Patent Publication Number: US-2021167451-A1

Title: Lid assembly, battery and battery pack

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation Application of PCT Application No. PCT/JP2018/043434, filed Nov. 26, 2018, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate to a lid assembly, a battery and a battery pack. 
     BACKGROUND 
     As an example, a battery is formed by assembling components such as a lid assembly, an outer case and an electrode group which are distributed individually. In order to obtain an electric power source having a larger capacity, a battery pack (battery module) has been developed in which a plurality of batteries are connected. 
     The capacity of the battery is preferably as large as possible. On the other hand, the size of the battery itself (height, width, and thickness in the case of a substantially rectangular parallelepiped shape) is preferably as small as possible. 
     For example, the internal space of the battery is formed to be as small as possible by appropriately arranging various components in the battery. A gas may be generated inside the battery due to repeated use or aging deterioration, or the like. When the internal pressure of the battery reaches a predetermined pressure due to the generation of a gas, it is sometimes required to vent the gas from a valve disposed in the battery. Thus, the battery is required to secure a gas flow channel from a gas generation source to the valve through an internal space formed as small as possible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic perspective view of a back face side of a lid assembly according to a first embodiment; 
         FIG. 1B  is a schematic exploded perspective view of the lid assembly shown in  FIG. 1A ; 
         FIG. 2A  is a schematic perspective view of a front face side of the lid assembly, which is opposite to the side of the lid assembly shown in  FIG. 1A ; 
         FIG. 2B  is a schematic exploded perspective view of the lid assembly shown in  FIG. 2A ; 
         FIG. 3A  is a schematic plan view of the back face side of the lid assembly shown in  FIG. 1A ; 
         FIG. 3B  is a schematic plan view of a part of a second face (back face side) of an insulating member of the lid assembly shown in  FIG. 1B ; 
         FIG. 4  is a schematic cross-sectional view taken along the IV-IV line in  FIG. 3A ; 
         FIG. 5  is a schematic cross-sectional view of a lid assembly according to a first modification of the first embodiment and of a wall having a shape different from that of the wall shown in  FIG. 4 , taken along the IV-IV line in  FIG. 3A ; 
         FIG. 6  is a schematic cross-sectional view of a lid assembly according to a second modification of the first embodiment and of an adjacent face having a shape different from that of the adjacent face (opposing face) shown in  FIG. 4 , taken along the IV-IV line in  FIG. 3A ; 
         FIG. 7  is a schematic cross-sectional view of a lid assembly according to a third modification of the first embodiment and of a support face having a shape different from those of the support faces of the support face group shown in  FIGS. 4 to 6 ; 
         FIG. 8  is a schematic cross-sectional view of a lid assembly according to a fourth modification of the first embodiment and of a support face having a shape different from those of the support faces of the support face group shown in  FIGS. 4 to 7 ; 
         FIG. 9  is a schematic perspective view of a back face side of a lid assembly according to a fifth modification of the first embodiment; 
         FIG. 10A  is a schematic plan view of the back face side of the lid assembly shown in  FIG. 9 ; 
         FIG. 10B  is a schematic plan view of a part of a second face (back face side) of an insulating member of the lid assembly shown in  FIG. 9 ; 
         FIG. 11  is a schematic cross-sectional view taken along the XI-XI line in  FIG. 10A ; 
         FIG. 12  is a schematic perspective view of a back face side of a lid assembly according to a sixth modification of the first embodiment; 
         FIG. 13  is a schematic plan view of the back face side of the lid assembly shown in  FIG. 12 ; 
         FIG. 14  is a schematic plan view of a back face side of a lid assembly according to a seventh modification of the first embodiment, showing that a valve having a size and a shape different from those of the valve shown in the  FIG. 3A  is provided; 
         FIG. 15  is a schematic perspective view of a battery according to a second embodiment; 
         FIG. 16  is a schematic exploded perspective view of the battery shown in  FIG. 15 ; 
         FIG. 17A  is a schematic perspective view of a state in which a part of the electrode group shown in  FIG. 16  is unwound; 
         FIG. 17B  is a schematic perspective view of the electrode group shown in  FIG. 17A ; 
         FIG. 18  is a schematic cross-sectional view taken along the XVIII-XVIII plane in  FIG. 15 ; 
         FIG. 19  is a schematic cross-sectional view taken along the XIX-XIX plane in  FIG. 15 ; 
         FIG. 20  is a schematic exploded perspective view of a battery pack according to a third embodiment; and 
         FIG. 21  is an example of a block diagram of the battery pack shown in  FIG. 20 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments will be described with reference to the drawings. 
     According to an embodiment, a lid assembly includes a plate-shaped lid, a pair of terminals, a pair of leads, an insulating member, and a valve. The lid is attached to an opening of an outer case housing an electrode group. The pair of terminals each having conductivity are separated from each other in an electrically insulated state, and are disposed on the lid. The pair of leads each having conductivity are separated from each other in an electrically insulated state. One of the pair of leads is electrically connected to one of the pair of terminals on a base portion thereof, and electrically connected to one current-collecting tab of the electrode group on a leg portion extending from the base portion. Another of the pair of leads is electrically connected to another of the pair of terminals on a base portion thereof and electrically connected to another current-collecting tab of the electrode group on a leg portion extending from the base portion. The insulating member includes a plurality of opposing faces positioned on a side opposite to the lid, a pair of support face groups, and an intermediate region provided with an opening facing the lid. The plurality of opposing faces are facing the electrode group and provided between the base portions of the pair of leads. The pair of support face groups are protruding toward a side opposite to the lid with respect to the plurality of opposing faces and supporting the electrode group. The intermediate region is continuous with at least a part of the plurality of opposing faces, and provided between the pair of support face groups. The valve is provided to the lid between the pair of terminals, and is adjacent to the opening of the intermediate region of the insulating member. The valve is configured to open toward a side on which the pair of terminals are disposed in response to a pressure on a side on which the pair of leads and the insulating member are disposed with respect to the lid reaching a predetermined pressure. A maximum possible opening area with which the valve is configured to open is equal to or smaller than an area of the plurality of opposing faces. 
     First, a lid assembly  10  that can be distributed in manufacturing a battery  310  will be described as a first embodiment. Next, the battery  310  including the lid assembly  10  will be described as a second embodiment. Further, a battery pack  510  including one or more batteries  310  will be described as a third embodiment. 
     First Embodiment 
     The first embodiment will be described with reference to  FIGS. 1A to 4 . 
     The lid assembly  10  according to the present embodiment is attached to an opening of an outer can (outer case) of a primary battery or a secondary battery, and is used as a lid member that closes the opening of the outer can in an airtight and liquid-tight manner. 
       FIGS. 1A and 1B  show the back face side of the lid assembly  10 , and  FIGS. 2A and 2B  show the front face side of the lid assembly  10 . 
     The lid assembly  10  includes a lid  12 , a pair of terminals  14   a  and  14   b , a pair of leads  16   a  and  16   b , an insulating member  18  having an electrical insulation property, and a valve (safety valve)  20  provided to the lid  12 . Gaskets  22   a  and  22   b  having an electrical insulation property are disposed between the lid  12  and the pair of terminals  14   a  and  14   b , respectively. 
     For this purpose, although the lid assembly  10  includes the gaskets  22   a  and  22   b  in the present embodiment, the gaskets  22   a  and  22   b  may be attached to the terminals  14   a  and  14   b  in advance. When a resin material having an electrical insulation property is applied to predetermined positions of the terminals  14   a  and  14   b , for example, the gaskets  22   a  and  22   b  may be unnecessary. 
     When the positive electrode terminal  14   a  and the negative electrode terminal  14   b  are arranged on the lid  12 , a hermetic seal using glass may be used instead of using the insulating gaskets  22   a  and  22   b.    
     For the lid assembly  10  according to the present embodiment, an XYZ orthogonal coordinate system is adopted, as shown in  FIGS. 1A to 3A . 
     As shown in  FIGS. 1B and 2B , the lid  12  has a substantially rectangular plate shape and has a front face  12   a  and a back face  12   b  in the present embodiment. The front face  12   a  is formed as a front face of the lid assembly  10 . The lid  12  has a flat plate shape or a substantially flat plate shape parallel to the XY plane and has an appropriate thickness in the Z-axis direction. The lid  12  is made of a metal such as aluminum, an aluminum alloy, iron, or stainless steel. The thickness of the lid  12  varies depending on the material of the lid  12 ; however, it is preferably, for example, 0.3 mm or more and 2 mm or less. 
     As shown in  FIG. 3A , the lid  12  includes, for example, a pair of long-side edges  13   a  and  13   b  parallel to the X-axis and a pair of short-side edges  13   c  and  13   d  parallel to the Y-axis. The distance between the pair of long-side edges  13   a  and  13   b , that is, the width T1 of the lid  12  (the thickness of the battery  310 ) is smaller than the distance W1 between the pair of short-side edges  13   c  and  13   d  (the width of the battery  310 ). In other words, the length W1 of the pair of long-side edges  13   a  and  13   b  (the length of the lid  12 ) is larger than the length T1 of the pair of short-side edges  13   c  and  13   d.    
     The relationship between the length W1 of the long side of the lid  12  (the distance between the pair of short-side edges  13   c  and  13   d ) and the length T1 of the short side of the lid  12  (the distance between the pair of long-side edges  13   a  and  13   b ) is preferably, for example, 7≤W1/T1≤9. As an example, T1=14 mm and W1=112 mm. In this case, W1/T1=8. 
     The measurement of the distance T1 between the pair of long-side edges  13   a  and  13   b  shown in the  FIG. 3A  is obtained by measuring the length in the Y-axis direction from the long-side edge  13   a  to the other long-side edge  13   b  at the central positions of the respective long-side edges in the X-axis direction. Likewise, the measurement of the distance W1 between the pair of short-side edges  13   c  and  13   d  is obtained by measuring the length in the X-axis direction from the short-side edge  13   c  to the other short-side edge  13   d  at the central positions of the respective short-side edges in the Y-axis direction. For example, Quick Mini PK-1012CPS manufactured by Mitsutoyo Corporation, or a device having a function equivalent thereto, is used for the measurement. 
     A resin material selected from polyester (PET), polyimide, polyphenylene sulfide (PPS), and polypropylene, for example, can be used for the insulating member  18 . As shown in  FIG. 3A , the insulating member  18  has a substantially rectangular shape in the present embodiment. The insulating member  18  includes, for example, a pair of long sides (long-side edges)  19   a  and  19   b  parallel to the X-axis and a pair of short sides (short-side edges)  19   c  and  19   d  parallel to the Y-axis. The distance between the pair of long sides  19   a  and  19   b , that is, the width T2 of the insulating member  18  is smaller than the distance W2 between the pair of short sides  19   c  and  19   d . In other words, the length W2 of the pair of long sides  19   a  and  19   b  (the length of the insulating member  18 ) is larger than the length T2 of the pair of short sides  19   c  and  19   d.    
     The distance T1 between the pair of long-side edges  13   a  and  13   b  of the lid  12  is larger than the distance T2 between the pair of long sides  19   a  and  19   b  of the insulating member  18 . The distance W1 between the pair of short-side edges  13   c  and  13   d  of the lid  12  is larger than the distance W2 between the pair of short sides  19   c  and  19   d . Thus, the outer edge of the insulating member  18  may be disposed inside the outer edge of the lid  12  in the XY plane. 
     In particular, the relationship between the length W2 of the long side of the insulating member  18  (the distance between the pair of short sides  19   c  and  19   d ) and the length T2 of the short side of the insulating member  18  (the distance between the pair of long sides  19   a  and  19   b ) is preferably, for example, 7≤W2/T2≤13. For example, W2 is set to 112 mm, and T2 is set to 14 mm. 
