JP6883441B2 - Flat alkaline primary battery - Google Patents

Description

The present invention relates to a flat alkaline primary cell.

Coin-shaped or button-shaped flat alkaline primary batteries are widely used as a power source for small electronic devices such as electronic wristwatches and portable electronic computers. Among these flat alkaline primary batteries, a primary battery containing silver oxide as an active material of a positive electrode is particularly preferably used for an electronic watch or the like because it can maintain a stable voltage until the end of discharge.

On the other hand, since silver oxide, which is the positive electrode active material of these primary batteries, is expensive, a part of the positive electrode active material is replaced with a cheaper material in order to reduce the cost. At this time, various measures are taken to solve the problem caused by replacing the silver oxide with another member. For example, when a part of the positive electrode active material is replaced with manganese dioxide from silver oxide, the problem of a decrease in the strength of the positive electrode mixture occurs, whereas the absorption of hydrogen gas generated from the negative electrode and the improvement of the moldability of the positive electrode mixture occur. It has been proposed to add a La—Ni (LaNi ₅ ) -based hydrogen storage alloy to the positive electrode active material for the purpose of. (See, for example, Patent Document 1.)

Japanese Unexamined Patent Publication No. 2006-302597

By the way, while an alkaline primary cell using silver oxide as a positive electrode active material can maintain a stable voltage until the end of discharge, an alkaline manganese battery using manganese dioxide as a positive electrode active material gradually has a voltage as the discharge progresses. Is known to decrease. Here, even in an alkaline primary battery in which a part of the positive electrode active material made of silver oxide is replaced with manganese dioxide, the voltage of the battery tends to gradually decrease as the discharge progresses.

Electronic watches equipped with alkaline primary batteries are usually designed with a final voltage of 1.2V, which causes the equipment to stop working, and even batteries with positive cathode active materials in which part of silver oxide is partially replaced with manganese dioxide can be used sufficiently. Is. On the other hand, some electronic wristwatches are designed with a final voltage of 1.4V. In such a battery, if a part of the positive electrode active material is replaced with manganese dioxide, there arises a problem that the time for the voltage to drop to the final voltage is significantly shortened. Therefore, it has been desired to provide an alkaline primary battery capable of sufficiently maintaining the operating time until the final voltage while reducing the content of silver oxide used as the positive electrode active material to reduce the cost.

In view of such problems, an object of the present invention is to provide a flat alkaline battery that can be used at low cost and even at a high final voltage.

The present invention has the following configuration as a means for solving the above problems.

The flat alkaline primary cell of the present invention is a flat alkaline primary cell in which an electrolytic solution composed of a positive electrode, a negative electrode, a separator, and an alkaline aqueous solution is housed in a container composed of a positive electrode can, a negative electrode can, and a gasket. It is characterized by containing silver, a silver-nickel composite oxide having a weight ratio of 12 to 22%, manganese dioxide having a weight ratio of 9 to 21%, and a conductive auxiliary agent having a weight ratio of 1 to 3%.

Further, in the above configuration, it is more preferable that the weight ratio of the silver / nickel composite oxide in the positive electrode is 19 to 22%.

Further, in the above configuration, it is more preferable that the conductive auxiliary agent is graphite and is contained in the positive electrode in an amount of 2 to 3% by weight.

According to the present invention, in addition to silver oxide, manganese dioxide and silver-nickel composite oxide, which are superior to silver oxide in terms of cost, are compositely added to the positive electrode as the positive electrode active material. By compositely adding manganese dioxide and silver / nickel composite oxide in this way, the operating time to the final voltage can be increased as compared with the case where only manganese dioxide is added, and the silver / nickel composite oxide can be added. The cost can be further reduced as compared with the case where only is added. Further, by adding a silver-nickel composite oxide which is a positive electrode active material having conductivity in addition to graphite which is a conductive auxiliary agent, the conductivity of the positive electrode mixture can be improved. As a result, it is possible to obtain an alkaline primary battery capable of obtaining a sufficiently large discharge capacity even when discharged under the condition of a high final voltage.

