Patent Publication Number: US-2013252075-A1

Title: Battery assembly and electrically conductive member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-065211 filed on Mar. 22, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a battery assembly and an electrically conductive member. 
     BACKGROUND 
     Conventionally, there is known a battery assembly provided with a bus bar for electrically connecting the electrodes of a plurality of electric accumulators. 
     For such battery assembly, a configuration that is hard to be broken by exerted external forces, etc., is preferred, for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. 
         FIG. 1  is a perspective view of an example of a battery assembly according to a first embodiment; 
         FIG. 2  is a cross-sectional view of the portion II of  FIG. 1 , in the first embodiment; 
         FIG. 3  is an exploded perspective view of an example of the battery assembly in the first embodiment; 
         FIG. 4  is a cross-sectional view of a portion of an example of an electrical accumulator of the battery assembly in the first embodiment; 
         FIG. 5  is an enlarged view of the portion V of  FIG. 2 , in the first embodiment; 
         FIG. 6  is a perspective view of an example of a second component of an electrically conductive portion included in the battery assembly in the first embodiment; 
         FIG. 7  is a perspective view of the example of the second component of the electrically conductive portion included in the battery assembly, as viewed from another angle than that of  FIG. 6 , in the first embodiment; 
         FIG. 8  is a perspective view of an example of an electrically conductive portion included in the battery assembly in the first embodiment; 
         FIG. 9  is a schematic side view of an example of a bus bar included in the battery assembly in the first embodiment; 
         FIG. 10  is a schematic side view of an example of a bus bar included in the battery assembly in a state in which a tensile force is acted to the bus bar, in the first embodiment; 
         FIG. 11  is a schematic side view of an example of a bus bar included in a battery assembly in a state in which the tensile force is acted to the bus bar, according to a reference example; 
         FIG. 12  is a perspective view of an example of a wall of a casing included in the battery assembly as viewed from inside the casing, in the first embodiment; 
         FIG. 13  is a plan view of a portion of the wall illustrated in  FIG. 12  as viewed from the inside of the casing, in the first embodiment. 
         FIG. 14  is a cross-sectional view taken along the line XIV-XIV of  FIG. 13 , in the first embodiment; 
         FIG. 15  is a perspective view of an example of a second component of an electrically conductive portion included in a battery assembly according to a first modification; 
         FIG. 16  is a cross-sectional view of a battery assembly taken at a position the same as that of  FIG. 5 , according to a second modification; and 
         FIG. 17  is a perspective view of an example of a bus bar included in a battery assembly according to a third modification. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a battery assembly comprises a casing, a plurality of electric accumulators, and a conductive member. The casing has a front surface and provided with a plurality of containers. The electric accumulators are housed in the containers, respectively. Each of the electric accumulators has a cathode and an anode. The conductive member has two first walls, two second walls, and a third wall. One of the first walls is connected to one of the cathode and the anode of one of the electric accumulators and extended along the front surface of the casing. Other one of the first walls is connected to one of the cathode and the anode of other one of the electric accumulators and extended along the front surface of the casing. The second walls are connected to the first walls via two first curve portions, respectively, and are extended in a direction crossing the front surface. The third wall is connected to the second walls via two second curve portions, respectively, and extended over between the two second walls in a direction along the front surface at a position apart from the front surface. 
     A plurality of exemplary embodiments and modifications described in the following include like components. In the following, therefore, like components will be referenced by common reference numerals and redundant explanation will be omitted. In the drawings, directions (X direction, Y direction, and Z direction) are illustrated for the convenience of explanation. The X direction, the Y direction, and the Z direction are orthogonal to one another. 
     In a first embodiment, as an example, a battery assembly  1  (a battery) includes a plurality of single cells  2  (single batteries or single cells, see  FIG. 3 , etc.) connected to each other in series or in parallel. The battery assembly  1  can be, as an example, constructed as a secondary battery (a storage battery or a rechargeable battery). The battery assembly  1  can be installed in a variety of devices, machines, and facilities. Specifically, the battery assembly  1  is used as power sources of relatively small-sized devices, etc., such as cellular phones, personal computers, and portable music players. The battery assembly  1  is also used as power sources of relatively large-sized devices such as electric bicycles, hybrid electric vehicles, and electric vehicles. The battery assembly  1  is also used as portable power sources such as power sources of vehicles and bicycles (movable bodies). The battery assembly  1  is also used as stationary power sources such as power sources of POS (point of sales) systems. A plurality of battery assemblies  1  in the present embodiment can be installed in a variety of devices, etc., as a set in which the battery assemblies  1  are connected to each other in series or in parallel. The battery assembly  1  can be therefore referred to as a battery module (a battery unit). The number, arrangement, etc., of the single cells  2  included in the battery assembly  1  are not limited by those disclosed in the present embodiment. The battery assembly  1  may include wiring for monitoring the voltage and temperature of the batteries, a monitoring board, a control board for battery control, etc. 
     In the present embodiment, each of the single cells  2  can be configured by, as an example, a lithium ion secondary battery. Each of the single cells  2  may be another secondary battery such as a nickel hydrogen battery, a nickel cadmium battery, and a lead battery. The lithium ion secondary battery is one type of non-aqueous electrolyte secondary batteries, in which lithium ions in an electrolyte play a role in electric conduction. The cathode material may include, for example, a lithium-manganese complex oxide, a lithium-nickel complex oxide, a lithium-cobalt complex oxide, a lithium-nickel-cobalt complex oxide, a lithium-manganese-cobalt complex oxide, a spinel type lithium-manganese-nickel complex oxide, and a lithium-phosphorous complex oxide having the olivine structure. The anode material may include, for example, an oxide-based material such as lithium titanate (LTO), a carbonaceous material, and a silicon-based material. The electrolyte (an electrolytic solution as an example) may include, for example, an organic solvent such as ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate to which, for example, a lithium salt such as a fluorine-based complex salt (for example, LiBF4 and LiPF6) is added may be used singly or in combination. 
