JPH06140043A - Lead-acid battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve a utilization factor of a negative electrode active material, obtain a long service life lead-acid battery having high weight efficiency and volume efficiency, improve charge receivable performance of the negative electrode active material, and also improve resistance to sulfation. CONSTITUTION:Electron conductive carbon whiskers or graphite whiskers having a diameter of 0.05-1.0mum and an aspect ratio less than 50 are added to a negative electrode active material. Carbon black is added to the negative electrode active material together with the electron conductive carbon whiskers or graphite whiskers. The carbon whiskers or the graphite whiskers are formed in a slurry shape by water, and it is added to the negative electrode active material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead storage battery.

[0002]

2. Description of the Related Art As is well known, the capacity of a lead storage battery is regulated by the positive and negative electrode active materials and the amount of sulfuric acid in the 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, it is necessary to decrease the amount of the active material and increase the amount of sulfuric acid, or to use a sulfuric acid electrolytic solution having a higher concentration. However, increasing the utilization rate of the positive electrode active material accelerates not only the softening and dropping of the active material but also the lattice corrosion. Therefore, there is a drawback that the cycle and float life performance of the battery is significantly shortened. On the other hand, when the utilization rate of the negative electrode active material is increased, the resistance of the active material to sulfation becomes low and the life thereof becomes short.

In order to prevent the active material from softening and falling off, it has been proposed in JP-A-54-105741 to allow carbon fibers to be present in the active material. Also,
JP-A-49-103135 proposes the presence of carbon fibers or metal whiskers such as lead. The carbon fiber proposed here is disclosed in Japanese Unexamined Patent Publication No.
No. 4-105741 "diameter 0.01-1.0 mm"
As described above, because of the large diameter and small surface area, according to the tests by the present inventors, the number of connections with the active material particles is small, the characteristics of carbon are maximized, and the conductivity is improved. I couldn't improve dramatically. JP-A-49-103135 discloses the presence of "metal whiskers such as lead" in addition to such carbon fibers. However, it is unclear how "a metal whisker such as lead" can be obtained, and what kind of characteristics, dimensions and morphology it has, and its effect has not been confirmed. When the present inventors mixed the lead material with a diameter of 30 μm cut into 2 mm obtained by the chattering vibration method into the active material, the density of the active material was increased and the contact density was improved. Therefore, the utilization rate of the active material and the charge acceptability were not improved.

In Japanese Patent Laid-Open No. 61-45565, "a polyolefin-based or polyester-based synthetic resin is mixed with carbon powder or acid-resistant metal powder".
It is shown that "the conductive synthetic resin fiber having a diameter of 1 to 10 µm" is mixed into the active material. However, although the conductive synthetic resin fiber thus obtained is sufficient to reinforce the active material, the conductivity of the fiber itself is insufficient to improve the electron conductivity between the particles, and The inclusion of fibers of 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 alloy lattice and the lattice body is improved. The function of "... prevention of barrier layer formation" could not be confirmed.

Japanese Unexamined Patent Publication No. 2-33853 and Japanese Unexamined Patent Publication No. 2-
No. 44647, No. 2-44658, No. 2-46653, No. 2-51862, No. 2-54871, No. 2-1772.
According to JP-A-60 and JP-A-3-15162, by adding a carbon whisker having an aspect ratio of 50 or more or a graphite whisker, it is possible to use an active material as well as an active material not only between active materials by taking advantage of a very thin and long feature. The current collector can also be electrically coupled.
Therefore, it is stated that it is possible to improve the utilization rate of positive and negative active materials, improve charge acceptance, extend life, improve sulfation resistance, and reduce the amount of formed electricity.

[0006]

An important point for maximizing the effect of carbon whiskers or graphite whiskers (hereinafter simply referred to as whiskers) described in the prior art is that whiskers and active material particles are combined. The purpose is to evenly disperse the whiskers in the active material for contact. However, the inventors of the present invention used an ultra-high speed mixer to uniformly disperse whiskers having an aspect ratio of 50 or more during paste kneading, but the whiskers became pill-like and could not be uniformly dispersed. Further, it is said that it is preferable to use whiskers by dispersing them in water with an ultra-high speed mixer in advance, or to treat the whiskers with a surfactant, or to directly attach a hydrophilic group to the surface in the gas phase. However, even if these methods were used, the whiskers became pill-like and could not be uniformly dispersed. In addition to that, the bulk density is so small that it can be transported.
Workability such as storage, weighing, and addition was poor, and it was necessary to take measures that did not adversely affect the respiratory system of the human body.

