JP7223870B2 - Positive electrode plate, lead-acid battery and manufacturing method thereof - Google Patents

Description

The present invention relates to positive plates, lead-acid batteries, and methods of manufacturing them.

Lead-acid batteries are widely used in industry, for example, as batteries in automobiles, backup power sources, and main power sources in electric vehicles. A positive electrode in a lead-acid battery is required to improve the utilization rate of a positive electrode active material held in a current collector. The use of a positive electrode with an excellent utilization rate of the positive electrode active material can, for example, reduce the amount of the positive electrode active material used to obtain a predetermined discharge capacity, and as a result, the weight of the lead-acid battery can be reduced.

On the other hand, for example, in Patent Document 1, in order to increase the utilization rate of the positive electrode active material, basic lead sulfate and graphite are added to the active material of the positive electrode, and phosphoric acid is added to the electrolyte solution in an amount of 1% by mass or less. A containing lead-acid battery is disclosed.

JP 2011-165378 A

However, there is still room for improvement in the utilization rate of the positive electrode active material. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a positive electrode plate for a lead-acid battery and a lead-acid battery including the positive electrode plate, which has an excellent utilization rate of the positive electrode active material.

One aspect of the present invention includes a positive electrode current collector and a positive electrode active material held by the positive electrode current collector, the positive electrode active material shrinks irregularly, and the shrinkage represented by the following formula (1) A positive electrode plate for a lead-acid battery containing fibers having a shrinkage ratio of 45% or more (hereinafter also referred to as "shrinkage fibers").
Shrinkage rate (%)=(y−x)/y×100 (1)
(In the formula, x is the shortest distance from one end of the fiber to the other, and y is the length along the longitudinal direction of the fiber.)

Another aspect of the present invention includes a step of holding a positive electrode active material on a positive electrode current collector, the positive electrode active material shrinks irregularly, and the shrinkage rate represented by the above formula (1) is 45%. It is a manufacturing method of the positive electrode plate for lead storage batteries containing the fiber which is the above.

In each of the above aspects, the shrinkage may be 80% or less, and the fibers may comprise polymer fibers.

Another aspect of the present invention is a lead-acid battery comprising the positive electrode plate described above.

Another aspect of the present invention is a method of manufacturing a lead-acid battery, comprising the steps of manufacturing a positive electrode plate by the manufacturing method described above and assembling a lead-acid battery including the positive electrode plate.

ADVANTAGE OF THE INVENTION According to this invention, the positive electrode plate for lead storage batteries which is excellent in the utilization factor of a positive electrode active material, and a lead storage battery provided with the said positive electrode plate can be provided.

1 is a perspective view showing the overall configuration and internal structure of a lead-acid battery according to one embodiment; FIG. FIG. 2 is a perspective view showing an electrode group of the lead-acid battery shown in FIG. 1; 1 is a schematic diagram showing one embodiment of a crimped fiber; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.

FIG. 1 is a perspective view showing the overall configuration and internal structure of a lead-acid battery according to one embodiment. As shown in FIG. 1 , a lead-acid battery 1 includes a container 2 with an open top and a lid 3 that closes the opening of the container 2 . The container 2 and the lid 3 are made of polypropylene, for example. The lid 3 is provided with a negative electrode terminal 4 , a positive electrode terminal 5 , and a liquid port plug 6 for closing the liquid inlet provided in the lid 3 .

Inside the container 2 are an electrode group 7, a negative electrode column 8 connecting the electrode group 7 to the negative electrode terminal 4, a positive electrode column (not shown) connecting the electrode group 7 to the positive electrode terminal 5, dilute sulfuric acid and the like. of electrolyte are contained.

FIG. 2 is a perspective view showing the electrode group 7. FIG. As shown in FIG. 2 , the electrode group 7 includes a negative plate 9 , a positive plate 10 , and a separator 11 interposed between the negative plate 9 and the positive plate 10 . The negative plate 9 includes a negative current collector (negative grid) 12 and a negative active material 13 held on the negative current collector 12 . The positive electrode plate 10 includes a positive electrode current collector (positive grid) 14 and a positive electrode active material 15 held on the positive electrode current collector 14 . In the present specification, the negative electrode plate after chemical forming from which the negative electrode collector is removed is referred to as "negative electrode active material", and the positive electrode plate after chemical conversion from which the positive electrode current collector is removed is referred to as "positive electrode active material". Define.