     In the present embodiment, as an example, as illustrated in  FIGS. 1 to 3 , etc., a casing  3  (case or housing) has a rectangular parallelepiped appearance that is relatively long in one direction (the Y direction, the arrangement direction of the single cells  2 , the alignment direction of the single cells  2 , or the overlapping direction of the single cells  2 ). In the present embodiment, as an example, the casing  3  has a plurality of walls (wall portions) such as a bottom wall  3   a , a side wall  3   b , an end wall  3   c , a top wall  3   d , and a plurality of partition walls  3   e . The bottom wall  3   a  (wall) is formed in a quadrangular (for example, rectangular) plate shape. The bottom wall  3   a  extends along the XY plane. The side wall  3   b  (wall) is formed in a quadrangular (for example, rectangular) plate shape. The side wall  3   b  is connected to the end of the bottom wall  3   a  in the lateral direction (the X direction) and extends in a direction crossing the bottom wall  3   a  (a direction orthogonal thereto or the YZ plane as an example in the present embodiment). The end wall  3   c  (wall) is formed in a quadrangular (for example, rectangular) plate shape and is connected to the end of the bottom wall  3   a  in the longitudinal direction (the Y direction). The end wall  3   c  extends in a direction crossing the bottom wall  3   a  (a direction orthogonal thereto or the XZ plane as an example in the present embodiment). The side wall  3   b  is connected to the adjacent end wall  3   c . The top wall  3   d  (wall) is formed in a quadrangular (for example, rectangular) plate shape. The top wall  3   d  is connected to the ends of the side wall  3   b  and the end wall  3   c  and extends in a direction crossing the side wall  3   b  and the end wall  3   c  (a direction perpendicular thereto or the XY plane as an example in the present embodiment). The bottom wall  3   a  and the top wall  3   d  are arranged collaterally with their inner surfaces (the inner surfaces of the casing  3 ) facing (opposing) each other (parallel to each other as an example in the present embodiment). The two side walls  3   b  are arranged collaterally with their inner surfaces facing (opposing) each other (parallel to each other as an example in the present embodiment). The two end walls  3   c  are arranged collaterally with their inner surfaces facing each other (parallel to each other as an example in the present embodiment). 
     The casing  3  has the partition walls  3   e  (wall). The partition walls  3   e  are each formed in a quadrangular (for example, rectangular) plate shape. The partition walls  3   e  are each positioned in between the bottom wall  3   a  and the top wall  3   d . The partition walls  3   e  are each arranged collaterally with the end walls  3   c  (in parallel therewith as an example in the present embodiment) and extends along the XZ plane. The partition walls  3   e  are arranged collaterally with the surfaces facing (opposing) each other (parallel to each other as an example in the present embodiment). The spaces (pitches or pitches in the Y direction) between the partition walls  3   e  are nearly constant. The spaces may be changed locally, in which, as an example, the spaces (pitches or pitches in the Y direction) in the intermediate part of the row of the partition walls  3   e  are wider than those in the ends of the row. The inside of the casing  3  is divided into a plurality of flat rectangular parallelepipedal chambers  4  (housing chambers or containers) by the partition walls  3   e . The chambers  4  are arranged in the Y direction. At the ends of the row of the chambers  4  in the longitudinal direction, the chamber  4  is surrounded by the bottom wall  3   a , the top wall  3   d , the partition wall  3   e , and the end wall  3   c . In the intermediate part of the row of the chambers  4  in the longitudinal direction (other than the ends in the longitudinal direction), the chamber  4  is surrounded by the bottom wall  3   a , the top wall  3   d , and the two partition walls  3   e . The widths (widths in the Y direction) of the chambers  4  are nearly constant. The widths may be changed locally, in which, as an example, the widths (the widths in the Y direction) in the intermediate part of the row of the chambers  4  are wider than those in the ends of the row. The casing  3  is formed of an insulating synthetic resin material (for example, modified PPE (polyphenylene ether)), PFA (perfluoro alkoxy alkane or tetrafluoroethylene-perfluoro alkyl vinyl ether copolymer), etc. The synthetic resin material for the casing  3  may be a thermoplastic resin, including an olefin resin such as PE, PP, and PMP, a polyester resin such as PET, PBT, and PEN, a POM resin, a polyamide resin such as PA6, PA66, and PA12, a crystalline resin such as a PPS resin and an LCP resin and an alloy resin formed thereof, and a non-crystalline resin such as PS, PC, PC/ABS, ABS, AS, modified PPE, PES, PEI, and PSF and an alloy resin formed thereof. 
     In the present embodiment, as an example, as illustrated in  FIGS. 2 and 3 , etc., the casing  3  is configured by a combination of a plurality of (two as an example in the present embodiment) members (a first member  31  and a second member  32 ). The first member  31  includes the bottom wall  3   a , the side wall  3   b , the end wall  3   c , and a portion (a part  3   e   1 ) of the partition wall  3   e , while the second member  32  includes the top wall  3   d  and a portion (a part  3   e   2 ) of the partition wall  3   e . The second member  32  (the top wall  3   d ) covers an opening  4   a  of the chamber  4 . 
     In the present embodiment, as an example, the casing  3  has a protruding portion  3   f . In the protruding portion  3   f , the periphery of the top wall  3   d  protrudes further outward than the outer surface of the side wall  3   b  in a flange manner. The protruding portion  3   f  has an upper wall  3   g  (wall), a lower wall  3   h  (wall), and a side wall  3   i  (wall). The upper wall  3   g  is the periphery of the top wall  3   d  of the second member  32 . The lower wall  3   h  projects from the end on the second member  32  side of the side wall  3   b  of the first member  31 , while facing the upper wall  3   g  spaced apart therefrom. The side wall  3   i  extends along a direction crossing the upper wall  3   g  and the lower wall  3   h  (a direction orthogonal thereto as an example in the present embodiment). The side wall  3   i  has a part  3   i   1  on the first member  31  side and a part  3   i   2  on the second member  32  side. A space  4   b  (a gap, housing chamber, or container) is formed within the protruding portion  3   f . In the present embodiment, as an example, as illustrated in  FIG. 2 , a portion of an electrically conductive portion  5  (connecting portions  5   d ,  5   e , etc., as an example in the present embodiment) is housed within the space  4   b . The members (the first member  31  and the second member  32  as an example in the present embodiment) are connected through, for example, heat seal, adhesion by an adhesive, and fastening by fixing members (for example, screws). In the present embodiment, as an example, the portion (the part  3   e   1 ) of the first member  31  and the portion (the part  3   e   2 ) of the second member  32  of the partition wall  3   e  are heat sealed, while other portion (the part  3   i   1 ) of the first member  31  and other portion (the part  3   i   2 ) of the second member  32  of the side wall  3   i  are heat sealed. In the present embodiment, as an example, the chambers  4  within the casing  3  are formed as spaces that do not communicate with each other and are independent (isolated) from each other. 
