JP2009259725A - Lead storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to give a lead storage battery a longer life by suppressing voltage drop during high-rate discharge and suppressing deformation of the electrode plate. <P>SOLUTION: A positive electrode current collector of an electrode plate for lead storage battery is formed by powder-rolling lead alloy powder having superior corrosion elongation performance than that of the conventional casting rolled material. The powder rolling material has a texture composed of crystal grains oriented in a specific direction having an aspect ratio of 3 to 13. The current collector is manufactured in such a manner that the tin concentration in alloy reduces as separating from the ear part. The tin concentration reduces at least in two stages. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to lead-acid batteries for uses such as automobile batteries, electric vehicles such as forklifts, and uninterruptible power supplies, and more particularly to a current collector for lead-acid batteries.

Lead storage batteries are in wide demand, such as backup power supplies for computer equipment and communication equipment, power sources for automobiles and electric vehicles, or emergency power supplies for buildings and hospitals, and there is an increasing demand for higher output batteries. In particular, batteries having excellent high rate discharge characteristics are used for batteries used for automobiles and emergency power supplies because large electric power is instantaneously used.

In order to improve the high-rate discharge characteristics, Patent Document 1 discloses a method for suppressing the voltage drop during high-rate discharge without increasing the battery weight and improving the discharge duration. In the following, it has been proposed that the lead concentration of the current collector increases with distance from the ear. In general, the current collector of the electrode plate for a lead storage battery uses an alloy having a composition such as lead-calcium-tin or lead-antimony to improve the strength of the current collector. Metals generally increase in strength and electrical resistance as they are alloyed (as the main component of the alloy decreases). Since the conventional current collector has the same alloy composition in all portions, the current collection efficiency decreases as the distance from the ear portion increases. In particular, during high rate discharge, loss due to voltage drop (IR Drop) due to internal resistance of the battery greatly affects the discharge capacity.
In Patent Document 1, as a countermeasure against this, the lead concentration of the current collector is increased as the distance from the ear portion increases so that it approaches that of pure lead. That is, since the electrical resistance decreases as the distance from the ear portion decreases, the voltage drop between the vicinity of the ear portion and the end of the current collector away from the ear portion decreases, and the high rate discharge characteristics are improved.

JP-A-10-199538

However, since the above invention uses a cast alloy, the alloy composition of the current collector changes as the distance from the ear portion increases. For this reason, during the use of the battery, the corrosion characteristics greatly change in each part of the electrode plate (the current collector filled with the active material). For this reason, there is a problem that the size of corrosion deformation occurs in the electrode plate, non-uniform electrode plate deformation occurs, and the battery has a short life.
An object of the present invention is to provide a lead-acid battery that can extend the life by suppressing electrode plate deformation and suppress voltage drop during high rate discharge.

In order to solve the above-mentioned problems, the current collector of the electrode plate for a lead storage battery of the present invention is formed by powder rolling a lead-based alloy powder, and is composed of crystal grains oriented in a specific direction with an aspect ratio of 3 to 13. In the positive electrode current collector of the lead storage battery having the above-described structure, the concentration of tin in the alloy decreases with increasing distance from the current collector ear. Patent Document 1 employs a so-called gravity casting method in which molten alloys having different compositions are poured into different collector molds from different gates. The current collector of the lead storage battery has a complicated lattice shape, and it is important to rotate the molten metal around the thin bones forming the lattice body. For this purpose, the preheating of the mold and the temperature of the molten metal are controlled. Since the technique of Patent Document 1 is a molten alloy of a different technique, the melting points are different from each other, and the control factors during casting are complicated. Even when a grid-like current collector is cast, the occurrence of a hot water boundary due to a discontinuity in composition and a difference in solidification temperature is inevitable. These casting defects are likely to become the starting point of corrosion deformation and concentrated deformation strain due to charge / discharge of the lead storage battery. In addition, non-uniform electrode plate deformation has led to a short battery life.
Since the current collector according to the present invention is formed by powder rolling a lead-based alloy powder, the nonuniformity of the composition is reduced as compared with the conventional casting method. Further, the corrosion deformation of the current collector due to charging / discharging of the battery is suppressed, and the life of the battery can be extended.

According to the present invention, the voltage drop between the vicinity of the ear portion and the end of the current collector away from the ear portion is reduced, the high rate discharge characteristic is improved, and the difference in the amount of corrosion deformation caused by the distance from the ear is conventionally increased. Compared to the casting type, it can be greatly reduced and the life can be extended.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the examples unless it exceeds the gist of the invention.

FIG. 1 shows a basic configuration of a lead storage battery according to the present invention. The lead acid battery has a negative electrode terminal 11, a positive electrode terminal 12, a positive electrode plate 13, a negative electrode plate 14, a separator 15, a battery case 16, and a battery case lid 17. Sulfuric acid is stored. A positive electrode active material paste is applied to the current collector of the positive electrode plate 13. A well-known thing may be used for a positive electrode active material, and after filling with the active material paste for positive electrodes containing lead powder, red lead, lead sulfate, an additive, etc., this can be obtained by aging and drying. In addition, by the chemical conversion, the positive electrode active material becomes lead dioxide (PbO ₂ ) at the interface with the current collector. Below, the manufacturing method of the electrical power collector of the positive electrode plate 13 is demonstrated.

