JPS5827625B2 - sealed lead acid battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sealed lead-acid battery in which a lead alloy substantially free of antimony is used in the positive and negative electrode grids, and water in the electrolyte is prevented from decreasing due to a sealed reaction caused by an oxygen cycle. It is something.

In conventional batteries of this type, the electrolyte is made non-fluid, gel-like, or impregnated into a porous material to facilitate the reaction between the oxygen gas generated from the positive electrode and the negative electrode. In addition to facilitating diffusion and contact with the electrode, the amount of negative electrode active material was larger than that of the positive electrode, and was used in excess.

Alternatively, it was common to make the capacity of the negative electrode greater than that of the positive electrode, such as by making the capacity of the negative electrode greater than the sum of the capacity of the positive electrode and the oxygen deficiency that occurs during the battery's life.

Furthermore, the lattice alloy used has been one that does not substantially contain antimony, such as a lead-calcium alloy or a lead-antimony-tin alloy containing less than 2% antimony.

This is to increase the overvoltage for hydrogen gas generation to L~ to prevent hydrogen gas generation from the negative electrode, reduce self-discharge of the negative electrode, and prevent water from decreasing in the electrolytic solution.

Because conventional batteries have this structure, they have the advantage that water decreases little while the battery is in use or left unused, and there is no need to refill it, and that it does not leak even if the battery is tipped over. The charge/discharge cycle caused by the 1. If the battery is left uncharged, the electrolyte becomes nearly neutral, and the degree of acetylation of lead increases, causing a short circuit between the positive and negative electrodes, which becomes irreversible.

The object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a sealed lead-acid battery that has a long charge/discharge cycle life due to deep discharge, deeply discharges due to slow discharge, and does not cause any abnormality even if left for a while. There is a particular thing.

The gist of the present invention to achieve the above object is to reduce the amount of active material in the negative electrode to make the slow discharge capacity smaller than that of the positive electrode, and to reduce the weight of sulfuric acid in the electrolyte to the amount of active material in the negative electrode. The aim is to maintain the electrolyte sufficiently acidic even when deep discharge is performed with a minute current.

The present invention was developed as a result of reconsidering the requirements that were common knowledge for this type of lead-acid battery.

That is, conventionally, (1) The amount of negative electrode active material is larger than that of the positive electrode, and is used in excess.

This prevents hydrogen gas from being generated from the negative electrode during charging, and -! In addition, this is necessary in order to facilitate the reaction between the oxygen gas generated from the positive electrode and the negative electrode, and to prevent deterioration of the negative electrode, which is oxidized by oxygen gas and does not reach a fully charged state.

(2) The amount of electrolyte must be kept as small as possible to provide as many paths for gas diffusion between the main and negative electrode plates.

This is also effective in preventing leakage when the product falls over.

It was thought that

The results of reexamining these two points are as follows.

Experiment 1. Examination of the ratio of the amounts of positive electrode and negative electrode active materials FIG. 1 shows the discharge characteristics of batteries in which the ratio of the amounts of positive electrode and negative electrode active materials was changed to change the relationship in discharge capacity.

The terminal voltage of a battery with a small positive electrode discharge capacity and the single electrode potential of the positive and negative electrodes are shown by solid lines, and the case where the negative electrode has a small discharge capacity is shown by a dotted line.

Although there is no difference in the terminal voltage between the two, it can be seen that the transition of the unipolar potential is completely different.

Figure 2 shows a battery using a lead-antimony alloy containing 5% antimony and a lead-calcium alloy, with a positive and negative electrode capacity ratio of approximately 2:3 or 3:2, respectively. This is the result of a first test of the charge/discharge cycle life formula.

In this test, the discharge is at the terminal voltage], 7V/'-+,z
The battery weight was measured at each appropriate cycle.

As a result, for lead-antimony alloys, those with a larger negative electrode capacity have a longer life and less loss of electrolyte, as is conventional wisdom.
In contrast, it was better to reduce the capacity of the negative electrode in the case of alloys.

After this life test path, the negative electrode plate was examined in detail.
When an alloy containing antimony was used, the surface area measured by the BET method was 1/5 to 1/10 of the initial value, and lead sulfate as an active material reached 40 to 70%. In the case of alloys without l, the surface area is between 2/3 of the initial
1/2, and lead sulfate was 5% or less.

In addition, looking at the weight of the battery, that is, the amount of water in the electrolyte reduced during one life test, the battery using a lead-antimony alloy for the lattice was larger and died compared to the lead-calcium alloy. Therefore, there is clearly less sealing reaction due to absorption of oxygen gas by the negative electrode plate.

