Battery pack with current interruption device using bimetal and method of operating same

Abstract

The present invention provides a battery pack and an operating method thereof, comprising: a pack case; a plurality of cylindrical battery cells disposed within the pack case; and a current interruption device disposed within the pack case to connect the plurality of cylindrical battery cells, the current interruption device being partially made of a bimetal, the current interruption device comprising: a fixed end bonded to an electrode terminal of a cylindrical battery cell; a free end that contacts the electrode terminal of a surrounding cylindrical battery cell; and an elastic member that biases the free end toward the surrounding cylindrical battery cell. The present invention also provides a battery pack and an operating method thereof, comprising a current interruption device using a bimetal that enables a battery cell that has been separated from its surroundings due to an abnormality to quickly restore connection with its surroundings when the state of the battery cell is restored.

Description

[Technical Field]

[0001] The present invention relates to a battery pack having a current interruption device using a bimetal and an operating method thereof, and more particularly to a battery pack having a current interruption device using a bimetal that can quickly restore connection with its surroundings when a battery cell that has been separated from its surroundings due to an abnormal state is restored, and an operating method thereof. [Background technology]

[0002] To meet the output and capacity requirements of large electronic devices such as electric vehicles, a large-capacity battery pack in which multiple battery cells are grouped and electrically connected is required. Such a battery pack includes a bus bar made of a metal plate material that electrically connects the multiple battery cells.

[0003] However, if an abnormality occurs in any one of the battery cells while they are operating, the remaining battery cells may become unstable. Therefore, when a large-capacity battery pack is constructed by grouping the battery cells, various current interruption structures are provided between the bus bars and the battery cells.

[0004] For example, Patent Document 1 listed below discloses a metal member that is designed to be disconnected at high temperatures as a current interruption structure. The metal member is provided between the bus bar and the electrode terminal of the battery cell, and is designed to be disconnected if an abnormality occurs in the battery cell and the temperature rises suddenly, mechanically separating the bus bar from the battery cell in question.

[0005] However, such a conventional current interruption structure has the disadvantage of being difficult to reuse. For example, even if the battery cell recovers after a predetermined time has passed, the recovered battery cell cannot be reused unless the battery pack is opened and the broken metal member is replaced.

[0006] The technology behind the present invention is disclosed in the following patent documents. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Republic of Korea Patent Publication No. 10-2018-0064221 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a reusable battery pack having a bimetallic current interrupt device and a method of operating the same.

[0009] The present invention provides a battery pack having a current interruption device using a bimetal that can quickly restore connection with the surroundings when the state of a battery cell that has been isolated from the surroundings due to an abnormality is restored, and a method for operating the same. [Means for solving the problem]

[0010] A battery pack with a current interruption device using a bimetal according to an embodiment of the present invention includes a pack case, a plurality of cylindrical battery cells arranged in the pack case, and a current interruption device arranged in the pack case to connect the plurality of cylindrical battery cells, the current interruption device being partially made of a bimetal, wherein the current interruption device includes a fixed end that contacts an electrode terminal of a cylindrical battery cell, a free end that contacts an electrode terminal of a surrounding cylindrical battery cell, and an elastic member that urges the free end toward the surrounding cylindrical battery cell, and the free end is fixed to the bimetal, and contact with the electrode terminal of the cylindrical battery cell is turned on / off according to a change in shape of the bimetal.

[0011] The fixed end and the free end may be arranged to face each other in a direction in which the plurality of cylindrical battery cells are arranged, and the elastic member and the free end may be arranged to face each other in a direction intersecting the direction in which the plurality of cylindrical battery cells are arranged.

[0012] The fixed end may have a surface that is bonded to the electrode terminal of the cylindrical battery cell by welding, and the free end may have a surface that is biased to contact the electrode terminal of the surrounding cylindrical battery cell.

