Patent Publication Number: US-2023163408-A1

Title: Cylindrical battery

Description:
TECHNICAL FIELD 
     The present disclosure relates to a cylindrical battery. 
     BACKGROUND ART 
     Conventionally, there has been a well-known cylindrical battery having a bottomed cylindrical exterior can and a sealing assembly which blocks an opening of the exterior can. In addition, the cylindrical battery is sometimes used as a set battery (battery pack) for which a plurality of cylindrical batteries are connected. 
     For the cylindrical battery, cases of resulting in ignition at the time of abnormality occurrence have been reported. When the cylindrical battery ignites, flames jet out from an exhaust port of the cylindrical battery and there is a risk that the adjacent cylindrical battery in the battery pack catches a fire. Patent Literature 1 discloses a battery pack for which a mesh member for extinguishing flames jetting out from an exhaust port of a cylindrical battery is disposed above the cylindrical battery. In addition, Patent Literature 2 discloses a configuration of providing a fire extinguisher in a battery pack. 
     CITATION LIST 
     Patent Literature 
     PATENT LITERATURE 1: Japanese Unexamined Patent Application Publication No. 
     PATENT LITERATURE 2: Japanese Unexamined Patent Application Publication No. Hei9-161754 
     SUMMARY 
     In the battery pack disclosed in Patent Literatures 1 and 2, since fire extinguishing parts are disposed as separate parts, a cost increases for increase of the number of parts compared to a normal battery pack. In addition, in the battery pack, since the fire extinguishing parts are disposed, it becomes difficult to miniaturize the battery pack and it also becomes difficult to miniaturize an apparatus into which the battery pack is to be incorporated. 
     A cylindrical battery which is one aspect of the present disclosure is a cylindrical battery having: an electrode assembly around which a positive electrode and a negative electrode are wound via a separator; an electrolyte; a bottomed cylindrical exterior can which houses the electrode assembly and the electrolyte; and a sealing assembly which blocks an opening of the exterior can, the sealing assembly has a cap disposed at an outermost part of the sealing assembly, the cap includes a projection formed at a center part, the projection includes a top surface part and a sidewall part, and a plurality of independent exhaust ports are formed respectively at the top surface part and the sidewall part. 
     According to one aspect of the present disclosure, in a case of ignition at the time of abnormality occurrence, the ignition may be extinguished by a battery alone. 
    
    
     
       BRIEF DESCRIPTION OF DRAWING 
         FIG.  1    is a sectional view of a cylindrical battery which is an example of an embodiment. 
         FIG.  2    is a perspective view of an internal terminal plate which is another example of the embodiment. 
         FIG.  3    is a perspective view of a cap which is an example of the embodiment. 
         FIG.  4    is a perspective view of the cap which is another example of the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the embodiment of the present disclosure will be explained using the drawings. Shapes, materials and numbers explained below are examples for explanation and can be appropriately changed according to specifications of a cylindrical battery. Same signs are attached to equivalent elements in all the drawings to give the explanation below. 
     A cylindrical battery  10  which is an example of the present embodiment will be explained using  FIG.  1   .  FIG.  1    is a sectional view of the cylindrical battery  10 . 
     As illustrated in  FIG.  1   , the cylindrical battery  10  has an electrode assembly  14 , an electrolyte, and an exterior can  16  which houses the electrode assembly  14  and the electrolyte. The electrode assembly  14  has a positive electrode  11 , a negative electrode  12  and a separator  13 , and has a wound structure for which the positive electrode  11  and the negative electrode  12  are wound in a helical shape via the separator  13 . The exterior can  16  has a bottomed cylindrical shape which is open on one side in an axial direction, and an opening of the exterior can  16  is blocked by a sealing assembly  17 . 
