Patent Publication Number: US-2013244073-A1

Title: Nonaqueous electrolyte battery

Description:
TECHNICAL FIELD 
     The present invention relates to a nonaqueous electrolyte battery, and more particularly to a nonaqueous electrolyte battery comprising a flattened winding body. 
     BACKGROUND ART 
     Conventionally, a structure of a nonaqueous electrolyte battery comprising a winding body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween has been well known. Further, a structure of a flattened winding body which is used in order to achieve a square or thinned battery has been well known. 
     Japanese Patent Application Laid Open Gazette No. 2001-273881 relates to a battery comprising an electrode group which is wound, and more particularly to a battery comprising a wound electrode having a flattened shape, and discloses a technique to prevent internal short-circuit and provide a highly reliable battery. 
     Japanese Patent Application Laid Open Gazette No. 2005-222884 discloses a technique relating to a multilayer electrode battery which is capable of preventing short-circuit of a positive electrode and a negative electrode and averaging the thickness of a positive electrode lead terminal side and that of a negative electrode lead terminal side, to thereby ensure safety and high volumetric energy density. 
     Japanese Patent Application Laid Open Gazette No. 2007-26939 discloses a technique relating to a winding type battery having an electrode body which is flatly wound around a flat winding core, in which a winding end portion can be arranged at a desired position without any effect on battery properties or the like. 
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     A positive electrode and a negative electrode used for a winding body are each formed by applying a mixture layer having an active material onto at least one surface of a strip-like current collector. For this reason, the winding body has a level difference in the thickness of the mixture layer at an application end of the mixture layer. Particularly in a case where the mixture layer is formed on both the surfaces of the current collector and the positions of the application ends of the mixture layers formed on both the surfaces are aligned, this level difference becomes larger. 
     In a nonaqueous electrolyte battery, charge and discharge are performed by giving and receiving guest ions between the positive electrode and the negative electrode. In a lithium-ion battery, for example, lithium ions are collected in the negative electrode during charge. The negative electrode is thereby expanded. With this expansion of the negative electrode, the whole winding body tends to be expanded. The winding body, however, is usually contained in a battery case with almost no clearance. For this reason, the winding body receives pressure from the battery case in a direction of suppressing the expansion. 
     In this case, if there is a level difference in the winding body as discussed above, the pressure received from the battery case is non-uniform on both sides of the level difference. When the winding body receives the non-uniform pressure, the negative electrode is non-uniformly expanded and there arises undulation in the winding body. 
     Further, inside the winding body, there are a positive electrode tab joined to the positive electrode and a negative electrode tab joined to the negative electrode. With the undulation of the winding body, there sometimes arises torsion in the current collector tab (the positive electrode tab or the negative electrode tab). In some cases, the torsion of the current collector tab cannot be resolved even if the nonaqueous electrolyte battery is discharged to remove the expansion of the winding body. 
     Such undulation of the winding body and torsion of the current collector tab deteriorate the battery properties of the nonaqueous electrolyte battery. Further, since the winding body is locally expanded against the pressure from the battery case, it is impossible to produce a thin battery having uniform thickness. 
     It is an object of the present invention to provide a nonaqueous electrolyte battery in which a winding body is uniformly expanded, to thereby prevent undulation. 
     According to the present invention, the nonaqueous electrolyte battery comprises a winding body having a flattened shape, in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, and a negative electrode tab joined to the negative electrode, extending in a winding axis direction of the winding body. In the nonaqueous electrolyte battery of the present invention, the positive electrode includes a positive electrode current collector having a strip-like shape, a first positive electrode mixture layer formed on one surface of the positive electrode current collector, and a second positive electrode mixture layer formed on the other surface of the positive electrode current collector, a direction parallel to a main surface of the winding body and perpendicular to the winding axis direction is assumed to be a width direction, a winding trailing end portion of the first positive electrode mixture layer is positioned on an inner side of the winding body with respect to the negative electrode tab in the width direction, and a winding trailing end portion of the second positive electrode mixture layer is positioned on an outer side of the winding body with respect to the negative electrode tab in the width direction. 
     In the above-discussed structure, the winding trailing end portion of the positive electrode mixture layer (first positive electrode mixture layer) formed on one surface of the positive electrode current collector and the winding trailing end portion of the positive electrode mixture layer (second positive electrode mixture layer) formed on the other surface of the positive electrode current collector are formed away from each other in the width direction of the winding body. The level differences at the end portions of the positive electrode mixture layers can be dispersed in the width direction of the winding body. Therefore, it is possible to alleviate the non-uniformity of pressure received from a battery case when the winding body is expanded during charge/discharge. Consequently, the force imposed on the negative electrode mixture layers, in particular, is uniform. Therefore, the expansion of the winding body  30  is uniform and the undulation in the winding body  30  is suppressed. Since the undulation in the winding body  30  is suppressed, the torsion of the negative electrode tab  36  can be also suppressed. 
     More specifically, the winding trailing end portion of the first positive electrode mixture layer is positioned on the inner side of the winding body with respect to the negative electrode tab in the width direction of the winding body. The winding trailing end portion of the second positive electrode mixture layer is positioned on the outer side of the winding body with respect to the negative electrode tab in the width direction of the winding body. In other words, the winding trailing end portions of the positive electrode mixture layers are positioned on both sides of the negative electrode tab. It is thereby possible to uniformize the pressure exerted on the negative electrode tab. 
     Thus, according to the present invention, the winding body can be uniformly expanded, and this prevents the undulation therein. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view schematically showing a structure of a nonaqueous electrolyte battery in accordance with a first embodiment of the present invention; 
         FIG. 2  is a cross section taken along the line A-A of  FIG. 1 ; 
         FIG. 3  is a cross section taken along the line B-B of  FIG. 1 ; 
         FIG. 4A  is an elevational view of a positive electrode tab, extractingly showing the vicinity of a winding trailing end portion of a positive electrode; 
         FIG. 4B  is an elevational view of a negative electrode tab, extractingly showing the vicinity of a winding leading end portion of a negative electrode; 
         FIG. 5  is a cross section schematically showing a structure of a nonaqueous electrolyte battery in accordance with a comparative embodiment; 
         FIG. 6A  is a view for explanation of undulation in a winding body and torsion of the negative electrode tab in the nonaqueous electrolyte battery in accordance with the comparative embodiment; 
         FIG. 6B  is a view for explanation of undulation in a winding body and torsion of the negative electrode tab in the nonaqueous electrolyte battery in accordance with the comparative embodiment; 
         FIG. 7  is a cross section schematically showing a structure of a nonaqueous electrolyte battery in accordance with a second embodiment of the present invention; 
         FIG. 8  is a cross section schematically showing a structure of a nonaqueous electrolyte battery in accordance with a third embodiment of the present invention; 
         FIG. 9  is a cross section schematically showing a structure of a nonaqueous electrolyte battery in accordance with a variation of the present invention; 
         FIG. 10  is a cross section schematically showing a structure of a nonaqueous electrolyte battery in accordance with another variation of the present invention; 
         FIG. 11  is a cross section schematically showing a structure of a nonaqueous electrolyte battery in accordance with still another variation of the present invention; and 
         FIG. 12  is a view showing thickness measurement points in an expansion measurement. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     Hereinafter, with reference to figures, the embodiments of the present invention will be discussed in detail. In figures, identical or corresponding constituent elements are represented by the same reference signs and redundant description will be omitted. The constituent members in figures are not faithfully shown at actual size, with actual size ratio, or the like. 
     The First Embodiment 
     &lt;Overall Structure&gt; 
       FIG. 1  is a perspective view schematically showing a structure of a nonaqueous electrolyte battery  1  in accordance with the first embodiment of the present invention. The nonaqueous electrolyte battery  1  comprises a bottomed cylindrical exterior can  10 , a cover plate  20  for covering an opening of the exterior can  10 , and a winding body  30  contained in the exterior can  10 . By attaching the cover plate  20  to the exterior can  10 , a battery case C having a space therein is achieved. Further, inside the battery case C, a nonaqueous electrolyte solution is encapsulated as well as the winding body  30 . 
     The exterior can  10  is formed of, e.g., an aluminum alloy. The exterior can  10  has a bottom surface  11  and a sidewall  12 . The sidewall  12  has a pair of planar portions  121  opposed to each other and semi-cylindrical portions  122  which connect the planar portions  121  to each other. 
