Patent Publication Number: US-2023143427-A1

Title: Button-type secondary battery

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of the priority of Korean Patent Application No. 10-2020-0087138, filed on Jul. 14, 2020, which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a button-type secondary battery having a shape having a diameter greater than a height thereof, and more particularly, to a button-type secondary battery capable of buffering an impact by embedding a swelling member and preventing an electrode assembly from being unwound. 
     BACKGROUND ART 
     A button-type battery commonly used as a coin-type battery or a button-type battery has a thin button shape and is widely used in various devices such as remote controllers, clocks, toys, computer parts, and the like. 
     Such a button-type battery is mainly manufactured as a non-rechargeable primary battery, but is also widely manufactured as a secondary battery that is chargeable and dischargeable as miniaturized devices are developed. Also, the button-type secondary battery also has a structure in which an electrode assembly and an electrolyte are embedded in a case to repeatedly perform charging and discharging, like a cylindrical or pouch-type secondary battery. 
       FIG.  1    is a cross-sectional view of a button-type secondary battery according to a related art. 
     As illustrated in the drawing, a button-type secondary battery has a structure, in which an upper can  4  and a lower can  3  are coupled to each other. Here, each of the upper can  4  and the lower can  3  has a flat cylindrical shape having a diameter greater than a height thereof, and the upper can  4  has a diameter slightly greater than that of the lower can  3 . 
     An electrode assembly  1 , in which a positive electrode, a separator, and a negative electrode are stacked, and an electrolyte (not shown) are mounted in the lower can  3 . The electrode assembly  1  has a structure in which the separator, the negative electrode, the separator, and the positive electrode are put in and wound on a rotating core in order, and a center pin  2  is inserted into a center hole from which the core is removed. Then, a negative electrode tab extending from the negative electrode and a positive electrode tab extending from the positive electrode protrude, and the negative electrode tab and the positive electrode tab are bonded to the lower can  3  and the upper can  4 , respectively. 
     In addition, in order to prevent short circuit from occurring when the upper can  4  and the lower can  3  are coupled to each other, an end of the upper can  4  may be coupled to the lower can  3  while being bent to press a gasket  5  in a state in which the gasket  5  having no conductivity is disposed at a contact point at which the upper can  4  and the lower can  3  are in contact with each other. 
     DISCLOSURE OF THE INVENTION 
     Technical Problem 
     However, in the above-described coupling method, since coupling force is determined only by friction force between the gasket and the upper can and a pressure at which the end of the upper can presses the gasket, when an external impact is applied, the upper can and the lower can may be separated from each other. 
     In addition, there is a possibility that the external impact is transmitted to the internal electrode assembly to cause unwinding and damage of the wound electrode assembly. 
     Therefore, a main object of the present invention for solving the above problems is to provide a button-type secondary battery having a structure that is more robust to an external impact and is capable of buffering an impact transmitted to an electrode assembly. 
     Technical Solution 
     According to the present invention for achieving the above objects, a button-type secondary battery, in which an upper can and a lower can are coupled to each other when an electrode assembly is mounted in the lower can comprises: the electrode assembly in which a negative electrode, a separator, and a positive electrode are wound in a state of being stacked; the lower can in which the electrode assembly is mounted, and a space portion is formed as a surplus space in addition to a space in which the electrode assembly is mounted; the upper can coupled to the lower can to close the lower can in a state in which the electrode assembly is mounted in the lower can, and an electrolyte is injected; and a swelling member mounted in the lower can in a state of being coupled to an outer surface of the electrode assembly, wherein, when the electrolyte is injected, the swelling member absorbs the electrolyte to be expanded in volume within the space portion. 
     The lower can may comprise: a first sidewall formed upward along a circumference of a flat bottom surface; a first inclined portion formed in a shape of which a diameter gradually increases from an end of the first sidewall; and a first distal end extending in a direction parallel to the first sidewall from an end of the first inclined portion. 
     In addition, the upper can may comprise: a second sidewall formed downward along a circumference of a flat top surface and parallel to the first distal end; a second inclined portion formed to have a diameter that is gradually narrowed from an end of the second sidewall and being parallel to the first inclined portion; and a second distal end extending from an end of the second inclined portion so as to be parallel to the first sidewall. 
