Patent Publication Number: US-2022216544-A1

Title: Rechargeable battery

Description:
TECHNICAL FIELD 
     The present invention relates to a rechargeable battery. More particularly, the present invention relates to a small rechargeable battery. 
     BACKGROUND ART 
     Unlike a primary battery that is incapable of being recharged, a rechargeable battery can be repeatedly charged and discharged. A low capacity rechargeable battery has been used for small electronic devices such as a mobile phone, a laptop computer, and a camcorder, and a large capacity battery has been widely used as a power source for driving a motor of a hybrid vehicle. 
     A representative rechargeable battery includes a nickel-cadmium (Ni—Cd) battery, a nickel-hydrogen (Ni-MH) battery, a lithium (Li) battery, and a lithium ion (Li-ion) rechargeable battery. Particularly, the lithium ion secondary battery has a higher operation voltage than the nickel-cadmium battery or the nickel-hydrogen battery that is mainly used as a portable electric equipment power source by about three times. Also, the lithium ion secondary battery is widely used in an aspect that energy density per unit weight is high. 
     In particular, as a demand for wearable devices such as headphones, earphones, smartwatches, and body-mounted medical devices which use Bluetooth has increased, the need for rechargeable batteries of which energy density is high and is ultra-small has been increasing. 
     As an example, the ultra-small rechargeable battery includes a coin cell or a button cell. In the case of the coin cell or the button cell button cell, since the entire height is low, if the thickness of the part where the electrode terminal is installed increases, the battery capacity may be reduced. Also, since the end of the bent lead tab is adjacent to both ends of the wound electrode assembly whose height is low compared to the diameter, the workability for welding the end of the lead tab and the electrode terminal may deteriorate. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     Disclosure 
     One aspect of the present invention is to provide a rechargeable battery that has increased capacity by reducing the thickness where the electrode terminal is installed, and facilitates the connection of the lead tab to the electrode terminal. 
     A rechargeable battery according to an embodiment of the present invention includes: an electrode assembly formed by disposing and winding a separator between a first electrode and a second electrode; a case facing one of wound ends of the electrode assembly and accommodating the electrode assembly; a cap plate facing the other of the wound ends, and closing and sealing an opening of the case; an electrode terminal installed in a terminal hole formed in the cap plate by interposing an insulating sealing material; a first lead tab connecting the first electrode to the electrode terminal; and a second lead tab connecting the second electrode to the case. 
     The insulating sealing material may be formed by a glass seal. 
     The electrode terminal may be formed as a plate with the same thickness as that of the cap plate. 
     The first lead tab may be connected to the electrode terminal, and the second lead tab may be connected to the case. 
     The electrode terminal may include a plate part of a second thickness t 2  that is thinner than a first thickness t 1  of the cap plate, and a both-sided flange part protruded from the exterior circumference of the plate part to both sides in the thickness direction and connected to the inner surface of the terminal hole with an insulating sealing material with a first height h 1 . 
     The both-sided flange part may be formed with the same first height (h 1 =t 1 ) as the first thickness of the cap plate. 
     The first lead tab may be connected to the plate part by welding, and the second lead tab may be connected to the case by welding. 
