A welded structure between a battery can, a current collector plate, and a cap, and a battery cell to which the welded structure is applied.

Abstract

A battery cell according to an embodiment of the present invention includes a current collector plate having a can connecting portion that extends axially so as to be pressed into a side wall member having multiple inner circumferential surfaces having different inner diameters. The battery cell according to an embodiment of the present invention is manufactured by inserting a cap into the open end of a can such that the axial inner surface of the periphery of the cap contacts the axial outer end surface of the can connecting portion, and the outer circumferential surface of the periphery of the cap contacts the inner circumferential surface of the side wall member. Then, a triple weld is formed by irradiating the contact area between the inner circumferential surface of the side wall member and the outer circumferential surface of the cap in an axial direction.

Description

Technical Field

[0001] This application claims priority based on Korean Patent Application No. 10-2023-0073032 filed on June 7, 2023, Korean Patent Application No. 10-2023-0135318 filed on October 11, 2023, and Korean Patent Application No. 10-2024-0069605 filed on May 28, 2024, and all the content disclosed in the specifications and drawings of those applications is incorporated into this application.

[0002] The present invention relates to a welding structure of a battery can, a current collector plate, and a cap, and a battery cell to which the welding structure is applied.

Background Art

[0003] In the process of manufacturing a battery cell using a cylindrical can, a metal sheet is deep-drawn to form a circular bottom member and a circular tubular side wall member connected to the bottom member. After accommodating an electrode assembly therein, the open end of the side wall member is covered with a cap and sealed.

[0004] On the other hand, a current collector plate that is in contact with and electrically connected to the electrode tab of the electrode assembly is provided at an end of the electrode assembly in the axial direction that faces the open end. The current collector plate is connected to the cap or the side wall member by a method such as welding so as to be in contact with and electrically connected to the cap or the side wall member.

[0005] When sealing the open end of the cylindrical can, the process of connecting the current collector plate to the cap or the side wall member and the process of connecting the cap to the side wall member are performed separately. Such an increase in the number of processes is a factor that reduces the production efficiency of the cylindrical battery cell and increases the production cost.

[0006] In order to reduce such individual welding processes, a scheme of welding the side wall member, the cap, and current collector plate at once is conceivable. And such welding can be performed by a laser.

[0007] However, it is not easy to assemble three parts (side wall members, caps, and current collector plates) that are not fixed to each other in a way that makes them strong enough to be welded together.

[0008] Furthermore, when a laser is shone on the sidewall members, caps, and current collector plates in a simply assembled state, gaps may occur due to the tolerances of each component (sidewall members, caps, and current collector plates) and assembly errors between them. If a laser is shone on the sidewall members, caps, and current collector plates in this state, the laser may penetrate directly into the inside of the can, potentially damaging the electrode assembly housed inside. Therefore, improvements to the assembly of cylindrical battery cells are needed. [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention was devised to solve the above-mentioned problems, and aims to provide a welding structure for a battery can, a current collector plate, and a cap, and a battery cell to which this welding structure is applied, which can increase the production efficiency and reduce the production cost of a cylindrical battery cell by integrating the process of welding the current collector plate to the can and the process of welding the cap to the side wall member into a single welding process.

[0010] Furthermore, the present invention aims to provide a welding structure for a battery can, a current collector plate, and a cap that can prevent the laser from directly penetrating the inside of the can during the laser welding process, even if component tolerances and assembly errors occur between the side wall member, the cap, and the current collector plate, and to provide a battery cell to which this welding structure is applied.

[0011] Furthermore, the present invention aims to provide a welding structure for a battery can, a current collector plate, and a cap, and a battery cell to which this welding structure is applied, which facilitates the assembly of the can, the current collector plate, and the cap, and enables correct alignment and close contact through the contact structure between them during the assembly process, thereby facilitating triple welding.

[0012] Furthermore, the present invention aims to provide a battery can, current collector plate, and cap with shapes that ensure weldability, enhance process stability, and guarantee welding durability, as well as a welding structure between the battery can, current collector plate, and cap having an engaging relationship, and a battery cell to which this welding structure is applied.

[0013] The technical problems of the present invention are not limited to those described above, and other problems and advantages can be understood from the following description and more clearly from embodiments of the present invention. Furthermore, the problems and advantages of the present invention can be realized by the means and combinations thereof shown in the claims. Although this specification describes cylindrical battery cells, the present invention is applicable not only to other similar battery forms that are not cylindrical (e.g., frustoconical or elliptical), but also to other battery form factors such as pouch cell batteries or prismatic cell batteries. [Means for solving the problem]

[0014] One aspect of the present invention for solving the above-mentioned problems is applied to a battery cell comprising an electrode assembly, a current collector plate electrically connected to the electrode assembly, and a can housing the electrode assembly and the current collector plate.

[0015] The can includes a side wall member extending in the axial direction and an open end provided at one axial end (first end) of the side wall member.

[0016] The battery cell includes a cap that covers the open end.

[0017] A bottom member is connected to the other axial end of the side wall member (the second end opposite the first end), thereby allowing the other axial end of the side wall member to form a closed end.

[0018] The electrode assembly may be in the form of a jelly roll wound around a predetermined axis.

[0019] Electrode tabs are provided at the ends of both axial ends of the electrode assembly corresponding to the open end, and the current collector plate can be electrically connected to the electrode tabs.

[0020] The current collector plate may include an electrode tab connecting portion that contacts the electrode tab and is electrically connected thereto.

[0021] The electrode tab connecting portion can be joined to the electrode tab. The joining can be performed by welding, brazing, or soldering.

[0022] The current collector plate includes a can connecting portion that contacts the can and is electrically connected thereto.

[0023] The can connecting portion and the electrode tab connecting portion can be electrically connected.

[0024] The can connecting portion can be arranged radially outside the electrode tab connecting portion.

[0025] The can connecting portion can extend in the axial direction.

[0026] The can connecting portion can be connected to the electrode tab connecting portion through a bent portion.

[0027] The bent portion can bend the current collector plate extending radially outward axially outward.

[0028] The can connecting portion can extend axially outward from the bent portion.

[0029] The can connecting portion has a contact outer peripheral surface defined by the outer periphery of the can connecting portion.

[0030] The contact outer peripheral surface faces the inner peripheral surface of the side wall member in the radial direction.

[0031] In the axial direction, at least a partial section of the contact outer peripheral surface defines a first section that contacts the inner peripheral surface of the side wall member in the radial direction.

[0032] The can connecting portion includes a cap contact surface defined by the axial outer end face.

[0033] The cap contact surface faces and contacts the inner surface of the cap in the axial direction.

[0034] The cap includes a joining outer surface that faces the inner circumferential surface of the side wall member in the radial direction.

[0035] The aforementioned joint outer circumferential surface may come into contact with the inner circumferential surface of the side wall member in the radial direction.

[0036] The cap has a current collector contact surface defined by its axial inner surface.

[0037] The current collector plate contact surface faces and contacts the cap contact surface of the can connecting portion of the current collector plate in the axial direction.

[0038] The outer circumferential surface of the cap may be positioned axially outward from the contact surface of the current collector plate.

[0039] The outer circumferential surface of the cap may be positioned radially outward from the contact surface of the current collector plate.

[0040] At least a portion of the inner circumferential surface of the side wall member and at least a portion of the contacting outer circumferential surface of the current collector plate can be joined together.

[0041] At least a portion of the inner circumferential surface of the side wall member and at least a portion of the joining outer circumferential surface of the cap can be joined together.

[0042] At least a portion of the cap contact surface of the current collector plate and at least a portion of the current collector plate contact surface of the cap can be joined together.

[0043] The aforementioned joining may be performed by welding.

[0044] The side wall member, the cap, and the current collector plate can be triple-welded together.

[0045] The welding can be performed by irradiating the contact area between the inner circumferential surface of the side wall member and the joining outer circumferential surface of the cap in the axial direction with a laser.

[0046] At least a portion of the inner circumferential surface of the side wall member, at least a portion of the joining outer circumferential surface of the cap, and at least a portion of the can-connecting portion of the current collector plate can be welded together to join them.

[0047] In the axial direction, the outer diameter of at least a portion of the contact outer circumferential surface may be larger than the inner diameter of the inner circumferential surface of the side wall member facing the portion in the radial direction.

[0048] The outer diameter of the first section of the contact outer surface may be larger than the inner diameter of the inner surface of the side wall member facing it in the radial direction. This allows the first section of the contact outer surface of the current collector plate to be forcibly pressed against the side wall member when the current collector plate is inserted into the can.

[0049] The battery cell may include a welded portion formed by welding together the inner circumferential surface of the side wall member, the joining outer circumferential surface of the cap, and the can-connecting portion of the current collector plate.

[0050] The joining outer circumferential surface of the cap and the contacting outer circumferential surface of the can connecting portion can each face the inner circumferential surface of the side wall member in the radial direction.

[0051] The joining outer circumferential surface of the cap and the contacting outer circumferential surface of the can connecting portion can each contact the inner circumferential surface of the side wall member in the radial direction.

[0052] The axial ends of the joint outer circumferential surfaces of the caps and the inner circumferential surfaces of the side wall members, which face each other or are in contact in the radial direction, may be exposed to the outside in the axial direction.

