JP2007018812A - Lattice body for lead acid battery and method for manufacturing the same - Google Patents

Abstract

An object of the present invention is to provide a long-life lead that suppresses the phenomenon of the negative electrode current collector tab and upper frame bone being thinned in a life cycle test simulating the use mode of an idling start / stop vehicle, thereby avoiding the possibility of starting failure and explosion. Provide a storage battery.
A lead-tin alloy foil containing strontium or barium is pressure-bonded to the surface layer of a current collecting tab portion 3 and an upper frame bone 4 of an expanded lattice by rolling, and the negative electrode current collecting tab 3 and the upper layer are bonded with the alloy layer. It suppresses that the frame bone 4 becomes thin.
[Selection] Figure 1

Description

  The present invention relates to a grid for a lead storage battery and a method for manufacturing the same.

Lead-acid batteries are widely used for starting automobiles and supplying electric power for electrical components. recent years,
As an effort to protect the environment and improve fuel efficiency, an idling start / stop (hereinafter abbreviated as ISS) that stops the engine when the vehicle is stopped and restarts the vehicle when the vehicle starts is beginning to be implemented. From the lead-acid battery side, the ISS is frequently started and stopped repeatedly, increasing the number of large current discharges at the time of start-up, increasing the use of electrical components while the vehicle is stopped and increasing the discharge load. The vehicle is charged by an alternator, which stops when the vehicle is stopped because the engine is used as a power source. Due to the use conditions peculiar to these ISSs, lead storage batteries are often used due to excessive discharge without being sufficiently charged.

  When the charge / discharge cycle is repeated in such a state, a part that is frequently used on the electrode plate in the lead-acid battery and a part that is not so appear. Specifically, there is a difference in the utilization rate of the active material between the upper part of the electrode plate close to the current collecting tab and the lower part of the electrode plate far from the current collecting tab. For this reason, at the lower part of the electrode plate, charging becomes insufficient due to repeated charging and discharging, accumulation of discharge products (sulfation) occurs, and reaction becomes impossible. In addition, a stratification phenomenon occurs in which the electrolyte concentration is thin at the top and thick at the bottom, and sulfation further proceeds.

  As a means for solving the sulfation phenomenon, a method for improving charge acceptability as described in Patent Document 1 has been proposed.

Japanese Patent Publication No. 6-44487

  However, when this was verified by a cycle life test simulating the use mode of an ISS vehicle, a unique phenomenon occurred. As described above, the current collecting tab serves as a current inflow path, and has a large electrical resistance because the thickness is as thin as about 0.7 mm. Here, when a charge / discharge cycle as shown in FIG. 4 described later was repeated, a phenomenon occurred in which the current collecting tab of the electrode plate and the thickness of the upper frame bone of the lattice that was the base of the tab were reduced. This can be seen as the current collecting tabs and the surface layer of the upper frame of the grid become thinner as they gradually peel off. The cause of this is not clear, but because of the large current discharge, a discharge product is generated in the current-concentrated portion, and the large current discharge is repeated before returning to the original lead alloy by charging. It is believed that the product peels. As the thickness of the current collecting tab and the upper frame of the lattice body is reduced, the cross-sectional area is reduced and the electrical resistance is increased. In this state, the battery voltage is gradually lowered by repeating frequent high-current discharge, and finally, discharge becomes impossible. Moreover, there is a possibility that the current collecting tab will break due to thinning, and if it breaks, there is a risk that it will ignite and explode by flammable gas (hydrogen) filled inside the battery with sparks.

  These problems are not assumed in Patent Document 1 described above, and new countermeasures are required. One possible countermeasure is to increase the thickness of the current collecting tab of the negative electrode plate. However, the expanded grid, which is currently the mainstream of negative plates, is stamped from a lead-calcium alloy sheet and developed, and it is difficult to increase the thickness of the current collecting tab alone. In addition, lead-acid batteries are also being reduced in weight to improve fuel efficiency, and should be avoided from increasing the thickness of the negative electrode plate, which increases the mass. That is, it is a problem to suppress a decrease in the thickness of the negative electrode current collector tab and the upper frame due to the use conditions peculiar to the ISS, and to suppress an increase in the mass of the electrode plate.

  In order to solve the above-mentioned problem, the progress of corrosion is suppressed by arranging an alloy layer having a fine structure on the surface of the current collecting tab portion and the upper frame bone of the expanded lattice body, and the increase in the mass of the electrode plate is also suppressed.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to the following Example, In the range which does not change the summary, it can change suitably and can implement.
(Comparative example)
The lead-acid battery grid of the comparative example will be described below. First, a belt-like sheet 1 made of lead (Pb) calcium (Ca) tin (Sn) alloy and having a composition of Pb-0.04% Ca-0.7% Sn and having a thickness of 0.7 mm and a width of 55.4 mm is manufactured. did. Slits were sequentially formed at both left and right end portions excluding the central portion in the width direction of the rolled sheet, and a mesh-like lattice portion 5 shown in FIG. 1 was formed by developing in the width direction of the rolled sheet. Further, an expanded lattice body was manufactured by cutting the current collecting tab 3 and the mesh lattice portion 5 into predetermined dimensions by punching from a non-development portion of the sheet.
(Example)
In the embodiment, as shown in FIG. 1, at the stage of producing the belt-like sheet, an alloy foil 2 containing strontium (Sr) or barium (Ba) having the composition shown in Table 1 at the center in the longitudinal direction of the belt-like sheet 1 is obtained using a rolling roller. An alloy layer was formed by pressure bonding. The width of the alloy foil is 36.0 mm, and the crimping position is to cover the current collecting tab 3 and the upper frame bone 4 of the lattice when expanded. Since the phenomenon that the thickness of the current collecting tab 3 and the upper frame 4 of the lattice body is reduced proceeds from both sides, the alloy foil is pressed from both sides of the belt-like sheet. The total thickness of the alloy layer after pressure bonding was set to 0.05 mm. After that, slit processing and punching were performed in the same manner as in the comparative example to produce an expanded lattice body of the present invention.

