JP3458899B2 - Nickel hydroxide positive plate for alkaline battery and alkaline battery thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a nickel hydroxide positive electrode plate for an alkaline battery and an alkaline battery.

[0002]

2. Description of the Related Art In recent years, with the development of electronic equipment, the emergence of new high-performance secondary batteries is expected. Currently, nickel-cadmium batteries, nickel-zinc batteries, nickel-based batteries such as nickel-hydride batteries, and lead batteries are used as power sources for electronic devices. These secondary batteries are required to have high capacity as well as rapid charging performance. Among them, nickel-based secondary batteries use a nickel hydroxide electrode as a positive electrode plate. The electrode reaction of this positive electrode plate is diffusion of H + ions, and is not a dissolution / precipitation mechanism like the electrode reaction of the positive electrode of a lead battery, so it is expensive, but it is used as a long-lived and high-performance electrode. . When this electrode is charged, nickel hydroxide becomes nickel oxyhydroxide (NiOOH). This nickel oxyhydroxide has β-type and γ-type, but it is γ-NiOO when charging.
When H is generated, a volume expansion of 31% occurs, and γ
When it becomes α-Ni (OH) ₂ which is a discharge product of —NiOOH, the expansion is 59%. In recent years, the high energy of batteries
To increase the density, if the active material is filled in a large amount, the residual porosity of the electrode becomes small, and when the active material expands, the electrode becomes thick, and the electrolytic solution of the separator moves to the electrode to increase the internal resistance. A so-called "dry-up" phenomenon may occur, or the electrodes may collapse to cause a short circuit. Furthermore, in applications where a reduction in charging time is required, that is, in the case of performing rapid charging, the production of γ-NiOOH is particularly likely to occur, and a countermeasure for it has become necessary.

Conventionally, a method of adding cobalt hydroxide to an active material for the purpose of improving the utilization rate of the nickel hydroxide active material (for example, Electrochemistry 31,47 (1936), Patent Publication 50-1).
32441), and after filling the nickel substrate with the active material, Co (O
H) 2 forming method (for example, Japanese Patent Publication No. 57-005018)
A method of forming a binary system of Cd (OH) 2-Ni (OH) 2 (for example, Japanese Patent Publication No. 2-39063, USP4603094 (1984), Japanese Patent Publication Sho 56).
-36796) -Method of forming a ternary system of Ni (OH) 2-Co (OH) 2-Cd (OH) 2 (for example, Japanese Patent Publication No. 3-20860, USP395686 (19
76)) etc. have been proposed. Further, a method of incorporating metallic cobalt into a sintered nickel substrate which is a holder of an active material has also been proposed (for example, Japanese Patent Publication No. 54-1010). However, it was insufficient from the viewpoint of suppressing the production of γ-NiOOH.

[0004]

SUMMARY OF THE INVENTION Nickel-based batteries such as nickel-cadmium batteries, nickel-zinc batteries, and nickel-hydride batteries are required to have high energy density and rapid charging. However, the nickel hydroxide positive electrode plate used in high energy density batteries and batteries for rapid charging swells and becomes thicker as the charge and discharge cycle progresses, and the electrolyte solution of the separator moves to the electrodes and increases the internal resistance. There is a drawback that the battery life is shortened due to an up phenomenon. Especially, nickel substrate, which is the active material holder, is 85%
If you use any of the above, the strength of the substrate is weak,
There is a problem that the swelling of the positive electrode plate increases.

[0005]

According to the present invention, there is provided a nickel substrate obtained by sintering metallic nickel powder and metallic cobalt powder, and nickel hydroxide having a solid solution formed with cobalt.
In a nickel hydroxide positive electrode plate for an alkaline battery comprising cadmium hydroxide not forming a solid solution and nickel or cobalt, the content ratio of cobalt dissolved in nickel hydroxide is higher than that of the nickel substrate. By using the nickel hydroxide positive electrode plate for alkaline batteries as described above, swelling of the positive electrode plate due to charging and discharging is suppressed, and a long-life high energy density battery and a battery for rapid charging are provided. Furthermore, the porosity of the nickel substrate is 85-98.
%, The long life of the high energy density positive electrode plate is achieved by using the nickel hydroxide positive electrode plate for alkaline batteries.

