Cylindrical battery

Abstract

Provided is a cylindrical battery comprising a bottomed cylindrical exterior can (15) formed from a metal chiefly comprising a first metal, an electrode body and a nonaqueous electrolyte solution accommodated in the exterior can (15), a sealing body (16) that closes up an opening (15D) in the exterior can (15), a gasket (21) disposed between the exterior can (15) and the sealing body (16), and a dissimilar metal layer (30) which is disposed in at least a part of a region of the inner surface of the exterior can (15) facing the gasket (21) and which is formed from a metal chiefly comprising a second metal different from the first metal, the cylindrical battery being characterized in that the standard electrode potential of the second metal is lower than the standard electrode potential of the first metal.

Description

Cylindrical battery

[0001] The present disclosure relates to a cylindrical battery.

[0002] Conventionally, a cylindrical battery including a bottomed cylindrical outer can that houses an electrode body and a non-aqueous electrolyte, and a sealing body that closes the opening of the outer can is known. The cylindrical battery seals the inside by caulking and fixing the sealing body between an annular groove portion formed on the side surface portion of the outer can and the opening end portion of the outer can (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2003-151516

[0004] By the way, during battery manufacturing, the non-aqueous electrolyte injected into the outer can may adhere to and remain at the opening of the outer can. If the non-aqueous electrolyte remains in the region of the opening of the outer can where the sealing body is caulked and fixed, moisture that has entered from the outside reacts with the remaining non-aqueous electrolyte, generating a gas with strong oxidizing action such as hydrogen fluoride, and the outer can may be corroded. From the viewpoint of improving the reliability of the cylindrical battery, it is required to suppress the corrosion of the outer can.

[0005] A cylindrical battery according to one aspect of the present disclosure includes a bottomed cylindrical outer can made of a metal mainly composed of a first metal, an electrode body and a non-aqueous electrolyte housed in the outer can, a sealing body that closes the opening of the outer can, a gasket disposed between the outer can and the sealing body, and a dissimilar metal layer disposed on at least a part of a region of the inner surface of the outer can facing the gasket and made of a metal mainly composed of a second metal different from the first metal. The cylindrical battery is characterized in that the standard electrode potential of the second metal is smaller than the standard electrode potential of the first metal.

[0006] According to the cylindrical battery according to one aspect of the present disclosure, corrosion of the outer can can be suppressed. As a result, the reliability of the cylindrical battery can be improved.

[0007] It is an axial cross-sectional view of a cylindrical battery which is an example of an embodiment. In FIG. 1, it is a figure which expands and shows the vicinity of the opening part of an outer can.

[0008] In the following, an example of an embodiment of the cylindrical battery according to this disclosure will be described in detail with reference to the drawings. In the following description, the specific shapes, materials, numerical values, directions, etc. are examples to facilitate understanding of the present invention and can be appropriately modified according to the specifications of the cylindrical battery.

[0009] Figure 1 is an axial cross-sectional view of a cylindrical battery 10, which is an example of an embodiment. The cylindrical battery 10 shown in Figure 1 comprises an electrode body 14, a non-aqueous electrolyte (not shown), and an outer casing 15 that houses the electrode body 14 and the non-aqueous electrolyte. The cylindrical battery 10 further comprises a sealing body 16 that closes the opening 15D of the outer casing 15, and a gasket 21 that is placed between the outer casing 15 and the sealing body 16. For the sake of explanation, the side with the sealing body 16 will be referred to as "upper," and the bottom 15A side of the outer casing 15 will be referred to as "lower."

[0010] The electrode body 14 has a wound structure in which, for example, a positive electrode 11 and a negative electrode 12 are wound around a separator 13. The positive electrode 11 has a strip-shaped positive electrode core and positive electrode mixture layers formed on both sides of the positive electrode core. As the positive electrode core, for example, a metal foil such as aluminum, or a film with the metal arranged on its surface, can be used.

[0011] The positive electrode mixture layer is prepared by, for example, applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and a solvent such as N-methyl-2-pyrrolidone (NMP) to both sides of the positive electrode core, followed by drying and compression. Examples of positive electrode active materials include lithium transition metal composite oxides containing transition metal elements such as Ni, Co, Mn, and Al. Examples of conductive agents include carbon materials such as carbon black (CB), acetylene black (AB), Ketjen black, and graphite. Examples of binders include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, and polyolefin resins.

[0012] The negative electrode 12 has a strip-shaped negative electrode core and negative electrode mixture layers formed on both sides of the negative electrode core. As the negative electrode core, for example, a metal foil such as copper, or a film with the metal arranged on its surface, can be used.

