Patent Publication Number: US-2023163423-A1

Title: High-voltage battery module and method for producing a coolable high-voltage battery module with busbar integration

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to German Patent Application No. 10 2021 130 443.1, filed Nov. 22, 2021, the content of such application being incorporated by reference herein in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a coolable high-voltage battery module, in which at least one busbar is integrated into an end plate disposed on the end face side. A method for producing the high-voltage battery module with busbar integration is described as well. 
     BACKGROUND OF THE INVENTION 
     Battery cells in electrically or partially electrically operated motor vehicles are actively cooled in the prior art, because, in particular at higher outputs, they can heat up so much that they are damaged. In the cooling systems used for this purpose, a distinction can generally be made between two approaches which are based, on the one hand, on a direct flow of a dielectric fluid around the battery cells and, on the other hand, on cooling of the battery cells by means of a self-contained cooling system, e.g., a flooded cooling plate, to which the battery cells are connected in a thermally conductive manner. In the aforementioned second case with thermal connection, in the prior art one or more sides of the battery cell are thermally connected to the cooling plates, e.g., via a thermally conductive paste, but not an electrical connector or a high-voltage terminal of the battery cell, also referred to as a cell tab. 
     A known design of the battery cell is the so-called pouch cell, also referred to in German as “Taschenzelle”, in which, for example, a flat lithium-ion accumulator is welded in between two films. The cell tab is disposed toward an end face of the pouch cell, for example, and during further assembly is connected to a busbar to form a high-voltage battery module. A significant portion of the heat generation comes from these cell tabs and busbars, whereby there is also a heat input into the cells and these are heated locally in the region of the cell tabs. However, cell tabs are difficult to connect to the cooling system in terms of installation space. 
     DE 10 2009 011 659 A1, which is incorporated herein by reference, discloses a system comprising a plurality of busbars which are connected to an end plate and also the cooling system, and are thermally connected to a battery component. Insulating plates are disposed between the busbars. 
     DE 10 2018 130 558 A1, which is incorporated herein by reference, describes a battery pack comprising a plurality of high-voltage battery modules disposed in rows, which, along or adjacent to the row, includes a backplane comprising multiple busbar assemblies the number of which corresponds to the number of high-voltage battery modules. While poles of the high-voltage battery modules are connected to the busbar assemblies, internal conduits carrying heat transfer fluid extend along the backplane. 
     DE 10 2020 103 126 A1, which is incorporated herein by reference, discusses a system comprising busbars connected to a cooling system. An insulation component is disposed between the busbars and a cooling plate of the cooling system. 
     SUMMARY OF THE INVENTION 
     Described herein is a coolable high-voltage battery module, wherein a cooling capacity is directed from the high-voltage battery module connected to the cooling plates to the busbars and the cell tabs. A connection to the cooling system should be electrically insulated. 
     A method for producing such a high-voltage battery module is to described as well. 
     A high-voltage battery module comprises a module housing, a cell stack which includes a plurality of cells comprising respective cell terminals, and an end plate which is disposed on at least one end face of the module housing, wherein at least one busbar is integrated into the end plate. At least one longitudinal side of the module housing is connected to a cooling plate. The end plate is made of an electrically insulating material, wherein the at least one busbar comprises at least one electrical contacting surface toward an outer side of the end plate and at least one thermal contacting surface toward at least one edge of the end plate. The at least one thermal contacting surface of the at least one busbar is thermally connected to the at least one longitudinal side of the module housing connected to the cooling plate. The cell terminals of the respective cells are passed in a material-locking manner through a respective opening of the end plate and welded to the at least one busbar at the at least one electrical contacting surface thereof. 
     In a preferred configuration of the high-voltage battery module according to aspects of the invention, the cooled longitudinal side of the module housing is orthogonal to the outer side of the end plate, on which the at least one electrical contacting surface of the at least one busbar integrated in the end plate welded to the cell terminals is located. The thermal connection of the at least one thermal contacting surface of the at least one busbar to the module housing or a battery cooling system can be thermally direct or indirect. 
     The at least one busbar integrated in the end plate advantageously increases the mechanical stability of the end plate. This is also advantageous for assembly processes, in which the cell terminals are passed in a material-locking manner through openings of the end plate in order to then be joined to the busbars. 
