JP3185529B2 - Method for producing sintered substrate 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 aims at preventing the corrosion of a nickel powder sintered body used for a sintered substrate for an alkaline storage battery and improving the battery life performance.

[0002]

2. Description of the Related Art A sintered substrate used in an alkaline storage battery is manufactured by applying a slurry composed of a binder solution and carbonyl nickel powder to an iron-nickel plated perforated plate and then sintering in a hydrogen reducing atmosphere. Have been.

[0003] The sintered substrate obtained as described above has a property of being easily corroded in an acidic atmosphere. Sintered Ni-Cd
In order to manufacture a battery electrode, the nickel sintered body is generally immersed in a nickel nitrate solution for the anode and a cadmium nitrate solution for the cathode, and the process of intermediate drying, alkali reaction, washing with water and drying is repeated several times. The material is impregnated with nickel hydroxide or cadmium hydroxide. At this time, since the impregnating liquid is strongly nitric acid acidic, the sintered substrate is corroded in the steps of impregnation and intermediate drying, and changes to hydroxide in alkali. The active material generated by the corrosion has a drawback that the utilization factor is reduced and the life performance is deteriorated.

[0004] In order to solve the above-mentioned drawbacks, a technique for forming an oxidation-resistant oxide film on the surface of a sintered substrate prior to the impregnation process has been proposed. For example,
There are techniques for providing a cobalt oxide layer on the substrate surface, oxidizing with a peroxide aqueous solution, and dipping in concentrated nitric acid. Among them, as a simple method, a method of performing a heat treatment in the presence of oxygen is disclosed in JP-A-59-78457 and JP-A-59-96659.

[0005]

The technique of providing a cobalt oxide layer on the substrate surface, oxidizing with a peroxide aqueous solution, or immersing in a concentrated nitric acid involves a large time loss due to the complicated processing steps. In addition, there is a problem that the manufacturing process of the electrode plate becomes complicated.

Therefore, a relatively simple method is to perform a heat treatment in the presence of oxygen. However, in this method, if the amount of oxidation is small, the effect of preventing corrosion cannot be obtained, and if the amount of oxidation is too large, the conductivity and the strength of the substrate are impaired, and the high-rate discharge characteristics are deteriorated. In addition, when the heat treatment temperature is increased, the oxidation amount increases in a relatively short time, so that control becomes difficult. In addition, the nickel oxide film formed by heat treatment at a low temperature contains low-order oxides, which change into hydroxides in an alkaline aqueous solution, and have a problem that they are not useful for subsequent corrosion prevention.

[0007]

SUMMARY OF THE INVENTION The present invention provides a porous nickel
Sintered substrate for alkaline storage battery with oxide layer formed on sintered substrate
In the plate manufacturing method, the oxygen weight in the oxide layer
The oxidation number of nickel is 0.5 wt% to 1.5 wt% of
When forming a larger oxide layer, at least once 9
Characterized by heat treatment in the presence of 0 vol% or more oxygen
And

[0008]

[Function] The oxygen weight in the oxide layer is 0.5 wt% of the whole.
Oxidation number of nickel greater than 2 at ~ 1.5 wt%
When forming a layer, at least once, at least 90 vol%
Porous Nickel Sintered Substrate Heated in the Presence of Various Oxygen
Changes the oxide layer into a dense and strong higher-order oxide layer.
Therefore, the corrosion resistance is excellent. Excellent in such corrosion resistance
Use of sintered substrate reduces conductivity and electrode strength
Low, the utilization rate of the active material is improved,
Thus, an alkaline storage battery having excellent life performance can be obtained.

[0009]

EXAMPLE A sintered substrate (porosity: 80%) was prepared by applying a slurry comprising a binder solution and carbonyl nickel powder to an iron-nickel plated perforated plate and then sintering in a hydrogen reducing atmosphere. After heat-treating at a temperature of ° C. for various times, an electrode impregnated with the anode active material was prepared, and the relationship between the amount of oxidation, the degree of corrosion of the sintered body, and the number of lifetimes was shown in FIG. Here, the oxidation amount is a value obtained by dividing the weight change due to the oxidation by the weight before the oxidation and multiplying by 100. If all Ni is changed to NiO, the oxidation amount is (16 / 58.7) × 1.
00 = 27.3%. The corrosion degree of the sintered body is a value obtained by subtracting the weight of the sintered substrate after extracting the anode active material from the weight of the sintered substrate before impregnation (the difference between the weight of the sintered body before and after the impregnation)
It is obtained by dividing by the value obtained by subtracting the core material from the sintered substrate before impregnation (the weight of the original sintered body) and multiplying by 100.

The charge / discharge conditions for measuring the number of life cycles include a charge current of 5 CmA and a charge peak voltage of 15 CmA.
The charging was completed when the voltage dropped by mV (hereinafter referred to as −ΔV = 15 mV), and the discharging was completed when the battery voltage became 1 V at a discharge current of 5 CmA. The life cycle number was determined when the discharge capacity became 1/2 or less of the nominal capacity. FIG. 2 shows the relationship between the amount of oxidation at the time of high-rate discharge and the utilization rate of the active material. High-rate discharge is 20 A after 1 CmA charge (-ΔV = 15 mV)
(Approximately 17 CmA) discharge, and the utilization rate of the active material was determined by calculation based on the amount of active material determined by extraction.

