JPS586275B2 - lead acid battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lead-acid battery that has a low self-discharge rate and a long period of time during which no rehydration is required.

In recent years, attempts have been made to improve the frequency of supplementary charging and water replenishment after long-term storage, which is a practical drawback of conventional lead-acid batteries.

When lead-acid batteries are left for a long period of time, the amount of stored electricity decreases due to self-discharge, and the discharge capacity decreases.The main cause of this is antimony leached into the electrolyte from the lattice made of lead-antimony alloy. This is because, during charging, it is deposited or adsorbed on the negative electrode plate, forms a local battery with the negative electrode active material, and the negative electrode plate causes self-discharge.

Furthermore, when antimony is deposited on the negative electrode, the water-splitting potential of the negative electrode shifts in the direction of penetration, promoting the water-splitting reaction at the negative electrode, increasing the amount of liquid loss, and increasing the frequency of water replenishment.

In order to improve the problems caused by antimony elution as described above, research is being carried out from the following three directions.

(1) Limiting the content of eluted metal in the alloy composition of the lattice.

(2) Change manufacturing specifications, such as changing the amount of current applied.

(3) The metal eluted into the electrolyte is removed by replacing the electrolyte.

Regarding (1), the alloy composition of the lattice body of a conventional lead-acid battery is mainly lead, antimony, arsenic, and tin, and contains 4 to 5% of antimony, which has the second largest content after lead.

When the antimony content is lowered, the amount of antimony eluted is slightly reduced, but since the antimony once eluted is deposited on the negative electrode, the expected effect is not observed.

Regarding (2), there is a drawback that if the amount of electricity supplied during formation or initial charging is reduced, the initial performance of the lead-acid battery will be significantly reduced, as shown in FIG.

Regarding (3), when the negative electrode plate is washed with water after chemical formation, the sponge-like lead that is the negative electrode active material becomes lead hydroxide, so a large amount of current is required at the first charge, and this first charge causes new elution. This results in antimony being deposited on the negative electrode, and the electrolyte in the lead-acid battery may be replaced with new electrolyte after the first charge, but the amount of electrolyte that can be discharged at that time is 3.
Since only about 0 to 40% remains and 60 to 70% remains, there is a drawback that the effect of replacing the electrolytic solution cannot be expected much and supplementary charging is required after replacing the electrolyte.

The present invention considers that the elution of metals such as antimony into the electrolyte is unavoidable in the manufacture of lead-acid batteries, and aims to prevent metal ions such as antimony species ions generated by elution from being deposited on the negative electrode plate. It is something to do.

In order to achieve the above object, the present invention uses a metal complexing agent that forms a stable metal complex with a metal eluted into an electrolytic solution and shifts the reduction (deposition) potential of the metal complex in the electrolytic solution to a base state. It is characterized by being present in an electrolytic solution.

An uninvented embodiment will be described.

Ethylenediaminetetraacetate acid (hereinafter referred to as EDTA) is used as a metal complexing agent that forms a stable metal complex with antimony species ions in dilute sulfuric acid and shifts the reduction (precipitation) potential of the metal complex in dilute sulfuric acid to a base value. We discovered this and manufactured an NS40ZL type lead-acid battery with this added to the electrolyte solution.We left it at 20℃ for 6 months and allowed it to self-discharge at a rate of 1.7.
．． The results measured at 6A discharge are shown in FIG.

Note that the specific gravity of the electrolytic solution is 1.260 (20° C.).

When EDTA is not added, the remaining capacity is 50%, whereas when EDTA is added, the remaining capacity is 1 to 10" p.
It was found that the residual capacity improved from 50% to 84% while adding 100 pm of EDTA, and that almost no further improvement was observed even when 10'ppm or more of EDTA was added, for example 10'ppm.

That is, by adding 10 to 10'' ppm of EDTA to the electrolytic solution, it is recognized that the self-discharge of the negative electrode caused by antimony can be significantly suppressed.

Further, in the same type of lead-acid battery, continuous constant voltage electrolysis was performed for 2400 hours at a liquid temperature of 25° C. and a set voltage of 14.8 V, and the liquid loss rate due to water splitting was measured. The results are shown in FIG.

When EDTA is not added, the liquid reduction rate is approximately 100%, that is, most of the water is decomposed and disappears, whereas E
When adding DTA, the liquid reduction rate decreased from 97% to 38% when adding 1 to 103 ppm;
It has been found that even if 0.03 ppm or more, for example 10' ppm, is added, almost no further change is observed.

That is, by adding 10 to 103 ppm of EDTA to the electrolytic solution, the effect of extremely significantly suppressing the water purchasing reaction of the negative electrode caused by antimony is observed.

In particular, even when 10'' ppm of EDTA is added to the electrolytic solution, the amount of self-discharge and the amount of liquid loss are halved compared to when no addition is made, which is sufficient for practical use.

As described above, the lead-acid battery of the present invention includes a metal complexing agent in the electrolyte that forms a stable metal complex with the metal eluted into the electrolyte and shifts the reduction potential of the metal complex in the electrolyte to a base state. As a result, battery performance deteriorates, manufacturing specifications change significantly, and the number of processes increases. It has great industrial value because it is extremely effective in reducing the self-discharge rate and lengthening the period during which water replenishment is not required, without causing any additional water replenishment.

[Brief explanation of drawings]

Figure 1 is a curve diagram showing the relationship between the amount of current applied during formation and the initial discharge capacity in a conventional lead-acid battery, and Figure 2 is the relationship between the amount of EDTA added and the remaining capacity after self-discharge in the lead-acid battery of the present invention. FIG. 3 is a curve diagram showing the relationship between the amount of EDTA added and the liquid reduction rate after continuous constant voltage electrolysis.

Claims (1)

[Claims] 1. A lead-acid battery in which a metal complexing agent is present in an electrolytic solution, which forms a stable metal complex with a metal eluted into the electrolytic solution and shifts the reduction potential of the metal complex in the electrolytic solution to a base state.