Patent Publication Number: US-2022238924-A1

Title: Method for Manufacturing Secondary Battery and Secondary Battery

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2020/010210, filed Aug. 3, 2020, published in Korean, which claims the benefit of the priority of Korean Patent Application No. 10-2019-0113711, filed on Sep. 16, 2019, both of which are hereby incorporated by reference in their entireties. 
     TECHNICAL FIELD 
     The present invention relates to a method for manufacturing a secondary battery and a secondary battery. 
     BACKGROUND ART 
     Secondary batteries are rechargeable unlike primarily batteries, and also, the possibility of compact size and high capacity is high. Thus, recently, many studies on secondary batteries are being carried out. As technology development and demands for mobile devices increase, the demands for secondary batteries as energy sources are rapidly increasing. 
     Rechargeable batteries are classified into coin type batteries, cylindrical type batteries, prismatic type batteries, and pouch type batteries according to a shape of a battery case. In such a secondary battery, an electrode assembly mounted in a battery case is a chargeable and dischargeable power generating device having a structure in which an electrode and a separator are stacked. 
     The electrode assembly may be approximately classified into a jelly-roll type electrode assembly in which a separator is interposed between a positive electrode and a negative electrode, each of which is provided as the form of a sheet coated with an active material, and then, the positive electrode, the separator, and the negative electrode are wound, a stacked type electrode assembly in which a plurality of positive and negative electrodes with a separator therebetween are sequentially stacked, and a stack/folding type electrode assembly in which stacked type unit cells are wound together with a separation film having a long length. 
     Lithium ion secondary batteries are manufactured through processes such as primary charging, aging, and de- gassing after accommodating an electrode assembly and an electrolyte in a pouch. Here, when a large amount of residual gas exists in the pouch after the primary charging, there has been a problem that difficulties in a transfer process for subsequent processes are caused due to an increase in volume of a cell. Particularly, the gas remaining in an electrode causes precipitation of lithium ions. 
     DISCLOSURE OF THE INVENTION 
     TECHNICAL PROBLEM 
     One aspect of the present invention is to provide a method for manufacturing a secondary battery, in which an internal gas generated during charging and activating when the secondary battery is manufactured is capable of being automatically discharged, and a secondary battery. 
     TECHNICAL SOLUTION 
     A method for manufacturing a secondary battery according to an embodiment of the present invention comprises: an accommodation step of accommodating an electrode assembly in a battery case comprising an accommodation part, in which the electrode assembly is accommodated, and a gas pocket part connected to the accommodation part to collect a gas generated in the accommodation part; a first sealing step of performing sealing along an outer circumferential surface of the battery case except for an end of the gas pocket part; an electrolyte injection step of injecting an electrolyte into the accommodation part through the end of the gas pocket part; a second sealing step of performing double sealing on the end of the gas pocket part so that a first sealing part is formed at a side closer to the accommodation part, and a second sealing part is formed at a side that is farther from the accommodation part; a second sealing part removing step of removing a portion, on which the second sealing part is formed, from the battery case; and a charging step of applying electricity to the electrode assembly to charge the secondary battery, wherein, in the second sealing step, the first sealing part is discontinuously formed so that a non- fused part for degassing and a fused part are formed along a sealing line, and when an internal pressure increases due to a gas generated through the charging step, the non-fused part for degassing is gaped to discharge the gas to an outside through the non-fused part for degassing. 
     The secondary battery according to an embodiment of the present invention may be manufactured through the method for manufacturing the secondary battery according to an embodiment of the present invention. 
     ADVANTAGEOUS EFFECTS 
     According to the present invention, the first sealing part may be formed on the gas pocket part of the battery case to form the non-fused part for degassing and the fused part. As a result, when the secondary battery is charged, the internal pressure may increase due to the generated gas, and thus, the non-fused part for degassing may be gaped to automatically discharge the internal gas to the outside through the non-fused part for degassing. Therefore, the secondary battery may be prevented from increasing in volume, and the gas may not remain in the electrode to prevent the lithium ions from being precipitated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flowchart illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. 
         FIG. 2  is a plan view illustrating a state before the electrode assembly is accommodated in an accommodation step in a method for manufacturing a secondary battery according to a first embodiment of the present invention. 
         FIG. 3  is a plan view illustrating a state in which the electrode assembly is accommodated in the accommodation step in the method for manufacturing the secondary battery according to the first embodiment of the present invention. 
