JP6706752B2 - Coin cell battery - Google Patents

Description

The present invention relates to a coin-type battery, and more particularly, to a coin-type battery with improved safety against accidental ingestion.

Coin cells are widely used as a power source for small devices and memory backups. Although the applications of coin type batteries are expanding, the importance of countermeasures against accidental ingestion of coin type batteries is increasing. When the coin-shaped battery is taken into the living body, the terminal surfaces of the coin-shaped battery case and the sealing plate come into contact with the body fluid, and the body fluid causes a short circuit between the positive and negative electrodes. Harm to. In addition, there is a risk that the outer casing material used for the positive electrode is melted and deposited on the negative electrode, causing heat generation due to an external short circuit, which may cause skin irritation.

Therefore, Patent Document 1 proposes to form a conductive coating film containing a bitter substance on the surface of the battery from the viewpoint of preventing accidental ingestion.

JP-A-4-312762

However, the method of Patent Document 1 cannot avoid the above harm when a living body swallows a coin-shaped battery without exhaling it.

In view of the above, it is an object of the present invention to provide a highly safe coin-type battery that can reduce the harm to the living body due to accidental ingestion.

The present invention, a case having a bottom plate portion and a side portion rising from the peripheral edge of the bottom plate portion, a top plate portion and a sealing plate having a peripheral portion extending from the top plate portion to the inside of the side portion, the side portion and the A gasket interposed between the peripheral portion and the casing; and a power generation element sealed by the case and the sealing plate, and at least the end portion of the side portion and the outer surface exposed portion of the gasket are filled with liquid. A coin-shaped battery covered with an organic film that absorbs and expands.

ADVANTAGE OF THE INVENTION According to this invention, the harm to a living body by accidental ingestion of a coin type battery can be reduced.

It is a longitudinal cross-sectional view showing a configuration of a coin battery according to an embodiment of the present invention.

The coin battery according to the embodiment of the present invention includes a power generating element and an outer casing that hermetically houses the power generating element. The exterior body includes a bottomed case having an opening, a sealing plate that closes the opening of the case, and a gasket that is interposed between a side end (opening end) of the case and a peripheral edge of the sealing plate. is doing. The power generation element includes a first electrode, a second electrode, a separator interposed therebetween, and an electrolytic solution. After the power generation element is filled in the space formed by the case and the sealing plate, the open end of the case is caulked to the peripheral edge of the sealing plate via the gasket, so that the power generation element is hermetically enclosed inside the exterior body. To be done. The coin type battery includes a button type. That is, the shape and diameter of the coin battery are not particularly limited. For example, a coin-type battery includes a button-type battery having a battery thickness larger than the diameter.

More specifically, the case has a bottom plate portion and a side portion rising from the peripheral edge of the bottom plate portion. The bottom plate portion is usually circular, but may have a shape close to a circle (for example, an ellipse). The sealing plate has a top plate part and a peripheral part extending from the top plate part to the inside of the side part of the case. The top plate portion corresponds to the shape of the bottom plate portion, and is usually a circular shape having a smaller diameter than the bottom plate portion. The thickness T of the coin-shaped battery is often smaller than the diameter D of the bottom plate portion (T<D), for example, 1.2 mm≦T≦5.0 mm and 9 mm≦D≦24.5 mm. A gasket is compressed and interposed between the side portion of the case and the peripheral portion of the sealing plate. Here, the side end of the case and the exposed outer surface of the gasket are covered with an organic coating that absorbs liquid and expands. The exposed portion of the outer surface of the gasket is a portion that is exposed to the outside without contacting the exterior body when the opening end portion of the case is caulked to the peripheral edge portion of the sealing plate for sealing.

The organic film has a function of reducing a short-circuit current generated by contact between the case and the sealing plate and body fluid when the coin-type battery is accidentally swallowed. If a coin-type battery is accidentally swallowed and comes into contact with body fluid, the positive and negative electrodes will be closest to each other, and the body fluid will be generated near the opening edge of the case and the peripheral edge of the sealing plate (particularly the boundary area with the gasket). A short circuit occurs between the positive electrode and the negative electrode, and a current accompanied by electrolysis of water flows. According to the configuration of the present invention, since the organic coating is provided between the positive and negative electrodes that are closest to each other, the amount of intervening body fluid can be reduced. In addition, the expansion of the organic coating can increase the distance between the positive and negative electrodes at the closest portion of the positive and negative electrodes exposed on the outer surface. As a result, it is possible to reduce the short-circuit current and suppress harm to the living body.

