JPH03203158A - Lead-acid battery - Google Patents

Abstract

PURPOSE:To enhance formation efficiency and to lengthen life by using a positive plate containing conductive fibers made of lead or carbon and also using a conductive mat on the surface in contact with the positive plate. CONSTITUTION:A carbon fiber layer 3 is positioned on the side in contact with a positive plate of a glass mat 2 and a separator 1 is attached to the glass mat 2. Carbon fibers each having a specified diameter are entangled and stacked on a 0.8mm thick glass mat, for example, and they are compressed so as to have the total thickness of 1.0mm, then the separator 1 made of reinforced fibers is sticked thereon. A positive plate is formed in such a way that carbon fibers are added to lead powder, and they are kneaded with dilute sulfuric acid to prepare active material paste, then the paste is filled in a lead alloy grid. Part of formation current is used for the formation of an active material near the grid and the residual current reaches the surface of the positive plate from the grid through the carbon fibers 3 and is used for the formation of the positive through the mat or a conductive porous sheet. Formation is advanced through the both passages and its efficiency is enhanced. The formation is conducted by small amount of electricity in a short time and the life of a battery is equal to or longer than ordinary batteries.

Description

[Detailed description of the invention] Industrial applications The present invention relates to lead acid batteries.

Conventional unformed electrode plates for lead batteries are generally made by applying lead paste (lead powder kneaded with dilute sulfuric acid) to a lattice made of lead alloy, followed by aging and drying steps. At this time, lignin and barium sulfate are added to the cathode lead paste as an antishrink agent. Lignin is an important additive for maintaining the performance of the cathode for a long period of time, but since it is difficult to undergo chemical conversion, carbon black such as acetylene black is also generally added at the same time.

On the other hand, in most cases, nothing is added to the lead paste for anode except for fibers to prevent the active material from falling off.

The above-mentioned unformed electrode plate is generally processed for one or two days.
It is chemically formed using a sufficient amount of electricity.

If an attempt is made to chemically form the anode in a short period of time for the purpose of reducing costs, the chemical formation of the anode will be insufficient, and unformed lead sulfate may remain in the active material, or white lead sulfate may appear on the surface of the anode plate. A large amount remains. In particular, the latter phenomenon develops into a significant appearance defect. As a means to prevent these phenomena, the addition of carbon black such as acetylene black, carbon fiber, or red lead to the lead paste for an anode has been considered. All of these additives are intended to form an electronically conductive network other than the lattice in the paste, thereby increasing the chemical conversion efficiency. Carbon black and other carbon fibers are selected as acid- and oxidation-resistant, electronically conductive materials, and red lead produces lead dioxide through a chemical reaction with dilute sulfuric acid, which is a chemical liquid, and this creates electrons in the paste. It will give conductivity. For example, the addition of carbon fiber is described in Japanese Patent Publication No. 38-14425.

Problems to be Solved by the Invention The method of adding powder such as carbon or red lead to the anode active material is such that the additive is uniformly dispersed in the anode active material, thereby increasing the bonding strength of the active material, that is, lead dioxide crystals. This has the disadvantage that the life performance is reduced because it weakens the crystal particles and promotes the shedding of crystal particles due to charging and discharging.

On the other hand, in the method of adding carbon fiber, the fiber diameter is several μm.
The particle size of carbon powder, for example, acetylene black, is several hundreds of micrometers, which is much larger than the several hundred amps. Therefore, in order to make the chemical conversion efficiency the same as that of carbon-added batteries, the amount of addition must be increased, and the active material in the lattice must be increased. The disadvantage is that troubles occur frequently in the filling process and the life performance is reduced.

The present invention aims to improve the chemical formation efficiency of the electrode plate, particularly the anode, without causing such a decrease in battery life performance.

Means to solve the problem: Either attach a conductive mantle to the anode plate to which a small amount of fibrous material such as lead, lead alloy, carbon, etc. is added so as not to affect the life performance of the anode plate, or Alternatively, a porous sheet mainly made of a conductive material such as lead, lead alloy, carbon, etc. is arranged between the anode plate and the glass mat or separator.

