Abstract:
Provided is a battery fabrication method capable of collecting foils by reforming a collector with ease and at a high quality. The battery fabrication method is to fabricate a battery ( 10 ) including an electrode body ( 30 ) formed such that a positive electrode foil ( 31 ), a part of the surface of which is coated with a positive electrode mixture, and a negative electrode foil ( 32 ), a part of which is coated with a negative electrode mixture, are stacked with a separator ( 33 ) interposed therebetween and the stacked foils are rolled. In the processes of the battery fabrication method, when the electrode body ( 30 ) is formed by the rolling, the mixture non-coated parts ( 35, 36 ) of the positive electrode foil ( 31 ) and negative electrode foil ( 32 ) are reformed by use of a reforming roll ( 50, 50 ), thereby collecting into bundles ( 35   a,   36   a ) a plurality of foils having different rounds in the radial direction of the electrode body ( 30 ) at the mixture non-coated parts ( 35, 36 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a method for manufacturing a battery, and particularly to a technique of manufacturing the battery with an electrode body formed as a wound body. 
       BACKGROUND ART 
       [0002]    A cylindrical lithium-ion secondary battery includes a cylindrical casing and a cylindrical electrode body formed by winding positive and negative electrode sheets and separators as these sheets and separators laminated. The electrode body housed in the casing is submerged in an electrolyte, and it works as a chargeable and dischargeable element. 
         [0003]    The casing has electrode terminals at the outside thereof. The terminals are connected to the electrode body via current collecting plates and lead terminals, and the terminals perform as electric paths between the inside of the battery (electrode body) and the outside. 
         [0004]    The positive and negative electrode sheets are partially coated with electrode compounds, and the electrode sheets are wound with the compound coated portions overlapping through the separators. The portions of these sheets where the compounds are not coated (non-coated portions) are projected toward the opposite directions each other. The non-coated portions of the sheets are arranged projecting from the each roll end surface of the wound body, and along the radial direction of the wound body, the non-coated portions at the different rounds are arranged in order. 
         [0005]    The non-coated portions projecting in the above-described manner perform as current collectors, to which the current collecting plates are connected. 
         [0006]    Because the positive and negative electrode sheets are thin metal foils, there are small connecting areas among the current collecting plates and the positive or negative electrode sheet. Therefore, the cylindrical battery has a problem in connection between the current collectors and the current collecting plates. 
         [0007]    For instance, JP 2008-258145 A discloses a current collecting plate including slots into which a group of current collectors of the electrode body is inserted. The current collecting plate is welded to the electrode body, with the collecting plate covering the top surface (roll end surface) of the electrode body, in which the gathered collectors are inserted into the slots of the collecting plate. The collecting plate contacts the gathered non-coated portions of the positive or negative electrode sheet, and so, the sheets are bundled in the slots of the collecting plate due to the gravity. The welding is performed on the condition that the multiple non-coated portions are gathered, thereby enlarging the connecting areas and ensuring the connecting strength. 
         [0008]    In the technique disclosed in JP 2008-258145 A, the current collectors are bent after winding the electrode sheets to configure the electrode body, so that the sheets may be damaged during the deformation. For example, when the variation occurs in the projecting amounts of the collectors or in the clearances between the adjacent collectors, the troubles may be lead such as damages due to overloads to the sheets and short circuits due to the deformations of the collectors, and thus it&#39;s difficult to keep product quality. 
       Citation List 
     Patent Literature 
       [0009]    PTL 1: JP 2008-258145 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    The present invention aims to provide a battery manufacturing method capable of gathering sheets by reforming a current collector with ease and at a high quality. 
       Technical Solution 
       [0011]    The first aspect of the present invention is a method for manufacturing a battery that comprises an electrode body formed by winding a positive electrode sheet partially coated with a positive electrode compound, a negative electrode sheet partially coated with a negative electrode compound and separators, with these sheets and separators laminated. While winding the electrode body, a non-coated portion where the electrode compound is not coated is reformed to gather multiple sheets having different rounds in a radial direction of the electrode body. 
         [0012]    In the advantageous embodiment, a reforming roll telescopically moving with respect to the winding core of the electrode body is used for pressing and reforming the non-coated portion cyclically. 
