Patent Publication Number: US-2022223959-A1

Title: Battery module

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit under 35 USC 119(a) of Korean Patent Application Nos. 10-2021-0005306 filed on Jan. 14, 2021 and 10-2021-0123342 filed on Sep. 15, 2021 in the Korean Intellectual Property Office, the entire disclosures of which are incorporated herein by reference for all purposes. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a secondary battery module. 
     2. Description of the Background 
     As technological developments and demand for mobile devices, electric vehicles, and the like increase, demands for secondary battery cells as an energy source are rapidly increasing. A secondary battery cell is a battery that can be repeatedly charged and discharged because conversion between chemical energy and electrical energy thereof is reversible. 
     Such a secondary battery cell typically includes an electrode assembly including a cathode, an anode, a separator, an electrolyte, and the like, and a laminated film casing for protecting the electrode assembly. 
     A plurality of secondary battery cells may be mounted and installed as a secondary battery module (also may be referred to as battery module) in an electric vehicle, an energy storage system (ESS), or the like. 
     The electrode assembly may generate heat during a charging or discharging process, and the generation of heat may cause an increase in temperature, resulting in a deterioration of performance of the secondary battery cell. 
     In addition, if gas is generated in a secondary battery cell due to some malfunction such as an excessive increase in the temperature of the secondary battery cell, the pressure inside the secondary battery cell may be increased and may cause the secondary battery cell to explode which in turn may cause successive explosions of other secondary battery cells in the battery module. 
     For example, as gas is generated inside a secondary battery cell, a terrace portion of the secondary battery cell may swell first, and then a sealing portion (a welding portion) of the secondary battery cell may also swell and burst. 
     In a battery module according to the related art, venting caused by bursting of a sealing portion occurs at relatively high speed after the terrace portion starts to swell. For example, a terrace portion of a secondary battery cell may swell, and a sealing portion may then be opened (exploded) rapidly by the force applied from the swelling terrace to the sealing portion. 
     When venting due to the opening (or bursting) of the sealing portion occurs, an electrolyte in the secondary battery cell is evaporated to rapidly decrease capacity of the secondary battery cell, so that the lifespan of the secondary battery cell and the battery module are significantly reduced. 
     SUMMARY 
     An aspect of the present disclosure is to provide a battery module which may delay venting of gas inside a secondary battery cell. 
     According to an aspect of the present disclosure, a battery module includes: a plurality of secondary battery cells, each including an electrode lead connected to an electrode assembly, a terrace portion forming a periphery of a cell body member in which the electrode assembly is accommodated, and a sealing portion formed to be connected to the terrace portion; a housing in which the plurality of secondary battery cells are accommodated; and a guard unit installed to face at least a portion of the terrace portion and at least a portion of the sealing portion to delay bursting of the sealing portion of at least one of the secondary battery cells. In the guard unit, a gap between internal surfaces facing the terrace portion is formed to be smaller than a thickness of the cell body member to limit expansion thickness of the terrace portion. 
     In the guard unit, a gap between internal surfaces facing the sealing portion may be formed to be smaller than the thickness of the cell body member. 
     In the guard unit, a gap between internal surfaces facing the sealing portion may be formed to be smaller than the gap between the internal surfaces facing the terrace portion. 
     In the guard unit, an average gap between internal surfaces facing the sealing portion may be formed to be smaller than an average gap between the internal surfaces facing the terrace portion. 
     The guard unit may have a shape facing half or more of a total length of the terrace portion and the sealing portion, in a length direction of the cell body member. 
     The guard unit may be installed to face an entirety of the sealing portion, based on a length direction of the cell body member. 
     The guard unit may include: a first block member in which a slit hole, into which the sealing portion is inserted, is formed; and a second block member in which an opening is formed to face at least a portion of the terrace portion. A gap between the sealing portion and an internal surface of the slit hole may be smaller than a gap between the terrace portion and an internal surface of the opening. 
     The gap between the sealing portion and the internal surface of the slit hole may be equal to at least 0.5 times or less of a length at which the sealing portion is inserted into the slit hole. 
     In the second block member, a corner, adjacent to the cell body member, of a portion facing the terrace portion may be formed to have a round shape. 
     The second block member may be provided on opposite sides of the terrace portion. 
     The guard unit may include: an extension guide member elastically moved in a thickness direction of the cell body member according to expansion of the terrace portion; and a movement of the extension guide member is limited within a range smaller than a thickness of the cell body member to limit expansion thickness of the terrace portion. 
     The guard unit may further include: a first block member in which a slit hole, into which the sealing portion is inserted, is formed; and a second block member in which an opening is formed to face at a portion of the terrace portion. The extension guide member may have one end portion, coupled to the first block member, and the other end portion extending to the second block member. 
     The guard unit may further include: a needle member coupled to the second block member, protruding in a direction of the terrace portion, and disposed to pass through a through-hole, formed in the extension guide member, to perforate the terrace portion. 
     The needle member may be provided in a form of a tube in which an internal hollow is formed, and an introduction hole may be formed to be perforated in a front tip portion of the needle member and a discharge hole may be formed in a central portion of the needle member such that the internal hollow communicates with an external entity. 
     The guard unit may further include: a reinforcing pad member provided on one surface of the extension guide member facing the terrace portion and applied with an adhesive material bonding the expanding terrace portion. 
     The guard unit may further include: a holding member, provided on the second block member, on which the other end portion of the extension guide member moved in a direction of the second block member is locked to be fixed. 
     The guard unit may be installed to face a portion, in which the electrode lead is disposed, of the sealing portion. 
     According to an aspect of the present disclosure, a battery module include: a plurality of secondary battery cells, each including an electrode lead connected to an electrode assembly, a terrace portion forming an periphery of a cell body member in which the electrode assembly is accommodated, and a sealing portion formed to be connected to the terrace portion; a housing in which the plurality of secondary battery cells are accommodated; a guard unit installed to face at least a portion of the terrace portion and at least a portion of the sealing portion to delay bursting of the sealing portion of the secondary battery cell and integrated to correspond to each of the plurality of secondary battery cells; and at least one bus bar member in which the integrated guard unit is embedded. The guard unit is formed such that a gap between internal surfaces facing the terrace portion is formed to be smaller than a thickness of the cell body member to limit expansion thickness of the terrace portion. The electrode leads of the plurality of secondary battery cells are electrically connected to the bus bar member. 
