Unit module stack with a path through which an internally supplied coolant can flow if thermal runaway occurs.

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 opening (126a) and the outlet opening (126b), wherein the cooling section (126c) has a larger cross-sectional area than the inlet opening (126a) and the outlet opening (126b).

Description

TECHNICAL AREA

[0001] The present disclosure relates to a unit module stack having a path through which a coolant introduced therein can flow when a thermal runaway phenomenon occurs, and in particular to a unit module stack having a structure in which a coolant introduced therein can move smoothly between adjacent unit modules when water is injected into a battery module in which a thermal runaway phenomenon occurs.

[0002] The present application claims priority over Korean patent application No. 10-2019-0063999, which was filed in South Korea on May 30, 2019.

[0003] The present application further claims priority over Korean patent application No. 10-2019-0068053, which was filed in South Korea on June 10, 2019. STATE OF THE ART

[0004] In a battery module containing numerous battery cells, thermal runaway occurs when an abnormality, such as a short circuit, affects some of the cells, causing a continuous temperature increase until the cell temperature exceeds a critical threshold. When thermal runaway occurs in some battery cells, as described above, it can pose a safety risk.

[0005] If a flame or similar phenomenon occurs due to thermal runaway in some battery cells, the flame can quickly raise the temperature of neighboring battery cells, and the thermal runaway can thus spread to neighboring cells in a short time.

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

[0007] Therefore, if a flame occurs due to the phenomenon of thermal runaway in some battery cells within the battery module, it is urgently necessary to quickly lower the temperature within 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 is arranged between each adjacent unit module to secure a space that can absorb swelling, with a certain number of battery cells being used as a unit module.

[0009] If thermal runaway occurs in the battery module with the above-mentioned structure, even though a coolant has been introduced into the battery module, the coolant cannot flow evenly 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 uniform flow of coolant while using the padded structure.

[0011] Furthermore, a battery module using an air-cooled structure has an air duct through which a coolant escapes without remaining inside, even though the coolant is introduced to lower the temperature within 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 duct when a coolant is introduced into a battery module where thermal runaway has occurred. REVELATION Technical Problem

[0012] The present disclosure is designed to solve the problems of the prior art, therefore the present disclosure is aimed at preventing a flame from spreading rapidly by quickly reducing the temperature within 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 problems which are not mentioned here will be apparent to the person skilled in the art from the following description. Technical solution

[0014] According to one aspect of the present disclosure, a unit module stack is provided comprising: a plurality of unit modules stacked on top of each other, 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; wherein the swelling absorption pad has a coolant channel configured to extend along a longitudinal direction thereof.

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

[0016] The entrance opening can be positioned higher than the exit opening.

[0017] The swelling absorption pad may contain materials made of silicon, graphite, expanded polypropylene (EPP) and expanded polystyrene (EPS).

[0018] The unit module stack may include a module housing configured to accommodate the unit module stack and the swelling absorption pad.

[0019] The unit module stack can have a pair of busbar frames, each coupled to one side and the other side of the unit module stack in a width direction.

[0020] The unit module stack may have an insertion hole for a coolant line formed through the module housing 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 busbar frame and the module housing. Beneficial effects

[0021] If a flame is generated in some battery cells within the battery module due to a thermal runaway phenomenon, it is possible, according to one aspect of the present disclosure, to prevent the further propagation of the flame by rapidly lowering the temperature within the battery module. That is, it is possible to rapidly lower the temperature within the battery module by solving the problem of a coolant not being able to flow uniformly between adjacent unit modules due to the cushions present when the coolant is introduced into the battery module, which has a structure in which each cushion is arranged to absorb swelling between adjacent unit modules.

[0022] Furthermore, according to another aspect of the present disclosure, if a coolant is introduced into the battery module in which thermal runaway occurs, it is possible to effectively prevent the propagation of the thermal runaway phenomenon in a battery pack containing an air-cooled battery module by using a structure in which the air channel for cooling is blocked, so that the coolant remains inside the battery module. DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings illustrate a preferred embodiment of the present disclosure and, together with the preceding disclosure, serve to improve the understanding of the technical features of the present disclosure. Therefore, the present disclosure is not to be understood as being limited to the drawings. Fig. Figure 1 is a diagram showing an energy storage system (ESS) according to an embodiment of the present disclosure. Fig. Figure 2 is a diagram illustrating the connection structure between a water tank and a battery module, as well as the relationship between the water tank and a controller in a battery pack according to an embodiment of the present disclosure. Fig. Figure 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. Figure 5 are respective views showing a battery module used in the battery pack according to one embodiment of the present disclosure. The Fig. 6 and Fig. Figure 7 are diagrams showing an internal structure of the module applied in the battery pack according to an embodiment of the present disclosure. The Fig. 8 and Fig. Figure 9 are diagrams showing a detailed structure of a swelling absorption pad used in the battery pack according to an embodiment of the present disclosure. Fig. Figure 10 is a diagram showing an expansion cushion used in the battery pack according to an embodiment of the present disclosure. Fig. Figure 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

