JP3249398B2 - Non-sintered nickel electrode for alkaline storage batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a non-sintered nickel electrode used as a positive electrode of an alkaline storage battery.

[0002]

2. Description of the Related Art
As a positive electrode of a nickel-hydrogen storage battery or a nickel-cadmium storage battery, a sintered nickel electrode obtained by impregnating a sintered substrate obtained by sintering nickel powder into a perforated steel plate or the like and impregnating an active material (nickel hydroxide) is often used. Are known.

In order to increase the amount of active material to be filled in a sintered nickel electrode, it is necessary to use a sintered substrate having high porosity. However, since the bond between the nickel particles due to sintering is weak, if the porosity of the sintered substrate is increased, the nickel particles are likely to fall off the sintered substrate. Therefore, in practice, the porosity of the sintered substrate cannot be made larger than 80%, and therefore, the sintered nickel electrode has a problem that the active material filling amount is small. In addition, since the pore size of the sintered body of nickel powder is generally as small as 10 μm or less, the filling of the active material into the sintered substrate must be performed by a solution impregnation method in which a complicated impregnation step needs to be repeated several times. There is also a problem.

[0004] Under such circumstances, a non-sintered nickel electrode has recently been proposed. In non-sintered nickel electrodes, a kneaded product (paste) of an active material (nickel hydroxide) and a binder (aqueous methylcellulose solution) is filled into a substrate with high porosity (foam metal plated with an alkali-resistant metal). It is produced by this. In the case of the non-sintered nickel electrode, a substrate having a high porosity can be used (a substrate having a porosity of 95% or more can be used). Filling the substrate is easy.

However, when a nonporous nickel electrode is used with a large porosity substrate to increase the active material filling amount, the current collecting capability of the substrate deteriorates, and the active material utilization rate decreases.

Therefore, in order to increase the utilization rate of the active material of the non-sintered nickel electrode, cobalt hydroxide powder is added to nickel hydroxide powder (see Japanese Patent Application Laid-Open No. 61-74261). It has been proposed to add metal cobalt powder, cobalt hydroxide powder and yttrium compound powder (see JP-A-5-28992).

However, as a result of investigations by the present inventors, it has been found that it is difficult for these conventional methods to obtain a non-sintered nickel electrode exhibiting a high active material utilization over a long period of charge / discharge cycles. Was. That is, in the former method, a high utilization rate of the active material at the beginning of the charge / discharge cycle can be obtained, but the cobalt gradually diffuses into the nickel hydroxide particles as the charge / discharge cycle is repeated. It is difficult to obtain a non-sintered nickel electrode having a high active material utilization rate over a long period.
In the latter method, β-CoOO of cobalt hydroxide is used.
Since the oxidation reaction to H (cobalt hydroxide functions as a conductive agent only after being oxidized to β-CoOOH) is inhibited by the yttrium compound, non-sintered nickel having a low active material utilization from the beginning of the charge / discharge cycle. You can only get poles.

Accordingly, an object of the present invention is to provide a non-sintered nickel electrode which exhibits a high active material utilization rate over a long period of time as well as at the beginning of a charge / discharge cycle.

[0009]

In order to achieve the above object, in the non-sintered nickel electrode for an alkaline storage battery according to the present invention (electrode of the present invention), sodium hydroxide is added to nickel hydroxide powder as an active material powder. A cobalt compound powder;
Metal yttrium powder and / or yttrium compound powder are added.

In the electrode of the present invention, a sodium-containing cobalt compound powder is added as a conductive agent to nickel hydroxide powder which is an active material powder. In the above nickel hydroxide powder, in addition to a single component powder consisting of only nickel hydroxide, nickel hydroxide, cobalt, zinc, cadmium, calcium, manganese, magnesium, bismuth,
A solid solution powder in which at least one element selected from aluminum and yttrium is dissolved is also included. By dissolving these elements in nickel hydroxide, swelling of nickel hydroxide during a charge / discharge cycle can be suppressed.

