Patent Publication Number: US-2023139477-A1

Title: Battery module, battery pack including the same, and method of manufacturing battery module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a US national phase of international Application No. PCT/KR2021/019807 filed on Dec. 24, 2021, and claims the benefit of Korean Patent Application No. 10-2021-0007655 filed on Jan. 19, 2021, the contents of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a battery module, a battery pack including the same, and a method of manufacturing the battery pack, and more particularly to a battery module with improved safety, a battery pack including the same, and a method of manufacturing the battery pack. 
     BACKGROUND 
     Along with the increase in technological development and demand for a mobile device, demand for a secondary battery as an energy source is increasing rapidly, and accordingly, research on a battery capable of meeting various demands is being increasingly performed. 
     A secondary battery has attracted considerable attention as an energy source for power-driven devices, such as an electric bicycle, an electric vehicle, and a hybrid electric vehicle, as well as an energy source for mobile devices, such as a mobile phone, a digital camera, and a laptop computer. 
     Recently, along with a continuous rise of the necessity for a large-capacity secondary battery structure, including the utilization of the secondary battery as an energy storage source, there is a growing demand for a battery pack having a multi-module structure which is an assembly of battery modules in which a plurality of secondary batteries are connected in series or in parallel. 
     Meanwhile, when a plurality of battery cells are connected in series or in parallel to configure a battery pack, a common method of configuring a battery module starts with at least one battery cell and then other components are added to the at least one battery module to configure the battery pack. Since the battery cells constituting these medium- or large-sized battery modules are composed of chargeable/dischargeable secondary batteries, such a high-output and large-capacity secondary battery generates a large amount of heat during a charging and discharging process. 
     The battery module may include a battery cell stack in which a plurality of battery cells are stacked, a housing that houses the battery cell stack, and a pair of end plates that cover the front and rear surfaces of the battery cell stack. 
       FIG.  1    illustrates a battery module mounted on the conventional battery pack at the time of ignition.  FIG.  2    is a cross-section view along line A-A of  FIG.  1    showing the appearance of a flame that affects adjacent battery modules during ignition of a conventional battery module. 
     As illustrated in  FIGS.  1  and  2   , the conventional battery module  10  includes a battery cell stack in which a plurality of battery cells  11  are stacked, a housing  20  that houses the battery cell stack, a pair of end plates  30  that are formed on the front and rear surfaces of the battery cell stack, a pair of terminal busbars  40  formed to protrude out of the end plate, and the like. 
     The housing  20  and the pair of end plates  30  can be coupled to be sealed through welding. When the housing  20  for housing the battery cell stack and the pair of end plates  30  are coupled in this way, the internal pressure of the battery cell  10  increases during overcharging of the battery module, whereby when the fusion strength limit value of the battery cell  10  is exceeded, the high-temperature heat, gas, and flame generated in the battery cell  10  may be discharged out of the battery cell  10 . 
     The high-temperature heat, gas and flame can be discharged through the openings formed in each of the pair of end plates  30 , but in a battery pack structure in which a plurality of battery modules are disposed such that the end plates  30  of adjacent battery modules face each other, battery modules adjacent to a battery module that ejects high-temperature heat, gas and flame can be affected. Thereby, the terminal busbar  40  formed on the end plate  30  of the adjacent battery module can be damaged, and the high-temperature heat, gas, and flame can enter the adjacent battery module via the openings formed in the end plate  30  of the adjacent battery modules and can damage the plurality of battery cells  10 . 
     An attempt was made to separately form a hole through which the flame is discharged to reduce the occurrence of the above problems, and to form such a venting hole and thus increase the safety of the battery module, it is necessary to control the flame emission intensity. 
     SUMMARY 
     It is an object of the present disclosure to provide a battery module with improved safety, a battery pack including the same, and a method of manufacturing the battery pack. 
     However, the technical problem to be solved by embodiments of the present disclosure is not limited to the above-described problems, and can be variously expanded within the scope of the technical idea included in the present disclosure. 
     According to one aspect of the present disclosure, there is provided a battery module comprising: a battery cell stack in which a plurality of battery cells are stacked, a housing that houses the battery cell stack, and a thermal conductive resin layer that is located between a lower surface of the housing and a first end of the battery cell stack, wherein the first end of the battery cell stack has a double-folded seal part. 
     At least one injection hole for injecting a thermal conductive resin may be formed on the lower surface of the housing. The plurality of injection holes may be formed at the center of the lower surface of the housing and at both ends along the longitudinal direction. 
     The battery module may further include a venting hole formed on an upper surface of the housing adjacent to a second end that is located on the opposite side of the first end of the battery cell stack. 
