JP2021061127A - Lead acid battery positive electrode and lead acid battery - Google Patents

Abstract

To provide a lead acid battery positive electrode having an excellent active material utilization rate and a lead acid battery provided with the positive electrode.SOLUTION: A lead acid battery positive electrode 10 includes a positive electrode current collector 14, and a positive electrode active material 15 held in the positive electrode current collector 14, and the positive electrode active material 15 includes a first fiber having a fiber diameter of 10 μm or more, and a second fiber having a fiber diameter of 7 μm or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a positive electrode for a lead storage battery and a lead storage battery.

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

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

Japanese Unexamined Patent Publication No. 2011-165378

However, there is still room for improvement in the active material utilization rate. Therefore, an object of the present invention is to provide a positive electrode for a lead storage battery having an excellent utilization rate of an active material and a lead storage battery provided with the positive electrode.

One aspect of the present invention relates to a positive electrode for a lead storage battery including a positive electrode current collector and a positive electrode active material held in the positive electrode current collector. This positive electrode active material includes a first fiber having a fiber diameter of 10 μm or more and a second fiber having a fiber diameter of 7 μm or less.

The mass-based content of the first fiber in the positive electrode active material may be greater than or equal to the mass-based content of the second fiber in the positive electrode active material. The first fiber and the second fiber may be polymer fibers or acrylic fibers.

Another aspect of the present invention relates to the lead-acid battery provided with the above-mentioned positive electrode.

According to the present invention, it is possible to provide a positive electrode for a lead storage battery having an excellent utilization rate of an active material and a lead storage battery including the positive electrode.

It is a perspective view which shows the overall structure and the internal structure of the lead storage battery which concerns on one Embodiment. It is a perspective view which shows the electrode group of the lead storage battery shown in FIG.

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 the lead storage battery according to the embodiment. As shown in FIG. 1, the lead-acid battery 1 includes an electric tank 2 having an open upper surface and a lid 3 that closes the opening of the electric tank 2. The battery case 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 injection port provided in the lid 3.

Inside the battery case 2, 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, and an electrolytic solution are provided. Is housed.

The electrolytic solution contains dilute sulfuric acid. The dilute sulfuric acid may be, for example, dilute sulfuric acid having a specific gravity (20 ° C.) of 1.25 to 1.33 after chemical conversion. The electrolytic solution may further contain, for example, sodium ions. Sodium ions can be contained in the electrolytic solution, for example, by dissolving sodium sulfate in dilute sulfuric acid. The concentration of sodium ions in the electrolytic solution may be, for example, 0.005 mol / L or more and 0.4 mol / L or less.

FIG. 2 is a perspective view showing the electrode group 7. As shown in FIG. 2, the electrode group 7 includes a negative electrode 9, a positive electrode 10, and a separator 11 arranged between the negative electrode 9 and the positive electrode 10. The negative electrode 9 includes a negative electrode current collector (negative electrode lattice body) 12 and a negative electrode active material 13 held by the negative electrode current collector 12. The positive electrode 10 includes a positive electrode current collector (positive electrode lattice body) 14 and a positive electrode active material 15 held by the positive electrode current collector 14. In this specification, the negative electrode after chemical conversion excluding the negative electrode current collector is defined as "negative electrode active material", and the positive electrode after chemical conversion excluding the positive electrode current collector is defined as "positive electrode active material". ..

The electrode group 7 has a structure in which a plurality of negative electrodes 9 and 10 are alternately laminated in a direction substantially parallel to the opening surface of the battery case 2 via a separator 11. That is, the negative electrode 9 and the positive electrode 10 are arranged so that their main surfaces extend in the direction perpendicular to the opening surface of the battery case 2. In the electrode group 7, the ears 12a of the negative electrode current collectors 12 in the plurality of negative electrodes 9 are collectively welded by the negative electrode strap 16. Similarly, the ears 14a of each of the positive electrode current collectors 14 in the plurality of positive electrodes 10 are collectively welded by the positive electrode strap 17. The negative electrode strap 16 and the positive electrode strap 17 are connected to the negative electrode terminal 4 and the positive electrode terminal 5 via the negative electrode column 8 and the positive electrode column, respectively.

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

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 and the like in addition to lead. Specifically, for example, an alloy containing lead, tin and calcium (Pb-Sn). -Ca-based alloy) may be used.

