Battery pack including heat diffusion suppression structure

Abstract

The present invention relates to a battery pack including a battery module housing that accommodates a plurality of battery cells, a battery pack case that accommodates one or more of the battery module housings, and a water tank that is located on one side of the battery module housing and contains cooling water, wherein the battery module housing has a structure that encloses the outer surfaces of the plurality of battery cells, and can prevent heat diffusion between adjacent battery modules in the event of a battery cell catching fire in a battery pack including a plurality of battery modules.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2020-0157817 filed on November 23, 2020, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a battery pack including a thermal diffusion suppression structure, and more particularly to a battery pack including a thermal diffusion suppression structure capable of injecting cooling water into a battery module containing a ignited battery cell in order to prevent the spread of a flame caused by a ignition in a battery cell inside the battery pack. [Background technology]

[0003] As a result of continuous research and development into lithium secondary batteries, it has become possible to manufacture and commercialize lithium secondary batteries with increased capacity and improved output. In addition, the demand for lithium secondary batteries is increasing as an energy source that can replace fossil fuels, which have environmental pollution problems.

[0004] Therefore, the application of lithium secondary batteries to various devices is increasing. For example, lithium secondary batteries are widely used as energy sources for wireless mobile devices, which are multi-functional small products, or wearable devices worn on the body, as well as being used as energy sources or power storage systems (ESS) for electric vehicles and hybrid electric vehicles, which are presented as alternatives to existing gasoline and diesel vehicles.

[0005] As lithium secondary batteries are used as large-capacity, high-output energy sources, the issue of ensuring the safety of the lithium secondary batteries has become a major concern.

[0006] Generally, in the event of a fire occurring in a battery cell housed therein, a power storage device employs a method of injecting water into the interior of a battery module or battery pack using a separate water injection device.

[0007] However, in this case, facilities and space are required to accommodate the water injection device, and there is a problem that the fire may spread due to the time lag between sensing the gas discharged by venting the battery cell and injecting water.

[0008] Alternatively, a method can be used in which insulating material or fire extinguishing agents are placed inside or outside the battery module or battery pack to block heat transfer between battery cells or to cool a battery cell that has caught fire.

[0009] However, when a heat insulating material is used, although the propagation of the flame can be prevented, there is a problem that the fire extinguishing function cannot be exhibited. When a fire extinguishing agent is used, the fire extinguishing agent is placed in the empty space inside the battery pack in consideration of the energy density, so there is a problem that the fire extinguishing agent is not accurately dispersed at the point where the fire started.

[0010] As such, as a technology for preventing thermal runaway in a battery pack, Patent Document 1 discloses a device in which an envelope containing water is placed on top of a battery, the envelope being made of a material with a relatively low melting point, and when the temperature of the battery increases, the envelope melts and the water inside is discharged into the battery.

[0011] In Patent Document 1, the entire envelope is made of a material with a low melting point, so when the battery temperature increases, water does not escape from only specific parts of the envelope, but rather the envelope melts and all of the water inside is expelled.

[0012] Therefore, if the envelope is placed under the battery cell, water cannot be injected into the battery cell and the fire extinguishing function cannot be achieved. Therefore, there is a restriction that the container must be used only in a certain direction so that the envelope is placed over the battery cell.

[0013] In Patent Document 2, an inner case and an inner case are housed in an outer case, a plurality of unit cells are housed in the inner case, a fire extinguishing agent is housed in the inner case, and an injection tube is included for injecting the fire extinguishing agent into the inner case when the unit cells heat up to an upper limit temperature or higher. When the unit cells heat up to an upper limit temperature or higher, the injection tube opens and the fire extinguishing agent housed in the inner case is injected into the inner case.

[0014] The device in Patent Document 2 includes compressed gas for spraying the extinguishing agent, a nozzle used as an injection tube, and an inner case that houses the extinguishing agent, and therefore requires additional space to accommodate these components, and further costs are incurred for providing the extinguishing agent and compressed gas.

