Battery

Abstract

To provide a battery which is capable of maintaining an airtight state in a case for a long period of time and is resistant to deterioration.SOLUTION: A battery includes: a power storage element 12 including a positive electrode, a negative electrode, and an insulating film that is disposed between the positive electrode and the negative electrode and electrically separates the positive electrode and the negative electrode from each other; and a case 11 that accommodates the power storage element 12 in an airtight state. The case 11 includes: a first member 1 having a bottom section 1a and a cylinder section 1b; a second member 2 having a lid-like section 2a covering an opening in the first member 1, and a circumferential wall section 2b that surrounds the cylinder section 1b from an outer side; and a gasket 3 disposed so as to be continuous between an end face 1c of the first member 1 and the second member 2 and between the cylinder section 1b and the second member 2. Non-contacting sections 41, 42, with which the gasket 3 is not in contact, are provided to one or both of a portion of a first surface 1d of the first member 1 opposing the gasket 3 and a portion of a second surface 2d of the second member 2 opposing the gasket 3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery.

Background Art

[0002] Conventionally, there is a battery in which a power storage element is housed in a case. The inside of the case is sealed using a gasket to be in an airtight state. For example, Patent Document 1 describes a coin-shaped lithium battery in which a negative electrode pellet and a positive electrode pellet made of lithium or a lithium alloy are arranged to face each other through a separator and housed in a battery can. In this coin-shaped lithium battery, at least one of the negative electrode pellet or the positive electrode pellet bulges in a curved shape at the central portion, and the battery can is elastically deformed along the curved surface. Further, Patent Document 1 describes that the negative electrode cap and the positive electrode can constituting the battery can are caulked through an insulating sealing gasket. Further, Patent Document 1 describes a negative electrode cap having a side wall in which the material at the edge is folded back and doubled.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional battery, when the power storage element housed in the case expands or gas is generated from the power storage element, the internal pressure in the case increases and the case may deform. As a result, when a force exceeding the elastic limit is applied to the gasket that maintains the airtight state inside the case, cracks may occur in the gasket. When cracks occur in the gasket, the sealing performance of the gasket deteriorates, making it difficult to maintain the airtight state inside the case, and the battery is likely to deteriorate.

[0005] Therefore, in order to suppress battery degradation, conventional batteries are required to maintain an airtight state inside the case for a long period of time, even if the internal pressure inside the case increases.

[0006] This invention has been made in view of the above circumstances, and aims to provide a battery that is less prone to deterioration and can maintain an airtight state inside the case for a long period of time. [Means for solving the problem]

[0007] [1] A power storage element comprising a positive electrode, a negative electrode, and an insulating film disposed between the positive electrode and the negative electrode to electrically separate the positive electrode and the negative electrode, The case comprises the aforementioned energy storage element in an airtight state, The case comprises a first member having a bottom and a cylindrical portion, A second member having a lid-like portion that covers the opening of the first member and a peripheral wall portion that covers the cylindrical portion from the outside, The gasket is continuously disposed between the end face of the first member and the second member, and between the cylindrical portion and the second member. A battery characterized in that an uncontacted portion is provided on either or both of the first surface of the first member facing the gasket and the second surface of the second member facing the gasket, where the gasket is not in contact.

[0008] [2] The battery according to [1], wherein the uncontact portion is provided on the second surface. [3] The cylindrical portion of the first member is cylindrical, and in the cross-section along the center of the cylindrical portion, The battery according to [2], wherein the ratio of the length of the uncontacted portion provided on the second surface to the length L2 in the longitudinal direction of the cylindrical portion from the outer surface of the lid portion to the end surface of the peripheral wall portion is 20% to 95%.

[0009] [4] The battery according to any one of [1] to [3], wherein the uncontact portion is provided on the first surface. [5] The cylindrical portion of the first member is cylindrical, and in the cross-section along the center of the cylindrical portion, The battery according to [4], wherein the ratio of the length of the uncontacted portion provided on the first surface to the length L1 of the cylindrical portion facing the peripheral wall portion is 40% to 80%.

[0010] [6] The cylindrical portion of the first member is cylindrical, and in the cross-section along the center of the cylindrical portion, A battery according to any one of [1] to [5], having a plurality of the aforementioned uncontacted portions with a length of 10 μm or more. [7] The cylindrical portion of the first member is cylindrical and has a first outer diameter portion, a second outer diameter portion having a longer outer diameter than the first outer diameter portion, and a stepped portion connecting the first outer diameter portion and the second outer diameter portion. The first outer diameter portion is positioned closer to the bottom than the second outer diameter portion. A battery according to any one of [1] to [6], wherein in a cross-section passing through the center of the cylindrical portion, the stepped portion is provided within a range of 1 / 3 of the length L1 of the cylindrical portion facing the peripheral wall, from the center position of the length L1 of the cylindrical portion facing the peripheral wall.

[0011] [8] The cylindrical portion of the first member is cylindrical, and in the cross-section along the center of the cylindrical portion, A battery according to any one of [1] to [7], wherein the length L3 of the gasket in the longitudinal direction of the cylindrical portion is longer than the distance L2 in the longitudinal direction of the cylindrical portion from the outer surface of the lid portion to the end face of the peripheral wall portion. [Effects of the Invention]

[0012] The battery of the present invention has a case that houses an energy storage element in an airtight state, and the case has a first member having a bottom portion and a cylindrical portion, a second member having a lid-like portion that covers the opening of the first member and a peripheral wall portion that covers the cylindrical portion from the outside, and a gasket that is continuously disposed between the end face of the first member and the second member and between the cylindrical portion and the second member, and an uncontacted portion that is not in contact with the gasket is provided on either a part of the first surface of the first member facing the gasket and a part of the second surface of the second member facing the gasket, or both. For this reason, the battery of the present invention can maintain an airtight state inside the case for a long period of time and is less prone to deterioration. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic cross-sectional view showing a battery according to the first embodiment, and is a cross-sectional view of the cut surface along the center of the cylindrical portion 1b of the first member 1 in a plan view. [Figure 2] Figures 2(a) and 2(b) are cross-sectional views illustrating the overall structure of the battery according to the first embodiment. Figure 2(a) is a cross-sectional view taken along line AA' in Figure 2(b). Figure 2(b) is a cross-sectional view of the cross-section along the center of the cylindrical portion 1b of the first member 1 in a plan view. [Figure 3] Figure 3 is a schematic cross-sectional view showing the battery of the second embodiment, and is a cross-sectional view of the cut surface along the center of the cylindrical portion 11b of the first member 1 in a plan view. [Modes for carrying out the invention]

[0014] The battery of the present invention will be described in detail below with reference to the drawings. <First Embodiment> [battery] Figs. 1, 2(a) and 2(b) are schematic cross-sectional views showing the battery of the first embodiment. Figs. 1 and 2(b) are cross-sectional views of a cut surface along the center in plan view of the cylindrical tubular portion 1b of the first member 1. Fig. 2(a) is a cross-sectional view taken along the line A-A' of Fig. 2(b). The battery 10 shown in Figs. 1, 2(a) and 2(b) is a coin-type battery and includes a power storage element 12 and a case 11 that houses the power storage element 12 in an airtight state. The case 11 in the battery 10 of the present embodiment includes a first member 1, a second member 2, and a gasket 3. The inside of the case 11 is sealed by the gasket 3 to be airtight.