Further, in the flat alkaline primary battery of the present invention, the silver oxide is in the form of granules having an average particle size of 75 to 300 μm, and the silver-nickel composite oxide is in the form of granules having an average particle size of 150 to 250 μm. The manganese dioxide is in the form of granules having an average particle size of 250 to 350 μm, and the conductive auxiliary agent has an average particle size of 10 to 20 μm.

According to the present invention, by forming pellets in which each component having the above particle size is combined as the positive electrode, the pellets are formed at a high density, and the particle spacing in the positive electrode pellets and the gaps on the pellet surface are sufficiently secured. can do. Thereby, the discharge capacity can be further improved.

In the flat alkaline primary battery of the present invention, it is preferable that the positive electrode further contains a hydrogen storage alloy having an average particle size of 30 to 40 μm.

According to the present invention, a sufficient hydrogen storage capacity can be maintained by further adding a hydrogen storage alloy having a predetermined particle size. As a result, the flat alkaline primary battery can be made into mercury-free without using zinc borohydride or the like for the negative electrode, and a high-density flat alkaline primary battery can be obtained.

According to the flat alkaline primary battery of the present invention, a flat alkaline primary battery which can obtain a sufficient discharge capacity by sufficiently maintaining the operating time until the final voltage even if the discharge progresses and is excellent in terms of cost is provided. can do.

It is sectional drawing of the flat alkaline primary cell which shows the embodiment of this invention.

Hereinafter, embodiments of the flat alkaline primary battery according to the present invention will be described with reference to the drawings.
(Outline of flat alkaline primary battery)
The flat alkaline primary battery 1 shown in FIG. 1 is a button-type primary battery. The flat alkaline primary battery 1 includes a positive electrode mixture 5, a separator 6, a negative electrode mixture 7, and an electrolytic solution (not shown) composed of an alkaline aqueous solution in a case 8.

More specifically, the flat alkaline primary battery 1 is fixed to the bottomed tubular positive electrode can 2 and the opening of the positive electrode can 2 via a gasket 4, and a closed space S is provided between the positive electrode can 2 and the positive electrode can 2. It has a bottomed tubular negative electrode can 3 to be formed. Then, by crimping the opening 2a of the positive electrode can 2 toward the gasket 4 and sealing the opening, the case 8 having the sealed space S is formed. A positive electrode mixture 5, a separator 6, a negative electrode mixture 7, and an electrolytic solution are housed in this closed space S, and the positive electrode mixture 5 is on the positive electrode can 2 side and the negative electrode mixture 7 is on the negative electrode can 3 side with the separator 6 interposed therebetween. Are arranged respectively.

The positive electrode can 2 is made of a metal material made of iron (Fe) or stainless steel (SUS) plated with nickel, and is formed into a cup shape. The positive electrode can 2 accommodates the positive electrode mixture 5 and functions as a positive electrode terminal.

The negative electrode can 3 is made of a clad material having a three-layer structure having an outer surface layer made of nickel, a metal layer made of stainless steel (SUS), and a current collector layer made of copper, and is formed in a cup shape. .. Further, in the negative electrode can 3, the opening 3a is formed by folding back, and the gasket 4 is attached to the opening 3a.

Then, the negative electrode can 3 is fitted into the circular opening 2a of the positive electrode can 2 from the opening 3a side to which the gasket 4 is attached, and the opening 2a of the positive electrode can 2 is crimped toward the gasket 4 to seal the can. As a result, a flat (button-shaped or coin-shaped) case 8 is formed. A closed space S is formed inside the case 8.

As shown in FIG. 1, the gasket 4 is formed in an annular shape along the inner peripheral surface of the positive electrode can 2 and has an annular groove portion. This annular groove is in contact with the opening 3a of the negative electrode can 3. For such a gasket 4, nylon or the like is used as a material, for example.