[0024] Preferred embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the description and the accompanying claims should not be interpreted as being limited to general and dictionary meanings. Rather, they are to be interpreted on the basis of the meanings and concepts that correspond to the technical aspects of the present disclosure, as well as on the basis of the principle that the inventor is permitted to define terms appropriately for the best explanation. Therefore, the description proposed here is only a preferred example for the purpose of illustration and is not intended to limit the scope of the disclosure.

[0025] With reference to Fig. 1 An energy storage system (ESS) according to an embodiment of the present disclosure comprises a plurality of battery packs 100 according to an embodiment of the present disclosure.

[0026] With reference to the Fig. According to one embodiment of the present disclosure, the battery pack 100 comprises a pack housing 110, a battery module 120, a water tank 130, a control unit 140, a coolant line 150 and a sensor 160.

[0027] The pack housing 110 is an approximately rectangular frame that defines the appearance of the battery pack 100 and has a chamber formed therein so that the multitude of battery modules 120, the water tank 130, the control unit 140, the coolant line 150 and the sensor 160 can be installed in it.

[0028] The battery module 120 is present in multiples, and the multiple battery modules 120 are stacked vertically in the pack housing 110 to form a single module stack. The specific structure of the battery module 120 will be described later with reference to the Fig. 4 to 10 described in detail.

[0029] The water tank 130 is located inside the pack housing 110 and stores a coolant that is to be delivered to the battery module 120 if a thermal runaway phenomenon occurs in the battery module 120. The water tank 130 can be positioned above the module stack to ensure a rapid and smooth delivery of the coolant. Although no separate coolant pump is used, the coolant can be quickly delivered to the battery module 120 by gravity and water pressure. Of course, a separate coolant pump can also be used for the water tank 130 to deliver the coolant more quickly and smoothly.

[0030] The controller 140 can 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 from the sensor 160. In addition, the controller 140 can also 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.

[0031] The controller 140 outputs a control signal to open the water tank 130 when gas or a temperature increase above a reference value is detected within the battery pack 100 due to a thermal runaway phenomenon occurring in at least one of the multiple battery modules 120, and it enables the coolant to be supplied to the battery module 120 accordingly.

[0032] 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 in a relatively upper section to a battery module 120 located in a relatively lower section. In this way, the flame in the battery modules 120 is extinguished and the battery modules 120 are also cooled, thus preventing the thermal runaway phenomenon from spreading further in the battery pack 100.

[0033] The coolant line 150 connects the water tank 130 and the battery module 120 and acts as a conduit to transport the coolant supplied by 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 each of those battery modules.

[0034] If the phenomenon of thermal runaway, as described above, occurs in at least one of the multiple 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 can be a temperature sensor, a gas detection sensor, or a combination of both.

[0035] The sensor 160 is mounted inside the pack housing 110 to detect a temperature increase or gas evolution within the battery pack 100. The sensor 160 can be attached to the inside or outside of any of the multiple battery modules 120 to quickly detect the temperature of the battery module 120 and / or gas evolving within the battery module 120.

[0036] Next, the battery module 120, which is used in the battery pack 100 according to an embodiment of the present disclosure, is described with reference to the Fig. 4 to 10 are described in more detail.

[0037] With reference to the Fig. From 4 to 10, the battery module 120 can be implemented to include a plurality of battery cells 121, a busbar frame 122, a module housing 123, an air inlet 124, an air outlet 125, and an expansion cushion 127. Furthermore, the battery module 120 can also include swelling absorption cushions 126 in addition to the above components.

[0038] The battery cell 121 is present in multiples, and the multiple battery cells 121 are stacked to form a unit module 121A. Multiple unit modules 121A are also stacked to form a single unit module stack. A battery cell can, for example, be used as a battery cell 121. The battery cell 121 has a pair of electrode terminals 121a, each extending longitudinally from both sides of it.

[0039] 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 lateral direction. The electrode terminal 121a of the battery cell 121 is guided through a slot formed on the busbar frame 122 and is bent and attached to the busbar frame 122 by welding or the like. That is, the plurality of battery cells 121 can be electrically connected by the busbar frame 122.

[0040] 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 longitudinally on one side and the other side of the module housing 123, respectively.

[0041] 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 on the other side of the battery module 120 in the longitudinal direction, and has a hole shape extending through the module housing 123.

