Sealing plate for flat battery and flat battery

Abstract

A sealing plate for a flat battery includes a molded body of a metal plate. The molded body includes a circular plate portion, a cylindrical side wall portion extending from a peripheral edge of the circular plate portion, and a folded-back portion. The side wall portion includes a step portion. At the folded-back part, the metal plate is folded back towards the inner side of the cylindrical shape of the side wall part at the end part of the side wall part.

Description

Technical Field

[0001] The present disclosure relates to a sealing plate for a flat battery and a flat battery. Background Art

[0002] Flat batteries are used as power sources for various electronic devices. Regarding the outer package of flat batteries, various solutions have been proposed in the past.

[0003] In FIG. 1 of Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-190758), a flat battery including a sealing can with an open end of a cylindrical portion not folded back is disclosed.

[0004] In Claim 1 of Patent Document 2 (Japanese Patent Application Laid-Open No. 9-283102), it is described that "a coin-shaped battery, a lithium-ion battery includes a sealing plate having a U-shaped folded-back portion at the periphery and a bottomed cylindrical positive electrode case, an insulating gasket is interposed between the positive electrode case and the sealing plate, and the opening of the positive electrode case is riveted to the inside to seal the power generation element. Among them, when the compression ratio of the insulating gasket between the U-shaped folded-back front end portion of the sealing plate and the positive electrode case is maintained at 40 to 60%, the compression ratio of the insulating gasket between the front end portion of the positive electrode case and the sealing plate is maintained at 60 to 80%, and the compression ratio of the insulating gasket between the front end portion of the sealing plate and the positive electrode case is maintained at 50 to 70%". In addition, in FIG. 1 of Patent Document 2, a sealing plate with a periphery folded outward is disclosed.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-190758

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 9-283102 Summary of the Invention

[0009] One aspect of the present disclosure relates to a sealing plate for a flat battery. The sealing plate includes a formed body of a metal plate. The formed body includes: a circular plate portion; a side wall portion having a cylindrical shape extending from a first end connected to the periphery of the circular plate portion to a second end; and a folded-back portion that folds back from a starting point connected to the second end of the side wall portion and extends to the front end. The side wall portion includes a height difference portion. The folded-back portion folds the metal plate back to the inside of the cylindrical shape of the side wall portion at the second end of the side wall portion.

[0010] Another aspect of the present disclosure relates to a flat battery including an outer package, a positive electrode, and a negative electrode disposed inside the outer package. The outer package includes a case, a sealing plate, and a gasket at least partially disposed between the case and the sealing plate. The sealing plate includes a formed body of a metal plate. The formed body includes: a circular plate portion; a first side wall portion having a cylindrical shape extending from a first end connected to the periphery of the circular plate portion to a second end; and a folded-back portion folded back and extending from a starting point connected to the second end of the side wall portion to a front end. The first side wall portion includes a height difference portion. The folded-back portion folds the metal plate toward the inside of the cylindrical shape of the first side wall portion at the second end of the first side wall portion. The case includes a circular plate-shaped bottom portion and a second side wall portion having a cylindrical shape extending from the periphery of the bottom portion. A part of the second side wall portion is bent toward the inside of the cylindrical shape of the second side wall portion so as to cover at least a part of the height difference portion with the gasket interposed therebetween.

[0011] According to the present disclosure, a sealing plate for a flat battery capable of achieving high airtightness between the sealing plate and the case and less occurrence of liquid leakage, and a flat battery using the sealing plate can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1A is a top view schematically showing an example of the sealing plate of Embodiment 1.

[0013] Figure 1B is schematically showing Figure 1A a cross-sectional view taken along line IB-IB of the sealing plate.

[0014] Figure 2A is a cross-sectional view of a metal plate schematically showing one step of a method for manufacturing an example of the sealing plate of Embodiment 1.

[0015] Figure 2B is schematically showing Figure 2A a cross-sectional view of a metal plate showing an example of one step after one step shown in.

[0016] Figure 3A is a top view schematically showing an example of the flat battery of Embodiment 2.

[0017] Figure 3B is schematically showing Figure 3A a cross-sectional view taken along line IIIB-IIIB of the flat battery.

[0018] Figure 4A is a cross-sectional view schematically showing one step of a method for manufacturing an example of the flat battery of Embodiment 2.

[0019] Figure 4BIs schematically shown Figure 4A A cross-sectional view of a flat battery showing an example of a process after the process shown.

[0020] Figure 4C Is schematically shown Figure 4B A cross-sectional view of a flat battery showing an example of a process after the process shown.

[0021] Figure 5 A cross-sectional view schematically showing the structure of an example of an existing flat battery.

[0022] Figure 6 A cross-sectional view schematically showing the structure of another example of an existing flat battery.

[0023] Figure 7 A graph showing the calculation results of the battery capacity of the flat battery according to Embodiment 2. Detailed implementation mode

[0024] Hereinafter, examples will be given to illustrate the embodiments related to the present disclosure, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials are sometimes exemplified, but other numerical values and other materials can also be applied as long as the effects of the present disclosure can be obtained. In this specification, the description of "numerical value A to numerical value B" includes numerical value A and numerical value B, and the statement can be replaced with "numerical value A or more and numerical value B or less". In the following description, when the lower limit and the upper limit of numerical values related to specific physical properties, conditions, etc. are exemplified, as long as the lower limit is not more than the upper limit, any one of the exemplified lower limits can be arbitrarily combined with any one of the exemplified upper limits. In the following description, when examples of components and examples of methods are listed, as long as there is no special description, only one of the listed examples can be used, or multiple of the listed examples can be used in combination.

