JPH03252055A - Alkaline dry cell - Google Patents

Abstract

PURPOSE:To improve the heavy load discharge property and to reduce the cost by using a mixture of a chemical synthetic manganese dioxide powder mainly of gamma type crystals and an electrolytic manganese dioxide powder as a positive electrode active substance. CONSTITUTION:This alkaline dry cell is composed of a metal can 1, a positive electrode body 2, a separator 3, a gel-form negative electrode composite 4, a negative electrode collector rod 5, a gasket 6, a metal plate 7, and a metal sealing plate 8. And as a positive electrode active substance, a mixture of a chemical synthetic manganese dioxide powder mainly of rho type crystals which is obtained by acid-processing a manganese oxide made by calcinating manganese sulfate, and an electrolytic manganese dioxide powder is used, and a mixture of graphite and an oil furnace black with the volatile component in the JIS K6221 less than 0.2% and the specific surface area 90-150g/m<2> is used as the positive electrode active material to a positive electrode body 2. By incorporating the mixture of the chemical synthetic manganese dioxide powder and the electrolytic manganese dioxide powder in the positive electrode body 2 as the positive electrode active substance in such a way, the discharge maintaining time is extended. Consequently, the high load discharge property can be improved and the cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an alkaline dry battery, and particularly to an alkaline dry battery in which the positive electrode mixture constituting the positive electrode body is improved.

(Prior art) Alkaline batteries have better continuous discharge and heavy load discharge performance than manganese batteries using zinc chloride electrolyte, so they are used as power sources for portable playback devices and camera flashlights. There is.

By the way, the positive electrode active material of the alkaline dry battery is as follows:
Electrolytic manganese dioxide (EMD), which has superior discharge performance and high density, has been widely used in the past.

In addition, because electrolytic manganese dioxide alone has low conductivity,
Usually, 5 to 1% of conductive additives such as graphite and acetylene black are added.
The conductivity was imparted by a concentration of about 5% by weight.

(Problem 8 to be solved by the invention) However, EMD requires a large amount of electrolysis time and electric power in the electrolytic oxidation process, making it expensive. Moreover, conventional chemically synthesized manganese dioxide (C
MD) and natural manganese dioxide (NMD) are lower in cost than EMD, but cannot exhibit sufficient performance in heavy load discharge. Therefore, in order to obtain high-performance, low-cost manganese dioxide that can replace EMD, development and research using chemical synthesis methods has been actively conducted in recent years. Synthetic manganese dioxide has not yet been discovered.

On the other hand, graphite and acetylene black, which are commonly used as conductive agents, both have inherent drawbacks and are not fully satisfactory. In other words, when graphite is used as a conductive agent, iron, lead, and other impurities contained in graphite powder
There are problems in that copper and the like react with the positive electrode active material, causing a decrease in the potential of the positive electrode and the capacity of the battery, and that the utilization rate of the positive electrode active material decreases due to low electrolyte retention. Further, although graphite itself has a low electrical resistance, when used in a positive electrode body, it has a drawback that the electrical resistance of the positive electrode body cannot be made sufficiently low due to its particle structure.

In this respect, acetylene black has fewer impurities than graphite powder and has a well-developed chain structure, so it can retain the electrolyte and improve the utilization rate of the positive electrode active material, while also reducing the electrical resistance of the positive electrode body. Can be made smaller. However, since the surface of acetylene black has a functional group that has strong reducing properties with respect to the positive electrode active material, batteries using this as a conductive agent have the disadvantage that the potential drop and the discharge capacity are greatly reduced.

The present invention has been made to solve the above-mentioned conventional problems, and has better heavy load discharge characteristics than when electrolytic manganese dioxide is used as a positive electrode active material and graphite as a positive electrode conductive agent. When electrolytic manganese dioxide and graphite are used, the present invention aims to provide an alkaline dry battery with a lower cost positive electrode body.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a chemically synthesized manganese dioxide powder mainly composed of γ-type crystals obtained by acid-treating manganese oxide obtained by roasting manganese sulfate, and an electrolytic manganese dioxide powder. a positive electrode active material consisting of a mixture of graphite and JIS K62;
The present invention is an alkaline dry battery characterized by using a positive electrode body comprising, as a positive electrode conductive material, a mixture with oil furnace black having a volatile content of 0.2% or less according to No. 21 and a specific surface area of 90 to 150 g/%.