     In the present embodiment, as an example, the single cells  2  are configured by the walls of the casing  3  (the bottom wall  3   a , side wall  3   b , end wall  3   c , top wall  3   d , partition wall  3   e , etc.), an electrical accumulator  7 , and the electrically conductive portion  5 . The walls of the casing  3  configure the chamber  4 . The electrical accumulator  7  is housed within the chamber  4 . The electrically conductive portion  5  is electrically connected to the electrical accumulator  7 . 
     In the present embodiment, as an example, the electrical accumulator  7  (a coil or charger and discharger) has a pair of sheet-shaped electrodes  7   a ,  7   b  (a cathode or anode) and sheet-shaped intervening members  7   c ,  7   d  (separators). The intervening members  7   c ,  7   d  are arranged in between the electrodes  7   a ,  7   b . The electrical accumulator  7  is configured by a layered body  7   e  illustrated in  FIG. 4  that is wound around (folded or folded back) for a plurality of times. The layered body  7   e  is configured by the intervening member  7   c , the electrode  7   a , the intervening member  7   d , and the electrode  7   b  that are stacked in this order.  FIG. 4  illustrates only a part in which the layered body  7   e  is wound two times at one end  7   f  of the electrical accumulator  7 . The layered body  7   e  is, as illustrated in  FIG. 3 , bent at the one end  7   f  and the other end  7   g . The layered body  7   e  is stacked in a flat manner between the one end  7   f  and the other end  7   g . The layered body  7   e  is wound spirally for a plurality of times to form a flat shape having an oval cross-sectional shape. The one end  7   f  and the other end  7   g  are an example of convex parts in which the perimeter of the electrical accumulator  7  are convex outward. In the present embodiment, as an example, in the layered body  7   e , the electrode  7   a  is displaced toward one of sides in the width direction of the intervening members  7   c ,  7   d . On the other hand, the electrode  7   b  is displaced toward other one of the sides in the width direction of the intervening members  7   c ,  7   d . The electrode  7   a  therefore projects to one side in the axial direction of the layered body  7   e  (the axial direction of the winding of the layered body  7   e  or the X direction as an example in the present embodiment). On the other hand, the electrode  7   b  projects to the other side in the axial direction of the layered body  7   e . In other words, protruding portions  7   h ,  7   i  of the electrodes  7   a ,  7   b  project in the axial direction of the winding of the layered body  7   e  (the X direction as an example of the present embodiment). A second part  5   b  of the electrically conductive portion  5  is electrically connected to the protruding portion  7   h  of the electrode  7   a . The second part  5   b  of another electrically conductive portion  5  is electrically connected to the protruding portion  7   i  of the electrode  7   b . In the present embodiment, as an example, the protruding portions  7   h ,  7   i  and the second part  5   b  are joined (coupled, fixed, connected, or electrically connected) by welding, etc. 
     In the present embodiment, as an example, the electrically conductive portion  5  (an electrically conductive member, electrically conductive component, lead component, terminal component, or component) has a first part  5   a , the second part  5   b , and a third part  5   c . The electrically conductive portion  5  is positioned on the top wall  3   d  side of the electrical accumulator  7 . The first part  5   a  is supported by the casing  3 . In the present embodiment, as an example, as illustrated in FIG.  5 , the first part  5   a  is integrated with the top wall  3   d  of the casing  3  by insert molding. As illustrated in  FIG. 2 , the second part  5   b  is in contact with the electrodes  7   a ,  7   b  of the electrical accumulator  7 . In the present embodiment, as an example, the second part  5   b  and the electrodes  7   a ,  7   b  are joined (coupled, fixed, or connected) by welding, etc., and are electrically connected. The third part  5   c  is positioned in between the first part  5   a  and the second part  5   b  and is twisted. In the present embodiment, as an example, the electrically conductive portion  5  has a plurality of (two as an example in the present embodiment) second parts  5   b . The second part  5   b  is formed in a band shape (a plate shape). The two second parts  5   b , with their surfaces facing each other (nearly parallel), hold the corresponding protruding portions  7   h ,  7   i  therebetween from both sides in the Y direction (the thickness direction of the electrical accumulator  7  (the layered body  7   e ) or the overlapping direction of the single cells  2  (the chambers  4 )). The two second parts  5   b  of the electrically conductive portion  5  and the corresponding protruding portions  7   h ,  7   i  held therebetween are joined (coupled, fixed, connected, or electrically connected) by welding, etc. With the foregoing configuration, the electrical accumulator  7  is supported by the top wall  3   d  through the electrically conductive portion  5 . With reference to  FIGS. 2 and 3 , in the present embodiment, as an example, it can be understood that the electrical accumulator  7  is supported by the top wall  3   d  through the two electrically conductive portions  5  through both ends. The electrically conductive portion  5  is, as an example, formed of a conductor with relatively high electric conductivity (a metallic material such as an alloy containing silver, copper, aluminum, etc.). 
     In the present embodiment, as an example, as illustrated in  FIG. 8 , the electrically conductive portion  5  is configured by integrating a plurality of components (electrically conductive members or a first component  51  and a second component  52  as an example in the present embodiment). Specifically, the connecting portion  5   d  of the first component  51  and the connecting portion  5   e  of the second component  52  are joined (coupled, fixed, connected, or electrically connected) by welding, etc., to configure the electrically conductive portion  5 . 
