JP2002008668A - Alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a battery having a high energy density and an improved discharge duration, by suppressing generation of hydrogen gas by self-discharge while maintaining high average actuation voltage, in the alkaline battery. SOLUTION: The battery improved in the above purpose is obtained by using iron (VI) acid salt as a positive electrode active material, and an electrolyte containing potassium hydroxide and zinc oxide. The best effect is acquired by making potassium hydroxide concentration in the electrolyte at 30 to 48 mass %, and making zinc oxide concentration at 2 to 6 mass %, especially.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an alkaline battery having a high energy density.

[0002]

2. Description of the Related Art Conventionally, electronic devices such as video cameras and headphone stereos have been reduced in size, and batteries having a large energy density have been demanded. As batteries for use in such miniaturized electronic devices,
Until now, primary batteries such as manganese batteries and alkaline manganese batteries using an alkaline electrolyte such as an aqueous potassium hydroxide solution having a larger capacity than the manganese batteries have been widely used. Also, silver oxide batteries, lithium batteries, and the like have been put into practical use. By the way, in recent years, due to the multifunctionality, miniaturization, and high performance of electronic devices, the performance of batteries serving as power sources for these electronic devices has been improved, that is, the quality and life of primary batteries have been improved, and particularly the discharge duration has been improved. The demand for is increasing.

[0003] In order to improve the quality of the battery, particularly to increase the battery capacity, it is necessary to increase the content of the positive electrode active material in the positive electrode mixture. It is necessary to reduce the amount of the added component, and the content of the carbon powder as the conductive assistant is also reduced. However, a positive electrode mixture comprising only a positive electrode active material containing no additive component is not only difficult to mold, but also does not contain a conductive auxiliary, so that the internal resistance increases and the battery performance deteriorates. On the other hand, when the content of the carbon powder is increased to reduce the internal resistance, the internal resistance of the battery is reduced, but the amount of the positive electrode active material is reduced, which leads to a decrease in the discharge capacity. And it was difficult to satisfy both at the same time.

On the other hand, batteries using ferrite (VI) having a high energy density as a positive electrode active material have been studied. This battery is considered to have a longer life than the conventional alkaline battery, and uses MFe (VI) O ₄ as a positive electrode active material, a zinc alloy as a negative electrode active material, and an aqueous potassium hydroxide solution as an electrolyte. It is a primary battery. By the way, when a battery is constructed using this ferrate (VI) as a positive electrode active material, a battery with a high energy density can be obtained, but the actual discharge duration is as long as expected compared to a conventional alkaline battery. There is a problem that a battery having a long discharge duration cannot be obtained.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high energy density battery which suppresses the generation of hydrogen gas due to self-discharge without lowering the average operating voltage and has an improved discharge duration. And

[0006]

According to the present invention, there is provided a battery comprising a positive electrode, a negative electrode and an electrolytic solution, wherein iron (VI) salt is used as an active material of the positive electrode, and hydroxide is used as an electrolytic solution. It is characterized by using an alkaline solution containing potassium and zinc oxide.

According to a second aspect of the present invention, the concentration of the electrolytic solution is 30 to 48% by mass of potassium hydroxide and 2 to 6% by mass of zinc oxide. is there.

Further, in the present invention according to claim 2, the optimum conductivity is obtained by setting the concentration of potassium hydroxide in the electrolytic solution in the range of 30 to 48% by mass, and the concentration of zinc oxide is set to 2 to
When the content is in the range of 6% by mass, self-discharge can be suppressed, and high capacity can be maintained. When the concentration of zinc oxide exceeds the above range, the discharge duration becomes short. On the other hand, when the concentration of zinc oxide is lower than the above range, the effect of suppressing the generation of hydrogen gas decreases, the pressure inside the battery increases after the battery is manufactured, and the container may be undesirably deformed. Further, in the alkaline electrolyte of the present invention, zinc oxide is
It dissolves in potassium hydroxide solution and exists in a state.

According to the present invention having the above structure, in a battery comprising a positive electrode, a negative electrode and an electrolyte, ferrate (VI) is stably present in an alkaline electrolyte as a material for the positive electrode, A battery with an operating voltage can be realized.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the battery of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to an LR44 button battery.

As shown in FIG. 1, a positive electrode mixture 6 is accommodated in a positive electrode case 7 made of stainless steel or the like.
A separator 4 is disposed on the positive electrode mixture 6.
On the surface of the separator 4, a barrier 3 made of a microporous polyethylene film or cellophane is arranged,
The electrolytic solution is impregnated and held in the separator 4. On the other hand, a gelled negative electrode 6 is disposed in the negative electrode case 1 having a smaller diameter than the positive electrode case 7. The negative electrode case 1 is connected to the positive electrode case 7 via a gasket 5 made of, for example, a polyamide resin. 7 and are caulked to the positive electrode case to be liquid-tightly sealed and fixed to each other.