[0053] The welded portion can be formed by a laser irradiated axially from the axial outer side of the battery cell toward the axial ends of the joining outer surface of the cap and the inner surface of the side wall member.

[0054] According to the present invention, since the first section of the contact outer surface of the current collector plate, which is positioned axially inward from the cap, is in contact with the inner surface of the side wall member, it is possible to prevent the laser from being directly irradiated into the internal space of the can.

[0055] The current collector plate may have a higher thermal conductivity than the side wall member. This allows welding heat to be quickly dispersed to the electrode assembly through the current collector plate, preventing the phenomenon in which welding heat is transmitted to the outer surface of the electrode assembly through the side wall member and damages the separation membrane provided on the outer surface of the electrode assembly.

[0056] An inner diameter expansion portion may be provided at one end of the side wall member in the axial direction.

[0057] The inner diameter of the first inner surface of the side wall member, which is provided axially inward from the inner diameter expansion portion, may be smaller than the inner diameter of the second inner surface of the side wall member, which is provided axially outward from the inner diameter expansion portion.

[0058] The inner diameter expansion portion may have a shape that expands the inner diameter of the side wall member as it extends outward in the axial direction.

[0059] The inner diameter expansion portion is provided on the inner surface of the side wall member and may include a sloping shape that extends radially outward as it moves outward in the axial direction.

[0060] The aforementioned inner diameter expansion portion can prevent laser light from penetrating into the gap between the side wall member and the cap or current collector plate.

[0061] In the axial direction, at least a portion of the first section of the contact outer circumferential surface may come into contact with the first inner circumferential surface.

[0062] In the axial direction, at least a portion of the first section of the contact outer peripheral surface may also contact the inner diameter expansion portion.

[0063] In the axial direction, at least a portion of the first section of the contact outer peripheral surface may also come into contact with the second outer peripheral surface.

[0064] The outer diameter of the first section of the contact outer surface may be larger than the inner diameter of the first inner surface.

[0065] The outer diameter of the contact outer surface of the can connecting portion of the current collector plate may be larger than the inner diameter of the first inner surface.

[0066] The material of the current collector plate may be softer than the material of the side wall member.

[0067] If the outer diameter of the contact outer surface is set to be slightly larger than the inner diameter of the first inner surface, the contact outer surface will be pressed against the first inner surface during the insertion of the current collector plate, and the contact outer surface and the first inner surface will be able to come into close contact in the radial direction.

[0068] As a result, when the current collector plate is inserted, the outer diameter of the first section of the contact outer surface that contacts the first inner circumferential surface can correspond to the inner diameter of the first inner circumferential surface.

[0069] The bent portion provides a curved surface axially inward from the cap connecting portion, where the outer diameter gradually decreases as it moves axially inward.

[0070] The minimum outer diameter of the curved surface may be smaller than the inner diameter of the first inner circumferential surface.

[0071] This allows for the forced pressing of the cap connecting portion against the first inner circumferential surface during the process of inserting the current collector plate.

[0072] The first inner surface of the side wall member, into which the first section of the contact outer surface is forcibly pressed, can be positioned closer to the bent portion in the axial direction than the second inner surface of the side wall member.

[0073] The joining outer circumferential surface of the cap may face the second inner circumferential surface in the radial direction.

[0074] The contact outer circumferential surface of the can connecting portion may face the second inner circumferential surface radially, further inward in the axial direction than the joining outer circumferential surface.

[0075] The joining outer surface of the cap and the contacting outer surface of the can connecting portion of the current collector plate can each contact the second inner surface.

[0076] The outer diameter of the contacting outer surface may correspond to or be smaller than the inner diameter of the second inner surface.

[0077] The aforementioned cap may comprise, in order from the radial center outward, a cap body, a thickness reduction portion, and a joint portion.

[0078] In other words, the thickness reduction portion may be provided on the radially outer side of the cap body, and the joint portion may be provided on the radially outer side of the thickness reduction portion.

[0079] The outer circumferential surface of the cap may be provided at the joint.

[0080] The first thickness may be the thickness of the joint measured in the axial direction.

[0081] The first thickness may be thinner than the second thickness of the cap body, which is measured in the axial direction.

[0082] This increases the second thickness of the cap body, which constitutes the overall shape of the cap, thereby minimizing deformation of the cap due to internal pressure in the can. At the same time, it reduces the axial dimension of the welding area to the side wall member, i.e., the joining outer surface, and by forming the weld over the entire axial length of the joining outer surface, both the strength of the cap itself and the bonding strength of the cap to the side wall member can be increased.

[0083] The thickness reduction portion may be provided on the axial inner surface of the cap.

[0084] By appropriately selecting the position where the thickness-reducing portion is provided, and ensuring that at least a part of the thickness-reducing portion contacts the current collector plate, the thickness-reducing portion of the cap will come into contact with the current collector plate during the cap insertion process, thereby aligning the center of the cap. In other words, the provision of the thickness-reducing portion of the cap effectively ensures alignment and center alignment of the cap when it is inserted into the can.

[0085] To enhance this alignment effect, the thickness reduction portion may include a sloping shape that extends outward in the axial direction as it moves outward in the radial direction.

[0086] The aforementioned thickness reduction portion and joint portion may be formed by forging.

[0087] By inserting the cap, the radial inner edge of the axial outer end of the cap connecting portion of the current collector plate can come into contact with the inclined surface of the thickness reduction portion.

[0088] As a result, the center of the cap and the center of the current collector plate can be aligned, and the axial outer end of the cap connecting portion of the current collector plate can be pressed radially outward, bringing it closer to or in close contact with the second inner circumferential surface of the side wall member.

[0089] Another aspect of the present invention provides a method for manufacturing the battery cell described above.

[0090] The battery cell includes a bottom member, a can including a side wall member connected to the bottom member and extending in the axial direction, and an open end provided at one axial end of the side wall member, a cap covering the open end, and an electrode assembly housed inside the can.

[0091] Such a method for manufacturing a battery cell includes a first step of joining a current collector plate to electrode tabs provided at the ends of the electrode assembly corresponding to the open end in the axial direction.

[0092] The manufacturing method includes a second step of inserting the current collector plate into the can and bringing a first section, which is at least a portion of the axial direction of the contact outer surface of the can connecting portion provided on the radial outer edge of the current collector plate, into contact with the inner surface of the side wall member.

[0093] In this case, the can-connecting portion of the current collector plate can be forcibly pushed into the first inner circumferential surface, which is positioned further inward in the axial direction than the inner diameter expansion portion of the side wall member, thereby increasing the adhesion force between the first inner circumferential surface and the joining outer circumferential surface of the current collector plate.

[0094] The manufacturing method includes a third step of covering the open end of the side wall member with a cap, while bringing the joining outer surface and the current collector contact surface provided on the periphery of the cap into contact with the inner surface of the side wall member and the cap contact surface of the current collector, respectively.

[0095] At this time, the inclined thickness reduction portion provided on the axial inner surface of the cap is brought into contact with the current collector plate to align the center of the cap, or the axial outer end of the cap contact surface of the current collector plate is pressed radially outward to bring it closer to or in close contact with the second inner circumferential surface of the side wall member.

[0096] The manufacturing method may include a fourth step of irradiating a laser from the outside in the axial direction onto the contact area between the inner circumferential surface of the side wall member and the joining outer circumferential surface of the cap, thereby welding the inner circumferential surface of the side wall member, the joining outer circumferential surface of the cap, and the can-connecting portion of the current collector plate together.

[0097] A battery cell according to another aspect of the present invention may include a can, a cap, an electrode assembly, and a current collector plate. The can may include an axially extending sidewall member and an open end provided at a first axial end of the sidewall member. The first axial end of the sidewall member may include a radially tapered first portion. The cap may cover the open end of the can. The electrode assembly may be located inside the can. The current collector plate may electrically connect the electrode assembly and the can. The radially outer portion of the current collector plate may include a first surface which is an outer contact surface defined by the outer circumference of the radially outer portion, the outer contact surface facing the inner surface of the sidewall member. The radially outer portion of the current collector plate may further include a second surface defined by an axially outward end of the radially outer portion of the current collector plate, the second surface facing and in contact with an axially inward surface of the cap. The cap may include an outer first cap surface facing the inner surface of the sidewall member. The cap may further include a second cap surface that faces inward in the axial direction, where the second cap surface is in contact with the second surface of the radially outer portion of the current collector plate.

[0098] Furthermore, in the above-described embodiment of the present invention, the first cap surface may be positioned radially and axially outward of the second cap surface. At least a portion of the inner surface of the sidewall member and at least a portion of the outer contact surface of the current collector plate may be joined by welding. At least a portion of the inner surface of the sidewall member and at least a portion of the first cap surface may be joined by welding. At least a portion of the second surface of the radially outer portion of the current collector plate and at least a portion of the second cap surface may be joined by welding. At least a portion of the inner surface of the sidewall member and at least a portion of the first cap surface and at least a portion of the radially outer portion of the current collector plate may be welded together. Since the outer diameter of the current collector plate before insertion into the can is larger than the inner diameter of the sidewall member, there are portions where the contact surfaces of the inner surface of the sidewall member and the outer surface of the current collector plate do not interlock, so the radially outer portion of the current collector plate is pushed into contact with the sidewall member.