     The positive electrode  11  has a positive electrode current collector and a positive electrode mixture layer formed on at least one surface of the current collector. For the positive electrode current collector, foil of a metal which is stable in a potential range of the positive electrode  11 , such as aluminum and an aluminum alloy, and a film for which the metal is disposed on a surface layer or the like can be used. The positive electrode mixture layer includes a positive electrode active material, a conductive agent such as acetylene black, and a binding agent such as polyvinylidene fluoride, and is preferably formed on both surfaces of the positive electrode current collector. For the positive electrode active material, lithium-containing transition metal composite oxide is used for example. The positive electrode  11  can be manufactured by applying positive electrode mixture slurry including the positive electrode active material, the conductive agent and the binding agent or the like on the positive electrode current collector, drying a coating film, then compressing the coating film and forming the positive electrode mixture layer on both surfaces of the positive electrode current collector. 
     The negative electrode  12  has a negative electrode current collector and a negative electrode mixture layer formed on at least one surface of the current collector. For the negative electrode current collector, foil of a metal which is stable in the potential range of the negative electrode  12 , such as copper and a copper alloy, and a film for which the metal is disposed on the surface layer or the like can be used. The negative electrode mixture layer includes a negative electrode active material and a binding agent such as styrene-butadiene rubber (SBR), and is preferably formed on both surfaces of the negative electrode current collector. For the negative electrode active material, graphite and a silicon-containing compound or the like is used for example. The negative electrode  12  can be manufactured by applying negative electrode mixture slurry including the negative electrode active material and the binding agent or the like on the negative electrode current collector, drying a coating film, then rolling the coating film and forming the negative electrode mixture layer on both surfaces of the current collector. 
     For the electrolyte, a non-aqueous electrolyte is used for example. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For the non-aqueous solvent, ester, ether, nitrile, amides and a mixed solvent of two or more kinds of them may be used for example. The non-aqueous solvent may contain a halogen substitute for which halogen atoms of fluorine or the like are substituted for at least a part of hydrogen of the solvents. Note that the non-aqueous electrolyte is not limited to a liquid electrolyte and may be a solid electrolyte. For the electrolyte salt, a lithium salt such as LiPF 6  is used for example. The kind of the electrolyte is not limited in particular, and may also be an aqueous electrolyte. 
     The cylindrical battery  10  has insulating plates  18  and  19  disposed respectively above and below the electrode assembly  14 . In an example illustrated in  FIG.  1   , a positive electrode lead  20  attached to the positive electrode  11  passes through a through-hole of the insulating plate  18  and extends to the sealing assembly  17 , and a negative electrode lead  21  attached to the negative electrode  12  passes through an outer side of the insulating plate  19  and extends to a bottom part side of the exterior can  16 . The positive electrode lead  20  is connected to a bottom surface of an internal terminal plate  23  disposed at an innermost part of the sealing assembly  17  by welding or the like. Thus, a cap  30  which is a top plate of the sealing assembly  17  electrically connected with the internal terminal plate  23  becomes a positive electrode external terminal. The negative electrode lead  21  is connected to a bottom part inner surface of the exterior can  16  by welding or the like. Thus, the bottom part of the exterior can  16  for example becomes a negative electrode external terminal. 
     The exterior can  16  is a bottomed cylindrical metal container. A gasket  27  is provided between the exterior can  16  and the sealing assembly  17 , and sealability inside the battery is secured. On the exterior can  16 , a grooved part  22  supporting the sealing assembly  17 , for which a part of a side face part is projected to an inner side, is formed. The grooved part  22  is preferably formed in an annular shape along a circumferential direction of the exterior can  16 , and supports the sealing assembly  17  with the upper surface. The sealing assembly  17  is fixed to an upper part of the exterior can  16  by the grooved part  22  and an opening end part of the exterior can  16  calked to the sealing assembly  17 . At the opening end part of the exterior can  16 , a calking part  28  is formed in the annular shape. 
