JP2003036831A - Sealed lead storage battery having gel electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed lead storage battery superior in discharge and charge-discharge cycle life performances which battery has a gel electrolyte, by improving separator arrangement and gel contents. SOLUTION: The sealed lead storage battery comprises: a separator 2 constituted of a thick mat-like sheet 3, a thin porous sheet 4 with a large average pore size, and a thin porous layer 5, a group of small projections or ribs; and the gel electrolyte 8 composed of a dilute sulfuric acid, and fine silica powders of less than 10 wt.%, a small quantity of soluble sulfates and phosphoric acid of 0.75 wt.% to 4.0 wt.%, wherein the gel electrolyte 8 is filled at least almost in the separators and around electrode plates, and the electrode plates are arranged in a strongly pressed state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed lead acid battery provided with a gel electrolyte, and more particularly to an electrode plate group including a separator and the content of the gel electrolyte.

[0002]

2. Description of the Related Art Sealed lead acid batteries based on oxygen cycle reaction have been generalized and used for various purposes. Looking at the history, first a gel type which made the electrolyte into a gel was commercialized, and then a retainer type in which a porous retainer mat was impregnated by reducing the amount of the electrolytic solution was developed.Currently, this is the mainstream in terms of performance. Is becoming. The main structure of the separator part in the seal type storage battery having the gel electrolyte that has been conventionally adopted is as follows. 1. A corrugated plate with holes with a diameter of 1 mm or more, on each side of which a thin cloth-like body is placed to contact the positive and negative plates, respectively. 2. A thin glass mat is placed on the rib side of a ribbed porous plate, and the glass mat is brought into contact with the positive electrode plate. 3. A microporous plate having ribs and having an average pore size of less than 2 μm, in which a group of ribs are brought into contact with a positive electrode plate. 4. Only using corrugated plates with holes with a diameter of 1 mm or more. 5. A retainer mat mainly composed of short glass fibers with an average diameter of 1 μm or less was used to reduce the amount of silica, and it was more like a retainer type.

In the gel type storage batteries other than the above-mentioned 5, unlike the retainer type storage battery assembled under a high pressure, it is not possible to strongly press the entire surface of the positive and negative electrode plates of the electrode plate group having these separator structures. Therefore, the pressing force on the positive electrode active material is small, and the short life due to deterioration of the positive electrode plate has been a problem. In order to solve this, the concentration of silica constituting the gel is increased to 10% by mass or more, and phosphoric acid is often added. As a result, migration of ions between electrode plates is inhibited and the amount of sulfuric acid is increased. There was a problem that the discharge performance was inferior and was inferior to that of the retainer type storage battery. In recent years, there have been examples of using storage batteries in a horizontal position for applications such as stationary use, small portable use, and electric vehicle use. In this case, the plates are arranged horizontally, and due to the gravity of the plates, the plate gap cannot be maintained at the bottom of the plate group, that is, at the part opposite to the plate ears fixed with straps, and the plate plates are narrow. There was a problem.

Further, in the case where a microporous plate having an average pore size of less than 2 μm is used as a separator, it is difficult for oxygen gas generated from the positive electrode plate to permeate and diffuse through the separator, resulting in low sealing reaction efficiency. However, in the case of using a corrugated separator having a large hole having a diameter of 1 mm or more, there is a problem that a short circuit occurs between the positive and negative electrode plates in the hole.

In a gel-type storage battery using a retainer mat, which is mainly composed of short glass fibers having an average diameter of 1 μm or less and has an extremely large surface area, and a gel containing silica fine particles and dilute sulfuric acid as an electrolyte, the silica fine particles are used as the retainer. Since it deposits on the surface of the mat fiber and is lost in a large amount, there is a problem that the gel state is not sufficiently exhibited. Further, even when a separator containing 15% by mass or more of silica powder is used, there is a defect that silica fine particles are deposited on the silica powder.

[0006]

