JPH10172563A - Manufacture of paste type nickel electrode and manufacture of alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a paste type nickel electrode with high utilization factor and long life by using past containing an active material mainly comprising nickel hydroxide having the specified value of more of the half-band width at peak of (101) planes in X-ray diffraction. SOLUTION: In the manufacture of a past type nickel electrode,the half-band width at peak of (101) planes in X-ray diffraction is used as an index, an active material mainly comprising nickel hydroxide, Ni(OH)2 , having a half-band width of 0.8 deg./2θ is prepared, paste containing the active material is prepared, and the paste is filled in a metal porous substrate. In this process, nickel hydroxide having a eutectic of cadmium or zinc can be used. The paste may contain metallic cobalt or cobalt oxide which is not a eutectic of the nickel hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a paste-type nickel electrode and a method for producing an alkaline storage battery including a paste-type nickel electrode and a negative electrode containing cadmium, zinc, a hydrogen storage alloy, or the like.

[0002]

2. Description of the Related Art Conventionally, as a nickel electrode for an alkaline storage battery, for example, a nickel salt such as nickel nitrate is filled into a substrate obtained by sintering carbonyl nickel on a punched metal in the form of an aqueous solution, and then the hydroxide is hydrated in an alkaline solution. The so-called sintering method converted to nickel was the mainstream. As an advantage of the sintering method, since the sintered body of carbonyl nickel as the substrate has a very fine pore structure with a pore diameter of 10 to 10 μm, the current collecting ability of nickel hydroxide, which is originally a non-conductor, is excellent. It is mentioned. On the other hand, the ratio of the substrate volume to the entire nickel electrode is required to be about 20%, and the amount of the active material to be charged is limited.
There is a drawback that only about 0 mAh / cc can be obtained.

[0003] As an attempt to improve these disadvantages, a paste-type nickel electrode has been proposed. The paste-type nickel electrode has a sponge-like or felt-like metal porous body having a pore diameter of 100 to 500 μm as a substrate, and the pores of the substrate are filled with powdered nickel hydroxide prepared in a paste form with an appropriate solvent or binder, It is obtained by drying and pressing. In addition, since the volume ratio of the substrate to the entire nickel electrode can be reduced to less than 10%, the amount of the active material to be filled can be increased, and the equivalent capacity density can be improved to about 600 mAh / cc. Can be. The powdered nickel hydroxide used for this paste-type nickel electrode is, in principle, an aqueous solution of a nickel salt such as nickel nitrate or nickel sulfate and an aqueous solution of an alkali such as caustic soda or caustic potash in the same manner as in the sintering method. 1 to number 1
The reaction is generally carried out so as to form 0-micron particles, and the precipitate is generally washed with water and dried to obtain a precipitate.

[0004] However, the paste-type nickel electrode produced by the above-mentioned method has a number of problems. In particular, there is a problem that the utilization rate of nickel hydroxide during charge / discharge is small, and a problem that the swelling of the active material due to the charge / discharge cycle is remarkable.

A cause of such a problem is a difference in current collecting performance of the substrate. As described above, the pore diameter of the sintered substrate is several to 10 μm, whereas the sponge-like and felt-like porous metal bodies, which are paste-type substrates, have a pore size of 100 to 5 μm.
00 μm, which is several tens of times larger. That is, the charge transfer distance in the active material at the time of the reaction becomes long, and polarization due to resistance tends to increase. Disadvantages of highly polarized electrodes include reduced discharge voltage and the formation of irreversible charge products during charging. This irreversible charge product is generally known as γ-NiOOH, is less likely to be discharged compared to β-NiOOH which is a normal nickel electrode charge product, and has a form in which the crystal extends in the C-axis direction. It is known that swelling of an active material is likely to occur. That is, comparing the sintering method and the paste method, when the same nickel hydroxide is used, the paste method has a drawback that the utilization rate decreases and the swelling of the active material is liable to occur due to the difference in current collecting ability of the substrate, It can be said that the cause is largely related to the production of γ-NiOOH which is an irreversible charge product.

As a countermeasure against this problem, the addition of a cobalt compound, which is widely known in the sintering method, is applied to the paste method, for example, in Japanese Patent Publication Nos. 57-5344 and 60-160.
No. 60449, metallic cobalt,
As shown in 138458, attempts to suppress polarization by blending cobalt having excellent conductivity, such as cobalt oxide, have been widely made. Also, Japanese Patent Application Laid-Open No. 1-26
0762 and JP-A-2-30061, attempts to add cadmium, zinc, or the like to a crystal of nickel hydroxide in a eutectic state have also been made. However, none of these methods can be said to be a sufficient measure against the above problems. For example, the sintering method has a utilization factor of 95% or more, while the paste method has a limit of about 90%. At present, the sintering method is inferior to about 300 cycles while the sintering method is 500 cycles or more, and these problems have been a major obstacle to the spread of the paste-type nickel electrode.

