JPH08203516A - Non-sintered nickel electrode and its manufacture - Google Patents

Abstract

PURPOSE: To provide a nickel electrode having a high utilizing ratio of positive electrode active material and capable of ensuring a stable battery capacity, and a manufacturing method in which such a nickel electrode can be easily manufactured. CONSTITUTION: A nickel electrode has a three-dimensional porous metal base 1 and a nickel hydroxide particle 2 filled and supported in the metal base 1, and the surface of the nickel hydroxide particle 2 is covered with cobalt oxyhydroxide 3. A method for manufacturing such a nickel electrode comprises a process for adding an alkali aqueous solution to a cobalt sulfide aqueous solution in which the nickel hydroxide particle is dispersed followed by stirring to cover the nickel hydroxide particle surface with a cobalt compound; a process for separating the nickel hydroxide particle covered with the cobalt compound, and heating and drying it to oxidize the cobalt compound into cobalt oxyhydroxide; a process for filling and supporting a paste material containing the nickel hydroxide particle covered with cobalt oxyhydroxide in the three- dimensional porous metal base; and a process for drying the filled and supported paste material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-sintered (non-sintered) nickel electrode and a method for manufacturing the same, and more specifically, to a non-sintered type alkaline alkaline battery with improved electrode utilization. The present invention relates to a nickel electrode and a manufacturing method thereof.

[0002]

2. Description of the Related Art Alkaline secondary batteries represented by nickel-hydrogen secondary batteries or nickel-cadmium secondary batteries are widely used as operating power sources for various equipment systems such as portable telephones and portable image pickup devices. Has been converted. In other words, this type of alkaline secondary battery can be repeatedly used to secure or store electric power by charging operation and to drive (discharge) a load using the secured or stored electric power as a power source. It is incorporated and put into practical use.

By the way, the alkaline secondary battery is equipped with
The positive electrode to be mounted has a three-dimensionally porous (porous) metal substrate that functions as a so-called current collector and has nickel hydroxide as a positive electrode active material filled and supported thereon. In addition, in this structure, conductive powder is also added to activate the positive electrode active material. When cobalt oxide (cobalt monoxide), cobalt hydroxide, or both are added, positive electrode active material It is also known that the utilization rate can be improved. That is, in the case where the cobalt compound is added to and contained in the nickel electrode, it is electrochemically oxidized by the first charge of the secondary battery, and as shown by the following formula, cobalt oxyhydroxide rich in conductivity is added. The generated nickel oxyhydroxide coats the peripheral surface of nickel hydroxide, which is the active material, to improve the conduction between the active materials and between the three-dimensional porous metal substrates, thereby improving the utilization efficiency of the nickel electrode. Will be improved.

CoO + OH ⁻ → HCoO ^{2 −} (1) HCoO ^{2 −} + H ₂ O → Co (OH) ₂ + OH ⁻ (2) Co (OH) ₂ + OH ⁻ → CoOOH + H ₂ O + e ⁻ (3) As shown in reaction formula (3), cobalt hydroxide is converted into cobalt oxyhydroxide by releasing an electron sum after the OH ⁻ ion contacts the surface.

The nickel electrode is generally manufactured as follows. That is, a three-dimensional porous metal substrate that functions as a current collector, for example, a nickel fiber-based substrate, is coated and filled with a paste containing a nickel oxide-based active material, and then heated and dried to produce a nickel electrode. There is. More specifically, a nickel oxide powder containing a required amount of conductive powder such as cobalt oxide powder or cobalt hydroxide powder, a binder resin component such as carboxymethyl cellulose, sodium polyacrylate, polytetrafluoroethylene or methyl cellulose, and water. A paste prepared with a medium such as the following is applied / filled to, for example, a nickel fiber-based substrate, and then heat-dried / treated as appropriate to fill / carry the required active material. I have a nickel electrode.

