JP2001332249A - Alkaline batteries - Google Patents

Abstract

(57) [Problem] To provide an alkaline dry battery having a high discharge performance, a small amount of gas generation during storage, and an excellent liquid leakage resistance. SOLUTION: This is an alkaline dry battery including a positive electrode mixture containing manganese dioxide and nickel oxyhydroxide as active materials, a negative electrode made of zinc, and an electrolytic solution consisting of an alkaline aqueous solution, wherein the positive electrode mixture contains manganese dioxide and manganese dioxide. An alkaline dry battery comprising 0.5 to 7 parts by weight of polyethylene powder based on a total of 100 parts by weight of nickel oxyhydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an alkaline battery. More specifically, the present invention relates to an alkaline dry battery excellent in heavy load discharge characteristics, storage performance, and liquid leakage resistance.

[0002]

2. Description of the Related Art In recent years, portable information devices, such as digital cameras, which require high load discharge performance have been developed. For devices that require heavy load discharge performance, conventional alkaline dry batteries have a short life and demand higher-power batteries.

As a means for improving the heavy load discharge performance of an alkaline dry battery, the use of a positive electrode active material obtained by adding nickel oxyhydroxide (NiOOH) to manganese dioxide has been proposed and put to practical use. For example, manganese dioxide 50-80% by weight and nickel oxyhydroxide 20-5%
An alkaline dry battery using a positive electrode mixture in which graphite is added as a conductive agent to a positive electrode active material containing 0% by weight is known (Japanese Patent Application Laid-Open No. 57-49168).

However, nickel oxyhydroxide has a problem that self-discharge is easy. When the nickel oxyhydroxide self-discharges, oxygen is generated, and the internal pressure of the battery increases, and as a result, the storage performance and leakage resistance of the battery decrease. Further, since nickel oxyhydroxide is a metastable phase, it is difficult to suppress self-discharge, and effective measures for suppressing this are desired.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to suppress the self-discharge of nickel oxyhydroxide and improve the storage performance of the battery, such as resistance to liquid leakage.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an alkaline dry battery comprising a positive electrode mixture containing manganese dioxide and nickel oxyhydroxide as active materials, a negative electrode comprising zinc, and an electrolytic solution comprising an aqueous alkaline solution. The present invention relates to an alkaline dry battery, wherein the positive electrode mixture contains 0.5 to 7 parts by weight of polyethylene powder based on 100 parts by weight of manganese dioxide and nickel oxyhydroxide in total. Among them, the average particle size of manganese dioxide is 35.
~ 40 µm, average particle size of nickel oxyhydroxide is 8 ~ 1
2 μm, and the average particle size of the polyethylene powder is 8 to 12
μm is preferred.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to manganese dioxide (Mn).
It is characterized in that a predetermined amount of polyethylene powder is contained in a positive electrode mixture containing O ₂ ) and nickel oxyhydroxide (NiOOH) as a positive electrode active material. As a result, N
Self-discharge of iOOH and accompanying oxygen generation are suppressed,
The storage performance and leakage resistance of the battery are improved.

[0008] When a predetermined amount of polyethylene powder is contained in the positive electrode mixture, the occupied volume of the active material particles is reduced because the polyethylene powder occupies a certain volume. As a result, the active material particles come into close contact with each other, and the contact area between the nickel oxyhydroxide particles and the manganese dioxide particles increases.

When a conventional positive electrode mixture containing no polyethylene powder is molded into a predetermined shape, its cross section is considered to be, for example, as shown in FIG. FIG.
In the figure, 11 indicates manganese dioxide particles, 12 indicates nickel oxyhydroxide particles, and 13 indicates particles of a conductive agent such as graphite. Generally, since the manganese dioxide particles 11 are larger than the particles of other components, the manganese dioxide particles 1
It is considered that the space of the space occupied by 1 is filled with particles of another component.

[0010] On the other hand, when the positive electrode mixture of the present invention containing polyethylene powder is molded into a predetermined shape, an enlarged cross section of the positive electrode mixture may be as shown in FIG. 2, for example.
In FIG. 2, reference numeral 14 denotes polyethylene powder particles. As shown in this figure, it is considered that the polyethylene particles 14 also enter the gaps of the space occupied by the manganese dioxide particles 11, similarly to the nickel oxyhydroxide particles 12. The nickel oxyhydroxide particles 12 are pushed away by the polyethylene powder particles 14 and pressed against the surface of the manganese dioxide particles 11. As a result, the contact area between both particles is large.

When the contact area between the manganese dioxide particles and the nickel oxyhydroxide particles increases, the self-discharge of the nickel oxyhydroxide is also suppressed. That is, when the nickel oxyhydroxide particles come into contact with the manganese dioxide particles, the potential of the noble nickel oxyhydroxide is pulled by the lower potential of the manganese dioxide, and the potential of the nickel oxyhydroxide decreases. As a result, reduction of nickel oxyhydroxide is suppressed, and generation of oxygen gas on the particle surface is suppressed.