     Herein, a direction of connecting the bottom surface  11  of the exterior can  10  and the cover plate  20  is referred to as a z direction. A direction perpendicular to the z direction and parallel to the planar portions  121  of the exterior can  10  is referred to as an x direction. A direction perpendicular to both the z direction and the x direction is referred to as a y direction. The size of the exterior can  10  in the y direction is smaller than that in the x direction. In other words, the exterior can  10  has a flattened shape. 
     The exterior can  10  also has a function of a positive electrode of the nonaqueous electrolyte battery  1  as discussed later. 
     The cover plate  20  is formed of, e.g., an aluminum alloy, like the exterior can  10 . The cover plate  20  is fitted in the opening of the exterior can  10  and joined thereto by welding. 
     A center portion of the cover plate  20  in the x direction is provided with a through hole  20   a . In the through hole  20   a , an insulation packing  21  made of polypropylene and a negative terminal  22  made of stainless steel are inserted. Specifically, the substantially columnar negative terminal  22  is inserted in the substantially cylindrical insulation packing  21  and the insulation packing  21  is inserted in the through hole  20   a.    
     The cover plate  20  is also provided with an inlet  20   b  for the nonaqueous electrolyte solution side by side with the through hole  20   a . The inlet  20   b  is sealed with a sealing plug  23 . A peripheral portion of the inlet  20   b  and an outer peripheral portion of the sealing plug  23  are joined to each other by welding. 
       FIG. 2  is a cross section taken along the line A-A of  FIG. 1  (xz-plane cross section). The winding body  30  has a positive electrode  31  having a strip-like shape, a negative electrode  32  having a strip-like shape, and two separators  33  and  34 . The winding body  30  has a multilayer structure in which the negative electrode  32 , the separator  33 , the positive electrode  31 , and the separator  34  are layered in this order and is wound around the z direction with the negative electrode  32  positioned on the inner side. In  FIG. 2 , the inner side of the winding body  30  is not shown. The number of turns of the winding body  30  may be arbitrarily chosen. 
     The size of the winding body  30  in the y direction is smaller than that in the x direction. In other words, the winding body  30  has a flattened shape. Herein, if the winding body  30  is regarded as a similar rectangular parallelepiped, a pair of the largest surfaces (surfaces perpendicular to the y direction) are sometimes referred to as main surfaces of the winding body  30 . Further, the x direction is sometimes referred to as a width direction of the winding body  30  and the y direction is sometimes referred to as a thickness direction of the winding body  30 . The z direction is sometimes referred to as a winding axis direction of the winding body  30 . 
     A positive electrode tab  35  is joined to the vicinity of a winding trailing end portion of the positive electrode  31 . On the other hand, a negative electrode tab  36  is joined to the vicinity of a winding leading end portion of the negative electrode  32 . Though the positive electrode tab  35  is not actually present on the plane of  FIG. 2 , for convenience of illustration, the positive electrode tab  35  is indicated by the one-dot chain line in  FIG. 2 . 
     Respective structures of the winding body  30 , the positive electrode tab  35 , and the negative electrode tab  36  will be described later in detail. 
     The positive electrode tab  35  is drawn to the outside of the winding body  30  and connected to the cover plate  20 . The positive electrode  31  and the cover plate  20  are thereby brought into conduction with each other. Since the cover plate  20  and the exterior can  10  are joined to each other, the positive electrode  31  and the exterior can  10  are also brought into conduction with each other. For this reason, the exterior can  10  also has a function as the positive electrode  31  as discussed earlier. 
     The negative electrode tab  36  is drawn to the outside of the winding body  30  and connected to the negative terminal  22  with a lead plate  25  interposed therebetween. The negative electrode  32  and the negative terminal  22  are thereby brought into conduction with each other. An insulator  24  is formed between the lead plate  25  and the cover plate  20 . The lead plate  25  and the cover plate  20  are thereby insulated from each other. 
     An insulator  13  made of a polyethylene sheet is formed between the winding body  30  and the bottom surface  11  of the exterior can  10 . Therefore, with the exterior can  10  interposed therebetween, the positive electrode  31  and the negative electrode  32  are not short-circuited. 
     &lt;Structure of Winding Body  30 &gt; 
     Hereinafter, with reference to  FIG. 3 , the structure of the winding body  30  will be described in detail.  FIG. 3  is a cross section taken along the line B-B of  FIG. 1  (xy-plane cross section).  FIG. 3  only shows an area of about one round from the innermost side of the winding body  30  and an area of about one round from the outermost side of the winding body  30  and omits an intermediate area. Though the negative electrode  32 , the separator  33 , the positive electrode  31 , and the separator  34  are very closely arranged with almost no clearance in actual cases,  FIG. 3  shows these constituent elements, being separated a little from one another, for easy visualization. 
     The positive electrode  31  includes a positive electrode current collector  310  having a strip-like shape and positive electrode mixture layers  311  and  312  formed on both sides of the positive electrode current collector  310 . The positive electrode mixture layer  311  is formed on a surface (outer surface) of the positive electrode current collector  310 , which is farther from the winding center of the winding body  30 , out of the front and back surfaces thereof. The positive electrode mixture layer  312  is formed on a surface (inner surface) of the positive electrode current collector  310 , which is nearer to the winding center of the winding body  30 , out of the front and back surfaces thereof. 
     As the positive electrode current collector  310 , for example, a foil made of aluminum, titanium, or the like, a plain weave wire mesh, expanded metal, a lath mesh, perforated metal, or the like may be used. The thickness of the positive electrode current collector  310  is, e.g., 5 to 30 μm. 
     The positive electrode mixture layers  311  and  312  are formed by mixing a positive electrode active material, an electroconductive aid, and a binder. As the positive electrode active material, lithium manganese oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium/nickel/cobalt composite oxide, vanadium oxide, molybdenum oxide, or the like may be used. As the electroconductive aid, graphite, carbon black, acetylene black, or the like may be used. As the binder, polyimide, polyamide imide, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or/and the like may be used solely or by mixture. 
     The positive electrode mixture layers  311  and  312  are controlled to have a predetermined density by a calendering process. The density of the positive electrode mixture layers  311  and  312  is 2.0 to 3.5 g/cm 3 , and more preferably 2.3 to 3.3 g/cm 3 . The thickness of each of the positive electrode mixture layers  311  and  312  is, e.g., 20 to 200 μm. 
     In the positive electrode  31 , part of the positive electrode current collector  310  is exposed on the winding trailing end portion side and the respective positions of the end portions of the mixture layers on the front and back surfaces thereof are different in the width direction (x direction) of the winding body  30 . Specifically, as shown in  FIG. 3 , a winding trailing end portion  310   b  of the positive electrode current collector  310 , a winding trailing end portion  311   b  of the positive electrode mixture layer  311 , and a winding trailing end portion  312   b  of the positive electrode mixture layer  312  are at different positions in the width direction (x direction) of the winding body  30 . 
     On the other hand, a winding leading end portion  310   a  of the positive electrode current collector  310 , a winding leading end portion  311   a  of the positive electrode mixture layer  311 , and a winding leading end portion  312   a  of the positive electrode mixture layer  312  are at substantially the same position in the width direction (x direction) of the winding body  30 . The structure on the winding leading end portion side of the positive electrode  31 , however, may be arbitrarily chosen. The winding leading end portions  310   a ,  311   a , and  312   a  may be at different positions in the width direction (x direction) of the winding body  30 . In the case where these portions are at the same position, however, it is possible to simplify the manufacturing process since it is not necessary to expose the positive electrode current collector  310 . 
     The negative electrode  32  includes a negative electrode current collector  320  having a strip-like shape and negative electrode mixture layers  321  and  322  formed on both sides of the negative electrode current collector  320 . The negative electrode mixture layer  321  is formed on a surface (outer surface) of the negative electrode current collector  320 , which is farther from the winding center of the winding body  30 , out of the front and back surfaces thereof. The negative electrode mixture layer  322  is formed on a surface (inner surface) of the negative electrode current collector  320 , which is nearer to the winding center of the winding body  30 , out of the front and back surfaces thereof. 
     As the negative electrode current collector  320 , for example, a foil made of copper, nickel, stainless, or the like, a plain weave wire mesh, expanded metal, a lath mesh, perforated metal, or the like may be used. The thickness of the negative electrode current collector  320  is, e.g., 5 to 150 μm. 
