Patent Publication Number: US-2009239133-A1

Title: Rolled electrode battery and manufacturing method therefor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation Application of PCT Application No. PCT/JP2008/054202, filed Mar. 7, 2008, which was published under PCT Article 21(2) in Japanese. 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2007-062589, filed Mar. 12, 2007, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rolled electrode battery, including an electrode body formed by rolling band-shaped positive and negative electrode plates into a flat shape with a separator therebetween, and a method of manufacturing the rolled electrode battery. 
     2. Description of the Related Art 
     With the recent increase of interest in environmental problems, the development of electric vehicles and hybrid electric vehicles has been advanced and attracting public attention. Batteries used in these electric vehicles require the ability to supply high output power to drive the vehicles, that is, to perform high-current discharge. 
     A battery as a power supply for conventional mobile equipment is improved in performance by using a rolled electrode body that is formed by rolling sheet-shaped electrode positive and negative electrode plates with a separator between them. Rolled electrode bodies for this purpose include a cylindrical rolled electrode body that is rolled into a spiral cylinder and a rolled electrode body that is rolled into a flat cube. 
     Conventionally, a battery with a rolled electrode body is provided with an outer case, and the rolled electrode body is sealed together with an electrolyte solution in the outer case. Electric power is extracted from the rolled electrode body through electrode terminals that are connected to the positive electrode plate and the negative electrode plate, individually. Another method of electric power extraction is proposed in which an electric current is extracted by, for example, fitting electrode plates individually with tabs and bonding these tabs to electrode terminals. 
     However, it is difficult to apply a battery in which electric power is extracted from the electrode body through the tabs to an electric vehicle. Specifically, a battery for an electric vehicle requires a large current. When a large current flows through a battery of this type, overheating/burning may be caused at junctions of the tabs. In order to extract a large current, therefore, it is necessary to provide each electrode plate with a large number of tabs. 
     A battery disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-8708, as a battery having a structure for extracting a large current, includes a rolled electrode body, a positive electrode terminal, and a negative electrode terminal. The rolled electrode battery is formed by rolling band-shaped positive and negative electrode plates, each coated with an electrode active material, with a band-shaped separator between them. Shaft portions of the positive and negative electrode terminals are connected to the positive and negative electrode plates, respectively, of the electrode body. The positive electrode plate and the negative electrode plate each include a band-shaped region to which the electrode active material is coated, and a side edge portion to which the electrode active material is not applied. The electrode plates are rolled with their side edge portions projecting in opposite directions in the axis of the electrode body. Thus, the electrode body is provided with regions to which no electrode material is coated at its axially opposite end portions, individually. The positive electrode terminal and the negative electrode terminal are connected to these regions and situated at the axially opposite end portions of the electrode body. 
     The aforementioned tabs are fixed to surfaces of the electrode plates by welding. If a large number of tabs are configured to be fixed to the electrode plates, therefore, the tabs require a troublesome mounting operation, the overall thickness of the electrode body is increased, and the battery is large-sized. 
     In the battery disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-8708, the regions to which no electrode material is applied and the positive and negative electrode terminals are provided at the axially opposite end portions of the electrode body. Accordingly, the axial dimension of the entire electrode body is greater than the width of the region to which the electrode active material is applied, which hinders reduction in size of the battery. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention has been made in consideration of these circumstances, and its object is to provide a rolled electrode battery, capable of ensuring extraction of a large current and reduction in size, and a method of manufacturing the same. 
     A rolled electrode battery according to an aspect of the invention comprises: a rolled electrode body including a band-shaped positive electrode plate and a band-shaped negative electrode plate formed individually with electrode active material layers, which are rolled with a band-shaped separator interposed between the positive and negative electrode plates and formed into a flat shape; and a case which contains the electrode body and an electrolyte solution therein and on which a positive electrode terminal and a negative electrode terminal are provided, the positive electrode plate and the negative electrode plate each including a band-shaped electrode portion formed with the electrode active material layer and contacting the separator and a side edge portion projecting from the separator to one axial side of the electrode body and not formed with an electrode active material layer, the side edge portion forming a plurality of lugs arranged at intervals along the lengths of the positive electrode plate and the negative electrode plate, the positive electrode plate and the negative electrode plate being rolled in layers so that the plurality of lugs of the positive electrode plate are laminated to one another to form a positive electrode tab and that the plurality of lugs of the negative electrode plate are laminated to one another to form a negative electrode tab. 
