Patent Publication Number: US-2015072201-A1

Title: Cylindrical secondary battery

Description:
TECHNICAL FIELD 
     This invention relates to a cylindrical secondary battery. 
     BACKGROUND ART 
     In cylindrical secondary batteries represented by lithium secondary batteries or the like, a positive electrode and a negative electrode are wound around the periphery of a hollow cylindrical axial core via a separator, thereby forming an electrode group as a power generation element. The electrode group is accommodated in a battery can, and one of the positive electrode and the negative electrode is welded to a can bottom of the battery can serving as an external terminal of one of the positive and negative electrodes, with the other being welded to a lid member serving as an external terminal of reverse polarity. Before being welded to the lid member, an electrolytic solution is injected into the interior of the battery can, the electrode group is welded to the lid member, and the lid member and the battery can are then hermetically sealed from the outside by means of caulking. 
     In order to weld the positive or negative electrode to the battery can or the lid member, there are a structure using a large number of conductive leads and a structure using a small number of conductive leads as from 1 to 2. The structure using a small number of conductive leads is mainly used for small-sized cylindrical secondary batteries with a low charge and discharge current. 
     In the cylindrical secondary batteries, since torsion acts on the welded portion between the conductive lead and the battery can or the lid member following expansion and contraction and vibration of the electrode group or displacement thereof into the axial direction, as generated at the time of charge and discharge, breakage is liable to be caused in the welded portion due to the long-term use. 
     Accordingly, a variety of structures for preventing the breakage of the welded portion have been studied. As an example thereof, there is known a structure in which a conductive lead is provided with a helical shape portion which does not close a gas-removal hole in its central portion (see, for example, PTL 1). The above-described patent literature does not describe a structure of the welded portion of the can bottom side. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: JP-A-2001-23608 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the above-described patent literature, the conductive lead is formed in a spiral shape so as not to close the gas-removal hole in the central portion, and an end portion for welding is welded to the lid member at a position out of the central portion of the axial core. As an example of a method of welding a conductive lead to a can bottom of a battery can, there is known a method in which an electrode rod is inserted into a hollow portion of an axial core, and an end portion for welding of an electrode lead is welded to a tip of the electrode rod by means of, for example, resistance welding or the like in a state of being pressed onto the can bottom of the battery can. The above-described method cannot be applied in the structure in which the end portion for welding of the conductive lead is positioned out of the central portion as in the above-described patent literature. Accordingly, for example, a method with low working efficiency, in which a conductive lead is preliminarily welded to an electrode plate, and the electrode plate is then accommodated together with an electrode group in a battery can, must be adopted. 
     Solution to Problem 
     A cylindrical secondary battery according to a first aspect of the present invention is concerned with a cylindrical secondary battery in which an electrode group having a positive electrode and a negative electrode wound around the periphery of an axial core having a hollow portion via a separator is accommodated in a battery can, and one of a conductive lead welded to the negative electrode and a conductive lead welded to the positive electrode is connected to a lid member covering an opening of the battery can, with the other being welded to a can bottom of the battery can, wherein at least the conductive lead welded to the can bottom of the battery can includes an end portion for welding which is extended to a position corresponding to a central portion of the hollow portion of the axial core and a routing portion which is deformable in the axial direction of the axial core and the perpendicular direction to the axial direction, and the end portion for welding is welded to the can bottom of the battery can. 
     A cylindrical secondary battery according to a second aspect of the invention is concerned with the cylindrical secondary battery according to claim  1 , wherein the routing portion of the conductive lead is routed around the periphery of the end portion for welding from the end portion for welding so as not to overlap planarly. 
     A cylindrical secondary battery according to a third aspect of the invention is concerned with the cylindrical secondary battery according to claim  1  or  2 , wherein the conductive lead includes a bending portion for bending the routing portion toward the outer periphery side in at least one place between the end portion for welding and the routing portion. 
     A cylindrical secondary battery according to a fourth aspect of the invention is concerned with the cylindrical secondary battery according to any one of claims  1  to  3 , wherein the routing portion of the conductive lead is in a spiral shape. 
     A cylindrical secondary battery according to a fifth aspect of the invention is concerned with the cylindrical secondary battery according to any one of claims  1  to  4 , wherein the conductive lead welded to the can bottom of the battery can is welded to the positive electrode or the negative electrode in a side edge on the winding start side of the axial core of the positive electrode or the negative electrode. 
     A cylindrical secondary battery according to a sixth aspect of the invention is concerned with the cylindrical secondary battery according to claim  5 , further including an insulating sheet disposed between the conductive lead and the can bottom of the battery can, the insulating sheet including a slit for inserting thereinto an opening corresponding to the hollow portion of the axial core and the conductive lead of the axial core. 
     A cylindrical secondary battery according to a seventh aspect of the invention is concerned with the cylindrical secondary battery according to anyone of claims  1  to  4 , wherein the conductive lead including the end portion for welding welded to the can bottom of the battery can is welded to the positive electrode or the negative electrode in an intermediate portion in the lengthwise direction in the positive electrode or the negative electrode. 
     A cylindrical secondary battery according to an eighth aspect of the invention is concerned with the cylindrical secondary battery according to claim  7 , further including an insulating sheet disposed between the conductive lead and the can bottom of the battery can, the insulating sheet including a first opening provided at a position corresponding to the hollow portion of the axial core, a second opening provided at a position corresponding to a root of the conductive lead in which the conductive lead is welded to the positive electrode or the negative electrode, and a slit for inserting thereinto the conductive lead which is lead out from the second opening into the outside. 
     A cylindrical secondary battery according to a ninth aspect of the invention is concerned with the cylindrical secondary battery according to anyone of claims  1  to  8 , wherein all of the conductive leads include a routing portion which is deformable in the axial direction of the axial core and the perpendicular direction to the axial direction. 
     A cylindrical secondary battery according to a tenth aspect of the invention is concerned with the cylindrical secondary battery according to anyone of claims  1  to  9 , wherein a welded portion between the end portion for welding and the can bottom of the battery can has a size of from 1 to 5 mm in terms of a radius. 
     Advantageous Effects of Invention 
     Since the conductive lead is deformable in the axial direction of the axial core and the perpendicular direction to the axial direction, the breakage of the welded portion can be prevented. In addition, since the end portion for welding is extended to a position corresponding to a central portion of the hollow portion of the axial core, by inserting an electrode rod into the hollow portion of the axial core, it is possible to weld the end portion for welding directly to the can bottom of the battery can. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of an embodiment of a cylindrical secondary battery according to the invention. 
