Patent Publication Number: US-2021164511-A1

Title: Battery Module Structured so as to Prevent Entry of Foreign Substances, and Battery Pack and Motor Vehicle Comprising Same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2019/017949, filed Dec. 18, 2019, which claims priority to Korean Patent Application No. 10-2018-0169968 filed on Dec. 26, 2018 in the Republic of Korea, the disclosures of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a battery module having a structure for preventing foreign matter from entering, and a battery pack and a vehicle including the battery module. More particularly, the present disclosure relates to a battery module having a structure for reinforcing rigidity of a portion where a nut is fixed, increasing the degree of freedom in selecting a length of a bolt inserted into the nut and also preventing foreign matter from entering the battery module, when applying a bolt/nut fastening structure to fasten a terminal of an electronic device or another battery module to a terminal of the battery module, and a battery pack and a vehicle including the battery module. 
     BACKGROUND ART 
     In order to supply electric energy to an application such as an electric vehicle using a battery module or a battery pack in which a plurality of battery modules are connected, a terminal or a connecting bar of a power cable must be fastened to a module terminal of the battery module. 
     When an external terminal such as a terminal or a connecting bar of a power cable is fastened to the module terminal of the battery module as described above, a bolt/nut fixing structure may be applied. In the bolt/nut fixing structure, a terminal nut is located at a lower part of the module terminal of the battery module, and an external terminal is located at an upper part of the module terminal. Then, if the external nut is inserted into a bolt and then rotated in a clockwise direction, the terminal nut is closely adhered to a lower surface of the module terminal, and also the external terminal is adhered and fixed on the module terminal. 
     For example, in the battery module applied to an electric vehicle, if the coupling force between the external terminal and the module terminal is weakened to cause a contact failure between the external terminal and the module terminal, components of the electric vehicle cannot be normally performed partly or entirely. Thus, the bolt must be tightened with very strong force. 
     In this case, the structure surrounding the periphery of the nut is usually made of a resin injection material for insulation so that the nut does not turn together when the bolt is rotated for fastening. 
     In addition, in the bolt/nut fixing structure, in order to obtain a high fastening force, the bolt must be sufficiently rotated in a state of being fastened to the nut. However, if a nut having a blocked lower surface is applied or the injection material accommodating the nut has a blocked structure at the surface supporting the nut, the bolt may not be sufficiently rotated, and accordingly the coupling force between the module terminal and the external terminal may not be sufficiently secured. 
     DISCLOSURE 
     Technical Problem 
     The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing a battery module, which has a structure in which a nut is stably fixed even though a bolt is strongly fastened, by reinforcing rigidity of a portion where the nut is fixed. 
     In addition, the present disclosure is also directed to providing a battery module, which has an additional space for accommodating the bolt so that the bolt may be sufficiently rotated, and also has a structure capable of preventing foreign matter, which may be generated by friction between the bolt and the nut as the bolt is rotated with strong force, from entering the inner space of the battery module. 
     However, the technical problem to be solved by the present disclosure is not limited to the above, and other objects not mentioned herein will be understood from the following description by those skilled in the art. 
     Technical Solution 
     In one aspect of the present disclosure, there is provided a battery module, comprising: a cell stack formed by stacking a plurality of battery cells; a bus bar frame assembly having a bus bar frame configured to cover a first longitudinal side and a second longitudinal side of the cell stack and a plurality of bus bars fixed on the bus bar frame and electrically connected to the battery cells; a module terminal having a lead connection portion fixed on the bus bar frame and electrically connected to the battery cells and a head portion connected to the lead connection portion to extend above the lead connection portion; a terminal nut located below the head portion; and a frame cover having a nut accommodation portion configured to accommodate the terminal nut and a bolt accommodation portion formed below the nut accommodation portion to accommodate a bolt passing through the head portion and the terminal nut, the frame cover being configured to cover the bus bar frame assembly so that the head portion is exposed to the outside. 
     The terminal nut may be a hexagonal nut. 
     The nut accommodation portion may have a size corresponding to the terminal nut, and an inner wall of the nut accommodation portion may be in contact with a side surface of the terminal nut so that the terminal nut does not rotate together when the bolt rotates. 
     The bolt accommodation portion may be shaped as a groove and may be formed at a bottom surface of the nut accommodation portion. 
