Battery cell having structure for preventing side wall of can from cracking

Abstract

Provided is a battery cell capable of preventing a side wall portion of a can from cracking during thermal runaway. The battery cell includes: a can including a side wall member extending in an axial direction and an open end portion provided at one axial end portion of the side wall member; a cap covering the open end; an electrode assembly accommodated in the can; and a collector plate electrically connecting the electrode assembly and the canister. An edge of the cover is joined to one axial end of the side wall member. The cap is provided with a fracture inducing portion having a ring shape concentric with an edge of the cap. The collector plate includes: a body portion connected to an electrode tab of the electrode assembly; an annular canister connection portion disposed centrifugally with respect to the main body portion and coupled to at least one of the side wall member or the lid; and a bridge extending radially and having a centripetal side connected to the body portion and a centrifugal side coupled to the canister connection portion. A fracture inducing portion of the cap is provided further outward in the radial direction than a centripetal edge of the tank connecting portion.

Description

Technical Field

[0001] The present disclosure relates to a battery cell for preventing rupture of a can's sidewall in the event of thermal runaway.

[0002] This application is based on and claims the benefit of priority from Korean Patent Application No. 10-2023-0182390 filed on December 14, 2023, in the Korean Intellectual Property Office, and Korean Patent Application No. 10-2024-0114839 filed on August 27, 2024, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference. Background Art

[0003] With the rapid growth of the electric vehicle market, demand for cylindrical lithium-ion batteries with high capacity and high voltage is increasing. Furthermore, safety requirements are increasing. Cylindrical batteries are typically designed with grooves on the cover surface to prevent fractures before thermal runaway occurs due to abnormal operation.

[0004] Due to the high cell capacity and voltage, the explosion force is strong, but in order to achieve high-capacity batteries, there is a huge demand to reduce the thickness of the battery can sidewalls. Therefore, the pressure and flames generated by thermal runaway are likely to damage the can sidewalls.

[0005] The manufacturing process of a battery cell including a cylindrical can includes the steps of deep drawing a metal sheet to form a circular bottom and a circular tubular sidewall connected to the circular bottom, housing an electrode assembly in the can, and covering an open end of the sidewall with a cover.

[0006] In addition, a current collecting plate is placed at one end of the electrode assembly facing the open ends of the electrode assembly in the axial direction, and contacts and is electrically connected to the electrode taps of the electrode assembly. The current collecting plate is connected to the cover or side wall by welding to make contact and electrical connection therebetween.

[0007] Reference Figure 23 When the open end of the cylindrical can 10 is completed, in a state where the electrode assembly 20 is accommodated in the can 10, a predetermined portion of the side wall at a position further outward in the axial direction than the electrode assembly is concavely crimped in the centripetal direction to form a crimping portion 117. Subsequently, the current collecting plate 32 is connected to the crimping portion 117. In addition, in a state where the edge of the cover 16 is placed on the top of the crimping portion 117, the end of the side wall in the axial direction is fixed by crimping in the centripetal direction. A gasket 169 is provided between the edge of the cover and the side wall to form a seal between the cover and the side wall.

[0008] In addition, the cover has an annular rupture induction portion 165 configured to rupture when the internal pressure of the can increases due to thermal runaway in the battery cell, so as to release gas and flame generated by the thermal runaway.

[0009] However, when the crimping structure is applied to fix the lid to the can as described above, it is difficult to increase the diameter D1 of the fracture induction portion because crimping portion 118 extends inward in the centripetal direction. That is, the diameter D1 of the fracture induction portion is smaller than the inner diameter of the end of crimping portion 118.

[0010] On the contrary, due to the structural feature that the cover 16 must be fixed, the inner diameter D2 of the recess of the pressing portion 117 is similar to or slightly smaller than the inner diameter of the curling portion. Therefore, in the event of thermal runaway, when the fracture inducing portion 165 fractures and discharge occurs, as shown in FIG. Figure 24 As shown, bottlenecks A, B are generated due to a narrow discharge passage that is smaller than the inner diameter D2 of the bead portion 117 , and therefore, the flame may break the bead portion 117 , thereby causing damage to the sidewall.

[0011] In electric vehicle modules or battery packs, when a sidewall rupture occurs in a single cell during thermal runaway, other adjacent cells may be affected, and thermal runaway may propagate across the entire battery pack system. Therefore, because sidewall rupture of cylindrical lithium-ion batteries is directly related to user safety, a protective structure is urgently needed. Summary of the Invention

[0012] Technical issues

[0013] The present disclosure is designed to solve the above-mentioned problems, and thus the present disclosure is directed to providing a battery cell having a structure for preventing a side wall of a battery can from being ruptured in the event of thermal runaway.

[0014] The technical problems of the present disclosure are not limited to the above-mentioned objects, and these and other objects and advantages of the present disclosure can be understood from the following description and become apparent from the embodiments of the present disclosure. Moreover, it will be easily understood that the objects and advantages of the present disclosure can be achieved by the means set forth in the appended claims and their combinations.

[0015] Technical Solution

[0016] To solve the above-mentioned problems, the present disclosure may be applied to a battery cell including an electrode assembly, a can accommodating the electrode assembly, and a cover closing and sealing an open end of the can.

[0017] The can includes a side wall extending in the axial direction, and an open end portion at an end portion of the side wall in the axial direction.

[0018] The edge of the cover is joined to the end of the side wall in the axial direction.In addition, the cover includes an annular fracture induction portion concentric with the edge of the cover.

[0019] A current collecting plate includes: a main body portion, which is connected to the electrode connector of the electrode assembly; an annular tank connecting portion, which is arranged on a side more centrifugal than the main body portion and is joined to at least one of the side wall or the cover; and a bridge member, which has a centripetal side portion connected to the main body portion and a centrifugal side portion connected to the tank connecting portion and extending in a radial direction, and the fracture inducing portion of the cover is arranged at a position further outward than the centripetal side edge of the tank connecting portion in the radial direction.

[0020] When one end portion of the side wall in the axial direction is joined to the end portion of the cover in the radial direction without a curling process for plastic deformation of the end portion of the side wall in the centripetal direction, the diameter of the fracture inducing portion can be increased.

[0021] The ratio of the diameter of the fracture inducing portion to the diameter of the battery cell may be equal to or greater than 38 / 46. More preferably, the ratio may be equal to or greater than 40 / 46.

