cap 40 (described later) by a method such as welding.

[0241] 26 and 27, the electrode assembly 20 is accommodated in the battery can 10 with the current collecting plate 31 aligned toward the bottom 12 of the battery can 10. At this time, an insulator 19 is interposed between the current collecting plate 31 and the bottom 12 of the battery can 10 to electrically insulate the current collecting plate 31 from the bottom 12.

[0242] The terminal connection portion 32 of the current collecting plate 31 is joined to the first electrode terminal 13 fixed to the battery can 10 by resistance welding, ultrasonic welding, laser welding, or the like. To weld the current collecting plate 31 to the first electrode terminal 13, a welding device may be positioned from the other axial end of the electrode assembly 20, through the hollow portion of the core of the electrode assembly 20, and approach the rear surface of the center of the terminal connection portion 32 of the current collecting plate 31 to perform welding. Of course, the current collecting plate 31 and the first electrode terminal 13 may also be joined by brazing or soldering.

[0243] 28 and 29, the notched tab 27 of the second electrode 22 may be in direct contact with the cap 40 covering the open end of the battery can 10 when the electrode assembly 20 is housed in the battery can 10 and the first electrode 21 is connected to the first electrode terminal 13.

[0244] With the cap 40 tightly attached to the notched tab 27, a laser beam is irradiated onto the surface of the cap 40 in a scanning manner along the radial direction, as shown in Fig. 29, to form a weld (W) extending in the radial direction. Of course, the laser beam is not irradiated onto the section of the scanning path where the injection hole is provided.

[0245] As a result, the second electrode 22 is electrically connected through the welded portion (W) between the notched tab 27 and the cap 40. Of course, the notched tab 27 and the cap 40 may also be joined by brazing, soldering, or other methods in addition to welding.

[0246] Unlike the embodiment, the tab of the second electrode 22 may be attached to the inner circumferential surface of the side wall 11 of the battery can 10 for electrical connection.

[0247] Also, unlike the above embodiment, the tab of the second electrode 22 can be joined to the cap 40 or the side wall 11 of the battery can 10 via a current collector plate (not shown).

[0248] In addition, the tab of the second electrode 22 or the current collector plate connected thereto may be joined and connected to both the inner circumferential surface of the side wall portion 11 and the cap 40 .

[0249] In addition, the cap 40 may be provided with a second electrode terminal, and the tab of the second electrode 22 or the current collector plate 31 may be connected to the second electrode terminal.

[0250] 29, the edge of the cap 40 is joined to the open end of the sidewall 11 of the battery can 10, electrically connected, and hermetically fixed. This allows the second electrode 22 to be electrically connected to the cap 40 and the battery can 10. The joining of the cap 40 and the battery can 10 can also be performed using various methods that allow for electrical connection and hermetic joining, such as welding, brazing, or soldering.

[0251] Unlike the embodiment, it is needless to say that the cap 40 may be fixed to the open end of the side wall portion 11 of the battery can 10 by a pressure sealing method such as crimping. It should be understood that the above-described filling port sealing structure can be applied to such a structure as well.

[0252] High heat may be generated during the process of welding the cap 40 and the side wall 11. If electrolyte is injected into the battery can 10 before the welding process, the high heat generated during the welding process may cause the electrolyte to denature or ignite.

[0253] Therefore, as described above, after the processing of the welded portion (W) and the joined portion (M) where high heat is generated is completed, the electrolyte can be poured through the pouring port 42.

[0254] The liquid filling port 42 may be provided at a position aligned with the hollow portion of the winding core of the electrode assembly 20. In this case, the injected electrolyte penetrates deeply through the hollow portion of the winding core of the electrode assembly 20, thereby enabling smooth impregnation.

[0255] After the injection is completed, as shown in Figure 30, the injection port 42 is covered with the plug 50, and the plug 50 is pressurized and heated using the above-mentioned thermal welding machine 60, heating the thermal welding layer and forming a thermal welding portion.

