JP2011028895A - Alkaline dry battery and positive electrode molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost alkaline dry battery high in a ratio of positive electrode active material utilization, excellent in discharge characteristics, and high in reliability. <P>SOLUTION: The alkaline dry battery includes a positive electrode containing positive electrode active material and graphite, a negative electrode containing a negative electrode active material, a separator arranged between the positive electrode and a negative electrode, and an electrolyte. The positive electrode contains 0.15-0.55 pts.wt. of a poorly water-soluble polyacrylic acid or a salt of it as a positive electrode additive based on 100 pts.wt. of the positive electrode active material. A ratio of the graphite in the positive electrode is 7.8-12.9 vol.%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an alkaline battery, and more particularly to improvement of the positive electrode.

Conventionally, alkaline batteries have been widely used as power sources for electronic devices such as portable devices.
In recent years, with the improvement in performance of electronic devices, demands for higher battery capacity and higher energy density are increasing.

  In the alkaline dry battery, the positive electrode is produced, for example, by the following method. A mixture containing manganese dioxide and graphite is compression-molded into a plate shape by a roll press, and then the molded product is crushed and classified to obtain a granulated mixture. The granulated mixture is filled in a predetermined molding die and subjected to pressure molding to obtain a hollow cylindrical positive electrode mixture pellet. A plurality of positive electrode mixture pellets are placed in a battery case and pressure molded again to obtain a positive electrode molded body. An electrolyte is injected into the battery case, and the electrolyte is sufficiently contained in the positive electrode molded body to obtain a positive electrode.

Various studies have been conducted on the positive electrode of the alkaline dry battery.
For example, in Patent Document 1, in an alkaline dry battery using a positive electrode containing manganese dioxide and graphite, a water-soluble binder of 0.6 to 1.5% by weight with respect to manganese dioxide is added to the positive electrode, and the molding density of the positive electrode is increased. It has been proposed to be 2.9 to 3.1 g / cm ³ . By reducing the forming density of the positive electrode and increasing the amount of the electrolyte retained in the positive electrode, the utilization factor of the positive electrode active material is improved and the discharge characteristics are improved. Moreover, the moldability of the positive electrode can be improved by increasing the amount of the water-soluble binder.

In Patent Document 2, a water-soluble binder is added to a positive electrode used in an alkaline battery for the purpose of improving the moldability of the positive electrode, and the water-soluble binder is 3% by weight in an aqueous solution containing 40% by weight potassium hydroxide. It has been proposed to use a binder having a viscosity of 200 Pa · s or more when added at a concentration of 1 to 2.
Patent Document 3 proposes that 0.03 to 0.1% by weight of cross-linked polyacrylic acid is added to manganese dioxide to a positive electrode used in an alkaline battery for the purpose of improving the formability of the positive electrode. .

JP-A-10-144304 JP 2005-129309 A JP 2000-294233 A

However, in Patent Document 1, since the amount of the water-soluble binder increases, the positive electrode easily swells (expands) due to the inclusion of the electrolytic solution, and it is difficult to control it. When the electrolyte is injected, the positive electrode may expand to the inner peripheral side, stress may concentrate on the inner peripheral side of the positive electrode, and the inner wall of the positive electrode may collapse. In addition, when the positive electrode expands in the height direction and the positive electrode collapses, a part of the collapsed positive electrode may come into contact with the negative electrode due to vibration during battery transportation, thereby causing an internal short circuit. Thus, the reliability of the battery may be reduced.
In Patent Documents 2 and 3, the binding property (formability) of the positive electrode is improved, but the improvement of the discharge characteristics is insufficient.

  Accordingly, an object of the present invention is to provide a low-cost and high-reliability alkaline dry battery having a high positive electrode active material utilization rate and excellent discharge characteristics in order to solve the above-described conventional problems. Another object of the present invention is to provide a positive electrode molded body used in the above alkaline dry battery.

The present invention is an alkaline dry battery comprising a positive electrode including a positive electrode active material and graphite, a negative electrode including a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution,
The positive electrode includes, as a positive electrode additive, 0.15 to 0.55 parts by weight of polyacrylic acid or a salt thereof that is hardly soluble in water per 100 parts by weight of the positive electrode active material,
The proportion of the graphite in the positive electrode is 7.8 to 12.9% by volume.
The proportion of the graphite in the positive electrode is preferably 8.9 to 11.8% by volume.