     The negative electrode mixture layers  321  and  322  are formed by mixing a negative electrode active material and a binder. As the negative electrode active material, natural graphite, mesophase carbon, amorphous carbon, or the like may be used. As the binder, cellulose such as carboxymethyl cellulose (CMC), Hydroxy Methyl cellulose (HPC), or the like, a rubber binder such as styrene-butadiene rubber (SBR), acrylic rubber, or the like, PTFE, PVDF, or/and the like may be used solely or by mixture. 
     As the negative electrode active material, instead of the above-discussed carbon-based negative electrode materials, an alloy-based negative electrode material containing a metallic material (Li, Si, Al, Ge, Pb, As, Sb, or the like) or an oxide-based negative electrode material containing an oxide (SiO, TiO 2 , Nb 2 O 5 , MoO 2 , or the like) may be used. Further, these may be used by mixture. 
     The negative electrode mixture layers  321  and  322  are controlled to have a predetermined density by a calendering process. The density of the negative electrode mixture layers  321  and  322  has to be optimally adjusted depending on the material to be used. In a case of using a graphite material, for example, the density is 1.0 to 1.8 g/cm 3 , and more preferably 1.2 to 1.6 g/cm 3 . The thickness of each of the negative electrode mixture layers  321  and  322  is, e.g., 20 to 200 μm. 
     In the negative electrode  32 , part of the negative electrode current collector  320  is exposed on the winding leading end portion side and the respective positions of the end portions of the mixture layers on the front and back surfaces thereof are different in the width direction (x direction) of the winding body  30 . Specifically, as shown in  FIG. 3 , a winding leading end portion  320   a  of the negative electrode current collector  320 , a winding leading end portion  321   a  of the negative electrode mixture layer  321 , and a winding leading end portion  322   a  of the negative electrode mixture layer  322  are at different positions in the width direction (x direction) of the winding body  30 . 
     Further, a winding trailing end portion  320   b  of the negative electrode current collector  320 , a winding trailing end portion  321   b  of the negative electrode mixture layer  321 , and a winding trailing end portion  322   b  of the negative electrode mixture layer  322  are at different positions in the width direction (x direction) of the winding body  30 . 
     On the outermost side of the winding body  30 , the positive electrode tab  35  is joined to the exposed portion of the positive electrode current collector  310 . In the present embodiment, the positive electrode tab  35  is joined to the surface of the positive electrode current collector  310  on the side where the positive electrode mixture layer  312  is formed. The positive electrode tab  35 , however, may be joined to the surface of the positive electrode current collector  310  on the side where the positive electrode mixture layer  311  is formed. 
       FIG. 4A  is an elevational view of the positive electrode tab  35 , extractingly showing the vicinity of the winding trailing end portion of the positive electrode  31 . As shown in  FIG. 4A , the positive electrode tab  35  extends in the winding axis direction (z direction) of the winding body  30 . As the positive electrode tab  35 , aluminum, titanium, or the like may be used. The thickness of the positive electrode tab  35  is, e.g., 2 to 10 μm. 
     One end portion  35   a  of the positive electrode tab  35  is positioned in the vicinity of one end portion  31   c  (on the side of the bottom surface  11 ) of the positive electrode  31  in the winding axis direction (z direction). It is preferable that a gap g 1  between the end portion  35   a  of the positive electrode tab  35  and the end portion  31   c  of the positive electrode  31  is 3 mm or less. More preferably, the gap g 1  is 1 mm or less, and the end portion  35   a  must not protrude from the positive electrode current collector  310 . 
     The other end portion  35   b  of the positive electrode tab  35  protrudes from the other end portion  31   d  (on the side of the cover plate  20 ) of the positive electrode  31  in the winding axis direction (z direction). It is preferable that a gap g 2  between the end portion  35   b  of the positive electrode tab  35  and the end portion  31   d  of the positive electrode  31  is about 10 mm. More preferably, the gap g 2  is 3 to 10 mm. 
     It is preferable that the positive electrode tab  35  is joined to the positive electrode  31  only at the vicinity of both the end portions of the positive electrode  31  in the winding axis direction (z direction) and a center portion thereof is not joined. More specifically, the positive electrode tab  35  and the positive electrode current collector  310  of the positive electrode  31  are joined to each other only at regions S 1  and S 2  surrounded by the one-dot chain line in  FIG. 4A . 
     Further, it is preferable that the area of the region S 1  in the end portion on the side of the bottom surface  11  is 18 to 27 mm 2 . More preferably, the area is 20 to 25 mm 2 . It is preferable that the area of the region S 2  in the end portion on the side of the cover plate  20  is 9 to 18 mm 2 . More preferably, the area is 12 to 15 mm 2 . 
     On the innermost side of the winding body  30 , the negative electrode tab  36  is joined to the exposed portion of the negative electrode current collector  320 . In the present embodiment, the negative electrode tab  36  is joined to the surface of the negative electrode current collector  320  on the side where the negative electrode mixture layer  322  is formed. The negative electrode tab  36 , however, may be joined to the surface of the negative electrode current collector  320  on the side where the negative electrode mixture layer  321  is formed. 
       FIG. 4B  is an elevational view of the negative electrode tab  36 , extractingly showing the vicinity of the winding leading end portion of the negative electrode  32 . As shown in  FIG. 4B , the negative electrode tab  36  extends in the winding axis direction (z direction) of the winding body  30 . As the negative electrode tab  36 , copper, nickel, stainless, or the like may be used. The thickness of the negative electrode tab  36  is, e.g., 2 to 10 μm. 
     One end portion  36   a  of the negative electrode tab  36  is positioned in the vicinity of one end portion  32   c  (on the side of the bottom surface  11 ) of the negative electrode  32  in the winding axis direction (z direction). It is preferable that a gap g 3  between the end portion  36   a  of the negative electrode tab  36  and the end portion  32   c  of the negative electrode  32  is 3 mm or less. More preferably, the gap g 3  is 1 mm or less, and the end portion  36   a  must not protrude from the negative electrode current collector  320 . 
     The other end portion  36   b  of the negative electrode tab  36  protrudes from the other end portion  32   d  (on the side of the cover plate  20 ) of the negative electrode  32  in the winding axis direction (z direction). It is preferable that a gap g 4  between the end portion  36   b  of the negative electrode tab  36  and the end portion  32   d  of the negative electrode  32  is about 10 mm. More preferably, the gap g 4  is 3 to 10 mm. 
     It is preferable that the negative electrode tab  36  is joined to the negative electrode  32  only at the vicinity of both the end portions of the negative electrode  32  in the winding axis direction (z direction) and a center portion thereof is not joined. More specifically, the negative electrode tab  36  and the negative electrode current collector  320  of the negative electrode  32  are joined to each other only at regions S 3  and S 4  surrounded by the one-dot chain line in  FIG. 4B . 
     Further, it is preferable that the area of the region S 3  in the end portion on the side of the bottom surface  11  is 18 to 27 mm 2 . More preferably, the area is 20 to 25 mm 2 . It is preferable that the area of the region S 4  in the end portion on the side of the cover plate  20  is 9 to 18 mm 2 . More preferably, the area is 12 to 15 mm 2 . 
     Referring back to  FIG. 3 , description of the winding body  30  will continue. As the separators  33  and  34 , a porous film or a nonwoven fabric made of polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenyl sulfide (PPS), or the like may be used. The thickness of each of the separators  33  and  34  is, e.g., 5 to 30 μm. More preferably, the thickness is 10 to 20 μm. 
     The nonaqueous electrolyte solution encapsulated in the battery case C together with the winding body  30  is a liquid solution in which lithium salt is dissolved in an organic solvent. As the organic solvent, vinylene carbonate (VC), propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone, or/and the like may be used solely or by mixture of two or more kinds. As the lithium salt, LiPF 6 , LiBF 4 , LiN(CF 3 SO 2 ) 2 , or the like may be used. 
     In the winding body  30 , the negative electrode mixture layer  321  is so arranged as to be opposed to the positive electrode mixture layer  312  with the separator  33  interposed therebetween. The negative electrode mixture layer  322  is so arranged as to be opposed to the positive electrode mixture layer  311  with the separator  34  interposed therebetween. In the charge/discharge of the nonaqueous electrolyte battery  1 , the guest ions (e.g., lithium ions) are given and received in a portion where the positive electrode mixture layer  311  and the negative electrode mixture layer  322  are opposed to each other and a portion where the positive electrode mixture layer  312  and the negative electrode mixture layer  321  are opposed to each other. 
