JP5213002B2 - Silver oxide battery - Google Patents

Description

  The present invention relates to a silver oxide battery, and more particularly, to a silver oxide battery excellent in heavy load characteristics.

Typical uses of silver oxide batteries using silver oxide as the positive electrode active material include watches and calculators. In these applications, for example, the current density is used at a relatively light load of about 10 to 50 μA / cm ^2, and it is assumed that the continuous use is generally over one year. Such applications take advantage of the characteristics of silver oxide batteries such as small size and high capacity.

  In recent years, taking advantage of the small size and high capacity of the silver oxide battery, application to a use for a short period of time in a heavy load use environment has been studied. Examples of such applications include medical devices (medical instruments).

  For example, recently, a capsule-type endoscope camera has been developed. This is an endoscopic camera that is swallowed from the mouth, observed inside the body for a certain period of time, and then discharged and taken out of the body. As a power source for small medical devices such as capsule-type endoscopic cameras, silver oxide is used. Applications of batteries are being considered.

  A silver oxide battery applied to such a medical device (for example, a capsule-type endoscopic camera) has characteristics that can withstand use under heavy load within a certain period of time when the device exists in the body, for example. There must be. For example, in an endoscopic camera used for observation inside the esophagus, the camera passes through the esophagus in an extremely short time (for example, several seconds to several tens of seconds), and thus it is necessary to take many photographs during this time. A silver oxide battery applied to such a device must be able to discharge at a very high current density in a short time, and the heavy load characteristics required for this silver oxide battery are the same as the conventional ones. This level is completely different from the required load characteristics.

However, since the silver oxide batteries that have been developed so far are based on the premise of continuous use over a relatively long period of time, they have been designed with particular emphasis on light load characteristics and storage characteristics. As in equipment, for example, when discharging at a very heavy load, such as a current density of about 50 mA / cm ² or above, the polarization is large and most of the battery capacity cannot be discharged. Is not applicable.

  By the way, conventionally, various attempts have been made to improve the characteristics of silver oxide batteries. For example, Patent Document 1 proposes a technique for achieving both closed circuit voltage characteristics and capacity storage stability by improving a separator disposed between positive and negative electrodes of a silver oxide battery. Further, zinc or zinc alloy particles are usually used for the negative electrode of a silver oxide battery. However, in Patent Document 2, the particle size of a negative electrode using such zinc-based particles is optimized. Thus, techniques for improving the characteristics of the battery have been proposed.

JP-A-5-205718 Special table 2001-512284 gazette

  The techniques of Patent Document 1 and Patent Document 2 described above have a certain effect in that they correspond to applications in which long-term discharge is required under the same light load as in the past. However, it is practically impossible to secure a heavy load characteristic that can be used for medical device applications as described above, even if the techniques of Patent Document 1 and Patent Document 2 are used.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a silver oxide battery having extremely excellent heavy load characteristics.

The silver oxide battery of the present invention that has achieved the above object has a positive electrode containing silver oxide as an active material, a negative electrode containing particulate zinc or a particulate zinc alloy as an active material, and a separator. The above-mentioned particulate zinc or particulate zinc alloy is such that all of them can pass through a 200 mesh sieve and 95 to 100% by mass can pass through a 330 mesh sieve. The separator has an electric resistance of 5 to 30 mΩ · (2.54 cm) ² , and when discharged at a temperature of 20 ° C. and a current density of 50 mA / cm ² , the closed circuit voltage after 1 minute is at least 1.35V and the closed circuit voltage after 10 minutes is at least 1.25V.

  According to the present invention, a silver oxide battery having extremely excellent heavy load characteristics can be provided. Therefore, the silver oxide battery of the present invention can be suitably used as a power source for small medical devices that require heavy load characteristics.

The silver oxide battery of the present invention has extremely good heavy load characteristics, and can be discharged under high current density conditions of 20 ° C. and 50 mA / cm ^2. Even after a minute, it has a high closed circuit voltage of 1.35V or more, preferably 1.40V or more.

As described above, the conventional silver oxide battery was developed mainly for light load characteristics, long-term continuous use characteristics and storage characteristics, and is completely intended for use under a high current density condition of 50 mA / cm ^2. Even if it couldn't even be discharged in real life, or even if it could be discharged, only a very low voltage could be obtained. As a result of intensive studies to enable application of a small and high-capacity silver oxide battery as a power source for medical devices as described above, the inventors have developed a silver oxide battery having the above characteristics. It was successful and the present invention was completed. With such a silver oxide battery, a heavy load is imposed in an extremely short time (for example, within 1 minute), and it is possible to sufficiently cope with an application in which a high voltage is required.

