JP2012209084A - Liquid type lead storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow high visibility of liquid level, with no electrolyte contaminated with carbon black and to allow improvement of charging acceptance property due to the carbon black.SOLUTION: A negative electrode active material of a liquid type lead storage battery includes an inner layer whose main components are carbon black of 0.4-7.5 mass% and lead powder, and a surface layer whose main component is lead powder with the carbon content being 0.3 mass% or less.

Description

  The present invention relates to a liquid lead acid battery.

  The inventor proposed adding 0.4 mass% or more and 7.5 mass% or less of carbon to the negative electrode active material of a sealed lead-acid battery (Patent Document 1: Patent 3185508). Patent Document 1 describes that carbon reduces the polarization of the negative electrode so that the charging reaction of the negative electrode takes precedence over the reduction of oxygen gas, and facilitates the reduction of lead sulfate. As carbon, for example, acetylene black is used. However, the storage battery of Patent Document 1 is not suitable for a liquid lead storage battery because carbon contaminates the electrolyte.

  However, in applications such as idling stop vehicles, it is conceivable to add a large amount of carbon black to the negative electrode active material of a liquid lead-acid battery as a means for solving negative electrode sulfation. For this purpose, it is necessary to prevent the outflow of carbon black from the negative electrode active material of the liquid lead acid battery, and the inventor provides a surface layer containing no carbon black or a small amount on the surface of the negative electrode active material. It has been found that carbon black can be prevented from flowing out.

Patent 3185508

  A basic object of the present invention is to provide a liquid lead-acid battery having high charge acceptability and little contamination of the electrolyte by carbon black.

In the present invention, a negative electrode in which a negative electrode active material is supported on a negative electrode lattice, a positive electrode in which a positive active material is supported in a positive electrode lattice, and an electrolyte in which the negative electrode and the positive electrode are immersed are electrically A liquid lead acid battery contained in a tank,
In the negative electrode active material, the inner layer mainly composed of carbon black and lead powder of not less than 0.4% by mass and not more than 7.5% by mass is coated with the surface layer mainly composed of lead powder having a carbon black content of not more than 0.3% by mass. It is characterized by.
The liquid lead acid battery is a lead acid battery in which a free electrolytic solution that can freely flow outside the separator and the electrode plate is present. The content of carbon black in the inner layer is preferably 0.4% by mass or more and 5% by mass or less, taking into account that the outflow of carbon black is more reliably prevented and that carbon black itself does not contribute to the capacity of the storage battery. Particularly preferably, the content is 0.4% by mass or more and 3% by mass or less.

  In this invention, since the inner layer of the negative electrode active material contains not less than 0.4 mass and not more than 7.5 mass% of carbon black, charge acceptability is improved. For example, FIG. 2 shows an example of the charge / discharge cycle life of the prototype storage battery when the carbon black content is changed. When the carbon black content is 0.2% by mass or less, the discharge duration at 5 hour rate current (0.2 CA) is rapidly decreased after about 100 cycles. On the other hand, when the carbon black content is 0.4 mass% or more and 7.5 mass% or less, the discharge duration can be maintained long, for example, to about 300 cycles. This is because carbon black has improved charge acceptability, and the storage battery of the present invention is less susceptible to sulfation, and is therefore suitable for idling stop vehicles and the like.

  When the surface layer is not provided with a negative electrode active material containing 0.4% by mass or more of carbon black, carbon black flows out, contaminates the electrolytic solution, and lowers the visibility of the liquid level. In the present invention, the inner layer is covered with a surface layer mainly containing lead powder with a carbon black content of 0.3% by mass or less, so that the carbon black flowing out from the inner layer is trapped in the surface layer and hardly contaminates the electrolyte. Therefore, the possibility that the visibility of the liquid level is lowered can be eliminated.

The battery case is made of a synthetic resin such as polypropylene or polyethylene. In the present invention, since the electrolyte solution is slightly contaminated by carbon black and the visibility of the electrolyte surface is increased, the battery case is preferably a white battery case.
The surface layer of the negative electrode active material in the present invention is a layer having a low charge-accepting property, and only needs to have a thickness sufficient to prevent carbon black from flowing out from the inner layer. The inventor has empirically found that this thickness is 20 μm. Since a surface layer that is too thick is not preferable, the thickness of the surface layer is preferably 200 μm or less, and the average thickness of the surface layer as a whole is 20 μm or more and 200 μm or less.

