Abstract:
A cylindrical alkaline storage battery including a spiraled electrode body composed of a pair of opposed electrodes spirally rolled up through a separator and coupled within a cylindrical casing, at least one of the electrodes being in the form of a non-sintered type electrode composed of an active material retention substrate of three dimensionally meshed structure impregnated with paste of an active material, and a current collector formed with a disc portion for connection to one end portion of the non-sintered type electrode and a lead portion for connection to a terminal, wherein the one end portion of the non-sintered type electrode is formed without impregnation of the paste of the active material, and wherein a perforated sheet metal welded to the one end portion of the non-sintered type electrode is welded at its side edge to the disc portion of the current collector.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cylindrical alkaline storage battery such as a nickel-hydrogen battery, a nickel-cadmium battery, a nickel-zinc battery in the like, and more particularly to an improvement of a conductive connection between a current collector and an electrode in the form of an active material retention substrate impregnated with an active material. 
     2. Discussion of the Prior Art 
     An electrode for use in a conventional alkaline storage battery such as a nickel-cadmium battery, a nickel-hydrogen battery, a nickel-zinc battery or the like is in the form of a sintered type electrode fabricated by the steps of sintering nickel powder on a perforated core substrate such as a punched sheet metal to produce a sintered base plate. impregnating the sintered base plate with solution of nickel and cadmium salts and subjecting the base plate to alkali treatment for activation. In case a sintered base plate of high porosity was used for fabrication of the sintered type electrode, the mechanical strength of the electrode would be weakened. For this reason, a sintered base plate of about 80% porosity is used for fabrication of the electrode in practical use. In addition, use of the perforated core substrate results in a decrease of impregnation density of the active material and difficulty for fabrication of an electrode of high energy density. Since the pore of the sintered base plate is less than 10 μm, to the impregnation process of the active material must be resealed by a solution impregnation method or an electrodepositive impregnation method. This results in an increase in the manufacturing cost of the batteries. 
     To avoid the problems described above, a non-sintered type electrode has been used, which is fabricated by directly impregnating paste of an active material into a porous metal substrate or an active material retention substrate of three dimensionally meshed structure such as a sintered substrate of metal fiber, foam nickel or nickel sponge. Since the porosity of the porous metal substrate of three dimensionally meshed structure is about 95%, the porous metal substrate can be impregnated with the active material of high density for manufacturing a battery of large capacity in a simple manner without a treatment for activation. 
     As the non-sintered type electrode of this kind does not include any core substrate, various methods have been proposed for conductive connection of the battery terminal with the electrode in the form of the porous metal substrate impregnated with the active material. For example, disclosed in Japanese Patent Laid-open Publication No. 61-218067 is a manufacturing method of an electrode the retention substrate of which is in the form of a sintered felt-like substrate of metal fiber. During the manufacturing process of the electrode, a felt-like plate of metal fiber is integrally formed with a conductive ancillary substrate such as a meshed substrate, a punched sheet metal, a wire material or a flat plate to enhance the mechanical strength of the felt-like plate of metal fiber and the current collectivity of the electrode. 
     However, as the sintered substrate of metal fiber is made of fine metal fibers of about 10 μm in diameter bundled in a longitudinal direction of the electrode, the fine metal fibers are disconnected when the sintered substrate of metal fiber is spirally rolled up through a separator after being coated with the active material. As a result, the positive and negative electrodes are electrically connected by fragments of the metal fibers that pierce the separator, resulting in the occurrence of a short circuit in the battery. 
     In the electrode fabricated by using the substrate of foam nickel, the foam nickel itself is prevented from disconnection even when the electrode is spirally rolled up through the separator after being impregnated with the active material. In this case, the active material of the electrode is peeled off to expose the foam nickel, and a current collector tab is welded to the exposed portion of the foam nickel for current collection. In such construction of the electrode, however, voltage drop will occur at the current collector tab when a large amount of current is discharged. 