     The battery module may further include a flame extinguishing mesh that covers the venting hole. 
     According to another aspect of the present disclosure, there is provided a method of manufacturing a battery module, the method comprising the steps of: stacking a plurality of battery cells to form a battery cell stack, housing the battery cell stack in a housing, inverting a lower surface of the housing so that the lower surface faces upwards, and injecting a thermal conductive resin through an injection hole formed in the lower surface of the housing, wherein the thermal conductive resin covers a first end of the battery cell stack having a double-folded seal part. 
     The method of manufacturing a battery module may further include, after the step of injecting the thermal conductive material, a step of inverting the lower surface of the housing so that the lower surface faces downwards. 
     The method of manufacturing a battery module may further include, before the step of housing the battery cells stack in the housing, a step of inverting the battery cell stack so that the first end of the battery cell stack is disposed on the lower surface of the housing. 
     The method of manufacturing a battery module may further include a step of forming a venting hole in the upper surface of the housing, and a step of forming a flame extinguishing mesh that covers the venting hole. 
     According to another aspect of the present disclosure, there is provided a battery pack comprising: the above-mentioned battery module, and a cooling plate located below the lower surface of the housing. 
     According to exemplary embodiments of the present disclosure, the thermal conductive resin can be applied to the junction part of the battery cell, thereby improving the robustness of the battery module. 
     Further, a flame extinguishing mesh can be mounted at the upper end of the housing located on the opposite side of the junction of the battery cell, thereby weakening the flame emission intensity and improving the flame extinguishing mesh. 
     The effects of the present disclosure are not limited to the effects mentioned above and additional other effects not described above will be clearly understood from the description of the appended claims by those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an illustration of a battery module mounted on a conventional battery pack at the time of ignition; 
         FIG.  2    is a cross-section view along line A-A of  FIG.  1    showing the appearance of a flame that affects adjacent battery modules during ignition of a conventional battery module. 
         FIG.  3    is an exploded perspective view of a battery module according to an embodiment of the present disclosure; 
         FIG.  4    is an illustration of the battery module components of  FIG.  3    after they are combined; 
         FIG.  5    is a perspective view of one battery cell included in the battery cell stack of  FIG.  3   ; 
         FIG.  6    is a perspective view of the battery module of  FIG.  4    when the battery module is inverted to face downwards; 
         FIG.  7    is a cross-sectional view taken along line B-B of  FIG.  6   ; 
         FIG.  8    is an enlarged perspective view of a section A of  FIG.  7   ; 
         FIG.  9    is an illustration of a thermal conductive resin layer according to an embodiment of the present disclosure; 
         FIG.  10    is an illustration of battery module that includes the thermal conductive resin layer of  FIG.  9   ; 
         FIG.  11    illustrates a method of manufacturing a battery module according to another embodiment of the present disclosure; 
         FIG.  12    is an illustration of a battery module according to a comparative example showing the ejection of gas and flame at the time of flame generation; 
         FIG.  13    is a cross-sectional view along line C-C of the yz plane of  FIG.  12   ; and 
         FIG.  14    is an illustration of a battery module according to an embodiment of the present disclosure showing the ejection of gas and flame at the time of flame generation. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the embodiments. The present disclosure can be modified in various different ways, and is not limited to the embodiments set forth herein. 
     Portions that are irrelevant to the description will be omitted to clearly describe the present disclosure, and like reference numerals designate like elements throughout the specification. 
     In the drawings, the size and thickness of each element are arbitrarily illustrated for convenience of the description, and the present disclosure is not necessarily limited to those illustrated in the drawings. In the drawings, the thickness of layers, regions, etc. are exaggerated for clarity. In the drawings, for convenience of the description, the thicknesses of some layers and regions are exaggerated. 
     It will be understood that when an element such as a layer, film, region, or plate is referred to as being “on” or “above” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, it means that other intervening elements are not present. Further, the word “on” or “above” means disposed on or below a reference portion, and does not necessarily mean being disposed “on” or “above” the reference portion toward the opposite direction of gravity. 
     Throughout the specification, when a portion is referred to as “including” a certain component, it means that the portion can further include other components, without excluding the other components, unless otherwise stated. 
     Throughout the specification, when a portion is referred to as “planar”, it means the target portion is viewed from the upper side, and when a portion is referred to as “cross-sectional”, it means the target portion is viewed from the side of a cross section cut vertically.  FIG.  3    is an exploded perspective view of a battery module according to an embodiment of the present disclosure.  FIG.  4    is an illustration of the battery module components of  FIG.  3    after they are combined.  FIG.  5    is a perspective view of one battery cell included in the battery cell stack of  FIG.  3   .  FIG.  6    is a perspective view of the battery module of  FIG.  4   , when the battery module is inverted to face downwards.  FIG.  7    is a cross-sectional view along the line B-B of  FIG.  6   .  FIG.  8    is an enlarged perspective view of a section A of  FIG.  7   . 
