JPH09167619A - Plate for lead-acid battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To abundantly supply electrolyte to an active material without changing a service life characteristic by mixing podwer-like porous polypyrrole, filling paste by kneading this by water and sulfuric acid in an aggregate, and forming it as a plate. SOLUTION: An aqueous solution by dissolving a prescribed quantity of persulfuric acid ammonium in water is put in a vessel, and it is agitated, and pyrrole being a monomer is dripped in this aqueous solution. The dripped pyrrole is oxidized and polymerized by the persulfuric acid ammonium, and produces powder. Polypyrrole powder is also washed by water, and the remaining persulfuric acid ammonium is removed, and hot blast drying or vacuum drying is performed, and moisture is removed to make a plate. Then, since a part of an active material is substituted with powder polypyrrole 1 and forms a porous structure of high density, active material particles 2 are firmly bound to each other. Therefore, the volume occupied by a pore 3 and a void part increases, and a holding quantity of electrolyte can be increased. The plate is made by filling paste by kneading resin in a solvent in a current collecting body lattice 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a lead storage battery, and in particular to an electrode plate which can form a long life lead battery excellent in high rate discharge characteristics.

[0002]

2. Description of the Related Art Lead acid batteries are popular as secondary batteries because they are relatively inexpensive and have stable performance. In recent years, it has also become popular as a mobile power supply for cycle use, which is used as a power supply for portable devices and electric vehicles, and a stationary power supply used for backup of computers and the like.

In recent years, the development of electric vehicles has been in the limelight as a measure for reducing the pollution of automobiles, and the cordless portable devices have been developed, and along with this, there has been a demand for high performance of lead acid batteries which are inexpensive as a power source. Is increasing. In order to improve the performance of these lead-acid batteries, improvement of high-rate discharge characteristics has been a problem.

The high rate discharge characteristics are largely controlled by the supply of the electrolytic solution to the active material. Lead-acid batteries have lead dioxide (PbO ₂ ) for the positive electrode, lead (Pb) for the negative electrode, and sulfuric acid (H ₂ S) for the electrolyte.
O ₄ ) aqueous solution is used, and the battery discharge reaction is as shown below. Positive electrode: PbO ₂ + 2H ⁺ + H ₂ SO ₄ + 2e ⁻ → PbS
O ₄ + 2H ₂ O negative electrode: Pb + SO ₄ ^2- → PbSO ₄ + 2e ⁻ As is clear from the above reaction formula, the active material of both the positive electrode and the negative electrode changes to lead sulfate (PbSO ₄ ) due to the discharge reaction. When lead and lead dioxide are converted to lead sulfate, the volume increases about twice. Therefore, as the discharge reaction progresses, pores in the electrode plate are blocked by the precipitated lead sulfate, and the ability to diffuse sulfate ions deteriorates. This leads to a decrease in battery voltage and a decrease in active material utilization rate. Also, this lead sulfate becomes lead dioxide at the positive electrode during charging,
Although it changes to lead at the negative electrode, if the electrolyte supply capacity into the electrode plate is poor, this reaction does not proceed smoothly and charging efficiency decreases. In particular, the effect becomes larger as the charge and discharge at a higher current density occur.

As described above, the deterioration of the supply capacity of sulfuric acid into the electrode plate has become a major issue for improving the high rate discharge characteristics and extending the life of the lead storage battery.

As a measure for solving these problems, conventionally, there has been proposed a method in which the packing density of the active material is lowered to form a large number of voids for holding or diffusing the electrolytic solution in the electrode plate.

[0007]

The above-mentioned method of reducing the packing density can increase the amount of the electrolytic solution in the electrode plate, so that the high rate discharge characteristics are improved. However, the voids are formed in the electrode plate, the bonding force between the active material particles is reduced, and the mechanical strength of the electrode plate is weakened. When the charge and discharge are repeated, the active material falls off sharply and the life characteristics are greatly reduced. There was a drawback. The present invention solves such problems, and provides a long-life lead-acid battery excellent in high rate discharge characteristics by configuring an electrode plate that can supply an electrolyte in abundance to an active material without adversely affecting life characteristics. The purpose is to do.

