JPH0254871A - Lead battery - Google Patents

Abstract

PURPOSE:To make it have high weight efficiency and volume efficiency, and to enable use of sulfuric acid electrolyte in high concentration, and to sharply improve utilization factor without sacrificing the life by elevating the utilization factor of positive and negative both poles active material and improving charge receiving property and improving resistance to sulfation. CONSTITUTION:With whiskers, which were selected from carbon graphite or titanic acid potassium whose diameter is 10mum or less, whose aspect ratio is 50 or more, and whose specific surface area is 2m/g or more in contact with negative electrode active material particles consisting of sponge-shaped metallic lead, and other additive at need, negative electrode active material constitutes a paste type negative electrode. This paste type negative electrode and a paste type positive electrode, that positive electrode active substance constitutes with positive electrode active particles having lead dioxide for its main ingredient and fiber substance being selected from carbon graphite or titanic acid potassium in contact with those particles and having conductivity, constitute a lead battery, and the electrolyte specific gravity of that lead battery is made higher than 1.350d.

Description

[Detailed description of the invention] Industrial applications The present invention relates to lead acid batteries.

Prior Art and its Problems As is well known, the capacity of lead-acid batteries is regulated by the amount of sulfuric acid in the positive and negative active materials and 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 significantly shortened.

On the other hand, if the utilization rate of the negative electrode active material is increased, the active material monkey 7
It has low resistance to Acine.

However, it has the disadvantage that its lifespan is shortened.

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 deterioration of the negative electrode active material, so it still has the disadvantage of resulting in a short-life battery. .

The electrode plates used in lead-acid batteries can be broadly classified into paste type and clad type. No matter which electrode plate is used, a large amount of electricity and time are required in the chemical conversion process for activating the unformed active material. In fact, an excessive amount of electricity in this chemical conversion step is necessary, especially in order to activate the positive electrode active material, and usually 2 to 4 times the theoretically necessary amount of electricity is applied.

This is due to the low electronic conductivity of lead dioxide, the positive electrode active material.
Further, it is thought that this is due to the fact that the electronic conductivity between the active material particles is maintained only by the 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 become a chemically formed electrode plate. Therefore, particles far away from the current collector are only chemically formed at the end of the chemical formation process. This means that during the chemical formation process, the density of the chemical formation current with respect to the active material particles is initially high; This means that the final phase is low, making the overall efficiency of the formation current even lower. To make chemical conversion easier, red lead (pb3o) is added.
4) may be added to the unformed active material. this is,
The amount of electricity required is simply decreasing due to the progress of oxidation. Even if this is done, the formation will still start from the vicinity of the current collector, and the efficiency of the amount of electricity for formation will still be low as a whole. Red lead is expensive, and the disadvantage of higher price is greater than the advantage of being able to reduce the amount of electricity used for chemical conversion.

USP 4,631,241 proposes mixing graphite 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 graphite has electron conductivity, it is possible to connect active material particles in an electron conductive manner. However, the graphite shown in the knee has a particle size of 34
0 Plfg, which is too large and too few in number to connect between active material particles. The number of active material particles per unit volume is 1X in the case of a positive electrode based on the specific surface area, pore size distribution, etc.
10~1x10''ms For negative electrode, fX10'~lX1
It is estimated that there are 0" pieces. On the other hand, this 540
When 1% of PfN-sized graphite is added, the number of graphite particles is only about 500 to 1000, which is too large to expect electronic conductive connections between active material particles in graphite. The amount is too small.

In order to improve the bond between the active material particles or between the active material particles and the lattice, it is disclosed in JP-A-61-128466 and JP-A-54-1 that carbon fibers or electron conductive fibers are present within the active material. Publication No. 10574, JP-A-58-57
This is proposed in Publication No. 264. Also, Japanese Patent Publication No. 49-10
No. 3135 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.
The diameter is 10~j ODD pwg as described in the publication as ``diameter 0.01~1.QmJ,
Due to the large diameter and small surface area, tests conducted by the present inventors showed that the number of contacts with the active material particles was small, making it impossible to maximize the characteristics of carbon and dramatically improve conductivity. Ta.