     The space portion may be formed using the first inclined portion, the first distal end, the top surface, and a side surface of the electrode assembly as boundaries. 
     A gasket may be formed between the first sidewall and the second distal end, between the first inclined portion and the second inclined portion, and between the first distal end and the second sidewall to prevent the upper can and the lower can from being in contact with each other. 
     An end of the gasket may protrude from the second distal end so as to be exposed to the outside. 
     At least two or more, i.e., a plurality of swelling members may be attached to the electrode assembly. In addition, any one of the swelling members may be expanded in volume that is different from that of the other. 
     The swelling member may be a swelling tape, and the swelling tape may be coupled to surround a circumference of the electrode assembly. 
     When the expansion of the swelling member in the space portion is completed, the surplus space may be formed in the space portion. 
     Furthermore, the present invention may additionally provide a secondary battery module in which the plurality of button-type secondary batteries having the above characteristics are connected to each other in parallel or in series. 
     Advantageous Effects 
     According to the present invention having the above-described technical characteristics, since the swelling member may absorb the electrolyte in the upper can and the lower can so as to be expanded in volume, it may be possible to buffer the external impact transmitted to the electrode assembly. 
     Thus, it may be possible to prevent the electrode assembly from being damaged, thereby further improving the durability of the secondary battery. 
     Since the space portion in which the swelling member is expanded is formed in the radial direction of the upper can and the lower can, the increase in height of the secondary battery may be suppressed. 
     In addition, since the top surface of the upper can has a diameter greater than that of the bottom surface of the lower can, the sealing performance may be further improved by coupling the upper can to the lower can in the press-fit method. 
     In addition, since the lower can and the upper can have the first inclined portion and the second inclined portion, respectively, it may be possible to reduce the impact applied to the gasket when the press-fitting is performed and to enable the more stable coupling. 
     At least two or more of the swelling members, i.e., the plurality of swelling members may be attached to the electrode assembly, and at least one of the swelling members may be expanded to be different in size from other swelling members, and thus, the internal space may be efficiently used according to the shape of the space portion. 
     Furthermore, the swelling member may be the swelling tape, and the swelling tape may be coupled to surround the circumference of the electrode assembly, thereby preventing the electrode assembly from being unwound. 
     In addition, the surplus space may be formed in the space portion, and thus, when the gas is generated therein, the surplus space may be used as the space in which the gas is collected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a longitudinal cross-sectional view of a button-type secondary battery according to the related art. 
         FIG.  2    is a longitudinal cross-sectional view illustrating a state in which a space portion is formed in a lower can according to an embodiment of the present invention. 
         FIG.  3    is a longitudinal cross-sectional view illustrating a state in which an electrode assembly, in which a swelling member is coupled in the lower can, is mounted according to an embodiment of the present invention. 
         FIG.  4    is a longitudinal cross-sectional view illustrating a state when the swelling member of  FIG.  3    is expanded. 
         FIG.  5    is a longitudinal cross-sectional view illustrating a state in which a gas is collected into a surplus space of the space portion. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings in such a manner that the technical idea of the present invention may easily be carried out by a person with ordinary skill in the art to which the invention pertains. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. 
     In order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification. 
     Also, terms or words used in this specification and claims should not be restrictively interpreted as ordinary meanings or dictionary-based meanings, but should be interpreted as meanings and concepts conforming to the scope of the present invention on the basis of the principle that an inventor can properly define the concept of a term to describe and explain his or her invention in the best ways. 
     The present invention relates to a button-type secondary battery having a diameter larger than a height thereof and comprises a swelling member  40  that is expanded in volume by absorbing an electrolyte. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     
       