The electrode group 7 has a structure in which a plurality of negative electrode plates 9 and positive electrode plates 10 are alternately laminated in a direction substantially parallel to the opening surface of the container 2 with separators 11 interposed therebetween. That is, the negative electrode plate 9 and the positive electrode plate 10 are arranged so that their main surfaces extend in the direction perpendicular to the opening surface of the container 2 . In the electrode group 7 , the tabs 12 a of the negative electrode current collectors 12 of the plurality of negative electrode plates 9 are collectively welded together with a negative strap 16 . Similarly, the tabs 14 a of the positive current collectors 14 of the plurality of positive plates 10 are collectively welded together with a positive strap 17 . The negative strap 16 and the positive strap 17 are connected to the negative terminal 4 and the positive terminal 5 through the negative pole 8 and the positive pole, respectively.

The separator 11 is formed in a bag shape, for example, and accommodates the negative electrode plate 9 . The separator 11 is made of, for example, polyethylene (PE), polypropylene (PP), or the like. The separator 11 may be a woven fabric, a non-woven fabric, a porous film, or the like made of these materials to which inorganic particles such as SiO ₂ and Al ₂ O ₃ are adhered.

The negative electrode current collector 12 and the positive electrode current collector 14 are each made of a lead alloy. The lead alloy may be an alloy containing tin, calcium, antimony, selenium, silver, bismuth, etc. in addition to lead. Specifically, for example, an alloy containing lead, tin and calcium (Pb—Sn -Ca-based alloy).

The negative electrode active material 13 contains at least Pb as a Pb component, and if necessary, further contains a Pb component other than Pb (for example, PbSO ₄ ) and an additive. The negative electrode active material 13 preferably includes porous spongy lead. The content of the Pb component may be 90% by mass or more or 95% by mass or more and may be 99% by mass or less or 98% by mass or less based on the total mass of the negative electrode active material. The total mass of the negative electrode active material is, for example, the mass of the negative electrode (negative electrode current collector and negative electrode active material), which is measured after the negative electrode (negative electrode current collector and negative electrode active material) is removed from the lead-acid battery, washed with water, and sufficiently dried. It can be calculated from the difference with the mass of the body. Drying is performed, for example, at 50° C. for 24 hours.

Examples of additives include resins having sulfo groups and/or sulfonate groups, barium sulfate, carbon materials (excluding carbon fibers) and fibers (acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, carbon fibers, etc.). are mentioned.

Resins having sulfo groups and/or sulfonic acid groups include ligninsulfonic acid, ligninsulfonate, and condensates of phenols, aminoarylsulfonic acid, and formaldehyde (for example, bisphenol, aminobenzenesulfonic acid, and formaldehyde). may be at least one selected from the group consisting of condensates). Examples of carbon materials include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black and ketjen black.

The positive electrode active material 15 includes PbO ₂ as a Pb component and shrinkage fibers. The positive electrode active material 15 may further contain a Pb component other than PbO ₂ (for example, PbSO ₄ ) and an additive, if necessary.

The positive electrode active material 15 preferably contains β-PbO ₂ as the Pb component. The positive electrode active material 15 may further contain α-PbO ₂ as a Pb component. That is, the positive electrode active material 15 may contain only β-PbO ₂ as the Pb component in one embodiment, and may contain α-PbO ₂ and β-PbO ₂ as the Pb component in another embodiment. good.

The content of the Pb component is preferably 90% by mass or more, more preferably 95% by mass or more, based on the total mass of the positive electrode active material, from the viewpoint of further improving low-temperature high-rate discharge performance and cycle performance. The content of the Pb component is preferably 99.9% by mass or less, more preferably 98% by mass or less, based on the total mass of the positive electrode active material, from the viewpoint of manufacturing cost reduction and weight reduction. The total mass of the positive electrode active material is, for example, the mass of the positive electrode (positive electrode current collector and positive electrode active material) taken out from the lead storage battery, washed with water, and measured after the positive electrode is sufficiently dried. It can be calculated from the difference with the mass of the body. Drying is performed, for example, at 50° C. for 24 hours.