JP-A-49-103135 discloses that in addition to such carbon fibers, "metal whiskers of ships, etc." are present. However, it is not clear how the "metal voice car such as lead" is obtained, what characteristics, dimensions, and form it has, and since no equivalent product is available, it is difficult to fully evaluate its effects. The inventors cannot admit it.

2IIll obtained by the inventors by the chatter vibration method
When lead fibers with a diameter of 30μ cut into I were mixed into the active material, the density of the active material increased and the contact density was thought to be improved, but the utilization rate of the active material and Charge acceptability was not improved.

In addition, Japanese Patent Application Laid-open No. 1-45565 describes that it is ``made by mixing polyolefin or polyester synthetic resin with carbon powder or Australian-resistant metal powder'' and ``with a diameter of 1 to 10P.
It has been shown that conductive synthetic resin fibers of 1N are 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 with a diameter of 1 to 10 m leads to a decrease in the apparent density of the active material, so l''Pb-0a as described there.
Improving the adhesion between the active material of the alloy grid and the grid body...
...The function of "preventing the formation of a barrier layer" could not be confirmed.

Further, in order to improve the charge acceptance of the negative electrode, it is widely practiced to add carbon black. in this case,
Carbon black mainly lowers the end-of-charge 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
It has a very small particle size compared to the graphite mentioned above.

Therefore, if 0.2 vt% is added, the number is sufficient to contact individual particles of the active material.

However, in this case, since carbon black has no length, its role is merely to exist between active material particles. That is, it has never been possible to connect tens or hundreds of active material particles in parallel. The improvement of the charge acceptance of the negative electrode by adding carbon plastic increases the charge current by lowering the final charge voltage, and current flows more easily to individual active material particles. isn't it. This means that a large current also flows to the positive electrode at the end of charging, which accelerates corrosion of the positive electrode grid due to an increase in the amount of overcharged air, so it is not a preferable method in terms of life performance. do not have. Adding carbon black to the negative electrode does not essentially improve charge acceptance.

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; ■ Improves the charge acceptance (charging efficiency) of positive and negative active materials and has long life cycle and long life performance. sulfuric acid electrolyte, thereby greatly improving the utilization rate without sacrificing life. ■ Significantly reducing the amount of tX required for forming the positive electrode plate. ■ Inexpensive. Our goal is to provide lead-acid batteries.

Structure of the Invention The present invention provides negative electrode active material particles made of sponge-like metal vessels and carbon, graphite, or potassium titanate having a diameter of 1 opm or less, an aspect ratio of 50 or more, and a specific surface area of 299 or more, which are in contact with the particles. A paste-type negative electrode plate in which a negative electrode active material is composed of selected whiskers and other additives as necessary, and positive electrode active material particles whose main component is lead difluoride are in contact with the particles. This lead-acid battery is characterized in that it consists of a paste-type positive electrode plate in which the positive electrode active material is composed of an electronically conductive fibrous material selected from carbon, graphite, or potassium titanate.

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 940 g of water using an ultra-high speed mixer. The carbon whiskers used in Knee were produced using hydrocarbons as raw materials and using a vapor phase growth method. As shown in the electron micrographs in Figure 1, the diameter is about 0.05 to 0.8 μm,
The length is about 10 to 100 μm, and the aspect ratio, that is, the ratio of diameter (D) to length (L) (L/D) is said to be about 100. has a long length. The density of this material is 1.96 Lie, the electronic conductivity is 7 x 10-'Ω-1,
BE'! According to the method, the specific surface area is 10-40'/q.

170 g of the carbon whisker dispersion prepared in this way
After adding and kneading lead oxide powder 10009 containing 30% metallurgy, 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.

