JPH11111329A - Lead-acid battery and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a lug part in a strap welded part of an negative electrode side from being cut and lost even at high temperatures, in a hybrid type lead- acid battery in which a Pb-Sb alloy grid body is used for a positive electrode plate current collector and a Pb-Ca alloy grid body is used for a negative electrode plate current collector. SOLUTION: A surface of a lug part 1 of a negative electrode grid body and a fillet 5, which is formed on a root part of the lug part 1 connected to a strap 2, are composed of a tertiary metal 13. The tertiary metal 13 is a metal which has a solidification temperature of less than the eutectic temperature of a Pb-Sb alloy which constitutes a negative electrode strap 2 and does not contain Sb. An eutectic 7 which is crystallized when the a Pb-Sb alloy constituting the strap 2 coagulates is disposed to be isolated from the root of the lug part land to have a constitution, where the fillet 5 ranges with the tertiary metal 13 of the surface of the lug part. Such a constitution is obtained by welding the strap to the lug part having a coated layer of the tertiary metal by COS(cast on strap) method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead-acid battery and a method of manufacturing the same, and more particularly to strap welding of an electrode group. This lead-acid battery and a method of manufacturing the same are based on a hybrid battery for automobiles using a Pb-Sb-based alloy grid as a current collector for an anode plate and a Pb-Ca-based alloy grid as a current collector for a cathode plate. (Hereinafter abbreviated as “HB battery”).

[0002]

2. Description of the Related Art Conventionally, as lead-acid batteries for automobiles, both positive and negative electrode plates are made of Pb-Sb-based alloy lattices (specifically, Pb-
Conventional type batteries (hereinafter abbreviated as “CV batteries”) using an Sb—As alloy or a lattice body such as a Pb—Sb alloy were common. Since about 20 years ago,
Both the positive and negative plates are Pb-Ca based alloy lattices (specifically, P
A so-called calcium battery using a b-Ca alloy or a lattice body such as a Pb-Ca-Sn alloy (hereinafter referred to as "Ca
(Abbreviated as "battery") has come into practical use. C
The battery a uses a Pb-Ca-based alloy having a higher hydrogen overpotential than the Pb-Sb-based alloy for the lattice, so that the generation of hydrogen gas at the cathode is small and the electrolyte is slightly reduced, so-called maintenance-free ( (Hereinafter abbreviated as “MF”). However, Ca batteries also had disadvantages. The problem is that the deformation (referred to as “elongation”) of the grid of the anode plate causes the active material to fall off or a short circuit (short circuit), thereby shortening the battery life. Cause "growth" of the anode plate grid is intergranular corrosion stress and Pb-Ca system alloy when PbO ₂ and PbSO ₄ is alternately generated in the charge-discharge process (preferentially occurring corrosion at grain boundaries) It is. Since the “elongation” of the grid of the anode plate becomes particularly remarkable at high temperatures, the recent situation in which the temperature of the engine room of an automobile increases and the battery temperature reaches about 90 ° C. is not preferable for the Ca battery.

Under such circumstances, a lead-acid battery that has been put into practical use has been developed as a so-called hybrid battery using a Pb-Sb-based alloy lattice for an anode plate and a Pb-Ca-based alloy lattice for a cathode plate ( Hereinafter, abbreviated as “HB battery”). The HB battery uses a Pb-
By changing from a Ca-based alloy to a Pb-Sb-based alloy, the problem of "elongation" of the anode plate lattice, which was remarkable in Ca batteries, has been solved. The Pb-Sb based alloy lattice is made of Pb
-The creep strength at high temperatures is larger than that of the Ca-based alloy lattice, and it is difficult to deform even under the above-mentioned stress, and
The fact that the corrosion of the Pb-Sb-based alloy is not intergranular corrosion but overall corrosion (the crystal grains themselves are uniformly corroded) contributes to solving the problem of the Ca battery. However, by changing the anode plate lattice alloy from a Pb-Ca-based alloy to a Pb-Sb-based alloy, the MF property of the HB battery is inferior to that of the Ca battery. Pb-Sb
Sb eluted into the electrolyte from the anode plate lattice of the base alloy
This is because they are deposited on the surface of the cathode plate to lower the hydrogen overvoltage, and as a result, the amount of the electrolyte solution decreases more than in the Ca battery.
However, since the HB battery uses a Pb-Ca-based alloy having a high hydrogen overvoltage for the cathode plate lattice, the positive and negative plates both use a more electrolytic solution than the CV battery that uses a Pb-Sb-based alloy for the lattice. The decrease is small enough.