     The electrode terminal may include a plate part of a third thickness t 3  that is thinner than the first thickness t 1  of the cap plate, and a one-sided flange part protruded from the exterior circumference of the plate part to one side in the thickness direction and connected to the inner surface of the terminal hole with an insulating sealing material with a second height h 2 . 
     The one-sided flange part may be formed with a second height (h 2 &gt;t 1 ) that is larger than the first thickness t 1  of the cap plate. 
     The one-sided flange part may be disposed to be centered in the thickness direction in the terminal hole, and the insulating sealing material may be formed in a symmetrical structure on the inside and outside along the thickness direction. 
     The one-sided flange part may be disposed to be centered in the thickness direction in the terminal hole, the terminal hole may have a protrusion protruding from the center of the thickness direction toward the center of the diameter direction, and the insulating sealing material may form a symmetrical structure on the inside and outside along the thickness direction while filling the protrusion. 
     The one-sided flange part may be disposed to be biased to the inner surface side rather than the outer surface of the cap plate at the terminal hole, the plate part may be disposed by forming a horizontal plane with the outer surface of the cap plate in the terminal hole, and the insulating sealing material may form a horizontal plane with the outer surface of the cap plate and the outer surface of the plate part, and form a structure that is biased inward along the thickness direction. 
     The rechargeable battery according to an embodiment of the present invention may further include a first insulating member interposed between the second lead tab and the electrode assembly at the bottom side of the case. 
     The rechargeable battery according to an embodiment of the present invention may further include a second insulating member interposed between the first lead tab and the electrode assembly at the cap plate side. 
     The rechargeable battery according to an embodiment of the present invention may further include a third insulating member interposed between the first lead tab and the cap plate. 
     A height H may be set as the minimum distance between the outer planes of the case and the cap plate, a diameter D may be set as the maximum distance of the case exterior circumference, and the ratio of the height to the diameter may be 1 or less (H/D≤1). 
     The cap plate and the electrode terminal may be formed of stainless steel. 
     As such, the embodiment of the present invention installs the electrode terminal by interposing the insulating sealing material in the terminal hole formed in the cap plate, and connects the electrode terminal to the electrode assembly with the first lead tab, so the thickness at which the electrode terminal is installed is reduced, thereby increasing the capacity. In addition, an embodiment of the present invention may facilitate the connection of the first lead tab and the electrode terminal because the first lead tab is laser welded to the thin electrode terminal of the thin thickness. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a rechargeable battery according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view taken along a line II-II of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of a rechargeable battery according to a second embodiment of the present invention. 
         FIG. 4  is an exploded perspective view of a rechargeable battery according to a third embodiment of the present invention. 
         FIG. 5  is a cross-sectional view taken along a line V-V of  FIG. 4 . 
         FIG. 6  is a cross-sectional view of a rechargeable battery according to a fourth embodiment of the present invention. 
         FIG. 7  is a cross-sectional view of a rechargeable battery according to a fifth embodiment of the present invention. 
     