[0256] The structure of the cap 40 applied to the battery cell of the fifth embodiment will be described in detail below with reference to FIGS.

[0257] The cap 40 may be manufactured from a circular metal sheet. The cap 40 includes an electrode connector 41 recessed in a direction corresponding to the axial direction of the battery cell 72. The electrode connector 41 may be formed by pressing the metal sheet.

[0258] The bottom surface of the electrode connector 41 is a portion that is closely bonded to the notched tab 27 of the second electrode 22 of the electrode assembly 20. The electrode connector 41, which is manufactured by pressing a metal sheet, has a thickness slightly thinner than the thickness of the metal sheet. When a laser is irradiated onto the surface of the electrode connector 41, the local heat generated by the laser melts and bonds the electrode connector 41 and the surface of the notched tab 27 that contacts the bottom surface thereof.

[0259] The electrode connectors 41 are provided in plural. In the fifth embodiment, four electrode connectors 41 are circumferentially spaced at equal intervals of approximately 90 degrees and radially formed. The electrode connectors 41 extend radially, and a weld (W) for joining the electrode connectors 41 to the notched tabs 27 of the second electrode 22 of the electrode assembly 20 may have a weld line shape formed radially to correspond to the extension direction of the electrode connectors 41, as shown in FIG.

[0260] According to the embodiment, a linear weld (W) extending in the radial direction is formed for each of the plurality of electrode connecting portions 41.

[0261] The cap 40 provides a receiving surface 44, which is a surface that comes into contact with the ground when the battery can 10 is placed upright with the cap 40 of the battery can 10 facing the floor. The receiving surface 44 is provided at a position raised higher than the electrode connecting portions 41 and is disposed between two electrode connecting portions 41 that are adjacent in the circumferential direction.

[0262] As a result, the receiving surfaces 44 on both circumferential sides of the electrode connecting portion 41 are pressed with a jig to bring the electrode connecting portion 41 and the notched tab 27 into close contact, and then, as shown in Fig. 29, a laser is irradiated onto the surface of the electrode connecting portion 41 to weld the electrode connecting portion 41 and the notched tab 27. Then, the pressure of the jig on both sides of the weld line along the length of the weld line presses the electrode connecting portion 41 into close contact with the notched tab 27, ensuring reliable welding.

[0263] A pair of electrode connectors 41 facing each other with respect to the center of the cap 40 are arranged on a straight line passing through the center of the cap 40. As a result, when forming a weld line, the weld line of two aligned electrode connectors 41 can be formed with just one movement of the laser welder. For example, if the first, second, third, and fourth electrode connectors are sequentially arranged along the circumferential direction of the cap 40 of the fifth embodiment, the first and third electrode connectors can be welded at one time, and the second and fourth electrode connectors can be welded at one time.

[0264] Furthermore, according to the embodiment, for example, when pressure is applied with a jig to the receiving surfaces 44 provided on both sides of the first electrode connecting part and the third electrode connecting part, which are arranged in a row around the center of the cap 40, the second-order moment of inertia formed by the recessed shapes of the second electrode connecting part and the fourth electrode connecting part is large, so that the cap 40 can operate as a rigid body without being distorted or bent despite the pressure of the jig.

[0265] In the embodiment, by configuring four electrode connectors 41 as described above, all four electrode connectors 41 can be welded with two laser scanning trajectories.

[0266] If an excessive number of electrode connectors 41 are formed, the strength of the cap 40 made of the metal sheet may be weakened. Also, if only two or three electrode connectors 41 are formed, it is difficult to form a cross section that can sufficiently secure the second moment of inertia along the circumferential direction.