The positive electrode preferably contains 0.40 to 0.55 parts by weight of the positive electrode additive per 100 parts by weight of the positive electrode active material.
The positive electrode preferably includes the graphite in an amount of 8.1 to 11.0 parts by weight per 100 parts by weight of the positive electrode active material.
The average particle diameter of the graphite is preferably 40 μm or less.
The positive electrode active material is preferably manganese dioxide.
The average particle diameter of the manganese dioxide is preferably 60 μm or less.
It is preferable that the positive electrode contains the electrolytic solution and has a weight of 3.15 to 3.27 per 1 cm ^{3 of the} positive electrode.

Further, the present invention is a hollow cylindrical alkaline dry battery positive electrode molded body,
The positive electrode molded body includes a positive electrode active material, graphite, an electrolytic solution, and polyacrylic acid or a salt thereof that is sparingly soluble in water as a positive electrode additive,
The positive electrode molded body contains the positive electrode additive in an amount of 0.15 to 0.55 parts by weight per 100 parts by weight of the positive electrode active material,
The proportion of the graphite in the positive electrode compact is 8 to 13% by volume.

The proportion of the graphite in the positive electrode compact is preferably 9.1 to 12.0% by volume.
The positive electrode compact preferably contains 6.7 to 12.1 parts by weight of graphite, more preferably 8.1 to 11.0 parts by weight, per 100 parts by weight of the positive electrode active material.
The weight per 1 cm ^{3 of the} positive electrode molded body is preferably 2.80 to 3.00 g, more preferably 2.85 to 3.00 g, and particularly preferably 2.85 g to less than 2.90 g.

According to the present invention, since the positive electrode contains polyacrylic acid or a salt thereof that is hardly soluble in water, the hollow cylindrical positive electrode that is in close contact with the inner surface of the battery case expands toward the inner peripheral side when the electrolyte is injected. The density of the positive electrode active material on the inner peripheral side is increased, and the contact between the positive electrode and the separator disposed on the inner peripheral side of the positive electrode is improved. Therefore, the reactivity on the inner peripheral side of the positive electrode is improved. Thereby, even if the positive electrode active material is reduced, the utilization rate of the positive electrode active material is improved, so that the discharge characteristics are improved.
Since graphite is present in such a ratio that the active material has good slip in the positive electrode, it is possible to suppress the collapse of the positive electrode due to stress concentration on the inner peripheral side of the positive electrode when the positive electrode expands.
Costs can be reduced by reducing the amount of positive electrode active material used.

It is the front view which made some alkaline dry batteries of one embodiment of the present invention a section.

  The present invention relates to a positive electrode including graphite as a positive electrode active material and a conductive agent, a negative electrode including a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, and an alkaline dry battery including an electrolytic solution. In the present invention, the positive electrode contains 0.1 to 0.55 weight of polyacrylic acid or a salt thereof (hereinafter referred to as polyacrylic acid) which is sparingly soluble in water as a positive electrode additive per 100 parts by weight of the positive electrode active material. The proportion of the graphite in the positive electrode is 7.8 to 12.9% by volume.

The positive electrode additive serves as a binder for maintaining the binding properties between the positive electrode active material particles and between the positive electrode active material particles and the graphite particles, and at the same time, serves as a positive electrode expansion agent.
At the time of manufacturing the battery, a hollow cylindrical positive electrode is placed in a bottomed cylindrical battery case. More specifically, the positive electrode is disposed so that the outer peripheral surface of the positive electrode is in contact with the inner peripheral surface of the battery case. After a separator is arranged on the inner peripheral surface of a hollow cylindrical positive electrode arranged in the battery case, an electrolytic solution is injected. At that time, the positive electrode absorbs the electrolytic solution. At this time, the presence of the positive electrode additive causes the positive electrode to expand toward the inner peripheral side (separator side).
Thereby, the density of the inner periphery side of the positive electrode (active material) is increased, the contact property of the positive electrode with the separator is improved, and the reactivity (utilization rate of positive electrode active material) on the inner peripheral side of the positive electrode is improved. Even if the amount of the positive electrode (active material) used is reduced, the discharge characteristics are improved by improving the utilization rate of the positive electrode active material.

