JPH08180859A - Alkaline secondary battery - Google Patents

Abstract

PURPOSE: To manufacture an alkaline secondary battery having a positive electrode having a high utilizing ratio by arranging, in a vessel, a non-sintered positive electrode consisting of nickel hydroxide particle, metal cobalt and copper oxide and a negative electrode with a separator in between, and receiving an alkaline electrolyte in the vessel. CONSTITUTION: A cylindrical alkaline secondary battery is manufactured by spirally winding a non-sintered positive electrode 2 and a negative electrode 1 with a separator 3 being interposed between them, housing them in a bottomed cylindrical vessel 4, and receiving an alkaline electrolyte in the vessel 4. The non-sintered positive electrode 2 contains nickel hydroxide particle, metal cobalt particle, and at least one compound of manganese dioxide, copper oxide and copper hydroxide, and at least one compound of manganese dioxide, copper oxide and copper hydroxide is contained 0.1-3 times the metal cobalt powder by chemical equivalent ratio. Thus, a high capacity alkaline secondary battery having the non-sintered positive electrode 2 having a high utilizing ratio is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline secondary battery, and more particularly to an alkaline secondary battery having an improved non-sintered positive electrode containing nickel hydroxide as an active material.

[0002]

2. Description of the Related Art A sintered positive electrode has been used as a positive electrode incorporated in an alkaline secondary battery. The sintered positive electrode is obtained by sintering nickel particles on a two-dimensional substrate such as a perforated steel or nickel net body, impregnating a dozen micron hole of the obtained porous plate with a nickel salt aqueous solution, and then subjecting it to alkali treatment. It is produced by changing the impregnated nickel salt into nickel hydroxide.

However, the sintered positive electrode requires complicated active material impregnation operations such as a nickel salt impregnation step and an alkali treatment step in its production. Further, in order to impregnate a predetermined amount of active material, the above-mentioned operation is usually carried out in 4 to 10
It needs to be repeated about once. As a result, there is a problem that the manufacturing cost becomes high. Furthermore, since the nickel particle sintered body obtained by the above-mentioned sintering has difficulty in maintaining the mechanical strength when the porosity exceeds 80%, it is not possible to increase the filling amount of the active material. was there.

Therefore, a conductive material, a binder and water are added to and mixed with nickel hydroxide particles to prepare a paste, and this paste is three-dimensionally formed into a sponge-like metal porous body or a metal fiber mat. It has been studied to manufacture a positive electrode by filling a conductive core having a structure. The positive electrode manufactured by such a method is called a non-sintered positive electrode (or a paste positive electrode) as opposed to a sintered positive electrode. The paste-type positive electrode has advantages that the porosity and average pore size of the metal porous body are larger than those of the sintered-type positive electrode, so that the active material can be easily filled and the filling amount can be increased.

By the way, as the conductive material added to the nickel hydroxide particles in the non-sintered positive electrode, metallic cobalt powder has been conventionally known. This metallic cobalt powder is oxidized to cobalt oxyhydroxide having high conductivity through cobalt hydroxide, and since it covers around nickel hydroxide particles that are the positive electrode active material, it becomes conductive between the active materials and between the active material and the conductive material. The utilization factor of the positive electrode can be improved in order to improve the conductivity with the core.

However, even if the metallic cobalt powder is added alone to the non-sintered positive electrode, it is not sufficiently oxidized to cobalt oxyhydroxide having high conductivity, so that the effect of improving the utilization factor of the positive electrode is sufficiently improved. I can't show it.

Therefore, in the initial charging step of the alkaline secondary battery provided with the non-sintered positive electrode containing the metallic cobalt powder, the metallic cobalt powder is charged so as to be preferentially oxidized. However, it was difficult to sufficiently oxidize the metal cobalt powder into cobalt oxyhydroxide having high conductivity.

[0008]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an alkaline secondary battery having a non-sintered positive electrode having a high utilization rate.

[0009]

An alkaline secondary battery according to the present invention is housed in a container and contains at least one compound selected from nickel hydroxide particles, metallic cobalt powder, manganese dioxide, copper oxide and copper hydroxide. And a non-sintered positive electrode containing, a negative electrode housed in the container, the negative electrode being sandwiched between the positive electrodes, and an alkaline electrolyte housed in the container. Is.