According to the present invention, since the anode active material contains a conductive fibrous material made of lead, lead alloy, or carbon, a part of the formation current is consumed for formation of the active material near the lattice. The rest passes from the lattice through the conductive fibrous material to the anode plate surface, and then through the conductive part of the mat that is in contact with it, or the conductive porous sheet.
Chemically convert the surface of the anode plate. That is, since chemical formation proceeds simultaneously from the vicinity of the lattice and the surface of the electrode plate, the chemical formation efficiency is improved.

As mentioned above, the conductive fibrous material such as carbon contained in the anode active material ensures electrical continuity between the grid and the surface of the electrode plate, so it is contained in a small amount that does not adversely affect the life performance. Even so, it is quite effective.

Examples Example 1 5 - Figure 1 shows a glass mat 2 in which a carbon fiber layer 3 is provided on the side of the glass mat that is in contact with the anode plate, which is a component of the present invention.
FIG. The carbon fibers 1i3 can be manufactured, for example, by interlacing and stacking carbon fibers in the same manner as in the manufacturing method of ordinary glass mats. It can also be manufactured by a papermaking method or the like.

In the case of this example, carbon fibers with a fiber diameter of 10 to 20 μm are stacked and stacked on a glass mat 2 with a thickness of 0.8 mm. /dr7! (The thickness of the carbon fiber layer and glass mat are all 1o19/di.
The total thickness is 1. On+n+, and a 0.25 mm separator 1 mainly made of reinforcing fibers was bonded thereto.

On the other hand, the anode plate is made by adding 0.05% carbon fiber with a diameter of about 10 μm and a length of about 1 mm to the lead powder, kneading this with dilute sulfuric acid in the usual manner, and using the resulting paste with a lead alloy grid. After filling the plate, the electrode plate is manufactured through the normal electrode plate manufacturing process.

In addition, as a result of various studies on the thickness of the carbon fiber layer 3 provided on the surface of the glass mat and the amount of carbon fiber added to the anode active material, it was found that the carbon fiber layer 3
The thickness of the anode active material is 0.1 mm or more, and the amount of carbon fiber added in the anode active material is about 10 μm in diameter and about IM in length.
It was clearly found that 0.05% or more is effective in improving the chemical formation efficiency of the anode plate.

When using a glass mat separator without a carbon fiber layer, the amount of carbon fiber added in the anode active material should be 0.
If it is set to 5% or more, the chemical conversion efficiency will improve, but if it is set to 0.
If 2% or more is added, carbon fibers tend to adhere to the stripping blade in the step of stripping the paste from the filling belt after filling the lead alloy grid, resulting in poor filling. Furthermore, it was found that when 0.4% or more was added, the performance deteriorated quickly in tests such as the JIS Tsuba-mei test where deep charging and discharging were repeated.

Example 2 Mat 4 with conductivity was prepared by immersing a glass mat with a thickness of 1.0 mm in an aqueous solution containing 5% acetylene black, then drying it and bonding it with a separator.
Figure 2 shows a cross-section of a structure in which a conventional separator plate and a conventional separator plate are laminated together.

A battery is assembled using the separator with this electrically conductive glass mat and the anode plate containing 0.05% carbon fiber of Example 1, and when this is chemically formed, most of the chemical formation is completed and oxygen is supplied from the anode plate. The chemical conversion efficiency improved until gas was generated, but once oxygen gas was generated, the chemical conversion efficiency decreased slightly.

This is because the acetylene black attached to the glass mat is separated by the bubbles of oxygen gas, and the conductivity of the glass mat is reduced.

1- However, even if this separator with a glass mat is used, the chemical conversion proceeds with high efficiency until the generation of oxygen gas, when most of the chemical conversion is completed, so the effect is almost the same as in Example 1. It was done. Although the acetylene black peeled off from the glass mat floats in the electrolyte, it is gradually oxidized at the anode and reduced, so we have confirmed that there is no problem with performance.

Example 3 Carbon fibers with a diameter of more than 10 μm and length were made into a 0.2 mm thick sheet using a paper-making method without pressure, and in order to further improve the conductivity, lead powder with a diameter of several μm was added to the carbon fiber. The fibers were impregnated in a volume ratio of about 5%, dried, and then pressed to a thickness of 0.15 mm to obtain a conductive porous sheet 5. This was placed between the anode plate 6 containing 0.05% carbon fiber of Example 1 and an ordinary glass mat with a separator 1, and a battery was assembled using the ordinary cathode plate 7 to measure the chemical conversion efficiency. As a result, it was confirmed that the results were the same as in Examples 1 and 2.

