JPS6077358A - Electrode for lead storage battery and its manufacture - Google Patents

Abstract

PURPOSE:To improve the capacity restoration of an electrode for a lead storage battery after it is left in an overdischarged state for a long period of time by causing only the surface of the grid to contain a perovskite compound consisting of lead and chromium as well as a perovskite compound consisting of lead and titanium. CONSTITUTION:A positive casted grid of 15g weight made of a lead-calcium-system alloy containing 0.1wt% of calcium is immersed in an aqueous sulfuric acid solution of 1.10 specific gravity containing 10<-1>mol/l of chromium sulfate and an aqueous sulfuric acid solution of 1.10 specific gravity containing 10<-1>mol/l of titanium sulfate to subject the grid to anodic polarization thereby forming a perovskite compound over the surface of the grid. After the anodic polarization is completed, the casted grid is taken out from the aqueous sulfuric acid solution before being washed with water. After that, a paste is packed over the grid thereby forming a plate. A sealed lead storage battery of about 3 AH capacity is obtained by subjecting three pieces of negative plates and two pieces of thus formed unformed plates used as positive plates to formation charging.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to an electrode for lead-acid batteries and a method for manufacturing the same.It is used in a wide variety of applications, particularly as portable televisions and emergency power sources, and has recently become rapidly popular. This invention relates to the improvement of small sealed lead-acid batteries, which are being used as a power source for VTRs and demand is increasing.

Conventional structure and problems Small sealed lead-acid batteries have the characteristics of not leaking even if they are overturned or placed upside down, and do not require water replenishment.

It is used for a variety of purposes, including portable televisions and emergency power supplies. Also, recently, the demand for power supplies for portable VTRs has increased. This requires a significantly higher level of energy density than conventional batteries, something that would be difficult to achieve with a lead-acid battery. It is required to have strict characteristics such as being able to withstand long-term storage even in an over-discharged state.

However, in general, if a lead-acid battery is over-discharged and then left unattended, it becomes difficult to charge it, and there is a drawback that capacity recovery performance deteriorates. By leaving this as a cause,
It is conceivable that a highly resistant corrosion layer, so-called a barrier layer, is formed on the surface of the positive electrode lattice or at the interface between the positive electrode lattice and the active material.

Therefore, it is desirable to have a structure that suppresses the formation of this barrier layer.

In this way, from the viewpoint of fj, studies have been made on lattice alloy compositions in which it is difficult to form a barrier layer. For example, lead-acid batteries using lead-silver alloys, lead-lithium alloys, lead-calcium-tin cages, etc. as grids were investigated for their charging capacity and capacity recovery after being allowed to over-discharge. As a result, these batteries are slightly better in terms of the above-mentioned characteristics than the widely used lead-hydrol/umium-based lead-acid batteries due to maintenance-free requirements, but they are not completely satisfactory. 0 All of these alloys have the disadvantage of being expensive. Generally speaking, lead-silver alloy or lead-lithium alloy is used for the grid in seat batteries.

Silver and lithium, which have a small hydrogen overvoltage in the lattice, have a strong tendency to dissolve in the electrolyte and precipitate on the negative electrode. Self-discharge is likely to occur in such batteries.

During the charging process, hydrogen gas is generated violently, so the electrolyte tends to decrease. -! Also, the lead-silver lattice has the disadvantage of low mechanical strength. As mentioned above, by changing the lattice alloy composition, it is possible to maintain the battery in an over-discharged state for a long period of time without deteriorating other battery characteristics. It has been difficult to improve capacity recovery after storage.

On the other hand, as an attempt to change the composition of only the lattice surface.

A possible method is to form a metal layer on the surface of the grid by immersing the grid in an aqueous solution containing metal ions or plating it in the aqueous solution, and then filling the grid with a paste and performing chemical charging.

However, in this method, metal adhering to the lattice surface dissolves into the electrolyte during the chemical charging process, and is further deposited on the negative electrode plate, which may adversely affect battery characteristics.

OBJECTS OF THE INVENTION The present invention aims to improve the above-mentioned conventional drawbacks, and particularly aims to improve the capacity recovery of lead-acid batteries after being left in an over-discharged state for a long period of time.

Structure of the Invention The present invention provides an electrode for a lead-acid battery, characterized in that a perovskite compound is held on the surface of a lattice alloy. The perovskite compound is characterized by the use of a compound of lead and chromium or lead and titanium. Furthermore, in the present invention, the above-mentioned perovskite compound is prepared by anodically polarizing a lead lattice in an aqueous solution containing chromium ions or titanium ions, then pulling the lattice out of the aqueous solution, washing it with water, and filling the surface of the lattice with a paste. The present invention provides a method for manufacturing a lead-acid battery, which is characterized by being held on a grid surface.

Description of examples An embodiment of the present invention will be described below.

The present invention is characterized in that a perovskite compound is formed only at the interface between the lattice and the active material. The method for forming perovskite compounds will be briefly described.

Specific gravity 1・ containing 10-' mol/(l of chromium sulfate)
A positive electrode casting having a weight of 159 and consisting of a lead-calcium alloy with a calcium content of 0.1% in a sulfuric acid aqueous solution with a specific gravity of 1.10 and a sulfuric acid aqueous solution with a specific gravity of 1.10 containing 1 o-' mol/β of titanium sulfate. The grid was immersed and polarized positively. When anodic polarization was performed, a pure lead plate was used as the counter electrode plate, a cast grid for the positive electrode was inserted between the two counter electrode plates via a polyethylene separator, and anodic polarization was performed at a constant current of 50111A. After anodic polarization, the cast grid was removed from the sulfuric acid aqueous solution and washed with water, and then the paste was filled onto the grid.

