JPH034458A - Sealed lead storage battery - Google Patents

Abstract

PURPOSE:To improve the utilization factor of positive and negative electrode materials by electrically connecting particles of positive and negative electrode materials with each other by carbon whiskers or graphite whiskers being added. CONSTITUTION:At least one hand of positive and negative electrode active materials contains carbon whiskers or graphite whiskers. And the wishers are the ones for making it easy for electron to flow to active material particles separated from a collector, and those are made in short fiber shapes with diameters being small and lengths being long as far as possible so as to conductively connect many active material particles to the best of its ability. Hereby, the utilization factor of positive and negative electrode active materials can be improved.

Description

[Detailed description of the invention] Industrial use bone The present invention relates to a sealed lead acid battery.

As is well known in the prior art, the capacity of lead-acid batteries is regulated by the positive and negative active materials and the amount of sulfuric acid in the electrolyte.

In order to improve the active material utilization of a lead-acid battery of constant volume or weight, the amount of active material must be reduced and the amount of sulfuric acid increased, or a higher concentration sulfuric acid electrolyte must be used. However, increasing the utilization rate of the positive electrode active material not only accelerates the 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 severely shortened.

On the other hand, increasing the utilization rate of the negative electrode active material has the disadvantage that the resistance of the active material to phase Vwn decreases, resulting in a shortened lifespan.

By using a highly concentrated sulfuric acid electrolyte, it is possible to improve the volumetric efficiency and weight efficiency of the battery.

However, although this has a small effect on the positive electrode plate, the highly concentrated sulfuric acid electrolyte promotes the phase Vwn of the negative electrode active material, resulting in a short battery life.

The chemical conversion process for activating the unformed active material in the impact plates used in lead-acid batteries requires a large amount of electricity and time. In fact, the excess amount of electricity in this chemical conversion step is particularly necessary for activating the positive electrode active material, and usually 2 to 4 times the amount of electricity that is theoretically required is applied. This is considered to be due to the fact that lead dioxide, which is a positive electrode active material, has low electronic conductivity, and the electronic conductivity between particles of the active material is maintained only by contact between the particles.

That is, during formation of the positive electrode plate, particles in contact with the current collector are oxidized and become lead dioxide. Next, the particles in contact with this lead dioxide are chemically formed, which is repeated to form a chemically formed electrode plate. Therefore, particles that leave the current collector quickly are
It is only at the final stage of the chemical conversion process that the chemical conversion occurs. This means that during the chemical formation process, the density of the chemical current with respect to the active material particles is high at the beginning and low at the final stage, making the efficiency of the chemical current even lower as a whole. There is. To make chemical conversion easier, red lead (Pb
304) may be added to the unformed active material. This is simply because the amount of electricity required is reduced due to its advanced oxidation. Even if this is done, the formation will still start from the vicinity of the current collector, and the efficiency of the formation electricity will still be low as a whole. Red lead is expensive, and the disadvantage of higher price advantage is greater than the advantage of being able to reduce the amount of electricity used for chemical conversion.

US Pat. No. 4,651,241 proposes mixing gutphite into the positive electrode active material and retaining an electrolyte between the layers to increase the pore volume and capacity of the positive electrode. Since gutsphite has electron conductivity, it is possible to form an electron conductive #c connection between active material particles. However, the graphite shown here has a large particle diameter of 340 μm, and is too small in number to connect active material particles. The number of active material particles per unit volume is calculated from the specific surface area, pore size distribution, etc. in the case of a positive electrode, lX
1012~lX10', in case of negative electrode, lX1O'~l
It is estimated that there are X10' pieces. On the other hand, these 3
When 1% of gutufite with a size of 40Ps is added, the number of gutufite particles is only about 500 to 1000, and this number is too large to expect electronic conductive connections between active material particles from gutufite. few.

In order to improve the bond between the active material particles or between the active material particles and the lattice, carbon fiber or electron conductive a is added within the active material.
It is disclosed in JP-A-61-128466, JP-A-54-10574, and JP-A-58-57 that m is allowed to exist.
This is proposed in Publication No. 264. Also, Japanese Patent Publication No. 49-10
No. 3155 proposes the presence of carbon fibers or metal whiskers such as lead. The carbon fiber proposed in the knee is disclosed in Japanese Patent Application Laid-Open No. 54-105741.
As stated in the publication as ``diameter 0.01 to 1, QwJ'', the diameter is 10 to 1000 ptm, and because the diameter is large and the surface area is small, according to the tests conducted by the present inventor, the active material Because the number of contacts with particles was small, it was not possible to maximize the characteristics of carbon and dramatically improve conductivity.

