JP2847761B2 - Sealed lead-acid battery and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sealed lead-acid battery.

2. Description of the Related Art As is well known, the capacity of a lead storage battery is regulated by both positive and negative electrode active materials and the amount of sulfuric acid in an electrolytic solution.

In a lead-acid battery having a constant volume or a constant weight, in order to improve the utilization rate of the active material, the amount of the sulfuric acid must be increased by decreasing the amount of the active material, or a sulfuric acid electrolyte having a higher concentration must be used. However, increasing the utilization rate of the positive electrode active material not only accelerates softening and falling off of the active material, but also accelerates lattice corrosion. This has the disadvantage that the cycle and float life performance of the resulting battery is significantly reduced.

On the other hand, when the utilization rate of the negative electrode active material is increased, the resistance of the active material to sulfation decreases, and the life of the active material is shortened. When a sulfuric acid electrolyte having a high concentration is used, the volume efficiency and the weight efficiency of the battery can be improved. However, although this has a small effect on the positive electrode plate, the high-concentration sulfuric acid electrolyte has a disadvantage that the battery has a short life because it promotes the sulfation of the negative electrode active material.

A large amount of electricity and time are required in a chemical conversion process for activating an unchemically active material of an electrode plate used in a lead storage battery. In fact, the excessive excess amount of electricity in this chemical conversion step is necessary particularly for activating the positive electrode active material, and usually, 2 to 4 times the theoretically necessary amount of electricity is supplied. This is considered to be because the electron conductivity of lead oxide, which is a positive electrode active material, is low, and the electron conductivity between active material particles is maintained only by contact between the particles. That is, during the formation of the positive electrode plate, first, the particles in contact with the current collector are oxidized to lead dioxide. Next, the formation of the particles in contact with the lead dioxide is repeated to form a chemical conversion electrode plate. Therefore, particles far away from the current collector will be formed only at the end of the formation process. This means that, when viewed during the formation process, the density of the formation current with respect to the active material particles is high at the beginning and low at the end, which further lowers the efficiency of the formation current as a whole. . In order to make the formation easier, lead red (pB ₃ O ₄ ) may be added to the unformed active material. This is because only the required amount of electricity is reduced due to the progress of oxidation. Even if it does in this way, formation will start from the vicinity of the current collector, and the efficiency of the amount of formed electricity will remain low as a whole. Leadtan is expensive and has a greater demerit that the price is higher than an advantage of being able to reduce the amount of chemical electricity.

It has been proposed in US Pat. No. 4,631,241 to mix graphite in a positive electrode active material and to hold an electrolyte between the layers to increase the pore volume and increase the capacity of the positive electrode.
Since graphite has electronic conductivity, it is possible to electronically connect active material particles. However, the graphite shown here has a particle size of 340 μm
In order to connect the active material particles, the number is too small. The number of active material particles per unit volume is 1 × 10 ¹² to 1 × 10
^In the case of ¹⁶ negative electrodes, the number is estimated to be 1 × 10 ⁹ to 1 × 10 ¹³ . On the other hand, when 1% of the graphite having a size of 340 μm is added, the number of graphite particles becomes 50%.
This number is only about 0 to 1000, and this number is too small to expect an electron conductive connection between active material particles in graphite.

In order to improve the bond between the active material particles or between the active material particles and the lattice, the presence of carbon fibers or electron conductive fibers in the active material is disclosed in JP-A-61-128466 and JP-A-54-128. No. 10574 and Japanese Patent Laid-Open No. 58-57264. JP-A-49-103135 proposes the presence of a metal whisker such as carbon fiber or lead. The carbon fiber proposed here has a diameter of 10 to 1000 μm as described in JP-A-54-105741 as `` diameter of 0.01 to 1.0 mm, '' and has a large diameter and a large surface area. Due to the small size, according to the tests of the present inventors, the number of contacts with the active material particles was small, the characteristics of carbon were exhibited to the maximum, and the conductivity could not be improved dramatically.

