KR20170105671A - Collector plates for bipolar electrodes of leadbatteries - Google Patents

Abstract

The present invention relates to a composite plate for a Pb/PbO_2 battery having a bipolar electrode in which wires are arranged in a regular arrangement, are stable to an acid medium, and are coated with lead and a polymer occurring strong bonding with a lead alloy forming the surface of the wire, thereby having unidirectional electric conductivity. The metal wire-wire volume of the surface of the lead or the lead alloy is only 4% of the total volume of the plate. The mass per unit area of the plate is maintained by approximately 15 g/dm^2.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a collector plate for a bipolar electrode,

The present invention relates to a method for producing composite plates for Pb-PbO 2 batteries with bipolar electrodes in which the electrical conductivity of the plates is at least on their surface by lead or lead alloys By a configured wire

And the wires are arranged in a regular arrangement perpendicular to the surface of the plate and these wires are coated with a polymer that is stable to the acid medium and can make strong bonds with the metal or alloy constituting the wire, the total volume of conductor wires is less than 4% of the volume of the plate.

There have been many attempts to produce conductor plates designed for the manufacture of bipolar plates for Pb-PbO2 batteries. Compared to the average architectural factor, the fundamental problem is to significantly reduce the weight while ensuring a long cycle life. Thus, polyaniline

the use of an intrinsically conductive polymer such as polyanilines or the use of other oxide fibers such as SnO 2 in insulating materials has been proposed. These new materials often have insufficient electrical conductivity, are expensive, and are not reliable.

More recently, several inventions have also aimed at using lead or an alloy thereof as a conductive element of the plate. In this light, the simplest case consists of using a thin sheet of lead or one of these alloys. However, due to the thickness of tens of millimeters, mechanical strength is not sufficient and therefore it is necessary to place a thin sheet between two grids made of polymer and also to ensure retention of active material while strengthening the assembly . If the lead sheet is 0.4 mm or less, this type of solution will puncture the lead sheet after dozens of charge-discharge cycles. However, the use of a thicker one is not preferable in terms of reducing the weight of the bipolar electrode, and the weight of the plate for 0.5 mm is approximately 55 g / dm 2.

Another system (PCT Publication No. WO 87/23917, 11/12/96) consists of using plates made conductive by adding powdered lead or one of these alloys to the polymer. In this case, it was confirmed that the weight of the plate should again be 30 g / dm 2 or more in consideration of the content of the powder sufficient to obtain sufficient conductivity by percolation.

Another solution consists in producing a composite sheet characterized by the fact that the fibrous structure made of polymer is made conductive by filling the pores with lead or lead alloys (French Patent Nos. 2 662 536, 14/10/91 ). In this case, it is difficult and costly to fill the entire pore, and the sealing obtained by the electrolytic means is scarce. Another solution is that the bipolar plate is composed of a polymer-metal composite material, It is conceived to be secured by a metal used in the form of fibers or pins. In the case of using metal fibers passing through a polymer plate (Japanese Patent No. 56-149776, 19/11/81), since the fibers are not parallel to each other, the distribution of the conductive fibers is not regular, The distance traveled is not constant. Japanese Patent No. 59-121787 (13/07/84) discloses a bipolar current collector in which a metal pin is made of a base material made of a resin penetrating resin and an end of which protrudes from both ends, Compared to the use of fibers, significant improvements have been made. A method for producing such a bipolar wall is constituted by punching a substrate made of a polypropylene resin and inserting a metal pin into the hole. The next step consists of forming the ends of the pins according to three different shapes, which is a complex and therefore costly process in industrial processes. In addition, since the method of introducing the metal pin into the hole of the support does not make it possible to form an effective bond between the metal and the resin, and the leakage of the acid electrolyte tends to occur on both sides of the bipolar wall, A shunt current is created between the single cells.

The object of the present invention is a composite plate which does not have the above problems and a method of manufacturing this type of plate.

It is included in the detailed contents for carrying out the invention.

The composite plate of the present invention can be used in a Pb-PbO 2 battery with bipolar electrodes and has been found to satisfy all of the considerable weight reduction, satisfactory conductivity and good sealability to the electrolyte.

Figure 1 shows a square pattern according to one embodiment of the present invention,
Figure 2 illustrates an equilateral triangle pattern according to one embodiment of the present invention.

The object of the present invention is a composite plate which does not have the above problems and a method of manufacturing this type of plate.

