JPH09180708A - Alkaline dry cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve discharging performance of an alkaline dry cell by regulating the porosity of a cathode mix pellet and the amount of an electrolytic liquid with which the pores are impregnated. SOLUTION: A cathode mix pellet 2 prepared by mixing manganese dioxide, with acetylene black or ketjen black and pressure molding the mixture and having fine pores not less than 0.14cc/g and not more than 0.24cc/g is set in a battery case 1 and impregnated with an electrolytic liquid, and a gel-state zinc anode 4 is put in the inside while having a separator 3 between them to give a dry cell. Consequently, excellent characteristic such as relatively high load discharge can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an alkaline dry battery using manganese dioxide as a positive electrode.

[0002]

2. Description of the Related Art Conventionally, an alkaline dry battery is manufactured by forming a positive electrode mixture, which is a mixture of manganese dioxide as a positive electrode active material and graphite as a conductive material, into pellets to form a positive electrode.
In particular, in a cylindrical alkaline dry battery, a positive electrode mixture is molded into donut-shaped pellets divided into several pieces and then inserted into a battery case to form a positive electrode. Alternatively, it may be formed into a positive electrode after being inserted into the battery case and then molded again.
The amount of pores of the positive electrode material mixture pellets at these time points is 3 nm to 400 μm in pore diameter measured by mercury porosimetry.
The porosity of the pores was 20 to 25%, and the amount of the pores was 0.07 to 0.09 cc / g. The reason for such a pore amount is determined by the composition of the mixture and the manufacturing method.
It is generally 0.06 cc or less per gram.

[0003]

It is known that it is effective to increase the amount of the electrolytic solution in the positive electrode mixture in order to improve the positive electrode utilization rate of the alkaline dry battery.
Particularly, in heavy load discharge, the polarization of the positive electrode is large, and increasing the amount of the electrolytic solution is very effective. In order to improve the discharge performance, there is one in which the amount of water in the positive electrode mixture is regulated to 9 to 13% as in JP-A-49-33128. It was difficult to absorb more electrolyte solution with the conventional positive electrode mixture (corresponding to 0.06 to 0.09 cc per 1 g of positive electrode mixture).

The present invention solves the above problems, and an object thereof is to provide an alkaline dry battery suitable for high load discharge.

[0005]

In order to solve the above problems, in the present invention, the positive electrode mixture pellets having a pore size of 3 nm to 400 μm as measured by mercury porosimetry have a pore volume of 0.14 cc. A positive electrode having a density of not less than / g and not more than 0.24 cc / g is used in an alkaline dry battery. More specifically, the amount of electrolytic solution impregnated into the pores is 0.0
The amount of the electrolytic solution in the positive electrode is optimized by limiting the amount to 9 cc / g or more and 0.12 cc / g or less. In this case, acetylene black or Ketjen black is preferable as the conductive material mixed with manganese dioxide. This is because the structure of those conductive materials has a high liquid absorbing property.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the positive electrode material mixture pellets have a pore amount of 0.14 with a pore size of 3 nm to 400 μm.
It is an alkaline dry battery of about 0.24 cc / g, and it is possible to increase the amount of electrolytic solution to be impregnated in the positive electrode and increase the amount of electrolytic solution existing in the vicinity of manganese dioxide, as compared with the conventional case. Therefore, when the above mixture is molded to produce the positive electrode mixture pellet having the optimum amount of pores, the optimum amount of the electrolytic solution can be impregnated. Under such conditions, the positive electrode reaction occurs more quickly than the conventional positive electrode mixture.
That is, the diffusion of hydroxide ions generated along with the discharge reaction of the positive electrode, the supply of water consumed in the discharge reaction becomes rapid, and the polarization during discharge under high load can be particularly reduced, so that the positive electrode utilization rate is high. Greatly improved. Further, when it is attempted to manufacture a porous positive electrode mixture having a high liquid absorption property, it is preferable to use acetylene black or Ketjen black as the conductive material mixed with manganese dioxide. The reason is that their structure has high liquid absorption and porosity, and when mixed with manganese dioxide, these conductive materials are entangled around manganese dioxide and form a liquid replacement layer near manganese dioxide. This is because it becomes a preferable state for supplying the electrolytic solution. On the other hand, when conventional flaky graphite or expanded graphite is used, even if the mixing amount and pellet molding pressure are optimized, it is not possible to obtain the same discharge performance as when acetylene black or Ketjen black is used. It is considered that this is because the water repellency of the graphite material hinders the supply of the electrolytic solution and that the above-described highly liquid-absorbent positive electrode material mixture pellets cannot be manufactured. For the above reasons, when an alkaline dry battery is manufactured using the positive electrode material mixture pellets of the present invention, the discharge performance of the alkaline dry battery under high load discharge is significantly improved. Further, in the above alkaline dry battery, since the utilization rate of the positive electrode is remarkably improved, it is possible to compensate for the decrease in the amount of manganese dioxide due to the increase in the amount of the conductive material mixed in the high load region.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment) FIG. 1 is a cross-sectional view of a constitutional example of an alkaline dry battery. In the figure, 1 is a battery case and a positive electrode current collector, 2
Is a positive electrode material mixture pellet made of manganese dioxide and a conductive material, 3 is a separator, 4 is a gelled zinc negative electrode, 5 is a negative electrode current collector, and 6 is a resin sealing body, and it was carried out in an AA alkaline battery.