[0013] The bimetal portion of the current interrupting device may be disposed between the plurality of cylindrical battery cells and the inner surface of the pack case such that a portion that expands due to heat faces a cylindrical battery cell and a surrounding cylindrical battery cell and a portion that is bent due to heat faces the inner surface of the pack case, the fixed end and the free end being disposed at the portion of the bimetal portion of the current interrupting device that expands due to heat, and the elastic member being disposed at the portion of the bimetal portion that is bent due to heat.

[0014] The current interruption device may include a bus bar including a plurality of materials expandable and contractible by heat, the bus bar being arranged above the cylindrical battery cell and the surrounding cylindrical battery cell; the fixed end extending from one side of the bus bar and being bonded to an electrode terminal of the cylindrical battery cell; the free end extending from the other side opposite to the one side of the bus bar and being in contact with the electrode terminal of the surrounding cylindrical battery cell; and the elastic member between the bus bar and an upper surface of the pack case, supporting the other side of the bus bar on the upper surface of the pack case.

[0015] The bus bar may be formed from a bimetal having an upper layer and a lower layer with different thermal expansion coefficients, the thermal expansion coefficient of the lower layer being greater than the thermal expansion coefficient of the upper layer, the fixed end and free end extending downward from the lower layer and spaced apart horizontally, and the elastic member supported by the upper layer so as to be spaced apart above the free end.

[0016] The elastic member may include an elastic spring whose elastic force is smaller than the expansion force of the bus bar.

[0017] The current interruption device may further include a transmission member arranged to thermally connect at least one of the bus bar, the fixed end, and the free end to the surrounding cylindrical battery cell.

[0018] A method for operating a battery pack having a current interruption device using a bimetal according to an embodiment of the present invention includes the steps of: connecting an electrode terminal of a cylindrical battery cell arranged in a pack case and an electrode terminal of a surrounding cylindrical battery cell to a fixed end and a free end arranged in the current interruption device; bending a bimetal portion arranged in the current interruption device to separate the free end from the electrode terminal of the surrounding cylindrical battery cell when heat of a predetermined value or more is transferred from either the cylindrical battery cell or the surrounding cylindrical battery cell; and restoring the bimetal portion to restore the connection between the free end and the electrode terminal of the surrounding cylindrical battery cell when the heat transferred to the bimetal portion is eliminated.

[0019] The separating step may include bending the bimetal portion around the fixed end in a direction away from the electrode terminal of the surrounding cylindrical battery cell.

[0020] The step of separating the bimetal portion may include a step of shortening an elastic member connected to the bimetal portion using the bending.

[0021] The recovering step may include a step in which an elastic member expands to bias the bent portion of the bimetal portion and press a free end supported by the bent portion against the electrode terminal of the surrounding cylindrical battery cell. [Effects of the Invention]

[0022] According to an embodiment of the present invention, a current interruption device can connect multiple battery cells to each other by expanding the shape of the current interruption device when heat is transferred from a battery cell whose temperature has risen due to an abnormality, thereby separating the battery cell from its surroundings, and then contracting the shape of the current interruption device when the heat is released, thereby connecting the battery cell to its surroundings.

[0023] In addition, the current interruption device is formed so that the portion whose shape expands and contracts can be biased, and thus when the heat is released, the device can be tightly attached to the electrode terminal of the battery cell using both the restoring force caused by the contraction of the shape and the load caused by the biasing, thereby stably connecting the battery cell to its surroundings.

[0024] This allows the current interruption device to be quickly separated from a battery cell whose temperature has risen due to an abnormality or from the surrounding battery cells connected to that battery cell, and when the condition of the battery cell recovers and the temperature drops, the battery cell can be stably reconnected to the surrounding battery cells.

[0025] Therefore, when the abnormality in the state of the battery cell is resolved, the battery cell and the current interruption device connected thereto can be reused without having to disassemble the battery pack incorporating the abnormal battery cell. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a diagram showing a battery pack according to an embodiment of the present invention; [Figure 2]1 is a diagram showing a current interruption device according to an embodiment of the present invention; [Figure 3] 1 is a diagram showing the inside of a battery pack according to an embodiment of the present invention; [Figure 4] 1 is a diagram showing a state in which a current interruption device according to an embodiment of the present invention passes a current; [Figure 5] 1A and 1B are diagrams illustrating how a current interruption device according to an embodiment of the present invention interrupts a current. [Figure 6] 10A and 10B are diagrams illustrating how a current interruption device according to a modified example of the present invention interrupts a current. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various different forms. The embodiments of the present invention are provided solely to complete the disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art. In order to explain the present invention, the drawings may be exaggerated, and parts irrelevant to the description may be omitted from the drawings. In the drawings, the same reference numerals refer to the same components.

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a battery pack having a current interruption device using a bimetal and an operating method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0029] 1. Battery pack according to an embodiment of the present invention 1 is a diagram showing a battery pack according to an embodiment of the present invention, and a battery pack according to an embodiment of the present invention will be described with reference to FIG.

[0030] A battery pack according to an embodiment of the present invention is a battery pack having a current interruption device using a bimetal, and comprises a pack case 100, a plurality of cylindrical battery cells 200 arranged in the pack case 100, and a current interruption device 300, part of which is made of a bimetal, arranged in the pack case 100 so as to connect the plurality of cylindrical battery cells 200.

[0031] In addition, the battery pack according to an embodiment of the present invention may include a connecting member 400 made of a conductive material and arranged in the pack case 100 to connect the plurality of cylindrical battery cells 200 on the opposite side of the current interruption device 300, a cooling member 500 thermally connected to the plurality of cylindrical battery cells 200 via the connecting member 400, a heat transfer member 600 interposed between the cooling member 500 and the connecting member 400 to facilitate heat transfer, and a cell holder (not shown) formed to fix the plurality of cylindrical battery cells 200 inside the pack case 100.

[0032] 1.1. Pack Case 100 The pack case 100 may have an internal space that can accommodate a plurality of cylindrical battery cells 200. The pack case 100 may be a rectangular cylindrical shape. Needless to say, the shape can be changed in various ways.

[0033] 1.2. A plurality of cylindrical battery cells 200 To increase the output and capacity of the battery pack, a plurality of cylindrical battery cells 200 may be disposed inside the pack case 100 of the battery pack. The plurality of cylindrical battery cells 200 may include secondary battery cells.

[0034] The secondary battery cell may be configured such that a separator is interposed between a positive electrode plate having a positive electrode tab attached thereto and a negative electrode plate having a negative electrode tab attached thereto, and the positive electrode plate, the separator, and the negative electrode plate are wound into a jelly roll shape and the electrode assembly is housed inside a cell case. The secondary battery cell may have electrode terminals formed on one side and the other side opposite the one side. In this case, if a positive electrode terminal is formed on one side of the secondary battery cell, a negative electrode terminal may be formed on the other side opposite the one side.

[0035] The plurality of cylindrical battery cells 200 may be arranged in a row direction and a column direction. In this case, the cylindrical battery cells arranged in the row direction may be housed inside the pack case 100 such that the positive electrode terminals and negative electrode terminals are alternately arranged on top, and the cylindrical battery cells arranged in the column direction have the same electrode terminals arranged on top. The plurality of cylindrical battery cells 200 may be connected in series in the row direction and in parallel in the column direction. Meanwhile, the row direction may be referred to as the left-right direction, and the column direction may be referred to as the front-rear direction. The left-right direction and the front-rear direction may be collectively referred to as the horizontal direction.

[0036] 1.3. Current Interrupter 300 2 is a diagram showing a current interruption device according to an embodiment of the present invention, and the current interruption device according to an embodiment of the present invention will be described with reference to FIG.

[0037] The current interruption device 300 is a current interruption device 300 for electrically connecting a plurality of cylindrical battery cells 200, and may be arranged above the plurality of cylindrical battery cells 200, or a plurality of current interruption devices 300 may be arranged inside the pack case 100 such that one current interruption device 300 is provided for every two cylindrical battery cells arranged in the left-right direction.