     Disclosed in Japanese Patent Laid-open Publication No. 62-139251 is a nickel-cadmium battery fabricated by the steps of compressing one end portion of an electrode substrate made of foam nickel in its width direction to form a dense layer without impregnation of any active material and welding the dense layer to a circular lead plate placed perpendicularly to the electrode surface. In the electrode of the nickel-cadmium battery, the electrode substrate made of foam nickel itself is prevented from disconnection even when the electrode is spirally rolled up through a separator, and the current collectivity at the compressed one end of the electrode substrate welded to the circular lead plate is enhanced. However, as the dense layer formed by compressing the one end portion of the electrode substrate in its width direction is inferior in elasticity, the dense layer is partly broken when the electrode is spirally rolled up through the separator. As a result, a short circuit in the battery will occur due to burrs of the dense layer that pierce the separator. If the dense layer is mixed with an elastic portion of the electrode, it becomes difficult to spirally roll up positive and negative electrodes under uniform pressure. 
     It has been also proposed to form one end portion of the substrate of foam nickel without impregnation of any active material thereby to fabricate an electrode by welding a ribbon-like sheet metal on the one end portion of the substrate. However, when the electrode is spirally rolled up with an opposed electrode through a separator, a portion -of the sheet metal is folded and brought into contact with the opposed electrode to cause a short circuit in the battery. 
     SUMMARY OF THE INVENTION 
     It is, therefore, a primary object of the present invention to provide a cylindrical alkaline storage battery in which a porous metal substrate of three dimensionally meshed structure is used as an active material retention substrate for an electrode of the battery to enhance the current collectivity of the electrode without causing an unexpected short circuit in the battery. 
     According to the present invention, there is provided a cylindrical alkaline storage battery including a cylindrical casing, a pair of opposed electrodes spirally rolled up through a separator and coupled within the cylindrical casing, at least one of the electrodes being in the form of a non-sintered type electrode composed of an active material retention substrate of three dimensionally meshed structure impregnated with paste of an active material, and a current collector formed with a disc portion for connection to one end portion of the non-sintered type electrode and a lead portion for connection to a terminal, wherein the one end portion of the non-sintered type electrode is formed without impregnating the paste of the active material therewith, and wherein a perforated sheet metal welded to the one end portion of the non-sintered type electrode is welded at its side edge to the disc portion of the current collector. 
     In a practical embodiment, the perforated sheet metal may be either one of a punched sheet metal or an expanded sheet metal. Preferably, either one of the punched sheet metal or the expanded sheet metal is formed with a side edge cut along its perforated portion and welded to the disc portion of the current collector. 
     According to an aspect of the present invention, there is provided a manufacturing method of a cylindrical alkaline storage battery comprising the steps of impregnating an active material retention substrate of three dimensionally meshed structure with paste of an active material to prepare a non-sintered type electrode, rolling up the non-sintered type electrode with an opposed electrode through a separator to form a spiraled electrode body, connecting one end portion of the non-sintered type electrode to a disc portion of a current collector, wherein the manufacturing method is characterized by the steps of forming one end portion of the active material retention substrate without impregnating the paste of the active material therewith, welding a perforated sheet metal to the one end portion of the active material retention substrate to prepare the non-sintered type electrode, rolling up the non-sintered type electrode with the opposed electrode through the separator to form the spiraled electrode body, and welding a side edge of the perforated sheet metal to the disc portion of the current collector. 
