JPS6112345B2 - - 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 producing an oxide and using it as a nickel active material, or an ozone oxidation method of oxidizing powdered nickel hydroxide in a dry state with an ozone-containing gas to form nickel oxide, which is used as a nickel active material. Of these, the method for producing nickel active materials by ozone oxidation is
Nickel is made into nickel oxide by directly contacting ozone with nickel, and compared to the former, it does not require washing, dehydration, drying, and pulverization processes, and it also eliminates the need for large amounts of alkaline solution and explosive sodium hypochlorite solution. It is an extremely effective method industrially, as it does not require any other substances, and it is easy to treat the exhaust gas after the reaction. 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 an alkaline battery, in which at least one of manganese, silver and their compounds, and caustic alkali are added to nickel hydroxide, and the mixture is then oxidized with an ozone-containing gas flow. In the present invention, the metal or metal compound coexisting during the ozone oxidation reaction is manganese, silver, or their oxides, hydroxides, sulfates, nitrates, etc., and these may be used alone or as a mixture of two or more. May be used. In addition, caustic alkalis include caustic potassium, caustic soda, lithium hydroxide, rubidium hydroxide,
Cesium hydroxide or the like can be used. In other words, in the present invention, when manganese, silver, etc. 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 the oxidation of nickel hydroxide. The process proceeds with high efficiency, significantly reduces the amount of unreacted ozone emitted, and synthesizes low-cost, high-quality nickel active materials. The present invention will be explained below with reference to Examples. Example I After thoroughly mixing 200 g of 80 mesh pass nickel hydroxide, 10 g of manganese dioxide, and 20 g of 80 mesh pass caustic potassium powder, the mixture was placed in a two-headed flask and the powder in the flask was stirred using a magnetic stirrer. At the same time, an ozone-containing gas was passed through the reactor to oxidize the primary nickel hydroxide to synthesize black nickel oxide and obtain a nickel active material. Next, 80g of this nickel active material and scaly graphite
After sufficiently mixing 1.5 g of polystyrene and 0.5 g of polystyrene, 1.0 g of this powder was taken and pressure molded to obtain a nickel anode, and a zinc plate having a discharge capacity three times that of this anode was used as a counter electrode to generate 5 mA/cm ^{2 .} Figure 1 shows the results of examining the relationship between the amount of ozone passing through and the discharge capacity when a constant current discharge was performed in a 30% caustic potassium solution electrolyte with a final voltage of 1.0V. In addition, as a comparative example, in Example I, manganese dioxide and caustic potassium were not added and hydroxide was used.
FIG. 1 also shows a case in which an active material was obtained by ozone oxidation of only nickel, and a case in which a nickel active material was obtained by ozone oxidation with only manganese dioxide added to primary nickel hydroxide. As is clear from Figure 1, according to the method of the present invention, the reaction efficiency is increased compared to the comparative example. For example, in the method of the present invention (curve A), 1 mole of nickel hydroxide is reacted with 1 mole of ozone. depending on the matter
An active material with a capacity of 250 mAn/g was obtained, whereas an active material with a similar capacity was obtained by adding only manganese dioxide to nickel hydroxide and ozone oxidation (curve B). more than four times the amount of ozone is required, and nickel active material by ozone oxidation of only nickel hydroxide (curve C)
requires even more ozone. Example After thoroughly mixing 100 g of 80 mesh pass nickel hydroxide, 5 g of silver oxide, and 10 g of 80 mesh pass caustic soda powder, the mixture was placed in a two-headed flask and the powder in the flask was stirred using a magnetic stirrer. One mole of nickel hydroxide was reacted with 1 mole of ozone to synthesize a black nickel oxide to obtain an active material. Next, 8.0 g of this nickel active material, 1.5 g of scaly graphite, and 0.5 g of polystyrene were thoroughly mixed, and then 0.5 g of this powder was collected and preformed.
The anode body 1 was then filled together with a metal ring 3 under pressure. However, 0.05 cc of an 8 mol/concentration caustic potassium aqueous solution was dropped onto the anode body 1, 0.25 g of a cathode body mainly composed of zinc was placed on the separator 4 made of nylon nonwoven fabric, and the cathode terminal lid 7 was insulated. A nickel-zinc battery was fabricated by sealing the opening of the anode can 2 with a plastic gasket 6 interposed therebetween. Tables 1 and 3 show the results of 500Ω continuous discharge of the nickel-zinc battery in the example (curve A). Comparative examples are a case where only silver oxide is added to nickel hydroxide (curve B) and a case where nickel hydroxide alone is added (curve C), and the oxidation is carried out by changing the amount of ozone passing through as shown in Table 1. These are the results of a 500Ω continuous discharge of a nickel-zinc battery fabricated using a nickel active material.