Although the chemical structure of the sodium-containing cobalt compound has not yet been determined by the present inventors,
Since this has an extremely high electrical conductivity, it is supposed that it is not an mere mixture of a cobalt compound and sodium, but an intercalation compound having a structure in which sodium is inserted into the crystal of the cobalt compound. If necessary, two or more sodium-containing cobalt compound powders may be added in combination.

The sodium-containing cobalt compound is produced, for example, by adding an aqueous solution of sodium hydroxide to a cobalt compound such as metallic cobalt or cobalt hydroxide or cobalt oxide and subjecting the mixture to heat treatment. The heat treatment temperature is preferably from 50 to 200 ° C. Heat treatment temperature is 50
If the temperature is lower than 200 ° C., CoHO ₂ having low electric conductivity is produced, whereas if the heat treatment temperature exceeds 200 ° C., tricobalt tetroxide (Co ₃ O ₄ ) having low electric conductivity is produced. Also, it becomes difficult to obtain a sodium-containing cobalt compound powder having high conductivity. The heat treatment time varies depending on the amount and concentration of the aqueous sodium hydroxide used, the heat treatment temperature and the like. Generally, it is 0.5 to 10 hours.

The preferred sodium content of the sodium-containing cobalt compound powder is 0.1 to 10% by weight. If the sodium content is out of this range, the conductivity becomes poor, and it becomes difficult to obtain a non-sintered nickel electrode having a high active material utilization rate.

The preferable addition amount of the sodium-containing cobalt compound powder to the nickel hydroxide powder is 1 to 100 parts by weight of the nickel hydroxide powder in the nickel hydroxide powder.
20 parts by weight. If the addition ratio is less than 1 part by weight,
It becomes difficult to obtain a non-sintered nickel electrode having a sufficiently high active material utilization rate. On the other hand, when the addition ratio exceeds 20 parts by weight, the filling amount of nickel hydroxide, which is an active material, decreases, so that the electrode capacity decreases.

In the electrode of the present invention, in addition to the above sodium-containing cobalt compound powder,
Further, metal yttrium powder and / or yttrium compound powder is added. If necessary, two or more yttrium compound powders may be added in combination. As the yttrium compound powder, yttrium trioxide powder,
Examples include yttrium carbonate powder, yttrium hydroxide powder, and yttrium fluoride powder. A suitable addition ratio of the metal yttrium powder and / or the yttrium compound powder to the nickel hydroxide powder is 0.05 to 5 with respect to 100 parts by weight of nickel hydroxide in the nickel hydroxide powder.
Parts by weight. If the addition ratio is less than 0.05 parts by weight, the diffusion of cobalt into the nickel hydroxide particles cannot be sufficiently suppressed, and the non-sintering which exhibits a high active material utilization rate over a long period of charge / discharge cycles. It becomes difficult to obtain a formula nickel electrode. On the other hand, when the addition ratio exceeds 5 parts by weight, the filling amount of nickel hydroxide as an active material decreases, and the electrode capacity decreases.

In the electrode of the present invention, since the conductivity of the electrode is enhanced by adding a sodium-containing cobalt compound powder having high conductivity to the nickel hydroxide powder, the active material utilization rate at the beginning of the charge / discharge cycle is high. . Further, in the electrode of the present invention, since the metal yttrium powder and / or the yttrium compound powder are further added to the nickel hydroxide powder, cobalt is unlikely to diffuse into the nickel hydroxide particles during the charge / discharge cycle. Moreover, unlike the cobalt hydroxide powder, the sodium-containing cobalt compound powder itself is a substance having a high electrical conductivity, and thus the addition of the yttrium compound hardly lowers the conductivity of the electrode. For this reason, the electrode of the present invention exhibits a high active material utilization rate not only at the beginning of the charge / discharge cycle but also over a long period of time.

[0017]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and the present invention may be practiced by appropriately changing the gist of the invention. Is possible.

