Patent Publication Number: US-2023135184-A1

Title: Battery module

Description:
TECHNICAL FIELD 
     The present invention relates to a battery module. 
     BACKGROUND ART 
     For example, as a power source for a vehicle or the like that requires a high output voltage, there has been known a battery module formed by electrically connecting a plurality of batteries to each other. In general, in each battery constituting a battery module, an internal electrode body, an electrolyte, and the like degrade over time, and bulge due to deposition or oxidation of a metal material, and a change appears in an outer shape. Regarding a battery module including such a battery, PTL 1 discloses a battery module including a battery stack in which a plurality of batteries are stacked and an insulating sheet is interposed between the batteries, and end plates provided at both ends in the stacking direction of the battery stack. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: WO 2013/161655 A 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     When the dimension of each battery in the battery module in the stacking direction increases with aging, a load due to a dimensional variation of all the batteries is applied to the end plates at both ends of the battery stack, and a reaction force thereof is applied to each battery, which may cause a failure such as breakage of the battery. 
     The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique for reducing a reaction force generated in a stacking direction in a battery module. 
     Solution to Problem 
     A battery module according to an aspect of the present invention includes: a battery stack in which a plurality of batteries are stacked; an end plate provided outside a battery at an end in a stacking direction of the plurality of batteries; and an end separator provided between the battery at the end and the end plate, the end separator being disposed in a part in the stacking direction and including a deformation allowing part in which deformation due to creep is larger than deformation of other parts. 
     Advantageous Effect of Invention 
     According to the present invention, the safety of a battery module can be enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view illustrating an appearance of a battery module according to an exemplary embodiment. 
         FIG.  2    is an exploded perspective view of a part of the battery module. 
         FIG.  3    is a perspective view of an end separator as viewed from a battery side. 
         FIG.  4    is a cross-sectional side view of the end separator. 
         FIG.  5    is a schematic diagram for explaining a positional relationship in a battery module at an initial stage. 
         FIG.  6    is a schematic diagram for explaining a state in which a battery in a battery module bulges in a stacking direction due to aged degradation. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinafter, the present invention will be described based on a preferred exemplary embodiment with reference to the drawings. The exemplary embodiment is not intended to limit the invention but is an example, and all features described in the exemplary embodiment and combinations thereof are not necessarily essential to the invention. The same or equivalent constituent elements, members, and processing illustrated in the drawings are denoted by the same reference numerals, and a redundant description will be omitted as appropriate. The scale and the shape of each part illustrated in each figure are set for the sake of convenience in order to facilitate the understanding of the description and should not be interpreted in a limited manner unless otherwise specified. In cases where terms such as “first” and “second” are used in the present description or claims, these terms do not represent any order or importance but are intended to distinguish one configuration from another configuration, unless otherwise specified. From each of the drawings, some of members not important for describing the exemplary embodiments are omitted. 
     Exemplary Embodiment 
       FIG.  1    is a perspective view illustrating an appearance of battery module  100  according to an exemplary embodiment, and  FIG.  2    is an exploded perspective view of a part of battery module  100 . Battery module  100  includes housing  1  having a rectangular-parallelepiped shape, battery stack  2 , separator  3 , and end separator  4 . In battery module  100 , end separator  4  is provided with a deformation allowing part in which the deformation due to the creep in the stacking direction is larger than the other parts, and the reaction force acting on the battery due to the creep of the deformation allowing part is reduced. 
     Housing  1  includes end plate  11 , side plate  12 , base plate  13 , and cover plate  14 . End plates  11  are provided outside batteries  20  positioned at both ends of battery stack  2  in the stacking direction of batteries  20 . Side plate  12  sandwiches end plate  11  and covers a side surface of battery stack  2 . Base plate  13  is configured by covering a bottom of battery stack  2 . Cover plate  14  covers an upper surface of battery stack  2 . 
     Battery stack  2  is housed inside housing  1 . Battery stack  2  is formed by stacking a plurality of batteries  20  in one direction. Separator  3  formed of a resin material or the like in a sheet shape or a plate shape is provided between the batteries. Separator  3  electrically insulates each battery  20  of battery stack  2 . Separator  3  may be considered to constitute a part of battery stack  2  because separator  3  is incorporated into and integrated with battery stack  2 . 
     Each battery  20  is a rechargeable secondary battery such as a lithium-ion battery, a nickel-metal-hydride battery, or a nickel-cadmium battery. Additionally, each battery  20  is a so-called prismatic battery, and has outer covering can  21  having a flat rectangular-parallelepiped shape. One surface of outer covering can  21  is provided with an opening having a substantially rectangular shape not illustrated, and an electrode body, an electrolyte, and the like are accommodated in outer covering can  21  through the opening. Sealing plate  21   a  that closes the opening of outer covering can  21  is disposed in the opening. 
