JPS5819862A - Manufacture of electrode for lead storage battery - Google Patents

Abstract

PURPOSE:To enhance the utilization rate of an active material by packing a supporting body with both the active material and a powder, which is obtained by making a core powder in contact with a dispersion prepared by dispersing silicone into a disperse midium before the mixture is dried and crushed. CONSTITUTION:As an original solution, a cold-vulcanized silicone rubber emulsion containing a stabilized silicone rubber is prepared by using one kind of liquid. Next, the original solution is diluted with water,and a carbon powder obtained by carrying out 100-200 mesh sieving is kneaded into the diluted original solution. Next, the carbon powder moistened with the solution by stiring is dropped onto a high-speed rotary disk, and the carbon powder cores are dried while being separted. After that, thus obtained carbon powder is added to a paste prepared by kneading lead powder, sulfuric acid and water together, and the mixture paste is applied to a lead alloy grid before the grid coated with the mixture paste is dried, thereby making a pasted electrode. As a result, the diffusion path of electrolyte into the electrode body is secured due to the porous elastic particles excisting in the porous matter. Consequently, the utilization rate of the active material can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an electrode for a lead-acid battery, in which porous elastic particles are present in the porous body of the electrode to ensure a diffusion path for electrolyte into the electrode body. In addition to improving the utilization rate of the active material, the elasticity of the elastic particles absorbs the stress of expansion and contraction of the active material during charging and discharging, and the purpose is to ensure long-term stability of the active material structure. .

In the present invention, a silicone dispersion liquid in which silicone is dispersed in a dispersion medium is brought into contact with a core powder that remains solid in the dispersion medium, and the powder obtained by drying and pulverizing the core powder is combined with an active material. It is characterized by being filled into a support.

It goes without saying that improving the active material utilization rate of porous electrodes generally requires sufficient diffusion of the electrolyte into the porous body, but especially in lead-acid batteries, the sulfuric acid in the electrolyte is the active material. Therefore, the influence of diffusion is large, and there is a strong tendency for sudden discharge to occur.

From this perspective, in order to generally improve the utilization rate,
One method is to reduce the packing density of the active material, but in this method, the bonds between the active material particles are weakly 3 Beco, and the higher the porosity, the shorter the life. One way to compensate for this drawback is to mix a porous material such as 5102 or glass powder into the active material and fill it up apparently densely, but the active material undergoes a large volume change during charging and discharging. In terms of true specific gravity, the positive and negative active materials after charging and discharging are P.
b O22-5cc/4 Le #Pb 18,3cc
Since 1 mol of discharge products PbSO4 and 9cq 1 mol change by 1.93 times and 2.67 times, respectively, the distortion cannot be absorbed by mixing rigid particles, and the fine particles of the active material This results in the promotion of

゛The present invention aims to achieve the purpose of absorbing this strain by ensuring a path for liquid diffusion into the active material porous body and at the same time forming an elastic porous body instead of the above-mentioned rigid body. It is something to do. When we think of an elastic body, we simply think of rubber, but fine rubber particles alone are not useful for promoting the diffusion of electrolyte, and it is important to form a fine powder that is both porous and elastic. It's coming.

The present inventors have developed a dispersion liquid in which silicone is dispersed in a dispersion medium, and a powder serving as a core that maintains a solid state in the dispersion medium.
It has been found that a powder having an elastic porous silicone material that meets the above purpose can be easily obtained by contacting the silicone powder with the silicone powder and drying it.

To obtain such a powder, there is a method of first adding a catalyst for forming silicone rubber to an oil-based silicone, water-based emulsion, etc., and then removing it by drying to a long chain polymerization degree of 105 to 106. There are few cases in which the rubberization conditions match the stability of the powder, and the state of rubberization tends to be uneven. Therefore, a one-component emulsion such as a one-component cold-vulcanizable aqueous emulsion of silicone rubber stabilized by proceeding with a reaction to form a long-chain silicone rubber is suitable. In this case, there are no side reaction products,
Upon drying of the water, a highly porous and elastic polymeric layer of silicone forms over the mixed powder. Moreover, although the material generally has high water repellency, it has considerable permeability to liquids, and the degree of permeability can be selected by adjusting the liquid properties at the time of drying. For example, with NaOH, p
When the pH is higher than 14, the porous material has strong strength and is slightly swellable.At pH 14 or higher, the material exhibits strong elasticity although the swelling property is low, and at pH 1 or below, the elasticity and binding strength are slightly weak, but it shows strong elasticity. It exhibits properties suitable for dispersing liquids.

In this way, by forming a porous silicone layer on the powder core and using it together with the active material, it is possible to not only shape the path of the electrolyte in the resulting electrode, but also to form a porous layer of silicone on the powder core. It plays the role of absorbing the strain that occurs between particles due to volume changes during charging and discharging of the active material.

The reason why the silicone porous body is formed on the powder is that the object obtained by drying only water from a silicone emulsion etc. becomes a well-bound solid body, which cannot be powdered. This is because it is extremely difficult and at the same time does not result in an object that has wettability to the electrolyte, and a porous layer can only be formed by forming it on powder.

゛Furthermore, if silicone is brought into contact with the powder in a wet state, and the powder particles are layered as they are and dried, it will be easier to powder than when no powder is used, but even then, strong silicone bonds will form between the powder particles. The layers are connected, which tends to result in a powder with non-uniform particle size.

Therefore, in the present invention, it is preferable to further add the following means. That is, the wet particles are dried while being dispersed. This method is possible because a porous body of silicone is formed during the process of water dissipation, and in a wet state, the bonding force of silicone is equal to zero, and the particles can be easily dispersed. . The dry silicone layer obtained in this way does not dissolve in water again and can therefore be handled as a powder.