Main part sectional drawing of the negative electrode in an Example Example characteristic diagram showing the relationship between the amount of carbon added to the negative electrode active material and the discharge duration during the charge / discharge cycle life test

  Hereinafter, an optimum embodiment of the present invention will be described. In carrying out the present invention, the embodiments can be appropriately changed in accordance with common sense of those skilled in the art and disclosure of prior art.

Produced lead acid battery (nominal voltage 2V, 5 hour rate capacity 20Ah). The positive electrode lattice used was a lead-calcium-tin alloy containing 0.07% by mass of calcium, 1.5% by mass of tin, and unavoidable impurities, and the balance being lead, but any other positive electrode lattice can be used. . The negative electrode lattice used was a lead-calcium-tin alloy containing 0.05 mass% calcium, 0.5 mass% tin and unavoidable impurities, and the balance being lead. However, any other negative electrode lattice can be used. . Each grid consists of a grid bone with a large number of slit-like holes, upper and lower edges, and ears, and is an expanded grid, but it may be a cast grid or a punched grid, and the size is both positive and negative The height is 115 mm, the width is 108 mm, and the thickness is 1.5 mm for the positive electrode and 1.0 mm for the negative electrode.

  As a positive electrode active material raw material, 0.1% by mass of acrylic fiber was added to 99.9% by mass of lead powder of the ball mill method to make a total of 100% by mass. 100% by mass of this mixture was mixed with 13% by mass of water and 10% by mass of diluted sulfuric acid having a specific gravity of 1.40 at 20 ° C. to obtain a positive electrode active material paste. The acrylic fiber may be replaced with other fibers or may not be added. The lead powder is not limited to the ball mill method, but may be a Barton method or the like, and may be a lead powder or a mixture of lead powder and lead powder instead of a normal lead powder.

  The negative electrode active material consists of an inner layer containing acetylene black of 0.4% by mass or more and 7.5% by mass or less, and a content of carbon black such as acetylene black of 0.3% by mass or less, and in the examples, a surface layer of 0% by mass. The surface layer has, for example, the same composition except for the acetylene black content. Lignin 0.15% by mass, barium sulfate 0.5% by mass, and acrylic fiber 0.1% by mass were added to 99.25% by mass of the lead powder of the ball mill method, and the total amount with the lead powder was 100% by mass. In the inner layer, by containing acetylene black in an amount of 0.38 mass% or more and 7.09 mass% or less with respect to 100 mass% of the above composition, the acetylene black content in the formed negative electrode active material is 0.4 mass% or more and 7.5 or less. It was set as the mass% or less. As a conventional example, a negative electrode active material having a single layer and a carbon black content of 0.2% by mass or less was prepared. Furthermore, the storage battery which comprised the negative electrode active material only by the inner layer material without using surface material was produced as a comparative example.

  The type of carbon black is not limited to acetylene black, but may be furnace black, thermal black, or the like. The acetylene black used has an aggregate size of about 0.5 mm and an average primary particle size in the aggregate of about 20 nm. In both the inner layer and the surface layer, the presence and content of lignin, barium sulfate, acrylic fiber, etc. are arbitrary. The lead powder is not limited to the ball mill method, but may be a Barton method.

  In the surface layer, it is preferable to use the above composition as a raw material for the active material as it is and not to contain carbon black. However, it may contain 0.3% by mass or less, preferably 0.2% by mass or less of carbon black in the stage of chemical conversion. The role of the surface layer is to trap carbon black flowing out from the inner layer, and in order to increase its strength, for example, carbon fiber, or synthetic resin fiber such as acrylic fiber, PTFE fiber, etc., for example, 0.05 mass% or more and 0.5 mass% or less Further, it may be contained in the surface layer. For both the inner layer and the surface layer, 100% by mass of the above material was mixed with 12% by mass of water and 10% by mass of diluted sulfuric acid having a specific gravity of 1.40 at 20 ° C. to obtain a negative electrode active material paste. It should be noted that the amount of water is set to 12% by mass when carbon black is contained by the above-described mass%, and it goes without saying that the amount of water needs to be increased when the content is increased.

