JPH1173950A - Manufacture of lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pore structure for improving the discharge capacity in high rate discharge and a low rate discharge by specifying the total pore volume of a positive pole plate and the total pore volume of pores having diameters within a specified range. SOLUTION: A pore structure of a positive pole plate is set so that the total pore volume is 0.14-0.18 cm<3> /g, the total pore volume of pores having diameters within a range of 0.01 or more and less than 0.1 is 0.02 cm<3> /g or more, the total pore volume of pores having diameters within the range of 0.1 or more and 4.0 m or less is 0.13 cm<3> /g. In order to provide this pore structure, chemical conversion charge is performed in mannitol or a diluted sulfuric acid containing mannitol and hydrazine sulfide, when a non-chemical conversion treated plate is used. Since the structure is determined in the process of converting the non-chemical conversion plate into lead dioxide when mannitol is added to the electrolyte in chemical conversion, the pore structure of the positive pole plate can be controlled by its addition quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead-acid battery, and more particularly to a structure of a positive electrode plate.

[0002]

2. Description of the Related Art At present, the paste method is most widely used as an industrial production method having high productivity in the production process of an electrode plate of a lead storage battery. The paste type electrode plate is filled with a paste made by adding dilute sulfuric acid and water to lead powder, and then aging and drying the voids of a current collector made of a cast or expanded lattice made of lead or a lead alloy, First, an unformed plate is prepared. In some cases, lead sulphate is generated on the surface of the electrode plate by acid immersion in dilute sulfuric acid after filling with the paste, and the electrode plate is dried after hardening.

[0003] Since the components of the unformed electrode plate obtained here do not yet have an electromotive ability, it is necessary to charge them in a dilute sulfuric acid electrolyte to convert them into active material components having an electromotive ability. This step is usually called a chemical conversion step. The electrode plate before charging is called an unformed plate. The formation charge includes a plate formation method performed in the state of an electrode plate and a battery formation method performed by configuring a battery in an unformed state. In any case, it is generally shipped in a charged state after the chemical conversion step.

[0004] The main component of the lead powder for a lead storage battery is generally lead monoxide, which contains 15 to 35% of metallic lead. However, if necessary, lead and the like may be added. A paste obtained by kneading lead powder and dilute sulfuric acid produces lead sulfate and partially basic lead sulfate, and has an appropriate hardness and decay strength. During the aging, the electrode plate is hardened by the cementation phenomenon in which the moisture is partially evaporated and the powder particles are bound together with the oxidation of the metallic lead and the crystal growth of the basic lead sulfate. This stage is the unformed plate. It is known that the positive electrode plate obtained by forming this unformed plate becomes porous, and the pore structure affects the discharge characteristics of the lead-acid battery.

The pore distribution of the porous body of the positive electrode plate generally has two peaks as shown in FIG. Here, pores having pore diameters in the range of 0.1 to 4.0 μm are referred to as pores A and 0.1.
Assuming that pores in the range of 01 to 0.1 μm are pores B,
As shown in FIG. 2, the pores A are the gaps 2 of the active material particles 1, and the pores B are formed of lead sulfate or basic lead sulfate during formation.
It is considered to be the gap 3 existing between the acicular crystals on the particle surface formed by the volume decrease when changing to bO ₂ .

[0006]

The pore structure of the electrode plate affects the discharge characteristics of the storage battery. This is because the pores A and B each play an important role in the discharge reaction. Pore A is mainly a diffusion path of sulfuric acid, and sulfuric acid diffuses into the inside of the electrode plate through the pores. Further, the pore B occupies most of the specific surface area of the electrode plate, and it is considered that the charge transfer reaction in the discharge occurs in the pore.

However, in the discharge of the lead storage battery, the precipitated lead sulfate changes the above-mentioned pore structure, and the discharge is terminated by the change in the pores. The mechanism by which discharge ends depends on the discharge rate, and is considered to be divided into the following two discharge rate regions.

[0008] When the discharge rate is small, sulfuric acid is sufficiently diffused into both the pores A and B, so that the dissolved P
b ²⁺ ions immediately react with SO ₄ ^{2 over} ion, so that the lead sulfate also precipitates in the pores B in the pore A. The discharge at this discharge rate ends when the pores B are closed by the lead sulfate, and the place where the above dissolution reaction occurs is lost. Hereinafter, this discharge rate region is referred to as a first region.

