JPH0896807A - Alkaline secondary battery - Google Patents

Abstract

PURPOSE: To provide an alkaline secondary battery having a positive electrode with high charging efficiency at high temperature. CONSTITUTION: An alkaline secondary battery has a positive electrode 1 prepared by filling paste containing nickel hydroxide powder as the main component in a current collector, a negative electrode 2, a separator 3 placed between the positive electrode 1 and the negative electrode 2, and an alkaline electrolyte. The positive electrode 1 contains metallic manganese or a manganese compound, and the content of the metallic manganese or the manganese compound is 1-10mg per Ah capacity of the positive electrode in manganese element equivalent.

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 having an improved positive electrode having a structure in which a current collector is filled with a paste containing nickel hydroxide powder as a main component.

[0002]

2. Description of the Related Art In an alkaline secondary battery, an electrode group made by interposing a separator made of synthetic resin fiber between a nickel positive electrode and a negative electrode is housed in a container together with an alkaline electrolyte made of potassium hydroxide, for example. It has a structure. The nickel positive electrode is prepared by kneading nickel hydroxide powder, a conductive agent such as cobalt oxide or cobalt hydroxide, a binder, and water to prepare a paste, and then forming the paste into, for example, a three-dimensional sponge form. It is manufactured by filling a current collector such as a metal porous body or a metal fiber mat.

When the secondary battery provided with the positive electrode is charged at a high temperature, the oxygen overvoltage of the positive electrode is lowered. Therefore, the charging reaction of the nickel hydroxide powder of the positive electrode represented by the following formula (1) and the following (2) The potential difference from the oxygen gas generation reaction as a side reaction shown in the formula becomes small. As a result, the two reactions compete with each other, so that there is a problem that the amount of NiOOH produced decreases and the charging efficiency of the positive electrode decreases.

Ni (OH) ₂ + OH ⁻ → NiOOH + H ₂ O + e ⁻ (1) 4OH ⁻ → 2H ₂ O + O ₂ + 4e ⁻ (2) Therefore, the nickel hydroxide powder contains several% of cadmium or zinc. The addition of lithium hydroxide to the alkaline electrolyte is performed. However, it is difficult to sufficiently improve the charging efficiency of the positive electrode in the high temperature state by these methods.

On the other hand, JP-A-5-47380 discloses a nickel hydroxide electrode for an alkaline secondary battery containing at least one manganese-based additive. The nickel hydroxide electrode is activated by mixing nickel hydroxide powder, metal manganese powder, and polytetrafluoroethylene as a binder in a weight ratio of 87: 10: 3 or 92: 5: 3. After manufacturing the material mixture, the active material mixture is filled in a foam nickel plate and pressure-molded. The nickel hydroxide electrode thus produced is used in an alkaline secondary battery to accelerate the absorption rate of hydrogen gas generated inside the battery and reduce the internal pressure.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the conventional problems, and it is an object of the present invention to provide an alkaline secondary battery having a positive electrode with improved charging efficiency at high temperatures. is there.

[0007]

According to the present invention, a positive electrode having a structure in which a paste containing nickel hydroxide powder as a main component is filled in a current collector, a negative electrode, and an interposition between the positive electrode and the negative electrode. In the alkaline secondary battery provided with a separator and an alkaline electrolyte, the positive electrode contains metal manganese or a manganese compound, and the content of the metal manganese or the manganese compound is 1 mg per 1 Ah of the positive electrode capacity in terms of element. The alkaline secondary battery is 10 mg.

The alkaline secondary battery of the present invention will be described below with reference to FIG. The positive electrode 1 is spirally wound with the separator 3 interposed between the positive electrode 1 and the negative electrode 2, and is housed in a bottomed cylindrical container 4. The negative electrode 2 is arranged on the outermost periphery of the prepared electrode group and is in electrical contact with the container 4. The alkaline electrolyte is contained in the container 4. A circular sealing plate 6 having a hole 5 in the center 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. One end of the positive electrode lead 8 is connected to the positive electrode 1, and the other end is the sealing plate 6.
Is attached to the underside of. Hat-shaped positive terminal 9
Is mounted on the sealing plate 6 so as to cover the hole 5. The rubber safety valve 10 is arranged so as to close the hole 5 in a space surrounded by the sealing plate 6 and the positive electrode terminal 9.

The positive electrode 1 contains metal manganese or a manganese compound, and the content of the metal manganese or the manganese compound is 1 mg to 10 mg per 1 Ah of the positive electrode capacity in terms of element.

For the positive electrode 1, a paste containing nickel hydroxide powder, the metal manganese or the manganese compound, a conductive agent, a binder, and water is prepared, and the paste is filled in a current collector, It is manufactured by drying, press-molding, and cutting into a desired size.