The negative electrode active material contains at least Pb as a Pb component, and further contains _{a Pb component other than Pb (for example, PbSO 4) and an additive, if necessary.} The negative electrode active material preferably contains 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 measured after the negative electrode (negative electrode current collector and negative electrode active material) is taken out from the lead storage battery, washed with water, and the negative electrode is sufficiently dried, and the negative electrode current collection. It can be calculated from the difference from the mass of the body. Drying is carried out, for example, at 50 ° C. for 24 hours.

Examples of additives include resins having a sulfo group and / or a sulfonic acid base, barium sulfate, carbon materials (excluding carbon fibers) and fibers (acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, carbon fibers, etc.). Can be mentioned.

Resins having a sulfo group and / or a sulfonic acid base include lignin sulfonic acid, lignin sulfonate, and a condensate of phenols, aminoaryl sulfonic acid, and formaldehyde (for example, bisphenol, aminobenzene sulfonic acid, and formaldehyde). It may be at least one selected from the group consisting of condensates). Examples of the carbon material 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 includes PbO ₂ which is a Pb component, a first fiber having a fiber diameter of 10 μm or more, and a second fiber having a fiber diameter of 7 μm or less. The first fiber and the second fiber are also called cut fibers. The positive electrode active material may further contain a Pb component (for example, PbSO _{4 ) other than PbO 2} and an additive, if necessary.

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 the low temperature and high rate discharge performance and the 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 reducing the production cost and weight. The total mass of the positive electrode active material is, for example, the mass of the positive electrode measured after taking out the positive electrode (positive electrode current collector and positive electrode active material) from the lead storage battery, washing the positive electrode with water, and sufficiently drying the positive electrode, and the positive electrode current collection. It can be calculated from the difference from the mass of the body. Drying is carried out, for example, at 50 ° C. for 24 hours.

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

The first fiber and the second fiber are fibrous (elongated) materials. In the present specification, "fiber" is defined as a material having a shape having an aspect ratio of 100 or more. The aspect ratio is the ratio (maximum length) of the maximum length of the fiber diameter calculated from the optical microscope image of the fiber to the minimum length (fiber diameter) of the fiber in the direction perpendicular to the direction having the maximum length. / Minimum length).

The first fiber and the second fiber may be, for example, a polymer fiber, a carbon fiber, or the like, respectively. Examples of the polymer fiber include polyolefin fiber (fiber containing polyethylene, polypropylene and the like), polyester fiber (fiber containing polyethylene terephthalate and the like), acrylic fiber (fiber containing polyacrylate, polymethacrylate and the like) and the like. The first fiber and the second fiber are preferably polymer fibers, more preferably acrylic fibers, respectively, from the viewpoint of obtaining excellent charge / discharge performance (charge acceptance performance, low temperature high rate discharge performance, etc.). The first fiber and the second fiber may be fibers of the same material as each other, or may be fibers of different materials from each other.

The fiber diameter of the first fiber is 10 μm or more, preferably 10.5 μm or more, more preferably 11 μm, as described above, from the viewpoint of ensuring the strength of the fiber and improving the dispersibility of the fiber in the positive electrode active material. That is all. The fiber diameter of the first fiber may be, for example, 15 μm or less.

The fiber diameter of the second fiber is 7 μm or less, preferably 6.5 μm or less, more preferably 6 μm or less, still more preferably 6 μm or less, as described above, from the viewpoint of being able to preferably form a diffusion path of sulfuric acid in the positive electrode active material. It is 5.5 μm or less. The fiber diameter of the second fiber may be 2 μm or more, and from the viewpoint of further improving the utilization rate of the active material, it is preferably 3 μm or more, more preferably 3.5 μm or more, still more preferably 4 μm or more, and particularly preferably 4 It is 5.5 μm or more.

It can be confirmed that the positive electrode active material contains the first fiber and the second fiber by observing an arbitrary cross section of the positive electrode active material using an optical microscope. The fiber diameters of the first and second fibers correspond to the minimum lengths of the fibers described above, and are measured from an optical microscope image of the fibers.

The first fiber can be obtained from, for example, Japan Exlan Co., Ltd. (model number K-701-1.0TS30, etc.). The second fiber can be obtained from, for example, Mitsubishi Chemical Corporation (model number D122, etc.).