[0006]

However, the nickel electrode obtained by the above-mentioned manufacturing method cannot be said to be sufficiently satisfactory in practical use. That is, in order to improve the utilization rate of the positive electrode active material, even if a structure in which a cobalt compound is added to and contained in a nickel electrode is adopted, in order to secure a stable battery capacity, the cobalt compound is sufficient at the time of initial charging. It is premised that it is oxidized to cobalt oxyhydroxide. When converting the cobalt oxyhydroxide during the initial charging, it is inevitably necessary to set proper initial charging conditions, and complicated operations are inevitable. Furthermore, as mentioned above, in the case of electrochemically producing cobalt oxyhydroxide, not only the operation becomes complicated, but also it is determined by the dispersion state of the cobalt compound, and relatively large and small in the places where many are dispersed. A relatively small amount is generated in the dispersed portion, and unevenness occurs in the cobalt oxyhydroxide layer formed on the surface of nickel hydroxide, and it often happens that nickel hydroxide in the nickel electrode cannot be effectively used. Therefore, in an alkaline secondary battery in which this type of nickel electrode is mounted / incorporated, at the time of first charging, selection and setting of charging conditions such that the cobalt compound added / contained in the nickel electrode is preferentially oxidized. However, various efforts are being made. However, the selection or setting of sufficient or effective charging conditions has not been successful yet, and the purpose of ensuring sufficient battery capacity is still unachieved.

The present invention has been made in consideration of such circumstances, and a nickel electrode which has a high utilization rate of a positive electrode active material and can secure a stable battery capacity, and such a nickel electrode An object of the present invention is to provide a manufacturing method that can be easily manufactured.

[0008]

A first nickel electrode according to the present invention comprises a three-dimensionally porous metal substrate and nickel hydroxide particles filled and supported on the metal substrate, and The surface of the nickel hydroxide particles is coated with cobalt oxyhydroxide.

The second nickel electrode according to the present invention is characterized in that the three-dimensional porous metal substrate forming the first nickel electrode is a nickel fiber-based plate.

The method for producing a nickel electrode according to the present invention comprises:
A process of adding and stirring an alkaline aqueous solution to an aqueous cobalt sulfate solution in which nickel hydroxide particles are dispersed, and separating the nickel hydroxide particles coated with the cobalt compound on the surface of the nickel hydroxide particles, and heating and drying. A step of applying a treatment to oxidize the cobalt compound into cobalt oxyhydroxide, and a step of filling and supporting a paste-like material containing the nickel hydroxide particles coated with the cobalt oxyhydroxide on a three-dimensional porous metal substrate. And a step of drying the filled and supported paste-like material.

As described above, in the non-sintered nickel electrode and the method for producing the same according to the present invention, the surface of the nickel hydroxide particles filled and supported on the three-dimensional porous metal substrate is previously made of cobalt oxyhydroxide. The outline is that it is covered. That is, the present invention, the surface of the nickel hydroxide particles as the active material filled and supported on the three-dimensional porous metal substrate is previously coated with a cobalt oxyhydroxide layer to obtain the required conductivity before the initial charging. Is added.

In the present invention, the three-dimensional porous metal substrate is made of, for example, a nickel fiber-based plate, a nickel-based porous plate, nickel steel, stainless steel, or an alkali-resistant material such as nickel-plated resin. Examples include those processed into a net shape, sponge shape, fiber shape, felt shape, etc. Generally, porosity is about 90 to 95%, thickness 1
It is preferably about 2 mm.

Further, in the present invention, the nickel hydroxide-based active material filled and supported on the three-dimensional porous metal substrate is
The nickel hydroxide particles are formed of nickel hydroxide particles whose surface is coated with cobalt oxyhydroxide, and a binder such as carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, polytetrafluoroethylene, and the like. You may take the form which added electroconductive powders, such as a metal cobalt powder and a metal nickel powder.

Further, in the present invention, the alkaline aqueous solution added when producing the nickel hydroxide particles coated with cobalt oxyhydroxide is, for example, a sodium hydroxide aqueous solution having a concentration of 1N or more, a potassium hydroxide aqueous solution, and water. Examples thereof include a lithium oxide aqueous solution. Here, if the concentration of the alkaline solution is less than 1N, the effect of immersion / treatment tends to be insufficient, so it is preferable to select 1N or more.

In the present invention, the heating and drying after the addition and stirring of the alkaline solution is generally carried out at a temperature of 40 to 2
It is desirable to select and set the temperature at about 00 ℃ for about 10 to 60 minutes. That is, this heat-drying treatment is preferably at least about 60 ° C. from the viewpoint of providing the energy required for converting a cobalt compound such as cobalt hydroxide to cobalt oxyhydroxide, and at 200 ° C. or higher, water forming the active material is used. Nickel oxide tends to oxidize to nickel oxide.