The optimum structure of the plate was determined on the basis of obtaining significant weight reduction, satisfactory conductivity and good sealability to the electrolyte.

A conductive plate according to the present invention designed for a Pb-PbO2 battery is composed of a plate made of a polymer which is safe in sulfuric acid medium, into which conductor wires are inserted, at least the surface of which is constituted by lead or lead alloy, And is disposed perpendicular to the surface to provide electrical conductivity.

In view of the electrical conduction properties of the plate, it has been demonstrated that if the conductive elements are arranged regularly and this conduction is substantially one-way, there is no need to attempt to obtain conductivity through the entire chunk of the plate. Thus, even at surface current densities as high as 200 mA / cm 2, for a 1 mm thickness of the plate (for conductive wires composed of lead) and a metal conductor volume of approximately 2% of the total plate volume, An ohmic drop can be obtained.

The element providing conductivity may be a wire, the cross-section of which is preferably circular and not necessarily required, and the wire is arranged perpendicular to the large area of the plate. The regularity required for the arrangement of these wires should ensure that the open cross-sections on the two surfaces of the plate are centered at the intersection of the regular arrays and that their pattern is square or, preferably, equilateral triangles. The optimum distance between the centers of the two conductive sections is essentially dependent on the electrical conduction properties of the active material finely covering the plate, not the conductivity in the wire, provided that the wire has a diameter of 0.2 mm or more for practical reasons.

FIG. 1 shows an arrangement of wires according to a square pattern, and FIG. 2 shows an arrangement of wires according to an equilateral triangle pattern.

The present inventors have shown that the ohmic resistance induced by the drain of dislocations in the active material is independent of the space of these conductive wires (A) due to the regular arrangement pattern of the conductive elements. Thus, in a square pattern,

, Where p is the resistivity of the active material, "e" is its thickness, and rho varies with the discharge conditions of the active material. Substantially, the following experimental data will be obtained.

In any case, the total ohmic degradation is due to ohmic degradation at the respective surfaces of the screen (positive and negative active substrates) and ohmic degradation in the wire ensuring electrical conduction from one surface to the other surface . Actually,

The degradation in the wire is negligible and the ohmic degradation in the positive active substrate is clearly overwhelmingly large as compared to that in the negative active substrate.

The latter conclusion is related to the fact that the arrangement according to an equilateral triangle corresponds to filling the space with the most compact.

The diameter of the conductor wire will be substantially determined by the device for obtaining a wire having sufficient mechanical properties to handle the wire, particularly during the state of contact with the polymer. If it is desired to keep the weight of the metal conductor below 25% of the total weight of the screen and, if possible, about 10% of the total weight of the screen, for a distance of 0.5 to 1.5 cm between the centers of the wire cross- Will be between 0.5 and 1.5 mm; Quot; a "which is larger and larger.

The distance between the diameter of the wire and the center of the wire cross-sections will be selected such that the total volume of the wire is between 0.2 and 4% of the total plate volume.

In addition to the limitations associated with the application of the polymer, the thickness of the plate must be greater than the threshold determined by the oxidation-related behavior of the lead or lead alloy constituting the surface of the wire. In fact, since the oxidation of the wire is observed after a very low thickness of the plate and a short length of the resulting wire, for example 0.2 mm, after a cycle (charge-discharge) has taken place, Can connect the two surfaces of the plate. This sealing disadvantage is clearly not acceptable for the satisfactory function of the bipolar electrode.

On the other hand, according to the research conducted by the present inventors, even in a small external surface (approximately 2% of the entire surface) of the lead constituting the wire, a thickness of 0.5 mm or more makes it possible to prevent these risks for many charge- . The plate will preferably have a thickness of 0.5 to 2 mm, more preferably 1 mm. The length of the conductor wire may preferably be slightly larger than the plate thickness, which makes it possible to ensure perfect contact with the active substrate . The overlap of the wires to each side of the plate is 0.1 to 0.3 mm.

In fact, even at the final stage of charging (overcharging of the elements), the current applied to the lead or lead alloy constituting the surface of the wire is only a small fraction of the total current, and most of the current is the metal lead, Is applied to the development of oxides that apply its alloys. In addition, the wider the contact surface between the wire and the polymer, the further the risk of leakage caused by the presence of the gap is further reduced.