     In one configuration of the high-voltage battery module according to aspects of the invention, each cell is designed as a pouch cell, also referred to in German as a “pocket cell.” The at least one busbar is inserted in a form-locking manner into the end plate during a production process of said end plate. The cell terminal of the respective pouch cell, which is also referred to as a cell tab, is passed through the respective opening of the end plate and bent around the at least one busbar for welding to the at least one electrical contacting surface thereof. For cell stacks comprising pouch cells, it is conceivable to dispose the region of the at least one busbar which is thermally connected to the cooled longitudinal side of the module housing between two respective cell tabs. 
     In a further configuration of the high-voltage battery module according to aspects of the invention, each cell is designed as a prismatic cell. The at least one busbar is inserted into the end plate in a movably mounted manner. 
     In yet another configuration of the high-voltage battery module according to aspects of the invention, the at least one thermal contacting surface of the at least one busbar and the at least one longitudinal side of the module housing connected to the cooling plate are spaced apart by a tolerance region. This tolerance region is filled with a thermally conductive paste. The tolerance region and a region between cells and module housing can form a contiguous region which can advantageously be filled with thermally conductive paste in a single assembly step. 
     During assembly of the high-voltage battery module, the thermally conductive paste is pressed or injected into the module housing through filling openings provided for this purpose. This advantageously results in a high rapid charging and discharging capacity of the high-voltage battery module according to aspects of the invention or of a traction battery comprising such high-voltage battery modules. 
     In a continuing yet further configuration of the high-voltage battery module according to aspects of the invention, the tolerance region and a spatial distancing of the cell stack are situated toward the same longitudinal side of the at least one longitudinal side of the module housing and are both thermally connected to this longitudinal side by a common layer of thermally conductive paste. The end plate comprises a seal which delimits a filling region of the thermally conductive paste inside the module. 
     In another continuing configuration of the high-voltage battery module according to aspects of the invention, the at least one thermal contacting region of the busbar is provided with an electrically insulating and thermally conductive coating. 
     In a yet further continuing configuration of the high-voltage battery module according to aspects of the invention, a closing plate is disposed on at least one end face via the end plate. The closing plate is configured to electrically connect the busbars welded to the cell tabs to terminals to a traction system. 
     As a result of connecting the cooling plate to the at least one busbar and the cell terminals welded thereto, the high-voltage battery module according to aspects of the invention advantageously exhibits increased rapid charging performance or improved rapid charging behavior. The cooling connection furthermore also makes it possible to extract higher outputs from the cell stack during discharging, which advantageously results in improved driving performance. 
     A method for producing a coolable high-voltage battery module is described as well, wherein the high-voltage battery module comprises a module housing, a plurality of cells comprising respective cell terminals, and, toward at least one end face of the module housing, an end plate comprising at least one busbar. The at least one busbar comprises at least one electrical contacting surface and at least one thermal contacting surface. In a production process, the following steps of producing the high-voltage battery module are carried out:
         a) stacking the cells to form a cell stack, the respective cell terminals of which are oriented toward the at least one end face of the module housing;   b) producing the end plate from an electrically insulating material, wherein the at least one busbar is integrated toward an outer side and toward at least one edge of the end plate such that the at least one electrical contacting surface can be contacted from outside the high-voltage battery module and such that the at least one thermal contacting surface can be thermally contacted toward the at least one edge of the end plate, and wherein openings for passing cell terminals through in a material-locking manner are provided between the inner side and the outer side of the end plate;   c) passing the cell terminals of the respective cells through the respective openings of the end plate;   d) joining the cell terminals to the at least one busbar;   e) welding the cell terminals to the at least one electrical contacting surface of the at least one busbar;   f) inserting the cell stack including the end plate into the module housing;   g) introducing a thermally conductive paste between cell stack and thermal contacting surface of the at least one busbar and an inner side of a directly adjacent longitudinal side of the module housing;   h) connecting an outer side of the directly adjacent longitudinal side of the module housing to a cooling plate.       

     In one embodiment of the method according to aspects of the invention, each cell is designed as a pouch cell. The at least one busbar is inserted in a form-locking manner into the end plate during the production process of said end plate. The joining of the cell terminals to the at least one busbar is carried out by folding the cell terminals until they rest against the at least one busbar. During the production process of the end plate, e.g., in the form of plastic injection molding, the busbars are directly overmolded with an injection molding compound while keeping the at least one electrical contacting surface and the at least one thermal contacting surface free. 
     In another embodiment of the method according to aspects of the invention, each cell is designed as a prismatic cell. The at least one busbar is inserted into the end plate in a movably mounted manner. During the production process of the end plate, it is formed by means of plastic injection molding, for example. The at least one busbar is not integrated into the end plate in a movably mounted manner until later or after the end plate has hardened. 