JP-A-49-103135 discloses the presence of "metal whiskers such as lead" in addition to such carbon fibers. However, it is not clear how "metal whiskers such as lead" can be obtained and what characteristics, dimensions, and forms they have, and since no equivalent product is available, the present invention will not be able to utilize its effects. The identity of the person cannot be confirmed.

When the inventor of the present invention mixed lead fibers with a diameter of 30 plN cut into two pieces obtained by the chatter vibration method into the active material, the density of the active material was increased and the contact density was thought to be improved. Despite this, the utilization rate of active materials and charge acceptance were not improved.

In addition, JP-A No. 61-45565 describes ``a conductive synthetic resin made by mixing polyolefin or polyester μ-based synthetic resin with carbon powder or acid-resistant metal powder'' and ``a conductive synthetic resin with a diameter of 1 to 10 mm. It has been shown that "resin fibers" can be mixed into the active material. However, although the conductive synthetic resin fibers obtained in this way are sufficient for reinforcing the active material, the conductivity of the fibers themselves is insufficient to improve the electronic conductivity between the particles, and Mixing fibers of 1 to 10 pm leads to a decrease in the apparent density of the active material, so as described in ``The adhesion between the active material and the lattice body of the Pb-Ca alloy lattice'' Improvement of...
...The function of "preventing the formation of a barrier layer" could not be confirmed.

Also, in order to improve the charge acceptance of the negative electrode, it is widely practiced to include a pump hook. in this case,
The car pump hook mainly lowers the final charging voltage, that is,
By reducing the hydrogen overvoltage of the negative electrode, the current flowing at the end of charging is increased. Carbon black is
The particle size is very small compared to the graph 1a) Ic above. Therefore, adding as much as 0.2 wt% is sufficient to contact individual particles of the active material.

However, in this case, since the car pump hook has no length, its role is merely to exist between the active material particles. That is, it has never been possible to connect the probes or hundreds of active material particles to each other. The improvement in charge acceptance of the negative electrode due to the addition of a car pump hook increases the charging current by lowering the final charging voltage, and it may be that current flows more easily to individual active material particles. do not have. This means that at the end of charging, positive gAl
c also means that a large current flows, which accelerates the corrosion of the positive electrode grid due to an increase in overcharging, so it cannot be said to be a preferable method in terms of life performance. In this way, adding a car pump hook to the negative electrode does not essentially improve charge acceptance.

On the other hand, a sealed lead-acid battery wire has a structure in which a separator and an electrode plate are stacked in a sealed container, and the electrolyte in the battery can flow into the separator and the holes in the positive and negative electrodes. It is kept as if it were not. This sealed lead-acid battery has characteristics such as excellent leakage resistance, no need for water replenishment, and low self-discharge.

By the way, as described in Japanese Patent Publication No. 65-27826, large-capacity sealed lead-acid batteries with high plate heights are repeatedly charged and discharged, even though the liquid is uniform during injection. and Sepa V-! Also, the concentration of the electrolytic solution held within the pores of the electrode plate differs in the vertical direction. That is, a stratification phenomenon occurs in which the concentration of the electrolyte becomes higher in the lower part of the separator. This layering phenomenon tends to occur mainly in the separator area, so in order to prevent this, it is necessary to increase the liquid holding capacity of the seven parators, to ensure that there is no difference in liquid holding capacity between the upper and lower parts of the separator, or to It is necessary to increase the viscosity of the liquid by adding fine silicic acid powder to the liquid.

Conventionally, separators mainly made of glass fiber have been used.

In order to prevent this layering phenomenon from occurring, various improvements have been attempted to improve the liquid retention properties (liquid retention characteristics) of the separators used.

For example, JP-A-62-J33669, JP-A-62-136
No. 751 includes 5i12,'! A separator coated with or mixed with a powder of 'io2 or rare earth element oxide is described. JP-A-63-152853, JP-A No. 62-
No. 221954 and No. 61-269852 describe the use of silica or foamed pearly F as a powder.

Also, JP-A-63-143742, JP-A No. 63-1463
No. 48 describes a separator made of hollow tubular glass fiber.

