JPH0449756B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrode plates for lead-acid batteries, including bipolar electrodes and current collectors having sufficient mechanical strength, particularly resistance to elongation that occurs during use of the battery. It concerns its manufacturing method.

As is well known, current collectors (grids) made of Pb-Sb alloys have traditionally been used for the electrode plates of lead-acid batteries, especially automobile batteries, but in order to meet the demand for maintenance-free batteries, current collectors (grids) have been used for the electrode plates of lead-acid batteries, especially automobile batteries. The material of electric bodies is changing from Pb-Sb alloy to Pb-Ca alloy. In other words, antimony-free lead alloys such as Pb-Ca-based alloys have a larger hydrogen overvoltage than the Pb-Sb-based alloys, so less hydrogen gas is generated during charging. This is significantly less than batteries using alloys as current collectors.

However, when a Pb-Ca alloy is used as a current collector, a phenomenon called "elongation" becomes a problem. In other words, while the battery is in use, _two layers of PbO are formed on the surface of the current collector of the anode plate, but during discharge, _PbO2 changes to _PbSO4 , which is accompanied by volumetric expansion, so the force As a result, the current collector is gradually stretched. Figure 1b shows a current collector of an anode plate taken out from a battery that has been tested on an actual vehicle, and is an expanded grid 1 made of a Pb-0.065Ca-0.5Sn alloy. As shown in the figure, it has deformed into a shape that is quite different from state a before the test. If the current collector on the anode plate stretches and changes beyond the external dimensions of the separator, short circuits may occur between the anode plate and the cathode plate, or the active material retention capacity may decrease, resulting in a shortened battery life. It becomes a thing.

FIG. 2 shows the state of deformation of the current collector 2 of the same automobile battery, which uses bipolar electrodes and which has also been tested in an actual vehicle. As is well known, a bipolar electrode uses the front and back sides of a single current collector as an anode and a cathode, respectively, and in this case, it is a Pb-0.07Ca-0.4Sn alloy sheet surrounded by a resin frame. An electrode active material is coated on one side of the plate and a cathode active material is applied on the other side to form an electrode plate. Due to the elongation on the anode side that occurs during battery use, the battery exhibits complex three-dimensional deformation. In particular, in this case, since the surrounding area is the resin frame 3, the deformation due to elongation appears in a complicated manner in the thickness direction of the current collector, and as a result, the active material falls off significantly, resulting in the failure of the target period. It has reached half its lifespan.

At present, there are not many active measures taken to prevent the above-mentioned elongation. For example, by increasing the cross-sectional area of the current collector within the allowable range, The only thing that has been done is to reduce this force, or stress, as much as possible. However, the idea of suppressing elongation by increasing the cross-sectional area of the current collector is incompatible with recent strict demands for weight reduction for automobile batteries.
In other words, increasing the cross-sectional area means using more material, which inevitably makes the current collector heavier, which goes against the objective of making the battery lighter. Batteries that use the bipolar type electrodes (electrode plates) mentioned above use only one cathode current collector instead of the two that would normally be used, so it goes without saying that the weight of the battery can be significantly reduced, and at the same time the voltage performance is improved. It becomes possible to dramatically improve the Therefore, it is one of the extremely effective methods of configuring the electrode plate group for the purpose of weight reduction, but its advantages will be significantly reduced unless the disadvantages due to elongation as described above can be eliminated.

The present invention aims to provide a highly reliable bipolar electrode for a lead-acid battery that suppresses elongation of the bipolar electrode as described above and has excellent voltage performance and life performance, and a method for manufacturing the same.

Next, details of the present invention will be described.

The phenomenon of "elongation" that is observed when the Pb-Ca alloy mentioned above is used as a current collector in lead-acid batteries is an essential problem, as is clear when considering the charging and discharging mechanism of lead-acid batteries. When using Pb-based alloys in electric bodies, it is considered extremely difficult to completely eliminate the occurrence of this phenomenon, although there are varying degrees of severity, as long as conventional alloy manufacturing methods are followed. Needless to say, the problem on the Pb alloy side, which is closely related to the phenomenon of "elongation", is its mechanical properties. It is necessary to consider measures to prevent elongation from the viewpoint of how to improve the cleave strength (which is different from that observed in electric materials), as well as how to improve the cleave strength.
This is because Pb alloy has a low melting point,
Even at the temperatures encountered when a battery is installed in the engine room of a car, it is easy for crystal grains to slip between each other, and it is easy to deform when a small stress is continuously applied in a static state. This is because it is conceivable. In addition, the Pb-Sb alloy or Pb-Ca alloy currently used as current collectors is an age-hardening alloy, and age-hardening treatment increases the strength of the material, making it ideal for use in battery assembly. This makes it easier to handle the board. For example, Pb−Ca
In the case of a current collector made of a series alloy, it is subjected to an age hardening treatment to have a tensile strength of 6 to 7 kg/mm ² before being used in battery production. However, even after increasing the strength in this way and using it, there is no guarantee that the current collector can maintain its strength while the battery is actually installed in an automobile and put into practical use. This is because when considering the temperature of a battery placed in the engine compartment, it is well known that the Pb alloy softens due to so-called overaging, and the high tensile strength obtained through age hardening treatment gradually decreases. Because it is possible.

Pb alloys currently used as current collectors, that is, Pb-Sb-based or Pb-Ca-based alloys, have the above-mentioned problems from the viewpoint of preventing "elongation." However, the features of the present invention In order to solve these problems, we determined that the conventional methods of changing the alloy composition or changing the age hardening treatment method did not meet the purpose, so we decided to change the material of the current collector. The goal is to use composite materials.
In other words, a composite material is assembled in which conductive or non-conductive filaments (fibers), which have a higher tensile strength than matrix materials such as glass or carbon, are unevenly arranged in a Pb or Pb alloy matrix. Anode active material is placed on the surface of the side where the filament is unevenly distributed,
A cathode active material is placed on the opposite surface to create a bipolar electrode that is lightweight and has excellent voltage characteristics.

Next, a method for manufacturing the bipolar electrode of the present invention, particularly a composite material for a current collector, will be described.

FIG. 3 shows a method for manufacturing a composite material used for the current collector of the bipolar electrode of the present invention. The method shown in the figure is a manufacturing method using electroforming, and 4 is a plating tank, 5 is a plating solution, and 6 is an anode plate. The target composite material is produced by electrolytically depositing Pb on the surface of the matrix 7.
In this case, the matrix 7 plays the role of a cathode as shown in the figure. In addition, when the matrix 7 is a non-conductive material, conductive treatment is performed by applying graphite powder on the surface, and when the matrix 7 is a conductor, an oxide film is formed by anodic electrolytic treatment. (The graphite coated on the non-conductive matrix 7 also serves as a mold release material.) Next, the mother mold 7 is immersed in the plating solution 5 as shown in the figure, and the anode plate 6 is placed in the positive direction, and the mother mold 7 is
Perform electrolysis with negative. At this time, matrix 7
It is better to rotate it at an appropriate speed. Note that the plating liquid 5 used includes, for example, lead borofluoride, borofluoric acid, boric acid, or the like. By the method described above, a thickness t ₁ is first formed on the surface of the matrix 7.
An electrodeposition layer 8 of Pb is formed.

Next, a composite layer of Pb and a filament of carbon, silicon carbide, glass, etc. is formed on the electrodeposited layer 8 of Pb having a thickness t ₁ thus formed.
FIG. 4 shows the situation. As shown in the figure, the above-described filament 9 is supplied onto the rotating matrix 7, and Pb is electrodeposited at the same time as it is wound. In this way, the electrodeposited Pb
After forming a composite layer of thickness t ₂ including the filament 9 in the matrix of (t ₁ +t ₂ ) from the matrix 7,
demolding a Pb-based composite material with a thickness of
It is cut into predetermined dimensions to make a current collector for bipolar electrodes.

FIG. 5 shows a cross-sectional view of the composite material 11 obtained by the method described above. Further, FIG. 6 shows an example of the structure of a bipolar electrode using the composite material 11 manufactured in this way as a current collector. In Figure 6, 12 is the Pb-based composite material 1 manufactured by the method described above.
1, which is surrounded by a resin frame 3. Furthermore, there is a resin lattice 13 on both sides of the current collector 12 for the purpose of holding the active material.
This is integrated with the resin frame 3. An active material is coated on both sides of the current collector 12, but in this case, as shown in the enlarged view of section C in the figure, an anode is placed on the side of the current collector 12 where the filaments 9 are unevenly distributed. An active material 14 and a cathode active material 15 are arranged on the opposite side.

