JP3375192B2 - Manganese dry cell - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manganese dry battery which has a significantly improved high load discharge characteristic by using a specific positive electrode active material.

[0002]

2. Description of the Related Art Batteries having a portable structure in which zinc is used as the negative electrode, manganese dioxide is used as the positive electrode, and ammonium chloride or zinc chloride-based aqueous solution is used as the electrolytic solution are collectively referred to as manganese dry batteries.

A Luclanche type manganese dry battery using ammonium chloride as an electrolyte was invented in 1866 and has been used for over 100 years now. The zinc chloride type manganese dry battery using zinc chloride as the main electrolyte is
Most of the manganese batteries that were put into practical use in Japan in the 1970s and are currently produced in Japan are zinc chloride type.
It is spreading worldwide.

As a characteristic of the discharge characteristic of the manganese dry battery,
The electromotive force gradually decreases as the discharge progresses,
Especially when discharged under high load, the electromotive force drops sharply,
In case of extremely high load discharge such as 1Ω discharge,
When about 1/3 of the theoretical capacity is discharged, the electromotive force decreases and the battery becomes unusable. This behavior is due to
It is said that the cause is the property of manganese dioxide, which is the positive electrode active material.

Manganese dioxide has been used as a positive electrode active material for manganese dry batteries. As manganese dioxide, natural manganese dioxide, chemically synthesized manganese dioxide,
There is electrolytic manganese dioxide and it is used properly depending on the application. Electrolytic manganese dioxide has the best discharge performance at the time of high-load discharge, and with the miniaturization of electronic devices, there is a demand for smaller batteries and higher capacity. is increasing. Therefore, there is a strong demand for the development of electrolytic manganese dioxide that can improve the performance of discharge characteristics under high load discharge.

Various attempts have been made to improve the performance of discharge characteristics under high load discharge. For example, JP-A-02-21348
No. 7 and JP-A-60-138085,
When producing electrolytic manganese dioxide, it is said that electrolytic manganese dioxide excellent in high-load discharge can be obtained by suspending carbon fiber or carbon particles in an electrolytic solution and electrolyzing. Further, in Japanese Patent Laid-Open No. 05-9773, monofilaments of carbon fibers or graphite fibers having a surface coated with manganese oxide are dispersed in a manganese electrolytic solution, and the monofilaments are co-deposited with manganese dioxide by electrolysis, When the content of manganese dioxide is 90% by weight or more, high-performance electrolytic manganese dioxide is said to be produced. Japanese Unexamined Patent Publication No. 63-21224 discloses that the characteristics of electrolytic manganese dioxide can be improved by suspending fine particles of manganese oxide in an electrolytic solution and performing electrolysis.

The above is aimed at improving the characteristics of electrolytic manganese dioxide itself by devising the electrolysis conditions, but there is also an attempt to devise the process of forming a positive electrode mixture after electrolysis. For example, in Japanese Patent Laid-Open Nos. 03-1444, 03-11554, and 03-47196, when chemically synthesized manganese dioxide and electrolytic manganese dioxide are mixed and used as a positive electrode active material, electrolytic manganese dioxide is used alone. It is said that the characteristics of high-load discharge will be improved compared to the case of using in. Further, in JP-A-62-103873,
It is said that high-load discharge performance will be improved if the once crushed electrolytic manganese dioxide is compression-molded and then pulverized again and used as a positive electrode mixture. In Japanese Patent Laid-Open No. 57-27929,
It is said that dry battery characteristics are improved by immersing the precipitated electrolytic manganese dioxide in dilute sulfuric acid and then neutralizing it.
Further, Japanese Patent Laid-Open No. 63-21225 discloses that characteristics are improved by adding an oxidizing agent after coarsely pulverizing, finely pulverizing and neutralizing after electrolysis. JP-A-63-40727
According to the publication, the performance of the fine powder of 2 μm or less and the coarse powder of 92 μm or more are inferior, so the performance is improved by removing them.

