JPH05307973A - Chemical conversion charging method of nickel-cadmium battery - Google Patents

Abstract

PURPOSE:To easily manufacture a battery without causing liquid leakage wherein voltage alteration of the battery can be detected based on the alteration of voltage potential sufficient to generate hydrogen in a nagative pole and charging of the battery is carried out under control. CONSTITUTION:A battery which retains an electrolytic liquid in an amount equivalent to the total of the void volume of a positive pole plate and a negative pole plate in charged condition and 20-80% volume of pores of a separator and is provided with a safety valve working at 0.05-4kg/cm<2> is charged at electricity in quantity equivalent to reduce cadmium oxide or cadmium hydroxide contained at least in the negative pole plate to metal cadmium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for chemical conversion charging of a nickel-cadmium battery, and more specifically, to a nickel-cadmium battery for controlling charging by detecting a change in battery voltage due to a potential change leading to hydrogen generation at the negative electrode. The present invention relates to a chemical charging method.

[0002]

2. Description of the Related Art In recent years, as a nickel-cadmium battery having a new function, a battery has been proposed which controls a charge by detecting a change in a battery voltage due to a potential change leading to hydrogen generation of a negative electrode (for example, Japanese Patent Laid-Open Publication No. Hei 3). No. 171564).
This battery is designed so that hydrogen generation in the negative electrode occurs immediately before or before the charging of the positive electrode is completed. The simplest way to make such a battery is to open the battery during chemical charging after assembling the battery, i.e., without a safety valve, until the oxygen gas and hydrogen gas are generated from the positive and negative electrodes, respectively. There is a method of charging and a method of overcharging a battery equipped with a safety valve.

[0003]

When the battery is overcharged after assembly, it is contained in the electrode plate and the separator due to oxygen gas generated from the positive electrode and hydrogen gas generated from the negative electrode at the end of charging. The electrolyte is pushed out of the element. At this time, if an excessive amount of electrolytic solution is present, the electrolytic solution flows out of the battery system through the liquid port. In a lead-acid battery or a large-capacity prismatic nickel-cadmium battery, a method of overcharging at the time of formation, flushing out excess electrolyte and then mounting a safety valve is adopted. However, this method has problems that the process is complicated and that the equipment for chemical conversion charging / discharging is easily damaged. In addition, since the electrolyte used in nickel-cadmium batteries is a strong alkali, it is difficult to wash it off completely once it has flowed out, and potassium carbonate crystals are deposited on the surface of the battery to stain it white or to insulate the battery pack. Problems such as defects are likely to occur.

[0004]

According to the present invention, as a result of systematically and in detail examining such problems including a charging method, a change in battery voltage due to a change in potential of a negative electrode is detected to control charging. This is based on the finding of the optimum liquid amount and optimum chemical charge conditions for nickel-cadmium batteries. Specifically, when the amount of the electrolyte is the charged volume, the void volume of the positive electrode plate and the negative electrode plate and the void volume of the separator are 2
Amount equivalent to 0 to 80%, 0.05 to 4 kg /
A battery equipped with a safety valve that operates at cm ² is characterized in that it is charged with an amount of electricity such that at least cadmium oxide or cadmium hydroxide contained in the negative electrode plate is reduced to metallic cadmium. The amount of electricity in this case is not the amount required to reduce all cadmium oxide or cadmium hydroxide to metallic cadmium, but means that at least the potential changes that lead to hydrogen generation during charging occur. It depends on the current and temperature. In particular, charging becomes easier when a mixed solution of an aqueous solution of potassium hydroxide and an aqueous solution of sodium hydroxide is used as the electrolytic solution. The charging current is 0.05-5C
When the range is A, the effect is great. Further, when the maximum current regulation constant voltage method or the quasi constant voltage method is applied as the charging method, the effect is particularly large.

[0005]

When the amount of electrolyte injected at the time of assembly is equal to or less than the total amount of the pore volume of the positive electrode plate and the negative electrode plate in the charged state and 80% of the pore volume of the separator, the positive electrode is charged from the positive electrode during overcharge. Most of the electrolytic solution extruded from the pores of the electrode plate by the oxygen gas generated and the hydrogen gas generated from the negative electrode is retained in the separator and therefore does not flow out of the battery system. In this case, when the amount of the electrolytic solution is equal to or less than the total amount of the pore volume of the positive electrode plate and the negative electrode plate in the charged state and 20% of the pore volume of the separator, the battery performance is deteriorated. It is desirable to do.