According to the present invention, a mat-like body having a thickness of 0.5 mm or more, which is mainly composed of long glass fibers or synthetic resin fibers having a diameter of 10 μm or more and 25 μm or less, which is in pressure contact with a positive electrode plate on one side, is provided. A sheet-like perforated plate having a maximum pore size of 50 μm or less and an average pore size of 2 μm or more and having a silica content of 15% by mass or less and a thickness of less than 0.5 mm is used as a separator, and a small amount of soluble sulfuric acid is used. Less than 10% by mass, preferably 5.0% by mass or more, containing salt and 0.75% by mass or more and 4.0% by mass or less, preferably 1.0% by mass or more and 3.0% by mass or less phosphoric acid 8.0
A gel electrolyte composed of silica fine particles of less than or equal to mass% and dilute sulfuric acid is arranged at least in the pores of the separator and in most of the cell space around the electrode plate group, wherein the negative electrode plate, the separator and the positive electrode. The plates form an electrode plate group in a state of being strongly pressed against each other, and in particular, a sheet of a porous thin layer having a diameter of 10 μm or more and 25 μm or less and mainly composed of long glass fibers or synthetic resin fibers and having a thickness of less than 0.5 mm Arranging and abutting on the other surface of the plate-shaped perforated plate, or integrating them,
Furthermore, a group of small protrusions or ribs with a height of less than 0.5 mm,
By integrally forming it on the other surface of the sheet-shaped porous plate, the problem of the conventional sealed lead-acid battery having a gel electrolyte is solved.

[0007]

The sealed lead-acid battery provided with the gel electrolyte according to the present invention has the following actions. (1) Since the negative electrode plate, the separator having the mat-like body, and the positive electrode plate form the electrode plate group in a state of being strongly pressed against each other, the positive electrode plate is suppressed from deterioration and has a long life. (2) Even when the storage battery is placed horizontally, the electrode plate group is assembled in a state of being strongly pressed from the beginning, so that the distance between the positive and negative electrode plates can be kept constant. (3) As a separator, a thin sheet-like porous plate having an average diameter of 2 μm or more and a slightly large hole and a mat-like member having a large hole are used, so that oxygen gas generated from the positive electrode plate easily permeates the separator. Since it can reach the negative electrode plate, a high closed reaction efficiency can be obtained. (4) The sheet-shaped perforated plate of the separator has a maximum diameter of 5
It is 0 μm or less, and it is possible to prevent the occurrence of a short circuit between the positive and negative electrode plates. This also contributes to the effect of adding a small amount of sulfate and an appropriate amount of phosphoric acid. (5) The amount of silica fine particles constituting the gel electrolyte is 1
Since it is less than 0% by mass and is not much, the discharge performance is excellent. (6) Since the diameter of the fibers forming the mat-shaped body of the separator is as large as 10 to 25 μm and the surface area thereof is small, and the silica powder of the separator is less than 15% by mass,
The amount of fine silica particles constituting the gel electrolyte solution deposited and fixed on the fibers or silica powder is small, and the electrolyte solution can sufficiently maintain the gel state. (7) Since the gel electrolyte contains a small amount of sulfate and 0.75 mass% or more of phosphoric acid, phosphoric acid migrates to the positive electrode plate during charging, which prevents corrosion of the grid and softening of the active material. Even if the sulfuric acid concentration becomes low during discharge, the electrolyte solution maintains a gel state due to the action of the returned phosphoric acid in addition to a small amount of sulfate, and lead ion elution and short circuit can be prevented.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. Reference numeral 1 is a negative electrode plate, 1'is an edge of the negative electrode plate, 2 is a separator, which is mainly composed of long glass fibers or synthetic fibers having a diameter of 10 to 25 μm, a thick mat-like body 3 having a thickness of 0.5 mm or more, and a maximum pore diameter. 50μm or less and average pore size 2μm
Above, thin sheet-like perforated plate 4 with a thickness of less than 0.5 mm
And a porous thin layer 5 mainly composed of long glass fibers or synthetic fibers having a diameter of 10 to 25 μm and having a thickness of less than 0.5 mm. These are attached in that order and are integrated.
The mat-like body 3 and the porous thin layer 5 have a diameter of 10 to 15 μm.
Is preferably a wet method mat in which glass long fibers are randomly oriented or a dry method mat in which glass long fibers having a diameter of about 20 μm are oriented in two different directions. Are fixed to form a mat-like body. The porous thin layer 5 is a group of small projections less than 0.5 mm in height formed integrally with the sheet-like porous plate 4, or a height of 0.5.
It may be replaced with a rib group of less than mm, or may be eliminated. The sheet-shaped perforated plate 4 has a thickness of 0.5 mm among paper-making separators generally used in lead-acid batteries.
Those having a length of less than 0.1 mm can be applied, but those having a diameter of 0.15 to 0.4 mm are particularly preferable. This material is mainly composed of hydrophilic polyethylene fibers, and is composed of a small amount of synthetic resin fibers, a curing agent, and diatomaceous earth and other silica powders. The storage battery of the present invention contains less silica powders and contains 15% by mass of a sheet-shaped porous plate. Hereafter, it is desirable that the content is preferably 10% by mass or less, and the average pore size is 2 μm or more. A micropore separator made of polyethylene and a large amount of silica fine powder and having an average pore diameter of less than 2 μm by an extrusion method has low sealing reaction efficiency and cannot be used from the viewpoint of durability. The maximum pore diameter is required to be 50 μm or less in order to prevent the occurrence of short circuit. Further, if the amount of silica powder is large, it is not preferable because the silica fine particles forming a gel are deposited and fixed to reduce the amount. Reference numeral 6 is a positive electrode plate, and 6'is a tab of the positive electrode plate. A lead alloy substantially free of antimony, for example, a Pb-Ca-Sn-Al alloy is used for the lattice substrates of the negative electrode plate 1 and the positive electrode plate 6. The negative electrode plate 1, the separator 2, and the positive electrode plate 6 are laminated in this order, and the electrode plate group is formed in a state where the mat-like body 3 is brought into contact with the positive electrode plate 6 and strongly pressed against each other, and the electrode plate group is formed in the battery case 7. It is stored.