  When the content of the positive electrode additive in the positive electrode is less than 0.15 parts by weight per 100 parts by weight of the positive electrode active material, the effect of the positive electrode additive is reduced. When the content of the positive electrode additive in the positive electrode exceeds 0.55 parts by weight per 100 parts by weight of the positive electrode active material, it is difficult to control the degree of expansion of the positive electrode, the positive electrode collapses, and an internal short circuit may occur. is there.

When the positive electrode additive is a water-soluble binder, it is possible to swell the positive electrode by increasing the amount added. However, since the volume occupied by the positive electrode in the battery is limited, when a large amount of water-soluble binder is used, it is necessary to excessively reduce the amount of the positive electrode active material, and it is difficult to improve the discharge characteristics. In addition, it is difficult to control the swelling of the positive electrode, and the positive electrode may swell too much, and a part of the positive electrode may come into contact with the negative electrode, causing an internal short circuit.
On the other hand, polyacrylic acid or the like which is hardly soluble in water may be a small amount and is advantageous in terms of cost, and it is not necessary to excessively reduce the amount of the positive electrode active material for the use of the polyacrylic acid or the like. . In addition, in the case of polyacrylic acid or the like that is hardly soluble in water, the positive electrode can be swollen with good control. Therefore, according to the present invention, improvement in discharge characteristics, improvement in reliability, and cost reduction can be realized at the same time.

  Polyacrylic acid or the like is hardly soluble in water. At room temperature (20 ° C. ± 15 ° C.), 1 g of polyacrylic acid or the like is added with 100 g of an electrolytic solution (concentration 39 wt% KOH and concentration 2 wt% ZnO). When the solution is stirred with an aqueous solution containing the electrolyte, the electrolyte solution becomes opaque. Such polyacrylic acid or the like is separated at a normal temperature (20 ° C. ± 15 ° C.) into 200 g of electrolytic solution and stirred, but if it is left for a while, it separates downward and does not dissolve.

Here, that the electrolytic solution is opaque means that the kaolin turbidity (based on JIS K 0101) is 300 degrees or more at room temperature (20 ° C. ± 15 ° C.).
Turbidity is calculated | required with the following method, for example. 1 g of polyacrylic acid or the like is added to 100 g of an aqueous solution containing 39% by weight of KOH and 2% by weight of ZnO, stirred for 30 minutes, and then allowed to stand for 24 hours to prepare a sample solution. The intensity of transmitted light having a wavelength of around 660 nm that has passed through the sample solution is measured, and the turbidity is determined from a calibration curve prepared using a commercially available kaolin standard solution (1000 degrees). For the measuring device, UV-250 manufactured by Shimadzu Corporation is used.

Examples of water-insoluble polyacrylic acid include PW-350P manufactured by Nippon Pure Chemical Co., Ltd., and HV-505E manufactured by Sumitomo Seika Co., Ltd. In the case of PW-350P and HV-505E, the turbidity obtained by the measurement method is 320 degrees and 300 degrees, respectively. In Patent Document 3, PW-150 manufactured by Nippon Pure Chemical Co., Ltd. is used, and the turbidity in this case is 260 degrees.
Examples of the salt of polyacrylic acid include sodium salt and potassium salt.

  Further, the graphite used in the present invention plays a role as a conductive agent and a lubricant. In other words, the presence of graphite in the above proportion in the positive electrode allows the positive electrode to ensure excellent electronic conductivity and good sliding properties of the active material particles. Stress generated on the circumferential side can be relaxed. Thereby, collapse of the positive electrode due to stress concentration on the inner peripheral side of the positive electrode during expansion of the positive electrode can be suppressed.

When the proportion of graphite in the positive electrode is 7.8 to 12.9% by volume, the positive electrode can be appropriately swollen with good control by the addition of a small amount of the positive electrode additive. Therefore, the collapse of the positive electrode due to excessive swelling can be suppressed.
Since the positive electrode has good sliding properties, the positive electrode does not collapse due to a volume change due to expansion during absorption of the electrolyte. Further, the positive electrode does not collapse during vibration, and excellent reliability with respect to vibration can be ensured.

When the proportion of graphite in the positive electrode is less than 7.8% by volume, the slipperiness of the positive electrode active material particles is lowered, and the positive electrode is easily collapsed. If the proportion of graphite in the positive electrode exceeds 12.9% by volume, the amount of active material in the positive electrode may be excessively reduced, and the discharge characteristics may be deteriorated.
In order to further improve the utilization rate of the positive electrode active material and obtain excellent discharge characteristics, the content of the positive electrode additive in the positive electrode is 0.40 to 0.55 parts by weight per 100 parts by weight of the positive electrode active material. The proportion of graphite in the positive electrode is preferably 8.9 to 11.8% by volume.