[0013] The negative electrode mixture layer is prepared, for example, by coating both sides of the negative electrode core with a negative electrode mixture slurry containing a negative electrode active material, a binder, and water, followed by drying and compression. Examples of negative electrode active materials include carbon materials such as natural graphite and artificial graphite, metals that alloy with lithium such as Si and Sn, or alloys and oxides containing these. Examples of binders include styrene-butadiene rubber (SBR), CMC or its salts, polyacrylic acid or its salts, polyvinyl alcohol, and the like.

[0014] As the separator 13, a porous sheet having ion permeability and insulating properties is used. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the separator 13 is preferably an olefin resin such as polyethylene or polypropylene.

[0015] As the non-aqueous solvent (organic solvent) for the non-aqueous electrolyte contained in the outer container 15, carbonates, lactones, ethers, ketones, esters, etc., can be used, and two or more of these solvents can be used in mixture form. When using a mixture of two or more solvents, it is preferable to use a mixed solvent containing a cyclic carbonate and a linear carbonate. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be used as the cyclic carbonate, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), etc. can be used as the linear carbonate. As the electrolyte salt of the non-aqueous electrolyte, LiPF ６ LiBF ４ LiCF ３ SO ３ These and mixtures thereof can be used. The solubility of the electrolyte salt in the non-aqueous solvent can be, for example, 0.5 mol / L or more and 2.0 mol / L or less.

[0016] Insulating plates 17 and 18 are provided above and below the electrode body 14, respectively. The positive electrode lead 19, connected to the positive electrode 11, extends upward through a through-hole in the insulating plate 17 and is welded to the lower surface of the filter 22, which is the bottom plate of the sealing body 16. As a result, the cap 26, which is the top plate of the sealing body 16 and is electrically connected to the filter 22, becomes the positive electrode terminal. On the other hand, the negative electrode lead 20, connected to the negative electrode 12, extends through a through-hole in the insulating plate 18 towards the bottom 15A side of the outer casing 15 and is welded to the inner surface of the bottom of the outer casing 15. As a result, the outer casing 15 becomes the negative electrode terminal. Note that the current collection configuration is not limited to the above configuration.

[0017] The outer container 15 is a bottomed cylindrical container with a bottom 15A and side portions 15B, and an open top. A grooved portion 15C is formed in the side portion 15B of the outer container 15, recessed radially inward. The grooved portion 15C supports the sealing body 16 on its upper surface. The grooved portion 15C can be formed, for example, by creating an annular recess in a part of the side portion 15B radially inward through spinning or the like. In addition, the opening 15D, which is the area of ​​the side portion 15B of the outer container 15 that is above the grooved portion 15C, is bent radially inward when the sealing body 16 is crimped and fixed to the outer container 15.

[0018] The outer container 15 is made of a metal whose main component is a first metal. In this specification, the main component refers to the component that has the largest mass percentage. The first metal is, for example, iron. The outer container 15 is made of, for example, carbon steel or stainless steel whose main component is iron.

[0019] The portion of the outer casing 15 below the grooved portion 15C houses the electrode body 14 and the non-aqueous electrolyte. During the manufacturing of the battery, the non-aqueous electrolyte poured into the inside of the outer casing 15 may adhere to and remain at the opening 15D. If non-aqueous electrolyte remains at the opening 15D, when moisture enters from outside the battery, the remaining non-aqueous electrolyte and moisture may react, generating a highly oxidizing gas such as hydrogen fluoride. This generated gas may then corrode the outer casing 15. As will be described in more detail later, the cylindrical battery 10 of this embodiment suppresses corrosion of the outer casing 15 by placing a dissimilar metal layer 30 on the inner surface of the outer casing 15.

[0020] The sealing body 16 has a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26, which are stacked in order from the electrode body 14 side. Each component of the sealing body 16 has, for example, a disc shape or a ring shape, and each component except the insulating member 24 is electrically connected to one another. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective centers, with the insulating member 24 interposed between their respective peripheries. If the internal pressure of the battery rises due to abnormal heat generation, for example, the lower valve body 23 may rupture, causing the upper valve body 25 to bulge towards the cap 26 and separate from the lower valve body 23, thereby interrupting the electrical connection between them. If the internal pressure rises further, the upper valve body 25 may rupture, and gas may be discharged from the opening 26A of the cap 26. Note that the configuration of the sealing body 16 is not limited to the above configuration, as long as it is possible to seal the opening 15D of the outer can 15.

[0021] Next, with further reference to Figure 2, the sealed state at the opening 15D of the cylindrical battery 10 and the dissimilar metal layer 30 will be described. Figure 2 is an enlarged view of the vicinity of the opening 15D of the outer casing 15.