[0004] As described above, the HB battery has been widely used for practical purposes by improving the durability at a high temperature, which is a weak point of the Ca battery, while sacrificing the MF property to some extent. Problems have come to be recognized. that is,
When the HB battery is used at a high temperature of about 90 ° C., the grid ears of the cathode plate are cut off due to corrosion at the base of the strap (near the fillet formed when the strap is welded to the ear). It is.

[0005] Lead-acid batteries for automobiles include HB batteries,
In both the Ca battery and the CV battery, a Pb-Sb alloy (Sb content: 2 to 3% by weight) is used for the strap. Was recognized as. This is because, on the anode side, Pb of the lattice or the strap changes to PbO ₂ or PbSO ₄ with charging and discharging, and does not return to Pb again. However, there has been no substantial problem since the life of the electrode plate expires earlier. On the other hand, on the cathode side, PbSO ₄ generated in the lattice or strap during discharging returns to Pb during charging.
It was thought that there was virtually no need to consider corrosion as a problem. However, in practice, when the HB battery is used at a high temperature of about 90 ° C., corrosion occurs on the cathode side within a short period in which corrosion on the anode side hardly causes a problem,
It was found that there was a concern that the ear would be cut near the fillet.

Here, a lead storage battery to which the present invention is applied will be described. The lead storage battery is composed of a plurality of electrode plates contained in a cell, the anode plate is a pair of anode plates, and the cathode plate is a pair of cathode plates. Is welded with a Pb alloy block called a strap. FIG. 2 illustrates this situation.
(A) is a front view, (b) is a side view. The straps 2 are welded to the ears 1 (five in the figure) of the lattice body, and the plurality of ears 1 are electrically connected by the straps 2. There are several ways to weld the strap. Among them, a burner method in which a lug is sandwiched between comb teeth of a chiller and a mold called a comb tooth, a Pb alloy filler rod is melted with a gas burner and poured into a mold to form a strap and a lug is welded. ,
A typical method is a cast-on-strap method (hereinafter abbreviated as "COS method") in which a molten Pb alloy is poured into a mold in the form of a strap, and the ears are immersed in the molten metal to solidify the molten alloy and perform welding. And has been put to practical use. In particular, since the COS method is easy to automate and has high productivity, its introduction has been promoted in place of the burner method.

FIG. 3 shows a cross section of the strap welding portion by the COS method (a cross section taken along line XX of FIG. 2B). FIG. 4 shows the process of reaching the welding state shown in FIG. 3 for one ear in the electrode plate group. FIG. 4 (a) shows the mold 3
(Only the bottom is shown in the figure)
This shows a state immediately after the lattice member ears 1 of the Pb-Ca alloy are immersed in the molten metal 4 of the -Sb alloy. At this stage, since the ear 1 has a low temperature, the ear 1 is hardly wet by the molten metal 4 and the contact angle θ of the molten metal with respect to the ear is sufficiently large. FIG. 4B shows a stage after a certain time has passed from FIG. 4A, and FIG. 4C shows a stage after a certain time has passed from FIG. The ear 1 absorbs heat from the molten metal 4 with the elapse of time and the temperature of the ear 1 itself rises. In addition, as the molten metal wets to the ears, the contact angle θ becomes 90 degrees or less in (c), which leads to a “wet state”, and a fillet (meniscus) 5 as evidence thereof is beginning to be formed. FIG. 4D shows a state immediately before the welding is completed. The wetting of the molten metal with respect to the ears proceeds sufficiently, the fillet 5 grows large, and the contact angle θ is sufficiently small. In such a state, welding is completed, and a fillet 5 is formed at the base of the ear 1 to the strap.