         FIG. 4  is a plan view illustrating a first sealing step in the method for manufacturing the secondary battery according to the first embodiment of the present invention. 
         FIG. 5  is a plan view illustrating a second sealing step in the method for manufacturing the secondary battery according to the first embodiment of the present invention. 
         FIG. 6  is a plan view illustrating a second sealing part removing step in the method for manufacturing the secondary battery according to the first embodiment of the present invention. 
         FIG. 7  is a plan view illustrating a third sealing step in the method for manufacturing the secondary battery according to the first embodiment of the present invention. 
         FIG. 8  is a plan view illustrating a second sealing step in a method for manufacturing a secondary battery according to a second embodiment of the present invention. 
         FIG. 9  is a plan view illustrating a second sealing step in a method for manufacturing a secondary battery according to a third embodiment of the present invention. 
         FIG. 10  is a plan view illustrating a second sealing step in a method for manufacturing a secondary battery according to a fourth embodiment of the present invention. 
         FIG. 11  is a plan view illustrating a second sealing step and a temporary sealing step in a method for manufacturing a secondary battery according to a fifth embodiment of the present invention. 
         FIG. 12  is a plan view illustrating a second sealing part removing step in the method for manufacturing the secondary battery according to the fifth embodiment of the present invention. 
         FIG. 13  is a cross-sectional view taken along line A- A′ of  FIG. 12 . 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     The objectives, specific advantages, and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. It should be noted that the reference numerals are added to the components of the drawings in the present specification with the same numerals as possible, even if they are illustrated in other drawings. Also, the present invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. In the following description of the present invention, the detailed descriptions of related arts which may unnecessarily obscure the gist of the present invention will be omitted. 
       FIG. 1  is a flowchart illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention,  FIG. 2  is a plan view illustrating a state before the electrode assembly is accommodated in an accommodation step in a method for manufacturing a secondary battery according to a first embodiment of the present invention, and  FIG. 3  is a plan view illustrating a state in which the electrode assembly is accommodated in the accommodation step in the method for manufacturing the secondary battery according to the first embodiment of the present invention. 
     In addition,  FIG. 4  is a plan view illustrating a first sealing step in the method for manufacturing the secondary battery according to the first embodiment of the present invention,  FIG. 5  is a plan view illustrating a second sealing step in the method for manufacturing the secondary battery according to the first embodiment of the present invention, and  FIG. 6  is a plan view illustrating a second sealing part removing step in the method for manufacturing the secondary battery according to the first embodiment of the present invention. 
     Referring to  FIGS. 1 to 6 , a method for manufacturing a secondary battery according to a first embodiment of the present invention comprises an accommodation step (S 10 ) of accommodating an electrode assembly  120  in a battery case  110 , a first sealing step (S 20 ) of performing sealing along outer circumferential surfaces a, b, and c of the battery case  110 , an electrolyte injection step (S 30 ) of injecting an electrolyte, a second sealing step (S 40 ) of forming a first sealing part  116  and a second sealing part  117 , a second sealing part removing step (S 50 ) of removing a portion on which the second sealing part  117  is formed, and a charging step (S 60 ) of applying electricity to the electrode assembly  120 . 
     In addition, the method for manufacturing the secondary battery according to the first embodiment of the present invention may further comprise an aging step in which a predetermined time elapses so that the electrode assembly  129  is impregnated in the electrolyte and a third sealing step of sealing a portion from which a gas pocket part  114  is removed. 
     In more detail, referring to  FIGS. 1 to 3 , in the accommodation step (S 10 ), the electrode assembly  120  may be accommodated in the battery case  110  that comprises an accommodation part  113  in which the electrode assembly  120  is accommodated and a gas pocket part  114  connected to the accommodation part  113  to collect a gas generated in the accommodation part  113 . 
     Here, in the accommodation step (S 10 ), after the electrode assembly  120  is accommodated in the accommodation part  113  formed in the battery case  110  having a sheet shape, the battery case  110  may be folded along a virtual line X to cover the accommodation part  113 . 
     Here, the battery case  110  may comprise an upper case  111  and a lower case  112 . 
     Also, the battery case  110  may be made of a flexible material. 
     The electrode assembly  120  may be a chargeable and dischargeable power generation element and have a shape in which an electrode and a separator are alternately stacked to be combined each other. 
