Abstract:
There is provided an anode can capable of preventing leakage of liquid, a method of fabricating the same, and a battery using the anode can and a method of fabricating the same. An anode can is formed of a material formed of a stack of layers including an aluminum alloy layer and a stainless steel layer formed on the aluminum alloy layer and it includes a flat, center portion and a peripheral side wall contiguous to and surrounding the flat center portion. The aluminum alloy layer located at the peripheral side wall is smaller in thickness than the aluminum alloy layer located at the flat center portion. At an edge of the peripheral side wall, the aluminum alloy layer and the stainless steel layer have their respective end surfaces aligned substantially in a single straight line in a plane substantially perpendicular to an outer peripheral surface of the peripheral side wall.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to secondary batteries miniaturized for example in forms of buttons, coins and the like and used as a main power source for electronics, a power source for backing up memory and the like, an anode or negative electrode cans thereof, and methods of manufacturing the same, and more specifically to anode cans of secondary batteries obtained by bending a material formed of layers stacked to combine materials different in hardness, secondary batteries using the anode can, and methods of manufacturing the same.  
           [0003]    2. Description of the Background Art  
           [0004]    [0004]FIG. 25 is a schematic partial cross section of a conventional battery. With reference to the figure the conventional battery will be described.  
           [0005]    The FIG. 25 battery is a so-called manganese (Mn)-lithium (Li) secondary battery and it includes a cathode or positive electrode can  101  also serving as a cathode terminal, an anode or negative electrode can  102  connected to cathode can  101  via a gasket  106  and also serving as an anode terminal, and a cathode  107 , a separator  109  and a lithium metal  108  accommodated in a space formed by cathode and anode cans  101  and  102 . Cathode can  101  is formed by shaping a stainless steel plate highly resistant to corrosion. Anode can  102  is formed by shaping a material including a stainless steel layer  102   a  formed of the same stainless steel that forms cathode can  101 , and a hard aluminum alloy layer  102   b  arranged on an inner circumference of stainless steel layer  102   a.  Note that the FIG. 25 battery has a structure in symmetry relative to a centerline  111 .  
           [0006]    Anode can  102  has a periphery provided with a shoulder  103  lower by one step than an upper surface of anode can  102 . Outer than shoulder  103  the periphery is angled  104 . From angled portion  104  a peripheral wall  105  extends in a downward direction substantially vertically. Anode can  102  thus includes shoulder  103 , angled portion  104  and peripheral wall  105 .  
           [0007]    Between cathode can  101  and anode can  102  there is arranged cathode  107  on cathode can  101 . Cathode  107  is covered by separator  109 . On separator  109 , lithium metal  108  forming an anode is arranged in contact with hard aluminum alloy layer  102   b  of anode can  102 . Cathode  107 , separator  109 , lithium metal  108  and an electrolyte configure a power generation cell.  
           [0008]    A gasket  106  electrically insulates cathode can  101  and anode can  102  and also closely seals cathode  107 , separator  109  and lithium metal  108  in a casing formed by cathode and anode cans  101  and  102 . Gasket  106  is arranged between an internal surface of an erected portion  101   a  of a periphery of cathode can  101  and an outer peripheral surface of anode can  102  extending from shoulder  103  to peripheral wall  105  and erected portion  101   a  is then folded to seal the battery.  
           [0009]    The present inventor studied the FIG. 25 conventional battery and has found that it has disadvantages, as described hereinafter.  
           [0010]    More specifically, in the FIG. 25 battery, anode can  102  is pressed to form shoulder  103 , angled portion  104 , peripheral wall  105  and the like. Anode can  102 , however, is formed of a material formed by a stack of layers including stainless steel layer  102   a  and hard aluminum alloy layer  102   b,  i.e., a clad material. As such, when the material is pressed, as described above, its peripheral wall having been pressed has an end, as shown in FIG. 26. More specifically, layer  102   b,  arranged inner than layer  102   a,  has an end  126  protruding relative to an end surface  116  of layer  102   a  (or layer  102   b  has an end surface  117  in a region protruding relative to end surface  116  of layer  102   a ). FIG. 26 is a schematic diagram for illustrating a disadvantage of the FIG. 25 battery. Furthermore, as can be understood from FIG. 26, end  126  is formed as layer  102   b  being pressed, as described above, is plastically deformed, extruded from an end of the layer. End  126  thus has a geometry having a gently curving surface, as shown in FIG. 26.  
           [0011]    Furthermore, in some case, anode can  102  is angled  104  by pressing it at peripheral wall  105  vertically using a die and a punch. This results in peripheral wall  105  having an end such that hard aluminum alloy layer  102   b  has an end  127  covering an end surface of stainless steel layer  102   a,  as shown in FIG. 27. FIG. 27 is another schematic diagram for illustrating a disadvantage of the FIG. 25 battery.  
