A sealing structure for the electrolyte filling port of a battery can, and a battery cell, battery pack, and automobile to which this structure is applied.

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 liquid injection 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 Art

[0002] A cylindrical battery cell has a structure in which a jelly-roll type electrode assembly is housed inside a cylindrical metal can, and is more resistant to impact and temperature than a pouch type battery. For this reason, there is an increasing demand to use a metal can type cell as a battery cell applied to a vehicle battery pack.

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

[0004] To cover the open end of the battery can with a cap and fix the cap to the battery can, crimping or seam welding can be applied.

[0005] Crimping is a method in which, after injecting an electrolytic solution into the battery can through the open end of the battery can, covering the open end with a cap, beading or crimping the tip of the side wall portion of the battery can, and crimping the edge of the cap to fix it. Although such a crimping method is advantageous in that the electrolytic solution filled inside the battery can does not generate heat enough to deteriorate or ignite during the processing, the fixing structure is complicated, and the fixing structure of the cap occupies the internal volume of the battery can and reduces the energy density.

[0006] Referring to Figures 1 to 6, seam welding is a method in which the tip of the side wall portion 11 of the battery can 10 and the edge of the cap 40 are butted together and welded along the circumferential direction. Because the fixing structure is simple, it is possible to secure an even larger volume of electrode assemblies that can be housed inside the battery can. Therefore, the seam welding method is even more advantageous in securing electrical capacity for the same volume of battery can.

[0007] However, if the electrolyte is filled into the battery can and then the open end of the battery can is covered with a cap and welded, the high heat generated by the welding may cause the electrolyte to deteriorate or ignite.

[0008] Therefore, when attempting to fix the open end of the battery can to the cap by seam welding, a method can be applied in which an electrolyte solution is injected through the electrolyte solution injection port 42 provided at the bottom of the battery can, an electrode assembly is placed inside the battery can, the battery can can 10 and the cap 40 are seam-welded, the electrolyte solution is injected through the electrolyte solution injection port 42 provided at the bottom of the cap or battery can, and after the injection is complete, the electrolyte solution is sealed with a stopper.

[0009] After injecting the electrolyte through the injection port 42, the method for closing the injection port can include a seam welding method with a metal stopper, a blind rivet method, a metal ball insertion method, and the like.

[0010] First, referring to Figures 1 and 2, the seam welding of the metal plug is a method in which the liquid filling port 42 provided on the battery can 10 is covered with a metal plug 50, and the frame of the plug 50 is seam-welded to the cap 40 to form a welded part (W). When the material of the battery can and cap is SUS, for example, the surface temperature of the seam welding can rise to 1400 degrees Celsius, which is the melting point of SUS. Such high temperatures can cause the electrolyte to ignite. In other words, the method of sealing the liquid filling port by seam-welding a metal plug when closing it completely contradicts the purpose of introducing the liquid filling port structure, which is to minimize the effect of the heat generated when seam-welding the open end of the battery can and the cap on the electrolyte. Furthermore, in order to prevent such a phenomenon, a structure to prevent the electrolyte from igniting can be applied, but this would only occupy an additional volume of the internal space of the battery cell, which is disadvantageous in securing the electrical capacity of the battery can.

[0011] The sealing method using blind rivets 58 shown in Figures 3 and 4 is a method of mechanically sealing by plastically deforming the metal, which places a lot of load on the joint. These loads can cause damage to the coating that was formed on the surface of the cap 40 and rivet 58 to prevent leakage. In other words, if the load is reduced to prevent damage to the coating, the sealing function will be weakened, and if the load is increased to improve the sealing function, the coating may be damaged and there is a concern that the seal may crack. Furthermore, since the rivet is inserted into the inside of the can before riveting, space must be secured inside the battery can for the rivet, which can cause a reduction in the soluble volume inside the battery can.

[0012] The metal ball insertion method shown in Figures 5 and 6 requires the inner circumferential surface of the liquid injection port 42 to extend axially to secure the metal ball 59. However, this structure is disadvantageous in terms of securing the internal volume of the battery can. Furthermore, forcibly inserting the ball 59 into the liquid injection port 42 applies a large load to the electrodes, which may damage them. [Overview of the project] [Problems that the invention aims to solve]

[0013] The present invention was devised to solve the above-mentioned problems, and aims to provide a sealing structure for a liquid injection port in which the stopper is chemically strongly bonded to the cap, ensuring a secure seal, without applying a large load to the cap portion around the liquid injection port or heating at high temperatures during the process of closing the injection port.

[0014] The present invention aims to provide a sealing structure for the cap filling port of a battery can that does not generate high temperatures, does not cause denaturation or ignition of the electrolyte, uses a chemical bonding seal rather than a mechanical seal, does not apply a large load to the cap and joint, and reliably prevents leakage.

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

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

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

[0018] The present invention aims to provide a battery pack including the battery cells, and a vehicle equipped with the battery pack and driven by the electrical energy provided by the battery pack.

[0019] The technical problems of the present invention are not limited to the objectives mentioned above. Other objectives and advantages of the present invention not mentioned can be understood from the following description and will become even clearer from the embodiments of the present invention. Furthermore, it is clear that the objectives and advantages of the present invention can be achieved by the means and combinations thereof shown in the claims. [Means for solving the problem]

[0020] In order to solve the above problems, the present invention provides a sealing structure for a liquid injection port that closes a liquid injection port provided in a battery can or a cap made of a metal material with a metal plug.

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

[0022] The material of the plug can include aluminum or steel.

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

[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 joined to the periphery of the other axial end of the side wall portion of the battery can.

[0026] The thermal joining can be performed by welding, brazing or soldering. [[ID=二十七]]

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

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

[0029] The liquid injection port may be provided at the central portion of the cap or at the central portion of the bottom.

[0030] The plug covering the liquid injection port includes the cross-section of the liquid injection port and has a cross-section larger than the cross-section of the liquid injection port.

[0031] The liquid injection port may be circular. The stopper may be concentric with the circular liquid injection port and may be a circular plate with a radius larger than the radius of the liquid injection port.

[0032] The area around the plug surface facing the liquid injection port may surround the liquid injection port and be in close contact with the bottom of the battery can or the area around the liquid injection port of the cap where the liquid injection port is formed.

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

[0034] In other words, the first surface and the second surface refer to the parts where the injection port and the stopper come into contact with each other when the injection port is closed with the stopper.

[0035] The heat-welded portion is fused to at least a portion of the first and second surfaces in a closed loop shape surrounding the liquid injection port.

[0036] The heat-welded portion includes a first chromium coating layer formed on the first surface; a second chromium coating layer formed on the second surface; and a heat-welded layer containing PP-MAH (polypropylene-maleic anhydride; polypropylene modified with maleic anhydride) whose two surfaces are in contact with the first chromium coating layer and the second chromium coating layer, respectively, and which is bonded to the first chromium coating layer and the second chromium coating layer by heat.

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

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

[0039] In other words, the heat-welded portion refers to a region in which the first chromium coating layer, the heat-welded layer, and the second chromium coating layer are all stacked in the thickness direction.

[0040] The heat-sealed layer may be a non-substrate layer containing PP-MAH.

[0041] The area of ​​the first chromium coating layer may correspond to or be larger than the area of ​​the heat-welded layer.

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

[0043] The first chromium coating layer can constitute the substrate of the PP-MAH heat-welded layer.

[0044] The area of ​​the second chromium coating layer may correspond to or be larger than the area of ​​the heat-welded layer.

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

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

[0047] The stopper may have a central projection that protrudes toward the liquid injection port at a position opposite to the liquid injection port.

[0048] The central projection may be inserted into the liquid injection port.

[0049] The central projection contacts the inner circumferential surface of the battery can or cap that defines the liquid injection port, so that the centers of the stopper and the liquid injection port can be aligned.

[0050] The aforementioned central projection can penetrate the liquid injection port in the depth direction.

[0051] The central projection may be inserted only to a portion of the depth of the liquid injection port.

[0052] The heat-welded portion may be interposed between the central projection and the inner circumferential surface of the battery can or cap defined by the liquid injection port.

[0053] The heat-welded portion does not necessarily have to be interposed between the central projection and the inner circumferential surface of the battery can or cap defined by the liquid injection port.

[0054] The central projection does not necessarily have to be inserted into the liquid injection port.

[0055] A recessed area for housing the stopper can be provided around the liquid injection port.

