Coin battery

Abstract

The present disclosure provides a coin battery that can suppress cracking in a gasket and leakage of an electrolytic fluid. A coin battery (10) according to the present disclosure comprises: a battery case (3) that has an opening; a sealing plate (8) that seals the opening; and a gasket (7) that is positioned between the battery case (3) and the sealing plate (8). The battery case (3) has a bottom plate section (3a), and a side wall section (3b) that stands upright from the circumferential edge thereof. The sealing plate (8) has a top plate section (8a), and a circumferential edge section (8b) that extends from the circumferential edge thereof to the inner side of the side wall section of the battery case. The gasket (7) is made of a polypropylene resin, and has an outer circumference section (7a) that follows along the inner circumferential surface of the side wall section (3b) of the battery case, and an extension section (7b) that extends from the bottom plate section (3a) side of the inner circumferential surface of the outer circumference section (7a) to a center section. The extension section (7b) has a lower end surface (7b1) that faces the bottom plate section (3a), and an upper end surface (7b2) that abuts a tip end section (8b1) of the circumferential edge section (8b) of the sealing plate (8). In a region of the extension section (7b) at a prescribed depth relative to the upper end surface (7b2), the amorphous phase-derived Raman spectroscopic peak intensity IB / the crystalline phase-derived Raman spectroscopic peak intensity IA is within a prescribed range.

Description

Coin cell battery

[0001] The present invention relates to a coin battery, and more particularly to a coin battery having a gasket made of polypropylene resin.

[0002] A coin battery includes, for example, a battery case with an opening, a power generating element containing an electrolyte and housed within the battery case, a sealing plate that seals the opening of the battery case, and a gasket disposed between the battery case and the sealing plate. Such coin batteries are typically sealed by crimping the battery case to the sealing plate via the gasket.

[0003] In the following Patent Document 1, in the coin-type battery as described above, the value of the elastic modulus is 7500 to 10000 kg / cm ２ and that a polyolefin resin (e.g., polypropylene resin) is used as the resin material. Furthermore, Patent Document 1 below describes that if the gasket is configured as described above, even if the internal pressure of the coin battery increases during long-term storage in a high-temperature environment, an increase in the internal resistance of the coin battery can be suppressed by releasing gas from gaps between the battery case and the sealing plate and the gasket.

[0004] Japanese Patent Application Laid-Open No. 2005-339995

[0005] In a coin battery that includes a gasket made of polypropylene resin and that is sealed by crimping the battery case to a sealing plate via the gasket, cracks may occur in the gasket after sealing is performed. Furthermore, even if no cracks occur in the gasket, electrolyte leakage may occur in such a coin battery.

[0006] However, in various publicly known documents, including Patent Document 1, it cannot be said that sufficient consideration has yet been given to preventing cracks from occurring in the gasket and leakage of the electrolyte in the above-mentioned coin-type battery.

[0007] Therefore, an object of the present disclosure is to provide a coin battery that can suppress the occurrence of cracks in the gasket and the occurrence of leakage of the electrolyte.

[0008] One aspect of the present invention provides a coin-type battery comprising: a battery case having an opening; a power generating element housed in the battery case; a sealing plate that seals the opening of the battery case; and a gasket disposed between the battery case and the sealing plate, wherein the battery case is formed in a cylindrical shape with a bottom and has a bottom plate portion and a side wall portion rising from a peripheral edge of the bottom plate portion; the sealing plate has a top plate portion and a peripheral edge portion extending from the peripheral edge of the top plate portion to the inside of a side wall portion of the battery case; and the battery case is sealed by crimping an end of the side wall portion of the battery case on the opening side to the sealing plate via the gasket, and the gasket is an annular body formed of polypropylene resin, and the annular body has an outer peripheral portion that follows the inner peripheral surface of the side wall portion of the battery case and a gasket disposed between the outer peripheral portion and the side wall portion of the battery case. and an extension portion extending from the bottom plate portion side of the inner peripheral surface of the polypropylene resin toward the center of the battery case, the extension portion having a lower end surface facing the bottom plate portion and an upper end surface abutting against the tip of the peripheral edge of the sealing plate, wherein, for the extension portion, a peak intensity IA of a Raman spectrum derived from the crystalline phase of the polypropylene resin and a peak intensity IB of a Raman spectrum derived from the amorphous phase of the polypropylene resin measured at a wavelength of 532 nm using a semiconductor laser are such that, when the distance from the upper end surface to the lower end surface is L, the minimum value of the ratio (IB / IA) of IB to IA is 0.75 or more and 0.90 or less.

[0009] According to the present disclosure, it is possible to provide a coin battery that can suppress the occurrence of cracks in the gasket and the occurrence of leakage of the electrolyte.

[0010] FIG. 1 is a longitudinal cross-sectional view of a coin-type lithium primary battery according to an embodiment of the present disclosure.

[0011] Below, embodiments of the present disclosure will be described using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values, materials, etc. may be applied as long as the effects of the present disclosure are obtained. Note that known components may be applied to components characteristic of the present disclosure. In this specification, when a "range from numerical value A to numerical value B" is mentioned, the range includes numerical value A and numerical value B.

[0012] In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties, conditions, etc. are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of them can be selected and used alone, or two or more can be used in combination, unless otherwise specified.

