Patent Publication Number: US-2023133138-A1

Title: Cylindrical secondary battery and method for manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0148843 filed on Nov. 2, 2021 in the Korean Intellectual Property Office, the contents of which in its entirety are herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     Embodiments relate to a cylindrical secondary battery in which an internal gas is removable, and a method for manufacturing the same. 
     2. Description of the Related Art 
     A secondary battery includes a cell provided with an electrode assembly, which includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and an electrolyte impregnated in the electrode assembly. 
     The secondary battery may be provided in a variety of outer appearances such as cylindrical, prismatic, pouch type, and the like depending on the use. Among them, the cylindrical secondary battery has a structure in which an electrode assembly and an electrolyte are accommodated inside a cylindrical can, and one end of the can is sealed with a cap assembly. In general, a secondary battery may generate a gas inside the secondary battery due to repetitive charging and discharging and internal chemical factors. There is a limitation in that the cap assembly and the can are deformed due to the generation of the gas. 
     The above-described information disclosed in the technology that serves as the background of the present invention is only for improving understanding of the background of the present invention and thus may include information that does not constitute the related art. 
     SUMMARY 
     An aspect of the present disclosure provides a cylindrical secondary battery, in which an internal gas is removable, and a method for manufacturing the same. 
     According to at least one of embodiments, a cylindrical secondary battery includes: a cylindrical can; an electrode assembly in which a first electrode plate, a second electrode plate, and a separator are wound and which is accommodated in the can; and a cap assembly which is insulated from the can and electrically connected to the electrode assembly and through which a degassing hole passes to communicate with the inside of the can. 
     The cap assembly may include: a vent plate coupled to one side of the can and spaced apart from the degassing hole to provide a notch; a cap down plate which is disposed between the vent plate and the electrode assembly so as to be electrically connected to the electrode assembly and through which a plurality of slots pass; and a gasket disposed between the vent plate and the can to insulate the vent plate and the can from each other. 
     The vent plate may include: a first support that is in contact with the cap down plate; a vent part which is connected to the outside of the first support so as to be integrated with the first support and in which the notch is provided; and a second support connected to the outside the vent part so as to be integrated with the vent part and coupled to the can with the gasket therebetween. 
     The second support may include: a first region disposed toward the vent part and having a thickness greater than that of the vent part; and a second region having a thickness relatively less than that of the first region. 
     The degassing hole may be defined in the first region. 
     The cap down plate may have a diameter less than that of the vent plate, and a top surface of an edge of the cap down plate may be in close contact with and welded to a portion of a bottom surface of an edge of the vent plate. 
     The cap assembly may further include a resin pin or rubber pin, which is press-fitted into the degassing hole to close the degassing hole after being assembled with the can. 
     The cap assembly may further include a sealing member that closes the degassing hole after removing the resin pin or rubber pin when a gas is generated inside the can. 
     The sealing member may include a press-fitting ball or resin or is coupled to the degassing hole in a male and female structure. 
     According to another embodiment, a method for manufacturing a cylindrical secondary battery includes: accommodating an electrode assembly in a can so as to be electrically connected to the can; electrically connecting a cap assembly to the electrode assembly; assembling the cap assembly with the can; inserting a resin pin or rubber pin into a hole passing through the cap assembly to close the hole; and coupling a sealing member to the hole passing through the cap assembly to close the hole after discharging a gas by removing the resin pin or rubber pin when the gas is generated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a cross-sectional view illustrating a cylindrical secondary battery according an embodiment; 
         FIG.  2    is a plan view illustrating a cap assembly of  FIG.  1   ; 
         FIG.  3    is a plan view illustrating a rear surface of the cap assembly of  FIG.  1   ; 
         FIG.  4    is a cross-sectional view illustrating the cap assembly of  FIG.  1   ; 
         FIG.  5    is a cross-sectional view illustrating a sealing member of the cap assembly of  FIG.  4   ; and 
         FIG.  6    is a cross-sectional view illustrating a sealing member according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that those skilled in the art thoroughly understand the present invention. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. 
     In addition, in the following drawings, the thickness or size of each layer is exaggerated for convenience and clarity of description, and the same reference numerals in the drawings refer to the same elements. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. In this specification, it will also be understood that when a member A is referred to as being connected to a member B, the member A can be directly connected to the member B or indirectly connected to the member B with a member B therebetween. 