When the operating pressure of the safety valve attached to the battery exceeds 4 kg / cm ² , the positive and negative electrode plates cannot be charged at the same charge level because the closed system is maintained by the gas absorption reaction. In this case, if the working pressure is set to 0.05 kg / cm ² or less, there is a problem in the sealing property. Therefore, it is practically necessary to set this value or more.

Further, when a mixed solution of an aqueous solution of potassium hydroxide and an aqueous solution of sodium hydroxide is used as the electrolytic solution, the negative electrode active material, cadmium oxide or cadmium hydroxide, can be easily charged, and the amount of hydrogen generated from the negative electrode can be minimized. It is possible to suppress the outflow of the liquid during chemical conversion.

Further, when the charging current is 5 CA or more, the charging efficiency of the negative electrode is greatly reduced, so that the amount of hydrogen generated from the negative electrode is increased and liquid leakage easily occurs. In this case, if the charging current is set to 0.05 CA or less, it takes a long time for the chemical conversion charging / discharging process, which is not preferable in practice.

Further, when the maximum current regulation constant voltage method or the quasi-constant voltage method is applied as the charging method, the amount of oxygen gas generated from the positive electrode and the amount of hydrogen gas generated from the negative electrode are decreased because the current decreases in the overcharge region. Can be done, and the effect is particularly large.

[0010]

EXAMPLES The present invention will be described below with reference to preferred examples.

First, in order to study in detail the optimum range of the amount of electrolytic solution, batteries having different amounts of electrolytic solution were manufactured and subjected to chemical charge / discharge with various charging currents.

Example 1 A 4.5 M nickel nitrate aqueous solution containing 8 mol% cobalt nitrate and 4 mol% cadmium nitrate was applied to a sintered nickel substrate having a porosity of about 80% at 70 ° C.
It is impregnated with water, immersed in a 5M aqueous solution of sodium hydroxide at 70 ° C, washed with hot water, and then dried at 80 ° C for 1 hour. This operation is repeated 7 times.
7 pieces were produced. Next, a paste-type cadmium negative electrode plate (22.5 × 50.5 × 0.50% by weight) containing 100 parts by weight of cadmium oxide and 40 parts by weight of metal cadmium as active materials.
57mm) 8 pieces were produced. Further, the above positive electrode plate was wrapped with a non-woven fabric made of polysulfone, ultrasonically welded, and then alternately combined with a negative electrode plate to form an electrode plate group. A sealing plate having a positive electrode terminal equipped with a safety valve with an operating pressure of 1.0 kg / cm ² is attached to this electrode plate group and inserted into the battery case, and the empty space of the positive electrode plate and the negative electrode plate when the amount of electrolyte is charged. An aqueous solution of potassium hydroxide having a specific gravity of 1.250 (20 ° C) was added to make the amount equivalent to the total of the pore volume and the pore volume of the separator 5 to 90%, followed by sealing, and the nominal capacity was 2.4 Ah. I made a battery. 3 after sealing these batteries
After leaving it for a day, it is charged to 150% of its nominal capacity with a current of 0.1, 0.5 or 1 CA, and it is 1.0 at 0.5 CA.
A chemical charge and discharge of discharging to V was performed.