The graphite content per 100 parts by weight of the positive electrode active material in the positive electrode is preferably 6.7 to 12.1 parts by weight, and more preferably 8.1 to 11.0 parts by weight.
As described above, when the positive electrode contains the positive electrode additive and graphite, a highly reliable and low-cost battery having excellent discharge characteristics can be obtained.

Hereinafter, an embodiment of the alkaline dry battery of the present invention will be described with reference to FIG. FIG. 1 is a front view of a cross section of a part of the alkaline dry battery of the present invention.
A hollow cylindrical positive electrode 2 is inserted in a bottomed cylindrical battery case 1 made of a nickel-plated steel plate. The positive electrode 2 is made of a mixture of manganese dioxide powder, graphite powder, alkaline electrolyte, and the above positive electrode additive. A graphite coating film (not shown) is formed on the inner surface of the battery case 1.

  The hollow portion of the positive electrode 2 is filled with a gelled negative electrode 3 via a separator 4. A bottom paper 9 is disposed between the bottom of the positive electrode 2 and the inner bottom surface of the battery case 1. The negative electrode 3 is composed of, for example, a mixture of a gelling agent such as sodium polyacrylate, an alkaline electrolyte, and a negative electrode active material. For the negative electrode active material, for example, zinc powder or zinc alloy powder is used. The zinc alloy contains, for example, Bi, In, or Al. For the separator, for example, a nonwoven fabric mainly composed of polyvinyl alcohol fiber and rayon fiber is used. For example, an aqueous potassium hydroxide solution is used as the electrolytic solution.

  The opening of the battery case 1 is sealed with an assembly sealing body. The assembly sealing body includes a resin gasket 5, a bottom plate 7 also serving as a negative electrode terminal, and a negative electrode current collector 6. The negative electrode current collector 6 is inserted into the gelled negative electrode 3. The body of the negative electrode current collector 6 is inserted into a through hole provided in the center of the gasket 5, and the head of the negative electrode current collector 6 is welded to the bottom plate 7. The open end of the battery case 1 is caulked to the peripheral edge of the bottom plate 7 via the outer peripheral end of the gasket 5. The outer surface of the battery case 1 is covered with an exterior label 8.

The positive electrode 2 is produced by the following method.
A raw material mixture containing manganese dioxide, graphite, electrolytic solution, and the above positive electrode additive (poorly soluble polyacrylic acid or salt thereof in water) is pressed into a plate shape with a roll press, and then the formed product is crushed. Classification is performed to obtain a granulated mixture. The particle size of the granulation mixture is, for example, 0.2 to 2.5 mm. A predetermined cylindrical mold is filled with a granulation mixture and subjected to pressure molding to obtain a hollow cylindrical positive electrode mixture pellet. After arranging a plurality of positive electrode mixture pellets in the battery case, it is pressure-molded again in the battery case to obtain a hollow cylindrical positive electrode molded body that is in close contact with the inner surface of the battery case. After placing the separator on the inner peripheral surface of the hollow part of the positive electrode molded body, a predetermined amount of electrolyte is injected into the battery case, and the positive electrode molded body absorbs a sufficient amount of the electrolyte, and the positive electrode molded body is swollen. Let In this way, a positive electrode is obtained.

The positive electrode compact (raw material mixture) contains a positive electrode additive in an amount of 0.15 to 0.55 parts by weight per 100 parts by weight of the positive electrode active material.
It is preferable that the positive electrode additive (dry state) used for preparation of the said granulation mixture is a powder form.
In order to uniformly disperse the positive electrode additive in the raw material mixture, the powdered positive electrode additive (in a dry state) preferably contains 80% by weight or more of particles of 250 μm or less. The powdered positive electrode additive (in the dry state) more preferably contains 80% by weight or more of particles of 250 μm or less.
The average particle diameter of the positive electrode additive is preferably 10 to 150 μm.

