JPH11273670A - Nickel positive electrode plate for alkaline storage battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance oxygen overvoltage by adding a cadmium compound into a positive electrode active material and to increase the capacity of a nickel positive electrode plate by restricting the amount of its addition to a minimum. SOLUTION: This manufacturing method includes an active material packing process whereby a positive electrode active material composed chiefly of nickel hydroxide is packed into a sintered base and a current-conducting process whereby the sintered base with the positive electrode active material packed therein by the active material packing process is made to conduct a current in an aqueous solution containing cadmium nitrate as its main component. A compound composed chiefly of cadmium hydroxide is electrolytically deposited on the surface of the positive electrode active material by the current conducting process. Therefore, the compound composed chiefly of the cadmium hydroxide can be deposited mainly on the highly conductive part of the plate packed with the positive electrode active material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery such as a nickel-hydrogen storage battery, a nickel-cadmium storage battery, and a nickel-zinc storage battery, and more particularly to a nickel positive electrode plate used for such an alkaline storage battery and the production of the nickel positive electrode plate. About the method.

[0002]

2. Description of the Related Art Conventionally, a nickel positive electrode plate used for an alkaline storage battery is prepared by immersing a porous nickel sintered plate as an active material holding member in an aqueous solution of an acidic nickel salt such as nickel nitrate, and placing the acid nickel salt in the substrate. After that, the step of replacing the acidic nickel salt with nickel hydroxide in an alkaline solution is repeated to perform an active material filling operation to convert the acidic nickel salt into a nickel hydroxide active material.

The charging reaction of this type of nickel positive electrode plate competes with the oxygen generation reaction. Factors that determine the charging efficiency of such a nickel positive electrode plate include charging current density, charging temperature, type of electrolyte, The oxygen overpotential of the active material is increased. In particular, a temperature higher than normal temperature (for example, 35 ° C to 65 ° C)
C), the oxygen overvoltage at the nickel positive electrode plate is reduced and oxygen gas is generated, so that charging of the nickel positive electrode plate does not proceed, and there is a problem that the discharge capacity is reduced due to insufficient charging. Was.

In order to solve such a problem, a cadmium compound has been added to a positive electrode active material filled in a nickel positive electrode plate. This aims at suppressing the generation of oxygen gas from the nickel positive electrode plate by adding a cadmium compound to the positive electrode active material, thereby making the oxygen generation potential noble. As a method of adding the cadmium compound to the positive electrode active material, a method of adding a cadmium compound to an acidic nickel salt aqueous solution to cause the cadmium compound to exist as a solid solution in the positive electrode active material, and a method of adding the cadmium compound to the positive electrode active material. A method is known in which a plate is immersed in an aqueous solution containing a cadmium compound to impregnate the cadmium compound.

For example, JP-A-56-143669 proposes a method in which a nickel positive electrode plate filled with a positive electrode active material is immersed in a cadmium nitrate aqueous solution to impregnate a cadmium compound. JP-A-56-14
In the method proposed in Japanese Patent No. 3669, the cadmium compound is distributed near the surface of the nickel positive electrode plate as if it covers the surface of the positive electrode active material particles.
The effect of suppressing the generation of oxygen gas is increased as compared with the case where the cadmium compound is present as a solid solution in the positive electrode active material.

On the other hand, in JP-A-59-68168, a nickel positive electrode plate filled with a positive electrode active material is immersed in an aqueous solution of cadmium nitrate, and then converted into cadmium hydroxide by an electrolytic reduction method in an aqueous solution of sodium hydroxide. A method of filling a nickel positive electrode plate has been proposed. In the method proposed in JP-A-59-68168, a cadmium compound covers the surface of the positive electrode active material particles in the same manner as the method proposed in JP-A-56-143669. Since the cadmium compound is distributed in the vicinity of the surface of the plate, the effect of suppressing the generation of oxygen gas is greater than the presence of the cadmium compound as a solid solution in the positive electrode active material.

[0007]

Incidentally, the above-mentioned Japanese Patent Application Laid-Open No. 56-143669 or Japanese Patent Application Laid-Open No.
According to the respective methods proposed in Japanese Patent No. 8168, in order to suppress the generation of oxygen gas by adding a cadmium compound to the positive electrode active material, and to improve the charge acceptability during high-temperature charging,
It is necessary to increase the amount of the cadmium compound added.