[0267] When the four electrode connectors 41 are formed in the cap 40 in a "+" shape as in the embodiment, the welding process can be performed accurately and easily, the distortion resistance and bending resistance of the cap 40 can be ensured, and weakening of the strength of the cap 40 due to the forming process can be prevented. That is, although the cap 40 also functions as a current collector, it is preferable that the cap 40 maintains its strength since it is primarily responsible for closing the open end of the battery can 10.

[0268] The radially outer edge of the cap 40 has a shape that can be joined to the other axial end of the side wall portion 11 of the battery can 10. For this reason, the radially outer edge of the cap 40 preferably has a circular outer peripheral surface or inner surface.

[0269] The cap 40 of the fifth embodiment has a circular inner edge, and the electrode connecting portion 41 is recessed from the radially inner side to the axially inner side. As shown in Fig. 29, the circular inner surface of the cap 40 contacts the axial end surface of the side wall portion 11 of the battery can 10 and can be welded by a laser irradiated from the outer periphery of the battery can 10 to the radially inner side to form a joint (M).

[0270] At this time, the radially outer edge of the recessed portion for forming the electrode connecting portion 41 forms an outer wall. The outer wall may form a press-in outer wall 45 having an outer diameter corresponding to the inner diameter of the battery can 10. Then, when the cap 40 is assembled to the battery can 10, as shown in FIG. 29, the press-in outer walls 45 of the electrode connecting portions 41 each come into contact with and press into the inner circumferential surface of the battery can 10, thereby guiding the center alignment of the cap 40 with respect to the battery can 10.

[0271] According to the fifth embodiment, the four push-in outer walls 45 are evenly spaced along the circumferential direction and come into contact with the battery can 10 in a portion of the entire area around the inner circumferential surface, so that the cap 40 can be easily pushed into the battery can 10 without increasing the pushing force of the cap 40.

[0272] As described above, the cap 40 of the embodiment has an advantage that it is easy to manufacture since the outer push-in wall 45 is molded together with the electrode connecting portion 41 when the electrode connecting portion 41 is molded.

[0273] Furthermore, according to the structure of the cap 40, a laser is irradiated in the radial direction to weld the cap 40 and the battery can 10. Therefore, even if an unexpected error causes the inner edge of the cap 40 and a portion of the end of the side wall 11 of the battery can 10 to not be in close contact, there is no risk of the laser being directly irradiated onto the inside of the battery can 10 and damaging the electrode assembly 20.

[0274] According to the fifth embodiment, the receiving surface 44 of the cap 40 is located further outward in the axial direction than the joint (M) between the cap 40 and the battery can 10. Therefore, even if the battery can 10 in FIG. 30 is turned upside down and stood correctly, the joint (M) does not come into direct contact with the ground, making it easier to protect the joint (M).

[0275] By applying the above-described cap 40, there is no need to use a current collector plate to electrically connect the tab of the second electrode 22 to the battery can 10, which reduces the number of parts and assembly steps, further secures internal volume, and increases energy density. The cap 40 electrically connected to the battery can 10 is directly connected to the metal foil 23 of the second electrode of the electrode assembly 20, but is connected via a weld (W) that extends long in the radial direction, so that the current path is uniformly distributed and internal resistance can be significantly reduced.

[0276] The liquid inlet 42 is provided in the center of the cap 40. The liquid inlet 42 can be provided on the bottom surface of the cap 40, that is, on a protrusion 43 that protrudes slightly above the electrode connecting portion 41 of the cap 40. The height of the protrusion 43 is set lower than the height of the receiving surface 44, and the height of the plug 50 may also be lower than the height of the receiving surface 44 when the plug 50 is covered and closed.

[0277] Since the protrusion 43 protrudes higher than the bottom, the thermal sealer 60 can easily approach the plug when covering and thermally sealing the plug 50 after injecting the electrolyte through the filling hole 42. In addition, although the temperature is low, the heat of the thermal sealer 60 can be minimized from being transferred to the inside of the battery can 10.

[0278] The plug 50 is also positioned lower than the receiving surface 44, so that the plug 50 does not receive a direct load even when the battery cell is in an upright position so that the cap 40 is in contact with the ground.

