JP2012209178A - Coin-shaped battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, under such case as exposed to a high temperature environment, a positive electrode case is expanded when the internal pressure of a battery rises to exceed an estimated level, discouraging contact between a positive electrode and the positive electrode case, resulting in rising of an internal resistance.SOLUTION: In a coin-shaped battery, a positive electrode 10 is arranged on the inner surface of a positive electrode case 13 which works as an external terminal as well. The positive electrode 10 faces a negative electrode 11 arranged on the inner surface of a negative electrode sealing plate 14 which works as an external terminal as well through a separator 12. The peripheral edges of the positive electrode case 13 and the negative electrode sealing plate 14 are sealed with a gasket 15 to hold an electrolyte inside it. At a position corresponding to the outer peripheral part of the positive electrode 10 on the inner bottom surface of the positive electrode case 13, a plurality of projections 13a are provided which more strongly contact to the peripheral surface of the positive electrode 10 because the positive electrode case 13 is expanded because of rising of internal pressure.

Description

  The present invention relates to a coin-type battery used for various portable electronic devices and the like.

  Coin-type batteries are also called button-type batteries and flat-type batteries, and when small size is required such as wristwatches and keyless entry by taking advantage of their small and thin characteristics, or long-term backup such as memory backup for OA equipment and FA equipment. Widely used when required. It is also used for various meters and power supplies for measuring machines, and its use is expanding. In recent years, there has been a demand for use in more severe environments such as automobiles and industrial equipment, and at the same time, improvements for further higher performance are being promoted.

  A coin-type battery is formed by placing a positive electrode and a negative electrode facing each other through a separator in a battery case, filling the electrolyte, and then caulking and sealing the opening of the positive electrode case with a negative electrode sealing plate via a gasket. Yes. In terms of electrical continuity, the positive electrode and the negative electrode are stacked via a separator, and are electrically connected to each other by contact with a positive electrode case that also serves as an external terminal and a negative electrode sealing plate. In such a coin-type battery, when the internal pressure of the battery rises, such as when exposed to a high temperature environment, the outer case swells, making it difficult to make contact between the positive electrode and the positive electrode case, which may increase the internal resistance.

  Therefore, the device which raises the contact property of the positive electrode and the inner surface of a positive electrode case, and suppresses a raise of internal resistance is made | formed. For example, in the coin-type battery of Patent Document 1, it is disclosed that a spring or the like is disposed on the inner bottom surface of the positive electrode case, and the contact between the positive electrode and the positive electrode case is ensured by the repulsive force of the spring or the like.

Japanese Patent Laid-Open No. 03-022346

  However, even in the battery shown in Patent Document 1, since contact in the vertical direction is the basis for conduction, if the battery internal pressure rises beyond the assumption and the outer case swells, the contact between the positive electrode and the positive electrode case is removed. In some cases, the internal resistance increased.

  An object of the present invention is to provide a highly reliable coin-type battery that can suppress an increase in contact resistance between a positive electrode and a positive electrode case even when the internal pressure of the battery increases beyond the assumption and the outer case swells.

  In order to solve the above problems, the coin-type battery of the present invention has a positive electrode disposed on the inner surface of a positive electrode case that also serves as an external terminal, and a negative electrode disposed on the inner surface of a negative electrode sealing plate that also serves as an external terminal via a separator. In the coin-type battery in which the positive electrode case and the sealing plate are opposed to each other and the peripheral edge thereof is sealed with a gasket so as to hold the electrolyte solution therein, it corresponds to the outer peripheral portion of the positive electrode on the inner bottom surface of the positive electrode case. A plurality of protrusions are provided at a position that come into stronger contact with the peripheral surface of the positive electrode when the positive electrode case swells due to an increase in internal pressure.