         FIG. 2  is an exploded perspective view of the cylindrical secondary battery illustrated in  FIG. 1 . 
         FIG. 3  is a perspective view showing a state before bending a conductive lead of an electrode group illustrated in  FIG. 2 . 
         FIG. 4  is a perspective view of a state where a part of the electrode group illustrated in  FIG. 3  is developed. 
         FIG. 5  is a plan view showing a connection state between a positive electrode and a conductive lead. 
         FIG. 6  is a plan view showing a connection state between a negative electrode and a conductive lead. 
         FIG. 7  is a perspective view for explaining a method of installing an insulating sheet in an electrode group. 
         FIG. 8  is a perspective view for explaining a structure of a conductive lead of an electrode group. 
         FIG. 9  is a view for explaining a detailed structure of a state where a conductive lead is bent, in which (A) is a perspective view, and (B) is a side view. 
         FIG. 10  is a cross-sectional view for explaining a method of welding a conductive lead to a battery can. 
         FIG. 11  is a table showing results of a torsion test. 
         FIG. 12  is a table showing results of a vibration test. 
         FIG. 13  is a cross-sectional view of Embodiment 2 of a cylindrical secondary battery according to the present invention. 
         FIG. 14  is a perspective view for explaining a method of installing an insulating sheet in an electrode group shown in  FIG. 13 . 
         FIG. 15  is a plan view showing a connection state between a positive electrode and a conductive lead as illustrated in  FIG. 14 . 
         FIG. 16  is a plan view showing a connection state between a negative electrode and a conductive lead as illustrated in  FIG. 14 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
     The cylindrical secondary battery according to the invention is hereunder described by reference to a lithium ion cylindrical secondary battery as an embodiment together with the drawings. 
     (Entire Configuration of Secondary Battery) 
       FIG. 1  is a cross-sectional view of a cylindrical secondary battery according to the invention, and  FIG. 2  is an exploded perspective view of the cylindrical secondary battery shown in  FIG. 1 . However, in  FIG. 2 , illustration of the battery can illustrated in  FIG. 1  is omitted. 
     A cylindrical secondary battery  1  has dimensions of an external shape of from about 14 to 26 mmφ and a height of from about 43 to 65 mm. 
     This cylindrical secondary battery  1  has a battery container  4  having a structure in which a closed-end cylindrical battery can  2  and a hat shaped lid body  3  are subjected to caulking processing via a seal member  43  generally called a gasket and hermetically sealed from the outside. The closed-end cylindrical battery can  2  is formed by subjecting a metal plate made of iron, aluminum, stainless steel, or the like to press processing, and in the case of an iron-made plate, for the purpose of preventing corrosion, a plated film of nickel or the like is formed over the entirety of the outer and inner surfaces thereof. The battery can  2  has an opening  202  on the upper end side that is an open side thereof. A groove  201  protruding inside the battery can  2  is formed on the side of the opening  202  of the battery can  2 . Respective constituent members for the power generation as described below are accommodated in the interior of the battery can  2 . 
     Reference numeral  10  stands for an electrode group which has an axial core  15  in its central portion, and a positive electrode and a negative electrode are wound around the periphery of the axial core  15 . The axial core  15  has a hollow cylindrical shape having a hollow portion  15   a  in the center thereof. 
       FIG. 3  is a perspective view showing a state before bending a conductive lead of the electrode group illustrated in  FIG. 2 , and  FIG. 4  is a perspective view in which a part of the electrode group illustrated in  FIG. 3  is developed. However, in  FIG. 4 , illustration of an insulating sheet (details of which will be described later) in  FIG. 3  is omitted. 
     As illustrated in  FIG. 4 , the electrode group  10  has a structure in which a positive electrode  11 , a negative electrode  12 , and first and second separators  13  and  14  are wound around the periphery of the axial core  15 . 
     The axial core  15  has a hollow cylindrical shape, and the negative electrode  12 , the first separator  13 , the positive electrode  11 , and the second separator  14  are laminated in this order and wound on the axial core  15 . Inside the innermost peripheral negative electrode  12 , the first separator  13  and the second separator  14  are wound by several turns. In addition, the negative electrode  12  and the second separator  14  wound on the outer periphery thereof appear on the outermost periphery. The second separator  14  on the outermost periphery is held down with an adhesive tape  19 , for example, KAPTON (registered trademark) tape or the like (see  FIGS. 2 and 3 ). 
     A conductive lead  21  of the positive electrode side is welded to the positive electrode  11 , and a conductive lead  22  of the negative electrode side is welded to the negative electrode  12 . 
       FIG. 5  is a plan view showing a connection state between the positive electrode  11  and the conductive lead  21  of the positive electrode side, and  FIG. 6  is a plan view showing a connection state between the negative electrode  12  and the conductive lead  22  of the negative electrode side. 
     As illustrated in  FIG. 5 , the positive electrode  11  has a positive electrode sheet  11   a  having a longitudinal shape, which is formed of an aluminum foil, and a positive electrode mixture  11   b  is coated and formed on the both surfaces of this positive electrode sheet  11   a  (in  FIG. 5 , only one surface of the positive electrode sheet  11   a  is illustrated). A side edge in the axial direction on the winding start side of the axial core  15  (described by a two-dotted chain line in  FIG. 5 ) of the positive electrode sheet  11   a  is a positive electrode mixture-untreated portion  11   c  in which the aluminum foil is exposed without being coated with the positive electrode mixture  11   b . The positive electrode mixture  11   b  is coated over the entirety of the positive electrode sheet  11   a  exclusive of the positive electrode mixture-untreated portion  11   c , and a width of the positive electrode sheet  11   a  and a width of the positive electrode mixture  11   b  are equal to each other. The conductive lead  21  of the positive electrode side, which protrudes upward in parallel to the axial core  15  and which is formed of an aluminum foil, is welded to the positive electrode mixture-untreated portion  11   c . Welding between the positive electrode sheet  11   a  and the conductive lead  21  of the positive electrode side is performed by means of, for example, resistance welding. 
     An example of the formation method of the positive electrode  11  is hereunder shown. 
     LiNi 0.33 Mn 0.33 Co 0.33 O 2  as a positive electrode active material, powdered carbon as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder are weighed in a weight ratio of 85/10/5, to which is then added an appropriate amount of N-methylpyrrolidone (NMP) as a solvent, and these are kneaded for 30 minutes using a kneader, thereby obtaining a positive electrode slurry. Examples of a method of coating the positive electrode slurry on the positive electrode sheet  11   a  include a roll coating method, a slit die coating method, and the like. This positive electrode slurry is coated on the both surfaces of the positive electrode sheet  11   a  made of an aluminum foil (thickness: 20 μm, width: 56 mm). An example of the coating thickness of the positive electrode slurry is about 40 μm per one side. Thereafter, the positive electrode sheet  11   a  is subjected to rolling molding under a load of from 13 tons to 14 tons using a press machine, followed by vacuum drying at 120° C. for 3 hours. 
