JPH0677452B2 - Nickel positive electrode plate for alkaline storage battery and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention forms a layer containing cobalt hydroxide or cobalt oxide as a sandwich structure between two layers containing nickel hydroxide as a main component. The present invention relates to a nickel positive electrode plate for an alkaline storage battery, or a nickel positive electrode plate for an alkaline storage battery in which a layer containing cobalt hydroxide or cobalt oxide as a main component is formed on the surface of the positive electrode active material having the above structure.

Problems to be Solved by Conventional Techniques and Inventions Conventionally, nickel positive electrode plates used for alkaline storage batteries are
Porous sintered nickel substrate obtained by sintering carbonyl nickel powder in a reducing atmosphere is impregnated with an acidic solution containing nickel salt as the main component, concentrated, and then immersed in a hot alkaline solution to hydrate the pores of the nickel substrate. It is manufactured by a method of filling a positive electrode active material containing nickel as a main component. Recently, with the miniaturization of equipment using alkaline storage batteries, there is a growing demand for market to increase the capacity density per unit volume of storage batteries. I could not meet. In addition to the sintered electrode plate, there is a foamed nickel positive electrode plate in which sponge nickel is physically filled with a positive electrode active material powder containing nickel hydroxide as a main component.
When the filling amount of the active material powder is increased, there is a problem that the utilization factor of the active material decreases, the substantial capacity density does not increase as expected, and the potential characteristic during discharge deteriorates.

There are two possible methods for increasing the capacity of the nickel positive electrode plate: increasing the amount of the positive electrode active material and increasing the utilization rate of the active material. The electrode plate is already close to the limit, and when it is further increased, the capacity is slightly increased, but the potential characteristic at the time of discharge is deteriorated, which is not appropriate. on the other hand,
As a method of increasing the utilization rate of the active material, generally, several percent of cobalt salt is added to an impregnating solution of acidic nickel salt, and cobalt hydroxide is uniformly dispersed in the active material after the impregnation step. According to this method, not only the utilization factor of the active material but also the high temperature characteristics are improved, but the effect of the utilization factor improvement itself is not so large, and it was not sufficient to increase the capacity of the nickel positive electrode plate.

Recently, as a method of improving the performance of the nickel positive electrode plate,
Mainly three known techniques have been proposed.

Known techniques 1 include, for example, Japanese Patent Laid-Open Nos. 51-121743 and Sho.
51-121744, these technologies use electrode plates holding nickel hydroxide as cobalt sulfate of pH 3.5 to 6.0 or pH 4.
By immersing in a cobalt acetate impregnating solution of 0 to 6.8 and changing the cobalt salt into cobalt hydroxide, the capacity of the electrode plate is increased.

A known technique 2 is, for example, Japanese Patent Laid-Open No. 59-163753.
In this technique, the electrode plate holding nickel hydroxide is dipped in a nitrate aqueous solution containing cobalt nitrate and then alkali-treated to form a layer of cobalt hydroxide alone on the surface of the active material of 0.5 to 5 wt%. It has a similar operation and effect.

In these techniques, the structure of the active material is a macroscopic two-layer structure, and a cobalt hydroxide layer is formed on the outside of nickel hydroxide.

Known technology 3 is, for example, Japanese Examined Patent Publication No. 57-5018, and this technology is to form a positive electrode plate by using an impregnating solution containing cobalt as a main component one or more times, so that cadmium that has not been preformed, that is, precharged When a battery is assembled using the negative electrode plate as the counter electrode, although most of the positive electrode cobalt can be charged, 20% of it can be discharged.
Since only ~ 25% can be produced, the capacity of cobalt that cannot be discharged has the same effect as precharging the negative electrode. However, the content thereof does not specify the timing of using the impregnating liquid containing a cobalt salt as a main component and the optimum amount of the cobalt compound to be impregnated. That is, the impregnating liquid containing a cobalt salt as a main component may be used at the beginning or at the end, and the content of the cobalt compound may be within a range where the utilization rate of the active material is low (described later). become.

The positive electrode plate according to the above-described conventional known techniques 1, 2 and 3 has a higher utilization ratio of the active material than the conventional positive electrode plate in which cobalt hydroxide is uniformly dispersed in the active material. However, this effect is effective when the active material packing density and the discharge rate on the porous metal substrate are not so high, but when the active material packing density is high, this effect is halved, especially at high rate discharge. There was a drawback that the effect was hardly recognized.