The separator 6 has a two-layer structure of a microporous membrane 6a and a non-woven fabric 6b. With this two-layer structure, the barrier property (insulation property and silver ion shielding effect) between the positive electrode and the negative electrode can be enhanced, and the storage capacity property can be improved. In addition, since the alkaline electrolytic solution can be effectively retained, the discharge characteristics can be improved. As the microporous film 6a, a polyethylene film, cellophane, a graft polymerized film, or the like can be used. Further, as the non-woven fabric 6b, a liquid absorbent paper or the like made of cellulose can be used.

When assembling the flat alkaline primary battery 1, the positive electrode mixture 5 formed into pellets is filled in the positive electrode can 2. Then, a gel-like negative electrode mixture is placed on the separator 6, and the negative electrode can 3 is placed on the gel negative electrode mixture. Further, the opening edge of the positive electrode can 2 is crimped to seal the case 8.

(Positive electrode mixture)
The positive electrode mixture 5, which is the positive electrode in the present invention, is composed of a positive electrode active material, a conductive auxiliary agent, a binder, and the like, and is formed into pellets. By impregnating the pellet-shaped positive electrode mixture 5 with the electrolytic solution, an electrode reaction can occur between the positive electrode active material and the electrolytic solution.

In the present invention, the material constituting the positive electrode active material is silver oxide (Ag ₂ O), silver / nickel composite oxide (AgNiO ₂ ), and manganese dioxide (MnO ₂ ).

Silver oxide is the main positive electrode active material in the positive electrode mixture 5. This silver oxide has a very large theoretical capacity per unit mass, and is a material capable of stably extracting the output voltage of the flat alkaline primary battery 1 until the end of discharge.

In the present invention, silver oxide is used in the form of granules having an average particle size of 75 to 300 μm, which are formed from fine powder having an average particle size of 5 to 15 μm. If the positive electrode mixture 5 contains a large amount of silver oxide, the discharge capacity of the battery can be increased.

Here, in the present invention, the value of D50 in the particle size distribution is expressed as the average particle size.

The silver-nickel composite oxide is an active material having a theoretical capacity per unit mass as large as silver oxide, and at the same time, is a material that exhibits good conductivity by itself. Therefore, by adopting this silver-nickel composite oxide as a material constituting the positive electrode active material in the present invention, it is possible to obtain a battery excellent in terms of cost while ensuring the discharge capacity of the battery.

Further, the silver-nickel composite oxide can maintain a high output voltage of the flat alkaline primary battery 1 until the end of discharge when used as a positive electrode active material, like silver oxide. As a result, a sufficient discharge capacity can be obtained even when used at a high final voltage.

In particular, by setting the weight ratio of the silver-nickel composite oxide in the positive electrode mixture 5 to 12 to 22% and combining it with the conductive auxiliary agent of the present invention, the discharge capacity of the battery in the high voltage region is secured. Therefore, it is possible to obtain a flat alkaline primary battery having excellent conductivity and excellent cost.

When the ratio of silver / nickel composite oxide is less than 12%, a relatively large amount of silver oxide causes a cost problem, and a relatively large amount of manganese dioxide causes a sufficient discharge capacity in a high final voltage region. Will not be obtained. On the other hand, when the ratio of the silver / nickel composite oxide is more than 22%, the merit of cost reduction becomes smaller than the case where the amount of manganese dioxide is increased. Therefore, the ratio of the silver / nickel composite oxide is preferably 12 to 22%, more preferably 19 to 22% in the positive electrode mixture 5 as described above.

Further, the silver-nickel composite oxide can increase the hardness of the pellet made of the positive electrode mixture 5 as compared with the case where only silver oxide and manganese dioxide are used as the positive electrode active material. As a result, the shape of the positive electrode pellets is sufficiently maintained by caulking when the battery is manufactured.

Further, the silver-nickel composite oxide has an excellent hydrogen storage capacity, and can absorb hydrogen gas generated by contact between the zinc powder in the negative electrode mixture 7 of the battery and the electrolytic solution. Thereby, the negative electrode mixture of the alkaline primary battery in the present invention can be made into mercury-free.

In the present invention, it is used as a silver-nickel composite oxide in the form of granules having an average particle size of 150 to 250 μm. When the silver / nickel composite oxide is used at this particle size, pellets made of the positive electrode mixture 5 can be formed at high density in combination with other materials constituting the positive electrode active material.

Manganese dioxide can function as a positive electrode active material although it has a smaller theoretical capacity per unit mass than silver oxide. Therefore, by replacing a part of the positive electrode active material from silver oxide with manganese dioxide, it is possible to reduce the cost while maintaining the desired minimum required discharge capacity.

Further, since manganese dioxide has a large particle size, it is possible to secure a gap in the pellet and maintain the impregnation property of the electrolytic solution even when the positive electrode mixture 5 is compression-molded at a high density. Therefore, when the positive electrode active material to which manganese dioxide is added is adopted, the discharge characteristics are improved as compared with the case where the positive electrode active material contains only silver oxide or the positive electrode active material contains only silver oxide and silver / nickel composite oxide. Can be stabilized.

The manganese dioxide in the present invention is preferably contained in the positive electrode mixture 5 in an amount of 9 to 21% by weight. With this content ratio, it is possible to combine with other positive electrode active materials to secure the discharge capacity of the battery and to obtain an excellent battery in terms of cost. On the other hand, when manganese dioxide is added in the positive electrode mixture 5 in a weight ratio of less than 9%, a sufficient effect cannot be obtained in terms of cost. On the other hand, if more than 21% is added, not only the discharge capacity cannot be sufficiently obtained, but also the voltage drops as the battery discharge progresses, so that it cannot be used for applications with a high final voltage.

Further, the manganese dioxide in the present invention is preferably used in the form of granules having an average particle size of 250 to 350 μm. With this particle size, a gap capable of sufficiently impregnating the electrolytic solution can be formed in the pellet made of the positive electrode mixture 5, and the discharge capacity of the battery can be secured. When the average particle size is smaller than this, such a gap cannot be sufficiently secured, and the discharge capacity of the battery cannot be secured. On the other hand, when the average particle size is larger than this, the discharge capacity of the battery is lowered because the gap is too large.

In the present invention, graphite is used as the conductive auxiliary agent. This graphite is preferably contained in the positive electrode mixture 5 in an amount of 1 to 3% by weight. By combining conductive silver-nickel composite oxide and graphite in the positive electrode mixture 5 at the ratio of the present invention, an alkaline primary battery having both excellent low resistance characteristics and discharge capacity characteristics is obtained. be able to. On the other hand, when the amount of graphite is less than 1%, the characteristics of sufficiently low resistance, which is the object of the present invention, cannot be obtained. On the other hand, if it is more than 3%, the ratio of the positive electrode active material in the positive electrode mixture 5 becomes relatively small, and sufficient capacity characteristics cannot be obtained. As described above, the content ratio of graphite is preferably 1 to 3% by weight in the positive electrode mixture 5, but the capacity characteristics can be further improved by combining with the above-mentioned silver / nickel composite oxide. it can. Specifically, if the ratio of the silver / nickel composite oxide is 19 to 22% by weight in the positive electrode mixture 5 and the proportion of graphite is 2 to 3%, the above-mentioned low resistance characteristics and discharge capacity characteristics Can further exert the effect of improving.

Further, the graphite used in the present invention preferably has an average particle size of 10 to 20 μm. With this particle size, pellets made of the positive electrode mixture 5 can be formed at high density by using the particle size in combination with the particle size of each positive electrode active material in the present invention.

As the conductive auxiliary agent, in addition to graphite, a carbon material such as Ketjen black or acetylene black can be used.

The binder can be added to bind the particles of the positive electrode active material or the conductive auxiliary agent to each other and maintain sufficient strength of the pellets. Examples of the binder include polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), polyacrylic acid (PA), carboxymethyl cellulose (CMC), polyimide (PI), polyamideimide (PAI), and the like. It can be appropriately used as one type or a combination of two or more types.

