Patent Publication Number: US-2023155197-A1

Title: Battery module

Description:
This nonprovisional application is based on Japanese Patent Application No. 2021-187139 tiled on Nov. 17, 2021, with die Japan Patent Office, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present technology relates to a battery module. 
     Description of the Background Art 
     In a battery module, bus bars for connecting cells are provided on both sides beside two rows of electrodes, and voltage detection wires for voltage detection are provided on these connection members. Such a structure is disclosed, for example, in Japanese Patent Laying-Open No. 2015-88426. 
     SUMMARY OF THE INVENTION 
     In each of regions in which the connection members (bus bars) are provided, the voltage detection wires occupy a large region, thus presenting a problem in attaining reduced space. Further, the number of the voltage detection wires is increased in proportion to the number of cells, so that the number of connection points for disposing the voltage detection wires on the cells is also increased, thus resulting in a complicated connecting operation. 
     It is an object of the present technology to provide a battery module so as to reduce the number of voltage detection wires to attain space saving (downsizing) for connection member (bus bar) portions, productivity improved by improved workability, and reduced cost. 
     A battery module according to the present technology includes: a plurality of battery cells stacked in a predetermined direction and electrically connected together, a plurality of bus bars that electrically connect the plurality of battery cells together; and a plurality of voltage detection wires each connected to one set of two or more battery cells electrically connected together. 
     The foregoing and other objects, features, aspects and advantages of the present invention become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view showing a battery module according to a first embodiment. 
         FIG.  2    is a perspective view showing an internal structure of the battery module in  FIG.  1   , 
         FIG.  3    is a perspective view showing a battery cell unit included in the battery module in  FIG.  1   . 
         FIG.  4    is a perspective view showing a battery cell included in the battery cell unit in  FIG.  3   . 
         FIG.  5    is an exploded assembly diagram showing a connection structure for a plurality of battery cells according to the first embodiment. 
         FIG.  6    is a partial enlarged view showing a wiring structure for voltage detection wires according to the first embodiment. 
         FIG.  7    is a perspective view showing another wiring structure for voltage detection wires according to the first embodiment. 
         FIG.  8    is a schematic diagram showing a first connection pattern of voltage detection terminals of a voltage detection wire to bus bars according to another embodiment. 
         FIG.  9    is a schematic diagram showing a second connection pattern of voltage detection terminals of voltage detection wires to bus bars according to another embodiment.  FIG.  10    is a schematic diagram showing a third connection pattern of a voltage detection terminal of a voltage detection wire to a bus bar according to another embodiment. 
         FIG.  11    is a schematic diagram showing a fourth connection pattern of a voltage detection terminal of a voltage detection wire to a bus bar according to another embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, each of embodiments of the present technology will be described. The same or corresponding portions are denoted by the same reference characters, and may not be described repeatedly. 
     In each of the embodiments described below, when reference is made to number, amount, and the like, the scope of the present technology is not necessarily limited to the number, amount, and the like unless otherwise stated particularly. Further, in the embodiments described below, each component is not necessarily essential to the present technology unless otherwise stated particularly. 
     In the present specification, the terms “comprise”, “include”, and “have” are open-end terms. That is, when a certain configuration is included, a configuration other than the foregoing configuration may or may not be included. Further, the present technology is not limited to one that necessarily exhibits all the functions and effects stated in the present embodiment. 
     The battery module according to each of the embodiments is typically a lithium ion secondary battery to be mounted on a vehicle. It should be noted that in the present specification, the term “battery” is not limited to a lithium ion battery, and may include another battery such as a nickel-metal hydride battery. 
     First Embodiment: Battery Module  100   
       FIG.  1    is a perspective view showing a battery module  100  according to the present embodiment.  FIG.  2    is a perspective view showing an internal structure of battery module  100  in  FIG.  1   .  FIG.  3    is a perspective view showing a battery cell unit  21  included in battery module  100  in  FIG.  1   . Referring to  FIGS.  1  to  3   , battery module  100  is used as a power supply for driving a vehicle such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a battery electric vehicle (BEV). 
     In the present specification, for convenience of description of the structure of battery module  100 , the “Y axis” represents an axis extending in parallel with a stacking direction of a plurality of below-described battery cells  11 , the “X axis” represents an axis extending in a direction orthogonal to the Y axis, and the “Z axis” represents an axis extending in a direction orthogonal to the Y axis and the X axis. An obliquely rightward upward direction in the plane of sheet of  FIG.  1    is “+Y axis direction”, and an obliquely leftward downward direction in the plane of sheet of  FIG.  1    is “−Y axis direction”. An obliquely rightward downward direction in the plane of sheet of  FIG.  1    is “+X axis direction” and an obliquely leftward upward direction in the plane of sheet of  FIG.  1    is “−X axis direction”. An upward direction in the plane of sheet of  FIG.  1    is “+Z axis direction” and a downward direction in the plane of sheet of  FIG.  1    is “−Z axis direction”. 