The chemically synthesized manganese dioxide powder used in the present invention preferably has an average particle size of 20 μm or less. It is desirable that the ratio of the γ-type crystals of chemically synthesized manganese dioxide be 70% or more.

An example of the method for producing the chemically synthesized manganese dioxide powder is as follows. First, manganese sulfate crystals are prepared by heating and concentrating a manganese sulfate (M n S 04) solution with a low potassium content. In this case, if a large amount of alkali metal, particularly potassium, is contained, chemically synthesized manganese dioxide containing many α-form crystals with low activity will be produced by roasting and acid treatment in the subsequent steps, which is not preferable. Next, this is roasted at 800 to 1100°C for 10 minutes or more in an air atmosphere or an oxygen atmosphere with a higher oxygen partial pressure than air, and the following formula (
1) As shown in (2), manganese sulfate is decomposed to produce M.
Manganese oxide whose main component is n3O4 or Mn2O3 is produced.

3MnSO4→Mn304 +SO2+2so3...
(1) 2Mnso4−*Mn2 o3+SO2+SO3...
(2) Next, the manganese oxide containing Mn3O4 as a main component is heated to 700 to
By roasting at 950°C and carrying out the reaction shown in the following formula (3),
It is converted into manganese oxide whose main component is Mn2O3, which has a good yield in acid treatment in the subsequent process.

4 Mn304 + 02 = 6 Mn203 −
(3) Next, the manganese oxide mainly composed of M n 203 is treated with sulfuric acid (or nitric acid, hydrochloric acid, or a mixed acid thereof).
Treat with acid. As a result, the disproportionation reactions shown in the following formulas (4) and (5) occur to produce chemically synthesized manganese dioxide.

Mn2 o3+H2504 1*Mn o2+Mn S 04 +H20-(4)M
n 3 04 + 2 H2S 04→Mn 02
+ 2Mn S 04 + 2 H20- (5) Next, the generated Mn 02 was washed with water, neutralized, and dried, and then the obtained powder was rolled by a roll press under a pressure of 1 to 10 tons/cd. A chemically synthesized manganese dioxide powder containing γ-type crystals as a main component is produced by compression molding into a plate shape and further pulverizing to a predetermined particle size.

Moreover, as the electrolytic manganese dioxide, commercially available products can be used.

The mixing ratio of the chemically synthesized manganese dioxide powder and the electrolytic manganese dioxide powder is 3
It is desirable that the electrolytic manganese dioxide powder be in the range of 0 to 60% by weight and 40 to 70% by weight of the electrolytic manganese dioxide powder.

In addition, the oil furnace black used as a conductive material in the present invention is produced by partially oxidizing liquid hydrocarbons in the presence of molecular oxygen and water vapor in a furnace, drying the by-product carbon produced at the same time as synthesis gas production, and then Obtained by heat treatment.

The liquid hydrocarbon used in this case means a carbon atom/hydrogen atom weight ratio of 9 or more, and such liquid hydrocarbons include, for example, naphtha pyrolysis oil (ethylene heavy end), Examples include liquid hydrocarbons (carbon oil) in which aromatic hydrocarbons are mixed with carbon, mixed oils in which aromatic liquid hydrocarbons are mixed with C heavy oil, and the like.

In order to obtain such oil furnace black, 200 to 800 kg of water vapor is required for 1 ton of liquid hydrocarbon.
Preferably, 400 to goob is used. The temperature inside the furnace is 1
200~1450℃ preferably 1300~1450"C
The pressure during the reaction is 10 to 80 atm, preferably 2
The pressure is 5 to 80 atmospheres.

Next, the above-mentioned by-product carbon was heated to 300 to 900 ml under nitrogen atmosphere.
The target oil furnace black is obtained by drying at 0.5 to 3 hours at 1000°C to 3000°C, and then heat-treating at 1000 to 3000°C for 0.5 to 5 hours in an inert gas atmosphere.