JP-A-49-103135 discloses that "metal whiskers such as lead" exist in addition to such carbon fibers. However, "metal whiskers such as lead"
How it is obtained, what kind of properties, dimensions and forms, it is not specified, and the equivalents are not available, so the inventors of the present invention,
I can't confirm.

Where the present inventors mixed the lead material having a diameter of 30 μm cut into 2 mm obtained by the chatter vibration method into the active material, the density of the active material was increased, and it was thought that the contact density was improved. Nevertheless, the utilization rate of the active material and the charge acceptance were not improved.

Japanese Unexamined Patent Publication No. 61-45565 discloses that "a polyolefin-based or polyester-based synthetic resin is mixed with a carbon powder or an acid-resistant metal powder", "a conductive synthetic resin fiber having a diameter of 1 to 10 µm". Is mixed in the active material. However, even if the conductive synthetic resin fiber thus obtained is sufficient for reinforcing the active material, the conductivity of the fiber itself is insufficient to improve the electron conductivity between the particles, and Mixing the fibers of 1 to 10 μm causes a decrease in the apparent density of the active material. Therefore, as described therein, the “adhesion between the active material of the Pb-Ca-based alloy lattice and the lattice body is described. The function of "improvement and inhibition of barrier layer formation" could not be confirmed.

Also, in order to improve the charge acceptability of the negative electrode, carbon black is widely used. In this case, carbon black increases the current flowing at the end of charging mainly by lowering the end-of-charge voltage, that is, by reducing the hydrogen overvoltage of the negative electrode. Carbon black has a very small particle size as compared to the graphite described above. Thus, adding as much as 0.2 wt% will be sufficient to contact individual particles of the active material. However, in this case, since the carbon black has no length, it has only a role to exist between the active material particles. That is, tens or hundreds of active material particles cannot be connected to each other. The improvement of the charge acceptability of the negative electrode by the addition of carbon black increases the charge flow by lowering the end-of-charge voltage, but does not make it easier for the current to flow through the individual active material particles. . This means that a large amount of current also flows to the positive electrode at the end of charging, and accelerates the corrosion of the positive electrode grid due to an increase in overcharged volume, which is a preferable method in terms of life performance. Absent. Thus, the addition of carbon black to the negative electrode has not substantially improved the charge acceptability.

On the other hand, a sealed lead-acid battery has a configuration in which a separator and an electrode plate are stacked in a sealed container, and the electrolyte in the battery does not flow into the separator and the holes of the positive and negative electrodes. So it is held. This sealed type lead-acid battery has the features that it has excellent liquid leakage resistance, does not require rehydration, and has little self-discharge.

By the way, as described in JP-B-63-27826, in a large-capacity sealed lead-acid battery having a high electrode plate height, charging and discharging are repeated despite being uniform at the time of liquid injection. The concentration of the electrolyte held in the pores of the separator and the electrode plate differs in the vertical direction. That is, a layering phenomenon occurs in which the concentration of the electrolytic solution becomes higher toward the lower part of the separator.
Since this layering phenomenon is likely to occur mainly in the separator portion, in order to prevent this, it is necessary to increase the liquid holding power of the separator and to make sure that there is no difference in liquid holding properties even above and below the separator, or that the electrolyte solution It is required to increase the viscosity by adding fine silica powder.

Conventionally, as the separator, those mainly composed of glass fiber are mainly used. In order to prevent the occurrence of the layering phenomenon, various improvements have been attempted with respect to improving the liquid retaining property (liquid retaining property) of the separator used.

For example, JP-A-62-133669 and JP-A-62-136751,
A separator coated or mixed with a powder such as SiO ₂ , TiO ₂ or a rare earth oxide is described. JP-A-63-15
Nos. 2853, 62-221954 and 61-269852 describe the use of silica or expanded perlite as a powder.

JP-A-63-143742 and JP-A-63-146348 describe separators made of hollow thin glass fibers.

