CN1146642A

CN1146642A - Electrolyte and lead accumulator using the same

Info

Publication number: CN1146642A
Application number: CN95109567A
Authority: CN
Inventors: 藤井贤一
Original assignee: 藤田贤一
Current assignee: Plume transportation Limited by Share Ltd
Priority date: 1995-09-29
Filing date: 1995-09-29
Publication date: 1997-04-02
Anticipated expiration: 2015-09-29
Also published as: CN1078753C

Abstract

The present invention relates to a PbO2 cathode for lead battery, and its surface is endowed with a COO-or-CO-group, and is activated by electrochemical doping produced by colloidal solution of electrochemically modified carbon. Said battery has the good characteristics: (1) can make special-raised large charge without temp. (2) high discharge, (3) long service life. Said invented process can be used for regeneration of degenerated battery and chemical conversion treatment of battery electrode of new product so as to obtain high-performance lead battery.

Description

Electrolyte for lead storage battery and lead storage battery using the same

The present invention relates to an electrolyte for a lead-acid battery and a lead-acid battery using the same, and more particularly, to an electrolyte for a lead-acid battery which is useful for improving the performance of a lead-acid battery for an automobile and regenerating a lead-acid battery with deteriorated performance or a discarded lead-acid battery, and a lead-acid battery using the same.

Lead storage batteries have performance problems and environmental problems.

First, the conventional lead storage battery has problems in terms of performance that it can be charged only with a small current during charging, and the charging time is too long and the weight is too large. Further, there is no battery function recovery technique for regenerating a discarded lead-acid battery to a new level, and the electrolyte additive used at present has only an effect of slightly improving the capacity of a lead-acid battery having a reduced performance.

Further, with respectto environmental problems, for example, lead-acid batteries for automobiles are discarded after about 3 years of use, and the cost for disposal and recycling of the waste is high, and they are often left or accumulated in the field. The dilute sulfuric acid and lead constituting the discarded lead storage battery are nuisance substances, which cause the 2 nd pollution. Further, since lead-acid batteries used in large ships are thrown out in deep sea, marine pollution on the earth scale by the discarded lead-acid batteries is accelerated.

The invention aims to develop an electrolyte which has high performance, light weight, long service life and can charge a lead storage battery with a large current for a short time, can greatly improve the performance of the lead storage battery regardless of the freshness of the lead storage battery, and also aims to provide an electrolyte which can regenerate the discarded lead storage battery.

As a means for improving the performance of lead-acid batteries, cathode-Active Material (MnO) is used₂、CuO、NiOOH、PbO₂CFx, and the like, and conductive materials using carbon powder, metal powder, and the like as a Cathode Mix (Cathode Mix), there are knownSeveral patent applications using carbon powder, for example, ① Japanese patent laid-open No. 53-10828 discloses a method of producing PbO₂The invention of coating carbon powder on an electrode, jp ② a s 54-61642 discloses a similar invention of coating with a carbon suspension, and jp ③ a s 57-158955 discloses an invention of incorporating carbon fibers inside metallic lead.

The activation of the cathode of a lead-acid battery using a carbon suspension is also carried out in the present invention, but as will be described later, is completely different from the conventional example described above, ① is essentially the same, that is, a carbon coating is formed on a lead lattice or a plastic lattice, and PbO is mixed₂Lead yellow is effective only for the first layer of particles on the surface of the lead yellow PbO2 in contact with the substrate, but is ineffective for most particles not in direct contact with the electrode substrate, and therefore, the influence on the entire electrochemical reaction is very small, and ③ similarly, carbon fibers are contained in the metal lead, which contributes to an increase in strength and weight of the cathode substrate, but the carbon fibers are shielded by the metal, and thus do not contribute to the electrochemical reaction of charge and discharge.

The present invention uses a Carbon Suspension (Carbon Suspension) for electrode activation of a lead storage battery, and is configured as follows.

First, the carbon suspension is an aqueous system, and is composed of a carbon suspension obtained by electrolytic oxidation (electrolytic oxidation) of a carbon anode, and a lead storage battery anode (PbO)₂) An electrolyte for lead-acid batteries activated by Electrochemical Doping (Electrochemical Doping). The electrolyte is characterized in that the carbon suspension is a suspension (suspension), and hydrophilic groups such as carbonyl groups, carboxyl groups, or hydroxyl groups are chemically modified on the surface of the carbon colloid particles (Chemical modification).

2, the above-mentioned carbon suspension is used as a regeneration supplementary liquid for a lead-acid battery in use or a discarded lead-acid battery which is difficult to regenerate for a long period of time, to activate the lead-acid battery. In addition, the lead-acid battery can be activated by drying the carbon suspension to obtain carbon powder and adding the carbon powder as a regenerant to the electrolyte.

And 3, when the lead storage battery is newly manufactured, taking the carbon suspension as a cured cathode lead yellow formation liquid, and activating the lead storage battery by using the carbon suspension.

Next, item 4 is an improvement of the electrode of the lead-acid battery, the lead-acid battery anode (PbO)₂) The cathode and the porous carbon sheet are in contact with each other, and the lead-acid battery is activated by a charging operation or a charging operation in a state where a carbon suspension is added. Here, the best results were obtained when the porous carbon sheet was a carbon fiber woven fabric.

The lead storage battery is activated by carbon in the carbon suspension in the anode material PbO₂And (2) electrochemical doping. This electrochemical doping is discussed later.

