Battery module with a path through which an internally supplied coolant can flow in the event of thermal runaway, and battery pack and energy storage system containing such a

Abstract

Unit module stack comprising the following: a plurality of unit modules (121A) stacked on top of each other, each unit module having a plurality of battery cells (121) stacked on top of each other; a swelling absorption cushion (126) inserted between the adjacent unit modules (121A); wherein the swelling absorption pad (126) has a coolant channel (P) which is designed to extend along a longitudinal direction thereof, wherein the coolant channel (P) contains the following: an inlet opening (126a) which is provided on one side of the swelling absorption pad (126) in the longitudinal direction; an outlet opening (126b) provided on the other side of the swelling-absorption pad (126) in the longitudinal direction; and a cooling section (126c) configured to connect the inlet port (126a) and the outlet port (126b).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a battery module having a path through which a coolant introduced therein can flow when a thermal runaway phenomenon occurs, a battery pack, and an energy storage system (ESS) including the battery module, and more particularly to a battery module having a structure in which a coolant introduced therein can move smoothly between adjacent unit modules when water is injected into a battery module where a thermal runaway phenomenon occurs, and a battery pack and an ESS including the battery module.

[0002] This application claims priority to Korean Patent Application No. 10-2019-0063999, filed in South Korea on May 30, 2019.

[0003] This application claims priority to Korean Patent Application No. 10-2019-0068053, filed in South Korea on June 10, 2019. STATE OF THE ART

[0004] In a battery module containing multiple battery cells, a thermal runaway phenomenon occurs when an abnormality such as a short circuit occurs in some battery cells, causing the temperature to continuously rise, causing the battery cell temperature to exceed a critical temperature. If a thermal runaway phenomenon such as the one described above occurs in some battery cells, a safety hazard may arise.

[0005] When a flame or the like is generated due to the thermal runaway phenomenon occurring in some battery cells, the flame may quickly increase the temperature of adjacent battery cells, and the thermal runaway may thus spread to adjacent cells in a short time.

[0006] If the thermal runaway phenomenon that occurs in some battery cells is not responded to quickly, it may lead to disasters such as the ignition and explosion of a battery module or a battery pack, which is a battery unit with a larger capacity than the battery cell, and this may not only cause property damage but also cause safety problems.

[0007] Therefore, when a flame occurs due to the phenomenon of thermal runaway in some battery cells inside the battery module, it is urgent to quickly lower the temperature inside the battery module to prevent the flame from spreading further.

[0008] A cell stack housed within the battery module has a structure in which a cushion for securing a space capable of absorbing swelling is arranged between each adjacent unit module, with a certain number of battery cells being used as a unit module.

[0009] When thermal runaway occurs in the battery module having the above structure even though a coolant is introduced into the battery module, the coolant cannot flow smoothly between the adjacent unit modules due to the cushion.

[0010] Therefore, there is a need to develop a battery module with a structure that can ensure a smooth flow of coolant while using the cushion-equipped structure.

[0011] Furthermore, a battery module using an air-cooled structure has an air passage through which a coolant escapes without remaining inside, even though the coolant is introduced to lower the temperature inside the battery module and extinguish the flame. Therefore, there is a need to develop a battery pack with a structure that can block the air passage when a coolant is introduced into a battery module in which a thermal runaway phenomenon has occurred. REVELATION Technical problem

[0012] The present disclosure is designed to solve the problems of the prior art, and therefore, the present disclosure is directed to preventing a flame from spreading greatly by quickly lowering the temperature inside a battery module when the flame is generated due to a thermal runaway phenomenon in a few battery cells in the battery module.

[0013] However, the technical problem to be solved by the present disclosure is not limited to the above, and other objects not mentioned here will be apparent to those skilled in the art from the following description. Technical solution

[0014] In one aspect of the present disclosure, there is provided a battery module comprising: a unit module stack formed by stacking a plurality of unit modules, each unit module having a plurality of battery cells stacked on top of one another; a swelling absorption pad interposed between the adjacent unit modules; and a module case configured to accommodate the unit module stack and the swelling absorption pad, wherein the swelling absorption pad has a coolant channel formed to extend along a longitudinal direction thereof.

[0015] The coolant channel may include an inlet port provided on one side of the swelling absorption pad in the longitudinal direction; an outlet port provided on the other side of the swelling absorption pad in the longitudinal direction; and a cooling portion configured to connect the inlet port and the outlet port to each other and having a larger cross-sectional area than the inlet port and the outlet port.

