Battery pack including a heat transfer member having a cooling fluid inlet and outlet formed therein

Abstract

The present invention relates to a battery pack including a battery cell stack including a plurality of battery cells, a cooling member for cooling the battery cell stack, a heat transfer member for dissipating heat from the plurality of battery cells to the cooling member, and a pack case that houses the battery cell stack, the cooling member, and the heat transfer member, the heat transfer member having an inlet and outlet for a cooling fluid, and the battery pack can adjust the temperature of the battery cells to a constant level when the temperature of the battery cells is below a danger temperature, and can rapidly cool the battery cells when the temperature is higher than the danger temperature.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0183490 dated December 21, 2021, 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 heat transfer member having an inlet and an outlet for a cooling fluid, more particularly, to a battery pack including a heat transfer member through which a cooling fluid can flow in and out so as to quickly cool a high-temperature battery cell among closely-arranged battery cells. [Background technology]

[0003] Lithium secondary batteries are used not only as energy sources for wireless mobile devices or wearable devices, which are multifunctional small products, but also as energy sources or power storage devices for electric vehicles and hybrid electric vehicles, which are presented as alternatives to existing gasoline and diesel vehicles that cause air pollution.

[0004] As the lithium secondary battery is used as a large-capacity, high-output energy source, ensuring the safety of the lithium secondary battery has become an important concern.

[0005] In a lithium secondary battery, the temperature increases during charging and discharging, and the high temperature phenomenon of the battery cells causes the performance of the battery cells to deteriorate. Therefore, in order to prevent the temperature of the battery cells from rising above a dangerous temperature, a heat transfer member made of a material with high thermal conductivity is provided in the battery pack, and the thermal energy of the battery cells is discharged through the heat transfer member.

[0006] However, when battery cells are arranged in close contact with each other to manufacture a battery pack with high energy density, heat is more likely to be transferred to adjacent battery cells rather than being discharged through the heat transfer member.

[0007] Furthermore, if the heat transfer member functions as a heat transfer path between the battery cells, the rate of heat transfer between the battery cells may increase dramatically.

[0008] Therefore, when a plurality of battery cells are arranged in close contact with each other and the temperature of a particular battery cell rises rapidly, a technology is required to prevent the heat from being transferred to other battery cells.

[0009] Patent Document 1 discloses a battery module including a battery cell, a cooling plate, and a heat absorbing member, and the cooling plate has a heat pipe inserted therein. Therefore, the heat pipe has a wide contact area with the battery cell, and the heat of the battery cell can be discharged to the cooling plate through the heat pipe.

[0010] Patent Document 2 discloses a battery pack in which a heat pipe is disposed between each of a number of battery cells, the heat pipe has a T-shaped cross section, and a cooling line is arranged at the lower end of the heat pipe.

[0011] However, the structures disclosed in Patent Documents 1 and 2 make it difficult to prevent thermal runaway of the battery cell when the temperature of the battery cell reaches or exceeds the vaporization temperature of the working fluid in the heat pipe.

[0012] Therefore, in a battery pack in which multiple battery cells are arranged in close contact, if a thermal runaway phenomenon occurs in a specific battery cell, a technology is needed that can prevent the thermal runaway from spreading by rapidly cooling the battery cell in which the thermal runaway has occurred. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Korean Patent Publication No. 10-2016-0041407 [Patent Document 2] Korean Patent Publication No. 10-2020-0104616 Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention has been made to solve the above problems, and aims to provide a battery pack including a heat transfer member that allows the inflow and outflow of cooling fluid to prevent the spread of thermal runaway of battery cells within the battery pack. [Means for solving the problem]

[0015] To achieve this object, a battery pack according to the present invention includes a battery cell stack including a plurality of battery cells, a cooling member for cooling the battery cell stack, a heat transfer member for dissipating heat from the plurality of battery cells to the cooling member, and a pack case that houses the battery cell stack, the cooling member, and the heat transfer member, and the heat transfer member is formed with an inlet and an outlet for a cooling fluid.

[0016] The heat transfer member may contain a coolant therein, and a phase transition may occur in which the coolant evaporates due to heat from the battery cells and condenses due to the cooling member, and heat may be transferred from the plurality of battery cells to the cooling member due to the phase transition of the coolant.

[0017] The heat transfer member may include a first heat transfer member disposed between the battery cell stack and the cooling member, and a second heat transfer member interposed between the plurality of battery cells.

[0018] The inlet and outlet of the heat transfer member may be provided with valves for controlling the inflow and outflow of the cooling fluid.