Conventionally, as a method for producing the current collector of the positive electrode plate 13, there are a casting method using a lead-antimony or lead-calcium alloy material and an expanding method using a lead-calcium alloy material. The former is a technique in which a molten lead alloy is poured into a mold and solidified to produce a grid-like current collector. FIG. 2 shows a schematic diagram of the current collector. In the latter, an alloy sheet is stretched and cut with a cutter to develop a diamond-like lattice. FIG. 3 shows a schematic diagram of the current collector. A portion protruding from each current collector main body is a portion called an ear portion, and these ear portions are welded together to form a current collector portion.
Next, the material of the positive electrode current collector according to the present invention will be described. In the present invention, lead-based alloy powder is used.
The lead-based alloy powder contains at least one alloy element of tin, calcium, antimony, barium, silver, and bismuth based on lead. The lead-based alloy powder may be a lead-tin-calcium-based alloy or a lead-tin-based alloy powder. The lead-based alloy powder is produced by a gas atomizing method in which a rapidly solidified powder is produced by spraying molten metal into dry air. The lead-containing powder is formed into a sheet by powder rolling. The rolled sheet thus formed has a structure composed of crystal grains oriented in a specific direction with an aspect ratio of 3 to 13. The rolled sheet is cut out to form a current collector. Moreover, you may form the electrical power collector which has a lattice structure by expanding a rolled sheet.

FIG. 4 shows a basic configuration of a powder rolling apparatus used for manufacturing a current collector according to the present invention. 2A is a top view of the apparatus, and FIG. 2B is a side view of the apparatus. The powder rolling apparatus includes a hopper 23, horizontally opposed rolling rolls 24a and 24b, feed rolls 25a and 25b, a feed conveyor 26, and a rolled sheet winder (not shown).

  A method for producing a powder rolled sheet that is a current collector material of the positive electrode plate 13 will be described below. The hopper 23 has a double structure, and is composed of an exterior part and an interior part provided with a three-section passage by slits on the inside. Lead alloy powder having a different composition is put into each section of the hopper 23, and the powder is rolled by horizontally opposed rolling rolls 24a and 24b. Subsequently, the feed rolls 25 a and 25 b are passed through, adjusted to a predetermined thickness by the adjustment roll 27 on the feed conveyor 26, and the rolled sheet 28 is produced. The rolled sheet 28 is wound into a roll by a rolled sheet winder (not shown).

  With reference to FIG. 5, the manufacturing method of the positive electrode electrical power collector for lead acid batteries by this invention is demonstrated. In step S101, lead-containing powder is prepared. The lead-containing powder is composed of a lead-based alloy powder. In the present invention, a plurality of lead-based alloy powders having different compositions are prepared. The lead-based alloy powder is produced by a gas atomization method.

  In step S102, the powder is subjected to powder rolling to produce a rolled sheet in which the concentration of tin in the alloy decreases with increasing distance from the side where the current collector ear portion of the positive electrode current collector exists. A rolled sheet is produced using the powder rolling apparatus shown in FIG.

  In step S103, a current collector is formed from the rolled sheet. The rolled sheet is cut into a rectangular shape to produce a flat plate-like positive electrode plate. Thus, the positive electrode active material paste is applied to the manufactured current collector plate and aged and dried to form the positive electrode plate.

  FIG. 6 is a photograph showing an example of the structure of a rolled sheet. Such a structure image is obtained by cutting the rolled sheet in parallel to the rolling direction and imaging the cut surface after immersing the cut surface in an etching solution. As shown in the figure, the structure of the rolled sheet is composed of fine particles of gas atomized powder which is a raw material for powder rolling, and the aspect ratio which is the aspect ratio of the particle diameter is 3 to 13.

  With reference to FIG. 7, the procedure of the experiment performed in order to evaluate the electrical power collector for lead acid batteries by this invention is demonstrated. In step S201, a positive electrode current collector was produced. In step S202, the positive electrode, the negative electrode, the separator, and the like were assembled to produce a single cell. In step S203, positive and negative electrodes were formed. In step S204, a high rate discharge test and an overcharge test were performed. The overcharge test is a test that accelerates the corrosion of the current collector.

  FIG. 8 shows an example of the structure of the current collector of the positive electrode plate used in the experiment. The flat positive electrode plate has a positive electrode active material application part 62 coated with a reaction active material and a masking part 61 masked with a sulfuric acid resistant adhesive insulating tape. The positive electrode active material application part 62 is provided with five through holes 63 having a diameter of 5 mm. This is to increase the adhesion between the positive electrode active material and the current collector during aging and to keep the coating amount constant. A lead wire 64 made of lead is soldered to the masking portion 61. The lead wire 64 serves as a connection portion with a test external power source (not shown).