The mass-based content of the first fiber in the positive electrode active material is preferably equal to or higher than the mass-based content of the second fiber in the positive electrode active material from the viewpoint of improving durability. From the same viewpoint, the mass-based content of the first fiber in the positive electrode active material is more preferably 1.3 times or more the mass-based content of the second fiber in the positive electrode active material. , 1.5 times or more, 2 times or more, 3 times or more, 3.5 times or more, or 4 times or more. From the viewpoint of further improving the utilization rate, the mass-based content of the first fiber in the positive electrode active material is preferably 8 times the mass-based content of the second fiber in the positive electrode active material. Below, it is 7 times or less, or 6 times or less.

The total content of the first fiber and the second fiber in the positive electrode active material is preferably 0.02 based on the total mass of the positive electrode active material from the viewpoint of suppressing the dropping of the positive electrode active material due to mudification. It is mass% or more, more preferably 0.05 mass% or more, still more preferably 0.1 mass% or more. The total content of the first fiber and the second fiber is preferably based on the total mass of the positive electrode active material from the viewpoint of obtaining excellent charge / discharge performance (charge acceptance performance, low temperature high rate discharge performance, etc.). Is 2.5% by mass or less, more preferably 0.8% by mass or less, still more preferably 0.4% by mass or less.

Examples of the additive include carbon materials (excluding carbon fibers). Examples of the carbon material include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black and Ketjen black.

As described above, when the positive electrode active material contains the first fiber and the second fiber, the active material utilization rate in the positive electrode is improved. The reason for the improvement in utilization rate is that the presence of fibers having different fiber diameters in the positive electrode active material increases the diffusion path of sulfuric acid, and as a result, the amount of the positive electrode active material that contributes to charging and discharging increases. The present inventors speculate that this is the case.

The lead-acid battery 1 is suitably used as a lead-acid battery for starting an engine of a vehicle and for an auxiliary machine. That is, one embodiment of the present invention is an application of the lead-acid battery 1 described above to a vehicle engine start or a vehicle auxiliary machine.

The lead-acid battery 1 is manufactured by, for example, a manufacturing method including an electrode manufacturing step of obtaining electrodes (negative electrode and positive electrode) and an assembly step of assembling constituent members including the electrodes to obtain the lead-acid battery 1.

In the electrode manufacturing process, for example, the negative electrode current collector 12 holds the negative electrode active material paste, and then matures and dries to obtain an unmodified negative electrode 9, and the positive electrode current collector 14 holds the positive electrode active material paste. After the aging, the unchemicald positive electrode 10 is obtained by aging and drying.

In the assembly step, for example, the obtained negative electrodes and positive electrodes are laminated via the separator 11 and the current collecting portions of electrodes having the same polarity are welded with a strap to obtain an electrode group. This group of electrodes is arranged in an electric tank to produce an unchemical lead-acid battery. Next, dilute sulfuric acid is put into a non-chemical lead-acid battery, and a direct current is applied to form an electric tank. Subsequently, the lead storage 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 conditions and the specific gravity of sulfuric acid can be adjusted according to the size of the electrode. The chemical conversion treatment may be carried out in the assembly process or in the electrode manufacturing process (tank chemical conversion).

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to the following examples.

<Example 1>
(Preparation of positive electrode)
Fiber A (acrylic fiber, fiber diameter (minimum length) 11 μm, maximum length 3 mm) 0.224 parts by mass and fiber B (acrylic fiber, fiber diameter 5.0 μm, fiber length) with respect to 100 parts by mass of lead powder. 3 mm) 0.051 part by mass of sodium sulfate, 0.025 part by mass of sodium sulfate, and lead tan were added and mixed dry. Next, 10.5 parts by mass of water was added to 100 parts by mass of the mixture composed of lead powder and fibers, and 16.3 parts by mass of dilute sulfuric acid (specific gravity 1.28) containing lead tan was added stepwise. The mixture was kneaded for 40 minutes to prepare a positive electrode active material paste. The total amount of lead tan was 10 parts by mass. An expanded positive electrode current collector produced by expanding a rolled sheet made of a lead alloy was filled with a positive electrode active material paste and then aged in an atmosphere of a temperature of 50 ° C. and a humidity of 98% for 24 hours. Then, it was dried at a temperature of 60 degreeC for 24 hours to obtain an unchemical positive electrode.

