JPS62122064A - Manufacture of nickel positive plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To obtain a nickel positive plate whose discharge potential is noble by impregnating a solution mainly comprising nickel salt or cobalt salt in a positive plate or a substrate, and immersing it in a mixed solution of chlorite or peroxydisulfate serving as oxidizing agent and caustic alkali for alkali treatment and oxidizing treatment. CONSTITUTION:100pts. nickel hydroxide powder, 5pts. metallic cobalt powder, and 15pts. carbonyl nickel powder are kneaded with 50pts. 1% methyl cellulose solution. 5pts. epoxy resin latex whose solid content is 50% and its curing agent are added to the kneaded mixture to prepare active material paste. The active material is applied to a perforated nickel plated steel core, dried at 90 deg.C, and immersed in nickel nitrate solution, and then immersed in sp.gr. 1.200 (20 deg.C) sodium hydroxide solution containing 2.0% of sodium chlorite for alkali treatment and oxidizing treatment, and a positive plate is manufactured. This positive plate evolves no oxigen gas from the initial stage of charge, and the battery using this positive plate is free from decrease in electrolyte and electro lyte leakage caused by increase in internal pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a nickel positive electrode plate for an alkaline storage battery.

Conventional technology and its problems Nickel positive electrode plates for alkaline storage batteries have traditionally been available in the pocket type and sintered type, but the proportion of sintered plates, which have excellent performance, is increasing year by year. ing.

Recently, foamed nickel type positive electrode plates, in which a sponge-like porous nickel material is physically filled with a positive electrode active material, are being commercialized with the main purpose of reducing costs. A method called a paste method, in which the material is simply painted, is also being developed.

Alkaline storage batteries, especially nickel-cadmium storage batteries,
As demand continues to increase in recent years, there is a strong desire in the market for improved energy density in terms of performance. The main methods for increasing the energy density include improving the active material utilization rate of the positive electrode plate, which is the capacity-limiting electrode, or the group m potential. While current products have almost reached their limits in improving the active material utilization rate, no effective means have been found for improving the discharge potential.

On the other hand, since the living substance in the unformed nickel positive electrode plate is divalent nickel hydroxide, which has low conductivity, the polarization during the first charge is greater than that during subsequent cycles, and the competitive reaction of oxygen gas generation occurs. In particular, in paste-type positive electrode plates, collapse of the electrode plate due to oxygen gas generation from the early stage of charging has become a major problem.

In addition, in a sealed battery using a positive electrode plate where oxygen gas is generated from the early stage of charging as described above, the charge of the negative electrode plate has not progressed sufficiently, and the internal pressure increases without enough metal cadmium, which is effective for gas absorption, being generated. As a result, the safety valve is activated, causing a decrease in electrolyte and leakage, which poses a risk of deteriorating battery performance and life.

The present invention aims to solve the problems of the prior art described above.

Means for Solving the Problems The present invention is a manufacturing method for nickel positive electrode plates for alkaline storage batteries, in which the U plate or electrode plate is impregnated with a solution containing nickel salt or cobalt salt as a main component by a chemical impregnation method. After that, it is immersed in a mixed solution of caustic alkali and an oxidizing agent to perform alkaline treatment and oxidation treatment at the same time, thereby retaining the active material of higher oxides with more than two valences, and when the oxidizing agent is chlorite or It is characterized by containing beroxonisulfate a salt as the main component. When the reaction is described using sodium hydroxide as the caustic alkali and sodium chlorite as the oxidizing agent, equations 1 and 2 are obtained.

4N! (NO3)2 +8Na 0)
-1+Na cl 0-4Ni 00H+8N
a NO3+Na cl +21-10・・・・・・
...1 type % formula % 0...2 type action divalent active substance * Ni (OH) 2 Ya CO (OH
) As mentioned earlier, 2 has a lower valence than 1, but compared to higher oxides with more than 2 valences, such as NiOH and CoO
OH has very high conductivity. As a result of repeated studies on this issue, we applied the treatment according to the present invention to paste-type positive electrode plates that tend to generate oxygen gas from the early stages of charging.
It has been found that even under RQ rate charging conditions such as time rate, oxygen gas generation does not occur from the initial stage of charging. Further investigation revealed that the above effect is influenced by the distribution of the higher oxide, and if it is uniformly distributed throughout the electrode plate, m of the higher oxide necessary to obtain the above effect is In contrast, in the present invention, the higher oxide is thought to form a three-dimensional network structure, and in such a case, it is necessary to
Very little ffi is required. Figure 1 shows the internal pressure rise at the end of charging of a sealed nickel-cadmium storage battery using a paste-type positive electrode plate to which the present invention is applied.
It can be seen that it is sufficient to contain 3% or more of higher oxides having a valence of more than 2.

