JPS6050034B2 - Lead alloy for lead-acid batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lead alloy for lead-acid batteries.
) By adding sulfur (S) as a third alloying element to the tin (Sn)-arsenic (As) alloy, Pb-Sn-As
The purpose is to improve the corrosion resistance of alloys.

The lead alloy traditionally used mainly in lead-acid batteries is Pb.
-Sb-based alloys, in particular Pb-Sb-As alloys, are most commonly used.

However, Pb-Sb alloys have a large self-discharge due to the low hydrogen overvoltage of Sb, and furthermore, the water electrolysis voltage during charging is low, resulting in a large decrease in water in the electrolytic solution, making maintenance complicated. To improve this, Pb-Ca system or Pb-
Br-based alloys have been developed and put into practical use, but when batteries using these alloys are discharged until the end-of-discharge voltage is low, for example, at a discharge current of about 5 hours, one cell can be discharged to below IV. Under such conditions, the cycle life will be extremely short and charging will become difficult. For this purpose, in practical terms, it is necessary to use a device that controls the discharge end voltage using a circuit, which has the disadvantage of increasing the cost of the power source, including the price of this device and the charger. From these points of view, recently Pb-Sn-As
Alloys were proposed. Since this alloy does not contain metals with low hydrogen overvoltage such as Sb, self-discharge and water loss in the electrolyte are comparable to Pb-Ca alloys, and since it contains Sn, it is less likely to overdischarge. It also has the advantage of very little deterioration. However, this alloy has inferior corrosion resistance compared to Pb-Ag alloy, which has been considered to be a typical corrosion-resistant lead alloy.

If a lead alloy with poor corrosion resistance is used for the grid or lead portion of a lead-acid battery, the battery life will be shortened, especially when used for the positive electrode. This is because the current collecting effect, which plays a role as a lattice or lead, deteriorates due to a decrease in surface area due to corrosion of the alloy, wire breakage, etc., and the mechanical strength of the lattice is weakened by the oxide, which causes the active material to become weaker. Due to the inability to hold it. That is, as a lead alloy for lead-acid batteries, the better the corrosion resistance, the better. The inventors
We thought that if the above-mentioned properties of the Pb-Sn-As alloy could be improved, it would become an even more excellent lead alloy, and we investigated a third additive element to improve the corrosion resistance. It is essential that the elements to be added do not harm battery performance, be cheap, and be not particularly harmful to the human body.From these points of view, as a result of considering relatively small amounts of added elements, we found that S
was found to be effective.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Since the interaction between Sn and As of the base Pb-Sn-As alloy and S is considered, the contents of Sn and As were also measured for some samples. First, pure Pb was heated and melted.

The heating source may be gas, petroleum, or electric heat, but since corrosion resistance is affected by the temperature of the molten material or the temperature of the mold, it is preferable to control the temperature as accurately as possible. The melting temperature was 500°C, and Sn,A
Add s and S, stir well and heat to about 150°C in a mold, size 20 x 100TnIIL) thickness 2Tf
A plate of UrL was cast and cooled. Note that the addition of As is
A Pb-As alloy containing a high concentration of M in advance was diluted and used.

S may be added directly as a single substance, but since it is difficult to control the content, similarly to M, a Pb-S alloy containing a high concentration of S was prepared in advance, and this was diluted before use. S may be added as a compound of Pb, Sn, or As and S. For these cast specimens, oxidation loss was measured as follows in order to compare the corrosion resistance.

That is, using a pure Pb plate as the counter electrode and SO with a ratio of 1.28 as the electrolyte, anodization was carried out at a constant current of 10 wLA/d, and the sample was taken out when the total current carrying capacity reached 10 Ah. The oxides were removed in an alkali or mannitol bath, and the weight loss in the metallic state was measured. The results are shown in Table 1.
Table 1 shows the results for a Pb-Sn-As-S alloy using a diluted master alloy to which S is added alone, but Pb-Sn-As-S with the same composition added as a compound The results of the corrosion resistance of the alloys were also almost the same as in Table 1.