The growth state of the fillet shown in FIG. 4 (d) is a preferable state, and FIG. 5 shows this state from a metallographic point of view. FIG. 5 (a) shows a case where the strap 2 is welded to a cast lattice (cast lattice), and FIG. 5 (b) shows a case where the strap 2 is welded to an expanded lattice (Ex lattice). Is shown. In both cases, a fillet 5 is formed at the base of the ear 1 on the strap lower surface 6. Fillet 5 is strap 2
Is a portion of the Pb-Sb-based alloy that has finally solidified, and is a structure called eutectic 7 in terms of metallography. Eutectic 7 has a composition of 89% by weight of Pb,
Pb containing 11% by weight of Sb but containing very little Sb
b (which may be regarded as substantially pure Pb) and Sb (which may be regarded as substantially pure Sb) containing a very small amount of Pb are crystallized at the same time. Each crystal has a layered structure.

The structure of the ear is different between the case of the cast lattice of FIG. 5A and the case of the Ex lattice of FIG. 5B. In the case of a cast lattice, there is no difference in the structure of the ear between the part inside the strap and the part outside the strap,
The crystal 8 when the lattice body was cast, that is, the solidified structure is maintained as it is. In the case of the Ex lattice, the structure of the ear part is completely different between the part inside the strap and the part outside the strap. The part inside the strap is granular crystal 9, and the part outside the strap is elongated fibrous. Crystal 10 is formed. In the case of the Ex lattice body, the difference in the structure of the ears inside and outside the strap is caused by the difference in the thermal effect on the ears when the strap is welded. Ex
In the lattice body, when a Pb—Ca alloy sheet, which is a raw material thereof, is rolled and expanded, the crystals are elongated in a fibrous form, and “working strain” is accumulated in the fibrous crystal 10. This “working strain” becomes a driving force, and the fibrous crystal 10 is recrystallized by the heat received from the molten metal 4 in the portion inside the strap. The result is a granular crystal 9.
On the other hand, in the part outside the strap, the recrystallization temperature (the temperature required for recrystallization) when welding the strap
Therefore, the structure composed of the fibrous crystals 10 is maintained as it is. In addition, in the case of the cast lattice, the structure of the ear portion does not change before and after welding of the strap, that is, recrystallization does not occur while being affected by the same heat as in the case of the Ex lattice during welding of the strap. For reasons. In the case of the cast lattice, there is no processing history of strength such as rolling and expanding, which was the case with the Ex lattice, and the cast lattice has the "work strain" required for recrystallization.
Is not stored inside.

The following is a description of how such metallographic features contribute to the corrosion of the strap weld on the cathode side. First, the crystal at the ear of the Ex lattice body will be described. From various examination results, the crystal grain boundary 11 newly formed by recrystallization at the edge of the Ex lattice body is Pb
-It has been found that the Ca-based alloy lattice is extremely susceptible to corrosion which causes the ear to be cut. When an Ex lattice is used, there is a greater concern about ear cuts than when a cast lattice is used. On the other hand, when the corrosion resistance of the non-recrystallized portion of the Ex lattice is compared with that of the cast lattice, the Ex lattice is superior. The structure of the non-recrystallized portion of the Ex lattice body has a state in which the crystal grain boundaries are elongated by rolling and are intricately complicated, so that remarkable intergranular corrosion hardly proceeds in the Pb-Ca alloy. I have. Next, regarding the fillet 5. As described above, the Pb-Sb-based alloy constituting the strap contains 2 to 3% by weight of Sb, and the fillet portion formed by solidifying this alloy has a eutectic structure containing 11% by weight of Sb as a whole. Become. The eutectic structure is composed of fine crystals that are substantially Pb and substantially Sb.
Is a structure in which fine crystals are layered, and it can be considered that Sb exists in a state of substantially pure Sb. As is well known, Sb is a metal that is electrochemically more noble than Pb, and the fillet portion of the eutectic structure may be considered to be more electrochemically noble than the ears of the Pb-Ca alloy in contact therewith. (A commonly used Pb-Ca alloy contains small amounts of Ca and Sn, but their amounts are small and can be electrochemically treated as pure Pb.) Therefore, fillet 5
A local cell is formed between and the ear 1 adjacent thereto, which accelerates the corrosion of the ear.
The relationship between the metallographic features around the welded portion of the strap, particularly around the fillet where there is concern about the cut of the ear, and the corrosion are as described above.