     As illustrated in  FIGS. 2 ,  5 , and  8 , the first component  51  has the first part  5   a , the connecting portion  5   d , and an intermediate portion  5   f  (a connecting portion or intervening portion). The first part  5   a  is formed in a cylindrical (columnar or tubular) shape and passes through the top wall  3   d . The first part  5   a  is formed with a recess  5   g  that communicates with the outside of the casing  3 . The recess  5   g  on the inside of the casing  3  is closed. A wall  5   h  surrounding the recess  5   g  and a bus bar  8  (an electrically conductive member) are joined (coupled, fixed, connected, or electrically connected) with each other by welding, etc. In other words, the wall  5   h  (the first part  5   a  or the first component  51 ) is an example of a terminal. The part of the electrically conductive portion  5  other than the wall  5   h  is an example of a lead. The connecting portion  5   d  is formed in a quadrangular plate shape. The connecting portion  5   d  is positioned along the top wall  3   d  and spaced apart from the top wall  3   d . The intermediate portion  5   f  is formed in a band shape (a plate shape) bent in an L shape. The intermediate portion  5   f  is positioned in between the first part  5   a  and the connecting portion  5   d . The intermediate portion  5   f  connects the first part  5   a  and the connecting portion  5   d  with each other. The intermediate portion  5   f  and the connecting portion  5   d  are a band-shaped (plate-shaped) part continuously bent in an S shape (a crank shape). 
     As illustrated in  FIGS. 6 to 8 , the second component  52  has the connecting portion  5   e , the plurality of (two as an example of the present embodiment) second parts  5   b , and the third part  5   c . The connecting portion  5   e  is formed in a quadrangular plate shape and is positioned on a side of the connecting portion  5   d  opposite the top wall  3   d . The connecting portion  5   d  of the first component  51  and the connecting portion  5   e  of the second component  52  are stacked in their thickness direction and are joined (coupled, fixed, connected, or electrically connected) by welding, etc. The third part  5   c  is positioned in between the connecting portion  5   e  and the second part  5   b . With reference to  FIGS. 6 to 8 , it can be understood that an end  5   i  on the connecting portion  5   e  side of the third part  5   c  and an end  5   j  on the second part  5   b  side of the third part  5   c  are twisted with respect to each other. With reference to  FIGS. 6 to 8 , it can be also understood that the third part  5   c  is twisted between the ends  5   i ,  5   j  about an axis in a direction along which the second part  5   b  extends (the Z axis). The second component  52  can be obtained by bending the second parts  5   b  and the third part  5   c  integrally starting from the end  5   i  from the connecting portion  5   e  about the Y axis by nearly 90° (deg) and twisting the third part  5   c  about the Z axis by nearly 90° (deg). In the present embodiment, by providing the electrically conductive portion  5  with the twisted third part  5   c , as an example, the flexibility and buffering effect of the second component  52  (electrically conductive portion  5 ) are likely to be improved as compared to a case in which the twisted third part  5   c  is absent. In the present embodiment, as an example, the two third parts  5   c  of the one second component  52  are twisted in opposite directions. 
     In the formation of the second component  52 , as an example, first, a long slender U-shaped original member (an original shape, a developed shape before forming the second component  52 , a punched shape, or a cut-off shape) in which two second parts  5   b  extend from the connecting portion  5   e  is obtained from a flat plate member (a metallic member) by press forming, etc. Then, the two second parts  5   b  are bent with respect to the connecting portion  5   e  starting from the end  5   i  (see  FIG. 6 ) by nearly 90° (deg). Furthermore, the basal part of the second part  5   b  with respect to the connecting portion  5   e  is twisted to obtain the third part  5   c . The bending and twisting may be performed nearly at the same time. Accordingly, in the present embodiment, as an example, the twisted third part  5   c  is provided, thereby obtaining the two second parts  5   b  that extend nearly in parallel and face each other in the thickness direction of the electrical accumulator  7  from the original member before forming (before bending) extending nearly in parallel from the connecting portion  5   e . Without the twisted third part  5   c , the original member becomes a T shape. Therefore, the arrangement number of the original member in the plate member before being pressed is likely to be small, and the component number (efficiency or layout efficiency) with respect to the area of the plate member is likely to be small. In the present embodiment, as an example, the layout efficiency of the second component  52  in the plate member is likely to be improved. The second component  52  may be appropriately subjected to heat treatment or surface treatment. 
     As can be understood from  FIG. 2 , in the present embodiment, as an example, the third part  5   c  is positioned apart from the one end  7   f  (the convex part) as viewed from the protruding direction (the Z direction) of the one end  7   f  of the electrical accumulator  7 . In other words, the third part  5   c  is positioned at one side of the one end  7   f  of the electrical accumulator  7  toward a direction in which the one end  7   f  protrudes, and is positioned between the one end  7   f  and the corner of the chamber  4 . The twisted third part  5   c  is likely to occupy a larger area within the casing  3  (within the chamber  4 ) as compared to a part that is not twisted. The one end  7   f  and the other end  7   g  protrude while being convex outward (the Z direction as an example in the present embodiment). A gap is therefore likely to be formed between the corner of the chamber  4  and each of the one end  7   f  and the other end  7   g . In the present embodiment, accordingly, the third part  5   c  is arranged using an area (a space, the corner of the chamber  4  facing the convex part of the electrical accumulator  7 , or a gap) between the one end  7   f  and the wall of the casing  3  positioned beside the one end  7   f  (the top wall  3   d , partition wall  3   e , or end wall  3   c  as an example in the present embodiment). Here, the layered body  7   e  of the electrical accumulator  7  is bent and protruded to form the one end  7   f . According to the present embodiment, therefore, as an example, the efficiency of the layout of the components is likely to be improved. As an example, therefore, the battery assembly  1  is likely to be formed in a smaller size. The position and the specifications such as the direction of twist and the number of twisting of the third part  5   c  may be appropriately changed. 