         [0013]    More advantageously, the reforming roll telescopically moves in response to the change of thickness of the electrode body accompanied by the winding and to the cycle of reforming. 
         [0014]    In the alternative embodiment, the reforming roll is disposed near the winding core to directly press the electrode body during the winding process. 
         [0015]    The reforming roll is preferably formed in conical shape having a bottom at the tip side of the non-coated portion. 
       Advantageous Effects of Invention 
       [0016]    According to the method of the present invention, the electrode sheets are gathered by reforming the current collecting portions with ease and high quality. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  schematically illustrates a battery manufactured by a method in accordance with the present invention. 
           [0018]      FIG. 2  illustrates an electrode body included in the battery, (a) is the perspective view, and (b) is the section view. 
           [0019]      FIG. 3  illustrates a current collecting plate connected to the electrode body. 
           [0020]      FIG. 4  depicts the current collecting plate, (a) is the plan view, and (b) is the enlarged section view along A-A line. 
           [0021]      FIG. 5  depicts a connection structure between a current collector of the electrode body and the current collecting plate. 
           [0022]      FIG. 6  shows a winding process for winding electrode elements of the electrode body. 
           [0023]      FIG. 7  shows a reforming roll pressing the electrode body. 
           [0024]      FIG. 8  illustrates a reforming structure of the current collector. 
           [0025]      FIG. 9  is a map for controlling the move of the reforming roll. 
           [0026]      FIG. 10  shows an embodiment of the reforming roll. 
           [0027]      FIG. 11  shows alternative embodiments of the reforming roll. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0028]    Referring to  FIGS. 1 to 3 , a structure of a battery  10  is described. The battery  10  is a secondary battery such as a lithium-ion battery, a nickel hydride battery and the like. 
         [0029]    As illustrated in  FIG. 1 , the battery  10  has a cylindrical casing  20  and an electrode body  30  housed in the casing  20 . The electrode body  30  is electrically connected to a positive electrode terminal  41  and a negative electrode terminal  42 , both of which work as the electric paths between inside and outside of the battery. 
         [0030]    The casing  20  is a cylindrical container made of a metal such as aluminum, and houses the electrode body  30 . The one end of the casing  20  is formed with the positive electrode terminal  41  projecting toward outwardly, and the other end is formed with the negative electrode terminal  42 . 
         [0031]    As illustrated in  FIG. 2 , the electrode body  30  is formed as a cylindrical wound body, in which a positive electrode sheet  31  and a negative electrode sheet  32  are laminated via separators  33  and those are wound around a winding core  34 . 
         [0032]    The positive electrode sheet  31  is a current collecting sheet made of a metal such as aluminum, and partially coated with a positive electrode compound containing an active material. The negative electrode sheet  32  is a current collecting sheet made of a metal such as copper, and partially coated with a negative electrode compound containing an active material. The separator  33  is a thin film with a number of pores made of polyethylene, polypropylene or polyolefin, and disposed between the positive electrode sheet  31  and the negative electrode sheet  32  to separate them. 
         [0033]    The core  34  is made of a resin having insulating property such as polypropylene. The core  34  is formed as a rod and used as the winding core of the electrode body  30 . 
         [0034]    As shown in  FIG. 2(   b ), the positive electrode sheet  31  and the negative electrode sheet  32  are wound via the separators  33  such that the compound coated portions are overlapped and non-coated portions of compound  35  and  36 , i.e. the portions where the compounds are not coated, are projected toward the opposite direction. At one end (upper end in  FIG. 2(   b )) of the electrode body  30 , the non-coated portion  35  comes out multiple times at the different rounds in the radial direction, and at the other end (lower end in  FIG. 2(   b )) of that, so does the non-coated portion  36 . 
         [0035]    The non-coated portions  35  and  36  work as the current collectors of the electrode sheets  31  and  32 , respectively. As illustrated in  FIG. 3 , the non-coated portions are connected to current collecting plates  37  and  38 , respectively. The collecting plates  37  and  38  are connected to the terminals  41  and  42  via lead terminals (no shown), respectively. Thus, the electrode body  30  is electrically connected to the terminals  41  and  42 , and thereby the terminals  41  and  42  perform as the electrical paths to the outside of the battery  10 . 