The present invention is related to the proposals of the above-mentioned known techniques 1, 2 and 3, but it is an object of the invention to discover a completely new fact by experiments and overcome the above-mentioned drawbacks of the known technique. It is intended to provide a positive electrode plate in which the utilization factor of the active material and the discharge potential characteristic are remarkably improved in a high density state. That is, according to the present invention, as a result of detailed examination of the formation state of cobalt hydroxide, in the two-layer structure in which a layer containing cobalt hydroxide as a main component is formed outside nickel hydroxide as in the known arts 1 and 2. , A sandwich structure in which a layer containing cobalt hydroxide as the main component or a layer containing cobalt oxide as the main component is formed by oxidizing the cobalt hydroxide between two layers containing nickel hydroxide as the main component. By forming three or more layers of nickel, it is possible to obtain a nickel positive electrode plate having a high active material utilization rate and discharge potential characteristics and good discharge rate dependence of each in a state of high active material packing density, which has not been obtained by the conventional manufacturing method. It is based on discovering what can be done. Furthermore, in the present invention, in addition to the structure of the active material, as a result of investigating the state of the porous metal substrate to be used, when the passive film is formed on the substrate surface, the active material utilization rate and It has also been found that the discharge potential characteristics and the respective discharge rate dependencies are further improved.

Means for Solving the Problems That is, according to the present invention, a layer mainly containing nickel hydroxide is first formed as a first layer on a porous metal substrate, and then a second layer is formed on the porous metal substrate as a second layer. A layer based on cobalt,
Alternatively, the layer containing cobalt hydroxide as a main component is chemically or electrochemically oxidized to form a layer containing cobalt oxide as a main component, and a third layer containing nickel hydroxide as a main component is further formed thereon. What has been obtained in the past by forming a positive electrode plate on which is formed a layer, that is, by forming a layer containing cobalt hydroxide or cobalt oxide as a main component in a sandwich structure between two layers containing nickel hydroxide as a main component. It has been made possible to obtain a nickel positive electrode plate having good active material utilization rate, discharge potential characteristics, and respective discharge rate dependency even in a state where the active material packing density is high. Further, by forming a fourth layer containing cobalt hydroxide as a main component on the surface of the positive electrode plate having the sandwich structure, the utilization rate of the active material can be further increased by several percent. In this case, 1 CA
The active material utilization rate at the discharge current of is close to 100%. Further, by forming a passivation film of a metal oxide on the surface of the porous metal substrate to be used, the discharge rate dependence of the active material utilization rate and the discharge potential characteristics can be further reduced.

Examples The experiments and examples relating to the present invention are shown below.