     Output terminal  22  of a positive electrode is disposed on sealing plate  21   a  at a position close to one end of sealing plate  21   a  in a longitudinal direction, and output terminal  22  of a negative electrode is disposed on sealing plate  21   a  at a position close to the other end of sealing plate  21   a  in the longitudinal direction. The pair of output terminals  22  is electrically connected to the corresponding one of a positive electrode plate and a negative electrode plate, constituting the electrode assembly. Respective output terminals  22  are inserted into through-holes (not illustrated) formed in sealing plate  21   a . A seal member (not illustrated) having an insulating property is interposed between respective output terminals  22  and respective through-holes. In the following description, for convenience, sealing plate  21   a  is an upper surface of battery  20 , and a bottom surface of outer covering can  21  facing sealing plate  21   a  is a lower surface of battery  20 . 
     Battery  20  has two main surfaces that connect the upper surface and the lower surface of battery  20  to each other. The main surfaces are surfaces having the largest area out of the six surfaces of battery  20 . The main surfaces are long side surfaces connected to the long sides of the upper surface and the long sides of the lower surface. Two remaining surfaces except for the upper surface, the lower surface, and the two main surfaces are referred to as the side surfaces of battery  20 . These side surfaces are a pair of short side surfaces connected to the short sides of the upper surface and the short sides of the lower surface. These directions and positions are defined for the sake of convenience. Therefore, for example, the part defined as the upper surface in the present invention does not necessarily mean a part located above the part defined as the lower surface. 
     Valve  24  is disposed on sealing plate  21   a  between the pair of output terminals  22 . Valve  24  is also referred to as a safety valve. Valve  24  is a mechanism for releasing a gas in each battery  20 . Valve  24  is configured to release an internal gas by opening valve  24  when an internal pressure of outer covering can  21  is increased to a predetermined value or more. For example, valve  24  includes: a thin part that is formed on a part of sealing plate  21   a  and is thinner than other parts of valve  24 ; and a linear groove formed on a surface of the thin part. In this configuration, when an internal pressure of outer covering can  21  increases, valve  24  is opened by tearing the thin wall part with the groove as a tearing starting point. 
     The plurality of batteries  20  are stacked at predetermined intervals with the main surfaces of adjacent batteries  20  facing each other. Note that the term “stack” means that a plurality of members are arranged in any one direction. Thus, stacking batteries  20  also includes arranging the plurality of batteries  20  horizontally. In the present exemplary embodiment, batteries  20  are stacked horizontally. Each battery  20  is disposed such that output terminals  22  are directed in the same direction. In the present exemplary embodiment, each battery  20  is disposed such that output terminals  22  are directed upward in the vertical direction. 
     End separator  4  is provided between batteries  20  positioned at an end of battery stack  2  in the stacking direction of batteries  20  and end plate  11 .  FIG.  3    is a perspective view of end separator  4  as viewed from battery  20  side, and  FIG.  4    is a cross-sectional side view of end separator  4 .  FIG.  4    corresponds to a cross section including a stacking direction and a vertical direction of batteries. 
     End separator  4  includes substrate  40  intersecting with the stacking direction of batteries  20 , deformation allowing part  41 , and air passage forming part  42 . Deformation allowing part  41  is a part of end separator  4  in the stacking direction of batteries  20 , and is formed of a resin material having larger deformation due to creep than other parts. Substrate  40  and air passage forming part  42  are made of a resin material having smaller deformation due to creep than deformation allowing part  41 . 
     Deformation allowing part  41  is formed in a trapezoidal shape so as to rise in the stacking direction from the central part of the surface of substrate  40  near end plate  11 , and end surface  41   a  comes into contact with end plate  11 . Air passage forming part  42  is formed of a plurality of strips protruding from the surface of substrate  40  near battery  20 , and air passage  43  is formed between the strips. 
     End separator  4  is in contact with end plate  11  at end surface  41   a  of the deformation allowing part  41 , and is in contact with battery  20  at end surface  42   a  of air passage forming part  42 . Battery  20  is fitted into wall  44  provided on a side part of substrate  40  and surrounding substrate  40 . Deformation allowing part  41  has large creep deformation as described above, and is formed of a material different from substrate  40  and air passage forming part  42 . Deformation allowing part  41  may be formed separately from substrate  40  and fixed to substrate  40  by adhesion or the like, or may be fixed to substrate  40  by integral molding with substrate  40  and air passage forming part  42 . 
     Next, the operation of battery module  100  will be described based on the generation of the reaction force due to the expansion of battery  20 .  FIG.  5    is a schematic diagram for explaining a positional relationship in battery module  100  at an initial stage.  FIG.  5    corresponds to a cross section including a stacking direction and a vertical direction of batteries. Each battery  20  does not expand at an initial stage after manufacturing, and a reaction force acting on each battery  20  in the stacking direction is small and is within a designed allowable value. 
