Patent Publication Number: US-2011072648-A1

Title: Method for manufacturing sealed battery

Description:
TECHNICAL FIELD 
     The present invention relates to a method for manufacturing a sealed battery for sealing an electrolyte pour hole by using a sealing plug with a resin washer interposed therebetween, and more particularly to a method for manufacturing a sealed battery in which a peripheral surface of an electrolyte pour hole rarely becomes clouded after manufacturing the battery. 
     BACKGROUND ART 
     Sealed batteries such as alkaline secondary batteries represented by a nickel-hydrogen secondary battery, and nonaqueous electrolyte secondary batteries represented by a lithium ion secondary battery have been mainly used as a power source of portable electronic devices such as mobile phones, portable personal computers, and portable music players. In recent years, emission regulations for carbon dioxide and similar gases causing global warming have been made more stringent, resulting in the development of electric vehicles (EVs) and hybrid electric vehicles (HEVs) instead of automobiles using only fossil fuels such as gasoline, diesel oil, and natural gas. Sealed batteries such as nickel-hydrogen secondary batteries and lithium ion secondary batteries have also been used as the batteries for these EVs and HEVs. 
     A related-art sealed battery  10  commonly used includes an outer can  11  in which an electric power generating element such as an electrode assembly is accommodated, a sealing plate  12  sealing the upper mouth portion of the outer can  11 , and two electrode terminals  13   a  and  13   d  projecting from both sides of the sealing plate  12 , as shown in  FIG. 4  The sealing plate  12  is further provided with a gas discharge valve  14  for releasing internal pressure when pressure in the outer can  11  becomes high, and an electrolyte pour hole  15  for pouring an electrolyte into the outer can  11 . In  FIG. 4 , the electrolyte pour hole  15  is not directly shown, and only a flange portion of a sealing plug  16  for sealing the electrolyte pour hole  15  is shown. In this manner, the electrolyte pour hole  15  has its opening sealed by the sealing plug  16  so that the electrolyte poured in does not leak out from the outer can  11  (for example, refer to JP-U-59-44027 and JP-A-2003-229118). 
       FIGS. 5A and 5B  show a sealing structure of the electrolyte pour hole by using the sealing plug of the sealed battery  10 .  FIG. 5A  is a cross-sectional view taken along line VA-VA in  FIG. 4 . An annular convex portion  17  projecting in an axial direction of the can is formed on the peripheral surface of the electrolyte pour hole  15  so as to surround the electrolyte pour hole  15 . The sealing plug  16  is made of, for example, aluminum, and includes an axis portion  16   a  inserted through the electrolyte pour hole  15 , a flange portion  16   b  covering the peripheral surface of the electrolyte pour hole  15 , and a crimping portion  16   c , and is crimped and fixed to the sealing plate  12  by interposing an annular resin washer  18  between the flange portion  16   b  and the sealing plate  12 . The annular resin washer  18  is interposed between the electrolyte pour hole  15  and the sealing plug  16 . The electrolyte pour hole  15  has a high sealing property since the inner circumference portion of the resin washer  18  is partially strongly compressed by the annular convex portion  17  and the flange portion  16   b  of the sealing plug  16 . 
     As described above, the sealing property of the electrolyte pour hole  15  is increased by forming the annular convex portion  17  on the peripheral surface of the electrolyte pour hole  15  because the inner circumference portion of the resin washer  18  is partially strongly compressed by the annular convex portion  17  and the flange portion  16   b  of the sealing plug  16 . However, the outer circumference portion of the resin washer that is not partially compressed by the annular convex portion  17  may bend downward, whereby only the side end portion of the resin washer may abut to the sealing plate  12 , as shown in  FIG. 5B . In such a case, a sealed space S is formed between the outer circumference portion of the resin washer and the surface of the sealing plate  12 . 
     Usually, in the electrolyte pouring step, the electrolyte adheres and remains on the peripheral surface of the electrolyte pour hole  15 . Therefore, cleansing is performed after sealing the electrolyte pour hole  15  in order to remove the adhered electrolyte. However, if the electrolyte remains in the sealed space S, the electrolyte may not be removed even by cleansing because of being blocked by the resin washer  18 . The electrolyte remaining in the sealed space S after the cleansing gradually leaches to the outside of the resin washer  18  after the battery testing step following cleansing step or after shipping. Therefore, there was a problem that the periphery of the resin washer  18  becomes clouded due to a reaction of a solute component of the electrolyte and water content in the air. In the case where the periphery of the resin washer  18  is clouded, there is a problem of not being able to determine whether the cloud is due to a non-progressive electrolyte remaining in the sealed space S, or due to electrolyte leakage caused by poor sealing of the electrolyte pour hole  15 . 