The positive electrode material mixture pellet 2 is prepared by mixing manganese dioxide and acetylene black as a conductive material, and the positive electrode material mixture pellet has a pore amount of 0.07 cc / g to 0.28 c.
The range of c / g was examined, and the electrolyte solution was injected into the positive electrode mixture pellets by using a vacuum injection method to impregnate about 25 to 88% of the pores of the positive electrode mixture pellets with the electrolyte solution. FIG. 2 shows a 1A constant current of an AA alkaline battery in which 75% of the pore volume of a positive electrode material mixture pellet having a pore amount of 0.07 cc / g to 0.28 cc / g is impregnated with an electrolytic solution. 0 at discharge.
It shows the relationship between the discharge capacity and the amount of pores until the end of 9V. As shown in the figure, when the amount of pores is small, sufficient improvement in discharge capacity cannot be obtained. On the other hand, the pore volume is 0.2
In the case of the positive electrode material mixture pellets of 4 cc / g or more, the contact between manganese dioxide and the conductive material particles becomes weak, the internal resistance of the battery increases and the discharge capacity decreases. In addition, FIG. 3 shows a pore amount of 0.1.
The relation between the discharge capacity and the amount of the electrolyte solution until the end of 0.9V at 1A constant current discharge of the AA alkaline battery manufactured by changing the amount of the electrolyte solution impregnated into the 6 cc / g positive electrode mixture pellet. Is. As described above, when the amount of the electrolyte solution is in the range of 0.09 cc or more and 0.12 cc or less per 1 g of the positive electrode pellet, a significant improvement in discharge capacity can be obtained. This indicates that the positive electrode can ideally react when the amount of the electrolytic solution is the optimum amount. On the contrary, when the amount of the electrolytic solution is small, not only the above effect is not obtained but also the internal resistance is increased. On the other hand, when the amount of the electrolytic solution is too large, problems such as loosening of the mixture occur. In addition, the pore amount of the positive electrode material mixture pellets is 0.12 cc /
In any of the cases of g to 0.24 cc / g, excellent discharge performance can be obtained with the amount of the electrolytic solution being 0.09 cc to 0.12 cc per 1 g of the positive electrode material mixture pellets. That is, the total amount of the electrolytic solution impregnated into the pores of the positive electrode material mixture pellet contributes more to the discharge performance than the proportion of the electrolytic solution in the pores of the positive electrode material mixture pellet. In addition, since the apparent density of the positive electrode material mixture pellets of the examples is 2.6 g / cc,
The amount of the electrolytic solution that provides excellent discharge performance is 0.23 to 0.31 cc per 1 cc of the positive electrode material mixture pellets.

