JP2002008650A - Positive active material and nickel zinc cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel zinc cell having excellent heavy-load characteristics. SOLUTION: The cell is a nickel zinc cell 1 having a positive electrode containing β-type nickel oxyhydroxide and a negative electrode containing zinc, and an inside-out structure which is the same structure as an alkali manganese cell. The shape of β-type nickel oxyhydroxide is substantially spherical, and the average particle diameter thereof is within a range of 19-40 μm. The bulk density of the β-type nickel oxyhydroxide falls within a range of 1.6-2.2 g/cm3, and the tap density is within a range of 2.2-2.7 g/cm3. The specific surface area of the β-type nickel oxyhydroxide as measured by the BET method is within a range of 3-50 cm2/g. The positive electrode contains graphite in a proportion of 4-8% by weight based on the total weight of the positive electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode active material comprising beta-type nickel oxyhydroxide. The present invention also relates to a nickel zinc battery having a positive electrode using beta-type nickel oxyhydroxide as a positive electrode active material and a negative electrode using zinc as a negative electrode active material.

[0002]

2. Description of the Related Art In recent years, the spread of small portable electronic devices, particularly portable game machines and digital cameras, has been extremely remarkable. It is expected that the battery will become more and more popular in the future, and with that, the demand for a battery as a power source is expected to increase rapidly. At present, AA size cylindrical batteries are mainly used for these devices, but since these electronic devices generally have a high operating voltage and require a large current, they are used as power sources under heavy loads. It must have excellent discharge characteristics.

The most widespread battery satisfying this requirement is an alkaline manganese battery using manganese dioxide as a positive electrode and zinc as a negative electrode, and using a high-concentration alkaline aqueous solution as an electrolyte. Since this battery is inexpensive for both manganese dioxide and zinc, and has a high energy density per unit weight, it is widely used, including power supplies for small portable electronic devices.

In view of the use in such small portable devices,
Numerous improvements have been made to alkaline manganese batteries from the battery material to the battery configuration in order to further improve the heavy load discharge characteristics. However, in this battery system, since the discharge of manganese dioxide, which is the positive electrode active material, is a uniform solid-phase reaction, the voltage gradually decreases due to the discharge and draws a downward-sloping discharge curve. For this reason, as described above, in a small portable electronic device that requires a high voltage and a large current, the discharge behavior of such an alkaline manganese battery is basically only slightly tolerable, and the usable time of the device is basically short. Even today, various improvements have been very small. In addition, small portable electronic devices tend to operate at relatively high voltage and high current in the early stages of their introduction to the market, and batteries with superior heavy load characteristics that can support such new devices in the future. Is essential.

As a battery satisfying such requirements, a nickel zinc battery has been conventionally proposed. This battery is
This is a battery using nickel oxyhydroxide for the positive electrode and zinc for the negative electrode. The battery has a higher operating voltage than the alkaline manganese battery and is excellent in heavy load characteristics. But on the other hand,
Nickel oxyhydroxide, which is a positive electrode active material, has a problem that oxygen is easily generated and self-discharge is large. As a method for solving this problem, for example, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 0-214621 discloses a gamma-type nickel oxyhydroxide (γ-NiOOH) having a low self-discharge.
There has been proposed a nickel zinc battery having an inside-out structure in which is used as a positive electrode active material.

[0006]

However, since the gamma-type nickel oxyhydroxide has a relatively low density, a battery constituted by using this gamma-type nickel oxyhydroxide certainly has a small self-discharge and a higher operation than an alkaline manganese battery. Although a potential is obtained, there is a disadvantage that the discharge capacity is considerably reduced.

Accordingly, the present invention provides a nickel zinc battery having a higher discharge potential than an alkaline manganese battery and excellent large current discharge characteristics, and has a higher density than a gamma type nickel oxyhydroxide synthesized by a method described later. ,
By using beta-type nickel oxyhydroxide (β-NiOOH), an object is to supply a nickel-zinc battery having a higher capacity.