[0042] The air inlet 124 and the air outlet 125 are arranged on diagonally opposite sides along the longitudinal direction of the battery module 120.

[0043] Simultaneously, an empty chamber is formed between the busbar frame 122 and the module housing 123. That is, the empty chamber, through which air flows to cool the battery cell 121, is formed between one of six surfaces of the module housing 123, which faces 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 transverse direction.

[0044] The air inlet 124 is formed at a location 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 location corresponding to the empty chamber formed on the other side of the battery module 120 in the width direction.

[0045] In battery module 120, the air introduced through air inlet 124 cools the battery cell 121 as it moves from the empty chamber formed on one side of battery module 120 in the width direction to the empty chamber formed on the other side of battery module 120 in the width direction, and then exits battery module 120 through air outlet 125. That is to say, battery module 120 is an air-cooled battery module.

[0046] The coolant line 150 runs from one side or the other of the module stack in the stacking direction through the module housing 123 and communicates with the empty chamber formed between the busbar frame 122 and the module housing 123. An entry hole 123a for the coolant line, into which the coolant line 150 can be inserted, is formed on one of the six surfaces of the module housing 123 where the air inlet 124 or the air outlet 125 is located. The entry hole 123a for the coolant line communicates with the empty chamber, and the coolant line 150 can be inserted into the battery module 120 through the entry hole 123a. The entry hole 123a for the coolant line can be formed on a side opposite the air inlet 124 or the air outlet 125 along the width direction of the battery module 120.

[0047] The coolant introduced into the battery module 120 via the coolant line 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 opposite side of the battery module 120 in the width direction, in order to fill the interior of the battery module 120, as shown in the Fig. 4 and Fig. 5 is shown.

[0048] With reference to the Fig. 7 to 9, the battery module 120 can contain a swelling absorption pad 126, which is inserted between the unit modules 121A of the module stack. The swelling absorption pad 126 can, for example, contain materials such as silicon, graphite, expanded polypropylene (EPP), expanded polystyrene (EPS), and the like, and exhibit elasticity to accommodate a volume expansion of the battery cell 121 caused by swelling.

[0049] With reference to the Fig. 7 and Fig. 8 The swelling absorption pad 126 contains a coolant channel P which 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.

[0050] The coolant channel P includes an inlet opening 126a, which is provided on one side of the swelling absorption pad 126 in the longitudinal direction, an outlet opening 126b, which is provided on the other side of the swelling absorption pad 126 in the longitudinal direction, and a cooling section 126c, which connects the inlet opening 126a and the outlet opening 126b.

[0051] 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, which are in contact with the swelling absorption pad 126.

[0052] The coolant flowing into the empty chamber formed on one side of the battery module 120 in the lateral direction passes stepwise through the inlet opening 126a, the cooling section 126c and the outlet opening 126b and moves to the empty chamber formed on the other side of the battery module 120 in the lateral direction to come into contact with the battery cell 121, thereby cooling the battery cell 121.

[0053] 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 between the adjacent battery cells 121 through the inlet opening 126a can remain there for as long as possible.

[0054] 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.

[0055] At the same time, with reference to Fig. 9, the inlet opening 126a is positioned higher than the outlet opening 126b. If, as described above, the inlet opening 126a is positioned higher than the outlet opening 126b, the coolant can flow more evenly, thereby improving the cooling performance.

[0056] With reference to Fig. 10 The expansion cushion 127 is arranged 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 cushion 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 uniformly through the air inlet 124 and the air outlet 125 when the battery module 120 is used normally.

[0057] The expansion pad 127 expands upon contact with the coolant introduced into the battery module 120, thereby closing the air inlet 124 and the air outlet 125. The expansion pad 126 contains a resin that exhibits a very high expansion rate when it absorbs moisture, for example, a resin whose volume doubles or more compared to its initial volume when it comes into contact with a sufficient amount of moisture. A polyester staple fiber is cited as an example of a resin used in the expansion pad 127.

[0058] By attaching the expansion cushion 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 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.

[0059] Next, with reference to Fig. 11 a battery pack according to a further embodiment of the present disclosure is described.

[0060] The battery pack according to the further embodiment of the present disclosure differs from the battery pack 100 according to the embodiment of the present disclosure described above only in that a valve 170 is fitted inside the coolant line 150, and the other components are essentially the same.

[0061] Thus, the battery pack according to the further embodiment of the present disclosure is described on the basis of valve 170, and the features identical to the previous embodiment are not described in detail.

[0062] The valve 170 is present as often as the number of multiple battery modules 120, and the valves 170 are each installed adjacent to the multitude of battery modules 120 so that they can individually allow or block the flow of the coolant flowing into the multitude of battery modules 120.