     According to an aspect of the present disclosure, a battery module includes: a plurality of secondary battery cells, each including an electrode lead connected to an electrode assembly, a terrace portion forming an periphery of a cell body member in which the electrode assembly is accommodated, and a sealing portion formed to be connected to the terrace portion; a housing in which the plurality of secondary battery cells are accommodated; and a guard unit installed to face at least a portion of the terrace portion and at least a portion of the sealing portion to delay bursting of the sealing portion of at least one of the secondary battery cells. In the guard unit, a space for expansion of the sealing portion is formed to be smaller than a space for expansion of the terrace portion. 
     In the guard unit, a gap between internal surfaces, respectively corresponding to the terrace portion and the sealing portion, is formed to be smaller than a thickness of the cell body member. 
     According to an aspect of the present disclosure, a battery module includes: a housing for accommodating a plurality of secondary battery cells, each of the secondary battery cells including an electrode assembly and a cell body member including a terrace portion and a sealing portion enclosing the electrode assembly, and a guard unit positioned around the terrace portion and the sealing portion of the cell body member, the guard unit being suitable for delaying bursting of the sealing portion of the secondary battery cells. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will be more clearly understood from the following detailed description, taken in conjunction with the accompanying drawings. 
         FIG. 1A  is an exploded perspective view of a battery module according to an example embodiment of the present disclosure. 
         FIG. 1B  is an perspective view of a secondary battery cell in a state before enclosing the electrode assembly into a cell body member according to an example embodiment of the present disclosure. 
         FIG. 2  is a perspective view illustrating only one secondary battery cell and a corresponding guard unit separated from a battery module according to an example embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view illustrating only a guard unit and a secondary battery cell in a battery module according to an example embodiment of the present disclosure. 
         FIG. 4  is a cross-sectional view illustrating a state in which a terrace portion of the secondary battery cell of  FIG. 3  swells. 
         FIG. 5  is a cross-sectional view illustrating a guard unit including an extension guide member in a battery module according to an example embodiment of the present disclosure. 
         FIG. 6  is a cross-sectional view illustrating a state in which a terrace portion of the secondary battery cell of  FIG. 5  swells. 
         FIG. 7  is an enlarged cross-sectional view of portion “A” of  FIG. 6 . 
         FIG. 8  is a cross-sectional view illustrating a modified embodiment of  FIG. 7  in which a needle member is in the form of a tube. 
         FIG. 9  is an enlarged cross-sectional view of portion “B” portion of  FIG. 6 . 
         FIG. 10  is a cross-sectional view illustrating a state in which a plurality of guard units and a plurality of secondary battery cells, illustrated in  FIG. 3 , are installed. 
         FIGS. 11A to 11C  are side views illustrating a state in which a guard unit is coupled to a secondary battery cell.  FIG. 11A  illustrates the guard unit and the secondary battery cell illustrated in  FIG. 2 , and  FIGS. 11B and 11C  illustrate a modified example in which a height of the guard unit is increased, as compared with  FIG. 11A . 
         FIGS. 12 to 16  are cross-sectional views illustrating various modified examples of a guard unit. 
     
    
    
     DETAILED DESCRIPTION 
     The terms and words used in the present specification and claims should not be interpreted as being limited to typical meanings or dictionary definitions, but should be interpreted as having meanings and concepts relevant to the technical scope of the present disclosure based on the rule according to which an inventor can appropriately define the concept of the term to describe most appropriately the appropriate method he or she knows for carrying out the present disclosure. Therefore, the configurations described in the embodiments and drawings of the present disclosure are merely appropriate embodiments but do not represent all of the technical spirit of the present disclosure. Thus, the present disclosure should be construed as including all the changes, equivalents, and substitutions included in the spirit and scope of the present disclosure at the time of filing this application. 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this case, it is to be noted that like reference numerals denote like elements in appreciating the drawings. Moreover, detailed descriptions related to well-known functions or configurations will be ruled out in order not to unnecessarily obscure the subject matter of the present disclosure. Based on the same reason, it is to be noted that some components shown in the drawings are exaggerated, omitted or schematically illustrated, and the size of each component does not exactly reflect its actual size. 
     Hereinafter, example embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. 
       FIG. 1A  is an exploded perspective view of a battery module according to an example embodiment of the present disclosure, and  FIG. 1B  is an perspective view of a secondary battery cell in a state before enclosing the electrode assembly into a cell body member according to an example embodiment of the present disclosure. Referring to the drawing, a battery module according to an example embodiment may include a plurality of secondary battery cells  10 , a housing  20 , and a guard unit  30 . 
     The plurality of secondary battery cells  10  may include a cell body member  10   a  in which the electrode assembly  14  is accommodated, an electrode lead  11  connected to a electrode tab  15  of the electrode assembly  14 , a terrace portion  12  forming an periphery of the cell body member  10   a  and being a portion in which pouch-type members accommodating the electrode assembly  14  are in contact with each other, and a sealing portion (a welding portion)  13 , connected to an external side of the terrace portion  12 , in which the pouch-type members are in contact with each other to be sealed or thermally welded. The terrace portion  12  and the sealing portion  13  may form an edge of the cell body member  10   a . The sealing portion  13  may be disposed between the electrode lead  11  and a cell body member  10   a  exposed outwardly. The housing  20  may include at least one bus bar member  21  to which the electrode lead  11  is coupled. The bus bar member  21  may be electrically connected to the electrode leads  11  of the plurality of secondary battery cells  10 . A plurality of secondary battery cells  10  may be accommodated inside the housing  20  in the state of being stacked. As an example, the guard unit  30  may be provided on the bus bar member  21 . The guard unit  30  may delay swelling or bursting of the sealing portion  13  when gas is generated in the secondary battery cell  10 . The guard unit  30  may have an integrated structure to correspond to each of the plurality of secondary battery cells  10 , and the integrated guard unit  30  may be installed on the bus bar member  21 . For example, the integrated guard unit  30  may be at least partially embedded in the bus bar member  21 . 
     Accordingly, the guard unit  30  of the battery module according to an example embodiment may delay venting of gas caused by bursting of the sealing portion  13  of the secondary battery cell  10 . Thus, a battery module according to the present disclosure may delay explosion of the secondary battery cell  10  caused by the venting of gas. 
     In addition, as the battery module according to the present disclosure delays a point in time at which the sealing portion  13  bursts, the battery module may also delay a point in time, at which the electrolyte in the secondary battery cell  10  is evaporated, thus suppressing a rapid decrease in the capacity of the secondary battery cell. 