[0025] (Sealing plate for flat battery)

[0026] The sealing plate according to the present embodiment is a sealing plate for a flat battery. Hereinafter, this sealing plate may sometimes be referred to as "sealing plate (P)". The sealing plate (P) includes a formed body of a metal plate. The formed body includes a circular plate portion, a side wall portion extending from the periphery of the circular plate portion, and a folded-back portion. The side wall portion includes a step portion. In the folded-back portion, the metal plate is folded back to the inside of the side wall portion at the end of the side wall portion. That is, the folded-back portion is formed by folding the metal plate to the inside of the side wall portion at the position that becomes the end of the side wall portion.

[0027] In Figure 5 A structure identical to the structure disclosed in FIG. 1 of Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2012-190758) is schematically shown. Figure 5The exterior body 1 of the flat battery shown includes a case 2, a sealing plate 3, and a gasket 4. Inside the exterior body 1, a positive electrode 5, a negative electrode 6, and a separator 7 are arranged. Figure 5 The end of the sealing plate 3 is not folded back. In this case, the portions of the gasket strongly compressed by the case 2 and the sealing plate 3 are the portions near the shoulder of the step portion of the sealing plate 3 and the portions near the open end of the sealing plate 3, these two places.

[0028] In Figure 6 a structure schematically shown that is the same as the structure disclosed in FIG. 1 of Patent Document 2 (Japanese Patent Laid-Open No. 9-283102) is shown. Figure 6 The exterior body 1 of the flat battery shown includes a case 2, a sealing plate 3, and a gasket 4. Inside the exterior body 1, a positive electrode 5, a negative electrode 6, and a separator 7 are arranged. Figure 6 The end of the sealing plate 3 is folded back outward. In this case, the portions of the gasket strongly compressed by the case 2 and the sealing plate 3 are the portion A near the shoulder of the step portion of the sealing plate 3, the portion B near the front end of the sealing plate 3, and the portion C near the open end of the sealing plate 3, these three places.

[0029] In Figure 6 the structure shown, the volume of the portion where the sealing plate is folded back outward does not contribute to the battery capacity, so the energy density decreases accordingly. In addition, in Figure 5 and Figure 6 the structure shown, since the edge of the sealing plate touches the gasket, especially when burrs or the like are generated at the edge, the gasket is likely to be damaged. Moreover, in Figure 5 the structure shown, the strength of the cylindrical portion of the sealing plate 3 is weak, so the compression rate of the gasket adjacent to this portion cannot be increased, and the sealing effect of this portion is weak. In addition, in Figure 6 the structure shown, if the compression rate of the gasket in the cylindrical portion of the sealing plate 3 is too high, the edge of the sealing plate 3 is likely to damage the gasket. Therefore, the compression rate of the gasket in this portion cannot be increased, and the sealing effect of this portion is weak.

[0030] On the other hand, by using the sealing plate (P), as described later, a high sealing effect can be achieved. Therefore, by using the sealing plate (P), a flat battery with less occurrence of electrolyte leakage and high reliability can be obtained. In particular, by using the sealing plate (P), the occurrence of leakage can be suppressed even in a high-temperature environment. Furthermore, by using the sealing plate (P), a flat battery with less occurrence of leakage and high capacity can be obtained.

[0031] In the step portion, the diameter of the side wall portion changes. In the step portion, the diameter of the side wall portion becomes larger on the side where the length from the circular plate portion (the length along the side wall portion) is long compared to the side where the length from the circular plate portion (the length along the side wall portion) is short.

[0032] The side wall portion generally includes a cylindrical portion (first cylindrical portion) between the starting point of the folded-back portion and the step portion. The side wall portion may also include a second cylindrical portion existing between the step portion and the circular plate portion. The diameter of the first cylindrical portion is larger than the diameter of the second cylindrical portion. The diameter of the first cylindrical portion may be constant or substantially constant although it may gradually change according to the position. The diameter of the second cylindrical portion may also change according to the position. For example, the second cylindrical portion may have a conical shape.

[0033] It may also be that the length L1 from the starting point of the folded-back portion to the front end of the folded-back portion in the direction parallel to the central axis of the formed body of the metal plate and the length L2 from the inner surface of the step portion to the starting point of the folded-back portion in the direction parallel to the central axis satisfy 0.2 < L1 / L2 < 0.8. By satisfying 0.2 < L1 / L2, the folding process becomes easy. By satisfying L1 / L2 < 0.8, it is easy to arrange the mold during the pressing process, so the pressing process becomes easy. L1 / L2 may be 0.3 or more and may be 0.7 or less.

[0034] The material and thickness of the sealing plate are not particularly limited as long as they can be used as the material and thickness of the sealing plate of the flat battery. The sealing plate includes a formed body of a metal plate having conductivity and is generally used as a terminal (for example, a negative terminal). Examples of the metal for the formed body of the metal plate include stainless steel, nickel-plated steel plate, etc. The thickness of the sealing plate may be 0.1 mm or more or 0.2 mm or more, and may also be 0.6 mm or less or 0.4 mm or less.

[0035] The sealing plate may also be composed only of the formed body of the metal plate. The metal plate may include a coating formed on the surface as needed. The coating is not particularly limited, and known coatings can be used.

[0036] When looking down on the sealing plate from the opening end side (the side opposite to the circular plate portion side) of the sealing plate, the folded-back portion may be located outside the circular plate portion. According to this structure, the space inside the outer package can be utilized particularly effectively, and it is particularly easy to achieve high capacity. In addition, the peripheral edge of the circular plate portion (the boundary between the circular plate portion and the side wall portion) is the portion where the flat circular plate portion starts to bend. In addition, when looking down on the sealing plate from the opening end side of the sealing plate, a part of the folded-back portion may also be located inside the peripheral edge of the circular plate portion.

[0037] The radius of curvature R of the metal plate (formed body) at the opening end of the sealing plate may be less than or equal to the thickness TM of the metal plate, or may be larger than the thickness TM. If the metal plate is compressed and flattened at the opening end in order to fold back the metal plate, the radius of curvature R may become less than or equal to the thickness TM of the metal plate. By making the radius of curvature R larger than the thickness TM, it is possible to suppress the force concentration on a part of the gasket at the opening end.