Further, the organic film has a function of suppressing an external short circuit when the coin type battery is accidentally swallowed. When a coin-type battery is accidentally swallowed and comes into contact with body fluid, the electrolysis of water contained in the body fluid proceeds, and in the case where it is electrically connected to the positive electrode, the case material is eluted. For example, when stainless steel is used for the case, the stainless steel melts and precipitates on the negative electrode closer thereto. Since this precipitate is conductive, the distance between the positive and negative electrodes becomes shorter as the amount of precipitation increases, and an external short circuit occurs. According to the configuration of the present invention, since the organic coating absorbs the body fluid containing the dissolved stainless steel, it inhibits the movement thereof and suppresses the deposition. As a result, it is possible to prevent external short circuit and prevent skin inflammation due to heat generation.

The organic coating covers the end surface of the side of the case and the exposed outer surface of the gasket. Furthermore, it is preferable to cover the outer surface side of the sealing plate. In particular, it is more preferable to cover the peripheral portion near the positive electrode (particularly the region in contact with the gasket) and further the outer peripheral portion of the top plate portion continuing from the peripheral portion. It is preferable to form the top plate avoiding the place of the contact that makes electrical contact with the equipment, but when the organic film is thin, the film is broken by the contact pressure of the terminal that takes the contact and directly contacts the exterior parts. In this case, the contact position may be covered. By widening the formation area of the organic coating, the closest distance between the positive and negative electrodes is further increased. Therefore, the electrolysis reaction of water is suppressed, and the risk of an external short circuit is also reduced.

The organic coating preferably contains an organic polymer showing acidity or neutrality, and more preferably contains an organic polymer showing neutrality, because the body tissue is weak against alkali. The pH value is preferably 6-8.

The following can be used as the organic coating.
Examples of the acidic organic polymer include polyacrylic acid and alginic acid. Examples of the neutral organic polymer include cellulose such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hypromellose or a derivative thereof, and acrylic acid such as sodium polyacrylate or a derivative thereof. In particular, hydroxyethyl cellulose, hydroxypropyl cellulose, sodium polyacrylate and the like are more preferable from the viewpoint of expansion. The thickness of the organic coating is preferably 1 μm to 200 μm, more preferably 50 μm to 150 μm.

The organic film can be formed by dissolving an organic polymer in a solvent to form a solution, applying the solution to a place where the organic film is to be formed, and removing the solvent by drying. As the solvent, water, toluene, xylene or the like is preferable.
Since the organic polymer that constitutes the organic coating is transparent or colorless, it is very difficult to determine the coating unevenness after coating and the presence or absence of coating. Therefore, it is preferable to mix a dye or a pigment with the organic polymer to color the organic coating. Such an organic coating can be easily formed by applying a solution in which a dye or a pigment is dissolved in a solvent together with an organic polymer, and applying the solution. By coloring the organic coating, the state after coating can be confirmed, so that the effect can be more reliably obtained.

Oil red and lake red can be used as the dye, and a phthalocyanine-based material can be used as the pigment. The amount of the dye or pigment added is 1 to 40% by mass, preferably 5 to 30% by mass, based on the organic polymer. When the amount added is too small to be discriminated, and when the amount is too large, the effect of the organic coating is weakened.

In addition to dyes and pigments, it is also possible to use organic asphalt pitch having no electroconductivity and a coloring function, and inorganic oxides such as iron oxide and titanium oxide.

Hereinafter, a coin battery according to an embodiment of the present invention will be described with reference to the drawings. However, the following embodiments do not limit the technical scope of the present invention.

FIG. 1 is a vertical sectional view of a coin battery according to an embodiment of the present invention. The coin-type battery 10 includes an exterior body including a case 1, a sealing plate 6, and a gasket 5. The case 1 is a cylindrical shallow battery can having a bottom plate portion 1a and a side portion 1b rising from the peripheral edge of the bottom plate portion 1a. The sealing plate 6 has a top plate portion 6a and a peripheral edge portion 6b extending from the top plate portion 6a to the inside of the side portion 1b of the case 1. A part of the gasket 5 is interposed between the side portion 1b of the case 1 and the peripheral portion 6b of the sealing plate 6 to seal the gap between the case 1 and the sealing plate 6.