[0013] The present disclosure encompasses any combination of two or more claims arbitrarily selected from the appended claims, i.e., any combination of two or more claims arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0014] [Coin Battery] A coin-type lithium battery according to an embodiment of the present disclosure is a coin-type battery including a battery case having an opening, a power generating element housed in the battery case, a sealing plate that seals the opening of the battery case, and a gasket disposed between the battery case and the sealing plate. In the coin-type battery according to an embodiment of the present disclosure, the power generating element includes a positive electrode, a negative electrode facing the positive electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte. Hereinafter, the assembly of the battery case, the sealing plate, and the gasket may be referred to as an exterior body.

[0015] The coin battery may be a primary battery or a secondary battery. The coin battery may be a non-aqueous electrolyte battery such as a lithium primary battery, a lithium secondary battery, or a lithium ion battery. In the following, an example will be described in which the coin battery is a lithium primary battery.

[0016] [Power-generating element] (Positive electrode) The positive electrode is formed by press-molding a positive electrode mixture into a predetermined shape. The positive electrode mixture contains manganese dioxide. The positive electrode mixture may further contain a boron compound. Note that manganese dioxide is a positive electrode active material, and the boron compound is an additive for forming a protective coating on the surface of the negative electrode. When the lithium primary battery has a coin shape (or button shape), the positive electrode mixture has a pellet shape or a cylindrical (disc) shape corresponding to the coin shape. When the lithium primary battery has a coin shape, the thickness T of the positive electrode may be, for example, 400 μm or more and 2000 μm or less.

[0017] The manganese dioxide is preferably electrolytic manganese dioxide. Electrolytic manganese dioxide can usually be obtained by electrolyzing an aqueous manganese sulfate solution. The electrolytic manganese dioxide may be neutralized with an alkali, washed with water, or calcined. For example, the electrolytic manganese dioxide may be calcined in air or oxygen at 300 to 450°C for approximately 2 to 12 hours. Calcining the electrolytic manganese dioxide can volatilize water and promote crystallization. Furthermore, by controlling the calcination process, the electrolytic manganese dioxide can be made to contain a large amount of β-type crystal structure. Furthermore, by promoting crystallization, the specific surface area can be reduced. This can improve the structural stability and water-resistant reactivity of the electrolytic manganese dioxide. When uncalcined electrolytic manganese dioxide is used, the crystallinity can be increased by adjusting the conditions during electrolysis to reduce the specific surface area. Note that manganese dioxide other than electrolytic manganese dioxide can also be made to contain a large amount of β-type crystal structure by controlling the calcination process.

[0018] Manganese dioxide may have a crystal structure other than the β-type. Manganese dioxide may have, for example, an α-type, γ-type, δ-type, ε-type, η-type, λ-type, or ramsdellite-type crystal structure. The crystal structure of manganese dioxide can be analyzed using a general X-ray diffraction device (e.g., MXP-3 manufactured by Mac Science). This analysis can be performed using CuKα radiation (λ=1.5405 Å) as the radiation source, employing a step scan as the measurement mode, setting the scan conditions to 0.04° / second, the measurement time to 3 seconds, and a measurement range of 2θ from 5° to 80°.

[0019] The boron compound is preferably a compound having at least one of a B—O bond and a B═O bond. Whether the boron compound is a compound having at least one of a B—O bond and a B═O bond can be confirmed, for example, by XPS analysis. The boron compound is preferably at least one selected from the group consisting of boric acid, boron oxide, and lithium borate, and H ３ BO ３ , B ２ O ３ , LiBO ２ , Li ２ B ４ O ７ , and Li ３ BO ３ It is more preferable that the boron compound is at least one selected from the group consisting of: By using such a boron compound, it becomes easier to form a good protective film on the surface of the negative electrode.

[0020] The positive electrode may further contain a binder. Examples of binders include fluororesins, rubber particles, and acrylic resins. Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and polyvinylidene fluoride (PVDF). Examples of rubber particles include styrene butadiene rubber (SBR) and modified acrylonitrile rubber. Examples of acrylic resins include ethylene-acrylic acid copolymers. One type of binder may be used alone, or two or more types may be used in combination.

[0021] The positive electrode may contain 1% by mass or more and 10% by mass or less of a binder, or 1% by mass or more and 5% by mass or less. When the positive electrode contains 1% by mass or more of a binder, a sufficient positive electrode capacity can be ensured and the strength of the positive electrode can be ensured. When the positive electrode contains 10% by mass or less of a binder, a sufficient positive electrode capacity can be ensured and an increase in internal resistance can be sufficiently suppressed.

[0022] The positive electrode may contain graphite. Graphite functions as a conductive additive. By including graphite in the positive electrode, a sufficient number of electron conduction paths are ensured within the positive electrode. As a result, the output of the lithium primary battery is ensured.

[0023] The graphite may contain expanded graphite. The expanded graphite particles have a flat shape. The expanded graphite may be one that begins to expand by inserting an agent such as sulfuric acid or an organic acid between the basal planes of the graphite to widen the spacing between the basal planes (interlayer expansion) at a temperature of about 150°C to 300°C. Expanded graphite has a large interplanar spacing in the c-axis direction perpendicular to the basal planes, making it prone to exfoliation and therefore prone to becoming flat. The interplanar spacing (d200) of the (002) plane of the expanded graphite may be, for example, 3.37 Å or more. The crystallite size Lc(002) in the c-axis direction may be, for example, 500 Å or less. The interplanar spacing (d002) and the crystallite size Lc(002) can be obtained by analyzing data obtained by powder X-ray diffraction using CuKα radiation. Expanded graphite usually contains trace amounts of sulfate ions (SO ３ － ) remains.