[0011] The corrosion degree gradually decreases to 0.5 wt%,
After that it does not change much. Conversely, the life is 0.5wt
%, And peaks at over 1000 cycles. When the oxidation amount exceeds 1.5 wt%, the cycle life decreases. The same can be said for the utilization rate during high-rate discharge. This is due to the loss of conductivity as the amount of oxidation increases. When these results are combined, the oxidation amount is 0.5 wt% or more.
It can be seen that a battery exhibiting very good characteristics can be obtained by controlling to 1.5 wt%.

In order to produce a substrate having an oxidation amount of 0.5 wt% to 1.5 wt% in a short time, it is necessary to raise the heat treatment temperature. However, when the temperature exceeds 500 ° C. in air, the oxidation time is sharply shortened. In such a high-temperature region, for example, at 600 ° C., it takes just over 1 minute to exceed the optimum range of 1.5 wt%, and it is difficult to always accurately control the oxidation amount. Therefore, the amount of oxidation was controlled by performing a heat treatment in a gas containing no oxygen more than necessary. Oxidation rate is slightly reduced as the oxygen concentration is reduced. However, according to this method, it is possible to obtain a 1.0 wt% substrate in, for example, 600 ° C. for 5 minutes. it can.
Further, when heat treatment is performed at 525 ° C to 565 ° C or at 565 ° C or higher, β-NiO is converted to β-NiO at 525 ° C to 565 ° C.
It becomes γ-NiO at a temperature of not less than ℃, and since these have high crystallinity, corrosion of the sintered body can be more effectively prevented.

Further, when heat treatment is performed at 350 to 400 ° C. in an oxygen atmosphere of 90 vol% or more, part of NiO changes to higher order oxide Ni ₂ O ₄ . this is,
It is excellent in acid resistance and has the same oxidation amount of 1 wt%, and the amount of corrosion after impregnation was reduced by about 30 wt%.

When the heat treatment was performed in an atmosphere in which the amount of oxygen was less than 90 vol%, the rate of change to Ni ₃ O ₄ was low, and the amount of corrosion was slightly reduced. Therefore, it can be said that an appropriate condition of the oxygen atmosphere is 90 vol% or more.

Next, for comparison, a sample which had not been subjected to anticorrosion oxidation treatment was subjected to a heat treatment at 500 ° C. for 5 minutes shown in Example of JP-A-59-96659 (oxidation degree: 0.1). 43 wt%) to B, which is the oxidation amount range of the present invention 5
Heat treated at 00 ° C for 6 minutes (oxidation degree 0.55wt
%) Was heated at 400 ° C. for 12 hours in C and air for about 1%.
What was oxidized by wt% was D, heat-treated at 500 ° C. for 20 minutes, and what was oxidized by about 1 wt% was E, and heat-treated at 600 ° C. for 5 minutes in a furnace controlled to reduce the amount of oxygen to about 1 wt%
% Is oxidized, F is heat-treated at 450 ° C. for 2 hours in air, and G is heat-treated at 350 ° C. for 2 hours in a high-concentration oxygen (90 vol% or more) atmosphere. Table 1 shows the amount of oxidation, the amount of corrosion, and the number of cycles at which the life was reached. According to Table 1, the life of the battery C of the present invention is nearly twice as long as that of the battery B using the conventional oxide substrate. The lifetimes of D and E having an oxidation amount of about 1 wt% are nearly double as compared with those using a conventional oxidized substrate.
Further, as shown in F, an oxide film is formed at a high temperature,
As shown in Fig. 7, when heat treatment was performed in a high-concentration oxygen (90 vol% or more) atmosphere, the anticorrosion effect was increased, and the life characteristics were more than doubled. The high rate discharge performance (20 A discharge-about 17 C discharge), which may be reduced by applying the oxide layer, showed good results, and the battery which had been oxidized and protected did not show any particular tendency.

[0016]

[Table 1]

[0017]

As described above, the present invention provides a porous nip
Sinter for alkaline storage battery with oxide layer formed on Kel sintered substrate
In the substrate manufacturing method, the total weight of oxygen in the oxide layer is
The oxidation number of nickel is 0.5wt% to 1.5wt% of the body
In forming an oxide layer larger than 2, at least once,
By performing heat treatment in the presence of 90 vol% or more oxygen
The oxide layer changes to a dense and strong higher-order oxide layer.
As a result, the corrosion resistance is excellent, and such corrosion resistance is excellent.
Use of sintered substrate reduces conductivity and electrode strength
Low, the utilization rate of the active material is improved,
And an alkaline storage battery with excellent life performance can be obtained.
Has the effect of

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amount of oxidation, the degree of corrosion of a sintered body, and the number of lifetimes.

FIG. 2 is a diagram showing a relationship between an oxidation amount and a utilization rate at 20 A discharge.

Continuation of the front page (56) References JP-A-59-121784 (JP, A) JP-A-1-120762 (JP, A) JP-A-5-109407 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) H01M 4/80

Claims (1)

(57) [Claims] 1. A method for manufacturing a sintered substrate for an alkaline storage battery in which an oxide layer is formed on a porous nickel sintered substrate , wherein the weight of oxygen in the oxide layer is 0.5 wt% to 1.5 wt% of the whole.
% To form an oxide layer with nickel oxidation number greater than 2
In this case, at least once, in the presence of 90 vol% or more of oxygen
Sintering for alkaline storage batteries characterized by heat treatment
Substrate manufacturing method.