JPH1145719A - Lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide good life performance without reducing the discharge capacity at the initial stage of charge/discharge, by forming a layer which contains lignin and carbon material absorbing the lignin on a surface of a negative electrode plate. SOLUTION: Negative electrode active material 2 on a surface of a negative electrode plate 1 contains lignin, and the lignin elutes into electrolyte from the electrode plate surface during formation of a battery jar or charge/discharge. Because the lignin in a layer 3 on the surface of the negative electrode plate 1 is absorbed into carbon material due to their mixing existence, the holding period of the lignin to the negative electrode plate 1 becomes longer, and the elution rate of the lignin from the layer 3 into electrolyte is moderated. Lignin elutes gradually from the negative electrode active material 2, but the layer 3 blocks elution passage and restrains elution of the lignin from the negative electrode active material 2. Because the layer 3 maintains its function even during charge/discharge cycle, it continues it effect all over the life period. Thickness of the layer 3 is 0.02-0.4 when the thickness of the negative electrode plate 1 before formation of the layer 3 is set to 1.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead storage battery.

[0002]

2. Description of the Related Art Generally, lignin made from pulp waste liquid is added to a negative electrode plate of a lead storage battery. Lignin is called an organic expander, and contacts the negative electrode active material to increase the surface area of the active material and increase the discharge capacity. Particularly, the effect is exhibited in high-rate discharge.
In the negative electrode plate manufacturing step, lignin is usually added to the negative electrode plate in the form of a powder. Lignin powder has the property of dissolving in dilute sulfuric acid as an electrolytic solution, and contacts the above-mentioned negative electrode active material in the dissolved state. Due to the above properties,
Lignin powder elutes from the negative electrode plate when exposed to the electrolyte for a long time. Then, naturally, the amount of lignin in the negative electrode plate decreases, and accordingly, the capacity of the negative electrode plate decreases, and the battery has a short life. For this reason, improvement of lignin has been conventionally attempted. Japanese Patent Laid-Open No. 8-287 discloses a method of processing lignin to be added in advance.
No. 904. In this method, a conventional powdered lignin is subjected to pressure processing to form a tablet, and the lignin obtained by crushing the tablet is used as an additive for a negative electrode plate. Since the ground lignin has a small specific surface area, the portion in contact with the electrolytic solution is reduced. Therefore, the lignin dissolution rate is reduced, and the life performance of the lead storage battery is improved.

[0003]

However, the pressure-milled lignin used in the above-mentioned prior art is not densely distributed in the negative electrode active material because of its larger particle size than the powder lignin that is not pressed. Therefore, there is a problem that a portion having a small amount of lignin is present in the cathode plate, and the initial battery performance has a lower discharge capacity than in the case of using conventional powdered lignin. The problem to be solved by the present invention is
An object of the present invention is to provide a lead-acid battery having excellent life performance without lowering the discharge capacity at the beginning of charge and discharge.

[0004]

Means for Solving the Problems To solve the above problems, a lead storage battery of the present invention is characterized in that a layer 3 in which lignin and a carbon material that adsorbs lignin are mixed is provided on the surface of a negative electrode plate 1. I do. The layer 3 present on the surface of the negative electrode plate may or may not include a part of the negative electrode active material 2. As the carbon material that adsorbs lignin, carbon black such as acetylene black, furnace black, and thermal black, graphite, and activated carbon can be suitably used. Negative electrode plate 1 of the present invention
1 is shown in FIG. 1 (a current collector portion is omitted).
The negative electrode active material 2 contains a predetermined amount of lignin, and the lignin is eluted from the surface of the electrode plate into the electrolytic solution during battery formation or cycle charge / discharge. At this time, the lignin in the layer 3 on the surface of the negative electrode plate is adsorbed on the carbon material by being mixed with the carbon material. For this reason, the retention time of lignin on the negative electrode plate is prolonged, and as a result, the rate of elution of lignin in layer 3 into the electrolytic solution becomes slow. Lignin is gradually eluted from the negative electrode active material 2, but the elution path is closed by the presence of the layer 3, and the elution of lignin from the negative electrode active material 2 can be suppressed as compared with the related art. In addition, since the layer 3 maintains its function during the charge / discharge cycle, the effect is maintained throughout the life. In addition, by providing the above configuration, the amount of lignin contacting the negative electrode active material from the initial charge / discharge stage is larger than in the case of using conventional pressure-processed lignin. Never.