[0015] As such, there is a high demand for a technology that can minimize the spread of flames when a battery cell housed inside a battery pack ignites, does not require additional space, and prevents a decrease in energy density. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] JP 2014-523622 A [Patent Document 2] JP 2012-252909 A Summary of the Invention [Problem to be solved by the invention]

[0017] The present invention is devised to solve the above problems, and aims to provide a battery pack including a heat diffusion suppression structure to prevent heat diffusion between battery modules in the event of fire or explosion of a battery cell in a battery pack including multiple battery modules. [Means for solving the problem]

[0018] To achieve this object, a battery pack according to the present invention includes a battery module housing that accommodates a plurality of battery cells, a battery pack case that accommodates one or more of the battery module housings, and a water tank that is located on an upper portion of one side of the battery module housing and contains cooling water, and the battery module housing may have a structure that encases the outer surfaces of the plurality of battery cells.

[0019] In the battery pack according to the present invention, the water tank may be integrated with a heat sink, and a flow path may be formed inside the water tank to guide the flow of the cooling water flowing in and out.

[0020] In the battery pack according to the present invention, the water tank may be formed to a size sufficient to cover an upper surface of the entire battery module housing.

[0021] In the battery pack according to the present invention, the water tank may be attached to an inner surface of an upper surface of the battery pack case.

[0022] In the battery pack according to the present invention, the battery pack case may have an open top, and the water tank may be coupled to the battery pack case in a manner covering the open top surface of the battery pack case.

[0023] In the battery pack according to the present invention, the water tank may have a through hole formed in one surface facing the battery module housing, and a sealing member may be attached to the through hole.

[0024] In the battery pack according to the present invention, the sealing member may be made of a material that melts due to high-temperature gas or sparks emitted from the battery cell.

[0025] In the battery pack according to the present invention, the through hole may be opened by melting the sealing member, and the cooling water stored inside the water tank may be injected through the through hole onto the outer surface of the battery module housing.

[0026] In the battery pack according to the present invention, the through hole may be formed in a form of a plurality of holes uniformly distributed on one surface of the water tank.

[0027] In the battery pack according to the present invention, a partition may be added between the battery module housings.

[0028] In the battery pack according to the present invention, the sealing member may fill the through hole and include an extension portion that extends from an outer surface of the water tank further outward than the periphery of the through hole.

[0029] In the battery pack according to the present invention, the battery cells may be pouch-shaped battery cells, prismatic battery cells or cylindrical battery cells. Effect of the Invention

[0030] As described above, the battery pack of the present invention is provided with a water tank inside the battery pack, which not only does not increase the external size of the battery pack but also makes it possible to quickly cool a battery module that includes a ignited battery cell, thereby preventing heat from spreading to adjacent battery modules.

[0031] In addition, since a sealing member is attached to one side of the water tank facing the battery module housing, if the sealing member melts and is removed, cooling water can be sprayed toward the battery module housing including the ignited battery cell, regardless of the position and orientation of the battery pack.

[0032] In addition, since a through hole is formed on one side of the water tank and the sealing member fills the through hole, an increase in weight of the battery pack due to the addition of the sealing member can be minimized.

[0033] In addition, even if a fire occurs in any of the multiple battery modules, cooling water can be accurately injected into the battery module housing, so the effect of blocking heat diffusion can be obtained even when applied to a large-capacity battery pack.