[0024] The interplanar spacing (d002) can be calculated using the Bragg formula (λ=2d×sin θ).

[0025] λ: wavelength of CuKα ray (= 0.15418 nm) d: average interplanar spacing d002 of the (002) plane θ: half angle of 2θ at the peak position determined by the centroid method (rad) The crystallite size Lc(002) can be calculated from the half width of the X-ray diffraction peak assigned to the (002) plane using Scherrer's formula (D(nm) = 0.9 × λ / (β × cos θ)).

[0026] λ: CuKα wavelength (= 0.15418 nm) D: crystallite size β: half-width of the peak θ: 1 / 2 angle (rad) of 2θ at the peak position determined by the centroid method The positive electrode may contain 1% by mass or more and 10% by mass or less of graphite, or 1% by mass or more and 5% by mass or less. By containing 1% by mass or more of graphite in the positive electrode, the positive electrode capacity can be sufficiently ensured and the function as a conductive additive can also be sufficiently ensured. The graphite may contain 80% by mass or more of expanded graphite, or may contain 90% by mass or more. Furthermore, the graphite may contain 100% by mass of expanded graphite. That is, the graphite may contain only expanded graphite.

[0027] The positive electrode may contain a conductive additive other than graphite. Examples of conductive additives other than graphite include carbon black, carbon nanotubes, and carbon fibers other than carbon nanotubes. The carbon nanotubes may have a single-layer structure or a multi-layer structure. From the viewpoint of improving conductivity, the positive electrode preferably contains ketjen black. The positive electrode may contain 0.1% by mass or more and 5% by mass or less of ketjen black, or 0.5% by mass or more and 2% by mass or less.

[0028] (Negative Electrode) The negative electrode can be obtained, for example, by processing a metal sheet or metal foil into a predetermined shape. The metal sheet is formed, for example, from at least one of lithium metal and a lithium alloy. Examples of lithium alloys include lithium-aluminum alloys, lithium-tin alloys, lithium-silicon alloys, and lithium-lead alloys. When the lithium primary battery has a coin shape, the negative electrode has a disk shape corresponding to the coin shape. When the lithium primary battery has a coin shape, a foil made of at least one of lithium metal and a lithium alloy may be punched into a circle and used as the negative electrode.

[0029] (Separator) The separator may be made of any material that can prevent short-circuiting between the positive electrode and the negative electrode and retain the electrolyte. Examples of the separator include woven fabric, nonwoven fabric, and microporous film made of polyolefin, polyester, etc. Among these, it is preferable to use a polypropylene nonwoven fabric as the separator.

[0030] (Electrolyte) The electrolyte contains a non-aqueous solvent and a solute (salt). The solute concentration in the electrolyte is, for example, 0.3 mol / L or more and 2.0 mol / L or less. As the non-aqueous solvent, propylene carbonate (PC), ethylene carbonate (EC), 1,2-dimethoxyethane (DME), etc. can be used. These may be used alone or in combination of two or more. As the solute, LiClO ４ , LiPF ６ , LiBF ４ , LiCF ３ SO ３ , LiN(CF ３ SO ２ ) ２ etc. can be used.

[0031] [Exterior Body] The exterior body includes a battery case having an opening, a sealing plate that seals the opening of the battery case, and a gasket disposed between the battery case and the sealing plate.

[0032] In the coin-type lithium battery according to the embodiment of the present disclosure, the battery case is cylindrical and has a bottom plate and a side wall rising from the periphery of the bottom plate. The sealing plate has a top plate and a peripheral edge extending from the periphery of the top plate toward the inside of the side wall of the battery case. The gasket is an annular body made of polypropylene resin. The annular body has an outer periphery that fits along the inner periphery of the side wall of the battery case, and an extension that extends from the bottom plate side of the inner periphery of the outer periphery toward the center of the battery case. The extension has a lower end surface that faces the bottom plate and an upper end surface that is located opposite the lower end surface and abuts against the tip of the peripheral edge of the sealing plate.

[0033] In the exterior body, the outer surface of the bottom plate of the battery case serves as a first terminal surface (e.g., a positive electrode terminal surface), and the outer surface of the top plate of the sealing plate serves as a second terminal surface (e.g., a negative electrode terminal surface). In addition, in the exterior body, the end of the side wall of the battery case is bent inward. This bending allows the end of the side wall to be crimped to the periphery of the sealing plate via a gasket. That is, the exterior body is sealed by crimping the end of the opening side of the side wall of the battery case to the sealing plate via a gasket.

[0034] In the coin-type lithium battery according to the embodiment of the present disclosure, the Raman spectrum of the extension portion measured at a wavelength of 532 nm using a semiconductor laser has a peak intensity IA derived from the crystalline phase of the polypropylene resin and a peak intensity IB derived from the amorphous phase of the polypropylene resin. In the region from a depth of 0.25L to a depth of 0.75L, where L is the distance from the top end face to the bottom end face, the minimum ratio of IB to IA (IB / IA) is 0.75 or more and 0.90 or less. Furthermore, by providing the above configuration, it is possible to prevent cracks from occurring in the gasket and leakage of the electrolyte. The reason for this is explained below.

