JPS5942948B2 - Manufacturing method of sintered anode plate - Google Patents

Description

[Detailed description of the invention] Invention: ◆; Sintering method in cadmium batteries□
This invention relates to a method for manufacturing electrode plates.

This type of electrode plate is made by immersing a nickel sintered substrate made by sintering nickel powder with a small apparent specific gravity in an impregnation amount of nickel nitrate solution to impregnate the porous parts of the substrate with active material salt, and then c. The substrate is treated with an alkali, the nickel nitrate is rewritten in one kelp of water, and the series of impregnating steps of washing and drying is repeated, followed by a chemical conversion treatment.

In the above-mentioned manufacturing process, the impregnation process in particular determines the battery capacity and is extremely important. During impregnation, the nickel sintered substrate is easily corroded by the amount of nitrate impregnated.

In this case, nickel hydroxide is formed due to corrosion, and since it is in the form of an active material, it can be expected to increase the volumetric efficiency and weight efficiency, but on the other hand, the variation in capacity increases due to the variation in corrosion. It is difficult to control the amount to a predetermined amount, and there are disadvantages in that the electrode plates become brittle due to corrosion. Therefore, it has been proposed in the past to add sodium nitrite or sodium sulfite to the amount of impregnation in order to prevent such corrosion, but the corrosion reaction depends on the amount of impregnation, temperature, flow rate, impurities, etc. Sufficient suppression was difficult, and stabilization was extremely difficult.

In view of this, the present invention devised a corrosion reaction from an electrochemical viewpoint, and discovered that Nitsukeno in nitric acid has an active potential range in which the corrosion reaction progresses and an inactive potential range in which the corrosion reaction does not proceed easily. This was done by focusing on the amount of Cl that exists, and its gist is that when a sintered nickel substrate is immersed in the amount of nitrate impregnated, the sintered nickel substrate is The purpose is to maintain the potential in an inactive state where corrosion is unlikely to occur, thereby suppressing corrosion of the nickel sintered substrate, making it possible to control battery capacity, and preventing weakening of the electrode plates.

Generally, the current-voltage curve of nickel in nitric acid is shown in FIG. 1, and is divided into potential ranges from □ to [F].

In the figure, potential regions 4 and [F] are hydrogen gas generation and oxygen gas generation regions, respectively, and 8 is a corrosion reaction, that is, Ni→Ni2
In the active state potential range, a dissolution reaction of + and a reaction of Ni2゛→Ni→Ni(OH)2 proceed, and -an apparent precipitation reaction of Ni2+Ni(OH)2 occurs, while O is in an equilibrium state and corrodes. O indicates the potential range of an inactive state in which it is difficult to occur, and O indicates the potential range of an over-inactive state. Incidentally, the current-voltage curve of Nickel shown in FIG. 1 above varies slightly depending on the concentration of the nitric acid solution, temperature, etc.

Next, we will explain in detail one experimental example.Specific gravity: 1.701 Liquid temperature: 8
A nickel substrate was immersed in nickel nitrate salt at 0°C, and impregnated and dried for 90 minutes while holding the nickel substrate at various voltages with respect to the impregnation bath.Then, the substrate was removed from the impregnation bath and immediately washed with water and dried. After removing the impregnated nickel nitrate, the weight change of the nickel substrate was measured, and the results shown in Table 1 were obtained. In addition, in Table 1, 0
``Potential'' indicates the potential of the nickel substrate relative to the impregnation bath, ``weight change amount'' indicates the ratio of the weight of the nickel substrate after impregnation to that before impregnation, and the negative sign indicates that only the dissolution reaction of nickel occurs and the weight decreases. The positive sign indicates the increase in weight due to the formation of nickel hydroxide and the electrodeposition of nickel.

From the above table, it can be inferred that if the nickel substrate is maintained near +0.5V, it will be in a so-called inactive state in which corrosion reactions are unlikely to occur.

An embodiment of the present invention will be described below with reference to FIG. 2. A nickel sintered substrate 1 manufactured by a known method has a specific gravity of 1.70,
Immerse for 9.0 minutes in nickel nitrate solution 2 at a liquid temperature of 80°C.

The substrate 1 is arranged in parallel with a counter electrode 3 made of nickel, and a voltage is applied between the two electrodes 1 and 3 so that the potential of the substrate 1 with respect to the reference electrode 4 is +0.5V.

After a predetermined period of time had elapsed, the substrate 1 was taken out from the impregnation tank 5 and immersed in a sodium hydroxide solution to precipitate nickel hydroxide as an active material, followed by washing and drying, which were repeated a predetermined number of times. After that, an anode plate is obtained through a chemical formation process.

Figure 3 shows the K made using the anode plate thus obtained.
An R-SC type (nominal capacity 1200 mAH) Nickel-cadmium battery manufactured by the method of the present invention and a conventional anode plate manufactured using the above-mentioned anode plate manufacturing method without adjusting the potential of the substrate during the impregnation operation. This is a battery capacity distribution diagram when the discharge capacity was measured by discharging at a current of 1200 mA using 100 of each Nickel-cadmium battery according to the method, the vertical axis shows the number of batteries, and the horizontal axis shows the discharge capacity, respectively. .

It can be seen from this drawing that the battery produced by the method of the present invention has less variation in battery capacity than the battery produced by the conventional method. This variation in battery capacity is due to variation in the amount of active material impregnated into the nickel substrate in the anode and variation in the active material due to corrosion of the nickel substrate.In conventional batteries, the corrosion resistance of the nickel substrate Depending on the condition of the impregnating liquid, etc., the potential of the substrate during impregnation may be +0.5 without corrosion.
The variation in battery capacity is large because the voltage varies from V to about -0.4V, where corrosion of 10% or more occurs, whereas in the battery according to the method of the present invention, there is almost no nickel hydroxide produced by this corrosion. The variation in battery capacity can be suppressed to about 5%, which is the variation in the amount of active material impregnated into a normal nickel substrate. As described above, the present invention relates to a method for manufacturing a sintered anode plate, and includes immersing a nickel sintered substrate in a nickel nitrate impregnation bath to impregnate the porous portions of the substrate with nickel salt. It is characterized by maintaining the potential in an inactive state where corrosion is unlikely to occur, and it is possible to prevent the weakening of the electrode plate and variation in battery capacity due to corrosion, which is extremely useful in the manufacturing method of this type of anode plate. .

[Brief explanation of the drawing]

Figure 1 is a current-voltage curve diagram of Nickel in nitric acid.
FIG. 2 is a schematic diagram of an apparatus during an impregnation process according to the present invention, and FIG. 3 is a diagram showing battery capacity distribution of batteries using anode plates produced by the method of the present invention and the conventional method. 1... Nickel sintered substrate, 2... Nickel nitrate impregnated bath, 3... Counter electrode, 4...
Reference electrode.

Claims (1)

[Claims] 1. When immersing a nickel sintered substrate in a nickel nitrate impregnation bath to impregnate the porous portions of the substrate with nickel salt, the nickel sintered substrate is held at an inert potential that is unlikely to cause corrosion with respect to the impregnation bath. A method for manufacturing a sintered anode plate, characterized by: