JP2001052694A - Nickel hydroxide powder in cobalt solid solution for positive electrode active material of alkaline storage battery, and manufacture of the powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide nickel hydroxide powder with an enhanced utilization factor of nickel hydroxide without resorting to improvement of the electroconductivity between active materials or between a positive electrode base material and active material. SOLUTION: Nickel hydroxide powder in the form of solid solution contains 0.5-10 wt.% solid-solution cobalt in metal conversion, 0-10 wt.% solid-solution zinc, cadmium, magnesium, calcium, and/or manganese, and no more than 0.2 wt.% lithium. The content of trivalent nickel and trivalent cobalt in total is below 10% of the total quantity of nickel and cobalt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cobalt solid solution nickel hydroxide powder for a positive electrode active material of an alkaline storage battery and a method for producing the same.

[0002]

2. Description of the Related Art Nickel hydroxide powder has conventionally been used as a positive electrode active material for alkaline storage batteries such as nickel-cadmium storage batteries and nickel-hydrogen storage batteries as a power source for various electronic devices, for example, small devices such as mobile phones and personal computers. It is widely used and, more recently, is being used as a large power source for electric vehicles. Therefore, recently, increasing the capacity of such alkaline storage batteries has become an important issue,
In particular, there is a strong demand for an improvement in the utilization of nickel hydroxide, which is a positive electrode active material.

As a method for improving the utilization rate of nickel hydroxide as a positive electrode active material of an alkaline storage battery, for example, Japanese Patent Application Laid-Open No. 7-22027 discloses a method of mixing nickel hydroxide with cobalt hydroxide as a conductive agent. Proposed. According to this method, cobalt hydroxide is oxidized to cobalt oxyhydroxide when the battery is charged to form a conductive matrix, and as a result, conductivity between the active materials is increased.

[0004] Also, Japanese Patent Application Laid-Open No. 62-234867,
JP-A-62-237667, JP-A-62-222
No. 566, Japanese Patent Application Laid-Open No. 7-22027 and the like propose that nickel compounds are coated on the surfaces of nickel hydroxide and particles mainly composed of nickel hydroxide to further improve the conductivity.

[0005] As described above, conventionally, cobalt hydroxide powder is added to nickel hydroxide powder, or a coating of cobalt hydroxide is formed on the surface of nickel hydroxide particles to provide conductivity between the active materials and the positive electrode base material. It has been proposed to increase the utilization of nickel hydroxide particles as an alkaline storage battery positive electrode active material by increasing the conductivity between the active material and the active material.

[0006]

However, if the conductivity of the active material is further increased by the above-described method, the amount of cobalt hydroxide added to nickel hydroxide and the amount of coating must be increased. In this case, not only the amount of the nickel hydroxide active material charged into the electrode substrate is relatively reduced, but also the raw material cost and the production cost are increased, and the cost merit is low.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem in improving the utilization rate of the conventional nickel hydroxide powder for a positive electrode active material of an alkaline storage battery. Compared to conventional nickel hydroxide powder, without depending on the improvement in conductivity between the active material and
An object of the present invention is to provide a nickel hydroxide powder whose utilization factor has been improved to a much higher level and a method for producing the same.

[0008]

According to the present invention, cobalt is solid-dissolved in a range of 0.5 to 10% by weight in terms of metal and at least one selected from zinc, cadmium, magnesium, calcium and manganese. Seed element
A nickel hydroxide powder containing 10% by weight of a solid solution and further containing lithium in a range of 0.2% by weight or less, based on the total amount of nickel and cobalt; Is provided in a range of 10% or less in total.