     In addition, the manufacturing step of the sealed battery includes an airtightness testing step after sealing and welding of the outer can  11  and the sealing plate  12 . In this airtightness testing step, a testing nozzle is inserted through the electrolyte pour hole  15 , and the testing gas is pressurized and injected. Due to the interference of the electrolyte pour hole  15  and the testing nozzle at the time of inserting the testing nozzle, the electrolyte pour hole  15  may be damaged. As a result, a problem emerges in that the sealing property of the sealing portion of the electrolyte pour hole is impaired. The same holds for the interference between the electrolyte pour hole  15  and the pouring nozzle in the electrolyte pour step, and the interference between the electrolyte pour hole  15  and the sealing plug  16  in the sealing step. 
     SUMMARY 
     The inventors have reexamined the related-art manufacturing step of the sealed battery, and have found out that the problems will be solved if the resin washer is arranged around the opening of the electrolyte pour hole at the time of inserting the airtightness testing nozzle, at the electrolyte pouring step, and at the time of inserting the sealing plug in the sealing step, and therefore, achieved to complete the present invention. Specifically, an advantage of some aspects of the invention is to provide a method for manufacturing a sealed battery that can prevent the electrolyte from remaining around the electrolyte pour hole, and can also prevent impairment of the sealing property of the sealing portion of the electrolyte pour hole by preventing the deformation of the electrolyte pour hole when manufacturing the sealed battery by having the resin washer arranged around the opening of the electrolyte pour hole at the time of inserting the airtightness testing nozzle, at the time of inserting the electrolyte pouring nozzle, and at the time of inserting the sealing plug. 
     A method for manufacturing a sealed battery according to an aspect of the invention includes: welding and fixing, by using an outer can having a mouth portion and a sealing plate having an electrolyte pour hole, the sealing plate to the mouth portion of the outer can; adhering and fixing a resin washer around an opening hole of the electrolyte pour hole before or after the welding and fixing of the sealing plate to the mouth portion of the outer can; pouring electrolyte in the outer can through the electrolyte pour hole after the welding and fixing and the adhering and fixing; and sealing the electrolyte pour hole with a sealing member. 
     In the method for manufacturing a sealed battery according the aspect of the invention, the resin washer is adhered and fixed around the opening hole of the electrolyte pour hole of the sealing plate when the electrolyte is poured into the outer can through the electrolyte pour hole. Generally, in the electrolyte pouring step, cleansing is performed to remove the adhered electrolyte since the electrolyte adheres and remains in the peripheral surface of the electrolyte pour hole. In the method for manufacturing a sealed battery according to the aspect of the invention, the electrolyte rarely enters between the resin washer and the sealing plate even if the electrolyte is adhering to the surface of the resin washer after the electrolyte is poured in since there is no gap between the resin washer and the sealing plate. Thus, with the method for manufacturing a sealed battery according to the aspect of the invention, the adhered electrolyte can be easily and thoroughly cleansed even if the electrolyte is adhering to the surface of the resin washer. 
     Also, contact between a nozzle for pouring the electrolyte and the electrolyte pour hole, contact between a testing nozzle for supplying a pressurized gas and the electrolyte pour hole in the airtightness testing step, and contact between a sealing member and the electrolyte pour hole when inserting the sealing member into the electrolyte pour hole can be prevented, and therefore the electrolyte pour hole can be prevented from being damaged, and the sealing property of the electrolyte pour hole can be preferably maintained. In addition, in the method for manufacturing a sealed battery of the aspect of the invention, judgment can be clearly made that the electrolyte leakage is due to poor sealing if the periphery of the resin washer is clouded in the battery testing step after cleansing or after shipping. 
     Polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxy ethylene copolymer (PFA), polypropylene (PP), polyphenylene sulfide (PPS), tetrafluoroethylene-ethylene copolymer (ETFE), and ethylene-propylene rubber (EPDM) and the like can be cited as the resin washer that can be used in the method for manufacturing a sealed battery according to the aspect of the invention regarding the resistance and the repelling property with respect to a nonaqueous electrolyte. 