[0038] (Manufacturing Method of Sealing Plate)

[0039] The manufacturing method of the sealing plate (P) is not particularly limited. The sealing plate (P) can be manufactured using known metal processing techniques. An example of the manufacturing method of the sealing plate (P) will be described later.

[0040] (Flat Battery)

[0041] The flat battery according to the present embodiment includes an outer package, a positive electrode, and a negative electrode disposed inside the outer package. Hereinafter, the flat battery according to the present embodiment may sometimes be referred to as a flat battery (B). The outer package includes a case, a sealing plate, and a gasket disposed at least partially between the case and the sealing plate. The sealing plate includes a formed body of a metal plate. The formed body includes a circular plate portion, a first side wall portion extending from the periphery of the circular plate portion, and a folded-back portion. The first side wall portion includes a step portion. In the folded-back portion, the metal plate is folded back toward the inside of the first side wall portion at the end of the first side wall portion. The case includes a circular plate-shaped bottom portion and a second side wall portion extending from the periphery of the bottom portion. A part of the second side wall portion is bent inward so as to cover at least a part of the step portion with the gasket interposed therebetween.

[0042] The sealing plate for the flat battery (B) is the above-described sealing plate (P). Therefore, regarding matters described for the sealing plate (P), repeated descriptions may sometimes be omitted. The above-mentioned "first side wall portion" corresponds to the "side wall portion" in the description of the sealing plate (P). Since the flat battery (B) uses the sealing plate (P), the effects brought by the sealing plate (P) can be obtained.

[0043] As described above, the first side wall portion of the sealing plate (P) generally includes a cylindrical portion existing between the starting point of the folded-back portion and the step portion.

[0044] Alternatively, the gasket may include: a first portion disposed between the open end of the formed body and the bottom of the case; a second portion disposed between the cylindrical portion and the second side wall portion; and a third portion disposed between the shoulder of the step portion and the second side wall portion. The ratio T / Tave of the thickness T at any position of the second portion to the average thickness Tave of the second portion may also be in the range of 0.8 to 1.2. That is, the thickness of the second portion may be substantially constant. T / Tave may be 0.8 or more, or 0.9 or more, and may be 1.2 or less, or 1.1 or less.

[0045] When using the sealing plate (P), by compressing it so that the thickness of the second part is approximately constant, the sealing effect of the second part can be improved. Additionally, the thickness T and the average thickness Tave are the thicknesses in the state of the flat battery (B) respectively. The thickness T can be obtained by cutting the flat battery (B) in the direction along the central axis and measuring the thickness of the gasket of its cross-section. The average thickness Tave can be obtained by measuring the thickness T at 5 arbitrarily selected points in the second part and performing an arithmetic average of the measured thicknesses T of the 5 points. In order to make the thickness T approximately constant, it is preferable that the thickness of the second part before compression (before battery assembly) is approximately constant. For example, the ratio T0 / T0ave of the thickness T0 at any position of the second part before compression to the average thickness T0ave of the second part before compression may also be in the range of 0.8 to 1.2. T0ave can be measured by the same method as Tave.

[0046] The thickness of the gasket of the part compressed between the housing and the sealing plate (P) can be 0.05 mm or more or 0.1 mm or more, and can also be 0.5 mm or less or 0.25 mm or less. The thickness of the gasket can be different according to the position or the same. For example, the thicknesses of the first part, the second part, and the third part can be the same or different. The thickness of the gasket of the compressed part can vary according to the thickness of the gasket before compression and the compression ratio. The compression ratio can vary according to the shape and size of the constituent elements of the exterior body, the shape of the mold used in the riveting process, etc.

[0047] It can also be that the gasket includes: a first part disposed between the open end of the formed body and the bottom of the housing; a second part disposed between the cylindrical part and the second side wall part; and a third part disposed between the shoulder of the step part and the second side wall part. In the flat battery (B), the following conditions (1) to (3) can be satisfied. By satisfying the following conditions (1) to (3), leakage of the electrolyte can be particularly suppressed. (1) The compression ratio of the gasket in the first part is in the range of 30 to 70% (for example, in the range of 40 to 60%). (2) The compression ratio of the gasket in the second part is in the range of 20 to 50% (for example, in the range of 30 to 40%). (3) The compression ratio of the gasket in the third part is in the range of 30 to 70% (for example, in the range of 40 to 60%).

[0048] In the flat battery (B), the gasket can be compressed not only in the first part and the third part but also in the second part. That is, in the flat battery (B), a high sealing effect can also be obtained in the second part. Therefore, leakage of the electrolyte can be particularly suppressed.

[0049] The compression ratio of the gasket can be obtained by measuring the thickness T0 before assembly into the battery and the thickness T1 after assembly into the battery for the part whose compression ratio is to be measured, according to the following formula. Compression ratio (%) = 100×(thickness T0 - thickness T1) / thickness T0

[0050] As described above, the lengths L1 and L2 can satisfy 0.2 < L1 / L2 < 0.8.

[0051] The flat battery (B) is a flat battery with a circular planar shape. Examples of the flat battery (B) include batteries known as button cells and coin cells. The dimensions of the flat battery (B) are not particularly limited. The diameter of the flat battery (B) can be in the range of 10 mm to 40 mm. The diameter of the sealing plate (P) can be selected from a range slightly smaller than the diameter of the flat battery (B). The height of the flat battery (B) can be in the range of 1 mm to 8 mm.

[0052] As long as it is a battery using a sealing plate, the type of the flat battery (B) is not particularly limited. The flat battery (B) can be a primary battery or a secondary battery. Examples of primary batteries include lithium primary batteries, alkaline manganese batteries, silver oxide batteries, and other primary batteries. Examples of secondary batteries include lithium secondary batteries, lithium-ion secondary batteries, nickel-metal hydride secondary batteries, and other secondary batteries.