[0038] The current interruption device 300 may be partially formed from a bimetal, and when an abnormality occurs in at least one of the two cylindrical battery cells connected to the current interruption device and the temperature rises, the bimetal portion may be deformed to separate from one of the two cylindrical battery cells, thereby interrupting the electrical connection between them. Needless to say, when the state of the two cylindrical battery cells connected to the current interruption device is restored and the temperature drops, the bimetal portion may be restored to its original state, thereby restoring the electrical connection between the two cylindrical battery cells.

[0039] 1.4. Details of the Structure of the Current Interruption Device 300 FIG. 3 is a view showing the inside of the battery pack according to the embodiment of the present invention.

[0040] Referring to FIG. 3 , the current interruption device 300 includes a fixed end 320 that is adhered to the electrode terminal of the cylindrical battery cell 210, a free end 330 that contacts the electrode terminal of the surrounding cylindrical battery cell 220, and an elastic member 340 that biases the free end 330 toward the surrounding cylindrical battery cell 220.

[0041] In this case, the fixed end 320 and the free end 330 may be arranged to face each other in a direction in which the plurality of cylindrical battery cells 200 are arranged, and the elastic member 340 and the free end 330 may be arranged to face each other in a direction intersecting the direction in which the plurality of cylindrical battery cells 200 are arranged. That is, the fixed end 320 and the free end 330 may be arranged to face each other in a horizontal direction, and the elastic member 340 and the free end 330 may be arranged to face each other in a vertical direction intersecting the horizontal direction.

[0042] The fixed end 320 may also be referred to as a "fixed lead." The fixed end 320 may have a surface 321 that is bonded to an electrode terminal of a cylindrical battery cell by welding. The free end 330 may also be referred to as a "free lead." The free end 330 may have a surface that comes into contact with the electrode terminal of the surrounding cylindrical battery cell 220 when biased. In this case, when the bimetal portion is bent due to thermal deformation, the biasing force of the bimetal portion may be greater than the force biasing the free end 330. Note that when the heat is removed from the bimetal portion and the bimetal portion is restored, the biasing force may bias the free end 330 downward together with the restoring force of the bimetal portion.

[0043] The bimetal portion may be formed from a bus bar 310. The bus bar 310 may be disposed between the plurality of cylindrical battery cells 200 and the inner surface of the upper wall 100a of the pack case 100, with the lower layer 312, which is a portion that expands due to heat, facing the cylindrical battery cell 210 and the surrounding cylindrical battery cell 220, and the upper layer 311, which is a portion that is bent due to heat, facing the inner surface of the upper wall 100a of the pack case 100. When heat is transferred, the lower layer 312 may expand and the upper layer 311 may be bent so that a portion where the free end 330 is located rises from below to above. In this case, the fixed end 320 and the free end 330 may be disposed in the lower layer 312, which is a portion of the bus bar 310 that expands due to heat, and the elastic member 340 may be disposed in the upper layer 311, which is a portion of the bus bar 310 that is bent due to heat.

[0044] The current interruption device 300 will be described in more detail below.

[0045] The current interruption device 300 may include: a bus bar 310 including a plurality of materials that can expand and contract due to heat, and arranged above the cylindrical battery cell 210 and the surrounding cylindrical battery cell 220 at a distance; a fixed end 320 extending downward from one side of the bus bar 310 and bonded to an electrode terminal of the cylindrical battery cell 210; a free end 330 extending downward from the other side opposite to the one side of the bus bar 310 and touching the electrode terminal of the surrounding cylindrical battery cell 220; and an elastic member 340 between the bus bar 310 and an upper surface of the pack case 100, for example, an inner surface of the upper wall 100 a, for supporting the other side of the bus bar 310 on the upper surface of the pack case 100.

[0046] The bus bar 310 may extend, for example, in the left-right direction, and the width of the extension may correspond to the width occupied by two cylindrical battery cells. Here, "corresponding" means that the width is the same as or is larger or smaller by a predetermined amount. The width (depth) of the bus bar 310 in the front-rear direction may correspond to the width (depth) occupied by one cylindrical battery cell.