     The pair of terminals  14   a  and  14   b  are formed of a conductive material. The material of the terminal  14   a  and the material of the terminal  14   b  vary depending on the type of the electrolyte of the battery, and the like. When the lid assembly  10  is used as a part of a lithium ion secondary battery, aluminum or an aluminum alloy is used for the positive electrode terminal  14   a . A metal such as copper, nickel, or nickel-plated iron is used for the negative electrode terminal  14   b . Aluminum or an aluminum alloy may also be used for the negative electrode terminal  14   b.    
     One of the terminals  14   a  and  14   b  is used as the positive electrode terminal  14   a , and the other of the terminals  14   a  and  14   b  is used as the negative electrode terminal  14   b . The positive electrode terminal  14   a  and the negative electrode terminal  14   b  are formed in a pin shape with head portions  32   a  and  32   b  and columnar portions  34   a  and  34   b , respectively. The head portions  32   a  and  32   b  have a rectangular parallelepiped shape in the examples shown in  FIGS. 1B and 2B , but may have various shapes such as a cylindrical shape. The columnar portions  34   a  and  34   b  are cylindrical in the examples shown in  FIGS. 1B and 2B , but may have various shapes such as a prismatic shape. 
     As shown in  FIG. 2B , a pair of concave portions  42   a  and  42   b  are formed in the front face  12   a  of the lid  12 . The concave portions  42   a  and  42   b  are substantially rectangular. A through hole  44   a  is formed in the concave portion  42   a , and a through hole  44   b  is formed in the other concave portion  42   b . The concave portions  42   a  and  42   b  may have the same shape or different shapes. A ring-shaped insulating gasket  22   a  having an electrical insulating property and having an opening at the center is disposed in the concave portion  42   a . A ring-shaped insulating gasket  22   b  having an electrical insulating property and having an opening at the center is disposed in the concave portion  42   b.    
     A small hole  46  through which a fluid such as a liquid can be taken in and out from the front face  12   a  side to the side facing the back face  12   b  is formed in the lid  12 . When assembling the battery  310  of the second embodiment shown in  FIG. 16 , which will be described later, the small hole  46  allows a fluid to be taken in and out from the front face  12   a  side to the side facing the back face  12   b . As shown in  FIG. 15 , when the battery  310  is assembled and formed, the small hole  46  is closed by welding, for example, and a communication between the front face  12   a  and the back face  12   b  of the lid  12  is prevented. The pressure resistance performance by the welding until the back face  12   b  and the front face  12   a  of the lid  12  communicate with each other is set larger than the operating pressure (e.g., 1.0 MPa) of the valve  20 . 
     The head portion  32   a  of the positive electrode terminal  14   a  is arranged in the concave portion  42   a  of the lid  12  with the insulating gasket  22   a  having an electrical insulation property interposed therebetween. The head portion  32   b  of the negative electrode terminal  14   b  is arranged in the concave portion  42   b  of the lid  12  with the insulating gasket  22   b  having an electrical insulation property interposed therebetween. The head portions  32   a  and  32   b  of the terminals  14   a  and  14   b  protrude from the front face  12   a  of the lid  12 . The columnar portions  34   a  and  34   b  of the terminals  14   a  and  14   b  protrude from the back face  12   b  of the lid  12 . On this occasion, the positive electrode terminal  14   a  and the negative electrode terminal  14   b  are prevented from electrically contacting the lid  12  by the gaskets  22   a  and  22   b , respectively. Thus, the positive electrode terminal  14   a  and the negative electrode terminal  14   b  are prevented from being electrically connected to each other. 
     As shown in  FIGS. 1B and 2B , the insulating member  18  includes a first face  18   a  in contact with or close to the back face  12   b  of the lid  12 , and a second face  18   b  opposite to the first face  18   a  and facing an electrode group  314 . The second face  18   b  collaborates with the leads  16   a  and  16   b  to form a part of the back face of the lid assembly  10 . 
     Similar to the back face  12   b  of the lid  12 , the first face  18   a  of the insulating member  18  is preferably flat or substantially flat and parallel to the XY plane. 
     For example, two pairs of concave portions  48   a ,  48   a ,  48   b , and  48   b  are formed in the back face  12   b  of the lid  12 . 
     For example, two pairs of protrusions  52   a ,  52   a ,  52   b , and  52   b  are formed on the first face  18   a  of the insulating member  18 . The protrusions  52   a ,  52   a ,  52   b , and  52   b  on the first face  18   a  of the insulating member  18  and the concave portions  48   a ,  48   a ,  48   b , and  48   b  in the back face  12   b  of the lid  12  are fitted to each other, so that the front face of the insulating member  18  may come into close contact with the back face  12   b  of the lid  12 . Also, positional deviation between the lid  12  and the insulating member  18  is suppressed. 
     In the examples shown in  FIGS. 1B and 2B , the number of protrusions  52   a ,  52   a ,  52   b , and  52   b  is the same as the number of concave portions  48   a ,  48   a ,  48   b , and  48   b . The number of protrusions may be smaller than the number of concave portions. 
     Herein, an example in which the short-side edge  13   c  of the lid  12  and the short side  19   c  of the insulating member  18  are close to each other is described; however, the short-side edge  13   c  of the lid  12  and the short side  19   d  of the insulating member  18  may be close to each other. 
     The first face  18   a  of the insulating member  18  includes: a pair of through holes  54   a  and  54   b  through which the columnar portions  34   a  and  34   b  of the terminals  14   a  and  14   b  pass; an opening  56  opposing the valve  20 ; and small holes  58   a  and  58   b  through which a fluid such as a liquid is taken in and out through the small hole  46  of the lid  12 . The through holes  54   a  and  54   b , the opening  56 , and the small holes  58   a  and  58   b  penetrate the second face  18   b . Here, the small holes  58   a  and  58   b  have the same shape. The small holes  58   a  and  58   b  may have different shapes. 
     The second face  18   b  of the insulating member  18  has appropriate irregularities. 
     The second face  18   b  of the insulating member  18  includes: a pair of receiving portions  62   a  and  62   b ; a pair of adjacent faces  64   a  and  64   b  (opposing faces to the electrode group  314 ) that are adjacent to the receiving portions  62   a  and  62   b ; a pair of support face groups  66   a  and  66   b ; and an intermediate region  68 . The adjacent faces  64   a  and  64   b  and the pair of support face groups  66   a  and  66   b  preferably extend in the X-axis direction. 
     As shown in  FIG. 3A , the opening  56  is formed in the intermediate region  68 . The opening  56  is formed between the long sides  19   a  and  19   b  of the insulating member  18  in the intermediate region  68 . The opening  56  is formed between an edge  83   h  of the support face  82   b  of the support face group  66   a  and an edge  85   c  of the support face  84   a  of the support face group  66   b.    
     As shown in  FIG. 1B , the receiving portion  62   a  is adjacent to the pair of adjacent faces  64   a  in the X-axis direction. The receiving portion  62   a  is separated from the intermediate region  68  and is continuous with the pair of adjacent faces (a plurality of opposing faces)  64   a . The support face group  66   a  is disposed between the pair of adjacent faces  64   a  in the Y-axis direction. The receiving portion  62   b  is adjacent to the pair of adjacent faces  64   b  in the X-axis direction. The receiving portion  62   b  is separated from the intermediate region  68  and is continuous with the pair of adjacent faces (a plurality of opposing faces)  64   b . The support face group  66   b  is disposed between the pair of adjacent faces  64   b  in the Y-axis direction. 
     As shown in  FIGS. 1B and 2B , the receiving portion  62   a  is adjacent to the short side  19   c , and the receiving portion  62   b  is adjacent to the short side  19   d . Each of the receiving portions  62   a  and  62   b  is formed as a substantially rectangular region. The through hole  54   a  through which the columnar portion  34   a  of the terminal  14   a  passes is formed in the receiving portion  62   a , and the through hole  54   b  through which the columnar portion  34   b  of the terminal  14   b  passes is formed in the receiving portion  62   b . A base portion  92   a  (described later) of the lead  16   a  is received in the receiving portion  62   a . The receiving portion  62   a  is adjacent to the adjacent face  64   a  and receives the base portion  92   a  of the lead  16   a . A base portion  94   a  (described later) of the other lead  16   b  is received in the receiving portion  62   b . The receiving portion  62   b  is adjacent to the adjacent face  64   a  and receives the base portion  94   a  of the lead  16   b . There may be a level difference between the adjacent face  64   a  and the receiving portion  62   a  and/or between the adjacent face  64   b  and the receiving portion  62   b.    
     As shown in  FIGS. 1A and 1B , the receiving portion  62   a  includes, for example, three walls  72   a ,  72   b , and  72   c . The wall  72   a  is at a position close to the short side  19   c  on the long side  19   a , the wall  72   b  is on the short side  19   c , and the wall  72   c  is at a position close to the short side  19   c  on the long side  19   b . The height of each of the walls  72   a ,  72   b , and  72   c  in the Z-axis direction is greater than the thickness of the base portion  92   a  of the lead  16   a . The walls  72   a  and  72   c  extend along the long sides  19   a  and  19   b  from the short side  19   c  to the adjacent face  64   a . The base portion  92   a  (described later) of the lead  16   a , the adjacent face  64   a , and the support face group  66   a  (support faces  82   a  and  82   b  described later) are arranged between the walls  72   a  and  72   c . The support faces  82   a  and  82   b  protrude relative to the edges of the walls  72   a  and  72   c  toward the side opposite to the lid  12  in the Z-axis direction. 
     Likewise, the receiving portion  62   b  includes, for example, three walls  74   a ,  74   b  and  74   c . The height of each of the walls  74   a ,  74   b  and  74   c  in the Z-axis direction is greater than the thickness of the base portion  94   a  of the lead  16   b . The walls  74   a  and  74   c  are preferably formed in a manner similar to the walls  72   a  and  72   c . The walls  74   a  and  74   c  extend along the long sides  19   a  and  19   b  from the short side  19   d  to the adjacent face  64   b . The base portion  94   a  (described later) of the lead  16   b , the adjacent face  64   b , and the support face group  66   b  (support faces  84   a  and  84   b  described later) are arranged between the walls  74   a  and  74   c . The support faces  84   a  and  84   b  protrude relative to the edges of the walls  74   a  and  74   c  toward the side opposite to the lid  12  in the Z-axis direction. 
     When the first face  18   a  of the insulating member  18  is a flat face parallel to the XY plane, the thickness between the first face  18   a  and the receiving portions  62   a  and  62   b  is preferably smaller than the thickness between the first face  18   a  and the adjacent faces  64   a  and  64   b  of the insulating member  18 . In this case, the receiving portions  62   a  and  62   b  are formed as sectioned regions where the base portions  92   a  and  94   a  of the leads  16   a  and  16   b  are received. 
     In the present embodiment, the pair of adjacent faces  64   a  and  64   b  and the pair of support face groups  66   a  and  66   b  are planes parallel to the XY plane. The pair of support face groups  66   a  and  66   b  (support faces  82   a ,  82   b ,  84   a , and  84   b ) are preferably in the middle position between the long-side edges  13   a  and  13   b  of the lid  12  and between the long sides  19   a  and  19   b  of the insulating member  18 . 
     As shown in  FIG. 3A , the support face group  66   a  includes a plurality of support faces  82   a  and  82   b . The support face group  66   a  includes edges  83   a  to  83   d  defining the support face  82   a  and edges  83   e  to  83   h  defining the other support face  82   b . A substantially rectangular small hole  58   b  is formed between the support faces  82   a  and  82   b . The small hole  46  of the lid  12  may communicate with the small hole  58   b . The small hole  58   b  includes four edges  59   a ,  59   b ,  59   c  and  59   d.    
     Here, each of the support faces  82   a  and  82   b  is a substantially rectangular plane. Thus, in the present embodiment, each of the edges  83   a  to  83   d  and the edges  83   e  to  83   h  is formed to be straight. 