         [0036]    Referring to  FIGS. 3 to 5 , a description will be given about structures of the current collecting plates  37  and  38 , and connection structures between the collecting plates  37  and  38  and the non-coated portions  35  and  36 . In this embodiment, the structures of the collecting plates  37  and  38  are same, and thus the below description will be given to the collecting plate  37  connected to the non-coated portion  35  that is the positive electrode side. The collecting plate  38  connected to the non-coated portion  36  that is the negative electrode side and the connecting structure between the collecting plate  38  and the non-coated portion  36  are not explained. 
         [0037]    As depicted in  FIGS. 3 and 4(   a ), the current collecting plate  37  is straight metal plate, and has a through hole  37   a  and multiple slots  37   b  (in drawings, from the center, there are three slots along one direction and three slots along the other direction). 
         [0038]    The through hole  37   a  has a diameter larger than the core  34  and disposed at the center of the plate  37 . The slots  37   b  are arranged symmetrically around the through hole  37   a.    
         [0039]    As shown in  FIG. 4(   b ), the slot  37   b  includes a straight slit portion  37   c  and two clip portions  37   d  forming the slit portion  37   c.    
         [0040]    The slit portion  37   c  is configured as a straight opening having a predetermined width, which opens perpendicular to the extending direction of the collecting plate  37  (see  FIG. 4(   a )). 
         [0041]    The clip portions  37   d  are extended toward one side (lower side in drawings) of the thickness direction of the collecting plate  37 , and bent such that the end is directed opposite to the extended direction thereof (upper direction in drawings). That is, the clip portion  37   d  is bent twice, at the base and the middle. 
         [0042]    The above-described structure provides elastic deformations of the clip portions  37   d  due to the force acted on the clip portions  37   d  when the member to be inserted between the clip portions  37   d  has larger width than the width of the slit portion  37   c,  and the elastic deformations lead the clip force against the force caused by the member inserted into the slit portion  37   c.    
         [0043]    As depicted in  FIG. 5 , the non-coated portion  35  is gathered into bundles  35   a  such that the multiple sheets having the different rounds in the radial direction are bundled. The bundle  35   a  gathered in such manner is inserted into the slit portion  37   c.  The clip portions  37   d  apply the clip force to the bundle  35   a  of the non-coated portion  35  inserted into the slit portion  37   c,  thereby contacting closely the gathered non-coated portion  35 . 
         [0044]    The non-coated portion  35  is inserted into the slit portion  37   c,  i.e. the non-coated portion  35  is fitted into the slots  37   b,  and the non-coated portion  35  is connected to the current collecting plate  37 . The connection is performed by welding, blazing or the like. 
         [0045]    As described above, the non-coated portion  35  is gathered into multiple bundles  35   a  and inserted into the slit portions  37   c,  thereby enhancing the contact. Therefore, the non-coated portion  35  is connected to the slots  37   b  without space between rounds. 
         [0046]    The number of the slots  37   b  of the collecting plate  37 , to which the non-coated portion  35  is connected, is not limited to six as this embodiment, and the number may be changeable in response to the connecting process, the connection structure to the electrode body  30  or the like. 
         [0047]    For instance, if the number of the slots  37   b  is low, the workability is improved due to the less connecting processes. If the number of the slots  37   b  is high, the connecting property between the electrode body  30  and the collecting plate  37  is enhanced. 
         [0048]    The width of the slit portion  37   c  of the slot  37   b  may be set in response to the thickness of the non-coated portion  35  or the like. 
         [0049]    As described above, the non-coated portion  35  as the current collector of the electrode body  30  is connected to the current collecting plate  37 , with the non-coated portion bundled into multiple bundles  35   a.  In other words, the process for manufacturing the electrode body  30  needs the bundle process for gathering the non-coated portion  35  into the bundles  35   a.    
         [0050]    In the conventional method for manufacturing the battery, the bundle process is performed after the winding process of the electrode body. However, when bundling the sheet of the wound electrode body, the sheet may be damaged or tore, so that the bundle process needs high accuracy. 