     In the present embodiment, as an example, the first component  51  and the second component  52  are joined (for example, by welding) after the first component  51  is integrated with the second member  32  including the top wall  3   d  by insert molding, etc., and the second component  52  is integrated with the electrical accumulator  7  by welding, etc. In other words, in the present embodiment, the first component  51  fixed to the second member  32  and the second component  52  fixed to the electrical accumulator  7  are integrated with each other. In the present embodiment, thus, the electrically conductive portion  5  is divided into a plurality of components. The electrically conductive portion  5  is, therefore, as an example, likely to be installed in the battery assembly  1  more easily and with higher precision. If the electrically conductive portion  5  is a one-piece component that is not divided into the first component  51  and the second component  52 , it becomes necessary to perform: (1) a process in which a plurality of electrically conductive portions  5  are insert-molded in the second member  32  while the electrically conductive portions are joined to the electrical accumulator  7 ; or (2) a process in which the electrically conductive portions  5  that are insert-molded in the second member  32  are joined to a plurality of the electrical accumulators  7 . Both Processes (1) and (2) are likely to require time and effort and likely to lead to increased errors. 
     In the present embodiment, as an example, as illustrated in  FIG. 2 , the connecting portions  5   d ,  5   e  of the first component  51  and the second component  52  are positioned further apart from a central part C of the electrical accumulator  7  than the second part  5   b . The connecting portions  5   d ,  5   e  are positioned apart from the electrical accumulator  7  as viewed from a direction in which the first component  51  and the second component  52  overlap with each other (a direction in which the first member  31  and the electrical accumulator  7  overlap with each other, a direction in which the first member  31  and the second member  32  overlap with each other, or the Z direction). The connecting portions  5   d ,  5   e  are provided extending (projecting) in a direction away from the center of the electrical accumulator  7  from ends  7   j ,  7   k  of the electrical accumulator  7  (ends  7   j ,  7   k  to which (the second part  5   b  of) the electrically conductive portion  5  is joined or ends  7   j ,  7   k  of the layered body  7   e  in the axial direction as an example in the present embodiment). In the present embodiment, as an example, therefore, in the process in which the first component  51  and the second component  52  are joined, influence by the electrical accumulator  7  (as an example, difficulty in work through the interference with the electrical accumulator  7 ) or influence on the electrical accumulator  7  (as an example, damage to the outer surface of the electrical accumulator  7 ) is likely to be reduced. When the first component  51  and the second component  52  are welded (adhered), the influence of heat is hard to be exerted on the electrical accumulator  7 . 
     In the present embodiment, as an example, as illustrated in  FIG. 5 , at least an area of the top wall  3   d  of the casing  3  through which the electrically conductive portion  5  passes is formed of a plurality of (two as an example in the present embodiment) synthetic resin materials having different quality. In this kind of battery assembly  1  (battery), it is important for gas generated in the chamber  4  not to leak outside of the casing  3 , thereby it is desired to ensure the airtightness at the boundary between the top wall  3   d  and the electrically conductive portion  5 . If the entire top wall  3   d  is insert molded with one kind of synthetic resin material with the electrically conductive portion  5  included, there is concern that it is hard to ensure pressure on the contact part between the electrically conductive portion  5  and the top wall  3   d  during forming. Furthermore, there is concern that the airtightness between the electrically conductive portion  5  and the top wall  3   d  degrades, making it hard to ensure desired airtightness. In this regard, in the present embodiment, as an example, a first part  32   a  of a first material is formed around the electrically conductive portion  5 , and a second part  32   b  of a second material is formed around the first part  32   a . Accordingly, as an example, first, the first part  32   a  of the first material can be formed while applying higher pressure to the periphery of the electrically conductive portion  5 , and then, the second part  32   b  of the second material can be formed around the first part  32   a . This, as an example, allows the airtightness between the first part  32   a  and the electrically conductive portion  5  to be more likely to be improved. As an example, the first material may have higher adhesiveness with respect to the material of the electrically conductive portion  5  (a metallic material as an example in the present embodiment) than that of the second material. As an example, the first material may be a crystalline material, while the second material may be a non-crystalline material. As an example, the first material may have a lower melting point than that of the second material. Accordingly, as an example, when forming the second part  32   b , the first part  32   a  is heated by the second material (before being solidified) in a state having higher temperature than the first part  32   a  and fluidity. This may allow the first part  32   a  to be partially softened and improve the airtightness between the first part  32   a  and the second part  32   b  or the electrically conductive portion  5 . In the present embodiment, as an example, the volume of the first part  32   a  is smaller than the volume of the second part  32   b . Specifically, as an example, the first part  32   a  is provided around (in the vicinity of) the electrically conductive portion  5 , and the other part of the top wall  3   d  (the second member  32 ) is the second part  32   b . According to the present embodiment, therefore, as an example, pressure during the formation of the first part  32   a  is likely to be increased than pressure during the formation of the second part  32   b , and the airtightness between the electrically conductive portion  5  and the first part  32   a  is likely to be improved. At the boundary between the first part  32   a  and the second part  32   b , airtightness is more likely to be improved, since both the first part  32   a  and the second part  32   b  are synthetic resin materials. Furthermore, by incorporating the same kind of substance or the same substance into the first material and the second material, the adhesion between the first part  32   a  and the second part  32   b  is more likely to be improved, and airtightness is more likely to be improved. In the present embodiment, as an example, the first material forming the first part  32   a  may be a crystalline resin such as a polyamide resin such as PA6, PA66, and PA12 and an alloy resin formed thereof, while the second material forming the second part  32   b  may be a non-crystalline resin such as modified PPE, PES, PEI, and PSF and an alloy resin formed thereof. 
     In the present embodiment, as an example, the through part (the first part  5   a ) of the top wall  3   d  of the electrically conductive portion  5  and the first part  32   a  of the top wall  3   d  are configured as a rotating body about an axis along the through direction of the electrically conductive portion  5  (the Z direction or the thickness direction of the top wall  3   d ). In other words, the cross section perpendicular to the axis of the through part and the first part  32   a  has a circular shape (ring-like shape). Specifically, as an example, the wall  5   h  is formed in nearly a cylindrical shape, and the first part  5   a  is formed in a circular shape. In the present embodiment, as an example, therefore, when forming the first part  32   a , and when forming the second part  32   b , fluctuations in pressure at the boundary between the electrically conductive portion  5  and the first part  32   a  and at the boundary between the first part  32   a  and the second part  32   b  are likely to be reduced. 