     As shown in  FIG. 4 , the width between the edges  83   a  and  83   b  of the support face  82   a  of the support face group  66   a  is defined as Wα. The width Wα with respect to the distance T1 between the long-side edges  13   a  and  13   b  of the lid  12  is preferably, for example, 0.20≤Wα/T1≤0.45. As an example, Wα is set to 3.9 mm, and T1 is set to 14 mm. In this case, Wα/T1=0.28. 
     The support faces  82   a  and  82   b  may have various shapes other than a substantially rectangular shape, such as a substantially elliptical shape. When the support face  82   a  has a substantially elliptical shape, the width Wα between the edges  83   a  and  83   b  may be defined as the length of the minor axis among the major axis and the minor axis of the ellipse. 
     As shown in  FIG. 3B , the other support face group  66   b  includes the plurality of support faces  84   a  and  84   b . The support face group  66   b  includes edges  85   a  to  85   d  defining the support face  84   a , and edges  85   e  to  85   h  defining the other support face  84   b . A substantially rectangular small hole  58   a  is formed between the support faces  84   a  and  84   b.    
     Here, the small holes  58   a  and  58   b  and the support face groups  66   a  and  66   b  are formed symmetrically with respect to the central axis Cx parallel to the X-axis and the central axis Cy parallel to the Y-axis, respectively. As shown in  FIGS. 3A and 3B , the lid assembly  10  is preferably symmetrical with respect to the central axis Cx parallel to the X-axis and symmetrical with respect to the central axis Cy parallel to the Y-axis, excluding the pair of leads  16   a  and  16   b . As shown in  FIG. 4 , the lid assembly  10  is preferably symmetrical with respect to the central axis Cz parallel to the Z-axis. 
     The small hole  46  of the lid  12  may communicate with the small hole  58   a  depending on the orientation of the insulating member  18  with respect to the lid  12 . The small hole  58   b  includes four edges  59   e ,  59   f ,  59   g  and  59   h.    
     Here, each of the support faces  84   a  and  84   b  is a substantially rectangular plane. The support faces  82   a ,  82   b ,  84   a , and  84   b  are flush with each other. In the present embodiment, each of the edges  85   a ,  85   b ,  85   c , and  85   d  and the edges  85   e ,  85   f ,  85   g , and  85   h  is formed to be straight. 
     In a manner similar to the support faces  82   a  and  82   b , the support faces  84   a  and  84   b  may be formed not only in a substantially rectangular shape but also in various shapes. 
     As shown in  FIG. 4 , the support face group  66   a  is at a position where it protrudes in the Z-axis direction with respect to the adjacent face  64   a , and the support face group  66   b  is at a position where it protrudes in the Z-axis direction with respect to the adjacent face  64   b . For example, standing faces  88   a  and  88   b  along the Z-axis direction are provided between the adjacent face  64   a  and the support face group  66   a . A boundary between the standing face  88   a  and the support face  82   a  forms the edges  83   a  to  83   d . A boundary between the standing face  88   b  and the support face  82   b  forms the edges  83   e  to  83   h . For example, standing faces  88   c  and  88   d  along the Z-axis direction are provided between the adjacent face  64   b  and the support face group  66   b . A boundary between the standing face  88   c  and the support face  84   a  forms the edges  85   a  to  85   d . A boundary between the standing face  88   d  and the support face  84   b  forms the edges  85   e  to  85   h.    
     A boundary between the standing face  88   a  and the adjacent face  64   a  forms edges  89   a  and  89   b . A boundary between the standing face  88   b  and the adjacent face  64   a  forms edges  89   c  and  89   d.    
     As shown in  FIGS. 3B and 4 , a region between the edge  89   a  of the adjacent face  64   a  and an edge  73   a  of the wall  72   a  that forms a boundary with the adjacent face  64   a , between the edge  89   c  of the adjacent face  64   a  and the edge  73   a , and between the edge  59   a  of the small hole  58   b  and the edge  73   a , is defined as S 1 . A region between the edge  89   b  of the adjacent face  64   a  and an edge  73   b  of the wall  72   c  that forms a boundary with the adjacent face  64   a , between the edge  89   d  of the adjacent face  64   a  and the edge  73   b , and between the edge  59   b  of the small hole  58   b  and the edge  73   b , is defined as S 2 . 
     A boundary between the standing face  88   c  and the adjacent face  64   b  forms edge  89   e  and  89   f . A boundary between the standing face  88   d  and the adjacent face  64   b  forms edges  89   g  and  89   h . A region between the edge  89   e  of the adjacent face  64   b  and an edge  73   c  of the wall  74   c  that forms a boundary with the adjacent face  64   b , between the edge  89   g  of the adjacent face  64   b  and the edge  73   c , and between the edge  59   e  of the small hole  58   a  and the edge  73   c  is defined as S 3 . A region between the edge  89   f  of the adjacent face  64   b  and an edge  73   d  of the wall  74   a  that forms a boundary with the adjacent face  64   b , between the edge  89   h  of the adjacent face  64   b  and the edge  73   d , and between the edge  59   f  of the small hole  58   a  and the edge  73   d  is defined as S 4 . 
     The plurality of adjacent faces  64   a  and  64   b  of the insulating member  18  are formed to be flush with each other for simplicity of description. The protruding amount of the support face groups  66   a  and  66   b  with respect to the plurality of adjacent faces  64   a  and  64   b  is larger than the thickness of the base portions  92   a  and  94   a  (described later) of the pair of leads  16   a  and  16   b . Thus, although the support face groups  66   a  and  66   b  may come into contact with the electrode group  314 , the base portions  92   a  and  94   a  of the pair of leads  16   a  and  16   b  do not come into contact with the electrode group  314 . 
     As shown in  FIG. 3A , the support face group  66   a  includes the plurality of edges  83   a  to  83   d  and  83   e  to  83   h  between the base portion  92   a  of the lead  16   a  received in the receiving portion  62   a  and the intermediate region  68 . The support face group  66   b  includes the plurality of edges  85   a  to  85   d  and  85   e  to  85   h  between the base portion  94   a  of the lead  16   b  received in the receiving portion  62   b  and the intermediate region  68 . 
     As shown in  FIG. 3B , the adjacent face  64   a  is formed as a region combining faces S 1  and S 2 . The other adjacent face  64   b  is formed as a region combining faces S 3  and S 4 . The intermediate region  68  also includes regions indicated by faces S 5  and S 6 . 
     As shown in  FIG. 4 , virtual faces VS 1  and VS 2  are supposed to be from the edges  73   a  and  73   b  in the flat adjacent face  64   a  toward the side opposite to the side where the lid  12  is disposed. It is assumed that the virtual faces VS 1  and VS 2  are parallel to the Z-axis. A virtual planar region R 1  parallel to the adjacent face  64   a  is defined between the virtual face VS 1  and the edge  83   a , and a virtual planar region R 2  parallel to the adjacent face  64   a  is defined between the virtual face VS 2  and the edge  83   b . The regions R 1  and R 2  are parallel to the XY plane. The regions R 1  and R 2  are substantially congruent with the faces S 1  and S 2 . That is, the areas of the regions R 1  and R 2  substantially coincide with the areas of the faces S 1  and S 2 . When one end of the region R 1  is defined to be on the virtual face VS 1 , the other end of the region R 1  may be at any position between the edge  83   a  and the edge  89   a . When the one end of the region R 2  is defined to be on the virtual face VS 2 , the other end of the region R 2  may be at any position between the edge  83   b  and the edge  89   b.    
     As shown in  FIGS. 1A and 1B , the lead  16   a  includes the base portion  92   a  and one leg portion  92   b  extending from the base portion  92   a . The base portion  92   a  and the leg portion  92   b  are formed of a single plate having the same thickness by press working or the like. The leg portion  92   b  is bent with respect to the base portion  92   a . The base portion  92   a  is formed in a substantially rectangular flat plate shape. The base portion  92   a  has an opening  92   c  in which the columnar portion  34   a  of the terminal  14   a  is disposed. The base portion  92   a  in a flat plate shape is preferably parallel to the XY plane. 
     The leg portion  92   b  may be in contact with a fixing member  354   a  of the electrode group  314  described later. The leg portion  92   b  extends in the Z-axis direction toward the side opposite to the lid  12 . The leg portion  92   b  does not extend straight in the Z-axis direction from the base portion  92   a , but is bent in the Y-axis direction, for example, in the region indicated by the reference numeral  93 . In particular, with the base portion  92   a  of the lead  16   a  arranged in the receiving portion  62   a , the leg portion  92   b  is bent from the wall  72   c  toward the wall  72   a  in the region indicated by the reference numeral  93 . This is for the purpose of imparting to the leg portion  92   b  such springiness that it is certainly brought into contact with the fixing member  354   a  of the electrode group  314 . The region indicated by the reference numeral  93  is preferably at a position close to the base portion  92   a  in the leg portion  92   b . This is for the purpose of making the contact area between the leg portion  92   b  and the fixing member  354   a  described later as large as possible. Also, the length of the leg portion  92   b  along the Z-axis direction is preferably as small as possible, although it depends on the positional relationship with the fixing member  354   a.    
     As shown in  FIG. 3A , the thickness of the leg portion  92   b  of the lead  16   a  (the thickness in the Y-axis direction) is defined as t. The thickness direction of the leg portion  92   b  of the lead  16   a  is parallel to the direction of the distance T1 between the long-side edges  13   a  and  13   b  of the lid  12  (Y-axis direction). In this case, 0.20≤t/T1≤0.45, for example, is preferably satisfied. As an example, t=3 mm and T1=14 mm. In this case, t/T1=0.21. 
     The size (width) of the leg portion  92   b  in the direction along the X-axis direction is preferably larger than the size (thickness t) thereof in the direction along the Y-axis direction. The length of the leg portion  92   b  along the Z-axis direction is larger than the width thereof in the X-axis direction and the thickness thereof along the Y-axis direction. 
     As shown in  FIG. 1B , the base portion  92   a  of the lead  16   a  of the pair of leads  16   a  and  16   b  having conductivity is disposed in the receiving portion  62   a  of the second face  18   b  of the insulating member  18 . The columnar portion  34   a  of the terminal  14   a  is disposed in the receiving portion  62   a  through the through hole  44   a  of the lid  12  and the through hole  54   a  of the insulating member  18 . The columnar portion  34   a  of the terminal  14   a  is caulked in a state of being disposed in the opening  92   c  of the base portion  92   a  of the lead  16   a  disposed in the receiving portion  62   a . Thus, the terminal  14   a  holds and fixes the lid  12 , the insulating member  18 , and the base portion  92   a  of the lead  16   a . On this occasion, the terminal  14   a  and the lead  16   a  are electrically connected to each other. 
     Likewise, the other lead  16   b  includes the base portion  94   a  and one leg portion  94   b  extending from the base portion  94   a . The base portion  94   a  is formed in a substantially rectangular flat plate shape. The base portion  94   a  has an opening  94   c  in which the columnar portion  34   b  of the terminal  14   b  is disposed. The base portion  94   a  in a flat plate shape is preferably parallel to the XY plane. 
     As shown in  FIG. 1B , the leg portion  94   b  may be in contact with a fixing member  356   a  of the electrode group  314  described later. The leg portion  94   b  extends in the Z-axis direction toward the side opposite to the lid  12 . The leg portion  94   b  does not extend straight in the Z-axis direction from the base portion  94   a , but is bent in the Y-axis direction, for example, in the region indicated by the reference numeral  95 . In particular, with the base portion  94   a  of the lead  16   h  arranged in the receiving portion  62   b , the leg portion  94   b  is bent from the wall  74   c  toward the wall  74   a  in the region indicated by the reference numeral  95 . This is for the purpose of imparting to the leg portion  94   b  such springiness that it is certainly brought into contact with the fixing member  356   a  of the electrode group  314 . The region indicated by the reference numeral  95  is preferably at a position close to the base portion  94   a  in the leg portion  94   b . This is for the purpose of making the contact area between the leg portion  94   b  and the fixing member  356   a  described later as large as possible. Also, the length of the leg portion  94   b  along the Z-axis direction is preferably as small as possible, although it depends on the positional relationship with the fixing member  356   a.    
