JPH01124958A - Sealed lead-acid battery - Google Patents

Abstract

PURPOSE:To improve high rate discharge performance without the sacrifice of low rate discharge capacity by using porous hollow microparticles mainly comprising lead dioxide or lead, each of which has a hollow in its inside and numerous micropores connecting the hollows to the outside in its wall, as an active material. CONSTITUTION:A lead acetate aqueous solution is dispersed in benzene by using a surface active agent, and this dispersion is dropped into dilute sulfuric acid solution with it stirred, and a precipitation is washed and dried to obtain porous hollow microparticles mainly comprising lead dioxide or lead each of which has a hollow 2 in its inside and micropores 4 connecting the hollows to the outside in its wall. The ratio d/D of the inner diameter d of the hollow 2 to the outer diameter D of the particle is larger than 40%. The particles are used in a part of or the whole positive and negative active materials. A sealed lead-acid battery having remarkably improved high rate performance without the sacrifice of low rate discharge capacity, excellent quick charge capacity, and long life is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sealed lead-acid battery, and is particularly suitable for use in emergency power sources, starting power sources, power sources for portable equipment, etc. This invention relates to sealed lead-acid batteries for applications that require charging characteristics at high speeds.

Conventional technology and its problems Sealed lead-acid batteries normally move oxygen gas generated at the positive electrode at the end of charging to the negative electrode, react with the negative electrode active material, and put the negative electrode in a discharged state, thereby removing oxygen gas from the battery system. It is sealed using a so-called oxygen cycle, which consumes and recombines hydrogen within the system without releasing it, and suppresses the generation of hydrogen gas from the negative electrode.

In order to quickly move the oxygen gas generated at the positive electrode at the end of charging to the negative electrode and react with the negative electrode active material, the separator and the electrode plate must be brought into close contact to prevent oxygen gas from escaping into the internal space of the battery. It is necessary to limit the amount of electrolyte to as low as possible to form voids in the micropores in the separator through which oxygen gas, which is not completely filled by the electrolyte, can easily move. For this purpose, a microporous glass separator that absorbs a large amount of electrolyte is usually impregnated with electrolyte, or the electrolyte is made into a gel of dilute sulfuric acid and fine silicic acid powder. In this way, in the case of a sealed lead-acid battery,
The amount of liquid must be slightly smaller than the total pore volume of the electrode group constituted by the positive electrode plate, negative electrode plate, and separator. By the way, since a sealed lead-acid battery is also a type of lead-acid battery, its capacity depends on the amount of positive and negative active materials and the amount of sulfuric acid in the electrolyte, so in a sealed lead-acid battery where the amount of electrolyte is limited, Its capacity is regulated by the amount of sulfuric acid. For example, in the case of low rate discharge such as 20HR, the utilization rate of the positive electrode active material is 55-40% and that of the negative electrode active material is 35-50%, while that of sulfuric acid in the electrolyte is 80-100%. It has become. Furthermore, in the case of high-rate discharge, since the diffusion of sulfuric acid is slow, the sulfuric acid in the separator is hardly utilized, and the obtained capacity is controlled by the amount of sulfuric acid contained in the positive and negative electrode active materials.

Therefore, in order to improve the high rate discharge characteristics, it is necessary to either increase the ratio of the electrode plate pore volume formed by the positive and negative electrode active materials to the total pore volume of the electrode group and lower the ratio of the pore volume of the separator; Or (2) The electrode plate must be extremely thin, for example, 0.8 to 1.0 ms thick, the electrode plate area must be wide, and the discharge current density must be set low. However, in the case of ■, increasing the ratio of the electrode plate hole volume means making the beseverator thinner compared to the electrode plate thickness, which is less active than the separator's porosity of 80 to 95%. Since the porosity of 50-60% of the material is extremely low, the total pore volume of the pole group is rather small when considered within a fixed volume.