[0022] The cover and side walls may be joined by welding, brazing or soldering.

[0023] The bottom portion may be connected to the other end portion of the side wall in the axial direction, and the other end portion of the side wall in the axial direction may form a closed end portion.

[0024] The electrode assembly may have a jellyroll shape wound around a predetermined axis.

[0025] The current collecting plate may be electrically connected to the electrode assembly.

[0026] The electrode assembly may have an electrode tap at an end portion corresponding to the open end portion among both end portions of the electrode assembly in the axial direction, and the current collecting plate may be electrically connected to the electrode tap.

[0027] The current collecting plate may include a body portion contacting and electrically connected to the electrode tab.

[0028] The body portion may include an electrode tab connecting portion coupled to the electrode tab.

[0029] The electrode tab connection portion and the electrode tab may be joined by welding, brazing, or soldering. Preferably, the joining may be performed by laser welding the surface of the electrode tab connection portion using laser irradiation.

[0030] The body portion may include an inner ring portion connected to the electrode tap connection portion on a centripetal side of the electrode tap connection portion.

[0031] The tank connection portion and the main body portion may be electrically connected to each other.

[0032] The main body portion may be disposed at a position further inward than the tank connection portion in the axial direction. That is, the tank connection portion may be disposed at a position further outward than the main body portion in the axial direction.

[0033] The portion of the can disposed at an outer position than the rupture induction portion in the radial direction may be disposed at an outer position than the can connection portion of the current collecting plate in the axial direction.

[0034] A ratio of an inner diameter of a centripetal side edge of the can connecting portion to a diameter of the battery cell may be equal to or less than 40 / 46.

[0035] The tank connection portion may be joined to the tank or the sidewall by welding, brazing or soldering.

[0036] The joining method between the tank connecting portion and the tank or the side wall may correspond to the joining method between the tank and the side wall.

[0037] The tank connection portion may include an axially extending portion extending in the axial direction from the centrifugal-side end portion.

[0038] The tank connecting portion may include a radially extending portion extending in a radial direction.

[0039] The axially extending portion may be connected to the radially extending portion by a bent portion.

[0040] The bent portion may bend the eccentrically extended radially extending portion outward in the axial direction.

[0041] The axially extending portion of the tank connecting portion may extend outwardly from the bent portion in the axial direction.

[0042] The tank connection portion may have a contact outer peripheral surface defined by an outer periphery of the tank connection portion.

[0043] The contact outer peripheral surface may be defined by an outer peripheral surface of the axially extending portion.

[0044] The contact outer peripheral surface may face the inner peripheral surface of the side wall in the radial direction.

[0045] The tank connecting portion may have a cover contact surface defined by the outer end surface in the axial direction.

[0046] The cover contact surface may be defined by an end surface of the axially extending portion.

[0047] The cover contact surface may face and contact an inner surface of the cover in an axial direction.

[0048] Therefore, the axial length of the axially extending portion creates an axial gap between the radially extending portion of the tank connection portion and the connection portion of the cover and the sidewall. In the corresponding area, the axially extending portion covers the inner circumferential surface of the sidewall. This further reduces the area of ​​the inner circumferential surface of the sidewall that could be directly exposed to flames.

[0049] Additionally, therefore, the radially extending portion can be disposed near the electrode assembly, and a portion of the sidewall disposed axially inward of the radially extending portion of the current collecting plate can be away from outdoor air, thereby preventing flames from reaching the portion of the sidewall.

[0050] The cover may include an engaging outer peripheral surface facing the inner peripheral surface of the side wall in a radial direction.

[0051] The engaging outer peripheral surface may contact the inner peripheral surface of the side wall in the radial direction.

[0052] The cover may have a current collecting plate contact surface defined by the inner surface in the axial direction.

[0053] The current collecting plate contact surface may face and contact a cap contact surface of the can connecting portion of the current collecting plate in an axial direction.

[0054] The engaging outer peripheral surface of the cover may be disposed at a position further outward in the axial direction than the current collecting plate contact surface.

[0055] The engaging outer peripheral surface of the cover may be disposed at an outer position than the current collecting plate contact surface in the radial direction.

[0056] At least a portion of the inner circumferential surface of the side wall and at least a portion of the contact outer circumferential surface of the current collecting plate may be joined together.

[0057] At least a portion of the inner peripheral surface of the side wall and at least a portion of the joint outer peripheral surface of the cover may be joined together. Preferably, the entire joint outer peripheral surface of the cover may be joined to the inner peripheral surface of the side wall.

[0058] At least a portion of the cover contact surface of the current collecting plate and at least a portion of the current collecting plate contact surface of the cover may be joined together.

[0059] The joining may be accomplished by welding.

[0060] The side walls, cover and collector plate can be triple welded together.

[0061] The triple weld may include welding together at least a portion of the sidewall, at least a portion of the cover, and at least a portion of the can connection portion of the current collector plate.

[0062] The welding may be performed by laser irradiating the contact area of ​​the inner peripheral surface of the side wall and the joint outer peripheral surface of the cover in the axial direction.

[0063] At least a portion of the inner circumferential surface of the side wall, at least a portion of the joint outer circumferential surface of the cover, and at least a portion of the tank connection portion of the current collecting plate may be joined together by welding.

[0064] The battery cell may include a welding portion in which the inner circumferential surface of the side wall, the joint outer circumferential surface of the cover, and the can connection portion of the current collecting plate are welded together.

[0065] Each of the engaging outer peripheral surface of the cover and the contact outer peripheral surface of the tank connection portion may face or contact the inner peripheral surface of the side wall in the radial direction.

[0066] End portions of the joining outer peripheral surface of the cover and the inner peripheral surface of the side wall in the axial direction may face or contact each other in the radial direction and be exposed to the outside in the axial direction.

[0067] The welded portion may be formed by laser irradiating the joint outer peripheral surface of the cover and the end portions of the inner peripheral surface of the side wall in the axial direction from the outside of the battery cell.

[0068] The cover may include a cover body, a reduced thickness portion, and an engagement portion disposed outward from a center in a radial direction.

[0069] In other words, the reduced thickness portion may be provided on the eccentric side of the cover main body, and the engaging portion may be provided on the eccentric side of the reduced thickness portion.