[0099] Furthermore, in the above-described embodiment of the present invention, the first tapered portion on the inner surface of the side wall member may taper radially outward as the inclined surface extends axially outward. The radially outward portion of the current collector plate may include a bent portion when the current collector plate is positioned in the can, and the radially outward portion may extend axially outward from the bent portion. The bent portion defines a curved surface that curves from the radial direction to the axial direction, and the outer diameter of the current collector plate may gradually decrease as the radially outward portion of the current collector plate extends axially inward. The minimum outer diameter of the curved surface may be smaller than the inner diameter of the side wall member.

[0100] Furthermore, in one embodiment of the present invention described above, the cap may include a cap body, a bevel provided on the radially outward side of the cap body, and a joint provided on the radially outward side of the cap body, comprising a first cap surface and a second cap surface. The first thickness of the joint, measured along the axial direction, may be thinner than the second thickness, measured along the axial direction of the cap body. The bevel of the cap body may be provided on the axially inner surface of the cap, and may extend axially outward as the bevel extends radially outward. At least a portion of the bevel of the cap body may be in contact with the current collector plate.

[0101] Furthermore, in one embodiment of the present invention described above, the side wall member may include a first inner circumferential surface adjacent to the first tapered portion that defines the first inner diameter of the can, and a second inner circumferential surface located adjacent to the first tapered portion and larger than the first inner diameter that defines the second inner diameter of the can.

[0102] According to another aspect of the present invention, a method for manufacturing a battery cell is provided, comprising the following steps: The method comprises providing a can including an axially extending side wall member and an open end provided at a first axial end of the side wall member; a cap covering the open end; and an electrode assembly disposed inside the can. The method comprises joining a current collector plate to the electrode assembly, which comprises inserting the current collector plate into the can, and deforming the radially outer portion of the current collector plate from a first shape to a second shape. The method comprises bringing the outer first cap surface and the axially inwardly extending second cap surface into contact with the inner surface of the side wall member. The method comprises bringing the second cap surface into contact with the second surface of the radially outer portion of the current collector plate while covering the open end of the side wall member with the cap. The method comprises irradiating the contact area between the inner surface of the side wall member and the first cap surface with a laser from the axially outside to weld the inner surface of the side wall member, the first cap surface, and the radially outer portion of the current collector plate.

[0103] Furthermore, in the above-described embodiment of the present invention, the radially outer portion of the current collector plate may come into contact with the inner surface of the side wall member during the insertion stage. During the stage in which the first cap surface and the second cap surface come into contact with the inner surface of the side wall member, the inclined surface of the axial inner surface of the cap may come into contact with the current collector plate.

[0104] A battery cell according to another aspect of the present invention may include a can, a cap, an electrode assembly, and a current collector plate. The can may include an axially extending side wall member and an open end provided at a first axial end of the side wall member. The cap may be configured to cover the open end. The electrode assembly may be configured to be housed within the can. The current collector plate may be configured to electrically connect the electrode assembly and the can. The current collector plate may define a first shape before it is positioned within the can, and a second shape different from the first shape when it is positioned within the can. The radially outer portion of the current collector plate may include a first surface which is an outer contact surface defined by the outer circumference of the radially outer portion when the current collector plate is in the second shape. The outer contact surface may face the inner surface of the side wall member. The second surface may be defined by the axially outer end of the radially outer portion of the current collector plate when the current collector plate is in the second shape. The second surface may face and contact the axial inner surface of the cap (e.g., the first cap surface) during battery cell assembly. The cap may include a radially outer first surface (e.g., the first cap surface) that faces the inner surface of the sidewall member during battery cell assembly. The cap may further include a second surface (e.g., the second cap surface) that faces axially inward. The second cap surface may face and contact the second surface of the radially outer portion of the current collector plate during battery cell assembly.

[0105] Furthermore, in the above-described embodiment of the present invention, the radially outer portion of the current collector plate may extend radially in a first shape, and the radially outer portion of the current collector may extend axially in a second shape. The current collector plate may be configured to elastically deform from the first shape to the second shape while being inserted into the can. [Effects of the Invention]

[0106] According to one aspect of the present invention, a forced pressing structure of the contact outer surface of the current collector plate against the inner circumferential surface of the side wall member ensures alignment between the side wall member and the current collector plate and the contact force of the welding area between the side wall member and the current collector plate, thereby preventing the laser irradiated axially for welding from being irradiated into the inside of the can.

[0107] According to one aspect of the present invention, by forming the cap connecting portion of the current collector plate to be elongated in the axial direction, even if a portion of the laser irradiated in the axial direction for welding penetrates into the gap between the cap connecting portion and the side wall member, it is possible to prevent the laser from directly irradiating the internal space of the can.

[0108] According to one aspect of the present invention, an inner diameter expansion portion is formed on the inner circumferential surface of the side wall member to provide a first inner diameter portion and a second inner diameter portion with different inner diameters. By forcibly pressing the cap connecting portion of the current collector plate into the first inner diameter portion, which is positioned further inward in the axial direction and has a smaller inner diameter, the pressing force between the current collector plate and the side wall member is concentrated in that area while reducing the pressing force required during assembly, thereby ensuring tight contact between the current collector plate and the side wall member.

[0109] According to one aspect of the present invention, the inner diameter expansion portion of the side wall member functions as a barrier that prevents the penetration of a laser irradiated axially for welding, thereby reliably preventing the laser from directly irradiating the inside of the can.

[0110] According to one aspect of the present invention, the portion of the axial section of the cap connecting portion closest to the bent portion is forcibly pushed into the first inner diameter portion, thereby further securing the radial support force of the bent portion and the electrode tab connecting portion with respect to the forcibly pushed portion.

[0111] According to one aspect of the present invention, the curved surface provided by the bent portion of the current collector plate guides the forced pushing of the current collector plate into the side wall member during the insertion process, thereby improving ease of assembly.

[0112] According to one aspect of the present invention, the cap is inserted until its axial inner surface contacts the axial outer end of the cap connecting portion of the current collector plate. This allows the insertion depth of the cap to be controlled by the axial extension length of the cap connecting portion, thereby improving assembly accuracy.

[0113] According to one aspect of the present invention, during the process of inserting the cap, the inclined surface provided on the thickness reduction portion of the cap comes into contact with the cap connecting portion of the current collector plate, thereby aligning the center of the cap with the center of the current collector plate, and thus improving ease of assembly.

[0114] According to one aspect of the present invention, the insertion of the cap causes the axial outer end of the cap connecting portion of the current collector plate to be pressed radially outward by the inclined surface of the thickness reduction portion of the cap. This brings the axial outer end of the cap connecting portion closer to, in contact with, or tightly attached to the second inner circumferential surface of the side wall member, thereby improving the adhesion of the welded portion.

[0115] According to one aspect of the present invention, weldability can be ensured so that the side wall member, the cap, and the current collector plate can be welded together.

[0116] According to one aspect of the present invention, process stability can be ensured so that the side wall member, the cap, and the current collector plate can be welded together.

[0117] According to one aspect of the present invention, the assembly time for the battery cell can be significantly reduced by welding the side wall member, cap, and current collector plate together. [Brief explanation of the drawing]

[0118] [Figure 1] This is a perspective view of a cylindrical battery cell according to one embodiment of the present invention. [Figure 2] Figure 1 is an exploded perspective view of the electrode assembly housed inside the can before winding. [Figure 3] Figure 2 is a perspective view of the electrode assembly in its stacked state before winding. [Figure 4] Figure 3 is a perspective view showing the laminated material wound up to form a cylindrical jelly-roll type electrode assembly. [Figure 5] This is a perspective view showing the state in which the first current collector plate is joined to the electrode tab of the first electrode of the electrode assembly. [Figure 6]This is a perspective view showing the state in which the second current collector plate is joined to the electrode tab of the second electrode of the electrode assembly. [Figure 7] This is a cross-sectional view showing the process of housing the electrode assembly, to which the current collector plates are joined, inside the can. [Figure 8] This is a cross-sectional view showing the joining process between the first current collector plate and the first electrode terminal of the electrode assembly housed in a can. [Figure 9] This is a cross-sectional view showing the process of covering the open end of the can containing the electrode assembly with a cap. [Figure 10] This is a cross-sectional view showing the process of sealing the liquid filling port of a cap, which is joined to the side wall member of a can and has its open end closed, with a stopper. [Figure 11] This is a cross-sectional view showing the process of sealing the liquid filling port of a cap, which is joined to the side wall member of a can and has its open end closed, with a stopper. [Figure 12] Figure 11 is a cross-sectional view showing an enlarged view of the area indicated by the dashed line at the open end of the battery cell, illustrating the state in which the cap is being inserted with the electrode assembly housed inside the can and the current collector plate inserted. [Figure 13] Figure 12 shows the state with the cap inserted. [Figure 14] Figure 13 is a magnified view showing the contact area between the side wall member, the current collector plate, and the cap. [Figure 15] Figure 13 shows the state in which the side wall member, current collector plate, and cap have been welded together to form a welded joint. [Figure 16] This is a flow diagram of a method for manufacturing a battery cell according to one embodiment of the present invention, wherein a cap provided with an injection port is applied to the method for manufacturing a battery cell. [Figure 17] This is a flowchart of a method for manufacturing a battery cell according to one embodiment of the present invention, wherein a cap without an injection port is applied to the method for manufacturing a battery cell. [Figure 18] This figure shows a battery pack to which a battery cell according to one embodiment of the present invention has been applied. [Figure 19] Figure 18 shows a car equipped with a battery pack. [Modes for carrying out the invention]

[0119] The aforementioned problems, features, and advantages will be described in detail later with reference to the attached drawings. This will enable a person with ordinary skill in the art to which the present invention pertains to be able to easily implement the technical idea of ​​the present invention. In the description of the present invention, if it is determined that a specific description of the relevant prior art may obscure the gist of the present invention, such detailed description will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0120] Furthermore, while terms such as "first," "second," etc., are used to indicate various components, these components are not limited by these terms. These terms are used to distinguish one component from another, and unless otherwise specified, the first component may be the second component.