[0008]

Means for Solving the Problems The positive electrode active material of the present invention comprises:
It is composed of beta-type nickel oxyhydroxide, and the beta-type nickel oxyhydroxide has a substantially spherical particle shape.

In the above-mentioned positive electrode active material, the average particle size of the beta type nickel oxyhydroxide is in the range of 19 to 40 μm.

The above-mentioned positive electrode active material has a bulk density of beta-type nickel oxyhydroxide in the range of 1.6 to 2.2 g / cm ³ . Further, the tap density of the beta type nickel oxyhydroxide is in the range of 2.2 to 2.7 g / cm ³ .

The above-mentioned positive electrode active material has a specific surface area of the beta-type nickel oxyhydroxide of 3 to 50 m ² / BET method.
g.

The nickel-zinc battery of the present invention comprises a positive electrode obtained by forming a mixed powder containing at least a beta-type nickel oxyhydroxide serving as a positive electrode active material and a graphite powder serving as a conductive agent into a hollow cylindrical shape on an outer peripheral portion thereof. A gelled negative electrode containing at least a gelling agent for keeping the active material zinc and the electrolytic solution and the zinc and the electrolytic solution uniformly dispersed therein was disposed at the center, and a separator was disposed between the positive electrode and the negative electrode. In the nickel-zinc battery having an inside-out structure, the beta-type nickel oxyhydroxide has a substantially spherical particle shape.

In the above-mentioned nickel zinc battery, the average particle size of the beta type nickel oxyhydroxide is in the range of 19 to 40 μm.

In the above-mentioned nickel zinc battery, the bulk density of the beta-type nickel oxyhydroxide is 1.6 to 2.2 g / c.
m ³ . Further, the tap density of the beta type nickel oxyhydroxide is in the range of 2.2 to 2.7 g / cm ³ .

In the above-mentioned nickel zinc battery, the specific surface area of the beta type nickel oxyhydroxide according to the BET method is 3 to 50.
m ² / g.

In the above nickel zinc battery, the positive electrode contains 4 to 8% by weight of graphite powder based on the total weight of the positive electrode.

According to the positive electrode active material and the nickel zinc battery of the present invention, since the particles of the positive electrode active material composed of beta-type nickel oxyhydroxide have a substantially spherical shape, the nickel oxyhydroxide has a high density. As a result, the weight of the positive electrode mixture per battery is large, that is, the positive electrode capacity is large.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention relating to a positive electrode active material and a nickel zinc battery will be described. FIG. 1 is a longitudinal sectional view showing a nickel sub-chlorite battery 1 as one configuration example of the battery according to the present embodiment. The nickel zinc battery 1 includes a battery can 2, a positive electrode section 3, a separator 4
And a negative electrode mixture 5, a sealing member 6, a washer 7, a negative electrode terminal plate 8, and a current collecting pin 9.

The battery can 2 is made of, for example, nickel-plated iron and serves as an external positive terminal of the nickel-zinc battery 1. The positive electrode part 3 has a hollow cylindrical shape, and is formed into a hollow cylindrical shape by mixing a positive electrode mixture including beta-type nickel oxyhydroxide, graphite powder as a conductive agent, and an aqueous solution of potassium hydroxide as an electrolytic solution. The positive electrode pellets 3 a, 3 b, 3 c are laminated inside the battery can 2.

The separator 4 has a hollow cylindrical shape.
It is arranged inside the positive electrode part 3. The negative electrode mixture 5 is formed of a granular zinc serving as a negative electrode active material, an electrolytic solution using an aqueous potassium hydroxide solution, and a gel for preparing the negative electrode mixture 5 in a gel state to uniformly disperse the granular zinc and the electrolytic solution. Agent.

The opening of the battery can 2 in which the positive electrode portion 3 and the separator 4 filled with the negative electrode mixture 5 are accommodated is fitted by a sealing member 6 to seal the opening. ing. The sealing member 6 is made of a plastic material, and a washer 7 and a negative electrode terminal plate 8 are attached so as to cover the sealing member 6. Further, a current collecting pin 9 made of brass is press-fitted from above into a through hole of the sealing member 6 to which the washer 7 is attached.