The alkaline secondary battery (for example, a cylindrical alkaline secondary battery) according to the present invention will be described in detail with reference to FIG. The negative electrode 1 has a separator 3 between it and the non-sintered positive electrode 2.
It is wound in a spiral shape with the interposition of, and is housed in a cylindrical container 4 having a bottom. The alkaline electrolyte is contained in the container 4. The circular sealing plate 6 having the hole 5 in the center is
It is arranged in the upper opening of the container 4. The ring-shaped insulating gasket 7 is arranged between the peripheral edge of the sealing plate 6 and the inner surface of the upper opening of the container 4, and the sealing plate is attached to the container 4 by caulking to reduce the diameter of the upper opening inward. 6 is airtightly fixed via the gasket 7.
The positive electrode lead 8 has one end connected to the positive electrode 2 and the other end connected to the lower surface of the sealing plate 6. The cap-shaped positive electrode terminal 9 is attached on the sealing plate 4 so as to cover the hole 5. The rubber safety valve 10 is provided with the sealing plate 4
Is arranged so as to close the hole 5 in a space surrounded by the positive electrode terminal 9.

Hereinafter, the negative electrode 1, the positive electrode 2 and the separator 3 will be described.
The alkaline electrolyte will be described in detail. 1) Negative Electrode 1 This negative electrode 1 is composed of, for example, a hydrogen storage alloy negative electrode containing hydrogen storage alloy particles that store and release hydrogen. Such a negative electrode has a structure in which a mixture having a composition including the hydrogen storage alloy powder, a conductive material, and a binder is fixed to a conductive core body which is a current collector.

As the hydrogen storage alloy to be mixed in the mixture of the negative electrode 1, for example, LaNi ₅ , MmNi ₅ (Mm is misch metal), LmNi ₅ (Lm is at least one selected from rare earth elements containing La), N of these alloys
Al, Mn, Co, Ti, Cu, Zn, Z
multi-element system substituted with elements such as r, Cr, B,
Alternatively, TiNi-based and TiFe-based materials can be used. In particular, the general formula _{LmNi w Co x Mn y Al z} ( atomic ratio w, x, y, the total value of z is 5.00 ≦ w + x + y +
A hydrogen storage alloy having a composition represented by z ≦ 5.50) is preferable because it can suppress the pulverization accompanying the progress of the charge / discharge cycle and improve the charge / discharge cycle life.

Examples of the conductive material include carbon black and graphite. Such a conductive material is used in an amount of 0.1 parts by weight based on 100 parts by weight of the hydrogen storage alloy powder.
It is preferable to blend in the range of 4 parts by weight.

Examples of the binder include polyacrylic acid salts such as sodium polyacrylate and potassium polyacrylate, fluororesins such as polytetrafluoroethylene (PTFE), and carboxymethyl cellulose (C).
MC) and the like. Such a binder is
It is preferable to add 0.1 to 5 parts by weight to 100 parts by weight of the hydrogen storage alloy.

Examples of the conductive core include a two-dimensional structure such as punched metal, expanded metal, and wire mesh, and a three-dimensional structure such as foam metal and reticulated sintered metal fiber.

2) Non-sintered positive electrode 2 This non-sintered positive electrode 2 comprises nickel hydroxide particles, metallic cobalt powder, at least one compound selected from manganese dioxide, copper oxide and copper hydroxide, and a binder. The conductive core has a structure in which a paste containing is applied and filled. Such a positive electrode 2 is prepared by preparing a paste by kneading nickel hydroxide particles, metallic cobalt powder, at least one compound selected from manganese dioxide, copper oxide and copper hydroxide, and a binder in the presence of water. The paste is applied to the conductive core, filled, dried, and optionally roller-pressed to manufacture.

The nickel hydroxide particles have an average particle size of 5
Preferably, the tap density is ˜30 μm and the tap density is 1.8 g / cm ³ or more. The nickel hydroxide particles preferably have a specific surface area of 8 to 25 m ² / g.

The nickel hydroxide particles preferably have a spherical shape or a shape similar thereto. The metallic cobalt powder is preferably contained in the positive electrode 2 in a proportion of 5 to 15% by weight based on the nickel hydroxide particles.

At least one compound selected from the manganese dioxide, copper oxide and copper hydroxide is the positive electrode 2
0.1 to 3 in chemical equivalent ratio to metallic cobalt powder
It is preferable that the content is double. When the content of the compound is less than 0.1 times the chemical equivalent ratio, it may be difficult to improve the utilization rate of the positive electrode. On the other hand, if the content of the compound exceeds 3.0 times in terms of chemical equivalent ratio, the oxide having poor conductivity is generated more, and as a result, the utilization factor of the positive electrode may decrease. The more preferable content of the compound is 0.5 to 3 times in chemical equivalent ratio to the metal cobalt powder.

Examples of the binder include carboxymethyl cellulose, polyacrylic acid salt, and fluororesin (eg polytetrafluoroethylene). It is desirable that the amount of such a binder is in the range of 1 to 5% by weight based on the nickel hydroxide particles.