     As illustrated in  FIGS.  3  and  4   , a battery module according to the present embodiment includes a battery cell stack  120  in which a plurality of battery cells  110  are stacked, and a housing  100  that houses the battery cell stack  120  and has a lower surface  101  and an upper surface  102  corresponding to each other, wherein an injection hole  135  and/or a checking hole  130  for injecting a thermal conductive resin are formed in the lower surface  101  of the housing  100 . A plurality of injection holes  135  can be formed at the center of the lower surface  101  of the housing  100  and at both ends in the longitudinal direction. Here, the longitudinal direction may be the same direction as the direction in which the battery cell stack  120  is inserted into the housing  100 . 
     The housing  100  according to the present embodiment surrounds the remaining outer surfaces except for the front and rear surfaces of the battery cell stack  120 , a pair of end plates  150  are located on the front and rear surfaces of the battery cell stack  120 , respectively, and a busbar frame  145  is located between the battery cell stack  120  and each of the end plates  150 . The remaining outer surfaces except for the front and rear surfaces of the battery cell stack  120  may be the upper, lower, left and right surfaces of the battery cell stack. The upper surface  102  and the lower surface  101  of the housing  100  may face each other in a direction perpendicular to the stacking direction of the battery cell stack  120 . The stacking direction of the battery cell stack  120  may be the y-axis direction of  FIG.  3   , and the direction perpendicular thereto may be the z-axis direction. 
     As illustrated in  FIGS.  3  and  6   , a thermal conductive resin layer  400  is located between the lower surface  101  of the housing  100  and the battery cell stack  120  according to the present embodiment. The thermal conductive resin layer  400  may be formed by curing the thermal conductive resin injected through the injection holes  135 , and may serve to transfer heat generated in the battery cell stack  120  to the outside of the battery module, and fix the battery cell stack  120  in the battery module. 
     As illustrated in  FIG.  7   , the battery module according to the present embodiment may further include a compression pad  116  located between the outermost battery cell  110  of the battery cell stack  120  and the corresponding side surface part of the housing  100 . The compression pad  116  may be formed using a polyurethane-based material. The compression pad  116  can absorb the thickness deformation due to swelling of the battery cell  110  and the change in the battery cell  110  due to an external impact. At least one compression pad  116  may be formed not only between the outermost battery cell  110  and the corresponding side surface part of the housing  100 , but also between adjacent battery cells  110 . 
     The battery cell stack  120  includes a plurality of battery cells  110  stacked in one direction, and the plurality of battery cells  110  may be stacked in the y-axis direction as illustrated in  FIG.  3   . The battery cell  110  is preferably a pouch-type battery cell. For example, as illustrated in  FIG.  5   , the battery cell  110  according to the present embodiment has a structure in which the two electrode leads  111  and  112  protrude from one end  114   a  and the other end  114   b,  respectively, of the battery body part  113  in mutually opposite directions. The battery cell  110  can be manufactured by joining both ends  114   a  and  114   b  of a cell case  114  and both side parts  114   c  connecting them when an electrode assembly (not shown) is housed in a cell case  114 . The battery cells  110  according to the present embodiment have a total of three seal parts  114   sa ,  114   sb  and  114   sc , the seal parts  114   sa ,  114   sb  and  114   sc  have a structure that is sealed by a method such as heat-sealing, and the remaining other one side part can be composed of a connection part  115 . Between both end parts  114   a  and  114   b  of the battery case  114  can be defined as the longitudinal direction of the battery cell  110 , and between one side part  114   c  connecting both end parts  114   a  and  114   b  of the battery case  114  and the connection part  115  can be defined as the width direction of the battery cell  110 . 
     The connection part  115  is a region extending along one edge of the battery cell  110 , and a protrusion  110   p  of the battery cell  110  can be formed at an end of the connection part  115 . The protrusion  110   p  may be formed on at least one of both ends of the connection part  115  and may protrude in a direction perpendicular to the extension direction of the connection part  115 . The protrusion  110   p  may be located between one of the seal parts  114   sa  and  114   sb  of both ends  114   a  and  114   b  of the battery case  114  and the connection part  115 . 