FIG. 1: ESCA pattern of electrolytically oxidized carbon particles of the present invention;

FIG. 2: ESCA plot of carbon particles that were not electrolytically oxidized;

FIG. 3: represents the C1 with the peak in FIG. 1 protruding in the range of 280-300eV_sESCA plot of the energy spectrum of (a);

FIG. 4: an ESCA plot representing the energy spectrum of C1S in FIG. 2;

FIGS. 5 to 9: a graph showing a voltage-time curve (discharge curve) at the time of discharge;

such as the first hairAs described in the specification, the electrolyte for a lead-acid battery of the present invention is an aqueous electrolyte, is composed of a carbon suspension obtained by electrolytic oxidation of a carbon anode, and is formed by electrochemically doping a lead-acid battery anode (PbO)₂) An activated electrolyte for lead-acid storage batteries.

The carbon material used for the carbon anode may be any of crystalline, amorphous, natural and artificial carbon materials, and may be sintered or unsintered. Among them, graphite is preferable.

The shape of the electrode may be any of a block shape, a plate shape, a rod shape, a fiber shape, a sheet shape, a felt shape, and the like, or may be an original powder shape. When used in the form of powder, it is difficult to form an electrode directly, and the electrode can be formed by filling the powder in a mesh cage. Or pressing into powder.

In fact, when carbon oxide is electrolyzed using water as an electrolyte, the pH of the electrolyte changes to 2 to 3 on the acidic side, and in view of this fact, the acid appears to be a carboxylic acid in nature. The electrolytic oxidation of carbon means that carbon powder is deposited as a mist around the anode at a certain current value (voltage varies depending on the distance between electrodes) when a direct current voltage is applied to water while increasing the current. The precipitated powder was suspended in colloidal form in water. When an electrode is inserted into the carbon suspension and a direct current voltage is applied, the precipitated carbon powder is adsorbed (adsorption) to the anode. In the present invention, this electrolytically precipitated Carbon Powder is referred to as Electrolytic Oxidized Carbon Powder (Electrolytic Oxidized Carbon Powder); this Treatment is referred to as Electrolytic Oxidation (Treatment of Electrolytic Oxidation).

In the present invention, the current value at which the dispersion of the carbon powder by electrolysis starts to appear visually is referred to as a critical current (strictly speaking, it is presumed that the electrodeposition to the extent that it is invisible to the naked eye at a lower current has already started to be obtained). The critical current varies depending on the area of the carbon anode, the distance between the anode and the cathode, the presence or absence of the electrolyte, and the amount thereof. When tap water was used as the electrolyte, the distance between the anode and the cathode was 3mm or less, and the anode area was 200mm2, 3-5A was the critical current.

The electrolyte used in electrolytic oxidation is preferably water, and water alone may be used, but depending on the purpose, the acid component of the battery electrolyte and other electrolytes such as NaCl and LiCl may be added to water. When pure water is used as the electrolyte, an acid component of the electrolyte and other electrolytes may be added to improve the conductivity. Tap water or the like containing a trace amount of mineral components can be used to obtain a high-quality carbon powder dispersion while ensuring appropriate conductivity without adding any chemical.

The carbon suspension of electrolytically oxidized powder dispersed in the electrolyte is a colloidal solution, synthesized by electrochemical oxidation, the carbon colloid in this solution acting as a dopant (a dopant) for the cathode of the lead-acid battery. The behavior of the carbon colloid on the cathode brings the following results: (1) regenerating the degraded battery; (2) obtaining large charging current under the condition that the temperature of the electrodeless end rises; (3) the discharge current increases; (4) the battery life is extended. According to the present invention, the carbon colloidal solution is prepared as follows.

There are various means available for carbon oxidation. Wherein (1) chemical oxidation is carried out with an oxidizing agent. Examples of the oxidizing agent include concentrated nitric acid, concentrated sulfuric acid, nitrohumic acid, potassium hypochlorite, and potassium permanganate. (2) Oxidation by ozone,(3) discharge oxidation, or plasma discharge oxidation, (4) irradiation with electron rays. Carbon oxidation by electrochemical means (electrolytic oxidation) is currently known, but has not been industrially adopted to the extent known to the present inventors. In the present invention, the electrochemical oxidation treatment of carbon can produce an aqueous, stable carbon suspension.

Here, a method for preparing a carbon suspension will be described. To make the carbon suspension, our procedure was: anodes and platinum cathodes are refined from an electrolyte containing a small amount of a salt such as lithium chloride, shaped, sintered carbon particles. The voltage between the electrodes is set to a sufficiently high voltage for the electrolyte. As the electrolysis proceeds, the carbon particles become suspended. The electrolysis was carried out until the pH of the solution was reduced to 2.5. The carbon particles are suspended in solution, without relying on any other dispersing agent. After 10 days from the completion of the preparation, no sedimentation of the carbon particles was observed. Even if the carbon particles subjected to electrolytic oxidation are dried to powder, the particles can be well dispersed and suspended in water. Therefore, the carbon powder can be used as a regenerant for lead-acid batteries. In this case, since a small amount of powder is added, the operation is convenient, and when the existing electrolyte is large, the electrolyte does not need to be drawn out for replenishing the carbon suspension, and the decrease in the sulfuric acid concentration can be prevented. The carbon powder may be added to the electrolyte in the form of paste or thick liquid by mixing with dilute sulfuric acid. That is, since the carbon particles obtained by electrolytic oxidation have good dispersibility in water or dilute sulfuric acid, a wide variety of commercially available regenerants in the form of a thick liquid, paste or powder having a concentration of from about 0.01 to 5% can be obtained.