[0121] Throughout the specification, unless otherwise specified, each component may be singular or plural.

[0122] Furthermore, the placement of any configuration "above (or below)" a component or "above (or below)" a component means not only that the configuration is placed in contact with the upper (or lower) surface of the component, but also that other configurations may be interposed between the component and any configuration placed above (or below) it.

[0123] Furthermore, when one component is described as being "connected," "joined," or "linked" to another component, this includes not only cases where the components are directly connected to or linked to each other, but also cases where other components are "interposed" between each component, or where each component is "connected," "joined," or "linked" through other components.

[0124] As used herein, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0125] Throughout this specification, "A and / or B" means A, B, or A and B unless otherwise specified, and "C-D" means C to D unless otherwise specified.

[0126] In the description of 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, the radial direction refers to the direction that is closer to (centripetal) or further away from (centrifugal) the axis, and the outer circumference (circumferential) direction refers to the direction that surrounds the axis.

[0127] Hereinafter, embodiments of a battery cell to which the welded structure of the present invention is applied will be described in detail with reference to Figures 1 to 13.

[0128] One embodiment of a battery cell may be a cylindrical battery cell in which the form factor ratio (defined as the ratio of the diameter to the height of a cylindrical battery cell, i.e., the ratio of height (H) to relative diameter (Φ)) is greater than approximately 0.4.

[0129] Here, form factor refers to a value indicating the diameter and height of a cylindrical battery cell. The cylindrical battery cell may be, for example, a 46110 cell, a 48750 cell, a 48110 cell, a 48800 cell, or a 46800 cell. In the numerical value indicating the form factor, the first two digits indicate the diameter of the cell, the following two digits indicate the height of the cell, and the last digit 0 indicates that the cross-section of the cell is circular.

[0130] The aforementioned battery cell may be a cylindrical battery cell that is substantially cylindrical in shape, with a diameter of approximately 46 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0131] A battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical, with a diameter of approximately 48 mm, a height of approximately 75 mm, and a form factor ratio of 0.640.

[0132] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical, with a diameter of approximately 48 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0133] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical, with a diameter of approximately 48 mm, a height of approximately 80 mm, and a form factor ratio of 0.600.

[0134] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is substantially cylindrical, with a diameter of approximately 46 mm, a height of approximately 80 mm, and a form factor ratio of 0.575.

[0135] The present invention can, of course, also 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, the diameter is approximately 18 mm, the height is approximately 65 mm, and the form factor ratio is 0.277. In the case of a 21700 cell, the diameter is approximately 21 mm, the height is approximately 70 mm, and the form factor ratio is 0.300.

[0136] One embodiment of the battery cell includes an electrode assembly 20, current collector plates 31 and 32 electrically connected to the electrode assembly 20, and a can 10 that houses the electrode assembly 20, the first current collector plate 31, and the second current collector plate 32.

[0137] The can 10 includes a bottom member 12, a side wall member 11 connected to the bottom member 12 and extending in the axial direction, and an open end provided at one axial end of the side wall member 11.

[0138] The can 10 includes a cap 16 that covers the open end.

[0139] The bottom member 12 may be a disc shape with a hole formed in the center, and the side wall member 11 may be a circular tube shape surrounding the internal space of the can 10.

[0140] The bottom member 12 and side wall member 11 can be manufactured by forming a metal sheet with nickel plating on the surface of steel using a deep drawing process, and then trimming the tip of the side wall member 11 with a punch while holding it in a blank holder. Of course, the material of the can 10 is not limited to this.

[0141] A first electrode terminal 13 can be fitted into the hole. The first electrode terminal 13 can be fixed to the bottom member 12 by riveting with a gasket 14 interposed between them. The gasket 14 is interposed between the first electrode terminal 13 and the bottom member 12 to seal the inside and outside of the can 10, prevent leakage of the electrolyte, and electrically insulate the first electrode terminal 13 from the bottom member 12.

[0142] However, the method of connecting the first electrode terminal 13 and the bottom member 12 is not limited to this. For example, as long as the structure can seal the space between the first electrode terminal 13 and the bottom member 12 and electrically insulate the first electrode terminal 13 and the bottom member 12, a variety of other fixing methods can be applied, such as a bolt-nut connection method, a glass seal method, or a chrome coating & PP-MAH thermal bonding method.

[0143] The first electrode terminal 13 may have a first polarity, and the can 10 may have a second polarity. That is, the bottom member 12 of the can 10, the side wall member 11 connected to the bottom member 12, and the cap 16, which will be described later and connected to the side wall member 11, may all have a second polarity.

[0144] As a result, the battery cell can have both the first electrode terminal 13 and the second electrode terminal 15 located at the axial end where the bottom member 12 is provided, i.e., at the closed end. Then, the battery cell can have both the busbar connected to the first electrode terminal 13 and the busbar connected to the second electrode terminal 15 located at the top of the battery cell.

[0145] As an example, the first electrode terminal 13 may be a positive terminal and the second electrode terminal 15 may be a negative terminal. As another example, the first electrode terminal 13 may be a negative terminal and the second electrode terminal 15 may be a positive terminal.

[0146] An electrode assembly 20 is housed inside the can 10. As shown in Figure 2, the electrode assembly 20 is prepared by preparing a first electrode 21, a second electrode 22, and a separation membrane 28 that have a predetermined width and extend in the longitudinal direction. As shown in Figure 3, 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, as shown in Figure 4, it is manufactured in the form of a jelly roll by winding it around a core shaft.

[0147] As an example, the first electrode 21 may be a positive electrode and the second electrode 22 may be a negative electrode. As another example, the first electrode 21 may be a negative electrode and the second electrode 22 may be a positive electrode.

[0148] 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.

[0149] The first electrode 21 and the second electrode 22 are arranged such that the plain portion 26 of both electrodes is exposed or protrudes in the width direction from the laminate, such that the plain portion 26 of the first electrode 21 protrudes from one axial end of the jelly roll, and the plain portion 26 of the second electrode 22 protrudes from the other axial end of the jelly roll. The plain portion 26 itself functions as at least one electrode tab 27.

[0150] The plain portion 26 can be formed with notches at predetermined intervals to create a plurality of flag-shaped notched tabs 27. The electrode tabs 27 may also be referred to as notched tabs 27.

[0151] In the embodiment, the multiple notching tabs 27 are exemplified to be in the shape of an equilateral trapezoid. However, this shape may be in a variety of shapes, such as semicircular, semielliptical, triangular, rectangular, or parallelogram shapes.

[0152] Furthermore, in the embodiment, an example is shown in which the notching tabs 27 arranged along the longitudinal direction have the same width. However, the width of the multiple notching tabs may be such that they gradually or stepwise increase from the core side to the outer circumference side.

[0153] Furthermore, in the embodiment, an example is given in which the height of the notching tab 27 increases in stages from the core side to the outer circumference side. However, the height of such multiple notching tabs may be constant or gradually decrease.

[0154] Furthermore, in the embodiment, a structure is exemplified in which the notching tab 27 is removed from a predetermined section at the centripetal end and a predetermined section at the centrifugal end of the plain portion 26. However, the notching tab may not be removed from the centripetal end of the plain portion, nor may it be removed from the centrifugal end of the plain portion.

[0155] In the jelly roll-type electrode assembly 20, the notching tab 27 can be bent radially and flattened, as shown in Figure 4. The notching tab 27 can be bent radially inward or outward. In this embodiment, a structure in which the notching tab 27 is bent radially inward is illustrated.

[0156] The notched tabs 27 can be bent one by one during the process of winding the laminate to form a 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.

[0157] The multiple notched tabs 27 of the first electrode 21 and the multiple notched tabs 27 of the second electrode 22, which are folded radially and overlapped in this manner, can each provide a plane substantially perpendicular to the axial direction at both axial ends of the electrode assembly 20.

[0158] The notched tabs 27 exposed at both axial ends of the electrode assembly 20 are bent to provide a substantially flat surface, which can then be bonded to the first current collector plate 31 and the second current collector plate 32, respectively, as shown in Figures 5 and 6.

[0159] In the embodiment, the first current collector plate 31 is a positive electrode current collector plate, and the second current collector plate 32 is a negative electrode current collector plate. The first current collector plate 31 may be made of aluminum, and the second current collector plate 32 may be made of copper.