[0053] Except for using the sealing plate (P), the components of the flat battery (B) are not particularly limited. Components other than the sealing plate (P) can also use known components used in flat batteries. The components of the flat battery (B) are exemplified below. However, the components of the flat battery (B) are not limited to the following examples.

[0054] (Battery elements)

[0055] The flat battery (B) includes a positive electrode and a negative electrode as battery elements. The flat battery (B) may include a separator disposed between the positive electrode and the negative electrode depending on its type. The flat battery (B) may include an electrolyte (electrolyte solution or solid electrolyte) depending on its type. Examples of the electrolyte solution include aqueous solutions and non-aqueous electrolyte solutions. The flat battery (B) is particularly preferably used for a battery containing an electrolyte solution due to the high sealing effect of the outer package.

[0056] Battery elements such as the positive electrode, negative electrode, separator, and electrolyte are selected according to the type of the battery. The positive electrode and the negative electrode can each be granular. Alternatively, the positive electrode and the negative electrode can each include a current collector and a mixture layer disposed on the current collector. The mixture layer contains an active material.

[0057] (Case)

[0058] The housing is not particularly limited, and a known housing used in a flat battery can be used. As the material of the housing, the materials exemplified as the material of the sealing plate (P) can be used. The thickness of the housing (the thickness of the metal plate constituting the housing) can be within the range exemplified as the thickness of the sealing plate (P). The housing generally functions as a terminal (for example, a positive terminal).

[0059] (Gasket)

[0060] The gasket is not particularly limited. As the material of the gasket, the materials of known gaskets used in flat batteries can also be used. Examples of the material of the gasket include polyolefins (such as polypropylene), polyphenylene sulfide (PPS), perfluoroalkoxy alkane (PFA), polyether ether ketone (PEEK), and other resins.

[0061] The shape of the gasket is not particularly limited, and a shape capable of sealing the outer package is selected. The gasket preferably includes at least the above-mentioned first to third parts.

[0062] (Manufacturing method of flat battery (B))

[0063] The manufacturing method of the flat battery (B) is not particularly limited. In addition to using the sealing plate (P), a known manufacturing method of a flat battery can also be used.

[0064] In the manufacturing method of one example, first, battery elements are arranged in the space between the sealing plate (P) and the housing. The battery elements include a positive electrode and a negative electrode, and optionally include a separator and an electrolyte. The sealing plate (P) and the housing are arranged to face each other with the gasket interposed therebetween. Then, by bending the end of the cylindrical portion of the housing inward, the space between the sealing plate (P) and the housing is sealed with the gasket (riveting process). In this way, the flat battery (B) is manufactured.

[0065] Hereinafter, examples of the sealing plate (P) and the flat battery (B) and examples of their manufacturing methods will be specifically described with reference to the drawings. The examples described below can be changed based on the above description. In addition, the matters described below can also be applied to the above-described embodiments.

[0066] (Embodiment 1)

[0067] In Embodiment 1, an example of the sealing plate (P) will be described. In Figure 1A a top view of the sealing plate 10 of Embodiment 1 is shown, and in Figure 1B a cross-sectional view taken along line IB-IB of Figure 1A is shown. Figure 1B The cross-section of Figure 1A, the sealing plate 10 is composed of a formed body 20 of a metal plate. The formed body 20 includes a circular plate portion 21, a side wall portion (first side wall portion) 22 extending from the peripheral edge 21a of the circular plate portion 21, and a folding portion 23. The side wall portion 22 includes a height difference portion 22st. The side wall portion 22 has an end portion 221 connected to the peripheral edge 21a of the circular plate portion 21 and an end portion 222 opposite to the end portion 221. The side wall portion 22 has a cylindrical shape surrounding the central axis 20c and extending from the end portion 221 to the end portion 222. The folding portion 23 is formed by folding the metal plate toward the inside of the cylindrical shape of the side wall portion 22 at the end portion 222 of the side wall portion 22. In Figure 1B , the starting point 23a of the folding portion 23 is indicated by a dotted line. The starting point 23a of the folding portion 23 is connected to the end portion 222 of the side wall portion 22. The folding portion 23 starts to bend from the starting point 23. A part of the folding portion 23 that is farthest from the circular plate portion 21 in the direction of the central axis 20c in the formed body 20 constitutes the opening end portion 20e of the formed body 20. Figure 1B shows an example in which the folding portion 23 is folded to such an extent that the front end 23b of the folding portion 23 contacts the side wall portion 22. That is, in Figure 1B , in the cross-section of the example shown, the folding portion 23 is folded so that the folding portion 23 is substantially parallel to the side wall portion 22. However, the folding portion 23 may also be folded obliquely with respect to the side wall portion 22. That is, the front end of the folding portion 23 may also be separated from the side wall portion 22.

[0068] In the height difference portion 22st, the diameter of the side wall portion 22 changes. In the height difference portion 22st, the diameter of the side wall portion 22 becomes larger on the side where the distance from the circular plate portion 21 (the distance along the side wall portion 22) is long compared to the portion on the side where the distance from the circular plate portion 21 (the distance along the side wall portion 22) is short. In addition, in Figure 1B , an example in which the height difference portion 22st is substantially parallel to the circular plate portion 21 is shown, but it may also be inclined with respect to the circular plate portion 21 in the same manner as the sealing plate 3 shown in Figure 7 .