A power generation element is housed inside the exterior body. The power generation element includes a positive electrode 2, a negative electrode 3, a separator 4 and an electrolytic solution (not shown). In the illustrated example, the positive electrode 2 is arranged so as to face the bottom plate portion 1 a of the case 1. Therefore, the first terminal surface on the outer surface of the bottom plate portion 1a functions as a positive electrode terminal. On the other hand, the negative electrode 3 is arranged so as to face the top plate portion 6 a of the sealing plate 6. Therefore, the second terminal surface on the outer surface of the top plate portion 6a functions as a negative electrode terminal.

In the illustrated example, it is desirable to use a metal plate having corrosion resistance at positive electrode potential as the material of the case 1. For example, it is desirable to use stainless steel (SUS430, SUS444, SUS329J, etc.), titanium, titanium alloy, etc. for the case 1 of the lithium battery.

As a material of the sealing plate 6, it is desirable to use a metal plate having excellent mechanical strength, and it is desirable to use stainless steel (SUS304, SUS316, etc.). However, it is also possible to use an inexpensive metal plate such as ordinary steel or carbon steel. Ordinary steel is steel such as SS material, SM material and SPCC material defined by JIS. Carbon steel is steel such as S10C, S20C, S30C, S45C, and S55C, and belongs to alloy steels for machine structural use.
The end portion 1t of the side portion of the case 1 and the outer surface exposed portion 5t of the gasket 5 are covered with an organic coating 7 that absorbs liquid and expands. Even if the coin-type battery is accidentally swallowed, the organic coating 7 can suppress the electrolysis reaction of water and suppress the heat generation of the external short circuit due to the dissolution or deposition of the material of the case.

Next, a method of manufacturing a coin battery will be described by taking a lithium battery as an example. The coin-shaped battery 10 includes a step (a) of preparing a power generation element, a step (b) of preparing the case 1, a step (c) of preparing a sealing plate 6, and a step (d) of preparing a gasket 5. After accommodating the power generation element in the case 1, a step (e) of closing the opening of the case 1 with the sealing plate 6 and caulking the opening end of the case 1 to the peripheral edge of the sealing plate 6 via the gasket 5. The step (f) of forming an organic coating 7 that absorbs a liquid and expands is provided on the side end 1t of the case and the outer surface exposed portion 5t of the gasket 5. The metal plate used for the case 1 and the sealing plate 6 has a thickness of, for example, 0.1 to 0.4 mm.

In the step (b), for example, the case 1 is manufactured by drawing a stainless steel plate and forming it into a bottomed cylindrical shape. A nickel plating layer is preferably formed on at least the surface of the stainless steel plate corresponding to the outer surface of the battery.

In the step (c), a sealing plate having a predetermined shape is formed by pressing a metal plate, for example. A nickel plating layer is preferably formed on at least the surface of the metal plate corresponding to the outer surface of the battery.

In the step (d), the gasket 5 having an annular groove portion that fits into the peripheral edge portion of the sealing plate 6 is prepared. The gasket 5 may be attached to the peripheral portion of the sealing plate 6 in advance. As the material of the gasket 5, for example, polypropylene (PP), polyphenylene sulfide (PPS), polyether ether ketone (PEEK) or the like can be used.

In the step (e), the power generation element is housed inside the case 1, and the sealing plate 6 is arranged so as to close the opening of the case 1. After that, the opening end portion (side end portion) of the case 1 is bent inward. As a result, the gasket 5 is compressed, and the lower end portion of the gasket 5 comes into close contact with the bottom plate portion of the case 1. The upper end of the gasket 5 is in close contact with the peripheral edge 6b of the sealing plate 6.

In the step (f), for example, an aqueous solution prepared by dissolving an organic coating that absorbs a liquid and expands in water is applied to the end 1t of the side portion 1b of the case 1 and the outer surface exposed surface 5t of the gasket 5, and water is applied. Can be dried. As a result, the organic coating that absorbs the liquid and expands adheres to the outer surface of the exterior body.

Next, the power generating element of the coin battery will be described by taking a lithium battery as an example. The positive electrode 2 is formed by pressing a positive electrode mixture into a coin shape. The positive electrode mixture contains a positive electrode active material, a conductive auxiliary agent, and a binder. The type of the positive electrode active material is not particularly limited, but an oxide (for example, manganese dioxide) or a composite containing at least one selected from the group consisting of transition metals such as manganese, cobalt, nickel, magnesium, copper, iron, and niobium. Oxides can be used. A composite oxide (for example, LiCoO ₂ ) containing lithium and containing at least one selected from the group consisting of metals such as manganese, cobalt, nickel, magnesium, copper, iron and niobium can also be used. Further, fluorinated graphite can also be used. The positive electrode active material may be used alone or in combination of two or more.