This oil furnace black is characterized by having few impurities and a well-developed chain structure. Surface area (rrf/g) of the above oil furnace black, acetylene black and graphite, hydrochloric acid absorption amount (al115g)
), carbon mesh spacing d (002) (human) and developed bone (
%) is shown in Table 1.

Table 1 The physical properties shown in Table 1 are all important in determining whether oil furnace black is suitable as a conductive agent for the positive electrode of an alkaline battery.

The volatile content is said to be caused by functional groups on the surface of carbon black, and refers to functional groups having reducing properties such as aldehyde groups, carboxyl groups, and hydrogen.

Naturally, the smaller the value of such volatile content, the lower the reducing ability to manganese dioxide, which is better, but if it exceeds 0.2%, it is not preferable because it reduces manganese dioxide in the positive electrode mixture and deteriorates it.

In addition, in the production process of the oil furnace black of the present invention, heat treatment at 1000 to 3000'C in an inert gas atmosphere is carried out for the purpose of removing surface functional groups, but excessive heat treatment may cause The structure is destroyed and the conductivity decreases. Therefore, it is desirable that the volatile content is 0.02 to 0.2.

Furthermore, it is desirable that the interplanar spacing d (002) of the carbon network, which indicates the degree of graphitization, is smaller, that is, the interplanar spacing of the carbon network of graphite is closer to 3.35 mm because the conductivity is higher, but the degree of graphitization becomes too high. However, the surface area and amount of hydrochloric acid absorbed decrease. Therefore, it is desirable that the interplanar spacing of the carbon mesh is 3.48 to 3.40. The specific surface area under these conditions is measured by the BET method, and it is desirable that the value is 90 to 150 g/g and the amount of hydrochloric acid absorbed is 20 m15 g or more.

Incidentally, the interplanar spacing d (002) of the carbon network indicating the degree of graphitization
was measured using silicon as a standard material using the X-ray diffraction method established by the 117th Committee of the Japan Society for the Promotion of Science, as described in Introduction to Carbon Materials, edited by the Carbon Materials Society, pages 184-192 (published by the Carbon Materials Society, 1979). It's Shitachino.

Here, in the alkaline dry battery of the present invention, the oil furnace black is used in combination with graphite. Table 2 shows the electrical resistance of oil furnace black and graphite alone.

As is clear from Table 2 above, when a mixture of oil furnace black and graphite is used, the electrical resistance per unit weight is reduced compared to the case of oil furnace black alone, and heavy load discharge performance can be further improved. . The mixing ratio of oil furnace black and graphite is preferably in the range of 98=2 to 50:50 by weight.

If the amount of graphite mixed is less than 2% by weight, there is no merit in mixing it, while if it is more than 50% by weight, the above-mentioned adverse effects of graphite will occur.

(Function) According to the present invention, by using a mixture of chemically synthesized manganese dioxide powder mainly composed of γ-type crystals and electrolytic manganese dioxide powder as the positive electrode active material, only the electrolytic manganese dioxide powder can be used as the positive electrode active material. Compared to using
An alkaline dry battery with excellent heavy load discharge characteristics can be obtained.

That is, in an alkaline dry battery incorporating a positive electrode body in which a mixture of the above-mentioned chemically synthesized manganese dioxide powder and electrolytic manganese dioxide powder is used as a positive electrode active material, the battery voltage decreases at the end of discharge and the discharge curve becomes flat. Or a rise phenomenon occurs. This is because in the X-ray diffraction at each final stage of discharge, the positive electrode body containing the positive electrode active material with the above composition shows heterolite (ZnO
- The diffraction intensity indicating crystal growth of Mn203) is higher than that of other manganese dioxide mixtures, and this is due to the composition of Mn203), which makes it easier for the heterolite production reaction to occur. The reason why the discharge potential flattens or increases due to the generation of heterolites is due to the discharge products (M
This is thought to be due to the fact that the reaction between Zn(OH)4) ions in the electrolyte solution and Zn(OH)4) ions in the electrolyte solution as shown in the following equation (6) is accompanied by a decrease in free energy.