     According to another aspect of the invention, there is provided a method of manufacturing a rolled electrode battery comprising a rolled electrode body including a band-shaped positive electrode plate and a band-shaped negative electrode plate formed individually with electrode active material layers, which are rolled with a band-shaped separator interposed between the positive and negative electrode plates and formed into a flat shape; and a case which contains the electrode body and an electrolyte solution therein and on which a positive electrode terminal and a negative electrode terminal are provided; the method comprising: 
     applying an electrode active material to a band-shaped metal film to form a band-shaped positive electrode plate and a band-shaped negative electrode plate each of which includes a band-shaped electrode portion formed with an electrode active material layer and a side edge portion to which the electrode active material is not applied; intermittently cutting out the side edge portion of the positive electrode plate along the length of the positive electrode plate, thereby forming a plurality of lugs arranged at intervals along the length of the positive electrode plate; intermittently cutting out the side edge portion of the negative electrode plate along the length of the positive electrode plate, thereby forming a plurality of lugs arranged at intervals along the length of the negative electrode plate; rolling the positive electrode plate and the negative electrode plate, which are formed with the plurality of lugs, into a flat shape with the band-shaped separator being interposed between the positive electrode plate and the negative electrode plate and contacting the electrode material layers, thereby forming the electrode body; and rolling the positive electrode plate and the negative electrode plate, thereby laminating the plurality of lugs of the positive electrode plate to form a positive electrode tab and laminating the plurality of lugs of the negative electrode plate to form a negative electrode tab. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a cutaway perspective view showing a rolled electrode battery according to a first embodiment of this invention; 
         FIG. 2  is a sectional view of the rolled electrode battery; 
         FIG. 3  is a partially developed perspective view showing an electrode body of the rolled electrode battery; 
         FIG. 4  is a plan view of the electrode body; 
         FIG. 5  is a perspective view showing the electrode body; 
         FIG. 6  is a plan view showing a positive electrode plate and a negative electrode plate that constitute the electrode body; 
         FIG. 7  is a plan view schematically showing a manufacturing apparatus for manufacturing the electrode body; 
         FIG. 8  is a plan view showing an electrode body of a rolled electrode battery according to a second embodiment; 
         FIG. 9  is a perspective view showing the electrode body according to the second embodiment; and 
         FIG. 10  is a plan view showing a positive electrode plate and a negative electrode plate that constitute the electrode body according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A rolled electrode battery according to a first embodiment of this invention will now be described in detail with reference to the drawing.  FIG. 1  is a cutaway perspective view of the rolled electrode battery,  FIG. 2  is a longitudinal sectional view of the rolled electrode battery, and  FIG. 3  shows a laminate structure of an electrode plate along with a partially developed electrode body. 
     As shown in  FIGS. 1 and 2 , the rolled electrode battery is provided with a case or can  10  in the form of a flat rectangular box and a rolled electrode body  14  in the form of a flat cube that is contained together with an electrolyte solution  12  in the case. The electrode body  14  integrally includes a positive electrode tab  16  and a negative electrode tab  18  that protrude in the same direction along its axis. A positive electrode terminal  20  having a shaft portion is joined to the positive electrode tab  16 , while a negative electrode terminal  22  having a shaft portion is joined to the negative electrode tab  18 . The positive electrode terminal  20  and the negative electrode terminal  22  air-tightly penetrate a lid portion  10   a  of the case  10  and project outward. Further, the positive electrode terminal  20  and the negative electrode terminal  22  are mounted on the lid portion  10   a  through insulators, e.g., gaskets  23 , provided on the lid portion  10   a . Electric power that is generated in the electrode body  14  is extracted through the positive electrode tab  16 , negative electrode tab  18 , positive electrode terminal  20 , and negative electrode terminal  22 . 
