Battery cell with a structure to prevent damage to the side wall material of the can

Abstract

The present invention provides a battery cell capable of preventing damage to the side wall portion of a can during thermal runaway. The battery cell includes a can including an axially extending side wall member and an open end provided at one axial end of the side wall member; a cap covering the open end; an electrode assembly housed inside the can; and a current collector plate electrically connecting the electrode assembly and the can. The peripheral edge of the cap is joined to the axial end of the side wall member. The cap is provided with a loop-shaped damage induction portion concentric with the peripheral edge of the cap. The current collector plate includes a main body connected to the electrode tab of the electrode assembly; a loop-shaped can connection portion positioned further centrifugal than the main body and joined to at least one of the side wall member and the cap; and a bridge extending radially, with its centripetal side connected to the main body and its centrifugal side connected to the can connection portion. The damage induction portion of the cap is positioned further radially outward than the centripetal peripheral edge of the can connection portion.

Description

Technical Field

[0001] The present invention relates to a battery cell capable of preventing the side wall portion of a can from being damaged during thermal runaway.

[0002] This application claims priority based on Korean Patent Application No. 10-2023-0182390 filed on December 14, 2023 and Korean Patent Application No. 10-2024-0114839 filed on August 27, 2024, and all contents disclosed in the specification and drawings of said applications are incorporated into the present application. Background Art

[0003] The recent expansion of the electric vehicle market is remarkable, and accordingly, the demand for large-capacity, high-voltage cylindrical lithium-ion batteries is growing rapidly. Along with this, requirements for battery safety are also further increasing. In general, a cylindrical battery is configured such that a fracture inducing portion formed by performing notch processing or the like on the surface of a cap fractures before thermal runaway caused by abnormal operation occurs.

[0004] On the other hand, for large-capacity and high-voltage cells, despite their large explosive force, there is a strong demand for thinning the side wall member of the battery can in order to increase the capacity of the battery. For this reason, there is a high possibility that pressure or flame generated by thermal runaway will damage the side wall member.

[0005] The manufacturing process of a battery cell using a cylindrical can comprises the steps of processing a metal sheet by deep drawing to form a circular bottom portion and a circular tubular side wall member connected thereto, accommodating an electrode assembly inside thereof, and then covering and finishing the open end of the side wall member with a cap.

[0006] On the other hand, at both ends of the electrode assembly in the axial direction, the ends facing the open end are provided with current collector plates that contact and electrically connect to the electrode tabs of the electrode assembly. The current collector plates are connected to the cap or side wall member by welding or other means so as to contact and electrically connect to the cap or side wall member.

[0007] Referring to Figure 23, when finishing the open end of the cylindrical can 10, first, with the electrode assembly 20 housed inside the can 10, a predetermined section of the side wall member located further axially outward from the electrode assembly is beaded in a concave shape toward the center to form a beaded portion 117. Next, the current collector plate 32 is connected to the beaded portion 117. Then, with the periphery of the cap 16 placed on top of the beaded portion 117, the axial end of the side wall member is crimped toward the center to fix it in place. A gasket 169 is interposed between the periphery of the cap and the side wall member to seal the gap between the cap and the side wall member.

[0008] On the other hand, the cap is provided with a loop-shaped rupture induction section 165 that ruptures when the battery cells overheat and the internal pressure of the can rises, allowing the gas and flame generated during the overheating to be discharged.

[0009] However, as mentioned above, when a crimping structure is applied when fixing the cap to the can, the crimping portion 118 extends and enters toward the center, making it difficult to secure the diameter D1 of the breakage guide portion. In other words, the diameter D1 of the breakage guide portion inevitably becomes even smaller than the inner diameter of the tip of the crimping portion 118.

[0010] In contrast, due to the structural characteristics that necessitate fixing the cap 16, the inner diameter D2 of the recess in the beading portion 117 is approximately the same as, or slightly smaller than, the inner diameter of the crimping portion. Therefore, when thermal runaway occurs and the failure induction portion 165 fails and venting occurs, as shown in Figure 24, a type of bottleneck phenomenon A and B occurs due to the vent passage, which is even smaller than the inner diameter D2 of the beading portion 117. This can cause the flame to damage the beading portion 117 and potentially lead to damage to the side wall.

[0011] In electric vehicle modules or battery packs, if a single cell experiences thermal runaway and its sidewall is damaged, it can affect other adjacent cells, potentially leading to thermal runaway of the entire battery pack system. Since damage to the sidewall of cylindrical lithium-ion batteries directly impacts user safety, there is a strong demand for a structure that can prevent this. [Overview of the project] [Problems that the invention aims to solve]

[0012] The present invention was created to solve the above-mentioned problems, and its objective is to provide a battery cell having a structure that can prevent damage to the side wall member of the battery can even if thermal runaway occurs.

[0013] The technical problems of the present invention are not limited in any way to the purposes described above, and other purposes and advantages of the present invention not mentioned can be understood from the following description and will be more clearly evident from the embodiments of the present invention. Furthermore, the purposes and advantages of the present invention can be realized by the means and combinations thereof shown in the claims. [Means for solving the problem]

[0014] The present invention, which solves the above-mentioned problems, may be applied to a battery cell comprising an electrode assembly, a can containing the electrode assembly, and a cap for closing and sealing the open end of the can.

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

[0016] The peripheral edge of the cap is joined to one end of the side wall member in the axial direction. The cap is provided with a loop-shaped breakage guide portion that is concentric with the peripheral edge of the cap.

[0017] The current collector plate includes a main body connected to the electrode tab of the electrode assembly, a loop-shaped can connection portion positioned further centrifugal than the main body and joined to at least one of the side wall member and the cap, and a bridge extending radially, with its centripetal side connected to the main body and its centrifugal side connected to the can connection portion, wherein the cap breakage guide portion is positioned further radially outward than the centripetal peripheral edge of the can connection portion.