           [0012]    When hard aluminum alloy layer  102   b  has end  126  protruding and having a curving surface, as shown in FIG. 26, or it has end  127  covering an end surface of stainless steel layer  102   a,  as shown in FIG. 27, there is a case in which anode can  102  cannot have peripheral wall  105  firmly fixed to gasket  106  (or peripheral wall  105  cannot have an end plunged into and fixed in gasket  106 ) when the battery is sealed. As a result, gasket  106  and anode can  102  bonded together provide poor hermeticity and the battery thus has poor characteristics, a reduced lifetime (or charging and discharging cycle lifetime), and other similar disadvantages.  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention contemplates a secondary battery free of poor characteristics and also extended in lifetime, an anode can thereof, and a method of manufacturing the same.  
           [0014]    In accordance with the present invention in one aspect an anode can of a secondary battery is formed of a material formed of a stack of layers including an aluminum alloy layer and a stainless steel layer formed on the aluminum alloy layer and it includes a flat, center portion and a peripheral side wall contiguous to and surrounding the flat center portion. The aluminum alloy layer located at the peripheral side wall is smaller in thickness than the aluminum alloy layer located at the flat center portion. The peripheral side wall has an edge with the aluminum alloy layer and the stainless steel layer having their respective end surfaces aligned substantially in a single straight line in a plane substantially perpendicular to an outer peripheral surface of the peripheral side wall.  
           [0015]    Thus the peripheral side wall has an edge without the aluminum alloy layer protruding relative to the stainless steel layer. This ensures that the aluminum alloy layer is free of a protrusion otherwise contributing to the anode can and the gasket or any other similar member being insufficiently bonded together. Consequently, the anode can and the gasket or any other similar member can be bonded together more closely and thus provide enhanced hermeticity.  
           [0016]    Furthermore when the stainless steel layer at the flat center portion and that at the peripheral side wall are substantially uniform in thickness, the peripheral side wall can be smaller in total thickness than the flat center portion. As such, when this anode can is used to fabricate a battery, the anode can&#39;s peripheral side wall can readily be plunged into a gasket or any other similar member used to connect and seal a cathode can and the anode can. This ensures that the anode can is firmly fixed to the gasket or any other similar member. Thus in the battery using the anode can the anode can and the gasket can be bonded together to provide enhanced hermeticity to prevent the battery&#39;s electrolyte or the like from leaking from the bonded portion thus prevent the battery from having poor characteristics and reduced lifetime.  
           [0017]    In accordance with the present invention in another aspect an anode can of a secondary battery is formed of a material formed of a stack of layers including an aluminum alloy layer and a stainless steel layer formed on the aluminum alloy layer and it includes a flat, center portion and a peripheral side wall contiguous to and surrounding the flat center portion. The peripheral side wall has an edge with the stainless steel layer having an end surface in a region protruding relative to an end surface of the aluminum alloy layer in a direction substantially parallel to an outer peripheral surface of the peripheral side wall.  
           [0018]    Thus the peripheral side wall has an edge with the stainless steel layer having an end protruding relative to that of the aluminum alloy layer. This ensures that if the anode can of the present invention is applied for example to an organic electrolyte secondary battery a gasket or any other similar member and the peripheral side wall can firmly be bonded together as the stainless steel layer has an end surface in close contact with the gasket or any other similar member. The anode can and the gasket or any other similar member can thus be bonded together more closely to provide enhanced hermeticity. This can prevent the battery&#39;s electrolyte or the like from leaking from the bonded portion and thus prevent the battery for example from having poor characteristics and reduced lifetime.  
           [0019]    In the above one or another aspect preferably the peripheral side wall has the aluminum alloy layer tapering toward the edge of the peripheral side wall.  
           [0020]    The anode can can thus have a peripheral side wall sharpened in geometry, tapering toward an edge thereof. The peripheral side wall can thus readily be plunged into a gasket or any other similar member. Consequently, the gasket or any other similar member and the peripheral side wall can be bonded together to provide further enhanced hermeticity.  
           [0021]    In accordance with the present invention in still another aspect a secondary battery includes the anode can provided in the above one or another aspect.  
           [0022]    The battery can thus free from leakage of liquid from a portion at which the anode can and the gasket are bonded together.  
           [0023]    In accordance with the present invention in still another aspect a method of fabricating an anode can of a secondary battery includes the steps of: (a) preparing a material formed of a stack of layers including an aluminum alloy layer and a stainless steel layer formed on the aluminum alloy layer, the material being cut to match in size an anode can to be obtained; (b) reducing the aluminum alloy layer in thickness at a periphery of the material; (c) after step (b), cutting an edge of the periphery of the material to allow the aluminum alloy layer and the stainless steel layer to have their respective side surfaces substantially in a single plane; and (d) after step (c), bending and thus erecting the periphery of the material in a direction.  