     According to another aspect of the present invention, there is provided a manufacturing method of a cylindrical alkaline storage battery comprising the steps of impregnating an active material retention substrate of three dimensionally meshed structure with paste of an active material, removing the impregnated paste of the active material from one end portion of the substrate, welding a perforated sheet metal to the one end portion of the substrate to prepare a non-sintered type electrode, rolling up the non-sintered type electrode with an opposed electrode through a separator to form a spiraled electrode body, welding the perforated sheet metal at its side edge to a disc portion of a current collector. 
     In a practical embodiment of the present invention, it is preferable that the step of removing the impregnated active material comprises the step of applying ultrasonic vibration to the one end portion of the active material retention substrate for removing therefrom the paste of the active material. 
     According to a further aspect of the present invention, there is provided a manufacturing method of a cylindrical alkaline storage battery comprising the steps of masking one end portion of an active material retention substrate of three dimensionally meshed structure with an adhesive tape, impregnating the active material retention substrate with paste of an active material, removing the adhesive tape from the one end portion of the substrate, welding a perforated sheet metal to the one end portion of the substrate formed without impregnation of the active material to prepare a non-sintered type electrode, rolling up the non-sintered type electrode with an opposed electrode through a separator to form a spiraled electrode body, and welding the perforated sheet metal at its side edge to a disc portion of a current collector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will be more readily appreciated from the following detailed description of preferred embodiments thereof when taken together with the accompanying drawings, in which: 
     FIG. 1 is a front view of an active material retention substrate made of foam nickel and a perforated sheet metal such as a punched sheet metal welded to an upper end portion of the substrate formed without impregnation of any active material; 
     FIG. 2 is a front view of an active material retention substrate made of foam nickel and a conventional sheet metal welded at an upper end portion of the substrate formed without impregnation of any active material; 
     FIG. 3 is a front view of an active material retention substrate made of foam nickel and a conventional current collector tab welded to an upper end portion of the substrate formed without impregnation of any active material; 
     FIG. 4 is an illustration of a vertical section of a cylindrical nickel-hydrogen storage battery in accordance with the present invention; and 
     FIG. 5 is a perspective view of a current collector for a positive electrode. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Preferred embodiments of a cylindrical alkaline storage battery manufactured by using a non-sintered type electrode according to the present invention will be described herein-after. 
     1. Manufacture of a Nickel Positive Electrode 
     EXAMPLE 1 
     90 weight part of nickel hydroxide, 5 weight part of metal cobalt powder and 5 weight part of cobalt hydroxide powder were mixed and kneaded with 1 wt. % methyl cellulose and 20 weight part of aqueous solution to prepare paste of an active material. The paste of active material was impregnated in an active material retention substrate made of foam nickel or nickel sponge of 600 g/m 2  in areal density and 1.5 mm in thickness. Thereafter, the active material retention substrate  10  was dried and rolled under pressure in thickness of about 0.7 mm. In this instance, the active material retention substrate was impregnated with the paste of active material in such a manner that the impregnation density of the active material becomes about 2.9 to 3.05 g/cc—void after rolled under pressure. 
     At the following step, an ultrasonic horn (not shown) was pressed into contact with an upper end portion  12  of the active material retention substrate  10  impregnated with the paste of active material  11  to apply ultrasonic vibration perpendicularly to the surface of the upper end portion  12  thereby to remove the impregnated active material  11  from the active material retention substrate  10 . In this instance, the upper end portion  12  of substrate  10  was compressed by the ultrasonic vibration and was formed as a compressed thin portion. 
     On the other hand, as shown in FIG. 1, a nickel sheet metal of 0.06 mm in thickness was punched to form a large number of circular holes in diameter of 0.30 to 1.00 mm alternately at each line thereby to prepare a punched nickel sheet metal  13  the perforation degree of which was determined to be 20 to 60%. The punched nickel sheet metal  13  was cut in width of 1.5 mm in such a manner that the circular holes are cut at each center thereof. 