[0016]

[Function] In the case of the first nickel electrode, the active material is filled
The surface of the nickel active material, that is, the nickel hydroxide particles, which are filled / supported on the supported three-dimensional porous metal substrate, is previously coated with cobalt oxyhydroxide having good conductivity. The conductivity between the active material particles and the conductivity between the nickel hydroxide particles and the three-dimensional porous metal substrate (current collector) are improved, and it is possible to function as a nickel electrode capable of ensuring a sufficient battery capacity. Become.

In the case of the second nickel electrode, in addition to the function of the first nickel electrode, the three-dimensional porous metal substrate is selected as the nickel fiber-based porous substrate.
Further, it is possible to more easily ensure the filling and supporting of the required active material, and it is possible to function as a nickel electrode with higher performance.

In the case of the method for producing a nickel electrode, a required highly conductive cobalt oxyhydroxide layer is formed on the surface of the positive electrode active material, that is, nickel hydroxide particles, and the nickel hydroxide particle system is three-dimensionally formed. Since the porous metal substrate is filled and supported, nickel electrodes corresponding to the first and second nickel electrodes can be obtained more easily and with good yield.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is an enlarged schematic cross-sectional view of the structure of the non-sintered nickel electrode according to the present invention, in which 1 is a three-dimensional porous metal substrate made of nickel fiber, for example, 2 Is nickel hydroxide particles having an average particle size of about 10 μm, which are filled and carried in the voids of the metal substrate 1, 3 is a cobalt oxyhydroxide layer covering the surface of the nickel hydroxide particles 2, and 4 is, for example, polytetrafluoroethylene Binder resin such as. Then, such a non-sintered nickel electrode according to the present invention can be easily manufactured through the following steps, for example. First, 1000 g of nickel hydroxide particles having an average particle size of about 10 μm was added to a saturated aqueous solution of cobalt sulfate.
A dispersion liquid dispersed in 800 ml was prepared. Next, while stirring the above dispersion liquid, 300 ml of an aqueous 8N sodium hydroxide solution was added to the stirring dispersion liquid, and stirring was continued after the addition was completed. Then, nickel hydroxide particles were filtered and separated from the dispersion liquid to obtain nickel hydroxide particles whose surface was coated with cobalt hydroxide (Sample a ... Reference Example). In addition, the nickel hydroxide particles coated with cobalt hydroxide (sample a) were divided into two parts, and a part of them was heated and dried at a temperature of 100 ° C. to obtain nickel hydroxide whose surface was coated with cobalt oxyhydroxide. Particles (Sample A ... Example) were obtained.

The properties of the above-obtained sample A ... Nickel hydroxide particles of the example and sample a ... Nickel hydroxide particles of the reference example were evaluated by SEM and EDX observation. It was observed that the surface of the nickel particles was uniformly coated.

100 parts by weight of nickel hydroxide particles coated with cobalt oxyhydroxide (Sample A ... Example) or 100 parts by weight of nickel hydroxide particles coated with cobalt hydroxide (Sample a ... Reference example) , As an adhesive (binder) 0.2510 parts by weight of carboxymethyl cellulose, 0.2510 parts by weight of sodium polyacrylate, 3.0 parts by weight of polytetrafluoroethylene, and 30 parts by weight of water as composition components, and kneading these two types of Paste-like active materials (Sample A ′ and Sample a ′) were prepared.

Next, the above-mentioned paste-like active material: sample A'and sample a'are applied and filled on a tape-like nickel fiber substrate prepared in advance, respectively, and then dried or pressed. And each active material:
Two types of non-sintered nickel electrodes were prepared to fill and carry the sample A or the sample a. The non-sintered nickel electrode produced in this manner was observed and evaluated by voltammogram measurement. As a result, in the case of the nickel electrode formed using the active material: sample A ′, cobalt divalent / trivalent oxidation was performed. No peak was observed, and cobalt oxyhydroxide was formed, whereas in the case of the nickel electrode formed using the active material: sample a ′, a divalent / trivalent cobalt oxidation peak was observed. .

For comparison, a nickel-based active material (sample b) was prepared by adding and blending 10 parts by weight of cobalt hydroxide particles to 90 parts by weight of nickel hydroxide particles having an average particle size of 10 μm. When their properties were evaluated by SEM and EDX observation, it was observed that cobalt compounds were scattered between the nickel hydroxide particles. Further, the active material (sample b) was made into a paste-like active material (sample b ') under the same conditions as above, and a non-sintered nickel electrode was manufactured.