(Preparation of negative electrode)
With respect to 100 parts by mass of lead powder, 0.3 parts by mass of Vanillex N (highly pure partially desulfonated sodium lignin sulfonate, trade name, manufactured by Nippon Paper Co., Ltd.), 0.1 parts by mass of polyethylene terephthalate (PET) fiber, sulfate. A mixture of 1.0 part by mass of barium and 0.1 part by mass of furnace black was added and mixed dry. Next, water was added to this mixture and kneaded, and then the mixture was further kneaded while adding dilute sulfuric acid having a specific gravity of 1.280 little by little to prepare a negative electrode active material paste. The expanded negative electrode current collector produced by expanding a rolled sheet made of a lead alloy was filled with this negative electrode active material paste and then aged in an atmosphere of a temperature of 50 ° C. and a humidity of 98% for 24 hours. Then, it was dried at a temperature of 50 degreeC for 16 hours to obtain an unchemical negative electrode.

(Assembly of lead-acid battery for evaluation)
An unchemical negative electrode was inserted into a bag-shaped polyethylene separator. Next, one unchemical positive electrode and two unchemical negative electrodes inserted into the bag-shaped separator were alternately laminated. Subsequently, terminals were manufactured by arc welding each electrode using a plate-shaped lead sheet. After that, the electrode is inserted into the electric tank, and dilute sulfuric acid having a specific gravity of 1.26 in which sodium sulfate is dissolved so that the sodium ion concentration becomes 0.05 mol / L is injected into the electric tank and placed in a water tank at 40 ° C. It was put in and allowed to stand for 40 minutes. Then, the chemical conversion was carried out with a charge amount (reference: theoretical chemical conversion electric amount of the positive electrode active material) of 300%. The specific gravity of the electrolytic solution (sulfuric acid solution) after chemical conversion was adjusted to 1.29 (20 ° C.). As described above, a 2V single plate cell (lead-acid battery for evaluation) was assembled.

<Example 2>
A lead-acid battery was prepared and each measurement was carried out in the same manner as in Example 1 except that the content of the fiber B used in the preparation of the positive electrode active material paste was changed to 0.106 parts by mass.

<Example 3>
A lead-acid battery was produced in the same manner as in Example 1 except that the content of the fiber B used in producing the positive electrode active material paste was changed to 0.161 parts by mass.

<Example 4>
A lead-acid battery was produced in the same manner as in Example 1 except that the fiber B used for producing the positive electrode active material paste was changed to fiber C (acrylic fiber, fiber diameter (minimum length) 3.3 μm, maximum length 3 mm). did.

<Comparative example 1>
A lead storage battery was produced in the same manner as in Example 1 except that the fiber B was not used when producing the positive electrode active material paste.

<Comparative example 2>
The lead-acid battery was prepared and each measurement was carried out in the same manner as in Example 1 except that the content of the fiber A used in the preparation of the positive electrode active material paste was changed to 0.33 parts by mass and the fiber B was not used.

(Evaluation of active material utilization rate)
The active material utilization rate in the positive electrode of the lead-acid batteries of each Example and Comparative Example was evaluated as follows.
In an environment of 25 ° C., a constant current discharge with a final voltage of 1.75 V was performed at a current value of 0.2 C, and the discharge capacity at this time was measured. Using the measured discharge capacity, the active material utilization rate was calculated by the following formula. The results are shown in Table 1.
Active material utilization rate (%) = [Measured discharge capacity] / [Theoretical capacity of positive electrode active material] x 100
The theoretical capacity of the positive electrode active material is determined by "weight of lead oxide in the positive electrode (g) x 0.22 (Ah / g)".

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

Claims (5)

A positive electrode current collector and a positive electrode active material held by the positive electrode current collector are provided.
A positive electrode for a lead storage battery, wherein the positive electrode active material includes a first fiber having a fiber diameter of 10 μm or more and a second fiber having a fiber diameter of 7 μm or less. The positive electrode according to claim 1, wherein the mass-based content of the first fiber in the positive electrode active material is equal to or greater than the mass-based content of the second fiber in the positive electrode active material. The positive electrode according to claim 1 or 2, wherein the first fiber and the second fiber are polymer fibers. The positive electrode according to any one of claims 1 to 3, wherein the first fiber and the second fiber are acrylic fibers. A lead-acid battery comprising the positive electrode according to any one of claims 1 to 4.

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