     As illustrated in  FIG. 5 , a recess and protrusion structure  32   c  (a recessed portion, a protruding portion, a recessed groove, or a protrusion) can be provided at the boundary between the electrically conductive portion  5  and the first part  32   a  and at the boundary between the first part  32   a  and the second part  32   b . The recess and protrusion structure  32   c  is formed to have circular shape (ring-like shape) about an axis along the thickness direction of the top wall  3   d . In the present embodiment, as an example, therefore, airtightness is more likely to be improved, since a path at the boundary becomes long, and resistance at the boundary increases. The first part  32   a  has a protrusion  32   d  (a projecting part) that cuts into (enters) the second part  32   b . Accordingly, as an example, when forming the second part  32   b , the protrusion  32   d  is heated by the second material (before being solidified) in a state having higher temperature than the first part  32   a  and fluidity, and the protrusion  32   d  may partially soften or melt, thereby improving the adhesion between the first part  32   a  and the second part  32   b . In other words, after the solidification of the second part  32   b , the protrusion  32   d  may be formed as a melted part. The fact that the protrusion  32   d  has been melted by molding is revealed by checking the cross section, etc., of a product. 
     In this part, ensuring desired chemical resistance against electrolytes is required. If the entire top wall  3   d  is formed by one kind of synthetic resin material, there is concern that it might be difficult to achieve both the adhesion with the electrically conductive portion  5  and chemical resistance. Accordingly, in the present embodiment, as an example, the chamber  4  side of the first part  32   a  (the inside of the casing  3 ) is covered with the second part  32   b  having higher chemical resistance against electrolytes than the first part  32   a . In the present embodiment, as an example, therefore, the first part  32   a  is not directly exposed to an electrolyte, thereby, as an example, making both the adhesion with the electrically conductive portion  5  and chemical resistance more likely to be achieved. 
     In the present embodiment, as an example, as illustrated in  FIG. 2 , (the wall  5   h  of) the first part  5   a  of the electrically conductive portion  5  passes through the top wall  3   d  of the second member  32  of the casing  3  to project out of the top wall  3   d  (casing  3 ) and is joined (coupled, fixed, connected, or electrically connected) to the bus bar  8  positioned outside the top wall  3   d . The bus bar  8  electrically connects the electrodes  7   a ,  7   b  and the electrodes  7   a ,  7   b  of a plurality of different single cells  2  (electrical accumulators  7 ). When the single cells  2  are connected in series, the bus bar  8  electrically connects the electrode  7   a  (one of the cathode and anode) and the electrode  7   b  (other of the cathode and anode). The bus bar  8  is provided with a protruding portion  8   b  having a cylindrical (tubular) wall  8   a . The protruding portion  8   b  protrudes toward outside of the casing  3 . A through hole is formed within the protruding portion  8   b . The cylindrical wall  5   h  (protruding portion) of the first part  5   a  is disposed within the tube (within the through hole) of the protruding portion  8   b  of the bus bar  8  being in nearly intimate contact therewith. The wall  5   h  and the wall  8   a  of the protruding portion  8   b  are joined (coupled, fixed, connected, or electrically connected) by welding, etc. 
     In the present embodiment, as an example, as illustrated in  FIG. 9 , the bus bar  8  has two first walls  8   c , two second walls  8   d , a third wall  8   e , two first curve portions  8   f , and two second curve portions  8   g . Specifically, the bus bar  8  is formed in a hat shape (a crank shape) by bending one plate-shaped (band-shaped or strip-shaped) member at four parts (the two first curve portions  8   f  and the two second curve portions  8   g ). The first walls  8   c , the second walls  8   d , and the third wall  8   e  are all formed in a quadrangular plate shape (band shape). The two first walls  8   c  (cross walls or bottom walls) are positioned along a front side  3   d   1  of the top wall  3   d . The protruding portion  8   b  is provided on the first wall  8   c . The two second walls  8   d  (standing walls or side walls) are connected to the first walls  8   c  via the first curve portions  8   f , respectively. The second walls  8   d  extend (stands up) in a direction crossing (a direction orthogonal to) the first walls  8   c  (the front side  3   d   1 ). The third wall  8   e  is provided apart from the two first walls  8   c  and the front side  3   d   1  of the top wall  3   d  across the two second walls  8   d . The third wall  8   e  is connected to the two second walls  8   d  through the two second curve portions  8   g . The third wall  8   e  is provided nearly parallel to the first walls  8   c  and the top wall  3   d  (the front side  3   d   1 ). The curvature (the curvature radius or bend radius) of the second curve portion  8   g  is smaller than the curvature (the curvature radius or bend radius) of the first curve portion  8   f . In  FIGS. 9 and 10 , the protruding portion  8   b  is omitted for convenience. 
     When an external force F is exerted on the bus bar  8  having the aforementioned configuration in a direction in which the two first walls  8   c  depart from each other (see  FIG. 10 ), the bus bar  8  becomes deformed from the state in  FIG. 9  to the state in  FIG. 10 . In this situation, as illustrated in  FIG. 10 , the third wall  8   e  is bent so as to be put into a state in which the third wall  8   e  is convex toward the first walls  8   c  (toward the front side  3   d   1 ) at a larger curvature (curvature radius or bend radius) than the first curve portion  8   f  and the second curve portion  8   g . According to research by the inventors, it has been found that, in a bus bar  8 R illustrated in  FIG. 11 , when an external force as is the case with the bus bar  8  according to the present embodiment is exerted, stress is concentrated at a center  8   i  of a curve portion  8   h , thereby making the maximum stress likely to be higher than that of the bus bar  8 . Thus, in the present embodiment, the configuration illustrated in  FIG. 9  is employed, as an example. As a result, it has been found that the concentration of the stress can be alleviated (reduced) because an area where the stress is increased lays over an area including the third wall  8   e  and/or the second curve portion  8   g , which is larger than an area defined by the center  8   i  of the curve portion  8   h  of the bus bar  8 R. Further, according to research by the inventors, it has been found that the bus bar  8  can alleviate (reduce) the concentration of stress when the third wall  8   e  has a shape of the bus bar  8  illustrated in  FIG. 10  at least at the time of being assembled, as compared to the bus bar  8 R. 