     The electrode may comprise a positive electrode and a negative electrode. The positive electrode, the separator, and the negative electrode may be alternately disposed. 
     Also, the electrode assembly  120  may further comprise an electrode lead  121  connected to an end of the electrode. Here, the electrode assembly  120  may be electrically connected to an external device through the electrode lead  121 . 
     Referring to  FIGS. 1 and 4 , in the first sealing step (S 20 ), sealing may be performed along the outer circumferential surfaces a, b, and c of the battery case  110 , except for an end of the gas pocket part  114 . That is, in the first sealing step (S 20 ), the remaining outer circumferential surfaces a, b, and c in three directions, except for the outer circumferential surface d disposed on the end of the gas pocket part  114 , among the entire outer circumferential surfaces a, b, c, and d of the battery case  110  in four directions may be sealed to form an initial sealing part  115 . 
     In the electrolyte injection step (S 30 ), the electrolyte may be injected into the accommodation part  113  through the end of the gas pocket part  114 . Here, in the electrolyte injection step (S 30 ), for example, a liquid injection tube may be inserted into the end of the gas pocket part  114  to inject the electrolyte from the gas pocket part  114  toward the accommodation part  113 . 
     Referring to  FIGS. 1 and 5 , in the second sealing step (S 40 ), the end of the gas pocket part  114  may be double- sealed. Here, the first sealing part  116  may be formed at a side closer to the accommodation part  113 , and the second sealing part  117  may be formed at a side that is farther from the accommodation part  113 . 
     Also, in the second sealing step (S 40 ), the first sealing part  116  may be discontinuously formed so that a non- fused part S 12  for degassing and a fused part S 11  are formed along a sealing line L. As a result, when an internal pressure increases due to the gas generated through the subsequent charging step (S 60 ), the non-fused part S 12  for degassing may be gaped to discharge the internal gas to the outside through the non-fused part S 12  for degassing. 
     Also, in the second sealing step (S 40 ), the upper case  111  and the lower case  112  may be thermally fused to each other to form the first sealing part  116  and the second sealing part  117 . Here, the first sealing part  116  may be sealed so that portions of the upper case  111  and the lower case  112 , which are disposed on the non-fused part S 12  for degassing, are in contact with each other. 
     Furthermore, the second sealing step (S 40 ) may be, for example, performed so that a plurality of non-fused parts S 12  for degassing are formed. 
     Also, in the second sealing step (S 40 ), the second sealing part  117  may be formed by continuously sealing an edge of the gas pocket part  114  in the battery case  110 . 
     That is, in the second sealing step (S 40 ), the end of the gas pocket part  114  may be double-sealed. Here, the first sealing part  116  may be partially sealed along the end of the gas pocket part  114 , and the second sealing part  117  may be completely sealed. Here, the first sealing part  116  may form a discontinuous sealing line to form an unsealed non-fused part, but the second sealing part  117  may form a continuous sealing line to form a continuous sealing line that is completely fused without the non-fused part. 
     Referring to  FIGS. 1, 5 and 6 , in the second sealing part removing step (S 50 ), the portion of the battery case  110 , on which the second sealing part  117  is formed, may be removed. 
     Here, in the second sealing part removing step (S 50 ), a portion of the battery case  110  may be cut along the virtual line between the first sealing part  116  and the second sealing part  117  to remove the portion on which the second sealing part  117  is formed. 
     In the charging step (S 60 ), electricity may be applied to the electrode assembly  120  to charge the secondary battery  100 . Here, the secondary battery  100  may be activated through the charging step (S 60 ). 
     In the aging step, after performing the charging step S 60 , a predetermined time may elapse so that the electrode assembly  120  is impregnated in the electrolyte. Here, the electrolyte may be filled between the electrode and the separator through the aging step, and thus, the lithium ions may smoothly move. 
       FIG. 7  is a plan view illustrating the third sealing step in the method for manufacturing the secondary battery according to the first embodiment of the present invention. 
     Referring to  FIGS. 1 and 7 , in the third sealing step, after performing the charging step (S 60 ), the gas pocket part  114  may be cut and removed from the battery case  110 , and the portion of the battery case  110 , from which the gas pocket part  114  is removed, may be sealed to manufacture the secondary battery  100 . Here, for example, after the charging step (S 60 ), the aging step may be further performed, and then, the third sealing step may be performed. 