However, although it is easy to add silica powder to the electrolyte solution, the process becomes complicated and the resulting battery becomes expensive.On the other hand, mixing silica in the separator requires the following steps. At present, it has not been put to practical use for such reasons.

That is, it is impossible to make paper as a separator only with silica powder, and therefore, it is necessary to mix silica powder with glass fiber as a main component. Is low, and conversely, if the ratio of silica powder is large, papermaking becomes difficult.

As described above, conventionally, there has not been provided a separator for a sealed lead-acid battery which has an excellent effect of preventing the layering phenomenon and is easy to manufacture. Therefore, the conventional sealed lead-acid battery is stratified and has a short life.

Object of the Invention The present invention is to solve the above conventional problems,
The aim is to improve the utilization rate of both positive and negative electrode active materials, improve the charge acceptance of positive and negative electrode active materials (charge efficiency), which have higher weight effect and volume efficiency than before, Long life cycle and float life performance, improved resistance to sulphation, enabled the use of higher concentration sulfuric acid electrolyte, thereby greatly improving utilization without sacrificing life An object of the present invention is to provide a low-cost sealed lead-acid battery in which the amount of electricity required for the formation of a positive electrode plate is greatly reduced, stratification of an electrolyte is unlikely to occur, and a long life and low cost are obtained.

Configuration of the Invention The present invention includes a negative electrode plate, a positive electrode plate, a separator, and an electrolytic solution. (A) The negative electrode plate is made of pure lead, a Pb-Ca-based lead alloy, or another lead alloy containing no antimony. Current collector and 0.01-10wt
%, More preferably 0.1 to 1.0% by weight, having a diameter of 10 μm or less, an aspect ratio of 50 or more, and a specific surface area of 2 m ² / g or more. A negative electrode active material mainly composed of sponge-like metal lead connected to the positive electrode plate; (b) the positive electrode plate includes a current collector made of pure lead or a lead alloy;
First, the carbon whiskers or the graphite whiskers are contained in an amount of 0.01 to 10% by weight, more preferably 0.01 to 1.0% by weight.
% Of a positive electrode active material containing lead dioxide as a main component in which voids are formed by removing the whiskers by anodic oxidation. (C) The separator has a diameter of 0.4 to 0.9 μm. Acid-resistant glass fiber 55-75wt% and coarse glass fiber 1μm or more in diameter 0
~ 15wt% and particle diameter 1 ~ 10m, more preferably 2 ~ 5
25-45wt% wet silica fine powder of 25μm was formed without using a binder, and the air permeability per sheet was 8 seconds / 300cc
A wet papermaking sheet having a specific surface area of greater than 20 m ² / g, which is in close contact with the positive and negative electrode plates, and (d) an electrolytic solution comprising the separator and the positive and negative electrode plates. A sealed lead-acid battery and a method for producing the same, wherein the battery is absorbed and fixed in micropores of an active material.

Examples Hereinafter, the present invention will be described in detail with reference to examples.

(Example 1) For 940 g of water, 60 g of carbon whiskers were uniformly dispersed by an ultra-high speed mixer. The carbon whiskers used here were produced by vapor-phase epitaxy using hydrocarbons as raw materials, and had a diameter of about 0.05 to 0.8 μm, a length of about 10 to 100 μm, and an aspect ratio of It is said that it is about 100 and has a long length for an extremely small diameter. Its density is 1.96g /
cm ³ , the electron conductivity is 7 × 10 ⁻⁴ Ω-cm, and the specific surface area is 10 to 40 m ² / g according to the BET method.

To 170 g of the carbon whisker dispersion liquid thus prepared, 1000 g of lead oxide powder containing about 30% metallic lead was added and kneaded. Then, kneading was continued while 75 cc of sulfuric acid having a specific gravity of 1.40 was gradually dropped, and the paste A for positive electrode was used. I got

A negative electrode paste B was prepared by the same operation except that a predetermined amount of lignin and barium sulfate were added to the carbon whisker dispersion. By the same operation except that no carbon whisker was used, the paste C for positive electrode was used.
And a paste D for a negative electrode.