The method for manufacturing a bipolar electrode for a lead-acid battery according to the present invention has been described, and the technical feature of the present invention is that a Pb-based fiber-reinforced composite material is used as a current collector, and the filament is The problem is that they are not arranged so as to be evenly distributed in the thickness direction of the material, but are arranged (unevenly distributed) toward one side as shown in FIG. 5 or 6. As described above, the anode active material is placed on the side where the filaments are unevenly distributed, and the cathode active material is placed on the opposite side.The reason for arranging the active materials in this manner is as follows. That is, as mentioned above, while the battery is in use, the current collector on the anode plate side gradually corrodes, and PbO ₂ is generated on its surface. This _PbO2
is involved in charging and discharging in the same way as active materials, and when discharging
It changes to PbSO ₄ , but at this time it is accompanied by volume expansion, and the stress causes so-called "elongation", and in the case of bipolar electrodes, three-dimensional waving mainly in the thickness direction as shown in Figure 2. It exhibits deformation. In this way, the source of "elongation" is on the anode side, and the problem is that the area of the current collector that has a certain thickness from the surface that is in contact with the anode active material expands from the cathode active material side. There is a reason. Therefore, if the filament is strengthened by placing it in the area on the side of the anode active material that is considered to be affected by the corrosion that occurs during battery use, it is possible to prevent "stretching".
This makes it possible to significantly reduce or eliminate the occurrence of

As a result of various studies based on this idea, we decided that the area where the filament is placed should be approximately 1/2 the thickness of the current collector, that is, t ₁ and t ₂ in Figure 5. It was found that it is desirable to set the ratio to about 1. Furthermore, due to the occurrence of “elongation”, 3
In order to prevent dimensional deformation, it has been found that it is extremely effective to arrange the filaments 9 so that they are orthogonal to each other in the thickness direction, as shown in FIG. In addition, as mentioned above, the filament material used for the current collector is made of carbon, silicon carbide, glass, etc., but its mechanical properties basically have greater tensile strength and elongation than the base Pb. It has to be something small. In addition, the chemical properties must be such that it cannot be easily oxidized by dilute sulfuric acid. In addition to these mechanical and chemical properties, it is even more preferable to use a material that is electrically conductive. The thickness of the filament is related to the thickness of the intended current collector, but if the thickness of the current collector is about 1 mm, it is 0.05 to 0.1 mm.
It is preferable that the degree of Furthermore, it has been found that elongation is particularly effectively prevented when the distance between the filaments is 0.5 mm or less.

Since the composite material according to the present invention is Pb-based and contains other components, it goes without saying that it is reinforced by the filament as mentioned above, so the tensile strength of the current collector itself is far greater than that of pure Pb. Even if pure lead is used as the base, there is no problem in terms of strength compared to the conventionally used Pb-Ca alloy.

Next, embodiments of the present invention will be described.

A bipolar electrode with a current collector made of a conventional Pb-Ca alloy (hereinafter referred to as the conventional type)
A battery using a bipolar electrode made of a composite material according to the present invention and a battery using a bipolar electrode made of a composite material according to the present invention (hereinafter referred to as the product of the present invention) were assembled and subjected to a life test to determine the degree of difference in life and the deformation of the current collector. We compared the condition.

The specifications, structure, etc. of the bipolar electrode of the battery used in the comparative experiment are as follows. That is, the batteries using both the conventional electrode and the electrode of the present invention have a nominal capacity of 48 Ah, and the size of the electrode plate is 120 x 250 mm. In the case of the conventional type, the current collector has a thickness of 0.8 mm.
A Pb-0.065Ca-0.5Sn alloy plate was used. On the other hand, in the case of the product of the present invention, the thickness of the current collector is 1 mm;
A carbon filament with a diameter of 0.05 mm is arranged within a 0.5 mm thick region from the surface in contact with the anode active material. In this case, filament 9
As shown in Figure 8, three layers are arranged parallel to the x axis at a pitch of 0.1 mm, with a layer spacing of 0.075 mm.
Next, three layers were arranged parallel to the Y axis at a pitch of 0.1 mm, with the same layer spacing of 0.075 mm. The base is blunt lead, and this composite material is manufactured by the method shown in Figures 3 and 4. The composition of the tamping solution used at this time is 300 g of lead borofluoride and 30 g of borofluoric acid. /, boric acid 40g/, and gelatin 0.2g/.

