Flat battery and method for manufacturing flat battery

Abstract

The present invention provides: a flat battery capable of achieving high capacity; and a method for manufacturing a flat battery. A flat battery 1 comprises: an outer can 10; a sealing can 20; and an electrode body 40 and an electrode body 50 which are housed between the outer can 10 and the sealing can 20. The electrode body 40 and the electrode body 50 respectively include: electrode-body bodies 41 and 51; positive electrode connection parts 42 and 52; and negative electrode connection parts 43 and 53. In a plan view, the positive electrode connection part 42 and the positive electrode connection part 52 are separated from each other, and the negative electrode connection part 43 and the negative electrode connection part 53 are separated from each other. Due to this configuration, when the positive electrode connection parts 42 and 52 and the negative electrode connection parts 43 and 53 are bent, the thicknesses of the positive electrode connection parts 42 and 52 and the thicknesses of the negative electrode connection parts 43 and 53 can be reduced, and the area of the positive electrode can be increased by a margin in the lateral space of the electrode body 40 and the electrode body 50.

Description

Flat battery and method for manufacturing flat battery

[0001] The present invention relates to a flat battery such as a coin battery and a method for manufacturing a flat battery.

[0002] A flat battery is known that includes a cylindrical outer can with a bottom, a cylindrical outer can with a bottom and a sealed can that is disposed in an inverted dish shape relative to the outer can so as to form a space between the outer can and the sealed can, and an electrode assembly disposed between the outer can and the sealed can. In such a flat battery, as disclosed in Patent Document 1, for example, an electrode assembly formed by alternately stacking multiple positive electrodes and multiple negative electrodes is housed in the space formed by the outer can and the sealed can.

[0003] Japanese Patent Laid-Open Publication No. 2013-187182 (Patent Document 1) discloses a flat battery having an electrode assembly in which multiple positive electrodes and negative electrodes are stacked. Each positive electrode has a positive electrode body and a positive electrode lead extending outward from the positive electrode body. Each negative electrode has a negative electrode body and a negative electrode lead extending outward from the negative electrode body in a direction different from that of the positive electrode lead. The positive electrode leads are stacked and bundled together and bent in the stacking direction of the electrode assembly. The negative electrode leads are stacked and bundled together and bent in the stacking direction of the electrode assembly.

[0004] JP 2013-187182 A

[0005] However, in the flat battery of Patent Document 1, as the number of stacked positive electrode bodies and negative electrode bodies increases, the thickness of the stacked and bundled positive electrode leads and negative electrode leads increases, which increases the proportion of the internal space of the flat battery occupied by the positive electrode leads and negative electrode leads, which hinders the flat battery from achieving a high capacity.

[0006] Therefore, an object of the present disclosure is to provide a flat battery that can achieve a high capacity and a method for manufacturing a flat battery.

[0007] In order to solve the above-mentioned problems, the flat battery of the present disclosure takes the following solution. That is, the flat battery of the present disclosure includes an outer can, a sealed can, a first electrode assembly housed between the outer can and the sealed can, and a second electrode assembly stacked on the first electrode assembly. The first electrode assembly has a first electrode assembly main body formed by alternately stacking a plurality of first positive electrodes and first negative electrodes, a positive electrode connection part formed by bundling together first positive electrode leads extending outward from each of the first positive electrodes, and a first negative electrode connection part formed by bundling together first negative electrode leads extending outward from each of the first negative electrodes in a direction different from that of the first positive electrode leads. The second electrode body has a second electrode body main body formed by alternately stacking a plurality of second positive electrodes and second negative electrodes, a second positive electrode connection portion formed by bundling together second positive electrode leads extending outward from each of the second positive electrodes, and a second negative electrode connection portion formed by bundling together second negative electrode leads extending outward from each of the second negative electrodes in a direction different from that of the second positive electrode leads. At least one of the first positive electrode connection portion and the second positive electrode connection portion and the first negative electrode connection portion and the second negative electrode connection portion is bent in the stacking direction of the first electrode body and the second electrode body so as to be separated from each other in a plan view.

[0008] According to the flat battery and the method for manufacturing a flat battery of the present disclosure, it is possible to increase the capacity of the flat battery.

[0009] Fig. 1 is a cross-sectional view of a flat battery according to a first embodiment of the present disclosure. Fig. 2 is a plan view of the positive electrode and positive electrode lead shown in Fig. 1. Fig. 3 is a plan view of the negative electrode and negative electrode lead shown in Fig. 1. Fig. 4 is a perspective view of the first electrode body and second electrode body shown in Fig. 1. Fig. 5 is a perspective view of the first electrode body and second electrode body of a flat battery according to a second embodiment of the present disclosure. Fig. 6 is a plan view showing the dimensions of a positive electrode according to an example. Fig. 7 is a flowchart showing a method for manufacturing a flat battery according to the present disclosure.