Dimensions made of Pb-Ca-Sn alloy without antimony
^The above-mentioned paste was filled into a casting grid having a size of ^W 38 × ^L 67 × ^T 3.3 (2.0) mm by a conventional method. The electrode plate filled with the paste was allowed to stand at 35 ° C. and 100% RH for 3 days to ripen and harden the paste. Then, it was dried at 50 ° C. for 1 day to obtain an unformed positive electrode plate AC and negative electrode plate BD.

The physical properties of the paste and the amount of the non-chemically activated material after drying were as shown in Table 1.

In addition, seven types of sheet-like separators were obtained by the papermaking method using the fiber constitutions shown in Table 2, but no binder was used in the papermaking. The properties of these separators were as shown in the table. The air permeability is JIS P-9117
The specific surface area was measured by the BET method. By combining these separators with the two positive plates and the three negative plates described above, an unformed battery having the structure shown in Table 3 was inserted into a battery case, and 45 ml of a specific gravity of 1.30 dH ₂ SO ₄ was injected per cell. And fitted a safety valve. After that, it was formed in a battery case at a constant current of 0.8 A for about 30 hours to obtain a sealed lead-acid battery, 20 HR capacity, each rate capacity test, cycle life test and the amount of lead sulfate under the negative electrode plate in 100 cycles, When the specific gravity of the electrolyte solution was analyzed at the top and bottom, the results shown in FIGS. 1, 2 and 3 were obtained. Here, the life test was performed at 25 ° C. as one cycle of discharging: 0.85 A × 3 H charging: 1.1 A × 2 H → 0.29 A × 3 H, and the point in time when the capacity reached 80% of the initial capacity was determined as life.

(Example 2) As a conventional negative electrode plate, a negative electrode plate E was prepared by adding 0.3% by weight of carbon black to the active material of the negative electrode plate D of Example 1. The specific surface area of this carbon black is
1500 m ² / g. By combining the negative electrode plate E and the positive electrode plate C, a conventional sealed lead-acid battery j was obtained.

Using three batteries, the sealed lead-acid battery b according to the present invention and the conventional sealed lead-acid batteries i and j, charging was performed at a constant current of 0.0001 to 0.1 CA, and the result of examining the relationship between charging current and battery voltage Is shown in FIG.

It is apparent from Example 1 that the sealed lead-acid battery according to the present invention has a high utilization rate of the active material and high weight efficiency and volume efficiency. The number of positive electrode active material particles per unit volume is 1 × 10 ¹² to 1 × 10 ¹⁶ , and the negative electrode has 1 × 10 ⁹ to 1 × 10 ⁹
As described above, it is estimated to be × 10 ¹³ . Example 1
As shown in the above, the number of whiskers when about 1% is added to the active material is estimated to be 1 × 10 ¹⁰ to 1 × 10 ¹³ . In addition, whiskers have a large aspect ratio,
The number of active material particles in contact with each whisker is 50 to 10
It is estimated to be as many as 00. Therefore, for example, in the negative electrode, it is estimated that a plurality of carbon whiskers are in contact with one active material particle. According to the present invention, distant particles that have not conventionally been electronically coupled are now connected in parallel. Therefore, current is extremely easy to flow not only in charge and discharge but also in the formation process,
High charge acceptability, larger discharge capacity, and extremely high formation current efficiency can be obtained. This is apparent from Example 1.

The negative electrode active material becomes a coarse crystal sulfate which is hardly reduced by charge / discharge at a high concentration of an electrolytic solution or at a high temperature, and its capacity is reduced.

On the other hand, not only lead-acid batteries with a large amount of flowing electrolyte, but also sealed lead-acid batteries with a small electrolytic capacity, the so-called stratification in which the lower part of the electrolyte becomes high and the upper part becomes low by repeated deep discharge. (Stratification).