[0015] (First member) As shown in Fig. 1, the first member 1 has a bottom portion 1a and a tubular portion 1b that is joined to the edge of the bottom portion 1a and integrated with the bottom portion 1a. The bottom portion 1a is circular in plan view, and the tubular portion 1b is cylindrical (see Figs. 2(a) and 2(b)). As shown in Fig. 1, the tubular portion 1b has a first outer diameter portion 1e, a second outer diameter portion 1f having an outer diameter longer than that of the first outer diameter portion 1e, and a stepped portion 1g that connects the first outer diameter portion 1e and the second outer diameter portion 1f. The first outer diameter portion 1e is disposed at a position closer to the bottom portion 1a than the second outer diameter portion 1f. The first outer diameter portion 1e and the second outer diameter portion 1f extend in a direction substantially perpendicular to the extending direction of the bottom portion 1a as shown in Fig. 1.

[0016] The inner surface side curvature radius r1 and the outer surface side curvature radius r2 of the first member 1 formed by the stepped portion 1g are not particularly limited, but are preferably 50 μm or more, and more preferably 60 μm to 200 μm. When the curvature radius r1 and the curvature radius r2 are both 50 μm or more, it is easy to form an uncontacted portion 41 having a length of 10 μm or more where the first surface 1d and the gasket 3 do not contact in the vicinity of the stepped portion 1g. Further, when the curvature radius r1 and the curvature radius r2 are both 200 μm or less, it is preferable because the difference in the outer diameters between the first outer diameter portion 1e and the second outer diameter portion 1f does not become too large. The inner surface side curvature radius r1 and the outer surface side curvature radius r are the same or different.

[0017] The difference in outer diameter between the first outer diameter portion 1e and the second outer diameter portion 1f (in other words, twice the length of the thickness direction height of the cylindrical portion 1b of the stepped portion 1g) can be, for example, 50 μm to 200 μm, and preferably 60 μm to 100 μm. If the difference in outer diameter between the first outer diameter portion 1e and the second outer diameter portion 1f is 50 μm or more, the height of the stepped portion 1g becomes sufficiently high. As a result, a larger uncontacted portion 41, where the gasket 3 does not make contact, is more easily formed near the bottom 1a side of the stepped portion 1g on the first surface 1d. Furthermore, if the difference in outer diameter between the first outer diameter portion 1e and the second outer diameter portion 1f is 200 μm or less, it becomes easier to ensure airtightness inside the case 11 by the gasket 3 when the battery 10 is completed, resulting in better airtightness inside the case 11.

[0018] In the cross-section along the center of the cylindrical portion 1b of the first member 1, the stepped portion 1g connecting the first outer diameter portion 1e and the second outer diameter portion 1f is provided within a range of 1 / 3 of the length L1 of the cylindrical portion 1b facing the peripheral wall portion 2b, from the center position of the length L1 of the cylindrical portion 1b facing the peripheral wall portion 2b of the second member 2. Therefore, the lengths of the first outer diameter portion 1e and the second outer diameter portion 1f can be sufficiently secured, and when the internal pressure inside the case 11 rises, the stepped portion 1g acts as a fulcrum for deformation, causing the first outer diameter portion 1e and the second outer diameter portion 1f of the cylindrical portion 1b to expand in a curved manner. As a result, when the internal pressure inside the case 11 rises, the space between the first outer diameter portion 1e and the gasket 3, and the space between the second outer diameter portion 1f and the gasket 3, can effectively absorb the forces caused by the deformation of the case 11. Therefore, if the stepped portion 1g is located within a length range of 1 / 3 of the length L1, the gasket 3 can more easily ensure airtightness inside the case 11, resulting in better airtightness inside the case 11.

[0019] Furthermore, if the stepped portion 1g is provided within a length range of 1 / 3 of the length L1, the position of the stepped portion 1g will not be too close to the end face 1c of the first member 1. Therefore, when the internal pressure inside the case 11 rises, the end face 1c of the first member 1 will not act as a fulcrum for deformation, causing the cylindrical portion 1b of the first member 1 to expand in a curved manner, and the force caused by the deformation of the case 11 will not be less effectively absorbed by the space between the first outer diameter portion 1e and the gasket 3. Also, if the stepped portion 1g is provided within a length range of 1 / 3 of the length L1, the position of the stepped portion 1g will not be too close to the bottom portion 1a of the first member 1. Therefore, when the internal pressure inside the case 11 rises, the force caused by the deformation of the case 11 will not be sufficiently absorbed by the space between the first outer diameter portion 1e and the gasket 3 and will reach the second member 2, preventing the second member 2 from deforming.

[0020] As the material for the first member 1, for example, a conductive material such as a foil or plate made of a metal selected from nickel, stainless steel, aluminum, or copper can be used.

[0021] (Second component) As shown in Figure 1, the second member 2 has a lid-like portion 2a that covers the opening of the first member 1 and a peripheral wall portion 2b that covers the cylindrical portion 1b of the first member 1 from the outside. The lid-like portion 2a is positioned substantially parallel to the bottom portion 1a of the first member 1. The peripheral wall portion 2b is connected to the edge of the lid-like portion 2a and is integrated with the lid-like portion 2a. As shown in Figures 2(a) and 2(b), the lid-like portion 2a is a substantially concentric circular shape in plan view, with its center substantially in the same position as the bottom portion 1a of the first member 1. The peripheral wall portion 2b is a cylindrical shape substantially concentric with the cylindrical portion 1b, and the inner diameter of the peripheral wall portion 2b is longer than the outer diameter of the cylindrical portion 1b of the first member 1. The peripheral wall portion 2b has substantially constant inner and outer diameters.

[0022] The length from the inner surface of the lid portion 2a to the end face 2c of the peripheral wall portion 2b is shorter than the length from the outer surface of the bottom portion 1a of the first member 1 to the end face 1c of the cylindrical portion 1b. Therefore, a portion of the cylindrical portion 1b of the first member 1 is exposed to the outer surface of the case 11.

[0023] As the material for the second member 2, for example, a conductive material such as a foil or plate made of a metal selected from nickel, stainless steel, aluminum, or copper can be used. The material of the second member 2 may be the same as or different from the material of the first member 1.