[0016] The coolant channel may have an open shape so that a coolant flowing through the coolant channel directly contacts a pair of battery cells that are in contact with the swelling absorption pad.

[0017] The entrance opening can be located higher than the exit opening.

[0018] The battery module may include an air inlet formed through the module case on one side of the unit module stack in a stacking direction; and an air outlet formed through the module case on the other side of the unit module stack in the stacking direction.

[0019] The battery module may include an expansion pad disposed within the air inlet and the air outlet and configured to expand upon contact with a coolant introduced into the battery module to close the air inlet and the air outlet.

[0020] The battery module may include a pair of busbar frames each coupled to one side and the other side of the unit module stack in a width direction.

[0021] The air inlet and the air outlet may be formed at locations corresponding to an empty chamber formed between the busbar frame and the module housing.

[0022] The battery module may include a coolant pipe insertion hole formed through the module case from one side and the other side of the unit module stack in the stacking direction to communicate with an empty chamber formed between the bus bar frame and the module case.

[0023] A battery pack according to an embodiment of the present disclosure includes a plurality of battery modules according to an embodiment of the present disclosure as described above.

[0024] An energy storage system (ESS) according to an embodiment of the present disclosure includes a plurality of battery modules according to an embodiment of the present disclosure as described above. Beneficial effects

[0025] According to one aspect of the present disclosure, when a flame is generated in some battery cells within the battery module due to a thermal runaway phenomenon, it is possible to prevent further spread of the flame by quickly lowering the temperature inside the battery module. That is, it is possible to quickly lower the temperature inside the battery module by solving the problem that a coolant cannot flow evenly between adjacent unit modules due to the pads when the coolant is introduced into the battery module having a structure in which each pad is arranged to absorb swelling between adjacent unit modules.

[0026] Moreover, according to another aspect of the present disclosure, when a coolant is introduced into the battery module in which thermal runaway occurs, in a battery pack including an air-cooled battery module, it is possible to effectively prevent the propagation of the thermal runaway phenomenon by using a structure in which the air passage for cooling is blocked so that the coolant remains within the battery module. DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings illustrate a preferred embodiment of the present disclosure and, together with the above disclosure, serve to provide a better understanding of the technical features of the present disclosure. Thus, the present disclosure should not be construed as limited to the drawings. Fig. 1 is a diagram illustrating an energy storage system (ESS) according to an embodiment of the present disclosure. Fig. 2 is a diagram illustrating the connection structure between a water tank and a battery module and the relationship between the water tank and a controller in a battery pack according to an embodiment of the present disclosure. Fig. 3 is a diagram illustrating the relationship between a sensor, the controller, and the water tank in the battery pack according to an embodiment of the present disclosure. The Fig. 4 and Fig. 5 are respective views showing a battery module applied to the battery pack according to an embodiment of the present disclosure. The Fig. 6 and Fig. 7 are diagrams showing an internal structure of the module applied to the battery pack according to an embodiment of the present disclosure. The Fig. 8 and Fig. 9 are diagrams showing a detailed structure of a swelling absorption pad employed in the battery pack according to an embodiment of the present disclosure. Fig. 10 is a diagram showing an expansion pad employed in the battery pack according to an embodiment of the present disclosure. Fig. 11 is a diagram illustrating the connection structure between a water tank and a battery module and the relationship between a valve, a controller, and the water tank in a battery pack according to another embodiment of the present disclosure. BEST EXECUTION

[0028] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before proceeding with the description, it should be understood that the terms used in the specification and the appended claims should not be construed as being limited to generic and dictionary meanings. Rather, they are to be interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure, as well as on the principle that the inventor is allowed to appropriately define terms for the best explanation. Therefore, the description proposed here is only a preferred example for illustrative purposes and is not intended to limit the scope of the disclosure, so it should be understood that other equivalents and modifications may be made thereto without departing from the scope of the disclosure.

[0029] With reference to Fig. 1, an energy storage system (ESS) according to an embodiment of the present disclosure includes a plurality of battery packs 100 according to an embodiment of the present disclosure.

[0030] With reference to the Fig. 1 to 3, the battery pack 100 according to an embodiment of the present disclosure includes a pack case 110, a battery module 120, a water tank 130, a controller 140, a coolant line 150, and a sensor 160.