     Further, according to research by the inventors, when an external force exerted in a direction in which the two first walls  8   c  move closer to each other (an external force Fi in the direction opposite the external force F in  FIG. 10 ), the third wall  8   e  is bent to be put into a state in which the third wall  8   e  is convex toward a direction opposite the first walls  8   c  (away from the front side  3   d   1 ) with a larger curvature (curvature radius or bend radius) than the first curve portion  8   f  and the second curve portion  8   g  as illustrated by the chain double-dashed line in  FIG. 10 . It has been found that in also such a case, stress is higher in the area of the third wall  8   e  and the second curve portions  8   g , which is wider than the center  8   i  of the curve portion  8   h  of the bus bar  8 R, thereby alleviating (reducing) the concentration of stress as compared to the bus bar  8 R illustrated in  FIG. 11 . According to research by the inventors, it has been found that the bus bar  8  can alleviate (reduce) the concentration of stress when the third wall  8   e  has a shape of the bus bar  8  illustrated by the chain double-dashed line in  FIG. 10  at least at the time of being assembled, as compared to the bus bar  8 R. 
     According to research by the inventors, it has been found that the sensitivity of the magnitude of the curvature of the first curve portion  8   f  with respect to the maximum stress of the bus bar  8  is lower than the sensitivity of the magnitude of the curvature of the second curve portion  8   g . It has been also found that the smaller the curvature of the second curve portion  8   g , the lower the maximum stress of the bus bar  8 . As an example, therefore, from the viewpoint of reduction in stress and manufacturability, etc., it is preferable that the curvature of the first curve portion  8   f  is larger than the curvature of the second curve portion  8   g.    
     In the present embodiment, as an example, it is preferable to join (couple, fix, connect, or electrically connect) the bus bar  8  and the electrically conductive portion  5  with each other before joining (coupling, fixing, connecting, or electrically connecting) the first component  51  and the second component  52 . This is because, when the bus bar  8  and the electrically conductive portion  5  are joined with respect to each other by welding, etc., after the first component  51  and the second component  52  are joined with each other, heat occurring on the joint between the bus bar  8  and the electrically conductive portion  5  is likely to be transmitted to the electrical accumulator  7  through the electrically conductive portion  5  (the connecting portions  5   d ,  5   e ). 
     In the present embodiment, as an example, when the first member  31  and the second member  32  are assembled, the electrical accumulators  7  integrated with the second member  32  through the electrically conductive portion  5  are housed within the chambers  4  provided in the first member  31 . In the chambers  4 , an electrolyte is placed before being assembled. The depth of the chambers  4  is set so that the electrical accumulators  7  are not in contact with the bottom wall  3   a  when the first member  31  and the second member  32  of the casing  3  are assembled. 
     In the present embodiment, as an example, as illustrated in  FIG. 2 , a boundary  3   p  (a boundary part, a connecting portion, a connecting part) between the first member  31  and the second member  32  is provided with a metallic layer  10  (a metallic part). The metallic layer  10  is provided across the first member  31  and the second member  32  to cover the boundary  3   p  between the first member  31  and the second member  32 . Specifically, recesses (recessed grooves or grooves)  3   k ,  3   m  are provided on the periphery of the parts at which the first member  31  and the second member  32  are joined (the parts  3   i   1 ,  3   i   2  of the side wall  3   i  of the protruding portion  3   f ). When the first member  31  and the second member  32  are abutted with each other, the recesses  3   k ,  3   m  form a recess  3   n  that opens toward the outside the casing  3  on the side wall  3   i  of the protruding portion  3   f . In other words, the recess  3   n  contains the recesses  3   k ,  3   m . The boundary  3   p  is provided in the recess  3   n , and the metallic layer  10  is provided within the recess  3   n . The recess  3   n  surrounds the entire perimeter of the protruding portion  3   f  in which the recess  3   n  is provided. In the present embodiment, as an example, as illustrated in  FIGS. 1 and 2 , after the first member  31  and the second member  32  are joined, a metallic material (for example, stainless steel, an aluminum alloy, a nickel alloy, a cobalt alloy, a copper alloy, copper, and tin) is thermally sprayed so as to fill the recess  3   n  therewith. This makes the salability (airtightness or fluid-tightness) at the joint between the first member  31  and the second member  32  likely to be improved. A metallic material having relatively high thermal conductivity is thermally sprayed (metal spraying) to provide the metallic layer  10  (the metallic part), thereby improving thermal conductivity in the battery assembly  1 . 
     In the present embodiment, as an example as illustrated in  FIGS. 1 ,  3 , and  12  to  14 , the top wall  3   d  is provided with a safety valve  9  (a valve) corresponding to each chamber  4 . In other words, a plurality of safety valves  9  are provided. The safety valve  9  opens the chamber  4  to the outside by allowing the top wall  3   d  to break at a thin portion  9   d  (a weak portion) provided on the top wall  3   d  due to increased pressure within the chamber  4 . The top wall  3   d  is an example of a wall that is provided on the casing  3  and covers at least portion of the chamber  4 . 
     The thin portion  9   d  is provided by a plurality of linear grooves  9   a  (first grooves) provided on the front side  3   d   1 . The grooves  9   a  may be provided on a back side  3   d   2  and may be provided on the front side  3   d   1  and the back side  3   d   2 . In other words, the grooves  9   a  may be provided on at least either one of the front side  3   d   1  and the back side  3   d   2 . The front side  3   d   1  is an example of a first side, and the back side  3   d   2  is an example of a second side opposite the front side  3   d   1 . The grooves  9   a  are, as an example, provided radially to form a crisscross shape. In the present embodiment, therefore, a plurality of thin portions  9   d  are provided, which extend radially. 
