JPS61203569A - Pasted negative plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To increase the energy density of the pasted negative plate of an alkaline storage battery and enable rapid charging of the battery by packing a given woven carbon fiber cloth or similar material with a paste prepared by mixing a powder mixture of cadmium oxide and the like with a solvent such as ethylene glycol and an ionic macromolecular compound. CONSTITUTION:A powdery mixture of cadmium oxide, metallic cadmium, nickel, etc. is mixed with a solvent such as ethylene glycol or isopropyl alcohol and at least one ionic macromolecular compound soluble in this solvent to prepare a paste. Next, after a woven or nonwoven cloth of carbon fibers with diameter of 4-100mu is immersed in the paste and continuously passed through it, the impregnated cloth is partially dried in a dryer maintained at a given temperature. Following that, the thickness of the partially dried cloth is adjusted to a given level and then a hot air dryer is used to remove the solvent such as ethylene glycol prior to cutting the cloth into given dimensions.

Description

[Detailed description of the invention] #Business field of use The present invention relates to a negative electrode plate for an alkaline storage battery.

In the prior art, sintered type and paste type electrode plates are generally known as negative electrode plates for point alkaline storage batteries.

However, the sintered electrode plate is made by sintering carbonyl niranal powder onto a perforated copper plate core, and the porosity that provides practical strength is limited to about 80%. In addition, since this sintered body consists of micropores of more than ten microns, it is impossible to directly fill the active material powder, so cadmium ions are formed in a nitric-acid or sulfuric acid-containing water solution, and then finely dispersed. After impregnating the pores, it is converted into the active material cadmium hydroxide in an alkaline aqueous solution. It cannot be filled without using the so-called solution impregnation method. This process is very complicated, and since the electrode plate has a core metal with low porosity, the ratio of the active material to the weight of the electrode plate is about 60 times.

In order to improve this drawback, a high-performance paste-type negative electrode plate is desired.

Conventional cadmium oxide, nickel powder, short fibers, etc. are replaced with P,
There is a paste-type negative electrode plate which is made by kneading a paste with an aqueous solution containing V and A thickeners and applying the paste to a core made of a nickel-plated perforated plate.

In this electrode plate, since the active material is held on the core metal only by organic polymers such as P, V, A, and short fibers, the active material falls off due to gutting during bonding or chemical formation. Furthermore, since there is a considerable distance from the core metal to the surface active material particles, the oxygen gas absorption rate during rapid charging is reduced.
It could only be used for relatively low rate charging. However, the active material ratio per electrode plate amount is 70 to 80%, which is improved compared to the sintered electrode plate.

In recent years, there has been a desire to develop negative electrode plates that are inexpensive, have high energy density, and are capable of rapid charging.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a negative electrode plate that has high energy density and can be rapidly charged.

Structure of the Invention In order to achieve the above object, the present invention has a fiber diameter of 4 to 100.
A mixed powder of cadmium oxide, metal cadmium, Nial, etc. is added to a carbon fiber woven or non-woven fabric made of microfibers in a solvent such as ethylene glycol, glycerin or isopropyl alcohol, and an ionic polymer that can be dissolved in this solvent is added to the carbon fiber woven or non-woven fabric. This is a paste-type negative electrode plate for alkaline storage batteries that is filled in a paste form with one or more seeds.

Example An embodiment of the present invention will be described in detail below.

Cadmium oxide 50-7 rwt%, metal cadmium 20
While thoroughly mixing ~40wt% and 5~10wt% of nickel powder, add 15~25wt% of ethylene glycol, glycerin, or isopropyl alcohol to which a small amount of carboxymethyl cellulose, starch, lignin, or surfactant, etc. has been added. It was made into a paste.

Fiber diameter 30μ, length 80pH, thick skin 9m.

A carbon fiber nonwoven fabric with a width of 50 strips and a porosity of 98% was immersed in this paste solution and passed through it continuously. The active material was filled by infiltrating the paste into the porous body of the fibrous nonwoven fabric.

