JPH0619990B2 - Nickel electrode manufacturing method for alkaline batteries - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a nickel electrode used in an alkaline storage battery such as a nickel-cadmium or nickel-iron storage battery, particularly an electrode using a sponge-like metal porous body as a support of an active material. Regarding

Conventional configuration and its problems Conventionally, nickel electrodes for alkaline storage batteries, typified by nickel-cadmium storage batteries, have a pocket type, a sintering type, and a paste type, depending on the structure and manufacturing method of the electrode. A foam metal type using a metal sponge-like porous body having a three-dimensionally continuous structure as a support for a substance has been proposed.

Among them, the foam metal type has a three-dimensional mesh-like structure of the sponge-like metal porous body as the support, which is similar to that of the sintered type substrate, and therefore has the same excellent electron conduction as that of the sintered type electrode. Therefore, the discharge performance and life characteristics comparable to those of the sintered electrode can be obtained. Moreover, in the case of a sponge-like metal porous body, any pore size can be selected within the range of several tens of μ to several mm, so a porous body with a pore size of several hundred μ is selected as the substrate, and the active material has a particle size of several μm. The powder can be directly filled by using the powder distributed from μ to hundreds of tens μ. Therefore,
A method similar to the pasting of paste type electrodes can be adopted, and the manufacturing method is simple. Furthermore, the porosity of the substrate is as high as around 95%, and the active material can be packed at a higher density than in the sintering method. In addition,
Since the sintered substrate has a porosity of about 80% and the number of holes is several μm or several tens μm, direct filling of the active material is difficult, and filling with a salt solution is common.

The foam metal type electrode is generally manufactured through the following steps. The electrode lead attachment part is formed on the substrate by pressing, the active material mainly of nickel hydroxide powder is made into a paste-like mixture and is filled inside the porous part of the substrate, the packing density of the active material is improved and kept by pressing, and dried. Reinforcement of retention of filler by addition of binder, drying, lead plate mounting The nickel electrode thus obtained is directly filled with nickel hydroxide, which is the active material. It can be incorporated into a battery without being subjected to conversion treatment and conversion treatment.

However, on the other hand, nickel hydroxide, which is an active material, is not in a state where the electrochemical activation is sufficiently performed.

The utilization rate of the active material exceeds 90% as the activation progresses by sufficiently repeating the charge and discharge in the battery, but the utilization rate of the active material is in the range of 75% to 90% in the initial charge and discharge. And there is a wide range of variation. In addition, the utilization rate may not be improved even after repeated charging and discharging.

It is known that cobalt ions are effective for increasing the utilization rate of such a paste-type electrode, and when cobalt is added in the form of salt, a similar amount can be obtained with a smaller amount than in the case of cobalt powder. The effect is obtained. However, in this case, it was necessary to sufficiently wash the cobalt salt with water to remove anions, and there was a problem that a large amount of water was consumed.

An object of the present invention is to provide a simple method for improving the utilization rate and stabilizing of the active material of the nickel electrode obtained by directly filling the active material powder mainly containing nickel hydroxide into the sponge-like metal porous body. With the goal.

Composition of the Invention The present invention is to fill a mixture containing at least nickel hydroxide powder and nickel powder and cobalt powder into a sponge-like metal porous body, and then impregnate a solution containing an acid and a cobalt salt alone or with a small amount of both, to obtain a water content. In this state, it is left in a high temperature atmosphere and then immersed in an alkaline solution to convert the cobalt salt into a hydroxide.

That is, by adding acid to the paste by this operation,
By partially converting the cobalt used in the paste with an acid into a cobalt salt and converting it into a hydroxide in an alkali, the same effect as when cobalt is added as a salt can be obtained.

In this case, the addition of a small amount of acid or cobalt salt facilitates the removal of anion ions after conversion. On the other hand, if it is converted immediately after the conversion, the effect of addition is not sufficiently exhibited. Therefore, it was found that this problem can be sufficiently solved by leaving it in a water-containing state for at least 12 hours after the addition.

It is desirable that the temperature during the standing is high, and a range of 50 to 100 ° C. is suitable for practical use, and the temperature may be arbitrarily set within this range.

Examples of the present invention will be described below.

Description of Examples For the support of the active material, the structure shown in FIG. 1 made of nickel had a thickness of 1.3 mm, a porosity of 95%, and a pore diameter of 100.
A sponge-like porous body of ˜500 μm was used. In the figure, 1 is nickel of the core material, and 2 is a hole.