[0035] In the coin-type battery according to the embodiment of the present disclosure, when the opening edge of the side wall of the battery case is crimped to the sealing plate via the gasket to seal the battery case, the leading edge of the peripheral edge of the sealing plate is pressed from the upper end face toward the lower end face into the extension of the gasket. If the leading edge of the peripheral edge of the sealing plate is not pressed sufficiently into the extension of the gasket, minute gaps may form between the upper end face of the extension of the gasket and the leading edge of the peripheral edge of the sealing plate, or between the lower end face of the extension of the gasket and the bottom plate of the battery case, and some of the electrolyte contained in the power generating element may leak through these gaps to the outside. Furthermore, if the stress generated in the extension of the gasket when the leading edge of the peripheral edge of the sealing plate is pressed into the extension of the gasket is large, the stress may cause cracks to form on the upper end face of the extension of the gasket, etc.

[0036] It is believed that the crystalline phase of polypropylene resin exhibits hard properties due to the regular arrangement of molecules, while the amorphous phase of polypropylene resin exhibits soft properties due to the random arrangement of molecules. For this reason, the higher the proportion of the crystalline phase of polypropylene resin (the lower the proportion of the amorphous phase) in the extended portion of the gasket, the harder the polypropylene resin will be, and the greater the stress caused by the impact when the tip of the peripheral edge of the sealing plate is pressed in, which may cause cracks to form on the upper end surface of the extended portion of the gasket. On the other hand, the higher the proportion of amorphous phase in the polypropylene resin (the lower the proportion of crystalline phase) in the extended portion of the gasket, the more flexible the properties that are exhibited, and the less stress caused by the impact when the tip of the peripheral edge of the sealing plate is pressed in. However, when a force is applied to push out the contents (electrolyte) due to, for example, an increase in pressure inside the coin-type battery, it is thought that the force cannot be resisted and the electrolyte may leak from at least one of the spaces between the upper end surface of the extended portion of the gasket and the tip of the peripheral edge of the sealing plate, and between the lower end surface of the extended portion of the gasket and the bottom plate of the battery case.

[0037] However, in the coin battery according to the embodiment of the present disclosure, when the distance from the top surface to the bottom surface of the extension portion is L, in the region from a depth of 0.25L to a depth of 0.75L from the top surface, the minimum ratio (IB / IA) of the peak intensity IB of the Raman spectrum derived from the amorphous phase of the polypropylene resin to the peak intensity IA of the Raman spectrum derived from the crystalline phase of the polypropylene resin is 0.75 or more and 0.90 or less. Therefore, it is believed that the extension portion of the gasket can exhibit a good balance of hardness derived from the crystalline phase and flexibility derived from the amorphous phase. Therefore, it is believed that the coin lithium battery according to the embodiment of the present disclosure can sufficiently suppress cracks in the gasket and leakage of electrolyte after sealing by crimping.

[0038] The peak intensity IA derived from the crystalline phase of the polypropylene resin and the peak intensity IB derived from the amorphous phase can be obtained by selecting any three locations in the region between the upper and lower end surfaces of the extension portion, measuring the peak intensity IA and the peak intensity IB at depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), and then arithmetically averaging the measured values. The Raman spectrum can be measured by microscopic laser Raman spectroscopy. The following conditions can be used for this measurement. It is preferable to measure the Raman spectrum of the gasket before it is placed in the battery case. If the gasket is manufactured by injection molding and a weld line is present, it is preferable to select a location that avoids the weld line for measurement.

[0039] <Measurement conditions for microscopic laser Raman spectroscopy> Apparatus: JASCO NSR-5100 Measurement method: microscopic measurement (×20) Irradiation laser light wavelength: 532 nm Output: 4.8 mW Slit: 100 × 1000 μm Aperture: φ4000 μm Exposure: 10 sec × 3 times In the Raman spectrum, the peak intensity IA derived from the crystalline phase of polypropylene resin is usually 805 cm－１ ~815cm －１ The peak intensity IB due to the amorphous phase of the polypropylene resin is usually detected in the range of 835 cm －１ Over 845cm －１ It is detected in the range.

[0040] The gasket can be produced by injection molding using a polypropylene resin. Furthermore, in the extended portion of the gasket, the ratio (IB / IA) of the peak intensity IB of the Raman spectrum derived from the amorphous phase of the polypropylene resin to the peak intensity IA of the Raman spectrum derived from the crystalline phase of the polypropylene resin can be adjusted by changing the molding conditions of the injection molding. For example, this can be adjusted by changing the mold temperature and the dwell pressure. The peak intensity IA of the Raman spectrum derived from the crystalline phase can be reduced by lowering the mold temperature or increasing the dwell pressure.

[0041] The polypropylene resin may be a homopolymer or a copolymer. Examples of monomers other than propylene that constitute the copolymer include ethylene and butene-1. The copolymer may be a random copolymer or a block copolymer. The polypropylene resin is preferably a homopolymer. When the polypropylene resin is a homopolymer, it has excellent stereoregularity. This makes it easier to adjust the ratio of the crystalline phase to the amorphous phase of the polypropylene resin in the extended portion of the gasket.