In the silver oxide battery of the present invention, the closed circuit voltage after 10 minutes when discharged at 20 ° C. and 50 mA / cm ² is preferably 1.25 V or more, more preferably 1.30 V or more. In such a silver oxide battery, for example, a heavy load is inherently imposed in an extremely short time (for example, within 1 minute), and in an application where a high voltage is required, it is higher than the originally scheduled time. Even when a situation in which discharge with voltage is required occurs, it is possible to cope with a margin. In addition, as described above, such a silver oxide battery requires a high voltage discharge in a short time of about 10 minutes, for example, in addition to an application that requires a high voltage discharge in an extremely short time of within 1 minute. It can also be applied to other uses.

Since the silver oxide battery of the present invention uses silver oxide as the positive electrode active material and zinc or zinc alloy as the negative electrode active material, the temperature is 20 ° C. and the current density is 50 mA / cm ² . The upper limit of the closing voltage after 1 minute and the closing voltage after 10 minutes when discharged is 1.50V.

  The silver oxide battery of this invention can be obtained by employ | adopting the following structures.

<Positive electrode>
As the positive electrode according to the silver oxide battery of the present invention, a silver oxide (a first silver oxide, a second silver oxide, etc.) that is a positive electrode active material, and a conductive assistant made of a carbonaceous material such as carbon black, graphite, graphite, A positive electrode mixture prepared by press-molding the mixed powder into a disk shape or the like is applied.

  The silver oxide used in the positive electrode according to the present invention is preferably granular. Usually, silver oxide is provided in the form of a fine powder having a diameter of 0.1 to 5 μm. When this silver oxide is granulated and used in a granular form, the positive electrode is used more than when used in a fine powder state. Since the arrangement of the conductive aid in the inside can be optimized, the resistance is lowered and the reactivity of the positive electrode can be improved, so that the heavy load characteristics of the silver oxide battery can be improved.

  When silver oxide is used in the form of fine powder, it is necessary to add a large amount of conductive aid to reduce the resistance, but the carbonaceous material used as the conductive aid has a low bulk density. When a large amount of is added, it becomes difficult to increase the filling amount of silver oxide as an active material. On the other hand, when granular silver oxide is used, weighability is improved and variation is reduced, and when press molding is performed, filling property is increased and moldability is improved, so that resistance is reduced, Individual characteristics are stabilized when a plurality of positive electrodes (and hence silver oxide batteries) are manufactured. Furthermore, the amount of the carbonaceous material added as the conductive auxiliary agent can be reduced to, for example, about half, and the filling amount of silver oxide can be increased.

Furthermore, for example, in the case of silver oxide, the discharge performance is deteriorated because the reaction is caused by the reaction of the following formula with the carbonaceous material.
2Ag ₂ O + C → 4Ag + CO ₂

  However, by making silver oxide into granules, the above reaction is suppressed, and the addition amount of the carbonaceous material can be reduced as described above. Characteristics (especially low temperature heavy load characteristics) are improved.

In the positive electrode according to the present invention, when granular silver oxide is used, the particle size is preferably 50 μm or more, more preferably 75 μm or more, preferably 500 μm or less, more preferably 300 μm or less, The bulk density is preferably 1.5 g / cm ³ or more, more preferably 1.8 g / cm ³ or more, preferably 3.5 g / cm ³ or less, more preferably 2.6 g / cm ^3. It is recommended that: If the silver oxide is in such a form, it has better fluidity than the powdered one, and as described above, the weighability and moldability are improved, the resistance is lowered, and the reactivity is improved. The heavy load characteristics of the positive electrode are improved, and the characteristics of the manufactured positive electrode (and thus the silver oxide battery) are stabilized. The particle size of granular silver oxide here is determined by measuring the number of particles n and the diameter d of each particle by scattering of laser light using a microtrack particle size distribution meter “9320-X100” manufactured by Honeywell. The calculated number average particle diameter. Further, the bulk density of the granular silver oxide referred to here is a value obtained by putting a predetermined amount of granular silver oxide into a container and using a bulk density measuring device in accordance with the bulk density measuring method specified in JIS R 1628. It is.