Thus, the current collection of the negative electrode is performed by the negative electrode terminal plate 8.
Is secured by being pressed into a through hole formed in the central part of the sealing member 6 and reaching the negative electrode mixture. In addition, current collection of the positive electrode is ensured by connecting the positive electrode part 3 and the battery can 2. The outer peripheral surface of the battery can 2 is covered with an exterior label (not shown), and the positive electrode terminal is located below the battery can 2. The positive electrode reaction, negative electrode reaction, total reaction and theoretical electromotive force in this battery are as follows.

Positive electrode: NiOOH + H ₂ O + e ⁻ → Ni
^{_{(OH) 2 + OH - E}} 0 = 0.49V ^{anode: Zn + 20H - → ZnO +} H 2 O + 2e - E 0 = -1.25V Total _{reaction: 2NiOOH + Zn + H 2 O} → 2Ni (OH)
₂ + ZnO theory electromotive force: E ₀ = 1.74V

As described above, nickel hydroxide and zinc oxide are generated from nickel oxyhydroxide and zinc by the discharge reaction.

It is a well-known fact that nickel oxyhydroxide, which is a positive electrode active material, is used as an active material for secondary batteries such as nickel-metal hydride batteries and nickel cadmium batteries, and exhibits excellent discharge performance. There are two types of nickel oxyhydroxide, beta type and gamma type, and these are usually easily obtained by electrolytic oxidation of nickel hydroxide (electrolytic oxidation method). Nickel, particularly beta-type nickel oxyhydroxide, has a large self-discharge and generates oxygen gas in association with the self-discharge, which is not preferable in terms of storage characteristics and leakage resistance of the battery. Therefore, in order to use it as an active material for a primary battery, it is necessary to reduce self-discharge.
Among nickel oxyhydroxides, a gamma-type nickel oxyhydroxide having less self-discharge has been used.

The self-discharge of nickel oxyhydroxide and the accompanying evolution of oxygen are contained in the crystal. NO ₃
^-, CO ₃ ^2-like ions, it is believed to occur by decomposition in the battery. Although these substances have impurities that remain in the crystal during the process of producing nickel hydroxide,
It is thought that reducing these substances will improve the self-discharge characteristics of nickel oxyhydroxide.

Thus, the authors oxidize nickel hydroxide in a liquid phase containing a suitable oxidizing agent, such as sodium hypochlorite, and a suitable alkali species, such as lithium hydroxide, sodium hydroxide, potassium hydroxide. When nickel oxyhydroxide is synthesized by a method (chemical oxidation method), the above-described impurity ions flow out into the synthetic liquid phase and are removed to some extent from the crystal, regardless of the beta type or the gamma type, in the process. As a result, less self-discharge than before,
It has been found that nickel oxyhydroxide more suitable for an active material for a primary battery can be obtained. Incidentally, the oxidation reaction at this time is as follows. 2Ni (OH) ₂ + ClO ⁻ → 2NiOOH + Cl ⁻ +
H ₂ O

At this time, the generated nickel oxyhydroxide varies depending on the pH in the liquid phase. That is, when the pH is lower than a certain value, high-density beta-type nickel oxyhydroxide (theoretical density: 4.68 g / cm ³ ) is obtained, and in the region above the low-density gamma-type nickel oxyhydroxide (theoretical density:
3.79 g / cm ³ ). In the nickel zinc battery 1 according to the present invention, in order to obtain a larger battery capacity,
Nickel oxyhydroxide, which is a positive electrode active material, is one of the nickel oxyhydroxides obtained by the chemical oxidation method,
It is desirable to use a dense beta type.

At this time, it is desirable to use nickel hydroxide as a starting material, which is called high-density nickel hydroxide in which the shape of each particle is substantially spherical. Normal nickel hydroxide is non-spherical and has a Tap density of 1.
While the density is 4 to 1.8 (g / cm ³ ) and the bulk density is 1.0 to 1.4 (g / cm ³ ), the above-mentioned high-density nickel hydroxide has substantially spherical particles. , Tap density 2.0 to 2.5 (g / c)
m ³ ), Bulk density 1.4-1.8 (g /
cm ³ ), which is higher than normal products.