[0070] The engaging outer peripheral surface of the cover may be provided in the engaging portion.

[0071] A first thickness of the joining portion may be smaller than a second thickness of the cover body.

[0072] Therefore, the deformation of the cover caused by the internal pressure of the tank can be minimized by increasing the second thickness of the cover body occupying the overall shape of the cover, and the welding portion can be formed on the joining peripheral surface in the axial direction by controlling the axial dimension of the welding portion to the side wall (i.e., the joining peripheral surface), thereby increasing the strength of the cover itself and the connection strength of the cover to the side wall.

[0073] The fracture induction portion may be provided in the cap body having the second thickness. Therefore, when the internal pressure of the can rises, deformation may be concentrated in the fracture induction portion, thereby inducing fracture.

[0074] Beneficial effects

[0075] According to the present disclosure, the diameter of the fracture inducing portion of the cap can be increased, and as a result, the radial length of the centrifugal portion of the fracture inducing portion that remains attached to the can after fracture can be reduced. This increases the discharge area for gases and flames generated by thermal runaway, while minimizing bottlenecks caused by the remaining cap portion. Consequently, sidewall rupture can be prevented.

[0076] According to the present disclosure, because the inner diameter of the tank connection portion of the current collecting plate at the bottom of the tank is smaller than the diameter of the fracture inducing portion, direct contact between the gas and flame generated by thermal runaway and the side wall between the tank and the current collecting plate can be minimized. Consequently, side wall rupture in the tank can be prevented.

[0077] According to the present disclosure, since the axially extending portion of the tank connecting portion is joined to the inner peripheral surface of the side wall in an overlapping manner, the side wall of the corresponding region can be reinforced, thereby preventing the side wall from being broken.

[0078] According to the present disclosure, the radially extending portion of the tank connection portion can be positioned close to the electrode assembly via the axially extending portion of the tank connection portion, thereby minimizing direct contact or access of gas and flames with or to the sidewall located axially inward of the radially extending portion. Consequently, rupture of the sidewall can be prevented.

[0079] According to the present disclosure, it is possible to ensure the bondability (weldability) for bonding the side wall, the cover, and the current collecting plate together.

[0080] According to the present disclosure, it is possible to ensure stability in a process for joining (welding) the side walls, the cover, and the current collecting plate together.

[0081] According to the present disclosure, the assembly work of the battery cell can be significantly reduced by joining the side wall, the cover and the current collecting plate together.

[0082] In addition to the above-described effects, the effects of the present disclosure will be described in detail below together with the detailed description of the embodiments of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 It is a perspective view of a cylindrical battery cell according to an embodiment.

[0084] Figure 2 is to be accommodated in Figure 1 Exploded perspective view of the electrode assembly in the can before winding.

[0085] Figure 3 yes Figure 2 A three-dimensional view of the electrode assembly in a stacked state before winding.

[0086] Figure 4 By winding Figure 3A three-dimensional view of a cylindrical jellyroll-type electrode assembly in an assembled state with stacked pieces.

[0087] Figure 5 is a perspective view illustrating a first current collecting plate joined to an electrode tap of a first electrode of an electrode assembly.

[0088] Figure 6 is a perspective view showing a second current collecting plate joined to an electrode tap of a second electrode of an electrode assembly.

[0089] Figure 7 yes Figure 6 A perspective view of the second current collecting plate.

[0090] Figure 8 yes Figure 7 A cross-sectional view taken along line 8-8.

[0091] Figure 9 yes Figure 7 A cross-sectional view taken along line 9-9.

[0092] Figure 10 It is a depiction Figure 8 A perspective view of a cross-sectional portion.

[0093] Figure 11 is a side sectional view illustrating a process of housing an electrode assembly in a can, to which a current collecting plate is joined.

[0094] Figure 12 is a side sectional view illustrating a process of joining a first electrode terminal and a first current collecting plate of an electrode assembly accommodated in a can.

[0095] Figure 13 is a side sectional view illustrating a process of covering an open end portion of a can accommodating an electrode assembly with a cover.

[0096] Figure 14 and Figure 15 is a side sectional view showing a process of closing the injection port of the cap coupled to the side wall of the tank with a plug to close the open end.

[0097] Figure 16 and Figure 17 are top and bottom perspective views of a cover of an embodiment.

[0098] Figure 18 is Figure 15 An enlarged cross-sectional view of the area indicated by the dotted line at the open end of the battery cell.

[0099] Figure 19 When Figure 18 Cross-sectional views of a battery cell when viewed from different positions in the circumferential direction.

[0100] Figure 20 It shows Figure 19 Diagram of the discharge state of the fracture-induced partial fracture of the cover.

[0101] Figure 21 and Figure 22 A battery pack including the battery cell of the embodiment and a vehicle including the battery pack are shown.

[0102] Figure 23 It is a cross-sectional view of a fixing structure of a cover having a pressed edge portion and a curled edge portion.

[0103] Figure 24 It shows Figure 23 Diagram of the discharge state of the fracture-induced partial fracture of the cover. DETAILED DESCRIPTION

[0104] The above-mentioned objects, features and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art of the present disclosure will easily practice the technical aspects of the present disclosure. When describing the present disclosure, when it is determined that the detailed description of the relevant known technology may unnecessarily obscure the subject matter of the present disclosure, the detailed description will be omitted. Hereinafter, exemplary embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals are used to indicate the same or similar elements.

[0105] Although the terms first, second, etc. are used to describe various elements, these elements are not limited by these terms. These terms are used to distinguish one element from another element, and unless explicitly stated otherwise, the first element may be the second element.

[0106] Throughout the specification, unless explicitly stated otherwise, each element may be in the singular or in the plural.

[0107] The term “on (or under)” may mean that an element is placed in contact with an upper surface (or lower surface) of another element, and intervening elements may be present.

[0108] In addition, when an element is referred to as being “connected to,” “coupled to,” or “contacting” another element, it should be understood that the element may be directly connected to or contacting the other element, or there may be intervening elements, or each element may be “connected,” “coupled,” or “contacting” each other through another element.

[0109] Unless the context clearly indicates otherwise, the singular forms used herein include the plural forms. In this specification, the term "comprise" or "include" should not be interpreted as necessarily including all the elements or steps, and should be interpreted as excluding some elements or steps, or further including additional elements or steps.