     In the method for manufacturing a sealed battery according to the aspect of the invention, the sealing plate is preferably used having a structure in which an annular convex portion is formed in the periphery of the opening of the electrolyte pour hole, and the resin washer also covers the surface of the annular convex portion. 
     Mechanical strength is applied to the periphery of the electrolyte pour hole by forming the annular convex portion in the periphery of the opening of the electrolyte pour hole. Therefore, the peripheral portion of the electrolyte pour hole can be prevented from being deformed even if a stress is applied to the peripheral portion of the electrolyte pour hole during sealing. Thus, in the sealed battery of the invention, a high sealing property can be maintained by applying high stress to the sealing member of the electrolyte pour hole. 
     In the method for manufacturing a sealed battery according to the aspect of the invention, a sealing plate having a structure in which the resin washer is integrally formed by the outsert molding method may be used as the sealing plate. 
     The sealing plate and the resin washer can be integrally formed by the outsert molding method. Therefore, in the method for manufacturing a sealed battery of the aspect of the invention, the electrolyte more rarely enters the gap between the resin washer and the sealing plate, and therefore, the above effects can further preferably be achieved. 
     In the method for manufacturing a sealed battery of the invention, a sealing plate having a structure in which the resin washer is thermally deposited or adhered by an adhesive may be used as the sealing plate. 
     Gaps can also be prevented from being generated between the sealing plate and the resin washer by thermally depositing or adhering by an adhesive the resin washer to the sealing plate. Thus, the above effects can further preferably be achieved by the invention. 
     In the method for manufacturing a sealed battery according to the aspect of the invention, a blind rivet is preferably used as the sealing member. 
     The blind rivet is made of metal, and can tightly seal the electrolyte pour hole. Also, once after the electrolyte pour hole is sealed, the sealed state can preferably be maintained. Thus, in the method for manufacturing a sealed battery according to the aspect of the invention, a sealed battery having a reliable sealing portion can be obtained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 1F  are diagrams showing a sealing step of an electrolyte pour hole of a sealed battery of an embodiment of the present invention. 
         FIG. 2A  is a cross-sectional view of a blind rivet for forming a sealing plug, and  FIG. 2B  is an enlarged view of a part IIB of  FIG. 1 . 
         FIGS. 3A to 3E  are diagrams showing a sealing step of an electrolyte pour hole of a related-art sealed battery. 
         FIG. 4  is a perspective view of a related-art sealed battery. 
         FIG. 5A  is a cross-sectional view taken along a line VA-VA of  FIG. 4 , and  FIG. 5B  is an enlarged view of a part VB of  FIG. 5A . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Embodiment 
     Hereinafter, an embodiment of the invention will be described in detail with reference to the accompanied drawings. The sealed battery of the embodiment has the same appearance as the related-art sealed battery shown in  FIG. 4 . Therefore, the same reference numerals are denoted for the same components as those of the related-art sealed battery, and the explanation will be given with reference to  FIG. 4  as necessary. The sealed battery  10  of the embodiment includes the outer can  11 , and the sealing plate  12  sealing the upper mouth portion of the outer can  11 , as shown in  FIG. 4 . The sealing plate  12  includes the two electrode terminals  13   a  and  13   b , the gas discharge valve  14 , and the electrolyte pour hole  15 . 
     As shown in  FIG. 1F  and  FIG. 2B , the sealing plug (corresponds to a “sealing member” of the invention)  16  formed of a blind rivet and the resin washer  18  are attached to the electrolyte pour hole  15 . Also, the annular convex portion  17  projecting in an axial direction of the can is formed on the peripheral surface of the electrolyte pour hole  15  of the sealing plate  12  so as to surround the electrolyte pour hole  15 . Although the annular convex portion  17  is not always necessary, the peripheral strength of the electrolyte pour hole  15  increases, and also the sealing property of the electrolyte pour hole  15  is increased by providing this annular convex portion. 
