JPH0256857A - Alkaline manganese battery - Google Patents

Abstract

PURPOSE:To obtain a battery with a high positive electrode utilization factor by fixing a specific carbon material on 1-2wt.% manganese dioxide grains for a whole manganese dioxide electrode and mixing and dispersing a carbon material satisfying the specific conditions for manganese dioxide. CONSTITUTION:Noncrystal carbon black 1B is heat-treated in advance into graphite with the average grain size of 0.03-0.05mum for used as a carbon material. This carbon material 1B is fixed on 1-2wt.% manganese dioxide grains 1A for a whole manganese dioxide electrode. A carbon material 1C satisfying the average grain size ratio of 10<-2>-10 for the manganese dioxide 1A is mixed and dispersed with the manganese dioxide 1A for use as the positive electrode black mix 1. A basic electron conducting network is formed, the arrangement that an electrolyte can be sufficiently absorbed via its distribution effect is established, the dispersibility of the manganese dioxide 1A and the carbon materials 1B and 1C is improved, and a battery with a high discharge utilization factor can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to improvements in alkaline manganese batteries, particularly in positive electrode mixtures.

BACKGROUND OF THE INVENTION Traditionally, alkaline manganese batteries have used a mixture of electrolytic manganese dioxide powder as a positive electrode active material and carbon powder as a conductive material as a positive electrode mixture. The reason why a conductive material is necessary is that manganese dioxide alone has a specific conductivity of 10 to 10.
This is because S/ exhibits a very low value on the order of H. Therefore, in order to impart electronic conductivity to individual manganese dioxide particles and promote a sufficient reduction reaction, 1. It is preferable that the non-conductivity of the positive electrode mixture is on the order of 10-2 to 10 S/cm, and for this reason, carbon powder having approximately the same average particle size as manganese dioxide is often used as the conductive material.

Conventionally, a method has been used in which manganese dioxide powder and carbon powder are simply mixed and stirred in a mixer to form a positive electrode mixture.

In addition, a method has been proposed in which a manganese dioxide and a carbon material are charged with opposite static charges, and a graphite layer is formed by electrostatic adsorption on manganese dioxide particles to form a positive electrode mixture (e.g., 214362). Also,
Amorphous carbon material particles may be used as the conductive material, or particles with a diameter of 0.
A method has also been proposed in which a positive electrode mixture is fixed on manganese dioxide particles by an impact method in a high-speed air flow using fiber graphite having a length of 1 to 1.0 μm and a length of 10 to 100 μm.

Problems to be Solved by the Invention However, in such a conventional configuration, it is difficult to uniformly disperse two different types of powder by simply mixing them.In this case, manganese dioxide powder and carbon Powders do not have enough contact with each other. As the frequency of these contacts decreases, the network formation for electron conduction decreases,
There is a problem in that a large amount of manganese dioxide that does not participate in the electrochemical reduction reaction remains, resulting in a decrease in the utilization rate of manganese dioxide for the electrode as a whole.

There is no problem like this when using a large amount of carbon powder, but
On the other hand, since the amount of manganese dioxide within a certain volume is reduced, the discharge capacity density of the battery is extremely reduced.

The main reason why sufficient contact cannot be obtained between such manganese dioxide particles and carbon material particles is that the carbon material particles aggregate to form secondary particles. This is due to the fact that in the conventional mixing method using simple mechanical stirring, the mixing rotation speed is low, which reduces the frequency of collisions and contact between particles due to rotational orientation, and the interaction between two types of powder due to contact friction. This was due to the fact that the charge adsorption effect was impaired and the dispersibility decreased.

On the other hand, a positive electrode mixture obtained by forming a graphite layer on manganese dioxide particles certainly forms a good electron conduction network and improves specific conductivity, but various problems occur at the reaction interface between the active material and the electrolyte. Because the graphite layer inhibited mass transfer, sufficient discharge characteristics could not be obtained. In addition, the positive electrode mixture obtained by immobilizing amorphous carbon material or fibrous graphite on manganese dioxide particles using the impact method in high-speed airflow can build a good electron conduction network, and has a specific electrical conductivity. will improve. Furthermore, the conductive carbon material can be immobilized on the manganese dioxide particles, and the reaction interface between the active material and the electrolyte can be maintained well.

However, amorphous carbon materials tend to have a large specific surface area due to their relatively small particle size, and this increases the contact interface with the electrolyte, causing a hybrid potential, resulting in a high open circuit potential. The problem was that I couldn't do it. In addition, since the above-mentioned fiber graphite has a fibrous shape, the fiber graphite
It is extremely difficult to completely unravel a single book, and from a microscopic perspective, it is no different from the occurrence of minute secondary agglomerations.