[0010] (Configuration 1) A flat battery according to an embodiment of the present disclosure includes an outer can, a sealed can, a first electrode assembly housed between the outer can and the sealed can, and a second electrode assembly stacked on the first electrode assembly. The first electrode assembly has a first electrode assembly main body formed by alternately stacking a plurality of first positive electrodes and first negative electrodes, a positive electrode connection part formed by bundling together first positive electrode leads extending outward from each of the first positive electrodes, and a first negative electrode connection part formed by bundling together first negative electrode leads extending outward from each of the first negative electrodes in a direction different from that of the first positive electrode leads. The second electrode body has a second electrode body main body formed by alternately stacking a plurality of second positive electrodes and second negative electrodes, a second positive electrode connection portion formed by bundling together second positive electrode leads extending outward from each of the second positive electrodes, and a second negative electrode connection portion formed by bundling together second negative electrode leads extending outward from each of the second negative electrodes in a direction different from that of the second positive electrode leads. At least one of the first positive electrode connection portion and the second positive electrode connection portion and the first negative electrode connection portion and the second negative electrode connection portion is bent in the stacking direction of the first electrode body and the second electrode body so as to be separated from each other in a plan view.

[0011] As a result, compared to simply stacking and bundling the positive and negative electrode leads in the internal space between the outer can and the sealed can, by bundling the positive and negative electrode leads in a dispersed manner and bending them so that they are spaced apart from each other in a plan view, it is possible to ensure space on the sides of the first and second electrode bodies and increase the area of ​​the first and second electrode body main bodies, thereby achieving a high capacity flat battery.

[0012] (Configuration 2) In the flat battery of Configuration 1, the first positive electrode connecting portion and the second positive electrode connecting portion may be bent in the stacking direction of the first electrode body and the second electrode body so as to be spaced apart from each other in a plan view, thereby more effectively increasing the capacity of the flat battery.

[0013] (Configuration 3) In the flat battery of Configuration 1, at least one of the first positive electrode connection portion and the second positive electrode connection portion and the first negative electrode connection portion and the second negative electrode connection portion may be spaced apart from each other in a plan view when the first electrode body is rotated circumferentially relative to the second electrode body, thereby efficiently increasing the capacity of the flat battery.

[0014] (Configuration 4) In the flat battery of Configuration 1, at least one of the first positive electrode connection portion and the second positive electrode connection portion, and the first negative electrode connection portion and the second negative electrode connection portion may be spaced apart from each other in plan view by being arranged so that the positions at which they extend outward from the first electrode body and the second electrode body are different from each other in plan view, thereby efficiently increasing the capacity of the flat battery.

[0015] (Configuration 5) In the flat battery of any one of Configurations 1 to 4, particularly in the flat battery of Configuration 3, the difference between the number of the plurality of first positive electrodes and the number of the plurality of second positive electrodes may be one or less. The difference between the number of the plurality of first negative electrodes and the number of the plurality of second negative electrodes may be one or less. The first electrode body may have a structure common to that of the second electrode body, except for the difference in the number of the first positive electrodes and the second positive electrodes and the difference in the number of the first negative electrodes and the second negative electrodes. As a result, for example, by rotating the first electrode body circumferentially relative to the second electrode body, at least one of the first positive electrode connection portion and the second positive electrode connection portion, and the first negative electrode connection portion and the second negative electrode connection portion, can be spaced apart from each other in a planar view, thereby achieving a high capacity flat battery.

[0016] (Configuration 6) In the flat battery of any one of Configurations 1 to 5, particularly in the flat battery of Configuration 4, the first electrode body may be formed with either a first positive electrode or a first negative electrode disposed on the outermost layer facing the second electrode body. The second electrode body may be formed with the other of a second positive electrode or a second negative electrode disposed on the outermost layer facing the first electrode body.

[0017] (Configuration 7) In the flat battery of any one of Configurations 1 to 6, the outer can may have an outer diameter of 10 mm or less. The flat battery of the present disclosure can be particularly suitably used in relatively small flat batteries, particularly those having an outer diameter of 10 mm or less.

[0018] (Configuration 8) In the method for manufacturing a flat battery of Configuration 1, the outer can may have a bottom and a cylindrical peripheral wall extending continuously from the bottom. The method for manufacturing a flat battery may include the steps of accommodating a first electrode body and a second electrode body inside the outer can, and closing the opening of the outer can with a sealing can to seal the internal space between the outer can and the sealing can. The first electrode body and the second electrode body may be stacked and accommodated inside the outer can such that at least one of the first positive electrode connection portion of the first electrode body and the second positive electrode connection portion of the second electrode body, and the first negative electrode connection portion of the first electrode body and the second negative electrode connection portion of the second electrode body, is spaced apart from each other in a plan view. This allows for a flat battery with a high capacity to be obtained.

[0019] (Configuration 9) In the method for manufacturing a flat battery of Configuration 8, the difference between the number of the plurality of first positive electrodes and the number of the plurality of second positive electrodes may be one or less. The difference between the number of the plurality of first negative electrodes and the number of the plurality of second negative electrodes may be one or less. The first electrode body may have a structure common to that of the second electrode body, except for the difference in the number of the first positive electrodes and the second positive electrodes and the difference in the number of the first negative electrodes and the second negative electrodes. The first electrode body and the second electrode body may be rotated relative to each other in a circumferential direction, so that at least one of the first positive electrode connection portion and the second positive electrode connection portion, and the first negative electrode connection portion and the second negative electrode connection portion, are separated from each other in a plan view, and the first electrode body and the second electrode body may be housed inside an outer can. This allows for a flat battery that can achieve high capacity even when the first electrode body and the second electrode body have a common structure.