     Typically, with regard to the form of battery module  100 , the Y axis direction represents a “long-side direction”, the X axis direction represents a “width direction”, which serves as a short-side direction, and the Z axis direction represents a “height direction”. Moreover, battery module  100  is mounted on a vehicle in such a posture that the  41  axis direction corresponds to the upward direction and the −Z axis direction corresponds to the downward direction, 
     An overall structure of battery module  100  will be described. As shown in  FIG.  1   , battery module  100  has a plurality of battery cell units  21  ( 21 A,  21 B,  21 C,  21 D,  21 E,  21 F) and a restraint member  41 . 
     The plurality of battery cell units  21  are stacked in the Y axis direction. The plurality of battery cell units  21  are collectively held by restraint member  41 . Battery cell unit  21 A, battery cell unit  21 B, battery cell unit  21 C, battery cell unit  21 D, battery cell unit  21 E, and battery cell unit  21 F are arranged side by side in this order from the negative side to the positive side in the Y axis direction. It should be noted that the number of battery cell units  21  included in battery module  100  is not particularly limited as long as two or more battery cell units  21  are included. 
     Restraint member  41  applies, to the plurality of battery cell units  21 , restraint force along the Y axis direction. Restraint member  41  has a pair of end plates  42  ( 42 P,  42 Q), a pair of first restraint bands  43 , and a second restraint band (not shown) 
     The pair of end plates  42  are disposed on both sides beside the plurality of battery cell units  21  stacked in the Y axis direction. End plate  42 P is disposed to face battery cell unit  21 A in the Y axis direction. End plate  42 Q is disposed to face battery cell unit  21 F in the Y axis direction. Each of end plates  42  is composed of a plate material having a thickness direction corresponding to the Y axis direction. 
     The pair of first restraint bands  43  are disposed on both sides beside the plurality of battery cell units  21  in the X axis direction. The second restraint band (not shown) is provided at a position facing the plurality of battery cells  11  in the Z axis direction. Each of first restraint bands  43  and the second restraint band extends in the Y axis direction. An end portion of each of first restraint hands  43  and the second restraint band in the −Y axis direction is connected to end plate  42 P. An end portion of each of first restraint bands  43  and the second restraint band in the +Y axis direction is connected to end plate  42 Q. 
     Each of first restraint bands  43  is provided with a plurality of openings  44 . The plurality of openings  44  are provided at intervals in the Y axis direction. Each of openings  44  is constituted of a through hole extending through first restraint band  43  in the X axis direction. Opening  44  is provided to expose ventilation ports  32  provided in a case body  31  described later. 
     Battery module  100  further has a pair of collective terminals  91  ( 91   p ,  91   q ) a plurality of voltage detection wires  92 , and an exhaust duct  93 . 
     The pair of collective terminals  91  are disposed on both sides beside the plurality of battery cell units  21  stacked in the Y axis direction. Collective terminal  91   p  is provided at a position overlapping with end plate  42 P when viewed in the Z axis direction. Collective terminal  91   q  is provided at a position overlapping with end plate  42 Q when viewed in the Z axis direction. Collective terminals  91  are connected to bus bars  50  described later. Each of collective terminals  91  is a terminal for connecting battery module  100  to a wiring such as a cable disposed outside battery module  100 . 
     Voltage detection wires  92  are provided at positions facing the plurality of battery cell units  21  in the Z axis direction. Voltage detection wires  92  are disposed opposite to the second restraint band (not shown) with the plurality of battery cell units  21  being interposed therebetween. Voltage detection wires  92  extend, in the Y axis direction, through the central portions of battery cell units  21  in the X axis direction. Voltage detection wires  92  are constituted of, for example, a flexible printed circuit board. In the present embodiment, voltage detection wires  92  are arranged above below-described exhaust duct  93 . 
     Each of the plurality of voltage detection wires  92  has a tip portion including a voltage detection terminal  94  extending from voltage detection wire  92 , and voltage detection terminal  94  is electrically connected to a selected bus bar  50  described later. The other end of voltage detection terminal  94  is connected to a control unit (not shown) for battery voltage monitoring. 
     Exhaust duct  93  extends in the Y axis direction. Exhaust duct  93  extends at a position overlapping with each of voltage detection wires  92  when viewed in the Z axis direction. Exhaust duct  93  is disposed between each of the plurality of battery cell units : 21  and each of voltage detection wires  92  in the Z axis direction. 