[0069] In Figure 1B , an example in which the side wall portion 22 includes a first cylindrical portion 22a and a second cylindrical portion 22b is shown. The first cylindrical portion 22a is present between the height difference portion 22st and the starting point 23a of the folding portion 23. The second cylindrical portion 22b is present between the height difference portion 22st and the circular plate portion 21. The first cylindrical portion 22a has a substantially constant diameter as a whole, but the diameter may also change. Similarly, the second cylindrical portion 22b has a substantially constant diameter as a whole, but the diameter may also change. For example, the second cylindrical portion 22b may also have a conical shape. In the Figure 1BIn the cross section, the second cylindrical portion 22b extends substantially perpendicular to the circular plate portion 21. The height difference portion 22st has a shoulder 22sh at the boundary with the first cylindrical portion 22a.

[0070] Figure 1B The length L1 from the starting point 23a of the folding portion 23 to the front end of the folding portion 23 in the direction parallel to the central axis 20c of the formed body 20 is shown. In addition, Figure 1B The length L2 from the inner surface of the height difference portion 22st to the starting point 23a of the folding back portion 23 in the direction parallel to the central axis 20c is shown. L1 / L2 preferably falls within the above range.

[0071] An example of the manufacturing method of the sealing plate 10 (formed body 20) will be described below. First, a circular plate-shaped metal plate is prepared. Then, as Figure 2A shown, the edge of the metal plate is folded inward to obtain the metal plate 20x. The folded portion becomes the folding portion 23. The method of implementing this process is not limited and can be carried out by a known method. For example, this process can also be carried out by a method called hemming bending.

[0072] Next, the metal plate 20x is bent to form the first cylindrical portion 22a, the second cylindrical portion 22b, and the height difference portion 22st. The method of bending is not limited. The bending can be carried out by a single pressing process or by multiple pressing processes.

[0073] In Figure 2B the cross-sectional view, the state of the final stage of the bending process showing an example of using a split mold is schematically shown. Figure 2B It is a state in which the metal plate 20x is arranged on the lower mold 210 and the metal plate 20x is deformed into the formed body 20 by pressing with the upper mold 220.

[0074] Figure 2B The lower mold 210 in the example shown includes three molds 211, 212, and 213. The shape of the pressing surface of each mold is a sector with a central angle of 120°. During the pressing process, as Figure 2B shown, pressing is carried out with a gap between them. The folding portion 23 is folded inward to the formed body 20. If the formed body 20 is separated from the lower mold 210 in the state Figure 2B shown, the folding portion 23 interferes with the lower mold 210. Therefore, after moving the three molds 211 toward the central axis 20c of the formed body 20, the formed body 20 is separated from the lower mold 210. In this way, the formed body 20 (sealing plate 10) can be manufactured.

[0075] (Embodiment 2)

[0076] In Embodiment 2, an example of a flat battery (B) will be described. InFigure 3A The top view of the flat battery 100 according to Embodiment 2 is shown. In Figure 3B Shown Figure 3A A cross-sectional view taken along line IIIB-IIIB. The flat battery 100 includes an outer package 110 and battery elements 140 disposed within the outer package 110. The outer package 110 includes a case 120, a gasket 130, and a sealing plate 10. The sealing plate 10 is the sealing plate (P), and may also be the sealing plate 10 described in Embodiment 1. The case 120 functions as a positive terminal, and the sealing plate 10 functions as a negative terminal.

[0077] The battery elements 140 include a positive electrode 141 and a negative electrode 142. In Embodiment 2, a battery element 140 including an example of a positive electrode 141, a negative electrode 142, and a separator 143 is shown. The positive electrode 141 and the negative electrode 142 are each granular electrodes. The separator 143 is disposed between the positive electrode 141 and the negative electrode 142.

[0078] The case 120 includes a disk-shaped bottom 121 and a side wall portion (second side wall portion) 122 extending from the peripheral edge 121a of the bottom 121. The side wall portion 122 has an end portion 1221 connected to the peripheral edge 121a of the bottom 121 and an end portion 1222 opposite to the end portion 1221. The side wall portion 122 has a cylindrical shape that extends from the end portion 1221 to the end portion 1222 surrounding the central axis 20c. The side wall portion 122 includes a cylindrical portion 122a and a riveting portion 122b. The cylindrical portion 122a is a cylindrical part configured to surround the first cylindrical portion 22a with the gasket 130 interposed therebetween. The riveting portion 122b bends inwardly of the cylindrical shape of the side wall portion 122 so as to cover at least a part (e.g., the shoulder 22sh) of the height difference portion 22st with the gasket 130 interposed therebetween. Thereby, the gasket 130 is fixed, and the outer package 110 is sealed.

[0079] The gasket 130 includes: a first portion 130a disposed between the opening end 20e (the folded-back portion 23) of the molded body 20 and the case 120; a second portion 130b disposed between the first cylindrical portion 22a and the side wall portion 122 (more specifically, the cylindrical portion 122a); and a third portion 130c disposed between the shoulder 22sh of the height difference portion 22st and the side wall portion 122.

[0080] The gasket 130 of the flat battery 100 is compressed not only in the first portion 130a and the third portion 130c but also in the second portion 130b. In addition, the second portion 130b is compressed by the first cylindrical portion 22a and the cylindrical portion 122a with substantially equal pressure. This is different from the case where it is difficult to compress evenly due to the height difference in this portion Figure 6The structures are different. Therefore, in the flat battery 100, the sealing performance between the sealing plate 10 and the housing 120 is high. According to the flat battery 100, leakage of the electrolyte in a high-temperature environment can be suppressed. Furthermore, in the flat battery 100, even if the gasket 130 is thinned, high sealing performance can be maintained. Therefore, the gasket 130 can be thinned to achieve high capacity.

[0081] In the flat battery 100, the folded-back portion 23 is folded back inward. Therefore, damage to the gasket 130 by the edge of the folded-back portion 23 can be suppressed. Thus, leakage of the electrolyte can be particularly suppressed.