In the above example, as a positive electrode mixture pellet, 91% by weight of manganese dioxide and 9% by weight of acetylene black were mixed to form a battery having an apparent density of 2.6 g / cc. Example 1, 94% by weight of manganese dioxide. And Ketjen Black 6% by weight are mixed to give an apparent density of 2.6 g /
A cc-molded battery was prepared in Example 2, 96% by weight of manganese dioxide and 4% by weight of graphite were mixed, and a molded battery was used as a comparative example.

Porosity (cc / g) of the positive electrode material mixture pellets and 1 g of the positive electrode material mixture pellets of Examples and Comparative Examples of the above batteries
The amount of the electrolytic solution impregnated therein and the ratio of the amount of the impregnated electrolytic solution to the positive electrode pore volume (electrolytic solution volume ratio (%)) are shown.

[0012]

[Table 1]

Usually, the amount of the electrolytic solution with which the positive electrode material mixture pellets and the separator are impregnated is set as the liquid injection amount, but the amount of the electrolytic solution shown here indicates the amount absorbed by the positive electrode material mixture pellets only.
In this case, the amount of pores and the amount of electrolytic solution have optimum values, and the amount of manganese that can be filled in a positive electrode material mixture pellet having an excessively large amount of pores becomes too small, which in turn reduces the discharge capacity. In addition, (Table 2) shows the discharge capacity at the end of 0.9 V in constant current discharge at room temperature of AA alkaline batteries manufactured using the positive electrode material mixture pellets.

[0014]

[Table 2]

As is clear from (Table 2), there is no difference in discharge capacity when the discharge current is as weak as 100 mA.
As the strength increases to 1000 mA and 1500 mA, a significant difference is observed between Examples 1 and 2 and Comparative Example. In Examples 1 and 2, it is considered that the structure of acetylene black or Ketjen black was partially cut during mixing, and carbon was surrounded by manganese dioxide. Moldability of these positive electrode material mixture pellets can be improved by adding 1 to 10% by weight of an electrolytic solution to the positive electrode material mixture before molding. Further, the positive electrode mixture is pressure-molded and then inserted into the battery case / positive electrode current collector 1. One of the advantages is that the positive electrode mixture pellets of Examples 1 and 2 do not need to be re-molded after being inserted unlike the conventional positive electrode mixture, because they expand and adhere to the battery case after the electrolyte solution is injected.

[0016]

As is clear from the above results, in alkaline dry batteries, by controlling the porosity of the positive electrode material mixture pellets and the amount of the electrolyte solution impregnated in the positive electrode material mixture pellets, a battery having excellent discharge performance can be obtained. I was able to. The effect of the present invention is to improve the utilization rate of manganese dioxide, thereby optimizing the filling ratio of the positive and negative electrodes to provide a dry battery suitable for relatively high load discharge.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an alkaline dry battery according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the pore amount of positive electrode material mixture pellets and the discharge capacity.

FIG. 3 is a diagram showing the relationship between the amount of electrolytic solution impregnated in the pores of the positive electrode material mixture pellets and the discharge capacity.

[Explanation of symbols]

 1 Battery Case and Positive Electrode Current Collector 2 Positive Electrode Mixture Pellet 3 Separator 4 Gel Zinc Negative Electrode 5 Negative Electrode Current Collector 6 Resin Sealing Body

Front page continuation (72) Inventor Seiji Toge, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. An alkaline dry battery using a positive electrode material mixture pellet obtained by pressure-molding a positive electrode material mixture comprising manganese dioxide as a main component and a conductive material, wherein the positive electrode material mixture pellet has a pore size of 3 nm to 400 μm. The amount of pores is 0.1
An alkaline dry battery of 4 cc / g or more and 0.24 cc / g or less. 2. 0.09 cc or more per gram of positive electrode material mixture.
The alkaline dry battery according to claim 1, wherein the alkaline dry battery is impregnated with an electrolyte solution of 12 cc or less. 3. The alkaline dry battery according to claim 1, wherein the conductive material contains at least one of acetylene black and Ketjen black.