JPH11268917A - Production of nickel hydroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce nickel hydroxide having a high filling density and good in high-rate discharge characteristics by using 1,3-propanediamine as a complexing agent for nickel ions when producing the nickel hydroxide from a nickel salt solution and an alkali solution. SOLUTION: The concentration of 1,3-propanediamine in a reactional solution is preferably 0.1-10 mol. The nickel salt is not especially limited and nickel sulfate, nickel chloride, etc., are used. For example, an alkali metal hydroxide (e.g. NaOH or KOH) is used as an alkali solution. The pH of the reactional solution is preferably 12-13. The reactional solution is kept at temperature of 40-100 deg.C. Thereby, the deposition rate of the nickel hydroxide becomes optimal and the spherical nickel hydroxide having a high tap density can be synthesized. The resultant nickel hydroxide is particles comprising an aggregate of a scaly crystal. Thereby, the specific surface area is high and the high-rate discharge characteristics and utilization ratio of active materials can remarkably be raised.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing nickel hydroxide used as a positive electrode active material of a nickel battery.

[0002]

2. Description of the Related Art Conventionally, spherical nickel hydroxide particles have been used as a positive electrode active material of a high capacity type Ni-Cd, Ni-MH battery. Since the nickel hydroxide particles are required to have a high packing density, a nickel ion solution and an alkaline aqueous solution are added to an aqueous ammonia solution in a stirred tank maintained at room temperature, and the pH is kept constant while the nickel hydroxide particles are maintained. (Japanese Patent Publication No. 4-80513).

[0003]

However, in the above-mentioned conventional method for producing nickel hydroxide, it takes a long time to produce spherical crystals because the spherical crystals grow slowly over time. Furthermore, when Zn is added to suppress the swelling of the Ni electrode, there is a problem that the surface is densified and the high-rate discharge characteristics deteriorate. In addition, there is a problem in that the working environment is deteriorated because the volatile ammonia is used.

Japanese Patent Application Laid-Open No. 54-99944 discloses a technique relating to the particle size distribution of a nickel compound.
Japanese Patent Application Laid-Open No. 102539 discloses a technique relating to the particle diameter of nickel hydroxide and the space diameter of foamed nickel.
No. 8 discloses a method for producing nickel hydroxide using glycine, but none of these methods sufficiently solves the above problems.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a method for producing nickel hydroxide which has good packing density and high-rate discharge characteristics and can be produced in a short time. is there.

[0006]

The present invention relates to a method for producing nickel hydroxide from a nickel salt solution and an alkaline solution,
A method for producing nickel hydroxide, comprising using 1,3-propanediamine as a complexing agent for nickel ions.

The operation and effect of the present invention will be described. In the present invention, 1,3-propanediamine (H ₂ N (C
H ₂ ) ₃ NH ₂ ) acts as a complexing agent, and when an alkaline solution and a nickel salt solution are added, the following excellent nickel hydroxide is obtained.

[0008] The obtained nickel hydroxide forms particles composed of aggregates of flaky crystals. As a result, the specific surface area is high, and the high-rate discharge characteristics and the active material utilization rate are much higher than conventional products. Moreover, the packing density is high. Although high-rate discharge cannot be specified unconditionally, in the present invention, it refers to a discharge condition in which a current value of 0.5 C or more, that is, all electricity stored in nickel hydroxide as a positive electrode active material is discharged within 2 hours. .

Further, in the conventional product, the specific surface area is reduced when Zn is added as a swelling inhibitor, but the surface area of the nickel hydroxide particles obtained in the present invention does not decrease. Further, according to the present invention, nickel hydroxide can be produced in a short time, and since the boiling point of 1,3-propanediamine is as high as 140 ° C., even if nickel hydroxide is synthesized at a high liquid temperature, it can be produced outside the container. Almost no 1,3-propanediamine vapor escapes. For this reason, it is possible to avoid deterioration of the working environment due to highly volatile ammonium.

Next, the details of the present invention will be described.
1,3-propanediamine in a reaction solution containing 1,3-propanediamine
The concentration of propanediamine is preferably from 0.1M to 10M. If it is less than 0.1 M, nickel hydroxide having a spherical shape and a high tap density may not be generated. If it exceeds 10M, 1,3-propanediamine remaining in the generated nickel hydroxide may not be completely removed in the washing step. Further, the concentration of 1,3-propanediamine is preferably 0.18M or more. As a result, nickel hydroxide having a high packing density can be obtained.

The nickel salt is not particularly limited, and for example, a nickel salt of an inorganic acid such as nickel sulfate, nickel nitrate and nickel chloride can be used. As the alkali solution, for example, an aqueous solution containing an alkali metal hydroxide can be used. As the alkali metal hydroxide, for example, NaOH, KOH, and LiOH can be used. The above reaction solution is preferably adjusted to pH 12 to 13 by adding the above alkaline solution. As a result, the deposition rate of nickel hydroxide is optimized, so that nickel hydroxide having a spherical shape and a high tap density can be easily synthesized.