[0006]

[Function] As a means for improving the utilization rate of the active material of the nickel hydroxide positive electrode plate, the active material holder such as a nickel porous body is filled with the active material, and then an aqueous cobalt solution such as cobalt nitrate or cobalt sulfate is impregnated with water. A method is generally used in which a layer of cobalt hydroxide is formed on the surface of the active material by neutralizing with an alkaline aqueous solution such as sodium oxide, and then charged to change to a layer of conductive cobalt oxyhydroxide. There is. Further, as an active material, cobalt hydroxide is added to the active material to form a solid solution with nickel hydroxide, or cadmium hydroxide is added to form a solid solution, thereby suppressing the production of γ-NiOOH. Therefore, a means for improving the utilization rate is also known as a universal technology. Further, in addition to nickel hydroxide, which is a positive electrode active material, a means for forming cadmium hydroxide that does not form a solid solution is a known means as a measure against overdischarge.

According to the present invention, the nickel hydroxide positive electrode plate used in a high energy density battery or a battery for rapid charging swells and becomes thicker as the charging / discharging cycle progresses, and the electrolytic solution of the separator moves to the electrode. Although it has been conventionally known that the cause of the increase in internal resistance, the dry-up phenomenon, and the shortening of battery life is that γ-NiOOH is produced as a charge product of the nickel hydroxide active material. In addition, the nickel porous body used as the active material holder is oxidized by charge and discharge to become nickel hydroxide,
It is based on the finding that the reason is that the positive electrode plate swells and becomes thicker because it becomes γ-NiOOH, and the electrolytic solution of the separator moves to the electrode plate. Then, as a countermeasure, by adding cobalt to nickel of the active material holder, further optimizing the active material, and by containing cadmium hydroxide hydroxide not forming a solid solution and nickel or cobalt hydroxide, the substrate The nickel hydroxide produced by the oxidation of
The present invention provides a means for suppressing the formation of NiOOH.

[0008]

The preferred embodiments of the present invention will be described below. [Example 1] Carbonyl nickel powder and 2 wt% metallic cobalt powder were mixed and then kneaded with a 0.1 wt% methylcellulose aqueous solution to form a slurry. This slurry was applied to a nickel plated 0.1 mm perforated plate, dried with a heater and then sintered at 950 ° C. in a hydrogen reducing atmosphere to form a sintered nickel substrate with a porosity of 85%. I made it. Next, this sintered nickel substrate was impregnated with a 5M aqueous solution of nickel nitrate containing 2 mol% of cobalt nitrate at 80 ° C. and then immersed in a 5M aqueous solution of sodium hydroxide at 80 ° C. After that, the operation of washing with water and drying is performed eight times, and finally, a 1.5 M aqueous solution of cobalt nitrate containing 10 mol% of cadmium is impregnated,
Then, it is immersed in a 5M aqueous sodium hydroxide solution at 80 ° C. (hereinafter, this operation is referred to as “postcoat”). Then, it was washed with hot water and dried to manufacture a positive electrode plate of the present invention having a theoretical capacity of 300 mAh and dimensions of 0.8 × 14 × 52 mm.

Two positive electrode plates in which the content of the metallic cobalt powder was changed to 0, 1, 2, 3, 5, 10 wt% in Example 1 and a conventionally known theoretical capacity of 500 mAh and a size of 0.7
Three x15x52 mm cadmium negative electrode plates were produced.

Next, this positive electrode plate was wrapped with a 0.12 mm polyamide nonwoven fabric separator and then heat-sealed. Subsequently, a positive electrode plate and a negative electrode plate were alternately stacked to form an electrode plate group. A nominal capacity of 500 is obtained by using this electrode group and 1.5 ml of an 8.5 M potassium hydroxide aqueous solution as an electrolytic solution.
A rectangular nickel-cadmium battery was manufactured using a mAh nickel-plated iron battery case. External dimensions are 67 x 1
6.5 × 6 mm 2, the battery has 0.5 kg / cm 2
It has a safety valve that operates at. The symbols of batteries having a metal cobalt content of 0, 1, 2, 3, 5, 10 wt% are A, B, C, D, E, and F, respectively.