[0110] Throughout the specification, "A" and / or "B" may refer to A or B or both, unless expressly stated otherwise, and "C to D" may refer to C or greater and D or less, unless expressly stated otherwise.

[0111] When describing the embodiments, the axial direction refers to the extension direction of the axis of the winding center forming the core-wound electrode assembly, the radial direction refers to the direction toward the axis (centripetal) or away from the axis (centrifugal), and the circumferential direction refers to the direction around the axis.

[0112] In addition, annular means circular or ring-shaped, “centrifugal” means a direction away from an axis forming a winding center of the jellyroll type electrode assembly, and “centripetal” means a direction toward an axis forming a winding center of the jellyroll type electrode assembly.

[0113] In the following, reference will be made to Figures 1 to 20 An embodiment of a battery cell having the sidewall anti-rupture structure of the present disclosure is described in detail.

[0114] The battery cell of the embodiment may be, for example, a cylindrical battery cell having a shape factor ratio (defined as a value obtained by dividing the diameter Φ of a cylindrical battery cell by its height H, ie, a height-to-diameter ratio) greater than about 0.4.

[0115] Here, the form factor refers to the value representing the diameter and height of a cylindrical battery cell. Cylindrical battery cells can be, for example, 46110 cells, 48750 cells, 48110 cells, 48800 cells, or 46800 cells. In the value representing the form factor, the first two digits represent the diameter of the cell, the next two digits represent the height of the cell, and the final digit, 0, indicates that the cell's cross-section is circular.

[0116] The battery cell may be a cylindrical battery cell having a generally cylindrical shape with a diameter of approximately 46 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0117] A battery cell according to another embodiment may be a cylindrical battery cell having a generally cylindrical shape with a diameter of approximately 48 mm, a height of approximately 75 mm, and a form factor ratio of 0.640.

[0118] A battery cell according to another embodiment may be a cylindrical battery cell having a generally cylindrical shape with a diameter of approximately 48 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0119] A battery cell according to another embodiment may be a cylindrical battery cell having a generally cylindrical shape with a diameter of approximately 48 mm, a height of approximately 80 mm, and a form factor ratio of 0.600.

[0120] A battery cell according to another embodiment may be a cylindrical battery cell having a generally cylindrical shape with a diameter of approximately 46 mm, a height of approximately 80 mm, and a form factor ratio of 0.575.

[0121] The present disclosure can also be applied to battery cells having a form factor ratio of about 0.4 or less, such as 18650 cells or 21700 cells. In the case of 18650 cells, the diameter is about 18 mm, the height is about 65 mm, and the form factor ratio is 0.277. In the case of 21700 cells, the diameter is about 21 mm, the height is about 70 mm, and the form factor ratio is 0.300.

[0122] The battery cell of the embodiment includes an electrode assembly 20 , current collecting plates 31 , 32 electrically connected to the electrode assembly 20 , and a can 10 accommodating the electrode assembly 20 and the current collecting plates 31 , 32 .

[0123] The can 10 includes a bottom 12 , a side wall 11 connected to the bottom 12 and extending in the axial direction, and an open end portion at one end of the side wall 11 in the axial direction.

[0124] The can 10 includes a lid 16 covering the open end.

[0125] The bottom 12 has a disk shape having a hole at the center, and the sidewall 11 may have a circular tube shape.

[0126] The bottom 12 and the side wall 11 can be manufactured by forming a metal plate with nickel plating on a steel surface by deep drawing and trimming using a punch while holding the end of the side wall 11 with a blank holder. The material of the can 10 is not limited thereto.

[0127] The first electrode terminal 13 may be fitted into the hole. The first electrode terminal 13 may be riveted to the bottom 12 with the gasket 14 interposed therebetween. The gasket 14 may be interposed between the first electrode terminal 13 and the bottom 12 to tightly seal the interior and exterior of the can 10, thereby preventing electrolyte leakage and electrically insulating the first electrode terminal 13 from the bottom 12.

[0128] However, the method for connecting the first electrode terminal 13 to the bottom 12 is not limited thereto. Any other method may be used, such as forming a seal between the first electrode terminal 13 and the bottom 12 and electrically insulating the first electrode terminal 13 from the bottom 12.

[0129] First electrode terminal 13 may have a first polarity, and can 10 may have a second polarity. That is, as described below, bottom 12 of can 10, sidewall 11 connected to bottom 12, and cover 16 connected to sidewall 11 may all have a second polarity.

[0130] Therefore, the battery cell can be positioned at the end where the bottom 12 is located in the axial direction (ie, Figure 1 The battery cell may have a first electrode terminal 13 and a second electrode terminal 15 at the closed end (as shown). Additionally, the battery cell may have a bus bar connected to the first electrode terminal 13 and a bus bar connected to the second electrode terminal 15 on the top of the battery cell. In one example, the first electrode terminal 13 may be a positive terminal and the second electrode terminal 15 may be a negative terminal, or vice versa.

[0131] The electrode assembly 20 is housed in the can 10. The electrode assembly 20 is manufactured by preparing the first electrode 21, the second electrode 22 and the separator 28. Figure 2 The first electrode 21, the separator 28, the second electrode 22 and the separator 28 are stacked in the order of the first electrode 21, the separator 28, the second electrode 22 and the separator 28 to form a Figure 3 and wound around a winding axis as shown; Figure 4 The first electrode 21 may be a positive electrode, and the second electrode 22 may be a negative electrode, or vice versa.

[0132] The first electrode 21 and the second electrode 22 are manufactured in a sheet shape. The electrode sheet is manufactured in such a manner that an active material layer 24 is coated on the surface of a metal foil 23. The electrode sheet has a coated area 25 coated with the active material layer 24 and an uncoated area 26 not coated with the active material layer 24. The positive electrode sheet has the uncoated area 26 on one side in the width direction, and the negative electrode sheet has the uncoated area 26 on the other side in the width direction.

[0133] The uncoated area 26 is exposed or protrudes from the stack in the width direction. The uncoated area 26 itself serves as the electrode tab 27.

[0134] In the uncoated region 26 , grooves may be formed at predetermined intervals to form flag-shaped slotted joints 27 .

