JP2840270B2 - Paste type cadmium electrode for alkaline storage battery and method for producing the same - Google Patents

Description

The present invention relates to a paste-type cadmium electrode used for an alkaline storage battery such as a nickel-lucadmium storage battery, and a method for producing the same.

(B) Conventional technology As a cadmium electrode used for a nickel-cadmium storage battery or the like, a non-sintering type cadmium electrode such as a paste type having a simple manufacturing process and a low manufacturing cost is widely used industrially. A cadmium electrode of this type is manufactured by applying a paste formed by kneading an active material such as cadmium oxide powder or cadmium hydroxide powder together with a paste liquid to a conductive core, filling the paste, and then drying the paste. ing. However, this type of non-sintered cadmium electrode has a problem that oxygen gas absorption performance is low, and various proposals have been made to solve this problem.

For example, JP-A-60-216449 and JP-A-61-240576 disclose a method of forming a conductive layer made of an alkali-resistant conductive material such as carbon or nickel on the surface of a paste-type cadmium electrode plate. Has been proposed. By doing so, the conductivity of the cadmium electrode plate surface can be increased, the generation of metal cadmium on the electrode plate surface can be promoted, and the oxygen gas absorbing ability can be increased.

However, even in such a method,
As the oxygen gas absorption capacity is further improved, another new problem has arisen.

(C) Problems to be Solved by the Invention When a conductive layer made of carbon powder is formed on the surface of a paste-type cadmium electrode plate, formation of metal cadmium at the interface between the conductive layer and the active material layer during charging is promoted. And
Oxygen gas absorption performance is improved. However, it does not have the effect of promoting the production of metal cadmium in and on the surface of the conductive layer where the reaction with oxygen gas is most likely to proceed, and there is room for improving the oxygen gas absorption performance.

On the other hand, when a conductive layer made of an amechanically resistant conductive material, for example, nickel powder is simply formed on the surface of the paste-type cadmium electrode plate, the generation of metal cadmium during charging is based on the high conductivity of the conductive material. Can be core. As a result, metal cadmium is generated in the conductive layer and on the surface thereof, and the oxygen gas absorbing performance is further improved as compared with the case where carbon powder is used. However, at the time of charging, new problems arise such as generation of hydrogen gas is promoted, storage characteristics of the battery are reduced, and generation of dendrites is promoted.

As an intermediate method between the above two methods, it is conceivable to form a mixed layer of carbon powder and alkali-resistant metal powder on the surface of the paste-type cadmium electrode plate. However, also in this method, simply using nickel, for example, as an alkali-resistant metal powder,
Basically, there are problems of the above two methods. Therefore, in order to solve the above problem while maintaining the effect of improving the oxygen gas absorption performance, it is necessary to consider the state of the alkali-resistant metal powder in the conductive layer.

Here, the apparent density of the alkali-resistant metal powder is usually 0.
Since it is 2 g / cc or more (for example, carbonyl nickel 0.5 g / cc), it is extremely difficult to uniformly disperse it in a slurry composed of carbon powder and a paste. Therefore, the conductive layer formed by applying and drying the slurry on the surface of the electrode plate is unlikely to be one in which the alkali-resistant metal powder is uniformly dispersed.

Further, for example, nickel as an alkali-resistant metal,
Metals such as iron have a lower hydrogen generation overpotential than cadmium compounds such as cadmium oxide as an active material, and may cause generation of hydrogen gas during charging at the liquid-solid interface. Therefore, it is necessary to regulate the form of addition of nickel and the additive.

Here, when nickel powder is used as the alkali-resistant conductive powder, the conductive portion with the conductive layer on the surface of the electrode plate,
It consists of "points". Therefore, only nickel in the conductive layer in the portion where the metal cadmium generated during charging reaches the electrode plate surface can contribute to the improvement in conductivity. If the amount of nickel added is increased to increase the amount of nickel used, a problem such as generation of hydrogen gas occurs.

On the other hand, when the surface of the paste-type cadmium electrode plate is nickel-plated, the surface of the electrode plate is closed by the nickel layer, and it is not preferable because the promotion of hydrogen gas generation and the inhibition of the electrode reaction are observed.

When metal fibers are added to the conductive layer, it is effective in that a network of metal cadmium is easily formed on the surface of the paste-type cadmium electrode plate. For example, nickel fibers have a fiber diameter of several μm to Since it is as thick as several tens of μm and has poor flexibility, the separator breaks. As a result, a short circuit inside the battery may occur.

