Patent Publication Number: US-2023134549-A1

Title: Battery module having improved electrode lead connection structure, and battery pack and vehicle including same

Description:
TECHNICAL FIELD 
     The present disclosure relates to a battery module including an improved electrode lead connection structure, and a battery pack and a vehicle including the battery module, and more particularly, to a battery module in which a shape of an electrode lead is changed to minimize the amount of use of a bus bar, and a battery pack and a vehicle including the battery module. 
     The present application claims priority to Korean Patent Application No. 10-2020-0101956 filed on Aug. 13, 2020 in the Republic of Korea, the disclosures of which are incorporated herein by reference. 
     BACKGROUND ART 
     A bus bar frame  2  including a bus bar  3  is generally used to electrically connect a plurality of pouch-type battery cells constituting a cell stack. In this case, an electrode lead  1  of each of adjacent pouch-type battery cells passes through a lead slit  2   a  formed in the bus bar frame  2 , and a pair of electrode leads  1  passing through the lead slits  2   a  are welded to the bus bar  3  formed of a conductive material and fixed to the bus bar frame  2 . Accordingly, the adjacent battery cells are electrically connected to each other. 
     In this case, the bus bar  3  includes a pair of plates  3   a  that are branched so that the pair of electrode leads  1  are respectively coupled to the pair of plates  3   a.    
     As such, when one pair of electrode leads  1  are electrically connected to each other by using the bus bar  3  including one pair of branched plates  3   a , as many plates  3   a  as the electrode leads  1  are required, thereby inevitably increasing manufacturing costs. Also, when one pair of electrode leads  1  are coupled to one pair of divided plates  3   a  in a one-to-one manner, a length of a path of current flowing between the one pair of electrode leads  1  increases and a resistance value increases, thereby increasing the risk of energy loss. 
     Accordingly, there is a need for structural improvement to improve a structure to minimize the amount of use of an expensive conductive metal material of the bus bar  3  and minimize a path of current flowing between a pair of adjacent electrode leads  1 . 
     DISCLOSURE 
     Technical Problem 
     The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to, when battery cells are electrically connected to one another, minimizing the amount of a conductive metal material required to manufacture a bus bar by minimizing a coupling area between the bus bar and an electrode lead while maintaining a sufficient coupling force, and thus reducing battery module manufacturing costs. 
     The present disclosure is also directed to preventing energy loss due to an increase in resistance by minimizing a path of current flowing between a pair of electrode leads electrically connected through one bus bar. 
     However, technical problems to be solved by the present disclosure are not limited to the above-described technical problems and one of ordinary skill in the art will understand other technical problems from the following descriptions. 
     Technical Solution 
     A battery module according to an embodiment of the present disclosure includes: a cell stack including a first battery cell including a first electrode lead and a second battery cell including a second electrode lead and adjacent to the first battery cell; a bus bar frame including a pair of lead slits through which the first electrode lead and the second electrode lead pass; and a bus bar fixed to the bus bar frame, wherein the first electrode lead and the second electrode lead are located on the bus bar in a state where a longitudinal end portion of the first electrode lead and a longitudinal end portion of the second electrode lead are engaged with each other, and a welding portion for bonding to the bus bar is formed in a region where the first electrode lead and the second electrode lead are engaged with each other. 
     The first electrode lead may include a plurality of first protrusions extending from the longitudinal end portion. 
     The plurality of first protrusions may be spaced apart from one another in a width direction of the first electrode lead. 
     The second electrode lead may include a plurality of second protrusions extending from the longitudinal end portion. 
     The plurality of second protrusions may be spaced apart from one another in a width direction of the second electrode lead. 
     Each of the plurality of second protrusions may be located in a space formed between adjacent first protrusions of the plurality of first protrusions. 
     The welding portion may be formed on the plurality of first protrusions and the plurality of second protrusions. 
     A length of each of the first protrusions and the second protrusions may correspond to a width of the bus bar. 
     The welding portion may be formed along the entire longitudinal direction of each of the first protrusion and the second protrusion. 
     The bus bar may be located between the pair of lead slits. 
     A surface of the longitudinal end portion of the first electrode lead and a surface of the longitudinal end portion of the second electrode lead may form a same plane. 
     A battery pack according to an embodiment of the present disclosure includes the battery module according to an embodiment of the present disclosure. 
     A vehicle according to an embodiment of the present disclosure includes the battery module according to an embodiment of the present disclosure. 
     Advantageous Effects 
     According to an aspect of the present disclosure, when battery cells are electrically connected to one another, the amount of a conductive metal material required to manufacture a bus bar may be minimized by minimizing a coupling area between the bus bar and an electrode lead while maintaining a sufficient coupling force, and thus battery module manufacturing costs may be reduced. 
     Also, according to another aspect of the present disclosure, a length of a path of current flowing between a pair of electrode leads electrically connected through one bus bar may be significantly reduced, and thus energy loss due to an increase in resistance may be prevented. 
    