     In a further embodiment of the method according to aspects of the invention, the at least one thermal contacting region of the busbar is provided with an electrically insulating and thermally conductive coating. 
     Further advantages and embodiments of the invention will emerge from the description and the accompanying drawing. 
     It goes without saying that the aforementioned features and the features yet to be explained in the following can be used not only in the respectively specified combination, but also in other combinations or on their own, without leaving the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The figures are described in a coherent and comprehensive manner, and the same reference signs are assigned to the same components. 
         FIG.  1    schematically shows a perspective illustration of a cell stack in one embodiment of the method according to aspects of the invention. 
         FIG.  2    schematically shows a top view onto an end plate comprising integrated busbars in the embodiment of the method according to aspects of the invention. 
         FIG.  3    schematically shows a perspective sectional view of the end plate comprising integrated busbars in the embodiment of the method according to aspects of the invention. 
         FIG.  4    schematically shows a perspective sectional view of a configuration of the high-voltage battery module according to aspects of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG.  1    schematically shows a perspective illustration  10  of a cell stack  13  in one embodiment of the method according to aspects of the invention. A plurality of energy storage cells or cells  14  are combined to form a cell stack  13 . In the illustration  10 , the cells  14  are designed as pouch cells. The respective cell terminals  15 , also referred to in the case of pouch cells as cell tabs, are passed through the end plate  11  disposed on the end face side of the cell stack and welded there. A lower end plate  12  closes the cell stack  13  off to the opposite side. 
       FIG.  2    schematically shows a top view  20  onto the end plate  11  comprising integrated busbars  22  in the embodiment of the method according to aspects of the invention. Openings  21  are provided in the end plate  11 , through which the cell terminals are passed in a material-locking manner. The term “material-locking” means that a respective opening  21  encloses a respective cell terminal without any gap or space. The busbars  22  integrated in the end plate  11  are enclosed by an electrically insulating material of the end plate  11 . The electrical contacting surface of the respective busbar  22  that is not covered by the electrically insulating material of the end plate  11  is visible in the top view  20 . After the respective cell terminal is passed through the respective opening  21  of the end plate  11 , the cell terminal is bent around the respective busbar  22 , as shown with reference sign  15  in  FIG.  1   , and welded to the electrical contacting surface thereof, for example in a region  23 . When filling with a thermally conductive paste, a seal  24  restricts the spread of said paste to an interior space of the module. 
       FIG.  3    schematically shows a perspective sectional view  30  of the end plate  11  comprising integrated busbars  22  in the embodiment of the method according to aspects of the invention. The thermal contacting surface  31  can be seen in the lateral section. Said surface is coated with an electrically insulating but thermally conductive layer, for example. Thermally conductive paste is applied to the thermal contacting surface  31  for better thermal connection to a cooling system. 
       FIG.  4    schematically shows a perspective sectional view  40  of a configuration of the high-voltage battery module according to aspects of the invention. A respective cell terminal  44  is welded to a respective busbar  22 . Cell terminals  15  passed through the end plate  11  adjacent to respective busbars  22  are bent around the respective busbar  22  and welded one above the other. Cells  14  comprising an end plate  11  are disposed in a module housing  41 , whereby a cooling plate  43  is located on a longitudinal side of the module housing  41 . This arrangement advantageously implemented in such a way that the thermal contacting surface  31  of the busbar  22  is located in the immediate vicinity of the longitudinal side of the module housing provided with the cooling plate  43 . Thermally conductive paste  45  is filled between this longitudinal side and the cells  14  or the thermal contacting surface  31  of the busbar  22  and spreads all the way to the seal  24 . A closing plate, which electrically connects the cell terminals welded to the busbars to terminals to a traction system, is disposed above the end plate  11  on the end face side. 
     LIST OF REFERENCE SIGNS 
     
         
           10  View of the cell stack 
           11  End plate 
           12  Lower end plate 
           13  Cell stack 
           14  Cell 
           15  Cell terminal welded to busbar 
           20  Top view of the end plate 
           21  Openings for cell terminals 
           22  Busbar 
           23  Region for cell welding 
           24  Seal for thermally conductive paste 
           30  Perspective sectional view of the end plate 
           31  Thermal contacting surface 
           40  Perspective sectional view of the high-voltage battery module 
           41  Module housing 
           42  Closing plate high-voltage battery module 
           43  Cooling plate with cooling fins 
           44  Cell terminal welded to busbar 
           45  Thermally conductive paste