Next, means which have been proposed for preventing or suppressing corrosion of the strap weld at high temperatures will be described. The first measure is to change the type of alloy used for the strap. For example, the alloy of the strap 2 is changed from a Pb-Sb-based alloy to a Pb-Sn-based alloy. This makes it possible to almost completely solve the problem of corrosion cutting of the ear. The second means is to cover the strap welding portion, that is, the portion located on the lower surface of the strap at the ear portion, with a Pb-Sn alloy. A specific example is disclosed in
No. 236101. The ear surface is covered with a high-concentration Sn-containing Pb-Sn alloy layer, and the Sn-containing Pb-Sn on the ear surface is located near the ear on the lower surface of the strap.
In this configuration, a Pb—Sn alloy layer is formed so as to be continuous with the alloy layer. To realize this configuration, the surface is made of Pb-50% Sn.
The gazette states that this is only possible by welding the straps to the ears coated with the alloy in a burner manner.

[0012]

Although the problem of corrosion of the cathode-side strap weld of the HB battery at high temperatures and the means of preventing corrosion have been described above, both the first means and the second means have not been described. Insufficient and not always effective. In the first means, the mechanical strength of the strap 2 and the poles 12 connected to the strap 2 is reduced due to the alloy composition. Considering the force (acceleration) acting on the battery when mounted on a vehicle, the reduction in strength is a major problem. To compensate for the decrease in strength, the thickness and width of the strap and pole must be Pb-S
It must be designed to be several tens of percent larger than when using a b-based alloy. Such a situation goes against the current situation in which all vehicles are required to be reduced in weight in order to improve the fuel efficiency of automobiles. The above-mentioned second means can be realized only by performing strap welding by a burner method, and it cannot be applied to a COS method widely used as a method for welding a strap. Furthermore, when the above-mentioned second means was verified, it was found that the configuration described in the same publication as “Sn on the ear surface melts and covers the lower surface of the strap between adjacent ear portions” with good reproducibility. It cannot be admitted, and the feasibility is questionable even when the second means is a burner method.

The problem to be solved by the present invention is that the conventional means is insufficient to prevent the cathode-side strap weld of the HB battery from corroding at high temperatures. An object of the present invention is to provide a highly reliable HB battery that eliminates the accompanying problems and prevents the ear from being cut off at the cathode-side strap weld even in use at high temperatures. Another object of the present invention is to obtain such a strap welding portion by the COS method.

[0014]

Means for Solving the Problems Locations in the HB battery where ears are likely to be cut (base to the cathode strap)
As a result of various examinations of the welding condition of the metal, by forming the metallographic structure near the fillet as shown in FIG.
It has been found that cutting of the ear can be prevented. That is, the surface of the ear 1 of the cathode plate lattice and the fillet 5 formed at the base of the ear 1 to the strap 2 by strap welding are made of the third metal 13. Then, the fillet 5 is positioned so as to isolate the eutectic 7 crystallized when the Pb-Sb-based alloy constituting the strap is solidified from the base of the ear 1, and the fillet 5 is formed of the third metal on the surface of the ear. 13. Here, the third metal is a metal having a solidification temperature lower than the eutectic temperature of the Pb-Sb-based alloy constituting the cathode strap 2 and containing no Sb. The metal may be an alloy. The fillet 5 made of the third metal 13 is located between the ear 1 and the eutectic 7 which is a factor of accelerating corrosion, and serves to prevent Sb in the eutectic 7 from attacking the base of the ear. I have. This solution can be applied to both the cast lattice and the Ex lattice.

