JPS5945185B2 - Manufacturing method for electrodes for lead batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of lead-acid batteries, particularly paste-type electrodes, by stabilizing the characteristics of electrodes that apply a manufacturing method of kneading fluororesin dispersion into paste.
The purpose is to increase reliability.

Among the various manufacturing methods for electrodes for lead-acid batteries, the paste method still occupies the mainstream position because it is relatively easy to obtain high performance.

However, on the one hand, it has been said that there is a weakness in lifespan, and that it is particularly difficult to achieve both high capacity and long life, and that there is a limit to performance improvement. As one method for solving this problem, a method has been proposed in which a fluororesin dispersion is added to the paste. However, even though this fluororesin dispersion is used, various conditions such as the properties of the dispersion and the method of adding it are important factors in order to obtain high performance and long-life performance. examined these conditions in detail. The paste to which fluororesin dispersion is added takes advantage of the property that when the dispersion comes into contact with sulfuric acid acidity during kneading, the resin turns into fibers, which form a network-like fine structure. The properties of the paste are completely different from those of the paste whose main components are lead powder, sulfuric acid, and water without the addition of a fluororesin, and it becomes a rubber-like plastic material.

Therefore, the water content will also be much different. Even when applying the above-mentioned kneaded paste to cast gratings, forged gratings, perforated plates, expanded metal, etc., the situation is different from when applying conventional fluororesin-free pastes. It is not just a matter of mixing and applying.

In reality, when a paste prepared by kneading together the above-mentioned fluororesin dispersions is applied, excellent results can be obtained in terms of properties, but there are cases in which the properties vary considerably.

Such non-uniformity of characteristics is not only undesirable in terms of actual specifications, but also becomes a major obstacle in determining design conditions, and is extremely inconvenient industrially. The present invention aims to solve this problem of non-uniformity of properties under special conditions in which this fluororesin is kneaded into a paste without impairing its high performance characteristics.

Paste electrodes are generally made by kneading a paste with a desired composition and applying it to a previously applied lead or lead alloy current collector on cellulose cloth or plastic cloth. In some cases, it is possible to air dry it directly after painting.
Or is it possible to straighten the surface with a roller or the like and then air dry it? In some cases, it is possible to straighten the surface by applying a cloth to the surface and then air dry it, or even put it in a dryer without air drying. Once shaped, the gourd can be used as an unformed plate, or it can be used as an electrode after going through processes such as immersing it in dilute acid.

In any case, these processes include coating and a subsequent drying process, but in the present invention, among these processes, the important point for stabilizing the properties is the paste before the coating process. It was found that the change in density lies in the density change between the density and the density of the coating material held on the current collector before entering the drying process, and that the absolute value of the density before drying is also an important factor. It is based on this.

Specifically, the density of the applied material before drying is 0.1 g/Cc or more compared to the paste density before application, preferably 0.3 f.
! Conditions are required to change the value to a value higher than /Cc, and the density of the coated material before drying is 3.5f! Control over /Cc is essential for properties and stability. Although this result is obtained over a wide range of paste densities,
The paste itself is relatively harder and more elastic than normal fluororesin-free pastes, so it is necessary to take into account the difficulty of application. In terms of simultaneous improvement, the paste density before coating is 3.89/Cc or less, preferably 3.59/Cc or less.
It is preferable to apply Cc or lower. On the other hand, as a means of regulating the paste density before drying to the above density and further increasing the density from the density before filling, dehydration is carried out by pressing a cloth against the surface of the object after application. By adding this method, an excellent electrode with higher performance and higher reliability can be obtained.This means applies a paste with a density of 3.51/Cc or less, and the density before drying is 3.69/Cc. Remarkable effects can be obtained when controlling to Cc or higher. Here, the term "before application" refers to the range in which no new additives are added and the properties of the paste do not change significantly during the process from kneading to application. Also, pre-drying refers to the stage before starting the process for the purpose of drying.
1 to 1 after painting or roller straightening in the previous process
The moving processing time, which is approximately 2 minutes, refers to the stage before drying. Sampling can be performed during this time period, and the density can be inspected by removing the coated material from the current collector. Although the exact reason why the above conditions of the present invention are effective in improving performance and stabilizing characteristics is not known, it is thought to be approximately as follows. First, the paste obtained by kneading this fluororesin dispersion has significantly different properties than conventional pastes that do not contain fluororesin.