[0056] A protruding portion defining the recessed portion can be provided around the recessed portion.

[0057] The outer circumferential surface of the stopper is in contact with the inner circumferential surface of the recessed portion, so that the centers of the stopper and the liquid injection port can be aligned.

[0058] The axial outer surface of the plug housed in the recessed portion may correspond axially to the surface of the protruding portion, or it may be positioned further inward in the axial direction.

[0059] The first surface includes a first-first surface facing outward in the axial direction of the battery cell, and the second surface may include a second-first surface facing inward in the axial direction, opposite the first-first surface.

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

[0061] The heat-welded portion can be provided between the first-1 surface and the second-1 surface.

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

[0063] The first- and second surfaces are the inner circumferential surfaces of the bottom or cap of the battery can that define the liquid filling port, and the second- and second surfaces may be the outer circumferential surfaces of the central projection of the stopper.

[0064] The first- and second surfaces are the inner circumferential surfaces of the bottom of the battery can or the protruding part of the cap that defines the recessed portion, and the second- and second surfaces may be the outer circumferential surfaces of the stopper.

[0065] The heat-welded portion can be provided between the first-second surface and the second-second surface.

[0066] The heat-welded portion can be provided between the first-second surface and the second-second surface.

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

[0068] These electrical connection paths may include contact areas between the first and second surfaces where the heat-welded portion is not interposed.

[0069] These electrical connection paths may include heat-welded portions, which include the heat-welded layer that is not a base material.

[0070] A first electrode terminal can be installed in the center of the bottom portion.

[0071] The first electrode terminal can be installed on the bottom while being insulated from the bottom.

[0072] The bottom portion surrounding the first electrode terminal constitutes a second electrode terminal, and the side wall portion connected to the bottom portion can also constitute a second electrode terminal.

[0073] An electrode assembly comprising 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 a first electrode and a second electrode, separated by a separation membrane, are wound together.

[0075] The electrode assembly may be housed inside the battery can, aligned axially with the battery can.

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

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

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

[0079] A current collector plate can be attached to the tab of the first electrode.

[0080] The current collector plate can be connected to the first electrode terminal.

[0081] As a result, the first electrode terminal can acquire 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 the portion of the metal foil of the second electrode that extends to the other axial end of the electrode assembly.

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

[0085] The tab of the second electrode may be positioned toward the open end.

[0086] The cap can be connected to the tab of the second electrode.

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

[0088] The electrode connecting portion may be recessed axially inward from the surface of the cap.

[0089] The electrode connecting portion may extend in a flattened manner in the radial direction.

[0090] The electrode connecting portion may be connected to the tab of the second electrode of the electrode assembly by thermal bonding.

[0091] The thermal joining of the cap and the tab of the second electrode may consist of one of the following processes selected from welding, brazing, or soldering.

[0092] As a result, the cap, the side wall portion to which the cap is connected, and the bottom portion connected to the side wall portion can acquire a second polarity.

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

[0094] The thermally bonded portion may be a welded portion (W) formed by a laser irradiated onto the surface of the electrode connecting portion in a scanning manner along the radial direction.

[0095] The liquid injection port may be located in the center of the cap.

[0096] The liquid injection port can be aligned with the hollow portion of the core of the electrode assembly.

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

[0098] The cap may be provided with a receiving surface that extends axially outward from the electrode connecting portion.

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

[0100] The axial outer surface of the plug may be positioned further inward in the axial direction than the receiving surface.

[0101] The liquid injection port can be provided on a protruding portion that protrudes axially from the electrode connecting portion.

[0102] Each of the caps may be recessed inside the battery case and may have two or more electrode connecting portions extending radially. There may be four of these electrode connecting portions.

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

[0104] Furthermore, the present invention provides a method for manufacturing a battery cell to which the sealing structure of the liquid injection 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 stopper preparation step, an electrode assembly housing step, a first electrode terminal connection step, a cap connection step, a liquid injection step, and a liquid injection port closing step.

[0106] The preparation step for the battery can includes preparing a battery can comprising a side wall, a bottom connected to one axial end of the side wall, and an open end provided at the other axial end of the side wall, and sealing and insulating the first electrode terminal in the center of the bottom.

[0107] The preparation step for the electrode assembly includes the step of manufacturing an electrode assembly comprising a first electrode and a second electrode, wherein the tabs of the first electrode and the tabs of the second electrode are arranged on both sides in the axial direction.

[0108] This may include the step of radially bending the tab of the first electrode and thermally bonding a current collector plate to the bent portion.

[0109] The preparation step for the cap includes the step of manufacturing a cap that comprises an electrode connecting portion electrically connected to the tab of the second electrode, and a liquid injection port provided in the center of the electrode connecting portion.

[0110] This may include a step of chromate surface treatment around the liquid injection port.

[0111] The preparation step for the stopper includes the steps of chromate surface treatment of the stopper and insert injection of a heat-welded layer containing PP-MAH into the chromium coating layer formed by the chromate surface treatment.

[0112] The electrode assembly housing step includes, after the battery can preparation step and the electrode assembly preparation step, housing the electrode assembly in the battery can such that the tab of the first electrode faces the bottom of the battery can.

[0113] The step of connecting the first electrode terminal includes, after the step of housing the electrode assembly, the step of connecting the tab of the first electrode or the current collector plate connected thereto to the first electrode terminal.

[0114] The cap connection step includes the steps of covering the open end of the battery can with the cap and making the electrode connection portion tightly attached to the tab of the second electrode, electrically connecting the electrode connection portion to the tab of the second electrode, and joining the outer circumference of the cap around the open end of the battery can.

[0115] The liquid injection step includes the step of connecting the first electrode terminals, and, after the step of connecting the cap, the step of injecting the electrolyte into the battery can through the liquid injection port.

[0116] The sealing step of the liquid injection port includes covering the liquid injection port with the stopper and heating the heat-sealed layer with a heat-sealing machine to chemically bond the PP-MAH to the chromium coating layer, including hydrogen bonding.

[0117] The second embodiment of the manufacturing method includes a battery can preparation step, an electrode assembly preparation step, a cap preparation step, a stopper preparation step, a second electrode connection step, an electrode assembly housing and can insertion step, a first electrode terminal connection and cap fixing step, a liquid injection step, and a liquid injection port closing step.

[0118] The preparation step for the battery can includes preparing a battery can comprising a side wall, a bottom connected to one axial end of the side wall, and an open end provided at the other axial end of the side wall, and sealing and insulating the first electrode terminal in the center of the bottom.

[0119] The preparation step for the electrode assembly includes the step of manufacturing an electrode assembly comprising a first electrode and a second electrode, wherein the tabs of the first electrode and the tabs of the second electrode are arranged on both sides in the axial direction.

[0120] This may include the step of radially bending the tab of the first electrode and thermally bonding a current collector plate to the bent portion.

[0121] The preparation step for the cap includes the step of manufacturing a cap that comprises an electrode connecting portion electrically connected to the tab of the second electrode, and a liquid injection port provided in the center of the electrode connecting portion.

[0122] This may include a step of chromate surface treatment around the liquid injection port.

[0123] The preparation step for the stopper includes the steps of chromate surface treatment of the stopper and insert injection of a heat-welded layer containing PP-MAH into the chromium coating layer formed by the chromate surface treatment.

[0124] The step of connecting the second electrode includes, after the preparation steps for the electrode assembly and the cap, joining the electrode connecting portion of the cap to the tab of the second electrode to electrically connect them.

[0125] The steps of housing the electrode assembly and inserting the cap include, after the battery can preparation step and the second electrode connection step, housing 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 steps of connecting the first electrode terminal and fixing the cap include, after the steps of housing the electrode assembly and inserting the cap, connecting the tab of the first electrode to the first electrode terminal and joining the outer circumference of the cap around the open end of the battery can to electrically connect them.

[0127] The aforementioned liquid injection step includes the step of injecting electrolyte into the battery can through the liquid injection port after the step of connecting the first electrode terminals and the step of fixing the cap.

[0128] The sealing step of the liquid injection port includes covering the liquid injection port with the stopper and heating the heat-sealed layer with a heat-sealing 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 battery cells described above.