The mechanism of electrochemical oxidation can be explained as follows. That is, the electrochemical oxidation starts from the reduction reaction of oxygen.

(1)

The Source of oxygen (Source of oxygen) is oxygen dissolved in solution or an electrolysis product formed at the anode. Since reaction (1) is dominant near the cathode, oxygen molecules drift from the anode to the cathode. O being a product of the reaction (1)₂ ^-Eventually becoming OH^-。

(2)

It is envisaged that this OH group^-And generating-OH groups on the surface of the carbon after reacting with the carbon anode. Further, -OH group becomes aldehyde (-CHO) group and/or carboxyl group (-COOH) under the oxidation at the next 2 nd stage. We successfully obtained evidence of the presence of these groups on the carbon surface.

FIG. 1 shows an ESCA (Electron Spectroscopy for Chemical Analysis ) energy spectrum of electrolytically oxidized treated carbon, which was measured using an X-ray photoelectron Emission spectrometer (Physical Electronic Co., Ltd., 5600Ci) and an A1K α X-ray source (350W).

ESCA provides information on the electron binding energy of the inner shell, e.g., 1s, 2s, 2p, etc., by measuring the kinetic energy of electrons emitted by X-rays of atoms on the surface of the sample. This can be a powerful weapon for surface analysis.

In fig. 1, peaks where C and O coexist and a small amount of N and S are shown.

ESCA gives information only on the surface (1 or 2 atomic layers from the surface) and is very sensitive to inclusions (contamination) on the surface. N may be nitrogen from the air, and S may be mixed in during the electrolytic oxidation of carbon. From fig. 1, it can be concluded that the amount of oxygen on the carbon surface is 15.33%. For comparison, we also determined the ESCA spectrum of carbon that was not subjected to electrolytic oxidation treatment. The results are shown in FIG. 2. The oxygen content is extremely small and can be seen at a glance. To this end, a conclusion can be drawn: the carbon particles are oxidized by electrolytic oxidation treatment. Further information is available from this ESCA spectrum. FIG. 3 shows the energy spectrum of C1s with peaks highlighted in the range of 280-300eV in FIG. 1. The red yeast rice line at the apex in fig. 3 represents its energy spectrum. The case where the curve of this vertex is composed of several peaks is clear. The respective components shown in fig. 3 can be obtained by the measurement operation. The measurement operation must match the total of the individual components to the original peak. The individual peaks are shown in table 1.

TABLE 1 ESCA in electrolytically oxidized treated carbon particles

C of the spectrum_1sIdentification peak energy (ev) color identification range (%) 290.91 green pi-pi of component of peak^*The concomitant peak 5.93288.77 blue-C-O-O- (carboxyl) 5.94286.78 purple-C-O-10.49285.01 yellow green-CH 12.43284.43 red C-C (graphite) 59.55

It is important to be able to clearly confirm the presence of the carboxyl group and the-C-O-group. Presumably, this isThese groups have a hydrogen atom at one end. I.e., -COOH and-OH. Further investigation is needed in this regard. The unoxidized particles of FIG. 2 are also employedThe same procedure was used, and the results are shown in FIG. 4. In this case, 2 peaks are visible. I.e., 290.69ev (π - π)^*Concomitant peaks of) and 284.39ev (graphite), no carbonyl groups and-C-O-groups were observed. The conclusion is that: the surface of the carbon particles in the carbon suspension obtained by the electrolytic oxidation is provided with a-COOH group and a-C-O-group, and electrochemically modified carbon particles are formed. Considering the case where a hydrogen solution becomes acidic by electrochemical oxidation treatment, the carbonyl group may be present as — COOH. Further, when the aforementioned electrochemical reaction is considered, it is possible that-C-O-exists as-C-OH. these-COOH groups and-C-OH groups, dispersibility (dispersion) of carbon particles and lead-acid battery PbO₂Activation of the cathode plays an important role. Although the carbon particles are originally hydrophobic, the surface thereof is hydrophilized by chemical modification (chemical modification) to form a stable suspension.

Where the carbon is graphite, when graphite is electrolytically oxidized, it is assumed that the layer structure of the graphite particles will undergo cracking (cleavage), and it is expected that the graphite particles will become flakes due to the electro-oxidation. This process, in turn, aids in the dispersion of the particles and thus results in an extremely stable colloidal carbon suspension.

The invention according to claim 2 is a lead-acid storage battery having dramatically improved performance, which is obtained by charging the carbon suspension obtained according to the invention according to claim 1 as an electrolyte in an original acid electrolyte, and as a result, adsorbing carbon powder to an anode.

On the other hand, the powder that has not been oxidized neither floats in water nor adsorbs to the anode, and the simple physical coating of the anode with the powder does not improve the battery characteristics.

In this case, although there is a risk of electrical short circuit between the anode and the cathode due to the carbon powder suspended in the electrolyte, the carbon powder in the carbon suspension of the present invention is attracted and adsorbed by the anode when a voltage is applied, and the electrolyte turns into a clear state as it is when observed with naked eyes, and does not cause electrical short circuit. This is because the concentration of carbon powder in the electrolyte used in the present invention is far below the percolation threshold (percolation threshold), and thus no electrical short circuit occurs.

In order to adsorb the carbon powder to the anode, it is necessary to apply a positive dc voltage to the anode, which corresponds to the case of charging the battery.