The above reaction solution is preferably kept at a temperature of 40 to 100 ° C. As a result, nickel hydroxide having a high packing density can be obtained. In particular, the lower limit is preferably 50 ° C. or higher. This further increases the packing density.

The method of adding the alkali solution and the nickel salt solution includes a method of dropping the reaction solution from above, and a method of injecting the solution into the reaction solution. When adding both separately, it is preferable to stir the reaction solution. This is for increasing the chance that 1,3-propanediamine in the reaction solution comes into contact with the nickel salt and the alkali solution.

When the alkali solution and the nickel salt solution are added to the reaction solution, nickel hydroxide particles grow. Then, after several hours, a precipitate of nickel hydroxide particles is formed. This precipitate is filtered if necessary,
Wash and dry. Thereby, the nickel hydroxide of the present invention is obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 A method for producing nickel hydroxide according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, 0.1 M was placed in a 2 liter glass cylindrical container 51.
400 ml of the above 1,3-propanediamine aqueous solution 8
The stirring rod 52 at the center was rotated at 400 to 2000 rpm. A nickel sulfate aqueous solution 6 of 1M or more and a sodium hydroxide aqueous solution 7 having a concentration twice that of the nickel sulfate aqueous solution 6 are separately added to the inner surface of the container from the opposing positions (for example, the positions of 3 o'clock and 9 o'clock in the clock display) at 0. 4 to 5 ml were added dropwise. The dropping time was 1 hour or more.

Even if the concentrated nickel sulfate solution 6 is added as described above, the complex of nickel (Ni ²⁺ ) ion and 1,3-propanediamine, ie, Ni ^{A 2 +} -ammine complex 86 is formed. Therefore, the concentration of nickel ions in the solution is extremely low. On the other hand, an alkaline solution (for example, NaOH)
Is dropped, the Ni ²⁺ -ammine complex 86 is decomposed to produce nickel hydroxide 87.

As the concentration of the Ni ²⁺ -ammine complex 86 increases, the nickel ion concentration also increases. Eventually,
When the amount of generated nickel hydroxide reaches a supersaturated state with respect to the solubility of nickel hydroxide, nickel hydroxide precipitates. At this time, the precipitation of nickel hydroxide progresses slowly, resulting in nickel hydroxide particles having a high tap density.
Compared with the case where ammonia (NH ₃ ) is used as a complexing agent as in the related art, flaky crystals grow on the particle surface, and nickel hydroxide particles having a high specific surface area can be obtained.

Next, the influence on the tap density of the nickel hydroxide particles when the concentration of 1,3-propanediamine and the temperature of the reaction solution were changed in the production method of this example was measured. The result is shown in FIG. The tap density refers to the measured weight of a particle per unit volume after the particle is filled in a container and one vertical oscillation is repeated 100 times per second.

FIG. 2 shows that the tap density is 1.6 / gcm ^-3.
The above high nickel hydroxide particles can be obtained only in 1,3
-It is understood that it is preferable that the concentration of propanediamine is 0.18 M or more and the temperature of the aqueous solution is 50 ° C or more.

Further, the nickel hydroxide particles obtained in this example and the nickel hydroxide particles obtained in the prior art (Japanese Patent Publication No. 4-80513) (this is referred to as Comparative Example 1) were scanned. Observed with an electron microscope
Each is shown in FIG. As shown in FIG. 3, flaky crystals were observed on the surface of the nickel hydroxide particles of this example.
As shown in FIG. 4, no nickel hydroxide particles were observed on the surface of the nickel hydroxide particles of Comparative Example 1. This shows that the nickel hydroxide particles of this example have a larger specific surface area than the nickel hydroxide particles of Comparative Example 1.

Next, a nickel-MH battery was manufactured using the nickel hydroxide particles of the present example and the nickel hydroxide particles of Comparative Example 1, and a charge / discharge test was performed. That is, 3 g of each of the nickel hydroxide particles of this example and the nickel hydroxide particles of Comparative Example 1 were weighed, and kneaded with 1 g of a 2% by weight aqueous solution of methylcellulose to obtain a positive electrode active material paste. Next, foamed nickel (Celmet # 7, manufactured by Sumitomo Electric Industries, Ltd.) cut into a 3 cm × 4 cm square was prepared, and the thickness was 60 μm.
Was spot-welded using the nickel plate as a terminal. The positive electrode active material paste was filled in the pores of the foamed nickel, dried, and pressed to produce a positive electrode. Filling amount of nickel hydroxide is 1.5g, theoretical capacity is 430mA
h.