[0160] The current collector plates 31 and 32 can be manufactured by punching, trimming, piercing, and / or bending a metal sheet.

[0161] Referring to Figure 5, the first current collector plate 31 includes terminal connecting portions 312 extending radially from the center, a ring portion 313 connecting the centrifugal periphery of the terminal connecting portions 312 in the circumferential direction, and an electrode connecting portion 314 extending centripetally from the ring portion 313 and not connected to the terminal connecting portions 312. The center of the terminal connecting portion 312 covers at least a portion of the hollow core of the electrode assembly 20. The terminal connecting portion 312 may be formed in a substantially X shape and connected to the ring portion 313 at four connection points arranged substantially equally apart along the inner edge of the ring portion 313. The terminal connecting portion 312 may be formed in other forms and extend along the first current collector plate 31 in other rules.

[0162] The electrode connecting portion 314 is joined to the notching 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 can 10. The laser welding line may extend radially.

[0163] Referring to Figure 6, the second current collector plate 32 includes an inner ring portion 321 that defines a hole 322 corresponding to the hollow portion of the core of the electrode assembly 20 and is provided in a manner that surrounds the hollow portion of the core, an electrode tab connecting portion 323 extending radially from the inner ring portion 321, and a can connecting portion 324 that is positioned centrifugal to the electrode tab connecting portion 323 and connected to the inner ring portion 321. The electrode tab connecting portion 323 may be in the form of a plurality of spokes extending radially outward from the inner ring portion. Here, one or more of the spokes may have a radially outer end that is connected to the peripheral edge of the second current collector plate 32, which is called the can connecting portion 324. In addition, one or more of the spokes of the electrode tab connecting portion 323 may have a radially outer end that does not reach the can connecting portion 324. The can connector 324 has an outer ring shape surrounding the electrode tab connector 323 and may include a step that moves it further away from the electrode assembly 20 in the axial direction. As a result, at least the outermost peripheral edge of the can connector 324 may be positioned further away from the electrode assembly 20 than the electrode tab connector 323, the inner ring 321, and other parts of the can connector 324.

[0164] The electrode tab connecting portion 323 may be joined to the notched tab 27 of the second electrode 22 of the electrode assembly 20 by a method such as laser welding before the electrode assembly 20 is placed in the can 10. The laser welding line may extend radially.

[0165] As shown in Figures 7 and 8, the electrode assembly 20 is housed in the can 10 with the first current collector plate 31 aligned toward the bottom member 12 of the can 10. At this time, an insulator 19 is interposed between the first current collector plate 31 and the bottom member 12 of the can 10 to electrically insulate the first current collector plate 31 from the bottom member 12.

[0166] The terminal connection portion 312 of the first current collector plate 31 is joined to the first electrode terminal 13 fixed to the can 10 by resistance welding, ultrasonic welding, or laser welding. The welding apparatus for welding the first current collector plate 31 and the first electrode terminal 13 can be positioned close to the back surface of the center of the terminal connection portion 312 of the first current collector plate 31 (the surface of the terminal connection portion 312 facing the electrode assembly 20) to perform welding. Specifically, the welding apparatus can be approached to the above-mentioned position on the first current collector plate 31 from the open end of the can 10 through the hollow core portion of the electrode assembly 20, as shown in Figure 8. Of course, the first current collector plate 31 and the first electrode terminal 13 may also be joined by brazing or soldering. In other words, a variety of methods can be applied as long as the coupling method allows the first current collector plate 31 and the first electrode terminal 13 to be electrically connected and fixed to each other.

[0167] With the electrode assembly 20 housed inside the can 10, the electrode tab 27 of the second electrode 22 and the second current collector plate 32 are positioned facing the open end of the side wall member 11.

[0168] After the first current collector plate 31 and the first electrode terminal 13 are joined, the open end of the side wall member 11 is covered and sealed by the cap 16, as shown in Figures 9 and 10. Then, the electrolyte can be injected into the can 10 through the injection port 18 provided in the center of the cap 16.

[0169] After the electrolyte is injected, the injection port 18 can be sealed by the stopper 40, as shown in Figures 10 and 11.

[0170] Of course, the welding structure of the present invention can also be applied to caps that do not have an electrolyte injection port. With this, the electrolyte can be injected before covering the open end of the side wall member 11 with the cap 16, and after the injection of the electrolyte is complete, the open end can be covered and sealed with the cap 16.

[0171] As shown in Figure 14, the periphery of the cap 16 is joined to the periphery of the side wall member 11 by laser seam welding, thereby sealing the can 10. The can 10 may be in a form in which the side wall member 11, the second current collector plate 32, and the cap 16 are welded together, as shown in Figure 15.

[0172] Referring to Figures 12 and 13, the side wall member 11 is provided with an inner diameter expansion portion 113 on the open end side. The inner diameter expansion portion 113 has a sloping shape provided on the inner circumferential surface of the side wall member 11 such that the inner diameter of the side wall member 11 expands as it extends outward in the axial direction. That is, the inner diameter expansion portion 113 is provided on the inner circumferential surface of the side wall member 11 and includes a sloping shape that extends radially outward as it extends outward in the axial direction. In other words, the side wall member 11 has a first thickness at the second inner circumferential surface 115, and the thickness decreases along the inner diameter expansion portion 113 as the side wall member 11 extends outward in the axial direction from the second inner circumferential surface 115. Furthermore, as shown in Figures 12 to 15, the side wall member has a second thickness at the first inner circumferential surface 111 which is thinner than the first thickness of the second inner circumferential surface 115. The first inner circumferential surface 111 is adjacent to the inner diameter expansion portion 113 such that the axial outer end of the inner diameter expansion portion 113 is connected to the axial inner end of the first inner circumferential surface 111. Similarly, the second inner circumferential surface 115 is adjacent to the inner diameter expansion portion 113 (on the side of the inner diameter expansion portion facing the first inner circumferential surface 111) such that the axial inner end of the inner diameter expansion portion 113 is connected to the axial outer end of the second inner circumferential surface 115. In this way, the inner surface of the side wall member 11 changes in the order of the first inner circumferential surface 111, the inner diameter expansion portion 113, and the second inner circumferential surface 115 as the side wall member 11 extends inward in the axial direction.

[0173] As a result, the inner circumferential surface of the side wall member 11 may include a first inner circumferential surface 111 provided axially inward from the inner diameter expansion portion 113 (for example, downward or relatively farther from the open end of the side wall member 11), and a second inner circumferential surface 115 provided axially outward from the inner diameter expansion portion 113 (for example, upward or relatively closer to the open end of the side wall member 11).

[0174] The outer diameter of the side wall member 11 is uniform along the axial direction, while the second inner surface 115 may have a larger inner diameter than the first inner surface 111. As a result, the thickness of the side wall member 11 measured radially in the portion where the second inner surface 115 is provided may be thinner than the thickness measured radially in the portion where the first inner surface 111 is provided.

[0175] The can connecting portion 324, which is provided on the periphery of the second current collector plate 32 and is electrically connected to the can 10 by contact, includes a first portion that faces or contacts the inner circumferential surface (first inner circumferential surface 111, inner diameter expansion portion 113, second inner circumferential surface 115) of the side wall member 11. The first portion (located on the radially outer part of the second current collector plate 32) is provided with a contact outer circumferential surface 325 that faces or contacts the inner circumferential surface (first inner circumferential surface 111, inner diameter expansion portion 113, second inner circumferential surface 115) of the side wall member 11 in the radial direction.

[0176] The can connecting portion 324, which can be referred to as the radially outer portion of the second current collector plate 32, includes a second portion that contacts the cap 16. The second portion is provided with a cap contact surface 326 that faces and contacts the inner surface (bottom surface) of the cap 16 in the axial direction.

[0177] The second current collector plate 32 includes a bent portion 327. The bent portion 327 is shaped to bend the second current collector plate 32, which extends radially outward, outward in the axial direction. The can connecting portion 324, which is the radially outer portion of the second current collector plate 32, is connected to the electrode tab connecting portion 323 through the bent portion 327 and through the inner ring portion 321 described above.

[0178] The can connecting portion 324 is connected to the axially outer side of the bent portion 327 and has a shape that extends axially outward from the bent portion 327. This allows for further securing of the area and axial length of the contact outer peripheral surface 325 of the second current collector plate 32 that contacts the can 10. Note that the can connecting portion 324 is shown as being located axially outward from the bent portion 327, as shown in Figures 12 and 13. Figures 12 and 13 show the configuration of the second current collector plate 32 after it has been inserted into the can 10. However, since the second current collector plate 32 is elastically deformable, the bent portion 327 may be formed after the second current collector plate 32 has been inserted. For example, the second current collector plate 32 can be elastically deformed to an angle of about 90° with respect to the horizontal plane on which the radially inner portion of the current collector plate extends. For example, the bent portion 327 may form an angle of approximately 70° to 85° with respect to the horizontal plane by contact with the inclined surface of the side wall member 11. The second current collector plate 32 may extend along a horizontal plane that is a single plane over its entire diameter before being inserted into the can 10. A bent portion (bent portion 327) may exist before the second current collector plate 32 is inserted into the can 10, but it may exist at a smaller angle than shown in Figures 12 and 13. Therefore, the cap contact surface 326 can also be called the radial outer surface of the second current collector plate 32, as it generally faces radially outward before the current collector plate is inserted into the can 10. Before the current collector plate is inserted into the can 10, the contact outer peripheral surface 325 of the second current collector plate 32 may face axially inward rather than radially inward as shown in Figures 12 and 13.

