JPH0652856A - Positive electrode active material for alkaline storage battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the use efficiency of a positive electrode and the sharp discharging property and cycle property of a battery by adding a small amount of nickel to a nickel hydroxide powder. CONSTITUTION:In the case a small amount of nickel is added to a nickel hydroxide powder, to react nickel with nitric acid or sulfuric acid, reaction is carried out so as to leave a small amount of not reacted nickel and thus nickel nitrate or nickel sulfate containing a small amount of not reacted nickel. Then, an alkali is added to neutralize it, countless nickel hydroxide particles containing a small amount of nickel are deposited and the deposite is separated, dried, and pulverized. Consequently, the nickel hydroxide powder itself bears conductivity and in the case the powder is applied to and packed in a porous substrate, a positive pole plate having uniform conductivity in the whole is obtained and the use efficiency of it is heightened and sharp discharging property is improved and at the same time a life of a battery is extended. In this case, the filling the porous substrate with the powder is improved by making the particles of the nickel hydroxide powder spherical.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode active material for an alkaline storage battery and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, positive electrode active materials for alkaline storage batteries have been
It can be obtained by reacting nickel and nitric acid to produce nickel nitrate, and then neutralizing and reacting with an alkali to precipitate and deposit innumerable particles of nickel hydroxide, filter the precipitate, and dry and pulverize the precipitate. To prepare a paste type positive electrode for an alkaline storage battery using this, a conductive agent is mixed with the positive electrode active material powder and kneaded with an aqueous solution of a thickening agent such as CMC to form a paste, which is then formed into a foamed nickel substrate or nickel fiber. It is obtained by coating and filling a porous metal substrate such as felt and drying.

[0003]

The paste type positive electrode plate using the above-mentioned conventional positive electrode active material can provide an alkaline storage battery having a higher capacity than that of the sintered type positive electrode. It has drawbacks such as low utilization rate and rapid discharge characteristics of batteries and short life, and it is desired to improve these characteristics.

[0004]

The present invention solves the drawbacks of conventional nickel positive electrode active materials and improves the positive electrode utilization rate, battery rapid discharge characteristics and cycle life positive electrode active material for alkaline storage batteries. The nickel hydroxide powder contains a small amount of nickel. The second invention provides a method for producing the positive electrode active material of the present invention, which comprises reacting nickel with nitric acid or sulfuric acid,
By reacting so that a small amount of unreacted nickel remains, nickel nitrate or nickel sulfate containing a small amount of the unreacted nickel is prepared and neutralized by adding an alkali to countless nickel containing a small amount. The method is characterized in that nickel hydroxide particles are precipitated, the precipitate is separated, dried and then ground.

[0005]

The nickel hydroxide powder, which is the positive electrode active material of the present invention, contains nickel in a metallic state, so that the nickel hydroxide powder itself has conductivity, and when this is coated and filled in a porous substrate. The present invention provides a positive electrode plate having uniform conductivity over the whole, enhances its utilization rate, improves rapid discharge characteristics, suppresses the collapse of nickel peroxide that occurs during battery overcharge, and contributes to the improvement of battery life. In this case, when the particles of the nickel hydroxide powder are spherical, the filling property in the porous substrate, particularly in the foamed substrate is improved. According to the method for producing a positive electrode active material of the above-mentioned second invention, as described above, nickel and an acid are insufficiently reacted to form a nickel salt in which nickel remains, and when this is neutralized with an alkali, Innumerable nickel hydroxide particles are deposited, and during the deposition, the nickel particles are entangled or sandwiched, so that a product containing innumerable metallic nickel particles in the precipitate is obtained. By grinding such a precipitate, the positive electrode active material powder of the present invention can be obtained. In this case, when the precipitate is ground with a light pressure so as to loosen it, a positive electrode active material powder composed of spherical nickel hydroxide particles is obtained.

[0006]

EXAMPLES Next, examples of the present invention will be described in detail. The positive electrode active material for alkaline storage batteries of the present invention is manufactured as follows.
That is, metal nickel powder, for example, carbonyl nickel powder is used as a starting material of the nickel positive electrode active material, and this is added to an aqueous solution of nitric acid or sulfuric acid having a desired concentration and reacted to generate nickel nitrate or nickel sulfate. According to the invention, a small excess of nickel powder is added in advance so that unreacted metallic nickel remains in a small amount,
By adjusting the reaction time and temperature, a reaction product in which unreacted nickel in a metallic state remains in the produced nickel nitrate or nickel sulfate is produced. Then, an alkaline aqueous solution of caustic soda or caustic potash is mixed with this, and the mixture is neutralized with stirring to precipitate innumerable nickel hydroxide particles by sedimentation, and the sedimented precipitate is filtered, dried, and then pulverized. In this case, the crushing, by applying a light pressure to the precipitate so as not to break the fine particles of nickel hydroxide constituting the precipitate, slow the rotation of the mill, or in the case of manual work,
The X-ray diffraction diagram of the nickel hydroxide powder in which the particles are granular, that is, the positive electrode active material powder, is shown in FIG. 1 by loosening the precipitate by hand. As is clear from FIG. 1, when the reaction between nickel and sulfuric acid or nitric acid is completely performed,
Only the diffraction line of nickel hydroxide was observed, but when the above-mentioned neutralization reaction was incomplete and nickel in the metallic state remained, the diffraction line of nickel in addition to the diffraction line of nickel hydroxide was observed. A diffraction line was observed. Nickel hydroxide Ni (OH) ₂
The residual rate of the metallic nickel Ni in the inside may be in the range of 0.1 to 1 wt.%.