[0024] (gasket) As shown in Figure 1, the gasket 3 is continuously positioned between the end face 1c of the first member 1 and the second member 2, and between the cylindrical portion 1b and the second member 2. As shown in Figure 1, in a cross-section along the center of the cylindrical portion 1b of the first member 1, it is preferable that the length L3 of the gasket 3 in the longitudinal direction of the cylindrical portion 1b is longer than the distance L2 in the longitudinal direction of the cylindrical portion 1b from the outer surface of the lid portion 2a of the second member 2 to the end face 2c of the peripheral wall portion 2b. When the length L3 of the gasket 3 in the longitudinal direction of the cylindrical portion 1b is longer than the above distance L2, the gasket 3 is placed over the entire area between the end face 1c of the first member 1 and the second member 2, and between the cylindrical portion 1b and the second member 2. Therefore, the gasket 3 is placed over the entire area of ​​the intrusion path of moisture attempting to enter the case 11 from the end face 2c of the peripheral wall portion 2b. As a result, it becomes easier to more reliably ensure airtightness inside the case 11 with the gasket 3, and the airtightness inside the case 11 becomes even better.

[0025] As the material for gasket 3, known insulating materials such as acid-modified polyethylene, polypropylene, acid-modified polypropylene, epoxy resin, polyvinylidene fluoride (PVDF), and polyvinylidene chloride (PVDC) can be used.

[0026] (uncontacted part) In the battery 10 of this embodiment, as shown in Figures 1, 2(a), and 2(b), an uncontacted portion 41 is provided on a part of the first surface 1d of the first member 1 that faces the gasket 3 and is not in contact with the gasket 3. The planar shape of the uncontacted portion 41 may be any shape, such as a substantially circular shape or a substantially polygonal shape, and may also be irregular in shape. The number of uncontacted portions 41 may be one or multiple, and it is preferable to provide multiple portions in order to more effectively maintain airtightness inside the case 11. Multiple uncontacted portions 41 may be arranged regularly or irregularly. Multiple uncontacted portions 41 may each have a different planar shape, or some or all of them may have the same planar shape.

[0027] As shown in Figure 1, in the battery 10 of this embodiment, the ratio of the length of the uncontact portion 41 provided on the first surface 1d to the length L1 of the cylindrical portion 1b facing the peripheral wall portion 2b of the second member 2 in a cross-section along the center of the cylindrical portion 1b of the first member 1 is preferably 40% to 80%, and more preferably 40% to 50%. When the ratio of the length of the uncontact portion 41 to the length L1 is 40% or more, it is possible to effectively prevent cracks from occurring in the gasket 3 due to forces caused by deformation of the case 11 of the battery 10. Furthermore, when the ratio of the length of the uncontact portion 41 to the length L1 is 80% or less, the sealing performance of the gasket 3 when the battery 10 is completed is good, and the airtightness inside the case 11 when the battery 10 is completed is better.

[0028] As shown in Figure 1, in the battery 10 of this embodiment, the first member 1 has a stepped portion 1g connecting the first outer diameter portion 1e and the second outer diameter portion 1f. The uncontacted portion 41 provided on the first surface 1d of the first outer diameter portion 1e is generally larger in area than the uncontacted portion 41 provided on the first surface 1d of the second outer diameter portion 1f. This is because the gasket 3 is pressed against the first surface 1d of the second outer diameter portion 1f when the peripheral wall portion 2b of the second member 2 is crimped and joined to the cylindrical portion 1b of the first member 1. Therefore, the larger the proportion of the first outer diameter portion 1e in the cylindrical portion 1b facing the peripheral wall portion 2b of the second member 2, the higher the ratio of the length of the uncontacted portion 41 to the length L1 tends to be.

[0029] As shown in Figures 1, 2(a), and 2(b), in the battery 10 of this embodiment, an uncontacted portion 42 is provided on a part of the second surface 2d of the second member 2 that faces the gasket 3 and is not in contact with the gasket 3. The planar shape of the uncontacted portion 42 may be any shape, such as a substantially circular shape or a substantially polygonal shape, and may also be irregular in shape. The number of uncontacted portions 42 may be one or multiple, and it is preferable to provide multiple portions in order to more effectively maintain airtightness inside the case 11. Multiple uncontacted portions 42 may be arranged regularly or irregularly. Multiple uncontacted portions 42 may each have a different planar shape, or some or all of them may have the same planar shape.

[0030] As shown in Figure 1, in the battery 10 of this embodiment, the ratio of the length of the uncontact portion 42 provided on the second surface 2d to the length L2 in the longitudinal direction of the cylindrical portion 1b from the outer surface of the lid portion 2a of the second member 2 to the end surface 2c of the peripheral wall portion 2b is preferably 20% to 95%, and more preferably 40% to 60%. If the ratio of the length of the uncontact portion 42 to the distance L2 is 20% or more, it is possible to effectively prevent cracks from occurring in the gasket 3 due to forces caused by deformation of the case 11 of the battery 10. Furthermore, if the ratio of the length of the uncontact portion 42 to the distance L2 is 95% or less, the sealing performance of the gasket 3 when the battery 10 is completed will be good, and the airtightness inside the case 11 when the battery 10 is completed will be better.

[0031] As shown in Figure 1, in the battery 10 of this embodiment, it is preferable that a plurality of uncontacted portions 41 and 42 with a length of 10 μm or more are provided on either or both of the first surface 1d and the second surface 2d in the cross-section along the center of the cylindrical portion 1b of the first member 1, and it is more preferable that a plurality of uncontacted portions 41 and 42 with a length of 10 μm or more are provided on both the first surface 1d and the second surface 2d. The uncontacted portions 41 and 42 with a length of 10 μm or more can effectively absorb the force caused by the deformation of the case 11 through the space between the first surface 1d or the second member 2d and the gasket 3. As a result, it is possible to more effectively prevent cracks from occurring in the gasket 3 facing the uncontacted portions 41 and 42 due to the force caused by the deformation of the case 11.

[0032] (Energy storage element) As shown in Figures 1, 2(a), and 2(b), the energy storage element 12 of the battery 10 in this embodiment has a substantially circular shape in plan view, with a diameter smaller than the bottom 1a of the first member 1. The energy storage element 12 has a laminated structure in which a negative electrode having a negative electrode active material layer 61 formed on a negative electrode current collector 6, a positive electrode having a positive electrode active material layer 71 formed on a positive electrode current collector 7, and a separator 5 disposed between the negative electrode active material layer 61 and the positive electrode active material layer 71 are stacked.

[0033] As the negative electrode current collector 6, a known one made of metal foil such as copper foil can be used. As shown in Figures 2(a) and 2(b), the negative electrode current collector 6 is approximately circular in plan view. The negative electrode current collector 6 is electrically connected to the bottom 1a of the first member 1 of the case 11 via a strip-shaped negative electrode lead wire 62 made of metal foil such as copper foil, which is integrated with the edge of the negative electrode current collector 6. As the negative electrode active material layer 61, one can be used that includes a known negative electrode active material such as graphite and a known binder such as polyvinylidene fluoride (PVDF).

