JP2925630B2 - Alkaline batteries - Google Patents

Description

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

(Conventional technology) Alkaline batteries are superior in continuous discharge and heavy load discharge performance as compared with manganese batteries using zinc chloride electrolyte, and are therefore used as power sources for portable playback devices and camera flashlights. I have.

By the way, as the positive electrode active material of the alkaline dry battery, electrolytic manganese dioxide (EMD), which has better discharge performance and higher density than before, has been widely used.

Further, since electrolytic manganese dioxide alone has low conductivity, a conductive auxiliary such as graphite, acetylene black or the like is usually used.
About 15% by weight was mixed to impart conductivity.

(Problems to be Solved by the Invention) However, EMD requires a large amount of electrolysis time and electric power in the electrolytic oxidation step, and thus has been expensive. Moreover, conventional chemically synthesized manganese dioxide (CM
D) and natural manganese dioxide (NMD) are less expensive than EMD, but did not perform well with heavy load discharges. Therefore, in order to obtain high-performance and low-cost manganese dioxide that can replace EMD, development and research by chemical synthesis methods have been actively conducted in recent years, but chemicals that can be used in large quantities as alkaline dry batteries have been developed. Synthetic manganese dioxide has not yet been found.

On the other hand, graphite and acetylene black, which are generally used as conductive agents, have inherent disadvantages and are not sufficiently satisfactory. That is, when graphite is used as the conductive agent, iron contained in graphite powder as an impurity,
Lead, copper, etc. react with the positive electrode active substance, causing a decrease in the potential of the positive electrode, a decrease in the capacity of the battery, and a decrease in the utilization rate of the positive electrode active material due to low electrolyte retention. is there. Although graphite itself has a small electric resistance, it has a drawback that when used for a positive electrode body, the electric resistance of the positive electrode body cannot be sufficiently reduced due to its particulate structure.

In this respect, acetylene black has less impurities compared to graphite powder and has a developed chain structure, so that it has a large retention of the electrolyte and can improve the utilization rate of the positive electrode active material, and can reduce the electric resistance of the positive electrode body. Can be smaller. However, since a functional group having a strong reducibility to the positive electrode active material is present on the surface of acetylene black, a battery using the same as a conductive agent has a drawback that a decrease in potential and a decrease in discharge capacity are increased.

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

[Configuration of the invention]

(Means for Solving the Problems) The present invention relates to a chemically synthesized manganese dioxide powder containing 30 to 60% by weight of a γ-type crystal obtained by subjecting a manganese oxide obtained by roasting manganese sulfate to an acid treatment. A positive electrode active material comprising a mixture of 40 to 70% by weight of electrolytic manganese dioxide powder;
An alkaline dry battery using a cathode body having a mixture of graphite and oil furnace black having a volatile content of 0.2% or less according to JIS K6221 and an oil furnace black having a specific surface area of 90 to 150 m ² / g as a cathode conductive material. .

Chemically synthesized manganese dioxide powder used in the present invention,
It is desirable to use one having an average particle size of 20 μm or less. It is desirable that the ratio of the chemically synthesized manganese dioxide to the γ-type crystal be 70% or more.

An example of a method for producing the above chemically synthesized manganese dioxide powder is as follows. First, a manganese sulfate (MnSO ₄ ) solution having a low potassium content is heated and concentrated to prepare a manganese sulfate crystal. In this case, it is not preferable to contain a large amount of alkali metal, particularly potassium, because roasting and acid treatment in the subsequent steps produce chemically synthesized manganese dioxide having a large amount of α-form crystals with low activity. Subsequently, this is placed in an air atmosphere or an oxygen atmosphere having a higher oxygen partial pressure than air.
It is roasted at 1001100 ° C. for 10 minutes or more, and manganese sulfate is decomposed as shown in the following formulas (1) and (2) to produce manganese oxide containing Mn ₃ O ₄ or Mn ₂ O ₃ as a main component.

3MnSO ₄ → Mn ₃ O ₄ + SO ₂ + 2SO ₃ (1) 2MnSO ₄ → Mn ₂ O ₃ + SO ₂ + SO ₃ (2) Then, for the manganese oxide containing Mn ₃ O ₄ as a main component, for example, a rotary kiln 700 ~ 950 ℃
And a reaction represented by the following formula (3) is carried out to convert into a manganese oxide containing Mn ₂ O ₃ as a main component, which has a good yield in acid treatment in the subsequent step.