     The punched nickel sheet metal  13  was placed on the upper end portion  12  of active material retention substrate  10  in such a manner that the cut portions of the circular holes are slightly projected from the upper edge of substrate  10 , In such a condition, the nickel sheet metal  13  was welded to the upper end portion  12  of substrate  10  at an interval of 2 mm by using a copper welding rod of 1.5 mm in diameter to produce a nickel positive electrode  10   a  provided with the punched nickel sheet metal  13  the cut portion of which is partly projected from the upper edge of substrate  10 . 
     EXAMPLE 2 
     The same active material retention substrate  10  as that in Example 1 was impregnated with paste of an active material  11  prepared in the same manner as in Example 1. Thereafter, the ultrasonic horn (not shown) was pressed into contact with an upper end portion  12  of active material retention substrate  10  to apply ultrasonic vibration perpendicularly to the surface of upper end portion  12  thereby to remove the impregnated active material  11  from the active material retention substrate  10 . In this instance, the upper end portion  12  of substrate  10  was compressed by the ultrasonic vibration and was formed as a compressed thin portion. 
     On the other hand, as shown in FIG. 1, a nickel sheet metal of 0.10 mm in thickness was punched to form a large number of circular holes in diameter of 0.30 to 1.00 mm alternately at each line thereby to prepare a punched nickel sheet metal  14  the perforation degree of which was determined to be 20 to 60%. The punched nickel sheet metal  14  was cut in width of 1.5 mm in such a manner that the circular holes are cut at each center thereof. 
     Thus, the punched nickel sheet metal  14  was placed on the upper end portion  12  of active material retention substrate  10  in such a manner that the cut portions of the circular holes are slightly projected from the upper edge of substrate  10 , In such a condition, the punched nickel sheet metal  14  was welded to the upper end portion  12  of substrate  10  at an interval of 2 mm by using the copper welding rod of 1.5 mm in diameter to produce a nickel positive electrode plate  10   b  provided with the punched nickel sheet metal  14  the cut portion of which is partly projected from the upper edge of substrate  10 . 
     EXAMPLE 3 
     The same active material retention substrate  10  as that in Example 1 was impregnated with paste of an active material  11  prepared in the same manner as in Example 1. Thereafter, the ultrasonic horn (not shown) was pressed into contact with an upper end portion  12  of active material retention substrate  10  to apply ultrasonic vibration perpendicularly to the surface of upper end portion  12  thereby to remove the impregnated active material  11  from the active material retention substrate  10 . In this instance, the upper end portion  12  of substrate  10  was compressed by the ultrasonic vibration and was formed as a compressed thin portion. 
     On the other hand, as shown in FIG. 1, a nickel sheet metal of 0.18 mm in thickness was punched to form a large number of circular holes in diameter of 0.30 to 1.00 mm alternately at each line thereby to prepare a punched nickel sheet metal  15  the perforation degree of which was determined to be 20 to 60%. The punched nickel sheet metal  15  was cut in width of 1.5 mm in such a manner that the circular holes are cut at each center thereof. 
     Thus, the punched nickel sheet metal  15  was placed on the upper end portion  12  of active material retention substrate  10  in such a manner that the cut portions of the circular holes are slightly projected from the upper edge of substrate  10 , In such a condition, the punched nickel sheet metal  15  was welded to the upper end portion  12  of substrate  10  at an interval of 2 mm by using the copper welding rod of 1.5 mm in diameter to produce a nickel positive electrode plate  10   c  provided with the punched nickel sheet metal  15  the cut portion of which is partly projected from the upper edge of substrate  10 . 
     Comparative Example 1 
     The same active material retention substrate  20  as that in Example 1 was impregnated with paste of an active material  21  prepared in the same manner as in Example 1. Thereafter, the ultrasonic horn (not shown) was pressed into contact with an upper end portion  22  of active material retention substrate  20  to apply ultrasonic vibration perpendicularly to the surface of upper end portion  22  thereby to remove the impregnated active material  21  from the active material retention substrate  20 . In this instance, the upper end portion  22  of substrate  20  was compressed by the ultrasonic vibration and was formed as a compressed thin portion. 