When used as a battery for an automobile, the battery is constantly charged during traveling, so that it is not necessary to recharge the battery, and carbon powder is naturally adsorbed on the anode. That is, when a device such as an automobile in which a discharge/charge mechanism is integrally incorporated into the device is used, the carbon powder is automatically adsorbed to the anode only by adding the carbon suspension to the electrolyte without recharging, and the battery characteristics are improved. On the other hand, if the charger is not integrally incorporated in the mechanism, it is necessary to add a charging operation to adsorb the carbon powder to the anode before use.

Here, a description will be given of how to activate the cathode of the lead-acid battery. Another feature of the present invention is the regeneration (revival of a degraded battery) of the degraded battery. We have chosen a degraded battery where the motor cannot start immediately after charging. Part of the electrolyte (dilute sulfuric acid) of the lead storage battery was then replaced with a carbon suspension and recharged, andit was found that after charging, carbon particles were adsorbed to the cathode and the battery was able to start the motor. When the carbon suspension is not added, the storage power is insufficient, but the degraded battery can store electric power after the treatment with the carbon suspension.

By replacing a part of the carbon suspension with the electrolyte solution, (1) a large charging current without temperature rise, (2) realization of a large discharging current, and (3) extension of the battery life can be made possible. The carbon suspension has such an effective function, which at first sight might not be surprising. But the present scientific knowledge can be explained as follows.

First, the mechanism of the structure of the carbon colloid will be explained. The constitution of carbon oxide by electrochemical treatment is well known. The fact that the carbon colloid state is generated can be easily understood by observing the reduction phenomenon of the carbon electrode for electrolysis. But has not been adopted in the industrial field. Generally, to obtain a carbon suspension, a method of pulverizing carbon particles in the presence of a dispersant is employed. The use of carbon suspensions for the modification of lead-acid batteries has not been practiced to date. The carbon suspensions used today are generally alkaline (alkaline solutions) containing a dispersant. In contrast, the carbon suspensions of the present invention are acidic and contain no dispersant. The carbon particles are inherently hydrophobic. However, they are electrolytically oxidized to become hydrophilic.

The carbon particles in the carbon suspension are adsorbed to PbO₂The cathode is an experimental fact. With the presence of PbO not sufficiently electrically connected to the electrodes₂The probability of particles. As is well known, PbO₂Is a semiconductor substance, andthe cathode is PbO₂An assembly of particles. Adsorption on PbO₂The carbon particles on the particle surface have PbO not effectively utilized₂The particles have the functions of conductivity and improving the discharge effect.

Further, the improvement effect by the adsorption of carbon particles on PbSO generated as a result of discharge₄The same is expected. PbSO₄Is an insulator, and as a result of charging, it becomes PbO₂. During this charging process, PbSO₄The electrons must be moved in the direction of the cathode. Thus, electrical connection of the cathode to PbSO₄Is an indispensable problem. Adsorbed on the anode material (a part of which becomes PbSO)₄) For PbSO₄Conductive lines are also formed between the anode and the anode, thereby being capable of leading PbSO₄To PbO₂. Thus, in the present invention, PbO plays an important role in both charge and discharge by the adsorbed carbon particles₂The cathode is activated.

The carbon particles in the carbon suspension of the present invention are chemically modified to have a structure of-COOH and-C-O-H. If in neutral aqueous solution, they dissociate immediately into-COO-and-C-O-. This can be envisaged as: they give off charge at the cathode and bind to the anode, but in acidic solution-COO-does not dissociate from-C-O-. However, since the proton concentration in the vicinity of the anode is very low in a lead-acid battery, the dissociation is possible, and it is assumed that-COO-and-C-O-lose electric charges at the anode and are adsorbed.

The assumption that conductive particles are formed in the vicinity of the cathode, e.g. Ag₂WO₄/LiClO₄It has been reported that in the case of Li batteries, conductive Ag particles are generated as a result of discharge, and thus, a conductive path between the electrode and the cathode is ensured.

The use of electrochemically modified carbon is expected to result in a reduction in the internal resistance of the battery, based on the mechanism of action on the electrochemically modified carbon.

Carbon is classified as an "active material" in the field of batteries. An example of this is a mixture of manganese dioxide and carbon as the cathode active material in a potassium manganese dioxide cell. In this case, carbon is used to increase the electrical conductivity between the manganese dioxide and the cathode. In all cases known today, the carbon substance is premixed with the active substance at the time of manufacturing the battery. The interaction of the carbon species with the active species is only a mechanical contact. Generally, a carbon substance is used only for the effect of either charging or discharging.

In the present invention, the results of the experiments clearly show that the electrochemically modified carbon is effective not only at the time of charging but also at the time of discharging. The application process of electrochemically modified carbon is not purely hybrid. By electrochemically modified carbon PbO₂The activation of the cathode is an electrochemical process in which electron transfer accompanying chemical reaction is involved. This process is known as "electrochemical doping". Thus, it is a completely new technology in the field of batteries.

