JPH0118546B2 - - Google Patents

Description

[Detailed description of the invention]

Methods for filling active materials in sintered anode plates for alkaline storage batteries include electrolysis, which involves vacuum impregnation with a nickel salt solution and then electrolysis in an alkaline solution, and immersion in a nickel salt solution, drying, and then immersion in an alkaline solution. There are chemical impregnation methods that use nickel hydroxide.
Both methods have the drawback of requiring a large amount of time and man-hours because several steps are combined and repeated. There is also an electrodeposition filling method in which a sintered porous substrate is immersed in nickel salt and hydroxide is deposited by negative electrolysis, but mass production is difficult because electrolysis requires a lot of electrical energy and requires complicated equipment. The disadvantage was that the capital investment would be large. Apart from these methods, there is a thermal decomposition method in which a sintered porous substrate is immersed in nickel salt and then thermally decomposed in steam to convert most of the nickel into nickel hydroxide, which has the advantage of being manufactured at low cost through a simple process. However, there is a drawback that if the immersion decomposition process is repeated to a certain extent, it cannot be filled beyond a certain limit. The present invention relates to improvements in this pyrolytic filling method. The reason why the nickel active material cannot be filled above the limit value in the thermal decomposition filling method is that the product of decomposition is a solid solution or mixture of nickel hydroxide and nickel salt, and the volume of this unreacted nickel salt is larger than the active material. The reason is that the volume is larger than that of nickel hydroxide. In the present invention, this unreacted nickel salt is immersed in an alkaline aqueous solution such as NaOH or KOH during repeated immersion pyrolysis to convert it to almost 100% nickel hydroxide, and the alkali content is removed by washing with water and drying. , promotes a reduction in the filling volume due to the change from nickel salt to nickel hydroxide,
The purpose of the present invention is to create residual voids in the sintered porous body and repeat immersion pyrolysis filling of nickel salt into the voids to obtain a high capacity density anode plate for an alkaline storage battery. Another method is to charge and discharge the thermal decomposition product in an alkaline solution to convert it into nickel hydroxide, but this requires a lot of electrical energy and the process is complicated. Alkaline solution immersion alone is sufficient for volume reduction. Experimental results according to examples of the present invention and conventional methods will be described below. The porosity obtained by applying paste-like nickel powder to a porous thin plate made of iron nickel metal and sintering it after drying.
A process of cutting a porous sintered substrate with a thickness of 80% and approximately 1 mm into 100 mm pieces both vertically and horizontally, leaving current collecting ears, and immersing this substrate in an aqueous nickel nitrate solution, pre-drying it, and thermally decomposing it in a steam atmosphere. After repeating 6 times,
It was immersed in a NaOH aqueous solution with a concentration of about 20%, washed with water, and dried, and then subjected to the above-described pyrolysis filling six times, and then combined with a separately prepared dummy electrode plate in NaOH with a concentration of about 10% and chemically formed to form an anode plate. Created. A nickel porous substrate made with the same recipe and the same dimensions was immersed in a nickel nitrate aqueous solution using the conventional method, pre-dried, and then thermally decomposed 12 times in the same manner.
It was formed into an anode plate in NaOH. A for the former
When compared with the latter as B, the packing density of nickel hydroxide after chemical formation was as shown in the following table.

[Table] The anode plates of A and B were combined with a cadmium cathode plate with a larger capacity than both samples prepared separately via a separator, and placed in a synthetic resin container with a specific gravity of 1.20.
Inject a KOH aqueous solution (calculated at 20℃) as an electrolyte.
The battery was charged with a current of 0.8A for 20 hours, then left to stand for about 1 hour, and then discharged with a current of 0.8A. The outside temperature during this charging and discharging was 20 to 25°C. As a result, the discharge duration to 1.0V for both A and B is 4.53Ah in 5 hours and 40 minutes for A and 4.53Ah for B in 4 hours and 31 minutes, as shown in the figure.
It was 3.61Ah per minute. In addition, in this experiment, after repeating pyrolysis filling six times, a process of immersion in an alkaline solution, washing with water, and drying was performed.
After that, pyrolytic filling was repeated 6 more times, but in another experiment, pyrolytic filling was performed 12 times as before, then immersed in an alkaline solution and dried, and pyrolytic filling was performed 3 more times, resulting in nickel hydroxide. Almost the same packing density was obtained, and the discharge capacity after formation under the same conditions was 4.45 Ah. As described above, the present invention is a simple method and is an excellent manufacturing method that can produce an anode plate with a high capacity density equivalent to or higher than that of electrolysis or the like.

[Brief explanation of drawings]

The figure shows the discharge characteristic curves of the anode plate according to the present invention and the anode plate prepared by the conventional pyrolysis method.

Claims (1)

[Claims] 1 In an anode active material filling method in which a sintered porous metal substrate mainly composed of nickel powder is immersed in a nickel salt solution, and then thermally decomposed in a steam atmosphere to form nickel hydroxide, the process is repeated. A method for producing an anode plate for an alkaline storage battery, which comprises immersing it in an alkaline solution, washing and drying it with water, immersing it again in a nickel salt solution, repeating thermal decomposition, and then charging and discharging in an aqueous alkaline solution.