     In the pair of the positive electrode mixture layer  311  and the negative electrode mixture layer  322 , the area of the negative electrode mixture layer  322  which is a side of receiving the guest ions has to be larger than the area of the positive electrode mixture layer  311 . Therefore, in the present embodiment, the winding leading end portion  322   a  of the negative electrode mixture layer  322  is positioned on the side of the winding leading end portion  320   a  of the negative electrode current collector  320  with respect to the winding leading end portion  311   a  of the positive electrode mixture layer  311 . Further, the winding trailing end portion  322   b  of the negative electrode mixture layer  322  is positioned on the side of the winding trailing end portion  320   b  of the negative electrode current collector  320  with respect to the winding trailing end portion  311   b  of the positive electrode mixture layer  311 . 
     Similarly, the area of the negative electrode mixture layer  321  has to be larger than the area of the positive electrode mixture layer  312 . Therefore, in the present embodiment, the winding leading end portion  321   a  of the negative electrode mixture layer  321  is positioned on the side of the winding leading end portion  320   a  of the negative electrode current collector  320  with respect to the winding leading end portion  312   a  of the positive electrode mixture layer  312 . Further, the winding trailing end portion  321   b  of the negative electrode mixture layer  321  is positioned on the side of the winding trailing end portion  320   b  of the negative electrode current collector  320  with respect to the winding trailing end portion  312   b  of the positive electrode mixture layer  312 . 
     In the nonaqueous electrolyte battery  1 , the winding trailing end portion  311   b  of the positive electrode mixture layer  311  is positioned on the inner side of the winding body  30  with respect to the negative electrode tab  36  in the width direction (x direction) of the winding body  30 . Further, the winding trailing end portion  312   b  of the positive electrode mixture layer  312  is positioned on the outer side of the winding body  30  with respect to the negative electrode tab  36  in the width direction (x direction) of the winding body  30 . In other words, the negative electrode tab  36  is positioned between the winding trailing end portions  311   b  and  312   b.    
     &lt;Method of Manufacturing Nonaqueous Electrolyte Battery  1 &gt; 
     A manufacturing method discussed below is illustrative and not restrictive of the present invention. 
     The positive electrode active material, the electroconductive aid, and the binder are sufficiently mixed in pure water or the organic solvent, to thereby produce a dispersing element (slurry). The slurry is applied onto both the surfaces of the positive electrode current collector  310  by using a die coater, a slit coater, a dip coater, or the like. After this coating, the slurry is dried and subsequently adjusted to have a predetermined thickness and a predetermined density by performing the calendering process. Through this process, the positive electrode  31  in which the positive electrode mixture layers  311  and  312  are formed on the positive electrode current collector  310  is achieved. In the positive electrode  31 , the positive electrode tab  35  is joined to the exposed portion of the positive electrode current collector  310  by welding or using a conductive adhesive or the like. 
     The negative electrode active material and the binder are sufficiently mixed in pure water or the organic solvent, to thereby produce a dispersing element (slurry). The slurry is applied onto both the surfaces of the negative electrode current collector  320  by using a die coater, a slit coater, a dip coater, or the like. After this coating, the slurry is dried and subsequently adjusted to have a predetermined thickness and a predetermined density by performing the calendering process. Through this process, the negative electrode  32  in which the negative electrode mixture layers  321  and  322  are formed on the negative electrode current collector  320  is achieved. In the negative electrode  32 , the negative electrode tab  36  is joined to the exposed portion of the negative electrode current collector  320  by welding or using a conductive adhesive or the like. 
     The negative electrode  32 , the separator  33 , the positive electrode  31 , and the separator  34  are layered in this order. This layered body is wound around a circular or elliptical winding core by a winding machine. After winding, the winding core is drawn out and pressure is imposed in one direction, to make the winding body  30  into a flattened shape. Alternatively, the layered body may be wound around a winding core having a flattened shape by the winding machine, to thereby produce the winding body  30  having a flattened shape. 
     The end portion  35   b  of the positive electrode tab  35  is welded to the cover plate  20  and the end portion  36   b  of the negative electrode tab  36  is welded to the lead plate  25 . The winding body  30  is put into the exterior can  10 , and the exterior can  10  and the cover plate  20  are welded to each other. The nonaqueous electrolyte solution is injected therein from the inlet  20   b  of the cover plate  20 . After injection, the inlet  20   b  is sealed with the sealing plug  23  and the peripheral portion of the inlet  20   b  and the outer peripheral portion of the sealing plug  23  are welded to each other. 
     &lt;Effects of Nonaqueous Electrolyte Battery  1 &gt; 
     In the structure of the nonaqueous electrolyte battery  1 , the winding trailing end portion  311   b  of the positive electrode mixture layer  311  formed on one surface of the positive electrode current collector  310  and the winding trailing end portion  312   b  of the positive electrode mixture layer  312  formed on the other surface of the positive electrode current collector  310  are away from each other in the width direction (x direction) of the winding body  30 . The level difference at the winding trailing end portion  311   b  and that at the winding trailing end portion  312   b  are thereby dispersed in the width direction (x direction) of the winding body  30 . Therefore, it is possible to alleviate the non-uniformity of the pressure received from the battery case C when the winding body  30  is expanded during the charge/discharge. Consequently, the force imposed on the negative electrode mixture layers  321  and  322 , in particular, is uniform. Therefore, the expansion of the winding body  30  is uniform and the undulation in the winding body  30  is suppressed. Since the undulation in the winding body  30  is suppressed, the torsion of the negative electrode tab  36  can be also suppressed. 
     More specifically, the winding trailing end portion  311   b  of the positive electrode mixture layer  311  is positioned on the inner side of the winding body  30  with respect to the negative electrode tab  36  in the width direction (x direction) of the winding body  30 . The winding trailing end portion  312   b  of the positive electrode mixture layer  312  is positioned on the outer side of the winding body  30  with respect to the negative electrode tab  36  in the width direction (x direction) of the winding body  30 . In other words, the winding trailing end portions  311   b  and  312   b  are arranged on both sides of the negative electrode tab  36 . It is thereby possible to uniformize the pressure exerted on the negative electrode tab  36 . 
     The winding body  30  is expanded also in the winding axis direction (z direction) and the width direction (x direction) of the winding body. For this reason, as shown in  FIG. 4A , it is preferable that the positive electrode tab  35  is joined to the positive electrode  31  only at the vicinity of both the end portions of the positive electrode  31  in the winding axis direction (z direction) and the center portion thereof is not joined. Since the entire surface is not fixed, it is possible to alleviate the distortion. The same applies to the negative electrode tab  36 , and specifically, it is preferable that the negative electrode tab  36  is joined to the negative electrode  32  only at the vicinity of both the end portions of the negative electrode  32  in the winding axis direction (z direction) and the center portion thereof is not joined. 
     The present invention can be preferably utilized particularly in the case where a material containing a metal or an oxide is used as the negative electrode active material. This is because the negative electrode  32  including such a negative electrode active material has especially large expansion coefficient during the charge/discharge. As one example, while the expansion coefficient of a carbon-based negative electrode material is about 120%, the expansion coefficient of the negative electrode material containing a metallic material sometimes reaches 200%. 
     Comparative Embodiment 
     Herein, a virtual comparative embodiment will be discussed in order to explain the effects of the nonaqueous electrolyte battery  1  in accordance with the present embodiment of the present invention.  FIG. 5  is a cross section schematically showing a structure of a nonaqueous electrolyte battery  9  in accordance with the comparative embodiment. The nonaqueous electrolyte battery  9  comprises a winding body  90  instead of the winding body  30  included in the nonaqueous electrolyte battery  1 . 
     The winding body  90  includes a positive electrode  91  consisting of a positive electrode current collector  910  and positive electrode mixture layers  911  and  912 , a negative electrode  92  consisting of a negative electrode current collector  920  and negative electrode mixture layers  921  and  922 , and the separators  33  and  34 . In  FIG. 5 , reference signs  910   a ,  911   a ,  912   a ,  920   a ,  921   a , and  922   a  represent winding leading end portions of the positive electrode current collector  910 , the positive electrode mixture layer  911 , the positive electrode mixture layer  912 , the negative electrode current collector  920 , the negative electrode mixture layer  921 , and the negative electrode mixture layer  922 , respectively. Reference signs  910   b ,  911   b ,  912   b ,  920   b ,  921   b , and  922   b  represent winding trailing end portions of the positive electrode current collector  910 , the positive electrode mixture layer  911 , the positive electrode mixture layer  912 , the negative electrode current collector  920 , the negative electrode mixture layer  921 , and the negative electrode mixture layer  922 , respectively. 