Another important aspect according to the present invention relates to the importance of the bonds that must be present between the lead constituting the surface of the wire or one of these alloys and the polymer coating the wire. In fact, the purpose is to prevent detachment between the metal wire and the polymer. Consequently, it has been confirmed that it is preferable to select an epoxy resin resistant to an acid medium, or an ebonite as a polymer.

In the case of epoxy resins, they are molded in a mold so that they are arranged according to a predetermined pattern before being polymerized around the wires.

In the case of an ebonite, the hot mixture is injected into a mold containing properly arranged wires.

The wires which ensure electrical conductivity are composed of pure lead or lead alloys, for example Pb-Sn, Pb-Ca or Pb-Sb, oxidation resistant metals (for example 316L stainless steel) Or one layer of these alloys described above.

According to the details described above, a 10 cm x 10 cm and 1 mm thick plate made of pure lead arranged in an equilateral triangular pattern with a side of 6 mm was produced. Lead wire (99.5% pure) had a diameter of 1 mm. The wire was arranged in the mold with the above-mentioned equilateral triangle pattern and the mixture ARALDITE (trade mark) AV138M + HV 998 curing agent (CIBA) was molded therebetween. After polymerization at 50 占 폚, the plate was taken out of the mold and its surface was lightly abraded.

One of the surfaces of the plate was partially coated with the cathode active material, and its surface weight was such that the capacity was 75 mAh / cm < 2 > during a 10 hour discharge. And the other surface was coated with a negative active material to carry out the same process as described above.

The electrode was placed in a screen between compartments each filled with a 490 g / l sulfuric acid solution. The PbO 2 anode was placed on one side of this partition and the Pb cathode was placed on the other side. A portion of the plate not coated with the active substrate made it possible to ensure sealing between the two seals by a sealing means.

After the active substrate of the electrode is formed according to a typical method,

(bi-element) was continuously charged and discharged as follows.

Charging for 7.2 hours with an equivalent current of 2.7 A;

Discharge for 6 hours with equivalent current of 2.7A.

After 800 cycles, the stable behavior of the bi-element was confirmed, demonstrating the excellent safety of the bipolar plate and hence the preservation of its sealing properties. In addition, it was also possible to measure that the weight of the bipolar plates was 15 g / dm 2 (before coating with the active substrate).

The foregoing embodiments are merely illustrative of the present invention, and the present invention is not limited thereto, and the present invention includes all various modifications.

Included in the brief description of the drawings

Claims (15)

The electrical conductivity is ensured by metal wires, which are arranged at least on the surface by lead or lead alloys and arranged in a regular arrangement perpendicular to the surface of the plate, which are stable to the acid medium and constitute the surface of the wire A composite plate designed for manufacturing a Pb / PbO 2 battery with a bipolar electrode, wherein the composite plate is coated by a polymer that forms strong bonds with the metal or alloy, and wherein the total volume of the conductor wire is no more than 4% of the total volume of the plate. 2. The method of claim 1, wherein the wires are arranged in a regular arrangement, the pattern being square or more preferably centered hexagonal, the cross-section of each wire being centered at the top of the square or at the top of an equilateral triangle Is open on the surface of the composite plate. 3. The composite plate according to claim 2, wherein the square or equilateral triangle constituting the wire distribution array has a side surface of 0.5 to 1.5 cm. The composite plate according to claim 1, wherein the thickness of the plate is 0.5 to 2 mm, and preferably 1 mm. The composite plate according to claim 1 or 4, wherein the length of the conductor wire is equal to the thickness of the plate, that is, 0.5 to 2 mm, preferably 1 mm. 5. The composite plate according to any one of claims 1 to 4, wherein the conductor wire is led out from the plate at a height of 0.1 to 0.3 mm at each of its surfaces. The composite plate according to claim 1, wherein the diameter of the wire is 0.5 to 1.5 mm. The composite plate according to any one of claims 1, 2, 3, and 5, wherein the total volume of the wire is 0.2 to 4% of the total volume of the plate. The composite sheet according to claim 1, wherein the polymer is ebonite. The composite sheet according to claim 1, wherein the polymer is an epoxy resin. The composite plate according to claim 1, wherein the wire is made of pure lead. The composite plate according to claim 1, wherein the wire is made of a Pb-Sn alloy. The composite plate according to claim 1, wherein the wire is made of a Pb-Ca alloy. The composite plate according to claim 1, wherein the wire is made of a Pb-Sb alloy. The composite sheet according to claim 1, wherein the wire is made of stainless steel coated with lead or a lead alloy.

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