JP2004185980A - Lead-acid battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead-acid battery capable of restraining a welding defect of a connection part between cells caused by intrusion of a resin into a blow hole formed in the connection part between the cells of a mono-block type lead-acid battery with a plurality of the cells integrated, and of exerting an excellent corrosion-resisting effect of Ag in using a Pb-Sn-Ag-based alloy, and having stable life performance. <P>SOLUTION: This lead-acid battery is characterized by using the Pb-Sn-Ag-based alloy for the connection parts between the cells, and by using a denatured polyphenylene ether resin (PPE) or an acrylnitrile-butadiene-styrene resin (ABS) for a battery jar resin material. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lead-acid battery, and more particularly to an improvement in welding at a connection between cells.
[0002]
[Prior art]
In the lead storage battery, a monoblock type storage battery in which a plurality of unit cells (hereinafter, referred to as cells) are integrated is often used. In these storage batteries, after an electrode plate group (element, hereinafter referred to as an element) as a power generation element is inserted into a resin container made up of a plurality of cells, each of the elements is electrically connected to each other by a cell-to-cell connection portion via a partition. Connected. There are several methods for the connection, but the resistance welding method is widely adopted because it has the highest reliability and is excellent in mass productivity. In this method, the connection between the cells is brought into contact with each other through a hole provided in the cell wall of the battery case, and the connection between the cells is pressurized with a water-cooled copper electrode. This is a method in which electricity is supplied for a period of time to generate heat, and the inter-cell connection portions are melted and joined.
[0003]
As is well known, the main cause of the deterioration of the lead-acid battery is corrosion of the positive and negative electrode grids. However, since the potential is applied to the connection between the cells, corrosion is inevitable. In particular, if the inter-cell connection portion is insufficiently welded and a gap is present, corrosion at that portion may proceed, and the storage battery may have a short life.
[0004]
Conventionally, a Pb-Sn alloy containing 1.0 to 5.0% by mass of Sn has been generally used for the inter-cell connection part with emphasis on meltability.
[0005]
The Pb-Sn-based alloy has a crystal structure composed of lead-rich primary crystals and Sn-rich phases precipitated at grain boundaries between primary crystals. Corrosion is caused by Sn precipitated at grain boundaries. Proceeds along the rich phase (intergranular corrosion). In addition, since the volume of the corrosion product is larger than that of the original material, cracks are generated in the crystal grain boundaries, and in the worst case, the intercell connection may be broken along the grain boundaries.
[0006]
In particular, the above-mentioned corrosion becomes a fatal problem on the negative electrode side of a control valve type lead-acid battery having a structure in which a connection portion between cells is exposed on an electrolytic solution. That is, when the inter-cell connection is exposed from the electrolyte, a reaction in which oxygen gas generated at the positive electrode is reduced at the negative-cell inter-cell connection tends to occur, as shown in equation (1). Once it becomes PbSO ₄ , a charging reaction that returns to Pb is unlikely to occur as in a lead-acid battery in which the electrolyte is sufficiently present.
[0007]
Pb + 1 / 2O ₂ + H ₂ SO ₄ → PbSO ₄ + H ₂ O (1)
Therefore, the corrosion reaction represented by the above formula (1) proceeds irreversibly, and PbSO ₄ is accumulated. When 1 mole of Pb is changed to PbSO _4, the volume becomes 2.6 times. Therefore, a stress accompanying the volume expansion of the corrosion product is applied to the grain boundary of the inter-cell connection portion, and there is a problem that the breakage of the portion is more likely to occur than other lead-acid batteries.
[0008]
As a method for improving the corrosion resistance of the Pb-Sn-based alloy, Japanese Patent Application Laid-Open No. Sho 62-64057 and Patent No. 1748824 propose that a suitable amount of Ag is contained in the Pb-Sn-based alloy.
[0009]
However, in a monoblock type storage battery in which a plurality of cells are integrated, a battery case made of a propylene-based resin generally used, specifically, an ethylene propylene copolymer (hereinafter abbreviated as EPP) is used. In the case where the inter-cell connection portions were joined to each other via the partition walls, the corrosion resistance of Ag was not sufficiently exhibited even when a Pb-Sn-Ag alloy was used for the inter-cell connection portions.