  It has been confirmed that the same effect can be obtained when the amount of Sr and Ba added is in the range of 0.1% to 1.0%. The additive element needs to coexist with Sn. Although the cause is not clear, it is considered that Ba and Sr are formed by the formation of Sn and an intermetallic compound to increase the corrosion resistance. With respect to Sn, when the addition amount exceeds 2.0%, corrosion tends to proceed, and this is also an expensive material.

  In addition, although the thickness of the said alloy foil was 0.05 mm in the present Example, the same effect is acquired in the range of 0.01 mm-0.1 mm. In order to suppress the increase in the mass of the lead storage battery, it is preferable that it is thin. However, since it becomes easy to cut in the crimping process to the belt-like sheet 1, it is appropriately selected according to the capacity of the manufacturing equipment (production speed and the like).

  FIGS. 2 and 3 show surface microstructure observation diagrams of the comparative example and the example using a metallographic microscope. It can be seen that the crystal size of the pressed alloy layer is finer in FIG. 3 of this embodiment than the lead-calcium alloy sheet surface of the comparative example of FIG.

  Next, both the positive electrode and the negative electrode were filled with an active material paste in a lattice, and aged and dried to produce a positive electrode and a negative electrode plate. About the negative electrode plate produced here, it inserted in the bag separator and produced the electrode plate group by laminating | stacking a positive electrode plate alternately. About these, the current collection tabs were welded by the COS (cast on strap) system, and the strap was formed. Further, the electrode plate group was inserted into a battery case, and diluted sulfuric acid was injected, followed by 42 hours of chemical conversion with an energizing current of 9.6 A. After the chemical conversion, the specific gravity of dilute sulfuric acid was adjusted to 1.280 to produce a 2V single cell corresponding to 55D23 size.

  The charge / discharge cycle pattern test shown in FIG. 4 was carried out for each battery taken up in the comparative example and the example. This is a pattern that simulates the use of the ISS described above. The time when the voltage dropped below 7.2 V during the cycle was regarded as the life. FIG. 5 shows the voltage transition during 300 A discharge during the cycle. In the comparative example, the voltage is lowered early and the life is reached, whereas in Examples 1 and 2, the voltage is high and the life is long.

  In order to investigate this cause, each test battery was disassembled at the time of 11000 cycles when the comparative example reached the end of life, the electrode plate group was taken out, and the thickness after the test with respect to the negative electrode grid current collecting tab 3 and the upper frame bone 4 The residual rate was calculated as shown in Equation (1).

  FIG. 6 shows the result of comparing these. In the comparative example, only about 14% remained in the initial stage, whereas in the specification given in the example, about 46% remained in the same cycle. From this, the corrosion of the negative electrode grid current collecting tab and the upper frame bone was suppressed, which can be said to be the reason why the life of the example was extended. That is, since the present embodiment has a fine alloy structure as shown in FIG. 3, it is possible to obtain effective corrosion resistance against a specific deterioration phenomenon in the ISS cycle pattern.

Schematic which produces an expanded lattice body from the strip | belt-shaped sheet | seat of this invention. The surface microstructure observation figure of a strip | belt-shaped sheet | seat. The surface microstructure observation figure of the alloy layer crimped | bonded to the strip | belt-shaped sheet | seat. Charge / discharge cycle pattern. Voltage transition at 300A discharge during life cycle test. The comparison figure of the residual rate of the current collection tab and upper frame bone | frame by a life cycle test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Strip-shaped sheet 2 Alloy foil 3 Current collection tab 4 Upper frame bone | frame 5 of grid | lattice-like lattice part

Claims (4)

  A lead-acid battery grid made of a lead-calcium alloy, wherein a lead-tin alloy layer containing strontium or barium is present on the surface of the current collector tab and upper frame of the grid. Storage battery grid.   The lead-acid battery grid according to claim 1, wherein the grid is an expanded grid.   3. The lead-acid battery grid according to claim 1, wherein a crystal size of an alloy layer present on the current collecting tab and the upper frame bone surface layer of the grid is smaller than that of a lead-calcium alloy.   A method for manufacturing a lead-acid battery grid made of a lead-calcium alloy, comprising rolling a lead-tin alloy foil containing strontium or barium onto a surface of a current collector tab and an upper frame of the grid by rolling. A method for producing a lead-acid battery grid.

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