[0034] As the positive electrode current collector 7, a known one made of metal foil such as aluminum foil can be used. As shown in Figures 2(a) and 2(b), the positive electrode current collector 7 is approximately circular in plan view, approximately concentric with the negative electrode current collector 6, and has a smaller diameter than the negative electrode current collector 6. The positive electrode current collector 7 is electrically connected to the lid portion 2a of the second member 2 of the case 11 via a strip-shaped positive electrode lead wire 72 made of metal foil such as aluminum foil, which is integrated with the edge of the positive electrode current collector 7. As the positive electrode active material layer 71, a known positive electrode active material such as lithium cobalt oxide, a known binder such as polyvinylidene fluoride (PVDF), and a known conductive additive such as acetylene black can be used.

[0035] The separator 5 electrically separates the positive electrode and the negative electrode. A known insulating film made of resin or the like can be used as the separator 5. As shown in Figures 2(a) and 2(b), the separator 5 is approximately circular in plan view and is approximately concentric with the negative electrode current collector 6, and has a larger diameter than both the negative electrode current collector 6 and the positive electrode current collector 7.

[0036] The energy storage element 12 of the battery 10 shown in Figures 1, 2(a), and 2(b) can be manufactured by conventionally known methods. For example, a positive electrode slurry is obtained by mixing a positive electrode active material, a binder, a conductive additive, and a known solvent such as N-methyl-2-pyrrolidone (NMP) to form a paste. Next, the positive electrode slurry is applied to a metal foil that will become the positive electrode current collector 7 to a predetermined thickness using a doctor blade method or the like. Subsequently, the metal foil coated with the positive electrode slurry is dried, for example, at 150°C. After that, the dried coating is pressed to increase its density using a known method to form a positive electrode active material layer 71.

[0037] Next, the metal foil having the positive electrode active material layer 71 is punched out into a predetermined shape, for example, using a Pinnacle Die (registered trademark). This gives the metal foil having the positive electrode active material layer 71 a shape corresponding to the shape of the substantially circular positive electrode current collector 7 and the strip-shaped positive electrode lead wire 72 extending from the edge of the positive electrode current collector 7. Next, the positive electrode active material layer 71 formed on the metal foil at the position that will become the positive electrode lead wire 72 is peeled off. Through these steps, a positive electrode consisting of the positive electrode current collector 7 and the positive electrode active material layer 71, and a positive electrode lead wire 72 integrated with the positive electrode current collector 7 are obtained.

[0038] Next, a negative electrode slurry is obtained by mixing the negative electrode active material, binder, and a known solvent such as N-methyl-2-pyrrolidone (NMP) to form a paste. Then, a negative electrode consisting of a negative electrode current collector 6 and a negative electrode active material layer 61, and a negative electrode lead wire 62 integrated with the negative electrode current collector 6 are manufactured in the same manner as when manufacturing the positive electrode and positive electrode lead wire 72, except that a metal foil that will become the negative electrode current collector 6 is used instead of the metal foil that will become the positive electrode current collector 7, and the negative electrode slurry is used instead of the positive electrode slurry.

[0039] Next, a separator 5 is placed on the negative electrode active material layer 61, and the positive electrode is stacked on the separator 5 so that the positive electrode active material layer 71 is in contact with it. Then, the stacked negative electrode, separator 5, and positive electrode are brought into close contact and fixed with insulating tape (not shown) as needed. Through these steps, the energy storage element 12 shown in Figures 1, 2(a), and 2(b) is obtained.

[0040] The energy storage element of the battery 10 in this embodiment is not limited to the energy storage element 12 shown in Figures 1, 2(a), and 2(b). For example, the planar shape of the energy storage element does not have to be approximately circular, but may be approximately elliptical or polygonal, and can be appropriately determined according to the planar shape of the first member 1, etc. Furthermore, the energy storage element may be a stacked structure in which a positive electrode, a separator, and a negative electrode are stacked, and multiple such stacks are stacked.

[0041] Furthermore, the energy storage element may include a positive electrode, a negative electrode, and an insulating film disposed between the positive and negative electrodes to electrically separate them; conventionally known elements can be used. As an energy storage element, for example, one that includes a positive electrode, a negative electrode, a separator (insulating film), and an electrolyte solution used in lithium batteries can be used. The energy storage element may also have a wound body formed by winding a strip-shaped composite in which a separator is disposed between the positive and negative electrodes. If the energy storage element has the above-mentioned wound body, the center position of the wound composite and the center position of the cylindrical portion 1b of the first member 1 may substantially overlap in a plan view.

[0042] The battery 10 shown in Figures 1, 2(a), and 2(b) consists of a first member 1 and a second member 2 made of conductive material, the negative electrode of the energy storage element 12 is electrically connected to the first member 1, the positive electrode is electrically connected to the second member 2, and the first member 1 and the second member 2 are electrically insulated by a gasket 3. In this embodiment, the battery 10 is such that one of the positive or negative electrodes of the energy storage element 12 is electrically connected to the first member 1 and the other is electrically connected to the second member 2, and the first member 1 and the second member 2 are electrically insulated by the gasket 3. Alternatively, the positive electrode of the energy storage element 12 may be electrically connected to the first member 1 and the negative electrode may be electrically connected to the second member 2.

[0043] [Battery manufacturing method] The battery 10 shown in Figures 1, 2(a), and 2(b) can be manufactured, for example, by the following method. A roughly circular first metal foil, which will become the first member 1, is prepared. Then, by drawing the first metal foil using a known method, the first member 1 having a predetermined shape with a bottom portion 1a and a cylindrical portion 1b is formed. Next, the energy storage element 12 is housed within the first member 1, and the negative electrode lead wire 62 of the energy storage element 12 (see Figure 2(a)) is electrically connected to the negative electrode of the energy storage element 12 by resistance welding to the bottom 1a of the first member 1.

[0044] Next, a strip-shaped insulating sheet having a substantially uniform thickness is prepared to serve as the gasket 3. Then, a plurality of recesses are formed on one or both sides of the insulating sheet. The plurality of recesses may be arranged regularly or irregularly. Furthermore, the plurality of recesses may be formed on the entire surface of the insulating sheet or on only a part of the insulating sheet. When the plurality of recesses are formed on only a part of the insulating sheet, it is preferable to form the plurality of recesses in the portion located between the cylindrical portion 1b of the first member 1 and the second member 2. The recesses in the insulating sheet can be formed, for example, by pressing a roller having a predetermined uneven surface against the insulating sheet.

[0045] Next, an insulating sheet is installed so as to cover the end face 1c of the first member 1 and to cover a part of the cylindrical portion 1b of the first member 1 from the outside. If multiple recesses are provided on only one side of the insulating sheet, it is preferable to install the insulating sheet so that the side with the recesses faces outwards. This makes it easier to form an uncontacted portion 42 on the second surface 2d of the second member 2 where the gasket 3 is not in contact.