  In the positive electrode, if the content of the conductive additive is increased, the conductivity of the positive electrode is improved, so that the discharge characteristics under heavy load are improved. However, if the conductive additive content is too much, the conductivity is improved. Contrary to this, the content of silver oxide, which is an active material, decreases, resulting in a decrease in the discharge capacity of the battery. Therefore, the composition of the positive electrode is desirably 1 part by mass or more, more preferably 2 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of silver oxide. Here, when using granular silver oxide in a positive electrode, it is preferable that a conductive support agent shall be 0.5 mass part or more and 2 mass parts or less.

  Further, the size of the positive electrode after pressure molding may be set according to the size of the silver oxide battery, and is not particularly limited. For example, the diameter is 6 to 10 mm and the thickness is 0.3 to 2 mm. Preferably there is.

<Negative electrode>
The negative electrode according to the present invention uses particulate zinc or particulate zinc alloy as an active material (hereinafter referred to as “zinc-based particles” collectively of particles composed of zinc or a zinc alloy as an active material). May be called). As an alloy component of the zinc alloy, for example, mercury (for example, the content is 1 to 5 mass%), indium (for example, the content is 50 to 500 mass ppm), bismuth (for example, the content is 50 to 500 mass ppm). ), Aluminum (for example, the content is 1 to 100 ppm by mass) and the like (the balance is zinc and inevitable impurities). The negative electrode may contain any one of these zinc particles or zinc alloy particles, and may contain two or more.

  However, it is more preferable that the zinc or zinc alloy constituting the zinc-based particles is one not containing mercury or one containing no lead. If the battery uses such zinc-based particles, for example, in the human body, even when zinc inside the battery leaks, the adverse effects on the human body can be minimized, Environmental pollution due to battery disposal can also be suppressed.

  By the way, the zinc-based particles are corroded by contact with the electrolytic solution in the battery and generate gas, but this corrosion reaction becomes remarkable particularly when the particle size is small. From the viewpoint of suppressing gas generation due to such a reaction, the zinc-based particles are preferably composed of a zinc alloy having bismuth or indium in the above content. This is because, in the case of an alloy containing bismuth or indium, the corrosion resistance of zinc is improved, so that the above corrosion reaction is suppressed and the generation of gas is suppressed.

  More preferably, the zinc-based particles have a small particle size. As the particle size is smaller, the specific surface area is relatively larger and the reactivity is improved, so that the heavy load characteristics of the battery can be enhanced. Specifically, it is preferable that all of the zinc-based particles included in the battery have a particle size capable of passing through a 200 mesh sieve, and have a particle size capable of passing through a 330 mesh sieve. More preferably. In addition, since the handleability falls when the size of the zinc-based particle which the negative electrode has is too small, for example, the minimum size of the zinc-based particle which the negative electrode has is desirably about 1 μm.

  The negative electrode is preferably non-gelled. The term “non-gel” as used herein means that it does not substantially contain a gelling agent (polymer or the like) related to a conventionally known gel electrode (in the present invention, zinc-based particles). Since it does not matter if the electrolyte present in the vicinity does not thicken, "substantially does not contain a gelling agent" means that it may be contained to the extent that it does not affect the electrolyte viscosity. is there). In a battery using zinc-based particles as a negative electrode, the negative electrode is generally configured by a gel electrode in which zinc-based particles are included in a gel composed of an electrolytic solution and a gelling agent. However, in the case of a gel-like electrode, the electrolyte solution present in the vicinity of the zinc-based particles is thickened by the action of the gelling agent, causing the electrolyte solution to move, and eventually the ions in the electrolyte solution to move. It is suppressed. For this reason, the reaction rate at the negative electrode is suppressed, which is considered to impede improvement of the heavy load characteristics of the battery. Therefore, by making the negative electrode non-gel, the reaction rate at the negative electrode is increased by keeping the moving speed of ions in the electrolytic solution high without increasing the viscosity of the electrolytic solution existing in the vicinity of the zinc-based particles. The heavy load characteristics can be improved. In addition, the battery of the present invention may be required to be small, for example, as a power source for a small medical device such as the capsule endoscope camera described above. In such a case, since the internal volume of the battery becomes extremely small, when the negative electrode is in a gel form, the amount of zinc-based particles that are active materials is limited by the addition of the gelling agent. However, when the negative electrode is made non-gelled, no gelling agent is required, and the ratio of zinc-based particles in the negative electrode can be increased, so that the battery capacity can be increased.