     As an example, under a condition that the secondary battery cell  10  is fully charged at a temperature of 60° C., a battery module according to the related art has a lifespan of about 42 days, whereas the battery module according to the present disclosure exhibited a lifespan of about 191 days. Thus, it was found that a battery module according to an example embodiment of the present disclosure demonstrates a significantly improved lifespan when compared to existing battery modules. 
     The secondary battery cell  10  may include an electrode assembly  14  and a cell body member  10   a  surrounding the electrode assembly  14 . 
     The electrode assembly  14  may substantially include an electrolyte, and the electrolyte may be accommodated in the cell body member  10   a  and used together with the electrode assembly  14 . The electrolyte may include a lithium salt, such as LiPF 6  or LiBF 4 , in an organic solvent, such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC). Furthermore, the electrolyte may be in a liquid, solid or gel phase. 
     The cell body member  10   a  is a component protecting the electrode assembly  14  while accommodating the electrolyte therein. The cell body member  10   a  may be provided, for example, as a pouch-type member. In another example, the cell body member  10   a  may be provided as a can-type member. The pouch-type member may be a film casing accommodating and fully enclosing the electrode assembly  14 . The film casing may be sealed on three or four sides and may fully cover the electrode assembly  14 . For example, the film casing may be sealed on three sides of the electrode assembly  14 , usually an upper side and both lateral sides except one side (for example, a lower side) in a state in which the electrode assembly  14  is accommodated in an accommodation space formed inside the film casing. The can-type member may be in the form of sealing the electrode assembly  14  by overlapping and bonding the can-type member on one side of the electrode assembly  14 , and may be a component configured to one surface, usually an upper surface, in a state in which the electrode assembly  14  is accommodated in the can-type member. 
     However, such a pouch-type secondary battery cell  10  or such a can-type secondary battery cell  10  is merely an example of the secondary battery cell  10  accommodated in the battery module according to the present disclosure, and the secondary battery cell  10  accommodated in the battery module according to the present disclosure is not limited to the above-described type. 
     The secondary battery cell  10  may include a terrace portion  12  forming a periphery of the cell body member  10   a  surrounding the electrode assembly  14 . The periphery of the cell body member  10   a  may be a portion that a film casing overlaps. In addition, the secondary battery cell  10  may be provided with a sealing portion  13  sealing or thermally welding the overlapping portion of the film casing. 
     In the detailed description and claims, the terrace portion  12  is defined to refer to a portion of the periphery of the cell body member  10   a , except for the sealing portion  13 . For example, the periphery or edge of the cell body member  10   a  (the portion that the film casing overlaps) may include a terrace portion  12  and a sealing portion  13  connected to the terrace portion  12 . 
     The electrode lead  11  is exposed outwardly of the film casing through the terrace portion  12  and the sealing portion  13 . 
     The sealing portion  13  may be sealed (thermally welded) to an external side of the terrace portion  12  to seal the edge of the cell body member  10   a . In addition, in a portion where the electrode lead  11  is disposed, the sealing portion  13  may seal the electrode lead  11  together with the edge of the cell body member  10   a.    
     The term “being sealed (thermally welded)” may refer a state in which the sealing portion  13  is solidified and pressurized after being melted by heat or the like. In addition, the sealing portion  13  may be sealed with an adhesive material such as a sealant. 
     In addition, the secondary battery cell  10  of the battery module according to an example embodiment may include an insulating member (not illustrated) disposed between the edge of the cell body member  10   a  (the portion with which the film casing is in contact and overlaps) and the electrode lead  11 . For example, the insulating member may have a structure covering the electrode lead  11 . Accordingly, the edge of the cell body member  10   a  may be electrically separated from the electrode lead  11  to be insulated therefrom. 
     The housing  20  may serve as a body of a battery module in which the plurality of secondary battery cells  10  are accommodated. 
     For example, the housing  20  may have a configuration in which a plurality of secondary battery cells  10  are installed, and may serve to transfer electrical energy, generated by the secondary battery cell  10 , to an external entity or to transfer external electrical energy to the secondary battery cell  10 . 
     To this end, the housing  20  may include a bus bar member  21 , connected to the electrode lead  11  of the secondary battery cell  10  to electrically connect the secondary battery cell  10  to an external entity, or the like. 
     Also, the housing  20  may include a bottom member  22  accommodating the plurality of secondary battery cells  10 . 
     The bottom member  22  may include an insulating member applied to a front end portion and a rear end portion coupled to the bus bar member  21 . The insulating member may also be attached in the form of a sheet. This is aimed at securing insulating properties of the bus bar member  21 . 
     In addition, the bottom member  22  may be configured such that a heat transfer material is applied to a portion in contact with the secondary battery cell  10  to more effectively transfer heat between the secondary battery cell  10  and the secondary battery cell  10 . However, this is only an example, and a heat transfer material may not be provided between the bottom member  22  and the secondary battery cell  10  of the present disclosure and the secondary battery cell  10  may be in direct contact with the bottom member  22 . 
     In addition, the housing  20  may include a sidewall member  24 , a front member  25 , a rear member  26 , a cover member  23 , and the like, to accommodate the secondary battery cell  10  in a surrounding shape. 
     The bottom member  22  may be disposed in a lower end portion of the secondary battery cell  10 . The sidewall member  24  may be provided on a corner of the bottom member  22 . The front member  25  may be provided in the front edge of the housing  20  and may be connected to a front bus bar member  21  coupled to an electrode lead  11  on one side of the secondary battery cell  10 . The rear member  26  may be provided at the rear edge of the housing  20 , and may be connected to the rear bus bar member  21  coupled to an electrode lead  11  on the other side of the secondary battery cell  10 . The cover member  23  may be provided on the upper ends of the sidewall member  24 , the front member  25 , and the rear member  26 , and may be configured to protect an upper end portion of the secondary battery cell  10 . 
     The bottom member  22  may be configured to transfer heat, generated by the secondary battery cell  10 , to an external heat sink to be cooled. The side wall member  24  may also discharge the heat, generated by the secondary battery cell  10 , to an external entity. 
     In addition, the housing  20  may be provided with a buffer pad member between the secondary battery cells  10  or between the secondary battery cell  10  and the sidewall member  24  to buffer swelling of the secondary battery cell  10 . 
     The guard unit  30  may serve to delay swelling or bursting of the sealing portion  13  of the secondary battery cell  10 . The guard unit  30  will be described with reference to  FIGS. 2 to 4 . 