Negative electrode paste was prepared using the same procedure except that a predetermined amount of lignin and barium sulfate were added to the carbon whisker dispersion)
B was prepared. Further, conventional positive electrode paste 0 and negative electrode paste D were obtained by the same operation except that carbon whiskers were not used.

Made of Pb-0a-3n alloy that does not contain antimony, the dimensions are 38 x L67 x T3.3 (2,0')
The above paste was filled into a cast grid body (U) by a conventional method. (0 indicates the negative electrode grid) The electrode plate filled with the paste was left standing at 35° C. and 100% RH for 5 days to age and harden the paste.

Thereafter, it was dried at 50° C. for one day to obtain an unformed positive electrode plate C 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: 2 positive electrode plates and 85 negative electrode plates under Patent No. 1272702
The sealed lead-acid battery Each lead-acid battery Y was produced. 45 ct of dilute sulfuric acid per cell was poured into this, 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.
Batteries X and Y were obtained. Various discharge currents (0
, 05-30), and the results of the investigation are shown in Figure 2. From this result, the active material utilization rate was calculated under the same conditions, and the results are shown in FIG.

Example 2 The negative electrode plate B and the positive electrode plate obtained in Example 1 were combined in the same manner to obtain a sealed lead-acid battery 2x according to the present invention and a battery 3x having a specific gravity of 1.550 at the end of chemical formation. The 20HR capacity, weight efficiency, and volumetric efficiency calculated from these batteries 2x and 3x and conventional battery Y are as shown in Table 2.

Table 2 The results of an alternate charge/discharge life test of these batteries are shown in FIG.

The test conditions are as follows.

0.250 discharge per 50 cycles [LV, 1,700V
/4 liter capacity test was conducted.

Example 3 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 of Example 1. The specific surface area of this carbon black was 1500''/p.

A conventional sealed lead acid battery 2 was obtained by combining the negative electrode plate E and the positive electrode plate 0.

Using three batteries, the sealed lead-acid battery X according to the present invention and the conventional sealed lead-acid batteries Y and 2, o, oooi to 0.
The battery was charged at a constant current of 5C5, and the relationship between charging current and battery voltage was investigated, and the results are shown in FIG.

Example 4 Graph 1 Ito whiskers and potassium titanate whiskers were added at a ratio of 1 wt% to the active material to form unformed positive and negative bipolar plates F, G, and H,1, of the present invention.
I got it. This Graph 1 Ito whisker is a carbon whisker that has been heat-treated at 3000℃, and its size has hardly changed, but its electronic conductivity is 5 × 10 Ω.
An order of magnitude higher than chew and carbon whiskers. Further, the potassium titanate whisker is Dentol BK-300 (manufactured by Otsuka Chemical Co., Ltd.), and has a diameter of 0.2 to 0.5 μm.
The length is 10~20 PIF+ and the electronic conductivity is 1X10- Ω.
On the order of -1, carbon whiskers are not very expensive.

The grid body is made of Pb-1,5% sb alloy and has dimensions W108X.
L110X"1.7 (1,1') m Tearl (0 indicates the negative electrode grid thickness). The obtained unformed electrode plates were stacked with a microporous polyethylene separator interposed therebetween, and after being inserted into a battery case, the lid was closed. The electrolytic solution was injected and left to stand.Next, 120% of the theoretical amount of electricity for chemical formation calculated from the amount of positive electrode active material was applied for chemical formation.
A lead-acid automotive battery of 28 μm h15 HR was obtained. Table 3 shows the results of examining the amount of residual whiskers after formation of these batteries, the amount of residual whiskers in the positive electrode, the capacity, and the charge acceptance performance according to JIS D 5301. In the charge acceptance test, the 10th minute current of the product of the present invention is smaller than that of the conventional product, but this is because the amount of electricity that has flowed up to the 10th minute is greater than that of the conventional product. Table 1 It is clear from Example 1 that the lead-acid battery according to the present invention has a high active material utilization rate and high weight efficiency and volumetric efficiency. It is. The number of positive electrode active material particles per unit volume is lX1012~
lX1016 pieces, and lX10' to 1X10 at the negative electrode
As already mentioned, it is estimated that there are 13 pieces. As shown in Example 1, the number of whiskers is estimated to be 1 x 10 to 1 x 1013 when about 1% is added to the active material.Furthermore, the aspect ratio of the whiskers is very large. Therefore, the number of active material particles in contact with one whisker is 50.
It is estimated that there will be ~1000 pieces. Therefore, it is presumed that, for example, in the negative electrode, a plurality of carbon whiskers are in contact with one active material particle. According to the present invention, particles that are far apart and have not conventionally been connected 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, larger discharge capacity, and extremely high chemical formation current efficiency. This is clear from what was shown in Examples 1 and 4.