<Separator>
The separator according to the silver oxide battery of the present invention has an electric resistance of, for example, 5 mΩ · (2.54 cm) ² or more, 30 mΩ · (2.54 cm) ² or less, more preferably 20 mΩ · (2. 54 cm) ² or less is desirable. By using a separator having such an electrical resistance, the heavy load characteristics of the battery can be enhanced. As a specific separator, it is desirable to include a cellophane film. Since the cellophane film has an electric resistance that is small enough to satisfy the above-mentioned preferred value, it can contribute to the improvement of the heavy load characteristics of the battery.

  You may comprise a separator only with a cellophane film. However, when a separator composed only of a cellophane film is used, reduction of capacity is likely to occur because Ag ions are reduced in cellophane due to contact between silver oxide and cellophane during storage of the battery. In addition, the above-described reaction consumes the reducing group of cellophane in a very short time, and Ag ions move to the negative electrode to react with zinc of the negative electrode, resulting in self-discharge and eventually causing a short circuit. It becomes. In order to suppress such a reaction, it is desirable to perform low-temperature storage or the like until the battery is assembled and used.

  In addition, when a separator is comprised only with a cellophane film, in addition to the above problem of capacity reduction due to reduction of Ag ions, problems such as damage during battery assembly due to the low strength of the separator are likely to occur. Therefore, it is also recommended that the separator be composed of a laminate formed by laminating a graft film composed of a specific polymer and a cellophane film. For example, Patent Document 1 proposes a separator having a three-layer structure of graft film / cellophane film / graft film, but has a two-layer structure of graft film / cellophane film as compared with a separator having such a structure. If it is the separator comprised by this laminated body, since the electrical resistance can be made low, the heavy load characteristic of a battery can be improved more.

  The graft polymer constituting the graft film has a form in which (meth) acrylic acid or a derivative thereof is graft-polymerized to a polyolefin (polyethylene, polypropylene, etc.) which is a trunk polymer, and the graft polymer may have such a form. It does not necessarily have to be produced by a method in which (meth) acrylic acid or a derivative thereof is graft polymerized to polyolefin.

In addition, (meth) acrylic acid or its derivative which comprises the said graft polymer is shown by the following general formula. In the following general formula, R ¹ is H or CH ₃ , and R ² means a hydrophilic substituent such as H or NH ₄ , Na, K, Rb, Cs.

  Since the above-mentioned graft film and cellophane film have a function in which the polymer itself constituting these films absorbs the electrolytic solution and permeates ions, the separators constituted by these films are substantially voids. (In addition, “substantially” as used herein means that it does not contain positively formed vacancies, excluding unavoidable vacancies in the film production process, etc. is there). Of course, the separator composed only of the above-described cellophane film is substantially free of pores.

  In a separator composed of a laminate of a graft film and a cellophane film, the cellophane film plays a role in reducing Ag ions that have permeated through the graft film, and the graft film has excellent ion selective permeability and strength. Therefore, it plays a role in suppressing unnecessary oxidation of the cellophane film and preventing damage to the separator during battery assembly.

Incidentally, the graft film, its electrical resistance, 25mΩ · ^{(2.54cm) 2} or less, and more preferably is 15mΩ · ^{(2.54cm) 2} or less. If the electrical resistance of the graft film is too large, the effect of improving the heavy load characteristics of the silver oxide battery may be reduced. In addition, as described above, in a battery using a separator composed only of a cellophane film, a capacity drop during storage is likely to occur. However, by configuring the separator with a laminate of a graft film and a cellophane film, the battery is stored. It is also possible to suppress a decrease in capacity at a certain level. In order to ensure such an effect, the electrical resistance of the graft film is, for example, 5 mΩ · (2.54 cm) ² or more, preferably 10 mΩ · (2.54 cm) ² or more. In addition, the electrical resistance of a separator and a graft film as used in this specification is a value obtained by the following alternating voltage drop method (1 kHz). The atmospheric temperature is set to 20 to 25 ° C., the film is immersed in a 40% KOH (specific gravity: 1.400 ± 0.005) aqueous solution at 25 ± 1 ° C., taken out after 5 to 15 hours, and the electric resistance is measured.

