JPS6118312B2 - - Google Patents

Description

[Detailed Description of the Invention] The capacity of current lead-acid batteries gradually declines from its maximum value as time passes, regardless of whether the battery is used or not, and reaches approximately 2.
After a year, the capacity is usually less than half of its original capacity. One of the major causes of this decrease in capacity is the generation of white lead sulfate within the Yin-Yang active material. Once white lead sulfate is formed, it is difficult to return to the original active material by normal charging. Moreover, in conventional lead-acid batteries using a sulfuric acid electrolyte, white lead sulfate is inevitably produced. The reason for this is due to the high concentration of sulfuric acid. In other words, it would be possible to use an extremely dilute sulfuric acid solution in an infinitely large volume, but in order to obtain the highest possible capacitance for something confined within a certain volume, it is usually necessary to completely discharge the product with a specific gravity of around 1.3 when fully charged. A relatively concentrated aqueous sulfuric acid solution with a concentration of up to about 1.18 is required and is generally used, but there are two possible causes for the generation of white lead sulfate in an electrolytic solution with this sulfuric acid concentration. One is that an aqueous solution of this concentration reacts with the electrode active material purely chemically without going through the electrochemical process of charging and discharging to create white lead sulfate, and the other is that a concentrated sulfuric acid solution has a dehydrating effect. This is the causative pathway in which the active material lead sulfate formed during discharge undergoes dehydration and changes into white lead sulfate. When sulfuric acid is added in an attempt to recover the fallen capacity, the electromotive force potential appears to have increased for a time, but the capacity hardly increases.

It is a well-known fact that the generation of white lead sulfate actually increases. Regardless of the details of the route behind the generation of white lead sulfate, the generation of white lead sulfate is significant when the sulfuric acid concentration is high.

The present invention is capable of restoring a conventional lead-acid battery using a sulfuric acid electrolyte to a usable capacity when the battery capacity has decreased to the point of being unusable due to the production of white lead sulfate. This method provides a method for modifying lead-acid batteries that enables them to be used for a long period of time while preventing the above-mentioned problems.In this method, aluminum hydroxide and magnesium hydroxide neutralizers are added to used lead-acid batteries, and one part of sulfuric acid is added to the lead-acid batteries after use. When preparing aluminum sulfate and magnesium sulfate, the weight ratio of aluminum hydroxide and magnesium hydroxide is 99 to 40.
It is characterized by adding a neutralizing agent mixed at a ratio of 1 to 60.

Conventionally, lead storage batteries using a sulfuric acid electrolyte or an electrolyte in which a metal such as aluminum is added and a part of the sulfuric acid is converted into a sulfate salt decrease the battery capacity and become unsuitable for use. According to the present invention, aluminum hydroxide and magnesium hydroxide are added to the used lead-acid battery, a part of the sulfuric acid is neutralized, and the aluminum hydroxide component is mixed with the water in the electrolyte. Magnesium oxide component ratio is 99 to 40 by weight
It has been found that when aluminum hydroxide or magnesium hydroxide is present at a ratio of 1 to 60%, the battery capacity can be recovered to a greater extent than when aluminum hydroxide or magnesium hydroxide is added alone. Its usage is in powder form,
When used as a granular mixed modifier of aluminum hydroxide and magnesium hydroxide in a predetermined ratio, it is convenient to transport and handle.

Detailed examples are listed next.

A cathode and anode electrode for a lead-acid battery is made by the usual method, and after forming the electrode plates, sulfuric acid with a specific gravity of 1.26 is added at room temperature to 300 c.c. per tank.
A large number of batteries with a capacity of approximately 20 ampere-hours were made using the electrolyte and used for testing.

Each tank was made at the same time using the same active material and the same manufacturing conditions, and the standard capacity was ±2 to 3 amps per hour.
% range. In the capacity test, each tank was connected in series and charged and discharged at room temperature. A constant current of 4 amps at a 5 hour rate is used.

