JP3108144B2 - Method for producing nickel positive electrode plate for alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a nickel positive electrode plate used for an alkaline storage battery such as a nickel-cadmium battery.

[0002]

2. Description of the Related Art Conventionally, as a method for manufacturing a nickel positive electrode plate for an alkaline storage battery, a porous sintered substrate as an active material holding member is immersed in an acidic nickel salt solution such as nickel nitrate to form a hole in the substrate. There is a method of manufacturing a nickel positive electrode plate by performing a series of active material filling operations in which a nickel salt is impregnated and then converted into an active material by changing the nickel salt to nickel hydroxide in an alkali. The filling amount of the active material into the nickel sintered substrate by this active material filling operation is 1
Since a sufficient amount of filling cannot be obtained by the above operations, a predetermined amount of the active material is obtained by repeating the operation several times.

Further, in the recent market, there is an increasing tendency to demand a battery having a high energy density. In order to satisfy the market demand, a plate having a large plate capacity and a high plate operating voltage is developed. There is a need.

Here, as a basic method for improving the electrode plate capacity, there is a method for increasing the utilization rate of the active material. As this method, generally, a method of adding cobalt nitrate to an impregnating liquid in the course of impregnation and adding cobalt to uniformly disperse cobalt in the active material, or adding cobalt to the surface of the positive electrode plate is performed. .

As an example of the above, Japanese Patent Application Laid-Open No. 63-285870
Japanese Patent Laid-Open Publication No. H11-15083 proposes a method of adding cobalt to a nickel positive electrode in which an electrode plate filled with an active material is immersed in a cobalt salt solution, and then the cobalt salt is changed into cobalt hydroxide.

However, although the addition of cobalt as described above can improve the utilization of the active material, it has a problem that the operating voltage of the positive electrode decreases with an increase in the amount of addition.

Therefore, as a method of increasing the utilization rate, attempts have been made to add lithium hydroxide to the electrolytic solution, but on the contrary, the discharge potential is remarkably fluctuated, which is not practically preferable.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a manufacturing method for improving the utilization rate of an active material without lowering the operating voltage of a positive electrode plate.

[0009]

In the method for producing a nickel positive electrode plate for an alkaline storage battery according to the present invention, a porous nickel sintered substrate is immersed in an acidic nickel salt aqueous solution, and then the sintered substrate is treated with lithium hydroxide and hydroxide. The method is characterized by performing an active material filling operation of neutralizing and drying with a mixed alkali aqueous solution composed of sodium.

It is preferable that the molar fraction of lithium hydroxide [lithium hydroxide / (lithium hydroxide + sodium hydroxide)] in the mixed alkaline aqueous solution be 50% or more and 90% or less.

[0011]

[Function] When a sintered substrate impregnated with nickel nitrate is immersed in an alkaline solution to cause a neutralization reaction, when lithium hydroxide is contained in the alkaline solution, nickel hydroxide is generated by the neutralization reaction. Then, it is considered that lithium enters the nickel hydroxide lattice and lattice deficiency of nickel hydroxide occurs.

According to knowledge from the past, when a lattice defect occurs in a lattice crystal, it is considered that the electrical resistance decreases. However, when lithium enters and a lattice defect occurs, contrary to expectation, an operating voltage is unexpectedly increased. Was found to improve.

This is because the above effect is produced by adding lithium hydroxide to the alkaline solution in the neutralization step as in the present invention, and even if lithium is added to the electrolyte or the active material. There is no effect as in the present invention.

[0014] In the production method of the present invention, when nickel nitrate is neutralized with lithium hydroxide to produce nickel hydroxide, lithium ions are simultaneously taken into the nickel hydroxide crystal lattice, and this lithium is charged. Even if the discharge is repeated, the effect is considered to be maintained because it is fixed to this portion.

However, in the case where lithium is added to the electrolyte or the active material, lithium is not taken into the nickel hydroxide crystal lattice, and lithium can freely enter and exit the lattice even after repeated charge and discharge. It is thought that the effect like is not sustained.