Further, a hydrogen storage alloy for absorbing hydrogen gas generated by contact between the zinc powder in the negative electrode mixture 7 of the battery and the electrolytic solution can be added to the positive electrode mixture 5. Examples of the hydrogen storage alloy include _{La-Ni alloys such as LaNi 5} , AB5 hydrogen storage alloys such as Lm-Ni alloys (Lm is La-enriched Mish metal), AB2 hydrogen storage alloys such as Ti, and Mg alloys. Various materials such as Ca-based alloys can be used. Of these, LaNi ₅ is particularly preferable because it has an extremely high hydrogen storage capacity.

The hydrogen storage alloy can exhibit the above hydrogen storage capacity if it is contained in 0.5 to 5% by weight in the positive electrode mixture 5. However, in order to keep the capacity of the battery high, it is preferable that the positive electrode mixture 5 contains 0.5 to 2% by weight so that the proportion of silver oxide does not decrease. As an embodiment of the hydrogen storage alloy, an alloy powder having an average particle size of 30 to 40 μm is used.
(Negative electrode mixture)
The negative electrode mixture 7, which is the negative electrode in the present invention, contains a negative electrode active material, a conductivity stabilizer, a gelling agent, and an electrolytic solution.

As the negative electrode active material, zinc powder or zinc alloy powder is used. As the conductivity stabilizer, zinc oxide (ZnO) or the like is used.

As the electrolytic solution, an aqueous solution of potassium hydroxide, an aqueous solution of sodium hydroxide, or a mixed solution thereof can be used.

Further, as the gelling agent, carboxymethyl cellulose (CMC), polyacrylic acid (PAS), or a mixture thereof can be used. By using these gelling agents, the lipophilicity and liquid retention property of the negative electrode mixture 7 with respect to the electrolytic solution can be improved.

Of these, CMC is particularly used as a gelling agent because it can maintain an appropriate viscosity of the negative electrode mixture 7 and has good handleability. On the other hand, in the negative electrode mixture 7 using CMC as a gelling agent, the concentration range with good handleability is narrow, and a process for adjusting the concentration is further required. Therefore, it is preferable to add PAS in a complementary manner. ..

Considering these, the gelling agent is preferably contained in the negative electrode mixture in an amount of 2 to 5% by weight. Further, in the gelling agent in which PAS is complementarily added to CMC, it is preferable that PAS is contained in an amount of 3 to 15% by weight based on the entire gelling agent.

Further, in order to improve the viscoelasticity of the negative electrode mixture 7, a viscoelasticity adjusting material can be further added. The viscoelasticity adjusting material is preferably a non-metallic insulating powder that does not react with the strongly alkaline electrolytic solution. As the viscoelasticity adjusting material, for example, a resin powder composed of one or more selected from polytetrafluoroethylene, polypropylene, polyamide, polyethylene, acrylic resin and the like can be used, and polyethylene is particularly easy to handle and is particularly easy to handle. preferable. These resin powders may have a particle size of 110 to 350 μm. When added to the negative electrode mixture 7, it is preferable that 1 to 25% by weight is added to the entire negative electrode mixture 7.

Next, a flat alkaline primary battery was produced using the positive electrode mixture 5 of the examples and comparative examples in which the composition was changed, and the effect of the present invention was verified.
(Example 1)
In this example, a SR626SW type (outer diameter 6.8 mm, height 2.6 mm) flat alkaline primary battery was produced.

Each composition constituting the negative electrode mixture 7 contained 66% by weight of zinc alloy powder, 3% by weight of zinc oxide (ZnO), and 3% by weight of carboxymethyl cellulose in the negative electrode mixture. Further, as the electrolytic solution, sodium hydroxide having a concentration of 28% was blended so as to be 28% by weight in the negative electrode mixture. At this time, the average particle size of the zinc alloy powder was set to 150 μm. These compositions were mixed to prepare a gel-like negative electrode mixture 7.