The proportion of graphite in the positive electrode compact (raw material mixture) is 8 to 13% by volume. At this time, the positive electrode can be appropriately swollen with good control by adding a small amount of the positive electrode additive.
When the proportion of graphite in the positive electrode molded body is less than 8% by volume, the effect of addition of graphite is reduced, the sliding property of the active material is deteriorated, and the swollen positive electrode may collapse. If the proportion of graphite in the positive electrode molded body exceeds 13% by volume, the amount of active material in the positive electrode may be excessively reduced, and the discharge characteristics may be deteriorated.
In order to further improve the utilization rate of the positive electrode active material and obtain excellent discharge characteristics, the content of the positive electrode additive in the positive electrode molded body is 0.40 to 0.55 parts by weight per 100 parts by weight of the positive electrode active material. The proportion of graphite in the positive electrode compact is preferably 9.1 to 12.0% by volume.
The graphite content per 100 parts by weight of the positive electrode active material in the positive electrode compact (raw material mixture) is preferably 6.7 to 12.1 parts by weight, more preferably 8.1 to 11.0 parts by weight.

The proportion of graphite in the positive electrode molded body is obtained by the following formula (1).
Ratio occupied by graphite (volume%) = volume of graphite / volume of positive electrode molded body × 100 (1)
The volume of the graphite is determined by the following formula (2).
Graphite volume = Graphite filling amount / True specific gravity of graphite (2)
Here, the true specific gravity of graphite in the above formula (2) is 2.3 g / cm ³ .

  The positive electrode compact (raw material mixture) preferably contains 1 to 3.6 parts by weight of the electrolyte solution per 100 parts by weight of the positive electrode active material. The electrolytic solution used for producing the positive electrode molded body is preferably a KOH aqueous solution having a concentration of 30 to 42% by weight.

From the viewpoint of improving discharge characteristics (positive electrode active material utilization rate) and reducing costs (positive electrode active material loss), the density of the positive electrode molded body (the amount of positive electrode molded body (g) per 1 cm ³ of the positive electrode molded body) is 2.80 to 3.00 g / cm ³ is preferred. From the viewpoint of production, the density of the positive electrode molded body is more preferably 2.85 to 3.00 g / cm ³ . More preferably, the density of the positive electrode molded body is 2.85 g / cm ³ or more and less than 2.90 g / cm ³ .
By using the positive electrode additive, the binding property (formability) of the positive electrode molded body is improved, so that a low density positive electrode molded body can be obtained without impairing the strength of the positive electrode molded body. Further, even when a low-density positive electrode molded body having a density of 2.80 to 3.00 g / cm ³ is used, the positive electrode active material utilization rate is improved. it can.

The density of the positive electrode active material (the amount of the positive electrode active material (g) per 1 cm ³ of the positive electrode molded body) is preferably 2.46 to 2.73 g / cm ³ , more preferably 2.51 to 2.58 g / cm ³ . is there. Even when a positive electrode molded body having a low density of the positive electrode active material is used, the utilization rate of the positive electrode active material is improved. Therefore, the discharge characteristics can be improved while reducing the positive electrode active material.

From the viewpoint of the formability and strength of the positive electrode, the average particle diameter of manganese dioxide is preferably 60 μm or less, more preferably 50 μm or less, and still more preferably 35 to 50 μm.
From the viewpoint of formability, slipperiness, and strength of the positive electrode, the average particle size of graphite is preferably 40 μm or less, more preferably 35 μm or less, and still more preferably 30 to 35 μm.
The average particle diameter is a volume-based median diameter (D50), and represents a particle diameter at which the volume integration is 50% of the whole in the particle size distribution (volume integration distribution).

A potassium hydroxide aqueous solution is used as the electrolytic solution. The concentration of potassium hydroxide in the electrolytic solution in the battery is preferably 30 to 42% by weight. The electrolytic solution may further contain zinc oxide. The concentration of zinc oxide in the electrolytic solution is preferably 1 to 3% by weight.
In the battery, the positive electrode is swollen by containing a sufficient amount of the electrolytic solution, and the weight per 1 cm ^{3 of} the positive electrode is preferably 3.15 to 3.27 g. Although the density of the positive electrode is low, since the utilization rate of the positive electrode active material is high, it is possible to achieve both high capacity and cost reduction.
In the above, manganese dioxide is used as the positive electrode active material, but nickel oxyhydroxide may be used. Moreover, you may use both manganese dioxide and nickel oxyhydroxide for a positive electrode active material. In this case, the content of nickel oxyhydroxide in the positive electrode is preferably 20 to 60 parts by weight per 100 parts by weight of manganese dioxide.