However, although it is easy to add 1 cVq powder to the electrolyte, it complicates the process and the resulting battery is expensive.On the other hand, mixing silica into the separator requires the following: For these reasons, it has not yet been put into practical use.

In other words, silica powder alone cannot be used to make paper as a separator, and therefore a material mainly composed of glass fibers fC
Silica powder is added and mixed into paper, but if the proportion of silica powder is small, the effect of preventing the layering phenomenon will be low;
If the proportion of y-force powder is high, paper making becomes difficult.

As described above, a separator for a sealed lead-acid battery that has an excellent effect of preventing the layering phenomenon and is easy to manufacture has not been provided in the past.

Therefore, conventional sealed lead-acid batteries suffer from stratification and have a short lifespan.

Purpose of the Invention The present invention solves the above-mentioned conventional problems, and its purpose is to: 1) improve the utilization rate of positive and negative polar active materials, and achieve higher weight efficiency and volumetric efficiency than before; ■ Improved charging acceptability (charging efficiency) of the positive and negative active materials, resulting in long cycle life and float life performance; ■ Improved resistance to surficial VW; ■ Chemical formation of the positive electrode plate. The purpose of the present invention is to provide a sealed lead-acid battery that greatly reduces the amount of electricity required for ■ ■ causing stratification of the electrolyte, has a long life, and ■ is inexpensive.

Structure of the Invention The present invention comprises a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. (b) The negative electrode plate has a current collector made of pure lead, a Pb-Ca based lead alloy, or other antimony-free lead alloy, and a sponge-like metal vessel in close contact with the current collector. (c) The separator is made of glass fiber with a diameter of 1μ#1 or less, and is made of glass fiber with a specific surface area of 1 specific surface area formed from a fine powder mainly composed of silica without using a binder. is 20f
1/9, and is in close contact with both the positive and negative plate surfaces, and 2) The electrolyte is in the micropores of the separator and the positive and negative plate active materials. (e) At least one of the positive and negative active materials contains 0.01 to 10vt%.
, more preferably 0.1 to 1. (This is a sealed lead-acid battery characterized in that the particles are electrically connected by carbon whiskers or graphite whiskers added at a ratio of 1c!).

Example Hereinafter, the details of the present invention will be explained with reference to Examples.

(Example 1) 60 g of carbon whiskers were uniformly dispersed in water 9409 using an ultra-high speed mixer. The carbon whiskers used here were manufactured from hydrocarbons by a vapor phase growth method, and had a diameter of about 0.05 to 0.
．． It is said to have a diameter of about 8 m, a length of about 10 to 100 P, and an aspect ratio of about 100, so it has a long length despite its extremely thin diameter. The density of this material is 1.96ρ/d, and the electronic conductivity is 7×1
o Ω-equipment, and according to the BET method, the specific surface area is 10~
It is 40i/9.

170 g of the carbon whisker dispersion prepared in this way
After adding and kneading lead oxide powder iooog containing about 30% metallic lead, kneading was continued while gradually dropping 75 cc of sulfuric acid having a specific gravity of 1.40 to obtain a paste for a positive electrode.

Corner hiding paste B was prepared w4Il! using the same procedure except that a predetermined amount of lignin and barium sulfate were added to the carbon whisker dispersion. Shita. In addition, paste 0 for positive electrode and paste D for *ti were obtained by the same operation except that carbon whiskers were not used.

Made of Pb-Ca-an alloy that does not contain antimony, the dimensions are W2B x L67 x T3.3 (2,0')
A cast grid made of Ml was filled with the above paste in a conventional manner. (The inside of c is a negative electrode grid.) The electrode plate filled with the paste was left standing at 35° C. and 100% RH for 3 days to age and harden the paste.

Thereafter, it was dried at 50° C. for one day to obtain an unformed positive electrode plate, O, and negative electrode plates B and D.

The physical properties of the paste and the amount of unformed active material after drying were as shown in Table 1.