[0135] In one embodiment, a slotted joint 27 having an equilateral trapezoidal shape is shown. However, the slotted joint 27 may have various shapes, such as a semicircular, semi-elliptical, triangular, rectangular, or parallelogram shape.

[0136] Furthermore, in one embodiment, the slotted joints 27 arranged along the length have the same width as shown. However, the slotted joints may widen gradually or stepwise in the outward direction.

[0137] Furthermore, in one embodiment, the height of the slotted joint 27 is shown increasing in an outward direction. However, the height of the slotted joint may be constant or gradually decreasing.

[0138] In addition, in one embodiment, as shown in the figure, there is no slotted joint 27 at a predetermined portion of the centrifugal end and a predetermined portion of the eccentric end of the uncoated region 26. However, there may be no slotted joint at the centrifugal end of the uncoated region, and there may be no slotted joint at the eccentric end of the uncoated region.

[0139] In the jelly jelly type electrode assembly 20, the slotted joint 27 may be bent and flattened in the radial direction, as shown in FIG. Figure 4 As shown. The slotted joint 27 can be bent in the centripetal direction or bent outward. In one embodiment, the slotted joint 27 is bent in the centripetal direction, as shown.

[0140] The slotted tabs 27 may be bent one by one during the process of winding the stack to form the jellyroll-type electrode assembly 20. Conversely, the slotted tabs 27 may be bent immediately after the stack is wound to form the jellyroll-type electrode assembly.

[0141] The slotted joints 27 of the first electrode 21 and the second electrode 22 that are bent and overlapped in the radial direction may respectively provide flat surfaces substantially perpendicular to the axial direction at both ends of the electrode assembly 20 in the axial direction.

[0142] like Figure 5 and Figure 6 As shown, the first and second current collecting plates 31 and 32 may be joined to substantially flat surfaces provided by bending slot joints 27 respectively exposed at both end portions in the axial direction.

[0143] In one embodiment, as shown in the figure, the first current collecting plate 31 is a positive electrode current collecting plate, and the second current collecting plate 32 is a negative electrode current collecting plate. The first current collecting plate 31 can be made of aluminum, and the second current collecting plate 32 can be made of copper.

[0144] The current collecting plates 31 , 32 may be manufactured by punching, trimming, piercing, and bending metal sheets.

[0145] Reference Figure 5 The first current collecting plate 31 has a terminal connection portion 312 extending radially from the center, an annular portion 313 connected to the centrifugal side edge of the terminal connection portion 312 in the circumferential direction, and an electrode connection portion 314 extending from the annular portion 313 in the centrifugal direction but not connected to the terminal connection portion 312. The central portion of the terminal connection portion 312 covers at least a portion of the winding core of the electrode assembly 20.

[0146] Before placing the electrode assembly 20 in the can 10, the electrode connection portion 314 may be joined to the slotted tab 27 of the first electrode 21 of the electrode assembly 20 by laser welding. The weld line of the laser may extend radially.

[0147] refer to Figures 6 to 9 The second current collecting plate 32 includes a main body portion 320 connected to the electrode tab 27 of the electrode assembly 20 and an outer annular can connection portion 324 provided around the edge of the second current collecting plate 32 on a side more eccentric than the main body portion 320. The annular can connection portion 324 is spaced apart from the main body portion 320 in the radial direction.

[0148] The second current collecting plate 32 includes a bridge 33 connected to a body portion 320 on the centripetal side and a tank connection portion 324 on the centrifugal side.

[0149] The main body portion 320 includes an inner ring portion 321 defining a hole 322 corresponding to the winding core of the electrode assembly 20 and disposed around the winding core, and an electrode tab connection portion 323 extending radially from the inner ring portion 321. The main body portion 320 can be welded and electrically connected to the electrode tab 27 of the electrode assembly 20 by laser irradiation of the electrode tab connection portion 323.

[0150] Before placing the electrode assembly 20 in the can 10, the electrode tab connection portion 323 may be joined to the slotted tab 27 of the second electrode 22 of the electrode assembly 20 by laser welding. The weld line of the laser may extend radially.

[0151] The tank connection portion 324 is electrically connected to the body portion 320 through a bridge 33 extending in the radial direction.

[0152] The tank connection portion 324 includes a radially extending portion 3242 extending in the radial direction, a bent portion 327 provided at a centrifugal-side end portion of the radially extending portion 3242 , and an axially extending portion 3241 extending outward from the bent portion 327 in the axial direction.

[0153] The bridges 33 may alternate with the electrode tap connection portions 323 in the circumferential direction. The bridges 33 may be connected to the inner ring portion 321 .

[0154] like Figure 11 and Figure 12 As shown, the electrode assembly 20 is housed in the can 10, and the first current collecting plate 31 is aligned toward the bottom 12 of the can 10. In this case, the insulator 19 is interposed between the first current collecting plate 31 and the bottom 12 of the can 10 to electrically insulate the first current collecting plate 31 from the bottom 12.

[0155] In addition, the terminal connection portion 312 of the first current collecting 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 device used to weld the first current collecting plate 31 and the first electrode terminal 13 can perform welding from the open end of the can 10 toward the rear surface of the center of the terminal connection portion 312 of the first current collecting plate 31 through the winding core of the electrode assembly 20. Furthermore, the first current collecting plate 31 and the first electrode terminal 13 can be joined by brazing or soldering. In other words, any other method of electrically connecting and fixing the first current collecting plate 31 and the first electrode terminal 13 can be used.

[0156] In a state where the electrode assembly 20 is accommodated in the can 10, the electrode tab 27 of the second electrode 22 and the second current collecting plate 32 are placed to face the open end of the side wall 11. In addition, the outer circumferential surface of the second current collecting plate 32 and the inner circumferential surface of the side wall 11 are tightly fitted into contact with each other.

[0157] After the first current collecting plate 31 and the first electrode terminal 13 are joined, Figure 13 and Figure 14 As shown, the open end of the side wall 11 is covered by a cover 16 and completed by seam welding, and then the electrolyte is injected into the tank 10 through an injection port 18 at the center of the cover 16.

[0158] After the electrolyte is injected, the injection port 18 can be closed by the plug 40, as shown in FIG. Figure 14 and Figure 15 shown.