On the other hand, JP-A-63-152866 discloses that the specific surface area is 60 m ² / g or more and the crystallinity is 14
The following describes a nickel active material for a storage battery, wherein a thin layer of β-type cobalt hydroxide is formed on nickel hydroxide particles as a main component. Further, after using an aqueous solution of nickel sulfate or nickel nitrate as a main component, depositing nickel hydroxide powder in an alkaline aqueous solution adjusted to PH 9.5 to 12.5 such as caustic potash or caustic soda, a cobalt sulfate salt is precipitated. Alternatively, there is described a method for producing a nickel active material for a storage battery, wherein the method is immersed in an aqueous solution of a cobalt nitrate salt and then neutralized with an aqueous alkaline solution. The “crystallinity” is (00) of nickel hydroxide.
1) The height of the characteristic peak on the surface is divided by the half width.

[0008]

However, an alkaline storage battery provided with a paste-type nickel electrode containing nickel hydroxide having the above-mentioned crystallinity and specific surface area as an active material has the above-mentioned nickel hydroxide containing cobalt or cadmium. Γ-N when charging the nickel electrode if not
Since the production rate of iOOH is high, there is a problem that the utilization rate and the cycle life are inferior. In addition, the above-described method for producing an active material includes production conditions other than PH of an aqueous alkaline solution,
For example, it is easily affected by the temperature of the reaction system, the concentration of the aqueous solution used, the stirring speed, and the like. Therefore, the paste-type nickel electrode containing the nickel active material manufactured by the above method has a problem that not only the performance is inferior but also the performance varies as described above.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method of producing a paste-type nickel electrode having a high utilization factor and a long life. An object of the present invention is to provide a method for manufacturing a long-life alkaline storage battery provided with a paste-type nickel electrode having a high utilization factor.

[0010]

The method for producing a paste-type nickel electrode according to the present invention comprises the steps of:
A method for producing a paste-type nickel electrode in which a paste containing an active material mainly composed of nickel hydroxide (Ni (OH) ₂ ) is filled, wherein the nickel hydroxide has a peak of (101) plane in X-ray diffraction. The half width is 0.8 ° / 2θ or more.

In the method for manufacturing an alkaline storage battery according to the present invention, nickel hydroxide (Ni
A method for manufacturing an alkaline storage battery having a paste-type nickel electrode filled with a paste containing an active material mainly composed of (OH) ₂ , wherein the nickel hydroxide has a peak (101) plane in X-ray diffraction. The half width is 0.8 ° / 2θ or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
According to the method of the present invention, the paste nickel electrode is
For example, a step of preparing an active material mainly composed of nickel hydroxide having a half width of 0.8 ピ ー ク / 2θ or more based on the half width of the peak on the (101) plane by X-ray diffraction as an index, It can be produced by a method including a step of preparing a paste containing the obtained active material, and a step of filling the paste into a substrate having a porous metal body.

In this method, the nickel hydroxide may be eutectic of cadmium or zinc.
In addition, metallic cobalt or cobalt oxide that is not eutectic with the nickel hydroxide may be present in the paste.

Examples of the porous metal include those having a three-dimensional structure such as sponge-like nickel and felt-like nickel. The method for producing the nickel hydroxide is obtained by a neutralization reaction between an aqueous solution of a nickel salt such as nickel nitrate or nickel sulfate and an aqueous alkali solution such as caustic soda or potassium caustic. Even with nickel oxide, a crystal having a different half width at the peak of the (101) plane in X-ray diffraction can be obtained.

Further, a metal element selected from cadmium and zinc is added to nickel hydroxide in a eutectic state, and metal cobalt and cobalt oxide (for example, cobalt hydroxide,
The performance is improved by adding generalized cobalt).

Even with the same nickel hydroxide Ni (OH) ₂ , the degree of γ-NiOOH tends to vary depending on the degree of crystallinity. It is Ni (O
H) ₂ crystals have a higher degree of freedom of proton transfer at the electrolyte interface depending on the degree of crystallization, and those having low crystallinity tend to have a higher degree of freedom of proton transfer, while those having less proton transfer have a higher γ. -NiOOH tends to be easily generated, so that Ni (O
H) ₂ can be said to be easy to generate γ-NiOOH.

There are a number of methods for indicating the crystallinity of Ni (OH) ₂ , and the inventors have found that the (101) plane in particular when X-ray diffraction is performed, and that 2θ is used when a Cu Kα tube is used.
The half-width of the peak seen near 38.7 °
The present invention was found by finding a high correlation between the production ratio of NiOOH. Β-NiOOH + γ-Ni during charging
The smaller the ratio of γ-Ni00H to the amount of OOH,
Since the utilization rate of the nickel electrode is high and the degree of swelling of the active material is small, the cycle life tends to be long.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail. First, nickel hydroxide as a main active material was prepared by the following method. An aqueous solution of nickel sulfate and an aqueous solution of caustic soda were sequentially added under an environment in which the pH of the reaction atmosphere was controlled to be constant, and crystal growth, washing with water, and drying were performed to produce nickel hydroxide having a particle size of 1 to 30 μm. By changing the pH value of the reaction atmosphere to four types, four types of Ni (OH) ₂ having different crystallinities could be obtained.