  Each positive electrode plate was filled with 65 g of a positive electrode active material paste, aged at 50 ° C. and 50% relative humidity for 48 hours, and then dried in a dry atmosphere at 50 ° C. for 24 hours. In the negative electrode plate, for example, 40 to 45 g of the negative electrode active material inner layer paste was filled, and then the front and back surfaces of the inner layer paste were filled with 10 to 5 g of the negative electrode active material surface layer paste, and aging and drying were performed in the same manner as the positive electrode plate. . In addition, after filling the negative electrode plate with the negative electrode active material inner layer paste, the surface layer may be formed by immersing in a slurry or the like corresponding to the negative electrode active material surface layer paste.

  The negative electrode plate was accommodated in a separator made of a bag in which a microporous polyethylene sheet was folded in half and both ends were mechanically sealed. In addition to polyethylene, the separator may be other microporous synthetic resin film such as polypropylene or fluorinated resin, or may be a non-woven sheet of synthetic fibers such as acrylonitrile or polyamide. Further, a glass fiber sheet may be used as the separator. The separator is an acid-resistant, oxidation-resistant, insulating, porous, and sheet-like material bag. For example, four positive electrodes connected to each other with a strap were sandwiched between, for example, five negative electrodes connected to each other with a strap to form an electrode plate group. The obtained electrode plate group is housed in a white polypropylene battery case, injected with an electrolyte consisting of dilute sulfuric acid with a specific gravity of 1.200 at 20 ° C, formed into a battery case in a 25 ° C water tank, and a nominal voltage of 2V A lead-acid battery with a 5-hour rate capacity of 20 Ah was used.

  FIG. 1 shows a cross section of the negative electrode 2, 4 is a negative electrode lattice frame, which is made of the lead-calcium-tin alloy, and a negative electrode active material is filled in a slit between the bone portions 4, 4. The active material inner layer 8 is a negative electrode active material surface layer, and both surfaces of the inner layer 6 are covered by the surface layers 8 and 8. The total thickness of the negative electrode active material is, for example, 1 mm on average, and more generally 0.95 mm or more and 1.05 mm or less. The thickness of the left and right surface layers 8 and 8 is preferably 20 μm or more and 200 μm or less on average. In the case of impregnating the slurry, if the average value is 20 μm or more and 100 μm or less, contamination of the electrolyte solution by carbon black was not recognized, and in the examples, the average value was 50 μm. When the surface layers 8 and 8 were filled with a filling machine, the average value was 50 μm or more and 200 μm or less, respectively. No contamination of the electrolyte was observed, and in the examples, the average value was 100 μm.

Test method Each lead storage battery was subjected to a charge / discharge cycle life test, and during this time, the presence or absence of the electrolyte solution contamination by carbon black was visually observed from the outside of the white battery case. In the charge / discharge cycle life test, the battery was discharged at 4.0 A of 5 hour rate current (0.2 CA) for 3.5 hours and then charged at the same 4.0 A for 3.675 hours corresponding to 105% of the discharge amount. For every 100 cycles of this test, the discharge duration (in hours and minutes) until the terminal voltage of the battery drops to 1.75 V at a discharge current of 4.0 A is obtained, and the results are shown in FIG. In the conventional example, the carbon black content is 0.0 mass% (conventional example 1), 0.1 mass% (conventional example 2), 0.2 mass% (conventional example 3), and 0.4 mass% (conventional example 4). There is no distinction between the inner layers. In the examples, the carbon black content of the inner layer is 0.4% by mass (Example 1), 1.0% by mass (Example 2), 3.0% by mass (Example 3), 5.0% by mass (Example 4), 7.5% by mass ( Five types of Example 5). In the examples, whether the surface layer material was filled with a filling machine or immersed in a slurry to form a surface layer, the results were the same, so the results when filled with a filling machine are shown. In addition, Comparative Example 1 in which the inner layer contained 9.0% by mass of carbon black was tested.