According to the present invention, such a nickel hydroxide powder for a positive electrode active material of an alkaline storage battery comprises a water-soluble nickel salt and a water-soluble cobalt salt in a metal conversion of 0.5 to 10% by weight.
And at least one selected from zinc, cadmium, magnesium, calcium and manganese
An aqueous solution containing a water-soluble salt of a species element in the range of 0 to 10% by weight, an aqueous solution of an ammonium salt and an aqueous solution of an alkali hydroxide are mixed while maintaining the pH of the mixture in the range of 9 to 13 by a single reaction. Introduced into a container to obtain a nickel hydroxide powder in which cobalt and the above elements are dissolved in the above range, and then trivalent nickel and trivalent cobalt are 10% or less in total with respect to the total amount of nickel and cobalt. Oxidation of the nickel hydroxide powder with an oxidizing agent so as to be included in the range of,
A nickel hydroxide powder containing trivalent nickel and trivalent cobalt is obtained. Then, an aqueous slurry containing the nickel hydroxide powder and a water-soluble lithium salt is heated to a temperature of 200 ° C. or lower at a temperature exceeding 100 ° C. under pressure. It can be obtained by heating.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The nickel hydroxide powder for a positive electrode active material of an alkaline storage battery according to the present invention has a solid solution of cobalt in the range of 0.5 to 10% by weight in terms of metal, and contains zinc,
It is composed of nickel hydroxide powder in which at least one element selected from cadmium, magnesium, calcium and manganese is dissolved in a range of 0 to 10% by weight.

In the nickel hydroxide powder, when the proportion of cobalt is less than 0.5% by weight in terms of metal, even if nickel and cobalt are partially oxidized to trivalent, hydroxyl as a positive electrode active material The utilization rate of nickel cannot be sufficiently improved. However, when the proportion of cobalt is more than 10% by weight with respect to nickel in terms of metal, the amount of nickel hydroxide, which is an active material, charged into the electrode substrate is relatively reduced, resulting in a reduction in capacity. . In particular, according to the present invention,
The proportion of cobalt in the nickel hydroxide powder is preferably in the range of 1 to 5% by weight relative to nickel in terms of metal.

According to the present invention, the nickel hydroxide powder comprises:
In addition to cobalt, zinc, cadmium, magnesium,
At least one selected from calcium and manganese may be contained in the range of 0 to 10% by weight in terms of metal. In particular, according to the present invention, the ratio of the above elements is preferably in the range of 1 to 10% by weight in terms of metal.

Further, the nickel hydroxide powder for the positive electrode active material of the alkaline storage battery according to the present invention is characterized in that trivalent nickel and trivalent cobalt in a total amount of 1 to the total amount of nickel and cobalt.
It is included in the range of 0% or less. Hereinafter, in the nickel hydroxide powder according to the present invention, the ratio of the total of trivalent nickel and trivalent cobalt to the total amount of nickel and cobalt is referred to as “oxidation rate”. When the oxidation rate exceeds 10%, the utilization rate of nickel hydroxide as a positive electrode active material decreases, and the capacity becomes smaller than that of conventional nickel hydroxide.
Further, according to the present invention, the oxidation rate is preferably 0.5% or more, and particularly preferably 1% or more.

In the present invention, cobalt, zinc, cadmium, magnesium, and the like contained in the nickel hydroxide powder are used.
The ratio of lithium to elements such as calcium or manganese is nickel, nickel, cobalt,
100% by weight of the above elements and lithium in total in terms of metal
The ratio (% by weight) is shown.

Similarly, in the production of the nickel hydroxide powder according to the present invention, in addition to the water-soluble nickel salt, the ratio of the cobalt water-soluble salt or the water-soluble salt of the above element is determined by the water solubility of the nickel salt, the cobalt salt and the above-mentioned element. Salt is 1 in total in metal conversion
It is shown as a ratio (% by weight) when it is set to 00% by weight.

The oxidation rate of the nickel hydroxide powder can be determined by a sodium thiosulfate titration method. According to the sodium thiosulfate titration method,
The total amount of trivalent nickel and trivalent cobalt in the nickel hydroxide powder can be determined. That is, as shown in the following formula (1), when a nickel hydroxide powder containing trivalent nickel and trivalent cobalt is dissolved in an aqueous solution of a salt containing iodide ions, for example, potassium iodide, the trivalent nickel is dissolved. Trivalent cobalt is converted to divalent nickel and
While being reduced to valent cobalt, iodine ions are oxidized to iodine. Then, as shown in the following formula (2), if this iodine is titrated with sodium thiosulfate, the total amount of trivalent nickel and trivalent cobalt in the nickel hydroxide powder can be determined.

[0017]

(Equation 1)

Therefore, the oxidation rate in the present invention is defined by the following equation.