4Mn ₃ O ₄ + O ₂ → 6Mn ₂ O ₃ (3) Next, the manganese oxide containing Mn ₂ O ₃ as a main component is treated with sulfuric acid (or nitric acid, hydrochloric acid, or a mixed acid thereof). Thereby, a disproportionation reaction represented by the following formulas (4) and (5) occurs, and chemically synthesized manganese dioxide is generated.

_{Mn 2 O 3 + H 2 SO} 4 → MnO 2 + MnSO 4 + H 2 O ... (4) Mn 3 O 4 + 2H 2 SO 4 → MnO 2 + 2MnSO 4 + 2H 2 O ... (5) Then, the resulting washed with water MnO _2, Medium sum processing, after a drying treatment, the resultant powder was compression molded into a plate by roll press under a pressure of 1-10 tons / cm ^2, mainly γ-form crystals by further ground to a predetermined particle size Manufacture chemically synthesized manganese dioxide powder as a component.

A commercially available electrolytic manganese dioxide can be used.

The mixing ratio of the chemically synthesized manganese dioxide powder and the electrolytic manganese dioxide powder is
It is desirable to set the range to 30 to 60% by weight and the electrolytic manganese dioxide powder to 40 to 70% by weight.

Further, in the present invention, the oil furnace black used as a conductive material, liquid hydrocarbons are partially oxidized in the presence of molecular oxygen and water vapor in a furnace, and the by-product carbon generated at the same time as the synthesis gas is produced is dried. Obtained by performing a heat treatment. The liquid hydrocarbon used at that time means a carbon atom / hydrogen atom having a weight ratio of 9 or more. Examples of such a liquid hydrocarbon include naphtha pyrolysis oil (ethylene heavy end), Examples thereof include a liquid hydrocarbon (carbon oil) in which carbon is mixed with an aromatic hydrocarbon, and a mixed oil in which C heavy oil and the like are mixed with an aromatic liquid hydrocarbon.

In order to obtain such an oil furnace black, 200 to 800 kg, preferably 400 to 800 kg of water vapor is used for 1 ton of liquid hydrocarbon. The temperature in the furnace is 1200-1450 ° C., preferably 1300-1450 ° C., and the pressure during the reaction is 10-80 atm, preferably 25-80 atm.

Next, the by-product carbon is heated at 300 to 900 ° C.
Dry for 0.5 to 3 hours, then in an inert gas atmosphere, 1000
The target oil furnace black is obtained by performing a heat treatment at 3000 ° C. for 0.5 to 5 hours.

This oil furnace black has few impurities,
In addition, there is a characteristic that a chain structure is developed. Physical properties of the above-mentioned oil furnace black, acetylene black and graphite, surface area (m ² / g), hydrochloric acid absorption (ml / 5g), interplanar spacing d (002) (Å) and output (%) of carbon net The comparison is shown in Table 1.

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

Volatile components are attributed to functional groups on the surface of carbon black, and refer to functional groups having reducing properties such as aldehyde groups, carboxyl groups, and hydrogen. Naturally, the smaller the volatile content is, the smaller the reduction property to manganese dioxide is, and the better it is. If it exceeds 0.2%, manganese dioxide of the positive electrode mixture is reduced and deteriorated, which is not preferable.

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

In addition, it is desirable that the plane spacing d (002) of the carbon net showing the degree of graphitization be small, that is, the direction closer to the carbon network plane spacing of graphite of 3.35Å be higher in conductivity, but even if the degree of graphitization becomes too high. Surface area and hydrochloric acid absorption are reduced. Therefore, it is desirable that the plane interval of the carbon net is 3.48 to 3.40 °. The specific surface area under these conditions is measured by the BET method, and the value is preferably 90 to 150 m ² / g, and the hydrochloric acid absorption is preferably 20 ml / 5 g or more.