[0047] The bus bar 310 may be formed of a bimetal including an upper layer 311 and a lower layer 312 having different thermal expansion coefficients. In this case, the thermal expansion coefficient of the lower layer 312 may be greater than that of the upper layer 311. Therefore, when the bus bar 310 is heated, the upper layer 311 and the lower layer 312 expand, but since the lower layer 312 expands more than the upper layer 311, it may appear that the lower layer 312 expands relatively and that the upper layer 311 contracts relatively.

[0048] The fixed end 320 extends downward from the lower layer 312, with its lower portion extending in the left-right direction and its upper portion extending at an angle in the up-down direction, and its upper end may be supported by a lower surface of the lower layer 312 of the bus bar 310. Here, the lower portion of the fixed end 320 may be welded and fixed to an electrode terminal of the cylindrical battery cell 210.

[0049] The free end 330 extends downward from the lower layer 312, spaced apart from the fixed end 320 in the horizontal direction, more specifically, in the left-right direction, with its upper portion extending at an angle in the vertical direction and its lower portion extending in the left-right direction, its upper end supported on the lower surface of the lower layer 312 of the bus bar 310, and its lower end contacting an electrode terminal of the surrounding cylindrical battery cell 220. Current may flow from the upper electrode terminal of the surrounding cylindrical battery cell 220 through the free end 330 touching the free end 330, via the bus bar 310, and to the upper electrode terminal of the cylindrical battery cell 210 welded to the fixed end 320.

[0050] At this time, if heat is generated due to an abnormality in the condition of at least one of the cylindrical battery cell 210 and the surrounding cylindrical battery cell 220, the generated heat is transferred to the bus bar 310, causing the bus bar 310 to bend, and the free end 330 rises, thereby interrupting the flow of current.

[0051] That is, the bus bar 310 is configured such that predetermined portions are bent upward by heat, causing the free end 330 connected to the lower portion thereof to stand up and become disconnected from the battery cell 220 to which the free end 330 is connected. In this way, the free end 330 turns on / off its electrical connection to the battery cell 220 depending on the state of heat applied to the bus bar 310, and the fixed end 320 is always connected to its adjacent battery cell 210.

[0052] In this case, elastic member 340 may include an elastic spring that makes the elastic force smaller than the expansion force that occurs when bus bar 310 is distorted by heat. This allows bus bar 310 to contract elastic member 340, allowing it to be smoothly bent by heat.

[0053] Furthermore, when the abnormal cylindrical cell recovers, the shape of the busbar 310 is restored and the free end 330 drops down to contact the upper electrode terminal of the surrounding cylindrical battery cell 220, thereby restoring current flow. At this time, the elastic member 340 may increase the restoring force of the busbar 310 so that the free end 330 can be connected to the electrode terminal of the battery cell 220.

[0054] As described above, the free end 320 may be spaced apart from the electrode terminal of the surrounding cylindrical battery cell 220 as the bus bar 310 expands and bends, or may come into contact with the electrode terminal of the surrounding cylindrical battery cell 220 due to the restoring force associated with the contraction of the bus bar 310 and the load associated with the bias of the elastic member 340.

[0055] That is, the elastic member 340 may have an elastic force set to assist both bending and loosening of the bus bar 310 when the free end 330 is bent by heat.

[0056] In this case, the elastic member 340 may be supported by the upper layer 311 so as to be positioned above the free end 330. That is, the upper end of the elastic member 340 may be supported so as to come into contact with the upper surface of the pack case 100, and the lower end may be supported by the upper layer 311 above the free end 330. This allows the elastic member 340 to press the free end 330 downward via the bus bar 310, thereby enabling stable contact between the free end 330 and the upper electrode terminal of the surrounding cylindrical battery cell 220. Meanwhile, at least one of the upper end and the lower end of the elastic member 340 may be electrically insulated.

[0057] 1.5.Connecting member 400 The connecting member 400 may be made of a metal plate material. A plurality of connecting members 400 may be provided to electrically connect a plurality of cylindrical battery cells 200. In this case, the connecting members 400 may be arranged to connect the cylindrical battery cells arranged in the row direction in series and the cylindrical battery cells arranged in the column direction in parallel.