However, when the amount of the cadmium compound is increased, the amount of the positive electrode active material is relatively reduced, which causes a problem that the capacity of the nickel positive electrode plate is reduced. In view of the above, the present invention has been made in view of the above-described problems, and a cadmium compound has been added to a positive electrode active material to improve oxygen overvoltage, and the amount of addition has been minimized to reduce the capacity of a nickel positive electrode plate. Is to increase.

[0009]

Means for Solving the Problems and Their Functions / Effects To solve the above problems, a nickel positive electrode plate for an alkaline storage battery according to the present invention comprises a sintered substrate filled with a positive electrode active material mainly composed of nickel hydroxide. A compound containing cadmium hydroxide as a main component is mainly deposited on a portion of the electrode plate having high conductivity. The nickel positive electrode plate for an alkaline storage battery has a variation in conductivity distribution on the surface of the nickel positive electrode plate because the shape of the electrode plate is not completely uniform chemically. When a variation occurs in the distribution of the conductivity, a portion having high conductivity has a high current density because an electrochemical reaction easily proceeds, and a portion having low conductivity has a difficulty in progressing the electrochemical reaction. The current density decreases.

For this reason, a portion having high conductivity has a large current density and the charging reaction proceeds rapidly, and a portion having low conductivity has a small current density and the charging reaction does not progress very much. It is considered that the portion where the charging reaction proceeds rapidly reaches the oxygen overvoltage early and generates oxygen gas early. Therefore, as in the present invention, when a compound containing cadmium hydroxide as a main component is mainly deposited on a portion having high conductivity of the nickel positive electrode plate, the oxygen overvoltage is improved on the portion having high conductivity. Since the compound containing cadmium hydroxide as a main component is precipitated, generation of oxygen gas at an early stage can be prevented.

As described above, when the compound containing cadmium hydroxide as the main component is deposited mainly on the portion having high conductivity, the amount of the compound containing cadmium hydroxide as the main component is minimized. Therefore, the oxygen overvoltage can be improved, and the capacity of the nickel positive plate can be increased.

In order to deposit a compound mainly composed of cadmium hydroxide mainly on a portion having high conductivity,
As in the present invention, an energization treatment step of subjecting the sintered substrate filled with the positive electrode active material in the active material filling step to an energization treatment in an aqueous solution containing cadmium nitrate as a main component may be provided.

As described above, when the nickel positive electrode plate filled with the positive electrode active material is subjected to the energization treatment in an aqueous solution containing cadmium nitrate as a main component, the current density in the highly conductive portion of the nickel positive electrode plate is increased. Become. Then, since cadmium hydroxide is concentrated on the high conductivity portion, a compound containing cadmium hydroxide as a main component can be deposited mainly on the high conductivity portion. As a result, a compound containing cadmium hydroxide as a main component can be deposited mainly on a highly conductive portion of the nickel positive electrode plate.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preparation of Sintered Substrate A slurry is prepared by kneading a thickener such as carboxymethylcellulose and water into nickel powder, and this slurry is applied to a conductive core made of a punched metal in which nickel is plated on iron. Thereafter, the conductive core coated with the slurry is sintered in a reducing atmosphere to produce a sintered substrate having a porosity of 80%.

2. Production of Nickel Positive Electrode Example The sintered substrate having a porosity of 80% produced as described above was
It is immersed in an aqueous solution mainly composed of nickel nitrate having a specific gravity of 1.75 at a temperature of ° C. to impregnate the aqueous solution mainly composed of nickel nitrate into the pores of the sintered substrate and then dried to deposit nickel nitrate. Then, the sintered substrate on which nickel nitrate was deposited was immersed in a 25% by weight aqueous sodium hydroxide solution,
The precipitated nickel nitrate is replaced with nickel hydroxide.
Thereafter, the operation returns to the operation of immersing the sintered substrate again in an aqueous solution mainly composed of nickel nitrate, and the same operation as described above is repeated a predetermined number of times (for example, five times) to deposit nickel hydroxide in the pores of the sintered substrate. Fill. The substrate in which the pores of the sintered substrate are filled with nickel hydroxide in this manner is called an active material-filled substrate.