[0031] The pack case 110 is a roughly rectangular frame that defines the appearance of the battery pack 100 and has a chamber formed therein so that the plurality of battery modules 120, the water tank 130, the controller 140, the coolant line 150, and the sensor 160 can be mounted therein.

[0032] The battery module 120 is provided in multiples, and the plurality of battery modules 120 are stacked vertically in the package case 110 to form a single module stack. The specific structure of the battery module 120 will be described later with reference to Fig. 4 to 10 are described in detail.

[0033] The water tank 130 is provided within the pack case 110 and stores a coolant to be supplied to the battery module 120 when a thermal runaway phenomenon occurs in the battery module 120. The water tank 130 can be arranged above the module stack so that the coolant can be supplied quickly and smoothly. Although a separate coolant pump is not used, in this case, the coolant can be quickly supplied into the battery module 120 by the free fall and water pressure of the coolant. Of course, a separate coolant pump can also be used for the water tank 130 to supply the coolant faster and more smoothly.

[0034] The controller 140 may be connected to the sensor 160 and the water tank 130 and output a control signal to open the water tank 130 according to the detection signal of the sensor 160. Furthermore, the controller 140 may additionally perform a function as a battery management system (BMS) connected to each battery module 120 to manage its charging and discharging, in addition to the above function.

[0035] The controller 140 outputs a control signal to open the water tank 130 when gas or a temperature rise above a reference value is detected within the battery pack 100 due to a thermal runaway phenomenon occurring in at least one of the plurality of battery modules 120, and allows the coolant to be supplied into the battery module 120 accordingly.

[0036] When the water tank 130 is opened according to the control signal from the controller 140, the coolant is gradually supplied from a battery module 120 located at a relatively upper portion to a battery module 120 located at a relatively lower portion. Thus, the flame in the battery modules 120 is extinguished and the battery modules 120 are also cooled, thereby preventing the thermal runaway phenomenon from spreading further in the battery pack 100.

[0037] The coolant line 150 connects the water tank 130 and the battery module 120 and functions as a passage for transporting the coolant supplied from the water tank 130 to the battery module 120. To perform this function, one end of the coolant line 150 is connected to the water tank 130, and the other end of the coolant line 150 is branched according to the number of battery modules 120 and connected to the plurality of battery modules 120, respectively.

[0038] When the thermal runaway phenomenon as described above occurs in at least a portion of the plurality of battery modules 120, the sensor 160 detects a temperature increase and / or a gas leak and transmits a detection signal to the controller 140. To perform this function, the sensor 160 may be a temperature sensor or a gas detection sensor, or a combination of the temperature sensor and the gas detection sensor.

[0039] The sensor 160 is mounted within the pack housing 110 to detect a temperature increase or gas evolution within the battery pack 100. The sensor 160 may be attached to an inside or outside of each of the plurality of battery modules 120 to quickly detect the temperature of the battery module 120 and / or gas evolution within the battery module 120.

[0040] Next, the battery module 120 applied to the battery pack 100 according to an embodiment of the present disclosure will be described with reference to FIG. Fig. 4 to 10 are described in more detail.

[0041] With reference to the Fig. 4 to 10, the battery module 120 may be implemented to include a plurality of battery cells 121, a busbar frame 122, a module case 123, an air inlet 124, an air outlet 125, and an expansion pad 127. Furthermore, the battery module 120 may further include swelling absorption pads 126 in addition to the above components.

[0042] The battery cell 121 is provided in multiples, and the plurality of battery cells 121 are stacked to form a unit module 121A. A plurality of unit modules 121A are also stacked to form a single unit module stack. For example, a battery cell can be used as the battery cell 121. The battery cell 121 has a pair of electrode terminals 121a, each extending from both sides thereof in a longitudinal direction.

[0043] The busbar frame 122 is provided in pairs, and the pair of busbar frames 122 covers one side and the other side of the unit module stack in a width direction. The electrode terminal 121a of the battery cell 121 is passed through a slot formed on the busbar frame 122 and is bent and fixed to the busbar frame 122 by welding or the like. That is, the plurality of battery cells 121 can be electrically connected through the busbar frame 122.

[0044] The module housing 123 has a substantially rectangular, cuboid shape and accommodates the unit module stack. The air inlet 124 and the air outlet 125 are formed on one side and the other side of the module housing 123 in the longitudinal direction.

