JPS6065458A - Manufacturing method for electrodes for lead-acid batteries - Google Patents

Abstract

PURPOSE:To increase the capacitive restoration of a lead storage battery after it is left over a long period of time by making a positive plate by subjecting a lead storage battery grid to anodic polarization in an aqueous solution containing tin ion before washing the grid with water prior to packing a paste over the surface of the grid. CONSTITUTION:A positive casted grid made of a lead-calcium alloy is immersed in an aqueous sulfuric-acid solution containing tin sulfate to subject the grid to anodic polarization before the grid is taken out of the solution and washed with water. Next, a paste is packed over the surface of the grid to form an unformed positive plate. After that, two pieces of thus obtained positive plates and three pieces of usual negative plates are subjected to formation charging so as to constitute a small sealed lead storage battery used as a portable VTR power supply or the like. As a result, a complex oxide of lead and tin is formed only on the surface of the grid and this complex oxide suppressed formation of a barrier layer on the surface of the positive grid. Accordingly, it is possible to increase the capacitive restoration of the battery after it is left in an overdischarged state for a long period of time without giving any bad influence to other battery characteristics.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a method for producing electrodes for lead-acid batteries, which are used in a wide variety of applications, particularly as portable televisions and emergency power sources, and have recently been rapidly increasing in demand. VT has been increasing
This invention relates to an improvement in the manufacturing method of electrodes for small-sized sealed lead-acid batteries used as R-type electrodes.

Conventional structure and its problems Small sealed lead-acid batteries do not leak even if they are turned over or placed upside down, and do not require water replenishment, so they are used in a variety of applications such as portable televisions and emergency power sources. . Also, recently, the demand for power supplies for portable VTRs has increased. This requires a significantly higher level of energy density than conventional batteries and the ability to withstand long-term storage even in over-discharge conditions, something that was difficult to achieve with conventional lead-acid batteries.

However, in general, if a lead-acid battery is left in an over-discharged state for a long period of time, it becomes difficult to charge it, and its capacity recovery performance deteriorates. One possible reason for this is that a high resistance 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 by leaving it for a long period of time. Therefore, it is desirable to have a structure that suppresses the formation of this barrier layer. In order to satisfy this requirement, it was thought that studying the lattice alloy composition would be effective. Furthermore, in small sealed lead-acid batteries, a lead-calcium alloy is generally used to suppress the electrolyte from decreasing due to charging.

From the above-mentioned viewpoint, the capacity recovery of a lead-acid battery using a lead-calcium alloy with tin added as a lattice after being left in an over-discharged state for a long period of time was investigated.

As a result, this battery was slightly superior in the above-mentioned characteristics compared to a battery using a lead-calcium alloy for the grid, but was still not satisfactory. Even if the tin content in the lattice is extremely increased, this tendency does not change; on the contrary, the mechanical strength of the lattice becomes weaker. Furthermore, in this battery, tin in the lattice with a small hydrogen overvoltage has a strong tendency to dissolve in the electrolyte and precipitate on the negative electrode.

Therefore, self-discharge is likely to occur, and hydrogen gas is generated violently during the charging process, so that the electrolyte is likely to decrease.

In this way, it has been difficult to improve capacity recovery after being left in an over-discharged state for a long period of time without deteriorating other battery characteristics by simply adding tin to the lattice alloy.

On the other hand, as an attempt to change the composition of only the surface of the lattice, plating the surface of the lattice with tin was considered. but,
This method has a problem in that tin adhering to the surface of the lattice body dissolves into the electrolytic solution during the chemical charging process, and is further deposited on the negative electrode plate, which adversely affects battery characteristics.

Object of the Invention The present invention aims to improve the above-mentioned conventional drawbacks, and in particular to improve capacity recovery after leaving a lead-acid battery in an over-discharged state for a long period of time. is characterized by comprising the steps of anodically polarizing a grid for a lead-acid battery in an aqueous solution containing tin ions, a step of taking out the grid from the aqueous solution and washing it with water, and a step of filling the surface of the grid with a paste. 0 With this configuration, it is possible to form a composite oxide of lead and tin only on the surface of the lattice body, thereby greatly improving the capacity recovery of a lead-acid battery after being left in an over-discharged state for a long period of time. It is possible.

Description of examples Examples of the present invention will be described below.

First, the method for manufacturing the electrode will be specifically described. 10-1 mol/
A cast grid for a positive electrode made of a lead-calcium alloy with a Cal/Rum content of 0.1% by weight and having an M content of 151 was immersed in a sulfuric acid aqueous solution having a specific gravity of 1.10 and containing 15% of tin sulfate for anodic polarization. did. 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 carried out with a constant current of 50 m.

After the anodic polarization, the cast grid was taken out of the sulfuric acid aqueous solution and washed with water, and the surface of the grid was filled with paste.