For each tank, the bath voltage was 2.15 volts for complete charging, and for discharge, the ampere-hours when the voltage reached 1.85 volts was defined as the respective capacity.
In the case of a sulfuric acid bath without the modifier of the present invention, the full charge was 2.2 volts and the discharge voltage was 1.9 volts. First, they made a regular lead-acid battery using sulfuric acid, and by charging and discharging it many times, they were able to reach a capacity of 65% of their original capacity. In this state, white lead sulfate appears to be attached to the electrode surface. In this state, a mixture containing each of the hydroxides of aluminum, sodium, and magnesium alone or the two components in various blending ratios was put into each battery tank and subjected to a capacity test. This input amount was calculated so that 50 g of sulfuric acid in each tank became each sulfate. In other words, as a single component, Al(OH) ₃ is 26.5g, Mg(OH) ₂ is
29.59g, NaOH requires 40.8g. In a two-component system, for example, when 50 g of sulfuric acid is to be neutralized with a mixture of Al(OH) ₃ and Mg(OH) ₂ in a weight ratio of 40 to 60 of the latter, Al(OH) ₃ is 26.5
×0.4g=10.6g and Mg(OH) ₂ is 29.8×0.6g=
A total of 28.48 g of the mixture with 17.88 g is required. The amount of 50 g of sulfuric acid for neutralization was determined as follows. In other words, since the battery has a capacity of approximately 20 ampere-hours, the minimum amount of sulfuric acid used to supply and remove this 20 ampere-hour capacity is determined by the well-established electromotive reaction formula: Pb + 2H ₂ SO ₄ + PbO ₂ = PbSO ₄ +2H ₂ O+
From PbSO ₄ it becomes 3.67×20=73.4g. From now on, 90g of sulfuric acid will remain.The amount of sulfuric acid contained in one container is 132g in 300 c.c. of dilute sulfuric acid with a specific gravity of 1.26, so the total amount will be 140g, taking into account the amount of electrode adhesion during chemical formation.
The amount to be neutralized was 140-90=50g. For an actual battery, add 3.67 x amp hours x 1/2g of sulfuric acid to 1
Numerous tests have confirmed that the objective can be achieved by neutralizing per tank.

Figure 1 A, B and C are Al(OH) ₃ and Mg respectively
(OH) ₂ , Al(OH) ₃ and NaOH, Mg(OH) ₂ and NaOH
Battery capacity when one part (50g) of the sulfuric acid electrolyte is neutralized with various combination ratios: 65
The results of testing and measuring the state of battery capacity recovery from % are shown, and the horizontal axis of each figure represents the distribution ratio of the two components, and the vertical axis represents the corresponding battery capacity stability %. Capacity stability is the ratio of the capacity to the initial capacity when the battery always obtains a stable capacity value through charging and discharging after applying the electrolyte.
This is the value shown in .

As is clear from Figure 1, Mg(OH) ₂ and
When a two-component neutralizing agent of NaOH was introduced, no recovery of battery capacity was observed, as shown in Figure 1C, and a two-component neutralizing agent of Al(OH) ₃ and NaOH was added. As shown in Figure 1B, NaOH has a slight recovery power depending on its blending ratio, but no recovery power is observed in most blending ratios, and NaOH is strongly alkaline and inconvenient to handle, making it impractical. It is highly inappropriate. In contrast,
_The mixing ratio of the two-component system of Al(OH) ₃ and Mg(OH) ₂ of the present invention is as shown in Figure 1A.
When the blending ratio of Mg(OH) ₂ is in the range of 99 to 40 to 1 to 60 (weight ratio), the battery capacity is recovered, and in particular,
It was confirmed that the battery capacity recovered to approximately 90% when the mixture ratio was 60 for _{the three} Al(OH) components and 40 for _{the two} Mg(OH) components.

According to the present invention, part of the sulfuric acid in the used lead-acid battery is neutralized with a neutralizing agent mixed in a weight ratio of 99 to 40 aluminum hydroxide to 1 to 60 magnesium hydroxide. Since aluminum sulfate and magnesium sulfate are used, it has the effect of significantly recovering the battery capacity compared to partially neutralizing with aluminum sulfate.

[Brief explanation of the drawing]

FIG. 1A is a diagram showing battery capacity characteristics including an example of the present method, and FIGS. 1B and 1C are diagrams showing comparative examples thereof.

Claims (1)

[Claims] 1. Adding a neutralizer for aluminum hydroxide and magnesium hydroxide to a used lead-acid battery, and converting part of the sulfuric acid into aluminum sulfate and magnesium sulfate, adjust the weight ratio of the aluminum hydroxide and magnesium hydroxide. A method for reforming lead-acid batteries characterized by adding a neutralizing agent mixed at a ratio of 99 to 40 to 1 to 60.