[0279] Meanwhile, the liquid filling hole 42 formed in the center of the cap 40 can serve as a passage through which equipment components can enter and exit for welding the first electrode terminal 13 and the current collector plate 31 of the first electrode 21. Therefore, unlike the assembly procedures first shown in Figures 26 to 29, the cap 40 can be first joined to the tab of the second electrode 22 of the electrode assembly 20, as shown in Figure 36, and then fitted into the battery can 10 when the electrode assembly 20 is placed in the battery can.

[0280] 36 , the electrode assembly 20 can be housed in a battery can 10 with a current collector 31 joined to the tab of the first electrode 21 of the electrode assembly 20 and a cap 40 joined to the tab of the second electrode 22. The current collector 31 and the first electrode terminal 13 can be welded together through the liquid inlet 42 of the cap 40 and the hollow portion of the core of the electrode assembly 20.

[0281] [Battery cell manufacturing method] The cap 40 of the fifth embodiment described above functions as a current collector for the second electrode and also has the original function of a cap, and therefore differs from conventional battery cells that include a current collector for the second electrode in its manufacturing method.

[0282] Furthermore, the cap 40 is provided with liquid filling holes 42, which can be used as passages for the joining process of the current collecting plate 31 and the first electrode terminal 13, thereby enabling further diversification of the manufacturing method of the battery cell.

[0283] First, an example of a method for manufacturing a battery cell will be described with reference to Fig. 37. This corresponds to the method for manufacturing a battery cell shown in Figs.

[0284] This includes the steps of preparing a battery can 10 to which a first electrode terminal 13 is fixed, and preparing an electrode assembly 20 including a first electrode 21 and a second electrode 22. At this time, the first electrode 21 and a current collector plate 31 may be joined and connected at one axial end of the electrode assembly 20.

[0285] Next, the electrode assembly 20 is inserted into the battery can 10 with the current collector plate facing the bottom 12 of the battery can 10, and the current collector plate 31 of the electrode assembly 20 is joined to the first electrode terminal 13 fixed to the bottom 12 of the battery can 10 by a method such as welding.

[0286] Next, the open end of the battery can 10 is covered with the cap 40. At this time, preferably, the electrode connecting portion 41 of the cap 40 and the tab of the second electrode 22 of the electrode assembly 20 are joined in close contact with each other, and then the periphery of the open end of the battery can 10 and the edge of the cap 40 are joined together.

[0287] Next, the electrolyte is poured into the battery can 10 through the pouring port 42 of the cap 40 .

[0288] Finally, the above-described sealing structure for the liquid filling port is applied, and the liquid filling port 42 of the battery can 10 is completely sealed with the plug 50.

[0289] These manufacturing methods not only eliminate the need for a separate current collector joining operation for the second electrode 22, but also allow joining of the cap 40 and the second electrode 22 and joining of the cap 40 and the battery can 10 before filling the interior of the battery can 10 with the electrolyte, thereby preventing the joining heat from affecting the electrolyte.

[0290] Next, the manufacturing method disclosed in FIG. 41 will be described.

[0291] This method includes the steps of preparing a battery can 10 to which a first electrode terminal 13 is fixed, and preparing an electrode assembly 20 including a first electrode and a second electrode. At this time, the first electrode 21 and a current collector plate 31 may be joined and connected to one axial end of the electrode assembly. In addition, the electrode connector 41 of the cap 40 and the tab of the second electrode 22 may be joined and connected to the other axial end of the electrode assembly.

[0292] That is, the cap 40 may be first joined to the second electrode of the electrode assembly before the electrode assembly is housed in the battery can.

[0293] Next, the electrode assembly 20 is inserted into the battery can 10 with the current collector plate facing the bottom 12 of the battery can 10. During this process, the cap 40 covers the open end of the battery can 10.