[0008]

The electrode plate for a lead storage battery of the present invention is characterized in that the electrode plate contains a powdery porous polypyrrole as a holding material for an electrolytic solution. By using this electrode plate, the above-mentioned object can be achieved, and a long-life lead-acid battery excellent in high rate discharge characteristics can be provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Polypyrrole is a material which has excellent acid resistance and is also known as a conductive polymer.
It has been proposed to process the material into a film and use it as a coating material for a current collector, as seen in No. -76821.

On the other hand, the present invention is characterized in that a powdery porous polypyrrole is contained in the electrode plate.
Further, as a porous polypyrrole powder suitable for this, one obtained by oxidizing and polymerizing a pyrrole as a monomer in a chemical oxidant solution and adjusting the particle size to an arbitrary particle size by pulverization as needed, is used. is there. The present invention has found that this powdery polypyrrole is excellent in liquid absorbability and is extremely suitable as an electrolyte holding material for lead batteries, and by containing it in an electrode plate, a large amount of electrolyte can be held, and This makes it possible to construct an electrode plate having excellent mechanical strength.

The electrode plate containing an appropriate amount of the powdery polypyrrole according to the present invention has the porous structure of the powdery polypyrrole itself in addition to the electrolytic solution held by the pores of the porous structure formed by the bonding between the particles. The electrolytic solution held in the pores is added, so that the electrode plate contains a large amount of electrolytic solution. Moreover, since the powdery polypyrrole contributes to the formation of the high-density porous structure of the electrode plate, the electrode plate strength is increased, and the discharge due to the active material falling off, which is the case with the conventional electrode plate, which merely reduces the packing density. Problems such as performance deterioration and cycle life reduction can also be avoided.

[0012]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an electrode plate used in an embodiment of the present invention, and FIGS. 2 and 3 are sectional views of electrode plates of Conventional Example 1 and Conventional Example 2, respectively. Here, 1 is a polypyrrole powder particle, 2 is an active material, 3 is an interparticle void, 4 is a current collector lattice, 5
Is a void. In the present invention, as shown in FIG. 1, a part of the active material is replaced with the powdered polypyrrole 1 to form a high density porous structure, so that the active material particles are firmly bound to each other.

Here, a method for producing a porous powdery polypyrrole will be described. First, an aqueous solution prepared by dissolving 20 g to 50 g of ammonium persulfate in 1000 g of water was placed in a container and stirred. Pyrrole (15 cc to 30 cc) as a monomer was added dropwise to this aqueous solution over about 1 to 2 minutes. The dropped pyrrole is oxidized and polymerized by ammonium persulfate to produce powdery polypyrrole. This polypyrrole powder is washed with water to remove residual ammonium persulfate,
It was dried with hot air or vacuum at 1 to 130 ° C for 1 hour to remove water, and then used to prepare an electrode plate.

A porous powdery polypyrrole can be obtained in the same manner by using an oxidizing agent such as ferric chloride instead of ammonium persulfate. Among them, when ammonium persulfate or a sulfuric acid component is added and oxidized and polymerized, the sulfate ion is doped into the polypyrrole, so that a porous powdery polypyrrole in which the electrolytic solution component is incorporated can be obtained. Such materials are preferably used in the practice of the present invention. Polypyrrole is also formed by electrolytic oxidation, but in this case, it is difficult to adjust the porosity in addition to the decrease in production efficiency with the generation of gas. In this respect, the chemical oxidation method as in this embodiment has an advantage that the porosity of the polypyrrole powder can be easily adjusted by the dropping rate and temperature of the pyrrole, the concentration of the oxidizing agent, and the like.