     The base portion  94   a  of the other lead  16   b  of the pair of leads  16   a  and  16   b  having conductivity is disposed in the receiving portion  62   b  of the second face  18   b  of the insulating member  18 . The base portion  94   a  of the other lead  16   b  has an opening  94   c  in which the columnar portion  34   b  of the terminal  14   b  is disposed. The columnar portion  34   b  of the terminal  14   b  is fixed to the base portion  94   a  by caulking. Thus, the terminal  14   b  holds and fixes the lid  12 , the insulating member  18 , and the base portion  94   a  of the lead  16   b . On this occasion, the terminal  14   b  and the lead  16   b  are electrically connected to each other. 
     Therefore, the pair of terminals  14   a  and  14   b  are separated from each other in an electrically insulated state and disposed on the lid  12 . The pair of leads  16   a  and  16   b  are separated from each other in a state of being electrically insulated from each other by the gaskets  22   a  and  22   b.    
     As shown in  FIGS. 1A and 1B , the valve  20  is integrally formed with the lid  12 . The valve  20  is provided on the lid  12  between the pair of terminals  14   a  and  14   b . The valve  20  is formed by, for example, press working. The valve  20  is adjacent to the opening  56  in the intermediate region  68  of the insulating member  18 . The valve  20  may be opened toward the side where the head portions  32   a  and  32   b  of the pair of terminals  14   a  and  14   b  are disposed (the front face  12   a  side of the lid  12 ) in response to the pressure on the side where the insulating member  18  and the pair of leads  16   a  and  16   b  are disposed on the lid  12  (the back face  12   b  side of the lid  12 ) reaching a predetermined pressure. The predetermined pressure for opening the valve  20  can be suitably set. 
     As shown in  FIG. 3A , the valve  20  includes an outer border  102  and groove  104  inside the outer border  102 . The groove  104  of the valve  20  is formed in an “X” shape inside the outer border  102 . A maximum possible opening area S (not shown) with which the valve  20  may be opened is equal to or smaller than the area of the pair of flat adjacent faces  64   a  and  64   b . That is, the maximum possible opening area S with which the valve  20  may be opened is equal to or smaller than the area of the region combining the faces S 1 , S 2 , S 3 , and S 4  (the area of the pair of adjacent faces  64   a  and  64   b ). 
     The maximum possible opening area S with which the valve  20  may be opened may be equal to or smaller than the area of the region combining the faces S 5  and S 6  in the intermediate region  68  in addition to the area of the pair of adjacent faces  64   a  and  64   b.    
     The maximum possible opening area with which the valve  20  may be opened is equal to or smaller than the area of the combination of the virtual planar regions R 1  and R 2  in the adjacent face  64   a  and the area of the combination of the virtual planar regions (not shown) in the adjacent face  64   b.    
     The maximum possible opening area with which the valve  20  may be opened is equal to or smaller than the area of the opening  56  of the insulating member  18 . 
     EXAMPLES 
     A lid assembly  10  having the structure shown in  FIGS. 1 to 4  was produced with the distance W1 between the pair of short-side edges  13   c  and  13   d  being 112 mm, the distance T1 between the pair of long-side edges  13   a  and  13   b  being 14 mm, and the thickness of the lid  12  being 1 mm. The operating pressure of the valve  20  of the lid assembly  10  was set to 1.0 MPa. 
     Then, an appropriate outer case was prepared for the lid assembly  10 , and the inside of the outer case was sealed with the lid assembly  10 . The internal pressure of the outer case was gradually increased from atmospheric pressure at a rate of, for example, 0.2 MPa/min. When the internal pressure of the outer case reached 1.0 MPa, the valve  20  was cut into an “X” shape along the groove  104 . Thus, the internal pressure of the outer case was decreased by the cutting of the groove  104  of the valve  20 . 
     When the internal pressure of the outer case reached 1.0 MPa, the pressure of 1.0 MPa was also applied to the leads  16   a  and  16   b  and the insulating member  18  in the same manner as applied to the valve  20 . Even with the application of such pressure and the cutting of the groove  104  of the valve  20 , there was no change in the appearance or the dimensions of the leads  16   a  and  16   b  and the insulating member  18 . Thus, it was confirmed that the leads  16   a  and  16   b  and the insulating member  18  according to the present embodiment can fulfill their respective functions even when the internal pressure of the outer case is increased to a predetermined state. 
     Therefore, the lid assembly  10  according to the present embodiment includes the valve  20  which is provided on the lid  12  between the pair of terminals  14   a  and  14   b , is adjacent to the opening  56  in the intermediate region  68  of the insulating member  18 , and may be opened toward the side where the pair of terminals  14   a  and  14   b  are disposed in response to the pressure on the side where the pair of leads  16   a  and  16   b  and the insulating member  18  are disposed on the lid  12  reaching a predetermined pressure. In the present embodiment, the lid assembly  10  is provided in which the maximum possible opening area with which the valve  20  may be opened is equal to or smaller than the area of the planes S 1 , S 2 , S 3 , and S 4  of the plurality of adjacent faces  64   a  and  64   b.    
     Also, a lid assembly  10  is provided in which, when virtual faces VS 1  and VS 2  are defined from the outer edges of the planes of the plurality of adjacent faces (opposing faces)  64   a  and  64   b  toward the side opposite to the lid  12  and virtual planar regions R 1  and R 2  parallel to the planes of the plurality of adjacent faces  64   a  and  64   b  are defined between the virtual faces VS 1  and VS 2  and the plurality of edges  83   a  and  83   b , the maximum possible opening area with which the valve  20  may be opened is equal to or smaller than the area of the planar regions R 1  and R 2 . 
     First Modification 
     Next, a first modification will be described with reference to  FIG. 5 . Here, the insulating member  18  will be described as including walls  72   a ,  72   c , and walls  74   a ,  74   c  that are almost the same as those described in the first embodiment. 
     In the first embodiment, the standing face  88   a  is described as being parallel to the Z-axis. In the present modification, the standing face  88   a  is inclined with respect to the Z-axis. 
     The walls  72   a  and  72   c  are also not parallel to the Z-axis, and are inclined with respect to the Z-axis. In the wall  72   a , an edge  75   a  separated from the adjacent face  64   a  to the side opposite to the side where the lid  12  is disposed is defined. A virtual face VS 1  is defined from the edge  75   a  toward the side opposite to the side where the lid  12  is disposed. In the wall  72   c , an edge  75   b  separated from the adjacent face  64   a  to the side opposite to the side where the lid  12  is disposed is defined. A virtual face VS 2  is defined from the edge  75   b  toward the side opposite to the side where the lid  12  is disposed. It is assumed that the virtual faces VS 1  and VS 2  are parallel to the Z-axis. A virtual planar region R 1  parallel to the adjacent face  64   a  is defined between the virtual face VS 1  and the edge  83   a , and a virtual planar region R 2  parallel to the adjacent face  64   a  is defined between the virtual face VS 2  and the edge  83   b . The regions R 1  and R 2  are parallel to the XY plane. 
     The region R 1  may be larger than the region S 1 , and the region R 2  may be larger than the region S 2 . In this case as well, the maximum possible opening area with which the valve  20  may be opened is equal to or smaller than the area of the combination of the virtual planar regions R 1  and R 2  in the adjacent face  64   a  and the area of the combination of the planar regions (not shown) in the adjacent face  64   b.    
     A maximum possible opening area S with which the valve  20  may be opened is equal to or smaller than the area of the pair of flat adjacent faces  64   a  and  64   b . That is, the maximum possible opening area S with which the valve  20  may be opened is equal to or smaller than the area of the region combining the faces S 1  (&lt;R 1 ), S 2  (&lt;R 2 ), S 3 , and S 4 . 
     Second Modification 
     Next, a second modification will be described with reference to  FIG. 6 . Here, the cross section of the region including the support face  82   a  of the support face group  66   a  will be described. Since the description applies to the cross section of the region including the support face  82   b  of the support face group  66   a  and the cross section of the region including the support faces  84   a  and  84   b  of the support face group  66   b , the description thereof will be omitted as appropriate. The same applies to the description of a third modification and subsequent modifications. 
     In the first embodiment and the first modification, the examples in which the adjacent faces (opposing faces)  64   a  and  64   b  are planes is described. In the present modification, an example in which the adjacent face (opposing face)  64   a  is a non-smooth face (uneven face) having unevenness will be described. Herein, an example in which the adjacent face  64   a  has unevenness will be described; however, the adjacent face (opposing face)  64   b  may be a non-smooth face (uneven face) having unevenness. The “non-smooth face (uneven face)” used herein includes all faces that are not flat, such as a concave face and a convex face. 
     As shown in  FIG. 6 , the adjacent face  64   a  is formed as a non-smooth face (uneven face) with a concave portion and/or a convex portion. In this case, in the adjacent face  64   a , the face S 1  is defined between the edge  73   a  of the wall  72   a  forming a boundary with the adjacent face  64   a  and the edge  89   a , and the face S 2  is defined between the edge  73   b  of the wall  72   c  forming a boundary with the adjacent face  64   a  and the edge  89   b . Herein, virtual planar regions R 1  and R 2  intersecting with the adjacent face  64   a  having a concave portion and/or a convex portion are defined. The area of the face R 1  is slightly smaller than the area of the face S 1 , and the area of the face R 2  is slightly smaller than the area of the face S 2 . 
     The adjacent face  64   a  may be approximated to a region combining the virtual planes R 1  and R 2 . 
     Therefore, the lid assembly  10  according to the present embodiment includes the plurality of adjacent faces (opposing faces)  64   a  and  64   b  which are arranged on the side opposite to the lid  12  and between the base portions  92   a  and  94   a  of the pair of leads  16   a  and  16   b , and for which the virtual planes R 1  and R 2  parallel to at least a part of the front face of the lid  12  are defined. A maximum possible opening area S (not shown) with which the valve  20  may be opened is equal to or smaller than the area of the pair of adjacent faces  64   a  and  64   b  as virtual planes. The virtual planes R 1  and R 2  can be approximated to the faces S 1  and S 2 . That is, the maximum possible opening area S with which the valve  20  may be opened is equal to or smaller than the approximated area of the region combining the faces S 1 , S 2 , S 3 , and S 4  (the area of the pair of adjacent faces  64   a  and  64   b ). Thus, in the present modification, a lid assembly  10  is provided in which the maximum possible opening area with which the valve  20  may be opened is equal to or smaller than the area of the faces S 1 , S 2 , S 3 , and S 4  of the plurality of adjacent faces  64   a  and  64   b.    
     Third Modification 
     Next, a third modification will be described with reference to  FIG. 7 . In  FIG. 7 , the adjacent face  64   a  is illustrated as being the same as those described in the first embodiment and the first modification; however, the adjacent face  64   a  may be the same as that described in the second modification. 
     In the first embodiment, the first modification, and the second modification, each support face  82   a  of the support face group  66   a  is described as being parallel to the XY plane. 
     As shown in  FIG. 7 , the support face  82   a  may be formed so as to protrude toward the side opposite to the lid  12  (Z-axis direction) with respect to the edges  83   a  and  83   b.    
     Fourth Modification 
     Next, a fourth modification will be described with reference to  FIG. 8 . This modification is a further modification of the third modification. 
     As shown in  FIG. 8 , the support face  82   a  may be formed so as to be depressed toward the back face  12   b  of the lid  12  with respect to the edges  83   a  and  83   b.    
     Although not shown, the support face  82   a  may be formed by combining one or more concave portions and/or one or more convex portions. The one or more concave portions and/or the one or more convex portions may include a non-slip feature such as pear skin finish. 
     Fifth Modification 
     Next, a fifth modification will be described with reference to  FIGS. 9 to 11 . The structures of the insulating members  18  of the first embodiment and the modifications described above can be appropriately combined with the insulating member  18  of the present modification. 
     The small holes  58   a  and  58   b  and the support face groups  66   a  and  66   b  of the insulating member  18  of the lid assembly  10  of the first embodiment have been described as being formed symmetrically with respect to the central axis Cx parallel to the X-axis and the central axis Cy parallel to the Y-axis, respectively. In the present modification, an example in which the small holes  58   a  and  58   b  and the support face groups  66   a  and  66   b  are asymmetrical with respect to the central axis Cy, as shown in  FIGS. 9 to 11 , will be described. 
     The walls  72   a  and  72   c  herein extend from the short side  19   c  along the long sides  19   a  and  19   b  to the boundary between the receiving portion  62   a  and the adjacent face  64   a . The base portion  92   a  (described later) of the lead  16   a  is arranged between the walls  72   a  and  72   c . Thus, the walls  72   a  and  72   c  are shorter than the walls  72   a  and  72   c  described in the first embodiment. The walls  74   a  and  74   c  herein extend from the short side  19   d  along the long sides  19   a  and  19   b  to the boundary between the receiving portion  62   b  and the adjacent face  64   b . The base portion  94   a  (described later) of the lead  16   b  is arranged between the walls  74   a  and  74   c . Thus, the walls  74   a  and  74   c  are shorter than the walls  74   a  and  74   c  described in the first embodiment. In this manner, the positions of the ends of the walls  72   a ,  72   c ,  74   a , and  74   c  are suitably set. 
     As shown in  FIGS. 10A and 10B , the lid assembly  10  of the present modification is symmetrical with respect to the central axis Cx parallel to the X-axis, excluding the pair of leads  16   a  and  16   b . The small hole  58   b  is formed in the same manner as described in the first embodiment. 
     A tubular portion  86  having a substantially cylindrical shape, for example, is formed between the support faces  84   a  and  84   b . The tubular portion  86  communicates with the small hole  58   a  having a shape different from that described in the first embodiment. The small hole  46  of the lid  12  may communicate with the tubular portion  86 . The small holes  58   a  and  58   b  may have different shapes. 
     Herein, the edges  85   d  and  85   g  are formed in the same arc shape as that of the outer edge of the tubular portion  86 . 
     As shown in  FIGS. 9 to 10B , the position in the Z-axis direction of the end face  86   a  of the tubular portion  86  that may face the electrode group  314  is different from that of the plurality of support faces  84   a  and  84   b . In particular, the height (distance) of the end face  86   a  with respect to the adjacent face  64   b  is smaller than the height (distance) of the support faces  84   a  and  84   b  with respect to the adjacent face  64   b . Thus, the end face  86   a  of the tubular portion  86  is not in contact with the electrode group  314 , and may be included as a part of the adjacent face (opposing face)  64   b . Therefore, the adjacent face  64   b  may include steps different in distance to the support faces  84   a  and  84   b  in the Z-axis direction. 
     A region of the end face  86   a  of the tubular portion  86  is defined as S 7 . The adjacent face  64   a  is formed as a region combining the faces S 1  and S 2 . The other adjacent face  64   b  is formed as a region combining the faces S 3 , S 4 , and S 7 . The intermediate region  68  also includes regions indicated by faces S 5  and S 6 . 
     Herein, as shown in  FIGS. 10B and 11 , a region between the edge  89   a  of the adjacent face  64   a  and the long side  19   a , between the edge  89   c  of the adjacent face  64   a  and the long side  19   a , and between the edge  59   a  of the small hole  58   b  and the long side  19   a  is defined as S 1 . A region between the edge  89   b  of the adjacent face  64   a  and the long side  19   b , between the edge  89   d  of the adjacent face  64   a  and the long side  19   b , and between the edge  59   b  of the small hole  58   b  and the long side  19   b  is defined as S 2 . 
     As shown in  FIGS. 10A and 10D , a region between the edge  89   e  of the adjacent face  64   b  and the long side  19   a , between the edge  89   g  of the adjacent face  64   b  and the long side  19   a , and between the edge  59   i  of the small hole  58   a  and the long side  19   a  is defined as S 3 . A region between the edge  89   f  of the adjacent face  64   b  and the long side  19   b , between the edge  89   h  of the adjacent face  64   b  and the long side  19   b , and between the edge  59   j  of the small hole  58   a  and the long side  19   b  is defined as S 4 . The maximum possible opening area S with which the valve  20  may be opened is equal to or smaller than the area of the region combining the faces S 1 , S 2 , S 3 , S 4 , and S 7 . 
     The maximum possible opening area S with which the valve  20  may be opened may be equal to or smaller than the area of the region combining the faces S 5  and S 6  in the intermediate region  68  in addition to the area of the pair of adjacent faces  64   a  and  64   b.    
     Sixth Modification 
     Next, a sixth modification will be described with reference to  FIGS. 12 and 13 . The structures of the insulating members  18  of the first embodiment and the modifications described above can be appropriately combined with the insulating member  18  of the present modification. 
     The support face group  66   a  of the lid assembly  10  of the first embodiment is described as including a plurality of support faces  82   a  and  82   b . In the present modification, as shown in  FIGS. 12 and 13 , the support face group  66   a  of the lid assembly  10  includes only one support face  82 . In  FIG. 12 , the tubular portion  86  is formed between the support faces  84   a  and  84   b  of the support face group  66   b . Instead of the tubular portion  86 , the small hole  58   a  (see  FIG. 1A ) may be formed. 
     As shown in  FIG. 4 , virtual faces VS 1  and VS 2  are defined from the edges  73   a  and  73   b  in the flat adjacent face  64   a  toward the side opposite to the side where the lid  12  is disposed. It is assumed that the virtual faces VS 1  and VS 2  are parallel to the Z-axis. A virtual planar region R 1  parallel to the adjacent face  64   a  is defined between the virtual face VS 1  and the edge  83   a , and a virtual planar region R 2  parallel to the adjacent face  64   a  is defined between the virtual face VS 2  and the edge  83   b . The regions R 1  and R 2  are parallel to the XY plane. The regions R 1  and R 2  are substantially congruent with the faces S 1  and S 2 . That is, the areas of the regions R 1  and R 2  substantially coincide with the areas of the faces S 1  and S 2 . Therefore, the maximum possible opening area S with which the valve  20  may be opened is equal to or smaller than the area of the region combining the faces S 1 , S 2 , S 3 , and S 4  (the area of the pair of adjacent faces  64   a  and  64   b ). 
     In the first embodiment, a description is given in which the short-side edge  13   c  of the lid  12  and the short side  19   d  of the insulating member  18  may be brought close to each other. Herein, because the small hole  46  is closed in this state, the short-side edge  13   c  of the lid  12  and the short side  19   c  of the insulating member  18  need to be brought close to each other. That is, in regard to the relationship between the lid  12  and the insulating member  18  according to the present embodiment, the orientations of the lid  12  and the insulating member  18  are appropriately defined. 
     Seventh Modification 
     Next, a seventh modification will be described with reference to  FIG. 14 . 
     In the first embodiment, the example in which the valve  20  has the X-shaped groove  104  is described. In the present modification, the groove  104  of the valve  20  is formed in a pair of “Y” shapes opposing to each other with a common leg inside the outer border  102 . 
     The outer border  102  of the valve  20  is not limited to a substantially rectangular shape, and may have various shapes such as a substantially elliptical shape. 
     In the first embodiment, the case where the valve  20  is exposed to the front face  12   a  of the lid  12  is described; however, the valve  20  need not necessarily be exposed to the front face  12   a  of the lid  12 . 
     Second Embodiment 
     Next, a second embodiment will be described with reference to  FIGS. 15 to 19 . 
     In the present embodiment, a battery  310  will be described in which the lid assembly  10  described in the first embodiment including the modifications may be used. 
     With the progress of electronic devices such as mobile phones and personal computers, secondary batteries used in these devices have been required to be reduced in size and weight. A lithium ion secondary battery is an example of a secondary battery having a high energy density that meets such demand. On the other hand, secondary batteries such as lead storage batteries and nickel-metal hydrogen batteries have been used as large-size and large-capacity power sources typified by use in electric vehicles, hybrid vehicles, electric motorcycles, forklifts, and the like. In recent years, the use of lithium ion secondary batteries having a high energy density has been actively developed. In the development of lithium ion secondary batteries to meet the demand, large-sized and large-capacity lithium ion secondary batteries have been developed while taking long life, safety, and the like into consideration. 
     In the nonaqueous electrolyte batteries such as lithium ion secondary batteries, batteries having approximately 10 Ah, for example, generally have a small thickness and a large height and width. However, it is considered that such a thin battery has difficulty in holding the electrode group and has difficulty in securing a gas flow channel. 
     In the present embodiment, an example will be described in which the representative lid assembly  10  among the modifications of the first embodiment is used. Although not shown in the figures, the lid assembly  10  described in each modification of the first embodiment may be used as a part of the battery  310 . 
     In the present embodiment, the battery  310  includes an outer case  312 , the electrode group  314 , and the lid assembly  10 . 
     In a manner similar to the first embodiment, an XYZ orthogonal coordinate system is adopted. The height of the battery  310  on the outer side of the battery is defined as H11, the width thereof is defined as W11, and the thickness thereof is defined as T11. 
     As an example of the battery  310 , a lithium ion secondary battery as a nonaqueous electrolyte battery capable of charge and discharge will be described. 
     The outer case  312  includes a bottom wall  322  and sidewalls  324 . The outer case  312  has a bottomed tubular shape, and an opening  326  is formed by the sidewalls  324 . 
     The bottom wall  322  is formed in a substantially rectangular shape. The bottom wall  322  is parallel to the XY plane and includes a pair of long-side edges  332   a  and  332   b  parallel to the X-axis direction and a pair of short-side edges  334   a  and  334   b  parallel to the Y-axis direction. The sidewalls  324  include: a pair of long-side sidewalls  336   a  and  336   b , with the long-side edge  332   a  of the bottom wall  322  as a boundary with the long-side sidewall  336   a , and with the long-side edge  332   b  of the bottom wall  322  as a boundary with the long-side sidewall  336   b ; and a pair of short-side sidewalls  338   a  and  338   b , with the short-side edge  334   a  of the bottom wall  322  as a boundary with the short-side sidewall  338   a , and with the short-side edge  334   b  of the bottom wall  322  as a boundary with the short-side sidewall  338   b . The sidewalls  336   a ,  336   b ,  338   a , and  338   b  extend parallel to the Z-axis from the bottom wall  322  toward the opening  326 . 
     In a manner similar to the bottom wall  322 , the opening  326  is parallel to the XY plane. The opening  326  has a substantially rectangular shape including a pair of long sides (long-side edges)  342   a  and  342   b  parallel to the X-axis direction and a pair of short sides (short-side edges)  344   a  and  344   b  parallel to the Y-axis direction. Therefore, the outer case  312  of the present embodiment has a square can shape. 
     The distance T12 (&lt;T11) between the long sides  342   a  and  342   b  of the opening  326  can be substantially equated with the distance between the inner walls of the pair of long-side sidewalls  336   a  and  336   b . The distance T12 can be substantially equated with the distance T2 between the pair of long sides  19   a  and  19   b  of the insulating member  18  of the lid assembly  10 . The distance W12 (&lt;W11) between the short sides  344   a  and  344   b  of the opening  326  can be substantially equated with the distance between the inner walls of the pair of short-side sidewalls  338   a  and  338   b . The distance W12 can be substantially equated with the distance W2 between the pair of short sides  19   c  and  19   d  of the insulating member  18  of the lid assembly  10 . 
     Herein, 7≤W12/T12≤13 is preferably satisfied. 0.02≤Wα/T12≤0.04 is preferably satisfied. 