  Also, in order to inspect the presence or absence of contamination of the electrolyte solution, the carbon black content is 0.0 mass% (conventional example 1), 0.1 mass% (conventional example 2), 0.2 mass% (single layer with no distinction between surface and inner layers) Conventional example 3) and 0.4 mass% (conventional example 4) storage batteries were tested. Further, the carbon black content of the inner layer is 0.4 mass% (Example 1), 1.0 mass% (Example 2), 3.0 mass% (Example 3), 5.0 mass% (Example 4), 7.5 mass% (Example) For the storage battery of 5), the same test was conducted by changing whether the surface layer was prepared by a filling machine or by impregnation with slurry and the thickness of the surface layer, and the presence or absence of electrolyte contamination was visually observed up to 300 cycles. Observed. The production conditions of these conventional examples and examples are the same as those of Comparative Example 1 except for carbon black. The number of samples is 3, and the results are shown as average values.

Results As is apparent from FIG. 2, when the carbon black content is 0.0 mass% (conventional example 1), 0.1 mass% (conventional example 2), and 0.2 mass% (conventional example 3), the discharge duration is about 100 cycles. It decreased to about 50% of the initial value. When it was judged that the battery had reached the end of its life in 100 cycles and the storage battery was disassembled, the cause of deterioration was sulfation with the negative electrode active material. In addition, when the carbon black content was 0.2% by mass or less (conventional examples 1 to 3), the electrolyte solution was not contaminated with carbon black even with a single layer negative electrode active material, but the carbon black content was 0.4% by mass. In the conventional example 4, the contamination of the electrolyte was observed.

  A surface layer and an inner layer are provided, and the carbon black content of the inner layer is 0.4% by mass (Example 1), 1.0% by mass (Example 2), 3.0% by mass (Example 3), 5.0% by mass (Example 4), In the storage battery of 7.5% by mass (Example 5), the discharge duration of 60% or more of the initial value is maintained even after 300 cycles. Since Example 1 and Conventional Example 4 have the same charge / discharge cycle life characteristics, they are shown as Example 1 in FIG. In addition, at the stage of 300 cycles, no electrolyte contamination was observed in any of the storage batteries. Furthermore, when the surface layer is provided from slurry, the contamination of the electrolyte solution is not detected when the left and right surface layers are each 20 μm or thicker, and when the surface layer is provided by a filling machine, the left and right surface layers are electrolyzed at a thickness of 50 μm or larger each. Liquid contamination was not detected. When the batteries of the examples were disassembled after 300 cycles, the progress of sulfation of the negative electrode was slow and the corrosion of the positive electrode was progressing. Therefore, when used in an idling stop vehicle or the like, the life factor of the storage battery is assumed to be positive electrode corrosion. In addition, in the storage battery in which the carbon black content of the inner layer is 9.0% by mass (Comparative Example 1), the negative electrode active material is dropped from the negative electrode grid when the battery case formation is completed, and the initial value of the discharge duration is 0 minute. there were.

  From the above, by providing a surface layer having a slight carbon black content and an inner layer containing a large amount of carbon black, it is possible to improve the charge acceptability of the storage battery and suppress sulfation and the like. In addition, the surface layer can prevent the carbon black from flowing out and prevent the electrolyte from being contaminated.

Although the small storage battery for trial manufacture was shown in the Example, it is not restricted to this. The composition of the positive electrode active material, the composition of the electrolytic solution, etc. are arbitrary, and the inner layer of the negative electrode active material is 0.4% by mass to 7.5% by mass, preferably 0.4% by mass to 5% by mass, particularly preferably 0.4% by mass. As long as the main component is lead powder containing 3% by mass or less of carbon, the presence or absence of antimony, tin or other additives is optional.

2 Negative electrode 4 Negative electrode lattice 6 Negative electrode active material inner layer 8 Negative electrode active material surface layer

Claims (3)

A negative electrode in which a negative electrode active material is supported on a negative electrode lattice, a positive electrode in which a positive active material is supported in a positive electrode lattice, and an electrolyte that immerses the negative electrode and the positive electrode are contained in a synthetic resin battery case. Liquid lead-acid battery,
In the negative electrode active material, the inner layer mainly composed of carbon black and lead powder of not less than 0.4% by mass and not more than 7.5% by mass is coated with the surface layer mainly composed of lead powder having a carbon black content of not more than 0.3% by mass. A liquid lead-acid battery, characterized in that   The liquid lead-acid battery according to claim 1, wherein the battery case is white.   3. The liquid lead-acid battery according to claim 1, wherein an average value of the thickness of the surface layer is 20 μm or more and 200 μm or less.