In order to arrange the fillet made of the third metal as described above, it is important to appropriately supply the third metal forming the fillet in strap welding. Therefore, the supply of the third metal for forming the fillet is performed in the process of welding the strap by the COS method. That is, prior to welding of the strap, a coating layer made of a third metal is formed on the ear of the cathode plate lattice (made of Pb-Ca alloy), and the Pb-Sb-based alloy is formed on the ear by the COS method. Weld the alloy strap. It has a freezing point lower than the eutectic temperature of the Pb-Sb alloy and
The third metal not containing b has, for example, an Sn content of 20.
It is a Sn-Pb alloy or pure Sn of not less than% by weight. In particular, Pb- (2-3)% S usually used as a strap alloy
An Sn-40% Pb alloy whose melting point is about 70 ° C. lower than the melting point of the b alloy (about 250 ° C.) is optimal. The third metal as described above has a lower specific gravity than the Pb-Sb alloy constituting the strap. Therefore, in the strap welding by the COS method, when the ears are immersed in the molten Pb-Sb alloy poured into the mold, the third metal on the surface of the ears is melted by the heat of the molten Pb-Sb alloy and melted on the molten Pb-Sb alloy. It is present around the ears while floating on the ears and wets the ears. The molten third metal floats on the Pb-Sb alloy melt until it solidifies, and hardly mixes with the surrounding Pb-Sb alloy melt. As a result, the fillet formed at the base of the ear is mainly made of the third metal that can substantially ignore the presence of Sb, despite the fact that the strap is made of a Pb-Sb alloy. In addition, the eutectic temperature of Pb and Sb generated by the solidification of the molten Pb-Sb alloy is about 250 ° C., which is higher than the solidification temperature of the third metal. Therefore, the eutectic solidifies, and then the third metal (fillet)
Solidifies. This makes it possible to locate the eutectic of Pb and Sb outside the fillet as viewed from the ears. It is also important for solidification to be completed in a short time to generate such a metallographic structure, and a COS method having a shorter welding time than the burner method is suitable. In the vicinity of the fillet, direct contact between the ear portion and the eutectic can be prevented, so that a local battery is not formed between the strap and the ear portion, which can prevent accelerated corrosion of the ear portion. Even if the strap weld on the cathode side of the HB battery using a Pb-Sb alloy for the strap is exposed from the electrolytic solution at high temperatures, the ears of the group weld are cut off due to corrosion,
Accidents such as battery explosion due to this can be completely prevented.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a method for supplying a third metal for forming a fillet is important.
Prior to the strap welding, a coating layer of the third metal is formed on the ear surface. The method of forming the coating layer includes the steps of (a)
There are various methods such as electroplating, (b) electroless plating, (c) plating by immersion in molten metal, and (d) application and heating of paste-like metal (for example, cream solder). Which method should be selected must consider not only the bonding property between the metal (alloy) to be coated and the Pb-Ca-based alloy lattice, but also the mass productivity, economy, and the like. The most preferred method is (c). However, this method is suitable for a cast lattice, and is not easily applied to an Ex lattice. This is because the ear portion of the Ex lattice body is thin (usually about 0.7 to 0.8 mm), so that the ear portion may be melted when immersed in the third molten metal. It is preferable to employ the above method (d) for the Ex lattice.

The above method (c) is preferably carried out immediately before the strap welding step (COS method) in order to keep the formed coating layer at an appropriate cleanliness until the strap welding. In practice, it is appropriate to carry out the process after the aging and drying process of the electrode plate is completed. From the viewpoint of productivity, there is an idea that the coating layer may be formed on a plurality of ears at once by performing after stacking the electrode plate and the separator and forming the electrode plate group. However, the practice at this stage is not preferable because a bridge of the third metal is easily formed between the ear portion and the adjacent ear portion when the ear portion is pulled up from the molten metal, which becomes an obstacle in the strap welding process. In order to form a good covering layer, it is preferable to clean the ear surface. It is effective to polish the surface of the ear portion with a wire brush or the like in advance, and to apply a flux to the surface of the ear portion and immerse it in the molten metal. The method (d) is applied to the Ex lattice body as shown in FIG. That is, as shown in FIG. 6A, the Pb—Ca-based alloy sheet 14 (hereinafter, referred to as “expanded”) before the expanding process is performed.
After applying a third metal paste 15 prepared by kneading a powder of the third metal and a flux or the like with a roll coater 16 to a portion corresponding to the ear portion of the “sheet 14”), as shown in FIG. The other portion is covered with a mask 17 and only the portion where the paste 15 has been applied is irradiated with infrared light from a lamp 18 to dissolve the third metal and form a coating layer 19. According to this energy efficient method, the third metal in the paste can be melted without excessively heating the sheet body.