     As shown in  FIGS. 3 ,  4  and  5 , the rolled electrode body  14  is formed into a flat shape in such a manner that a band-shape positive electrode plate  30 , a band-shaped negative electrode plate  32 , and a separator  34  interposed between the two electrode plates are rolled. The positive electrode tab  16  and the negative electrode tab  18  of the electrode body  14  are formed by laminating together a plurality of lugs that constitute a part of the positive electrode plate  30  and laminating together a plurality of lugs that constitute a part of the negative electrode plate  32 , and project in the same direction from one axial end side of the electrode body  14 . 
     As shown in  FIGS. 3 and 6 , the positive electrode plate  30  is formed of an electrically-conductive metal foil, e.g., a band-shaped aluminum sheet 65 mm wide and 4 m long, and a positive electrode active material layer  40  is formed on each surface of the positive electrode plate. The positive electrode active material layer  40  is formed to be band-shape, covering the overall length of the positive electrode plate  30 , and no positive electrode active material layer is formed on one transverse end portion of the positive electrode plate, that is, one side edge portion of the positive electrode plate. Thus, the positive electrode plate  30  includes an electrode portion  30   a  on which the positive electrode active material layer  40  is formed and a side edge portion  30   b  on which no positive electrode active material layer is formed. The side edge portion  30   b  is formed to have a width of, for example, 10 mm from an end edge of the positive electrode plate  30 . For example, lithium-manganese oxide is used as a positive electrode active material. 
     The side edge portion  30   b  of the positive electrode plate  30  is intermittently cut at intervals along the length of the positive electrode plate to form a plurality of, e.g., a number, n, of trapezoidal lugs  50 . The lugs  50  are arranged at intervals C( 1 ˜n) along the length of the positive electrode plate  30 , that is, with notches between them, and these intervals are gradually extended. Widths b( 1 ˜n) of the lugs  50  along the length of the positive electrode plate  30  are gradually extended from the lug that is situated on one end side of the positive electrode plate, that is, the lug that is situated on the one end side on the side of the center of the turns of the electrode body  14 , toward the lug that is situated on the other end side of the positive electrode plate. 
     If the width of the rolled electrode body  14  and the distance between the positive electrode tab  16  and the negative electrode tab  18  are W and x, respectively, a width b 1  of the smallest-width lug  50  that is situated at the one end of the positive electrode plate  30  is adjusted to (W−D−x), and a width bn of the largest-width lug  50   n  that is situated at the other end of the positive electrode plate  30  is adjusted to (b 1 +πD/2). 
     Among the intervals between the centers of the adjacent lugs  50 , moreover, the interval between the centers of the two adjacent lugs  50  that are situated on the extreme one end side of the positive electrode plate  30  is adjusted to (2W−2D), and that between the centers of the two lugs  50  that are situated on the extreme other end side of the positive electrode plate  30  is adjusted to (2W−2D+πD). 
     Among the intervals C( 1 ˜n) between the adjacent lugs  50 , the interval C 1  between the two adjacent lugs  50  that are situated on the extreme one end side of the positive electrode plate  30  is adjusted to (W−D+x), and the interval Cn−1 between the two lugs  50  that are situated on the extreme other end side of the positive electrode plate  30  is adjusted to approximately (C 1 +πD/2). 
     The negative electrode plate  32  is formed of an electrically-conductive metal foil, e.g., a band-shaped copper sheet 65 mm wide and 4 m long, and a negative electrode active material layer  42  is formed on each surface of the negative electrode plate. The negative electrode active material layer  42  is formed to be band-shape, covering the overall length of the negative electrode plate, and no negative electrode active material layer is formed on one transverse end portion of the negative electrode plate, that is, one side edge portion of the negative electrode plate. Thus, the negative electrode plate  32  includes an electrode portion  32   a  on which the negative electrode active material layer  42  is formed and a side edge portion  32   b  on which no electrode active material layer is formed. The side edge portion  32   b  is formed to have a width of 10 mm from an end edge of the negative electrode plate  32 . For example, carbon is used as a negative electrode active material. 
     The side edge portion  32   b  of the negative electrode plate  32  is intermittently cut at intervals along the length of the negative electrode plate to form a plurality of, e.g., a number n of trapezoidal lugs  52 . The lugs  52  are arranged at the intervals C( 1 ˜n) along the length of the negative electrode plate  32 , that is, with notches between them, and these intervals are gradually extended. Widths b( 1 ˜n) of the lugs  52  along the length of the negative electrode plate  32  are gradually extended from the lug that is situated on one end side of the negative electrode plate toward the lug that is situated on the other end side of the negative electrode plate. 