[0010]
This is because, as a result of investigating the welded part of the cell-to-cell connection part joined by the resistance welding method, blowholes were generated in the welded part (nugget) of the joint part during welding, and the surrounding resin softened at a high temperature during welding was blown out. This is because insufficient welding occurs due to biting into the blowhole, and the portion is locally corroded, so that even if Ag is added, the corrosion resistance effect has not been fully utilized.
[0011]
[Problems to be solved by the invention]
The problem to be solved by the present invention is that resin entrapment in the welded portion is suppressed, stable welding of the inter-cell connection portion is possible, corrosion of the inter-cell connection portion due to poor welding is reduced, and an excellent An object of the present invention is to provide a lead storage battery having a life performance.
[0012]
[Means for Solving the Problems]
As means for solving the problem, according to claim 1, the content of silver (Ag) is 0.05% by mass or more and 0.5% by mass or less, and the content of tin (Sn) is 0.5% by mass. As described above, it has a connection part between cells made of a Pb-Sn-Ag alloy of 5% by mass or less, and uses a modified polyphenylene ether resin or acrylonitrile-butadiene-styrene resin as a resin material for a battery case. It is.
[0013]
When a Pb-Sn-Ag alloy is used for a cell-to-cell connection part and an EPP resin that is generally widely used as a battery case material is used, a weld generated due to a low softening point of the resin. Although the effect of corrosion resistance of the Pb-Sn-Ag alloy was not sufficiently obtained due to biting of the resin into the blowholes formed at the time (poor welding), a high softening point was used instead of the EPP resin. By using a modified polyphenylene ether resin (hereinafter abbreviated as PPE resin) or an acrylonitrile-butadiene-styrene resin (hereinafter abbreviated as ABS resin), biting of the resin into the blowhole is suppressed. As a result, it was found that poor welding at the inter-cell connection portion was reduced, and the original corrosion resistance of the Pb-Sn-Ag alloy could be maximized.
[0014]
When the content of Ag in the Pb-Sn-Ag-based alloy is less than 0.05% by mass, the effect of the corrosion resistance of Ag is reduced, and the addition of more than 0.5% by mass hardly improves the corrosion resistance. The content is preferably 0.05% by mass or more and 0.5% by mass or less. On the other hand, if the content of Sn is less than 0.5% by mass, the strength of the alloy itself is reduced, the connection between cells is excessively deformed, welding becomes difficult, and practicality is lost. On the other hand, if it exceeds 5% by mass, the corrosion resistance is reduced due to Sn itself. Therefore, it turned out that 0.5 mass% or more and 5 mass% or less are preferable.
[0015]
【Example】
The effects of the present invention will be described in detail based on examples.
(Example 1)
In the Pb-Sn-Ag alloy, an alloy in which the content of Sn is fixed to 2% by mass and the content of Ag is variously changed in the range of 0 to 0.7% by mass is prepared, and the alloy at the connection part between cells is prepared. Prepared as
[0016]
The positive and negative electrode active materials are applied to positive and negative electrode grids made of a Pb-Ca-Sn-based alloy, and the dried positive and negative electrode plates are alternately laminated via a fine glass fiber separator. Thus, an element for a control valve type lead-acid battery having a nominal voltage of 12 V and a rated capacity of 20 Ah (20 hR) was produced.
[0017]
As the battery case resin, three types of the conventional EPP resin, the PPE resin of the present invention, and the ABS resin were prepared.
[0018]
A mold having a shape in which a strap and an inter-cell connection portion are integrated is filled with a molten lead alloy, the element is inverted, and an electrode plate ear is inserted into the mold, and a strap, an inter-cell connection portion, and an electrode plate are inserted. An element having a strap made of seven kinds of alloys and a cell-to-cell connection portion was produced by a cast-on-strap (COS) method for integrally forming the ear portion. The thickness of the strap was 5 mm.
[0019]
Next, the element was inserted into a battery case having a partition wall thickness of 1.4 mm, and the connection portions between cells were joined to each other by a resistance welding method to assemble a control valve type lead storage battery.
[0020]
Dilute sulfuric acid having a predetermined specific gravity was injected into the storage battery, and formed in a battery case.