The wall surface of the battery case parallel to the electrode plate group strongly presses the electrode plate group, and when several cells are stacked horizontally, the bending strength is sufficiently large so as not to be depressed by the gravity of the upper cell. It is desirable to have However, when the storage battery group is held by a metal box or frame, the bending strength of the wall surface of the battery case may be slightly small.

[0010] 8 is a gel electrolyte, less than 10% by mass,
Desirably, the main component is 5.0 to 8.0 mass% of silica fine particles and dilute sulfuric acid, but a small amount of soluble sulfate,
For example, about 1% by mass of sodium sulfate, magnesium sulfate, lithium sulfate, aluminum sulfate, etc., and 0.75
It is preferably 1.0 to 3.0% by mass or more and 4.0% by mass or less.
It contains 0% by mass of phosphoric acid, and these sulfate and phosphoric acid are necessary components from the viewpoint of storage battery performance. The former is an effect that when the storage battery is over-discharged and the sulfuric acid in the gel electrolyte is consumed, it keeps the electrolyte in a good gel state and prevents lead ions from eluting from the electrode plate and causing a short circuit. There is. The latter migrates to the positive electrode plate in the charged state to become lead phosphate, which has the effect of preventing corrosion of the lattice and preventing softening / falling off of the active material. If the added amount is less than 0.75% by mass or significantly exceeds 3.0% by mass, for example, more than 4.0% by mass, the life of the storage battery is rather adversely affected. This phosphoric acid returns from the positive electrode plate to the electrolytic solution due to discharge, and has the action of maintaining the gel state of the electrolytic solution when the sulfuric acid concentration of the electrolytic solution decreases. Incidentally, instead of the above-mentioned sulfate and phosphoric acid, even if a phosphate such as sodium phosphate, magnesium phosphate, lithium phosphate, aluminum phosphate, etc. is added, these are dissociated in the gel electrolyte. Since they exist as respective ions, they have the same meaning. Furthermore, since phosphoric acid migrates to the positive electrode plate by charging, the effective addition amount varies slightly depending on the thickness of the positive electrode plate and the ratio of the electrolytic solution amount to the positive electrode active material amount. The effective phosphoric acid amount tended to increase as the electrode plate became thinner and the ratio of the electrolyte amount decreased.

The gel electrolyte 8 is disposed in a state in which it is filled in the voids around the electrode plate group and most of the pores of the separator 2, and also partially in the pores of the positive and negative electrode active materials. Exists.

The gel electrolyte is prepared by injecting into the cell a sol-like substance in which fine silica particles having a diameter of 5 to 40 nm are dispersed in water, for example, a trade name Snowtex, which is a mixture of colloidal silica and dilute sulfuric acid. Obtainable. The mixture of colloidal silica and dilute sulfuric acid is a low-viscosity sol at the beginning, and can be easily impregnated into the large pores of the separator. The active material of the positive and negative electrode plates contains relatively large pores and fine pores. Therefore,
Even the silica fine particles in the sol-like electrolyte are bound to water molecules, albeit weakly, to form a hydrate, and their size is so large that they cannot enter the fine pores of the active material. , Only large pores are impregnated.

As a result, in the vicinity of the electrode plate surface, a larger amount of silica than the prepared amount is present. The sol containing silica and dilute sulfuric acid injected into the cell is gelated by leaving van der Waals bonds between oxygen of silica and hydrogen of sulfuric acid when left standing. Since this binding force is weak, it exhibits a so-called denaturation in which the gel is mechanically or physically stimulated to become a sol. The particles of colloidal silica are
It is preferable to use a large number of linked materials such as thread-shaped, ring-shaped, or cage-shaped ones, rather than those that exist independently, because a hard gel state is exhibited even if the amount of silica is reduced.