FIG. 3 is a schematic diagram showing one embodiment of a crimped fiber. The crimped fibers 18 are irregularly crimped. Crimped fibers 18 are different from regularly crimped fibers (eg, coiled (helical) fibers). The shape (how it shrinks) of the shrinkable fibers 18 is arbitrary as long as it satisfies the shrinkage rate described later.

The crimped fibers have a shrinkage of 45% or greater. The shrinkage ratio is represented by the following formula (1).
Shrinkage rate (%)=(y−x)/y×100 (1)
In the formula, x represents the shortest distance from one end 18a to the other end 18b of the crimped fiber 18 (distance of a straight line connecting the one end 18a and the other end 18b of the crimped fiber 18), as shown in FIG. y represents the length along the longitudinal direction of the crimped fiber 18 (the length of the crimped fiber 18 itself), as shown in FIG. x and y can be calculated from the SEM image of the crimped fiber 18 . For example, y can be calculated by dividing the longitudinal direction of the crimped fiber 18 and approximating a plurality of straight lines (for example, 10 straight lines) and calculating the sum of the lengths of the plurality of straight lines.

The shrinkage of the shrinkage fibers 18 may be 50% or more, 55% or more, 60% or more, 65% or more, or 70% or more, and 80% or less, 75% or less, 70% or less, or 65% or less. may be

The shrinkage rate of the shrinkable fibers 18 can be adjusted, for example, by applying a predetermined stress to the longitudinal direction of the fibers for a certain period of time. The shrinkage tends to increase as the applied stress increases and as the stress is applied for a longer period of time.

Crimp fibers 18 may include, for example, polymer fibers, carbon fibers, and the like. Examples of polymer fibers include polyolefin fibers (fibers containing polyethylene, polypropylene, etc.), polyester fibers (fibers containing polyethylene terephthalate, etc.), and acrylic fibers (fibers containing polyacrylate, polymethacrylate, etc.). From the viewpoint of obtaining excellent charge-discharge performance (charge acceptance performance, low-temperature high-rate discharge performance, etc.), the shrunken fibers 18 preferably contain polymer fibers, more preferably acrylic fibers.

From the viewpoint of further improving the utilization rate of the positive electrode active material, the content of the crimped fiber 18 is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably, based on the total mass of the positive electrode active material. is 2% by mass or more. From the viewpoint of reducing the electrical resistance of the positive electrode plate, the content of the crimped fiber 18 is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass, based on the total mass of the positive electrode active material. It is below.

Examples of additives include carbon materials (excluding shrinkage fibers (carbon fibers)). Examples of carbon materials include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black and ketjen black.

In the lead-acid battery 1, since the positive electrode active material 15 contains the shrinkable fibers 18, an excellent utilization rate of the positive electrode active material can be obtained. The reason for this is that the shrunken fibers 18 adhere more strongly to the positive electrode current collector during aging and drying of the positive electrode plate than fibers with a small shrinkage rate (relatively non-shrunk fibers). The present inventors speculate that this is because the more uniform growth direction of PbSO ₄ keeps the electron conduction and the electrolyte migration favorable.

The lead-acid battery 1 described above includes, for example, a negative electrode plate manufacturing process for manufacturing a negative electrode plate, a positive electrode plate manufacturing process for manufacturing a positive electrode plate, and an assembly process for assembling the lead-acid battery 1 including the negative electrode plate and the positive electrode plate. Manufactured by the manufacturing method. The order of the negative electrode plate manufacturing process and the positive electrode plate manufacturing process is arbitrary.

In the negative electrode plate manufacturing process, the negative electrode current collector 12 is caused to hold the negative electrode active material 13 . Specifically, first, a negative electrode active material paste is held on the negative electrode current collector 12, and the negative electrode active material paste is aged and dried to obtain an unformed negative electrode active material. chemically.

The negative electrode active material paste contains, for example, lead powder, additives, a solvent (such as water or an organic solvent) and sulfuric acid (such as dilute sulfuric acid). The negative electrode active material paste is obtained, for example, by mixing lead powder and an additive to obtain a mixture, and then adding a solvent and sulfuric acid to the mixture and kneading the mixture.