In order to weld the strap to the ear by the COS method, care must be taken that the tip positions of the plurality of ears of the electrode plate group are sufficiently aligned. Apply flux to the ears in preparation for strap welding. Flux is applied to the side of the anode plate lattice, but it is sometimes easier to obtain a favorable welding condition by limiting the flux application to the tip only to the cathode plate lattice. is there. For example, when the cathode plate lattice is an Ex lattice, the ears are thin and the temperature is likely to rise more than necessary during strap welding by the COS method. In such a case, the coating layer of the third metal having a low melting point may diffuse into the strap alloy melt and may not sufficiently contribute to fillet formation. Therefore, if the application of the flux is limited to the tip of the ear and the flux is not applied to the side, the wetting of the molten metal of the strap alloy to the ear is suppressed, and the third metal constituting the coating layer is appropriately melted. A good fillet of the third metal is formed because the ear surface rises upward (on the side where the active material is filled). Another advantage of limiting flux application to the ear tips is that no voids remain inside the strap after strap welding. The flux applied to the ears comes into contact with the high-temperature molten metal during strap welding and is decomposed and vaporized, thereby generating voids (bubbles). Since the voids are lighter than the molten metal, they float up and try to escape to the outside. However, when the welding method is the COS method, the molten metal solidifies rapidly and may remain in the strap. The remaining voids increase as the amount of applied flux increases, so it is important to select a method that requires a small amount of application.According to the method of limiting the application to only the ear tip, Substantially no voids can remain. Whether the application of the flux to the ears of the cathode plate grid body is limited to the tip or to the side only depends on the welding condition (the amount of melting of the ears,
It is determined appropriately in consideration of the state of fillet formation, the number and size of remaining voids, and the like.

In the strap welding by the COS method, there are many factors for obtaining a good welding condition, and these factors are complicatedly entangled with each other to influence the welding result.
It is difficult to select welding conditions. Use solidification simulation to optimize conditions.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described for a 95D31 type automotive lead storage battery (HB battery). In the following, an example in which the cathode plate lattice is an Ex lattice and an example in which the cathode plate lattice is a cast lattice will be described. For each cathode plate lattice, the alloy composition is Pb-0.07Ca-0.5Sn. ,
The size of the ear part was 13 mm in width and 17 mm in length. The electrode group has a configuration of eight anode plates and nine cathode plates, and the cathode strap has an alloy composition of Pb-2.7Sb-0.2As.
The dimensions were 17 mm in width, 44 mm in length, and 8 mm in thickness. The same applies to the alloy composition of the anode strap. The strap welding method is a COS method.

Example 1 A paste made of Sn-40Pb alloy powder and a flux as a third metal was applied to a portion corresponding to a lug portion of a 0.7 mm thick lead alloy sheet, and the paste was irradiated with infrared rays and melted. A coating layer of about 0.03 mm of a Sn-40Pb alloy was formed. The lead alloy sheet was expanded to produce an Ex lattice having a coating layer made of a third metal on the lugs, and the lattice was filled with an active material and dried to form a cathode plate.
The cathode plate, the separator and the anode plate are alternately superposed to form an electrode plate group.Flux is applied only to the tip of the cathode plate lattice member, and flux is applied to the side of the anode plate lattice member. Was applied and subjected to strap welding by the COS method to obtain a weld having a metallographic structure shown in FIG. The strap welding conditions were as follows: die engraving part temperature 180 ° C, strap alloy melt temperature 480 ° C during pouring,
The ear immersion speed is 30 mm / min. The electrode group with the straps welded is housed in a battery case, and connections between cells by penetration welding,
The battery was completed by heat welding of the lid to the battery case and terminal welding.