Here, "electrochemical doping" is defined as follows. First, the "doping" will be explained. In general, in athletic competition, there is a meaning for taking medicines, and here, the meaning is closest to the term used in the semiconductor field. A semiconductor is a substance having electrical conductivity between a conductor and an insulator. Silicon semiconductors are well known as such materials.Semiconductors made of pure substances are called true semiconductors. Such a true semiconductor is called an impurity-containing semiconductor in which a small amount of impurities such as aluminum and arsenic is added. In this case, the semiconductor layers are p-type and n-type semiconductors. This addition of impurities is called "doping", and the added impurities are called "dopants". This contact between p-type and n-type is called p-n junction (junction), and is an essential part of the transistor structure. The term is used for conductive polymers, in general, as opposed to semiconductors such as silicon. A typical conductive polymer polyacetylene is almost an insulator in the cis form, and has an increased conductivity in the trans form, resulting in conductivity in the semiconductor field. Similarly to the case of a silicon semiconductor, it is known that the conductivity can be increased by several digits by doping iodine into trans-polyacetylene. Besides polyacetylene, polymers such as polyaniline, polypyrrole, polythiophene and the like also show heteropotential, and the conductivity can be increased by doping. When these polymers are used, a polymer film can be obtained on the electrode by electrochemical electrolytic polymerization, but in this case, the supporting salt (supporting electrode) is doped simultaneously with the polymerization. The doped dopant (dopant) may be removed electrochemically (this is called dedoping), or the desired dopant may be doped electrochemically. The latter is called electrochemical doping.

As described above, attention must be paid to the carbon content in the electrolytic solution. If a sufficient amount of carbon particles is added to the electrolyte, the battery is short-circuited. The relationship between conductivity and carbon content has been studied, and a calculation model thereof, called "percolation model", has been published. According to this model, the limit of increase in conductivity is considered to start from about 30% by volume. If the carbon content is an order of magnitude less than the percolation threshold, the effect of the carbon can be completely disregarded. In the present invention, as seen in example 6, an effect is exhibited at 5 wt% or less, even at 0.02 wt%, and thus there is no fear of short-circuiting of the battery at all. As mentioned above, black turbidity appears when a carbon suspension is added to the electrolyte, but once charged, the electrolytically oxidized carbon particles adsorb to the anode and the electrolyte returns to its original transparent state. However, if the lead-acid battery is deteriorated seriously, the carbon particles are not adsorbed to the anode, and as a result, the turbidity cannot be eliminated. Such a lead-acid battery is difficult to regenerate, but is useful as a method for determining non-regenerability.

Although the present invention has been described above with respect to a battery that has already been manufactured, regardless of whether it is a new product, an old product, or a waste product, the present invention can also be applied to a process for manufacturing an anode, particularly to a chemical conversion process, in which carbon powder is adsorbed.

That is, the invention according to claim 3 is a lead-acid battery activated by using the carbon suspension as a liquid for forming aged positive electrode lead yellow.

When the anode lattice is filled with the anode active material and chemical conversion treatment is performed, carbon powder is similarly adsorbed to the anode by using the carbon suspension or the dilute sulfuric acid solution in which carbon powder is suspended as the chemical conversion treatment solution. After the obtained anode was mounted on a battery, activation was caused as in the case of using the aforementioned finished electrode.

PbO₂Activation (electrochemical doping) of the cathode not tomention the partial PbO in the production of lead-acid batteries₂The electrodes are equally effective. The cathode material of a lead-acid battery is basically a Pb lattice filled with Pb particles (grains) and lead oxide particles. It is electrolyzed in dilute sulfuric acid solution to be PbO₂So-called chemical conversion (Fromation Process). In the chemical conversion process, an electrolytic oxidation number manufacturing method is adopted, namely, electrochemically modified carbon glue is usedAnd in vivo, chemical conversion and activation are carried out simultaneously. Pbo doped with electrochemically modified carbon particles₂Can be obtained by the chemical conversion process.

With the usual carbon granulate and PbO₂With PbO activated by electrochemical doping with the carbon suspension of the invention₂In contrast, comparative studies were conducted on the effect of mixing carbon particles alone. However, as shown in the examples, the simple mixture did not bring any improvement effect on the performance of the battery.

The invention according to claim 4 is a lead-acid battery comprising an anode surface of a lead-acid battery and a porous carbon material coated on the surface of the anode, wherein carbon powder obtained by electrolytic oxidation is adsorbed on the surface of the anode or the surface of the porous carbon material. Here, the porous carbon material means a porous sheet, felt, or aggregate of carbon particles having water permeability; the carbon fibers may be used as a woven fabric or a nonwoven fabric, and may be a porous material or a material having fine pores formed in a plate, but a sheet or a felt using carbon fibers is most preferable in terms of area ratio of pores, flexibility, price, durability, and the like.

The carbonaceous material can be any carbonaceous material, whether crystalline, amorphous, natural or artificial, and can be sintered or unsintered.

Generally, a mesh separator having an insulator function is interposed between the anode and the cathode. In the present invention, a sheet, felt or granular carbon material is filled in the gap between the anode and the separator to cover the anode surface.

The porous carbon does not have to be one sheet covering the entire surface of the anode, and a plurality of sheets may be stacked to cover the anode.

The thin slice, felt and carbon grain contact with the active material surface of the anode and press to prevent the active material from falling off. Also, since the anode is electrically conducted at the same time, the part becomes equipotential with the anode. By coating the surface of the anode with a porous carbon material, the charging ability can be improved. The number of electrode plates is reduced from the combination of 2 anodes and 3 cathodes of the existing battery to the combination of 1 anode and 2 cathodes, and the charging amount is about 2 times or more. Thus, the lead-acid battery can be reduced in weight.