As mentioned above, the present invention was originally devised for the purpose of improving paste-type positive electrode plates, but in the process, unexpected new effects were discovered. In other words, the positive electrode plate to which the present invention is applied, regardless of whether it is a sintered type, a foamed type, or a paste type, has a higher discharge potential than a positive electrode plate manufactured by a conventional method, and the tendency is that the larger the discharge current, the higher the discharge potential.
The deeper the depth of discharge, the more remarkable it becomes. It was also found that this effect was not temporary but continued.

The cause of the above is not yet well understood, but it can be inferred from the fact that the discharge potential is negative that when treated according to the present invention, higher oxides with more than two valences form a three-dimensional network structure inside the electrode plate. This is thought to form γ-NiOO, which makes the conductivity inside the electrode plate very good, so that the active material is easily charged, and most of the charging products are γ-NiOO.
It is considered that β-Nio+ has a nobler discharge potential than H.

There are conventionally known techniques for producing higher nickel oxides, particularly γ-Ni OOH. This was a method for producing the active material itself, in which a mixture of caustic alkali and an oxidizing agent was placed in a reaction tank, and nickel hydroxide or nickel salt was added thereto to produce an n-class oxide of nickel. However, this method has several drawbacks.

First, because extra manufacturing equipment, purification equipment, washing water, labor costs, etc. are required to carry out the above reaction, the final manufacturing cost of the electrode plate will be considerably higher than the current cost.

Second, a facility is required to store the produced high-grade nickel oxide, and because the high-grade nickel oxide gradually decomposes during storage, it is necessary to store the product periodically. need to be managed.

Thirdly, it cannot be applied to a sintered nickel positive electrode plate.

Fourth, when applied to a paste-type or foam-type positive electrode plate, since the higher nickel oxide is uniformly dispersed in the electrode plate, the minimum amount necessary to obtain the same effect as the present invention is required. For example, the amount of higher nickel oxide added increases.

On the other hand, since the present invention relates to a method for manufacturing a nickel positive electrode plate, it is fundamentally different from the above-mentioned known techniques, and the present invention has almost no drawbacks that exist in the above-mentioned known techniques.

In other words, in the case of the present invention, it can be applied to sintered positive electrode plates, there is only a slight increase in cost compared to the current manufacturing method, and the time from the electrode plate manufacturing process to the battery assembly process is short, so it is possible to The amount of oxide decomposition is almost negligible, and it is thought that higher oxides contact each other within the electrode plate to form a three-dimensional network structure.
Although its current collecting properties are good, it requires less amount of higher oxide stones.

The present invention is also different from a method of oxidizing using an oxidizing agent alone. In other words, if the oxidizing agent is used alone, not only the effect of the present invention cannot be obtained, but also the metal support such as nickel or iron in addition to the active material may be oxidized, causing mechanical damage to the electrode plate. In contrast, in the case of the present invention, the strength is reduced.
Since the solution used for the oxidation treatment is strongly alkaline, it does not affect the gold R support.

Example Examples of the present invention will be described in detail below.

Example 1 A sintered nickel substrate with a porosity of 85% was impregnated with a mixed solution of nickel nitrate and cobalt nitrate, and then the usual chemical impregnation process of alkali treatment with an aqueous solution of lithium hydroxide was repeated five times. The substrate is filled with active materials of divalent nickel hydroxide and cobal hydroxide h. In the sixth chemical impregnation step, sodium chlorite 2.
A positive electrode plate was prepared by filling an active material in the same manner as before except that an alkali treatment and an oxidation treatment were performed simultaneously using an aqueous sodium hydroxide solution containing 0% and a ratio m of 1.20. This is designated as sample A.

Example 2 A positive electrode plate was produced in the same manner as in Example 1, except that potassium peroxonisulfate was used instead of sodium chlorite in the sixth chemical impregnation step of Example 1. This is designated as sample B.

Example 3 A positive electrode plate was produced in the same manner as in Example 1 except that sodium hypochlorite was used instead of sodium chlorite in the sixth chemical impregnation step of Example 1. This is designated as sample C.

Example 4 For comparison, a positive lfj provisional was prepared in the same manner as in Example 1, except that the alkali treatment in the sixth chemical impregnation step of Example 1 was performed solely with an aqueous sodium hydroxide solution with a ratio fi of 1.20. Created. Use this as a sample.

Specific gravity of the sample positive electrode plate prepared as above: 1.250
(20° C.) The discharge characteristics in an aqueous KOI-1 solution are shown in FIG. Samples B and B treated according to the present invention have a higher discharge potential than samples prepared by the conventional method, and the intermediate potential is about 20 mV.

Further, the discharge potential of Sample C using sodium hypochlorite was not significantly different from that of the conventional sample, and no effect of increasing the discharge potential was observed.

Next, an example of a paste type positive electrode plate will be described.

Example 5 100 parts of nickel hydroxide powder, 5 parts of metal cobalt powder, and 15 parts of carbonyl nickel powder were kneaded with 50 parts of 1% methyl cellulose solution, and then 5 parts of epoxy resin latex with a solid content of 50% and a curing agent for epoxy resin were kneaded. In addition, an active material paste was prepared. After applying this active material paste to the nickel-plated core of a perforated steel plate,
A base positive electrode plate was prepared by drying at 0°C. Next, after impregnating this base positive electrode plate with an aqueous solution of nickel nitrate,
．． A positive electrode plate was prepared by alkali treatment in a sodium hydroxide aqueous solution at 200° C. (20° C.). This is designated as sample E.

