JP3284860B2 - Electrode for lead-acid battery and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a lead-acid battery, and more particularly to an electrode plate capable of forming a long-life lead battery having excellent high-rate discharge characteristics.

[0002]

2. Description of the Related Art Lead storage batteries are widely used because they have relatively low cost and stable performance as secondary batteries. In recent years, it has also become widespread as a portable power supply for use in portable devices and electric vehicles, and a stationary power supply used as a backup for computers and the like.

[0003] In recent years, the development of electric vehicles has been spotlighted as a measure to reduce the pollution of automobiles, and the trend toward cordless portable devices has been progressing. Is growing. In order to improve the performance of these lead-acid batteries, improvement of high-rate discharge characteristics has been a problem.

[0004] The high-rate discharge characteristics largely depend on the supply of the electrolytic solution to the active material. The lead storage battery has lead oxide (PbO ₂ ) for the positive electrode, lead (Pb) for the negative electrode, and sulfuric acid (H ₂ S) for the electrolyte.
An O ₄ ) aqueous solution is used, and the battery discharge reaction is as follows. 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 ) by the discharge reaction. When lead and lead dioxide are changed 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 the active material utilization rate. Also, this lead sulfate is converted to lead dioxide at the positive electrode during charging,
At the negative electrode, it changes to lead, but when the ability to supply the electrolytic solution into the electrode plate is poor, this reaction does not proceed smoothly and the charging efficiency decreases. In particular, the effect becomes larger as the charge and discharge at a higher current density occur.

[0005] As described above, deterioration of the ability to supply sulfuric acid into the electrode plate has been a major problem in improving the high-rate discharge characteristics and extending the life of the lead storage battery.

As a measure for solving these problems, conventionally, a method has been proposed in which the packing density of the active material is reduced to form more voids for holding or diffusing the electrolyte in the electrode plate.

[0007]

The above-described method of reducing the packing density can increase the amount of the electrolyte in the electrode plate, thereby improving the high-rate discharge characteristics. However, voids are formed in the electrode plate, the bonding force between the active material particles is reduced, the mechanical strength of the electrode plate is reduced, and when the charge and discharge are repeated, the active material falls off sharply, and the life characteristics are greatly reduced. There was a disadvantage. The present invention solves such a problem and provides an electrode plate capable of supplying an abundant amount of electrolyte to an active material without adversely affecting the life characteristics, and provides a long-life lead-acid battery having excellent high-rate discharge characteristics. The purpose is to do.

[0008]

According to the present invention, there is provided an electrode plate for a lead storage battery, wherein a powdery porous polypyrrole as a holding material for an electrolyte is contained in the electrode plate in a weight ratio of 0.1% to 2% with respect to the lead component. % . By using this electrode plate, the above object is achieved, and a long-life lead-acid battery having excellent high-rate discharge characteristics can be provided.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Polypyrrole is a material having excellent acid resistance and also known as a conductive polymer.
It has been proposed to process it into a film and use it as a covering material of a current collector as seen in -76821.

On the other hand, the present invention is characterized in that the powdery porous polypyrrole is contained in the electrode plate in a weight ratio of 0.1% to 2% with respect to the lead component , and further suitable for this. As the porous polypyrrole powder, a material obtained by oxidizing and polymerizing pyrrole, which is a monomer, in a chemical oxidizing agent solution is used after being adjusted to an arbitrary particle size by pulverization, if necessary. The present invention has found that this powdery polypyrrole has excellent liquid absorbing properties and is extremely suitable as an electrolyte holding material for lead batteries, and by containing it in an electrode plate, it can hold a large amount of electrolyte, and This makes it possible to form an electrode plate having excellent mechanical strength.

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

[0012]

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

FIG. 1 is a cross-sectional view of an electrode plate used in an embodiment of the present invention, and FIGS. 2 and 3 are cross-sectional views of a conventional example 1 and a conventional example 2 respectively. Here, 1 is polypyrrole powder particles, 2 is an active material, 3 is pores between particles, 4 is a current collector grid, 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, whereby the active material particles are firmly bonded.