[0018] By joining the axial end of the side wall member to the radial end of the cap without crimping to fix one axial end of the side wall member toward the center, it is possible to further increase the diameter of the fracture induction portion.

[0019] The ratio of the diameter of the damage induction portion to the diameter of the battery cell may be 38 / 46 or more. More preferably, the ratio may be 40 / 46 or more.

[0020] The cap and the side wall member can be joined by welding, brazing, or soldering.

[0021] A bottom member is connected to the other axial end of the side wall member, thereby allowing the other axial end of the side wall member to form a closed end.

[0022] The electrode assembly may be in the form of a jelly roll wound around a predetermined axis.

[0023] A current collecting plate may be electrically connected to the electrode assembly.

[0024] An electrode tab is provided at an end portion on the side corresponding to the open end portion among both axial end portions of the electrode assembly, and the current collecting plate may be electrically connected to the electrode tab.

[0025] The current collecting plate may include a main body portion that is in contact with and electrically connected to the electrode tab.

[0026] The main body portion may include an electrode tab connection portion joined to the electrode tab.

[0027] The joining between the electrode tab connection portion and the electrode tab may be performed by welding, brazing, or soldering. Preferably, the joining may be performed by laser welding that irradiates the surface of the electrode tab connection portion with a laser.

[0028] The main body portion may include an inner ring portion connected to the electrode tab connection portion on the centripetal side of the electrode tab connection portion.

[0029] The can connection portion and the main body portion may be electrically connected.

[0030] The main body portion may be arranged further inward in the axial direction than the can connection portion. That is, the can connection portion may be arranged further outward in the axial direction than the main body portion.

[0031] The can portion arranged further outward in the radial direction than the break induction portion may be arranged further outward in the axial direction than the can connection portion of the current collecting plate.

[0032] The ratio of the inner diameter of the peripheral edge portion on the centripetal side of the can connection portion to the diameter of the battery cell may be 40 / 46 or less.

[0033] The can connection portion may be joined to the can or the side wall member by a welding, brazing or soldering method.

[0034] The method of joining the can connection portion to the can or side wall member may correspond to the method of joining the can to the side wall member.

[0035] The can connection portion may include an axially extending portion that extends axially from the centrifugal end.

[0036] The can connection portion may include a radially extending portion.

[0037] The axial extension can be connected to the radial extension via a bent portion.

[0038] The bent portion can be bent outward in the axial direction, with respect to the radially extending portion that extends toward the centrifugal side.

[0039] The axially extended portion of the can connection may extend outward in the axial direction from the bent portion.

[0040] The can connection portion may have a butt-joint outer surface defined by the outer circumference of the can connection portion.

[0041] The aforementioned abutting outer surface may be defined by the outer surface of the axially extending portion.

[0042] The aforementioned abutted outer circumferential surface may face the inner circumferential surface of the side wall member in the radial direction.

[0043] The can connection portion may include a cap abutting surface defined by the axially outer end face.

[0044] The abutting surface of the cap may be defined by the tip surface of the axially extending portion.

[0045] The abutting surfaces of the caps can come into contact with the inner surface of the caps in an axial direction.

[0046] This ensures that the axial distance between the radial extension of the can connection portion and the connection point between the cap and the side wall member is equal to the axial length of the axial extension. In this section, the axial extension covers the inner circumferential surface of the side wall member. This further reduces the area where the inner circumferential surface of the side wall member is directly exposed to flames.

[0047] Furthermore, this allows the radially extending portion to be positioned closer to the electrode assembly, and the section of the side wall member, which is located further axially inward than the radially extending portion of the current collector plate, is positioned farther away from the outside air, thus preventing flames from reaching the section.

[0048] The cap may include a joining outer surface that faces the inner circumferential surface of the side wall member in the radial direction.

[0049] The aforementioned joining outer circumferential surface may contact the inner circumferential surface of the side wall member in the radial direction.

[0050] The aforementioned cap may have a current collector plate abutting surface defined by its axial inner surface.

[0051] The abutting surfaces of the current collector plates can come into contact with the abutting surfaces of the caps of the can connection portion of the current collector plates in the axial direction.

[0052] The outer circumferential surface of the cap may be positioned further outward in the axial direction than the abutting surface of the current collector plate.

[0053] The outer circumferential surface of the cap may be positioned further outward in the radial direction than the abutting surface of the current collector plate.

[0054] At least a portion of the inner circumferential surface of the side wall member and at least a portion of the abutting outer circumferential surface of the current collector plate can be joined together.

[0055] 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. Preferably, the joining outer circumferential surface of the cap can be joined entirely to the inner circumferential surface of the side wall member.

[0056] At least a portion of the abutting surface of the current collector plate and at least a portion of the abutting surface of the current collector plate of the cap can be joined together.

[0057] The aforementioned joining may be performed by welding.

[0058] The side wall member, the cap, and the current collector plate can be triple-welded together simultaneously.

[0059] The triple welding described above can be performed by simultaneously welding at least a portion of the side wall member, at least a portion of the cap, and at least a portion of the can connection portion of the current collector plate.

[0060] The welding can be performed by irradiating a laser in the axial direction onto the abutting point between the inner circumferential surface of the side wall member and the joining outer circumferential surface of the cap.

[0061] 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 connection portion of the current collector plate can be welded and joined at the same time.

[0062] The battery cell may include a welded portion in which the inner circumferential surface of the side wall member, the joining outer circumferential surface of the cap, and the can connection portion of the current collector plate are welded together at the same time.

[0063] The joining outer surface of the cap and the butting outer surface of the can connection portion may each face or come into contact with the inner surface of the side wall member in a radial direction.