Example 2 In Example 1, pure Sn powder was used as the third metal in place of the Sn-40Pb alloy, and a coating layer of pure Sn having a thickness of about 0.03 mm was formed at a position corresponding to the lug of the lead alloy sheet. Was formed. Expanding the lead alloy sheet to produce an Ex lattice having a coating layer made of a third metal on the ears,
The grid portion was filled with an active material and dried to form a cathode plate. The cathode plate, the separator and the anode plate are alternately overlapped to form an electrode plate group, and flux is applied to both sides of the cathode plate lattice member and the anode plate lattice member to the side surface, and the COS method is used. It was subjected to strap welding to obtain a weld having a metallographic structure shown in FIG. The strap welding conditions were as follows: the die engraving part temperature was 200 ° C., the temperature of the strap alloy molten metal at the time of pouring was 480 ° C., and the ear immersion speed was 25 mm / min. Thereafter, a battery was completed in the same procedure as in Example 1.

Example 3 A cathode plate lattice body having a thickness of 1.1 mm was produced by casting, the active material was filled in the lattice portion, and dried to form a cathode plate. The lug was dipped in a Sn-40Pb alloy (third metal) melt at 220 ° C. for 10 seconds to form a coating layer of a third metal having a thickness of about 0.02 mm on the lug surface. The cathode plate, the separator and the anode plate are alternately overlapped to form an electrode plate group, and flux is applied to both sides of the cathode plate lattice member and the anode plate lattice member to the side surface, and the COS method is used. It was subjected to strap welding to obtain a weld having a metallographic structure shown in FIG. Strap welding conditions were as follows: mold engraving part temperature 195 ° C, strap alloy melt temperature 500 during pouring.
° C, ear immersion speed 25 mm / min. Thereafter, a battery was completed in the same procedure as in Example 1.

Conventional Example 1 In Example 1, the third metal coating layer was not formed on the cathode plate lattice member ears, and the cathode plate lattice member ears and anode plate lattice member ears were not formed. The flux was applied to the side surface and subjected to strap welding by the COS method.

Conventional Example 2 In Example 2, the third metal coating layer was not formed on the cathode plate lattice member ears. The flux was applied to the side surface and subjected to strap welding by the COS method.

Conventional Example 3 In Example 3, the third metal coating layer was not formed on the cathode plate lattice member ears, and the cathode metal plate lattice member ears and the anode plate lattice member ears were not formed on both sides. The flux was applied to the side surface and subjected to strap welding by the COS method.

The batteries of Examples 1 to 3 described above and Conventional Examples 1 to
Regarding the battery of No. 3, the corrosion resistance of the welded portion of the cathode plate lattice body ear was evaluated. In the evaluation method, each battery is subjected to a charge / discharge cycle test at a high temperature (a charge / discharge pattern corresponding to a JIS light load life test) to evaluate the progress of corrosion. During the charge / discharge test, the electrolyte surface is under the strap and 15mm below it
And the vicinity of the fillet was exposed from the electrolyte. The battery ambient temperature during the test was set to 80 ° C. For each of the three batteries in each example, the number of charge / discharge cycles until the end of the life, the number of missing ears after the test (the number of cathode plate lattice body missing ears per battery), and the number of voids (one battery) In Table 1, six cathode straps were collected, and the average value of the number of voids detected by cross-sectional observation was shown in Table 1.

[0028]

[Table 1]

In all of the batteries of the conventional example, the cutout of the ear portion of the cathode plate lattice was recognized, but in the batteries of the examples, the same cutout was not recognized. The fact that there is no ear cutout despite the fact that the vicinity of the fillet is exposed from the electrolytic solution indicates that it is extremely excellent in corrosion resistance. Further, the battery of Example 1 has no void remaining in the strap. In the batteries of Examples 2 and 3, some residual voids were observed because the flux was applied to the side surfaces of the ears of the cathode plate lattice at the time of strap welding. However, the voids were significantly smaller than those of the conventional batteries.