Example 6 The alkaline treatment in Example 5 was carried out in a sodium hydroxide aqueous solution with a specific gravity of 1.200 (20° C.) containing 2.0% sodium chlorite, and the alkali treatment and oxidation treatment were simultaneously performed to prepare a positive electrode plate. This is sample F.
shall be.

Example 7 All the same as Example 6 except that cobalt nitrate was used instead of nickel nitrate in Example 6, and potassium peroxonisulfate was used instead of sodium chlorite.
A positive electrode plate was prepared in the same manner as above. This is designated as sample G.

Example 8 All the same as Example 6 except that sodium hypochlorite was used instead of sodium chlorite in Example 6.
A positive electrode plate was prepared in the same manner as above.

This is designated as sample H.

The sample positive electrode plate prepared as described above was combined with a sintered cadmium negative electrode plate prepared by the usual chemical impregnation method to prepare a cylindrical sealed battery, and the internal pressure when charged at a rate of 1 hour to the nominal capacity. is shown in Figure 3. As is clear from the figure, in the conventional sample E, oxygen gas generation occurred from the early stage of charging, whereas in the samples F and G treated according to the present invention, oxygen gas generation did not occur from the early stage of charging. There is no risk of electrolyte loss or leakage due to abnormal increase in internal pressure.

In Sample H, which used sodium hypochlorite for oxidation treatment, the internal pressure started to rise somewhat later than in the conventional product, but when compared with Samples F and G, which were treated according to the present invention. Obviously bad. For confirmation, the sample electrode plate was cut to a size of 4 CIIX 4 C1l, and two sintered cadmium negative electrode plates of the same size were placed in a large amount of alkaline electrolyte at a rate of 1 hour relative to the theoretical capacity. As a result of charging, samples F and G treated according to the present invention did not change their shape even after being charged to 150%, whereas sample E, a conventional product, was charged at about 30% and did not contain sodium hypochlorite. The result of the sample used was that all of the active material fell off from the core at about 60% charge.

From the above, the effects of the present invention are clear.

Effects of the Invention As described above, based on the present invention, after impregnating a positive electrode plate or substrate with a solution containing nickel salt or cobalt salt as the main component, a mixed solution of chlorite or belloxonia amm oxidizing agent and caustic alkali is applied. A nickel positive electrode plate with a group N potential of the same can be obtained by immersing the nickel plate in a liquid and performing an alkali treatment and an oxidation treatment at the same time. Furthermore, in the case of a paste-type nickel positive electrode plate, collapse of the electrode plate during charging can be suppressed and charging efficiency can be improved.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between the content of higher oxides exceeding 2I11i in the positive electrode plate immediately before the first charge and the battery internal pressure.
The figure is a characteristic diagram comparing the discharge potential of positive electrode plates produced by the method of the present invention and the conventional method. Figure 3 is the charging of a cylindrical sealed battery using the positive electrode plates produced by the method of the present invention and the conventional method. FIG. 3 is a characteristic diagram showing a comparison of internal pressure increases during operation. π 1 Former z@hfilt) Shimebe Chit Uso HikoZ Hikari g1. Karima/Aio 7 Figure/CA”1=/Outside procedure?RTT official document (spontaneous) December 23, 1985 1. Display of the incident 1985 Patent application No. 263039 2. Name of the invention Alkaline storage battery 4, "Detailed Description of the Invention" column of the specification subject to amendment. 5. Contents of amendment (1) r4Ni (NO3)2 +8Na OH+Na c on page 4, line 11 of the specification
l 0=4Ni 00)-l+8Na NO3+l',
la C1+2HO・・・・・・・・・1 formula %formula% O・・・・・・・・・2 formula” to “4 N i (N O3) 2 +
8 Na Otl + Na
Cl 02-4Ni 0OII+8Na NO3
+Na C+ +21-120・・・・・・・・・・・・
・Correct it to ``1 formula % formula % 0......2 formula.''that's all

Claims (2)

[Claims] (1) After impregnating a porous metal substrate or a nickel positive electrode plate holding an active material mainly composed of nickel hydroxide with a solution mainly composed of nickel salt or cobalt salt, it is placed in a mixed solution of caustic alkali and an oxidizing agent. It has a process of immersing it in water and performing alkali treatment to retain the active material of a higher oxide with a valence of more than 2, and the oxidizing agent is mainly composed of peroxodisulfate or chlorite. A method for manufacturing nickel positive electrode plates for alkaline storage batteries. (2) Claim No. 1 in which 3% or more of the retained active material is changed into a higher oxide with a valence exceeding divalent.
) A method for producing a nickel positive electrode plate for an alkaline storage battery as described in item 2.