(C) Problems to be Solved by the Invention The present invention has been made in view of the problems described above, and a main object of the present invention is to further improve the oxygen gas absorbing performance of a paste-type cadmium electrode. is there.

Another object is to suppress generation of hydrogen gas from the cadmium electrode during charging.

Still another object is to suppress dendrite generation from the cadmium electrode during charging.

Another object of the present invention is to propose a method for uniformly dispersing an alkali-resistant metal powder when a conductive layer made of an alkali-resistant conductive powder is formed on the surface of a paste-type cadmium electrode plate.

(D) Means for Solving the Problems The first paste-type cadmium electrode for an alkaline storage battery of the present invention is characterized in that carbon powder is applied to the surface of an active material layer mainly composed of cadmium oxide applied to a conductive core. It has a conductive layer in which an alkaline metal powder is mixed, and the surface area of the alkali-resistant metal powder is based on 1 g of the active material.
Characterized in that it is a 0.001~0.05m ^2.

Further, the manufacturing method is such that an active material containing cadmium oxide as a main component is applied to a conductive core to form an active material layer, and a carbon powder and an alkali-resistant metal powder are mixed on the surface of the active material layer. A conductive layer to be provided, wherein the surface area of the alkali-resistant metal powder, the active material 1 g
It is characterized by being 0.001 to 0.05 m ² .

The paste-type cadmium electrode for an alkaline storage battery according to the second invention is a conductive layer in which a carbon powder and an alkali-resistant metal powder are mixed on the surface of an active material layer mainly containing cadmium oxide applied to a conductive core. Wherein the conductive layer has a carbon powder, a paste, and an apparent density of 0.2 g / cc.
It is characterized by comprising the following alkali-resistant metal powder.

Further, the manufacturing method is such that an active material containing cadmium oxide as a main component is applied to a conductive core to form an active material layer, and the surface of the active material layer has carbon powder, a paste, and an apparent density. 0.
The method is characterized in that a slurry obtained by kneading an alkali-resistant metal powder of 2 g / cc or less is applied and dried to form a conductive layer.

The paste-type cadmium electrode for an alkaline storage battery according to the third aspect of the present invention comprises a first conductive material comprising an alkali-resistant metal powder and a paste on the surface of an active material layer containing cadmium oxide as a main component applied to a conductive core. And a second conductive layer made of carbon powder and a paste, wherein the first conductive layer is disposed in close contact with the active material layer.

Further, in the manufacturing method, a first slurry composed of an alkali-resistant metal powder and a paste is adhered to the surface of an active material layer containing cadmium oxide as a main component, which is applied to a conductive core, and the first slurry is dried and dried. After the formation of the conductive layer, a second slurry composed of carbon powder and a paste is applied thereto and dried to form a second conductive layer.

In the paste-type cadmium electrode for an alkaline storage battery and the method for producing the same, it is preferable to use a nickel powder as the alkali-resistant metal powder.

(E) Function In the paste-type cadmium electrode for an alkaline storage battery according to the first aspect of the present invention, the alkali-resistant metal powder in the conductive layer containing carbon powder has itself as a nucleus, and the metal cadmium is applied to the surface of the electrode plate during charging. It has the effect of generating. Oxygen gas absorption performance of the cadmium electrode is further improved by this effect and the effect of promoting the generation of metal cadmium at the interface between the conductive layer originally contained in the conductive layer made of carbon powder and the active material layer on the surface of the electrode plate. I do.

In addition, in the effect of improving the oxygen gas absorption performance, it is sufficient that the generation of metal cadmium on the electrode plate surface is uniform, and the generation of an excessive amount of metal cadmium causes adverse effects such as active material migration and dendrite formation. cause. Therefore, it is not preferable to add the alkali-resistant metal powder in excess. Also, excessive addition of alkali-resistant metal powder,
In some cases, the storage characteristics of the battery may be degraded or hydrogen gas may be generated. Therefore, the present inventor studied various conditions, and found that the most important factor related to the generation of hydrogen gas in the physical properties of the alkali-resistant metal powder was the total surface area of the metal powder per unit weight of the active material. Was. Then, in order to solve the above-mentioned problem, on the basis that the alkali-resistant metal powder is a nucleus for the production of metal cadmium and its surface area is preferably large, the total surface area of the metal powder is 1 g of the active material.
It has been found that the optimum value is 0.001 to 0.05 m ² per unit.