       FIG. 2  is a perspective view illustrating only one secondary battery cell  10  and a corresponding guard unit  30  separated from a battery module according to an example embodiment,  FIG. 3  is a cross-sectional view illustrating only a guard unit  30  and a secondary battery cell  10  in a battery module according to an example embodiment, and  FIG. 4  is a cross-sectional view illustrating a state in which a terrace portion  12  of the secondary battery cell  10  of  FIG. 3  swells. In  FIGS. 3 and 4 , an exterior of the secondary battery cell  10  is illustrated for ease and clarity of the drawings. 
     Referring to  FIGS. 2 to 4 , the guard unit  30  may be configured such that the terrace portion  12  extends within a limited range but the expansion of the sealing portion  13  is limited as much as possible. For example, the guard unit  30  may be provided such that a gap G 1  from the sealing portion  13  is smaller than the distance G 2  from the terrace portion  12 , and thus, a space for expansion of the sealing portion  13  may be provided to be relatively small while a space for expansion of the terrace portion  12  may be provided in a range smaller than the thickness T 3  of the cell body member  10   a.    
     In this case, the sealing of the sealing portion  13  may be maintained while accommodating the gas, generated inside the secondary battery cell  10 , in a space secured by the expansion of the terrace portion  12 . Accordingly, explosion of the secondary battery cell  10  caused by gas venting may be prevented. The guard unit  30  of the battery module according to an example embodiment may include a first block member  31  and a second block member  32 . 
     A slit hole  31   a , into which the sealing portion  13  is inserted, may be formed in the first block member  31 . The second block member  32  may be integrated with the first block member  31 , and may face the terrace portion  12 . An opening  32   a , through which the sealing portion  13  and the terrace portion  12  enter, may be formed in the second block member  32 . A gap G 1  between the sealing portion  13  and an internal surface of the slit hole  31   a  may be smaller than a gap G 2  between the terrace portion  12  and an internal surface of the second block member  32 . 
     For example, since the gap G 1  between the first block member  31  and the sealing portion  13  is relatively small, the expansion of the sealing portion  13  may be suppressed, and since the gap G 2  between the second block member  32  and the terrace portions  12  is relatively large, the expansion of the terrace portion  12  may be performed within a space between internal surfaces of the first block member  32 . 
     Accordingly, the sealing of the sealing portion  13  may be maintained while accommodating the gas, generated inside the secondary battery cell  10 , in the space secured by the expansion of the terrace portion  12 . 
     The gap G 1  between the sealing portion  13  and the internal surface of the slit hole  31   a  of the battery module according to an example embodiment may be equal to at least 0.5 times or less of a length L at which the sealing portion  13  is inserted into the slit hole  31   a.    
     For example, in the battery module according to an example embodiment, there may also be a gap G 1  between the sealing portion  13  and the slit hole  31   a  of the first block member  31 . 
     Accordingly, the sealing portion  13  may also be expanded by the gas generated in the secondary battery cell  10 . However, a gap G 1  at which the sealing portion  13  may be expanded, that is, a gap G 1  between the sealing portion  13  and the slit hole  31   a , may be 0.5 times or less of the length L at which the sealing portion  13  is inserted. In addition, when the sealing portion  13  is split due to introduction of gas, it may be gradually split from one end portion of the sealing portion  13 , coupled to the terrace portion  12 , to the other end portion of the sealing portion  13  adjacent to an external side. 
     A maximum distance, at which one end of the sealing portion  13  may be spaced apart from an original position as one end portion of the sealing portion  13  is split, may be the gap G 1  between the sealing portion  13  and the slit hole  31   a . In addition, the gap G 1  may be less than half of the length L at which the sealing portion  13  is inserted. 
     Accordingly, even when one end portion of the sealing portion  13  is split to the maximum, the other end portion of the sealing portion  13  is not split. Therefore, the sealing can be maintained in the other end portion of the sealing portion  13 . 
     Referring to  FIGS. 3 and 4 , the guard unit  30  may be divided into a first area A 1 , corresponding to the terrace portion  12 , and a second area A 2  facing the sealing portion  13 . For example, the guard unit  30  may be installed to face both at least a portion of the terrace portion  12  and at least a portion of the sealing portion  13 . In this case, a first gap T 1  is a distance between internal surfaces in the first area A 1 , and a second gap T 2  is a distance between internal surfaces in a second area A 2 . The first gap T 1  may correspond to a space in which the terrace portion  12  may be expanded, and the second gap T 2  may correspond to a space in which the sealing portion  13  may be expanded. Since the guard unit  30  is provided with a second block member  32  forming an opening  32   a , the first gap T 1  between the internal surfaces in the first area A 1  facing the terrace portion  12  may be smaller than a thickness T 3  of the cell body member  10   a  due to the thickness of the second block member  32 . Accordingly, a thickness of the expanded terrace portion  12  may be limited to the first gap T 1  between the internal surfaces of the first area A 1  facing the terrace portion  12 . 
     The battery module according to the prior art has a problem in which the terrace portion of the secondary battery cell swells, and then the sealing portion is rapidly opened (burst) due to force applied from the swelling terrace portion to the sealing portion. However, according to example embodiments of the present disclosure, since the thickness of the expanded terrace portion  12  is limited within a certain range (for example, T 1 ), rapid opening of the sealing portion  13  caused by excessive expansion of the terrace portion  12  may be prevented and delay gas venting. 
     In addition, due to the thickness of the first block member  31 , the guard unit  30  may be formed such that a second gap T 2  between the internal surfaces in the second area A 2  facing the sealing portion  13  is smaller than the thickness T 3  of the cell body member  10   a . Accordingly, a range in which the sealing portion  13  expands may be limited. 
     As illustrated in  FIGS. 3 and 4 , the guard unit  30  may be formed such that a second gap T 2  between the internal surfaces in the second area A 1  facing the sealing portion  13  is smaller than the first gap T 1  between the internal surfaces of the first area A 1  facing the terrace portion  12 . 
     In addition, the first gap T 1  between the internal surfaces in the first area A 1  facing the terrace portion  12  may have a value greater than a thickness of the terrace portion  12  such that the terrace portion  12  enters the opening  32   a  of the guard unit  30 . 