           [0024]    With the cutting step, the material formed of a stack of layers can have a periphery with the aluminum alloy layer and the stainless steel layer having their respective side surfaces in alignment (or the layers&#39; respective side surfaces can form a single, continuous plane). After the side surfaces are aligned, the material&#39;s periphery is bent and thus erected. The periphery&#39;s aluminum alloy layer has a reduced thickness, which can prevent a material of the aluminum alloy layer from plastically flowing to the periphery from a center of the material formed of the stack of layers when the periphery is bent and erected. The periphery can thus have an end without the aluminum alloy layer having a side surface protruding relative to that of the stainless steel layer. As such, if a battery with the anode can fabricated in the present method can be free from leakage of liquid as the aluminum alloy layer can be free of a protrusion otherwise contributing to the anode can and the gasket or any other similar member being insufficiently bonded together.  
           [0025]    Preferably the method further includes before step (c) and after step (d) the step of re-processing the aluminum alloy layer at the periphery of the material to prevent the aluminum alloy layer from having an end extending over the side surface of the stainless steel layer in step (d).  
           [0026]    This can prevent the aluminum alloy layer from having an edge protruding relative to a side surface of the stainless steel layer when the material&#39;s periphery is bent and erected in a direction.  
           [0027]    Preferably the step of re-processing includes the step of reducing the aluminum alloy layer in thickness at the periphery of the material.  
           [0028]    Furthermore the method may further include after step (d) the step of causing the aluminum alloy layer to recede from the stainless steel layer at an end surface of the periphery of the material.  
           [0029]    This ensures that the material&#39;s periphery has an end surface with the stainless steel layer protruding relative to the aluminum alloy layer. As such when the anode can fabricated in the present method is applied to a battery the anode can&#39;s end can contribute to enhanced hermetically.  
           [0030]    In accordance with the present invention in still another aspect a method of fabricating a secondary battery uses the method of fabricating the anode can in the above still another aspect.  
           [0031]    This can provide a battery free of liquid leaking from a portion at which the anode can and a gasket are bonded together.  
           [0032]    The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0033]    In the Drawings:  
         [0034]    [0034]FIG. 1 is a schematic partial cross section of a first embodiment of a battery of the present invention;  
         [0035]    FIGS.  2 - 8  are schematic cross sections for illustrating first to seventh steps, respectively, of a method of manufacturing an anode can used in the FIG. 1 battery;  
         [0036]    [0036]FIG. 9 is a schematic partial cross section of a second embodiment of the battery of the present invention;  
         [0037]    FIGS.  10 - 15  are schematic cross sections for illustrating first to sixth steps, respectively, of a method of manufacturing an anode can used in the FIG. 9 battery;  
         [0038]    [0038]FIG. 16 is a schematic partial cross section of a third embodiment of the battery of the present invention;  
         [0039]    FIGS.  17 - 22  are schematic cross sections for illustrating first to sixth steps, respectively, of a method of manufacturing an anode can used in the FIG. 16 battery;  
         [0040]    [0040]FIG. 23 is a schematic cross section for illustrating an exemplary variation of the third embodiment of the present invention providing the method of manufacturing the anode can;  
         [0041]    [0041]FIG. 24 is a schematic partial cross section of an anode can manufactured through the FIG. 23 step;  
         [0042]    [0042]FIG. 25 is a schematic partial cross section of a conventional battery;  
         [0043]    [0043]FIG. 26 is a schematic diagram for illustrating a disadvantage of the FIG. 25 battery; and  
         [0044]    [0044]FIG. 27 is another schematic diagram for illustrating a disadvantage of the FIG. 25 battery. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]    Hereinafter with reference to the drawings the present invention will be described in embodiments. Note that in the figures, like components are denoted by like reference characters.  
         [0046]    First Embodiment With reference to FIG. 1, a battery will be described.  
         [0047]    The FIG. 1 battery  20  is a manganese (Mn)-lithium (Li) secondary battery, a so-called organic electrolyte secondary battery, and it includes a cathode or positive electrode can  1  also serving as a cathode terminal, an anode or negative electrode can  1  connected to cathode can  1  via a gasket  6  and also serving as an anode terminal, and a cathode  7 , a separator  9  and a lithium metal  8  accommodated in a space formed by cathode and anode cans  1  and  2 . Cathode can  1  is formed by shaping a stainless steel plate highly resistant to corrosion. Battery  20  may for example be a manganese dioxide-lithium secondary battery. Anode can  2  is formed by shaping a material including a stainless steel layer  2   a  formed of the same stainless steel that forms cathode can  1 , and a hard aluminum alloy layer  2   b  arranged on an inner circumference of stainless steel layer  2   a.  Anode can  2  at a terminal portion  10  has a total thickness T 3  of approximately 0.3 mm, hard aluminum alloy layer  2   b  having a thickness T 1  of approximately 0.2 mm and stainless steel layer  2   a  having a thickness of approximately 0.1 mm. Hard aluminum alloy layer  2   b  contains 5% by mass of manganese (Mn). Hard aluminum alloy layer  2   b  may be replaced with hard aluminum.  