[0130] This invention provides an automobile equipped with a high-energy-density battery pack, thereby reducing the volume and weight occupied by the battery pack. [Effects of the Invention]

[0131] According to the present invention, since the liquid injection port is not sealed with rivets that apply load for plastic deformation or metal balls that apply load for forced pressing, there is no concern that the cap will deform or that the internal electrodes of the battery can will be damaged. Furthermore, there is no need to secure space inside the battery can for rivets to be inserted for riveting or space for metal balls to be pressed in, which allows for further securing of the soluble internal volume of the battery cell and increases the energy density of the battery cell.

[0132] According to the present invention, the liquid injection port can be closed at temperatures even lower than high-temperature joining methods such as welding, and medium-temperature joining methods such as brazing and soldering. Furthermore, to prevent heat from being transferred to the electrolyte or electrode assembly while the liquid injection port is closed, the liquid injection port does not need to protrude from the cap or battery case. In other words, the cap to which the liquid injection port structure is applied can be designed to be flat, meeting the same standards, and further securing the internal volume of the battery case is possible.

[0133] According to the present invention, since the stopper is joined to the cap and the liquid injection port is sealed at a temperature even lower than soldering, without applying external force that would deform the cap or battery can, there is no risk of deformation of the cap, damage or deformation of the electrode assembly and related parts housed inside the battery can, or deterioration or ignition of the electrolyte.

[0134] According to the present invention, when joining a metal cap and a metal stopper, the heat-welded layer chemically forms hydrogen bonds between the two metal surfaces to be joined, resulting in excellent sealing performance.

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

[0136] According to the present invention, the PP-MAH heat-sealed layer chemically bonds with the chromium coating layer of the battery can and the stopper, ensuring a secure seal and significantly reducing the possibility of electrolyte leakage.

[0137] The effects described above, as well as the specific effects of the present invention, will be explained and described below in relation to the embodiments for carrying out the invention. [Brief explanation of the drawing]

[0138] [Figure 1] This is a diagram showing a conventional method for sealing the electrolyte filling port on a battery can. [Figure 2] This is a diagram showing a conventional method for sealing the electrolyte filling port on a battery can. [Figure 3] This is a diagram showing a conventional method for sealing the electrolyte filling port on a battery can. [Figure 4] This is a diagram showing a conventional method for sealing the electrolyte filling port on a battery can. [Figure 5] This is a diagram showing a conventional method for sealing the electrolyte filling port on a battery can. [Figure 6] This is a diagram showing a conventional method for sealing the electrolyte filling port on a battery can. [Figure 7] This drawing shows a first embodiment of the sealing structure for the electrolyte inlet of a battery can and the sealing method thereof according to the present invention. [Figure 8] This drawing shows a first embodiment of the sealing structure for the electrolyte inlet of a battery can and the sealing method thereof according to the present invention. [Figure 9] This drawing shows a first embodiment of the sealing structure for the electrolyte inlet of a battery can and the sealing method thereof according to the present invention. [Figure 10] This diagram shows the chemical bonding structure between chromium oxide and PP-MAH in the chromium coating layer. [Figure 11] This is a diagram showing the manufacturing process of an electrolyte plug. [Figure 12] This is a diagram showing the manufacturing process of an electrolyte plug. [Figure 13] This drawing shows a second embodiment of the sealing structure for the electrolyte inlet of a battery can. [Figure 14] This drawing shows a second embodiment of the sealing structure for the electrolyte inlet of a battery can. [Figure 15]This drawing shows a third embodiment of the sealing structure for the electrolyte inlet of a battery can. [Figure 16] This drawing shows a third embodiment of the sealing structure for the electrolyte inlet of a battery can. [Figure 17] This drawing shows a fourth embodiment of the sealing structure for the electrolyte inlet of a battery can. [Figure 18] This is a perspective view of the battery cell in the embodiment. [Figure 19] This is a perspective view showing the state of the first electrode, the second electrode, and the separation membrane before lamination, in order to manufacture the electrode assembly that will be housed in the battery can. [Figure 20] This is a perspective view showing the state after lamination of the first electrode, the second electrode, and the separation membrane, for the purpose of fabricating an electrode assembly to be housed in a battery can. [Figure 21] Figure 20 is a plan view of the stacked state. [Figure 22] Figures 20 and 21 show perspective views of electrode assemblies fabricated by winding the laminated material into a jelly roll. [Figure 23] Figures 20 and 21 show side views of electrode assemblies fabricated by winding the laminated material into a jelly roll. [Figure 24] This is a perspective view showing the electrode assembly with a current collector plate attached to the upper part and no current collector plate attached to the lower part. [Figure 25] This is a perspective view showing the electrode assembly with a current collector plate attached to the upper part and no current collector plate attached to the lower part. [Figure 26] Figures 24 and 25 are multi-view diagrams showing the process of housing the electrode assemblies into the battery case. [Figure 27] This is a cross-sectional view showing the process of welding the first electrode terminal to the current collector plate. [Figure 28] This diagram shows the process of covering the open end of a battery can with a cap. [Figure 29] This is a cross-sectional view showing the process of joining the electrode connection portion of the cap to the tab of the second electrode of the electrode assembly, and joining the edge of the cap around the open end of the battery can. [Figure 30] This diagram shows the process of closing the liquid injection port with a stopper. [Figure 31] This is a top perspective view of the cap of the fifth embodiment. [Figure 32] This is a lower perspective view of the cap of the fifth embodiment. [Figure 33] This is a plan view of the cap of the fifth embodiment. [Figure 34] This is a cross-sectional view of the relevant area in Figure 33. [Figure 35] This is a cross-sectional view of the relevant area in Figure 33. [Figure 36] This is a perspective view showing the electrode assembly with the cap attached to the bottom. [Figure 37] This is a procedure diagram of the first embodiment of a method for manufacturing a battery cell using a liquid injection port sealing structure. [Figure 38] This is a procedure diagram of a second embodiment of a method for manufacturing a battery cell using a liquid injection port sealing structure. [Figure 39] This is a drawing showing a battery pack to which the battery cells of the embodiment are applied. [Figure 40] This is a drawing showing an automobile equipped with a battery pack to which the battery cells of the embodiment are applied. [Modes for carrying out the invention]

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

[0140] The present invention is not limited to the embodiments disclosed below, and can be modified in various ways and embodied in various different forms. However, these embodiments are provided to complete the disclosure of the present invention and to fully inform those in the ordinary skill of the scope of the invention. Therefore, the present invention is not limited to the embodiments disclosed below, and should be understood to include any modifications, equivalents, or substitutions that fall within the technical spirit and scope of the present invention, as well as the substitution or addition of any configuration of one embodiment to that of another embodiment.

[0141] The accompanying drawings are provided to facilitate understanding of the embodiments disclosed herein and should not be understood as limiting the technical concept disclosed herein, but rather as including any modifications, equivalents, or substitutions that fall within the concept and technical scope of the present invention. Components in the drawings may be exaggerated in size or thickness for ease of understanding, but this should not be interpreted as restricting the scope of protection of the present invention.

[0142] The terms used herein are used solely to describe specific examples or embodiments and are not intended to limit the invention. Furthermore, singular expressions include plural expressions unless otherwise clearly indicated in the context. Terms such as "includes" and "contains" in the specification are intended to indicate the existence of features, figures, stages, operations, components, parts, or combinations thereof described in the specification. That is, terms such as "includes" and "contains" in the specification should not be understood as preemptively excluding the existence or possibility of adding one or more other features, figures, stages, operations, components, parts, or combinations thereof.

[0143] Terms including ordinal numbers, such as "First," "Second," etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely for the purpose of distinguishing one component from others.

[0144] When it is mentioned that one component is “linked” or “connected” to another component, it must be understood that it is directly linked to or may be connected to the other component, but that other components may exist in between. On the other hand, when it is mentioned that one component is “directly linked” or “directly connected” to another component, it must be understood that there are no other components in between.

[0145] When one component is described as being "above" or "below" another component, it must be understood that this means not only is it positioned directly above the other component, but other components may exist between them.

[0146] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as they would be generally understood by a person of ordinary skill in the art to which this invention pertains. Terms that are commonly used, similar to those defined in dictionaries, should be interpreted as having the meaning consistent with their meaning in the context of the relevant art, and not, unless explicitly defined in this application, should be interpreted in an ideal or overly formal sense.

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

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

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

[0150] In the embodiment, the liquid injection port 42 is provided on the cap 40 as an example. However, it goes without saying that the liquid injection port 42 may also be provided on the can 10. In the case of a cylindrical battery can, the liquid injection port 42 can 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 materials. The material of the stopper 50 may also be aluminum, steel, or an alloy containing these materials. In this embodiment, aluminum is used as the material for the battery can 10 and the cap 40.