In order to improve the charge acceptance of the negative electrode,
It is widely practiced to include carbon black in the active material, but in this case, carbon black mainly decreases the end-of-charge voltage, that is, reduces the hydrogen overvoltage of the negative electrode, thereby increasing the current flowing at the end of charge. ing. Carbon black has a very small particle size as compared with the above-mentioned whiskers. Therefore, if 0.2 wt% is also added, the number is sufficient to connect with individual particles of the active material. However, in this case, the carbon black does not have a length for connecting the active material particles and therefore has only a role of existing. That is, dozens or hundreds of active material particles are not connected in parallel with each other.

[0008] The addition of carbon black improves the charge acceptability of the negative electrode by increasing the charging current by lowering the end-of-charge voltage, and does not facilitate the flow of current through the individual active material particles. . This means that a large current also flows through the positive electrode at the end of charging, and the corrosion of the positive electrode grid is accelerated by an increase in the amount of overcharge electricity, which is not a preferable method in terms of life performance. Thus, the addition of carbon black to the negative electrode has not been a substantial improvement in charge acceptability.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide (1) a lead storage battery having a high weight efficiency and a high volume efficiency by improving the utilization rate of the negative electrode active material. (2) The charge acceptability of the negative electrode active material is improved, the resistance to sulfation is improved, and a long-life lead-acid battery is provided. (3) Whiskers can be uniformly dispersed in the active material to improve workability. An object of the present invention is to provide an excellent lead storage battery manufacturing method, and (4) to provide a lead storage battery manufacturing method that does not adversely affect the human body when the whiskers are added to the active material.

[0010]

In order to achieve the above object, the first invention of the present invention has a diameter of 0.05 to 1.0 μm.
It is characterized in that a carbon whisker or a graphite whisker having a ratio of diameter to length of m, that is, an aspect ratio of less than 50 is added to the negative electrode active material. The second invention is characterized in that carbon black or graphite whiskers are added to the negative electrode active material, and carbon black is also added to the negative electrode active material. Furthermore, the third invention is to add carbon whiskers or graphite whiskers in a slurry form with water to the negative electrode active material.

[0011]

[Working] The diameter of the whiskers added to the active material is 0.05
By setting the aspect ratio to be less than 50 μm and having an aspect ratio of less than 50 μm, whiskers can be completely dispersed in the paste even if a conventional kneading method is used. As a result, the same characteristics can be obtained with a smaller addition amount of whiskers as compared with those having an aspect ratio of 50 or more. The present inventor found that when a battery in which whiskers having an aspect ratio of 50 or more was added to the negative electrode active material was disassembled at the end of its life, there were almost no whiskers having an aspect ratio of 50 or more. This is because long fibers are cut and the aspect ratio becomes less than 50 due to the rotating force of the kneader or the frictional force between lead powders, or the active material expands and contracts during charging and discharging of the battery.
It is thought that the whiskers were cut and shortened.

Further, making the fibers of the whiskers lengthen the time required for manufacturing the whiskers.
As the occupation time of the reactor increases, the amount of electricity used to maintain the high temperature also increases significantly. Therefore, the use of short fibers leads to the use of industrially inexpensive whiskers because the reaction time is short and the electricity usage is low. Therefore, if the same characteristics can be obtained as a battery, it is effective to attach an inexpensive whisker having an aspect ratio of less than 50. Further, when carbon black is added to the negative electrode active material to improve charge acceptance, whiskers are added to connect the active material particles by the whiskers, so that the charging current easily flows and the life is improved.

When the whiskers are slurried with water, the steps of transportation, storage, weighing and addition are dramatically simplified. In terms of safety, whiskers do not scatter in the event of an accident during truck transportation, and there is no danger of dust explosion. The high bulk density allows a large amount of whiskers to be transported at one time and saves a small space. Moreover, since it does not scatter, it does not enter the respiratory system of the human body, so it is safe. Furthermore, the whiskers can be evenly dispersed in the paste without creating pills.

