JP2950935B2 - Alkaline storage battery - Google Patents

Description

The present invention relates to an alkaline storage battery provided with a negative electrode using cadmium as an active material and a separator using polyolefin resin fibers.

(B) Conventional technology Conventionally, for example, a nylon nonwoven fabric has been often used as a separator for a nickel-cadmium storage battery. This is because the nylon nonwoven fabric has appropriate strength, gas permeability and hydrophilicity.

However, it is difficult to say that nylon itself has sufficient alkali resistance and oxidation resistance, especially at high temperatures of 45 ° C. or higher, and carbonates and ammonia which decompose relatively easily and adversely affect battery performance. Generate. Further, as the decomposition proceeds, the insulating ability as a separator decreases, and eventually, a short circuit inside the battery is caused.

In order to solve this problem, attempts have been made to change the material of the separator to a polyolefin-based resin, and a polypropylene non-woven fabric has come to be used especially for batteries used at high temperatures. Polypropylene nonwoven fabrics are excellent in alkali resistance and oxidation resistance, and have the same strength and gas permeability as nylon nonwoven fabrics. However, since the material itself has poor hydrophilicity, it lacks the ability to hold an electrolytic solution. For this reason, the battery using the polypropylene nonwoven fabric has a drawback in that the so-called dry-out of the electrolytic solution in the separator occurs earlier than the nylon nonwoven fabric as the charge / discharge cycle progresses.

Attempts have been made to use fine fibers or fibers with irregular cross-sections as the fibers constituting the nonwoven fabric in order to improve the electrolytic solution holding capacity of the polypropylene nonwoven fabric, but the effect is not sufficient. Further, it has been proposed to graft polymerize a hydrophilic group by irradiation of radiation or the like, or to improve the hydrophilicity of the separator by sulfonation treatment, but there is a problem that the effect cannot be maintained for a long time.

On the other hand, Japanese Patent Application Laid-Open No. Sho 60-109171 proposes imparting hydrophilicity to a polypropylene separator by reacting with a reactive gas containing fluorine. Hydrophilicity can be maintained. However, this method is not without its problems, and batteries using a separator treated with fluorine gas are:
At a relatively early stage of the charge / discharge cycle, the discharge performance of the cadmium negative electrode deteriorates, whereby the battery becomes the dominant negative electrode,
There is a problem that the capacity is significantly reduced.

(C) Problems to be Solved by the Invention The present invention solves the problem that when a separator treated with a fluorine gas is used in a battery together with a positive electrode and a cadmium negative electrode, the leaving performance of the cadmium negative electrode is reduced. Another object of the present invention is to provide an alkaline storage battery that can make use of the effect of imparting hydrophilicity by fluorine gas treatment.

(D) Means for Solving the Problems The alkaline storage battery of the present invention includes a positive electrode, a cadmium negative electrode to which polyvinylpyrrolidone is added, and a separator using a polyolefin-based resin fiber that has been contacted and reacted with a reaction gas containing fluorine. It is characterized by having.

(E) Operation Generally, when a fiber is spun, the fiber is treated with a surfactant called an oil agent for the purpose of preventing static electricity. As for the separator produced using the fiber treated with the surfactant as described above, the surfactant is present on the fiber surface unless the treatment such as washing with water is performed.

It is known that the above-mentioned surfactant generally has a function of suppressing a decrease in discharge performance accompanying a charge / discharge cycle of a cadmium negative electrode, that is, a function of suppressing aggregation and accumulation of non-dischargeable metal cadmium. However, it is considered that the effect of suppressing a decrease in the discharge performance of the cadmium negative electrode is lost because the surfactant on the fiber surface of the separator treated with fluorine gas is decomposed when treated with fluorine gas.

Therefore, based on the idea that if a substance having the same effect as a surfactant is added to the battery, the problem will be solved, as a result of examining various addition methods, by adding polyvinylpyrrolidone to the cadmium negative electrode, It has been found that an effect equivalent to that of a surfactant can be obtained.

That is, the action of polyvinylpyrrolidone can suppress a decrease in the discharge performance of the cadmium negative electrode, and can provide an alkaline storage battery having extremely excellent cycle characteristics due to a synergistic effect with imparting hydrophilicity to the separator by fluorine gas treatment. .