[0045] The air inlet 124 is formed on one side of the module stack in the stacking direction, namely, on one side of the battery module 120 in the longitudinal direction, and has a hole shape extending through the module housing 123. The air outlet 125 is formed on the other side of the module stack in the stacking direction, namely, the other side of the battery module 120 in the longitudinal direction, and has a hole shape extending through the module housing 123.

[0046] The air inlet 124 and the air outlet 125 are arranged on diagonally opposite sides along the longitudinal direction of the battery module 120.

[0047] At the same time, an empty chamber is formed between the busbar frame 122 and the module case 123. That is, the empty chamber, in which air flows to cool the battery cell 121, is formed between one of six surfaces of the module case 123 facing one side and the other side of the battery cell 121 in the longitudinal direction and the busbar frame 122. The empty chamber is formed on each of the two sides of the battery module 120 in the width direction.

[0048] The air inlet 124 is formed at a position corresponding to the empty chamber formed on one side of the battery module 120 in the width direction, and the air outlet 125 is formed at a position corresponding to the empty chamber formed on the other side of the battery module 120 in the width direction.

[0049] In the battery module 120, the air introduced therein through the air inlet 124 cools the battery cell 121 while moving from the empty chamber formed on one side of the battery module 120 in the width direction to the empty chamber formed on the other side of the battery module 120 in the width direction, and then exits the battery module 120 through the air outlet 125. That is, the battery module 120 corresponds to an air-cooled battery module.

[0050] The coolant pipe 150 extends from one side or the other side of the module stack in the stacking direction through the module case 123 and communicates with the empty chamber formed between the busbar frame 122 and the module case 123. A coolant pipe insertion hole 123a, into which the coolant pipe 150 can be inserted, is formed on one of six surfaces of the module case 123 where the air inlet 124 or the air outlet 125 is formed. The coolant pipe insertion hole 123a communicates with the empty chamber, and the coolant pipe 150 can be inserted into the battery module 120 through the coolant pipe insertion hole 123a. The coolant pipe insertion hole 123a may be formed on a side opposite the air inlet 124 or the air outlet 125 along the width direction of the battery module 120.

[0051] The coolant introduced into the battery module 120 through the coolant passage 150 flows from the empty chamber formed on one side of the battery module 120 in the width direction to the other empty chamber formed on the other side of the battery module 120 in the width direction to fill the interior of the battery module 120, as shown in FIGS. Fig. 4 and Fig. 5 is shown.

[0052] With reference to the Fig. 7 to 9, the battery module 120 may include a swelling absorption pad 126 interposed between the unit modules 121A of the module stack. The swelling absorption pad 126 may include materials such as silicon, graphite, expanded polypropylene (EPP), expanded polystyrene (EPS), and the like, for example, and may have elasticity to absorb volume expansion of the battery cell 121 caused by swelling.

[0053] With reference to the Fig. 7 and Fig. 8, the swelling absorption pad 126 includes a coolant channel P that provides a path through which the coolants can flow so that the coolant can cool the battery cell 121 while passing between the adjacent unit modules 121A.

[0054] The coolant channel P includes an inlet port 126a provided on one side of the swelling absorption pad 126 in the longitudinal direction, an outlet port 126b provided on the other side of the swelling absorption pad 126 in the longitudinal direction, and a cooling portion 126c connecting the inlet port 126a and the outlet port 126b.

[0055] The coolant channel P has an open shape so that the coolant flowing through the coolant channel P directly contacts the pair of battery cells 121 in contact with the swelling absorption pad 126.

[0056] The coolant flowing into the empty chamber formed on one side of the battery module 120 in the width direction gradually passes through the inlet opening 126a, the cooling portion 126c, and the outlet opening 126b, and moves to the empty chamber formed on the other side of the battery module 120 in the width direction to come into contact with the battery cell 121, thereby cooling the battery cell 121.

[0057] The cooling section 126c has a larger cross-sectional area than the inlet opening 126a and the outlet opening 126b, so that the coolant entering through the inlet opening 126a between the adjacent battery cells 121 can remain there as long as possible.

[0058] Consequently, the coolant introduced through the inlet opening 126a has a slow flow rate in the cooling section 126c and has sufficient time to contact the battery cell 121. After complete heat exchange with the battery cell 121, the coolant exits through the outlet opening 126b.

[0059] At the same time, with reference to Fig. 9, the inlet opening 126a may be positioned higher than the outlet opening 126b. As described above, if the inlet opening 126a is positioned higher than the outlet opening 126b, the coolant can flow more smoothly, thereby improving the cooling performance.