(Example 1) [Preparation of sodium-containing cobalt compound powder] Cobalt hydroxide powder and a 30% by weight aqueous sodium hydroxide solution were mixed at a weight ratio of 1:10 and heat-treated at 80 ° C for 8 hours. After that, the resultant was washed with water and dried at 60 ° C. to prepare a sodium-containing cobalt compound powder. When the sodium content of the produced sodium-containing cobalt compound powder was determined by an atomic absorption method, it was 1% by weight.

[Preparation of Non-Sintered Nickel Electrode] Ni (OH) ₂ powder (average particle size: 10 μm) 100 as an active material powder
Parts by weight and the above sodium-containing cobalt compound powder 1
0 parts by weight and yttrium trioxide (Y ₂ O ₃ ) powder 3
Parts by weight and 20 parts by weight of a 1% by weight aqueous solution of methylcellulose as a binder are kneaded to prepare a paste, and the paste is nickel-plated into a foam metal (porosity 95%).
%, An average pore diameter of 200 μm), dried, and press-molded to prepare an electrode a of the present invention.

[Preparation of Alkaline Storage Battery] The above electrode a (positive electrode) of the present invention, a known paste-type cadmium electrode (negative electrode) having a larger electrochemical capacity than the positive electrode, a polyamide nonwoven fabric (separator), and 30% by weight hydroxide An AA-size alkaline storage battery A (battery capacity: about 1000 mAh) was prepared using a potassium aqueous solution (alkaline electrolyte), a metal battery can, a metal battery lid, and the like.

Comparative Example 1 A paste was prepared by kneading 100 parts by weight of Ni (OH) ₂ powder, 10 parts by weight of cobalt hydroxide powder, and 20 parts by weight of a 1% by weight aqueous solution of methylcellulose. Fill a porous substrate made of plated foamed metal (porosity 95%, average pore diameter 200 μm), dry, press-mold, and form a comparative electrode x
Then, an alkaline storage battery X was prepared in the same manner as in Example 1 except that the comparative electrode x was used as a positive electrode. This battery was manufactured in accordance with the method disclosed in Japanese Patent Application Laid-Open No. 61-74261.

Comparative Example 2 100 parts by weight of Ni (OH) ₂ powder (average particle size: 10 μm), 5 parts by weight of cobalt hydroxide powder, 7 parts by weight of metal cobalt powder, and 3 parts by weight of yttrium trioxide powder And 20 parts by weight of a 1% by weight aqueous solution of methylcellulose are kneaded to prepare a paste, and the paste is nickel-plated foam metal (porosity 95%,
Filling a porous substrate having an average pore size of 200 μm),
Drying and pressure molding were performed to produce a comparative electrode y, and then an alkaline storage battery Y was produced in the same manner as in Example 1 except that the comparative electrode y was used as a positive electrode. This battery was manufactured according to the method disclosed in Japanese Patent Application Laid-Open No. 5-28992.

<Active Material Utilization of Each Non-Sintered Nickel Electrode>
About each battery produced in Example 1 and Comparative Examples 1 and 2,
After charging 160% at 0.1 ° C at 25 ° C, 25 ° C
, A charge / discharge cycle test was performed in which the process of discharging to 1.0 V at 1 C was defined as one cycle, and the active material utilization rates of the non-sintered nickel electrode used in each battery at the 10th and 300th cycles were determined. . The active material utilization was calculated based on the following equation.

Active material utilization rate (%) = {discharge capacity at 10th or 300th cycle (mAh) / [amount of nickel hydroxide (g) × 288 (mAh / g)]} × 100

The results are shown in Table 1. However, the active material utilization in Table 1 is an index when the active material utilization of the electrode a of the present invention is 100.

[0026]

[Table 1]

As shown in Table 1, the electrode a of the present invention
The active material utilization rates at the 100th cycle and the 300th cycle are 100 and 97, respectively. On the other hand, in the comparative electrode x, the active material utilization at the 10th cycle is as high as the electrode a of the present invention, but the active material utilization at the 300th cycle is lower than that of the electrode a of the present invention. This is presumably because cobalt was diffused into the nickel hydroxide particles with the progress of the charge / discharge cycle because yttrium trioxide was not added, and as a result, the conductivity of the electrode was reduced. In the comparative electrode y, the active material utilization rates at the tenth cycle and the 300th cycle are extremely low, 80 and 65, respectively. This is due to the β-C of metallic cobalt and cobalt hydroxide.
It is presumed that the oxidation reaction to oOOH was reduced by the metal yttrium and / or the yttrium compound.