Next, the active material-filled substrate is added in an amount of 10% by weight.
Cadmium nitrate aqueous solution, and the active material-filled substrate was used as a negative electrode, and a cadmium rod was used as a positive electrode using a cadmium rod at 0.5 C (where C is the theoretical capacity of the electrode plate when a constant current was applied for 1 hour). Is supplied with a current having a current value of 1% to produce a nickel positive electrode plate in which 1% by weight of cadmium hydroxide is deposited on the active material-filled substrate with respect to the mass of the active material. This nickel positive plate is referred to as a nickel positive plate a1 of the embodiment.

Similarly, a nickel positive electrode plate obtained by depositing 2% by weight of cadmium hydroxide based on the mass of the active material on the active material-filled substrate is referred to as a nickel positive electrode plate a2 of the embodiment. Similarly,
A nickel positive electrode plate obtained by depositing 4% by weight of cadmium hydroxide based on the mass of the active material on the active material-filled substrate is referred to as a nickel positive electrode plate a3 of the example. The amount of cadmium hydroxide deposited was changed by adjusting the energization time.

Comparative Example 1 Using the same active material-filled substrate as in the example, this active material-filled substrate was immersed in an aqueous cadmium nitrate solution, dried, and then immersed in an alkaline aqueous solution (aqueous sodium hydroxide solution). A nickel positive electrode plate is prepared in which cadmium hydroxide is precipitated on the surface of the nickel hydroxide active material by 1% by weight based on the mass of the active material. This nickel positive plate is referred to as a nickel positive plate b1 of Comparative Example 1. Similarly, a nickel positive electrode plate obtained by depositing 2% by weight of cadmium hydroxide based on the mass of the active material on the active material-filled substrate is referred to as a nickel positive electrode plate b2 of Comparative Example 1. Similarly, a nickel positive electrode plate obtained by depositing 4% by weight of cadmium hydroxide with respect to the mass of the active material on the active material-filled substrate is referred to as a nickel positive electrode plate b3 of Comparative Example 1. The amount of cadmium hydroxide deposited was changed by adjusting the concentration of the cadmium nitrate aqueous solution and the immersion time of the active material-filled substrate.

Comparative Example 2 Using the same active material-filled substrate as in the example, the active material-filled substrate was immersed in a cadmium nitrate aqueous solution, dried, and then subjected to electrolytic reduction in a sodium hydroxide aqueous solution. A nickel positive electrode plate is prepared in which cadmium hydroxide is precipitated on the surface of the nickel hydroxide active material by 1% by weight based on the mass of the active material. This nickel positive plate is referred to as a nickel positive plate c1 of Comparative Example 2. Similarly, a nickel positive electrode plate obtained by depositing 2% by weight of cadmium hydroxide with respect to the mass of the active material on the active material-filled substrate is referred to as a nickel positive electrode plate c2 of Comparative Example 2. Similarly, a nickel positive electrode plate in which 4% by weight of cadmium hydroxide based on the mass of the active material was deposited on the active material-filled substrate was used in Comparative Example 2
Of the nickel positive electrode plate c3.

3. Measurement of Active Material Utilization Nickel Positive Electrodes a1-a of Examples Prepared as Above
3 and the nickel positive plates b1 to b3 of Comparative Example 1 and the nickel positive plates c1 to c3 of Comparative Example 2, and these nickel positive plates a1 to a3, b1 to b3, and c1 to c3 were used.
Was charged in a potassium hydroxide aqueous solution having a specific gravity of 1.2 using a nickel plate as a counter electrode under a temperature condition of 25 ° C., and then discharged under a temperature condition of 25 ° C., and the active material utilization rate X (%) was measured. After charging under the temperature condition of 45 ° C., 2
Active material utilization rate Y after discharge at temperature condition of 5 ° C
(%) Was measured.

The battery was charged for 16 hours with a current of 0.1 C (where C is a theoretical value of the electrode plate when a constant current was applied for 1 hour) at each temperature condition, and then charged at 25 ° C. 1/3
The discharge is performed under charging and discharging conditions of discharging at C, and the discharge capacity is determined from the discharge time. The ratio of each of the discharge capacities thus obtained to the theoretical discharge capacity obtained from the total amount of the positive electrode active material was obtained, and the active material utilization was calculated. The results shown in Table 1 below were obtained.