     The guard unit  30  may have a structure in which the first gap T 1  between the internal surfaces in the first area A 1  facing the terrace portion  12  and/or the second gap T 2  between the internal surfaces in the second area A 1  facing the sealing portion  13  varies (see  FIGS. 5 and 6 ). As described above, when the gaps T 1  and T 2  between the internal surfaces of the guard member  30  vary, each and average gap may be considered. For example, an average gap between the internal surfaces in the second area A 1  facing the sealing portion  13  may be smaller than an average gap between the internal surfaces in the first area A 1  facing the terrace portion  12 . In this case, the average gap (average value) may be defined as a value obtained by summing the gaps T 1  and T 2  between the internal surfaces of the guard member  30  and dividing a value, obtained by the sum, by a length of each area. 
     In addition, the guard unit  30  may limit the expansion of the terrace portion  12  and the sealing portion  13  in the first area A 1  facing the terrace portion  12  and the second area A 1  facing the sealing portion  13  within a predetermined range. In this case, an expansion limitation length LC of the terrace portion  12  and the sealing portion  13  of the guard unit  30  may correspond to a sum of the lengths corresponding to the terrace portion  12  and the sealing portion  13 , based on a length direction (an X1 direction) of the cell body member  10   a.    
     In this case, to limit the expansion range of the terrace portion  12 , the guard unit  30  may have a shape facing at least half of an entire length LA of the terrace portion  12  and the sealing portion  13 . For example, the expansion limitation length LC of the guard unit  30  may have a value of 50% (half) or more of the total length LA of the terrace portion  12  and the sealing portion  13 . In addition, the expansion limitation length LC of the guard unit  30  may have a value of 60% or more, 70% or more, 80% or more, or 90% or more of the total length LA of the terrace portion  12  and the sealing portion  13 . When the expansion limitation length LC is reduced, a distance LD between a side surface of the cell body member  10   a  and the guard unit  30  may be increased, and thus, an area of the terrace portion  12 , in which an expansion thickness is not limited, may be increased. 
     In addition, the guard unit  30  may be installed to face the entire sealing portion  13  to limit expansion of the entire sealing portion  13 , in a length direction (an X1 direction) of the cell body member  10   a.    
     In the second block member  32  of the battery module according to an example embodiment, a corner, adjacent to the cell body member  10   a , of a portion facing the terrace portion  12  may be formed to have a round shape (round corner). 
     As described above, the second block member  32  may have a round shape on a side of the corner adjacent to the cell body member  10   a  to further secure the expansion space of the terrace portion  12 . 
     In addition, the second block member  32  may include a round shape on the side of the corner adjacent to the cell body member  10   a  to prevent the terrace portion  12  from being in close contact with the corner portion, or the like, and bursting during the expansion of the terrace portion  12 . 
     In addition, the second block member  32  of the battery module according to an example embodiment may be provided on both sides of the terrace portion  12 . Therefore, the first gap T 1  between the internal surfaces in the first area A 1  facing the terrace portion  12  may have a value smaller than the thickness T 3  of the cell body member  10   a  due to the thickness of the second block member  32 . 
     Accordingly, the second block member  32  may induce an expansion shape of the terrace portion  12  while securing a portion of the expansion spaces of opposite side surfaces of the terrace portion  12 . For example, the second block member  32  may induce uniform expansion of the opposite side surfaces of the terrace portion  12  without asymmetric expansion of one side surface of the terrace portion  12 . Accordingly, an expansion space may be secured to the maximum extent while preventing the terrace portion  12  from swelling or bursting. 
       FIG. 5  is a cross-sectional view illustrating a case in which a guard unit  30  includes an extension guide member  33  in a battery module according to an example embodiment, and  FIG. 6  is a cross-sectional view illustrating a state in which a terrace portion  12  of the secondary battery cell  10  of  FIG. 5  swells. In  FIGS. 5  and  6 , an exterior of the secondary battery cell  10  is illustrated for ease and clarity of the drawings. 
     Referring to the drawings, the guard unit  30  of the battery module according to an example embodiment may further include an extension guide member  33 . The guard unit  30  illustrated in  FIGS. 5 and 6  has the same configuration as the guard unit  30  described with reference to  FIGS. 2 to 4 , except that it further includes the extension guide member  33 . The extension guide member  33  may be made of a flexible material. Therefore, to avoid unnecessary duplication, descriptions of the same or similar components will be omitted and will be replaced with the descriptions of  FIGS. 2 to 4 . 
     The extension guide member  33  may be formed such that one end portion thereof is coupled to the first block member  31  and the other end portion thereof extends to the second block member  32 . According to the expansion of the terrace portion  12 , the other end portion of the extension guide member  33  may be elastically moved in a direction of the second block member  32 . For example, the extension guide member  33  may be elastically moved in a thickness direction X2 of the cell body member  10   a.    
     As described above, the expansion of the terrace portion  12  may be guided by the extension guide member  33  during expansion. For example, an expansion shape and expansion pressure of the terrace portion  12  may be adjusted by the extension guide member  33 . 
     Accordingly, the terrace portion  12  may be prevented from bursting due to an impact caused by sudden extension of the terrace portion  12 . For example, the terrace portion  12  may be induced to gradually extend to be prevented from swelling or busting. 
     In addition, a movement of the extension guide member  33  may be limited within a range smaller than a thickness of the cell body member  10   a  to limit expansion thickness of the terrace portion  12 . For example, gaps T 1   a  and T 1   b  between internal surfaces in the first area A 1  facing the terrace portion  12  may be smaller than the thickness T 3  of the cell body member  10   a  due to a thickness of the second block member  32  and a thickness of the extension guide member  36 . Accordingly, the expansion thickness of the terrace portion  12  may be limited within a range smaller than the gaps T 1   a  and T 1   b  between the internal surfaces in the first area A 1  facing the terrace portion  12 . 
     In addition, the guard unit  30  illustrated in  FIGS. 5 and 6  may have a shape in which the gaps T 1   a  and T 1   b  between the internal surfaces of the first area A 1  facing the terrace portion  12  vary. In this case, an average gap between the internal surfaces in the first area A 1  facing the terrace portion  12  may be greater than an average distance between the internal surfaces in the second area A 1  facing the sealing portion  13 . 
     In addition, the guard unit  30  may be formed such that a gap T 2  between the internal surfaces in the second area A 1  facing the sealing portion  13  is smaller than the gaps T 1   a  and T 1   b  between the internal surfaces in the first area A 1  facing the terrace portion  12 . 
     The extension guide member  33  of the battery module according to an example embodiment may be formed to have a shape in which a central portion facing the terrace portion  12  includes a round surface. 
     For example, since the extension guide member  33  includes a round surface on a corner side adjacent to the cell body member  10   a , an expansion space of the terrace portion  12  may be further secured. 