[0179] The material of the second current collector plate 32 may be softer than the material of the side wall member 11.

[0180] The thermal conductivity of the second current collector plate 32 may be higher than that of the side wall member 11.

[0181] For example, the material of the second current collector plate 32 may include copper, and the material of the side wall member 11 may include iron.

[0182] The outer diameter of the contact outer peripheral surface 325 of the can connecting portion 324 is set to be larger than the inner diameter of the first inner peripheral surface 111. The outer diameter of the contact outer peripheral surface 325 may correspond to (be substantially the same as or smaller than) the inner diameter of the second inner peripheral surface 115.

[0183] As a result, during the process of inserting the second current collector plate 32 into the open end of the side wall member 11, the bent portion 327 is elastically deformed, and the contact outer peripheral surface 325 is forcibly pushed against the first inner peripheral surface 111, causing the contact outer peripheral surface 325 and the first inner peripheral surface 111 to come into close contact in the radial direction. Consequently, the outer diameter of the first section a of the contact outer peripheral surface 325 that has been pushed against the first inner peripheral surface 111 in the axial direction corresponds to the inner diameter of the first inner peripheral surface 111.

[0184] Thus, due to the multi-stage structure of the inner circumferential surface of the side wall member 11 and the structure of the can connecting portion 324 of the second current collector plate 32, at least a portion of the axial direction of the contact outer circumferential surface 325 is reliably in close contact with the inner circumferential surface of the side wall member 11.

[0185] The bent portion 327 provides a curved surface whose outer diameter gradually decreases from the outer diameter of the can connecting portion 324 as it moves inward in the axial direction. Furthermore, the minimum outer diameter d of the curved surface measured at the lower end of the second current collector plate 32 may be smaller than the inner diameter of the first inner circumferential surface 111. This shape guides the forced pushing of the can connecting portion 324 into the first inner circumferential surface 111 during the process of inserting the second current collector plate 32 into the internal space of the side wall member 11. Therefore, the forced pushing process of the second current collector plate 32 is made easier.

[0186] In short, according to the embodiment of the present invention, regardless of the dimensional tolerances of the parts, as long as the minimum outer diameter d of the bent portion 327 is made smaller than the inner diameter of the first inner circumferential surface 111 of the side wall member 11, and the outer diameter of the joining outer circumferential surface 171 of the second current collector plate 32 is made larger than the inner diameter of the first inner circumferential surface 111, the effect of the first section a of the contact outer circumferential surface 325 being in close contact with the first inner circumferential surface 111 of the side wall member 11 can be achieved.

[0187] As a result, even if a portion of the laser L penetrates the interior during the welding process described later, as shown in Figure 14, the present invention reliably prevents the laser L from directly irradiating the inside of the can 10 through the can connecting portion 324 of the second current collector plate 32 which extends long in the axial direction, the forced pressing and tightening portion P between the first inner circumferential surface 111 of the side wall member 11 and the first section a of the contact outer circumferential surface 325 of the second current collector plate 32, and the inner diameter expansion portion 113 of the side wall member 11.

[0188] The cap 16 comprises, in order from the radial center outward, a cap body 160, a thickness reduction portion 161, and a joint portion 17. That is, the cap body 160 is aligned with the central part of the cap 16, the thickness reduction portion 161 is provided on the radially outer side of the cap body 160, and the joint portion 17 is provided on the radially outer side of the thickness reduction portion 161. This defines an annular region of the cap 16 having a thickness that is relatively reduced with respect to the cap body 160. As a result, the first thickness t1 of the joint portion 17, measured in the axial direction, is thinner than the second thickness t2 of the cap body 160, measured in the axial direction.

[0189] A joining outer surface 171 is provided along the radial outer surface of the cap 16, specifically along the radial outer surface of the joining portion 17, which is very close to or in contact with the second inner circumferential surface 115 of the side wall member 11 in the radial direction. The joining outer surface 171 may be referred to as the first outer surface of the cap 16. Furthermore, a current collector plate contact surface 173 is provided on the axial inner surface of the joining portion 17 of the cap 16, which is in contact with the cap contact surface 326 of the can connecting portion 324 of the second current collector plate 32 in the axial direction. The current collector plate contact surface 173 may be referred to as the second axial inward surface of the cap 16. The cap contact surface 326 may be referred to as the second surface of the radial outer portion of the second current collector plate 32.

[0190] The thickness reduction portion 161 is a thickness change portion provided on the cap 16.

[0191] By appropriately selecting the position where the thickness reduction portion 161 is provided, if at least a part of the thickness reduction portion 161 is brought into contact with the second current collector plate 32, the effect can be achieved in which the center of the cap 16 is aligned as the thickness reduction portion 161 of the cap 16 comes into contact with the second current collector plate 32 during the process of inserting the cap 16.

[0192] In this embodiment, in order to enhance the alignment effect, the thickness reduction portion 161 is realized in the form of a sloping surface that extends axially outward as it extends radially outward. That is, the thickness reduction portion 161 is defined as a slope that reduces the axial thickness of the cap 16. In this way, the axially inward surface of the cap body 160 extends along the first plane. The current collector plate contact surface 173 of the cap 16 (also referred to as the second axially inward surface of the cap 16) can be substantially parallel to the first plane and extends along the second plane located axially outward from the first plane by the slope between the axially inner surface of the cap body 160 and the current collector plate contact surface 173 of the cap 16.

[0193] During the process of inserting the cap 16 into the side wall member 11, the slanted thickness reduction portion 161 may come into contact with the radial inner end of the cap contact surface 326. As a result, the axial outer end of the can connecting portion 324 of the second current collector plate 32, on which the cap contact surface 326 is provided, is pressed radially outward by the thickness reduction portion 161, so that it is positioned closer to or makes even closer contact with the second inner circumferential surface 115 of the side wall member 11.

[0194] In other words, the slanted thickness-reducing portion 161 not only guides the center alignment of the cap 16 with the center of the second current collector plate 32 by contacting the can-connecting portion 324 of the second current collector plate 32 during the process of inserting the cap 16 at the open end of the side wall member 11, but also functions to press the axial outer end of the can-connecting portion 324 of the second current collector plate 32 radially outward, thereby ensuring that the axial outer end of the can-connecting portion 324 of the second current collector plate 32 is in close contact with the second inner circumferential surface 115 of the side wall member 11. This combination of forces generated by the shapes of each component achieves a tight interlocking fit, creating a secure enclosure structure for the elements contained within the battery.

[0195] With the cap 16 inserted into the open end of the side wall member 11, in the radial direction, the joining outer peripheral surface 171 of the cap 16 and the abutting outer peripheral surface 325 of the second current collector plate 32 are very close to or in contact with the second inner peripheral surface 115 of the side wall member 11. In other words, the joining outer peripheral surface 171 of the cap 16 may face or contact the second inner peripheral surface 115 in the radial direction, and the abutting outer peripheral surface 325 of the can connecting portion 324 may face or contact the second inner peripheral surface 115 in the radial direction, axially inward from the joining outer peripheral surface 171.

[0196] Furthermore, in the axial direction, the cap contact surface 326 provided on the axial outer end face of the can connecting portion 324 of the second current collector plate 32 contacts the current collector plate contact surface 173 provided on the inner surface of the joint portion 17 of the cap 16.

[0197] With this assembly structure, the insertion depth of the cap 16 can be precisely controlled by the height H of the second current collector plate 32, which is determined by the axial extension length of the can connecting portion 324.

[0198] On the other hand, even if some error occurs between the outer diameter dimension of the joining outer peripheral surface 171 of the cap 16, the inner diameter dimension of the second inner peripheral surface 115 of the side wall member 11, and the outer diameter dimension of the contact outer peripheral surface 325 of the second current collector plate 32, and the joining outer peripheral surface 171 of the cap 16 and the contact outer peripheral surface 325 of the second current collector plate 32 are unable to make close contact with the second inner peripheral surface 115 of the side wall member 11, as shown in Figure 14, the structure of the interlocking portion P and the inner diameter expansion portion 113 ensures that there is absolutely no risk of the laser L irradiated for welding penetrating into the interior of the can 10.

[0199] In the battery cell, a welded portion W is formed at the contact area between the side wall member 11, the cap 16, and the second current collector plate 32, where the second inner circumferential surface 115 portion of the side wall member 11, the joining outer circumferential surface 171 portion of the cap 16, and the can connecting portion 324 portion of the second current collector plate 32 are welded together.

[0200] As shown in the diagram, the axial ends of the joint outer circumferential surface 171 of the cap 16 and the inner circumferential surface of the side wall member 11, which are in contact with each other in the radial direction, are exposed to the outside in the axial direction.

[0201] The welded portion W is formed by a laser that is irradiated from the axial outside of the battery cell to the joining outer peripheral surface 171 of the cap 16 and the axial end of the second inner peripheral surface 115 of the side wall member 11.