[0005] As described above, by providing the structure of the present invention, it is possible to provide a lead-acid battery having excellent life performance without reducing the discharge capacity at the beginning of charge and discharge. In general, the high-rate discharge characteristics of a lead storage battery depend on the diffusion of the electrolyte on the surface of the negative electrode plate and the surface area of the negative electrode active material. By providing the structure of the present invention, the lignin amount of the negative electrode plate can be ensured, so that the surface area of the active material can be constantly increased as compared with the conventional case, and a lead storage battery excellent in high-rate discharge capacity can be provided. On the other hand, the amount of lignin eluted from the conventional negative electrode active material into the electrolytic solution was large in the surface layer portion of the negative electrode plate and small in the inside of the negative electrode plate, thereby providing a lead-acid battery having excellent life performance and high-rate discharge characteristics. Could not.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Lignin is dissolved in water while stirring to obtain a 30 wt% aqueous solution. Carbon black (acetylene black) of the same weight as the amount of lignin in this aqueous solution
Is added with stirring to obtain a dispersion. In this way, the carbon black mixed with lignin is dispersed in the aqueous solution and adsorbs lignin. Lead alloy lattice (current collector)
The above-described dispersion is applied to the surface of the negative electrode plate filled with a predetermined amount of conventional (non-pressurized) lignin powder-containing lead paste, and the mixture is subjected to known aging and drying, whereby lignin and carbon black are removed. An unformed negative electrode plate 1 provided with a mixed layer 3 is produced. At this time, the layer 3 exists on the surface of the negative electrode plate 1 and is in a state where a part of the negative electrode active material 2 is included. The average thickness of the layer 3 is 0.24 mm, while the average original thickness of the negative electrode plate 1 is 1.60 mm. That is, the thickness of the layer 3 is 0.15 with respect to the thickness when the thickness of the negative electrode plate before the formation of the layer 3 is 1. The state in which a part of the negative electrode active material 2 is included refers to a state in which the negative electrode active material powder is slightly shaved when the layer 3 is applied and a part of the powder is in the layer 3 or the negative electrode plate 1 This is a state in which the dispersion liquid has penetrated. In this example, both of them can be confirmed by observing the cross section of the negative electrode plate 1. The numerical values of the respective thicknesses are also numerical values measured by observing the cross section of the negative electrode plate 1.

Subsequently, the unformed negative electrode plate 1 is combined with a known unformed positive electrode plate via a separator, and
A D23 type 12V battery is manufactured. Dilute sulfuric acid is injected into the battery, and electricity is supplied to form a battery case. After the formation, the specific gravity of the diluted sulfuric acid was adjusted to 1.280 ± 0.005 (converted to 20 ° C.) to produce a lead storage battery. It should be noted that carbon black is hydrophilic or hydrophobic depending on the type of the functional group coordinated. Hydrophobic carbon black is difficult to disperse in water, so it seems to be difficult to use in the above manufacturing method,
Since lignin is both a surfactant and a dispersant, it can be easily dispersed in an aqueous solution and can be used in almost the same manner as hydrophilic carbon black. Carbon black having hydrophilicity and a large specific surface area, such as so-called Ketjen black, can also be preferably used. The dispersion of lignin and carbon black thus produced is a slurry having fluidity.

In this embodiment, a so-called liquid type lead storage battery is described, but the present invention is not limited to this. However, as the amount of free electrolyte increases, the elution of lignin increases. Therefore, it is considered that applying the present invention to a liquid type lead-acid battery has a greater effect than applying the present invention to a lead-acid battery having substantially no free electrolyte. In this example, a method of applying a dispersion of carbon black (acetylene black) and lignin to the negative electrode plate was used. However, in order to provide the layer 3, an acid-resistant sheet or a porous film was impregnated with the dispersion. Alternatively, the carbon fiber sheet may be impregnated with a lignin aqueous solution, and these may be disposed in close contact with the surface of the negative electrode plate 1.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Lead-acid battery (battery A) according to the embodiment of the present invention
And pressurized lignin disclosed in Japanese Patent Application Laid-Open No. 8-287904 were added to the negative electrode active material paste in the same amount as the conventional lignin in Battery A, and the same method as in Battery A was used except that the layer 3 was not provided. (Battery B) was manufactured. Further, a lead storage battery (battery C) was produced by the same method as that for battery A except that the layer 3 was not provided. Hereinafter, results of a comparative study of the batteries A to C are shown.