In the paste-type cadmium electrode for an alkaline storage battery according to the second aspect of the present invention, the conductive layer made of carbon powder basically promotes the production of metal cadmium at the interface with the active material layer, as described above. When the alkali-resistant metal powder is added to the conductive layer, the alkali-resistant metal powder promotes generation of metal cadmium inside the conductive layer.

And the generation of metal cadmium inside this conductive layer is
It is effective to generate the metal cadmium more uniformly, and in this way, metal cadmium can be generated in a wide range within the conductive layer and at the interface with the active material layer. As a result, the oxygen gas absorbing performance is improved, and the cycle life is not reduced. Therefore, it is important to uniformly disperse the alkali-resistant metal powder constituting the conductive layer in the conductive layer, and it has been found that a powder having a small apparent density is suitable for that purpose. Therefore, various experiments were conducted, and when the apparent density was 0.2 g / cc or less, it was found that the dispersibility was dramatically improved and the oxygen gas absorbing performance was increased, and the present invention was completed.

Further, when only the second conductive layer made of carbon powder and the paste is formed on the surface of the active material layer, the interface between the active material layer and the second conductive layer is charged with metal during charging. Cadmium forms.

Therefore, like the alkaline storage battery paste-type cadmium electrode of the third invention, a first conductive layer made of an alkali-resistant metal powder and a paste is interposed between the active material layer and the second conductive layer, By bringing the first conductive layer into close contact with the active material layer, the alkali-resistant metal powder is covered with metal cadmium during charging. As a result, generation of hydrogen gas from the alkali-resistant metal powder during charging can be suppressed. In addition, the generation of metal cadmium is promoted based on the high conductivity of the alkali-resistant metal powder, and a significant improvement in oxygen gas absorption performance can be expected.

As the above-mentioned alkali-resistant metal powder, nickel powder is suitable.

(F) Example Hereinafter, the present invention will be described in detail with reference to a comparison between the present invention and a comparative example.

[First experimental example] An active material composed of 900 g of cadmium oxide powder and 100 g of metal cadmium powder, 20 g of magnesium oxide as a dendritic inhibitor, 6 g of hydroxypropyl cellulose as a binder, and 10 g of nylon fiber as a reinforcing agent Then, 300 cc of an aqueous sodium phosphate solution as a hydration inhibitor was kneaded to obtain an active material sheet. The sheet was coated on both surfaces of a conductive core made of punched metal and dried to obtain a cadmium electrode plate, which was used as a base electrode plate.

Next, a predetermined amount of nickel powder having a specific surface area of 5 m ² / g by BET method and acetylene black were mixed, and hydroxypropylcellulose (HPC) as a paste was added to obtain a slurry.

This slurry was applied to the base electrode plate by a roller transfer method, and dried at 60 ° C. to obtain a cadmium electrode.

The amount of acetylene black added was 0.5% by weight based on the weight of the active material.

A cadmium electrode was also obtained in the same manner as described above using a nickel powder having a specific surface area of 2 m ² / g by the BET method.

These cadmium electrodes and a sintered nickel positive electrode plate are wound through a separator to produce a spiral electrode body, and a sealed nickel-cadmium storage battery with a nominal capacity of 1.3 Ah (SC
Size), and compared each performance.

(Test 1) Using a battery provided with the cadmium electrode, the relationship between the total surface area of nickel powder in the conductive layer per unit weight of the active material and the equilibrium internal gas pressure of the battery was examined. The condition at this time is 25
At ℃, the battery is charged continuously with a current of 1.3A (1C).

The result is shown in FIG. In FIG. 1, the solid line shows the case using a nickel powder having a specific surface area of 5 m ² / g, and the chain line shows the case using a nickel powder having a specific surface area of 2 m ² / g.

From Figure 1, a specific surface area of 5 m ² / g, even those different from 2m ² / g, when the total surface area of the nickel powder to the addition becomes 0.001 m ² or more with respect to the active material 1g, oxygen gas It can be seen that the absorption performance has been significantly improved.

(Test 2) Next, similarly to the above, using a battery, the relationship between the total surface area of nickel powder in the conductive layer per unit weight of the active material and the amount of hydrogen gas generated in the battery was examined. The condition at this time is to charge the battery 160% with a current of 2.6 A (2 C) at 10 ° C.