2Mn0OH+Zn (OH)4 ” -Z n OφM n 203 +2 H20+20
H-... (6) From the above, an alkaline dry battery incorporating a positive electrode body using a mixture of the chemically synthesized manganese dioxide powder and electrolytic manganese dioxide powder as the positive electrode active material has a longer discharge duration. , heavy load discharge characteristics can be significantly improved.

In addition, the electrolytic manganese dioxide used in conventional alkaline batteries is obtained by electrolyzing manganese sulfate, which not only takes a long time but also consumes a lot of electricity.
Since the manganese dioxide used in the positive electrode body of the present invention is obtained by chemical synthesis, it can be produced at a lower cost than electrolytic manganese dioxide.

In addition, as mentioned above, oil furnace black has few impurities and has a well-developed chain structure, so it has a high electrolyte retention ability, improves the utilization rate of the positive electrode active substance, and reduces the electrical resistance of the positive electrode body. This also improves heavy load discharge performance. Since the oil furnace black used in the present invention is heat-treated in an inert gas atmosphere, it has very few surface functional groups, so it cannot reduce the positive electrode active material and reduce the potential and discharge capacity like acetylene black. are extremely rare.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Example 1 30% by weight of chemically synthesized manganese dioxide powder containing 92% MnO2 with an average particle size of about IO μm and 70% by weight of commercially available electrolytic manganese dioxide powder were uniformly stirred and mixed using a stirring mixer. A positive electrode active material was prepared.

A JIS standard LRB type (AA type) 7/l potash dry battery having the structure shown in FIG. 1 was assembled using the positive electrode active material produced by the method described above.

That is, 1 in the figure is a cylindrical metal can with a bottom that also serves as a positive electrode terminal. This metal can 1 is filled with a positive electrode body 2 which is press-formed into a cylindrical shape. The positive electrode body 2 includes 90 parts by weight of the positive electrode active material prepared by the method described above, 9 parts by weight of oil furnace black and 1 part by weight of graphite as conductive materials, and an alkaline electrolyte consisting of potassium hydroxide at a concentration of 30%. Add 3 parts by weight and mix with stirring to produce 3 tons/cj
It is press-molded into a hollow cylindrical shape at a pressure of . In addition,
In order to improve contact with the metal can 1, the positive electrode body 2 is repressurized at a pressure of, for example, 3 tons/C- after filling the metal can 1.

The hollow part of the cylindrical positive electrode body 2 is filled with a gelled negative electrode mixture 4 via a bottomed cylindrical separator 3 made of a nonwoven fabric of acetalized polyvinyl alcohol fibers. This gelled negative electrode mixture 4 contains 3 sodium polyacrylates.
It has a structure in which amalgamated zinc powder, which is a negative electrode active material, is dispersed in a potassium hydroxide electrolyte containing % by weight of potassium hydroxide. A negative electrode current collector rod 5 made of brass is inserted into the gelled negative electrode mixture 4 so that its upper end protrudes beyond the negative electrode mixture 4 . An insulating gasket 6 made of a double-ring-shaped polyamide resin is interposed on the outer circumferential surface of the protrusion of the negative electrode current collector rod 5 and on the inner circumferential surface of the upper part of the metal can 1 . Further, a ring-shaped metal plate 7 is disposed between the double annular portions of the gasket 6, and a cap-shaped metal sealing plate 8 that also serves as a negative electrode terminal is attached to the top of the current collector rod 5. It is arranged so that it comes into contact with. By bending the opening edge of the metal can 1 inward, the inside of the metal can 1 is sealed by the gasket 6 and the metal sealing plate 8.

Example 2 An alkaline dry battery having the same structure as in Example 1 was assembled, except that the cathode active material used was 40% by weight of chemically synthesized manganese dioxide powder and 60% by weight of electrolytic manganese dioxide powder.

Example 3 An alkaline dry battery having the same structure as in Example 1 was assembled, except that a cathode active material having a composition of 50% by weight of chemically synthesized manganese dioxide powder and 50% by weight of electrolytic manganese dioxide powder was used.