     As shown in  FIGS.  2  and  3   , each of battery cell units  21  has a plurality of battery cells  11  and a holding member  30 . 
     Battery cell unit  21  has four battery cells  11  ( 11   a ,  11   b ,  11   c ,  11   d ). Battery cell unit  21  has an even number of battery cells  11 . It should be noted that the number of battery cells  11  included in each battery cell unit  21  is not particularly limited as long as two or more battery cells  11  are included. 
     In each battery cell unit  21 , i.e., in each of battery cell unit  21 A, battery cell unit  21 B, battery cell unit  21 C, battery cell unit  21 D, battery cell unit  21 E, and battery cell unit  21 F, the plurality of battery cells  11  are arranged side by side continuously in the Y axis direction. Battery cell  11   a , battery cell  11   b , battery cell  11   c , and battery cell  11   d  are arranged side by side in this order from the negative side to the positive side in the Y axis direction. 
     The stacking direction of the plurality of battery cells  11  in each battery cell unit  21  is the same as the stacking direction of the plurality of battery cell units  21 . 
     Holding member  30  collectively holds the plurality of battery cells  11  ( 11   a ,  11   b ,  11   c ,  11   d ). Holding member  30  includes case body  31 . Case body  31  has an external appearance having a rectangular parallelepiped shape. The plurality of battery cells  11  are accommodated in case body  31 . 
     Case body  31  is provided with the plurality of ventilation ports  32 . The plurality of ventilation ports  32  are provided in the both side surfaces of case body  31  orthogonal to the X axis direction. Each of ventilation ports  32  is constituted of a through hole extending through case body  31  in the X axis direction. Ventilation port  32  is provided as a path for introducing cooling air into a space between battery cells  11  adjacent to each other in the Y axis direction. 
       FIG.  4    is a perspective view showing a battery cell  11  included in battery cell unit  21  in  FIG.  3   .  FIG.  5    is an exploded assembly diagram showing a connection structure for a plurality of battery cells  11 . 
     Referring to  FIGS.  4  and  5   , battery cell  11  is a lithium ion battery. Battery cell  11  has an output density of 8000 W/L or more. Battery cell  11  has a prismatic shape and has a thin plate shape in the form of a rectangular parallelepiped. The plurality of battery cells  11  are stacked such that the Y axis direction corresponds to the thickness direction of each battery cell  11 . 
     Each of battery cells  11  has an exterior package  12 . Exterior package  12  is constituted of a housing having a rectangular parallelepiped shape, and forms the external appearance of battery cell  11 . An electrode assembly and an electrolyte solution are accommodated in exterior package  12 . 
     Exterior package  12  has a first side surface  13 , a second side surface  14 , and a third side surface  15 . Each of first side surface  13  and second side surface  14  is constituted of a flat surface orthogonal to the Y axis direction. First side surface  13  and second side surface  14  are oriented oppositely in the Y axis direction. Each of first side surface  13  and second side surface  14  has the largest area among the areas of the plurality of side surfaces of exterior package  12 . Each of first side surface  13  and second side surface  14  has a rectangular shape when viewed in the Y axis direction. Each of first side surface  13  and second side surface  14  has a rectangular shape in which the X axis direction corresponds to the long-side direction and the Z axis direction corresponds to the short-side direction when viewed in the Y axis direction. Third side surface  15  is constituted of a flat surface orthogonal to the Z axis direction. Third side surface  15  is oriented in the +Z axis direction. 
     Battery cell  11  further includes a gas-discharge valve  17 . Gas-discharge valve  17  is provided in third side surface  15 . When internal pressure of exterior package  12  becomes more than or equal to a predetermined value due to gas generated inside exterior package  12 , gas-discharge valve  17  discharges the gas to the outside of exterior package  12 . The gas from gas-discharge valve  17  flows through exhaust duct  93  in  FIG.  1    and is discharged to the outside of battery module  100 . 
     Battery cell  11  further has electrode terminals  16  including a pair of a positive electrode terminal  16 P and a negative electrode terminal  16 N. Each of electrode terminals  16  is composed of a metal. Electrode terminal  16  is provided on third side surface  15 . Positive electrode terminal  16 P and negative electrode terminal  16 N are provided to be separated from each other in the X axis direction. Positive electrode terminal  16 P and negative electrode terminal  16 N are provided beside voltage detection wires  92  and exhaust duct  93  in the X axis direction. 