     The frame cover may include a barrier formed between the bolt accommodation portion and the bus bar frame assembly to prevent foreign matter generated when the bolt and the terminal nut are fastened from entering the bus bar frame assembly. 
     The battery module may further comprise an end plate configured to cover the frame cover. 
     The battery module may further comprise a reinforcing frame interposed between the end plate and the frame cover at a location corresponding to the nut accommodation portion. 
     The battery cell may include an electrode assembly; a pair of electrode leads connected to the electrode assembly to extend in opposite directions along a longitudinal direction of the battery cell; and a cell case configured to accommodate the electrode assembly and sealed so that the electrode lead is exposed to the outside. 
     The pair of electrode leads may be formed at locations and biased downward from a center of the cell stack in a height direction thereof. 
     The module terminal may be disposed in a space formed above the electrode lead due to the biasing of the pair of electrode leads. 
     In another aspect of the present disclosure, there are also provided a battery pack and a vehicle, which comprises the battery module according to an embodiment of the present disclosure. 
     Advantageous Effects 
     According to an embodiment of the present disclosure, even if the bolt is tightened with a strong force to fasten an external terminal to the module terminal, the nut may be stably fixed. 
     In addition, according to another embodiment of the present disclosure, since an additional space for accommodating the bolt protruding below the nut is provided, the bolt may be sufficiently rotated. Also, it is possible to prevent foreign matter, which may be generated by friction between the bolt and the nut as the bolt is rotated with a strong force, from entering the inner space of the battery module. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The accompanying drawings illustrate a preferred embodiment of the present disclosure and together with the foregoing disclosure, serve to provide further understanding of the technical features of the present disclosure, and thus, the present disclosure is not construed as being limited to the drawing. 
         FIG. 1  is a perspective view showing a battery module according to an embodiment of the present disclosure. 
         FIG. 2  is a perspective view showing a state in which an end plate is removed from the battery module according to an embodiment of the present disclosure. 
         FIG. 3  is a perspective view showing a state in which an end plate and a frame cover are removed from the battery module according to an embodiment of the present disclosure. 
         FIG. 4  is a perspective view showing a cell stack applied to the battery module according to an embodiment of the present disclosure. 
         FIG. 5  is a plan view showing a battery cell applied to the battery module according to an embodiment of the present disclosure. 
         FIG. 6  is a side view showing a state in which a mono frame, an upper cover, an end plate and a frame cover are removed from the battery module according to an embodiment of the present disclosure. 
         FIG. 7  is a partially enlarged view showing a region in which a module terminal is located, in the battery module depicted in  FIG. 2 . 
         FIG. 8  is a cross-sectioned view, taken along the line X-X′ of  FIG. 2 . 
         FIG. 9  is a cross-sectioned view, taken along the line Y-Y′ of  FIG. 1 . 
         FIG. 10  is a diagram for illustrating a principle that a nut applied to the battery module according to an embodiment of the present disclosure moves according to the rotation of the bolt. 
     
    
    
     BEST MODE 
     Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the disclosure, so it should be understood that other equivalents and modifications could be made thereto without departing from the scope of the disclosure. 
     Referring to  FIGS. 1 to 4 , a battery module according to an embodiment of the present disclosure may include a cell stack  100 , a FPCB assembly  200 , a bus bar frame assembly  300  (see  FIG. 8 ), a module terminal  400 , an upper cover  450 , a mono frame  500 , a frame cover  600  and an end plate  700 . 
     As shown in  FIG. 4 , the cell stack  100  includes a plurality of battery cells  110  stacked to face each other at wide surfaces thereof. The cell stack  100  may include at least one buffer pad P interposed at an outermost battery cell  110  and/or between adjacent battery cells  110 . 
     That is, the cell stack  100  may be inserted into the mono frame  500  in a state of being coupled with the bus bar frame assembly  300 , the module terminal  400  and the upper cover  450 . At this time, in order to insert the cell stack  100  easily while securing a maximum volume of the cell stack  100 , the buffer pad P made of an elastic material such as a sponge may be additionally applied. 
     Referring to  FIG. 5 , a specific structure of the battery cell  110  is illustrated. A pouch-type battery cell may be applied as the battery cell  110 . The pouch-type battery cell  110  includes an electrode assembly (not shown), a pair of electrode leads  111  and a cell case  112 . 