[0046] Next, a circular second metal foil, which will become the second member 2, is prepared. The second metal foil is then placed on the first member 1 via an insulating sheet having multiple recesses. Subsequently, the end of the second metal foil is bent along the cylindrical portion 1b of the first member 1 using a known method, and the bent portion is crimped and joined to the cylindrical portion 1b of the first member 1. This forms a second member 2 of a predetermined shape having a lid portion 2a and a peripheral wall portion 2b, making the inside of the case 11 airtight. Next, the positive electrode lead wire 72 of the energy storage element 12 (see Figure 2(b)) is electrically connected to the lid-shaped portion 2a of the second member 2 by resistance welding. Through the above steps, the battery 10 shown in Figures 1, 2(a), and 2(b) is obtained.

[0047] The battery 10 shown in Figures 1, 2(a), and 2(b) has a case 11 that houses an energy storage element 12 in an airtight state. The case 11 has a first member 1 having a bottom portion 1a and a cylindrical portion 1b, a second member 2 having a lid portion 2a that covers the opening of the first member 1 and a peripheral wall portion 2b that covers the cylindrical portion 1b from the outside, and a gasket 3 that is continuously arranged between the end face 1c of the first member 1 and the second member 2, and between the cylindrical portion 1b and the second member 2. In the battery 10, both a part of the first surface 1d of the first member 1 that faces the gasket 3 and a part of the second surface 2d of the second member 2 that faces the gasket 3 are provided with uncontacted portions 41 and 42 where the gasket 3 does not come into contact.

[0048] In the battery 10, over time, the energy storage element 12 housed in the case 11 may expand or gas may be generated from the energy storage element 12, causing the internal pressure inside the case 11 to rise. In the uncontacted portions 41 and 42, even if the internal pressure inside the case 11 rises and the case 11 expands and deforms, a portion of the force caused by the deformation of the case 11 is absorbed by the space between the first surface 1d and / or the second member 2d and the gasket 3. As a result, the force caused by the deformation of the case 11 applied to the gasket 3 facing the uncontacted portions 41 and 42 is mitigated. Consequently, it is possible to prevent cracks from forming in the gasket 3 facing the uncontacted portions 41 and 42 due to the force caused by the deformation of the case 11.

[0049] Furthermore, if the force caused by the deformation of case 11 becomes large, the air between the uncontacted portions 41, 42 and the gasket 3 is pushed out, the space between the first surface 1d and / or the second member 2d and the gasket 3 collapses, and the gasket 3 facing the uncontacted portions 41, 42 is pressed against the uncontacted portions 41, 42. As a result, even if cracks occur in the gasket 3 that has been in contact with the first surface 1d and the second member 2d since the completion of the battery 10 due to the force caused by the deformation of case 11, the airtight state inside case 11 is maintained by the sealing properties of the gasket 3 pressed against the uncontacted portions 41, 42. Based on these factors, the battery 10 of this embodiment can maintain an airtight state inside the case 11 for a long period of time, is less prone to deterioration, and is highly reliable.

[0050] In contrast, in the case of a battery in which the entire surface 1d of the first member 1 facing the gasket 3 and the entire surface 2d of the second member 2 facing the gasket 3 are in contact with the gasket 3, for example, the airtightness inside the case is good upon completion. However, in this battery, cracks easily occur in the gasket 3 due to the force caused by the deformation of the case due to the increase in internal pressure inside the case, and the airtight state inside the case could not be maintained for a long period of time.

[0051] Furthermore, in the battery case 11 shown in Figures 1, 2(a), and 2(b), the cylindrical portion 1b of the first member 1 is cylindrical and has a first outer diameter portion 1e, a second outer diameter portion 1f which has a longer outer diameter than the first outer diameter portion 1e, and a stepped portion 1g which connects the first outer diameter portion 1e and the second outer diameter portion 1f, with the first outer diameter portion 1e positioned closer to the bottom portion 1a than the second outer diameter portion 1f. In a cross-section passing through the center of the cylindrical portion 1b, the stepped portion 1g is provided within a range of 1 / 3 of the length L1 of the cylindrical portion facing the peripheral wall portion 2b of the second member 2, from the center position of the length L1 of the cylindrical portion 1b facing the peripheral wall portion 1b, as shown in Figure 1. For the reasons (1) to (3) below, even if the internal pressure inside the case 11 rises, the airtight state inside the case 11 can be maintained for a longer period of time due to the sealing properties of the gasket 3.

[0052] (1) Near the bottom 1a side of the stepped portion 1g, the force applied to the periphery wall portion 2b of the second member 2 toward the cylindrical portion 1b is weaker compared to the near the end face 1c side of the stepped portion 1g. Therefore, when the internal pressure inside the case 11 increases, the area near the bottom 1a side of the stepped portion 1g expands preferentially, suppressing deformation of other parts of the case 11. This prevents cracks from occurring in the gasket 3 located in areas other than near the bottom 1a side of the stepped portion 1g. (2) A large uncontacted area 41 is more likely to form near the bottom 1a side of the stepped portion 1g on the first surface 1d, and a large uncontacted area 42 is more likely to form on the second surface 2d which is positioned opposite the first outer diameter portion 1e, where the gasket 3 is not in contact. Therefore, even if the area near the bottom 1a side of the stepped portion 1g expands, the force caused by the expansion is absorbed by the large uncontacted areas 41 and 42, and the force caused by the expansion of the case 11 applied to the gasket 3 opposite the uncontacted areas 41 and 42 is mitigated.

[0053] (3) When the internal pressure inside the case 11 rises, the gasket 3 facing the second outer diameter portion 1f, where the gap between the peripheral wall portion 2b and the cylindrical portion 1b of the second member 2 is narrow, is pressed against the uncontacted portions 41 and 42. Subsequently, when the internal pressure inside the case 11 rises further, the expansion near the bottom portion 1a of the stepped portion 1g becomes even greater, and the uncontacted portions 41 and 42 can no longer absorb it, causing the gasket 3 facing the uncontacted portions 41 and 42 to be pressed against the uncontacted portions 41 and 42. For this reason, even if cracks occur in the gasket 3 that has been in contact with the first surface 1d and the second member 2d since the completion of the battery 10, the airtight state inside the case 11 is maintained by the sealing properties of the gasket 3 pressed against the uncontacted portions 41 and 42.

[0054] <Second Embodiment> Figure 3 is a schematic cross-sectional view showing a battery of the second embodiment. In the battery 10a of the second embodiment shown in Figure 3, the same reference numerals are used for the same components as in the battery 10 of the first embodiment described above, and their descriptions are omitted. In the battery 10a shown in Figure 3, the first component 1 of the case 11a has a cylindrical cylindrical portion 11b, similar to the battery 10 of the first embodiment. Figure 3 is a cross-sectional view of the cut surface along the center of the cylindrical portion 11b in a plan view.

[0055] The battery 10a of the second embodiment differs from the battery 10 of the first embodiment in that the cylindrical portion 11b of the first member 1 of the case 11a has a substantially constant outer diameter and does not have a stepped portion. As shown in Figure 3, the cylindrical portion 11b extends in a direction substantially perpendicular to the extending direction of the bottom portion 1a.