[0009] In accordance with the discharge rate increases, the diffusion of SO ₄ ^{2 over} ions into small pores B becomes too late with respect to the reaction rate, some or nearly all of the Pb ²⁺ ions that have dissolved pores B , And diffuses into the pores A, and precipitates as lead sulfate. Although will be precipitated lead sulfate in both pores A and B in this situation, discharge pores A is blocked by the lead sulfate, SO ₄ results in the diffusion of ^2-ions is limited ends. Hereinafter, this discharge rate region is referred to as a second region.

[0010] From these facts, it has generally been considered that increasing the pores A having a large pore diameter is important for increasing the capacity during high-rate discharge. As means for that purpose, methods of increasing the amount of water or sulfuric acid in the paste or controlling the particle size of lead powder as a raw material have been tried.

[0011] However, the above-mentioned method did not provide the expected effect, and conversely reduced the low rate discharge capacity and the life characteristics. As a result of examining these phenomena in detail, in order to improve the high rate discharge characteristics, the current density must be reduced by increasing the pores B and the diffusion of sulfuric acid by the pores A must be satisfied. It turned out that it was important to balance the quantities.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide an appropriate pore structure for improving discharge capacity in high-rate discharge and low-rate discharge.

[0013]

According to the present invention, in order to achieve the above object, the pore structure of the positive electrode plate is adjusted to a total pore volume of 0.1.
4 to 0.18 cm3 / g, the total pore volume of pores having a diameter in the range of 0.01 to less than 0.1 μm is 0.02 cm3 / g or more, and the diameter is 0.1 to 4.0 μm. The total pore volume of the pores in the range of 0.13 cm3 / g or less.

In this electrode plate, the pores B are increased, and the current density is smaller in each of the pores B than in the conventional electrode plate even at a high rate discharge. Therefore, Pb per pore B
^The amount of ²⁺ ions dissolved is small, and the diffusion into the pore A is also small. As a result, the blocking of the pores A, which are diffusion paths for sulfuric acid, is delayed, and the high-rate discharge capacity is improved.

As a manufacturing method for the above constitution, when an unformed plate is used, formation and charging are performed in mannitol or dilute sulfuric acid containing mannitol and hydrazine sulfate.

Mannitol is a kind of organic compound,
It has the effect of dissolving lead oxide. If mannitol is added to the electrolytic solution during chemical formation, the structure is determined in the process of converting the unformed plate to lead dioxide, and the amount of the added material controls the pore structure of the positive electrode plate. Can be. The above operation is the same regardless of whether the method is carried out by electrode plate formation or battery case formation.

When a chemically formed electrode plate is used, H
The step of overdischarging the battery in the range of −1.10 V to −1.60 V based on g / Hg ₂ SO ₄ and then charging it again is performed at least once.

This utilizes the phenomenon that Pb ²⁺ ions are over-dissolved due to overdischarge. In this case, the same effect can be obtained even after the battery is constructed or outside the battery case.

Furthermore, a synergistic effect can be obtained when the production method by overdischarge is performed in the above-mentioned mannitol or dilute sulfuric acid to which mannitol and hydrazine sulfate are added.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a lead powder having an average particle diameter of 3 .mu.m consisting of 25% by weight of metallic lead and 75% of lead monoxide (degree of oxidation: 75%) is used as a raw material for a positive electrode or a negative electrode based on a conventional recipe. In addition, a mixture was prepared by adding 2% by weight of barium sulfate, 1% of carbon powder, and 0.5% of lignin to the negative electrode. Incidentally, as the additive for the positive electrode, in addition to the above, a lead compound such as lead red, basic lead sulfate, and lead dioxide can be added.

The following three types were used as unformed plates. <Unformed plate 1> A paste obtained by adding dilute sulfuric acid having a specific gravity of 1.40 and water to the above raw material powder and kneading the mixture was filled in an expand lattice, and then aged and dried to obtain an unformed electrode plate. <Non-chemical conversion plate 2> It manufactured using the paste which added 30% of the amount of water added to the non-chemical conversion plate 1. <Unformed plate 3> A lead powder having an average particle size of 1 μm was used, and was produced in the same manner as the above-mentioned unformed plate 1.