     As illustrated in  FIG. 6 , the negative electrode  12  has a negative electrode sheet  12   a  having a longitudinal shape, which is formed of a copper foil, and a negative electrode mixture  12   b  is coated and formed on the both surfaces of this negative electrode sheet  12   a  (in  FIG. 6 , only one surface of the negative electrode sheet  12   a  is illustrated). A side edge in the axial direction on the winding start side of the axial core  15  (described by a two-dotted chain line in  FIG. 6 ) of the negative electrode sheet  12   a  is a negative electrode mixture-untreated portion  12   c  in which the copper foil is exposed without being coated with the negative electrode mixture  12   b . The negative electrode mixture  12   b  is coated over the entirety of the negative electrode sheet  12   a  exclusive of the negative electrode mixture-untreated portion  12   c , and a width of the negative electrode sheet  12   a  and a width of the negative electrode mixture  12   b  are equal to each other. The conductive lead  22  of the negative electrode side, which protrudes upward in parallel to the axial core  15  and which is formed of a nickel foil, is welded to the negative electrode mixture-untreated portion  12   c . Welding between the negative electrode sheet  12   a  and the conductive lead  22  of the negative electrode side is performed by means of, for example, resistance welding. 
     An example of the formation method of the negative electrode  12  is hereunder shown. 
     Natural graphite as a negative electrode active material, powdered carbon as a conductive agent, and PVDF as a binder are weighed in a weight ratio of the negative electrode active material to the conductive agent to the binder of 90/5/5, to which is then added an appropriate amount of N-methylpyrrolidone (NMP) as a solvent, and these are kneaded for 30 minutes using a kneader, thereby obtaining a negative electrode slurry. The obtained negative electrode slurry is coated on the both surfaces of the negative electrode sheet  12   a  made of a copper foil having a thickness of 10 μm (thickness: 10 μm, width: 57 mm). Examples of a method of coating the negative electrode slurry on the negative electrode sheet  12   a  include a method of coating a dispersion solution of constituent materials of the negative electrode slurry on the negative electrode sheet  12   a . Examples of the coating method include a roll coating method, a slit die coating method, and the like. Thereafter, the sheet is subjected to rolling molding under a load of from 13 tons to 14 tons using a press machine, followed by vacuum drying at 120° C. for 3 hours. An example of the coating thickness of the negative electrode slurry is about 40 μm per one side. 
     As illustrated in  FIG. 4 , a width W C  of the negative electrode mixture  12   b  which is formed on the negative electrode sheet  12   a  is made larger than a width W A  of the positive electrode mixture  11   b  which is formed on the positive electrode sheet  11   a . In addition, a width W S  of each of the first separator  13  and the second separator  14  is made larger than the width W C  of the negative electrode mixture  12   b  which is formed on the negative electrode sheet  12   a.    
     Namely, there is a relation of W A &lt;W C &lt;W S . 
     In view of the fact that the width W C  of the negative electrode mixture  12   b  is larger than the width W A  of the positive electrode mixture  11   b , an internal short circuit to be caused due to deposition of extraneous materials is prevented. This is because in the case of a lithium ion secondary battery, lithium that is a positive electrode active material is ionized to permeate the separator; however, if a negative electrode active material is not formed on the negative electrode side, and the negative electrode sheet  12   a  is exposed, lithium is deposited on the negative electrode sheet  12   a , thereby causing the generation of an internal short circuit. 
     The first and second separators  13  and  14  are, for example, a polyethylene-made porous film having a thickness of 40 μm. 
     The conductive lead  21  of the positive electrode side is disposed so as to come into contact with the outer periphery of the axial core  15  via the side edge on the winding start side of each of the first and second separators  13  and  14  and protrudes into the upper side of the electrode group  10 . The conductive lead  22  of the negative electrode side is disposed so as to come into contact with the outer periphery of the axial core  15  via the side edge on the winding start side of each of the first and second separators  13  and  14  and protrudes into the lower side of the electrode group  10 . The conductive lead  21  of the positive electrode side has a spiral shape portion (routing portion)  21   b  which is bent from a main body portion  21   a  welded to the positive electrode sheet  11   a . The conductive lead  22  of the negative electrode side has a spiral shape portion (routing portion)  22   b  which is bent from a main body portion  22   a  welded to the negative electrode sheet  12   a . Though details of each of the spiral shape portions  21   b  and  22   b  are described later, its tip portion constitutes end portions  21   c  and  22   c  for welding, respectively, each of which is extended to a position corresponding to the hollow portion  15   a  of the axial core  15 . 
     On each of the upper surface side and the lower surface side of the electrode group  10 , an insulating sheet  25  (see  FIG. 2 ) having an opening  25   a  having a diameter slightly larger than the outer periphery of the axial core  15  is disposed at a position corresponding to the axial core  15 . A slit  25   b  reaching the opening  25   a  from the outer periphery is formed on the insulating sheet  25 . 
       FIG. 7  is a perspective view showing a state before installing the respective insulating sheets  25  to the electrode group  10 . 
     In order to install the insulating sheet  25 , the slit  25   b  is registered with the main body portion  21   a  or  22   a  of the respective conductive lead  21  or  22  of the positive or negative electrode side. Then, in  FIG. 7 , the insulating sheet  25  is moved in the horizontal direction, thereby accommodating the main body portion  21   a  or  22   a  of the conductive lead  21  or  22  within the opening  25   a . A radius of the opening  25   a  of the insulating sheet  25  is made slightly larger than a radius of from the center of the axial core  15  to the position of the main body part  21   a  or  22   a  of the conductive lead  21  or  22 . Accordingly, the insulating sheet  25  is made coaxial with the axial core  15  in a state where the main body portions  21   a  or  22   a  of the respective conductive lead  21  or  22  is disposed within the opening  25   a  of the insulating sheet  25 . In this state, the outer periphery of the insulating sheet  25  is made to have a size such that it is positioned on substantially the same plane as the outer periphery of the electrode group  10  or slightly inward relative to the outer periphery of the electrode group  10 . 
     A lid unit  5  (see  FIG. 2 ) is disposed in an upper portion of the conductive lead  21  of the positive electrode side. The lid unit  5  is configured of a collector plate  27 , an insulating plate  34 , a connection plate  35 , a diaphragm  37 , and a lid body  3 . 
