JPS6340023B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for producing nickel active materials for alkaline batteries using an ozone oxidation method. Conventionally, nickel active materials for alkaline batteries have been produced by adding a nickel salt solution such as nickel nitrate or nickel sulfate to a mixed solution of a caustic alkaline solution and an oxidizing agent such as bromine water or a hypochlorite solution. There is a method of generating oxide and using this as a nickel active material, or an ozone oxidation method that oxidizes powdered nickel hydroxide in a dry state with an ozone-containing gas to form nickel oxide, which is used as a nickel active material. . Among these methods, the method for producing nickel active materials using the ozone oxidation method involves directly contacting powdered nickel hydroxide with ozone to form nickel oxide.
Compared to the former, it not only does not require the processes of washing, dehydration, drying, and pulverization, it also does not require large amounts of alkaline solution or explosive sodium hypochlorite solution, and it is easier to treat exhaust gas after the reaction. This is an extremely effective method industrially. However, the conventional production of nickel oxide by ozone oxidation has low reaction efficiency, and to obtain a nickel active material with a high degree of oxidation, it is necessary to contact it with a large amount of ozone for a long time, which not only makes the produced nickel active material expensive. Usually, the nickel oxide produced by this method is insufficiently oxidized, and only the surface of the nickel hydroxide is oxidized, and the center of the powder does not change to nickel oxide, resulting in a high electrical resistance of the nickel oxide hydroxide. remains in the center. Therefore, when this material is used as a battery active material, there are drawbacks such as an increase in battery internal resistance, a small capacity of the battery active material, and a rapid decline in discharge performance. An object of the present invention is to provide a method for producing a nickel active material for alkaline batteries, which can efficiently obtain a nickel active material with significantly improved discharge capacity and uniform discharge characteristics using a small amount of ozone. shall be. The present invention is a method for producing a nickel active material for alkaline batteries, in which cobalt oxide and caustic alkali are added to nickel hydroxide, and then oxidized by an ozone-containing gas flow. As the caustic alkali, caustic potassium, caustic soda, lithium hydroxide, rubidium hydroxide, cesium hydroxide, etc. can be used. In other words, in the present invention, when cobalt oxide and caustic alkali coexist during the oxidation of nickel hydroxide, they synergistically play a role like a catalyst and promote the oxidation reaction, resulting in a high oxidation of nickel hydroxide. The process proceeds efficiently, significantly reduces the amount of unreacted ozone emitted, and synthesizes low-cost, high-quality nickel active materials. The present invention will be explained below using examples. 80 mesh hydroxide 1st nickel powder 100g
After sufficiently mixing 4 g of cobalt oxide powder and 8 g of 80 mesh pass caustic potassium powder, the mixture was placed in a two-headed flask, and while stirring the powder in the flask using a magnetic stirrer, ozone-containing gas was passed through. A black nickel oxide was synthesized by oxidizing the primary nickel hydroxide to obtain a nickel active material. Next, 8.0g of this nickel active material and 1.5g of scaly graphite
After thoroughly mixing 1.0 g of this powder with 0.5 g of polystyrene, a nickel anode obtained by collecting and press-molding the powder and a zinc plate having a discharge capacity three times that of this anode was used as a counter electrode at 5 mA/cm ^{2 .} constant current discharge of 30
% caustic potassium solution electrolyte, final voltage
We investigated the relationship between the amount of ozone passing through and the discharge capacity when the voltage was set to 1.0V. The results are shown in Table 1. In addition, as a comparative example, 80% without adding caustic potassium
80 mesh pass 100g of nickel hydroxide powder and 4 g of cobalt oxide powder mixed together, 80 mesh pass of 100 g of 1st nickel hydroxide powder, and 80 mesh pass of 100 g of nickel hydroxide powder and 4 g of cobalt hydroxide powder. A mixture of 8 g of 80 mesh pass caustic potassium powder and 8 g of caustic potassium powder was placed in a two-headed flask in the same manner as in the example, and the ozone-containing gas was passed through the flask while stirring the powder in the flask with a magnetic stirrer. Then, each nickel hydroxide was oxidized to synthesize a black nickel oxide to obtain a nickel active material. Next, using these active materials, the relationship between the amount of ozone passing through and the discharge capacity was investigated under the same conditions as in the examples. These results are also listed in Table 1.

[Table] Furthermore, FIG. 1 shows examples according to the present invention shown in Table 1 (curve A), comparative examples of nickel hydroxide + cobalt oxide (curve B), nickel hydroxide (curve C), The relationship between the amount of ozone passing through and the discharge capacity in each case of nickel hydroxide + cobalt hydroxide + caustic potassium (curve D) is shown. These first
As can be seen from the table and FIG. 1, according to the manufacturing method of the present invention, an active material with a high discharge capacity can be obtained with a smaller amount of ozone than in the conventional method. Furthermore, since cobalt oxide as an additive is involved not only in the oxidation of nickel hydroxide but also in the properties of nickel oxide after oxidation, the battery using the nickel active material according to the method of the present invention is different from the comparative example. It was confirmed that the battery had smoother discharge characteristics and increased discharge capacity compared to batteries using nickel active materials. Similar effects were also obtained using caustic soda, lithium hydroxide, rubidium hydroxide, cesium hydroxide, etc. as the caustic alkali. As described above, in the method of the present invention, cobalt oxide and caustic alkali coexist during oxidation of nickel hydroxide, the oxidation reaction is promoted, and nickel hydroxide is oxidized.
Not only does the oxidation of nickel proceed with high efficiency, but the nickel active material produced by these additives also has a large discharge capacity and a flat discharge curve, making it extremely valuable industrially.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between the discharge capacity and the amount of ozone passing through nickel active materials according to the method of the present invention and the conventional method.

Claims (1)

[Claims] 1. A method for producing a nickel active material for an alkaline battery, which comprises adding cobalt oxide and caustic alkali to nickel hydroxide, and then oxidizing it with ozone gas.