Dismantling the battery 1 - The results also show that the gel of the lead-antimony alloy is dry, which is a suitable state for diffusion of scum from the positive electrode to the negative electrode and for contact between the negative electrode and the gas.

Despite this, the reason why the sealing reaction is small is that the negative electrode active material has deteriorated to an uncharged state.

On the other hand, in a battery using a lead-calcium alloy, the negative electrode plate is always active and remains in a state where it can easily accept charging.

Next, let's consider the oxygen cycle that occurs during charging within this battery.

In the latter half of charging, oxygen gas first begins to be generated from the positive electrode, the amount of which gradually increases, and when the positive electrode is fully charged, all of the charging current is consumed for gas generation.

Since the negative electrode does not contain antimony in its lattice alloy and has a large overvoltage for hydrogen gas generation, while lead sulfate is present in the active material, little hydrogen gas is generated and the lead sulfate is charged.

On the other hand, the oxygen gas generated from the positive electrode reacts with the negative electrode, and the metal lead that is the negative electrode active material becomes lead oxide, which easily reacts with the electrolyte and eventually becomes lead sulfate, so the negative electrode The positive electrode will be charged to a level corresponding to the degree to which the positive electrode is charged.

Furthermore, let us consider the relationship between the ratio of the amount of negative electrode active material to that of the positive electrode and the sealing reaction.

In both the positive and negative electrodes, when the active material is fully charged, all of the charging current is consumed for gas generation, but when it contains a large amount of discharge products, as long as the electrode plate is active, the active material consumed for charging.

That is, the generation of gas depends not on the amount of active material but on the ratio of the amount of discharged active material to the amount of charged active material.

The amount of discharge active material is determined uniquely by the amount of electricity discharged through the external circuit, regardless of the amount of active material, and is exactly the same for the positive and negative electrodes (however, the amount of discharge active material is the same for the positive and negative electrodes (however, the electrochemical equivalent of lead dioxide and lead (although they are proportional to each other).

Therefore, when the amount of active material is made excessive, the ratio of the amount of discharged active material decreases, and the charging efficiency during charging becomes lower.

On the contrary, the smaller the amount of active material is, the more it is discharged, and the higher the ratio of the amount of active material is, the better the charging efficiency is, and the less gas is produced as a side reaction of charging.

That is, the generation of hydrogen gas from the negative electrode causes the amount of negative electrode active material to be smaller than that of the positive electrode, and the sealed reaction of the oxygen cycle proceeds smoothly.

(El, l, If the negative electrode active material has deteriorated and is inactive, the reaction with oxygen gas will be slow, so it is effective to increase the amount of active material and increase the reaction area. .

From the above, the conventional wisdom that the amount of negative electrode active material must be in excess of that of the positive electrode is correct only for batteries using alloys containing antimony, and in any case antimony is the core. Since the negative electrode active material becomes large and causes sulfation, it is effective in compensating for its deterioration and capacity reduction.Batteries that do not contain antimony have less capacity loss due to this phenomenon, so the negative electrode active material There is no need to increase the capacity of the positive electrode, and in fact, it is better to decrease the capacity so that the sealing reaction 1d is carried out smoothly.Also, by making the positive electrode active material layer excessive in this way and keeping the utilization rate of the positive electrode active material low during discharge, It was found that the cycle life performance was significantly improved.

Note that the ratio of the electrochemical equivalent of the negative electrode to the flood electrode is the same as the molecular weight ratio, which is 207/2390.87, so if the utilization rate is 1i, then the negative electrode active material is At a substance amount of 0.87, the discharge capacity of both becomes the eyelid.

Since the utilization rate of the active material varies depending on the thickness of the electrode plate, the porosity of the active material, etc., it is not possible to simply express the discharge capacity of the positive and negative electrode plates.

That is, the capacitance of the positive and negative electrodes cannot be compared in size unless they are actually discharged.

However, there is a strong tendency that the greater the amount of active material, the greater the discharge capacity.If the weight of the negative electrode active material is about 0.6 of that of the positive electrode, the capacity of the negative electrode will never be greater than that of the positive electrode. From then on, the number will definitely decrease by 1.

Experiment 1 Experiment 2. Consideration of the amount of electrolyte In sealed lead-acid batteries that use oxygen cycle reactions, in order to facilitate contact between oxygen gas and the negative electrode active material, it is necessary to use a small amount of flowing electrolyte and create a gap between the IE and the negative electrode plate. is necessary.

On the other hand, it is possible to increase the amount of non-fluidized electrolyte by widening the gap between the electrode plates or by utilizing the space above the electrode plate group.

