JPH04229955A - Alkaline storage battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an alkaline storage battery having a high capacity and a good discharge property by improving a spongy metal porous body for a base material of an electrode. CONSTITUTION:A spongy porous metal body having an electric resistance of less than 10X1/wmOMEGA for a sample of a surface density of 200-400g/m<2>, a length of 1mm, and a width of wmm is used for a base material for holding active material of an electrode. The electric resistance is reduced by this spongy porous metal body, thereby a high capacity alkaline storage battery having a good discharge property can be provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the characteristics of alkaline storage batteries.

0002

2. Description of the Related Art A typical example of an alkaline storage battery is a nickel/cadmium storage battery (hereinafter referred to as a nickel-cadmium battery). When comparing nickel-cadmium batteries and lead-acid batteries as a power source for portable devices, nickel-cadmium batteries have higher energy density per unit weight and unit volume, and are superior in reliability such as cycle life, making them suitable as power sources for various portable devices. Widely used.

However, a storage battery with reliability similar to that of a nickel-cadmium battery and a higher energy density is desperately needed as a power source for portable equipment. In recent years, high-capacity nickel-cadmium batteries with a battery capacity of more than 1.3 times that of conventional nickel-cadmium batteries, nickel/zinc storage batteries that use zinc instead of the cadmium negative electrode of nickel-cadmium batteries, and electrochemical hydrogen storage and release reactions ( Nickel/hydrogen storage batteries using hydrogen storage alloys that are capable of charge/discharge reactions are attracting attention.

[0004] The nickel positive electrode used in these alkaline storage batteries is of the sintered type or the paste type, and is made of a sponge-like porous nickel material with an areal density of 500 to 700 g/m2 and mainly composed of nickel oxide. The foamed metal positive electrode filled with active material has a capacity density of 60
It reaches 0mAh/cm3. Ni-Cd batteries using such high-capacity foamed metal positive electrodes are different from conventional Ni-Cd batteries 1.
．． It is possible to achieve a higher capacity of 6 times or more.

[0005]

[Problem to be solved by the invention] When a high-capacity alkaline storage battery is constructed by simply combining the foam metal positive electrode used in conventional alkaline storage batteries and a negative electrode, as the volume of the positive electrode increases, The thickness of the positive electrode increases.

As a result, the content of the electrically conductive substance in the positive electrode decreases, and the electrical conductivity of the positive electrode decreases. Further, as the capacity increases, the discharge current density increases when discharge is performed at a constant discharge rate. For these reasons, there was a problem that the discharge voltage decreased.

Furthermore, in order to improve the discharge characteristics, when increasing the area of the positive electrode and decreasing the thickness of the electrode plate, it is necessary to increase the areas of the negative electrode and the separator as well as the area of the positive electrode. As a result, there was a problem in that the volume ratio of the positive electrode in the battery case decreased, resulting in a decrease in capacity.

[0008] The present invention solves these problems, and aims to provide an alkaline storage battery with high capacity and excellent discharge characteristics.

[0009]

[Means for Solving the Problem] In order to solve this problem, the present invention provides a positive electrode in which an active material mainly consisting of a metal oxide is held in a sponge-like metal porous body with an areal density of 200 to 400 g/m2. and an alkaline storage battery consisting of a negative electrode, an alkaline electrolyte, and a separator, characterized in that the electrical resistance of the sponge-like porous metal material is 10×l/wmΩ or less in a specimen having a length of 1 mm and a width of w mm. It is something to do.

The present invention also provides a novel method for producing this sponge-like porous metal body.

[0011]

[Function] This structure reduces the amount of metal that does not contribute to battery capacity in the positive electrode, making it possible to increase the amount of active material and increasing the capacity density at a constant thickness.

As a result, high capacity can be achieved even when the area of the positive electrode is increased. Furthermore, when discharging at a constant discharge rate, the discharge current density decreases due to an increase in the area of the positive electrode, and the use of a highly electrically conductive sponge-like porous metal material makes it possible to obtain an alkaline storage battery with excellent discharge characteristics. .

[0013]

EXAMPLE A sponge-like porous nickel body was obtained by applying carbon to a sponge-like urethane having a thickness of 1.5 mm to impart electrical conductivity, electroplating with nickel, washing with water, and roasting. The areal density was adjusted by varying the amount of electricity during electrolytic plating. Further, the electrical resistance value at a constant surface density was adjusted by changing the number of repetitions of the carbon coating process to 2, 3, and 4 times.

Table 1 shows the areal density of the sponge-like porous nickel material thus obtained and the electrical resistance of a sample having a length of 100 mm and a width of 10 mm.

The electrical resistance of the sponge-like porous nickel material is
Connecting terminals were provided at both lengthwise ends of a specimen with a length of 100 mm and a width of 10 mm, and the voltage generated when a current of 1 A was applied was measured and calculated from the relationship of resistance value = voltage / current.

[0016]

[Table 1] Paste-type positive electrodes are made by mixing active materials nickel hydroxide powder and metal cobalt powder with water, filling them into a paste, drying them, pressing them, and then using a fluororesin dispersant. The material was immersed in John, dried, and cut into predetermined dimensions. Sponge-like porous nickel material No. 1 used in the paste-type positive electrode thus obtained. Table 2 shows the dimensions of the positive electrode.