The simplest way to use the powder for the core is to use a material that is insoluble in water or an electrolyte, such as carbon or various organic polymers such as polyester. After forming the above silicone porous layer using powders of metals and compounds that remain stable but dissolve in strong acids and strong alkalis, or compounds that are solid in water but dissolve in organic substances, this core is When using the method of dissolving and removing the powder for the core, it is possible to obtain an elastic powder of porous silicone that is close to pure. Although it may be used, the powder obtained by drying and pulverizing is coated with a porous silicone material and has poor conductivity, so it mainly serves as a core material.

Now, the elastic porous body obtained in this way (including powders with the above-mentioned porous bodies formed on the particle surface) is mixed with commonly used lead or lead compound powder to form porous bodies of glass and plastics. It is mixed in powder form, filled, and constructed into a clad plate.

It is also possible to mix the above-mentioned materials with water or sulfuric acid into a kneaded mixture and apply this to a grid to form a paste-type electrode, or to fill a porous body of a cladding. Some of these finished electrode structures include n
There is a porous body with the strong elasticity of silicone and the permeability of the electrolyte, and even if the electrode is apparently completely filled,
It is clear that the electrolyte is introduced deep into the electrode, intervening between the active material particles, absorbing the strain caused by the volume change of the active material during charging and discharging, and maintaining excellent long-term stable characteristics. .

Hereinafter, the features and effects of the present invention will be described with reference to Examples.

Example 1 A one-component cold-curable silicone rubber emulsion containing 46% by weight of silicone rubber stabilized with a degree of polymerization of 104 to 106 as a stock solution.The emulsion was kept in a wet state while adjusting the pH to 14, and then rotated at high speed in a dry atmosphere. It was dropped onto a disc to separate and dry the carbon powder of the core. The obtained powder was added to a conventional paste made by mixing lead powder, sulfuric acid, and water in an amount of 6% by weight based on the amount of lead powder, and this mixture was made into a lead 9-7' alloy grid according to a conventional method. This electrode, which was coated and dried to obtain a paste electrode, is designated as A.

Example 2 In the same manner as in Example 1, 100 to 200 pieces of iron powder was used as a core material and brought into contact with a silicone rubber emulsion,
The dried powder was further immersed in hydrochloric acid several times to sufficiently dissolve the iron, then washed with water until no chlorine ions were detected, and dried to obtain a hollow porous elastic silicone porous body. This powder was added to a commonly used paste of lead powder, water, and sulfuric acid in an amount of 0.6% by weight based on the lead powder, and kneaded to prepare a pastera, and a paste electrode was constructed in the same manner. This electrode is designated as B.

Example 3 Soy was separated out of the mixed powder of Pb, Pbo, PbO2, Pb2O3, and 60 f of the silicone rubber emulsion stock solution of Example 1 was mixed with it, pre-dried to a wet state, and then dispersed. It was then mixed with the remaining lead powder. This mixture was filled into a commercially available cladding tube into which a connected lead alloy core bar was inserted to form a cladding electrode plate. This electrode is designated as C. In this case, the lead powder forming the silicone porous body has almost no conductivity.

In order to clarify the effects of the present invention, six positive electrodes filled with electrodes A and B to the same thickness were used, and a negative electrode was a commercially available electrode 6.
A battery with a nominal capacity of 36 Ah was constructed using the same electrode, and as a comparative example, a battery was constructed using electrode D in which carbon powder and silicone rubber were not used in Example 1, and electrode E in which only carbon powder was applied without applying the present invention. was constructed. These batteries were repeatedly charged and discharged by discharging them at a current of 1 OA for 1.5 hours and charging them at 4 A for 4 hours, and their capacities were checked every 20 cycles. The results are shown in FIG.

As is clear from this figure, the battery using the positive electrode to which the present invention is applied is superior in both capacity and life.

On the other hand, E had a higher capacity than D, but after a certain point the capacity suddenly decreased and the amount of debris increased. This suggests that the cause is that it does not have an elastic structure like the present invention.

Next, a clad plate F having the same total filling amount as C and a conventional composition was constructed, a battery of about aOAh was constructed, and the current-voltage characteristics were examined. In this case, the lifespan itself is long because it is a clad type, and the difference is difficult to notice, but the difference appears in the discharge characteristics.

An example of the discharge characteristics at 2OA is shown in Figure 2. In other words, the polarization is slightly reduced in the present invention, and the discharge capacity is
Although the amount of active material has actually decreased by about 5 inches, it has increased.

As described above, in the present invention, silicone's elasticity and porous structure help the electrolyte to diffuse into the electrode porous body, and also absorb the strain caused by the volume change of the active material during charging and discharging, making it stable. It is easy to understand that the same effect can be obtained not only with the positive electrode but also with the negative electrode.

Such effects of the present invention broadly improve the characteristics and stability of lead-acid batteries.

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Figure 11 Number of photodrinking Figure 12 290-

Claims (1)

[Claims] hl A step of bringing a silicone dispersion in which silicone is dispersed in a dispersion medium into contact with core powder that remains solid in the dispersion medium, then drying to remove the dispersion medium, and pulverization. A method for producing an electrode for a lead-acid battery, comprising a step of filling the obtained powder into a support together with an active material. (2) The method for producing an electrode for a lead-acid battery according to claim 1, wherein the silicone dispersion is a one-component room-temperature vulcanizable silicone rubber emulsion. (3) The method for producing an electrode for a lead-acid battery according to claim 1, wherein the drying step is performed while dispersing the core powder in a silicone dispersion. (4) The method for producing an electrode for a lead-acid battery according to claim 1, further comprising the step of eluting the core powder after the drying step.