[0063] As described above, at least one sensor 160 is provided for each battery module 120 to operate the multiple valves 170 independently. Therefore, if the sensor 160 is provided for each battery module 120, it is possible to introduce the coolant only into those battery modules 120 where a thermal runaway phenomenon occurs.

[0064] That is, when the controller 140 receives a detection signal from some sensors 160, the controller 140 determines that a thermal runaway phenomenon is occurring in the battery modules 120 to which the sensors 160 sending the detection signal are attached, and opens the valves 170 from the plurality of valves 170 adjacent to the battery modules 120 in which the thermal runaway is occurring, so that the coolant can be directed into them.

[0065] The present disclosure has been described in detail. However, it is understood that while the detailed description and specific examples represent preferred embodiments of the disclosure, they serve only for illustrative purposes, since the person skilled in the art can infer from the detailed description various changes and modifications that are within the scope of the disclosure. EXECUTION FORMS 1. A battery module comprising the following: a unit module stack formed by stacking a plurality of unit modules, each unit module comprising a plurality of battery cells stacked on top of each other; a swelling absorption pad inserted between adjacent unit modules; and a module housing configured to accommodate the unit module stack and the swelling absorption pad, wherein the swelling absorption pad has a coolant channel which is designed to extend along a longitudinal direction thereof. 2. The battery module according to embodiment 1, wherein the coolant channel comprises the following: an inlet opening provided on one side of the swelling absorption pad in the longitudinal direction; an outlet opening provided on the other side of the swelling-absorption pad in the longitudinal direction; and a cooling section configured to connect the inlet opening and the outlet opening, and which has a larger cross-sectional area than the inlet opening and the outlet opening. 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 that are in contact with the swelling absorption pad. 4. The battery module according to embodiment 2, wherein the inlet opening is arranged higher than the outlet opening. 5. The battery module according to embodiment 1, wherein the battery module comprises the following: an air inlet formed through the module housing on one side of the unit module stack in one 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 cushion arranged within the air inlet and air outlet and configured to expand upon contact with a coolant introduced into the battery module in order to close the air inlet and air outlet. 7. The battery module according to embodiment 6, wherein the battery module includes a pair of busbar 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 air outlet are formed at locations corresponding to an empty chamber formed between the busbar frame and the module housing. 9. The battery module according to embodiment 7, wherein the battery module includes an insertion hole for a coolant line formed through the module housing 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 busbar frame and the module housing. 10. A battery pack comprising the following: a packaging container; a large number of battery modules stacked in the pack housing; a water tank positioned above a module stack including the multiple 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 installed inside the pack housing to detect a thermal runaway phenomenon occurring in at least some of the multiple battery modules; and a controller configured to output a control signal to introduce 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, the battery pack contains a multitude of valves that are installed in the coolant line, and The multitude of valves are each attached adjacent to the multitude of battery modules of the module stack in order to individually allow or block the flow of the coolant introduced into the multitude 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 from the plurality of valves that is 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 comprises the following: 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 cushion inserted between adjacent unit modules; and a module housing configured to accommodate the unit module stack and the swelling absorption pad, wherein the swelling absorption pad has a coolant channel which is designed to extend along a longitudinal direction thereof. 15. The battery pack according to embodiment 14, wherein the coolant channel comprises the following: an inlet opening provided on one side of the swelling absorption pad in the longitudinal direction; an outlet opening provided on the other side of the swelling-absorption pad in the longitudinal direction; and a cooling section configured to connect the inlet opening and the outlet opening, and having a larger cross-sectional area than the inlet opening and the outlet opening. 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 that are in contact with the swelling absorption pad. 17. The battery pack according to embodiment 16, wherein the inlet opening is arranged higher than the outlet opening. 18. An energy storage system (ESS) comprising a plurality of battery modules according to one of embodiments 1 to 9. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts 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 inlet opening (126a) and the outlet opening (126b), wherein the cooling section (126c) has a larger cross-sectional area than the inlet opening (126a) and the outlet opening (126b). [2] The unit module stack according to claim 1, wherein the input opening (126a) is arranged higher than the output opening (126b). [3] The unit module stack of claim 1 or 2, wherein the swelling absorption pad (126) includes materials selected from the group consisting of silicon, graphite, expanded polypropylene (EPP), and expanded polystyrene (EPS). [4] The unit module stack of any one of claims 1 to 3, wherein the unit module stack comprises a module housing (123) configured to receive the unit module stack and the swelling absorption pad (126). [5] The unit module stack according to claim 4, 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. [6] The unit module stack according to claim 5, 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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