[0082] Furthermore, in Figure 6 In the structure shown, by folding the folded-back portion outward, the sealing thickness Z (refer to Figure 3B ) becomes thick. Here, the sealing thickness Z is the distance between the innermost circumference of the first cylindrical portion 22a of the sealing plate 10 and the outermost circumference of the cylindrical portion 122a of the housing 120. On the other hand, in the flat battery 100, since the folded-back portion 23 is folded back inward, the sealing thickness Z can be reduced. When viewing the molded body 20 from above at the opening end portion 20e of the molded body 20, the entire folded-back portion 23 can be arranged outside the circular plate portion 21. For example, the portion of the folded-back portion 23 that overlaps with the first cylindrical portion 22a can be arranged at a position that overlaps with the height difference portion 22st in a top view. Therefore, in the flat battery 100, the volume of the battery element 140 that can be arranged per unit volume of the outer package 110 can be increased. That is, according to the flat battery 100, the battery capacity (energy density) per unit volume can be increased.

[0083] Hereinafter, a manufacturing method of an example of the flat battery 100 will be described. First, the components of the flat battery 100 are prepared. Then, the battery element 140 is arranged in the outer package 110x before the riveting process (assembly process). The outer package 110x in which the battery element is arranged is placed on the first mold 201. Figure 4A An example of the state at this time is shown. In addition, for easy understanding, in Figures 4A to 4C , the illustration of the battery element is omitted. Next, as shown in Figure 4B and Figure 4C , the riveting process is performed using the first mold 201, the second mold 202, and the third mold 203.

[0084] As shown in Figure 4B , the diameter of the space inside the second mold 202 is set such that the second portion 130b of the gasket 130 is compressed by the riveting process. Figure 4C This represents the final stage of the riveting process. In the state of Figure 4C , the gasket 130 is compressed in a wide area. In this way, the flat battery 100 can be manufactured.

[0085] (Supplementary Note)

[0086] Through the above description, the following technologies are disclosed.

[0087] (Technology 1)

[0088] A sealing plate for a flat battery, comprising a formed body of a metal plate, the formed body including a circular plate portion, a side wall portion extending from the periphery of the circular plate portion, and a folded-back portion, the side wall portion including a height difference portion, and in the folded-back portion, the metal plate is folded back to the inside of the side wall portion at the end of the side wall portion.

[0089] (Technology 2)

[0090] The sealing plate according to Technology 1, wherein the side wall portion includes a cylindrical portion existing between the starting point of the folded-back portion and the height difference portion.

[0091] (Technology 3)

[0092] The sealing plate according to Technology 1 or 2, wherein the length L1 from the starting point of the folded-back portion to the front end of the folded-back portion in the direction parallel to the central axis of the formed body and the length L2 from the inner surface of the height difference portion to the starting point of the folded-back portion in the direction parallel to the central axis satisfy 0.2 < L1 / L2 < 0.8.

[0093] (Technology 4)

[0094] A flat battery, comprising an outer package, a positive electrode and a negative electrode disposed inside the outer package, the outer package including a housing, a sealing plate, and a gasket disposed at least partially between the housing and the sealing plate, the sealing plate including a formed body of a metal plate, the formed body including a circular plate portion, a first side wall portion extending from the periphery of the circular plate portion, and a folded-back portion, the first side wall portion including a height difference portion, and in the folded-back portion, the metal plate is folded back to the inside of the first side wall portion at the end of the first side wall portion, the housing including a circular plate-shaped bottom portion and a second side wall portion extending from the periphery of the bottom portion, and a part of the second side wall portion is bent inward so as to cover at least a part of the height difference portion with the gasket interposed therebetween.

[0095] (Technology 5)

[0096] The flat battery according to Technology 4, wherein the first side wall portion includes a cylindrical portion existing between the starting point of the folded-back portion and the height difference portion.

[0097] (Technology 6)

[0098] The flat-shaped battery according to Technique 5, wherein the gasket includes: a first portion disposed between the open end of the formed body and the bottom of the housing; a second portion disposed between the cylindrical portion and the second side wall portion; and a third portion disposed between the shoulder of the height difference portion and the second side wall portion, and the ratio T / Tave of the thickness T at any position of the second portion to the average thickness Tave of the second portion is in the range of 0.8 to 1.2.

[0099] (Technique 7)

[0100] The flat-shaped battery according to Technique 5 or 6, wherein the gasket includes: a first portion disposed between the open end of the formed body and the bottom of the housing; a second portion disposed between the cylindrical portion and the second side wall portion; and a third portion disposed between the shoulder of the height difference portion and the second side wall portion, the compression ratio of the gasket at the first portion is in the range of 30 to 70%, the compression ratio of the gasket at the second portion is in the range of 20 to 50%, and the compression ratio of the gasket at the third portion is in the range of 30 to 70%.

[0101] (Technique 8)

[0102] The flat-shaped battery according to any one of Techniques 4 to 7, wherein the length L1 from the starting point of the folded portion to the front end of the folded portion in the direction parallel to the central axis of the formed body and the length L2 from the inner surface of the height difference portion to the starting point of the folded portion in the direction parallel to the central axis satisfy 0.2 < L1 / L2 < 0.8.

[0103] Examples

[0104] The present disclosure will be further described in detail by way of examples.

[0105] (Experimental Example 1)

[0106] In Experimental Example 1, a plurality of flat-shaped batteries (primary lithium batteries) having different shapes of sealing plates were fabricated and evaluated. In addition, in any of the flat-shaped batteries, the diameter was set to 20 mm and the height was set to 3.2 mm.

[0107] (Fabrication of Battery A1)

[0108] Fabricate a battery A1 having the same structure as the flat-shaped battery 100 shown in Figure 3A and Figure 3B That is, use a sealing plate having the same shape as the sealing plate 10 shown in Figure 3A and Figure 3B to fabricate battery A1.

[0109] The thickness of the gasket before compression (the thickness of the part in contact with the housing) is set to 0.15 mm. The sealing plate is formed of stainless steel (thickness: 0.25 mm). The housing is formed of stainless steel (thickness: 0.25 mm).