The tap density and the bulk (B)
The method of measuring the ULK density (also referred to as “bulk density”) is as follows. That is, the target powder is naturally dropped and filled in a specific container, the mass at this time is A (g), the volume is B (cm ³ ), the container is lifted, and the bottom of the container is placed on a desk or the like.
C (cm)
³ ) is defined by the following equation. Bulk density = A / B (g / cm ³ ) Tap density = A / C (g / cm ³ )

It is preferable that the tap (Tap) density and the bulk (Bulk) density of the beta-type nickel oxyhydroxide, which is the positive electrode active material of the present embodiment, fall within the following ranges. That is, the beta (nickel) oxyhydroxide desirably has a tap (Tap) density in the range of 2.2 to 2.7 g / cm ³ . The bulk density of the beta-type nickel oxyhydroxide is 1.6 to 2.2 g / cm.
It is desirable to be in the range of ³ .

If the tap density and the bulk density are smaller than the lower limits of these ranges, it is difficult to increase the discharge capacity. Further, it is difficult to produce beta-type nickel oxyhydroxide having a tap density and a bulk density higher than the upper limits of these ranges.

FIG. 2 is a diagram showing a substantially spherical beta-type nickel oxyhydroxide (A) according to the present embodiment and a conventional non-spherical beta-type nickel oxyhydroxide (B).
Here, in FIG. 2A and FIG. 2B, the upper row shows electron micrographs of the beta-type nickel oxyhydroxide of the present embodiment and the conventional beta-type nickel oxyhydroxide, respectively. The outline of the particles in the photograph is shown for easy understanding.

As can be seen from FIG. 2A, the beta-type nickel oxyhydroxide according to the present embodiment has a substantially spherical particle shape. That is, the surfaces of the particles are relatively smooth with sharp corners, and the overall shape is slightly elongated and slightly flat, but generally spherical.

On the other hand, as can be seen from FIG. 2B,
Conventional beta-type nickel oxyhydroxide is non-spherical. That is, the shape is such that a large mass is crushed and shattered, each particle is angular, and the overall shape is various such as a shape close to a flat plate, a slender shape, and a shape close to a cube.

FIG. 3 shows an example of the particle size distribution of the beta type nickel oxyhydroxide according to the present embodiment. The beta-type nickel oxyhydroxide, which is the positive electrode active material according to the present embodiment, desirably falls within the following ranges of the average particle size and the particle size distribution. That is, the average particle size of the beta-type nickel oxyhydroxide is desirably in the range of 19 to 40 μm. If the average particle size is smaller than 19 μm or larger than 40 μm, battery production becomes difficult. The particle size distribution of the beta-type nickel oxyhydroxide is preferably in the range of 5 to 80 μm.

The average particle size of the beta type nickel oxyhydroxide is preferably in the range of 19 to 25 μm, and more preferably the particle size distribution is in the range of 5 to 70 μm. The minimum value of the particle size distribution is a value of 5% below the sieve, and the maximum value of the particle size distribution is a value of 95% below the sieve.

In the case where beta-type nickel oxyhydroxide is obtained by the above method, if the starting material is high-density nickel hydroxide, the tap (Tap) density and the bulk (Bul) are increased.
k) Nickel oxyhydroxide having a high density is obtained, which is convenient for increasing the capacity of a battery.

The beta-type nickel oxyhydroxide B
The specific surface area by the ET method is desirably in the range of 3 to 50 m ² / g. The specific surface area by the BET method is 3 m ² /
If the value is smaller than g, it becomes difficult to increase the discharge capacity particularly at the time of large current discharge. On the other hand, if the specific surface area by the BET method is larger than 50 m ² / g, even if it is beta-type nickel oxyhydroxide, the self-discharge amount becomes relatively large, and it becomes difficult to obtain sufficient storage characteristics.