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

[0153] The cap 40 can cover the open end provided on 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 to this, and a polygonal cap is also applicable.

[0154] The edge of the cap 40 can be joined to the side wall portion 11 of the battery can 10 in a state where it abuts against the other axial end.

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

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

[0157] A central projection 51 is provided in the center of the inner surface (bottom surface) of the stopper 50, corresponding to the inner diameter of the liquid injection port 42 and extending toward the liquid injection port 42.

[0158] With the stopper 50 covering the liquid inlet 42, the central projection 51 penetrates the liquid inlet 42 and protrudes further inward than the inner surface of the cap 40.

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

[0160] When a chromium coating layer is formed on an aluminum cap 40 or stopper 50, a metal-chromium oxide is coated onto the aluminum surface, as shown in Figure 10.

[0161] With the stopper 50 covering the liquid inlet 42, the outer surface of the cap 40 on which the first chromium coating layer 46 is formed and the inner circumferential surface of the liquid inlet 42 are in contact with the bottom surface of the stopper 50 and the outer circumferential surface of the central projection 51, respectively, on which the second chromium coating layer 53 is formed.

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

[0163] The heat-sealable layer 55 may be a base-less layer containing PP-MAH.

[0164] In this manner, with the heat-sealing layer 55 in between, the surface of the plug 50 is pressed and heated by the heat-sealing machine 60. These heating temperatures may be lower than the thermal decomposition temperature of the electrolyte solution injected into the inside of the battery can 10.

[0165] In the example, the thermal decomposition temperature of the electrolyte is, for example, around 200 degrees Celsius, and the heating temperature of the heat-welded layer 55 may be lower than this.

[0166] As a result, a chemical bond, including hydrogen bonds, is formed between the PP-MAH and the chromium coating layer of the heat-welded layer 55 shown in Figure 10, forming a heat-welded portion. Thus, by applying the sealing structure of the pouring port of the embodiment, a strong chemical bond is formed between the stopper and the cap, without applying strong external force to the cap 40 and the stopper 50, and without applying high heat, thereby reliably sealing the pouring port.

[0167] For convenience in the process, PP-MAH can be injected into the bottom surface of the plug 50 as an insert, and provided in a state where it has been laminated beforehand to form a heat-sealed layer 55.

[0168] Therefore, first, the bottom surface of the stopper 50 and the outer circumferential surface of the central projection 51 may be coated with a second chromium coating layer 53, as shown in Figure 11.

[0169] Then, as shown in Figure 12, PP-MAH can be insert-injected onto the bottom surface of the plug 50 and the outer circumferential surface of the central projection 51, which are coated with the second chromium coating layer 53, to form a heat-sealed layer 55.

[0170] Although the heat-welded layer containing the PP-MAH is a base layer, the second chromium coating layer 53 functions as a base layer for the PP-MAH, so the heat-welded layer can be laminated onto the plug 50 very stably.

[0171] As a result, the heat-sealed layer 55 can be provided integrally laminated on the bottom surface of the stopper 50, as shown in Figure 7. Then, the sealing of the liquid inlet can be easily completed by simply covering the liquid inlet 42 with the stopper 50 on which the heat-sealed layer 55 is formed, and then pressurizing and heating the stopper 50 with a heat welding machine 60 so that the heat-sealed layer 55 is heat-bonded to the chromium coating layer in contact with it, while chemically bonding including hydrogen bonds.

[0172] In the first embodiment, the heat-sealed layer 55 is laminated using the second chromium coating layer 53 of the stopper 50 as the base material. Since the stopper 50 is not introduced into the battery cell manufacturing process until the liquid injection port 42 is closed, there is no risk of the heat-sealed layer 55 being damaged during the manufacturing process, and the handling of the part becomes even easier.

[0173] However, it goes without saying that the heat-welded layer 55 can be provided by laminating it with the first chromium coating layer 46 of the can 10 as the base material. When the stopper 50 is heated under pressure in a heat welding machine 60 to form the heat-welded portion, heat first reaches the area between the second chromium coating layer 53 and the heat-welded layer 55 along the heat conduction path, and then reaches the area between the heat-welded layer 55 and the first chromium coating layer 46. Therefore, when the heat-welded layer 55 is formed with the first chromium coating layer 46 of the can 10 as the base material, there is an advantage in that the chemical bonding between the second chromium coating layer 53 and the heat-welded layer 55 and the chemical bonding between the heat-welded layer 55 and the first chromium coating layer 46 are achieved in a more balanced manner.

[0174] In the first embodiment, the heat-welded layer 55 is first laminated onto the plug 50. Since the heat-welded layer 55 laminated onto the plug 50 is formed by insert injection molding in the mold, the alignment of the second chrome coating layer 53 and the heat-welded layer 55 can be precisely performed.

[0175] Referring to Figure 9, the radially outer end of the first chromium coating layer 46 provided on the outer surface of the cap 40 may be coated to extend radially further outward than the radially outer end of the stopper 50. This prevents the first chromium coating layer 46 of the can 10, which is necessary for forming the heat-sealed portion, from leaking in 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 similar reasons, the central projection 51 of the stopper 50 can be manufactured to extend further than the depth of the pouring port 42. This prevents the risk of the second chromium coating layer 53 and the heat-sealed layer 55, which are necessary for forming the heat-sealed portion, leaking in a portion of the inner surface of the pouring port 42 due to manufacturing errors of the stopper 50 and the can 10, or assembly errors in the sealing process.

[0177] According to the sealing structure of the battery can's liquid filling port described above, the sealing is performed at a temperature sufficient for the heat-sealed layer when closing the liquid filling port, so there is no possibility of the electrolyte deteriorating or igniting. Furthermore, since the heat-sealed layer is formed using a part with PP-MAH inserted and injected into the stopper, the sealing process is simple, and the PP-MAH chemically bonds with the chromium coating layer, ensuring a secure seal.

[0178] [Second Example] Next, the sealing structure of the liquid injection port of the 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 embodiment, any content that is not specifically explained can be understood from the other embodiments. Furthermore, it will be easy to understand that the configurations of one embodiment can be substituted, added, omitted, or combined with those of other embodiments.

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

[0180] In order to form a heat-welded portion between the inner circumferential surface of the liquid injection port 42 and the outer circumferential surface of the central projection 51, appropriate contact must occur between the heat-welded layer 55 and the chrome coating layer. Furthermore, the stopper 50 is assembled to the cap 40 in the axial direction. Therefore, due to manufacturing tolerances and assembly tolerances of each component, appropriate contact required to form a heat-welded portion may not occur between the inner circumferential surface of the liquid injection port 42 and the outer circumferential surface of the central projection 51, which face each other radially, between the heat-welded layer 55 and the chrome coating layer.

[0181] Therefore, in the second embodiment, the configuration for forming a heat-welded portion between the inner circumferential surface of the liquid injection port 42 and the outer circumferential surface of the central projection 51 (first chromium coating layer, second chromium coating layer, and heat-welded layer) is omitted, and a seal structure is provided in which the central projection 51 is configured to directly contact the inner circumferential surface of the liquid injection port 42.

[0182] The central projection 51 can function to align the centers of the stopper 50 and the liquid injection port 42. The outer diameter of the central projection 51 can also be made slightly larger than the inner diameter of the liquid injection port 42 so that the central projection 51 can be pushed into the liquid injection port 42.

[0183] According to this, the central projection 51 does not need to extend beyond the depth of the liquid injection port 42. On the contrary, the length of the central projection 51 can be made shorter than the depth of the liquid injection port 42 so that the central projection 51 is inserted only into a portion of the liquid injection port 42 in the depth direction, thereby reducing the pushing force and securing more internal space in the battery can 10.

[0184] The cap 40 can function as an electrode, and it is even more preferable that the stopper 50 also functions as an electrode like the cap. Therefore, the second embodiment, in which the stopper 50 and the cap 40 are in direct contact, has further advantages compared to the first embodiment, in which the stopper 50 and the cap 40 are connected via a heat-welded portion. Of course, the heat-welded portion does not electrically insulate the stopper 50 and the cap 40.

[0185] The heat-sealed layer 55 of the second embodiment may also be laminated using an insert injection method, similar to the first embodiment, with the second chromium coating layer 53 coated on the plug 50 as the base material.