The present invention solves these problems, and aims to improve the dispersibility of manganese dioxide and carbon material and provide a battery with a high discharge utilization rate.

Means for Solving the Problems The present invention solves the problems of the prior art described above, and is a battery using a manganese dioxide electrode whose main constituent materials are manganese dioxide and a carbon material. Quality carbon black is heat-treated in advance, and the average particle size is o, 03~
0.05 μm graphitized carbon material is used, and this carbon material is immobilized on manganese dioxide particles at a weight ratio of 1 to 2% with respect to the total manganese dioxide electrode, and the average particle size of the carbon material with respect to manganese dioxide is A positive electrode mixture in which a carbon material satisfying a ratio of 10 to 10 is mixed and dispersed in manganese dioxide is used.

Effect With this configuration, the manganese dioxide particles and some of the carbon material particles are well fixed, and for example, when the specific conductivity of the positive electrode mixture is measured in a dry state in an inert atmosphere, it is 10 S.
It showed a value of 7 cm or more.

In addition, when an AA alkaline manganese battery (LR6) was constructed using this positive electrode mixture, IKtlz
The AC impedance measurement results and the open circuit potential measurement results were almost the same as those of the conventional example.

On the other hand, when one person conducted a constant current continuous discharge test, the utilization rate was significantly improved, about 30 inches higher than conventional batteries.

Such an effect can be obtained by adding 1 to 2% of the weight of the mixture.
The graphitized carbon black of H is immobilized on the surface of the manganese dioxide particles, forming a basic electron conduction network and its dispersion effect, creating an arrangement that can sufficiently absorb the electrolyte. It depends on what happened. When amorphous carbon black is used, the above-mentioned electronic conduction network is formed, but its surface is very hydrophobic, making contact with the electrolyte difficult. For this purpose, carbon black whose surface is graphitized to improve its affinity with alkaline electrolytes should be used. Further, due to the graphitization treatment, sintering occurs in minute portions of the carbon surface, and the surface area is considerably reduced, so that the decrease in open circuit potential due to the mixed potential is reduced. The specific conductivity of manganese dioxide with carbon thus obtained is on the order of 1oS/cm, which is a value that hardly affects battery characteristics in terms of conductivity. However, when the moldability of the positive electrode pellet is taken into account, it is necessary to further fill the positive electrode pellet with carbon material.

Therefore, the average particle size ratio of carbon material to manganese dioxide is 1.
A carbon material having a relatively small surface area and a large tap density that satisfies the ratio of 0 to 10 was added and mixed and stirred.

This makes it possible to obtain a positive electrode mixture that is less affected by the mixed potential due to the carbon material and has a high discharge capacity density.

The present invention has been proposed based on such facts, and examples thereof will be described below.

Example The heat-treated carbon black used in the present invention is amorphous carbon black, such as acetylene black, heated at a heating rate of 1.
It was obtained by heating at 70'C/min and firing at 2300°C for 2 hours. As a result, graphitization progresses in minute portions of the structural surface of carbon black.

Note that most ordinary carbon blacks have an average particle size of several tens of millimeters, but even if heat treatment is performed for graphitization, some sintering is observed, but in most cases, the particle size does not change. We have confirmed that there are no.

In the positive electrode mixture according to the present invention, the graphitized carbon black described above is immobilized on manganese dioxide particles by an impact method in a high-speed air flow. That is, manganese dioxide and graphitized carbon black are dispersed in a gas phase, and the graphitized carbon black is ordered on the surface of manganese dioxide particles by the adsorption effect of triboelectric charging, which is caused by collisions and friction between particles. Let it absorb well. Next, while dispersing this in the gas phase again, the rotating body was mechanically heated to approximately 500°C.
By rotating at high speeds at speeds of , p, and m, the respective powders undergo strong collisions and contact friction with each other, and the graphitized carbon black, which was arranged in an orderly manner on the surface of the manganese dioxide particles, is implanted onto the surface. It is fixed and a strong adhesive state can be achieved. The carbon material-attached manganese dioxide obtained in this manner does not easily peel off even when an external force is applied, for example during pellet molding.

Next, on the manganese dioxide with carbon material, a carbon material having an average particle size ratio of carbon material to manganese dioxide of 10-2 to 10 is mixed and dispersed in the same manner as described above, or a positive electrode is formed by simply mixing. get the agent.

A specific positive electrode mixture consists of electrolytic manganese dioxide as an active material and acetylene black as a conductive material at 2300'C.
Graphitized black with an average particle size of 0.045 μm, which was graphitized by time treatment, and artificial graphite with an average particle size of 1 μm were used.