One is that water is much more inclusive;
One is that the intertwined skeleton of fibrous fluororesin produced during kneading has the property of retaining its shape.
The physical properties of the porous bodies to which these pastes are applied and dried are similar to those of wall soil, and are largely influenced by the state of distribution of particles and moisture before drying. In other words, the original shape of the porous body is almost limited before drying. Here, unless the active material particles are bonded stably to some extent, the properties and strength will be non-uniform. Pastes using fluororesin have good water inclusion properties and have little shrinkage due to water separation, so unlike conventional pastes, the active material particles come close to each other during the drying process and granulate secondary particles. few. Therefore, it is necessary to ensure the minimum necessary contact between particles at the stage before drying, and this seems to correspond to the result of specific gravity of 3.5 g/c°C or more. Next, regarding increasing the paste density during the application process, due to the good inclusion of this type of paste water and the presence of the resin skeleton, the application range is lower than that of conventional pastes. Shifts to the paste side.

In order to secure the desired amount of filling within the volume of two current collectors, such as a grid with a fixed thickness of rigid bodies, it is necessary to consciously release water during the filling process rather than with conventional pastes.
The lower the density of the paste, the more water needs to be removed, and the higher the density, the less water needs to be removed. It is necessary to remove the water between the particles protected by the resin skeleton 1 in a short period of time during coating, and to obtain a favorable state of closeness of the particles during coating. Since the resistance to deformation that reorganizes the bonds between comrades is not eliminated, it is necessary to extract as much moisture from all the macropores as possible to the outside as quickly as possible, which results in a change in density of 0.39/Cc or more. It seems that they will respond as follows. Next, the effect of pressing the cloth after coating and dehydrating it with a roller etc. is as follows.
This is especially true as this type of paste tends to have low density and good grass properties, with a much higher moisture content than conventional pastes, and conditions that make it more difficult to release.

However, conversely, high porosity means that the degree of contact between particles becomes significantly non-uniform, resulting in variations in properties and non-uniformity in life. The above-mentioned intention is to solve this problem without impairing this excellent property. Forms a dense layer. This should be done by removing the water that appears on the surface, rather than simply applying a roller to push the water out, and it is best to press the cloth to do this. By adding such a step, an excellent electrode having a highly reactive and highly porous interior layer and a strong, low-porosity layer on the surface can be obtained. 4 At this time, the effect is that the amount of water released is slightly larger, so the density of the applied coating before drying must be 3.69/Cc or higher.

Such conditions are particularly important for making the most of the characteristics when kneading the fluororesin dispersion into a paste. Hereinafter, the present invention will be explained with reference to examples thereof.

FIG. 1 is a schematic diagram showing an example of a filling device for paste electrodes for lead batteries. 1 is the filling part of the paste, -2 is the conveyor belt, 3 is its driving roller, 4 is the cloth belt, 5 is the dryer for the belt 4, 6 is the paste before application, 7 is the lead alloy grid, 8 is the paste application The lattice after installation, 9 is the electrode plate prototype corrected by pressing the cloth belt, and 10 is the Q holder.

Using the above apparatus, an electrode plate with a thickness of about 2 m1 was constructed.