Example 4 An alkaline dry battery having the same structure as in Example 1 was assembled, except that a cathode active material having a composition of 60% by weight of chemically synthesized manganese dioxide powder and 40% by weight of electrolytic manganese dioxide powder was used.

Comparative Example 1 An alkaline dry battery having the same structure as in Example 1 was assembled, except that a cathode active material consisting only of chemically synthesized manganese dioxide powder was used.

Comparative Example 2 An alkaline dry battery having the same structure as in Example 1 was assembled, except that a cathode active material having a composition of 20% by weight of chemically synthesized manganese dioxide powder and 80% by weight of electrolytic manganese dioxide powder was used.

Comparative Example 3 An alkaline dry battery having the same structure as in Example 1 was assembled, except that a cathode active material having a composition of 70% by weight of chemically synthesized manganese dioxide powder and 30% by weight of electrolytic manganese dioxide powder was used.

Comparative Example 4 An alkaline dry battery having the same structure as Example 1 was assembled, except that only electrolytic manganese dioxide powder was used as the positive electrode active material.

Comparative Example 5 Except for using a composition of 40% by weight of chemically synthesized manganese dioxide powder and 60% by weight of electrolytic manganese dioxide powder as the positive electrode active material and 10 parts by weight of graphite as the positive electrode conductive material.
An alkaline dry battery having the same structure as in Example 1 was assembled.

Comparative Example 6 Except for using a composition of 60% by weight of chemically synthesized manganese dioxide powder and 40% by weight of electrolytic manganese dioxide powder as the positive electrode active material and 10 parts by weight of graphite as the positive electrode conductive material.
An alkaline dry battery having the same structure as in Example 1 was assembled.

Thus, the alkaline dry batteries of Examples 1 to 4 and Comparative Examples 1 to 6 were continuously discharged with a load resistance of 2Ω, and the discharge duration until the discharge voltage reached 0.9V was measured. The results are shown in Table 3 below.

(Left below) As is clear from Table 3 above, the alkaline dry batteries of Examples 1 to 4 were , the dry battery of Comparative Example 1 equipped with a positive electrode body containing only chemically synthesized manganese dioxide powder of γ-type crystal as a positive electrode active material, and the dry battery of Comparative Example 4 equipped with a positive electrode body containing only electrolytic manganese dioxide powder as a positive electrode active material. It can be seen that the heavy load discharge characteristics are improved. In particular, the alkaline dry batteries of Examples 1 to 4 were equipped with a positive electrode body containing a positive electrode active material made of a mixture of 30 to 60% by weight of chemically synthesized manganese dioxide powder of γ-type crystals and 40 to 70% by weight of electrolytic manganese dioxide powder. , Comparative Example 2.3 in which the blending ratio of chemically synthesized manganese dioxide powder and electrolytic manganese dioxide powder is outside the above range.
It can be seen that the heavy load discharge characteristics are improved even for alkaline dry batteries.

In addition, 90% oil furnace and 10% graphite are used as the positive electrode conductive agent.
It can be seen that the heavy load discharge characteristics of the alkaline dry batteries of Examples 2 and 4 using % were further improved compared to Comparative Examples 5 and 6 using only graphite.

〔Effect of the invention〕

As detailed above, according to the present invention, the electrolytic manganese dioxide and graphite have better heavy load discharge characteristics than when using electrolytic manganese dioxide as the positive electrode active material and graphite as the positive electrode conductive agent. It is possible to provide an alkaline dry battery equipped with a positive electrode body at a lower cost than when using this method.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an alkaline dry battery showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Metal can, 2... Positive electrode body, 3... Separator, 4... Gel-like negative electrode mixture, 5... Negative electrode current collector rod, 8... Metal sealing plate.

Claims (1)

[Claims] A positive electrode active material consisting of a mixture of chemically synthesized manganese dioxide powder and electrolytic manganese dioxide powder whose main component is γ-type crystals obtained by acid-treating manganese oxide obtained by roasting manganese sulfate, and graphite according to JIS K6221. Volatile content is 0.2% or less and specific surface area is 90 to 150 g/m
An alkaline dry battery characterized by using a positive electrode body whose positive electrode conductive material is a mixture with oil furnace black, which is ^2.