     The terms used herein are for illustrative purposes of the present invention only and should not be construed to limit the meaning or the scope of the present invention. As used in this specification, a singular form may, unless definitely indicating a particular case in terms of the context, include a plural form. Also, the expressions “comprise/include” and/or “comprising/including” used in this specification neither define the mentioned shapes, numbers, steps, operations, members, elements, and/or groups of these, nor exclude the presence or addition of one or more other different shapes, numbers, steps, operations, members, elements, and/or groups of these, or addition of these. The term “and/or” used herein includes any and all combinations of one or more of the associated listed items. 
     As used herein, terms such as “first,” “second,” etc. are used to describe various members, components, areas, layers, and/or portions. However, it is obvious that the members, components, areas, layers, and/or portions should not be defined by these terms. The terms do not mean a particular order, up and down, or superiority, and are used only for distinguishing one member, component, area, layer, or portion from another member, component, area, layer, or portion. Thus, a first member, component, area, layer, or portion which will be described may also refer to a second member, component, area, layer, or portion, without departing from the teaching of the present invention. 
     Spatially relative terms, such as “below”, “beneath”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. These spatially relative terms are intended for easy comprehension of the prevent invention according to various process states or usage states of the prevent invention, and thus, the present invention is not limited thereto. For example, an element or feature shown in the drawings is turned inside out, the element or feature described as “beneath” or “below” may change into “above” or “upper”. Thus, the term “lower” may encompass the term “upper” or “below”. 
     Hereinafter, a cylindrical secondary battery according to an embodiment will be described in detail with reference to the accompanying drawings (for convenience, an upper side is defined as an upper portion, and a lower side is defined as a lower portion based on  FIG.  1   ). 
       FIG.  1    is a cross-sectional view illustrating a cylindrical secondary battery according an embodiment.  FIG.  2    is a plan view illustrating a cap assembly of  FIG.  1   .  FIG.  3    is a plan view illustrating a rear surface of the cap assembly of  FIG.  1   .  FIG.  4    is a cross-sectional view illustrating the cap assembly of  FIG.  1   . 
     As illustrated in  FIG.  1   , a cylindrical secondary battery  10  according to an embodiment may include a cylindrical can  100 , an electrode assembly  200  inserted into the can  100 , first and second electrode collector plates  300  and  400  electrically connected to the electrode assembly  200 , and a cap assembly  500  coupled to one end of the can  100 . 
     The can  100  may include a circular bottom part  110  and a side part  130  extending upward from the bottom part  110 . The side part  130  has a cylindrical shape, and an upper end of the side part  130  is opened to define an opening. The bottom part  110  and the side part  130  may be integrated with each other or may be separately provided to be coupled to each other. In a process of manufacturing the secondary battery  10 , the electrode assembly  200  and an electrolyte may be accommodated into the can  100  through the opening, and the cap assembly  500  may be coupled to the opening to seal the can  100 . The can  100  may be made of steel, a steel alloy, nickel-plated steel, a nickel-plated steel alloy, aluminum, an aluminum alloy, or an equivalent thereof, but is not limited thereto. A beading part  132  may be concavely recessed inward adjacent to an upper end of the side part  130 , and a crimping part  134  in which an end of the side part  130  is bent may be disposed on an upper portion of the beading part  132 . The beading part  132  supports a lower portion of the cap assembly  500 , and the crimping part  134  supports an upper portion of the cap assembly  500 . 
     The electrode assembly  200  may include a first electrode plate, a second electrode plate, and a separator. The first electrode plate may be a positive electrode plate on which a positive electrode active material layer (e.g., transition metal oxide (LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , etc.)) is disposed on each of both surfaces thereof. A first electrode non-coating portion to which the positive electrode active material layer is not applied may be disposed on a portion of the first electrode plate. For example, the first electrode non-coating portion may be disposed to face the opening of the can  100 . In addition, the second electrode plate may be a negative electrode plate on which a negative electrode active material layer (e.g., graphite, carbon, etc.) is disposed on each of both surfaces thereof. A second electrode non-coating portion to which the negative electrode active material layer is not applied may be disposed on a portion of the second electrode plate. For example, the second electrode non-coating portion may be disposed to face the bottom part  110  of the can  100 . The separator may be interposed between the first electrode plate and the second electrode plate to prevent short circuit from occurring and allow lithium ions to move only. For example, the first electrode plate may be aluminum (Al) foil, the second electrode plate may be copper (Cu) or nickel (Ni) foil, and the separator may be made of polyethylene (PE) or polypropylene (PP), but the embodiment is not limited to the above materials. The first electrode plate, the second electrode plate, and the separator may be wound in a substantially cylindrical shape and accommodated in the can  100 . Here, the first electrode non-coating portion may be electrically connected to the first electrode collector plate, and the second electrode non-coating portion may be electrically connected to the second electrode collector plate  400 . 