[0159] The welding structure of the present disclosure can be applied to a cover without an injection port. Therefore, electrolyte injection can be performed before covering the open end of the side wall 11 with the cover 16, and the open end can be covered with the cover 16 after the electrolyte injection is completed.

[0160] like Figure 18 As shown, the edge of the lid 16 and the edge of the sidewall 11 may be joined by laser welding to seal the can 10 .

[0161] The tank connection portion 324 provided at the edge of the second current collecting plate 32 and contacting and electrically connected to the tank 10 includes a first region facing or contacting the inner circumferential surface of the sidewall 11. The first region has a contact outer circumferential surface 325 facing or contacting the inner circumferential surface of the sidewall 11 in a radial direction.

[0162] The tank connection portion 324 includes a second region that contacts the cover 16. The second region has a cover contact surface 326 that faces and contacts the inner surface of the cover 16 in the axial direction.

[0163] The first region and the second region are located at the axially extending portion 3241 of the tank connecting portion 324 .

[0164] The axially extending portion 3241 of the tank connection portion 324 is axially connected to the outer side of the bent portion 327 and has a shape extending axially outward from the bent portion 327. Therefore, the area contacting the outer circumferential surface 325 and the axial length of the second current collecting plate 32 can be increased.

[0165] The material of the second current collecting plate 32 may be softer than that of the sidewall 11 .

[0166] The thermal conductivity of the second current collecting plate 32 may be higher than the thermal conductivity of the sidewall 11 .

[0167] For example, the material of the second current collecting plate 32 may include copper, and the material of the sidewall 11 may include iron.

[0168] The outer diameter of the contact outer peripheral surface 325 of the tank connection portion 324 is set to be equal to or larger than the inner diameter of the inner peripheral surface of at least a portion of the side wall 11 in the axial direction.

[0169] Therefore, during the insertion of the second current collecting plate 32 , the bent portion 327 is elastically deformed, and the contact outer circumferential surface 325 and the inner circumferential surface of the sidewall 11 are forced to closely contact each other in the radial direction.

[0170] When the bent portion 327 receives a force in the centripetal direction and is elastically deformed, the radially extending portion 3242 of the tank connecting portion 324 supports the outside of the tank connecting portion 324 .

[0171] The curved portion 327 provides a curved surface with a gradually decreasing outer diameter below the outer diameter of the axially extending portion 3241 of the tank connection portion 324. Therefore, during the insertion of the second current collecting plate 32 into the inner space of the sidewall 11, the force fit between the tank connection portion 324 and the inner circumferential surface of the sidewall 11 can be guided.

[0172] Reference Figures 16 to 20 The cover 16 includes a cover body 160, a thickness-reduced portion 161, and a joining portion 17, which are arranged in order from the center outward in the radial direction. That is, the thickness-reduced portion 161 is provided at the centrifugal side of the cover body 160, and the joining portion 17 is provided at the centrifugal side of the thickness-reduced portion 161.

[0173] The engaging portion 17 of the cover 16 has an engaging outer peripheral surface 171 that very closely faces or contacts the inner peripheral surface of the side wall 11 in the radial direction. In addition, the inner surface of the engaging portion 17 of the cover 16 in the axial direction has a current collecting plate contact surface 173 that faces and contacts the cover contact surface 326 of the tank connecting portion 324 of the second current collecting plate 32 in the axial direction.

[0174] The reduced thickness portion 161 is a portion where the thickness of the cover 16 varies.

[0175] When the reduced thickness portion 161 is provided at an appropriately selected position so that at least a portion of the reduced thickness portion 161 can contact the second current collecting plate 32, during the insertion of the cover 16, the reduced thickness portion 161 of the cover 16 contacts the second current collecting plate 32, and the center of the cover 16 is aligned. In one embodiment, to enhance the alignment effect, the reduced thickness portion 161 is in the shape of an inclined surface that extends outward in the axial direction as it travels toward the centrifugal side.

[0176] During the insertion of the cap 16 into the side wall 11, the inclined surface-shaped reduced thickness portion 161 contacts the centripetal side edge of the cap contact surface 326. Therefore, the outer end portion of the tank connection portion 324 of the second current collecting plate 32 having the cap contact surface 326 in the axial direction can be pressed by the reduced thickness portion 161 in the centrifugal direction and move closer to or become closer to the inner circumferential surface of the side wall 11.

[0177] Additionally, in the axial direction, the cap contact surface 326 located on the outer end surface of the tank connection portion 324 of the second current collecting plate 32 axially contacts the current collecting plate contact surface 173 located on the inner surface of the engagement portion 17 of the cap 16. According to this assembly structure, the insertion depth of the cap 16 can be precisely adjusted by the height of the second current collecting plate 32, which can depend on the extension length of the tank connection portion 324 in the axial direction.

[0178] In the battery cell, in the contact area between the side wall 11, the cover 16 and the second current collecting plate 32, a welding portion W is formed where the inner circumferential surface of the side wall 11, the joint outer circumferential surface 171 of the cover 16 and the axial extension portion 3241 of the tank connecting portion 324 of the second current collecting plate 32 are welded together.

[0179] As shown in the drawings, the joint outer peripheral surface 171 of the cover 16 and the end portion of the inner peripheral surface of the side wall 11 in the axial direction are in contact with each other in the radial direction and are exposed to the outside in the axial direction.

[0180] The weld portion W is formed by laser irradiating the joint outer peripheral surface 171 of the cover 16 and the end portion of the second inner peripheral surface 115 of the side wall 11 in the axial direction from the outside of the battery cell in the axial direction.

[0181] The weld portion W includes a joint portion between at least a portion of the inner circumferential surface of the sidewall 11 and at least a portion of the contact outer circumferential surface 325 of the current collecting plate 32, a joint portion between at least a portion of the inner circumferential surface of the sidewall 11 and at least a portion of the contact outer circumferential surface 171 of the cover 16, and a joint portion between at least a portion of the cover contact surface 326 of the current collecting plate 32 and at least a portion of the current collecting plate contact surface 173 of the cover 16. Preferably, the entire contact outer circumferential surface 171 of the cover 16 can be welded. That is, the weld portion W can be formed by triple welding.

[0182] The contact area of ​​the side wall 11 and the cover 16 is heated to a high temperature by the irradiated laser light L to form a welded portion W.