         [0048]    Anode can  2  is peripherally provided with a shoulder  3  lower by one step than an upper surface of anode can  2 . Outer than shoulder  3  there is an angled portion  4  bent by a predetermined angle (for example of 90 degrees ±10 degrees), as seen from shoulder  3 . From angled portion  4  a peripheral wall  5  extends in a downward direction substantially vertically. Anode can  2  is formed to extend from a flat center portion or terminal portion  10  through shoulder  3  and angled portion  4  to peripheral wall  5 .  
         [0049]    As can be seen in FIG. 1, thickness T 1  of layer  2   b  located at terminal portion  10  is smaller than thickness T 2  of a peripheral wall  5   b  of the hard aluminum alloy layer located at peripheral wall  5 . Thus, thickness T 4  of peripheral wall  5  is smaller than thickness T 3  of anode can  2  of the terminal portion  10 . Furthermore, peripheral wall  5  has an end provided with a protrusion  23  (FIG. 8) raised (or increased in thickness) at peripheral wall  5   b  inwards.  
         [0050]    Cathode can  1  and anode can  2  together form a space, in which cathode  7  is arranged, overlaying cathode can  1 . Cathode  7  is covered by separator  9 . On separator  9 , lithium metal  8  forming an anode is arranged in contact with hard aluminum alloy layer  2   b  of anode can  2 . Cathode  7 , separator  9 , lithium metal  8  and an electrolyte configure a power generation cell.  
         [0051]    A gasket  6  electrically insulates cathode can  1  and anode can  2  and also serves as a member hermetically sealing cathode  7 , separator  9 , lithium metal  8  and an electrolyte in a casing formed by cathode and anode cans  1  and  2 . Gasket  6  is arranged between an internal surface of an erected portion la of a periphery of cathode can  1  and an outer peripheral surface of anode can  2  extending from shoulder  3  to peripheral wall  5  and erected portion  1   a  is then folded to seal the battery. It should be noted that anode can  2  has peripheral wall  5  plunged into gasket  6 . Note that the FIG. 1 battery has a structure in symmetry relative to a centerline  11  and it has a diameter for example of approximately 4 mm.  
         [0052]    Thus, for anode can  2  of battery  20 , thickness T 2  of peripheral wall  5   b  of the layer at peripheral wall  5  serving as a peripheral side wall is smaller than thickness T 1  of hard aluminum alloy layer  2   b  at terminal portion  10  serving as a flat center portion. Furthermore, the hard aluminum alloy layer&#39;s peripheral wall  5   b  and the stainless steel layer&#39;s peripheral wall  5   a  have their respective end side surfaces substantially in a single plane. This can help to plunge peripheral wall  5  of anode can  2  into gasket  6  and thus ensures that peripheral wall  5  can firmly be fixed to gasket  6 . Battery  20  can thus be prevented from having gasket  6  and anode can  2  bonded insufficiently and thus providing poor hermeticity resulting in the battery having poor characteristics. Furthermore, the battery can also be free from leakage of its internal electrolyte from the portion at which anode can  2  and gasket  6  are bonded together.  
         [0053]    Furthermore anode can  2  has peripheral wall  5  with the mechanically relatively strong stainless steel layer providing peripheral wall  5   a  substantially equal in thickness to stainless steel layer  2   a  of terminal portion  10  to allow peripheral wall  5  to have a level of mechanical strength maintained by peripheral wall  5   a  to some extent.  
         [0054]    Reference will now be made to FIGS.  2 - 8  to describe a method of manufacturing the anode can of the present invention shown in FIG. 1.  
         [0055]    Initially, as shown in FIG. 2, there is prepared a clad material  21  formed of stainless steel layer  2   a  and hard aluminum alloy layer  2   b  stacked thereon. Clad material  21  is cut to have a predetermined size and geometry in accordance with the size of the anode can.  