[0056] The battery 10a shown in Figure 3, like the battery 10 of the first embodiment, has a case 11a that houses the energy storage element 12 in an airtight state, and the case 11a has a first member 1, a second member 2, and a gasket 3. Furthermore, uncontacted portions 41 and 42 are provided on both a part of the first surface 1d of the first member 1 that faces the gasket 3 and a part of the second surface 2d of the second member 2 that faces the gasket 3, where the gasket 3 does not come into contact. Therefore, the battery 10a shown in Figure 3, like the battery 10 of the first embodiment, can maintain an airtight state inside the case 11a for a long period of time, is less prone to deterioration, and has excellent reliability.

[0057] (Other examples) The battery of the present invention is not limited to the embodiments described above. For example, in the batteries 10 and 10a shown in Figures 1 and 3, the explanation described an example in which uncontacted portions 41 and 42 are provided on a part of the first surface 1d of the first member 1 facing the gasket 3 and a part of the second surface 2d of the second member 2 facing the gasket 3, respectively, where the gasket 3 does not come into contact with them. However, the uncontacted portions may be provided on only one of the parts of the first surface 1d and the part of the second surface 2d.

[0058] If an uncontacted portion is provided on only one of the parts of the first surface 1d and the second surface 2d, it is preferable that the uncontacted portion 42 is provided on the part of the second surface 2d facing the gasket 3 of the second member 2. This is because the force caused by the deformation of the cases 11 and 11a can be absorbed more effectively by the space between the second member 2d, which has a larger surface area than the first surface 1d, and the gasket 3, thereby more effectively preventing cracks from forming in the gasket 3.

[0059] In Figures 1 and 3, the batteries 10 and 10a are described using the example where the bottom 1a of the first member 1 is circular in plan view and the cylindrical parts 1b and 11b are cylindrical. However, the planar shapes of the bottom 1a and cylindrical parts 1b and 11b of the first member 1 do not have to be circular. For example, they may be polygons such as squares, rectangles, or hexagons, or they may be elliptical or oblong, and are not particularly limited.

[0060] In the batteries 10 and 10a shown in Figures 1 and 3, the case where the lid portion 2a of the second member 2 is circular in plan view was used as an example for explanation. However, the planar shape of the lid portion 2a is not limited to a circular shape, and is preferably substantially similar to the planar shape of the bottom portion 1a of the first member 1, and can be appropriately determined according to the planar shape of the bottom portion 1a. In the batteries 10 and 10a shown in Figures 1 and 3, the case where the peripheral wall portion 2b of the second member 2 is cylindrical was used as an example for explanation. However, the planar shape of the peripheral wall portion 2b is not limited to a circular shape, and is preferably substantially similar to the planar shape of the cylindrical portions 1b and 11b of the first member 1, and can be appropriately determined according to the planar shape of the cylindrical portions 1b and 11b.

[0061] Although embodiments of the present invention have been described in detail above, the configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications to the configurations are possible without departing from the spirit of the present invention. [Examples]

[0062] "Example 1" (Manufacturing of energy storage elements) A positive electrode slurry was obtained by mixing lithium cobalt oxide, the positive electrode active material, polyvinylidene fluoride (PVDF), the binder, acetylene black, the conductive additive, and N-methyl-2-pyrrolidone (NMP), the solvent, and forming a paste. Next, the positive electrode slurry was applied to an aluminum foil, which would become the positive electrode current collector 7, using the doctor blade method. Subsequently, the aluminum foil coated with the positive electrode slurry was dried at 150°C. After that, the dried coating was pressed to increase its density, thereby forming a positive electrode active material layer 71.

[0063] Next, an aluminum foil having a positive electrode active material layer 71 was punched out using a Pinnacle Die (registered trademark). This gave the aluminum foil having the positive electrode active material layer 71 a shape corresponding to a circular positive electrode current collector 7 with a diameter of 10 mm and a strip-shaped positive electrode lead wire 72 with a length of 20 mm and a width of 5 mm extending from the edge of the positive electrode current collector 7. Next, the positive electrode active material layer 71 formed in the position that would become the positive electrode lead wire 72 on the aluminum foil was peeled off. Through these steps, a positive electrode consisting of a positive electrode current collector 7 and a positive electrode active material layer 71, and a positive electrode lead wire 72 integrated with the positive electrode current collector 7 were obtained.

[0064] Next, a negative electrode slurry was obtained by mixing graphite, which is the negative electrode active material, polyvinylidene fluoride (PVDF), which is the binder, and N-methyl-2-pyrrolidone (NMP), which is the solvent, and forming a paste. Subsequently, a negative electrode consisting of a circular negative electrode current collector 6 with a diameter of 13 mm and a negative electrode active material layer 61, and a strip-shaped negative electrode lead wire 62 with a length of 3 mm and a width of 5 mm integrated with the negative electrode current collector 6 were manufactured in the same manner as when manufacturing the positive electrode and positive electrode lead wire 72, except that copper foil was used as the negative electrode current collector 6 instead of aluminum foil, and the negative electrode slurry was used instead of the positive electrode slurry.

[0065] Next, a circular separator 5 with a larger diameter than the negative electrode current collector 6 was placed on the negative electrode active material layer 61, and the positive electrode was stacked on the separator 5 so that the positive electrode active material layer 71 was in contact with it. Then, the stacked negative electrode, separator 5, and positive electrode were brought into close contact and fixed with insulating tape. Through these steps, the energy storage element 12 shown in Figure 1 was obtained.

[0066] (Battery manufacturing) Next, a first metal foil, consisting of a roughly circular stainless steel foil with a thickness of 100 μm, was prepared to become the first component 1. Subsequently, the first metal foil was subjected to a drawing process to form the first component 1, which has a circular bottom portion 1a and a cylindrical portion 1b, and a height of 4.0 mm. As the first member 1, a cylindrical portion 1b was formed having a first outer diameter portion 1e with an outer diameter of 20.0 mm, a second outer diameter portion 1f with an outer diameter of 20.4 mm, and a stepped portion 1g connecting the first outer diameter portion 1e and the second outer diameter portion 1f. The radius of curvature r1 on the inner surface of the first member 1 formed by the stepped portion 1g was 100 μm, and the radius of curvature r2 on the outer surface was 100 μm. The stepped portion 1g was formed so as to be at the center of the length L1 of the cylindrical portion 1b facing the peripheral wall portion 2b of the second member 2. Next, the energy storage element 12 was housed within the first member 1, and the negative electrode lead wire 62 of the energy storage element 12 was electrically connected to the first member 1 by resistance welding to the bottom 1a of the first member 1.

[0067] Next, a strip-shaped insulating sheet made of polypropylene with a nearly uniform thickness of 100 μm was prepared to serve as gasket 3. Then, multiple recesses were formed on both sides of the insulating sheet. The recesses on the insulating sheet were formed by pressing a roller, which had multiple rectangular protrusions measuring 30 μm in height, 50 mm in length, and 50 μm in width, spaced 200 μm apart within the roller surface, against the insulating sheet. Next, an insulating sheet was installed so as to cover the end face 1c of the first member 1 and to cover a part of the cylindrical portion 1b of the first member 1 from the outside.

