JP3475650B2 - Manufacturing method of current collector for lead-acid battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a lead storage battery, and more particularly to an improvement in current collector to improve reliability of an electrode plate and a battery.

[0002]

Lead acid batteries are widely used as uninterruptible power sources for automobiles and computer backups. In these applications, batteries are always overcharged and equipped as a power source when needed. One of the important issues in this type of application is prevention of deterioration due to overcharge. This deterioration phenomenon at the time of overcharge is related to the oxidative corrosion of the current collector which also holds the active material, and it is basically unavoidable although it is slightly different depending on the type of alloy of the current collector.

In recent years, in particular, in order to obtain a high output and a high utilization rate, in place of a conventional grid-shaped or expanded metal skeletal current collector, a flat plate-shaped structure or a small number of openings is formed in order to increase a contact area with an active material. Various solid perforated bodies tend to be applied. In the structure of so-called thin electrode plate, in which a sulfuric acid-free slurry or a low-viscosity kneaded product of a lead powder, a solvent, and a resin is formed in a thin layer, the rate at which the current collector surface receives the overcharge current is active. There is a tendency for the deterioration of overcharge characteristics to be amplified as compared to the case of substances.

This kind of problem is caused by corrosion of the current collector. Basically, it is ideal if a coating layer that is acid resistant and conductive and that is stable during charge and discharge can be formed and maintained. Solution. However, the existence of a suitable conductive material that withstands the harsh corrosive environment of being exposed to a high potential in a sulfuric acid electrolyte solution having a concentration of 30 to 40% is extremely rare.

[0005]

For this purpose, a method has recently been proposed in which barium lead perovskite-based perovskite is synthesized by firing and transferred onto the surface of the lattice. It is difficult to apply to the current collector. Furthermore, in order to produce a corrosion-resistant current collector having a complicated shape by a simple method, a lead or lead alloy current collector base material is electrolytically oxidized to form lead dioxide on the surface, and then a barium salt solution or slurry is formed. A method of infiltrating into the above and heat treating it at 200 ° C. or higher is disclosed. However, since the creep temperature of the current collector substrate is generally around 100 ° C., the current collector substrate is softened by the heat treatment as described above, and the electrode plate strength becomes weak particularly in the case of a thin current collector, There is a problem that handling during the manufacturing process is difficult and battery performance is adversely affected.

The object of the present invention is to solve the above-mentioned problems of the prior art, to cope with various current collector shapes, and to protect the base material without weakening the strength of the base material and having an excellent acid resistance and conductivity. The purpose of the present invention is to provide a current collector having a surface formed with a simple method, thereby suppressing deterioration of the electrode plate during overcharge and obtaining a battery having excellent characteristics such as cycle life characteristics. .

[0007]

In order to achieve the above object, the present invention provides a current collector substrate made of lead or lead alloy with barium (Ba), strontium (Sr), bismuth (Bi), tin ( Sn), titanium (Ti), germanium (Ge), selenium (Se), in a dilute sulfuric acid containing ions of at least one or more metals, electrolytic oxidation at a potential higher than that of lead dioxide is provided. It is characterized by that. By this electrolytic oxidation method, even if the current collector base material has a complicated shape, it is possible to cover the entire surface of the base material with a protective coating layer having acid resistance and conductivity, and further heat treatment is required. Since it does not exist, the mechanical strength of the current collector can be secured.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is different from lead dioxide in the case of no addition when lead or lead alloy is oxidized at a high potential such that lead dioxide is produced in dilute sulfuric acid containing the above metal ions. It was made based on the discovery of the phenomenon that a protective layer of various metal oxides is formed. Such a metal oxide layer is not formed in an aqueous solution of the above compound containing no dilute sulfuric acid, and is not formed at a potential lower than the natural electrode potential of lead dioxide even in the presence of dilute sulfuric acid. The chemical structure of this special metal oxide cannot be easily classified from lead dioxide by X-ray diffraction.