Experiment 1 The operation of the chemical impregnation method was repeated several times using an impregnating liquid containing nickel nitrate as the main component to form a first layer containing nickel hydroxide as the main component in the sintered nickel substrate. Next, the operation of the chemical impregnation method was performed once using cobalt nitrate solutions of various concentrations to form a second layer of cobalt hydroxide alone, and this cobalt hydroxide was electrochemically oxidized. A layer of cobalt oxide such as cobalt oxyhydroxide was formed. Further, a third layer containing nickel hydroxide as a main component was formed thereon in the same manner as the first layer. The utilization ratio of the active material of the nickel positive electrode plate (referred to as electrode plate group A) thus produced was measured in a KOH solution having a specific gravity of 1.250 (20 ° C.). For some cobalt nitrate impregnation solutions, after forming the second layer of cobalt hydroxide alone,
Without electrochemically oxidizing this cobalt hydroxide,
An electrode plate (referred to as electrode plate group B) having a third layer containing nickel hydroxide as a main component was also prepared, and the active material utilization rate was measured by the same method. FIG. 1 shows the relationship between the ratio of the cobalt compound in the second layer and the utilization rate of the active material with respect to the amount of nickel hydroxide filled as the active material. The theoretical capacity of the electrode plate was calculated on the basis of the amounts of impregnated nickel hydroxide and cobalt hydroxide, and each one follows a one-electron reaction. As a nickel sintered substrate, carbonyl nickel powder, water and a paste are kneaded to form a nickel slurry, and the nickel slurry is applied to a nickel-plated metal plate of iron, and then nickel is sintered at 900 ° C. in a reducing atmosphere. I used one.
In FIG. 1, in the case of the electrode group A obtained by electrochemically oxidizing the second layer of cobalt hydroxide, the amount of cobalt compound was 0.
The active material utilization rate is high in the range of 6 to 10.0 mol%. This is because the reversible potential of cobalt hydroxide and cobalt oxides such as oxyhydroxide is less than that of nickel. Cobalt oxide is charged to cobalt oxide such as cobalt oxyhydroxide, and when discharging, nickel oxyhydroxide is discharged first, and cobalt oxide such as cobalt oxyhydroxide has good conductivity. From this, it is considered that the second layer of cobalt alone has a high current utilization factor due to the collector-like effect. However, when the amount of cobalt compound is increased, The cause of the decrease in active material utilization is unknown. On the other hand, in the case of the electrode plate group B in which the second layer of the cobalt hydroxide alone was not electrochemically oxidized, the active material utilization rate was hardly increased, and The results are quite different. The third reason is
In the formation of the layer containing nickel hydroxide as the main component, when the solution of nickel nitrate was impregnated, the second layer of cobalt hydroxide alone was dissolved, and in the subsequent neutralization step, nickel hydroxide was added to nickel hydroxide. It is considered that the current collector-like effect was reduced because the cobalt hydroxide was dispersed, and as a result, the active material utilization rate did not increase. From this, when forming a layer of cobalt compound alone, it is considered necessary to prevent it from mixing with the layer containing nickel hydroxide as the main component before and after it, so that the positive electrode plate should be prepared by the chemical impregnation method. In the case of manufacturing, it is necessary to form a second layer of cobalt hydroxide alone and then oxidize it to change it into a cobalt oxide that is difficult to dissolve in the impregnating liquid. However, this does not apply when the active material is filled by a method other than the chemical impregnation method, for example, when the active material is physically filled like a foamed electrode plate, and the active material is not required to be oxidized even if cobalt hydroxide is not oxidized. It has been confirmed that the active material utilization rate is high with a high packing density of the material.

In this experiment, cobalt hydroxide was electrochemically oxidized, but other methods such as hydrogen peroxide solution, sodium hypochlorite, and potassium persulfate were used. Similar results were obtained when oxidized by heat treatment in an air atmosphere.

Experiment 2 Among the samples prepared in Experiment 1 in which the utilization rate of the active material was improved in the electrode plate group A, the sample containing 0.6 mol% of the smallest amount of cobalt compound in the second layer and the largest amount of 10.0 mol %
Using the above sample, the chemical impregnation method was performed once to prepare a positive electrode plate (electrode plates C1 and C2) on which a layer of cobalt hydroxide alone was formed as the fourth layer. Then, the utilization rate of the active material was measured. FIG. 2 shows the relationship between the ratio of cobalt hydroxide in the fourth layer to the amount of nickel hydroxide filled as the active material and the utilization rate of the active material. As can be seen from Fig. 2, in the case of the electrode plate group C1 in which the amount of the cobalt compound in the second layer is 0.6 mol%, the amount of cobalt hydroxide in the fourth layer is 0.
High utilization rate of active material in the range of 8 to 7.0 mol%, almost 100%
It has become. On the other hand, if the amount of cobalt compound in the second layer is
In the case of the electrode plate group C2 of 10.0 mol%, the utilization rate is close to 100% because the amount of cobalt hydroxide in the fourth layer is 0.4 to 6.0.
It is in the range of mol%. When the optimum value of the cobalt content is obtained from the results of the above Experiment 1 and this Experiment 2, the content of the cobalt compound in the second layer is 0.6 to 10.0 mol% with respect to the amount of nickel hydroxide filled as the active material, When the content of the cobalt compound in the fourth layer is in the range of 0.4 to 7.0 mol%, a positive electrode plate having a high utilization ratio of the active material can be obtained.

Experiment 3 In this experiment, the influence of the active material packing density on the active material utilization rate of the product of the present invention described in Experiments 1 and 2 and the conventional product described in the known art was examined.