     
     First Embodiment 
     
       
     
       FIG.  2    is a longitudinal cross-sectional view illustrating a state in which a space portion C is formed in a lower can  10 , and  FIG.  3    is a longitudinal cross-sectional view illustrating a state in which an electrode assembly  1 , in which a swelling member  40  is coupled in the lower can C, is mounted. 
     Referring to the drawings, in the present invention, the electrode assembly  1  is mounted in an upper can  20  and the lower can  10 , the electrode assembly  1  is mounted in a state in which the swelling member  40  is coupled, and an electrolyte is injected before the upper can  20  and the lower can  10  are coupled to each other. 
     The electrode assembly  1  has a structure in which a negative electrode, a separator, and a positive electrode are wound in a state of being stacked. In addition, a positive electrode tab  1   a  extending from the positive electrode protrudes upward, and a negative electrode tab  1   b  extending from the negative electrode protrudes downward. Here, before the lower can  10  and the upper can  20  are coupled to each other, the positive electrode tab  1   a  is bonded to the upper can  20 , and the negative electrode tab  1   b  is bonded to the lower can  10 . 
     Then, the electrode assembly  1  is mounted in the lower can  10  having a cup shape. In the lower can  10 , the space portion C is formed as a surplus space in addition to a space in which the electrode assembly  1  is mounted. That is, as shown in the drawing, an upper end of the lower can  10  has a structure that is expanded along a circumference thereof in a direction in which a diameter thereof increases. 
     In more detail, the lower can  10  comprises a first sidewall  12  formed upward along a circumference of a flat bottom surface  11 , a first inclined portion formed in a shape of which a diameter gradually increases from an end of the first sidewall  12 , and a first distal end  14  extending in a direction parallel to the first sidewall  12  from an end of the first inclined portion  13 . 
     Also, the upper can  20  is coupled to the lower can  10  to close the lower can  10  in a state in which the electrode assembly  1  is mounted in the lower can  10 , and the electrolyte is injected. The upper can  20  comprises a second sidewall formed downward along a circumference of a flat top surface  21  and parallel to the first distal end  14 , a second inclined portion  23  formed to have a diameter that is gradually narrowed from an end of the second sidewall  22  and being parallel to the first inclined portion  13 , and a second distal end  24  extending from an end of the second inclined portion  23  so as to be parallel to the first sidewall  12 . 
     Thus, when the lower can  10  and the upper can  20  are coupled to each other, the space portion C is formed using the first inclined portion  13 , the first distal end  14 , the top surface  21 , and a side surface of the electrode assembly  1  as boundaries. 
     Furthermore, as described above, since the upper can  20  is connected to the positive electrode, and the lower can  10  is connected to the negative electrode, a gasket  30  made of a material having an electrical insulation is inserted into the coupled points of the upper can  20  and the lower can  10  to prevent short circuit from occurring. That is, the gasket  30  is formed between the first sidewall  12  and the second distal end  24 , between the first inclined portion  13  and the second inclined portion  23 , and between the first distal end  14  and the second sidewall  22  to prevent the upper can  20  and the lower can  10  from being in contact with each other. Here, an end of the gasket  30  protrudes from the second distal end  24  by a predetermined length so that an end of the second distal end  24  is pressed. 
     Also, in this embodiment, the electrode assembly  1  is mounted in the lower can  10  in a state in which the swelling member  40  is coupled to an outer surface thereof. When the electrode assembly  1  is mounted in the lower can  10 , the swelling member  40  is coupled to an upper portion of the electrode assembly  1  so as to be placed in the space portion C. 
     When the electrolyte is injected into the lower can  10  after the electrode assembly  10  is mounted, the swelling member  40  absorbs the electrolyte and is expanded in volume. That is, as illustrated in  FIG.  4    that illustrates a state when the swelling member  40  is expanded, the volume of the swelling member  40  is expanded in the space portion C by absorbing the electrolyte. 
     The expanded swelling member  40  may buffer an external impact transmitted to the electrode assembly  1 . Thus, it may be possible to prevent the electrode assembly  1  from being damaged, thereby further improving durability of the secondary battery. In addition, in this embodiment, since the space portion C in which the swelling member  40  is expanded is formed in a radial direction of the upper can  20  and the lower can  10 , an increase in height of the secondary battery may be suppressed. 
     When an impact is transmitted from the outside, the swelling member  40  may buffer impact energy transmitted to the electrode assembly  1  by discharging the absorbed electrolyte. Also, as time elapses, the swelling member  40  may again absorb the electrolyte so as to be maintained in buffering performance. 
     