[0019] The valve may open to allow the cooling fluid to pass through an interior of the heat transfer member if the temperature of the battery cell rises to a dangerous temperature range.

[0020] Only the valve of the heat transfer member located adjacent to the battery cell whose temperature rises above a certain level can be opened.

[0021] The first heat transfer member and the second heat transfer member may have a flat plate shape.

[0022] The danger temperature range may be 150° C. or higher.

[0023] The battery pack may further include a temperature sensor that measures a temperature of the battery cell, and a controller that controls opening and closing of the valve according to the temperature measured by the temperature sensor.

[0024] The heat transfer member may be a heat pipe.

[0025] The inlet and outlet of the heat transfer member may be repeatedly opened and closed, and the inlet and outlet may be closed while a small amount of refrigerant remains inside the heat transfer member.

[0026] The exhaust portion may include a pressure reducing valve for reducing pressure so that the internal space of the heat transfer member, excluding the small amount of refrigerant, becomes a vacuum state.

[0027] The second heat transfer member or the heat insulating material may be disposed between the battery cells.

[0028] The insulating material may be made of an elastic material.

[0029] The present invention provides a device including the battery pack as an energy source.

[0030] Furthermore, the present invention can also be provided in the form of a combination of various means for solving the above problems. Effect of the Invention

[0031] As described above, the battery pack according to the present invention includes a heat transfer member for dissipating heat from a plurality of battery cells to a cooling member, and therefore can prevent a sudden increase in temperature of the battery cells.

[0032] Furthermore, if the temperature of a battery cell rises to a dangerous level, the battery cell can be rapidly cooled by injecting a cooling fluid into the heat transfer member, thereby effectively preventing thermal runaway. [Brief description of the drawings]

[0033] [Figure 1] 1 is a perspective view of a battery pack according to the present invention; [Diagram 2] 1 is a perspective view of a portion of a battery pack according to a first embodiment. [Diagram 3] 3 is a cross-sectional view taken along line AA' in FIG. 2. [Figure 4] 5A to 5C are vertical cross-sectional views showing states before and after the inlet and outlet portions of the heat transfer member are opened. [Diagram 5] FIG. 11 is a perspective view of a portion of a battery pack according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, in which a person having ordinary skill in the art to which the present invention pertains can easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, detailed description of related well-known functions or configurations will be omitted if it is determined that such detailed description may unnecessarily obscure the gist of the present invention.

[0035] 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 not only the case where the part is directly connected to another part, but also the case where the part is indirectly connected via another element between the two parts. In addition, when a part includes a certain component, it does not mean that the other component is excluded, but that the part may further include the other component, unless otherwise specified.

[0036] Furthermore, descriptions that limit or add specific elements are applicable to all inventions and are not limited to a particular invention unless otherwise specified.

[0037] Furthermore, throughout the description of the present invention and the claims, the singular includes the plural unless otherwise stated.

[0038] In addition, throughout the description of the present invention and the claims, unless otherwise stated, "or" includes "and." Therefore, "including A or B" means three cases: including A, including B, or including both A and B.

[0039] The invention will now be explained with reference to the drawings and in conjunction with detailed embodiments.

[0040] FIG. 1 is a perspective view of a battery pack according to the present invention.

[0041] Referring to FIG. 1, a battery pack according to the present invention includes a battery cell stack 100 including a plurality of battery cells 110, a cooling member 200 for cooling the battery cell stack 100, a heat transfer member 300 for dissipating heat from the plurality of battery cells 110 to the cooling member 200, and a pack case 400 that houses the battery cell stack 100, the cooling member 200, and the heat transfer member 300, and the heat transfer member 300 is formed with an inlet portion 321 and an outlet portion 322 for a cooling fluid.

[0042] The heat transfer member 300 includes a first heat transfer member 310 disposed between the battery cell stack 100 and the cooling member 200 , and a second heat transfer member 320 interposed between the plurality of battery cells 110 .

[0043] The heat transfer member 300 contains a refrigerant inside, and the case that contains the refrigerant is made of a material with excellent thermal conductivity. Therefore, the battery cells can be cooled and heat can be transferred between the battery cells through the heat transfer member 300, so that the first heat transfer member 310 can prevent temperature deviation between the battery cells, and the heat generated in the battery cells 110 can be discharged to the cooling member 200 through the first heat transfer member 310.

[0044] Specifically, a cooling member 200 for cooling the battery cells 110 is disposed under a battery cell stack 100 including a plurality of battery cells 110, and a first heat transfer member 310 is disposed between the battery cell stack 100 and the cooling member 200. Thus, heat from the battery cell stack 100 can be dissipated to the cooling member 200 via the first heat transfer member 310. Thus, the temperature of the battery cells 110 can be maintained within a certain range.