Here, a method for producing porous powdery polypyrrole will be described. First, an aqueous solution in which 20 g to 50 g of ammonium persulfate was dissolved in 1000 g of water was placed in a container and stirred. To this aqueous solution, 15 to 30 cc of pyrrole as a monomer was added dropwise over about 1 to 2 minutes. The dropped pyrrole is oxidized and polymerized by ammonium persulfate to produce powdery polypyrrole. This polypyrrole powder was washed with water to remove residual ammonium persulfate,
Hot air drying or vacuum drying was performed at -130 ° C for 1 hour to remove water, and used for preparing an electrode plate.

Incidentally, even if an oxidizing agent such as ferric chloride is used in place of ammonium persulfate, a porous powdery polypyrrole can be obtained in the same manner. Among them, when ammonium persulfate or a sulfuric acid component is added and oxidized and polymerized, sulfate ions are doped into polypyrrole, so that a porous powdery polypyrrole incorporating an electrolyte component is obtained. Preferably, such materials are used in the practice of the present invention. Polypyrrole is also formed by electrolytic oxidation. In this case, however, it is difficult to control the porosity, in addition to reducing the production efficiency with the generation of gas. In this respect, the chemical oxidation method as in the present embodiment has an advantage that the porosity of the polypyrrole powder can be easily adjusted by the dropping speed and temperature of pyrrole, the concentration of the oxidizing agent, and the like.

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

In addition, in addition to the above, additives such as lead tin, lead sulfate, basic lead sulfate, and lead compounds such as lead dioxide powder are often added to the mixed material. It can be applied to other cases.

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

The above two positive electrode plates and three negative electrode plates were combined with a mat-shaped separator made of glass fiber interposed therebetween, and impregnated with dilute sulfuric acid as an electrolyte to achieve a capacity of 2A.
h, 2V battery was prepared. By the way, in this embodiment, the casting grid is used as the current collector, but the present invention can be implemented by using an expanded grid.

For comparison, a prototype battery (conventional example 1) was prepared under exactly the same conditions as the above-mentioned electrode plate except that the powdered polypyrrole was not contained, and the amount of water added during the preparation of the paste containing no powdered polypyrrole was increased. A battery (conventional example 2) with a reduced material density was prototyped.

The battery of the present invention and the batteries of Conventional Examples 1 and 2 are used in the same manner as in Example 1.
The discharge capacity when discharging at a constant current of 1 C to 3.0 C is shown in Table 1.

[0022]

[Table 1]

Also, 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). In addition, the cycle life number was the number of cycles until it decreased to 50% of the initial discharge capacity. 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 assuming that all of them performed a two-electron reaction.

[0024]

[Table 2]

As is evident from Table 1, the battery using the electrode plate according to the present invention is much superior to the conventional example 1 in the high-rate discharge characteristics as in the conventional example 2. On the other hand, with respect to the cycle characteristics shown in Table 2, the battery using the electrode plate according to the present invention has a larger cycle life than 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 result was 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 polypyrrole powder, and the polypyrrole itself contains sulfate ions doped therein. Therefore, a larger amount of electrolyte is contained in the electrode plate as compared to the densely packed electrode plate of Conventional Example 1 as shown in FIG. 2 which contains the electrolyte only in the interparticle pores of the electrode plate, The reaction proceeds smoothly even at a high rate discharge. In addition, the active material is reduced in the low-density-filled electrode plate of Conventional Example 2 in FIG. However, the strength of the porous structure decreases, the active material falls off, and the cycle life deteriorates. In contrast, in the product of the present invention, the powdered polypyrrole contributes to the formation of the high-density porous structure, so that the bonding force between the particles is increased and the deterioration of the cycle life is effectively suppressed.