<Relationship between sodium content and active material utilization of sodium-containing cobalt compound powder> Instead of 30% by weight aqueous sodium hydroxide solution, 0.1% by weight, 5% by weight, 10% by weight, 20% by weight, The sodium content was 0.00% by weight, 0.05% by weight in the same manner as in Example 1 except that an aqueous solution of 35% by weight, 40% by weight, 45% by weight or 50% by weight of sodium hydroxide was used. %,
0.1 wt%, 0.5 wt%, 5 wt%, 10 wt%,
A sodium-containing cobalt compound powder of 12% by weight or 15% by weight was prepared. Next, a non-sintered nickel electrode and an alkaline storage battery were produced in the same manner as in Example 1 except that these sodium-containing cobalt compound powders were used as a conductive agent.

A charge / discharge cycle test was performed on each of the above batteries under the same conditions as above, and the active material utilization of the non-sintered nickel electrode used in each battery at the tenth cycle was determined. The results are shown in FIG. FIG. 1 shows the relationship between the sodium content of the sodium-containing cobalt compound powder and the active material utilization rate at the tenth cycle, the active material utilization rate at the tenth cycle on the vertical axis, and the sodium content rate on the horizontal axis. It is a graph shown. FIG. 1 also shows the active material utilization rate at the tenth cycle of the electrode a of the present invention (sodium content: 1% by weight). The ordinate indicates the active material utilization rate of the electrode a of the present invention. Is 100.

FIG. 1 shows that the sodium content of the sodium-containing cobalt compound is preferably 0.1 to 10% by weight in order to obtain a non-sintered nickel electrode having a high active material utilization rate.

<Relationship between heat treatment temperature and active material utilization rate> The heat treatment was performed at 45 ° C, 50 ° C, 100 ° C, and 150 ° C.
A sodium-containing cobalt compound powder was produced in the same manner as in Example 1 except that the temperature was 200, 220, or 250 ° C. Next, a non-sintered nickel electrode and an alkaline storage battery were produced in the same manner as in Example 1 except that these sodium-containing cobalt compound powders were used as a conductive agent. Incidentally, the sodium content of the sodium-containing cobalt compound is, in order,
They were 0.05% by weight, 1% by weight, 1% by weight, 1% by weight, 1% by weight, 0.05% by weight and 0.02% by weight.

A charge / discharge cycle test was performed on each of the above batteries under the same conditions as above, and the active material utilization of the non-sintered nickel electrode used in each battery at the tenth cycle was determined. The results are shown in FIG. FIG. 2 shows the relationship between the heat treatment temperature and the active material utilization rate at the tenth cycle, the vertical axis shows the active material utilization rate at the tenth cycle, and the horizontal axis shows the heat treatment temperature (° C.). It is a graph. FIG. 2 shows the electrode a of the present invention.
The active material utilization rate at the 10th cycle of (heating temperature: 80 ° C.) is also shown, and the active material utilization rate on the vertical axis is an index when the active material utilization rate at the 10th cycle of the electrode a of the present invention is 100. It is.

FIG. 2 shows that it is preferable to perform the heat treatment at a temperature of 50 to 200 ° C. in order to obtain a non-sintered nickel electrode having a high active material utilization rate.

<Relationship between Addition Ratio of Sodium-Containing Cobalt Compound Powder and Utilization Rate of Active Material and Electrode Capacity> Ni (O
H) The addition ratio of the sodium-containing cobalt compound powder (same as that prepared in Example 1) to 100 parts by weight of the ₂ powder was 0.5 parts by weight, 1 part by weight, 5 parts by weight, and 15 parts by weight.
A non-sintered nickel electrode and an alkaline storage battery were produced in the same manner as in Example 1 except that the amount was 20 parts by weight, 20 parts by weight, 22.5 parts by weight, or 25 parts by weight.