     The battery case  114  generally has a laminated structure of a resin layer/a metal thin film layer/a resin layer. For example, when the surface of the battery case is formed of an O (oriented)-nylon layer, it tends to slide easily due to external impact when stacking a plurality of battery cells to form a medium- or large-sized battery module. Therefore, an adhesive member such as a cohesive-type adhesive such as a double-sided tape or a chemical adhesive bonded by chemical reaction during adhesion can be attached to the surface of the battery case to form a battery cell stack  100  to prevent these problems and maintain a stable stacked structure of the battery cells  110 . According to the present embodiment, the battery cells  110  can be stacked along the y-axis direction, and housed inside the housing  180  in the z-axis direction so that cooling can be performed by a thermal conductive resin layer described later. As a comparative example, the battery cells are formed of cartridge-shaped parts, and the fixing between the battery cells is made by assembling the battery housing. In such a comparative example, there is almost no cooling action, or the cooling can proceed in the plane direction of the battery cell, due to the presence of the parts in the form of a cartridge and the cooling is not well performed in the height direction of the battery module. 
     As also illustrated in  FIG.  3   , the battery module according to the present embodiment may further include a venting hole  105  formed in the upper surface  102  of the housing adjacent to the second end that is located on the opposite side of the first end of the battery cell stack  120 . A flame extinguishing mesh  107  covers the venting hole  105 , so that the strength of the flame generated inside the battery module being discharged to the outside can be reduced. 
     As illustrated in  FIG.  8   , an air gap may exist between the lower surface  101  of the housing and the battery cell stack  120 . The air gap can degrade the heat conducting characteristics, and the cooling efficiency may be decreased by the heat of the upper end of the battery cell  110 , particularly the portion of the battery cell  110  adjacent to the double-folded seal part DSF. According to the present embodiment, the thermal conductive resin layer  400  formed by injecting the thermal conductive resin through the injection hole  135  of  FIG.  7    can cover the first end of the battery cell stack  120  having the double folded seal part DSF. 
       FIG.  9    is an illustration of a thermal conductive resin layer according to the present embodiment.  FIG.  10    is an illustration of the battery module including the thermal conductive resin layer of  FIG.  9   . 
     As illustrated in  FIGS.  9  and  10   , the thermal conductive resin layer  400  according to the present embodiment is located between the lower surface  101  of the housing and the battery cell stack  120 . The thermal conductive resin layer  400  has a recessed pattern  400 DP formed on a surface facing the battery cell stack  120 . The recessed pattern  400 DP may have a sawtooth shape. The recessed pattern  400 DP has a structure corresponding to the first end of the battery cell  110 , and the first end of the battery cell  110  may have a double side folded shape. The double-sided folded shape is that of the double-folded seal part DSF formed by folding the seal part of the cell case at least twice. Specifically, the first end part of the battery cell  110  may be a portion  114   sc  where both side surfaces  114   c  of the cell case  114  connecting both ends  114   a  and  114   b  of the cell case  114  are bonded as described with reference to  FIG.  5   . As illustrated in  FIG.  5   , the electrode leads  111  and  112  may be located at both ends of the battery cell  110  that is located in a direction perpendicular to the first end of the battery cell  110 , and the battery cell  110  may have a rectangular structure in which the electrode leads  111  and  112  are formed long in a protruding direction. 
     As also illustrated in  FIGS.  9  and  10   , the recessed pattern  400 DP of the thermal conductive resin layer  400  according to the present embodiment includes a plurality of recessed parts  401 DP corresponding to the double folded seal part DSF of each of the plurality of battery cells  110 . 
     The first end of the battery cell  110  has two different inclined surfaces, and the thermal conductive resin layer  400  also has a first inclined surface SP 1  and a second inclined surface SP 2  to correspond thereto. The first inclined surface SP 1  of the thermal conductive resin layer  400  may come into contact with the first end of the battery cell  110 , and the second inclined surface SP 2  of the thermal conductive resin layer  400  may come into contact with the inclined surface of the double-folded seal part DSF. In order to form such a structure, the double-folded seal part DSF may come into close contact with the recessed part  401 DP of the thermal conductive resin layer  400 . By realizing such a structure, the contact area between the battery cell stack  120  and the thermal conductive resin layer  400  can be maximized and thus the cooling performance can be improved. 
     Due to the structure of the double folded seal part DSF, an air gap can be formed between the battery cell  110  and the double-folded seal part DSF. Consequently, the adhesive force of the portion where the second inclined surface SP 2  of the heat conductive resin layer  400  and the inclined surface of the double folded seal part DSF come into contact with each other may be weaker than the adhesive force of the portion where the first inclined surface SP 1  of the thermal conductive resin layer  400  comes into contact with the first end of the battery cell  110 . Therefore, as illustrated in  FIG.  9   , the heat moving in the arrow direction passing through the second inclined surface SP 2  may be relatively small compared to the heat moving in the arrow direction passing through the first inclined surface SP 1 . Specifically, the thermal efficiency of the die sealing gap existing therebetween may be complemented through the thermal conductive resin layer  400  because the double folded seal part (DSF) folds twice to tighten the seal part. 