  According to the present invention, the positive electrode is disposed on the inner surface of the positive electrode case also serving as the external terminal, and the negative electrode disposed on the inner surface of the negative electrode sealing plate also serving as the external terminal is opposed to the positive electrode via the separator. In a coin-type battery in which the peripheral part is sealed with a gasket so as to hold the electrolyte solution inside the sealing plate, even if the battery internal pressure rises beyond expectation and the outer case swells, the positive electrode and the positive electrode case It is possible to provide a highly reliable coin-type battery that can suppress an increase in contact resistance.

Sectional drawing which shows typically the structure of the coin-type battery which is one embodiment of this invention The top view of the bottom face of the positive electrode case which formed the circular-arc-shaped protrusion which is one embodiment of this invention The top view of the bottom face of the positive electrode case which formed the dotted | punctate protrusion which is one embodiment of this invention Sectional drawing which shows typically the structure of the coin-type battery which is other embodiment of this invention. Sectional drawing which shows typically the structure of the coin-type battery which is other embodiment of this invention. Sectional drawing which shows the structure of the coin-type battery of a comparative example typically

  According to a first aspect of the present invention, a positive electrode is disposed on the inner surface of a positive electrode case that also serves as an external terminal, and the negative electrode disposed on the inner surface of a negative electrode sealing plate that also serves as an external terminal is opposed to the positive electrode via a separator. In a coin-type battery in which a peripheral portion is sealed with a gasket so as to hold an electrolyte solution inside the case and a sealing plate, the positive electrode case is located at a position corresponding to the outer peripheral portion of the positive electrode on the inner bottom surface of the positive electrode case. A coin-type battery comprising a plurality of protrusions that come into contact with the peripheral surface of the positive electrode by swelling due to an increase in internal pressure.

  With this configuration, not only the vertical contact that weakens when the exterior case swells but also the lateral contact that becomes stronger as the exterior case swells, the battery internal pressure rises beyond the assumption and the exterior case swells. Even in this case, it is possible to provide a highly reliable coin-type battery that can suppress an increase in contact resistance between the positive electrode and the positive electrode case.

  According to a second aspect of the present invention, in the first aspect, the tip of the protrusion is shaped to face the center side of the positive electrode.

  With this configuration, contact between the positive electrode and the positive electrode case can be more reliably ensured even with a slight expansion, and a highly reliable coin-type battery can be provided.

  According to a third aspect of the present invention, in the first aspect of the present invention, a metal ring is disposed on the outer periphery of the positive electrode with which the protrusion is in strong contact, and the positive case swells by restricting the protrusion to the inside. It is set as the structure which suppresses.

  With this configuration, when the internal pressure rises and the positive electrode case is about to expand, the metal ring prevents the protrusion from inclining toward the center side of the positive electrode, so that the positive electrode case is prevented from expanding and the highly reliable coin A battery can be provided.

  Embodiments of the present invention will be described below. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

FIG. 1 is a half sectional view schematically showing a configuration of a coin-type battery 1 according to an embodiment of the present invention. The coin-type battery 1 is a coin-type battery including a positive electrode 10, a negative electrode 11, a separator 12, a positive electrode case 13 on the positive electrode side, a negative electrode sealing plate 14 on the negative electrode side, a gasket 15, and a non-aqueous electrolyte (not shown). In this embodiment, a coin-type lithium primary battery will be described as an example.

  The positive electrode 10 includes a positive electrode active material, a conductive material, and a binder, and is provided to face the negative electrode 11 with a separator 12 interposed therebetween.

  As the positive electrode active material, those commonly used in the field of lithium primary batteries can be used, and among them, fluorinated graphite, metal oxides and the like are preferable. As the fluorinated graphite, those represented by the chemical formula CF (0.8 ≦ x ≦ 1.1) are preferable. Fluorinated graphite is excellent in terms of long-term reliability, safety, and high-temperature stability. Fluorinated graphite is obtained by fluorinating petroleum coke, artificial graphite and the like. Examples of the metal oxide include manganese dioxide and copper oxide. A positive electrode active material can be used individually by 1 type or in combination of 2 or more types.