[0022] As shown in Figure 2, the sealing body 16 is crimped and fixed at the opening 15D of the outer can 15. Specifically, the sealing body 16 is compressed and fixed between the grooved portion 15C and the open end 15X, which is the upper end of the outer can 15 that is bent radially inward, via an annular gasket 21.

[0023] The gasket 21 is a flexible insulating member that electrically isolates the sealing body 16, which is the positive terminal, from the outer can 15, which is the negative terminal, while ensuring airtightness inside the outer can 15 by being compressed vertically. The material of the gasket 21 is not particularly limited as long as it is a compressible insulating material, and for example, polypropylene (PP), polyphenylene sulfide (PPS), polyethylene (PE), polybutylene terephthalate (PBT), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), polyamide (PA), etc. can be used.

[0024] In this embodiment, the radial inner end of the gasket 21 is positioned radially inward from the opening end 15X of the outer can. In other words, the vicinity of the radial inner end of the gasket 21 is not covered by the outer can 15. However, the radial inner end of the gasket 21 may be covered by the outer can 15.

[0025] As shown in Figure 2, a dissimilar metal layer 30 is arranged on at least a portion of the inner surface of the outer can 15 in the area facing the gasket 21. The dissimilar metal layer 30 is a layer made of a metal whose main component is a second metal different from the first metal that constitutes the outer can 15, and is electrically connected to the outer can 15.

[0026] Here, the standard electrode potential of the second metal is lower than that of the first metal. As a result, when the non-aqueous electrolyte remaining in the opening 15D reacts with water and generates a highly oxidizing gas such as hydrogen fluoride, the dissimilar metal layer 30 is preferentially corroded (oxidized). In other words, the dissimilar metal layer 30 plays a role in sacrificial corrosion. Consequently, the progression of corrosion of the outer can 15 can be suppressed.

[0027] When iron is used as the first metal, examples of the second metal include zinc, magnesium, and aluminum. Among these, zinc or magnesium is preferred as the second metal from the viewpoint of effectively suppressing the progression of corrosion of the outer can 15. The dissimilar metal layer 30 may contain materials other than the second metal, as long as it is mainly composed of the second metal and is electrically connectable to the outer can 15.

[0028] It is preferable that the dissimilar metal layer 30 is formed around the entire circumference of the cylindrical battery 10. By forming the dissimilar metal layer 30 around the entire circumference, corrosion of the outer casing 15 can be further suppressed.

[0029] Preferably, the dissimilar metal layer 30 is formed to cover, for example, 30% or more of the inner surface area of ​​the opening 15D of the outer can 15, and more than 50% of the inner surface area of ​​the opening 15D of the outer can 15. By increasing the area covered by the dissimilar metal layer 30, corrosion of the outer can 15 can be further suppressed.

[0030] Preferably, the dissimilar metal layer 30 is formed on the inner surface of the opening 15D at a bent portion that is bent radially inward when the sealing body 16 is crimped and fixed. Near this bent portion, a gap is easily formed between the outer casing 15 and the gasket 21, and non-aqueous electrolyte tends to remain. Also, since the vicinity of this bent portion is close to the opening end 15X of the outer casing 15, moisture that enters from outside the battery tends to accumulate there. Therefore, corrosion of the outer casing 15 is particularly likely to progress near this bent portion. For this reason, forming the dissimilar metal layer 30 on the inner surface of this bent portion provides a more significant effect in suppressing corrosion of the outer casing 15.

[0031] In this embodiment, the dissimilar metal layer 30 is formed on the inner surface of the outer can 15, from near the opening end 15X to the upper surface of the grooved portion 15C. By forming the dissimilar metal layer 30 on the inner surface of the grooved portion 15C in addition to the inner surface of the opening 15D, corrosion of the outer can 15 can be further suppressed. However, from the viewpoint of ensuring battery performance, it is preferable not to place the dissimilar metal layer 30 in the area below the grooved portion 15C.

[0032] The thickness of the dissimilar metal layer 30 is preferably 0.5 μm or more, and more preferably 1 μm or more. By making the thickness of the dissimilar metal layer 30 0.5 μm or more, the dissimilar metal layer 30 can better play a role in sacrificial corrosion, thereby suppressing corrosion of the outer casing 15. Furthermore, the thickness of the dissimilar metal layer 30 is preferably 10 μm or less, and more preferably 8 μm or less. By making the thickness of the dissimilar metal layer 30 10 μm or less, it becomes easier to ensure airtightness inside the battery. Therefore, the thickness of the dissimilar metal layer 30 is preferably 0.5 μm or more and 10 μm or less, and more preferably 1 μm or more and 8 μm or less.

[0033] In the example shown in Figure 2, the thickness of the dissimilar metal layer 30 is constant throughout, but the thickness of the dissimilar metal layer 30 may vary within the plane. For example, the thickness of the dissimilar metal layer 30 located in the region facing the upper surface of the gasket 21, which is easily compressed by the outer can 15, may be smaller than the thickness of the dissimilar metal layer 30 located in the region facing the side surface of the gasket 21.