FIG. 1 shows the relationship between the amount of electrolyte and the amount of weight loss after chemical conversion charging / discharging. Further, FIG. 2 shows the relationship between the electrolytic solution amount and the discharge capacity. The amount of electrolytic solution in the figure is the ratio of the remaining amount of electrolytic solution to the pore volume of the separator when all the holes of the positive electrode plate and the negative electrode plate are filled with the electrolytic solution in the charged state. From FIG. 1, the amount of weight reduction is almost constant when the amount of the electrolytic solution is equal to or less than the total amount of the pore volume of the positive electrode plate and the negative electrode plate and 80% of the pore volume of the separator. From the point where this value was exceeded, the value increased sharply, and at this time point, the outflow of the electrolytic solution was observed.
Furthermore, substantially the same results were obtained when positive electrode plates and negative electrode plates having different residual porosities and separators having different thicknesses were used. Therefore, when the amount of the electrolytic solution during assembly is set to be equal to or less than the total amount of the pore volume of the positive electrode plate and the negative electrode plate and 80% of the pore volume of the separator, the oxygen gas generated from the positive electrode during overcharge and the negative electrode It is considered that most of the electrolytic solution extruded from the electrode plate by the generated hydrogen gas does not flow out of the battery system because it is held in the separator. Also, from FIG. 2, the amount of electrolyte is 20% of the pore volume of the positive electrode plate and the negative electrode plate and the pore volume of the separator.
When the amount is less than the amount corresponding to the total of%, the discharge capacity is significantly reduced. Therefore, it can be said that the optimum amount of the electrolytic solution is an amount corresponding to the total of the void volume of the positive electrode plate and the negative electrode plate and 20 to 80% of the void volume of the separator.

Next, in order to examine in detail the range of the optimum operating pressure of the safety valve attached to the battery, batteries having safety valves with different operating pressures were manufactured and subjected to chemical charge / discharge.

[Embodiment 2] A battery case is prepared by attaching a sealing plate having a positive electrode terminal equipped with a safety valve having an operating pressure of 0.01 to 8 kg / cm ² to an electrode plate group manufactured in the same manner as in Embodiment 1. And the amount of electrolyte is 75% of the void volume of the positive electrode plate and the negative electrode plate in the charged state and the void volume of the separator.
Specific gravity 1.250 (20 ° C) so that the amount corresponds to the total of
After adding the potassium hydroxide aqueous solution of (1) and sealing, a battery having a nominal capacity of 2.4 Ah was manufactured. After leaving it for 3 days after sealing, it is charged with the amount of electricity required to reduce all the cadmium oxide contained in the negative electrode plate to metallic cadmium at a current of 1 CA, and then discharged to 1.0 V at 0.5 CA. The chemical charge and discharge was performed.

FIG. 3 shows the relationship between the safety valve operating pressure and the weight reduction amount after chemical conversion charging / discharging. From the figure, it can be seen that when the weight exceeds 4 kg / cm ² , the weight loss has disappeared, and neither oxygen gas nor hydrogen gas has come out of the battery system. This means that the charge levels of the positive electrode plate and the negative electrode plate have not changed even after the formation and charge / discharge. Therefore, when the operating pressure of the safety valve attached to the battery is 4 kg / cm ² or more, it is impossible to manufacture a battery that controls the charging by detecting the change in the battery voltage due to the potential change resulting in the hydrogen generation of the negative electrode. In this case, the working pressure is 0.05kg / cm ²
It has been found that if the amount is less than the range, a problem occurs in the sealing property, and the leak of the liquid increases during long-term use. Therefore, the operating pressure must be above this value.

Further, the composition of the electrolytic solution was examined.

[Embodiment 3] A sealing plate having a positive electrode terminal equipped with a safety valve having an operating pressure of 1.0 kg / cm ² was attached to an electrode plate group prepared in the same manner as in Example 1 to have a specific gravity of 1.250.
Mixed solution of potassium hydroxide aqueous solution (20 ℃) and sodium hydroxide aqueous solution with specific gravity 1.250 (20 ℃) (volume ratio 3: 1)
Insert it into the battery case together with 5.4 ml and then seal it.
A battery A having a nominal capacity of 2.4 Ah was manufactured. The electrolyte solution amount of 5.4 ml corresponds to the total of the pore volume of the positive electrode plate and the negative electrode plate in the charged state and 75% of the pore volume of the separator.

[Comparative Example 1] In the above battery A, the electrolytic solution was 5.4 m in an aqueous potassium hydroxide solution having a specific gravity of 1.250 (20 ° C).
A comparative battery B was manufactured in the same manner as battery A except that 1 was used.