Next, in the paste kneading step, in the present embodiment, a lead powder containing 25% by weight metallic lead and 75% lead monoxide (lead powder having an oxidation degree of 75%) was used for the positive electrode. Is 2% by weight of synthetic resin cut fiber, 2% barium sulfate and 1% for negative electrode
% Carbon powder and 0.5% lignin were added to prepare a mixed material. Porous powder polypyrrole of 1.0% based on the weight of the lead component in the lead powder was added to this mixed material and uniformly mixed, and water and dilute sulfuric acid were added to this mixture and kneaded to form a paste.

By the way, in addition to the above, lead oxide, lead sulfate and other lead compounds such as lead dioxide powder are often added to the mixed material in many cases. It can be applied in any case.

Next, the above-mentioned paste was filled in a casting grid made of a lead-calcium alloy, aged in a high temperature and high humidity according to a conventional method, and then subjected to chemical conversion to prepare a positive electrode plate and a negative electrode plate. In these steps, raw materials such as lead powder containing lead components in the mixed material are converted into lead sulfate and basic lead carbonate by kneading with sulfuric acid and aging, and in the case of positive electrode plate due to chemical conversion. By being oxidized and converted to lead dioxide, and in the case of the negative electrode plate, reduced and converted to lead, they become positive and negative electrode active materials, respectively.

The above two positive electrode plates and three negative electrode plates were used, and a mat-like separator made of glass fiber was interposed between them to combine them, and dilute sulfuric acid was impregnated as an electrolytic solution to obtain a capacity of 2A.
A 2 h battery was prepared. Incidentally, although the casting grid is used as the current collector in this embodiment, the present invention can be carried out by using the expanded grid.

For comparison, a battery (conventional example 1) manufactured under the same conditions as those of the above-mentioned electrode plates except that the powdered polypyrrole was not included, and the powdered polypyrrole was not included, and the amount of water added at the time of preparing the paste was increased. A battery (Conventional Example 2) having a reduced material density was manufactured as a prototype.

The battery of the present invention and the batteries of Conventional Examples 1 and 2 were compared with each other.
The discharge capacity when discharged at a constant current of 1 C to 3.0 C is shown in (Table 1).

[0022]

[Table 1]

Further, 1C discharge of each battery (final voltage 1.3
V) The life performance of the charge / discharge cycle at 1 C charge (150% charge of the discharge capacity) is shown in (Table 2). The cycle life number was the number of cycles until the initial discharge capacity was reduced to 50%. The amount of electricity was calculated by calculating the number of moles of lead atoms contained in the filled paste, and using the theoretical capacity when it is assumed that they all carry out a two-electron reaction.

[0024]

[Table 2]

As is clear from (Table 1), the battery using the electrode plate according to the present invention is significantly superior to the conventional example 1 in the high rate discharge characteristics as in the conventional example 2. On the other hand, regarding the cycle characteristics of (Table 2), the battery using the electrode plate of the present invention has a larger cycle life number than that of Conventional Example 2 as in Conventional Example 1. From these facts, it was demonstrated that by applying the present invention, a battery having both excellent high-rate discharge characteristics and a long life can be configured. The reason why the above results are obtained can be explained as follows. In the electrode plate according to the present invention shown in FIG. 1, the electrolyte solution is held in the pores inside the powdery polypyrrole, and the polypyrrole itself contains the doped sulfate ions. Therefore, compared with the electrode plate filled with high density of Conventional Example 1 as shown in FIG. 2 in which only the interparticle pores of the electrode plate contain the electrolyte solution, the electrode plate contains more electrolyte solution, The reaction proceeds smoothly even at high rate discharge. In addition, in the low-density packed electrode plate of Conventional Example 2 in FIG. 3, the active material is reduced, and the volume occupied by the pores 3 and voids is increased accordingly, and the amount of electrolyte retained is greater than in Conventional Example 1. However, the strength of the porous structure decreases, the active material falls off, and the cycle life deteriorates. On the other hand, in the product of the present invention, since the powdered polypyrrole contributes to the formation of the high-density porous structure, the bonding force between particles is increased, and the deterioration of the cycle life is effectively suppressed.