As the conductive additive, carbon black such as acetylene black and Ketjen black, and graphites such as artificial graphite can be used. The conductive aid may be used alone or in combination of two or more.

Examples of the binder include fluororesin, styrene-butadiene rubber (SBR), modified acrylonitrile rubber, ethylene-acrylic acid copolymer and the like. The binder may be used alone or in combination of two or more.

The negative electrode 3 is, for example, a coin-shaped lithium metal or lithium alloy. Examples of lithium alloys include Li-Al alloys, Li-Sn alloys, Li-Si alloys, and Li-Pb alloys. The negative electrode 3 may be formed by pressing a negative electrode mixture containing a negative electrode active material and a binder into a coin shape. The type of the negative electrode active material is not particularly limited, but it is possible to use a carbon material such as natural graphite, artificial graphite, non-graphitizable carbon, or a metal oxide such as silicon oxide, lithium titanate, niobium pentoxide, or molybdenum dioxide. it can. As the binder, for example, the materials exemplified as the materials that can be used for the positive electrode can be arbitrarily used. A conductive auxiliary agent may be included in the negative electrode mixture.

The electrolytic solution contains a non-aqueous solvent and a solute (salt) that dissolves in the non-aqueous solvent. The solute concentration in the electrolytic solution is preferably 0.3 to 2.0 mol/L. As the non-aqueous solvent, cyclic carbonic acid ester, chain carbonic acid ester, chain ether, cyclic ether and the like can be used. These may be used alone or in combination of two or more. The _solute, such as _{LiBF 4, LiPF 6, LiClO 4} , LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2 is used.

The separator 4 may be any material that can prevent a short circuit between the positive electrode 2 and the negative electrode 3. For example, woven cloth, non-woven cloth, microporous film and the like formed of polyolefin, polyester and the like can be mentioned.

Next, the present invention will be specifically described based on Examples. However, the following examples do not limit the present invention. In this example, a coin battery having a structure as shown in FIG. 1 was manufactured.
<<Example 1>>
(1) Case A stainless steel plate (SUS430, thickness 200 μm) having a nickel plating layer with a thickness of 3 μm formed on the surface is drawn to form a case 1 having a bottom plate diameter of 20 mm and a side portion 1b height of 2.8 mm. It was made.

(2) Sealing plate SUS430 (thickness: 250 μm) having a nickel plating layer with a thickness of 3 μm on the surface was pressed to produce a sealing plate 6 with a top plate portion 6a having a diameter of 17 mm.

(3) Power Generation Element 100 parts by mass of manganese dioxide, which is a positive electrode active material, 7 parts by mass of graphite, which is a conductive additive, and 5 parts by mass of polytetrafluoroethylene, which is a binder, are mixed to form a positive electrode mixture. Prepared. The positive electrode mixture was molded into a coin shape having a diameter of 15 mm and a thickness of 2 mm to prepare a positive electrode 2. On the other hand, a negative electrode was prepared by punching a metal lithium foil having a thickness of 0.6 mm into a circular shape having a diameter of 16 mm. As the electrolytic solution, an organic electrolytic solution prepared by dissolving LiClO ₄ as a solute at a concentration of 1.0 mol/L in a non-aqueous solvent in which propylene carbonate and 1,2-dimethoxyethane were mixed at a volume ratio of 2:1 was used. .

(4) Assembly of coin-shaped battery Inside the side portion 1b of the case 1, a polypropylene gasket 5 coated with a sealing agent made of blown asphalt and mineral oil is arranged, and a bottom plate portion 1a made of SUS430 current collector. A body (not shown) was placed, and the positive electrode 2 was placed thereon. Next, a polypropylene nonwoven fabric having a thickness of 300 μm was placed as the separator 4 on the positive electrode 2. Then, the organic electrolyte was poured into the case 1. The negative electrode 3 was attached to the inside of the top plate portion 6 a of the sealing plate 6. Next, the sealing plate 6 was arranged so as to close the opening of the case 1, and the end of the side portion 1b of the case 1 was caulked to the peripheral edge of the sealing plate 6 via the gasket 5.