[0183] Therefore, the heat generated by the laser from the side wall 11 can be quickly diffused and conducted through the second current collecting plate 32 having a wider contact area, and the heat generated by the laser from the cover 16 can be diffused and conducted more slowly through the second current collecting plate 32 having a narrower contact area. Therefore, the melting of the side wall 11, which is thinner than the joint portion 17 of the cover 16, can be slowed down.

[0184] Furthermore, since most of the welding heat transferred through the sidewall 11 is diffused through the second current collecting plate 32 , heat transfer to the separator 28 of the electrode assembly 20 in contact with the inner circumferential surface of the sidewall 11 may be reduced.

[0185] In addition, as described above, in the cover 16, the first thickness of the joint portion 17 is smaller than the second thickness of the cover body 160 measured in the axial direction. Therefore, the weld depth between the cover 16 and the side wall 11 is determined by the first thickness, and the resistance to bulging in the cover 16 caused by the internal pressure rise due to thermal runaway of the tank 10 is determined by the second thickness.

[0186] According to the present disclosure, even when the cover 16 and the side wall 11 are welded as deep as the first thickness, the contact area of ​​the cover 16 and the side wall 11 can be fully joined and connected, thereby preventing stress concentration in the event of bulging, and the thicker cover body 160 with the second thickness can have greater bulging resistance.

[0187] Furthermore, according to the present disclosure, the reduced-thickness portion 161 of the lid 16, which interacts with the tank connection portion 324 during assembly, is located centripetally relative to the engaging outer peripheral surface 171 and has the same radial thickness as the tank connection portion 324. This increases the area of ​​the lid body 160 having the second thickness, further enhancing bulging resistance. Since the second current collecting plate 32 is typically manufactured through a forming process involving pressing a thin metal sheet, it should be understood that the reduced-thickness portion 161 can be positioned very close to the centrifugal edge of the lid 16.

[0188] Cover 16 has an annular fracture inducing portion 165 substantially concentric with the edge of cover 16. Fracture inducing portion 165 may be defined as a grooved portion having a small thickness in each of a surface of cover 16 and an opposite surface thereof.

[0189] Fracture inducing portion 165 may be provided adjacent to the edge of lid 16. According to one embodiment, sidewall 11 extends in the axial direction, and the end portion of sidewall 11 in the axial direction is welded to the edge of lid 16 in an unbent state in the centripetal direction. Therefore, the joined portion of can 10 and lid 16 occupies almost no space in the radial direction. Therefore, fracture inducing portion 165 may be provided adjacent to the edge of lid 16.

[0190] The larger the diameter of fracture inducing portion 165, the greater the Figure 20 The radial area of ​​the cover 16 connected to the remainder C of the tank 10 when ruptured in the illustrated thermal runaway scenario is smaller. Thus, bottlenecks where gases and flames are not immediately vented and remain in the interior space of the tank during venting can be minimized or eliminated.

[0191] Therefore, flames are prevented from directly contacting the side walls 11, thereby preventing side wall rupture and thermal runaway from propagating to other adjacent cylindrical battery cells during gas and flame discharge in the event of thermal runaway occurring in any battery cell of the battery pack.

[0192] The ratio of the diameter of fracture inducing portion 165 to the diameter of can 10 may be equal to or greater than 38 / 46. Obviously, this ratio is less than 1.

[0193] Preferably, the diameter ratio may be equal to or greater than 40 / 46. Experimental results have shown that, in a structure in which the edge of the lid 16 is connected to the can 10 in a plane perpendicular to the sidewall, when the ratio is equal to or greater than 38 / 46, sidewall rupture does not occur during discharge. Furthermore, when the ratio is equal to or greater than 40 / 46, it was confirmed that no bottleneck occurs during discharge, thereby preventing direct contact of the flame with the sidewall.

[0194] Fracture inducing portion 165 of cover 16 may be positioned radially outward from the centripetal edge of tank connection portion 324 of second current collecting plate 32. During discharge, when tank connection portion 324 extends further in the centripetal direction than fracture inducing portion 165 of cover 16, gas and flame are released near the centripetal edge of tank connection portion 324, and little or no oxygen flows axially into the interior space of tank connection portion 324. Consequently, direct contact of the flame with sidewall 11 axially inward from tank connection portion 324 can be minimized.

[0195] The ratio of the inner diameter of the centripetal side edge of the radially extending portion 3242 of the tank connecting portion 324 to the diameter of the tank 10 may be equal to or less than 42 / 46. Preferably, the ratio may be equal to or less than 40 / 46.

[0196] When the ratio of the inner diameter of the radial extension portion 3242 is equal to or greater than 42 / 46, it is impossible to sufficiently increase the length of the radial extension portion 3242, so when tightly fitting the inner periphery of the side wall 11 of the tank 10 and the second collecting plate 32, the radial extension portion 3242 alone is insufficient to support the axial extension portion 3241 in the centrifugal direction, and it is difficult to avoid direct contact between the flame and the side wall in the event of thermal runaway.

[0197] The ratio of the inner diameter of the centripetal side edge of the radially extending portion 3242 of the tank connecting portion 324 to the diameter of the tank 10 may be equal to or greater than 36 / 46. Preferably, the ratio may be equal to or greater than 38 / 46. When the ratio is less than 36 / 46, the release of gas and flame may be hindered during discharge.

[0198] According to the present disclosure, the distance between the radially extending portion 3242 of the tank connecting portion 324 and the tank 10 can be defined by the extension length of the axially extending portion 3241 of the tank connecting portion 324. Therefore, the distance in the axial direction between the radially extending portion 3242 and the electrode assembly 20 can be adjusted. As the distance between the radially extending portion 3242 and the electrode assembly 20 increases, the effect of the welding heat of the tank 10 and the cover 16 on the electrode assembly 20 may decrease, but the sidewall 11 between the radially extending portion 3242 and the electrode assembly 20 in the axial direction is more likely to be directly exposed to the flame during discharge.

[0199] According to the present disclosure, the length of the axial extension portion 3241 can be determined within a range where the welding heat of the can 10 and the cover 16 does not affect the electrode assembly 20, and the portion of the side wall 11 that is further inward in the axial direction than the radial extension portion 3242 is not exposed to the flame during discharge, so as to avoid the influence of the welding heat on the electrode assembly 20 and prevent the side wall 11 from being exposed to the flame during discharge.