A charge / discharge cycle test was performed on each of the above batteries under the same conditions as described above, and the active material utilization of the non-sintered nickel electrode used in each battery at the tenth cycle was determined.
The electrode capacity at the cycle was determined. Table 2 shows the results.
And FIG. FIG. 3 shows the relationship between the addition ratio of the sodium-containing cobalt compound powder and the electrode capacity at the 10th cycle, the vertical axis shows the electrode capacity at the 10th cycle, and the horizontal axis shows the addition ratio (parts by weight) of the sodium-containing cobalt compound powder. ,
It is the graph shown respectively. In Table 2,
The active material utilization in the tenth cycle of the electrode a of the present invention (the addition ratio of the sodium-containing cobalt compound: 10 parts by weight) is also shown. The active material utilization in Table 2 is 1% of the electrode a of the present invention.
It is an index with the active material utilization rate at the 0th cycle as 100. FIG. 3 also shows the electrode capacity at the tenth cycle of the electrode a of the present invention. The electrode capacity in FIG. 3 is an index when the electrode capacity at the tenth cycle of the electrode a of the present invention is 100.

[0036]

[Table 2]

As can be seen from Table 2, in order to obtain a non-sintered nickel electrode having a high active material utilization rate, the addition ratio of the sodium-containing cobalt compound powder to 100 parts by weight of nickel hydroxide in the nickel hydroxide powder was 1 part by weight or more. It is understood that it is preferable that

Further, from FIG. 3, in order to obtain a non-sintered nickel electrode having a large electrode capacity, the addition ratio of the sodium-containing cobalt compound powder to 100 parts by weight of nickel hydroxide in the nickel hydroxide powder should be 20 parts by weight or less. It is understood that it is preferable that

Compiling the results shown in Table 2 and FIG.
It is understood that the addition ratio of the sodium-containing cobalt compound powder to 100 parts by weight of nickel hydroxide in the nickel hydroxide powder is preferably 1 to 20 parts by weight.

<Relationship between Addition Ratio of Metal Yttrium or Yttrium Compound, Utilization of Active Material and Electrode Capacity> Ni
The addition ratio of the yttrium trioxide powder to 100 parts by weight of the (OH) ₂ powder is 0.03 parts by weight, 0.05 parts by weight, 0.5 parts by weight, 1 part by weight, 5 parts by weight, 7 parts by weight or 10 parts by weight. A non-sintered nickel electrode and an alkaline storage battery were produced in the same manner as in Example 1 except that the weight parts were used.

A charge / discharge cycle test was performed on each of the above batteries under the same conditions as above, and the active material utilization rate at the 10th and 300th cycles of the non-sintered nickel electrode used for each battery and the 10th cycle The eye electrode capacitance was determined.
The results are shown in Table 3 and FIG. 4, respectively. FIG. 4 shows the relationship between the addition ratio of yttrium trioxide powder and the electrode capacity at the 10th cycle, the vertical axis shows the electrode capacity at the 10th cycle, and the horizontal axis shows the addition ratio of yttrium trioxide powder (parts by weight).
Are graphs respectively shown. Table 3 also shows the active material utilization rates at the 10th and 300th cycles of the electrode a of the present invention a (addition ratio of yttrium trioxide powder: 3 parts by weight). The rate is 1% of the active material utilization rate of the electrode a of the present invention at the 10th cycle.
The index is set to 00. FIG. 4 shows the electrode a of the present invention.
4 is also shown. The electrode capacity in FIG. 4 is an index with the electrode capacity at the 10th cycle of the electrode a of the present invention being 100.

[0042]

[Table 3]

According to Table 3, in order to obtain a non-sintered nickel electrode having a high active material utilization rate, the addition ratio of the yttrium trioxide powder to the nickel hydroxide powder of 100 parts by weight was 0.05% by weight. It can be seen that it is preferable to set the number of parts or more.