[0186] [Third Embodiment] Next, the sealing structure of the liquid injection port of the third embodiment will be described with reference to Figures 15 and 16.

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

[0188] With the stopper 50 covering the liquid inlet 42, the height of the axial outer surface of the stopper 50 may correspond to or be lower than the height of the surface of the protrusion 43.

[0189] As a result, the stopper 50 does not protrude at all from the surface of the cap 40, and there is absolutely no risk of the seal being broken due to external force or impact on the part of the stopper 50 that protrudes from the surface of the cap 40.

[0190] The inner circumferential surface of the protrusion 43 defined by the recessed portion 47 can come into contact with the outer circumferential surface of the stopper 50. When the stopper 50 covers the liquid inlet 42, the inner circumferential surface of the protrusion 43 guides the alignment of the stopper 50 and the liquid inlet 42.

[0191] Therefore, the upper end of the inner circumferential surface of the protrusion 43 can be provided with a tapered surface such that its diameter gradually decreases as it moves axially inward from the boundary between the protrusion 43 and the recessed portion 47. These tapered shapes can be naturally formed when the cap 40 is press-formed to create the protrusion 43 and the recessed portion 47.

[0192] There is no heat-welded portion between the inner surface of the protrusion 43 and the outer surface of the plug 50. As a result, the inner surface of the protrusion 43 and the outer surface of the plug 50 can come into direct contact, and the plug 50 can be electrically connected to the protrusion 43.

[0193] Therefore, if the height of the protrusion 43 and the height of the stopper 50 are manufactured to correspond to each other, the protrusion 43 and the stopper 50 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 stopper 50 can be made to correspond to or slightly larger than the inner diameter of the protruding portion 43, so that the stopper 50 is pushed into the recessed portion 47.

[0195] On the other hand, according to the third embodiment, the structure of the protruding portion 43 and the recessed portion 47 guides the alignment of the liquid injection port 42 and the stopper 50, so there is no need for the central projection 51 and the liquid injection port 42 to overlap and guide each other. In fact, if they overlap, it may be difficult to fit the stopper 50 if there is a positional error in either of them.

[0196] Therefore, unlike the second embodiment, the third embodiment is configured such that the central projection 51 protrudes so low that it does not fit into the liquid injection port 42, and the layers 53, 55, and 46 of the heat-welded portion are laminated in contact with each other, while preventing the central projection 51 from being inserted into the liquid injection port 42.

[0197] Therefore, as shown in Figure 16, the height of the central projection 51 can be formed to be longer than the sum of the thicknesses of the second chromium coating layer 53 and the heat-welded layer 55, and shorter than the sum of the thicknesses of the second chromium coating layer 53, the heat-welded layer 55, and the first chromium coating layer 46.

[0198] In this case, the diameter of the central projection 51 may be the same as the diameter of the liquid injection port 42, or slightly smaller. The central projection 51 can define the radial inner boundary of the heat-sealed layer 55 during the process of inserting the heat-sealed layer 55 into the stopper 50.

[0199] According to the third embodiment, the stopper 50 covering the liquid injection port 42 of the cap 40 is protected by the protruding portion 43 and the recessed portion 47, and together with the protruding portion 43, it can reliably function as an electrode terminal.

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

[0201] The sealing structure of the liquid injection port in the fourth embodiment differs from that of the third embodiment in that it uses a stopper 50 in which the central projection 51 is omitted.

[0202] Furthermore, the sealing structure of the liquid injection port in the fourth embodiment differs in that the heat-sealed layer 55 is laminated by insert injection using the first chromium coating layer 46 formed on the bottom of the recessed portion 47 of the cap 40 as a base material.

[0203] In the process of insert-injecting the heat-welded layer 55 into the cap 40, the inner circumferential surface of the recessed portion 47 defines the boundary with the outer circumferential surface of the heat-welded layer 55. Therefore, it is very easy to laminate the heat-welded layer 55 onto 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 stopper 50 in the fourth embodiment can be formed to have an inner diameter smaller than the liquid inlet 42 of the cap 40. This ensures that even if manufacturing errors or assembly tolerances occur, when the stopper 50 covers the liquid inlet 42 and the bottom surface of the stopper 50 comes into contact with the heat-welded layer 55 laminated on the cap 40, the second chromium coating layer 53 is reliably present across the entire surface of the heat-welded layer 55. This ensures a sufficient area for the heat-welded portion.

[0205] In the fourth embodiment, compared to the third embodiment, there is no need to precisely machine the height of the central projection 51, and since the heat-welded layer 55 is laminated on the surface of the recessed portion 47 of the cap 40, there is no risk of damage to the heat-welded layer 55 during the handling process of the cap 40 when assembling the battery cell.

[0206] [Fifth Example] The manufacturing method of battery cells to which the above-described liquid injection port sealing structure is applied, and the structure of these battery cells, will be explained below with reference to Figures 18 to 30.

[0207] Figure 18 discloses a cylindrical battery cell.

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

[0209] Here, form factor refers to a value indicating the diameter and height of a cylindrical battery cell. The cylindrical battery cells applied to the pressure tester may be, for example, 46110 cells, 48750 cells, 48110 cells, 48800 cells, or 46800 cells. In the numerical value indicating the form factor, the first two digits indicate the diameter of the cell, the next two digits indicate the height of the cell, and the last digit 0 indicates that the cross-section of the cell is circular.

[0210] The battery cell used in the pressure tester may be a cylindrical battery cell, which is approximately cylindrical in shape, with a diameter of approximately 46 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0211] Other embodiments of the battery cell may be a cylindrical battery cell, which is substantially cylindrical in shape, with a diameter of approximately 48 mm, a height of approximately 75 mm, and a form factor ratio of 0.640.

[0212] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell having a substantially cylindrical shape, with a diameter of substantially 48 mm, a height of substantially 110 mm, and a form factor ratio of 0.418.

[0213] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell having a diameter of approximately 48 mm, a height of approximately 80 mm, and a form factor ratio of 0.600.

[0214] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell having a substantially cylindrical shape, with a diameter of substantially 46 mm, a height of substantially 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. In the case of an 18650 cell, its diameter is approximately 18 mm, its height is approximately 65 mm, and its form factor ratio is 0.277. In the case of a 21700 cell, its diameter is approximately 21 mm, its height is approximately 70 mm, and its form factor ratio is 0.300.

[0216] The battery can 10 includes a cylindrical side wall portion 11 and a bottom portion 12 connected to one axial end of the side wall portion 11. Here, the term “bottom” is used when the bottom portion 12 is placed on the floor during the assembly process of the battery cell, as shown in Figures 26 to 30, in which the open end of the battery can 10 faces upward. It should be understood that the bottom portion 12 may actually be located at the top together with the first electrode terminal 13 during the actual use of the battery cell, as shown in Figure 18.

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

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

[0219] However, the method of connecting the first electrode terminal 13 and the bottom 12 is not limited to this. For example, any other fixing method that can seal the space between the first electrode terminal 13 and the bottom 12 and electrically insulate the first electrode terminal 13 and the bottom 12 is also applicable, such as a bolt-nut connection method, a glass seal method, or a thermal bonding method of a PP-MAH insulating gasket using an insulating film such as PP (polypropylene) as the substrate.

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

[0221] In this case, the battery can 10 may have both the first electrode terminal 13 and the second electrode terminal 15 located at one axial end. As a result, the busbar connected to the first electrode terminal 13 and the busbar connected to the second electrode terminal 15 may both be located at one axial end, i.e., the upper part, of the battery can 10.

[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. Of course, the reverse may also be true.

[0223] An electrode assembly 20 is housed inside the battery can 10. As shown in Figure 19, the electrode assembly 20 is prepared by preparing a first electrode 21, a second electrode 22, and a separation membrane 28 having a predetermined width and extending in the longitudinal direction. As shown in Figures 20 and 21, a laminate is formed by stacking the first electrode 21, separation membrane 28, second electrode 22, and separation membrane 28 in that order, and then this is wound around a core shaft to produce a jelly roll.

[0224] The first electrode 21 may be a positive electrode, and the second electrode 22 may be a negative electrode. Of course, the reverse may also be true.