The result is shown in FIG. In FIG. 2, the solid line shows the specific surface area of 5 m ² / g nickel powder, and the dashed line shows the specific surface area of 2
Those using m ² / g nickel powder are shown.

From FIG. 2, the specific surface area of the nickel powder is 5 m ² / g, 2 m ²
Even if the total surface area of the nickel powder to be added exceeds 0.05 m ² / g with respect to 1 g of the active material, generation of hydrogen gas will be remarkably observed even if the surface area is different from that of the nickel powder.

As described above, from the results of Tests 1 and 2, the addition amount of the nickel powder to 1 g of the alkali-resistant metal powder in the conductive layer, that is, 1 g of the active material is optimally 0.001 to 0.05 m ^{2 in} terms of surface area.

[Second Experimental Example] To a solution of acetylene black as carbon powder and hydroxypropylcellulose (HPC) as a paste, nickel powder of various apparent densities (by a Kawakita-type measuring instrument) was added and thoroughly stirred. , Mixed to obtain a slurry. This slurry was applied to the base electrode plate used in the first experimental example by a roller transfer method, and dried at 60 ° C. to form a conductive layer on the electrode plate surface. Thus, a cadmium electrode having a conductive layer in which carbon powder and alkali-resistant metal powder were mixed was obtained.

The amount of acetylene black added was 0.8% by weight based on the weight of the active material.

The addition amount of the nickel powder was set so that the weight ratio with respect to acetylene black was 1/2.

A cadmium electrode using nickel powder having various apparent densities obtained in this way, and a sintered nickel positive electrode plate are wound through a separator to produce a spiral electrode body, and a sealed type having a nominal capacity of 1.3 Ah. Nickel-cadmium storage batteries (SC size) were obtained and their performances were compared.

(Test 3) Using a battery provided with the cadmium electrode, the relationship between the apparent density of nickel powder in the conductive layer and the equilibrium internal gas pressure of the battery was examined. The condition at this time is 1.3A at 25 ° C.
(1.0C) to charge continuously.

The result is shown in FIG. According to FIG. 3, the internal pressure of the battery can be reduced by reducing the apparent density of the nickel powder to be added to 0.2 g / cc or less.

[Third Experimental Example] Carbonyl nickel powder (2.5 μm in particle diameter) and HPC as a paste were kneaded to obtain a first slurry, and the surface of the base electrode plate used in the first experimental example was The slurry was applied by a roller transfer method and dried at 60 ° C. Thus, a first conductive layer was formed. Next, acetylene black as a carbon powder and HPC as a paste are kneaded to obtain a second slurry, which is applied and dried on the first conductive layer in the same manner as described above. A conductive layer was formed.

Thus, a cadmium electrode A according to the present invention was obtained. The amount of carbonyl nickel added in the conductive layer was 0.1% by weight based on the weight of the active material, and the amount of carbon powder added was 0.5% by weight based on the weight of the active material.

On the other hand, as a first comparative example, a comparative electrode B in which only the second conductive layer was formed on the base electrode plate was manufactured. The amount of carbon powder added in this conductive layer was 0.5% based on the weight of the active material.
% By weight.

Next, as a second comparative example, a comparative electrode C in which only the first conductive layer was formed on the base electrode plate was manufactured. The amount of nickel powder added in the conductive layer was 0.1% by weight based on the weight of the active material.

Using these electrodes A, B, and C, a sealed nickel-cadmium storage battery (SC size) having a nominal capacity of 1.3 Ah was obtained in the same manner as in the first and second experimental examples, and their performances were compared.

(Test 4) Using the battery, the relationship between the charging time and the battery internal pressure was examined. The condition at this time is that the battery is continuously charged with a current of 1.3 A (1 C) at 25 ° C.

The result is shown in FIG. Thus, the comparative battery c having the second conductive layer made of only carbonyl nickel was obtained.
However, it can be seen that the sample has the same low internal pressure as the battery a of the present invention.

(Test 5) Next, using the battery in the same manner as described above, the partial pressure of hydrogen gas in the battery after charging for a certain time was examined. The condition at this time is that charging is performed at 0 ° C. with a current of 1.3 A (1 C) for 2 hours (200% charging).

 The results are shown in Table 1.

From these results, it can be seen that the battery a of the present invention and the comparative battery b have a lower hydrogen gas partial pressure in the battery than the comparative battery c, and the generation of hydrogen gas is suppressed.