[0042] The polypropylene resin may contain an isotactic structure, a syndiotactic structure, or an atactic structure as a structural unit portion derived from propylene. From the viewpoint of industrial availability, it is preferable that the polypropylene resin contains an isotactic structure as a structural unit portion derived mainly from propylene. The polypropylene resin may contain a resin component other than polypropylene. The polypropylene resin may contain 1 to 30 parts by mass of a resin component other than polypropylene per 100 parts by mass of polypropylene. The polypropylene resin may also contain additives such as antioxidants and fillers.

[0043] In the coin battery according to the embodiment of the present disclosure, the change A of IB / IA in the region from the upper end surface of the extension portion of the gasket to a depth of 0.25 L is Ｃ is preferably -0.68 or more and less than 0. In other words, it is preferable that the ratio of the crystalline phase to the amorphous phase of the polypropylene resin does not change too much in the surface layer portion of the extended portion of the gasket. This makes it possible to more suitably suppress the occurrence of cracks on the upper end surface of the extended portion of the gasket. Note that the change A of IB / IA Ｃ can be obtained by subtracting the value of IB / IA at the upper end surface (0.00L) from the value of IB / IA at 0.25L and dividing the obtained value by 0.25.

[0044] In the coin-type lithium battery according to the embodiment of the present disclosure, the peripheral edge of the sealing plate may be folded back at the leading end to form a double structure, or may be not folded back at the leading end but have a single structure. When the peripheral edge of the sealing plate is folded back at the leading end, the leading end of the peripheral edge also has a double structure, and when the peripheral edge of the sealing plate is not folded back at the leading end, the leading end of the peripheral edge also has a single structure. When the leading end of the peripheral edge has a single structure, at least the side facing the outer periphery of the gasket is chamfered.

[0045] In gaskets for coin-type batteries, cracks often occur on the upper end surface, etc., starting from the boundary between the upper end surface and the outer periphery. However, if the leading edge of the sealing plate's peripheral edge is chamfered, at least on the side facing the outer periphery of the gasket, the contact area between the leading edge of the sealing plate's peripheral edge and the upper end surface of the gasket's extension can be reduced, thereby reducing the area where stress occurs on the upper end surface of the gasket's extension when the leading edge of the sealing plate's peripheral edge is pressed in. In addition, since the contact surface and the boundary can be spaced apart, when stress generated on the contact surface propagates to the boundary, the stress can be sufficiently dispersed between the contact surface and the boundary. In other words, most of the stress generated on the contact surface can be prevented from being directly applied to the boundary. Therefore, even when the upper end of the chamfered portion reaches the boundary when the leading edge of the sealing plate's peripheral edge is pressed in, the stress generated at that portion can be reduced. This prevents cracks from occurring on the upper end surface of the gasket, etc., starting from the boundary.

[0046] As described above, when the leading edge of the peripheral edge of the sealing plate is chamfered, the chamfered leading edge is preferably an R-surface with a curvature radius of 0.25L or more or a C-surface with a dimension of 0.25L or more.

[0047] In gaskets for coin batteries manufactured by injection molding or other molding processes, residual molding stress is often high in the region of the extension from the top surface of the extension to a depth of 0.25L (hereinafter referred to as the first region), i.e., the surface region of the extension. In contrast, residual molding stress is often significantly lower in regions deeper than 0.25L (e.g., a region to a depth of 0.75L; hereinafter referred to as the second region). In such cases, when the tip of the peripheral edge of the sealing plate is pressed into the top surface of the gasket's extension, the first region has poorer resistance to impact during pressing than the second region. However, by chamfering the tip of the peripheral edge of the sealing plate as described above, the stress caused by impact during pressing in the first region can be reduced. This effectively prevents cracks from occurring on the top surface of the gasket's extension due to the impact during pressing.

[0048] When the peripheral edge of the sealing plate is folded back at the tip to form a double structure as described above, the tip of the peripheral edge of the sealing plate is preferably chamfered so that the radius of curvature of at least the side facing the outer periphery of the gasket is 0.25L or more. Even when the tip of the peripheral edge of the sealing plate is chamfered as described above, it is possible to more sufficiently prevent cracks from occurring on the upper end surface of the extension of the gasket due to the impact when the sealing plate is pressed in. The tip of the peripheral edge of the sealing plate may also be chamfered so that the side not facing the outer periphery of the gasket has a radius of curvature of 0.25L or more.

[0049] Next, a specific configuration of a coin-type battery according to an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a longitudinal cross-sectional view of a coin-type lithium primary battery according to an embodiment of the present disclosure.

[0050] The coin-type lithium primary battery 10 includes an exterior body composed of a case 3, a sealing plate 8, and a gasket 7. The case 3 is a battery can having a bottom plate 3a and a side wall 3b rising from the periphery of the bottom plate 3a. In the case 3, the bottom plate 3a and the side wall 3b are connected via a bent portion 9. In the example shown in FIG. 1, the case 3 is formed in a shallow cylindrical shape. The sealing plate 8 has a top plate 8a and a peripheral edge portion 8b extending from the periphery of the top plate 8a to the inside of the side wall 3b of the case 3. In the example shown in FIG. 1, the peripheral edge portion 8b of the sealing plate 8 is folded back at its tip, forming a double-layered structure at its tip 8b1. The gasket 7 is annular and has an outer peripheral portion 7a that fits along the inner periphery of the side wall 3b of the case 3 and an extension portion 7b that extends from the bottom plate 3a side of the inner periphery of the outer peripheral portion 7a toward the center of the case 3. The extension portion 7b has a lower end surface 7b1 facing the bottom plate portion 3a, and an upper end surface 7b2 located on the opposite side to the lower end surface.

