KR19980026469A - Nickel electrode and its manufacturing method - Google Patents

Abstract

The nickel electrode according to the present invention comprises the steps of preparing an active material paste by mixing nickel hydroxide and a cobalt oxide and an alkali solution which is a conductivity enhancer under a high temperature oxygen atmosphere; And applying the active material paste to a porous nickel current collector to dry the nickel electrode. According to the present invention, an alkali solution is added during the preparation of the active material paste and a mixed reaction is performed in a high temperature oxygen atmosphere to form a cobalt oxyhydroxide film on the surface of nickel hydroxide, thereby preventing the reduction of the size of the charging reservoir that may occur during supercharge. It becomes possible. Therefore, it is possible to prevent the internal pressure of the battery from rising, thereby improving the battery life.

Description

Nickel electrode and its manufacturing method

The present invention relates to a nickel electrode and a method for manufacturing the same, and more particularly to a nickel electrode and a method for manufacturing the same that can reduce the breakdown voltage of the battery and improve the life characteristics.

In the nickel-hydrogen secondary battery, the nickel electrode includes a porous nickel current collector having a plurality of holes and a cathode active material filled in the pores of the porous nickel current collector, and is generally manufactured by a sintering method. In this method, a slurry containing nickel powder as a main component is applied to a perforated nickel plated steel sheet, dried and sintered to form a porous nickel current collector, and the porous nickel current collector thus formed is repeatedly repeatedly deposited in a nickel salt solution and an alkaline solution. To precipitate nickel hydroxide in the pores of the nickel current collector and convert the nickel hydroxide into an alkali electrolyte solution to produce an electrode.

However, the sintered nickel electrode has disadvantages of excellent durability but small size, complicated manufacturing process, and long manufacturing time.

As another method of manufacturing the nickel electrode to compensate for these shortcomings, the paste type manufacturing method has been put into practical use since the late 80s. This method is a method of manufacturing a nickel electrode by spraying or applying an active material mixed with a paste, such as a conductive agent, an adhesive, or the like, onto a surface of a porous nickel current collector, such as foamed nickel or nickel felt, using a roller or the like, followed by drying.

In the paste-type nickel electrode manufacturing method, the porous nickel current collector used as the current collector has a large average pore size, so that it is easy to fill the active material and has a large filling amount. Therefore, the nickel electrode manufactured by the paste method can increase the size of the electrode as well as simplify the manufacturing process as compared with the nickel electrode produced by the sintering method.

Due to these advantages, the nickel electrode of the nickel-metal hydride secondary battery has recently been manufactured by a paste manufacturing method.

Since nickel hydroxide used as a positive electrode active material is an insulator, much effort has been made to add cobalt compounds, metal compounds, or other conductive agents to impart conductivity and improve utilization of active materials.

Among the conductive agents, cobalt compounds are most preferably used. The cobalt compound contained in the nickel electrode is dissolved in an alkaline electrolyte to form cobalt complex ions, which are precipitated in the form of cobalt hydroxide on the surface of nickel hydroxide, and then oxidized with cobalt oxyhydroxide, which is highly conductive during supercharge, to form a conductive coating Improve the conductivity of the nickel electrode.

The cobalt compound is very effective to improve the conductivity of the nickel electrode, but the amount of charge is insufficient until the cobalt oxyhydroxide film is formed on the surface of the nickel active material at the anode. . However, as the size of the discharge reservoir increases, the size of the charge reservoir of the positive electrode decreases, so that oxygen gas that may occur during overcharging cannot be sufficiently stored, thereby causing an undesirable result of high internal pressure of the battery.

The technical problem to be achieved by the present invention is to provide a nickel electrode capable of reducing the breakdown voltage of the battery and improving the life characteristics by forming a conductive film on the surface of nickel hydroxide in advance.

In addition, another technical problem to be achieved by the present invention is to provide a method for manufacturing a nickel electrode that can reduce the breakdown voltage of the battery and improve the life characteristics by forming a conductive film on the surface of nickel hydroxide in advance.