[0064] The axial ends of the joining outer circumferential surface of the cap and the inner circumferential surface of the side wall member, which are facing each other radially or butting together, may be exposed to the outside in the axial direction.

[0065] 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.

[0066] The aforementioned cap may comprise, in this order, a cap body, a thinned portion, and a joint portion, starting from the center in the radial direction and moving outward.

[0067] In other words, the thinned portion may be provided on the centrifugal side of the cap body, and the joint portion may be provided on the centrifugal side of the thinned portion.

[0068] The outer circumferential surface of the cap may be provided at the joint.

[0069] The first thickness of the joint may be even smaller than the second thickness of the cap body.

[0070] This increases the second thickness of the cap body, which makes up the overall shape of the cap, thereby minimizing deformation of the cap due to the pressure inside the can. At the same time, by reducing the axial dimensions of the welding points to the side wall member, i.e., the welding area on the outer circumferential surface of the joint, the welded portion is formed over the entire axial length of the outer circumferential surface of the joint, thereby increasing both the strength of the cap itself and the bonding strength of the cap to the side wall member.

[0071] The rupture induction portion may be provided in the cap body having the second thickness. This allows deformation to concentrate in the rupture induction portion when the internal pressure of the battery can increases, enabling smooth rupture. [Effects of the Invention]

[0072] According to the present invention, the diameter of the rupture guide portion provided in the cap can be made larger, thereby shortening the radial length of the centrifugal portion of the rupture guide portion that remains attached to the can even after rupture. This allows for a wider discharge area when the gas and flame generated during thermal runaway are discharged, and minimizes the occurrence of a bottleneck phenomenon due to the remaining portion of the cap. This prevents damage to the side wall.

[0073] According to the present invention, since the inner diameter of the can connection portion of the current collector plate provided at the bottom of the can is even smaller than the diameter of the damage induction portion, the phenomenon in which the gas and flame generated during thermal runaway directly hit the side wall member present between the can and the current collector plate can be suppressed as much as possible. This prevents damage to the side wall portion of the can.

[0074] According to the present invention, the axially extended portion of the can connection is joined to the inner circumferential surface of the side wall member in a shape that overlaps it, thereby reinforcing the side wall member at that location and preventing damage to the side wall.

[0075] According to the present invention, the axially extended portion of the can connection portion allows the radially extended portion of the can connection portion to be positioned near the electrode assembly. This minimizes the phenomenon of gas and flame directly contacting or reaching the side wall member located further axially inward than the radially extended portion. This prevents damage to the side wall portion.

[0076] According to the present invention, it is possible to ensure joinability (weldability) that allows the side wall member, the cap, and the current collector plate to be joined together simultaneously (by welding).

[0077] According to the present invention, process stability can be ensured that the side wall member, the cap, and the current collector plate can be joined together (by welding) at the same time.

[0078] According to the present invention, the side wall member, cap, and current collector plate can be joined simultaneously, significantly reducing the assembly time for the battery cell.

[0079] In addition to the effects described above, the specific effects of the present invention will be described simultaneously while explaining the specific matters for carrying out the invention below. [Brief explanation of the drawing]

[0080] [Figure 1] This is a perspective view of a cylindrical battery cell according to an embodiment. [Figure 2] Figure 1 is an exploded perspective view of the electrode assembly housed inside the can before it is wound up. [Figure 3] Figure 2 is a perspective view of the stacked state of the electrode assembly before winding. [Figure 4] Figure 3 is a perspective view showing the laminated material in the image 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 perspective view of the second current collector plate in Figure 6. [Figure 8] This is a cross-sectional view taken along the line 8-8 in Figure 7. [Figure 9] This is a cross-sectional view taken along the line 9-9 in Figure 7. [Figure 10] Figure 8 is a perspective view showing a portion of the cross-section. [Figure 11] This is a side cross-sectional view showing the process of housing the electrode assembly, to which the current collector plates are joined, inside the can. [Figure 12] This is a side 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 13] This is a side cross-sectional view showing the process of covering the open end of the can containing the electrode assembly with a cap. [Figure 14] This is a side cross-sectional view showing the process of finishing 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 15]This is a side cross-sectional view showing the process of finishing 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 16] These are an upper perspective view and a lower perspective view of the cap of the embodiment. [Figure 17] These are an upper perspective view and a lower perspective view of the cap of the embodiment. [Figure 18] This is a cross-sectional view showing a magnified view of the area indicated by the dashed line at the open end of the battery cell in Figure 15. [Figure 19] This is a cross-sectional view of a battery cell, viewed from a different position than the circumferential direction in Figure 18. [Figure 20] Figure 19 shows the vented state when the breakage induction part of the cap is damaged. [Figure 21] This figure shows a battery pack to which the battery cells of the embodiment are applied. [Figure 22] This figure shows an automobile equipped with a battery pack to which the battery cells of the embodiment are applied. [Figure 23] This is a cross-sectional view of a cap fixing structure that incorporates beading and crimping sections. [Figure 24] Figure 23 shows the vented state when the breakage induction part of the cap is damaged. [Modes for carrying out the invention]

[0081] The aforementioned objectives, features, and advantages should become even clearer from the following detailed description in conjunction with the attached drawings, thereby enabling a person with ordinary skill in the art to easily implement the technical concept of the present invention. In describing the present invention, if it is deemed that a specific description of known technologies related to the present invention would ambiguously obscure the gist of the present invention, such detailed description will be omitted.

[0082] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In the drawings, the same reference numerals refer to the same or similar functional components.

[0083] Although phrases such as "first" and "second" can be used to describe various components, it goes without saying that these components are not limited in any way by these phrases. These phrases are used simply to distinguish one component from another, and unless otherwise specified, it goes without saying that the first component could be the second component.