As the positive electrode plate according to the present invention, in the electrode plate group A (three-layer structure) produced in Experiment 1, the amount of the cobalt compound in the second layer was 3 mol% with respect to the amount of nickel hydroxide filled as the active material.
And a positive electrode plate (referred to as sample A ′) and a four-layer structure similar to samples C1 and C2 prepared in Experiment 2, and the amount of the cobalt compound in the second layer is the amount of nickel hydroxide filled as the active material. On the other hand, a positive electrode plate (referred to as sample C ′) in which the amount of cobalt hydroxide in the fourth layer was 2 mol% was used. As a conventional product, a positive electrode plate (referred to as sample D) was used in which a nickel hydroxide active material layer was formed on a sintered substrate and then a cobalt hydroxide layer was formed on the surface thereof. The amount of cobalt hydroxide on the surface is 3 mol% with respect to the amount of nickel hydroxide
I adjusted it to be.

FIG. 3 shows the relationship between the active material packing density of each sample electrode plate and the active material utilization rate. The active material packing density on the horizontal axis was calculated assuming that the impregnated nickel hydroxide and cobalt hydroxide each undergo a one-electron reaction.

As is clear from FIG. 3, the sample D prepared based on the known technique shows a decrease in the active material utilization rate with an increase in the active material packing density, whereas the sample A ′ according to the present invention.
It can be seen that C and C'are more suitable for increasing the capacity of the positive electrode plate than the conventional product, since there is almost no decrease in the active material utilization rate.
It is considered that this is because the current collector of the active material of the present invention is better and more uniform than the conventional one.

Experiment 4 In Experiments 1 to 3, the impregnating solution of cobalt nitrate alone was used to form the second and fourth layers of the cobalt compound alone. In this experiment, the impregnating solution was cobalt nitrate and nickel nitrate. The active material utilization rate of the electrode plate having a structure similar to that of the electrode plate group A was measured for the case of the mixture of No. 1, and the content of the minimum required cobalt compound for the second layer and the fourth layer was determined. . As the sample electrode plate, an electrode plate (referred to as electrode plate group E) was prepared by the chemical impregnation method with the amount of the cobalt compound in the second layer being 4 mol% with respect to the amount of nickel hydroxide filled as the active material. FIG. 4 shows the relationship between the active material composition of the second layer and the active material utilization rate. As can be seen from FIG. 4, the active material utilization rate is influenced by the active material composition, and when the active material composition is 100 mol% of the cobalt compound, the active material utilization rate is the highest and the content rate of the cobalt compound decreases. As a result, the utilization rate of active materials is also decreasing. When the active material composition is around 70 mol% of the cobalt compound, the active material utilization rate is largely reduced, and when the content ratio is less than that, the effect of forming the second layer containing the cobalt compound as the main component is hardly obtained. Has become. From this, it is desirable that the active material composition contains at least 70 mol% or more of the cobalt compound, and if possible, the composition is 100 mol%.

Experiment 5 In this experiment, two types of nickel sintered substrates were prepared in order to study the effect of the nickel sintered body becoming an active material in the impregnation process, and the same impregnating liquid was used for filling the active material by the same method. The performance of the prepared electrode plate was investigated. One of the nickel sintered substrates used was the same as used in Experiments 1-4.
The nickel slurry was applied to a metallic current collector and then sintered at 900 ° C in a reducing atmosphere (referred to as substrate 1), and the other was sintered at 900 ° C in a reducing atmosphere while adding water vapor. After that, heat treatment was performed at 200 ° C. in an air atmosphere to form a nickel oxide passivation film on the surface of the nickel sintered body (referred to as a substrate 2). Using these two nickel sintered substrates, a positive electrode plate was prepared in which the amount of the cobalt compound in the second layer was 4 mol% in the same manner as in electrode plate group A (three-layer structure) of Experiment 1, and the active material was used. The results of examining the discharge rate dependence of the discharge rate and the discharge intermediate potential are shown in FIGS. 5 and 6, respectively. The electrode plate using the substrate 1 on which the nickel oxide passivation film is not formed on the surface of the nickel sintered body is A1, and the electrode plate using the substrate 2 on which the nickel oxide is formed is A2. Fifth
In the comparison of the active material utilization rates in the figure, there is almost no difference between A1 and A2 in the low rate discharge of 0.2 CA, but the difference increases as the high rate discharge of 3 CA, 10 CA is achieved. This is also the case with the discharge intermediate potential shown in Fig. 6. The electrode plate A2 with a nickel oxide passivation film formed on the surface of the nickel sintered body has a conventionally thought of nickel sintering compared to A1 without it. In addition to the prevention of the reduction of the electrode plate strength due to the active material of the body, a new effect was found that the discharge rate dependence was small, and the active material utilization rate and the discharge potential characteristics at a high rate discharge were small. This is because in the case of sample A1 that does not form a passive film on the surface of the nickel sintered body, it is corroded by the acidic impregnating solution and the nickel chain becomes thin and the conductivity decreases, and the surface area of the nickel sintered body decreases. It is considered that this is because the performance decrease is more remarkable especially at higher rate discharges due to a decrease in the contact area with the active material. It is known that such conversion of the nickel sintered body into the active material occurs not only during the chemical impregnation step, but also at the noble potential during charging of the positive electrode plate. It is expected that the electrode performance will change and the battery performance will gradually decrease. On the other hand, in the sample A2 on which the passivation film was formed, the corrosion of the nickel sintered body by the acidic impregnating solution and the activation of the nickel sintered body as the active material due to the charging of the positive electrode plate did not occur. The electrode plate performance can be obtained continuously. That is, in order to stably obtain the inherent effect of the sandwich structure of the present invention, a passive film of nickel oxide is formed on the surface of the nickel sintered body, and the active material is impregnated and the positive electrode plate is charged. It is effective to prevent the nickel sintered body from becoming an active material.