    
    
     MODE FOR INVENTION 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
     A rechargeable battery according to an embodiment of the present invention is an ultra-small battery, and may be a coin cell or a button cell. Here, the coin cell or the button cell is a thin coin-type or button-type cell, and means a battery having a ratio (H/D) of a height (H) to a diameter (D) of 1 or less. 
     Since the coin cell or the button cell is mainly cylindrical, a horizontal cross-section is circular, but the present invention is not limited thereto, and a horizontal cross-section may be oval or polygonal. In this case, the diameter means the maximum distance based on the horizontal direction of the battery, and the height means the minimum distance from the flat bottom surface of the battery to the upper cross-section of the flat top of the battery. 
     However, the present invention is not limited to the coin cell or the button cell that is an example of the present invention, and a battery of the present invention may be a cylindrical-type or pin-type battery. Hereinafter, a case in which a rechargeable battery according to an embodiment of the present invention is a coin cell or a button cell will be described in detail as an example. 
       FIG. 1  is an exploded perspective view of a rechargeable battery according to a first embodiment of the present invention, and  FIG. 2  is a cross-sectional view taken along a line II-II of  FIG. 1 . Referring to  FIG. 1  and  FIG. 2 , the rechargeable battery  1  according to the first embodiment includes an electrode assembly  10 , a case  20 , a cap plate  30 , an electrode terminal  40 , a first lead tab  51 , and a second lead tab  52 . 
     The electrode assembly  10  includes a first electrode ( 11 , for example, a negative electrode) and a second electrode ( 12 , for example, a positive electrode) provided on respective surfaces of a separator  13  that is an electrical insulating material, and is formed by winding the first electrode  11 , the separator  13  and the second electrode  12 . Accordingly, the electrode assembly  10  may have a jelly-roll shape, and is configured to charge and discharge a current. 
     At this time, the wound axis of the electrode assembly  10  may be arranged parallel to the height direction of the case  20 , and the lower surface (one end of both ends) and the upper surface (the other end of both ends) of the electrode assembly  10  are flat and parallel to each other. 
     The electrode assembly  10  has a center pin  15  in a place of the wound shaft. When welding the first and second lead tabs  51  and  52  to the electrode terminal  40  and the case  20 , one end of the center pin  15  adheres the first lead tab  51  and the electrode terminal  40  and the other adheres the second lead tab  52  and the case  20 , thereby improving the welding performance. The center pin  15  is formed as a cylinder to enable the flow of a gas and an electrolyte solution therein. Also, the center pin may be formed as a circular cylinder (not shown). 
     Hereinafter, a case where the first electrode  11  and the second electrode  12  are a negative electrode and a positive electrode is described as an example, but the present invention is not limited thereto, and the first electrode  11  and the second electrode  12  may be a positive electrode and a negative electrode, respectively. 
     The negative electrode ( 11 , a first electrode) is formed of a long band shape, and includes a negative electrode coating region as a region in which an active material layer is coated on a current collector of a metal foil (e.g., a Cu foil) and a negative uncoated region of a region in which the active material is not coated. The negative uncoated region may be positioned at one end of one side in the length direction of the negative electrode. 
     The positive electrode ( 12 , a second electrode) is formed of a long band shape, and includes a positive electrode coating region as a region in which a positive electrode active material layer is coated to a current collector of a metal foil (e.g., an Al foil) and a positive electrode uncoated region as a region where the active material is not coated. The positive electrode uncoated region may be disposed at the end of one side of the positive electrode in the length direction. 
     The case  20  allows the electrode assembly  10  to be inserted through an opening  21  formed on one side and accommodated. The case  20  sets a space inside which the electrode assembly  10  and the electrolyte solution are accommodated. For example, the case  20  may have a cylindrical shape with a low height, and may have a circular opening  21  at an upper end to insert the electrode assembly  10  of the cylindrical shape. 
     The cap plate  30  closes and seals the opening  21  of the case  20  and may be coupled and welded to the opening  21 . The cap plate  30  is formed corresponding to the opening  21  and has a terminal hole  31 . 
     The electrode terminal  40  is installed with the insulating sealing material  60  in the terminal hole  31  through the sealing process. That is, the electrode terminal  40  and the cap plate  30  are electrically insulated and have different polarities from each other. Since the insulating sealing material  60  does not exist in the disassembled state but in the assembled state, it is omitted  FIG. 1  and is shown in  FIG. 2 . 