     In addition, since the extension guide member  33  includes a round shape on the edge side adjacent to the cell body member  10   a , the terrace portion  12  may be prevented from being brought into close contact with a corner portion, or the like, and bursting when the terrace portion  12  expands. 
       FIG. 7  is an enlarged cross-sectional view of portion “A” of  FIG. 6 , and  FIG. 8  is a cross-sectional view illustrating a modified embodiment of  FIG. 7  in which a needle member  34  is in the form of a tube. 
     Referring to the drawings, the guard unit  30  of the battery module according to an example embodiment may further include a needle member  34 . 
     The needle member  34  may be coupled to the second block member  32 , and may protrude in a direction of the terrace portion  12 . The needle member  34  may be disposed to pass through a through-hole  33   a , formed in the extension guide member  33 , to perforate the expanding terrace portion  12 . 
     As described above, the needle member  34  may serve to perforate a portion of the expanding terrace portion  12  to discharge the gas inside the terrace portion  12  to an external entity. 
     The needle member  34  may be configured to intentionally and constantly vent the gas, generated in the secondary battery cell  10 , in the battery module according to the present disclosure. For example, the needle member  34  may perforate the terrace portion  12  to prevent explosion caused by sudden gas venting. 
     In addition, the needle member  34  of the battery module according to an example embodiment may be provided in the form of a tube in which an internal hollow is formed, and an introduction hole  34   a  may be formed to be perforated in a front tip portion of the needle member  34  and a discharge hole  34   b  may be formed in a central portion of the needle member  34  such that the internal hollow communicates with an external entity. 
     The needle member  34  may be provided in the form of a general column having no hollow therein as illustrated in  FIG. 7 , or may be provided in the form of a tube having an internal hollow as illustrated in  FIG. 8 . 
     When the needle member  34  is provided in the form of a tube and is provided with the introduction hole  34   a  and the discharge hole  34   b , the gas inside the terrace portion  12  may be discharged to the discharge hole  34   b  through the introduction hole  34   a . For example, even when the needle member  34  is not removed after passing through the terrace portion  12 , the gas inside the terrace portion  12  may be discharged. 
     In addition, the guard unit  30  of the battery module according to an example embodiment may include a reinforcing pad member  35 . 
     The reinforcing pad member  35  may be provided on one surface of the extension guide member  33  facing the terrace portion  12 , and an adhesive material may be applied to bond the expanding terrace portion  12 . 
     As described above, the reinforcing pad member  35  may be bonded to the terrace portion  12  when the terrace portion  12  expands. In addition, the terrace portion  12  may be prevented from tearing and bursting even when a portion of the terrace portion  12  is perforated by the needle member  34  as the pad member is bonded to the terrace portion. 
       FIG. 9  is an enlarged cross-sectional view of portion “B” in  FIG. 6 . Referring to the drawing, the guard unit  30  of the battery module according to an example embodiment may include a holding member  36 . 
     The holding member  36  may be provided on the second block member  32 , and the other end portion of the extension guide member  33  moved in the direction of the second block member  32  may be locked on the holding member  36  to be fixed. 
     For example, the holding member  36  may be provided to fix the extension guide member  33 , so that the extension guide member  33  does not press the terrace portion  12  after the terrace portion  12  expands. 
     Accordingly, after intentional venting occurs, the shape of the welling terrace portion  12  may be maintained to significantly reduce exposure of the perforated portion to external air. 
     On the other hand, when the holding member  36  is not provided, the terrace portion  12  pressed by the extension guide member  33  may return to the original shape thereof and the perforated portion perforated by the needle member  34  may be exposed as it is. Accordingly, due to circulation of an inside of the secondary battery cell  10  and the external air, introduction of oxygen into the secondary battery cell  10  or leakage of an electrolyte inside the secondary battery cell  10  to an external entity may become more severe. 
     As a result, the battery module according to the present disclosure may include the holding member  36  to address the above issue. 
     To this end, the holding member  36  of the battery module according to an example embodiment may include, for example, a support tab portion  36   a  and a hook portion  36   b.    
     The support tab portion  36   a  may be coupled to the second block member  32 . One end portion of the hook portion  36   b  may be hingedly coupled to the support tab portion  36   a , and the other end portion thereof may be in the form of a wedge to be fitted into a fixing hole  33   b  formed in the extension guide portion and may be pressed in a direction of the second block member  32  by an elastic member  36   c  provided in the support tab portion  36   a.    
     Accordingly, as the extension guide member  33  approaches the second block member  32  due to the expansion of the terrace portion  12 , the other end portion of the extension guide member  33  may be moved between the other end of the hook portion  36   b  and an external surface of the second block member  32 . In addition, when the other end portion of the extension guide member  33  is completely in close contact with the second block member  32 , the other end portion of the wedge-shaped hook portion  36   b  may be locked on the fixing hole  33   b , formed in the other end portion of the extension guide member  33 , to be fitted thereinto. 
       FIG. 10  is a cross-sectional view illustrating a state in which a plurality of guard units  30  and a plurality of secondary battery cells  10 , illustrated in  FIG. 3 , are installed.  FIG. 3  illustrates a state in which the guard units  30  are disposed on opposite sides of the terrace portion  12  of one secondary battery cell  10 , while  FIG. 10  illustrates a state in which the guard unit  30  illustrated in  FIG. 3  includes a plurality of units connected to each other. An example of the guard unit  30  illustrated in  FIG. 10  is the same as the example of the guard unit  30  illustrated in  FIG. 3 , except that a plurality of units have an integrated shape. Therefore, the same or similar detailed description of the configuration will be replaced with the above description, and only differences will be described. 
     As illustrated in  FIG. 10 , the guard unit  30  may include a plurality of units disposed between the terrace portions  12  of adjacent secondary battery cells  10 , and the plurality of units may constitute an integrated guard unit  30 . When the integrated guard unit  30  is used, an advantage for easily installing the guard unit  30  may be obtained. In addition, as illustrated in  FIG. 1 , the integrated guard unit  30  may be integrated with the bus bar member  21  to be embedded in the bus bar member  21 . 
     As illustrated in  FIG. 10 , the guard unit  30  may be disposed between the terrace portions  12  in a state of being separated from the bus bar member ( 21  of  FIG. 1 ) to which the electrode lead  11  is coupled. For example, the guard unit  30  and the bus bar member  21  may be separately configured. Alternatively, the guard unit  30  may be disposed between the terrace portions  12  in a state of being coupled to the bus bar member  21  (for example, an integrated state) as illustrated in  FIG. 1 . 