[0202] In this case, the contact outer peripheral surface 325 of the second current collector plate 32, which is positioned axially inward from the cap 16, comes into contact with the inner peripheral surface of the side wall member 11, thereby preventing the laser from being irradiated into the internal space of the can through the gap between the side wall member 11 and the cap 16.

[0203] Furthermore, the inner diameter expansion portion 113 of the side wall member 11 also prevents the laser from penetrating inside the gap between the side wall member 11 and the cap 16 or the second current collector plate 32.

[0204] The welded portion W includes a portion where at least a part of the inner circumferential surface of the side wall member 11 and at least a part of the contact outer circumferential surface 325 of the second current collector plate 32 are joined, a portion where at least a part of the inner circumferential surface of the side wall member 11 and at least a part of the joining outer circumferential surface 171 of the cap 16 are joined, and a portion where at least a part of the cap contact surface 326 of the second current collector plate 32 and at least a part of the current collector plate contact surface 173 of the cap 16 are joined.

[0205] In other words, the welded portion W can be formed by triple welding.

[0206] The contact area between the side wall member 11 and the cap 16 is heated to a high temperature by the laser L irradiated to form the weld W.

[0207] As a result, the heat generated in the sidewall member 11 by the laser is quickly dispersed and conducted through the second current collector plate 32, which has a larger contact area, while the heat generated in the cap 16 by the laser can be dispersed and conducted somewhat more slowly through the second current collector plate 32, which has a smaller contact area. This further delays the melting point of the sidewall member 11, which is relatively thinner than the joint portion 17 of the cap 16.

[0208] Furthermore, since most of the welding heat transmitted through the side wall member 11 is dispersed through the second current collector plate 32, heat transfer from the electrode assembly 20 in contact with the first inner circumferential surface 111 of the side wall member 11 to the separation membrane 28 side can be further reduced.

[0209] On the other hand, as described above, in the cap 16, the first thickness t1 of the joint 17 is thinner than the second thickness t2 of the cap body 160, which is measured in the axial direction. As a result, the welding depth between the cap 16 and the side wall member 11 is determined by the first thickness t1, and the resistance of the cap 16 to the bulging phenomenon caused by the rise in internal pressure of the can 10 due to thermal runaway of the battery cells is determined by the second thickness t2.

[0210] According to an embodiment of the present invention, even if the cap 16 and the side wall member 11 are welded together by a first thickness t1, the contact portion between the cap 16 and the side wall member 11 that contacts the side wall member 11 is completely joined, preventing the formation of areas where stress is concentrated when bulging occurs. Furthermore, since the cap body 160 has a second thickness t2 that is greater than the first thickness t1 of the radially outer portion of the cap 16, it can have greater bulging resistance.

[0211] Furthermore, according to embodiments of the present invention, during the assembly process, the thickness reduction portion 161 of the cap 16 for interaction with the can connecting portion 324 is positioned radially inward from the joining outer peripheral surface 171 to an extent corresponding to the radial thickness of the can connecting portion 324. This allows for a larger area of ​​the cap body 160 with the second thickness t2, thereby further increasing the bulging resistance. Typically, current collectors such as the second current collector plate 32 are manufactured by forming a thin metal sheet by pressing it, so it can be understood that the thickness reduction portion 161 may be positioned very close to the radial outer edge of the cap 16.

[0212] According to the embodiments described above, despite the wide range of the welding process, sealing force can be ensured without perforation or leakage, improving weldability; thermal damage to cell components and separation membranes due to welding heat can be prevented, improving process stability; and dimensional deformation due to internal pressure can be suppressed, ensuring dimensional stability and bulging resistance, thereby improving durability.

[0213] A first embodiment of the battery cell manufacturing method described above will be explained below with reference to Figures 7 to 11 and Figure 16.

[0214] According to the battery cell manufacturing method described above, first, a can 10 is prepared in which a first electrode terminal 13 is fixed to a bottom member 12, and an electrode assembly 20 is prepared in which a first current collector plate 31 and a second current collector plate 32 are joined to both ends in the axial direction, respectively.

[0215] Then, the electrode assembly 20 is inserted and housed in the can 10 so that the first current collector plate 31 faces the bottom member 12. As a result, the second current collector plate 32 is positioned on the open end side of the can 10. In the process of housing the electrode assembly 20 in the can 10 in this way, the contact outer peripheral surface 325 of the can connecting portion 324 provided at the radial outer end of the second current collector plate 32 is brought into contact with the first inner peripheral surface 111 of the side wall member 11.

[0216] Next, the first current collector plate 31 and the first electrode terminal 13 are joined together.

[0217] Then, while covering the open end of the side wall member 11 with the cap 16, the joining outer peripheral surface 171 and the current collector plate contact surface 173 provided on the periphery of the cap 16 are brought into contact with the second inner peripheral surface 115 of the side wall member 11 and the cap contact surface 326 of the second current collector plate 32, respectively.

[0218] At this time, the inclined thickness reduction portion 161 provided on the axial inner surface of the cap 16 is brought into contact with the second current collector plate 32 to align the center of the cap 16, and the axial outer end of the can connecting portion 324 is pressed radially outward to contact the second inner circumferential surface 115. That is, after the second current collector plate 32 is inserted into the can 10, the radial outer portion of the second current collector plate 32 (for example, the can connecting portion 324) is elastically deformed so as to bend axially. The outer portion of the can connecting portion 324 may extend at an angle slightly less than 90° with respect to the horizontal plane on which the inner portion of the current collector plate extends. The angle of the can connecting portion 324 may be slightly less than 90° due to the inclination of the radial inner surface of the side wall member 11.

[0219] Next, a laser is irradiated from the outside in the axial direction to the contact area between the second inner circumferential surface 115 of the side wall member 11 and the joining outer circumferential surface 171 of the cap 16, thereby triple-welding the inner circumferential surface of the side wall member 11, the joining portion 17 of the cap 16, and the can connecting portion 324 of the second current collector plate 32 together. As a result, the formed welded portion W joins the side wall member 11, the cap 16, and the second current collector plate 32 together.

[0220] Subsequently, the electrolyte is injected into the can 10 through the injection port 18 of the cap 16. After the injection of the electrolyte is complete, the injection port 18 is sealed with the stopper 40. The sealing of the injection port 18 can be done, for example, by welding. However, such sealing may be done by applying a variety of known techniques that can seal and join.

[0221] Referring to Figure 17, a second embodiment of the battery cell manufacturing method will be described. The manufacturing method of the second embodiment is applicable when using a cap that does not have an injection port.

[0222] First, a can 10 is prepared with a first electrode terminal 13 fixed to the bottom member 12, and an electrode assembly 20 is prepared with a first current collector plate 31 and a second current collector plate 32 joined to both ends in the axial direction.

[0223] Then, the electrode assembly 20 is inserted and housed in the can 10 so that the first current collector plate 31 faces the bottom member 12. As a result, the second current collector plate 32 is positioned on the open end side of the can 10. In the process of housing the electrode assembly 20 in the can 10 in this way, the contact outer peripheral surface 325 of the can connecting portion 324 provided at the radial outer end of the second current collector plate 32 is brought into contact with the first inner peripheral surface 111 of the side wall member 11.

[0224] Next, the first current collector plate 31 and the first electrode terminal 13 are joined together.

[0225] Then, before covering the open end of the side wall member 11 with the cap 16, the electrolyte is injected into the can 10.

[0226] After the electrolyte injection is complete, the open end of the side wall member 11 is covered with the cap 16, and the joining outer peripheral surface 171 and the current collector contact surface 173 provided on the periphery of the cap 16 are brought into contact with the second inner peripheral surface 115 of the side wall member 11 and the cap contact surface 326 of the second current collector 32, respectively.

[0227] Next, a laser is irradiated from the outside in the axial direction to the contact area between the second inner circumferential surface 115 of the side wall member 11 and the joining outer circumferential surface 171 of the cap 16, thereby triple-welding the inner circumferential surface of the side wall member 11, the joining portion 17 of the cap 16, and the can connecting portion 324 of the second current collector plate 32 together. As a result, the formed welded portion W joins the side wall member 11, the cap 16, and the second current collector plate 32 together.

[0228] The battery cells 72 produced through the welded structure and welding process described above can be housed in the housing 71 of the battery pack 70, as shown in Figure 18. The battery pack 70 may be constructed using battery modules, which are an intermediate form of assembly, or the battery pack 70 may be constructed directly without battery modules, as shown.

[0229] Because the aforementioned battery cell 72 has a large volume, the battery pack 70 can be easily realized without using an intermediate structure such as a battery module. Furthermore, the battery cell 72 has low internal resistance and an even higher energy density. As a result, the battery pack 70 equipped with the battery cell 72 can achieve an even higher energy density.

[0230] By increasing the energy density in this way, the battery pack 70 can reduce its volume and weight while storing the same amount of energy. Therefore, if a battery pack 70 incorporating such battery cells 72 is installed in a vehicle such as an automobile 80 that uses electricity as an energy source, as shown in Figure 19, the vehicle's driving range relative to its energy can be further expanded.