     The plurality of battery cells  11  are stacked such that first side surfaces  13  of battery cells  11 ,  11  adjacent to each other in the Y axis direction face each other and second side surfaces  14  of battery cells  11 ,  11  adjacent to each other in the Y axis direction face each other. Thus, positive electrode terminals  16 P and negative electrode terminals  16 N are alternately arranged in the Y axis direction in which the plurality of battery cells  11  are stacked. 
     It should be noted that when an odd number of battery cells  11  are included in battery cell unit  21 , the posture of battery cell unit  21  may be turned by 180° with respect to the Z axis between battery cell units  21  adjacent to each other in the Y axis direction. 
     Next, a connection structure for electrode terminals  16  will be described. Referring to  FIGS.  1  to  5   , battery module  100  further has the plurality of bus bars  50 . Each of bus bars  50  is composed of an electric conductor. The plurality of bus bars  50  are provided to electrically connect the plurality of battery cells  11  of battery module  100  together. 
     Each of bus bars  50  extends in the Y axis direction. Bus bar  50  has ends that both extend in the Y axis direction and that are connected to battery cells  11 ,  11  adjacent to each other in the Y axis direction. Bus bar  50  is provided between battery cells  11 ,  11  adjacent to each other in the Y axis direction so as to connect positive electrode terminal  16 P and negative electrode terminal  16 Q arranged side by side in the Y axis direction. The plurality of battery cells  11  are electrically connected together in series by the plurality of bus bars  50 . 
     Referring to  FIG.  5   , the plurality of bus bars  50  include a plurality of first bus bars  51  and a plurality of second bus bars  52 . In each of first bus bars  51 , a first bus-bar-divided body  61  and a second bus-bar-divided body  62  are joined to each other using joining means such as a bolt or welding. 
     First bus bar  51  electrically connects between battery cells  11  adjacent to each other in the Y axis direction between a first battery cell unit of the plurality of battery cell units  21  and a second battery cell unit of the plurality of battery cell units  21 , the second battery cell unit being adjacent to the first battery cell unit in the Y axis direction. That is, first bus bar  51  electrically connects between outer battery cells  11  of battery cell units  21  adjacent to each other in the stacking direction of battery cell units  21 . First bus bars  51  are arranged on one side in the width direction. 
     For explanation in a range shown in  FIG.  5   , battery cell unit  21 B corresponds to the first battery cell unit, and battery cell unit  21 C corresponds to the second battery cell unit. Between battery cell units  21 B,  21 C, first bus bar  51  connects negative electrode terminal  16 N of battery cell  11   d  in battery cell unit  21 B to positive electrode terminal  16 P of battery cell  11   a  in battery cell unit  21 C. The same applies to the other battery cell units. 
     In each battery cell unit  21 , second bus bar  52  electrically connects between battery cells  11 ,  11  adjacent to each other in the Y axis direction. That is, second bus bar  52  electrically connects between battery cells  11  inside battery cell unit  21 . 
     For explanation in the range shown in  FIG.  5   , second bus bar  52  connects negative electrode terminal  16 N of battery cell  11   b  to positive electrode terminal  16 P of battery cell  11   c  in battery cell unit  218 . This second bus bar  52  is located between first bus-bar-divided body  61  and second bus-bar-divided body  62 , and is arranged on one side in the width direction. The same applies to the other battery cell units. 
     Further, other second bus bar  52  connects negative electrode terminal  161  of battery cell  11   a  to positive electrode terminal  16 P of battery cell  11   b , and connects negative electrode terminal  16 N of battery cell  11   c  to positive electrode terminal  16 P of battery cell  11   d . Second bus bars  52  are disposed on the other side in the width direction. The same applies to other battery cell units. 
     In the present embodiment, it has been illustrated that four battery cells  11  are provided in each battery cell unit  21 ; however, for example, when two battery cells  11  are provided in one battery cell unit, first bus bar  51  is disposed on one end side in the width direction and second bus bar  52  is disposed on the other end side in the width direction. 
     Next, connection of voltage detection wires  92  to battery cells  11  will be described with reference to  FIG.  6   .  FIG.  6    is a partial enlarged view only showing a wiring structure for voltage detection wires in battery cell unit  21 B. The same applies to the other battery cell units. 
     For explanation in the range shown in  FIG.  6   , in the present embodiment, each voltage detection wire  92  is connected to one set of two or more battery cells  11  electrically connected together. In the present embodiment, two battery cells are handled as one set, and two voltage detection wires  92  are connected to battery cell unit  21 B. 