     Although not shown in the drawings, the electrode assembly has a form in which separators are interposed between positive electrode plates and negative electrode plates that are repeatedly stacked alternately, and separators are preferably positioned at both outermost sides for insulation. 
     The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer coated on one side of the positive electrode current collector, and a positive electrode uncoated region not coated with a positive electrode active material is formed at one side end of the positive electrode plate. The positive electrode uncoated region functions as a positive electrode tab. 
     The negative electrode plate may include a negative electrode current collector and a negative electrode active material layer coated on one surface or both sides of the negative electrode current collector, and a negative electrode uncoated region not coated with a negative electrode active material is formed at one side end of the negative electrode plate. The negative electrode uncoated region functions as a negative electrode tab. 
     In addition, the separator is interposed between the positive electrode plate and the negative electrode plate to prevent electrode plates having different polarities from directly contacting each other. The separator may made of a porous material so that ions may be moved using the electrolyte as a medium between the positive electrode plate and the negative electrode plate. 
     The pair of electrode leads  111  are connected to the positive electrode tab (not shown) and the negative electrode tab (not shown), respectively, and are drawn out of the cell case  112 . The pair of electrode leads  111  are drawn out at one longitudinal side and the other longitudinal side of the battery cell  110 , respectively. That is, the battery cell  110  applied to the present disclosure corresponds to a bidirectional draw-out battery cell in which the positive electrode lead and the negative electrode lead are drawn in opposite directions. In addition, the pair of electrode leads  111  are positioned to be biased to one side from a center of the battery cell  110  in a width direction (the Z-axis direction of  FIG. 5 ). Specifically, the pair of electrode leads  111  are positioned to be biased to one side from the center of the battery cell  110  in the width direction, preferably to be biased downward along the height direction (the Z-axis direction of  FIG. 4 ) of the cell stack  100 . 
     If the pair of electrode leads  111  are positioned to be biased to one side from the center of the battery cell  110  in the width direction as described above, it is possible to give a space for installation of the module terminal  400 , explained later, so that the energy density of the battery module is improved. The increase in energy density due to the structure in which the electrode lead  111  is installed to be biased will be described in detail later. The cell case  112  includes two regions, namely an accommodation portion accommodating the electrode assembly and a sealing portion extending in a circumferential direction of the accommodation portion and thermally fused in a state where the electrode lead  111  is drawn out to seal the cell case  112 . 
     Although not shown in the figures, the cell case  112  is sealed by affixing and thermally fusing edge portions of an upper case and a lower case made of a multi-layered pouch film in which a resin layer, a metal layer and a resin layer are stacked in order. 
     In the sealing portion, a terrace portion  112   a  corresponding to a region located in the direction in which the electrode lead  111  is drawn out has a tapered shape such that both sides of the terrace portion  112   a  are cut so that the width thereof is gradually reduced along the drawing direction of the electrode lead  111 . As described above, if the width of the terrace portion  112   a  is gradually reduced toward the outer direction of the battery cell  110 , the electrode lead  111  may be disposed to be biased, and the energy density of the battery module may be improved. 
     Meanwhile, the battery cell  110  applied to the present disclosure is a long cell where a ratio of width (W) to length (L) is about 3 or more and 12 or less. In the battery module according to the present disclosure, if the long cell type battery cell  110  is employed, it is possible to improve the capacity of the battery while minimizing the increase in the height of the battery module, which makes it easy to install the battery module at a lower part of a seat or a trunk of a vehicle. 
     Referring to  FIG. 3 , the FPCB assembly  200  may be implemented to include a flexible printed circuit board (FPCB)  210  and a connector  220 . 
     The FPCB  210  extends along the longitudinal direction of the battery module (the Y-axis direction of  FIG. 3 ) to cover at least a portion of the top surface of the cell stack  100 , and both ends of the FPCB  210  are bent and placed on the bus bar frame assembly  300 . Connection terminals  211  are provided at both ends of the bent FPCB  210 , and the connection terminals  211  are connected to the bus bar  320  and the module terminal  400  to electrically connect the FPCB  210  to the battery cell  110 . 