     Here, when a sealed sealing part  118  is formed on the portion of the battery case  110 , from which the gas pocket part  114  is removed, through the third sealing step, the inside of the battery case  110  may be sealed. 
     Referring to  FIGS. 1, 5, and 6 , in the method for manufacturing the secondary battery, which comprises the above-described constituents, according to the first embodiment of the present invention, in the second sealing step (S 40 ), the first sealing part  116  is formed so that the non-fused part S 12  for degassing and the fused part S 11  may be formed on the gas pocket part  114  of the battery case  110 , and when the secondary battery  100  is charged, if the internal pressure increases due to the generated gas, the non-fused part S 12  for degassing may be gaped to automatically discharge the internal gas to the outside through the non-fused part S 12  for degassing. Therefore, the secondary battery  100  may be prevented from increasing in volume, and the gas may not remain in the electrode to prevent the lithium ions from being precipitated. 
     Also, the battery case  110  may be double-sealed so that the first sealing part  116  that is partially sealed and the second sealing part  117  that is completely sealed are formed in the second sealing step (S 40 ). Then, the second sealing part  117  may be removed before the charging step (S 60 ) to prevent an external gas from being introduced into the battery case  110  in the manufacturing process during the charging step (S 60 ) after the electrolyte is injected into the battery case  110  through the electrolyte injection step (S 30 ). 
     Referring to  FIGS. 1 and 5 , in the method for manufacturing the secondary battery according to the first embodiment of the present invention, for example, in the sealing second step (S 40 ), for example, the sealing may be performed so that the non-fused part S 12  for degassing has a width that is gradually narrowed toward the end of the battery case  110 . 
       FIG. 8  is a plan view illustrating a second sealing step in a method for a manufacturing secondary battery according to a second embodiment of the present invention. 
     Referring to  FIGS. 1 and 8 , a method for manufacturing a secondary battery according to a second embodiment of the present invention is different from the method for manufacturing the secondary battery according to the foregoing first embodiment in that a first sealing part  216  is formed in a different shape in a second sealing step (S 40 ) to manufacture a secondary battery  200 . Thus, contents of this embodiment, which are duplicated with those according to the first embodiment, will be omitted, and also, differences therebetween will be mainly described. 
     In the method for manufacturing the secondary battery according to the second embodiment of the present invention, in the second sealing step (S 40 ), a first sealing part  216  and a second sealing part  217  are formed. Here, the first sealing part  216  may be discontinuously formed so that a non- fused part S 22  for degassing and a fused part S 21  are formed along a sealing line. Here, in the second sealing step (S 40 ), for example, the sealing may be performed so that the non- fused part S 22  for degassing has a width that is gradually narrowed toward an end of a battery case  210 . 
     Here, in the second sealing step (S 40 ), the first sealing part  216  may be formed so that one side of both sides of the non-fused part S 22  for degassing is formed in a linear shape, and the other side is formed in a diagonal shape. 
       FIG. 9  is a plan view illustrating a second sealing step in a method for manufacturing a secondary battery according to a third embodiment of the present invention. 
     Referring to  FIGS. 1 and 9 , a method for manufacturing a secondary battery according to the third embodiment of the present invention is different from the method for manufacturing the secondary battery according to the foregoing first and second embodiments in that a first sealing part  316  is formed in a different shape in a second sealing step (S 40 ) to manufacture a secondary battery  300 . Thus, contents of this embodiment, which are duplicated with those according to the foregoing embodiments, will be omitted, and also, differences therebetween will be mainly described. 
     In the method for manufacturing the secondary battery according to the third embodiment of the present invention, in the second sealing step (S 40 ), a first sealing part  316  and a second sealing part  317  are formed. Here, the first sealing part  316  may be formed so that a non-fused part S 32  for degassing and a fused part S 31  are formed. Here, in the second sealing step (S 40 ), for example, the first sealing part  316  may be formed so that the non-fused part S 32  for degassing is bent in plurality. As a result, when an internal pressure increases due to a gas generated through a subsequent charging step (S 60 ), the non-fused part S 12  for degassing may be gaped to form a path that is bent in plurality, thereby discharging the internal gas to the outside of the battery case  310  through the non-fused part S 32  for degassing. 
       FIG. 10  is a plan view illustrating a second sealing step in a method for manufacturing a secondary battery according to a fourth embodiment of the present invention. 
