JPS61264673A - Manufacture of sintered cathode plate - Google Patents

Abstract

PURPOSE:To increase the efficiency of alkali treatment by repeating a treatment cycle in which a sintered substrate is immersed in a solution mainly comprising nickel nitrate, dried in an atmosphere of inert gas, immersed in alkaline solution and washed to convert the nickel nitrate into active material. CONSTITUTION:A sintered nickel substrate having a porousty of about 82% is immersed in a nickel nitrate solution, dried in an atmosphere of nitrogen, immersed in a sodium hydroxide solution, washed, then dried. This treatment cycle is repeated six times. By this process, the removal of nitrate radical in alkaline solution is facilitated, and the nickel nitrate is quickly converted into active material, and the decomposition of nickel nitrate in the intermediate drying process is retarded, and the formation of decomposition produces is substantially decreased and the efficiency of alkali treatment is increased.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a sintered anode plate.
The present invention relates to a method for manufacturing a sintered anode plate that is used as an anode plate for alkaline storage batteries and uses nickel hydroxide as an active material.

<Prior art> As a method for manufacturing the above-mentioned sintered anode plate, a sintered substrate such as a porous nickel substrate is immersed in an impregnating liquid containing nickel nitrate as a main component, and nickel nitrate is added into the micropores of the substrate. After impregnating the sintered substrate with alkali treatment, the nickel nitrate in the micropores of the substrate is replaced with nickel hydroxide, an active material, and the series of operations of washing and drying are repeated several times. A so-called chemical impregnation method is known in which a predetermined amount of active material is filled into a substrate.

By the way, this chemical impregnation method has the disadvantage that during alkali treatment, only the nickel nitrate adhering to the entrances of the micropores of the porous substrate becomes an active material, and nickel nitrate does not enter the substrate during subsequent impregnation. . In order to eliminate such inconvenience, for example, Japanese Patent Application Laid-Open No. 57-2059
It is widely practiced to provide an intermediate drying step at 60 to 120° C. between the steps of immersion in an impregnating liquid and alkali treatment, as disclosed in Japanese Patent No. 68.

This intermediate drying removes the moisture in the nickel nitrate aqueous solution adhering to the substrate surface, which causes a film to form on the substrate surface and close the pores, and also removes the moisture in the nickel nitrate aqueous solution in the substrate pores. NO> ) ・Part of the crystal water of 6H20 is dehydrated (N! (NO3>2 >2 ・4H2C)
(N f (NO3>2>2''2H20), the crystals of nickel nitrate are made finer, and as a result, formation of the active material and subsequent impregnation are facilitated.

<Problems to be solved by the invention> However, according to the research of the present inventor, when the above-mentioned intermediate drying is performed in air, partial decomposition of nickel nitrate occurs on the sintered substrate. was found by X-ray diffraction, and the mixture of nickel hydroxide and nickel nitrate, which is a decomposition product at this time, is relatively stable in water and alkali, which means that it takes time to remove nitrate radicals in the alkali treatment process. It has been found that there is a problem in that this causes the alkali treatment to become inefficient.

<Means for Solving the Problems> The present inventor conducted research to fully achieve the purpose of intermediate drying as described above, and to prevent the decomposition of nickel nitrate and shorten the time required to remove nitrate roots during alkali treatment. In order to consider
When we investigated the decomposition of nickel nitrate that occurs during intermediate drying, we found that this decomposition reaction depends on the drying temperature, the activity of the nickel substrate,
This invention was completed after learning that this phenomenon is expected to occur on the three-phase interface of substrate metal nickel, nickel nitrate aqueous solution, and adsorbed oxygen due to the presence of oxygen gas (M elementary ions).

The method for producing a sintered anode plate of the present invention includes soaking a sintered substrate in an impregnating solution containing nickel nitrate as a main component, drying it in an inert gas atmosphere, then treating it with alkali, and washing it with water. The gist of this method is to repeatedly perform a series of operations for converting the nickel nitrate into an active material. An example of the above-mentioned inert gas atmosphere is a nitrogen atmosphere.

That is, the present invention attempts to remove the effect of oxygen on the decomposition reaction as much as possible by performing intermediate drying in an inert gas atmosphere, thereby slowing down and mitigating the decomposition reaction.

By using the above means, the decomposition reaction during intermediate drying is relaxed and the generation of decomposition products as mentioned above is suppressed, so that nitrate radicals can be removed in a short time during alkali treatment. It becomes like this.

<Example> A sintered nickel substrate with a porosity of approximately 82% was heated at 70°C with a specific gravity of 1.
, 7 in the nickel nitrate aqueous solution for 20 minutes, then intermediately dried at 90°C for 30 minutes in a nitrogen atmosphere, and then further dried at 80°C.
immersed in a 25% caustic soda aqueous solution for 30 minutes, then
A series of operations such as washing with water and drying was repeated six times to produce a sintered electrode plate (electrode plate A) according to the present invention. Further, a sintered electrode plate (electrode plate B) according to the present invention was produced in the same manner except that the immersion time in the caustic soda aqueous solution was changed to 120 minutes. On the other hand, for comparison, intermediate drying was performed in air.
Immersion time in caustic soda aqueous solution for 30 minutes, 12
Sintered electrode plates (electrode plates C and D) were made using the conventional method in the same manner except that the heating time was 0 minutes.

Regarding the above four electrode plates A to D, the amount of nitrate radicals (mg/CC) in the electrode plates was measured using an ion chromatoanalyzer, and the results obtained are shown in the table below.

From the table above, it can be seen that in the products of the present invention, nitrate radicals can be easily removed in an alkali, and active materials can be formed very quickly and in a very short time.

In addition, -1 Figure 1 (A) shows an electrode plate that was intermediately dried in a nitrogen atmosphere according to the present invention, and Figure 1 (B) shows an electrode plate that was intermediately dried in air as in the conventional method. The X-ray diffraction diagrams are shown immediately after intermediate drying, where Δ indicates metallic nickel and ○ indicates nickel nitrate hydrate (N 1-(NO3>
2 > 2 ・4 days 20, (N i (NO3)2 ) 2
・2 days 20, × indicates decomposition products, respectively. From the same figure,
It can be seen that in the case of the present invention, generation of decomposition products after intermediate drying is significantly suppressed.

<Effects of the Invention> According to the method for manufacturing a sintered anode plate of the present invention configured as described above, the decomposition reaction of nickel nitrate during intermediate drying is suppressed, and the generation of the above-mentioned decomposition products is significantly reduced. As a result, nitrate radicals can be easily removed during alkali treatment, and active material can be formed in a very short time, resulting in the effect that the alkali treatment and electrode plate manufacturing process can be made more efficient.

[Brief explanation of the drawing]

Figure 1 (^) is a diagram of the electrode plate manufactured according to the present invention.
B) is an X-ray diffraction diagram of the electrode plates produced by the conventional method, each immediately after intermediate drying.

Claims (1)

[Claims] 1. After immersing the sintered substrate in an impregnating solution containing nickel nitrate as its main component, it is dried in an inert gas atmosphere, then treated with alkali, and washed with water to turn the nickel nitrate into an active material. A method for producing a sintered anode plate characterized by repeated steps.