     The collector plate  27  is formed of, for example, aluminum and has a dish-like shape in which a center side thereof protrudes toward the side of the electrode group  10 . The end portion  21   c  for welding of the conductive lead  21  of the positive electrode side is welded to the lower surface of the collector plate  27  by means of ultrasonic welding or spot welding. The conductive lead  21  and the collector plate  27  are welded to each other at a position of the outside of the radial direction of the hollow portion  15   a  of the axial core (see  FIG. 1 ). However, as described later, the welded portion between the conductive lead  21  and the collector plate  27  may also be a position corresponding to the hollow portion  15   a  of the axial core  15 . In the collector plate  27 , a plurality of openings  27   a  (see  FIG. 2 ) for releasing a gas generated in the interior of the battery are formed. 
     Since the collector plate  27  is oxidized by an electrolytic solution, its reliability can be enhanced by forming it with aluminum. As for aluminum, when its surface is exposed by some kind of processing, an aluminum oxide film is immediately formed on the surface, and the oxidation by the electrolytic solution can be prevented due to this aluminum oxide film. 
     The insulating plate  34  has an annular shape formed of an insulating resin material. The insulating plate  34  has an opening  34   a  (see  FIG. 2 ) and a side portion  34   b  protruding downward. In the inside of the opening  34   a  of the insulating material  34 , the collector plate  27  and the connection plate  35  are brought into contact with each other in terms of peripheral portions thereof and engaged in an electrically connected state. 
     The connection plate  35  is formed of an aluminum alloy and has a substantially dish-like shape in which substantially the entirety exclusive of the central portion is uniform, and the center side is slightly bent at a low position. A thickness of the connection plate  35  is, for example, about 1 mm. A thin-walled protruding portion  35   a  formed in a dome shape is formed in the center of the connection plate  35 , and a plurality of openings  35   b  (see  FIG. 2 ) are formed on the periphery of the protruding portion  35   a . The openings  35   b  are formed for the purpose of releasing a gas generated in the interior of the battery. 
     The protruding portion  35   a  of the connection plate  35  is welded to the bottom surface of the central portion of the diaphragm  37  by means of resistance welding or friction stir welding. The diaphragm  37  is formed of an aluminum alloy and has a circular notch  37   a  centering on a central portion of the diaphragm  37 . The notch  37   a  is one in which its upper surface side is crushed in a V shape by means of pressing, with the remainder being made thin in wall thickness. 
     The diaphragm  37  is provided for the purpose of ensuring the safety of the battery. When the internal pressure of the battery increases, in a first stage, the diaphragm  37  bends upward to detach the junction to the protruding portion  35   a  of the connection plate  35  so that it separates from the connection plate  35 , thereby breaking the electrical continuity with the connection plate  35 . In a second stage, in the case where the internal pressure still increases, the diaphragm  37  ruptures in the notch  37   a  to function to release the gas in the inside. 
     In a peripheral portion of the diaphragm  37 , it is fixed to a peripheral portion  3   a  of the lid body  3 . As illustrated in  FIG. 2 , in the peripheral portion of the diaphragm  37 , it has a side portion  37   b  which initially stands up vertically toward the side of the lid body  3 . The lid body  3  is accommodated within this side portion  37   b , and the side portion  37   b  is bent and fixed to the upper surface side of the lid body  3  by means of caulking processing. 
     The lid body  3  is formed of iron such as carbon steel, and a plated film of nickel or the like is formed over the entirety of the outer and inner surfaces thereof. The lid body  3  has a hat shape having the disk-shaped peripheral portion  3   a  coming into contact with the diaphragm  37  and a headed, bottomless cylindrical portion  3   b  which protrudes upward from this peripheral portion  3   a . An opening  3   c  is formed in the cylindrical portion  3   b . This opening  3   c  is formed for allowing a gas which has been generated in the interior of the battery to release outside the battery at the time of rupture of the diaphragm  37  due to the gas pressure. 
     Incidentally, in the case where the lid body  3  is formed of iron, at the time of joining with another cylindrical secondary battery in series, it is possible to join with another cylindrical secondary battery formed of iron by means of spot welding. 
     The lid body  3 , the diaphragm  37 , the insulating plate  34 , the connection plate  35 , and the collector plate  27  are integrated to configure the lid unit  5 . A method of assembling the lid unit  5  is hereunder shown. 
     First of all, the lid body  3  is fixed to the diaphragm  37 . The fixation of the lid body  3  to the diaphragm  37  is performed by means of caulking or the like. As illustrated in  FIG. 2 , since the side wall  37   b  of the diaphragm  37  is initially formed vertically to the base portion  37   a , the peripheral portion  3   a  of the lid body  3  is disposed within the side wall  37   b  of the diaphragm  37 . Then, the side wall  37   b  of the diaphragm  37  is deformed by means of pressing or the like, so that it is brought into press contact with the upper and lower surfaces of the peripheral portion of the lid body  3  and also the outer peripheral side surface and covers them. 
     On the other hand, the connection plate  35  is engaged and installed in the opening  34   a  of the insulating plate  34 . Subsequently, the protruding portion  35   a  of the connection plate  35  is welded to the bottom surface of the diaphragm  37  to which the lid body  3  is fixed, in a state of interposing the insulating plate  34  therebetween. In that case, as for the welding method, resistance welding or friction stir welding can be adopted. Subsequently, the collector plate  27  is engaged in the opening  34   a  of the insulating plate  34  and held by the insulating plate  34  in a state of bringing the peripheral portion into contact with the connection plate  35 . The collector plate  27  and the connection plate  35  may be welded to each other as the need arises. In this way, the diaphragm  37  is caulked with the lid body  3 , the connection plate  35  is welded to the diaphragm  37 , the insulating plate  34  is held by the connection plate  35 , and the collector plate  27  is held by the insulating plate  34 , whereby the lid unit  5  is configured. 
     As described above, the lid body  3  of the lid unit  5  is connected to the positive electrode  11  via the conductive lead  21  of the positive electrode side, the collector plate  27 , the connection plate  35 , and the diaphragm  37 . The lid body  3  connected to the positive electrode  11  in this way acts as an external terminal of one side. 
     The seal member  43  which is generally called a gasket is provided so as to cover the peripheral portion of the side portion  37   b  of the diaphragm  37 . The seal member  43  is formed of rubber. While it is not intended to limit the seal member  43 , as one of preferred examples thereof, there can be exemplified an ethylene propylene copolymer (EPDM). A thickness of the seal member  43  is about 1.0 mm. 