[0110] (Manufacture of Battery A2)

[0111] Battery A2 was manufactured under the same conditions as Battery A1, except that the thickness of the gasket before compression (the thickness of the part in contact with the housing) was set to 0.30 mm and the diameter of the sealing plate was accordingly reduced.

[0112] (Manufacture of Battery C1)

[0113] Battery C1 having the same structure as the flat battery shown Figure 5 was manufactured. The same materials as those of Battery A1 were used for the positive electrode, negative electrode, separator, electrolyte, sealing plate, housing, and gasket. The thickness of the gasket before compression between the side wall portion of the housing and the side wall portion of the sealing plate was set to 0.30 mm.

[0114] (Manufacture of Battery C2)

[0115] Battery C2 having the same structure as the flat battery shown Figure 6 was manufactured. The same materials as those of Battery A1 were used for the positive electrode, negative electrode, separator, electrolyte, sealing plate, housing, and gasket. The thickness of the gasket before compression between the side wall portion of the housing and the side wall portion of the sealing plate was set to 0.30 mm.

[0116] (Compression Ratio of Gasket)

[0117] For the gaskets of the above-mentioned Batteries A1, A2, C1, and C2 respectively, the compression ratio inside the battery was measured. The compression ratio was measured at four points: the part adjacent to the shoulder of the height difference portion of the sealing plate (shoulder), the part adjacent to the cylindrical portion of the sealing plate (cylindrical portion), the part adjacent to the open end of the sealing plate (bottom), and the part adjacent to the edge of the sealing plate (edge portion). As described above, the compression ratio was obtained by cutting the battery and measuring the thickness of the cross-section of the gasket.

[0118] (High-Temperature Storage Test)

[0119] Ten of each of the above-mentioned Batteries A1, A2, C1, and C2 were manufactured. Then, these batteries were placed in an environment with a relative humidity of 90% RH and a temperature of 60 °C, and the presence or absence of electrolyte leakage was investigated every certain number of days. Furthermore, the same test was also carried out in an environment with a relative humidity of 90% RH and a temperature of 85 °C.

[0120] The number of batteries with liquid leakage detected through tests is shown in Table 1. The compression ratio of the gasket in each battery is also shown in Table 1. Battery A1 and Battery A2 are flat batteries (B) according to this embodiment that use a sealing plate (P).

[0121] [Table 1]

[0122]

[0123] As shown in Table 1, in Battery A1 and Battery A2, the gasket is compressed in a wide area from the bottom to the shoulder of the cylindrical part. On the other hand, in Battery C1, the gasket is mainly compressed at two positions, the shoulder and the bottom, and in Battery C2, the gasket is mainly compressed at three positions, the shoulder, the bottom, and the edge. The reason why the cylindrical part is not compressed in Battery C1 is that, as described above, the strength of the cylindrical part of the sealing plate in Battery C1 is weak, so it is difficult to compress the gasket adjacent to this part. In addition, the reason why the cylindrical part is not compressed in Battery C2 is that in Battery C2, if the gasket in the cylindrical part of the sealing plate is compressed, the edge of the sealing plate is likely to damage the gasket.

[0124] The results of the high-temperature storage test of the gasket in each battery are shown in Table 2. The number of liquid leakage in Table 2 refers to the number of batteries in which electrolyte leakage has occurred among 10 batteries.

[0125] [Table 2]

[0126]

[0127] As shown in Table 2, no electrolyte filtration occurred in Battery A1 and A2 according to this embodiment. On the other hand, in Battery C1 and C2, the number of batteries with electrolyte leakage increased over time. As shown in Table 2, Battery A1 and A2 according to this embodiment do not have electrolyte leakage even during high-temperature storage, showing high reliability.

[0128] (Experimental Example 2)

[0129] In Experimental Example 2, for Battery A1, C1, and C2 fabricated in Experimental Example 1, the battery capacity (discharge capacity) was calculated respectively when the thickness of the gasket before compression (before battery assembly) was changed. In addition, the diameter of the sealing plate was changed according to the thickness of the gasket. Conditions other than the thickness of the gasket and the diameter of the sealing plate were the same as in Experimental Example 1.

[0130] In Experimental Example 2, first, the sealing thickness Z when using a gasket with a specified thickness was obtained (refer to Figure 3B). Then, based on the sealing thickness Z, the battery capacity is calculated. The diameter and height of the battery are the diameter and height described in Experimental Example 1. Therefore, by changing the sealing thickness Z, the volume of the battery element that can be arranged inside the outer package also changes. Using the volume of the battery element that can be arranged inside the outer package, the volume of the battery element of the reference battery, and the measured value of the battery capacity, the battery capacity of the battery in Experimental Example 2 is calculated.

[0131] The calculation results of the battery capacity are shown in Figure 7 . In Figure 7 , the "gasket thickness" before battery assembly is the thickness at the part (cylindrical part) of the sealing plate adjacent to the cylindrical part (such as the first cylindrical part 22a). In Figure 7 , the "compression ratio" and "thickness" after battery assembly are the compression ratio and thickness at the cylindrical part of the gasket. The "thickness Z" after battery assembly is the sealing thickness Z.

[0132] As Figure 7 shown, under the condition that the thickness of the gasket before battery assembly is the same, the battery capacity of Battery A1 is the highest. As shown in Experimental Example 1, in the case of Battery A1, even if the thickness of the gasket before battery assembly is set to 0.15 mm or less, leakage of the electrolyte can be suppressed. Therefore, further high-capacity of the battery can be achieved. On the other hand, in the case of Batteries C1 and C2, even if the thickness of the gasket before battery assembly is set to 0.30 mm, leakage of the electrolyte cannot be sufficiently suppressed. Therefore, when comparing Battery A1 with Batteries C1 and C2, Battery A1 can achieve a significant increase in capacity. When the suppression effect of electrolyte leakage is equivalent to that of conventional batteries, Battery A1 can achieve a significant increase in capacity.