  As the conductive material, those commonly used in the field of lithium primary batteries can be used. For example, carbon black such as acetylene black and ketjen black, and graphite such as artificial graphite can be used. A conductive material can be used individually by 1 type or in combination of 2 or more types. As the binder, those commonly used in the field of lithium primary batteries can be used. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), modified PVDF, tetrafluoroethylene-hexafluoropropylene copolymer Copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer Polymer (ETFE resin), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene Pyrene - fluororesin such as tetrafluoroethylene copolymer, styrene-butadiene rubber (SBR), modified acrylonitrile rubber, ethylene - like acrylic acid copolymer.

  A binder can be used individually by 1 type or in combination of 2 or more types.

  The negative electrode 11 contains lithium or a lithium alloy, and is provided so as to face the positive electrode 10 with the separator 12 interposed therebetween. As the lithium alloy, those commonly used in the field of lithium primary batteries can be used, and examples thereof include Li—Al, Li—Sn, Li—NiSi, and Li—Pb.

  The separator 12 is not particularly limited as long as it can prevent the short-circuit between the positive electrode 10 and the negative electrode 11 as long as it can be used in the coin-type battery field. It is desirable that it has excellent properties and does not become an ion migration resistance. Typical materials include polyolefin, polyester, polycarbonate, polyacrylate, polymethacrylate, polyamide, polytetrafluoroethylene, polyvinylidene fluoride, polysulfone, polyethersulfone, polybenzimidazole, polyetheretherketone, polyphenylene, etc. Examples of the shape include a nonwoven fabric and a microporous film.

  The nonaqueous electrolytic solution contains a solute and a nonaqueous solvent.

As the solute, those commonly used in the field of lithium primary batteries can be used. For example, lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ) , Lithium-bispentafluoroethylsulfonic acid imide (LiN (SO ₂ C ₂ F ₅ ) ₂ ), lithium bis (trifluoromethylsulfonyl) imide (LiN (CF ₃ SO ₂ ) ₂ ), lithium tris (trifluoromethylsulfonyl) ) Methide (LiC (CF ₃ SO ₂ ) ₃ ), lithium perchlorate (LiClO ₄ ) and the like. Solutes can be used alone or in combination of two or more.

  As the non-aqueous solvent, those commonly used in the field of lithium primary batteries can be used. For example, γ-butyrolactone (γ-BL), γ-valerolactone (γ-VL), propylene carbonate (PC), ethylene carbonate ( EC), cyclic carbonates such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), 1,3-dioxolane, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), N, N-dimethylformamide, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, trimethoxyme Emissions, dioxolane derivatives, sulfolane, methyl sulfolane, propylene carbonate derivatives, tetrahydrofuran derivatives. A non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types.

  The solute concentration in the nonaqueous electrolytic solution is not particularly limited, but is preferably 0.5 to 1.5 mol / L. If the solute concentration is less than 0.5 mol / L, the discharge characteristics at room temperature or the discharge characteristics after long-term storage may be deteriorated. If the solute concentration exceeds 1.5 mol / L, the increase in viscosity and decrease in ionic conductivity of the nonaqueous electrolyte solution may become prominent under a low temperature environment of about −40 ° C.

  The positive electrode case 13 serves as a positive electrode current collector and a positive electrode terminal. On the inner bottom surface of the positive electrode case 13, the positive electrode case 13 comes into contact with the peripheral surface of the positive electrode 10 more strongly as the positive pressure case 13 swells due to an increase in internal pressure at positions corresponding to the outer peripheral portion of the positive electrode 10. The protrusion 13a is provided. As long as the shape of the protrusion 13a is not a single circle with the whole circumference connected, it may be an arc shape as shown in FIG. 2 or a dot shape as shown in FIG. Moreover, what processed the inner bottom face of the positive electrode case 13 and what was fixed to the inner bottom face of the positive electrode case 13 by welding etc. may be sufficient.