     On the other hand, as shown in FIG. 2, a nickel sheet metal  23  of 0.10 mm in thickness was cut in width of 1.5 mm and placed on the compressed thin portion of retention substrate  20 . In such a condition, the nickel sheet metal  23  was welded to the upper end portion  22  of retention substrate  20  at an interval of 2 mm by using the copper welding rod of 1.5 mm in diameter to produce a nickel positive electrode plate  20   a  as a comparative example 1. 
     Comparative Example 2 
     The same active material retention substrate  30  as that in Example 1 was impregnated with paste of an active material  31  prepared in the same manner as in Example 1. Thereafter, an ultrasonic horn (not shown) was pressed into contact with an upper end central portion  32  of active material retention substrate  30  to apply ultrasonic vibration perpendicularly to the surface of upper end central portion  32  thereby to remove the impregnated active material  31  from the active material retention substrate  30 . In this instance, the upper end central portion  32  of substrate  30  was compressed by the ultrasonic vibration and was formed as a compressed thin portion. 
     Thus, as shown in FIG. 3, a rectangular current collector tab  33  made of a nickel sheet metal of 3.0 mm in width and 0.10 mm in thickness was placed on the compressed thin portion  32  of substrate  30 . In such a condition, the current collector tab  33  was welded to the compressed thin portion  32  of substrate  30  by using a copper welding rod of 3.0 in diameter and covered with a tape of polypropylene adhered thereto to produce a nickel positive electrode plate  30   a  as a comparative example 2. 
     Manufacture of Nickel-Hydrogen Storage Battery: 
     a) Nickel-hydrogen storage batteries using the nickel positive electrode plates of the Examples 1 to 3: 
     The nickel positive electrode plates  10   a ,  10   b  and  10   c  each were used to manufacture a nickel-hydrogen storage battery in such a manner as described hereinafter. In the manufacturing process of the battery, a negative electrode plate  41  shown in FIG. 4 was fabricated by coating a punched sheet metal with a hydrogen storage alloy material. Thus, the nickel positive electrode plates  10   a ,  10   b  and  10   c  each were spirally rolled up with the negative electrode plate  41  through a separator  50  made of unwoven polypropylene fabric in such a manner that the negative electrode  41  is located outside. Thus, a spiraled electrode body A was prepared. 
     On the other hand, a positive current collector  60  of nickel metal was prepared as shown in FIG.  5 . The positive current collector  60  has a disc portion  61  and a rectangular lead portion  62 . The disc portion  61  of positive current collector  60  is formed with a plurality of openings  63 , a pair of diametrically opposed slits  64  for positioning a pair of welding electrodes and a center hole  65  for entry of electrolyte. Similarly, a disc-like negative current collector  70  of nickel metal was prepared. 
     As shown in FIG. 4, the positive current collector  60  was welded at its disc portion  61  to an upper side edge of the punched sheet metal  13  of the nickel positive electrode plates  10   a , while the negative current collector  70  was welded to a bottom end  41  of the negative electrode plate  40 . During the welding process, a pair of welding electrodes were positioned in place by engagement with the slits  64  of current collector  60  and applied with a welding current so that the disc portion  61  of current collector  60  is welded to the upper side edge of punched sheet metal  13  by the welding current applied at its bottom surface. In this instance, the projections formed on the upper side edge of punched sheet metal  13  cause the welding current to concentrate into the peripheries of openings  63  of current collector  60  retained in engagement therewith. 
     After the current collectors  60  and  70  were welded to the positive and negative electrodes  10   a  and  40 , the spiraled electrode body A was coupled within a bottomed cylindrical casing  80 , and one of the welding electrodes was inserted into a cylindrical space in the spiraled electrode body A through the center hole  65  of current collector  60  and engaged with the negative current collector  70 . In such a condition, the other welding electrode was engaged with the bottom of casing  80  and applied with the welding current to weld the negative current collector  70  to the bottom of casing  80 . 
     At the following step, a cover plate  92  of a closure cap assembly  90  was brought into engagement with and welded to the lead portion  62  of positive current collector  60 . In FIG. 4, the reference numeral  91  designates a positive electrode cap welded to the cover plate  92 . Thereafter, the cylindrical casing  80  was filled with electrolyte such as aqueous solution of 30 wt.% potassium hydroxide (KOH) supplied through the center hole  65  of positive current collector  60 , and the cover plate  92  of closure cap assembly  90  was coupled within an opening end  81  of casing  80  through an annular gasket  82  and secured in place by caulking the opening end  81  of casing  80  to seal the interior of casing  80 . Thus, a nickel hydrogen storage battery of nominal capacity 2700 mAH was manufactured by using the nickel positive electrodes of the Examples 1 to 3. 