     A width b 1  of the smallest-width lug  52  that is situated at the one end of the negative electrode plate  32  is adjusted to (W−D−x), and a width bn of the largest-width lug  52   n  that is situated at the other end of the negative electrode plate  32  is adjusted to (b 1 +πD/2). Among the intervals between the centers of the adjacent lugs  52 , the interval between the centers of the two adjacent lugs  52  that are situated on the extreme one end side of the negative electrode plate  32  is adjusted to (2W−2D), and that between the centers of the two lugs  52  that are situated on the extreme other end side of the negative electrode plate  32  is adjusted to (2W−2D+πD). 
     Among the intervals C between the adjacent lugs  52 , the interval C 1  between the two adjacent lugs  52  that are situated on the extreme one end side of the negative electrode plate  32  is adjusted to (W−D+x), and the interval Cn−1 between the two lugs  52  that are situated on the extreme other end side of the negative electrode plate  32  is adjusted to approximately (C 1 +πD/2). 
     The separator  34  is formed of a band of polyethylene or polypropylene 55 mm wide and 4.4 m long. The separator  34  is formed with a width substantially equal to those of the electrode portions  30   a  and  32   b  on which the electrode active material layers  40  and  42  of the electrode plates  30  and  32  are formed, respectively, and a length greater than that of the electrode plates. 
     As shown in  FIGS. 3 to 6 , the separator  34  is located between the electrode portion  30   a  of the positive electrode plate  30  and the electrode portion  32   a  of the negative electrode plate  32  so as to be in contact with them. The positive electrode plate  30  and the negative electrode plate  32  are superposed so that their side edge portions  30   b  and  32   b  project in the same direction from the separator  34  and also that the lugs  50  of the positive electrode plate  30  and the lugs  52  of the negative electrode plate  32  are superposed to be alternately situated along the lengths of the two electrode plates. 
     The flat electrode body  14  is formed by rolling the positive electrode plate  30 , separator  34 , negative electrode plate  32 , and separator  34  so as to be turned back at respective central portions of the lugs  50  and  52 . Further, the plurality of lugs  50  of the positive electrode plate  30  are laminated to one another in the radial direction of the electrode body to form the positive electrode tab  16  that is integral with the electrode body  14 . Furthermore, the plurality of lugs  52  of the negative electrode plate  32  are laminated to one another in the radial direction of the electrode body to form the negative electrode tab  18  that is integral with the electrode body  14 . 
     The electrode body  14  has a flat shape such that its outer peripheral shape is spread transversely. Further, the electrode body  14  has, in its central part, a flat hollow portion  14   a  that is defined by the innermost peripheral surface of the electrode body. The electrode body  14  may be either an electrode body such that the positive electrode plate  30  and the negative electrode plate  32  are rolled into a flat shape with the separator between them or one that is deformed into a flat shape after the positive electrode plate and the negative electrode plate are rolled with the separator between them. 
     The positive electrode tab  16  and the negative electrode tab  18  are situated individually at the opposite end portions of the electrode body  14  in the direction of the width W thereof and are spaced at the distance x from each other. Preferably, the plurality of lugs  50  that constitute the positive electrode tab  16  are bonded together in such a manner that they are compressed in the direction of lamination. Likewise, the plurality of lugs  52  that constitute the negative electrode tab  18  are preferably bonded together in such a manner that they are compressed in the direction of lamination. 
     As shown in  FIGS. 1 and 2 , the electrode body  14  constructed in this manner is contained in the case  10 , and its positive and negative electrode tabs  16  and  18  are situated opposite the lid portion  10   a  of the case. The positive electrode terminal  20  is formed of, for example, aluminum, while the negative electrode terminal  22  is formed of, for example, a copper alloy. The positive electrode terminal  20  and the negative electrode terminal  22  are bonded to the positive electrode tab  16  and the negative electrode tab  18 , respectively, of the electrode body  14 . The bonding is performed by, for example, welding. 