[0020] (Configuration 10) In the method for manufacturing a flat battery of Configuration 8, the first electrode body may be formed by disposing one of the polarities of the first positive electrode and the first negative electrode in the outermost layer facing the second electrode body. The second electrode body may be formed by disposing the other polarity of the second positive electrode and the second negative electrode in the outermost layer facing the first electrode body. The first electrode body and the second electrode body may be stacked and housed inside an outer can such that the first positive electrode connection portion, the second positive electrode connection portion, and the first negative electrode connection portion, the second negative electrode connection portion, and the first negative electrode connection portion are spaced apart from each other in a plan view. This allows for a flat battery with a high capacity to be obtained.

[0021] First Embodiment A flat battery 1 according to a first embodiment of the present disclosure will be specifically described below with reference to Figures 1 to 4. Note that identical or corresponding components in the figures are designated by the same reference numerals, and the same description will not be repeated. Note that, to facilitate understanding of the description, the drawings referred to below show simplified or schematic configurations, and some components are omitted.

[0022] As shown in Fig. 1, the flat battery 1 includes a cylindrical outer can 10 with a bottom, a sealing can 20 that covers the opening of the outer can 10, a gasket 30 that is disposed between the outer periphery of the outer can 10 and the outer periphery of the sealing can 20, an electrode assembly 40 that is housed in the space formed between the outer can 10 and the sealing can 20, and an electrode assembly 50 that is stacked on the electrode assembly 40. Therefore, by combining the outer can 10 and the sealing can 20, the flat battery 1 has a flat coin shape as a whole. In other words, the outer can 10 and the sealing can 20 form a case with an internal space. In addition to the electrode assembly 40 and the electrode assembly 50, a nonaqueous electrolyte (not shown) is also enclosed in the case space.

[0023] The outer can 10 is made of a metal material such as stainless steel and is formed into a cylindrical shape with a bottom by press molding. The outer can 10 has a circular bottom 11 and a cylindrical peripheral wall 12 formed on the outer periphery of the bottom 11 and continuous with the bottom 11. The peripheral wall 12 extends substantially perpendicularly from the outer peripheral edge of the bottom 11 in a vertical cross-sectional view (as shown in FIG. 1 ). As described below, the outer can 10 is crimped to the sealing can 20 with a gasket 30 sandwiched between the outer can 10 and the sealing can 20, with the open end of the peripheral wall 12 folded inward. The outer can 10 has an outer diameter of 10 mm or less. The present disclosure can effectively increase the capacity of a relatively small, flat-type battery 1.

[0024] The sealing can 20 is made of a metal material such as stainless steel and is formed into a cylindrical shape with a bottom by press molding. The sealing can 20 has a cylindrical peripheral wall portion 22 that is smaller in outer diameter than the peripheral wall portion 12 of the outer can 10, and a circular flat portion 21 that closes one opening of the peripheral wall portion 22. The peripheral wall portion 22 is provided so as to extend substantially perpendicular to the flat portion 21 in a vertical cross-sectional view.

[0025] The peripheral wall 22 of the sealable can 20 is formed with an expanded diameter portion 22b whose diameter is stepped larger than that of the base end 22a on the flat portion 21 side. That is, the peripheral wall 22 is formed with a step 22c between the base end 22a and the expanded diameter portion 22b. As shown in FIG. 1 , the opening end side of the peripheral wall 12 of the outer can 10 is bent and crimped relative to the step 22c. That is, the opening end side of the peripheral wall 12 of the outer can 10 is fitted into the step 22c of the sealable can 20.

[0026] The gasket 30 is made of polypropylene (PP). The gasket 30 is disposed between the peripheral wall 22 of the sealing can 20 and the peripheral wall 12 of the outer can 10 so as to be sandwiched between them. The material of the gasket 30 is not limited to PP, and may be a resin composition containing an olefin-based elastomer in polyphenylene sulfide (PPS), polytetrafluoroethylene (PFA), polyamide-based resin, or the like.

[0027] The electrode body 40 has an electrode body main body 41 , a positive electrode connecting portion 42 , and a negative electrode connecting portion 43 .

[0028] The electrode body 41 has a substantially disc-shaped positive electrode 411 and a substantially disc-shaped negative electrode 412 housed in a bag-shaped separator 44. However, the separator 44 is omitted from Fig. 4. The positive electrodes 411 and negative electrodes 412 are stacked in multiple layers so that they are alternately arranged in the thickness direction. This gives the electrode body 40 an overall cylindrical shape.

[0029] Although not shown, the positive electrode 411 is formed by disposing positive electrode active material layers containing a positive electrode active material such as lithium cobalt oxide on both sides of a positive electrode current collector made of a metal foil such as aluminum. As shown in FIG. 2 , the positive electrode 411 has a circular shape with a cutout. That is, the positive electrode 411 has a cutout 411a and a cutout 411b so that opposing portions are parallel to each other in a plan view. The positive electrode lead 421 extends outward from the positive electrode current collector near the center of the cutout 411a. The positive electrode connection 42 is formed by bundling the positive electrode leads 421 extending outward from the multiple positive electrodes 411 while bending them. The positive electrode connection 42 is connected to a positive electrode connection 52, which will be described later. The positive electrode connection 52 is connected to the positive electrode foil 46 via an insulating sheet 47, which will be described later and which is disposed between the electrode assembly 50 and the bottom 11 of the outer can 10. The positive electrode foil 46 is in contact with the bottom 11 of the outer can 10. Therefore, in this embodiment, the outer can 10 functions as a positive electrode can. The positive electrode foil 46 is made of a metal such as an aluminum alloy.