[0051] In the coin-type lithium primary battery 10, the end of the side wall 3b of the case 3 is bent inward. This bending causes the end of the side wall 3b to be crimped onto the peripheral edge 8b of the sealing plate 8 via the gasket 7. In this manner, the case 3 and the sealing plate 8 are crimped together. That is, in the coin-type lithium primary battery 10, the opening end of the side wall 3b of the case 3 is crimped onto the sealing plate 8 via the gasket 7 to seal the opening. This seals the gap between the case 3 and the sealing plate 8 in the coin-type lithium primary battery 10. Furthermore, by crimping the case 3 and the sealing plate 8 together as described above, the tip 8b1 of the peripheral edge 8b of the sealing plate 8 comes into contact with the upper end surface 7b2 of the extension 7b of the gasket 7.

[0052] The exterior housing contains a power generating element. The power generating element includes a positive electrode 4, a negative electrode 5, a separator 6, and an electrolyte. In the example shown in FIG. 1 , the positive electrode 4 is disposed so as to face the bottom plate portion 3a of the case 3. Therefore, the outer surface of the bottom plate portion 3a functions as a positive electrode terminal surface. On the other hand, the negative electrode 5 is disposed so as to face the top plate portion 8a of the sealing plate 8. Therefore, the outer surface of the top plate portion 8a functions as a negative electrode terminal surface.

[0053] As described above, the coin battery according to the embodiment of the present disclosure is not limited to a lithium primary battery. The coin battery according to the embodiment of the present disclosure may be a lithium secondary battery. When the coin battery is a lithium secondary battery, a material capable of reversibly absorbing and releasing lithium ions is used as the positive electrode active material. Examples of such materials include lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), lithium iron phosphate (LiFePO ４ ), general formula: Li ｘ MnO ｙ Examples of the lithium-containing manganese oxide include lithium-containing transition metal oxides represented by the following formula:

[0054] (Additional Note) The above description discloses the following techniques.

[0055] (Technology 1) A coin-type battery comprising: a battery case having an opening; a power-generating element housed in the battery case; a sealing plate that seals the opening of the battery case; and a gasket arranged between the battery case and the sealing plate, wherein the battery case is formed in a cylindrical shape with a bottom and has a bottom plate portion and a side wall portion rising from a peripheral edge of the bottom plate portion, and the sealing plate has a top plate portion and a peripheral edge portion extending from the peripheral edge of the top plate portion to the inside of the side wall portion of the battery case, and the coin-type battery is sealed by crimping an end of the side wall portion of the battery case on the opening side to the sealing plate via the gasket, wherein the gasket is an annular body made of polypropylene resin, and the annular body has an outer circumferential portion that follows the inner circumferential surface of the side wall portion of the battery case, and an extension portion that extends from the bottom plate side of the inner circumferential surface of the outer circumferential portion toward the center of the battery case, the extension portion has a lower end surface facing the bottom plate portion, and an upper end surface located opposite the lower end surface and abutting against a tip end of the peripheral edge portion of the sealing plate, wherein a peak intensity IA of the Raman spectrum derived from the crystalline phase of the polypropylene resin and a peak intensity IB of the Raman spectrum derived from the amorphous phase of the polypropylene resin measured for the extension portion using a semiconductor laser at a wavelength of 532 nm have a minimum value of 0.75 to 0.90 in a region from a depth of 0.25L to a depth of 0.75L, where L is the distance from the upper end surface to the lower end surface.

[0056] (Technology 2) In a region having a depth of 0.25L from the upper end surface, the change amount A of the IB / IA Ｃ is greater than or equal to −0.68 and less than 0.

[0057] The coin battery according to Technology 1.

[0058] (Technology 3) The coin battery according to Technology 1 or 2, wherein the peripheral edge of the sealing plate is not folded back at the tip end and has a single-layer structure, and the tip end of the peripheral edge of the sealing plate is chamfered at least on the side facing the outer periphery of the gasket.

[0059] (Technology 4) The coin battery according to Technology 3, wherein the chamfered tip is an R-surface with a curvature radius of 0.25L or more or a C-surface with a dimension of 0.25L or more.

[0060] (Technology 5) The coin battery according to Technology 1 or 2, wherein the peripheral edge of the sealing plate is folded back at the tip to form a double structure, and the tip of the peripheral edge of the sealing plate is chamfered so that the radius of curvature of at least the side facing the outer periphery of the gasket is 0.25 L or more.

[0061] While the present invention has been described with respect to presently preferred embodiments, such disclosure should not be interpreted as limiting. Various variations and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all variations and modifications that do not depart from the true spirit and scope of the invention.

[0062] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0063] [Example 1] (1) Positive Electrode Electrolytic manganese dioxide, expanded graphite, and ketjen black were dry-mixed in a mass ratio of 100:4:1 (electrolytic manganese dioxide:expanded graphite:ketjen black) to obtain a dry mixture. Next, an aqueous dispersion containing polytetrafluoroethylene (PTFE) was added to the obtained dry mixture, followed by wet-mixing to obtain a wet mixture. The aqueous dispersion was added so that the polytetrafluoroethylene content was 2% by mass relative to 100% by mass of electrolytic manganese dioxide. The wet mixture was then dried to obtain a positive electrode mixture. This positive electrode mixture was tableted into a cylindrical shape with a diameter of 14.5 mm and a thickness of 1.92 mm to prepare a positive electrode. The cylindrical positive electrode pellets were dried at 250°C for 8 hours.