In addition, another problem of the positive electrode is that both nickel oxyhydroxide and nickel hydroxide as a discharge product thereof have low electron conductivity.
Therefore, in order to increase the utilization rate of the positive electrode active material, graphite powder is mixed in the positive electrode mixture, and the content of the graphite powder at this time may be 4 to 8% by weight based on the total weight of the positive electrode. preferable.

When the content of the graphite powder is less than 4% by weight, the effect of improving the electron conductivity in the positive electrode is not sufficient. When the content is more than 8% by weight, the effect of improving the electron conductivity in the positive electrode is not sufficient. However, the filling amount of nickel oxyhydroxide as the positive electrode active material decreases, and the battery capacity decreases. In the nickel zinc battery 1 according to the present invention, by setting the content of the graphite powder in the positive electrode mixture as described above, it is possible to obtain appropriate electron conductivity and battery capacity.

In the embodiment of the present invention described above, the nickel-zinc battery as the primary battery has been described. However, the present invention is not limited to this primary battery. Of course, the present invention can be applied. Further, in the embodiment of the invention described above, a cylindrical nickel zinc battery was described, but the present invention is not limited to this cylindrical battery, and other shapes such as a flat nickel zinc battery are also applicable.
Of course, the present invention can be applied. In addition, the present invention is not limited to the above-described embodiment, but can adopt various other configurations without departing from the gist of the present invention.

[0043]

Next, specific examples of the present invention will be described. Here, batteries were manufactured by changing the positive electrode portion, and the characteristics of these batteries were evaluated. However, it goes without saying that the present invention is not limited to these examples.

(Consideration on Positive Electrode Active Material) First, electrolytic manganese dioxide and beta-type nickel oxyhydroxide obtained by chemically oxidizing high-density nickel hydroxide (shape: substantially spherical, tap density: 2.5 g / cm) ^3. Bulk density: 2.
0 g / cm ³ , average particle size: 20 μm, particle size distribution: 5-7
0 μm) and gamma-type nickel oxyhydroxide (shape:
Substantially spherical, tap density: 1.8 g / cm ³ , bulk density:
1.6 g / cm ³ ) and beta-type nickel oxyhydroxide obtained by chemically oxidizing nickel hydroxide (shape: non-spherical, tap density: 1.8 g / cm ³ , bulk density:
1.4 g / cm ³ ), graphite (high-purity powdered graphite having an average particle size of 6 μm, a particle size distribution of 1 to 25 μm, and an ash content of 0.3% by weight or less) and an aqueous potassium hydroxide solution (40% by weight). Then, the positive electrode mixture was sufficiently mixed with the compositions shown in Table 1 to form a positive electrode mixture, and the positive electrode mixture was pressurized under the same conditions and molded into a hollow cylinder to produce a positive electrode portion.

[0045]

[Table 1]

Then, the positive electrode was inserted inside the battery can. Next, a non-woven fabric separator (a polyolefin-based separator subjected to hydrophilic treatment) is provided inside the positive electrode portion.
Was inserted, and about 1 g of the electrolytic solution was injected, and further, a gelled negative electrode mixture prepared by mixing zinc, a gelling agent, and the electrolytic solution was filled therein. Finally, the opening of the battery can was sealed with a sealing member to which a spring and a collecting pin were attached to produce AA alkaline batteries.

Here, in Table 1, the composition (% by weight) of each material constituting the positive electrode part and the nickel zinc battery 1
The amount (g) of the positive electrode mixture per unit is shown. Sample 1 is an alkaline manganese battery, and sample 2 is nickel using beta-type nickel oxyhydroxide obtained by chemically oxidizing high-density nickel hydroxide. Zinc batteries (hereinafter “β
-Nickel-zinc battery (1) "), sample 3 is a nickel-zinc battery using gamma-type nickel oxyhydroxide obtained by chemically oxidizing high-density nickel hydroxide (hereinafter, referred to as" nickel-zinc battery (1) ").
Sample 4 is a nickel-zinc battery using a beta-type nickel oxyhydroxide obtained by chemically oxidizing nickel hydroxide (hereinafter referred to as “β-nickel zinc battery”).
-Nickel zinc battery (2) "). By the way, in each sample, the filling amount of the positive electrode mixture per one battery is different because the density of the used positive electrode active material is different for each sample.