9 is a fiber made of glass or synthetic resin,
Alternatively, it is a block-shaped body made of a synthetic resin foam or the like, and is arranged at the side end or the upper end of the gel electrolyte,
It has the function of holding down the gel electrolyte and protecting it, as well as holding a small amount of separating liquid generated from the electrode plate group.

(10) is a negative electrode strap, (11) is an exhaust valve, (12) is an upper lid, (13) is a negative electrode terminal, (14)
Is a positive electrode terminal.

[0016]

EXAMPLE Next, the charge / discharge cycle life performance of the sealed lead acid battery provided with the gel electrolyte according to the present invention will be shown in comparison with that of the conventional gel type sealed type and retainer mat type.

The electrode plate group consists of a positive electrode plate 6 having a thickness of 3.0 mm.
A single cell structure consisting of one sheet and seven sheets of negative electrode plates having a thickness of 2.1 mm and a 5-hour rate discharge capacity of about 20 ampere hour (Ah), and the thickness between the positive and negative electrode plates, that is, the separator portion is 2.
It was set to 2 mm and these values were the same for all the test storage batteries.

The positive and negative electrode plates were formed by tank formation. This is because in dilute sulfuric acid containing phosphoric acid, the current efficiency during formation of the positive electrode plate becomes low. A Pb-Ca-Sn-Al alloy was used for the grid of the positive and negative electrodes. Further, as a sheet-like perforated plate, the maximum pore size is 25 μm, and the average pore size is about 1
Among the conventional separators mainly composed of 0 μm hydrophilic polyethylene fiber, the amount of silica is small, about 5% by mass, and the thickness is 0.2 mm.
I chose a thin one and used it mainly. As the mat-like body, a mat by a dry method mainly containing long glass fibers with a diameter of 19 μm was used, and as a thin porous layer, a mat by a wet method mainly containing long glass fibers with a diameter of 12 μm was used. The thickness of the mat-like body is adjusted by changing the thickness according to the thickness of the sheet-like perforated plate and the presence or absence of the thin porous layer, and the degree of pressure when assembling without electrolyte is 30 kg / dm ² or more. The liquid was impregnated and kept at 10 kg / dm ² or more. The constitution of the separator and the gel composition in each of the test storage batteries of Examples and Comparative Examples are as shown in Table 1. Examples are No1 to N
o. 9, the comparative example is No. 10-No. It is 14.

The conventional storage battery No. A to C are gel type, and the separator part has a diameter of 1.5 mm.
A corrugated perforated plate with a thickness of 1.6 mm and a non-woven fabric made of synthetic resin fiber with a thickness of 0.3 mm attached to both sides. B has a rib with a height of 1.5 mm and a rib with a thickness of 0.2 mm on one side. The thickness of the substrate on the surface is 0.5 mm and the average pore size is 1.0 μm.
Is a microporous plate with a rib of 1.5 mm facing the positive electrode plate, and C is a retainer mat made of glass fiber having an average diameter of 0.7 μm. In addition, the conventional storage battery No. D is a re-themed type, and a retainer mat made of short glass fibers having an average diameter of 1 μm or less was used, and each was tested. In the electrolytic solution, 1.0% by mass of sodium sulfate was dissolved in dilute sulfuric acid.

The charging / discharging cycle condition of the storage battery is that discharging is 2
The charging time was 0.5 h at 0 A, the charging time was 5.5 h at 2.0 A, and the ambient temperature was room temperature. The storage battery performance was confirmed by obtaining the capacity when the final voltage was 1.50 V / cell at 20 A discharge, and the life of the storage battery was evaluated by the number of cycles at which the discharge capacity was 60% of the initial value. The storage battery was placed horizontally and the electrode plate was placed horizontally.

[0021]

[Table 1]

Table 1 shows the results of the comparison test of the constitution and contents of the test storage battery, the initial capacity and the charge / discharge cycle life.

In the storage batteries A and B using the conventional gel electrolyte, the pressure on the electrode plate was insufficient, and the service life was short due to deterioration of the positive electrode plate and reduction of the electrode plate spacing. In C where the retainer mat having a large surface area was used as the separator and the electrolytic solution was in the form of gel, the gap between the electrode plates could be maintained, but the retainer mat and the silica fine particles for forming the gel overlap, and therefore sulfuric acid is used. The amount was small and the initial performance was poor, and the life performance was poor. Even if a glass mat having a small surface area is brought into contact with the positive electrode plate and strongly pressed, if the thickness of the sheet-shaped perforated plate is as large as 0.7 mm (Comparative Example No. 10), the porosity of that portion is increased. , The electric resistance was increased, the movement of oxygen gas was hindered, and both the initial capacity and the life performance were deteriorated.