Table 1 shows only typical examples of M and Sn, but as the Sn content increases, the oxidation loss decreases, that is, the corrosion resistance improves, but as the M content increases, the corrosion resistance decreases. Regarding S, it can be seen that when 0.001 to 0.05% by weight of S is added to the Pb-Sn-M alloy, the corrosion resistance is improved compared to a product without the addition. This effect of S is not particularly related to the content of Sn or As in the Pb-Sn-As alloy; It is effective in the range of OOl to 0.05% by weight. In particular, when the S content is 0.1% by weight, the corrosion resistance tends to decrease. Although not shown in Table 1,
As a result of measuring the transverse rupture strength, which is one of the mechanical strengths of these alloys, there was no particular change in the Pb-Sn-As alloy to which 0.001 to 0.05% by weight of S was added.

That is, from the point of view of mechanical strength, under the conditions of adding S;
In SnO. % by weight, ASO. % by weight or more of the alloy is preferred. However, regarding As, 0. Heel weight % or less is preferable. S
It is difficult to determine the upper limit of n from alloy specimens. Next, we will explain the performance comparison results when grids made of these alloys are applied to actual batteries.

The raw materials of each alloy composition are heated and melted at approximately 500°C,
A mold heated to about 150℃, width 25Twt, length 36
TWt1 thickness 2.57r$t and 1.8? A grid with a conventional structure was cast, water-cooled, heated at about 120° C. for 20 hours, and then cooled. An active material was coated on this grid using a conventional method to produce a chemically formed electrode plate. In addition, there are 2 on the positive electrode plate.
．． A grid with a thickness of 5TTUTL and a thickness of 1.8TWL was used for the negative electrode plate. Next, an electrode plate group was assembled using these four positive electrode plates, five negative electrode plates, and a separator, and a battery was constructed using H2SO4 with a specific gravity of 1.28 as the electrolyte, and these batteries were heated at a current of 240 rnA. 1? Charge for 48
The initial capacity was confirmed by discharging at 0 mA.

As a result, the initial capacity is approximately 2.4 regardless of alloy composition.
Ah, it was hot. The following tests were conducted using these batteries.

(1) Self-discharge characteristics After being fully charged, the battery was left in an atmosphere at 40°C, and the capacity was checked after 1 month and 3 months to measure the self-discharge rate.

(2) Overdischarge cycle life characteristics 240m. Charged for 1 hour with a current of A, 5Ω per cell
A cycle of discharging for 8 hours was repeated with a resistance of 1, and the number of cycles until the discharge duration reached the initial value of 112 was measured.

The discharge duration in this case was evaluated as the time required for each cell to reach 1.8V. In this test, the final voltage after 8 hours of discharge was approximately 0.1 to 0.6 V per cell. This test allows the overdischarge characteristics to be determined. (3)
Capacity recovery after overdischarging After being fully charged, discharge continuously for 5 days at 50℃ with a resistance of 50Ω per cell, and then discharge at 50℃
After opening the circuit and leaving it for one month, 2.5V per cell.
The battery was charged for two hours at a constant voltage of 480 wLA, and then discharged at 480 wLA to measure the capacity recovery rate.

This test also evaluates overdischarge characteristics. (4) Overcharge and overdischarge cycle life characteristics Continuously charged for one week at 240T1,A, 5Ω per cell
Repeat the cycle of discharging for 8 hours with a resistance of
The number of cycles until reaching No. 2 was measured.

This test allows comparison of the corrosion resistance of the alloys used. In other words, the main cause of the lifespan in this test was corrosion of the grid used for the positive electrode. Representative examples of these results are shown in Table 2.

For comparison, representative examples of a Pb-Sb-As alloy, a Pb-Ca alloy, and a Pb-Sn-As alloy to which S is not added are also shown. These results show that batteries using Pb-Ca alloy and Pb-Sn-As alloy have significantly better self-discharge characteristics than batteries using Pb-Sb-As alloy, and - The addition of S to the As alloy does not deteriorate the self-discharge characteristics, and regarding the overdischarge cycle life, the life of the Pb-Sn-M alloy containing 5J weight % is somewhat short, but other than that, the Pb- It is clear that this is significantly improved compared to the Ca alloy, and that the addition of S does not deteriorate the overdischarge cycle.

Claims (1)

[Claims] 1 A lead alloy for a lead-acid battery, comprising 0.3 to 3.0% by weight of Sn, 0.1 to 0.3% by weight of As, 0.001 to 0.05% by weight of S, and the balance Pb.