[0014]

EXAMPLES The details of the present invention will be described below with reference to examples.

(Example 1) To 940 g of water, 50 g of carbon whiskers, a predetermined amount of lignin and barium sulfate were added and dispersed by a kneader, and 1000 g of lead oxide powder containing about 30% of metallic lead was added. After kneading, 75 cc of sulfuric acid having a specific gravity of 1.40 was gradually added dropwise to continue kneading to obtain a paste A for negative electrode. The carbon whiskers used here are manufactured by vapor phase growth method using hydrocarbon as a raw material. As shown in the electron micrograph of FIG. 1, the diameter is about 0.05 to 1 μm and the aspect ratio is in the range of 5 to 40. A negative electrode paste B was obtained in the same manner as in the above formulation, except that 60 g of carbon whiskers having an aspect ratio of 50 or more were dispersed in 90 g of water by an ultra-high speed mixer. Next, a conventionally used negative electrode paste C containing no carbon and a conventional positive electrode paste D were obtained. Pb-Ca-S containing no antimony
The size of the cast lattice made of n alloy is W38 × L67 × T
The above paste was filled into 3.3 (2.0 in negative electrode grid) mm by a conventional method. The electrode plate filled with paste is 35
The paste was left to stand for 3 days in a temperature of 100 ° C and a humidity of 100% to age and cure the paste. Then, it dried at 50 degreeC for 1 day, and the unformed negative electrode plate A, B, C and the positive electrode plate D were obtained. The physical properties of the paste and the amount of non-activated material after drying were as shown in Table 1.

[0016]

(Example 2) Two positive electrode plates D and three negative electrode plates A obtained in Example 1 were superposed with a fine glass separator according to Japanese Patent No. 1272702 interposed therebetween to form a pole group and housed in a battery case. The sealed lead-acid battery X according to the present invention was manufactured by the same method using the electrode plates D and B, and the conventional sealed lead-acid battery Y was manufactured using the electrode plates D and C, respectively. . H ₂ SO ₄ was added to this at 45 cc per cell
Injected liquid and attached a safety valve. Then with current of 0.8A 3
The batteries X, Y, and Z thus formed were subjected to a capacity test at various discharge currents (0.05 to 3 C). The result of calculating the utilization rate of the negative electrode active material from the obtained capacity is shown in FIG. In addition, the conventional battery Z 20H
Table 2 shows weight efficiency and volume efficiency based on the R capacity.

[0018]

The results of the alternating charge and discharge life test of these batteries are shown in FIG. The test conditions are as follows. Discharge: 0.25CA × 2H, Charge: 0.1CA × 6H,
3 cycles / day, temperature 25 ℃, 0.2 every 50 cycles
A capacity test of 5 C discharge and discharge end voltage of 1.70 V / cell was carried out.

(Example 3) Carbon whiskers having an aspect ratio of 50 or more and in the range of 5 to 40 were added to lead powder in an amount of 0.7 to 1.5 wt% to form unformed electrode plates B and A (W6).
7 × L38 × T3.35) was prepared. In order to investigate the resistivity of the unformed active material, the unformed electrode plate was impregnated with resin in vacuum, the vertical bones of the grid were removed, and the grid was cut to a width of 10 mm so that the horizontal bones of the grid were evenly spaced on the active material. I cut out what exists. Electric current was applied to both ends of this test piece to measure the voltage between the transverse bones present at equal intervals to determine the active material resistance including the contact resistance between the lattice and the active material. The results are shown in Fig. 4.

It is clear from Example 1 that the lead storage battery according to the present invention has a high utilization rate of the active material and a high weight efficiency and volume efficiency. Further, it is clear from the disassembly result of the battery that even when carbon whiskers and graphite whiskers having an aspect ratio of 50 or more are added, short fibers having an aspect ratio of less than 50 are formed at the end of charge / discharge of the battery. It was also found that whiskers in the active material were found to be pilled. However, the aspect ratio is 50
It was found that the whiskers of less than 1 were dispersed uniformly without any pills. From the results of Example 3, looking at the resistance of the non-activated material with the carbon whiskers having an aspect ratio of 50 or more and less than 50, those of 50 or more in which pills are present show larger values than those of less than 50 even with the same addition amount. As described above, by using the one having the aspect ratio of less than 50, the addition amount can be reduced, the whiskers can be easily manufactured, and in addition to being inexpensive, the paste obtained by adding the whiskers to the lead powder can be used. It was also found that filling the current collector was easy. From these characteristics, it is obvious that the use of whiskers having an aspect ratio of less than 50 is advantageous in many fields.