Each composition constituting the positive electrode mixture 5 has a weight ratio of silver oxide (Ag ₂ O) of 65%, silver / nickel composite oxide (AgNiO ₂ ) of 12%, and manganese dioxide (MnO _{2) in the positive electrode mixture, respectively.} ) 21%, graphite 1%, hydrogen storage alloy (LaNi ₅ ) 1%, respectively.

For Ag ₂ O, granules having a particle size of 75 to 300 μm were used. As for AgNiO ₂ and MnO ₂ , granular ones having an average particle size of 200 μm and 300 μm were used, respectively. Graphite was used in the form of a powder having an average particle size of 15 μm. LaNi ₅ was used in the form of a powder having an average particle size of 35 μm. Then, the positive electrode mixture 5 in which each composition was mixed by a granulator was compression-molded into pellets to prepare a positive electrode.

The positive electrode mixture 5 thus produced was housed in a nickel-plated iron positive electrode can 2, and a separator 6 was laid on the positive electrode mixture 5. Further, a ring-shaped gasket 4 to be press-fitted was inserted into the positive electrode can 2. Further, the negative electrode mixture 7 was placed on the separator, and the negative electrode can 3 was placed on the negative electrode mixture 7 via the gasket 4. Then, the flat alkaline primary battery 1 described above was manufactured by crimping the opening edge of the positive electrode can 2.

The separator 6 is made of a polyethylene film, cellophane and a non-woven fabric, and the gasket 4 is made of nylon.
(Examples 2 to 7)
The difference from Example 1 was that _{the blending ratio (% by weight) of AgNiO 2} , MnO ₂ , and graphite in the positive electrode mixture 5 was set to the ratio shown in Table 1, and the other configurations were the same as in Example 1. ..

具体的に、実施例２では、正極合剤５中の配合割合を重量比で、ＡｇＮｉＯ₂１４％、ＭｎＯ₂１９％、グラファイト１％とした他は、実施例１と同様の構成とした。

Specifically, in Example 2, the composition was the same as in Example 1 except that the mixing ratio in the positive electrode mixture 5 was AgNiO ₂ 14%, MnO ₂ 19%, and graphite 1% in terms of weight ratio.

In Example 3, the composition was the same as in Example 1 except that the mixing ratio in the positive electrode mixture 5 was AgNiO ₂ 16%, MnO _{2 17%, and graphite 1% by weight.}

In Example 4, the mixing ratio in the positive electrode mixture 5 in a weight _{ratio, AgNiO 2 18%, MnO 2} 15%, except that a 1% graphite was the same structure as in Example 1.

In Example 5, the composition was the same as that of Example 1 except that the mixing ratio in the positive electrode mixture 5 was AgNiO ₂ 19%, MnO _{2 13%, and graphite 2% by weight.}

In Example 6, the mixing ratio in the positive electrode mixture 5 in a weight _{ratio, AgNiO 2 20%, MnO 2} 11%, except that a 3% graphite, and the same structure as in Example 1.

In Example 7, the proportion in the positive electrode mixture 5 in a weight _{ratio, AgNiO 2 22%, MnO 2} 9%, except that a 3% graphite, and the same structure as in Example 1.
(Comparative Example 1)
To Example, Ag ₂ O65% the proportion in the positive electrode mixture 5 in a weight ratio, MnO ₂ 35% graphite 3%, differs only in that the LaNi ₅ 1% Other configurations, Example 1 It was the same as.
(Evaluation)
Then, the positive electrode mixture 5 of Examples and Comparative Examples and the flat alkaline primary battery 1 using the same were prepared, and the discharge capacity was measured. The measurement was performed in an environment of room temperature (24 ° C.) when six batteries of each of the examples and comparative examples were continuously discharged with a load resistance of 43 kΩ and the final voltage (cutoff) was set to 1.2 V and 1.4 V. The discharge capacity (mAh) was measured. Table 1 shows a comparison of the averages of the measurement results.
(Evaluation results)
The evaluation results are shown in Table 1.

