JPH0252387B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing nickel electrodes used in nickel-cadmium storage batteries and the like, and particularly to aging of active material mixtures used in non-sintered nickel electrodes. Normally, nickel electrodes for alkaline batteries are manufactured using the pocket method, sintering method, paste method as a non-sintering method, and method using a sponge-like metal porous material, but the most common method is the sintering method. It is. This method involves applying carbonyl nickel powder to nickel or nickel-plated iron punching metal, sintering it to create a substrate, impregnating the sintered substrate with active material salt, and then applying heat or chemical reaction to the active material. The electrode is obtained by converting it into This method has good electrode plate performance, long life, and is excellent in high rate charging and discharging, but the process is complicated, so an alternative method to obtain nickel electrodes without sintering has been proposed. . The active material mixture used in the non-sintered electrode contains nickel hydroxide as a main component, powder of metal, carbon, etc. as a conductive material, and cobalt powder as an additive. Methods to increase the active material utilization rate of this non-sintered electrode include increasing the proportion of conductive material or increasing the proportion of cobalt. The amount of active material decreases due to the addition of active material, resulting in a lack of capacity. The latter method uses 4 to 7
The amount of cobalt in % by weight is sufficient, and no improvement in the utilization rate is observed even if the amount is increased beyond that. On the other hand, a method can be considered in which the paste is left to dry without changing the composition ratio, and the paste is occasionally stirred to oxidize the cobalt and increase the active material utilization rate. However, this method requires leaving the paste for a long time, so
The disadvantage is that the place where it is left is used for a long time. In view of the above, the present invention has discovered that kneading the paste for a short time with a low water content has the same effect as leaving the paste to dry, and increases the active material utilization rate by efficiently oxidizing cobalt. It proposes ways to improve this. Hereinafter, the details of the present invention will be explained using an example in which a sponge-like porous nickel material is used as a core material. 100 parts by weight of nickel hydroxide powder, 20 parts by weight of nickel powder, and 5 parts by weight of cobalt powder were mixed, and a 0.5% by weight aqueous solution of carboxymethyl cellulose was added thereto and kneaded. At this time, 10 types of pastes A to J shown in Table 1 were prepared depending on the amount of carboxymethylcellulose aqueous solution, kneading time, and surrounding excess.

[Table] Pastes A to J were filled into a sponge-like porous nickel material with a porosity of 95%, and the size was 38 x 210 mm.
Ten nickel electrodes each having a thickness of 0.68±0.1 mm were obtained.
Let these be A′ to J′. Next, a cadmium electrode manufactured as follows was used. First, a paste mainly composed of cadmium oxide is applied to both sides of a nickel-plated iron punching metal, passed through a slit set to a predetermined thickness, and subjected to a drying process to obtain an electrode plate with a thickness of 0.7 mm. Ta. Thereafter, it was partially charged in a 10% by weight aqueous solution of caustic potassium to convert some of the cadmium oxide into metallic cadmium, washed with water, dried, and then pressurized to a thickness of 0.60 mm. A polyamide nonwoven fabric was used as the separator, and an appropriate amount of a small amount of lithium hydroxide dissolved in a 25% by weight aqueous solution of caustic potash was used as the electrolyte. Using the nickel electrodes of A′ to J′ and the cadmium electrodes obtained from the above formulation, batteries a to
I got j. Table 2 shows the battery capacity and active material utilization rate when this battery was charged to 160% at 0.1C and discharged at 0.2C, and the battery capacity at the 300th cycle in the above charge/discharge cycle. All values show the average value of 10 cells.

[Table] Thus, it can be seen that batteries b and j are particularly excellent in terms of active material utilization. The capacity of other batteries also tends to increase as the number of cycles increases, and these batteries are sufficiently satisfactory in terms of utilization rate and capacity. Considering the paste kneading conditions from Table 2, the optimal water content is around 23%; if it is less than 15%, kneading is difficult, and if it is more than 30%, the oxidation of cobalt is hindered by water; There is no improvement in utilization rate. The longer the kneading time, the better, and it is thought that this is because the cobalt is easily oxidized due to the long exposure to air. However, depending on the conditions of temperature and moisture content, kneading for about 30 minutes may be sufficient. The temperature needs to be at least 10°C or higher, and if it is below 10°C, it is necessary to carry out the infusion for a long time. On the other hand, at high temperatures, although the oxidation rate of cobalt is fast, water evaporates quickly during kneading, making it necessary to replenish water. In addition, in the example, a method for manufacturing a nickel electrode using a sponge-like porous nickel material as a core material was shown. It is also possible to use it as an active material for a nickel electrode. As described above, in the present invention, an active material mixture containing nickel hydroxide and cobalt is kneaded for a short time at a low moisture content, thereby improving the utilization rate of the active material.

Claims (1)

[Claims] 1. A paste mixture containing nickel hydroxide powder as a main component and containing at least cobalt powder with a water content of 15.
A method for producing nickel electrodes for alkaline batteries, which includes a step of kneading ~30% for 30 minutes or more. 2. The method for producing a nickel electrode for an alkaline battery according to claim 1, wherein the temperature during paste kneading is 10° C. or higher.