     The sealing plug  16  includes the axis portion  16   a  inserted through the electrolyte pour hole  15 , the flange portion  16   b  covering the peripheral surface of the electrolyte pour hole  15 , and the crimping portion  16   c , and is crimped and fixed to the sealing plate  12  by the flange portion  16   b  and the crimping portion  16   c . The annular resin washer  18  is interposed between the peripheral surface of the electrolyte pour hole  15  and the flange portion  16   b  of the sealing plug  16 . The resin washer  18  is partially strongly compressed by the annular convex portion  17  formed so as to surround the electrolyte pour hole  15 , and thereby maintaining the high sealing property of the electrolyte pour hole  15 . 
     Next, a sealing step of the electrolyte pour hole  15  of the sealed battery of the embodiment will be explained with reference to  FIG. 1 . At first as shown in  FIG. 1A , the sealing plate  12  is prepared in which the resin washer  18  is formed so as to cover the periphery of the opening of the electrolyte pour hole  15  and the surface of the annular convex portion  17 . The resin washer  18  needs to be formed so as not to generate gaps between the resin washer  18  and the surface of the sealing plate  12 . Therefore, the resin washer  18  is preferably formed integrally with the sealing plate  12  by the outsert molding method. PFA, PP, PPS, PTFE, ETFE, EPDM, and the like may be used as a latching member of the resin washer  18  regarding the resistance and the repelling property with respect to a nonaqueous electrolyte. Among these, the resin washer  18  made of PFA, PP, PPS, ETFE, and the like that is thermoplastic resin can easily be formed integrally with the sealing plate  12  by thermal deposition. Also, by adhering by a rubber-based adhesive, the resin washer  18  and the sealing plate  12  can be formed integrally. 
     Next, the two electrode terminals  13   a  and  13   b , and the gas discharge valve  14  can be formed in the sealing plate  12 , as shown in  FIG. 4 . Further, although not shown in the drawings, an electrode assembly including a positive electrode, a negative electrode, and a separator is prepared. A positive collector and a negative collector are respectively connected to the electrode terminals  13   a  and  13   b . Next, the electrode assembly is inserted into the outer can  11 , the sealing plate  12  is fitted in the mouth portion of the outer can  11 , and the joint section of the outer can  11  and the sealing plate  12  is welded by laser welding, for example.  FIG. 1A  illustrates the above state. Note that, in  FIG. 1A , the structure of the electrode assembly is omitted (hereinafter, the same is said for  FIG. 1B  to  FIG. 1F ). 
     Next, an electrolyte pouring device  20  is prepared. The electrolyte pouring device  20  has on its upper portion an electrolyte tank  22  filled with an electrolyte  21 , and on its lower portion is a tapered nozzle  23  for pouring the electrolyte  21  into the sealed battery  10 . The inside of the electrolyte tank  22  can be pressurized in order to enhance the pouring speed of the electrolyte  21 . 
     First, as shown in  FIG. 1B , the nozzle  23  of the electrolyte pouring device  20  is inserted in the electrolyte pour hole  15  formed on the sealing plate  12 . The inside of the electrolyte tank  22  is pressurized as necessary, and a predetermined amount of electrolyte  21  is poured. After pouring a predetermined amount of electrolyte  21   a , the electrolyte pouring device  20  is lifted up so as to withdraw the nozzle  23  of the electrolyte pouring device  20  from the electrolyte pour hole  15  of the sealing plate  12 . At this time, as shown in  FIG. 1C , although the predetermined amount of electrolyte  21   a  is poured in the outer can  11 , an electrolyte  21   b  is adhering to the surface of the resin washer  18  by atomizing or dripping the electrolyte during electrolyte pouring. The electrolyte  21   b  adhering to the surface of the resin washer  18  is removed by cleansing or wiping.  FIG. 1D  shows the state after the removing. 
     Next, as shown in  FIG. 1E , a blind rivet  16 ′ for forming the sealing plug  16  is inserted in the electrolyte pour hole  15 . As shown in  FIG. 2 , this blind rivet  16 ′ includes the cylindrical axis portion  16   a  to be inserted in the electrolyte pour hole  15  and the flange portion  16   b  formed on the upper end portion of the axis portion  16   a  with each formed of aluminum metal, for example. The tip end portion of the axis portion  16   a  is shaped like a bag. A stainless-steel core axis portion  16   f  with a large-diameter portion  16   d  formed on its tip end and a small-diameter portion  16   e  formed over the large-diameter portion  16   d  is provided inside of the axis portion  16   a . The axis portion  16   a  of the sealing plug  16  is inserted in the electrolyte pour hole  15  from the annular resin washer  18  side so that the flange portion  16   b  and the annular resin washer  18  are contacting each other. 