The present invention will be described in more detail with reference to examples. Example 1 (production of carbon suspension 1) example of crystalline carbon and rod-shaped electrode

A graphite rod having a diameter of 20mm and a length of 100mm was inserted as an anode into a cylindrical cathode having a diameter of 100mm and made of a mesh-like plate of bent stainless steel using water (pH: 7) as an electrolyte, and the cathode was energized with a direct current of 3A for 24 hours to prepare a colloidal carbon suspension.

The carbon suspension liquid is still standing for 10 days without powder sedimentation, and the carbon powder is dispersed in a carbon colloidstate. The concentration of carbon powder in the suspension was 3.1% by weight. The pH of the electrolyte changed to 2.5. (surface analysis of carbon)

As described above, atoms present on the surface of the electrolytically oxidized carbon were analyzed by ESCA. The ESCA analysis of the electrolytically oxidized treated carbon is shown in FIG. 1, while FIG. 2 shows the ESCA analysis of the untreated carbon.

Present on the carbon surface is C (C)_1sPeak of (d), O (O)_1s，O_2sPeak of) and a small amount of N (N)_1sWave crest of), S (S)_2s，S_2pThe peak of (d).

Oxygen: 15.33 percent

Nitrogen: 0.18 percent

Carbon: 84.39 percent

Sulfur: 0.10 percent

It can thus be seen that the carbon surface has been chemically modified by electrolytic oxidation (chemi-cal modification). And carbon surface, O, not subjected to electrolytic oxidation treatment_1sOnly to the extent of the traces. (form of oxygen present)

Regarding the presence form of oxygen on the carbon surface, the following peaks (1) and (2) were confirmed as a result of the same investigation using ESCA.

(1)-C-O-(286.78ev) 8.40％

(2) -C-O- (carboxy) (288.77ev) 9.98%

(1) The right side of O in (2) is supposed to be bonded with hydrogen, and it is supposed that the presence of-OH contributes to hydrophilization and suspension of the carbon surface. The reason why the pH of the electrode solution was changed to 2 to 3 was presumed to be mainly due to the presence of the carboxyl group of (2). (production of carbon suspension 2) examples of crystalline carbon, felt electrode

A felt made of graphite fibers and having a vertical dimension of 100mm, a lateral dimension of 100mm and a thickness of 10mm was used as an anode, and stainless steel mesh plates (cathodes) were disposed on both surfaces thereof at intervals of 2 mm.

At this time, in order to prevent the short circuit of the anode and the cathode and to maintain a constant interval, a resin mesh plate having a thickness of 2mm was interposed therebetween. The electrolyte is tap water. The carbon powder suspended was charged with a direct current of 3A for 24 hours, and the concentration of the suspended carbon powder was 4.8% by weight. The pH of the electrolyte was 2. (production of carbon suspension 3) examples of amorphous carbon and powder electrodes

Amorphous carbon powder having an average diameter of 1mm was filled in a filter of a cylindrical stainless mesh (325# or less) having a diameter of 20mm and a length of 100mm and a bottom, and this was used as an anode and a stainless steel plate having a diameter of 50X 100mm was used as a cathode, and this was immersed in a beaker containing tap water, and applied with a direct current of 3A for 30 hours to prepare a colloidal carbon suspension of amorphous carbon powder.

The carbon suspension was left for 10 days as in example 1, and no powder was precipitated. The concentration of the carbon powder was 5.5 wt%. The pH of the electrolyte was 2. With respect to the dispersing ability, it was 99.3% after 24 hours.

Dispersion stability (%) } sample concentration after 24 hours (wt%)/sample concentration at 0 hour (wt%) } × 100%

The value of the dispersing ability was obtained by the above formula. Example 2 (regeneration of used Battery)

An electrolyte was extracted from a lead storage battery (model G X80D 26) which could notbe used in a general car, and after the storage battery was cleaned, a carbon colloidal liquid of the carbon powder of manufacture 1 of example 1 was added thereto, and a positive dc voltage was applied to the anode for 15V 12 hours. The anode is covered by carbon powder. The carbon suspension was then extracted from the cell, and the extracted electrolyte was returned to the cell, followed by charging at 15V for 24 hours at 3A. The voltage before charging was 9V, and the specific gravity of the battery fluid was 1.18. After charging, the voltage returns to 14V, and the motor can be started. After 10 days, the motor is started again, and the starting can be carried out similarly. This was repeated later, and over 6 months, no change in properties occurred. Incidentally, the battery (which has not been used) not covered with the carbon powder is charged to change only the specific gravity to 1.10, and the motor cannot be started. Example 3 (regeneration of used Battery)

3%, 5%, 10%, 30%, 50%, 70%, 90% by volume of the battery fluid of an already unusable lead-acid battery (model G X80D 26) was replaced with the carbon suspension of production 2 of example 1, and charged with 14V and 3A for 24 hours. After charging, a start test of the motors was performed, and as a result, all the motors could be started. After 10 days, the motor is started again, and the starting can be carried out similarly. This was repeated later, and over 6 months, no change in properties occurred. Example 4 (regeneration of used Battery)

In a lead-acid battery (model number 38B20R) which had been unusable, the carbon suspension of production 2 of example 1 was added to each battery at 50cc (total electrolyte volume of 1 battery was 416cc), and charged at 14V for 12 hours at 3A. The specific gravity of the battery fluid before charging was 1.10. After charging, the voltage returns to 14V, the specific gravity returns to 1.26, and the motor can start. After 10 days, the motoris started again, and the starting can be carried out similarly. This was repeated later, and over 6 months, no change in properties occurred. Incidentally, when a battery (which has not been used) to which no carbon colloidal solution is added is charged only, the specific gravity is still 1.120, and the motor cannot be started. Example 5 (regeneration of used Battery)

Rapid charging was tested for a lead storage battery (model No. GS (trademark) 38B20L) manufactured by japanese battery company, which has been unable to be used for a general car. The electrolyte was replenished before charging, but the voltage was 5V and the specific gravity was 1.110. For this, the normal charging voltage was 14V and 3.8A, but the rapid charging was performed with 15V and 10A. However, only the liquid temperature rises, and electrolysis cannot be performed, and charging cannot be performed.