Table 1 Furthermore, seven types of y-) type separators were obtained by the papermaking method using the fiber compositions shown in Table 2, but no binder was used in the papermaking. The characteristics of these sepano vines are as shown in the same table. Nao, transparent ff1t! J.I.
The specific surface area of SF-91171c was measured by the BET method. These separators, the two positive electrode plates and three negative electrode plates described above were combined to form an unformed battery having the configuration shown in Table 3, and the battery was inserted into a battery case with a specific gravity of 1.30 dHzsOa.
45 sZ of liquid was injected per μ, and a safety valve was attached. After that, chemical formation was carried out in a battery container for about 30 hours at a constant current of 0.8 µm to obtain a sealed lead acid battery, which was subjected to 20HR capacity, various rate capacity tests, cycle life tests, and the amount of lead sulfate at the bottom of the negative electrode plate at 100 cycles µm. , the electrolyte specific gravity above and below the separator was analyzed as shown in Figures 1 and 2 and! 1! The results shown in Table 3 were obtained.

Here, the life test is as follows: discharge [: 0.85 m x 3 H, charge: 1.1 m x 2 H → 0.29 m x 3 H for 1 cycle μ
Table 2 Conventional Examples (Example 2) A negative electrode plate E was prepared in which 0.3% by weight of carbon black was added to the material. The specific surface area of this car pump hook was 1500"7g.

A conventional sealed lead-acid battery j was obtained by combining the negative electrode plate E and the positive electrode plate 0.

Five batteries, a sealed lead acid battery according to the present invention and a conventional sealed lead acid battery 1 and j, were used to produce a battery with a battery life of 0.0001 to 0.0.
The battery was charged at a constant current of 50 μm, and the relationship between charging current and battery voltage was investigated. The results are shown in FIG.

It is clear from Example 1 that the sealed lead-acid battery according to the present invention has a high active material utilization rate and high weight efficiency and volume efficiency. The number of positive electrode active material particles per unit volume is 1X1012 to 1X1016, and the number of particles of the negative electrode is 1X1.
As mentioned above, it is estimated that the number of whiskers is 0' to lX10"'. As shown in Example 1, the number of whiskers when added at about 1% to the ζ active material is lX1010 to lX101
It is estimated that there are 5 pieces. Furthermore, since the whiskers have a large aspect ratio, it is estimated that the number of active material particles that come into contact with one whisker is 50 to 1000. Therefore, it is presumed that, for example, in the negative electrode, a plurality of carpon whiskers are in contact with one active material particle. According to the present invention, distant particle quanta that were conventionally not coupled in an electronically conductive manner are connected in parallel. Therefore, current flows extremely easily not only during charging and discharging but also during the chemical formation process, resulting in high charge acceptance, greater discharge capacity, and extremely high chemical conversion current efficiency. This is clear from Example 1.

The negative electrode active material becomes a coarse crystalline sulfate that is difficult to reduce due to charging and discharging in a highly concentrated electrolyte or at high temperatures.
Its capacity decreases.

On the other hand, not only lead-acid batteries with a large amount of flowing electrolyte, but even sealed lead-acid batteries with a small amount of electrolyte, due to repeated deep discharges, the electrolyte becomes more concentrated in the lower part and lower in the upper part. 5trification
).

The separator used in the sealed lead-acid battery of the present invention has fine silica powder therein, and therefore has high resistance to layering of the electrolyte. Therefore, when charging and discharging the same cycle, the difference in specific gravity between the upper and lower parts is small. This is clear from Table 3. The second point is that the resistance to layering can be substituted by the air permeability, specific surface area, etc. of the separator.
It is clear from Table and Table 3. Therefore, based on these results, it is preferable that the air permeability of the separator is 8 seconds/300 cc or more, and the specific surface area is larger than 20 d7g.

In order to obtain such a separator, it is preferable to form a separator mainly made of glass fibers having a diameter of 1P or less and a fine powder containing silica as a main component without using a binder.

Particularly preferred compositions include 75 to 55 wt% of acid-resistant glass fibers with a diameter of 0.4 to 0.9 μm, 0 to 15 wt% of coarse glass fibers with a diameter of jpg or more, and particle diameters of 1 to 10 μm.
More preferably than plHs, it is a V-t made by wet processing of 25 to 45 vt% of wet silica fine powder of 2 to 5 μm without using a binder. The diameter of the main glass fiber is 1 m or less, especially 0.5 m.
It is preferable that the time is 4 to 0.9 us because the pores of the separator can be made small and the price will not increase unnecessarily. The fine powder containing silica as a main component may be produced either wet or dry, but wet production is more suitable from the viewpoint of yield to the separator, specific surface area, etc., and the particle diameter is preferably 1 to 10 tones. A 2-5P solution is optimal.@When making a separator by wet papermaking, it is better to use y-) without using a binder because the resulting separator has higher flexibility and can adhere tightly to the electrode plate surface. This is preferable because there is no possibility of elution of substances harmful to the battery.