The average discharge capacity when the final voltage was 1.2 V was 27.4 to 28.4 mAh in Examples 1 to 7, while it was 23.8 mAh in Comparative Example 1, and the capacity in Examples was slightly larger. showed that. On the other hand, the average discharge capacity when the final voltage was 1.4 V was 24.0 to 25.8 mAh in Examples 1 to 7, while it was 17.2 mAh in Comparative Example 1, which is a large difference between the two. Has occurred.

This is because, in the case of Comparative Example 1 in which only _{MnO 2} was used as the active material other than _{Ag 2} O, the pellets of the positive electrode mixture 5 could not be made denser as compared with each example in which _{AgNiO 2 was also used.} It is due to that. On the other hand, in each of the examples, the density of the pellets could be made sufficiently high, so that the discharge capacity when the final voltage was 1.2 V could be increased.

Further, in _{Comparative Example 1 in which the amount of MnO 2} accounts for 35%, the discharge capacity when the final voltage is 1.4 V is significantly lower than in each implementation. This is because the discharge time cannot be maintained in the voltage region of 1.4 V or higher when _{MnO 2 is used as the active material. Therefore, by suppressing the amount of MnO 2} in the positive electrode to 9 to 21% by weight _{and securing the total amount of Ag 2} O and _{Ag Ni O 2} , the discharge capacity is sufficiently maintained even when the final voltage is 1.4 V. The amount of Ag ₂ O can be suppressed.

Further, as shown in Examples 5 to 7, when AgNiO ₂ was 19% or more by weight, the discharge capacity when the final voltage was 1.4 V was further improved. In these examples, among the active material other than Ag ₂ O, since the AgNiO ₂ big theoretical capacity than MnO ₂ is relatively large, sufficient capacity is obtained. By that amount, the amount of the conductive auxiliary agent can be increased, and it becomes easier to take out the electric charge from the active material, so that the capacity can be further obtained in the voltage region of 1.4 V or more.

In this way, in the example in which a part of the positive electrode active material was replaced with manganese dioxide and silver / nickel composite oxide from silver oxide, the final voltage was 1.2 V as compared with the comparative example in which only manganese dioxide was replaced. However, I was able to maintain sufficient capacity. It was also found that under the condition that the final voltage is 1.4 V, the high voltage is further maintained even if the discharge progresses by increasing the compounding ratio of the silver / nickel composite oxide. Therefore, with such a flat alkaline primary battery, a sufficient discharge capacity can be obtained by sufficiently maintaining the operating time until the final voltage even if the discharge progresses, while reducing the cost.

1 ... Flat alkaline primary battery 2 ... Positive electrode can 3 ... Negative electrode can 4 ... Gasket 5 ... Positive electrode mixture 6 ... Separator 7 ... Negative electrode mixture 8 ... Case

Claims (4)

In a flat alkaline primary cell in which an electrolytic solution composed of a positive electrode, a negative electrode, a separator, and an alkaline aqueous solution is housed in a container composed of a positive electrode can, a negative electrode can, and a gasket.
The positive electrode, viewed contains a silver oxide, the weight ratio 12 to 22% of the silver-nickel composite oxide, the weight ratio 9-21% manganese dioxide, and the weight ratio 1-3% of conductive additive, a,
The silver oxide is in the form of granules having an average particle size of 75 to 300 μm, the silver-nickel composite oxide is in the form of granules having an average particle size of 150 to 250 μm, and the manganese dioxide is in the form of granules having an average particle size of 250 to 350 μm. A flat alkaline primary battery characterized in that it is granular and the average particle size of the conductive auxiliary agent is 10 to 20 μm. The flat alkaline primary battery according to claim 1, wherein the weight ratio of the silver / nickel composite oxide in the positive electrode is 19 to 22%. The flat alkaline primary battery according to claim 2, wherein the conductive auxiliary agent is graphite and is contained in the positive electrode in an amount of 2 to 3% by weight. The flat alkaline primary battery according to any one of claims 1 to 3 , wherein the positive electrode further contains a hydrogen storage alloy having an average particle size of 30 to 40 μm.

Images