As the lead powder, for example, lead powder produced by a ball mill type lead powder manufacturing machine or a Barton pot type lead powder manufacturing machine (in the ball mill type lead powder manufacturing machine, a mixture of main component PbO powder and scaly metal lead) ).

Aging may be carried out for 15 to 60 hours in an atmosphere with a temperature of 35 to 85° C. and a humidity of 50 to 98 RH%. Drying may be carried out at a temperature of 45-80° C. for 15-30 hours.

In the positive electrode plate manufacturing process, the positive electrode current collector 14 holds the positive electrode active material 15 . Specifically, first, the positive electrode current collector 14 is caused to hold the positive electrode active material paste, and the positive electrode active material paste is aged and dried under the same conditions as in the negative electrode plate manufacturing process to remove the unformed positive electrode active material. After obtaining, the unformed positive electrode active material is formed.

The positive electrode active material paste includes, for example, the same lead powder as that used in the negative electrode active material paste, the above-described shrunken fibers, additives added as necessary, a solvent (such as water or an organic solvent) and sulfuric acid (such as dilute sulfuric acid). The positive electrode active material paste may further contain red lead (Pb ₃ O ₄ ) from the viewpoint of shortening the formation time.

In the assembly process, for example, first, the negative electrode plate obtained in the negative electrode plate manufacturing process and the positive electrode plate obtained in the positive electrode plate manufacturing process are laminated with the separator 11 interposed therebetween, and the current collectors of the electrode plates of the same polarity are formed. are welded with a strap to obtain an electrode group. This electrode group is arranged in a container to produce an unformed lead-acid battery. Next, dilute sulfuric acid is added to the unformed lead-acid battery, and direct current is applied to form the container. Subsequently, the lead-acid battery 1 is obtained by adjusting the specific gravity (20° C.) of the sulfuric acid after chemical conversion to an appropriate specific gravity of the electrolytic solution.

The specific gravity (20° C.) of sulfuric acid used for chemical conversion may be 1.15 to 1.25. The specific gravity (20° C.) of sulfuric acid after chemical conversion is preferably 1.25 to 1.33, more preferably 1.26 to 1.30. The chemical conversion conditions and the specific gravity of sulfuric acid can be adjusted according to the size of the electrode plate. The chemical conversion treatment may be performed in the assembly process, or may be performed in each of the negative electrode plate manufacturing process and the positive electrode plate manufacturing process (tank chemical conversion).

EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples.

<Example 1>
(Preparation of positive electrode plate)
2.2 parts by mass of acrylic fiber (shrinked fiber) having a shrinkage rate of 45% was added to 100 parts by mass of lead powder and dry mixed. Next, to 100 parts by mass of a mixture of lead powder and shrunken fibers, 3 parts by mass of water are added, and 9 parts by mass of dilute sulfuric acid (specific gravity: 1.28) are added stepwise, followed by kneading for 1 hour to activate the positive electrode. A substance paste was made. An expanded positive electrode current collector prepared by subjecting a rolled sheet made of a lead alloy to an expanding process was filled with a positive electrode active material paste, and then aged for 24 hours in an atmosphere at a temperature of 50° C. and a humidity of 98%. After that, it was dried at a temperature of 50° C. for 16 hours to obtain an unformed positive electrode plate.

(Preparation of negative electrode plate)
Per 100 parts by mass of lead powder, Bisperz P215 (condensate of bisphenol, aminobenzenesulfonic acid and formaldehyde, trade name, manufactured by Nippon Paper Industries Co., Ltd.) 0.2 parts by mass (resin solid content), acrylic fiber 0.1 A mixture of parts by weight, 1.0 parts by weight of barium sulfate, and 0.2 parts by weight of furnace black was added and dry mixed. Next, after adding water to this mixture and kneading, the mixture was further kneaded while adding little by little dilute sulfuric acid having a specific gravity of 1.280 to prepare a negative electrode active material paste. An expanded negative electrode current collector prepared by subjecting a rolled sheet made of a lead alloy to expansion processing was filled with this negative electrode active material paste, and then aged for 24 hours in an atmosphere at a temperature of 50° C. and a humidity of 98%. Then, it was dried at a temperature of 50° C. for 16 hours to obtain an unformed negative electrode plate.