Next, the positive electrode mixture, the gelled negative electrode, and the separator will be described in detail.

(1) Positive Electrode Mixture The positive electrode mixture of the present invention is obtained by adding a mixture containing ferrate (VI), which is a positive electrode active material, and a conductive additive for accelerating the electron transfer speed in the positive electrode. It is created by pressing.

The positive electrode active material used in the present invention has a chemical formula
AFeO₄Is a ferrate (VI) salt represented by Where A is
From among alkali metals, alkaline earth metals and divalent metals
You can choose. Specifically, K₂FeO₄, N
a₂FeO₄, Li₂FeO ₄, Cs₂FeO₄, Ag
₂FeO₄, SrFeO₄, MgFeO₄, CaFeO
₄, BaFeO₄, ZnFeO₄, Etc.
These can be used alone or in combination.
Of these substances, K₂FeO₄But the theoretical capacity is high
Is preferred.

These ferrates (VI) (AFeO ₄ )
It can be manufactured by the following method. Iron (V
I) Sodium acid salt (Na ₂ FeO ₄ ) is iron (III) nitrate
(Fe (NO ₃ ) ₃ ) with concentrated sodium hydroxide (Na
OH) Sodium hypochlorite (NaClO) in aqueous solution
It can be produced by oxidation using Iron (VI) potassium _(K 2 FeO ₄₎ is potassium peroxide generated by oxidation of potassium amide (KNH _{2) (K 2}
O ₂ ) and iron (III) oxide (Fe ₂ O ₃ ) can be produced by heating at 350 to 370 ° C. in an oxygen stream. It can also be produced by burning a mixture of iron and potassium nitrate (KNO ₃ ) in air. In addition, sodium ferrate (VI) (N
It can also be produced by adding potassium hydroxide (KOH) to an aqueous solution of a ₂ FeO ₄ ) and subjecting it to metathesis. Further, a mixed aqueous solution of potassium hypochlorite (KClO) and potassium hydroxide (KOH) is added to an aqueous solution of iron nitrate (Fe (N
It can also be produced by adding O ₃ ) ₃ ). In addition, barium ferrate (VI) (BaFeO ₄ )
Barium chloride (BaCl ₂ ) was added to an aqueous solution of potassium ferrate (VI) (K ₂ FeO ₄ ) to precipitate crystals.
It can be produced by drying at 0 ° C. Other substances can also be produced by a method according to these.

In the present invention, in order to improve the conductivity of the positive electrode active material, a conductive auxiliary is used by being mixed with the positive electrode active material. As the conductive auxiliary used in the present invention, carbon-based material particles are preferable, for example, artificial graphite,
Examples include particles of an amorphous carbon material such as acetylene black, Ketjen black, and furnace black. Among these substances, it is particularly preferable to use amorphous carbon material particles such as artificial graphite and acetylene black in terms of excellent moldability and liquid retention. The carbon-based material particles in the present invention have an average particle size of 1 to 100 μm.
It is desirable to have a range of When the average particle size exceeds this range, a problem occurs in that the conductive auxiliary agent is not uniformly dispersed. On the other hand, when the average particle size is below this range, there is a problem in that strength after molding is reduced, which is not preferable.

The mixing ratio of the conductive additive in the positive electrode mixture is preferably in the range of 3 to 20% by mass. If the amount of the conductive additive exceeds this range, the discharge capacity decreases and the discharge duration decreases, which is not preferable. On the other hand, below this range, the internal resistance increases, which is not preferable.

(2) Negative Electrode The negative electrode 2 used in the present invention is obtained by gelling granular zinc as the negative electrode active material using the gelling agent and the electrolytic solution of the present invention containing potassium hydroxide and zinc oxide. Is preferred. As the granular zinc, granular zinc or a zinc alloy used in a general alkaline dry battery can be used, and in particular, the non-melted zinc particles are most preferable because there is no risk of environmental pollution. As the gelling agent, polyvinyl alcohol, polyacrylate, CMC, alginic acid,
Etc. can be used. In particular, polyacrylates are preferable because they have excellent chemical resistance to strong alkalis.

(3) Separator In the present invention, the separator 4 separates the positive electrode material and the negative electrode material so that they do not come into physical contact with each other. A material having excellent permeability and being chemically stable to the electrolytic solution is used. Examples of such a material include a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, and an acetalized polyvinyl alcohol nonwoven fabric.