The positive electrode mixture to which polyethylene powder is added is
Since a strong molded body can be formed, it is considered that the addition of the polyethylene powder also has an effect of suppressing an increase in the internal resistance of the battery during storage.

The particle size of the polyethylene powder is preferably at least 5 μm from the viewpoint of securing the pressure on the active material particles. The manganese dioxide particles and the nickel oxyhydroxide particles are uniformly applied to the entire active material by applying pressure. Is preferably 15 μm or less from the viewpoint of efficiently increasing the contact area. And the average particle size of the polyethylene powder is
It is preferably from 8 to 12 μm.

The mixing ratio of the polyethylene powder to the total of 100 parts by weight of manganese dioxide and nickel oxyhydroxide is preferably 0.5 to 7 parts by weight. In particular, from the viewpoint of sufficiently securing the initial discharge performance, the amount is preferably 0.5 to 2 parts by weight. If the blending ratio of the polyethylene powder is less than 0.5 part by weight, the effect of suppressing self-discharge of nickel oxyhydroxide becomes small, and the deterioration of discharge performance after high-temperature storage tends to increase. On the other hand, when the mixing ratio exceeds 7 parts by weight, the internal resistance of the battery tends to increase, and the initial discharge performance tends to decrease.

The positive electrode active material is manganese dioxide 20-90.
% By weight and from 10 to 80% by weight of nickel oxyhydroxide are preferable from the viewpoint of excellent discharge performance after initial storage and high-temperature storage of the battery. In addition, from the viewpoint of obtaining a battery having particularly excellent initial discharge performance, the positive electrode active material contains 20 to 80% by weight of manganese dioxide and nickel oxyhydroxide 2
Preferably, it is comprised between 0 and 80% by weight.

The particle size of the manganese dioxide particles is from 20 to 50.
It is preferably within the range of μm. Therefore, the average particle size is preferably 35 to 40 μm.
The particle size of the nickel oxyhydroxide particles is 5 to 15 μm.
It is preferably within the range of m. The average particle size is preferably 8 to 12 μm.

The positive electrode mixture of the alkaline dry battery of the present invention includes:
Manganese dioxide and nickel oxyhydroxide, which are active materials,
In addition to the polyethylene powder, an appropriate amount of a conductive agent such as graphite powder may be added. The particle size of the conductive agent particles is
It is preferable that it is within the range of 10 to 25 μm. Therefore, the average particle size is preferably 15 to 20 μm.

As the negative electrode of the alkaline dry battery of the present invention, a known one may be used. For example, a gelled negative electrode comprising a gelling agent such as sodium polyacrylate, an alkaline electrolyte, and zinc powder as a negative electrode active material is preferably used.

FIG. 3 shows an AA according to an embodiment of the present invention.
FIG. 3 is a semi-longitudinal sectional view of an alkaline dry battery having a size. In an alkaline dry battery, the positive electrode mixture is generally formed into a short cylindrical pellet and then housed in a positive electrode case of the dry battery.

In FIG. 3, a positive electrode mixture 2, a separator 4, and a gelled negative electrode 3 formed into a short cylindrical pellet are placed inside a positive electrode case 1 having an insulating label sheath 9 on the outer surface. Is housed. As the positive electrode case 1, a steel case or the like whose inner surface is plated with nickel is used. A plurality of positive electrode mixtures 2 are housed in a state of being in close contact with the inner surface of the positive electrode case 1. A separator 4 is disposed further inside the positive electrode mixture 2, and the inside thereof is further filled with a gelled negative electrode 3.

Here, a predetermined amount of electrolytic solution for wetting the positive electrode mixture 2 and the separator 4 is generally injected into the positive electrode case prior to filling the gelled negative electrode 3. As the electrolyte, an aqueous solution of about 40% by weight of potassium hydroxide is preferably used. After the electrolyte is injected, the gelled negative electrode 3 is filled inside the separator 4.

Subsequently, the negative electrode current collector 6 is inserted into the center of the gelled negative electrode 3. The negative electrode current collector 6 is integrated with a gasket 5, an insulating washer 7, and a bottom plate 8 also serving as a negative electrode terminal. Then, the opening end of the positive electrode case 1 is crimped to the peripheral edge of the bottom plate 8 via the end of the gasket 5 to seal the opening of the positive electrode case 1. Finally,
When the outer surface of the positive electrode case 1 is covered with the outer label 9, an alkaline dry battery is completed.

[0023]

EXAMPLES Next, the alkaline dry battery of the present invention will be described more specifically based on examples.

Example 1 In this example, an AA size alkaline battery was manufactured and its performance was evaluated. First,
50 parts by weight of manganese dioxide (average particle size: 40 μm), 50 parts by weight of nickel oxyhydroxide (average particle size: 10 μm), 5 parts by weight of graphite powder (average particle size: 15 μm), 0.5 part by weight of polyethylene powder (average particle size: 10 μm) Of a positive electrode mixture consisting of 1 part by weight of a 40% by weight aqueous solution of potassium hydroxide and 1 part by weight of an electrolytic solution were uniformly mixed with a mixer and sized to a constant particle size. Note that manganese dioxide has a particle size of 20 to 50 μm, nickel oxyhydroxide has a particle size of 5 to 15 μm, graphite powder has a particle size of 10 to 25 μm, and polyethylene powder has a particle size of 5-1.
Those within the range of 5 μm were classified. Subsequently, the positive electrode mixture sized to a certain particle size was formed into a short cylindrical pellet.