The graft polymer constituting the graft film preferably has a graft rate defined by the following formula (1) of 160% or more. Since there is a correlation between the graft ratio of the graft polymer and the electrical resistance of the graft film, the graft film has the above-mentioned preferred value by using the graft polymer having the graft ratio as described above. Can be controlled.
Graft ratio (%) = 100 × (A−B) / B (1)
[In the above formula (1), A is the mass (g) of the graft polymer, and B is the mass (g) of the trunk polymer in the graft polymer. ]
In addition, “B (mass of the trunk polymer in the graft polymer)” in the above formula (1) means, for example, that the graft polymer is graft polymerized with (meth) acrylic acid or a derivative thereof onto the polyolefin that is the trunk polymer. When forming by the method, the mass of the trunk polymer used for the graft polymerization may be measured in advance. In the above graft polymer, the graft ratio may exceed 100% when the monomers [(meth) acrylic acid and its derivatives] used in the graft polymerization are polymerized and the graft molecule becomes a long chain. Because there is. The upper limit of the graft ratio of the graft polymer defined by the above formula (1) is preferably 400%.

  In the case of a separator composed of only a cellophane film, the thickness is, for example, 15 μm or more, 40 μm or less, more preferably 30 μm or less. In the case of a separator composed of a laminate of a graft film and a cellophane film, the total thickness of the graft film and the cellophane film is, for example, 30 μm or more, more preferably 40 μm or more, and 70 μm or less, more preferably 60 μm or less. It is desirable that If the separator is too thin, the strength may be reduced and problems may occur during production. On the other hand, when the separator is too thick, the volume occupied by the separator inside the battery increases, and the amount of active material that can be contained in the positive electrode or the negative electrode is reduced.

  Moreover, in the case of the separator comprised by the laminated body of a graft film and a cellophane film, the thickness of a graft film is 15 micrometers or more, for example, More preferably, it is 25 micrometers or more, and it is desirable that it is 30 micrometers or less. By using the graft film having such a thickness, the heavy load characteristic of the silver oxide battery can be enhanced, and the storage characteristic can also be improved.

  Examples of the laminate of the graft film and the cellophane film for constituting the separator include those commercially available from Yuasa Membrane System Co., Ltd. under the names “YG9132”, “YG9122”, and “YG2152”.

<Electrolyte>
In the silver oxide battery of the present invention, an alkaline aqueous solution is used as the electrolytic solution. As the alkali, alkali metal hydroxides (sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.) are preferably used. Alkali metal hydroxides may be used singly or in combination of two or more. Among the above, potassium hydroxide is particularly preferable. The concentration of the electrolytic solution is, for example, in the case of an aqueous solution of potassium hydroxide, potassium hydroxide is 28% by mass or more, more preferably 30% by mass or more, further preferably 32% by mass or more, and 36% by mass or less. More preferably, the content is 35% by mass or less. When the concentration of the aqueous solution is lower than the above concentration range, the ionic conductivity is high and the initial closed-circuit voltage is improved. However, as the amount of hydroxide ions decreases as the discharge progresses, the voltage decreases rapidly and the dischargeable time is reduced. May be. When the concentration of the aqueous solution is higher than the above concentration range, the dischargeable time is long and the aqueous solution has a high viscosity, so that it is difficult to leak, but the initial closed circuit voltage may be low. Therefore, it can be set as the electrolyte solution excellent in electroconductivity by adjusting the density | concentration of aqueous solution to such a value.

  In addition to the above-described components, various known additives may be added to the electrolytic solution as necessary within a range not impairing the effects of the present invention. For example, it is desirable to add zinc oxide for the purpose of preventing the corrosion (oxidation) of zinc-based particles used for the negative electrode of a silver oxide battery and improving the storage characteristics of the battery. However, when zinc oxide is added, the conductivity of the electrolytic solution is lowered, so that the effect of improving the heavy load characteristics of the battery may be reduced. For this reason, it is desirable that the amount of zinc oxide added is 0.1% by mass or more, 10% by mass or less, more preferably 5% by mass or less.

<Structure of silver oxide battery and other components>
The structure of the silver oxide battery of the present invention and other components will be described with reference to FIG. FIG. 1 is a partial cross-sectional view showing an example of a silver oxide battery of the present invention, and FIG. 1 shows a coin-shaped one. In FIG. 1, 1 is a positive electrode, 2 is a separator, 3 is a negative electrode, 4 is a positive electrode can, 5 is a negative electrode terminal plate, and 6 is an annular gasket. Further, an electrolytic solution is injected into the silver oxide battery of FIG. 1 (not shown). In the battery industry, a flat battery with a diameter larger than the height is called a coin-type battery or a button-type battery, but there is a clear gap between the coin-type battery and the button-type battery. There is no difference, and the coin-type battery shown in FIG. 1 does not exclude what is called a button-type battery, and such a battery called a button-type battery is also included in the above-mentioned coin-type battery. .