[0045] After the battery cell stack 100, heat transfer member 300, and cooling member 200 are housed inside the pack case 400, the open top surface of the pack case 400 is covered and sealed with a top plate 410, thereby assembling the battery pack.

[0046] However, unlike that shown in FIG. 1, the pack case 400 may have a monoframe shape in which an end plate is assembled in the direction in which the electrode terminals protrude, or a U-shaped frame shape, and the method of sealing the battery pack may vary depending on the shape of the pack case.

[0047] The cooling member 200 may have a configuration in which a refrigerant flows inside the case, and the cooling member 200 may be formed with an inlet and an outlet for the inflow and outflow of the refrigerant, and the refrigerant may be supplied from the outside of the pack case 400 and discharged to the outside of the pack case 400.

[0048] The battery cell may be a pouch-type battery cell in which an electrode assembly is housed in a pouch-type battery case made of a laminate sheet including a metal layer and a resin layer, or may be a prismatic battery cell or a cylindrical battery cell in which an electrode assembly is housed in a prismatic or cylindrical metal can.

[0049] In addition, although FIG. 1 shows a bidirectional pouch-type battery cell in which the positive electrode lead 111 and the negative electrode lead 112 protrude in opposite directions, it goes without saying that a unidirectional pouch-type battery cell in which the positive electrode lead 111 and the negative electrode lead 112 protrude in the same direction can also be applied.

[0050] FIG. 2 is a perspective view of a portion of the battery pack according to the first embodiment, and FIG. 3 is a cross-sectional view taken along line AA' in FIG. 2, and a valve 326 shown in FIG. 3 is omitted in FIG.

[0051] 2 and 3, the pack case and the cooling member are omitted from FIG.

[0052] The first heat transfer member 310 and the second heat transfer member 320 have a plate-like shape.

[0053] The lengths in the y and z directions of the second heat-transfer member 320 may be longer than or equal to the lengths in the y and z directions of the corresponding battery cells 110. Thus, the contact area between the battery cells 110 and the second heat-transfer member 320 can be maximized to achieve rapid heat exchange.

[0054] The inlet portion 321 and the outlet portion 322 of the second heat-transfer member 320 are formed at the upper and lower portions along the y direction, respectively. The length in the z direction of the first heat-transfer member 310 on which the battery cell stack and the second heat-transfer member 320 are disposed may be formed to be equal to or shorter than the length in the z direction of the structure in which the battery cells 110 and the second heat-transfer member 320 are closely attached to each other. However, the length in the x direction of the first heat-transfer member 310 may be formed to be approximately equal to the length in the x direction of the structure in which the battery cells 110 and the second heat-transfer member 320 are closely attached to each other. Thus, the first heat-transfer member 310 may be formed so that the area for heat exchange between the battery cells 110 and the second heat-transfer member 320 and the cooling member is maximized within a possible range.

[0055] Meanwhile, the inlet and outlet portions of the first heat transfer member 310 may be configured to protrude parallel to the x direction or parallel to the z direction.

[0056] In one specific example, when the temperature at which thermal runaway may occur due to heat generation from the battery cell is approximately 150°C, a state in which the temperature of the battery cell is below 150°C is defined as the safe temperature range, and a state in which the temperature of the battery cell is above 150°C is defined as the dangerous temperature range, the first heat transfer member 310 and the second heat transfer member 320 become flat in the safe temperature range and maintain a state in which the contact area with the battery cell is maximized, so that the battery cell can be smoothly cooled and overheating can be prevented.

[0057] FIG. 4 is a vertical cross-sectional view showing the states before and after the inlet and outlet portions of the heat transfer member are opened.

[0058] FIG. 4 is a vertical cross-sectional view of a second heat transfer member 320 among the heat transfer members, and the following description of the second heat transfer member can be similarly applied to the first heat transfer member.

[0059] The second heat-transfer member 320 may contain a refrigerant 325 therein, and may be configured in a vacuum state in which the remaining space excluding the refrigerant 325 is space. In the vacuum space, a phase transition may occur in which the refrigerant 325 evaporates due to heat and is condensed by the cooling member 200. Due to this phase transition of the refrigerant, heat from the plurality of battery cells 110 may be transferred to the cooling member 200 via the second heat-transfer member 320 and the first heat-transfer member 310.

