JP2001160394A - Method of chemical conversion for lead battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrode plate, in which α-PbO2 is less and β-PbO2 is more in the amount in active material, and in which α-PbO2 exists at the lattice-active substance interface, to produce a battery with less self-discharge, large service capacity, and hard-to-occur early decrease in capacity. SOLUTION: Allowing time is inserted between the point, when lead dioxide layer with the thickness of 50-550 μm is generated in the active substance surrounding the positive electrode lattice and the point, when total sum of lead dioxide and anglesite reaches 90 wt.% of the total amount if positive active substance, after the chemical conversion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a lead storage battery.

[0002]

2. Description of the Related Art The formation of an active material on an electrode plate by passing a current through a positive electrode plate and a negative electrode plate in dilute sulfuric acid is called chemical formation. The reaction occurring on the positive electrode plate during chemical formation is mainly considered as follows.

First, the periphery of an electrode plate is filled with diluted sulfuric acid (referred to as liquid injection). At this time, lead monoxide (PbO) and sulfuric acid (H ₂ SO ₄ ) in the unformed active material react with each other to generate lead sulfate (PbSO ₄ ) and water (H ₂ O). After the injection, the mixture is allowed to stand for a certain period of time, and then a current is applied to form a chemical. At this time, it is considered that the following reaction formulas (1) and (2) mainly occur. PbO + H ₂ SO ₄ → PbSO ₄ + H ₂ O PbSO ₄ + 2H ₂ O → [β-PbO ₂ ] + H ₂ SO ₄ +2
H ⁺ + 2e ⁻ (2) PbO + H ₂ O → [α-PbO ₂ ] + 2H ⁺ + 2e ^{− From} the reaction of the formula (1), β-PbO ₂ is mainly produced,
Α-PbO ₂ is mainly produced from the reaction of the formula (2). β
-PbO ₂ is more electrochemically active than α-PbO ₂ , and by increasing it, the discharge capacity can be increased. However, if it exists at the interface between the lattice and the active material,
A phenomenon in which only the interface is discharged first and the active material cannot be discharged (early capacity reduction) is likely to occur.

On the other hand, α-PbO_TwoContained in active material
Discharge capacity decreases and self-discharge during standing
Will increase. However, α at the interface between the lattice and the active material
-PbO_TwoIf there is, the early capacity decrease mentioned above
Problems are less likely to occur. After injecting dilute sulfuric acid, the electrode surface
PbO in the vicinity quickly becomes PbSO_FourReacts to. PbS
O_FourHas about twice the molecular volume of PbO. This PbS
O_FourIs generated in the pores in the unactivated active material, so the pore volume
To reduce sulfate ions (SO_Four ^2-) Expansion
PbSO of PbO inside electrode plate_FourReaction to
Suppress. Also, when energized, the current density inside the electrode plate
Because it is large, PbO_TwoIs generated from inside the electrode plate. Yo
With the progress of chemical formation, PbO
α-PbO _TwoIs generated, and PbSO_FourOr
Β-PbO_TwoIs generated.

[0005]

However, as described above,
If PbO inside the electrode plate also reacts with PbSO ₄ , β-PbO ₂ can be increased and the discharge capacity can be increased by increasing the standing time after the injection, but such an electrode plate has an early decrease in capacity. Problems are likely to occur. An ideal positive electrode plate is one in which α-PbO ₂ in the active material is low and β-PbO ₂ is high, and α-PbO ₂ is present at the lattice-active material interface. If such an electrode plate can be obtained, it is possible to produce a battery that has a small self-discharge, a large discharge capacity, and is unlikely to cause early capacity reduction.

[0006] Therefore, an object of the present invention is to provide a chemical conversion method capable of obtaining such a lead storage battery.

[0007]

According to a first aspect of the present invention, there is provided a method for forming a lead-acid battery according to the first aspect, wherein the thickness of the active material in contact with the surface of the positive electrode grid is from 150 μm or more to 55 μm or more.
Let stand between the time when a layer of lead dioxide up to 0 μm or less is generated and the time when the total mass of lead dioxide and lead sulfate is 90 wt% with respect to the total mass of the positive electrode active material after the formation. It is characterized by putting.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION After conducting a chemical conversion experiment in advance and charging various amounts of electricity, and conducting a metallographic observation and a chemical analysis on the positive electrode plate after completion of the chemical conversion, a lead dioxide layer around the lattice surface is obtained. And the total mass of the positive electrode active material, and the total mass of lead dioxide and lead sulfate.

When a lead-acid battery is formed, the point at which a lead dioxide layer having a thickness of 150 to 550 μm is formed around the surface of the positive electrode grid, and the total amount of lead dioxide and lead sulfate is determined by the total amount of the positive electrode active material after formation. After the charging is temporarily stopped and allowed to stand, the charging is further performed to complete the formation. This makes it possible to obtain a battery having a large discharge capacity, no early capacity reduction, and a small self-discharge.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. An unformed battery of 2 V, 48 Ah was produced according to a conventional method. Next, a predetermined amount of diluted sulfuric acid was injected, and after one hour had passed, a current was started to flow to start chemical formation. As in the conventional case, a formation was performed in which a predetermined amount of electricity was continuously supplied without leaving the battery, and a formation in which the battery was left in the middle of supplying various amounts of electricity was performed. Here, all of the standing was performed at room temperature for 10 hours.