     b) Nickel-Hydrogen Storage Battery Using the Nickel Positive Electrode of the Comparative Example 1: 
     The nickel positive electrodes  20   a  was used to manufacture a nickel-hydrogen storage battery in such a manner as described hereinafter. In the manufacturing process of the battery, a negative electrode plate  40  was fabricated by coating a punched sheet metal  41  with a hydrogen storage alloy material, and the nickel positive electrode plate  20   a  of the comparative example 1 was spirally rolled up with the negative electrode plate  40  through a separator  50  made of unwoven polypropylene fabric in such a manner that the negative electrode plate  40  is located outside. Thus, a spiraled electrode body A was prepared. 
     On the other hand, positive and negative current collectors  60  and  70  of nickel metal were prepared in the same manner as in the foregoing embodiment. The positive current collector  60  was welded at its disc portion  61  to an upper side edge of the ribbon-like sheet metal  23  of the nickel positive electrode  20   a , while the negative current collector  70  was welded to a bottom end  41  of negative electrode  40  in the spiraled electrode body A. In this instance, the disc portion  61  of current collector  60  could not be firmly connected to the sheet metal  23  since the welding current was irregularly applied to the upper side edge of sheet metal  23 . 
     After the current collectors  60  and  70  each were welded to the positive and negative electrodes  20   a  and  40 , the spiraled electrode body A was coupled within a bottomed cylindrical casing  80  in the same manner as described above. The negative current collector  70  was welded to the bottom of casing  80 , while the cover plate  92  of the closure cap assembly  90  was welded at its bottom surface to the lead portion  62  of positive current collector  60 . Thereafter, the casing  80  was filled with electrolyte such as aqueous solution of 30 wt.% potassium hydroxide (KOH) supplied through the center hole  65  of positive current collector  60 , and the closure cap assembly  90  was coupled within the opening end  81  of casing  80  through the annular gasket  82  and secured in place by caulking the opening end  81  of casing  80  to seal the interior of casing  80 . Thus, a nickel-hydrogen storage battery of nominal capacity 2700 mAH was manufactured by using the nickel positive electrode  20   a  of the comparative example 1. 
     c) Nickel-Hydrogen Storage Battery Using the Nickel Positive Electrode of the Comparative Example 2: 
     The nickel positive electrode  30   a  was used to manufacture a nickel-hydrogen storage battery in such a manner as described hereinafter. In the manufacturing process of the battery, a negative electrode plate  40  was fabricated by coating a punched sheet metal  41  with a hydrogen storage alloy material, and the nickel positive electrode  30   a  of the comparative example 2 was spirally rolled up with the negative electrode plate  40  through the separator  50  made of unwoven polypropylene fabric in such a manner that the negative electrode plate  40  is located outside. Thus, a spiraled electrode body A was prepared. 
     On the other hand, positive and negative current collectors  60  and  70  of nickel metal were prepared as in the foregoing embodiment. After the negative electrode  40  of the spiraled electrode body A was welded at its lower end to the bottom of casing  80  in the same manner as described above, the cover plate  92  of closure cap assembly  90  was welded at its bottom surface to the current collector tab  33  of nickel positive electrode plate  30   a . Thereafter, the cylindrical casing  80  was filled with electrolyte such as aqueous solution of 30 wt. % potassium hydroxide (KOH) supplied through the center hole  65  of positive current collector  60 , and the closure cap assembly  90  was coupled within the opening end  81  of casing  80  through the annular gasket  82  and secured in place by caulking the opening end  81  of casing  80  to seal the interior of casing  80 . Thus, a nickel hydrogen storage battery of nominal capacity 2700 mAH was manufactured by using the nickel positive electrode  30   a  of the comparative example 2. 
     3. Result of Experiments 
     a) Defective Rate: 
     Listed on the following Table 1 is the occurrence rate of defects such as a short-circuit in the batteries during the manufacturing process described above. 
     