[0022]

[Table 1]

As is apparent from Table 1, the nickel positive electrode plate b2 of Comparative Example 1 and the nickel positive electrode plate c2 of Comparative Example 2 in which the amount of cadmium hydroxide added was 2% by weight based on the total mass of the active material, The active material utilization rate when charged at a high temperature is equivalent to that of the nickel positive electrode plate a1 of the example in which the amount of addition is smaller than that (1% by weight). Further, the nickel positive electrode plate b3 of Comparative Example 1 and the nickel positive electrode plate c3 of Comparative Example 2 in which the amount of cadmium hydroxide added was 4% by weight based on the total mass of the active material, and the amount of addition was smaller (2% by weight). %) The active material utilization rate when charged at a high temperature is equal to that of the nickel positive electrode plate a2 of the example. From this, it can be said that the addition of cadmium hydroxide by electrolytic deposition according to the present invention can improve the active material utilization rate by adding a small amount.

This is because, when a nickel positive electrode plate filled with a positive electrode active material is energized in an aqueous solution containing cadmium nitrate as a main component, the current density in a highly conductive portion of the nickel positive electrode plate increases, This is probably because cadmium hydroxide collects and concentrates on the high-potential portion. As described above, when cadmium hydroxide is mainly deposited on a portion having high conductivity, it becomes possible to selectively deposit only cadmium hydroxide only at a site where the cadmium hydroxide is to be deposited. It is possible to sufficiently improve the oxygen overvoltage.

4. Production of Nickel-Cadmium Battery Next, using the nickel positive electrode plate a1 of the example produced as described above and a well-known non-sintered cadmium negative electrode plate, these were spirally wound through a separator made of nonwoven fabric made of polypropylene. To form a spiral electrode body. A current collector is connected to each electrode plate at each of the upper and lower ends of the spiral electrode body, and after these are housed in a metal outer can, a lead plate extending from each current collector is connected to each terminal. By filling the outer can with an electrolyte solution comprising potassium hydroxide, and attaching a sealing body to the opening of the outer can to seal the outer can.
Example nickel capacity of 1200 mAh nominal capacity
A cadmium storage battery A1 is manufactured.

Similarly, by using the nickel positive electrode plate a2 of the embodiment and the well-known non-sintering type cadmium negative electrode plate, the nickel-cadmium storage battery A2 of the embodiment having a nominal capacity of 1200 mAh of A size is connected to the nickel positive electrode plate of the embodiment. The nickel-cadmium storage battery A3 of the example having the nominal capacity of 1200 mAh of the A size is manufactured using the a3 and the well-known non-sintered cadmium negative electrode plate.

Similarly, by using the nickel positive electrode plate b1 of Comparative Example 1 and a well-known non-sintered cadmium negative electrode plate, the nickel-cadmium storage battery B1 of Comparative Example 1 having a nominal size of 1200 mAh was replaced with the nickel cadmium storage battery B1 of Comparative Example 1. Using a nickel positive electrode plate b2 and a well-known non-sintered cadmium negative electrode plate, a nickel-cadmium storage battery B2 of Comparative Example 1 having a nominal size of 1200 mAh and an A-size nickel cadmium storage plate B3 and a well-known non-sintered nickel cadmium battery b3 of Comparative Example 1 A nickel-cadmium storage battery B3 of Comparative Example 1 having a nominal capacity of 1200 mAh is manufactured using a cadmium negative electrode plate.

Similarly, by using the nickel positive electrode plate c1 of Comparative Example 2 and the well-known non-sintered cadmium negative electrode plate, the nickel-cadmium storage battery C1 of Comparative Example 2 having a nominal size of 1200 mAh was replaced with the nickel cadmium storage battery C1 of Comparative Example 2. Using a nickel positive electrode plate c2 and a well-known non-sintering type cadmium negative electrode plate, an A-size nickel-cadmium storage battery C2 of Comparative Example 2 having a nominal capacity of 1200 mAh was replaced with a nickel positive electrode plate c3 of Comparative Example 2 and a well-known non-sintering method. A nickel-cadmium storage battery C3 of Comparative Example 2 having a nominal capacity of 1200 mAh and an A-size was manufactured using the cadmium negative electrode plate.