A discharge test and a mounting test using a digital camera were performed on the batteries of Samples 1 to 4 manufactured as described above. As a discharge test, the battery voltage was 1 at a constant power of 1500 mW. The discharge was performed until the voltage became 0.0V. As a mounting test, a commercially available digital camera (with LCD monitor, 4 AA batteries (trade name:
CAMEDIA C-2000 ZOOM, manufactured by Olympus Optical Industrial Co., Ltd.)
Here, the usage conditions in the mounting test were as follows: the still image shooting mode was set to flash OFF, the liquid crystal monitor was turned on, and
Photographs were taken every minute at 0 ° C).

The discharge curves and discharge capacities of the batteries of Samples 1 to 4 are shown in FIG. FIG. 5 shows mounting test results of the digital camera for the batteries of Samples 1 to 4.

[0050]

[Table 2]

As shown in Table 2 and FIG. 4, the β-nickel zinc battery of sample 2 using nickel oxyhydroxide for the positive electrode (1), the γ-nickel zinc battery of sample 3, and the β-nickel zinc battery of sample 4 (2 ) Is sample 1
It was found that the battery exhibited extremely excellent heavy-load discharge characteristics as compared with the alkaline manganese battery of No. 1. In addition, as shown in FIG. 5, it can be seen that Sample 2, Sample 3, and Sample 4 can be used for a longer time than Sample 1 even when they are mounted on an actual small portable electronic device. Was.

When Sample 2 is compared with Samples 3 and 4, Sample 2 shows more excellent discharge characteristics. This is because, among the nickel oxyhydroxides used, the nickel oxyhydroxide of Sample 2 has the highest density, and as a result, the weight of the positive electrode mixture per battery is higher in Sample 2 than in Samples 3 and 4. Is large, that is, the positive electrode capacity is large.

Next, the specific surface area of the positive electrode active material will be considered. Various types of beta-type nickel oxyhydroxide (shape: substantially spherical) obtained by chemically oxidizing high-density nickel hydroxide having a specific surface area of 1 to 60 m ² / g (BET method) are prepared. Beta-type nickel oxyhydroxide, graphite, and an aqueous solution of potassium hydroxide (40% by mass) were sufficiently mixed at a mass ratio of 85: 8: 7 to form a positive electrode mixture. Samples 5 to 20 were used as the alkaline batteries. The specific surface area of the gamma-type nickel oxyhydroxide obtained by chemically oxidizing high-density nickel hydroxide is 3%.
AA alkaline batteries were prepared in the same manner as in Sample 3 except that various types were prepared in the range of ５０50 m ² / g (BET method) and used as the positive electrode active material. 24. In addition, the specific surface area of the beta-type nickel oxyhydroxide obtained by generally electrolytically oxidizing nickel hydroxide is 3 to 50 m ² / g (BET).
A) AA alkaline batteries were prepared in the same manner as in Sample 4 except that various different materials were prepared in the range of Example 25).
And 8.

Samples 5 to 5 prepared as described above
A discharge test was performed on the battery of Sample 28. In the discharge test, the battery was discharged at a constant power of 1500 mW in an atmosphere of 20 ° C. until the battery voltage became 1.0 V. Is 2 in an atmosphere of 20 ° C.
After a lapse of a week, the test was further performed on an atmosphere stored at 60 ° C. for 20 days.

Table 3 and FIGS. 6 to 8 show the discharge test results for the batteries of Samples 5 to 28.