Examples of the conductive core include sponge-like metal porous bodies and felt-plated substrates. 3) Separator 3 Examples of the separator 3 include those made of polypropylene non-woven fabric, nylon non-woven fabric, non-woven fabric made by mixing polypropylene fiber and nylon fiber, and the like. In particular, a polypropylene nonwoven fabric whose surface is hydrophilized is suitable as the separator 3.

4) Alkaline Electrolyte Solution Examples of the alkaline electrolyte solution include a mixed solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH),
Mixture of potassium hydroxide (KOH) and LiOH, or N
A mixed solution of aOH, KOH and LiOH or the like can be used.

In FIG. 1 described above, the separator 3 is interposed between the negative electrode 1 and the non-sintered positive electrode 2 and wound in a spiral shape and housed in a cylindrical container 4 having a bottom. Alternatively, a separator may be interposed between each of the positive electrodes and the plurality of positive electrodes to form a laminated body, and the laminated body may be housed in a bottomed rectangular tubular container.

[0024]

The non-sintered positive electrode incorporated in the alkaline secondary battery according to the present invention contains nickel hydroxide particles, metallic cobalt powder, and at least one compound selected from manganese dioxide, copper oxide and copper hydroxide. , With high utilization.

That is, the metal cobalt powder is oxidized through cobalt hydroxide into cobalt oxyhydroxide having high conductivity, thereby improving the utilization rate of the positive electrode. However, since the metal cobalt powder forms an inactive oxide film on its surface in the alkaline electrolyte, hydroxide ions cannot penetrate to the inside of the metal cobattle powder,
Oxidation to cobalt hydroxide does not occur sufficiently. As a result, the rate of oxidation to cobalt oxyhydroxide also decreases.

Therefore, according to the present invention, at least one compound selected from manganese dioxide, copper oxide and copper hydroxide is added to a non-sintered positive electrode containing nickel hydroxide and metallic cobalt powder to obtain the above-mentioned compound. Since a compound such as copper oxide acts as an oxidizing agent in the alkaline electrolyte, it is possible to suppress the formation of an inactive oxide film on the surface of the metallic cobalt powder. In addition, the compound can accelerate the oxidation of the metallic cobalt powder to cobalt hydroxide. As a result, the ratio of the metallic cobalt powder oxidized to cobalt oxyhydroxide having high conductivity via cobalt hydroxide can be increased, so that the nickel hydroxide particles as the active material can be further activated and the utilization rate of the positive electrode can be improved. Can be improved. Therefore, the capacity of the alkaline secondary battery including the non-sintered positive electrode having such a high utilization rate is remarkably improved.

[0027]

The preferred embodiments of the present invention will be described in detail below. Example 1 1 part of cobalt metal to 90 parts by weight of nickel hydroxide particles
0 parts by weight and 7 parts by weight of manganese dioxide as an oxidizing agent (the same chemical equivalence ratio as the metal cobalt powder) were added, and 0.25 parts by weight of carboxymethyl cellulose, 0.25 parts by weight of sodium polyacrylate, poly A paste was prepared by adding 3.0 parts by weight of tetrafluoroethylene and 30 parts by weight of water and kneading. A non-sintered positive electrode was produced by applying this paste to a conductive core made of nickel fiber and filling it, followed by drying and roller pressing.

Further, commercially available Mm (Misch metal; mixture of rare earth elements), Ni, Co, Mn and Al are in a weight ratio of 4.0: 0.4: 0.3: 0.3, respectively. After being weighed in this manner, it is melted in a high frequency melting furnace and the melt is cooled to obtain MmNi _4.0 Co _0.4 Mn _0.3 A
An alloy ingot having a composition of _0.3 was prepared. Subsequently, the alloy ingot was mechanically crushed and sieved to obtain a hydrogen storage alloy powder having a particle size of 50 μm or less.
Subsequently, carboxymethyl cellulose, carbon and water were added to this hydrogen storage alloy powder to prepare a paste. Then, the above-mentioned paste was applied to punched metal, dried, and molded to prepare a negative electrode.

A separator made of hydrophilically treated polypropylene non-woven fabric is arranged between the positive electrode and the negative electrode thus obtained,
After these positive electrode groups are housed in a metal container, an electrolytic solution containing potassium hydroxide as a main component is housed in the container, and an AA battery having the structure shown in FIG. Size cylindrical nickel-hydrogen secondary battery (theoretical capacity;
1.1 Ah) was assembled.