Examples of the manganese compound include Mn
_{O, Mn 2 O 3, Mn} (OH) 2, KMnO 2 can be mentioned. The reason for limiting the content of the manganese compound in the positive electrode 1 to the above range in terms of elements is as follows. Positive electrode capacity of 1 Ah in terms of elemental content
When the amount is less than 1 mg, the positive electrode 1 at high temperature
Charging efficiency decreases. On the other hand, when the content exceeds 10 mg per 1 Ah of the positive electrode capacity in terms of element, the charging efficiency of the positive electrode 1 in a high temperature state decreases. Further, an excessive amount of manganese or a manganese compound adversely affects the charge / discharge of the secondary battery, and the utilization rate of the positive electrode 1 is reduced.
A more preferable content is 2 per 1 Ah of positive electrode capacity in terms of element.
mg to 5 mg.

Zinc or cobalt is preferably coprecipitated with nickel metal in the nickel hydroxide powder to be contained as a solid solution. The positive electrode containing such nickel hydroxide powder can further improve the charging efficiency in a high temperature state.

Examples of the conductive agent include cobalt compounds such as cobalt monoxide, dicobalt trioxide, and cobalt hydroxide. Examples of the binder include polytetrafluoroethylene, carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, and polyvinyl alcohol.

The current collector has a sponge-like, fibrous-like, or felt-like porous structure made of, for example, an alkali-resistant metal such as nickel or stainless steel or an alkali-resistant nickel-plated resin. Can be mentioned.

The negative electrode 2 is prepared by adding a conductive material to a negative electrode active material, kneading it with a binder and water to prepare a paste, filling the conductive substrate with the paste, drying and molding the paste. Manufactured.

Examples of the negative electrode active material include cadmium compounds such as metal cadmium and cadmium hydroxide, and hydrogen storage alloys. Above all, the hydrogen storage alloy is preferable because it can improve the capacity of the secondary battery as compared with the case where the cadmium compound is used. The hydrogen storage alloy is not particularly limited as long as it can store hydrogen electrochemically generated in the electrolytic solution and can easily release the stored hydrogen during discharge. For example, LaNi ₅ and MmNi ₅ (Mm is La,
Ce, Pr, Nd, Sm, etc. means a misch metal which is a mixture of lanthanum-based elements), LnNi ₅ (L
n; lanthanum-enriched misch metal), and some of these Nis are 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. Above all, the general formula LnNi _x Mn _y A _z (However, A
Is at least one metal selected from Al and Co, and the atomic ratios x, y, and z have a total value of 4.8 ≦ x + y + z ≦ 5.
4) is preferable because it has a desired hydrogen equilibrium pressure and can improve the charge / discharge cycle life of the secondary battery. More preferred formula _{LmNi w Co x Mn y Al z} ( where atomic ratios w, x, y, z are each 3.1 ≦ w ≦ 4.8,0.2
≤x≤0.8, 0.2≤y≤0.8, 0.2≤z≤0.
8, the sum of these values is 5.1 ≦ w + x + y + z ≦ 5.
4) is a hydrogen storage alloy. Such a hydrogen storage alloy can significantly improve the charge / discharge cycle life.

Examples of the conductive material include carbon black. The same binder as the positive electrode 1 can be used as the binder. Examples of the conductive substrate include two-dimensional substrates such as punched metal, expanded metal, perforated rigid plate, and nickel net, and three-dimensional substrates such as felt-like metal porous bodies and sponge-like metal porous bodies. You can

Examples of the separator 3 include a nonwoven fabric made of polyamide fiber and a nonwoven fabric made of polyolefin fiber such as polyethylene and polypropylene to which a hydrophilic functional group is added.

As the alkaline electrolyte, it is possible to use, for example, a potassium hydroxide solution or a mixed solution in which either or both of sodium hydroxide and lithium hydroxide are added to potassium hydroxide. Among them, an electrolytic solution containing lithium hydroxide and sodium hydroxide is preferable because it can further improve the charging efficiency of the positive electrode in a high temperature state.

[0020]

According to the alkaline secondary battery of the present invention, the current collector has a structure in which a paste containing nickel hydroxide powder and metal manganese or a manganese compound is filled, and By providing the positive electrode whose content is 1 mg to 10 mg per 1 Ah of positive electrode capacity in terms of element, the oxygen overvoltage of the positive electrode in a high temperature state can be increased. As a result, in the high temperature state, the oxygen gas generation reaction represented by the above formula (2) is suppressed, and the charging reaction of the nickel hydroxide powder represented by the above formula (1) occurs preferentially. It is possible to increase the charging efficiency of the positive electrode. Further, since the battery capacity of the secondary battery can be improved, the charge / discharge cycle life can be improved.

[0021]

Embodiments of the present invention will now be described in detail with reference to the drawings. Examples 1 to 4 First, Mn (OH) ₂ was converted into manganese in a mixture of 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide, and 1 mg, 3 mg, 5 m per 1 Ah of capacity of the positive electrode.
g, 10 mg was added. 0.3 wt% of carboxymethyl cellulose and 1.0 wt% of polytetrafluoroethylene were added to each mixture, 45 wt% of water was added thereto, and the mixture was kneaded to prepare a paste. A nickel-plated fiber substrate having a porosity of 95% as a current collector was filled with each of the above-mentioned pastes, dried, and then roller-pressed to be roll-formed to produce a positive electrode having a capacity of 1100 mAh.