Battery A and battery B were charged with an amount of electricity required for reducing all the cadmium oxide contained in the negative electrode plate to metallic cadmium at a current of 3C. The charging characteristics are shown in FIG. Battery A has a larger amount of electricity charged until a rapid rise in battery voltage due to hydrogen generation is observed. Therefore, it is understood that the amount of hydrogen generated in the battery A is smaller when the amount of electricity charged is constant. Further, Table 1 shows the number of defective liquid leaks that occurred when 100 cells of each of the batteries A and B were charged and discharged under the above conditions.

[0021]

[Table 1] From Table 1, when a mixed solution of an aqueous solution of potassium hydroxide and an aqueous solution of sodium hydroxide is used as the electrolytic solution, almost no liquid leakage failure occurs. This is because when the electrolytic solution contains sodium hydroxide, it becomes easier to charge cadmium oxide in the negative electrode plate, so that the amount of hydrogen generated is reduced as compared with the case where the electrolytic solution is a potassium hydroxide aqueous solution, and the negative electrode plate This is because it was possible to minimize the amount of the electrolyte solution extruded from the pores.

Finally, the charging conditions were also examined in detail.

Example 4 In Battery B of Comparative Example 1,
A battery C was manufactured in the same manner as the battery B, except that the amount of the electrolytic solution was the amount corresponding to the total of the void volume of the positive electrode plate and the negative electrode plate and 80% of the void volume of the separator. This battery C100 cell was charged at 20 ° C. for 3 hours by the maximum current regulation constant voltage method (maximum current 0.5 CA, 1.7 V / cell).

Example 5 A battery C100 cell was placed at 20 ° C.
Quasi-constant voltage method (initial current 0.5 CA, 1.7 V / cell)
The battery was charged for 3 hours.

[Comparative Example 2] A battery C100 cell was placed at 20 ° C.
Was charged for 3 hours by the constant current method (0.5 CA).

Table 2 shows the number of defective liquid leakage cells generated in each of Examples 4 and 5 and Comparative Example 2.

[0027]

[Table 2] From Table 2, it can be seen that the number of defective liquid leakage cells is reduced when the maximum current regulated constant voltage charging or the quasi-constant voltage charging is performed, as compared with the case where the constant current charging is performed. This is because when these methods are applied, the current decreases in the overcharge region, so that oxygen gas generation from the positive electrode and hydrogen gas generation from the negative electrode are suppressed, and the amount of the electrolyte solution extruded to the outside of the element is reduced. This is because it has decreased.

[0028]

As described above, according to the present invention, a battery capable of controlling the charging by detecting the change in the battery voltage due to the potential change resulting in the hydrogen generation of the negative electrode can be used to prevent liquid leakage. It can be easily manufactured without occurring.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the amount of electrolytic solution and the amount of weight loss after chemical conversion charging / discharging.

FIG. 2 is a diagram showing the relationship between the amount of electrolytic solution and the discharge capacity during chemical charge / discharge.

FIG. 3 is a diagram showing a relationship between a safety valve operating pressure and a weight reduction amount after chemical charge / discharge.

FIG. 4 is a diagram comparing the 3C charge characteristics when the electrolytic solution is an aqueous solution of potassium hydroxide and when the electrolytic solution is a mixed solution of potassium hydroxide and a sodium hydroxide solution.

Claims (4)

[Claims] 1. An electrolytic solution is retained in an amount corresponding to the total of the void volume of the positive electrode plate and the negative electrode plate in a charged state and 20 to 80% of the void volume of the separator, and 0.05 to 4 is held.
A method of forming and charging a nickel-cadmium battery, characterized in that a battery equipped with a safety valve that operates at kg / cm ² is charged with an amount of electricity that reduces cadmium oxide or cadmium hydroxide contained in at least a negative electrode plate to cadmium metal. .. 2. The method of chemical conversion charging of a nickel-cadmium battery according to claim 1, wherein the electrolytic solution is a mixed solution of an aqueous solution of potassium hydroxide and an aqueous solution of sodium hydroxide. 3. The method for chemical conversion charging of a nickel-cadmium battery according to claim 1, wherein the charging current is 0.05 to 5 CA based on the theoretical capacity of the positive electrode active material. 4. The method for chemical conversion charging of a nickel-cadmium battery according to claim 1, wherein the charging is performed by a maximum current regulation constant voltage method or a quasi-constant voltage method.