Examples of the present invention will be described in detail below, but the present invention is not limited to these examples.
<< Examples 1-8 and Comparative Examples 1-10 >>
(1) Production of positive electrode pellets Table 1 shows electrolytic manganese dioxide (EMD) powder (purity 92%, average particle size 60 μm), graphite powder (average particle size 40 μm), electrolyte solution, and positive electrode additive as positive electrode active materials. Mixed at the indicated weight ratio. This mixture was uniformly stirred and mixed with a mixer, and then sized to a constant particle size. The obtained granular material (particle size: 0.2 to 2.5 mm) was pressure-molded to obtain a hollow cylindrical positive electrode pellet.
An alkaline aqueous solution containing KOH (concentration 39% by weight) and ZnO (concentration 2% by weight) was used as the electrolytic solution.

As the positive electrode additive, water-poor polyacrylic acid (PA) powder (PW-350P manufactured by Nippon Pure Chemical Co., Ltd.) was used. This powdery polyacrylic acid had an average particle size of 13 μm, and the proportion of particles of 250 μm or less was 99% by weight.
The positive electrode mixture pellet had a height of 47.65 mm and a volume of 21.89 cm ³ .

(2) Production of Alkaline Dry Battery A single alkaline battery shown in FIG. 1 was produced as follows using the positive electrode pellet obtained above. FIG. 1 is a front view of a section of a single alkaline battery according to an embodiment of the present invention.
After two positive electrode pellets were inserted into a bottomed cylindrical battery case 1 (inner diameter 32.3 mm, height 60.5 mm) made of nickel-plated steel sheet with a graphite coating film formed on the inner surface, the battery case 1 Then, it was pressure-molded again to obtain a hollow cylindrical positive electrode compact that was in close contact with the inner surface of the battery case 1.
After the separator 4 and the bottom paper 9 were arranged in the hollow part of the positive electrode molded body, the electrolytic solution was injected into the battery case 1. An alkaline aqueous solution containing KOH (concentration 33 wt%) and ZnO (concentration 2 wt%) was used as the electrolytic solution. In this way, the positive electrode formed body was allowed to contain the electrolytic solution to obtain a swollen positive electrode 2.
The separator 4 is a non-woven fabric (thickness 0.2 mm) mainly composed of polyvinyl alcohol fiber and rayon fiber, and two sheets of this non-woven fabric are overlapped in a cylindrical shape to form a separator (thickness of about 0.8 mm). The outer diameter of the cylindrical separator was 21.4 mm. For the bottom paper 9, a non-woven fabric mainly composed of polyvinyl alcohol fibers and rayon fibers having a thickness of 0.8 mm was used.

After the injection, the gelled negative electrode 3 was filled inside the separator 4. The gelled negative electrode 3 was prepared by mixing a negative electrode active material, an electrolytic solution, and sodium polyacrylate as a gelling agent at a weight ratio of 182: 100: 2.
A mixture (mixing weight ratio 2: 1) of (PW-150 (manufactured by Nippon Pure Chemicals Co., Ltd.)) and DK500B (manufactured by Sanyo Chemical Co., Ltd.) was used as sodium polyacrylate.
As the negative electrode active material, zinc alloy powder (average particle size 150 μm) containing Bi 50 ppm, Al 300 ppm, and In 200 ppm was used.
The body of the negative electrode current collector 6 was inserted into a through hole provided in the center of the gasket 5, and the head of the negative electrode current collector 6 was welded to the bottom plate 7 to obtain an assembly sealant. The opening of the battery case 1 was sealed with an assembly sealing body. At this time, the negative electrode current collector 6 was inserted into the negative electrode 3, and the opening end portion of the battery case 1 was caulked to the peripheral portion of the bottom plate 7 via the outer peripheral portion of the gasket 5. Next, the exterior label 8 was coated on the outer surface of the battery case 1. In this manner, an alkaline battery was produced.

In the production of the battery, the amount of the electrolyte solution injected and the amounts of the positive electrode active material, graphite, and positive electrode additive were changed to the values shown in Tables 1 and 2.
The amount of electrolyte in Table 1 is the amount of electrolyte injected into the battery case (separator and positive electrode molded body).
The content (parts by weight) of the positive electrode additive (PA) and graphite in the positive electrode compact in Table 2 is an amount per 100 parts by weight of EMD.