[0294] Next, the current collector 31 of the electrode assembly 20 is joined to the first electrode terminal 13 fixed to the bottom 12 of the battery can 10 by a method such as welding, and the periphery of the open end of the battery can 10 is joined to the edge of the cap 40.

[0295] Next, the electrolyte is poured into the battery can 10 through the pouring port 42 of the battery can 10 .

[0296] Finally, the above-described sealing structure for the liquid filling port is applied, and the liquid filling port 42 of the battery can 10 is completely sealed with the plug 50.

[0297] According to these manufacturing methods, a separate current collector joining operation is not required for the second electrode 22, and joining of the cap 40 to the second electrode 22 and joining of the cap 40 to the battery can 10 can be performed before filling the interior of the battery can 10 with the electrolyte, preventing the joining heat from affecting the electrolyte. Furthermore, the cap 40 can be integrated into the electrode assembly 20 in advance without being separately managed, further simplifying the assembly equipment.

[0298] In this way, when the cap 40 having the liquid injection port 42 is used to manufacture a battery cell, various manufacturing methods can be configured.

[0299] Furthermore, when sealing the liquid filling hole 42, strong pressure is not applied to the cap 40, and the cap 40 is not heated to a high temperature, so there is no risk of the internal structure of the battery can 10 being damaged or being denatured or ignited by heat.

[0300] [Battery pack and vehicle] 39, a battery cell 72 to which the above-described sealing structure for the liquid filling port is applied and / or a battery cell 72 to which the above-described manufacturing method is applied can be housed in a housing 71 of a battery pack 70. The battery pack 70 can be constructed using a battery module that is an intermediate assembly form, or, as shown in the figure, the battery pack 70 can be constructed directly without a battery module.

[0301] Since the battery cell 72 itself has a large volume, it is easy to implement the battery pack 70 without using an intermediate structure such as a battery module. In addition, since the second electrode of the battery cell 72 is connected via a cap, the internal resistance is low and the energy density is higher. Therefore, the energy density of the battery pack 70 can be further increased.

[0302] In this way, the battery pack 70 with increased energy density can store the same amount of energy while reducing its volume and weight. Therefore, when the battery pack 70 using these battery cells 72 is installed in a vehicle such as an automobile 80 that uses electricity as its energy source, as shown in Fig. 40, the vehicle's mileage relative to the energy can be further extended.

[0303] It should be understood that the above-described embodiments are illustrative in all respects and are not limiting, and the scope of the present invention is defined by the following claims rather than the above detailed description. All modifications and variations within the meaning and scope of the following claims, as well as equivalent concepts, should be construed as being included within the scope of the present invention.

[0304] Although the present invention has been described above with reference to illustrative drawings, the present invention is not limited to the embodiments and drawings disclosed in this specification, and it is obvious that various modifications can be made by those skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention are not explicitly described and explained while describing the embodiments of the present invention, it is natural that the effects that can be predicted by the configuration should also be recognized. [Explanation of symbols]

[0305] 10 Battery can 11 Side wall 12 Bottom 13 Positive electrode terminal (first electrode terminal) 14 Terminal gasket 15 Negative electrode terminal (second electrode terminal) 19 Insulator 20 Electrode assembly 21 First electrode 22 Second electrode 23 Metal foil 24 Active material layer 25 Grounded part 26 Ungrounded part 27 Notch tab 28 Separation membrane 31 Current collector plate 32 Terminal connection part 33 Ring part 34 Electrode connection part 40 Cap 41 Electrode connection part W Welding part 42 Liquid injection port 43 Protrusion 44 Receiving surface 45 Press-in outer wall M Joint part 46 First chromium coating layer 47 Depression 50 Plug 51 Central protrusion 53 Second chromium coating layer 55 PP-MAH (heat-sealing layer) 58 Rivet 59 Ball 60 Heat-sealing machine 70 Battery pack 71 Housing 72 Battery cell 80 Vehicle