         [0056]    Then, as shown in FIG. 3, clad material  21  is pressed by a punch  12   a  and a die  12   b.  Punch  12   a  has a protrusion  13  at a portion abutting against a periphery of clad material  21 . Clad material  21  thus has a periphery pressed, as shown in FIG. 3, to have hard aluminum alloy layer  2   b  reduced in thickness. This provides a thin portion  19  and the hard aluminum alloy thus partially, plastically flows toward an end of thin portion  19 , resulting in an extruded portion  14  protruding from a side surface  15  of punch  12   a  and die  12   b.  Stainless steel layer  2   a  also has end  16  protruding from side surface  15 .  
         [0057]    Then, as shown in FIG. 4, clad material  21  and punch  12   a  are moved relative to a die  12   c  in a direction indicated by an arrow to cut and separate extruded portion  14  of layer  2   b  and end  16  of layer  2   a  from clad material  21 . As a result, layers  2   b  and  2   a  have their respective side surfaces  17  and  18  substantially in a single plane.  
         [0058]    Then, as shown in FIGS. 5 and 6, a punch  12   d  and a die  12   e  are used to press clad material  21  to bend and thus erect a periphery thereof upward as seen in the figure. More specifically, clad material  21  and punch  12   d  are moved relative to die  12   e  in a direction indicated by an arrow shown in FIG. 5 to bend a periphery of clad material  21 , as shown in FIG. 6. As a result, thin portion  19  formed in the FIG. 3 step is bent and thus erected and peripheral wall  5  is thus formed. Peripheral wall  5  includes the stainless steel layer&#39;s peripheral wall  5   a  and the hard aluminum arrow layer&#39;s peripheral wall  5   b.  Since peripheral wall  5   b  corresponds to thin portion  19  (FIG. 3), a pressed portion, peripheral wall  5   b  is smaller in thickness than layer  2   b  located at terminal portion  10 . Pressing thin portion  19 , as shown in FIGS. 5 and 6, and thus bending and thus erecting the same forms a protrusion  22  at an end of peripheral wall  5   b  located at an inner circumference of peripheral wall  5 . Protrusion  22  slightly protrudes relative to an end surface of peripheral wall  5   a.  However, thin portion  19  with peripheral wall  5   b  smaller in thickness than layer  2   b  located at terminal portion  10  can reduce a material flowing to peripheral wall  5   b.  Thus protrusion  22  only protrudes in a significantly small amount.  
         [0059]    Then, as shown in FIG. 7, a punch  12   f  and a die  12   g  are used to press clad material  21  to form anode can  2  with terminal portion  10  peripherally provided with shoulder  3  and angled portion  4 , as shown in FIG. 8. More specifically, with reference to FIG. 7, clad material  21  and punch  12   f  are moved relative to die  12   g  in a direction indicated by an arrow shown in the figure to push a periphery of clad material  21  upward as seen in the figure. Shoulder  3  (FIG. 8) is thus formed.  
         [0060]    At a periphery of clad material  21  bent and erected in the FIG. 7 step, hard aluminum alloy layer  2   b  has a smaller thickness. This can prevent a material forming layer  2   b  from plastically flowing from a center portion of clad material  21  into the periphery thereof in the FIG. 7 step. The periphery can thus be free of an end with hard aluminum alloy layer  5   b  having side surface  17  significantly protruding relative to side surface  16  of stainless steel layer  2   a.    
         [0061]    Then, as shown in FIG. 8, punches  12   h  and  12   i  are used to press clad material  21  to deform and thus extend protrusion  22  (FIG. 7) inward. More specifically, punches  12   h  and  12   i  are moved in the same direction that peripheral wall  5  extends (to press peripheral wall  5 ) to cause punches  12   h  and  12   i  to crush protrusion  22 . Punches  12   h  and  12   i  each have a geometry as determined to be able to deform protrusion  22  inwards. As a result, as shown in FIG. 8, the hard aluminum alloy layer&#39;s peripheral wall  5   b  and the stainless steel layer&#39;s peripheral wall  5   a  can have their respective end surfaces substantially matching in position (or substantially in a single plane). Peripheral wall  5   b  has an end provided with protrusion  23  protruding (or raised) inwards. This can facilitate plunging peripheral wall  5  into gasket  6  and also prevent peripheral wall  5   b  from having an end covering an end of peripheral wall  5   a.  Consequently, anode can  2  and gasket  6  can be bonded together to provide significantly enhanced hermeticity.  
         [0062]    Furthermore the FIG. 8 step also allows angled portion  4  to have a tip sharper in geometry.  
         [0063]    Anode can  2  thus manufactured and the FIG. 1 cathode can  1 , cathode  7 , separator  9 , lithium metal  8  and the like can be used to fabricate the FIG. 1 battery.  
         [0064]    Second Embodiment  
         [0065]    With reference to FIG. 9, a battery will be described.  