[0200] In addition, when the axially extending portion 3241 is joined to the sidewall 11 of the tank 10 between the radially extending portion 3242 and the tank 10 , the tank connecting portion 324 can prevent the flame from directly contacting the sidewall 11 .

[0201] The battery cell 72 having the assembled structure of the second current collecting plate, the cover, and the can as described above may be housed in the case 71 of the battery pack 70, as shown in FIG. Figure 21 The battery pack 70 may be formed using the battery modules as an intermediate form of components, or the battery pack 70 may be directly formed without the battery modules shown.

[0202] Because the battery cells 72 themselves are large, intermediate structures or battery modules may not be used to manufacture the battery pack 70. Furthermore, the battery cells 72 have low internal resistance and high energy density. Therefore, the energy density of the battery pack 70 including the battery cells 72 can be higher.

[0203] According to the present disclosure, it is possible to ensure sufficient energy density of the battery cells 72 and prevent sidewall rupture in the event of thermal runaway caused by abnormal operation of the battery cells, thereby preventing the thermal runaway from propagating to adjacent battery cells. Therefore, even when a battery pack is formed directly from battery cells without intermediate modules, it is possible to prevent thermal runaway from propagating throughout the entire battery pack.

[0204] The battery pack 70 with improved safety and higher energy density can reduce the volume and weight of the same energy storage capacity. Therefore, when the battery pack 70 including the battery cells 72 is installed on a vehicle 80 using electricity as an energy source, such as Figure 22 As shown, the vehicle's mileage relative to energy can be increased.

[0205] The above embodiments are provided for the purpose of illustration, but are not intended to be limiting, and the scope of the present disclosure will be limited by the appended claims rather than the foregoing description. In addition, it should be understood that all possible changes and modifications of the meaning and scope of the appended claims and their equivalent concepts are included within the scope of the present disclosure.

[0206] Although the present disclosure has been described with reference to the accompanying drawings illustrating the present disclosure, the present disclosure is not limited to the disclosed embodiments and drawings, and it is apparent that various modifications can be made thereto by those skilled in the art within the scope of the technical aspects of the present disclosure. In addition, when describing the embodiments of the present disclosure, even if the technical effects of the configuration of the present disclosure are not explicitly described in the preceding description, it should be acknowledged that the predictable effects from the corresponding configurations can be obtained.

[0207] [Reference Number List]

[0208] 10: Can

[0209] 11: Sidewall

[0210] 117: Edge pressing part

[0211] 118: Curled part

[0212] 12: Bottom

[0213] 13: First electrode terminal (positive terminal)

[0214] 14: Padding

[0215] 15: Second electrode terminal

[0216] 16: Cover

[0217] 160: Cover body

[0218] 161: Thickness reduction part

[0219] 165: Fracture induction part

[0220] 169: Padding

[0221] 17: Joint

[0222] 171: Joining peripheral surface

[0223] 173: Collector plate contact surface

[0224] 18: Injection port

[0225] 19: Insulator

[0226] 20: Electrode assembly

[0227] 21: First electrode

[0228] 22: Second electrode

[0229] 23: Metal foil

[0230] 24: Active material layer

[0231] 25: coating part

[0232] 26: Uncoated part

[0233] 27: Electrode connector (slotted connector)

[0234] 28: Diaphragm

[0235] 31: First current collecting plate (positive current collecting plate)

[0236] 312: Terminal connection part

[0237] 313: Ring part

[0238] 314: Electrode connection part

[0239] 32: Second current collecting plate (negative current collecting plate)

[0240] 320: Main part

[0241] 321: Inner ring

[0242] 322: Hole

[0243] 323: Electrode connector connection part

[0244] 324: Tank connection part

[0245] 3241: Axial extension

[0246] 3242: radial extension

[0247] 325: Contact with peripheral surface

[0248] 326: Cover contact surface

[0249] 327: curved part

[0250] 33: Bridge piece

[0251] 40: Plug

[0252] W: welding part

[0253] 70: Battery Pack

[0254] 71: Shell

[0255] 72: Battery cells

[0256] 80: Vehicle

Claims

1. A battery cell, comprising: A can comprising: a side wall extending in an axial direction; an open end portion at an end portion of the side wall in the axial direction; and a cover covering the open end portion; an electrode assembly housed in the can; and a current collecting plate electrically connecting the electrode assembly and the can, wherein the edge of the cover is joined to the end of the side wall in the axial direction, wherein the cover includes an annular fracture inducing portion concentric with the edge of the cover, Wherein, the current collecting plate comprises: a main body portion connected to an electrode connector of the electrode assembly; an annular tank connection portion disposed on a more eccentric side than the main body portion and joined to at least one of the side wall or the cover; and a bridge having a centripetal side connected to the main body portion and a centrifugal side connected to the tank connection portion, the bridge extending in a radial direction, and The rupture inducing portion of the cover is provided at a position further outward than a centripetal side edge of the tank connecting portion in the radial direction.

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

3. The battery cell according to claim 1, in, A ratio of a diameter of the fracture inducing portion to a diameter of the battery cell is equal to or greater than 38 / 46.

4. The battery cell according to claim 1, in, The tank connecting portion is joined to the tank or the side wall by welding, brazing or soldering.

5. The battery cell according to claim 1, in, The joining method of the tank connecting portion and the tank or the side wall corresponds to the joining method of the cover and the side wall.

6. The battery cell according to claim 1, in, A ratio of an inner diameter of the centripetal side edge of the can connecting portion to a diameter of the battery cell is equal to or less than 40 / 46.

7. The battery cell according to claim 1, in, The tank connection part includes: a radially extending portion extending in a radial direction; an axially extending portion extending in the axial direction from a centrifugal end portion of the radially extending portion; a contact outer peripheral surface defined by an outer peripheral surface of the axially extending portion and facing and contacting an inner peripheral surface of the side wall; and A cover contact surface is defined by an outer end surface of the axially extending portion in the axial direction and faces and contacts an inner surface of the cover in the axial direction.

8. The battery cell according to claim 7, in, The cover includes a current collecting plate contact surface defined by the inner surface in the axial direction and facing and contacting the cover contact surface of the can connecting portion of the current collecting plate in the axial direction.

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