     In the electrode assembly  10 , the first lead tab ( 51 , a negative electrode tab) is fixedly installed on the negative electrode  11 , and the second lead tab ( 52 , a positive electrode tab) is fixedly installed on the positive electrode  12 . Therefore, in the first embodiment, the electrode terminal  40  has a negative electrode property, and the cap plate  30  has a positive electrode property. Although not shown separately, the electrode terminal  40  may have a positive electrode property and the cap plate  30  may have a negative electrode property. 
     The first lead tab  51  and the second lead tab  52  are installed in the negative uncoated region and the positive electrode uncoated region, respectively, and after extending parallel to the wound axis, their ends may be bent toward the wound axis. For example, the bent ends of the first lead tab  51  and the second lead tab  52  may be disposed to the upper portion (the cap plate  30  side) and the lower portion (the case  20  side) of the electrode assembly  10 , respectively. 
     The first lead tab  51  is made of an electrically conductivity material such as copper or nickel, and is directly electrically connected to the electrode terminal  40 . For example, the bent end of the first lead tab  51  may be connected to the electrode terminal  40  by laser welding. 
     The second lead tab  52  is made of an electrically conductivity material such as nickel and aluminum, and is electrically connected to the case  20 . For example, the bent end of the second lead tab  52  may be connected to the bottom surface of the case  20  by laser welding. 
     The insulating sealing material  60  interposed between the electrode terminal  40  and the terminal hole  31  and around the electrode terminal  40  may be formed of, for example, a glass seal. The insulating sealing material  60  electrically insulates the cap plate  30  and the electrode terminal  40  while sealing between the inner surface of the terminal hole  31  and the outer surface of the electrode terminal  40 . 
     If the insulating sealing material  60  is a glass seal, the cap plate  30  and the electrode terminal  40  may be made of stainless steel. In addition, the insulating sealing material  60  must be able to overcome a thermal impact even at a high temperature of about 1000° C. 
     For example, the insulating sealing material  60  should have crack resistance when undergoing a thermal impact and thermal expansion due the charging and discharging and during the welding of the first lead tab  51  to the electrode terminal  40 . The glass seal may overcome this thermal impact. The area of the electrode terminal  40  may be set so that the insulating sealing material  60  may be applied within a range that can overcome the required thermal impact. 
     As an example, since the electrode terminal  40  is formed of a plate having the same thickness t as the thickness t of the cap plate  30 , air-tightness performance and bonding performance by the insulating sealing material  60  may be improved. And in the cap plate  30  and the electrode terminal  40 , the outer surfaces are formed to be coplanar, and the inner surfaces are formed to be coplanar. 
     The insulating sealing material  60  is formed by injecting molten glass between the circumferential outer surface of the electrode terminal  40  and the inner surface of the terminal hole  31  due to a process characteristic, so it may be more protruded than the outer surfaces of the electrode terminal  40  and the cap plate  30  and may be more protruded than the inner surfaces. 
     In the first embodiment, the first lead tab  51  is connected to the electrode terminal  40  formed as a plate, and the second lead tab  52  is connected to the case  20 . First lead tab  51  is welded to the electrode terminal  40 , but the electrode terminal  40  is not protruded outward and forms the same outer surface as the cap plate  30 . 
     Since the first lead tab  51  is laser welded directly to the electrode terminal  40 , the process of connecting the first lead tab  51  to the electrode terminal  40  is facilitated. And the second lead tab  51  is laser welded directly to the bottom of case  20 . 
     At this time, the center pin  15  supports the first and second lead tabs  51  and  52  so that the first lead tab  51  and the electrode terminal  40  are in close contact, and the second lead tab  52  and the case  20  are in close contact, thereby improving the welding performance of each. 
     Again referring to  FIG. 1  and  FIG. 2 , the rechargeable battery  1  of the first embodiment further includes a first insulating member  71  interposed between the second lead tab  52  and the electrode assembly  10  at the bottom side of the case  20 . The first insulating member  71  electrically insulates between the electrode assembly  10  and the bent second lead tab  52 . 
     The rechargeable battery  1  of the first embodiment further includes, at the cap plate  30  side, a second insulating member  72  interposed between the first lead tab  51  and the electrode assembly  10 , and a third insulating member  73  interposed between the first lead tab  51  and the cap plate  30 . 
     The second insulating member  72  electrically insulates between the electrode assembly  10  and the bent first lead tab  51 . The third insulating member  73  electrically further insulates between the bent first lead tab  51  and the cap plate  30 . 
     In the present embodiment, the first and second insulating members  71  and  72  have a through hole through which the center pin  15  passes so that the center pin  15  more firmly supports the first and second lead tabs  51  and  52 . Although not shown, the first and second insulating members may not have a through hole, and the center pin may support the first and second insulating members to support the first and second lead tabs. 