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 highly concentrated in the lower part and low in the upper part. stratification
).

The layering caused by the fact that the lower part of the negative electrode plate is usually far from the ears, the resistance of the high concentration sulfuric acid electrolyte is large, and the solubility of lead sulfate is low is due to the layering of the negative electrode active material in the lower part. Invite Ace I. However, according to the present invention, since the resistance within the electrode plate is low, sufficient current flows even in the lower part of the negative electrode plate even though it is far from the ear, resulting in a shortened battery life due to the lower part of the plate. Can solve problems.

This is clear from Example 2.

While the conventional sealed lead-acid battery Y has a short life due to the lower part of the negative electrode plate, the life of the sealed lead-acid battery 2x and the high specific gravity electrolyte of the present invention is 1.350 (iH
The battery 5X)i[L using 2so4 exhibited excellent life performance.

A high-density electrolyte is an electrolyte with a small amount of 170, which does not participate in charge/discharge reactions, and whether it is of a sealed type or
Regardless of whether or not this is the case, it is possible to greatly improve the weight efficiency and volumetric efficiency of the battery. In conventional lead-acid batteries, the negative electrode plate had poor corrosion resistance against high-density electrolytes, so the use of high-density electrolytes meant that the batteries had a short lifespan.

However, according to the present invention, it is possible to make a lead-acid battery with high weight and volume efficiency without sacrificing the life span. This is clear from Example 2.

The unformed active material is lead sulfate (=basic or tetrabasic) or lead oxide (when filled with cladding), which has no electronic conductivity.

Therefore, when the particles are chemically formed, the chemical formation proceeds in the order starting from the particles that are in contact with the lattice or core metal that is the current collector. Therefore, active material particles that are not in contact with the current collector are not chemically converted until they receive electrons via the particles existing between the active material particles and the current collector. For this reason, in the past, especially positive electrode plates had to be formed over a long period of time and with a large amount of electricity.
It required ~4 times as much. However, according to the present invention,
Even particles that are far away from the current collector are bonded to the current collector by electronically conductive whiskers, so that the active material particles are formed as soon as the formation starts. Therefore, the efficiency of chemical conversion is extremely high, and even in the case of clad batteries, there is no need to mix red lead, etc., and the amount of electricity required for chemical conversion is within twice the theoretically required amount, and depending on the conditions, it can be up to 1. .1 times is sufficient. Furthermore, the formation time and amount of electricity can be reduced to i-% of the conventional amount, resulting in a highly productive and extremely inexpensive lead-acid battery. This is clear from Example 4.

Conventionally, carbon black has been added to improve the charge acceptance of the negative electrode plate. This has the effect of lowering the hydrogen overvoltage at the negative electrode and thickening the current flowing at the end of charging, thereby increasing the charging capacity.However, in practical use, This means that the amount of water in the electrolytic solution is large, which 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 positive electrode grid corrosion.

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 separated from the current collector also start being charged at the same time as charging starts, charging efficiency is very high.