[0058] For example, when the current interruption device 300 connects the cylindrical battery cell 210 to the surrounding cylindrical battery cell 220, the connecting member 400 is not arranged to connect the cylindrical battery cell 210 to the surrounding cylindrical battery cell 220, but may be arranged to connect the cylindrical battery cell 210 preceding the cylindrical battery cell 210 in the direction of current flow with the cylindrical battery cell 210, and may be arranged to connect the cylindrical battery cell following the surrounding cylindrical battery cell 220 with the surrounding cylindrical battery cell 220.

[0059] 1.6. Cooling Member 500 and Heat Transfer Member 600 The cooling member 500 may include a heat sink. The cooling member 500 may be disposed on the bottom surface 100b of the pack case 100, and may be configured to be able to discharge heat to the outside of the pack case 100.

[0060] A thermal interface material (TMI) 600 may bring the cooling member 500 into thermal contact with the connecting member 400. Therefore, heat generated from the plurality of cylindrical battery cells 200 is transferred to the heat transfer member 600 via the connecting member 300, and can be discharged to the outside of the pack case 100 via the cooling member 500.

[0061] 1.7.Cell holder The cell holder (not shown) may contact the outer peripheral surfaces of the plurality of cylindrical battery cells 200 to fix the plurality of cylindrical battery cells 200 inside the pack case 100.

[0062] 2. Method of Operating a Battery Pack According to an Embodiment of the Present Invention FIG. 4 is a diagram showing how a current interruption device according to an embodiment of the present invention passes a current, and FIG. 5 is a diagram showing how a current interruption device according to an embodiment of the present invention interrupts a current.

[0063] Hereinafter, a method for operating a battery pack according to an embodiment of the present invention will be described with reference to FIGS.

[0064] A method for operating a battery pack according to an embodiment of the present invention may include the following steps.

[0065] 2.1. In the process of connecting the electrode terminals of the cylindrical battery cell 210 and the surrounding cylindrical battery cell 220 arranged in the pack case 100 to the fixed end 320 and free end 330 arranged in the current interruption device, the cylindrical battery cell 210 and the surrounding cylindrical battery cell 220 are electrically connected via the current interruption device. At this time, the negative electrode terminal at the top of the cylindrical battery cell 210 and the fixed end 320 of the current interruption device may be connected by welding, and the positive electrode terminal at the top of the surrounding cylindrical battery cell 220 and the free end 330 of the current interruption device may be connected by contact.

[0066] 4, the elastic member 340 may apply a downward force, for example, an elastic force f1, to urge the free end 330 via the bus bar 310. That is, the positive electrode terminal at the top of the surrounding cylindrical battery cell 220 and the free end 330 may be brought into close contact with each other. This allows the electrical connection between the cylindrical battery cell 210 and the surrounding cylindrical battery cell 220 to be stably maintained.

[0067] Meanwhile, if an abnormality occurs in one of the cylindrical battery cells during operation of the battery pack, for example, during high-rate charging and discharging, high heat may be generated from the cell, which may affect the operation of the other cylindrical battery cells located around it. For this reason, the cylindrical battery cell that has become abnormal and whose temperature rises rapidly must be electrically isolated from its surroundings as quickly as possible. This is accomplished through the following process.

[0068] 2.2. When heat T is transferred from either the cylindrical battery cell or the surrounding cylindrical battery cell, in the process of bending the bimetal portion provided in the current interruption device to separate the free end 330 from the electrode terminal of the surrounding cylindrical battery cell 220, as shown in FIG. 5 , the bimetal portion, i.e., the bus bar 310, is bent around the fixed end 320 in a direction away from the electrode terminal of the surrounding cylindrical battery cell 220. At this time, because the bending force f2 is greater than the elastic force of the elastic member 340, the bending of the bus bar 310 can be used to contract the elastic member connected to the bus bar 310. This allows the free end 330 to smoothly separate from the electrode terminal of the surrounding cylindrical battery cell 220. This allows the electrical connection between the battery cells to be interrupted.