Then, the carbon colloidal fluid of production 1 of example 1 was injected into this cell, and 21 to 30cc (total electrolyte amount of 1 cell is 416cc) was added for each cell, and as a result, electrolysis was started. Further, the voltage was increased, and the liquid temperature did not increase even when the current of 20A was applied, and the charging was performed smoothly. After 2 hours, the motor was started and smoothly started, and after 3 hours of operation as such, the specific gravity of the battery electrolyte was measured to be 1.20 at a value of 1.25 or less, which was not problematic at the time of discharge. Generally, the charging takes about 5 to 10 hours, but in this example, the charging is completed in only 2 hours. Similar tests were carried out on lead-acid batteries of type 46B 25L (trademark) and type Yuasa 55B 24L (trademark), and 100% recovery was observed. After that, the cells were left for 4 months without any problem in electromotive force. Natural discharge occurred when left alone for 4 months, but no problem occurred and was usable as it is, example 6 (regeneration of old battery)

The electrolyte of a lead acid battery of type GS38 (trademark) which had been unusable was drawn out and the electrolyte described below was injected instead. The sulfuric acid concentration of the electrolyte was the same, and the amount of the suspended carbon powder was changed in the following 5 steps.

Carbon concentration (weight%) (1)0.02, (2)0.1, (3)1.0, (4)3.0, (5)5.0

The carbon concentration was adjusted by concentrating and diluting the carbon colloidal liquid of production 2 of example 1. Charging was carried out for 2 hours at 15V and 2A, and charging was completed without any problem. The lead storage battery is then mounted on the vehicle to start the motor. The motor can be started without any problem. The operation was carried out at 2 hours, 60 days, and 120 hours in total, without any trouble occurring therebetween. Example 7 (regeneration of used Battery)

An old battery (GS28) for a light vehicle (550cc) was regenerated and used in a vehicle of class 2,000 cc. About 10% of the electrolyte was replaced with the carbon suspension of production 2 of example 1 and charged with 20A for 1 hour. A 2,000cc motor can be started in a normal state. Thus, it was found that a 2,000cc motor can be started by the battery of the light vehicle. From this it can be deduced that: when a carbon suspension is used for the electrolyte, miniaturization of the battery is fully possible. Example 8 (regeneration of import vehicle Battery)

When a battery mounted on a courier (trademark) originally shipped from germany to date passes through the equator during transportation, the battery is deeply discharged due to the influence of the outside air temperature, and becomes unusable or non-chargeable. For this reason, a battery regeneration test was performed in whichthe battery became unusable due to deep discharge. A total of 250cc of carbon suspension was replenished to each battery of a Benz 4.5 liter motor (estimated 100AH) that became non-chargeable, and charging was performed for 15 minutes at 60A. The battery was mounted on a car and then started, and the start was successful. It was thus found that the method of short-time rapid charging with a carbon suspension is capable of recovering a deeply discharged battery. Example 9 (variation of electrolyte temperature)

The liquid temperature change during rapid charging was investigated.

Brand of battery: GS (trade Mark) 6N4-2A

The conventional dilute sulfuric acid solution battery was charged with 10 times of current (4A) for 1 hour. The temperature after charging was 64 ℃. Then, 50% of the electrolytic solution was taken out and filled in the carbon dispersion prepared in production 1 of example 1, and similarly, charged at a current (4A) of 10 times for 1 hour. The temperature after charging was 47 ℃. The situation that the existing sulfuric acid liquid battery is charged under the normal condition (0.4A multiplied by 10 hours) is 45-50 ℃, and the invention is proved to be comparable with the sulfuric acid liquid battery. Example 10 (variation of internal resistance)

Brand of battery: GS (trade Mark) 6N4-2A

The existing dilute sulphuric acid liquid battery: 691 omega

A battery in which 50% by volume of the electrolytic solution was replaced with the carbon dispersion prepared in production 3 of example 1: 316 omega

It can be seen that the batteries of the invention are therefore capable of rapid charging, relying largely on the effect of the injection of the carbon suspension on the reduction of the internal resistance. EXAMPLE 11 test of Battery Capacity (test at ambient temperature 25 ℃ C.)

Brand of battery: GS (trade Mark) 6N4-2A

The charging method comprises the following steps: 1A × 1 hr

The discharge method comprises the following steps: the batteries 3 are connected in series to light a head of 37.5W

The lamp, discharge at constant current (1.2A).