ζζ paste is made by adding an appropriate amount of water and an aqueous dispersion of polytetrafluoroethylene (specific gravity 1.5) to 1 kg of lead powder.
Then, while adding 411 J (resin content: 60% by weight) and continuing kneading, 100 d of sulfuric acid having a specific gravity of 1.35 is added dropwise. The paste thus obtained can be left applied to the lead alloy grid, or after straightening with a cloth belt, it can be immersed in dilute sulfuric acid and then aged and dried. To make it easier to understand the effects of this, we will discuss here the case where drying is performed after coating, and the case where straightening drying is performed with a cloth belt after coating.
Drying was performed by air drying at room temperature for 12 to 24 hours. After drying, the electrodes were made in the usual manner, using 4 positive electrodes and 5 negative electrodes, with a nominal capacity of about 3.
Is it rare to configure a 0Ah battery? A container was formed by adding sulfuric acid.
In this case, electrodes were constructed by first changing various paste densities and the paste density conditions after applying the paste to the grid and before entering the drying process.

In order to change the paste density before drying in the blue coating process, we changed the mesh of the pine that is rotated by a roller under the grid during filling, the degree of drying, and the conditions for pressing the paste. In order to determine the degree of variation in characteristics caused by the combination of these various paste changes, we measured the discharge capacity at 0.1C for 20 cells at each measurement point, and calculated the percentage of cells that fell within 5q6 of the average value. Examined.

The results are shown in FIG. % in the figure indicates the percentage of cells falling within 5% of the average discharge capacity. As is clear from this result, when the paste density before drying is 3.5 g/Cc or more, the uniformity of properties increases, and when the difference from the paste before filling is 0.1 g/Cc, the density before drying is 3.5 g/Cc or more. .59
/Cc or above, 90% or more is 5% of the average value
At 0.3 g/Cc or more, 95 to 100% exhibit characteristics within 5q1) of the average value.

Next, when a cloth belt was applied, the relationship between the density before drying after straightening with the cloth belt and the density before painting was found in the same way, and similar results were obtained regarding uniformity, but
Especially focusing on high output characteristics and life characteristics, -15℃, 10
C discharge for 70 seconds or more, life at room temperature is 0.2C
The conditions are such that the life span is 400 cycles or more by repeating charging and discharging, discharging 60% of the discharge amount and charging 120% of the discharge amount, and 5% of the initial performance average value.
The range in which 90% or more of the characteristics can be concentrated within % was determined and shown in FIG. The paste before filling is less than 3.5g/Cc, and the coating density before drying is 3.69/Cc. It was necessary that it be at least c. Also, plotted in FIG. 2 (paste density before filling, coating density before drying) is A (3.0, 4.
0), C(3.0, 3.6), and B in Figure 3.
(3.0, 4.0) and D(3.0, 3.6) are shown in FIG. 4.

From the figure, it can be seen that the electrodes pressed with a cloth after applying the paste exhibit excellent life characteristics. As described above, the present invention focuses on the special properties of electrodes using fluororesin dispersion, improves the uniformity of characteristics without impairing the characteristics of using this paste, and establishes design conditions. The industrial value is extremely large.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram showing an example of a paste filling device;
Figure 2 is a diagram showing the relationship between paste density and non-defective rate in discharge capacity, Figure 3 is a diagram showing the relationship between paste density, high output characteristics, life characteristics, and non-defective rate, and Figure 4 is a diagram showing the relationship between repeat charge/discharge cycles. This shows the change in discharge capacity due to 1... Paste filling part, 4... Cloth belt, 6... Paste, 7... Grid,
8... Lattice after applying paste, 9...
Plate prototype.

Claims (1)

[Claims] 1. A paste-type electrode comprising a step of applying a paste containing at least lead powder, water, sulfuric acid, and fluororesin dispersion as main components to a current collector, and a drying step after the application work. is a manufacturing method, in which the density of the coating material held on the current collector before entering the drying process is made higher than the paste density before coating by pressing a dry cloth against the electrode plate after coating. 0
．． High density of 3g/cc or more, and 3.5g/cc
A method for producing an electrode for a lead-acid battery, characterized in that the electrode is made to have a density higher than or equal to the density. 2. The method for producing an electrode for a lead battery according to claim 1, wherein the paste density before coating is 3.5 g/cc or less.