Based on the results of the above five experiments, the positive electrode plate according to the present invention and the conventional product will be compared by examples. Two types of sintered metal substrates 1 and 2 (porosity 85
%) And foamed nickel porous body (porosity 95%) in total 3
Prepared types.

Example 1 (invention product) Sintered substrate 1 was impregnated with 5.0 mol / l nickel nitrate aqueous solution, concentrated, and neutralized with hot alkali to fill the pores of the nickel sintered body with nickel hydroxide. The normal chemical impregnation method is performed three times to form the first layer of nickel hydroxide, and then the chemical impregnation method is performed once using 1.4 mol / l cobalt nitrate aqueous solution. After forming the second layer of cobalt hydroxide alone, the cobalt hydroxide was oxidized by applying electricity in a KOH aqueous solution having a specific gravity of 1.250 (20 ° C.). After washing and drying this electrode plate, similarly to the formation of the first layer,
The step of the chemical impregnation method was performed 5 times to form a third layer of nickel hydroxide, and the positive electrode plate was obtained. This is designated as Sample F.

Example 2 (Invention product) A positive electrode plate was prepared in the same manner as in Example 1 except that the sintered substrate 2 was used. This is designated as Sample G.

Example 3 (invention product) Based on the sample F prepared in Example 1, further 2.2 mol / l
The step of the chemical impregnation method was performed once using the cobalt nitrate aqueous solution described above to form a fourth layer of cobalt hydroxide alone as a positive electrode plate. This is designated as Sample H.

Example 4 (Invention product) Based on the sample G prepared in Example 2, a fourth layer of cobalt hydroxide alone was formed as a positive electrode plate in the same manner as in Example 3. This is designated as Sample I.

Example 5 (conventional product) The process of chemical impregnation was performed 8 times on the sintered substrate 1 using a 5.0 mol / l nickel nitrate aqueous solution to fill the nickel sintered substrate with nickel hydroxide, and then 2.6 mol / l. Using the cobalt nitrate aqueous solution (1), the step of chemical impregnation was performed once to form a layer of cobalt hydroxide alone on the surface to obtain a positive electrode plate. This is designated as Sample J.

Example 6 (Conventional product) A chemical impregnation process was performed 8 times using an aqueous solution of (4.7 mol nickel nitrate + 0.3 mol cobalt nitrate) / l on the sintered substrate 1 to form nickel hydroxide on the nickel sintered substrate. A positive electrode plate was prepared by filling a mixture of cobalt hydroxide. This is designated as Sample K.

Example 7 (product of the present invention) 86 parts of nickel hydroxide powder, 10 carbonyl nickel powders
Part, and a powder of 200 mesh pass consisting of 4 parts of metallic cobalt powder to form an active material paste by adding water and methylcellulose to a foam-like nickel porous body with a porosity of 95% in an amount of about 50% of the specified amount. Physical filling was performed to form a first layer containing nickel hydroxide as a main component. next,
After the chemical impregnation step was performed once using a 1.4 mol / l cobalt nitrate aqueous solution to form a second layer of cobalt hydroxide alone, the remaining active material was formed in the same manner as in the formation of the first layer. The paste was filled to form a third layer containing nickel hydroxide as a main component. Further, as a post-process, the above electrode plate was impregnated with fluorine dispersion, dried and pressed to obtain a positive electrode plate. This is designated as sample L.