[0225] The first electrode 21 and the second electrode 22 are manufactured in sheet form. The electrode sheet is manufactured in a form in which an active material layer 24 is coated on the surface of a metal foil 23. The electrode sheet comprises a textured area 25 on which the active material layer 24 is coated and a plain area 26 on which the active material layer 24 is not coated. The positive electrode sheet has a plain area 26 on one side in the width direction, and the negative electrode sheet has a plain area 26 on the other side in the width direction.

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

[0227] The plain portion 26 can be modified by forming notches at predetermined intervals to create flag-shaped notched tabs 27.

[0228] In this embodiment, the notched tab 27 is shown to be an isosceles trapezoid. However, these shapes may vary, including semicircular, semi-elliptical, triangular, rectangular, and parallelogram shapes.

[0229] Furthermore, the embodiment illustrates a configuration in which the notched tabs 27 arranged along the length have the same width. However, the width of the notched tabs may be progressively or stepwise wider from the core side to the outer circumference side.

[0230] Furthermore, in the embodiment, a configuration is shown in which the height of the notched tab 27 gradually increases from the core side to the outer circumference side. However, the height of these notched tabs can also be constant or gradually decrease.

[0231] Furthermore, the embodiment illustrates a structure in which the notched tabs 27 are removed from predetermined sections of the center-facing end and the centrifugal end of the plain portion 26. However, it goes without saying that the notched tabs at the center-facing end of the plain portion do not have to be removed, nor do the notched tabs at the centrifugal end of the plain portion.

[0232] In the jelly roll-type electrode assembly 20, the notched tab 27 can be bent radially to flatten it. The notched tab 27 may be bent radially inward or outward. In the embodiment, a structure in which the notched tab 27 is bent radially inward is illustrated, as shown in Figures 22 and 23.

[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 the laminate has been wound 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 overlapping, can provide planes substantially perpendicular to the axial direction at both axial ends of the electrode assembly 20, as shown in Figure 23.

[0235] A current collector plate 31 may be bonded to a substantially flat surface, as shown in Figure 24, which is provided by bending notched tabs 27 exposed at both axial ends of the electrode assembly 20.

[0236] The current collector plate 31 can be manufactured by punching, trimming, piercing, and bending a metal sheet.

[0237] Referring to Figure 24, the current collector plate 31 comprises terminal connecting portions 32 extending radially from the center, a ring portion 33 connecting the centrifugal edges of the terminal connecting portions 32 in the circumferential direction, and an electrode connecting portion 34 extending centripetally from the ring portion 33 but not connected to the terminal connecting portions 32. The central part of the terminal connecting portions 32 covers at least a portion of the hollow core of the electrode assembly 20.

[0238] The electrode connecting portion 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 before the electrode assembly 20 is placed in the battery can 10.

[0239] Unlike the embodiment, in battery cells of other structures, for example, the notched tab 27 of the first electrode 21 and the current collector plate 31 can be joined to the bottom 12 of the battery can 10 by welding or other means, and can be electrically connected. In other words, it must be understood that the fifth embodiment is an example of a battery cell to which the aforementioned sealing structure for the liquid injection port can be applied. That is, it is clear that the sealing structure for the liquid injection port disclosed above is not a technology that can be applied only to the battery cell structure disclosed in the fifth embodiment.

[0240] Referring to Figure 25, the notched tab 27 of the second electrode 22 of the electrode assembly 20 does not necessarily have a current collector plate connected to it. This can be electrically connected by directly welding or other methods to the cap 40, which will be described later.

[0241] As shown in Figures 26 and 27, the electrode assembly 20 is housed in the battery can 10 with the current collector plate 31 aligned so that it faces the bottom 12 of the battery can 10. At this time, an insulator 19 is interposed between the current collector plate 31 and the bottom 12 of the battery can 10 to electrically insulate the current collector plate 31 from the bottom 12.

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

[0243] Referring to Figures 28 and 29, the notched tab 27 of the second electrode 22 can directly contact the cap 40 that covers 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 in close contact with the notched tab 27, as shown in Figure 29, a laser can be irradiated onto the surface of the cap 40 in a scanning manner along the radial direction to form a radially extending weld (W). Of course, the laser is not irradiated in sections of the scanning path where a liquid injection port is provided.

[0245] As a result, the second electrode 22 is electrically connected via 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 methods other than welding, such as brazing or soldering.

[0246] Unlike the embodiment, the tab of the second electrode 22 can also be electrically connected by joining it to the inner circumferential surface of the side wall portion 11 of the battery can 10.

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

[0248] Furthermore, 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] Furthermore, the cap 40 is provided with a second electrode terminal, and the tabs and current collector plates 31 of the second electrode 22 can be connected to these second electrode terminals.

[0250] Referring further to Figure 29, the edge of the cap 40 is joined to the open end of the side wall portion 11 of the battery can 10, thereby electrically connecting and sealing it. This allows the second electrode 22 to be electrically connected to the cap 40 and the battery can 10. Various methods such as welding, brazing, and soldering can be applied to join the cap 40 and the battery can 10, as they allow for electrically connected and sealed joints.

[0251] Unlike the embodiment, the cap 40 may be fixed to the open end of the side wall portion 11 of the battery can 10 by a crimping or other pressure sealing method. It must be understood that the above-described liquid inlet sealing structure can be applied even with such a structure.

[0252] High heat may be generated during the welding process between the cap 40 and the side wall portion 11. If electrolyte has been injected into the battery can 10 before these welding operations, 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 part (W) and the joint part (M), which generate high heat, is completed, the electrolyte can be injected through the injection port 42.

[0254] The injection port 42 may be positioned in alignment with the hollow core of the electrode assembly 20. In this case, the injected electrolyte penetrates deeply through the hollow core of the electrode assembly 20, thereby enabling smooth impregnation.

[0255] After the liquid injection is complete, as shown in Figure 30, the injection port 42 is covered with a stopper 50, and the stopper 50 is pressurized and heated using the heat welding machine 60 described above to heat the heat welding layer and form a heat-welded 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 Figures 31 to 35.

[0257] The cap 40 may be made from a circular metal sheet. The cap 40 has an electrode connecting portion 41 recessed in a direction corresponding to the axial direction of the battery cell 72. The electrode connecting portion 41 can be formed by pressing the metal sheet.

[0258] The bottom surface of the electrode connecting portion 41 is the part that is in close contact with and joined to the notched tab 27 of the second electrode 22 of the electrode assembly 20. The electrode connecting portion 41, which is manufactured by press-forming a metal sheet, is slightly thinner than the thickness of the metal sheet. As a result, when a laser is irradiated onto the surface of the electrode connecting portion 41, the localized heat generated by the laser can melt and join the surfaces of the electrode connecting portion 41 and the notched tab 27 that is in contact with its bottom surface.

[0259] The electrode connecting portion 41 comprises a plurality of portions. In the fifth embodiment, a structure is illustrated in which four electrode connecting portions 41 are arranged at equal intervals of approximately 90 degrees in the circumferential direction to form a radial structure. The electrode connecting portion 41 extends in the radial direction, and the weld portion (W) for joining the electrode connecting portion 41 to the notched tab 27 of the second electrode 22 of the electrode assembly 20 may have a weld line shape formed in the radial direction corresponding to the extending direction of the electrode connecting portion 41, as shown in Figure 29.

[0260] According to the embodiment, a radially extending line-shaped weld (W) is formed for each of the multiple electrode connecting portions 41.

[0261] The cap 40 provides a receiving surface 44 that contacts the ground when the battery can 10 is placed upright with the cap 40 facing the floor. The receiving surface 44 is positioned higher than the electrode connecting portion 41 and is located between two adjacent electrode connecting portions 41 in the circumferential direction.

[0262] This allows the receiving surfaces 44 on both sides of the circumferential direction of the electrode connection portion 41 to be pressed with a jig, bringing the electrode connection portion 41 and the notched tab 27 into close contact. Then, as shown in Figure 29, a laser is irradiated onto the surface of the electrode connection portion 41 to weld the electrode connection portion 41 and the notched tab 27. As a result, the pressure from the jig along the length of the welding line on both sides of the welding line presses the electrode connection portion 41 tightly against the notched tab 27, ensuring reliable welding.

[0263] The pair of electrode connecting portions 41, which face 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 welding line, the welding line of the two electrode connecting portions 41, which are aligned in a line with each other, is formed with just one movement of the laser welding machine. For example, if the first electrode connecting portion, second electrode connecting portion, third electrode connecting portion, and fourth electrode connecting portion are arranged sequentially along the circumferential direction in the cap 40 of the fifth embodiment, the first electrode connecting portion and the third electrode connecting portion can be welded at once, and the second electrode connecting portion and the fourth electrode connecting portion can be welded at once.