[0060] In FIG. 4, the lower part of the second heat transfer member 320 where the refrigerant is present is in contact with the first heat transfer member 310, and the first heat transfer member 310 is arranged to be in contact with the cooling member, so that the temperature of the first heat transfer member 310 is lower than the temperature of the second heat transfer member 320.

[0061] Therefore, within the second heat transfer member 320, the refrigerant can condense in the lower portion, which is in contact with the first heat transfer member and has a relatively low temperature, and evaporate in the upper portion, which is relatively high temperature.

[0062] The first heat transfer member 310 may also undergo a phase transition in the same manner as the second heat transfer member 320 with respect to the vertical direction.

[0063] For example, the first and second heat transfer members may be heat pipes, and the heat transfer member of the present invention is applicable regardless of the type of known heat pipe.

[0064] In one specific example, when the temperature of a battery cell rises above 150°C and into the dangerous temperature range, the battery cell can be rapidly cooled by injecting a cooling fluid into the heat transfer member to suppress thermal runaway of the battery cell and prevent flames from being transmitted to adjacent battery cells.

[0065] In detail, the inlet 321 and the outlet 322 of the heat transfer member may each be provided with a valve 326 for controlling the inflow and outflow of the cooling fluid 327. If the temperature of the battery cell rises to a dangerous temperature range, the valve 326 opens to allow the cooling fluid 327 to pass through the inside of the heat transfer member 300.

[0066] When the valve 326 at the inlet 321 and the valve 326 at the outlet 322 are opened and the cooling fluid is continuously supplied to flow through the heat transfer member, the battery cells in contact with the second heat transfer member 320 through which the cooling fluid flows can be rapidly cooled.

[0067] The shape and position of the valve 326 are not particularly limited, and any type of valve known in the art can be used as long as it can regulate the inflow and outflow of the cooling fluid.

[0068] Meanwhile, the temperature of only a specific battery cell among a plurality of battery cells constituting a battery cell stack may rise to a dangerous temperature range. The valves of the inlet 321 and the outlet 322 may be opened only in the second heat transfer member 320 adjacent to the specific battery cell. That is, the valves of the heat transfer member may have a shape that can be individually adjusted to open and close.

[0069] Here, the first heat transfer member 310 arranged under the battery cell stack and the second heat transfer member may include an inlet and outlet portion like the second heat transfer member 320, but unlike the second heat transfer member 320 in which the cooling fluid flows vertically, the inlet and outlet portions may be arranged so that the cooling fluid flows horizontally.

[0070] For example, in a first heat transfer member having a rectangular structure on a plane, an inlet portion may be formed at one of the corner portions where two outer circumferences intersect at a right angle, and an outlet portion may be formed at one of the remaining three corner portions excluding the corner portion where the inlet portion is formed.

[0071] As described above, since the valve opens and closes depending on the temperature of the battery cell, the battery pack according to the present invention may further include a temperature sensor that measures the temperature of the battery cell, and a control unit that controls opening and closing of the valve depending on the temperature measured by the temperature sensor.

[0072] For example, in order to prevent a contact area between the battery cell and the heat transfer member from being reduced by the temperature sensor, the temperature sensor may be attached to an outer surface of the battery cell stack opposite to the outer surface facing the second heat transfer member. That is, when the lower surface of the battery cell stack faces the second heat transfer member, the temperature sensor may be disposed on the upper surface of the battery cell stack.

[0073] In the battery pack according to the present invention, when a battery cell overheats and thermal runaway occurs, posing a risk of fire, the overheated battery cell can be rapidly cooled by opening the heat transfer member and supplying a cooling fluid, thereby ensuring safety.

[0074] During normal use of the battery pack, the heat transfer member contains a small amount of refrigerant in a vacuum state, and the temperature of the battery cells can be maintained at a constant level through the phase transition process of the refrigerant.

[0075] However, if thermal runaway occurs in the battery cell, the vacuum state of the heat transfer member can be released by supplying a cooling fluid to the heat transfer member.

[0076] In such a case, the heat transfer member loses its function and must be replaced.

[0077] Therefore, in order to reuse the heat transfer member, the present invention has valves at the inlet and outlet that are repeatedly opened and closed, and when the open heat transfer member is closed, the inlet and outlet are closed in a state in which a small amount of cooling fluid remains as a refrigerant inside the heat transfer member, and a pressure reducing valve is provided at the outlet, so that the internal space of the heat transfer member except for the small amount of refrigerant can be made into a vacuum state.

[0078] The refrigerant 325 may be selected taking into consideration the temperature required for the expansion deformation, and may be selected, for example, from the group consisting of methanol, ethanol, and water.