[0064] (2) Electrolyte: Propylene carbonate (PC) and 1,2-dimethoxyethane (DME) were mixed in a volume ratio of 50:50 (PC:DME) to obtain a mixed non-aqueous solvent, and then lithium perchlorate (LiClO) was added as a solute to the mixed non-aqueous solvent.４ ) was dissolved at a concentration of 1.0 mol / L to obtain an electrolyte solution.

[0065] (3) Negative Electrode A lithium metal foil having a thickness of 0.6 mm was punched into a circle having a diameter of 16 mm to prepare a negative electrode.

[0066] (4) Separator and Gasket A polypropylene nonwoven fabric was used as the separator. The gasket was manufactured by injection molding using polypropylene resin to form a ring-shaped body. Specifically, the gasket had an outer peripheral portion that fit along the side wall of the battery case and an extension portion that extended from the bottom plate portion (bottom plate portion of the battery case) of the inner peripheral surface of the outer peripheral portion toward the center of the battery case. The injection molding conditions were a mold temperature of 55°C and a holding pressure of 139 MPa. A homopolymer was used as the polypropylene resin.

[0067] For the extension portion of the gasket, a semiconductor laser was used at 532 nm to measure the peak intensity I of the Raman spectrum derived from the crystalline phase of the polypropylene resin. Ａ and the peak intensity I of the Raman spectrum derived from the amorphous phase of the polypropylene resin. Ｂ The peak intensities IA and IB were measured according to the method described in the embodiment section above. At this time, if a weld line was formed during injection molding, a location was selected that avoided the weld line. Then, when the distance from the upper end face to the lower end face is L, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end face), 0.25L, 0.50L, 0.75L, and 1.00L (lower end face). In addition, in the region from the upper end face to a depth of 0.25L, the change A of IB / IA was calculated. Ｃ The slope of IB / IA (the slope of IB / IA in the range of 0.00 L or more and 0.25 L or less) was calculated. The results are shown in Table 1 below. The lower end surface of the extension portion refers to the surface facing the bottom plate portion of the battery case, and the upper end surface of the extension portion refers to the surface located opposite the lower end surface.

[0068] (4) Battery Case A battery case having a bottom plate diameter of 20 mm and a side wall height of 1.1 mm was fabricated by drawing SUS430 (thickness 250 μm) having a 3 μm thick nickel plating layer on its surface.

[0069] (5) Sealing Plate A sealing plate with a top diameter of 17 mm was fabricated by pressing SUS430 (thickness: 250 μm) having a 3 μm-thick nickel-plated layer on its surface. As shown in FIG. 1 , the sealing plate had a top plate and a peripheral edge extending from the periphery of the top plate to the inside of the side wall of the case.

[0070] (6) Assembly of a Coin-Type Lithium Primary Battery A polypropylene gasket was placed on the sealing plate. A negative electrode was attached to the inside of the top plate of the sealing plate. Next, one side of a 300 μm-thick polypropylene nonwoven fabric (separator) was placed on the negative electrode. Next, a positive electrode was placed on the other side of the polypropylene nonwoven fabric. Next, an electrolyte was injected into the sealing plate. A sealant consisting of blown asphalt and mineral oil was applied to the inside of the sides of the battery case in advance, and the battery case was then placed on the sealing plate. The end of the side wall of the case was then bent inward. This bending allowed the end of the side wall to be crimped to the peripheral edge of the sealing plate via the gasket. This resulted in the production of a coin-type lithium primary battery according to Example 1.

[0071] [Example 2] A coin-type lithium primary battery according to Example 2 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 45°C and a holding pressure of 159 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, the change A of IB / IA in the region from the upper end surface to a depth of 0.25L was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0072] [Example 3] A coin-type lithium primary battery according to Example 3 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 45°C and a holding pressure of 98 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, in the region from the upper end surface to a depth of 0.25L, the change A of IB / IA was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0073] [Example 4] A coin-type lithium primary battery according to Example 4 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 50°C and a holding pressure of 122 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, the change A of IB / IA in the region from the upper end surface to a depth of 0.25L was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0074] [Example 5] A coin-type lithium primary battery according to Example 5 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 45°C and a holding pressure of 134 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, in the region from the upper end surface to a depth of 0.25L, the change A of IB / IA was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0075] [Example 6] A coin-type lithium primary battery according to Example 6 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 57°C and a holding pressure of 168 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, in the region from the upper end surface to a depth of 0.25L, the change A of IB / IA was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0076] [Example 7] A coin-type lithium primary battery according to Example 7 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 45°C and a holding pressure of 147 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, in the region from the upper end surface to a depth of 0.25L, the change A of IB / IA was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0077] [Comparative Example 1] A coin-type lithium primary battery according to Comparative Example 1 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 70°C and a holding pressure of 110 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, in the region from the upper end surface to a depth of 0.25L, the change A of IB / IA was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0078] [Comparative Example 2] A coin-type lithium primary battery according to Comparative Example 2 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 80°C and a holding pressure of 110 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, in the region from the upper end surface to a depth of 0.25L, the change A of IB / IA was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0079] [Comparative Example 3] A coin-type lithium primary battery according to Comparative Example 3 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 80°C and a holding pressure of 134 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, in the region from the upper end surface to a depth of 0.25L, the change A of IB / IA was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0080] [Comparative Example 4] A coin-type lithium primary battery according to Comparative Example 4 was obtained in the same manner as in Example 1, except that a gasket manufactured under molding conditions of a mold temperature of 39°C and a holding pressure of 134 MPa was used. Furthermore, for the extension portion of the gasket, the ratio of IB to IA (IB / IA) was calculated for depths of 0.00L (upper end surface), 0.25L, 0.50L, 0.75L, and 1.00L (lower end surface), where L is the distance from the upper end surface to the lower end surface. Furthermore, in the region from the upper end surface to a depth of 0.25L, the change A of IB / IA was calculated. Ｃ The slope of IB / IA in the range of 0.00 L to 0.25 L was calculated. The results are shown in Table 1 below.