[0034] Also, production costs can be reduced when water is used instead of expensive extinguishing agents. [Brief description of the drawings]

[0035] [Figure 1] 1 is a perspective view of a battery pack according to a first embodiment of the present invention; [Diagram 2] 1 is an exploded perspective view of a battery pack according to a first embodiment. [Diagram 3] 2 is a cross-sectional view taken along line AA' in the battery pack shown in FIG. 1. [Figure 4] 4A to 4C are schematic diagrams for explaining a situation in which a flame is extinguished when a fire occurs in the battery pack according to the first embodiment. [Diagram 5] FIG. 11 is an exploded perspective view of a battery pack according to a second embodiment. [Figure 6] FIG. 11 is a cross-sectional view of a battery pack according to a second embodiment. [Figure 7] 13 is a schematic diagram for explaining a situation in which a flame is extinguished when a fire occurs in the battery pack according to the second embodiment. FIG. [Figure 8] FIG. 11 is an exploded perspective view of a battery pack according to a third embodiment. [Figure 9] FIG. 11 is a cross-sectional view of a battery pack according to a third embodiment. [Figure 10] 13 is a schematic diagram for explaining a situation in which a flame is extinguished when a fire occurs in the battery pack according to the third embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of an embodiment of the present invention that can be easily implemented by a person having ordinary skill in the art to which the present invention pertains. However, when describing the operation principle of the preferred embodiment of the present invention in detail, if it is determined that a detailed description of related publicly known functions or configurations may obscure the gist of the present invention, the detailed description will be omitted.

[0037] In addition, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes a direct connection as well as an indirect connection via another element between them. Furthermore, unless otherwise specified, the inclusion of a certain component does not mean the exclusion of other components, but means that other components may also be included.

[0038] Furthermore, unless otherwise specified, the description of the specific embodiment by limiting or adding components can be applied to any invention, and is not limited to the description of a specific invention.

[0039] Furthermore, throughout the description of the invention and the claims of this application, the singular "a" or "an" includes the plural, unless otherwise specified.

[0040] In addition, throughout the description of the invention and claims of this application, unless otherwise specified, "or" includes "and." Therefore, "including A or B" means any of the three cases including A, including B, or including both A and B.

[0041] Additionally, all numerical ranges include the endpoints and all intermediate values ​​therebetween unless expressly stated to exclude.

[0042] The present invention will now be described by way of detailed examples with reference to the drawings.

[0043] FIG. 1 is a perspective view of a battery pack according to a first embodiment of the present invention, and FIG. 2 is an exploded perspective view of the battery pack according to the first embodiment.

[0044] 1 and 2, the battery pack according to the present invention includes a battery module housing 210 that accommodates a plurality of battery cells 220, a battery pack case 100 that accommodates one or more battery module housings 210, and a water tank 300 that is located on one side of the battery module housing 210 and contains cooling water, and the battery module housing 210 has a structure that encases the outer surfaces of the plurality of battery cells 220.

[0045] A through hole is formed on the bottom of the water tank, and a sealing member 320 is attached to prevent the cooling water from being discharged from the through hole when the battery pack is in a normal state. The sealing member 320 is attached to the bottom of the water tank and cannot be seen from the outside of the battery pack, but is shown by a solid line in Figures 1 and 2 for convenience of explanation.

[0046] In one specific example, the plurality of battery cells 220 may be pouch-shaped battery cells, and the pouch-shaped battery cells may be stacked such that the electrode assembly housings are in close contact with each other and arranged such that the bottoms of the electrode assembly housings are vertical to the ground.

[0047] The pouch-shaped battery cell may be a bidirectional battery cell in which the positive and negative leads protrude in opposite directions, or a unidirectional battery cell in which the positive and negative leads protrude in the same direction.

[0048] The water tank 300 is integrated with a heat sink, and a flow path 310 is formed inside the water tank 300 to guide the flow of cooling water flowing in and out, so that the temperature of the cooling water flowing in / out of the water tank 300 can be maintained at a constant level.

[0049] The water tank 300 may be formed in the shape of a rectangular parallelepiped with a wide bottom surface facing the battery module housing 210 and a wide top surface on the opposite side, and the areas of the top and bottom surfaces are large enough to cover the top surfaces of all of the battery module housings 210 accommodated in the battery pack case 100.

