JP7565516B2 - Method for regenerating lead-acid batteries and method for manufacturing regenerated lead-acid batteries - Google Patents

Description

The present invention relates to a method for regenerating lead-acid batteries used as emergency power supplies (UPS), home energy storage systems, and batteries for automobiles, buses, and motorcycles, and a method for manufacturing regenerated lead-acid batteries.

As a lead-acid battery is used repeatedly, the lead sulfate that is produced during discharge becomes less likely to return to its original state during charging. This is because the lead sulfate that is produced hardens. This hardened lead sulfate is an insulating substance, and becomes electrical resistant on the electrode surface. This causes the battery's performance to decline, and is one of the factors that shorten its lifespan. When lead sulfate hardens and becomes resistant in this way, it is called sulfation.

Conventionally, there are two known methods for inhibiting sulfation: electrical and chemical. The electrical method involves generating a special pulse current and supplying it to the lead-acid battery. The pulse current flows over the surface of the plate (skin effect), which breaks down lead sulfate into dilute sulfuric acid and lead, inhibiting deterioration of the lead-acid battery.

For example, Patent Document 1 discloses a method for removing lead sulfate coating by repeatedly applying negative and positive pulses with a pulse frequency of 8 kHz to 16 kHz. Patent Document 2 discloses a lead-acid battery maintenance device that applies a pulse current with a pulse frequency of approximately 9.51 kHz to the battery to break down and remove sulfation that occurs on the electrode plates.

On the other hand, chemical methods involve the introduction of additives to promote chemical reactions and thereby decompose lead sulfate. For example, Patent Document 3 discloses a method for regenerating a lead battery, which is characterized by adding at least one organic additive selected from the group consisting of polyvinyl alcohol, polyacrylic acid, and lignin to the electrolyte of a lead battery, and discharging the battery continuously or intermittently with a current of 0.3 C or more, preferably 1 C or more, for an amount of electricity of 3% or more, preferably 10% or more, of the nominal capacity of the battery.

Patent Document 4 discloses an additive containing a carboxyl group and a sulfo group, Patent Document 5 discloses the addition of polyvinyl alcohol or polyacrylic acid, Patent Document 6 discloses an additive of an organic compound or an inorganic compound, Patent Document 7 discloses an additive of fine carbon particles or polyvinyl alcohol, and Patent Document 8 discloses a regenerator having a polymer liquid for cleaning substrates, a mineral liquid for increasing voltage, and a carbon liquid for stabilizing discharge.

International Publication No. WO 2005/083830 Registered Utility Model No. 3143629 JP 2004-356076 A JP 2013-48074 A JP 2009-16324 A JP 2003-22845 A JP 2000-150004 A JP 2005-63876 A

In the conventional electrical method, the detailed mechanism of sulfation inhibition has not been elucidated, and although deterioration of lead-acid batteries is inhibited by applying a pulse current with a pulse frequency of about 10 kHz, the effect is insufficient. In addition, since a high pulse frequency of about 10 kHz is required, high costs are unavoidable. Meanwhile, various types of additives have been developed for the conventional chemical method, but the effect is not sufficient.

The present invention aims to provide a method for regenerating lead-acid batteries and a method for manufacturing regenerated lead-acid batteries that enable sufficient suppression of sulfation at a low pulse frequency.

The regeneration method for a lead-acid battery of the present invention is a regeneration method for a lead-acid battery in which a positive electrode, a negative electrode, and an electrolyte are contained in a battery case, and is characterized in that it includes adding an additive that increases hydrogen overvoltage to the electrolyte, containing the electrolyte in the battery case, and applying a pulse current with a pulse frequency of 1 kHz or less between the positive electrode and the negative electrode.

According to the method for regenerating a lead-acid battery of the present invention, by applying a pulse current with a pulse frequency of 1 kHz or less between the positive and negative electrodes while an additive that increases hydrogen overvoltage is added to the electrolyte, the lead sulfate on the electrode surfaces of the positive and negative electrodes is effectively destroyed at a low pulse frequency of 1 kHz or less, and the additive makes it difficult for lead sulfate to adhere to the electrodes, so that the conductive state of the electrodes is maintained in good condition.

The method for producing a regenerated lead-acid battery of the present invention is characterized in that it includes adding an additive that increases hydrogen overvoltage to the electrolyte of a lead-acid battery in which a positive electrode, a negative electrode, and an electrolyte are contained in a battery case, containing the battery in the battery case, and applying a pulse current with a pulse frequency of 1 kHz or less between the positive electrode and the negative electrode.