The electrode plate created in this way is used as an unformed plate for the positive electrode,
A sealed lead-acid battery with a capacity of about 38 H was fabricated by chemical charging with a configuration of two positive electrode plates and three negative electrode plates. In addition, a normal electrode plate was used as the negative electrode plate, and a glass mat was used as the separator. After that, a battery using a lattice body was exposed for 10 minutes in a sulfuric acid aqueous solution containing tin sulfate. B, a battery using a lattice body which was outer-poled for 10 minutes in an aqueous sulfuric acid solution with a specific gravity of 1.10 that does not contain tin ions; Specific gravity 1
．． After immersing the grid body in a sulfuric acid aqueous solution of No. 10 for 10 minutes,
The grid was taken out from the aqueous solution, washed with water, and the battery filled with the paste was designated as C. Further, a battery D was prepared using a lead-calcium-tin alloy having a tin content of 1.0% by weight and a calcium content of 0.1% by weight as a lattice alloy. However, no treatment was applied to the grid of battery D.

In addition, 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. first,
Check the initial capacity by discharging at a rate of 6 hours, then 2.45
After charging at a constant voltage of V for 6 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 2.45V for 5 hours.

Finally, check the capacity by discharging at a 5 hour rate as at the beginning,
The ratio between this and the initial capacity, that is, the capacity recovery rate, was determined. Incidentally, all steps except for leaving after overdischarge were carried out under a temperature condition of 25°C.

The figure shows the relationship between capacity recovery rate and storage period for batteries A, B, C, and D, and for comparison, a battery using a lead-calcium lattice (referred to as battery E) that has not undergone any treatment. Indicated. From this figure, it can be seen that the capacity recovery rate of battery A is extremely superior compared to other batteries.

The following factors can be considered to bring about the above effects.

Generally, when tin is added to the lattice alloy, capacity recovery after being left in an over-discharged state for a long period of time is slightly improved. The reason for this is thought to be that tin in the lattice changes the structure of the lattice surface and suppresses the formation of a barrier layer during long-term storage. That is, in the chemical charging process, there is a strong possibility that some kind of composite oxide of lead and tin is formed on the surface of the lattice body, and this oxide suppresses the formation of a barrier layer.

The present invention discloses a method for preferentially forming the above-described composite oxide of lead and tin on the surface of the lattice body. When the lattice is anodically polarized in an aqueous sulfuric acid solution, β-PbO is formed on the surface of the lattice.
In the process of forming β-Pbo2, lead on the surface of the lattice first becomes divalent lead ions and dissolves, and then becomes β-Pb02 and precipitates. if,
If a large amount of tin ions exist around dissolved lead ions, it is thought that the lead ions and tin ions will combine with each other to form a composite oxide and precipitate on the surface of the lattice. When we actually confirmed the existence of this complex oxide, we found that it was not possible to quantify it by X-ray diffraction because it was formed only on the surface of the lattice, but when we observed the surface of the lattice with a scanning electron microscope. The presence of large crystalline oxides other than β-P))C)2 and PbSO4 was revealed. This oxide is considered to be a composite oxide of lead and tin. This oxide exhibits good electronic conductivity, and is also highly acid resistant and has little reactivity, so it is thought that it will continue to exist stably on the surface of the lattice even after overdischarge and subsequent long-term storage. Therefore, even if a barrier layer is formed on the surface of the lattice due to long-term storage, this composite oxide exists in the barrier layer and makes a large contribution to electron conduction between the lattice and the active material.

As described above, the present invention is characterized by anodic polarization in an aqueous solution containing tin ions. Adding tin to the lattice alloy or adhering tin to the surface of the lattice had some effect on capacity recovery after overdischarging, but in these cases, composite oxidation of lead and tin Things are thought to be formed.

The reason for this is thought to be that tin in the lattice body and tin on the surface of the lattice body are dissolved in sulfuric acid, so that the amount of tin ions existing in the vicinity of the lattice body is small.

On the other hand, in the method of the present invention, since the lattice is anodically polarized in an aqueous solution containing tin from the beginning, tin is added to the lattice alloy or thi Y is attached to the surface of the lattice. It is thought that a larger amount of tin ions are present than in the case where a large amount of the composite oxide is formed.

Further, in the present invention, since the composite oxide is formed only on the surface of the lattice body, there is no influence on the mechanical strength and corrosion resistance of the lattice body itself. Furthermore, when a composite oxide of lead and tin is formed on the surface of the counterfeit lattice, this oxide rarely decomposes or dissolves to become tin ions and leak into the electrolyte. Further, in the present invention, a method is adopted in which the grid body is anodically polarized in an aqueous solution containing tin ions and then washed with water, so that tin ions attached to the grid body are not dissolved into the electrolyte solution. As described above, the present invention does not have any adverse effect on the battery characteristics. Effects of the Invention The present invention does not affect other battery characteristics such as 1pj by forming a lead and tin composite oxide only on the surface of the lattice body. This significantly improves capacity recovery after being left in an over-discharged state for a long period of time without causing any adverse effects. Therefore, the present invention greatly increases the reliability of small sealed lead-acid batteries, which have recently been utilized as a power source for portable VTRs, and its industrial value is extremely large.

[Brief explanation of drawings]

The figure is a characteristic diagram showing the relationship between the capacity recovery rate and the leaving period after being left in an over-discharged state for a long time in an embodiment of the present invention.

Claims (1)

[Claims] Separating grids for lead-acid batteries in an aqueous solution containing tin ions.
1. A method for manufacturing an electrode for a lead-acid battery, comprising the steps of: immersing the grid body in the aqueous solution and washing it with water; and filling the surface of the grid body with a paste.