     Next, the core axis portion  16   f  is lifted up while pressing the flange portion  16   b  of the blind rivet  16 ′ towards the sealing plate  12  side, and the large-diameter portion  16   d  at the tip end of the core axis portion  16   f  moves upward. Then, the diameter of the bag-like portion at the tip end of the axis portion  16   a  of the blind rivet  16 ′ increases, and the crimping portion  16   c  is formed. Thus, the blind rivet  16 ′ is fixed in the electrolyte pour hole  15 , and the core axis portion  16   f  of the blind rivet  16 ′ is cut off at the small-diameter portion  16   e  formed over the large-diameter portion  16   d . As a result, as shown in  FIG. 1F , the electrolyte pour hole  15  can be tightly sealed by the sealing plug  16 . 
     Comparative Example 
     Next, with reference to  FIG. 3  to  FIG. 5 , a sealing step of an electrolyte pour hole in the related-art sealed battery will be explained as a comparative example in order to confirm the effect of the method for manufacturing a sealed battery of the above embodiment. Also, in  FIG. 3 , the same reference numerals are denoted for the same components as those in the sealing step of the electrolyte pour hole in the above embodiment, and the detailed descriptions thereof will be omitted. 
     First, a battery having a structure in which the annular convex portion  17  projecting in an axial direction of the can is formed on the peripheral surface of the electrolyte pour hole  15  of the sealing plate  15  so as to surround the electrolyte pour hole  15 . Next, as shown in  FIG. 4 , the two electrode terminals  13   a  and  13   b , and the gas discharge valve  14  are formed in the sealing plate  12 . Further, although omitted in the drawings, an electrode assembly including a positive electrode, a negative electrode, and a separator is prepared, and a positive collector and a negative collector are respectively connected to the electrode terminals  13   a  and  13   b . Next, the electrode assembly is inserted in the outer can  11 , the sealing plate  12  is fitted in the mouth portion of the outer can  11 , and the joint section of the outer can  11  and the sealing plate  12  are welded by laser welding, for example. Thereafter, the nozzle  23  of the electrolyte pouring device  20  is inserted in the electrolyte pour hole  15  formed in the sealing plate  12 , the inside of the electrolyte tank  22  is pressurized as necessary, and a predetermined amount of the electrolyte  21  is poured.  FIG. 3A  illustrates the above state. However, in  FIG. 3A , the structure of the electrode assembly is omitted (hereinafter, the same is said for  FIG. 3B  to  FIG. 3E ). 
     After pouring a predetermined amount of electrolyte  21   a , the electrolyte pouring device  20  is lifted up and the nozzle  23  of the electrolyte pouring device  20  is withdrawn from the electrolyte pour hole  15  of the sealing plate  12 . At this time, as shown in  FIG. 3B , although the predetermined amount of electrolyte  21   a  is poured in the outer can  11 , an electrolyte  21   b  adheres to the peripheral surface of the electrolyte pour hole  15  of the sealing plate  12  by atomizing or dripping the electrolyte during electrolyte pouring. The electrolyte  21   b  adhering to the peripheral surface of the electrolyte pour hole  15  of the sealing plate  12  is removed by cleansing or wiping.  FIG. 3C  shows the state after removal. 
     Next, as shown in  FIG. 3D , the resin washer  18  is inserted into the tip end of the blind rivet  16 ′, and the tip end of the blind rivet  16 ′ is inserted in the electrolyte pour hole  15 . Thereafter, the core axis portion  16   f  is lifted up while pressing the flange portion  16   b  of the blind rivet  16 ′ towards the sealing plate  12  side, and whereby the electrolyte pour hole  15  can be sealed in a liquid tight manner by the sealing plug  16  as shown in  FIG. 3E . 
     Leaching Text 
     A leaching test was performed as described below by using the sealed battery of the embodiment manufactured by performing the sealing step of the electrolyte pour hole of the embodiment as described above, and the sealed battery of the comparative example manufactured by performing the sealing step of the related-art electrolyte pour hole. Note that a lithium ion secondary battery was used as the sealed battery. 
     First, the overall battery was cleansed and visually checked. Thereafter, a battery with no faults was charged until the charge depth reached SOC=60% (where the charging voltage 4.1V is SOC=100%) by a predetermined charging method. This battery was placed in a constant-temperature bath maintained at a relative humidity RH=90% and 60° C. for 24 hours. Thereafter, the periphery of the sealing plug  16  was checked for the presence of leaching by observing with a 50-power microscope. In this case, the case where a white-colored smudge was confirmed at the periphery of the sealing plug  16  was judged as a presence of leaching. The batteries used in the comparative examples 1 and 2, and the embodiment were manufactured as follows. 
     Comparative Example 1 
     A battery with no resin washer formed was manufactured by performing the following steps (1) to (7) and used as the battery of the comparative example 1. 
     (1) a step of pouring electrolyte
 