     In the winding body  90 , the winding trailing end portion  911   b  of the positive electrode mixture layer  911  and the winding trailing end portion  912   b  of the positive electrode mixture layer  912  are at substantially the same position in the width direction (x direction) of the winding body  90 . For this reason, in this position, there is a relatively large level difference caused by the total thickness of the positive electrode mixture layers  911  and  912 . Further, both the winding trailing end portions  911   b  and  912   b  are positioned on the outer side of the winding body  90  with respect to the negative electrode tab  36  in the width direction (x direction) of the winding body  90 . 
       FIGS. 6A and 6B  are views for explanation of undulation in the winding body  90  and torsion of the negative electrode tab  36  in the nonaqueous electrolyte battery  9 .  FIGS. 6A and 6B  are cross section schematically showing the vicinity of the winding trailing end portion  911   b  of the positive electrode mixture layer  911  and the winding trailing end portion  912   b  of the positive electrode mixture layer  912  and the negative electrode tab  36 , which are extracted from the structure of the nonaqueous electrolyte battery  9 . In  FIGS. 6A and 6B , the positive electrode current collector  910 , the negative electrode current collector  920 , and the separators  33  and  34  are not shown. 
     When the nonaqueous electrolyte battery  9  is charged, the negative electrode  92  is expanded, as indicated by the arrows in  FIG. 6A . With the expansion of the negative electrode  92 , the whole winding body  90  tends to be expanded. The winding body  90 , however, is usually contained in the battery case C with almost no clearance. For this reason, the winding body  90  receives pressure from the battery case C (the planar portion  121  of the sidewall  12  of the battery case C in  FIG. 6A ) in a direction of suppressing the expansion. 
     In this case, there is a relatively large level difference caused by the winding trailing end portion  911   b  of the positive electrode mixture layer  911  and the winding trailing end portion  912   b  of the positive electrode mixture layer  912  in the winding body  90 . The pressure imposed from the battery case C is non-uniform depending on the position relative to the level difference. By receiving the non-uniform pressure, the negative electrode mixture layers  921  and  922  are non-uniformly expanded. Consequently, as shown in  FIG. 6B , there arises undulation in the winding body  90 . 
     Further, in the nonaqueous electrolyte battery  9 , both the winding trailing end portions  911   b  and  912   b  are positioned on the outer side of the winding body  90  with respect to the negative electrode tab  36  in the width direction (x direction) of the winding body  90 . For this reason, the negative electrode mixture layers  921  and  922  are non-uniformly expanded depending on the position relative to the negative electrode tab  36 . In other words, the negative electrode tab  36  receives a non-uniform force through the undulation in the winding body  90  in the width direction (x direction) of the winding body  90 . Consequently, there arises torsion in the negative electrode tab  36 . In some cases, the torsion of the negative electrode tab  36  cannot be resolved even if the nonaqueous electrolyte battery  9  is discharged to remove the expansion of the winding body  90 . 
     Such undulation in the winding body  90  and torsion of the negative electrode tab  36  deteriorate the battery properties of the nonaqueous electrolyte battery  9 . Further, since the winding body  90  is locally expanded against the pressure from the battery case C, the nonaqueous electrolyte battery  9  cannot sometimes meet the thickness specification. 
     In the structure of the nonaqueous electrolyte battery  1  in accordance with the present embodiment of the present invention, the level difference at the winding trailing end portion  311   b  and the level difference at the winding trailing end portion  312   b  are dispersed in the width direction (x direction) of the winding body  30 . Therefore, it is possible to alleviate the non-uniformity of the pressure received from the battery case C when the winding body  30  is expanded during the charge/discharge. Further, the winding trailing end portions  311   b  and  312   b  are arranged on both sides of the negative electrode tab  36 . It is thereby possible to uniformize the pressure exerted on the negative electrode tab  36 . 
     The Second Embodiment 
       FIG. 7  is a cross section schematically showing a structure of a nonaqueous electrolyte battery  2  in accordance with the second embodiment of the present invention. The nonaqueous electrolyte battery  2  comprises a winding body  40  instead of the winding body  30  included in the nonaqueous electrolyte battery  1 . 
     In the winding body  40 , the structure of the negative electrode is different from that in the winding body  30 . Specifically, the winding body  40  includes a negative electrode  42  instead of the negative electrode  32 . The negative electrode  42  includes a negative electrode current collector  420  and negative electrode mixture layers  421  and  422 . In  FIG. 7 , reference signs  420   a ,  421   a , and  422   a  represent winding leading end portions of the negative electrode current collector  420 , the negative electrode mixture layer  421 , and the negative electrode mixture layer  422 , respectively. Reference signs  420   b ,  421   b , and  422   b  represent winding trailing end portions of the negative electrode current collector  420 , the negative electrode mixture layer  421 , and the negative electrode mixture layer  422 , respectively. 
     In the present embodiment, the winding trailing end portion  421   b  of the negative electrode mixture layer  421  is positioned between the winding trailing end portion  312   b  of the positive electrode mixture layer  312  and the negative electrode tab  36  in the width direction (x direction) of the winding body  40 . With this arrangement, the winding trailing end portion  421   b  of the negative electrode mixture layer  421  is not positioned between both the end portions of the negative electrode tab  36  in the width direction (x direction) of the winding body  40 . Further, the winding trailing end portion  422   b  of the negative electrode mixture layer  422  is positioned between the winding trailing end portion  311   b  of the positive electrode mixture layer  311  and the positive electrode tab  35  in the width direction (x direction) of the winding body  40 . 
     In the structure of the nonaqueous electrolyte battery  2 , neither the winding trailing end portion  421   b  of the negative electrode mixture layer  421  nor the winding trailing end portion  422   b  of the negative electrode mixture layer  422  is positioned between both the end portions of the negative electrode tab  36  in the width direction (x direction) of the winding body  40 . In other words, when the winding trailing end portions  421   b  and  422   b  are projected on the xz plane, neither the winding trailing end portion  421   b  nor the winding trailing end portion  422   b  overlaps the negative electrode tab  36 . When the negative electrode  42  is expanded, it is thereby possible to prevent the torsion of the negative electrode tab  36  with the difference in expansion between the winding trailing end portions  421   b  and  422   b.    
     Further, in the structure of the nonaqueous electrolyte battery  2 , the negative electrode tab  36  is positioned not only between the winding trailing end portion  311   b  of the positive electrode mixture layer  311  and the winding trailing end portion  312   b  of the positive electrode mixture layer  312  but also between the winding trailing end portion  421   b  of the negative electrode mixture layer  421  and the winding trailing end portion  422   b  of the negative electrode mixture layer  422  in the width direction (x direction) of the winding body  40 . This makes the pressure received from the winding body  40  symmetrical with respect to the negative electrode tab  36 . It is therefore possible to prevent the torsion of the negative electrode tab  36 . 
     The structure of the nonaqueous electrolyte battery  2  is more preferable than that of the nonaqueous electrolyte battery  1 . This is because the winding trailing end portion  321   b  of the negative electrode mixture layer  321  overlaps the negative electrode tab  36  in the nonaqueous electrolyte battery  1  ( FIG. 3 ) when it is projected on the xz plane. This is further because the negative electrode tab  36  is not positioned between the winding trailing end portions  321   b  and  322   b  in the nonaqueous electrolyte battery  1 . In other words, one winding trailing end portion ( 312   b ) is present on one side of the negative electrode tab  36  and two winding trailing end portions ( 311   b  and  322   b ) are present on the other side thereof in the structure of the nonaqueous electrolyte battery  1  while two winding trailing end portions ( 312   b  and  421   b ) are present on one side of the negative electrode tab  36  and another two winding trailing end portions ( 311   b  and  422   b ) are present on the other side thereof in the structure of the nonaqueous electrolyte battery  2 . This makes the force exerted on the negative electrode tab  36  symmetrical in the nonaqueous electrolyte battery  2 . Therefore, the torsion of the negative electrode tab  36  is less likely to occur in the structure of the nonaqueous electrolyte battery  2  than in the structure of the nonaqueous electrolyte battery  1 . 