Thereafter, it was partially dried in a dryer equipped with an infrared lamp adjusted so that the temperature near the surface of the electrode plate was 60 to 80°C.

Next, it was adjusted to a predetermined thickness using a roller press.

The thickness-adjusted electrode plate was passed through a hot air dryer at a temperature of 190°C to completely remove the solvent such as ethylene glycol or isopropyl alcohol, and then cut into a size suitable for the battery size. In this electrode plate, the weight ratio of the active material to the weight of the negative electrode plate was 85 to 90%.

This negative electrode plate, a sintered positive electrode plate in a fully discharged state, and a separator made of polypropylene nonwoven fabric are rolled up.
Insert it into the battery. ′! An aqueous potassium hydroxide solution was injected as the t# solution, and the container was sealed. After sealing, the battery was left for day and night to develop affinity with the electrolyte.

The battery thus prepared was a sealed nickel-cadm battery of AA size and a nominal capacity of 700 #lAh.

In the same size using a conventional sintered negative electrode plate, the nominal capacity was 500 mAh. After charging these batteries for 1.5 hours at room temperature 1.0, the final voltage of 1.5 hours was reached. oov
The energy density (Ah/&g) was measured.

The battery of the present invention has an energy density of 33 μh/#,
The battery according to the conventional method had a power consumption of 22 Ah/.

The metal cadmium used in the present invention forms the discharge reserve required to limit the positive electrode capacity of ordinary sealed nickel cadmium, and the appropriate amount was about 30%.

Ionic polymers such as carboxymethyl cellulose, starch, lignin sulfonic acid, or surfactants improve the utilization rate of active materials, and when a few dabs were added per cell, the utilization rate increased by about 70%. Admitted.

Normally, when carbon fibers are used in an alkaline solution, they are coated with nickel plating or the like, but the carbon fibers of the present invention do not generate harmful carbonate radicals even when charged and discharged without plating. Ta.

When carbon fiber is used as a positive electrode conductive material, a large amount of carbonate radicals are generated due to oxidative decomposition due to active oxygen generated at the end of charging.

However, in the case of the present invention, since it is used for the negative electrode plate, oxygen is not generated during charging. In the negative electrode plate, hydrogen at the end of charging may decompose OH4, etc. However, since the present invention is applied to a sealed nickel cadmium battery, the negative electrode plate has a charge reserve, which is called a charge reserve, and one positive electrode plate is fully charged. Since it still has extra cadmium hydroxide,
No hydrogen is generated.

When carbon fiber was used as the conductive material, the negative electrode active material utilization rate was approximately 40%, which was inferior to approximately 65% for sintered electrode plates, but by incorporating an anionic polymer into the paste liquid. In this case, the active material utilization rate improved to 68%, which was equal to or higher than that of the sintered electrode plate.

The thinner the carbon fibers used, the better the high rate discharge characteristics, but in consideration of cost or tensile strength of the fibers, it is practically desirable that the carbon fibers be about 4 to 100 microns.

Effects of the Invention As mentioned above, the paste-type negative electrode plate for alkaline storage batteries according to the present invention has high energy density and is capable of rapid charging, and can provide an inexpensive electrode plate with excellent productivity, and its industrial value is extremely high. It's large.

Claims (2)

[Claims] (1) Mixed powders of cadmium oxide, metal cadmium, nickel, etc. are added to a carbon fiber woven or nonwoven fabric made of fibers with a fiber diameter of 4 to 100 μm, and a solvent such as ethylene glycol, glycerin, or isopropyl alcohol, and an ionic polymer. A paste type negative electrode plate for an alkaline storage battery, characterized in that it is filled in a paste form with one or more types. (2) The ionic polymer is carboxymethyl cellulose,
The paste-type negative electrode plate for an alkaline storage battery according to claim 1, which is made of starch, lignin sulfonic acid, surfactant, etc.