However, the oxide layer obtained by this method is denser than the electrolytic oxide layer obtained in dilute sulfuric acid to which metal ions are not added, and it is self-discharged by allowing it to stand naturally in dilute sulfuric acid. Or a slow discharge with a small electric current, and further lowering the potential from the natural potential of lead dioxide via the normal discharge potential of lead dioxide, lead or lead alloy of the current collector base material It was found that some components exhibiting stable potential exist before reaching the potential. From these facts, it is considered that a compound such as a perovskite such as barium leadate or a mixed oxide with lead dioxide may be formed during the process of crystal growth of lead dioxide.

Not all kinds of metal ions are incorporated into the crystal, but even if a highly soluble oxide such as alkali metal or alkaline earth beryllium or magnesium is added alone. It has almost no effect, but if it is added together with other effective additives, it may coexist with both components and affect the denseness of crystals.

In any case, the above oxide layer is a substance that can exist in dilute sulfuric acid and has excellent oxidation resistance. Further, since it has a basic crystal structure of lead dioxide, it is also a highly conductive substance. Strong oxidation resistance. Furthermore, this oxide is at a potential lower than the discharge potential of lead dioxide, and it is always polarized in the oxidizing direction during normal charge and discharge, so that a stable layer is maintained. As a result, the present invention provides a current collector and an electrode plate having excellent overcharge resistance. In addition, if electrolytic oxidation is performed and then exposed to an atmosphere containing oxygen, such as air, there is a further effect of preventing life deterioration due to overcharge. Although the reason has not been clarified, it is considered that oxygen contributes to the stabilization of the surface oxide.

The manufacturing process of the current collector of the present invention and the structural features of the current collector and the electrode plate will be described below. FIG. 1 is a flow diagram illustrating the features of the process of the present invention. Step I is an electrolytic oxidation step, in which the current collector substrate that has undergone necessary pretreatment such as cleaning is supplied to the electrolytic cell. The electrolyte is Ba, Sr,
It is a dilute sulfuric acid containing at least one metal ion selected from Bi, Sn, Ti, Ge, and Se. The oxidation current can be arbitrarily selected. For example, by applying an electric current for about 10 to 30 minutes at a current density of about 100 mA / cm ^{2 with} respect to the exposed surface area of the current collector substrate, the current is collected while generating oxygen gas. An oxide layer is formed on the surface of the electric substrate. Step II is an oxygen exposure step, and after electrolytic oxidation, it is immediately exposed to an atmosphere containing oxygen, for example, air.
Next, step III is a step of filling the active material. Subsequently, an unformed plate is manufactured through necessary steps such as aging and drying, and an electrode plate is formed through a chemical charging step. still,
The exposure step II after electrolytic oxidation can be omitted depending on the required oxidation resistance level, but it is preferable to use the steps I and II together. Also, after repeating step I and step II, step III
Is more effective for increasing the oxidation resistance of the current collector.

Next, FIG. 2 is a partial sectional view of the current collector of the present invention and a structure of the electrode plate using the current collector. Reference numeral 1 denotes a collector base material made of lead or a lead alloy, and the shape and structure of the collector are arbitrary. Reference numeral 2 is an oxide layer formed according to the present invention, and 3 is an active material layer obtained by forming and charging the active material material charged thereon. Thus, since the oxide layer of the present invention is an oxide that is oxidized at a higher potential than lead dioxide, it is not further oxidized, and as long as it is covered by this, the current collector is prevented from oxidation due to overcharge. Be protected.

[0014]

EXAMPLES In order to further clarify the concrete method of implementing the present invention and its effects, the examples will be described. A solid perforated body of lead-calcium-tin alloy having an aperture ratio of 10% was used as a current collector base material, and 100 m of a solution prepared by adding various metal ion compounds to 36% of dilute sulfuric acid according to the present invention.
Electrolytic oxidation was performed at A / cm ² for 20 minutes. The metal ions were added by adding 5 g / l of sulfate of each metal to dilute sulfuric acid. Many sulfates are sparingly soluble, resulting in a saturated solution. After electrolysis, it was exposed to air within 30 minutes. The collector thus obtained was filled with a sulfuric acid-free kneaded product prepared by dissolving polyvinylidene fluoride as a binder in an organic solvent and kneading it with lead powder to prepare an unformed plate. Next, this unformed plate is used as a positive electrode plate obtained by chemical conversion in dilute sulfuric acid, and these are separately combined with a negative electrode plate prepared by a conventional method to obtain a theoretical filling amount of 1
A 0 Ah example battery was constructed.