     The Third Embodiment 
       FIG. 8  is a cross section schematically showing a structure of a nonaqueous electrolyte battery  3  in accordance with the third embodiment of the present invention. The nonaqueous electrolyte battery  3  comprises a winding body  50  instead of the winding body  30  included in the nonaqueous electrolyte battery  1 . 
     In the winding body  50 , the structure of the negative electrode is different from that in the winding body  30 . Specifically, the winding body  50  includes a negative electrode  52  instead of the negative electrode  32 . The negative electrode  52  includes a negative electrode current collector  520  and negative electrode mixture layers  521  and  522 . In  FIG. 8 , reference signs  520   a ,  521   a , and  522   a  represent winding leading end portions of the negative electrode current collector  520 , the negative electrode mixture layer  521 , and the negative electrode mixture layer  522 , respectively. Reference signs  520   b ,  521   b , and  522   b  represent winding trailing end portions of the negative electrode current collector  520 , the negative electrode mixture layer  521 , and the negative electrode mixture layer  522 , respectively. 
     In the present embodiment, the winding trailing end portion  521   b  of the negative electrode mixture layer  521  is positioned between the negative electrode tab  36  and the positive electrode tab  35  in the width direction (x direction) of the winding body  50 . Further, the winding trailing end portion  522   b  of the negative electrode mixture layer  522  is positioned between the winding trailing end portion  311   b  of the positive electrode mixture layer  311  and the positive electrode tab  35  in the width direction (x direction) of the winding body  50 . 
     In the structure of the nonaqueous electrolyte battery  3 , like in the nonaqueous electrolyte battery  2 , neither the winding trailing end portion  521   b  of the positive electrode mixture layer  521  nor the winding trailing end portion  522   b  of the positive electrode mixture layer  522  is positioned between both the end portions of the negative electrode tab  36  in the width direction (x direction) of the winding body  50 . In other words, when the winding trailing end portions  521   b  and  522   b  are projected on the xz plane, neither the winding trailing end portion  521   b  nor the winding trailing end portion  522   b  overlaps the negative electrode tab  36 . When the negative electrode  52  is expanded, it is thereby possible to prevent the torsion of the negative electrode tab  36  with the difference in expansion between the winding trailing end portions  521   b  and  522   b.    
     Further, in the structure of the nonaqueous electrolyte battery  3 , both the winding trailing end portions  521   b  and  522   b  are positioned between the positive electrode tab  35  and the negative electrode tab  36 . Since the positive electrode tab  35  and the negative electrode tab  36  each have a certain thickness, the thickness (the size in the y direction) of the winding body  50  is the thinnest in the portion between the positive electrode tab  35  and the negative electrode tab  36 . By positioning the winding trailing end portions  521   b  and  522   b  in this portion, the thickness of the thickest portion of the winding body  50  can be thinned. Therefore, the structure of the nonaqueous electrolyte battery  3  is more preferable than those of the nonaqueous electrolyte batteries  1  and  2 . 
     Further, in the present embodiment, the winding trailing end portion  520   b  of the negative electrode current collector  520 , the winding trailing end portion  521   b  of the negative electrode mixture layer  521 , and the winding trailing end portion  522   b  of the negative electrode mixture layer  522  are at different positions in the width direction (x direction) of the winding body  50 . The structure on the side of the winding trailing end portion of the negative electrode  52 , however, may be arbitrarily chosen. A pair of any two of the winding trailing end portions  520   b ,  521   b , and  522   b  or all the winding trailing end portions  520   b ,  521   b , and  522   b  may be at the same position in the width direction (x direction) of the winding body  50 . In the case where all the winding trailing end portions  520   b ,  521   b , and  522   b  are at the same position, particularly, it is possible to simplify the manufacturing process since it is not necessary to expose the negative electrode current collector  520 . 
     &lt;Variations of Nonaqueous Electrolyte Batteries  1  to  3 &gt; 
       FIGS. 9 to 11  are cross sections schematically showing structures of nonaqueous electrolyte batteries  4  to  6  in accordance with variations of the nonaqueous electrolyte batteries  1  to  3 , respectively. The nonaqueous electrolyte batteries  4  to  6  comprise winding bodies  60 ,  70 , and  80 , respectively. 
     The winding bodies  60 ,  70 , and  80  include a positive electrode  61  and the separators  33  and  34  in common. The positive electrode  61  includes a positive electrode current collector  610  and positive electrode mixture layers  611  and  612 . In  FIGS. 9 to 11 , reference signs  610   a ,  611   a , and  612   a  represent winding leading end portions of the positive electrode current collector  610 , the positive electrode mixture layer  611 , and the positive electrode mixture layer  612 , respectively. Reference signs  610   b ,  611   b , and  612   b  represent winding trailing end portions of the positive electrode current collector  610 , the positive electrode mixture layer  611 , and the positive electrode mixture layer  612 , respectively. 
     In the nonaqueous electrolyte batteries  4  to  6 , the winding trailing end portion  612   b  of the positive electrode mixture layer  612  is positioned on the inner side of the winding body  60  ( 70 ,  80 ) with respect to the negative electrode tab  36  in the width direction (x direction) of the winding body  60  ( 70 ,  80 ). Further, the winding trailing end portion  611   b  of the positive electrode mixture layer  611  is positioned on the outer side of the winding body  60  ( 70 ,  80 ) with respect to the negative electrode tab  36  in the width direction (x direction) of the winding body  60  ( 70 ,  80 ). In other words, the negative electrode tab  36  is positioned between the winding trailing end portions  611   b  and  612   b  in the width direction (x direction) of the winding body  60  ( 70 ,  80 ). 
     Like in the nonaqueous electrolyte batteries  1  to  3 , the level difference at the winding trailing end portion  611   b  and that at the winding trailing end portion  612   b  are thereby dispersed in the width direction (x direction) of the winding body  60  ( 70 ,  80 ). Therefore, it is possible to alleviate the non-uniformity of the pressure received from the battery case C when the winding body  60  ( 70 ,  80 ) is expanded during the charge/discharge. Further, by arranging the winding trailing end portions  611   b  and  612   b  with the negative electrode tab  36  between them, it is possible to uniformize the pressure exerted on the negative electrode tab  36 . 
     In the nonaqueous electrolyte batteries  4  to  6 , the winding trailing end portion  612   b  of the positive electrode mixture layer  612  on the outer side of the winding body  60  ( 70 ,  80 ) is positioned on the inner side of the winding body  60  ( 70 ,  80 ) with respect to the negative electrode tab  36  in the width direction (x direction) of the winding body  60  ( 70 ,  80 ). 
     As the structure in which the negative electrode tab  36  is positioned between the winding trailing end portions  611   b  and  612   b , there are two possible structures, i.e., a structure (A) in which the winding trailing end portion  612   b  is positioned on the outer side with respect to the negative electrode tab  36  and the winding trailing end portion  611   b  is positioned on the inner side with respect to the negative electrode tab  36  and a structure (B) in which the winding trailing end portion  612   b  is positioned on the inner side with respect to the negative electrode tab  36  and the winding trailing end portion  611   b  is positioned on the outer side with respect to the negative electrode tab  36 . The structure of the nonaqueous electrolyte batteries  1  to  3  corresponds to the structure (A) and the structure of the nonaqueous electrolyte batteries  4  to  6  corresponds to the structure (B). 
     It can be clearly seen from  FIGS. 9 to 11  that in the structure (B), the winding trailing end portion  611   b  on the inner side of the winding body  60  ( 70 ,  80 ) is positioned on the outer side with respect to the winding trailing end portion  612   b  positioned outward in the width direction (x direction) of the winding body  60  ( 70 ,  80 ). Therefore, when the positive electrode  61 , a negative electrode  62  ( 72 ,  82 ), and the separators  33  and  34  are closely arranged without any clearance and wound, there arises a bent portion in at least the positive electrode mixture layer  612 , which is caused by the winding trailing end portion  611   b . On the other hand, it can be clearly seen from  FIGS. 3 ,  7 , and  8  that in the structure (A), there arises no bent portion. Therefore, the structure (A) is more preferable than the structure (B). 