Example 2 A non-sintered positive electrode was prepared in the same manner as in Example 1 except that 12 parts by weight of copper oxide (the same equivalence ratio as the metal cobalt powder) was used as the oxidizing agent. Using this positive electrode, the same negative electrode as in Example 1, a separator and an electrolytic solution, an AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. 1 was assembled.

Example 3 A non-sintered positive electrode was produced in the same manner as in Example 1 except that 8 parts by weight of copper hydroxide (the same equivalence ratio as the metal cobalt powder) was used as the oxidizing agent. Using this positive electrode, the same negative electrode as in Example 1, a separator and an electrolytic solution, an AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. 1 was assembled.

Comparative Example 1 90 parts by weight of nickel hydroxide particles and 1 part of metallic cobalt
Add 0 parts by weight, 0.25 parts by weight of carboxymethyl cellulose, 0.25 parts by weight of sodium polyacrylate, 3.0 parts by weight of polytetrafluoroethylene and 30 parts by weight of water and knead to the mixture. An agent-free paste was prepared. After coating and filling this paste into a conductive core made of nickel fibers,
A non-sintered positive electrode was produced by drying and roller pressing. Using this positive electrode, the same negative electrode as in Example 1, a separator and an electrolytic solution, an AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. 1 was assembled.

The nickel-hydrogen secondary batteries of Examples 1 to 3 and Comparative Example 1 thus obtained were charged at 0.1 CmA for 15 hours and discharged to 1.0 V at 1 CV. I checked. The results are shown in Table 1 below.

[0034] As is clear from Table 1, the non-sintered positive electrode incorporated in the secondary batteries of Examples 1 to 3 of the present invention has a higher utilization factor than the non-sintered positive electrode of the secondary battery of Comparative Example 1. You know that you have.

Example 4 1 part of cobalt metal to 90 parts by weight of nickel hydroxide particles
0.35 parts by weight, 0.7 parts by weight, 3.5 parts by weight, 7 parts by weight, 14 parts by weight, 21 parts by weight, 28 parts by weight (metal The chemical equivalence ratio to cobalt powder was 0.
05 times, 0.1 times, 0.5 times, 1 time, 2 times, 3 times, 4
2 times), and 0.25 parts by weight of carboxymethyl cellulose, 0.25 parts by weight of sodium polyacrylate, 3.0 parts by weight of polytetrafluoroethylene and 30 parts by weight of water are added to each of these mixtures and kneaded. Seven pastes were prepared. Each of these pastes was applied to and filled in a conductive core made of nickel fiber, dried, and roller-pressed to produce seven kinds of non-sintered positive electrodes. In addition, a positive electrode was produced by the same method except that manganese dioxide as an oxidizing agent was not included in the production of such a non-sintered positive electrode. Eight kinds of AA having the structure shown in FIG. 1 described above using the positive electrode, the same negative electrode as in Example 1, the separator, and the electrolytic solution.
A size-sized cylindrical nickel-hydrogen secondary battery was assembled.

Each of the nickel-hydrogen secondary batteries obtained in Example 4 was charged at 0.1 CmA for 15 hours to obtain 1.0 CmA.
The utilization rate of the non-sintered positive electrode when discharged to 1 V was investigated. The result is shown in FIG.

As is apparent from FIG. 2, the non-sintered positive electrode in which the addition amount of manganese dioxide which is an oxidizing agent is 0.1 to 3 times as much as the chemical equivalence ratio with respect to the metal cobalt powder may have a high utilization rate. Recognize.

[0038]

As described in detail above, according to the present invention, it is possible to provide a high-capacity alkaline secondary battery provided with a non-sintered positive electrode having a high utilization rate.

[Brief description of drawings]

FIG. 1 is a partially exploded perspective view showing a nickel-hydrogen secondary battery according to the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the amount of manganese dioxide added and the utilization rate of the positive electrode in the non-sintered positive electrode in Example 4 of the present invention.

[Explanation of symbols]

1 ... Negative electrode, 2 ... Positive electrode, 4 ... Container, 6 ... Sealing plate, 7 ... Insulating gasket, 9 ... Positive electrode terminal.

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

Claims (2)

[Claims] 1. A non-sintered positive electrode which is housed in a container and contains nickel hydroxide particles, metallic cobalt powder, and at least one compound selected from manganese dioxide, copper oxide, and copper hydroxide. An alkaline secondary battery comprising: a negative electrode that is housed and arranged with the separator interposed between the positive electrode and an alkaline electrolyte solution that is housed in the container. 2. The at least one compound selected from manganese dioxide, copper oxide and copper hydroxide is 0.1 to 3 in a chemical equivalent ratio to the metal cobalt powder in the positive electrode.
The alkaline secondary battery according to claim 1, wherein the alkaline secondary battery is contained twice.