Next, the nickel electrodes of the above-mentioned Examples, Reference Examples and Comparative Examples were each wound with a separator made of a hydrogen electrode layer and a polyolefin fiber non-woven fabric to form an electromotive element part. Then, this electromotive element part (rolled body) is mounted in a battery outer can (container) which also serves as a negative electrode terminal, and an alkaline electrolyte is injected in a form of impregnating the electromotive element part by a conventional means. , Three types of AA size sealed nickel hydride batteries (theoretical capacity 1.1Ah) were manufactured. In addition,
The hydrogen electrode layer is LmNi _4.0 Co _0.4 Mn _0.3 Al _0.3 (however, Lm
Is a misch metal), 100 parts by weight of hydrogen storage alloy powder having a composition of 0.5 parts by weight, polyacrylate salt 0.5 parts by weight, carboxymethyl cellulose 0.125 parts by weight, polytetrafluoroethylene 1.5 parts by weight, carbon powder 1.0 part by weight and pure water 50 A paste prepared by kneading and adding parts by weight,
It is manufactured by coating and drying on a net made of nickel and roller pressing.

Each nickel-hydrogen battery produced as described above was charged at a constant current of 0.1 C for 15 hours, and then discharged to a battery voltage of 1 V at a constant current of 1.0 C. Utilization rate of nickel positive electrode When the (%) was tested and evaluated, it was as shown in the following table. As can be seen from the above table, the nickel electrode according to the present invention,
That is, in the case of an alkaline secondary battery incorporating a non-sintered nickel electrode having a configuration in which nickel hydroxide particles whose surface is coated with cobalt oxyhydroxide are filled and supported on a current collector, reference examples and It can be seen that the nickel positive electrode has higher utilization efficiency and higher performance than the comparative example.

In the above, the production example of the nickel electrode for the nickel-hydrogen secondary battery is shown, but the same result can be obtained by applying it to the nickel-cadmium secondary battery.

[0028]

As described above, in the case of the non-sintered nickel electrode according to the present invention, the active material filled in and supported on the three-dimensional porous metal substrate functioning as a current collector, that is, nickel hydroxide. The surface of the particles has already been layered with cobalt oxyhydroxide to give good conductivity. In other words, the surface (peripheral surface) of the nickel hydroxide particles is covered with the cobalt oxyhydroxide layer having good conductivity, without the need for separately performing a complicated electrochemical treatment. The conduction and the conduction between the nickel hydroxide particles and the three-dimensionally porous metal substrate (current collector) are improved, sufficient battery capacity can be secured, and high performance of the secondary battery can be achieved.

Further, in the case of the method for producing a non-sintered nickel electrode according to the present invention, a non-sintered nickel electrode having the above-described actions and effects can be easily obtained with a high yield. It becomes possible.

[Brief description of drawings]

FIG. 1 is an enlarged schematic sectional view of a structure of a non-sintered nickel electrode according to the present invention.

[Explanation of symbols]

1 ... Three-dimensional porous metal substrate 2 ... Nickel hydroxide particles 3 ... Cobalt oxyhydroxide layer 4
...... Binder fat

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Sugano 3-4-10 Minami-Shinagawa, Shinagawa-ku, Tokyo Inside Toshiba Battery Co., Ltd.

Claims (3)

[Claims] 1. A three-dimensionally porous metal substrate, and nickel hydroxide particles filled and supported on the metal substrate, wherein the surface of the nickel hydroxide particles is coated with cobalt oxyhydroxide. The non-sintered nickel electrode is characterized in that 2. A non-sintered nickel electrode, wherein the three-dimensional porous metal substrate according to claim 1 is a nickel fiber-based plate. 3. A step of adding an alkali aqueous solution to a cobalt sulfate aqueous solution in which nickel hydroxide particles are dispersed and stirring the mixture to coat the surface of the nickel hydroxide particles with a cobalt compound, and the nickel hydroxide particles coated with the cobalt compound. Separation, heating and drying treatment to oxidize cobalt compound to cobalt oxyhydroxide, and filling paste containing nickel hydroxide particles coated with the cobalt oxyhydroxide into a three-dimensional porous metal substrate A method for producing a non-sintered nickel electrode, comprising a step of supporting and a step of drying the filled and supported paste-like material.