This means that the low rate discharge capacity with a high electrolyte utilization rate will decrease, and in fact, when the 20HR capacity is taken as 100, the capacity at 30 discharges is 55 to 60 at best, and in the case of ■ But it's on the same level. Furthermore, in case (2), since the electrode plate is thin, the lattice must also be thin, and therefore the positive electrode lattice in particular undergoes significant corrosion and elongation resulting from the corrosion, resulting in a short service life. This elongation can be suppressed by increasing the pressure applied to the electrode plate, but the elongation can be suppressed by increasing the pressure applied to the electrode plate.
Regardless of the case where a pressure such as kg/d is applied, in the case of a prismatic battery that uses a flat plate, which is the most volume efficient in use, the limit is several tens of 9/a, which is applied to the plate. In practice, it is extremely difficult to suppress this elongation by pressure.

On the other hand, in order to enable rapid charging,
Since it is necessary to diffuse sulfuric acid produced by oxidizing or reducing lead sulfate formed by electric discharge into the separator in a short time, the proportion occupied by the separator must be made as small as possible as in method (2).

In this way, in order to improve the high rate discharge characteristics and enable rapid charging, it is advantageous to increase the ratio of the electrode plate hole volume to the electrode group hole volume and to lower the ratio of the separator. . Improving high-rate discharge characteristics and rapid charging characteristics without reducing the capacity per fixed volume cannot be achieved simply by reducing the thickness of the separator; it is necessary to reduce the proportion occupied by the lattice to the maximum allowable limit, and This can only be achieved by making the porosity of the active material as high as possible. Conventionally, the external ratio of active materials used is 5.3 to 3.9 (corresponding to about 55 to 47% in porosity) for the positive electrode, and 5.0 to 6.5 (corresponding to about 60 to 54% in terms of porosity) for the negative electrode. In order to achieve the above-mentioned purpose, the outer diameter of the positive and negative active materials must be approximately 1.8 to 2.4 (corresponding to
The porosity must be lowered to about 76% to 68% (equivalent to about 76% to 68%), but the outer surface of a clad plate active material that is simply filled with active material is about 2.6%. As is clear from the above, it is impossible to obtain a paste-type electrode plate with such a low surface area by extension of the conventional technology. In addition, reducing the external ratio of the active material increases the amount of electrolyte near the lattice, which not only accelerates the corrosion of the lattice, but also, especially in the case of a positive electrode lattice that does not contain sb, repeating deep discharges will cause lattice corrosion. Another drawback is that the layer discharges first and the lead sulfate that forms there creates a so-called barrier, which insulates the grid and the active material, leading to premature end-of-life.

Purpose of the Invention The present invention solves the problems that cannot be overcome by extending the conventional technology, significantly improves high rate discharge characteristics without making low rate discharge capacity a characteristic, and provides long life performance with excellent quick charging performance. The purpose is to provide a good sealed lead acid battery.

Structure of the Invention The present invention provides that a part or all of the positive and negative electrode active material is mainly composed of lead dioxide or lead, which has a hollow space inside and has micropores in the wall that communicate with the outside and the hollow part. It is made of porous micro hollow particles and is characterized in that the ratio (d/D) between the outer diameter (DJ) of the particles and the inner diameter (dl) of the hollow part is greater than 40%.

Example The configuration of the present invention will be explained according to examples.

An aqueous lead acetate solution was dispersed in benzene using a surfactant, and was well dispersed in benzene.

While stirring, dilute sulfuric acid was added dropwise to the mixture, followed by washing with water and drying to obtain fine particles of lead sulfate. The diameter of fine particles is 0.2~10μ
It is roughly spherical and has a specific surface area of 85fIr/m.
g and 1.5t//l of conventional lead powder whose main component is lead oxide.
significantly higher than that of This is the interface between the surfactant and the acetic acid aqueous solution, that is, the surface part, where lead sulfate is first formed, and the reaction progresses to the inside, eventually creating a part where there are no lead ions inside, which becomes a hollow part. This is because micropores communicating with the outside and the hollow part were formed in the part where the sulfuric acid penetrated and remained as a part.