[0020]

EXAMPLES Examples and comparative examples relating to the battery of the present invention will be described below.

(Examples 1 to 12) First, using potassium ferrate (VI) powder as a positive electrode active material and artificial graphite as a conductive auxiliary, the conductive auxiliary becomes 10% by mass based on the positive electrode active material. The mixture was stirred and mixed as described above, and was molded under pressure to prepare a positive electrode mixture 6. On the other hand, the negative electrode was stirred with granular zinc, potassium hydroxide having the concentration shown in Table 1 below, and an alkaline electrolyte containing zinc oxide also having the concentration shown in Table 1 and sodium polyacrylate as a gelling agent. By mixing, a gelled zinc negative electrode 2 was prepared. Using the positive and negative electrodes thus obtained, the positive electrode mixture 6 was filled in the positive electrode case 7, the separator 4 and the barrier 3 were placed, and the negative electrode 2 was filled in the negative electrode case 1. These two were combined via a gasket 5, and the opening of the positive electrode case 7 was bent inward by a press to seal it. Thus, LR4 as shown in FIG.
Twelve types of four type button batteries were assembled. With respect to the batteries obtained as described above, the average operating voltage of 30 mA continuous discharge, the discharge duration, and the total battery height (number of surveys: 20)
(Mean value). Table 1 shows the results.

Comparative Example 1 Twenty batteries were assembled in the same manner as in Example 1 except that a zinc oxide was not used as the alkaline electrolyte, and the battery characteristics were evaluated in the same manner as in Example 1. went. The results are shown in Table 1.

Comparative Example 2 Twenty batteries were prepared in the same manner as in Example 1 except that manganese dioxide was used as the positive electrode active material and the concentration of the alkaline electrolyte was as shown in Table 1. The battery characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0024]

[Table 1]

As is clear from Table 1, according to Examples 1 to 3 and Comparative Example 2, those using ferrate (VI) for the positive electrode had a high average operating voltage and a long discharge duration. It can be seen that it is increased by about 30% as compared with the alkaline manganese battery. According to Comparative Example 1, the battery without zinc oxide has a longer discharge duration, but has no suppression of hydrogen gas generation, so that the total battery height is increased. Examples 4, 5,
According to Examples 10 and 11, when the concentration of zinc oxide in the alkaline electrolyte is low, the suppression of hydrogen gas generation is insufficient and the total battery height is increased. Further, according to Examples 6 and 9, it was found that those having a high zinc oxide concentration in the alkaline electrolyte had a shorter discharge duration. When the concentration of potassium hydroxide was 28% by mass and the concentration of zinc oxide was 7% by mass, zinc oxide was not completely dissolved, and a solid portion remained partially. Although there was no particular problem in terms of the battery function, it was found that it was preferable to select a concentration range in which zinc oxide was completely dissolved, since the solution was a heterogeneous solution. From the above results, it was found that the potassium hydroxide concentration and the zinc oxide concentration were most preferably in the range of 30 to 48% by mass and 2 to 6% by mass, respectively.

It should be noted that even in batteries using an alkaline electrolyte and a zinc alloy other than those in this experimental example, iron (V
I) It was confirmed that high performance and long life could be achieved by using an acid salt. Further, similar effects have been confirmed with batteries having a form other than the experimental example, for example, a cylindrical type.

[0027]

As described in detail above, by using the positive electrode active material and the alkaline electrolyte of the present invention, it is possible to provide a high-performance battery having a high energy density, a long discharge duration and a reduced generation of hydrogen gas. it can.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an LR44 button battery according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Negative electrode case 2 ... Negative electrode 3 ... Barrier 4 ... Separator 5 ... Gasket 6 ... Positive electrode 7 ... Positive case

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyoto Yoda 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation F-term (reference) 5H024 AA02 AA14 CC03 EE06 FF09 FF10 GG01 GG04 GG06 HH02 5H050 AA00 AA08 BA04 BA11 CA07 CB13 DA02 DA09 DA13 EA12 FA17 HA01

Claims (2)

[Claims] 1. A battery comprising a positive electrode, a negative electrode and an alkaline electrolyte, wherein iron (VI) is used as an active material of the positive electrode.
An alkaline battery using an acid salt and an alkaline solution containing potassium hydroxide and zinc oxide as an electrolytic solution. 2. The method according to claim 1, wherein the alkaline electrolyte is 30 to 48% by mass.
2. The alkaline battery according to claim 1, comprising potassium hydroxide and 2 to 6% by mass of zinc oxide.