         [0066]    The FIG. 9 battery  20  is a manganese (Mn)-lithium (Li) secondary battery, one of so-called organic electrolyte secondly batteries. It is basically similar in structure to the FIG. 1 battery, except for the geometry of peripheral wall  5  of anode can  2 . More specifically, for the FIG. 9 battery  20 , anode can  2  has peripheral wall  5  with the hard aluminum alloy layer providing peripheral wall  5   b  reduced in thickness as it approaches an end of peripheral wall  5  (i.e., peripheral wall  5   b  tapers). As well as in the FIG. 1 battery, peripheral wall  5  has an end with peripheral wall  5   b  having an end provided with protrusion  23  (see FIG. 15).  
         [0067]    The battery of the present embodiment can thus be as effective as the FIG. 1 battery and furthermore anode can  2  having peripheral wall  5  tapering (or sharpened) toward an end thereof ensures that anode can  2  is plunged into gasket  6  more reliably. Anode can  2  and gasket  6  can thus be bonded together more closely and thus provide enhanced hermeticity.  
         [0068]    Reference will now be made to FIGS.  10 - 15  to describe a method of manufacturing the anode can of the present invention shown in FIG. 9.  
         [0069]    Initially, as described in the first embodiment with reference to the FIG. 2 step, there is prepared a clad material  21  formed of stainless steel layer  2   a  and hard aluminum alloy layer  2   b  stacked thereon (see FIG. 2). Clad material  21  is previously cut to have a predetermined size and geometry to match the size of the anode can.  
         [0070]    Then, as shown in FIG. 10, punch  12   a  and die  12   b  are used to press clad material  21 . Punch  12   a  is provided with protrusion  13  at a portion abutting against a periphery of clad material  21 . A surface of protrusion  13  that abuts against clad material  21  tapers relative to a surface of clad material  21 . Clad material  21  thus has a periphery pressed, as shown in FIG. 3, to taper hard aluminum alloy layer  2   b  toward an end of clad material  21 . A tapering thin portion  19  is thus formed.  
         [0071]    Furthermore, the formation of tapering thin portion  19  causes the hard aluminum alloy to partially, plastically flow toward an end of thin portion  19 . As a result, extruded portion  14  results. Extruded portion  14  protrudes relative to side surface  15  of punch  12   a  and die  12   b.  Furthermore, stainless steel layer  2   a  also has end  16  protruding relative to side surface  15 .  
         [0072]    Then, as shown in FIG. 11, clad material  21  and punch  12   a  are moved relative to a die  12   c  in a direction indicated by an arrow to cut and separate extruded portion  14  of layer  2   b  and end  16  of layer  2   a  from clad material  21 . As a result, layers  2   b  and  2   a  have their respective side surfaces  17  and  18  substantially in a single plane.  
         [0073]    Then, as shown in FIGS. 12 and 13, a punch  12   d  and a die  12   e  are used to press clad material  21  to bend and thus erect a periphery thereof upward as seen in the figure. More specifically, as well as in the FIGS. 5 and 6 steps, clad material  21  and punch  12   d  are moved relative to die  12   e  in a direction indicated by an arrow shown in FIG. 12 to bend a periphery of clad material  21 , as shown in FIG. 13. As a result, thin portion  19  formed in the FIG. 3 step is bent and thus erected and peripheral wall  5  is thus formed. Peripheral wall  5  includes the stainless steel layer&#39;s peripheral wall  5   a  and the hard aluminum arrow layer&#39;s peripheral wall  5   b.  Since peripheral wall  5   b  corresponds to thin portion  19  (FIG. 10), a pressed portion, peripheral wall  5   b  tapers toward an end of peripheral wall  5 . Pressing thin portion  19 , as shown in FIGS. 12 and 13, and thus bending and thus erecting the same forms a protrusion  22  at an end of peripheral wall  5   b  located at an inner circumference of peripheral wall  5 . Protrusion  22  slightly protrudes relative to an end surface of peripheral wall  5   a.  However, thin portion  19  with peripheral wall  5   b  smaller in thickness than layer  2   b  located at terminal portion  10  can reduce a material flowing to peripheral wall  5   b.  Thus protrusion  22  only protrudes in a significantly small amount.  
         [0074]    Then, as shown in FIG. 14, a punch  12   f  and a die  12   g  are used to press clad material  21  to form anode can  2  with terminal portion  10  peripherally provided with shoulder  3  and angled portion  4 , as shown in FIG. 15. More specifically, with reference to FIG. 14, clad material  21  and punch  12   f  are moved relative to die  12   g  in a direction indicated by an arrow shown in the figure to push a periphery of clad material  21  upward as seen in the figure. Shoulder  3  (FIG. 15) is thus formed.  