The micro hollow lead sulfate particles obtained in this way were kneaded with dilute sulfuric acid, and the positive electrode had external dimensions of 40"W x 70"L x 4.
．． The filling volume is 9.5 CC/sheet at O"T, .pb-
o. Door-jAn lattice and brick.

The negative electrode was made so that the paste weight was about 27.59/sheet.
The external dimensions are 40"W x 70 L x 3.5" 11T and the filling volume is 8.3 CC/piece pb-o, o"; the dry brick paste weight on the almost A grid is about 24g/piece. , normal amounts of barium sulfate and lignin were added and filled.This was chemically formed by a conventional method to obtain positive and negative electrode plates, but the amount of active material in the positive electrode plate after chemical formation was approximately 21.597 sheets. The amount of sulfuric acid absorbed is about 6.5cc/sheet, which is 0.50cc/g per 1g of active material, and that of the negative electrode is about 16.89cc/g.
0.360C per 1g of active material at approximately 6.10C/sheet
/ It was 9. Two positive electrode plates and three negative electrode plates obtained in this way were formed into a sheet shape mainly made of glass fiber with a diameter of 1 μm or less.
Obtain a group of poles that are alternately overlapped through microporous glass separators with a thickness of 0.4 mm under 20#/1 load at "L",
After inserting this into a battery case according to the usual method and attaching the lid, 1.5 cc of 57 cc per cell was added. ? i0 d H2SO4 (which contains 209 parts of sodium sulfate per 14 parts) is injected;
The external dimension according to the present invention after inserting the valve is 481111W.
X B 51111HX 2z 7″llL theal, 2
A V-sealed lead acid battery (2) was obtained.

Using the same lattice as a conventional sealed lead-acid battery, a sealed lead-acid battery was manufactured from a raw material containing lead oxide powder as a main component according to a conventional method. That is, the weight of the active material after chemical formation is 5 for the positive electrode.
The amount of sulfuric acid absorbed is approximately 5.297 sheets for the negative electrode, and 27.5997 sheets for the negative electrode. Oct/sheet, negative electrode approximately 4.9CC/
The positive electrode is 0.15cc/g per 1g of active material.
The negative electrode was 0.18 cc/g. The outer dimensions of the two positive electrode plates and the five negative electrode plates are 45=W x 75ssL, 20 kg, 7a, and the thickness under a load fE of 1.5 mm. After stacking the electrodes alternately through microporous glass separators to obtain a group of electrodes, inserting them into a battery case and attaching the lid, 45 cc of electrolyte was injected per cell, making the conventional external dimensions 48W x 85"HX.
A 2V sealed lead-acid battery (Bl) of 2B, 5''L was fabricated.

When these two batteries were discharged to 1.75V at 25°C and 250mA, the capacity of A was 5.001h, and the capacity of SB was 5.10Ah. 20H with various discharge currents
FIG. 1 shows the relationship between the capacity retention rate and the discharge current when the R capacity is 100. Also, when the volumetric efficiency was calculated from this result, it was as shown in the following table.

Table 1 Volumetric efficiency (Wb/l) This battery is also alternately charged and discharged, with one cycle of ``discharging to 1.70V with a running resistance of 1.3Ω, then charging for 5 hours at a constant voltage of z4ov with a maximum current of 2μ''. When a life test was conducted, the results shown in Figure 2 were obtained.

As is clear from FIG. 1, in the sealed lead-acid battery according to the present invention, the extent to which the capacity obtained when the discharge current is increased is extremely small compared to the conventional one. While the conventional product has a capacity of about 49 hours, the capacity of the present invention is about 72 hours.

The volumetric efficiency is also excellent across all discharge rates, from low to high, and is 1.2 to 1.8 times higher than conventional products.