The plane distance d (002) of the carbon net showing the degree of graphitization
Was measured using silicon as a standard substance by the X-ray diffraction method established by the 117th Committee of the Japan Society for the Promotion of Science, described in the Carbon Materials Society of Japan, Introduction to Carbon Materials, pages 184-192 (Carbon Materials Society, 1979). Things.

Here, in the alkaline dry battery of the present invention, the above-mentioned oil furnace black is used by being mixed with graphite.
Table 2 shows the electrical resistance of the oil furnace black and graphite alone.

As is clear from Table 2, when a mixture of oil furnace black and graphite is used, the electric resistance per unit weight is reduced as compared with the case where the oil furnace black is used alone, and the heavy load discharge performance can be further enhanced. . The mixing ratio of the oil furnace black and graphite is desirably in the range of 98: 2 to 50:50 by weight. If the amount of graphite is less than 2% by weight, there is no merit of mixing, while if it is more than 50% by weight, the above-mentioned adverse effect of graphite occurs.

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

That is, in an alkaline dry battery incorporating a positive electrode body having a composition of the above-mentioned chemically synthesized manganese dioxide powder and electrolytic manganese dioxide powder as a positive electrode active material, a decrease in battery voltage at the end of discharge is small and the discharge curve is flattened. Or a rising phenomenon occurs. This is due to the fact that in the X-ray diffraction at each terminal stage of the discharge, the heterolite (ZnO)
The diffraction intensity indicating the crystal growth of Mn ₂ O ₃ ) is higher than that of other manganese dioxide mixtures, and this is due to the composition in which the heterolite generation reaction easily occurs. The cause of the flattening or rising of the discharge potential due to the formation of the heterolite is that the discharge product (MnOOH) on the surface of the MnO ₂ particles and the Zn (OH) ₄ ²⁻ ion in the solution electrolyte have the following formula (6). It is considered that the reaction shown in (1) is accompanied by a decrease in free energy.

^{_{2MnOOH + Zn (OH) 4 2-}} → ZnO · Mn 2 O 3 + 2H 2 O + 2OH - ...
(6) From the above, in the alkaline dry battery incorporating the positive electrode body using the mixture of the composition of the chemically synthesized manganese dioxide powder and the electrolytic manganese dioxide powder as the positive electrode active material, the discharge duration becomes longer, and the heavy load discharge characteristics are increased. Can be significantly improved.

The electrolytic manganese dioxide used in the conventional alkaline dry battery is obtained by electrolysis of manganese sulfate, and the electrolysis takes a long time and consumes a lot of power. Since manganese is obtained by chemical synthesis, cost reduction can be realized as compared with electrolytic manganese dioxide.

Further, as described above, since the oil furnace black has a small amount of impurities and a developed chain structure, the retention of the electrolyte is large, the utilization rate of the positive electrode active substance can be improved, and the electric resistance of the positive electrode body is reduced. 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, and therefore reduces the positive electrode active material like acetylene black to lower the potential and discharge capacity. Is extremely small.

Hereinafter, embodiments 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 of γ-type crystal containing 92% of MnO ₂ having an average particle size of about 10 μm and 70% by weight of commercially available electrolytic manganese dioxide powder were uniformly stirred using a stirring mixer. By mixing, a positive electrode active material was prepared.

Using the positive electrode active material manufactured by the above-described method, a JIS standard LR6 type (AA) alkaline dry battery having a structure shown in FIG. 1 was assembled.

That is, reference numeral 1 in the drawing denotes a bottomed cylindrical metal can also serving as a positive electrode terminal. This metal can 1 is filled with a positive electrode body 2 formed into a cylindrical pressure. The positive electrode body 2 is composed of 90 parts by weight of the positive electrode active material prepared by the above-mentioned method, 9 parts by weight of oil furnace black and 1 part by weight of graphite as conductive materials, and an alkaline electrolyte comprising 30% potassium hydroxide. 3 parts by weight of the stirred mixture is obtained by pressure molding into a hollow cylindrical shape at a pressure of 3 tons / cm ² to this. The positive electrode body 2 is pressurized again at a pressure of, for example, 3 tons / cm ² after filling the metal can 1 in order to enhance the contact property with the metal can 1.