  In the silver oxide battery of FIG. 1, a negative electrode terminal plate 5 having a negative electrode 3 embedded therein is fitted via an annular gasket 6 having an L-shaped cross section into an opening of a positive electrode can 4 having a positive electrode 1 and a separator 2 embedded therein. The opening end of the positive electrode can 4 is tightened inward, whereby the annular gasket 6 is brought into contact with the negative electrode terminal plate 5 so that the opening of the positive electrode can 4 is sealed and the inside of the battery is sealed. It has become. That is, in the silver oxide battery of FIG. 1, a power generation element including the positive electrode 1, the negative electrode 3, and the separator 2 is loaded in a space (sealed space) formed by the positive electrode can 4, the negative electrode terminal plate 5, and the annular gasket 6. . As described above, the positive electrode 1 is a molded body of a positive electrode mixture having silver oxide (preferably granular silver oxide) as an active material and a conductive additive. Moreover, it is preferable that the negative electrode 3 exists with the zinc-type particle | grains with a particle | grain.

  As the positive electrode can 4, for example, iron plated with nickel can be used, but in consideration of application to a medical device which is the main use of the silver oxide battery of the present invention, the chromium content is 23% by mass or more. It is desirable to use an iron-based alloy (for example, stainless steel having a chromium content of 23% by mass or more, more specifically, SUS329J1). Such an iron-based alloy with a chromium content can increase the sealing strength of the battery, prevent leakage of the alkaline electrolyte inside, and improve the corrosion resistance. Even when body fluid adheres to the battery in the body, adverse effects on the human body can be suppressed. In addition, in the case of an iron-based alloy having a chromium content equal to or higher than the above lower limit value, it is possible to transport a positive electrode can using a magnet at the time of battery production, which is also recommended from the aspect of battery production. The upper limit of the chromium content of the iron-based alloy used for the positive electrode can is preferably 30% by mass.

  As the negative electrode terminal plate 5, for example, the surface in contact with the negative electrode 3 is made of a copper alloy such as copper or brass, the main body portion is made of stainless steel, and is on the outer surface side, that is, the side opposite to the surface in contact with the negative electrode 3. The surface is preferably made of nickel. In this negative electrode terminal plate 5, the surface in contact with the negative electrode 3 is made of copper or a copper alloy in order to suppress the formation of a local battery with zinc, but the main body portion is made of stainless steel or the outer surface side. It is not always necessary to form nickel with nickel, and it may be composed of other materials, and the surface in contact with the negative electrode 3 may not be copper or a copper alloy as long as it does not form a local battery with zinc. . As the annular gasket 6, for example, a material made of nylon 66 or the like is recommended.

  Moreover, the fragmentary sectional view which shows the other example of the silver oxide battery of this invention is shown in FIG. In the battery of FIG. 2, the electrolyte solution holding layer 7 is provided on the negative electrode agent 3 side of the separator 2. The electrolytic solution holding layer 7 is an element for holding the electrolytic solution and further improving the power generation efficiency. For example, a vinylon-rayon mixed paper used in a conventionally known battery separator can be used. .

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

Example 1
After pressure-molding silver oxide (Ag ₂ O) alone as a positive electrode active material, the compact is pulverized and sieved to form granules having an average particle size of 150 μm and a bulk density of 2.0 g / cm ³ . The prepared silver oxide was prepared. The positive electrode is made by adding 2 parts by mass of scaly graphite as a conductive additive to the granulated silver oxide and mixing it with 100 parts by mass of the silver oxide to prepare a positive electrode mixture. This was prepared by pressure molding into a disk shape having a packing density of 6 g / cm ³ and a diameter of 7 mm and a height of 0.5 mm, and this was impregnated with a part of an alkaline electrolyte.

  As the negative electrode, 0.03 g of zinc alloy particles in which all of the 200 mesh sieve passes and the ratio of the particles that can pass through the 330 mesh sieve is 95% by mass with respect to the total amount of zinc alloy particles is used. . The zinc alloy particles are composed of a zinc alloy containing 5 mass ppm of aluminum, 400 mass ppm of bismuth, and 500 mass ppm of indium.