(2) a step of pressing and wiping with a nonwoven fabric
 
(3) a step of aging the battery after leaving it for a predetermined period of time
 
(4) a step of degassing the outer can by reducing the pressure inside the outer can
 
(5) a step of pressing and wiping with a nonwoven fabric
 
(6) a step of sealing the battery by using a blind rivet
 
(7) a step of cleansing the battery by using purified water
 
     Comparative Example 2 
     A battery with no resin washer formed was manufactured by performing the following steps (1) to (8) and used as the battery of comparative example 2. 
     (1) a step of pouring electrolyte
 
(2) a step of pressing and wiping with a nonwoven fabric
 
(3) a step of aging the battery after leaving it for a predetermined period of time
 
(4) a step of degassing the outer can by reducing the pressure inside the outer can
 
(5) a step of dropping dimethyl carbonate (DMC) in the periphery of the pour hole
 
(6) a step of pressing and wiping with a nonwoven fabric
 
(7) a step of sealing the battery by using a blind rivet
 
(8) a step of cleansing the battery by using purified water
 
     Embodiment 
     A battery with a resin washer formed was manufactured by performing the same steps as those in the comparative example 1 and used as the battery for the embodiment. 
     The results of the leaching tests of the batteries of the comparative examples 1 and 2, and the embodiment are summarized below in Table 1. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 DMC  
                   
                   
               
               
                   
                 Cleansing 
                 Leaching test result 
                 (%) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Comparative 
                 No 
                 225 cells among 353 cells 
                 63.7% 
               