The nickel-cadmium storage batteries A1 to A3 of the embodiment, the nickel-cadmium storage batteries B1 to B3 of the comparative example 1, and the nickel-cadmium storage batteries C1 to C3 of the comparative example 2, which were respectively manufactured as described above, were respectively 25
At a charging current of 120 mA (0.1 C)
After charging for 6 hours, 1200 mA at 25 ° C.
The battery is discharged at a current of (1C) until the battery voltage becomes 1.0 V, and a discharge capacity X is obtained from the discharge time. On the other hand, the nickel-cadmium storage batteries A1 to A3 of the example, the nickel-cadmium storage batteries B1 to B3 of the comparative example 1, and the nickel-cadmium storage batteries C1 to C3 of the comparative example 2 which were respectively manufactured as described above were respectively subjected to a temperature of 45 ° C. Condition 4
After charging for 48 hours at a charging current of 0 mA (1/30 C), the battery is discharged at a temperature of 25 ° C. at a current of 1200 mA (1 C) until the battery voltage reaches 1.0 V, and a discharge capacity Y is obtained from the discharging time. . The discharge capacity X and the discharge capacity Y obtained as described above are as shown in Table 2 below.

[0030]

[Table 2]

As is clear from Table 2, as the amount of cadmium hydroxide added increases, the battery was charged at room temperature (25 ° C.).
, The discharge capacity at high temperature charging (45 ° C.) increases. Then, the battery A1 of the example in which the addition amount of cadmium hydroxide was equal and the battery B1 of the comparative example 1
And the battery C1 of Comparative Example 2, respectively, show that when cadmium hydroxide is added by electrolytic deposition as in the present invention, the discharge capacity at normal temperature charge (25 ° C.) and the high temperature charge (45 ° C.) It can be seen that the discharge capacities in ()) increase respectively. Similarly, the battery A2 of the example and the battery B2 of the comparative example 1 in which the addition amount of cadmium hydroxide was equal,
Even when the battery C2 of the comparative example 2 is compared, or the battery A3 of the example, the battery B3 of the comparative example 1, and the battery C3 of the comparative example 2 are compared.
When cadmium hydroxide was added by electrolytic deposition as in the present invention, the discharge capacity at room temperature charge (25 ° C.) and the discharge capacity at high temperature charge (45 ° C.) It can be seen that the capacities increase respectively.

This is because, when a nickel positive electrode plate filled with a positive electrode active material is energized in an aqueous solution containing cadmium nitrate as a main component, the current density in the highly conductive portion of the nickel positive electrode plate increases, This is probably because cadmium hydroxide collects and concentrates on the high-potential portion. As described above, when cadmium hydroxide is mainly deposited on a portion having high conductivity, it is possible to selectively deposit only cadmium hydroxide at a site where the cadmium hydroxide is desired to be deposited. Therefore, it is considered that the discharge capacity is improved.

As described above, according to the present invention,
With the addition of a small amount of cadmium hydroxide, a nickel positive plate excellent in both normal temperature characteristics and high temperature characteristics can be obtained. As a result, the performance of the battery using the nickel positive electrode plate of the present invention can be dramatically improved.

In the above-described embodiment, an example is described in which cadmium nitrate is used as a solution for electrolytically depositing cadmium hydroxide. However, the solution for electrolytically depositing cadmium hydroxide contains cadmium nitrate as a main component. The same effect can be obtained by using a solution having the same composition.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuaki Ozaki 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A nickel positive electrode plate for an alkaline storage battery in which a sintered substrate is filled with a positive electrode active material mainly composed of nickel hydroxide, wherein the sintered substrate is filled with a positive electrode active material mainly composed of nickel hydroxide. A sintered nickel positive electrode plate for an alkaline storage battery, characterized in that a compound containing cadmium hydroxide as a main component is mainly deposited on a portion of the electrode plate having high conductivity. 2. A method for producing a nickel positive electrode plate for an alkaline storage battery, comprising forming a sintered substrate with a positive electrode active material mainly composed of nickel hydroxide, wherein the sintered substrate contains nickel hydroxide as a main component. An active material filling step of filling the positive electrode active material, and an energization treatment step of performing an energization treatment on the sintered substrate filled with the positive electrode active material in the active material filling step in an aqueous solution containing cadmium nitrate as a main component. A method for producing a nickel positive electrode plate for an alkaline storage battery, wherein a compound containing cadmium hydroxide as a main component is electrolytically deposited on the surface of the positive electrode active material by the energization treatment step.