  Moreover, it is preferable that the tip of the protrusion 13a has a shape facing the center side of the positive electrode. With this configuration, contact between the positive electrode and the positive electrode case can be more reliably ensured even with a slight expansion, and a highly reliable coin-type battery can be provided.

  Furthermore, it is more preferable that a metal ring is disposed on the outer peripheral portion of the positive electrode with which the protrusion 13a contacts. With this configuration, when the internal pressure rises and the positive electrode case is about to expand, the metal ring prevents the protrusion from inclining toward the center side of the positive electrode, so that the positive electrode case is prevented from expanding and the highly reliable coin A battery can be provided.

  The negative electrode sealing plate 14 also serves as a negative electrode current collector and a negative electrode terminal. The gasket 15 is ring-shaped and has a L-shaped cross section, and mainly insulates the positive electrode case 13 and the negative electrode sealing plate 14. As the positive electrode case 13, the negative electrode sealing plate 14, and the gasket 15, those commonly used in the field of lithium primary batteries can be used. For the positive electrode case 13 and the negative electrode sealing plate 14, for example, those made of stainless steel can be used. For the gasket 15, for example, a synthetic resin such as polypropylene can be used.

  The positive electrode case 13 and the negative electrode sealing plate 14 are caulked and sealed at the peripheral edge via a gasket 15 so as to hold the electrolytic solution therein.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Example 1
A coin-type battery shown in FIG. 1 was produced.

1) Production of positive electrode 100 parts by mass of manganese dioxide (positive electrode active material) heat-treated at 450 ° C. and 10 parts by mass of graphite (conductive material) were dry-mixed, and polytetrafluoroethylene (binder) 5 was added to the obtained dry-type mixture. Mass parts were added and further kneaded, and the obtained kneaded product was dried and pulverized to prepare a powdered positive electrode mixture. This positive electrode mixture was filled in a cylindrical mold having a diameter of 14.0 mm and pressure-molded to produce a disk-shaped positive electrode 10.

2) Production of negative electrode Lithium metal was used for the negative electrode active material. A lithium metal foil was punched out to form a disc-shaped negative electrode 11, which was pressure-bonded to the inner surface of the negative electrode sealing plate 14 equipped with a gasket 15.

3) Separator A polypropylene nonwoven fabric having a thickness of 100 μm was punched out into a circular shape and molded into a cup shape to produce a separator 12.

4) Preparation of non-aqueous electrolyte A solution obtained by dissolving lithium perchlorate at a ratio of 1 mol / L in a mixed solvent of propylene carbonate and 1,2-dimethoxyethane was used.

5) Battery assembly A sealant is applied to the inner surface of the positive electrode case 13, the positive electrode 10 is placed inside the arc-shaped protrusion 13a on the inner bottom surface as shown in FIG. After covering, 1.0 g of non-aqueous electrolyte was poured into the positive electrode case 13, and the positive electrode 10 and the separator 12 were impregnated with the electrolyte. Next, the negative electrode sealing plate 14 to which the negative electrode 11 is crimped is attached to the positive electrode case 13 so that the negative electrode 11 and the positive electrode 10 face each other, and the peripheral edge of the positive electrode case 13 is attached to the negative electrode sealing plate 14. The coin-type battery of Example 1 (diameter 20 mm, thickness 3.2 mm) was produced. The assembly process was performed in dry air with a dew point of −40 ° C. or lower.

(Example 2)
As shown in FIG. 4, a coin-type battery of Example 2 was fabricated in the same manner as Example 1 except that the tip of the protrusion 13a on the inner bottom surface of the positive electrode case 13 faced the center side.

(Example 3)
As shown in FIG. 5, a coin-type battery of Example 3 was fabricated in the same manner as in Example 1 except that a metal ring 16 was provided on the outer peripheral portion of the positive electrode 10.

(Comparative Example 1)
As shown in FIG. 6, a coin-type battery of Comparative Example 1 was fabricated in the same manner as in Example 1 except that the positive electrode case 13 without the inner bottom protrusion 13a was used.