[0068] Next, a second metal foil, consisting of a roughly circular stainless steel foil with a thickness of 100 μm, was prepared to serve as the second component 2. The second metal foil was then placed on the first component 1 via an insulating sheet having multiple recesses. Subsequently, the ends of the second metal foil were bent along the cylindrical portion 1b of the first component 1, and the bent portion was crimped and joined to the cylindrical portion 1b of the first component 1. This creates a second member 2 having a circular lid-like portion 2a and a peripheral wall portion 2b with an outer diameter of 20.6 mm, thereby making the inside of the case 11 airtight.

[0069] Next, the positive electrode lead wire 72 of the energy storage element 12 was electrically connected to the second member 2 by resistance welding the lid-shaped portion 2a of the second member 2. Through the above process, the battery 10 of Example 1 shown in Figure 1 was obtained.

[0070] In the battery 10 of Example 1, the length L3 of the gasket 3 in the longitudinal direction of the cylindrical portion 1b at the cross-section along the center of the cylindrical portion 1b of the first member 1 was 3.5 mm, and the distance L2 in the longitudinal direction of the cylindrical portion 1b from the outer surface of the lid portion 2a of the second member 2 to the end face 2c of the peripheral wall portion 2b was 3.0 mm.

[0071] Example 2 Except for changing the arrangement of the insulating sheets, the battery 10 of Example 2 was obtained in the same manner as in Example 1. In the battery 10 of Example 2, the length L3 of the gasket 3 in the longitudinal direction of the cylindrical portion 1b at the cross-section along the center of the cylindrical portion 1b of the first member 1 was 2.8 mm. "Example 3" Except for the cylindrical portion 11b of the first member 1 having a constant outer diameter of 20.4 mm and no stepped portion, the battery 10a of Embodiment 3 shown in Figure 3 was obtained in the same manner as in Embodiment 1.

[0072] "Example 4" Battery 10 of Example 4 was obtained in the same manner as in Example 1, except that a roller was used which had multiple rectangular parallelepiped protrusions measuring 30 μm in height, 10 mm in length, and 10 μm in width, spaced 200 μm apart on the roller surface. Example 5 Battery 10a of Example 5 was obtained in the same manner as in Example 3, except that a roller was used which had multiple rectangular parallelepiped protrusions measuring 30 μm in height, 10 mm in length, and 10 μm in width, spaced 200 μm apart on the roller surface. "Example 6" Except for changing the arrangement of the insulating sheets, the battery 10a of Example 6 was obtained in the same manner as in Example 3. In the battery 10a of Example 6, the length L3 of the gasket 3 in the longitudinal direction of the cylindrical portion 1b at the cross-section along the center of the cylindrical portion 1b of the first member 1 was 2.8 mm.

[0073] " Reference example 7" Except for forming multiple recesses on the entire surface of one side of the insulating sheet and installing the insulating sheet so that the side with the recesses faces inward, the procedure was the same as in Example 6. Reference example I obtained a 7-cell battery with a current of 10A. " Reference example 8. Reference example 9" Aside from changing the number of times the roller was pressed against the insulating sheet, Reference example In the same manner as in 7, Reference example 8. Reference example I obtained a 9-cell battery with a current of 10A.

[0074] "Example 10" Battery 10a of Example 10 was obtained in the same manner as in Example 6, except that multiple recesses were formed on the entire surface of one side of the insulating sheet using a roller having multiple rectangular parallelepiped protrusions with a height of 30 μm, a length of 10 mm, and a width of 10 μm, spaced 200 μm apart within the roller surface, and the insulating sheet was installed so that the side with the recesses was facing outwards. "Examples 11 and 12" Except for changing the number of times the roller was pressed against the insulating sheet, the batteries 10a of Examples 11 and 12 were obtained in the same manner as in Example 10. "Examples 13 to 16" Except for varying the number of times the roller was pressed against the insulating sheet on each side of the insulating sheet, the batteries 10a of Examples 13 to 16 were obtained in the same manner as in Example 6.

[0075] "Comparative Example 1" A battery 10 of Comparative Example 1 was obtained in the same manner as in Example 6, except that an insulating sheet was used without forming a recess. "Comparative Example 2" A comparative example battery 10 was obtained in the same manner as in Example 1, except that an insulating sheet was used without forming a recess.

[0076] [Measurement of deterioration rate] Examples 1 obtained in this manner... Examples 6, 10, and beyond Example 16, Reference example 7~Reference example 9, For each of the batteries 10 and 10a in Comparative Example 1 and Comparative Example 2, constant current charging was performed using a battery charge / discharge device (SM-8; manufactured by Hokuto Denko Co., Ltd.) at a current of 0.1C until the voltage reached 4.2V. After reaching 4.2V, constant voltage charging was performed until the current reached 0.05C. Subsequently, constant current discharge was performed at a current of 0.1C until the voltage reached 3.0V, and the discharge capacity was measured (capacity before storage).

[0077] Subsequently, each battery (10A) whose pre-storage capacity was measured was charged to a fully charged state and stored for one month in an environment with a temperature of 60°C and a humidity of 95%. Each of the 10A and 10C batteries, after storage, was discharged at a constant current of 0.1C down to 3.0V. Then, charging and discharging were performed under the same conditions as before measuring the pre-storage capacity, and the discharge capacity was measured in the same manner as before measuring the pre-storage capacity (post-storage capacity). Then, the rate of volume degradation ([Volume after storage / Volume before storage] × 100 (%)) was calculated from the volume before and after storage. The results are shown in Table 1.

[0078] [Table 1]

[0079] After measuring the capacity degradation rate, the battery 10 of Example 1 was embedded in resin, and two arbitrary points along the center of the cylindrical portion 1b of the first component 1 were cut using a precision cutting machine (product name: Isomed, manufactured by Bühler Co., Ltd.). The two resulting cut surfaces were polished using sandpaper. Then, surface milling was performed by irradiating each cut surface with an Ar ion beam using an ion milling device (product name: IM4000, manufactured by Hitachi High-Tech Corporation) to obtain cross-sectional observation samples.

[0080] The cross-sections of each sample were observed using a laser microscope (product name: VK-X, manufactured by Keyence Corporation), and the number and length of uncontacted portions 41 and 42 with a length of 100 μm or more were examined on the obtained images. Furthermore, the cross-sections of each cross-sectional observation sample were observed using a scanning electron microscope (SEM) (product name: SU8220, manufactured by Hitachi High-Tech Corporation), and the number and length of uncontacted portions 41 and 42 less than 100 μm in length were examined on the obtained images.