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

The layering caused by the fact that the lower part of the negative electrode plate is usually far from the ears, the high concentration sulfuric acid electrolyte has high resistance, and the solubility of lead sulfate is low is due to the fact that the lower part of the negative electrode active material is 7A V, Invite N. However, according to the present invention, IcrM has high resistance to layering of the separator.
Because the resistance inside the plate is low, sufficient current flows even in the lower part of the negative electrode plate, even though it is far from the ear, and the lower μ phase Vw
The problem of shortened battery life due to :/ can be solved.

This is shown in Table 3.

The conventional sealed lead-acid battery 1 has a lower sy-phase F of the negative electrode plate.
In contrast, the sealed lead-acid battery according to the present invention exhibited extremely excellent life performance.

Since the unformed active material does not have electronic conductivity, when it is chemically formed, the chemical formation proceeds in order from the particles that are in contact with the grid or the core metal that is the current collector. Therefore, the distant active material particles that are not in contact with the current collector are not chemically converted until they are supplied with electrons via the particles present between the active material particles and the current collector. For this reason, conventionally, the positive electrode plate in particular had to be formed over a long period of time and with a large amount of electricity, two to four times the theoretically required amount of electricity. However, according to the present invention, even particles that are far from the current collector are bonded to the current collector by electronically conductive whiskers, so that the active material particles are chemically formed as soon as chemical formation begins. Therefore, the efficiency of chemical conversion is extremely high,
The amount of electricity required for chemical formation may be within twice the theoretically required amount, and depending on the conditions, even 1.1 times may be sufficient.

In addition, it is possible to reduce the formation time and electricity to h-% of the conventional value, resulting in a sealed lead-acid battery with high productivity and extremely low cost.

Conventionally, carbon black has been added to improve the charge acceptance of the negative electrode plate. This has the effect of increasing the charging capacity by lowering the hydrogen overvoltage of the negative electrode and increasing the current flowing at the end of charging. However, in practical use, this means that the amount of electricity that is overcharged is large. This is not at all preferable because it causes a decrease in water in the electrolytic solution due to electrolysis, an increase in the frequency of water replenishment, and acceleration of corrosion of the positive electrode grid.

This is because the electron conduction between the current collector and the active material particles that are far from the current collector depends only on the reduced active material particles and carbon black particles that exist between them. are doing.

According to the present invention, since the active material particles removed from the current collector also begin to be charged at the same time as charging starts, charging efficiency is very high.

Moreover, the characteristic feature 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 conventional car pump hooks, such as increased water replenishment frequency and accelerated corrosion of the construction grid. The fact that the negative electrode has good charge acceptance is the same as having high resistance to the above-mentioned μ phase Vwn.

Therefore, it is clear that the sealed lead-acid battery of the present invention will have a longer life than the conventional one even when used as a float. This can be easily understood from Example 2.

As described above, the whiskers used in the present invention are used to facilitate the flow of electrons to active material particles that are distant from the current collector. Therefore, it is preferable that the whiskers themselves have high electronic conductivity, are long in size, and have a large number of whiskers. The electron conductivity of the whisker is preferably l×10'Ω, 1 or more. ◎What is more important is that as many active material particles as possible are used in an electron conductive manner in an amount that does not drastically reduce the amount of active material. is to connect to. For this purpose, it must be in the form of short fibers with the smallest possible diameter and long length. Considering the above-mentioned active material particles present per unit volume, those having a diameter of 30 μm or more cannot be used because their number is small in relation to the volume they occupy. The diameter should be less than 10 pm, more preferably less than 1 pm, and the aspect ratio should be 50 or more. Most preferably, the diameter is 0.01-1.
The whiskers have an aspect ratio of 100 to 1000 at 0 pm.

As the material for the whiskers, in addition to the carbon shown in the above embodiments, gutphite, which is prepared by treating carbon at high temperatures, can also be used.