[0231] While the seam welding structures and methods described above are disclosed in relation to cylindrical battery cans, it should be understood that within the scope of this disclosure, such techniques can be similarly applied to other battery form factors. For example, the relevant battery cells do not need to have a circular cross-sectional profile perpendicular to the central longitudinal axis, and may use other cross-sectional shapes, including elliptical, square, rectangular, and partially circular shapes. Furthermore, the longitudinal axis does not need to be oriented perpendicular to the bottom member and / or the caps at each end. For example, the side wall members of the can (along with the internal components of the can) may form tubes extending along axes oriented obliquely to the plane defined by the bottom member and / or caps. Also, the welding techniques disclosed herein can be used outside the scope of cylindrical battery cans and can be applied to batteries having, for example, rectangular and pouch-type form factors.

[0232] The components for forming a battery cell, as described throughout this specification, may be provided separately, for example, as a kit, or they may be individually formed or manufactured and then assembled to form a battery cell. For example, individually manufactured components may include cans, caps, electrode assemblies, current collector plates, etc. As described above, the current collector plates are provided in a first shape extending substantially along a single plane and can be elastically deformed from the first shape to a second shape during insertion of the current collector plates into the can.

[0233] It should be understood that the embodiments described above are illustrative in all respects and not limiting. The scope of the present invention is indicated more by the claims described below than by the detailed description above. Furthermore, the meaning and scope of the claims described below, as well as all modifiable forms derived from their equivalent concepts, are to be interpreted as being included within the scope of the present invention.

[0234] As described above, the present invention has been explained with reference to the embodiments and drawings, but it is obvious that the present invention is not limited to the embodiments and drawings disclosed herein, and that various modifications are possible by an ordinary person within the scope of the technical concept of the present invention. Furthermore, it goes without saying that even if the effects of the configuration of the present invention are not explicitly stated in the description of the embodiments of the present invention, the effects that can be predicted by such configuration should also be recognized. [Explanation of symbols]

[0235] 10: Can, 11: Side wall member, 111: First inner surface, 113: Inner diameter expansion section, 115: Second inner surface (joint inner surface), 12: Bottom member, 13: First electrode terminal (positive electrode terminal), 14: Gasket, 15: Second electrode terminal, 16: Cap, 160: Cap body, t1: First thickness, 161: Thickness reduction section, 17: Joint section, t2: Second thickness, 171: Joint outer surface, 173: Current collector plate contact surface, 18: Liquid injection port, 19: Insulator, 20: Electrode assembly, 21: First electrode, 22: Second electrode, 23: Metal foil, 24: Active material layer, 25: Surface area, 26 : Plain part, 27: Electrode tab (notching tab), 28: Separating membrane, 31: First current collector plate (positive electrode current collector plate), 312: Terminal connection part, 313: Ring part, 314: Electrode connection part, 32: Second current collector plate (negative electrode current collector plate), 321: Inner ring part, 322: Hole, 323: Electrode tab connection part, 324: Can connection part, a: First section, 325: Contact outer surface, 326: Cap contact surface, 327: Bent part, d: Diameter, 40: Stopper, H: Height of second current collector plate, P: Tightening fit part, W: Welded part, 70: Battery pack, 71: Housing, 72: Battery cell, 80: Automobile

Claims

1. A can comprising a side wall member extending in the axial direction, and an open end provided at a first axial end of the side wall member, wherein the first axial end of the side wall member includes a first tapered portion that is radially inclined, A cap covering the open end, An electrode assembly disposed inside the can, A battery cell comprising a current collector plate that electrically connects the electrode assembly and the can, The radially outer portion of the current collector plate is A first surface that faces the inner surface of the side wall member and forms a contact outer peripheral surface defined by the outer circumference of the radial outer portion, A second surface is defined by the axial outer end of the radial outer portion of the current collector plate and is in contact with the axial inner surface of the cap, The aforementioned cap is The first cap surface facing the inner surface of the side wall member, A second cap surface that faces inward in the axial direction and contacts the second surface of the radially outer portion of the current collector plate, Battery cell.

2. The battery cell according to claim 1, wherein the first cap surface is located radially and axially outward of the second cap surface.

3. The battery cell according to claim 1, wherein at least a portion of the inner surface of the side wall member and at least a portion of the first surface of the current collector plate are joined by welding.

4. The battery cell according to claim 3, wherein at least a portion of the inner surface of the side wall member and at least a portion of the surface of the first cap are joined by welding.

5. The battery cell according to claim 3, wherein at least a portion of the second surface of the radially outer portion of the current collector plate and at least a portion of the second cap surface are joined by welding.

6. The battery cell according to claim 1, wherein at least a portion of the inner surface of the side wall member, at least a portion of the surface of the first cap, and at least a portion of the radially outer portion of the current collector plate are welded together.

7. The battery cell according to claim 1, wherein the outer diameter of the current collector plate before it is inserted into the can is larger than the inner diameter of the inner surface of the side wall member, and the first surface of the radially outer portion of the current collector plate is forcibly pressed against the inner surface of the side wall member.

8. The battery cell according to claim 1, wherein as the side wall member extends outward in the axial direction, the first tapered portion of the side wall member tapers outward in the radial direction.

9. The battery cell according to claim 1, wherein, when the current collector plate is placed in the can, the radially outer portion of the current collector plate includes a bent portion, and the radially outer portion extends axially outward from the bent portion.

10. The bent portion defines a curved surface that curves from the radial direction to the axial direction, and the outer diameter of the current collector plate gradually decreases as the radial outer portion of the current collector plate extends inward in the axial direction. The battery cell according to claim 9, wherein the minimum outer diameter of the curved surface is smaller than the inner diameter of the inner surface of the side wall member.

11. The aforementioned cap is The cap body and A slope is provided on the radially outer portion of the cap body, A joint portion provided on the radially outer side of the cap body, comprising the first cap surface and the second cap surface, The battery cell according to any one of claims 1 to 6, wherein the first thickness of the joint, measured in the axial direction, is thinner than the second thickness of the cap body, measured in the axial direction.

12. The battery cell according to claim 11, wherein the inclined surface of the cap body is provided on the axial inner surface of the cap and extends axially outward as it extends radially outward.

13. The battery cell according to claim 11, wherein at least a portion of the inclined surface of the cap body is in contact with the current collector plate.

14. The inner surface of the side wall member is A first inner surface, which is positioned adjacent to the first tapered portion and defines the first inner diameter of the can, The battery cell according to claim 1, comprising: a second inner surface disposed adjacent to the first tapered portion and defining a second inner diameter of the can that is larger than the first inner diameter.

15. The present invention provides a can having a side wall member extending in the axial direction and an open end provided at the first axial end of the side wall member, a cap for covering the open end, and an electrode assembly disposed inside the can. A current collector plate is joined to the electrode assembly. The current collector plate is inserted into the can while deforming the radially outer portion of the current collector plate from the first shape to the second shape. The inner surface of the side wall member and the surface of the first cap are brought into contact. While covering the open end of the side wall member with the cap, the surface of the second cap is brought into contact with the surface of the radially outer portion of the current collector plate on the axially inner side. A method for manufacturing a battery cell, comprising irradiating a laser from the axial outside between the inner surface of the side wall member and the surface of the first cap, thereby welding the inner surface of the side wall member, the surface of the first cap, and the radially outer portion of the current collector plate together.

16. The method for manufacturing a battery cell according to claim 15, wherein, in the process of inserting the current collector plate into the can, the radially outer portion of the current collector plate is brought into contact with the inner surface of the side wall member.

17. A method for manufacturing a battery cell according to claim 15 or 16, wherein, in the process of bringing the inner surface of the side wall member into contact with the surface of the first cap, the inclined surface of the cap is brought into contact with the current collector plate.

18. A can including a side wall member extending in the axial direction, and an open end provided at the first axial end of the side wall member, A cap covering the open end, An electrode assembly housed inside the aforementioned can, A battery cell assembly kit comprising a current collector plate for electrically connecting the electrode assembly and a can, the current collector plate having a first shape defined before being placed in the can and a second shape different from the first shape defined when placed inside the can, The radially outer portion of the current collector plate is With the current collector plate in the second shape, the first surface is defined by the outer circumference of the radially outer portion, and the first surface faces the inner surface of the side wall member, The current collector plate, in the state of having the second shape, includes a second surface defined by the axial outer end of the radially outer portion of the current collector plate, which contacts the axial inner surface of the cap when the battery cell is assembled, The aforementioned cap is The first cap surface, which faces the inner surface of the side wall member when the battery cell is assembled, The battery cell includes a second cap surface that, when assembled, faces and contacts the second surface of the radially outer portion of the current collector plate, Assembly kit.

19. The assembly kit according to claim 18, wherein the radially outer portion of the current collector plate extends radially in a first shape, and the radially outer portion of the current collector plate extends axially in a second shape.

20. The assembly kit according to claim 18 or 19, wherein the current collector plate is elastically deformed from the first shape to the second shape during the process of inserting the current collector plate into the can.

21. The side wall member is provided with an inner diameter expansion portion having a slanted shape on the inner circumferential surface of the side wall member, on the open end side, such that the inner diameter of the side wall member expands as it extends outward in the axial direction. The battery cell according to claim 1, wherein the inner circumferential surface of the side wall member and the abutting outer circumferential surface of the current collector plate are tightly fitted together.

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