[0060] With reference to Fig. 10, the expansion pad 127 is disposed within the air inlet 124 and the air outlet 125 and has a smaller size than the open area of ​​the air inlet 124 and the air outlet 125. The expansion pad 127 preferably has a size of less than 30% compared to the open area of ​​the air inlet 124 and the air outlet 125 so that the air can flow smoothly through the air inlet 124 and the air outlet 125 when the battery module 120 is used normally.

[0061] The expansion pad 127 expands upon contact with the coolant introduced into the battery module 120 to close the air inlet 124 and the air outlet 125. The expansion pad 126 contains a resin that has a very high expansion rate when absorbing moisture, for example, a resin whose volume increases by twice or more compared to its initial volume when it comes into contact with a sufficient amount of moisture. Polyester staple fiber, for example, is mentioned as the resin for the expansion pad 127.

[0062] By attaching the expansion pad 127, the air inlet 124 and the air outlet 125 are closed when a thermal runaway phenomenon occurs in at least some battery modules 120, thus introducing a coolant into the battery modules 120. When the air inlet 124 and the air outlet 125 are closed as described above, the coolant introduced into the battery module 120 does not escape to the outside but remains inside the battery modules 120, thereby quickly resolving the thermal runaway phenomenon occurring in the battery modules 120.

[0063] Next, with reference to Fig. 11 describes a battery pack according to another embodiment of the present disclosure.

[0064] The battery pack according to the further embodiment of the present disclosure differs from the battery pack 100 according to the above-described embodiment of the present disclosure only in that a valve 170 is mounted within the coolant line 150, and the other components are substantially the same.

[0065] Thus, the battery pack according to the further embodiment of the present disclosure will be described based on the valve 170, and the features identical to the previous embodiment will not be described in detail.

[0066] The valve 170 is provided as many times as the number of the plurality of battery modules 120, and the valves 170 are each installed adjacent to the plurality of battery modules 120 to individually allow or block the flow of the coolant flowing into the plurality of battery modules 120.

[0067] As described above, at least one sensor 160 is provided for each battery module 120 to independently operate the plurality of valves 170. Therefore, by providing the sensor 160 for each battery module 120, it is possible to introduce the coolant only into some battery modules 120 in which a thermal runaway phenomenon occurs.

[0068] That is, when the controller 140 receives a detection signal from some sensors 160, the controller 140 determines that a thermal runaway phenomenon occurs in the battery modules 120 to which the sensors 160 transmitting the detection signal are attached, and opens the valves 170 among the plurality of valves 170 adjacent to the battery modules 120 in which the thermal runaway occurs so that the coolant can be supplied therein.