According to the method for producing a regenerated lead-acid battery of the present invention, by applying a pulse current with a pulse frequency of 1 kHz or less between the positive and negative electrodes of a used and deteriorated lead-acid battery with an additive that increases hydrogen overvoltage added to the electrolyte, the lead sulfate on the electrode surfaces of the positive and negative electrodes is effectively destroyed at a low pulse frequency of 1 kHz or less, and the additive makes it difficult for lead sulfate to adhere to the electrodes, resulting in a regenerated lead-acid battery in which the conductive state of the electrodes is well maintained.

According to the present invention, by adding an additive that increases hydrogen overvoltage to the electrolyte, storing it in a battery container, and applying a pulse current with a pulse frequency of 1 kHz or less between the positive and negative electrodes, it is possible to sufficiently suppress sulfation at a low pulse frequency of 1 kHz or less, thereby extending the life of the lead-acid battery and extending the period of use before disposal. As a result, the number of discarded lead-acid batteries can be reduced, making it possible to reduce the burden on the environment.

1 is a conceptual diagram of a method for regenerating a lead-acid battery according to an embodiment of the present invention. FIG. 11 is a diagram showing the relationship between S/Pb and O/Pb of each pulse waveform versus frequency. FIG. 1 is a graph comparing the CCA values of (a) Comparative Example 1 and (b) Example 1. FIG. 1 is a graph comparing cycle test results of (a) Comparative Example 1 and (b) Example 1.

Figure 1 is a conceptual diagram of a method for regenerating a lead-acid battery in an embodiment of the present invention. As shown in Figure 1, a pulse generator 2 is connected between the positive terminal 15 and the negative terminal 16 of a used and deteriorated lead-acid battery 1 (which needs replacing), and the lead-acid battery 1 is regenerated by applying a pulse current with a pulse frequency of 1 kHz or less.

The lead-acid battery 1 is a conventionally known battery that contains a positive electrode 11, a negative electrode 12, and an electrolyte 13 in a battery case 10. A separator 14 is disposed between the positive electrode 11 and the negative electrode 12. Although not shown in the figure, the positive electrodes 11 and the negative electrodes 12 are usually stacked alternately with the separators 14 between them, and are contained in the battery case 10 together with the electrolyte 13 as a group of electrodes.

The positive electrode 11 may be one in which a positive electrode active material is filled between the positive electrode grids. The positive electrode grid may be one formed of lead or a lead alloy. The lead alloy may be an alloy containing lead and elements such as calcium, tin, or bismuth. The positive electrode active material is usually lead dioxide (PbO ₂ ). Also, lead dioxide to which elements such as calcium are added may be used as the positive electrode active material. Each positive electrode 11 constituting the electrode plate group has a lug for collecting current, and these lugs are integrated by a strap portion and connected to the positive terminal 15.

The negative electrode 12 may be configured such that the negative electrode active material is filled between the negative electrode grids. The negative electrode grid may be made of lead or a lead alloy. The lead alloy may be an alloy containing lead and elements such as calcium, tin, or bismuth. The negative electrode active material is usually lead (Pb). Each negative electrode 12 constituting the electrode plate group has a lug for collecting current, and these lugs are integrated with a strap portion and connected to the negative terminal 16.

The separator 14 is disposed between the positive electrode 11 and the negative electrode 12, and serves to prevent short circuits caused by contact between the positive electrode 11 and the negative electrode 12, and to retain the electrolyte 13 and allow sulfate ions and hydrogen ions to pass through. As the separator 14, a nonwoven sheet mainly made of chemical fibers or glass fibers is usually used. Alternatively, a microporous sheet made of synthetic resin or inorganic filler may be used. The thickness and number of separators 14 to be interposed between the negative electrode 12 and the positive electrode 11 are appropriately selected according to the distance between the electrodes.

The battery case 10 is a container with an opening on the upper side, and is capable of containing an electrode group consisting of a positive electrode 11 and a negative electrode 12, and an electrolyte 13. The battery case 10 is made of a material that is resistant to the electrolyte 13, and is usually made of a synthetic resin such as polyethylene, polypropylene, or ABS resin. The opening of the battery case 10 is sealed with a lid (not shown). The lid can be made of a synthetic resin, just like the battery case 10.

The battery case 10 may have a configuration having multiple cells that contain an electrode group consisting of a positive electrode 11 and a negative electrode 12 and an electrolyte 13. A lid that seals the openings of multiple cells at once can be used. For example, a 12V battery can be made by having six cells with an electromotive force of 2V.

Dilute sulfuric acid (H ₂ SO ₄ ) is generally used as the electrolyte 13. In the method for regenerating a lead-acid battery in this embodiment, an additive that increases hydrogen overvoltage is added to the electrolyte 13. In this embodiment, an additive for lead-acid batteries containing polyvinyl alcohol is used as the additive. In particular, in this embodiment, an additive for lead-acid batteries in which a 5 mass % aqueous solution of polyvinyl alcohol has a viscosity of 1 to 30 mPa·s is used.