         [0075]    At a periphery of clad material  21  bent and erected in the FIG. 14 step, hard aluminum alloy layer  2   b  has a smaller thickness. This can prevent a material forming layer  2   b  from plastically flowing from a center portion of clad material  21  into the periphery thereof in the FIG. 14 step. The periphery can thus be free of an end with hard aluminum alloy layer  5   b  having side surface  17  significantly protruding relative to side surface  16  of stainless steel layer  2   a.    
         [0076]    Then, as shown in FIG. 15, punches  12   h  and  12   i  are used to press clad material  21  to deform and thus extend protrusion  22  inward. More specifically, punches  12   h  and  12   i  are moved in the same direction that peripheral wall  5  extends, so that punches  12   h  and  12   i  crush protrusion  22 . Punches  12   h  and  12   i  each have a geometry as determined to be able to deform protrusion  22  inwards. As a result, as shown in FIG. 15, the hard aluminum alloy layer&#39;s peripheral wall  5   b  and the stainless steel layer&#39;s peripheral wall  5   a  can have their respective end surfaces substantially matching in position (or substantially in a single plane). Peripheral wall  5   b  has an end provided with protrusion  23  protruding (or raised) inwards.  
         [0077]    Anode can  2  thus manufactured and the FIG. 9 cathode can  1 , cathode  7 , separator  9 , lithium metal  8  and the like can be used to fabricate the FIG. 9 battery.  
         [0078]    Third Embodiment  
         [0079]    With reference to FIG. 16, a battery will be described.  
         [0080]    The FIG. 16 battery  20  is a manganese (Mn)-lithium (Li) secondary battery, one of so-called organic electrolyte secondly batteries. It is basically similar in structure to the FIG. 1 battery, except for the geometry of an end of peripheral wall  5  of anode can  2 . More specifically, for the FIG. 16 battery  20 , anode can  2  has peripheral wall  5  with the hard aluminum alloy layer providing peripheral wall  5   b  free of a protrusion raised inwards (or increased in thickness), as shown in FIG. 1. In other words, in peripheral wall  5  the hard aluminum alloy layer provides peripheral wall  5   b  substantially uniform in thickness.  
         [0081]    This can provide an effect similar to that of the FIG. 1 battery.  
         [0082]    Reference will now be made to FIGS.  17 - 22  to describe a method of fabricating the anode can of the present invention shown in FIG. 16.  
         [0083]    Initially in accordance with the first embodiment of the present invention the FIGS.  2 - 4  steps are followed. As a result, as described in the method of the first embodiment, clad member  21  has a periphery with hard aluminum alloy layer  2   b  reduced in thickness to provide a thin portion and hard aluminum alloy layer  2   b  and stainless steel layer  2   a  also have their respective side surfaces substantially in a single plane.  
         [0084]    Then, as shown in FIG. 17, a punch  12   k  and a die  12   j  are used to press an end of clad material  21 . The surface of punch  12   k  that abuts against an end of clad material  21  is substantially parallel to a surface of hard aluminum alloy layer  2   b.  Punch  12   k  is moved in a direction indicated by an arrow shown in the figure and it is thus pressed against an end of layer  2   b  of clad material  21 . As a result, as shown in FIG. 17, layer  2   b  has an end reduced in thickness to provide a re-pressed portion  28  and simultaneously layer  2   b  is partially extruded  26 .  
         [0085]    It should be noted that re-pressed portion  28  is variable in size and thickness to match the geometry of clad material  21 , the thicknesses of layers  2   b  and  2   a,  the levels in strength of materials respectively forming the layers, the degree of processing in subsequent process steps, and the like.  
         [0086]    Then, as shown in FIG. 18, clad material  21  and punch  12   k  are moved relative to a die  12   p  in a direction indicated by an arrow to cut and separate extruded portion  26  of layer  2   b  and end  27  of layer  2   a  from clad, material  21 . As a result, layers  2   b  and  2   a  have their respective side surfaces  17  and  18  substantially in a single plane.  
         [0087]    Then, as shown in FIGS. 19 and 20, a punch  12   d  and a die  12   e  are used to press clad material  21  to bend and thus erect a periphery thereof upward as seen in the figure. More specifically, as well as in the FIGS. 5 and 6 steps, clad material  21  and punch  12   d  are moved relative to die  12   e  in a direction indicated by an arrow shown in FIG. 19 to bend a periphery of clad material  21 , as shown in FIG. 20. As a result, a thin portion located at a periphery of clad material  21  is bent and thus erected and peripheral wall  5  is thus formed.  
