Patent Application
20230246291
This application claims the benefit of priority to Korean Patent Application No. 2020-0157816 filed on Nov. 23, 2020, the disclosure of which is incorporated herein by reference in its entirety.
The present invention relates to a battery pack including a thermal spread inhibition structure. More particularly, the present invention relates to a battery pack including a thermal spread inhibition structure capable of directly injecting a coolant into an ignited battery cell in order to prevent spread of flames of the ignited battery cell in the battery pack.
As the result of continuous research and development of a lithium secondary battery, it has been possible to manufacture and commercialize a lithium secondary battery having increased capacity and improved output. In addition, demand for the lithium secondary battery as an energy source replaceable fossil fuels, which cause environmental pollution, has increased.
Accordingly, application of the lithium secondary battery to various devices has increased. For example, the lithium secondary battery has been widely used as an energy source for wireless mobile devices, which are small multifunctional products, and wearable devices, which are worn on the body, and has also been used as an energy source for electric vehicles and hybrid electric vehicles presented as alternatives to existing gasoline and diesel vehicles or as an energy storage system (ESS).
As the lithium secondary battery is used as a large-capacity, high-output energy source, as described above, securing safety of the lithium secondary battery becomes an important subject of interest.
Generally, in the case in which fire breaks out in a battery cell received in the energy storage system, a method of injecting water into a battery module or a battery pack through a separate watering device is used.
In this case, however, facilities and space for the watering device are required, and the fire may spread due to a time difference between sensing time of gas discharged due to venting of the battery cell and watering time.
Alternatively, a method of disposing an insulating material or a fire extinguishing agent inside or outside the battery module or the battery pack in order to interrupt heat transfer between battery cells or to cool the ignited battery cell may be used.
In the case in which the insulating material is used, however, a fire extinguishing function is not performed although propagation of flames is interrupted. In the case in which the fire extinguishing agent is used, the fire extinguishing agent is not exactly spread to the point at which fire breaks out, since the fire extinguishing agent is disposed in an empty space in the battery pack in consideration of energy density.
As technology for preventing thermal runaway of the battery pack, Patent Document 1 discloses an apparatus configured such that a bag containing water is located above a battery, the bag is made of a material that has a relatively low melting point, and when the temperature of the battery is increased, the bag is melted and the water in the bag is discharged to the battery.
In Patent Document 1, the entirety of the bag is made of material that has a low melting point. When the temperature of the battery is increased, therefore, the water is not discharged from a specific portion of the bag but the entirety of the water in the bag is discharged while the bag is melted.
In the case in which the bag is disposed so as to be located under the battery cell, therefore, the water cannot be injected into the battery cell, whereby it is not possible to exhibit a fire extinguishing function. Consequently, there is a limitation in that the bag must be used only in a specific direction such that the bag is disposed above the battery cell.
Patent Document 2 discloses a battery pack configured to have a structure in which a plurality of battery cells is received in a case body and in which the space between the plurality of battery cells is filled with an insulative coolant.
In Patent Document 2, the battery cells are received so as to be spaced apart from each other in order to fill the space between the battery cells with the insulative coolant, whereby energy density is remarkably reduced.
Patent Document 3 is configured such that a middle case and an inner case are received in an outer case, a plurality of cells is received in the middle case, a fire extinguishing agent is received in the inner case, and when the cells generate heat to an upper limit temperature or higher, the fire extinguishing agent is introduced into the middle case through an injection pipe. When the cells generate heat to an upper limit temperature or higher, the injection pipe is opened, whereby the fire extinguishing agent received in the inner case is injected into the middle case.
In Patent Document 3, compressed gas for spraying the fire extinguishing agent, a nozzle used as the injection pipe, and the inner case configured to receive the fire extinguishing agent are included, whereby an additional space therefor is necessary, and expense necessary to purchase the fire extinguishing agent and the compressed gas is also further incurred.
Therefore, there is a high necessary for technology capable of minimizing spread of flames and preventing a decrease in energy density without needing an additional space when fire breaks out in a battery cell received in a battery pack.
The present invention has been made in view of the above problems, and it is an object of the present invention to provide a battery pack including a fire extinguishing and thermal spread inhibition structure capable of extinguishing ignition of a battery cell when the battery cell catches fire or explodes and preventing spread of flames to battery cells adjacent thereto.
A battery pack according to the present invention to accomplish the above object includes a battery pack case configured to receive one or more battery modules; and a heat sink located above the battery modules, wherein each of the battery modules includes a plurality of battery cells, a water tank located above the plurality of battery cells, and a module case configured to receive the plurality of battery cells and the water tank.
In the battery pack according to the present invention, the water tank may be mounted integrally to the inside of an upper surface of the module case.