A paste type nickel positive electrode plate is manufactured by a conventional method using the positive electrode active material powder of the present invention composed of the nickel hydroxide powder containing a small amount of nickel thus obtained. That is, for example, 5 wt.% Cobalt powder and 10 nickel powder as a conductive agent are added to the positive electrode active material powder of the present invention.
wt.% was added and mixed, and a 1 wt.% aqueous solution of carboxymethyl cellulose as a thickener was added and kneaded to obtain a paste. This paste was applied and filled on a porous substrate, for example, a foamed nickel substrate, dried, and then pressed to a predetermined thickness to manufacture a paste-type nickel electrode plate. The filling efficiency of the active material into the foamed nickel substrate is particularly improved when the particles of the positive electrode active material powder of the present invention are spherical.

The above positive electrode plate and the negative electrode plate manufactured as described below are laminated and wound with a nylon separator interposed therebetween to form an electrode plate group, which is housed in a cylindrical battery container and a predetermined amount of caustic potash electrolytic solution is injected. Then, a regulated AA size nickel-hydrogen battery with a theoretical capacity of the positive electrode of 1180 mAh was produced. A battery in which a positive electrode using the positive electrode active material of the present invention is incorporated is called a battery A. For comparison, a nickel-hydrogen battery was manufactured by incorporating a pasted positive electrode plate prepared in the same manner as above using a conventional nickel hydroxide powder containing no metallic nickel prepared by a conventional method in the same manner as above.
This battery is referred to as battery B.

The above-mentioned negative electrode plate is manufactured by a conventional method as follows. Commercially available Mm (Misch metal), Ni,
Co and Al powders were weighed and mixed so as to have a constant composition ratio, and this was heated and melted by the high frequency melting method, and MmNi
A hydrogen storage alloy with an alloy composition of _3.55 Co _1.0 Al _0.45 was manufactured, and this was pulverized into alloy powder of 150 mesh or less,
To 100 wt.% Of this alloy powder, 15 wt.% Of carbonyl nickel powder as a conductive agent and 3 wt.% Of polyvinylidene fluoride powder as a binder were added and mixed, and further 1% carboxymethyl cellulose aqueous solution was added and kneaded. , Slurry, apply this dust slurry to a nickel-plated iron-made porous substrate, fill, dry, and then roll it.
A hydrogen storage alloy electrode plate was manufactured by firing at 200 ° C. for 2 hours.

200 mAh for the above batteries A and B
After charging for 7.5 hours at the same current, the battery voltage is
The capacity was measured by discharging to 1.0 V, and this was divided by the theoretical capacity of the positive electrode to obtain the utilization rate of the positive electrode. Furthermore,
The rapid discharge capacities of these batteries A and B were tested.
In the test, the battery was charged at a current of 200 mAh for 7.5 hours and then discharged at a current of 3 A until the battery voltage became 1.0 V, and the rapid discharge capacity was measured. Furthermore, a cycle life test was performed on these batteries A and B. In the test, charging was performed for 1.2 hours at a current of 1 A, and then discharging was repeated at the same current until the battery voltage became 1.0 V, and the life was reached when the capacity reached 600 mAh. The results of the above tests are shown in Table 1 below.

[0011]

[Table 1]

As is clear from Table 1 above, the battery A in which the positive electrode using the positive electrode active material made of nickel hydroxide powder containing a small amount of nickel in the particles is incorporated is nickel hydroxide containing no nickel in the particles. It can be seen that the utilization factor of the positive electrode, the rapid discharge capacity of the battery, and the cycle life are all significantly improved as compared with the battery B incorporating the positive electrode using the conventional positive electrode active material made of powder.

[0013]

As described above, according to the present invention, since the nickel hydroxide powder containing a small amount of nickel is used as the positive electrode active material for the alkaline storage battery, the utilization factor of the positive electrode, the rapid discharge capacity of the battery and the cycle life of the conventional battery can be improved. It has an effect that it can be remarkably improved as compared with the positive electrode active material. Furthermore, according to the second invention, when reacting nickel with an acid, the reaction is carried out so that a small amount of nickel remains, and then the reaction product is reacted with alkali to precipitate nickel hydroxide particles innumerably. As a result, a precipitate containing innumerable nickel is obtained, and by pulverizing the precipitate, it is possible to obtain a positive electrode active material powder made of nickel hydroxide containing a small amount of nickel in a metallic state. In this case, it is preferable to grind the precipitate with a small pressure because a granular nickel hydroxide powder which improves the efficiency of filling the foamed metal substrate with the active material can be obtained.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of a positive electrode active material according to an embodiment of the present invention.

[Table 1]

Claims (4)

[Claims] 1. A positive electrode active material for an alkaline storage battery, which comprises a small amount of nickel in nickel hydroxide powder. 2. The positive electrode active material for an alkaline storage battery, wherein particles of the nickel hydroxide powder containing a small amount of nickel according to claim 1 are spherical. 3. Reacting nickel with nitric acid or sulfuric acid so that a small amount of unreacted nickel remains to prepare nickel nitrate or nickel sulfate containing a small amount of the unreacted nickel. To neutralize, to deposit a myriad of nickel hydroxide particles containing a small amount of nickel, to separate the precipitate, to dry, and then to pulverize, the production of a positive electrode active material for alkaline storage batteries Law. 4. The alkaline storage battery according to claim 3, wherein the crushing of the precipitate is performed by lightly pressing the precipitate to obtain innumerable spherical hydroxide particles containing a small amount of nickel. Manufacturing method of positive electrode active material.