     The connector  220  is exposed out of the upper cover  450  and the mono frame  500  and mounted on the FPCB  210  that is bent toward the bus bar frame assembly  300 . The connector  220  is disposed in a space formed above the electrode lead  111  due to the biasing of the electrode lead  111 , similar to the installation position of the module terminal  400  described above. The arrangement position of the connector  220  minimizes the increase in the volume of the battery module due to the installation of the connector  220 , thereby increasing the energy density of the battery module. 
     The connector  220  is electrically connected to the battery cells  110  through the FPCB  210 . In addition, a control device (not shown) such as a BMS is connected to the connector  220 , and the control device receives information about the voltage of the battery cell  110  and controls charging and discharging of the battery module with reference to the information. 
     Referring to  FIG. 3 , the bus bar frame assembly  300  may be implemented to include a bus bar frame  310  configured to cover one longitudinal side and the other longitudinal side of the cell stack  100  and a plurality of bus bars  320  fixed on the bus bar frame  310  and electrically connected to the battery cell  110 . 
     The bus bar frame  310 , for example, may be made of an insulating material such as resin, and includes a bus bar placing portion  311  formed to protrude at a position corresponding to electrode leads  111  of the battery cell  110 . The bus bar placing portion  311  is formed at a position biased downward from the center of the cell stack  100  in the height direction (the Z-axis direction of  FIGS. 3 and 4 ), like the electrode lead  111 . The biasing of the bus bar placing portion  311  is to secure a space for installing components such as the connector  220  or the module terminal  400 , similar to the biasing of the electrode lead  111 . 
     The bus bar placing portion  311  has a plurality of lead slits S formed at positions corresponding to the electrode leads  111 . Through the lead slits S, the electrode leads  111  are drawn out of the bus bar frame assembly  300 , and the drawn electrode leads  111  are bent and fixed by welding or the like on the bus bar  320 . 
     Referring to  FIG. 3 , the module terminal  400  is provided in a pair, and each module terminal  400  includes a lead connection portion  410  and a head portion  420 . 
     The lead connection portion  410  is fixed on the bus bar placing portion  311  of the bus bar frame  310  and is connected to the electrode lead  111  located at both outermost sides along the width direction of the cell stack  100  (the X-axis direction of  FIGS. 3 and 4 ). The head portion  420  is connected to the lead connection portion  410  and extends above the lead connection portion  410 . The head portion  420  has a terminal hole  421  (see  FIG. 7 ) into which a bolt B is inserted for fastening an external terminal (not shown) to the module terminal  400 . 
     Referring to  FIG. 6  along with  FIG. 3 , the head portion  420  of the module terminal  400  is located in the space formed above the electrode lead  111  and the bus bar placing portion  311  due to the biasing of the electrode lead  111  (upward along the Z axis based on  FIGS. 3 and 5 ). The formation position of the head portion  420  is to minimize the volume of the battery module increased due to the installation of the module terminal  400  by utilizing the space formed by the biased installation of the electrode lead  111 . 
     Referring to  FIGS. 3 and 4  together, the upper cover  450  corresponds to a part that covers the top surface of the cell stack  100  (a surface parallel to the X-Y plane of  FIG. 4 ). The upper cover  450  is hinged with a pair of bus bar frames  310 , respectively. Thus, the pair of the bus bar frames  310  may be rotated relative to the upper cover  450 , based on the hinged portion. 
     Referring to  FIGS. 7 to 10  along with  FIG. 2 , the frame cover  600  covers the bus bar frame assembly  300  so that the head portion  420  of the module terminal  400  is exposed to the outside. The frame cover  600  includes a nut accommodation portion  610 , a bolt accommodation portion  620 , and a barrier  630 . 
     The nut accommodation portion  610  accommodates a terminal nut N located below the head portion  420  of the module terminal  400 . In order to supply electric energy to an application such as an electric vehicle by using the battery module or a battery pack in which a plurality of battery modules are connected, an external terminal T such as a terminal or a connecting bar of a power cable provided in the vehicle must be fastened to the module terminal  400  of the battery module (see  FIG. 10 ). As described above, in order to fasten the external terminal T to the module terminal  400  of the battery module, the battery module according to an embodiment of the present disclosure uses a bolt/nut fixing structure. 