         [0051]    In this embodiment enable to overcome the problems involved in the conventional method, the method for manufacturing the battery includes a winding process for winding the electrode body  30  and bundling the sheets thereof. 
         [0052]    Referring to  FIGS. 6 to 9 , a method for manufacturing the battery  10  is described below. 
         [0053]    The manufacturing method for the battery  10  includes the winding process in which the positive electrode sheet  31 , the negative electrode sheet  32  and the separators  33 , which are the electrode elements constructing the electrode body  30 , are laminated and the laminated sheets are wound around the core  34  to configure the electrode body  30 , and some subsequent processes such as assembly process for assembling the battery  10  in which the electrode body  30  is housed in the casing  20 . 
         [0054]    As shown in  FIG. 6 , in the winding process, from the core  34  (winding center), the positive electrode sheet  31 , the separator  33 , the negative electrode sheet  32 , and the separator  33  are arranged in order, and the ends thereof are fixed to the outer surface of the core  34 . The core  34  rotates to form the electrode body  30  wound around the core  34 , in which the sheets-fixed point becomes the starting point of laminating the electrode element. 
         [0055]    In this process, the electrode elements  31 ,  32  and  33  are arranged with respect to the axis of the core such that the non-coated portion  35  of the positive electrode sheet  31  and the non-coated portion  36  of the negative electrode sheet  32  are projected to the opposite directions. More specifically, each of the non-coated portions  35  and  36  projects along the axis of the core  34 . 
         [0056]    As illustrated in  FIGS. 7 and 8 , the winding process uses reforming rolls  50  to reform the non-coated portions  35  and  36  while the electrode elements  31 ,  32  and  33  are wound around the core  34  and to bundle the non-coated portions  35  and  36  into bundles  35   a  and  36   a.    
         [0057]    The reforming rolls  50  are positioned near the core  34  and opposite to the laminating starting point of the electrode elements  31 ,  32  and  33  (the point on the outer periphery of the core  34  where the electrode elements  31 ,  32  and  33  are fixed). The reforming rolls  50  are movable with respect to the core  34  and along the radial direction of the core  34 . 
         [0058]    The move of the reforming roll  50  is controlled by the transfer device to move the roll telescopically and the control device to operate the transfer device for controlling the reforming structure. 
         [0059]    The forming roll  50  moves with respect to the center of the core  34 , thereby contacting the middle portion of the non-coated portion  35  or  36  and pressing the portion toward the core  34  (winding center). Thus, the non-coated portions  35  and  36  are deformed to incline toward the winding center. As described above, the reforming rolls  50  press the non-coated portions  35  and  36  toward the core  34  (winding center), and deform those into the predetermined shape, which is defined as “reform for the non-coated portions  35  and  36 ” in this embodiment. 
         [0060]    As shown in  FIG. 8 , the non-coated portions  35  and  36  are gathered into bundles  35   a  and  36   a  by using the reforming rolls  50 . The non-coated portions  35  and  36  are bundled into multiple groups, where each group contains multiple rounds (five rounds in drawings) of sheets counted from the inner side, and the adjacent groups are spaced each other. Due to the telescopic move of the reforming roll  50  to the core  34 , the non-coated portion  35  or  36  is pressed and reformed cyclically. As a result, the non-coated portions  35  and  36  are formed with multiple gathered portions having constant cycle (bundles  35   a  and  36   a ). 
         [0061]    The structures of the bundles  35   a  and  36   a  formed in the non-coated portions  35  and  36  are preferably set in accordance with the connecting structure such as the number or shapes of the slots of the current collecting plates  37  and  38 , considering the connection stability of the collecting plates  37  and  38 . 
         [0062]    When winding the electrode elements  31 ,  32  and  33 , the reforming rolls  50  are controlled to move with respect to the core  34  to reform the non-coated portions  35  and  36 . 
         [0063]    As the electrode elements  31 ,  32  and  33  are wound, the wound electrode body  30  has bigger diameter shown in broken line in  FIG. 9 . In order to reform the non-coated portions  35  and  36  into the desired shapes, the reforming rolls  50  are needed to contact and press the non-coated portions  35  and  36  as shown in dashed double-dotted line in  FIG. 9 . 