[0084] Throughout this specification, unless otherwise specifically noted or clearly inconsistent with the context, each component shall be construed as encompassing both singular and plural parts.

[0085] In the following, the placement of any component "above (or below)" or "above (or below)" a component means not only that the component is in contact with the top (or bottom) surface of the component, but also that other components may be interposed between the component and any component placed above (or below) it.

[0086] Furthermore, when it is stated that one component is “linked,” “joined,” or “connected” to another component, it should be understood that the components may be directly linked or connected to one another, or other components may be “interposed” between them, or each component may be “linked,” “joined,” or “connected” through other components.

[0087] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “composed of,” “including,” or “equipped with” should not be interpreted as necessarily including all of the various components or steps described in the specification, and should be interpreted as including some of these components or steps, or including additional further components or steps.

[0088] Throughout this specification, "A and / or B" means A, B, or A and B unless otherwise specifically noted or clearly contradicts the context, and "C to D" means C or greater and D or less, unless otherwise specified.

[0089] In describing the embodiments, the axial direction refers to the direction in which the axis forming the winding center of the jelly roll type electrode assembly extends, the radial direction refers to the direction of approaching (centripetal) or moving away from (centrifugal) the axis, and the circumferential direction refers to the direction surrounding the axis.

[0090] Furthermore, "loop-shaped" refers to an annular shape having a ring or circular form, "centrifugal side" refers to the direction away from the axis forming the winding center of the jelly roll type electrode assembly, and "centripetal side" refers to the direction approaching the axis forming the winding center of the jelly roll type electrode assembly.

[0091] Hereinafter, an embodiment of a battery cell equipped with the side wall member damage prevention structure of the present invention will be described in detail based on Figures 1 to 20.

[0092] The battery cell of the embodiment may be, for example, a cylindrical battery cell with a form factor ratio (defined as the ratio of diameter to height of a cylindrical battery cell, i.e., the ratio of diameter (Φ) to height H) that is greater than approximately 0.4.

[0093] Here, form factor refers to a value that indicates the diameter and height of a cylindrical battery cell. Cylindrical battery cells may be, for example, 46110 cells, 48750 cells, 48110 cells, 48800 cells, or 46800 cells. In the numerical value indicating the form factor, the first two digits indicate the diameter of the cell, the next two digits indicate the height of the cell, and the last digit, 0, indicates that the cross-section of the cell is circular.

[0094] The battery cell may be a cylindrical battery cell that is generally cylindrical in shape, with a diameter of approximately 46 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0095] A battery cell according to another embodiment may be a cylindrical battery cell that is generally cylindrical in shape, with a diameter of approximately 48 mm, a height of approximately 75 mm, and a form factor ratio of 0.640.

[0096] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is generally cylindrical in shape, with a diameter of approximately 48 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0097] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is generally cylindrical in shape, with a diameter of approximately 48 mm, a height of approximately 80 mm, and a form factor ratio of 0.600.

[0098] Furthermore, a battery cell according to another embodiment may be a cylindrical battery cell that is generally cylindrical in shape, with a diameter of approximately 46 mm, a height of approximately 80 mm, and a form factor ratio of 0.575.

[0099] Needless to say, the present invention is applicable to battery cells with a form factor ratio of approximately 0.4 or less, such as 18650 cells and 21700 cells. In the case of an 18650 cell, its diameter is approximately 18 mm, its height is approximately 65 mm, and its form factor ratio is 0.277. In the case of a 21700 cell, its diameter is approximately 21 mm, its height is approximately 70 mm, and its form factor ratio is 0.300.

[0100] The battery cell of the embodiment 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 and the current collector plates 31 and 32.

[0101] 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 end of the side wall member 11 in the axial direction.

[0102] The can 10 includes a cap 16 that covers the open end.

[0103] The bottom member 12 may be disc-shaped with a hole in the center, and the side wall member 11 may be circular and tubular.

[0104] The bottom member 12 and the 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 with a blank holder. Needless to say, the material of the can 10 is not limited to this.

[0105] 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 to prevent leakage of the electrolyte and to electrically insulate the first electrode terminal 13 from the bottom member 12.

[0106] However, the method of connecting the first electrode terminal 13 and the bottom member 12 is not limited to this. For example, any other method can be used as long as it is possible to 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.

[0107] 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 thereto, and the cap 16, which will be described later and connected to the side wall member 11, may all have a second polarity.

[0108] As a result, the battery cell can have both the first electrode terminal 13 and the second electrode terminal 15 positioned at the axial end where the bottom member 12 is provided, i.e., the closed end, as shown in Figure 1. 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. In one example, the first electrode terminal 13 may be the positive terminal and the second electrode terminal 15 may be the negative terminal. Needless to say, the reverse is also true.

[0109] The electrode assembly 20 is housed inside the can 10. The electrode assembly 20 is prepared by preparing a first electrode 21 having a predetermined width and extending in the longitudinal direction, a second electrode 22, and a separator 28, as shown in Figure 2. After forming a laminate by stacking the first electrode 21, separator 28, second electrode 22, and separator 28 in that order, as shown in Figure 3, these are wound around a core shaft to create a jelly roll type. The first electrode 21 can be the positive electrode, and the second electrode 22 can be the negative electrode. Needless to say, the reverse is also true.

[0110] The first electrode 21 and the second electrode 22 are manufactured in sheet form. The electrode sheet is manufactured in a shape 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.

[0111] The plain area 26 is exposed (or protrudes) in the width direction from the laminate. The plain area 26 itself functions as an electrode tab 27.

[0112] The plain portion 26 can be cut out at predetermined intervals to form flag-shaped notched tabs 27.