[0050] In one specific example, the battery pack case 100 may be in the form of a box with the top removed from a rectangular parallelepiped, and the top may be open, and the water tank 300 may be combined with the battery pack case 100 in a form covering the open top surface of the battery pack case 100.

[0051] That is, the water tank 300 is disposed on the upper surface of the battery module housing 210, and can thus function as a lid for the battery pack case whose upper surface is open.

[0052] In another specific example, the battery pack case 100 may have a structure including a case body formed in a shape in which the upper surface is removed from a rectangular parallelepiped to open the upper portion, and a top plate coupled to the open upper surface. In this case, the water tank may be coupled to the top plate. That is, the water tank may be attached to the inner surface of the upper surface of the battery pack case.

[0053] Alternatively, the top plate may be the upper surface of the water tank, and the water tank may be integral with the top plate.

[0054] The battery module housing 210 may be in a form that encloses both sides, upper and lower sides of the battery cell stack that are parallel to the bottom of the electrode assembly housing portion of the pouch-type battery cell in the battery cell stack that is arranged so that the bottom of the electrode assembly housing portion is vertical to the ground.

[0055] In addition to the expansion and contraction of the electrode assembly during repeated charging and discharging, gas is also generated as a by-product of charging and discharging in the battery cell 220. As a result, the battery module housing may expand, but by adding a partition wall 110 between the battery module housings 210, the impact of the volumetric expansion of the battery module housing 210 on the adjacent module case can be minimized and the battery module housing 210 can be fixed and supported.

[0056] FIG. 3 is a cross-sectional view taken along line A-A' in the battery pack shown in FIG. 1, and FIG. 4 is a schematic diagram for explaining the situation in which a flame is extinguished when a fire occurs in the battery pack according to the first embodiment.

[0057] 3 and 4, a plurality of battery module housings 210 are disposed in a battery pack case 100, and a plurality of battery cells 220 are disposed inside the battery module housings 210. A water tank 300 is disposed above the plurality of battery module housings 210, and the water tank 300 is filled with cooling water for lowering the temperature of the battery modules that has increased due to overheating or catching fire from battery cells.

[0058] A through hole is formed on one surface of the water tank 300 facing the battery module housing 210, and a sealing member 320 is attached to the through hole to seal the through hole. The sealing member 320 is made of a material that melts due to high-temperature gas or sparks emitted from the battery cell 220. That is, when the battery cell 220 is in a normal state, the sealing member 320 keeps the through hole sealed, but as the temperature of a ignited battery cell such as the battery cell 220' increases, the temperature of the battery module housing 210 enclosing the battery cell 220' may also increase above the melting temperature of the sealing member. At this time, the sealing member 320 adjacent to the high-temperature battery module housing melts, and the through hole 330 opens.

[0059] The cooling water stored in the water tank 300 is vaporized as the temperature of the battery module housing increases, and the volume increases and the pressure increases, so that the cooling water is sprayed toward the battery module housing when the through hole 330 is opened.

[0060] Since the battery module housing of the present invention is a closed type in which the battery cells are not exposed, the sprayed cooling water is not directly applied to the ignited battery cell, but is sprayed on the outer surface of the battery module housing 210 where the ignited battery cell is located. In this way, by spraying the cooling water on the outer surface of the battery module housing 210, the temperature of the high-temperature battery module housing 210 can be reduced, and the spread of heat to adjacent battery modules can be prevented or delayed.

[0061] The sealing member may be made of a thermoplastic polymer resin having a melting point of about 200°C or less. For example, the thermoplastic polymer resin may be a material having a melting point of about 100°C or more and 200°C or less, such as polyethylene or polypropylene.

[0062] The sealing member 320 fills the through hole and may include an extension 325 extending from the outer surface of the water tank further outward than the periphery of the through hole. Since the extension 325 extends further from the outer surface of the water tank, it may improve the bonding strength of the sealing member 320 to the water tank in a normal state, and may begin to melt from the extension due to an increase in temperature in the event of a fire in the battery cell, thereby opening the through hole.