Further, from FIG. 4, in order to obtain a non-sintered nickel electrode having a large electrode capacity, the addition ratio of yttrium trioxide powder to 100 parts by weight of nickel hydroxide in the nickel hydroxide powder is 5 parts by weight or less. It is understood that it is preferable that

By summing up the results shown in Table 3 and FIG.
The addition ratio of yttrium trioxide powder to 100 parts by weight of nickel hydroxide in the nickel hydroxide powder is 0.0
It turns out that 5-5 weight part is preferable.

In the above embodiment, a single component powder consisting of only nickel hydroxide was used as the nickel hydroxide powder, but the nickel hydroxide was replaced with cobalt, zinc, cadmium, calcium, manganese, magnesium, bismuth,
It was confirmed that excellent effects were obtained in the same manner as described above even when a solid solution powder containing at least one element selected from aluminum and yttrium was used as a solid solution.

In the above embodiment, yttrium trioxide was used. However, when yttrium carbonate, yttrium hydroxide, yttrium fluoride, metal yttrium, or the like is used, the same excellent effects as described above can be obtained. It was confirmed.

[0048]

The electrode of the present invention exhibits a high active material utilization rate not only at the beginning of the charge / discharge cycle but also over a long period of time.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the sodium content of a sodium-containing cobalt compound powder and the active material utilization at the tenth cycle.

FIG. 2 is a graph showing the relationship between the heat treatment temperature during the synthesis of a sodium-containing cobalt compound powder and the active material utilization rate at the tenth cycle.

FIG. 3 is a graph showing a relationship between an addition ratio of a sodium-containing cobalt compound powder to a nickel hydroxide powder and an electrode capacity at the tenth cycle.

FIG. 4 is a graph showing the relationship between the addition ratio of yttrium trioxide powder to nickel hydroxide powder and the electrode capacity at the tenth cycle.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mutsumi Yano 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Kozo Nogami 2-5-2 Keihanhondori, Moriguchi-shi, Osaka No. 5 Inside Sanyo Electric Co., Ltd. (72) Inventor Ikuro Yonezu 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Prefecture Inside Sanyo Electric Co., Ltd. (72) Koji Nishio 2-5-2 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (56) References JP-A-9-219198 (JP, A) JP-A-10-12238 (JP, A) JP-A-1-200555 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01M 4/24-4/62

Claims (7)

(57) [Claims] A nickel hydroxide powder as an active material powder,
A non-sintered nickel electrode for an alkaline storage battery to which a sodium-containing cobalt compound powder, a metal yttrium powder and / or a yttrium compound powder are added. 2. The nickel hydroxide powder is a solid solution powder in which at least one element selected from cobalt, zinc, cadmium, calcium, manganese, magnesium, bismuth, aluminum and yttrium is dissolved in nickel hydroxide. The non-sintered nickel electrode for an alkaline storage battery according to claim 1. 3. The method according to claim 1, wherein the sodium-containing cobalt compound powder is prepared by adding an aqueous solution of sodium hydroxide to metal cobalt or a cobalt compound and heat-treating the mixture at 50 to 200 ° C. Non-sintered nickel electrode for alkaline storage batteries. 4. The sodium-containing cobalt compound powder contains 0.1 to 10% by weight of sodium.
A non-sintered nickel electrode for an alkaline storage battery according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the sodium-containing cobalt compound powder is nickel hydroxide 100 in the nickel hydroxide powder.
The non-sintered nickel electrode for an alkaline storage battery according to any one of claims 1 to 4, wherein the non-sintered nickel electrode is added in an amount of 1 to 20 parts by weight relative to parts by weight. 6. The non-sintered type for an alkaline storage battery according to claim 1, wherein said yttrium compound powder is yttrium trioxide powder, yttrium carbonate powder, yttrium hydroxide powder or yttrium fluoride powder. Nickel pole. 7. The metal yttrium powder and / or the yttrium compound powder is used in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of nickel hydroxide in the nickel hydroxide powder.
The non-sintered nickel electrode for an alkaline storage battery according to any one of claims 1 to 6, which is added by part by weight.