(F) Example [Example] A known polypropylene fiber having a fiber diameter of about 1.0 to 1.5 denier and an ES fiber (manufactured by Chisso Corporation), which is a polyethylene-polypropylene conjugate fiber of about 1.0 denier, as an adhesive fiber. The mixture was uniformly mixed at a weight ratio of 1: 1 and then heated and melted to produce a nonwoven fabric having a basis weight of 80 g / m ² and a thickness of 0.20 mm. After the nonwoven fabric was placed in a reaction vessel made of iron and evacuated, a reaction gas obtained by diluting fluorine gas with nitrogen gas was introduced into the vessel until it reached atmospheric pressure, and reacted for a certain time.

On the other hand, a known sintered cadmium negative electrode plate obtained by repeating a predetermined number of active material filling operations of impregnating a nickel sintering substrate with a cadmium nitrate solution, drying and then performing an alkali treatment is used for about 2 times. After being immersed in an aqueous solution of polyvinylpyrrolidone by weight, it was dried.

The separator, a known sintered nickel positive plate,
Wound with the cadmium negative electrode plate, nominal capacity 1.2AH
A sealed nickel-cadmium storage battery A (product of the present invention) of SC size was manufactured.

Comparative Example 1 An SC-size sealed nickel-cadmium storage battery with a nominal capacity of 1.2 AH was prepared in the same manner as in Example 1 except that the steps of dipping and drying the sintered cadmium negative electrode plate in an aqueous solution of polyvinylpyrrolidone were omitted. B was prepared.

[Comparative Example 2] The same procedure as in Example 1 except that the polyethylene nonwoven fabric was used without being treated with fluorine gas, and that the steps of immersing the sintered cadmium negative electrode plate in an aqueous solution of polyvinylpyrrolidone and drying were omitted. Similarly, nominal capacity 1.
2AH SC size sealed nickel-cadmium storage battery C
Was prepared.

[Experiment] After the batteries A to C were charged at 25 ° C. with a current of 1.8 A (1.5 C) for 1 hour, a voltage of 1.0 V was continuously applied at a current of 1.2 A (1 C).
The battery was subjected to a cycle test under the condition that the battery was discharged. FIG. 1 is a drawing showing the number of cycles and the capacity ratio to the initial capacity of the battery at this time.

From this drawing, the battery A of the present invention has a smaller decrease in battery capacity with the progress of the cycle number than the comparative batteries B and C,
It can be seen that the cycle characteristics were extremely excellent.

In Comparative Battery B, since the separator was treated with fluorine gas, cycle deterioration due to dryout could be prevented, and the cycle life was long, but due to the decomposition of the surfactant on the fiber surface during fluorine gas treatment, The discharge performance of the cadmium negative electrode plate has decreased, and the capacity decrease in the initial stage of the cycle has increased. Conversely, in Comparative Battery C, although the capacity decrease at the initial stage of the cycle was small due to the effect of the surfactant originally present on the fiber surface, the result was that the cycle life was shortened by dryout due to the poor hydrophilicity of the separator. It has become.

On the other hand, the battery A of the present invention has a longer life due to dryout by imparting hydrophilicity to the separator by the fluorine gas treatment, and also has a decrease in the discharge performance of the cadmium negative electrode due to the decomposition of the surfactant during the gas treatment. Since the problem is compensated for by the addition of polyvinylpyrrolidone in the negative electrode, there is almost no decrease in capacity at the initial stage of the cycle, and extremely excellent cycle characteristics are exhibited.

(G) Effects of the Invention The alkaline storage battery of the present invention includes a separator using a fiber obtained by contacting a polyolefin-based resin fiber with a reactive gas containing fluorine, and a cadmium negative electrode to which polyvinylpyrrolidone is added. Therefore, even if the separator's electrolyte retention capacity is improved and the decomposition of the surfactant of the separator occurs during the fluorine gas treatment, the discharge performance of the cadmium anode in the initial stage of the cycle can be improved by adding polyvinylpyrrolidone to the cadmium anode. Can be prevented from deteriorating and exhibit extremely excellent cycle characteristics.

In this embodiment, a nonwoven fabric made of a mixed fiber of polypropylene and polyethylene has been described as an example. However, similar effects can be expected with a polyolefin resin.

[Brief description of the drawings]

FIG. 1 is a cycle characteristic diagram of the battery of the present invention and the comparative battery. A: battery of the present invention, B, C: comparative battery.

Claims (1)

(57) [Claims] An alkaline storage battery comprising: a positive electrode; a cadmium negative electrode to which polyvinylpyrrolidone is added; and a separator using a polyolefin-based resin fiber that has been contacted and reacted with a fluorine-containing reaction gas.