[0081] Then, for each cross-section, the ratio of the length of the uncontacted portion 41 on the first surface 1d to the length L1 of the cylindrical portion 1b facing the peripheral wall portion 2b of the second member 2 was calculated, and the average value (hereinafter sometimes referred to as "ratio of uncontacted portion 41") was determined. The results are shown in Table 1. Furthermore, for each cross-section, the ratio of the length of the uncontacted portion 42 on the second surface 2d to the length L2 in the longitudinal direction of the cylindrical portion 1b from the outer surface of the lid portion 2a of the second member 2 to the end surface 2c of the peripheral wall portion 2b was calculated, and the average value (hereinafter sometimes referred to as "ratio of uncontacted portion 42") was determined. The results are shown in Table 1.

[0082] Furthermore, for each cross-section, we examined whether multiple uncontacted portions 41 and 42 with a length of 10 μm or more were present using images obtained from observation with the laser microscope and scanning electron microscope (SEM) described above. The results are shown in Table 1. In Table 1, if multiple uncontacted portions 41 (or multiple uncontacted portions 42) with a length of 10 μm or more were present in all cross-sections, it is indicated as "Present," and all other cases are indicated as "Absent."

[0083] Example 2 after measuring the rate of capacity degradation Examples 6, 10, and beyond Example 16, Reference example 7~Reference example 9, For each of the batteries 10 and 10a in Comparative Example 1 and Comparative Example 2, after measuring the capacity degradation rate, two arbitrary cross-sections along the center of the cylindrical portion 1b of the first member 1 were observed in the same manner as in Example 1, and the number and length of the uncontacted portions 41 and 42 were investigated. Example 1~ Examples 6, 10, and beyond Example 16, Reference example 7~Reference example 9, Table 1 shows the differences between the outer diameter of the first outer diameter portion 1e and the outer diameter of the second outer diameter portion 1f of the first member 1 (1f-1e), the proportion of uncontacted portions 41, the proportion of uncontacted portions 42, whether or not there are multiple uncontacted portions 41 and 42 with a length of 10 μm or more, the presence or absence of stepped portions 1g, and whether or not the difference (L3-L2) between the length L3 of the gasket 3 in the longitudinal direction of the cylindrical portions 1b and 11b at the cross-section along the center of the cylindrical portions 1b and 11b of the first member 1 and the distance L2 in the longitudinal direction of the cylindrical portions 1b and 11b from the outer surface of the lid portion 2a of the second member 2 to the end face 2c of the peripheral wall portion 2b is greater than 0 for each battery 10 and 10a of Comparative Example 1 and Comparative Example 2.

[0084] As shown in Table 1, Example 1 has uncontacted portions 41 and / or uncontacted portions 42. Examples 6, 10, and beyond Example 16, Reference example 7~Reference example 9 The batteries 10 and 10a showed a higher capacity degradation rate compared to the batteries of Comparative Examples 1 and 2, in which the entire surface of the opposing surfaces of the gasket 3 and the first member 1 and the second member 2 were in contact (the proportion of uncontacted portions 41 and 42 was 0%). Examples 6, 10, and beyond Example 16, Reference example 7~Reference example 9 It is presumed that the batteries 10 and 10a were able to maintain an airtight state within the storage cases 11 and 11a because they had uncontacted portions 41 and 42. In particular, Examples 1- Examples 6, 10, and beyond Example 16, Reference example 7~Reference example 9 In Example 1, of the batteries 10 and 10a, the proportion of the uncontacted portion 41 is 20% to 95%, and / or the proportion of the uncontacted portion 42 is 40% to 80%. Example 6, Reference Example 7 In Example 12, batteries 10 and 10a showed a capacity degradation rate of 80% or more, confirming that they are resistant to degradation. [Explanation of symbols]

[0085] 1...First component, 1a...Bottom, 1b, 11b...Cylindrical part, 1c...End face, 1d...First surface, 1e...First outer diameter part, 1f...Second outer diameter part, 1g...Stepped part, 2...Second component, 2a...Lid-shaped part, 2b...Peripheral wall part, 2c...End face, 2d...Second surface, 3...Gasket, 5...Separator, 6...Negative electrode current collector, 7...Positive electrode current collector, 10, 10a...Battery, 11, 11a...Case, 12...Energy storage element, 41, 42...Uncontacted part, 61...Negative electrode active material layer, 62...Negative electrode lead wire, 71...Positive electrode active material layer, 72...Positive electrode lead wire, r1...Radius of curvature on the inner side, r2...Radius of curvature on the outer side.

Claims

1. A power storage element comprising a positive electrode, a negative electrode, and an insulating film disposed between the positive electrode and the negative electrode to electrically separate the positive electrode and the negative electrode, The case comprises the aforementioned energy storage element in an airtight state, The case comprises a first member having a bottom and a cylindrical portion, A second member having a lid-like portion that covers the opening of the first member and a peripheral wall portion that covers the cylindrical portion from the outside, The gasket is continuously disposed between the end face of the first member and the second member, and between the cylindrical portion and the second member. A portion of the second surface of the second member facing the gasket is provided with an uncontacted portion where the gasket does not make contact, or the uncontacted portion is provided on both a portion of the first surface of the first member facing the gasket and a portion of the second surface of the second member facing the gasket. The cylindrical portion of the first member is cylindrical, and in the cross-section along the center of the cylindrical portion, A battery characterized in that the ratio of the length of the uncontacted portion provided on the second surface to the length L2 in the longitudinal direction of the cylindrical portion from the outer surface of the lid-like portion to the end surface of the peripheral wall portion is 20% to 95%.

2. The battery according to claim 1, wherein the uncontacted portion is provided on the first surface.

3. The cylindrical portion of the first member is cylindrical, and in the cross-section along the center of the cylindrical portion, The battery according to claim 2, wherein the ratio of the length of the uncontacted portion provided on the first surface to the length L1 of the cylindrical portion facing the peripheral wall portion is 40% to 80%.

4. The cylindrical portion of the first member is cylindrical, and in the cross-section along the center of the cylindrical portion, The battery according to any one of claims 1 to 3, having a plurality of uncontacted portions with a length of 10 μm or more.

5. The cylindrical portion of the first member is cylindrical and has a first outer diameter portion, a second outer diameter portion having a longer outer diameter than the first outer diameter portion, and a stepped portion connecting the first outer diameter portion and the second outer diameter portion. The first outer diameter portion is positioned closer to the bottom than the second outer diameter portion. The battery according to any one of claims 1 to 4, wherein in a cross-section passing through the center of the cylindrical portion, the stepped portion is provided within a range of 1 / 3 of the length L1 of the cylindrical portion facing the peripheral wall, from the center position of the length L1 of the cylindrical portion facing the peripheral wall.

6. The cylindrical portion of the first member is cylindrical, and in the cross-section along the center of the cylindrical portion, The battery according to any one of claims 1 to 5, wherein the length L3 of the gasket in the longitudinal direction of the cylindrical portion is longer than the distance L2 of the cylindrical portion in the longitudinal direction from the outer surface of the lid portion to the end face of the peripheral wall portion.

Images