The low specific resistance of the non-activated material means that the specific resistance of the active material is small even at the end of discharge when a large amount of insulating PbSO ₄ is present in the active material. Therefore,
Since the negative electrode lower sulfation that occurs when the battery is cycled can be prevented, the battery life can be extended. The fact that this reasoning is verified is clear from the cause of the life of the battery performed in Example 2. That is, the whisker added was due to corrosion of the positive electrode current collector, whereas that of the conventional product was due to negative electrode lower sulfation.

Example 4 An unformed electrode plate A in which 0.5 wt% of carbon whiskers was added to the positive and negative electrode active materials, and an unformed electrode plate B in which 0.5 wt% of graphite whiskers was added to the positive and negative electrode active materials, Unformed electrode plate C in which carbon whiskers were added to the positive electrode active material in an amount of 0.5 wt% and carbon whiskers and carbon black were each added in an amount of 0.5 wt% in the negative electrode active material, and an unformed electrode in which carbon black was added to the positive and negative electrode active materials The plate D was manufactured, and the embossed separator was used to manufacture the pole groups A ′, B ′, C ′, and D ′ each including two anode plates and three cathode plates. After forming these electrode groups up to 125% of the theoretical amount of electricity of the positive electrode active material, a capacity test of 1.0 A discharge was conducted. Then, after two cycles of charging and discharging, the charging and charging characteristics of the automobile battery according to the JIS standard were investigated. The results are shown in Table 3.

[0024]

From Table 3, the pole group C'added with carbon whiskers and carbon black is superior in charge acceptability to the pole group A'added only with carbon whiskers. Furthermore, the initial capacity of the pole group C ′ is significantly superior to that of the pole group D ′ containing only carbon black. Therefore, when carbon whiskers are added and carbon black is further added, a lead storage battery excellent in both initial capacity and charge acceptability can be obtained.

(Example 5) Instead of the negative electrode paste A produced in Example 1, 50 g of carbon whiskers and 10 times by weight of water were added, and whiskers slurried in a pressure-applied kneader and 440 g of To an aqueous solution in which water, lignin and barium sulfate were added and dispersed by a kneader, 1000 g of lead oxide powder containing about 30% of metallic lead was added and kneaded, and then 75 cc of sulfuric acid having a specific gravity of 1.40 was gradually dropped and kneaded. Subsequently, a negative electrode paste E was produced. Further, using this paste E, an unformed electrode plate E ′ was obtained in the same manner as in Example 1. The apparent density of the paste E at this time was 3.76 g / cm ³ , and the filling amount in the electrode plate E ′ was 1
6.6 g / sheet, the amount of unformed substance after drying paste E is 1
The amount was 2.1 g / sheet, which was almost the same as in the case of paste A. Next, in the same manner as in Example 2, the unformed polar plate E
The battery W of the present invention using the above-mentioned battery was manufactured, the capacity, weight efficiency and volume efficiency were investigated, and the battery X of the present invention using the powdery whiskers was prepared.
Compared with. The results are shown in Table 4.

[0027]

From these results, it can be seen that whiskers are uniformly dispersed in the active material without deteriorating the battery characteristics even when the carbon whiskers are made into a slurry with water.
It was also found that if the whiskers were made into a slurry, the operations such as transportation, storage, weighing and addition of the whiskers could be facilitated.

[0029]

Since the present invention is configured as described above, it has the following effects. (1) According to claim 1, since the whiskers do not form a pill shape, they can be uniformly dispersed in the active material, the utilization rate of the negative electrode active material is improved, and a lead storage battery having high weight efficiency and volume efficiency can be obtained. In addition, sulfation at the bottom of the negative electrode plate can be prevented, and a long-life lead acid battery can be provided. (2) According to claim 2, it is possible to provide a lead storage battery having improved charge acceptance and a long life. (3) According to claim 3, the whiskers can be handled easily, and the manufacturing cost can be reduced. Also, the working environment can be improved without the dust of the whiskers scattering.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing powdery carbon whiskers added to an active material.