Claims

1. a battery can 10 made of metal; a metal cap 40 for covering the open end of the battery can 10; a liquid filling port 42 provided in the battery can 10 or the cap 40; a metal plug 50 for covering the inlet 42; and a heat-sealed portion interposed between a first surface of the battery can (10) or the cap (40) surrounding the liquid inlet (42) and a second surface of the plug (50) in contact with the first surface, and fused to at least a partial area of the first surface and the second surface in a closed loop shape surrounding the liquid inlet (42); The heat-sealed portion is a first chromium coating layer 46 formed on the first surface; a second chromium coating layer 53 formed on the second surface; and and a thermal welding layer 55, which is in contact with the first chromium coating layer 46 and the second chromium coating layer 53 on both sides and contains PP-MAH (maleic anhydride modified polypropylene) that bonds to the first chromium coating layer 46 and the second chromium coating layer 53 by heat. Battery cell.

2. The PP-MAH is provided by insert injection onto either the first chromium coating layer 46 formed on the first surface or the second chromium coating layer 53 formed on the second surface. The battery cell of claim 1 .

3. Either the first chromium coating layer 46 or the second chromium coating layer 53 constitutes a substrate of the PP-MAH of the thermal welding layer 55. The battery cell according to claim 1 or 2.

4. The thermal welding layer 55 is a non-substrate layer containing PP-MAH. The battery cell according to claim 1 or 2.

5. The plug 50 has a central protrusion 51 that is inserted into the liquid inlet 42, The central protrusion 51 contacts the inner peripheral surface of the battery can 10 or the cap 40 that defines the liquid inlet 42, and the centers of the plug 50 and the liquid inlet 42 are aligned. The battery cell according to claim 1 or 2.

6. The central protrusion 51 penetrates the liquid injection port 42 in the depth direction. The battery cell of claim 5 .

7. The central protrusion 51 is inserted into only a portion of the depth direction of the liquid injection hole 42. The battery cell of claim 5 .

8. The stopper 50 has a central protrusion 51 that protrudes toward the liquid inlet 42 at a position facing the liquid inlet 42, The central protrusion 51 is not inserted into the liquid inlet 42. The battery cell according to claim 1 or 2.

9. A recess 47 for receiving the stopper 50 is provided around the inlet 42. The outer circumferential surface of the stopper 50 contacts the inner circumferential surface of the recess 47, and the centers of the stopper 50 and the inlet 42 are aligned. The battery cell according to claim 1 or 2.

10. A recess 47 for receiving the stopper 50 is provided around the inlet 42. A protrusion 43 is provided around the recess 47 to define the recess 47, The axially outer surface of the plug 50 accommodated in the recess 47 corresponds to the surface of the protrusion 43 in the axial direction or is arranged further inward in the axial direction. The battery cell according to claim 1 or 2.

11. the first surface includes a first-1 surface facing axially outward of the battery cell; the second surface includes a second-first surface facing axially inwardly opposite the first-first surface; The thermal welding portion is provided between the first-1 surface and the second-1 surface. The battery cell according to claim 1 or 2.

12. the first surface includes a first-second surface facing radially inward of the battery cell; the second surface includes a second-second surface facing radially outward opposite the first-second surface; The thermal welding portion is provided between the first-2 surface and the second-2 surface, The battery cell of claim 11 .

13. the first surface includes a first-second surface facing radially inward of the battery cell; the second surface includes a second-second surface facing radially outward opposite the first-second surface; The thermal welding portion is not provided between the first-2 surface and the second-2 surface. The battery cell of claim 11 .

14. The plug 50 and the battery can 10 or the cap 40 to which the plug 50 is joined by the thermal welding portion are electrically connected. The battery cell according to claim 1 or 2.

15. The liquid inlet 42 is provided in the cap 40, The open end side edge of the battery can 10 and the edge of the cap 40 are thermally bonded. The battery cell according to claim 1 or 2.