     With reference to  FIG. 9 , the winding body  60  included in the nonaqueous electrolyte battery  4  includes the negative electrode  62 . The negative electrode  62  includes a negative electrode current collector  620  and negative electrode mixture layers  621  and  622 . In  FIG. 9 , reference signs  620   a ,  621   a , and  622   a  represent winding leading end portions of the negative electrode current collector  620 , the negative electrode mixture layer  621 , and the negative electrode mixture layer  622 , respectively. Reference signs  620   b ,  621   b , and  622   b  represent winding trailing end portions of the negative electrode current collector  620 , the negative electrode mixture layer  621 , and the negative electrode mixture layer  622 , respectively. 
     Like in the nonaqueous electrolyte battery  1 , since the area of the negative electrode mixture layer  622  has to be larger than the area of the positive electrode mixture layer  611  which is opposed thereto, the winding trailing end portion  622   b  of the negative electrode mixture layer  622  is positioned on the side of the winding trailing end portion  620   b  of the negative electrode current collector  620  with respect to the winding trailing end portion  611   b  of the positive electrode mixture layer  611 . Since the area of the negative electrode mixture layer  621  has to be larger than the area of the positive electrode mixture layer  612  which is opposed thereto, the winding trailing end portion  621   b  of the negative electrode mixture layer  621  is positioned on the side of the winding trailing end portion  620   b  of the negative electrode current collector  620  with respect to the winding trailing end portion  612   b  of the positive electrode mixture layer  612 . 
     With reference to  FIG. 10 , the winding body  70  included in the nonaqueous electrolyte battery  5  includes the negative electrode  72 . The negative electrode  72  includes a negative electrode current collector  720  and negative electrode mixture layers  721  and  722 . In  FIG. 10 , reference signs  720   a ,  721   a , and  722   a  represent winding leading end portions of the negative electrode current collector  720 , the negative electrode mixture layer  721 , and the negative electrode mixture layer  722 , respectively. Reference signs  720   b ,  721   b , and  722   b  represent winding trailing end portions of the negative electrode current collector  720 , the negative electrode mixture layer  721 , and the negative electrode mixture layer  722 , respectively. 
     The winding trailing end portion  722   b  of the negative electrode mixture layer  722  is positioned between the winding trailing end portion  611   b  of the positive electrode mixture layer  611  and the negative electrode tab  36  in the width direction (x direction) of the winding body  70 . With this arrangement, the winding trailing end portion  722   b  of the negative electrode mixture layer  722  is not positioned between both the end portions of the negative electrode tab  36  in the width direction (x direction) of the winding body  70 . Further, the winding trailing end portion  721   b  of the negative electrode mixture layer  721  is positioned between the winding trailing end portion  612   b  of the positive electrode mixture layer  612  and the positive electrode tab  35  in the width direction (x direction) of the winding body  70 . 
     In the structure of the nonaqueous electrolyte battery  5 , when the winding trailing end portions  721   b  and  722   b  are projected on the xz plane, neither the winding trailing end portion  721   b  nor the winding trailing end portion  722   b  overlaps the negative electrode tab  36 . When the negative electrode  72  is expanded, it is thereby possible to prevent the torsion of the negative electrode tab  36  with the difference in expansion between the winding trailing end portions  721   b  and  722   b . Further, the negative electrode tab  36  is positioned between the winding trailing end portions  721   b  and  722   b . This makes the pressure received from the winding body  70  symmetrical with respect to the negative electrode tab  36 . Therefore, the structure of the nonaqueous electrolyte battery  5  is more preferable than that of the nonaqueous electrolyte battery  4 . This is because the winding trailing end portion  622   b  of the negative electrode mixture layer  622  overlaps the negative electrode tab  36  in the nonaqueous electrolyte battery  4  ( FIG. 9 ) when it is projected on the xz plane. This is further because the negative electrode tab  36  is not positioned between the winding trailing end portions  621   b  and  622   b  in the nonaqueous electrolyte battery  4 . In other words, one winding trailing end portion ( 611   b ) is present on one side of the negative electrode tab  36  and two winding trailing end portions ( 612   b  and  621   b ) are present on the other side thereof in the structure of the nonaqueous electrolyte battery  4  while two winding trailing end portions ( 611   b  and  722   b ) are present on one side of the negative electrode tab  36  and another two winding trailing end portions ( 612   b  and  721   b ) are present on the other side thereof in the structure of the nonaqueous electrolyte battery  5 . This makes the force exerted on the negative electrode tab  36  symmetrical in the nonaqueous electrolyte battery  5 . Therefore, the torsion of the negative electrode tab  36  is less likely to occur in the structure of the nonaqueous electrolyte battery  5  than in the structure of the nonaqueous electrolyte battery  4 . 
     With reference to  FIG. 11 , the winding body  80  included in the nonaqueous electrolyte battery  6  includes the negative electrode  82 . The negative electrode  82  includes a negative electrode current collector  820  and negative electrode mixture layers  821  and  822 . In  FIG. 11 , reference signs  820   a ,  821   a , and  822   a  represent winding leading end portions of the negative electrode current collector  820 , the negative electrode mixture layer  821 , and the negative electrode mixture layer  822 , respectively. Reference signs  820   b ,  821   b , and  822   b  represent winding trailing end portions of the negative electrode current collector  820 , the negative electrode mixture layer  821 , and the negative electrode mixture layer  822 , respectively. 
     The winding trailing end portion  822   b  of the negative electrode mixture layer  822  is positioned between the negative electrode tab  36  and the positive electrode tab  35  in the width direction (x direction) of the winding body  80 . Further, the winding trailing end portion  821   b  of the negative electrode mixture layer  821  is positioned between the winding trailing end portion  612   b  of the positive electrode mixture layer  612  and the positive electrode tab  35  in the width direction (x direction) of the winding body  80 . 
     In the structure of the nonaqueous electrolyte battery  6 , like in the nonaqueous electrolyte battery  5 , when the winding trailing end portions  821   b  and  822   b  are projected on the xz plane, neither the winding trailing end portion  821   b  nor the winding trailing end portion  822   b  overlaps the negative electrode tab  36 . When the negative electrode  82  is expanded, it is thereby possible to prevent the torsion of the negative electrode tab  36  with the difference in expansion between the winding trailing end portions  821   b  and  822   b.    
     In the structure of the nonaqueous electrolyte battery  6 , further, both the winding trailing end portions  821   b  and  822   b  are positioned between the positive electrode tab  35  and the negative electrode tab  36 . Since the positive electrode tab  35  and the negative electrode tab  36  each have a certain thickness, the thickness (the size in the y direction) of the winding body  80  is the thinnest in the portion between the positive electrode tab  35  and the negative electrode tab  36 . By positioning the winding trailing end portions  821   b  and  822   b  in this portion, the thickness of the thickest portion of the winding body  80  can be thinned. Therefore, the structure of the nonaqueous electrolyte battery  6  is more preferable than those of the nonaqueous electrolyte batteries  4  and  5 . 
     In summary, among the embodiments disclosed in the present specification, the nonaqueous electrolyte battery  3  ( FIG. 8 ), the nonaqueous electrolyte battery  2  ( FIG. 7 ), the nonaqueous electrolyte battery  1  ( FIG. 3 ), the nonaqueous electrolyte battery  6  (FIG.  11 ), the nonaqueous electrolyte battery  5  ( FIG. 10 ), and the nonaqueous electrolyte battery  4  ( FIG. 9 ) are more preferable in this order. 
     Other Embodiments 
     Though the embodiments of the present invention have been discussed above, the present invention is not limited to the above-discussed embodiments, but allows various variations. 
     As shown in the nonaqueous electrolyte batteries  1  to  6 , in the nonaqueous electrolyte battery in accordance with the present invention, the winding trailing end portion ( 311   b ,  612   b ) of one of the positive electrode mixture layers has only to be positioned on the inner side of the winding body with respect to the negative electrode tab in the width direction of the winding body and the winding trailing end portion ( 312   b ,  611   b ) of the other positive electrode mixture layer has only to be positioned on the outer side of the winding body with respect to the negative electrode tab in the width direction of the winding body. This is because it is thereby possible to disperse the level differences at the winding trailing end portions. 
     In the above-discussed structure, as shown in the nonaqueous electrolyte batteries  1  to  3 , it is preferable that the winding trailing end portion ( 312   b ) of the positive electrode mixture layer which is positioned on the outer side of the winding body with respect to the negative electrode tab should be positioned on the outer side of the winding body with respect to the winding trailing end portion ( 311   b ) of the other positive electrode mixture layer in the width direction of the winding body. This is because there arises no bent portion in the positive electrode mixture layer on the outer side. 