[0030] Although not particularly shown, the negative electrode 412 is formed by disposing negative electrode active material layers containing a negative electrode active material such as graphite on both sides of a negative electrode current collector made of a metal foil such as copper. As shown in FIG. 1 , the negative electrode 412 closest to the flat surface 21 of the sealing can 20 has the negative electrode active material, etc., formed only on one side of the negative electrode current collector so that the negative electrode current collector faces the flat surface 21. Furthermore, the negative electrode 412 closest to the electrode assembly 50 has the negative electrode active material, etc., formed only on one side of the negative electrode current collector so that the negative electrode current collector faces the electrode assembly 50. Note that, in the negative electrodes 512 of the electrode assembly 50 described below, the negative electrodes 512 closest to the bottom 11 of the outer can 10 and the negative electrodes 512 closest to the electrode assembly 40 also have the negative electrode active material, etc., formed only on one side of the negative electrode current collector so that the respective negative electrode current collectors face the bottom 11 and the electrode assembly 40.

[0031] As shown in FIG. 3 , the negative electrode 412 has a shape in which a portion of a disk is cut out. That is, the negative electrode 412 has a cutout 412a and a cutout 412b so that opposing portions are parallel to each other in a plan view. The negative electrode lead 431 extends outward from the negative electrode current collector described above near the center of the cutout 412a. The negative electrode connection portion 43 is formed by bundling the negative electrode leads 431 extending outward from the multiple negative electrodes 412 while bending them. The negative electrode connection portion 43 is connected to the negative electrode current collector of the negative electrode 412 closest to the flat portion 21 of the sealing can 20 described above. Therefore, in this embodiment, the sealing can 20 functions as a negative electrode can.

[0032] By providing the cutouts 411a and 411b in the positive electrode 411 and the cutouts 412a and 412b in the negative electrode 412 in this way, the positive electrode connecting portion 42 and the negative electrode connecting portion 43 can be compactly arranged to the sides of the electrode body 40 in the internal space of the case. This allows the flat battery 1 to have a high capacity.

[0033] The separator 44 is a bag-shaped member that is circular in plan view and is sized to accommodate the positive electrode 411 and the base end of the positive electrode lead 421 on the positive electrode 411 side. The separator 44 is made of a microporous thin film made of polyethylene, which has excellent insulating properties. By forming the separator 44 from a microporous thin film in this manner, lithium ions can pass through the separator 44. The separator 44 is formed by sandwiching the positive electrode 411 and a portion of the positive electrode lead 421 closer to the positive electrode 411 between two rectangular microporous thin film sheets, bonding the overlapping portions of the two sheets, i.e., the outer portion of the peripheral edge of the positive electrode 411 and the outer portion of a portion of the positive electrode lead 421, by heat welding or the like, and punching out the bonded portion along the outer shapes of the positive electrode 411 and the positive electrode lead 421.

[0034] 1 and 4 , the positive electrode lead 421 and the negative electrode lead 431 extend outward from the positive electrode 411 and the negative electrode 412 in different directions. That is, the positive electrode lead 421 and the negative electrode lead 431 are stacked so as to extend on opposite sides of the positive electrode 411 and the negative electrode 412.

[0035] As shown in FIGS. 1 and 4 , the electrode body 50 has an electrode body main body 51 , a positive electrode connecting portion 52 , and a negative electrode connecting portion 53 .

[0036] The electrode body 51 has a substantially disc-shaped positive electrode 511 and a substantially disc-shaped negative electrode 512 housed in a bag-shaped separator 54. The positive electrodes 511 and negative electrodes 512 are stacked in multiple layers so that they are alternately arranged in the thickness direction. This gives the electrode body 50 an overall cylindrical shape.

[0037] The difference between the number of stacked positive electrodes 411 and the number of stacked positive electrodes 511 can be 1 or less. The difference between the number of stacked negative electrodes 412 and the number of stacked negative electrodes 512 can be 1 or less. That is, in the electrode body main body 41 and the electrode body main body 51, the number of stacked positive electrodes 411 and negative electrodes 412 can be the same as the number of stacked positive electrodes 511 and negative electrodes 512, or the difference in the number of stacked electrodes can be 1.

[0038] The electrode assembly 50 may have a structure common to the electrode assembly 40, except for the difference in the number of stacked positive electrodes 411 (negative electrodes 412) and positive electrodes 511 (negative electrodes 512) described above. Here, the electrode assembly 40 and the electrode assembly 50 are assumed to have a common structure, and a detailed description thereof will be omitted. In the present disclosure, "the electrode assembly 40 and the electrode assembly 50 have a common structure" more specifically means that all or at least one of the following elements are the same or substantially the same: The respective elements are "the planar shape of the positive electrode 411 and the positive electrode 511," "the planar shape of the negative electrode 412 and the negative electrode 512," "the notch 411a of the positive electrode 411 and the notch shape of the notch of the positive electrode 511 corresponding to the notch 411a," "the notch 411b of the positive electrode 411 and the notch shape of the notch of the positive electrode 511 corresponding to the notch 411b," "the notch 412a of the negative electrode 412 and the notch shape of the notch of the negative electrode 512 corresponding to the notch 412a," "the notch 412b of the negative electrode 412 and the notch shape of the notch of the negative electrode 512 corresponding to the notch 412b," "the arrangement position of the positive electrode lead 421 and the positive electrode lead 521 relative to the positive electrode," or "the arrangement position of the negative electrode lead 431 and the negative electrode lead 531 relative to the negative electrode." Note that the fact that each of these elements is "substantially the same" means that manufacturing tolerances for each of these elements are allowed for.