     Although not shown, the electrode assembly  10  is covered with an insulating tape along the diameter direction of the external circumferential surface. The insulating tape electrically insulates between the external circumferential surface of the electrode assembly  10  and the inner surface of case  20  while protecting the outside of the electrode assembly  10 . 
     When the rechargeable battery  1  of the first embodiment is applied to a coin-type battery or a button-type battery, the height H is set as the minimum distance between the outer planes of the case  20  and the cap plate  30 , and the diameter D is set as the maximum distance of the exterior circumference of the case  20 . Also, the ratio of the height H for the diameter D is 1 or less (H/D≤1). 
     As such, in the case of the coin-type or button-type battery with a low height compared to the diameter, since the connection structure between the electrode terminal  40  and the first lead tab  51  is thinly formed, in the case of having the same height H and diameter D, as compared with the case where the connection structure is thick, while the size of the electrode assembly  10  increases, the capacity of the rechargeable battery  1  may be increased as a whole. 
     Hereinafter, a second embodiment of the present invention is described. Compared with the first embodiment, the same components are omitted and different components are described. 
       FIG. 3  is a cross-sectional view showing a rechargeable battery according to a second embodiment of the present invention. Referring to  FIG. 3 , in the rechargeable battery  2  of the second embodiment, the electrode terminal  240  includes a plate part  241  and a both-sided flange part  242 . 
     The plate part  241  is formed with a second thickness (t 2 &lt;t 1 ) that is thinner than the first thickness t 1  of the cap plate  30 . The both-sided flange part  242  is protruded from the exterior circumference of the plate part  241  to both sides in the thickness direction, has a first height h 1 , and is connected to the inner surface of the terminal hole  31  with an insulating sealing material  61 . 
     Since the both-sided flange part  242  is formed with the same first height (h 1 =t 1 ) as the first thickness t 1  of the cap plate  30 , the air-tightness performance and the joint performance by the insulating sealing material  61  may be improved. And in the both-sided flange part  242  of the electrode terminal  240  and the cap plate  30 , the outer surfaces are formed in the same plane, and the inner surfaces are formed in the same plane. 
     The plate part  241  is positioned lower than the outer surface of the cap plate  30 . The insulating sealing material  61  may be protruded more than the outer surfaces of the electrode terminal  40  and the cap plate  30 , and may be protruded more than the inner surfaces due to the process characteristics. 
     In the second embodiment, the first lead tab  251  is connected to the plate part  241  by welding, and the second lead tab  52  is connected to the case  20  by welding. Since the first lead tab  251  is laser welded to the plate part  241 , the welding is easy. Therefore, since the plate part  241  is formed with a second thickness t 2  that is thinner than the first thickness t 1 , the laser welding with the first lead tab  251  becomes easier. 
     In this case, the center pin  215  supports the first and second lead tabs  251  and  52  so that the first lead tab  251  and the plate part  241  of the electrode terminal  240  are closely in contact with each other, and the second lead tab  52  and the case  20  are closely in contact with each other, thereby improving the welding performance of each. 
       FIG. 4  is an exploded perspective view of a rechargeable battery according to a third embodiment of the present invention, and  FIG. 5  is a cross-sectional view taken along a line V-V of  FIG. 4 . Referring to  FIG. 4  and  FIG. 5 , in the rechargeable battery  3  of the third embodiment, the electrode terminal  340  includes a plate part  341  and a one-sided flange part  342 . 
     The plate part  341  is formed with a third thickness t 3  that is thinner than the first thickness t 1  of the cap plate  30 . The one-sided flange part  342  is protruded from the exterior circumference of the plate part  341  to one side in the thickness direction, has a second height h 2 , and is connected to the inner surface of the terminal hole  31  with the insulating sealing material  62 . 
     The one-sided flange part  342  is formed with a second height (h 2 &gt;t 1 ) that is greater than the first thickness t 1  of the cap plate  30 . The second height h 2  increases the sealing area with the terminal hole  31  by the insulating sealing material  62 , thereby improving the air-tightness performance and the bonding performance. 
     And the one-sided flange part  342  is disposed at the center of the thickness direction in the terminal hole  31 , and the insulating sealing material  62  is formed symmetrically on the inside and outside along the thickness direction. The outer side means the outer side of the rechargeable battery  3  based on the cap plate  30 , and the inner side means the inner side of the rechargeable battery  3  based on the cap plate  30 . 
     That is, the plate part  341  is more protruded out of the outer surface of cap plate  30 , and the one-sided flange part  342  is more protruded into the inner surface of the cap plate  30 . Therefore, the insulating sealing material  62  may seal the one-sided flange part  342  and the terminal hole  31  while maintaining the balance of the bonding performance on the outside and inside in the thickness direction. 