Oxidation rate = ((moles of sodium thiosulfate required for titration) / moles of total amount of nickel and cobalt in nickel hydroxide powder used for titration)) × 100 (%)

The number of moles of sodium thiosulfate required for the titration is the total number of moles of trivalent nickel and trivalent cobalt in the nickel hydroxide powder.

Further, the nickel hydroxide powder according to the present invention contains lithium in a range of 0.2% by weight or less, and preferably in a range of 0.01 to 0.1% by weight. Thus, when the electrode substrate is filled with the nickel hydroxide powder according to the present invention to form an alkaline storage battery, the expansion of the positive electrode can be suppressed during charging and discharging.

The nickel hydroxide powder for a positive electrode active material of an alkaline storage battery contains a water-soluble nickel salt and a water-soluble cobalt salt in a metal conversion range of 0.5 to 10% by weight, and contains zinc, cadmium, magnesium, An aqueous solution containing a water-soluble salt of at least one element selected from calcium and manganese in a range of 0 to 10% by weight, an aqueous solution of an ammonium salt and an aqueous solution of an alkali hydroxide are adjusted to a pH of 9 to 13 in a mixture thereof. While holding, the mixture was introduced into a single reaction vessel to obtain a nickel hydroxide powder in which cobalt and the above elements were dissolved in the above range as a coprecipitate, and then trivalent with respect to the total amount of nickel and cobalt. In order that nickel and trivalent cobalt are included in a range of 10% or less in total,
The nickel hydroxide powder is oxidized with an oxidizing agent to obtain a nickel hydroxide powder containing trivalent nickel and trivalent cobalt,
Next, the nickel hydroxide powder can be obtained by dispersing the nickel hydroxide powder in water containing a water-soluble lithium salt to form an aqueous slurry, which is heated to a temperature of more than 100 ° C. and 200 ° C. or less under pressure.

In particular, according to the present invention, 0.5 to 10% by weight of a water-soluble nickel salt and a water-soluble cobalt salt in terms of metal, and at least one element selected from zinc, cadmium, magnesium, calcium and manganese 1 water-soluble salt
Aqueous solution, ammonium salt aqueous solution and alkali hydroxide aqueous solution containing the aqueous solution in the range of 10 to 10% by weight;
While maintaining in the range of 9 to 13, was introduced into a single reaction vessel to obtain a nickel hydroxide powder in which cobalt and the above elements were dissolved in the above range as a coprecipitate. It is preferable to heat the partially oxidized and thus partially oxidized slurry of the nickel hydroxide powder together with the water-soluble lithium salt under pressure.

The water-soluble nickel salt and water-soluble cobalt salt are not particularly limited, but usually, mineral salts such as sulfates, nitrates, and chlorides are preferably used. Similarly, mineral salts such as sulfates, nitrates, and chlorides are preferably used as the water-soluble cadmium salts, magnesium salts, calcium salts, and manganese salts.

As the aqueous alkali hydroxide solution, sodium hydroxide is preferably used. As the ammonium salt aqueous solution, ammonia water is typically used.

In this way, nickel hydroxide powder in which cadmium, magnesium, calcium or manganese is dissolved as necessary together with cobalt is obtained as a coprecipitate, which is then dispersed in water. An oxidizing agent is added to the slurry under stirring to partially oxidize nickel and cobalt to trivalent, whereby the nickel hydroxide powder for an alkaline storage battery positive electrode active material according to the present invention can be obtained.

As the oxidizing agent, an aqueous solution such as sodium hypochlorite and potassium peroxodisulfate and a gas such as ozone are preferably used.

According to the present invention, as described above, the nickel hydroxide powder, which is obtained by partially oxidizing nickel and cobalt, is dispersed in water containing a water-soluble lithium salt to form an aqueous slurry, which is heated to 100 ° C. under pressure. By heating to above 200 ° C., the nickel hydroxide powder according to the invention can be obtained. Hereinafter, this reaction is referred to as lithiation. According to the present invention, the temperature of this lithiation reaction is
From the viewpoints of operability and economy, preferably 120 to 180
Temperatures in the range of ° C.

The water-soluble lithium salt is not particularly limited, but usually lithium hydroxide, lithium carbonate, lithium sulfate, lithium nitrate, lithium chloride and the like are used.

[0030]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by this embodiment.