[0039] The positive electrode connection portion 52 is formed by bundling together the positive electrode leads 521 extending outward from the notches in the positive electrode current collectors of the plurality of positive electrodes 511. As described above, the positive electrode connection portion 52 is connected to the positive electrode foil 46. On the other hand, the negative electrode connection portion 53 is formed by bundling together the negative electrode leads 531 extending outward from the notches in the negative electrode current collectors of the plurality of negative electrodes 512. The negative electrode connection portion 53 is connected to the negative electrode current collector of the negative electrode 412 that is closest to the flat portion 21 of the sealing can 20 described above.

[0040] As shown in FIG. 4 , the electrode bodies 40 and 50 are stacked in the internal space of the case. The electrode bodies 40 are stacked in a state rotated horizontally, i.e., circumferentially, with respect to the electrode body 50, with the center of the stacked electrode bodies 40 and 50 in a planar view as axis C. As a result, the positive electrode connection portion 42 of the electrode body 40 and the positive electrode connection portion 52 of the electrode body 50 do not overlap in a planar view, and the negative electrode connection portion 43 of the electrode body 40 and the negative electrode connection portion 53 of the electrode body 50 do not overlap in a planar view. That is, in a planar view, the positive electrode connection portion 42 and the positive electrode connection portion 52 are spaced apart, and the negative electrode connection portion 43 and the negative electrode connection portion 53 are spaced apart. The rotation angle θ of the electrode body 40 with respect to the electrode body 50 is, for example, 40°. However, the rotation angle θ of the electrode body 40 is not limited to this and may be changed as appropriate depending on the widths, etc., of the positive electrode connection portions 42 and 52, and the negative electrode connection portions 43 and 53 in a plan view so that they do not overlap each other in a plan view, and may be changed as appropriate depending on the widths, etc., of the positive electrode lead 421, the positive electrode lead 521, the negative electrode lead 431, and the negative electrode lead 531 in a plan view. Note that, as shown in Fig. 4 , in this embodiment, the positive electrode connection portion 42, the positive electrode connection portion 52, the negative electrode connection portion 43, and the negative electrode connection portion 53 extend outward in an X-shape so as to be spaced apart from each other in a plan view, but the electrode bodies 40 and 50 may be rotated relatively in the circumferential direction so that either the positive electrode connection portions 42 and 52 or the negative electrode connection portions 43 and 53 are bundled together and the other is spaced apart from each other, thereby extending outward in a Y-shape in a plan view. Furthermore, in the present disclosure, "a state in which the electrode body 40 is rotated circumferentially relative to the electrode body 50" means that the electrode body 40 is rotated relative to the electrode body 50 so that the above-mentioned rotation angle θ ultimately becomes a predetermined angle, and does not limit the method of arranging the electrode body 40 and the electrode body 50 relative to each other when stacked to a method of rotating them circumferentially.

[0041] In this way, by stacking the electrode bodies 40 and 50 so that the positive electrode connection portion 42 and the positive electrode connection portion 52 are spaced apart and the negative electrode connection portion 43 and the negative electrode connection portion 53 are spaced apart in a plan view, it is possible to reduce the thicknesses of the positive electrode connection portion 42 formed by stacking multiple positive electrode leads 421, the positive electrode connection portion 52 formed by stacking multiple positive electrode leads 521, the negative electrode connection portion 43 formed by stacking multiple negative electrode leads 431, and the negative electrode connection portion 53 formed by stacking multiple negative electrode leads 531. This creates extra space on the sides of the electrode bodies 40 and 50 in the internal space of the case, thereby increasing the area of ​​the positive electrode 411, the negative electrode 412, the positive electrode 511, and the negative electrode 512 in a plan view. As a result, the capacity of the flat battery 1 can be increased. In particular, in the embodiment, even if the electrode body 40 and the electrode body 50 have the same structure, the electrode body 40 can be rotated circumferentially relative to the electrode body 50, thereby more efficiently increasing the capacity of the flat battery.

[0042] In this embodiment, two electrode bodies, the electrode body 40 and the electrode body 50, are stacked, but three or more electrode bodies may be stacked. When three or more electrode bodies are stacked, as long as the positive electrode connection portion and the negative electrode connection portion of at least two of the electrode bodies are spaced apart in a plan view, the capacity of the flat battery 1 described above can be increased. Note that, for example, even when three electrode bodies are stacked with another electrode body interposed between the electrode body 40 and the electrode body 50, the electrode body 40 and the electrode body 50 are defined as being stacked in the present disclosure.