[0113] In this embodiment, the notched tab 27 is exemplified as being an isosceles trapezoid. However, it is not limited to this and can be a wide variety of shapes, such as semicircles, semi-ellipses, triangles, rectangles, and parallelograms.

[0114] Furthermore, in the embodiment, the notched tabs 27 arranged along the longitudinal direction are exemplified to have a shape in which they are of equal width. However, the width of the notched tabs can also be shaped to gradually or stepwise increase in width as they progress from the core side towards the outer circumference.

[0115] Furthermore, in the embodiment, a shape is exemplified in which the height of the notched tab 27 increases in stages as it progresses from the core side toward the outer circumference. However, the height of these notched tabs may be constant, or they may be realized in a shape that gradually decreases.

[0116] Furthermore, in the embodiment, a structure is exemplified in which the notched tabs 27 are removed from a predetermined section at the centripetal end and a predetermined section at the centrifugal end of the plain portion 26. However, it goes without saying that the notched tabs may be removed from the centripetal end of the plain portion, or they may not be removed from the centrifugal end of the plain portion.

[0117] In the jelly roll type electrode assembly 20, the notched tab 27 can be bent radially and flattened, as shown in Figure 4. The notched tab 27 can be bent towards the center or outward. In one embodiment, a structure in which the notched tab 27 is bent towards the center is illustrated.

[0118] 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 can be bent all at once after the laminate has been wound to form the jelly roll type electrode assembly.

[0119] In this way, the notched tabs 27 of the first electrode 21 and the second electrode 22, which are folded radially and overlap, can each provide a plane substantially perpendicular to the axial direction at both axial ends of the electrode assembly 20.

[0120] The notched tabs 27 exposed at both axial ends of the electrode assembly 20 are bent to provide substantially flat surfaces, to which the first current collector plate 31 and the second current collector plate 32 can be bonded, as shown in Figures 5 and 6.

[0121] In this 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.

[0122] The current collector plates 31 and 32 can be manufactured by punching out and trimming metal sheets, piercing them, and bending them.

[0123] Referring to Figure 5, the first current collector plate 31 includes terminal connection portions 312 extending radially from the center, a ring portion 313 connecting the centrifugal peripheral edges of the terminal connection portions 312 in the circumferential direction, and an electrode connection portion 314 extending centripetally from the ring portion 313 but not connected to the terminal connection portions 312. The central part of the terminal connection portion 312 covers at least a portion of the hollow core of the electrode assembly 20.

[0124] The electrode connection portion 314 is joined to the notched tab 27 of the first electrode 21 of the electrode assembly 20 by a method such as laser welding before the electrode assembly 20 is placed in the can 10. The laser welding line may extend radially.

[0125] Referring to Figures 6 to 9, the second current collector plate 32 includes a main body portion 320 connected to the electrode tab 27 of the electrode assembly 20, and an outer ring-shaped can connector portion 324 positioned further centrifugal than the main body portion 320 and surrounding the periphery of the second current collector plate 32. The loop-shaped can connector portion 324 is positioned radially away from the main body portion 320.

[0126] The second current collector plate 32 includes a bridge 33, the centripetal side of which is connected to the main body 320 and the centrifugal side of which is connected to the can connection part 324.

[0127] The main body 320 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 arranged in a shape surrounding the hollow portion of the core, and an electrode tab connecting portion 323 that extends radially from the inner ring portion 321. The main body 320 can be electrically connected to the electrode tabs 27 of the electrode assembly 20 by welding with a laser irradiated onto the electrode tab connecting portion 323.

[0128] The electrode tab connector 323 may be joined to the notched tab 27 of the second electrode 22 of the electrode assembly 20 by methods such as laser welding before the electrode assembly 20 is placed in the can 10. The laser welding line may extend radially.

[0129] The can connection portion 324 is electrically connected to the main body portion 320 via a radially extending bridge 33.

[0130] The can connection portion 324 comprises a radially extending portion 3242 extending in the radial direction, a bent portion 327 provided at the centrifugal end of the radially extending portion 3242, and an axially extending portion 3241 extending axially outward from the bent portion 327.

[0131] The bridge 33 may be arranged alternately with the electrode tab connectors 323 in the circumferential direction. The bridge 33 may be connected to the inner ring 321.

[0132] As shown in Figures 11 and 12, the electrode assembly 20 is housed in the can 10 with the first current collector plate 31 positioned so that it faces 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 so that the first current collector plate 31 and the bottom member 12 are electrically insulated.

[0133] 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 approached from the open end of the can 10 through the hollow core portion of the electrode assembly 20 to the back surface of the center of the terminal connection portion 312 of the first current collector plate 31 and perform the welding. Needless to say, the first current collector plate 31 and the first electrode terminal 13 can also be joined by methods such as brazing or soldering. In other words, various methods can be used for welding the first current collector plate 31 and the first electrode terminal 13, as long as they are a coupling method that electrically connects and fixes them to each other.

[0134] 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 to face the open end of the side wall member 11. The outer surface of the second current collector plate 32 is then pressed against the inner surface of the side wall member 11 in contact with it.

[0135] 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 with a cap 16, as shown in Figures 13 and 14, and finished by seam welding or the like. Then, the electrolyte can be injected into the can 10 through the liquid injection port 18 provided in the center of the cap 16.

[0136] After the electrolyte is injected, the injection port 18 can be finished with a stopper 40, as shown in Figures 14 and 15.

[0137] Needless to say, 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 first before covering the open end of the side wall member 11 with the cap 16, and then the open end can be covered with the cap 16 after the electrolyte injection is complete.

[0138] As shown in Figure 18, the periphery of the cap 16 is joined to the periphery of the side wall member 11 by laser seam welding, thereby enabling the can 10 to be sealed.