[0056]

[Table 3]

According to Table 3 and FIGS.
Using beta-type nickel oxyhydroxide by the aluminum method
5 to 20, the specific surface area by the BET method is 3 to 5
0m ^Two/ G beta-type nickel oxyhydroxide
Samples 7 to 18 have excellent heavy load discharge characteristics.
It was found to show the properties and storage characteristics. Chemical oxidation method for positive electrode
Using gamma-type nickel oxyhydroxide by HPLC
21 to 24 have excellent storage characteristics
However, sufficient heavy load discharge characteristics could not be obtained. Also positive
Electrolytic oxidation of beta-type nickel oxyhydroxide
In Samples 25 to 28,
Load discharge characteristics are obtained, but storage characteristics are extremely low
Was.

From the above results, in the nickel zinc battery according to the present embodiment, the nickel oxyhydroxide used as the positive electrode active material was beta-type nickel oxyhydroxide obtained by chemically oxidizing high-density nickel hydroxide. Has been found to be preferable.

(Consideration Regarding Graphite Content) A beta-type nickel oxyhydroxide obtained by chemically oxidizing high-density nickel hydroxide, graphite, and an aqueous solution of potassium hydroxide were each sufficiently mixed with the composition shown in Table 4. The mixture was mixed to form a positive electrode mixture, and the positive electrode mixture was molded into a hollow cylindrical shape to produce a positive electrode portion. As the beta-type nickel oxyhydroxide obtained by chemically oxidizing the high-density nickel hydroxide, the same one as used in Sample 2 in the above discussion on the positive electrode active material was used. The same graphite and aqueous solution of potassium hydroxide as those used in the discussion on the positive electrode active material were used. Hereinafter, AA alkaline batteries were manufactured in the same manner as in the discussion on the positive electrode active material, and these batteries were referred to as Samples 29 to 37.

[0060]

[Table 4]

Then, the batteries of Samples 29 to 37 were prepared in the same manner as Samples 1 to 4.
Discharge was performed at a constant power of 1500 mW until the battery voltage reached 1.0 V. Table 5 and FIG. 9 show the discharge capacities of the batteries of Samples 29 to 37.

[0062]

[Table 5]

From Table 5 and FIG. 9, it was found that the amount of graphite contained in the positive electrode mixture was effective when contained in the range of 4% by weight to 8% by weight based on the total weight of the positive electrode. This is because nickel oxyhydroxide and nickel hydroxide, which is a discharge product thereof, both have low electron conductivity. Therefore, when the graphite content is less than 4% by weight, the effect of improving the electron conductivity in the positive electrode is obtained. Is not enough. On the other hand, if the graphite content is more than 8% by weight,
Although the effect of improving the electron conductivity in the positive electrode is sufficient, it is considered that the battery capacity was reduced as a result of the decrease in the amount of nickel oxyhydroxide as the positive electrode active material was reduced.

From these results, it was found that the amount of graphite contained in the positive electrode mixture was desirably about 4 to 8% by weight based on the total weight of the positive electrode.

As described above, the battery of the present invention was oxidized in a liquid phase containing an oxidizing agent such as sodium hypochlorite and an alkali species such as lithium hydroxide, sodium hydroxide and potassium hydroxide. A nickel-zinc battery having an inside-out structure, which has a positive electrode containing beta-type nickel oxyhydroxide and a negative electrode containing zinc, and has a structure similar to that of an alkaline manganese battery. A battery having a higher discharge capacity and discharge potential than the above and having excellent discharge characteristics at a large current can be supplied. In addition, by using a highly versatile battery, it is possible to realize long-term use in a small portable electronic device requiring a large current and a high voltage, such as a portable game machine and a digital camera.

[0066]

The present invention has the following effects. Since the positive electrode active material composed of beta-type nickel oxyhydroxide has a substantially spherical particle shape, excellent heavy load discharge characteristics can be obtained in a nickel zinc battery using the same.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one configuration example of a battery according to the present embodiment.

FIG. 2 is a diagram showing a substantially spherical beta-type nickel oxyhydroxide (A) according to the present embodiment and a conventional non-spherical beta-type nickel oxyhydroxide (B).

FIG. 3 is a diagram showing an example of a particle size distribution of beta-type nickel oxyhydroxide according to the present embodiment.

FIG. 4 shows the batteries of sample 1 to sample 4
It is a figure which shows the discharge curve at the time of discharging to 1.0V by the electric power of 00mW.

