JPS5924500B2 - lead acid battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a maintenance-free lead-acid battery using a lead alloy lattice that does not contain antimony. The purpose is to improve the constant current overcharge life and cycle life of the battery.

Recently, there has been a strong trend in the market for lead-acid batteries toward maintenance-free batteries, which have advantages such as saving the time and effort of refilling with water, and having low self-discharge and being able to be stored for long periods of time in an injected state.

This type of battery generates a small amount of gas, so there is almost no corrosion of its terminals, and it also has the advantage of being able to be placed in any location since it does not require water replenishment. As a maintenance-free method, there are structural improvements such as lowering the cell saddle and wrapping the electrode plate with a separator, and using a labyrinth-shaped exhaust section, but the biggest difference from conventional lead-acid batteries is the alloy of the lattice. The reason is that the composition has been changed.

Examples include lead-antimony alloys in which the antimoso content is reduced from the conventional 4-6 wt% to 2-3 wtCfb, or lead-calcium alloys or lead-strontium alloys that do not contain antimony at all. I can list what was adopted. However, lead-acid batteries that use a lead alloy grid that does not contain antimony have significantly poorer constant current overcharging characteristics than those that use a lead-antimony alloy grid, and have a relatively deep low-rate discharge. Under these conditions, there is a drawback that the capacity rapidly decreases before the charge/discharge cycle progresses much, and the charge acceptance characteristics become extremely poor after the capacity decreases.

These phenomena are thought to occur because the lattice corrosion layer 1 and lead sulfate are likely to be generated intensively during discharge.
. Furthermore, lead-acid batteries with short constant current overcharge lifespans have the following problems. That is, 2.30 to 2.
In constant voltage charging by applying a voltage of 50V/cell, after the constant current range limited by the capacity of the charger has passed, the current gradually decreases as charging progresses, suppressing gas generation and grid corrosion. . However, if a minute short circuit occurs in one cell in the battery, the current will not decrease even at the end of charging, resulting in the same condition as constant current overcharging. It is known that in such a case, a lead-acid battery using a lead-calcium alloy as a lattice material rapidly loses its capacity. The present invention has been made in view of the above points, and by adding cadmium to the conventional lead-calcium-tin alloy, the interface properties are improved and a corrosion layer with low resistance during discharge is generated, which is particularly effective at constant current. This was based on the discovery that the overcharge life can be significantly improved.

Examples based on the present invention will be described below.

0.05 to 3.0wt to conventional lead-calcium-tin alloy
An NS4OZ type battery was prototyped using a lattice made of an alloy containing 30% cadmium, and a JIS overcharge test (JIS
D53Ol), the results shown in Table 1 were obtained. The JIS overcharge test is (1) overcharging at 4.5A for 110 hours at 40-45℃, (2) 48
(3) Discharge at 150A for 30 seconds as one cycle, and the life is defined as the time when the voltage reaches 7.2V at the 30th second of 150A discharge. Also, JIS life cycle number (
The results of JISD53Ol) are also shown in Table 1. The JIS life test was conducted under the conditions of 40-45℃, (1) 20A
(2) One cycle is discharge for 4 hours at 5A, and the life is defined as 42 minutes at 20A5. As can be seen from Table 1, by adding cadmium to the lattice alloy, it is possible to significantly improve the constant current overcharge life of lead-acid batteries using a lead-calcium-tin alloy lattice. , it can be seen that performance equivalent to that of conventional lead-antimony alloy batteries can be obtained.

Generally, lead-calcium-tin alloy batteries are often used for floats, and it is expected that the characteristics of lead-acid batteries will further improve in this field, and demand will increase.

Moreover, it is also found that the addition of cadmium to the lead-calcium-tin alloy extends the alternate charge-discharge life. However, since cadmium is relatively easily attacked by sulfuric acid, which is an electrolytic solution, if the amount of cadmium added is 2.0 wt%, corrosion of the lattice will increase and the life of the battery will be shortened. Further, cadmium precipitates on the negative electrode plate and causes dendrite-like crystals to grow, causing shoots through the separator. Therefore, the amount of cadmium added is preferably 2.0 wt% or less. One test was also conducted on a lead-acid battery using a grid other than the alloy composition shown in Table 1.
Calcium-cadmium alloys have poor corrosion resistance and low lattice strength after age hardening, so it is necessary to add tin.

It was also found that the appropriate amount of tin to be added is 0.1 to 1.5 wt%. That is, Table 2 shows the test results of a lead-acid battery not according to the present invention using a lead-calcium alloy lattice that does not contain tin.

The overcharging conditions according to JISD53Ol are general float (
(constant voltage) charging conditions are extremely harsh compared to charging, and corrosion of the grid is accelerated.

Comparing Tables 1 and 2, it can be seen that adding cadmium and tin at the same time is effective in improving the constant current overcharge life of lead-acid batteries using a lead-calcium alloy for the lattice. . The following is thought to be the reason why the effect is so great when cadmium and tin are added at the same time.

That is, the causes of the life span of a lead-acid battery using a lead-calcium alloy as a lattice under constant current overcharge conditions according to JISD53Ol are the formation of a high-resistance oxide film on the surface of the lattice and corrosion of the lattice itself. The former high-resistance oxide film is estimated to be composed of α-PbO or PbOx, and is very dense, and serves as an insulator in the form of a lattice/living substance.

However, this film exhibits an insulating effect only during discharge, and is considered to be a type of semiconductor. By the way, when cadmium is present, cadmium itself is easily corroded in terms of specific efficiency, so the corrosion layer becomes porous and β-PbO2, which is an electric conductor, is generated, and the corrosion layer also enters the lattice in a complicated manner, causing the lattice/ Facilitates the movement of electrons in living matter. However, in the case of cadmium-added sol, corrosion progresses and the service life is limited due to lattice corrosion. It is believed that tin prevents leaching of cadmium, thus maintaining the corroded layer with appropriate porosity and conductivity, and as a result, the galvanostatic overcharge life is significantly improved. In addition, we investigated alloys with aluminum added to improve the strength of the lattice and prevent calcium oxidation during alloy melting, but the effect of cadmium was the same in the presence or absence of aluminum. It may also be used as an alloy.

The amount of aluminum added is 0.005 to 0.1w
It was found that within the range of t%, there was no effect on battery performance. In the above embodiment, the same lead-calcium-tin-cadmium (-aluminum) alloy was used for both the positive and negative electrode plates, but a conventional lattice made of lead-calcium-tin alloy could be used as the negative electrode plate. I don't mind. As described above, the present invention is effective in significantly extending the constant current overcharge life of lead-acid batteries and improving the cycle life, and is of great industrial value.

Claims (1)

[Claims] 1. Calcium 0.03-0.12wt%, Tin 0.1-0.1%
A lead-acid battery characterized by using a lead alloy lattice body consisting of 1.5 wt% cadmium, 0.1 to 2.0 wt% cadmium, and the balance lead. 2 Calcium 0.03~0.12wt%, Tin 0.1~
A lead-acid battery characterized by using a lead alloy lattice body consisting of 1.5 wt%, cadmium 0.1 to 2.0 wt%, aluminum 0.005 to 0.1 wt%, and the balance lead.