[0069] Meanwhile, a cylindrical battery cell that has been electrically disconnected from its surroundings due to an abnormality can be restored to its original state after a predetermined time has passed. In this case, the restored cylindrical battery cell is electrically connected to its surroundings by performing the following process.

[0070] 2.3. When the heat transferred to the bus bar 310, which is a bimetal part, is eliminated, the bus bar 310 is restored to its original state, and the connection between the free end 330 and the electrode terminal of the surrounding cylindrical battery cell 220 is restored, and the restored cylindrical battery cell is electrically connected to the surroundings. At this time, the elastic member 340 is expanded to bias the bent portion of the bus bar 310, and the free end 330 supported by the bent portion is pressed against the electrode terminal of the surrounding cylindrical battery cell 220.

[0071] Then, the bus bar 310 is biased by the elastic member 340 provided in the current interruption device 300, and a stable connection between the free end 330 and the electrode terminal of the surrounding cylindrical battery cell 220 can be maintained.

[0072] 3. Battery pack and its operating method according to a modified example of the present invention 6 is a diagram showing how a current interruption device according to a modified example of the present invention interrupts a current. A battery pack according to a modified example of the present invention and a method of operating the same will be described with reference to FIGS.

[0073] Referring to FIG. 5, when heat is generated from the cylindrical battery cell 210 attached to the fixed end 320 of the current interrupting device, and the free end 330 of the current interrupting device is separated from the surrounding cylindrical battery cell 220, the heat continues to be transferred to the bus bar 310 until the abnormal condition of the cylindrical battery cell 210 is resolved, thereby making it possible to maintain a smooth bending state of the bus bar 310.

[0074] Meanwhile, when heat is generated from the surrounding cylindrical battery cells 220 that are in contact with the free end 330 of the current interruption device and the bus bar 310 is bent, the heat from the surrounding cylindrical battery cells 220 can be transferred to the bus bar 310 by convection and radiation.

[0075] 6 , the current interruption device 300 of the battery pack according to the modified example of the present invention may further include a transmission member 350 arranged to thermally connect the surrounding cylindrical battery cell 220 to at least one of the bus bar 310, the fixed end 320, and the free end 330. For example, the transmission member 350 may be arranged inside the pack case 100 to connect the outer surface of the surrounding cylindrical battery cell 220 to the bus bar 310.

[0076] Therefore, the method of operating a battery pack according to a modified example of the present invention may further include, after the step of separating the free end 330 from the electrode terminal of the surrounding cylindrical battery cell 220, a step of exchanging heat through a heat transfer path between the surrounding cylindrical battery cell 220 and the bus bar 310. In this step, heat generated from the surrounding cylindrical battery cell 220 can be transferred to the bus bar 310 more smoothly.

[0077] The above-described embodiments of the present invention are intended to be illustrative of the present invention and are not intended to limit the present invention. It should be noted that the configurations and methods disclosed in the above-described embodiments of the present invention may be combined or interwoven into various forms, and such modifications are also considered to fall within the scope of the present invention. In other words, the present invention may be embodied in various different forms within the scope of the claims and the technical concepts equivalent thereto, and those skilled in the art to which the present invention pertains should understand that various embodiments are possible within the scope of the technical concepts of the present invention. [Explanation of symbols]

[0078] 100: Pack case 200: Multiple cylindrical battery cells 210: Cylindrical battery cell 220: Cylindrical battery cell 300: Current interrupter 310: Busbar 320: Fixed end 330: Free end 340: Elastic member 400: Connecting member

Claims

1. Pack case and a plurality of cylindrical battery cells disposed in the pack case; a current interruption device disposed within the pack case so as to connect the plurality of cylindrical battery cells; It is equipped with The current interruption device is a fixed end that contacts an electrode terminal of a cylindrical battery cell, a free end that contacts an electrode terminal of a surrounding cylindrical battery cell, a bus bar formed from a bimetal, the bus bar having the fixed end and the free end; and an elastic member that is provided on the bus bar and biases the free end toward the surrounding cylindrical battery cell, the bus bar electrically connects in series the cylindrical battery cell that the fixed end touches and the surrounding cylindrical battery cell that the free end touches; The battery pack is characterized in that the free end makes and breaks contact with the electrode terminal of the cylindrical battery cell according to the change in shape of the bimetal.