     A groove  9   b  surrounding the safety valve  9  (a second groove) is provided on the back side  3   d   2  of the top wall  3   d . The groove  9   b  is provided for each safety valve  9 , and the grooves  9   b  surround the respective safety valves  9 . The grooves  9   b  may be provided on the front side  3   d   1  and may be provided on the front side  3   d   1  and the back side  3   d   2 . In other words, the grooves  9   b  may be provided on at least either one of the front side  3   d   1  and the back side  3   d   2  of the top wall  3   d . The groove  9   b , as an example, surrounds the perimeter of the safety valve  9  circularly. By the groove  9   b , the top wall  3   d  is provided with a thin portion  9   e  (a second thin-walled part) that extends to surround the thin portions  9   d . The thickness of the top wall  3   d  (wall) of an area  9   c  that is on the safety valve  9  side of the groove  9   b  is smaller than the thickness of the top wall  3   d  of an area  9   f  that is on the side of the groove  9   b  opposite the safety valve  9 . 
     According to the foregoing configuration, when pressure within the chamber  4  (the pressure of gas) increases, the thin portion  9   d  breaks, and the gas within the chamber  4  exits to the outside. When the pressure within the chamber  4  increases, the part in which the groove  9   a  is provided (the thin portion  9   d ) becomes deformed toward the outside of the casing  3  more largely, and stress concentrates on the groove  9   a  and its surrounding area. In the present embodiment, as an example, since the groove  9   b  is provided, stress concentration is likely to occur at the part in which the groove  9   b  is provided (the thin portion  9   e ), and in addition, stress is not likely to concentrate on the outside of the groove  9   b . When the top wall  3   d  (the casing  3 ) is formed of a synthetic resin, the material is likely to become deformed (is likely to become elongated) as compared to a case in which it is formed of a metallic material. When the groove  9   b  is not provided, therefore, there is concern that through the action of a load on the top wall  3   d , the part in which the groove  9   a  is provided becomes deformed and elongated, and stress concentrates on the corner between the top wall  3   d  and the partition wall  3   e  (the part  3   e   2 ), from which a break starts. In this regard, in the present embodiment, as an example, since the groove  9   b  is provided, the concentration of stress in the corner between the top wall  3   d  and the partition wall  3   e  (the part  3   e   2 ) is likely to be reduced. 
     As described above, in the present embodiment, as an example, the bus bar  8  has two first walls  8   c , the two second walls  8   d , and the third wall  8   e . The first walls  8   c  are extended along the front side  3   d   1  of the casing  3 . The second walls  8   d  are connected to the two first walls  8   c , respectively, through the first curve portions  8   f , respectively, and extend in a direction crossing the front side  3   d   1 . The third wall  8   e  is connected to the two second walls  8   d  through the second curve portions  8   g , respectively, and extends in a direction along the front side  3   d   1  at a position apart from the front side  3   d   1  across the two second walls  8   d . In the present embodiment, as an example, therefore, stress concentration when an external force is exerted is likely to be alleviated, and local stress is more likely to be reduced. 
     In the present embodiment, as an example, the battery assembly  1  includes at least one bus bar  8  that is bent to a state in which the third wall  8   e  is convex toward the front side. According to the present embodiment, as an example, with respect to the bus bar  8  in that state, stress concentration when an external force is exerted is likely to be relaxed, and local stress is more likely to be reduced. 
     In the present embodiment, as an example, the battery assembly  1  includes at least one bus bar  8  that is bent to a state in which the third wall  8   e  is convex toward a direction away from the front side. According to the present embodiment, as an example, with respect to the bus bar  8  in that state, stress concentration when an external force is exerted is likely to be alleviated, and local stress is more likely to be reduced. 
     In the present embodiment, as an example, the battery assembly  1  includes at least one bus bar  8  in which the curvature of the first curve portion  8   f  is larger than the curvature of the second curve portion  8   g . According to the present embodiment, as an example, with respect to the bus bar  8 , stress concentration when an external force is exerted is likely to be alleviated, and local stress is more likely to be reduced. As an example, manufacturability is likely to be improved. 
     In the present embodiment, as an example, the first wall  8   c  is provided with the protruding portion  8   b . According to the present embodiment, as an example, the deformation of the protruding portion  8   b  is reduced, and as an example, an increase in stress along with the deformation is likely to be reduced. 
     A second component  52 A illustrated in  FIG. 15  may be used instead of the second component  52  of the first embodiment. According to a first modification, the shape of the third part  5   c  is different from the above-described embodiment. The same effect as the above-described embodiment can be achieved by also the present modification. 
     The first part  32   a , and the second part  32   b  (the top wall  3   d  or the second member  32 ), a first component  51 B (an electrically conductive portion  5 B), a first part  32   a B, and a second part  32   b B (a top wall  3   d B or a second member  32 B) illustrated in  FIG. 16  may be used instead of the first component (the electrically conductive portion  5 ). A second modification differs from the first embodiment in that the recess and protrusion structure  32   c  and the protrusion  32   d  are absent. The same effect as the above-described embodiment can be achieved by also the present modification. 
     A bus bar  8 C illustrated in  FIG. 17  may be used instead of the bus bar  8  of the first embodiment. According to a third modification, the presence of an external connection terminal  8   j  is different from the above-described embodiment. The same effect as the above-described embodiment can be achieved by also the present modification. 
     While certain embodiments and modifications have been described above, the above-described embodiments and modifications have been presented by way of example only, and are not intended to limit the scope of the invention. These embodiments and modifications may be embodied in a variety of other forms, furthermore, various omissions, substitutions, combinations, and alterations may be made without departing from the spirit of the invention. These embodiments and modifications are included in the scope and spirit of the invention and are included in the invention described in the claims and its equivalents. The components may be partially substituted between the embodiments and modifications. The specifications of each component (structure, type, direction, shape, size, length, width, thickness, height, number, arrangement, position, materials, etc.) may be appropriately changed to be embodied. The electrically conductive portion may be a one-piece component, and the one-piece electrically conductive portion may include a third part. The battery assembly does not necessarily have a projecting part. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.