The first technical problem of the present invention is a nickel electrode including nickel hydroxide as an active material, the surface of the nickel hydroxide can be achieved by a nickel electrode, characterized in that the coating with a cobalt oxyhydroxide film.

A second technical problem of the present invention is to prepare an active material paste by mixing nickel hydroxide and a cobalt oxide and an alkali solution, which is a conductivity enhancer, under a high temperature oxygen atmosphere; And it may be achieved by a method for producing a nickel anode comprising the step of applying the active material paste to a porous nickel current collector to dry.

In the production method of the present invention, the cobalt oxide is preferably cobalt monooxide, and 30 to 40% of potassium hydroxide solution is preferably used as the alkaline solution. In addition, the active material paste manufacturing step is preferably carried out at 45 to 80 ℃.

According to the manufacturing method of the present invention, the cobalt oxide is dissolved in an alkaline solution and reacts with oxygen at a high temperature to form a cobalt oxyhydroxide film on the surface of nickel hydroxide. Therefore, it is possible to prevent the size reduction phenomenon of the charging reservoir that may occur during supercharge, thereby preventing the increase in the battery internal pressure, and thus the life of the battery may be improved.

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to this.

[Example 1-6]

After adding 12 g of cobalt monooxide to 100 g of spherical nickel hydroxide, the nickel hydroxide, cobalt monooxide and potassium hydroxide solution were prepared while controlling the concentration of potassium hydroxide solution, the time required for mixing, and the temperature at the time of mixing as shown in Table 1 below. By mixing, active material pastes A to F were prepared.

Each of the active material paste was filled with foamed nickel, followed by drying and rolling to prepare nickel electrodes A to F.

The nickel electrodes were assembled with a hydrogen storage alloy negative electrode and a polypropylene nonwoven separator, respectively, to prepare batteries A to F having a nominal capacity of 1200 mAh, and then the internal pressure after 100 charge and discharge cycles were performed for each of the batteries. The life is measured and shown in Table 2 below. In this case, the internal pressure is the maximum pressure when the battery is charged at 200% with a charging rate of 1C, and the service life is when the battery reaches 90% of its initial capacity by repeating the charging and discharging process of charging 1,130% and discharging to 1.0V at 1C. .

[Comparative Example 1]

Battery G was prepared according to the method as described in the Examples, except that an alkali solution was added and nickel hydroxide and cobalt monooxide were mixed at room temperature according to a conventional method to prepare an active material paste. The internal pressure and lifetime of the was measured and the results are shown in Table 2 below.

As can be seen from the results in Table 2, in the case of a battery employing a nickel electrode manufactured according to a conventional method (comparative example), the breakdown voltage is remarkably high while the life is very short.

According to the present invention, when an alkali solution is added during the preparation of the cathode active material paste and mixed reaction in a high temperature oxygen atmosphere, a cobalt oxyhydroxide film is formed on the surface of nickel hydroxide, thereby preventing the size of the charging reservoir that may occur during supercharge. You can do it. Therefore, it is possible to prevent the internal pressure of the battery from rising, thereby improving the battery life.

Claims (5)

In a nickel electrode containing nickel hydroxide as an active material, A nickel electrode, wherein the surface of the nickel hydroxide is coated with a cobalt oxyhydroxide film. Preparing an active material paste by mixing nickel hydroxide and a cobalt oxide and an alkali solution, which is a conductivity enhancer, under a high temperature oxygen atmosphere; And The method of manufacturing a nickel electrode comprising the step of applying the active material paste to a porous nickel current collector to dry. 3. The method of claim 2, wherein the cobalt oxide is cobalt monooxide. The method of claim 2, wherein the alkaline solution is 30 to 40% potassium hydroxide solution. The method of claim 2, wherein the active material paste manufacturing step is carried out at 45 to 80 ℃.