Example 8 (conventional product) A positive electrode plate was prepared by filling the same amount of the same active material paste as that used in Example 7 in the foamed nickel porous body without forming a cobalt hydroxide layer. This is designated as sample M.

Example 9 (conventional product) Based on the sample M prepared in Example 8, 2.6 mol / l was further added.
The step of chemical impregnation is performed once using the aqueous cobalt nitrate solution to form a layer of cobalt hydroxide alone on the surface of the active material,
The positive electrode plate was used. This is designated as Sample N.

The theoretical capacities of the samples F to N produced as described above are shown in Table 1.
Table 2 shows the active material composition. The theoretical capacity was calculated assuming that nickel hydroxide and cobalt hydroxide follow a one-electron reaction.

Next, cut each sample to a size of 40 × 40 (mm) and
Charge and discharge were performed using two sintered cadmium negative electrode plates of the same size in a 1.250 (20 ° C) KOH aqueous solution as counter electrodes, and the discharge rate dependence of the active material utilization rate and discharge potential characteristics was investigated. The formation charge in the first cycle was performed at a current of 0.1 CA to 160% of the theoretical capacity and after the second cycle was performed at a current of 0.2 CA to 120%, and the discharge was performed up to the mercury oxide electrode reference OV. 7th
The figure shows the results of examining the discharge rate dependence of the active material utilization rate of Samples F to K filled with the active material by a chemical impregnation method using a sintered substrate. From the highest utilization rate, 1>H>G>F>J> K
In this order, the present invention products I, H, G, and F, which have a sandwich structure in which a layer obtained by oxidizing cobalt hydroxide is formed between two nickel hydroxide layers, are compared with the conventional products J and K. The utilization rate is clearly improving. Further, in the high rate discharge of 3 CA and 10 CA, the difference between the product of the present invention and the conventional product is further widened. This tendency is the same in FIG. 8 in which the discharge potential characteristics are examined. Samples I and H, which have a 4-layer structure of the active material, have 3
Compared to the layered samples F and G, the utilization rate of the active material was improved, and the samples I and G with the nickel oxide passivation film formed on the surface of the nickel sintered body were compared with the samples F and H that did not. , Mainly the improvement of discharge potential characteristics is observed. In FIG. 8, the reason why the potential of Sample K is low even at a low rate discharge of 0.2 CA is considered to be because the content of cobalt hydroxide dispersed in the active material is higher than that of the other samples.

Further, the performance of Samples L to N obtained by physically filling the foam-like nickel porous body with the active material is shown in FIGS. 9 and 10, and the performance of the sintered electrode plate is shown in FIG. The same tendency as in FIGS. 8 and 9 is shown, and the sample L which is the product of the present invention has better active material utilization rate and discharge potential characteristics at the time of higher rate discharge than the samples M and N of the conventional products. Recognize.

Thus, when the active material was filled by a method other than the chemical impregnation method, good discharge characteristics were obtained in a state where the active material filling density was high without oxidizing the second layer of cobalt hydroxide.

As described above, the discharge property of the present invention product is clearly better than that of the conventional product.

EFFECTS OF THE INVENTION As shown in the above examples, according to the present invention, a layer containing cobalt hydroxide or cobalt oxide as a main component is sandwiched between two layers containing nickel hydroxide as a main component. By using the three-layer active material structure described above, it is possible to obtain a nickel positive electrode plate for alkaline storage batteries, which has better discharge characteristics than the conventional one. Further, by forming a layer containing cobalt hydroxide as a main component as the fourth layer on the three-layer structure, the utilization factor of the active material can be further improved by several percent. Further, in order to stably obtain these inherent effects of the present invention, it is effective to form a passivation film of a metal oxide on the surface of the porous metal substrate, and thereby a better discharge characteristic can be obtained.