     Initially, as illustrated in  FIG. 2 , the seal member  43  has a shape including an outer peripheral wall portion  43   b  formed on the peripheral side edge of an annular base portion  43   a  so as to standup substantially vertically toward the upper direction, and a cylindrical portion  43   c  formed on the inner peripheral side of the annular base portion  43   a  so as to hang down substantially vertically toward the lower direction. 
     Then, caulking processing is performed by bending the outer peripheral wall portion  43   b  of the seal member  43  together with battery can  2  by means of pressing or the like, thereby bringing the diaphragm  37  and the lid body  3  into press contact with each other in the axial direction by the base portion  43   a  and the outer peripheral wall portion  43   b . According to this, the lid unit  5  in which the lid body  3 , the diaphragm  37 , the insulating plate  34 , the connection plate  35 , and the collector plate  27  are integrally formed is fixed to the battery can  2  via the seal member  43 . 
     The conductive lead  22  of the negative electrode side has the end portion  22   c  for welding which is extended to the central portion of the hollow portion  15   a  of the axial core  15 . As illustrated in  FIG. 1 , the end portion  22   c  for welding is welded to a can bottom  203  of the battery can  2  by means of resistance welding or the like (see  FIG. 1 ). 
     The battery can  2  connected to the negative electrode  12  by the conductive lead  22  of the negative electrode side acts as an external terminal of the other side. It becomes possible to discharge an electric power stored in the electrode group  10  and charge it in the electrode group  10  by the lid body  3  functioning as an external termination with polarity of one side and the battery can  2  functioning as an external terminal of polarity of the other side. 
     A prescribed amount of a nonaqueous electrolytic solution is injected into the interior of the battery can  2 . It is preferable to use a solution of a lithium salt dissolved in a carbonate-based solvent as an example of the nonaqueous electrolytic solution. Examples of the lithium salt include lithium fluorophosphate (LiPF 6 ), lithium fluoroborate (LiBF 4 ), and the like. In addition, examples of the carbonate-based solvent include ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), methyl ethyl carbonate (MEC), and mixtures with a solvent selected from one or more kinds of the above-described solvents. 
     (Structure of Conductive Lead) 
     Next, detailed structures of the conductive leads  21  and  22  of the positive electrode side and the negative electrode side are described. 
     The conductive lead  21  of the positive electrode side and the conductive lead  22  of the negative electrode side are the same as each other, except that the positions of the end portions  21   c  and  22   c  for welding are different from each other. 
     Then, the conductive lead  22  of the negative electrode side is described, and thereafter, the difference of the conductive lead  21  of the positive electrode side from the conductive lead  22  of the negative electrode side is described. 
     As illustrated in  FIG. 6 , the conductive lead  22  is initially formed in a shape by pressing a nickel foil to have the spiral shape portion  22   b  in one end side (lower end side in  FIG. 6 ) of the main body portion  22   a . The spiral shape as referred to in the present description is defined as a shape which is spirally expanded and routed from the central portion toward the foot side and which does not have portions overlapping each other in the planar view. Since the spiral shape portion  22   b  having such a spiral shape is a shape which does not have portions overlapping each other in the planar view, it can be efficiently formed by means of pressing. 
     The tip portion of the spiral shape portion  22   b  has the end portion  22   c  for welding positioned on the central axis of the main body portion  22   a . The main body portion  22   a  of the conductive lead  22  is welded to the negative electrode mixture-untreated portion  12   c  of the negative electrode sheet  12 , and thereafter, the negative electrode sheet  12   a  is wound around the outer periphery of the axial core  15 . Then, the electrode group  10  is formed, and thereafter, bending is performed between the main body portion  22   a  and the spiral shape portion  22   b.    
       FIG. 8  is a perspective view for explaining the structure of the conductive lead of the electrode group illustrated in  FIG. 1 ; and  FIG. 9(A)  is a perspective view for explaining the detailed structure of a state where the conductive lead is bent, and  FIG. 9(B)  is a side view thereof. 
     The conductive lead  22  is bent toward the outside of the electrode group  10  in the vicinity of the main body portion  22   a  which is positioned in the vicinity of the outer periphery of the axial core  15  and protrudes from the negative electrode sheet  12   a  (see also  FIG. 1 ). Then, the conductive lead  22  is bent toward the center side of the electrode group  10  at a position at which the outer peripheral portion of the spiral shape portion  22   b  is coincident with the outer peripheral portion of the electrode group  10 . According to this, the end portion  22   c  for welding of the tip side of the conductive lead  22  becomes substantially coaxial with the axial core  15  of the electrode group  10 . Then, by drawing the tip side of the conductive lead  22  to the direction separated from the electrode group  10 , the conductive lead  22  is deformed such that the whole of the spiral shape portion  22   b  is inclined at substantially the same angle, as also shown in  FIG. 1 . 
     As an example, in  FIG. 8 , as for the conductive lead  22 , a length L of from a lower end surface of the electrode group  10  to the end portion  22   c  for welding is from about 25 to 35 mm. 
       FIG. 10  is a cross-sectional view showing a state where the conductive lead  22  of the negative electrode side is welded to the can bottom  203  of the battery can  2 . 
     The electrode group  10  is accommodated within the battery can  2 , and an electrode rod  61  is inserted into the hollow portion  15   a  of the axial core  15 . 
     In this state, the end portion  21   c  for welding of the tip side of the conductive lead  21  of the positive electrode side is positioned outside the hollow portion  15   a  of the axial core  15 . When the electrode group  10  is accommodated within the battery can  2 , the end portion  22   c  for welding of the conductive lead  22  of the negative electrode side is disposed at a position corresponding to the hollow portion  15   a  of the axial core  15 . Then, by pressing the end portion  22   c  for welding of the conductive lead  22  against the inner surface of the can bottom  203  of the battery can  2  in the tip portion of the electrode rod  61 , the conductive lead  22  can be welded to the can bottom  203  in this state. 
     In this way, according to the present embodiment, the conductive lead  22  can be welded directly to the battery can  2  by the electrode rod  61  by merely accommodating the electrode group  10  within the battery can  2 . Accordingly, the workability can be significantly enhanced. 
     In the cylindrical secondary battery, the electrode group  10  expands and contracts in the radial direction at the time of charge and discharge. In addition, the electrode group  10  is displaced in the axial direction due to vibration or the like. Accordingly, torsion acts in the welded portion where the conductive lead  22  and the can bottom  203  of the battery can  2  are welded to each other, and breakage is liable to be generated in the welded portion due to the long-term use. 