As the alkaline electrolyte, a 33% by mass potassium hydroxide aqueous solution in which 4% by mass of zinc oxide was dissolved was used. Moreover, the positive electrode can was produced using SUS319J1 (chromium content 23 mass%). Furthermore, the negative electrode terminal plate was produced using a copper-stainless steel-nickel clad plate. Moreover, the cellophane film whose thickness is 20 micrometers was used for the separator. The electrical resistance of this separator was 10 mΩ · (2.54 cm) ² . The separator and the electrolyte solution holding layer were used by punching into a circle having a diameter of 7.5 mm.

  Using the above positive electrode, negative electrode, alkaline electrolyte, positive electrode can, negative electrode terminal plate, separator and electrolyte holding layer, and further using an annular gasket made of nylon 66, the structure shown in FIG. A coin-shaped silver oxide battery having a thickness of 2.1 mm was produced.

Example 2
A silver oxide battery was produced in the same manner as in Example 1 except that the concentration of the aqueous potassium hydroxide solution used as the alkaline electrolyte was changed as shown in Table 1.

Example 3
A silver oxide battery was produced in the same manner as in Example 1 except that the concentration of the aqueous potassium hydroxide solution used as the alkaline electrolyte was changed as shown in Table 1.

Reference example 4
A silver oxide battery was produced in the same manner as in Example 1 except that the zinc alloy particles used for the negative electrode were changed as shown in Table 1.

Reference Example 5
A silver oxide battery was produced in the same manner as in Example 1 except that the separator was changed to a cellophane film having a thickness of 15 μm and a graft film having a thickness of 15 μm. The electrical resistance of this separator was 45 mΩ · (2.54 cm) ² .

Comparative Example 1
A silver oxide battery was produced in the same manner as in Example 1 except that the zinc alloy particles used for the negative electrode were changed as shown in Table 1 and the separator was changed to a cellophane film having a thickness of 15 μm and a graft film having a thickness of 30 μm. did. The electrical resistance of this separator was 90 mΩ · (2.54 cm) ² .

The following heavy load characteristic evaluation was performed for each battery of the example and the comparative example. Discharge was performed at 20 ° C. with a current density of 50 mA / cm ² , and the change in the closed circuit voltage with respect to the discharge time was measured. The result is shown in FIG. 3, and the value of the closed circuit voltage in a predetermined discharge time (time from the start of discharge) is shown in Table 2.

As can be seen from Table 2 and FIG. 3, the silver oxide batteries of Examples 1 to 3 have a high closed-circuit voltage for 1 minute after the start of discharge and can provide batteries having excellent heavy load discharge characteristics. Here, the battery of Example 1 had a higher closed-circuit voltage after 10 minutes than the silver oxide battery of Reference Example 4 in which the negative electrode zinc alloy particles had a large particle size, and discharge under heavy load A silver oxide battery having a long duration and excellent heavy load discharge characteristics can be provided. Furthermore, the silver oxide battery of Example 1 has a higher closed-circuit voltage after 10 minutes than the silver oxide battery of Reference Example 5 using a separator having high resistance, and the discharge duration under heavy load is larger. Silver oxide batteries having excellent heavy load discharge characteristics can be provided.

It is a fragmentary sectional view which shows an example of the silver oxide battery of this invention. It is a fragmentary sectional view which shows the other example of the silver oxide battery of this invention. It is a graph which shows the change of closed circuit voltage with respect to the discharge time obtained when carrying out heavy load characteristic evaluation about the silver oxide battery of Examples 1-3, the reference examples 4 and 5, and the comparative example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Separator 3 Negative electrode 4 Positive electrode can 5 Negative electrode terminal board 6 Annular gasket 7 Electrolyte holding layer

Claims (1)

A silver oxide battery comprising a positive electrode containing silver oxide as an active material, a negative electrode containing particulate zinc or a particulate zinc alloy as an active material, and a separator ,
The particulate zinc or the particulate zinc alloy is 95-100% by mass, all of which can pass through a 200 mesh screen and can pass through a 330 mesh screen,
The separator has an electrical resistance of 5 to 30 mΩ · (2.54 cm) ² ,
When discharged at a temperature of 20 ° C. and a current density of 50 mA / cm ² , the closing voltage after 1 minute is at least 1.35 V, and the closing voltage after 10 minutes is at least 1.25 V. A featured silver oxide battery.

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