By adding this additive to the electrolyte 13 and applying a pulse current with a pulse frequency of 1 kHz or less between the positive electrode 11 and the negative electrode 12, the lead sulfate on the electrode surfaces of the positive electrode 11 and the negative electrode 12 is effectively destroyed at a low pulse frequency of 1 kHz or less, and the additive makes it difficult for lead sulfate to adhere to the electrodes (positive electrode 11 and negative electrode 12), resulting in a regenerated lead-acid battery in which the conductive state of the electrodes is well maintained. In addition, the lead sulfate that adheres to the electrodes is in a fine state such as a fibrous state, so the conductivity of the electrodes is not easily hindered, and the conductive state of the electrodes is well maintained. As a result, sulfation is suppressed and deterioration of battery performance is suppressed.

The inventors have found that there is a certain degree of correlation between the current change near the rising edge of the oxidation wave peak obtained by cyclic voltammetry (CV) and the amount of lead sulfate attached to the surface of the negative electrode. When a mixture of dilute sulfuric acid and additives is used as an electrolyte and evaluated by CV, the greater the current change near the rising edge of the oxidation wave peak, the more sulfation can be suppressed and the more the deterioration of battery performance can be suppressed.

The inventors have also found that by using an additive containing polyvinyl alcohol with a viscosity of 1 to 30 mPa·s in a 5% by mass aqueous solution, the current change near the rise of the oxidation wave peak obtained by CV can be increased, and deterioration of battery performance can be suppressed compared to conventional additives. The reason for this is unclear, but it is presumed that by using an additive containing polyvinyl alcohol with a viscosity of 1 to 30 mPa·s in a 5% by mass aqueous solution, polyvinyl alcohol remains appropriately on the electrode surface, suppressing the formation of sulfation, while not interfering with the exchange of ions between the positive electrode 11 and the negative electrode 12, making battery performance less likely to deteriorate.

The polyvinyl alcohol contained in the additive in this embodiment has a viscosity of 1 to 30 mPa·s when it is a 5% by weight aqueous solution. In this embodiment, the "viscosity of a 5% by weight aqueous solution of polyvinyl alcohol" refers to the average value of five measurements taken at temperatures in the range of 25 to 30°C using a tuning fork type vibration viscometer (SV-1A) manufactured by A&D Co., Ltd.

The lower the viscosity of polyvinyl alcohol, the less polyvinyl alcohol remains on the electrode surface, and the less effective it is at inhibiting sulfation. Therefore, the viscosity of a 5% by mass aqueous solution of polyvinyl alcohol is preferably 5 mPa·s or more, more preferably 10 mPa·s or more, and even more preferably 15 mPa·s or more.

In addition, the greater the viscosity of the polyvinyl alcohol, the greater the amount of polyvinyl alcohol present on the electrode surfaces of the positive and negative electrodes, and the more likely it is that polyvinyl alcohol will hinder the exchange of ions between the positive and negative electrodes. Therefore, the viscosity of a 5% by mass aqueous solution of polyvinyl alcohol is preferably 25 mPa·s or less, and more preferably 20 mPa·s or less.

The lower the proportion of hydroxyl groups in polyvinyl alcohol (the smaller the degree of saponification), the more hydrophobic it becomes, and the less likely it is to mix with the aqueous sulfuric acid solution, which is a component of the electrolyte. Therefore, the degree of saponification of polyvinyl alcohol is preferably 70 mol% or more, and more preferably 80 mol% or more. In particular, 90 mol% or more is preferable, 93 mol% or more is more preferable, and 95 mol% or more is even more preferable.

In addition, the higher the proportion of hydroxyl groups in polyvinyl alcohol (the higher the degree of saponification, the lower the proportion of acetate groups), the lower the conductivity of the electrode surface, the more likely sulfation occurs, and the greater the electrolyte resistance tends to be. Therefore, the degree of saponification is preferably 99.5 mol% or less, more preferably 99 mol% or less, and even more preferably 97 mol% or less.

The additive in this embodiment may contain one or more types of polyvinyl alcohol having a viscosity of 1 to 30 mPa·s in a 5% by mass aqueous solution. The polyvinyl alcohol contained in the additive of the present invention may be a commercially available polyvinyl alcohol. Among them, it is preferable to use one or more selected from the group consisting of Gohsenol C-500, Gohsenol N-300, and Gohsenol A-300 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., and it is preferable to use any one selected from the group consisting of Gohsenol C-500, Gohsenol N-300, and Gohsenol A-300 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.

The additive in this embodiment may contain other components such as an antifoaming agent. On the other hand, since other components may affect the conductivity of the electrode surface of the lead-acid battery 1, it is preferable to use polyvinyl alcohol as the main component. The content of polyvinyl alcohol in the additive in this embodiment is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The additive in this embodiment may also be made of polyvinyl alcohol. Since impurities may be contained in polyvinyl alcohol, the content of polyvinyl alcohol in the additive in this embodiment may be 99% by mass or less, 97% by mass or less, or 95% by mass or less.