Moreover, a characteristic feature of carbon whiskers and graphite whiskers is that they do not lower the hydrogen overvoltage of the negative electrode, as shown in Example 4. This means that, as shown in Example 5, the charge acceptability at the initial stage of charging is excellent, and the charge current flowing into the battery at the end of charging is smaller than that of the conventional battery. It overcomes the drawbacks of conventional carbon black-added products, such as increased water replenishment frequency and accelerated corrosion of the positive electrode grid. The fact that the negative electrode has good charge acceptance is the same as the fact that it has high resistance to the above-mentioned monkey attack.

Therefore, it is clear that the 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 Examples 2 and 3.

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 whiskers is preferably lX10=Ω·1 or more, preferably lX10−′Ω·1 or more. What is more important is to electronically conductively connect as many active material particles as possible without drastically reducing the amount of active material. 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 50 pw@ or more cannot be used because their number is small in relation to the volume they occupy. Diameter is 10μ
m or less, preferably less than 1 μm, and the aspect ratio must be 50 or more.

Most preferred are whiskers having a diameter of 0.01 to 1.0#jjl and an aspect ratio of 100 to 1000.

As for the material of the whisker, in addition to carbon, graphite, potassium titanate, etc. shown in the above embodiments, whiskers having electron conductivity that are not harmful to lead-acid batteries can also be used.

When whiskers are used as the positive electrode, not only carbon but also graphite, which has excellent oxidation resistance and is made by treating it at high temperatures, is physically removed from the active material by the oxygen gas that is incubated or generated. Nearly half of it is lost during the chemical conversion process. Therefore, when a lead-acid battery according to the present invention is assembled using chemically formed electrode plates, the amount of whiskers present in the positive electrode plate is less than the amount initially mixed with the active material. If the whisker effect is expected after that, the ratio to the active material must be increased initially.If only the effect during the chemical formation process is expected, the ratio may be lower.

In the former, the ratio to the unformed positive electrode active material is 1 to fo
vt%, more preferably 1-5vt%,
In the latter, 0.01-3vt%, more preferably 0.0
It should be between 1 and 2.0 wt%.

In the case of a negative electrode, no carbon or graphite whiskers are 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 3 wt%, more preferably 0.01 to 2.0 wt%.

Another important point in order 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 1, it is preferable to use the lead powder after dispersing it in water using an ultra-high-speed mixer instead of directly adding it to the raw material.

In order to improve dispersibility in water, carbon or graphite whiskers may be treated with a surfactant or hydrophilic groups may be added directly to their surfaces 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 antimony-free pure lead, calcium alloys, or other antimony-free lead alloys as the positive electrode grid, if the apparent density of the active material is small, the electrolyte will diffuse well (too much). , before the active material is completely discharged, the corroded layer on the surface of the lattice discharges, and this turns into lead sulfate, an insulator.This breaks the electrical bond between the active material and the lattice, and the capacitance cannot be extracted.

In order to prevent this, for example, when using carbine whiskers, if you use a paste prepared by adding and kneading an alkali metal salt of metaphosphoric acid or birophosphoric acid, such as sodium metaphosphate or common sodium biroline, the ratio of whiskers to active material This is advantageous because a high-density active material can be obtained even if there is a large amount of . Such an alkali gold Jl 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 the negative electrode, 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. can get.

The appropriate ratio of these alkali metal salts of birophosphoric acid or metaphosphoric acid to the active material varies depending on the amount of sulfur and water used to prepare the paste. However, the appropriate positive electrode paste density for ordinary paste type electrode plates is 5.7 to 4.59/7.
, when trying to obtain a negative electrode paste density of 3.5 to 4.597-, the setting is 0.001 to Swt with respect to the active material.
%Must. In this way, the apparent density of the positive electrode active material is 5.5 to 4.0 and the apparent density of the negative electrode active material is 3.1 to 4.0. 09- 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 μm 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, this will not happen if the whiskers of the present invention are used. In fact, the apparent density without additives is 4.
When approximately 1% of carbon fiber was added to the positive electrode active material of 02, the apparent density decreased to 2.6 in the case of carbon fiber, but only 3.75 in the case of whiskers. .