As the gelled negative electrode, a gel comprising 1 part by weight of sodium polyacrylate as a gelling agent, 33 parts by weight of a 40% by weight aqueous solution of potassium hydroxide and 66 parts by weight of zinc powder was used.

The obtained positive electrode mixture pellet, gelled negative electrode,
A battery a having a structure similar to that of the battery shown in FIG. 1 was assembled using a separator mainly composed of polyvinyl alcohol fiber and rayon fiber. And battery a
Was evaluated as follows.

Evaluation Content After the battery a was stored at 60 ° C. for one week, the amount of gas generated inside the battery a was measured. Also, the initial condition of the battery a and 80 ° C.
And the discharge performance after storage for 3 days was compared. The discharge performance was evaluated by a discharge time until reaching a final voltage of 0.9 V when the battery was continuously discharged at a temperature of 20 ° C. and a current of 1000 mA. Table 1 shows the results. Here, each of the gas generation amount and the discharge time at 60 ° C. is an average value of 10 batteries a, and both are the gas amounts and the initial values obtained in the evaluation of the battery e of Comparative Example 1 described later. Are expressed as relative values when the discharge time is 100.

[0028]

[Table 1]

Example 2 A battery b having the same structure as that of the battery a was assembled, except that the blending amount of the polyethylene powder in the positive electrode mixture was changed from 0.5 parts by weight to 2 parts by weight. Was evaluated. Table 1 shows the results.

Example 3 A battery c having the same configuration as the battery a was assembled, except that the blending amount of the polyethylene powder in the positive electrode mixture was changed from 0.5 parts by weight to 5 parts by weight. Was evaluated. Table 1 shows the results.

Example 4 A battery d having the same structure as that of the battery a was assembled, except that the blending amount of the polyethylene powder in the positive electrode mixture was changed from 0.5 parts by weight to 7 parts by weight. Was evaluated. Table 1 shows the results.

Comparative Example 1 A battery e having the same configuration as the battery a was assembled except that no polyethylene powder was added to the positive electrode mixture, and the same evaluation as the battery a was performed. Table 1 shows the results.

Table 1 shows that all of the batteries a to d using the positive electrode mixture to which the polyethylene powder was added were 60 ° C. higher than the battery e using the positive electrode mixture to which the polyethylene powder was not added.
Indicates that the amount of generated gas after storage for one week is small, and the discharge performance is excellent. In addition, from the viewpoint of sufficiently securing the initial discharge performance, the blending amount of the polyethylene powder in the positive electrode mixture is 0.5 to 100 parts by weight of the active material.
It is understood that 2 parts by weight is particularly preferable.

[0034]

According to the present invention, an alkaline dry battery having a high discharge performance and a small amount of gas generated during storage can be obtained. In addition, the alkaline dry battery of the present invention has a small amount of gas generated during storage, so that the internal pressure of the battery can be kept low, and the battery is excellent in liquid leakage resistance.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic view of a cross section of a positive electrode mixture containing no polyethylene powder molded into a predetermined shape.

FIG. 2 is an enlarged schematic diagram of a cross section of a positive electrode mixture containing a polyethylene powder molded into a predetermined shape.

FIG. 3 is a semi-longitudinal sectional view of an AA alkaline battery according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode case 2 Positive electrode mixture 3 Gelled negative electrode 4 Separator 5 Gasket 6 Negative current collector 7 Insulating washer 8 Bottom plate 9 Label covering 11 Manganese dioxide particles 12 Nickel oxyhydroxide particles 13 Conductive agent particles 14 Polyethylene powder particles

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shinichi Sumitomo 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. F term (reference) 5H024 AA02 AA03 AA14 CC02 DD17 EE09 FF07 HH01 HH13 5H050 AA09 AA20 BA04 CA03 CA05 CB13 DA02 DA09 EA23 FA07 FA17 HA01 HA05

Claims (2)

[Claims] 1. An alkaline dry battery comprising a positive electrode mixture containing manganese dioxide and nickel oxyhydroxide as active materials, a negative electrode made of zinc, and an electrolytic solution consisting of an aqueous alkaline solution, wherein the positive electrode mixture is made of manganese dioxide. And 0.5 to 7 parts by weight of polyethylene powder based on a total of 100 parts by weight of nickel oxyhydroxide. 2. The manganese dioxide has an average particle size of 35 to 40.
μm, average particle size of nickel oxyhydroxide is 8 to 12μ
m, and the average particle size of the polyethylene powder is 8 to 12 μm
The alkaline dry battery according to claim 1, wherein