Excess paste adhered to the surface of the porous body by uniformly filling the above porous body with a mixture of 81% by weight of nickel hydroxide powder, 15% by weight of nickel powder and 4% by weight of cobalt powder in the form of a paste having a water content of about 35% by weight. Were removed to obtain a size 80 × 240 mm as an active material-filled porous body. After pressurizing this,
Electrode A impregnated with 0.1 mol / cobalt acetate aqueous solution
And 0.1% acetic acid in an aqueous solution of the same concentration used for A.
Electrode B impregnated in a solution containing mol / mol, and acetic acid 0.
An electrode C impregnated with a 1 mol / aqueous solution was prepared. These A, B, C are contained in a water-containing state while preventing evaporation of water.
It was left for 12 hours in an atmosphere of 0, 50, 80 and 100 ° C.
Then, after drying, 10 in a caustic potash solution with a specific gravity of 1.05
It was immersed for a minute, washed with water and dried. Then add a suspension of tetrafluoroethylene as a binder and measure 40 × 60 mm
Was cut into pieces.

Next, these electrode plates A, B and C and the untreated electrode D were used as positive electrodes, the negative electrode was a known cadmium electrode, the separator was polyamide nonwoven fabric, and the electrolyte solution was 30% containing lithium hydroxide.
AA batteries were constructed using a concentrated caustic potash solution.

Battery can be charged at an ambient temperature of 20 ° C with a current of 1 / 10C 160
%, The discharge was repeated at a current of 1/5 C up to 1.0 V. From the discharge capacity of each battery, the theoretical capacity of the positive electrode (289 m per 1 g of Ni (OH) ₂
The performance was evaluated by obtaining the active material utilization rate (calculated as h).

FIG. 2 is a diagram showing the relationship between the standing temperature of the electrode B and the active material utilization rate in the present invention.

In the same figure, the active material utilization rate shows the sufficiently stable 10th cycle. As is clear from the figure, the discharge characteristics are improved by leaving it in a high temperature atmosphere. This is 50-8
This is because the dissolution of cobalt in the paste was promoted under the high temperature condition of 0 ° C., and it took two days or more to obtain the same effect at a temperature near room temperature. Further, in the atmosphere of 100 ° C., the water content in the electrode plate is more likely to be evaporated, so that the discharge characteristics tend to be slightly deteriorated.

FIG. 3 shows the relationship between the charge / discharge cycle and the active material utilization rate of a battery under the conditions in which the electrode plates A, B and C of the present invention were left to stand at 80 ° C. for 12 hours, and the electrode plate D of the conventional formulation. It is a figure. The batteries using the electrodes of A, B, and C of the present invention all showed a performance of about 95%, and almost no deterioration in discharge performance was observed even after 100 cycles. on the other hand,
The battery using the electrode D of the conventional formulation has a utilization rate of around 85%, and no improvement in discharge characteristics is observed due to repeated charging / discharging, and is stabilized with low performance. If the concentration of the aqueous solution of the cobalt salt or acid to be impregnated is too high, residual anions in the electrode may cause problems such as deterioration of self-discharge characteristics. Therefore, the concentration is preferably 0.2 mol / or less. The standing time after impregnation, which affects the electrode performance, varies depending on the standing temperature, but if it is 12 hours or more, a high active material utilization rate can be stably obtained.

Further, although cobalt acetate and acetic acid were used as the cobalt salt and the acid in the above-mentioned examples, other common acids such as nitric acid, hydrochloric acid, phosphoric acid, and formic acid, which dissolve cobalt, and
Similar effects can be obtained by using those cobalt salts.

EFFECTS OF THE INVENTION As described above, the method of the present invention is simple but has a problem in the active material utilization rate. The performance of the nickel electrode for filling the sponge-like metal porous body with the active material in the form of a paste is simple. It can be easily improved by various methods.

[Brief description of drawings]

FIG. 1 is an enlarged view of a sponge-like metal porous body used in an example of the present invention, FIG. 2 is a view showing a relationship between an ambient temperature of an electrode of the present invention and an active material utilization rate, and FIG. FIG. 4 is a diagram showing changes in active material utilization rate with charge and discharge of a battery using the electrode of the present invention and an electrode of a conventional formulation.

Front page continuation (72) Inventor Motohide Masui 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Minoru Yamaga 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Hideo Kaitani 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A conductive porous material is coated with a paste-like mixture containing at least nickel hydroxide powder, nickel powder and cobalt powder, and then impregnated with a solution containing a cobalt salt or an acid and a mixture thereof, and then a water-containing state. And 50 ~
A method for producing a nickel electrode for an alkaline battery, which comprises leaving it in an atmosphere of 100 ° C. for at least 12 hours and then immersing it in an alkali. 2. The production of a nickel electrode for an alkaline battery according to claim 1, wherein the cobalt salt is any one selected from the group consisting of cobalt acetate, cobalt nitrate, cobalt phosphate, cobalt hydrochloride and cobalt sulfate. Law. 3. The method for producing a nickel electrode for an alkaline battery according to claim 1, wherein the acid is selected from the group consisting of acetic acid, nitric acid, phosphoric acid, hydrochloric acid and sulfuric acid. 4. The concentration of the aqueous solution of cobalt salt and acid is 0.
The method for producing a nickel electrode for an alkaline battery according to any one of claims 1 to 3, wherein the amount is 2 mol / or less.