[Brief description of drawings]

FIG. 1 shows the relationship between the cobalt content of the second layer and the active material utilization rate with respect to the impregnation increase, and FIG. 2 shows the relationship between the cobalt content of the fourth layer and the active material utilization rate with respect to the impregnation increase. FIGS. 3A and 3B are diagrams showing a comparison of the active material utilization rate with respect to the active material packing density of the nickel positive electrode plate of the present invention and a conventional product,
FIG. 4 is a diagram showing the relationship between the active material composition of the second and fourth layers and the active material utilization rate, and FIG. 5 is the effect of the nickel sintered substrate surface on the discharge rate dependence of the active material utilization rate. And FIG. 6 are views showing the influence of the nickel sintered substrate surface on the discharge rate dependence of the discharge potential characteristics, FIG. 7, and FIG.
The figures compare the discharge rate dependence of the active material utilization rate between the nickel positive electrode plate of the present invention and the conventional product, FIG. 8, FIG.
The figure compares the nickel positive electrode plate of the present invention and the conventional product in comparison with the discharge rate dependence of the discharge potential characteristics.

Claims (10)

[Claims] 1. A nickel positive electrode plate in which a positive electrode active material layer containing nickel hydroxide as a main component is formed on a porous metal substrate, and the positive electrode active material layer has the following structure, that is, a porous metal. The first layer on the substrate is a layer containing nickel hydroxide as a main component, the second layer is a layer containing cobalt hydroxide or cobalt oxide as a main component, and the third layer thereabove is What is a layer containing nickel hydroxide as a main component, that is, a layer containing cobalt hydroxide or cobalt oxide as a main component is sandwiched between two layers containing nickel hydroxide as a main component. Characteristic nickel positive electrode plate for alkaline storage batteries. 2. The amount of cobalt compound contained in the second layer containing cobalt hydroxide or cobalt oxide as a main component is 0.6 to 10.0 mol% with respect to the amount of nickel hydroxide.
The nickel positive electrode plate for alkaline storage batteries according to claim (1). 3. The alkaline storage battery according to claim 1, wherein the content of the cobalt compound in the second layer containing cobalt hydroxide or cobalt oxide as a main component is 70 mol% or more. Nickel positive electrode plate. 4. A nickel positive electrode plate for an alkaline storage battery according to claim 1, wherein a passivation film of a metal oxide is formed on the surface of the porous metal substrate. 5. The ordinary chemical impregnation step of impregnating a porous metal substrate with an oxidizing solution containing nickel salt as a main component, followed by concentration and alkali treatment is repeated several times to form a first layer on the porous metal substrate. A second layer of cobalt hydroxide is formed by forming a second layer of nickel hydroxide as a main component, and then performing a chemical impregnation step at least once using an acidic solution containing a cobalt salt as a main component. After the layer containing the main component is formed, it is electrochemically or chemically oxidized to change the layer containing cobalt hydroxide as a main component into a layer containing cobalt oxide as a main component. A method for producing a nickel positive electrode plate for an alkaline storage battery, which comprises performing a chemical impregnation step several times in the same manner as forming to form a layer containing nickel hydroxide as a main component as a third layer. 6. A nickel positive electrode plate in which a positive electrode active material layer containing nickel hydroxide as a main component is formed on a porous metal substrate, wherein the positive electrode active material layer has the following structure, that is, a porous metal. The first layer on the substrate is a layer containing nickel hydroxide as a main component, the second layer is a layer containing cobalt hydroxide or cobalt oxide as a main component, and the third layer is a layer containing nickel hydroxide. The layer containing the main component, and the fourth layer on top of it is the layer containing cobalt hydroxide as the main component, that is, the layer containing nickel hydroxide as the main component and the layer containing the cobalt compound as the main component. A nickel positive electrode plate for an alkaline storage battery, characterized by being alternately laminated. 7. The amount of cobalt compound contained in the second layer containing cobalt hydroxide or cobalt oxide as a main component is 0.6 to 10.0 mol% with respect to the amount of nickel hydroxide.
The nickel positive electrode plate for an alkaline storage battery according to claim (6). 8. The amount of cobalt hydroxide contained in the fourth layer containing cobalt hydroxide as a main component is 0.4 to 7.0 mol% with respect to the amount of nickel hydroxide. A nickel positive electrode plate for an alkaline storage battery according to the item (6). 9. The content of the cobalt compound in the second and fourth layers containing cobalt hydroxide or cobalt oxide as a main component is 70 mol% or more, claim (6). A nickel positive electrode plate for an alkaline storage battery as described above. 10. The nickel positive electrode plate for an alkaline storage battery according to claim 6, wherein a passivation film of a metal oxide is formed on the surface of the porous metal substrate.