At this time, three batteries are required for one type of contents.
Each was tested, and one was disassembled before starting to stand, and the positive electrode plate was examined. Table 1 shows the test contents and the results of the positive electrode plate inspection before the start of standing. Here, the thickness of the PbO ₂ layer at the start of standing was measured at 10 points at random. Also, the amount of electricity
Assuming that 100% of the energizing current is used for PbO ₂ generation, the calculation was made assuming that the amount of electricity required to convert all the unactivated active material of the positive electrode to PbO ₂ was 100%.

[0012]

[Table 1] List of test contents

[0013] Each of the batteries of each content is 0.2CA
(Discharge end voltage 1.70 V), and subjected to a cycle of charging 125% of the discharge capacity at the same current as the discharge. FIG. 1 shows the result of the first cycle, and FIG. 2 shows the transition of the discharge duration during the cycle. The discharge duration of the first cycle was longer as the amount of electricity passed before being left was smaller. This is considered to be due to the following. During the standing, PbO remaining inside the electrode plate diffuses SO ₄ ^2-
And PbSO ₄ is produced. Therefore, the smaller the amount of energized electricity, the larger the amount of PbO left inside the electrode plate at the time of starting standing, so that PbSO ₄ produced by reaction during standing is left.
The amount increases, and the amount converted from PbSO ₄ to PbO ₂ increases. As a result, β-
The amount of PbO ₂ increases.

When the total amount of PbO ₂ and PbSO ₄ became 90% or more, the battery left to stand had almost no change in the discharge duration. This is because even if the storage is performed, there is almost no PbO that becomes PbSO ₄ during the storage, so that the amount of β-PbO ₂ contained in the converted active material is equivalent to that of the conventional product without the storage. That seems to be the cause.

Further, when the cycle is repeated,
PbO generated around the lattice surface _Two30-130 layers
Batteries less than μm have a relatively short discharge duration relatively early
became. This is because the early capacity reduction occurred.
Seem. In other words, the P of 150 to 550 μm
bO_TwoThe layer that was formed was α-PbO around the lattice surface._Two
Capacity decreases early due to the presence of a layer containing a large amount of
Probably did not happen.

A PbO ₂ layer of 150 to 55 is provided around the lattice surface.
The battery which was left after generating 0 μm, and which was left when the total amount of PbO ₂ and PbSO ₄ was less than 90%, had a larger discharge capacity at the first cycle than the conventional product, and had an early capacity. No drop occurred.

Next, an evaluation test of self-discharge characteristics was performed on one battery of each content. The content of the test was
After measuring the discharge capacity at 2 CA, the battery was fully charged, then each battery was left in a water bath at 40 ° C. for 3 months, and finally, after leaving at 40 ° C., the discharge capacity at 0.2 CA was measured. 40 ℃
By comparing the 0.2 CA discharge capacity before and after standing, it can be evaluated that the smaller the decrease in the capacity, the slower the self-discharge. Here, it is presumed that leaving at 40 ° C. for 3 months corresponds to leaving at room temperature for 1 year. FIG. 3 shows the capacity reduction rate of each battery. The smaller the amount of electricity passed before leaving during the formation, the smaller the capacity reduction rate. Although the reason is not clear, α-Pb
O ₂ is more likely to self-discharge than β-PbO _2, and the smaller the amount of α-PbO ₂ contained in the active material, the smaller the amount of self-discharge, resulting in a smaller capacity reduction rate. Seem.

[0018]

As described above, according to the present invention, it is possible to obtain a positive electrode plate which has a large initial discharge capacity, does not cause an early drop in capacity, and has less self-discharge.

Further, in this embodiment, the standing during the formation was carried out at room temperature for 10 hours. However, since the greater the amount of PbSO ₄ generated during the standing, the greater the effect, the longer the standing period during the formation, the better. Of PbO in the reaction to PbSO ₄ is S
Since the diffusion of O ₄ ^2- into the inside of the electrode plate is rate-determining, the standing period can be shortened by increasing the standing temperature. Furthermore, the total amount of lead dioxide and lead sulfate was reduced to about 9
The effect was seen when it went to 0 wt%,
From the magnitude of the improvement effect, it is desirable to leave during chemical formation at a point in time when the total amount is smaller.

[Brief description of the drawings]

FIG. 1 Discharge duration of the first cycle

FIG. 2 shows the results of a 0.2CA discharge repetition cycle test

FIG. 3 shows the results of an evaluation test of self-discharge.

Claims (1)

[Claims] An active material in contact with a surface of a positive electrode grid has a thickness of 1%.
Between the point in time when a layer of lead dioxide from 50 μm or more to 550 μm or less is generated and the point in time when the total mass of lead dioxide and lead sulfate becomes 90 wt% with respect to the total mass of the positive electrode active material after the formation is completed A method for forming a lead storage battery, wherein the method is to leave the battery unattended.