The hollow portion 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 fiber. The gelled negative electrode mixture 4 has a structure in which amalgamated zinc powder, which is a negative electrode active material, is dispersed in a potassium hydroxide electrolyte solution containing 3% by weight of sodium polyacrylate. In the gelled negative electrode mixture 4, a negative electrode current collector rod 5 made of brass is inserted so that its upper end protrudes from the negative electrode mixture 4. An insulating gasket 6 made of a double annular polyamide resin is interposed on the outer peripheral surface of the projecting portion of the negative electrode current collector rod 5 and the upper inner peripheral surface of the metal can 1. Also,
A ring-shaped metal plate 7 is disposed between the double annular portions of the gasket 6, and a hat-shaped metal sealing plate 8 serving also as a negative electrode terminal is provided on the metal plate 7 so as to contact the head of the current collecting rod 5. It is arranged so that it may touch. The inside edge of the metal can 1 is sealed by the gasket 6 and the metal sealing plate 8 by bending the opening edge of the metal can 1 inward.

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

Example 3 An alkaline dry battery having the same structure as that of 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 composed of only 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 positive electrode 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 in Example 1 was assembled except that only the electrolytic manganese dioxide powder was used as the positive electrode active material.

Comparative Example 5 The same structure as in Example 1 was used except that a cathode active material having a composition of 40% by weight of chemically synthesized manganese dioxide powder and an electrolytic manganese dioxide powder of 60% by weight and a cathode conductive material having 10 parts by weight of graphite were used. An alkaline battery was assembled.

Comparative Example 6 The same structure as in Example 1 was used except that a cathode active material having a composition of chemically synthesized manganese dioxide powder of 60% by weight and an electrolytic manganese dioxide powder of 40% by weight and a cathode conductive material of 10 parts by weight of graphite were used. An alkaline battery was assembled.

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

As is clear from Table 3 above, the alkaline dry batteries of Examples 1 to 4 each having a positive electrode body containing a positive electrode active material obtained by mixing a chemically synthesized manganese dioxide powder of γ-type crystal and an electrolytic manganese dioxide powder, The battery of Comparative Example 1 provided with the positive electrode body containing only the chemically synthesized manganese dioxide powder as the positive electrode active material, and the heavy battery as compared with the dry battery of Comparative Example 4 provided with the positive electrode body containing only the electrolytic manganese dioxide powder as the positive electrode active material It can be seen that the discharge characteristics are improved. In particular, the alkaline dry batteries of Examples 1 to 4 each having a positive electrode body including a positive electrode active material in which 30 to 60% by weight of chemically synthesized manganese dioxide powder of γ-type crystal and 40 to 70% by weight of electrolytic manganese dioxide powder are mixed It can be seen that the heavy-load discharge characteristics are improved even for the alkaline dry batteries of Comparative Examples 2 and 3 in which the compounding ratio of the chemically synthesized manganese dioxide powder and the electrolytic manganese dioxide powder is out of the above range.

In addition, 90% of oil furnace and 10% of graphite are used for 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 Pb were further improved as compared with Comparative Examples 5 and 6 using only graphite.

〔The invention's effect〕

As described in detail above, according to the present invention, electrolytic manganese dioxide has a more excellent heavy-load discharge characteristic as compared with the case where graphite is used as a positive electrode conductive material, and the electrolytic manganese dioxide and graphite Can provide an alkaline dry battery provided with a positive electrode body which is lower in cost than the case of using an alkaline battery.

[Brief description of the 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 body, 3 ... Separator, 4 ... Gelled negative electrode mixture, 5 ... Negative current collector rod, 8 ... Metal sealing plate.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 4/06-4/08 H01M 4/50 H01M 4/62

Claims (1)

(57) [Claims] 1. A chemically synthesized manganese dioxide powder containing 30 to 60% by weight of γ-type crystal obtained by subjecting a manganese oxide obtained by roasting manganese sulfate to an acid treatment and an electrolytic manganese dioxide powder of 40 to 70% by weight. % Of a positive electrode material comprising a mixture of
An alkaline dry battery using a positive electrode body having a positive electrode conductive material containing a mixture of graphite and oil furnace black having a volatile content of 0.2% or less according to JIS K6221 and a specific surface area of 90 to 150 m ² / g.