[0264] Furthermore, according to the embodiment, for example, when the receiving surfaces 44 provided on both sides of the first electrode connecting portion and the third electrode connecting portion, which are arranged in a line with respect to the center of the cap 40, are pressed with a jig, the second moment of inertia formed by the recessed shape of the second electrode connecting portion and the fourth electrode connecting portion is large, so that the cap 40 can operate as a rigid body without deforming or bending despite the pressure of the jig.

[0265] In the embodiment, as described above, by forming the four electrode connection parts 41, all of the four electrode connection parts 41 can be welded with two laser scan trajectories.

[0266] If the number of the electrode connection parts 41 is processed excessively, the strength of the cap 40 formed on the metal sheet may become weak. Also, if only two or three electrode connection parts 41 are formed, it is difficult to form a cross-section for sufficiently ensuring the secondary moment of inertia along the circumferential direction.

[0267] As in the embodiment, when the four electrode connection parts 41 are configured in a “+” shape on the cap 40, the welding process can be performed accurately and simply, the distortion resistance and bending resistance of the cap 40 can be ensured, and it is also possible to prevent the strength of the cap 40 from becoming weak due to the forming process. That is, although the cap 40 also functions as a current collector plate, it is preferable to maintain the strength for its original function of 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 axially other 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 and inner surface.

[0269] The cap 40 of the fifth embodiment has an inner surface with a circular edge, and the electrode connection part 41 is formed to sink axially inward from radially inside thereof. As shown in FIG. 29, the circular inner surface of the cap 40 contacts the axially end surface of the side wall portion 11 of the battery can 10 and can be welded by a laser irradiated radially inward from the outer peripheral side of the battery can 10 to form a joint portion (M).

[0270] At this time, the radially outer edge of the recessed and molded portion that constitutes the electrode connecting portion 41 constitutes the outer wall. The outer wall can constitute a recessed outer wall 45 with 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 Figure 29, the recessed outer walls 45 of the plurality of electrode connecting portions 41 each come into contact with and press against the inner circumferential surface of the battery can 10, guiding the center alignment of the cap 40 relative to the battery can 10.

[0271] According to the fifth embodiment, the four press-fitting outer walls 45 are evenly arranged along the circumferential direction and come into contact with the battery can 10 in a portion of the area around the entire inner surface, so the cap 40 can be easily pressed into the battery can 10 without requiring a high pressing force for the cap 40.

[0272] Thus, the cap 40 of this embodiment has the advantage of being easy to manufacture because the indented outer wall 45 is formed together with the electrode connecting portion 41 when the cap 40 is formed.

[0273] Furthermore, with the structure of the cap 40, since the laser is irradiated radially to weld the cap 40 and the battery can 10, even if the inner edge of the cap 40 and a portion of the end of the side wall portion 11 of the battery can 10 do not come into close contact due to unforeseen errors, the laser will not be directly irradiated into the inside of the battery can 10 and there is no risk of 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 Figure 30 is turned upside down and stood upright, the joint (M) does not come into direct contact with the ground, making it easier to protect the joint (M).

[0275] By applying the cap 40 described above, there is no need to use a current collector plate when electrically connecting the tab of the second electrode 22 to the battery can 10, reducing the number of parts and assembly steps, further securing internal volume, and increasing energy density. The cap 40, which is 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 because it is connected via a radially extending welded section (W), the current path is uniformly distributed and internal resistance can be greatly reduced.

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

[0277] Since the protrusion 43 protrudes higher than the bottom, when the stopper 50 is covered and heat-sealed after the electrolyte is injected through the injection port 42, the heat welding machine 60 can easily approach the stopper. In addition, although the temperature is low, the phenomenon of heat from the heat welding machine 60 being transferred to the inside of the battery can 10 can be minimized.

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

[0279] On the other hand, the liquid injection port 42 formed in the center of the cap 40 can serve as a passage through which the equipment components can enter and exit for welding the first electrode terminal 13 and the current collector plate 31 of the first electrode 21. Thus, unlike the assembly procedure shown in Figures 26 to 29, the cap 40 can first be joined to the tab of the second electrode 22 of the electrode assembly 20, as shown in Figure 36, and then fitted together with the battery can 10 when the electrode assembly 20 is housed in the battery can.

[0280] In other words, as shown in Figure 36, the electrode assembly 20 can be housed in the battery can 10 with the current collector plate 31 attached to the tab of the first electrode 21 and the cap 40 attached to the tab of the second electrode 22. The welding of the current collector plate 31 and the first electrode terminal 13 can be performed through the liquid injection port 42 of the cap 40 and the hollow core portion of the electrode assembly 20.

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

[0282] Furthermore, since the cap 40 is equipped with an injection port 42, and these injection ports 42 can be used as passages for the joining process between the current collector plate 31 and the first electrode terminal 13, the manufacturing method of the battery cell can be configured in a variety of ways.

[0283] First, an example of a battery cell manufacturing method will be described with reference to Figure 37. This corresponds to the battery cell manufacturing method shown in Figures 26 to 30.

[0284] This includes the steps of preparing a battery can 10 with the first electrode terminal 13 fixed to it, and preparing an electrode assembly 20 equipped with a first electrode 21 and a second electrode 22. At this time, the first electrode 21 and the current collector plate 31 can 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 so that the current collector plate faces 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 welding or other means.

[0286] Next, cover the open end of the battery can 10 with the cap 40. At this time, preferably, the electrode connection portion 41 of the cap 40 is joined in a state of being in close contact with the tab of the second electrode 22 of the electrode assembly 20, and then, the periphery of the open end of the battery can 10 and the edge of the cap 40 are joined.

[0287] Next, inject an electrolytic solution into the battery can 10 through the liquid injection port 42 of the cap 40.

[0288] And finally, apply the above-described seal structure of the liquid injection port, and seal and tighten the liquid injection port 42 of the battery can 10 with the plug 50.

[0289] According to these manufacturing methods, not only is the joining operation of a separate current collector plate unnecessary for the second electrode 22, but also, before filling the inside of the battery can 10 with the electrolytic solution, the joining of the cap 40 and the second electrode 22 and the joining of the cap 40 and the battery can 10 can be performed, and it is possible to prevent the joining heat from affecting the electrolytic solution.

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

[0291] This includes a step of preparing a battery can 10 with the first electrode terminal 13 fixed, and a step of preparing an electrode assembly 20 including a first electrode and a second electrode. At this time, at one axial end of the electrode assembly, the first electrode 21 and the current collector plate 31 can be joined and connected. Also, at the other axial end of the electrode assembly, the electrode connection portion 41 of the cap 40 and the tab of the second electrode 22 can be joined and connected.

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

[0293] Next, insert the electrode assembly 20 into the battery can 10 such that the current collector plate faces the bottom 12 of the battery can 10. In this process, the cap 40 comes to cover the open end of the battery can 10.

[0294] Next, 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 welding or other means, and the area around the open end of the battery can 10 and the edge of the cap 40 are joined.

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

[0296] Finally, the sealing structure for the liquid injection port described above is applied to seal and close the liquid injection port 42 of the battery can 10 with the stopper 50.

[0297] According to these manufacturing methods, there is no need for a separate current collector plate joining process for the second electrode 22. The cap 40 and the second electrode 22 can be joined, and the cap 40 and the battery can 10 can be joined, before the electrolyte is filled inside the battery can 10. This prevents the joining heat from affecting the electrolyte. The cap 40 can be integrated into the electrode assembly 20 beforehand without separate management, further simplifying the assembly equipment.

[0298] Thus, when manufacturing battery cells using a cap 40 equipped with a liquid injection port 42, the manufacturing method can be configured in various ways.

[0299] Furthermore, when sealing the liquid injection port 42, strong pressure is not applied to the cap 40, nor is the cap 40 heated to a high temperature, so there is no risk of damage to the internal structure of the battery can 10, or of it deforming or igniting due to heat.

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

[0301] Because the aforementioned battery cell 72 has a large volume, there is no difficulty in realizing the battery pack 70 without using an intermediate structure such as a battery module. Furthermore, since the second electrode of the battery cell 72 is connected via a cap, the internal resistance is low and the energy density is even higher. Therefore, the energy density of the battery pack 70 can be realized to be even higher.