Next, the addition amount of powdered polypyrrole was examined by trial production of a positive electrode plate and a negative electrode plate by changing the addition amount of powdered polypyrrole in the same manner as in the above example. The theoretical capacities of the electrode plates were 1 Ah and 0.8 Ah, respectively, and the addition amount of powdered polypyrrole was 3%, 2%, 1%, 0.3%, and 0.1%, respectively, by weight relative to the lead component in the mixed material.

These electrodes were discharged at a constant current of 1 C using a pure lead plate as a counter electrode in a system containing a large excess of an electrolytic solution, and 0.2 V with respect to the initial voltage using a reference electrode (HgSO ₄ / Hg).
The discharge capacity until polarization was measured. FIG. 4 shows the discharge result of the positive electrode. For comparison, the discharge performance of an electrode plate containing no powdered polypyrrole is also shown.

As shown in FIG. 4, 0.1% of polypyrrole powder was added.
Although the discharge capacity can be improved by the above addition, the effect is weakened when the amount of addition exceeds 2% by weight with respect to the lead component in the mixed material. At 3%, the effect is superior to the conventional product. can not see. From this result, it is preferable that the addition amount of the powdered polypyrrole be in the range of 0.1% to 2% by weight based on the lead component in the mixed material. A similar experiment was conducted for the negative electrode, but the same results as in the case of the positive electrode were obtained. The appropriate amount of addition was in the range of 0.1% to 2% by weight with respect to the lead component in the mixed material. Was revealed.

Further, a 1% porous polypyrrole powder based on the weight of the lead component in the mixture is mixed with the mixture mainly composed of lead powder, and the mixture is mixed with polyvinylidene fluoride as a binder. A battery was prepared in the same manner as in the above example, using a paste kneaded with a solution dissolved in N-methylpyrrolidone. The discharge capacity of this battery at a high rate discharge of 1 C or more was increased by 10 to 15% as compared with the battery without the addition of the porous polypyrrole powder, and the cycle life was 250 cycles. Therefore, the present invention is also applicable to a case where an electrode plate is formed using a paste obtained by kneading a mixed material with a liquid obtained by dissolving this in a solvent using an organic polymer resin as a binder. Was found to be effective.

[0030]

As described above, the porous powdered polypyrrole is contained in the electrode plate of the lead storage battery in a weight ratio of 0.1 to the lead component.
% To 2% , a large amount of electrolyte 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, excellent high-rate discharge characteristics and cycle life can be obtained. It is possible to obtain a combined use for a lead storage battery.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lead-acid battery 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 sectional view of a conventional low-density packed electrode plate.

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 polypyrrole powder 2 active material particles 3 pores between particles 4 current collector grid 5 voids

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/62 H01M 4/14-4/23

Claims (5)

(57) [Claims] 1. An electrode for a lead-acid battery, wherein the active material is lead or lead dioxide, wherein a powdery porous polypyrrole is used.
An electrode plate for a lead storage battery , comprising 0.1% to 2% by weight relative to a lead component . 2. A powdery porous polypyrrole is added to a mixture mainly composed of lead powder in a weight ratio of 0.1% to a lead component.
A method of manufacturing a lead-acid battery electrode plate, which comprises mixing a paste of about 2% and kneading them with water and sulfuric acid, filling a lead alloy current collector with a paste, and then subjecting the paste to an aging step and a chemical conversion step. 3. A powdered porous polypyrrole is added to a lead material-based mixed material at a weight ratio of 0.1% to the lead component.
~ 2% mixed, and a paste obtained by kneading these with a solution obtained by dissolving an organic polymer-based resin as a binder in a solvent is applied to a lead alloy current collector, followed by drying and forming processes. A method for manufacturing a lead storage battery electrode plate to be used as an electrode plate. 4. The electrode for a lead-acid battery according to claim 1, further comprising polypyrrole formed by mixing a solution containing a chemical oxidizing agent with pyrrole. 5. The electrode for a lead-acid battery according to claim 4, wherein the chemical oxidizing agent is ammonium persulfate.