In the battery pack according to the present invention, the module case may be configured to have a structure in which an upper part of the module case is open, and the water tank may be coupled to the module case so as to cover the open upper surface of the module case.
In the battery pack according to the present invention, the heat sink may be configured to have a size that covers upper surfaces of all of the battery modules.
In the battery pack according to the present invention, the battery pack case may be configured to have a structure in which an upper part of the battery pack case is open, and the heat sink may be coupled to the battery pack case so as to cover the open upper surface of the battery pack case.
In the battery pack according to the present invention, a through-hole may be formed in one surface of the water tank that faces the plurality of battery cells, and a sealing member may be added to the through-hole.
In the battery pack according to the present invention, the sealing member may be made of a material that is melted by high-temperature gas or sparks discharged from the battery cell.
In the battery pack according to the present invention, the through-hole may be opened as the result of melting of the sealing member, and a coolant received in the water tank may be introduced into the battery cell through the through-hole.
In the battery pack according to the present invention, the through-hole may be configured to have a structure in which a plurality of holes is formed in one surface of the water tank so as to be uniformly dispersed.
In the battery pack according to the present invention, a flow path configured to guide flow of a coolant may be formed in the heat sink.
In the battery pack according to the present invention, a partition wall may be added between the module cases.
In the battery pack according to the present invention, the through-hole may be filled with the sealing member, and the sealing member may include an extension portion further extending outwards from an outer surface of the water tank than the circumference of the through-hole.
In the battery pack according to the present invention, each of the battery cells may be a pouch-shaped battery cell, a prismatic battery cell, or a cylindrical battery cell.
As is apparent from the above description, a battery pack according to the present invention has a water tank disposed therein, whereby it is possible to rapidly cool an ignited battery cell without increasing the external size of the battery pack, and therefore it is possible to securely inhibit a thermal runaway phenomenon of the battery cell.
In addition, a sealing member is added to one surface of the water tank that faces battery cells. When the sealing member is removed as the result of melting, it is possible to spray a coolant toward the ignited battery cell irrespective of the position or orientation of the battery pack.
In addition, a through-hole is formed in one surface of the water tank, and the through-hole is filled with the sealing member, whereby it is possible to minimize an increase in weight of the battery pack due to addition of the sealing member.
In addition, even though fire breaks out in any one of battery cells constituting a battery cell stack, it is possible to exactly inject the coolant into the ignited battery cell. Even when the present invention is applied to a large-capacity battery pack, therefore, it is possible to obtain a thermal spread interruption effect.
Also, in the case in which water is used instead of a fire extinguishing agent, it is possible to reduce production cost.
Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that the preferred embodiments of the present invention can be easily implemented by a person having ordinary skill in the art to which the present invention pertains. In describing the principle of operation of the preferred embodiments of the present invention in detail, however, a detailed description of known functions and configurations incorporated herein will be omitted when the same may obscure the subject matter of the present invention.
In addition, the same reference numbers will be used throughout the drawings to refer to parts that perform similar functions or operations. In the case in which one part is said to be connected to another part throughout the specification, not only may the one part be directly connected to the other part, but also, the one part may be indirectly connected to the other part via a further part. In addition, that a certain element is included does not mean that other elements are excluded, but means that such elements may be further included unless mentioned otherwise.
In addition, a description to embody elements through limitation or addition may be applied to all inventions, unless particularly restricted, and does not limit a specific invention.
Also, in the description of the invention and the claims of the present application, singular forms are intended to include plural forms unless mentioned otherwise.
Also, in the description of the invention and the claims of the present application, “or” includes “and” unless mentioned otherwise. Therefore, “including A or B” means three cases, namely, the case including A, the case including B, and the case including A and B.
In addition, all numeric ranges include the lowest value, the highest value, and all intermediate values therebetween unless the context clearly indicates otherwise.
Embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Referring to
A through-hole is formed in the lower surface of the water tank 230. A sealing member 231 is added to the through-hole in order to prevent discharge of a coolant received in the water tank 230 through the through-hole when the battery cells are in a normal state. Since the sealing member 231 is added to the lower surface of the water tank, the sealing member is not visible from above the water tank 230. For the convenience of description, however, the sealing member 231 is shown in
In a concrete example, each of the plurality of battery cells 220 may be a pouch-shaped battery cell, and outer edge sealed surfaces of electrode assembly receiving portions are disposed so as to be perpendicular to the ground in the state in which the pouch-shaped battery cells are stacked such that the electrode assembly receiving portions are in tight contact with each other.
The pouch-shaped battery cell may be a bidirectional battery cell having a positive electrode lead and a negative electrode lead protruding in opposite directions or a unidirectional battery cell having a positive electrode lead and a negative electrode lead protruding in the same direction.