     The first electrode collector plate  300  may be welded to the first electrode non-coating portion of the positive electrode plate and may be electrically connected to the cap assembly  500  by a first electrode lead  310 . Thus, the first electrode plate and the cap assembly  500  may be electrically connected to each other. The first electrode collector plate  300  may have an approximately circular plate shape. Alternatively, although not shown in the drawings, a base material tab may be disposed on the first electrode plate, and the first electrode collector plate  300  may be directly welded to the base material tab of the first electrode plate. 
     The second electrode collector plate  400  may be welded to the second electrode non-coating portion of the negative electrode plate and may be welded to the bottom part  110  of the can  100 . Accordingly, the second electrode plate and the can  100  may be electrically connected to each other. The second electrode collector plate  400  may have an approximately circular plate shape. Alternatively, although not shown in the drawings, a substrate tab may be disposed on the second electrode plate, and the second electrode collector plate  400  may be welded to the bottom part  110  of the can  100 . 
     As illustrated in  FIGS.  2  to  4   , the cap assembly  500  may include a vent plate  510 , a cap down plate  520 , and a gasket  530 . 
     As illustrated in  FIGS.  2  and  4   , the vent plate  510  may have an approximately circular plate and include a first support  512  that is in contact with the cap down plate  520 , a vent part  514  which is connected to the first support  512  and in which a notch  514   a  is provided, and a second support  516  connected to the vent part  514  and coupled to the side part  130  of the can  100 . 
     The first support  512  may be a portion having a predetermined thickness, and a bottom surface of the first support  512  may be in contact with a top surface of the cap down plate  520 . The first support  512  may have a thickness that is gradually reduced toward the outside. The vent part  514  may be integrally provided outside the first support  512 . 
     The vent part  514  is disposed between the first support  512  and the second support  516  and has a relatively thin thickness compared to each of the first support  512  and the second support  516 . The notch  514   a  is provided in a circular shape on the vent part  514 , and when the gas is generated, if a gas pressure exceeds a predetermined level, the notch  514   a  is broken to serve as a gas discharge passage. The notch  514   a  may be provided at a side closer to the second support  516 . 
     The second support  516  may be an edge portion of the vent plate  510 , be connected to the outside of the vent part  514 , and be integrated with the vent part  514 . The second support  516  may include a first region  516   a  having a thickness similar to or greater than that of the first support  512  and a second region  516   b  having a thickness that relatively less than that of the first region  516   a.  A degassing hole  516   c  is defined to pass through the first region  516   a.  To secure rigidity for defining the degassing hole  516   c,  the thickness of the first region  516   a  may be greater than that of the second region  516   b  or the first support  512 . A height of a top surface of the first region  516   a  may be greater than that of an edge of the vent part  514 . On the other hand, a height of the top surface of the second region  516   b  may be less than that of the top surface of the first region  516   a.  The gasket  530  is coupled to the outside of the second region  516   b,  and the vent plate  510  is fixed by the crimping part  134  of the can  100  with the gasket  530  therebetween. Also, a portion of the cap down plate  520  is in close contact with a bottom surface of the first region  516   a.    
     The degassing hole  516   c  is a hole penetrated from the top surface to the bottom surface of the first region  516   a.  The degassing hole  516   c  may be defined to be adjacent to the notch  514   a  in the first region  516   a.  For example, the degassing hole  516   c  may have a shape of which a diameter gradually decreases from an upper portion to a lower portion. A portion of the lower portion of the degassing hole  516   c  may have a shape of which the reduced diameter is maintained. The degassing hole  516   c  communicates with the inside of the can  100  through the cap down plate  520 . When a gas is generated inside the secondary battery  10 , the gas may be discharged between the vent plate  510  and the cap down plate  520  through a slot  524  defined in the cap down plate  520  and then be discharged to the outside through the degassing hole  516   c . A bottom surface of the first support  512  may protrude downward from a bottom surface of the second support  516 . 