[0139] The can connection portion 324, provided on the periphery of the second current collector plate 32 and electrically connected to the can 10 by contact, includes a first location that faces or contacts the inner circumferential surface of the side wall member 11. The first location is provided with a butt outer circumferential surface 325 that faces or contacts the inner circumferential surface of the side wall member 11 in the radial direction.

[0140] The can connection portion 324 includes a second portion that contacts the cap 16. The second portion is provided with a cap abutment surface 326 that contacts the inner surface of the cap 16 in the axial direction.

[0141] The first and second locations are provided on the axially extended portion 3241 of the can connection portion 324.

[0142] The axially extended portion 3241 of the can connection portion 324 is connected to the axially outside of the bent portion 327 and has a shape that extends axially outward from the bent portion 327. This makes it possible to further secure the area and axial length of the abutting outer peripheral surface 325 of the second current collector plate 32.

[0143] The material of the second current collector plate 32 may be even more brittle than the material of the side wall member 11.

[0144] The thermal conductivity of the second current collector plate 32 may be even higher than that of the side wall member 11.

[0145] 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.

[0146] The outer diameter of the butt joint outer surface 325 of the can connection portion 324 is set to correspond to, or be even larger than, the inner diameter of the inner surface of at least a portion of the axial direction of the side wall member 11.

[0147] Then, during the process of inserting the second current collector plate 32, the bent portion 327 is elastically deformed, and the abutting outer surface 325 is forcibly pressed into the inner surface of the side wall member 11, resulting in a tight fit in the radial direction.

[0148] The radially extending portion 3242 of the can connection portion 324 supports the outer shape of the can connection portion 324 when the bent portion 327 is elastically deformed while receiving a force toward the center.

[0149] The bent portion 327 provides a curved surface whose outer diameter decreases further than the outer diameter of the axially extended portion 3241 of the can connection portion 324 as it extends inward in the axial direction. This allows the can connection portion 324 to be forcibly pressed into the inner circumferential surface of the side wall member 11 during the process of inserting the second current collector plate 32 into the internal space of the side wall member 11.

[0150] Referring to Figures 16 to 20, the cap 16 comprises the cap body 160, the thinned portion 161, and the joint portion 17 in that order, starting from the center in the radial direction and moving outward. That is, the thinned portion 161 is located on the centrifugal side of the cap body 160, and the joint portion 17 is located on the centrifugal side of the thinned portion 161.

[0151] The joint portion 17 of the cap 16 is provided with a joint outer circumferential surface 171 that faces or contacts the inner circumferential surface of the side wall member 11 in a radial direction, so as to be very close. In addition, the inner surface of the joint portion 17 of the cap 16 in the axial direction is provided with a current collector plate abutting surface 173 that contacts the cap abutting surface 326 of the can connection portion 324 of the second current collector plate 32 in a state facing the axial direction.

[0152] The thinned portion 161 is a point in the cap 16 where the thickness changes.

[0153] By appropriately selecting the position where the thinned portion 161 is provided so that at least a part of the thinned portion 161 can contact the second current collector plate 32, the center of the cap 16 is aligned with the thinned portion 161 of the cap 16 while it is in contact with the second current collector plate 32 during the process of inserting the cap 16. In this embodiment, in order to enhance the alignment effect, the thinned portion 161 is made into a shape of an inclined surface that extends outward in the axial direction as it moves toward the centrifugal side.

[0154] During the process of inserting the cap 16 into the side wall member 11, the thinned portion 161 of the inclined surface can come into contact with the centrifugal peripheral edge of the cap abutting surface 326. As a result, the axial outer end of the can connection portion 324 of the second current collector plate 32, on which the cap abutting surface 326 is provided, is pressed centrifugally by the thinned portion 161, so as to be positioned closer to or pressed against the inner circumferential surface of the side wall member 11.

[0155] Then, in the axial direction, the cap abutting surface 326 provided on the axial outer end face of the can connection portion 324 of the second current collector plate 32 contacts the current collector plate abutting surface 173 provided on the inner surface of the joint portion 17 of the cap 16. With such an assembly structure, the insertion depth of the cap 16 can be precisely controlled by the height of the second current collector plate 32, which can be determined by the axial extension length of the can connection portion 324.

[0156] In the battery cell, a welded joint W is formed at the abutting point between the side wall member 11, the cap 16, and the second current collector plate 32, where the inner circumferential surface of the side wall member 11, the joining outer circumferential surface 171 of the cap 16, and the axially extended portion 3241 of the can connection portion 324 of the second current collector plate 32 are simultaneously welded.

[0157] As shown in the figure, 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 butted together radially, are exposed to the outside in the axial direction.

[0158] The welded joint W is formed by a laser 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.

[0159] 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 butt outer circumferential surface 325 of the 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 butt surface 326 of the current collector plate 32 and at least a part of the current collector plate butt surface 173 of the cap 16 are joined. Preferably, the joining outer circumferential surface 171 of the cap 16 can be welded as a whole. That is, the welded portion W can be formed by triple welding.

[0160] The laser L, which is irradiated to form the welded joint W, heats the butt joint between the side wall member 11 and the cap 16 to a high temperature.

[0161] As a result, the heat generated in the side wall member 11 by the laser is quickly dispersed and conducted through the second current collector plate 32, which has an even larger contact area, while the heat generated in the cap 16 by the laser is dispersed and conducted somewhat more slowly through the second current collector plate 32, which has an even smaller contact area. This further delays the melting point of the side wall member 11, which is relatively thinner than the joint portion 17 of the cap 16.

[0162] Furthermore, since most of the welding heat transmitted through the side wall member 11 is dispersed via the second current collector plate 32, the phenomenon of heat being transferred to the separator 28 side of the electrode assembly 20 that is in contact with the inner circumferential surface of the side wall member 11 can be further reduced.