The thus produced electrode plates were used as unformed plates for positive electrode plates, and a sealed lead-acid battery with a capacity of about 31 H was created by chemical charging with a configuration of two positive electrode plates and three negative electrode plates.

Note that a normal electrode plate was used as the negative electrode plate, and a glass mat was used as the separator.

Hereafter, A is a battery using a grid that was anodically polarized for 10 minutes in a sulfuric acid aqueous solution containing chromium sulfate, B is a battery using a lattice that was anodically polarized for 10 minutes in a sulfuric acid aqueous solution containing titanium sulfate, and chromium ion battery is for comparison. Specific gravity 1 that does not contain titanium ions or titanium ions
．． A battery using a grid that was anodically polarized for 10 minutes in a sulfuric acid aqueous solution of 10% was designated as C.

The following test method was adopted to examine capacity recovery after a lead-acid battery was left in an over-discharged state for a long period of time.

1. Check the initial capacity by discharging at a rate of 5 hours, then 2.4
After charging at a constant voltage of 5V (7) for 5 hours, constant resistance discharge of 10Ω was performed for 4 consecutive days. Next, after being left at 40° C. for a long period of time, it was charged at a constant voltage of 2.46 V for 6 hours. Finally, as in the beginning, the battery was discharged at a rate of 6 hours to check the capacity, and the ratio of this to the initial capacity, ie, the capacity recovery rate, was checked. Figure 1 shows batteries A, B, and C, and for comparison, a lead-Cal/RAM battery without any treatment. The relationship between the capacity recovery rate of a battery using a grid (referred to as battery D) and the storage period is shown.

From this figure, it can be seen that the capacity recovery rates of Batteries A and B are extremely superior compared to other batteries.

The following may be the cause of the above results: Generally, chromium and titanium are lead, PbCrO4 and PbT.
Forms a perovskite compound of iO4. As shown in this example, when the lattice is anodically polarized in an aqueous sulfuric acid solution containing chromium ions or titanium ions, the above-mentioned perovskite compound is thought to be formed on the lattice surface. because.

When a lead lattice is anodically polarized in an aqueous sulfuric acid solution, β-
PbO2 is formed, but in the process of forming β-Pb02, it is thought that lead on the surface of the small lattice becomes divalent lead ions and dissolves, and then becomes β-pbo2 and precipitates. If a large amount of chromium or titanium ions exist for each dissolved lead ion, the lead ions and chromium ions, or the lead ions and titanium ions, bond to each other and form a perovskite compound of PbCrO4 and PbTiO4 in the lattice. It is thought that it precipitates on the surface. When we actually confirmed the existence of these perovskite compounds, we were unable to quantify them by X-ray diffraction because these compounds are formed only on the lattice surface, but when we observed the lattice surface with a scanning electron microscope, we found that The existence of perovskite compounds has been revealed.

These perovskite compounds have semiconducting properties and are electronically conductive, but they have very strong surface acidity and poor reactivity, so even after overdischarge or after long-term storage, the perovskite compound remains on the lattice surface. is considered to continue to exist stably.

Therefore, even if a barrier layer is formed on the lattice surface due to long-term storage, the perovskite compound exists within the barrier layer and is considered to greatly contribute to electron conduction between the lattice and the active material. For this reason, it is thought that even if the battery is left in an over-discharged state for a long period of time, the capacity is recovered with a good recovery rate by charging.

In this way, the present invention uses lead and chromium only on the lattice surface.

It is characterized by holding a perovskite compound of lead and titanium. Therefore, the mechanical strength and corrosion resistance of the lattice itself are not affected in any way.

Furthermore, the present invention is characterized in that a perovskite compound is formed on the lattice surface before filling with the paste. That is, before filling the paste, the perovskite compound -! Once formed on the lattice surface, the perovskite compound will not decompose into chromium or titanium ions and dissolve into the electrolyte. In the present invention,
Since the grid is anodically polarized in an aqueous solution containing metal ions and then washed with water, the chromium and titanium ions attached to the grid will not dissolve into the battery electrolyte. As described above, the present invention does not have any adverse effect on battery characteristics.

Figure 2 shows the anodic polarization time and the overdischarge rate for a battery using a grid that was anodically polarized at 50 mA in an aqueous sulfuric acid solution with a specific gravity of 1.1o containing 10-' mol/l of chromium sulfate. The relationship between the capacity recovery rate after being left unused for several months is shown. From this figure, it is clear that if a certain amount of perovskite compound is formed on the lattice surface, the capacity recovery rate (d) is significantly improved. By forming a perovskite compound of lead and titanium, the battery has significantly improved capacity recovery after being left in an over-discharged state for a long period of time without having any adverse effects on other battery characteristics. The present invention greatly increases the reliability of small sealed lead-acid batteries, which have recently been fully utilized as power sources for portable VTRs.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the capacity recovery rate and the period of storage after a lead-acid battery equipped with a battery electrode according to an embodiment of the present invention is left in an over-discharged state for a long period of time. In a battery containing a perovskite compound of lead and chromium in an example. FIG. 3 is a characteristic diagram showing the relationship between the time of positive polarization and the capacity recovery rate after being left in an over-discharged state for three months.

Claims (3)

[Claims] (1) An electrode for lead-acid batteries characterized by holding a perovskite compound on the surface of a lattice alloy. (2) The electrode for a lead-acid battery according to claim 1, wherein the perovskite compound on the surface of the lattice alloy is a compound of lead and chromium, or lead and titanium. (3) A perovskite compound is formed on the lattice surface by a process of anodically polarizing the lattice in an aqueous solution containing metal ions of chromium or titanium, then pulling the lattice out of the aqueous solution and washing it with water, and then filling the lattice surface with a paste. A method for producing an electrode for a lead-acid battery, characterized by forming an electrode.