On the contrary, Japanese Patent Publication No. 51-21125 discloses that the discharge characteristics can be improved by setting the average particle diameter to 5 μm or less. Further, Japanese Patent Publication No. 51-21129 discloses that the discharge characteristics can be improved by combining an electrolyte solution and electrolytic manganese dioxide having an average particle size of 5 μm or less. JP-A-58-14470 discloses that the characteristics of high-load discharge can be improved by setting the average particle size of electrolytic manganese dioxide to 10 μm or less under the condition that the electrolytic solution contains sodium perchlorate. In JP-A-02-195647 and JP-A-02-226656, it is stated that when carbon black obtained by the furnace method is used as a conductive material, the characteristics of high load discharge are improved. Japanese Patent Application Laid-Open No. 63-121256 discloses that by forming a thin film layer of a carbon material on the surface of manganese dioxide particles, the conductivity of the positive electrode material is improved and the high load discharge performance is improved. Further, in JP-A-63-167570, a carbon material fine powder having an average particle size ratio of 10 ^-1 to 10 ^-3 is used to cover 0.5
It is said that the performance of high-load discharge is improved by making it adhere in the range of -15%. In this case, the main purpose is to improve conductivity, and it is necessary that the particle size of the carbon material is smaller than that of manganese dioxide.

[0009]

Although various attempts have been made as described above, the effects are very small, the actual production is extremely difficult, and the mass production is impossible. The improvement of characteristics is still insufficient until now.

It is an object of the present invention to solve the drawbacks of the conventional positive electrode active material for dry batteries made of electrolytic manganese dioxide and to use the positive electrode active material for dry batteries which can be mass-produced, so that it is extremely high. It is intended to provide a manganese dry battery having load discharging performance.

[0011]

According to the present invention, there is provided a positive electrode active material comprising a mixture of electrolytic manganese dioxide particles in the form of needle crystals having an aspect ratio of 2 to 20 and graphite. A manganese dry battery is provided.

In order for the dry battery to discharge, electrons must be absorbed in the positive electrode. In order to continuously absorb electrons, it is necessary for protons, electrons or oxygen to move in electrolytic manganese dioxide. During high-load discharge, the amount of movement per unit time increases, so the movement path deteriorates,
It is considered that the electromotive force is lowered because the movement is hindered. Therefore, it is considered to be advantageous for high load discharge that the particle size of electrolytic manganese dioxide is as small as possible and the reaction area is large. However, conventionally, when the pulverization is strengthened to reduce the particle size, the electrolytic manganese dioxide is deteriorated and the characteristics are rather deteriorated. Even if the particle size is reduced, the effect of reducing does not appear unless the aggregated particles remain and the conductive material such as graphite does not completely reach the surface of each particle.
Further, if fine particles are used, the density at the time of compacting may not increase, and the result may be that the filling amount in the same volume decreases.

As a result of accumulating systematic studies on the bond, structure and physical properties of electrolytic manganese dioxide, the inventor has found that electrolytic manganese dioxide has the highest reactivity when it has the structure shown in the figure. The present invention has been completed.

FIG. 1 shows particles of electrolytic manganese dioxide. In this example, the average particle size is 30 μm and the particle size is 2 to 80 μm. FIG. 2 is an enlarged view of a part of this, in which crystal grains having a grain size of 0.2 to 0.6 μm are present. FIG. 3 is an enlarged view of one of the crystal grains, and the acicular grains are gathered with their crystal orientations aligned. FIG. 4 is a further enlarged view of one of the acicular particles, and the acicular particles have an aspect ratio of 2 to 20.

In the present invention, it is important that the acicular crystals are a constituent of electrolytic manganese dioxide. The aspect ratio, which is the ratio of the major axis to the minor axis of the needle-shaped crystal, must be a long and narrow one in the range of 2 to 20. Even if acicular crystals are present, if the aspect ratio is less than 2, improvement in high-load discharge performance cannot be obtained. It is difficult to make more than 20. There is no limitation on the size of the crystal of electrolytic manganese dioxide as long as it is within such an aspect ratio range, but the size of the crystal easily manufactured by electrolysis is 0.05 to 0.3 μm in the major axis, and the minor axis in the minor axis. 0.01-0.
It is 05 μm, and this size is suitable for the present invention.