In order to confirm the effects of the present invention, five types of unformed HB55D23 type batteries were prototyped using the method of Example 1 (method A) and the following four methods for comparison.

Method B: A separator with a glass mat provided with a carbon fiber layer according to the method of Example 1 was used, and an anode plate without carbon fiber added (-) was used.

Method C: A method using the anode plate added with carbon fiber according to the method of Example 1 and a separator plate with a glass mat without a carbon fiber layer.

Method D: The amount of carbon fiber added to the anode active material is 0.
Same as method C except that a 5% anode plate is used.

Method E: Conventional method.

First, in order to confirm the effect of the present invention on chemical conversion efficiency, dilute sulfuric acid with a specific gravity of 1.22 was injected into these batteries for 1-10 minutes.
．． After starting chemical formation with a current of 4 CA, the battery was taken out at regular intervals and discharged with a current of 0.16 CA. The results are shown in FIG. Battery 8 of method A and battery 9 of method A of the present invention
The chemical conversion efficiency is the highest, followed by the system cio, and the systems Bll, El, and 2 are the lowest.

The reason why the formation efficiency of the battery 8 of method A is the highest is as mentioned above, but the reason why the battery 9 of method A is almost the same as method A is that the amount of carbon fiber added to the anode active material is 0.
．． This is because it is as high as 5%. On the other hand, in the battery 10 of method C, this amount is extremely small at 0.05%, and since there is no mat that imparts conductivity, chemical formation proceeds from the surface of the anode plate.
-0, so the conversion efficiency is slightly higher than methods B and E, but considerably lower than methods A and D.

The reason why method B has the lowest rate as well as method E is that the conversion efficiency during conversion from the lattice to the surface is the same as that of conventional products, and it is not until the part of the surface that is finally converted that it becomes conductive. This is because the remaining unformed portion of the surface is chemically converted from the mat to which it has been applied.

Next, in order to confirm the life performance of method A of the present invention,
A JIS life test was conducted using a battery of Method A, a method showing approximately the same chemical conversion efficiency, and a conventional method E for comparison, and the results are shown in FIG. It can be seen that while methods A and E are almost equivalent, the method is extremely short.

The reason for this method is thought to be that carbon fiber is added in a large amount of 0.5% to the anode active material, which reduces the bonding strength of the active material.

As mentioned above, Example 1 has been described in terms of the effective chemical formation efficiency and life performance of the present invention, but it has been confirmed that Examples 2 and 3 have almost the same effects.

Effects of the Invention As mentioned above, the battery of the present invention has extremely high chemical conversion efficiency, so it can be chemically formed in a short time and with a small amount of electricity, and its life performance is equal to or higher than that of conventional products, so it has great industrial value. .

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of a separator with a mat provided with conductivity, which is a component of the present invention, and Fig. 2 is a diagram showing an example of a separator with a mat provided with conductivity, which is also a component of the present invention. Figure 3 is a cross-sectional view showing the electrode plate group of the embodiment of the present invention, and Figure 4 is the chemical composition of the present invention and batteries for comparison at a current of 0.4 CA. time and 0.16
FIG. 5 is a characteristic diagram showing the relationship with discharge time when discharging with a current of CA, and FIG. 5 is a characteristic diagram of a JIS life test of a battery of the present invention and a battery for comparison thereto. 2 glass mat, 3: carbon fiber layer, 4: acetylene black attached glass mat, 5: conductive porous sheet,
6: Anode plate.

Claims (4)

[Claims] (1) Use an anode plate containing conductive fibers such as lead, lead alloy, carbon, etc. in the active material, and attach a mat with conductivity to the surface in contact with the anode plate, or use a conductive porous sheet. This lead-acid battery is characterized by being placed between this anode plate and a glass mat. (2) The lead-acid battery according to item 1, wherein the conductive mat is a glass mat with a mat layer made of carbon fiber integrally provided on the side in contact with the anode plate. (3) The lead-acid battery according to item 1, wherein the conductive mat is a glass mat to which carbon powder is attached. (4) The lead-acid battery according to item 1, wherein the conductive porous sheet is mainly made of a conductive substance such as lead, lead alloy, or carbon.