As the lead-based alloy powder, an air-cooled gas atomized powder having a particle size of less than 75 μm based on a lead-tin-calcium alloy is prepared. In order to reduce the concentration of tin in the alloy as it moves away from the side where the current collector ear part of the positive electrode current collector in the alloy exists as it moves away from the current collector ear part, there are three types in the powder rolling apparatus of FIG. This powder will be used. That is, there are two stages of tin concentration reduction with respect to the reference composition.

  Specifically, based on lead-0.05% calcium, three kinds of powders having different tin compositions of 0.5%, 1.0%, and 1.5% are prepared. These powders are put into the hopper 23 of FIG. Since the current collector produced in this example forms an ear portion in front of the paper surface, in FIG. 2 (A), the composition introduced into each section of the hopper 23 has a tin content of 0.5% and 1.0% from the top. %, 1.5%. In addition, although the color difference of each powder cannot be discerned visually, for convenience of explanation, the difference in tin concentration of the powder will be expressed in gray tone (the higher the tin concentration, the darker the color). Each powder passes through a passage in the hopper 23 by gravity and is rolled by horizontally opposed rolling rolls 24a and 24b. Subsequently, the rolled body passes through the feed rolls 25a and 25b, and is adjusted by the preparation roll 27 on the feed conveyor 26 to obtain a rolled sheet 28 having a thickness of 0.5 mm. The rolled sheet 28 is wound into a roll by a rolled sheet winder (not shown). This rolled sheet is cut out to produce a plate-like current collector shown in FIG.

As Comparative Example 1, a cast-rolled sheet of lead-0.05% calcium-1.5% tin-based alloy is prepared as a base material.
As Comparative Example 2, a cast and rolled sheet having a difference in composition in three equal parts in the width direction of the rolled sheet is produced. Specifically, lead-0.05% calcium-based alloy is used as a base material, and three types of alloys with tin addition amounts of 0.5%, 1.0%, and 1.5% are prepared. A cast-rolled sheet having three concentrations of these alloys is prepared by the method of Patent Document 1.
Comparative Examples 1 and 2 were cut out in the same manner as in the present invention to produce a plate-like current collector shown in FIG. The current collector is filled with lead paste, aged and dried by a conventional method. Then, it used for the test with the flowchart of FIG.

  Table 1 shows the conditions of the high rate discharge test and overcharge test used in the experiment of this example, and Table 2 shows the test results of Table 1.

From this result, the high rate discharge performance is the product of the present invention≈Comparative Example 2> Comparative Example 1, and the overcharge performance is the product of the present invention> Comparative Example 1> Comparative Example 2. Excellent lifetime performance.
In the embodiment, the hopper 23 is divided into three sections. As described above, since the hopper 23 has a double structure, the interior portion can be replaced. Thereby, the density separation band can be changed as appropriate, and the change in density can be selected depending on the size and application of the electrode plate. In three compartments, there will be two stages of tin concentration reduction, so at least two stages of tin concentration reduction are required.
Further, the addition range of tin is desirably 0.5% or more and less than 2.5%. This is because the desired effect is not observed at less than 0.5%, and the corrosion amount of the current collector does not change or tends to increase at 2.5% or more.

It is a figure which shows the structure of a lead acid battery. It is the schematic of the electrical power collector of a casting method. It is the schematic of the electrical power collector of an expanding method. It is a figure which shows the structure of the powder rolling apparatus used for manufacture of the positive electrode electrical power collector by this invention. It is a figure explaining the manufacturing method of the positive electrode electrical power collector by this invention. It is a figure which shows the structure | tissue of the rolled sheet by this invention. It is a figure which shows the procedure of the evaluation experiment of the positive electrode electrical power collector by this invention. It is a figure which shows the positive electrode electrical power collector for evaluation by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Negative electrode terminal, 12 ... Positive electrode terminal, 13 ... Positive electrode plate, 14 ... Negative electrode plate, 15 ... Separator, 16 ... Battery case, 17 ... Battery case cover, 23 ... Hopper, 24a, 24b ... Horizontally opposed rolling roll, 25a, 25b ... feed roll, 26 ... feed conveyor, 27 ... adjustment roll, 28 ... rolled sheet, 61 ... masking section, 62 ... positive electrode active material coating section, 63 ... through hole, 64 ... lead wire

Claims (3)

In the current collector for a positive electrode of a lead storage battery formed by powder rolling of a lead-based alloy powder containing tin and having a structure composed of crystal particles oriented in a specific direction with an aspect ratio of 3 to 13, A lead-acid battery, characterized in that the concentration of tin in the alloy decreases as the current collector away from the side where the current collector ears are present. The lead acid battery according to claim 1, wherein the tin concentration is reduced in at least two stages. The lead storage battery according to claim 2, wherein the tin addition range is 0.5% or more and less than 2.5%.

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