       FIGS. 11A to 11C  are side views illustrating a state in which a guard unit  30  is coupled to a secondary battery cell  10 , and  FIG. 11A  illustrates the guard unit  30  and the secondary battery cell  10  illustrated in  FIG. 2 , and  FIGS. 11B and 11C  illustrate a modified example in which a height of the guard unit  30  is increased, as compared with  FIG. 11A . 
     As illustrated in  FIG. 11A , the guard unit  30  may be installed to face a portion, in which an electrode lead  11  is disposed, of the terrace portion  12  and the sealing portion  13 . A height H 1  of the guard unit  30  has a value greater than that of a height HL of the electrode lead  11 I such that the guard unit  30  overall corresponds to the portion in which the electrode lead  11  is disposed. A portion, in which the electrode lead  11  is exposed to an external entity, of the sealing portion may have relatively weak bonding strength, as compared with the other portions of the sealing portion  13 . According to an example embodiment, expansion of the terrace portion  12  may be limited through the guard unit  30  to delay the swelling or bursting of the sealing portion  13  in the portion in which the electrode lead  11  is exposed to the external entity. 
     The height H 1  of the guard unit  30  may have a value of half or more of the height H 3  of the cell body member  10   a , as illustrated in  FIG. 11B . In addition, the guard unit  30  may be installed to have a height similar to or the same as a height H 3  of a cell body member  10   a , as illustrated in  FIG. 11C . As described above, when a height of the guard unit  30  is increased, the expansion of the terrace portion  12  may be suppressed in a large area to delay the swelling or bursting of the sealing portion  12 . 
     In addition, to limit an expansion range of the terrace portion  12 , the guard unit  30  may have a shape facing at least 50% (half) of a total length LA of the terrace portion  12  and the sealing portion  13 . The guard unit  30  may have a shape facing 60% or more, 70% or more, 80% or more, or 90% or more of the total length LA. When an area in which the guard unit  30  covers the terrace portion  12  is decreased, a distance LD between a side surface of the cell body member  10   a  and the guard unit  30  may be increased. Thus, an area of the terrace portion  12 , in which an expansion thickness is not limited, may be increased. 
       FIG. 12  is a cross-sectional view illustrating a modified example of the guard unit  30 . A guard unit  30  illustrated in  FIG. 12  is different from the guard unit  30  illustrated in  FIG. 10  only in that positions of a terrace portion  12  and a sealing portion  13  are different from each other. To avoid unnecessary duplication, descriptions of the same or similar components will be omitted and will be replaced with the descriptions of  FIGS. 3 to 10 . 
     The guard unit  30  illustrated in  FIG. 12  may include a first area A 1 , facing at least a portion of the terrace portion  12 , and a second area A 2  installed to face the sealing portion  13 . 
     First gaps T 1   a  and T 1   b  are distances between internal surfaces of the first area A 1 . Since the first gaps T 1   a  and T 1   b  are smaller than a thickness T 3  of a cell body member  10   a , an expansion thickness of the terrace portion  12  may be limited to delay venting of gas inside the battery cell  10 . In addition, a second gap T 2  is a distance between internal surfaces of a second area A 2 . Since the second gap T 2  also has a value smaller than a value of the thickness T 3  of the cell body member  10   a , an expansion thickness of a sealing portion may be limited. 
     The first gaps T 1   a  and T 1   b  may vary within the first area A 1 . For example, a distance T 1   a  between internal surfaces of the guard member  30  on one side close to the cell body member  10   a  in the first area A 1  may have a value different from a value of a distance T 1   b  between internal surfaces of the guard member  30  on the other side of the first area A 1 . In this case, a minimum value T 1   b  of the first gap may have the same value as the second gap T 2 . For example, the distance T 1   b  between the internal surfaces of the guard member  30  on the other side of the first area A 1  close to the electrode lead  11  may be the same as the second gap T 2 . In addition, an average value of the first gap may have a value higher than a value of the second gap T 2 . The average value of the first gap may be obtained from a value obtained by integrating the gap between the internal surfaces of the guard member  30  and dividing the value, obtained by the integration, by a length of the first area A 1 . 
     The guard unit  30  may include a first block member  31 , having a slit hole  31   a  into which the sealing portion  13  is inserted, and a second block member  32  having an opening  32   a  facing at least a portion of the terrace portion  12 . The first area A 1  may be formed across an opening  32   a  and the slit hole  31   a.    
     In the guard unit  30  illustrated in  FIG. 12 , the expanded thickness of the terrace portion  12  may be limited by the first gaps T 1   a  and T 1   b  between the internal surfaces in the first area A 1  facing the terrace portion  12 . Accordingly, rapid opening of the sealing portion  13 , caused by excessive expansion of the terrace portion  12 , may be reduced to delay gas venting of the secondary battery cell  10 . 
       FIG. 13  is a cross-sectional view illustrating another modified example of the guard unit  30 . A guard unit  30  illustrated in  FIG. 13  may has a different arrangement of gaps between internal surfaces of first and second areas A 1  and A 2 , as compared with the guard unit  30  illustrated in  FIG. 12 . To avoid unnecessary duplication, descriptions of the same or similar components will be omitted and will be replaced with the descriptions of  FIGS. 3 to 10 . 
     The guard unit  30  illustrated in  FIG. 13  may include a first area A 1 , facing at least a portion of a terrace portion  12 , and a second area A 2  facing a sealing portion  13 . 
     First gaps T 1   a  and T 1   b  are distances between internal surfaces of the first area A 1 . Since the first gaps T 1   a  and T 1   b  are smaller than a thickness T 3  of a cell body member  10   a , an expansion thickness of the terrace portion  12  may be limited to delay venting of gas inside a secondary battery cell  10 . Second gaps T 2   a  and T 2   b  are distances between internal surfaces of the second area A 2 . Since the second gaps T 2   a  and T 2   b  also have a smaller value than the thickness T 3  of the cell body member  10   a , an expansion thickness of a sealing portion may be limited. 
     The second gaps T 2   a  and T 2   b  may have a value greater than or equal to a value of the first gaps T 1   a  and T 1   b . In addition, a minimum value T 1   a  of the first gap may be smaller than the value of the second gaps T 2   a  and T 2   b.    