[0021]
In order to evaluate the corrosion resistance of the inter-cell connection part of each of the storage batteries, they were subjected to a float charging test. The test conditions are shown below.
[0022]
Charging voltage: 13.65V
Maximum charging current: 4A
Test temperature: 60 ° C
Test period: 10 months When the above test was completed, each storage battery was disassembled, the inter-cell connection portion was taken out, and its corrosion state was investigated.
[0023]
FIG. 1 is a perspective view of an essential part showing a state in which inter-cell connecting portions are joined via a partition between inter-cells by a resistance welding method, wherein 1 is an inter-cell connecting portion, 2 is a strap, and 3 is a battery case. The partition between cells is shown respectively.
[0024]
In order to evaluate the corrosion resistance of the inter-cell connection, the inter-cell connection was pulled in the direction of the double arrow shown in FIG. 1 to break it, and the corrosion state of the fractured surface was observed. FIG. 2 is a front view of an essential part schematically showing a fractured surface thereof. Reference numeral 4 denotes a penetrating portion of the battery case, that is, an initial welding area, 5 denotes a corroded portion, and 6 denotes a remaining alloy portion. The degree of corrosion (corrosion rate) was represented by the area ratio (%) of the corroded portion 5 to the initial welding area 4. The result is shown in FIG.
[0025]
As shown in FIG. 3, the Pb-Sn based alloy containing no Ag and the corrosion rate when the conventional battery case resin EPP was used was 55%, whereas the PPE resin of the present invention was changed from the EPP resin. Alternatively, it was reduced to about 40% by changing to ABS resin. Further, in the resin battery case of the present invention, the corrosion resistance was further improved by using a Pb-Sn-Ag alloy for the inter-cell connection part, and the corrosion resistance was improved as the content was increased. Specifically, the corrosion rate of the Ag content of 0.05% by mass is about 25%, and that of 0.2% by mass is reduced to about 12%. In the latter case, the Pb- The corrosion rate was 1/4 or less as compared with the storage battery using the Sn-based alloy. However, when the Ag content is 0.3% by mass or more, the improvement in corrosion resistance reaches a plateau, and considering the high price of Ag, it can be said that the limit is 0.5% by mass.
[0026]
On the other hand, in the conventional EPP resin battery case, by containing 0.05 mass% of Ag, the corrosion rate of the Pb-Sn alloy was reduced to 40% as compared with 55%, but the Ag content was further increased. Even so, the corrosion rate was not reduced. As described above, it has been clarified that the conventional EPP resin does not exert the corrosion resistance effect of Ag because the resin bites into the blowhole at the fusion part of the inter-cell connection part and the welding state is not good.
[0027]
Next, the inter-cell connecting portions having a diameter of 13.5 mm produced using the above-mentioned match gold were joined to each other by a resistance welding method, and a rotational force (shear stress) was applied to the joined portion with a torque wrench to join the joints. The maximum shear stress when the part was threaded was measured. FIG. 4 shows the results obtained by determining the relationship between the amount of Ag (% by mass) in the alloy for connection between cells subjected to the test and the maximum shear stress (N · cm).
[0028]
As shown in FIG. 4, when the Ag content is 0.1% by mass, the maximum shear stress is 1352 (N · cm) when the battery case resin material is the conventional EPP, and is 1420 (N · cm) when the ABS of the present invention is used. ), 1519 (N · cm) for PPE resin. From this measurement result, by changing the battery case material from EPP to ABS or PPE, the above-mentioned resin was not caught and the weldability was improved, and the connection between cells was improved. It was found that the strength of the weld surface between the parts increased. In the conventional EPP resin, even when the Ag content was increased, the maximum shear stress hardly increased and the effect of Ag was not recognized. On the other hand, in the case of PPE and ABS, the maximum Shear stress tended to increase. This is because the softening temperature of the resin is high, the biting of the resin into the blowhole formed in the molten portion of the connection between the cells is suppressed, stable welding is performed, and the strength of the alloy due to the presence of Ag is increased. It can be said that the maximum shear stress increased due to a synergistic effect with the increase.