[Battery evaluation]
(1) Evaluation regarding positive electrode mixture at the time of injection of electrolyte solution into battery case At the time of producing the battery, a predetermined amount of electrolyte solution was injected into the battery case, and the electrolyte was included in the positive electrode molded body. In this way, a swollen positive electrode containing a sufficient amount of electrolyte was obtained. At this time, it was visually confirmed whether cracks or cracks occurred on the inner wall of the positive electrode and the positive electrode was not collapsed.
The number of tests for each battery was 100. Out of 100, if even one battery with the positive electrode collapsed was rejected.

(2) Vibration test A
A vibration test A based on JIS C 8514 was performed for each battery.
Test conditions are shown below.
Acceleration: 0.3 to 9.7G
Frequency: 10-55Hz
Sweep: 45 min / sweep (1 Hz / min)
Test direction: 3 directions (x, y, z)
Test time: 90 min (one reciprocation) for each direction
The number of tests for each battery was 10. In a battery in which the battery voltage after the test dropped by 5 mV or more compared to the battery voltage before the test, it was determined that an internal short circuit occurred due to the collapse of the positive electrode. Defective.

(3) Discharge test Each battery was intermittently discharged in an environment of 20 ± 2 ° C. Specifically, after each battery was discharged at a constant current of 600 mA for 2 hours, a step of resting for 22 hours was repeatedly performed. This intermittent discharge was performed until the battery voltage reached 0.9V. The discharge capacity was determined from the total discharge time.

(4) Measurement of utilization rate of positive electrode active material The discharge capacity per 1 g of manganese dioxide was obtained from the actual discharge capacity obtained in (3) above and the amount of manganese dioxide used in producing the positive electrode (purity 92%).
And the positive electrode active material utilization factor was measured by the following formula.
Positive electrode active material utilization rate (%) = discharge capacity per gram of manganese dioxide / theoretical capacity per gram of manganese dioxide × 100
In addition, the theoretical capacity per 1 g of manganese dioxide in the formula is 0.309 Ah.
These evaluation results are shown in Table 3. Table 3 shows the results of examining the volume, weight, and density of the positive electrode and the proportion of graphite in the positive electrode after disassembling the battery after one month of battery assembly.

The positive electrode of the battery of Comparative Example 1 did not expand when the electrolyte solution was absorbed, whereas the positive electrodes of the batteries of Examples 1 to 6 and Comparative Examples 2 to 10 expanded when the electrolyte solution was absorbed.
In the batteries of Examples 1 to 8, the positive electrode did not collapse at the time of expansion and vibration, whereas in the batteries of Comparative Examples 2, 4, 5, 7, 9, and 10, the battery at the time of expansion and vibration. At least one of the times, the positive electrode collapsed.
In the batteries of Comparative Examples 1 to 3, it is difficult to reduce the cost because the amount of the positive electrode active material is large.
In the batteries of Examples 1 to 8, a low-density positive electrode molded body having a density of 3.00 g / cm ³ or less was used. However, since the utilization rate of the positive electrode active material was improved, excellent discharge characteristics were obtained. In the batteries of Examples 1 to 6, the amount of the positive electrode active material was small as compared with the batteries of Comparative Examples 1 to 3, but a high capacity was obtained.
Further, in the battery of Example 1, the battery of the comparative example was prepared in the same manner as in Example 1 except that a water-soluble binder (DK-500B manufactured by Sanyo Chemical Co., Ltd.) was used instead of the positive electrode additive. A vibration test A was made. In this case, since the strength of the positive electrode molded body decreased after the electrolyte solution was injected, there was a battery in which the positive electrode collapsed due to vibration and caused an internal short circuit.

<< Examples 9 and 10 >>
An alkaline dry battery was produced in the same manner as in Example 1 except that graphite having an average particle size shown in Table 4 was used. And the battery was evaluated by the same method as the above.
The evaluation results are shown in Table 4 together with the battery of Example 1.

  As shown in Table 4, in the batteries of Examples 9 and 10, the same results as in the battery of Example 1 were obtained.

Furthermore, the following vibration test B was carried out for Examples 1, 9, and 10. The vibration test B is a stricter condition than the vibration test A described above. Test conditions are shown below.
Acceleration: 5, 6, 8, or 10G
Frequency: 50-2000Hz
Sweep: 15min / sweep (one way)
Test direction: Battery axial direction Test time: 2.5h (5 reciprocations)
The number of tests for each battery was 20, and the battery voltage (open circuit voltage) was measured before and after the vibration test. And in the battery in which the battery voltage after the test dropped by 5 mV or more compared with the battery voltage before the test, it was determined that an internal short circuit occurred due to the collapse of the positive electrode, and the number of batteries that were internally short-circuited was examined.
The test results are shown in Table 5. The numerical values in the column of Table 5 indicate the number of internally short-circuited batteries.