     Also, since the second height h 2  of the one-sided flange part  342  is larger than the first thickness t 1  of the cap plate  30 , the insulating sealing material  62  is formed thickly on the one-sided flange part  342  and thinly on the cap plate  30  side, and forms an inclined plane therebetween. 
     In the third embodiment, the first lead tab  351  is connected to the plate part  341  by welding, and the second lead tab  52  is connected to the case  20  by welding. Since the first lead tab  351  is laser welded to the plate part  341 , the welding is easy. Therefore, as the plate part  341  is formed with the third thickness t 3  that is thinner than first thickness t 1 , the laser welding with the first lead tab  251  becomes easier. 
     In addition, since the plate part  341  is positioned more outward in the thickness direction than the inner surface of the cap plate  30 , the first lead tab  351  is positioned inside the one-sided flange part  342 . That is, by the one-sided flange part  342 , the welding space between the plate part  341  and the first lead tab  351  may be secured larger in the thickness direction. 
     In this case, the center pin  315  supports the first and second lead tabs  351  and  52  to firmly closely contact the first lead tab  351  and the plate part  341  of the electrode terminal  340 , and the second lead tab  52  and the case  20 , thereby Improving the welding performance. 
       FIG. 6  is a cross-sectional view of a rechargeable battery according to a fourth embodiment of the present invention. Referring to  FIG. 6 , in the rechargeable battery  4  of the fourth embodiment, the one-sided flange part  342  of the electrode terminal  340  is disposed at the center of the thickness direction in the terminal hole  41 . 
     The terminal hole  41  further has a protrusion  411  protruding from the thickness direction center toward the diameter direction center. The insulating sealing material  63  forms a symmetrical structure on the inside and outside along the thickness direction while filling the protrusion  411 . 
     At this time, the insulating sealing material  63  increases the bonding area between the one-sided flange part  342  and the terminal hole  41  due to the protrusion  411 , so that the sealing performance and bonding performance may be further improved. 
       FIG. 7  is a cross-sectional view of a rechargeable battery according to a fifth embodiment of the present invention. Referring to  FIG. 7 , in the rechargeable battery  5  of the fifth embodiment, a plate part  341  of the electrode terminal  540  is disposed to form the horizontal surface with the outer surface of the cap plate  30  at the terminal hole  31 . The electrode terminal  540 , that is, the one-sided flange part  342 , is biased and disposed from the terminal hole  31  to the inner surface side. 
     The insulating sealing material  64  forms the horizontal plane with the outer surface of the cap plate  30  and the outer surface of plate part  341 , and forms a structure that is biased inward along the thickness direction by the one-sided flange part  342 . 
     At this time, the insulating sealing material  64  secures the bonding area with the one-sided flange part  342  and the terminal hole  31  to secure the sealing performance and the bonding performance while preventing the electrode terminal  540  from being protruded out of the outer surface of the cap plate  30 . 
     In this case, the center pin  415  supports the first and second lead tabs  451  and  52  to firmly adhere the first lead tab  451  and the plate part  341  of the electrode terminal  340 , and the second lead tab  52  and the case  20 , thereby improving the welding performance of each. 
     While this invention has been described in connection with what is presently considered to be practical embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims. 
     
       
         
           
               
             
               
                   
               
               
                 &lt;Description of symbols&gt; 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 1, 2, 3, 4, 5: rechargeable battery 
                 10: electrode assembly 
               
               
                 13: separator 
                 11: first electrode (negative electrode) 
               
               
                 12: second electrode (positive electrode) 
                 15, 215, 315, 415: center pin 
               
               
                 20: case 
                 21: opening 
               
               
                 30: cap plate 
                 31, 41: terminal hole 
               
               
                 40, 240, 340, 540: electrode terminal 
                 51, 251, 351, 451: first lead tab 
               
               
                 52: second lead tab 
                 60, 61, 62, 63, 64: insulating sealing material 
               
               
                 71: first insulating member 
                 72: second insulating member 
               
               
                 73: third insulating member 
                 24, 341: plate part 
               
               
                 242: both-sided flange part 
                 342: one-sided flange part 
               
               
                 411: protrusion 
                 D: diameter 
               
               
                 H: height 
                 h1: first height 
               
               
                 t: thickness 
                 t1: first thickness 
               
               
                 t2: second thickness 
                 t3: third thickness