[0069] The present disclosure has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are for illustrative purposes only, since various changes and modifications within the scope of the disclosure will become apparent to those skilled in the art from the detailed description. EMBODIMENTS 1. A battery module comprising: a unit module stack formed by stacking a plurality of unit modules, each unit module having a plurality of battery cells stacked on top of each other; a swelling absorption pad interposed between the adjacent unit modules; and a module case configured to accommodate the unit module stack and the swelling absorption pad, wherein the swelling absorption pad has a coolant channel formed to extend along a longitudinal direction thereof. 2. The battery module according to embodiment 1, wherein the coolant channel includes: an entrance opening provided on one side of the swelling absorption pad in the longitudinal direction; an exit opening provided on the other side of the swelling absorption pad in the longitudinal direction; and a cooling section configured to connect the inlet port and the outlet port, and having a larger cross-sectional area than the inlet port and the outlet port. 3. The battery module according to embodiment 1, wherein the coolant channel has an open shape so that a coolant flowing through the coolant channel directly contacts a pair of battery cells in contact with the swelling absorption pad. 4. The battery module according to embodiment 2, wherein the input opening is arranged higher than the output opening. 5. The battery module according to embodiment 1, wherein the battery module includes: an air inlet formed through the module housing at one side of the unit module stack in a stacking direction; and an air outlet formed through the module housing on the other side of the unit module stack in the stacking direction. 6. The battery module according to embodiment 5, wherein the battery module includes an expansion pad disposed within the air inlet and the air outlet and configured to expand upon contact with a coolant introduced into the battery module to close the air inlet and the air outlet. 7. The battery module according to Embodiment 6, wherein the battery module includes a pair of bus bar frames each coupled to one side and the other side of the unit module stack in a width direction. 8. The battery module according to embodiment 7, wherein the air inlet and the air outlet are formed at positions corresponding to an empty chamber formed between the bus bar frame and the module case. 9. The battery module according to Embodiment 7, wherein the battery module includes a coolant pipe insertion hole formed through the module case from one side and the other side of the unit module stack in the stacking direction to communicate with an empty chamber formed between the bus bar frame and the module case. 10. A battery pack comprising: a packing housing; a plurality of battery modules stacked in the pack housing; a water tank disposed above a module stack including the plurality of battery modules and configured to store a coolant; a coolant line configured to connect the water tank and the battery module; at least one sensor mounted within the pack housing for detecting a thermal runaway phenomenon occurring in at least a portion of the plurality of battery modules; and a controller configured to output a control signal for introducing a coolant into the battery module through the coolant line when a thermal runaway phenomenon is detected by the sensor. 11. The battery pack according to embodiment 10, wherein the battery pack includes a plurality of valves mounted in the coolant line, and the plurality of valves are each mounted adjacent to the plurality of battery modules of the module stack to individually permit or block the flow of coolant introduced into the plurality of battery modules. 12. The battery pack according to embodiment 11, wherein the sensor is attached to each of the plurality of battery modules. 13. The battery pack according to embodiment 12, wherein the controller is configured to output a control signal to open the valve of the plurality of valves mounted adjacent to a battery module in which a thermal runaway phenomenon has been detected by the sensor. 14. The battery pack according to embodiment 10, wherein the battery module includes: a unit module stack formed by stacking a plurality of unit modules, each unit module having a plurality of battery cells stacked on top of each other; a swelling absorption pad inserted between the adjacent unit modules; and a module housing configured to receive the unit module stack and the swelling absorption pad, wherein the swelling absorption pad has a coolant channel formed to extend along a longitudinal direction thereof. 15. The battery pack according to embodiment 14, wherein the coolant channel includes: an entrance opening provided on one side of the swelling absorption pad in the longitudinal direction; an exit opening provided on the other side of the swelling absorption pad in the longitudinal direction; and a cooling section configured to connect the inlet port and the outlet port and having a larger cross-sectional area than the inlet port and the outlet port. 16. The battery pack according to embodiment 14, wherein the coolant channel has an open shape so that a coolant flowing through the coolant channel directly contacts a pair of battery cells in contact with the swelling absorption pad. 17. The battery pack according to embodiment 16, wherein the input port is arranged higher than the output port. 18. An energy storage system (ESS) comprising a plurality of battery modules according to any one of embodiments 1 to 9. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] KR 10-2019-0063999

[0002] KR 10-2019-0068053

[0003]

Claims

[1] Unit module stack comprising: a plurality of unit modules (121A) stacked on top of each other, each unit module having a plurality of battery cells (121) stacked on top of each other; a swelling absorption pad (126) inserted between the adjacent unit modules (121A); wherein the swelling absorption pad (126) has a coolant channel (P) formed to extend along a longitudinal direction thereof, wherein the coolant channel (P) contains: an entrance opening (126a) provided on one side of the swelling absorption pad (126) in the longitudinal direction; an exit opening (126b) provided on the other side of the swelling absorption pad (126) in the longitudinal direction; and a cooling section (126c) configured to connect the input port (126a) and the output port (126b). [2] The unit module stack according to claim 1, wherein the input opening (126a) is arranged higher than the output opening (126b). [3] A unit module stack according to claim 1 or claim 2, wherein the cooling section (126c) has a larger cross-sectional area than the inlet opening (126a) and the outlet opening (126b). [4] The unit module stack of any one of claims 1 to 3, wherein the swelling absorption pad (126) includes materials of silicon, graphite, expanded polypropylene (EPP) and expanded polystyrene (EPS). [5] The unit module stack of any one of claims 1 to 4, wherein the unit module stack comprises a module housing (123) configured to receive the unit module stack and the swelling absorption pad (126). [6] The unit module stack according to claim 5, wherein the unit module stack includes a pair of bus bar frames (122) each coupled to one side and the other side of the unit module stack in a width direction. [7] The unit module stack according to claim 6, wherein the unit module stack includes a coolant pipe insertion hole (123a) formed through the module case (123) from one side and the other side of the unit module stack in the stacking direction to communicate with an empty chamber formed between the bus bar frame (122) and the module case (123).

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