The separator used in the sealed lead-acid battery of the present invention has a high resistance to stratification of the electrolyte because silica fine powder is present inside the separator. Therefore, the specific gravity difference between the upper and lower parts when charging and discharging are performed in the same cycle is small. This means
This is clear from Table 3. It is also clear from Tables 2 and 3 that the resistance to layering can be substituted by the air permeability, specific surface area, etc. of the separator. Therefore, from these results, it is preferable that the air permeability of the separator is 8 seconds / 300 cc or more, and that the specific surface area is more than 20 m ² / g.

In order to obtain such a separator, it is preferable to form a glass fiber having a diameter of 1 μm or less as a main component and a fine powder mainly composed of silica without using a binder. Particularly preferred constitutions are 75 to 55 wt% of acid-resistant glass fibers having a diameter of 0.4 to 0.9 μm, 0 to 15 wt% of coarse glass fibers having a diameter of 1 μm or more, and wet silica fine powder having a particle diameter of 1 to 10 μm, more preferably 2 to 5 μm. It is a sheet obtained by wet-making 25 to 45% by weight without using a binder.

The diameter of the main glass fiber is 1 μm or less, especially 0.4
The thickness is preferably 0.9 μm since the pores of the separator can be reduced and unnecessary cost increase does not occur. The fine powder containing silica as a main component may be either of a wet type or a dry type, but a wet type is more suitable from the viewpoint of the yield to the separator, the specific surface area and the like, and the particle diameter thereof is 1 to 10 μm, more preferably 2 to 10 μm. Optimally, it is ５5 μm.

At the time of wet papermaking of the separator, it is better to make a sheet without using a binder because the obtained separator has high flexibility and tight adhesion to the electrode plate surface, and the possibility of elution of substances harmful to the battery It is preferable because there is no such material.

In order to further improve the mechanical strength of the separator, it is advisable to mix coarse fibers having a diameter of 1 μm or more, preferably 10 μm or more as glass fibers. In that case, the amount must be up to 15 wt% in order to avoid increasing the pore size and reducing the resistance to stratification.

The lower part of the negative electrode plate is usually far from the ear, and the high-concentration sulfuric acid electrolyte has high resistance and low solubility of lead sulfate. Invite. However, according to the present invention, since the resistance to the layering of the separator is high and the resistance in the electrode plate is low, sufficient current flows even in the lower part of the negative electrode plate despite being far from the ear, and the lower sulfation Can shorten the battery life. This is clear from the results in Table 3.

While the conventional sealed lead-acid battery i has a short life due to the lower sulfation of the negative electrode plate, the sealed lead-acid battery according to the present invention showed extremely excellent life performance.

Since the unformed active material does not have electron conductivity, when forming it, the formation proceeds in order from the particles in contact with the current collector grid or core metal. Therefore, the active material particles which are not in contact with the current collector are not formed until they are supplied with electrons via the particles existing between the particles and the current collector. For this reason, in the past, particularly the positive electrode plate had to be formed by a long time and a large amount of electricity, and required 2 to 4 times the theoretically required amount of formation electricity. However, according to the present invention, even particles that are distant from the current collector are bonded to the current collector by the whiskers having electron conductivity, so that the active material particles are formed as soon as formation starts. Therefore, the efficiency of chemical formation is extremely high,
Within twice the theoretical amount of chemical electricity required, depending on conditions
1.1 times is enough. In addition, the formation time and the amount of electricity
/ 2 to 1/4, and high productivity.
It becomes an inexpensive sealed lead-acid battery.

Conventionally, carbon black has been added to improve the charge acceptability of the negative electrode plate. This has the effect of reducing the hydrogen overvoltage of the negative electrode and increasing the current flowing at the end of charging, thereby increasing the amount of charge. However, this means that a large amount of electricity is overcharged in practical use. This is unfavorable because it causes a decrease in the water in the electrolytic solution due to electrolysis, an increase in the frequency of water replenishment, and an acceleration of positive electrode grid corrosion.