[0017]

[Table 2] The hydrogen storage alloy negative electrode used for the negative electrode is CaCu
Hydrogen storage alloy MmNi3.55 with type 5 crystal structure
Mn0.4Al0.3Co0.75 in a ball mill
The powder was crushed to a particle size of 8 μ or less, immersed in a KOH aqueous solution, washed with water, and dried. The powder was mixed with water to form a paste, and the powder was made into a sponge-like nickel porous material with an areal density of 650 g/m2 and a porosity of 93-94%. A body was filled with a predetermined amount, dried and pressed, and then cut into a predetermined size.

[0018] Next, we used the above paste type positive electrode, which has a thickness of 0.15 mm, a width of 38 mm, and a length twice that of the positive electrode + 40 m.
A separator made of polypropylene non-woven fabric with a thickness of 35 mm and a theoretical capacity of 1.6 to 1.7 times the theoretical capacity of the positive electrode and a binding rate of 90 to 100%, a width of 35 mm, and a length equal to the length of the positive electrode. The above combination of hydrogen storage alloy negative electrodes with a diameter of +35 mm was spirally wound to form a 4/5A size sealed battery. The bondage rate was calculated using Equation 1 below.

[0019]

[Formula 1] The electrolyte used was a KOH aqueous solution with a specific gravity of 1.30 in which 40 g/l of LiOH/H2O was dissolved.
2.5 cm3 of liquid was injected per cell. These sealed batteries were charged at 0.1 CmA for 15 hours in an atmosphere at 20° C., and then discharged to 1.0 V at 0.2 CmA for two cycles. The positive electrode No. used in the battery at this time. Table 3 shows the battery capacity, and the positive electrode capacity density obtained by dividing the battery capacity by the volume of the positive electrode that constituted the battery.

[0020] Also, Fig. 1 shows that 1CmA (1500m
A) Shows the discharge voltage during discharge. When the positive electrode h was spirally wound, it broke due to insufficient strength, and the battery could not be constructed. This shows that a paste-type positive electrode using a sponge-like porous nickel material with an areal density of less than 200 g/m2 cannot constitute a battery due to insufficient strength.

[0021]

[Table 3] From Tables 1, 2, 3, and Figure 1, when a nickel/hydrogen storage battery is constructed using a conventional sponge-like porous nickel material with an areal density of 650 g/m2 as a paste type positive electrode (
Battery a) High capacity is obtained, but the average discharge voltage at 1CmA discharge is 1.18V or less.Battery in which the electrode plate area is increased and the electrode plate thickness is decreased to improve the discharge voltage (b)
In this case, the capacity is only 2.0 times lower than that of a 4/5A size Ni-Cd battery (700mAh) using a sintered nickel positive electrode, and it has little industrial value when considering cost and other factors.

[0022] When a sponge-like porous nickel material with an areal density of 200 to 400 g/m2 is used, the electrode plate area increases;
Even batteries with reduced electrode plate thickness (c, d, e, f, g) can achieve more than 2.0 times the capacity compared to a 4/5A size nickel-cadmium battery (700mAh) using a sintered nickel positive electrode. It was done. In addition, batteries (c, d, e, g) using sponge-like porous nickel materials with electrical resistance of 100 mΩ or less in specimens with a length of 100 mm and a width of 10 mm showed excellent discharge characteristics; The battery (f) using
Discharge voltage has decreased.

As described above, the batteries c, d, e, and g of the present invention have a capacity that is more than 2.0 times higher than that of a 4/5A size nickel-cadmium battery (700mAh) using a sintered nickel positive electrode.
Moreover, excellent discharge characteristics were obtained.

Furthermore, in this example, carbon coating was used as a method of imparting electrical conductivity to the sponge-like porous polymer material, but by using nickel vacuum evaporation or nickel chemical plating, A sponge-like porous metal body with low electrical resistance can be obtained, and an alkaline storage battery with high capacity and excellent discharge characteristics can be constructed.

Although a nickel/hydrogen storage battery has been described in this embodiment, an alkaline storage battery such as a nickel/zinc storage battery or a nickel-cadmium battery can also be used to construct an alkaline storage battery with high capacity and excellent discharge characteristics.

[0026]

As described above, according to the present invention, a sponge-like metal porous material having an areal density of 200 to 400 g/m2 and an electrical resistance of 10×l/wmΩ or less in a specimen having a length of 1 mm and a width of w mm is provided. By using a positive electrode in which an active material mainly composed of metal oxides is retained, an effect can be obtained in that an alkaline storage battery with high capacity and excellent discharge characteristics can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing discharge characteristics according to an embodiment of the present invention.

[Explanation of symbols]

a, b, f Comparative example c, d, e, g Example

Claims (2)

[Claims] Claim 1: An alkaline storage battery consisting of a positive electrode, a negative electrode, an alkaline electrolyte, and a separator, in which an active material mainly composed of metal oxides is held in a sponge-like metal porous body with an areal density of 200 to 400 g/m2. An alkaline storage battery, wherein the electrical resistance of the sponge-like metal porous body is 10×l/wmΩ or less in a test piece having a length of 1 mm and a width of w mm. 2. A sponge-like porous metal body is obtained by imparting electrical conductivity to a sponge-like organic polymer, electroplating with nickel, and burning off the polymer,
A method for producing an alkaline storage battery, wherein the method for imparting electrical conductivity is any one of a carbon coating method, a nickel vacuum deposition method, and a nickel chemical plating method.