[0063] In a battery cell made of a lithium secondary battery, when a defect occurs in the battery cell or when the battery cell is overcharged or overheated, a thermal runaway phenomenon may occur in the battery cell. When the battery cell enters a thermal runaway state, the temperature of the battery cell may rise to about 260°C, the temperature at which gas venting occurs. In addition, the temperature of the battery cell may continue to rise even while gas venting is occurring.

[0064] When manufacturing a battery pack by housing multiple battery cells in a battery pack case, if one battery cell goes into a thermal runaway state, high heat and flames can be transferred to the adjacent battery cells, causing the adjacent battery cells to overheat and go into a thermal runaway state as well. Furthermore, the battery cell in a thermal runaway state can heat other adjacent battery cells, causing a chain reaction of thermal runaway. Therefore, if a thermal runaway battery cell occurs in a battery pack case, it can cause thermal runaway in multiple battery cells, which can spread to a wider area and cause major damage. If multiple battery cells go into a thermal runaway state in this way, the temperature can reach more than 1,000°C, which can continue until the battery cells are completely burned out, putting users in a dangerous situation.

[0065] Therefore, it is very important to extinguish the fire in the battery cell before the flame and high heat of the battery cell spread to the adjacent battery cells.

[0066] Therefore, the battery pack according to the present invention includes a water tank 300 containing cooling water at a position adjacent to the upper part of the battery module housing 210, and a through hole through which the cooling water flows out is sealed with a sealing member having a low melting point, and when the sealing member 320 melts due to a ignited battery cell, the through hole 330 opens. Therefore, the cooling water contained inside the water tank 300 is sprayed from the through hole onto the outer surface of the battery module housing 210. Since the battery module housing according to the present invention is a closed type in which the battery cells are not exposed to the cooling water sprayed from the water tank, the cooling water is sprayed onto the outer surface of the battery module housing, thereby preventing or delaying the diffusion of heat to adjacent battery modules.

[0067] This process can prevent a fire caused by an overheated or ignited pouch-type battery cell from spreading between battery modules, and can allow time for an external water injection facility to extinguish the fire in the battery cell.

[0068] In addition, when the battery pack of the present invention is installed in a position close to a user, such as in an electric vehicle, the spread of a flame in the battery cell can be delayed, ensuring time for the user to take action safely.

[0069] The through holes formed in the water tank 300 may be formed in a form in which a plurality of holes are evenly distributed on one side of the water tank, so that even if a fire occurs inside any battery module, cooling water can be accurately sprayed onto the battery module housing including the ignited battery cell. That is, the number of through holes formed in the water tank may be designed in consideration of the size and number of the battery module housings, and the shape, size, and number of the battery cells arranged in the battery module housings.

[0070] FIG. 5 is an exploded perspective view of a battery pack according to the second embodiment, FIG. 6 is a cross-sectional view of the battery pack according to the second embodiment, and FIG. 7 is a schematic diagram for explaining a situation in which a flame is extinguished when a fire occurs in the battery pack according to the second embodiment.

[0071] 5 to 7, the battery pack includes a battery module housing 210 that houses a plurality of battery cells, a battery pack case 100 that houses one or more battery module housings 210, and a water tank 300 that is located on top of the battery module housing 210 and contains cooling water. The battery module housing 210 has a structure that encloses the outer surfaces of the plurality of battery cells 220.

[0072] The plurality of battery cells 220 may be rectangular battery cells having an overall hexahedral structure with an electrode assembly housed in a battery case made of a metal material, and the positive and negative terminals may protrude from the upper surface to face the water tank 300. The rectangular battery cells may be closely arranged such that the sides with the relatively larger areas are adjacently stacked.