     The case  10  is a tank-like container of aluminum, iron, or stainless steel that can be internally sealed. The electrolyte solution  12  used is, for example, a solution that is formed by adding LiPF 6  to a solvent mixture of ethylene carbonate and diethylene carbonate. 
     The following is a description of a method for manufacturing the rolled electrode battery provided with the electrode body  14  constructed in this manner. 
     The rolled electrode battery can be manufactured by forming the rolled electrode body  14  that includes the positive electrode plate  30  and the negative electrode plate  32  rolled with the separator therebetween, welding the positive electrode terminal  20  and the negative electrode terminal  22  to the positive electrode tab  16  and the negative electrode tab  18 , respectively, of the electrode body  14 , and then sealing the electrode body together with the electrolyte solution  12  into the case  10 . 
     The following is a detailed description of a method for manufacturing the electrode body  14 . 
     First, the positive electrode plate  30  is formed having the positive electrode active material layer  40  on each surface of the band-shaped aluminum sheet. In forming the positive electrode plate  30 , a paste mixture that contains a positive electrode active material is applied to a surface of the band-shaped aluminum sheet, dried, and then pressure-bonded by means of a press. Further, the negative electrode plate  32  that includes the negative electrode active material layer  42  on each surface of the band-shaped copper sheet is formed in the same manner as the positive electrode plate. 
     Subsequently, the active material layer is removed from respective end portions of the positive electrode plate  30  and the negative electrode plate  32  on their one transverse side to form the side edge portions  30   b  and  32   b  to which no positive electrode active material is applied and through which the electrically-conductive sheet is exposed. Thereafter, the positive electrode plate  30  and the negative electrode plate  32  are rolled with the separator  43  between them. 
     In this case, the rolling is performed by using a rolling device shown in  FIG. 7 . Specifically, the positive electrode plate  30  formed in the above-described manner is rolled around a first reel  62  of the rolling device, while the negative electrode plate  32  is rolled around a second reel  64 . Likewise, the two band-shaped separators  34  are wound individually around a third reel  66   a  and a fourth reel  66   b  to form rolls of the separators. 
     Then, the positive electrode plate  30 , negative electrode plate  32 , and separators  34  are drawn out individually from the first to fourth reels  62 ,  64 ,  66   a  and  66   b , and they are superposed on one another and wound around a take-up hub  70 . As this is done, the side edge portion  30   b  of the positive electrode plate  30  drawn out from the first reel  62  is intermittently cut by means of a cutter  72   a , whereupon the plurality of lugs  50  are formed arranged at predetermined intervals. After dust, chips, etc., produced by the cutting are then removed from the positive electrode plate  30  by a dust collector  74   a , the positive electrode plate is wound around the take-up hub  70 . Likewise, the side edge portion  32   b  of the negative electrode plate  32  drawn out from the second reel  64  is intermittently cut by means of a cutter  72   b , whereupon the plurality of lugs  52  are formed arranged at predetermined intervals. After dust, chips, etc., produced by the cutting are then removed from the negative electrode plate  32  by a dust collector  74   b , the negative electrode plate is wound around the take-up hub  70 . 
     As the take-up hub  70  is then rotated, the positive electrode plate  30  and the negative electrode plate  32  are wound up on the take-up hub  70  in such a manner that they are superposed so that their side edge portions  30   b  and  32   b  project in the same direction from the separators  34  and also that the lugs  50  of the positive electrode plate  30  and the lugs  52  of the negative electrode plate  32  are superposed to be alternately situated along the lengths of the two electrode plates. 
     The take-up hub  70  is formed with a flat oval cross-sectional shape, and the positive electrode plate  30 , separator  34 , negative electrode plate  32 , and separator  34  are rolled around the hub  70  so as to be turned back at respective central portions of the lugs  50  and  52 . After the electrode body  14  is formed by rolling these plates for a predetermined length, the positive electrode plate  30 , negative electrode plate  32 , and separators  34  are cut. Subsequently, the resulting roll is removed from the take-up hub  70 , and this roll is stamped into a flat shape. Thus, the electrode body  14  is obtained that integrally includes the positive electrode tab  16  and the negative electrode tab  18 . 