     The outer case  312  is formed of, for example, a plate made of a metal. For example, aluminum, an aluminum alloy, iron, stainless steel, or the like may be used as the metal. The lid  12  of the lid assembly  10  is preferably made of the same material as that of the outer case  312 , but may be made of a different material. 
     The long-side sidewalls  336   a  and  336   b  of the outer case  312  occupy the largest area of the outer case  312 . Therefore, it is preferable to reduce the thickness of the plate forming the long-side sidewalls  336   a  and  336   b  of the outer case  312  to the extent possible to improve the heat dissipation capability of the battery  310 . The thickness of the plate forming the long-side sidewalls  336   a  and  336   b  of the outer case  312  is preferably 2.0 mm or less, and more preferably 1.0 mm or less. 
     On the other hand, the stiffness decreases as the plate thickness of the long-side sidewalls  336   a  and  336   b  of the outer case  312  decreases. Thus, for example, the thickness of the plate forming the long-side sidewalls  336   a  and  336   b  of the outer case  312  is preferably 0.3 mm or more, and more preferably 0.5 mm or more. 
     Like the plate thickness of the long-side sidewalls  336   a  and  336   b , the thickness of the plate forming the short-side sidewalls  338   a  and  338   b  of the outer case  312  is also preferably 2.0 mm or less, and more preferably 1.0 mm or less. Like the plate thickness of the long-side sidewalls  336   a  and  336   b  and the plate thickness of the short-side sidewalls  338   a  and  338   b , the plate thickness of the bottom wall  322  is also preferably 2.0 mm or less, and more preferably 1.0 mm or less. 
     The plate thickness of each of the bottom wall  322 , the long-side sidewalls  336   a  and  336   b , and the short-side sidewalls  338   a  and  338   b  of the outer case  312  is obtained by measuring the thickness of the central portion of the plate using a micrometer. For example, Quick Mini PK-1012CPS manufactured by Mitsutoyo Corporation, or a device having a function equivalent thereto is used as the micrometer. 
     The plate thickness of the bottom wall  322  of the outer case  312  is obtained by the following process. First, the plate forming the bottom wall  322  is cut in parallel with the YZ plane at the central position along the X-axis direction. Next, the plate thickness is measured at the central position along the Y-axis direction of the cut face, and set as the plate thickness of the bottom wall  322  of the outer case  312 . 
     The thickness of the plate forming the long-side sidewalls  336   a  and  336   b  of the outer case  312  is obtained by the following process. First, the plate forming the long-side sidewalls  336   a  and  336   b  is cut in parallel with the XY plane at the central position along the Z-axis direction. Next, the plate thickness is measured at the central position along the X-axis direction of the cut face, and set as the plate thickness of the long-side sidewalls  336   a  and  336   b  of the outer case  312 . 
     The thickness of the plate forming the short-side sidewalls  338   a  and  338   b  of the outer case  312  is obtained by the following process. First, the plate forming the short-side sidewalls  338   a  and  338   b  is cut in parallel with the XY plane at the central position along the Z-axis direction. Next, the plate thickness is measured at the central position along the Y-axis direction of the cut face, and set as the plate thickness of the short-side sidewalls  338   a  and  338   b  of the outer case  312 . 
     The electrode group  314  includes a positive electrode  362 , a negative electrode  364 , and a plurality of separators (electrical insulating layers)  366 . Each of the positive electrode  362 , the negative electrode  364 , and the separators  366  is formed in, for example, a strip shape with a sufficient length with respect to the width. The separator  366  is disposed between the positive electrode  362  and the negative electrode  364 . When the positive electrode  362 , the separator  366 , and the negative electrode  364  are wound in a roll shape about a winding axis Ra in this state, a rolled body  352  is formed. The rolled body  352  is formed into a flat shape after it is wound or while it is wound. 
     In this case, the electrode group  314  includes the rolled body  352  formed in a flat shape, a positive electrode current-collecting tab  354 , and a negative electrode current-collecting tab  356 . The positive electrode current-collecting tab  354  and the negative electrode current-collecting tab  356  are separated from each other along the winding axis. The separator  366  is exposed on an outer face of the rolled body  352 . 
     The positive electrode  362  of the rolled body  352  of the electrode group  314  includes a positive electrode current collector  362   a  and a positive electrode active material-containing layer  362   b . The positive electrode current-collecting tab  354  is a portion not covered with the positive electrode active material-containing layer  362   b  on the positive electrode current collector  362   a.    
     The positive electrode current collector  362   a  is, for example, a metal foil of aluminum, an aluminum alloy, copper, nickel, or the like. The positive electrode current-collecting tab  354  may not be integrated with the positive electrode current collector  362   a . That is, the positive electrode current-collecting tab  354  may be formed by bonding a metal foil to one of the long sides of the positive electrode current collector  362   a . The metal foil may be the same as that used for the positive electrode current collector  362   a.    
     The positive electrode active material-containing layer  362   b  may be provided on either both or one of the main surfaces of the positive electrode current collector  362   a . The positive electrode active material-containing layer  362   b  includes a positive electrode active material. The positive electrode active material-containing layer  362   b  may include a conductive agent and a binder in addition to the positive electrode active material. 
     For example, a lithium transition metal composite oxide is used as the positive electrode active material. Examples of the lithium transition metal composite oxide include LiCoO 2 , LiNi 1-x Co x O 2  (0&lt;x&lt;0.3), LiMn x Ni y Co z O 2  (0&lt;x&lt;0.5, 0&lt;y≤0.8, 0≤z&lt;0.5), LiMn 2-x M x O 4  (M is at least one element selected from the group consisting of Mg, Co, Al and Ni, 0&lt;x&lt;0.2), and LiMPO 4  (M is at least one element selected from the group consisting of Fe, Co, Ni and Mn). 
     The average particle size of the secondary particles of the positive electrode active material is preferably 10 μm or less, and more preferably 6 μm or less. When the average particle size of the secondary particles of the positive electrode active material is small, the internal resistance is small, and thus heat dissipation accompanying charge and discharge tends to be small. Therefore, when the average particle size of the secondary particles of the positive electrode active material is small, the life performance of the battery  310  can be improved. 
     The conductive agent improves the electron conductivity of the electrode. A carbonaceous material such as acetylene black, carbon black, or graphite may be used as the conductive agent. 
     The binder increases the adhesion between the active material, the conductive agent, and the current collector. Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, or the like may be used as the binder. 
     In the positive electrode active material-containing layer  362   b , the mixing ratio of the positive electrode active material, the conductive agent, and the binder is preferably set as follows: the positive electrode active material in the range of 80% to 95% by mass, the conductive agent in the range of 3% to 18% by mass, and the binder in the range of 2% to 7% by mass. 
     The density of the positive electrode active material-containing layer  362   b  is preferably from 2.79/cm 3  to 3.39/cm 3 . It has been found that when the density of the positive electrode active material-containing layer  362   b  is within this range, the life performance of the battery  310  tends to be high. That is, when the density of the positive electrode active material-containing layer  362   b  is 3.39/cm 3  or less, twisting of the positive electrode is less likely to occur during gas generation, and widening of the distance between the electrodes can be suppressed, allowing for improvement of the performance of the battery  310 . Also, when the density of the positive electrode active material-containing layer  362   b  is 2.79/cm 3  or more, the distance between the positive electrode active material particles becomes appropriate, and thus the internal resistance tends to be decreased. 
     The negative electrode  364  of the rolled body  352  of the electrode group  314  includes a negative electrode current collector  364   a  and a negative electrode active material-containing layer  364   b . The negative electrode current-collecting tab  356  is a portion not covered with the negative electrode active material-containing layer  364   b  on the negative electrode current collector  364   a.    
     The negative electrode current collector  364   a  is, for example, a metal foil of aluminum, an aluminum alloy, copper, nickel, or the like. The negative electrode current-collecting tab  356  may not be integrated with the negative electrode current collector  364   a . That is, the negative electrode current-collecting tab  356  may be formed by bonding a metal foil to one of the long sides of the negative electrode current collector  364   a . The metal foil may be the same as that used for the negative electrode current collector  364   a.    
     The negative electrode active material-containing layer  364   b  may be provided on either both or one of the main surfaces of the negative electrode current collector  364   a . The negative electrode active material-containing layer  364   b  includes a negative electrode active material. The negative electrode active material-containing layer  364   b  may include a conductive agent and a binder in addition to the negative electrode active material. 
     Preferably used as the negative electrode active material is a compound whose lower limit of the potential at which lithium ions can be charged and discharged is 1.0 V (vs. Li/Li+) or more. A lithium titanium composite oxide is preferably used as such a compound. Lithium titanium composite oxides hardly undergo a volume change accompanying charge-and-discharge reaction. Therefore, when a lithium titanium composite oxide is used as the negative electrode active material, expansion and contraction of the electrode can be suppressed. Accordingly, when a lithium titanium composite oxide is used as the negative electrode active material, twisting of the electrode is even less likely to occur during gas generation. Also, lithium titanium composite oxides exhibit low heat dissipation accompanying charge and discharge. Therefore, when a lithium titanium composite oxide is used as the negative electrode active material, the life performance of the battery  310  can be improved even when the areas of the long-side sidewalls  336   a  and  336   b  of the outer case  312  are relatively small and the heat dissipation capability is low. 
     Examples of the lithium titanium composite oxide include Li 4+x Ti 5 O 12  (0≤x≤3) having a spinel structure, Li 2+y Ti 3 O 7  (0≤y≤3) having a ramsdellite structure, and orthorhombic titanium-containing oxides. Examples of the orthorhombic titanium-containing oxides include sodium-containing niobium titanium composite oxides. Examples of the sodium-containing niobium titanium composite oxides include compounds represented by the general formula Li 2+v Na 2-w M1 x Ti 6-y-z Nb y M2 z O 14+δ  (0≤v≤4, 0&lt;w&lt;2, 0≤x&lt;2, 0&lt;y&lt;6, 0≤z&lt;3, y+z&lt;6, −0.5≤δ≤0.5; M1 includes at least one selected from Cs, K, Sr, Ba, and Ca; M2 includes at least one selected from Zr, Sn, V, Ta, Mo, W, Fe, Co, Mn, and Al). 
     When a sodium-containing niobium titanium composite oxide is used as the negative electrode active material, the negative electrode potential can be decreased, as compared to the case where Li 4+x Ti 5 O 12  is used, and thus the voltage of the battery  310  can be increased. 
     The average primary particle size of the negative electrode active material is preferably 1 μm or less. When the average particle size of the primary particles of the negative electrode active material is small, the internal resistance decreases, and thus heat dissipation accompanying charge and discharge tends to be decreased. Therefore, when the average particle size of the primary particles of the negative electrode active material is small, the life performance of the battery  310  can be improved. 
     The negative electrode active material-containing layer  364   b  may include a negative electrode active material other than a lithium titanium composite oxide. Examples of such another negative electrode active material include carbonaceous materials such as graphite and tin-silicon-based alloy materials. 
     The conductive agent improves the electron conductivity of the electrode. Acetylene black, carbon black, graphite, or the like may be used as the conductive agent. 
     The binder increases the adhesion between the active material, the conductive agent, and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, and styrene-butadiene rubber. 
     In the negative electrode active material-containing layer  364   b , the mixing ratio of the negative electrode active material, the conductive agent, and the binder is preferably set as follows: the negative electrode active material in the range of 73% to 98% by mass, the conductive agent in the range of 0% to 20% by mass, and the binder in the range of 2% to 7% by mass. 
     The separator  366  functions as an insulating layer. The separator  366  is, for example, a porous film or a non-woven fabric. The porous film and the non-woven fabric may each include at least one compound selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, and cellulose. The separator  366  may be an organic fiber film or an inorganic film that covers at least a part of the main surfaces of the positive electrode  362  and the negative electrode  364 . Instead of the separator  366 , a solid electrolyte layer may be used as the insulating layer. 