[0079] The cooling fluid 327 is not particularly limited in material as long as it can rapidly cool the battery cells that are heated to a dangerous temperature range, and can be the same material as the refrigerant 325. For example, it can be selected from the group consisting of methanol, ethanol, and water.

[0080] FIG. 5 is a perspective view of a portion of a battery pack according to the second embodiment.

[0081] Referring to FIG. 5, a state in which the pack case and the cooling member are omitted from the battery pack according to the present invention is shown.

[0082] A first heat transfer member 310 is disposed under the battery cells 110 , and a second heat transfer member 320 or a heat insulating material 330 is disposed between the battery cells 110 .

[0083] That is, either the second heat transfer member 320 or the insulating material 330 is disposed between one battery cell 110 and another battery cell 110, and all the battery cells are in contact with the second heat transfer member 320 on at least one outer surface.

[0084] Therefore, heat exchange between adjacent battery cells can be blocked via the heat insulating material 330, and heat from the battery cells can be discharged to the outside via the heat transfer member.

[0085] Meanwhile, since the battery cells are lithium secondary batteries that expand and contract in volume during repeated charging and discharging, the volume of the battery cells may change during use of the battery pack. However, since it is preferable that the volume of the battery cell stack does not exceed a certain space provided in the battery pack, the increase in the volume of the battery cell stack can be buffered by disposing an insulating material made of an elastic material as the insulating material 330.

[0086] A device may be provided that includes the battery pack according to the present invention as an energy source, such as an electric vehicle, a hybrid electric vehicle, an ESS, an electric cart, an electric two-wheeler, etc.

[0087] In this way, even if the battery pack according to the present invention is applied to a device requiring high capacity and high output, a sudden increase in temperature of the battery cells can be prevented and heat conduction between the battery cells can be blocked, thereby providing a battery pack with improved safety.

[0088] 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]

[0089] 100 Battery Cell Stack 110 Battery Cell 111 Positive lead 112 Negative lead 200 Cooling material 300 Heat transfer material 310 First heat transfer member 320 Second heat transfer member 321 Inlet 322 Discharge section 325 Refrigerant 326 Valve 327 Cooling Fluid 330 Insulation 400 pack case 410 Top Plate

Claims

1. a battery cell stack including a plurality of battery cells; a cooling member for cooling the battery cell stack; a heat transfer member for dissipating heat from the plurality of battery cells to the cooling member; a pack case that accommodates the battery cell stack, the cooling member, and the heat transfer member therein; Including, The heat transfer member is provided with an inlet and an outlet for a cooling fluid, the heat transfer member is a heat pipe, a valve for controlling the inflow and outflow of the cooling fluid is attached to the inlet and outlet of the heat transfer member; A battery pack in which only the valve of the heat transfer member disposed adjacent to a battery cell whose temperature has risen above a certain level opens.

2. The heat transfer member contains a refrigerant therein, A phase transition occurs in which the refrigerant evaporates due to the heat of the battery cell and condenses due to the cooling member, The battery pack according to claim 1 , wherein heat is transferred from the plurality of battery cells to the cooling member by a phase transition of the refrigerant.

3. The heat transfer member is a first heat transfer member disposed between the battery cell stack and the cooling member; A second heat transfer member interposed between the plurality of battery cells; The battery pack of claim 1 , comprising:

4. The battery pack according to claim 1 , wherein the valve opens to allow the cooling fluid to pass through an inside of the heat transfer member if the temperature of the battery cell rises to a dangerous temperature range.

5. The battery pack according to claim 3 , wherein the first heat transfer member and the second heat transfer member have a flat plate shape.

6. The battery pack according to claim 4 , wherein the dangerous temperature range is 150° C. or higher.

7. The battery pack according to claim 1 , further comprising: a temperature sensor that measures a temperature of the battery cell; and a control unit that controls opening and closing of the valve according to the temperature measured by the temperature sensor.

8. The inlet and outlet of the heat transfer member may be repeatedly opened and closed, The battery pack according to claim 1 , wherein the inlet and the outlet are closed in a state where a small amount of refrigerant remains inside the heat transfer member.

9. The battery pack according to claim 8 , wherein the exhaust portion includes a pressure reducing valve for reducing pressure so that an internal space of the heat transfer member except for the small amount of refrigerant is in a vacuum state.

10. The battery pack according to claim 3 , wherein the second heat transfer member or the heat insulating material is disposed between the battery cells.

11. The battery pack according to claim 10 , wherein the heat insulating material is made of an elastic material.

12. A device comprising a battery pack according to any one of claims 1 to 11 as an energy source.

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