(Assembly of lead-acid battery)
An unformed negative electrode plate was inserted into a bag-shaped separator made of polyethylene. Next, seven sheets of the positive electrode plate which had not been chemically formed and eight sheets of the negative electrode plate which had not been chemically formed which was inserted into the bag-shaped separator were alternately laminated. Subsequently, by a cast-on-strap (COS) method, the tabs of electrode plates of the same polarity were welded together to produce an electrode group. A 2V single cell battery (equivalent to a D23 size single cell defined in JIS D 5301) was assembled by inserting the electrode group into a battery case. After that, sulfuric acid having a specific gravity of 1.240 was injected, and the mixture was placed in a water bath at 40° C. and allowed to stand for 1 hour. After that, formation was carried out at a constant current of 17 A for 18 hours. The specific gravity of the electrolytic solution (sulfuric acid solution) after chemical conversion was adjusted to 1.29 (20° C.).

<Examples 2 to 5 and Comparative Example 1>
A positive electrode plate and a negative electrode plate were produced in the same manner as in Example 1, except that acrylic fibers having a shrinkage rate shown in Table 1 were used instead of acrylic fibers having a shrinkage rate of 45% (shrinkage fibers) in the production of the positive electrode plate. and assembled a lead-acid battery.

[Evaluation of utilization rate of positive electrode active material]
The utilization rate of the positive electrode active material in the lead-acid battery of each example and comparative example was evaluated as follows. Table 1 shows the results.
The produced lead-acid battery was subjected to constant current discharge at a current value of 0.2 C and a final voltage of 1.75 V in an environment of 25° C., and the discharge capacity (Ah) at this time was measured. Using the measured discharge capacity, the utilization rate of the positive electrode active material is calculated by the following formula:
Utilization rate (%) = [measured discharge capacity (Ah)] / [theoretical capacity of positive electrode active material (Ah)] x 100
Based on the utilization rate calculated by the following evaluation. In addition, the theoretical capacity of the positive electrode active material is obtained by "the lead oxide weight (g) in the positive electrode×0.22 (Ah/g)".
A: Utilization rate of 60% or more B: Utilization rate of 50% or more and less than 60% C: Utilization rate of less than 50%

DESCRIPTION OF SYMBOLS 1... Lead-acid battery, 9... Negative electrode plate, 10... Positive electrode plate, 11... Separator, 12... Negative electrode collector, 13... Negative electrode active material, 14... Positive electrode collector, 15... Positive electrode active material.

Claims (8)

A positive electrode current collector and a positive electrode active material held by the positive electrode current collector,
The positive electrode active material includes fibers that are irregularly shrunk and have a shrinkage rate represented by the following formula (1) of 45% or more,
A positive electrode plate for a lead-acid battery, wherein the fiber content is 0.5% by mass or more and 10% by mass or less based on the total mass of the positive electrode active material .
Shrinkage rate (%)=(y−x)/y×100 (1)
(In the formula, x represents the shortest distance from one end of the fiber to the other, and y represents the length along the longitudinal direction of the fiber.) 2. The positive electrode plate according to claim 1, wherein said shrinkage rate is 80% or less. 3. The positive electrode plate of claim 1 or 2, wherein said fibers comprise polymer fibers. A lead-acid battery comprising the positive electrode plate according to any one of claims 1 to 3. A step of holding the positive electrode active material on the positive electrode current collector,
The positive electrode active material includes fibers that are irregularly shrunk and have a shrinkage rate represented by the following formula (1) of 45% or more,
A method for producing a positive electrode plate for a lead-acid battery, wherein the fiber content is 0.5% by mass or more and 10% by mass or less based on the total mass of the positive electrode active material .
Shrinkage rate (%)=(y−x)/y×100 (1)
(In the formula, x represents the shortest distance from one end of the fiber to the other, and y represents the length along the longitudinal direction of the fiber.) The manufacturing method according to claim 5, wherein the shrinkage rate is 80% or less. 7. The manufacturing method according to claim 5 or 6, wherein said fibers comprise polymer fibers. a step of manufacturing the positive electrode plate by the manufacturing method according to any one of claims 5 to 7;
and a step of assembling a lead-acid battery including the positive electrode plate.

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