     The sealing assembly  17  has a structure for which the internal terminal plate  23 , a lower vent member  24 , an insulating member  25 , an upper vent member  26  and the cap  30  are laminated in order from the side of the electrode assembly  14 . The individual members configuring the sealing assembly  17  present a disk shape or a ring shape for example, and the individual members except the insulating member  25  are electrically connected to each other. The lower vent member  24  and the upper vent member  26  are connected to each other at individual center parts, and the insulating member  25  is interposed between individual peripheral edge parts. When an internal pressure of the cylindrical battery  10  rises at the time of abnormality occurrence, the lower vent member  24  is deformed so as to push up the upper vent member  26  to the side of the cap  30  and breaks, and a current path between the lower vent member  24  and the upper vent member  26  is shut off. When the internal pressure rises further, the upper vent member  26  breaks and a gas is discharged from exhaust ports  33 H and  34 H to be described later of the cap  30 . 
     Note that the structure of the sealing assembly is not limited to the structure illustrated in  FIG.  1   . For example, the sealing assembly may have a structure not having the internal terminal plate, and the electrode lead may be connected to the lower vent member. In addition, a vent member may be configured by one member. 
     Using  FIG.  2   , another example of the internal terminal plate  23  configuring the sealing assembly  17  will be explained.  FIG.  2    is a perspective view illustrating the internal terminal plate  23 . 
     The internal terminal plate  23  is disposed at the innermost part of the sealing assembly  17  as described above. To a lower surface of the internal terminal plate  23 , the positive electrode lead  20  is connected by welding or the like (see  FIG.  1   ). As illustrated in  FIG.  2   , the internal terminal plate  23  includes a recess  23 A formed at the center part of a metal plate and an outer peripheral part  23 B formed around the recess  23 A. The recess  23 A is swollen to the inner side of the cylindrical battery  10 . At the recess  23 A, a plurality of exhaust ports  23 H are formed. The exhaust ports  23 H have a diameter similar to that of the exhaust ports  33 H at a top surface part  33  of the cap  30  to be described later for example. 
     According to the internal terminal plate  23 , in a case of ignition at the time of abnormality occurrence, jetting of flames can be suppressed by shutting off the flames by the recess  23 A. In addition, according to the internal terminal plate  23 , a temperature of the flames is lowered by absorbing heat from the jetted flames by the recess  23 A and the jetting of the flames can be suppressed. Further, in the internal terminal plate  23 , since the plurality of exhaust ports  23 H are formed at the recess  23 A, the gas generated inside the cylindrical battery  10  can be easily released to the outside at the time of abnormality occurrence. 
     Using  FIG.  3   , the cap  30  configuring the sealing assembly  17  will be explained.  FIG.  3    is a perspective view illustrating the cap  30 . 
     The cap  30  is disposed at an outermost part of the sealing assembly  17  and forms a top surface of the cylindrical battery  10 . The cap  30  is a terminal for welding on a positive electrode side for connecting the cylindrical batteries  10  with each other in series or in parallel or attaching a safety element to the cylindrical battery  10  when incorporating the cylindrical battery  10  inside an apparatus for example. 
     As illustrated in  FIG.  3   , the cap  30  is formed roughly in a disk shape. In addition, the cap  30  is formed of a metal plate. A composition of the metal plate is not limited in particular, but is generally iron or an iron alloy (for example, stainless steel). An example of thickness of the metal plate is 0.1 mm-0.8 mm. The cap  30  is manufactured by deep-drawing the metal plate for example. The cap  30  includes a projection  31  formed at the center part of the metal plate and a flange part  32  formed around the projection  31 . 
     The projection  31  is swollen to the outer side of the cylindrical battery  10 . While the projection  31  of the present embodiment is swollen to the outer side of the cylindrical battery  10 , the projection may be swollen to the inner side of the cylindrical battery  10 . A degree (height) of swelling of the projection  31  is not limited in particular, but is about 1 mm-5 mm as an example. The projection  31  is preferably formed such that a center of the top surface part  33  coincides with a center in a radial direction of the cap  30  in a plan view. The projection  31  includes the top surface part  33  and a sidewall part  34  connected to the flange part  32 . 
     The top surface part  33  is a part which shuts off the flames in the case of the ignition at the time of abnormality occurrence of the cylindrical battery  10 , while details are to be described later, and to which a lead wire or the like is connected by welding or the like as described above. The top surface part  33  is formed roughly in a circular shape in the plan view. The top surface part  33  is flat and is formed in parallel with the flange part  32 . The top surface part  33  does not need to be entirely flat, and an outer peripheral part may be chamfered for example. The top surface part  33  is preferably formed as wide as possible in consideration of a flame shutoff effect in the case of the ignition at the time of abnormality occurrence of the cylindrical battery  10  as described above and workability and welding strength of weldbonding or the like. 