The weight of each unformed plate after drying was the same, and a battery having a nominal capacity of 3 Ah was composed of two positive electrodes and three negative electrodes. These batteries also have a positive electrode capacity limitation.

The following two chemical conversion solutions were used. <Chemical conversion solution 1> Dilute sulfuric acid adjusted to a specific gravity of 1.20. <Chemical solution 2> A chemical solution in which mannitol and hydrazine sulfate are added at a ratio of 100 mg / l and 500 mg / l to dilute sulfuric acid adjusted to a specific gravity of 1.20.

In Example 1, a battery was produced using the unformed electrode plate 1 and the chemical solution 2. Further, in order to compare with the present embodiment 1, the conventional example 1 uses the unformed electrode plate 1 and the chemical liquid 1, the conventional example 2 uses the unformed electrode plate 2 and the chemical liquid 1, and the conventional example 3 As a result, a battery using the unformed electrode plate 3 and the chemical conversion solution 1 was produced.

The formation was performed under the same conditions for each battery.
The battery formation was performed at a constant current of 0.2 C in terms of nominal capacity for 17 hours.

FIG. 3 shows the pore structure 4 of the first embodiment and the pore structures 5, 6, and 7 of the conventional examples 1, 2, and 3. From the figure, it can be seen that each electrode plate has a different pore structure. Among them, the feature of the positive electrode pore structure according to the first embodiment is as follows.
The pores B are much more developed and the pores A are less than those of other electrode plates.

FIG. 4 shows these electrodes in a nominal capacity of 0.3.
FIG. 5 shows the result of discharging at a discharge rate of 2C, and FIG. 5 shows the result of discharging at a rate of 3C.

FIG. 4 shows the superiority of the first embodiment in low-rate discharge. The pore structure of the first embodiment has a very large number of pores B as compared with the conventional example. This discharge rate corresponds to the first region of the discharge, and it is considered that the discharge ends when the pores B are covered with lead sulfate and the reaction surface disappears. Therefore, the discharge capacity of the first embodiment is larger than that of the conventional examples 1, 2, and 3 having a small number of pores B.

From FIG. 5, it can be seen that the first embodiment can be applied to a high-rate discharge.
Shows superiority. This discharge rate corresponds to the second region of the discharge. In the conventional example, since the discharge is terminated by restricting the diffusion of sulfuric acid in this region, the method of increasing the capacity by increasing the pores A has been mainly used. In that sense, Conventional Examples 2 and 3 in which the volume of the pores A is large have a certain effect compared to Conventional Example 1. However, it was found that Example 1 in which the volume of the pores A was balanced in an appropriate range exhibited much higher characteristics than the conventional example in which only the pores A were increased. The reason for this is not yet clear, but can be considered as follows.

The large number of pores B means that the reaction area is large. If the discharge rate is the same, the current density decreases as the reaction area increases. Therefore, in Example 1, the amount of Pb ²⁺ ions dissolved per pore B is smaller than that in Conventional Examples 1, 2, and 3, and the diffusion amount of Pb ²⁺ ions from pores B to A is also small. it is conceivable that. Then, the pore A is delayed from being blocked by the precipitation of lead sulfate, and as a result, the discharge capacity is improved.

Further, in order to evaluate the cycle life, the batteries of Example 1 and Conventional Examples 1, 2 and 3 were each discharged at 1 C (1.7 V cut), charged at 1 C constant current and charged at 2.35 V constant voltage (1.5 V). Cycle time). The cycle life was defined as the end point when the discharge capacity decreased to 50% of the initial capacity. Table 1 shows the results.

[0032]

[Table 1]

From Table 1, it can be seen that the battery using the positive electrode of Example 1 has a superior cycle life as compared with the conventional product.
The reason why such a characteristic difference appears is considered as follows.

One of the factors greatly affecting the cycle life is the mechanical strength of the electrode plate. This strength tends to decrease as the total pore volume of the electrode plate increases. Since the total pore volume of the electrode plate depends on the volume of pores having a large diameter, it is expected that if the pores A are too large, the cycle life will be shortened. It is thought that the cycle life of the battery of the present invention is excellent.