Further, the amount of anode active material per bipolar electrode was 410 g, and the amount of cathode active material was 310 g, which were the same for both the conventional electrode and the product of the present invention.

Next, for the life test, a constant voltage charge/discharge test was conducted. In other words, [200A discharge x 1
25A limit 15V constant voltage charge for 11 minutes → 10A constant current discharge for 16.5 minutes → 24 minutes pause] for a charge/discharge cycle, followed by a heat cycle from -15℃ for 24 hours to 45℃ for 24 hours. It is a layered one. Such a life test was conducted to compare the degree of progress of deterioration and the state of deformation of the current collector after the end of its life.

Figure 9 shows the evaluation results. As is clear from the figure, the battery using the bipolar electrode according to the present invention (product of the present invention) has a lifespan approximately 40% longer than that using the conventional electrode (conventional product), showing extremely good results. ing. Further, after the life test, the batteries were disassembled and the deformation (elongation) of the current collectors of both batteries was examined. As a result, the conventional type was significantly deformed and the active material was noticeably falling off.

[Brief explanation of the drawing]

Figure 1 shows the shape of the expanded lattice of the battery subjected to the actual vehicle test, a is the plan view before the test, b is the plan view after the test, and Figure 2 is the current collector in the conventional bipolar electrode of the battery after the actual vehicle test. Indicates the deformation status of a
is a plan view, b is a sectional view along line A-A', Fig. 3,
FIG. 4 is a perspective view showing a method for manufacturing a composite material for a current collector of a bipolar electrode according to the present invention, FIG. 5 is a sectional view of the composite material for a current collector of a bipolar electrode according to the present invention, and FIG. 1 shows an example of the structure of a bipolar electrode according to the present invention, a is a plan view, and b is a B-
A cross-sectional view along line B', c is an enlarged view of part C, Fig. 7,
Fig. 8 is a perspective view of the main parts showing an example of the arrangement of fibers in the composite material used as the current collector of the bipolar electrode according to the present invention, and Fig. 9 shows the life characteristics of the battery in which the effects of the present invention were evaluated. FIG. 3 is a resin frame, 4 is a plating tank, 5 is a plating liquid, 7
8 is a matrix, 8 is an electrodeposited layer, 9 is a filament, 11 is a composite material, 12 is a current collector, 13 is a resin grid, 14
15 is an anode active material, and 15 is a cathode active material.

Claims (1)

[Claims] 1 A current collector is a composite material in which filaments having a higher tensile strength than the material of the matrix are unevenly distributed in a Pb or Pb alloy matrix, and the filaments of the current collector are unevenly distributed. A bipolar electrode for a lead-acid battery, characterized in that an anode active material is disposed on one side of the electrode, and a cathode active material is disposed on the other side. 2. The bipolar electrode for a lead-acid battery according to claim 1, wherein the filament is unevenly distributed in a portion having a thickness of 1/2 or more of the thickness of the current collector. 3. A bipolar electrode for a lead-acid battery according to claim 1 or 2, wherein the filaments are arranged perpendicularly to each other in the thickness direction of the current collector. 4 Step of forming an electrodeposited layer of Pb of a predetermined thickness on the matrix using the matrix immersed in a plating bath as a cathode, then winding a filament around the matrix having the electrodeposited layer of Pb and simultaneously electrolyzing Pb. to form a composite layer of a predetermined thickness of filament and Pb.
A step of obtaining a Pb-based composite material in which filaments are unevenly distributed and arranged on one surface side, and then, using the composite material as a current collector, an anode active material is placed on the side where the filaments are unevenly distributed, and a cathode active material is placed on the opposite side. A method for manufacturing a bipolar electrode for a lead-acid battery, comprising the step of arranging a bipolar electrode for a lead-acid battery. 5 Claim 4, in which Pb is electrodeposited and the filament is wound while rotating the matrix.
A method for manufacturing a bipolar electrode for a lead-acid battery as described in .