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

[0303] The embodiments described above should be understood to be illustrative and not limiting in all respects, and the scope of the present invention is indicated more by the claims described below than by the detailed description above. The meaning and scope of the claims described below, as well as any modifications and deformable forms conceived from their equivalent concepts, should be interpreted as being included within the scope of the present invention.

[0304] As described above, the present invention has been explained with reference to the illustrative drawings. However, the present invention is not limited by the embodiments and drawings disclosed herein, and it is obvious to an ordinary person skilled in the art that various modifications can be made 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 embodiments of the present invention are described above, it is natural to acknowledge that predictable effects can be obtained from such configurations. [Explanation of symbols]

[0305] 10 Battery cans 11 Side wall section 12 Bottom 13. Positive terminal (first electrode terminal) 14 Terminal gasket 15 Negative terminal (second electrode terminal) 19 Insulator 20 Electrode assembly 21 First electrode 22 Second electrode 23 Metal foil 24 Active material layer 25 Ground portion 26 Non-ground portion 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 [[ID=4]]43 Protrusion 44 Receiving surface 45 Pushing outer wall M Joint part 46 First chromium coating layer 47 Depression<001049>50 Plug 51 Central protrusion 53 Second chromium coating layer 55 PP-MAH (heat-sealing layer) 58 Rivet [[ID=6]]59 Ball 60 Heat-sealing machine 70 Battery pack 71 Housing 72 Battery cell 80 Vehicle

Claims

1. Metal battery case 10; A metal cap 40 covering the open end of the battery can 10; A liquid filling port 42 provided on the battery can 10 or cap 40; A metal stopper 50 covering the liquid injection port 42; and A heat-welded portion interposed between the first surface of the battery can 10 or cap 40 surrounding the liquid injection port 42 and the second surface of the stopper 50 in contact with the first surface, which fuses to at least a portion of the first and second surfaces in a closed loop shape surrounding the liquid injection port 42; The heat-welded portion is The first chromium coating layer 46 formed on the first surface; The second chromium coating layer 53 formed on the second surface; and A heat-welded layer 55 is provided, which contains PP-MAH (maleic anhydride modified polypropylene) on both sides, respectively, in contact with the first chromium coating layer 46 and the second chromium coating layer 53, and which is bonded to the first chromium coating layer 46 and the second chromium coating layer 53 by heat; The plug 50 and the battery can 10 or cap 40 to which the plug 50 is joined by the heat-welded portion are electrically connected. 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 according to claim 1.

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

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

5. The stopper 50 is equipped with a central projection 51 that is inserted into the liquid injection port 42, The central projection 51 is in contact with the inner circumferential surface of the battery can 10 or cap 40 that defines the liquid filling port 42, so that the centers of the stopper 50 and the liquid filling port 42 are aligned. The battery cell according to claim 1 or 2.

6. The central projection 51 penetrates the liquid injection port 42 in the depth direction. The battery cell according to claim 5.

7. The central projection 51 is inserted only to a portion of the depth of the liquid injection port 42. The battery cell according to claim 5.

8. The stopper 50 is positioned opposite the liquid injection port 42 and has a central projection 51 that protrudes toward the liquid injection port 42. The central projection 51 is not inserted into the liquid injection port 42. The battery cell according to claim 1 or 2.

9. A recessed portion 47 for housing the stopper 50 is provided around the liquid injection port 42. The outer circumferential surface of the stopper 50 is in contact with the inner circumferential surface of the recessed portion 47, and the centers of the stopper 50 and the liquid injection port 42 are aligned. The battery cell according to claim 1 or 2.

10. A recessed portion 47 for housing the stopper 50 is provided around the liquid injection port 42. A protruding portion 43 is provided around the recessed portion 47, which defines the recessed portion 47. The axial outer surface of the plug 50 housed in the recessed portion 47 corresponds axially to the surface of the protruding portion 43, or is positioned further inward in the axial direction. The battery cell according to claim 1 or 2.

11. The first surface includes a first-first surface facing outward in the axial direction of the battery cell, The second surface includes a second-first surface facing the first-first surface and facing axially inward, The heat-welded portion is provided between the first-first surface and the second-first surface, The battery cell according to claim 1 or 2.

12. The first surface includes the first-second surface facing radially inward of the battery cell, The second surface includes a second-second surface that faces radially outward and is opposite to the first-second surface. The heat-welded portion is provided between the first-second surface and the second-second surface, The battery cell according to claim 11.

13. The first surface includes the first-second surface facing radially inward of the battery cell, The second surface includes a second-second surface that faces radially outward and is opposite to the first-second surface. The heat-welded portion is not provided between the first-second surface and the second-second surface. The battery cell according to claim 11.

14. The liquid injection port 42 is provided on the cap 40. The open end edge of the battery can 10 and the edge of the cap 40 are heat-bonded. The battery cell according to claim 1 or 2.

15. The thermal bonding of the battery can 10 and the cap 40 is performed by one of the following processes selected from welding, brazing, or soldering. The battery cell according to claim 14.

16. The battery can 10 is housed inside and comprises an electrode assembly 20 having 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 arranged on both sides in the axial direction; In the axial direction, a first electrode terminal 13 is installed on the bottom 12 of the battery can 10, which is located on the opposite side of the open end, and is electrically insulated and fixed to the bottom 12. The first electrode 21 of the electrode assembly 20 is connected to the first electrode terminal 13 via a current collector plate 31 joined to the tab of the first electrode 21. The battery cell according to claim 14.

17. The battery can 10 is housed inside and comprises an electrode assembly 20 having 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 arranged on both sides in the axial direction; The cap 40 includes an electrode connecting portion 41 that is thermally bonded to the tab of the second electrode 22 of the electrode assembly 20. The battery cell according to claim 14.

18. The thermal bonding of the cap 40 and the tab of the second electrode 22 is performed by one of the following processes selected from welding, brazing, or soldering. The battery cell according to claim 17.

19. The liquid injection port 42 is provided in the center of the cap 40. The electrode connecting portion 41 extends radially around the liquid injection port 42, The battery cell according to claim 17.

20. The cap 40 is provided with a receiving surface 44 that extends axially outward from the electrode connecting portion 41. The axial outer surface of the plug 50 is positioned further inward in the axial direction than the receiving surface 44. The battery cell according to claim 17.

21. The liquid injection port 42 is provided on a protruding portion 43 that protrudes axially from the electrode connecting portion 41. The battery cell according to claim 17.

22. Preparation of a battery can 10 comprising a side wall portion 11, a bottom portion 12 connected to one axial end of the side wall portion 11, and an open end provided at the other axial end of the side wall portion 11, and a first electrode terminal 13 sealed and insulated and fixed in the center of the bottom portion 12; Preparing an electrode assembly 20 comprising a first electrode 21 and a second electrode 22, wherein the tabs of the first electrode 21 and the tabs of the second electrode 22 are arranged on both sides in the axial direction; Cap preparation step: Prepare a cap 40 having a liquid injection port 42 and a first chromium coating layer 46 provided around the liquid injection port 42; A stopper preparation step in which a stopper 50 provided with a second chromium coating layer 53 is prepared; After the preparation steps for the battery can and the electrode assembly, 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 the first electrode terminal is connected in a step that connects the tab of the first electrode 21 to the first electrode terminal 13; After the preparation steps for the electrode assembly and the cap, the second electrode connection step involves connecting the cap 40 to the tab of the second electrode 22; After the connection step of the first electrode terminal, the cap fixing step is to fix the cap 40 to the battery can 10; After the steps of connecting the first electrode terminal, connecting the second electrode, and fixing the cap, an electrolyte solution is poured into the battery can 10; and The following steps are taken after the liquid injection step and the stopper preparation step: a liquid injection port closing step is taken, in which a heat-welding layer containing PP-MAH, interposed between the first chromium coating layer 46 and the second chromium coating layer 53, is heated to form a heat-welded portion, thereby closing the liquid injection port 42 with the stopper 50; The plug 50 and the battery can 10 or cap 40 to which the plug 50 is joined by the heat-welded portion are electrically connected. A method for manufacturing battery cells.

23. The heat-sealable layer is provided by insert injection onto the second chromium coating layer 53 during the preparation stage of the plug. A method for manufacturing a battery cell according to claim 22.

24. A battery pack comprising the battery cell described in claim 1 or 2.

25. An automobile comprising the battery pack described in claim 24.

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