  As shown in Table 5, excellent reliability with respect to vibration was obtained in the order of the batteries of Examples 10, 9, and 1. The smaller the average particle size of graphite, the more reliable the vibration.

<< Examples 11 and 12 >>
An alkaline dry battery was produced in the same manner as in Example 1 except that electrolytic manganese dioxide (EMD) having an average particle size shown in Table 6 was used. And the battery was evaluated by the same method as the above.
The evaluation results are shown in Table 6 together with the battery of Example 1.

  As shown in Table 6, in the batteries of Examples 11 and 12, the same results as in the battery of Example 1 were obtained.

Further, the vibration test B was performed on the batteries of Examples 11 and 12.
The test results are shown in Table 7 together with the battery of Example 1. The numerical values in the column of Table 7 indicate the number of internally short-circuited batteries.

  As shown in Table 7, excellent reliability with respect to vibration was obtained in the order of the batteries of Examples 12, 11, and 1. As the average particle diameter of the positive electrode active material is smaller, the reliability with respect to vibration is improved.

  The alkaline dry battery of the present invention is suitably used as a power source for electronic devices such as portable devices.

DESCRIPTION OF SYMBOLS 1 Battery case 2 Positive electrode 3 Negative electrode 4 Separator 5 Gasket 6 Negative electrode collector 7 Bottom plate 8 Exterior label 9 Bottom paper

Claims (13)

A positive electrode comprising a positive electrode active material and graphite,
A negative electrode containing a negative electrode active material,
A separator disposed between the positive electrode and the negative electrode, and an alkaline dry battery including an electrolytic solution,
The positive electrode includes, as a positive electrode additive, 0.15 to 0.55 parts by weight of polyacrylic acid or a salt thereof that is hardly soluble in water per 100 parts by weight of the positive electrode active material,
The proportion of the graphite in the positive electrode is 7.8 to 12.9% by volume.   The alkaline dry battery according to claim 1, wherein a ratio of the graphite in the positive electrode is 8.9 to 11.8% by volume.   The alkaline battery according to claim 1, wherein the positive electrode contains 0.40 to 0.55 parts by weight of the positive electrode additive per 100 parts by weight of the positive electrode active material.   The alkaline dry battery according to claim 1, wherein the graphite has an average particle size of 40 μm or less.   The alkaline dry battery according to claim 1, wherein the positive electrode active material is manganese dioxide.   The alkaline dry battery according to claim 5, wherein the manganese dioxide has an average particle size of 60 μm or less. 2. The alkaline dry battery according to claim 1, wherein the positive electrode contains the electrolyte solution and has a weight of 3.15 to 3.27 g per 1 cm ^{3 of the} positive electrode. A hollow cylindrical alkaline battery positive electrode molded body,
The positive electrode molded body includes a positive electrode active material, graphite, an electrolytic solution, and polyacrylic acid or a salt thereof that is sparingly soluble in water as a positive electrode additive,
The positive electrode molded body contains the positive electrode additive in an amount of 0.15 to 0.55 parts by weight per 100 parts by weight of the positive electrode active material,
The positive electrode molded body for an alkaline dry battery, wherein the proportion of the graphite in the positive electrode molded body is 8 to 13% by volume.   The positive electrode molded body for an alkaline dry battery according to claim 8, wherein a ratio of the graphite in the positive electrode molded body is 9.1 to 12.0% by volume.   The said positive electrode molded object is a positive electrode molded object for alkaline dry batteries of Claim 1 which contains the said positive electrode additive 0.40-0.55 weight part per 100 weight part of said positive electrode active materials. The positive electrode molded body for an alkaline dry battery according to claim 8, wherein the weight per 1 cm ^{3 of the} positive electrode molded body is 2.80 to 3.00 g. The positive electrode molded body for an alkaline dry battery according to claim 8, wherein the weight per 1 cm ^{3 of the} positive electrode molded body is 2.85 to 3.00 g. The positive electrode molded body for an alkaline dry battery according to claim 8, wherein a weight per 1 cm ^{3 of the} positive electrode molded body is 2.85 g or more and less than 2.90 g.

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