       FIG.  6    is a schematic diagram for explaining a state in which batteries  20  in battery module  100  bulge in the stacking direction due to aging degradation.  FIG.  6    corresponds to a cross section including a stacking direction and a vertical direction of batteries. As described above, in each battery  20 , an internal electrode body, an electrolyte, and the like degrade over time, and bulge due to deposition or oxidation of a metal material, and a change appears in an outer shape. Each battery  20  is a prismatic battery and includes the outer covering can  21  having a flat rectangular-parallelepiped shape, and among the six surfaces of battery  20 , the main surface having the largest area is deformed so as to expand. 
     The deformation in the stacking direction caused by the expansion of each battery  20  in battery module  100  is absorbed when the dimension of deformation allowing part  41  of end separator  4  in the stacking direction decreases due to the creep deformation. Therefore, battery module  100  can reduce the reaction force generated in the stacking direction. 
     Deformation allowing part  41  is provided so as to be in contact with end plate  11 , and can uniformly receive a load from end plate  11  formed of a highly rigid material such as metal on end surface  41   a  as a contact surface. 
     Deformation allowing part  41  does not need to be in contact with the entire opposing surface of end plate  11 , and is formed in a trapezoidal shape so as to rise in the stacking direction from the central part of the surface near substrate  40  on end plate  11 , so that the contact area can be reduced and the generated stress can be increased. 
     End separator  4  includes air passage forming part  42  on the side in contact with battery  20 , so that air passage  43  for air cooling of battery  20  can be secured. Since air passage forming part  42  is formed of a material having a smaller creep deformation than deformation allowing part  41 , it is possible to suppress a decrease in the flow passage area of air passage  43 . 
     Deformation allowing part  41  is integrally formed with substrate  40  and air passage forming part  42  by a manufacturing method such as two-color molding, so that the manufacturing cost can be reduced. 
     In the above-described exemplary embodiment, deformation allowing part  41  is provided near end plate  11 , but deformation allowing part  41  may be provided near battery  20 . Even in this configuration, deformation allowing part  41  receives a load due to the expansion of battery  20  and is creep-deformed, whereby the reaction force generated in the stacking direction in battery module  100  can be reduced. 
     The present invention has been described based on the exemplary embodiment of the present invention. As a person skilled in the art understands, the exemplary embodiment is exemplified, and the exemplary embodiment is variously varied and modified within a scope of claims of the present invention. Further, such variations and modified examples fall within the scope of the claims of the present invention. Therefore, it should be understood that the description and the drawings herein are not limitative, but are illustrative. 
     The exemplary embodiment may be defined by the following items. 
     [Item 1] 
     Battery module ( 100 ) including: battery stack ( 2 ) in which a plurality of batteries ( 20 ) are stacked; end plate ( 11 ) provided outside battery ( 20 ) at an end in a stacking direction of the plurality of batteries ( 20 ); and end separator ( 4 ) provided between battery ( 20 ) at the end and end plate ( 11 ), the end separator ( 4 ) being disposed in a part in the stacking direction and including deformation allowing part ( 41 ) in which deformation due to creep is larger than deformation of other parts. Thus, battery module ( 100 ) can reduce the reaction force generated in the stacking direction. 
     [Item 2] 
     Battery module ( 100 ) according to Item 1, in which deformation allowing part ( 41 ) is disposed in a part of the end separator ( 4 ) in contact with end plate ( 11 ). Consequently, deformation allowing part ( 41 ) of battery module ( 100 ) can uniformly receive a load from end plate ( 11 ) made of a highly rigid material such as metal on the contact surface. 
     [Item 3] 
     Battery module ( 100 ) according to Item 1 or 2, in which deformation allowing part ( 41 ) is disposed to rise in a trapezoidal shape from a surface intersecting the stacking direction. As a result, deformation allowing part ( 41 ) of battery module ( 100 ) can reduce the contact area with end plate ( 11 ) and increase the generated stress. 
     [Item 4] 
     Battery module ( 100 ) according to any one of Items 1 to 3, in which air passage ( 43 ) is disposed between battery ( 20 ) at the end and end separator ( 4 ). Thus, battery module ( 100 ) can secure air passage ( 43 ) for air cooling of battery ( 20 ). 
     [Item 5] 
     Battery module ( 100 ) according to any one of Items 1 to 4, in which deformation allowing part ( 41 ) and other parts are integrally disposed in end separator ( 4 ). Thus, the manufacturing cost of battery module ( 100 ) can be reduced. 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
         
           
               11  end plate 
               2  battery stack 
               20  battery 
               4  end separator 
               41  deformation allowing part 
               43  air passage 
               100  battery module