When whiskers are used as a positive electrode, not only carbon but also gutphite, which is supposed to have excellent oxidation resistance after being treated at high temperatures, is oxidized or physically removed from the active material by the generated oxygen gas. During the chemical conversion process, nearly all of that work is lost. Therefore, when a lead-acid battery according to the present invention is assembled with a chemically formed electrode plate, the amount of whiskers remaining in the positive electrode plate is less than the amount originally mixed with the active material. However, the voids after the whiskers are removed become effective pores that can retain the electrolyte, increasing the capacity of sealed lead-acid batteries.
It is particularly effective in improving high rate discharge performance. If the effect of whiskers is to be expected not only during the chemical conversion process but also afterward, the ratio of whiskers to the active material must be initially increased. If only the effect during the chemical conversion process is expected, the amount may be less.

The ratio to the unformed positive electrode active material is 0.01 to 10v.
t%, more preferably 0.1-1. In the case of a negative electrode, carbon, gutphite, and whiskers are not lost. Its effect is maintained throughout the life of the battery, and it is easier to chemically form than the positive electrode. Therefore, the amount of whiskers should be determined based on the desired effect and economy, and this is a matter within the scope of design.

The amount of carbon whiskers and graphite whiskers relative to the negative electrode active material is 0.01 to 10 wt%, more preferably 0.1 to 1. Ovt≦.

Another important point to maximize the effect of the whiskers is to bring the whiskers into contact with the active material particles.
- to ensure uniform dispersion. For this reason, as shown in Example 11C, instead of directly adding it to the lead powder raw material,
It is best to use it by dispersing it in water using an ultra-high-speed mixer.

In order to improve the dispersibility in water, in the case of carbon or guttophite rice, it is preferable to treat it with a surfactant or to attach a hydrophilic group directly to its surface in the gas phase.

In this way, uniform dispersion can be obtained without using an ultra-high speed mixer.

Another issue that must be considered when using whiskers is getting the active material density right. When using pure lead that does not contain antimony, IWV five-alloy alloy, or other lead alloy that does not contain antimony as the positive electrode grid, the electrolyte will diffuse better if the apparent density of the active material is small. If this occurs too much, the corroded layer on the lattice surface will discharge before the active material is completely discharged, and this will turn into lead sulfate, an insulator. This breaks the electrical connection between the active material and the lattice, making it impossible to extract the capacitance.

In order to prevent this, for example, when using carbon whiskers, if you use a paste prepared by adding ci to an alkali metal salt of metaphosphoric acid or birophosphoric acid such as sodium metaphosphate or Fium pyrophosphate and kneading, it is possible to prevent whiskers from forming on the active material. This is advantageous because a high density active material can be obtained even if the ratio is high. Such an alkali metal salt of phosphoric acid changes the form of the corroded layer on the surface of the lattice, and the corroded layer does not form a form that insulates the lattice and the active material, so that the discharge can be maintained. Therefore, it is even more convenient.

The amount of negative electrode active material greatly influences high rate discharge capacity. Even when non-metallic whiskers are used for negative FM, if an alkali metal salt of birophosphoric acid or metaphosphoric acid is kneaded into the paste to increase its density, a lead-acid battery with better high rate discharge characteristics can be obtained. is obtained.

The appropriate ratio of the alkali metal salt of pyrophosphoric acid or metaphosphoric acid to the active material is 1liSIi.
! It varies depending on the amount of sulfuric acid and water used. However, the appropriate positive electrode base F density of a normal paste type electrode plate is 3.7 to 4.
．． 59/d, when trying to obtain a negative electrode paste density of 3.5 to 4.5 Lee, the ratio is 0.00 to the active material.
It must be between 1 and 5 wt%. In this way, both life performance and high rate discharge performance can be fully satisfied.The apparent density of the positive electrode active material is 3.3 to 4.0C, and the apparent density of the negative electrode active material is 3.1 to 4.0. '/, 4 is obtained.

This is because if it is less than 0.001 vt%, the apparent density of the paste cannot be increased, and if it is more than 5 vt%, the self-discharge rate of the resulting battery becomes too high, which is not preferable.

When conventional carbon fibers having a diameter of, for example, 7 to 20 pm are mixed into an active material, there is a problem in that the apparent density of the active material decreases and the life span is shortened, as described above.

However, if the whiskers of the present invention are used, this will not happen. In fact, the apparent density without additives is 4.0
When approximately 1% of carbon fiber was added to the upper cylinder active material, which is 2, the apparent density decreased to 2.6 in the case of carbon fiber, but it only became 3.73 in the case of whiskers. do not have.