This is due to the fact that electron conduction between the current collector and the active material particles remote from the current collector depends only on the reduced active material particles and carbon black particles present between them. doing. According to the present invention, since the active material particles separated from the current collector also start charging at the same time as the charging starts, the charging efficiency is very high. What is characteristic is that carbon whiskers and graphite whiskers do not lower the hydrogen overvoltage of the negative electrode as shown in Example 2. It overcomes the drawbacks of increasing the frequency of water refilling and accelerating the corrosion of the positive electrode grid, such as those obtained by adding conventional carbon black. The good charge acceptability of the negative electrode is the same as the high resistance to sulfation described above.

Therefore, it is clear that even when the float is used for the sealed lead-acid battery of the present invention, the life thereof will be longer than that of the conventional one. This can be easily understood from the second embodiment.

As described above, the whiskers used in the present invention are for facilitating the flow of electrons to the active material particles remote from the current collector. Therefore, it is preferable that the whiskers have high electron conductivity, long dimensions, and a large number of whiskers.
The electron conductivity of the whiskers is preferably 1 × 10 ⁻³ Ω · cm or more. What is more important is to connect as many active material particles as possible in an electronically conductive manner without significantly reducing the amount of active material. For this purpose, it must be in the form of short fibers having a diameter as small as possible and a long length. Considering the active material particles existing per unit volume described above, those having a diameter of 30 μm or more are:
The number that exists is small for the volume occupied and cannot be used.
A diameter of less than 10 μm, more preferably less than 1 μm,
And the aspect ratio must be 50 or more. Most preferably, the whisker has a diameter of 0.01 to 1.0 μm and an aspect ratio of 100 to 1000.

As the material of the whiskers, graphite obtained by treating the whiskers at a high temperature can be used in addition to the carbon shown in the above embodiment.

When whiskers are used for the positive electrode, not only carbon but also graphite which should be excellent in oxidation resistance treated at high temperature is oxidized or physically excluded from the active material by generated oxygen gas. Nearly half of them are lost during the chemical conversion process. Therefore, when the lead-acid battery according to the present invention is assembled from the formed electrode plates, the amount of whiskers remaining in the positive electrode plate is smaller than the amount initially mixed with the active material. However, the whiskers removed by anodization leave voids therein, making the positive electrode plate more porous and increasing the amount of electrolyte that can be contained. Therefore, it is preferable because the capacity can be increased, particularly the high rate discharge performance can be improved. If the effect of whiskers is expected not only in the chemical conversion step but also thereafter, the ratio to the active material must be initially increased. When only the effect during the chemical conversion step is expected, the number may be small.

The ratio to the unformed positive electrode active material is 0.01 to 10 wt%,
More preferably, it should be 0.01 to 1.0 wt%.

In the case of the negative electrode, the whiskers of carbon or graphite are not lost. The effect is maintained throughout the life of the battery, and the formation is easier than that of the positive electrode. Therefore, the amount of whiskers should be determined by the expected effect and economy, which is an issue within the scope of the design.

The amount of the carbon whiskers and the graphite whiskers based on the negative electrode active material is 0.01 to 10% by weight, more preferably 0.1 to 10% by weight.
1 to 1.0 wt%.

Another important point in achieving the maximum effect of the whiskers is that the whiskers and the active material particles are uniformly and uniformly dispersed in order to come into contact with each other. For this,
As shown in the first embodiment, it is preferable to disperse the material in water with an ultrahigh-speed mixer before using it directly in the lead powder raw material. In order to improve the dispersibility in water, in the case of carbon or graphite whiskers, it is preferable to treat the surface with a surfactant or to provide a hydrophilic group directly on the surface in the gas phase. In this way, uniform dispersion can be obtained without using an ultra-high-speed mixer.

Another problem that must be considered when using whiskers is to make the active material density appropriate. As the positive electrode grid, when using a material obtained from pure lead or calcium alloy containing no antimony or a lead alloy containing no other antimony, the diffusion of the electrolyte becomes too good if the apparent density of the active material is small, Before the active material is completely discharged, the corrosion layer on the lattice surface is discharged, and this becomes lead sulfate which is an insulator. This breaks the electrical coupling between the active material and the lattice, and the capacitance cannot be cut out.