[0034] Furthermore, as described above, the thickness of the dissimilar metal layer 30 placed at the bent portion of the opening 15D of the outer can 15, where corrosion is likely to occur, may be greater than the thickness of the dissimilar metal layer 30 placed in parts other than the bent portion.

[0035] The method for manufacturing the dissimilar metal layer 30 is not particularly limited. For example, the dissimilar metal layer 30 can be formed by placing metal powder mainly composed of a second metal on the inner surface of the outer can 15 and applying pressure with a roll or the like. After applying pressure, heat treatment may be performed as needed. Alternatively, the dissimilar metal layer 30 may be formed by bonding a film made of a metal mainly composed of a second metal to the inner surface of the outer can 15. This film can be bonded to the inner surface of the outer can 15 by, for example, pressure bonding.

[0036] The process of creating a dissimilar metal layer 30 on the inner surface of the outer can 15 may be performed before forming the grooved portion 15C on the outer can 15, or it may be performed after forming the grooved portion 15C on the outer can 15.

[0037] As described above, in this embodiment, the cylindrical battery 10 has a dissimilar metal layer 30 made of a metal whose main component is a second metal having a lower standard electrode potential than the first metal constituting the outer casing 15, arranged on at least a portion of the inner surface of the outer casing 15 facing the gasket 21. As a result, when the non-aqueous electrolyte adhering to the opening 15D reacts with water during liquid injection, generating a highly oxidizing gas such as hydrogen fluoride, the dissimilar metal layer 30 is preferentially corroded (oxidized) rather than the outer casing 15. Consequently, the progression of corrosion of the outer casing 15 can be suppressed.

[0038] The embodiments described above can be modified without altering the purpose of this disclosure. For example, in the embodiments described above, the dissimilar metal layer 30 is in contact with the gasket 21, but other members may be placed between the dissimilar metal layer 30 and the gasket 21. Other members include, for example, sealants to improve the airtightness of the outer can 15. As for the sealant, materials that have been conventionally used as sealants can be used, such as rubber polymers, pitch, asphalt, or vinyl, silicone, acrylic, urethane, and fluorine polymers. The sealant can be made, for example, by applying a coating liquid containing the above material to the surface of the dissimilar metal layer 30 placed on the inner surface of the outer can 15.

[0039] This disclosure is further illustrated by the following embodiments: Configuration 1: A cylindrical battery comprising a bottomed cylindrical outer casing made of a metal mainly composed of a first metal, an electrode body and a non-aqueous electrolyte housed in the outer casing, a sealing body that closes the opening of the outer casing, a gasket disposed between the outer casing and the sealing body, and a dissimilar metal layer disposed on at least a portion of the inner surface of the outer casing facing the gasket, and made of a metal mainly composed of a second metal different from the first metal, wherein the standard electrode potential of the second metal is smaller than the standard electrode potential of the first metal. Configuration 2: The cylindrical battery according to Configuration 1, wherein the thickness of the dissimilar metal layer is 0.5 μm or more and 10 μm or less. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the dissimilar metal layer is disposed around the entire circumference. Configuration 4: The cylindrical battery according to any one of Configurations 1 to 3, wherein the first metal is iron, and the second metal is zinc or magnesium.

[0040] 10 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Outer casing, 15A Bottom, 15B Side, 15C Grooved section, 15D Opening, 15X Opening end, 16 Sealing body, 17, 18 Insulating plate, 19 Positive electrode lead, 20 Negative electrode lead, 21 Gasket, 22 Filter, 23 Lower valve body, 24 Insulating member, 25 Upper valve body, 26 Cap, 26A Opening hole, 30 Different metal layer

Claims

1. A cylindrical battery comprising: a bottomed cylindrical outer casing made of a metal mainly composed of a first metal; an electrode body and a non-aqueous electrolyte housed in the outer casing; a sealing body that closes the opening of the outer casing; a gasket disposed between the outer casing and the sealing body; and a heterogeneous metal layer disposed on at least a portion of the inner surface of the outer casing facing the gasket, and made of a metal mainly composed of a second metal different from the first metal, wherein the standard electrode potential of the second metal is smaller than the standard electrode potential of the first metal.

2. The cylindrical battery according to claim 1, wherein the thickness of the dissimilar metal layer is 0.5 μm or more and 10 μm or less.

3. The cylindrical battery according to claim 1, wherein the dissimilar metal layers are arranged around the entire circumference.

4. The cylindrical battery according to claim 1, wherein the first metal is iron and the second metal is zinc or magnesium.

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