(Example 2)
In the Pb-Sn-Ag alloy, an alloy in which the Ag content is fixed to 0.1% by mass and the Sn content is variously changed in the range of 0 to 7% by mass is prepared, and the alloy at the connection portion between cells is prepared. Prepared as
[0029]
After forming the strap and the inter-cell connection portion by the COS method using these match moneys and joining the inter-cell connection portions by the resistance welding method as in the first embodiment, the same 12 V, as in the first embodiment, A control valve type lead-acid battery of 20 Ah was manufactured.
[0030]
These storage batteries were subjected to the same float charging test as in Example 1, and after the test, the corrosion state of the inter-cell connection was investigated by the same method as in Example 1.
[0031]
As the battery case resin, three types of conventional EPP resin, PPE resin of the present invention and ABS resin were used.
[0032]
FIG. 5 shows the result of determining the relationship between the corrosion rate (%) and the Sn content (% by mass).
[0033]
As shown in FIG. 5, when the Sn content is 0.5% by mass or more and 5% by mass or less, a synergistic effect between the PPE or ABS resin container of the present invention and the Pb-Sn-Ag alloy is obtained, and the corrosion resistance is improved. However, if the Sn content is less than 0.5%, the strength of the alloy itself is insufficient, so that when pressure is applied to the inter-cell connection part during resistance welding, it is excessively deformed, making welding difficult and difficult in practical use. Problem has occurred. On the other hand, when the Sn content was more than 5% by mass, the corrosion resistance of the alloy itself was reduced due to Sn. From these results, it was found that the Sn content for obtaining the effect of the present invention was 0.5% by mass or more and 5% by mass or less.
[0034]
In the above embodiment, the method of integrally forming the strap, the inter-cell connection portion, and the electrode plate ear by COS has been described. However, the inter-cell connection portion and the electrode plate ear formed in advance by casting are connected to each other by a burner. Using an element in which the inter-cell connection, electrode plate ears and straps are integrally formed by supplying additional lead of the same alloy composition as the inter-cell connection while partially melting, the inter-cell connection by resistance welding It goes without saying that the same effect can be obtained when welding them together.
[0035]
【The invention's effect】
In a lead storage battery of a monoblock type in which a plurality of cells are integrated, even when a Pb-Sn-Ag-based alloy having excellent corrosion resistance is used as an alloy of a connection portion between cells when cells are connected by a resistance welding method. According to the present invention, however, according to the present invention, the welding failure occurred due to the penetration of the battery case resin into the blowhole formed at the time of welding, and the effect of improving the corrosion resistance of Ag was not sufficiently obtained. Pb-Sn-Ag alloy having a silver (Ag) content of 0.05% by mass or more and 0.5% by mass or less and a tin (Sn) content of 0.5% by mass or more and 5% by mass or less By using PPE or ABS resin instead of the conventional EPP resin for the battery case material, biting of the resin at the welded portion is suppressed, stable welding is possible, and the excellent corrosion resistance of Ag Can be used effectively, and lead-acid batteries, especially Excellent life performance in Gobenshiki lead-acid battery is obtained, its industrial effect is very large.
[Brief description of the drawings]
FIG. 1 is a perspective view of an essential part showing a state where inter-cell connection portions are welded and joined by a resistance welding method.
FIG. 2 is a schematic front view of a main part showing a fractured surface of a connection part between cells.
FIG. 3 is a diagram showing a relationship between an Ag amount (% by mass) and a corrosion rate (%) in Example 1 of the present invention.
FIG. 4 is a diagram showing the relationship between the amount of Ag (% by mass) and the maximum shear stress (N · cm) in Example 1 of the present invention.
FIG. 5 is a diagram showing the relationship between the amount of Sn (% by mass) and the corrosion rate (%) in Example 2 of the present invention.
[Explanation of symbols]
1 Cell connection part 2 Strap 3 Cell partition part of battery case 4 Cell partition penetration part (initial welding area)
5 Corroded part 6 Residual alloy part

Claims (1)

From a Pb-Sn-Ag alloy having a silver (Ag) content of 0.05% by mass or more and 0.5% by mass or less and a tin (Sn) content of 0.5% by mass or more and 5% by mass or less Between the cells,
A lead-acid battery using a modified polyphenylene ether resin or an acrylonitrile-butadiene-styrene resin as a resin material of a battery case.

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