     The thickness of the separator  366  is preferably 6 μm to 15 μm. When the thickness of the separator  366  is within this range, the safety, capacity, and life performance of the battery  310  can be improved. That is, when the thickness of the separator  366  is 6 μm or more, the probability of a short circuit between the positive electrode  362  and the negative electrode  364  may be decreased, and thus the safety and reliability of the battery  310  may be improved. On the other hand, when the thickness of the separator  366  is 15 μm or less, an increase in the amount of the auxiliary material in the battery  310  is suppressed, likely leading to an improved energy density. Also, when the thickness of the separator  366  is 15 μm or less, appropriate gaps are present in the outer case  312 ; and thus, the battery  310  is less likely to expand during gas generation, and the battery characteristics can be improved. 
     An electrolyte (not shown) may be held by the positive electrode  362 , the negative electrode  364 , and the separator  366 . The electrolyte may be a nonaqueous electrolyte including an electrolyte salt and an organic solvent. That is, the battery  310  according to the embodiment may be a nonaqueous electrolyte battery. The nonaqueous electrolyte may be in the form of a liquid or a gel. The liquid nonaqueous electrolyte is prepared by dissolving an electrolyte in an organic solvent. The gel nonaqueous electrolyte is prepared by gelling a liquid nonaqueous electrolyte using a polymeric material. The concentration of the electrolyte salt in the liquid nonaqueous electrolyte is, for example, 0.5 mol/L to 2.5 mol/L. 
     Examples of the electrolyte include lithium salts such as lithium perchlorate (LiCl 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), hexafluoro arsenic lithium (LiAsF 6 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), bistrifluoromethylsulfonylimide lithium [LiN(CF 3 SO 2 ) 2 ], and mixtures thereof. The electrolyte is preferably resistant to oxidation even at a high potential, and LiPF 6  is most preferred. 
     Examples of the organic solvent include: cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate; chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2-MeTHF), and dioxolan (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); and γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents may be used either alone or in the form of a mixture of two or more thereof. 
     Examples of the polymeric material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO). 
     A room temperature molten salt (ionic melt) containing lithium ions or the like may be used as the nonaqueous electrolyte. 
     As shown in  FIG. 18 , the fixing member  354   a  having conductivity is fixed to the positive electrode current-collecting tab  354 . The fixing member  354   a  is preferably fixed at a position close to an upper face  352   d  (described later) of the electrode group  314  relative to the winding axis Ra. The fixing member  354   a  has a substantially U-shaped cross section parallel to the XY plane and clamps a part of the positive electrode current-collecting tab  354 . Thus, the fixing member  354   a  fixes a part of the positive electrode current-collecting tab  354 . The fixing member  354   a  has an appropriate length along the Z-axis direction and may be in surface contact with the leg portion  92   b  of the lead  16   a.    
     As shown in  FIG. 16 , the fixing member  356   a  having conductivity is fixed to the negative electrode current-collecting tab  356 . The fixing member  356   a  is preferably fixed at a position close to the upper face  352   d  of the electrode group  314  relative to the winding axis Ra. The fixing member  356   a  has a substantially U-shaped cross section parallel to the XY plane and clamps a part of the negative electrode current-collecting tab  356 . Thus, the fixing member  356   a  fixes a part of the negative electrode current-collecting tab  356 . The fixing member  356   a  has an appropriate length along the Z-axis direction and may be in surface contact with the leg portion  94   b  of the lead  16   b.    
     The fixing members  354   a  and  356   a  are preferably made of a metal material having conductivity, such as aluminum, an aluminum alloy, copper, or nickel. 
     The rolled body  352  includes a first surface  352   a  facing or in contact with the inner face of the long-side sidewall  336   a , a second surface  352   b  facing or in contact with the inner face of the long-side sidewall  336   b , a bottom face  352   c  facing or in contact with the bottom wall  322 , and the upper face  352   d  facing or in contact with the insulating member  18  of the lid assembly  10 . 
     The nominal capacity A of the battery  310  in the present embodiment is, for example, 7 Ah or more. Thus, the battery  310  according to the embodiment can be suitably used as a high-capacity battery. The upper limit of the nominal capacity A is not particularly limited, but is, for example, 15 Ah. That is, the battery capacity of the battery  310  according to the present embodiment is preferably from 7 Ah to 15 Ah. 
     The nominal capacity of the battery  310  is a discharge capacity obtained by the following procedure. First, the battery is charged at a constant current at a rate of 0.05 C up to a maximum working voltage in an environment of 25° C. Next, the battery is further charged until the current value becomes 0.01 C in a state that the maximum working voltage is maintained. Thereafter, the battery is discharged at a rate of 0.05 C to final voltage to obtain a discharge capacity. 
     The aforementioned “maximum working voltage” is a maximum voltage at which the battery  310  can be used without any danger or defect, and is a value unique to each battery  310 . The maximum working voltage is, for example, a voltage described as a “charge voltage”, “security maximum voltage”, and the like in the specification sheet or the like of the battery  310 . The “final voltage” is the lowest working voltage at which the battery  310  can be used while suppressing overdischarge of both the positive electrode  362  and the negative electrode  364  of the battery  310 , that is, suppressing deterioration of the battery  310 , and is a value unique to each battery  310 . 
     As shown in  FIG. 16 , an insulating cover  372  having an electrical insulation property is disposed on the positive electrode current-collecting tab  354  and the fixing member  354   a  of the electrode group  314 . An insulating cover  374  having an electrical insulation property is disposed on the negative electrode current-collecting tab  356  and the fixing member  356   a  of the electrode group  314 . When the inner face of the outer case  312  is coated with an insulating material, the insulating covers  372  and  374  may be unnecessary. 
     The insulating cover  372  prevents the current-collecting tab  354  and the fixing member  354   a  from coming into contact with the inner walls of the sidewalls  336   a ,  336   b , and  338   a  of the outer case  312 . The insulating cover  374  prevents the current-collecting tab  356  and the fixing member  356   a  from coming into contact with the inner walls of the sidewalls  336   a ,  336   b , and  338   b  of the outer case  312 . 
     The insulating cover  372  includes a support portion  372   a  that supports the bottom face  352   c  of the rolled body  352 . The insulating cover  374  includes a support portion  374   a  that supports the bottom face  352   c  of the rolled body  352 . 
     For example, a resin material selected from polyester (PET), polyimide, polyphenylene sulfide (PPS), and polypropylene can be used as the insulating covers  372  and  374 . 
     The electrode group  314  is inserted through the opening  326  of the outer case  312  in a state that the fixing members  354   a  and  356   a  and the insulating covers  372  and  374  are attached to predetermined positions. On this occasion, the support portions  372   a  and  374   a  of the insulating covers  372  and  374  are brought into contact with the bottom wall  322 . 
     The lid  12  of the lid assembly  10  described in the first embodiment is disposed on the opening  326  of the outer case  312 . On this occasion, the cross section of the battery  310  taken along the XVI-XVI plane in  FIG. 15  is formed as shown in  FIG. 18 . The outer case  312  and the electrode group  314  are preferably symmetrical with respect to the central axis Cz parallel to the Z-axis. The leg portion  92   b  of the lead  16   a  of the lid assembly  10  is in surface contact with the fixing member  354   a . Although not shown in the figure, the leg portion  94   b  of the lead  16   b  of the lid assembly  10  is in surface contact with the fixing member  356   a.    
     As shown in  FIG. 16 , the lid  12  of the lid assembly  10  is fixed to the opening  326  of the outer case  312  by, for example, welding. On this occasion, the front face  12   a  and the back face  12   b  of the lid  12  of the lid assembly  10  are preferably parallel to the bottom wall  322  of the outer case  312 . 
     Then, an electrolyte is filled into the outer case  312  from the small hole  46 , and the small hole  46  is sealed by welding. 
     The cross section of the battery  310  taken along the XVII-XVII plane in  FIG. 15  is formed as shown in  FIG. 19 . The upper face  352   d  of the rolled body  352  of the electrode group  314  is pressed toward the bottom wall  322  of the outer case  312  by the support faces  82   a ,  82   b ,  84   a , and  84   b  of the support face groups  66   a  and  66   b . The bottom face  352   c  of the rolled body  352  is supported by the support portions  372   a  and  374   a  of the insulating covers  372  and  374  and is in contact with the bottom wall  322  of the outer case  312 . Therefore, the rolled body  352  is supported with the portion between the bottom face  352   c  and the upper face  352   d  sandwiched by the bottom wall  322  of the outer case  312  and the support face groups  66   a  and  66   b  of the insulating member  18  of the lid assembly  10 . 
     The first surface  352   a  of the rolled body  352  is in contact with the long-side sidewall  336   a  of the outer case  312 , and the second surface  352   b  of the rolled body  352  is in contact with the long-side sidewall  336   b  of the outer case  312 . 
     Thus, even if vibration or impact is applied to the battery  310 , the electrode group  314  is prevented from unintentionally moving inside the outer case  312  because the rolled body  352  of the electrode group  314  is supported inside the outer case  312 . 
     Whether the support face  82   a  of the support face group  66   a  has, for example, the shape shown in  FIG. 7  or the shape shown in  FIG. 8 , the upper face  352   d  of the rolled body  352  of the electrode group  314  is pressed toward the bottom wall  322  of the outer case  312  by the support face groups  66   a  and  66   b . Thus, the shape of the support face group  66   a  that prevents the electrode group  314  from unintentionally moving inside the outer case  312  is not limited to a flat face, and may be an appropriate shape such as a curved face. 
     In general, it is considered that when gas is generated inside the battery  310 , it is generated, for example, from the rolled body  352 . On this occasion, the gas escapes, along the winding axis Ra of the rolled body  352 , to the outside of the electrode group  314  from the position of the current-collecting tab  354  that is away from the position where the fixing member  354   a  is fixed. Likewise, the gas escapes, along the winding axis Ra of the rolled body  352 , to the outside of the electrode group  314  from the position of the current-collecting tab  356  that is away from the position where the fixing member  356   a  is fixed. 
     As the amount of gas generated increases, the gas is accumulated inside the battery  310 , and the internal pressure of the battery  310  gradually increases. The gas is accumulated in the gap between the electrode group  314  and the lid assembly  10  inside the outer case  312 . 
     In the outer case  312 , the areas of the long-side sidewalls  336   a  and  336   b  parallel to the XZ plane are larger than the areas of the short-side sidewalls  338   a  and  338   b  parallel to the YZ plane. The thicknesses of the sidewalls  336   a ,  336   b ,  338   a , and  338   b  are the same. Thus, the long-side sidewalls  336   a  and  336   b  are subjected to higher pressure (internal pressure) than the short-side sidewalls  338   a  and  338   b  because the areas of the long-side sidewalls  336   a  and  336   b  are larger than those of the short-side sidewalls  338   a  and  338   b . Accordingly, it is assumed that as the amount of gas generated inside the battery  310  increases, the swelling of the long-side sidewalls  336   a  and  336   b  gradually increases as compared with the short-side sidewalls  338   a  and  338   b.    
     In the present embodiment, the lead  16   a  includes one leg portion  92   b , and the lead  16   b  includes one leg portion  94   b . The lead may include two leg portions so as to clamp the fixing member  354   a . However, by providing a region  93  created by appropriately bending the leg portion  92   b , the contact area between the leg portion  92   b  of the lead  16   a  and the fixing member  354   a  is secured. Also, the leg portion  92   b  has an appropriate thickness t. Thus, it is possible to form the lead  16   a  to have the same level of performance as that of a lead with two leg portions while making the volume of the leg portion  92   b  of the lead  16   a  with respect to the inside of the battery  310  smaller than in the case where the lead includes two leg portions. Accordingly, even when the outer case  312  has the same internal volume, the space capable of storing gas inside the battery  310  can be increased by the volume of the leg portion  92   b  of the lead  16   a.    
     Herein, 0.02≤t/T12≤0.04 is preferably satisfied. 