[Table] As is clear from Table 1 and Figure 3, the method of the present invention is not only capable of synthesizing a nickel active material with a larger capacity than the comparative example with a fraction of the amount of ozone compared to the comparative example. It can be seen that the battery using the nickel active material according to the method of the present invention has more flat discharge characteristics than the battery using the nickel active material of the comparative example. This indicates that the synergistic effect of silver oxide and caustic soda as additives is involved not only in the oxidation of nickel hydroxide, but also in the properties of nickel oxide after oxidation. Example After thoroughly mixing 100 g of 80 mesh pass nickel hydroxide, 4 g of silver oxide or 4 g of manganese oxide, and 8 g of 80 mesh caustic potassium powder, the mixture was placed in a two-headed flask and stirred using a magnetic stirrer. Ozone-containing gas was passed through the powder while stirring to oxidize the primary nickel hydroxide to synthesize black nickel oxide and obtain a nickel active material. Next, 8.0g of this nickel active material and 1.5g of scaly graphite,
After thoroughly mixing with 0.5g of polystyrene, this powder
A nickel anode obtained by collecting 1.0g and press-molding it,
The amount of ozone passing through and the discharge capacity when a constant current discharge of 5 mA/cm ² is performed in a 30% caustic potassium solution electrolyte with a zinc plate having three times the discharge capacity as the counter electrode and the final voltage is 1.0 V. Table 2 shows the results of examining the relationship between. In the comparative example, the relationship between the discharge capacity of the active material and the amount of ozone passing through was determined for the case of using nickel hydroxide alone and the case of using cobalt hydroxide (4 g), respectively.

[Table] As is clear from Table 2, the method of the present invention can obtain an active material with a high discharge capacity with a smaller amount of ozone than the conventional method. In addition, since silver and manganese as additives are 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 flatter discharge characteristics and increased discharge capacity compared to batteries using nickel active materials. In addition, for comparison, the second
The discharge characteristics when cobalt hydroxide and caustic potassium shown in the table were ozone oxidized with 4 mol of ozone gas are also shown as curve D in FIG. Curve A in FIG. 3 is obtained by ozone oxidation with 1 mol of ozone gas using silver oxide and caustic soda as described above. As is clear from the figure, it can be seen that the device of the present invention (curve A) has good discharge characteristics despite having less ozone gas than the comparative device (curve D). In the above examples, manganese dioxide,
Silver oxide, caustic potassium, and caustic soda were used, but in addition, manganese and silver compounds such as their sulfates,
Similar effects were obtained by using hydroxides and lithium hydroxide, rubidium hydroxide, cesium hydroxide, etc. as caustic alkalis. As described above, in the method of the present invention, the oxidation reaction is promoted by the coexistence of at least one of elemental manganese or silver or a compound thereof and caustic alkali during the oxidation of nickel hydroxide. Oxidation proceeds with high efficiency, and due to these additives, the produced nickel active material 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 curve diagram showing the relationship between the discharge capacity of the nickel active material and the amount of ozone passing through according to the method of the present invention;
FIG. 2 is a cross-sectional view of a nickel-zinc battery using the nickel active material according to the method of the present invention, and FIG. 3 is a curve diagram showing the continuous discharge characteristics of the nickel-zinc battery using the nickel active material according to the method of the present invention. DESCRIPTION OF SYMBOLS 1...Nickel anode body, 2...Anode can, 3...Metal ring, 4...Separator, 5...Zinc cathode, 6...Insulating packing, 7...Cathode terminal lid.

Claims (1)

[Claims] 1. A method for producing a nickel active material for an alkaline battery, which comprises adding at least one of manganese, silver, and their compounds, and a caustic alkali to nickel hydroxide, and then oxidizing the mixture with ozone gas.