JPH08339794A - Lead acid battery - Google Patents

Abstract

PURPOSE: To suppress a stress corrosion crack in a rack part so so to improve corrosion resistance, by connecting lattice lug parts to each other of a plate composed of Pb-Sn-Ca alloy by the rack part consisting of supplement lead composed of Pb-Sn-Se alloy. CONSTITUTION: For instance, a cast lattice of Pb-Sb alloy and an expanded lattice of Pb-Sn-Ca alloy are formed in a positive/negative plate by applying respective active material paste, to be used in a plate group of a hybrid type battery. Here is used a Pb-Sn-Se alloy as supplement lead of a strap for connecting a lug part to each other of a negative plate lattice, preferably with Sn concentration 0.5 to 2.5wt.% and Se concentration 10 to 200ppm. Thus by fining a rack part alloy with selenium serving as a crystalline nucleus of lead alloy particle at welding time, corrosion due to penetrating a crystal grain boundary by an electrolyte and oxygen is suppressed. Further in connecting different polarity plates of a cell chamber adjacent to each other, a Pb-Sn alloy is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead storage battery, and more particularly to suppression of stress corrosion cracking and improvement of corrosion resistance of a strap integrally formed with an ear portion of an electrode plate grid.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for maintenance-free lead-acid batteries for automobiles due to the diversification of the environment in which they are used. In such a flow, a battery called a calcium type using a lead-calcium alloy in the positive and negative electrode grids, a lead-antimony alloy in the positive electrode grid, and a lead-tin-calcium alloy in the negative electrode grid, respectively. The hybrid type batteries used have come to be used.

As a strap forming method for these batteries, a method is used in which the ears of the electrode plate grid are welded together by using added lead made of a lead-antimony alloy to form a shelf.

At the time of welding for forming the strap, calcium contained in the lead alloy forming the ears of the electrode plate lattice and antimony in the added lead are melted with each other, so that the boundaries between the ears of the lattice and the shelves are very large. Intermetallic compounds are formed which are susceptible to corrosion. Then, when this strap portion is exposed from the electrolytic solution, corrosion has occurred at the boundary portion, progresses, and eventually the ear portion is cut off.

Regarding the above problems, Japanese Patent Publication No. 3-2589
Japanese Unexamined Patent Publication No. 5 (1993) discloses that pure lead or a lead alloy containing no antimony is used for the shelf connected to the electrode plate grid and the pole. Recently, among such lead alloys, antimony is used. Lead-tin based alloys that do not contain are commonly used.

[0006]

However, when a lead-tin alloy is used for the additional lead forming the shelf, the crystal grain size of the lead alloy in the shelf becomes coarse. When the electrolytic solution or oxygen in the air penetrates into the grain boundary portion of the coarse crystal grain, corrosion of the lead alloy in the shelf progresses and lead sulfate is precipitated in the grain boundary portion. And this lead sulfate tries to spread the grain boundary part. As a result, stress acts near the crystal grain boundaries of the shelf portion, and there is a problem that so-called stress corrosion cracking easily occurs in the shelf portion.

The present invention solves the above problems and suppresses stress corrosion cracking that occurs along the crystal grain boundary portion of the shelf portion, and has excellent corrosion resistance even when the strap portion is exposed from the electrolytic solution. And a strap having:

[0008]

In order to solve the above-mentioned problems, the lead-acid battery of the present invention comprises a lead-tin-calcium alloy electrode plate made of a lead-tin-selenium alloy, the grid ears of which are made of a lead-tin-selenium alloy. It is connected by a shelf using additional lead.

The content of tin in the lead-tin-selenium alloy is preferably 0.5 to 2.5% by weight, and that of selenium is preferably 10 to 200 ppm.

[0010]

[Function] Addition of 10 to 2 to the lead-tin alloy as a lead alloy
By adding 00 ppm of selenium, selenium becomes the nucleus of the crystal of the lead alloy particles during welding, and promotes the refinement of the crystal particles of the shelf alloy. Therefore, it is possible to suppress the occurrence of corrosion due to the permeation of the electrolytic solution and oxygen in the air into the crystal grain boundaries.

[0011]

Embodiments of the present invention will be described below.

The positive electrode grid is a cast grid in which a lead-2.5 wt% antimony alloy is cast, and the negative electrode grid is made of lead-0.
Expanded grids obtained by subjecting a lead alloy sheet made of a 5 wt% tin-0.08 wt% calcium alloy to an expanding process were used. An active material paste was applied to these electrode plate grids to prepare positive and negative electrode plates.

A plurality of these electrode plates are alternately superposed on each other with a separator interposed therebetween, and the ears of the same polarity electrode plate grid are connected by straps to form an electrode plate group to form a hybrid type battery. And

The strap was formed by mounting the lattice ears on a welding jig, arranging lead on the jig, and using a burner from above the lead to add and melt the lead by burning welding. .

As the additional lead forming the negative electrode strap, a lead alloy having various tin concentrations in the range of 0.25 wt% to 2.75 wt% and selenium concentration in the range of 0 ppm to 220 ppm was used. In addition, a lead-tin alloy was used for the inter-cell connection body that connects the different polarity electrode plates of the adjacent cell chambers.

The above electrode plate group was inserted into a battery case, and a nominal voltage of 12
Five hybrid type V batteries were prepared. Using these batteries, while keeping the electrolyte solution surface constant,
Under a 5 ° C. environment, overcharge was performed at 13.8 V for 8 weeks.

The state of occurrence of cracks and cracks on the negative electrode shelf before and after the test was confirmed. Further, the center of the negative electrode shelf portion was cut in the thickness direction of the electrode plate, and the welded portion of the shelf portion and the ear portion was observed. (Table 1) and (Table 2) show the occurrence status of cracks in the strap and the disconnection status of the ears with various tin and selenium concentrations. The rupture state of the ears due to corrosion indicates the degree of corrosion, and the symbols ◯, Δ, and × in the table indicate that the ratio of the ears to be broken (breaking rate) to the total number of ears is less than 10%, 10% or more. It indicates less than 40% and 40% or more, respectively.

[0018]

[Table 1]

[0019]

[Table 2]

As is clear from these (Table 1) and (Table 2), in the lead-tin-selenium based alloy, the tin concentration was 0.1.
5 wt% or more and 2.5 wt% or less, and the selenium content is 1
By using an alloy of 0 ppm or more and 200 ppm or less, the occurrence of stress corrosion cracking in the shelf portion can be suppressed, and at the same time, the corrosion resistance of the welded portion of the shelf portion and the ear portion can be improved.

In addition to selenium, sulfur or copper may be used as an element for refining the crystal grains of the lead-tin alloy.
In the shelf portion made of a lead alloy containing a trace amount of these elements, the crystal grains become finer, and the same effect as that of this embodiment can be obtained.

[0022]

As described above, according to the present invention, it is possible to obtain a highly reliable strap which suppresses the occurrence of stress corrosion cracking of the shelf portion and has improved corrosion resistance.

Claims (2)

[Claims] 1. A lead storage battery characterized in that the ears of the electrode plate grid made of a lead-tin-calcium alloy are connected to each other by a shelf made of a lead-tin-selenium alloy. 2. The lead-tin-selenium alloy forming the shelf has a tin content and a selenium content of 0.5 to 2.5% by weight and 10 to 200 ppm, respectively. Lead acid battery described.