[0163] On the other hand, as described above, in the cap 16, the first thickness of the joint 17 is even smaller than the second thickness of the cap body 160, which is measured in the axial direction. As a result, the depth to which the cap 16 must be welded to the side wall member 11 is determined by the first thickness, and the resistance to the swelling phenomenon of the cap 16 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.

[0164] According to the present invention, even if welding is performed between the cap 16 and the side wall member 11 to a depth corresponding to the first thickness, the butt joint between the cap 16 and the side wall member 11 is completely joined and connected, so that no area of ​​stress concentration occurs when bulging occurs, and the cap body 160 has an even larger second thickness, so it can have an even higher resistance to the bulging phenomenon.

[0165] Furthermore, according to the present invention, during the assembly process, the thinned portion 161 of the cap 16 for interaction with the can connection portion 324 is located centrifugally from the joining outer surface 171 by an amount corresponding to the radial thickness of the can connection portion 324. This allows for an even larger area of ​​the cap body 160 with the second thickness, further increasing resistance to bulging. Typically, current collectors such as the second current collector plate 32 are manufactured by a molding process in which a thin metal sheet is pressed with a press. This should be understood as enabling the thinned portion 161 to be positioned very close to the centrifugal peripheral edge of the cap 16.

[0166] The cap 16 is provided with a loop-shaped breakage guide portion 165 that is substantially concentric with the periphery of the cap 16. The breakage guide portion 165 may be defined as a thin-walled portion by forming notches on the front and back surfaces of the cap 16, respectively.

[0167] The rupture guide portion 165 can be positioned adjacent to the periphery of the cap 16. According to this embodiment, the side wall member 11 extends in an elongated shape in the axial direction, and the axial end of the side wall member 11 is also joined to the periphery of the cap 16 by welding or other means without being bent toward the center, so that the joint between the can 10 and the cap 16 occupies almost no space in the radial direction. This makes it possible to position the rupture guide portion 165 adjacent to the periphery of the cap 16.

[0168] As the diameter of the failure induction section 165 increases, as shown in Figure 20, the area of ​​the cap 16 that remains connected to the can 10 when thermal runaway occurs and the failure induction section 165 fails may be narrowed in the radial direction. This makes it possible to minimize or eliminate bottleneck phenomena, such as when gas and flame are ejected but cannot be ejected immediately and instead remain in the internal space of the can.

[0169] This prevents the flame from directly contacting the side wall member 11, thus preventing side wall rupture. Furthermore, when thermal runaway occurs in one battery cell in a battery pack, causing gas and flame venting, it prevents other cylindrical battery cells located next to it from being affected.

[0170] The ratio of the diameter of the rupture guide portion 165 to the diameter of the can 10 may be 38 / 46 or greater. Needless to say, the ratio is obviously less than 1.

[0171] Preferably, the diameter ratio can be 40 / 46 or greater. Experimental results showed that in a structure where the periphery of the cap 16 is connected to the can 10 in a plane perpendicular to the side wall member, when the ratio was 38 / 46 or greater, no damage to the side wall member occurred during the venting process. Furthermore, when the ratio was 40 / 46 or greater, it was confirmed that the bottleneck phenomenon did not occur during the venting process, resulting in the side wall member not coming into direct contact with the flame.

[0172] The damage induction portion 165 of the cap 16 may be positioned further outward in the radial direction than the centripetal peripheral edge of the can connection portion 324 of the second current collector plate 32. When venting, if the can connection portion 324 extends further centripetally than the damage induction portion 165 of the cap 16, gas and flame ejection will be vigorous near the centripetal peripheral edge of the can connection portion 324, making it difficult for external oxygen to flow into the space located further axially inward from the can connection portion 324. This minimizes the phenomenon of flames directly contacting the side wall member 11 further axially inward from the can connection portion 324.

[0173] The ratio of the inner diameter of the centrifugal peripheral edge of the radially extending portion 3242 of the can connection portion 324 to the diameter of the can 10 may be 42 / 46 or less. Preferably, the ratio may be 40 / 46 or less.

[0174] If the ratio of the inner diameters of the radially extending portion 3242 is 42 / 46 or greater, it becomes impossible to secure a sufficient length for the radially extending portion 3242. As a result, when the second current collector plate 32 is pushed into the inner circumference of the side wall member 11 of the can 10, the radially extending portion 3242 alone cannot provide sufficient support to support the axially extending portion 3241 centrifugalally, making it difficult to eliminate the possibility of flames directly contacting the side wall member during thermal runaway.

[0175] The ratio of the inner diameter of the centripetal peripheral edge of the radially extending portion 3242 of the can connection portion 324 to the diameter of the can 10 may be 36 / 46 or greater. Preferably, the ratio may be 38 / 46 or greater. If the ratio is less than 36 / 46, there is room to prevent the ejection of gas and flame during the venting process.

[0176] According to the present invention, the distance between the can connection portion 324 and the can 10 can be determined by the extension length of the axial extension portion 3241 of the can connection portion 324. This also allows adjustment of the axial distance between the radial extension portion 3242 and the electrode assembly 20. As the separation distance between the radial extension portion 3242 and the electrode assembly 20 increases, the influence of the welding heat between the can 10 and the cap 16 on the electrode assembly 20 can be reduced, but the side wall member 11 located between the radial extension portion 3242 and the electrode assembly 20 in the axial direction is more likely to be directly exposed to the flame during the venting process.

[0177] According to the present invention, the length of the axially extending portion 3241 is determined to the extent that, while preventing the welding heat between the can 10 and the cap 16 from affecting the electrode assembly 20, the portion of the side wall member 11 that is located further axially inward than the radially extending portion 3242 in the axial direction during the venting process is not exposed to the flame, thereby preventing the welding heat from affecting the electrode assembly 20 while ensuring that the side wall member 11 is not exposed to the flame during venting.