     Next, a method of manufacturing a battery module according to another embodiment of the present disclosure will be described with reference to  FIG.  11   . 
     As illustrated in  FIG.  11   , the method of manufacturing the battery module according to the present embodiment may include (a) a step of stacking a plurality of battery cells to form a battery cell stack, (b) a step of inverting the battery cell stack so that the first end of the battery cell stack is disposed on the lower surface of the housing, (c) a step of coupling busbar frames to the front and rear surfaces of the battery cell stack, (d) a step of housing the battery cell stack in the housing, and coupling each of a pair of end plates to the open front and rear ends, respectively, of the housing, (e) a step of inverting a lower surface of the housing so that it faces up, and (f) a step of injecting a thermal conductive resin through at least one injection hole formed in the lower surface of the housing. 
     In the step (a) of stacking a plurality of battery cells to form a battery cell stack, the battery cells  110  may be sequentially stacked along the y-axis direction as shown in  FIG.  3   . 
     In the step (b) of inverting the battery cell stack so that the first end of the battery cell stack is disposed on the lower surface of the housing, the first end having the double folded seal part may face downward. 
     In the step (e) of inverting a lower surface of the housing so that it faces up, the lower surface  101  of the housing in which the at least one injection hole  135  is formed may face upward to inject the thermal conductive resin through the injection hole  135 , as shown in  FIG.  7   . 
     In the step (f) of injecting a thermal conductive resin through at least one injection hole formed in the lower surface of the housing, the thermal conductive resin may cover the first end of the battery cell stack having the double-folded seal part DSF as shown in  FIG.  10   . 
     The method of manufacturing the battery module according to the present embodiment may further include a step of forming a venting hole  105  in the upper surface  102  of the housing  100 , and a step of forming a flame extinguishing mesh  107  to cover the venting hole  105  as shown in  FIG.  4   . 
       FIG.  12    is an illustration of a battery module according to a comparative example showing the ejection of gas and flame during flame generation.  FIG.  13    is a cross-sectional view along a cross-section C-C of the yz plane of  FIG.  12   . 
     As illustrated in  FIGS.  12  and  13   , unlike the battery module according to the present embodiment, the end of the battery cell stack having a double-folded seal part is disposed on the opposite side of the lower surface of the housing on which the thermal conductive resin layer is formed. Because of such a structure, when a flame occurs in the battery module, gas and flame may be ejected through three junction parts corresponding to the weak part of the battery cell, wherein flames are ejected very strongly through the venting hole and the flame extinguishing mesh formed at the upper end of the battery module, and it may be difficult for the flame extinguishing mesh to function properly. 
       FIG.  14    is an illustration of the battery module according to an embodiment of the present disclosure showing the ejection of gas and flame at the time of flame generation. 
     As illustrated in  FIG.  14   , the first end of the battery cell stack having a double-folded seal part in the battery module according to the present embodiment can be covered with a thermal conductive resin layer, whereby the flame through the first end of the battery cell stack is shut off while consolidating the cell stack, and flame ejection from the upper end of the battery module located on the opposite side of the first end of the battery cell stack can be minimized Therefore, it is possible to obtain the effect of maximizing the function of the flame extinguishing mesh by weakening the intensity of the flame emitted through the flame extinguishing mesh because the flame is mainly ejected only at the lead end of the battery module through the flame extinguishing mesh formed at the upper end of the battery module. 
     Meanwhile, one or more battery modules according to an embodiment of the present disclosure can be packaged in a pack case to form a battery pack. Although not shown in the figure, a cooling plate may be located under the lower surface of the housing, and the battery cell stack may be housed in the housing so that the double-folded seal part is disposed on the lower surface of the housing adjacent to the cooling plate. 
     The above-mentioned battery module and the battery pack including the same can be applied to various devices. Specifically, such a device can be applied to a vehicle means such as an electric bicycle, an electric vehicle, or a hybrid vehicle, but the present disclosure is not limited thereto, and is applicable to various devices that can use a battery pack, which also falls within the scope of the present disclosure. 
     Although the invention has been shown and described above with reference to the preferred embodiments, the scope of the present disclosure is not limited thereto, and numerous other modifications and improvements can be made by those skilled in the art by using the basic principles of the invention defined in the appended claims, which also falls within the spirit and scope of the present disclosure. 
     housing