Moreover, in this case, the number of carbons m # present per 1 d of lost volume of the active material is approximately 2×10', and the m# surface area is 80 c
On the other hand, in the case of carbon whiskers, it is about 1 x 10" whiskers, which is about 4900 -, which is an order of magnitude larger. This is preferable, and it is better to have more than 1 x 10" whiskers present per 1 d of active material. When carbon fibers with a large diameter are used, not only the contact pressure of the active material but also the contactable area and number of fibers are extremely small compared to the case of whiskers.

Therefore, when using carbon fibers with a diameter of 7 to 20 μm, in order to maximize the effect, in order to bring the carbon fibers into strong contact with as many active material particles as possible,
It was found that the active material density must be increased.

In order to make carbon fiber exist while maintaining a high active material density, the above-mentioned alkali metal salt of metaphosphoric acid and/or
Alternatively, the addition of an alkali metal salt of pyrophosphoric acid is extremely effective; without this addition, the effect of incorporating carbon fibers cannot be fully exerted. When carbon fiber is mixed, the apparent density of the active material at the negative electrode is 3.0 or more, preferably 3.0 or more.
1 to 4.0, 3.3 or more at the positive electrode, more preferably 3.3
If the value is not set to 4.0, problems such as negative electrode phase V1 and discharge of the positive electrode lattice corrosion layer will occur, resulting in a shortened lifespan. However, in order to achieve this while ensuring adhesion to the grid, it is necessary to coexist the alkali metal salt of metaphosphoric acid and/or the alkali metal salt of birophosphoric acid in an amount of 0.001 to 5 vt%. This means that the whisker diameter is 7 to 1
Needless to say, this also applies when the temperature reaches Odate at around 0 Pm. In other words, even in the case of whiskers, if the amount is up to about 1vt%, the active material is sufficiently high even without the presence of the alkali metal salt of metaphosphoric acid and/or the alkali metal salt of pyrophosphoric acid. Density is obtained. but,
When the amount is increased further, or in the case of whiskers with a diameter of 5-10 pM greater than 1 μm, 1
It is essential that an alkali gold TI4 salt of metaphosphoric acid and/or an alkali metal salt of birophosphoric acid coexist.

In view of such contact density, it is preferable that the whiskers have a specific surface area of 2 or more, more preferably 10 to 40'/9. The present invention limits the type of the electrode plate. Instead, it can be applied to sealed lead-acid batteries using paste-type positive electrode plates, *W plates, and Kufufud-type electrode plates, excluding Cheet μ-type plates, and the effect was recognized.

Effects 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 active materials, and has higher weight efficiency and volumetric efficiency than conventional active materials. It has improved charge acceptance (charging efficiency), has long life cycle and float life performance, improves the resistance of the negative electrode active material to heat flux, and can also prevent stratification of the electrolyte. Furthermore, the amount of electricity required for forming the binding board with a long life is greatly reduced, and it can be made inexpensive, so its industrial value is extremely low.

[Brief explanation of drawings]

Figure 1 is a diagram comparing the relationship between capacity and discharge current between the sealed lead-acid battery according to the present invention and a conventional product, and Figure 2 is a diagram in which the capacity in Figure 1 is converted into 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...Sealed lead acid battery 1 according to the present invention, j...Conventional sealed lead acid battery

Claims (1)

[Scope of Claims] 1) A positive electrode plate, a negative electrode plate, a separator, and an electrolytic solution, (a) the positive electrode plate includes a current collector made of pure lead or a lead alloy, and a current collector in close contact with the current collector; (b) the negative electrode plate comprises a current collector made of pure lead, a Pb-Ca-based lead alloy, or other antimony-free lead alloy; (c) The separator is mainly composed of glass fibers with a diameter of 1 μm or less, and the glass fibers and fine powder mainly composed of silica. A wet-formed sheet having a specific surface area larger than 20 m^2/g, formed without using a binder, and in close contact with the surfaces of the positive and negative electrode plates, (d) the electrolyte is contained in the separator and (e) at least one of the positive and negative active materials contains carbon whiskers or graphite whiskers;
A sealed lead acid battery, wherein particles of the active material are electrically connected by the carbon whisker or the graphite whisker. 2) The sealed lead-acid battery according to claim 1, wherein the carbon whisker or graphite whisker is present in an amount of 0.01 to 10 wt% based on the active material. 3) The sealed lead-acid battery according to claim 1, wherein the carbon whisker or graphite whisker is present in an amount of 0.1 to 1.0 wt% based on the active material.