In addition, as a comparative example, a current collector was prepared by electrolytically oxidizing a current collector base material in dilute sulfuric acid to which different kinds of ions were not added in the same manner as above, and a positive electrode plate and a battery using the current collector were prepared. Was constructed in the same manner as in the example.

These batteries were subjected to a charge / discharge cycle test at a temperature of 60 ° C., overcharged with a constant current of 0.2 C (A) and a quasi-constant voltage system of 2.25 V per cell, and the discharge capacity was changed every one week. Was measured, and the point at which 50% of the initial discharge capacity could not be maintained was defined as the life cycle.

FIG. 3 shows the relationship between the metal ions added to dilute sulfuric acid during the production of the current collector and the life cycle of the battery. A is Ba, Sn, Bi, Ti, Sr
B is Ba-
Bi, Ba-Sn, Ba-Ti, and Bi-Sn are included, and C is Ba and at least one of Li, Na, and K, Sn and at least one of Li, Na, and K, and Ba. And Be, and at least one of Mg is contained. As a result, the battery using the current collector electrolytically oxidized in the solution containing at least one of Ba, Sn, Bi, Ti, and Sr ions has a life cycle level higher than that of the battery (R) of the comparative example. It was proved that the positive electrode was excellent in overcharge resistance. Further, the effect was higher when a plurality of metal ions were added in combination than when the above-mentioned effective metal ions were added alone. In addition, when an ion of a metal such as Li, Na, K having a small atomic number among alkali metals and alkaline earth metals is added alone, the effect is small, but when added together with the above effective metal ions, the effect is promoted. It was from these things,
The effective added ions (Ba, Sn, Bi,
In addition to Ti and Sr ions), it was found that the addition effect by itself is also effective when the present invention is applied to the present invention by allowing thin metal ions to coexist with effective addition ions.

FIG. 4 shows the results of comparing the effects on the life cycle of the battery due to the difference in the timing of filling the active material when Ba ions were added. A better life cycle is obtained when the active material is filled after exposure to the atmosphere (step II) through step I (S2) than when the active material is filled after electrolytic oxidation (step I) (S1). Was given. It has been found that when the active material material is filled after repeating the steps I and II a plurality of times (S3), a life cycle more excellent than that of S2 is obtained, and the effect of the present invention is further enhanced. In addition, after the surface is once oxidized from the lead alloy cloth,
Even when the oxide layer is once discharged to form lead sulfate on the surface and the lead sulfate is oxidized to form an oxide layer, basically the same effect as that of the present invention can be obtained.

[0019]

EFFECTS OF THE INVENTION The present invention comprises a current collector having a protective layer with high oxidation resistance formed through a process of electrolytic oxidation in dilute sulfuric acid containing a specific metal ion other than lead.
It is intended to improve the overcharge resistance of the positive electrode of the electrode plate and greatly improve the life cycle of the lead storage battery using the same.

[Brief description of drawings]

1 is a flow diagram illustrating the features of the process of the present invention.

FIG. 2 is a sectional view of a current collector and an electrode plate for explaining the structure of the present invention.

FIG. 3 is a diagram showing the relationship between additive components and life cycle.

FIG. 4 is a diagram showing the relationship between the timing of the filling process and the life cycle.

[Explanation of symbols]

1 Current collector base material 2 Electrolytic oxidation layer 3 Lead dioxide active material layer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-83616 (JP, A) JP-A-60-77358 (JP, A) JP-A-53-19531 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01M 4/68

Claims (2)

(57) [Claims] 1. A current collector base material made of lead or a lead alloy in a dilute sulfuric acid containing at least one metal ion selected from barium, strontium, bismuth, tin, germanium, and selenium and having a potential of lead dioxide or more. A method of manufacturing a current collector for a lead storage battery, comprising a step of electrolytically oxidizing at a potential of 1. 2. The method for producing a current collector for a lead storage battery according to claim 1, further comprising the step of exposing the current collector base material to an atmosphere containing oxygen after the step of electrolytic oxidation.