In the present invention, the graphite is flaky,
It has been found that the performance of the positive electrode active material is further improved when the crystals of electrolytic manganese dioxide are attached to the scaly graphite plate. In order to increase the electron conductivity of the positive electrode active material, rubbing fine graphite particles on the surface of electrolytic manganese dioxide, or using an electrolytic solution in which carbon fibers are suspended to cause co-deposition with electrolytic manganese dioxide has been a conventional example. However, in the present invention, in order to maximize the electronic conductivity of graphite, using graphite as thin as possible while maintaining the scaly shape, the surface of the structure of particles of electrolytic manganese dioxide smaller than graphite adhered It was sometimes found that the activity as a positive electrode active material was the highest. Therefore, the particle size of electrolytic manganese dioxide is preferably 10 μm or less. Further, since the acicular particles are used as the constitutional unit, the minimum unit cannot be smaller than this.

Further, in the present invention, even when the conventional electrolytic manganese dioxide is mixed with the positive electrode active material having the above-mentioned structure, it is effective in improving the high load discharge. Conventional electrolytic manganese dioxide may be mixed after the positive electrode active material is manufactured, or the same effect is obtained even if a mixed product is formed in the manufacturing process.

Conventionally, a mixed powder of electrolytic manganese dioxide and carbon black has been used as a positive electrode material for manganese dry batteries. This is because carbon black is more convenient as a conductive material than graphite in order to retain a large amount of electrolytic solution. Also in the battery of the present invention, the electrolyte retaining function is required, and carbon black must be used as a conductive material. Since the presence of graphite is indispensable for miniaturization while maintaining the active structure, graphite is added as a miniaturization aid rather than as a conductive material.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Electrolytic manganese dioxide having a structure as shown in the figure can be produced by various methods. As an example, an electrolytic solution of manganese sulfate is used to electrolyze an acidic solution of manganese sulfate at 90.degree. It can be made by precipitating. The deposited roof tile-like electrolytic manganese dioxide is roughly pulverized, neutralized, washed, dried, and then finely pulverized by a dry method to obtain a product having an average particle size of about 30 μm. Or 30 μm
The product is finely pulverized with a wet method, neutralized, washed, and dried.

The positive electrode active material used in the battery of the present invention can be prepared by mixing graphite and electrolytic manganese dioxide and then pulverizing them together. The mixing ratio of graphite powder and electrolytic manganese dioxide is preferably 1% to 50%. If it is 1% or less, there is no effect of mixing and pulverization, and if it is 50% or more,
The volume ratio of carbon powder is too large to be ground. The carbon powder is added in order to obtain sufficient conductivity and for the purpose of holding the electrolytic solution, but it is not necessary to add an amount necessary for those purposes at the time of mixing and pulverizing. For example, even if the addition amount of graphite powder of 1% is mixed and pulverized and then the carbon powder is mixed according to the conventional method, there is an effect of improving the high load discharge. Further, even if 50% of the graphite powder is mixed and pulverized and then the powder of electrolytic manganese dioxide is mixed by the conventional method, there is an effect that the high load discharge characteristics are improved. As the graphite used, graphite having good crystallinity is effective. When finely divided electrolytic manganese dioxide is obtained by mixing and grinding, it may be classified and then the graphite may be removed before mixing with a conductive material such as carbon black that has a large water retaining effect on the electrolytic solution, or by mixing graphite and electrolytic manganese dioxide. The powder may be mixed with carbon black as it is. Further, when the mixed powder already has sufficient conductivity, a material such as a water absorbing polymer having only a water retaining function may be added.