     However, according to the present embodiment, the conductive lead  22  expands and contracts in the axial direction against the displacement of the electrode group  10  in the axial direction. In addition, the conductive lead  22  expands and contracts in the radial direction against the torsion to be caused following the rotation of the electrode group  10  in the circumferential direction. According to this, it is possible to reduce an external force acting in the welded portion between the end portion  22   c  for welding of the conductive lead  22  and the can bottom  203  of the battery can  2 , thereby preventing the breakage of the welded portion. 
     As for the conductive lead  21  of the positive electrode side, the end portion  21   c  for welding of the tip side is not positioned on the axial center of the electrode group  10 , and as illustrated in  FIG. 1 , the conductive lead  21  is welded to the collector plate  27  of the lid unit  5  in the outside of the radial direction of the hollow portion  15   a  of the axial core  15 . However, it is possible to easily deform the conductive lead  21 . Then, as shown in  FIG. 10 , since the electrode rod  61  can be inserted into the hollow portion  15   a  of the axial core  15  by temporarily deforming the conductive lead  21  outside the hollow portion  15   a  of the axial core  15 , as described above, the end portion  21   c  for welding of the conductive lead  21  of the positive electrode side may be disposed on the axial center of the hollow portion  15   a  of the axial core  15 . 
     In any way, since the conductive lead  21  of the positive electrode side expands and contracts in the axial direction against the displacement in the axial direction of the electrode group  10  and also expands and contracts in the radial direction against the torsion to be caused following the rotation of the electrode group  10  in the circumferential direction, similar to the conductive lead  22  of the negative electrode side, the conductive lead  21  has an action to prevent the breakage of the welded portion. 
     (Manufacturing Method of Cylindrical Secondary Battery) 
     A manufacturing method of the cylindrical secondary battery shown as the embodiment of the invention is hereunder described. 
     [Fabrication of Electrode Group] 
     First of all, the electrode group  10  is fabricated. The positive electrode  11  in which the positive electrode mixture  11   b  is coated on the both surfaces of the positive electrode sheet  11   a  exclusive of the positive electrode mixture-untreated portion  11   c  is fabricated. In addition, the positive electrode  11  in which the negative electrode mixture  12   b  is coated on the both surfaces of the negative electrode sheet  12   a  exclusive of the negative electrode mixture-untreated portion  12   c  is fabricated. 
     The main body portion  21   a  of the conductive lead  21  of the positive electrode side is welded to the positive electrode mixture-untreated portion  11   c , thereby fabricating the positive electrode  11  having the conductive lead  21  joined therewith as illustrated in  FIG. 5 . In addition, the main body portion  22   a  of the conductive lead  22  of the negative electrode side is welded to the negative electrode mixture-untreated portion  12   c , thereby fabricating the negative electrode  12  having the conductive lead  22  joined therewith as illustrated in  FIG. 6 . 
     Subsequently, the innermost side edge portions of the first separator  13  and the second separator  14  are welded to the axial core  15 . Subsequently, the first separator  13  and the second separator  14  are wound by one to several turns around the axial core  15 , the negative electrode  12  is interposed between the second separator  14  and the first separator  13 , and the axial core  15  is wound at a prescribed angle. Subsequently, the positive electrode  11  is interposed between the first separator  13  and the second separator  14 . Then, in this state, the resultant is wound by prescribed turns, thereby fabricating the electrode group  10 . 
     Subsequently, as illustrated in  FIG. 7 , the slit  25   b  of the insulating sheet  25  is inserted into the root portions of the main body portions  21   a  and  22   a  of the conductive leads  21  and  22  protruding from the upper and lower surfaces of the electrode group  10 , respectively, thereby disposing the insulating sheet  25  substantially coaxially with the electrode group  10 . 
     According to this, the main body portion  21   a  of the conductive lead  21  and the main body portion  22   a  of the conductive lead  22  are disposed, respectively within the opening  25   a  of the insulating sheet  25 , and substantially the entirety of each of the upper and lower surfaces of the electrode group  10  is covered by the insulating sheet  25 , exclusive of a region corresponding to the opening  25   a.    
     Subsequently, as illustrated in  FIG. 9 , the conductive lead  21  and the conductive lead  22  are respectively bent toward the outer periphery side of the electrode group  10  in the root portions of the main body portions  21   a  and  22   a , respectively. In addition, the conductive lead  21  and the conductive lead  22  are further bent toward the axial center side of the electrode group  10  in the vicinity of the outer peripheries of the spiral shape portions  21   b  and  22   b , respectively. According to this, the end portion  22   c  for welding of the conductive lead  22  is disposed coaxially with the axial core  15  of the electrode group  10 . In addition, the end portion  21   c  for welding of the conductive lead  21  is disposed outside the radial direction of the hollow portion  15   a  of the axial core  15  of the electrode group  10 . In this way, as illustrated in  FIG. 2 , the electrode group  10  in which the spiral shape portions  21   b  and  22   b  have the conductive leads  21  and  22  protruding from the upper surface side and the lower surface side, respectively, and the upper surface side and the lower surface side are covered by the insulating sheet  25 . 
     [Fabrication of Battery can] 
     On the other hand, as illustrated in  FIG. 1 , the headless, closed-end battery can  2  having the opening  202  is fabricated. The outer and inner surfaces of the battery can  2  are entirely plated. 
     [Accommodation into Battery Container] 
     Subsequently, the electrode group  10  is accommodated within the battery can  2 . 
     [Joining of Negative Electrode] 
     Then, as illustrated in  FIG. 10 , the electrode rod  61  is inserted into the hollow portion  15   a  of the axial core  15 . The end portion  22   c  for welding of the conductive lead  22  is welded to the can bottom  203  of the battery can  2 . The electrode rod  61  generally has a radius of from 1 to 5 mm, and an area of the end portion  22   c  for welding is desirably larger than an area of the electrode rod  61 . According to this, a size of the welded portion between the end portion  22   c  for welding of the conductive lead  22  and the can bottom  203  of the battery can  2  is from about 1 to 5 mm in terms of a radius. In that case, the size of the welded portion is more preferably from about 3 to 5 mm in terms of a radius. 
     Subsequently, a part of the upper end side of the battery can  2  is protruded inward upon being subjected to drawing processing, thereby forming the groove  201  that is a substantially U-shaped. 
     [Injection of Electrolytic Solution] 
     Subsequently, a prescribed amount of a nonaqueous electrolytic solution is injected into the interior of the battery can  2  having the electrode rod  10  accommodated therein. The nonaqueous electrolytic solution is injected from the hollow portion  15   a  of the upper end of the axial core  15 . As described above, for example, a solution of a lithium salt dissolved in a carbonate-based solvent is used as the nonaqueous electrolytic solution. 