Next, the amount of powdered polypyrrole to be added was examined by making a positive electrode plate and a negative electrode plate by changing the amount of powdered polypyrrole added according to the same method as in the above-mentioned embodiment. The theoretical capacity of the electrode plate was 1 Ah and 0.8 Ah, respectively, and the amount of the powdered polypyrrole added was 3%, 2%, 1%, 0.3% and 0.1% by weight relative to the lead component in the mixed material.

A constant current discharge of 1 C was carried out in a system containing a large amount of an electrolyte solution using these electrode plates with a pure lead plate as a counter electrode, and a reference electrode (HgSO ₄ / Hg) was used to obtain 0.2 V with respect to the initial voltage.
The discharge capacity until polarization was measured. The result of discharging the positive electrode is shown in FIG. For comparison, the discharge performance of an electrode plate containing no powdered polypyrrole is also shown.

As shown in FIG. 4, 0.1% of powdered polypyrrole was added.
Although the addition of the above makes it possible to improve the discharge capacity, the effect becomes weaker when the added amount exceeds 2% by weight relative to the lead component in the mixed material, and the effect becomes weaker at 3% than the conventional product. can not see. From this result, the amount of powdered polypyrrole added is preferably in the range of 0.1% to 2% by weight with respect to the lead component in the mixed material. The same experiment was performed for the negative electrode, but the same results as for the positive electrode were obtained, and it is appropriate that the addition amount is in the range of 0.1% to 2% by weight with respect to the lead component in the mixed material. Became clear.

Further, 1% of porous polypyrrole powder based on the weight of the lead component in the mixed material is mixed with a mixed material mainly containing lead powder, and this is mixed with polyvinylidene fluoride as a binder. Using the paste kneaded with the liquid dissolved in N-methylpyrrolidone as described above, a battery was prepared in the same manner as in the above example. The discharge capacity at a high rate discharge of 1 C or more of this battery was increased by 10 to 15% as compared with the battery in which the porous polypyrrole powder was not added, and the cycle life number was 250 cycles. From this, the present invention can be applied to the case where an organic polymer resin is used as a binder, and the electrode plate is formed by using a paste prepared by kneading a mixed material with a liquid obtained by dissolving the organic polymer resin in a solvent. Was confirmed to be effective.

[0030]

As described above, by adding porous powdery polypyrrole to the electrode plate of the lead storage battery, a large amount of electrolytic solution can be retained in the electrode plate, and at the same time, the electrode plate strength can be increased. Therefore, by using this electrode plate, it is possible to obtain a lead-acid battery having excellent high rate discharge characteristics and cycle life.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lead-acid battery electrode plate according to the present invention.

FIG. 2 is a cross-sectional view of a conventional high-density packed electrode plate.

FIG. 3 is a cross-sectional view of a conventional low-density packed electrode plate.

FIG. 4 is a diagram showing the relationship between the amount of powdered polypyrrole added and the positive electrode discharge characteristics.

[Explanation of symbols]

 1 powdered polypyrrole 2 active material particles 3 interparticle voids 4 current collector lattice 5 voids

Claims (5)

[Claims] 1. An electrode plate for a lead storage battery, wherein the active material is lead or lead dioxide, which contains a powdery and porous polypyrrole. 2. A mixed material mainly composed of lead powder is mixed with powdery and porous polypyrrole, and the mixture is kneaded with water and sulfuric acid to fill a current collector made of lead alloy with aging. A method of manufacturing an electrode plate for a lead storage battery, which is made into an electrode plate through a process and a chemical conversion process. 3. A powdery and porous polypyrrole is mixed with a lead powder-based mixture, and these are kneaded with a solution prepared by dissolving an organic polymer resin as a binder in a solvent. A method for manufacturing an electrode plate for a lead storage battery in which the paste is applied to a lead alloy current collector, dried, and then subjected to a chemical conversion process to form an electrode plate. 4. The lead plate for a lead storage battery according to claim 1, which contains polypyrrole produced by mixing pyrrole with a solution containing a chemical oxidant. 5. The lead plate for a lead storage battery according to claim 4, wherein the chemical oxidant is ammonium persulfate.