Test method

A battery (STD) using a conventional dilute sulfuric acid electrolyte was compared with a battery (IVD) in which 10% by volume of the electrolyte was replaced with the carbon suspension prepared in example 1, 2. The results are shown in the voltage vs. time curve of fig. 5. The discharge time of the battery of the present invention to the point where the voltage is reduced to 4.8V, i.e., the time that the battery can be used, can be extended by about 20% as compared with the conventional battery. Example 12 (carbon suspension concentration and startability)

The carbon suspension produced in production example 2 of example 1 was tested for the degree of concentration and starting performance at about 10% of the electrolyte of light-weight vehicle battery GS (trademark) 28 AH. The test was carried out using Mitsubishi パジェ port (trade mark) diesel engine 3,000 cc. The concentration degree was 2 times, 4 times, 6 times, and 10 times. At any concentration, the start-up of the motor is not problematic. Example 13 (Battery Capacity at Normal temperature)

A battery (model 6N4-2A) comprising 1 cell each of 2 anodes and 3 cathodes was charged for 1A by subtracting 1 sheet from each of the anodes and cathodes to obtain a combination of 1 anode sheet and 2 cathode sheets, and a graphite felt of 50mm X2 mm in thickness was inserted between the anodes and separators, and 5% by volume of the electrolyte of the above battery was replaced with the carbon suspension prepared in example 1, and the battery was charged for 1A X1 hours. After charging, the battery was connected to a 37.5W head lamp for 1.2V, and discharged at a constant current (1.2A). The discharge curve (voltage-time curve) is shown in FIG. 6. For comparison, fig. 6 shows the discharge curve (thin line) when the graphite felt was not interposed between the anode and the cathode and the carbon suspension was not added to the electrolyte in the case of the combination of the anode 1 sheet and the cathode 2 sheet. As is apparent from fig. 6, when the carbon felt and the carbon suspension were used in combination, it was confirmed that the discharge amount was increased and the discharge voltage was also increased. Example 14 (accumulator capacity of 65 ℃ C.)

Brand of battery: GS (trade Mark) 6N4-2A

The charging method comprises the following steps: 1A × 1 hr

The lamp, discharge at constant current (1.2A).

Test method

A battery (STD) using a conventional dilute sulfuric acid electrolyte was compared with a battery (IVD) in which 10% by volume of the electrolyte was replaced with the carbon suspension prepared in example 1, 2. The results are shown in the voltage vs. time plot of fig. 7. The discharge time of the battery of the invention when the voltage is reduced to 4.8V, namely the usable time of the battery, is prolonged by 1.8 times compared with the prior battery. At high temperatures, the performance difference from the conventional battery is further increased. Example 15(-20 ℃ C. Battery capacity)

Brand of battery: GS (trade Mark) 6N4-2A

The charging method comprises the following steps: 1A × 1 hr

The discharge method comprises the following steps: the batteries 3 are connected in series, and a 37.5W head lamp is turned on to discharge the battery at a constant current (1.2A).

Test method

A battery (STD) using the conventional dilute sulfuric acid electrolyte was compared with a battery (IVD) in which 10% by volume of the electrolyte was replaced with the carbon suspension prepared in example 1, 2. The results are shown in the voltage vs. time plot of fig. 8. The discharge time until the voltage of the battery of the present invention is reduced to 4.8V, that is, the usable time of the battery, is not much different from the conventional battery, but it can be understood from the voltage-time curve at the time of charging: the battery of the invention can be charged with low voltage, i.e. with small internal resistance and easy charging. EXAMPLE 16 (production of electrode)

The anode used was GS (trade mark) 6N4-2A anode with lead-free lattice active material, and the cathode used was GS 6N4-2A cathode without modification.

The anode active material was prepared by kneading 30g of lead oxide, 6g of lead tetraoxide and 8ml of dilute sulfuric acid having a specific gravity of 1.12 into a paste, uniformly filling the spaces between the anode cells, and aging the paste at room temperature for 12 hours. The chemical conversion treatment was carried out by interposing a nonwoven fabric of glass fiber between the anode and the cathode which had been cured, insulating and fixing the same, immersing the same in the colloidal solution of carbon powder prepared in production 1 of example 1, applying a direct current voltage between the anode and the cathode, and applying a current of 200mA for 12 hours. Carbon powder is adsorbed on the anode which is subjected to chemical conversion treatment. In the charge/discharge test, the formed liquid was taken out, filled with dilute sulfuric acid (specific gravity 1.25), charged at 0.5A for 1 hour, and then discharged at a constant current (0.4A) to examine the change in voltage, and the results are shown in fig. 9. The adsorption of the carbon powder produced by this method to the anode is effective not only in activating the used battery but also in the intermediate production process of a new anode.

Claims

1. An electrolyte for lead-acid batteries, comprising an aqueous carbon suspension obtained by electrolytic oxidation of a carbon anode, characterized by comprising a lead-acid battery anode (PbO)₂) Electrochemical doping to activate it.

2. The electrolyte for lead-acid storage batteries according to claim 1, wherein the carbon suspension is a colloidal suspension, and the surface of the carbon colloidal particle is chemically modified with a hydrophilic group such as a carbonyl group, a carboxyl group, or a hydroxyl group.

3. A lead-acid battery, characterized in that the carbon suspension described in claim 1 is activated by being additionally added to an electrolyte as a regenerant for lead-acid batteries.

4. A lead-acid battery, characterized in that the carbon powder obtained by drying the carbon suspension described in claim 1 is added to an electrolyte as a regenerant for lead-acid batteries and is activated.

5. A lead-acid battery, characterized in that it is activated by using the carbon suspension described in claim 1 as a liquid for forming aged positive electrode lead yellow.

6. A lead-acid battery characterized in that PbO₂The cathode and the porous carbon sheet are in contact and activated by a charging operation or a charging operation in a state where the carbon suspension described in claim 1 is added.

7. The lead-acid battery according to claim 6, wherein the porous carbon sheet is a carbon fiber fabric.