    
     
       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. 
         FIGS.  1  and  2    are views illustrating a conventional battery module structure. 
         FIG.  3    is a view illustrating a battery module according to an embodiment of the present disclosure. 
         FIG.  4    is a view illustrating a cell stack of the present disclosure. 
         FIG.  5    is a view illustrating a bus bar frame and a bus bar of the present disclosure. 
         FIG.  6    is an enlarged partial view illustrating a coupling portion between a pair of electrode leads and a bus bar in a battery module according to an embodiment of the present disclosure. 
         FIG.  7    is an enlarged partial view illustrating a coupling portion between a pair of electrode leads and a bus bar in a battery module according to another embodiment of the present disclosure. 
     
    
    
     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 present disclosure, so it should be understood that other equivalents and modifications could be made thereto without departing from the scope of the present disclosure. 
     Hereinafter, a battery module according to an embodiment of the present disclosure will be described with reference to  FIGS.  3  through  7   . Referring to  FIGS.  3  through  7   , a battery module according to an embodiment of the present disclosure includes a cell stack  10 , a bus bar frame  20 , and a bus bar  30 . 
     The cell stack  10  is formed by stacking a plurality of battery cells including a first battery cell  11  and a second battery cell  12  adjacent to each other. The battery cells constituting the cell stack  10  may be, for example, pouch-type battery cells, and in this case, a pair of electrode leads having different polarities are drawn out in opposite directions. 
     The first battery cell  11  and the second battery cell  12  facing each other are stacked so that a first electrode lead  11   a  extending to a side in a longitudinal direction of the first battery cell  11  and a second electrode lead  12   a  extending to a side in a longitudinal direction of the second battery cell  12  adjacent to the first battery cell  11  and adjacent to the first electrode lead  11   a  have opposite polarities. 
     Such a stacked arrangement of the cell stack  10  is to connect the plurality of battery cells including the first battery cell  11  and the second battery cell  12  in series. That is, the first battery cell  11  and the second battery cell  12  adjacent to each other are connected to each other in series by electrically connecting the first electrode lead  11   a  and the second electrode lead  12   a  having different polarities. 
     The bus bar frame  20  has a substantially rectangular plate shape, and is located on one side and on the other side in a longitudinal direction (direction parallel to a Y-axis) of the cell stack  10 . It is preferable that the bus bar frame  20  is formed of a non-conductive material for insulation between a plurality of bus bars  30  described below. One pair of bus bar frames  20  are provided to connect the plurality of battery cells constituting the cell stack  10  in series. 
     The bus bar frame  20  includes at least one lead connection area S. When a plurality of lead connection areas S are provided, the plurality of lead connection areas S are spaced apart from one another in a longitudinal direction (parallel to an X-axis) of the bus bar frame  20 . A pair of lead slits  21  are formed in each of the lead connection area S. Each of the lead slits  21  has a length corresponding to a width of one electrode lead and a width corresponding to a thickness of the electrode lead so that the electrode lead passes through the lead slit  21 , and the lead slit  21  extends in a width direction (direction parallel to a Z-axis) of the bus bar frame  20 . Also, the pair of lead slits  21  are spaced apart from each other in the longitudinal direction (direction parallel to the X-axis) of the bus bar frame  20 . 
     The bus bar  30  is formed of a conductive metal, and as many bus bars  30  as the lead connection areas S are provided. The bus bar  30  is fixedly provided between the pair of lead slit  21  located in the lead connection area S. The bus bar  30  longitudinally extends in the width direction (direction parallel to the Z-axis) of the bus bar frame  20 . 
     The first electrode lead  11   a  and the second electrode lead  12   a  extending parallel to each other in the same direction are located to correspond, in a one-to-one manner, to the pair of lead slits  21  formed in one lead connection area S. 
     Referring to  FIG.  6   , the first electrode lead  11   a  passes through the lead slit  21  and is bent toward the bus bar  30 . Likewise, the second electrode lead  12   a  passes through the lead slit  21  and is bent toward the bus bar  30  and the first electrode lead  11   a.    
     The first electrode lead  11   a  and the second electrode lead  12   a  are located on the bus bar  30  in a state where longitudinal end portions of the first electrode lead  11   a  and the second electrode lead  12   a  are engaged with each other. In this case, a surface of the longitudinal end portion of the first electrode lead  11   a  and a surface of the longitudinal end portion of the second electrode lead  12   a  may form the same plane. That is, the first electrode lead  11   a  and the second electrode lead  12   a  may not overlap each other. According to this coupling structure, the risk of welding failure caused by an increase in a thickness of an object to be welded during welding between the first electrode lead  11   a  and the bus bar  30  and welding between the second electrode lead  12   a  and the bus bar  30  may be greatly reduced. A welding portion W for bonding to the bus bar  30  is formed in a region where the first electrode lead  11   a  and the second electrode lead  12   a  are engaged with each other. That is, each of the first electrode lead  11   a  and the second electrode lead  12   a  is welded to the bus bar  30 . 