After thoroughly mixing the electrolytic manganese dioxide and the graphite by a dry type with a V type mixer or a rotary tumbling type mixer,
Water is added and wet pulverization is performed at a slurry concentration of 10 to 80%. If it is 10% or less, the pulverization efficiency is poor and impurities are often mixed. If it is 80% or more, the viscosity is too high to pulverize. For the wet pulverization, a medium agitation type pulverizer such as a ball mill or a bead mill is preferable, but a mortar type pulverizer such as a raikai machine or a stone mill type pulverizer may be used.
It is more effective to thoroughly knead with a kneader such as a kneader before wet pulverizing. If the pulverization is promoted without the presence of graphite, the structure of electrolytic manganese dioxide is destroyed and the characteristics are rather deteriorated. Even in the case of mixed pulverization, if the pulverization is advanced too much, the structure of electrolytic manganese dioxide is destroyed and the characteristics are rather deteriorated. When the graphite and electrolytic manganese dioxide are sufficiently mixed and subjected to shearing crushing, the graphite is cleaved into flakes and becomes flaky thin plates. When crushing progresses in the form of a sandwich sandwiched between the graphite thin plates, the internal structure of electrolytic manganese dioxide is not destroyed by the lubricating action of graphite, and the crystal of electrolytic manganese dioxide is maintained while maintaining its activity. Are aggregates of particles adhering to the scaly graphite plate.

The graphite used in the present invention is preferably one having a good crystallinity which is easy to be cleaved into a scaly form.
Any graphite that is cleavable is effective. The particle size is preferably larger than that of electrolytic manganese dioxide. If mixed and pulverized using electrolytic manganese dioxide with an average particle size of 30 μm, it is more effective to use graphite with an average particle size of 30 μm or more, but even if there is a large difference in particle size, preliminary kneading is performed. Any size of graphite will work, provided it is done well.

The smaller the particle size of electrolytic manganese dioxide, the higher the efficiency of mixing and pulverizing, but the fine pulverization destroys the internal structure. Therefore, graphite pulverized to an average particle size of about 30 μm was mixed and pulverized. In this case, the positive electrode active material having the above structure can be obtained. An electrolytic solution may be added to the slurry that has been pulverized to form a positive electrode active material, or the slurry may be pulverized and dried, and then the electrolytic solution may be added to form a positive electrode active material. Alternatively, the electrolytic solution may be added from the beginning and mixed and ground.

Since the positive electrode active material of the present invention is a fine powder of graphite and electrolytic manganese dioxide as compared with the conventional ones, the bulk density at the time of molding becomes low only by mixing and pulverizing and then drying. As a result, there may be a problem in that the filling amount in a fixed volume cannot be increased. In such a case, dried powder may be granulated. Since it has been pulverized, it can be granulated by adding only water and without adding other binders.

[0025]

The present invention will be specifically illustrated by the following examples.

(Example 1) Concentration of manganese sulfate 20 g /
1, a sulfuric acid concentration of 30 g / l, and a current density of 40 A / m ³ were used to electrolytically deposit a manganese sulfate aqueous solution at a temperature of 90 ° C. on a titanium anode to obtain a 1 cm-thick electrolytic manganese dioxide tile block. As a result of cutting out this block and observing it with a transmission electron microscope, it was confirmed that it had a structure as shown in the figure composed of acicular particles having an aspect ratio of 2 to 20. The block was coarsely pulverized, neutralized, washed, dried and finely pulverized to obtain particles of electrolytic manganese dioxide having an average particle diameter of 30 μm. This electrolytic manganese dioxide 7.2 having an average particle size of 30 μm
After sufficiently mixing 0.8 kg of graphite powder with 0.8 kg of graphite powder, 6 kg of distilled water was added to form a slurry, which was pulverized by a horizontal bead mill. Residence time in the mill is 1 minute, 2
The sample was taken out for 5 minutes, 10 minutes, 20 minutes, 30 minutes, 3 hours, put in a dryer at 60 ° C. for drying, and then crushed. Sample No. No. Set from 1 to 7. When the powder was observed with a transmission electron microscope, the following could be confirmed.