       
         
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                 Comparative 
               
               
                 Kind of electrodes 
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 1 
               
               
                   
               
             
             
               
                 Occurrence rate 
                 0.5 
                 1.0 
                 1.6 
                 2.4 
               
               
                 of defects 
               
               
                   
               
             
          
         
       
     
     As shown in Table 1, it has been found that the occurrence rate of defects in the battery manufactured by using the nickel positive electrode  10   b  of the example 2 is reduced to half in comparison with the occurrence rate of defects in the battery manufactured by using the nickel positive electrode  20   a  of the comparative example 1. The result was obtained by the facts that the elasticity of the nickel positive electrode  10   b  was increased by using the punched sheet metal and that the nickel positive electrode  10   b  was spirally rolled up without causing any separation at the welded portion. It has been also found that the occurrence rate of defects in the battery manufactured by using the nickel positive electrode  10   c  of the example 3 is reduced less than that in the battery manufactured by using the nickel positive electrode  20   a  of the comparative example 1. As is understood from the above facts, the punched sheet metal  13 ,  14  or  15  welded to the upper end portion of the active material retention substrate  10  is useful to reduce the occurrence rate of defects in the batteries. 
     Although the punched sheet metal  13 ,  14  or  15  in the foregoing embodiments was formed with circular holes, the sheet metal may be formed with appropriate holes such as triangular holes, rectangular holes, pentagonal holes or the like. In addition, the punched sheet metal may be replaced with an expanded sheet metal. 
     b) Battery Capacity and Operation Voltage: 
     Discharge characteristics of the nickel-hydrogen storage batteries manufactured as described above were measured. In the measurement, the nickel-hydrogen storage batteries were discharged respectively at a current of 10 A after fully charged. In this instance, the batteries each were discharged at the current of 10 A until the voltage becomes 1.0 V to measure each discharge capacity of the batteries. In addition, the nickel-hydrogen storage batteries were connected to a load after fully charged and discharged at the current of 10 A until the voltage becomes an intermediate value of 1.00 V to measure each operation voltage of the batteries. A result of the measurement is shown in the following table 2. 
     
       
         
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Kind of electrodes 
                 Discharge capacity (mAh) 
                 Operation voltage (V) 
               
               
                   
               
             
             
               
                 Example 1 
                 2300 
                 1.13 
               
               
                 Example 2 
                 2500 
                 1.14 
               
               
                 Example 3 
                 2600 
                 1.15 
               
               
                 Comparative 
                 2500 
                 1.14 
               
               
                 Example 1 
               
               
                 Comparative 
                  200 
                 1.03 
               
               
                 Example 2 
               
               
                   
               
             
          
         
       
     
     As is understood from the table 2, it has been found that the discharge capacity and operation voltage are increased in accordance with an increase of thickness of the punched sheet metal used respectively for the nickel positive electrodes  10   a ,  10   b  and  10   c  in the examples 1, 2 and 3. In this respect, it is believed that the result of the measurement is obtained by the fact that the voltage drop at the punched sheet metal increases in accordance with a decrease of thickness of the punched sheet metal when the batteries are discharged at the current of 10 A. 
     It has been also found that in the nickel-hydrogen storage battery using the nickel positive electrode  30   a  of the comparative example 2, the operation voltage decreases as the discharge capacity is extremely decreased. In this respect, it is believed that the result of the measurement is caused by the fact that the voltage at the current collector tab  33  is extremely decreased when the battery is discharged at the current of 10 A. 
     Furthermore, it has been found that the discharge capacity and operation voltage of the battery using the nickel positive electrode  10   b  of the example 2 become substantially equal to those of the battery using the nickel positive electrode  20   a  of the comparative example 1. However, the sheet metal  23  of the positive electrode  20   a  may not be thickened since the elasticity of positive electrode  20  is deteriorated. On the other hand, the punched sheet metal  14  of the positive electrode  10   b  can be thickened without causing any deterioration of its elasticity. 
     As is understood from the above description, the punched sheet metal  13 ,  14  or  15  welded to the upper compressed thin portion  12  of the active material retention plate  10  can be spirally rolled up without causing any damage in its structure. As a result, the punched sheet metal  13 ,  14  or  15  of the spiraled electrode body A can be connected to the positive current collector  60  without causing any short circuit in the battery. This is useful to enhance the discharge capacity and operation voltage of the battery. 
     Although in the embodiments described above, ultrasonic vibration was applied to the upper end portion of the active material retention plate  10  to remove the active material therefrom, the upper end portion of the active material retention plate  10  may be preliminarily masked with an adhesive tape such as a synthetic adhesive tape prior to impregnation of the active material. In such a case, the adhesive tape is removed after impregnation of the active material, and the punched sheet metal is welded to the upper end portion of the active material retention plate. Alternatively, the punched sheet metal may be welded to the upper end portion of the active material retention plate prior to impregnation of the active material. 
     In actual practices of the present invention, the negative electrode  41  may be prepared in the same manner as the nickel positive electrode  10   a ,  10   b  or  10   c  and welded to the negative current collector  70  as in the preferred embodiments described above.