The crystallinity of the nickel hydroxide was measured by mounting a Cu Kα tube and a graphite monochromator on an XD-34 type X-ray diffraction analyzer manufactured by Shimadzu Corporation. A chart is shown in which the half width of the peak near 38.7 ° corresponds to 0.9, 0.8, 0.7, 0.6 °. One example of the chart is shown in FIG. Cobalt monoxide 10 per 100 parts by weight of this nickel hydroxide
Parts by weight, and 0.3 parts by weight of carboxymethylcellulose are kneaded together with 30 parts by weight of water to prepare a paste. The paste is filled in a sponge-like porous nickel body having a pore diameter of 300 μm, dried, pressed, and subjected to lead welding. A paste-type nickel electrode of the present invention was produced.

This paste-type nickel electrode is wound together with a paste-type cadmium electrode and a nylon separator and inserted into a battery can to produce an AA-size nickel-cadmium storage battery, and a charge / discharge cycle of 0.3 C charge / 1 C charge is performed.
00 cycles were performed. FIG. 2 shows the transition of the utilization rate with respect to the theoretical capacity of the nickel electrode with respect to the number of cycles at that time.

Next, after 500 cycles, the battery is disassembled in a charged state, the nickel electrode is taken out and pulverized, and similarly subjected to X-ray diffraction analysis.
The peak height (P-γ) of NiOOH and the peak height (P-β) of β-NiOOH observed around 19 ° were measured, and (P−γ) / ｛(P−γ) + (P− β) The ratio of γ-NiOOH in the whole was calculated from the value of｝. FIG. 3 shows the ratio of γ-NiOOH to the half width.

According to FIG. 2, in the case of a nickel electrode using nickel hydroxide having a (101) plane peak having a half width of 0.9 or 0.8 °, the utilization factor is as high as 95% and 500 cycles are required. Almost no change in usage rate is seen even after passing through. FIG.
Also tend to be as small as less than 20%. On the other hand, in the case of 0.7, 0.6%, the utilization rate is 90% at the maximum, and the decrease during the cycle is remarkable, and drops to less than the initial 50% around 300 cycles. Correspondingly, the γ-NiOOH ratio is between 40% and 80%.
%, Which is very high, and uneven distribution of the electrolytic solution was caused by swelling of the active material.

In this embodiment, cobalt monoxide is used as a cobalt-based additive. However, similar effects can be obtained by using a cobalt oxide such as metal cobalt or cobalt hydroxide instead. I will not show detailed results here,
3-7% by weight of cadmium or zinc in nickel hydroxide
The eutectic-added paste-type nickel electrode did not show any change in utilization even after 700 cycles, and exhibited good characteristics.

[0024]

As described above in detail, according to the present invention, it is possible to provide a method of manufacturing a paste-type nickel electrode and a method of manufacturing an alkaline storage battery having a high utilization rate of nickel hydroxide and a long life. Its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a chart of an X-ray diffraction analysis of nickel hydroxide.

FIG. 2 is a characteristic diagram showing the relationship between the half-value width of the peak at 2θ of the (101) plane of nickel hydroxide by X-ray diffraction and the active material utilization of the nickel electrode.

FIG. 3 shows the half-value width of the peak at 2θ of the (101) plane obtained by X-ray diffraction of nickel hydroxide and γ after 500 cycles.
FIG. 3 is a characteristic diagram showing a relationship with a production ratio of NiOOH.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Katsuyuki Hata 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation

Claims (4)

[Claims] 1. A method for producing a paste-type nickel electrode, comprising filling a substrate having a porous metal body with a paste containing an active material mainly composed of nickel hydroxide (Ni (OH) ₂ ). Is a method for producing a paste-type nickel electrode, wherein the half-value width of the peak of the (101) plane in X-ray diffraction is 0.8 ° / 2θ or more. 2. The method according to claim 1, wherein the nickel hydroxide is eutectic of cadmium or zinc. 3. A method for manufacturing an alkaline storage battery having a paste nickel electrode in which a substrate having a porous metal body is filled with a paste containing an active material mainly composed of nickel hydroxide (Ni (OH) ₂ ). The method for producing an alkaline storage battery according to claim 1, wherein the nickel hydroxide has a peak half width at (101) plane in X-ray diffraction of 0.8 線 / 2θ or more. 4. The method according to claim 3, wherein the nickel hydroxide is eutectic of cadmium or zinc.