To prevent this, for example, when using a carbon whisker, when using a paste obtained by adding an alkali metal salt of metaphosphoric acid or pyrophosphoric acid such as sodium metaphosphate or sodium pyrophosphate to the paste and kneading the paste,
Even if the ratio of whiskers to the active material is large, an active material having a high density can be obtained, which is advantageous. Such an alkali metal salt of phosphoric acid changes the form of the corrosion layer on the lattice surface, and the corrosion layer does not form a form that insulates between the lattice and the active material, so that discharge can be maintained. It is even more convenient.

The amount of the negative electrode active material greatly affects the high rate discharge capacity.
Even when a nonmetallic whisker is used for the negative electrode, if such an alkali metal salt of pyrophosphoric acid or metaphosphoric acid is kneaded in the paste to increase the density, a lead-acid battery having better high-rate discharge characteristics can be obtained. can get.

The appropriate ratio of these alkali metal pyrophosphates or metaphosphates to the active material will vary with the amounts of sulfuric acid and water that make up the paste. However, appropriate positive electrode paste of conventional pasted type electrode plate density 3.7~4.5g / cm ^3, when trying to obtain a negative electrode paste density 3.5~4.5g / cm ^3, 0.001~5wt the ratio for the active material %Must. In this way, the apparent density of the positive electrode active material which can sufficiently satisfy both the life performance and the high rate discharge performance 3.
^{3 to} 4.0 g / cm ³ and an apparent density of the negative electrode active material of 3.1 to 4.0 g / cm ³ are obtained. If the amount is less than 0.001% by weight, the apparent density of the paste cannot be increased. If the amount is more than 5% by weight, the resulting battery has a too high self-discharge rate, which is not preferable.

When a conventional carbon fiber having a diameter of, for example, 7 to 20 μm is mixed into an active material, there is a problem that the apparent density of the active material is reduced and the life is shortened as described above.
However, this is not the case with the whiskers of the present invention. In fact, when about 1% was added to the positive electrode active material having an apparent density of 4.02 without addition, the apparent density was lowered to 2.6 in the case of carbon fiber, while it was 3.73 in the case of whiskers. It just became.

In addition, in this case, about 2 × 10 ⁶ carbon fibers are present per 1 cm ³ of apparent volume of the active material, and the total surface area is about 80 cm ² , whereas that of the carbon whisker is about 1 cm ^3.
× 10 ¹¹ pieces, about 4900cm ² , an order of magnitude larger. This is preferable, and 1 × 10 ⁹ or more per cm ^{3 of} the active material is preferably present. Therefore, when carbon fibers having a large diameter are used, not only the contact pressure of the active material but also the area and the number of contactable active materials are much smaller than those in the case of whiskers.

Therefore, when using carbon fibers having a diameter of 7 to 20 μm, the active material density must be increased in order to bring the active material particles and the carbon fibers as strongly as possible in order to maximize the effect. I knew I had to.

In order to allow carbon fibers to be present while maintaining a high active material density, it is extremely effective to add the above-mentioned alkali metal salt of metaphosphoric acid and / or alkali metal salt of pyrophosphoric acid. If this is not used, carbon fibers are mixed. The effect cannot be fully demonstrated. When mixing carbon fibers, the apparent density of the active material is 3.0 or more at the negative electrode, preferably 3.1 to 4.
If the value is not 3.3 or more, more preferably 3.3 to 4.0, for the positive electrode, problems such as negative electrode sulfation and discharge of the positive electrode lattice corrosion layer occur, resulting in a short life. However, in order to achieve this while securing the coating property on the lattice, the alkali metal salt of metaphosphoric acid and / or the alkali metal salt of pyrophosphoric acid is added in an amount of 0.1%.
It is necessary that 001 to 5 wt% coexist. It goes without saying that this applies to the case where the diameter of the whisker is as large as about 7 to 10 μm. That is, even in the case of whiskers, if the amount is up to about 1 wt%, a sufficiently high active material density can be obtained without the presence of an alkali metal salt of metaphosphoric acid and / or an alkali metal salt of pyrophosphoric acid. But when you increase that amount more,
Alternatively, in the case of a whisker having a diameter of 5 to 10 μm exceeding 1 μm, it is essential to coexist an alkali metal salt of metaphosphoric acid and / or an alkali metal salt of pyrophosphoric acid. In view of such a contact density, the whisker preferably has a specific surface area of ² m ² / g or more, more preferably 10 to 40 m ² / g.