[0081] <Evaluation> Number of cracks and leakages The coin-type lithium primary batteries according to each example (Examples 1 to 7 and Comparative Examples 1 to 4) were evaluated for the number of cracks and leakages according to the following procedure. The evaluation results for the number of cracks and leakages are shown in Table 1 below.

[0082] <Procedure> (1) 100 coin-type lithium primary batteries according to each example are fabricated. (2) The fabricated coin-type lithium primary batteries are subjected to an aging treatment at 45°C for 4 days. (3) The coin-type lithium primary batteries after the aging treatment are subjected to an X-ray inspection, and the number of batteries for which white dots are confirmed on the circumference corresponding to the extended portion of the gasket is counted. This evaluates the number of cracks that have occurred. (4) For the coin-type lithium primary batteries after the X-ray inspection, the number of batteries for which leakage has occurred is visually counted. This evaluates the number of batteries for which leakage has occurred.

[0083]

[0084] As can be seen from Table 1, no cracks occurred in the gasket and no leakage of electrolyte was confirmed in the coin-type lithium primary batteries according to Examples 1 to 7. In contrast, no leakage of electrolyte was confirmed in the coin-type lithium primary batteries according to Comparative Examples 1 to 3, but cracks occurred in the gasket. Furthermore, in the coin-type lithium primary battery according to Comparative Example 4, no cracks occurred in the gasket, but leakage of electrolyte was confirmed.

[0085] The coin-type lithium battery according to the present disclosure can be used in applications where it is necessary to prevent cracks from occurring in the gasket and leakage of the electrolyte.

[0086] 3: Case 3a: Bottom plate portion, 3b: Side wall portion 4: Positive electrode 5: Negative electrode 6: Separator 7: Gasket 7a: Outer periphery portion, 7b: Extension portion, 7b1: Lower end surface, 7b2: Upper end surface 8: Sealing plate 8a: Top plate portion, 8b: Peripheral edge portion, 8b1: ​​Tip portion 9: Bent portion 10: Coin-type lithium primary battery

Claims

1. A coin-type battery comprising: a battery case having an opening; a power generating element housed within the battery case; a sealing plate that seals the opening of the battery case; and a gasket arranged between the battery case and the sealing plate, wherein the battery case is formed in a cylindrical shape with a bottom and has a bottom plate portion and a side wall portion rising from the peripheral edge of the bottom plate portion, and the sealing plate has a top plate portion and a peripheral edge portion extending from the peripheral edge of the top plate portion to the inside of the side wall portion of the battery case, and the coin-type battery is sealed by crimping the end of the side wall portion of the battery case on the opening side to the sealing plate via the gasket, wherein the gasket is an annular body made of polypropylene resin, and the annular body has an outer circumferential portion that follows the inner circumferential surface of the side wall portion of the battery case, and an extension portion that extends from the bottom plate side of the inner circumferential surface of the outer circumferential portion toward the center of the battery case, the extension portion has a lower end surface facing the bottom plate portion and an upper end surface abutting against a tip end of the peripheral edge portion of the sealing plate, and the extension portion has a peak intensity IA of a Raman spectrum derived from a crystalline phase of the polypropylene resin and a peak intensity IB of a Raman spectrum derived from an amorphous phase of the polypropylene resin measured at a wavelength of 532 nm using a semiconductor laser, and the minimum value of the ratio (IB / IA) of IB to IA in a region from a depth of 0.25L to a depth of 0.75L is 0.75 or more and 0.90 or less, where L is the distance from the upper end surface to the lower end surface.

2. In the region from the upper end surface to a depth of 0.25L, the change amount A of the IB / IA Ｃ is greater than or equal to −0.68 and less than 0. The coin battery according to claim 1 .

3. The coin battery according to claim 1 or 2, wherein the peripheral edge of the sealing plate has a single-layer structure without being folded back at the tip, and at least the tip of the peripheral edge of the sealing plate is chamfered on the side facing the outer periphery of the gasket.

4. The coin battery according to claim 3, wherein the chamfered tip is an R-surface with a radius of curvature of 0.25L or more or a C-surface with a dimension of 0.25L or more.

5. The coin battery according to claim 1 or 2, wherein the peripheral edge of the sealing plate is folded back at the tip to form a double structure, and the tip of the peripheral edge of the sealing plate is chamfered so that the radius of curvature of at least the side facing the outer periphery of the gasket is 0.25L or more.

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