As described above, the results of Tests 4 and 5 show that Battery A of the present invention has excellent oxygen gas absorption performance and suppresses generation of hydrogen gas. Therefore, as in the case of the electrode A of the present invention, after the first conductive layer containing the alkali-resistant metal powder is formed on the surface of the cadmium electrode plate, the second conductive layer containing the carbon powder is disposed to exhibit the above characteristics. In addition, an alkaline storage battery having excellent cycle characteristics can be provided.

In the embodiments of the present invention, the roller transfer method has been exemplified as a method for forming the conductive layer. However, the present invention is not limited to this, and a spray method, an immersion method, or the like may be used.

(G) Effects of the Invention According to the present invention, the oxygen gas absorption performance of the paste-type cadmium electrode can be further improved, and its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the surface area of the nickel powder to be added and the internal pressure of the battery, FIG. 2 is a diagram showing the relationship between the surface area of the nickel powder to be added and the partial pressure of hydrogen in the battery, and FIG. FIG. 4 is a diagram showing the relationship between the apparent density of the nickel powder and the battery internal pressure, and FIG. 4 is a diagram showing the relationship between the charging time and the battery internal pressure.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 4/24-4/26 H01M 10/24-10/34

Claims (12)

(57) [Claims] 1. An active material layer comprising cadmium oxide as a main component applied to a conductive core and having a conductive layer in which a carbon powder and an alkali-resistant metal powder are mixed on the surface, wherein the alkali-resistant metal The paste-type cadmium electrode for an alkaline storage battery, wherein the surface area of the powder is 0.001 to 0.05 m ² per 1 g of the active material. 2. The paste-type cadmium electrode for an alkaline storage battery according to claim 1, wherein said alkali-resistant metal powder is a nickel powder. 3. An active material containing cadmium oxide as a main component is coated on a conductive core to form an active material layer, and a carbon powder and an alkali-resistant metal powder are mixed on the surface of the active material layer. a manufacturing method for disposing a layer, the surface area of the alkali-resistant metal powder, a manufacturing method of the active material 1g per 0.001～0.05M ² and alkaline storage battery paste cadmium electrode, characterized in that the. 4. The method for producing a paste-type cadmium electrode for an alkaline storage battery according to claim 3, wherein nickel powder is added as said alkali-resistant metal powder. 5. An active material layer containing cadmium oxide as a main component applied to a conductive core and having, on the surface thereof, a conductive layer in which a carbon powder and an alkali-resistant metal powder are mixed, wherein the conductive layer is , Carbon powder, glue, apparent density 0.2g / c
c. A paste-type cadmium electrode for an alkaline storage battery, comprising: the following alkali-resistant metal powder. 6. The paste-type cadmium electrode for an alkaline storage battery according to claim 5, wherein said alkali-resistant metal powder is a nickel powder. 7. An active material containing cadmium oxide as a main component is applied to a conductive core to form an active material layer, and a carbon powder, a paste, and an apparent density of 0.2 g are formed on the surface of the active material layer. A method for producing a paste-type cadmium electrode for an alkaline storage battery, comprising applying a slurry obtained by kneading an alkali-resistant metal powder of / cc or less and drying the mixture to form a conductive layer. 8. The method for producing a paste-type cadmium electrode for an alkaline storage battery according to claim 7, wherein nickel powder is added as said alkali-resistant metal powder. 9. A first conductive layer composed of an alkali-resistant metal powder and a paste, and a second conductive layer composed of a carbon powder and a paste, on a surface of an active material layer containing cadmium oxide as a main component applied to a conductive core. 2. A paste-type cadmium electrode for an alkaline storage battery, comprising: a first conductive layer disposed in close contact with the active material layer. 10. The paste-type cadmium electrode for an alkaline storage battery according to claim 9, wherein said alkali-resistant metal powder is a nickel powder. 11. A first slurry composed of an alkali-resistant metal powder and a paste is adhered to the surface of an active material layer containing cadmium oxide as a main component, which is coated on a conductive core, and dried to form a first conductive material. A method for producing a paste-type cadmium electrode for an alkaline storage battery, comprising: forming a layer, adhering a second slurry composed of carbon powder and a paste, and drying to form a second conductive layer. 12. The method for producing a paste-type cadmium electrode for an alkaline storage battery according to claim 11, wherein nickel powder is added as said alkali-resistant metal powder.