[0073] In addition, the water tank 300 has a through hole formed on one side facing the multiple battery module housings, and a sealing member 320 made of a material with a low melting point is attached to the through hole. Therefore, when the battery cell ignites, the sealing member melts and opens the through hole, and the cooling water stored inside the water tank can be sprayed from the through hole onto the outer surface of the battery module housing 210.

[0074] In addition, the description of the battery pack according to the second embodiment may be the same as the description of the battery pack according to the first embodiment. Also, the same reference numerals are used to designate the same components in the first and second embodiments.

[0075] FIG. 8 is an exploded perspective view of a battery pack according to the third embodiment, FIG. 9 is a cross-sectional view of the battery pack according to the third embodiment, and FIG. 10 is a schematic diagram for explaining a situation in which a flame is extinguished when a fire occurs in the battery pack according to the third embodiment.

[0076] 8 to 10, the battery pack includes a battery module housing 210 that accommodates a plurality of battery cells, a battery pack case 100 that accommodates one or more battery module housings 210, and a water tank 300 that is located on top of the battery module housing 210 and contains cooling water, and the battery module housing 210 has a structure that encloses the outer surfaces of the plurality of battery cells 220.

[0077] The plurality of battery cells 220 may be cylindrical in shape, with an electrode assembly housed in a battery case made of a metal material, and may be arranged such that the positive terminal protrudes upward to face the water tank 300.

[0078] In addition, the water tank 300 has a through hole formed on one side facing the multiple battery module housings, and a sealing member 320 made of a material with a low melting point is attached to the through hole. Therefore, when the battery cell ignites, the sealing member melts and opens the through hole, and the cooling water stored inside the water tank can be sprayed from the through hole onto the outer surface of the battery module housing 210.

[0079] In addition, the description of the battery pack according to the third embodiment may be the same as the description of the battery pack according to the first embodiment. Also, the same reference numerals are used to designate the same components as those in the first and third embodiments.

[0080] Those skilled in the art will appreciate that various applications and modifications within the scope of the present invention will be possible based on the above content. [Explanation of symbols]

[0081] 100 Battery pack case 110 Bulkhead 210 Battery module housing 220,220' battery cell 300 Water Tank 310 Flow Path 320 Sealing material 325 Extension 330 Through hole

Claims

1. a battery module housing that houses a plurality of battery cells; A battery pack case that houses one or more of the battery module housings; and a water tank located on one side of the battery module housing and containing cooling water; Including, In a battery pack having a structure in which the battery module housing encloses outer surfaces of the plurality of battery cells, The water tank has a through hole formed on one surface facing the battery module housing, and a sealing member is attached to the through hole. The sealing member is made of a material that melts when exposed to high-temperature gas or sparks emitted from the battery cell; The through-hole is opened by melting the sealing member, and the cooling water stored in the water tank is poured into the outer surface of the battery module housing through the through-hole. The through-hole is formed in a form in which a plurality of holes are uniformly distributed on one surface of the water tank, the sealing member fills the through hole, and includes an extension portion extending from an outer surface of the water tank to an outer side beyond the periphery of the through hole only on a lower surface of the water tank; The water tank is integrated with a heat sink, and the heat sink keeps the temperature of the cooling water at a constant level.

2. The battery pack according to claim 1 , wherein a flow path is formed inside the water tank to guide the flow of the cooling water that flows in and out.

3. The battery pack according to claim 1 , wherein the water tank is formed to a size that covers an upper surface of the entire battery module housing.

4. 4. The battery pack according to claim 1, wherein the water tank is attached to an inner surface of an upper surface of the battery pack case.

5. The battery pack case has an open top, The battery pack according to claim 1 , wherein the water tank is coupled to the battery pack case in a manner that covers an upper surface of the open battery pack case.

6. The battery pack according to any one of claims 1 to 5, wherein a partition is added between the battery module housings.

7. The battery pack according to any one of claims 1 to 6, wherein the battery cells are pouch-shaped battery cells, rectangular battery cells or cylindrical battery cells.

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