Furthermore, in this case, the number of carbon fibers present per 1 d of apparent volume of the active material is approximately 2 x 10', and the total surface area is approximately 80 e.
j, whereas in the case of carbon whiskers, it is about 1 x 10'', or about 4900 -, which is an order of magnitude larger. This is preferable, and it is better to have 1 x 10' or more 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 birophosphoric acid is extremely effective, and unless it is used, 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 5.1.
~4.0, more preferably 3.3 to 4 at the positive electrode
．． If it is not set to 0, problems such as damage to the negative electrode and corrosion of the water-stop electrode grid 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%.

Needless to say, this also applies when the whisker diameter is as large as about 7 to 10 μm.

In other words, even in the case of whiskers, the amount is 1 vt%
To a certain degree, a sufficiently high active material density can be obtained even without the presence of an alkali metal salt of metaphosphoric acid and/or an alkali metal salt of birophosphoric acid. However, when the amount is increased further, or 5-10 μm above 1 pM
In the case of whiskers having a diameter of From the viewpoint of such contact density, it is preferable that the whiskers have a specific surface area of 2'/q or more, more preferably 10 to 40 d/q.

Lead-acid batteries typically require 105 to 1
I have to charge it to about 20%.

Due to this overcharging, the water in the electrolyte is electrolyzed and the electrolyte is lost, so water must be periodically replenished. In order to reduce or eliminate this type of water work, the alloy of the current collector may be made of a calcium-based alloy that does not contain antimony, or the amount of electrolyte may be reduced and absorbed and retained in a microporous material. ing. In addition, it is gelled with silicon dioxide, superabsorbent polymer, etc., and is sealed by combining the oxygen gas generated at the positive electrode with the negative electrode active material at the end of charging. The present invention can be applied to any of these lead-acid batteries.

Effects of the Invention As described above, the 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 ones, and is capable of charging the positive and negative active materials. It has improved acceptability (charging efficiency), long life cycle and float life performance, improved resistance of the negative electrode active material to acid attack, allows the use of higher concentration sulfuric acid electrolyte, and has a longer life cycle. Its industrial value is extremely large, as it greatly improves the utilization rate without sacrificing quality, greatly reduces the amount of electricity required to form the positive electrode plate, and makes it inexpensive. .

[Brief explanation of the drawing]

FIG. 1 is an electron micrograph showing carbon whiskers used in the lead-acid battery of the present invention, and FIG. 2 is a diagram comparing the relationship between capacity and discharge current between the lead-acid battery of the present invention and a conventional product. Figure 3 is a diagram in which the capacity in Figure 2 is converted into an active material utilization rate, Figure 4 is a diagram in which the life performance of the lead-acid battery according to the present invention is compared with a conventional product, and Figure 5 is a diagram in which the lead-acid battery according to the present invention and a conventional product are compared. This is a diagram comparing the relationship between charging current and battery voltage with conventional products.

Claims (2)

[Claims] (1) Negative electrode active material particles made of sponge-like metal lead and those in contact with the particles have a diameter of 10 μm or less and an aspect ratio of 50.
The above is a paste-type negative electrode plate in which the negative electrode active material is composed of whiskers selected from carbon, graphite, or potassium titanate having a specific surface area of 2 m^2/g or more, and other additives as necessary. The positive electrode active material is composed of positive electrode active material particles containing lead dioxide as a main component and an electronically conductive fibrous material selected from carbon, graphite, or potassium titanate that is in contact with the particles. A lead-acid battery characterized by consisting of a paste-type positive electrode plate. (2) The lead-acid battery according to claim 1, wherein the specific gravity of the electrolyte is higher than 1.350 d.