The reason why the capacity is large and the high rate discharge characteristics are particularly excellent is that the active material particles used in the sealed lead-acid battery according to the present invention are spherical particles as schematically shown in FIG. The wall 3 is composed of an outer side 1 and a hollow part 2, and there are countless micropores 4 communicating with the outer side 1 and the hollow part 2, and the injected electrolyte flows through the micropores 4. Hollow part 2 through
The amount of electrolyte in contact with the grooved active material particles inside is extremely large compared to conventional ones, and the specific surface area is an order of magnitude larger due to the presence of hollow parts 2 and micropores 4. It is presumed that this is due to the high level of Moreover, the same degree of contact can be secured on the outside of the particles as with conventional active materials densely packed.

The ratio of the size of the hollow part 2 to the outside 1 is at least 40
%, more preferably about 50 to 80%. That is, for example, when the particle diameter is 2 pm, the diameter of the hollow part is at least 0.8 p''s, preferably 1.0 to 1.6
pms (therefore the thickness of the wall 5 should be less than 60%, more preferably 50-20%, in this example 1.2 pyms, more preferably 1.0-0.4 pyms). If this ratio is lower than 40%, the volume that can absorb the electrolyte will not increase much, so the effect of increasing low rate discharge capacity will be small; if it is set too high, such as over 90%, the active material utilization rate will increase. If it is too high, the life will be shortened and the physical strength of the active material will also be weakened, so it is more preferably 50 to 8.
It should be 0%.

The sulfuric acid absorption amount in the examples is a value measured by the following method.

The steps of the measurement method are as follows: 1. Measure the weight of the electrode plate. (Wl) 2 The electrode plate is immersed in a dilute sulfuric acid aqueous solution having a specific gravity of 1.50, and is forcibly impregnated by vacuum reduction.

3. Pull up the electrode plate and hang it in air for 1 minute, then measure the polymerization. (W2) 4. Remove the active material and remove the remaining lattice! ! measure quantity. (W3) The active material used in the sealed lead-acid battery according to the present invention has a significantly larger amount of electrolyte that can be retained within the active material than conventional ones.

The amount of sulfuric acid absorbed is at least 0.17 CC/
g, in the case of a negative electrode, it cannot exhibit its characteristics as a hollow fine particle active material unless it is at least 0.21 cc/g. Preferably, in the case of a positive electrode, 0.19 to 0.44 cc/g,
For negative electrode, it should be 0.24-0.54cc/9. If the amount is more than this, the active material utilization rate becomes too high and the physical strength of the particles decreases, making it unsuitable. Furthermore, as shown in FIG. Under test conditions of repeated discharging and constant voltage charging, it exhibits extremely excellent longevity performance. This result shows that charging was carried out at a constant voltage of 2.40V, and it is presumed that conventional product B was not sufficiently charged under this condition, but product A of the present invention was charged and had a lower charge compared to the conventional product. The lifespan is more than twice as long. This is because the active material particles themselves are porous and have hollow parts, which increases the amount of electrolyte in the electrode plates, making the separator thickness (gap between the electrode plates) extremely thinner than conventional products. It is presumed that this is because the charging efficiency is high because there are fewer separator layers through which sulfuric acid generated by charging must diffuse. Therefore, the thickness of the separator is equal to the thickness of the positive electrode plate, as shown in the examples. It is possible to make it as thin as possible. The separator of the sealed lead-acid battery according to the present invention needs to play a role as a "separator" that isolates the positive and negative electrode plates so that they do not come into contact with each other, rather than the role of the conventional "liquid retaining material". The thinner the electrode, the better, as long as it can prevent the positive and negative electrode plates from coming into direct contact and causing a short circuit. For example, in addition to the fine glass separator shown in the examples, a microporous synthetic resin separator having a thickness of approximately 0.05 to 0.21111 mm may also be used. In this case, almost all of the necessary electrolyte can be retained within the pores of the electrode plate, so that the high rate discharge characteristics can be significantly improved. In this way, about 85% of the liquid in the battery is retained within the electrode active material in the embodiment, but it is possible to increase this to 90% or more.