The module case 210 may be configured to wrap opposite ends of a battery cell stack, in which the bottoms of the electrode assembly receiving portions are disposed so as to be perpendicular to the ground, parallel to the bottoms of the electrode assembly receiving portions and to wrap the upper surface and the lower surface of the battery cell stack.
In the module case 210, the water tank 230 is disposed above the battery cell stack. The battery cell stack and the water tank 230 may be disposed so as to be adjacent to each other, or the battery cell stack and the water tank may be disposed so as to be spaced apart from each other.
The water tank 230 may be mounted integrally to the inside of the upper surface of the module case 210, and the water tank 230 may be the upper surface of the module case 210.
In another embodiment, the module case 210 may be configured in a U shape in order to wrap the opposite ends of the battery cell stack parallel to the bottoms of the electrode assembly receiving portions and the lower surface of the battery cell stack.
Alternatively, the module case 210 may be a box open at the upper part thereof configured to wrap the other surfaces of the battery cell stack excluding the upper surface, and the water tank 230 may be coupled to the module case 210 so as to cover the open upper surface of the module case 210.
That is, the water tank 230 is disposed at the upper surface of the battery cell stack, and therefore the water tank may serve as a cover of the module case 210 having the open upper surface.
The heat sink 300 is configured to have a size that covers the upper surfaces of all of the battery modules 220 received in the battery pack case 100, and heat exchange between coolants received in all of the water tanks may be performed through the heat sink 300.
In connection therewith, a flow path 310 configured to guide flow of the coolant is formed in the heat sink 300, and the temperature of the coolant introduced into and discharged from the heat sink 300 may be maintained at a predetermined level.
The battery pack case 100 may be configured to be open at the upper part thereof, and the heat sink 300 may be coupled to the battery pack case 100 so as to cover the upper surface of the battery pack case 100. Of course, it is obvious that a separate upper cover may be further provided above the heat sink 300.
The water tank 230 is formed in a rectangular parallelepiped shape in which the lower surface of the water tank that faces the plurality of battery cells and the upper surface of the water tank, which is opposite the lower surface, are wide, and the area of each of the upper surface and the lower surface corresponds to the area of the upper surface of the battery cell stack.
During repeated charging and discharging of the battery cell 220, the electrode assembly is expanded and contracted, and gas is generated as a byproduct of charging and discharging. As a result, the module case may swell. A partition wall 110 may be added between one module case 210 and another module case 210 in order to minimize the effect of swelling of one module case 210 on module cases adjacent thereto and to fix and support the module cases 210.
Referring to
A through-hole is formed in one surface of the water tank 230 that faces the plurality of battery cells 220, and a sealing member 231 is added to the through-hole in order to hermetically seal the through-hole. The sealing member 231 is made of a material that is melted by high-temperature gas or sparks discharged from the battery cell 220. That is, when the battery cell 220 is in a normal state, the state in which the through-hole is hermetically sealed by the sealing member 231 is maintained. When the temperature of an ignited battery cell, e.g. a battery cell 220′, exceeds the melting temperature of the sealing member 231, however, the sealing member 231 is melted, whereby the through-hole is opened. Consequently, a coolant W1 in the water tank 230 may be directly introduced into the battery cell.
The coolant received in the water tank 230 is evaporated by fire outbreak in the battery cell, whereby the volume of the coolant is increased and thus the coolant is transformed into a high pressure state. When the through-hole 232 is opened, therefore, the coolant may be sprayed toward the ignited battery cell at a high pressure.
At this time, the shape of the sealing member 231 that is not adjacent to the ignited battery cell 220′ may be maintained without melting. Consequently, the coolant may be ejected through only the through-hole from which the sealing member has been removed.
The sealing member may be made of a thermoplastic polymer resin having a melting point of about 200° C. or less. For example, a material having a melting point of about 100° C. to about 200° C., such as polyethylene or polypropylene, may be used as the thermoplastic polymer resin.
The through-hole 232 is filled with the sealing member 231, and the sealing member may include an extension portion 235 further extending outwards from the outer surface of the water tank than the circumference of the through-hole. The extension portion 235 is a portion that further extends from the outer surface of the water tank. In a normal state, the extension portion may increase the force of coupling between the water tank and the sealing member 231. When fire breaks out in the battery cell, the extension portion may be rapidly melted to open the through-hole.
Meanwhile, in consideration of the fact that the coolant W1 is directly injected into the pouch-shaped battery cell, it is necessary to prevent flames of the pouch-shaped battery cell from expanding or to prevent explosion of the pouch-shaped battery cell due to injection of the coolant. Consequently, it is preferable for no combustible material to be used as an additive included in the coolant. Alternatively, in the case in which a combustible material is used as the additive, the additive may be added in an amount sufficient to prevent secondary explosion of the pouch-shaped battery cell and in such an amount that the additive is used as an antifreeze solution in order to prevent freezing of the coolant.