               
                 Example 1 
                   
                   
                   
               
               
                 Comparative 
                 Yes 
                  21 cells among 207 cells  
                 10.1% 
               
               
                 Example 2 
                   
                   
                   
               
               
                 Embodiment 
                 No 
                  2 cells among 247 cells 
                  0.8% 
               
               
                   
               
               
                 DMC: dimethyl carbonate 
               
            
           
         
       
     
     The leaching rate difference between the comparative examples 1 and 2, and the embodiment can be understood as follows. Specifically, in the methods for manufacturing the sealed batteries of the comparative examples 1 and 2, the electrolyte  21   b  adhering to the peripheral surface of the electrolyte pour hole  15  of the sealing plate  12  when the electrolyte is poured in from the electrolyte pour hole  15  is removed only by wiping in the comparative example 1, and by cleansing and wiping in the comparative example 2, as shown in  FIG. 3C . However, thoroughly removing the electrolyte adhering to the surface of the sealing plate  12  even by cleansing is difficult in a micro view since the sealing plate made of metal and the electrolyte have good wettability, for example. 
     Also, in the methods for manufacturing the sealed batteries of the comparative examples 1 and 2, the resin washer  18  is inserted in the tip end of the blind rivet  16 ′, and the tip end of the blind rivet  16 ′ is inserted in the electrolyte pour hole  15  after removing the electrolyte  21   b  adhering to the peripheral surface of the electrolyte pour hole  15  of the sealing plate  12 , as shown in  FIG. 3D , whereby the resin washer  18  is fixed so as to cover the electrolyte pour hole  15  and the annular convex portion  17 . Thus, with the methods for manufacturing the sealed batteries of the comparative examples 1 and 2, a sealed space S may be formed between the resin washer  18  and the sealing plate  12 , and therefore, the electrolyte adhering to the surface of the sealing plate  12  may remain in the sealed space S, as shown in  FIG. 5B . This is considered the reason of confirmation of the white-colored smudge in the periphery of the sealing plug  16  as described above due to the electrolyte remained in the sealed space S. 
     On the other hand, with the method for manufacturing the sealed battery of the embodiment, the electrolyte rarely enters the sealed space S even if the sealed space S as shown in  FIG. 5B  is formed between the resin washer  18  and the sealing plate  12 , since the resin washer  18  is formed in advance in the periphery of the electrolyte pour hole  15  of the sealing plate  12  which is clean before pouring the electrolyte. Also, it is considered that the above described white-colored smudge is rarely generated around the sealing plug  16  since the electrolyte adhering to the surface of the resin washer  18  can be easily removed. 
     In addition, with the method for manufacturing a sealed battery according to the embodiment, contact between the nozzle  23  of the electrolyte pouring device  20  and the electrolyte pour hole  15 , contact between the testing nozzle for supplying a pressurized gas in the airtightness testing step and the electrolyte pour hole  15 , and contact between the blind rivet  16 ′ and the electrolyte pour hole  15  in the step shown in  FIG. 1E  can be prevented, and therefore, the electrolyte pour hole  15  can be prevented from being damaged, and the sealing property of the electrolyte pour hole  15  can be preferably maintained. In addition, with the method for manufacturing the sealed battery of the invention, judgment can be clearly made that the electrolyte leakage is due to poor sealing in a case where the periphery of the resin washer is clouded in a battery testing step after cleansing or after shipping. 
     Moreover, as the embodiment, the example shown is the one in which the resin washer is adhered and fixed around the opening hole of the electrolyte pour hole before welding and fixing the sealing plate to the outer can. However, the resin washer may be formed before pouring the electrolyte. Therefore, the resin washer can be adhered and fixed around the opening hole of the electrolyte pour hole after welding and fixing the sealing plate to the outer can. Also, although the blind rivet is used as the sealing plug in the above embodiment, a resin or ceramic sealing plug can also be used in addition to the blind rivet. In this case, the resin or ceramic sealing plug is preferably fixed in the electrolyte pour hole by an adhesive.