As a result of comprehensive examination of these facts, the volume of the pore A was 0.13 cm3 / g or less and the volume of the pore B was 0.13 cm3 / g.
It was found that when the density was not less than 02 cm3 / g, both the discharge characteristics and the cycle characteristics were superior to the conventional example.

Next, a description will be given of a structure control method using overdischarge to realize an appropriate structure according to the present invention. According to this method, a battery or a positive electrode plate prepared according to an ordinary method using an unformed chemical plate 1 and a chemical conversion solution 1 is applied to a Hg / Hg ₂ SO ₄ standard electrode.
It includes a step of overdischarging from 1.1V to -1.6V potential and charging again.

The same effect can be obtained even if the positive electrode formed by using the unformed plate 1 and the chemical conversion liquid 2 is overdischarged in the same manner as described above. This effect reduces the rate of discharge to the first region, the second
It can be obtained in any of the regions. In order to clarify the effects of the present invention, Examples 2 and 3 were produced and compared with Conventional Example 1.

In Example 2, the battery obtained in Conventional Example 1 was discharged until the potential of the positive electrode became -1.4 V on the basis of Hg / Hg ₂ SO ₄ , and then again at 1 C at 120% of the nominal capacity.
The above was charged.

As Example 3, 100 mg / l of mannitol and 500 mg / l of hydrazine sulfate were added to the electrolyte of the above-mentioned Example 2 and the same overdischarge treatment as in Conventional Example 2 was performed.

FIG. 6 shows the discharge results of Example 2 and Example 3 of the present invention and 3C of Conventional Example 1. As is clear from this figure, high-rate discharge can be improved using the same battery of Conventional Example 1. Further, it can be seen that mannitol has a synergistic effect to improve this effect.

The reason why the effect of overdischarge appears is not clear, but can be considered as follows. In the positive electrode, a part of lead sulfate is reduced to lead in the positive electrode, and fine pores are generated due to a decrease in volume at that time. When charged in this state, the electrode plate is oxidized while maintaining the fine pores, and an electrode plate having excellent characteristics is obtained. For this reason, the overdischarge potential must be less than or equal to -1.1 V, which is the reduction potential of lead sulfate. However, when the voltage is -1.6 V or less, the decomposition of the electrolytic solution becomes severe, which is not preferable in production. It is considered that the action of mannitol in this case contributes to partially decomposing the active material and reconstructing the pore structure.

[0042]

As described above, according to the present invention, a lead storage battery having both excellent discharge characteristics and cycle life can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a distribution of pore diameters of a general positive electrode for a lead storage battery.

FIG. 2 shows a model of pores A and B.

FIG. 3 is a diagram showing the distribution of pore diameters in Example 1 and a conventional example.

FIG. 4 is a diagram showing a discharge curve at 0.2 C discharge of batteries using Example 1 and a conventional example.

FIG. 5 is a diagram showing a discharge curve at 3.0 C discharge of batteries using Example 1 and a conventional example.

FIG. 6 shows the battery using Examples 2 and 3 and Conventional Example 1.
Diagram showing discharge curve in 0C discharge

[Description of Signs] 1 Active material particles 2 Pores A 3 Pores B

Claims (4)

[Claims] The total pore volume of the positive electrode plate is 0.14 to 1.
A 0.18 cm ³ / g, and the total volume of pores less than 0.1μm is 0.01 or more in diameter is 0.02 cm ³ / g or more,
A lead-acid battery characterized in that the total volume of pores having a diameter of 0.1 or more and 4.0 μm or less is 0.13 cm ³ / g or more. 2. A process for charging a current collector containing a lead powder containing a main component, sulfuric acid and water, kneading the paste, and aging and drying the paste. A method for producing a lead-acid battery, wherein the battery is formed and charged in dilute sulfuric acid containing hydrazine. 3. An electrode plate containing a lead powder as a main component, a paste obtained by adding sulfuric acid and water to the current collector, and filling the current collector is subjected to formation charge, and thereafter, is charged to −1.% Based on Hg / Hg ₂ SO ₄ . 10V ~ -1.6
A method for producing a lead storage battery, comprising performing at least one step of overdischarging to a range of 0 V and then recharging at least once. 4. The method for producing a lead-acid battery according to claim 3, wherein the solution used for the formation charge is a mannitol or a sulfuric acid solution containing mannitol and hydrazine sulfate.