[0133] Industrial Applicability

[0134] The present disclosure can be applied to a sealing plate and a flat battery.

[0135] Description of Reference Numerals

[0136] 10: Sealing plate

[0137] 20: Formed body

[0138] 20c: Central axis

[0139] 20e: Open end

[0140] 21: Circular plate part

[0141] 22: Side wall part (first side wall part)

[0142] 22sh: Shoulder

[0143] 22st: Level difference part

[0144] 23: Folding-back part

[0145] 23a: Starting point of the folding-back part

[0146] 100: Flat battery

[0147] 110: Outer package

[0148] 120: Housing

[0149] 121: Bottom

[0150] 122: Side wall part (second side wall part)

[0151] 122a: Cylindrical part

[0152] 122b: Riveting part

[0153] 130: Gasket

[0154] 141: Positive electrode

[0155] 142: Negative electrode.

Claims

1. A sealing plate, which is a sealing plate for a flat battery, The sealing plate includes a formed body of a metal plate, The formed body includes: A circular plate portion; A side wall portion having a cylindrical shape extending from a first end connected to the periphery of the circular plate portion to a second end; and A folded-back portion that folds back from a starting point connected to the second end of the side wall portion and extends to the front end, The side wall portion includes a height difference portion, The folded-back portion folds the metal plate back toward the inside of the cylindrical shape of the side wall portion at the second end of the side wall portion.

2. The sealing plate according to claim 1, Wherein, The side wall portion includes a cylindrical portion existing between the starting point of the folded-back portion and the height difference portion.

3. The sealing plate according to claim 1 or 2, Wherein, The length L1 from the starting point of the folded-back portion to the front end of the folded-back portion in the direction parallel to the central axis of the formed body and the length L2 from the inner surface of the height difference portion to the starting point of the folded-back portion in the direction parallel to the central axis satisfy 0.2 < L1 / L2 < 0.

8.

4. A flat battery, which includes an outer package, and a positive electrode and a negative electrode disposed inside the outer package, The outer package includes a housing, a sealing plate, and a gasket at least partially disposed between the housing and the sealing plate, The sealing plate includes a formed body of a metal plate, The formed body includes: A circular plate portion; A first side wall portion having a cylindrical shape extending from a first end connected to the periphery of the circular plate portion to a second end; and A folded-back portion that folds back from a starting point connected to the second end of the side wall portion and extends to the front end, The first side wall portion includes a height difference portion, The folded-back portion folds the metal plate back toward the inside of the cylindrical shape of the first side wall portion at the second end of the first side wall portion, The housing includes: A circular plate-shaped bottom; and A second side wall portion having a cylindrical shape extending from the periphery of the bottom, A part of the second side wall portion bends toward the inside of the cylindrical shape of the second side wall portion so as to cover at least a part of the height difference portion with the gasket interposed therebetween.

5. The flat battery according to claim 4, Wherein, The first side wall portion includes a cylindrical portion existing between the starting point of the folded-back portion and the height difference portion.

6. The flat battery according to claim 5, Wherein, A part of the folded-back portion of the formed body constitutes an open end portion of the formed body, The gasket includes: A first part disposed between the open end portion of the formed body and the bottom of the housing; A second part disposed between the cylindrical portion and the second side wall portion; And A third part disposed between the shoulder of the height difference portion and the second side wall portion, The ratio T / Tave of the thickness T at any position of the second part to the average thickness Tave of the second part is in the range of 0.8 to 1.

2.

7. The flat battery according to claim 5, Wherein, The gasket includes: A first part disposed between the open end portion of the formed body and the bottom of the housing; The second part is disposed between the cylindrical portion and the second side wall portion; and the third part is disposed between the shoulder of the step portion and the second side wall portion, the compression ratio of the gasket at the first part is in the range of 30 to 70%, the compression ratio of the gasket at the second part is in the range of 20 to 50%, the compression ratio of the gasket at the third part is in the range of 30 to 70%.

8. The flat battery according to claim 4 or 5, wherein the length L1 from the starting point of the folded portion to the front end of the folded portion in the direction parallel to the central axis of the molded body and the length L2 from the inner surface of the step portion to the starting point of the folded portion in the direction parallel to the central axis satisfy 0.2 < L1 / L2 < 0.

8.

9. A sealing plate configured for a flat battery, the sealing plate includes a molded body of a metal plate, the molded body includes: a circular plate portion; a first side wall portion having a cylindrical shape extending from a first end connected to the peripheral edge of the circular plate portion to a second end; and a folded portion that folds back from a starting point connected to the second end of the side wall portion and extends to the front end, the first side wall portion includes a step portion, the folded portion folds the metal plate inward of the cylindrical shape of the first side wall portion at the second end of the first side wall portion, the flat battery includes an outer package and a positive electrode and a negative electrode disposed inside the outer package, the outer package includes a housing, the sealing plate, and a gasket at least a part of which is disposed between the housing and the sealing plate, the housing includes: a circular plate-shaped bottom; and a second side wall portion having a cylindrical shape extending from the peripheral edge of the bottom, a part of the second side wall portion is configured to bend inward of the cylindrical shape of the second side wall portion so as to cover at least a part of the step portion of the sealing portion with the gasket interposed therebetween.

10. The sealing plate according to claim 9, wherein the side wall portion includes a cylindrical portion existing between the starting point of the folded portion and the step portion.

11. The sealing plate according to claim 9 or 10, wherein the length L1 from the starting point of the folded portion to the front end of the folded portion in the direction parallel to the central axis of the molded body and the length L2 from the inner surface of the step portion to the starting point of the folded portion in the direction parallel to the central axis satisfy 0.2 < L1 / L2 < 0.8.

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