In addition, LaNi _4.0 Co _0.4 Mn _0.3 Al
_To 95 parts by weight of hydrogen storage alloy powder having a composition of _0.3 , 3 parts by weight of polytetrafluoroethylene powder, 1 part by weight of carbon powder, and 1 part by weight of carboxymethyl cellulose as a binder are added and mixed with 50 parts by weight of water. To prepare a paste. The paste was applied to a nickel net, dried, and then pressure-molded to prepare a hydrogen storage alloy negative electrode.

Next, a separator made of a non-woven fabric made of an olefin resin subjected to a hydrophilic treatment was interposed between each of the positive electrodes and the negative electrodes, and the electrodes were wound in a spiral shape. An alkaline electrolyte containing these electrode groups and 8N potassium hydroxide was placed in a bottomed cylindrical container to assemble an AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. Comparative Example 1 Mn (OH) ₂ was converted into manganese and the capacity of the positive electrode was 1 Ah.
The nickel-hydrogen secondary battery shown in FIG. 1 was assembled with the same structure as in Examples 1 to 4 except that 20 mg was added per unit. Comparative Example 2 The nickel-hydrogen secondary battery shown in FIG. 1 was assembled in the same configuration as in Examples 1 to 4 except that Mn (OH) ₂ was not added.

100 each of the obtained secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2 were prepared and aged at 45 ° C. for 24 hours. Each battery was 0.1C at 25 ° C.
After charging up to a depth of 150% with the current of, the charging / discharging cycle of discharging with the current of 1C was repeated 20 cycles to stabilize the discharge capacity. For each type of battery, 10 batteries having substantially the same discharge capacity at the 20th cycle were selected.
0.1C at high temperature of 45 ° C for selected batteries
After being charged to a depth of 150% with a current of 1, the battery was discharged at a current of 1C at 25 ° C. From the measured discharge capacity, the discharge capacity ratio (the discharge capacity at the 20th cycle of capacity selection was 10
2) and the charging efficiency when charging 0.1 C at 45 ° C. is shown. The results are shown in FIG.

As is clear from FIG. 2, Mn (OH) ₂
And the content of manganese equivalent is 1
Example 1 with a positive electrode of 1 mg to 10 mg per Ah
It can be seen that the secondary batteries Nos. 4 to 4 have a high charging efficiency of more than 75 at a high temperature of 45 ° C. On the other hand, Mn
The secondary battery of Comparative Example 1 including a positive electrode containing (OH) ₂ and having a content of 20 mg per Ah of the positive electrode in terms of manganese and a secondary battery including a positive electrode without a manganese compound added were at high temperature. Charging efficiency in each state is 6
It turns out that it is remarkably low as 8,69. Example 6 Examples 1 to 4 except that MnO was added instead of Mn (OH) ₂ in an amount of 5 mg per 1 Ah of the capacity of the positive electrode in terms of manganese.
A positive electrode similar to that was manufactured. The nickel-hydrogen secondary battery shown in FIG. 1 was assembled using the positive electrode, the same negative electrode as in Examples 1 to 4, a separator, and an alkaline electrolyte.

The obtained secondary battery of Example 6 was manufactured by the same method as in Examples 1 to 4 at a high temperature of 45 ° C.
When the charging efficiency at the time of 1C charging was obtained, it was as high as 85. Comparative Example 3 A positive electrode containing nickel hydroxide powder co-precipitated with 3 to 5% by weight of zinc as an active material and containing no manganese compound, and an alkali containing 1N lithium hydroxide and 7N potassium hydroxide. Examples 1 to 4 except that an electrolytic solution was used
The nickel-hydrogen secondary battery shown in FIG. 1 was assembled with the same structure as described above.

With respect to the obtained secondary battery of Comparative Example 3, the same procedure as in Examples 1 to 4 was carried out at a high temperature of 45 ° C.
When the charging efficiency when 1C charging was performed, it was as low as 69.

[0028]

As described above in detail, according to the alkaline secondary battery of the present invention, the charging efficiency of the positive electrode in a high temperature state can be improved, and the battery capacity can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an alkaline secondary battery according to the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the manganese conversion amount of Mn (OH) ₂ and the charging efficiency of the positive electrode in a high temperature state in the example of the present invention.

[Explanation of symbols]

1 ... Positive electrode, 2 ... Negative electrode, 3 ... Separator, 4 ... Container, 6 ...
Seal plate, 7 ... Insulation gasket.

Claims (1)

[Claims] 1. A positive electrode having a structure in which a paste containing nickel hydroxide powder as a main component is filled in a current collector, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte. In the alkaline secondary battery, the positive electrode contains metal manganese or a manganese compound, and the content of the metal manganese or the manganese compound is 1 mg per 1 Ah of the positive electrode capacity in terms of element.
An alkaline secondary battery, which is 10 mg.