A cycle test was conducted in which these batteries were charged at 25 ° C. and 1 C for 70 minutes and then discharged to 1.0 V at a current of 0.5 C. FIG. 1 shows the change in the value of the internal resistance with the progress of cycles. From the figure, A with a metal cobalt content of 0% has a charge / discharge cycle of 3%.
It can be seen that the value of the internal resistance reaches 300 mΩ at about 00 times. Thus, when the value of the internal resistance rapidly increased, the discharge capacity of the battery also decreased and the charging voltage also increased. On the other hand, B containing 1% or more of metallic cobalt,
In C, D, E, and F, the increase in internal resistance is extremely small. When battery A was disassembled and the elements of the battery were examined, the separator electrolyte was depleted and the positive electrode plate was swollen thickly. Since there was almost no decrease in the weight of the battery, it is considered that when the content of metallic cobalt is 0%, the nickel substrate is oxidized to produce γ-NiOOH. This γ-Ni
The formula of OOH is K _0.33 · NiO ₂ · 0.67H ₂
O 2, which means that the electrolytic solution is absorbed by the positive electrode.

The optimum content of metallic cobalt depends on the porosity of the sintered nickel substrate and the residual porosity after filling the active material. In Example 1, the positive electrode plate (G, with a residual porosity of 30% and a metal cobalt content of 1, 2, or 3 wt%) was used.
H and I) is manufactured and 8M-KOH is used as an electrolytic solution.
, 2 nickel plates are used as counter electrodes, and the charging rate is 2C
After charging 200% of the nominal capacity with, 0V at 0.5C
FIG. 2 shows the change in the thickness of the electrode plate after discharging to (Hg / HgO) and further charging under the same conditions. It has been empirically found that the internal resistance value of the battery rises when the increase rate of the electrode thickness exceeds 15%. From the figure, in order to set the increase rate of the thickness of the electrode plate to 15% or less, when the porosity of the nickel substrate is 80%, the content ratio of metallic cobalt is 1 wt% and the porosity is 85%. 2wt in case of
%, The porosity is 90%, it can be seen that the addition amount of 3 wt% or more is required.

Next, 6 mol% of cobalt nitrate was added to a nickel substrate having a metal cobalt content of 2% and a porosity of 80%.
After impregnating it with a 5 M aqueous solution of nickel nitrate containing 80 ° C., it is immersed in a 5 M aqueous solution of sodium hydroxide at 80 ° C. After that, after performing the operation of washing with water and drying eight times, 0, 5, 10, 20, 30, 6 as a post coat.
After impregnating with a 1.5 M aqueous solution of cobalt nitrate containing 0, 70 and 80 mol% of cadmium, it is immersed in a 5 M aqueous solution of sodium hydroxide at 80 ° C. After that, it is washed with hot water and dried to have a theoretical capacity of 300 mAh and dimensions of 0.8 x 14 x.
A 52 mm positive electrode plate of the present invention was manufactured.

Using these positive plates as an electrolyte, 8M-KO
H, using two nickel plates as the counter electrode, the charge rate is 2
After charging 200% of the nominal capacity with C, 0 with 0.5C
After discharging to V (Hg / HgO), charging under the same conditions, washing with hot water and then drying, an X-ray diffraction analysis of the active material was performed. The amount of γ-NiOOH produced is γ-Ni
Peak of OOH (003) / (β-NiOOH (00
It is determined from the peak of 1) + the peak of γ-NiOOH (003)) and is shown in FIG. From the figure, it can be seen that when the cadmium content of the postcoat is 10 mol% or more, the production of γ-NiOOH is suppressed, and particularly when it is 50 mol% or more, the production amount is small. Practically, the cadmium content is preferably 10 to 80 mol%. Even if the cobalt-containing solution and the cadmium-containing solution were separated by post-coating, the same effect was obtained, but using a mixed solution of cobalt and cadmium requires only one process and is simple and easy. is there.

Next, these two positive electrode plates and a conventionally known theoretical capacity of 500 mAh and dimensions of 0.7 × 15 ×
Three 52 mm cadmium negative electrode plates were manufactured.

The positive electrode plate was wrapped with a 0.12 mm polyamide nonwoven fabric separator and then heat-sealed. Subsequently, a positive electrode plate and a negative electrode plate were alternately stacked to form an electrode plate group. A nominal capacity of 500 is obtained by using this electrode group and 1.5 ml of an 8.5 M potassium hydroxide aqueous solution as an electrolytic solution.
A rectangular nickel-cadmium battery was manufactured using a mAh nickel-plated iron battery case. External dimensions are 67 x 1
6.5 × 6 mm ² , the battery has 0.5 kg / cm ²
It has a safety valve that operates at. Batteries using the positive electrode having a post-coating cadmium content of 2, 5, 10, and 15 mol% are J, K, L, and M. FIG. 4 shows the capacity transition when a cycle test was conducted in which the battery was charged at 1 C for 1.2 hours and then discharged at 0.2 C to 0.5 V. From the figure, the cadmium content is 2 mol%
In the case of (J) and 5 mol% (K), the discharge capacity decreases when the number of charge / discharge cycles exceeds 600, but the cadmium content is 10 mol% (L) and 15 mol%.
It can be seen that the capacity of the battery (M) is stable and good.