         [0064]    As described above,  FIG. 9  shows the control of reforming roll  50  in view of the diameter change of the electrode body  30  (shown in solid line in  FIG. 9 ). When the outer surface of the core  34  facing the roll  50  is defined as zero point and the distance between the roll  50  and the zero point is defined as a distance (a), the distance (a) is controlled to satisfy the relationship between the time change of the diameter accompanied by the winding (the time change of the distance between the outer surface of the wound body and the core  34 ) and that of the reform cycle. 
         [0065]    In the winding process in this embodiment, the electrode elements  31 ,  32  and  33  are laminated and wound, and at the same time, the non-coated portions  35  and  36  are bundled. 
         [0066]    Therefore, there is no bundle process after the winding process, and the sheets can be bundled without having influence from the production error of the bundles or the error of winding. 
         [0067]    As a result, the electrode sheets are gathered by reforming the current collectors, that is the non-coated portions  35  and  36 , with ease and at a high quality. 
         [0068]    Moreover, in the reforming roll  50 , the distance (a) between the roll and the core  34  is controlled in response to the change of the wound thickness of the electrode body  30 . 
         [0069]    The reforming structures of the non-coated portions  35  and  36  are easily controlled with high quality. 
         [0070]    Therefore, the connection quality between the non-coated portions  35  and  36  and the current collecting plates  37  and  38  are enhanced and the battery  10  is provided with high product quality. 
         [0071]    The reforming rolls  50  telescopically move in the radial direction with respect to the outer surface of the core  34 . That is, the rolls  50  are disposed near the core  34 , and the rolls can directly press and deform the non-coated portions  35  and  36  during the winding process. 
         [0072]    Thus, the rolls  50  continuously press the portion of the group of the gathered sheets at the same point in the different rounds, and the non-coated portions  35  and  36  contained in the group are unfailingly pressed, thereby improving the accuracy of reforming. 
         [0073]    The alternative embodiment of the reforming roll  50  may be disposed apart from the core  34  and contact the non-coated portions  35  and  36  of the electrode elements  31  and  32  before they reach the core  34 . In this embodiment, the reforming direction can be not only core side but also the opposite side. 
         [0074]    As shown in  FIG. 10 , the reforming rolls  50  have conical shape whose bottom is at the tip side of the non-coated portions  35  and  36 . The reforming rolls  50  are formed in the conical or circular truncated cone shape tapered from the center side to the tip side of the non-coated portions  35  and  36 , and the pressures acted to the tips of the non-coated portions  35  and  36  are larger than those acted on the center side. 
         [0075]    Due to the configuration, the non-coated portions  35  and  36  are naturally bent, thereby reducing the force acted on the compound coated portions of positive and negative electrode sheets  31  and  32 . Therefore, the current collectors of the electrode body  30  are bundles with high quality. 
         [0076]    The other embodiment of the reforming roll  50  considering the productivity thereof is shown in  FIG. 11 .  FIG. 11(   a ) shows the spherical shape, and  FIG. 11(   b ) shows columnar shape. The shape of the reforming roll can be applicable to the shape enable to press the non-coated portions  35  and  36  in the radial direction during the winding process. 
         [0077]    In this embodiment, considering the productivity in the winding process, the positive electrode sheet  31 , the negative electrode sheet  32 , and the separators  33  are laminated and wound around the core  34  in one process. However, the laminating process for laminating the positive electrode sheet  31 , the negative electrode sheet  32 , and the separators  33  may be separated from the winding process for winding the laminated sheets around the core  34 . In this case, the laminating can be operated with high accuracy. 
         [0078]    The reforming rolls  50  may be disposed upstream side of the core  34 . In this case, the rolls can reform the sheets toward both sides of closing and separating with respect to the core  34 . Such arrangement makes the desired reforming easy. 
       INDUSTRIAL APPLICABILITY 
       [0079]    The present invention is applicable to the method for manufacturing a cylindrical battery, and particularly to the bundling method for bundling the current collectors of the electrode body by reforming the collectors with high accuracy.