[0043] Furthermore, if at least either the positive electrode connection parts 42 and 52 or the negative electrode connection parts 43 and 53 are spaced apart in a plan view, it is possible to increase the capacity of the flat battery 1. However, since the positive electrode connection parts 42 and 52 are typically thicker than the negative electrode connection parts 43 and 53, it is more effective to space the positive electrode connection parts 42 and 52 apart in a plan view to increase the capacity of the flat battery 1.

[0044] Second Embodiment Next, a flat battery 1 according to a second embodiment will be described in detail using Figure 5. Descriptions of the same components as those in the flat battery 1 of the first embodiment will be omitted, and only components different from those in the flat battery 1 of the first example will be described. The separator 44 is also omitted from Figure 5.

[0045] In the flat battery 1 of the second embodiment, the electrode body 40 is not stacked on the electrode body 50 when rotated circumferentially relative to the electrode body 50. In the flat battery 1 of the second embodiment, as shown in Fig. 5, the positive electrode connection portion 42 is formed to extend outward and be misaligned with respect to the positive electrode connection portion 52 in a plan view. In this embodiment, each positive electrode lead 421 forming the positive electrode connection portion 42 is formed to extend outward and positioned near one end of the cutout portion 411a in a plan view, and each positive electrode lead 521 forming the positive electrode connection portion 52 is formed to extend outward and positioned near the other end of the cutout portion of the positive electrode 511 of the electrode body 50 in a plan view. Furthermore, each negative electrode lead 431 forming the negative electrode connection portion 43 is positioned toward one end of the cutout portion 412a in a plan view and extends outward, while each negative electrode lead 531 forming the negative electrode connection portion 53 is positioned toward the other end of the cutout portion of the negative electrode 512 of the electrode body 50 in a plan view and extends outward. This allows the positive electrode connection portion 42 and the positive electrode connection portion 52, and the negative electrode connection portion 43 and the negative electrode connection portion 53, to be spaced apart in a plan view. As a result, the thicknesses of the positive electrode connection portion 42 and the positive electrode connection portion 52, and the negative electrode connection portion 43 and the negative electrode connection portion 53 can be reduced, and the areas of the positive electrode 411, the negative electrode 412, the positive electrode 511, and the negative electrode 512 in a plan view can be increased, thereby increasing the capacity of the flat battery 1.

[0046] The electrode body main body 41 (see FIG. 1 , etc.) formed by laminating the positive electrode 411 and the negative electrode 412 may be formed by disposing the negative electrode 412 in the outermost layer (the bottom layer of the electrode body main body 41 in the illustration) facing the electrode body main body 51. The electrode body main body 51 formed by laminating the positive electrode 511 and the negative electrode 512 may be formed by disposing the positive electrode 511 in the outermost layer (the top layer of the electrode body main body 51 in the illustration) facing the electrode body main body 41. The positive electrode 411 may be disposed in the bottom layer of the electrode body main body 41, and the negative electrode 512 may be disposed in the top layer of the electrode body main body 51. That is, the electrode body main body 41 may be formed by disposing one of the polarities of the positive electrode 411 and the negative electrode 412 in the outermost layer facing the electrode body main body 51, and the electrode body main body 51 may be formed by disposing the other polarity of the positive electrode 511 and the negative electrode 512 in the outermost layer facing the electrode body main body 41.

[0047] In the first and second embodiments, the outer can 10 functions as a positive electrode can and the sealing can 20 functions as a negative electrode can, but conversely, the sealing can may be the positive electrode can and the outer can may be the negative electrode can.

[0048] (Flat Battery Manufacturing Method) Next, a method for manufacturing the flat battery 1 of the first and second embodiments will be specifically described using Fig. 7 while referring to Figs. 1 to 6. As shown in Fig. 7, the method for manufacturing the flat battery 1 can include a preparation step S1, an accommodation step S2, and a sealing step S3.

[0049] First, the outer can 10, the sealing can 20, the electrode assembly 40, and the electrode assembly 50 are prepared (preparation step S1). Details of the outer can 10, the sealing can 20, the electrode assembly 40, and the electrode assembly 50 are as described above, and therefore will not be described here.

[0050] Next, the electrode assembly 40 and the electrode assembly 50 are accommodated inside the outer can 10 (accommodating step S2). The electrode assembly 40 and the electrode assembly 50 may be stacked in advance before being accommodated inside the outer can 10. Alternatively, the electrode assembly 40 may be accommodated inside the outer can 10, and then the electrode assembly 50 may be accommodated inside the outer can 10. In other words, the electrode assembly 40 and the electrode assembly 50 may be stacked inside the outer can 10.

[0051] 4 or 5 , the electrode bodies 40 and 50 are stacked such that at least one of the positive electrode connection portion 42 of the electrode body 40 and the positive electrode connection portion 52 of the electrode body 50, and the negative electrode connection portion 43 of the electrode body 40 and the negative electrode connection portion 53 of the electrode body 50, are spaced apart from each other in a planar view, and are housed inside the outer can 10. The method for spacing the positive electrode connection portion 42 and the positive electrode connection portion 52 from each other in a planar view, and the method for spacing the negative electrode connection portion 43 and the negative electrode connection portion 53 from each other in a planar view, are as described for the flat battery of the first or second embodiment described above.