(Experiment 1) A comparative experiment on the elution of lignin was carried out. Lignin was eluted during the formation of the battery tank, so the distribution after the formation was compared. First, the batteries A to C are disassembled after forming the battery case, and the negative electrode plate is washed with water and dried. The electrode plate is buried in resin, cut and polished to prepare a sample whose cross section can be observed. Since lignin contains a large amount of sodium, using this as an index of lignin distribution, the sodium distribution in the electrode plate cross-sectional direction was measured with an X-ray microanalyzer. The results are shown in FIG. In each of the batteries B and C, the amount of lignin in the surface layer of the electrode plate is smaller than that in the electrode plate. Battery B has a larger total lignin amount than battery C, but has less lignin on the surface of the electrode plate and is considered to be eluted during chemical formation. On the other hand, the battery A of the present invention
It can be seen that the amount of lignin eluted from the surface layer is reduced due to the presence of the lignin.

(Experiment 2) Batteries A to C were converted to JIS D5
It was subjected to a light load life test specified in 301. This test result was calculated by comparing the number of charge / discharge cycles by 3
FIG. 3 shows the relationship between the 0-second voltage. Battery B to which pressurized lignin was added had a longer life cycle number than Battery C, but the discharge voltage at the beginning of the cycle (proportional to capacity)
Is low. On the other hand, it can be seen that the battery A of the present invention has a higher discharge voltage than the batteries B and C and improves the life performance even under such a high-rate discharge condition.

(Experiment 3) Next, in the battery A, a lead-acid battery was separately manufactured by the same method by changing the thickness of the layer 3 in which lignin and carbon black were mixed, and they were compared and examined. The thickness of the layer 3 is set such that the thickness of the negative electrode plate before the formation of the layer 3 is 1
It will be shown as a relative value when The thickness of the layer 3 is 0.01, 0.02, 0.05, 0.08, 0.10,
0.15, 0.20, 0.24, 0.30, 0.35,
The batteries of 0.40 and 0.45 were subjected to a light load life test, and the relationship between the ratio of the thickness and the number of cycles leading to the life was examined. FIG.
It can be seen from the results shown in FIG. 3 that the existence of the layer 3 extends the life as compared with the conventional battery C. In particular, when the thickness of the layer 3 is 0.02 to 0.4, more preferably 0.1 to 0.
When it is 3, it turns out that it is good. For this reason,
When the thickness ratio is smaller than 0.02, it is insufficient to suppress the elution of lignin from the surface layer of the negative electrode plate, and when the thickness ratio is larger than 0.4, the layer 3 is formed of an electrolytic solution. It is conceivable that they hinder the movement of the metal and hinder the battery reaction.

From the above results, it can be seen that the present invention was able to provide a lead-acid battery having excellent life performance without reducing the discharge capacity at the beginning of charge and discharge.

In the battery A, carbon black was used as the carbon material. However, even when graphite or activated carbon was used as the carbon material for adsorbing lignin, the same effect as that of the battery A was obtained.

[0015]

According to the present invention, it is possible to provide a lead-acid battery which is excellent in life performance without lowering the discharge capacity at the initial stage of charge and discharge, and is also excellent in high-rate discharge capacity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a negative electrode plate of the present invention.

FIG. 2 is a diagram showing a lignin distribution in a cross section of a negative electrode plate after chemical conversion.

FIG. 3 is a diagram showing a light load life test result.

FIG. 4 is a diagram showing the relationship between the number of cycles to life and the relative thickness of a layer in which lignin and carbon black are mixed, where the thickness of the negative electrode plate before forming a layer is 1;

[Explanation of symbols]

 1. Negative electrode plate 2. Negative electrode active material 3. layer

Claims (2)

[Claims] 1. A lead-acid battery using a negative electrode plate in which lignin is present in the negative electrode plate, wherein the surface of the negative electrode plate has a layer on which lignin and a carbon material that adsorbs the lignin are mixed. Storage battery. 2. The thickness of the negative electrode plate before formation of the layer is 1
The lead-acid battery according to claim 1, wherein the thickness is 0.02 to 0.4 with respect to the thickness.