The additive in this embodiment may be in the form of a liquid or a solid. For example, an aqueous polyvinyl alcohol solution, which is a mixture of polyvinyl alcohol and water, may be used as the additive. From the viewpoint of ease of handling, it is preferable that the additive is a solid such as fine powder, granules, or powder.

<Confirmation of sulfation suppression effect against frequency>
The sulfation suppression effect at a pulse frequency of 1 kHz or less in the regeneration method for a lead acid battery of the present invention was confirmed. The relationship between the S/Pb and O/Pb of each pulse waveform and the frequency is shown in FIG.

As shown in Figure 2, for square waves, the lower the frequency, the lower the values of both S/Pb and O/Pb, confirming that the changes in voltage and current at the rise are effective. For ramp waves, both S/Pb and O/Pb tend to have a mountain-like shape around a frequency of 15 kHz, demonstrating that the effect can be seen at both low and high frequencies.

For sine waves, the S/Pb tends to have a mountain-like tendency around a frequency of 15 kHz, while the O/Pb tends to decrease as the frequency decreases, showing the same tendency as the square wave. Therefore, it was confirmed that square waves and sine waves with low pulse frequencies of 1 kHz or less have a sulfation suppression effect.

<Tests using actual lead-acid batteries>
A cycle test was carried out under the following conditions for the case where an additive was added to the electrolyte and a pulse current was applied (Example 1), and for the case where only the additive was used (Comparative Example 1). The measurement was carried out by instantaneously passing a current from the battery to the load (corresponding to the part in the figure where the discharge voltage changes suddenly), and the current value flowing through the load at this time was recorded as the CCA value. The CCA (Cold Cranking Ampere) value is generally considered to be a value that indicates the engine starting performance of a car or the like.

Experimental sample: Discarded battery (ENEOS VFL-60B19L)
Additive: Gohsenol C-500 (cationic surfactant) manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
Pulse conditions: AC waveform (sine wave), frequency 60 Hz
Evaluation index: CCA value

Figure 3 is a diagram comparing the CCA values of (a) Comparative Example 1 and (b) Example 1. As shown in Figure 3, (b) Example 1 had a CCA value of 360, which was about 14% higher than the CCA value of 315 of (a) Comparative Example 1. Also, Figure 4 is a comparison of cycle tests of (a) Comparative Example 1 and (b) Example 1. As shown in Figure 4, (b) Example 1 was effective. Thus, in a test in which a low-frequency 60 Hz AC wave was combined with an additive, it was shown that there was a sulfation suppression effect.

Furthermore, under the above conditions, a frequency of 1 kHz was used, and a cycle test was conducted in which an additive was added to the electrolyte and a pulse current was applied (Example 2), and in which only the additive was used (Comparative Example 2). The CCA value of Example 2 was 320, and the CCA value of Comparative Example 2 was 310. From these results, it was confirmed that the increase rate of Example 2 at a pulse frequency of 1 kHz was low at about 3%, and that a pulse frequency of 60 Hz was more effective.

The present invention is useful as a method for regenerating lead-acid batteries used as emergency power sources (UPS), home energy storage systems, and batteries for automobiles, buses, and motorcycles, and as a method for manufacturing regenerated lead-acid batteries.

REFERENCE SIGNS LIST 1 Lead-acid battery 2 Pulse generator 10 Battery case 11 Positive electrode 12 Negative electrode 13 Electrolyte 14 Separator 15 Positive terminal 16 Negative terminal

Claims (2)

A method for regenerating a lead-acid battery in which a positive electrode, a negative electrode, and an electrolyte are contained in a battery case, comprising the steps of:
an additive that increases hydrogen overvoltage and contains 50 mass% or more of polyvinyl alcohol having a viscosity of 1 to 30 mPa·s in a 5 mass% aqueous solution and a saponification degree of 70 mol% or more and 99.5 mol% or less, is added to the electrolytic solution, and the electrolytic solution is housed in the battery container;
A method for regenerating a lead-acid battery, comprising: applying a pulse current with a pulse frequency of 1 kHz or less between the positive electrode and the negative electrode. For a lead-acid battery in which a positive electrode, a negative electrode, and an electrolyte are contained in a battery case , an additive that increases hydrogen overvoltage and contains 50 mass% or more of polyvinyl alcohol having a viscosity of 1 to 30 mPa·s in a 5 mass% aqueous solution and a saponification degree of 70 mol% or more and 99.5 mol% or less is added to the electrolyte, and the battery case is then housed therein;
applying a pulse current having a pulse frequency of 1 kHz or less between the positive electrode and the negative electrode.