         [0088]    Peripheral wall  5  includes the stainless steel layer&#39;s peripheral wall  5   a  and the hard aluminum arrow layer&#39;s peripheral wall  5   b.  Since peripheral wall  5   b  corresponds to the thin portion, a pressed portion, peripheral wall  5   b  is smaller in thickness than layer  2   b  located at terminal portion  10 . Furthermore, hard aluminum alloy layer  2   b  has an end reduced in thickness to provide re-pressed portion  28 . As such, if pressing thin portion  19 , as shown in FIGS. 19 and 20, to bend and erect it results in layer  2   b  plastically flowing to some extent, layer  2   b  only has an end with a significantly small protrusion  22  slightly protruding relative to an end surface of peripheral wall  5   a  of the stainless steel layer. Furthermore, the end of peripheral wall  5   b  is provided with a step  29  at a boundary of repressed portion  28  and the remaining region.  
         [0089]    Then, as shown in FIG. 21, a punch  12   f  and a die  12   g  are used to press clad material  21  to form shoulder  3  and angled portion  4  surrounding terminal portion  10  (FIG. 22). More specifically, with reference to FIG. 21, clad material  21  and punch  12   f  are moved relative to die  12   g  in a direction indicated by an arrow shown in the figure to push a periphery of clad material  21  upward as seen in the figure. Shoulder  3  and angled portion  4  are thus formed.  
         [0090]    At a periphery of clad material  21  bent and erected in the FIG. 21 step, hard aluminum alloy layer  2   b  has a smaller thickness. This can prevent a material forming layer  2   b  from plastically flowing from a center portion of clad material  21  into the periphery thereof in the FIG. 21 step. The periphery can thus be free of an end with hard aluminum alloy layer  5   b  having a side surface significantly protruding relative to a side surface of stainless steel layer  2   a.    
         [0091]    Then, as shown in FIG. 22, punches  12   h  and  12   i  are used to press clad material  21  to allow the hard aluminum alloy layer&#39;s peripheral wall  5   b  to have an end so that the hard aluminum alloy layer&#39;s peripheral wall  5   b  and the stainless steel layer&#39;s peripheral wall  5   a  have their respective end surfaces in a single plane. More specifically, punches  12   h  and  12   i  are moved in the same direction that peripheral wall  5  extends, so that the punches press an end surface of peripheral wall  5 . Punches  12   h  and  12   i  each have a geometry determined to allow peripheral wall  5  to have an end surface with the aluminum alloy layer and the stainless steel layer providing their respective peripheral walls  5   b  and  5   a  having their respective end surfaces in alignment. As a result, as shown in FIG. 22, peripheral walls  5   b  and  5   a  can have their respective end surfaces substantially matched in position or substantially in a single plane.  
         [0092]    Herein prior to the FIG. 22 step the FIGS. 17 and 18 steps previously provide an end of hard aluminum alloy layer  2   b  with re-pressed portion  28 . As such, the hard aluminum alloy layer&#39;s peripheral wall  5   b  would not have an end surface significantly protruding relative to that of the stainless steel layer&#39;s peripheral wall  5   a.  Thus, despite the FIG. 22 step, peripheral wall  5   b  can be prevented from having an end disadvantageously covering that of peripheral wall  5   a.    
         [0093]    Anode can  2  thus fabricated and the FIG. 16 cathode can  1 , cathode  7 , separator  9 , lithium metal  8  and the like can be used to fabricate a battery similar to the FIG. 16 battery.  
         [0094]    Furthermore, the FIG. 22 step may be followed by such a step as shown in FIG. 23.  
         [0095]    The FIG. 23 step is basically similar to the FIG. 22 step, except that a punch  12   n  is different in geometry from the FIG. 22 punch  12   h.  Punch  12   n  used in the FIG. 23 step is provided with a step at a portion abutting against an end surface of peripheral wall  5 . Such a punch  12   n  can be used to provide a step similar to the FIG. 22 step to obtain anode can  2  having a geometry as shown in FIG. 24. FIG. 24 is a schematic, partial cross section of an anode can fabricated through the FIG. 23 step.  
         [0096]    With reference to FIG. 24, anode can  2  is basically similar in structure to that of battery  20  shown in FIG. 16, except for the geometry of an end of peripheral wall  5 . More specifically, for the FIG. 24 anode can  2 , peripheral wall  5  has an end with the hard aluminum alloy layer providing peripheral wall  5   b  having an end surface receding from that of peripheral wall  5   a  of the stainless steel layer (or peripheral wall  5   a  has an end surface protruding relative to that of peripheral wall  5   b ). If anode can  2  having such a step  25  is applied to a battery, anode can  2  and gasket  6  (see FIG. 16) can be bonded together more closely and thus provide enhanced hermeticity. Note that the receding end surface of peripheral wall  5   b  is positionally variable, as appropriate, to match the specification of anode can  2 .  
         [0097]    Note that the FIG. 22 step may be replaced with the FIG. 23 step.  
         [0098]    Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.