     In the above-discussed structure, as shown in the nonaqueous electrolyte batteries  2 ,  3 ,  5 , and  6 , it is preferable that the winding trailing end portion ( 421   b ,  521   b ,  722   b ,  822   b ) of one of the negative electrode mixture layers is positioned between the winding trailing end portion of the positive electrode mixture layer opposed thereto and the positive electrode tab and not positioned between both the end portions of the negative electrode tab in the width direction of the winding body and the winding trailing end portion ( 422   b ,  522   b ,  721   b ,  821   b ) of the other negative electrode mixture layer is positioned between the winding trailing end portion of the positive electrode mixture layer opposed thereto and the positive electrode tab in the width direction of the winding body. This is because it is possible to prevent the torsion of the negative electrode tab with the difference in expansion between both the winding trailing end portions of the negative electrode mixture layers. 
     In the above-discussed structure, as shown in the nonaqueous electrolyte batteries  3  and  6 , it is preferable that both the winding trailing end portions are positioned between the positive electrode tab and the negative electrode tab in the width direction. This is because the thickness of the thickest portion of the winding body can be thinned. 
     This specification shows the exemplary structure in which the positive electrode tab is formed on the outermost side of the winding body. The positive electrode tab, however, may be formed on the innermost side of the winding body (on the side of the winding leading end portion of the positive electrode). 
     This specification shows the exemplary structure in which the winding body is contained in the battery case consisting of the exterior can and the cover plate which are formed of, e.g., an aluminum alloy or the like. The present invention is not limited to this structure, but there may be another structure in which the winding body is contained in a laminate outer package or the like. 
     This specification shows the exemplary case where the nonaqueous electrolyte battery is a lithium-ion secondary battery. The present invention can be preferably utilized particularly in the case where the nonaqueous electrolyte battery is a lithium-ion secondary battery. The present invention, however, is not limited to this case, but the present invention can be utilized as various kinds of nonaqueous electrolyte batteries within the scope of an investigation. 
     EXAMPLES 
     Hereinafter, the present invention will be discussed more specifically on the basis of Example. This Example does not limit the present invention. 
     Example 
     &lt;Production of Positive Electrode&gt; 
     100 parts by mass of a positive electrode active material in which Li 1.0 Ni 0.5 Co 0.2 Mn 0.3 O 2  and Li 1.036 Co 0.0991 Al 0.004 Mg 0.002 Sr 0.001 Ti 0.002 Zr 0.001 O 2  are mixed in the proportion of 3:7 (mass ratio), 20 parts by mass of a N-Methyl-2-pyrrolidone (NMP) solution containing 10% by mass of PVDF serving as a binder, 1 parts by mass of artificial graphite serving as an electroconductive aid, and 1 parts by mass of Ketjen Black are kneaded by using a biaxial kneading machine and NMP is further added thereto for adjustment of viscosity, to thereby prepare a positive electrode mixture-containing paste. 
     After applying the positive electrode mixture-containing paste (slurry) onto both surfaces of an aluminum foil (positive electrode current collector) having a thickness of 15 μm, the aluminum foil is dried in a vacuum at 100° C. for seven hours, to thereby form the positive electrode mixture layers on both the surfaces of the aluminum foil. After that, a press (calendering) process is performed to thereby adjust the thickness and the density of the positive electrode mixture layer, and a positive electrode tab made of nickel is welded to an exposed portion of the aluminum foil, to thereby produce a strip-like positive electrode having a length of 543 mm and a width of 50 mm. The positive electrode mixture layer for each side in the produced positive electrode has a thickness of 65 mm. 
     &lt;Production of Negative Electrode&gt; 
     97.5 parts by mass of a mixture, serving as a negative electrode active material, in which a complex in which an SiO surface having an average particle diameter D50% of 8 μm is coated with a carbon material (the amount of the carbon material is 10% by mass in the complex) and graphite having an average particle diameter D50% of 16 μm are mixed so that the amount of the complex in which the SiO surface is coated with the carbon material is 3.75% by mass, 1.5 parts by mass of SBR serving as a binder, and 1 part by mass of CMC serving as a thickener are mixed with water added thereto, to thereby prepare a negative electrode mixture-containing paste. 
     After applying the negative electrode mixture-containing paste (slurry) onto both surfaces of a copper foil (negative electrode current collector) having a thickness of 8 μm, the copper foil is dried in a vacuum at 160° C. for twenty-four hours, to thereby form the negative electrode mixture layers on both the surfaces of the copper foil. After that, a press (calendering) process is performed to thereby adjust the thickness and the density of the negative electrode mixture layer, and a negative electrode tab made of nickel is welded to an exposed portion of the copper foil, to thereby produce a strip-like negative electrode having a length of 626 mm and a width of 51 mm. The negative electrode mixture layer for each side in the produced negative electrode has a thickness of 60 μm. 
     &lt;Preparation of Nonaqueous Electrolyte Solution&gt; 
     LiPf 6  is dissolved in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in the proportion of 3:7 (volume ratio) at a concentration of 1.1 mol/L, and 2.0% by mass of fluoroethylene carbonate (FEC) and 2.0% by mass of vinylene carbonate (VC) are added thereto, to thereby prepare a nonaqueous electrolyte solution. 
     &lt;Assembly of Battery&gt; 
     The strip-like positive electrode is superposed on the strip-like negative electrode with a PE separator having a thickness of 16 μm for lithium-ion secondary battery interposed therebetween and the layered body is wound, and then pressure is imposed thereon to make the layered body into a flattened shape. The winding body is so produced as to have a structure in conformance with that of the winding body  30  ( FIG. 3 ) in accordance with the first embodiment. 
     Next, the electrode winding body is inserted into a square battery case made of an aluminum alloy having an external thickness of 4.4 mm, an external width of 45.8 mm, and an external height of 55.3 mm, a current collector tab is welded thereto, and a cover plate made of an aluminum alloy is welded to an opening end portion of the battery case. Then, the nonaqueous electrolyte solution is injected from an inlet provided in the cover plate, and after still standing for one hour, the inlet is sealed. After that, through a chemical conversion treatment, a lithium-ion secondary battery having such a structure as shown in  FIG. 1  is achieved. 
     Comparative Example 
     Herein, a winding body is so produced as to have a structure in conformance with the winding body  90  ( FIG. 5 ) of the comparative embodiment. A lithium-ion secondary battery in which constituent elements other than the above are identical to those in Example is used in Comparative Example. 
     &lt;Expansion Measurement&gt; 
     As a thickness meter, used is Digital Micrometer (manufactured by Mitutoyo Corporation). Thickness measurement is performed at a measuring pressure of 5 to 10 N by using a measuring terminal of φ6 mm on ten batteries manufactured in each of Example and Comparative Example. 
       FIG. 12  is a view showing thickness measurement points in an expansion measurement.  FIG. 12(   a ) is an elevational view of a lithium-ion secondary battery, and  FIG. 12(   b ) is a plan view thereof, with dimensions. In  FIG. 12(   a ), the respective positions of the positive electrode tab  35  and the negative electrode tab  36  are hatched and schematically shown. For each battery, the thickness is measured at twelve points (P 1  to P 12 ) in the vicinity of the negative electrode tab  36  before and after the chemical conversion treatment. The thickness of each point is measured five times, and an average value is obtained. At a point which has the largest difference in thickness between before and after the chemical conversion treatment, the difference in thickness between before and after the chemical conversion treatment (the amount of expansion) is checked. 
     For each of ten batteries manufactured in Example, the amount of expansion (mm) is obtained in the above-discussed manner and an average value is calculated. Also for each of ten batteries manufactured in Comparative Example, the amount of expansion (mm) is obtained in the above-discussed manner and an average value is calculated. The result is shown in Table 1. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Amount of Expansion (mm) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Example 
                 0.287 
               
               
                   
                 Comparative Example 
                 0.314 
               
               
                   
                   
               
            
           
         
       
     
     As shown in Table 1, the amount of expansion in the lithium-ion secondary battery in Example is smaller than that in the lithium-ion secondary battery in Comparative Example. It can be thought that by the present invention, the winding body can be uniformly expanded and this prevents undulation. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be industrially used as a nonaqueous electrolyte battery comprising a flattened winding body.