     As illustrated  FIGS.  3  and  4   , the cap down plate  520  is disposed below the vent plate  510  and is electrically connected to the vent plate  510  and the first electrode collector plate  300 . Although the cap down plate  520  is illustrated in  FIG.  1    as being electrically connected to the first electrode collector plate  300  by the first electrode lead  310 , the cap down plate  520  may be directly connected to the first electrode collector plate  300  through welding. The cap down plate  520  may have an approximately circular shape and may have a diameter less than that of the vent plate  510 . A top surface of an edge of the cap down plate  520  is in close contact with the bottom surface of the second support  516  of the vent plate  510 . This portion is defined as a third support  526 . A top surface of each of other portions with respect to the third support  526  may have a height less than that of a top surface than the third support  526 . That is, the top surface of the cap down plate  520  excluding the third support  526  may be concave toward the first electrode collector plate  300 . A plurality of slots  524  serving as passages when a gas is generated may be defined to pass through a plate surface of the cap down plate  520 . The slots  524  may be defined between a central portion of the cap down plate  520  and the third support  526 . 
     The top surface of the cap down plate  520  is in close contact with the bottom surface of the first support  512 , and the top surface of the third support  526  is in close contact with the bottom surface of the second support  516 . The portion at which the second support and the third support  526  are in close contact with each other may be welded to provide a welded part. Since the second support  516  and the third support  526  are welded to each other, even though the notch  514   a  is ruptured when the gas is generated inside the secondary battery  10  to remove a portion of the first support  512 , the coupling between the vent plate  510  and the cap down plate  520  may be maintained, and thus, the electrical connection between the electrode assembly  200  and the cap assembly  500  may be maintained. 
     Referring to  FIG.  1   , the gasket  530  has an approximately ring shape and may have a predetermined width. The gasket  530  may be provided to surround a portion or the whole of the second region  516   b  of the second support  516 . The cap assembly  500  is insulated from the can  100  by the gasket  530  and is electrically connected to the first electrode collector plate  300 . Therefore, when the first electrode collector plate  300  is a positive electrode collector plate, the cap assembly  500  may serve as a positive electrode. 
     Hereinafter, a method for manufacturing a secondary battery having the above-described structure will be briefly described. 
       FIG.  5    is a cross-sectional view illustrating a sealing member of the cap assembly of  FIG.  4   . 
     After welding each of a first electrode collector plate  300  and a second electrode collector plate  400  to an electrode assembly  200 , the electrode assembly  200  may be inserted into a can  100  so that the first electrode collector plate  300  faces upward, and then, an electrolyte is injected. After welding a vent plate  510  and a cap down plate  520  and coupling a gasket  530  to form a cap assembly  500 , the cap assembly  500  is seated on a beading part  132  of a side part  130 . Thereafter, a crimping part  134  is formed to assemble the cap assembly  500  to the can  100 . 
     In this state, a resin pin (e.g., PP, PE, etc.) or a rubber pin is temporarily press-fitted into a degassing hole  516   c  to seal the secondary battery  10 . That is, during the assembly process of the secondary battery  10 , the degassing hole  516   c  is temporarily sealed by the resin pin or the rubber pin. 
     When a gas is generated inside the secondary battery  10  by charging and discharging before the secondary battery is released, the resin may be removed to discharge the internal gas through the degassing hole  516   c.  When the gas is completely discharged, as illustrated in  FIG.  5   , the sealing member may be press-fitted into the degassing hole  516   c  to close the degassing hole  516   c.  For example, the sealing member  540  may include a press-fitting ball or resin. For performing the press-fitting process, the sealing member  540  may have a size greater than that of the degassing hole  516   c.    
     Other types may be applied instead of the above-described sealing member. 
       FIG.  6    is a cross-sectional view illustrating a sealing member according to another embodiment. 
     As illustrated in  FIG.  6   , a sealing member  540 ′ according to another embodiment may be coupled to a degassing hole  516   c ′ in the form of insertion rather than press fitting. That is, the sealing member  540 ′ is manufactured to have a shape and size corresponding to those of the degassing hole  516   c ′, thereby sealing the degassing hole  516   c ′. In this case, the sealing member  540 ′ and the degassing hole  516   c ′ may be provided in a male and female structure so that the sealing member  540 ′ is separated from the degassing hole  516   c ′, or a gas does not leak. Various structures may be applied to the male and female structure, such as a screw thread and screw groove structure, a concave-convex structure, and a tapered hook and hook groove structure. 
     According to the embodiment, since the degassing function is applied to remove the gas generated before the product shipment, the deformation of the can and the cap assembly may be reduced. In addition, the swelling of the electrode assembly due to the generation of the internal gas may be prevented from occurring to reduce the performance deterioration of the secondary battery. 
     The above-mentioned embodiment is merely an embodiment, and thus, the present invention is not limited to the foregoing embodiment, and also 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 as defined by the following claims.