No. For 1, 2, 3 and 4, major axis is 0.05
It was confirmed that the crystals of electrolytic manganese dioxide composed of needle-like crystals having a size of ˜0.3 μm and an aspect ratio of 2 to 20 adhered to the scaly graphite plate. The particle size of electrolytic manganese dioxide becomes smaller as the grinding time becomes longer. In 3 and 4, many needle-shaped crystals were found to be scattered one by one. No. 5,
In Nos. 6 and 7, there are many crystals of electrolytic manganese dioxide composed of acicular particles having a major axis of 0.05 to 0.3 μm and an aspect ratio of 2 to 20 attached on a scaly graphite plate. In many cases, the acicular particles had a rounded shape instead of the structure generated during electrolysis. The proportion of rounded particles increases as the grinding time increases.

Sample No. Electrolyte solutions of acetylene black and 30% zinc chloride were thoroughly mixed with 1 to 7 so as to have a weight ratio of 50: 8: 42 to obtain positive electrode active materials. Using this positive electrode active material, an R-20 type manganese dry battery having the structure shown in FIG. 5 was produced, and the discharge time until the electromotive force reached 0.9 V at 2Ω discharge was measured. In FIG. 5, reference numeral 11 is a metal jacket, 12 is a vinyl tube, 13 is a zinc can, 14 is a separator, 15 is a carbon rod, 16 is a cap plate, 17 is an insulating plate, 18 is a bottom plate, 19 is a minus plate, and 20 is a Insulating plate, 21 is top cover paper, 22 is sealing material, 23
Indicates a sealing body, and 24 indicates a mixture.

(Comparative Example 1) 6 kg of distilled water was added to 7.2 kg of electrolytic manganese dioxide having an average particle diameter of 30 μm to prepare a slurry, which was pulverized by a horizontal bead mill. After pulverizing for 3 minutes with a residence time in the mill, 0.8 kg of graphite was added and further pulverized for 10 minutes. The sample was taken out, put in a dryer at 60 ° C. to be dried, and then crushed. This sample is N
o. 8 When this powder was observed with a transmission electron microscope, particles of electrolytic manganese dioxide of 0.05 to 10 μm adhered on the plate of scaly graphite, but needle-like crystal particles generated during electrolysis and this crystal particle No particles composed of aggregates in which the crystal orientations were aligned were observed.
Sample No. 8 in acetylene black, zinc chloride 30
% Of the electrolytic solution was sufficiently mixed so as to have a weight ratio of 50: 8: 42 to obtain a positive electrode active material. An R-20 type manganese dry battery was produced using this positive electrode active material, and the discharge time until the electromotive force reached 0.9 V at 2Ω discharge was measured.

A similar operation was carried out with a residence time of 30 in the mill.
The discharge time was measured by performing the discharge for 3 minutes. These samples are 9 and 10.

(Comparative Example 2) Electrolytic manganese dioxide 7.2k
Distilled water (6 kg) was added to g to prepare a slurry, which was pulverized by a horizontal bead mill. Residence time in the mill is 1 minute, 2 minutes,
Samples were taken out at 5 minutes, 10 minutes, 20 minutes, 30 minutes, and 3 hours, 10% of graphite powder was added by a wet method, mixed with a ribbon blender, put in a dryer at 60 ° C., dried, and crushed. . This sample is 11, 12, 13, 1
4, 15, 16, and 17. 50% by weight of an electrolyte solution of acetylene black and zinc chloride is added to these mixed powders:
The mixture was thoroughly mixed to give a ratio of 8:42 to obtain a positive electrode active material. An R-20 type manganese dry battery was produced using this positive electrode active material, and the discharge time until the electromotive force reached 0.9 V at 2Ω discharge was measured.