     If the gas is vented from an unintended position in the battery  310 , the design of a battery pack  510  or the like described later in a third embodiment may also be affected. Thus, it is considered preferable that the gas is vented from a predetermined position in the battery  310  when the internal pressure of the battery  310  reaches a predetermined pressure due to the generation of the gas. 
     In the present embodiment, the lid assembly  10  includes the valve  20 . The insulating member  18  of the lid assembly  10  includes the adjacent faces (opposing faces)  64   a  and  64   b  adjacent to the valve  20  and facing the upper face  352   d  of the rolled body  352  of the electrode group  314 . A gap through which gas may be transferred is formed between the upper face  352   d  of the rolled body  352  of the electrode group  314  and the adjacent faces (opposing faces)  64   a  and  64   b  of the insulating member  18 . That is, a channel  316  through which gas may be transferred is formed between the upper face  352   d  of the rolled body  352  of the electrode group  314  and the adjacent faces (opposing faces)  64   a  and  64   b  of the insulating member  18 , as shown in  FIG. 19 . 
     As shown in  FIG. 16 , an appropriate gap is formed between the insulating cover  372  and the fixing member  354   a , and between the insulating cover  327  and the current-collecting tab  354 . An end  372   b  of the insulating cover  372  opposite to the support portion  372   a  is opened. Thus, the gas also flows and is accumulated between the adjacent face  64   a  of the lid assembly  10  and the upper face  352   d  of the rolled body  352  of the electrode group  314 . 
     Thus, the valve  20  of the battery  310  is pressurized by the generated gas from the inside of the battery  310  toward the outside of the battery  310  through the opening  56  of the intermediate region  68  between the adjacent faces (opposing faces)  64   a  and  64   b.    
     The valve  20  is set to a predetermined pressure of 1.0 MPa, for example. 
     Herein, a maximum possible opening area with which the valve  20  may be opened is equal to or smaller than the area of the planes of the plurality of adjacent faces (opposing faces)  64   a  and  64   b . Thus, when the valve  20  is opened and the gas in the channel  316  is vented to the outside of the battery  310 , a flow for which the gas is vented through the valve  20  can be created. 
     Therefore, by forming the valve  20  to be appropriately small, the upper face  352   d  of the rolled body  352  of the electrode group  314  can be reliably pressed toward the bottom wall  322  of the outer case  312  by the support faces  82   a ,  82   b ,  84   a , and  84   b  of the support face groups  66   a  and  66   b , even when the upper face  352   d  of the rolled body  352  of the electrode group  314  is likely to move in the Y-axis direction toward the long-side sidewall  336   a  or the long-side sidewall  336   b  due to, for example, vibration, impact, or the like. Accordingly, even in a large-sized battery  310  having a small thickness and a large height and width, for example, the electrode group  314  can be reliably held inside the battery  310 . Also, even when gas is generated inside the battery  310 , the gas can be vented to the outside of the battery  310  through the valve  20  by securing a gas flow channel when the pressure inside the battery  310  exceeds a predetermined pressure. 
     When the possible opening area with which the valve  20  may be opened is larger than the area of the planes of the plurality of adjacent faces (opposing faces)  64   a  and  64   b , the efficiency of the gas vent through the valve  20  is highly likely to be worse than in the case where the possible opening area is equal to or smaller than the area of the planes of the plurality of adjacent faces (opposing faces)  64   a  and  64   b.    
     EXAMPLES 
     A nonaqueous electrolyte battery  310  having the structure shown in  FIG. 15  and having a width W11 of 112 mm, a height H11 of 140 mm, a thickness T11 of 14 mm, and a battery capacity of 11 Ah was produced. The operating pressure of the valve  20  of the lid assembly  10  was set to 1.0 MPa. A lithium nickel cobalt manganese composite oxide represented by LiNi 0.33 Co 0.33 Mn 0.33 O 2  was used as a positive electrode active material. Li 4 Ti 5 O 12  having a spinel-type crystal structure was used as a negative electrode active material. A cellulose nonwoven fabric having a thickness of 20 μm was used as a separator. On the other hand, used as a nonaqueous electrolyte was a nonaqueous electrolytic solution prepared by dissolving, at a concentration of 1 mol/L, lithium hexafluorophosphate LiPF 6  as an electrolyte in a nonaqueous solvent prepared by mixing ethylene carbonate and dimethyl carbonate at a volume ratio of 1:1. 
     &lt;Capacity Check Test&gt; 
     The nonaqueous electrolyte battery  310  was charged at a constant current of 11 A at an ambient temperature of 25° C. When the battery voltage reached 2.8 V, the battery was charged at a constant voltage of 2.8 V. The charging was terminated when the current value reached 0.5 A. After the suspension for 60 minutes, the battery was discharged at a constant current of 11 A. The discharging was terminated when the battery voltage reached 1.3 V. The discharge capacity was 11 Ah. 
     &lt;Oven Test (High-Temperature Exposure Test)&gt; 
     In a state that the nonaqueous electrolyte battery  310  was restrained, a voltage (2.7 V) corresponding to SOC (state of charge) of 100% was set as a starting voltage, and the temperature was increased from 30° C. by 5° C./30 min. At this time, the valve  20  was opened at 130° C. to release the gas, and the test was terminated. Explosion, rupture, and ignition did not occur in the battery  310 . 
     From the above tests, it was confirmed that the battery  310  according to the present embodiment was excellent in safety and capacity performance. 
     Therefore, according to the present embodiment, a battery  310  is provided which includes: the outer case  312  with the opening  326  and the bottom wall  322 ; the electrode group  314  which includes the pair of current-collecting tabs  354  and  356  and is housed in the outer case  312  through the opening  326 ; and the lid assembly  10  fixed to the opening  326  of the outer case  312  in a state that the lid  12  and the pair of terminals  14   a  and  14   b  are exposed to the outside, the leg portions  92   b  and  94   b  of the pair of leads  16   a  and  16   b  are electrically connected to the pair of current-collecting tabs  354  and  356 , respectively, and the pair of support face groups  66   a  and  66   b  support the electrode group  314  with the bottom wall  322 . 
     According to the present embodiment, the lid assembly  10  that can contribute to secure a gas flow channel to the valve  20  in the battery  310 , and the battery  310  including the lid assembly  10  are provided. 
     In the present embodiment, the battery  310  including the lid assembly  10  described in the first embodiment is described; however, even when the battery  310  is formed using the lid assembly  10  described in each modification of the first embodiment, the battery  310  can exhibit the performance described in the second embodiment. 
     Third Embodiment 
     Next, a third embodiment will be described with reference to  FIGS. 20 and 21 . 
     In the present embodiment, a battery pack  510  that may be used by connecting the batteries  310  described in the second embodiment will be described. 
     The battery pack  510  according to the third embodiment may include a plurality of batteries  310 . The plurality of batteries  310  may be electrically connected in series or in parallel. Alternatively, the plurality of batteries  310  may be connected in a combination of in-series and in-parallel. 
     The battery pack  510  according to the third embodiment may include, for example, five batteries  310 . These batteries  310  may be connected in series. The batteries  310  connected in series may constitute a battery module  512 . That is, the battery pack  510  according to the third embodiment may include the battery module  512 . 
     The battery pack  510  according to the third embodiment may include a plurality of battery modules  512 . The plurality of battery modules  512  may be connected in series, in parallel, or in a combination of in-series and in-parallel. 
       FIG. 20  is an exploded perspective view of an example of the battery pack  510  according to the third embodiment.  FIG. 21  is a block diagram showing an example of an electric circuit of the battery pack  510  shown in  FIG. 20 . 
     The battery pack  510  shown in  FIG. 20  includes a battery module  512  including a plurality of unit cells  310 , a circuit board  514 , a housing container  516 , and a protective sheet  518 . For example, the unit cell described in the second embodiment may be used as the unit cell  310 . 
     As shown in  FIG. 21 , the plurality of unit cells  310  are electrically connected to each other in series. 
     A printed wiring board  514  is disposed so as to face the side surface from which the positive electrode-side lead  532  and the negative electrode-side lead  534  of the battery module  512  extend. As shown in  FIG. 21 , the printed wiring board  514  is provided with a thermistor  546 , a protective circuit  548 , and a terminal  550  for energizing an external device. An insulating plate (not shown) is attached to the surface of the printed wiring board  514  facing the battery module  512  in order to avoid unnecessary connection with the wiring of the battery module  512 . 
     A distal end  532   a  of the positive electrode-side lead  532  is electrically connected to a positive electrode-side connector  542  of the printed wiring board  514 . A distal end  534   a  of the negative electrode-side lead  534  is electrically connected to a negative electrode-side connector  544  of the printed wiring board  514 . These connectors  542  and  544  are connected to the protective circuit  548  through wiring  542   a  and  544   a  formed on the printed wiring board  514 . 
     The thermistor  546  detects the temperature of the unit cells  310 , so that the detection signals are transmitted to the protective circuit  548 . Under a predetermined condition, the protective circuit  548  can shut off plus-side wiring  549   a  and minus-side wiring  549   b  between the protective circuit  548  and the terminal  550  (terminals  552  and  554 ) for energizing an external device. An example of the predetermined condition is a point of time when the temperature detected by the thermistor  546  becomes equal to or higher than a predetermined temperature. Another example of the predetermined condition is a point of time when overcharge, overdischarge, overcurrent, or the like of the unit cell  310  is detected. The detection of the overcharge or the like is performed for the individual unit cells  310  or the battery module  512  as a whole. In the case of detecting the individual unit cells  310 , a battery voltage may be detected, or a positive electrode potential or a negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell  310 . In the battery pack  510  shown in  FIGS. 20 and 21 , wiring  560  for voltage detection is connected to each of the unit cells  310 . Detection signals are transmitted to the protective circuit  548  through the wiring  560 . 
     Protective sheets  518  made of rubber or resin are arranged on three side surfaces of the battery module  512 , excluding the side surface from which the positive electrode-side lead  532  and the negative electrode-side lead  534  protrude. 
     The battery module  512  is housed in the housing container  516  together with each protective sheet  518  and the printed wiring board  514 . That is, the protective sheets  518  are arranged on both of the inner side surfaces in the long-side direction and one of the inner side surfaces in the short-side direction of the housing container  516 , and the printed wiring board  514  is arranged on the other inner side surface in the short-side direction. The battery module  512  is positioned in a space surrounded by the protective sheets  518  and the printed wiring board  514 . A cover  516   a  is attached to an upper face of the housing container  516 . 
     A heat-shrinkable tape may be used to fix the battery module  512  instead of an adhesive tape  512   a . In this case, the protective sheets  518  are disposed on the respective side surfaces of the battery module  512 , and a heat-shrinkable tape is wound around the battery module  512  and then thermally shrunk to bind the battery module  512 . 
       FIGS. 20 and 21  show the configuration in which the unit cells  310  are connected in series; however, the unit cells  310  may be connected in parallel to increase the battery capacity. Further, assembled battery packs  510  may be connected in series and/or in parallel. 
     The configuration of the battery pack  510  according to the third embodiment is altered appropriately depending on the application. The battery pack  510  according to the third embodiment is preferably used in applications where cycle performance with large current performance is desired. Specific applications are as power supplies for digital cameras, and on-vehicle applications for two- or four-wheel hybrid electric automobiles, two- or four-wheel electric automobiles, assisted bicycles, and the like. The battery pack  510  according to the third embodiment is particularly suitable for use in the on-vehicle applications. 
     The battery pack  510  according to the third embodiment includes the battery  310  according to the second embodiment. Therefore, the battery pack  510  according to the third embodiment exhibits excellent impregnating properties of the electrolytic solution and has low resistance. 
     The battery pack  510  of the third embodiment described in detail above includes the battery  310  of the second embodiment including the lid assembly  10  described in the first embodiment including each modification. Therefore, the battery pack  510  according to the third embodiment can achieve excellent life performance. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.