(5) Formation of Organic Film 1 part by mass of hydroxypropyl cellulose (HPC) (manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in 100 parts by mass of water to prepare an aqueous solution of HPC. This aqueous solution is applied to the end portion 1t on the side of the case and the outer surface exposed portion 5t of the gasket, and dried to form an organic coating containing HPC having a thickness of 100 μm on the end portion 1t of the case side portion and the outer surface exposed portion of the gasket. It was attached to 5t.

As a result, a coin-shaped battery A1 having a diameter of 20 mm, a thickness of 3.2 mm and an electric capacity of 225 mAh was completed.

<<Example 2>>
A coin-shaped battery similar to the battery A1 except that the aqueous solution of HPC was applied to the side end 1t of the case, the exposed outer surface 5t of the gasket, and the peripheral edge of the sealing plate to form an organic film containing HPC. Completed A2.

<<Example 3>>
Instead of HPC, sodium polyacrylate (PA-Na) was dissolved, an aqueous solution of PA-Na was prepared, and an organic coating film containing PA-Na was formed. Completed A3.

<<Comparative Example 1>>
A coin type battery B1 was completed in the same manner as the battery A1 except that the organic film containing HPC was not formed.

[Evaluation]
Ten coin-shaped batteries of the invention batteries A1 to 3 and the comparative battery B1 were produced.
The processed meat (ham) made from pork was placed on the bottom of a petri dish having a depth of 15 mm, and then physiological saline was poured into the petri dish instead of the body fluid, and the ham was completely immersed in the physiological saline. Next, the battery for evaluation was placed so that the sealing plate was in contact with the ham. At this time, the bottom surface of the case of the battery was set slightly below the liquid surface of the physiological saline solution so that the battery would not float, so that the saline solution film was formed on the bottom surface of the case. In this state, it was left at 25° C. for 30 minutes. After that, when the state of the ham that was in contact with the sealing plate was visually observed, the hams on which the batteries of invention batteries A1 to A3 were mounted showed only slight discoloration. On the other hand, the ham on which the battery of the comparative battery B1 was placed showed severe discoloration. All 10 batteries of each example showed the same tendency.

Next, the pH of the surface of the ham was measured, and the average value of 10 pieces was calculated for each. The results are shown in Table 1.

From the above, according to the present invention, it has been clarified that even if the coin-type battery is accidentally ingested by the living body, the harm to the living body can be greatly reduced.

In the above examples, the organic coating that absorbs and swells water is formed of hydroxypropyl cellulose and sodium polyacrylate, but the same applies to the case where the coating is formed of an organic polymer that absorbs and swells other liquids. It is thought that the safety of the coin battery can be improved.

INDUSTRIAL APPLICABILITY The present invention can be applied to various batteries including primary batteries and secondary batteries such as lithium batteries, alkaline batteries, and alkaline storage batteries, but is particularly useful for batteries having a battery voltage of more than 3.0 V (for example, lithium batteries).

DESCRIPTION OF SYMBOLS 1 Battery case 1a Bottom plate part 1b Side part 2 Positive electrode 3 Negative electrode 4 Separator 5 Gasket 5t Outer surface exposed part 6 Sealing plate 6a Top plate part 6b Peripheral part 7 Organic coating 10 Coin type battery

Claims (7)

A case having a bottom plate portion and a side portion rising from the peripheral edge of the bottom plate portion;
A sealing plate having a top plate part and a peripheral part extending from the top plate part to the inside of the side part,
A gasket interposed between the side portion and the peripheral portion by being compressed,
A power generation element sealed by the case and the sealing plate;
At least the end portion of the side portion and the outer surface exposed portion of the gasket are covered with an organic coating that absorbs liquid and expands. The coin-shaped battery according to claim 1, wherein at least a region of the peripheral portion that is in contact with the gasket is covered with the organic coating. The coin-shaped battery according to claim 1, wherein at least a part of the peripheral portion and the top plate portion continuing from the peripheral portion are covered with the organic coating. The coin battery according to any one of claims 1 to 3, wherein the organic coating contains an organic polymer having a pH value of 6 to 8. The organic polymer, hydroxypropyl cellulose, at least one selected from the human profile Merosu the group consisting of sodium polyacrylate, a coin-shaped battery according to claim 4. The coin battery according to claim 1, wherein the organic coating has a thickness of 1 μm to 200 μm. The coin-type battery according to claim 1, wherein the organic coating further contains at least one selected from the group consisting of dyes and pigments .

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