       
     
     Second Embodiment 
     
       
     
     In this embodiment, a configuration in which at least two or more swelling members  40  are coupled to an electrode assembly  1  is provided. 
     That is, as illustrated in  FIGS.  2  and  3   , a plurality of swelling members  40  may be individually coupled to the electrode assembly  1 . Here, expanded volumes of the swelling members  40  may be provided differently according to a size and shape of a space portion C. 
     For example, the lowermost swelling member  40  disposed on a first inclined portion  13  formed with a relatively small inner diameter is expanded to a relatively small size to match an inner diameter formed by the first inclined portion  13 . However, each of the swelling members  40  disposed at the first distal end  14  and formed with a relatively larger inner diameter may be expanded to have a diameter greater than that of the lowermost swelling member  40 . 
     Furthermore, in this embodiment, the swelling member  40  may be provided as a swelling tape that is capable of being wound around the electrode assembly  1 . 
     That is, after the winding of a negative electrode, a separator, and a positive electrode, which constitute the electrode assembly  1 , is completed, a tape provided to prevent unwinding may be provided as the swelling member  40 . Thus, since the swelling tape  40  may be provided in an attached state during a process of manufacturing the electrode assembly  1 , a separate additional assembling process for coupling the swelling member  40  may be deleted. 
     Here, the swelling tape may not be attached only to an end at which the winding of any one of the negative electrode, the separator, and the positive electrode is completed, but be attached to being wound around the entire electrode assembly  1  to more efficiently suppress the problem, in which the electrode assembly  1  is unwound by an external impact. 
     As the plurality of swelling members  40  are attached as described above, a surplus space C 1  (see  FIG.  5   ) may be formed in the space portion C. 
     As illustrated in  FIG.  5    that illustrates a state in which a gas is collected in the surplus space C 1 , a gas that is generated during charging and discharging of the secondary battery may be collected in the form of air bubbles g. As described above, as the air bubbles g are collected, swelling of the upper can  20  and/or the lower can  10  may be suppressed. 
     Therefore, in this embodiment, at least two or more. i.e., the plurality of swelling members  40  may be attached to the electrode assembly  1 . Here, at least one of the swelling members  40  may be expanded in size that is different from that of the other and thus be expanded to match the shape of the space portion C to more efficiently utilize the inner space. 
     Furthermore, the swelling member  40  may be the swelling tape, and the swelling tape may be coupled to be wound around a circumference of the electrode assembly  1 , thereby preventing the electrode assembly  1  from being unwound. 
     In addition, the surplus space C 1  may be formed in the space portion C, and thus, when the gas is generated therein, the surplus space C may be used as the space in which the air bubbles are collected. 
     Furthermore, the present invention may additionally provide a secondary battery module in which the plurality of button-type secondary batteries having the above characteristics are connected to each other in parallel or in series. 
     While the embodiments of the present invention have been described with reference to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. 
     DESCRIPTION OF THE SYMBOLS 
       1 : Electrode assembly 
       10 : Lower can 
       11 : Bottom surface 
       12 : First sidewall 
       13 : First inclined portion 
       14 : First distal end 
       20 : Upper can 
       21 : Top surface 
       22 : Second sidewall 
       23 : Second inclined portion 
       24 : Second distal end 
       30 : Gasket 
       40 : Swelling member.