     That is, the terminal nut N is located under the head portion  420  of the module terminal  400 , the external terminal T is located above the head portion  420 , and then a bolt B (see  FIG. 10 ) is inserted to pass through the external terminal T and the head portion  420  in order and is rotated clockwise. In this case, the bolt B moves downward along a thread formed on the terminal nut N, and the terminal nut N moves upward (in a direction shown by the arrows in  FIG. 10 ). Accordingly, the external terminal T is fixed between the bolt B and the head portion  420 . As the bolt B is rotated clockwise more, the fixing force becomes stronger. 
     In this way, in order for the terminal nut N to move upward with the rotation of the bolt B, the terminal nut N must be fixed without rotating together according to the rotation of the bolt B. That is, an inner wall of the nut accommodation portion  610  is in contact with a side surface of the terminal nut N to fix the terminal nut N so that the terminal nut N does not rotate according to the rotation of the bolt B. 
     To this end, the nut accommodation portion  610  has a size corresponding to the terminal nut N. Specifically, the nut accommodation portion  610  and the terminal nut N may be formed to have the same width (D 1 ) and the same vertical width (D 2 ), and the terminal nut N may be a hexagonal nut whose cross section is approximately hexagonal. 
     When the bolt B passes through the terminal nut N to protrude downward below the terminal nut N according to the clockwise rotation of the bolt B, the bolt accommodation portion  620  accommodates the protruding portion of the bolt B. The bolt accommodation portion  620  has a groove shape formed at the bottom surface of the nut accommodation portion  610 . 
     The barrier  630  is formed between the bolt accommodation portion  620  and the bus bar frame assembly  300  to form an inner wall of the bolt accommodation portion  620 . The barrier  630  prevents the bolt accommodation portion  620  and the bus bar frame assembly  300  from communicating with each other, thereby preventing foreign matter, such as metal powder generated when the bolt B and the terminal nut N are fastened, from entering the bus bar frame assembly  300 . 
     By preventing foreign matter such as metal powder from entering the bus bar frame assembly  300  as above, it is possible prevent that an unnecessary electrical connection occurs between the electrode leads  111  due to foreign matter to cause a problem such as a short. 
     Referring to  FIGS. 1 and 9  together, the end plate  700  covers the frame cover  600  such that the head portion  420  of the module terminal  400  is exposed to the outside. Meanwhile, as shown in  FIG. 9 , the battery module according to an embodiment of the present disclosure may further include a reinforcing frame F interposed between the frame cover  600  and the end plate  700 . 
     Referring to  FIG. 10  along with  FIG. 9 , the reinforcing frame F is interposed at a position corresponding to the nut accommodation portion  610  of the frame cover  600  to enhance the fixing force of the nut N. That is, the frame cover  600  may be made of a resin material for insulation. In this case, if the bolt B is strongly rotated and tightened, the inner wall of the nut accommodation portion  610  may be bent or damaged not to fix the terminal nut N. 
     In order to prevent this situation from occurring, the reinforcing frame F may be made of a metal material with a higher rigidity than resin, and the bolt B may be strongly tightened by applying the reinforcing frame F to strengthen the fastening force between the external terminal T and the head portion  420 . 
     As described above, since the head portion  420  of the module terminal  400  is disposed using the space formed by the biasing of the electrode lead  111 , the battery module according to an embodiment of the present disclosure may minimize the increase in the volume of the battery module due to the installation of the module terminal  400 , thereby improving the energy density. 
     In addition, the battery module according to an embodiment of the present disclosure includes the bolt accommodation portion  620  accommodating the bolt B protruding below the terminal nut N, thereby increasing the degree of freedom in selecting the length of the bolt B. Accordingly, by using the bolt B having a sufficiently long length to pass through the terminal nut N, the fastening force between the external terminal T and the head portion  420  of the module terminal  400  may be further strengthened. 
     In addition, the battery module according to an embodiment of the present disclosure includes the barrier interposed between the bolt accommodation portion  620  and the bus bar frame assembly  300  so that the bolt accommodation portion  620  and the bus bar frame assembly  300  cannot communicate with each other. By doing so, it is possible to prevent foreign matter such as metal powder from entering the bus bar frame assembly  300  and causing an event such as a short. 
     The present disclosure has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the scope of the disclosure will become apparent to those skilled in the art from this detailed description.