The effect of the amount of phosphoric acid added to the gel electrolyte was 0.75 to 3.0% by mass (Example No. 4 to
No. In 7), the life was remarkably long and the initial performance was excellent. When the amount of phosphoric acid is 0.4% by mass (Comparative Example No. 1
2) It has a short life. Although the reason is unknown, in the battery (Comparative Example No. 13) in which a large amount such as 5.0% by mass was added, a minute short circuit was observed along with the crack generated in the gel due to the dissolution / protrusion of lead. It was Looking at the influence of the amount of silica constituting the gel, the initial capacity became smaller as the amount of silica increased, and remarkably decreased especially in the case of more than about 10% by mass (Comparative Example No. 14).

Regarding the life performance, the larger the amount of silica in the range of 5 to 8 mass% (Examples No. 1 to No. 8), the longer the life was, but the storage battery of 13.0 mass% (Comparative example No. 8). 1
In 4), it was rather inferior. Incidentally, in the storage battery provided with the gel electrolyte according to the present invention, the amount of silica fine particles was 5.
Even if the amount is reduced to 0% by mass, the amount of silica powder contained in the sheet-like porous plate constituting the separator is small,
Moreover, since the fiber diameter of the mat-like body is large and its surface area is small, the amount of silica fine particles deposited and fixed on the separator is small, and a sufficiently good gel state is exhibited.

When the amount of silica powder contained in the sheet-like porous plate is more than 15% by mass, the gel state becomes soft when the silica fine particles in the gel electrolyte are 5.0% by weight. Since it became defective, the experiment with the storage battery was not conducted.

[0027]

INDUSTRIAL APPLICABILITY The present invention is to improve the life performance of a gel type storage battery by improving the gel content including the separator structure and additives without lowering the initial performance.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part.

[Explanation of symbols]

1 ... Negative electrode plate 1 '... negative electrode plate ear 2 ... Separator 3 ・ ・ ・ Mat-like body 4 ... Sheet-shaped perforated plate 5 ... Porous thin layer 6 ... Positive electrode plate 6 '... Positive electrode plate ear 7 ... Battery case 8 ... Gel electrolyte 9 ... Block-shaped porous body 10 ... Negative electrode strap 11 ... Exhaust valve 12 ... Top lid 13 ... Negative electrode terminal 14 ... Positive electrode terminal

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 10/10 H01M 10/10 G 10/12 10/12 K F term (reference) 5H021 AA06 BB02 BB11 CC02 CC03 CC04 CC05 CC09 EE02 EE22 EE23 EE28 EE33 HH01 HH03 HH06 HH10 5H028 AA01 AA05 AA06 CC02 CC05 CC08 CC24 EE02 EE05 EE08 FF02 FF09 FF10 HH02 HH05

Claims (3)

[Claims] 1. A mat-like body having a diameter of 10 μm or more and 25 μm or less and mainly composed of long glass fibers or synthetic resin fibers and having a thickness of 0.5 mm or more, and a maximum pore diameter of 50 μm or less and an average pore diameter of 2
A sheet-like porous plate having a thickness of less than 0.5 mm and a silica content of 15% by mass or less and a thickness of less than 0.5 mm is brought into contact with or integrated with each other to form a separator, and a small amount of soluble sulfate and 0.75% by mass. % Or more and 4.0% by mass or less, preferably 1.0% by mass or more and 3.0% by mass or less, and
A gel electrolyte consisting of dilute sulfuric acid containing less than 10% by mass, preferably 5.0% by mass or more and 8.0% by mass or less of silica fine particles, and a cell at least in the pores of the separator and around the electrode plate group. The electrode plate group is disposed in most of the inner space, and the electrode plate group is formed by alternately stacking positive electrode plates and negative electrode plates with separators interposed therebetween, and the positive electrode plates are in pressure contact with the mat-shaped body of the separator. A sealed lead-acid battery with a gel electrolyte characterized by the following. 2. A diameter of 10 μm or more and 25 μm on the other surface of the sheet-like porous plate of the separator on which the mat-like body is not in contact.
The gel electrolyte according to claim 1, wherein the following porous thin layers mainly made of long glass fibers or synthetic resin and having a thickness of less than 0.5 mm are arranged, brought into contact with or integrated with each other. Sealed lead acid battery provided 3. A small projection group or rib group having a height of less than 0.5 mm is integrally formed on the other surface of the sheet-shaped porous plate of the separator not contacting the mat-shaped body. A sealed lead-acid battery provided with the gel electrolyte according to Item 1.