     Referring to  FIGS. 1 and 10 , a method for manufacturing a secondary battery according to the fourth embodiment of the present invention is different from the method for manufacturing the secondary battery according to the foregoing first to third embodiments in that a first sealing part  416  is formed in a different shape in a second sealing step (S 40 ) to manufacture a secondary battery  400 . Thus, contents of this embodiment, which are duplicated with those according to the foregoing embodiments, will be omitted, and also, differences therebetween will be mainly described. 
     In the method for manufacturing the secondary battery according to the fourth embodiment of the present invention, in the second sealing step (S 40 ), a first sealing part  416  and a second sealing part  417  are formed. Here, the first sealing part  416  may be formed so that a non-fused part S 42  for degassing and a fused part S 41  are formed. Here, in the second sealing step (S 40 ), for example, the sealing is performed so that the non-fused part S 42  for degassing is bent in plurality. 
     Here, in the second sealing step (S 40 ), the non-fused part (S 42 ) for degassing may be sealed to be bent in a zig- zag shape. 
     As a result, when an internal pressure increases due to a gas generated through a subsequent charging step (S 60 ), the non-fused part S 42  for degassing may be gaped to form a path that is bent in the zig-zag shape, thereby discharging the internal gas to the outside of the battery case  410  through the non-fused part S 42  for degassing. 
       FIG. 11  is a plan view illustrating a second sealing step and a temporary sealing step in a method for manufacturing a secondary battery according to a fifth embodiment of the present invention,  FIG. 12  is a plan view illustrating a second sealing part removing step in the method for the secondary battery according to the fifth embodiment of the present invention, and  FIG. 13  is a cross- sectional view taken along line A-A′ of  FIG. 12 . 
     Referring to  FIGS. 1 to 11 , a method for manufacturing the secondary battery according to a fifth embodiment of the present invention is different from the method for manufacturing the secondary battery according to the foregoing first to fourth embodiments of the present invention in that a temporary sealing step is further performed to manufacture a secondary battery  500 . Thus, contents of this embodiment, which are duplicated with those according to the foregoing embodiments, will be omitted, and also, differences therebetween will be mainly described. 
     Referring to  FIGS. 1 and 11 to 13 , in the method for manufacturing the secondary battery according to the fifth embodiment of the present invention, in the second sealing step (S 40 ), a first sealing part  516  and a second sealing part  517  are formed. Here, the first sealing part  516  may be formed so that a non-fused part S 52  for degassing and a fused part S 51  are formed. Here, in the second sealing step (S 40 ), for example, the sealing is performed so that the non-fused part S 52  for degassing is bent in a zig-zag shape. 
     In the temporary sealing step, an adhesive solution V is placed on an end of the non-fused part S 52  for degassing, and an upper case  111  and a lower case  112 , which are disposed on the non-fused part S 52  for degassing, adhere to each other. Thus, it may prevent foreign substances or moisture from being introduced into a battery case  510  through the non-fused part S 52  for degassing after the second sealing part is removed through a second sealing part removing step (S 50 ). Here, when the internal pressure reaches a predetermined pressure or more, adhesive force between the upper case  111  and the lower case  112 , which are disposed on the non-fused part S 52  for degassing, may be released to discharge a gas. 
     The temporary sealing step may be, for example, performed after forming the first sealing part  516  in the second sealing step (S 40 ). 
     Also, for another example, the temporary sealing step may be performed in a state in which the second sealing part  517  is removed after the second sealing part removing step S 50 . 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the method for manufacturing the secondary battery according to the present invention. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention. 
     Furthermore, the scope of protection of the present invention will be clarified by the appended claims. 
     [Description of the Symbols] 
       100 ,  200 ,  300 ,  400 ,  500 : Secondary battery 
       110 ,  210 ,  310 ,  410 ,  510 : Battery case 
       111 : Upper case 
       112 : Lower case 
       113 : Accommodation part 
       114 : Gas pocket part 
       115 : Initial sealing part 
       116 ,  216 ,  316 ,  416 ,  516 : First sealing part 
       117 ,  217 ,  317 ,  417 ,  517 : Second sealing part 
       118 : Sealed sealing part 
       120 : Electrode assembly 
       121 : Electrode lead 
     a, b, c, d: Outer circumferential surface 
     S 11 , S 21 , S 31 , S 41 , S 51 : Fused part 
     S 12 , S 22 , S 32 , S 42 , S 52 : Non-fused part 
     V: Adhesive solution