     In addition, at least one of the first gaps T 1   a  and T 1   b  and the second gaps T 2   a  and T 2   b  may vary within each of their respective areas A 1  and A 2 . For example, a distance T 1   a  between internal surfaces of the guard member  30  on one side, close to the cell body member  10   a , of the first area A 1  may have a value different from a value of a distance T 1   b  between internal surfaces of the guard member  30  on the other side of the first area A 1 . A distance T 2   a  between internal surfaces of the guard member  30 , close to the cell body member  10   a , of the second area A 1  may have a value different from a value of a distance T 2   b  between internal surfaces of the guard member  30  on the other side of the second area A 2 . In this case, an average value of a second gap may be greater than or equal to an average value of a first gap. An average value of the first and second gaps may be obtained from a value obtained by integrating the gaps between the internal surfaces of the guard member  30  and dividing the value, obtained by the integration, by the lengths of the respective areas A 1  and A 2 . 
     The guard unit  30  may include a first block member  31  having a slit hole  31   a  into which the sealing portion  13  is inserted, a second block member  32  having an opening  32   a  facing at least a portion of the terrace portion  12 , and an intermediate block member  31 ′ disposed between the first block member  31  and the second block member  32 . A connection opening  31 ′ a , accommodating the sealing portion  13  and the terrace portion  12  together, may be formed in the intermediate block member  31 ′. In this case, both the first area A 1  and the second area A 2  may be disposed in the connection opening  31 ′ a .  FIG. 13  illustrates a configuration in which an inclined surface is formed in the connection opening  31 ′ a , but the connection opening  31 ′ a  may have a step structure between the opening  32   a  and the slit hole  31   a . In addition, the guard unit  30  may be provided with only the first block member  31  and the second block member  32  without being provided with the intermediate block member  31 ′ illustrated in  FIG. 13 . 
     In the guard unit  30  illustrated in  FIG. 13 , the expansion thickness of the terrace portion  12  may be limited to the first gaps T 1   a  and T 1   b  between the internal surfaces in the first area A 1  facing the terrace portion  12 . Thus, rapid opening of the sealing portion  13 , caused by excessive expansion of the terrace portion  12 , may be reduced to delay gas venting of the secondary battery cell  10 . 
     Hereinafter, a modified example of the above-described guard unit  30  will be described with reference to  FIGS. 14 to 16 . 
     The guard unit  40  illustrated in  FIGS. 14 to 16  is configured to include a first area A 1  facing at least a portion of a terrace portion  12  to delay swelling or bursting of the sealing portion  13 . Unlike the example embodiment illustrated in  FIGS. 3 to 6, 10, 12, and 13 , the guard unit  40  illustrated in  FIGS. 14 to 16  is not provided with an area facing the sealing portion  13 . 
     The guard unit  40  has a shape in which the first gap T 1 , a distance between internal surfaces of the first area A 1 , is smaller (or less) than a thickness T 3  of a cell body member  10   a , so that an expansion thickness of the terrace portion  12  may be limited. For example, even in the case of the guard unit  40  illustrated in  FIGS. 14 to 16 , rapid opening of the sealing portion  13 , caused by excessive expansion of the terrace portion  12 , may be reduced to delay gas venting of the secondary battery cell  10 . 
     As illustrated in  FIG. 14 , the first gap T 1  of the guard unit  40  may have a constant value within the first area A 1 . For example, the guard unit  40  may have the same gap T 1  on one side  41  and the other side  42 . In this case, the guard unit may be in the form of a bar having a rectangular cross-section. 
     As illustrated in  FIGS. 15 and 16 , the first gaps T 1   a  and T 1   b  of the guard unit  40  may be configured to vary within the first area A 1 . For example, a distance T 1   a  between internal surfaces of the guard member  40  in a portion, adjacent to one side  41  of the first area A 1  may have a value different from a value of a distance T 1   b  between internal surfaces of the guard member  40  in a portion, adjacent to the other side  42  of the first area A 1 . As illustrated in  FIG. 15 , the first gaps T 1   a  and T 1   b  of the guard unit  40  may have a large value in a portion adjacent to the other side  42  far from the cell body member  10   a . Alternatively, as illustrated in  FIG. 16 , the first gaps T 1   a  and T 1   b  of the guard unit  40  may have a large value in a portion adjacent to one side  41  close to the cell body member  10   a . Although not illustrated in the drawings, a first gap between central portions of the one side  41  and the other side  42  may have a largest value. 
     When the first gaps T 1   a  and T 1   b  of the guard unit  40  vary, an average value of the first gaps may be smaller than a value of a thickness T 3  of the cell body member  10   a  to limit expansion thickness of the terrace portion  12 . Similarly, a maximum value of the first gaps may also be smaller than the value of the thickness T 3  of the cell body member  10   a.    
     The first gaps T 1 , T 1   a , and T 1   b  between internal surfaces in the first area A 1 , facing the terrace portion  12 , may have a value greater than a thickness of the terrace portion  12  such that the terrace portion  12  enters an opening  43  of the guard unit  40 . 
     In addition, the guard unit may be in the form of a bar, and may be disposed between the terrace portions  12  in a state of being separated from the bus bar member ( 21  of  FIG. 1A ). 
     While a ‘battery module’ has been mainly described in example embodiments of the present disclosure, a ‘battery module’ according to an example embodiment of the present disclosure is not limited to a conventional battery module accommodated in a battery pack. For example, a ‘battery pack’ according to the present disclosure may include a battery pack provided with a plurality of secondary battery cells  10  and a battery management system (BMS) in a housing. For example, the ‘battery module’ according to the present disclosure may have a cell-to-pack structure in which a plurality of secondary battery cells  10  are directly installed inside a pack housing (a housing). In consideration of this, in claims, a ‘battery module’ according to the present disclosure will be defined as including both conventional battery modules and conventional battery packs. 
     As described above, a battery module according to the present disclosure may delay gas venting caused by bursting of a sealing portion of a secondary battery cell. 
     Accordingly, the battery module according to the present disclosure may delay explosion of the secondary battery cell caused by the gas venting. 
     In addition, by delaying a point in time at which the sealing portion bursts, a point in time at which an electrolyte in the secondary battery cell is evaporated may also be delayed to suppress a rapid decrease in capacity of the secondary battery cell. 
     In another aspect, a battery module according to the present disclosure may intentionally and constantly vent gas, generated in the secondary battery cell, to prevent explosion caused by rapid gas venting. 
     While example embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present disclosure as defined by the appended claims. 
     For example, the present disclosure may be implemented by deleting some components in the above-described embodiments, and each of the embodiments may be implemented in combination with each other.