     [Fabrication of Lid Unit] 
     On the other hand, separately from the above-described assembling process, the lid unit  5  is fabricated. 
     As described above, the lid unit  5  is configured of the insulating plate  34 , the collector plate  27  fitted in the opening  34   a  of the insulating plate  34 , the connection plate  35 , the diaphragm  37  welded to the connection plate  35 , and the lid body  3  fixed to the diaphragm  37  by means of caulking. The fabrication method of the lid unit  5  is as described previously. 
     [Joining of Positive Electrode] 
     The electrode group  10  and the lid unit  5  are electrically connected to each other. First of all, the seal member  43  is placed on the groove  201  of the battery can  2 . As illustrated in  FIG. 2 , the seal member  43  in this state has a structure having, in an upper portion of the annular base portion  43   a , the outer peripheral wall portion  43   b  that is vertical to the base portion  43   a.    
     Subsequently, on the base portion  43   a  of the seal member  43 , the lid unit  5  is placed in an inclined state. This may be done in such a manner that in a state where the lid unit  5  is made substantially vertical, apart of the outer periphery thereof is placed on the base portion  43   a  of the seal member  43 , and the opposite side of the outer periphery of the lid unit  5  is inclined toward the side of the battery can  2  at an appropriate angle. In this state, the end portion  21   c  for welding of the conductive lead  21  is welded to the lower surface of the collector plate  27  of the lid unit  5 . 
     [Sealing] 
     After completion of welding between the collector plate  27  and the conductive lead  21 , the lid unit is flattened substantially horizontally, thereby bringing the entirety of the lower surface of the peripheral portion of the diaphragm  27  into contact with the base portion  43   a  of the seal member  43 . In this state, the battery can  2  and the battery unit  5  are subjected to caulking processing to achieve sealing, followed by hermetically sealing from the exterior. There is thus obtained the cylindrical secondary battery  1  illustrated in  FIG. 1 . 
     (Confirmation of Effects) 
     For the purpose of confirming the effects of the invention, a torsion test and a vibration test were carried out using the cylindrical secondary battery according to the invention and a cylindrical secondary battery of Comparative example. 
     For the torsion test and the vibration test, a sample obtained by fabricating the cylindrical secondary battery  1  and then subjecting it to a prescribed aging process was used. 
     The torsion test was carried out in such a manner that in the cylindrical secondary battery  1 , charge and discharge of 3 C rate was repeated 100 times in the range of from 0% of SOC to 100% of SOC (from 2.8 V to 4.2 V), and a force derived due to the increase or decrease of volume of the active material was applied to the electrode group  10 . 
     The vibration test was carried out in such a manner that the cylindrical secondary battery  1  was repeatedly vibrated in the axial direction of the cylinder can in a vibration width of 10 mm at a frequency of 100 Hz for 24 hours, and a force of the axial direction was applied to the electrode group  10 . 
     The evaluation of each of the torsion test and the vibration test was carried out in such a manner that after the test, the cylindrical secondary battery  1  was taken apart, and the presence or absence of breakage of the welded portion was confirmed by visual inspection. 
     Incidentally, the term “SOC” means the state of charge, and 0% of SOC is in a state of complete discharge, whereas 100% of SOC is in a state of full charge. In addition, the term “C” means a unit of the charge and discharge current, and 1 C expresses a current at which the battery capacity can be charged or discharged within one hour. 
       FIG. 11  shows results of the torsion test, and  FIG. 12  shows results of the vibration test. 
     In each of the tests, a sample obtained by bending a tape-shaped conductive foil in a zigzag form and welding the positive electrode sheet  11   a  to the lid unit  5  and the negative electrode sheet  12   a  to the can bottom  203  of the battery can  2 , respectively was used as the Comparative Example. 
     According to the results of the torsion test shown in  FIG. 11 , in the Comparative Example, the breakage was observed in 12 of the 20 test specimens, whereas in the conductive leads  21  and  22  of the above-described embodiment, the generation of breakage was not observed at all. 
     In addition, according to the results of the vibration test shown in  FIG. 12 , in the Comparative Example, the breakage was observed in 14 of the 20 test specimens, whereas in the conductive leads  21  and  22  of the above-described embodiment, the generation of breakage was not observed at all. 
     In the light of the above, in all of the torsion test and the vibration test, the effects of the above-described embodiment were perceived. 
     Embodiment 2 
       FIG. 13  is a cross-sectional view of Embodiment 2 of the cylindrical secondary battery according to the invention. 
     A difference of a cylindrical secondary battery  1 A of Embodiment 2 from the cylindrical secondary battery  1  of Embodiment 1 resides in a point in which each of the main body portion  21   a  of a conductive lead  21 ′ of the positive electrode side and the main body portion  22   a  of a conductive lead  22 ′ of the negative electrode side of the electrode group  10 A is positioned substantially in the center of the radial direction of the electrode group  10 . 
       FIG. 14  is a perspective view of the electrode group  10 A. 
     As illustrated in  FIG. 14 , in the conductive lead  21 ′ of the positive electrode side, the main body portion  21   a  protrudes toward the upper surface side from the intermediate portion in the radial direction of the electrode group  10 A. In addition, in the conductive lead  22 ′ of the negative electrode side, the main body portion  22   a  protrudes toward the lower surface side from the intermediate portion in the radial direction of the electrode group  10 A. 
     An insulating sheet  25 ′ has the opening  25   a  corresponding to the axial core  15  and an opening  25   c  in which the main body portion  21   a  or  22   a  of the conductive lead  21  or  22  is disposed. A slit  25   b ′ for inserting the main body portion  21   a  or  22   a  of the conductive lead  21  or  22  into the opening  25   c  is provided upon being extended to the outer periphery from the opening  25   c.    
       FIG. 15  is a plan view showing a joining state between a positive electrode  11 ′ and the conductive lead  21 ′, and  FIG. 16  is a plan view showing a joining state between a negative electrode  12 ′ and the conductive lead  22 ′. 
     In the positive electrode  11 ′, the positive electrode mixture-untreated portion  11   c  in which the positive electrode mixture  11   b  is not coated is provided in an intermediate portion in the longer direction of the longitudinal positive electrode sheet  11   a . The conductive lead  21 ′ is welded to the positive electrode mixture-untreated portion  11   c  at this position. 
     In addition, in the negative electrode  12 ′, the negative electrode mixture-untreated portion  12   c  in which the negative electrode mixture  12   b  is not coated is provided in an intermediate portion in the longer direction of the longitudinal negative electrode sheet  12   a . The conductive lead  22 ′ is welded to the negative electrode mixture-untreated portion  12   c  at this position. 