EXAMPLE 1 (Production of zinc-cobalt solid solution nickel hydroxide powder) 10
While maintaining the temperature at 50 ° C. with stirring in a reaction vessel having a stirrer of L capacity, nickel sulfate having a concentration of 250 g / L and 4.0 g /
A mixed aqueous solution containing 13 L of cobalt sulfate and 11.8 g / L of zinc sulfate and 13% by weight of ammonia water are continuously supplied,
At this time, the pH of the mixture was maintained at 28 so as to maintain the pH at 12.1.
A weight percent aqueous sodium hydroxide solution was added intermittently to the reactor. The resulting coprecipitate is filtered, washed, dried in vacuo,
1.5% by weight of cobalt and 4.5% by weight of zinc in metal conversion
Nickel hydroxide powder A having an average particle diameter of 11.6 μm and a tap density of 2.1 g / cc was obtained.

Next, 1 kg of the nickel hydroxide powder A thus obtained was added together with 2.5 L of water to a 5 L reactor equipped with a stirrer. 80 cc of a 111 g / L sodium hypochlorite aqueous solution was added to partially oxidize nickel and cobalt in nickel hydroxide.

After filtering and washing and vacuum-drying 300 g of this nickel hydroxide, it was poured into water together with 21 g of lithium hydroxide monohydrate to obtain a 500 mL aqueous slurry in total. This slurry was charged into an autoclave having a capacity of 1 L, and kept at 150 ° C. for 4 hours under pressure to obtain nickel hydroxide powder B containing lithium.

Similarly, 1 kg of nickel hydroxide powder A
Is partially oxidized with 150 cc of an aqueous solution of sodium hypochlorite having an effective chlorine concentration of 118 g / L, in the same manner as above, after partially oxidizing nickel and cobalt in nickel hydroxide.
A nickel hydroxide powder C containing lithium was obtained.

Similarly, 1 kg of nickel hydroxide powder A
Was partially oxidized with 288 cc of an aqueous solution of sodium hypochlorite having an effective chlorine concentration of 123 g / L, and in the same manner as described above,
A nickel hydroxide powder D containing lithium was obtained.

Similarly, 1 kg of nickel hydroxide powder A
Using 460 cc of an aqueous solution of sodium hypochlorite having an effective chlorine concentration of 116 g / L, nickel and cobalt in nickel hydroxide are partially oxidized, and in the same manner as above,
A nickel hydroxide powder E containing lithium was obtained.

Similarly, 1 kg of nickel hydroxide powder A
Using a 606 cc aqueous solution of sodium hypochlorite having an effective chlorine concentration of 117 g / L, nickel and cobalt in nickel hydroxide were partially oxidized,
A nickel hydroxide powder F containing lithium was obtained.

The nickel hydroxide powder A thus obtained
Table 1 shows the oxidation rate and lithium content of each of Examples 1 to 3. Further, regarding these nickel hydroxide powders, Cu
X-ray diffraction measurement was performed using a Kα ray under the measurement conditions of a tube voltage of 40 kV, a tube current of 30 mA, and a scanning speed of 1.2 deg / min, and the half width of the diffraction peak (101) plane was obtained. The results are shown in Table 1.

(Measurement of Utilization of Active Material) A positive electrode was prepared by using the above nickel hydroxide powders A to F by the following method. That is, the nickel hydroxide powder and cobalt oxide were mixed at a weight ratio of 40: 7, and carboxymethylcellulose, water and polytetrafluoroethylene dispersion were added thereto to form a paste.
% Of nickel foam, and dried at 80 ° C.

A simple cell was prepared by using a foamed nickel electrode as the negative electrode, a silver chloride electrode as the reference electrode, and a 30% by weight aqueous solution of potassium hydroxide in which lithium hydroxide monohydrate was added to the electrolyte at 1.6% by weight. Was prepared.

Using this simple cell, under the following conditions:
The utilization rate of the nickel hydroxide active material was measured. That is, at a temperature of 20 ° C. and a charging current of 0.2 CmA, the battery is charged to 150% of the theoretical capacity calculated from the nickel hydroxide active material,
After suspending for 1 hour, continuous discharge was performed to -0.25 V at a discharge current of 0.2 CmA. Charge / discharge was repeated four times by this method, and the utilization rate of the active material in each cycle was calculated from the following equation.