Further, in the present invention, it has been found that a certain range of the ratio of sodium hydroxide to lithium hydroxide in the alkaline solution has effects of improving the utilization rate of the electrode plate and suppressing a decrease in operating voltage.

[0017]

EXAMPLE First, seven kinds of alkaline aqueous solutions for neutralization are prepared. The molar ratio of LiOH: NaOH was 50:50 for (a), 70:30 for (b), and 9 for (c).
0:10, (d) is 100: 0, (e) is 40:60,
As for (f), a sample having only KOH as 0: 100 and (g) is prepared. The hydroxide ion concentrations of these seven kinds of alkaline aqueous solutions are fixed.

Next, a nickel sintered substrate having a porosity of 80% is immersed in an aqueous solution of nickel nitrate having a specific gravity of 1.75 at 80 ° C. to impregnate the substrate with nickel nitrate. This substrate is immersed in each of the above seven types of alkaline aqueous solutions to neutralize nickel nitrate and convert it to nickel hydroxide as an active material.

This series of operations was repeated five times to produce nickel positive plates a, b, c, d, e, f and g, respectively. In addition, the code | symbol of this nickel positive electrode plate corresponds to the code | symbol of the alkaline aqueous solution at the time of neutralization.

These nickel positive plates a, b, c, d,
e, f, and g were cut to the same size, charged in a potassium hydroxide aqueous solution having a specific gravity of 1.20 at a theoretical capacity of 10 hours at a current of 16 hours, and discharged at a 5 hours rate of current. The discharge conditions at this time are such that Hg / HgO / KOH is used as a reference electrode, and the potential of the nickel positive electrode plate is 0.
It discharges until it reaches 2V.

Each of the nickel positive plates a, b, c,
The utilization rates of the active materials were calculated from the electrode plate capacities of d, e, f and g and are shown in Table 1.

[0022]

[Table 1]

Table 1 shows that the nickel positive plates a, b, and c have a high active material utilization rate.

Next, the nickel positive plates a, b, c,
d, e, f, and g and a known sintered cadmium negative electrode plate were wound with a separator interposed therebetween to produce electrode bodies. Insert these electrode bodies into the battery can, inject electrolyte,
Sealed to produce nickel-cadmium batteries A, B, C, D, E, F and G with a nominal capacity of 1.2 AH.

Here, the batteries A, B, C, D, E, F and G correspond to the signs of the nickel positive plates a, b, c, d, e, f and g, respectively.

After charging these batteries A, B, C, D, E, F and G at a current of 1.8 A, they were discharged at a current of 1.2 A until the battery voltage reached 1.0 V.

FIG. 1 shows batteries A, B, C, D, E, F and G
2 shows a discharge curve of the sample.

As shown in FIG. 1, batteries A, B and C correspond to batteries D and
It can be seen that the battery has superior characteristics in battery capacity and operating voltage as compared with E, F and G.

[0029]

According to the method for producing a nickel positive electrode plate for an alkaline storage battery of the present invention, a porous nickel sintered substrate is immersed in an aqueous solution of an acidic nickel salt, and then the sintered substrate is mixed with lithium hydroxide and sodium hydroxide. It is neutralized with an alkaline aqueous solution, and when nickel nitrate and lithium hydroxide undergo a neutralization reaction in an alkaline aqueous solution to produce nickel hydroxide, lithium ions are simultaneously taken into the nickel hydroxide crystal lattice, Since lithium is fixed to this portion even after repeated charging and discharging, the battery capacity and operating voltage can be improved by improving the utilization factor, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a diagram showing a discharge curve of a battery.

Claims (2)

(57) [Claims] 1. An active material filling operation in which a porous nickel sintered substrate is immersed in an acidic nickel salt aqueous solution, and then the sintered substrate is neutralized with a mixed alkaline aqueous solution composed of lithium hydroxide and sodium hydroxide and dried. A method for producing a nickel positive electrode plate for an alkaline storage battery. 2. The molar fraction of lithium hydroxide in the mixed alkaline aqueous solution [lithium hydroxide / (lithium hydroxide +
The method for producing a nickel positive electrode plate for an alkaline storage battery according to claim 1, wherein the content of (sodium hydroxide)] is 50% or more and 90% or less.