[0052] Finally, the opening of the outer can 10 is closed with the sealing can 20, sealing the internal space between the outer can 10 and the sealing can 20 (sealing step S3). As described above, with the gasket 30 sandwiched between the outer can 10 and the sealing can 20, the opening end side of the peripheral wall portion 12 of the outer can 10 is folded inward and crimped to the sealing can 20. This seals the internal space between the outer can 10 and the sealing can 20; however, the sealing method is not limited to this as long as it can sufficiently seal the internal space between the outer can 10 and the sealing can 20.

[0053] Although the embodiments have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0054] The present invention can contribute to the achievement of Goal 7 "Ensure access to affordable, reliable, sustainable and modern energy for all" and Goal 12 "Ensure sustainable consumption and production patterns" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0055] Flat batteries of the examples and comparative examples shown in Table 1 below were fabricated, and the area of ​​the positive electrode that could be accommodated in a case of the same size and shape for each flat battery was compared to confirm whether the flat batteries of the examples had a higher capacity.

[0056]

[0057] Example: For the flat battery of the example, two electrode bodies were prepared. Each of the two electrode bodies was fabricated by stacking five positive electrodes and six negative electrodes housed in a pouch-shaped separator, as in the flat battery of the first embodiment described above. Each of the five positive electrodes had a positive electrode lead extending outward, and each of the six negative electrodes had a negative electrode lead extending outward. One of the two electrode bodies was rotated 40° circumferentially, and the two electrode bodies were stacked so that the positive electrode leads of one electrode body and the other electrode body did not overlap in a planar view, and the negative electrode leads of one electrode body and the other electrode body did not overlap in a planar view. As described above, the negative electrode located at the outermost position of each electrode body, i.e., the negative electrode closest to the flat portion of the sealed can, the negative electrode closest to the bottom of the outer can, and each negative electrode facing each electrode body had a negative electrode active material provided only on one surface of the negative electrode current collector. The two stacked electrode bodies were housed in a case to produce a flat battery of the example having an outer diameter of 6.8 mm and a height of 4.0 mm. The thickness of the positive electrode connection part where the positive electrode leads of the electrode bodies were bundled and folded was 120 μm, and the thickness of the negative electrode connection part where the negative electrode leads were bundled and folded was 96 μm.

[0058] (Comparative Example) For the flat battery of the comparative example, one electrode assembly was prepared. The electrode assembly was fabricated by stacking 10 positive electrodes and 11 negative electrodes housed in a bag-shaped separator. The negative electrodes closest to the flat surface of the sealed can and the negative electrodes closest to the bottom of the outer can had negative electrode active material provided only on one surface of the negative electrode current collector. The stacked electrode assembly was housed in a case to fabricate a flat battery of the comparative example having an outer diameter of 6.8 mm and a height of 4.0 mm. The thickness of the positive electrode connection portion where the positive electrode leads of the electrode assembly were bundled and folded was 240 μm, and the thickness of the negative electrode connection portion where the negative electrode leads were bundled and folded was 176 μm.

[0059] The thicknesses of the positive electrode connection portion and the negative electrode connection portion of each of the examples and comparative examples were compared. The thickness of the positive electrode connection portion of the example was 120 μm smaller than the thickness of the positive electrode connection portion of the comparative example. Furthermore, the thickness of the negative electrode connection portion of the example was 80 μm smaller than the thickness of the negative electrode connection portion of the comparative example. That is, it was confirmed that, in the flat battery of the example, the thicknesses of the positive electrode connection portion and the negative electrode connection portion, which are folded and accommodated along the sides of the electrode body, are small, and therefore, a large amount of internal space can be secured on the sides of the electrode body within the case to accommodate the electrode body.

[0060] By securing space on the sides of the electrode assembly in this way, the dimensions r1 and r2 of the dimensions R, r1, r2, L1, and L2 of the positive electrode of the example could be increased compared to the comparative example, as shown in Table 1 and Figure 6. This increased the area of ​​the positive electrode in a plan view by 3.6%, resulting in a higher capacity flat battery. Note that in Figure 6, dimension R is the radius of the circular positive electrode 411 excluding the notches 411a and 411b, L2 is the length of the notch 411a through which the positive electrode lead 421 protrudes, L1 is the length of the notch 411b opposite to L2, r2 is the orthogonal length from the center of the circular positive electrode 411 excluding the notches 411a and 411b to L2, and r1 is the orthogonal length from the center of the positive electrode 411 to L1.

[0061] In addition, a flat battery was constructed in which the protruding positions of the positive electrode lead and the negative electrode lead of one electrode body and the other electrode body were offset so that the positive electrode connection portion and the negative electrode connection portion did not overlap, as in the second embodiment, and the results were compared with the comparative example. As a result, similar to the results of the comparison between the example and the comparative example, it was found that the area of ​​the positive electrode in a plan view could be increased by 3.6%, thereby achieving a high capacity flat battery.

[0062] 1: Flat battery, 10: Outer can, 20: Sealing can, 30: Gasket, 40: Electrode body, 41: Electrode body main body, 42: Positive electrode connection part, 43: Negative electrode connection part, 44: Separator, 411: Positive electrode, 412: Negative electrode, 421: Positive electrode lead, 431: Negative electrode lead, 411a: Notch, 411b: Notch, 50: Electrode body, 51: Electrode body main body, 52: Positive electrode connection part, 53: Negative electrode connection part, 511: Positive electrode, 512: Negative electrode, 521: Positive electrode lead, 531: Negative electrode lead

Claims

1. A battery comprising: an exterior can; a sealing can; a first electrode body accommodated between the exterior can and the sealing can; and a second electrode body stacked on the first electrode body, wherein the first electrode body has a first electrode body main body formed by alternately stacking a plurality of first positive electrodes and first negative electrodes, a first positive electrode connection portion formed by bundling together first positive electrode leads extending outward from each of the first positive electrodes, and a first negative electrode connection portion formed by bundling together first negative electrode leads extending outward from each of the first negative electrodes and in a direction different from that of the first positive electrode leads; and the second electrode body has a second electrode body main body formed by alternately stacking a plurality of second positive electrodes and second negative electrodes, a second positive electrode connection portion formed by bundling together second positive electrode leads extending outward from each of the second positive electrodes, and a second negative electrode connection portion formed by bundling together second negative electrode leads extending outward from each of the second negative electrodes and in a direction different from that of the second positive electrode leads; A flat battery, in which at least one of the first positive electrode connection portion and the second positive electrode connection portion, and the first negative electrode connection portion and the second negative electrode connection portion are folded in the stacking direction of the first electrode body and the second electrode body so as to be separated from each other in a planar view.

2. A flat battery as described in claim 1, wherein the first positive electrode connection portion and the second positive electrode connection portion are bent in the stacking direction of the first electrode body and the second electrode body so as to be spaced apart from each other in a plan view.

3. A flat battery as described in claim 1, wherein at least one of the first positive electrode connection portion and the second positive electrode connection portion, and the first negative electrode connection portion and the second negative electrode connection portion are spaced apart from each other in a plan view when the first electrode body is rotated circumferentially relative to the second electrode body.

4. A flat battery as described in claim 1, wherein at least one of the first positive electrode connection portion and the second positive electrode connection portion, and the first negative electrode connection portion and the second negative electrode connection portion are spaced apart from each other in a planar view by being positioned such that the positions at which they extend outward from the first electrode body and the second electrode body are different from each other in a planar view.

5. A flat battery as described in claim 1, wherein the difference between the number of the plurality of first positive electrodes and the number of the plurality of second positive electrodes is one or less, the difference between the number of the plurality of first negative electrodes and the number of the plurality of second negative electrodes is one or less, and the first electrode body has a structure common to that of the second electrode body except for the difference in the number of the first positive electrodes and the second positive electrodes and the difference in the number of the first negative electrodes and the second negative electrodes.

6. A flat battery as described in claim 1, wherein the first electrode body is formed by arranging one of the polarities of the first positive electrode and the first negative electrode on the outermost layer facing the second electrode body, and the second electrode body is formed by arranging the other polarity of the second positive electrode and the second negative electrode on the outermost layer facing the first electrode body.

7. A flat battery according to any one of claims 1 to 6, wherein the outer can has an outer diameter of 10 mm or less.

8. A method for manufacturing a flat battery as described in claim 1, wherein the outer can has a bottom and a cylindrical peripheral wall portion extending continuously from the bottom, the method comprising the steps of: accommodating the first electrode body and the second electrode body inside the outer can; and closing an opening of the outer can with the sealing can to seal an internal space between the outer can and the sealing can, wherein the first electrode body and the second electrode body are stacked such that at least one of the first positive electrode connection portion of the first electrode body and the second positive electrode connection portion of the second electrode body, and the first negative electrode connection portion of the first electrode body and the second negative electrode connection portion of the second electrode body are separated from each other in a plan view, and are accommodated inside the outer can.

9. A method for manufacturing a flat battery as described in claim 8, wherein the difference between the number of the plurality of first positive electrodes and the number of the plurality of second positive electrodes is one or less, and the difference between the number of the plurality of first negative electrodes and the number of the plurality of second negative electrodes is one or less, the first electrode body has a structure common to that of the second electrode body except for the difference in the number of the first positive electrodes and the second positive electrodes and the difference in the number of the first negative electrodes and the second negative electrodes, and the first electrode body and the second electrode body are rotated relative to each other in a circumferential direction, so that at least one of the first positive electrode connection portion and the second positive electrode connection portion, and the first negative electrode connection portion and the second negative electrode connection portion are separated from each other in a planar view, and the flat battery is housed inside the outer can.

10. A method for manufacturing a flat battery as described in claim 8, wherein the first electrode body main body is formed by arranging one of the polarities of the first positive electrode and the first negative electrode on the outermost layer facing the second electrode body main body, and the second electrode body is formed by arranging the other polarity of the second positive electrode and the second negative electrode on the outermost layer facing the first electrode body main body, and the first positive electrode connection portion and the second positive electrode connection portion, and at least one of the first negative electrode connection portion and the second negative electrode connection portion are arranged such that the positions at which they extend outward from the first electrode body main body and the second electrode body main body in a planar view are different from each other, so that the first electrode body and the second electrode body are stacked such that the first positive electrode connection portion and the second positive electrode connection portion, and at least one of the first negative electrode connection portion and the second negative electrode connection portion are spaced apart from each other in a planar view, and the flat battery is contained inside the outer can.

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