     Thereafter, the positive electrode terminal  20  and the negative electrode terminal  22  are ultrasonically bonded to the positive electrode tab  16  and the negative electrode tab  18 , respectively, which projects on the one axial end side of the electrode body  14 . Electric welding, such as spot welding, seam welding, etc., ultrasonic welding, or the like may be used as a method for bonding the electrode terminals and the tabs. Then, the electrode body  14 , including the positive electrode terminal  20  and the negative electrode terminal  22  thus bonded, is put into the case  10 . After the lid portion  10   a  is closed to seal the case, the electrolyte solution  12  is injected into the case  10  through an inlet (not shown). The electrode battery is completed when the inlet is then sealed. 
     With the rolled electrode battery according to the present embodiment constructed in this manner, the electrode body includes the positive electrode tab and the negative electrode tab formed by laminating the plurality of lugs that are formed of parts of the electrode plates. Thus, the positive electrode tab and the negative electrode tab are formed of the electrode plates themselves, so that there are no such junctions as conventional ones between independent tabs and electrode plates. Even if a large current flows, therefore, overheating/burning cannot be caused. Since each tab is formed by laminating the plurality of lugs, moreover, a large current can be extracted as in the case where a plurality of independent tabs are joined. When compared with the case where the plurality of independent tabs are joined, moreover, the overall thickness of each tab can be reduced, so that the entire electrode body can be reduced in size. 
     Further, the positive electrode plate and the negative electrode plate are constructed so that their side edge portions project only on one side of the separator and that half or more of each side edge portion is cut. Thus, the overall volume of the electrode body can be reduced to ensure compactification. 
     In consequence, a rolled electrode battery can be obtained that ensures extraction of a large current and reduction in size. 
     According to the method of manufacturing the rolled electrode battery according to the present embodiment, furthermore, the tabs are formed of the electrode plates themselves. In contrast with the conventional case, therefore, the electrode body can be efficiently manufactured without requiring a plurality of independent tabs to be welded to the electrode plates. Since each lug has the shape of a trapezoid or the like that has inclined sides, the electrode body can be continuously cut with ease by means of a cutter or laser cutter. Thus, the electrode body can be manufactured efficiently. 
     The lugs may be formed by punching the side edge portions of the electrode plates with a press or the like, instead of cutting out with a cutter. In this case, the lugs may be formed after the electrode active material layers are formed on the electrode plates, or alternatively, the electrode active material layers may be formed on the electrode plates after the lugs are formed. 
     With a rolled electrode battery according to a second embodiment, lugs of an electrode body  14  are formed by means of a press. As shown in  FIGS. 8 to 10 , in this case, intervals C 1  to Cn−1 between lugs  50  of a positive electrode plate  30  are adjusted to a constant value C, and intervals C 1  to Cn−1 between lugs  52  of a negative electrode plate  32  are also adjusted to the constant value C. Further, a width b 1  of the smallest-width lugs  50  and  52  that are situated at one ends of the positive electrode plate  30  and the negative electrode plate  32  is adjusted to (W−D−x), and a width bn of the largest-width lugs  50  and  52   n  that are situated at the other ends of the positive electrode plate and the negative electrode plate is adjusted to (bn+2b 1 +πD). 
     A positive electrode tab  16  and a negative electrode tab  18  are formed based on the lugs  50  and  52  by rolling the positive electrode plate  30  and the negative electrode plate  32  described above to form the electrode body  14 . These positive and negative electrode tabs  16  and  18  have bent end edge portions, individually. 
     The same function and effect of the foregoing first embodiment can also be obtained with the second embodiment constructed in this manner. Further, the lugs of the electrode plates can be easily formed by means of a press by equalizing the intervals between the lugs. 
     This invention is not limited to the embodiments described above, and in carrying out the invention, its components may be embodied in modified forms without departing from the spirit of the invention. Further, various inventions may be made by suitably combining a plurality of components disclosed in connection with the foregoing embodiments. Some of all the components according to the embodiments may be omitted, or components according to different embodiments may be combined as required. 
     For example, the shape and size of the electrode body, the shape and size of lugs, etc., are not limited to the foregoing embodiments and may be suitably modified. The material of the electrode plates, the electrode active material, and the electrolyte solution are not limited to the foregoing embodiments and may be variously selected as required.