2. the fixed end and the free end are arranged to face each other in a direction in which the plurality of cylindrical battery cells are arranged, The battery pack according to claim 1 , wherein the elastic member and the free end are disposed to face each other in a direction intersecting a direction in which the plurality of cylindrical battery cells are arranged.

3. the fixed end has a surface that is adhered to the electrode terminal of the cylindrical battery cell by welding; 3. The battery pack according to claim 1, wherein the free end has a surface that comes into contact with the electrode terminal of the surrounding cylindrical battery cell when biased.

4. the bimetal portion of the bus bar in the current interruption device is disposed between the plurality of cylindrical battery cells and the inner surface of the pack case such that a portion that is expanded by heat faces the cylindrical battery cell and a surrounding cylindrical battery cell, and a portion that is bent by heat faces the inner surface of the pack case; the fixed end and the free end are disposed at a position of the bimetal part of the current interrupting device that expands due to heat; 4. The battery pack according to claim 1, wherein the elastic member is disposed at a position of the bimetal portion that is bent by heat.

5. The current interruption device is the bus bar including a plurality of materials that can expand and contract by heat and disposed above the cylindrical battery cell and the surrounding cylindrical battery cell; a fixed end extending from one side of the bus bar and bonded to the electrode terminal of the cylindrical battery cell; the free end extending from the other side opposite to the one side of the bus bar and contacting the electrode terminal of the surrounding cylindrical battery cell; 2. The battery pack according to claim 1, further comprising: the elastic member between the bus bar and the upper surface of the pack case, the elastic member supporting the other side of the bus bar on the upper surface of the pack case.

6. the bus bar is made of a bimetal having an upper layer and a lower layer with different thermal expansion coefficients; the coefficient of thermal expansion of the lower layer is greater than the coefficient of thermal expansion of the upper layer; the fixed end and the free end extend downward from the lower layer and are horizontally spaced apart from one another; The battery pack according to claim 5 , wherein the elastic member is supported by the upper layer so as to be spaced apart above the free end.

7. The battery pack according to claim 5 or 6, wherein the elastic member includes an elastic spring whose elastic force is smaller than the expansion force of the bus bar.

8. The current interruption device is 6. The battery pack according to claim 5, further comprising a transmission member arranged to thermally connect at least one of the bus bar, the fixed end, and the free end to the surrounding cylindrical battery cell.

9. a step of connecting electrode terminals of cylindrical battery cells disposed in the pack case and electrode terminals of surrounding cylindrical battery cells to fixed ends and free ends disposed on bus bars of a current interrupting device; bending a bimetal portion of the bus bar of the current interruption device to separate the free end from the electrode terminal of the surrounding cylindrical battery cell when heat of a predetermined value or more is transferred from either the cylindrical battery cell or the surrounding cylindrical battery cell; When the heat transferred to the bimetal portion is removed, the bimetal portion is restored to its original state to restore the connection between the free end and the electrode terminal of the surrounding cylindrical battery cell; comprising a bus bar electrically connecting the cylindrical battery cell that the fixed end touches to the surrounding cylindrical battery cell that the free end touches in series;

10. The step of spacing comprises:

10. The method of claim 9, further comprising bending the bimetal portion around the fixed end in a direction away from the electrode terminal of the surrounding cylindrical battery cell.

11. The step of spacing comprises:

11. The method of claim 9, further comprising the step of shortening an elastic member connected to the bimetal portion using the bending.

12. The recovering step comprises:

12. The method for operating a battery pack according to claim 9, further comprising a step of expanding an elastic member to bias the bent portion of the bimetal portion and press the free end supported by the bent portion against the electrode terminal of the surrounding cylindrical battery cell.

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