     Specifically, each voltage detection wire  92  includes voltage detection terminal  94  extending from the tip of voltage detection wire  92 , and voltage detection terminal  94  is electrically connected to first bus-bar-divided body  61  connected to positive electrode terminal  16 P of battery cell  11   a  in battery cell unit  21 B. Further, voltage detection terminal  94  of other voltage detection wire  92  is electrically connected to second bus bar  52  connected to positive electrode terminal  16 P of battery cell  11   c  in battery cell unit  21 B. The same applies to the other battery cell units, 
     Thus, in the present embodiment, since the battery voltage is detected for every two battery cells  11 , voltage detection wires  92  can be drawn only on the same, one end side in the width direction of battery cell  11 . As a result, voltage detection wires  92  can be avoided from being densely arranged, thereby attaining a reduced number of electric wires. Further, since each of voltage detection terminals  94  is connected to one side of a corresponding bus bar, the size of the bus bar cart be reduced. 
     In the present embodiment, it is illustrated in the figures that a strip-shaped flexible printed circuit board in which the plurality of voltage detection wires  92  are bundled is disposed above exhaust duct  93 ; however, the plurality of voltage detection wires  92  can be installed to be displaced to one side (the side on which first bus bars  51  are located) when viewed from exhaust duct  93 . 
       FIG.  7    shows another installation state of voltage detection wires  92 .  FIG.  7    is a perspective view showing another wiring structure for voltage detection wires.  FIG.  7    is a diagram showing a state in which in a battery module  100 A, voltage detection wires  92  are installed to be displaced to the other end side (the side on which second bus bars  52  are located) when viewed from exhaust duct  93 . When each of voltage detection wires  92  is disposed at such a position, voltage detection terminal  94  of voltage detection wire  92  is connected to second bus bar  52  located on the other end side. This relation of connection will be described below. 
     Other Embodiments 
     Connection patterns of voltage detection terminal(s)  94  of voltage detection wire(s)  92  to the bus bar(s) will be described with reference to  FIGS.  8  to  11   .  FIGS.  8  to  11    are schematic views showing first to fourth connection patterns of voltage detection terminal(s)  94  of voltage detection wire(s)  92  to the bus bar(s). 
     The connection pattern of voltage detection terminals  94  of voltage detection wires  92  to the bus bars as shown in  FIG.  8    is the connection pattern shown in  FIG.  6    in the first embodiment. The voltage detection terminals are disposed on one end side in the width direction of battery cell  11 . Specifically, a voltage detection terminal is electrically connected to first bus-bar-divided body  61  connected to positive electrode terminal  16 P of battery cell  11   a  in battery cell unit  21 B. Voltage detection terminal  94  of other voltage detection wire  92  is electrically connected to second bus bar  52  connected to positive electrode terminal  16 P of battery cell  11   c  in battery cell unit  21 B. The same applies to the other battery cell units. 
     In the connection pattern of voltage detection terminals  94  of voltage detection wires  92  to the bus bars as shown in  FIG.  9   , the voltage detection terminals are disposed on the other end side in the width direction of battery cell  11 . Specifically, a voltage detection terminal is electrically connected to second bus bar  52  connected to positive electrode terminal  16 P of battery cell  11   b  in battery cell unit  21 B. Voltage detection terminal  94  of other voltage detection wire  92  is electrically connected to second bus bar  52  connected to positive electrode terminal  16 P of battery cell  11   d  in battery cell unit  21 B. The same applies to the other battery cell units. This connection pattern corresponds to the arrangement of voltage detection terminals  94  shown in  FIG.  7   . 
     In each of the connection patterns shown in  FIGS.  8  and  9   , two battery cells  11  are handled as one set; however, four battery cells  11  included in one battery cell unit may be handled as one set. 
     In the connection pattern of voltage detection terminal  94  of voltage detection wire  92  to the bus bar as shown in  FIG.  10   , the voltage detection terminal is disposed on one end side in the width direction of battery cell  11 . Specifically, the voltage detection terminal is electrically connected to first bus-bar-divided body  61  connected to positive electrode terminal  16 P of battery cell  11   a  in battery cell unit  21 B. The same applies to the other battery cell units. 
     In the connection pattern of voltage detection terminal  94  of voltage detection wire  92  to the bus bar as shown in  FIG.  11   , the voltage detection terminal is disposed on the other end side in the width direction of battery cell  11 . Specifically, the voltage detection terminal is electrically connected to second bus bar  52  connected to positive electrode terminal  16 P of battery cell  11   b  in battery cell unit  21 B. The same applies to the other battery cell units. 
     Since each of the plurality of voltage detection wires is provided to be connected to one set of two or more battery cells electrically connected together as described above, the number of the voltage detection wires can be reduced, thereby attaining reduced sizes of the bus bars, productivity improved by improved workability, and reduced cost. 
     Although the embodiments of the present invention have been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by the terms of the appended claims. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.