[0022] negative electrode, using the AB ₅ type hydrogen storage alloy. This was packed in a polypropylene-polyethylene nonwoven fabric having a fiber diameter of 10 μm or less as a separator. The capacity was about 700 mAh.

An electrolyte (6.8 M-KOH + 0.8 M-LiOH) is sandwiched between one positive electrode and two negative electrodes.
Was injected to form a nickel-MH battery. These batteries were charged in a 20 ° C. constant temperature bath at 120% charge at 0.2 C, stopped for 30 minutes, and discharged at 0.2 C (cutoff voltage = 1.0).
A charge / discharge test was performed under the condition of V). After the capacity of the positive electrode became substantially constant, the relationship between the discharge rate and the active material utilization was determined. Since the capacity of the positive electrode is one third of the capacity of the negative electrode, the obtained discharge capacity indicates the positive electrode capacity.
The measurement results are shown in FIG.

In the figure, it can be seen that the nickel hydroxide particles of this example show a higher active material utilization rate even at a higher discharge rate than the nickel hydroxide particles of Comparative Example 1 used. This is considered to be because the nickel hydroxide particles of this example have many irregularities due to the scale-like crystals on the surface and have a large contact area with the electrolytic solution.

Second Embodiment 400 ml of a 2M 1,3-propanediamine aqueous solution is placed in the 2 liter glass cylindrical container used in the first embodiment.
And the central stirring rod was rotated at 2000 rpm.
To a 1.71M aqueous nickel sulfate solution, add zinc sulfate (a swelling inhibitor) to a concentration of 0.29M, and separately with a 4M aqueous sodium hydroxide solution from the opposite position on the inner surface of the cylindrical container at 0.46 ml / min. Was added.

These dropping experiments were performed by immersing the cylindrical container in a constant temperature water bath at 65 ° C. Approximately 10 minutes after the start of the dropping, formation of a plurality of aggregated nuclei was observed, and the dropping was continued for further 4 hours to synthesize nickel hydroxide particles having a solid solution of zinc.
Thereafter, filtration, sufficient washing with water, and drying were performed to obtain powdery nickel hydroxide particles. This was used as the nickel hydroxide particles of this example.

For comparison, Japanese Patent Publication No. 4-8051
According to the method described in No. 3, nickel hydroxide particles in which the same amount of zinc was dissolved in solid solution were prepared, and this was used as the nickel hydroxide particles of Comparative Example 2.

When the nickel hydroxide particles obtained in this example and the nickel hydroxide particles of Comparative Example 2 were observed with a scanning electron microscope, the surface of the nickel hydroxide particles of this example showed scaly crystals. Was observed, but was not observed on the surface of the nickel hydroxide particles of Comparative Example 2. This indicates that the nickel hydroxide particles of this example have a larger specific surface area than the nickel hydroxide particles of Comparative Example 2.

A battery was fabricated using the nickel hydroxide particles of this example and the nickel hydroxide particles of Comparative Example 2 in the same manner as in Example 1, and the cycle characteristics were determined. FIG. 6 shows the result. FIG. 6 shows that the initial cycle characteristics of the nickel hydroxide particles of this example are improved as compared with the case where the nickel hydroxide particles of Comparative Example 2 are used. This is considered to be because the nickel hydroxide particles of this example have many irregularities due to the scale-like crystals on the surface and have a large contact area with the electrolytic solution.

[0030]

As described above, according to the present invention, it is possible to provide a method for producing nickel hydroxide which can produce nickel hydroxide having a high filling density and good high-rate discharge characteristics in a short time.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method for producing nickel hydroxide in a first embodiment.

FIG. 2 is a characteristic diagram showing manufacturing conditions for obtaining nickel hydroxide having a high tap density in the first embodiment.

FIG. 3 is a scanning electron micrograph showing the structure of nickel hydroxide particles of Example 1;

FIG. 4 is a scanning electron micrograph showing the structure of nickel hydroxide particles of Comparative Example 1.

FIG. 5 is a diagram showing charge / discharge test results of the nickel hydroxide particles of Example 1 and the nickel hydroxide particles of Comparative Example 1.

FIG. 6 is a diagram showing charge / discharge test results of nickel hydroxide particles of Example 2 and nickel hydroxide particles of Comparative Example 2.

[Explanation of symbols]

6. . . 6. Nickel sulfate solution, . . 7. sodium hydroxide solution, . . 1,3-propanediamine, 51. . . Cylindrical container, 52. . . Stir bar, 86. . . Ni ²⁺ -ammine complex 87. . . Nickel hydroxide,

Claims (1)

[Claims] 1. A method for producing nickel hydroxide from a nickel salt solution and an alkaline solution, wherein 1,3-propanediamine is used as a complexing agent for nickel ions.