In the example, the positive electrode active material utilization rate at 20HH is 5X
21.5-IX2-I X4.463-0.519 and 5
It exceeds 0%, which is 30% to 30% of the conventional usage rate.
This is extremely high compared to 40%.

Normally, when using a lattice that does not contain antimony, if the utilization rate of the positive electrode active material is increased, the life will be shortened at an earlier stage due to repeated deep discharges, but the sealed lead-acid battery according to the present invention has such a problem as shown in Nothing happens. It is believed that this early life is mainly caused by the large diffusion of the electrolyte in the vicinity of the grid, whereas in the sealed lead-acid battery according to the present invention, it is retained within the electrode plates. This is because the electrolyte is consumed within the electrode plate, and only the same level of voids as in the case of a conventional active material packed with high density remain on the outside of the active material particles. In the case of the example, if we take the positive electrode as an example, if there were no hollow part and communicating micropores in the wall, 27.399 sheets of active material would be filled, which is the same as in Conventional Example B.
The same amount of voids as in Conventional Example B are formed on the outside of the active material particles.

Although the hollow portion of the hollow active material of the example has a remarkable effect on increasing the amount of electrolyte absorbed, the continuous micropores in the wall do not have such a large effect. This is because the size of these communicating micropores is from several tens of lambda to several hundred, which is significantly smaller than the voids formed in the hollow parts and between the particles. Therefore, the existence of communicating micropores
This contributes to improving the activity of the active material by moving the electrolyte inside and outside the particles and increasing the surface area.゛In the above example, an example was shown in which an aqueous lead acetate solution was used as the starting material, and lead dioxide or lead active material was obtained through porous micro hollow particles of lead sulfate, but the present invention is not limited to this. . As a starting material, any water-soluble lead salt such as lead nitrate or lead chloride may be used.Also, lead dioxide or lead active material particles themselves can be synthesized directly from these starting materials. It may also be filled into a grid. In this way, it is possible to omit the chemical formation step, and a cheaper sealed lead acid battery can be provided. Moreover, if -lead oxide is synthesized, it is possible to make a sealed lead-acid battery using the same process as the conventional method. In any case, as long as the active material having the structure described in the present invention is used in the completed electrode plate, similar effects can be achieved.

Furthermore, the examples show examples in which all of the positive and negative electrode active materials are composed of monoporous micro hollow particles,
The present invention is not limited to this. It is also possible to mix the active material made of such porous microscopic hollow particles with the conventionally used non-hollow active material derived from lead powder mainly composed of lead oxide. In that case,
The pore volume of the electrode plate changes depending on the mixing ratio of both active materials and the paste preparation method, and the amount of electrolyte that can be absorbed also changes, so specifications must be determined according to the desired quality. It is within design.

Effects of the Invention As described above, according to the present invention, it is possible to provide a sealed lead-acid battery with significantly improved high-rate discharge characteristics without sacrificing low-rate discharge capacity, excellent rapid charging performance, and long life performance. and its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing discharge current and capacity retention rate, FIG. 2 is a diagram showing life performance, and FIG. 3 is a diagram showing the structure of active material particles used in the present invention.

Claims (3)

[Claims] (1) Part or all of the positive and negative electrode active materials are porous, mainly composed of lead dioxide or lead, which has a hollow space inside and countless micropores in the wall that communicate with the outside and the hollow space. Consisting of micro hollow particles, the outer diameter of the particle (D) and the inner diameter of the hollow part (d)
A sealed lead-acid battery characterized in that (d/D) is greater than 40%. (2) The sealed lead-acid battery according to claim 1, wherein the ratio (d/D) is 50 to 80%. (3) Electrolyte absorption amount per 1g of positive electrode active material is 0.19~
The sealed lead-acid battery according to claim 1, wherein the electrolyte absorption amount per gram of negative electrode active material is 0.24 to 0.54 cc/g.