(Comparative Example 3) Concentration of manganese sulfate 14 g /
1, a sulfuric acid concentration of 10 g / l, and a current density of 52 A / m ^3, a manganese sulfate aqueous solution having a temperature of 80 ° C. was electrolytically deposited on a titanium anode to obtain a 1 cm-thick electrolytic manganese dioxide tile block. As a result of cutting out this block and observing it with a transmission electron microscope, it was confirmed that the block was composed of spherical particles having an aspect ratio of 2 or less. This block is coarsely pulverized, neutralized, washed, dried and finely pulverized to obtain an average particle size of 30μ.
m of electrolytic manganese dioxide particles were obtained.

Example 1 using this electrolytic manganese dioxide
Did the same work as. These samples are No. 18,
It is set as 19, 20, 21, 22, 23, and 24.

The electrolytic manganese dioxide used in Example 1 was acetylene black, and the electrolytic solution containing 30% zinc chloride was 5% by weight.
The mixture was thoroughly mixed to give a positive electrode active material of 0: 8: 42. An R-20 type manganese dry battery was produced using this positive electrode active material, and the discharge time until the electromotive force reached 0.9 V at 2Ω discharge was measured. This result is set to 100, and the other results are shown in Table 1 as a relative value with respect to this time.

[0035]

[Table 1]

[0036]

As described above, the manganese battery of the present invention uses the mixture of electrolytic manganese dioxide particles in the form of needle crystals having an aspect ratio of 2 to 20 and graphite as the positive electrode active material. In particular, a remarkable and unique effect that the characteristics of a manganese battery at the time of high load discharge of the battery are significantly improved can be obtained. Further, the positive electrode active material of the present invention uses electrolytic manganese dioxide particles produced under certain conditions,
Since it can be easily manufactured by crushing under predetermined conditions, it can be mass-produced and is advantageous in terms of cost.

[Brief description of drawings]

FIG. 1 is an explanatory view sketching a TEM photograph of particles of electrolytic manganese dioxide constituting a positive electrode active material for a dry battery of the present invention.

FIG. 2 is an explanatory diagram showing a lump of crystal forming the particles of FIG.

FIG. 3 is an explanatory view showing crystal grains forming the crystal mass of FIG. 2.

FIG. 4 is an explanatory diagram showing needle-like crystals that form the crystal grains in the figure.

FIG. 5 is a side sectional view showing an example of a manganese battery using the positive electrode active material of the present invention.

[Explanation of symbols]

1 Crystal block 2 crystal grains 3 needle crystals 11 metal jacket 12 vinyl tubes 13 zinc can 14 Separator 15 carbon rod 16 cap plate 17 Insulation plate 18 Bottom plate 19 minus plate 20 insulating plate 21 Top Paper 22 Sealant 23 Sealed body 24 mixture

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 2000-211923 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 6/06 H01M 4/06 H01M 4/50 H01M 4/62

Claims (5)

(57) [Claims] 1. A manganese dry battery comprising a positive electrode active material composed of a mixture of electrolytic manganese dioxide particles in the form of needle crystals having an aspect ratio of 2 to 20, and graphite. Wherein said graphite has the form of scaly leaf, according to claim 1, wherein the acicular crystalline particles of electrolytic manganese dioxide, characterized in that it is deposited on the flake graphite plate The manganese dry battery according to. 3. An aggregate of electrolytic manganese dioxide crystal particles in which needle-like crystal particles having an aspect ratio of 2 to 20 are aggregated with their crystal orientations aligned to form a grain boundary of 0.2 to 0.6 μm, and A manganese dry battery comprising a positive electrode active material made of a mixture of graphite. 4. The manganese dry battery according to claim 2, wherein the acicular crystalline particles of the electrolytic manganese dioxide have a particle size of 0.2 to 10 μm. 5. The graphite has the form of a scaly plate, and the aggregate of the acicular crystalline particles of the electrolytic manganese dioxide is adhered onto the scaly graphite plate. The manganese dry battery according to claim 3 or 4.