The coolant W2 introduced into and discharged from the heat sink may be the same liquid as the coolant W1 received in the water tank. For example, water may be used as the coolant W1 and/or the coolant W2.
When a battery cell constituted by a lithium secondary battery is defective, overcharged, or overheated, a thermal runaway phenomenon occurs in the battery cell. When the battery cell is in a thermal runaway state, the temperature of the battery cell may rise up to a temperature at which gas venting occurs, e.g. about 260° C. In addition, the temperature of the battery cell may be continuously increased while gas venting occurs.
In the case in which a plurality of battery cells is received in a battery pack case to manufacture a battery pack, when one battery cell is in a thermal runaway state, heat and flames may be transferred to a battery cell adjacent thereto, whereby the adjacent battery cell may be overheated and may thus be in a thermal runaway state. The battery cell in the thermal runaway state may heat another battery cell adjacent thereto, whereby a thermal runaway chain reaction may occur. When a battery cell in a thermal runaway state is present in the battery pack case, therefore, thermal runaway of a plurality of battery cells may occur, and this may spread more widely, whereby great damage may be caused. In the case in which a plurality of battery cells is in a thermal runaway state, the battery cells may reach a temperature of about 1000° C. or higher, and this temperature is maintained until the battery cells are completely destroyed by fire, whereby a user may be in danger.
Consequently, it is very important to extinguish the ignited battery cell before flames and heat of the ignited battery cell spread to a battery cell adjacent thereto.
In the battery pack according to the present invention, therefore, the water tank 230 containing the coolant W1 is provided at a position adjacent to the upper parts of the plurality of battery cells 220, and the through-hole, through which the coolant W1 flows out, is hermetically sealed by the sealing member having a low melting point. When fire breaks out in the battery cell 220′, therefore, the sealing member 231 adjacent thereto is melted to open the through-hole 232. Consequently, the coolant received in the water tank 230 is directly introduced into the battery cell 220′ through the through-hole. The overheated or ignited pouch-shaped battery cell is rapidly extinguished or cooled through the above process, whereby it is possible to rapidly prevent spread of thermal runaway, and therefore it is possible to secure time necessary to extinguish flames of the battery cell using a watering facility located at the outside.
In addition, even though the battery pack according to the present invention is mounted at a position close to a user, e.g. in an electric vehicle, it is possible to rapidly extinguish flames of the battery cell, and therefore it is possible to secure user safety.
The through-hole 232 formed in the water tank 230 may be configured to have a structure in which a plurality of holes is formed in one surface of the water tank so as to be uniformly dispersed. Even though fire breaks out in a certain battery cell, therefore, a sealing member located so as to be adjacent thereto may be melted. Even though fire breaks out in a battery cell located at a certain position, therefore, the coolant may be directly injected into the ignited battery cell irrespective of the position of the battery cell. That is, the number of through-holes formed in the water tank may be set in consideration of the size and number of battery module housings and the shape, size, and number of battery cells disposed in the battery module housing.
Referring to
Each of the plurality of battery cells 220 is a prismatic battery cell that is generally configured to have a hexahedral structure and that has an electrode assembly received in a battery case made of a metal material, wherein a positive electrode terminal and a negative electrode terminal may protrude from the upper surface of the prismatic battery cell so as to face the water tank 230. The prismatic battery cells may be disposed in tight contact with each other such that relatively wide side surfaces of the prismatic battery cells are stacked so as to be adjacent to each other.
In addition, a through-hole is formed in one surface of the water tank 230 that faces the plurality of battery cells, and a sealing member 231 made of a material that has a low melting point is added to the through-hole. When fire breaks out in the battery cell, the sealing member may be melted to open the through-hole, and the coolant received in the water tank may be directly introduced into the battery cell 220 through the through-hole.
In addition thereto, the description of the battery pack according to the first embodiment is equally applicable to the battery pack according to the second embodiment. In addition, the same components of the second embodiment as the first embodiment may be denoted by the same reference numerals.
Referring to
In addition, a through-hole is formed in one surface of the water tank 230 that faces the plurality of battery cells, and a sealing member 231 made of a material that has a low melting point is added to the through-hole. When fire breaks out in the battery cell, the sealing member may be melted to open the through-hole, and the coolant received in the water tank may be directly introduced into the battery cell 220 through the through-hole.
In addition thereto, the description of the battery pack according to the first embodiment is equally applicable to the battery pack according to the third embodiment. In addition, the same components of the third embodiment as the first embodiment may be denoted by the same reference numerals.
Those skilled in the art to which the present invention pertains will appreciate that various applications and modifications are possible within the category of the present invention based on the above description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2020-0157816 | Nov 2020 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2021/016687 | 11/16/2021 | WO |