     For engagement between the first electrode lead  11   a  and the second electrode lead  12   a , the first electrode lead  11   a  includes a plurality of first protrusions P 1  extending from the longitudinal end portion, and the second electrode lead  12   a  includes a plurality of second protrusions P 2  extending from the longitudinal end portion. The first protrusions P 1  may extend from the longitudinal end portion of the first electrode lead  11   a , in a longitudinal direction of the first electrode lead  11   a . Likewise, the second protrusions P 2  may extend from the longitudinal end portion of the second electrode lead  12   a , in a longitudinal direction of the second electrode lead  12   a . Accordingly, the first protrusions P 1  and the second protrusions P 2  may extend toward each other. The plurality of first protrusions P 1  are spaced apart from one another in a width direction of the first electrode lead  11   a , and likewise, the plurality of second protrusions P 2  are spaced apart from one another in a width direction of the second electrode lead  12   a . Each of the plurality of second protrusions P 2  is located to fill a space formed between adjacent first protrusions P 1 . In this case, the first protrusion P 1  and the second protrusion P 2  may be in close in contact with each other so that surfaces of the first protrusion P 1  and the second protrusion P 2  form the same plane. 
     The welding portion W may be formed on the plurality of first protrusions P 1  and the plurality of second protrusions P 2 . Although the welding portion W is formed in a dot shape only on a portion of the entire area of each of the first protrusion P 1  and the second protrusion P 2  in  FIG.  6   , this is merely an example. The welding portion W may be formed over the entire area where the first electrode lead  11   a  and the bus bar  30  overlap each other and the entire area where the second electrode lead  12   a  and the bus bar  30  overlap each other, in order to firmly fix the first electrode lead  11   a  and the second electrode lead  12   a  to the bus bar  30 . Alternatively, for ease of welding, the welding portion W may be longitudinally formed in a longitudinal direction (direction parallel to the Z-axis) of the bus bar  30  to pass through a central portion in a longitudinal direction (direction parallel to the X-axis) of the first protrusion P 1  and a central portion in a longitudinal direction (direction parallel to the X-axis) of the second protrusion P 2 . 
     When viewed from the top of the bus bar  30 , each of the first protrusion  11   a  and the second protrusion  12   a  may have a trapezoidal shape as shown in  FIG.  6   , or may have a rectangular shape, a triangular shape, or a shape having a round longitudinal end portion. 
     Referring to  FIG.  7   , in order to increase a coupling force between the first electrode lead  11   a  and the bus bar  30  and a coupling force between the second electrode lead  12   a  and the bus bar  30 , each of the first protrusion P 1  and the second protrusion P 2  may be formed so that a length D of each of the first protrusion P 1  and the second protrusion P 2  corresponds to a width of the bus bar  30 . That is, the length D of each of the first protrusion P 1  and the second protrusion P 2  may be substantially the same as the width of the bus bar  30 . In this case, it is preferable that the welding portion W is formed along the entire longitudinal direction (direction parallel to the X-axis) of the first protrusion P 1  and along the entire longitudinal direction of the second protrusion P 2 . 
     According to the battery module according to the present disclosure as described above, because one pair of electrode leads  11   a ,  12   a  are located on the bus bar  30  in a state where the pair of electrode leads  11   a ,  12   a  are engaged with each other and the welding portion W is formed in a region where the pair of electrode leads  11   a ,  12   a  are engaged with each other, a width of the bus bar  30  may be minimized and a width of a coupling area between the electrode leads  11   a ,  12   a  and the bus bar  30  may not be reduced. Accordingly, costs of materials required to manufacture the bus bar  30  formed of a conductive metal material may be minimized and a coupling force between the electrode leads  11   a ,  12   a  and the bus bar  30  may be secured, thereby improving productivity and product quality. 
     A battery pack according to an embodiment of the present disclosure includes at least one battery module according to the present disclosure as described above. Also, a vehicle according to an embodiment of the present disclosure includes at least one battery module according to the present disclosure as described above or at least one battery pack according to an embodiment of the present disclosure. 
     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 present disclosure, are given by way of illustration only, since various changes and modifications within the scope of the present disclosure defined by the appended claims will become apparent to one of ordinary skill in the art from this detailed description.