  Twenty coin-type batteries obtained in Examples 1, 2, 3 and Comparative Example 1 were produced and subjected to a high temperature storage test at 85 ° C. for 30 days. Table 1 shows a comparison of internal resistance and battery thickness in the high temperature storage test.

  As can be seen from Table 1, in the coin batteries of Examples 1 to 3 of the present invention, the increase in internal resistance was suppressed in the high temperature storage test. On the other hand, in Comparative Example 1, there was a large increase in the internal resistance variation.

  In Examples 1 to 3 of the present invention, the longitudinal contact between the inner bottom surface of the positive electrode case and the positive electrode was weakened due to the swelling of the outer case accompanying the increase in internal pressure due to the temperature increase during high temperature storage. Even in this case, the increase in internal resistance was suppressed by obtaining a lateral contact in which the protrusion provided on the inner bottom surface of the positive electrode case and the outer peripheral portion of the positive electrode contacted more strongly as the case expanded. In Example 1, only the contact between the inner bottom surface of the positive electrode case and the positive electrode is only in the vertical direction. If the case swells beyond the assumption, the contact may be insufficient, and the internal resistance may increase.

  Similarly, as can be seen from Table 1, in the coin battery of Example 3 of the present invention, the increase in battery thickness in the high temperature storage test is suppressed. On the other hand, in Comparative Example 1, the battery thickness increases, and even the batteries of Examples 1 and 2 have a slight suppression effect compared to the comparative example. In Embodiment 3 of the present invention, when the internal pressure increases due to temperature increase during high temperature storage, the protrusion provided on the inner bottom surface of the positive electrode case and the metal ring on the outer periphery of the positive electrode act to move the inside of the protrusion. In contrast to the fact that the swelling of the case was suppressed by restricting the collapse of the case, in Comparative Example 1, there was no restriction on the swelling, and in Examples 1 and 2, the protrusions bite into the positive electrode, so that the swelling was suppressed. It is thought that it was slight.

  In the present embodiment, an example using a coin-type lithium primary battery has been shown. However, the present invention is not limited to a coin-type lithium primary battery, but can be applied to a coin-shaped battery such as a coin-type lithium secondary battery. Needless to say.

  According to the present invention, the positive electrode is disposed on the inner surface of the positive electrode case also serving as the external terminal, and the negative electrode disposed on the inner surface of the negative electrode sealing plate also serving as the external terminal is opposed to the positive electrode via the separator. In a coin-type battery in which the peripheral part is sealed with a gasket so as to hold the electrolyte solution inside the sealing plate, even if the battery internal pressure rises beyond expectation and the outer case swells, the positive electrode and the positive electrode case It is possible to provide a highly reliable coin-type battery that can suppress an increase in the contact resistance, and is industrially useful.

DESCRIPTION OF SYMBOLS 1 Coin type battery 10 Positive electrode 11 Negative electrode 12 Separator 13 Positive electrode case 13a Protrusion 14 Negative electrode sealing plate 15 Gasket 16 Ring

Claims (3)

The positive electrode is disposed on the inner surface of the positive electrode case also serving as the external terminal, and the negative electrode disposed on the inner surface of the negative electrode sealing plate also serving as the external terminal is opposed to the positive electrode via the separator, and the positive electrode case and the sealing plate are disposed inside the electrolyte solution. In the coin-type battery in which the peripheral edge is sealed with a gasket so as to hold the positive electrode case, the positive electrode case swells due to an increase in internal pressure at a position corresponding to the outer peripheral portion of the positive electrode on the inner bottom surface of the positive electrode case. A coin-type battery comprising a plurality of protrusions that come into stronger contact with a peripheral surface. The coin-type battery according to claim 1, wherein the tip of the protrusion is shaped to face the center side of the positive electrode. The coin-type battery according to claim 1, wherein a metal ring is disposed on an outer peripheral portion of the positive electrode with which the protrusion is in strong contact, and the expansion of the positive electrode case is suppressed by restricting the inward tilt of the protrusion.