First, rotate manganese dioxide and graphitized black at 150 rpm.
It was put into a gas phase dispersion mixer rotating at Or, p, In and operated for 3 minutes, then a certain amount of this was put into another gas phase dispersion mixer capable of high speed rotation, and the rotation speed was 5ooor, p. ,
The reactor was operated at m for 2 minutes to obtain manganese dioxide with carbon. Next, this so-called pre-treatment manganese dioxide and average particle size 1
Starting with 0 μm artificial graphite, after 1000 r, p, m, 6
000 r, p, m for 2 minutes each,
A positive electrode mixture was obtained.

In order to clarify the concept of the manganese dioxide particles of this positive electrode mixture, a cross-sectional model diagram thereof is shown in FIG.

In FIG. 1, 1 is manganese dioxide, 1B is graphitized black, and 1C is artificial graphite.

Next, an LR6 type battery shown in FIG. 2 was constructed using the obtained positive electrode mixture, and a constant current continuous discharge test was conducted by one person.

In FIG. 2, reference numeral 1 denotes a positive electrode mixture according to the present invention, that is, a positive electrode mixture obtained by mixing artificial graphite after subjecting manganese dioxide particles to a pretreatment of causing graphitized black to run on them. 2 is a gelled zinc powder negative electrode, 3 is a separator,
4 is a current collector for the gel negative electrode, 5 is a positive electrode cap, 6 is a metal case, 7 is a battery case, 8 is a synthetic resin sealing body,
9 is a bottom plate.

Table 1 shows that the total carbon content in the positive electrode mixture is fixed at 10%, and the weight fraction of graphitized black filled in the pretreatment is 0%.
．． 6 to 3.0% and the remaining amount of artificial graphite is added, the open circuit potential and IKHz AC impedance measurement results are shown.

(The following is a blank space) Table (Measurement at 20°C) As can be seen from Table 1, the weight fraction of graphitized black is 1.
If 0 to 2.0% of the positive electrode mixture is used, a battery with excellent open circuit potential and impedance characteristics can be provided. Incidentally, the open circuit potential is about 10 mV higher than when all 10% graphitized black is used as the conductive material, and the drop in potential due to the mixed potential can be improved. Note that when a positive electrode mixture obtained by mixing 10% by weight of artificial graphite by the conventional mixing method was used, the open circuit potential was 1.59V and the impedance was 0.0 and 13Ω.

Next, for example, the weight fraction of graphitized black for pretreatment is set to 2.
A one-person constant current continuous discharge test was conducted using the positive electrode mixture when the weight fraction of artificial graphite for post-treatment was 8.0%. As a result, the utilization rate can be maintained at 34% or more, and when using the positive electrode mixture obtained by the conventional mixing method (artificial graphite 1
Since the utilization rate of (0% by weight) is 26%, the positive electrode mixture of the present invention shows the possibility of improving the utilization rate by about 30%.

The graphitized black for pretreatment used here had an average particle size of 0.045 μm, but because the acetylene black was sintered, the average particle size was Q, 030 μm.
A size smaller than μm could not be experimentally obtained. On the other hand, when the average particle size is 0.050 μm or more, the vapor phase mixing and dispersion effect with manganese dioxide tends to decrease significantly.
It does not contribute to the above-mentioned improvement in the positive electrode utilization rate. This is thought to be due to an imbalance in the surface charges between the carbon material and manganese dioxide.

However, the average particle size of the carbon material that should be added to post-treatment is large;
It is desirable to select a material that also has a relatively high density. The positive electrode mixture for alkaline manganese batteries shown in this example includes:
By using artificial graphite with an average particle size of 1 Cμm, we were able to obtain extremely good formability and battery characteristics, but since secondary particles of graphite material may be present, manganese dioxide is not recommended for boat fishing. The average particle size of the carbon material with respect to the particles is 1
It should be between o and 10.

Effects of the Invention As described above, by using the positive electrode mixture according to the present invention, it is possible to provide a battery with a high positive electrode utilization rate.

[Brief explanation of the drawing]

Figure 1 is a model diagram schematically showing the cross section of particles obtained by fixing graphitized black on the surface of manganese dioxide particles and then mixing and dispersing artificial graphite, and Figure 2 is a battery in an example of the present invention. FIG. 1 person...manganese dioxide, 1B...graphitized black, 1C...artificial graphite, 1...
... Positive electrode mixture, 2 ... Gel negative electrode, 3 ... Separator.

Claims (1)

[Claims] A battery using a manganese dioxide electrode mainly composed of manganese dioxide and a conductive carbon material, wherein the conductive carbon material is amorphous carbon black that has been heat-treated in advance and has an average particle size of 0.
．． This carbon material has a weight ratio of 1 to 2 to the total manganese dioxide electrode.
% manganese dioxide particles, and the average particle size ratio of the carbon material to manganese dioxide is 10^-^
An alkaline manganese battery characterized in that a carbon material satisfying 2 to 10 is mixed and dispersed.