Utilization rate of active material = ((discharge capacity up to −0.25 V / theoretical nickel hydroxide capacity)) × 100 (%)

Table 2 shows the utilization ratio of each nickel hydroxide powder.

(Evaluation of Degree of Expansion of Positive Electrode) Further, in order to examine the degree of expansion of the positive electrode in the above simple cell,
The swelling ratio of the positive electrode was determined from the following equation. Table 2 shows the results.

Swelling ratio = ((thickness of positive electrode after 4 cycles)
/ Thickness of positive electrode before charging / discharging)) × 100 (%)

[0046]

[Table 1]

[0047]

[Table 2]

As is clear from the results in Table 2, the powders B to E show a higher utilization factor than the conventional nickel hydroxide powder A. The aqueous nickel powder F has an oxidation rate of 1
Since it exceeds 0%, the utilization factor is lower than that of the conventional nickel hydroxide powder A.

Further, the positive electrode using the nickel hydroxide powder according to the present invention is suppressed from swelling as compared with the conventional one.

[0050]

As described above, the nickel hydroxide powder for the positive electrode active material of an alkaline storage battery according to the present invention has a significantly improved utilization factor. An alkaline storage battery can be obtained, and further, the positive electrode using the nickel hydroxide powder according to the present invention as an active material suppresses expansion as compared with a conventional positive electrode. In addition, such nickel hydroxide powder is prepared by coprecipitating a hydroxide from an aqueous solution containing a nickel salt and a cobalt salt, oxidizing the hydroxide with an oxidizing agent, and then dispersing the hydroxide in water containing a water-soluble lithium salt. The slurry can be easily obtained by pressurizing and heating the slurry to lithium the nickel hydroxide.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4G048 AA03 AA04 AA05 AB02 AB03 AB06 AC06 AD03 AE05 5H003 AA02 AA04 BA01 BA02 BA03 BA07 BB04 BD00 BD01 BD04 BD06

Claims (4)

[Claims] (1) 0.5 to 10% by weight of cobalt in metal conversion
And at least one element selected from zinc, cadmium, magnesium, calcium and manganese in a range of 0 to 10% by weight, and lithium in a range of 0.2% by weight or less. And nickel hydroxide powder containing trivalent nickel and trivalent cobalt in a total amount of 1 to the total amount of nickel and cobalt.
Nickel hydroxide powder for an alkaline storage battery positive electrode active material contained in a range of 0% or less. 2. The nickel hydroxide powder according to claim 1, wherein at least one element selected from the group consisting of zinc, cadmium, magnesium, calcium and manganese is dissolved in a range of 1 to 10% by weight. 3. A water-soluble nickel salt and a water-soluble cobalt salt in the range of 0.5 to 10% by weight in terms of metal, and at least one element selected from zinc, cadmium, magnesium, calcium and manganese. 0 to water-soluble salt
An aqueous solution containing 10% by weight, an aqueous solution of ammonium salt and an aqueous solution of alkali hydroxide are introduced into a single reaction vessel while maintaining the pH of the mixture in the range of 9 to 13. And a nickel hydroxide powder in which the above-mentioned elements are dissolved. Then, trivalent nickel and trivalent cobalt are added in a total amount of 1 to the total amount of nickel and cobalt.
The nickel hydroxide powder is oxidized with an oxidizing agent so as to be contained in a range of 0% or less to obtain a nickel hydroxide powder containing trivalent nickel and trivalent cobalt. Dispersed in water containing a neutral lithium salt to form an aqueous slurry,
The method for producing a nickel hydroxide powder according to claim 1, wherein the heating is performed at a temperature of 200C or less. 4. A water-soluble nickel salt and a water-soluble cobalt salt in the range of 0.5 to 10% by weight in terms of metal, and at least one element selected from zinc, cadmium, magnesium, calcium and manganese. 1 to water-soluble salt
An aqueous solution containing 10% by weight, an aqueous solution of ammonium salt and an aqueous solution of alkali hydroxide are introduced into a single reaction vessel while maintaining the pH of the mixture in the range of 9 to 13. 4. A method for producing a nickel hydroxide powder according to claim 3, wherein a nickel hydroxide powder in which the above-mentioned elements are dissolved is obtained.