     Similar to the case of Embodiment 1, each of the positive electrode  11 ′ and the negative electrode  12 ′, to which the conductive leads  21 ′ and  22 ′ are welded, respectively, is wound around the outer periphery of the axial core  15  from the side edge of the tip side via the first and second separators  13  and  14 . 
     Since other configurations of Embodiment 2 are the same as those of Embodiment 1, the same reference numbers are given to the corresponding members, and explanations thereof are omitted. 
     Even in such cylindrical secondary battery  1 A shown in Embodiment 2, the same effects as those in the case of Embodiment 1 are brought. 
     According to the above-described embodiments, the following effects are brought. 
     (1) Each of the conductive leads  22  and  22 ′ has the end portion  22   c  for welding extended to a position corresponding to the hollow portion  15   a  of the axial core  15  in the tip of the spiral shape portion  22   b . Accordingly, it becomes possible to insert the electrode rod  61  from the hollow portion  15   a  of the axial core  15  in a state of accommodating the electrode group  10  or  10 A within the battery can  2  and weld the end portion  22   c  for welding to the can bottom  203  of the battery can  2 , so that the assembling workability is enhanced. 
     (2) Each of the conductive leads  21  and  21 ′ of the positive electrode side and each of the conductive leads  22  and  22 ′ of the negative electrode side have the spiral shape portions  21   b  and  22   b , respectively. Since the spiral shape portion  21   b  or  22   b  is deformed in the axial center direction and the radial direction, the torsion of the electrode group  10  and the external force which is applied to the welded portion following the movement in the axial direction are reduced. According to this, the breakage of the welded portion can be prevented. 
     (3) Each of the conductive leads  21  and  21 ′ of the positive electrode side and each of the conductive leads  22  and  22 ′ of the negative electrode side have a spiral shape which does not have portions overlapping each other in the planar view. Accordingly, each of the conductive leads  21 ,  21 ′,  22  and  22 ′ can be formed by means of pressing and can be efficiently processed. 
     (4) Each of the conductive leads  21  and  21 ′ of the positive electrode side and each of the conductive leads  22  and  22 ′ of the negative electrode side have the spiral shape portions  21   b  and  22   b , respectively having substantially the same outer diameter as an outer diameter of the electrode group  10 . In the case where the tape-shaped conductive lead is bent and welded to the lid unit  5  or the can bottom  203  of the battery can  2 , the bent portions comes into contact with the inner surface of the battery can  2  to generate an internal short circuit. However, according to the present embodiments, it is possible to prevent such generation of an internal short circuit to be caused due to the contact of each of the conductive leads  21 ,  21 ′,  22  and  22 ′ with the inner surface of the battery can  2 . 
     Incidentally, in the above-described embodiments, though the spiral shape of each of the conductive leads  21 ,  21 ′,  22  and  22 ′ was made rectangular in the planar view, it can also be made circular or oval. 
     In addition, in the above-described embodiments, though the number of turn of each of the conductive leads  21 ,  21 ′,  22  and  22 ′ is substantially one, the number of turn may be further increased. 
     In the above-described embodiments, both of the welding positions of the conductive leads  21  and  22  were the same position of the side edge on the winding start side or the intermediate portion of the positive electrode sheet  11   a  or the negative electrode sheet  12   a . However, the welding positions of the conductive leads  21  and  22  may be welded to the positive electrode sheet  11   a  and the negative electrode sheet  12   a  at a different position from each other between the positive electrode side and the negative electrode side by, for example, welding the conductive lead  21  of the positive electrode side to the winding start side of the positive electrode sheet  11   a  and welding the conductive lead  22  of the negative electrode side to the intermediate portion of the negative electrode sheet  12   a . In that case, the welding position of each of the conductive leads  21  and  22  in the intermediate portion may be a different distance from the side edge of the winding start side of the positive electrode sheet  11   a  or the negative electrode sheet  12   a . In that case, the welding position of the conductive lead  21  or  22  may be an end of a winding end side of the positive electrode sheet  11   a  or the negative electrode sheet  12   a.    
     In the above-described embodiments, the conductive leads  21  of the positive electrode side and the conductive leads  22  of the negative electrode side had a spiral shape which does not have portions overlapping each other in the planar view. 
     However, the invention is not limited thereto, and the shape may be a spiral shape or a helical shape which has portions overlapping each other in the planar view, or the like. In short, the shape may be a shape capable of being deformed in the axial direction and the radial direction. 
     In the above-described embodiments, the positive electrode  11  was welded to the lid unit  5 , and the negative electrode  12  was welded to the can bottom  203  of the battery can  2 . However, the invention is also applicable to a cylindrical secondary battery in which the positive electrode  11  is welded to the can bottom  203  of the battery can  2 , and the negative electrode  12  is welded to the lid unit  5 . 
     In the above-described embodiments, the lid unit  5  was configured of the lid body  3 , the diaphragm  37 , the insulating plate  34 , the connection plate  35 , and the collector plate  27 . However, the configuration of the lid unit  5  is an example, and configurations composed of other members may also be adopted. In addition, the lid member may be made of a single body but not a unitized body, and it may be an electrode terminal member having a function as an electrode terminal. 
     The above-described embodiments have been described by reference to the lithium ion cylindrical secondary battery as the battery. However, it should not be construed that the invention is limited to the lithium battery, but the invention can also be applied to other cylindrical secondary batteries such as a nickel-hydrogen battery, a nickel-cadmium battery. 
     Besides, it is possible to configure the cylindrical secondary battery according to the invention upon being deformed in various ways within the range of the gist of the invention. In short, the cylindrical secondary battery may be a cylindrical secondary battery in which an electrode group having a positive electrode and a negative electrode wound around the periphery of an axial core having a hollow portion via a separator is accommodated in a battery can, and one of a conductive lead welded to the negative electrode and a conductive lead welded to the positive electrode is connected to a lid member covering an opening of the battery can, with the other being welded to a can bottom of the battery can, wherein at least the conductive lead welded to the can bottom of the battery can includes an end portion for welding which is extended to a position corresponding to a central portion of the hollow portion of the axial core and a routing portion which is deformable in the axial direction of the axial core and the perpendicular direction to the axial direction, and the end portion for welding is welded to the can bottom of the battery can. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 ,  1 A: Cylindrical secondary battery 
               2 : Battery can 
               203 : Can bottom 
               3 : Lid body 
               5 : Lid unit 
               10 ,  10 A: Electrode group 
               21 ,  22 : Conductive lead 
               21   b ,  22   b : Spiral shape portion (routing portion)