     At the outer peripheral part of the top surface part  33 , the plurality of exhaust ports  33 H are formed. In the example illustrated in  FIG.  3   , the plurality of exhaust ports  33 H are annularly formed only for one round at roughly equal intervals along the circumferential direction. The exhaust ports  33 H are preferably in a perfect circle shape in the plan view, but may be polygonal, elliptic or roughly circular for example. The exhaust ports  33 H are preferably formed together with exhaust ports  34 H to be described later before the cap  30  is manufactured by being deep-drawn for example. 
     The exhaust ports  33 H have the diameter of 0.01 mm-9 mm, and preferably have the diameter of 0.5 mm-3 mm. In the example illustrated in  FIG.  2   , the diameter of the exhaust ports  33 H is 1 mm. In addition, each of the exhaust ports  33 H formed at least at the top surface part  33  preferably has almost the same diameter but may has a different diameter. A sum total of an opening area of the exhaust ports  33 H is formed to be 1-30 mm 2 , and more preferably 5-15 mm 2 . In the example illustrated in  FIG.  2   , the sum total of the opening area of the exhaust ports  33 H is 9 mm 2 . 
     A total aperture ratio of all the exhaust ports  33 H at the top surface part  33  is 1-60%, and is preferably 10-30%. The total aperture ratio is a ratio of the sum total of the opening area of all the exhaust ports  33 H in a surface area of the top surface part  33 . In the example illustrated in  FIG.  3   , the total aperture ratio of the exhaust ports  33 H is 24%. 
     The center part of the top surface part  33  has a flat top surface without the exhaust ports  33 H being formed there. According to the center part of the top surface part  33 , the workability at the time of weldbonding can be improved and the welding strength or the like can be improved. The center part of the top surface part  33  may be formed by forming the exhaust ports  33 H in a step of manufacturing the cap  30 , welding the lead wire and thereby blocking the exhaust ports  33 H by the lead wire and a welded part. 
     The sidewall part  34  is a part which connects the flange part  32  and the top surface part  33 , and is formed roughly vertically to the flange part  32 . An angle formed by the sidewall part  34  to a swelling direction of the projection  31  is preferably about 90°-110°, and is more preferably about 90°-100°. 
     At the sidewall part  34 , the plurality of exhaust ports  34 H are formed. The exhaust ports  34 H are preferably in the perfect circle shape in a view from a direction vertical to the sidewall part  34 , but may be polygonal, elliptic or roughly circular for example. The exhaust ports  34 H are preferably formed together with the exhaust ports  33 H before the cap  30  is manufactured by being deep-drawn as described above. 
     The exhaust ports  34 H have the diameter of 0.01 mm-9 mm, and preferably have the diameter of 0.5 mm-2 mm. In the example illustrated in  FIG.  2   , the diameter of the exhaust ports  34 H is 0.5 mm. In addition, each of the exhaust ports  34 H formed at least at the sidewall part  34  preferably has almost the same diameter but may has a different diameter. 
     A total aperture ratio of all the exhaust ports  34 H at the sidewall part  34  is 1-60%, and is preferably 10-30%. The total aperture ratio is the ratio of the sum total of the opening area of all the exhaust ports  34 H in the surface area of the sidewall part  34 . Here, the total aperture ratio of the exhaust ports  33 H at the top surface part  33  described above is preferably greater than the total aperture ratio of the exhaust ports  34 H at the sidewall part  34 . 
     While the plurality of independent exhaust ports  33 H and  34 H are formed at the top surface part  33  and the flange part  32  respectively at the projection  31  of the present embodiment, exhaust ports may be formed at a boundary part of the top surface part  33  and the flange part  32 . 