FIG. 2 is a graph comparing active material utilization rates of a negative electrode plate A according to the present invention and conventional negative electrode plates B and C.

FIG. 3 is a graph comparing the life performance of the battery X of the present invention and the conventional batteries Y and Z.

FIG. 4 is a graph comparing the specific resistances of the negative electrodes A and B used in the battery X of the present invention and the conventional batteries Y and Z.

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[Procedure amendment]

[Submission date] November 9, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005] JP-A 2-3385 9 JP, Hei 2-
No. 44647, No. 2-44658, No. 2-46653, No. 2-51862, No. 2-54871, No. 2-1772.
According to JP-A-60 and JP-A-3-15162, by adding carbon whiskers or graphite whiskers having an aspect ratio of 50 or more,
By taking advantage of its extremely thin and long characteristics, it is possible to electrically couple not only between active materials but also between active materials and current collectors. The <br/> Therefore, improved utilization of the positive and negative polarities active material, improvement in the charge acceptance is described with long service life, improved resistance to sulfation resistance, it is possible to reduce the conversion electric quantity .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Further, making the fibers of the whiskers lengthen the time required for manufacturing the whiskers.
As the occupation time of the reactor increases, the amount of electricity used to maintain the high temperature also increases significantly. Therefore, the use of short fibers leads to the use of industrially inexpensive whiskers because the reaction time is short and the electricity usage is low. Thus as long as the resulting the same characteristics as the battery, the whiskers less than inexpensive aspect ratio 50 added pressure to <br/> Rukoto is effective. Further, when carbon black is added to the negative electrode active material to improve charge acceptance, whiskers are added to connect the active material particles by the whiskers, so that the charging current easily flows and the life is improved.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

When the whiskers are slurried with water, the steps of transportation, storage, weighing and addition are dramatically simplified. In terms of safety, whiskers do not scatter in the event of an accident during truck transportation, and there is no danger of dust explosion. On capable of transporting a large amount of whiskers at a time by the bulk density increases, location also requires only a small space. Moreover, since it does not scatter, it does not enter the respiratory system of the human body, so it is safe.
Furthermore, the whiskers can be evenly dispersed in the paste without creating pills.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

[0016]

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

(Example 5) Instead of the negative electrode paste A produced in Example 1, 50 g of carbon whiskers and 10 times by weight of water were added, and whiskers slurried in a pressure-applied kneader and 440 g of To an aqueous solution in which water, lignin and barium sulfate were added and dispersed by a kneader, 1000 g of lead oxide powder containing about 30% of metallic lead was added and kneaded, and then 75 cc of sulfuric acid having a specific gravity of 1.40 was gradually dropped and kneaded. Subsequently, a negative electrode paste E was produced. Further, using this paste E, an unformed electrode plate E ′ was obtained in the same manner as in Example 1. The apparent density of the paste E at this time was 3.76 g / cm ³ , and the filling amount in the electrode plate E ′ was 1
4 . 6 g / sheet, the amount of unformed substance after drying paste E is 1
The amount was 2.1 g / sheet, which was almost the same as in the case of paste A. Next, in the same manner as in Example 2, the unformed polar plate E
The battery W of the present invention using the above-mentioned battery was manufactured, the capacity, weight efficiency and volume efficiency were investigated, and the battery X of the present invention using the powdery whiskers was prepared.
Compared with. The results are shown in Table 4.

Claims (3)

[Claims] 1. A lead storage battery, wherein a carbon whisker or a graphite whisker having a diameter of 0.05 to 1.0 μm and an aspect ratio of less than 50 and having electron conductivity is added to a negative electrode active material. 2. A lead-acid battery, wherein carbon whiskers or graphite whiskers having electronic conductivity and carbon black are added to a negative electrode active material. 3. A carbon whisker or graphite whisker having electronic conductivity in the form of a water slurry,
A method of manufacturing a lead storage battery, which comprises adding to a negative electrode active material.