However, (-7) In a battery made by making the electrolyte non-fluid, after discharging 1° with a small current and a low terminal voltage at 1, if left without charging, the battery will drop to zero, and even after charging from 1 to 1, the battery will recover from 1- Therefore, by changing the amount of active material in the positive and negative electrodes, the capacity ratio of the negative electrode to the iF electrode is set to about 2/3.7 or about 3/2 in a battery. Prototype batteries in which the amount of sulfuric acid in the electrolyte was varied over a wide range by changing the concentration of the electrolyte were produced at a terminal voltage of 1 to .20 hours at a rate of current of 1.
Table 1 shows the results of discharging the battery at a temperature of 0.1 to 0.01 and then leaving it in an atmosphere of 30°C at t' to check for abnormalities in the first month.

Incidentally, numbers 1 to 13 in Table 1 indicate the test batteries, respectively, and the abnormality indicates a battery in which an abnormal phenomenon occurred in which the voltage became zero due to being left unattended after being discharged and did not recover even after being charged.

As is clear from Table 1, in a conventional battery with a negative electrode capacity of 1-7, which is larger than that of the positive electrode, the voltage drops to zero when left after discharging, and the IF11 recovery [
- Abnormal phenomena such as "no" were often observed, and the negative electrode capacity was reduced, and it was less in batteries.

Also, the ratio of sulfuric acid 4 to the weight of the negative electrode active material is 0.6.
5.C causes an abnormal U-11 phenomenon as described in i'Th1-1.
This abnormality did not occur after 2007.

From the experiment in I-H, it was found that in Schiff/ and sealed lead-acid batteries using an alloy that does not contain antimony and using an oxygen cycle,
Contrary to conventional wisdom, the amount of material in the negative electrode is reduced to make the discharge capacity smaller than that of the positive electrode, and the weight of sulfuric acid in the electrolyte is 0.7 or more of the weight of the negative electrode active material. It can be seen that a product with excellent performance cannot be obtained.

Specific measures to reduce the capacity of the negative electrode include thinning the electrode plate]-7 to reduce the amount of active material, making the electrode plate smaller than the positive electrode plate, or reducing the number of electrode plates. do it.

Regarding the number of electrode plates, in normal electricity, the negative electrode has one more plate than the positive electrode, but if this is reversed, the number of negative electrode plates can be reduced by one.

In addition, in a normal battery, one positive electrode plate and one negative electrode plate are arranged alternately, but if two positive electrode plates and one negative electrode plate are arranged alternately, the number of negative electrode plates can be reduced. It can be reduced to 1/2 that of the positive electrode.

In order to make the capacity of the negative electrode smaller than that of the positive electrode, the ratio of the amounts of active materials between the two cannot be determined in general because the utilization rate varies depending on the electrode plate thickness and temperature.

However, in the case of slow discharge, it is preferable to make the weight of the active material of the negative electrode 0.50 or less of that of the positive electrode, since the capacity of the battery is limited by the negative electrode regardless of the electrode plate thickness or temperature.

Since the utilization rate of the active material of the negative electrode is limited to approximately 60%, in this case, the utilization rate of the positive electrode active material can be suppressed to approximately 35% or less, and even if an alloy that does not contain antimony is used for the lattice, discharge will not occur. It is shallow and has a long life.

The present invention has the above-mentioned advantages: a. The capacity of the battery is limited by the negative electrode, and the utilization rate of the positive electrode active material is kept low, so the charge-discharge cycle life performance is excellent. There is.

b. Even if the amount of sulfuric acid is further reduced by reducing the amount of electrolyte or lowering its concentration, no abnormality will occur when left after deep slow discharge.

Even though an alloy that does not contain C or antimony is used for the lattice, the characteristics of long charge/discharge cycle life and little deterioration due to self-discharge and storage are not lost.

[Brief explanation of drawings]

Figure 1 shows the discharge characteristics of a battery with a large capacity positive electrode and a battery with a large capacity negative electrode. Figure 2 shows the capacity ratio of the positive and negative electrodes using a lead-antimony alloy and a lead-calcium alloy in the grid. It is a figure which shows the charge-discharge cycle life test result of the changed battery.

Claims (1)

[Claims] 1. A lead alloy that does not substantially contain antimony is used for the positive and negative electrode grids, and the electrolyte is made non-fluid so that the oxygen gas generated from the positive electrode and the negative electrode come into contact and react, and at the same time, outside air enters the battery. The slow discharge capacity of the negative electrode is smaller than that of the positive electrode, and the weight of sulfuric acid in the electrolyte is 0.7 or more of the weight of the negative electrode active material. A sealed lead-acid battery.