     The cap  30  includes the flange part  32  formed around the projection  31  as described above. Since the flange part  32  is a part to be pressurized by the calking part  28  of the exterior can  16 , it is needed to secure the flange part  32  having certain measure of width. In addition, exhaust ports may be formed at the flange part  32 . 
     An effect of the cylindrical battery  10  will be explained. According to the cylindrical battery  10 , the cylindrical battery  10  alone can extinguish the ignition at the time of abnormality. 
     In the cylindrical battery  10 , there are cases of resulting in the ignition at the time of abnormality occurrence. In such ignition of the cylindrical battery  10 , the flames jet out from an exhaust part formed by breakage of the upper vent member  26  of the cylindrical battery  10 . In the cap  30  of the cylindrical battery  10 , only the plurality of exhaust ports  33 H and  34 H are formed respectively at the top surface part  33  and the sidewall part  34  of the projection  31 , and an opening of a size to allow the flames to jet is not provided compared to a conventional cap for which the exhaust ports are formed large at the sidewall part. Therefore, the jetting of the flames can be suppressed by shutting off the flames by the top surface part  33  and the sidewall part  34 . 
     In addition, in the cap  30  of the cylindrical battery  10  of the present embodiment, the temperature of the flames is lowered by absorbing the heat from the jetted flames by the top surface part  33  and the sidewall part  34  of the projection  31 , and the jetting of the flames can be suppressed. 
     Since the cylindrical battery  10  alone extinguishes the ignition at the time of abnormality, it is not needed to dispose fire extinguishing parts as separate parts in a battery pack for which the plurality of cylindrical batteries  10  are packaged as before. Therefore, there is no cost increase for increase of the number of parts of the battery pack. In addition, it is also possible to miniaturize the cylindrical battery or the battery pack. 
     Further, in the cap  30  of the cylindrical battery  10  of the present embodiment, the plurality of exhaust ports  33 H and  34 H are formed respectively at the top surface part  33  and the sidewall part  34  of the projection  31  so that the gas generated inside the battery can be released to the outside. In the cap  30  of the cylindrical battery  10  of the present embodiment, the plurality of exhaust ports  33 H are formed also at the top surface part  33  of the projection  31 , and the gas is easily released to the outside compared to a conventional cap for which the exhaust ports are formed only at the sidewall part. 
     Using  FIG.  4   , the cap  30  which is another example of the present embodiment will be explained.  FIG.  4    is a perspective view illustrating the cap  30 . 
     As illustrated in  FIG.  4   , the cap  30  is configured similarly to the above-described cap  30  illustrated in  FIG.  3   , except that the diameter and the number of the plurality of exhaust ports  33 H formed at the top surface part  33  are different. In the example illustrated in  FIG.  4   , the plurality of exhaust ports  33 H are annularly formed only for two rounds at roughly equal intervals along the circumferential direction. In the example illustrated in  FIG.  4   , the exhaust ports  33 H have the diameter of 0.5 mm, the sum total of the opening area of the exhaust ports  33 H is 5 mm 2 , and the total aperture ratio of the exhaust ports  33 H at the top surface part  33  is 13%. Even the cap  30  illustrated in  FIG.  4    demonstrates the effect similar to that of the above-described cap  30  illustrated in  FIG.  3   . 
     Note that the present invention is not limited by the embodiment described above and the modifications and it is needless to say that various changes and improvements are possible within a range of matters described in claims of the present application. 
     REFERENCE SIGNS LIST 
     
         
           10  cylindrical battery 
           11  positive electrode 
           12  negative electrode 
           13  separator 
           14  electrode assembly 
           16  exterior can 
           17  sealing assembly 
           18 ,  19  insulating plate 
           20  positive electrode lead 
           21  negative electrode lead 
           22  grooved part 
           23  internal terminal plate 
           23 A recess 
           23 B outer peripheral part 
           23 H exhaust port 
           24  lower vent member 
           25  insulating member 
           26  upper vent member 
           27  gasket 
           30  cap 
           31  projection 
           32  flange part 
           33  top surface part 
           33 H exhaust port 
           34  sidewall part 
           34 H exhaust port