Thus, the cadmium content is 10 m.
If it is ol% or more, the charge / discharge cycle life is improved because the nickel hydroxide formed by the oxidation of the active material and nickel of the nickel substrate becomes less likely to become γ-NiOOH during charging as the charge / discharge cycle progresses. It is thought to be due to change. The mechanism is considered as follows. That is, when the content of cadmium in the post-coat liquid is 10 mol% or more, the hydroxide produced in the neutralization step is not only cadmium hydroxide which forms a solid solution with cobalt hydroxide, but also hydroxide which does not form a solid solution. Cadmium is produced. Γ when nickel hydroxide is charged
-NiOOH and its discharge product is α-Ni (O
H) ₂ , but this α-Ni (OH) ₂ dissolves in an alkaline aqueous solution and undergoes a phase change to β-Ni (OH) ₂ .
At that time, cadmium hydroxide that does not form a solid solution is incorporated into the crystal as a solid solution in the active material. Then, in the subsequent charging, it is considered that the generation of γ-Ni (OH) ₂ is suppressed, the swelling of the electrode plate is reduced, and the life is extended. The relationship between the content of cobalt in the nickel substrate and the content of cobalt in solid solution in nickel hydroxide is that the content of cobalt in solid solution in nickel hydroxide is higher than the content of cobalt in the nickel substrate. Was good. This is because when the amount of cobalt contained in nickel hydroxide generated by the oxidation of the nickel substrate is large, it becomes more active than the active material, and during discharge, it is discharged preferentially over the bulk active material, and the discharge product is It is considered that it becomes resistance and deteriorates the discharge performance of the positive electrode.

[0018]

As described above, a nickel substrate formed by sintering metallic nickel powder and metallic cobalt powder,
Nickel hydroxide forming a solid solution with cobalt, in a nickel hydroxide positive electrode plate for alkaline batteries comprising cadmium hydroxide not forming a solid solution and nickel or cobalt, the content rate of cobalt solid-solving in nickel hydroxide, By providing a nickel hydroxide positive electrode plate for an alkaline battery characterized by having a content ratio higher than that of the nickel substrate, swelling of the positive electrode plate due to charging and discharging is suppressed, and a long-life high energy density battery and a battery for rapid charging are provided. To do. If a nickel substrate having a porosity of 85 to 98% is used, the positive electrode plate having a higher energy density can have a longer life.

[Brief description of drawings]

FIG. 1 is a diagram comparing changes in the internal resistance of a sealed nickel-cadmium battery with the progress of charge / discharge cycles.

FIG. 2 is a diagram showing the relationship between the increase rate of the electrode plate thickness of the positive electrode plate and the porosity of the substrate.

FIG. 3 is a diagram showing a relationship between a production state of γ-NiOOH in a charged state and a cadmium content rate.

FIG. 4 is a diagram comparing capacity retention rates with charge / discharge cycles.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H01M 10/30 H01M 10/30 Z (56) Reference JP-A-61-263047 (JP, A) JP-A-2-253559 ( JP, A) JP 56-143669 (JP, A) JP 52-10538 (JP, A) JP 62-66572 (JP, A) JP-B 2-39063 (JP, B2) JP 48-3332 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/00-4/84

Claims (3)

(57) [Claims] 1. A nickel substrate obtained by sintering metallic nickel powder and metallic cobalt powder, nickel hydroxide which forms a solid solution with cobalt, and nickel or cadmium hydroxide which does not form a solid solution with cobalt. In the nickel hydroxide positive electrode plate for alkaline batteries, the content ratio of cobalt dissolved in nickel hydroxide is higher than the content ratio of cobalt in the nickel substrate. 2. The nickel hydroxide positive electrode plate for an alkaline battery according to claim 1, wherein the nickel substrate has a porosity of 85 to 98%. 3. An alkaline battery provided with the nickel hydroxide positive electrode plate according to claim 1.