FIG. 5 is a diagram showing test results of a mounting test using a digital camera for the batteries of Sample 1 to Sample 4.

FIG. 6 is a diagram showing the relationship between the specific surface area of the positive electrode active material and the discharge capacity for the batteries of Samples 5 to 20.

FIG. 7 shows the batteries of Samples 21 to 24;
FIG. 4 is a diagram showing a relationship between a specific surface area of a positive electrode active material and a discharge capacity.

FIG. 8 shows the batteries of Samples 25 to 28.
FIG. 4 is a diagram showing a relationship between a specific surface area of a positive electrode active material and a discharge capacity.

FIG. 9 is a diagram showing the relationship between the graphite content in the positive electrode mixture and the discharge capacity.

[Explanation of symbols]

1 Nickel zinc battery, 2 Battery can, 3 Positive electrode part, 4 Separator, 5 Negative electrode mixture, 6 Sealing member, 7 Washer, 8 Negative electrode terminal plate, 9 ‥‥ Current collection pin

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01M 10/30 H01M 10/30 Z (72) Inventor Honda Kazuyoshi Honda 2nd Hinoguchi, Motomiyacho, Adachi-gun, Fukushima Prefecture Sony Fukushima (72) Inventor Kuniyasu Oya 2nd Hinoguchi, Motomiya-cho, Adachi-gun, Fukushima Prefecture Sony Fukushima Corporation F-term (reference) 5H024 AA01 AA14 CC02 DD14 EE03 GG01 HH01 HH08 HH13 5H028 AA01 CC17 EE01 EE05 FF09 HH01 HH03 H05 5H050 AA02 BA04 BA11 CA03 CB13 DA10 DA14 EA09 FA07 FA17 HA01 HA05 HA07 HA08

Claims (9)

[Claims] 1. A positive electrode active material comprising beta-type nickel oxyhydroxide, wherein the beta-type nickel oxyhydroxide has a substantially spherical particle shape. 2. The positive electrode active material according to claim 1, wherein the average particle size of the beta type nickel oxyhydroxide is in a range of 19 to 40 μm. 3. The beta-type nickel oxyhydroxide has a bulk density in the range of 1.6 to 2.2 g / cm ³ , and the beta-type nickel oxyhydroxide has a tap density of 2.2 to 2.2 g / cm ^3.
The positive electrode active material according to claim 1, wherein the positive electrode active material is in a range of 2.7 g / cm ³ . 4. BET of beta-type nickel oxyhydroxide
The positive electrode active material according to claim 1, wherein a specific surface area by a method is in a range of 3 to 50 m ² / g. 5. A positive electrode obtained by molding a mixed powder containing at least a beta-type nickel oxyhydroxide as a positive electrode active material and a graphite powder as a conductive agent into a hollow cylindrical shape on the outer periphery, and zinc as a negative electrode active material. Nickel having an inside-out structure in which a gelled negative electrode including at least an electrolytic solution and zinc and a gelling agent for uniformly dispersing the electrolytic solution are disposed at the center, and a separator is disposed between the positive electrode and the negative electrode. In the zinc battery, the beta-type nickel oxyhydroxide has a substantially spherical particle shape. 6. The nickel zinc battery according to claim 5, wherein the average particle size of the beta type nickel oxyhydroxide is in a range of 19 to 40 μm. 7. The beta-type nickel oxyhydroxide has a bulk density in the range of 1.6 to 2.2 g / cm ³ , and the beta-type nickel oxyhydroxide has a tap density of 2.2 to 2.7.
The nickel zinc battery according to claim 5, wherein the nickel zinc battery is in a range of g / cm ³ . 8. BET of beta-type nickel oxyhydroxide
7. The nickel zinc battery according to claim 5, wherein a specific surface area by a method is in a range of 3 to 50 m ² / g. 9. The nickel zinc battery according to claim 5, wherein the positive electrode contains 4 to 8% by weight of graphite powder based on the total weight of the positive electrode.