16. The battery can 10 and the cap 40 are thermally joined by any one of welding, brazing, and soldering.

16. The battery cell of claim 15.

17. an electrode assembly 20 accommodated inside the battery can 10 and including a first electrode 21 and a second electrode 22, the tabs of the first electrode 21 and the tabs of the second electrode 22 being disposed on opposite sides in the axial direction; a first electrode terminal 13 is installed on a bottom 12 of the battery can 10 provided on the opposite side of the open end in the axial direction, the first electrode terminal 13 being fixed to the bottom 12 while being electrically insulated from the bottom 12; The first electrode 21 of the electrode assembly 20 is connected to the first electrode terminal 13 via a current collecting plate 31 joined to a tab of the first electrode 21.

16. The battery cell of claim 15.

18. an electrode assembly 20 accommodated inside the battery can 10 and including a first electrode 21 and a second electrode 22, the tabs of the first electrode 21 and the tabs of the second electrode 22 being disposed on opposite sides in the axial direction; The cap 40 includes an electrode connection portion 41 that is thermally bonded to a tab of the second electrode 22 of the electrode assembly 20.

16. The battery cell of claim 15.

19. The cap 40 and the tab of the second electrode 22 are thermally joined by any one of welding, brazing, and soldering.

20. The battery cell of claim 18.

20. The liquid inlet 42 is provided in the center of the cap 40, The electrode connecting portion 41 extends radially around the liquid inlet 42.

20. The battery cell of claim 18.

21. The cap 40 includes a receiving surface 44 extending axially outward from the electrode connecting portion 41, The axially outer surface of the plug 50 is disposed axially further inward than the receiving surface 44.

20. The battery cell of claim 18.

22. The liquid injection port 42 is provided in a protruding portion 43 that protrudes in the axial direction from the electrode connecting portion 41.

20. The battery cell of claim 18.

23. a battery can preparation step of preparing a battery can 10 including a side wall portion 11, a bottom portion 12 connected to one axial end of the side wall portion 11, and an open end portion provided at the other axial end of the side wall portion 11, and sealingly and insulatingly fixing a first electrode terminal 13 to the center of the bottom portion 12; a step of preparing an electrode assembly, which includes a first electrode 21 and a second electrode 22, the tabs of the first electrode 21 and the tabs of the second electrode 22 being disposed on opposite axial sides of each other; a cap preparation step of preparing a cap 40 having a liquid inlet 42 and a first chromium coating layer 46 formed around the liquid inlet 42; a plug preparation step of preparing a plug 50 provided with a second chromium coating layer 53; After the battery can preparation step and the electrode assembly preparation step, the electrode assembly 20 is placed in the battery can 10 so that the tab of the first electrode 21 faces the bottom 12 of the battery can 10, and a first electrode terminal connection step is performed in which the tab of the first electrode 21 is connected to the first electrode terminal 13; a second electrode connecting step of connecting the cap 40 to the tab of the second electrode 22 after the electrode assembly preparing step and the cap preparing step; a cap fixing step of fixing the cap 40 to the battery can 10 after the first electrode terminal connecting step; a step of injecting an electrolyte into the battery can 10 after the step of connecting the first electrode terminal, the step of connecting the second electrode, and the step of fixing the cap; and and a step of closing the inlet 42 with a plug 50 by heating a thermal weld layer containing PP-MAH, which is interposed between the first chrome coating layer 46 and the second chrome coating layer 53, to form a thermal weld after the inlet filling step and the plug preparation step. A method for manufacturing a battery cell.

24. The heat-sealed layer is provided by insert injection onto the second chromium coating layer 53 during the preparation of the plug.

24. The method of manufacturing the battery cell of claim 23.

25. A battery pack comprising the battery cell according to claim 1 or 2.

26. 26. A motor vehicle comprising the battery pack of claim 25.

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