[0178] On the other hand, in the section between the radially extending portion 3242 and the can 10, the axially extending portion 3241 is joined to the side wall member 11 of the can 10, thus preventing the flame from directly contacting the can connection portion 324 with the side wall member 11.

[0179] The battery cell 72, which includes the second current collector plate described above and the assembly structure of the cap and can, can be housed in the housing 71 of the battery pack 70, as shown in Figure 21. The battery pack 70 may be constructed using battery modules in an intermediate assembly form, or the battery pack 70 may be constructed directly without battery modules, as shown in the figure.

[0180] Because the aforementioned battery cell 72 has a large volume on its own, there are no particular difficulties in realizing the battery pack 70 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, it is possible to achieve an even higher energy density in the battery pack 70 equipped with the battery cell 72.

[0181] According to the present invention, the energy density of the battery cell 72 can be sufficiently ensured, and even if thermal runaway occurs due to abnormal operation of the battery cell, damage to the side wall will not occur, thus preventing the thermal runaway from being propagated to surrounding battery cells. As a result, even if the battery pack is constructed directly without first configuring the battery cells as modules, the phenomenon of thermal runaway being propagated throughout the entire battery pack can be prevented.

[0182] Thus, the battery pack 70, which enhances safety while increasing energy density, can store the same amount of energy while reducing its volume and weight. Therefore, when a battery pack 70 incorporating such battery cells 72 is installed in a vehicle such as an electric automobile 80, as shown in Figure 22, the vehicle's driving range per unit of energy consumption can be further increased.

[0183] The embodiments described above should be understood to be illustrative and not limiting in any respect, and the scope of the present invention is expressed more by the appended claims than by the detailed description above. Furthermore, all modifications or alterations derived from the meaning and scope of the appended claims and the concept of equivalents thereto should be interpreted as being included within the scope of the present invention.

[0184] Although the present invention has been described above based on the illustrative drawings, the present invention is not limited by the embodiments and drawings disclosed herein, and it goes without saying that a wide variety of modifications can be made by an ordinary person within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention are not explicitly described in the description of the embodiments of the present invention, it goes without saying that the effects that can be predicted by such configuration should also be recognized. [Explanation of symbols]

[0185] 10 cans 11 Side wall member 117 Beading section 118 Crimping section 12 Bottom member 13. First electrode terminal (positive terminal) 14 Gasket 15. Second electrode terminal 16 caps 160 Cap Body 161 Thinned part 165 Damage Induction Section 169 Gasket 17 Joint 171 Joint outer surface 173 Current collector plate butt joint surface 18 Inlet 19 Insulators 20 Electrode assembly 21 First electrode 22 Second electrode 23 Metal foil 24 Active material layer 25 Landed section 26 Plain section 27 Electrode tabs (notched tabs) 28 Separator 31. First current collector plate (positive electrode current collector plate) 312 Terminal connection section 313 Ring section 314 Electrode connection section 32. Second current collector plate (negative current collector plate) 320 Main body 321 Inner Ring Section 322 holes 323 Electrode tab connection section 324 Can connection part 3241 Axial extension 3242 Radial extension 325 Butt joint outer surface 326 Cap butt joint surface 327 Folding section 33 Bridge 40 Stopper W Weld 70 Battery Pack 71 Housing 72 battery cells 80 vehicles

Claims

1. A battery cell comprising a can including a side wall member extending in the axial direction and an open end provided at one end of the side wall member in the axial direction, a cap covering the open end, an electrode assembly housed inside the can, and a current collector plate electrically connecting the electrode assembly and the can, The peripheral edge of the cap is joined to one end of the side wall member in the axial direction. The cap is provided with a loop-shaped damage-inducing portion that is concentric with the peripheral edge of the cap. The aforementioned current collector plate is The main body portion connected to the electrode tab of the electrode assembly, A loop-shaped can connector is positioned further centrifugally than the main body and is joined to at least one of the side wall member and the cap, The centripetal side is connected to the main body, the centrifugal side is connected to the can connection part, and the bridge extends radially, Includes, The battery cell wherein the breakage induction portion of the cap is positioned further outward in the radial direction than the centripetal peripheral edge of the can connection portion.

2. The battery cell according to claim 1, wherein the cap and the side wall member are joined by welding, brazing, or soldering.

3. The battery cell according to claim 1 or 2, wherein the ratio of the diameter of the damage induction portion to the diameter of the battery cell is 38 / 46 or more.

4. The battery cell according to claim 1 or 2, wherein the can connection portion is joined to the can or the side wall member by welding, brazing, or soldering.

5. The battery cell according to claim 1 or 2, wherein the method of joining the can connection portion to the can or the side wall member corresponds to the method of joining the cap to the side wall member.

6. The battery cell according to claim 1 or 2, wherein the ratio of the inner diameter of the centripetal peripheral edge of the can connection portion to the diameter of the battery cell is 40 / 46 or more.

7. The aforementioned can connection part is, A radially extending portion that extends in the radial direction, An axial extension portion extending in the axial direction from the centrifugal end of the radial extension portion, The outer circumferential surface defined by the outer circumferential surface of the axially extending portion and in contact with the inner circumferential surface of the side wall member, The cap abutting surface, defined by the axial outer end face of the axially extending portion, and in contact with the inner surface of the cap in the axial direction, A battery cell according to claim 1 or 2, comprising:

8. The battery cell according to claim 7, wherein the cap is defined by the inner surface in the axial direction and includes a current collector plate abutting surface that is in contact with the cap abutting surface of the can connection portion of the current collector plate in the axial direction.

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