[0030]

As described above, the lead storage battery according to the present invention has a structure in which the surface of the ear plate of the cathode plate made of a Pb-Ca alloy is Sb-based.
And a coating layer made of a third metal, which does not contain, and this coating layer is connected to a fillet also made of the third metal formed by strap welding. The fillet is located so as to isolate the eutectic of Pb and Sb, which crystallizes when the Pb-Sb-based alloy constituting the strap is solidified, from the ear, so that the local battery is located between the ear and the eutectic. Restrain what can be done,
Corrosion of the ears and cutting due to corrosion can be prevented.
Further, according to the method of the present invention, the fillet positioned as described above can be favorably formed by strap welding using the COS method.

[Brief description of the drawings]

FIG. 1 is a metallographic cross-sectional view showing a strap welded portion of a cathode side ear portion in a lead storage battery according to the present invention.

FIG. 2 is an explanatory view showing a structure of a strap welding portion of the electrode plate group.

FIG. 3 is a cross-sectional view of a strap welding portion by the COS method.

FIG. 4 is an explanatory view showing a process of strap welding by the COS method.

FIG. 5 is a cross-sectional view showing a metallographic view of a strap welded portion of a cathode side ear portion in a conventional lead storage battery. (A)
Shows a case of a cast lattice, and (b) shows a case of an Ex lattice.

FIG. 6 is a cross-sectional view illustrating a method for covering a Pb—
It is explanatory drawing which showed the method of forming the coating layer of the 3rd metal on the surface of Ca system alloy sheet.

[Explanation of symbols]

 1. Ear 2. Strap 3. Mold 4. Molten metal 5. Fillet 6. Under the strap 7. Eutectic 8. 8. Crystal of cast lattice body 10. Ex lattice granular crystals 10. Ex-lattice fibrous crystal 11. Ex-crystal lattice boundaries Pole 13. Third metal 14. Pb-Ca alloy sheet 15. Third metal paste 16. Roll coater 17. Mask 18. Lamp 19. Coating layer

Claims (6)

[Claims] The current collector of the cathode plate constituting the electrode plate group is Pb-
In a lead-acid battery made of a Ca-based alloy and welded to the ear of the current collector, a lead storage battery made of a Pb-Sb-based alloy was formed on the surface of the ear and the base of the ear by the welding. The fillet is made of a third metal having a solidification temperature lower than the eutectic temperature of the cathode strap alloy and containing no Sb, and the fillet is crystallized when the Pb-Sb alloy forming the strap is solidified. A lead-acid battery, wherein the eutectic is located so as to be isolated from the ear portion and is connected to a third metal on the surface of the ear portion. 2. The method according to claim 1, wherein the third metal is a Pb-Sn alloy or pure Sn.
The lead-acid battery according to claim 1, wherein 3. The current collector of the cathode plate constituting the electrode plate group is Pb-
In manufacturing a lead-acid battery made of a Ca-based alloy and welding a strap made of a Pb-Sb-based alloy to the ear of the current collector by a cast-on-strap method, prior to welding, the ear is made of a cathode strap alloy. A method for producing a lead-acid battery, comprising forming a coating layer made of a third metal having a solidification temperature lower than the crystallization temperature and containing no Sb. 4. A method for forming a coating layer made of a third metal by using a grid formed by expanding a Pb-Ca-based alloy sheet as a current collector of a cathode plate. 4. The method for producing a lead-acid battery according to claim 3, wherein the method is performed by integrally forming a layer of a third metal at a portion corresponding to the part. 5. The step of integrally forming a third metal layer at a position corresponding to a lug of a Pb-Ca alloy sheet, wherein the third metal and the flux are mainly composed at a position corresponding to a lug of the Pb-Ca alloy sheet. 5. The method for producing a lead-acid battery according to claim 4, wherein the method is a step of applying a paste, and heating and melting the third metal by irradiation of energy rays. 6. The method for producing a lead-acid battery according to claim 3, wherein, when welding the strap, the range of application of the flux applied to the ears is limited to the tip of the ears.