The present invention is not limited to the type of the electrode plate, except for the tudle-type electrode plate, can be applied to a sealed lead-acid battery using a paste-type positive electrode plate, a negative electrode plate and a clad-type electrode plate,
The effect was recognized.

Effect of the Invention As described above, the sealed lead-acid battery of the present invention can improve the utilization rate of the positive and negative electrode active materials, and has a higher weight efficiency and volume efficiency than the conventional positive and negative electrode active materials. It has improved charge acceptability (charging efficiency), has a long life cycle and float life performance, improves the resistance to sulfation of the negative electrode active material, prevents layering of the electrolyte, and has a longer life. Since the amount of electricity required for the formation of the positive electrode plate can be greatly reduced and the cost can be reduced, the industrial value thereof is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram showing a comparison between the capacity and discharge current of a sealed lead-acid battery according to the present invention and a conventional product, FIG. 2 is a diagram obtained by converting the capacity of FIG. 1 into an active material utilization rate, FIG. 3 is a diagram comparing the relationship between charging current and battery voltage between a sealed lead-acid battery according to the present invention and a conventional product. b: The sealed lead-acid battery according to the present invention i, j ...: Conventional sealed lead-acid battery

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification symbol FI H01M 4/62 H01M 4/62 B (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 10/12 H01M 4 / 14 H01M 2/16

Claims (3)

(57) [Claims] 1. A negative electrode plate, a positive electrode plate, a separator, and an electrolytic solution. (A) The negative electrode plate is a current collector made of pure lead, a Pb—Ca alloy, or another lead alloy containing no antimony. Body and 0.01-10wt%
The sponge-like metal lead electrically connected between particles by a carbon whisker or a graphite whisker having an electron conductivity of 10 μm or less in diameter, an aspect ratio of 50 or more, and a specific surface area of 2 m ² / g or more added at a ratio of (B) The positive electrode plate comprises a current collector made of pure lead or a lead alloy;
A cathode active material mainly containing lead dioxide containing carbon whiskers or graphite whiskers added at a ratio of 01 to 10% by weight; ~ 75wt% and coarse glass fiber 1μm or more in diameter
Wet silica fine powder of 15wt% and particle diameter of 1-10μm 25-45
wt% without using a binder, the air permeability per sheet is greater than 8 seconds / 300cc, and the specific surface area is 20%.
a wet-laid sheet larger than m ² / g;
(D) The sealed lead-acid battery is characterized in that: (d) the electrolytic solution is absorbed and fixed in the pores of the separator and the positive and negative electrode active materials. 2. The ratio of carbon whiskers or graphite whiskers added to the negative electrode active material is 0.1 to 1.0 wt%, and the ratio of carbon whiskers or graphite whiskers added to the positive electrode active material is 0.01 to 1.0 wt%. ,
Particle diameter of the wet silica forming the separator is 2 to 5 μm
2. The sealed lead-acid battery according to claim 1, wherein m is m. 3. A current collector comprising pure lead or a lead alloy;
A positive electrode plate composed of a positive electrode active material mainly composed of lead dioxide having carbon whiskers or graphite whiskers added at a ratio of 10 wt% is formed, and the whiskers are partially removed by anodizing to remove the positive electrode. 3. The method for producing a sealed lead-acid battery according to claim 1, wherein voids are formed in the substance.